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  • 1
    Electronic Resource
    Electronic Resource
    Photoluminescence study of high quality InGaN–GaN single heterojunctions (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 668-670 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this letter we report the results of room-temperature continuous wave and pulsed photoluminescence measurements on InGaN–GaN single heterojunctions. These InGaN–GaN heterojunctions were deposited over basal plane sapphire substrates using low pressure metalorganic chemical vapor deposition. We suggest the use of vertical cavity stimulated emission instead of spontaneous emission peak position as a good measure of the InGaN band edge. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.117800
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  • 2
    Electronic Resource
    Electronic Resource
    Curve resolution and figures of merit estimation for determination of trace elements in geological materials by inductively coupled plasma atomic emission spectrometry (1987)
    s.l. : American Chemical Society
    Analytical chemistry 59 (1987), S. 1260-1266 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac00136a003
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  • 3
    Electronic Resource
    Electronic Resource
    Determination of trace elements in zeolites by laser ablation ICP-MS (2000)
    Springer
    Fresenius' journal of analytical chemistry 368 (2000), S. 79-87 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Laser ablation inductively coupled plasma mass spectrometry using a quadrupole-based mass spectrometer (LA-ICP-QMS) was applied for the analysis of powdered zeolites (microporous aluminosilicates) used for clean-up procedures. For the quantitative determination of trace element concentrations three geological reference materials, granite NIM-G, lujavrite NIM-L and syenite NIM-S, from the National Institute for Metallurgy (South Africa) with a matrix composition corresponding to the zeolites were employed. Both the zeolites and reference materials were fused with a lithium borate mixture to increase the homogeneity and to eliminate mineralogical effects. In order to compare two different approaches for the quantification of analytical results in LA-ICP-MS relative sensitivity coefficients (RSCs) of chemical elements and calibration curves were measured using the geostandards. The experimentally obtained RSCs are in the range of 0.2-6 for all elements of interest. Calibration curves for trace elements were measured without and with Li or Ti as internal standard element. With a few exceptions the regression coefficients of the calibration curves are better than 0.993 with internal standardization. NIM-G granite reference material was employed to evaluate the accuracy of the technique. Therefore, the measured concentrations were corrected with RSCs which were determined using lujavrite reference material NIM-L. This quantification method provided analytical results with deviations of 1–11% from the recommended and proposed values in granite reference material NIM-G, except for Co, Cs, La and Tb. The relative standard deviation (RSD) of the determination of the trace element concentration (n = 5) is about 1% to 6% using Ti as internal standard element. Detection limits of LA-ICP-QMS in the lower μg/g range (from 0.03 μg/g for Lu, Ta and Th to 7.3 μg/g for Cu, with the exception of La) have been achieved for all elements of interest. Under the laser ablation conditions employed (λ: 266 nm, repetition frequency: 10 Hz, pulse energy: 10 mJ, laser power density: 6 × 109 W/cm2) fractionation effects of the determined elements relative to the internal standard element Ti were not observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160000514
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  • 4
    Electronic Resource
    Electronic Resource
    The geochemistry of a lenticular manganese-ore deposit (Um Bogma, Southern Sinai) (1979)
    Springer
    Mineralium deposita 14 (1979), S. 1-13 
    Details
    ISSN: 1432-1866
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Trace element distributions and interrelationships in the lenticular Mn ore bodies of Um Bogma, Sinai, are utilized to establish physicochemical conditions of formation and diagenesis. The deposits are considered to be shallow marine in origin. Mineralogical and chemical data suggest that these ores were subjected to various diagenetic processes which resulted in the separation of manganese from iron, several ore types being recognized: a) a mixture of Fe and Mn considered to be the original one (mixed ore); b) Mn-rich types; c) Fe-rich types. In this investigation, chemical and mineralogical data and interrelationships are employed to evaluate environmental conditions prevailing during diagenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00201863
