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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 529-535 
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reflection of modified Korteweg–de Vries solitons from the sheath in front of a negatively biased metal disk is experimentally investigated in a negative ion plasma. Both rarefactive and compressive solitons are reflected and the polarity of the reflected solitons is the same as that of the incident solitons. The points of reflection for the rarefactive and compressive solitons are at different locations. As the magnitude of the negative bias potential that is applied to the reflector is increased, the two reflection points move away from the reflector. An interpretation in terms of the sheath characteristics is presented. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: We have investigated which α2-receptor subtypes are expressed in cultured cortical astroglia, and their coupling to second messengers. Binding assays using [3H]rauwolscine showed a very low number of α2 receptors in the astrocytic cultures. Treatment of cultures with dibutyryl cyclic AMP (dBcAMP) increased significantly the number of receptors. The RNase protection assay was used to investigate which receptor subtype the cells express. The α2B message was expressed at a low level in both treated and untreated cells, the levels of mRNA for the α2A/D subtype were up-regulated significantly in cells treated with dBcAMP and no expression of mRNA for the α2C subtype was detected. The α2 agonist dexmedetomidine inhibited forskolin-induced increases in cyclic AMP both in treated and untreated cultures in a pertussis toxin-dependent manner. This effect was abolished by the α2-receptor antagonist rauwolscine. Selective α2-receptor agonists dexmedetomidine, clonidine, and UK14,304 all increased intracellular calcium only in dBcAMP-treated cells. The antagonist rauwolscine abolished this effect. Ca2+ responses were also seen in the absence of extracellular Ca2+ and they were inhibited by the phospholipase C inhibitor U-73122, suggesting that astroglial α2 receptors are coupled to the inositol phospholipid pathway. We therefore also tested the effect of dexmedetomidine directly on inositol 1,4,5-trisphosphate accumulation. A significant increase was seen that was blocked by the antagonist rauwolscine and, as expected, by U-73122. In short, the results demonstrate that the α2 receptors in astroglia are coupled to multiple second messenger pathways. They are up-regulated in cells treated with dBcAMP, which simultaneously assume a process-bearing morphology. If this morphological change reflects some in vivo process such as reactive gliosis, the up-regulation of α2-receptor expression could mean an adaptive change in astrocytic responses to a common neurotransmitter, noradrenaline.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1540-8191
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract Background and Aims: Chronic renal failure (CRF) is known to increase the morbidity and mortality in patients undergoing cardiac operations. Successful outcome of coronary artery bypass grafting (CABG) in some patients with CRF has been reported, but remains controversial. Methods: Forty-four patients with CRF who underwent CABG were examined. Two groups were analyzed. Group I consisted of 13 patients with end-stage renal disease on hemodialysis. Group II consisted of 31 patients with a creatinine ± 1.6 gm/dL for a minimum of 6 months, but were not on dialysis. There were 36 male and 8 female patients, with a mean age of 71 years. Results: The hospital mortality was 10 patients (23%) with 4 (31%) hospital deaths in Group I, and 6 (19%) in Group II. There was major morbidity in 35 (80%) patients. In Group II there were 8 (26%) patients who required permanent postoperative dialysis. A control group of 547 patients 70 years of age who underwent CABG had 30 hospital mortalities (5%) and 75 morbidities (13%). The average length of stay was 27 days. Fifteen patients died at a mean of 34 months after being discharged from the hospital. Nineteen of the original 44 patients remain alive at a mean of 32 months. The total mortality at 6 years and 4 months was 57%. Conclusions: Older and sicker patients with CRF who undergo CABG are at an exceptionally high risk for mortality and morbidity. For CRF patients not on dialysis with a creatinine 2.5 gm/dL, there is a strong likelihood of permanent postoperative dialysis. Long-term follow-up shows survival to be well below their non-CRF counterparts.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of cardiac surgery 11 (1996), S. 0 
    ISSN: 1540-8191
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract Objectives and Background: The purpose of this study was to document our initial experience with patients 90 years of age and older and to determine whether cardiac surgery is justified in this age group. Cardiac surgery in octogenarians has proven to be a successful and worthwhile procedure. A small group of nonagenarians with severe coronary artery disease (CAD) and aortic valve disease refractory to medical therapy have been considered for surgery. Methods: Fourteen patients aged 90 or more underwent cardiac surgery for symptomatic CAD or aortic valvular disease refractory to medical therapy. Eight patients underwent isolated coronary artery bypass grafting (CABG) and six patients underwent aortic valve replacement (AVR). All patients were in NYHA Class IV preoperatively. Results: Hospital mortality occurred in one patient (7%). Hospital morbidity occurred in 10 patients (71%) and included 7 cardiac, 5 neurological, 1 gastrointestinal, 1 infectious, and 1 pulmonary event. All survivors left the hospital symptomatically improved. The mean length of stay was 26 days. Four CABG patients went on to die at a mean of 2 years and 2 months, and 3 remain alive at a mean of 2 years and 4 months. Three AVR patients expired at a mean of 3 years and 4 months, and 3 remain alive at 4 years and 1 month. Conclusions: Cardiac surgery in carefully selected nonagenarians is justified and can be performed with acceptable results.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 3853-3860 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The spatial and temporal evolution of the components of a plasma surrounding a 90° convex and a 90° concave electrode whose potential is suddenly decreased in a three-component plasma is numerically investigated. The quasineutral plasma consists of positive ions and various proportions of negative ions and electrons. The results are compared and contrasted with those that are obtained in a normal two-component plasma. The transient or ion matrix sheath is identified and its subsequent evolution is investigated. Effects of perturbations in the electrode are investigated. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Addiction 91 (1996), S. 0 
