bluuebunny/crossref_metadata_2025_split huggingface dataset:
Abnormal brain tryptophan metabolism and clinical correlates in Tourette syndrome
Authors: Behen Michael , Chugani Harry T. , Juhász Csaba , Helder Emily , Ho Albert , Maqbool Mohsin , Rothermel Robert D. , Perry Jacquie , Muzik Otto 
Published: August 2007

AbstractSymptoms in Tourette syndrome (TS) are likely related to abnormalities involving multiple neurotransmitter systems in striatal‐thalamo‐cortical circuitry. Although prior studies have found abnormal levels of tryptophan, serotonin, and their metabolites in blood, cerebrospinal fluid and brain tissue of TS patients, understanding of focal brain disturbances and their relationship to clinical phenotype remains poor. We used α‐[11C]methyl‐L‐tryptophan (AMT) positron emission tomography (PET) to assess global and focal brain abnormalities of tryptophan metabolism and their relationship to behavioral phenotype in 26 children with TS and nine controls. Group comparisons on regional cortical and subcortical AMT uptake revealed decreased AMT uptake in bilateral dorsolateral prefrontal cortical and bilaterally increased uptake in the thalamus (P = 0.001) in TS children. The ratio of AMT uptake in subcortical structures to dorsolateral prefrontal cortex was significantly increased bilaterally (P < 0.01) in TS patients also. Behaviorally defined subgroups within the TS sample revealed differences in the pattern of AMT uptake in the fronto‐striatal‐thalamic circuit. This study demonstrates cortical and subcortical abnormalities of tryptophan metabolism in TS and provides neuroimaging evidence for a role of serotonergic mechanisms in the pathophysiology of TS. © 2007 Movement Disorder Society
A hybrid‐cell EBG power plane for ultra‐wideband suppression of ground bounce noise
Authors: Kim D.‐Y. , Joo S.‐H. , Lee H.‐Y. 
Published: August 2007

AbstractA new power/ground plane using the hybrid‐cell electromagnetic bandgap (EBG) structure is proposed for ultra‐wideband suppression of the ground bounce noise (GBN) in high‐speed digital circuit boards. The hybrid‐cell EBG structure achieves both a high series inductance and a shorter period of the EBG lattice. The −30 dB stop‐band of the proposed structure has about a 7.9‐GHz bandwidth and starts at 370 MHz where the GBN energy is dominantly distributed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2853–2855, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22831
A novel investigation on size reduction of a frequency selective surface
Authors: Pain M. K. , Bhunia S. , Biswas S. , Sarkar D. , Sarkar P. P. 
Published: August 2007

AbstractThe study presents theoretical and experimental investigation of a novel, reduced size Microstrip Frequency Selective Surface. The novel design is achieved by cutting some rectangular slots at four sides of a square patch. Compared with conventional square patch Frequency Selective Surface (FSS), this slotted square patch Microstrip FSS can achieve reduction in patch area of 36%. The structure acts like a band pass filter with a resonant frequency 8 GHz. Both theoretical and experimental investigations are done. Theoretical investigation is done by IE3D software. Experimental investigation is performed using standard microwave test bench. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2820–2821, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22833
A 2‐GHz fully‐differential CMOS power amplifier with virtual grounds to suppress ground bounce
Authors: Yan Tao , Liao Huailin , Li Chen , Huang Ru 
Published: August 2007

AbstractThis article presents a 2‐GHz fully‐differential CMOS power amplifier (PA) fabricated in a standard 0.35‐μm RF CMOS process. Virtual grounds are introduced at both drive‐stage and output‐stage transistors' sources of the two‐stage differential PA, which guarantees a stable reference ground and thus improves the PA performance. A performance of 15‐dB gain, 26.6 dBm Pout, and 26% PAE is achieved. At 15 dBm Pout, the ACPR1 and ACPR2 are −35.3 and −66.3 dBc, respectively. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2780–2784, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22849
Polymerizability, copolymerizability, and properties of cyanoacrylate‐telechelic polyisobutylenes II: copolymerization of three‐arm star cyanoacrylate‐ telechelic polyisobutylene with ethyl cyanoacrylate
Authors: Kwon Yongmoon , Kennedy Joseph P. 
Published: August 2007

