959 resultados para Surface Organometallic Chemistry on Metals
Resumo:
Planktonic foraminifera are used to identify late Pliocene-Quaternary near surface water masses on the northeastern flank of Chatham Rise by comparison with faunas in core-tops east of New Zealand. In an overview study, distance measures, ordinations, and discriminant analysis are applied to 32 faunas from Site 1123B to identify similar faunas among 35 core-tops between 35 and 61°S east of New Zealand. Many Site 1123B faunas in the 2.72 myr interval sampled compare with those in core-tops on the northern side of Chatham Rise from a similar latitude, and are identified as transitional zone assemblages now associated with the subtropical gyre. This result is consistent with studies of late Quaternary planktonic foraminifera from this region and suggests that, typically, the Subtropical Front was locked to Chatham Rise through glacial and interglacial periods, at least back to the late Pliocene. However, a fauna at ca. 1.17 Ma compares with subpolar assemblages in core-tops between 44 and 48°S and identifies cooler surface water. Expectedly, closer sampling may reveal additional periods when southern water moved over the northeastern flank of Chatham Rise. Although the dominance of Globorotalia inflata, a species typical of the southern margin of subtropical gyres, is a principal feature of Site 1123B faunas, in a minority it is replaced as the most abundant species by dextral populations of Neogloboquadrina pachyderma, particularly about the time of the middle Pleistocene transition. Close analogues of these variant transitional assemblages are not present in core-tops about Chatham Rise but sediment trap and coretop data from other regions suggest that they identify high fertility in the mixed layer associated with upwelling or mixing of water masses. The proportion of sinistrally coiled Neogloboquadrina pachyderma rises to ca. 0.6 between ca. 2.45 and 2.57 Ma, soon after the intensification of Northern Hemisphere glaciation. Although the coiling data indicate subantarctic near surface water, the species remains rare. As the faunas retain their transitional zone character, only minor entrainment of subantarctic water may have occurred.
Resumo:
We measured the chemical composition of 100 samples from the 250-m sediment sequence retrieved from Ocean Drilling Program Site 1256 in the Guatemala Basin using a newly developed microwave-assisted acid digestion protocol followed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analysis. We compared these data gathered onshore to the results from the flux fusion prepared samples analyzed by shipboard ICP-AES during the leg and published in the Leg 206 Initial Reports volume, as well as to 35 randomly selected samples that were prepared by flux fusion at Boston University and analyzed by ICP-AES. Comparison of the newly developed acid digestion protocol to shore-based flux fusion demonstrates that the microwave-assisted acid technique yields a complete digestion, and because this procedure includes boric acid, it is safe for use with HF acid as boric acid neutralizes excess HF. The precision for nearly all elements in shore-based acid digestions is better than 3% of the measured values, including for elements such as Ni, Cr, and V, which are typically difficult to measure in biogenic-rich sediments. The shore-based flux fusions, while better than shipboard reported precision values (as expected), has precision better than 3% of their respective measured values for all major elements (Si, Al, Ti, Fe, Mn, Ca, Mg, Na, and K) and several trace elements (Ba and Sr). Results for P, Cr, Ni, V, Sc, and Zr are better than 5% of their measured values. Not only does the newly developed acid digestion provide better analytical results than the typical flux fusion method, the shore-based acid procedure also exhibits downhole lithologic and chemical characteristics similar to the shipboard flux fusion prepared results. These results confirm that the current shipboard methods are adequate for first-order geochemical interpretations and that the microwave-assisted acid digestion holds great potential to be the primary technique of preparing sediments on future Integrated Ocean Drilling Program expeditions.