    ISSN: 1360-0443
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine , Psychology
    Notes: Peer influence is generally believed to be a major cause of adolescent drug behavior. This paper reviews research findings on friend selection and projection to suggest that the magnitude of friend influence may be overestimated. This paper also observes that, although adolescent drug use is assumed to begin in response to peer group influence, peer groups have rarely been measured in studies of drug behavior. Social network analysis is identified as a promising method for measuring peer groups. The implications of this review for research and programs are considered.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 32 (1996), S. 0 
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : Algal blooms, defined as chlorophyll α concentrations greater than 40 μg l−1, are common in Lake Okeechobee, Florida. Using logistic regression techniques, we have developed equations that relate limnological variables to algal bloom occurrence in four distinct open-water regions of this large shallow lake: central pelagic, northwest, southwest, and a transition region between the western and pelagic regions. Wind velocity and total phosphorus, which are closely related to resuspended material in the central region, are negatively related to algal bloom occurrence there. In the transition region, algal bloom occurrence is positively related to total nitrogen and wind velocity. Algal bloom occurrence is strongly and positively related to total nitrogen and total phosphorus concentrations in the western regions. The logistic regression model predicts an algal bloom probability greater than 95 percent in the northwest region when total phosphorus exceeds 0.10 mg l−1 and total nitrogen exceeds 2.5 mg l−1. In the southwest region the model predicts algal bloom probability of 100 percent when total phosphorus exceeds 0.10 mg l−1 and total nitrogen exceeds 2.8 mg l−1. Given 1994 mean total phosphorus concentrations of 0.05 and 0.04 mg l−1 in the northwest and southwest regions, respectively, total nitrogen would have to remain below 1.32 and 1.43 mg l−1, respectively, to keep the algal bloom probability below 10 percent. Because the lake is heterogenous, such nutrient standards should be considered on an in-lake regional basis for Lake Okeechobee.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Lakes & reservoirs 2 (1996), S. 0 
    ISSN: 1440-1770
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geography
    Notes: Long-term eutrophication data collected by the South Florida Water Management District at eight stations in the pelagic region of Lake Okeechobee since 1980 were combined with those from littoral region stations collected since 1986. These data were supplemented by those collected by the University of Florida in conjunction with the Lake Okeechobee Ecosystem Study. Generalized additive models (GAM) were fit to the chlorophyll a response for each of five previously documented‘ecological zones’, each using the same predictor variables for comparison between zones. Significant nonlinear increasing relationships between log10 TP and log10 chlorophyll a were found for littoral and near littoral regions of the lake, which change to decreasing at certain (high) levels of log10 TP. This change to a decreasing function suggests light limitation associated with high TP levels due to particle resuspension. The error distribution of the GAM compare favourably to those of linear models. The relationship of the chlorophyll a response to the predictors used in the GAM appear similar for littoral and near littoral regions, as they do for north pelagic and central pelagic ecological zones, with intermediate shapes of these functions found in the transition zone between these two groups.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1572-8889
    Keywords: nestmate recognition ; nest surface hydrocarbons ; Polistes metricus ; Vespidae ; Hymenoptera
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nestmate recognition was observed inPolistes metricus Say workers only if the workers were exposed to their nest surface hydrocarbons after eclosion. If the newly emerged workers were never exposed to the nest hydrocarbons as adults, they showed no discrimination between nestmates and nonnestmates. Furthermore, the newly emerged workers were accepted more readily by their experienced nestmates than by experienced nonnestmates only if the newly emerged wasps had been exposed to the nest surface hydrocarbons. This reciprocal recognition implies that the nest recognition cues are nest surface hydrocarbons that are learned and that may be acquired byP. metricus workers as adults on the natal nest.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-0843
    Keywords: Key words Microdialysis ; Methotrexate ; Tissue ; Recovery ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  We used a microdialysis technique to determine tissue methotrexate (MTX) levels during steady state in a rodent model. Two different approaches were employed to measure the actual extracellular MTX concentrations in muscle, liver, and kidney tissues of anesthetized Wistar rats. With the reduced-perfusion-rate technique, the flow in the microdialysis perfusate was gradually decreased toward zero to permit calculation of zero-flow intercepts. Using the net change technique, microdialysis probes were perfused with different MTX concentrations to allow an assessment of equilibrium drug levels. For these two methods to be used, drug concentrations in the matrix to be analyzed must remain unchanged during the experimental procedure. In the animal model, steady state was attained after 1.5 h and maintained throughout the rest of the experiments by the administration of MTX as continuous infusions through a venous catheter. In vitro and in vivo, both the reduced-perfusion-rate and net change techniques gave reproducible data that permitted the estimation of extracellular drug concentrations in the dialyzed tissue compartments. The data suggest that the level of unbound MTX in the circulation is fairly similar to the extracellular concentrations in the muscle and liver. In the kidney, MTX levels were measured to be 3–8 times higher than those of unbound, circulating MTX, and a considerable discrepancy between the two methods used for estimations was apparent. These results demonstrate that both the net change and reduced-flow microdialysis techniques can produce reproducible and precise data. The results may constitute a basis for determining recoveries and, thus, true extracellular drug levels during in vivo microdialysis of MTX. This may be of importance in delineation of the relationship between tissue MTX levels and outcome in a variety of normally inaccessible compartments during cancer pharmacotherapy.
    Type of Medium: Electronic Resource
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