Delineation of Subsea Freshwater Extension by Marine Geoelectromagnetic Soundings (SE Mediterranean Sea)

This study presents a novel application of marine geoelectromagnetic technique, in an attempt to delineate freshwater extension of the coastal sub-aquifers beneath the SE Mediterranean Sea, along central Israel. The novel marine Ex-Bz time domain electromagnetic (TDEM) geophysical method was applied, demonstrating high sensitivity to the presence of sub-seafloor electrically resistive structures up to several kilometers offshore (shallow marine environment). The study included 19 marine measurements located offshore between Ashdod in the south to Tel-Aviv in the north, where a previous onshore study detected fresh groundwater below seawater intrusion at the coast line. The offshore measurements were conducted to distances of up to 3 km from the shoreline. It was found that the lower sub-aquifer contains fresh groundwater (resistivity >10 Ω-m) to a distance of 2.8 km offshore along the 30 km strip, and is probably constrained by lateral geo-facial changes.     

Degradation and stabilization of poly(3-hexylthiophene) thin films for photovoltaic applications

Polymer-based solar cells (PSC) represent a promising technology in the field of photovoltaics, although they still suffer from poor environmental stability. Poly(3-hexylthiophene) (P3HT) is one of the most commonly employed electron-donor materials for the preparation of the photo-active layer of PSC and it is known to undergo degradation when exposed to light. In this work, the degradation of P3HT was studied by irradiating polymer films by means of simulated sunlight. The results of this study highlighted a remarkable instability of P3HT. Substantial modifications of the infrared as well as of the UV–Vis spectra of the polymer were reported and a degradation pathway was suggested, in agreement with recent literature results. In order to stabilize the structure, two additives were evaluated namely a standard Hindered Amine Light Stabilizer (HALS) and Multi-Walled Carbon Nanotubes (MWCNT). The addition of MWCNT appeared to significantly reduce the rate of degradation.     

Cleaner bioprocesses for promoting zero-emission biofuels production in Vojvodina

In this study, the policy, market conditions and food security of biomass energy sources are assessed for supplying the future needs of Vojvodina. The Autonomous Province of Vojvodina is an autonomous province in Serbia, containing about 27% of its total population according to the 2002 Census. It is located in the northern part of the country, in the Pannonia plain, in southeastern Europe. Vojvodina is an energy-deficient province. The incentives to invest human and financial resources in the research and development of cleaner bioprocesses are high, considering the benefits which might be achieved in terms of environment protection and manufacturing costs. In the near and medium tenu, the development of bioprocesses for waste recycling and resource recovery might be one of the most viable options, considering much research work has already been done. In Vojvodina, there are technological solutions that biofuels produced in a closed cycle, so that the quantity of waste reduced to a minimum. These solutions include the stillage (remainder after distillation) used for fattening cattle, and cattle excrement to produce biogas and manure as fertilizer. The energy required for the production of bioethanol is obtained combustion lignocelullose residual waste from the production of basic raw materials starch, or biogas. Ash from the burned biomass returned to soil as a source of minerals for plants and replacement of mineral fertilizer. Such a closed cycle is economical for small farms in Vojvodina.     

Size-dependent absorption and defect states in CdSe nanocrystals in various multilayer structures

GeS2-CdSe superlattices and composite films are prepared by consecutive thermal evaporation of CdSe and GeS2 in vacuum. CdSe layer thickness varies between 1 and 10 nm, while the thickness of GeS2 layers is either equal (in superlattices) to or 20 times greater (in composite films) than that of CdSe layers. Standard spectral photocurrent measurements and various constant photocurrent methods are used to study optical absorption of all samples. An overall blueshift is observed with decreasing CdSe layer thickness of superlattices. This shift is related to a size-induced increase of the optical band gap of CdSe due to one-dimensional carrier confinement in the continuous nanocrystalline CdSe layers. A number of features are observed in the absorption spectra of composite films containing CdSe nanocrystals with average radii of approximately 2.5 and approximately 3.3 nm. They are discussed in terms of three-dimensional carrier confinement and are considered a manifestation of excited electron states in CdSe nanocrystals embedded in GeS2 thin film matrix. In addition to these discrete features, the exponential dependence of the optical absorption (Urbach) edge indicates a distribution of "valence band" tail states associated with disorder. Transient photoconductivity measurements made on similarly prepared SiOx-CdSe superlattices exhibit a rapid fall in photocurrent by a power law decay over several orders of magnitude of time, which is consistent with multi-pletrapping transport via an extensive distribution of deep defects.     

