bluuebunny/crossref_metadata_2025_split huggingface dataset:
B(C6F5)3‐Catalyzed Reduction of Ketones and Imines Using Silicon‐Stereogenic Silanes: Stereoinduction by Single‐Point Binding
Authors: Hog Daniel T. , Oestreich Martin 
Published: September 2009

AbstractWe recently employed a silicon‐stereogenic silane as astereochemical probe to clarify the mechanism of the B(C6F5)3‐catalyzed hydrosilylation of ketones. When using a prochiral ketone, reasonable stereoinduction was seen, originating from the stereogenicity at the silicon atom, a chirality transfer from silicon to carbon through single‐point binding of the chiral silane to the carbonyl oxygen atom. In the present investigation, we further elaborated on this remarkable observation by systematic variation of the ketone substitution pattern. We then included prochiral imines as well to test for diastereocontrol. Unexpectedly, these substance classes, ketones and imines, yielded diametrically opposed results in the reduction with a silicon‐stereogenic silane. While the level of diastereoselection was decent in the C=O reduction (dr ≈ 80:20), no asymmetric induction was detected in the C=NR reduction. On the basis of these experimental data and our previous mechanistic insight, we propose different reaction pathways for the reduction step of these related B(C6F5)3 catalyses. Aside from these mechanistic implications, we also report an unusual 1,6‐ rather than conventional 1,2‐reduction of a sterically encumbered diaryl‐substituted ketone.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Effects of heterogeneous electron‐transfer rate on the resolution of electrophoretic separations based on microfluidics with end‐column electrochemical detection
Authors: Wang Joseph , Tian Baomin , Chatrathi Madhu Prakash , Escarpa Alberto , Pumera Martin 
Published: September 2009

AbstractWe demonstrate here that the electrode kinetics of an electrochemical detector contributes greatly to the resolution of the analyte bands in microchip electrophoresis systems with amperometric detection. The separation performance in terms of resolution and theoretical plate number can be improved and tailored by selecting or modifying the working electrode and/or by controlling the detection potential. Such improvements in the separation performance reflect the influence of the heterogeneous electron‐transfer rate of electroactive analytes upon the post‐channel band broadening, as illustrated for catechol and hydrazine compounds. The electrode kinetics thus has a profound effect not only on the sensitivity of electrochemical detectors but on the separation efficiency and the overall performance of microchip electrochemistry systems.
Online purification and determination of β‐antagonists in blood sample based on heart‐cutting CE with electrochemical detection
Authors: Zhang Zhaoxiang , Zhang Mingzhe , Zhang Shusheng 
Published: September 2009

AbstractA novel method to detect β‐antagonists in rat blood was developed by combining heart‐cutting 2‐D CE in a single capillary with on‐column electrochemical (EC) detection. The blood sample was purified in first dimension by non‐micellar CZE separation. Then only a desirable fraction of the first dimension separation was transferred into the second dimension of the capillary by pressure. Finally, the purified sample was separated by MEKC. On‐line dual concentration method, field amplified sample stacking and sweeping, was employed to accumulate the purified components that effectively counteracted the sample zone diffusion during the mobilization pressure step. A field decoupler joint and an EC detection cell were employed for on‐column EC detection. After optimizing the analytical conditions, the RSD of peak height, peak area and migration time were 2.1–4.3%, 1.5–3.9% and 0.7–1.8% (n=10), respectively. This method has been successfully applied to determine β‐antagonists in postdosing rat blood sample. The pharmacokinetic study also demonstrated that the proposed heart‐cutting 2‐D CE with on‐column EC detection was convenient, sensitive and would become an attractively alternative method for on‐line sample cleanup and separation in complex samples.
Liquid–liquid ion transport junctions based on paired gold electrodes in generator–collector mode
Authors: French Robert W. , Chan Yohan , Bulman‐Page Philip C. , Marken Frank 
Published: September 2009

