bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elucidating the Structure of Chiral Molecules by using Amplified Vibrational Circular Dichroism: From Theory to Experimental Realization
Authors: Domingos Sérgio R. , Hartl František , Buma Wybren Jan , Woutersen Sander 
Published: August 2015

AbstractRecent experimental observations of enhanced vibrational circular dichroism (VCD) in molecular systems with low‐lying electronically excited states suggest interesting new applications of VCD spectroscopy. The theory describing VCD enhancement through vibronic coupling schemes was derived by Nafie in 1983, but only recently experimental evidence of VCD amplification has demonstrated the extent to which this effect can be exploited as a structure elucidation tool to probe local structure. In this Concept paper, we give an overview of the physics behind vibrational circular dichroism, in particular the equations governing the VCD amplification effect, and review the latest experimental developments with a prospective view on the application of amplified VCD to locally probe biomolecular structure.
A Study of the Solvation Structure of l‐Leucine in Alcohol–Water Binary Solvents through Molecular Dynamics Simulations and FTIR and NMR Spectroscopy
Authors: Takamuku Toshiyuki , Hatomoto Yohei , Tonegawa Junko , Tsutsumi Youichi , Umecky Tatsuya 
Published: August 2015

AbstractThe solvation structures of l‐leucine (Leu) in aliphatic‐alcohol–water and fluorinated‐alcohol–water solvents are elucidated for various alcohol contents by using molecular dynamics (MD) simulations and IR, and 1H and 13C NMR spectroscopy. The aliphatic alcohols included methanol, ethanol, and 2‐propanol, whereas the fluorinated alcohols were 2,2,2‐trifluoroethanol and 1,1,1,3,3,3‐hexafluoro‐2‐propanol. The MD results show that the hydrophobic alkyl moiety of Leu is surrounded by the alkyl or fluoroalkyl groups of the alcohol molecules. In particular, TFE and HFIP significantly solvate the alkyl group of Leu. IR spectra reveal that the Leu C−H stretching vibration blueshifts in fluorinated alcohol solutions with increasing alcohol content, whereas the vibration redshifts in aliphatic alcohol solutions. When the C−H stretching vibration blueshifts in the fluorinated alcohol solutions, the hydrogen and carbon atoms of the Leu alkyl group are magnetically shielded. Consequently, TFE and HFIP molecules may solvate the Leu alkyl group through the blue‐shifting hydrogen bonds.
Understanding of Surface Redox Behaviors of Li2MnO3 in Li‐Ion Batteries: First‐Principles Prediction and Experimental Validation
Authors: Kim Duho , Lim Jin‐Myoung , Lim Young‐Geun , Park Min‐Sik , Kim Young‐Jun , Cho Maenghyo , Cho Kyeongjae 
Published: August 2015

AbstractCritical degradation mechanism of many cathode materials for Li‐ion batteries is closely related to phase transformations at the surface/interface. Li2MnO3 in x Li2MnO3⋅(1−x) LiMO2 (M=Ni, Co, Mn) provides high capacity, but the Li2MnO3 phase is known to degrade during cycling through phase transformation and O2 evolution. To resolve such degradation problems, it is critical to develop a fundamental understanding of the underlying mechanism. Using first‐principles calculations, we identified the surface delithiation potential (<4.5 V vs. Li/Li+) of Li2MnO3, which is significantly lower than the bulk redox potential. A lower Mn oxidation state at the surface would reduce the delithiation potential compared with the fully oxidized Mn4+ in the bulk. As a result, the delithiation would be initiated from the surface, which induces a phase transformation of Li2MnO3 into a spinel‐like structure from the surface. These theoretical findings have been confirmed by experimental analyses. Based on these detailed mechanistic understanding, it would be possible to develop rational approaches to modify and coat the surface to suppress degradation mechanisms.
Tunable selective receiver front end with impedance transformation filtering
Authors: Qazi Fahad , Duong Quoc‐Tai , Dąbrowski Jerzy 
Published: August 2015

