TY - CONF
A1 - Sittner, Jonathan
A1 - Hoffmann, T.
A1 - Bertmer, M.
A1 - Neubert, M.
A1 - Schuster, T.
A1 - Gluth, Gregor
ED - Rogge, Andreas
ED - Meng, Birgit
T1 - Optimizing calcination methods towards a more sustainable production of calcined clays
N2 - Calcined clays are emerging as sustainable alternatives for cement production due to their potential to reduce carbon footprint and energy consumption. This study investigates the calcination of low-grade kaolinitic clays, using rotary kiln and fluidized bed. The calcined clays from the rotary kiln showed enhanced performance in the cement paste. The fluidized bed method demonstrated the potential for significant energy savings, achieving near-complete dehydroxylation with just 30 minutes of calcination. These findings highlight the promise of fluidized bed calcination for efficient clay activation, though further optimization is needed.
T2 - 11. Jahrestagung des DAfStb mit 63. Forschungskolloquium der BAM Green Intelligent Building
CY - Berlin, Germany
DA - 16.10.2024
KW - Calcination methods
KW - Optimizing
KW - Blended cement pastes
KW - XRD results
KW - Thermogravimetric analysis (TGA)
PY - 2024
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-612891
SN - 978-3-9818564-7-7
SP - 37
EP - 45
PB - Bundesanstalt für Materialforschung und -prüfung (BAM)
CY - Berlin
AN - OPUS4-61289
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Abbas, Ioana M.
A1 - Hoffmann, Holger
A1 - Montes-Bayón, M.
A1 - Weller, Michael G.
T1 - Improved LC-MS/MS method for the quantification of hepcidin-25 in clinical samples
N2 - Mass spectrometry-based methods play a crucial role in the quantification of the main iron metabolism regulator hepcidin by singling out the bioactive 25-residue peptide from the other naturally occurring N-truncated isoforms (hepcidin-20, -22, -24), which seem to be inactive in iron homeostasis. However, several difficulties arise in the MS analysis of hepcidin due to the sticky character of the peptide and the lack of suitable standards. Here, we propose the use of amino- and fluoro-silanized autosampler vials to reduce hepcidin interaction to laboratory glassware surfaces after testing several types of vials for the preparation of stock solutions and serum samples for isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS). Furthermore, we have investigated two sample preparation strategies and two chromatographic separation conditions with the aim of developing an LC-MS/MS method for the sensitive and reliable quantification of hepcidin-25 in serum samples. A chromatographic separation based on usual acidic mobile phases was compared with a novel approach involving the separation of hepcidin-25 with solvents at high pH containing 0.1% of ammonia. Both methods were applied to clinical samples in an intra-laboratory comparison of two LC-MS/MS methods using the same hepcidin-25 calibrators with good correlation of the results. Finally, we recommend an LC-MS/MS-based quantification method with a dynamic range of 0.5–40 μg/L for the assessment of hepcidin-25 in human serum that uses TFA-based mobile phases and silanized glass vials.
KW - HPLC
KW - Liquid chromatography
KW - Mass spectrometry
KW - Silanization
KW - Mobile phase
KW - Adsorption
KW - Peptide losses
KW - Recovery
KW - Validation
KW - Quality control
KW - QC
KW - Iron disorders
KW - Chronic kidney disease
KW - Metrology
KW - Round robin exercise
KW - Basic solvent
KW - Peptide analysis
PY - 2018
DO - https://doi.org/10.1007/s00216-018-1056-0
SN - 1618-2642
SN - 1618-2650
VL - 410
IS - 16
SP - 3835
EP - 3846
PB - Springer Nature
CY - Heidelberg
AN - OPUS4-45053
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schlichting, S.
A1 - Hönig, Gerald
A1 - Müßener, J.
A1 - Hille, P.
A1 - Grieb, T.
A1 - Westerkamp, S.
A1 - Teubert, J.
A1 - Schörmann, J.
A1 - Wagner, M.R.
A1 - Rosenauer, A.
A1 - Eickhoff, M.
A1 - Hoffmann, A.
A1 - Callsen, G.
T1 - Suppression of the quantum-confined Stark effect in polar nitride heterostructures
N2 - Recently, we suggested an unconventional approach (the so-called Internal-Field-Guarded-Active-Region Design “IFGARD”) for the elimination of the quantum-confined Stark effect in polar semiconductor heterostructures. The IFGARD-based suppression of the Stark redshift on the order of electronvolt and spatial charge carrier separation is independent of the specific polar semiconductor material or the related growth procedures. In this work, we demonstrate by means of micro-photoluminescence techniques the successful tuning as well as the elimination of the quantum-confined Stark effect in strongly polar [000-1] wurtzite GaN/AlN nanodiscs as evidenced by a reduction of the exciton lifetimes by up to four orders of magnitude. Furthermore, the tapered geometry of the utilized nanowires (which embed the investigated IFGARD nanodiscs) facilitates the experimental differentiation between quantum confinement and Stark emission energy shifts. Due to the IFGARD, both effects become independently adaptable.
KW - Nanophotonics
KW - Photonic devices
KW - Single photon and quantum effects
PY - 2018
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-457884
DO - https://doi.org/10.1038/s42005-018-0044-1
SN - 2399-3650
VL - 1
SP - 1
EP - 8
PB - Springer Nature
CY - London
AN - OPUS4-45788
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Holm, Olaf
A1 - Rein, A.
A1 - Trapp, S.
A1 - Popp-Hoffmann, S.
A1 - Bittens, M.
A1 - Leven, C.
A1 - Dietrich, P.
T1 - Comparison of phytoscreening and direct-push-based site investigation at a rural megasite contaminated with chlorinated ethenes
N2 - The reliable characterization of subsurface contamination of spatially extended contaminated sites is a challenging task, especially with an unknown history of land use. Conventional technologies often fail due to temporal and financial constraints and thus hinder the redevelopment of abandoned areas in particular. Here we compare two site screening techniques that can be applied quickly at relatively low cost, namely Direct Push (DP)-based groundwater sampling and tree core sampling. The effectiveness of both methods is compared for a rural megasite contaminated with chlorinated hydrocarbons. Unexpected pollution hot spots could be identified using both of these methods, while tree coring even enabled the delineation of the contaminant plume flowing into an adjacent wetland inaccessible for DP units. Both methods showed a good agreement in revealing the spatial pattern of the contamination. The correlation between groundwater concentrations and equivalent concentrations in wood was linear and highly significant for trichloroethene. Correlation was less obvious for its metabolite cis-dichloroethene, but still significant. As outcome of our study we recommend tree coring and for initial screening in combination with a DP sampling to retrieve quantitative data on groundwater pollutants in order to assess the contamination situation of a non- or only partly investigated site. The subsequent placement of monitoring wells for long-term monitoring of contamination levels is recommended. A combination of methods would achieve more relevant information at comparable or possibly even lower efforts in comparison to a conventional site investigation.
KW - non-invasive investigation
KW - phytoscreening
KW - direct-push
KW - screening
KW - trichloroethene
KW - trichloroethylene
KW - groundwater contamination
KW - tree core sampling
PY - 2015
UR - http://onlinelibrary.wiley.com/doi/10.1111/gwmr.12122/abstract
DO - https://doi.org/10.1111/gwmr.12122
SN - 1745-6592
VL - 35
IS - 4
SP - 45
EP - 56
PB - Wiley Online Library
AN - OPUS4-35595
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kerner-Gang, Waltraut
A1 - Hoffmann, Horst P. M.
