Er-doped polycrystalline silicon for light emission at λ=1.54 µm

We deposited amorphous silicon films, implanted them with erbium/oxygen, and then recrystallized them with a series of thermal treatments. Recrystallization is necessary to remove implantation damage and optically activate Er/O complexes for light emission at 1.54 μm. Photoluminescence and glancing angle x-ray diffraction were used to characterize the polycrystalline Si:Er. Following 30-minute isochronal anneals and isothermal anneals at 575°C and 600°C, the erbium luminescence intensity was observed to increase in direct relation to the degree of recrystallization during the anneal. Hydrogen passivation of dangling bonds further increased the luminescence intensity to about one half of the intensity found in a comparable single crystal material. The optically active Er is shown to be located within the recrystallized grains, and it exhibits a de-excitation (backtransfer) mechanism similar to that of single crystal Si:Er.     

In Depth: Inscribing the Indian Landscape

When India was colonised by the British in the 18th and 19th centuries, it was systematically surveyed and delineated in map form for administrative and political purposes. Here, Anuradha Mathur and Dilip da Cunha urge a new, ‘deeper’ reading of the landscape that fully acknowledges the multiple uses and potential initiations of public spaces. Copyright © 2007 John Wiley & Sons, Ltd.     

Multi-class blind steganalysis using deep residual networks

Multimedia Tools and Applications - Camouflaged communication using a media is known as Steganography. It is different than encryption as the presence of message is also concealed in case of...     

Secure image transmission through crypto‐OFDM system using Rubik's cube algorithm over an AWGN channel

Confidentiality of information must be maintained when it is required to be transmitted over a communication channel or when it is stored in a computer for further information access. Establishing a highly reliable and secure means of wireless communication for the transfer of digital data (text, images, audio, and video) from source to destination is becoming a prime requirement in present‐day wireless communications. Security can be achieved at the network level as well as at the data level. Data‐level security is made through cryptographic techniques. This paper emphasizes data‐level security aspects in a wireless communication system for the secure transmission of images over an AWGN channel condition. Here, a crypto orthogonal frequency division multiplexing system (crypto‐OFDM system) is designed using Rubik's cube encryption algorithm scheme for secured transmission of images under the MATLAB environment. The quality of the image transmission is analyzed using peak signal to noise ratio (PSNR) and BER at different SNR conditions. The quality of the encryption algorithm was also tested with statistical metrics, which are the histogram, NPCR, UACI, entropy, correlation coefficient analysis, etc. The numerical results reveal that a DCT‐based crypto‐OFDM system with Rubik's cube algorithm show a better performance over earlier cryptosystems and also perform superior to the original/basic OFDM system. The statistical analysis tests prove that Rubik's cube algorithm is one of the most robust algorithms for security point of view and is easy to implement, as Rubik's cube algorithm makes use of natural characteristics of pixel values, which form the basis for designing the secret key .     

Energy and Velocity Based Tree Multicast Routing in Mobile Ad-Hoc Networks

Wireless Personal Communications - Nodes in ad hoc networks are mostly mobile, moving with arbitrary velocity and direction. Therefore, it is always beneficial if nodes are equipped with...     

Gelatin electrospun nanofibrous matrices for cardiac tissue engineering applications

The generation of in vitro tissue constructs using biomaterials and cardiac cells is a promising strategy for screening novel therapeutics and their effects on cardiac regeneration. Current cardiac mimetic tissue constructs are unable to stably maintain functional characteristics of cardiomyocytes for long-term cultures. The objective of our study was to fabricate and characterize nanofibrous matrices of gelatin for prolonged cultures of primary cardiomyocytes which previously has been used as copolymer or hydrogels. Gelatin nanofibrous matrices were successfully electrospun using a benign binary solvent, cross-linked without swelling and fusing and evaluated by scanning electron microscopy (SEM) and uniaxial tensile measurement. Scaffolds exhibited modulus 19.6 ± 3.6 kPa similar to native human myocardium tissue with fiber diameters of 200–600 nm and average porosity percentage of 49.9 ± 5.6. Myoblasts showed good cell adhesion and proliferation. Neonatal rat cardiomyocytes cultured on gelatin nanofibrous matrices showing synchronized contracting cardiomyocytes (beating) for 27 days were studied by video microscopy. Confocal microscopic analysis of immunofluorescence stained sections indicated the presence of cardiac specific Troponin T in long-term cultures. Semiquantitative RT-PCR analysis of 3D versus 2D cultures revealed enhanced expression of contractile protein desmin. Our studies show that the biophysical and mechanical properties of electrospun gelatin nanofibers are ideal for in vitro engineered cardiac constructs (ECC), to explore cardiac function in drug testing and tissue replacement. Together with stem cell techniques, they may be an ideal platform for prolongedin vitro studies in alternatives to animal usage for the pharmaceutical industry.     

