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1.
Gertrud K. Nürnberg Lewis A. Molot Eavan O'Connor Hamdi Jarjanazi Jennifer Winter Joelle Young 《Journal of Great Lakes research》2013
Hypoxia and cyanobacterial blooms were extensive in Lake Simcoe during the 1980s and are still a problem to a lesser degree despite extensive nutrient load reduction from the catchment basin. The continuing signs of productivity indicate a potential internal phosphorus (P) source. Internal P load, as a redox-dependent release from bottom sediments, is hard to determine in a large, relatively shallow and partially unstratified lake such as Lake Simcoe. Of the lake's three major basins, only Kempenfelt Bay stratifies long enough to develop hypoxia in the stagnant summer hypolimnion. The following indications of sediment P release are available from historic data: 1) hypolimnetic hypoxia still occurs in Kempenfelt Bay although the hypoxic factor (number of days that an area equal to the bay's surface area is overlain by water of ≤ 2 mg/L dissolved oxygen, DO) has decreased substantially and significantly from 15.8 d/yr (1980–1994) to 4.0 d/yr (1995–2011); 2) hypoxic factors for other lake sections and at different DO levels also indicate widespread hypoxia; 3) concentrations of redox dependent metals, Fe and Mn, increase with depth; and 4) euphotic zone P and chlorophyll concentrations increase and water clarity decreases during fall turnover. Cyanobacterial blooms appear to occur in response to internal load as supported by occasional cyanobacteria counts. These indicators provide evidence that internal loading is likely occurring and affecting the water quality in Lake Simcoe. We expect that further monitoring, specific for internal load, will corroborate these results. 相似文献
2.
Low temperature silicon direct bonding for application in micromechanics: bonding energies for different combinations of oxides 总被引:3,自引:0,他引:3
Gertrud Kräuter Andreas Schumacher Ulrich Gösele 《Sensors and actuators. A, Physical》1998,70(3):100-275
Plain or structured hydrophillic silicon wafers covered with native oxide or with thermally grown oxide layers have been directly bonded at room temperature; afterwards, the samples were annealed at 100°C to 400°C. There is a significant difference in the observed bonding energy depending on the wafer pairing chosen. If one or both wafers are covered with a native oxide layer, high bonding strengths are reached even at low temperatures. This can be explained by the different diffusion behaviour of water molecules through a thick thermal oxide layer on one hand, and through a thin native oxide layer on the other hand. Two different methods for the activation of the wafer surfaces just prior to bonding are described. 相似文献
3.
A combination of immuno-electron microscopy and electron energy-loss spectrum-imaging was used to map the distributions of endocrine polypeptide hormones and proteins in mouse pancreatic islet of Langerhans. Tissue was analyzed from control animals and from mice that were heterozygous for the Anx7 gene, which defines a Ca2+/GTP-dependent membrane fusion and ion channel protein. The heterozygous Anx7 (+/-) mouse displays defects in IP3 receptor mediated Ca2+ signaling and insulin secretion. Therefore, information was obtained about the distributions of the hormones insulin and glucagon, as well as the proteins ANX7 and the IP3 receptor. Insulin secretion appears to be defective in the mutants. It was found from immunolabeling experiments that expression of the IP3 receptor is reduced in mutant islets compared to control islets. Subcellular distributions of sulfur and nitrogen obtained by electron energy-loss spectrum-imaging showed that the insulin concentrations of beta granules were essentially the same in control and mutant islets. By contrast, immunogold labeling of mutant islets shows more insulin immunoreactivity in the beta granules. It follows that insulin may be packaged differently in mutant islets, making antigenic determinants more available to the labeling antibody. The increased rate of insulin secretion in the hyperplastic mutant islets can be explained by compensatory increases in islet size, rather than by an increased insulin concentration in the beta cells. The results indicate that reduced ANX7 expression leads to defects in the IP3 receptor expression in the endocrine cells of the mutant mouse. Increased size of the islet or of adrenal medulla may be a compensatory mechanism for secretion defect by individual endocrine cells. Defects in IP3 receptor expression, and documented consequences of a Ca2+ signaling defect, lead to other changes in organelles such as the mitochondrial number in islet beta-cells. The effects and consequences of reduced ANX7 expression on mitochondria are evident in ultrastructural observations. 相似文献
4.
Hafstad Gertrud Sofie; Kilmer Ryan P.; Gil-Rivas Virginia 《Canadian Metallurgical Quarterly》2011,3(2):130
This study examined posttraumatic growth (PTG), positive change experienced as a result of the struggle with trauma, in children and adolescents exposed to a high-impact disaster, after which their experience of secondary adversity was minimal. The study also examined whether reduction in posttraumatic stress symptoms (PTSS) over time related to reports of PTG. There were 105 participants, age 6 to 17 years, who were directly exposed to the 2004 tsunami in Southeast Asia. They were interviewed 10 and 30 months after the disaster—PTSS was assessed at both time points, and PTG was assessed at 30 months. The individual's subjective reactions to the event and concurrent PTSS (30-months post-tsunami) were independently and positively related to PTG, whereas the decrease in PTSS was not related to growth. Children and youth in this study reported lower absolute levels of PTG than those in other studies. Taken in sum, findings suggest that secondary adversities may influence posttraumatic reactions and ongoing distress, which are hypothesized to play a key role in the development of PTG. In the absence of such secondary stressors, continued distress in the form of PTSS may serve to catalyze the growth process. Implications for clinical practice are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
5.
