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991.
Fred Cohen 《Network Security》2001,2001(10):16-18
Networks dominate today's computing landscape and commercial technical protection is lagging behind attack technology. As a result, protection programme success depends more on prudent management decisions than on the selection of technical safeguards. Managing Network Security takes a management view of protection and seeks to reconcile the need for security with the limitations of technology. 相似文献
992.
Farhad Nadim George E. Hoag Fred L. Ogden Glenn S. Warner Amvrossios C. Bagtzoglou 《Lakes & Reservoirs: Research and Management》2007,12(3):187-202
The Mansfield Hollow Lake (MHL) and Willimantic Reservoir (WR) are two reservoirs located in eastern Connecticut in the north‐eastern USA. The MHL was constructed by the US Army Corps of Engineers in 1952, being primarily fed by the Fenton, Mount Hope and Natchaug Rivers. The WR lies downstream from the Mansfield Hollow Dam. The physical and chemical characteristics of MHL, WR, and the three streams discharging into them were intensively evaluated during four sampling quarters in 2001 and 2002. This study focused on possible sources of eutrophication, and occurrence of trace amounts of selected priority pollutants, in the sediments and waters of MHL and WR. Analytical results for total dissolved nitrogen and phosphorus and chlorophyll‐a indicated that, in terms of eutrophication status, the waterbodies can be classified as mesotrophic. Comparison of the analytical results in this study to historical limnological data reported for lakes in southern New England and eastern Connecticut indicates that the median levels of total nitrogen, total phosphorus, dissolved inorganic carbon, calcium, magnesium, and iron measured in this study were higher than previously reported median values. 相似文献
993.
Afusat O. Dirisu Grace Silva Zhijun Liu Claire F. Gmachl Fred J. Towner John Bruno Deborah L. Sivco 《Photonics Technology Letters, IEEE》2007,19(4):221-223
We demonstrate the reduction of the facet reflectivity of quantum-cascade lasers (QCLs) by using subwavelength gratings. The gratings were fabricated on lambda=4.9- and 9.8-mum QCLs using focused ion beam milling. Reflectivities as low as 1%-3% for the 4.9-mum QCL and as low as 4%-8% for the 9.8-mum QCL are reported 相似文献
994.
Ahmed M. El-Hadi Saeed D. Mohan Fred J. Davis Geoffrey R. Mitchell 《Journal of Polymer Research》2014,21(12):1-12
Novel hydrogel films composed of hydroxyethylacryl chitosan (HC) and sodium alginate (SA) were prepared for biomedical application by using calcium chloride (CaCl2) as a nontoxic ionic crosslinker to form a semi-interpenetrating polymer network (semi-IPN). HC was successfully prepared by following a Michael addition reaction of chitosan (CS) and hydroxyethylacrylate completely dissolved in distilled water at 70 °C. The distribution pattern of Ca2+ ions were well-dispersed within the hydrogel films examined by scanning electron microscope-energy dispersive spectrometry (SEM-EDS), implying uniformity of crosslinking. The swelling behavior of the hydrogel films in distilled water, simulated gastric fluid (SGF, pH?=?1.2) and phosphate buffer solution (PBS, pH?=?7.4) were investigated. The equilibrium swelling degree of the hydrogel films in distilled water increased with a decreas of either the SA content or the concentration of CaCl2. The hydrogel films showed pH-dependent behavior in that the shapes of the hydrogel films were stable in SGF while they degraded in PBS. The tensile strength and elongation of the hydrogel films reached 12.1 MPa and 162%, respectively, which presented reasonable mechanical properties during use and enough flexibility to follow skin movement. Cell viability of the hydrogels was measured using a methylthiazol tetrazolium (MTT) assay. The results indicated that the hydrogel films are not cytotoxic. 相似文献
995.
Alan J. Blayney Igor F. Perepichka Fred Wudl Dmitrii F. Perepichka 《Israel journal of chemistry》2014,54(5-6):674-688
We provide an overview of the current progress in the synthesis of poly(p-phenylene vinylene) (PPV) polymers. The described synthetic approaches can be divided into four main categories: polymerization of quinodimethane intermediates, metathesis polymerization, nucleophilic polycondensation, and palladium-catalyzed cross-coupling. While such variety is remarkable and very high-molecular-weight PPV can be prepared by some methods, the synthetic chemistry of PPV still limits the structural variety and purity of arylene vinylene polymers. In particular, palladium-catalyzed cross-coupling reactions, the method of choice in the contemporary conjugated polymer chemistry, often shows limited success in PPV series. On the other hand, the possibility of using metathesis polymerization creates new opportunities not available for other classes of conjugated polymers. 相似文献
996.
