930 resultados para cool
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Mode of access: Internet.
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Mode of access: Internet.
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Mode of access: Internet.
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Cover title.
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Part II "2e geheel herziene druk" has subtitle: Determineertabellen en beschrijving der soorten.
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Understanding flow path connectivity within a geothermal reservoir is a critical component for efficiently producing sustained flow rates of hot fluids from the subsurface. I present a new approach for characterizing subsurface fracture connectivity that combines petrographic and cold cathodoluminescence (CL) microscopy with stable isotope analysis (δ18O and δ13C) and clumped isotope (Δ47) thermometry of fracture-filling calcite cements from a geothermal reservoir in northern Nevada. Calcite cement samples were derived from both drill cuttings and core samples taken at various depths from wells within the geothermal field. CL microscopy of some fracture filling cements shows banding parallel to the fracture walls as well as brecciation, indicating that the cements are related to fracture opening and fault slip. Variations in trace element composition indicated by the luminescence patterns reflect variations in the composition and source of fluids moving through the fractures as they opened episodically. Calcite δ13C and δ18O results also show significant variation among the sampled cements, reflecting multiple generations of fluids and fracture connectivity. Clumped isotope analyses performed on a subset of the cements analyzed for conventional δ18O and δ13C mostly show calcite growth temperatures around 150°C—above the current ambient rock temperature, which indicates a common temperature trend for the geothermal reservoir. However, calcite cements sampled along faults located within the well field showed both cold (18.7°C) and hot (226.1°C) temperatures. The anomalously cool temperature found along the fault, using estimates from clumped isotope thermometry, suggests a possible connection to surface waters for the geothermal source fluids for this system. This information may indicate that some of the faults within the well field are transporting meteoric water from the surface to be heated at depth, which then is circulated through a complex network of fractures and other faults.
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Thesis (Ph.D.)--University of Washington, 2016-06
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The terrestrial biogeography of Gondwana during Jurassic-Early Cretaceous times is poorly resolved, and the flora is usually considered to have been rather uniform. This is surprising given the size of Gondwana, which extended from the equator to the South Pole. Documenting Gondwanan terrestrial floristic provincialism in the Jurassic-Early Cretaceous times is important because it provides a historical biogeographic context in which to understand the tremendous evolutionary radiations that occurred during the mid-Cretaceous. In this paper, the distribution of Jurassic-Early Cretaceous fossil wood is analysed at generic level across the entire supercontinent. Specifically, wood assemblages are analyzed in terms of five climatic zones (summer wet, desert, winter wet, warm temperate, cool temperate) established on the basis of independent data. Results demonstrate that araucarian-like conifer wood was a dominant, cosmopolitan element, whereas other taxa showed a greater degree of provincialism. Indeed, several narrowly endemic morphogenera are recognizable from the data. Finally, comparisons with Laurasian wood assemblages indicate strong parallelism between the vegetation of both hemispheres. (C) 2004 Elsevier B.V. All rights reserved.
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The biology and phenology of the eriophyid mite, Floracarus perrepae Knihinicki and Boczek,a potential biological control agent of Lygodium microphyllum (Cav.) R. Br., was studied in its native range - Queensland, Australia. F. perrepae forms leaf roll galls oil tile subpinnae of L. microphyllum. It has a simple biology, with females and males produced throughout the year. Tile Population was female biased at 10.5 to 1. The immature development time was 8.9 ± 0.1 and 7.0 ± 0.1 days; adult longevity was 30.6 ± 1.6 and 19.4 ± 1.2 days and mean fecundity per female was 54.5 ± 3.2 and 38.5 ± 1.6 eggs at 21 and 26 ° C, all respectively. Field studies showed that tile mite was active year round, with populations peaking when temperatures were cool and soil moisture levels were highest. Two species of predatory mites, Tarsonemus sp. and a species of Tydeidae, along with the pathogen Hirsutella thompsonii, had significant effects oil all life stages of F. perrepae. Despite high levels of predators and the pathogen, F. perrepae caused consistent damage to L. microphyllum at all the field sites over the entire 2 years of the study.
