bluuebunny/crossref_metadata_2025 huggingface dataset:
Evidence of mutual benefits of nest association among freshwater cyprinids and implications for conservation
Authors: Peoples Brandon K. , Frimpong Emmanuel A.
Published: May 2013

Although nest association among Nocomis chubs and other minnows (Cyprinidae) is common throughout North America, the overall outcome of this relationship and its mechanisms of costs and benefits remain unclear. Because imperilment of stream fishes is affected by reproductive traits, the implications of this widespread interaction must be understood.

Nest association mechanisms were explored using a multiple working hypotheses framework on fish assemblage data from 25 reaches in three tributaries of the New River, Virginia, USA. Multiple linear regression models predicting reproductive success (age‐0 abundance) of chubs and associates were compared based on model weights (wi) calculated from Akaike's Information Criterion, adjusted for small sample size (AICc), and relative change in AICc among models. For age‐0 chubs, models represented hypotheses emphasizing the additive effects of adult abundance, nest abundance, and egg dilution by juvenile associates (causing decreased egg predation). For age‐0 associates, models represented hypotheses emphasizing adult associate abundance, gravel substrate availability, nest abundance, parental care (as nest defence) from chubs, and egg dilution by chubs.

Model evidence suggests that chubs can sustain themselves (w = 0.61), but their reproductive success is enhanced by a dilution effect from juvenile strong associates (w = 0.37). Strong associate reproductive success was best described by variables emphasizing nest association interactions (w = 0.46) and natural sources of habitat variability (w = 0.45), whereas that of weak associates was more closely related to availability of unmodified habitat (w = 0.50).

Chubs and associates appear to receive a net benefit from the association, suggesting a mutualistic relationship. Community‐wide conservation strategies may be useful for protecting symbiotic spawning fishes. In addition to competition and predation, conservation practitioners should consider positive interactions in conservation plans of imperiled mutualists.

Copyright © 2013 John Wiley & Sons, Ltd.
Answering academic questions for education by recommending cyberlearning resources
Authors: Liu Xiaozhong , Jia Han
Published: May 2013

In this study, we design an innovative method for answering students' or scholars' academic questions (for a specific scientific publication) by automatically recommending e‐learning resources in a cyber‐infrastructure‐enabled learning environment to enhance the learning experiences of students and scholars. By using information retrieval and metasearch methodologies, different types of referential metadata (related Wikipedia pages, data sets, source code, video lectures, presentation slides, and online tutorials) for an assortment of publications and scientific topics will be automatically retrieved, associated, and ranked (via the language model and the inference network model) to provide easily understandable cyberlearning resources to answer students' questions. We also designed an experimental system to automatically answer students' questions for a specific academic publication and then evaluated the quality of the answers (the recommended resources) using mean reciprocal rank and normalized discounted cumulative gain. After examining preliminary evaluation results and student feedback, we found that cyberlearning resources can provide high‐quality and straightforward answers for students' and scholars' questions concerning the content of academic publications.
Revisiting ontologies: A necessary clarification
Authors: Almeida Mauricio Barcellos
Published: May 2013

Looking for ontology in a search engine, one can find so many different approaches that it can be difficult to understand which field of research the subject belongs to and how it can be useful. The term ontology is employed within philosophy, computer science, and information science with different meanings. To take advantage of what ontology theories have to offer, one should understand what they address and where they come from. In information science, except for a few papers, there is no initiative toward clarifying what ontology really is and the connections that it fosters among different research fields. This article provides such a clarification. We begin by revisiting the meaning of the term in its original field, philosophy, to reach its current use in other research fields. We advocate that ontology is a genuine and relevant subject of research in information science. Finally, we conclude by offering our view of the opportunities for interdisciplinary research.
Human umbilical cord–derived mesenchymal stem cells can secrete insulin in vitro and in vivo
Authors: Niki Boroujeni Zahra , Aleyasin Ahmad
Published: May 2013

Diabetes mellitus is characterized by autoimmune destruction of pancreatic beta cells, leading to decreased insulin production. Differentiation of mesenchymal stem cells (MSCs) into insulin‐producing cells offers novel ways of diabetes treatment. MSCs can be isolated from the human umbilical cord tissue and differentiate into insulin‐secreting cells. Human umbilical cord–derived stem cells (hUDSCs) were obtained after birth, selected by plastic adhesion, and characterized by flow cytometric analysis. hUDSCs were transduced with nonintegrated lentivirus harboring PDX1 (nonintegrated LV‐PDX1) and was cultured in differentiation medium in 21 days. Pancreatic duodenum homeobox protein‐1 (PDX1) is a transcription factor in pancreatic development. Significant expressions of PDX1, neurogenin3 (Ngn3), glucagon, glucose transporter2 (Glut2), and somatostatin were detected by quantitative RT‐PCR (P < 0.05). PDX1 and insulin proteins were shown by immunocytochemistry analysis. Insulin secretion of hUDSCsPDX1+ in the high‐glucose medium was 1.8 μU/mL. They were used for treatment of diabetic rats and could decrease the blood glucose level from 400 mg/dL to a normal level in 4 days. In conclusion, our results demonstrated that hUDSCs are able to differentiate into insulin‐producing cells by transduction with nonintegrated LV‐PDX1. These hUDSCsPDX1+ have the potential to be used as a viable resource in cell‐based gene therapy of type 1 diabetes.
Hydrogen‐producing Escherichia coli strains overexpressing lactose permease: FT‐IR analysis of the lactose‐induced stress
Authors: Grube Mara , Dimanta Ilze , Gavare Marita , Strazdina Inese , Liepins Janis , Juhna Talis , Kalnenieks Uldis
Published: May 2013

