Refine
Year of publication
Document Type
- Article (848) (remove)
Has Fulltext
- no (848) (remove)
Is part of the Bibliography
- yes (848)
Keywords
- cybersecurity (9)
- Shodan (7)
- Censys (6)
- Maltego (6)
- OSINT (6)
- Internet of Things (4)
- IoT (4)
- security (4)
- smart home (4)
- Computational complexity (3)
Institute
Live music is often linked to elaborate light shows, particularly at large outdoor music festivals. However, artificial light at night is one form of environmental pollution, light pollution, and because outdoor festivals emit a substantial amount of artificial light into the environment, they are a potential source of light pollution. So far, no studies that quantified the impact of such festivals on urban light pollution and skyglow exist. Here, the light pollution produced by a major rock festival (Lollapalooza Berlin 2016 with 70,000 visitors per day in an urban park) was investigated with ground-based radiometry and night-time light data. A small night-sky radiometer installed near the main stages and a calibrated digital camera from a nearby observation spot inside of the park were used to quantify changes in night sky brightness and direct light emissions within the park. The impact of the music festival on the urban skyglow was indeed measurable. Zenith luminance increased locally by up to a factor of 8 and illuminance increased by about 50% at the observation spot within the park. The radiance detected by night-time satellite was also increased during the festival. This is the first time, that light pollution from such a major rock music event was quantified.
Light pollution has increased globally, with 80% of the total population now living under light-polluted skies. In this Review, we elucidate the scope and importance of light pollution and discuss techniques to monitor it. In urban areas, light emissions from sources such as street lights lead to a zenith radiance 40 times larger than that of an unpolluted night sky. Non-urban areas account for over 50% of the total night-time light observed by satellites, with contributions from sources such as transportation networks and resource extraction. Artificial light can disturb the migratory and reproductive behaviours of animals even at the low illuminances from diffuse skyglow. Additionally, lighting (indoor and outdoor) accounts for 20% of global electricity consumption and 6% of CO2 emissions, leading to indirect environmental impacts and a financial cost. However, existing monitoring techniques can only perform a limited number of measurements throughout the night and lack spectral and spatial resolution. Therefore, satellites with improved spectral and spatial resolution are needed to enable time series analysis of light pollution trends throughout the night.
Artificial light at night originating from bridge illumination can cause polarised light pollution when it is reflected at water body surfaces. This alters the optical conditions of a river at night and potentially interferes with natural polarisation signals from, for example, moonlight. Therefore, this type of light pollution could detrimentally change the behaviour of organisms sensitive to polarised light, a navigational cue and signal known to be used e.g. by flying water-seeking insects to detect suitable aquatic habitats to reproduce and lay eggs. So far, polarised light pollution from artificial light at night is understudied. Here, we quantify polarised light pollution at the water’s surface near seven illuminated bridges crossing the river Spree in Berlin. Our measurements show for the first time, that nocturnal bridge illumination induces polarised light pollution towards potential flying paths of polarotactic aquatic insects. On average, around 9% of the water surfaces at the investigated bridges were highly polluted by polarised light, with values ranging between 3 and 12 % for each bridge. Thus, polarised light pollution from artificial light at night is an emergent pollutant for aquatic systems. Future work on this topic should include more comprehensive measurements, further ecological studies on its impacts and the development of sustainable lighting solutions that can contribute to the protection of riverine nightscapes.
Coarsening of Quasi Two-Dimensional Emulsions Formed by Islands in Free-Standing Smectic Films
(2024)
We study the coarsening behavior of assemblies of islands on smectic A freely suspended films in ISS microgravity experiments. The islands can be regarded as liquid inclusions in a two-dimensional fluid in analogy to liquid droplets of the discontinuous phase of an emulsion. The coarsening is effectuated by two processes, predominantly by island coalescence, but to some extend also by Ostwald ripening, whereby large islands grow at the expense of surrounding smaller ones. A peculiarity of this system is that the continuous and the discontinuous phases consist of the same material. We determine the dynamics, analyze the self-similar aging of the island size distribution and discuss characteristic exponents of the mean island growth.
Smectic islands on a thin freely suspended smectic film form a quasi two-dimensional emulsion, without a liquid subphase. We describe the coarsening dynamics that involves island coalescence and Ostwald ripening.