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  • 5
    Electronic Resource
    Electronic Resource
    Impact of heat exposure and moderate, intermittent exercise on cytolytic cells (1996)
    Springer
    European journal of applied physiology 74 (1996), S. 162-171 
    Details
    ISSN: 1439-6327
    Keywords: Heat ; Intermittent exercise ; Cytolytic activity ; Immune function ; Interleukin receptors ; Stress hormones
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study examined the impact of heat exposure and moderate, intermittent exercise on the CD16+ and CD56+ cell counts and cytolytic activity. Eleven healthy male subjects [mean (SD): age = 27.1(3.0) years, peak oxygen intake, VO2maxO2 peak = 47.6 (6.2) ml · kg−1 · min−1] were assigned to each of four different experimental conditions according to a randomized-block design. While in a climatic chamber maintained at a comfortable temperature (23°C) or heated (40°C, 30% relative humidity, r.h.), subjects performed either two 30-min bouts of cycle-ergometer exercise at ≈50% VO2maxO2 peak (separated by a 45-min recovery interval), or remained seated for 3 h. Blood samples were analyzed for CD16+ and CD56+ cell counts, cytolytic activity and the concentrations of various exercise stress hormones (norepinephrine, epinephrine and cortisol). Heat exposure alone had no significant effect on cytolytic cells. The (CD16+ and CD56+) cell count increased significantly (P 〈 0.0001) during each exercise bout under both environmental conditions, but returned to baseline levels 15–45 min following each exercise bout. Total cytolytic activity (determined by a standard 51Cr release assay using K562 cells) followed a similar pattern, but cytolytic activity per CD16+ or CD56+ cell was not significantly modified by exercise. Our findings show a strong association between hemodynamic factors and recruitment of cytolytic cells into the peripheral circulation. Alterations in cytolytic activity of the whole blood during and following moderate exercise seem to be the result of changes in CD16+ and CD56+ cell counts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00376509
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  • 6
    Electronic Resource
    Electronic Resource
    The Impact of heat exposure and repeated exercise on circulating stress hormones (1997)
    Springer
    European journal of applied physiology 76 (1997), S. 445-454 
    Details
    ISSN: 1439-6327
    Keywords: Key words Heat exposure ; Repeated exercise ; Cortisol ; Growth hormone ; Catecholamines
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To determine if heat exposure alters the hormonal responses to moderate, repeated exercise, 11 healthy male subjects [age = 27.1 (3.0) years; maximal oxygen consumption, V˙O2max = 47.6 (6.2) ml · kg · min−1; mean (SD)] were assigned to four different experimental conditions according to a randomized-block design. While in a thermoneutral (23°C) or heated (40°C, 30% relative humidity) climatic chamber, subjects performed either cycle ergometer exercise (two 30-min bouts at ≈50% V˙O2max, separated by a 45-min recovery interval, CEx and HEx conditions), or remained seated for 3 h (CS and HS conditions). Blood samples were analyzed for various exercise stress hormones [epinephrine (E), norepinephrine (NE), dopamine, cortisol and human growth hormone (hGH)]. Passive heating did not alter the concentrations of any of these hormones significantly. During both environmental conditions, exercise induced significant (P 〈 0.001) elevations in plasma E, NE and hGH levels. At 23°C during bout 1: E = 393 (199) pmol · l−1 (CEx) vs 174 (85) pmol · l−1 (CS), NE = 4593 (2640) pmol · l−1 (CEx) vs 1548 (505) pmol · l−1 (CS), and hGH = 274 (340) pmol · l−1 (CEx)vs 64 (112) pmol · l−1 (CS). At 40°C, bout 1: E = 596 (346) pmol · l−1 (HEx) vs 323 (181) pmol · l−1 (HS), NE = 7789 (5129) pmol · l−1 (HEx) vs 1527 (605) pmol · l−1 (HS), and hGH = 453 (494) pmol · l−1 (HEx) vs 172 (355) pmol · l−1 (HS). However, concentrations of plasma cortisol were increased only in response to exercise in the heat [HEx = 364 (168) nmol · l−1 vs HS = 295 (114) nmol · l−1). Compared to exercise at room temperature, plasma levels of E, NE and cortisol were all higher during exercise in the heat (P 〈 0.001 in all cases). The repetition of exercise did not significantly alter the pattern of change in cortisol or hGH levels in either environmental condition. However, repetition of exercise in the heat increased circulatory and psychological stress, with significantly (P 〈 0.001) higher plasma concentrations of E and NE. These results indicate a differential response of the various stress hormones to heat exposure and repeated moderate exercise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050274
