124 research outputs found

    14 new eclipsing white dwarf plus main-sequence binaries from the SDSS and Catalina surveys

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    We report on the search for new eclipsing white dwarf plus main-sequence (WDMS) binaries in the light curves of the Catalina surveys. We use a colour-selected list of almost 2000 candidate WDMS systems from the Sloan Digital Sky Survey, specifically designed to identify WDMS systems with cool white dwarfs and/or early M-type main-sequence stars. We identify a total of 17 eclipsing systems, 14 of which are new discoveries. We also find three candidate eclipsing systems, two main-sequence eclipsing binaries and 22 non-eclipsing close binaries. Our newly discovered systems generally have optical fluxes dominated by the main-sequence components, which have earlier spectral types than the majority of previously discovered eclipsing systems. We find a large number of ellipsoidally variable binaries with similar periods, near 4 h, and spectral types M2–3, which are very close to Roche lobe filling. We also find that the fraction of eclipsing systems is lower than found in previous studies and likely reflects a lower close binary fraction among WDMS binaries with early M-type main-sequence stars due to their enhanced angular momentum loss compared to fully convective late M-type stars, hence causing them to become cataclysmic variables quicker and disappear from the WDMS sample. Our systems bring the total number of known detached, eclipsing WDMS binaries to 71

    Seasonality of Leaf and Fig Production in Ficus squamosa, a Fig Tree with Seeds Dispersed by Water

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    The phenology of plants reflects selection generated by seasonal climatic factors and interactions with other plants and animals, within constraints imposed by their phylogenetic history. Fig trees (Ficus) need to produce figs year-round to support their short-lived fig wasp pollinators, but this requirement is partially de-coupled in dioecious species, where female trees only develop seeds, not pollinator offspring. This allows female trees to concentrate seed production at more favorable times of the year. Ficus squamosa is a riparian species whose dispersal is mainly by water, rather than animals. Seeds can float and travel in long distances. We recorded the leaf and reproductive phenology of 174 individuals for three years in Chiang Mai, Northern Thailand. New leaves were produced throughout the year. Fig production occurred year-round, but with large seasonal variations that correlated with temperature and rainfall. Female and male trees initiated maximal fig crops at different times, with production in female trees confined mainly to the rainy season and male figs concentrating fig production in the preceding months, but also often bearing figs continually. Ficus squamosa concentrates seed production by female plants at times when water levels are high, favouring dispersal by water, and asynchronous flowering within male trees allow fig wasps to cycle there, providing them with potential benefits by maintaining pollinators for times when female figs become available to pollinate

    Identification of Close Relatives in the HUGO Pan-Asian SNP Database

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    The HUGO Pan-Asian SNP Consortium has recently released a genome-wide dataset, which consists of 1,719 DNA samples collected from 71 Asian populations. For studies of human population genetics such as genetic structure and migration history, this provided the most comprehensive large-scale survey of genetic variation to date in East and Southeast Asia. However, although considered in the analysis, close relatives were not clearly reported in the original paper. Here we performed a systematic analysis of genetic relationships among individuals from the Pan-Asian SNP (PASNP) database and identified 3 pairs of monozygotic twins or duplicate samples, 100 pairs of first-degree and 161 second-degree of relationships. Three standardized subsets with different levels of unrelated individuals were suggested here for future applications of the samples in most types of population-genetics studies (denoted by PASNP1716, PASNP1640 and PASNP1583 respectively) based on the relationships inferred in this study. In addition, we provided gender information for PASNP samples, which were not included in the original dataset, based on analysis of X chromosome data

    Istraživanja 3,4-diaril-1,2,5-oksadiazola i njihovih N-oksida: Potraga za boljim COX-2 inhibitorima