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Following injury, it is inherently difficult to completely restore the biomechanical properties of ligaments. Relatively little is known about the cellular mechanisms controlling ligament healing. Numerous studies have implicated fibroblast growth factors (FGFs) as key molecules during the initiation of the cellular proliferation, differentiation, migration and matrix deposition that characterise wound healing. While current surgical emphasis concentrates on growth factor intervention, the role of their cognate receptors (FGFRs) has largely been overlooked. Following transection of the medial collateral ligament (MCL) in rabbits, we examined FGFR expression over a 14-day healing period. Using semiquantitative RT-PCR, we observed a significant upregulation in FGFR2 expression after 3 days. By 7 days post injury, FGFR2 expression fell to basal levels in line with those of FGFR1 and 3, both of which remained unaffected by surgical transection. These results demonstrate a role for FGFR2 in fibroblast and endothelial cell proliferation in damaged ligament, and suggest a window for FGF therapy.
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Although neural progenitor cells (NPCs) may provide a source of new neurons to alleviate neural trauma, little is known about their electrical properties as they differentiate. We have previously shown that single NPCs from the adult rat hippocampus can be cloned in the presence of heparan sulphate chains purified from the hippocampus, and that these cells can be pushed into a proliferative phenotype with the mitogen FGF2 [Chipperfield, H., Bedi, K.S., Cool, S.M. & Nurcombe, V. (2002) Int. J. Dev. Biol., 46, 661-670]. In this study, the active and passive electrical properties of both undifferentiated and differentiated adult hippocampal NPCs, from 0 to 12 days in vitro as single-cell preparations, were investigated. Sparsely plated, undifferentiated NPCs had a resting membrane potential of approximate to -90 mV and were electrically inexcitable. In > 70%, ATP and benzoylbenzoyl-ATP evoked an inward current and membrane depolarization, whereas acetylcholine, noradrenaline, glutamate and GABA had no detectable effect. In Fura-2-loaded undifferentiated NPCs, ATP and benzoylbenzoyl-ATP evoked a transient increase in the intracellular free Ca2+ concentration, which was dependent on extracellular Ca2+ and was inhibited reversibly by pyridoxalphosphate-6-azophenyl-2'-4'-disulphonic acid (PPADS), a P2 receptor antagonist. After differentiation, NPC-derived neurons became electrically excitable, expressing voltage-dependent TTX-sensitive Na+ channels, low- and high-voltage-activated Ca2+ channels and delayed-rectifier K+ channels. Differentiated cells also possessed functional glutamate, GABA, glycine and purinergic (P2X) receptors. Appearance of voltage-dependent and ligand-gated ion channels appears to be an important early step in the differentiation of NPCs.
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An enduring challenge for contemporary physics is to experimentally observe and control quantum behavior in macroscopic systems. We show that a single trapped atomic ion could be used to probe the quantum nature of a mesoscopic mechanical oscillator precooled to 4 K, and furthermore, to cool the oscillator with high efficiency to its quantum ground state. The proposed experiment could be performed using currently available technology.
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Adult neural progenitors have been isolated from diverse regions of the CNS using methods which primarily involve the enzymatic digestion of tissue pieces; however, interpretation of these experiments can be complicated by the loss of anatomical resolution during the isolation procedures. We have developed a novel, explant-based technique for the isolation of neural progenitors, Living CNS regions were sectioned using a vibratome and small, well-defined discs of tissue punched out. When Cultured. explants from the cortex, hippocampus, cerebellum, spinal cord, hypothalamus, and caudate nucleus all robustly gave rise to proliferating progenitors. These progenitors were similar in behaviour and morphology to previously characterised multipotent hippocampal progenitor lines. Clones from all regions examined could proliferate from single cells and give rise to secondary neurospheres at a low but consistent frequency. Immunostaining demonstrated that clonal cortical progenitors were able to differentiate into both neurons and glial cells, indicating their multipotent characteristics. These results demonstrate it is possible to isolate anatomically resolved adult neural progenitors from small amounts of tissue throughout the CNS, thus, providing a tool for investigating the frequency and characteristics of progenitor cells from different regions. (c) 2005 Elsevier B.V. All rights reserved.