ED - Becker, Günther
T1 - Untersuchungen zum Verhalten von Schimmelpilzen gegenüber Klebstoffen für Holzwerkstoffe
PY - 1982
SN - 0025-5270
VL - 17
IS - 4
SP - 253
EP - 268
PB - Duncker & Humblot
CY - Berlin
AN - OPUS4-36291
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CHAP
A1 - Grotheer, E.
A1 - Vogel, Christian
A1 - Kolomiets, O.
A1 - Hoffmann, U.
A1 - Unger, M.
A1 - Siesler, H.W.
ED - Salzer, R.
ED - Siesler, H.W.
T1 - FT-IR and NIR spectroscopic imaging: principles, practical aspects, and applications in material and pharmaceutical science
PY - 2014
SN - 978-3-527-33652-4
SN - 978-3-527-67816-7
SN - 978-3-527-67815-0
SN - 978-3-527-67814-3
SN - 978-3-527-67813-6
SP - Chapter 8, 341
EP - 396
PB - Wiley-VCH Verlag GmbH & Co. KGaA
ET - 2nd Edition
AN - OPUS4-31432
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Pietschmann, S.
A1 - Hoffmann, Katrin
A1 - Voget, M.
A1 - Pison, U.
T1 - Synergistic effects of miconazole and polymyxin B on microbial pathogens
N2 - The therapeutic value of antibiotics depends on the susceptibility of the infecting microorganism and the pharmacological profile of the drugs. To assess the value of an antibiotic combination of polymyxin B and miconazole this study examined the in vitro synergistic potential of the two drugs on Gram-negative and Gram-positive bacteria and yeast. Antifungal and antibacterial activity was tested by minimum inhibitory concentration (MIC) of broth macrodilution and urea broth microdilution, by fluorescence microscopy and flow cytometry. Synergism was calculated using the fractional inhibitory concentration index (FICi). With Staphylococcus intermedius as target we found up to an eightfold reduction of the individual MICs when both drugs were combined. However, the FICi was 0.63 suggesting no real interaction between the two drugs. With Escherichia coli, Pseudomonas aeruginosa, and Malassezia pachydermatis as targets the antimicrobial drug combination reduced the MICs of polymyxin B and miconazole from fourfold to hundredfold resulting in FICi between 0.06 and 0.5 which defines a synergistic action. Thus, if polymyxin B and miconazole are combined their effect is greater than the sum of the effects observed with polymyxin B and miconazole independently, revealing bactericidal and fungicidal synergism. Our results indicate a strong therapeutic value for the combination of these antimicrobial agents against Gram-negative bacteria and yeast and a weaker value against Gram positive bacteria for clinical situations where these pathogens are involved.
KW - Miconazale
KW - Polymyxin
KW - Antibiotic synergism
KW - Otitis externa
PY - 2009
DO - https://doi.org/10.1007/s11259-008-9194-z
SN - 0165-7380
VL - 33
IS - 6
SP - 489
EP - 505
PB - Kluwer
CY - Dordrecht [u.a.]
AN - OPUS4-19661
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hoffmann, Horst P. M.
A1 - Petrowitz, Hans-Joachim
T1 - Über ein neues Verfahren zur Bor-Bestimmung in behandeltem Holz
PY - 1976
SN - 0025-5270
VL - 11
IS - 1
SP - 71
EP - 76
PB - Duncker & Humblot
CY - Berlin
AN - OPUS4-8483
LA - deu
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Weh, K.
A1 - Noack, M.
A1 - Hoffmann, Katrin
A1 - Schröder, K.-P.
A1 - Caro, J.
T1 - Change of gas permeation by photoinduced switching of zeolite-azobenzene membranes of type MFI and FAU
N2 - FAU membranes of type NaX and MFI membranes of type silicalite-1 which contain adsorbed azobenzene (AZB), have photoswitchable permeation properties due to the transcis photoisomerization of AZB. The change of gas permeation through these hostguest composite membranes depends on the irradiation wavelength, the quality of the membranes and the amount of adsorbed AZB. The permeances of the gases in the trans-form of the zeolite-encapsulated AZB were higher than those in the cis-form. The separation factors of equimolar mixtures of N2/CO2 and CH4/CO2 fed through the FAUAZB membrane were higher at trans-switching than at cis-switching. The changes of the permeances of single gases and of the separation factors of equimolar gas mixtures by photoinduced transcis switching were found to be reversible over numerous switching cycles. The experimental results are in agreement with predictions made by Monte Carlo simulations for passing of permeant gases through these hostguest systems with the zeolite-hosted AZB in the trans- and in the cis-configuration.
PY - 2002
DO - https://doi.org/10.1016/S1387-1811(02)00331-1
SN - 1387-1811
SN - 1873-3093
VL - 54
IS - 1-2
SP - 15
EP - 26
PB - Elsevier
CY - Amsterdam
AN - OPUS4-1752
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Descalzo López, Ana Belén
A1 - Rurack, Knut
A1 - Weißhoff, Hardy
A1 - Martínez-Mánez, Ramon
A1 - Marcos, M. Dolores
A1 - Amorós, P.
A1 - Hoffmann, Katrin
A1 - Soto, J.
T1 - Rational Design of a Chromo- and Fluorogenic Hybrid Chemosensor Material for the Detection of Long-Chain Carboxylates
N2 - A strategy for the rational design of a new optical sensor material for the selective recognition of long-chain carboxylates in water is presented. The approach relies on the combination of structure-property relationships to single out the optimal molecular sensor unit and the tuning of the sensing characteristics of an inorganic support material. A spacer-substituted 7-urea-phenoxazin-3-one was employed as the signaling moiety and a mesoporous trimethylsilylated UVM-7 (MCM-41 type) material served as the solid support. The sensor material shows the advantageous features of both modules that is absorption and emission in the visible spectral range, a fluorescence red-shift and enhancement upon analyte coordination, and the amplification of noncovalent (binding) and hydrogen-bonding (recognition) interactions in the detection event. Besides these basic results that are related to the design and performance of the sensor material, the paper discusses general aspects of amido-substituted phenoxazinone photophysics and addresses some general features of molecular anion recognition chemistry in aqueous vs nonaqueous media, utilizing steady-state and time-resolved optical as well as NMR spectroscopies. Detailed studies on potentially competing biochemical species and a first access to the schematic model of the response of the sensor material as obtained by a combination of fluorescence lifetime distribution analysis and Langmuir-type fitting of the gross binding constants complement the key issues of the paper.
KW - Chemosensor
KW - Carboxylate
KW - Rationales Design
KW - Hybridmaterialien
KW - Fluoreszenz
PY - 2005
DO - https://doi.org/10.1021/ja045683n
SN - 0002-7863
SN - 1520-5126
VL - 127
SP - 184
EP - 200
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-5985
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hoffmann, V.
A1 - Uhlemann, M.
A1 - Richter, Silke
A1 - Pfeifer, jens
T1 - Calibration capacity of hot-pressed hydrogen standards for glow discharge optical emission and mass spectrometry
N2 - Mixed copper and titanium hydride powder was hot-pressed and characterized by Carrier Gas Hot Extraction, XRay Diffraction, Thermal Gravimetric Analysis coupled with Mass Spectrometry, and Scanning Electron Microscopy.
The hot-pressed and five conventional samples were applied for calibration of hydrogen in Glow Discharge Optical Emission and Mass Spectrometry. Up to the introduction of 15 ng/s hydrogen the Emission yield model is useful in Glow Discharge Optical Emission Spectrometry. A correlation between saturation and even reversal of the emission yield of the spectral lines H121, H486 and H656 and low sputtering rates was found. Hydrogen effects exist for the spectral lines of Cu(II) 219 and Ti(I) 399. In Glow Discharge Mass Spectrometry, a linear dependency of the 1H ion current on the sputtered mass per time exists over the total range of hydrogen content investigated. Hydrogen effects also exist for the sensitivity of 48Ti and 63Cu. The sputtering rate of two-phase materials depends linearly on the sputtered mass per time of one phase, which allows the sputtering rate of two-phase materials with known composition to be predicted.
