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ABSTRACT: Tuberculosis (TB) is the frequent major opportunistic infection in HIV-infected patients, and is the leading cause of mortality among HIV-infected patients. Genetic susceptibility to TB in HIV negative subjects is well documented. Since coinfections can influence the way in which immune system respond to different pathogens, genetic susceptibility to TB in HIV patients might also change. Studies from India and other parts of the world have shown that genetic susceptibility to TB is influenced by HIV infection. In the present review, we emphasize the role of genetic factors in determining susceptibility to HIV infection, disease progression and development of TB in HIV-infected patients. Polymorphisms in human leukocyte antigen (HLA), MBL2, CD209, vitamin D receptor, cytokine, chemokine and chemokine receptor genes have been shown to be associated with development of TB in HIV patients. However, the results are inconclusive and larger well-defined studies with precise clinical data are required to validate these associations. Apart from candidate gene approach, genome-wide association studies are also needed to unravel the unknown or to establish the previously reported genetic associations with HIV associated TB. Despite the preliminary status of the reported associations, it is becoming clear that susceptibility to development of TB in HIV patients is influenced by both environmental and genetic components. Understanding the genetic and immunologic factors that influence susceptibility to TB in HIV patients could lead to novel insights for vaccine development as well as diagnostic advances to target treatment to those who are at risk for developing active disease.
Tuberculosis (Edinburgh, Scotland) 09/2011; 92(1):18-30. · 2.54 Impact Factor
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ABSTRACT: With the continued demand for fine features, enhanced assembly yield, and improved reliability in the microelectronic packaging industry, there is a need to reduce substrate warpage. Factors such as coefficient of thermal expansion mismatch among several materials in the packaging substrate, modulus of different materials, thickness of different layers, orientation of features in each layer, thermal and mechanical loading conditions influence the substrate warpage, and any effort to reduce substrate warpage needs to address one or more of these factors. One technique to reduce warpage will be through the viscoelastic relaxation of the dielectric material, when other factors cannot be changed for performance, processing, or cost reasons. Thus, it is important to accurately model the viscoelastic relaxation of the dielectric material, and study how the warpage can be reduced either by changing dwell times at different temperatures and/or by introducing appropriate mechanical loads in combination with thermal loads. In this paper, we present two approaches to reduce substrate warpage: 1) by modifying the temperature-time profile of the sequential processing steps, and 2) by using an external mold to reduce the substrate warpage. Based on the simulation results, it appears that significant warpage reduction is achievable through the proposed techniques.
IEEE Transactions on Components, Packaging, and Manufacturing Technology 08/2011; · 0.98 Impact Factor
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ABSTRACT: To mitigate intentional and unintentional in-band interference problems in today's navigation and communication frequency bands, spread-spectrum techniques such as direct sequence (DS) or frequency hopped (FH) systems are frequently used. <sup>1 2</sup> A key component of an FH spread-spectrum system is the frequency hop synthesizer used to generate the hop frequencies. Spreading of the communication or the navigation signals is done over a wider transmission bandwidth to lessen the impact of any intentional or unintentional interference. Typically, frequency synthesizers are driven by a secure code generator called Transec (transmission security) to avoid follow-on interference. The wideband frequency synthesizers must be designed to support wideband communication data rates and waveforms employed with adequate margin to close the link. In this paper, issues related to FH synthesizer implementation in modern survivable communications such as the required frequency step size, hop rate, hop bandwidth, phase noise, spreading process gain, and the settling time are addressed. A typical FH synthesizer implementation and the associated link analysis example is given in this paper. FH spread spectrum helps in the link closure in interference condition.