AbstractSimultaneous electrochemically driven double anion transfer across liquid–liquid interfaces is demonstrated at a gold–gold junction electrode. In the presence of two closely spaced electrodes (generator and collector), anion uptake into the organic phase (oxidation) and anion expulsion into the aqueous phase (reduction) can be combined to result in a generator–collector anion transport system across the liquid–liquid interface. In this report we are employing a paired gold junction grown by electro‐deposition to ca. 5 μm gap size with the N,N‐diethyl‐N′,N′‐didodecyl‐phenylene‐diamine water immiscible redox liquid immobilized into the gap to demonstrate simultaneous perchlorate anion uptake and expulsion. The effects of redox liquid volume and scan rate on the magnitude of currents and two mechanistic pathways for ion transport are discussed in the context of micro‐electrophoretic processes.
Assessment of ion transfer amperometry at liquid–liquid interfaces for detection in CE
Authors: Sisk Garry D. , Herzog Grégoire , Glennon Jeremy D. , Arrigan Damien W. M. 
Published: September 2009

AbstractIn this research, ion transfer across the interface between two immiscible electrolyte solutions (ITIES) was used as a method of detection in a CE separation system. This method allows for the electrochemical detection of ionic analytes that cannot be easily oxidized or reduced. Method development revealed that the optimal separation conditions for three model ions (tetraethylammonium, tetrabutylammonium, and benzensulfonate) were found to be 5 mM sodium tetraborate buffer pH 9.2 with a separation voltage of 20 kV using a 40 cm, 50 μm id fused silica capillary. Constant potential amperometry and pulsed amperometric detection were applied at the ITIES in which the organic phase was gelled. A miniaturized ITIES within a pipette tip was investigated, which resulted in improved separation efficiency and LOD. To demonstrate the ability of the system to detect substances of bioanalytical interest, the β‐adrenergic receptor blockers timolol and propranolol were detected. The simplicity of the detection platform means that it may be useful for analytical situations not requiring trace or ultratrace detection capabilities.
Structural analysis of spatio‐temporal threshold exceedances
Authors: Angulo J. M. , Madrid A. E. 
Published: September 2009

AbstractDue to both the complexity of real systems and the technical difficulties inherent to extremal analysis, the statistics of extremes in spatio‐temporal processes has become one of the most challenging research areas in relation to the increasingly demanding interest on risk assessment tools in many fields of application. Recent advances in spatio‐temporal statistical analysis are focused, in particular, on the formulation and study of new model families, flexible to represent such real complexities and, at the same time, suitable for technical treatment and interpretation, as well as on related system dynamics problems.In this paper, significant characteristics of threshold exceedances with reference to structural properties of the processes generating such events, particularly in the context of input/output systems, are analyzed. Specifically, the effect of spatial deformation and blurring transformations on the second order structure and the geometrical properties of excursion sets is studied and illustrated through some simulated cases. A spatio‐temporal model based on spatial deformation and blurring, which provides a suitable representation for a variety of environme‐ntal applications, is formulated, and further aspects regarding the temporal structure of threshold exceedances are explored and discussed. Copyright © 2009 John Wiley & Sons, Ltd.
Discrete‐time linear‐quadratic (LQ) optimal and nonlinear flow control in multi‐source connection‐oriented communication networks
Authors: Ignaciuk Przemysław , Bartoszewicz Andrzej 
Published: September 2009

AbstractIn this paper, control theoretic approach is applied to design a new, optimal flow controller for multi‐source connection‐oriented communication networks. The networks are modelled as discrete time, nth order systems. On the basis of the system state space description, a feedback control law is derived by minimising a quadratic cost functional. The proposed analytical solution to the optimisation problem allows the expression of control law in a closed form, which is simple in implementation and guarantees efficient rate computations. Afterwards, nonlinearity is introduced into the basic controller operation, which limits the transmission rates to the network transfer capabilities. The closed‐loop system stability of the obtained solution is demonstrated, and conditions for data loss elimination and full bandwidth usage at the node implementing the designed algorithm are presented, and strictly proved. Copyright © 2009 John Wiley & Sons, Ltd.
The phosphorylation of ephrin‐B2 ligand promotes glioma cell migration and invasion
Authors: Nakada Mitsutoshi , Anderson Eric M. , Demuth Tim , Nakada Satoko , Reavie Linsey B. , Drake Kelsey L. , Hoelzinger Dominique B. , Berens Michael E. 
Published: September 2009