Finding an optimal balance between risk and returns in investment portfolios is a central challenge in quantitative finance, often addressed through Markowitz portfolio theory (MPT). While traditional portfolio optimization is carried out in a continuous fashion, as if stocks could be bought in fractional increments, practical implementations often resort to approximations, as fractional stocks are typically not tradeable. While these approximations are effective for large investment budgets, they deteriorate as budgets decrease. To alleviate this issue, a discrete Markowitz portfolio theory (DMPT) with finite budgets and integer stock weights can be formulated, but results in a non-polynomial (NP)-hard problem. Recent progress in quantum processing units (QPUs), including quantum annealers, makes solving DMPT problems feasible. Our study explores portfolio optimization on quantum annealers, establishing a mapping between continuous and discrete Markowitz portfolio theories. We find that correctly normalized discrete portfolios converge to continuous solutions as budgets increase. Our DMPT implementation provides efficient frontier solutions, outperforming traditional rounding methods, even for moderate budgets. Responding to the demand for environmentally and socially responsible investments, we enhance our discrete portfolio optimization with ESG (environmental, social, governance) ratings for EURO STOXX 50 index stocks. We introduce a utility function incorporating ESG ratings to balance risk, return and ESG friendliness, and discuss implications for ESG-aware investors.
Deutsche Telekom, one of the world's leading integrated telecommunications companies, has recently shifted its focus in event marketing to prioritize more personal co-creational communication on regional occasions, rather than largescale events. This paper outlines the three-part LAW-principle that Deutsche Telekom follows in its brand communication in Germany, providing examples for each of the three pillars. The co-creation resulting from brand communication is changing the role of marketing and brand practitioners. They are now required to negotiate with various stakeholders.
The energy transfer between bouncing particles and rigid boundaries during impacts is crucially influenced not only by restitution coefficients of the material but also by particle shapes. This is particularly important when such particles are mechanically agitated with vibrating plates. Inertial measurement units are able to measure all acceleration and rotational velocity components of an object and store these data for subsequent analysis. We employ them to measure the dynamics of cubes and icosahedra on vibrating plates to study the efficiency of energy transfer into the individual degrees of freedom (DOFs) of the excited object. The rotational DOFs turn out to be much less excited than the vertical translational motion. Most remarkably, there is only little difference between the two Platonic solids in both the absolute energies and the energy partition ratios.
1. Introduction
(2023)
The problem of increasing the efficiency of existing photodetectors and creating their new types attracts much research attention. Among new photodetector types are photosensitive structures based on cascade concentrators, whose operational principle involves the absorption of optical radiation followed by its reemission at a longer wavelength and radiation concentration onto a highly efficient small-area photodetector. The absorption and re-emission spectra of each cascade layer depend on the characteristics of the material used. Сolloidal quantum dots are among the most promising materials for cascade layers due to their manufacturing technology, which provides for accurate control over the photoluminescence maximum position. It seems highly relevant to develop and to study photosensitive structures with cascade concentrators of various shapes based on CdS, CdSe/ZnS, and PbS colloidal quantum dots. Aim . To develop photosensitive structures with a wide-range sensitivity spectrum based on concentrators containing arrays of metal chalcogenide CQDs and to study their characteristics. Materials and methods . Cascade photosensitive structures were manufactured based on layers made of polymethyl methacrylate and layers of colloidal quantum dots embedded in a polystyrene matrix. Results . Three-layer concentrators were manufactured with different colloidal quantum dots in each concentrator layers. A 22 % increase in the output power was observed for a three-layer cascade structure based on different cascade layer materials compared to a similar structure using a single layer concentrator. Conclusion . The conducted studies showed an increase in the efficiency of photosensitive structures with a cascade concentrator based on colloidal quantum dots of various types (CdS, CdSe/ZnS, and PbS) in the cascade layers.
Illuminated bridges have become important assets to navigable aquatic systems. However, if artificial light at night (ALAN) from illuminated bridges reaches aquatic habitats, such as rivers, it can threaten the river's natural heterogeneity and alter the behavioural responses of migratory fish. Here, via a pilot study, we quantified levels of ALAN at illuminated bridges that cross a river and, propose a conceptual model to estimate its potential implications on two migrating fish species with contrasting life histories. Night-time light measurements on the river Spree in Berlin were performed continuously along a transect and in detail at seven illuminated bridges. Photometric data of the pilot study showed rapidly increased and decreased light levels at several illuminated bridges from which we derived several model illumination scenarios. These illumination scenarios and their potential effect on migrating Atlantic salmon smolts (Salmo salar) and European silver eel (Anguilla anguilla) are presented as a conceptual model, considering illuminated bridges as behavioural barriers to fish migration. ALAN's adverse effects on freshwater habitats must be better researched, understood, managed, and properly communicated to develop future sustainable lighting practices and policies that preserve riverscapes and their biodiversity.