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    A series of 3,4-diaryl-1,2,5-oxadiazoles and 3,4-diaryl-1,2,5-oxadiazole N-oxides were prepared and evaluated for COX-2 and COX-1 binding affinity in vitro and for anti-inflammatory activity by the rat paw edema method. p-Methoxy (p-OMe) substituted compounds 9, 21, 34, 41, 42 showed COX-2 enzyme inhibition higher than that showed by compounds with other substituents. 3,4-Di(4-methoxyphenyl)-1,2,5-oxadiazole N-oxide (42) showed COX-2 enzyme inhibition of 54% at 22 µmol L-1 and COX-1 enzyme inhibition of 44% at 88 µmol L-1 concentrations, but showed very low in vivo anti-inflammatory activity. Its deoxygenated derivative (21) showed lower COX-2 enzyme inhibition (26% at 22 µmol L-1) and higher COX-1 enzyme inhibition (53% at 88 µmol L-1) but marked in vivo anti-inflammatory activity (71% at 25 mg kg-1) vs. celecoxib (48% at 12.5 mg kg-1). Molecular modeling (docking) studies showed that the methoxy group is positioned in the vicinity of the COX-2 secondary pocket and it also participates in hydrogen bonding interactions in the COX-2 active site. These preliminary studies suggest that the p-methoxy (p-OMe) group in one of benzene rings may give potentially active leads in this series of oxadiazole/N-oxides.Sintetizirana je serija 3,4-diaril-1,2,5-oksadiazola i 3,4-diaril-1,2,5-oksadiazol N-oksida i ocijenjena njihova sposobnost vezivanja na COX-2 i COX-1 in vitro i protuupalno djelovanje na edem šape štakora. Spojevi sa p-metoksi (p-OMe) supstituentom 9, 21, 34, 41, 42 bolje su inhibirali COX-2 nego ostali spojevi. 3,4-Di(4-metoksifenil)-1,2,5-oksadiazol N-oksid (42) inhibirao je COX-2 za 54% u koncentraciji od 22 µmol L-1, a COX-1 za 44% u koncentraciji 88 µmol L-1, ali je in vivo slabo djelovao protuupalno. Njegov deoksigenirani derivat 21 pokazao je slabiju inhibiciju COX-2 enzima (26% u koncentraciji 22 µmol L-1) i jaču inhibiciju COX-1 (71% u koncentraciji 25 mg kg-1) što je bolje od standarda celekoksiba (48% u koncentraciji 12,5 mg kg-1). Molekularno je modeliranje pokazalo da je metoksi skupina smještena u blizini sekundarnog džepa na enzimu COX-2 i da utječe na vodikove veze interakcija na aktivnom mjestu COX-2. Ova preliminarna istraživanja sugeriraju da bi se u seriji oksadiazol/N-oksida mogao naći predvodni spoj s p-metoksi skupinom na benzenskom prstenu

    Population Genetic Structure of Peninsular Malaysia Malay Sub-Ethnic Groups

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    Patterns of modern human population structure are helpful in understanding the history of human migration and admixture. We conducted a study on genetic structure of the Malay population in Malaysia, using 54,794 genome-wide single nucleotide polymorphism genotype data generated in four Malay sub-ethnic groups in peninsular Malaysia (Melayu Kelantan, Melayu Minang, Melayu Jawa and Melayu Bugis). To the best of our knowledge this is the first study conducted on these four Malay sub-ethnic groups and the analysis of genotype data of these four groups were compiled together with 11 other populations' genotype data from Indonesia, China, India, Africa and indigenous populations in Peninsular Malaysia obtained from the Pan-Asian SNP database. The phylogeny of populations showed that all of the four Malay sub-ethnic groups are separated into at least three different clusters. The Melayu Jawa, Melayu Bugis and Melayu Minang have a very close genetic relationship with Indonesian populations indicating a common ancestral history, while the Melayu Kelantan formed a distinct group on the tree indicating that they are genetically different from the other Malay sub-ethnic groups. We have detected genetic structuring among the Malay populations and this could possibly be accounted for by their different historical origins. Our results provide information of the genetic differentiation between these populations and a valuable insight into the origins of the Malay sub-ethnic groups in Peninsular Malaysia
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