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  • 1
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of the American Chemical Society 117 (1995), S. 7830-7831 
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-0495
    Keywords: Key words Aquifer properties ; Mining ; Subsidence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Subsidence due to longwall underground coal mining changes the hydraulic properties, heads, yields, and in some cases the groundwater chemistry of overlying bedrock aquifers. A 7-year study of a sandstone aquifer overlying an active longwall mine in Illinois has supported a comprehensive model of these impacts. Subsidence caused increases in permeability and storativity over the longwall panel. These changes initially caused a major decline in water levels in the sandstone, but the aquifer recovered slightly within a few months and fully within several years after mining. The enhanced hydraulic properties combined with potentiometric recovery resulted in a zone of greater well yield. However, at sites with very poor transmissivity and inadequate recharge pathways, recovery may not occur. Also, at the study site, the physical enhancement was accompanied by a deterioration in groundwater quality from slightly brackish, sodium bicarbonate water to more brackish water with increased sulfate levels.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0495
    Keywords: Key words Mercury pollution ; Mining ; Fluvial geomorphology ; Sedimentation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  The historic processing of precious metal ores mined from the Comstock Lode of west-central Nevada resulted in the release of substantial, but unquantified amounts of mercury-contaminated mill tailings to the Carson River basin. Geomorphic and stratigraphic studies indicate that the introduction of these waste materials led to a period of valley-floor aggradation that was accompanied by lateral channel instability. The combined result of these geomorphic responses was the storage of large volumes of mercury-enriched sediment within a complexly structured alluvial sequence located along the Carson River valley. Much of the contaminated sediment is associated with filled paleochannels produced by the cutoff and abandonment of meander loops, and their subsequent infilling with contaminated particles. Geochemically, these deposits are characterized by variations in mercury levels that exceed three orders of magnitude. Continued lateral instability, coupled with an episode of channel-bed incision, followed the decline of Comstock mining, and has reexposed contaminated debris within the banks of the river. Erosion of bank sediments reintroduces mercury-enriched particles to the modern channel bed. It is suggested on the basis of geochemical and sedimentological data that during the bank erosion process, much of the mercury associated with fine (〈63 μ) valley-fill deposits are carried downstream without being incorporated to any appreciable extent within the channel-bed sediments. In contrast, mercury associated with larger and denser particles, particularly mercury-gold-silver amalgam grains, are accumulated in the channel-bed sediments as the river traverses polluted reaches of the Carson River valley. Concentration patterns developed along the modern channel indicate that the valley fill is the primary source of mercury to the river today. Thus, these data imply that efforts to reduce the influx of mercury to the aquatic environment should examine methods for reducing bank erosion rates.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1106
    Keywords: Motoneuron ; Stretch reflex ; Cutaneous ; Contralateral ; Spinal ; Cat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of bilateral focal cooling of dorsolateral thoracic spinal cord on segmental reflex pathways to the triceps surae muscles were assessed in decerebrate cats from the reflex forces produced by single shocks or trains of electrical stimuli applied to the ipsilateral caudal cutaneous sural and the contralateral tibial nerves. The validity of the dorsal cold block technique as a substitute for acute surgical dorsal hemisection was established by showing that focal cooling reliably reproduced the stretch-induced “clasp knife” inhibition of triceps surae reflexive force seen following dorsal hemisection. Under control (warm) conditions, the inhibitory components of electrically evoked ipsilateral sural and contralateral tibial reflexes faded rapidly during sustained trains, with a resultant production of large-amplitude reflex force as measured from either the entire triceps surae or from the medial gastrocnemius muscle alone. Dorsal cold block greatly reduced the amplitude of reflexive force evoked by sustained electrical stimulation of either nerve. Indeed, the cold block completely reversed the sign of train-evoked reflexes to a net inhibition of reflex force output in one-half of the sural and one-half of the contralateral tibial stimulation experiments. Peak transient forces evoked by single shocks to the sural or contralateral tibial nerves were also sometimes reduced, but this result was more variable than for prolonged nerve stimulation. The persistence of activity in segmental inhibitory pathways during dorsal cold block, as indicated by instances of reflex sign reversal, suggests that descending bulbospinal pathways traversing the dorsolateral funiculi may be responsible for “fading” of segmental inhibitory reflex components in decerebrate cats with intact spinal cords during sustained afferent input. The possibility that the enhanced magnitude and duration of segmental inhibition during cold block will increase the likelihood of disruption of the size principle for motoneuron recruitment is also discussed.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1106
    Keywords: Temporomandibular ; Joint ; Biomechanics ; Gender ; Nociception
