bluuebunny/crossref_metadata_2025_split huggingface dataset:
Testing for genetic association in the presence of population stratification in genome‐wide association studies
Authors: Wang Kai 
Published: February 2009

AbstractGenome‐wide case‐control association study is gaining popularity, thanks to the rapid development of modern genotyping technology. In such studies, population stratification is a potential concern especially when the number of study subjects is large as it can lead to seriously inflated false‐positive rates. Current methods addressing this issue are still not completely immune to excess false positives. A simple method that corrects for population stratification is proposed. This method modifies a test statistic such as the Armitage trend test by using an additive constant that measures the variation of the effect size confounded by population stratification across genomic control (GC) markers. As a result, the original statistic is deflated by a multiplying factor that is specific to the marker being tested for association. This deflating multiplying factor is guaranteed to be larger than 1. These properties are in contrast to the conventional GC method where the original statistic is deflated by a common factor regardless of the marker being tested and the deflation factor may turn out to be less than 1. The new method is introduced first for regular case‐control design and then for other situations such as quantitative traits and the presence of covariates. Extensive simulation study indicates that this new method provides an appealing alternative for genetic association analysis in the presence of population stratification. Genet. Epidemiol. 33:637–645, 2009. © 2009 Wiley‐Liss, Inc.
Recurrent seizures induce a reversible impairment in a spatial hidden goal task
Authors: Lin Hai , Holmes Gregory L. , Kubie John L. , Muller Robert U. 
Published: February 2009

AbstractA major question concerning the learning and memory deficits characteristic of epilepsy is the relative importance of the initial insult that leads to recurrent, unprovoked seizures versus the seizures themselves. A related issue is whether seizure‐induced cognitive decline is permanent or reversible when convulsions cease. To address these problems, adult rats were extensively trained in the “spatial accuracy task,” a dry‐land analog of the Morris water maze. This task allows the rat's estimate of the location of a hidden goal zone to be repeatedly measured within each behavioral session. One aim was to measure, in well‐trained animals, the time course of any cognitive impairment caused by a daily flurothyl‐induced generalized seizure over 11 days. A second aim was to look for possible recovery during 9 subsequent days with no seizures. We saw a cumulative degradation in spatial performance during the seizure days and reversal of the deficit after seizures were stopped such that performance returned to baseline. Interestingly, the rate of learning to an asymptote, the rate of performance decline during one‐per‐day seizures and the rate of relearning during the recovery period were all similar. Given that the hippocampus plays an important role in spatial memory and that it is the brain structure most vulnerable to abnormal excitation the implication is that the hippocampus remains essential for precise spatial navigation even after prolonged training in locating a fixed goal zone. Clinically, this finding questions the assumption that patients who experience seizures should return to a baseline cognitive level within hours. © 2009 Wiley‐Liss, Inc.
Rigid Alicyclic Molecules from Bicyclo[2.2.1]hept‐2‐enes (=8,9,10‐Trinorbornenes) and 1,4‐Dipyridin‐2‐ylphthalazines as Stereoselective Coupling Agents
Authors: Margetić Davor , Murata Yasujiro , Komatsu Koichi , Marinić Željko 
Published: February 2009

Abstractmagnified imageFor the preparation of rigid polycyclic molecules from 8,9,10‐trinorbornenes (=bicyclo[2.2.1]hept‐2‐enes), 1,4‐dipyridin‐2‐ylphthalazines were used. Cycloaddition reactions with trinorbornenes gave coupled products in a stereoselective manner. In these reactions, the phthalazines delivered a new bicyclo[2.2.2] moiety at the junction of two trinorbornene units, which could bear appropriate functional groups (Schemes 4and5). The crystal structure of a key cycloadduct,i.e., of18was also determined (Fig. 2). Relative reactivities for a series of phthalazines (Fig. 3) were estimated by density‐functional‐theory (DFT) calculations at the B3LYP/6‐31G* level (Table). The calculations indicated an increase of reactivity when the aromaticity of the phthalazine moiety is decreased. Finally, experimentally observed stereoselectivities of the phthalazine reactions with trinorbornenes were readily predicted by DFT calculations (Fig. 4).
Ceramides and Cerebrosides from Ligusticum chuanxiongHort.
Authors: Yang Nian‐Yun , Ren Dong‐Chun , Duan Jin‐Ao , Xu Xiao‐Hua , Xie Ning , Tian Li‐Juan 
Published: February 2009

