Library

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 11
    Electronic Resource
    Electronic Resource
    Evolution of the rheological properties during the reactive processing of thermoplastic/thermoset epoxy (1991)
    Springer
    Rheologica acta 30 (1991), S. 184-196 
    Details
    ISSN: 1435-1528
    Keywords: Epoxy ; gel time ; reaction kinetics ; reactioninjection molding ; dynamic mechanical analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The melt state reaction, or fusion process of bisphenol-A and the diglycidyl ether of bisphenol-A can produce both linear phenoxy backbone chains and crosslinked network structures. The linear chains can be thought of as thermoplastic polymer, while the crosslinked molecular matrix is a thermoset; therefore, this resin system can be termed a thermoplastic/thermoset epoxy. Rheological analysis has been performed on this system to determine the occurrence of the crossover of the storage and loss moduli during the reaction using three techniques: isothermal cure, interval frequency sweep, and interval stress relaxation. Determination of the activation energy of the reaction by consideration of the conventional gel-point determination prove unsatisfactory as compared to that which is determined by FTIR. An alternative technique is presented which yields a value in good agreement with that obtained by following epoxide consumption. The thermoplastic/thermoset nature of this material leads to the deviation from traditional thermoset cure behavior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01134608
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 12
    Electronic Resource
    Electronic Resource
    Density-associated changes in platelet-activating factor acetylhydrolase activity and membrane fluidity of human erythrocytes (1994)
    Springer
    Annals of hematology 69 (1994), S. 139-145 
    Details
    ISSN: 1432-0584
    Keywords: Aging ; Erythrocytes ; Platelet-activating factor ; Acyltransferases ; Membrane fluidity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Platelet-activating factor acetylhydrolase is known to degrade oxidatively fragmented phospholipids which are similar in structure to platelet-activating factor. We examined changes of acetylhydrolase activity during in vivo aging of human erythrocytes and tried to assess its role in maintaining the membrane properties of erythrocytes. Higher-density erythrocytes are enriched with older cells. Erythrocytes obtained from seven healthy colleagues were separated into four density fractions by centrifugation in discontinuous Percoll density gradients. Both membrane and cytosolic acetylhydrolase decreased with increasing erythrocyte density. Membrane and cytosolic acetylhydrolase activities in the lightest fraction were 2.0±1.0 (SD) nkat/g protein and 362±58 pkat/g protein, respectivley, and these values were significantly higher than those in the densest fraction: 1.3±0.7 nkat/g protein and 286±70 pkat/g protein, respectively. Membrane acyltransferase activity also decreased with red cell density and the average values in the lightest and densest fractions were 51.2±23.6 and 27.0±20.2 μkat/g protein, respectively. Generation of thiobarbituric acid-reactive substances induced byt-butyl hydroperoxide treatment decreased with increasing cell density, and the inhibition of acetylhydrolase with diisopropylfluorophosphate resulted in enhanced peroxide-induced lipid oxidation, particularly in lower-density fractions. There was no significant change in basal levels of thiobarbituric acid-reactive substances in red cell membrane. Membrane fluidity was evaluated by fluorescence recovery after photobleaching and it decreased as erythrocyte density increased. We conclude that the activity of the deacylation/reacylation cycle maintained by acetylhydrolase and acyltransferase is gradually reduced during in vivo aging of erythrocytes. This may be connected with decreases of polyunsaturated fatty acids and membrane fluidity in old eryhtrocytes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01695695
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 13
    Electronic Resource
    Electronic Resource
    Glucagon, insulin and somatostatin secretion in response to sympathetic neural activation in streptozotocin-induced diabetic rats. A study with the isolated perfused rat pancreas in vitro (1992)
    Springer
    Diabetologia 35 (1992), S. 1035-1041 
    Details
    ISSN: 1432-0428
    Keywords: Glucagon ; insulin ; somatostatin ; streptozotocin ; sympathetic nerve ; diabetic rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Changes in glucagon, insulin and somatostatin secretion induced by electrical splanchnic nerve stimulation were examined in rats treated with streptozotocin as neonates and as adults. In order to study the direct neural effects we used the isolated perfused rat pancreas with intact left splanchnic nerve in vitro. In normal rats splanchnic nerve stimulation causes significant decreases in insulin (30–40%) and somatostatin (30–50%) secretion at both 16.7 mmol/l and 1 mmol/l glucose concentrations. In the neonatal streptozotocin-diabetic rats splanchnic nerve stimulation at 16.7 mmol/l glucose decreased insulin secretion (14%) further than in the control rats (30%), however, somatostatin secretion did not decrease to the same extent. Similar results were also observed at the low (1 mmol/l) glucose concentration. On the other hand, percent decreases of insulin and somatostatin secretion induced by splanchnic nerve stimulation in the streptozotocin-diabetic rats were similar to the values observed in the normal control rats. The glucagon secretion in response to splanchnic nerve stimulation at 16.7 mmol/l glucose from pancreatic Alpha cells in both types of induced diabetes is exaggerated, and the degree of exaggeration seems to parallel the severity of the hyperglycaemia. However, the splanchnic nerve stimulation-induced glucagon secretion at 1 mmol/l glucose was impaired in the streptozotocin-diabetic rats, but not in the neonatal streptozotocin-diabetic rats. These data suggest that the sensitivity of diabetic Alpha and Delta cells to sympathetic neural activation are blunted, whereas the sensitivity of Beta cells is enhanced in the diabetic animal model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02221678
