bluuebunny/crossref_metadata_2025_split huggingface dataset:
Facile Rearrangement of a Bis(N‐heterocyclic carbene)borate Chelate Ligand and Access to [:GeX]+ Complexes (X = H, Cl)
Authors: Xiong Yun , Yao Shenglai , Szilvási Tibor , Driess Matthias 
Published: April 2015

AbstractThe unexpected isomerization of the potassium bis(N‐heterocyclic carbene)borate [BPh2(tBuNHC)2]K (2′) (tBuNHC = 3‐tert‐butylimidazole‐2‐ylidene) in toluene, affording the unique potassium imidazolyl–NHC–borate [BPh2(tBuIm)(tBuNHC)]K (2) (tBuIm = 3‐tert‐butyl‐2‐imidazolyl), is reported. The latter crystallizes as the centrosymmetric dimer 22. According to the results of DFT calculations, the rearrangement of 2′ is basically triggered by the solvation of the K+ ion: while 2′ is most stable in THF solutions, the formation of 2 is feasible in least coordinating toluene and drastically favored through dimerization to give 22. The latter reacts with GeCl2·dioxane to form solely the unprecedented chlorogermyliumylideneborate [BPh2(tBuIm)(tBuNHC)]GeCl (3). Treatment of 3 with KHB(sBu)3 furnishes the corresponding hydridogermyliumylideneborate complex [BPh2(tBuIm)(tBuNHC)]GeH (4) in 66 % yield.
Comparative Study of the Reactivity of Zirconium(IV)‐Substituted Polyoxometalates towards the Hydrolysis of Oligopeptides
Authors: Ly Hong Giang T. , Absillis Gregory , Parac‐Vogt Tatjana N. 
Published: April 2015

AbstractThe hydrolytic activity of the ZrIV‐substituted Keggin‐type (Et2NH2)8[{α‐PW11O39Zr‐(μ‐OH)(H2O)}2]·7H2O (1), Lindqvist‐type (Me4N)2[W5O18Zr(H2O)3] (2), and Wells–Dawson‐type Na14[Zr4(P2W16O59)2(μ3‐O)2(OH)2(H2O)4]·57H2O (3) polyoxometalates (POMs) towards the peptide bonds in the oligopeptides triglycine, tetraglycine, glycylglycylhistidine, and glycylserylphenylalanine was investigated by kinetic methods and multinuclear NMR spectroscopy. 31P NMR and UV/Vis spectroscopy showed that 1–3 were stable under the conditions used to study peptide bond hydrolysis. The reactivity of 1–3 towards oligopeptides was compared on the basis of the amount of free glycine produced at a certain time increment. In the presence of 1–3, rate constants in the range 6.25 × 10–7 to 10.14 × 10–7 s–1 were obtained, whereas no hydrolysis was observed after one month in the absence of these POMs. The results showed that the Keggin‐type complex 1 was the most active towards peptide bond hydrolysis in tri‐ and tetrapeptides. 1H and 13C NMR spectroscopy showed that triglycine, tetraglycine, and glycylserylphenylalanine interact with 1 and 2 preferentially through the amine nitrogen atom and the N‐terminal amide oxygen atom to activate the peptide bond towards hydrolysis. The coordination of glycylglycylhistidine resulted in multiple complexes with 1–3 as a result of additional imidazole coordination to the ZrIV centers.
Urea Azines (Bisguanidines): Electronic Structure, Redox Properties, and Coordination Chemistry
Authors: Herrmann Hendrik , Reinmuth Matthias , Wiesner Sven , Hübner Olaf , Kaifer Elisabeth , Wadepohl Hubert , Himmel Hans‐Jörg 
Published: April 2015