KW - Hot-pressing
KW - GD-OES
KW - GD-MS
KW - Calibration
KW - Hydrogen
KW - Titanium hydride
KW - Sputtering
KW - Two-phase system
PY - 2021
DO - https://doi.org/10.1016/j.sab.2020.106039
VL - 176
SP - 106039
PB - Elsevier B.V.
CY - Amsterdam
AN - OPUS4-52074
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Schrezenmeier, E.
A1 - Hoffmann, F.
A1 - Jaeger, C.
A1 - Schrezenmeier, J.
A1 - Lisec, Jan
A1 - Glander, P.
A1 - Algharably, E.
A1 - Kreutz, R.
A1 - Budde, K.
A1 - Duerr, M.
A1 - Halleck, F.
T1 - Pharmacokinetics of Daclatasvir, Sofosbuvir and GS-331007 in a Prospective Cohort of HCV positive Kidney Transplant Recipients
N2 - Limited data exist on the pharmacokinetic profile of novel direct acting antivirals in kidney transplant recipients. Daclatasvir is primarily eliminated via the biliary route and sofosbuvir via the renal route; here we report the pharmacokinetic profile of combined treatment with these compounds in a prospective study of hepatitis C virus positive kidney transplant recipients (EudraCT: 2014-004551-32). In this study plasma samples of 16 HCV positive kidney transplant recipients receiving daclatasvir and sofosbuvir were collected at 4 time points at day 1, 7, 14, 21, 56, and 84 after start of treatment. Inclusion criteria were stable graft function and an estimated GFR (eGFR) > 30mL/min/1.73m. Daclatasvir, sofosbuvir and GS-331007 (inactive metabolite of sofosbuvir) plasma concentrations were determined using ultra-performance liquid chromatography quadrupole time of flight mass spectrometry. All patients showed a rapid virological response with HCV RNA below the detection limit 21 days after the start of therapy (medium time to viral clearance). No difference of the areas under the concentration-time curve (AUC) of daclatsavir, sofosbuvir and GS-331007 was observed between patients with an eGFR below or ≥ 60mL/min. For GS-331007, no relevant changes of trough levels were observed over time. Mean GS-331007 trough levels were 339.5±174.9 ng/mL in patients with an eGFR ≥ 60mL/min and 404.3±226 ng/mL in patients with an eGFR < 60mL/min at day 7 (p=0.52). At day 84, GS-331007 trough levels were 357.8±200.8 ng/mL and 404.2±70.2 ng/mL in patients with an eGFR ≥ 60 mL/min and in patients with an eGFR < 60 mL/min, respectively (p=0.51). The accumulation ratios of renally eliminated GS-331007 for AUC and Cmax did not significantly differ between the two eGFR groups at day 7. An impaired eGFR (30-60 mL/min) does not lead to a dose accumulation of daclatasvir, sofosbuvir and GS-331007. This study provides the rationale for future studies investigating the pharmacokinetic profile of sofosbuvir based HCV treatment in kidney transplant recipients with an eGFR < 30 mL/min.
KW - Mass-Spectrometry
PY - 2018
DO - https://doi.org/10.1097/FTD.0000000000000567
SN - 0163-4356
VL - 41
IS - 1
SP - 53
EP - 58
PB - Wolters Kluwer
AN - OPUS4-46647
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Kage, Daniel
A1 - Hoffmann, Katrin
A1 - Wittkamp, M.
A1 - Ameskamp, J.
A1 - Göhde, W.
A1 - Resch-Genger, Ute
T1 - Luminescence lifetime encoding in time-domain flow cytometry
N2 - Time-resolved flow cytometry represents an alternative to commonly applied spectral or intensity multiplexing in bioanalytics. At present, the vast majority of the reports on this topic focuses on phase-domain techniques and specific applications. In this report, we present a flow cytometry platform with time-resolved detection based on a compact setup and straightforward time-Domain measurements utilizing lifetime-encoded beads with lifetimes in the nanosecond range. We provide general assessment of time-domain flow cytometry and discuss the concept of this platform to address achievable resolution limits, data analysis, and requirements on suitable encoding dyes. Experimental data are complemented by numerical calculations on photon count numbers and impact of noise and measurement time on the obtained lifetime values.
KW - Flow cytometry
KW - Fluorescence
KW - Life sciences
KW - Lifetime encoding
KW - Polymer particles
PY - 2018
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-465765
DO - https://doi.org/10.1038/s41598-018-35137-5
SN - 2045-2322
VL - 8
IS - 1
SP - 16715, 1
EP - 11
PB - Nature
CY - London
AN - OPUS4-46576
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Preiss, J.
A1 - Kage, Daniel
A1 - Hoffmann, Katrin
A1 - Martínez, T. J.
A1 - Resch-Genger, Ute
A1 - Presselt, M.
T1 - Ab initio prediction of fluorescence lifetimes involving solvent environments by means of COSMO and vibrational broadening
N2 - The fluorescence lifetime is a key property of fluorophores that can be utilized for microenvironment probing, analyte sensing, and multiplexing as well as barcoding applications. For the rational design of lifetime probes and barcodes, theoretical methods have been developed to enable the ab initio prediction of this parameter, which depends strongly on interactions with solvent molecules and other chemical species in the emitters' immediate environment. In this work, we investigate how a conductor-like screening model (COSMO) can account for variations in fluorescence lifetimes that are caused by such fluorophore−solvent interactions. Therefore, we calculate vibrationally broadened fluorescence spectra using the nuclear ensemble method to obtain distorted molecular geometries to sample the electronic transitions with time-dependent density functional theory (TDDFT). The influence of the solvent on fluorescence lifetimes is accounted for with COSMO. For example, for 4-hydroxythiazole fluorophore containing different heteroatoms and acidic and basic moieties in aprotic and protic solvents of varying polarity, this approach was compared to experimentally determined lifetimes in the same solvents. Our results demonstrate a good correlation between theoretically predicted and experimentally measured fluorescence lifetimes except for the polar solvents Ethanol and acetonitrile that can specifically interact with the heteroatoms and the carboxylic acid of the thiazole derivative.
KW - Fluorescence lifetime
KW - Ab initio calculation
KW - COSMO
KW - Conductor-like screening model
PY - 2018
DO - https://doi.org/10.1021/acs.jpca.8b08886
SN - 1089-5639
SN - 1520-5215
VL - 122
IS - 51
SP - 9813
EP - 9820
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-47177
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Denißen, M.
A1 - Nirmalananthan-Budau, Nithiya
A1 - Behnke, Thomas
A1 - Hoffmann, Katrin
A1 - Resch-Genger, Ute
A1 - Müller, T. J. J.
T1 - 3-Piperazinyl propenylidene indolone merocyanines: consecutive three-component synthesis and electronic properties of solid-state luminophores with AIE properties
N2 - A series of twelve 3-piperazinyl propenylidene indolone merocyanines was synthesized in a one-pot fashion using a consecutive three-component insertion-coupling-Michael addition sequence. Physicalorganic treatment of the absorption data of a consanguineous series of this library allows semiquantitative Linear Free Energy Relationships (LFERs) to be established and confirmation of the positive Absorption solvatochromicity. All Boc-substituted piperazinyl merocyanines display aggregation induced Emission (AIE), which was corroborated for two solvent systems. In particular, crystallization-induced Emission enhancement (CIEE) induced by ultrasonication could be shown for a model chromophore by confocal laser scanning microscopy (CLSM).
