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251.
TL Vaughan DC Farrow PD Hansten WH Chow MD Gammon HA Risch JL Stanford JB Schoenberg ST Mayne H Rotterdam R Dubrow H Ahsan AB West WJ Blot JF Fraumeni 《Canadian Metallurgical Quarterly》1998,7(9):749-756
Incidence of adenocarcinomas of the esophagus and gastric cardia has risen dramatically over the past 2 decades in the U. S., for reasons that are not yet clear. A number of common medications (e.g., calcium channel blockers, tricyclic antidepressants, and certain asthma medications) promote gastroesophageal reflux by relaxing the lower esophageal sphincter (LES). Reflux is thought to increase cancer risk by promoting cellular proliferation, and by exposing the esophageal epithelium to potentially genotoxic gastric and intestinal contents. Recent studies have suggested that calcium channel blockers may also increase cancer risk by inhibiting apoptosis. Using personal interview data from a multicenter, population-based case-control study conducted between 1993 and 1995 in three areas of the U. S., we evaluated whether the use of LES-relaxing drugs was associated with increased risk of adenocarcinomas of the esophagus and gastric cardia. Cases of esophageal adenocarcinoma (n = 293) and gastric cardia adenocarcinoma (n = 261) were compared with general population controls (n = 695). Information on additional case groups of esophageal squamous cell carcinoma (n = 221) and noncardia gastric cancer (n = 368) were also available for comparison. Overall, 27.4% of controls had used one or more of these drugs for at least 6 months, compared with 30.2% of esophageal adenocarcinoma and 23.8% of gastric cardia adenocarcinoma cases. The adjusted odds ratios (ORs) for ever use were 1.0 [95% confidence interval (CI) = 0.7-1.5] and 0.8 (95% CI = 0.5-1.1), respectively. There was little evidence of increasing risk with increasing duration of use of all LES-relaxing drugs together. We found an increased risk of esophageal adenocarcinoma among persons reporting use of asthma drugs containing theophylline (OR = 2.5; 95% CI = 1.1-5.6) or beta agonists (OR = 1.7; 95% CI = 0.8-3.8). Risks were higher among long-term users (>5 years) of these drugs (OR = 3.1; 95% CI = 0.9-10.3 and OR = 2.3; 95% CI = 0.8-7.0, respectively). In contrast, there was no evidence that the use of calcium channel blockers or other specific groups of drugs increased the risk of any of the cancers studied. These results provide reassuring evidence that the increases in incidence of adenocarcinomas of the esophagus and gastric cardia are not likely to be related to the use of LES-relaxing drugs as a group, or calcium channel blockers in particular, but they do suggest that persons treated for long-standing asthma may be at increased risk of esophageal adenocarcinoma. 相似文献
252.
Pattern Analysis and Applications - As a typical unsupervised learning technique, clustering has been widely applied. However, in many cases, prior information about the number of clusters is... 相似文献
253.
Abdul Jabbar Ahsan Ahmad Muhammad Adnan Yasir Nawab Zafar Javed Muhammad Irfan 《应用聚合物科学杂志》2021,138(25):50683
In this study, high-performance polyethylene (HPPE) fiber-based needle punched nonwovens were interleaved in cross-plied woven carbon fabric/epoxy composite laminates to enhance their interlaminar and impact properties. The placement of needle punched nonwoven interleaves exhibited considerable enhancement in interlaminar shear strength (ILSS), impact damage tolerance, and compression after impact (CAI) strength of laminates as evidenced by higher interlaminar strength, less absorbed energy, higher elastic energy, reduced damage degree, reduced out-of-plane deformation, higher load-bearing capacity, and higher residual compressive strength as compared to control sample. In particular, the composite laminate with placement of interleaves in alternating sequence between carbon plies resulted in 205.76% increase in ILSS and 129, 103 and 85% increase in CAI at 10, 25, and 40 J impact energy, respectively. Moreover, damaged surface area and out-of-plane deformation reduced to 38.75% and 62.5%, respectively for the same specimen impacted at 40 J energy. These results suggest that the HPPE fiber-based needle punched nonwoven interleaving can be adopted as a simple and low-cost approach compared with other interleaving techniques, to enhance the resistance to delamination, impact performance, and damage tolerance of traditional structural laminates. 相似文献
254.
R.U.Ahsan Xuesong Fan Gi-Jeong Seo Changwook Ji Mark Noakes Andrzej Nycz Peter K.Liaw Duck Bong Kim 《材料科学技术学报》2021,74(15):176-188
Bimetallic additively manufactured structures (BAMSs) can replace traditionally-fabricated functionally-graded-components through fusion welding processes and can eliminate locally-deteriorated mechanical properties arising from post-processing.The present work fabricates a BAMS by sequentially depositing the austenitic stainless-steel and Inconel625 using a gas-metal-arc-welding (GMAW)-based wire + arc additive manufacturing (WAAM) system.Elemental mapping shows a smooth compositional transition at the interface without any segregation.Both materials being the face-center-cubic (FCC) austenite,the electron backscattered diffraction (EBSD) analysis of the interface shows the smooth and cross-interface-crystallographic growth of long-elongated grains in the <001> direction.The hardness values were within the range of 220-240 HV for both materials without a large deviation at the interface.Due to the controlled thermal history,mechanical testing yielded a consistent result with the ultimate tensile strength and elongation of 600 MPa and 40 %,respectively,with the failure location on the stainless-steel side.This study demonstrates that WAAM has the potential to fabricate BAMS with controlled properties. 相似文献
255.