Abstractmagnified imageTwo new ceramides, (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxypentadec‐8‐en‐2‐yl]heptacosanamide (1) and (2R)‐2‐hydroxy‐N‐{(3S,4S,5S)‐4‐hydroxy‐5‐[(4E)‐undec‐4‐en‐1‐yl]tetrahydrofuran‐3‐yl}heptacosanamide (2), were isolated from the aerial parts of Ligusticum chuanxiong, along with one known ceramide, (2R)‐2‐hydroxy‐N‐[(2S,3S,4R,8E)‐1,3,4‐trihydroxyicos‐8‐en‐2‐yl]tetracosanamide (3), and two known cerebrosides, (2R)‐N‐[(2S,3R,4E,8E)‐1‐(β‐D‐glucopyranosyloxy)‐3‐hydroxydodeca‐4,8‐dien‐2‐yl]‐2‐hydroxydocosanamide (4) and (2R)‐N‐[(2S,3S,4R,8E)‐1‐(β‐D‐glucopyranosyloxy)‐3,4‐dihydroxyoctadec‐8‐en‐2‐yl]‐2‐hydroxyhexadecanamide (5). Their structures were elucidated by extensive spectroscopic analysis, including 1D‐ and 2D‐NMR, as well as HR‐ESI‐MS experiments.
Imaging Technique with Liquid Crystals of Halogen‐Containing 3,6‐Distyrylpyridazines (=3,6‐Bis(2‐phenylethenyl)pyridazines)
Authors: Lifka Thorsten , Seus Peter , Oehlhof Annette , Meier Herbert 
Published: February 2009

Abstractmagnified imageThe 3,6‐bis{(1E)‐2‐[4‐(dodecyloxy)phenyl]ethenyl}pyridazine (1a) was regio‐ and stereoselectively brominated or chlorinated to the (Z,Z)‐compounds 3 and 6, respectively. The conjugated core of these systems represents a mesogen for smectic (and nematic) liquid crystals and, moreover, a chromophore with an absorption at the UV/VIS border. Irradiation and efficient intersystem crossing to the triplet state leads to isomerization reactions (Z,Z)→(E,Z) in solution as well as in the thermotropic LC phases. Since (E,Z)‐configurations are only tolerated to a very small extent by the mesophases, the photoinduced transition S→N→I of 6 can be used as an imaging technique.
Sesquiterpenes and Dimers Thereof from Chloranthus fortunei
Authors: Wang Xia‐Chang , Wang Li‐Li , Ouyang Xiao‐Wei , Ma Shi‐Ping , Liu Jing‐Han , Hu Li‐Hong 
Published: February 2009

Abstractmagnified imageFour new compounds, including one new sesquiterpene dimer, i.e., shizukaol P (1), one new dimeric sesquiterpene glycoside, i.e., 9‐O‐β‐glucopyranosylcycloshizukaol A (2), and two new sesquiterpenes, i.e., shizukanolides G and H (3 and 4, resp.), together with eight known compounds, were isolated from the aerial part of Chloranthus fortunei. The structures and relative configurations were elucidated on the basis of spectroscopic data and by comparison with those of the related compounds reported in the literature.
Two New Securinega Alkaloids from Securinega suffruticosa
Authors: Qin Song , Liang Jing‐Yu , Guo Yue‐Wei 
Published: February 2009