AbstractTo reveal molecular drivers of glioma invasion, two distinct glioblastoma (GBM) cell phenotypes (invading cells and tumor core cells) were collected from 19 GBM specimens using laser capture microdissection. Isolated RNA underwent whole human genome expression profiling to identify differentially expressed genes. Pathway enrichment analysis highlighted the bidirectional receptor/ligand tyrosine kinase system, EphB/ephrin‐B, as the most tightly linked system to the invading cell phenotype. Clinical relevance of ephrin‐B genes was confirmed in a clinically annotated expression data set of 195 brain biopsy specimens. Levels of ephrin‐B1 and ‐B2 mRNA were significantly higher in GBM (n = 82) than in normal brain (n = 24). Kaplan–Meier analysis demonstrated ephrin‐B2, but not ephrin‐B1, expression levels were significantly associated with short term survival in malignant astrocytomas (n = 97, p = 0.016). In human brain tumor specimens, the production and phosphorylation of ephrin‐B2 were high in GBM. Immunohistochemistry demonstrated ephrin‐B2 localization primarily in GBM cells but not in normal brain. A highly invasive glioma cell line, U87, expressed high levels of ephrin‐B2 compared with relatively less invasive cell lines. Treatment with EphB2/Fc chimera further enhanced migration and invasion of U87 cells, whereas treatment with an ephrin‐B2 blocking antibody significantly slowed migration and invasion. Forced expression of ephrin‐B2 in the U251 cell line stimulated migration and invasion in vitro and ex vivo, concomitant with tyrosine phosphorylation of ephrin‐B2. These results demonstrate that high expression of ephrin‐B2 is a strong predictor of short‐term survival and that ephrin‐B2 plays a critical role in glioma invasion rendering this signaling pathway as a potential therapeutic target.
Risk of cancer among children of cancer patients—a nationwide study in Finland
Authors: Madanat‐Harjuoja Laura‐Maria S. , Malila Nea , Lähteenmäki Päivi , Pukkala Eero , Mulvihill John J. , Boice John D. , Sankila Risto 
Published: September 2009

AbstractCancer treatments have the potential to cause germline mutations that might increase the risk of cancer in the offspring of former cancer patients. This risk was evaluated in a population‐based study of early onset cancer patients in Finland. Using the nationwide registry data, 26,331 children of pediatric and early onset cancer patients (diagnosed under age 35 between 1953 and 2004) were compared to 58,155 children of siblings. Cancer occurrence among the children was determined by linkage with the cancer registry, and the standardized incidence ratios (SIRs) were calculated comparing the observed number of cancers with that expected, based on rates in the general population of Finland. Among the 9,877 children born after their parent's diagnosis, cancer risk was increased (SIR 1.67; 95% CI 1.29–2.12). However, after removing those with hereditary cancer syndromes, this increase disappeared (SIR 1.03; 95% CI 0.74–1.40). The overall risk of cancer among the offspring of siblings (SIR 1.07; 95% CI 0.94–1.21) was the same as among the offspring of the patients with nonhereditary cancer. Risk of cancer in offspring, born before their parents cancer diagnosis, was elevated (SIR 1.37, 95% CI 1.20‐1.54), but removing hereditary syndromes resulted in a diminished and nonsignificant association (SIR 1.08, 95% CI 0.93‐1.25). This study shows that offspring of cancer patients are not at an increased risk of cancer except when the patient has a cancer‐predisposing syndrome. These findings are directly relevant to counseling cancer survivors with regard to family planning.
The effect of a transaction tax on exchange rate volatility
Authors: Lanne Markku , Vesala Timo 
Published: September 2009

AbstractWe argue that a transaction tax is likely to amplify, not dampen, volatility in foreign exchange markets. Our argument stems from the decentralized trading practice and the presumable discrepancy between ‘informed’ and ‘uninformed’ traders' valuations. Given that the informed valuations are likely to be less dispersed, a transaction tax penalizes informed trades disproportionately, leading to increased volatility. Empirical support for this prediction is found by investigating the effect of transaction costs on the volatility of DEM/USD and JPY/USD returns. High‐frequency data are used and an increase in transaction costs is found to have a significant positive effect on volatility. Copyright © 2009 John Wiley & Sons, Ltd.
Young African American mothers' changing perceptions of their infants during the transition to parenthood
Authors: Lashley Cynthia O. , Hans Sydney L. , Henson Linda G. 
Published: September 2009