AbstractThis research concerned the synthesis and characterization of novel conetworks containing polyisobutylene (PIB) and polyethyl‐2‐cyanoacrylate [poly(Et‐CA)] sequences. The syntheses involved the copolymerization of CA‐telechelic three‐arm star PIB [Ø(PIB‐CA)3] with ethyl‐2‐cyanoacrylate (Et‐CA) mediated by nucleophiles or by living tissue (fresh eggs). The conetworks were characterized by swelling in hexanes, tetrahydrofuran (THF), and acetone, and the results indicate co‐continuous PIB and poly(Et‐CA) domains. The conetworks exhibit two Tgs indicating phase‐separation between PIB and poly(Et‐CA). The outstanding oxidative resistance of the conetworks was demonstrated by exposure to concentrated nitric acid. The tensile strengths, moduli, and elongations of a series of conetworks with different overall compositions were investigated and the findings interpreted in terms of covalently linked rubbery and glassy domains. AFM also suggests the presence of phase‐separated rubbery and glassy domains. DMTA spectra of a Ø(PIB‐CA)3 homonetwork, and Ø(PIB‐CA)3/Et‐CA conetworks were analyzed and interpreted in terms of coexisting rubbery and glassy domains. Observations made during the exposure of Ø(PIB‐CA)3/Et‐CA mixtures to proteinaceous tissue, in combination with characterization data, were used to propose a structural model for the conetworks. Copyright © 2007 John Wiley & Sons, Ltd.
Degradation behaviors of monomethoxy poly(ethylene glycol)‐b‐poly(ε‐caprolactone) nanoparticles in aqueous solution
Authors: Shen Chunhua , Guo Shengrong , Lu Chengfei 
Published: August 2007

AbstractMonomethoxy poly(ethylene glycol)‐b‐poly(ε‐caprolactone)(MPEG‐b‐PCL) diblock copolymers were synthesized via a ring‐opening polymerization. The polymeric nanoparticles prepared by precipitation/solvent evaporation exhibit a core–shell structure, characterized by dynamic light scattering (DLS), nuclear magnetic resonance (NMR), and atomic force microscopy (AFM). The hydrolytic degradation of those nanoparticles was studied by DLS, NMR, and gel permeation chromatography (GPC). It was found that the molecular weight of PCL block in a copolymer significantly affects the stability of nanoparticles in aqueous solution and nanoparticles with shorter PCL block length degraded faster. The degradation behaviors could be divided into two stages with slow degradation at the interface region via swelling effect and fast degradation at inner core via caves and channels formed by cleavage of ester bonds. Copyright © 2007 John Wiley & Sons, Ltd.
Cationic poly(methacryl oxyethyl trimethylammonium) and its poly(ethylene glycol)‐grafted analogue as capillary coating materials in electrophoresis
Authors: Wiedmer Susanne K. , Andersson Toni , Sündermann Marika , Riekkola Marja‐Liisa , Tenhu Heikki 
Published: August 2007

AbstractCationic polyelectrolytes were synthesized and used as semipermanent coating materials for capillaries in electrophoresis. The polyelectrolytes used were a homopolymer of poly(methacryl oxyethyl trimethylammonium chloride) (PMOTAC) and its poly(ethylene glycol) (PEG)‐grafted analogue. Two PMOTAC polyelectrolytes, with molar masses of 85,000 and 300,000 g/mol, and PEG‐grafted PMOTAC with a molar mass of 280,000 g/mol were synthesized and then characterized by size exclusion chromatography (SEC) and nuclear magnetic resonance (NMR) spectroscopy. Attachment of the polyelectrolytes to the wall of the fused silica capillary for electrophoresis caused the electroosmotic flow (EOF) to reverse. The polyelectrolyte coatings were tested over the pH range 2–11 at different buffer ionic strengths, and the most stable and strongest anodic EOFs were obtained at acidic pH values with low ionic strength buffers. Between runs the capillary is merely rinsed for 2 or 3 min with the background electrolyte solution. With the PMOTAC coatings at pH values ≤5, the RSDs of the EOFs were less than 2.9% after 60 injections. The effects of the molar mass of the polycation and of PEGylation of PMOTAC on the interactions between the polycations and basic proteins were studied at acidic pH values. The differences in the effective electrophoretic mobilities, resolution values, and plate numbers of the proteins with the different coatings were due to the EOF, as demonstrated through calculations of reduced mobilities, relative resolution values, and relative plate numbers. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2655–2663, 2007
Attract‐and‐kill strategy. Laboratory studies on hatched larvae of Culex pipiens
Authors: Michaelakis Antonios , Mihou Anastasia P , Koliopoulos George , Couladouros Elias A 
Published: August 2007

