bluuebunny/crossref_metadata_2025 huggingface dataset:
Modèle de prévision pour la gestion en temps réel : application aux réseaux d'assainissement
Authors: Assabbane Abderrahman , Bennis Saad
Published: April 2011

The work presented here aims at developing a flow forecast model dedicated to real-time management. The proposed model is based on the notion of a transfer function for a linear system identified through the Kalman filter algorithm. In a first step, the transfer function model is linked to the Muskingum semi-empirical model; then it is modified to eliminate the autoregressive component. The Kalman filter algorithm allows the parameters of the proposed model to be updated upon the reception of each new measure with respect to the forecast errors observed in real time. To analyze the performance of the proposed model, its results are compared with those obtained using the dynamic wave model and the simplified kinematic wave model. Because of the absence of measured downstream flow values corresponding to the input hydrograph, the results from the dynamic wave model are used as reference values to evaluate the performance of the other models. These results are also used with the addition of noises to simulate measured values and feed, in "real-time," the identification algorithm of the transfer function in order to adjust, a posteriori, its parameters according to its differences in the flow prediction. The results obtained by the transfer function model agree with those obtained by the dynamic model following the three performance criteria employed. The Nash coefficient and the ratio between the peak flows are close to unity in all of the cases. Also, the lag between the peak flows estimated by the two models is negligible.Key words: waste water networks, real-time management, flow propagation models, forecast, transfer function, Kalman filter.[Journal Translation]
Characterization and use of pulp mill fly ash and lime by-products as road construction amendments
Authors: Zhou Hongde , Smith Daniel W , Sego David C
Published: April 2011

Fly ash and lime by-products are the two main waste streams generated by the pulp and paper industry. Traditionally, these wastes are disposed of either in surface impoundment or landfills. Greater environmental concerns and limited land availability have made these disposal practices increasingly unacceptable and costly. Thus, the objective of this study was to determine the feasibility of beneficial utilization alternatives with emphasis on their use as road construction amendment materials based on technical, economical, and environmental considerations. The experiments were conducted to comprehensively characterize the chemical, physical, engineering, and environmental properties for both waste samples and their mixtures prepared with local soils at different curing conditions. Field road tests were then conducted to verify and assess the performance of the mixtures in terms of load bearing capacity, serviceability, and compaction. The results showed that pulp mill wastes would have little adverse environmental impact and could be used as road construction amendments to improve soil strength and reduce deformation. This improvement was significantly affected by soil types, moisture contents, and waste addition rates. During waste-soil amendment, the metal leachability would be further reduced by the occurrence of solidification processes.Key words: wood ash, fly ash, lime by-products, solid waste management, pulp mill waste, waste utilization, leaching tests.
Torsional strength of reinforced concrete beams
Authors: Rahal Khaldoun N
Published: April 2011

A simple method for predicting the ultimate strength and mode of failure of reinforced concrete beams subjected to pure torsion is presented. This method is an extension of a recently developed method for predicting the strength of membrane elements subjected to pure shear that was also applied to beams subjected to combined shearing forces, bending moments, and axial loads. The torsional strength is related to the amounts of transverse and longitudinal reinforcement and to the concrete strength. To check the adequacy of this simple method, the calculated strength and mode of failure are checked against the experimental results of 66 beam tests available in the literature, and good agreement is found. The simplicity of the method is illustrated by an example.Key words: beams, building codes, mode of failure, reinforced concrete, shear, strength, torsion.
Length effect on the tensile strength of truss chord members
Authors: Lam Frank
Published: April 2011

Length effects on the tensile strength of multiple member truss chords have been studied. Simulation and reliability studies have been presented to evaluate the impact of length and multiple member effects on the target safety index for tensile failure. Results indicate significant length effect can be expected for long multiple tension chord members. Based on the Weibull weakest link theory, length effect adjustment parameters have been established. Further simulation and reliability studies have demonstrated the robustness of the proposed length effect adjustment procedures. A procedure has been developed for the design of truss chord members considering Weibull weakest link based size effect and non-uniform loading along the length of bottom chord truss members such that the target reliability index can be maintained.Key words: length effect, tensile strength, trusses.
Modeling bond-slip deformations in reinforced concrete beam-column joints
Authors: Elmorsi Mostafa , Kianoush M Reza , Tso W K
Published: April 2011

A new finite element model for reinforced concrete beam-column joints is proposed. The model considers the effects of bond-slip and shear deformations in the joint panel region. The problems associated with modeling bond-slip of anchored reinforcing bars are discussed. The proposed bond-slip model is examined at the element level by comparing its predictions with other analytical and experimental results. The ability of the model to simulate bond deterioration and eventual pullout of anchored reinforcing bars under severe cyclic excitation is demonstrated. This model is incorporated into the global beam-column joint element. Further comparisons are made between the predictions of the proposed beam-column joint model and other analytical and experimental results under reversed cyclic loading to show the validity of the model to describe the bond-slip behavior of the joints.Key words: bond, bond-slip, finite element, beam-column, reinforced concrete, cyclic.
Draining function of porous asphalt during snowmelt and temporary freezing
Authors: Bäckström M , Bergström A
Published: April 2011

