The after-hours mutant reveals a role for Fbxl3 in determining mammalian circadian period     

Godinho SI  Maywood ES  Shaw L  Tucci V  Barnard AR  Busino L  Pagano M  Kendall R  Quwailid MM  Romero MR  O'neill J  Chesham JE  Brooker D  Lalanne Z  Hastings MH  Nolan PM 《Science (New York, N.Y.)》2007,316(5826):897-900

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Retention of xenon in quartz and Earth's missing xenon     

Sanloup C  Schmidt BC  Chamorro Perez EM  Jambon A  Gregoryanz E  Mezouar M 《Science (New York, N.Y.)》2005,310(5751):1174-1177

The reactivity of xenon with terrestrial oxides was investigated by in situ synchrotron x-ray diffraction. At high temperature (T > 500 kelvin), some silicon was reduced, and the pressure stability of quartz was expanded, attesting to the substitution of some xenon for silicon. When the quartz was quenched, xenon diffused out and only a few weight percent remained trapped in samples. These results show that xenon can be covalently bonded to oxygen in quartz in the lower continental crust, providing an answer to the missing xenon problem; synthesis paths of rare gas compounds are also opened.  相似文献   

Self-Assembled Smectic Phases in Rod-Coil Block Copolymers   总被引：1，自引：0，他引：1  

JT Chen  EL Thomas  CK Ober  G Mao 《Science (New York, N.Y.)》1996,273(5273):343-346

Rod-coil block copolymers are self-assembling polymers that combine the physics of orientational ordering of rodlike polymers and the microphase separation of coil-coil block copolymers. Several new solid-state morphologies were observed in a series of anionically synthesized model poly(hexyl isocyanate-b-styrene) rod-coil diblock copolymers examined by transmission electron microscopy and selected-area electron diffraction. The rod-coils formed smectic C-like and O-like morphologies with domain sizes ranging from tens of nanometers to almost 1 micrometer. Both structural and orientational changes were found for increasing rod volume fractions. In addition, some morphologies exhibited spontaneous long-range orientational order over many tens of micrometers.  相似文献   

A new dawn for science in Africa     

Hassan MH 《Science (New York, N.Y.)》2007,316(5833):1813

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Revolutionize Egypt's science culture     

El-Sherbeini M 《Science (New York, N.Y.)》2011,333(6050):1702-1703

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Explaining disparities in food safety compliance by food stores: does community matter?     

Kameshwari Pothukuchi  Rayman Mohamed  David A. Gebben 《Agriculture and Human Values》2008,25(3):319-332

This paper provides a conceptual framework to explain why disparities may exist in food safety code compliance by food stores in different neighborhoods. Explanations include market dynamics, community characteristics, retailer attributes, inspector characteristics, and enforcement approaches, and interactions among the factors. A preliminary and limited empirical test of some of these relationships in Detroit, Michigan shows a higher rate of food safety violations by stores in poorer neighborhoods and in neighborhoods with higher concentrations of African-American residents. Stores inspected by female inspectors also scored higher numbers of critical violations, suggesting a need for greater examination of the social relations associated with enforcement interactions in food safety studies.

Kameshwari PothukuchiEmail:

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Kameshwari Pothukuchi   PhD, is Associate Professor of Urban Planning at Wayne State University. She conducts research on issues related to urban food security, including grocery stores, community gardens, and community and regional food planning. A policy guide on community and regional food planning, co-authored by her, was recently adopted by the American Planning Association (). Rayman Mohamed   PhD, is Assistant Professor of Urban Planning at Wayne State University. He conducts research on land use and environmental planning. His recent articles examine decision making by developers, the economics of conservation subdivisions, and the relationship between sprawl and the costs of infrastructure. David A. Gebben   is a graduate student of agricultural economics and a research assistant in the Global Urban Studies Program at Michigan State University.  相似文献   

A Burkholderia pseudomallei toxin inhibits helicase activity of translation factor eIF4A     

Cruz-Migoni A  Hautbergue GM  Artymiuk PJ  Baker PJ  Bokori-Brown M  Chang CT  Dickman MJ  Essex-Lopresti A  Harding SV  Mahadi NM  Marshall LE  Mobbs GW  Mohamed R  Nathan S  Ngugi SA  Ong C  Ooi WF  Partridge LJ  Phillips HL  Raih MF  Ruzheinikov S  Sarkar-Tyson M  Sedelnikova SE  Smither SJ  Tan P  Titball RW  Wilson SA  Rice DW 《Science (New York, N.Y.)》2011,334(6057):821-824