AbstractThe attract‐and‐kill strategy is a new pest management technique that presupposes the intelligent combination of an attracting agent (e.g. pheromone) and a killing agent (e.g. insecticide). In the present study, the potential combination of the microencapsulated synthetic oviposition pheromone 6‐acetoxy‐5‐hexadecanolide with an insecticide has been tested. Initially, polyurea microcapsules containing 6‐acetoxy‐5‐hexadecanolide, the synthetic mixture of diastereomers of the oviposition pheromone of the mosquito species Culex quinquefasciatus Say (Diptera: Culicidae), were studied. Laboratory bioassays were performed to confirm the bioactivity of the microencapsulated pheromone on the oviposition activity of Culex pipiens L. biotype molestus Førskal (Diptera: Culicidae) with the aim of determining the optimum dose for oviposition response. Its effect was dose dependent, revealing an optimum dose of 300 mg of dried microcapsules. Attractancy over time was also studied. The microencapsulated pheromone was found to be sufficiently attractive to gravid female mosquitoes for a period of 40 days. Finally, the combination of the synthetic pheromone with the control agent temephos showed both an acceptable oviposition activity and sufficient larvicidal effect. Copyright © 2007 Society of Chemical Industry
Development of a qualitative liquid chromatography/tandem mass spectrometric method for the detection of narcotics in urine relevant to doping analysis
Authors: Deventer Koen , Pozo Oscar J. , Van Eenoo Peter , Delbeke Frans T. 
Published: August 2007

AbstractA new screening procedure for 18 narcotics in urine for anti‐doping purposes has been developed using liquid chromatography/triple quadrupole mass spectrometry (LC/MS). Electrospray ionization (ESI) was used as interface. Infusion experiments were performed for all substances to investigate their mass spectrometric behaviour in terms of selecting product specific ions. These product ions were then used to develop a tandem mass spectrometric method using selected reaction monitoring (SRM). For the LC/MS analysis, chromatography was performed on an octadecylsilane column. The total run time of the chromatographic method was 5.5 min. For the sample preparation prior to LC/MS analysis, the urine samples were liquid‐liquid extracted at pH 9.5 after overnight enzymatic hydrolysis. Two extraction solvents were evaluated: dichloromethane/methanol 9/1 (v/v), which is currently used for the extraction of narcotics, and diethyl ether, used for the extraction of steroids. With diethyl ether the detection limits for all compounds ranged between 0.5 and 20 ng/mL and with the mixture containing dichloromethane the detection limits ranged between 0.5 and 10 ng/mL. Taking into account the minimum required performance limits of the World Anti‐Doping Agency of 200 ng/mL for narcotics, diethyl ether can also be considered as extraction solvent for narcotics. Finally, the described method was applied to the analysis of urine samples previously found to contain narcotics by our routine gas chromatography/mass spectrometry (GC/MS) method. Copyright © 2007 John Wiley & Sons, Ltd.
Development of novel guanidino‐labelling derivatisation (GLaD) reagents for liquid chromatography/matrix‐assisted laser desorption/ionisation analysis
Authors: Brancia Francesco L. , Bereszczak Jessica Z. , Piatkowska Elzbieta , Delneri Daniela 
Published: August 2007

AbstractA new generation of guanidino‐labelling (GLaD) reagents were developed for quantitative proteomics using offline microcapillary liquid chromatography (LC) matrix‐assisted laser desorption/ionisation mass spectrometry (MALDI‐MS). In order to reduce the unwanted overlapping between the isotopic envelopes of the two differentially labelled peptide ions, a novel synthetic route was described for production of both 13C‐ and 15N‐containing isotopomers of N,O‐dimethylisourea. The use of these types of isotopes has no deleterious effect on the retention times of both differentially labelled peptides during offline microbore reversed‐phase LC. In addition, the possibility to incorporate a mass difference of 4 Da can be exploited during post‐source decay analysis to generate product ion spectra in which fragment ions containing the modifications appear as doublets in the corresponding product ion spectra, thus facilitating identification of the C‐terminal fragment ions. Copyright © 2007 John Wiley & Sons, Ltd.
Peptide Fragment Ion Analyser (PFIA): a simple and versatile tool for the interpretation of tandem mass spectrometric data and de novo sequencing of peptides
Authors: Jagannath Swaminathan , Sabareesh Varatharajan 
Published: August 2007