Catalytic gasification of coal using eutectic salts: identification of eutectics

Different eutectic salt mixture catalysts for the gasification of Illinois No. 6 coal were identified and various impregnation or catalyst addition methods to improve catalyst dispersion were evaluated in this study. In addition, the effects of major process variables such as temperature, pressure, and steam/carbon ratio were investigated in a thermogravimetric analyzer (TGA) and fixed-bed bench scale reactor systems. The TGA studies showed that the eutectic catalysts increased CO₂ gasification rate significantly. The methods of catalyst preparation and addition had significant effect on the catalytic activity and coal gasification. Based on the TGA studies of several eutectic systems, the 43.5% Li₂CO₃-31.5% Na₂CO₃-25% K₂CO₃ and 39% Li₂CO₃-38.5% Na₂CO₃-22.5% Rb₂CO₃ ternary eutectics, the 29% Na₂CO₃-71% K₂CO₃ binary eutectic and the K₂CO₃ single salt catalysts were selected for the fixed-bed studies. The catalyst loading increased the gasification rate and almost complete conversion of carbon was observed when 10 wt.% of catalyst was added to the coal. Upon further increasing the catalyst amount to 20 wt.% and above, there was no significant rise in gasification rate.     

Synthesis of photocatalytic La(1-x)AxTiO3.5-δ(A=Ba,Sr, Ca) nano perovskites and their application for photocatalytic oxidation of congo red dye in aqueous solution

A-site substituted La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nano perovskites were prepared by sol-gel method and characterized using thermogravimetry/differential thermal analysis(TGA/DTA), X-ray diffraction(XRD), ultraviolet-visible(UV-Vis) spectroscopy and transmission electron microscopy(TEM). XRD analysis showed that the La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nano perovskites derived after calcination at 800 oC were in single phase with orthorhombic structure. The particle size of all nano perovskites was found to be ~20 nm. The synthesized nano perovskites were tested for the photocatalytic decomposition of an azo dye, Congo red. The sequential behavior of La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nanoperovskites for photocatalytic decomposition of congo red in aqueous solution by visible light at room temperature was studied at various time intervals and the efficiency of degradation of the nanoperovskites was compared. Among all the A-site substituted La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nano perovskites, Ba substituted compound showed the highest dye degradation.     

Optimization of chromium removal by the chromium resistant mutant of the cyanobacterium Anacystis nidulans in a continuous flow bioreactor

BACKGROUND: Chromium removal potential of the cyanobacterium Anacystis nidulans and its chromium resistant strain Cr^rI8 has been optimized. Optimized parameters include biomass load, pH, temperature and dilution rate of the bioreactor. RESULTS: Results show that chromium resistant strain has high EC₅₀ dose for chromium compared to wild strain. Chromium removal potential of both strains is strongly influenced by various factors. Optimized conditions in batch system included pH 6.5, temperature 28 °C, biomass load 150 µg protein mL^?1 for 30 µmol L^?1 Cr⁶⁺ solution. In continuous flow bioreactor at optimum pH (6.5) and temperature (28 °C) at a fixed biomass of 10 mg protein and 30 µmol L^?1 Cr⁶⁺, metal removal efficiency varied with dilution rate. For A. nidulans continuous flow bioreactor, optimum dilution rate was 0.076 h^?1 (64.6 per cent metal removal) while for Cr^rI8 it was 0.152 h^?1 (85.8 per cent metal removal). Operative time of the Cr^rI8 bioreactor was also more (85 h) compared to A. nidulans bioreactor (45 h). CONCLUSION: Under optimized conditions resistant strain Cr^rI8 removed more Cr⁶⁺ compared to A. nidulans and thus has the potential to be exploited for Cr⁶⁺ removal from industrial effluents at large scale. Copyright © 2007 Society of Chemical Industry