Abstractmagnified imageTwo new Securinega alkaloids, 2‐episecurinol A (1) and 8‐(diethylamino)‐2‐episecurinol A (2), together with the five known related analogues 3–7, were isolated from Securinega suffruticosa (Pall.) Rehd. Their structures were determined by detailed analysis of 1D‐ and 2D‐NMR spectra and by comparison with the related model compounds.
Two New Sesquiterpenes from Salvia roborowskiiMaxim
Authors: Liu Yong , Li Chong , Shi Jian‐Gong , Shi Yan‐Ping 
Published: February 2009

Abstractmagnified imageTwo new sesquiterpenes, (1β,3β,4α,5α,6α,8α)‐guai‐10(14)‐ene‐3,4,6,8‐tetrol 3,6,8‐triacetate (1) and (3β,4α,6α,8β,9β,10α)‐8‐(acetyloxy)‐3,4 : 9,10‐diepoxygermacr‐7(11)‐eno‐12,6‐lactone (2) were isolated from the EtOH extract of Salvia roborowskii Maxim. Their structures were established by spectroscopic methods, including one‐ and two‐dimensional NMR techniques, and the relative configurations of these compounds were determined on the basis of NOE experiments.
Sesquiterpenes and Lignans from Tephrosia vogelii
Authors: Wei Huan‐Huan , Xu Han‐Hong , Xie Hai‐Hui , Xu Liang‐Xiong , Wei Xiao‐Yi 
Published: February 2009

Abstractmagnified imageA new guaiane sesquiterpene, (1β,6α,10α)‐guai‐4(15)‐ene‐6,7,10‐triol (1), and a new lignan, (+)‐lariciresinol 9′‐stearate (2), were isolated from the aerial parts of a leguminosae plant, Tephrosia vogelii, together with three known compounds, teclenone B, (1β,7R*)‐opposit‐4(15)‐ene‐1,7‐diol, and pinoresinol. Their structures were elucidated on the basis of spectral data.
ent‐Abietanoids and ent‐Isopimaranoid Glycosides from Isodon nervosus
Authors: Li Li‐Mei , Li Guo‐You , Ding Li‐Sheng , Pu Jian‐Xin , Xiao Wei‐Lie , Han Quan‐Bin , Sun Han‐Dong 
Published: February 2009

Abstractmagnified imageThree new and one known ent‐abietanoids, i.e., ent‐abienervonins A–C (1–3, resp.) and hebeiabinin B (4), and two new ent‐isopimaranoid glycosides, i.e., ent‐isopimanervosides A and B (5 and 6, resp.), along with seven known phenolic glycosides were isolated from the aerial parts of Isodon nervosus. The structures of the new compounds were elucidated on the basis of spectroscopic and chemical evidence.
Three New Diterpenoids from Salvia przewalskiiMaxim
Authors: Xu Gang , Peng Li‐Yan , Tu Lin , Li Xiao‐Li , Zhao Yu , Zhang Peng‐Tao , Zhao Qin‐Shi 
Published: February 2009

Abstractmagnified imageThree new compounds including one ortho‐quinone‐type icetexane diterpenoid, i.e., przewalskin E (1), one abietane dinorditerpenoid, i.e., przewalskin F (2), and one 7,20‐epoxyabietane diterpenoid, i.e., przewalskin G (3), were isolated from Salvia przewalskii Maxim. The identification and structure elucidation of these compounds were based on 1D‐ and 2D‐NMR spectral‐data analysis. It is noteworthy that przewalskin E (1), featured with an 11,12‐dioxoicetexane skeleton, represents the second example of a naturally occurring ortho‐quinone‐type icetexane diterpenoid from Salvia plants.
A New Tricyclo[6.3.1.02,5]dodecane Sesquiterpene from Cultures of the Basidiomycete Campanella junghuhnii
Authors: Liu Rong , Zhou Zhong‐Yu , Xu Di , Wang Fei , Liu Ji‐Kai 
Published: February 2009