Aerospace Conference, 2011 IEEE; 04/2011
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ABSTRACT: CMOS devices are scaling down to nano ranges resulting in increased process variations and short channel effects which not only affect the reliability of the device but also performance expectations. Carbon Nanotube Field Effect Transistor (CNTFET) is a very promising and superior technology for its applications to circuit design. In this paper we intend to evaluate and compare the performance parameters of a traditional 6T SRAM cell between a predictive 16nm Complementary Metal Oxide Semiconductor (CMOS) technology and CNTFET. The model used to simulate CNT transistor is a tentative model from the researchers of Stanford University, which is not yet practically implemented. Since the dimensions of MOSFETS are reduced aggressively, it is essential to know the potential of what both the technologies have to offer, with their least dimensions available. The SRAM design uses the smallest transistors possible and is also susceptible to reliability issues and process variations, making it an ideal benchmark circuit to compare the two technologies. Our simulations results show that CNTFET based SRAM design is a viable design to choose compared to its CMOS counterpart. The results show that there is a 52.7% increase in SNM of the memory cell. Meanwhile, the cell becomes 5% faster. These results clearly justify that CNTFET is more suitable for circuit design rather than MOSFETs, although both the models under consideration are predictive models. This comparative study would definitely help us choose better technology alternatives in near future.
SOC Conference (SOCC), 2010 IEEE International; 10/2010
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ABSTRACT: In recent years, computer - aided design approach based Artificial Neural Network has been introduced to microwave modeling, simulation & optimization. In this paper, a neural network model is proposed for the design of spiral strip monopole antenna fed by a coplanar waveguide (CPW) for radio frequency identification (RFID) applications is presented. The designed antenna, which, including the FR-4 substrate, with 16.5 mm in length and 20 mm in width, can operate at the frequency of 5.8 GHz and 4.15 dBi gain, respectively. This antenna is suitable for radio frequency identification applications in the 5.8 GHz band. The fundamental parameters of the antenna such as return loss, VSWR, gain and magnitude which meets the acceptable antenna standards are obtained. Simulation tool, based on the method of moments (ZELAND IE3D version 12.0) has been used to analyze and optimize the antenna. This model is prepared using feed forward multilayer perceptron neural network back propagation Levenberg Marqurat algorithm. The neural results are compared with the results of IE3D which shows a very good agreement.
Computing Communication and Networking Technologies (ICCCNT), 2010 International Conference on; 08/2010
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ABSTRACT: This paper presents the analysis of simple, compact, CPW- fed flower shaped monopole aperture antenna with 10dB return loss (VSWR<;;2) band from 3.365 GHz to 10.235GHz except the band 4.775-5.825GHz(5GHz WLAN) for UWB applications. The antenna consists of ground plane, rectangular slot and a flower - shaped exciting stub. The flower - shaped stub is simple and has less parameter, which are convenient to optimize. The proposed antenna is designed on an inexpensive FR4-epoxy substrate with dielectric constant ϵ<sub>r</sub> =4.4 and with a size 30mm×25mm×1.5mm. The fundamental parameters of the antenna such as bandwidth, return loss, gain, radiation pattern and polarization are obtained. All meets the acceptable antenna standards. Simulation tool, based on the method of moments (ZELAND IE3D version 12.0) has been used to analyze and optimize the proposed antenna.
