关于偶完全数和n-完全数（英文）

对于任意的正整数a,设δ(a)表示a的所有除数之和.如果δ(x)=2x,则正整数x称作完全数.设n是一个给定的正整数.如果δ(y)+δ(ny)=2(n+1)y,则n称作n-完全数.为了得到偶完全数和n-完全数之间的关系,本文利用δ(a)的性质,证明了如果x是偶完全数,y是x-完全数,那么有(x,y)=(6,13).     

论物理测量中的直接有效数字和间接有效数字

以解决用放大法进行物理测量时有效数字可能出现的概念上的矛盾和问题,提出了将有效数字分为直接有效数字与间接有效数字的概念。直接有效数字与间接有效数字概念的明确提出,可在不改变有效数字定义与运算规则的前提下,协调有效数字与仪器误差和测量误差的基本关系,维护有效数字理论的完整性和统一性;两类有效数字的概念在放大法中的应用,为放大法降低测量误差,增加直接有效数字位数的特点提供了理论依据;此外,两类有效数字在放大法中的合理转换,不仅能改进测量手段,提高实验质量,而且体现了物理实验的独特思维方式。由此可以看出,直接有效数字与间接有效数字的提出及相应规则的建立,能充分发挥有效数字在物理实验与数据处理中的作用,完善、丰富和发展有效数字的理论体系。     

美国加州的葡萄

1 美国和加州的葡萄栽培现状美国葡萄面积和产量仅次于意大利、法国、西班牙而居世界第四位,据统计,1998年全美葡萄栽培面积39.8万公顷、葡萄产量590.29万吨、葡萄酒产量约250万吨。1998年加州葡萄栽培面积32.1万公顷、葡萄产量537.3万吨,分别占美国全国葡萄栽培面积和葡萄产量的80.65％和91.02％,平均每公顷产葡萄16.74吨（折合我国每市亩1115.89kg）加州位于美国西南部、太平洋东海岸的狭长地带,四周为山脉,中央为谷地,具有夏干、冬湿的独特气候类型,为优质葡萄的理想产区。尽管如此,他们还是十分重视“适地适栽”的原则,严格实…     

比利时海关查获一批美国假冒香槟酒

2008年1月8日,比利时海关查获并销毁了3200多瓶André起泡酒.据悉,这批葡萄酒由加州E.& J.Gallo Winery葡萄酒厂生产,贴有"加州香槟(California Champagne)"和"André香槟酒庄(André Champagne Cellars)"的标签,违反了欧盟条例有关禁止在法国香槟产区之外的葡萄酒上使用"香槟"商标的规定.     

Fibonacci数和Lucas数平方的积和式

利用第一、二类Chebyshev多项式的性质得到了关于Fibonacci数和Lucas数的平方的积和式。     

荣誉源于实力 实力成就明天--访莱伯泰科有限公司总裁胡克

在"2009中国科学仪器发展年会"上,仪器信息网根据各厂商2008年度在仪器信息网被用户搜索的次数、收到的用户反馈数量、在仪器信息网网展展位的独立JP点击量等数据,经综合计算评选出"2008年度最受关注厂商".……     

Organic matter in central California radiation fogs

Organic matter was studied in radiation fogs in the San Joaquin Valley of California during the California Regional Particulate Air Quality Study (CRPAQS). Total organic carbon (TOC) concentrations ranged from 2 to 40 ppm of C. While most organic carbon was found in solution as dissolved organic carbon (DOC), 23% on average was not dissolved inside the fog drops. We observe a clear variation of organic matter concentration with droplet size. TOC concentrations in small fog drops (<17 microm) were a factor of 3, on average, higher than TOC concentrations in larger drops. As much as half of the dissolved organic matter was determined to have a molecular weight higher than 500 Da. Deposition fluxes of organic matter in fog drops were high (0.5-4.3 microg of C m(-2) min(-1)), indicating the importance of fog processing as a vector for removal of organic matter from the atmosphere. Deposition velocities of organic matter, however, were usually found to be lower than deposition velocities for fogwater, consistent with the enrichment of the organic matter in smaller fog drops with lower terminal settling velocities.     