The structure of BPSL1549, a protein of unknown function from Burkholderia pseudomallei, reveals a similarity to Escherichia coli cytotoxic necrotizing factor 1. We found that BPSL1549 acted as a potent cytotoxin against eukaryotic cells and was lethal when administered to mice. Expression levels of bpsl1549 correlate with conditions expected to promote or suppress pathogenicity. BPSL1549 promotes deamidation of glutamine-339 of the translation initiation factor eIF4A, abolishing its helicase activity and inhibiting translation. We propose to name BPSL1549 Burkholderia lethal factor 1.  相似文献   

Exploitation of SSR,SRAP and CAPS-SNP markers for genetic diversity of Citrus germplasm collection     

Mohamed Hamdy Amar  Manosh Kumar Biswas  Zongwen Zhang  Wen-Wu Guo 《Scientia Horticulturae》2011

The present study was to assess informativeness and efficiency of three different molecular markers for genetic diversity among 24 Citrus and its relative species. Sixty one SSR, 33 SRAP and 24 CAPS-SNP markers were used to evaluate the level of polymorphism and discriminating capacity. A total of 596, 656 and 135 polymorphic amplicons were observed in SSR, SRAP and CAPS-SNP markers with average polymorphism information content (PIC) of 0.97, 0.98 and 0.89, respectively. High levels of polymorphism were recorded for SSR and SRAP compared with CAPS-SNP markers. The highest correlations (r = 0.930) were obtained between SSR and SRAP markers, whereas SSR and CAPS-SNP were poorly correlated (r = 0.833). Cluster analysis was performed to construct dendrograms using UPGMA. And the dendrogram from SSR data was most congruent with the general dendrogram. These findings provide basis for future efficient use of these molecular markers in the genetic analysis of Citrus and its relatives.  相似文献   

Performance assessment of small irrigation schemes along the Mauritanian banks of the Senegal River     

Mariana García-Bolaños  Cecilia Borgia  Noemí Poblador  Mamadou DiaOuld Mohamed Vadel Seyid  Luciano Mateos 《Agricultural Water Management》2011,98(7):1141-1152

Irrigation plays a fundamental role in world food provision but, to date, it has performed below expectations in Sub-Saharan Africa. The present study assesses and diagnoses the performance of 22 small and medium size community-managed irrigation schemes, mainly devoted to rice production, in different locations along the Mauritanian banks of the Lower Senegal River. The evaluations followed the Rapid Appraisal Process in which semi-structured interviews were held with representatives of the Cooperatives’ Boards in charge of each scheme to obtain information about the organisation of the cooperative, land tenure, irrigation system and organization, cropping pattern and soils. Additionally, for each irrigation scheme, the water-delivery service was characterized by making qualitative and comparative observations during field inspections; the pumping station's performance was diagnosed by a local specialist; the discharge at the head of the system was measured; daily irrigation time was recorded; and crop yields were determined by plot sampling. Then a set of performance indicators was computed. Water delivery capacity referred to irrigated areas was insufficient in a third of the schemes, and this insufficiency was exacerbated by poor maintenance. Irrigation intensity in habilitated areas was rather low being less than 0.66 in 50% of the schemes. The average productivity of land, irrigation water, and fuel (3.38 t ha⁻¹, 0.30 kg m⁻³ and 2.37 kg kWh⁻¹, respectively) were well below potential.  相似文献   

Cuticular hydrocarbons in two parapatric species of ants and their hybrid     

Mohamed EL‐SHEHABY  Mohamed Sayed SALAMA  Elisabeth BRUNNER  Jürgen HEINZE 《Integrative zoology》2011,6(3):259-265

Discrimination between nestmates and non‐nestmates in social insects is thought to rely on the pattern of cuticular hydrocarbons. We investigated the cuticular hydrocarbon profiles of 2 parapatric sibling ant species, Temnothorax nylanderi (Förster, 1850) and Temnothorax crassispinus (Karavaiev, 1926), and their hybrid. We found that although the profiles show considerable similarities, a discriminant analysis based on the relative peak areas of cuticular hydrocarbons separates the 3 taxa. The profiles of hybrids were not consistently intermediate between those of the paternal species, suggesting either non‐additive interactions among the parental biosynthetic pathways or systematic differences in environment‐derived odor cues.  相似文献