Computing Communication and Networking Technologies (ICCCNT), 2010 International Conference on; 08/2010
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ABSTRACT: A novel dual-band square microstrip patch antenna for bandwidth improvement and antenna size reduction in a single design is proposed. It can operate at dual frequencies of 1.7 GHz and 5.5 GHz. The fundamental parameters of the antenna such as bandwidth, return loss, gain, radiation pattern, and polarization are obtained. This square piece patch antenna has less return loss of −40 dB with bandwidth of 40 MHz and 200 MHz in two bands, respectively. The sensitivity of patch antenna towards its patch shape is also discussed. Simulation tool, based on the method of moments (ZELAND IE3D version 12.0) has been used to analyze and optimize the antenna. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1513–1516, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25270
Microwave and Optical Technology Letters 04/2010; 52(7):1513 - 1516. · 0.62 Impact Factor
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ABSTRACT: It is well known that spectral lines of the Global Positioning System (GPS) coarse acquisition (C/A) codes increase the amount of code division multiple access (CDMA) noise generated, occasionally far exceeding what is typically expected, depending on the user-satellite geometry. This degrades the available effective carrier-to-noise density ratio (C/N<sub>0</sub>)<sub>effective</sub> to a GPS receiver to a greater degree than when spectral line effects are ignored. (C/N<sub>0</sub>)<sub>effective</sub> is a key metric widely used to characterize the performance of the GPS receivers in terms of code acquisition, carrier loss of lock, and data bit error rates. Because of the short duration, limited geographical extent and a limited number of signals in the GPS frequency band that existed most analysis performed several years ago ignored the spectral line effects altogether. But in the changed signal environment with the growing number of Global Navigation Satellite Systems (GNSSs) in the Radio Navigation Satellite System (RNSS) band, there is a need to account for all the interference sources accurately to make sure that the intersystem and intrasystem Radio Frequency Compatibility (RFC) is achieved. Since C/A code is very widely used currently and will be used possibly in the foreseeable future in a number of applications, some of them of a critical nature, interference into C/A code receivers must be carefully considered. Since C/A code intrasystem interference is a significant contributor to (C/N<sub>0</sub>)<sub>effective</sub>, the focus of many studies done in the past couple of years have been on C/A code spectral line issues. A number of methods based on quasi-analytical models of the correlator output, simulation models of GPS satellite constellation and the receivers, and limited laboratory measurements were employed in earlier studies. In this paper we take a different approach to provide an upper bound on the C/A code spectral separation coefficient (CA-S-
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SC) based on the code spectral line properties. This upper bound is computationally much simpler to obtain. This bound is also applicable to other spreading codes, resulting in spread-spectrum signals with spectral line effects.
Aerospace Conference, 2010 IEEE; 04/2010
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ABSTRACT: A novel design of compact coplanar waveguide (CPW)-fed slot antenna for wireless applications is presented. It can operate in the IEEE 802.11a frequency band from 5 GHz to 5.5 GHz. The antenna is designed on a RT/duroid 5880 substrate with a permittivity 2.22 and with the size of 18.8 mm × 12.3 mm × 3.175 mm. The antenna has a 5% voltage standing wave ratio (VSWR) (2.3:1) bandwidth around 5.24 GHz. The fundamental parameters of the antenna, such as impedance, return loss, VSWR, and polarization are obtained. All meets the acceptable antenna standards. Simulation tool, based on the method of moments (ZELAND IE3D version 12.0), has been used to analyze and optimize the antenna. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1258–1261, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25210
Microwave and Optical Technology Letters 03/2010; 52(6):1258 - 1261. · 0.62 Impact Factor
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ABSTRACT: A novel compact Ultra wideband antenna fed by CPW is presented. The antenna has a size of 29 mm à 32 mm. It provides band width ranging from 2.9 GHz to 11.1 GHz. The antenna can be easily integrated with radio frequency circuit for low cost. Details of antenna are presented with parametric study. The bandwidth is varied by varying the width and height of inner tuning stub and ultra wideband with is obtained. The antenna is Omni directional in operating range and it has good radiation efficiency. The fundamental parameters return loss, VSWR, radiation pattern are obtained, which meet standard specifications. Method of moments based IE3D simulator is used to analyze antenna.
India Conference (INDICON), 2009 Annual IEEE; 01/2010
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ABSTRACT: In the recent decade, metamaterials have become one of the popular areas of interest. Some of the various structures of Split-Ring Resonators (SRR) we have come across are circular, square, spiral and omega shaped. All these structures produce effective permeability and permittivity as negative over a certain range of frequencies. In this paper, a new structure of triangular split ring resonator with edge-coupling is proposed. The structure consists of two equilateral concentric triangles made of metal with dielectric medium filled in the gaps. The advantage of this structure includes the reduction in size of the SRR and the wide range of resonant frequencies possible. The layout or the structure with the equivalent circuit and the Computer Aided Design model (CAD) design are presented. The variation of the resonant frequencies with respect to the conductor and dielectric width is also shown.