AbstractAlthough theory and empirical research with middle‐class, mostly White women have suggested that motherhood is an important developmental transition for women, rarely have investigations of adolescent motherhood systematically examined developmental change. This study examines one aspect of change during the transition to parenthood: the mother's emerging perception of her infant. During pregnancy and at 4 months' postpartum, 220 urban African American mothers between the ages of 13 and 21 years were asked to describe their infants. Content analysis of their responses and ratings of the affective tone of the responses suggest that there are changes from pregnancy to 4 months after the birth that parallel shifts noted in literature on women going through the transition to motherhood as adults. Between pregnancy and 4 months, there was a decreasing focus on infant health and physical appearance and an increasing focus on infant behavioral achievements and personality characteristics. Of particular importance to mothers was that their infants be “good” babies who were easy to care for and were easily accepted by the family. Mothers imagined physical similarities with their infants during pregnancy and describe aspects of their interaction and emotional bond with their infants at 4 months. Overall, mothers' descriptions of their babies were quite positive, increasingly positive over time, and offered little evidence that for these young African American women the transition to parenthood was problematic.
What are infants learning aboutrace? A look at a sample of infants from multipleracialgroups
Authors: Njoroge Wanjiku , Benton Tami , Lewis Marva L. , Njoroge Njoroge M. 
Published: September 2009

AbstractLittle empirical knowledge exists about the importance of culture and the sociopolitical context ofrace'sinfluence on the social development of infants and young children. In this article, we review current research on the transmission of race and culture to the developing child. Utilizing a historical theoretical framework proposed by Margaret Mahler and colleagues' (1975) theory of infant's development of a separate self, we will examine the potential influence ofracialcontext on children's development. Observational videotaped research methods will be used to describe several young children ages 6 months to 36 months from several racial/ethnic groups and their preferences for “same‐race” and “different‐race” dolls during structured play. How infants at different stages of social development notice differences associated with racial phenotype of toys during their play, how parents of these young children discuss issues of culture and race with their children, and the reasons underlying these discussions will be described for this sample. Finally, we discuss future research questions and areas of study suggested by the findings of this pilot study.
Application of quantitative structure–activity relationships for modeling drug and chemical transport across the human placenta barrier: a multivariate data analysis approach
Authors: Giaginis Costas , Zira Athina , Theocharis Stamatios , Tsantili‐Kakoulidou Anna 
Published: September 2009

AbstractPharmacological agents and environmental pollutants can transfer from mother to fetus across the placental barrier, leading to reproductive toxic effects.Ex vivohuman placental perfusion constitutes the most widely used method to study placental transfer and metabolism of drugs and chemicals. The aim of the present study was to evaluate whether quantitative structure–activity relationship (QSAR) methodology could serve as an effective alternative tool to estimate drugs and chemicals transport across the human placental barrier on the basis of easily interpretable molecular, physicochemical and structural properties. Multivariate data analysis (MVDA) was applied to a set of 88 structurally diverse drugs and chemicals to model placental transfer expressed by clearance index values compiled from literature sources. An adequate and robust QSAR model (r2= 0.73,Q2= 0.71, RMSEE = 0.15) was established, providing an informative illustration of the contributing physicochemical, molecular and structural properties of the compounds in placental transfer process. Descriptors reflecting the polarity of compounds proved to be the most important with a negative sign. Lipophilicity and, at a lower extent, molecular size parameters exerted positive contribution in the model. Thus, QSAR analysis may be considered as a promising alternative tool to support high‐throughput screening of drugs and chemicals in respect to their transport across placental barrier. Copyright © 2009 John Wiley & Sons, Ltd.
Fetal and offspring arrhythmia following exposure to nicotine during pregnancy
Authors: Feng Yu , Caiping Mao , Li Cao , Can Rui , Feichao Xu , Li Zhao , Zhice Xu 
Published: September 2009

