bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of enantiomeric excess by chiral liquid chromatography without enantiomerically pure starting standards
Authors: Sánchez F. G. , Navas Díaz A. , Sánchez Torreño E. , Aguilar A. , Medina Lama I. , Algarra M. 
Published: February 2012

ABSTRACTA facile approach for the enantiomeric excess determination of enantiomeric mixtures without the necessity of pure enantiomer standards is presented. Promethazine and trimeprazine commercial nonracemic mixtures were used as cases study to probe the validity of the method. Chromatographic resolutions obtained with a chiral column AGP in reverse phase mode were 1.32–1.16 (promethazine) and 1.20–0.93 (trimeprazine) for the three detectors (circular dichroism, photometric and fluorimetric) in series. Results obtained showed that enantiomeric excess was 10.4, 8.71 and 8.58% for promethazine and 1.60, 1.23 and 1.80% for trimeprazine (medium values of 9.23 ± 1.01% and 1.54 ± 0.29%, respectively). Recovery assay over human serum samples, at three concentration levels, spiked with prometazine and submitted to solid‐phase extraction, gave values of 99.09–93.48% [S‐(−) enantiomer] and 98.51–91.89% [R‐(+)‐enantiomer]. Detection limits of promethazine enantiomers were between 0.02 µg (fluorimetric) and 1 µg (circular dichroism), and 0.02–1.1 µg for trimeprazine. Copyright © 2012 John Wiley & Sons, Ltd.
Maximizing the Accessibility of Active Species in Weakly Acidic Zr‐SBA‐15 Materials
Authors: Iglesias Jose , Gracia Maria Dolores , Luque Rafael , Romero Antonio A. , Melero Juan Antonio 
Published: February 2012

AbstractWeakly acidic Zr‐SBA‐15 materials were synthesized by using a novel method to maximize the accessibility of zirconium sites in view of their catalytic applications. Synthesized materials at different ageing temperatures were characterized by means of several techniques such as XRD, N2 physisorption, TEM, ammonia temperature‐programmed desorption, and X‐ray photoelectron spectroscopy and subsequently used in a test acid‐catalyzed process such as the microwave‐assisted alkylation of anisole with benzyl chloride. Reaction results revealed the very high catalytic activity of the prepared Zr‐SBA‐15 materials, which depended mostly on the accessibility of the supported zirconium species and their speciation.
Three‐Component Self‐Assembly of a Series of Triply Interlocked Pd12 Coordination Prisms and Their Non‐Interlocked Pd6 Analogues
Authors: Bar Arun Kumar , Raghothama Srinivasarao , Moon Dohyun , Mukherjee Partha Sarathi 
Published: February 2012

AbstractTemplate‐assisted formation of multicomponent Pd6 coordination prisms and formation of their self‐templated triply interlocked Pd12 analogues in the absence of an external template have been established in a single step through PdN/PdO coordination. Treatment of cis‐[Pd(en)(NO3)2] with K3tma and linear pillar 4,4′‐bpy (en=ethylenediamine, H3tma=benzene‐1,3,5‐tricarboxylic acid, 4,4′‐bpy=4,4′‐bipyridine) gave intercalated coordination cage [{Pd(en)}6(bpy)3(tma)2]2[NO3]12 (1) exclusively, whereas the same reaction in the presence of H3tma as an aromatic guest gave a H3tma‐encapsulating non‐interlocked discrete Pd6 molecular prism [{Pd(en)}6(bpy)3(tma)2(H3tma)2][NO3]6 (2). Though the same reaction using cis‐[Pd(NO3)2(pn)] (pn=propane‐1,2‐diamine) instead of cis‐[Pd(en)(NO3)2] gave triply interlocked coordination cage [{Pd(pn)}6(bpy)3(tma)2]2[NO3]12 (3) along with non‐interlocked Pd6 analogue [{Pd(pn)}6(bpy)3(tma)2](NO3)6 (3′), and the presence of H3tma as a guest gave H3tma‐encapsulating molecular prism [{Pd(pn)}6(bpy)3(tma)2(H3tma)2][NO3]6 (4) exclusively. In solution, the amount of 3′ decreases as the temperature is decreased, and in the solid state 3 is the sole product. Notably, an analogous reaction using the relatively short pillar pz (pz=pyrazine) instead of 4,4′‐bpy gave triply interlocked coordination cage [{Pd(pn)}6(pz)3(tma)2]2[NO3]12 (5) as the single product. Interestingly, the same reaction using slightly more bulky cis‐[Pd(NO3)2(tmen)] (tmen=N,N,N′,N′‐tetramethylethylene diamine) instead of cis‐[Pd(NO3)2(pn)] gave non‐interlocked [{Pd(tmen)}6(pz)3(tma)2][NO3]6 (6) exclusively. Complexes 1, 3, and 5 represent the first examples of template‐free triply interlocked molecular prisms obtained through multicomponent self‐assembly. Formation of the complexes was supported by IR and multinuclear NMR (1H and 13C) spectroscopy. Formation of guest‐encapsulating complexes (2 and 4) was confirmed by 2D DOSY and ROESY NMR spectroscopic analyses, whereas for complexes 1, 3, 5, and 6 single‐crystal X‐ray diffraction techniques unambiguously confirmed their formation. The gross geometries of H3tma‐encapsulating complexes 2 and 4 were obtained by universal force field (UFF) simulations.
Formation of a Hydrogen‐Bonded Heptazine Framework by Self‐Assembly of Melem into a Hexagonal Channel Structure
Authors: Makowski Sophia J. , Köstler Pia , Schnick Wolfgang 
Published: February 2012