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 14
    Electronic Resource
    Electronic Resource
    Reduced sensitivity of dihydroxyacetone on ATP-sensitive K+ channels of pancreatic beta cells in GK rats (1994)
    Springer
    Diabetologia 37 (1994), S. 1082-1087 
    Details
    ISSN: 1432-0428
    Keywords: Dihydroxyacetone ; ATP-sensitive K+ channels ; GK rat ; glycerol phosphate shuttle ; pancreatic beta cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the GK (Goto-Kakizaki) rat, a genetic model of non-insulin-dependent diabetes mellitus, glucose-induced insulin secretion is selectively impaired. In addition, it has been suggested by previous studies that impaired glucose metabolism in beta cells of the GK rat results in insufficient closure of ATP-sensitive K+ channels (KATP channels) and a consequent decrease in depolarization, leading to a decreased insulin release. We have recently reported that the site of disturbed glucose metabolism is probably located in the early stages of glycolysis or in the glycerol phosphate shuttle. In the present study, in order to identify the impaired metabolic step in diabetic beta cells, we have investigated insulin secretory capacity by stimulation with dihydroxyacetone (DHA), which is known to be directly converted to DHA-phosphate and to preferentially enter the glycerol phosphate shuttle. In addition, using the patch-clamp technique, we also have studied the sensitivity of DHA on the KATP channels of beta cells in GK rats. The insulin secretion in response to 5 mmol/l DHA with 2.8 mmol/l glucose was impaired, and DHA sensitivity of the KATP channels was reduced in beta cells of GK rats. From these results, we suggest that the intracellular site responsible for impaired glucose metabolism in pancreatic beta cells of GK rats is located in the glycerol phosphate shuttle.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418371
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 15
    Electronic Resource
    Electronic Resource
    Reduced sensitivity of dihydroxyacetone on ATP-sensitive K+ channels of pancreatic beta cells in GK rats (1994)
    Springer
    Diabetologia 37 (1994), S. 1082-1087 
    Details
    ISSN: 1432-0428
    Keywords: Key words Dihydroxyacetone ; ATP-sensitive K+ channels ; GK rat ; glycerol phosphate shuttle ; pancreatic beta cell.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the GK (Goto-Kakizaki) rat, a genetic model of non-insulin-dependent diabetes mellitus, glucose-induced insulin secretion is selectively impaired. In addition, it has been suggested by previous studies that impaired glucose metabolism in beta cells of the GK rat results in insufficient closure of ATP-sensitive K+ channels (KATP channels) and a consequent decrease in depolarization, leading to a decreased insulin release. We have recently reported that the site of disturbed glucose metabolism is probably located in the early stages of glycolysis or in the glycerol phosphate shuttle. In the present study, in order to identify the impaired metabolic step in diabetic beta cells, we have investigated insulin secretory capacity by stimulation with dihydroxyacetone (DHA), which is known to be directly converted to DHA-phosphate and to preferentially enter the glycerol phosphate shuttle. In addition, using the patch-clamp technique, we also have studied the sensitivity of DHA on the KATP channels of beta cells in GK rats. The insulin secretion in response to 5 mmol/l DHA with 2.8 mmol/l glucose was impaired, and DHA sensitivity of the KATP channels was reduced in beta cells of GK rats. From these results, we suggest that the intracellular site responsible for impaired glucose metabolism in pancreatic beta cells of GK rats is located in the glycerol phosphate shuttle. [Diabetologia (1994) 37: 1082–1087]
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418371
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 16
    Electronic Resource
    Electronic Resource
    Macroscopic intraheptic portal-hepatic venous shunt not associated with chronic hepatic disease (1994)
    Springer
    Abdominal imaging 19 (1994), S. 153-156 
    Details
    ISSN: 1432-0509
    Keywords: Color Doppler ; Portal-hepatic venous shunt ; Liver ; Ultrasound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Asymptomatic macroscopic portal-hepatic venous shunt (MPVS) without chronic hepatic disease is a rare vascular lesion. Two cases of this disorder are reported, and the usefulness of color Doppler sonography for studying hemodynamics of such small vascular lesions is stressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00203492
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 17
    Electronic Resource
    Electronic Resource
    Color doppler findings in small abdominal aneurysms (1994)
    Springer
    Abdominal imaging 19 (1994), S. 410-412 
    Details
    ISSN: 1432-0509