Gertrud Blauwhof 《Scientometrics》1997,38(1):117-140
In this contribution relations between scientific articles, conference proceedings and patents relating to telephone switching
are analyzed. The state-of-the-art in scientometrics and science and technology studies leads one to expect relations among
these documents. Empirical findings show the opposite. To interpret these findings I focus on two key issues in scientometrics,
namely the frequency of linkages among documents and the nature of communication. The resulting conclusion is that scientometrics
should be informed by theories concerning the evolutionary dynamics of science and technology. 相似文献
6.
Gertrud Zwicknagl 《Journal of Low Temperature Physics》2007,147(3-4):123-134
Electronic structure results are presented for the heavy fermion compound CeCu2Ge2. The main focus of the present paper is interplay of Kondo effect and antiferromagnetic instability. We examine properties
such as the dispersion of the conduction states and the Fermi surface topology. Electronic band structure calculations are
compared treating the Ce 4f electron as localized (atomic-like) and as itinerant (band-like). The results suggest that the
incipient Kondo effect as reflected in the transfer of f spectral weight to the low-energy regime is important for the formation
of the observed long-range magnetic order. 相似文献
7.
Rudolf K. Zahn Gertrud Zahn-Daimler W.E.G. Müller Martin L. Michaelis Branko Kurelec Marija Rijavec Renato Batel Nevenka Bihari 《The Science of the total environment》1983,26(2):137-156
The sponge Tethya lyncurium from the Northern Adriatic has been used as an experimental species.A method is outlined for preparation of DNA which yields a highly purified DNA with a double-strand (ds) molecular weight of 25 M-dalton between single-strand (ss) breaks, which when properly damaged can be cut opposite to ss-breaks with nuclease s1. The molecular weights of the resulting ds-DNA pieces and their distribution has been evaluated by electron microscope photographs.Sponges exposed to benzo[a]pyrene (BaP) in the dark only incorporate BaP-derivatives (BaPD) in small amounts, if any. However, in the presence of light, derivatization to BaP derivatives enables effective coupling to occur, as shown previously (R. K. Zahn et al., 1981). Sponges were exposed to radiolabeled BaP in the presence of light. Coupling of BaPD to the DNA as well as the induction of ss-breaks were measured.Light-mediated coupling is concentration dependent from 0.01 – 20 ppb BaP with a correlation coefficient of r = 0.84.Under conditions of possible repair, ss-breaks completely disappear from sponge DNA in the course of three weeks while a substantial fraction of the BaP derivatives persists.Double label experiments show that substantial DNA synthesis occurs during this time. Pollution causes a decrease of the molecular weight of unnicked DNA, re-incubation in clean water an increase. A DNA species of 24 M-dalton seems to play a critical role. If its percentage in the DNA population drops below a critical level, recovery is not longer possible. DNA damage by PAH and repair in sponges seems to differ from that of most eucaryotes. 相似文献
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10.
The effects on eating quality and meat quality of two different forms of post-slaughter treatment, performed in an abattoir, were studied in carriers and non-carriers of the RN(-) allele. Carcasses were subjected to rapid and slow chilling, and pelvic and Achilles suspension in a factorial experimental design. A temperature of 10?°C was achieved in the centre of M. longissimus dorsi (LD) within 3.5 h in rapidly chilled carcasses and within 8 h in slowly chilled carcasses. In deep M. semimembranosus (SM) a temperature of 10?°C was achieved within 11.5 h in rapidly chilled carcasses and within 14 h in slowly chilled carcasses. LD from slowly chilled RN(-) carriers suspended by the pelvis exhibited the greatest tenderness, while LD from rapidly chilled non-carriers suspended from the Achilles tendon exhibited the lowest tenderness. Pelvic suspension or slow chilling of non-carriers produced the same improvement in tenderness, and when combined the tenderness increased further. However, the tenderness of the RN(-) carriers was already high, and no significant improvement was seen following any of the studied post-slaughter treatments. Pelvic suspension prevented shortening of muscle fibres, as seen by longer sarcomeres in LD from pelvic-suspended sides. However, longer sarcomeres were associated with greater tenderness only in LD from non-carriers of the RN(-) allele. The presence of the RN(-) allele and a slow chilling regime increased the rate of pH decline in LD. Achilles suspension also increased the rate of pH fall in SM, in addition to the RN(-) allele and slow chilling. The overall tenderness of LD was mainly related to the course of pH decline during rigor; lower pH values between 3 and 7 h post-mortem contributing to greater tenderness. The myofibrillar length was predominantly related to RN genotype and was shorter in RN(-) carriers than in non-carriers. The RN(-) allele and slow chilling contributed to higher evaporation losses and RN(-) carriers exhibited increased frequency of PSE meat in the ham muscles. The use of pelvic suspension appears advantageous over slower chilling, since it improved tenderness without any negative influence on drip loss, evaporation or cooking loss. 相似文献