Design and analysis of rate aware ad hoc 802.11 networks

802.11 WLANs are characterized by high bit error rate and frequent changes in network topology. The key feature that distinguishes WLANs from wired networks is the multi-rate transmission capability, which helps to accommodate a wide range of channel conditions. This has a significant impact on higher layers such as routing and transport levels. While many WLAN products provide rate control at the hardware level to adapt to the channel conditions, some chipsets like Atheros do not have support for automatic rate control. We first present a design and implementation of an FER-based automatic rate control state machine, which utilizes the statistics available at the device driver to find the optimal rate. The results show that the proposed rate switching mechanism adapts quite fast to the channel conditions. The hop count metric used by current routing protocols has proven itself for single rate networks. But it fails to take into account other important factors in a multi-rate network environment. We propose transmission time as a better path quality metric to guide routing decisions. It incorporates the effects of contention for the channel, the air time to send the data and the asymmetry of links. In this paper, we present a new design for a multi-rate mechanism as well as a new routing metric that is responsive to the rate. We address the issues involved in using transmission time as a metric and presents a comparison of the performance of different metrics for dynamic routing.

The identification of 14 alpha,17 beta-dihydroxyandrost-4-en-3-one monohydrate and 14 alpha,17 beta-dihydroxyandrosta-1,4-dien-3-one monohydrate, metabolites of androstenedione in Mucor piriformis

The microorganism Mucor piriformis transforms androst-4-ene-3,17-dione into a major and several minor metabolites. X-ray crystallographic analysis of two of these metabolites was undertaken to determine unambiguously their composition and chirality. Crystals belong to the orthorhombic space-group P2(1)2(1)2(1), with a = 7.199(4) angstrom and a = 6.023(3) angstrom, b = 11.719(3) angstrom and b = 13.455(4) angstrom, c = 20.409(3) angstrom and c = 20.702(4) angstrom for the two title compounds, respectively. The structures have been refined to final R values of 0.060 and 0.040, respectively.

New Concepts for PVC Detection

A new scheme is proposed for the detection of premature ventricular beats, which is a vital function in rhythm monitoring of cardiac patients. A transformation based on the first difference of the digitized electrocardiogram (ECG) signal is developed for the detection and delineation of QRS complexes. The method for classifying the abnormal complexes from the normal ones is based on the concepts of minimum phase and signal length. The parameters of a linear discriminant function obtained from a training feature vector set are used to classify the complexes. Results of application of the scheme to ECG of two arrhythmia patients are presented.

A study of cubic bismuth oxides of the type bi(26-X)m(X)O(40-delta) (m=ti, mn, fe, co, ni or pb) related to gamma-bi2O3

A structural investigation of cubic oxides (space group I23) of the formula Bi(26-x)M(x)O(40-delta) (M = Ti, Mn, Fe, Co, Ni and Pb) related to the Y-Bi2O3 phase has been carried out by the Rietveld profile analysis of high-resolution X-ray powder diffraction data in order to establish the cation distributions. Compositional dependence of the cation distribution has been examined in the case of Bi26-xCoxO40-delta (1 < x < 16). The study reveals that in Bi(26-X)M(X)O(40-delta) with M = Ti, Mn, Fe, Co or Pb, the M cations tend to occupy tetrahedral (2a) sites when x < 2 while the octahedral (24f) sites are shared by the excess Co or Ni cations with Bi atoms when x > 2. Also experimental magnetic moments of Mn, Co and Ni derivatives have been used to establish the valence state and distribution of these cations.

Integrated optics � technology and applications

The emergence of optoelectronics and photonics as viable alternatives to electronics in many key areas of engineering relevance is indeed significant. This paper presents a tutorial review of integrated optics � a technologically important development in photonics. Materials, processes, device technology and applications are highlighted.

