一类数论函数及其模N原根的均值分布

文章研究了一类数论函数及其模N原根的均值分布,并给出了关于n∑a=1 n∑b=1ab(=)1(n)|a-b|≤δna,b∈Af(|a-b|)较强的渐近公式.     

一个新的伪Smarandache函数及其均值

引入了一个新的伪Smarandche函数Z0（n）．当n为偶数时,定义Z0（n）=m,m为最小的正整数,使得竹整除2＋4＋6＋…＋2m=m（m＋1）,即Z0（n）=min{m：m∈N,n｜m（m＋1）};当行为奇数时,m为最小的整数使得n｜1＋3＋5＋…＋（2m-1）=m^2．即Z0（n）=min{m：m∈N,n｜m^2}．利用解析方法以及Perron公式研究函数Z0（2n-1）的均值性质,并给出了一个较强的渐近公式．     

关于e-因子函数的一个渐近公式

（A）n∈N＋,设n=n=p1^a1P2^a1…pk^ak为n的标准素因数分解式,如果对于m=p1^β1P2^β2 …pr^βr有βi｜αi （I=1,2,...,k）,则称m为n的e-因子.令de（n）表示n的所有e-因子的个数.研究了k-full数集合上函数de（n）的均值性质,并得到了一个有趣的渐近公式.     

关于Smarandache函数的β次混合均值

研究了Smarandache函数与最大素因子函数P（n）之差的β次方的值分布问题.利用初等方法给出了∑n≤x（S（n）-P（n））β的一个较强的渐近公式,其中x≥3,β〉1为任意实数.     

Smarandache Ceil函数的均值

Smarandache函数的相关性质是初等数论和解析数论研究的一个重要问题.本文利用初等方法给出了Smarandache Ceil函数Sk(n)与n的k次补数函数ak(n)之间的关系式(Sk(n))k=ak(n)·n,再利用解析方法给出了Sk(n)一个渐近公式∑n≤xSk(n)=ζ(2k-1)/2x2∏p(1-1/p2+p-1/p2k-1+p2k-2)+O(x3/2+ε).     

广义特征值的稳定性及刻画

设A是复Hilbert空间X上的有界线性算子,任意λ∈C,如果存在X上的非零有界线性算子B使得AB=λBA,那么就称λ是A的一个广义特征值．记A的全体广义特征值所构成的集合为∑（A）．利用算子分块的技巧,讨论了上三角算子矩阵的广义特征值的稳定性问题．此外,对X上的正可逆算子A,证得∑（A^n/m）=（∑（A））n/m,其中n,m∈Z,并且m≠0．     

关于双曲函数方幂之和

设shx,chx和sinβ,cosβ是双曲正、余弦函数和三角函数,用发生函数的方法得到双曲正,余弦函数方幂与等比序列乘积之和n∑k=0 dkshrkx,n∑k=0 dk chrkx和双曲正、余弦函数带有三角函数方幂n∑k=0 shrkxsinkβ,n∑k=0 shrkxcoskβ的计算公式.     

一个关于SmarandacheLCM对偶函数的方程

橙 n ∈ N＋,著名的Smarandache LCM 函数的对偶函数定义为 SL ＊（n）＝ max｛k｜[1,2,？,k]｜ n ,k∈ N＋｝,Ω（n）表示n的所有素因子的个数。利用初等数论和分类讨论的方法研究了一个包含SL ＊（n）及素因子函数方程∑d｜n 1SL＊（d）＝Ω（n）的可解性,并给出了这个方程的所有正整数解的具体形式。     

包含Smarandache幂函数的均值问题

利用初等数论和解析数论的方法研究著名的Smarandache幂函数SP(n)的均值估计问题.首先给出Smarandache幂函数SP(n)的定义,几个重要的性质和相关引理.在此基础上得到了一些有意义的结果,即在简单数序列上得到了∑n∈A n≤x1/S(SP(n))和∑n∈A n≤x S(SP(n))的均值.     

