Surfactant free, non-aqueous method, for the deposition of ZnO nanoparticle thin films on Si(100) substrate with tunable ultraviolet (UV) emission

We report, strong ultraviolet (UV) emission from ZnO nanoparticle thin film obtained by a green synthesis, where the film is formed by the microwave irradiation of the alcohol solution of the precursor. The deposition is carried out in non-aqueous medium without the use of any surfactant, and the film formation is quick (5 min). The film is uniform comprising of mono-disperse nanoparticles having a narrow size distribution (15-22 nm), and that cover over an entire area (625 mm(2)) of the substrate. The growth rate is comparatively high (30-70 nm/min). It is possible to tune the morphology of the films and the UV emission by varying the process parameters. The growth mechanism is discussed precisely and schematic of the growth process is provided.

Deposition and characterization of pure and Cd doped SnO2 thin films by the nebulizer spray pyrolysis (NSP) technique

Pure and cadmium doped tin oxide thin films were deposited on glass substrates from aqueous solution of cadmium acetate, tin (IV) chloride and sodium hydroxide by the nebulizer spray pyrolysis (NSP) technique. X-ray diffraction reveals that all films have tetragonal crystalline structure with preferential orientation along (200) plane. On application of the Scherrer formula, it is found that the maximum size of grains is 67 nm. Scanning electron microscopy shows that the grains are of rod and spherical in shape. Energy dispersive X-ray analysis reveals the average ratio of the atomic percentage of pure and Cd doped SnO2 films. The electrical resistivity is found to be 10(2) Omega cm at higher temperature (170 degrees C) and 10(3) Omega cm at lower temperature (30 degrees C). Optical band gap energy was determined from transmittance and absorbance data obtained from UV-vis spectra. Optical studies reveal that the band gap energy decreases from 3.90 eV to 3.52 eV due to the addition of Cd as dopant with different concentrations.

Cyclic AMP-dependent protein lysine acylation in mycobacteria regulates fatty acid and propionate metabolism

Acetylation of lysine residues is a posttranslational modification that is used by both eukaryotes and prokaryotes to regulate a variety of biological processes. Here we identify multiple substrates for the cAMP-dependent protein lysine acetyltransferase from Mycobacterium tuberculosis (KATmt). We demonstrate that a catalytically important lysine residue in a number of FadD (fatty acyl CoA synthetase) enzymes is acetylated by KATmt in a cAMP-dependent manner and that acetylation inhibits the activity of FadD enzymes. A sirtuin-like enzyme can deacetylate multiple FadDs, thus completing the regulatory cycle. Using a strain deleted for the KATmt ortholog in Mycobacterium bovis Bacillus Calmette-Guerin (BCG), we show for the first time that acetylation is dependent on intracellular cAMP levels. KATmt can utilize propionyl CoA as a substrate and, therefore, plays a critical role in alleviating propionyl CoA toxicity in mycobacteria by inactivating acyl CoA synthetase (ACS). The precision by which mycobacteria can regulate the metabolism of fatty acids in a cAMP-dependent manner appears to be unparalleled in other biological organisms and is ideally suited to adapt to the complex environment that pathogenic mycobacteria experience in the host.

Cyclic nucleotide signaling in intestinal epithelia: getting to the gut of the matter

The intestine is the primary site of nutrient absorption, fluid-ion secretion, and home to trillions of symbiotic microbiota. The high turnover of the intestinal epithelia also renders it susceptible to neoplastic growth. These diverse processes are carefully regulated by an intricate signaling network. Among the myriad molecules involved in intestinal epithelial cell homeostasis are the second messengers, cyclic AMP (cAMP) and cyclic GMP (cGMP). These cyclic nucleotides are synthesized by nucleotidyl cyclases whose activities are regulated by extrinsic and intrinsic cues. Downstream effectors of cAMP and cGMP include protein kinases, cyclic nucleotide gated ion channels, and transcription factors, which modulate key processes such as ion-balance, immune response, and cell proliferation. The web of interaction involving the major signaling pathways of cAMP and cGMP in the intestinal epithelial cell, and possible cross-talk among the pathways, are highlighted in this review. Deregulation of these pathways occurs during infection by pathogens, intestinal inflammation, and cancer. Thus, an appreciation of the importance of cyclic nucleotide signaling in the intestine furthers our understanding of bowel disease, thereby aiding in the development of therapeutic approaches.

