Performance Comparison of Different Flat Plate Solar Collectors by Means of the Entropy Generation Rate Using Computational Fluid Dynamics.

In this work, a numerical analysis of three different flat plate solar collectors was conducted using their entropy generation rates. Specifically, the Computational Fluid Dynamics (CFD) technique was used to compare the detailed performance of conventional and zigzag tube geometries of flat plate solar collectors (FPCs) in terms of their entropy generation rates. The effects of fluid viscosity, heat transfer, and heat loss of the flat plate solar collectors were considered for the local and global entropy generation rate analyses. Variations on the inlet volumetric flow rate of the FPCs from 1.0 to 9.0 L/min were simulated under the average solar radiation for one year in the state of Guanajuato, Mexico. The results illustrate and discuss the temperatures, pressures, and global entropy generation rates for volumetric flow variations. The velocity, temperature, and pressure distributions and the maps of the local entropy generation rates inside the collectors are presented and analyzed for the case with a flow rate of 3.0 L/min. These results demonstrate that the zigzag geometries achieved higher outlet temperatures and greater entropy generation rates than the conventional geometry for all the volumetric flow rates considered.

Housing accessibility problems for people with Parkinson's disease.

OBJECTIVES: Promoting accessible housing for all citizens is high on the political agenda. Knowledge is, however, limited regarding housing accessibility problems for people with Parkinson's disease (PD). The objectives were to investigate housing accessibility problems among people with PD at different stages of disease severity and to analyze the potential impact of improved functional ability on accessibility problems. MATERIALS AND METHODS: The study included 253 participants with PD (61% men; mean age 70 years). Disease severity was assessed by the Hoehn and Yahr (HY) I-V stages: HY I, n=50; II, n=73, III, n=66; IV-V, n=64. Using the Housing Enabler (HE) instrument, accessibility problems were investigated by combining assessments of the person's functional capacity with assessments of physical barriers in the housing environment into a person-environment fit measure (HE-score). To analyze potential impact of improved functional ability on housing accessibility problems, data simulation was applied. RESULTS: HE-scores differed significantly (P<.001) in relation to HY stages. Overall balance problems explained 22% and walking devices 17% of the HE-scores, whereas environmental barriers contributed to a lesser extent. The environmental barriers generating the most HE-scores were "no grab bar at shower/bath/toilet" and "wall-mounted cupboards and shelves placed high". A simulation of improved balance significantly (P<.001) lowered the HE-scores in all HY stages. CONCLUSIONS: The results suggest that actions targeting balance problems and dependence on walking devices have the greatest potential for reducing housing accessibility problems for people with PD. The study also details environmental barriers that need specific attention when providing housing adaptation services.

Rapid identification and discrimination of bacterial strains by laser induced breakdown spectroscopy and neural networks.

Identification and discrimination of bacterial strains of same species exhibiting resistance to antibiotics using laser induced breakdown spectroscopy (LIBS) and neural networks (NN) algorithm is reported. The method has been applied to identify 40 bacterial strains causing hospital acquired infections (HAI), i.e. Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, Salmonella typhimurium, Salmonella pullurum and Salmonella salamae. The strains analyzed included both isolated from clinical samples and constructed in laboratory that differ in mutations as a result of their resistance to one or more antibiotics. Small changes in the atomic composition of the bacterial strains, as a result of their mutations and genetic variations, were detected by the LIBS-NN methodology and led to their identification and classification. This is of utmost importance because solely identification of bacterial species is not sufficient for disease diagnosis and identification of the actual strain is also required. The proposed method was successfully able to discriminate strains of the same bacterial species. The optimized NN models provided reliable bacterial strain identification with an index of spectral correlation higher than 95% for the samples analyzed, showing the potential and effectiveness of the method to address the safety and social-cost HAI-related issue.

Identification and discrimination of bacterial strains by laser induced breakdown spectroscopy and neural networks.