Urban runoff creates problems with flooding and pollution of receiving waters. Furthermore, cold climate conditions have a degenerating effect on stormwater systems and road constructions. Porous asphalt has been used as a wearing course on highways and in porous pavement constructions all around the world. The main focus of this study was to evaluate the function of porous asphalt in cold climates. Measurements of the draining function of porous asphalt were carried out in a climate room with adjustable temperature in the range -10°C to +20°C. At freezing point, the infiltration capacity of porous asphalt was approximately 50% of the infiltration capacity at +20°C. When the porous asphalt was exposed to alternating melting and freezing during 2 days, conditions similar to the snowmelt period, the infiltration capacity was reduced by approximately 90%. Based on the results of this study and previous studies, the infiltration capacity of porous asphalt was estimated to be 1-5 mm/min for snowmelt conditions.Key words: cold climate, infiltration, porous asphalt, porous pavement, stormwater.
Strategic highway improvements to minimize environmental impacts within the Canadian Rocky Mountain National Parks
Authors: McGuire T M , Morrall J F
Published: April 2011

This paper describes how strategic highway engineering improvements have been developed or adopted to mitigate the unique environmental impact highways and roads have within Canadian Rocky Mountain national parks, which are also World Heritage Sites. Three levels of strategic highway development are presented. The first is the recapitalization of existing park roads. Examples are presented from several national parks where parkways and low-volume roads were reconstructed or repaired in ways to reduce terrain impacts. The second is the development of the passing lane system on the Trans-Canada Highway in the Rocky Mountain national parks to defer twinning. The third example is the twinning of 18.6 km of the Trans-Canada Highway. Twinning represents a logical next step following the passing lane phase. This paper describes how highway engineering improvements were developed to address and mitigate numerous potential twinning impacts identified during environmental assessment. Included within the environmental mitigation measures are fencing and animal crossing structures, addressing wildlife movement, biodiversity, and mortality as well as stream, terrain, and vegetation disturbance minimization techniques. Research has found that the mitigation measures have been effective in reducing wildlife and vehicle collisions by 97%.Key words: highway, sustainable, national park, environment.
The effects of high temperatures on soybean nodulation and growth with different strains of bradyrhizobia
Authors: Favre Adrienne K. La , Eaglesham Allan R. J.
Published: April 2011

The effects on nodulation by diurnally administered high temperatures were studied with soybean (Glycine max (L.) Merr.) and diverse strains of bradyrhizobia. The strains were differentially affected in their symbiotic performances by the higher temperature regimes, and only with the most stressful treatments imposed, 42 °C for 12 h per day and 45 °C for 9 h per day, did some strains fail to nodulate. There was no correlation between the ability of a strain to grow on agar at high incubation temperatures and its ability to nodulate at high temperatures. Effectiveness of a strain at normal temperatures was a more reliable indicator of its symbiotic potential at high temperatures.
Effect of pineal indoles on activities of the antioxidant defense enzymes superoxide dismutase, catalase, and glutathione reductase, and levels of reduced and oxidized glutathione in rat tissues
Authors: Liu F , Ng T B
Published: April 2011

Male Sprague-Dawley rats were randomly divided into four groups. Two of the groups received a single intraperitoneal injection of melatonin and 5-methoxytryptamine (5 mg/kg body weight), respectively, at 9 PM. One group received an intraperitoneal injection of 5-methoxytryptophol (5 mg/kg body weight) at 9 AM. The remaining group received alcoholic saline (vehicle) and served as the control. All rats were sacrificed 90 min after injection and the livers, kidneys, and brains were dissected. The activities of superoxide dismutase, catalase, and glutathione reductase in the organs were measured. It was found that both melatonin and 5-methoxytryptamine were approximately equipotent in enhancing the activities of superoxide dismutase and glutathione reductase in the kidney and liver, while 5-methoxytryptophol displayed a weaker effect. Both melatonin and 5-methoxytryptamine augmented the level of reduced glutathione in the kidney and liver, while 5-methoxytryptophol did so only in the kidney. All three pineal indoles increased the activity of superoxide dismutase and lowered the ratio of oxidized to reduced glutathione in the brain.Key words: pineal indoles, catalase, superoxide dismutase, glutathione reductase.
Pituitary adenylate cyclase activating polypeptide as a novel hypophysiotropic factor in fish
Authors: Wong Anderson OL , Li Wen Sheng , Lee Eric KY , Leung Mei Yee , Tse Lai Yin , Chow Billy KC , Lin Hao Ren , Chang John P
Published: April 2011