Low temperature and rapid deposition of ZnO nanorods on Si(100) substrate with tunable optical emissions

This research article describes the large scale fabrication of ZnO nanorods of various shapes on Si(100) substrate, by using metalorganic precursor of Zn in solutions with microwave as the source of energy. This is a low temperature, environmental friendly and rapid thin film deposition process, where ZnO nanorods (1-3 mu m length) were grown only in 1-5 min of microwave irradiation. All as-synthesized nanorods are of single crystalline grown along the < 0001 > crystallographic direction. The coated nanorods were found to be highly dense having a thickness of similar to 1-3 mu m over the entire area 20 mm x 20 mm of the substrate. The ZnO thin film comprising of nanorods exhibits good adhesion with the substrate. A possible mechanism for the initial nucleation and growth of ZnO is discussed. A cross over from a strong visible light emission to an enhanced UV emission is observed, when the nature of the surfactants are varied from polymeric to ionic and nonionic. The position of the chromaticity coordinates in yellow region of the color space gives an impression of white light generation from these coatings by exciting with a blue laser.

CMOS-Compatible and Scalable Deposition of Nanocrystalline Zinc Ferrite Thin Film to Improve Inductance Density of Integrated RF Inductor

Development towards the combination of miniaturization and improved functionality of RFIC has been stalled due to the lack of high-performance integrated inductors. To meet this challenge, integration of magnetic material with high permeability as well as low conductivity is a must. Ferrite films are excellent candidates for RF devices due to their low cost, high resistivity, and low eddy current losses. Unlike its bulk counterpart, nanocrystalline zinc ferrite, because of partial inversion in the spinel structure, exhibits novel magnetic properties suitable for RF applications. However, most scalable ferrite film deposition processes require either high temperature or expensive equipment or both. We report a novel low temperature (< 200 degrees C) solution-based deposition process for obtaining high quality, polycrystalline zinc ferrite thin films (ZFTF) on Si (100) and on CMOS-foundry-fabricated spiral inductor structures, rapidly, using safe solvents and precursors. An enhancement of up to 20% at 5 GHz in the inductance of a fabricated device was achieved due to the deposited ZFTF. Substantial inductance enhancement requires sufficiently thick films and our reported process is capable of depositing smooth, uniform films as thick as similar to 20 mu m just by altering the solution composition. The method is capable of depositing film conformally on a surface with complex geometry. As it requires neither a vacuum system nor any post-deposition processing, the method reported here has a low thermal budget, making it compatible with modern CMOS process flow.

Device Fabrication of insoluble donor-acceptor-donor structured molecule by pulsed laser deposition- A comparative study using different laser source

Many of the conducting polymers though having good material property are not solution processable. Hence an alternate method of fabrication of film by pulsed laser deposition, was explored in this work. PDTCPA, a donor-acceptor-donor type of polymer having absorption from 900 nm to 300 nm was deposited by both UV and IR laser to understand the effect of deposition parameters on the film quality. It was observed that the laser ablation of PDTCPA doesn't alter its chemical structure hence retaining the chemical integrity of the polymer. Microscopic studies of the ablated film shows that the IR laser ablated films were particulate in nature while UV laser ablated films are deposited as smooth continuous layer. The morphology of the film influences its electrical characteristics as current-voltage characteristic of these films shows that films deposited by UV laser are p rectifying while those by IR laser are more of resistor in nature.

Post-deposition annealing influenced structural and electrical properties of Al/TiO2/Si gate capacitors

Titanium dioxide (TiO2) thin films are deposited on unheated p-Si (100) and quartz substrates by employing DC reactive magnetron sputtering technique. The effect of post-deposition annealing in air at temperatures in the range 673-973 K on the structural, electrical, and dielectric properties of the films was investigated. The chemical composition of the TiO2 films was analyzed with X-ray photoelectron spectroscopy. The surface morphology of the films was studied by atomic force microscope. The optical band gap of the as-deposited film was 3.50 eV, and it increased to 3.55 eV with the increase in annealing temperature to 773 K. The films annealed at higher temperature of 973 K showed the optical band gap of 3.43 eV. Thin film capacitors were fabricated with the MOS configuration of Al/TiO2/p-Si. The leakage current density of the as-deposited films was 1.2 x 10(-6) A/cm(2), and it decreased to 5.9 x 10(-9) A/cm(2) with the increase in annealing temperature to 973 K. These films showed high dielectric constant value of 36. (C) 2013 Elsevier Ltd. All rights reserved.

