bluuebunny/crossref_metadata_2025_split huggingface dataset:
Changes in anatomy instruction and USMLE performance: Empirical evidence on the absence of a relationship
Authors: Cuddy Monica M. , Swanson David B. , Drake Richard L. , Pawlina Wojciech 
Published: January 2013

AbstractAnatomy instruction has evolved over the past two decades as many medical schools have undergone various types of curricular reform. To provide empirical evidence about whether or not curricular changes impact the acquisition and retention of anatomy knowledge, this study investigated the effect of variation in gross anatomy course hours, curricular approach (stand‐alone versus integrated), and laboratory experience (dissection versus dissection and prosection) on USMLE Steps 1 and 2 Clinical Knowledge (CK) scores. Gross anatomy course directors at 54 United States schools provided information about their gross anatomy courses via an online survey (response rate of 42%). Survey responses were matched with USMLE scores for 6,411 examinees entering LCME‐accredited schools in 2007 and taking Step 1 for the first time in 2009. Regression analyses were conducted to examine relationships between gross anatomy instructional characteristics and USMLE performance. Step 1 total scores, Step 1 gross anatomy sub‐scores, and Step 2 CK scores were unrelated to instructional hours, controlling for MCAT scores. Examinees from schools with integrated curricula scored slightly lower on Steps 1 and 2 CK than those from stand‐alone courses (effect sizes of 2.1 and 1.9 on score scales with SDs of 22 and 20, respectively). Examinees with dissection and prosection experience performed slightly better on Step 2 CK than examinees in courses with dissection only laboratories (effect size of 1.2). Results suggest variation in course hours is unrelated to performance on Steps 1 and 2 CK. Although differences were observed in relation to curricular approach and laboratory experience, effect sizes were small. Anat Sci Educ 6: 3–10. © 2012 American Association of Anatomists.
The Oxidative Mechanism in Electrophilic CH Activation: The Case of CH2F2 and CH2Cl2
Authors: de Petris Giulia , Rosi Marzio , Ursini Ornella , Troiani Anna 
Published: January 2013

AbstractThe H.‐atom transfer (HAT) reaction is investigated in the gas phase, starting from two different entrance channels, O2.+/CH2X2 and CH2X2.+/O2 (X=F, Cl), that correspond to a step of hydride transfer and to HAT, respectively. Analysis of the spin and charge along the reaction pathway shows that HAT occurs through the same reacting configuration, irrespective of whether the reactants are formed within the complex or are free isolated species.
Simulations of Guest Transport in Clathrates of Dianin’s Compound and Hydroquinone
Authors: Nemkevich Alexandra , Spackman Mark A. , Corry Ben 
Published: January 2013

AbstractClathrates have been proposed for use in a variety of applications including gas storage, mixture separation and catalysis due to the potential for controlled guest diffusion through their porous lattices. Here molecular dynamics simulations are employed to study guest transport in clathrates of hydroquinone (HQ) and Dianin’s compound (DC). Systems investigated were HQ with methanol and acetonitrile, and DC with methanol and ethanol. Simulations were set up with one guest in the pore, two guests in the pore and one vacancy in the pore and a filled pore, and free‐energy barriers for movement between cavities of the pore were estimated for all cases. Comparison between these simulations indicates that guest transport most likely proceeds by molecules moving from full to empty cavities consecutively, one by one, rather than in a concerted manner. Thus, the presence of empty cavities is very important for guest transport, which becomes more energetically demanding in fully loaded systems. Flexibility of the host can assist guest transport. In the studied DC clathrates transport occurs via an intermediate conformation in which the hydroxyl group of the alcohol guest molecule participates in the hydrogen‐bonded ring of the host. We also address the issue of the number of methanol guest molecules that DC accommodates, for which conflicting information exists. We found that this is likely to be temperature dependent and suggest that under some conditions the system is most likely non‐stoichiometric.
The Hydride‐Ion Affinity of Borenium Cations and Their Propensity to Activate H2 in Frustrated Lewis Pairs
Authors: Clark Ewan R. , Del Grosso Alessandro , Ingleson Michael J. 
Published: January 2013