SummaryA highly selective impedance transformation filtering technique suitable for tunable selective RF receivers is presented in this paper. To achieve blocker rejection comparable with surface acoustic wave (SAW) filters, we use a two‐stage architecture based on a low‐noise transconductance amplifier (LNTA). The filter rejection is captured by a linear periodically varying model that includes band limitation by the LNTA output impedance and the related parasitic capacitances of the impedance transformation circuit. This model is also used to estimate ‘back folding’ by interferers placed at harmonic frequencies. Discussed is also the effect of thermal noise folding and phase noise on the circuit noise figure. As a proof of concept, a chip design of a tunable RF front end using 65 nm complementary metal‐oxide‐semiconductor (CMOS) technology is presented. In measurements, the circuit achieves blocker rejection competitive to SAW filters with noise figure 3.2–5.2 dB, out of band IIP3 > +17 dBm, and blocker P1dB > +5 dBm over frequency range of 0.5–3 GHz. Copyright © 2015 John Wiley & Sons, Ltd.
Examining biological vulnerability in environmental context: Parenting moderates effects of low resting respiratory sinus arrhythmia on adolescent depressive symptoms
Authors: Mezulis Amy H. , Crystal Sarah I. , Ahles Joshua J. , Crowell Sheila E. 
Published: August 2015

ABSTRACTPolyvagal theory suggests that parasympathetic regulation of cardiac function, indexed by resting respiratory sinus arrhythmia (RSA), may be a marker of emotion regulatory capacity and associated with youth psychopathology. Contemporary models of psychopathology suggest that the effects of biological vulnerability may be moderated by developmental context. The aim of the present study was to examine whether parenting, particularly parental responses to youth's negative emotions, moderated the effects of resting RSA on depressive symptoms among early adolescents. We examined resting RSA, depressive symptoms, and parental responses to youth negative emotions among 120 adolescents aged 11–14 years (M = 12.86, SD = .85; 52.5% female). Resting RSA and lack of supportive parenting interacted to predict youth depressive symptoms, such that low resting RSA predicted more depressive symptoms only in the context of low levels of supportive parental responses to youth's negative emotions. By contrast, high resting RSA buffered the effects of low supportive parenting on youth depressive symptoms. These findings highlight the importance of understanding joint contributions of biological vulnerability and developmental context on youth depression outcomes. © 2015 Wiley Periodicals, Inc. Dev Psychobiol 57: 974–983, 2015.
Characterizing dominant controls governing evapotranspiration within a natural saline fen in the Athabasca Oil Sands of Alberta, Canada
Authors: Phillips T. , Petrone R. M. , Wells C. M. , Price J. S. 
Published: August 2015

AbstractNatural Boreal saline fens provide analogues for reclaimed wetland systems constructed with sodium‐rich tailings materials. These natural analogues can improve our understanding of vegetative controls on dominant ecohydrological processes (i.e. evapotranspiration (ET)) in constructed landscapes. Therefore, the objective of this study is to characterize ET within a natural boreal saline fen over a growing season to determine the primary hydro‐climatic controls using community‐scale ET measurements targeting dominant vegetation communities within different microforms along with environmental controls.ET rates were highest during periods of peak vegetation growth and temperatures between June and August, with rates decreasing slightly in July. Vegetation species' physiology was the dominant variable governing ET. The more salt tolerant species maintained higher ET rates despite the lower leaf area index and water table levels found within these species. The lower ET rates measured in July can be attributed to high water tables from above average precipitation causing soil inundation and salt stress, increasing stomatal closure. However, community plots containing Triglochin maritima maintained transpiration rates under the coupled stress conditions. Therefore, this is a potentially important species for use in boreal reclamation planting schemes. Last, the findings emphasize that the dominant vegetation selected for reclamation projects must coincide with the materials used (peat and subsurface materials), as results within this study demonstrate that some native boreal fen species (Calamagrostis inexpansa, Hordeum jubatum, and Juncus balticus) were unable to maintain transpiration rates during flood and saline conditions that can occur within the mining area of this region. Copyright © 2015 John Wiley & Sons, Ltd.
Coal Char Gasification on a Circulating Fluidized Bed for Hydrogen Generation: Experiments and Simulation
Authors: Zhang Rui , Liu Dong , Wang Qinhui , Luo Zhongyang , Fang Mengxiang , Cen Kefa 
Published: August 2015