AbstractSelf‐assembly of melem C6N7(NH2)3 in hot aqueous solution leads to the formation of hydrogen‐bonded, hexagonal rosettes of melem units surrounding infinite channels with a diameter of 8.9 Å. The channels are filled with strongly disordered water molecules, which are bound to the melem network through hydrogen bonds. Single‐crystals of melem hydrate C6N7(NH2)3⋅xH2O (x≈2.3) were obtained by hydrothermal treatment of melem at 200 °C and the crystal structure (R $\bar 3$c, a=2879.0(4), c=664.01(13) pm, V=4766.4(13)×106 pm3, Z=18) was elucidated by single‐crystal X‐ray diffraction. With respect to the structural similarity to the well‐known adduct between melamine and cyanuric acid, the composition of the obtained product was further analyzed by solid‐state NMR spectroscopy. Hydrolysis of melem to cyameluric acid during syntheses at elevated temperatures could thus be ruled out. DTA/TG studies revealed that, during heating of melem hydrate, water molecules can be removed from the channels of the structure to a large extent. The solvent‐free framework is stable up to 430 °C without transforming into the denser structure of anhydrous melem. Dehydrated melem hydrate was further characterized by solid‐state NMR spectroscopy, powder X‐ray diffraction, and sorption measurements to investigate structural changes induced by the removal of water from the channels. During dehydration, the hexagonal, layered arrangement of melem units is maintained whereas the formation of additional hydrogen bonds between melem entities requires the stacking mode of hexagonal layers to be altered. It is assumed that layers are shifted perpendicular to the direction of the channels, thereby making them inaccessible for guest molecules.
Solid Acid‐Catalyzed Cellulose Hydrolysis Monitored by In Situ ATR‐IR Spectroscopy
Authors: Zakzeski Joseph , Grisel Ruud J. H. , Smit Arjan T. , Weckhuysen Bert M. 
Published: February 2012

AbstractThe solid acid‐catalyzed hydrolysis of cellulose was studied under elevated temperatures and autogenous pressures using in situ ATR‐IR spectroscopy. Standards of cellulose and pure reaction products, which include glucose, fructose, hydroxymethylfurfural (HMF), levulinic acid (LA), formic acid, and other compounds, were measured in water under ambient and elevated temperatures. A combination of spectroscopic and HPLC analysis revealed that the cellulose hydrolysis proceeds first through the disruption of the glycosidic linkages of cellulose to form smaller cellulose molecules, which are readily observed by their distinctive CO vibrational stretches. The continued disruption of the linkages in these oligomers eventually results in the formation and accumulation of monomeric glucose. The solid‐acid catalyst accelerated the isomerization of glucose to fructose, which then rapidly reacted under hydrothermal conditions to form degradation products, which included HMF, LA, formic acid, and acetic acid. The formation of these species could be suppressed by decreasing the residence time of glucose in the reactor, reaction temperature, and contact with the metal reactor. The hydrolysis of regenerated cellulose proceeded faster and under milder conditions than microcrystalline cellulose, which resulted in increased glucose yield and selectivity.
Synthesis of Furfural from Xylose, Xylan, and Biomass Using AlCl3⋅6 H2O in Biphasic Media via Xylose Isomerization to Xylulose
Authors: Yang Yu , Hu Chang‐Wei , Abu‐Omar Mahdi M. 
Published: February 2012

