1,068 research outputs found

    Microsatellite markers: An important fingerprinting tool for characterization of crop plants

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    Microsatellites are simple sequence repeats (SSR) of 1-6 nucleotides. They appear to be ubiquitous in higher organisms, both in animal and plant genomes and involving repetitive as well as unique sequences, although the frequency of microsatellites varies between species. They are abundant, dispersed throughout the genome and show higher levels of polymorphism than do other genetic markers. These features coupled with their ease of detection have made them useful markers. Their potential for automation and their inheritance in a co-dominant manner are additional advantages when compared with other types of molecular markers. SSRs are highly polymorphic, genome specific, abundant and co-dominant, and have recently become important genetic markers in cereals including wheat and barley.Key words: Simple sequence repeat, allelic diversity, polymorphism, co-dominance, microsatellites, geneticdiversity

    Plant mitochondrial genome: “A sweet and safe home’’ for transgene

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    Transfer of transgene through pollens to related plant species is a big environmental concern. Mitochondrion is also a superb and putative aspirant for transgene containment like plastids. Having its own transcription and translation machinery, and maternal inheritance gives assurance of transgene containment with high expression level. Regulation of mtDNA is under nuclear control, mediated by nuclear encoded proteins and protein complexes. These features offer a novel way, to engineer plant mtDNA and reduce the risk of transgene escape.Keywords: mtDNA, genome, transgene, organis

    Experimental investigation of the performance of different modulation techniques under controlled FSO turbulence channel

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    This paper experimentally investigates and compares the performance of the free space optics system employing three different modulation schemes, on-off keying (OOK) with nonreturn- to-zero (NRZ) and return-to-zero (RZ) and the binary phase shift keying (BPSK) operating under the turbulent atmosphere. The received average signal is measured and used to characterize the strength of the turbulence. The experiment is performed with a temperature gradient of 4 degrees at a wind velocity of 4 m/s. The temperature gradient within the controlled channel results in turbulence of a log irradiance variance of 0.002, which is classified as a very weak turbulence. The received signal eye diagram and power histograms are presented and analyzed for performance evaluation of the selected modulation schemes in the weak turbulence model

    Compensating for source depth change and observing surface waves using underwater communication signals

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    Underwater communications impose great challenges due to the unpredictable changes in the environment. In order to accommodate for these changes, equalizers are used to track the Impulse Responses (IRs) and compensate the intersymbol interference (ISI). Source and array depth shifts are one of the major contributing factors to continuous amplitude and phase changes in IR. These changes magnify the problem of data processing in which correlation between successive received signals is involved, e.g. passive Time Reversal (pTR) where a probe signal is sent ahead of the data for post cross-correlation. In this paper, an environment based algorithm is used for pTR equalization, where an appropriate frequency shift of the estimated IR compensates for the geometric changes such as source and array depth shifts. We have applied this Frequency Shift pTR equalizer (FSpTR) on real data collected from Underwater Acoustic Barrier 2007 (UAB’07) sea trial having 1000 baud BPSK signaling at carrier frequency of 6.25 KHz with a sudden source depth change of 0.5 m at various known instants of time. The results illustrate that a considerable gain can be attained using the environment based equalizer in the presence of source and/or array depth changes. Moreover by close analysis of the FSpTR results we have detected surface wave motion through the frequency shifts caused by the array depth variations

    Arrival-based equalizer for underwater communication systems

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    One of the challenges in the present underwater acoustic communication systems is to combat the underwater channel effects which results in time and frequency spreading of the transmitted signal. The time spreading is caused by the multipath effect while the frequency spreading is due to the time variability of the underwater channel. The passive Time Reversal (pTR) equalizer has been used in underwater communications because of its time focusing property which minimizes the time spreading effect of the underwater channel. In order to compensate for the frequency spreading effect, an improved version of pTR was proposed, called Frequency shift passive time reversal (FSpTR). FSpTR tries to compensate for the frequency spreading by applying a frequency shift in the estimated channel impulse response (IR). In the multipath environment, multiple replicas of the transmitted signal reaches the receiver through different paths where each path is affected differently by environmental variations. In such cases, a single frequency shift fails to compensate for the environmental variations on each path, resulting in degradation in the performance. In this paper, an arrival-based equalizer is proposed to compensate for the environmental variations on each path. The concept of beamforming is integrated with FSpTR equalizer, in this paper, to compensate each arrival separately for the environmental variations. The proposed equalizer is tested with the real data and the results showed that the proposed approach outperforms pTR and FSpTR equalizers and provides a mean MSE gain of 4.9 dB and 4.2 dB respectively.This work is supported by Portuguese Foundation for Science Technology under PHITOM (PTDC/EEATEL/71263/2006) and COGNAT (PTDC/MAR/112446/2009) projects. This work was also supported by European Community’s Sixth Framework Program through the grant to the budget of the Integrated Infrastructure Initiative HYDRALAB III within the Transnational Access Activities, Contract no. 022441

    Malaysian Halal Standard (Ms1500:2004) : Do Halal Food Manufacturers Have Intention To Be Certified ?

