Theory of Transmission through disordered superlattices

We derive a theory for transmission through disordered finite superlattices in which the interface roughness scattering is treated by disorder averaging. This procedure permits efficient calculation of the transmission thr ough samples with large cross-sections. These calculations can be performed utilizing either the Keldysh or the Landauer-B\"uttiker transmission formalisms, both of which yield identical equations. For energies close to the lowest miniband, we demonstrate the accuracy of the computationally efficient Wannier-function approximation. Our calculations indicate that the transmission is strongly affected by interface roughness and that information about scale and size of the imperfections can be obtained from transmission data.Comment: 12 pages, 6 Figures included into the text. Final version with minor changes. Accepted by Physical Review

Occurrence of Escherichia coli harbouring stx genes in popiah, a Malaysian street food

Irrespective of its health effects, street foods are very popular with the consumers. The main purpose of this research was to study the biosafety of Escherichia coli in popiah, a Malaysian street food sold at a roadside food stall and a restaurant in Sri Serdang, Selangor, Malaysia, using the combination of the most probable number (MPN)-Polymerase Chain Reaction (PCR) assay-plating on Eosin Methylene Blue (EMB) agar methods. Using these biomolecular methods, E. coli was detected in 12/15 (80%) and 11/15 (73%) of the collected samples from the roadside food stall and the restaurant respectively. The incidence of stx virulence-associated genes was detected in 1/15 (7%) among the E. coli isolated from samples taken from the roadside food stall while the E. coli isolated from the restaurant was 3/15 (20%). The density of E. coli ranged from 1100 MPN/g and the density of E. coli positive with stx genes was <3 to 53 MPN /g in samples from both the roadside food stall and the restaurant. The presence of the stx-positive E. coli in popiah are significant to risk assessments of food and epidemiological studies. Therefore, from the information obtained in this study, it is obvious that the screening for STEC markers in food samples would be useful for food safety survey

Epigenome-wide association of PTSD from heterogeneous cohorts with a common multi-site analysis pipeline

Compelling evidence suggests that epigenetic mechanisms such as DNA methylation play a role in stress regulation and in the etiologic basis of stress related disorders such as Post traumatic Stress Disorder (PTSD). Here we describe the purpose and methods of an international consortium that was developed to study the role of epigenetics in PTSD. Inspired by the approach used in the Psychiatric Genomics Consortium, we brought together investigators representing seven cohorts with a collective sample size of N = 1147 that included detailed information on trauma exposure, PTSD symptoms, and genome-wide DNA methylation data. The objective of this consortium is to increase the analytical sample size by pooling data and combining expertise so that DNA methylation patterns associated with PTSD can be identified. Several quality control and analytical pipelines were evaluated for their control of genomic inflation and technical artifacts with a joint analysis procedure established to derive comparable data over the cohorts for meta-analysis. We propose methods to deal with ancestry population stratification and type I error inflation and discuss the advantages and disadvantages of applying robust error estimates. To evaluate our pipeline, we report results from an epigenome-wide association study (EWAS) of age, which is a well-characterized phenotype with known epigenetic associations. Overall, while EWAS are highly complex and subject to similar challenges as genome-wide association studies (GWAS), we demonstrate that an epigenetic meta-analysis with a relatively modest sample size can be well-powered to identify epigenetic associations. Our pipeline can be used as a framework for consortium efforts for EWAS

Epigenome-wide meta-analysis of PTSD across 10 military and civilian cohorts identifies methylation changes in AHRR

Epigenetic differences may help to distinguish between PTSD cases and trauma-exposed controls. Here, we describe the results of the largest DNA methylation meta-analysis of PTSD to date. Ten cohorts, military and civilian, contribute blood-derived DNA methylation data from 1,896 PTSD cases and trauma-exposed controls. Four CpG sites within the aryl-hydrocarbon receptor repressor (AHRR) associate with PTSD after adjustment for multiple comparisons, with lower DNA methylation in PTSD cases relative to controls. Although AHRR methylation is known to associate with smoking, the AHRR association with PTSD is most pronounced in non-smokers, suggesting the result was independent of smoking status. Evaluation of metabolomics data reveals that AHRR methylation associated with kynurenine levels, which are lower among subjects with PTSD. This study supports epigenetic differences in those with PTSD and suggests a role for decreased kynurenine as a contributor to immune dysregulation in PTSD. PTSD has been associated with DNA methylation of specific loci in the genome, but studies have been limited by small sample sizes. Here, the authors perform a meta-analysis of DNA methylation data from 10 different cohorts and identify CpGs in AHRR that are associated with PTSD.Stress-related psychiatric disorders across the life spa

21. Yüzyılda Kayseri Kentsel Gelişme Stratejileri

In this contribution the performance of adaptive modulation - applied in conjunction with a Decision Feedback Equalizer (DFE) - is characterized in a co-channel interference impaired environment over a slowly varying wideband multi-path Rayleigh fading channel. Specifically, Joint Detection (JD) techniques in conjunction with convolutional coding are invoked, in order to mitigate the effects of co-channel interference in a Time Division Multiple Access (TDMA) environment. Finally, the throughput of the adaptive system is compared to that of a range of fixed modulation systems in an interference-limited environment

Burst-by-Burst Adaptive Joint Detection CDMA

Adaptive Quadrature Amplitude Modulation (AQAM) is combined with Joint Detection Code Division Multiple Access (JD-CDMA) in order to increase the throughput of a communications system, while maintaining a target BER. The QAM modes are adaptively switched, by estimating the Signal to Interference plus Noise Ratio (SINR) at the output of the joint detection receiver. For an eight-user AQAM/JD-CDMA scheme, a BPS performance of about 3.5 bits/symbol is achieved at an average SNR of about 18 dB, with a BER of approximately 0.02%, when using three different modulation modes, namely BPSK, 4-QAM and 16-QAM