The lactose permease gene (lacY) was overexpressed in the septuple knockout mutant of Escherichia coli, previously engineered for hydrogen production from glucose. It was expected that raising the lactose transporter activity would elevate the intracellular lactose concentration, inactivate the lactose repressor, induce the lactose operon, and as a result stimulate overall lactose consumption and conversion. However, overexpression of the lactose transporter caused a considerable growth delay in the recombinant strain on lactose, resembling to some extent the “lactose killing” phenomenon. Therefore, the recombinant strain was subjected to selection on lactose‐containing media. Selection on plates with 3% lactose yielded a strain with a decreased content of the recombinant plasmid but with an improved ability to grow and produce hydrogen on lactose. Macromolecular analysis of its biomass by means of Fourier transform‐infrared spectroscopy demonstrated that increase of the cellular polysaccharide content might contribute to the adaptation of E. coli to lactose stress.
Hedonic Evaluation over Short and Long Retention Intervals: The Mechanism of the Peak–End Rule
Authors: Geng Xiaowei , Chen Ziguang , Lam Wing , Zheng Quanquan
Published: May 2013

The peak–end rule is used to explain how people make retrospective hedonic evaluations. This study advances our understanding of its mechanism by identifying the different effects of the rule on such evaluations over short and long retention intervals. The results of two experiments show that (i) respondents constructed their retrospective hedonic evaluations on the basis of the peak and end affects only over a short retention interval, not over a long one; and (ii) respondents relied on episodic information to construct their evaluations over a short retention interval, whereas they relied on both semantic and episodic information to construct their evaluations over a long retention interval. Our study also suggests that the “watershed” between short and long retention intervals is likely to lie between 3 and 7 weeks. Copyright © 2012 John Wiley & Sons, Ltd.
Social supergenes of superorganisms: Do supergenes play important roles in social evolution?
Authors: Linksvayer Timothy A. , Busch Jeremiah W. , Smith Chris R.
Published: May 2013

We suggest that supergenes, groups of co‐inherited loci, may be involved in a range of intriguing genetic and evolutionary phenomena in insect societies, and may play broad roles in the evolution of cooperation and conflict. Supergenes are central in the evolution of an array of traits including self‐incompatibility, mimicry, and sex chromosomes. Recently, researchers identified a large supergene, described as a social chromosome, which controls social organization in the fire ant. This system was previously considered to be a remarkable example of a single gene affecting a complex social trait. We describe how selection may commonly favor reduced recombination and the formation of supergenes for social traits, and once formed, supergenes may strongly influence further evolutionary dynamics within and between lineages. The evolution of supergenes, and even wholly non‐recombining genomes, may be particularly common in systems in which genetically distinct lineages can form mutually reinforcing socially parasitic relationships.
Flow‐injection chemiluminescence determination of olanzapine using N‐chlorosuccinimide–calcein reaction sensitized by zinc (II)
Authors: Zhao Fang , Fan Qi , Cai Huan
Published: May 2013

A novel, rapid and sensitive chemiluminescence (CL) method combined with flow‐injection (FI) has been established for the estimation of olanzapine. This method is based on the CL signal generated between N‐chlorosuccinimide and olanzapine in an alkaline medium in the presence of calcein and Zn(II). Under optimum conditions, the CL signal was proportional to the olanzapine concentration ranging from 1.0 × 10‐10 to 3.0 × 10‐7 g/mL. The detection limit is 8.9 × 10‐11 g/mL olanzapine (3σ) and the relative standard deviation for 3.0 × 10‐9 g/mL of olanzapine is 1.9% (n = 11). The current CL method was applied to determine olanzapine in pharmaceutical formulations and biological fluids with satisfactory results. The possible CL reaction mechanism is discussed briefly. Copyright © 2013 John Wiley & Sons, Ltd.
Frameshifting dynamics
Authors: Tinoco Ignacio , Kim Hee‐Kyung , Yan Shannon
Published: May 2013

Translation of messenger RNA by a ribosome occurs three nucleotides at a time from start signal to stop. However, a frameshift means that some nucleotides are read twice or some are skipped, and the following sequence of amino acids is completely different from the sequence in the original frame. In some messenger RNAs, including viral RNAs, frameshifting is programmed with RNA signals to produce specific ratios of proteins vital to the replication of the organism. The mechanisms that cause frameshifting have been studied for many years, but there are no definitive conclusions. We review ribosome structure and dynamics in relation to frameshifting dynamics provided by classical ensemble studies, and by new single‐molecule methods using optical tweezers and FRET. 2013 Wiley Periodicals, Inc. Biopolymers 99: 1147–1166, 2013.
Structural identification of the metabolites of ganoderic acid B from Ganoderma lucidum in rats based on liquid chromatography coupled with electrospray ionization hybrid ion trap and time‐of‐flight mass spectrometry
Authors: Guo Xiaoyu , Shen Xuan , Long Jie , Han Jian , Che Qingming
Published: May 2013