KW - Indolone merocyanines
KW - AIE
KW - CIEE
KW - CLSM
PY - 2017
DO - https://doi.org/10.1039/c7qm00198c
SN - 2052-1537
N1 - Geburtsname von Nirmalananthan-Budau, Nithiya: Nirmalananthan, N. - Birth name of Nirmalananthan-Budau, Nithiya: Nirmalananthan, N.
VL - 1
IS - 10
SP - 2013
EP - 2026
AN - OPUS4-43213
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Denißen, M.
A1 - Hannen, R.
A1 - Itskalov, D.
A1 - Biesen, L.
A1 - Nirmalananthan-Budau, Nithiya
A1 - Hoffmann, Katrin
A1 - Reiss, G. J.
A1 - Resch-Genger, Ute
A1 - Müller, T. J. J.
T1 - One-pot synthesis of a white-light emissive bichromophore operated by aggregation-induced dual emission (AIDE) and partial energy transfer
N2 - Merocyanine–triarylamine bichromophores are readily synthesized by sequentially Pd-catalyzed insertion alkynylation–Michael–Suzuki four-component reactions. White-light emissive systems form upon aggregation in 1 : 99 and 0.1 : 99.9 vol% CH2Cl2–cyclohexane mixtures, ascribed to aggregation-induced dual emission (AIDE) in combination with partial energy transfer between both chromophore units as supported by spectroscopic studies.
KW - Energy transfer
KW - Nano
KW - Nanoparticle
KW - Photoluminescence
KW - Fluorescence
KW - Quantum yield
KW - Photophysics
KW - Lifetime
KW - Sensor
KW - Dye
KW - Enhancement
KW - Particle
KW - Polarity
KW - AIE
KW - Aggregation
KW - Aggregation-induced emission
KW - Solid state emission
KW - Merocyanine
PY - 2020
DO - https://doi.org/10.1039/d0cc03451g
VL - 56
IS - 54
SP - 7407
PB - Royal Society of Chemistry
AN - OPUS4-50936
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Xu, R.
A1 - Teich, W.
A1 - Frenzel, Florian
A1 - Hoffmann, Katrin
A1 - Radke, J.
A1 - Rösler, J.
A1 - Faust, K.
A1 - Blank, A.
A1 - Brandenburg, S.
A1 - Misch, M.
A1 - Vajkoczy, P.
A1 - Onken, J. S.
A1 - Resch-Genger, Ute
T1 - Optical characterization of sodium fluorescein in vitro and ex vivo
N2 - Objective: The utilization of fluorescein-guided biopsies and resection has been recently discussed as a suitable strategy to improve and expedite operative techniques for the resection of central nervous system (CNS) tumors. However, little is known about the optical properties of sodium fluorescein (NaFl) in human tumor tissue and their potential impact on ex vivo analyses involving fluorescence-based methods.
Methods: Tumor tissue was obtained from a study cohort of an observational study on the utilization of fluorescein-guided biopsy and resection (n=5). The optical properties of fluorescein-stained tissue were compared to the optical features of the dye in vitro and in control samples consisting of tumor tissue of high-grade glioma patients (n=3) without intravenous (i.v.) application of NaFl. The dye-exposed tumor tissues were used for optical measurements to confirm the detectability of NaFl emission ex vivo. The tissue samples were fixed in 4%PFA, immersed in 30% sucrose, embedded in Tissue-Tek OCT compound, and cut to 10 mm cryosections. Spatially resolved emission spectra from tumor samples were recorded on representative slides with a Confocal Laser Scanning Microscope FV1000 (Olympus GmbH, Hamburg, Germany) upon excitation with lexc = 488 nm.
Results: Optical measurements of fluorescein in 0.9% sodium chloride (NaCl) under in vitro conditions showed an absorption maximum of lmax abs = 479 nm as detected with spectrophotometer Specord 200 and an emission peak at lmax em = 538 nm recorded with the emCCD detection system of a custom-made microscope-based single particle setup using a 500 nm long-pass filter. Further measurements revealed pH- and concentration-dependent emission spectra of NaFl. Under ex vivo conditions, confocal laser scanning microscopy of fluorescein tumor samples revealed a slight bathochromic shift and a broadening of the emission band.
Conclusion: Tumor uptake of NaFl leads to changes in the optical properties – a bathochromic shift and broadening of the emission band – possibly caused by the dye’s high pH sensitivity and concentration-dependent reabsorption acting as an innerfilter of the dye’s emission, particularly in the short wavelength region of the Emission spectrum where absorption and fluorescence overlap. Understanding the ex vivo optical properties of fluorescein is crucial for testing and validating its further applicability as an optical probe for intravital microscopy, immunofluorescence localization studies, and flow cytometry analysis.
KW - Fluorescence
KW - Optical probe
KW - Sensor
KW - Fluorescein
KW - PH
KW - Imaging
KW - Tissue
KW - Cancer
KW - Medical diagnostics
KW - Tumor
KW - In vivo
KW - Ex vivo
KW - Quantum yield
KW - Dye
KW - Quality assurance
KW - Microscopy
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-527843
DO - https://doi.org/10.3389/fonc.2021.654300
SN - 2234-943X
VL - 11
SP - 1
EP - 8
PB - Frontiers Media
CY - Lausanne
AN - OPUS4-52784
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Felbeck, Tom
A1 - Hoffmann, Katrin
A1 - Resch-Genger, Ute
A1 - Lezhnina, M.M.
A1 - Kynast, U.H.
T1 - Fluorescent nanoclays: Covalent functionalization with amine reactive dyes from different fluorophone classes and surface group quantification
N2 - The ever increasing applications of fluorescence techniques in conjunction with the interest in enhanced detection sensitivities in bioanalysis, biosensing, and bioimaging are closely linked to the rational design of novel nontoxic fluorescent nanomaterials with improved brightness and stability that can be reproducibly synthesized from inexpensive starting materials in simple one-pot reactions and easily surface functionalized. This encouraged us to investigate the potential of the commercially available water-dispersible nanoclay Laponite RD with the empirical formula Na0.7(H2O)n{(Li0.3Mg5.5)[Si8O20(OH)4]}, forming 25 nm sized disk-shaped particles, as nanocarriers for different fluorophores. The Si–OH functions at the rims of these disks can be selectively grafted with 3-aminopropyldimethylethoxysilane (APES), thereby enabling subsequent coupling to amine-reactive molecules ranging from target-specific organic ligands and biomolecules to amine-reactive fluorescent labels. Here, we present different strategies for the surface functionalization of nanoclays and the subsequent quantification of the density of synthetically introduced surface amino groups exploiting analytical methods which rely on different detection schemes including elemental analysis, colorimetric assays, and fluorophore labeling strategies. In this respect, we systematically assess the potential of negatively and positively charged, neutral, and zwitterionic dyes to act as fluorescent labels for amino functionalities at the surface of negatively charged nanoclays. Our studies underline the strong influence of dye charge and aggregation tendency on the brightness of the bound dyes and on surface group quantification. Best results regarding surface group analysis and coupling yield were obtained for a neutral dansyl derivative and fluorescamine.
PY - 2015
DO - https://doi.org/10.1021/acs.jpcc.5b01482
SN - 1932-7447
SN - 1089-5639
VL - 119
IS - 23
SP - 12978
EP - 12987
PB - Soc.