AbstractUrea azines are a largely neglected class of compounds. We show herein that they can easily be synthesized and sublimed at higher temperatures (90–100 °C) without decomposition. Our discussion includes the derivatives N,N′‐diisopropylurea azine (2), tetramethylurea azine (3), and N,N′‐dimethylethyleneurea azine (4) as examples. Vibrational spectroscopy and quantum chemical calculations were used to study their electronic structure in detail. A clear trend in the calculated decomposition to N2 and carbene is found, but the analysis reveals that this trend reflects the stability of the carbene decomposition product rather than changes in the electronic structure of the urea azines. Using cyclic voltammetry (CV) measurements we show that the urea azines are strong organic electron donors, which can be oxidized reversibly in two well‐separated one‐electron steps. The radical salt 4(TCNQ), featuring radical monocations and radical monoanions, which form mixed stacks in the solid state, was prepared by reaction of neutral 4 with tetracyanoquinodimethane (TCNQ). Oxidation of 4 with silver salts Ag+X– (X = BF4 or PF6) was accompanied by dehydrogenation, leading to intensively red‐brown colored radical azoimidazolium dyes. Furthermore, urea azines were used as chelating ligands. In the case of 2, coordination to late transition metals initiates tautomerization. Reaction of 2 with boron hydrides leads to hydrogen elimination and formation of new B,N bi‐heterocyclic ring structures.
Highly Enantioselective Synthesis of Chiral Pyranonaphthoquinone‐Fused Spirooxindoles through Organocatalytic Three‐Component Cascade Reactions
Authors: Zhao Hong‐Wu , Li Bo , Tian Ting , Meng Wei , Yang Zhao , Song Xiu‐Qing , Chen Xiao‐Qin , Pang Hai‐Liang 
Published: April 2015

AbstractIn the presence of cinchona‐thiourea organocatalyst C1, the developed organocatalytic three‐component cascade reaction of isatins, malononitrile, and 2‐hydroxynaphthalene‐1,4‐diones readily proceeded to furnish chiral pyranonaphthoquinone‐fused spirooxindoles in excellent chemical yields and high enantioselectivities (up to 99 % yield and 97 % ee). The absolute configurations of the spirooxindoles were assigned on the basis of an X‐ray single crystal structure. Moreover, a reaction mechanism is proposed that accounts for the stereocontrolled formation of the chiral spirooxindoles,.
Evaluating aquatic invertebrate vulnerability to insecticides based on intrinsic sensitivity, biological traits, and toxic mode of action
Authors: Rico Andreu , Van den Brink Paul J. 
Published: April 2015

Abstract

In the present study, the authors evaluated the vulnerability of aquatic invertebrates to insecticides based on their intrinsic sensitivity and their population-level recovery potential. The relative sensitivity of invertebrates to 5 different classes of insecticides was calculated at the genus, family, and order levels using the acute toxicity data available in the US Environmental Protection Agency ECOTOX database. Biological trait information was linked to the calculated relative sensitivity to evaluate correlations between traits and sensitivity and to calculate a vulnerability index, which combines intrinsic sensitivity and traits describing the recovery potential of populations partially exposed to insecticides (e.g., voltinism, flying strength, occurrence in drift). The analysis shows that the relative sensitivity of arthropods depends on the insecticide mode of action. Traits such as degree of sclerotization, size, and respiration type showed good correlation to sensitivity and can be used to make predictions for invertebrate taxa without a priori sensitivity knowledge. The vulnerability analysis revealed that some of the Ephemeroptera, Plecoptera, and Trichoptera taxa were vulnerable to all insecticide classes and indicated that particular gastropod and bivalve species were potentially vulnerable. Microcrustaceans (e.g., daphnids, copepods) showed low potential vulnerability, particularly in lentic ecosystems. The methods described in the present study can be used for the selection of focal species to be included as part of ecological scenarios and higher tier risk assessments. Environ Toxicol Chem 2015;34:1907–1917. © 2015 SETAC
Lipooligosaccharides from Mycobacteria: Structure, Function, and Synthesis
Authors: Bai Bing , Chu Chun‐jui , Lowary Todd L. 
Published: April 2015

AbstractMycobacteria produce a number of ‘extractable glycolipids’, which are present at the outer periphery of their cell wall structure. These molecules are believed to play important roles in mycobacteriahost interactions, although for many of these species the manner in which they mediate biological events is poorly understood. We summarize here the structures of one class of these molecules (lipooligosaccharides), highlight briefly their biological role, and discuss synthetic work done to access this complex and diverse group of bacterial glycolipids.
Kinetics and equilibria of 5‐hydroxymethylfurfural (5‐HMF) sequestration from algal hydrolyzate using granular activated carbon
Authors: Rolly Gonzales Ralph , Hong Yongseok , Park Jong‐Hun , Kumar Gopalakrishnan , Kim Sang‐Hyoun 
Published: April 2015

