A hexameric transmembrane pore revealed by two-dimensional crystallization of the large mechanosensitive ion channel (MscL) of Escherichia coli

We have established a reconstitution method of the detergent-solubilized recombinant large mechanosensitive ion channel of Escherichia coli (MscL) that yielded two-dimensional crystals. For that purpose, we have developed a new protocol using Triton X-100 to solubilize and purify the MscL protein. This protocol not only allowed an increase in the protein yield but also made it possible to obtain a homogeneous delipidated and reproducible preparation of the purified protein. When examined by the patch-clamp method MscL channels were found to be fully functional, exhibiting characteristic conductance and activation by pressure. For electron crystallography the homogeneous Triton X-100-purified recombinant MscL was further reconstituted at low lipid-to-protein ratios using Bio-Beads SM2 to remove the detergent. Two-dimensional crystals, exhibiting a p6 plane group symmetry, have been produced and examined by negative stain electron microscopy. Image processing of selected micrographs yielded a projection map at 15-A resolution that provided the first explicit structural information about the molecular boundary and homohexameric organization of the MscL channels in the membrane bilayer.     

New upgrading options of heavy oil fractions from Algerian refineries

The global demand for petroleum products is increasing year by year quantitatively and qualitatively. Besides the clear products supplied by the fractionation of crude oil, there are a number of heavy petroleum products obtained from the secondary treatment, which are not the proper use; they are often used as components of fuel oil. Now, all the refineries are equipped by hydrotreating facilities aimed to transform these fractions heavy in market value of products most important. Consequently, the choice of adequate processes is a major challenge for oil refineries. The objective of this work is to value these heavy cuts by the catalytic cracking process, which is the most suitable method and is the only one existing in Algeria.     

Improvement in the field-weakening performance of switched reluctance machine with continuous mode

A new operation mode for switched reluctance motors (SRMs), called 'continuous mode', is described. By using this mode, the torque and then power in field-weakening mode can be considerably increased without any hardware modifications. Consequently, power and torque densities of SRMs become comparable to other technologies (synchronous and induction motors) and with a field weakening operation over a large speed range. This new degree of freedom makes it possible to improve the motor design, by modifying the rotor pole arc size or the windings turns per pole. Only simulation results are presented here, for a 12/8 SRM. Results confirm that the maximum power is improved (constant power on a very large speed range) and with a higher efficiency than that in the classical discontinuous mode.     

Implicit shift scheduling with multiple breaks and work stretch duration restrictions

This paper considers a shift scheduling problem that includes different forms of flexibility in terms of shift starting times, break lengths and break placement. Two particular forms are studied: fractionable breaks and work stretch duration restrictions. Unlike standard breaks, fractionable breaks are not required to be attributed as a whole. They can be divided into fractions of breaks under some conditions. The distribution of breaks within a shift is done with respect to work stretch duration restrictions to ensure a correct mix of periods of work and rest. Two implicit models are proposed. They extend previous work on implicit modeling of break placement to incorporate the concepts of fractionable breaks and work stretch duration restrictions. In this context, we show the merits of using the so-called forward and backward constraints to model work stretch duration restrictions. We also introduce a new formulation of the forward and backward constraints and demonstrate that it considerably reduces the density of the constraint matrix of the two proposed models. Finally, we study the impact of fractionable breaks and work stretch duration restrictions and show that, for some instances, the use of these concepts considerably reduces the workforce size when compared to other traditional approaches.     

The instructional benefits of dynamic visualizations in the acquisition of basketball tactical actions

Recent studies exploring the effects of dynamic visualizations on learning compared with static visualizations have yielded mixed results. Procedural motor learning is one of the few fields in which dynamic representations have shown to be effective. Many of the studies have suggested that this advantage is mainly due to the activation of the “mirror‐neuron system.” This study explores this explanation in physical education domain and analysed the effects of instructional media (video vs. photographs), showing tactical actions in basketball, on learning outcomes (i.e., game understanding and game performance), cognitive load (i.e., mental effort invested and estimated difficulty), and attitudes (i.e., attention, enjoyment, engagement, and challenge) in secondary school students. For all of the indicators, the results show that learning from video was more effective than learning from photographs. These findings have implications for the effective design of instructional media and provide confirmation of the superiority of video for teaching tactical actions involving the entire body.     

