Efficient E-beam excitation of XeCl

Efficient laser output at 308 nm has been obtained from XeCl in an Ne/Xe/HCl mixture at a pressure of 4 atm bye-beam excitation and bye-beam controlled discharge pumping. Maximum energy extraction is 7 J/1 fore-beam excitation and 9 J/1 for thee-beam controlled discharge. Efficiencies based on total energy deposited in the gas are approximately 4 percent. Similar results were obtained with KrF in the same device, indicating that undere-beam ore-beam controlled discharge excitation, XeCl may be as efficient as KrF.     

Rapid measurement of lifetime using a ramped mos capacitor transient

A modification of the Zerbst method is presented for the measurement of generation lifetime in MOS capacitors. In the new method, the voltage applied to the gate consists of a combination of a step and a ramp instead of just a step as in the case of the Zerbst method. This results in a considerable saving in the time taken to complete the measurement, which is a significant advantage when a large number of capacitors is being probed. The new method is especially suitable for a computer-aided measurement system. Experimental results using this method are presented and compared with the theoretical predictions.     

Analysing social behaviour and message dissemination in human based delay tolerant network

Recent advances in mobile communication shows proliferation in networks formed by human carried devices known as the pocket switched network (PSN). Human beings are social animals. They tend to form groups and communities, and have repetitive mobility pattern which can be used to disseminate information in PSNs. In this paper, we give a deeper insight to the nature of community formation and how such information can be used to help opportunistic forwarding in mobile opportunistic networks. Using real world mobility traces, we first derive the adjacency list for each node and form the contact graph. Using tools from social network analysis we then determine various node properties like centrality and clustering coefficient and graph properties like average path length and modularity. Based on the derived graph properties, node encounter process and nature of message dissemination in PSNs, we propose two social based routing, known as the contact based routing and community aware two-hop routing. We compare the proposed routing techniques with generic epidemic and prophet routing and Bubble-Rap, a social based routing. Results show that the proposed algorithms is able to achieve better delivery ratio and lower delay than Bubble Rap, while reducing the high overhead ratio of epidemic and prophet routing.     

Promising fluorescent dye for solar energy conversion based on a perylene perinone

We describe the synthesis of a dye based on a perylene perinone and evaluate its potential as the functional material for use in the luminescent solar concentrator (LSC). The dye extends the absorption wavelength of LSCs using the perylene-based dye Lumogen Red 305 by more than ~50 nm, translating into the collection of potentially 25% more photons at a reasonable fluorescent quantum yield and photostability. When the new perinone is used in a two-waveguide LSC in conjunction with Red 305, the integrated edge emission of the total LSC system may be increased more than 24% when compared to the Red 305 dye alone.     

Incorporation of tin in different types of pores in SBA-15: Synthesis, characterization and catalytic activity

Mesoporous Sn-SBA-15 has been synthesized by three different methods such as conventional hydrothermal route, using cocatalyst NH₄F and in the presence of organosilane precursor. All the materials are thoroughly characterized by powder X-ray diffraction (XRD), SEM, TEM, N₂ sorption and surface area measurements, diffuse-reflectance UV–visible and FTIR spectroscopy, TG–DTA and elemental analysis through ICP. Nitrogen adsorption data, XRD patterns, and TEM observations suggests that the textural properties are retained during the isomorphous substitution of silicon by tin. ICP chemical analysis indicates that tin can be substituted in the range of Si/Sn = 69–162. UV–visible spectra of samples synthesized by the cocatalytic approach exhibit unique absorption band at 213 nm characteristics of tin atom substituted in the smaller pores (2–3 nm) located inside the walls of mesopores. Further, an additional band at 224 nm can be assigned to Sn atoms located in the distorted tetrahedral position along the primary mesopores. In contrary, only one absorption band centered at 224 nm is observed for all the samples synthesized by conventional hydrothermal as well as in the presence of organosilane precursor. ¹⁹F NMR spectra confirmed (no signal) the absence of occluded F⁻ ions in the samples made with NH₄F. Observed high catalytic activity in Baeyer–Villiger oxidation and Meerwin–Pondorf–Verly reduction under the liquid-phase conditions suggest the incorporation of a portion of tin in the smaller pores for the Sn-SBA-15 materials synthesized through cocatalyst method.     