Pituitary adenylate cyclase activating polypeptide (PACAP) is a novel member of the secretin-glucagon peptide family. In mammals, this peptide has been located in a wide range of tissues and is involved in a variety of biological functions. In lower vertebrates, especially fish, increasing evidence suggests that PACAP may function as a hypophysiotropic factor regulating pituitary hormone secretion. PACAP has been identified in the brain-pituitary axis of representative fish species. The molecular structure of fish PACAP is highly homologous to mammalian PACAP. The prepro-PACAP in fish, however, is distinct from that of mammals as it also contains the sequence of fish GHRH. In teleosts, the anterior pituitary is under direct innervation of the hypothalamus and PACAP nerve fibers have been identified in the pars distalis. Using the goldfish as a fish model, mRNA transcripts of PACAP receptors, namely the PAC1 and VPAC1 receptors, have been identified in the pituitary as well as in various brain areas. Consistent with the pituitary expression of PACAP receptors, PACAP analogs are effective in stimulating growth hormone (GH) and gonadotropin (GTH)-II secretion in the goldfish both in vivo and in vitro. The GH-releasing action of PACAP is mediated via pituitary PAC1 receptors coupled to the adenylate cyclase-cAMP-protein kinase A and phospholipase C-IP3-protein kinase C pathways. Subsequent stimulation of Ca2+entry through voltage-sensitive Ca2+channels followed by activation of Ca2+-calmodulin protein kinase II is likely the downstream mechanism mediating PACAP-stimulated GH release in goldfish. Although the PACAP receptor subtype(s) and the associated post-receptor signaling events responsible for PACAP-stimulated GTH-II release have not been characterized in goldfish, these findings support the hypothesis that PACAP is produced in the hypothalamus and delivered to the anterior pituitary to regulate GH and GTH-II release in fish.Key words: PACAP, VIP, PAC1 receptor, VPAC1 receptor, VPAC2 receptor, growth hormone, gonadotropin-II, cAMP, protein kinase A, protein kinase C, calcium, pituitary cells, goldfish, and teleost.
Kidney proximal tubule cells: Epithelial cells without EGTA-extractable annexins?
Authors: Tribolo Sandra , Maroux Suzanne , Massey-Harroche Dominique
Published: April 2011

The expression and the subcellular localizations of annexins I, II, IV, VI, and XIII in renal epithelial cells were investigated, using immunological techniques with specific monoclonal antibodies. Upon performing Western blotting experiments, no annexins VI and XIII were detected in kidney, whereas annexins I, II, and IV were. Immunofluorescence labelling procedure performed on thin frozen renal sections showed the presence of these three annexins along the plasma membrane of the collecting duct cells with a restricted expression of annexin I at principal cells. Annexin I was also found present in some glomerular cells. None of these annexins, however, were detected in the proximal tubular cells upon performing immunofluorescence labelling and electrophoretic analysis on an EGTA (ethylenebis(oxyethylenenitrilo)tetraacetic acid)-extractable annexin fraction prepared from freshly isolated cells. This is the first time a mammalian epithelial cell has been found to express non-typical annexin (at least partly solubilized with EGTA). However, when these cells were grown in primary culture, they were found to express annexins I, II, IV, and V. As well as being located along the basolateral membrane, annexins I and II are also present on vesicles, which suggests that these annexins may be involved in vesicular traffic under cell culture conditions.Key words: annexin, kidney, proximal tubule, primary culture.
Distal-less-related homeobox genes of vertebrates: Evolution, function, and regulation
Authors: Zerucha Ted , Ekker Marc
Published: April 2011

Homeobox genes of the Distal-less family have been identified in virtually all metazoan groups where they play roles in the ontogeny of these animals. The vertebrate Distal-less related genes (Dlx genes) are thought to have arisen as a result of a tandem gene duplication event followed by a number of larger genomic scale duplications and thus represent an interesting model with which to study the evolution of clustered gene families. Dlx genes are involved in the development of the forebrain, branchial arches, sensory organs, and limbs. Here we describe the current state of knowledge of the Dlx genes in terms of their developmental expression, how this expression is regulated and how the products of these genes function, once expressed. We highlight a number of recent studies that have shed light on the transcriptional regulation of this gene family. These findings have not only contributed to our understanding of the selective pressures involved in the maintenance of familial gene clustering in genomes, but also to our understanding of how genes may diverge in function during the course of evolution as a result of divergence of regulatory mechanisms.Key words: genome, homeodomain, inner ear, olfactory placode, transcription.
Intermediate filaments modulation in an in vitro model of the hepatic stellate cell activation or conversion into the lipocyte phenotype
Authors: Guma Fatima C.R , Mello Tanira G , Mermelstein Claudia S , Fortuna Vitor A , Wofchuk Susana T , Gottfried Carmem , Guaragna Regina M , Costa Manoel L , Borojevic Radovan
Published: April 2011

Hepatic stellate cells are intralobular connective tissue cells expressing the myofibroblast or the lipocyte phenotypes. They participate in homeostasis of the liver extracellular matrix, repair, regeneration, and fibrosis under the former phenotype, and control the retinol metabolism, storage, and release under the latter one. They are heterogeneous in terms of their tissue distribution, function, and expression of cytoskeletal proteins. We have studied the expressions of intermediate filaments in the cloned GRX cell line representative of murine hepatic stellate cells, by immunolabeling, reverse transcription polymerase chain reaction (RT-PCR), immunoprecipitation and Western blots. GRX cells expressed vimentin, desmin, glial fibrillary acidic protein (GFAP), and smooth muscle α actin (SM-αA). Vimentin, desmin, and SM-αA were expressed in all cultures. GFAP showed a heterogeneous intensity of expression and did not form a filamentous cytoskeletal network, showing a distinct punctuate cytoplasmic distribution. When activated by inflammatory mediators, GRX cells increased expression of desmin and GFAP. Retinol-mediated induction of the lipocyte phenotype elicited a strong decrease of intermediate filament protein expression and the collapse of the filamentous structure of the cytoskeleton. Quiescent hepatic stellate precursors can respond to physiologic or pathologic stimuli, expressing activated myofibroblast or lipocyte phenotypes with distinct patterns of cytoskeleton structure, metabolic function, and interaction with the tissue environment.Key words: intermediate filaments, desmin, glial fibrillary acidic protein, GFAP, hepatic stellate cells, liver.
Yap1 overproduction restores arsenite resistance to the ABC transporter deficient mutantycf1by activatingACR3expression
Authors: Bouganim Nathaniel , David Jocelyn , Wysocki Robert , Ramotar Dindial
Published: April 2011