CY - Washington, DC
AN - OPUS4-33614
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Felbeck, Tom
A1 - Behnke, Thomas
A1 - Hoffmann, Katrin
A1 - Grabolle, Markus
A1 - Lezhnina, M.M.
A1 - Kynast, U.H.
A1 - Resch-Genger, Ute
T1 - Nile-red-nanoclay hybrids: Red emissive optical probes for use in aqueous dispersion
N2 - Water-dispersible and (bio)functionalizable nanoclays have a considerable potential as inexpensive carriers for organic molecules like drugs and fluorophores. Aiming at simple design strategies for red-emissive optical probes for the life sciences from commercial precursors with minimum synthetic effort, we systematically studied the dye loading behavior and stability of differently functionalized laponites. Here, we present a comprehensive study of the absorption and emission properties of the red emissive hydrophobic and neutral dye Nile Red, a well-known polarity probe, which is almost insoluble and nonemissive in water. Adsorption of this probe onto disk-shaped nanoclays was studied in aqueous dispersion as function of dye concentration, in the absence and presence of the cationic surfactant cetyltrimethylammonium bromide (CTAB) assisting dye loading, and as a function of pH. This laponite loading strategy yields strongly fluorescent nanoclay suspensions with a fluorescence quantum yield of 0.34 at low dye loading concentration. The dye concentration-, CTAB-, and pH-dependent absorption, fluorescence emission, and fluorescence excitation spectra of the Nile-Red6#8211;nanoclay suspensions suggest the formation of several Nile Red species including emissive Nile Red monomers facing a polar environment, nonemissive H-type dimers, and protonated Nile Red molecules that are also nonfluorescent. Formation of all nonemissive Nile Red species could be suppressed by modification of the laponite with CTAB. This underlines the great potential of properly modified and functionalized laponite nanodisks as platform for optical probes with drug delivery capacities, for example, for tumor and therapy imaging. Moreover, comparison of the Nile Red dimer absorption spectra with absorption spectra of previously studied Nile Red aggregates in dendrimer systems and micelles and other literature systems reveals a considerable dependence of the dimer absorption band on microenvironment polarity which has not yet been reported so far for H-type dye aggregates.
KW - Nile Red
KW - Dye
KW - Laponite
KW - Nanoclay
KW - Photoluminescence
KW - Fluorescence
KW - Polarity probe
KW - Aggregate
KW - Dimer
PY - 2013
DO - https://doi.org/10.1021/la402165q
SN - 0743-7463
SN - 1520-5827
VL - 29
IS - 36
SP - 11489
EP - 11497
PB - American Chemical Society
CY - Washington, DC
AN - OPUS4-29017
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Behnke, Thomas
A1 - Laux, Eva-Maria
A1 - Hoffmann, Katrin
A1 - Peters, S.
A1 - Haueisen, J.
A1 - Klemm, M.
A1 - Resch-Genger, Ute
T1 - Simple approaches to fluorescence lifetime standards using dye-quencher pairs
N2 - Photoluminescence techniques are amongst the most widely used tools in the material and life sciences, with new and exciting applications continuously emerging. Advantages include their comparative ease of use, unique sensitivity, non-invasive character, and potential for multiplexing, remote sensing, and miniaturization. Increasing applications of fluorescence techniques in the life sciences and emerging medical applications of fluorescence microscopic techniques including 1P and 2P fluorescence microscopy combined with fluorescence lifetime imaging (FLIM) in e.g. in vivo eye diagnostics boosted the demand for robust, easy-to-use, and reliable fluorescence standards to ensure the reliability and comparability of fluorescence data. This includes fluorescence standards for the consideration of instrument-specific spectral and intensity distortions of measured signals and instrument performance validation, fluorescence intensity standards for the quantification of measured intensities and for signal referencing, and lately, also fluorescence lifetime standards.
T2 - BMT 2012 - 46. DGBMT Jahrestagung
CY - Jena, Germany
DA - 16.09.2012
PY - 2012
DO - https://doi.org/10.1515/bmt-2012-4499
SN - 0013-5585
SN - 1862-278X
VL - 57
IS - Suppl. 1
SP - 613
PB - De Gruyter
CY - Berlin
AN - OPUS4-27682
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hoffmann, M.
A1 - Schubert, Nils
A1 - Günster, Jens
A1 - Stawarczyk, B.
A1 - Zocca, Andrea
T1 - Additive manufacturing of glass-ceramic dental restorations by layerwise slurry deposition (LSD-print)
N2 - This study is dedicated to the additive manufacturing of a feldspar glass-ceramic for dental applications by LSD-print (layerwise slurry deposition) technology, a variation of binder jetting using water-based ceramic slurries as feedstock. This technology was investigated for the manufacturing of single tooth restoration demonstrators with good aesthetic properties, and to compare the additively manufactured material with a commercial reference. Model restorations with > 99 % relative density were processed with a debinding and firing cycle of 45 min, however the whole process chain accounts for up to 30 hours. Significant differences between LSD-printed and reference materials were found for fracture strength, fracture toughness and Martens parameters. Printing orientation affected shrinkage and fracture strength, but not fracture toughness and Martens parameters. Nevertheless, the results suggest that the LSD-print technology processing the developed slurry is a promising option for manufacturing dental restorations meeting class 1a requirements according to DIN EN ISO 6871:2019–01.
KW - Additive Manufacturing
KW - 3D-printing
KW - LSD-print
KW - Dental ceramics
KW - Glass-ceramic
KW - Debinding
KW - Firing
KW - Sinter-crystallization
PY - 2025
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-624768
DO - https://doi.org/10.1016/j.jeurceramsoc.2025.117235
VL - 45
IS - 7
SP - 1
EP - 13
PB - Elsevier Ltd.
AN - OPUS4-62476
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - CONF
A1 - Hodoroaba, Vasile-Dan
A1 - Hoffmann, V.
A1 - Steers, E. B. M.
T1 - Exploitation of the hydrogen effect on an analytical glow discharge
T2 - Final General Meeting of the EU-GDS Network
CY - Wiener Neustadt, Austria
DA - 2002-03-02
PY - 2002
SP - 1(?)
EP - 6(?)
AN - OPUS4-1467
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Ferreira da Silva, F.
A1 - do N. Varella, M. T.
A1 - Jones, N. C.
A1 - Vrönning Hoffmann, S.
A1 - Denifl, S.
A1 - Bald, Ilko
A1 - Kopyra, J.
T1 - Electron-Induced Reactions in 3-Bromopyruvic Acid
N2 - 3-Bromopyruvic acid (3BP) is a potential anticancer drug, the action of which on cellular metabolism is not yet entirely clear. The presence of a bromine atom suggests that it is also reactive towards low-energy electrons, which are produced in large quantities during tumour Radiation therapy. Detailed knowledge of the interaction of 3BP with secondary electrons is a prerequisite to gain a complete picture of the effects of 3BP in different forms of Cancer therapy. Herein, dissociative electron attachment (DEA) to 3BP in the gas phase has been studied both experimentally by using a crossed-beam setup and theoretically through scattering and quantum chemical calculations. These results are complemented by a vacuum ultraviolet absorption spectrum.
The main fragmentation channel is the formation of Br@ close to 0 eV and within several resonant features at 1.9 and 3–8 eV. At low electron energies, Br@ formation proceeds through s* and p* shape resonances, and at higher energies through core-excited resonances. It is found that the electron-capture cross-section is clearly increased compared with that of non-brominated pyruvic acid, but, at the same time, fragmentation reactions through DEA are significantly altered as well. The 3BP transient negative ion is subject to a lower number of fragmentation reactions than those of pyruvic acid, which indicates that 3BP could indeed act by modifying the electron-transport chains within oxidative phosphorylation. It could also act as a radio-sensitiser.
