"Coulomb Staircase" at Room Temperature in a Self-Assembled Molecular Nanostructure

Double-ended aryl dithiols [alpha,alpha'-xylyldithiol (XYL) and 4,4'-biphenyldithiol] formed self-assembled monolayers (SAMs) on gold(111) substrates and were used to tether nanometer-sized gold clusters deposited from a cluster beam. An ultrahigh-vacuum scanning tunneling microscope was used to image these nanostructures and to measure their current-voltage characteristics as a function of the separation between the probe tip and the metal cluster. At room temperature, when the tip was positioned over a cluster bonded to the XYL SAM, the current-voltage data showed "Coulomb staircase" behavior. These data are in good agreement with semiclassical predictions for correlated single-electron tunneling and permit estimation of the electrical resistance of a single XYL molecule (approximately18 ± 12 megohms).     

多年麦稻轮作免耕土壤细菌对土壤养分和酶活性的影响

为了探索连续多年免耕轮作对土壤养分与微生物的影响,以麦稻水旱轮作免耕试验为对象,采用常规土壤养分测定法、土壤微生物宏基因组测序技术及京都基因和基因组百科全书(KEGG)数据库、冗余(RDA)分析等方法,对连续多年田间保留农作物残茬免耕及传统耕作土壤的养分、微生物种群、酶活性等进行了检测分析。结果表明,连续13年田间保留农作物秸秆、残茬免耕轮作与传统耕作轮作0～20 cm土壤微生物种群结构丰度在农作物不同生长发育时期发生了变化,第一核心种群的变形菌门(Proteobacteria)、酸性杆菌门(Acidobac-teria)丰度最高,呈增加趋势;第二核心种群的放线菌门(Actinobacteria)、绿弯菌门(Chloroflexi)丰度呈下降趋势;连续多年免耕轮作处理土壤中心土壤脲酶、蔗糖酶、蛋白酶含量分别比传统耕作处理提高了4.9%、22.8%、21.7%;免耕轮作处理的作物在绝大部分生长阶段与土壤酶的关联性优于传统耕作轮作处理。免耕处理Z4与传统耕种处理T4比较,土壤有机质、全氮、全磷、水解性氮、有效磷含量分别提高了27.7%、20.3%、16.1%、30.8%、19.3%;两种土壤的微生物代谢通路差异主要表现为氨基酸类通路,免耕轮作处理的绝大多数氨基酸类通路在第1时期(小麦拔节期)和第3时期(水稻孕穗期)比传统耕作轮作激活程度强的差异达到显著或极显著水平。在免耕轮作处理中,硝基螺菌属(Nitrospira)、厌氧黏细菌属(Anaromyxobacter)与全钾、速效钾、有机质、全氮、水解性氮含量,鞘氨醇单胞菌属(Sphingomonas)与有效磷含量呈正相关。连续多年田间保留作物残茬、秸秆,为微生物提供了较多的“食物”,以及连续多年免耕轮作措施减少土壤微生物生存环境的破坏是培肥地力的根本原因。而合理轮作免耕土壤中的变形菌门、酸性杆菌门等核心优势细菌种群,以及土壤酶的催化作用优于传统耕作,它们共同促进了土壤有机质和土壤养分转化和循环是提高土壤肥力的推动力。     

Mechanical, barrier, and antimicrobial properties of apple puree edible films containing plant essential oils

Edible films, as carriers of antimicrobial compounds, constitute an approach for incorporating plant essential oils (EOs) onto fresh-cut fruit surfaces. The effect against Escherichia coli O157:H7 of oregano, cinnamon, and lemongrass oils in apple puree film-forming solution (APFFS) and in an edible film made from the apple puree solution (APEF) was investigated along with the mechanical and physical properties of the films. Bactericidal activities of APFFS, expressed as BA50 values (BA50 values are defined as the percentage of antimicrobial that killed 50% of the bacteria under the test conditions) ranged from 0.019% for oregano oil to 0.094% for cinnamon oil. Oregano oil in the apple puree and in the film was highly effective against E. coli O157:H7. The data show that (a) the order of antimicrobial activities was oregano oil > lemongrass oil > cinnamon oil and (b) addition of the essential oils into film-forming solution decreased water vapor permeability and increased oxygen permeability, but did not significantly alter the tensile properties of the films. These results show that plant-derived essential oils can be used to prepare apple-based antimicrobial edible films for various food applications.     