Ycf1 and Acr3 are transporters that have been previously shown to protect Saccharomyces cerevisiae cells from the toxic effects of arsenite. Ycf1 and Acr3 are positively regulated by distinct, but related bZIP transcriptional activators, Yap1 and Yap8, respectively. In this study, we show that overexpression of Yap1 complemented the arsenite hypersensitivity of the ycf1 null mutant, but only if the ACR3 gene is functional. We further show that the expression of either an ACR3-lacZ promoter fusion reporter or the endogenous ACR3 gene was stimulated by the overproduction of Yap1 upon exposure to arsenite. These data suggest that Yap1 confers arsenite resistance to the ycf1 null mutant by activating expression of the Yap8-dependent target gene, ACR3. Our data also show Yap8-dependent ACR3-lacZ expression was greatly stimulated by arsenite in a dose-dependent manner in the parental strain. However, overproduction of Yap1 in the parental strain severely limited dose-dependent activation of the reporter by arsenite. We conclude that Yap1 may compete with Yap8 for binding to the ACR3 promoter, but is unable to act as a potent activator.Key words: arsenite, ABC transporters, AP-1 factors, overproduction, element, yeast.
Neurofilament phosphorylation
Authors: Pant Harish C. , Veeranna
Published: April 2011

Neurofilament proteins (NFPs) are highly phosphorylated molecules in the axonal compartment of the adult nervous system. The phosphorylation of NFP is considered an important determinant of filament caliber, plasticity, and stability. This process reflects the function of NFs during the lifetime of a neuron from differentiation in the embryo through long-term activity in the adult until aging and environmental insult leads to pathology and ultimately death. NF function is modulated by phosphorylation–dephosphorylation in each of these diverse neuronal states. In this review, we have summarized some of these properties of NFP in adult nervous tissue, mostly from work in our own laboratory. Identification of sites phosphorylated in vivo in high molecular weight NFP (NF-H) and properties of NF-associated and neural-specific kinases phosphorylating specific sites in NFP are described. A model to explain the role of NF phosphorylation in determining filament caliber, plasticity, and stability is proposed.Key words: neurofilament proteins, phosphorylation, kinases, phosphatases, regulators, inhibitors, multimesic complex, domains.
Modulation of actin dynamics during stress and physiological stimulation by a signaling pathway involving p38 MAP kinase and heat-shock protein 27
Authors: Landry Jacques , Huot Jacques
Published: April 2011

HSP27, like other proteins of the heat-shock protein family, accumulates to high levels after exposure of cells to a short period of hyperthermia and contributes to the development of a transient state of thermoresistance. In vitro, HSP27 behaves as an actin cap-binding protein and can inhibit actin polymerization. In vivo, the protective function of HSP27 is exerted mainly at the level of the microfilaments and appears as an extension of a normal function of the protein. This function is regulated by phosphorylation in a mitogen- and stress-sensitive signaling pathway involving the newly characterized p38 MAP kinase. The phosphorylation-modulated function of HSP27 can contribute to agonist-induced reorganization of the actin cytoskeleton and, in the case of stress activation, provides an actin-based adaptive response of cells to the new environmental conditions.Key words: actin cytoskeleton, heat-shock protein, HSP27, signal transduction, stress response, mitogen activated protein kinases.
Calreticulin, a component of the endoplasmic reticulum and of cytotoxic lymphocyte granules, regulates perforin-mediated lysis in the hemolytic model system
Authors: Fraser Stephanie A , Michalak Marek , Welch William H , Hudig Dorothy
Published: April 2011

Cytotoxic lymphocytes kill virally infected cells with specialized cytotoxic granules containing perforin, a protein that forms toxic pores in the target cell membrane. These specialized cytotoxic granules also contain calreticulin, an endoplasmic reticulum chaperone protein. The calcium-independent association of perforin and calreticulin prompted our evaluation of calreticulin's potential to function as a regulatory molecule that protects cytotoxic lymphocytes from their own perforin. We report here that 10-7 M calreticulin blocked perforin-mediated lysis in the hemolytic model system using erythrocytes as targets. Previously, we found that millimolar levels of calcium in the hemolytic assays dissociate high-affinity perforin-calreticulin complexes, which makes it unlikely that perforin associates with calreticulin in solution when hemolysis is blocked. Calreticulin may affect perforin at the erythrocyte membrane. We observed calcium-dependent binding of calreticulin to erythrocyte membranes with a Kd of 2.7 × 10-7 M and a saturation average of 105 molecules calreticulin per erythrocyte. At concentrations that blocked hemolysis, calreticulin occupied many of the calreticulin membrane-binding sites and was in molar excess of perforin. These observations open the possibilities that membrane-bound calreticulin prevents hydrophobic entry of perforin into membranes and (or) prevents perforin from assembling into polyperforin pores.Key words: calreticulin, cytotoxicity, perforin.
Structural and functional consequences of an N-glycosylation mutation (HEMPAS) affecting human erythrocyte membrane glycoproteins
Authors: Kameh Homa , Landolt-Marticorena Carolina , Charuk Jeffrey HM , Schachter Harry , Reithmeier Reinhart AF
Published: April 2011