Abstractmagnified imageA new sesquiterpene with a tricyclo[6.3.1.02,5]dodecane skeleton, 2,3,6‐trihydroxycaryol‐5‐en‐7‐one (1), was isolated from the culture of the basidiomycete Campanella junghuhnii. The structure of 1 was elucidated on the basis of extensive spectroscopic analysis including IR, UV, MS, 1D‐ and 2D‐NMR experiments.
Identification of Major Alkaloids in Rat Urine by HPLC/DAD/ESI‐MS/MS Method Following Oral Administration of Cortex Phellodendri Decoction
Authors: Ma Chun‐Hui , Li Zhi‐Xiong , Wang Long‐Xing , Tang Yi‐Hong , Xiao Hong‐Bin , Huang Cheng‐Gang 
Published: February 2009

Abstractmagnified imageA rapid, sensitive, and specific high‐performance liquid chromatography (HPLC), diode‐array detection, and mass‐spectrometry techniques were developed for an identification of the constituents of Cortex Phellodendri and their metabolites in rat urine. The dose of 10 ml/kg of Cortex Phellodendri decoction was used for rats' oral administration. 0–24‐h Urine was purified using a C18 solid‐phase extraction cartridge, and then analyzed by an on‐line MS detector. A total of 13 characteristic HPLC peaks were detected in the urine samples. Nine of them, including five alkaloids and four of their metabolites, were tentatively elucidated as magnoflorine (1), the glucuronide conjugate of demethyleneberberine (2), menisperine (3), jatrorrhizine 3‐O‐glucuronide (4), berberubine 9‐O‐glucuronide (5), jatrorrhizine (6), the monomethyl and monohydroxy catabolite of berberubine (7), palmatine (8), and berberine (9). Identification and structural elucidation of the metabolites were performed by comparing their MSn spectra data with those reported.
Optimized Batchwise and Continuous Microreactor Synthesis of a (Bathophenanthroline)ruthenium(II) Complex Carrying Different Ligands
Authors: Kramer Rolf A. , Rumi Luigi , Bannwarth Willi 
Published: February 2009

Abstractmagnified imageBy changing the Ru‐source, the reaction conditions, and the workup/purification procedure, the batchwise synthesis of a mixed [RuII(bathophenanthroline)] complex, i.e., of 4b, could substantially be improved (bathophenanthroline=4,7‐diphenyl‐1,10‐phenanthroline). In addition, we were able to adapt both steps of the synthesis to a microreactor system leading to the desired Ru‐complex in a continuous preparation in very high yields. The latter approach is especially suited for an envisaged scale‐up.
Development of a new method of wavelet aided trend detection and estimation
Authors: Adamowski Kaz , Prokoph Andreas , Adamowski Jan 
Published: February 2009

AbstractThe detection and estimation of trends in the presence of noise, periodicities, or discontinuous patterns is important in hydrology and climate research studies. The basic idea of currently available trend estimation techniques (tests) is that the trends should be smooth and monotonic; however, hydro‐climatologic variables contain multiple signals, and have segments of increasing and decreasing trends. As a result, estimating trends in time series is an essential but arcane art and it is therefore important to continue developing the theory and practice of trend analysis.In this paper, a new technique is proposed based on the continuous wavelet transform (CWT). CWT permits the transformation of observed time series into wavelet coefficients according to time and scale simultaneously. These coefficients can be used to detect and estimate trends or to reconstruct signals that are of interest. The proposed CWT method was first tested on computer‐generated data exhibiting both periodic and noise components. It was then applied to observed monthly minimum streamflow observations extracted from the Reference Hydrometric Basin Network (RHBN) for five different eco‐zones in Canada.It was concluded that the proposed wavelet transform (WT) based method provides a very flexible and accurate tool for detecting and estimating complicated signals. The results from monthly minimum observations indicate that short period fluctuations are decreasing, while multi‐annual variability is increasing in Canada. And finally, a persistent ∼55‐year signal is well correlated with the Pacific Decadal Oscillation in all records, which indicates that trends are not controlled by a single factor. Copyright © 2009 John Wiley & Sons, Ltd.
Scaling properties and spatial organization of snow depth fields in sub‐alpine forest and alpine tundra
Authors: Trujillo Ernesto , Ramírez Jorge A. , Elder Kelly J. 
Published: February 2009