Resumo:
The intestinal spirochaete Brachyspira pilosicoli causes colitis in a wide variety of host species. Little is known about the structure or protein constituents of the B. pilosicoli outer membrane (OM). To identify surface-exposed proteins in this species, membrane vesicles were isolated from B. pilosicoli strain 95-1000 cells by osmotic lysis in dH(2)O followed by isopycnic centrifugation in sucrose density gradients. The membrane vesicles were separated into a high-density fraction (HDMV; p = 1.18 g CM-3) and a low-density fraction (LDMV; rho=1.12 g cm(-3)). Both fractions were free of flagella and soluble protein contamination. LDMV contained predominantly OM markers (lipo-oligosaccharide and a 29 kDa B. pilosicoli OM protein) and was used as a source of antigens to produce mAbs. Five B. pilosicoli-specific mAbs reacting with proteins with molecular masses of 23, 24, 35, 61 and 79 kDa were characterized. The 23 kDa protein was only partially soluble in Triton X-114, whereas the 24 and 35 kDa proteins were enriched in the detergent phase, implying that they were integral membrane proteins or lipoproteins. All three proteins were localized to the B. pilosicoli OM by immunogold labelling using specific mAbs. The gene encoding the abundant, surface-exposed 23 kDa protein was identified by screening a B. pilosicoli 95-1000 genome library with the mAb and was expressed in Escherichia coli. Sequence analysis showed that it encoded a unique lipoprotein, designated BmpC. Recombinant BmpC partitioned predominantly in the OM fraction of E. coli strain SOLR. The mAb to BmpC was used to screen a collection of 13 genetically heterogeneous strains of B. pilosicoli isolated from five different host species. Interestingly, only strain 95-1000 was reactive with the mAb, indicating that either the surface-exposed epitope on BmpC is variable between strains or that the protein is restricted in its distribution within B. pilosicoli.
Resumo:
Infection of humans with the West Nile flavivirus principally occurs via tick and mosquito bites. Here, we document the expression of antigen processing and presentation molecules in West Nile virus (WNV)-infected human skin fibroblast (HFF) cells. Using a new Flavivirus-specific antibody, 4G4, we have analyzed cell surface human leukocyte antigen (HLA) expression on virus-infected cells at a single cell level. Using this approach, we show that West Nile Virus infection alters surface HLA expression on both infected HFF and neighboring uninfected HFF cells. Interestingly, increased surface HLA evident on infected HFF cultures is almost entirely due to virus-induced interferon (IFN)alpha/beta because IFNalpha/beta-neutralizing antibodies completely prevent increased surface HLA expression. In contrast, RT-PCR analysis indicates that WNV infection results in increased mRNAs for HLA-A, -B, and -C genes, and HLA-associated molecules low molecular weight polypeptide-2 (LMP-2) and transporter associated with antigen presentation-1 (TAP-1), but induction of these mRNAs is not diminished in HFF cells cultured with IFNalpha/beta-neutralizing antibodies. Taken together, these data support the idea that that both cytokine-dependent and cytokine-independent mechanisms account for WNV-induced HLA expression in human skin fibroblasts. (C) 2004 Elsevier Inc. All rights reserved.
Resumo:
Objectives: In this paper, we present a unified electrodynamic heart model that permits simulations of the body surface potentials generated by the heart in motion. The inclusion of motion in the heart model significantly improves the accuracy of the simulated body surface potentials and therefore also the 12-lead ECG. Methods: The key step is to construct an electromechanical heart model. The cardiac excitation propagation is simulated by an electrical heart model, and the resulting cardiac active forces are used to calculate the ventricular wall motion based on a mechanical model. The source-field point relative position changes during heart systole and diastole. These can be obtained, and then used to calculate body surface ECG based on the electrical heart-torso model. Results: An electromechanical biventricular heart model is constructed and a standard 12-lead ECG is simulated. Compared with a simulated ECG based on the static electrical heart model, the simulated ECG based on the dynamic heart model is more accordant with a clinically recorded ECG, especially for the ST segment and T wave of a V1-V6 lead ECG. For slight-degree myocardial ischemia ECG simulation, the ST segment and T wave changes can be observed from the simulated ECG based on a dynamic heart model, while the ST segment and T wave of simulated ECG based on a static heart model is almost unchanged when compared with a normal ECG. Conclusions: This study confirms the importance of the mechanical factor in the ECG simulation. The dynamic heart model could provide more accurate ECG simulation, especially for myocardial ischemia or infarction simulation, since the main ECG changes occur at the ST segment and T wave, which correspond with cardiac systole and diastole phases.
