Effect of van-Hove singularities in single-walled carbon nanotube leads on transport through double quantum dot system

The double quantum dot system with single-walled metallic armchair carbon nanotube leads has been studied using Non-equilibrium Green function in the Keldysh formalism. The effect of relative spacing between the energy levels of the dots, interdot tunneling matrix-element, interdot Coulomb interaction and van-Hove singularities in density of states characteristics of quasi-one-dimensional carbon nanotube leads on the conductance of the double quantum dot system has been studied. The conductance and dot occupancies are calculated at finite temperature. It is observed that the density of states of the carbon nanotube leads play a significant role in determining the conductance profile. In particular, whenever the chemical potential of the isolated double quantum dot system is aligned with the position of a van-Hove singularity in the density of states of armchair carbon nanotube leads, the height of the corresponding conductance peak falls considerably. It is further observed that the suppression in the heights of the alternate peaks depends on the relative positions of the energy levels of the dots and their magnitude of separation.Comment: 16 pages and 16 figure

Unexpected cell type-dependent effects of autophagy on polyglutamine aggregation revealed by natural genetic variation in C. elegans.

BACKGROUND: Monogenic protein aggregation diseases, in addition to cell selectivity, exhibit clinical variation in the age of onset and progression, driven in part by inter-individual genetic variation. While natural genetic variants may pinpoint plastic networks amenable to intervention, the mechanisms by which they impact individual susceptibility to proteotoxicity are still largely unknown. RESULTS: We have previously shown that natural variation modifies polyglutamine (polyQ) aggregation phenotypes in C. elegans muscle cells. Here, we find that a genomic locus from C. elegans wild isolate DR1350 causes two genetically separable aggregation phenotypes, without changing the basal activity of muscle proteostasis pathways known to affect polyQ aggregation. We find that the increased aggregation phenotype was due to regulatory variants in the gene encoding a conserved autophagy protein ATG-5. The atg-5 gene itself conferred dosage-dependent enhancement of aggregation, with the DR1350-derived allele behaving as hypermorph. Surprisingly, increased aggregation in animals carrying the modifier locus was accompanied by enhanced autophagy activation in response to activating treatment. Because autophagy is expected to clear, not increase, protein aggregates, we activated autophagy in three different polyQ models and found a striking tissue-dependent effect: activation of autophagy decreased polyQ aggregation in neurons and intestine, but increased it in the muscle cells. CONCLUSIONS: Our data show that cryptic natural variants in genes encoding proteostasis components, although not causing detectable phenotypes in wild-type individuals, can have profound effects on aggregation-prone proteins. Clinical applications of autophagy activators for aggregation diseases may need to consider the unexpected divergent effects of autophagy in different cell types

On the analytic solution for the steady drainage of magnetohydrodynamic (MHD) Sisko fluid film down a vertical belt

This paper presents an analytic study for the steady drainage of magnetohydrodynamic (MHD) Sisko fluid film down a vertical belt. The fluid film is assumed to be electrically conducting in the presence of a uniform transverse magnetic field. An analytic solution for the resulting non linear ordinary differential equation is obtained using the Adomian decomposition method. The effects of various available parameters especially the Hartmann number are observed on the velocity profile, shear stress and vorticity vector to get a physical insight of the problem. Furthermore, the shear thinning and shear thickening characteristics of the Sisko fluid are discussed. The physical quantities discussed for the Sisko fluid film have also been discussed for the Newtonian fluid film and comparison between them made

Analytic Solution for the Drainage of Sisko Fluid Film Down a Vertical Belt

This paper deals with the drainage of Sisko fluid film down a vertical belt. It provides an approximate solution of the resulting non-linear and inhomogeneous ordinary differential equation using perturbation method (PM) and Adomian decomposition method (ADM). Comparison of the results obtained by both methods demonstrate that these series solutions are strictly identical but ADM is easy to compute and can be extended to any higher order. The important physical quantities like velocity profile, volume flow rate, average film velocity, shear stress, force exerted by the fluid film and vorticity vector are derived. The effects of fluid behaviour index, Stokes number and Sisko fluid parameter on some of these physical quantities are observed. Furthermore, we also made a comparison between the Sisko fluid film and Newtonian fluid film

