Methylenetetrahydrofolate reductase gene polymorphism in type 1 diabetes mellitus: Relationship to microvascular complications

In patients with type-I diabetes mellitus folate deficiency is associated with endothelial dysfunction. So, polymorphism in genes involved in folate metabolism may have a role in vascular disease. This study was designed to evaluate the relationship between methylenetetrahydrofolate reductase (MTHFR) gene polymorphism and microvascular complications in adolescents with type I diabetes mellitus. A total of 99 patients with disease duration of more than 5 years aged 11–18 years participated in the study. History taking, physical, neurological and fundus examinations were performed. Laboratory investigations included mean glycated hemoglobin in the last year, urinary albumin excretion, serum creatinine, nerve conduction velocity and MTHFR genotype determination. Results revealed that 54 (54.5%) of our patients had normal MTHFR genotype (C/C subgroup), 36 (36.4%) had heterozygous MTHFR gene polymorphism (C/T subgroup) and 9 (9.1%) had homozygous MTHFR gene polymorphism (T/T subgroup). No significant difference was found between the three studied groups as regards age, disease duration or glycemic control. When testing for microalbuminuria, the T/T subgroup showed a significantly higher number of patients with microalbuminuria when compared with C/C and C/T subgroups. Regarding fundus changes, the C/C subgroup showed a significantly lower number of patients with fundus changes when compared with C/T and T/T subgroups .On the other hand the T/T subgroup showed a significantly higher number of patients with fundus changes when compared with the C/T subgroup. For nerve conduction abnormalities, the T/T subgroup showed a significantly higher number of patients with nerve conduction abnormalities when compared with C/C and C/T subgroups. Multivariate forward stepwise logistic regression analysis for determination of independent risk factors that best predicts the occurrence of microalbuminuria, fundus changes and nerve conduction abnormalities revealed MTHFR gene polymorphism to be the most important variable. MTHFR gene polymorphism (T/T) subtype is an important risk factor for the development of micro-vascular complications in patients with type I diabetes mellitus.Keywords: Methylenetetrahydrofolate reductase gene polymorphism; Microvascular complications; Type 1 diabetes; Microalbuminuri

Stochastic analysis of finite population bufferless multiplexing in optical packet/burst switching systems

In this letter, we study the blocking probabilities in an asynchronous optical packet/burst switching system with full wavelength conversion. Most of the existing work use Poisson traffic models that is well-suited for an infinite population of users. In this letter, the optical packet traffic arriving at the switching system is modeled through a superposition of a finite number of identical on-off sources. We propose a block tridiagonal LU factorization algorithm to efficiently solve the two dimensional Markov chain that arises in the modeling of the switching system. Copyright © 2007 The Institute of Electronics, Information and Communication Engineers

Dimensioning Shared-per-Node Recirculating Fiber Delay Line Buffers in an Optical Packet Switch

Cataloged from PDF version of article.Optical buffering based on fiber delay lines (FDLs) has been proposed as a means for contention resolution in an optical packet switch. In this article, we propose a queuing model for feedback-type shared-per-node recirculating FDL optical buffers in asynchronous optical switching nodes. In this model, optical packets are allowed to recirculate over FDLs as long as the total number of recirculations is less than a pre-determined limit to meet signal loss requirements. Markov Modulated Poisson Process (MMPP)-based overflow traffic models and fixed-point iterations are employed to provide an approximate analysis procedure to obtain blocking probabilities as a function of various buffer parameters in the system when the packet arrival process at the optical switch is Poisson. The proposed algorithm is numerically efficient and accurate especially in a certain regime identified with relatively long and variably-sized FDLs, making it possible to dimension optical buffers in next-generation optical packet switching systems. © 2013 Elsevier B.V. All rights reserved

Maternal risk factors in young Egyptian mothers of Down syndrome

Introduction: We investigated the possible maternal risk factors that mayincrease the incidence of Down syndrome (DS) in young Egyptian mothers(younger than 35 years) especially methylene tetrahydrofolate reductase(MTHFR) enzyme C677T polymorphism.Subjects and Methods: The study included 200 mothers of karyotypicallyascertained non-disjunction DS attending Genetics clinic, Children’s hospital, Ain Shams University (100 mothers were < 35 years and 100 mothers ≥ 35 years). 50 mothers of none-DS children served as a control group. For all cases, history was taken laying stress on: Parental ages at conception, maternal grandparent’s ages at conception of mother, DS birth order, history of oral contraceptive use 6 months before conception, genital infection, vitamin supplementation and smoking or exposure to irradiation.Results: MTHFR C677T mutational analysis was done to twenty DS motherswith ages ≤ 35 years revealed that 35% of young mothers had C677T mutation (10% had homozygous mutation and 25% had heterozygous mutation). MTHFR C677T polymorphism was found to be a possible maternal genetic risk factor for DS although statistically non-significant.Other maternal risk factors included the use of oral contraceptive pills (OCP) 6 months before pregnancy which was significantly higher only in DSmothers ≥ 35 years. on the other hand, parental consanguinity, maternal grandparents’ ages, the presence of genital infection and birth order did not show a significant difference between young and old mothers of DS.Conclusion: MTHFR C677T could not be considered as a maternal risk factor in young Egyptian mothers of DS. The risk effect may depend on gene-environment interaction between the genotype and dietary intake in particular folic acid consumption which should be further studied on a larger scale population including other MTHFR polymorphisms and environmental factors. Other risk factors may include the use of OCP in older mothers. Parents consanguinity, paternal age and maternal grandparents’ ages were not found to be risk factors in DS in this study.Keywords: Down syndrome, risk factors, mothers, MTHFR