Ganoderic acid B (GAB), a representative triterpenoid in Ganoderma lucidum, possesses various pharmaceutical effects and has been used as a chemical marker in quality control of G. lucidum and related products. The metabolites of GAB in vivo after its oral administration to rats were investigated by liquid chromatography coupled with electrospray ionization hybrid ion trap and time‐of‐flight mass spectrometry. A total of 14 metabolites of GAB in rat plasma, bile and various organs were detected and identified by direct comparison with the authentic compounds and their characteristic mass fragmentation patterns. The results showed that oxidization and hydroxylation were the common metabolic pathways for GAB in rats. Moreover, some reduction metabolites of GAB were detected in rat kidney and stomach and glucuronidation only appeared in rat bile. This is the first report on the metabolites of GAB in vivo. Copyright © 2013 John Wiley & Sons, Ltd.
LC‐MS/MS determination of bakkenolide D in rats plasma and its application in pharmacokinetic studies
Authors: Dai Dongmei , Pei Lixia , Tang Lin , Chen Feng , Chen Xiuping
Published: May 2013

A sensitive and rapid liquid chromatography–tandem mass spectrometry (LC‐MS/MS) method was developed and validated for determination of bakkenolide D (BD), which was further applied to assess the pharmacokinetics of BD. In the LC‐MS/MS method, the multiple reaction monitoring mode was used and columbianadin was chosen as internal standard. The method was validated over the range of 1–800 ng/mL with a determination coefficient >0.999. The lower limit of quantification was 1 ng/mL in plasma. The intra‐ and inter‐day accuracies for BD were 91–113 and 100–104%, respectively, and the inter‐day precision was <15%. After a single oral dose of 10 mg/kg of BD, the mean peak plasma concentration of BD was 10.1 ± 9.8 ng/mL at 2 h. The area under the plasma concentration–time curve (AUC0–24 h) was 72.1 ± 8.59 h ng/mL, and the elimination half‐life (T1/2) was 11.8 ± 1.9 h. In case of intravenous administration of BD at a dosage of 1 mg/kg, the AUC0–24 h was 281 ± 98.4 h⋅ng/mL, and the T1/2 was 8.79 ± 0.63 h. Based on these results, the oral bioavailability of BD in rats at 10 mg/kg is 2.57%. Copyright © 2013 John Wiley & Sons, Ltd.
Influence of compound danshen tablet on the pharmacokinetics of losartan and its metabolite EXP3174 by liquid chromatography coupled with mass spectrometry
Authors: Yuan Yongfang , Zhang Hai , Ma Weina , Sun Sen , Wang Benwei , Zhao Liang , Zhang Guoqing , Chai Yifeng
Published: May 2013

Losartan is an effective anti‐hypotension drug frequently used in clinic. Compound danshen tablet (CDST) is an important traditional Chinese multiherbal formula composed of Danshen, Sanqi and Bingpian, which is widely used for the treatment of cardiovascular and cerebrovascular diseases in China. More often, losartan and CDST are simultaneously used for the treatment of anti‐hypertension in the clinic. The aim of this study was to compare the pharmacokinetics of losartan and EXP3174 after oral administration of single losartan and both losartan and CDST, and to investigate the influence of CDST on the pharmacokinetics of losartan and its metabolite EXP3174. Male Sprague–Dawley rats were randomly assigned to two groups: a losartan‐only group and a losartan and CDST group. Plasma concentrations of losartan and EXP3174 were determined by LC‐MS at designated points after drug administration, and the main pharmacokinetic parameters were estimated. It was found that there were significant differences (p < 0.05) between the pharmacokinetic parameters of losartan and EXP3174, which showed that CDST influenced the metabolism and excretion of losartan in vivo. The result could be used for clinical medication guidance of losartan and CDST to avoid the occurrence of adverse reactions. Copyright © 2013 John Wiley & Sons, Ltd.
Development and validation of a sensitive method for simultaneous determination of rosuvastatin and N‐desmethyl rosuvastatin in human plasma using liquid chromatography/negative electrospray ionization/tandem mass spectrometry
Authors: Lee H. K. , Ho C. S. , Hu M. , Tomlinson B. , Wong C. K.
Published: May 2013

A sensitive and specific liquid chromatography tandem mass spectrometric method was developed and validated for the simultaneous determination of rosuvastatin (ROS) and N‐desmethyl rosuvastatin (NOR‐ROS) in human plasma using deuterium‐labeled internal standards. The plasma samples were prepared using liquid–liquid extraction with diethyl ether. Chromatographic separation was accomplished on an Xterra MS C18 column. The mobile phase consisted of a gradient mixture of 15 µmol/L ammonium acetate in water and in methanol, maintained at a flow rate of 0.4 mL/min. Mass spectrometric detection was carried out in negative electrospray ionization mode and monitored by quantification and qualification transitions for each analyte. Using 300 μL plasma samples, the lower limits of quantification of ROS and NOR‐ROS were 0.05 and 0.02 µg/L respectively. The linearity of ROS and NOR‐ROS ranged from 0.05 to 42 and 0.02 to 14 µg/L respectively. The relative standard deviations of ROS and NOR‐ROS were <13 and 9%, respectively, while the deviations from expected values were within −4.7–9.8 and −5.2–4.6%, respectively. The present method offered high sensitivity and was successfully applied to a 24 h pharmacokinetic study of ROS and NOR‐ROS in healthy subjects receiving a single dose of 10 mg ROS. Copyright © 2013 John Wiley & Sons, Ltd.
Percutaneous closure of patent ductus arteriosus in small infants with significant lung disease may offer faster recovery of respiratory function when compared to surgical ligation
Authors: Abu Hazeem Anas A. , Gillespie Matthew J. , Thun Haley , Munson David , Schwartz Matthew C. , Dori Yoav , Rome Jonathan J. , Glatz Andrew C.
Published: May 2013

Objectives

To describe our experience with percutaneous closure of patent ductus arteriosus (PDA) in small infants and compare outcomes to matched surgical patients.