Band 3, the human erythrocyte anion exchanger (AE1), and the glucose transporter (GLUT1) proteins each contain a single site of N-glycosylation that is heterogeneously glycosylated. Lectin binding and enzymatic deglycosylation assays showed that the polylactosaminyl oligosaccharide structure of these glycoproteins was altered to a high mannose or hybrid glycan form in three patients with hereditary erythroblastic multinuclearity, with a positive acidified-serum lysis test (HEMPAS). Offspring from one of the HEMPAS patients had intermediate levels of polylactosaminyl oligosaccharide associated with AE1 and GLUT1, suggesting they may have been heterozygous for the genetic defect. The array of polylactosaminyl-containing glycoproteins present in EBV-transformed lymphoblasts derived from fresh blood of HEMPAS patients was similar to control lymphoblasts. HEMPAS lymphoblasts do not therefore express the defect in polylactosamine synthesis found in erythroid cells, indicating that lymphoid cells are not deficient in the processing enzymes or contain an alternative oligosaccharide processing pathway. Purified HEMPAS band 3 had an unaltered oligomeric structure but dimers aggregated more rapidly in detergent solution than normal band 3. The altered oligosaccharide structure did not affect the sensitivity of band 3 to proteolytic digestion in intact red cells but a greater amount of HEMPAS band 3 was associated with the cytoskeleton. The transport activities of AE1 and GLUT1 in HEMPAS erythrocytes were similar to those in normal controls. This shows that the HEMPAS glycosylation defect does not impair the functional accumulation of these two important erythrocyte membrane transporters even though it produces subtle structural changes in band 3 that result in its increased cytoskeletal interaction and self association in detergent solution.Key words: anion exchanger, band 3, erythrocyte, glycoprotein, HEMPAS.
Expression of a mammalian Na+/H+antiporter inSaccharomyces cerevisiae
Authors: Montero-Lomelí Mónica , Okorokova Façanha. Anna L
Published: April 2011

The basolateral Na+/H+antiporter (NHE) from LLC-PK1cells was expressed in Saccharomyces cerevisiae. Two different strategies were tested for expression. In the first, we used a yeast strain that contains a temperature-sensitive mutation in the SEC-6 gene, whose product is required for the fusion of secretory vesicles with the plasma membrane. This strain was transformed with a vector containing the coding region of the NHE1 isoform under control of a heat shock (HS) promoter (pYNHE1-HS). In the second strategy, we replaced the heat shock promoter from pYNHE1-HS with a galactose (GAL) promoter (pYNHEI-GAL) and transformed wild-type yeast. In both cases, Northern blots demonstrated a transcript that hybridized against a probe containing the membrane region of the exchanger. When an antibody against the last 40 amino acids of the carboxy-terminus of NHE1 was used for immuno-blots, a protein with a Mrof 73 000 was seen in total membranes from both yeast transformants. Subcellular fractionation revealed that NHE1 was expressed in the endoplasmic reticulum. In the case of the pYNHEI-GAL transformant, the 100 000 × g membrane pellet was reconstituted in phosphatidylcholine liposomes, and ethylisopropyl-amiloride-sensitive Na+/H+exchange was observed. These results have paved the way for expression of the Na+/H+exchanger in a genetically well-known microorganism.Key words: Na+/H+exchanger, NHE1, expression, yeast.
Hemangioblast development and regulation
Authors: Choi Kyunghee
Published: April 2011

Hematopoietic and endothelial cell lineages are the first to mature from mesoderm in the developing embryo. However, little is known about the molecular and (or) cellular events leading to hematopoietic commitment. The recent applications of technology utilizing gene targeted mice and the employment of many available in vitro systems have facilitated our understanding of hematopoietic establishment in the developing embryo. It is becoming clear that embryonic hematopoiesis occurs both in the extra-embryonic yolk sac and within the embryo proper in the mouse. The existence of the long pursued hemangioblast, a common progenitor of hematopoietic and endothelial cells, is now formally demonstrated. Based on this new information, many studies are being conducted to understand hematopoietic commitment events from mesoderm. In this review, we will first discuss the establishment of the hematopoietic system with special emphasis on the most primitive hematopoietic committed cells, the hemangioblast. We will then discuss mesoderm-inducing factors and their possible role in hematopoietic lineage commitment.Key words: hematopoietic commitment, hemangioblast, in vitro embryonic stem cell differentiation.
Molecular dissection of the human multidrug resistance P-glycoprotein
Authors: Loo Tip W , Clarke David M
Published: April 2011