AbstractChar is the solid product of coal pyrolysis and its utilization is closely related to the scale of coal pyrolysis and tar processing. Char gasification is a promising choice for char utilization as it can provide hydrogen, which is needed for tar hydrogenation and chemical synthesis. However, reliable and mature coal char gasification technology has not yet been developed. The fluidized bed has been adopted as a gasifier in many studies, and its gasification temperature is relatively low. In this work, the feasibility of char gasification using a fluidized bed has been studied. A pyrolyzed bituminous coal char was gasified in a mixture of O2 and steam using a circulating fluidized bed. The height of the fluidized bed is 2360 mm and the inner diameter is 66 mm. The reactor is made of Ni‐Cd alloy steel, and a loopseal was used for solid circulation. In the experiments, the gasification temperature was varied between 870 and 900 °C, and the effects of O2/char and steam/char mass ratios on the gasification results were analyzed. The volume fraction of combustible gas, dry gas yield, carbon conversion, and lower heating value of the best case were 43.92 %, 1.64 Nm3 kg−1, 0.85, and 5.17 MJ N m−3, respectively. In addition, a simple model and a complex model were established by using Aspen Plus software. The two models were used to simulate char gasification, and the simulation results were validated with the experimental results. The results indicated that the complex model is more accurate than the simple model and is more suitable to simulate char gasification in a circulating fluidized bed.
Reliability correction for functional connectivity: Theory and implementation
Authors: Mueller Sophia , Wang Danhong , Fox Michael D. , Pan Ruiqi , Lu Jie , Li Kuncheng , Sun Wei , Buckner Randy L. , Liu Hesheng 
Published: August 2015

AbstractNetwork properties can be estimated using functional connectivity MRI (fcMRI). However, regional variation of the fMRI signal causes systematic biases in network estimates including correlation attenuation in regions of low measurement reliability. Here we computed the spatial distribution of fcMRI reliability using longitudinal fcMRI datasets and demonstrated how pre‐estimated reliability maps can correct for correlation attenuation. As a test case of reliability‐based attenuation correction we estimated properties of the default network, where reliability was significantly lower than average in the medial temporal lobe and higher in the posterior medial cortex, heterogeneity that impacts estimation of the network. Accounting for this bias using attenuation correction revealed that the medial temporal lobe's contribution to the default network is typically underestimated. To render this approach useful to a greater number of datasets, we demonstrate that test‐retest reliability maps derived from repeated runs within a single scanning session can be used as a surrogate for multi‐session reliability mapping. Using data segments with different scan lengths between 1 and 30 min, we found that test‐retest reliability of connectivity estimates increases with scan length while the spatial distribution of reliability is relatively stable even at short scan lengths. Finally, analyses of tertiary data revealed that reliability distribution is influenced by age, neuropsychiatric status and scanner type, suggesting that reliability correction may be especially important when studying between‐group differences. Collectively, these results illustrate that reliability‐based attenuation correction is an easily implemented strategy that mitigates certain features of fMRI signal nonuniformity. Hum Brain Mapp, 2015. © 2015 Wiley Periodicals, Inc.
Functional morphology of durophagy in black carp,Mylopharyngodon piceus
Authors: Gidmark Nicholas J. , Taylor Chantel , LoPresti Eric , Brainerd Elizabeth 
Published: August 2015

ABSTRACTThe black carp,Mylopharyngodon piceus(Osteichthyes: Cyprinidae), crushes its snail and other molluscan prey with robust pharyngeal jaws and strong bite forces. Using gross morphology, histological sectioning, and X‐ray reconstruction of moving morphology (XROMM), we investigated structural, behavioral, and mechanical aspects of pharyngeal jaw function in black carp. Strut‐like trabeculae in their pharyngeal jaws support large, molariform teeth. The teeth occlude with a hypertrophied basioccipital process that is also reinforced with stout trabeculae. A keratinous chewing pad is firmly connected to the basioccipital process by a series of small bony projections from the base of the pedestal. The pharyngeal jaws have no bony articulations with the skull, and their position is controlled by five paired muscles and one unpaired median muscle. Black carp can crush large molluscs, so we used XROMM to compare pharyngeal jaw postures as fish crushed ceramic tubes of increasing sizes. We found that black carp increase pharyngeal jaw gape primarily by ventral translation of the jaws, with ventral rotation and lateral flaring of the jaws also increasing the space available to accommodate large prey items. A stout, robust ligament connects left and right jaws together firmly, but allows some rotation of the jaws relative to each other. Contrasting with the pharyngeal jaw mechanism of durophagous perciforms with fused left and right lower pharyngeal jaws, we hypothesize that this ligamentous connection may serve to decouple tensile and compressive forces, with the tensile forces borne by the ligament and the compressive forces transferred to the prey. J. Morphol. 276:1422–1432, 2015. © 2015 Wiley Periodicals, Inc.
Effect of increasing the flip angle during the hepatocyte phase of gadobenate dimeglumine‐enhanced 1.5T MRI in cirrhotic patients with hepatocellular carcinoma
Authors: Lee Eun Jung , Kim Dae Jung , Cho Eun‐Suk , Kim Kyoung Ah 
Published: August 2015