Resumo:
Endometriosis is a common gynaecological disease with symptoms of pelvic pain and infertility which affects 7-10% of women in their reproductive years. Activation of an oncogenic allele of Kirsten rat sarcoma viral oncogene homologue (KRAS) in the reproductive tract of mice resulted in the development of endometriosis. We hypothesized that variation in KRAS may influence risk of endometriosis in humans. Thirty tagSNPs spanning a region of 60.7 kb across the KRAS locus were genotyped using iPLEX chemistry on a MALDI-TOF MassARRAY platform in 959 endometriosis cases and 959 unrelated controls, and data were analysed for association with endometriosis. Genotypes were obtained for most individuals with a mean completion rate of 99.1%. We identified six haplotype blocks across the KRAS locus in our sample. There were no significant differences between cases and controls in the frequencies of individual single-nucleotide polymorphisms (SNPs) or haplotypes. We also developed a rapid method to screen for 11 common KRAS and BRAF mutations on the Sequenom MassARRAY system. The assay detected all mutations previously identified by direct sequencing in a panel of positive controls. No germline variants for KRAS or BRAF were detected. Our results demonstrate that any risk of endometriosis in women because of common variation in KRAS must be very small.
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Complete rare earth element (except Eu) and Y concentrations from the estuarine mixing zone (salinity =0.2 to 33) of Elimbah Creek, Queensland, Australia, were measured by quadrupole ICP-MS without preconcentration. High sampling density in the low salinity regime along with high quality data allow accurate tracing of the development of the typical marine rare earth element anomalies as well as Y/Ho fractionation. Over the entire estuary, the rare earth elements are strongly removed relative to a freshwater endmember (60-80% removal). This large overall removal occurs despite a strong remineralisation peak (190% for La, 130% for Y relative to the freshwater endmember) in the mid-salinity zone. Removal and remineralisation are accompanied by fractionation of the original (freshwater) rare earth element pattern, resulting in light rare earth element depletion. Estuarine fractionation generates a large positive La anomaly and a superchondritic Y/Ho ratio. Conversely, we observe no evidence to support the generation of the negative Ce anomaly in the estuary. With the exception of Ce, the typical marine rare earth element features can thus be attributed to estuarine mixing processes. The persistence of these features in hydrogenous sediments for at least 3.71 Ga highlights the importance of estuarine processes for marine chemistry on geological timescales. (c) 2005 Elsevier B.V. All rights reserved.
Resumo:
Background. Previous studies have identified no strong correlation between patients' height and tracheal length in anaesthetized patients. We have attempted to compare vocal cords-carina distance (VCD) in Chinese patients with the dimensions of five commonly used tracheal tubes. In addition, we attempted to find a surface anatomy measurement that would identify patients with 'short tracheas'. Methods. We measured VCD in 130 anaesthetized Chinese patients with a fibreoptic bronchoscope. Also measurements were obtained of the distal ends of five commonly used tracheal tubes. We undertook various surface anatomy measurements on the patients' chest and neck region to predict those patients with short tracheas. Results. VCD averaged 12.6 ((SD) 1.4) cm. In seven patients (5%) this distance was particularly short (between 8.8 and 10.4 cm). Many of the commonly used tracheal tubes would be placed close to or beyond the carina when the black intubation guide mark(s) is (are) at the level of the vocal cords. The VCD of
Resumo:
Este estudo busca investigar e compreender o fenômeno do envelhecimento da população no Brasil e também como as organizações estão se preparando para o envelhecimento da sua força de trabalho e para a gestão e transferência do conhecimento acumulado por seus colaboradores. A questão que norteia este estudo é: a transferência do conhecimento acontece entre as gerações antes da saída de pessoas para a aposentadoria? Para responder a estas questões, os referenciais foram os estudos de Ferrigno (2006), Davenport e Prusak (2003) e Takeuchi e Nonaka (2008) que apresentam categorias norteadoras para esta pesquisa, delimitada em duas empresas metalúrgicas no ABC Paulista e no Sindicato da categoria. A metodologia utilizada neste estudo foi qualitativa, com pesquisa exploratório-descritiva, por meio da aplicação de entrevista semiestruturada. De acordo com a pesquisa realizada constatou-se que as organizações compreendem a importância de lidarem com o processo de envelhecimento da força de trabalho em seu contexto organizacional e que é preciso estabelecer práticas para disseminação do conhecimento gerado por seu principal ativo (seu colaborador com maior idade) e promover a relação de aprendizagem intergeracional e a transferência do conhecimento acumulado.