分析荷兰乌特勒支中央火车站地区公私合作的更新改造历程,指出公法建立了弹性动态的规划管控模式;私法通过开发协议促进政企合作.公法与私法并行运作推动规划主动实施,公私合作的开发协议贯穿项目开发全过程管理,提升了项目的创造力和可持续性.公私法的相互融合是现代法律制度的发展方向,也是我国推动市场主体参与城市更新的重要制度背景.建议在公法角度建立具有适应性和弹性的详细规划制度,完善规划许可的类型与程序;在私法角度重视各类协议的作用和地位,发挥公私合作的潜力,保障土地增值的公共还原. 相似文献
997.
工程因素对页岩气产量的影响——以北美Haynesville页岩气藏为例 总被引:6,自引:0,他引:6
我国页岩气开发尚处于前期探索阶段,分析国外成功的开发案例具有重要的借鉴作用和参考价值。在对北美Haynesville 页岩气藏生产数据进行统计和分析的基础上,总结了工程因素对该页岩气藏开发的影响规律。结论认为:页岩气井水平段长度、压裂级数、加砂量、油嘴尺寸、井底压力和是否采取重复压裂施工对累积产量有显著影响;水平段长度在1 500~1 650 m之间、压裂级数12~17级、加砂量1 500~3 000 t、油嘴尺寸8~9 mm为该地区常用且效果较好的设计方案;井底压力高的区域页岩气产量相应较高,这与井底超压改善页岩脆性、优化压裂效果有关;重复压裂能够显著提高页岩气总产量,作业时机的选择与增产效果关系密切。 相似文献
998.
Previous research has established that Asian Americans use mental health services less frequently and hold poorer attitudes toward psychological counseling than Caucasians. The authors directly tested whether stigmatizing beliefs regarding mental illness might explain such differential attitudes toward counseling in a South Asian and Caucasian student sample. Using mediation analyses, the authors examined 2 aspects of stigma posited to affect help-seeking attitudes: personal stigmatizing views and perceptions of the public's stigmatizing views directed toward persons with mental illness. First, the authors found that Caucasian (n = 74) college students revealed more positive attitudes toward counseling than did South Asian (n = 54) students. Second, in terms of mediation, increased personal stigma, but not perceived stigma, expressed by South Asians partially mediated and accounted for 32% of the observed difference in attitudes toward counseling services. These findings support a long-standing conjecture in the literature regarding the increased significance of stigma processes on disparities in majority-minority help-seeking attitudes. They also suggest that efforts to reduce disparities in attitudes toward counseling for South Asian students specifically should incorporate interventions to reduce the increased stigma expressed by this community, particularly related to a desire for social distance from persons with a mental illness. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
999.
Kathleen B. Alexander Fred J. Walker Rodney A. McKee Fred A. List III 《Journal of the American Ceramic Society》1990,73(6):1737-1743
Titanium oxide/aluminum oxide films have been deposited using molecular beam epitaxy methods and characterized by reflection high-energy electron diffraction and transmission electron microscopy techniques. Growth on silicon substrates below 973 K resulted in primarily amorphous multilayers. At 1323 K, the deposition of titanium in an oxygen atmosphere on (0001) Al2 O3 substrates resulted in films of Ti2 O3 . These films consisted of small domains, up to 60 nm, slightly misoriented from a [1120] ∥ [1120] orientation relationship. Two variants of Ti2 O3 were observed due to multiple positioning during growth. Closing the titanium shutter during growth resulted in an oriented TiO2 film. 相似文献
1000.
Outbreaks of acid-resistant foodborne pathogens in acid foods with pH values below 4.0, including apple cider and orange juice, have raised concerns about the safety of acidified vegetable products. For acidified vegetable products with pH values between 3.3 and 4.6, previous research has demonstrated that thermal treatments are needed to achieve a 5-log reduction in the numbers of Escherichia coli O157:H7, Listeria monocytogenes, or Salmonella enterica. For some acidified vegetable products with a pH of 3.3 or below, heat processing can result in unacceptable product quality. The purpose of this study was to determine the holding times needed to achieve a 5-log reduction in E. coli O157:H7, L. monocytogenes, and S. enterica strains in acidified vegetable products with acetic acid as the primary acidulant, a pH of 3.3 or below, and a minimum equilibrated temperature of 10 degrees C. We found E. coli O157:H7 to be the most acid-resistant microorganism for the conditions tested, with a predicted time to achieve a 5-log reduction in cell numbers at 10 degrees C of 5.7 days, compared with 2.1 days (51 h) for Salmonella or 0.5 days (11.2 h) for Listeria. At 25 degrees C, the E. coli O157:H7 population achieved a 5-log reduction in 1.4 days (34.3 h). 相似文献