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Small organic molecule drugs are one of the key classes, taking increasingly important roles in modern drug development strategies. With the focus on small molecule drugs, difficulties originate frequently from a pronounced lipophilic character, resulting in poor water solubility, low bioavailability and unfavored pharmacokinetics. Recently, peptide-poly(ethylene glycol) conjugates (peptide-PEG conjugates) were described as precisely tunable platforms to solubilize a broad scope of fluorescent or non-fluorescent small organic molecules [1-2]. Selection of drug hosting peptides was achieved by combinatorial means, which can further be extended by implementation of a drug release screening step.
One-bead-one-compound peptide libraries are powerful tools to select high affinity binders. However, the selection of positive hits from the peptide libraries remains tedious as it occurs by handpicking, strongly limiting the pool of investigated beads. Here we report our recent results on improving the analytical platform, using automated fluorescence scanning and MALDI-ToF-ToF MS/MS imaging to screen larger sets of beads, broadening the statistical base and unraveling more precisely suitable peptides. The screening puts special emphasis on loading capacities and drug-release of transporters by performing additional washing steps in different media (cf. Fig. 1). Peptides representing strong, medium, weak releaser were chosen for further analysis and synthesized as peptide-polymer transporters. Release was analyzed by fluorescence anisotropy and fluorescence correlation spectroscopy, due to the fluorescent characteristics of the drug.
Solubilization studies confirmed sufficient loading capacities for a potential anti-Alzheimer disease drug of three transporter molecules representing strong/weak drug releaser, reaching solubilization of up to 1:3.4 (µmol drug/µmol conjugate). Fluorescence anisotropy and fluorescence correlation spectroscopy of the drug-loaded transporter showed significant differences in drug releasing properties, confirming the screening process.
Ultrasonic monitoring, making use of the sensitivity of the coda of repeated transmission meas-urements to changes in stress, temperature, moisture, as well as localized or distributed damage, has gotten at-tention in structural health monitoring (SHM) research recently. Analysis methods such as coda wave inter-ferometry (CWI), including its nonlinear extension, have been shown to be able to measure ultrasonic wave velocity changes with a 1∙10-5 resolution, while indicators such as cross-correlation or cross-coherence have been used to distinguish between reversible and irreversible changes. Several small- and large-scale laboratory experiments have demonstrated that stress changes in structures can be captured or damage detected in a very early stage. The use of this technique for pre-warning before failure are currently under investigation, as well as detailed research on the physical causes and the connection between ultrasonic wave properties and materi-al/structural behavior. Recently, several of large-scale laboratory and real structures have been instrumented with embedded ultrasonic transducers to gather experience and evidence on how to use this technology in re-al-world applications. Preliminary results from installations on a new bridge, an existing bridge, a tunnel, a la-boratory earthquake test as well as a historic stadium in Germany, Poland, and the United States, respectively, are presented. Environmental influences (mainly temperature) and validation by load tests are discussed.
Ultrasonic monitoring, making use of the sensitivity of the coda of repeated transmission meas-urements to changes in stress, temperature, moisture, as well as localized or distributed damage, has gotten at-tention in structural health monitoring (SHM) research recently. Analysis methods such as coda wave inter-ferometry (CWI), including its nonlinear extension, have been shown to be able to measure ultrasonic wave velocity changes with a 1∙10-5 resolution, while indicators such as cross-correlation or cross-coherence have been used to distinguish between reversible and irreversible changes. Several small- and large-scale laboratory experiments have demonstrated that stress changes in structures can be captured or damage detected in a very early stage. The use of this technique for pre-warning before failure are currently under investigation, as well as detailed research on the physical causes and the connection between ultrasonic wave properties and materi-al/structural behavior. Recently, several of large-scale laboratory and real structures have been instrumented with embedded ultrasonic transducers to gather experience and evidence on how to use this technology in re-al-world applications. Preliminary results from installations on a new bridge, an existing bridge, a tunnel, a la-boratory earthquake test as well as a historic stadium in Germany, Poland, and the United States, respectively, are presented. Environmental influences (mainly temperature) and validation by load tests are discussed.
In the framework of non-destructive-testing advanced seismic imaging techniques have been applied to ultrasonic echo data in order to examine the integrity of an engineered test-barrier designed to be used for sealing an underground nuclear waste disposal site. Synthetic data as well as real multi-receiver ultrasonic data acquired at the test site were processed and imaged using Kirchhoff prestack depth migration reverse time migration (RTM). In general, both methods provide a good Image quality as demonstrated by various case studies, however deeper parts within the test barrier containing inclined reflectors were reconstructed more accurately by RTM. In particular, the image quality of a specific target reflector at a depth of 8 m in the test-barrier has been significantly improved compared to previous investigations using synthetic aperture Focusing technique, which justifies the considerable computing time of this method.
Ultrasonic transmission measurements are used to monitor concrete elements mostly on a laboratory scale since decades.