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  • 7
    Electronic Resource
    Electronic Resource
    Impact of three different types of exercise on components of the inflammatory response (1999)
    Springer
    European journal of applied physiology 80 (1999), S. 452-460 
    Details
    ISSN: 1439-6327
    Keywords: Key words Natural killer cell ; Cytolytic activity ; Cytokines ; Creatine kinase ; Aerobic and resistance exercise
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It was hypothesized that muscle injury would be greater with eccentric than with all-out or prolonged exercise, and that immune changes might provide an indication that supplements the information provided by traditional markers such as creatine kinase (CK) or delayed-onset muscle soreness. Eight healthy males [mean (SE): age = 24.9 (2.3) years, maximum oxygen consumption (V˙O2max)=43.0 (3.1) ml · kg−1 · min−1] were each assigned to four experimental conditions, one at a time, using a randomized-block design: 5 min of cycle ergometer exercise at 90% V˙O2max (AO), a standard circuit-training routine (CT), 2 h cycle ergometer exercise at 60% V˙O2max (Long), or remained seated for 5 h. Blood samples were analyzed for CK, natural killer (NK) cell counts (CD3−/CD16+56+), cytolytic activity and plasma levels of the cytokines interleukin (IL)-6, IL-10, and tissue necrosis factor α (TNF-α). CK levels were only elevated significantly 72 h following CT. NK cell counts increased significantly during all three types of exercise, but returned to pre-exercise baseline values within 3 h of recovery. Cytolytic activity per NK cell was not significantly modified by any type of exercise. Prolonged exercise induced significant increases in plasma IL-6 and TNF-α. We conclude that the lack of correlation between traditional markers of muscle injury (plasma CK concentrations and muscle soreness rankings) and immune markers of the inflammatory response suggests that, for the types and intensities of exercise examined in this study, the exercise-induced inflammatory response is modified by humoral and cardiovascular correlates of exercise.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050617
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  • 8
    Electronic Resource
    Electronic Resource
    Effects of heat and intermittent exercise on leukocyte and sub-population cell counts (1996)
    Springer
    European journal of applied physiology 74 (1996), S. 234-245 
    Details
    ISSN: 1439-6327
    Keywords: Cell proliferation ; Granulocytes ; Immune function ; Immunoglobulin production ; Lymphocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study examined the combined effects of heat stress and intermittent exercise on circulating leukocyte and sub-population cell counts. Using a randomized-block design, 11 healthy male subjects [mean (SD) age = 29.1 (3.0) years maximal oxygen consumption ( $$\dot V{\text{O}}_{{\text{2max}}}$$ ) = 47.6 (6.1) ml/(kg-min)] were assigned to four conditions. Each subject exercised on a cycle ergometer at 50% $$\dot V{\text{O}}_{{\text{2max}}}$$ (two 30-min bouts, with 45 min rest between), or acted as his own control by sitting at 23°C, or at 40°C, 30% relative humidity, for 3 h. Blood samples taken prior to, during, and after each rest and exercise bout, and at corresponding times when sitting were used for Coulter cell counter and flow cytometric analysis. Sitting conditions did not produce any significant immunological changes. Intermittent exercise induced a biphasic response of granulocytosis, monocytosis and lymphocytosis, with a return to baseline between exercise bouts. One hour following the second exercise bout, samples showed a consistent granulocytosis, monocytosis and lymphocytosis (CD3+, CD4+, CD8+ and CD19+ cell counts). The second exercise bout produced a larger response than the first, further exacerbated when exercising at 40°C. We conclude there is a synergism between heat and exercise exposure. An increase in core temperature and exercise stress recruit leukocytes into the peripheral circulation, with potentiation of the response during a second bout of exercise. However, while the increase of core temperature remains moderate, the disturbance of immune function does not appear to have great clinical significance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377446