AbstractThis paper reports on a study analysing the spatial distribution functions, the correlation structures, and the power spectral densities of high‐resolution LIDAR snow depths (∼1 m) in two adjacent 500 m × 500 m areas in the Colorado Rocky Mountains, one a sub‐alpine forest the other an alpine tundra. It is shown how and why differences in the controlling physical processes induced by variations in vegetation cover and wind patterns lead to the observed differences in spatial organization between the snow depth fields of these environments. In the sub‐alpine forest area, the mean of snow depth increases with elevation, while its standard deviation remains uniform. In the tundra subarea, the mean of snow depth decreases with elevation, while its standard deviation varies over a wide range. The two‐dimensional correlations of snow depth in the forested area indicate little spatial memory and isotropic conditions, while in the tundra they indicate a marked directional bias that is consistent with the predominant wind directions and the location of topographic ridges and depressions. The power spectral densities exhibit a power law behaviour in two frequency intervals separated by a break located at a scale of around 12 m in the forested subarea, and 65 m in the tundra subarea. The spectral exponents obtained indicate that the snow depth fields are highly variable over scales larger than the scale break, while highly correlated below. Based on the observations and on synthetic snow depth fields generated with one‐ and two‐dimensional spectral techniques, it is shown that the scale at which the break occurs increases with the separation distance between snow depth maxima. In addition, the breaks in the forested area coincide with those of the corresponding vegetation height field, while in the tundra subarea they are displaced towards larger scales than those observed in the corresponding vegetation height field. Copyright © 2009 John Wiley & Sons, Ltd.
Carbon and nitrogen cycling in a vegetated lowland chalk river impacted by sediment
Authors: Trimmer M. , Sanders I. A. , Heppell C. M. 
Published: February 2009

AbstractWe investigated the accumulation and biogeochemical cycling of organic matter beneath Ranunculus plants in a lowland river. Organic carbon accumulated beneath the plants at a mean rate of 20 mmol C m−2 h−1. Annual gross primary production for both Ranunculus and its biofilm, and the microphytobenthos, could account for 26% of the carbon accumulated. The remainder was attributable to organic carbon in both suspended particulate matter (77%) and that associated with sands saltating along the bottom (33%). Maximum carbon oxidation occurred in spring and early summer and declined thereafter. The efflux of CO2 was greater than the carbon equivalents due to reduction of O2, NO3− and SO42− measured at the surface, which suggested a significant contribution to carbon oxidation from the subsurface and some oxidation via alternative electron acceptors. The peak in carbon oxidation could not be accounted for by either rising temperature or primary production but tracked the quality of recently deposited allochthonous organic matter. The ratio of carbon oxidation to total organic carbon accumulation suggested that 19% of the organic matter deposited was remineralised on an annual basis, although this reached 58% in June. We calculate that a total of 3·6 mol N m−2 y−1 was mineralised in the sediment, of which 11% could be accounted for by the measured efflux of NH4+. The remainder could be accounted for by the N demand from primary production (67% macrophytes/biofilm; 36% phytobenthos). Copyright © 2009 John Wiley & Sons, Ltd.
Quantifying the impact of groundwater discharge on the surface–subsurface exchange
Authors: Boano Fulvio , Revelli Roberto , Ridolfi Luca 
Published: February 2009

