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  • 1
    Electronic Resource
    Electronic Resource
    Syndrome of Alagille: radiological and sonographic findings A review of 37 cases (1997)
    Springer
    European radiology 7 (1997), S. 115-118 
    Details
    ISSN: 1432-1084
    Keywords: Key words: Alagille's syndrome ; Ultrasonography ; Cholestasis ; Osseous abnormalities
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract. The objective of this study was to evaluate the association of intrahepatic cholestasis, pulmonary stenosis, and hyperlipemia with osseous and renal abnormalities in Alagille's syndrome. A total of 37 patients (25 males and 12 females) with ages ranging between 8 months and 27 years were included. Clinical records as well as radiological and ultrasonographic studies were reviewed. Chronic cholestasis was observed in all patients. Thirteen had favorable clinical outcome and normal hepatic sonograms. Clinical and sonographic evidence of portal hypertension was found in 13 patients and of cirrhosis in 8 patients. The remaining 3 patients required hepatic transplantation due to severe cholestasis. Hyperlipemia correlated with hepatic malfunction. Pulmonary stenosis and renal hypoplasia were the most frequently associated abnormalities. All patients showed a peculiar facies. Abnormal “butterfly” vertebrae were present in 18 patients and ulnar or phalangeal shortening in 11 patients. Ultrasonography allowed hepatobiliary disease assessment and helped to establish indications for hepatic transplantation. Renal and osseous abnormalities were not specific but in the appropriate clinical setting reinforced the diagnosis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003300050122
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  • 2
    Electronic Resource
    Electronic Resource
    Analysis of the electrical coupling of root cells: implications for ion transport and the existence of an osmotic pump (1992)
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    Details
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: An equivalent circuit was developed to model the radial electrical coupling between root cells. The results of several experiments were analysed using the circuit to determine whether the electrogenic pumps of the inner cortical cells were active. This analysis indicated that, while in some roots electrogenic pumps appear to be active in all cortical layers, they may be inactive in the inner cortical cells in some cases. The circuit was used to show that, in spite of intercellular symplasmic coupling, if the inner cortical cells have inactive electrogenic pumps, their membrane potentials can be significantly less negative than those of the epidermal cells. The radial difference in membrane potential may in part account for observations that the uptake of ions occurs primarily on the root periphery. This implication is developed in an appendix to show that an osmotic water pump may exist in roots to allow them to extract water from soil at a lower water potential. It is hypothesized that, as a result of a radial difference in membrane potential, there is an efflux of solutes from the inner cortical cells as the symplastic solution moves inward. As a result, the water potential of the root interior is elevated with respect to its exterior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3040.1992.tb00984.x
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  • 3
    Electronic Resource
    Electronic Resource
    Long-term follow-up of patients with biliary atresia successfully treated with hepatic portoenterostomy. The importance of sequential treatment (1998)
    Springer
    Pediatric surgery international 13 (1998), S. 327-330 
    Details
    ISSN: 1437-9813
    Keywords: Key words Biliary atresia ; Hepatic portoenterostomy ; Long-term follow-up ; Liver transplantation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The outcome of 18 biliary atresia (BA) patients (5 male, 13 female; age range 10.7–22.5 years; mean 15.4±0.7 years) treated with hepatic portoenterostomy (HPE) and jaundice-free for more than 10 years without liver transplantation (LT) is analyzed retrospectively. Eight of these patients subsequently required LT (age at LT 12.8±0.5 years, range 10.5–15.2 years); 3 children (aged 11.6, 13.2 and 14.1 years, respectively) had episodes of gastrointestinal variceal bleeding associated with other signs of severe disease and are now candidates for LT; and among the 7 asymptomatic patients (age range 11.2–22.5 years; mean 15.9±2.1 years), 5 had sonographic and biochemical signs of moderate portal hypertension (PH). In order to analyze whether the age at transplantation influences the survival of children transplanted for BA, we also reviewed the outcome of 71 BA patients transplanted at our hospital between 1986 and 1996. All the children older than 10 years at the time of LT were alive; only patients younger than 10 years died following LT (n= 15). We conclude that the natural outcome of extrahepatic BA is toward PH, fibrosis, and cirrhosis, even in those cases successfully treated with HPE. In our experience, the results of sequential treatment with HPE and LT were excellent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003830050331