A method based on laser induced breakdown spectroscopy (LIBS) and neural networks (NNs) has been developed and applied to the identification and discrimination of specific bacteria strains (Pseudomonas aeroginosa, Escherichia coli and Salmonella typhimurium). Instant identification of the samples is achieved using a spectral library, which was obtained by analysis using a single laser pulse of representative samples and treatment by neural networks. The samples used in this study were divided into three groups, which were prepared on three different days. The results obtained allow the identification of the bacteria tested with a certainty of over 95%, and show that only a difference between the bacteria can cause identification. Single-shot measurements were sufficient for clear identification of the bacterial strains studied. The method can be developed for automatic real time, fast, reliable and robust measurements and can be packaged in portable systems for non-specialist users.

[Oligomeric forms, functions and cellular localization of alpha-crystallin type protein from Acholeplasma laidlawii].

Alpha-Crystallin type heat shock protein (alpha-HSP) IbpA from Acholeplasma laidlawii was expressed in Escherichia coil and isolated from cell extract on Ni-sepharose column. Recombinant IbpA, like other alpha-HSPs, spontaneously formed oligomeres in vitro. High resolution electron microscopy revealed regular structures with 15 nm in diameter. Evaluation of molecular mass of IbpA oligomers was performed by gel filtration. Most of oligomers consist of 24 subunits. Recombinant IbpA prevents heat denaturation of soluble proteins in cell extract of E. coli and displays a mild positive effect on thermotolerance of E. coli cells during severe heat shock. We investigated a localization of IbpA in A. laidlawii cell by immunocytochemistry. We suppose that IbpA may protect various intracellular structures from damage during heat shock.

[Cloning and expression of the Mycoplasma hominis ftsZ for a cell division protein]. / Klonirovanie i ékspressiia gena, kodiruiushchego belok deleniia mikoplazmy (ftsZ, Mycoplasma hominis).

A Mycoplasma hominis chromosomal fragment containing the full-length ftsZ gene was cloned and sequenced. Natural expression of this gene was demonstrated by reverse transcription-polymerase chain reaction (RT-PCR) with total RNA. The M. hominis FtsZ protein was shown to differ substantially from its counterparts of two other Mycoplasma species, M. genitalium and M. pneumoniae. The possibility of M. hominis ftsZ expression in Escherichia coli was demonstrated with several bacterial strains. The M. hominis FtsZ protein was isolated from E. coli cells transformed with recombinant plasmids carrying the M. hominis ftsZ gene. Complementation between the E. coli and M. hominis FtsZ proteins was observed in transformants.

Control de la anemia en hemodiálisis. Base de datos EuCliD (European Clinical Database) en España / Anaemia management in haemodialysis. EuCliD® database in Spain

Nos planteamos evaluar el manejo de la anemia en los centros Fresenius Medical Care de España. Presentamos datos de 4.426 pacientes en hemodiálisis prevalentes en el año 2001 recogidos en la base de datos European Clinical Database (EuCliD®). Evaluamos mediante el índice de respuesta a la Eritropoyetina (IRE): cociente entre dosis de Eritropoyetina (UI/kg de peso/semana) y Hemoglobina (g/dl), la respuesta a la eritropoyetina en función de diferentes variables. Comparamos nuestros resultados con los aparecidos en el estudio ESAM2.El 70 por ciento de la población alcanza una hemoglobina superior a 11 g/dl utilizando dosis de eritropoyetina de 111,9 UI/kg de peso/semana (n = 3.700; SD 74,9).Resultado similar al medido al inicio del ESAM2 donde es del 65 por ciento. La dosis empleada de eritropoyetina es ligeramente superior a la utilizada en el ESAM2 (111,9 UI/kg de peso/semana y 105,5 UI/kg de peso/semana respectivamente), quizá relacionado con la menor proporción de pacientes en tratamiento por vía subcutánea (70 por ciento frente a 79 por ciento) y con la inclusión de pacientes en diálisis peritoneal dentro del estudio ESAM2. Efectivamente según nuestros datos, el IRE es mayor en los pacientes que reciben tratamiento por vía intravenosa en comparación con la vía subcutánea (11,66 y 9,6 respectivamente p 20 por ciento (135 UI/kg de peso/semana frente a 110,52 UI/kg de peso/semana respectivamente, p < 0,005).Observamos también que variables relacionados de forma directa o indirecta con la inflamación como la elevación de proteína C reactiva, la hipoalbuminemia o la elevación de la ferritina, presentan peor respuesta a la eritropoyetina (AU)

Characterization of the Mycoplasma hominis ftsZ gene and its sequence variability in mycoplasma clinical isolates.