Background

Ligation via thoracotomy has been used to close PDAs in small infants, but has been associated with respiratory and hemodynamic compromise. We hypothesized that percutaneous closure would offer faster recovery of respiratory function.

Methods

Patients <4 kg requiring positive pressure ventilation who underwent percutaneous PDA closure between January 2000 and April 2012 were reviewed and matched to contemporary surgical patients on gestational age (GA), birth weight (BW), procedure weight (WT), and ventilation mode. Patients returned to baseline respiratory status when the product of mean airway pressure and FiO2 returned to pre‐procedural levels.

Results

Eight matched pairs were included. Median BW, GA, and WT were 1.43 kg (0.52–2.97), 29.8 weeks (24–39), and 2.8 kg (2.2–3.9) for catheter patients and 1.55 kg (0.48–3.04), 29 weeks (23–37), and 2.75 kg (2.3–4.2) for surgical patients. Complete PDA closure occurred in all. The median time to return to baseline respiratory status was significantly shorter in the percutaneous group (17 hr (range 0–113) vs. 53 hr (range 13–219), P < 0.05). In the percutaneous group, two patients developed mild aortic coarctation, one mild left pulmonary artery stenosis, and four femoral vascular thromboses which all resolved with medical therapy. Surgical complications included significant respiratory and cardiac compromise, rib fractures and urinary retention.

Conclusions

Percutaneous closure of PDA in small infants on respiratory support is equivalent in safety and efficacy and may offer shorter recovery time than surgical ligation. © 2013 Wiley Periodicals, Inc.
Deprotonation ofC‐Alkyl Groups of Cationic Triruthenium Clusters Containing CyclometalatedC‐Alkylpyrazinium Ligands: Experimental and Computational Studies
Authors: Cabeza Javier A. , Fernández‐Colinas José M. , García‐Álvarez Pablo , Pérez‐Carreño Enrique , Pruneda Vanessa , Van der Maelen Juan F.
Published: May 2013

TheC‐alkyl groups of cationic triruthenium cluster complexes of the type [Ru3(μ‐H)(μ‐κ2N1,C2 ‐L)(CO)10]+(HL represents a genericC‐alkyl‐N‐methylpyrazium species) have been deprotonated to give kinetic products that contain unprecedentedC‐alkylidene derivatives and maintain the original edge‐bridged decacarbonyl structure. When the starting complexes contain variousC‐alkyl groups, the selectivity of these deprotonation reactions is related to the atomic charges of the alkyl H atoms, as suggested by DFT/natural‐bond orbital (NBO) calculations. Three additional electronic properties of theC‐alkyl CH bonds have also been found to correlate with the experimental regioselectivity because, in all cases, the deprotonated CH bond has the smallest electron density at the bond critical point, the greatest Laplacian of the electron density at the bond critical point, and the greatest total energy density ratio at the bond critical point (computed by using the quantum theory of atoms in molecules, QTAIM). The kinetic decacarbonyl products evolve, under appropriate reaction conditions that depend upon the position of theC‐alkylidene group in the heterocyclic ring, toward face‐capped nonacarbonyl derivatives (thermodynamic products). The position of theC‐alkylidene group in the heterocyclic ring determines the distribution of single and double bonds within the ligand ring, which strongly affects the stability of the neutral decacarbonyl complexes and the way these ligands coordinate to the metal atoms in the nonacarbonyl products. The mechanisms of these decacarbonylation processes have been investigated by DFT methods, which have rationalized the structures observed for the final products and have shed light on the different kinetic and thermodynamic stabilities of the reaction intermediates, thus explaining the reaction conditions experimentally required by each transformation.
Adsorption Sequence of Multifunctional Groups: A Study on the Reaction Pathway and the Adsorption Structure of Homocysteine on the Ge(100) Surface
Authors: Park Youngchan , Lee Myungjin , Lee Hangil
Published: May 2013

We investigated the adsorption mechanism of homocysteine (HSCH2CH2CH(NH2)COOH) on the Ge(100) surface along with its electronic structures and adsorption geometries to determine the sequence of adsorption of this amino acid′s functional groups using core‐level photoemission spectroscopy (CLPES) in conjunction with density functional theory (DFT) calculations. We found that the “SH‐dissociated OH‐dissociated N‐dative‐bonded structure” and the “SH‐dissociated OH‐dissociation‐bonded structure” were preferred at a monolayer (ML) coverage of 0.30 (lower coverage) and 0.60 (higher coverage), respectively. The “SH‐dissociated OH‐dissociated N‐dative‐bonded structure” was the most stable structure. Moreover, we systematically confirmed the sequence of adsorption of the functional groups of the homocysteine molecule on the Ge(100) surface, which is thiol group (SH), carboxyl group (COOH), and amine group (NH2).
Site‐directed zebrafish transgenesis into single landing sites with the phiC31 integrase system
Authors: Mosimann Christian , Puller Ann‐Christin , Lawson Katy L. , Tschopp Patrick , Amsterdam Adam , Zon Leonard I.
Published: May 2013