ABSTRACTBACKGROUND5‐hydroxymethylfurfural (5‐HMF), the major by‐product in hydrolyzates from lignocelluloses and algal biomass, is known as an inhibitor of several microorganisms as well as a promising precursor for biorefinery. In this study, the feasibility of 5‐HMF sequestration was investigated using granular activated carbon (GAC) as the adsorbent.RESULTSEquilibria for the 5‐HMF adsorption onto GAC were derived. Positive isosteric heat values showed the reaction was exothermic and favored at low temperature. The pseudo‐second order dynamics and the estimated activation energy, 227.4 kJ mol−1, implied that the removal mechanism would be chemical adsorption. The adsorption was not interfered with by the presence of sugar and sugar compounds were not adsorbed onto GAC.CONCLUSIONBatch and column tests on dilute acid hydrolyzate of red algal biomass showed that GAC adsorption would be a feasible option for sequestration of 5‐HMF in hydrolyzate for the biofuel and biorefinery industries. © 2015 Society of Chemical Industry
Variability in the start, end, and length of frost‐free periods across the conterminous United States during the past century
Authors: McCabe Gregory J. , Betancourt Julio L. , Feng Song 
Published: April 2015

ABSTRACTThe timing of last spring frost dates (LSFDs), first fall frost dates (FFFDs), and frost‐free period lengths (FFPLs) constrains freeze–thaw processes in hydrology, paces the annual life cycles of plants and animals, affects human food production, and influences land–atmosphere interactions, including the water and carbon cycles. Daily minimum temperature data for the conterminous United States (CONUS) from the Global Historical Climatology Network for the 1920–2012 period are used to determine LSFDs, FFFDs, and FFPLs. Analyses of trends and variability in these growing season components indicate a trend towards earlier LSFDs, later FFFDs, and longer FFPLs for most locations in the CONUS. A general change to earlier LSFDs appears to have occurred after about 1983, whereas a change to later FFFDs is most noticeable after about 1993. Comparisons of time series of LSFDs and FFFDs with well‐known climate indices indicate only weak correlations for most sites.
Spatial analysis of sunshine duration in complex terrain by non‐contemporaneous combination of station and satellite data
Authors: Frei Christoph , Willi Marco , Stöckli Reto , Dürr Bruno 
Published: April 2015

ABSTRACTClimate monitoring and environmental modelling are in need of spatial datasets of sunshine duration or surface radiation. Their development is complicated by the coarse resolution of station measurements and the limited temporal extent and consistency of satellite retrievals. We present a method for spatial analysis that combines station and satellite data. Instead of merging contemporaneous measurements from both sources, our approach relies on statistical patterns distilled from satellite data over a limited time period. This permits application outside the satellite period and reduces inconsistencies across satellite generations. The non‐contemporaneous merging builds on principal component analysis and kriging with external drift. Its strengths are in regions of complex orography. We develop the non‐contemporaneous combination to derive km‐scale analyses of relative sunshine duration (monthly and daily) for Switzerland (1971–2012). The monthly analysis has a mean absolute error of 3–5% (per cent relative sunshine duration), and it explains 60–80% of the spatial variance in individual months. Errors of the daily analysis are 7–10% with an explained spatial variance of about 60% but strongly varying from day to day. The integration of satellite data systematically improves the analysis compared to interpolation from station data alone. The improvement is largest in autumn and winter, particularly because of better representation of low‐level stratus. The non‐contemporaneous merging realizes more than half the accuracy gain from satellite data obtained with the more informative contemporaneous merging. Hence, our alternative involves only a moderate compromise for the return of making pre‐satellite Campbell–Stokes measurements exploitable for long‐term grid datasets.
Impacts of farmland conversion to apple (Malus domestica) orchard on soil organic carbon stocks and enzyme activities in a semiarid loess region
Authors: Shi Zonglin , Li Xiaoyun , Zhang Lu , Wang Yiquan 
Published: April 2015

AbstractLand‐use change often affects the sizes of soil organic carbon (SOC) stocks and the activities of soil enzymes. Responses of relevant soil quality indices caused by farmland conversion to orchard are largely unknown in the semiarid loess regions. This study was conducted at orchard sites, which have been under very intensive cultivation, to evaluate the impacts of farmland conversion to apple (Malus domestica) orchard on SOC stocks and soil enzyme activities in the semiarid loess region of Weibei, Shaanxi province, China. The spatial and temporal changes in a variety of soil quality indices were measured for the 0–100 cm soil profile in apple orchards of three age groups (< 10 y, juvenile; 10–15 y, mature; > 15 y, over‐mature) and adjacent farmlands (control). After farmland conversion, total SOC (TOC) content and density and soil alkaline phosphatase activity significantly decreased, while soil catalase activity increased for the 0–100 cm soil profile. The labile SOC (LOC) content, its proportion to TOC content, and carbon management index (CMI, changes in the total content and lability of SOC) significantly increased in the 0–40 cm soil layer, whereas soil urease and invertase activities only increased in the 0–20 cm layer (P < 0.05). With increasing age of apple orchards, SOC stocks significantly increased after 10 y, being more than 10% larger in mature and over mature orchards than in adjacent farmlands. The LOC content and CMI value also had an increasing trend, while soil enzyme activities showed different response patterns. There were significant correlations between soil enzyme activities, SOC fractions, and CMI value (P < 0.05). We concluded that farmland conversion to apple orchard affected soil quality by reducing SOC stocks in the soil profile and changing SOC content as well as soil enzyme activities at various depth intervals. Long‐term apple cultivation was effective to restore SOC stocks, although it took over a decade to rebuild a new increasing trend after farmland conversion.
Effect of commercial starter cultures on volatile compound profile and sensory characteristics of dry‐cured foal sausage
Authors: Lorenzo José M , Gómez María , Purriños Laura , Fonseca Sonia 
Published: April 2015