加州:采果机器人受到更多关注

随着美国当局对移民的严格管理，依靠移民的农场主将目光瞄向了采果机器人和高科技拖拉机。     

未涂布不含磨木浆纸表面强度与机械强度的关系

衡量未涂布不含磨木浆纸质量的主要指标是表面强度和纸张其他机械强度。在中试纸机上通过添加表面施胶剂或剥离剂、改变填料的种类（GCC或PCC）及用量、改变压光条件等,可生产出不同质量的未涂布不含磨木浆纸,评价了这些纸张表面强度和其他机械强度的关系。结果表明,添加剥离剂或施胶剂对纸张的表面强度和抗张强度有相同的影响;增加填料用量或用PCC代替GCC可降低表面强度、抗张强度及内结合强度;对于添加GCC和PCC的纸张,提高压光压力会降低表面强度,但抗张强度和内结合强度未受影响;增加压光负荷对PCC用量为25%的纸张的表面强度的影响比GCC用量为25%的纸张影响更大;压光对高加填PCC纸张的表面强度的影响尤为明显。     

Survey of Molds in California Processing Tomatoes

From 2009 to 2011, freshly harvested processing tomatoes from California commercial fields were surveyed for mold species present in the mature fruit. Molds were recovered from the majority of fruit that had visual symptoms of black mold and other decays and from about a quarter of randomly sampled, asymptomatic fruit. Alternaria, Fusarium, and Geotrichum spp. were the most commonly recovered fungi in both symptomatic and random samples. Based on pairwise statistical analysis, the frequencies of 2 different fungal genera in a composite 11 kg‐sample were, in general, statistically independent events, with the exception of a weak association between the incidence of Geotrichum with Alternaria, Cladosporium, or Stemphylium. The mold genera distribution data in this study provide the processing tomato industry with a valuable informational resource that can be used in the management of fungal infection in both the crop and in the final thermally processed finished product. Because of the relative abundance of these fungi, this survey supported the development of genera‐specific immunochromatographic diagnostic assays to detect and quantify mold occurrence in Californian processing tomatoes as a potential alternative to the current subjective visual methods, which are characterized by imprecision and nonuniform species sensitivity. A simulation of 1 million 11 kg‐composite samples based upon the distributional survey data projected that a multiantibody immunochromatographic assay using monoclonal antibodies for Alternaria, Cladosporium, Fusarium, and Geotrichum could successfully detect the presence of mold in 94% of moldy processing tomato samples collected randomly at harvest.     

美国加州果酒的酿造

在美国加州由于各种水果的成熟期不同,利用鲜果为原料制作果酒每年有6～7个月的时间.如果用冷冻的果汁为原料,果酒便可实现周年生产.     

Accumulation of trifluoroacetate in seasonal wetlands in California

Trifluoroacetate (TFA, CF3COO-) is a stable and mildly phytotoxic breakdown product of several fluorinated organic compounds including the hydro(chloro)fluorocarbons (HFC/HCFCs) that have largely replaced the stratospheric ozone-depleting chlorofluorocarbons (CFCs). TFA enters aquatic ecosystems primarily through precipitation and has the potential to accumulate in water bodies with little or no outflow to the point where toxic concentrations could be achieved. This study demonstrated that seasonal wetlands lacking outflow concentrated TFA as they evaporated during the dry season. In addition, the TFA within the pools was retained between years, which may result in long-term TFA accumulation. Since plants acquire TFA from their growing media, the plants exposed to high aqueous concentrations of TFA within the pools had elevated TFA concentrations with a median concentration of 279 ng/g dry weight in their tissues as compared to 33 ng/g for species growing outside the pools. The highest TFA concentrations in water, which occurred just prior to the pools drying up, were in the 2-10 micrograms/L range. These concentrations are approximately 190 or less than reported toxic concentrations for the most sensitive species tested, but our evidence suggests that these concentrations will increase with continued TFA deposition into the pools.