Molecular Dynamics Investigation of the Structural and Mechanical Properties of Off-Stoichiometric Epoxy Resins

We carried out molecular dynamics (MD) simulations to measure the mechanical properties of various off-stoichiometric polymers regarding amine to epoxy ratios (r) and to understand the stiffness of the polymers in terms of their structures. The aerospace-grade API-60 epoxy resin is used as an adhesive bond for assembling large-scale composite structures via the co-curing-ply bonding method. This method will produce a reliable and certifiable composite joint without additional fasteners. Calculated Young's modulus was measured from the uniaxial tension simulation with several high strain rates, and the experimental modulus was estimated by extrapolating the simulation results. We found that the stiffness was associated with molecular packing caused by chemical cross-linking. We also found that the number of network clusters gradually decreased as the ratio approached r = 1.0, which made the tighter cluster and the system much stiffer with an increase in the molecular weight and the degree of cross-linking. Structural properties such as Rg, MSD were measured to figure out the degree of stiffness with respect to the r

Meteorological characteristics and assessment of the effect of local emissions during high PM10 concentration in the Seoul Metropolitan Area

In this study, we investigate the meteorological characteristics and the effect of local emissions during high PM10 concentrations in the Seoul Metropolitan Area (SMA) by utilizing data from a high-resolution urban meteorological observation system network (UMS-Seoul) and The Air Pollution Model (TAPM). For a detailed analysis, days with PM10 concentrations higher than 80 ??g m-3 for daily average PM10 concentration (classified as unhealthy by the Korean Ministry of Environment) in the Seoul Metropolitan Area (SMA) were classified into 3 Cases. Case I was defined as when the prevailing effect was from outside the SMA. Case II was defined as when the prevailing effect was a local effect with outside. Case III was defined as when the prevailing effect was local. Overall, high PM10 concentrations in the SMA mostly occurred under weak migratory anticyclone systems over the Korean Peninsula during warm temperatures. Prior to the PM10 concentration reaching the peak concentration, the pattern in each case was distinctive. After peak concentrations, however, the pattern for the 3 cases became less distinct. This study showed that nearly 50% of the high PM10 concentrations in the SMA occurred in spring and were governed by the conditions for Case II more than these for Cases I and III. In spring, the main sources of the high PM10 concentrations in the SMA were local emissions due to the predominance of weak winds and local circulation. The simulation showed that the non-SMA emissions were about 63 to 73% contribution to the spring high PM10 concentrations in the SMA. Specifically, local point sources including industrial combustion, electric utility, incineration and cement production facilities scattered around the SMA and could account for PM10 concentrations more than 10 ??g m-3 in the SMA

A Case of Santorinicele without Pancreas Divisum: Diagnosis with Multi-detector Row Computed Tomography

A santorinicele is defined as a focal cystic dilatation of the terminal portion of the dorsal pancreatic duct at the minor papilla. Most cases reported previously were associated with pancreas divisum and a santorinicele without pancreas divisum is known to be rare. We recently experienced a typical case of a santorinicele without pancreas divisum in a 67-yr-old woman with abdominal pain and hematochezia, subsequently proven to be the result of an ischemic colitis. The santorinicele was diagnosed incidentally with multi-detector row computed tomography using a minimum intensity projection technique, which clearly showed a cystic dilatation of the terminal portion of the dorsal pancreatic duct and a communication between the ventral and dorsal pancreatic ducts. This finding was also confirmed by a magnetic resonance cholangiopancreatography

Impact Comparison of Synoptic Meteorology and Nationwide/local Emissions on the Seoul Metropolitan Area during High PM Multi-event and Non-event Days

Meteorology and emissions play very important roles in the concentrations of air pollutants during severe haze/smog periods. This study compares the impacts of synoptic meteorology and nationwide/local emissions during high PM10 multi-event and non-event days in the Seoul Metropolitan Area (SMA). The multi-event and non-event cases were selected based on daily mean PM10 concentrations in Seoul from January 2014 to March 2019. The multi-event cases in spring and winter were closely associated with weak synoptic winds, while that in autumn was due to the strong winds at the rear side of a strong cold front, which induced the Asian dust event in northeastern China and Korea. The multi-event case in spring was found to be mainly due to series of migratory anticyclones, while winter case was due to the stagnant system after northerly winds. The surrounding low pressure systems as well as high pressure systems could be important to determine whether the synoptic systems would be stagnant or not. The fractional contributions of SMA emissions to the mean PM10 and PM2.5 concentrations were 24%-35% and 22%-35% for the multi-event cases, respectively. The contributions to the maximum PM10 and PM2.5 concentrations were larger than those to the mean concentrations by 16%-23% and 19%-26% for the multi-event cases, respectively

A Case of Severe Aortic Valve Regurgitation Caused by an Ascending Aortic Aneurysm in a Young Patient With Autosomal Dominant Polycystic Kidney Disease and Normal Renal Function