Comparative study of limited-range wavelength conversion policies for asynchronous optical packet switching

We study an asynchronous optical packet (OP)-switching node equipped with a number of limited range (LR) wavelength converters shared per output link. We study both circular and noncircular LR-wavelength-conversion schemes. A wavelength conversion policy governs the selection of the outgoing wavelength for an OP if the incoming wavelength is in use. Through simulations, we show that the so-called far-conversion policy for which the OP is switched onto the farthest available wavelength in the tuning range, outperforms the other policies we studied. We point out the clustering effect in the use of wavelengths to explain this phenomenon. We also provide an approximate analytical method to find the packet-blocking probability in circular-type LR-wavelength-conversion systems. Based on the simulation results, the approximate method appears to lead to a lower bound for blocking probabilities for all the conversion policies we study. © 2007 Optical Society of America

Effect of surface contamination on interfacial mass transfer rate

The influence of surface contamination upon the mass transfer rate of a low diffusivity gas across a flat surface is studied using direct numerical simulations. The interfacial mass transfer is driven by isotropic turbulence diffusing from below. Similar to Shen et al. (J. Fluid Mech. 506, 2004, pp. 79-115) the surface contamination is modelled by relating the normal gradient of the horizontal velocities at the top to the horizontal gradients of the surfactant concentrations. A broad range of contamination levels is considered, including clean to severely contaminated conditions. The time-averaged results show a strong correlation between the gas transfer velocity and the clean surface fraction of the surface area. In the presence of surface contamination the mass transfer velocity KL is found to scale as a power of the Schmidt number, i.e. Sc−q, where q smoothly transitions from q = 1/2 for clean surfaces to q = 2/3 for very dirty interfaces. A power law KL ∝ Sc−q is proposed in which both the exponent q and the constant of proportionality become functions of the clean surface fraction

Factor V G1691A (Leiden) is a major etiological factor in Egyptian Budd-Chiari syndrome patients

Objective: Budd-Chiari syndrome is a multifactorial disease in which several prothrombotic disorders may predispose patients to the development of thrombosis at this uncommon location (hepatic veins). The aim of this study was to determine the prevalence and characteristics of inherited thrombophilia in Egyptian Budd-Chiari syndrome patients.Materials and Methods: The study included 47 Budd-Chiari syndrome patients (20 children and 27 adults). Genotyping of Factor V G1691A (Leiden), prothrombin G20210A (PT), and methylenetetrahydrofolate reductase C677T were performed using real-time PCR and fluorescence melting curve detection analysis.Results: Factor V Leiden was observed in 29 patients (61.7%). It is the only factor that caused Budd-Chiari syndrome in 18 of the patients and in 5 of the patients with inferior vena cava involvement. Myeloproliferative disease was noted in 12 (25.5%) patients, antiphospholipid syndrome in 5 (10.6%), and Behcet’s disease in 3 (6.4%). Interestingly, 3 of the children with Budd-Chiari syndrome had lipid storage disease.Conclusion: Factor V Leiden was a major etiological factor in Egyptian Budd-Chiari syndrome patients, which may have been related to the high frequency of this mutation in the study region. Factor V Leiden was also a strong thrombophilic factor and the leading cause of inferior vena cava thrombosis in these patients. Lipid storage disease should be included as a risk factor for Budd-Chiari syndrome

Using ICP-OES and SEM-EDX in biosorption studies

We have compared the analytical results obtained by inductively coupled plasma optical emission spectroscopy (ICP-OES) and by scanning electron microscopy with an energy dispersive X-ray analytical system (SEM-EDX) in order to explore the mechanism of metal ions biosorption by biomass using two independent methods. The marine macroalga Enteromorpha sp. was enriched with Cu(II), Mn(II), Zn(II), and Co(II) ions via biosorption, and the biosorption capacity of alga determined from the solution and biomass composition before and after biosorption process was compared. The first technique was used to analyze the composition of the natural and metal-loaded biomass, and additionally the composition of the solution before and after biosorption. The second technique was used to obtain a picture of the surface of natural and metal ion-loaded macroalgae, to map the elements on the cell wall of dry biomass, and to determine their concentration before and after biosorption. ICP-OES showed a better precision and lower detection limit than EDX, but SEM-EDX gave more information regarding the sample composition of Enteromorpha sp. Both techniques confirmed that biosorption is a surface phenomenon, in which alkali and alkaline earth metal ions were exchanged by metal ions from aqueous solution

First Observation of CP Violation in B0->D(*)CP h0 Decays by a Combined Time-Dependent Analysis of BaBar and Belle Data

We report a measurement of the time-dependent CP asymmetry of B0->D(*)CP h0 decays, where the light neutral hadron h0 is a pi0, eta or omega meson, and the neutral D meson is reconstructed in the CP eigenstates K+ K-, K0S pi0 or K0S omega. The measurement is performed combining the final data samples collected at the Y(4S) resonance by the BaBar and Belle experiments at the asymmetric-energy B factories PEP-II at SLAC and KEKB at KEK, respectively. The data samples contain ( 471 +/- 3 ) x 10^6 BB pairs recorded by the BaBar detector and ( 772 +/- 11 ) x 10^6, BB pairs recorded by the Belle detector. We measure the CP asymmetry parameters -eta_f S = +0.66 +/- 0.10 (stat.) +/- 0.06 (syst.) and C = -0.02 +/- 0.07 (stat.) +/- 0.03 (syst.). These results correspond to the first observation of CP violation in B0->D(*)CP h0 decays. The hypothesis of no mixing-induced CP violation is excluded in these decays at the level of 5.4 standard deviations.Comment: 9 pages, 2 figures, submitted to Physical Review Letter