We cloned and sequenced Mycoplasma hominis chromosomal fragment containing ftsZ gene. The wild-type expression of the gene was shown at RNA level by reverse transcription followed by PCR amplification. We revealed that M. hominis FtsZ had a comparatively low similarity to proteins of Mycoplasma genitalium and Mycoplasma pneumoniae. After full ftsZ gene sequencing for 14 clinical isolates of M. hominis, single-nucleotide substitutions were found in 21 positions, 6 of them being common for almost all isolates. This ftsZ gene polymorphism may be used for subtyping of M. hominis in clinical samples. Expression of the M. hominis ftsZ gene in different Escherichia coli strains was also demonstrated, and M. hominis FtsZ protein was purified from E. coli cells transformed with recombinant expression plasmid. Complementation between the M. hominis FtsZ and E. coli FtsZ could be shown. The comparison of FtsZ protein structures may also be used for investigation of bacterial phylogenetic relationships.

[Anemia management in haemodialysis. EuCliD database in Spain]. / Control de la anemia en hemodiálisis. Base de datos EuCliD (European Clinical Database) en España.

We present the results on Anaemia Management in Fresenius Medical Care Spain dialysis centres as reported by EuCliD (European Clinical Database), evaluating a population of 4,426 patients treated in Spain during the year 2001. To analyse the erythropoietin dose and the haemoglobin levels we divided the population in two groups according to the time with dialysis treatment: patients treated less than six months and patients between six months, and four years on therapy. We compared our results with the evidence based recommendations Guidelines: the European Best Practice Guidelines (EBPG) and the US National Kidney Foundation (NKF-K/DOQI). We also compared our results with those presented by the ESAM2 on 2,618 patients on dialysis in Spain carried out in the second half of the year 2000. We observed that 70% of the population reaches an haemoglobin value higher that 11 g/dl, with a mean erythropoietin (rHu-EPO) dose of 111.9 Ul/kg weight/week (n = 3,700; SD 74.9). However, for those patients on treatment for less than six months, the mean Haemoglobin only reaches 10.65 g/dl (n = 222; SD 1.4). The rHu-EPO was administrated subcutaneously in 70.2% of the patients. About the iron therapy, 86% of the patients received iron treatment and the administration route was intravenous in 93% of the population. The ferritin levels were below 100 micrograms/dl in 10% of the patients and 26.4% showed a transferrin saturation index (TSAT) below 20%. The erythropoieting resistance index (ERI), as rHu-EPO/haemoglobin, has been used to evaluate the response to rHu-Epo, according to different variables. It was observed that the following factors lead to a higher rHu-EPO resistance: intravenous rHu-EPO as administration route, the presence of hypoalbuminemia, increase of protein C reactive, Transferrin saturation below 20% and starting dialysis during the last six months.

Analysis of the O-antigen chain length distribution during extracellular and intracellular growth of Shigella flexneri.

This study has established that there were no changes in the general structure of LPS of Shigella flexneri M90T either when the bacteria grew free in the cytoplasm of the eucaryotic host cell or during extracellular growth in liquid LB medium at 37 degrees C. In both cases there was a similar bi-modal O-antigen chain length distribution with the mean modal values between 1 and 2, and between 11 and 14 subunits. This suggests that the intracellular localization is not a significant stimulus perceived by Shigella to regulate the length of its O-side chains. However, when the bacteria grew under extracellular conditions (liquid medium) at 30 degrees C, even though there were no changes in the modal values, the pattern of the O-antigen chain length distribution of LPS was different, with an increase in the amount of the long chains relative to the short chains.

Biological cost of AmpC production for Salmonella enterica serotype Typhimurium.

