1,721,170 research outputs found
CREEP-RUPTURE IN A NICKEL-BASED SUPERALLOY
No full textSmooth bar creep rupture tests were conducted under constant loads at 1033 and 1144 K using RENE 80. Creep deformation occurred dominantly by the dislocation creep mechanism, but creep rupture proceeded by the continual nucleation and growth of cavities. Rupture times were well predicted by the constrained diffusive growth model of Riedel, particularly at low applied stresses, but their temperature dependence and the Monkman-Grant product were better related to the unconstrained diffusive growth models. Interruption tests showed development of microcracks in the tertiary stage of creep and sometimes revealed edge cracks, the growth of which provided the creep crack growth rate
Effects of Paraspinal Intramuscular Injection of Atelocollagen in Patients with Chronic Low Back Pain: A Retrospective Observational Study
Get PDFBackground/Objectives: Atelocollagen is used for soft tissue repair and reconstruction by replacing defective or damaged muscles, membranes, ligaments, and tendons. This study aimed to evaluate the clinical efficacy and safety of additional paraspinal intramuscular injection of atelocollagen on lumbar epidural steroid injection for reducing pain and improving functional capacity of patients with chronic low back pain (CLBP). Methods: We retrospectively enrolled 608 consecutive patients with CLBP who received lumbar epidural steroid injection with or without additional paraspinal intramuscular injection of atelocollagen. The Numerical Rating Scale and the Oswestry Disability Index were used to assess pain and functional capacity, respectively, before the procedure, and three months after the injection. Also, we analyzed the relationship between the additional paraspinal intramuscular injection of atelocollagen and the success rate. Results: Both Numerical Rating Scale and the Oswestry Disability Index scores were significantly reduced in both groups at three months after injection. However, there was a significant difference between the two groups. Furthermore, the success rate was significantly higher in the additional paraspinal intramuscular injection of atelocollagen group. Conclusions: This study’s results showed that additional paraspinal intramuscular injection of atelocollagen on lumbar epidural steroid injection reduced pain and improved functional capacity for patients with CLBP. Therefore, the paraspinal intramuscular injection of atelocollagen may be a promising option for the treatment of patients with CLBP
Refining oxygen management through rigorous Oxygen Reserve Index (ORi) monitoring in patients undergoing general anesthesia: a randomized controlled trial: ORi to avoid excessive hyperoxia
No full textOptimizing oxygenation for patients necessitates a delicate balance between sufficient oxygen delivery and mitigating the potential hazards of hyperoxemia. We hypothesized that integrating Oxygen Reserve Index (ORi) monitoring would effectively reduce intraoperative hyperoxemia compared to reliance solely on pulse oximetry. This single-center randomized controlled trial included multiple trauma patients with ASA class 3 or higher undergoing general anesthesia. FiO(2) adjustments to 0.5 started at T0 with arterial blood gas analysis (ABGA) every 30-minutes. Patients were randomized into Group O (ORi monitoring) and Group N (pulse oximetry). In Group O, FiO(2) was reduced if ORi > 0.05; unchanged if ORi was 0-0.05. Group N decreased FiO(2) if SpO(2) was 100%, unchanged if SpO(2) was < 99%, and increased FiO(2) by 0.05 until SpO(2) reached 95% or above. 54 participants were randomized, and 51 analyzed. Group O demonstrated a significantly higher percentage of normoxemia (80 /= 120mmHg and >/= 150mmHg at 0.06 and 0.22, respectively. Simultaneous ORi and pulse oximetry reduce intraoperative hyperoxemia through safe and meticulous protocol adherence in patients
Synthesis and characterization of thermotropic liquid crystalline poly(ester-imide)s
No full textA series of thermotropic liquid crystalline poly(esterimide)s was synthesized by melt polymerization of diacetoxynaphthalene acid and n-(omega-carboxyalkylene) trimellitic imides. All polymers with 2,6 substituent positions (n-2,6 PEIM) on the napthalene ring exhibit liquid crystalline phases, whereas polymers with 2,7 substituent positions (n-2,7 PEIM) do not. This result suggests that the kink structure of n-2,7 PEIMS would hinder the formation of liquid crystalline polymer. The copoly(ester-imide)s with an irregular sequence of aliphatic units and aromatic mesogens showed the liquid crystallinity with the lower transition temperatures and a lesser tendency to crystallize than homopoly(ester-imide)s. The semicrystalline polymers with more regular monomeric sequence in the main chain showed the hysteresis of viscoelastic property in the temperature cycle. A nematic glassy copolymer gave the higher molecular orientation to the fiber than a semicrystalline polymer. (C) 1997 by John Wiley & Sons, Ltd.The authors thank the Korea Science & Engineering Foundation
for partial financial support through the grants-in-aid
(KOSEF 94–0300–04–01–3)
Synthesis and rheological investigation on phase behaviors of semiflexible type amorphous liquid crystalline poly(ester-imide)s
No full textMain chain type thermotropic poly(ester-imide)s composed of N-(omega-carboxyalkylene) trimellitic imides and methylhydroquinone diacetate or hydroquinone diacetate were prepared by melt transesterification condensation. DSC and polarized light microscopy observation revealed that polymers made from hydroquinone diacetate showed both crystal melting and mesophase to isotropic phase transition but those from methylhydroquinone diacetate showed only mesophase to isotropic phase transition. The amorphous type liquid crystalline polymers showed extremely slow crystallization velocities. The mesophase of all polymers was verified as a nematic one from the drops of moduli and viscosities at the isotropic to mesophase transition during cooling. For an amorphous liquid crystalline polymer the changes of dynamic rheological properties were checked around the mesophase to isotropic phase transition. Both isotropic and nematic phases succeeded in time-temperature superposition but biphase failed. (C) 2000 Elsevier Science Ltd. All rights reserved.This work was financially supported by the Korea
Science and Engineering Foundation, KOSEF, under
contract 971-0804-039-2
Crystallization kinetics of thermotropic liquid crystalline poly(ester-imide)s
No full textA thermotropic liquid crystalline poly(ester-imide) was synthesized from trimellitic anhydride, 5-aminovaleric acid and 2,6-dihydroxynaphthalene by the melt polymerization. The isothermal crystallization kinetics of the thermotropic liquid crystalline poly(ester-imide) was studied by using DSC in temperature range 190-240 degrees C. Crystallization occurs in two stages (a fast crystallization process and a slow crystallization process), leading to different levels of perfection and crystal sizes. The apparent Avrami exponent has the low values of 0.11-0.98, which represents a highly restricted one-dimensional (fibrillar) crystal growth. It tends to be depressed because the high ordered molecules (crystals) will prevent a polymer chain from the translational motion along the chain axis and the matching of crystallizable sequences with other chains. The fast crystallization process produces the relatively ordered crystals and the slow crystallization generates the less ordered crystals. WAXD shows that the dual endothermic peaks are related to the existence of two different crystal sizes. (C) 1997 Elsevier Science Ltd.The authors thank Korea Science &
Engineering Foundation for the partial financial support
through the grants-in-aid (KOSEF 94-0300-04-01-3)
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