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  • 1
    ISSN: 1435-604X
    Keywords: Port-wine stain ; Photothermolysis ; Laser treatment ; Vascular injury ; Laser pulse length ; Blood vessel diameter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract A thermal model of blood vessel damage during the laser treatment of port-wine stains (PWS) is presented. The model depends on the heat generation in a blood vessel caused by the absorption of laser light and the thermodiffusion of that heat through the dermis. The criterion of vessel injury adopted was an average vessel temperature of 70 °C. Results show that for a chosen combination of pulse length and radiant exposure, only blood vessels within a certain diameter range will be injured. This is in agreement with the pulse length selective photothermolysis criteria suggested previously by Anderson and Parrish (1). The Anderson and Parrish model relies on the cooling behaviour of instantaneously heated vessels, whereas the present study utilizes the heating of the vessel by a Gaussian temporal laser pulse profile. Predictions based on one blood vessel were verified in a skin model with multiple blood vessels by simulating vessel coagulation with a single laser treatment. The diameter of the blood vessels that are damaged during laser treatment of PWS depends on the laser pulse length.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary An ultra-high strength polyethylene fiber with an initial tensile strength at break of 3.0 GPa, was irradiated at room temperature under vacuum by means of 60Co γ-radiation. Gelcontent and equilibrium volume degree of swelling of the gelfraction, were determined as a function of dose. From a plot of the effective network chain density versus dose, it was concluded that the fiber contained about 2 entanglements per number average molecule. Furthermore, a crosslinking efficiency of 0.33 crosslink per 100 eV of absorbed energy was found.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Ultra-High Molecular Weight Polyethylene (UHMWPE) is frequently used in artificial joints because of its high wear resistance. To extend the lifetime of these joints even further, it is necessary to decrease the wear rate. The wear rate may be decreased by blending UHMWPE with short aramid fibers. On account of the extremely high viscosity of UHMWPE mixing was accomplished by swirling the UHMWPE powder and the chopped fibers with compressed dry nitrogen, and a composite with fairly uniformly distributed and randomly oriented fibers was obtained by compression moulding. The failure behaviour of the composite changes from ductile for low fiber content to brittle failure for higher fiber content. The deviation of the experimental Young's modulus from the theoretical value can be explained by, among others, the void content. Preliminary results show that the wear rate of UHMWPE indeed decreases with incorporation of the aramid fibers.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Ultra-high strength polyethylene fibers, with a tensile strength at break varying from 1.6 up to 3.5 GPa, were irradiated, at room temperature under vacuum by means of 60Co γ-radiation. Sol-gel analysis showed a ratio of crosslinking to main-chain scissioning of about 1. The tensile strength at break decreased upon irradiation. The decrease of tensile strength at break depended on initial fiber strength and could be attributed to main-chain scissioning. It was concluded that stressed chains break preferentially upon irradiation. “Fiber” networks exhibited a deformation ratio of 16 during stress-strain measurements.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-1238
    Keywords: Sepsis ; Coagulation ; Fibrinolysis ; Septic shock
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Abnormalities in coagulation and fibrinolysis are frequently observed in septic shock. The most pronounced clinical manifestation is disseminated intravascular coagulation. Recent studies in human volunteers and animal models have clarified the early dynamics and route of activation of both coagulation and fibrinolytic pathways. In healthy subjects subjected to a low dose of either endotoxin or TNF an imbalance in the procoagulant and the fibrinolytic mechanisms is apparent, resulting in a procoagulant state. Also in patients with septic shock a dynamic process of coagulation and fibrinolysis is ongoing with evidence of impaired fibrinolysis. These abnormalities have prognostic significance; the extent of disturbances of coagulation and fibrinolysis is related to the development of multiple organ failure and death.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-1017
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-069X
    Keywords: UVB phototherapy ; Minimal erythema dose (MED) ; Water uptake ; Psoriasis ; Bathing in water and salt solutions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The influence of tap-water (TW) and salt solutions on the minimal erythema dose (MED) was investigated for normal human skin and uninvolved skin of psoriasis patients. MED (UVB) determinations on the forearm revealed that: (1) the MED definitely decreases whenever the arm is immersed in TW or NaCl solutions with a low concentration (4%) prior to UVB exposure, whereas almost saturated NaCl solution (26%), as well as locum Dead Sea water (LDSW), do not produce a change in the MED, and (2) the decrease in MED obtained by wetting the skin with TW was no longer present when the skin was allowed to dry for 20 min. A decrease in water uptake by skin (in vivo) and by callus (in vitro) was found as the salt concentration of the external solution increased. It is proposed that water taken up by the skin plays an important role in the sensitivity of the skin to UVB exposure. Bathing in TW or 4% NaCl prior to UVB exposure offered a slight to moderate improvement in psoriasis over UVB irradiation alone. Finally, it was shown that there is no obvious difference in clearance of the psoriatic skin between a bath in TW, 4% NaCl, or LDSW prior to UVB exposure.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Mathematische Annalen 172 (1967), S. 238-246 
    ISSN: 1432-1807
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Naturwissenschaften 21 (1933), S. 204-205 
    ISSN: 1432-1904
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Stress has been shown to affect brain structural plasticity, promote long-term changes in multiple neurotransmitter systems and cause neuronal atrophy. However, the mechanisms involved in these stress-related neural alterations are still poorly understood. Mitogen-activated protein kinase (MAPK) cascades play a crucial role in the transduction of neurotrophic signal from the cell surface to the nucleus and are implicated in the modulation of synaptic plasticity and neuronal survival. An intriguing possibility is that stress might influence brain plasticity through its effects on selective members of such intracellular signalling cascades responsible for the transduction of neurotrophin signals. Here, we have investigated the effects of stress on the expression of three members of the MAPK/extracellular-regulated kinase (ERK) pathway such as phospho-ERK1, phospho-ERK2 and phospho-cAMP/calcium-responsive element-binding protein (CREB) in the adult rat brain. Male rats were subjected to mild footshocks and the patterns of protein expression were analysed after 21 consecutive days of stress. We found that chronic stress induced a pronounced and persistent ERK1/2 hyperphosphorylation in dendrites of the higher prefrontocortical layers (II and III) and a reduction of phospho-CREB expression in several cortical and subcortical regions. We hypothesized that defects in ERK signalling regulation combined with a reduced phospho-CREB activity may be a crucial mechanism by which sustained stress may induce atrophy of selective subpopulations of vulnerable cortical neurons and/or distal dendrites. Thus, ERK-mediated cortical abnormalities may represent a specific path by which chronic stress affects the functioning of cortical structures and causes selective neural network defects.
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