Analytical Study of Low-Field Diffusive Transport in Highly Asymmetric Bilayer Graphene Nanoribbon

We present a simplified theory of carrier backscattering coefficient in a twofold degenerate asymmetric bilayer graphene nanoribbon (BGN) under the application of a low static electric field. We show that for a highly asymmetric BGN(Delta = gamma), the density of states in the lower subband increases more that of the upper, in which Delta and gamma are the gap and the interlayer coupling constant, respectively. We also demonstrate that under the acoustic phonon scattering regime, the formation of two distinct sets of energy subbands signatures a quantized transmission coefficient as a function of ribbon width and provides an extremely low carrier reflection coefficient for a better Landauer conductance even at room temperature. The well-known result for the ballistic condition has been obtained as a special case of the present analysis under certain limiting conditions which forms an indirect validation of our theoretical formalism.

Computational interrogation of cis-regulatory elements of genes that are common targets of luteotropin and luteolysin in the primate corpus luteum

The rapid recent increase in microarray-based gene expression studies in the corpus luteum (CL) utilizing macaque models gathered increasing volume of data in publically accessible microarray expression databases. Examining gene pathways in different functional states of CL may help to understand the factors that control luteal function and hence human fertility. Co-regulation of genes in microarray experiments may imply common transcriptional regulation by sequence-specific DNA-binding transcriptional factors. We have computationally analyzed the transcription factor binding sites (TFBS) in a previously reported macaque luteal microarray gene set (n = 15) that are common targets of luteotropin (luteinizing hormone (LH) and human chorionic gonadotropin (hCG)) and luteolysin (prostaglandin (PG) F-2 alpha). This in silico approach can reveal transcriptional networks that control these important genes which are representative of the interplay between luteotropic and luteolytic factors in the control of luteal function. Our computational analyses revealed 6 matrix families whose binding sites are significantly over-represented in promoters of these genes. The roles of these factors are discussed, which might help to understand the transcriptional regulatory network in the control of luteal function. These factors might be promising experimental targets for investigation of human luteal insufficiency. (C) 2012 Elsevier B.V. All rights reserved.

A Bottom-Up Approach toward Fabrication of Ultrathin PbS Sheets

Two-dimensional (2D) sheets are currently in the spotlight of nanotechnology owing to high-performance device fabrication possibilities. Building a free-standing quantum sheet with controlled morphology is challenging when large planar geometry and ultranarrow thickness are simultaneously concerned. Coalescence of nanowires into large single-crystalline sheet is a promising approach leading to large, molecularly thick 2D sheets with controlled planar morphology. Here we report on a bottom-up approach to fabricate high-quality ultrathin 2D single crystalline sheets with well-defined rectangular morphology via collective coalescence of PbS nanowires. The ultrathin sheets are strictly rectangular with 1.8 nm thickness, 200-250 nm width, and 3-20 mu m length. The sheets show high electrical conductivity at room and cryogenic temperatures upon device fabrication. Density functional theory (DFT) calculations reveal that a single row of delocalized orbitals of a nanowire is gradually converted into several parallel conduction channels upon sheet formation, which enable superior in-plane carrier conduction.

Structural, EPR, optical and magnetic properties of alpha-Fe2O3 nanoparticles

alpha-Fe2O3 nanoparticles were synthesized by a low temperature solution combustion method. The structural, magnetic and luminescence properties were studied. Powder X-ray diffraction (PXRD) pattern of alpha-Fe2O3 exhibits pure rhombohedral structure. SEM micrographs reveal the dumbbell shaped particles. The EPR spectrum shows an intense resonance signal at g approximate to 5.61 corresponding to isolated Fe3+ ions situated in axially distorted sites, whereas the g approximate to 2.30 is due to Fe3+ ions coupled by exchange interaction. Raman studies show A(1g) (225 cm(-1)) and E-g (293 and 409 cm(-1)) phonon modes. The absorption at 300 nm results from the ligand to metal charge transfer transitions whereas the 540 nm peak is mainly due to the (6)A(1) + (6)A(1) —> T-4(1)(4G) + T-4(1)(4G) excitation of an Fe3+-Fe3+ pair. A prominent TL glow peak was observed at 140 C at heating rate of 5 degrees C s(-1). The trapping parameters namely activation energy (E), frequency factor (s) and order of kinetics (b) were evaluated and discussed. (C) 2012 Elsevier B.V. All rights reserved.