The human multidrug resistance P-glycoprotein is an ATP-dependent drug pump that extrudes a broad range of cytotoxic agents from the cell. Its physiological role may be to protect the body from endogenous and exogenous cytotoxic agents. The protein has clinical importance because it contributes to the phenomenon of multidrug resistance during chemotherapy. In this review, we discuss some of the results obtained by using molecular biology and protein chemistry techniques for studying this important and intriguing protein.Key words: P-glycoprotein, ABC transporters, drug transport, dibromobimane, mutagenesis, disulfide crosslinking, metal-chelate chromatography, ATPase activity.
DNA wrapping in transcription initiation by RNA polymerase II
Authors: Coulombe Benoit
Published: April 2011

The DNA wrapping model of transcription stipulates that DNA bending and wrapping around RNA polymerase causes an unwinding of the DNA helix at the enzyme catalytic center that stimulates strand separation prior to initiation and during transcript elongation. Recent experiments with mammalian RNA polymerase II indicate the significance of DNA bending and wrapping in transcriptional mechanisms. These findings have important implications in our understanding of the role of the general transcription factors in transcriptional initiation and the mechanisms underlying transcriptional regulation.Key words: mRNA synthesis, transcription initiation, RNA polymerase II, DNA wrapping, general transcription factors.
SR protein kinases: the splice of life
Authors: Stojdl David F , Bell John C
Published: April 2011

The eukaryotic genome codes for most of its proteins though discontinuous coding sequences called exons, which are separated by noncoding sequences known as introns. Following transcription of a gene, these exons must be spliced precisely, removing the intervening introns, to form meaningful mature messenger RNAs (mRNA) that are transported to the cytoplasm and translated by the ribosomal machinery. To add yet another level of complexity, a process known as alternative splicing exists, whereby a single pre-mRNA can give rise to two or more mature mRNAs depending on the combination of exons spliced together. Alternative splicing of pre-mRNAs is emerging as an important mechanism for gene regulation in many organisms. The classic example of splicing as a regulator of genetic information during a developmental process is sex determination in Drosophila. The now well-characterized cascade of sex-specific alternative splicing events demonstrates nicely how the control of splice site selection during pre-mRNA processing can have a profound effect on the development of an organism. The factors involved in pre-mRNA splicing and alternative splice site selection have been the subject of active study in recent years. Emerging from these studies is a picture of regulation based on protein-protein, protein-RNA, and RNA-RNA interactions. How the interaction of the various splicing constituents is controlled, however, is still poorly understood. One of the mechanisms of regulation that has received attention recently is that of posttranslational phosphorylation. In the following article, we cite the evidence for a role of phosphorylation in constitutive and alternative splicing and discuss some of the recent information on the biochemistry and biology of the enzymes involved.Key words: phosphorylation, splicing, spliceosome, Clk kinases, SR proteins.
Kinetics of oxidation of serotonin by myeloperoxidase compounds I and II
Authors: Dunford H Brian , Hsuanyu Yuchiong
Published: April 2011

The oxidation of serotonin (5-hydroxytryptamine) by the myeloperoxidase intermediates compounds I and II was investigated by using transient-state spectral and kinetic measurements at 25.0 ± 0.1°C. Rapid scan spectra demonstrated that both compound I and compound II oxidize serotonin via one-electron processes. Rate constants for these reactions were determined using both sequential-mixing and single-mixing stopped-flow techniques. The second order rate constant obtained for the one-electron reduction of compound I to compound II by serotonin is (1.7 ± 0.1) × 107M-1·s-1, and that for compound II reduction to native enzyme is (1.4 ± 0.1) × 106M-1·s-1at pH 7.0. The maximum pH of the compound I reaction with serotonin occurs in the pH range 7.0-7.5. At neutral pH, the rate constant for myeloperoxidase compound I reacting with serotonin is an order of magnitude larger than for its reaction with chloride, (2.2 ± 0.2) × 106M-1·s-1. A direct competition of serotonin with chloride for myeloperoxidase compound I oxidation was observed. Our results suggest that serotonin may have a role to protect lipoproteins from oxidation and to prevent enzymes from inactivation caused by the potent oxidants HOCl and active oxygen species.Key words: serotonin oxidation, myeloperoxidase, chloride, competition of serotonin, blood platelets, neutrophils.
Free clathrin triskelions are required for the stability of clathrin-associated adaptor protein (AP-2) coated pit nucleation sites
Authors: Brown Claire M , Petersen Nils O
Published: April 2011