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Studies have demonstrated that polymeric biomaterials have the potential to support osteoblast growth and development for bone tissue repair. Poly( beta- hydroxybutyrate- co- beta- hydroxyvalerate) ( PHBV), a bioabsorbable, biocompatible polyhydroxy acid polymer, is an excellent candidate that, as yet, has not been extensively investigated for this purpose. As such, we examined the attachment characteristics, self- renewal capacity, and osteogenic potential of osteoblast- like cells ( MC3T3- E1 S14) when cultured on PHBV films compared with tissue culture polystyrene ( TCP). Cells were assayed over 2 weeks and examined for changes in morphology, attachment, number and proliferation status, alkaline phosphatase ( ALP) activity, calcium accumulation, nodule formation, and the expression of osteogenic genes. We found that these spindle- shaped MC3T3- E1 S14 cells made cell - cell and cell - substrate contact. Time- dependent cell attachment was shown to be accelerated on PHBV compared with collagen and laminin, but delayed compared with TCP and fibronectin. Cell number and the expression of ALP, osteopontin, and pro- collagen alpha 1( I) mRNA were comparable for cells grown on PHBV and TCP, with all these markers increasing over time. This demonstrates the ability of PHBV to support osteoblast cell function. However, a lag was observed for cells on PHBV in comparison with those on TCP for proliferation, ALP activity, and cbfa- 1 mRNA expression. In addition, we observed a reduction in total calcium accumulation, nodule formation, and osteocalcin mRNA expression. It is possible that this cellular response is a consequence of the contrasting surface properties of PHBV and TCP. The PHBV substrate used was rougher and more hydrophobic than TCP. Although further substrate analysis is required, we conclude that this polymer is a suitable candidate for the continued development as a biomaterial for bone tissue engineering.
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Seasonal variations of phenolic compounds in fresh tea shoots grown in Australia were studied using an HPLC method. Three principal tea flavanols [epigallocatechin gallate (EGCG), epicatechin gallate (ECG), and epigallocatechin (EGC)] and four grouped phenolics [total catechins (Cs), total catechin gallates (CGs), total flavanols (Fla), and total polyphenols (PPs)] in fresh tea shoots were analyzed and compared during the commercial harvest seasons from April 2000 to May 2001. The levels of EGCG, ECG, and CGs in the fresh tea shoots were higher in the warm months of April 2000 (120.52, 34.50, and 163.75 mg/g, respectively) and May 2000 (128.63, 44.26, and 183.83 mg/g, respectively) and lower during the cool months of July 2000 (91.39, 35.16, and 132.30 mg/g, respectively), August 2000 (91.31, 31.56, and 128.64 mg/g, respectively), and September 2000 (96.12, 33.51, and 136.90 mg/g, respectively). Thereafter, the levels increased throughout the warmer months from October to December 2000 and remained high until May 2001. In the warmer months, the levels of EGCG, ECG, and CGs were in most cases significantly higher (P < 0.05) than those in the samples harvested in the cooler months. In contrast, the levels of EGC and Cs were high and consistent in the cooler months and low in the warmer months. The seasonal variations of the individual and grouped catechins were significant (P < 0.05) between the cooler and warmer months. This study revealed that EGCG and ECG could be used as quality descriptors for monitoring the seasonal variations of phenolics in Australia-grown tea leaves, and the ratio (EGCG + ECG)/EGC has been suggested as a quality index for measuring the differences in flavanol levels in fresh tea shoots across the growing seasons. Mechanisms that induce seasonal variations in tea shoots may include one or all three of the following environmental conditions: day length, sunlight, and/or temperature, which vary markedly across seasons. Therefore, further studies under controlled conditions such as in a greenhouse may be required to direct correlate flavonoid profiles of green tea leaves with their yields and also to with conditions such as rainfall and humidity.