关于平方补数的一些渐近公式

设n∈N ，a(n)是n的平方补数，x≥1，a≥0，t≥0，p，p1，p2(p1≠p2)是任意素数，有关文献得到了∑n≤xa(n)和∑n≤x1/a(n)的两个形式最简单的渐近公式。通过对平方补数的进一步研究，对其作了更一般形式的推广，得到了∑n≤xn^aa^t(n)，∑n≤xp|nn^ad(n)和∑n≤xp1|np2|nn^ad(n)的3个主要渐近公式，并根据这3个渐近公式得到了一系列有趣的推论。     

Subtelomeric sequence from the right arm of Schizosaccharomyces pombe chromosome I contains seven permease genes

The sequence has been determined of 80 888 bp of contiguous subtelomeric DNA, including the isp5 gene, from the right arm of chromosome I of Schizosaccharomyces pombe; 27 open reading frames (ORFs) longer than 100 codons are present, giving a density of one gene per 3.0 kb. Seven of the predicted proteins are members of the major facilitator superfamily (MFS) of transport proteins, including four amino acid permease homologues, bringing this family of amino acid permease sequences to 17 in Sz. pombe, and a phylogenetic analysis is presented. Also encoded is an allantoate permease homologue, a sulphate permease homologue and a probable urea active transporter. Predicted non-membrane proteins include a 1-aminocyclopropane-1-carboxylate deaminase (ACC deaminase), a class III aminotransferase, serine acetyltransferase, protein-L-isoaspartate O-methyltransferase, alpha-glucosidase, alpha-galactosidase, esterase/lipase, oxidoreductase of the short-chain dehydrogenase/reductase (SDR) family, aldehyde dehydrogenase, formamidase, amidase, flavohaemoprotein, a putative translation initiation inhibitor and a protein with similarity to a filamentous fungal conidiation-specific protein. The remaining six ORFs are likely to encode proteins, either because they have sequence similarity with hypothetical proteins or because they are known to be transcribed. Introns are scarce in the sequenced region: only three ORFs contain introns, with only one having multiple introns. The sequenced region also contains a single Tf1 transposon long terminal repeat (LTR). The sequence is derived from cosmid clones c869, c922 and c1039 and has been submitted to the EMBL database under entries SPAC869 (Accession No. AL132779), SPAC922 (AL133522) and SPAC1039 (AL133521).     

Trends in mercury in hair of Greenlandic polar bears (Ursus maritimus) during 1892-2001

Mercury concentrations in hair from 397 Greenland polar bears (Ursusmaritimus) sampled between 1892 and 2001 were analyzed for temporal trends. In East Greenland the concentrations showed a significant (p < 0.0001, n = 27) increase of 3.1%/year in the period 1892-1973. In Northwest Greenland, a similar (p < 0.0001, n = 69) increase of 2.1%/year was found, which continued until 1991, when the most recent samples were obtained. In East Greenland, a significant (p = 0.009, n = 322) decrease of 0.8%/year was observed after 1973. Two Northwest Greenland samples from 1300 A.D. had a mean value of 0.52 mg/kg of dry weight, which can be considered as a baseline level. The Hg concentration during 1985-1991 from Northwest Greenland (mean value of 7.45 mg/kg of dry weight) was more than 14-fold higher than the assumed baseline level from 1300 A.D. from the same region (i.e., about 93% anthropogenic). Although a decrease was found in East Greenland after 1973, the concentration is still ca. 11-fold higher than the baseline level (i.e., about 90% anthropogenic).     