Effect of Ti(C,N) addition on sintering behaviour and properties of binder-modified WC-10Co cemented carbide

In the present investigation the microstructure and mechanical properties of WC-10Co, WC-8.3Ti(C,N)-12Co, WC-8.3Ti(C,N)-6Co-6Ni and WC-7Ti(C,N)-2Mo₂C-6Co-6Ni cemented carbides were studied. Introduction of Ti(C,N) in WC-10Co cemented carbide imposed sintering difficulties and hot isostatic pressing was required to obtain fully dense material. The modification of the binder cobalt with nickel and molybdenum did not noticeably affect the sintered microstructure. In general the mechanical properties of Ti(C,N)-containing cemented carbides were inferior to those of WC-10Co cemented carbide.     

Theoretical investigations on some rigid-rod polymers used as high-performance materials

This review focuses on a new type of para-catenated aromatic polymer being used in the preparation of high-performance films and fibers of exceptional strength, thermal stability, and environmental resistance, including inertness to essentially all common solvents. Polymers of this type include cis and transpoly(p-phenylene benzobisoxazole) (PBO), and the cis and trans forms of the corresponding poly(p-phenylene benzobis-thiazole)(PBT). The purpose of this paper is to summarize the authors' theoretical work on the structures, conformational energies, intermolecular interactions, and electronic properties of PBO and PBT chains, including the protonated forms known to exist in strong acids. The emphasis is on how such studies provide a molecular understanding of the unusual properties and processing characteristics of this new class of materials.     

A novel and simple approach to enhance ultraviolet photosensitivity: activated-carbon-assisted growth of ZnO nanoparticles

An activated-carbon (AC) assisted route is developed to synthesize a ZnO nanoparticle network. The route involves simple addition of AC to the solution containing the zinc salt and finally removing them by burning at higher temperature to form a sponge-like porous ZnO nanoparticles. The surface area measurements show that AC-assisted ZnO nanoparticles (AC-ZnO) have a higher surface area than those synthesized without AC (B-ZnO), which is further confirmed by the field emission scanning electron microscope (FESEM) and high resolution transmission electron microscope (HRTEM) images. Ultraviolet (UV) absorbance results show that the optical quality remains almost unchanged for both types of nanoparticles. Enhanced and faster UV photosensitivity has been observed for the AC-ZnO. The change in the UV photosensing properties demonstrated here provides a new approach to synthesizing other high surface area materials for novel physical and chemical properties.     

A probability-based spectroscopic diagnostic algorithm for simultaneous discrimination of brain tumor and tumor margins from normal brain tissue

This paper reports the development of a probability-based spectroscopic diagnostic algorithm capable of simultaneously discriminating tumor core and tumor margins from normal human brain tissues. The algorithm uses a nonlinear method for feature extraction based on maximum representation and discrimination feature (MRDF) and a Bayesian method for classification based on sparse multinomial logistic regression (SMLR). Both the autofluorescence and the diffuse-reflectance spectra acquired in vivo from patients undergoing craniotomy or temporal lobectomy at the Vanderbilt University Medical Center were used to train and validate the algorithm. The classification accuracy was observed to be approximately 96%, 80%, and 97% for the tumor, tumor margin, and normal brain tissues, respectively, for the training data set and approximately 96%, 94%, and 100%, respectively, for the corresponding tissue types in an independent validation data set. The inherently multi-class nature of the algorithm facilitates a rapid and simultaneous classification of tissue spectra into various tissue categories without the need for a hierarchical multi-step binary classification scheme. Further, the probabilistic nature of the algorithm makes it possible to quantitatively assess the certainty of the classification and recheck the samples that are classified with higher relative uncertainty.