Loading Rate and Temperature Interaction Effects on the Mode I Fracture Response of a Ductile Polyurethane Adhesive Used in the Automotive Industry

Due to their high elongation at failure and damping capacity, polyurethanes are one of the main types of adhesives used in automotive structures. However, despite the wide range of applications of adhesives, their fracture mechanics behavior is still poorly studied in the literature, especially when both the loading rate and ambient temperature change. Accordingly, the main aim of the current work is to deal with the research gap. In the current research, mode I fracture energy of a ductile polyurethane adhesive with adaptive properties for its industrial application is determined at different test speeds and temperatures. Tests were done at quasi-static, intermediate, and high-speed levels and each at three different temperatures, including low, high, and room temperature. Mode I fracture toughness was determined using DCB tests. Increasing the loading rate from quasi-static to 6000 mm/min was found to significantly increase the maximum strength of the tested DCBs (from 1770 N to about 4180 N). The greatest sensitivity to the loading rate was observed for the DCBs tested at room temperature, where the fracture energy increased by a factor of 3.5 from quasi-static (0.2 mm/min) to a high loading rate (6000 mm/min). The stiffness analysis of the DCB samples showed that the transition from below the T_g to room temperature decreases the bond stiffness by about 60%, while a further temperature increase (from 23 °C to 60 °C) has no significant effect on this parameter. Since polyurethane-bonded joints often experience a wide range of temperatures and loading rates in service, the obtained results can be used to design these joints more securely against such loading/environmental conditions.     

Innovative Structural Fuse Systems for Various Prototype Applications

To resist the imposed lateral forces on the structures, hysteric dampers are developed from steel plates and strategically implemented within various structural applications. Structural shear dampers have recently been used to alleviate damage, while remaining members remain intact and undamaged. The practical use of the innovative dampers in structural applications is investigated in this study. For this purpose, the design methodology for a set of innovative shear dampers is initially elaborated, for which the dampers are designed considering the governing shear and flexural ductile limit states, while the brittle buckling limit state is prevented. Subsequently, the finite element modeling methodology is verified and compared to laboratory tests for computationally analyzing various shapes of the shear damper in structural applications. Three major general prototype structures are established, and shear dampers are designed to be incorporated in prototype applications. For each of the proposed applications, at least six different shapes of shear dampers are designed and subsequently compared with conventional systems. The results determined that the use of innovative shear dampers could effectively reduce demand forces on the boundary elements by more than 40% on average, while the strength and the stiffness alter within margin of difference less than 5%.     

Metabolic syndrome and leptin concentrations in obese children

Objective Obesity and its complications including metabolic syndrome has been increased in children and adolescents recently. Leptin is known to play an important role in the pathogenesis of obesity. Methods The objective of this study was to evaluate the relationship of leptin and metabolic syndrome in obese Iranian children. A cross sectional study was carried out in 65 primary schools in Tehran. The children with waist circumferences equal or above 90^th percentile for their height and age were chosen for further evaluations. 505 children aged 7–12 years participated in the study. Anthropometric variables measurements, blood pressure, fasting plasma glucose, triglyceride, high-density lipoprotein cholesterol and serum leptin were obtained from the study sample. Results Serum leptin levels were significantly higher in girls in comparison to the boys (with median 11.0 Vs 8.25 ng/dl; P value =0.007). Serum level of leptin were higher in children with metabolic syndrome (median 11.3 Vs 8.9 ng/dl; P value=0.045). However, after adjustment for sex, this association was removed. Conclusion Leptin did not appear to have a major role in metabolic syndrome, even though it was strongly associated with obesity parameters. More studies evaluating the relationship between leptin and metabolic syndrome in various ethnic groups are recommended.     

Systemic Hyperthermia Masks the Neuroprotective Effects of MK‐801, but not Rosiglitazone in Brain Ischaemia

Abstract: The use of neuroprotective agents has been under investigation for the treatment of ischaemic brain stroke. In this study, we examined the effects of rosiglitazone and MK‐801, two potential neuroprotectants, on thromboembloic focal stroke in hyperthermic rats. The animals were assigned into groups of rosiglitazone, MK‐801 and control, all under both normothermic and hyperthermic conditions. A focal ischaemia was induced by injection of preformed clot into the origin of the middle cerebral artery. The animals were assessed by measuring infarct size and brain oedema and also evaluating neurological deficit and seizure activity. Rosiglitazone improved infarct volume and neurological deficit in both normo‐ (36%) and hyperthermic (63%) animals; but MK‐801 only improved normothermic animals. Our results do not support the use of MK‐801 in hyperthermic conditions of brain stroke but suggest that rosiglitazone may preserve its efficiency even in hyperthermia.     