Background: Linear DNA‐based and Tol2‐mediated transgenesis are powerful tools for the generation of transgenic zebrafish. However, the integration of multiple copies or transgenes at random genomic locations complicates comparative transgene analysis and makes long‐term transgene stability unpredictable with variable expression. Targeted, site‐directed transgene integration into pre‐determined genomic loci can circumvent these issues. The phiC31 integrase catalyzes the unidirectional recombination reaction between heterotypic attP and attB sites and is an efficient platform for site‐directed transgenesis. Results: We report the implementation of the phiC31 integrase‐mediated attP/attB recombination for site‐directed zebrafish transgenics of attB‐containing transgene vectors into single genomic attP landing sites. We generated Tol2‐based single‐insertion attP transgenic lines and established their performance in phiC31 integrase‐catalyzed integration of an attB‐containing transgene vector. We found stable germline transmission into the next generation of an attB reporter transgene in 34% of all tested animals. We further characterized two functional attP landing site lines and determined their genomic location. Our experiments also demonstrate tissue‐specific transgene applications as well as long‐term stability of phiC31‐mediated transgenes. Conclusions: Our results establish phiC31 integrase‐controlled site‐directed transgenesis into single, genomic attP sites as space‐, time‐, and labor‐efficient zebrafish transgenesis technique. The described reagents are available for distribution to the zebrafish community. Developmental Dynamics 242:949–963, 2013. © 2013 Wiley Periodicals, Inc.
First Evidence of a Phase Transition in a High‐Pressure Metal Iodate: Structural and Thermal Studies of AgIO3 Polymorphs
Authors: Suffren Yan , Gautier‐Luneau Isabelle , Darie Céline , Goujon Céline , Legendre Murielle , Leynaud Olivier
Published: May 2013

A new phase of silver iodate, β‐AgIO3, was obtained at 2.7 GPa by heating the α‐AgIO3 precursor above 240 °C. β‐AgIO3 is the first iodate obtained at high pressure that stabilizes under normal conditions. The crystal structure was determined by X‐ray powder diffraction and Rietveld refinement. In comparison to α‐AgIO3, which crystallizes in the Pbc21 acentric orthorhombic space group with the lattice parameters a = 7.265(2) Å, b = 15.17(4) Å, c = 5.786(2) Å, and V = 638(2) Å3, β‐AgIO3 crystallizes in the Pbca centric orthorhombic space group, with the following parameters: a = 6.137(2) Å, b = 16.980(4) Å, c = 5.827(1) Å, and V = 607.3(3) Å3. Differential thermal analysis under high pressure (2.7 GPa) and structural studies showed an endothermic transformation at 260 °C corresponding to a first‐order reconstructive phase transition from α‐AgIO3 to β‐AgIO3. The thermal behaviors of α‐AgIO3 and β‐AgIO3 were studied by differential scanning calorimetry at ambient pressure and in situ temperature‐dependent X‐ray powder diffraction.
Can Diels–Alder Reactions Lead to trans‐Fused Products? A Computational Study of the Competitive [4+2] and [2+4] Cycloaddition of Dienes to α‐Aryl‐Substituted Cyclohexenones
Authors: Bakalova Snezhana M. , Santos A. Gil
Published: May 2013

The Diels–Alder reaction is one of the most interesting processes known in organic chemistry. Its one‐step nature, which allows exceptional control of the stereoselectivity of the reaction, is one of its most important characteristics. However, it is also a limitation of the process, as it prevents the formation of trans products. In spite of this, it is believed that trans products can be formed in two‐step Diels–Alder reactions, and there is a classic example that illustrates this possibility. In this paper we study this system by theoretical methods and have concluded that not only the reported Diels–Alder reaction follows a one‐step mechanism, but also that the trans product observed by the authors can only originate by a [3,3] sigmatropic rearrangement of a previously formed Diels–Alder intermediate. The study of a model system also suggests that trans fusion in two‐step Diels–Alder reactions will not happen under conventional reaction conditions as the transition states involved in such processes would have prohibitive activation energies. The large calculated values result from very poor stabilization of the zwitterionic intermediate when it adopts the conformation that allows the trans approach of the diene moiety to the activated dienophile. The analysis of the potential energy surfaces obtained by two‐dimensional scans indicates that the one‐step DA reaction that would lead to trans‐fused products also will not occur under conventional reaction conditions.
BBr3‐Assisted Cleavage of Most Ethers Does Not Follow the Commonly Assumed Mechanism
Authors: Sousa Carla , Silva Pedro J.
Published: May 2013

Density‐functional computations were used to probe the reaction mechanism of BBr3‐assisted ether cleavage. After the initial formation of an ether–BBr3 adduct, secondary and tertiary alkyl ethers are cleaved through Br– transfer from the activated BBr3 to the alkyl moiety, as postulated in the literature. In contrast, all other ethers studied react through a novel pathway involving two ether–BBr3 adducts, one of which acts as Br– donor, and the second as the reaction substrate. The identification of the novel bimolecular mechanism for this classical reaction has further applications, because it implies that BBr3‐assisted ether cleavage may become impossible if the ether is surrounded by bulky portions of the molecule that prevent the approach of the attacking BBr3 adduct. Our data also allow the construction of an order of reactivity of alkyl ether deprotection: isopropyl, benzyl, tertiary alkyl, allyl, isobutyl and ethyl can be removed sequentially as their bromo derivatives; phenyl, cyanomethyl and chloromethyl groups can be sequentially removed as their corresponding alcohols.
Perceived system longevity increases system justification and the legitimacy of inequality
Authors: Blanchar John C. , Eidelman Scott
Published: May 2013

