Ultra-compact Spatial Terahertz Switch Based on Graphene Plasmonic-Coupled Waveguide

We are proposing graphene (G)-based multilayered plasmonic spatial switch, operating at 10 THz. It is composed of hBN/Ag/hBN/G/hBN/G/hBN/SiO₂/p⁺-Si multilayers. When a 10-THz transverse magnetic (TM)-polarized signal is normally incident upon the structure top surface, the nanoaperture devised in the Ag nanolayer, acting as a grating, excites surface plasmons at the top graphene micro-ribbons/hBN interface. These surface plasmons depending on the graphenes chemical potentials can be coupled to the lower-right or left graphene micro-ribbons and continue to propagate laterally towards the corresponding output port. Numerical simulations show that a change of ∆V_G ≈ ± 2.7 V in the voltage, applied to the gated micro-ribbons, can modulate their chemical potentials sufficiently to switch the right (left) output port from ON (OFF) to OFF(ON) and vice versa. Besides its low power consumption, the switch ultra-small dimensions make it a potential spatial router suitable for THz-integrated circuit applications.

     

HIV-1 Vpr Modulates Macrophage Metabolic Pathways: A SILAC-Based Quantitative Analysis

Human immunodeficiency virus type 1 encoded viral protein Vpr is essential for infection of macrophages by HIV-1. Furthermore, these macrophages are resistant to cell death and are viral reservoir. However, the impact of Vpr on the macrophage proteome is yet to be comprehended. The goal of the present study was to use a stable-isotope labeling by amino acids in cell culture (SILAC) coupled with mass spectrometry-based proteomics approach to characterize the Vpr response in macrophages. Cultured human monocytic cells, U937, were differentiated into macrophages and transduced with adenovirus construct harboring the Vpr gene. More than 600 proteins were quantified in SILAC coupled with LC-MS/MS approach, among which 136 were significantly altered upon Vpr overexpression in macrophages. Quantified proteins were selected and clustered by biological functions, pathway and network analysis using Ingenuity computational pathway analysis. The proteomic data illustrating increase in abundance of enzymes in the glycolytic pathway (pentose phosphate and pyruvate metabolism) was further validated by western blot analysis. In addition, the proteomic data demonstrate down regulation of some key mitochondrial enzymes such as glutamate dehydrogenase 2 (GLUD2), adenylate kinase 2 (AK2) and transketolase (TKT). Based on these observations we postulate that HIV-1 hijacks the macrophage glucose metabolism pathway via the Vpr-hypoxia inducible factor 1 alpha (HIF-1 alpha) axis to induce expression of hexokinase (HK), glucose-6-phosphate dehyrogenase (G6PD) and pyruvate kinase muscle type 2 (PKM2) that facilitates viral replication and biogenesis, and long-term survival of macrophages. Furthermore, dysregulation of mitochondrial glutamate metabolism in macrophages can contribute to neurodegeneration via neuroexcitotoxic mechanisms in the context of NeuroAIDS.     

Isolation of spore-forming bacilli from mosquitoes in natural breeding habitats in Iraq

New isolates of spore-forming bacilli from larvae and pupae of 3 species of mosquitoes are recorded in central Iraq.Bacillus sphaericus Meyer and Neide was isolated fromCulex pipiens (L.) larva.Bacillus carotarum Koch andBacillus cereus Frankland & Frankland were isolated fromTheobaldia longiareolata (Macquart) pupae.Bacillus laterosporus Laubach andBacillus thuringiensis (H 18) were isolated fromAedes caspius (Pallas) larvae. In addition, unidentifiedBacillus spp. were isolated fromCx. pipiens, T. longiareolata andAe. caspius larvae. Examination of soil samples collected from mosquito natural breeding habitats revealed isolates ofB. cereus, Bacillus thuringiensis H4a 4b; H 12 and H 16 and an unidentifiedBacillus sp.

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Résumé Des souches bactériennes sporogènes sont isolées de moustiques qui se trouvent dans la région centrale de l'Irak. Les résultats obtenus sont les suivants:Bacillus sphaericus Meyer & Neide [Culex pipiens (L.), larve],Bacillus carotarum Koch etBacillus cereus Frankland & Frankland [Theobaldia longiareolata (Macquart), nymphe],Bacillus laterosporus Laubach etBacillus thuringiensis (H 18) [Aedes caspius (Pallas), larvel]. L'examen des larves deCulex pipiens. T. longiareolata etAe. caspius, ainsi que l'analyse des échantillons du sol prélevés dans la région montrent la présence deBacillus cereus, Bacillus thuringiensis H4a 4b; H12 plus H16 et d'autresBacillus non identifiés.