PurposeTo evaluate the effects of increasing the flip angle during the hepatocyte phase of gadobenate dimeglumine‐enhanced magnetic resonance imaging (MRI) in cirrhotic patients with hepatocellular carcinoma (HCC).Materials and MethodsSixty‐three patients with liver cirrhosis underwent gadobenate dimeglumine‐enhanced 1.5T MRI with 90‐minute delayed hepatocyte phase with flip angles of 10°, 20°, 30°, consecutively. Relative enhancement and signal‐to‐noise ratio (SNR) of liver parenchyma at hepatocyte phase according to flip angle were calculated. The liver‐to‐lesion (low signal intensity HCCs, n = 63; ≥1 cm) and contrast‐to‐noise ratio (CNR) at the hepatocyte phase according to flip angle were calculated. Two radiologists independently assessed the presence of HCCs using a 5‐point scale, and detection sensitivity of HCCs was calculated according to flip angle.ResultsThe relative enhancement of hepatic parenchyma differed significantly according to flip angle (10°, mean relative enhancement = 0.69 ± 0.46; 20°, mean relative enhancement = 0.63 ± 0.47; 30°, mean relative enhancement = 0.49 ± 0.45; P = 0.043). The SNR of hepatic parenchyma was significantly different according to flip angle (10°, mean SNR = 26.2 ± 5.6; 20°, mean SNR = 25.3 ± 5.7; 30°, mean SNR = 22.8 ± 6.1; P = 0.004). The CNR of lesion was not significantly different according to flip angle (10°, mean CNR = 7.5 ± 6.6; 20°, mean CNR = 10.2 ± 6.9; 30°, mean CNR = 10.1 ± 7.1; P = 0.051). The sensitivities with 10° and 20° for HCCs were significantly higher than those with 30° for one reader (P < 0.05).ConclusionIn patients with cirrhosis, hepatocyte phase gadobenate dimeglumine‐enhanced 1.5T MRI with 20° flip angle should be recommended rather than 10° and 30° flip angle. J. MAGN. RESON. IMAGING 2016;43:713–719.
Analysis of wild sunflower (Helianthus annuus L.) root exudates using gas chromatography‐mass spectrometry
Authors: Bowsher Alan W. , Ali Rifhat , Harding Scott A. , Tsai Chung‐Jui , Donovan Lisa A. 
Published: August 2015

AbstractPlant root systems mediate ecological processes in the rhizosphere through the exudation of organic compounds. Although exudate composition is thought to depend strongly on plant nutrient status, little is known about the influence of multi‐nutrient stresses. In this study, we examined responses to short‐term (3 d) nutrient limitation in Helianthus annuus (common sunflower), and root exudates were collected for 2, 4, or 6 h with the trap‐solution method. Root exudates, analyzed by means of gas chromatography‐mass spectrometry, consisted of over 60 sugars, sugar alcohols, amino acids, organic acids, and phosphates, with sugars and organic acids generally detected in the highest quantities. Twenty‐five of the detected metabolites, including half of the organic acids, sugars, and sugar alcohols, differed in relative abundance among the three sampling intervals, exhibiting higher abundance in sampling intervals greater than 2 h. Similarly, 24 of the detected metabolites, including half of the amino acids, phosphates, and sugar alcohols, were affected by nutrient supply, with 20 exhibiting higher abundance in the high‐nutrient treatment. Fumaric acid, quinic acid, and glucose were detected at significantly higher levels in the low‐nutrient treatment, potentially representing an adaptive response to nutrient limitation in sunflower. However, as sampling interval exerted a strong influence on the apparent effects of nutrient supply, future studies should consider the potential impacts of sampling‐interval length in comparative analyses of genotypes or treatments.
Root morphological traits related to phosphorus‐uptake efficiency of soybean, sunflower, and maize
Authors: Fernandez Mariana Cecilia , Rubio Gerardo 
Published: August 2015