In two studies, we test the prediction that perceived longevity increases system justification and the legitimacy of inequality. In Study 1, the foundations of the capitalist system were portrayed as younger or older on a timeline. Participants scored higher on economic system justification and perceived capitalism as more legitimate when they were led to believe that this economic system was older. In Study 2, we manipulated the longevity of the Indian caste system and recruited both Indians and Americans. Both groups judged the caste system as more justifiable and legitimate when it was described as more longstanding. In addition, Indians reported more system dependence and judged the caste system as more justifiable and legitimate than Americans. Feelings of system dependence explained the effects of nationality, but not the effects of longevity, on the justification and legitimacy of the caste system. Perceived longevity is a novel contributor to system justification. Copyright © 2013 John Wiley & Sons, Ltd.
History of a suspected delirium is more common in dementia with Lewy bodies than Alzheimer's disease: a retrospective study
Authors: Vardy Emma , Holt Rachel , Gerhard Alex , Richardson Anna , Snowden Julie , Neary David
Published: May 2013

Background

Delirium is common and is associated with an increased risk of dementia. However, it is not clear whether delirium confers increased risk of any particular type of dementia. We performed a retrospective study of Alzheimer's disease (AD) and Dementia with Lewy bodies (DLB) to ascertain whether a suspected episode of preceding delirium was more common prior to diagnosis in either type of dementia.

Methods

The study was carried out in a tertiary referral unit for the diagnosis of dementia. Clinic letters from the first presentation to the unit of 85 cases with DLB and 95 cases of AD were reviewed for documentation of any previous episodes of suspected delirium.

Results

In this study, 25% of DLB cases had at least one reported episode of suspected delirium as compared to 7% of AD cases (p = 0.001). For the DLB cases who had a prior suspected delirium, 23% had more than one episode compared with 14% of the AD group. The median time between most recent suspected episode of delirium and diagnosis of dementia in both groups was less than a year

Conclusions

A greater proportion of those presenting and diagnosed with DLB had a documentation of a suspected delirium than those diagnosed with AD. Delirium may lead to a higher risk of DLB as opposed to other forms of dementia, or delirium may, at least in some cases, represent the early stages of DLB. These data suggest that a diagnosis of DLB should be specifically considered in those presenting with a delirium. Copyright © 2013 John Wiley & Sons, Ltd.
Permeability impairment of a limestone reservoir triggered by heterogeneous dissolution and particles migration during CO2‐rich injection
Authors: Mangane Papa O. , Gouze Philippe , Luquot Linda
Published: May 2013

A CO2‐rich brine core‐flood experiment in calcite limestone for conditions representative of underground storage (P = 12 MPa and T = 100°C) was performed in order to explore the dissolution mechanisms arising at moderate CO2 partial pressure (0.3 MPa). An increase of the total porosity (φT) accompanied by a persistent permeability (k) decrease was measured. The mechanisms controlling this atypical anticorrelated k − φT relationship were investigated from the analysis of high‐resolution X‐ray microtomography images of the sample acquired before and after the experiment. All the evidences converge to the conclusion that the ubiquitous decrease of permeability measured during the 44 h of dissolution is due to the clogging of a fraction of the macroporosity by microporous material triggered by the rearrangement of the detached undissolved particles. This mechanism results in the development of low permeability zones bridging the macroporosity.
The location of old groundwater in hydrogeologic basins and layered aquifer systems
Authors: Gassiat Claire , Gleeson Tom , Luijendijk Elco
Published: May 2013

The age of groundwater, the time since the water recharged the subsurface, is a fundamental characteristic of groundwater that impacts diverse geologic processes and practical applications. The distribution of groundwater age depends on many factors including permeability, recharge rate, aquifer geometry, and topography. Seminal work simulated topography‐driven regional groundwater flow with various topographies, localized high‐permeability zones, and more recently with permeability decreasing with depth, but the role of layered aquifer systems which are common in both consolidated and unconsolidated sediments has not been systematically explored. Here we show that high age zones with predictable locations occur in layered geologic systems across a wide range of hydraulic gradients, basin geometries, and permeabilities. Numerical simulations of a generic three‐layer aquifer system indicate that high age zones consistently form in the low‐permeability layer near the middle of the basin. The zones of older groundwater result from low groundwater velocities in the low‐permeability layer and the rejuvenation of the groundwater through mixing of different flow paths near discharge zones. The high age zones are not hydraulic stagnation points but are associated with areas of low velocity. Formation and location of zones of high groundwater ages in low‐permeability units are important as these units are targeted for radioactive waste disposal and shale gas extraction. High age zones are also likely to affect geologic processes that depend on groundwater or solute fluxes and may serve as archives of past hydrological or climatological conditions.
Marked freshening of North Pacific subtropical mode water in 2009 and 2010: Influence of freshwater supply in the 2008 warm season
Authors: Sugimoto Shusaku , Takahashi Nobuto , Hanawa Kimio
Published: May 2013

Changes in salinity of the North Pacific subtropical mode water (STMW) were investigated using profiles for 2003–2011. In 2009 and 2010, the STMW freshened markedly (S < 34.7 psu), with salinity 0.1 psu lower than other years. Freshening in 2009 was caused by excess rainfall in the 2008 warm season, which was related to an increase in the number of low pressures passing over the STMW formation region associated with a southeastward shrinkage of the summertime North Pacific subtropical high. The freshening signal persisted under the seasonal pycnocline during the 2009 warm season. This resulted in the freshening of STMW in 2010.
Recurrence statistics of great earthquakes
Authors: Ben‐Naim E. , Daub E. G. , Johnson P. A.
Published: May 2013