Applied Electromagnetics Conference (AEMC), 2009; 01/2010
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ABSTRACT: A novel design of spiral strip monopole antenna fed by a coplanar waveguide (CPW) for radio frequency identification (RFID) applications is presented. The designed antenna, which, including the FR-4 substrate is, only 16.5 mm in length and 20 mm in width, can operate at the frequency of 5.798 GHz and 4.15 dBi gain, respectively. This antenna is suitable for radio frequency identification applications in the 5.8 GHz band. The fundamental parameters of the antenna such as return loss, VSWR, gain and polarization which meets the acceptable antenna standards are obtained. Simulation tool, based on the method of moments (ZELAND IE3D version 12.0) has been used to analyze and optimize the antenna. These properties with compact and uniplanar structure make the antenna suitable for use as RFID tags.
Applied Electromagnetics Conference (AEMC), 2009; 01/2010
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Ioannis Roudas,
Athanasios Vgenis,
Constantinos S Petrou,
Dimitris Toumpakaris,
Jason Hurley,
Michael Sauer,
John Downie,
Yihong Mauro,
Srikanth Raghavan,
J Hurley,
M Sauer,
J Downie,
Y Mauro, S Raghavan
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ABSTRACT: Spectrally-efficient optical communications systems employ polarization division multiplexing (PDM) as a practical solution, in order to double the capacity of a fiber link. Polar-ization demultiplexing can be performed electronically, using polarization-diversity coherent optical receivers. The primary goal of this paper is the optimal design, using the maximum-likeli-hood criterion, of polarization-diversity coherent optical receivers for polarization-multiplexed optical signals, in the absence of polarization mode dispersion (PMD). It is shown that simulta-neous joint estimation of the symbols, over the two received states of polarization, yields optimal performance, in the absence of phase noise and intermediate frequency offset. In contrast, the commonly used zero-forcing polarization demultiplexer, followed by individual demodulation of the polarization-multiplexed trib-utaries, exhibits inferior performance, and becomes optimal only if the channel transfer matrix is unitary, e.g., in the absence of polarization dependent loss (PDL), and if the noise components at the polarization diversity branches have equal variances. In this special case, the zero-forcing polarization demultiplexer can be implemented by a 2 2 lattice adaptive filter, which is controlled by only two independent real parameters. These parameters can be computed recursively using the constant modulus algo-rithm (CMA). We evaluate, by simulation, the performance of the aforementioned zero-forcing polarization demultiplexer in coherent optical communication systems using PDM quadrature phase shift keying (QPSK) signals. We show that it is, by far, superior, in terms of convergence accuracy and speed, compared to conventional CMA-based polarization demultiplexers. Finally, we experimentally test the robustness of the proposed constrained CMA polarization demultiplexer to realistic imperfections of polarization-diversity coherent optical receivers. The PMD and PDL tolerance of the proposed demultiplexer can be used as a benchmark in order to compare the performance of more sophis-ticated adaptive electronic PMD/PDL equalizers.
01/2010; 28(1).
