Epitaxial n+ layer GaAs mesa-finger interdigital surfacephotodetectors

Several varieties of interdigital surface photodetectors have been fabricated on semi-insulating GaAs using mesa-etched n⁺ epitaxial layers as the carrier collection electrodes. This structure provides a significant responsivity improvement over conventional metal-semiconductor-metal (MSM) photodiodes by eliminating the surface reflection of the metal fingers and by providing increased photoconductive gain. High-speed testing using 100-ps doubled Nd:YAG pulses gave FWHM (full width at half maximum) responses of less than 500 ps for a 4-μm finger width and spacing and showed minimal degradation from standard MSM detectors of the same surface geometry. By introducing no additional process steps, the mesa-finger detectors are also monolithically compatible with mesa-etched GaAs MESFET technology     

Crack growth in a mixed-mode loading on marble beams under three point bending

A combined theoretical and experimental study of a crack growth in a mixed-mode I–II loading is presented. A 160×40×20 mm marble beam, with an artificial crack 8 mm and 10 mm long each, was subjected to three point bending. The crack was located vertically to the beam's lower longitudinal fiber, through the whole width of the beam. The position of the crack was displaced from the center of the beam to one of the supporting points. The vertical force P, placed on the middle of the upper fiber of the beam, imposed the combination of the opening (mode I) and the sliding (mode II) modes on the crack mouth, creating the mixed-mode I–II loading case. The stress intensity factors K _I and K _II, which describe the local stress and strain field around the crack tip, were determined by a suitable finite element program. The crack growth was defined by two classical fracture criteria of LEFM; the minimum strain energy density and the maximum circumferential stress criteria. The initial crack growth angle () was calculated from both criteria and the critical load (P _c) from the minimum strain energy density (SED) criterion. These theoretical predictions were compared with some experimental results found from three marbles with different elastic constants; the Krystallina of Kavala, the Snow-white of Thassos and the White of Piges Drama. The theoretical results showed the same trend of and P _c as the experimental ones and they are in good agreement.Presented at Fourth Greek National Congress on Mechanics, 26–29 June 1995, held at Xanthi, Greece.     

An Adversarial Neuro-Tensorial Approach for Learning Disentangled Representations

International Journal of Computer Vision - Several factors contribute to the appearance of an object in a visual scene, including pose, illumination, and deformation, among others. Each factor...     

Performance vs. freshness in web database applications

In this work, we present a novel approach for the efficient materialization of dynamic web pages in e-commerce applications such as an online retail store with millions of items, hundreds of HTTP requests per second and tens of dynamic web page types. In such applications, user satisfaction, as measured in terms of response time (QoS) and content freshness (QoD), determines their success especially under heavy workload. The novelty of our materialization approach over existing ones is that, it considers the data dependencies between content fragments of a dynamic web page. We introduce two new semantic-based data freshness metrics that capture the content dependencies and propose two materialization algorithms that balance QoS and QoD. In our evaluation, we use a real-world experimental system that resembles an online bookstore and show that our approach outperforms existing QoS-QoD balancing approaches in terms of server-side response time (throughput), data freshness and scalability.     

Comparison of number of citations to full original articles versus brief reports

Most biomedical journals accept original research articles in the form of “brief reports”. We compared the citations to full papers versus brief reports in a sample of journals on Infectious Diseases, Clinical Microbiology, and Antimicrobial Agents. Brief reports were cited less often than full-size articles [regression coefficient: 10.94 (95 % CI: 5.19, 16.69)] even after adjustment for the journal’s impact factor. Our findings may influence decisions of editors and authors regarding brief reports.     

Development and Laboratory Performance Evaluation of a Personal Multipollutant Sampler for Simultaneous Measurements of Particulate and Gaseous Pollutants

A personal multipollutant sampler has been developed. This sampler can be used for measuring exposures to particulate matter and criteria gases. The system uses asingle personalsampling pump that operates at a flow rate of 5.2 l/min. The basic unit consists of two impaction-based samplers for PM_2.5 and PM₁₀ attached to a single elutriator. Two mini PM_2.5 samplers are also attached to the elutriator for organic carbon (OC), elemental carbon (EC), sulfate, and nitrate measurements. For the collection of nitrate and sulfate, the minisampler includes a miniaturized honeycomb glass denuder that is placed upstream of the filter to remove nitric acid and sulfur dioxide and to minimize artifacts. Two passive samplers can also be attached to the elutriator for measurements of gaseous copollutants such as O₃, SO₂, and NO₂. The performance of the multipollutant sampler was examined through a series of laboratory chamber tests. The results showed a good agreement between the multipollutant sampler and the reference methods. The overall sampler performance demonstrates its suitability for personal exposure assessment studies.     

Overlay networks for task allocation and coordination in large-scale networks of cooperative agents

This paper proposes a novel method for scheduling and allocating atomic and complex tasks in large-scale networks of homogeneous or heterogeneous cooperative agents. Our method encapsulates the concepts of searching, task allocation and scheduling seamlessly in a decentralized process where no accumulated or centralized knowledge or coordination is necessary. Efficient searching for agent groups that can facilitate the scheduling of tasks is accomplished through the use of a dynamic overlay structure of gateway agents and the exploitation of routing indices. The task allocation and the scheduling of complex tasks are accomplished by combining dynamic reorganization of agent groups and distributed constraint optimization methods. Experimental results display the efficiency of the proposed method.     

Peptidomimetic–functionalized carbon nanotubes with antitrypsin activity

Water-soluble functionalized carbon nanotubes (CNTs) have been prepared and further conjugated through a stable covalent bond with two peptidomimetics. The structural design of the covalently grafted peptidomimetics to the CNTs is based on their structural similarity with the metabolites of antagonist G of substance P. A variety of analytical spectroscopic methods, in combination with electron microscopy and thermal analysis, aided the structural and morphological characterization of the four newly synthesized peptidomimetic–CNT conjugates. It is demonstrated that the trypsin inhibitory effect of the peptidomimetic–CNT is enhanced as a result of the high-loading of peptidomimetics onto the skeleton of the modified water-soluble CNTs. Additionally, the peptidomimetic–functionalized CNT conjugates can be recovered and re-employed up to six biological evaluation cycles showing the same trypsin inhibitory activity. Such a nanosized system is extremely advantageous for the inhibition of inflammation or malignancy and could find potential future biological applications in the area of drug delivery systems.