Anticonvulsant effect of celecoxib on pentylenetetrazole-induced convulsion: Modulation by NO pathway

This study aimed to examine whether celecoxib influences clonic seizure thresholds through modulation of nitric oxidergic (NO) pathway. The effect of celecoxib (1-5 mg per kg, p.o.) was investigated on clonic seizures induced by pentylenetetrazole (PTZ, 50 and 80 mg per kg, i.p.) in male Swiss mice. The interaction of celecoxib-induced effects with NO pathway was examined using a NO synthase (NOS) inhibitor, N(G)-omega-nitro-L-arginine methyl ester (L-NAME, 20 and 50 mg per kg, i.p.) and a NOS substrate, L-arginine (100 and 200 mg per kg, i.p.). The criteria for the development of seizure activity were the possibility for appearance of generalized clonus and prolongation of latency to the onset of convulsions following administration of 50 and 80 mg per kg of PTZ, respectively. Pretreatment with celecoxib (2.5 and 5 mg per kg) or L-NAME (50 mg per kg) induced anticonvulsant effect on the PTZ-induced clonic seizures. L-arginine at the dose of 200 mg per kg had proconvulsant effect. A sub-effective dose of celecoxib (1 mg per kg) induced an additive anticonvulsant effect when co-administered with L-NAME (20 mg per kg). Although L-arginine (100 mg per kg) per se did not influence PTZ-induced convulsion, it could attenuate the anticonvulsant effect of celecoxib (5 mg per kg). Our results indicate that celecoxib induces an anticonvulsant effect on clonic seizure threshold that may involve NO pathway.     

Vancomycin-Variable Enterococcus faecium: In Vivo Emergence of Vancomycin Resistance in a Vancomycin-Susceptible Isolate

We report the emergence of vancomycin resistance in a patient colonized with a vanA-containing, vanRS-negative isolate of Enterococcus faecium which was initially vancomycin susceptible. This is a previously undescribed mechanism of drug resistance with diagnostic and therapeutic implications.     

Mitotic Index is an Independent Predictor of Recurrence‐Free Survival in Meningioma

While World Health Organization (WHO) grading of meningioma stratifies patients according to recurrence risk overall, there is substantial within‐grade heterogeneity with respect to recurrence‐free survival (RFS). Most meningiomas are graded according to mitotic counts per unit area on hematoxylin and eosin sections, a method potentially confounded by tumor cellularity, as well as potential limitations of accurate mitotic figure detection on routine histology. To refine mitotic figure assessment, we evaluated 363 meningiomas with phospho‐histone H3 (Ser10) and determined the mitotic index (number of mitoses per 1000 tumor cells). The median mitotic indices among WHO grade I (n = 268), grade II (n = 84) and grade III (n = 11) tumors were 1, 4 and 12. Classification and regression tree analysis to categorize cut‐offs identified three subgroups defined by mitotic indices of 0–2, 3–4 and ≥5, which on univariate analysis were associated with RFS (P < 0.01). In multivariate analysis, mitotic index subgrouped in this manner was significantly associated with RFS (P < 0.01) after adjustment for Simpson grade, WHO grade and MIB‐1 index. Mitotic index was then examined within individual WHO grade, showing that for grade I and grade II meningiomas, mitotic index can add additional information to RFS risk. The results suggest that the use of a robust mitotic marker in meningioma could refine risk stratification.     

Liver transplantation as a definitive treatment for familial hypercholesterolemia: A series of 36 cases

FH is a genetic disorder characterized by an increase in serum LDL and total cholesterol values. The afflicted patients are at increased risk of premature atherosclerosis and myocardial infarction. Different treatment modalities are present, including pharmacological agents and surgical procedures. The most effective method of therapy in refractive cases is liver transplantation. Herein, we report our experience on 36 cases of patients with FH undergoing liver transplantation in our center, the main referral center of liver transplantation in Iran. The clinical findings, hospital courses, post‐operative complications, and patient follow‐up are also described.