Excitation of surface plasmons in thin noble metallic film of copper, silver and gold paper

The formation of surface plasmons in a different type of noble metallic film was successfully simulated using MATLAB program software. The thicknesses of copper, silver and gold metal films were varied between 20 nm to 80 nm. The narrowness and depth of surface plasmon resonance (SPR) curves were observed to determine the excitation of surface plasmons. The simulation results indicate that the maximum excitation of surface plasmons can be achieved by using silver thin film with thicknesses of 50 nm at the minimum reflectivity of 0.0038 a.u and full width at half maximum value of 0.2592°. The silver film that produces a deeper and sharper SPR curve has potential in the development of a low cost and high sensitivity of SPR sensing device

Study of the Rheological Behavior of Polyamide 5,6 (PA5,6

The rheological behavior of polymer melts and polymer solutions are of great importance in polymer processing, particularly for the analysis and design of processing operations as well as understanding the relationship between structures and properties of the final-products. The objective of the present work was to investigate the rheological behavior of polyamide 5,6  (PA5,6) to obtain information on the effect of temperature on the melt behavior of polyamide 5,6 compared to that of polyamide 6. The rheological properties of polyamide 5,6 (PA5,6) have been studied by means of a Haake  rheometer. The effect of temperature on the storage modulus, loss modulus, and complex viscosity was studied. The obtained results showed that the complex viscosity, storage modulus, and loss modulus of PA5,6 and PA6 decrease with increase of the temperature. It is worth noting that the complex viscosity of PA5,6 remains almost constant showing a Newtonian behavior, on the other hand, the complex viscosity of PA6 slightly decreases with the increase of shear rate exhibits a much nearly Newtonian behavior. Similar behavior was observed for other polyamides such as polyamide 6.6 and polyamide 6.,1

Genetic diversity of beta-thalassemia mutations in Pakistani population

Background: beta-thalassemia is one of the most common inherited single gene disorder in Pakistan. It is characterized by reduced or absent beta-globin gene expression resulting in abnormal maturation and survival of red blood cells. Due to high prevalence of this disease in the local population, it has become important for the health care providers to encourage people to utilize laboratory facilities for carrier and prenatal genetic testing. Objective: To study the frequency of beta-thalassemia mutations in Pakistani population. Setting: A tertiary care teaching hospital. Methods: Blood samples of 72 couples and chorionic villus (CV) biopsy specimen collected at the Aga Khan University Hospital, Karachi were tested by Amplified Refractory Mutation Systems (ARMS) for the 12 most common mutations in the beta-globin gene. Results: Out of 72 chorionic villus biopsy specimen analyzed, 17 (23%) had mutations in both alleles of the beta-globin gene. Homozygosity was identified in 6 CV samples, whereas 11 CV specimens were diagnosed as double heterozygous. Almost 60% of the CV biopsies showed mutations in one allele and were diagnosed as carriers. IVSI-5 (G-C) was the most common mutation identified in this study. It was found in 53% of the subjects and was represented equally in all the ethnic groups except Pathans. Several regional and ethnic differences were observed in the distribution of common mutations, for example in Pathan families Fr 8-9 (+G) mutation was most prevalent. In addition, variation in the distribution of mutations was also observed between the Northern and the Southern regions. Conculsion: This study indicates that in Pakistan, the five most common mutations are IVS1-5 (G-C), IVS1-1 (G-T), Fr 41-42 (-TTCT) Fr 8-9 (+G) and deletion 619 bp. An important factor contributing to high incidence of thalassemia is the unawareness among people about the available diagnostic facilities for the prenatal diagnosis in Pakistan. Strict implementation of collective measures including carrier identification, genetic counseling and prenatal diagnosis are required for preventing beta-thalassemia in Pakistan