In this study image correlation spectroscopy was used to demonstrate the presence of two populations of clathrin in situ, on intact cells. In the periphery of the cell ~35% of the clathrin triskelions are free within the cytosol while ~65% are in large aggregates, presumably coated pits. Although endocytosis is inhibited at low temperature, free clathrin triskelions are still present and small AP-2 aggregates (of ~20 proteins), or coated pit nucleation sites, are still observed. Following hypertonic treatment, or cytoplasmic acidification, free clathrin triskelions within the cytosol are depleted and all of the clathrin becomes associated with the membrane. Under these conditions coated pit associated AP-2 remains while the smaller AP-2 aggregates, or coated pit nucleation sites, dissociate. This indicates that the stabilization of AP-2 coated pit nucleation sites requires the presence of free clathrin triskelions within the cytosol. Furthermore, this indicates that free clathrin is required for the early stages of coated pit formation and presumably the continuation of the clathrin-mediated endocytic process. We also provide indirect evidence that AP-2 binding to the membrane in coated pit nucleation sites may be regulated in part by binding to internalization-competent membrane receptors.Key words: adaptor protein (AP-2), clathrin, distribution, nucleation sites, endocytosis.
The phosphatase domains of LAR, CD45, and PTP1B: structural correlations with peptide-based inhibitors1
Authors: Glover Nicholas R , Tracey Alan S
Published: April 2011

PTP1B is a cytosolic protein tyrosine phosphatase that is a regulator of the kinase activity of the insulin receptor; the two protein tyrosine phosphatases LAR and CD45 are receptor type phosphatases crucially important to cell function. LAR also is involved in regulation of the insulin receptor while CD45 is critical for T-cell activation. Although LAR and CD45 are both transmembrane phosphatases, these enzymes manifest their phosphatase activity through a catalytic cytosolic domain. We have utilized X-ray coordinates of related phosphatases (RPTPalpha and RPTPµ) and comparative protein modeling to obtain molecular models of the D1 catalytic domains of CD45 and LAR. The models were tested using established protocols and found to be comparable to low resolution X-ray structures. The structure obtained for LAR was compared with the recently reported X-ray structure. Both the CD45-D1 and LAR-D1 structures were then compared to and contrasted with PTP1B. The active site of pockets of the three enzymes were found to be very uniform in structure and charge distribution. Also, the gross surface topology around the active site was found to be somewhat similar for the 3 phosphatases. However, there were significant differences in surface topology, and, more importantly, large changes in surface charge distribution. The differences between the surface features of these enzymes provide an explanation for the selectivity of inhibition by a number of peptides.
Interacting fermions in a two-dimensional trap and fractional exclusion statistics
Authors: Srivastava M K , Bhaduri R K , Law J , Murthy M.V.N.
Published: April 2011

We consider N fermions in a two-dimensional harmonic oscillator potential interacting with a very short-range repulsive pair-wise potential. The ground-state energy of this system is obtained by performing a Thomas-Fermi as well as a self-consistent Hartree-Fock calculation. The two results are shown to agree even for a small number of particles. We next use the finite-temperature Thomas-Fermi method to demonstrate that in the local density approximation, these interacting fermions are equivalent to a system of noninteracting particles obeying the Haldane-Wu fractional exclusion statistics. It is also shown that mapping onto a system of N noninteracting quasiparticles enables us to predict the energies of the ground and excited states of the N-body system.

PACS Nos.: 05.30-d, 73.20Dx
Molecular materials for micro-electronics
Authors: D'Iorio M
Published: April 2011

Molecular organic materials have had an illustrious past but the ability to deposit these as homogeneous thin films has rejuvenated the field and led to organic light-emitting diodes (OLEDs) and the development of an increasing number of high-performance polymers for nonlinear and electronic applications. Whereas the use of organic materials in micro-electronics was restricted to photoresists for patterning purposes, polymeric materials are coming of age as metallic interconnects, flexible substrates, insulators, and semiconductors in all-plastic electronics. The focus of this topical review will be on organic light-emitting devices with a discussion of the most recent developments in electronic devices.PACS Nos.: 85.60Jb, 78.60Fi, 78.55Kz, 78.66Qn, 73.61Ph, 72.80Le
Large-amplitude solitary waves in a relativistic nonisothermal plasma with warm ions
Authors: Roychoudhury R , Chatterjee P
Published: April 2011

Large amplitude solitary waves in a relativistic plasma with non-isothermal electrons and finite ion temperature are studied using Sagdeev's pseudopotential technique. It is found that there exists a critical value of beta, the ratio of the temperatures of the free and trapped electrons respectively, beyond which soliton solutions cease to exist. This critical value depends on other parameters. Also the relativistic effect and finite ion temperature restrict the region of existence of solitary waves. A small amplitude expansion of the pseudopotential is derived to find different kinds of solitary waves.PACS Nos.: 52.35 Fp, 52.35 Sb, 52.35 Tc
Overtone spectra of parahydrogen and orthodeuterium in the liquid phase
Authors: Mengel M , Winnewisser B P , Winnewisser M
Published: April 2011

We report the results of our observations of liquid parahydrogen in the mid-infrared and of liquid parahydrogen and orthodeuterium in their first and second overtone regions using a Bruker IFS 120 HR Fourier transform spectrometer. We have determined intensity parameters for individual absorption features where possible and indicate analogies between the spectrum of the liquid and the corresponding spectrum of the solid phase of the hydrogens. PACS Nos.: 33.20Ea, 33.70Fd, 67.90+z
Hiemenz magnetic flow of a non-Newtonian fluid of second grade with heat transfer
Authors: Attia H A
Published: April 2011

The steady laminar flow of an incompressible viscous electrically conducting non-Newtonian fluid of second grade impinging normal to a plane wall with heat transfer is investigated. An externally applied uniform magnetic field is applied normal to the wall, which is maintained at a constant temperature. A numerical solution for the governing momentum and energy equations is obtained. The effect of the characteristics of the non-Newtonian fluid and the magnetic field on both the flow and heat transfer is outlined.