Novel Positive Multi-Layer Graph Based Method for Collaborative Filtering Recommender Systems

Recommender systems play an increasingly important role in a wide variety of applications to help users find favorite products. Collaborative filtering has remarkable success in terms of accuracy and becomes one of the most popular recommendation methods. However, these methods have shown unpretentious performance in terms of novelty, diversity, and coverage. We propose a novel graph-based collaborative filtering method, namely Positive Multi-Layer Graph-Based Recommender System (PMLG-RS). PMLG-RS involves a positive multi-layer graph and a path search algorithm to generate recommendations. The positive multi-layer graph consists of two connected layers: the user and item layers. PMLG-RS requires developing a new path search method that finds the shortest path with the highest cost from a source node to every other node. A set of experiments are conducted to compare the PMLG-RS with well-known recommendation methods based on three benchmark datasets, MovieLens-100K, MovieLens-Last, and Film Trust. The results demonstrate the superiority of PMLG-RS and its high capability in making relevant, novel, and diverse recommendations for users.

     

A Study of Structural and Physical Properties of Heavily Co-doped LaSr2Mn2O7 Bi-layered Manganite

In this paper, we report the influence of cobalt doping on the structure and magnetic properties of bilayered-perovskite LaSr₂Mn_2?x Co _x O₇ (x=0.25,0.3). Parent and doped samples were synthesized through the sol-gel method under optimized conditions. X-ray diffraction studies coupled with the Rietveld refinement of xrd data, show that both doped and parent samples crystallize in a Sr₃Ti₂O₇-type layered perovskite structure. Temperature dependent magnetic behavior of the parent sample exhibits an antiferromagnetic and a charge-ordering state around 220 K. Magnetic field dependence of magnetization M(H) for doped samples at 20 K show well-defined M–H loops confirming the formation of intrinsic ferromagnetic ordering due to the Co doping. Additionally, we studied the ac–magnetic susceptibility and magnetization relaxation process in our samples. Dynamic scaling analysis hints an existence of glassy magnetic states in doped samples. Electrical and magnetic properties of our samples further demonstrate that Co doping suppresses charge ordering in bilayered LaSr₂Mn₂O₇.     

Flexural strength and cracking behavior of hybrid strength concrete beams

The flexural and cracking behavior of hybrid strength concrete beams cast with two concrete compressive strengths of 20 and 70 MPa were compared with 20 MPa normal and 70 MPa high strength beams. The hybrid beams showed an improvement in the load carrying capacity at cracking, yielding and ultimate loading as compared to normal strength beams. The increase in load carrying capacity was (1.80–70.8%) higher than normal strength beams and only (3.3–9.8%) lower than corresponding high compressive strength beams. Also from experimental results the crack spacing of hybrid beams were between those of normal strength and high strength beams, but the crack width in the hybrid beams were narrower than both types of beams at all loading stages. At service and ultimate loading stages, the crack width in the hybrid beams were 19.5–26.0% narrower than those of corresponding normal strength beams, and 9.2–15.1% narrower than high strength beams.     

Fungal membrane responses induced by plant defensins and thionins

Treatment of hyphae of Neurospora crassa with antifungal plant defensins, i.e. Rs-AFP2 and Dm-AMP1 isolated from radish and dahlia seed, respectively, induced a rapid K+ efflux, Ca2+ uptake, and alkalinization of the incubation medium. The Rs-AFP2-induced alkalinization of the incubation medium could be inhibited with G-protein inhibitors. alpha-Hordothionin, an antifungal thionin from barley seed, caused a sustained increased Ca2+ uptake at subinhibitory concentrations but only a transient increased uptake at inhibitory concentrations. alpha-Hordothionin also caused increased K+ efflux and alkalinization of the medium, but these fluxes occurred more rapidly compared to those caused by plant defensins. Furthermore, alpha-hordothionin caused permeabilization of fungal hyphae to the non-metabolite alpha-aminoisobutyric acid and, in addition, altered the electrical properties of artificial lipid bilayers, consistently leading to rupture of the lipid bilayers. The plant defensins did not form ion-permeable pores in artificial membranes and did not exhibit substantial hyphal membrane permeabilization activity. Our results are consistent with the notion that thionins inhibit fungal growth as a result of direct protein-membrane interactions, whereas plant defensins might act via a different, possibly receptor-mediated, mechanism.     

Retinal-specific guanylate cyclase gene mutations in Leber''s congenital amaurosis

We report a 68 years old male with a polymyositis associated to HTLV-I. Diagnosis was based on clinical picture, an increased creatin-phosphokinase levels, electromyography and muscle biopsy. The patient had positive HTLV-I antibodies, measured by particle agglutination test, indirect immunofluorescence and polymerase chain reaction in lymphocytes. Skin biopsy showed a mycosis fungoides. Schirmer test and minor salivary gland biopsy showed a dacryosialoadenitis. There was no central nervous system involvement. This patient is the only with positive HTLV-I antibodies, among 18 patients with polymyositis in whom these antibodies were measured.