KW - Density functional calculations
KW - Dissociative electron attachment
KW - Drug discovery
KW - Gas-phase reactions
KW - Sensitizers
PY - 2019
DO - https://doi.org/10.1002/chem.201806132
SN - 0947-6539
VL - 25
IS - 21
SP - 5498
EP - 5506
PB - WILEY-VCH Verlag GmbH & Co. KGaA
CY - Weinheim
AN - OPUS4-48003
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Geißler, Daniel
A1 - Wegmann, Marc
A1 - Jochum, T.
A1 - Somma, V.
A1 - Sowa, M.
A1 - Scholz, J.
A1 - Fröhlich, E.
A1 - Hoffmann, Katrin
A1 - Niehaus, J.
A1 - Roggenbuck, D.
A1 - Resch-Genger, Ute
T1 - An automatable platform for genotoxicity testing of nanomaterials based on the fluorometric γ-H2AX assay reveals no genotoxicity of properly surface-shielded cadmium-based quantum dots
N2 - The large number of nanomaterial-based applications emerging in the materials and life sciences and the foreseeable increasing use of these materials require methods that evaluate and characterize the toxic potential of these nanomaterials to keep safety risks to people and environment as low as possible. As nanomaterial toxicity is influenced by a variety of parameters like size, shape, chemical composition, and surface chemistry, high throughput screening (HTS) platforms are recommended for assessing cytotoxicity. Such platforms are not yet available for genotoxicity testing. Here, we present first results obtained for application-relevant nanomaterials using an automatable genotoxicity platform that relies on the quantification of the phosphorylated histone H2AX (γ-H2AX) for detecting DNA double strand breaks (DSBs) and the automated microscope system AKLIDES® for measuring integral fluorescence intensities at different excitation wavelengths. This platform is used to test the genotoxic potential of 30 nm-sized citrate-stabilized gold nanoparticles (Au-NPs) as well as micellar encapsulated iron oxide nanoparticles (FeOx-NPs) and different cadmium (Cd)-based semiconductor quantum dots (QDs), thereby also searching for positive and negative controls as reference materials. In addition, the influence of the QD shell composition on the genotoxic potential of these Cd-based QDs was studied, using CdSe cores as well as CdSe/CdS core/shell and CdSe/CdS/ZnS core/shell/shell QDs. Our results clearly revealed the genotoxicity of the Au-NPs and its absence in the FeOx-NPs. The genotoxicity of the Cd-QDs correlates with the shielding of their Cd-containing core, with the core/shell/shell architecture preventing genotoxicity risks. The fact that none of these nanomaterials showed cytotoxicity at the chosen particle concentrations in a conventional cell viability assay underlines the importance of genotoxicity studies to assess the hazardous potential of nanomaterials.
KW - Nanomaterial
KW - Genotoxicity testing
KW - γ-H2AX assay
KW - Quantum dot
PY - 2019
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-486318
DO - https://doi.org/10.1039/C9NR01021A
SN - 2040-3372
SN - 2040-3364
VL - 11
IS - 28
SP - 13458
EP - 13468
PB - The Royal Society of Chemistry
AN - OPUS4-48631
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hodoroaba, Vasile-Dan
A1 - Hoffmann, V.
A1 - Steers, E. B. M.
A1 - Wetzig, K.
T1 - Exploitation of the effect of hydrogen on an analytical glow discharge
T2 - Winter Conference on Plasma Spectrochemistry 2002
CY - Scottsdale, AZ, USA
DA - 2002-01-06
PY - 2002
SN - 0161-6951
SP - 261
EP - 262
PB - ICP Information Newsletter, Inc.
CY - Amherst, Mass.
AN - OPUS4-1589
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Gomes, Bruna F.
A1 - Prokop, Martin
A1 - Bystron, Tomas
A1 - Loukrakpam, Rameshwori
A1 - Melke, Julia
A1 - Lobo, Carlos M. S.
A1 - Fink, Michael
A1 - Zhu, Mengshu
A1 - Voloshina, Elena
A1 - Kutter, Maximilian
A1 - Hoffmann, Hendrik
A1 - Yusenko, Kirill V.
A1 - de Oliveira Guilherme Buzanich, Ana
A1 - Röder, Bettina
A1 - Bouzek, Karel
A1 - Paulus, Beate
A1 - Roth, Christina
T1 - Following Adsorbed Intermediates on a Platinum Gas Diffusion Electrode in H3PO3-Containing Electrolytes Using In Situ X-ray Absorption Spectroscopy
N2 - One of the challenges of high-temperature polymer electrolyte membrane fuel cells is the poisoning of the Pt catalystwith H3PO4. H3PO4 is imbibed into the routinely used polybenzimidazole-based membranes, which facilitate Proton conductivity in the temperature range of 120−200 °C. However, when leached out of the membrane by water produced during operation, H3PO4 adsorbs on the Pt catalyst surface, blocking the active sites and hindering the oxygen reduction reaction (ORR).
The reduction of H3PO4 to H3PO3, which occurs at the anode due to a combination of a low potential and the presence of gaseous H2, has been investigated as an additional important contributing factor to the observed poisoning effect. H3PO3 has an affinity toward adsorption on Pt surfaces even greater than that of H2PO4 −. In this work, we investigated the poisoning effect of both H3PO3 and H3PO4 using a half-cell setup with a gas diffusion electrode under ambient conditions. By means of in situ X-ray absorption spectroscopy, it was possible to follow the signature of different species adsorbed on the Pt nanoparticle catalyst (H, O, H2PO4 −, and H3PO3) at different potentials under ORR conditions in various electrolytes (HClO4, H3PO4, and H3PO3). It was found that H3PO3 adsorbs in a pyramidal configuration P(OH)3 through a Pt−P bond. The competition between H3PO4 and H3PO3 adsorption was studied, which should allow for a better understanding of the catalyst poisoning mechanism and thus assist in the development of strategies to mitigate this phenomenon in the future by minimizing H3PO3 generation by, for example, improved catalyst design or adapted operation conditions or changes in the electrolyte composition.
KW - H3PO4 life cycle
KW - XAS
KW - In situ coupling
KW - High-temperature fuel cells
KW - H3PO3,
KW - Δμ XANES
PY - 2022
DO - https://doi.org/10.1021/acscatal.2c02630
SN - 2155-5435
VL - 12
IS - 18
SP - 11472
EP - 11484
PB - American Chemical Society (ACS)
AN - OPUS4-64733
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Bui, M.
A1 - Hoffmann, K. F.
A1 - Braun, T.
A1 - Riedel, S.
A1 - Heinekamp, Christian
A1 - Scheurell, K.
A1 - Scholz, G.
A1 - Stawski, Tomasz
A1 - Emmerling, Franziska
T1 - An Amorphous Teflate Doped Aluminium Chlorofluoride:
A Solid Lewis-Superacid for the Dehydrofluorination of
Fluoroalkanes
N2 - Ananion-dopedaluminiumchlorofluoride AlCl0.1F2.8(OTeF5)0.1(ACF-teflate) was synthesized.The material contains pentafluor-oorthotellurate(teflate)groups, which mimic fluoride ions electronically, but are sterically more demanding. They are embedded into the amorphous structure. The latter was studied by PDF analysis, EXAFS data and MAS NMR spectroscopy. The mesoporous powder is a Lewis superacid, and ATR-IR spectra of adsorbed CD3CN reveal a blue-shift of the adsorption band by73 cm-1, which is larger than the shift for SbF5. Remarkably,ACF-teflate catalyzes dehydrofluorination reactions of mono-fluoroalkanes to yield olefins in C6D6. In these cases,no Friedel-Crafts products were formed.