AbstractFurfural was prepared in high yields (75 %) from the reaction of xylose in a water–tetrahydrofuran biphasic medium containing AlCl3⋅6 H2O and NaCl under microwave heating at 140 °C. The reaction profile revealed the formation of xylulose as an intermediate en route to the dehydration product (furfural). The reaction under these conditions reached completion in 45 min. The aqueous phase containing AlCl3⋅6 H2O and NaCl could be recycled multiple times (>5) without any loss of activity or selectivity for furfural. Extension of this biphasic reaction system to include xylan as the starting material afforded furfural in 64 % yield. The use of corn stover, pinewood, switchgrass, and poplar gave furfural in 55, 38, 56, and 64 % yield, respectively, at 160 °C. Even though AlCl3⋅6 H2O did not affect the conversion of crystalline cellulose, moderate yields of the by‐product 5‐hydroxymethylfurfural (HMF) were noted. The highest HMF yield of 42 % was obtained from pinewood. The coproduction of HMF and furfural from biomass was attributed to the weakening of the cellulose network in the biomass, as a result of hemicellulose hydrolysis. The multifunctional capacity of AlCl3⋅6 H2O (hemicellulose hydrolysis, xylose isomerization, and xylulose dehydration) in combination with its ease of recyclability make it an attractive candidate/catalyst for the selective synthesis of furfural from various biomass feedstocks.
Prospectively assessed early life experiences in relation to cortisol reactivity in adolescents at risk for asthma
Authors: Kelsay Kim , Leung Donald Y.M. , Mrazek David A. , Klinnert Mary D. 
Published: February 2012

AbstractAltered cortisol reactivity in individuals with asthma likely increases the risk of inflammation in the face of stress. Understanding antecedents of cortisol reactivity enhances knowledge of factors affecting asthma. Forty‐eight subjects genetically predisposed for asthma, recruited from a study that assessed them from birth, completed a laboratory stress procedure and self‐report measures at ages 17–19 years. Observation and parent reports from age 0 to 2 years were used to create a parent child relationship risk variable and to define criteria for a cumulative risk variable. In repeated measures analysis of 46 adolescents, those who had experienced early parent child relationship problems, specifically insecure attachment, had an attenuated cortisol stress response, even after controlling for concurrent psychological function and recent stressors (F = 4.6, p < .005). Cortisol stress response was not related to asthma status. This study supports a relationship between the parent child relationship during the first 2 years of life and later cortisol response to stress in youth at genetic risk for asthma. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 133–144, 2013
Salivary alpha‐amylase during pregnancy: Diurnal course and associations with obstetric history, maternal demographics, and mood
Authors: Giesbrecht Gerald F. , Granger Douglas A. , Campbell Tavis , Kaplan Bonnie ,   the APrON Study Team
Published: February 2012

AbstractDiurnal patterns of salivary alpha amylase (sAA) in pregnant women have not previously been described. The current study employed ecological momentary assessment to examine the association between the diurnal sAA, obstetric history, maternal demographics, and mood during pregnancy. Saliva was self‐collected by 83 pregnant women (89% White, age 25.3–43.0 years; mean gestational age 21.9 weeks, range 6–37 weeks; gravida 1–6) at home over three days. Results indicated that current pregnancy (gestational age and fetal sex) and maternal demographics were not related to diurnal sAA. In contrast, a history of previous miscarriage (Parameter = −.17; SE = .05; p < .05) was associated with an atypical diurnal pattern. Even after accounting for obstetric history, trait anxiety (Parameter = .16; SE = .04; p < .001) was associated with increased sAA over the day while chronic levels of fatigue (Parameter = −.06; SE = .03; p < .05) were associated with decreased sAA. In a separate model, we also tested the time varying covariation of sAA and mood. The effects of momentary mood were in contrast to those for trait mood. Both momentary depression (Parameter = .22; SE = .09; p < .01) and vigour/positive mood (Parameter = .12; SE = .04; p < .001) were associated with momentary increases in sAA while momentary anxiety and fatigue were not related to sAA. The findings suggest that basal sAA during pregnancy is sensitive to emotional arousal. Evaluating diurnal patterns of sAA holds promise for advancing understanding of how emotional arousal during pregnancy may affect fetal development. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 156–167, 2013
Early maternal care predicts reliance on social learning about food in adult rats
Authors: Lindeyer Charlotte M. , Meaney Michael J. , Reader Simon M. 
Published: February 2012