AbstractA range of frustrated Lewis pairs (FLPs) containing borenium cations have been synthesised. The catechol (Cat)‐ligated borenium cation [CatB(PtBu3)]+ has a lower hydride‐ion affinity (HIA) than B(C6F5)3. This resulted in H2 activation being energetically unfavourable in a FLP with the strong base PtBu3. However, ligand disproportionation of CatBH(PtBu3) at 100 °C enabled trapping of H2 activation products. DFT calculations at the M06‐2X/6‐311G(d,p)/PCM (CH2Cl2) level revealed that replacing catechol with chlorides significantly increases the chloride‐ion affinity (CIA) and HIA. Dichloro–borenium cations, [Cl2B(amine)]+, were calculated to have considerably greater HIA than B(C6F5)3. Control reactions confirmed that the HIA calculations can be used to successfully predict hydride‐transfer reactivity between borenium cations and neutral boranes. The borenium cations [Y(Cl)B(2,6‐lutidine)]+ (Y=Cl or Ph) form FLPs with P(mesityl)3 that undergo slow deprotonation of an ortho‐methyl of lutidine at 20 °C to form the four‐membered boracycles [(CH2{NC5H3Me})B(Cl)Y] and [HPMes3]+. When equimolar [Y(Cl)B(2,6‐lutidine)]+/P(mesityl)3 was heated under H2 (4 atm), heterolytic cleavage of dihydrogen was competitive with boracycle formation.
Coordination‐Driven Switching of a Preorganized and Cooperative Calix[4]pyrrole Receptor
Authors: Bähring Steffen , Olsen Gunnar , Stein Paul C. , Kongsted Jacob , Nielsen Kent A. 
Published: January 2013

AbstractThe study of preorganization in receptors, particularly in cooperative receptors, and their reversible control by external stimuli is important for elucidating design strategies that can lead to increased sensitivity and external control of molecular recognition. In this work we present the design, synthesis, and operation of an asymmetric tetrathiafulvalene (TTF)–calix[4]pyrrole receptor appended with a pyridine moiety. 1H NMR spectroscopy was employed to demonstrate that intramolecular complexation between the receptor and the pyridine moiety leads to a preorganized receptor. Absorption and 1H NMR spectroscopy along with a computational investigation were used to demonstrate the ability of the receptor to complex the substrate 1,3,5‐trinitrobenzene (TNB) and that the receptor can be reversibly modulated between negative and positive cooperativity by employing external stimuli in the form of ZnII. Fitting procedures incorporating multiple datasets and fitting to multiple equilibria simultaneously have been employed to quantitatively determine the preorganization effects.
Quantum Chemical Insight of the Dimetallic Sulfide Endohedral Fullerene Sc2S@C70: Does It Possess the Conventional D5h Cage?
Authors: Yang Tao , Zhao Xiang , Nagase Shigeru 
Published: January 2013

AbstractLike C60, C70 is one of the most representative fullerenes in fullerene science. Even though there are 8149 C70 isomers, only two of them have been found before: the conventional D5h and an isolated pentagon rule (IPR)‐violating C2v(7854). Through the use of quantum chemical methods, we report a new unconventional C70 isomer, C2(7892), which survives in the form of dimetallic sulfide endohedral fullerene Sc2S@C70. Compared with the IPR‐obeying C70 and the C2v(7854) fullerene with three pairs of pentagon adjacencies, the C2(7892) cage violates the isolated pentagon rule and has two pairs of pentagon adjacencies. In Sc2S@C2(7892)‐C70, two scandium atoms coordinate with two pentalene motifs, respectively, presenting two equivalent ScS bonds. The strong coordination interaction, along with the electron transfer from the Sc2S cluster to the fullerene cage, results in the stabilization of the non‐IPR endohedral fullerene. The electronic structure of Sc2S@C70 can be formally described as [Sc2S]4+@[C70]4−; however, a substantial overlap between the metallic orbitals and cage orbitals has also been found. Electrochemical properties and electronic absorption, infrared, and 13C NMR spectra of Sc2S@C70 have been calculated theoretically.
Facile Synthesis and Thermoelectric Properties of Self‐assembled Bi2Te3 One‐Dimensional Nanorod Bundles
Authors: Song Shuyan , Fu Jipeng , Li Xiyan , Gao Wei , Zhang Hongjie 
Published: January 2013