Cyclic AMP in Mycobacteria: the second messenger comes first

Cyclic AMP (cAMP) has emerged as a pivotal molecule for signalling in all life forms. Mycobacterial genomes have been found to encode for numerous proteins that are involved in cAMP generation, degradation and utilization. Many of these proteins have domain organizations unique to mycobacteria. This review summarizes recent advances in mechanisms of cAMP synthesis and degradation, focusing on the processes by which cAMP modulates mycobacterial signalling. We explore its impact on the physiology of the organism and on the discourse between M. tuberculosis and its host.

RF plasma MOCVD of Y2O3 thin films: Effect of RF self-bias on the substrates during deposition

Yttrium oxide (Y203) thin films have been deposited by radio frequency plasma assisted metal organic chemical vapor deposition (MOCVD) process using (2,2,6,6-tetramethy1-3,5-heptanedionate) yttrium (commonly known as Y(thd)3) precursor in a plasma of argon and oxygen gases at a substrate temperature of 350 C. The films have been deposited under influence of varying RF self-bias (-50 V to 175 V) on silicon, quartz, stainless steel and tantalum substrates. The deposited coatings are characterized by glancing angle X-ray diffraction (GIXRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), spectroscopic ellipsometry and scanning electron microscopy (SEM). GIXRD and FTIR results indicate deposition of Y2 03 (BCC structure) in all cases. However, XPS results indicate nonstoichiometric cubic phase deposition on the surface of deposited films. The degree of nonstoichiometry varies with bias during deposition. Ellipsometry results indicate that the refractive index for the deposited films is varying from 1.70 to 1.83 that is typical for Y203. All films are transparent in the investigated wavelength range 300-1200 nm. SEM results indicate that the microstructure of the films is changing with applied bias. Results indicate that it is possible to deposit single phase cubic Y203 thin films at low substrate temperature by RF plasma MOCVD process. RF self-bias that decides about the energy of impinging ions on the substrates plays an important role in controlling the texture of deposited Y203 films on the substrates. Results indicate that to control the structure of films and its texture, it is important to control the bias on the substrate during deposition. The films deposited at high bias level show degradation in the crystallinity and reduction of thickness. (C) 2013 Elsevier B.V. All rights reserved.

Generalization of deviated linear cyclic pursuit

Earlier work on cyclic pursuit systems has shown that using heterogeneous gains for agents in linear cyclic pursuit, the point of convergence (rendezvous point) can be chosen arbitrarily. But there are some restrictions on this set of reachable points. The use of deviated cyclic pursuit, as discussed in this paper, expands this set of reachable points to include points which are not reachable by any known linear cyclic pursuit scheme. The limits on the deviations are determined by stability considerations. Such limits have been analytically obtained in this paper along with results on the expansion in reachable set and the latter has also been verified through simulations.

High catalytic activity of Au-PEDOT nanoflowers toward electrooxidation of glucose

Electrochemically deposited porous film of poly(3,4-ethylenedioxythiophene) (PEDOT) on carbon paper current collector is used as the substrate for electrochemical deposition of Au. PEDOT facilitates the formation of Au nanoflowers with an enhanced electrochemical active surface area, when compared with sub-micron size Au particles deposited on bare carbon paper electrode. Owing to enhanced surface area of Au nanoflowers, the Au-PEDOT/C electrode shows greater activity than Au/C electrode toward electrooxidation of glucose in 0.5 M NaOH electrolyte. Cyclic voltammetry studies show that the peak current density increases with increase in concentrations of glucose and NaOH in the electrolyte. H-1-NMR spectroscopy data indicates that sodium formate and gluconate are the primary products of electrooxidation of glucose on Au-PEDOT/C electrode. Repetitive cyclic voltametry and amperometry studies suggest that the electrochemical stability of Au-PEDOT/C electrode is higher than that of Au/C electrode. Thus, electrochemically deposited nanostructured Au on PEDOT/C is an efficient catalyst for direct glucose oxidation in alkaline media. (C) 2013 The Electrochemical Society. All rights reserved.