Microbiological quality of Australian sheep meat in 2004

The third national baseline microbiological survey of Australian sheep carcases and frozen boneless sheep meat was conducted in 2004. Carcases (n=1117) sampled at 20 slaughter establishments were found to have a mean log total viable count (TVC, 25°C) of 2.28 cfu/cm(2) and Escherichia coli was isolated from 43.0% carcases with a mean log 0.03cfu/cm(2) on positive samples. In samples from 10 boning (fabrication) plants (n=560) the mean log TVC for frozen boneless sheep meat was 1.85cfu/g and the mean log count for the 8.2% of samples with detectable E. coli was 1.39cfu/g. E. coli O157:H7 was isolated from 6/1117 carcases and from 1/560 boneless samples. Salmonella was isolated from 0/1117 carcases and from 3/560 samples of boneless product. Campylobacter sp. were isolated from 4/1117 carcases and from 1/560 boneless samples. Coagulase positive staphylococci were isolated from 23.4% to 32.7% of carcases and boneless sheep meat samples, respectively, with positive samples having a mean log count of 0.93cfu/cm(2) and 1.14cfu/g, respectively. The low level of bacteria described here is consistent with a very low risk to human health due to bacterial hazards in Australian sheep meat.     

Variation in arsenic speciation and concentration in paddy rice related to dietary exposure

Ingestion of drinking water is not the only elevated source of arsenic to the diet in the Bengal Delta. Even at background levels, the arsenic in rice contributes considerably to arsenic ingestion in subsistence rice diets. We set out to survey As speciation in different rice varieties from different parts of the globe to understand the contribution of rice to arsenic exposure. Pot experiments were utilized to ascertain whether growing rice on As contaminated soil affected speciation and whether genetic variation accounted for uptake and speciation. USA long grain rice had the highest mean arsenic level in the grain at 0.26 microg As g(-1) (n = 7), and the highest grain arsenic value of the survey at 0.40 microg As g(-1). The mean arsenic level of Bangladeshi rice was 0.13 microg As g(-1) (n = 15). The main As species detected in the rice extract were AsIII, DMAV, and AsV. In European, Bangladeshi, and Indian rice 64 +/- 1% (n = 7), 80 +/- 3% (n = 11), and 81 +/- 4% (n = 15), respectively, of the recovered arsenic was found to be inorganic. In contrast, DMAV was the predominant species in rice from the USA, with only 42 +/- 5% (n = 12) of the arsenic being inorganic. Pot experiments show that the proportions of DMAV in the grain are significantly dependent on rice cultivar (p = 0.026) and that plant nutrient status is effected by arsenic exposure.     

Nationwide evaluation of quality and composition of colostrum on dairy farms in the United States

The objective of this study was to characterize the quality of maternal colostrum (MC) fed to newborn dairy calves in the United States and identify the proportion of MC that meets industry standards for IgG concentration and total plate count (TPC). Samples of MC (n=827) were collected from 67 farms in 12 states between June and October 2010. Samples were collected from Holsteins (n=494), Jerseys (n=87), crossbred (n=7), and unidentified dairy cattle (n=239) from first (n=49), second (n=174), third or greater (n=128), and unknown (n=476) lactations. Samples were identified as fresh (n=196), refrigerated (n=152), or frozen (n=479) before collection, as well as whether the sample was from an individual cow (n=734) or pooled (n=93). Concentration of IgG in MC ranged from <1 to 200mg/mL, with a mean IgG concentration of 68.8 mg/mL (SD=32.8). Almost 30% of MC contained <50 mg of IgG/mL. The IgG concentration increased with parity (42.4, 68.6, and 95.9 mg/mL in first, second, and third and later lactations, respectively). No differences in IgG concentration were observed among breeds or storage method; however, IgG was highest in samples collected in the Midwest and lowest in samples collected in the Southwest (79.7 vs. 64.3 mg/mL). Total plate count of samples ranged from 3.0 to 6.8 log(10) cfu/mL, with a mean of 4.9 log(10) cfu/mL (SD=0.9) and was greater in samples collected in the Southeast compared with other regions of the country. Pooled samples had greater TPC than individual samples and refrigerated samples had greater TPC than frozen and fresh samples. Almost 43% of samples collected had TPC >100,000 cfu/mL, 16.9% of the samples had >1 million cfu/mL. Only 39.4% of the samples collected met industry recommendations for both IgG concentration and TPC. Almost 60% of MC on dairy farms is inadequate, and a large number of calves are at risk of failure of passive transfer or bacterial infections, or both. Also, the data indicate that regional differences exist in colostrum quality.     