KW - Aluminium fluorides
KW - Aluminium teflates
KW - C-F bond activation
KW - Lewis superacids
KW - Silanes
PY - 2023
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-572290
DO - https://doi.org/10.1002/cctc.202300350
SN - 1867-3880
SP - 1
EP - 7
PB - Wiley VHC-Verlag
AN - OPUS4-57229
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hoferer, J.
A1 - Hoffmann, L.M.
A1 - Goebbels, Jürgen
A1 - Last, G.
A1 - Weil, W.
A1 - Kasper, G.
T1 - Reconstruction algorithms for the internal packing density distribution of fibrous filter media based on tomographic data
N2 - Algorithms were developed to approximate the 3-dimensional internal packing density distributions of fibrous filter media at different levels of detail and complexity. Each algorithm uses certain input information derived from X-ray tomographic data of filter samples.
Algorithm 1 creates a binary media structure consisting of the true (i.e. tomographically determined) void distribution plus regions of uniform packing density. The average packing density of the media is maintained constant. Algorithm 2 creates a model fibrous structure of straight fibres of equal diameter and random length positioned randomly in space, while maintaining the true (i.e. tomographically determined) fibre orientation distribution. The number and length of the fibres on average adds up to the packing density of the filter. The model fibrous structure is recreated by a stationary Poisson process of convex bodies. Algorithm 3 distributes pores of random size and location within a homogeneous matrix, such that the average packing density again coincides with the true (i.e. tomographically determined) packing density. This algorithm is also based on a stationary Poisson process of convex bodies.
The capability of each algorithm to recreate the essential structural features of the media was tested against 'reality' by computing the respective overall pressure drop of the filter as well as the velocity distribution in the filter interior, and comparing with the results obtained for the 'true' packing density distribution of a sample measured by tomography. Compared to the assumption of a completely homogenous filter (which gives roughly 2 times the actual Δp), all algorithms are closer to reality. The binary algorithm deviates in Δp by a factor of 1.8; algorithm 3 comes within a factor of 1.6 of the true Δp. The best approximation is by algorithm 2 which narrows the difference in Δp to a factor of 1.4.
KW - X-ray tomography
KW - Fibrous filter
KW - Packing density
PY - 2009
SN - 1479-0602
VL - 9
IS - 2
SP - 147
EP - 154
PB - Filtration Solutions
CY - Newbold, Coleorton, Coalville
AN - OPUS4-22880
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Engel, A.
A1 - Ottermann, C.
A1 - Resch-Genger, Ute
A1 - Hoffmann, Katrin
A1 - Schweizer, S.
A1 - Selling, J.
A1 - Spaeth, J.-M.
A1 - Rupertus, V.
ED - Grzymala, R.
ED - Haeberlé, O.
T1 - Glass based fluorescence reference materials used for optical and biophotonic applications
N2 - Fluorescence techniques are known for their high sensitivity and are widely used as analytical tools and detection methods for product and process control, material sciences, environmental and biotechnical analysis, molecular genetics, cell biology, medical diagnostics, and drug screening. For routine measurements by fluorescence techniques the existence of an improved quality assurance is one of the basic needs. According to DIN/ISO 17025 certified standards are used for fluorescence diagnostics having the drawback of giving relative values only. Typical requirements onto fluorescence reference materials or standards deal with the verification of the instrument performance as well as the improvement of the data comparability. Especially for biomedical applications fluorescence labels are used for the detection of proteins. In particular these labels consist of nano crystalline materials like CdS and CdSe. The field of Non-Cadmium containing materials is under investigation. In order to evaluate whether glass based materials can be used as standards it is necessary to calculate absolute values like absorption/excitation cross sections or relative quantum yields. This can be done using different quantities of dopands in glass, glass ceramics or crystals. The investigated materials are based on different types of glass, silicate, phosphate and boron glass, which play a dominant role for the absorption and emission mechanism. Additional to the so-called elementary fluorescence properties induced by raw earth elements the formation of defects lead to higher cross sections additionally. The main investigations deal with wavelength accuracy and lifetime of doped glasses, glass ceramics and crystalline samples. Moreover intensity patterns, homogeneity aspects and photo stability will be discussed.
KW - Fluorescence
KW - Reference material
KW - Glass
KW - Glass ceramics
KW - Biophotonic
KW - Multiplexing
PY - 2006
DO - https://doi.org/10.1117/12.663627
SN - 1605-7422
VL - 6191
SP - 619110-1-619110-10
AN - OPUS4-14429
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hoffmann, A.
A1 - Lischeid, G.
A1 - Koch, Matthias
A1 - Lentzsch, P.
A1 - Sommerfeld, Thomas
A1 - Müller, M.H.
T1 - Co-Cultivation of Fusarium, Alternaria, and Pseudomonas on Wheat-Ears Affects Microbial Growth and Mycotoxin Production
N2 - Mycotoxigenic fungal pathogens Fusarium and Alternaria are a leading cause of loss in cereal production. On wheat-ears, they are confronted by bacterial antagonists such as pseudomonads.
Studies on these groups’ interactions often neglect the infection process’s temporal aspects and the associated priority effects. In the present study, the focus was on how the first colonizer affects the subsequent ones. In a climate chamber experiment, wheat-ears were successively inoculated with two different strains (Alternaria enuissima At625, Fusarium graminearum Fg23, or Pseudomonas simiae Ps9).
Over three weeks, microbial abundances and mycotoxin concentrations were analyzed and visualized via Self Organizing Maps with Sammon Mapping (SOM-SM). All three strains revealed different characteristics and strategies to deal with co-inoculation: Fg23, as the first colonizer, suppressed the establishment of At625 and Ps9. Nevertheless, primary inoculation of At625 reduced all of the Fusarium toxins and stopped Ps9 from establishing. Ps9 showed priority effects in delaying and blocking the production of the fungal mycotoxins. The SOM-SM analysis visualized the competitive strengths: Fg23 ranked first, At625 second, Ps9 third. Our findings of species-specific priority effects in a natural environment and the role of the mycotoxins involved are relevant for developing biocontrol strategies.
KW - Antagonists
KW - Microbe interactions
KW - Mycotoxins
KW - Priority effect
KW - SOM-SM
PY - 2021
UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-521554
DO - https://doi.org/10.3390/microorganisms9020443
VL - 9
IS - 2
SP - 443
PB - MDPI
AN - OPUS4-52155
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hodoroaba, Vasile-Dan
A1 - Steers, E.B.M.
A1 - Hoffmann, V.
A1 - Unger, Wolfgang
A1 - Paatsch, Wolfgang
A1 - Wetzig, K.
T1 - Influence of hydrogen on the analytical figures of merit of glow discharge optical emission spectroscopy - friend or foe?
PY - 2003
DO - https://doi.org/10.1039/b305384a
SN - 0267-9477
SN - 1364-5544
VL - 18
SP - 521
EP - 526
PB - Royal Society of Chemistry
CY - London
AN - OPUS4-2290
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hodoroaba, Vasile-Dan
A1 - Steers, E.B.M.
A1 - Hoffmann, V.
A1 - Wetzig, K.