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Chronic pain in the temporomandibular (TM) joint is predominantly manifested in women. We examined biomechanical and neural factors that could contribute to this differential representation. Relationships between jaw rotation, soft tissue strains and soft tissue forces were examined in the goat TM joint. Strains were minimal until the jaw was rotated beyond the normal range of motion (7.25 deg). There were no significant differences in rotation-strain patterns in males and females. Stress developed as strains were introduced by jaw rotation. Gender differences were observed. Males manifested higher failure loads (15.94±1.98 and 11.37±2.02 N, for males and females respectively) and higher elastic stiffness than females (5.62±1.19 N/mm and 1.64±0.31 N/mm, for males and females respectively). Recordings were made from cell bodies in the trigeminal ganglion whose distal processes innervated the retrodiscal tissue of the temporomandibular joint of the goat (n=48). Nociceptor reactivity was characterized with respect to the capacity to transduce mandibular rotation (rotation-interval functions;n=29). On the basis of established relationships between rotation, strain and tissue forces, rotation-interval functions were transformed into strain-interval and force-interval functions. Comparisons were made between nociceptor properties grouped by gender. No differences in properties were observed when nociceptors were characterized with respect to jaw rotation; however, gender differences were obtained when nociceptor reactivity was characterized with respect to retrodiscal strains or forces. Consistent with smaller failure loads, nociceptors of retrodiscal tissues of females manifested a smaller range (1.12 vs 4.33 N), force to average (1.51 vs 4.64 N), force to minimum (0.95 vs 2.48 N) and force to asymptotic discharge (2.07 vs 6.81 N). Consistent with lower elastic stiffness, nociceptors of female tissues manifested higher average strain (54.4% vs 41.9%) and peak strain (74.0% vs 58.1%) to asymptotic discharge relative to those sampled from male tissues. The implications of these findings for TM joint injury and chronic pain are considered.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1399-0047
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: The α-toxin of Clostridium perfringens is the major virulence determinant for gas gangrene in man. The gene encoding the α-toxin has been cloned into E. coli from two strains of the bacterium (NCTC8237 and CER89L43) and subsequently purified to homogeneity. The two strains of α-toxin differ by five amino acids, resulting in the toxin from NCTC8237 being sensitive to chymotrypsin digestion while that from CER89L43 is resistant. The α-toxin from each of these strains has been crystallized in two different forms by the hanging-drop vapour-diffusion method at 293 K. CER89L43 form I crystals belong to space group R32 and have two molecules in the crystallographic asymmetric unit and a unit cell with a = b = 151.4, c = 195.5 Å, α = β = 90, γ = 120°. The crystals diffracted to dmin = 1.90 Å. The characteristics of the NCTC8237 form I crystals have already been reported. The form II crystals from both strains belong to space group C2221 with one molecule in the crystallographic asymmetric unit and, for strain CER89L43, have cell dimensions a = 61.05, b = 177.50, c = 79.05 Å, α = β = γ = 90°, while for strain NCTC8237 the cell dimensions are a = 60.50, b = 175.70, c = 80.20 Å, α = β = γ = 90°. The crystals diffracted to maximum resolutions of 1.85 and 2.1 Å for the CER89L43 and the NCTC8237 strains, respectively.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Marine mammal science 14 (1998), S. 0 
    ISSN: 1748-7692
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Growth of Atlantic walruses (Odobenus rosmarus rosmarus) was investigated using morphological data collected in association with Inuit subsistence walrus hunts. Four growth models were examined. The growth parameters of a constrained Richards model were used to quantify growth and to test for sexual dimorphism. The asymptotic length of male walruses (315.2 cm ± 3.8 (SE), n= 103) was significantly larger (t= 7.21, df = 191, P 〈 0.05) than the asymptotic length of females (276.6 cm ± 3.4, n= 90). Sexual size dimorphism in adults was due to a longer growth period and a faster growth rate in males. The predictive equation relating mass (M, kg) to standard length (SL, cm) was: Log10M= -3.74 + 2.68(Log10SL), n= 25, r2= 0.98. There were no significant differences in the size of male walruses from Foxe Basin collected in the 1950s and this study. There were too few data to compare females. There were no significant differences in size between walruses sampled in Greenland and Foxe Basin in the 1980s and 1990s. Foxe Basin walruses were significantly larger than walruses sampled in northern Hudson Bay in the 1950s. Female Atlantic walruses sampled in Foxe Basin were larger than female Pacific walruses (Odobenus rosmarus divergens) sampled in Alaska.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 70 (1999), S. 4562-4568 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We investigate the shielding of superconducting and μ-metal forms in axial and transverse directed background magnetic noise fields. Analytical expressions are obtained for the improvement in signal-to-noise ratio obtained by placing a superconducting disk in the presence of a dipole source and a uniform noise field. Axial and transverse shielding factors are then compared for identical superconducting and μ-metal cylinders. The signal-to-noise ratio is found to be infinite at certain points inside a superconducting cylinder as well as a superconducting cylinder with a central partition. Shielding factors obtained here are relevant to SQUID measurements of small dipole source fields in the presence of large background noise fields such as those encountered in biomagnetism and nondestructive evaluation. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Entomology 40 (1995), S. 389-415 
    ISSN: 0066-4170
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Type of Medium: Electronic Resource
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