AbstractBACKGROUNDThe present work deals with the evaluation of the effect of three different commercial starter cultures (Chr. Hansen, Hørsholm, Denmark) on the volatile compound profile and sensory properties, as well as some important physicochemical parameters, of dry‐fermented foal sausages at the end of ripening in order to select the most suitable starter culture for this elaboration. The sausage batches were named as follows: CO (non‐inoculated control), FS (Lactobacillus sakei + Staphylococcus carnosus), SM (L. sakei + S. carnosus + Staphylococcus xylosus + Pediococcus pentosaceus + Debaryomyces hansenii) and TR (L. sakei + S. carnosus +S. xylosus).RESULTSThe pH values differed significantly among batches, with the highest values corresponding to CO followed by TR, SM and FS. The highest amounts of volatile compounds were found in FS batch. Hexanal was the most abundant compound, especially in FS and SM batches. These batches also showed higher levels of compounds derived from carbohydrate fermentation and amino acid catabolism. Sensory results showed that acid taste was significantly lower in CO batch than in inoculated batches.CONCLUSIONAccording to most parameters, batches inoculated with FS and SM starters showed marked acidity compared with TR and CO batches, as expected from the manufacturer's indications. Therefore the most suitable starter culture for use in the manufacture of foal sausages in Mediterranean countries such as Spain with a preference for low‐acidity products was found to be TR culture. © 2015 Society of Chemical Industry
Beef flavor: a review from chemistry to consumer
Authors: Kerth Chris R , Miller Rhonda K 
Published: April 2015

AbstractThis paper briefly reviews research that describes the sensation, generation and consumer acceptance of beef flavor. Humans sense the five basic tastes in their taste buds, and receptors in the nasal and sinus cavities sense aromas. Additionally, trigeminal senses such as metallic and astringent are sensed in the oral and nasal cavities and can have an effect on the flavor of beef. Flavors are generated from a complex interaction of tastes, tactile senses and aromas taken collectively throughout the tongue, nasal, sinus and oral cavities. Cooking beef generates compounds that contribute to these senses and result in beef flavor, and the factors that are involved in the cookery process determine the amount and type of these compounds and therefore the flavor generated. A low‐heat, slow cooking method generates primarily lipid degradation products, while high‐heat, fast cookery generates more Maillard reaction products. The science of consumer acceptance, cluster analyses and drawing relationships among all flavor determinants is a relatively new discipline in beef flavor. Consumers rate beef that has lipid degradation products generated from a low degree of doneness and Maillard flavor products from fast, hot cookery the highest in overall liking, and current research has shown that strong relationships exist between beef flavor and consumer acceptability, even more so than juiciness or tenderness. © 2015 Society of Chemical Industry
Does Collaboration Make Any Difference? Linking Collaborative Governance to Environmental Outcomes
Authors: Scott Tyler 
Published: April 2015

AbstractThis paper addresses two research questions: (1) Does collaborative environmental governance improve environmental outcomes? and (2) How do publicly supported collaborative groups with different levels of responsibility, formalization, and representativeness compare in this regard? Using a representative watershed quality data series, the EPA's National Rivers and Streams Assessment and Wadeable Streams Assessment, in conjunction with a watershed management regime database coded for this analysis, I test the relationship between collaborative governance and watershed quality for 357 watersheds. Since these are observational data, a multilevel propensity score matching method is used to control for selection bias. Using an augmented inverse propensity weighted estimator, I estimate the average treatment effect on the treated for six different water quality and habitat condition metrics. Collaborative watershed groups are found to improve water chemistry and in‐stream habitat conditions. I then use hierarchical linear regression modeling to examine how group responsibilities, membership diversity, and formalization affect the predicted impact of a collaborative group. Groups that engage in management activities (in comparison to coordination or planning) are found to achieve greater environmental gains. Limited differentiation is found with regards to the presence of a group coordinator, increased goal specificity, or greater stakeholder diversity.
Pharmacological Inhibition of Protein Kinase G1 Enhances Bone Formation by Human Skeletal Stem Cells Through Activation of RhoA-Akt Signaling
Authors: Jafari Abbas , Siersbaek Majken S. , Chen Li , Qanie Diyako , Zaher Walid , Abdallah Basem M. , Kassem Moustapha 
Published: April 2015