AbstractSelf‐assembled Bi2Te3 one‐dimensional nanorod bundles have been fabricated by a low‐cost and facile solvothermal method with ethylene diamine tetraacetic acid as an additive. The phase structures and morphologies of the samples were characterized by X‐ray diffraction, scanning electron microscopy, Fourier‐transform infrared spectrometry, and transmission electron microscope measurements. The growth mechanisms have been proposed based on the experimental results. The full thermoelectric properties of the nanorod bundles have been characterized and show a large improvement in the thermal conductivity attributed to phonon scattering of the nanostructures and then enhance the thermoelectric figure of merit. This work is promising for the realization of new types of highly efficient thermoelectric semiconductors by this method.
Gold(I) and Silver(I) Complexes of Diphosphacyclobutadiene Cobaltate Sandwich Anions
Authors: Malberg Jennifer , Wiegand Thomas , Eckert Hellmut , Bodensteiner Michael , Wolf Robert 
Published: January 2013

AbstractThe synthesis and structural characterization of the first coordination compounds of bis(diphosphacyclobutadiene) cobaltate anions [M(P2C2R2)2]− is described. Reactions of the new potassium salts [K(thf)3{Co(η4‐P2C2tPent2)2}] (1) and [K(thf)4{Co(η4‐P2C2Ad2)2}] (2) with [AuCl(tht)] (tht=tetrahydrothiophene), [AuCl(PPh3)] and Ag[SbF6] afforded the complexes [Au{Co(P2C2tPent2)2}(PMe3)2] (3), [Au{Co(P2C2Ad2)2}]x (4), [Ag{Co(P2C2Ad2)2}]x (5), [Au(PMe3)4][Au{Co(P2C2Ad2)2}2] (6), [K([18]crown‐6)(thf)2][Au{Co(P2C2Ad2)2}2] (7), and [K([18]crown‐6)(thf)2][M{Co(P2C2Ad2)2}2] (8: M=Au 9: M=Ag) in moderate yields. The molecular structures of 2 and 3, and 6–9 were elucidated by X‐ray crystallography. Complexes 4–9 were thoroughly characterized by 31P and 13C solid state NMR spectroscopy. The complexes [Au{Co(P2C2Ad2)2}]x (4) and [Ag{Co(P2C2Ad2)2}]x (5) exist as coordination polymers in the solid state. The linking mode between the monomeric units in the polymers is deduced. The soluble complexes 1–3, 6, and 7 were studied by multinuclear 1H‐, 31P{1H}‐, and 13C{1H} NMR spectroscopy in solution. Variable temperature NMR measurements of 3 and 6 in deuterated THF reveal the formation of equilibria between the ionic species [Au(PMe3)4]+, [Au(PMe3)2]+, [Co(P2C2R2)2]−, and [Au{Co(P2C2R2)2}2]− (R=tPent and Ad).
An Efficient Method for the Synthesis of Indolo[3,2‐c]quinoline Derivatives Catalyzed by Iodine
Authors: Zhou Yujing , Zhang Meimei , Yin Mingyue , Wang Xiangshan 
Published: January 2013

AbstractThe reaction of Schiff base and indole catalyzed by iodine in DMA, subsequently treated with DDQ, gave indolo[3,2‐c]quinoline derivatives in good yields. The structure of 3e was confirmed by X‐ray diffraction analysis.
Four New Indole Alkaloids from Neolamarckia cadamba
Authors: Liu Lingli , Li Shifei , Zhang Qiang , Zhu Feng , Yang Wei , He Hongping , Hao Xiaojiang 
Published: January 2013