Phenotypically divergent classification of preweaned heifer calves for feed efficiency indexes and their correlations with heat production and thermography

The aims of this study were (1) to assess if there is phenotypical divergence for feed efficiency (FE) during the preweaning phase; (2) if FE is correlated with heat production (HP) measured by the face mask method or (3) by surface skin temperature via thermography, and (4) whether these methods are applicable to preweaned calves. Holstein × Gyr heifer calves (n = 36, birth body weight = 32.4 ± 6.6 kg) were enrolled and on trial between 4 and 12 wk of age and were classified into 2 residual feed intake (RFI) and residual body weight gain (RG) groups: high efficiency (HE; RFI, n = 10; and RG, n = 9) and low efficiency (LE; RFI, n = 10; and RG, n = 8). Calves were fed milk (6 L/d) and solid feed (95% starter and 5% chopped Tifton 85 hay, as fed). Growth was monitored weekly and feed intake (milk and solid feed) daily, during the whole period. Gas exchanges (O₂ consumption and production of CO₂ and CH₄) were obtained using a face mask at 45 ± 5 d of age and HP was estimated. Maximum temperatures were measured at 7 sites with an infrared camera at 62 ± 7 d of age. There was divergence in RFI and RG. Respectively, HE and LE calves had RFI of ?0.14 and 0.13 kg/d, and RG of 0.05 and ?0.07 kg/d. Dry matter intake was 15% lower in HE-RFI compared with LE-RFI, but no differences were observed in average daily weight gain. Within the RG test, no differences were observed in dry matter intake or average daily gain. The HE-RFI calves consumed less O₂ (L/d) and produced less CO₂ (L/d). Heart rate and HP were lower for HE-RFI calves compared with LE-RFI. Residual feed intake was correlated with HP (r = 0.48), O₂ consumption (r = 0.48), CO₂ production (r = 0.48), and heart rate (r = 0.40). No differences were observed in HP and gas exchanges between RG groups. Methane production was null in both groups. Eye temperature measured by thermography was 0.5°C greater in HE-RG than LE-RG calves. Differences in skin temperature between HE and LE calves were not observed at the other sites. These results support the hypothesis that calves are divergent for RFI, RG, and FE during preweaning and divergence tests are applicable during this phase. The face mask method described here is a useful tool for estimating differences in HP among phenotypically divergent RFI calves. Eye temperature measured by infrared thermography may have potential to screen phenotypically divergent RG calves.     

尼日利亚纳萨拉瓦州市售灌木芒果、腰果、秋葵、芝麻和高粱的真菌毒素污染情况研究（网络首发、推荐阅读）

采用LC-MS/MS真菌毒素检测法,对尼日利亚纳萨拉瓦州市场出售的食物作物（灌木芒果（n=12）、烤腰果（n=12）、干秋葵（n=12）、芝麻（n=35）、高粱（n=36））进行了分析研究。结果显示具致肝癌性黄曲霉毒素B1在灌木芒果、干秋葵和高粱样品中检出率分别为42%、25% 和19%,其平均浓度分别为19.2、8.27和4.75 µg/kg,伏马毒素B1污染了9%的芝麻样品（平均浓度为12.5 µg/kg）和47%的高粱样品（平均浓度为461 µg/kg）;同时受到黄曲霉毒素 B1和伏马毒素B1污染的高粱样本至少有19%。灌木芒果、高粱和干秋葵中检测到了具致肾毒性的赭曲霉毒素A,这是首次在干秋葵中报道检测到该毒素。可见,当地市场出售的这些食物作物受到真菌毒素的污染,可能威胁消费者的健康,需要采取积极措施防控污染。     

A national survey of the microbiological quality of beef carcasses and frozen boneless beef in Australia

