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  • Springer  (34)
  • American Chemical Society  (7)
  • Geological Society of America (GSA)
  • Periodicals Archive Online (PAO)
  • 2000-2004
  • 1995-1999  (41)
  • 1950-1954
  • 1925-1929
  • 1999  (20)
  • 1996  (21)
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  • 2000-2004
  • 1995-1999  (41)
  • 1950-1954
  • 1925-1929
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  • 1
    ISSN: 1573-2657
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Mechanically skinned fibre preparations from the extensor digitorum longus muscle of the rat were used to test whether a rise in myoplasmic [NH4 +] in the range 2–10 mm interferes with the mechanism of excitation-contraction coupling in fast-twitch mammalian muscle. Under our conditions (pH 7.10, Mg2+ 1 mm, temperature 23° C), [NH4 +] up to 10 mm had little effect on the Ca+-activated force and on the peak of the t-system depolarization-induced force response. However, the duration of the depolarization-induced force response was decreased significantly at [NH4 +] ≥2 mm. From these data we conclude that the intracellular accumulation of NH4 + is not likely to play a major role in fatigue. Nevertheless, the build up of NH4 + during fatigue, may have a significant inhibitory effect on the force output by decreasing the duration of the t-system depolarization-induced activation of the contractile apparatus.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1435-604X
    Keywords: Keywords: Adenocarcinoma; Aminolaevulinic acid; Barrett's oesophagus; Dysplasia; Photodynamic therapy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract . Photodynamic therapy (PDT) may have a role in the prevention of oesophageal cancer. Ten patients with Barrett's oesophagus, three with low-grade dysplasia (LGD), four with high-grade dysplasia (HGD), one with carcinoma in situ and two with invasive carcinoma, were treated with PDT. All received 30 mg/kg aminolaevulinic acid (ALA) followed 4 h later by laser endoscopy. Half were treated with red light (630 nm; 100 mW/cm2 for 1000 s) and half with green light (514 nm; 100 mW/cm2 for 500 s). Columnar epithelial regression was seen in all patients with dysplasia (mean area decrease 44%; range 10–100%), with apparent elimination of dysplasia in all cases. In patients with in situ or invasive carcinoma, no response was seen. ALA-induced PDT, using either red or green light, produces effective ablation of dysplastic Barrett's oesophagus, hence may have a role in the prevention of oesophageal carcinoma, but has little effect on in situ or invasive adenocarcinoma.
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Journal of paleolimnology 15 (1996), S. 99-106 
    ISSN: 1573-0417
    Keywords: lake sediments ; gravity core ; freeze core ; coring artifacts ; contaminant concentration ; contaminant inventory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract Sediments of Lake 382, Experimental Lakes Area, Canada, were sampled at six sites using a 5-cm Wildco KB core sampler (KB), a similar device incorporating a ball check valve (BC), and a 0.2 m by 1.2 m flat-faced aluminum freeze core sampler (FC). Cores were sectioned at 1-cm intervals to a depth of 15 cm. Contaminant (210Pb and 137Cs) concentrations (Bq g-1) were measured by gamma spectroscopy, and inventories (Bq cm-2) were calculated following standard methods. Sediments collected using FC, BC and KB had similar contaminant concentrations, however, cores collected by FC and BC had lower estimated inventories than KB cores. Differences between estimates appear to be caused by differences in the water content (WC) of core material. Laboratory studies confirm that FC sediments have higher WC than tube-cored sediment. We hypothesize that ice crystal formation increases the WC of freeze cores, resulting in lower contaminant inventories. Loss of surficial sediment caused by a ‘bow wave’ may have a similar effect on BC samples. We conclude that KB core gear is appropriate for sampling sediments to measure contaminant concentrations and inventories in recently deposited sediments.