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  • 4
    Electronic Resource
    Electronic Resource
    The use of DSC to characterize structural relaxation in thermosetting polymers (1997)
    Springer
    Journal of thermal analysis and calorimetry 49 (1997), S. 79-85 
    Details
    ISSN: 1572-8943
    Keywords: cross-linking degree ; DSC ; enthalpy relaxation ; epoxy resins ; physical aging ; reactive diluent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Structural relaxation in different epoxy-anhydride and epoxy-diamine resins has been investigated by differential scanning calorimetry using annealing and cooling rate experiments. The annealing experiments lead to the determination of enthalpy loss,δH, at an equivalent annealing temperatureT a=T g-20, and for periods of annealing time, ta, between 1 h and 4 months. The variation ofδH with logta, defines a relaxation rate per decade,rrpd, which is very sensitive to changes of the epoxy network. The cooling rate experiments allow the determination of the apparent activation energy,δh *. The effect of the degree of crosslinking, the addition of a reactive diluent, which acts as flexibilizer, and the length of cross-link onrrpd and δh* was studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01987423
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  • 5
    Electronic Resource
    Electronic Resource
    Physical ageing studies in semicrystalline poly(ethylene terephthalate) (1995)
    Springer
    Journal of materials science 30 (1995), S. 1790-1793 
    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 The physical ageing of semicrystalline poly(ethylene terephthalate) (c-PET) of different crystallinities and morphological structures was studied using differential scanning calorimetry. Samples of c-PET of crystallinity content χ c = 0.12, crystallized at low temperatures (105 °C for 13 min), submitted to physical ageing in a temperature range between 50 and 65 °C for different periods of time, showed two endothermic peaks. The first peak (P1) of higher intensity, appeared at a temperature close to the glass transition temperature, T g, of the amorphous PET, and the other peak (P2) of lower intensity, merged as a shoulder of the first one, at a higher temperature. These peaks have been attributed to the enthalpy relaxation process of two different amorphous regions: one amorphous phase outside the spherulitic structure (interspherulitic amorphous region) and another amorphous phase inside the spherulites (interlamellar amorphous region). The separation between P1 and P2 indicates that DSC, via enthalpy relaxation, is a good technique to detect the real double glass transition of the semicrystalline PET. However, the physical ageing of a semicrystalline PET of χ c = 0.32, crystallized at 114 °C during 1 h, showed a main endothermic peak shifted to a higher temperature, which probably corresponds to the enthalpy relaxation of the more restricted interlamellar amorphous region, and a small endothermic peak at lower temperature which could be a reflection of the hindered interspherulitic amorphous region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00351611
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  • 6
    Electronic Resource
    Electronic Resource
    Addition of a reactive diluent to a catalyzed epoxy-anhydride system. I. Influence on the cure kinetics (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 61 (1996), S. 1663-1674 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The effect of a reactive diluent (RD) on the kinetics of the curing of an epoxy resin, based on diglycidyl ether of bisphenol A (DGEBA), with a carboxylic anhvdride derived from methyl-tetrahydrophthalic anhydride (MTHPA) catalyzed by a tertiary amine has been studied. The reactive diluent was a low-viscosity aliphatic diglycidyl ether, and the compositions per 100 parts by weight (pbw) of DGEBA were 10, 30, and 50 pbw of RD with the stoichiometric quantity of MTHPA and 1 pbw of catalyst. The curing kinetics was monitored by differential scanning calorimetry (DSC), and the kinetic parameters were determined from the nonisothermal DSC curves by the method described by Málek. The kinetic analysis suggests that the two-parameter autocatalytic model is the more appropriate to describe the kinetics of the curing reaction of this epoxy-anhydride system. The kinetic parameters thus derived satisfactorily simulate both the nonisothermal DSC curves and the isothermal conversion-time plots. Increasing the RD content leads to a small increase in both the nonisothermal and the isothermal heats of curing and has a slight effect on the kinetic parameters E, ln A, m, and n, and, consequently, on the overall reactivity of the system. On the other hand, the increase of the RD content significantly affects the structure of the crosslinked epoxy. It is confirmed that the introduction of aliphatic chains in the structure of the epoxy increases the mobility of the segmental chains in the glass transition region. The consequence of this chemical modification is a decrease of the glass transition temperature, Tg. © 1996 John Wiley & Sons, Inc.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Enthalpy relaxation in a partially cured epoxy resin (1996)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 34 (1996), S. 229-239 