AbstractThe software Peptide Fragment Ion Analyser (PFIA) aids in the analysis and interpretation of tandem mass spectrometric data of peptides. The software package has been designed to facilitate the analysis of product ions derived from acyclic and cyclic peptide natural products that possess unusual amino acid residues and are heavily post‐translationally modified. The software consists of two programmes: (a) PFIA‐I lists the amino acid compositions and their corresponding product ion types for ‘a queried m/z value’ (z = +1) and (b) PFIA‐II displays fragmentation pattern diagram(s) and lists all sequence‐specific product ion types for the protonated adduct of ‘a queried sequence’. The unique feature of PFIA‐II is its ability to handle cyclic peptides. The two programmes used in combination can prove helpful for deriving peak assignments in the de novo sequencing of novel peptides. Copyright © 2007 John Wiley & Sons, Ltd.
Diffusivity fractionations of HO/HO and HO/HO in air and their implications for isotope hydrology
Authors: Barkan Eugeni , Luz Boaz 
Published: August 2007

AbstractWe have determined the isotope effects of 17O and 18O substitution of 16O in H2O on molecular diffusivities of water vapor in air by the use of evaporation experiments. The derived diffusion fractionation coefficients 17αdiff and 18αdiff are 1.0146 ± 0.0002 and 1.0283 ± 0.0003, respectively. We also determined, for the first time, the ratio ln(17αdiff)/ln(18αdiff) as 0.5185 ± 0.0002. This ratio, which is in excellent agreement with the theoretical value of 0.5184, is significantly smaller than the ratio in vapor‐liquid equilibrium (0.529). We show how this new experimental information gives rise to 17O excess in meteoric water, and how it can be applied in isotope hydrology. Copyright © 2007 John Wiley & Sons, Ltd.
Identification of β‐sitosterol, stigmasterol and ergosterin in A. roxburghii using supercritical fluid extraction followed by liquid chromatography/atmospheric pressure chemical ionization ion trap mass spectrometry
Authors: Huang Liying , Zhong Tianhua , Chen Tianwen , Ye Zhao , Chen Guonan 
Published: August 2007

Abstractβ‐Sitosterol and stigmasterol are the most common phytosterols in traditional Chinese medicine. They have been proved to have many important bioactivities. To the best of our knowledge, this is the first report that β‐sitosterol, stigmasterol and ergosterol coexisting in A. roxburghii herbs can be simultaneously extracted by a supercritical fluid extraction (SFE) procedure; then a simple high‐performance liquid chromatography/atmospheric pressure chemical ionization ion trap mass spectrometry (HPLC/APCI/MS) method was developed for simultaneous identification and determination of these three compounds. The ion trap MS/MS detector was equipped with an atmospheric pressure chemical ionization source operating in the positive ion mode, APCI(+). The linear responses were obtained in the concentration range of 0.50–150 µg/mL (r = 0.9999) for ergosterol, 5–400 µg/mL (r = 0.9999) for stigmasterol, and 10–2000 µg/mL (r = 0.9998) for β‐sitosterol. An orthogonal L9 (33) test design was employed for optimization of the SFE process. Under the optimized conditions, i.e. pressure of 25 mPa, temperature of 45°C and ethanol as modifier, the concentrations of sterols in the extract were found to be 2.89% (g/g) for β‐sitosterol, 3.56% (g/g) for stigmasterol and 2.96% (g/g) for ergosterin. The SFE method was also compared with a previously developed Soxhlet extraction. The SFE method produced higher yields of sterols than that of the Soxhlet extraction. The proposed method has been successfully used for identification and quantitation of β‐sitosterol, stigmasterol and ergosterin in a real A. roxburghii sample. Copyright © 2007 John Wiley & Sons, Ltd.
Testing logistic regression coefficients with clustered data and few positive outcomes
Authors: Hunsberger Sally , Graubard Barry I. , Korn Edward L. 
Published: August 2007