Four legs or two: up front with you--preventing tragedies by keeping children and pets out of the cargo areas of pickup trucks.

Dogs and children riding in the cargo area of pickup trucks are common sights on our nation's highways, country roads, and small town streets. This scene brings to mind idyllic childhoods filled with summer days spent bouncing down roads in the back of grandpa's pickup truck, wind catching the laughter from children's throats. For hundreds of families each year, this activity is the cause of heartache, traumatic injuries, and senseless deaths. More than 200 people die each year, half of whom are younger than 18 years of age, as a direct result of falls from cargo areas of pickup trucks. Injuries and deaths resulting from riding in cargo areas of pickup trucks are not limited to humans. In a recent survey, 71% of veterinarians reported treating dogs for injuries sustained by falling or jumping from cargo areas of pickup trucks. This percentage does not take into account countless dogs that were killed and not treated. Injuries and deaths resulting from riding in cargo areas of pickup trucks are preventable. Whereas it may take millions of dollars and many years to cure diseases such as cancer, heart disease, and AIDS, pickup truck-associated deaths can be prevented simply by educating the public to not allow children and pets to ride in cargo areas. The primary objective of "Four legs or two: Up front with you" is to educate the public on the risks involved with travel in the cargo areas of pickup trucks. Making people aware that children and pets are not cargo is the first step toward decreasing senseless injuries and deaths.     

Uranium-series dated authigenic carbonates and acheulian sites in southern egypt

Field investigations in southern Egypt have yielded Acheulian artifacts in situ in authigenic carbonate deposits (CaCO(3)-cemented alluvium) along the edges of nowaggraded paleovalleys (Wadi Arid and Wadi Safsaf). Uranium-series dating of 25 carbonate samples from various localities as far apart as 70 kilometers indicates that widespread carbonate deposition occurred about 45, 141 and 212 ka (thousand years ago). Most of the carbonate appears to have been precipitated from groundwater, which suggests that these three episodes of deposition may be related to late Pleistocene humid climates that facilitated human settlement in this now hyperarid region. Carbonate cements from sediments containing Acheulian artifacts provide a minimum age of 212 ka for early occupation of the paleovalleys.     

Modelling spatial exclusion of a vulnerable native fish by introduced trout in rivers using landscape features: a new tool for conservation management

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Evaluation of Efficacy and Safety of Zinc Gluconate Associated with Dimethyl Sulphoxide for Sexually Mature Canine Males Chemical Neutering

The aim of this research was to evaluate the efficacy of zinc gluconate associated with dimethyl sulphoxide (DMSO) for chemical neutering in canine males. Fifteen sexually mature male dogs were divided in two groups, named control and treated. An injection was administered to both testicles, at a concentration of 26.2 mg zinc gluconate per ml and 0.5% DMSO in the treated group (11 dogs). The control group was given injections of saline solution (four dogs). Clinical examination and blood collection for a haemogram were done both before and after drug injection. There were 12 spermograms performed to analyse sperm motility, sperm vigour, ejaculate volume, testicle size, pathology and sperm concentrations. Libido was also measured. An ultrasound examination and histopathology were performed at the end of the experiment. Dogs’ libido after chemical injection was reduced by over 50%. The spermogram analysis showed final mean results of 14.54% for sperm motility, 0.72 of sperm vigour and 37 150 per million spermatozoa per millilitre, values considered below the necessary levels at which fertilization can occur. Ultrasound and histopathology analyses of testicles for the treated group revealed more intense injuries when compared with the control group, with compromised testicular parenchyma and a decrease of germ cell number leading to total atrophy, indicating that the treatment reduced the fertilizing potential of male dogs, promoting a possible subfertile status.