We investigate the sequence of great earthquakes over the past century. To examine whether the earthquake record includes temporal clustering, we identify aftershocks and remove those from the record. We focus on the recurrence time, defined as the time between two consecutive earthquakes. We study the variance in the recurrence time and the maximal recurrence time. Using these quantities, we compare the earthquake record with sequences of random events, generated by numerical simulations, while systematically varying the minimal earthquake magnitudeMmin. Our analysis shows that the earthquake record is consistent with a random process for magnitude thresholds 7.0≤Mmin≤8.3, where the number of events is larger. Interestingly, the earthquake record deviates from a random process at magnitude threshold 8.4≤Mmin≤8.5, where the number of events is smaller; however, this deviation is not strong enough to conclude that great earthquakes are clustered. Overall, the findings are robust both qualitatively and quantitatively as statistics of extreme values and moment analysis yield remarkably similar results.
Oxygen dynamics in the Black Sea as seen by Argo profiling floats
Authors: Stanev E. V. , He Y. , Grayek S. , Boetius A.
Published: May 2013

Observations collected in the Black Sea from May 2010 until December 2011 from two Argo floats with oxygen sensors demonstrated the potential of the applied technique to deliver high‐quality oxygen data in this oxic/anoxic environment where the oxygen concentration varies from the level of saturation to zero. It was demonstrated that the dynamics of the oxic‐anoxic interface was dominated by vigorous mesoscale processes displacing locally anoxic waters up to about 70 m below the sea surface. Alternatively, oxygenation (ventilation) in the coastal zone penetrated down to about 150–200 m. The range of mesoscale variability, which appeared to reach half of the range of climatic trend during the last 50 years, helped to objectively assess the validity of interpretation of historical data. It was proved that the shift of the suboxic zone from isopycnal depth σt = 16.5 to σt = 15.5 during 1960–2010, interrupted by its deepening between 1990 and 2000, was greater than the possible error limit caused by insufficient sampling of mesoscale variability. Furthermore, profiling floats shed a new light into the seasonal variability of the subsurface oxygen maximum. It was also demonstrated that the assumption of isopycnal alignment of oxygen was coarsely applicable to the suboxic layer in both the coastal and interior part of the Black Sea where the isopycnal mixing revealed large temporal and spatial variability. Therefore, deeper understanding of the dynamics of suboxic zone necessitated continuous basin‐wide sampling.
Human and experimental evidence supporting a role for osteopontin in alcoholic hepatitis
Authors: Morales-Ibanez Oriol , Domínguez Marlene , Ki Sung H. , Marcos Miguel , Chaves Javier F. , Nguyen-Khac Eric , Houchi Hakim , Affò Silvia , Sancho-Bru Pau , Altamirano José , Michelena Javier , García-Pagán Juan Carlos , Abraldes Juan G. , Arroyo Vicente , Caballería Juan , Laso Francisco-Javier , Gao Bin , Bataller Ramón
Published: May 2013

We identified, in the transcriptome analysis of patients with alcoholic hepatitis (AH), osteopontin (OPN) as one of the most up-regulated genes. Here, we used a translational approach to investigate its pathogenic role. OPN hepatic gene expression was quantified in patients with AH and other liver diseases. OPN protein expression and processing were assessed by immmunohistochemistry, western blotting and enzyme-linked immunosorbent assay. OPN gene polymorphisms were evaluated in patients with alcoholic liver disease. The role of OPN was evaluated in OPN−/− mice with alcohol-induced liver injury. OPN biological actions were studied in human hepatic stellate cells (HSCs) and in precision-cut liver slices. Hepatic expression and serum levels of OPN were markedly increased in AH, compared to normal livers and other types of chronic liver diseases, and correlated with short-term survival. Serum levels of OPN also correlated with hepatic expression and disease severity. OPN was mainly expressed in areas with inflammation and fibrosis. Two proteases that process OPN (thrombin and matrix metalloproteinase 7) and cleaved OPN were increased in livers with AH. Patients with AH had a tendency of a lower frequency of the CC genotype of the +1239C single-nucleotide polymorphism of the OPN gene, compared to patients with alcohol abuse without liver disease. Importantly, OPN−/− mice were protected against alcohol-induced liver injury and showed decreased expression of inflammatory cytokines. Finally, OPN was induced by lipopolysaccharide and stimulated inflammatory actions in HSCs.

Conclusion:

Human and experimental data suggest a role for OPN in the pathogenesis of AH. Further studies should evaluate OPN as a potential therapeutic target. (Hepatology 2013;58:1742–1756)
Relative adrenal insufficiency in decompensated cirrhosis: Relationship to short-term risk of severe sepsis, hepatorenal syndrome, and death
Authors: Acevedo Juan , Fernández Javier , Prado Verónica , Silva Anibal , Castro Miriam , Pavesi Marco , Roca Daria , Jimenez Wladimiro , Ginès Pere , Arroyo Vicente
Published: May 2013

The prevalence of relative adrenal insufficiency (RAI) in critically ill cirrhosis patients with severe sepsis is over 60% and associated features include poor liver function, renal failure, refractory shock, and high mortality. RAI may also develop in noncritically ill cirrhosis patients but its relationship to the clinical course has not yet been assessed. The current study was performed in 143 noncritically ill cirrhosis patients admitted for acute decompensation. Within 24 hours after hospitalization adrenal function, plasma renin activity, plasma noradrenaline and vasopressin concentration, and serum levels of nitric oxide, interleukin-6 and tumor necrosis factor alpha were determined. RAI was defined as a serum total cortisol increase <9 μg/dL after 250 μg of intravenous corticotropin from basal values <35 μg/dL. Patients were followed for 3 months. RAI was detected in 26% of patients (n = 37). At baseline, patients with RAI presented with lower mean arterial pressure (76 ± 12 versus 83 ± 14 mmHg,