AbstractApplications frequently involve logistic regression analysis with clustered data where there are few positive outcomes in some of the independent variable categories. For example, an application is given here that analyzes the association of asthma with various demographic variables and risk factors using data from the third National Health and Nutrition Examination Survey, a weighted multi stage cluster sample. Although there are 742 asthma cases in all (out of 18 395 individuals), for one of the categories of one of the independent variables there are only 25 asthma cases (out of 695 individuals). Generalized Wald and score hypothesis tests, which use appropriate cluster‐level variance estimators, and a bootstrap hypothesis test have been proposed for testing logistic regression coefficients with cluster samples. When there are few positive outcomes, simulations presented in this paper show that these tests can sometimes have either inflated or very conservative levels. A simulation‐based method is proposed for testing logistic regression coefficients with cluster samples when there are few positive outcomes. This testing methodology is shown to compare favorably with the generalized Wald and score tests and the bootstrap hypothesis test in terms of maintaining nominal levels. The proposed method is also useful when testing goodness‐of‐fit of logistic regression models using deciles‐of‐risk tables. Published in 2007 by John Wiley & Sons, Ltd.
The cost of checking proportional hazards
Authors: Shepherd Bryan E. 
Published: August 2007

AbstractConfidence intervals (CIs) and the reported predictive ability of statistical models may be misleading if one ignores uncertainty in the model selection procedure. When analyzing time‐to‐event data using Cox regression, one typically checks the proportional hazards (PH) assumption and subsequently alters the model to address any violations. Such an examination and correction constitute a model selection procedure, and, if not accounted for, could result in misleading CI. With the bootstrap, I study the impact of checking the PH assumption using (1) data to predict AIDS‐free survival among HIV‐infected patients initiating antiretroviral therapy and (2) simulated data. In the HIV study, due to non‐PH, a Cox model was stratified on age quintiles. Interestingly, bootstrap CIs that ignored the PH check (always stratified on age quintiles) were wider than those which accounted for the PH check (on each bootstrap replication PH was tested and corrected through stratification only if violated). Simulations demonstrated that such a phenomenon is not an anomaly, although on average CIs widen when accounting for the PH check. In most simulation scenarios, coverage probabilities adjusting and not adjusting for the PH check were similar. However, when data were generated under a minor PH violation, the 95 per cent bootstrap CI ignoring the PH check had a coverage of 0.77 as opposed to 0.95 for CI accounting for the PH check. The impact of checking the PH assumption is greatest when thep‐value of the test for PH is close to the test's chosen Type I error probability. Copyright © 2007 John Wiley & Sons, Ltd.
A Bayesian hierarchical modeling approach for studying the factors affecting the stage at diagnosis of prostate cancer
Authors: Zhou Huafeng , Lawson Andrew B. , Hebert James R. , Slate Elizabeth H. , Hill Elizabeth G. 
Published: August 2007

AbstractWe extend the baseline‐category logits model for categorical response data to accommodate two distinct kinds of clustering. Our extension introduces random effects that have one component exhibiting spatial dependence and a second component that is distributed independently. We use this enhanced categorical logits model for investigating the factors that affect the geographical distribution of the diagnostic stage of prostate cancer (PrCA) in South Carolina (SC). Using incidence data from the SC registry, we fit three types of models: the baseline‐category logits model, the proportional odds model, and the adjacent‐categories logits model, each incorporating our two‐component random effects. The deviance information criterion (DIC) is used for selecting the best‐fitting model. The results from the best model are presented and interpreted. The county‐specific random effects are mapped to characterize the spatial distribution pattern of diagnostic stage of PrCA in the study region. In terms of spatial distribution of the diagnostic stage of PrCA, an area of excess (unexplained) risk was found in the north‐west area, and an area of low excess risk in the north‐east area for regional‐stage cancer in SC was identified through the analysis of the cancer registry data. Copyright © 2007 John Wiley & Sons, Ltd.
Estimation and prediction in linear mixed models with skew‐normal random effects for longitudinal data
Authors: Lin Tsung I. , Lee Jack C. 
Published: August 2007

AbstractThis paper extends the classical linear mixed model by considering a multivariate skew‐normal assumption for the distribution of random effects. We present an efficient hybrid ECME‐NR algorithm for the computation of maximum‐likelihood estimates of parameters. A score test statistic for testing the existence of skewness preference among random effects is developed. The technique for the prediction of future responses under this model is also investigated. The methodology is illustrated through an application to Framingham cholesterol data and a simulation study. Copyright © 2007 John Wiley & Sons, Ltd.