    Details
    ISSN: 0887-6266
    Keywords: enthalpy relaxation ; physical aging ; epoxy resin ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The enthalpy relaxation of a partially cured (70%) epoxy resin, derived from diglycidyl ether of bisphenol-A cured by methyl-tetrahydrophthalic anhydride with accelerator, has been investigated. The key parameters of the structural relaxation (the apparent activation energy Δh*, the nonlinearity parameter x, and the nonexponentiality parameter β) are compared with those of the fully cured epoxy resin. The aging rates, characterized by the dependences of the enthalpy loss and peak temperature on log(annealing time), are greater in the partially cured epoxy than they are in the fully cured resin at an equivalent aging temperature (Ta = Tg - 20°C). There is a significant reduction in Δh*, from 1100 kJ mol-1 for the fully cured system to 615 kJ mol-1, as the degree of cure is reduced. The parameter x determined by the peak-shift method appears essentially independent of the degree of cure (x = 0.41 ± 0.03 for the partially cured resin compared with 0.42 ± 0.03 obtained previously for the fully cured resin), and does not follow the usually observed correlation of increasing x as Δh* decreases. This invariability of the parameter x seems to indicate that it is determined essentially by the local chemical structure of the backbone chain, and rather little by the supramolecular structure. On the other hand, the estimated nonexponentiality parameter β lies between 0.3 and 0.456, which is significantly lower than in the fully cured epoxy (β ≅ 0.5), indicative of a broadening of the distribution of relaxation times as the degree of cross-linking is reduced. Like the parameter x, this also does not follow the usual correlation with Δh*. These results are discussed in the framework of strong and fragile behavior of glass-forming systems, but it is difficult to reconcile these results in any simple way with the concept of strength and fragility. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Physical aging studies of amorphous linear polyesters. Part II. Dependence of structural relaxation parameters on the chemical structure (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 113-126 
    Details
    ISSN: 0887-6266
    Keywords: enthalpy relaxation ; physical aging ; DSC ; glassy state ; thermoplastic polymers ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The enthalpy relaxation of a series of linear amorphous polyesters (poly(propylene isophthalate) (PPIP), poly(propylene terephthalate) (PPTP), poly(ethylene terephthalate) (PETP), and poly(dipropylene terephthalate) (PDPT)) has been investigated by differential scanning calorimetry (DSC). These polyesters have been annealed at equal undercooling below their respective glass transition temperatures, Tg, (Tg - 27°C, Tg - 15°C, and Tg - 9°C) for periods of time from 15 min to 480 h. The key parameters of structural relaxation, namely the apparent activation energy (Δh*), the nonlinearity parameter (x) and the nonexponentiality parameter (β), have been determined for each polyester and related to an effective relaxation rate (1/τeff) and to the chemical structure. We observe that the variation of the structural relaxation parameters shows a trend that is common to other polymeric systems, whereby an increase of x and β corresponds a decrease in Δh*. The comparison of these parameters in PETP and in PPTP gives information about the effect of the introduction of a methyl group pendant from the main chain; the x parameter increases (i.e., a reduced contribution of the structure to the relaxation times), β increases (i.e., a narrow distribution of relaxation times), and Δh* decreases. Additionally, enthalpy relaxation experiments show that a decrease of Δh* correlates with an increase of 1/τeff, when they are measured at a fixed value of the excess enthalpy, δH. The introduction of an isopropyl ether group in PDPT with respect to PPTP decreases both x and β, but increases Δh*, which the rate of relaxation decreases. The ring substitution in PPTP and PPIP originates less significant changes in the structural parameters. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 113-126, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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