The third national baseline microbiological survey of Australian beef carcasses and frozen boneless beef was conducted in 2004. Carcasses (n=1155) sampled at 27 slaughter establishments had a mean aerobic plate count (at 25 degrees C) of 1.3 log CFU/cm2. Escherichia coli was isolated from 8.0% of the cacasses, with a mean count of -0.8 log CFU/cm2 for positive samples. On samples from 24 boning (fabrication) plants (n=1082), the mean aerobic plate count for frozen boneless beef was 1.3 log CFU/g, and the mean count for the 1.8% of samples with detectable E. coli was 1.5 log CFU/g. E. coli O157: H7 was isolated from 1 of 1,143 carcasses and from 0 of 1082 boneless samples. Salmonella was isolated from 0 of 1155 carcasses and from 1 of 1082 samples of boneless product. No Campylobacter spp. were isolated from carcasses or boneless beef. Coagulase-positive staphylococci were isolated from 28.7% of beef carcasses and 20.3% of boneless beef samples, and positive samples had a mean count of 0.3 log CFU/cm2 and 0.8 log CFU/g, respectively.     

Response to kisspeptin and gonadotropin-releasing hormone agonist administration in Holstein-Friesian dairy heifers with positive or negative genetic merit for fertility traits

Previous research has identified that Holstein-Friesian dairy heifers with positive (POS) genetic merit for fertility traits (FertBV) reach puberty earlier than heifers with negative (NEG) FertBV. The hypothalamus-pituitary-gonadal (HPG) axis is functional in heifers before the onset of puberty, with increased LH release evident as heifers progress toward puberty. We investigated the functionality of the HPG axis in peripubertal Holstein-Friesian dairy heifers with divergent POS or NEG FertBV, hypothesizing that the earlier puberty onset of POS heifers is associated with earlier activation of the HPG axis than in NEG heifers. In experiment 1, we tested the dose responsiveness of POS heifers to an intravenous injection of either kisspeptin [Kiss; 2, 4, or 8 µg/kg of body weight (BW); n = 3 per dose] or a GnRH agonist (buserelin; 5, 10, or 20 ng/kg of BW; n = 3 per dose). The use of these 2 agonists investigates the status of the HPG axis in both the hypothalamus (Kiss) and pituitary (buserelin) glands. Doses of 4 µg/kg BW of Kiss and 10 ng/kg BW of buserelin produced submaximal LH responses and were used in experiment 2, in which previously unused POS (n = 22) and NEG (n = 18) FertBV heifers were challenged with both agonists at 10 and 12 mo of age in a partial crossover design. Heifers were randomly allocated to treatment groups, balanced for age and BW. The LH response to buserelin was greater in POS heifers than NEG heifers at 10 mo of age, with no difference in response at 12 mo. The FSH response to buserelin and the LH and FSH responses to Kiss did not differ between the POS and NEG heifers at either age. These results indicate an association between divergent genetic merit for fertility and the LH release to buserelin at 10 mo of age, supporting the hypothesis that gonadotropin responsiveness to a GnRH agonist is more advanced in POS heifers than in NEG heifers.     

Subsite affinities of beta-glucosidase from Aspergillus sojae on various xylooligosaccharides

The subsite affinities of beta-glucosidase (EC 3.2.1.21) with high beta-xylosidase activity from Aspergillus sojae on various xylooligosaccharides (degree of polymerization: n = 2-6) were investigated by steady-state kinetic analysis. The molecular activity (k0) value of the enzyme for xylobiose was not markedly different from those of other substrates (n = 3-6). The arrangement of the subsite affinities (A(i), i = 1-6) was evaluated; A1 = 2.93 kcal/mol, A2 = 3.67 kcal/mol, A3 = 0.64 kcal/mol, A4 = 0.12 kcal/mol, A5 = -0.07 kcal/mol, A6 = -0.05 kcal/mol, and the intrinsic rate constant (K(int)) was 7.6 s(-1). The subsite structure was similar to those of beta-glucosidase from A. niger and alpha-glucosidases from A. niger and Mucor javanicus, where the values for A1 were much larger than those for A3.