AbstractAlthough recent studies have demonstrated prenatal nicotine can increase cardiovascular risk in the offspring, it is unknown whether exposure to nicotine during pregnancy also may be a risk for development of arrhythmia in the offspring. In addition, in previous studies of fetal arrhythmia affected by smoking, only two patterns, bradycardia and tachycardia, were observed. The present study examined acute effects of maternal nicotine on the fetal arrhythmiain utero, and chronic influence on offspring arrhythmia at adult stage following prenatal exposure to nicotine. Nicotine was administered to pregnant ewes and rats. In the fetal sheep, intravenous nicotine not only induced changes of fetal heart rate, but also caused cardiac cycle irregularity, single and multiple dropped cardiac cycles. Although maternal nicotine had no influence on fetal blood pH, lactic acid, hemocrit, Na+, K+levels and plasma osmolality, fetal blood PO2levels were significantly decreased following maternal nicotine in ewes. In offspring rats at 4–5 months after birth, prenatal exposure to nicotine significantly increased heart rate and premature ventricular contraction in restraint stress. In addition, arrhythmias induced by injection of nicotine were higher in the offspring prenatal exposure to nicotinein utero. The results provide new evidence that exposure to nicotine in pregnancy can cause fetal arrhythmia in various patterns besides tachycardia and bradycardia, the possible mechanisms for nicotine‐induced fetal arrhythmia includedin uterohypoxia. Importantly, following exposure to nicotine significantly increased risk of arrhythmia in the adult offspring. The finding offers new insight for development of cardiac rhythm problems in fetal origins. Copyright © 2009 John Wiley & Sons, Ltd.
Enrichment of omega3 fatty acids from Tyulka oil by supercritical CO2 extraction
Authors: Zakizadeh Nei Nei H. , Fatemi Sh. , Salimi A. R. , Vatanara A. , Rouholamini Najafabadi A. 
Published: September 2009

AbstractBACKGROUND: Supercritical CO2 enrichment of omega3 essential fatty acids (FAs) from Tyulka oil, using a batch process was investigated. Fractional factorial design was applied to evaluate the effects of the five process parameters: pressure (20.26 to 25.33 MPa); temperature (40 to 50 °C); packing fraction (0.5 to 0.7); modifier fraction (2 to 5%); and dynamic time (15 to 25 min), and their binary interactions on the enrichment of extracted omega3 FAs. By employing experimental design and analysis of variance, the variables were evaluated according to the significance of their effect on the yield of extracted omega3.RESULTS: The experimental results confirmed that pressure and dynamic time were the most important factors affecting enrichment of omega3. The amount of modifier in the feed also showed an increasing effect on the response. The binary interaction effects were investigated, and are discussed in detail.CONCLUSION: Optimum conditions were found at 25.33 MPa, 46.65 °C, packing fraction 0.50, modifier 5% and dynamic time 25 min, improving the enrichment of omega3 FAs up to 2.9 times. Copyright © 2009 Society of Chemical Industry
A facile method for the synthesis of thiocoumestan derivatives
Authors: Nematollahi Davood , Azizian Javad , Sargordan‐Arani Mohsen , Hesari Mahdi , Mirza Behrooz 
Published: September 2009

Abstract
magnified imageAn efficient synthesis of thiocoumestan derivatives, starting from catechols and 4‐mercaptocoumarin in the presence of potassium ferricyanide as an oxidizing agent (Decker oxidation) was developed. The results indicate that the 4‐mercaptocoumarin participates in Michael addition reactions with in situ generated o‐benzoquinones. The present work has led to the development of a one‐pot oxidative method for the synthesis of the 6H‐benzothieno[3,2‐c][1]benzopyron‐6‐one derivatives. J. Heterocyclic Chem., (2009).
One‐pot three‐component synthesis of dihydrobenzo‐ and naphtho[e]‐1,3‐oxazines in water
Authors: Mathew Bijoy P. , Nath Mahendra 
Published: September 2009

Abstract
magnified imageA simple, green and efficient method has been developed for the synthesis of biologically and materially important dihydrobenzo/naphtho[e]‐1,3‐oxazines in good to excellent yields through a Mannich‐type condensation cyclization reaction of aromatic alcohols with HCHO and primary amines in aqueous media at ambient temperature. J. Heterocyclic Chem., (2009).
New access to the one‐pot solvent‐free synthesis of 4,5‐dihydro‐pyrido[2,3‐b][1,4]diazepines and 2,3‐dihydro‐benzo[b][1,4]diazepines by microwave irradiation
Authors: Goswami Shyamaprosad , Hazra Anita , Jana Subrata 
Published: September 2009

Abstract
magnified imageA series of diversely substituted pyridodiazepines and benzodiazepines have been synthesized in solvent and catalyst free microwave condition from aryl/heteroaryl diamines and β‐aryl vinyl ketones. The yields of the reactions varied with the substituents attached to the aryl/heteroaryl diamines. This common protocol is equally effective for the synthesis of pyridodiazepines and benzodiazepines with pharmacological interest, though in case of pyridodiazepines required time is comparatively higher than benzodiazepines. J. Heterocyclic Chem., (2009).