Recently, coda wave interferometry, a technique adapted from seismology, has been introduced to civil Engineering experiments. It can be used to reveal subtle changes in concrete samples and even large construction elements without having a transducer directly at the location where the change is taking place. The methodology works best with embedded transducers to avoid coupling issues or excessive environmental influence. These transducers can be used for newly built and existing structures. Recently, large concrete beams have been equipped with a network of transducers and loaded until failure. Using code wave interferometry, it was possible to visualize stress fields and damaged areas.
Previous work has shown that ultrasonic monitoring using externally applied or embedded transducers and imaging methods based on coda wave interferometry are able to detect subtle changes in concrete elements. In this study, a limited number of embedded transducers has been used to monitor changes in several 12 m long two-span concrete beams subjected to point or linear loads until failure.
The ultrasonic results showed the high sensitivity to stress changes and the nonlinear character of the associated effects. However, the ultrasonic features showed a very good correlation to several conventional monitoring parameters. For higher loads (significant amount of cracking), the technique had to be modified to cope with large wave velocity variations and high decorrelation compared to the reference signal.
Using a very simple imaging procedure, the 2D stress field inside the beam has been visualized including inhomogeneities and artifact at places where cracking occurred at higher loads. The technique has the potential to be included in real time monitoring systems.
Ultrasonic coda wave interferometry can detect small changes in scattering materials like concrete. We embedded ultrasonic transducers in the Gänstorbrücke Ulm, a monitored road bridge in Germany, to test the methodology. Since fall 2020, we've been monitoring parts of the bridge and comparing the results to commercial monitoring systems. We calculate signal and volumetric velocity changes using coda waves, and long-term measurements show that the influence of temperature on strains and ultrasound velocity changes can be monitored. Velocity change maps indicate that different parts of the bridge react differently to environmental temperature changes, revealing local material property differences. A load experiment with trucks allows calibration to improve detectability of possibly damaging events. Our work focuses on measurement reliability, potential use of and distinction from temperature effects, combination with complementary sensing systems, and converting measured values to information for damage and life cycle assessment.
Ultrasonic coda wave interferometry can detect small changes in scattering materials like concrete. We embedded ultrasonic transducers in the Gänstorbrücke Ulm, a monitored road bridge in Germany, to test the methodology. Since fall 2020, we've been monitoring parts of the bridge and comparing the results to commercial monitoring systems. We calculate signal and volumetric velocity changes using coda waves, and long-term measurements show that the influence of temperature on strains and ultrasound velocity changes can be monitored. Velocity change maps indicate that different parts of the bridge react differently to environmental temperature changes, revealing local material property differences. A load experiment with trucks allows calibration to improve detectability of possibly damaging events. Our work focuses on measurement reliability, potential use of and distinction from temperature effects, combination with complementary sensing systems, and converting measured values to information for damage and life cycle assessment.
Ultrasonic transmission measurements are used to monitor concrete elements mostly on a laboratory scale since decades. Recently, coda wave interferometry, a technique adapted from seismology, has been introduced to civil engineering experiments. It can be used to reveal subtle changes in concrete samples and even large construction elements without having a transducer directly at the location where the change is taking place. The methodology works best with embedded transducers to avoid coupling issues or excessive environmental influence. These transducers can be used for newly built and existing structures. Recently, large concrete beams have been equipped with a network of transducers and loaded until failure. Using code wave interferometry, it was possible to visualize stress fields and damaged areas. This paper gives an overview of the state of the art, recent results achieved at BAM and a task list for further results and development.
Ultrasonic transmission measurements are used to monitor concrete elements mostly on a laboratory scale since decades. Recently, coda wave interferometry, a technique adapted from seismology, has been introduced to civil engineering experiments. It can be used to reveal subtle changes in concrete samples and even large construction elements without having a transducer directly at the location where the change is taking place. The methodology works best with embedded transducers to avoid coupling issues or excessive environmental influence. These transducers can be used for newly built and existing structures. Recently, large concrete beams have been equipped with a network of transducers and loaded until failure. Using code wave interferometry, it was possible to visualize stress fields and damaged areas. This paper gives an overview of the state of the art, recent results achieved at BAM and a task list for further results and development.
For more than 60 years ultrasonic rail inspection is used as non-destructive testing method to ensure the safe operation of rail tracks. Constantly increasing traffic density and heavy loads have been the motor for the development of new test equipment from handheld devices to rail inspection trains. (Krull 2003)Up to the present most of the system solutions feature conventional ultrasonic transducers housed in wheel-type and slide-type probes. Different tasks have to be carried out during an in-service inspection for flaws in the rail head, rail web and rail foot as well as rolling contact fatigue (Heckel 2018). The more tasks the inspection system has to perform, the more probes are needed. Compared against standard ultrasonic testing methods the application of array probes offers advantages and flexibility by the electronic steering possibilities to control the transmitted and received sound fields. This allows to increase functionality by software while decreasing the number of probes needed in hardware in parallel. One drawback in application of phased array probes is that the repetition frequency of the subsequent measurements will be reduced by the number of virtual probe functions each phased array probe has to perform. This may limit the range of use for phased array probes in high speed applications. To overcome these limits special designs for array probes and signal processing are necessary.