Chromosomally mediated AmpC-type beta-lactamases are frequently found among Enterobacteriaceae. Hyperproduction of AmpC beta-lactamase results in high-level resistance to beta-lactam antibiotics. One striking feature of Salmonella is the absence of the structural ampC gene, encoding AmpC beta-lactamase, in contrast with other members in the Enterobacteriaceae family, such as Escherichia, Citrobacter, or Enterobacter. The horizontal acquisition of ampC genes is one of the causes of the increased resistance to extended-spectrum cephalosporins and beta-lactamase inhibitors among gram-negative rods. Nevertheless, despite the high number of beta-lactam-resistant Salmonella isolates so far described, only two strains expressing resistance to cephalosporin and beta-lactamase inhibitors which is mediated by AmpC-type enzymes have been found. In this work, data are provided which support the possibility that the maintenance and expression of the ampC gene may represent an unbearable cost for Salmonella in terms of reduction of some of its lifestyle attributes, such as growth rate and invasiveness. The deleterious AmpC burden can be eliminated by decreasing the production of AmpC when both the regulatory gene, ampR, and ampC are present in Salmonella. Thus, it is suggested that the two genes have to be acquired together by Salmonella, leading to an inducible beta-lactam resistance phenotype. AmpC synthesis did not produce major variations in the peptidoglycan composition of Salmonella.

The catalytic, glycosyl transferase and acyl transferase modules of the cell wall peptidoglycan-polymerizing penicillin-binding protein 1b of Escherichia coli.

The penicillin-binding protein (PBP) 1b of Escherichia coli catalyses the assembly of lipid-transported N-acetyl glucosaminyl-beta-1, 4-N-acetylmuramoyl-L-alanyl-gamma-D-glutamyl-(L)-meso-diaminopimelyl+ ++- (L)-D-alanyl-D-alanine disaccharide pentapeptide units into polymeric peptidoglycan. These units are phosphodiester linked, at C1 of muramic acid, to a C55 undecaprenyl carrier. PBP1b has been purified in the form of His tag (M46-N844) PBP1bgamma. This derivative provides the host cell in which it is produced with a functional wall peptidoglycan. His tag (M46-N844) PBP1bgamma possesses an amino-terminal hydrophobic segment, which serves as transmembrane spanner of the native PBP. This segment is linked, via an congruent with 100-amino-acid insert, to a D198-G435 glycosyl transferase module that possesses the five motifs characteristic of the PBPs of class A. In in vitro assays, the glycosyl transferase of the PBP catalyses the synthesis of linear glycan chains from the lipid carrier with an efficiency of congruent with 39 000 M-1 s-1. Glu-233, of motif 1, is central to the catalysed reaction. It is proposed that the Glu-233 gamma-COOH donates its proton to the oxygen atom of the scissile phosphoester bond of the lipid carrier, leading to the formation of an oxocarbonium cation, which then undergoes attack by the 4-OH group of a nucleophile N-acetylglucosamine. Asp-234 of motif 1 or Glu-290 of motif 3 could be involved in the stabilization of the oxocarbonium cation and the activation of the 4-OH group of the N-acetylglucosamine. In turn, Tyr-310 of motif 4 is an important component of the amino acid sequence-folding information. The glycosyl transferase module of PBP1b, the lysozymes and the lytic transglycosylase Slt70 have much the same catalytic machinery. They might be members of the same superfamily. The glycosyl transferase module is linked, via a short junction site, to the amino end of a Q447-N844 acyl transferase module, which possesses the catalytic centre-defining motifs of the penicilloyl serine transferases superfamily. In in vitro assays with the lipid precursor and in the presence of penicillin at concentrations sufficient to derivatize the active-site serine 510 of the acyl transferase, the rate of glycan chain synthesis is unmodified, showing that the functioning of the glycosyl transferase is acyl transferase independent. In the absence of penicillin, the products of the Ser-510-assisted double-proton shuttle are glycan strands substituted by cross-linked tetrapeptide-pentapeptide and tetrapeptide-tetrapeptide dimers and uncross-linked pentapeptide and tetrapeptide monomers. The acyl transferase of the PBP also catalyses aminolysis and hydrolysis of properly structured thiolesters, but it lacks activity on D-alanyl-D-alanine-terminated peptides. This substrate specificity suggests that carbonyl donor activity requires the attachment of the pentapeptides to the glycan chains made by the glycosyl transferase, and it implies that one and the same PBP molecule catalyses transglycosylation and peptide cross-linking in a sequential manner. Attempts to produce truncated forms of the PBP lead to the conclusion that the multimodular polypeptide chain behaves as an integrated folding entity during PBP1b biogenesis.

mraW, an essential gene at the dcw cluster of Escherichia coli codes for a cytoplasmic protein with methyltransferase activity.