Ahsan?MianEmail author Golam?Newaz Tonfiz?Mahmood Greg?Auner 《Journal of Materials Science》2007,42(19):8150-8157
This paper discusses the laser-irradiated microjoints between glass and polyimide for applications in neural implants. To
facilitate bonding between them, a thin titanium film with a thickness of approximately 0.2 μm was deposited on glass wafers
using the physical vapor deposition (PVD) process. Two sets of samples were fabricated where the bonds were created using
diode and fiber lasers. The samples were subjected to tension using a microtester for bond strength measurements. The failure
strengths of the bonds generated using fiber laser are quite consistent, while a wide variation of failure strengths are observed
for the bonds generated with diode laser. Few untested samples were sectioned and the microstructures near the bond areas
were studied using an optical microscope. The images revealed the presence of a sharp crack in the glass substrate near the
bond generated with the diode laser. However, no such crack was observed in the samples made using fiber laser. To investigate
the reasons behind such discrepancy in bond quality further, uncoupled three-dimensional finite element analyses (FEA) were
conducted only for the samples created using diode laser. First, the transient heat diffusion-based FEA was conducted by using
the laser power intensity distribution as a time dependent heat source. This model calculates the temperature distribution
within the substrates as a function of time. Next, the structural model predicts the amount of residual stresses developed
in the joint system as it is cooled down to room temperature. The out-of-plane normal component of residual stresses was within
the failure strength range of glass that may have caused fracture initiation in the substrate. 相似文献
256.
Mohamed Zaidul Islam Sarker Jinap Selamat Abu Sayem Md. Ahsan Habib Sahena Ferdosh Mohamed Jahurul Haque Akanda Juliana Mohamed Jaffri 《International journal of molecular sciences》2012,13(9):11312-11322
Fish oil was extracted from the viscera of African Catfish using supercritical carbon dioxide (SC-CO2). A Central Composite Design of Response Surface methodology (RSM) was employed to optimize the SC-CO2 extraction parameters. The oil yield (Y) as response variable was executed against the four independent variables, namely pressure, temperature, flow rate and soaking time. The oil yield varied with the linear, quadratic and interaction of pressure, temperature, flow rate and soaking time. Optimum points were observed within the variables of temperature from 35 °C to 80 °C, pressure from 10 MPa to 40 MPa, flow rate from 1 mL/min to 3 mL/min and soaking time from 1 h to 4 h. However, the extraction parameters were found to be optimized at temperature 57.5 °C, pressure 40 MPa, flow rate 2.0 mL/min and soaking time 2.5 h. At this optimized condition, the highest oil yields were found to be 67.0% (g oil/100 g sample on dry basis) in the viscera of catfish which was reasonable to the yields of 78.0% extracted using the Soxhlet method. 相似文献
257.
Surface energetics of ground calcium carbonates (GCC), with or without stearic acid treatment, were determined by Inverse Gas Chromatography (IGC). The surface energy data were utilized as a predictive tool to explain the optimum coating level often needed on calcium carbonate minerals to obtain the desirable mechanical strength in filled polypropylene composites. The dispersive components of the surface energies for the uncoated carbonates were also correlated with the corresponding impact resistance data. The surface with the highest energy was found to be the least resistant while the least energetic mineral, on a comparative scale, was the most resistant to impact. It is suggested that understanding the surface energetics of finely-divided solids may be a key for the development of future mineral-filled polymer composites. 相似文献
258.
Naveed Ahsan Christer Svensson Rashad Ramzan Jerzy Dabrowski Aziz Ouacha Carl Samuelsson 《Analog Integrated Circuits and Signal Processing》2012,70(1):79-90
This paper presents the design and implementation of a low power, highly linear, wideband RF front-end in 90 nm CMOS. The
architecture consists of an inverter-like common gate low noise amplifier followed by a passive ring mixer. The proposed architecture
achieves a high linearity in a wide band (0.5–6 GHz) at very low power. Therefore, it is a suitable choice for software defined
radio (SDR) receivers. The chip measurement results indicate that the inverter-like common gate input stage has a broadband
input match achieving S11 below −8.8 dB up to 6 GHz. The measured single sideband noise figure at an LO frequency of 3 GHz
and an IF of 10 MHz is 6.25 dB. The front-end achieves a voltage conversion gain of 4.5 dB at 1 GHz with 3 dB bandwidth of
more than 6 GHz. The measured input referred 1 dB compression point is +1.5 dBm while the IIP3 is +11.73 dBm and the IIP2
is +26.23 dBm respectively at an LO frequency of 2 GHz. The RF front-end consumes 6.2 mW from a 1.1 V supply with an active
chip area of 0.0856 mm2. 相似文献
259.
Ashis Kumer Biswas Author VitaeAuthor Vitae Ahsan Raja Chowdhury Author Vitae Author Vitae 《Microelectronics Journal》2008,39(12):1693-1703
Reversible logic has become one of the most promising research areas in the past few decades and has found its applications in several technologies; such as low-power CMOS, nanocomputing and optical computing. This paper presents improved and efficient reversible logic implementations for Binary Coded Decimal (BCD) adder as well as Carry Skip BCD adder. It has been shown that the modified designs outperform the existing ones in terms of number of gates, number of garbage outputs, delay, and quantum cost. In order to show the efficiency of the proposed designs, lower bounds of the reversible BCD adders in terms of gates and garbage outputs are proposed as well. 相似文献
260.
Transistor laser (TL) model based on InGaP/GaAs/InGaAs/GaAs is analyzed and presented. It is realized that quantum well (QW) with width of 10 nm may be formed for low base threshold current density J th . The emission wavelength is found to be 1.05 μm, and the indium (In) composition is 0.25 for optimal QW width. It is identified that J th decreases with the movement of QW towards the base-emitter (B-E) interface. Small signal optical response is calculated, and the effect of QW position is studied. The bandwidth is enhanced due to the movement of the QW towards the emitter base junction. 相似文献