Substrate impact on the growth of InN nanostructures by droplet epitaxy

The substrate effect on InN nanostructures grown by droplet epitaxy has been studied. InN nanostructures were fabricated on Si(111), silicon nitride/Si(111), AlN/Si(111) and Ge(100) substrates by droplet epitaxy using an RF plasma nitrogen source. The morphologies of InN nanostructures were investigated by field emission scanning electron microscopy (FESEM). The chemical bonding configurations of InN nanostructures were examined by x-ray photoelectron spectroscopy (XPS). Photoluminescence spectrum slightly blue shifted compared to the bulk InN, indicating a strong Burstein-Moss effect due to the presence of high electron concentration in the InN dots.

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.

GYROSONICS: SIGNATURE ANALYSIS AND REDUCED-ORDER MODELS

In this paper, the authors study the structure of a novel binaural sound with a certain phase and amplitude modulation and the response to this excitation when it is applied to natural rewarding circuit of human brain through auditory neural pathways. This novel excitation, also referred to as gyrosonic excitation in this work, has been found to have interesting effects such as stabilization effects on the left and right hemispheric brain signaling as captured by Galvanic Skin Resistance (GSR) measurements, control of cardiac rhythms (observed from ECG signals), mitigation of psychosomatic syndrome, and mitigation of migraine pain. Experimental data collected from human subjects are presented, and these data are examined to categorize the extent of systems disorder and reinforcement reward due to the gyrosonic stimulus. A multi-path reduced-order model has been developed to analyze the GSR signals. The filtered results are indicative of complicated reinforcing reward patterns due to the gyrosonic stimulation when it is used as a control input for patients with psychosomatic and cardiac disorders.

Structural, iono and thermoluminescence properties of heavy ion (100 MeV Si7+) bombarded Zn2SiO4:Sm3+ nanophosphor

Structural, iono (IL) and thermoluminescence (TL) studies of Zn2SiO4:Sm3+ (1-5 mol%) nanophosphor bombarded with swift heavy ions in the fluence range 3.91 x 10(12)-21.48 x 10(12) cm(-2) have been carried out. The average crystallite sizes for pristine and ion irradiated for 3.91 x 10(12) ions cm(-2) and 21.48 x 10(12) ions cm(-2) were found to be 34, 26 and 20 nm. With increase of ion fluence, the intensity of XRD peaks decreases and FWHM increases. The peak broadening indicates the stress induced point/clusters defects produced due to heavy ion irradiation. IL studies were carried out for different Sm3+ concentrations in Zn2SiO4 by irradiating with ion fluence of 15.62 x 10(12) ions cm(-2). The characteristic emission peaks at similar to 562, 599, 646 and 701 nm were recorded by exciting Si7+ ions in the fluence range 3.91 x 10(12)-21.48 x 10(12) ions cm(-2). These peaks were attributed to (4)G(5/2)-> H-6(5/2) (562 nm), (4)G(5/2)-> H-6(7/2) (599 nm), (4)G(5/2)-> H-6(9/2) (646 nm), and (4)G(5/2)-> H-6(5/2) (701 nm) transitions of Sm3+. The highest emission was recorded at 3 mol% of Sm3+ doped Zn2SiO4. TL studies were carried out for 3 mol% Sm3+ concentration in the fluence range 3.91 x 10(12)-21.48 x 10(12) ions cm(-2). Two U glow peaks at 152 and 223 degrees C were recorded. The kinetic parameters (E, b, and s), were estimated using Chen's peak shape method. Simple glow curve structure (223 degrees C), highly resistive, increase in TL. intensity up to 19.53 x 10(12) ions cm(-2), simple trap distribution makes Zn2SiO4:Sm3+ (3 mol%) phosphor highly useful in radiation dosimetry.