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  • 4
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract. Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) were analyzed in storm water collected from 15 outfalls in San Francisco Bay, California, considered representative of areas located adjacent to petroleum refineries and mixed urban/commercial/residential land uses. Storm water sampling was conducted hourly over a 12-h period at two outfalls located near the city of Oakland and the suburban community of Benicia, which represent urban and mixed urban/light industrial land uses, respectively. Sampling was conducted hourly to determine temporal changes in the concentrations and distributions of PCDD/Fs during the first major rainstorm event of the 1995/96 winter season. In addition, storm water sampling was conducted in December 1995 and February/April 1996 at six publicly owned treatment work (POTW) outfalls located adjacent to developed, undeveloped, mixed residential/commercial, and industrial lands. Storm water sampling also was conducted at five outfalls located adjacent to petroleum refineries. The sampling results were used to examine changes in PCDD/F loadings to San Francisco Bay at the onset and midway through the winter rainy season and to characterize differences in PCDD/F concentrations, if any, between refinery and nonrefinery areas. The concentrations of tetra- through octa-chlorinated homologues and 2,3,7,8-substituted congeners were assayed in filtered storm water samples according to US EPA Method 1613A. Principal components analysis (PCA) was used as an exploratory technique to examine the similarities and differences in the distributions of PCDD/Fs in storm water from different outfalls. The sampling results showed few significant differences between storm water discharged from outfalls located in mixed urban/commercial/residential areas and outfalls located adjacent to petroleum refineries. The concentrations of 2,3,7,8-TCDD were below the analytical limits of detection in all storm water samples, with the exception of samples collected after the sixth hour of sampling at the Oakland outfall. Fingerprint patterns were generally dominated by the higher chlorinated PCDD/F congeners including OCDD, OCDF, and 1,2,3,4,6,7,8-HpCDD. Total TEQs were generally below US EPA ambient water quality criteria and aquatic ecotoxicology guideline values. The results of this study strongly suggest that discrete sampling of storm water outfalls is insufficient to characterize the concentrations and distributions of persistent hydrophobic contaminants such as PCDD/Fs. In addition to surface water runoff from the city of Oakland, other nonindustrialized urban locations may represent important sources of PCDD/Fs to San Francisco Bay.
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  • 5
    ISSN: 1432-0495
    Keywords: Key words Natural potential technique ; Topographic effect ; Karst terrane ; Groundwater recharge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The natural (electrical) potential (NP) method – also known as self-potential, spontaneous potential and streaming potential (SP) – has been used to locate areas of groundwater flow in karst terrane. NP is the naturally occurring voltage at the ground surface resulting from ambient electrical currents within the earth. The measurement of NP can be used to characterize groundwater flow in karst terrane because electrical potential gradients are generated by the horizontal flow of water along fractures or conduits and the vertical infiltration of water into fractures or shafts. NP data from a site on the Mitchell Plain of southern Indiana, USA, revealed that NP data can be decomposed into three components: topographic effect, residual NP and noise. At this site, NP was inversely proportional to elevation, but the correlation varied with time. The topographic correction factor varied from –2.5 to –1.2 mV/m (NP change per unit elevation increase), with an average linear correlation coefficient (R) of 0.95. Because the site slopes toward an adjacent creek that is the local groundwater discharge zone, one possible explanation for this effect is a streaming-potential mechanism generated by groundwater movement toward the creek. The residual NP data revealed three negative anomalies at the survey area. Two of them coincide with sinkholes. A part of the third anomaly is coincident with a small valley, and concentrated infiltration does occur at this elevation in other valleys at the site, as evidenced by the existence of sinkholes. However, the dispersed, low-magnitude nature of the third anomaly does not prove the existence of concentrated groundwater recharge activity.
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  • 6
    ISSN: 0992-7689
    Keywords: Magnetospheric physics (auroral phenomena; storms and substorms)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Early auroral observations recorded in various oriental histories are examined in order to search for examples of strictly simultaneous and indisputably independent observations of the aurora borealis from spatially separated sites in East Asia. In the period up to AD 1700, only five examples have been found of two or more oriental auroral observations from separate sites on the same night. These occurred during the nights of AD 1101 January 31, AD 1138 October 6, AD 1363 July 30, AD 1582 March 8 and AD 1653 March 2. The independent historical evidence describing observations of mid-latitude auroral displays at more than one site in East Asia on the same night provides virtually incontrovertible proof that auroral displays actually occurred on these five special occasions. This conclusion is corroborated by the good level of agreement between the detailed auroral descriptions recorded in the different oriental histories, which furnish essentially compatible information on both the colour (or colours) of each auroral display and its approximate position in the sky. In addition, the occurrence of auroral displays in Europe within two days of auroral displays in East Asia, on two (possibly three) out of these five special occasions, suggests that a substantial number of the mid-latitude auroral displays recorded in the oriental histories are associated with intense geomagnetic storms.