AbstractDevelopment of novel approaches to enhance bone regeneration is needed for efficient treatment of bone defects. Protein kinases play a key role in regulation of intracellular signal transduction pathways, and pharmacological targeting of protein kinases has led to development of novel treatments for several malignant and nonmalignant conditions. We screened a library of kinase inhibitors to identify small molecules that enhance bone formation by human skeletal (stromal or mesenchymal) stem cells (hMSC). We identified H-8 (known to inhibit protein kinases A, C, and G) as a potent enhancer of ex vivo osteoblast (OB) differentiation of hMSC, in a stage- and cell type-specific manner, without affecting adipogenesis or osteoclastogenesis. Furthermore, we showed that systemic administration of H-8 enhances in vivo bone formation by hMSC, using a preclinical ectopic bone formation model in mice. Using functional screening of known H-8 targets, we demonstrated that inhibition of protein kinase G1 (PRKG1) and consequent activation of RhoA-Akt signaling is the main mechanism through which H-8 enhances osteogenesis. Our studies revealed PRKG1 as a novel negative regulator of OB differentiation and suggest that pharmacological inhibition of PRKG1 in hMSC implanted at the site of bone defect can enhance bone regeneration. Stem Cells 2015;33:2219–2231
Cerebrolysin reverses hippocampal neural atrophy in a mice model of diabetes mellitus type 1
Authors: Sanchez‐Vega Lizzette , Juárez Ismael , De Jesus Gomez‐Villalobos Maria , Flores Gonzalo 
Published: April 2015

ABSTRACTThe animal model of streptozotocin‐induced diabetes mellitus type 1 (DM1) is used to study neuronal and behavioral changes produced by an increase in blood‐glucose levels. Our previous report showed that chronic streptozotocin administration induced atrophy of dendritic morphology of pyramidal neurons of the CA1 dorsal hippocampus. In addition, we showed that Cerebrolysin (Cbl), a neurotrophic peptide mixture, reduces the dendritic atrophy in animal models of aging. This study aimed to determine whether Cbl was capable of reducing behavioral and neuronal alterations, after 6 weeks of hyperglycemia in mice (streptozotocin‐induced DM1). The levels of glucose in the blood were evaluated before and after streptozotocin administration and only animals with more than 240 mg/dL of blood‐levels of glucose were used. After streptozotocin treatment, the mice received 6 weeks of Cbl, locomotor activity was measured and dendritic morphological changes were evaluated using Golgi‐Cox stain procedure, and analyzed by the Sholl method. In mice treated with streptozotocin there was a clear reduction in the dendritic length of pyramidal neurons of the CA1 and granular cells of the dental gyrus of the dorsal hippocampus. Interestingly, Cbl reversed the morphological changes induced by streptozotocin. Our results extend the list of abnormal morphological changes detected in this model of DM, and support the possibility that Cbl may have beneficial effects in the management of brain alterations induced by DM. Synapse 69:326–335, 2015. © 2015 Wiley Periodicals, Inc.
Interactive Read‐Alouds for English Learners in the Elementary Grades
Authors: Giroir Shannon , Grimaldo Leticia Romero , Vaughn Sharon , Roberts Greg 
Published: April 2015

AbstractThis article describes the implementation of a read‐aloud routine focused on the development of vocabulary knowledge and comprehension for English Learners (ELs) in grades K‐3. This paper describes the steps of a daily read‐aloud system, including key applications of second language acquisition and culturally responsive pedagogy with examples of how they are integrated with literacy instruction for ELs. The routine was implemented across three campuses, and qualitative data was collected throughout the implementation period to inform model development. Data sources include formal observations, focus‐group interviews, documents from professional development activities, and researcher field notes. The article concludes with a discussion of the successes and challenges to implementing the read‐aloud routine in K‐3 classrooms.