AbstractMany vertebrates rely extensively on social information, but the value of information produced by other individuals will vary across contexts and habitats. Social learning may thus be optimized by the use of developmental or current cues to determine its likely value. Here, we show that a developmental cue, early maternal care, correlates with social learning propensities in adult rodents. The maternal behavior of rats Rattus norvegicus with their litters was scored over the first 6 days postpartum. Rat dams show consistent individual differences in the rate they lick and groom (LG) pups, allowing them to be categorized as high, low, or mid‐LG mothers. The 100‐day old male offspring of high and low‐LG mothers were given the opportunity to learn food preferences for novel diets from conspecifics that had previously eaten these diets (“demonstrators”). Offspring of high‐LG mothers socially learned food preferences, but offspring of low‐LG mothers did not. We administered oxytocin to subjects to address the hypothesis that it would increase the propensity for social learning, but there were no detectable effects. Our data raise the possibility that social learning propensities may be both relatively stable throughout life and part of a suite of traits “adaptively programmed” by early developmental experiences. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 168–175, 2013
Amniotic fluid elicits appetitive responses in human newborns: Fatty acids and appetitive responses
Authors: Contreras Carlos M. , Gutiérrez‐García Ana G. , Mendoza‐López Remedios , Rodríguez‐Landa Juan Francisco , Bernal‐Morales Blandina , Díaz‐Marte Cynthia 
Published: February 2012

AbstractIn humans, maternal cues guide newborns to the maternal breast, and transitional cues may be present in maternal–fetal fluids. The aim of the present study was to determine the consistent presence of sensorial cues in three maternal–fetal fluids—amniotic fluid, colostrum, and milk—and test the ability of these cues to produce appetitive responses in newborns. In the analytical study, gas chromatography‐mass spectrometry (GC‐MS) detected eight fatty acids consistently present in the amniotic fluid, colostrum, and milk from 12 healthy volunteers, but we do not find a mammalian pheromone, identified in another mammalian species (rabbits), in another 30 volunteers. In the behavioral study, we explored the ability of amniotic fluid or its fatty acids to produce appetitive responses in 19 human newborns <24 hr after birth. Exposure to swabs impregnated with amniotic fluid or an artificial fatty acid mixture produced a longer duration of facial reactions that suggested appetitive (sucking) movements compared with respective vehicles (i.e., propylene glycol or centrifuged amniotic fluid with a low fatty acid content verified by GC‐MS). We conclude that the fatty acids contained in amniotic fluid may constitute a transitional sensorial cue that guides newborns to the maternal breast. © 2012 Wiley Periodicals, Inc. Dev Psychobiol 55: 221–231, 2013
Altruism and the evolution of resource generalism and specialism
Authors: Bonsall Michael B. , Wright Alison E. 
Published: February 2012

AbstractThe evolution of resource specialism and generalism has attracted widespread interest. Evolutionary drivers affecting niche differentiation and resource specialization have focused on the role of trade‐offs. Here, however, we explore how the role of cooperation, mediated through altruistic behaviors, and classic resource–consumer dynamics can influence the evolution of resource utilization. Using an evolutionary invasion approach, we investigate how critical thresholds in levels of altruism are needed for resource specialization to arise and be maintained. Differences between complementary (essential) and substitutable resources affect the evolution of resource generalists. The strength of resource preferences coupled with the levels of altruism are predicted to influence the evolution of generalism. Coupling appropriate evolutionary game and ecological dynamics lead to novel expectations in the feedbacks between social behaviors and population dynamics for understanding classic ecological problems.
Inelastic displacement ratio of near‐source pulse‐like ground motions
Authors: Iervolino Iunio , Chioccarelli Eugenio , Baltzopoulos Georgios 
Published: February 2012

SUMMARYNear‐source pulse‐like records resulting from rupture's directivity have been found to depart from so‐called ordinary ground motions in terms of both elastic and inelastic structural seismic demands. In fact, response spectra may be strong if compared with what is expected from common ground motion prediction equations. Moreover, because not all spectral ordinates are affected uniformly, a peculiar spectral shape, with an especially amplified region depending on the pulse period, may follow. Consequently, inelastic seismic demand may show trends different to records not identified as pulse‐like (i.e., ordinary). This latter aspect is addressed in the study reported in this short communication, where a relatively large dataset of identified impulsive near‐source records is used to derive an analytical‐form relationship for the inelastic displacement ratio. It is found that, similar to what was proposed in literature for soft soil sites, a double‐opposite‐bumps form is required to match the empirical data as a function of the structural period over the pulse period ratio. The relationship builds consistently on previous studies on the topic, yet displays different shape with respect to the most common equations for static structural assessment procedures. Copyright © 2012 John Wiley & Sons, Ltd.
Bedload transport measurements at the Erlenbach stream with geophones and automated basket samplers
Authors: Rickenmann Dieter , Turowski Jens M. , Fritschi Bruno , Klaiber Angela , Ludwig Andreas 
Published: February 2012