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ABSTRACT: We have shown the association of HLA-A*11 with resistance and HLA-B*40 and -DR2 with susceptibility to HIV and HIV-TB. In the present study, we performed high-resolution subtyping of HLA-A*11 and -B*40 to identify the subtype level association, using the polymerase chain reaction-based sequence-specific oligonucleotide probe method. Underrepresentation of HLA-A*1101 was observed in overall HIV [p(c) = 0.012, OR 0.42 (95% confidence interval (CI) 0.24-0.72)] and HIV(+)TB(+) [p(c) = 0.001, OR 0.18 (95% CI 0.06-0.46)] compared to healthy controls. Significantly higher frequencies of HLA-B*4006 were observed in overall HIV [p = 0.0001, p(c) = 0.004, OR 2.71 (95% CI 1.58-4.75)], HIV(+)TB(-) [p = 0.0003, p(c) = 0.008, OR 2.82 (95% CI 1.56-5.17)], and HIV(+)TB(+) [p = 0.003, p(c) = 0.086, OR 2.56 (95% CI 1.33-4.95)] compared to healthy controls. An in silico analysis of potential T cell epitopes of consensus Gag and Pol sequences of HIV-1 subtype C Indian strains revealed relatively higher number of promiscuous HLA-B40, HLA-DRB1*1501, and -DRB1*1502 (HLA-DR2)-restricted epitopes in contrast to limited numbers of promiscuous binders restricted by HLA-A*1101. The results suggest that HLA-A*1101 may be associated with protection against HIV and the development of TB in HIV patients while HLA-B*4006 may be associated with susceptibility to HIV and TB development in HIV patients. The present study also suggests that the extent of promiscuity of T cell epitopes of HIV-1 subtype C restricted by HLA alleles exerting opposing effects might differ.
AIDS research and human retroviruses 10/2009; 25(10):1023-8. · 2.18 Impact Factor
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ABSTRACT: Variability in the clinical outcome of persons exposed to and infected with HIV-1 and tuberculosis (TB) is determined by multiple factors including host genetic variations. The aim of the present study was to find out whether chemokine, chemokine receptor and DC-SIGN gene polymorphisms were associated with susceptibility or resistance to HIV and HIV-TB in south India.
CCR2 V64I (G/A), monocyte chemoattractant protein-1 (MCP-1) -2518 A/G, stromal cell derived factor-1alpha; (SDF-1alpha) 3'UTR G/A and DC-SIGN gene polymorphisms were studied by polymerase chain reaction based methods in HIV-1 infected patients without TB (n=151), with pulmonary TB (PTB) (n=81) and extrapulmonary TB (n=31), 155 PTB patients without HIV and 206 healthy controls.
The genotype frequencies of CCR2 V64I, MCP-1 -2518 and DC-SIGN polymorphisms did not differ significantly between the study groups. A significantly increased frequency of GG genotype of SDF-1alpha polymorphism was observed among HIV+PTB+ patients compared to healthy controls (P=0.009, Pc=0.027).
Our data suggest that GG genotype of SDF-1alpha 3'UTR polymorphism may be associated with susceptibility to PTB in HIV-1 infected patients. A better understanding of genetic factors that are associated with TB could help target preventive strategies to those HIV patients likely to develop tuberculosis.
The Indian journal of medical research 10/2009; 130(4):444-50. · 1.84 Impact Factor
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ABSTRACT: We have shown earlier the association of human leucocyte antigen (HLA)-A11 with resistance and HLA-B40 and -DR2 with susceptibility to HIV and HIV-TB. In the present study, we have attempted to find out the HLA-DR2 subtypes and the possible HLA-A/-B/-DRB1 haplotype combinations that are associated with susceptibility or resistance to HIV and HIV with pulmonary tuberculosis (HIV+PTB+). HLA-DR2 subtyping was carried out by polymerase chain reaction-based sequence-specific oligonucleotide probe method. Overrepresentation of HLA-DRB1*1501 in HIV-positive PTB-negative (HIV+PTB-) patients (P = 0.004, P(c) = 0.06) and -DRB1*1502 in HIV-positive PTB-positive (HIV+PTB+) patients (P = 0.019) was observed as compared to healthy controls. Haplotype analysis revealed an increased frequency of HLA-A2-DRB1*1501 haplotype in HIV+PTB- patients (P = 0.008) and HLA-A2-DRB1*1502 among HIV+PTB+ patients (P = 0.01) compared to healthy controls. The haplotypes B40-DRB1*1501 and B40-DRB1*04 were found to be moderately increased in HIV+PTB(-) and HIV+PTB+ patients (P < 0.05). The study suggests that HLA-A2-DRB1*1501 haplotype may be associated with HIV infection while HLA-A2-DRB1*1502 haplotype might be associated with susceptibility to PTB in HIV patients. Moreover, HLA-B40-DRB1*1501 and HLA-B40-DRB1*04 haplotypes may be associated with susceptibility to HIV infection and to PTB in HIV patients.