Three new open reading frames, mraZ, mraW and mraR (also called ftsL), were revealed by DNA sequencing immediately upstream of gene pbpB in the dcw cluster of Escherichia coli. We have found that mraW and mraZ are active genes, coding for two proteins with relative molecular masses of 34 800 and 17 300, respectively. MraW is a cytoplasmic protein that under overproduction condition is also loosely bound to the membrane. Soluble MraW was purified up to 90% by a single high performance electrophoresis (HPEC) step from an extract of an overproducing strain. The protein exhibits a S-adenosyl-dependent methyltransferase activity on membrane-located substrates.

Characterization of Acholeplasma laidlawii ftsZ gene and its gene product.

The ftsZ gene was found among representatives of all bacterial groups. FtsZ protein is an essential component of cell division ring. Contraction of this cytoskeleton-like ring is believed to be the universal way of bacterial division. Acholeplasma laidlawii possesses all features of the minimal mycoplasma cell and some traits of cell-wall bacteria and seems to be a promising object for study of basic principles of the bacterial division process. We cloned an A. laidlawii chromosomal fragment containing ftsZ gene and two flanking orf which also were identified. A. laidlawii FtsZ protein has been determined with polyclonal antibodies raised in rabbit. It was demonstrated that ftsZ gene of A. laidlawii could be expressed in E. coli cells. We also revealed that A. laidlawii FtsZ had a low similarity to proteins of Mycoplasma genitalium and M. pneumoniae. The comparison of FtsZ structures may be used for investigation of bacterial phylogenetic relations.

Cell division inhibition in Salmonella typhimurium histidine-constitutive strains: an ftsI-like defect in the presence of wild-type penicillin-binding protein 3 levels.

Histidine-constitutive (Hisc) strains of Salmonella typhimurium undergo cell division inhibition in the presence of high concentrations of a metabolizable carbon source. Filaments formed by Hisc strains show constrictions and contain evenly spaced nucleoids, suggesting a defect in septum formation. Inhibitors of penicillin-binding protein 3 (PBP3) induce a filamentation pattern identical to that of Hisc strains. However, the Hisc septation defect is caused neither by reduced PBP3 synthesis nor by reduced PBP3 activity. Gross modifications of peptidoglycan composition are also ruled out. D-Cycloserine, an inhibitor of the soluble pathway producing peptidoglycan precursors, causes phenotypic suppression of filamentation, suggesting that the septation defect of Hisc strains may be caused by scarcity of PBP3 substrate.

Regulation of transcription of cell division genes in the Escherichia coli dcw cluster.

The Escherichia coli dcw cluster contains cell division genes, such as the phylogenetically ubiquitous ftsZ, and genes involved in peptidoglycan synthesis. Transcription in the cluster proceeds in the same direction as the progress of the replication fork along the chromosome. Regulation is exerted at the transcriptional and post-transcriptional levels. The absence of transcriptional termination signals may, in principle, allow extension of the transcripts initiated at the up-stream promoter (mraZ1p) even to the furthest down-stream gene (envA). Complementation tests suggest that they extend into ftsW in the central part of the cluster. In addition, the cluster contains other promoters individually regulated by cis- and trans-acting signals. Dissociation of the expression of the ftsZ gene, located after ftsQ and A near the 3' end of the cluster, from its natural regulatory signals leads to an alteration in the physiology of cell division. The complexities observed in the regulation of gene expression in the cluster may then have an important biological role. Among them, LexA-binding SOS boxes have been found at the 5' end of the cluster, preceding promoters which direct the expression of ftsI (coding for PBP3, the penicillin-binding protein involved in septum formation). A gearbox promoter, ftsQ1p, forms part of the signals regulating the transcription of ftsQ, A and Z. It is an inversely growth-dependent mechanism driven by RNA polymerase containing sigma s, the factor involved in the expression of stationary phase-specific genes. Although the dcw cluster is conserved to a different extent in a variety of bacteria, the regulation of gene expression, the presence or absence of individual genes, and even the essentiality of some of them, show variations in the phylogenetic scale which may reflect adaptation to specific life cycles.