PACS Nos.: 47.50 and 47.15
Harmonic superspace with four-dimensional Euclidean space
Authors: McKeon D.G.C.
Published: April 2011

The supersymmetry algebra in four-dimensional Euclidean space is formulated in such a way that an SU(2) invariance of the algebra is apparent. This leads to a superfield formalism for representations of the algebra that can be adapted to harmonic superspace. Models in this harmonic superspace are quite similar to N = 2 models in four-dimensional Minkowski space.PACS Nos.: 11.30Pb, 03.65Fd
Response above a plane-conducting earth to a pulsed vertical magnetic dipole at the surface
Authors: Abo-Seida O M , Bishay S T
Published: April 2011

A theoretical study of the pulsed electromagnetic radiation from a vertical magnetic dipole placed on a plane-conducting earth is presented. The application of a Laplace transformation in time and a Fourier transformation in the two orthogonal, horizontal, spatial components leads, under consideration of initial, boundary, and transition conditions, to an integral representation of the solution of the wave equation in frequency space. A modified Cagniard method is then used to derive closed-form expressions for the magnetic Hertz vector anywhere above the conducting earth. The method is used to perform numeric calculations of the magnetic Hertz vector, for different source-receiver distances, as well as different values of the earth's conductivity and permittivity.

PACS Nos.: 41.20Jb, 42.25Bs, 42.25Gy, 44.05+e
Surface light-induced drift resulting from inelastic scattering
Authors: Streater A D , Vaksman M A
Published: April 2011

Surface light-induced drift (SLID) is known to give rise to an extremely sensitive method of studying the state-specificity of gas-surface interactions. SLID occurs under velocity-selective laser excitation of a resonant gas whenever the scattering, trapping, or chemisorption by the cell walls are state dependent. In this brief report we derive and solve kinetic equations to analyze SLID arising in the case of inelastic scattering. We analyze both (a) the case when the coefficients describing the inelasticity of gas-surface quasi-specular scattering are state dependent, but are not dependent upon the velocity of the impinging particle, and (b) the case of velocity-dependent coefficients. Finally, we briefly outline the way to use this approach to interpret the results of possible experiments on SLID for atoms interacting with simple surfaces. PACS Nos.: 34.50Dy, 78.66-w
Rotational tomographic reconstruction of multiple in-line holograms
Authors: Shegelski M R.A. , Rothwell T A
Published: April 2011

Calculated electron in-line holograms, for the low-energy electron point source (LEEPS) microscope and based on scattering theory, give reconstructions that exhibit atomic resolution perpendicular to the optical axis. The depth resolution is not as sharp, and spurious peaks also result. We show that overall atomic resolution in the reconstruction of LEEPS in-line holograms can be obtained by using a tomographic approach. We examine a few reconstructions for holograms obtained by rotating the object about an axis passing through the object and parallel to the screen. We show that the reconstructions obtained from a small number of such "rotational tomographic holograms" can be combined in a manner such that almost all spurious peaks are eliminated and almost all atomic peaks are retained. The experimental implications of our theoretical results are discussed. PACS No.: 61.14Nm
Metallic rough surface retrieval from the specular intensity of scattered optical waves
Authors: Genchev Z D , Stoyanov H Y
Published: April 2011

We present a solution to the direct determination of the statistical parameters (root mean square deviation and correlation length), characterizing the profile of a random rough metallic surface with small slopes and heights, thus producing single scattering as well as a slight multiple scattering. This is done from the specular, coherent, component of the mean intensity of the optical waves scattered from the surface. In the frame of second-order perturbation theory, analytical expressions are derived for the specular component of the scattered radiation, and a retrieval of the rough surface parameters from the measured optical intensity is described. PACS Nos.: 02.25Fx, 03.40Kf, 41.20jb, 84.40
The interaction effect between two neutron absorbers using Wallace's method
Authors: Williams M MR
Published: April 2011

The dependence of Galanin's constant on fuel-plate separation is studied. Galanin's constant arises in the sourcesink method of lattice calculations and normally its value for an isolated fuel plate is used. Our calculations therefore enable the accuracy of that assumption to be assessed. To illustrate the problem, two absorbing and scattering plates, embedded in an infinite moderator and separated by a distance b are considered, with a source in the moderator region. The calculations are carried out via the integral form of the transport equation using the little-known method of Wallace. This approach enables the integral equation to be cast into a particularly useful form for evaluation of the flux and absorption rate in the plates. A variational method and a numerical solution provide results that show that there are significant deviations from the isolated plate approximation. Tables and figures are provided to illustrate these conclusions. In addition to the main result, we take the opportunity to show how Wallace's method can be used to simplify the transport equation for an infinitely reflected slab reactor. We also obtain results for the flux in a half-space in which there is a constant source, using a novel approximation procedure. Comparison with the exact result shows high accuracy.