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  • 7
    ISSN: 1572-8986
    Keywords: Spectroscopy ; volatilization ; iron ; nickel ; chromium ; waste vitrification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Atomic emission spectroscopy (AES) is used to monitor volatilization during waste vitrification with thermal plasmas. Model baste specimens consist of am alumino-silicate clay spiked with 10 wt. % Fe, Ni, or Cr. Specimens are vitrified in processing atmospheres with 0, 8.5, and 17 vol. % oxygen/argon concentrations. Particulate generated from condensation of the volatilized materials is collected following each specimen run and analyzed by energy dispersive X-ray analysis to determine composition. Spectra are collected from the ultraviolet range 240–380 nm in where the presence of metal vapor is readily detected. Correlation between line emission intensities and volatilization rates allows the establishment of provisional detection limits for the volatilization of Ni, Cr, Si, and Fe, of 1 × 103 g/s, 4 × 104 g/s, 2 × 104 g/s, and 5 × 105 g/s, respectively. The results of this investigation support the concept of using AES as an in-situ process monitor for feedback to optimize plasma processing of hazardous metal-containing waste.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 15 (1996), S. 2033-2035 
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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  • 9
    ISSN: 1432-1424
    Keywords: Key words: Barbiturates — Glucose transport — Anesthetics — Pharmacologic specificity — Isoform selectivity — Binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract. Barbiturates inhibit GLUT-1-mediated glucose transport across the blood-brain barrier, in cultured mammalian cells, and in human erythrocytes. Barbiturates also interact directly with GLUT-1. The hypotheses that this inhibition of glucose transport is (i) selective, preferring barbiturates over halogenated hydrocarbon inhalation anesthetics, and (ii) specific, favoring some GLUT-# isoforms over others were tested. Several oxy- and thio-barbiturates inhibited [3H]-2-deoxyglucose uptake by GLUT-1 expressing murine fibroblasts with IC50s of 0.2–2.9 mm. Inhibition of GLUT-1 by barbiturates correlates with their overall lipid solubility and pharmacology, and requires hydrophobic side chains on the core barbiturate structure. In contrast, several halogenated hydrocarbons and ethanol (all ≤10 mm) do not significantly inhibit glucose transport. The interaction of these three classes of anesthetics with purified GLUT-1 was evaluated by quenching of intrinsic protein fluorescence and displayed similar specificities and characteristics. The ability of barbiturates to inhibit other facilitative glucose transporters was determined in cell types expressing predominantly one isoform. Pentobarbital inhibits [3H]-2-deoxyglucose and [14C]-3-O-methyl-glucose uptake in cells expressing GLUT-1, GLUT-2, and GLUT-3 with IC50s of ∼1 mm. In contrast, GLUT-4 expressed in insulin-stimulated rat adipocytes was much less sensitive than the other isoforms to inhibition by pentobarbital (IC50 of 〉10 mm). Thus, barbiturates selectively inhibit glucose transport by some, but not all, facilitative glucose transporter isoforms.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 92 (1996), S. 885-890 
    ISSN: 1432-2242
    Keywords: Key words  Microgametophyte selection ; Pollen selection ; Pollen competition ; Cucurbita texana ; Cucurbita pepo
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract   We examined the effects of pollen selection for rapid pollen-tube growth on progeny vigor. First, we crossed a wild gourd (Cucurbita texana) to a cultivated zucchini (Cucurbita pepo cv `Black Beauty') to produce an F1 and then an F2 generation. Half of the F1 seeds were produced by depositing small loads of C. texana pollen onto the stigmas of C. pepo. These small pollen loads were insufficient to produce a full complement of seeds and, consequently, both the fast- and the slow-growing pollen tubes were permitted to achieve fertilization. An F2 generation was then produced by depositing small loads of F1 pollen onto stigmas of F1 plants. The F2 seeds resulting from two generations of small pollen loads are termed 'the non-selected line' because there was little or no selection for pollen-tube growth rate on these plants. The other half of the F1 and F2 seeds were produced by depositing large pollen loads (〉10000 pollen grains) onto stigmas and then allowing only the first 1% or so of the pollen tubes that entered the ovary to fertilize the ovules. We did this by excising the styles at the ovary at 12–15 h after pollination. The resulting F2 seeds are termed `the selected line' because they were produced by two generations of selection for only the fastest growing pollen tubes. Small pollen loads from the F2 plants, both the selected and the non-selected lines, were then deposited onto stigmas of different C. pepo flowers, and the vigor of the resulting seeds was compared under greenhouse and field conditions. The results showed that the seeds fertilized by pollen from the selected line had greater vegetative vigor as seedlings and greater flower and fruit production as mature plants than the seeds fertilized by pollen from the non-selected line. This study demonstrates that selection for fast pollen-tube growth (selection on the microgametophyte) leads to a correlated increase in sporophyte (progeny) vigor.
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