AbstractPhytochemical investigation on the leaves of Neolamarckia cadamba led to the isolation of four new indole alkaloids, spirocadambine (1), dehydraisodihydrocadambine (2), nitrocadambines A and B (3 and 4). The structures and relative configurations were established by 1D and 2D NMR spectra. Spirocadambine (1) represents a new type of screw ring containing indole glucoalkaloids.
One‐pot Synthesis of Aromatic Fused 2,3‐Dihydroindanone by Tandem Pauson‐Khand/Michael/Henry Reaction
Authors: Li Mingming , Xing Ping , Huang Zuogang , Jiang Biao 
Published: January 2013

AbstractThe intermolecular Pauson‐Khand reaction between 2‐ethynylbenzaldehyde and ethylene promoted by dimethyl sulfide can be utilized to synthesize 2‐(2‐formylphenyl)cyclopentenone efficiently. This compound and its derivatives undergo a cascade process of Michael addition reaction followed by Henry reaction with nitromethane to construct substituted aromatic fused 2,3‐dihydroindanones. Furthermore, direct one‐pot synthesis of aromatic fused 2,3‐dihydroindanones from 2‐ethynylbenzaldehyde is achieved.
An Efficient Semi‐Synthetic Method to Construct Docetaxel via Sterically Crowded Linear Side Chain Esterification
Authors: Shen Xin , Yang Jidong , Zhan Huaxing , Wang Hu , Wu Shaohong , Chen Zili 
Published: January 2013

AbstractAn efficient semi‐synthetic method was developed to construct docetaxel 1 by using N,N‐di‐Boc protected linear isoserine derivative 5 as the side chain source, in which, bulky protecting group on the nitrogen atom blocked C‐2′ position and prohibited unavoidable racemization in previous studies.
Immunohistochemical distribution of calretinin and calbindin (D‐28k) in the brain of the cladistian Polypterus senegalus
Authors: Graña Patricia , Folgueira Mónica , Huesa Gema , Anadón Ramón , Yáñez Julián 
Published: January 2013

AbstractPolypteriform fishes are believed to be basal to other living ray‐finned bony fishes, and they may be useful for providing information of the neural organization that existed in the brain of the earliest ray‐finned fishes. The calcium‐binding proteins calretinin (CR) and calbindin‐D28k (CB) have been widely used to characterize neuronal populations in vertebrate brains. Here, the distribution of the immunoreactivity against CR and CB was investigated in the olfactory organ and brain of Polypterus senegalus and compared to the distribution of these molecules in other ray‐finned fishes. In general, CB‐immunoreactive (ir) neurons were less abundant than CR‐ir cells. CR immunohistochemistry revealed segregation of CR‐ir olfactory receptor neurons in the olfactory mucosa and their bulbar projections. Our results confirmed important differences between pallial regions in terms of CR immunoreactivity of cell populations and afferent fibers. In the habenula, these calcium‐binding proteins revealed right‐left asymmetry of habenular subpopulations and segregation of their interpeduncular projections. CR immunohistochemistry distinguished among some thalamic, pretectal, and posterior tubercle‐derived populations. Abundant CR‐ir populations were observed in the midbrain, including the tectum. CR immunoreactivity was also useful for characterizing a putative secondary gustatory/visceral nucleus in the isthmus, and for distinguishing territories in the primary viscerosensory column and octavolateral region. Comparison of the data obtained within a segmental neuromeric context indicates that some CB‐ir and CR‐ir populations in polypteriform fishes are shared with other ray‐finned fishes, but other positive structures appear to have evolved following the separation between polypterids and other ray‐finned fishes. J. Comp. Neurol. 521:2454–2485, 2013. © 2013 Wiley Periodicals, Inc.
Expression of voltage‐gated calcium channel α2δ4 subunits in the mouse and rat retina
Authors: De Sevilla Müller Luis Pérez , Liu Janelle , Solomon Alexander , Rodriguez Allen , Brecha Nicholas C. 
Published: January 2013