International Journal of Immunogenetics 05/2009; 36(3):129-33. · 1.29 Impact Factor
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ABSTRACT: In this paper, a new conformal mapping quasi static approximation method based on ANNs is used to calculate accurately the odd-and even-mode characteristic impedances, coupling coefficient and effective permittivities of CB-ECCPWs. ANNs have been recently recognized as a fast and flexible tool for RF and microwave modeling, analysis and design. ANN models are developed from measured or simulated microwave data training process. Resulting ANN models are used in place of CPU-intensive theoretical for fast accurate microwave design, analysis and optimization. The ANN employed in this paper is the MLPNN. Four learning algorithms BR, LM, QN and SCG are used to train the MLPNNs. These learning algorithms are employed to obtain better performance and faster convergence with simpler structure.
Microwave Conference, 2008. APMC 2008. Asia-Pacific; 01/2009
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ABSTRACT: In this paper the analysis and design of compact CPW-fed slot antenna that operates in the IEEE 802.11a frequency band from 5.15 GHz to 5.35 GHz for wireless applications through a single grounded coplanar waveguide port for achieving sectorized radiation pattern is presented. The antenna is designed on a RT/duroid 5880 substrate with a permittivity 2.22 and with the size of 18.8 mm times 12.3 mm times 3.175 mm. The antenna has a 5 % VSWR (2.3:1) bandwidth around 5.24 GHz. The fundamental parameters of the antenna such as impedance, return loss, VSWR and polarization are obtained. All meets the acceptable antenna standards. Simulation tool, based on the method of moments (ZELAND IE3D version 12.0) has been used to analyze and optimize the antenna.
Recent Advances in Microwave Theory and Applications, 2008. MICROWAVE 2008. International Conference on; 12/2008
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ABSTRACT: We investigate transmitter and receiver imperfections in coherent QPSK systems, and how their impact can be mitigated using DSP algorithms. Quadrature imbalance was found to be a particularly significant effect that will require compensation.
IEEE Lasers and Electro-Optics Society, 2008. LEOS 2008. 21st Annual Meeting of the; 12/2008
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ABSTRACT: Vitamin D receptor (VDR) genotypes have been shown to be associated with differential susceptibility or resistance to tuberculosis. The influence of FokI, BsmI, ApaI and TaqI variants of VDR gene on 1, 25(OH)(2) D(3) modulated granzyme A expression of cytotoxic lymphocytes induced by culture filtrate antigen (CFA) of Mycobacterium tuberculosis was studied in 40 pulmonary tuberculosis (PTB) patients and 49 normal healthy subjects (NHS) by flow cytometry. In both the study groups, addition of 1, 25(OH)(2) D(3) (10(-7)M) significantly reduced the percentage of granzyme A positive cells in both unstimulated (NHS, p<0.0001; PTB, p=0.02) and stimulated culture conditions (CFA, NHS, p<0.0001; PTB, p=0.0001) which correlated positively with the IFN-gamma levels (unstimulated, p=0.01; CFA stimulated, p=0.004) in NHS. The ApaI aa genotype and bbaaTT extended genotype were associated with a significantly decreased percentage of granzyme A positive cells in NHS (p<0.05). Our results suggest that 1, 25(OH)(2) D(3) suppresses granzyme A probably by down-regulating Th1 cytokine response. Moreover, the VDR gene variants might regulate cytotoxic T-cell response via 1, 25(OH)(2) D(3) mediated suppression of granzyme A expression in tuberculosis.
Experimental and Molecular Pathology 10/2008; 86(1):69-73. · 2.42 Impact Factor