AbstractMany of the plant acquisition strategies for immobile nutrients, such as phosphorus (P), are related to the maximization of soil exploration at minimum metabolic cost. Previous studies have suggested that soybean (Glycine max L.), sunflower (Helianthus annuus L.), and maize (Zea mays L.) differ in their P uptake efficiency. In this investigation we employed these three species to evaluate: (1) the effect of suboptimal P conditions on root morphological traits related to root porosity and fineness and (2) how these traits are related to P‐uptake efficiency. Opaque 25‐L plastic containers were used to grow plants hydroponically. The three species were compared under two P availability levels (low P and high P). Most of the observed responses were in the direction to favor P uptake under low‐P conditions. Compared to P‐sufficient plants, P‐stressed plants of the three species showed higher root‐to‐shoot ratio, specific root length, root porosity and root aerenchyma, and a lower root density. For example, P‐stress increased root porosity by a factor of 2.0, 1.4, and 1.4 in soybean, sunflower, and maize, respectively. Soybean and sunflower were the species with the highest P‐uptake efficiency, expressed as P uptake either per unit root biomass or length. The results demonstrate the central role of aerenchyma development in modifying root length per unit root biomass and, thus, reducing the root's foraging costs. Consequently, aerenchyma is suggested to be a possible mechanism for better P‐uptake efficiency.
Sensitive determination of methadone in human serum and urine by dispersive liquid–liquid microextraction based on the solidification of a floating organic droplet followed by HPLC–UV
Authors: Taheri Salman , Jalali Fahimeh , Fattahi Nazir , Jalili Ronak , Bahrami Gholamreza 
Published: August 2015

Dispersive liquid–liquid microextraction based on solidification of floating organic droplet was developed for the extraction of methadone and determination by high‐performance liquid chromatography with UV detection. In this method, no microsyringe or fiber is required to support the organic microdrop due to the usage of an organic solvent with a low density and appropriate melting point. Furthermore, the extractant droplet can be collected easily by solidifying it at low temperature. 1‐Undecanol and methanol were chosen as extraction and disperser solvents, respectively. Parameters that influence extraction efficiency, i.e. volumes of extracting and dispersing solvents, pH, and salt effect, were optimized by using response surface methodology. Under optimal conditions, enrichment factor for methadone was 134 and 160 in serum and urine samples, respectively. The limit of detection was 3.34 ng/mmL in serum and 1.67 ng/mL in urine samples. Compared with the traditional dispersive liquid–liquid microextraction, the proposed method obtained lower limit of detection. Moreover, the solidification of floating organic solvent facilitated the phase transfer. And most importantly, it avoided using high‐density and toxic solvents of traditional dispersive liquid–liquid microextraction method. The proposed method was successfully applied to the determination of methadone in serum and urine samples of an addicted individual under methadone therapy.
Spatial Heterogeneity of Soil C:N Ratio in a Mollisol Watershed of Northeast China
Authors: Zhang Shaoliang , Yan Lilong , Huang Jing , Mu Linlin , Huang Yiquan , Zhang Xingyi , Sun Yankun 
Published: August 2015

AbstractThe spatial variability of the soil C:N ratio (C:N) influences C and N leaching and basic fertility in the field. This paper aims to identify the spatial heterogeneity of C:N in a Mollisol watershed of Northeast China and determine the main mechanisms that drive these differences. A random sampling method was used, with both geostatistical and traditional analysis being used to describe the spatial distribution of the C:N at various depths. C:N was also compared between slope position, previous vegetation and tillage methods in the watershed. The horizontal distribution of the C:N was mainly influenced by structural factors (88·4–99·9%) and often gradually deceased along the hydrographic flow direction, becoming lowest at the watershed outlet. The C:N increased as soil depth increased at all slope positions, and was higher on the back slope than on summit slope, followed by bottom slope in all soil depths. C:N was negatively (significant at p < 0·01) correlated to TN, and positively (significant at p < 0·05) correlated to elevation at all soil depths. Compared to the reforested area, C:N was typically greater in the agricultural area in the 20–60 cm depth. The planting of soybean (Glycine max L) can significantly increase the C:N at the 40–50 cm depth. C:N was higher in cross‐slope tillage than in down‐slope tillage, especially at soil depths of 40–50 cm. Generally, topographical factors, land use, crop planting and tillage methods can effectively influence the spatial heterogeneity of C:N in this watershed. Copyright © 2015 John Wiley & Sons, Ltd.