Resumo:
A chip shooter machine for electronic component assembly has a movable feeder carrier, a movable X–Y table carrying a printed circuit board (PCB), and a rotary turret with multiple assembly heads. This paper presents a hybrid genetic algorithm (HGA) to optimize the sequence of component placements and the arrangement of component types to feeders simultaneously for a chip shooter machine, that is, the component scheduling problem. The objective of the problem is to minimize the total assembly time. The GA developed in the paper hybridizes different search heuristics including the nearest-neighbor heuristic, the 2-opt heuristic, and an iterated swap procedure, which is a new improved heuristic. Compared with the results obtained by other researchers, the performance of the HGA is superior in terms of the assembly time. Scope and purpose When assembling the surface mount components on a PCB, it is necessary to obtain the optimal sequence of component placements and the best arrangement of component types to feeders simultaneously in order to minimize the total assembly time. Since it is very difficult to obtain the optimality, a GA hybridized with several search heuristics is developed. The type of machines being studied is the chip shooter machine. This paper compares the algorithm with a simple GA. It shows that the performance of the algorithm is superior to that of the simple GA in terms of the total assembly time.
Resumo:
The electrical and optical characteristics of a cylindrical alumina insulator (94% Al203) have been measured under ultra-high vacuum (P < 10-8 mBar) conditions. A high-resolution CCD camera was used to make real-time optical recordings of DC prebreakdown luminescence from the ceramic, under conditions where DC current magnitudes were limited to less than 50μA. Two concentric metallized rings formed a pair of co-axial electrodes, on the end-face of the alumina tube; a third 'transparent' electrode was employed to study the effect of an orthogonal electric field upon the radial conduction processes within the metallized alumina specimen. The wavelength-spectra of the emitted light was quantified using a high-speed scanning monochromator and photo-multiplier tube detector. Concurrent electrical measurements were made alongside the recording of optical-emission images. An observed time-dependence of the photon-emission is correlated with a time-variation observed in the DC current-voltage characteristics of the alumina. Optical images were also recorded of pulsed-field surface-flashover events on the alumina ceramic. An intensified high-speed video technique provided 1ms frames of surface-flashover events, whilst 100ns frames were achieved using an ultra high-speed fast-framing camera. By coupling this fast-frame camera to a digital storage oscilloscope, it was possible to establish a temporal correlation between the application of a voltage-pulse to the ceramic and the evolution of photonic emissions from the subsequent surface-flashover event. The electro-optical DC prebreakdown characteristics of the alumina are discussed in terms of solid-state photon-emission processes, that are believed to arise from radiative electron-recombination at vacancy-defects and substitutional impurity centres within the surface-layers of the ceramic. The physical nature of vacancy-defects within an alumina dielectric is extensively explored, with a particular focus placed upon the trapped electron energy-levels that may be present at these defect centres. Finally, consideration is given to the practical application of alumina in the trigger-ceramic of a sealed triggered vacuum gap (TVG) switch. For this purpose, a physical model describing the initiation of electrical breakdown within the TVG regime is proposed, and is based upon the explosive destabilisation of trapped charge within the alumina ceramic, triggering the onset of surface-flashover along the insulator. In the main-gap prebreakdown phase, it is suggested that the electrical-breakdown of the TVG is initiated by the low-field 'stripping' of prebreakdown electrons from vacancy-defects in the ceramic under the influence of an orthogonal main-gap electric field.