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    The Malaysian government has a vision of becoming a global halal hub. In line with this MS1500:2004 Halal Standard was introduced as extension to the existing halal logo and certification. Kerajaan Malaysia mempunyai visi untuk menjadi hub halal global. Selaras dengan ini, Standard Halal MS1500:2004 diperkenalkan sebagai tambahan kepada pensijilan logo halal yang sedia ada

    Potential of vertical line array beamforming in underwater acoustic communications

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    Um dos principais tópicos atuais de pesquisa é ́ a concepçãoo de técnicas de processamento de sinal eficazes para comunicações submarinas. Este interesse é reforç ̧ado pelos desafios inerentes às condições incontroláveis, como a batimetria, a temperatura, e as variações temporais (geométricas) das profundidades da fonte e da antena de receptores. A obtenção de taxas de transmissão modestas é ainda um desafio, devido a estas variações. O presente trabalho aborda o uso potencial do formador de feixes (beamformer) no sistema de comunicações submarinas. O propósito de usar um beamformer neste trabalho é o de separar os diferentes caminhos que chegam do transmissor para o recetor, o que é motivado pelo fato de que, num ambiente real, não é possível distinguir todos os caminhos de propagação, no domínio do tempo. Neste trabalho, é usado o beamformer de atraso-e-soma, que aplica atrasos diferentes para cada hidrofone da antena vertical, e adiciona as saídas resultantes. Cada um dos atrasos é função do ângulo de chegada e da profundidade do hidrofone. O objetivo do beamformer é aplicar os atrasos opostos a cada elemento da antena vertical, para garantir a soma coerente da frente de onda numa direção particular. Ambos resultados com dados simulados e dados reais são apresentados neste trabalho, para mostrar o desempenho do beamformer. Os resultados do beamformer são comparados com os resultados da análise Doppler, para caracterizar chegadas diferentes e fazer corresponder essas chegadas às variações Doppler, mostrando que cada chegada é afetada pelas variações ambientais de uma maneira diferente, resultando numa quantidade diferente de Doppler

    Experimental study of bit error rate of free space optics communications in laboratory controlled turbulence

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    This paper reports experimental results for the performance of an free space optical (FSO) communication link employing different modulation schemes under the influence of the atmospheric scintillation. A dedicated experimental atmospheric simulation chamber has been developed where weak and medium turbulence can be generated and its effect on the FSO link is investigated. The experimental data obtained is compared to the theoretical prediction. The paper also shows that the effect on the data transmission performance depends on the position of turbulence source positioned within the chamber

    Doppler Domain Decomposition of the Underwater Acoustic Channel Response

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    Most underwater applications are very sensitive to environmental perturbations like source/receiver motion and surface variations. In real conditions, the transmitted signal reaches the receiver through different paths where each path is affected by different environmental perturbations. Due to the interaction with these environmental variations different Doppler is induced in each path. By observing the Doppler for the whole signal it is not possible to determine the contribution of each environmental variation. The main goal of this paper is to isolate different paths and analyse the effects of the environmental variations on each path in terms of the induced Doppler. A new technique called Time Windowed Doppler Spectrum is proposed which has been found very effective in tracking the Doppler due to each path separately. By using this technique it can be shown that it is possible to distinguish between surface reflected and direct path by observing the Doppler variations associated with each path. The surface induced Doppler was observed using this technique by analysing the temporal evolution of the surface reflected path. The surface variability effects the Doppler in terms of stretching and shortening the path between the transmitter and receiver. The data processed in this paper was acquired during CALCOMM'10 Experiment which took place in June 2010 at the south coast of Portugal

    Relationship of Computer Usage and Work Self-Efficacy of Employees in the Organizations

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    An individual’s perceived ability to adopt computer or information technology successfully has been shown to be major factor affecting his or her willingness to accept new technology. Hence, the relationship of self-efficacy with information system usage (computer, Internet, new information technology, etc.) is noteworthy. This research aims at studying exactly that. Four major constructs of self-efficacy presented by Albert Bandura are discussed in the paper. The literature review and the relevant researches, mentioned previously, all suggest that a relationship exists between Computer/Information System Usage and Self-efficacy, both in learning institutions and workplace environments. This study, however aims at interrogating this relationship at workplace environments of Rawalpindi/Islamabad regions of Pakistan, in particular. To conclude the results 150 questionnaires were distributed out of which we received 127 back. The participants have matriculation to doctorate qualification; however, majority had master’s degree which is sixteen years of education in Pakistan. This study and its findings are significant on another level as well. Throughout the literature review, the researches that have been quoted have all been carried out abroad. Although, there is an advent of Information Technology in Pakistan and individuals are getting to be computer savvy, little to no research can be found that has been conducted here. This may be an initial step and that too in the small cities of Rawalpindi/Islamabad; the results nonetheless are promising and can pave a way for more thorough and large scale future investigations on the matter. In conclusion, the findings can also assist in creating awareness regarding the association between computer self-efficacy and work self-efficacy amongst the population. This in turn, can help bring about a change in the opinions and attitudes of individuals thus, creating a constructive and optimistic approach toward Information System and Computer usage whereby, increasing employee productivity and performance. Keywords: Self-Efficacy, Technological Self-Efficacy, Work Self-Efficacy, Information System’s Usage, Organizations and Computer Usage
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