Elastic-plastic contact conditions for frictionally constrained bodies under cyclic tangential loading

A Frictionally constrained condition implies dependence of friction force on tangential displacement amplitude. The condition may occur due to chemical, physical, and/or mechanical interaction between the contacting surfaces. The condition, sometimes also referred to as the presliding condition or partial slip condition, is characterized under fretting. Under such conditions, various experimental studies indicate the existence of two distinguishable regions, that is, stick region and slip region. In the present study, frictionally constrained conditions are identified and the evolutions of stick-slip regions are investigated in detail. Investigations have been performed on self-mated stainless steel and chromium carbide coated surfaces mated against stainless steel, under both vacuum and ambient conditions. Contact conditions prevailing at the contact interface were identified based on the mechanical responses and were correlated with the surface damage observed. Surface degradation has been observed in the form of microcracks and material transfer. Detailed numerical analysis has also been performed in order to understand the energy dissipation and the damage mode involved in the surface or subsurface damage. It has been observed that under frictionally constrained conditions, the occurrence of annular slip features are mainly due to the junction growth, resulting from elastic-plastic deformation at the contact interface. Ratcheting has been observed as the governing damage mode under cyclic tangential loading condition.

Role of melt convection on optimization of PCM-based heat sink under cyclic heat load

In this article, we study the thermal performance of phase-change material (PCM)-based heat sinks under cyclic heat load and subjected to melt convection. Plate fin type heat sinks made of aluminum and filled with PCM are considered in this study. The heat sink is heated from the bottom. For a prescribed value of heat flux, design of such a heat sink can be optimized with respect to its geometry, with the objective of minimizing the temperature rise during heating and ensuring complete solidification of PCM at the end of the cooling period for a given cycle. For given length and base plate thickness of a heat sink, a genetic algorithm (GA)-based optimization is carried out with respect to geometrical variables such as fin thickness, fin height, and the number of fins. The thermal performance of the heat sink for a given set of parameters is evaluated using an enthalpy-based heat transfer model, which provides the necessary data for the optimization algorithm. The effect of melt convection is studied by taking two cases, one without melt convection (conduction regime) and the other with convection. The results show that melt convection alters the results of geometrical optimization.

Nitrogen deposition: how important is it for global terrestrial carbon uptake?

Global carbon budget studies indicate that the terrestrial ecosystems have remained a large sink for carbon despite widespread deforestation activities. CO2 fertilization, N deposition and re-growth of mid-latitude forests are believed to be key drivers for land carbon uptake. In this study, we assess the importance of N deposition by performing idealized near-equilibrium simulations using the Community Land Model 4.0 (CLM4). In our equilibrium simulations, only 12-17% of the deposited nitrogen is assimilated into the ecosystem and the corresponding carbon uptake can be inferred from a C : N ratio of 20 : 1. We calculate the sensitivity of the terrestrial biosphere for CO2 fertilization, climate warming and N deposition as changes in total ecosystem carbon for unit changes in global mean atmospheric CO2 concentration, global mean temperature and Tera grams of nitrogen deposition per year, respectively. Based on these sensitivities, it is estimated that about 242 PgC could have been taken up by land due to the CO2 fertilization effect and an additional 175 PgC taken up as a result of the increased N deposition since the pre-industrial period. Because of climate warming, the terrestrial ecosystem could have lost about 152 PgC during the same period. Therefore, since pre-industrial times terrestrial carbon losses due to warming may have been more or less compensated by effects of increased N deposition, whereas the effect of CO2 fertilization is approximately indicative of the current increase in terrestrial carbon stock. Our simulations also suggest that the sensitivity of carbon storage to increased N deposition decreases beyond current levels, indicating that climate warming effects on carbon storage may overwhelm N deposition effects in the future.