For more than 60 years ultrasonic rail inspection is used as non-destructive testing method to ensure the safe operation of rail tracks. Constantly increasing traffic density and heavy loads have been the motor for the development of new test equipment from handheld devices to rail inspection trains. (Krull 2003)Up to the present most of the system solutions feature conventional ultrasonic transducers housed in wheel-type and slide-type probes. Different tasks have to be carried out during an in-service inspection for flaws in the rail head, rail web and rail foot as well as rolling contact fatigue (Heckel 2018). The more tasks the inspection system has to perform, the more probes are needed. Compared against standard ultrasonic testing methods the application of array probes offers advantages and flexibility by the electronic steering possibilities to control the transmitted and received sound fields. This allows to increase functionality by software while decreasing the number of probes needed in hardware in parallel. One drawback in application of phased array probes is that the repetition frequency of the subsequent measurements will be reduced by the number of virtual probe functions each phased array probe has to perform. This may limit the range of use for phased array probes in high speed applications. To overcome these limits special designs for array probes and signal processing are necessary.
The elemental analysis of seawater is often critical to the understanding of marinechemistry, marine geochemistry, and the deep-sea ecosystems. Laser-induced breakdownspectroscopy (LIBS) with the advantage of rapid multi-elements detection, has a greatpotential for in-situ elemental analysis of seawater. In practice, it is crucial to create acompact, low cost and power saving instrument for the long-term deep-sea observation. Arecently appeared diode-pumped solid-state (DPSS) laser seems to be a promising candidateas it is both compact and robust. Additionally, its high repetition rate up to hundreds of kHzcan provide a considerable throughput for LIBS analysis. However, the DPSS lasers operateat moderate pulse energies, usually less than one mJ, which cannot sustain stablebreakdowns in bulk water. To ensure stable laser-induced plasmas underwater with such aμJ-DPSS laser, we introduced an ultrasound source to assist the breakdown process. Thephase interface and mass flow generated by the near-field ultrasound can greatly reduce thebreakdown threshold and enhance element-specific emissions. Meanwhile, the highrepetition-rate pulses can also improve the breakdown probability and generate uniqueemission lines originated from the water molecule. We further demonstrate that the highrepetition-rate DPSS laser combined with the Echelle spectrometer can provide effectivequantitative analysis for metal elements in bulk water.
Secondary fluorescence is an inevitable effect that has to be taken into account in any algorithm for quantitative electron probe microanalysis (EPMA) as an additional correction. Moreover, secondary fluorescence worsens spatial resolution of EPMA, as discussed once more in two recent papers. Secondary fluorescence is excited both by characteristic radiation and by the X-ray continuum. In most cases the correction is small. There are, however, cases, e.g. the determination of low heavy metal concentration in a light matrix, where the contribution of secondary fluorescence exceeds 10% of the measured X-ray line intensity.
For secondary fluorescence correction the measured X-ray line intensity has to be divided by the correction factor (1+I_flchar/I_p +I_flcont/I_p )≈(1+I_flchar/I_p )(1+I_flcont/I_p ) in order to get those intensity I_p, which is excited only by the primary electrons and enables the determination of specimen composition. I_flchar and I_flcont mean the calculated characteristic and continuums fluorescence intensities. In order to get the intensity of fluorescence radiation, the absorption of the exciting radiation in the specimen, the photoionization probability and the self-absorption of the emitted line must be calculated. This can be performed in a straightforward way. The critical quantity is the X-ray yield of the exciting atoms in case of fluorescence by characteristic radiation and the bremsstrahlung yield of the specimen in case of continuum fluorescence. In the former case it is reasonable to apply the same physical model to calculate I_flchar and I_p.
Secondary fluorescence is an inevitable effect that has to be taken into account in any algorithm for quantitative electron probe microanalysis (EPMA) as an additional correction. Moreover, secondary fluorescence worsens spatial resolution of EPMA. Secondary fluorescence is excited both by characteristic radiation and by the X-ray continuum. In most cases the correction is small. There are, however, cases, e.g. the determination of low heavy metal concentration in a light matrix, where the contribution of secondary fluorescence exceeds 10% of the measured X-ray line intensity.
For secondary fluorescence correction the measured X-ray line intensity has to be divided by the correction factor (1+I_flchar/I_p +I_flcont/I_p )≈(1+I_flchar/I_p )(1+I_flcont/I_p ) in order to get those intensity I_p, which is excited only by the primary electrons. I_flchar and I_flcont mean the calculated characteristic and continuums fluorescence intensities. In order to get the intensity of fluorescence radiation, the absorption of the exciting radiation in the specimen, the photoionization probability and the self-absorption of the emitted line must be calculated. The critical quantity is the X-ray yield of the exciting atoms in case of fluorescence by characteristic radiation and the bremsstrahlung yield of the specimen in case of continuum fluorescence. In the former case it is reasonable to apply the same physical model to calculate I_flchar and I_p.