     

Binding of dantrolene-Na to the ciliated membrane ofParamecium aurelia

Summary Dantrolene-Na is a muscular relaxant which binds to sarcoplasmic reticulum (SR) with high affinity and decreases the availability of Ca²⁺ channels. The binding of fluorescent compounds, dantrolene-Na, nifedipine and chlortetracycline to the ciliary membrane ofParamecium aurelia has been studied. Dantrolene at the concentrations of 1.9 · 10^–5, 3.8 · 10^–5 and 7.9 · 10^–5 M manifested a punctuated binding pattern to the cell membrane. Isolated cilia also bound dantrolene at their basal portion, whereas deciliated cell bodies lost their dotted binding pattern. Chlortetracycline showed a similar but weaker fluorescent staining. Nifedipine treated cells revealed no sign of fluorescent binding to the membrane and was only taken up in food vacuoles.Based on these observations we propose that dantrolene binding regular arrays ofParamecium cell membrane could be identical to granular plaques observed by electron microscope. The possible functioning of these structures as Ca²⁺ reservoirs is also discussed.     

Performance modeling of a manufacturing cell with a single material transporter: An approximation

We consider a flexible manufacturing system with a number of workstations, a single material transporter, and a common storage space of finite capacity. The material handling delay times are explicitly considered in the model and assumed to follow a two-stage Coxian distribution. The material processing times on a workstation also have a two-stage Coxian distribution. The routing of parts within the system follows a Markov chain. An approximate performance model is developed and the results are compared with the exact or simulation results. We also investigate how this performance model compares to a simulation with deterministic routing and processing times. Finally, we study the effect, on the performance measures, of ignoring the material transporter or of modeling the transporter as a central server with aggregation of routing information.     

Interaction of facilitative glucose transporter with glucokinase and its modulation by ADP and glucose-6-phosphate

Bacterial glucokinase (GK) binds to purified, human erythrocyte glucose transporter (GT) reconstituted in vesicles. The binding is largely abolished if GT is predigested with trypsin, indicating that GK binds to the cytoplasmic domain of GT. The binding is a saturable function of GK concentration showing two distinct affinities with apparent K_D of 0.33 and 5.1 μM. The binding is stimulated by an increasing concentration of ADP with the 50% maximal effect at 5 mM. Glucose-6-phosphate (G6P) also stimulates the binding with a distinct optimum at 25 mM. The binding is stimulated only slightly by ATP. D-glucose has no affect on the binding. KCl enhances the binding with the maximal effect at physiological intracellular concentrations. The binding is sensitive to changes in pH with an optimum at pH 4. The binding causes no detectable functional change in GT. However, the enzymatic activity of GK measured at nanomolar concentrations of GK is significantly greater in the presence of GT vesicles than in its absence or in the presence of protein-free vesicles, indicating that GK interacts with GT at this low concentration range with an apparent K_D of 10 mM. Although its physiological significance is not known, the GK-GT interaction in vitro described here suggests that these two proteins may also interact in the cell and regulate carbohydrate metabolism. © 1993 Wiley-Liss, Inc.     

Does Gγ/Aγ ratio and Hb F level influence the severity of sickle cell anaemia

Sickle cell anaemia (SCA) exhibits significant variations in clinical presentation in different populations for which several genetic factors including SCA-associated -and -thalassaemias, G-6-PD deficiency and elevated Hb F level have been implicated as possible ameliorating factors. Saudi Arabia is unique in that mild and severe forms of the disease occur at a high frequency. We investigated the G/A ratio and Hb F level and correlated these values with the severity of SCA. The results showed that Hb F level varies significantly in both groups of patients with no evident correlation with the mild clinical manifestations. However, G/A ratio correlated significantly with the disease severity where a high ratio was observed in patients with the mild and a low ratio in patients with the severe disease. The results are evaluated and discussed in the light of correlation studies and regression analysis.