AbstractHigh‐voltage activated Ca channels participate in multiple cellular functions, including transmitter release, excitation, and gene transcription. Ca channels are heteromeric proteins consisting of a pore‐forming α1 subunit and auxiliary α2δ and β subunits. Although there are reports of α2δ4 subunit mRNA in the mouse retina and localization of the α2δ4 subunit immunoreactivity to salamander photoreceptor terminals, there is a limited overall understanding of its expression and localization in the retina. α2δ4 subunit expression and distribution in the mouse and rat retina were evaluated by using reverse transcriptase polymerase chain reaction, western blot, and immunohistochemistry with specific primers and a well‐characterized antibody to the α2δ4 subunit. α2δ4 subunit mRNA and protein are present in mouse and rat retina, brain, and liver homogenates. Immunostaining for the α2δ4 subunit is mainly localized to Müller cell processes and endfeet, photoreceptor terminals, and photoreceptor outer segments. This subunit is also expressed in a few displaced ganglion cells and bipolar cell dendrites. These findings suggest that the α2δ4 subunit participates in the modulation of L‐type Ca2+ current regulating neurotransmitter release from photoreceptor terminals and Ca2+‐dependent signaling pathways in bipolar and Müller cells. J. Comp. Neurol. 521:2486–2501, 2013. © 2013 Wiley Periodicals, Inc.
Differential connectivity of short‐ vs. long‐range extrinsic and intrinsic cortical inputs to perirhinal neurons
Authors: Unal Gunes , Pare Jean‐Francois , Smith Yoland , Pare Denis 
Published: January 2013

AbstractThe perirhinal cortex plays a critical role in recognition and associative memory. However, the network properties that support perirhinal contributions to memory are unclear. To shed light on this question, we compared the synaptic articulation of short‐ and long‐range inputs from the perirhinal cortex or temporal neocortex with perirhinal neurons in rats. Iontophoretic injections of the anterograde tracer Phaseolus vulgaris‐leucoagglutinin (PHAL) were performed at different rostrocaudal levels of the ventral temporal neocortex or perirhinal cortex, and electron microscopic observations of anterogradely labeled (PHAL+) axon terminals found at perirhinal sites adjacent to or rostrocaudally distant from the injection sites were performed. After neocortical injections, the density of PHAL+ axons in the perirhinal cortex decreased steeply with rostrocaudal distance from the injection sites, much more so than following perirhinal injections. Otherwise, similar results were obtained with neocortical and perirhinal injections. In both cases, most (76–86%) PHAL+ axon terminals formed asymmetric synapses, typically with spines (type A, 83–89%) and less frequently with dendritic profiles (type B, 11–17%). The remaining terminals formed symmetric synapses with dendritic profiles (type C, 14–23%). Type B and C synapses were 2.4–2.6 times more frequent in short‐ than long‐range connections. The postsynaptic elements in type A–C synapses were identified with immunocytochemistry for CAMKIIα, a marker of glutamatergic cortical neurons. Type A and C terminals contacted CAMKIIα‐positive principal cells, whereas type B synapses contacted presumed inhibitory neurons. Overall, these results suggest that principal perirhinal neurons are subjected to significantly more inhibition from short‐ than from long‐range cortical inputs, an organization that likely impacts perirhinal contributions to memory. J. Comp. Neurol. 521:2538–2550, 2013. © 2013 Wiley Periodicals, Inc.
Cell death atlas of the postnatal mouse ventral forebrain and hypothalamus: Effects of age and sex
Authors: Ahern Todd H. , Krug Stefanie , Carr Audrey V. , Murray Elaine K. , Fitzpatrick Emmett , Bengston Lynn , McCutcheon Jill , De Vries Geert J. , Forger Nancy G. 
Published: January 2013