Aortic aneurysm is one several well-known cardiovascular complications in patients with autosomal dominant polycystic kidney disease (ADPCKD). Commonly affected site of aortic aneurysm and its related dissection in ADPCKD is abdominal aorta. Long standing hypertension, haemodialysis, old age are closely related with discovering of aortic aneurysm and dissection in ADPCKD. However, thoracic aortic aneurysms and its related severe aortic regurgitations (ARs) are rare in younger patients suffering from ADPCKD, especially ones who have normal renal function. Here, we report a case involving a 27-year-old Asian male patient with severe AR due to an ascending aneurysm of the thoracic aorta associated with ADPCKD. The patient had normal renal function without Marfan's habitus. The AR and thoracic aortic aneurysm were corrected surgically

Extrahepatic Biliary Schwannomas: A Case Report

Benign schwannomas arise in neural crest-derived Schwann cells. They can occur almost anywhere in the body, but their most common locations are the central nervous system, extremities, neck, mediastinum, and retroperitoneum. Schwannomas occurring in the biliary tract are extremely rare and mostly present with obstructive jaundice. We recently experienced a case of extrahepatic biliary schwannomas in a 64-yr-old female patient who presented with intra- and extrahepatic bile duct and gallbladder stones during a screening program. To the best of our knowledge, extrahepatic biliary schwannomas associated with bile duct stones have not been reported previously in the literature

A Degenerative Intraspinal Cyst Mimicking a Nerve Root: A Case Report on an Intraoperative Challenge

Various intraspinal cysts have been described in the literature. Sometimes these cysts are difficult to recognize intraoperative and can place a surgeon in dilemma. We report a case of a degenerative intraspinal cyst with severe adhesion with dura, which was mimicking as a nerve root and posed a diagnostic dilemma during surgery. A Sixty-year-old man presented with insidious onset, gradually progressing lower back pain, right leg pain and neurological claudication of six months duration. The pain radiated to the right S1 dermatome. Right side straight leg raise test was positive at 45°. Sensations were diminished over the right L5 and S1 dermatomes. Motor function was normal. MRI showed a large cystic lesion at right L5-S1 level. The cyst appeared to compress the dural sac and traversing right S1 root at L5-S1 level. The lesion was isointense on T1-weighted image and hyperintense on T2-weighted image. While treating this condition using the uniportal full endoscopic technique the cyst appeared as nerve root. Meticulous dissection was required to separate the cyst from neural structures. Histology confirmed the diagnosis of a degenerative intraspinal cyst. The patient had significant improvement after surgery and at six months follow up he was completely asymptomatic. Various cysts can occur in the intraspinal canal, and careful attention should be paid to minimize the nerve injury in the presence of severe adhesions

Efficacy of two different self-expanding nitinol stents for atherosclerotic femoropopliteal arterial disease (SENS-FP trial): study protocol for a randomized controlled trial

BACKGROUND: There have been few randomized control trials comparing the incidence of stent fracture and primary patency among different self-expanding nitinol stents to date. The SMART™ CONTROL stent (Cordis Corp, Miami Lakes, Florida, United States) has a peak-to-valley bridge and inline interconnection, whereas the COMPLETE™-SE stent (Medtronic Vascular, Santa Rosa, California, United States) crowns have been configured to minimize crown-to-crown interaction, increasing the stent's flexibility without compromising radial strength. Further, the 2011 ESC (European society of cardiology) guidelines recommend that dual antiplatelet therapy with aspirin and a thienopyridine such as clopidogrel should be administered for at least one month after infrainguinal bare metal stent implantation. Cilostazol has been reported to reduce intimal hyperplasia and subsequent repeat revascularization. To date, there has been no randomized study comparing the safety and efficacy of two different antiplatelet regimens, clopidogrel and cilostazol, following successful femoropopliteal stenting. METHODS/DESIGN: The primary purpose of our study is to examine the incidence of stent fracture and primary patency between two different major representative self-expanding nitinol stents (SMART™ CONTROL versus COMPLETE™-SE) in stenotic or occlusive femoropopliteal arterial lesion. The secondary purpose is to examine whether there is any difference in efficacy and safety between aspirin plus clopidogrel versus aspirin plus cilostazol for one month following stent implantation in femoropopliteal lesions. This is a prospective, randomized, multicenter trial to assess the efficacy of the COMPLETE™-SE versus SMART™ CONTROL stent for provisional stenting after balloon angioplasty in femoropopliteal arterial lesions. The study design is a 2x2 randomization design and a total of 346 patients will be enrolled. The primary endpoint of this study is the rate of binary restenosis in the treated segment at 12 months after intervention as determined by catheter angiography or duplex ultrasound. DISCUSSION: This trial will provide powerful insight into whether the design of the COMPLETE™-SE stent is more fracture-resistant or effective in preventing restenosis compared with the SMART™ CONTROL stent. Also, it will determine the efficacy and safety of aspirin plus clopidogrel versus aspirin plus cilostazol in patients undergoing stent implantation in femoropopliteal lesions. TRIAL REGISTRATION: Registered on 2 April 2012 with the National Institutes of Health Clinical Trials Registry (ClinicalTrials.gov identifier# NCT01570803)