T1 - The effect of small quantities of hydrogen on a glow discharge in neon. Comparison with the argon case
N2 - In order to gain an insight into the numerous effects caused by the addition of hydrogen to an argon glow discharge, comparison experiments have been made with neon as carrier gas. In some cases the effects are diminished or even disappear. Using various bulk samples, such as copper, steel and titanium, sputtered in a neon glow discharge, the intensities of the analytical lines are affected by the presence of hydrogen in different ways from argon; the dependent parameter (the discharge current in this work) and the sputtering rate vary less than in argon. The crater shape and roughness are also affected and these effects are discussed qualitatively. Probably the most important spectral feature caused by hydrogen in the case of a discharge in argon is the emission of a continuous background. This does not appear in neon under similar discharge conditions and only weakly at high hydrogen concentrations. This supports the suggestion, made in previous work, that an effective quenching process of the argon metastables (11.55 and 11.72 eV) is Penning excitation of the hydrogen molecules, and subsequent decay to a repulsive state with emission of the continuum; in neon the energy match does not occur. It was found with neon, as with argon, that similar features occur as when hydrogen is introduced in different ways into the glow discharge: as a molecular gas contamination or as a constituent of the sample. Glow discharge mass spectrometry (GD-MS) experiments carried out with both argon and neon support the results obtained by optical emission spectrometry (OES) and provide further relevant information.
PY - 2001
DO - https://doi.org/10.1039/b007527m
SN - 0267-9477
SN - 1364-5544
VL - 16
SP - 43
EP - 49
PB - Royal Society of Chemistry
CY - London
AN - OPUS4-6887
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hodoroaba, Vasile-Dan
A1 - Hoffmann, V.
A1 - Wetzig, K.
A1 - Steers, E.B.M.
T1 - Investigations of the effect of hydrogen in an argon glow discharge
N2 - Clear evidence of the effects caused by hydrogen, introduced in different forms in an analytical glow discharge source (GDS) operated with argon, is presented for the different matrix elements copper, stainless steel, titanium, aluminium and silicon. When hydrogen is present even in small quantities in argon, not only are there significant changes in the emission line intensities of most elements (analyte and plasma species), but also new spectral features, such as emission bands of new compounds (hydrides of sputtered sample constituents) and a continuous background in the range ~220440 nm. Moreover, the discharge current (the dependent parameter in our experiments) decreases with increasing hydrogen concentration. Different modes of hydrogen introduction, externally in gaseous form or sputtered as a sample constituent, cause very similar effects in terms of discharge current, line intensity (of analyte and plasma gas) and emission continua, which implies similar changes in the discharge processes in the two cases. The excitation of the hydrogen continuum appears to quench the population of the argon metastables (11.55 and 11.72 eV) and, consequently, other elementary processes in the plasma in which the argon metastables take part, but to a different extent for each analyte.
PY - 2000
DO - https://doi.org/10.1039/b002367l
SN - 0267-9477
SN - 1364-5544
IS - 15
SP - 1075
EP - 1080
PB - Royal Society of Chemistry
CY - London
AN - OPUS4-964
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hodoroaba, Vasile-Dan
A1 - Hoffmann, V.
A1 - Wetzig, K.
A1 - Steers, E.B.M.
T1 - Emission spectra of copper and argon in an argon glow discharge containing small quantities of hydrogen
N2 - The influence of hydrogen contained in a sample or otherwise introduced into a glow discharge source (GDS) is here extensively experimentally presented for the case of copper as a sample by means of the addition of small quantities of molecular hydrogen (<1% relative partial pressure) to the argon carrier gas. The progressive addition of molecular hydrogen causes different intensity changes particular to the individual lines of different species such as atomic (Cu I) and ionic (Cu II) copper, and also atomic (Ar I) and ionic (Ar II) argon. Some interesting features of the emission spectrum of hydrogen such as its line, band and even continuum spectrum are observed. It was also found that the depth resolution becomes worse even at very low concentrations of hydrogen.
PY - 2000
DO - https://doi.org/10.1039/b001565m
SN - 0267-9477
SN - 1364-5544
IS - 15
SP - 951
EP - 958
PB - Royal Society of Chemistry
CY - London
AN - OPUS4-965
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Hodoroaba, Vasile-Dan
A1 - Hoffmann, V.
A1 - Steers, E.B.M.
A1 - Griepentrog, Michael
A1 - Dück, Alexander
A1 - Beck, Uwe
T1 - Round Robin exercise: Coated materials for glow discharge spectroscopy
N2 - A Round Robin (RR) exercise on selected coated materials has been carried out with the aim of finding the optimal conditions for the analysis of nitride layers with GD-OES. Such pre-normative work is necessary for the evaluation of parallel development of the production of nitride layers as certified reference materials (CRMs). Two types of samples, TiN layer and VN layer, respectively, with chemical compositions close to stoichiometry and a thickness of ~3 µm, deposited on a steel substrate, have been provided to the RR participants. Additionally, another type of sample, a (100 nm CrNi/100 nm Cu) multilayer (ML) stack deposited on silicon wafer has also been included in the RR. This sample can be used as a CRM for checking GD spectrometer conditions and it has been proved helpful in further development of GDS instrumentation and methodology. The RR exercise has been performed in the frame of the EC Thematic Network on Glow Discharge Spectroscopy for Spectrochemical Analysis (GDS-Net).
KW - Coated/Layered Reference Materials
KW - Nitrides
KW - Multilayer
KW - GDS
KW - Round Robin
PY - 2006
DO - https://doi.org/10.1039/B513426A
SN - 0267-9477
SN - 1364-5544
VL - 21
IS - 1
SP - 74
EP - 81
PB - Royal Society of Chemistry
CY - London
AN - OPUS4-11762
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -
TY - JOUR
A1 - Appelhans, Dietmar
A1 - Oertel, U.
A1 - Mazzeo, R.
A1 - Komber, H.
A1 - Hoffmann, J.
A1 - Weidner, Steffen
A1 - Brutschy, B.
A1 - Voit, B.
A1 - Ottaviani, M.F.
T1 - Dense-shell glycodendrimers: UV/Vis and electron paramagnetic resonance study of metal ion complexation
N2 - The development of dendritic metal ion carrier systems for use in a biological environment is a challenging task as the carrier system must possess multiple features (e.g. a protective shell for metal decomplexation, targeting functions, metal-intradendrimer complexes, etc.) to substitute for the function of metal proteins in processes such as copper metabolism. Thus, Cu(II) complexation by a series of poly(propyleneimine) glycodendrimers ranging up to the fifth generation that have either a dense maltose or maltotriose shell was investigated by UV/Vis spectroscopy and electron paramagnetic resonance (EPR). As a necessary step towards potential biological application, we elucidated the complexation capacity, location of the Cu(II)-dendrimer complexes and the Cu(II) coordination sphere in the dendritic environment. A generation-dependent Cu(II) complexation was found. Furthermore, analysis of the EPR spectra revealed that internal and external Cu(II) coordination and the symmetry (axial and rhombic) of the generated complexes depend on the oligosaccharide shell, dendrimer generation and the relative concentrations of Cu(II) and the dendrimers. Both axial and rhombic symmetries are generation dependent, but also distort with increasing generation number. External coordination of Cu(II) is supported by sugar groups and water molecules. Finally, a third-generation dendrimer with a maltose shell was used to explore the general complexation behaviour of the dendritic poly(propyleneimine) scaffold towards different metal ions [Cu(II), Ag(I), VO(IV), Ni(II), Eu(III) and UO2(VI)].
KW - Glycodendrimers
KW - Metal ion complexation
KW - Metal ion-intradendrimer complexes
KW - Electron paramagnetic resonance study
PY - 2010
DO - https://doi.org/10.1098/rspa.2009.0107
SN - 1364-5021
SN - 0962-8444
SN - 0080-4630
SN - 0950-1207
SN - 1471-2946
VL - 466
SP - 1489
EP - 1513
CY - London, UK
AN - OPUS4-21622
LA - eng
AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany
ER -