AbstractNaturally occurring cell death is essential to the development of the mammalian nervous system. Although the importance of developmental cell death has been appreciated for decades, there is no comprehensive account of cell death across brain areas in the mouse. Moreover, several regional sex differences in cell death have been described for the ventral forebrain and hypothalamus, but it is not known how widespread the phenomenon is. We used immunohistochemical detection of activated caspase‐3 to identify dying cells in the brains of male and female mice from postnatal day (P) 1 to P11. Cell death density, total number of dying cells, and regional volume were determined in 16 regions of the hypothalamus and ventral forebrain (the anterior hypothalamus, arcuate nucleus, anteroventral periventricular nucleus, medial preoptic nucleus, paraventricular nucleus, suprachiasmatic nucleus, and ventromedial nucleus of the hypothalamus; the basolateral, central, and medial amygdala; the lateral and principal nuclei of the bed nuclei of the stria terminalis; the caudate‐putamen; the globus pallidus; the lateral septum; and the islands of Calleja). All regions showed a significant effect of age on cell death. The timing of peak cell death varied between P1 to P7, and the average rate of cell death varied tenfold among regions. Several significant sex differences in cell death and/or regional volume were detected. These data address large gaps in the developmental literature and suggest interesting region‐specific differences in the prevalence and timing of cell death in the hypothalamus and ventral forebrain. J. Comp. Neurol. 521:2551–2569, 2013. © 2013 Wiley Periodicals, Inc.
Morphological analysis of the primary center receiving spatial information transferred by the waggle dance of honeybees
Authors: Ai Hiroyuki , Hagio Hiromi 
Published: January 2013

AbstractThe waggle dancers of honeybees encodes roughly the distance and direction to the food source as the duration of the waggle phase and the body angle during the waggle phase. It is believed that hive‐mates detect airborne vibrations produced during the waggle phase to acquire distance information and simultaneously detect the body axis during the waggle phase to acquire direction information. It has been further proposed that the orientation of the body axis on the vertical comb is detected by neck hairs (NHs) on the prosternal organ. The afferents of the NHs project into the prothoracic and mesothoracic ganglia and the dorsal subesophageal ganglion (dSEG). This study demonstrates somatotopic organization within the dSEG of the central projections of the mechanosensory neurons of the NHs. The terminals of the NH afferents in dSEG are in close apposition to those of Johnston's organ (JO) afferents. The sensory axons of both terminate in a region posterior to the crossing of the ventral intermediate tract (VIT) and the maxillary dorsal commissures I and III (MxDCI, III) in the subesophageal ganglion. These features of the terminal areas of the NH and JO afferents are common to the worker, drone, and queen castes of honeybees. Analysis of the spatial relationship between the NH neurons and the morphologically and physiologically characterized vibration‐sensitive interneurons DL‐Int‐1 and DL‐Int‐2 demonstrated that several branches of DL‐Int‐1 are in close proximity to the central projection of the mechanosensory neurons of the NHs in the dSEG. J. Comp. Neurol. 521:2570–2584, 2013. © 2013 Wiley Periodicals, Inc.
Biomolecule‐Assisted Construction of Cadmium Sulfide Hollow Spheres with Structure‐Dependent Photocatalytic Activity
Authors: Wei Chengzhen , Zang Wenzhe , Yin Jingzhou , Lu Qingyi , Chen Qun , Liu Rongmei , Gao Feng 
Published: January 2013

AbstractIn this study, we report the synthesis of monodispersive solid and hollow CdS spheres with structure‐dependent photocatalytic abilities for dye photodegradation. The monodispersive CdS nanospheres were constructed with the assistance of the soulcarboxymthyi chitosan biopolymer under hydrothermal conditions. The solid CdS spheres were corroded by ammonia to form hollow CdS nanospheres through a dissolution–reprecipitation mechanism. Their visible‐light photocatalytic activities were investigated, and the results show that both the solid and the hollow CdS spheres have visible‐light photocatalytic abilities for the photodegradation of dyes. The photocatalytic properties of the CdS spheres were demonstrated to be structure dependent. Although the nanoparticles comprising the hollow spheres have larger sizes than those comprising the solid spheres, the hollow CdS spheres have better photocatalytic performances than the solid CdS spheres, which can be attributed to the special hollow structure.