Modeling Robot “Psycho-Physical” State and Reactions – A New Option in Human–Robot Communication Part 2: Modeling and Simulation

This part of the paper examines numerically the possibility of modeling robot fatigue being representative of a human psychophysical state that can be applied to robots. Temperatures of driving motors are suggested as analogs to fatigue in muscles. Simulation of robot behavior is performed on a typical human task, namely handwriting. Three phases of task execution, characteristic for humans, are observed, i.e. regular motion, reconfiguration after symptoms of fatigue, and degeneration caused by the too long, hard work.     

N-acryloyl–N′-phenylpiperazine as curing activator of unsaturated resins

N-acryloyl–N′-phenylpiperazine and three of its homopolymers of different molecular weight are tested as low toxicity redox activators in the BPO curing of unsaturated polyester resins. Gel times and other time and temperature parameters drawn from standard exothermal curves are determined with two kinds of resin, at different bath temperatures and amounts of activator. The reciprocal of gel time follows a kinetic equation with average order 0.85 with respect to the activator, and an activation energy of 19 kcal/mol. With polymeric activators it is a simple decreasing exponential function of intrinsic viscosity. Correlations are observed for other parameters relative to the second, faster step of the curing process, in general less sensitive to the mentioned variables. The crosslinked resins show mechanical properties similar to those obtainable with dimethylaniline as activator.     

The radiographic and imaging characteristics of porous tantalum implants within the human cervical spine

STUDY DESIGN: Seven cadaveric cervical spines were implanted with a porous tantalum spacer and a titanium alloy spacer, and their radiographic and imaging characteristics were evaluated. OBJECTIVE: To determine the radiographic characteristics of porous tantalum and titanium implants used as spacers in the cervical spine. SUMMARY OF BACKGROUND DATA: Anterior decompressive surgery of the disc space or the vertebral body creates a defect that frequently is repaired with autologous bone grafts to promote spinal fusion. Donor site morbidity, insufficient donor material, and additional surgical time have spurred the development of biomaterials to replace or supplement existing spinal reconstruction techniques. Although the promotion of a solid bony fusion is critical, the implanted biomaterial should be compatible with modern imaging techniques, should allow visualization of the spinal canal and neural foramina, and should permit radiographic assessment of bony ingrowth. METHODS: Cadaveric spines containing the implants were imaged with plain radiography, computerized tomography, and magnetic resonance imaging. The image distortion produced by the implants was determined qualitatively and quantitatively. RESULTS: The tantalum and titanium spacers were opaque on plain radiographic films. On computed tomographic scans, more streak artifact was associated with the tantalum implants than with the titanium. On magnetic resonance imaging, the porous tantalum implant demonstrated less artifact than did the titanium spacer on T1- and T2-weighted spin echo and on T2*-weighted gradient-echo magnetic resonance images. Overall, the tantalum implant produced less artifact on magnetic resonance imaging than did the titanium spacer and therefore allowed for better visualization of the surrounding bony and neural structures. CONCLUSION: The material properties of titanium and porous tantalum cervical interbody implants contribute to their differential appearance in different imaging methods. The titanium implant appears to image best with computed tomography, whereas the porous tantalum implant produces less artifact than does the titanium implant on several magnetic resonance imaging sequences.     

A weighted graph embedding technique and its application to automatic circuit Layout

The extension of a known technique for graph embedding is presented for the solution of a class of problems arising in computer aided circuit layout. The embedding of a weighted graphX onto another weighted graphY is studied, with concurrent minimization of a cost function whose value depends on node and are associations. The embedding process is based on a partially enumerative covering technique on a Node Correspondence Table. Two applications are described, namely the placement of electrical components on a card in printed circuit design, and the allocation of a cards in a rack for the optimal design of backboard connections. An example of this latter problem is discussed in detail. The research described in this report was carried out while the authors were visiting the Department of Electrical Engineering, New York University, and was supported by a New York State Post Doctoral Fellowship in Electrical Engineering, Number SSF (8)-23 and a National Science Foundation Senior Foreign Scientist Fellowship.