Effects of temperature on cuticular lipids and water balance in a desert Drosophila: is thermal acclimation beneficial?

The desert fruit fly Drosophila mojavensis experiences environmental conditions of high temperature and low humidity. To understand the physiological mechanisms allowing these small insects to survive in such stressful conditions, we studied the effects of thermal acclimation on cuticular lipids and rates of water loss of adult D. mojavensis. Mean hydrocarbon chain length increased at higher temperatures, but cuticular lipid melting temperature (Tm) did not. Lipid quantity doubled in the first 14 days of adult life, but was unaffected by acclimation temperature. Despite these changes in cuticular properties, organismal rates of water loss were unaffected by either acclimation temperature or age. Owing to the smaller body size of warm-acclimated flies, D. mojavensis reared for 14 days at 33 degrees C lost water more rapidly on a mass-specific basis than flies acclimated to 25 degrees C or 17 degrees C. Thus, apparently adaptive changes in cuticular lipids do not necessarily result in reduced rates of water loss. Avoidance of high temperatures and desiccating conditions is more likely to contribute to survival in nature than changes in water balance mediated by surface lipids.

Fetal fibronectin: a new tool for the prediction of successful induction of labor.

OBJECTIVE: The Bishop score is the only available tool for predicting successful labor induction. Vaginal fetal fibronectin has been shown to predict which patients will enter labor spontaneously, usually within 2 weeks. This study was designed to determine whether fetal fibronectin can also predict the success of labor induction. STUDY DESIGN: Term patients undergoing labor induction had a single swab from the vagina tested for fetal fibronectin before initiation of cervical ripening or oxytocin. The swab was tested with a blinded qualitative immunoassay for fetal fibronectin (positive > or = 50 ng/ml). RESULTS: Of the overall 160 subjects, 108 had a positive and 52 had a negative fetal fibronectin result. Patients with a positive result had a lower cesarean section rate (15% vs 27%, p = 0.05) and shorter intervals to delivery, including first dose of prostaglandin to delivery interval (21.3 vs 35.8 hours, p = 0.0001) and first stage of labor (14.8 vs 21.2 hours, p = 0.0009). These differences remain similar even in nulliparous women with Bishop scores < or = 5, with patients with positive results having statistically shorter intervals to delivery and similar differences in cesarean section rates (22% vs 35%), although this difference was not significant. In this subgroup more than half the patients in the negative results group (11/20) were undelivered after 24 hours and were judged to require a second dose of prostaglandin compared with only 2 of 53 in the group with positive results (p = 0.000001). By stepwise logistic regression analysis the predictive ability of a positive result for fetal fibronectin was found to be independent of the Bishop score. CONCLUSIONS: Vaginal fetal fibronectin appears to be an efficacious new test that independently predicts which patients will have shorter and easier inductions of labor and lower cesarean section rates, even nulliparous patients with low Bishop scores. This test has the potential for clinical utility and cost reduction.

dacD, an Escherichia coli gene encoding a novel penicillin-binding protein (PBP6b) with DD-carboxypeptidase activity.

In the course of a study of genes located at min 44 of the Escherichia coli genome, we identified an open reading frame with the capacity to encode a 43-kDa polypeptide whose predicted amino acid sequence is strikingly similar to those of the well-known DD-carboxipeptidases penicillin-binding proteins PBP5 and PBP6. The gene product was shown to bind [3H]benzylpenicillin and to have DD-carboxypeptidase activity on pentapeptide muropeptides in vivo. Therefore, we called the protein PBP6b and the gene dacD. As with other E. coli DD-carboxypeptidases, PBP6b is not essential for cell growth. A quadruple dacA dacB dacC dacD mutant was constructed and shown to grow as well as its isogenic wild-type strain, indicating that the loss of any known PBP-associated DD-carboxypeptidase activity is not deleterious for E. coli. We also identified the homologous gene of dacD in Salmonella typhimurium as one of the components of the previously described phsBCDEF gene cluster.