    Keywords: Abdomen, ultrasound-Aneurysm, color, Doppler US ; Visceral aneurysms, hemodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Four cases of small abdominal aneurysms were assessed by color Doppler ultrasonography. The aneurysms demonstrated interesting and highly complicated internal hemodynamics, including a swirling blood flow pattern and/or a color mosaic pattern. These findings suggested the usefulness of color Doppler ultrasonography for obtaining details on internal hemodynamics, which cannot be obtained with other modalities, such as angiography or computed tomography (CT).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206926
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 18
    Electronic Resource
    Electronic Resource
    Effect of prostaglandin E2 on mineralization of bone nodules formed by fetal rat calvarial cells (1994)
    Springer
    Calcified tissue international 55 (1994), S. 451-457 
    Details
    ISSN: 1432-0827
    Keywords: Prostaglandin E2 ; Rat calvarial cell ; Differentiation ; Mineralization ; Osteopontin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Physics
    Notes: Abstract The effects of PGE2 on mineralized bone nodule formation were studied in fetal rat calvarial (RC) cells in vitro. Continuous exposure of RC cells to 3x10-8M PGE2 induced a twofold increase in mineralized bone nodule formation and a 1.5-fold increase in alkaline phosphatase (ALPase) activity without affecting RC cell growth. These stimulatory effects were evoked by concentrations of 3x 10-9-3x10-6 M PGE2 and the maximal effect was observed with 3x10-8 M PGE2. The in vitro effects of PGE2 were evident when RC cells were exposed to it on days 8–14 and 8–21, which correspond to the post-confluent culture stage, but no effects were observed when the cells were exposed on days 1–7, the growth stage. The ALPase activity was also higher (1.2–1.4-fold) when 3x10-8 M PGE2 was added during the post-confluent stage. In order to determine the effect of PGE2 during the mineralization phase of bone nodules in the presence of a large population of osteoprogenitor cells, RC cells were exposed to dexamethasone for 7 days before PGE2 was added during the post-confluent stage. A significantly higher percentage of nodules mineralized were observed with 3x10-8-3x10-9 M PGE2 (1.6-and 1.4-fold, respectively), than in control cultures. Analysis of the mineral-related proteins by EDTA extraction of bone nodules followed by electrophoresis and Stains-All staining revealed an increased total amount of osteopontin extracted from the mineralized matrix after PGE2 treatment. The osteopontin content was highest after 3x10-8 M PGE2, with a 73% increase of the densitometric intensity of the bands, although this increase, reflected the increased number of mineralized bone nodules due to PGE2. These findings suggest that PGE2 may increase the proportion of functional osteoblasts able to produce mineralized bone nodules in the population by stimulating differentiation during the postconfluent stage of RC cell culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00298559
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 19
    Electronic Resource
    Electronic Resource
    Malignant thymoma in a patient with growth hormone deficiency during growth hormone therapy (1993)
    Springer
    European journal of pediatrics 152 (1993), S. 802-804 
    Details
    ISSN: 1432-1076
    Keywords: Growth hormone deficiency ; Growth hormone therapy ; Malignant thymoma
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Malignant thymoma was found in an 8-year-old Japanese boy with growth hormone (GH) deficiency who had received GH therapy for 3 years and 5 months. There may be a possible relationship between the occurrence of malignant thymoma and GH therapy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02073374
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 20
    Electronic Resource
    Electronic Resource
    Characterization of polyethylene/EPDM/silicon dioxide multicomponent composites by solid-state dynamic mechanical spectroscopy (1991)
    Springer
    Journal of materials science 26 (1991), S. 5708-5716 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Various composites of polyethylene, ethylene propylene diene rubber (EPDM), and filler are milled and analysed by solid-state dynamic mechanical spectroscopy. The filler used is silicon powder with an oxidized surface. This filler is a model for materials with siliceous surfaces. The torsion pendulum measurements show that the multicomponent composites exhibited complex viscoelastic behaviour. For composites of polyethylene and silicon dioxide, there is evidence of particle-particle interactions. In composites which include polyethylene, rubber and filler, interactions of the polyethylene and especially of the rubber with the filler surface are significant. Treatment of the filler surface with gamma-aminopropyltriethoxysilane (γ-APS) or gamma-methacryloxypropyltrimethoxysilane (γ-MPS) has a significant influence on the resultant composite dynamic mechanical spectrum. Maleic anhydride grafting of the EPDM rubber also changes the character of the composites. These composites appear to exhibit complex morphologies, which may be controlled to a certain extent by filler surface treatment and grafting to the rubber. There is evidence for a chemical reaction between the maleic anhydride modification of the EPDM and γ-APS during processing on the roll mill. Prediction of the composite properties using the extended van der Poel model is qualitatively useful.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01130106
    Library Location Call Number Volume/Issue/Year Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...