ABSTRACTIn the Erlenbach stream, a pre‐alpine steep channel in Switzerland, sediment transport has been monitored for more than 25 years. Near the confluence with the main valley river, stream flow is monitored and sediment is collected in a retention basin with a capacity of about 2000 m3. The basin is surveyed at regular intervals and after large flood events. In addition, sediment transport has been continuously monitored with piezoelectric bedload impact and geophone sensors since 1986. In 2008–2009, the measuring system in the Erlenbach stream was enhanced by installing an automatic system to obtain bedload samples. Movable metal baskets are mounted on a rail at the downstream wall of the large check dam above the retention basin, and they can be moved automatically into the flow to take bedload transport samples. The wire mesh of the baskets has a spacing of 10 mm to sample all sediment particles coarser than this size (which is about the limiting grain size detected by the geophones). The upgraded measuring system permits to obtain bedload samples over short sampling periods and to measure the grain size distribution of the transported material and its variation over time and with discharge. The analysis of calibration relationships for the geophone measuring system confirms findings from very similar measurements which were performed until 1999 with piezoelectric bedload impact sensors; there is a linear relationship between impulse counts and bedload mass passing over the sensors. Findings from flume experiments are used to discuss the most important factors which affect the calibration of the geophone signal. The bedload transport rates as measured by the moving baskets are among the highest measured in natural streams, with values of the order of several kilograms per meter per second. Copyright © 2012 John Wiley & Sons, Ltd.
The acute effects of kava and oxazepam on anxiety, mood, neurocognition; and genetic correlates: a randomized, placebo‐controlled, double‐blind study
Authors: Sarris J. , Scholey A. , Schweitzer I. , Bousman C. , LaPorte E. , Ng C. , Murray G. , Stough C. 
Published: February 2012

RationaleKava (Piper methysticum) is a psychotropic plant medicine with history of cultural and medicinal use. We conducted a study comparing the acute neurocognitive, anxiolytic, and thymoleptic effects of a medicinal dose of kava to a benzodiazepine and explored for the first time specific genetic polymorphisms, which may affect the psychotropic activity of phytomedicines or benzodiazepines.MethodsTwenty‐two moderately anxious adults aged between 18 and 65 years were randomized to receive an acute dose of kava (180 mg of kavalactones), oxazepam (30 mg), and placebo 1 week apart in a crossover design trial.ResultsAfter exposure to cognitive tasks, a significant interaction was revealed between conditions on State–Trait Anxiety Inventory‐State anxiety (p = 0.046, partial ŋ² = 0.14). In the oxazepam condition, there was a significant reduction in anxiety (p = 0.035), whereas there was no change in anxiety in the kava condition, and there was an increase in anxiety in the placebo condition. An increase in Bond–Lader “calmness” (p = 0.002) also occurred for the oxazepam condition. Kava was found to have no negative effect on cognition, whereas a reduction in alertness (p < 0.001) occurred in the oxazepam condition. Genetic analyses provide tentative evidence that noradrenaline (SLC6A2) transporter polymorphisms may have an effect on response to kava.ConclusionAcute “medicinal level” doses of this particular kava cultivar in naive users do not provide anxiolytic activity, although the phytomedicine also appears to have no negative effects on cognition. Copyright © 2012 John Wiley & Sons, Ltd.
Preparation of 2‐, 4‐, 5‐, and 6‐aminonicotinic acid tert‐butyl esters
Authors: Wright Stephen W. 
Published: February 2012

AbstractProcedures are reported to prepare the tert‐butyl esters of 2‐aminonicotinic acid, 4‐aminonicotinic acid, 5‐aminonicotinic acid, and 6‐aminonicotinic acid from 2‐chloronicotinic acid, 4‐chloronicotinic acid, 5‐bromonicotinic acid, and 6‐chloronicotinic acid, respectively, without need for purification of intermediates. J. Heterocyclic Chem., (2012).