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  • 9
    Electronic Resource
    Electronic Resource
    Spectral analysis of heart rate variability during heat exposure and repeated exercise (1997)
    Springer
    European journal of applied physiology 76 (1997), S. 145-156 
    Details
    ISSN: 1439-6327
    Keywords: Key words Heat ; Repeated exercise ; Heart rate variability ; Coarse-graining spectral analysis ; Vagal and sympathetic activities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract This study examined indices of parasympathetic (PNS) and sympathetic (SNS) nerve activity during exposure to heat and/or two successive bouts of exercise. Seven healthy males [age = 27.1 (3.6) years; mean (SD), maximum oxygen consumption (V˙O2 max )= 48.1 (7.6) ml · kg−1 · min−1] were assigned to each of four experimental conditions according to a randomized-block design. While in a thermoneutral (23°C) or heated (40°C, 30% relative humidity) climatic chamber subjects performed exercise on a cycle ergometer (two 30-min bouts at ≈50% V˙O2 max , separated by a 45-min recovery period, (CEx and HEx, respectively) or remained seated (CS and HS, respectively) for 2 h. The R-R intervals of the subjects' ECGs were analyzed for selected near-steady-state time periods [termed Phase I (25–40 min) and Phase II (100–115 min)] according to the method of Yamamoto and Hughson (J Appl Physiol 71:1143–1150, 1991). Total (PT), low-frequency (PLF = 0–0.15 Hz) and high-frequency (PHF = 0.15–0.5 Hz) power spectra were calculated using coarse-graining spectral analysis. Heat exposure alone did not alter autonomic balance or levels of circulating catecholamines significantly. Exercise in both environmental conditions induced a significant decrease in an index of PNS tone (PHF : PT) [PNS indicator for CS = 0.084 (0.04) vs CEx = 0.023 (0.015) and HS = 0.065 (0.027) vs HEx = 0.015 (0.009)], with an increase in catecholamine concentrations. Although the index of SNS activity (PLF:PHF) tended to rise with exercise in both environmental conditions, increments reached levels of significance only during exercise in the heat [SNS indicator for CS = 8.22 (5.58) vs CEx = 34.06 (21.73) and HS = 8.94 (5.49) vs HEx = 54.29 (49.80)]. The relative magnitudes of SNS and PNS indicators did not differ significantly between the first and second bouts of exercise. These results indicate the substantial contribution of vagal withdrawal and catecholamine secretion to the increase in heart rate that occurs during repeated moderate exercise at room temperature and the additional contribution from SNS activity during such exercise in the heat.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004210050227
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  • 10
    Electronic Resource
    Electronic Resource
    Evaluation of an ultrasonic nebulizer-membrane separation interface (USN-MEMSEP) with ICP-AES for the determination of trace elements by solvent extraction (1996)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 355 (1996), S. 774-777 
    Details
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The introduction of volatile organic solvents and metal organic complexes into an inductively coupled plasma (ICP) is problematic due to overloading and pyrolysis effects. These include carbon built up in the torch and spectral interferences. As a consequence, solvent extraction as a method for preconcentrating trace metals for the determination by ICP has been limited. In this report a commercial ultrasonic nebulizer-membrane separation interface (USN-MEMSEP) for the direct introduction and separation of organic solvents using ICP atomic emission spectrometry (AES) and a sequential spectrometer has been evaluated for solvent extraction of chelated trace metals. The ability of the MEMSEP to separate volatile organic flows from metal aerosols has been demonstrated by determining the recoveries of several transition metals in an oil-based methyl-isobutyl ketone (MIBK) standard relative to an aqueous solution. However, low recoveries of several metal chelates have been found evidently due to the volatilization of the organic metal species at the boiling point of MIBK (160° C). Moreover, the multielement capability and limits of detection have been limited due to sequential atomic emission detection. Advantages of the technique include enhanced limits of detection (LODs) and reduced plasma and spectral interferences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s0021663550774
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