P

= 0.009) and serum sodium (131 ± 7 versus 135 ± 5 mEq/L,

P

= 0.007) and higher blood urea nitrogen (32 ± 24 versus 24 ± 15 mg/dl,

P

= 0.06), plasma renin activity (7.1 ± 9.9 versus 3.4 ± 5.6 ng/mL*h,

P

= 0.03), and noradrenaline concentration (544 ± 334 versus 402 ± 316 pg/mL,

P

= 0.02). During follow-up, patients with RAI exhibited a higher probability of infection (41% versus 21%,

P

= 0.008), severe sepsis (27% versus 9%,

P

= 0.003), type-1 hepatorenal syndrome (HRS) (16% versus 3%,

P

= 0.002), and death (22% versus 7%,

P

= 0.01).

Conclusion:

RAI is frequent in noncritically ill patients with acute decompensation of cirrhosis. As compared with those with normal adrenal function, patients with RAI have greater impairment of circulatory and renal function, higher probability of severe sepsis and type-1 HRS, and higher short-term mortality. (Hepatology 2013;58:1757–1765)
Peritransplant absolute lymphocyte count as a predictive factor for advanced recurrence of hepatitis C after liver transplantation
Authors: Nagai Shunji , Yoshida Atsushi , Kohno Keisuke , Altshuler David , Nakamura Mio , Brown Kimberly A. , Abouljoud Marwan S. , Moonka Dilip
Published: May 2013

Lymphocytes play an active role in natural immunity against hepatitis C virus (HCV). We hypothesized that a lower absolute lymphocyte count (ALC) may alter HCV outcome after liver transplantation (LT). The aim of this study was to investigate the impact of peritransplant ALC on HCV recurrence following LT. A total of 289 LT patients between 2005 and 2011 were evaluated. Peritransplant ALC (pre-LT, 2-week, and 1-month post-LT) and immunosuppression were analyzed along with recipient and donor factors in order to determine risk factors for HCV recurrence based on METAVIR fibrosis score. When stratifying patients according to pre- and post-LT ALC (<500/μL versus 500-1,000/μL versus >1,000/μL), lymphopenia was significantly associated with higher rates of HCV recurrence with fibrosis (F2-4). Multivariate Cox regression analysis showed posttransplant ALC at 1 month remained an independent predictive factor for recurrence (

P

= 0.02, hazard ratio [HR] = 2.47 for <500/μL). When peritransplant ALC was persistently low (<500/μL pre-LT, 2-week, and 1-month post-LT), patients were at significant risk of developing early advanced fibrosis secondary to HCV recurrence (F3-4 within 2 years) (

P

= 0.02, HR = 3.16). Furthermore, severe pretransplant lymphopenia (<500/μL) was an independent prognostic factor for overall survival (

P

= 0.01, HR = 3.01). The use of rabbit anti-thymocyte globulin induction (RATG) had a remarkable protective effect on HCV recurrence (

P

= 0.02, HR = 0.6) despite its potential to induce lymphopenia. Subgroup analysis indicated that negative effects of posttransplant lymphopenia at 1 month (<1,000/μL) were significant regardless of RATG use and the protective effects of RATG were independent of posttransplant lymphopenia.

Conclusion :

Peritransplant ALC is a novel and useful surrogate marker for prediction of HCV recurrence and patient survival. Immunosuppression protocols and peritransplant management should be scrutinized depending on peritransplant ALC.
Quantifying the effects of pesticide exposure on annual reproductive success of birds
Authors: Etterson Matthew A , Bennett Richard S
Published: May 2013

The Markov chain nest productivity model (MCnest) was developed for quantifying the effects of specific pesticide-use scenarios on the annual reproductive success of simulated populations of birds. Each nesting attempt is divided into a series of discrete phases (e.g., egg laying, incubation, nestling rearing), and results from avian toxicity tests are used to represent the types of effects possible in the field during each breeding phase. The expected exposure dose each day throughout the breeding season can be compared to the toxicity thresholds assigned to each breeding phase to determine whether the nest attempt is at risk. The primary output of the model is an estimate of the number of successful nest attempts per female per year, which is multiplied by the number of fledglings per successful nest to estimate the number of fledglings per female per breeding season (i.e., annual reproductive success). In this article, we present a series of MCnest simulations to demonstrate the extent to which the magnitude of change in annual reproductive success can be affected by considering life history attributes and the timing of pesticide applications relative to a species' typical breeding phenology. For a given pesticide-use scenario, MCnest can identify which species are at greatest risk. By allowing multiple species to be run under a single scenario, it can also help to identify the life-history traits that contribute to a species' vulnerability to a given pesticide-use scenario. It also can determine which application dates have the greatest impact and demonstrate the extent to which pesticide characteristics (e.g., residue half-life, mode of action) affect productivity. MCnest goes beyond the current qualitative screening-level assessments of risks to avian reproduction to provide an approach for quantifying the reduction in annual reproductive success by integrating species life history and timing of pesticide exposures, despite limitations in existing information on species life history and toxicity responses from existing laboratory tests. Integr Environ Assess Manag 2013;9:590–599. © 2013 SETAC