AbstractThe exchange of oxygen and nutrients between the well‐aerated stream water and the subsurface water is crucial for the biochemical conditions of the hyporheic zone. The metabolic activity of the hyporheic microorganisms controls the fate of nitrogen and phosphorus in the pore water, and influences the fate of these nutrients at the catchment scale. Unfortunately, the incomplete knowledge of the complex hydrodynamics of the coupled surface‐subsurface flow field often hinders the understanding of the ecological relevance of the hyporheic processes. Here, we analyse the influence of groundwater discharge through the streambed on bedform‐induced hyporheic exchange. A simple mathematical model of a coupled stream‐aquifer system is developed in order to describe the essential feature of the surface‐subsurface exchange. The most representative characteristics of the hyporheic exchange, e.g. the depth of the hyporheic zone ‐ are parametrized in terms of a small number of easily measurable quantities. This information on the hyporheic flow field provides the fundamental basis for the study of the ecological function of the hyporheic zone. Copyright © 2009 John Wiley & Sons, Ltd.
Development of a cell‐derived matrix: Effects of epidermal growth factor in chemically defined culture
Authors: Throm Angela M. , Liu Wai‐Ching , Lock Chi‐Hung , Billiar Kristen L. 
Published: February 2009

AbstractExtracellular matrices without animal components and with high mechanical strength are needed for the development of the next generation of viable skin replacements. The goal of this study was to determine the optimal concentration of epidermal growth factor (EGF) to maximize the strength and collagen content of cell‐derived matrix (CDM) produced by fibroblasts in vitro in serum‐free media. Scaffold‐free CDM samples were produced by human dermal fibroblasts in the presence of 0–50 ng/mL EGF in chemically defined media. After 21 days of culture, a membrane inflation system was used to measure the biaxial tensile strength, failure stretch ratio, and thickness of each treatment group. The fibroblasts treated with 5 ng/mL EGF produced the thickest matrix (270 μm). A thinner (130 μm) matrix, produced when the fibroblasts were treated with 0.5 ng/mL, had an ultimate tensile strength (895 kPa), greater than two times that of the other treatment groups. The fibroblasts treated with 0.5 ng/mL also had the highest collagen density (23.5 mg/cm3). Fibroblasts stimulated with the lowest (0.05 ng/mL) and highest (50 ng/mL) concentrations of EGF produced significantly weaker matrices and lower collagen densities. There was no significant correlation between UTS and collagen density suggesting that mechanisms other than density contribute to the strength of the matrix. Taken together, these data indicate that the optimal EGF concentration depends upon the relative importance of matrix strength and volume in a given application and that 0.5–5.0 ng/mL EGF promotes production of a robust extracellular matrix in only 3 weeks. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2010
Composite fibrous membranes of PLGA and chitosan prepared by coelectrospinning and coaxial electrospinning
Authors: Wu Lili , Li Hua , Li Shuo , Li Xiaoran , Yuan Xiaoyan , Li Xiulan , Zhang Yang 
Published: February 2009

AbstractMembranes made of hybrid poly(lactide‐co‐glycolide)/chitosan fibers (H‐PLGA/chitosan) and core/shell structured PLGA/chitosan fibers (C‐PLGA/chitosan) were produced by coelectrospinning and coaxial electrospinning, respectively. The morphology, mechanical properties, water uptakes of the electrospun fibrous membranes were characterized, and the cytocompatibility of human embryo skin fibroblasts (hESFs) was investigated in comparison with each other as well as with the electrospun PLGA and chitosan membranes. Results of transmission electron microscope and X‐ray photoelectron spectroscopy confirmed the core/shell structure of the C‐PLGA/chitosan fiber. Because of the introduction of chitosan, both H‐PLGA/chitosan and C‐PLGA/chitosan membranes showed significantly higher water uptakes than that of PLGA but there was no significant difference between those of C‐PLGA/chitosan and chitosan membranes. In dry state, the C‐PLGA/chitosan membranes exhibited extremely higher Young's moduli (178.7 ± 50.4 MPa) and strength (2.73 ± 0.30 MPa) than those of H‐PLGA/chitosan membranes (40.48 ± 4.07, 1.44 ± 0.12 MPa), respectively, but the values in wet state went down sharply because of the large amount (about 91%) of chitosan as the shell. Both H‐PLGA/chitosan and C‐PLGA/chitosan membranes showed better cytocompatibility than the PLGA membrane in adhesion, viability assays as well as morphology observation. The obtained composite H‐ or C‐PLGA/chitosan membranes would be potentially applied in wound dressings or skin tissue engineering. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res, 2010