bluuebunny/crossref_metadata_2025_split huggingface dataset:
BiSbTe‐Based Nanocomposites with High ZT: The Effect of SiC Nanodispersion on Thermoelectric Properties
Authors: Li Jianhui , Tan Qing , Li Jing‐Feng , Liu Da‐Wei , Li Fu , Li Zong‐Yue , Zou Minmin , Wang Ke 
Published: April 2013

AbstractThermoelectric materials have potential applications in energy harvesting and electronic cooling devices, and bismuth antimony telluride (BiSbTe) alloys are the state‐of‐the‐art thermoelectric materials that have been widely used for several decades. It is demonstrated that mixing SiC nanoparticles into the BiSbTe matrix effectively enhances its thermoelectric properties; a high dimensionless figure of merit (ZT) value of up to 1.33 at 373 K is obtained in Bi0.3Sb1.7Te3 incorporated with only 0.4 vol% SiC nanoparticles. SiC nanoinclusions possessing coherent interfaces with the Bi0.3Sb1.7Te3 matrix can increase the Seebeck coefficient while increasing the electrical conductivity, in addition to its effect of reducing lattice thermal conductivity by enhancing phonon scattering. Nano‐SiC dispersion further endows the BiSbTe alloys with better mechanical properties, which are favorable for practical applications and device fabrication.
Recent Developments in Amine‐catalyzed Non‐asymmetric Transformations
Authors: Ren Qiao , Wang Jian 
Published: April 2013

AbstractAmine catalysis has emerged as a powerful and elegant method to construct diverse chiral scaffolds in asymmetric synthesis. However, amine‐based non‐asymmetric organocatalysis is still in its infancy. This Focus Review examines recent developments in amine‐catalyzed non‐asymmetric transformations based on enamine, iminium, di‐ or trienamine, and oxidative enamine catalysis.
The Photocatalyzed Meerwein Arylation: Classic Reaction of Aryl Diazonium Salts in a New Light
Authors: Hari Durga Prasad , König Burkhard 
Published: April 2013

AbstractThe use of diazonium salts for aryl radical generation and CH arylation processes has been known since 1896 when Pschorr first used the reaction for intramolecular cyclizations. Meerwein developed it further in the early 1900s into a general arylation method. However, this reaction could not compete with the transition‐metal‐mediated formation of C(sp2)C(sp2) bonds. The replacement of the copper catalyst with iron and titanium compounds improved the situation, but the use of photocatalysis to induce the one‐electron reduction and activation of the diazonium salts is even more advantageous. The first photocatalyzed Pschorr cyclization was published in 1984, and just last year a series of papers described applications of photocatalytic Meerwein arylations leading to aryl–alkene coupling products. In this Minireview we summarize the origins of this reaction and its scope and applications.
Fractional‐Order Dynamic Output Feedback Sliding Mode Control Design for Robust Stabilization of Uncertain Fractional‐Order Nonlinear Systems
Authors: Dadras Sara , Momeni Hamid Reza 
Published: April 2013

AbstractA robust fractional‐order dynamic output feedback sliding mode control (DOF‐SMC) technique is introduced in this paper for uncertain fractional‐order nonlinear systems. The control law consists of two parts: a linear part and a nonlinear part. The former is generated by the fractional‐order dynamics of the controller and the latter is related to the switching control component. The proposed DOF‐SMC ensures the asymptotical stability of the fractional‐order closed‐loop system whilst it is guaranteed that the system states hit the switching manifold in finite time. Finally, numerical simulation results are presented to illustrate the effectiveness of the proposed method.
Ständig Neues aus dem Stock
Authors: Tautz Jürgen , Vonend Kristina 
Published: April 2013

AbstractÜber das Internet‐Projekt HOBOS können Schülerinnen und Schüler das drittwichtigste Nutztier des Menschen nach Rind und Schwein online kennenlernen. Sie können sehen und messen, was gerade live im Stock und außerhalb vor sich geht und eigenständig auf einfache, aber auch auf hochkomplexe Prozesse rund um den Bienenstaat schließen.
Tirucallane Triterpenoids from the Stems of Brucea mollis
Authors: Chen Hui , Ma Shuang‐Gang , Fang Zhen‐Feng , Bai Jian , Yu Shi‐Shan , Chen Xiao‐Guang , Hou Qi , Yuan Shao‐Peng , Chen Xia 
Published: April 2013

AbstractThree new tirucallane triterpenoids, brumollisols A–C (1–3, resp.), together with five known analogues, (23R,24S)‐23,24,25‐trihydroxytirucall‐7‐ene‐3,6‐dione (4), piscidinol A (5), 24‐epipiscidinol A (6), 21α‐methylmelianodiol (7), and 21β‐methylmelianodiol (8), were isolated from an EtOH extract of the stems of Brucea mollis. Their structures were elucidated by means of spectroscopic methods including 1D‐ and 2D‐NMR techniques and mass spectrometry. In the in vitro assays, compound 6 exhibited significant cytotoxic activity against A549 and BGC‐823 cancer cells with IC50 values of 1.16 and 3.01 μM, respectively. At a concentration of 10 μM, compounds 1–5, 7, and 8 were found to inhibit NO production in mouse peritoneal macrophages with inhibitory ratios ranging from 39.8±7.7 to 68.2±4.5%.
Triterpene Glucosides from the Leaves of Aralia elata and Their Cytotoxic Activities
Authors: Kuang Hai‐Xue , Wang Zhi‐Bin , Wang Qiu‐Hong , Yang Bing‐You , Xiao Hong‐Bin , Okada Yoshihito , Okuyama Tohru 
Published: April 2013

AbstractThree new triterpene glucosides, named congmuyenosides C–E (1–3, resp.), along with four known ones, were isolated from an EtOH extract of Aralia elata (Miq.) Seem. leaves. The structures of the new compounds were identified as 3‐O‐{β‐D‐glucopyranosyl‐(1→3)‐β‐D‐glucopyranosyl‐(1→3)‐[β‐D‐glucopyranosyl‐(1→2)]‐β‐D‐glucopyranosyl}caulophyllogenin (1), 3‐O‐{β‐D‐glucopyranosyl‐(1→3)‐β‐D‐glucopyranosyl‐(1→3)‐[β‐D‐glucopyranosyl‐(1→2)]‐β‐D‐glucopyranosyl}hederagenin 28‐O‐β‐D‐glucopyranosyl ester (2), 3‐O‐{β‐D‐glucopyranosyl‐(1→3)‐β‐D‐glucopyranosyl‐(1→3)‐[β‐D‐glucopyranosyl‐(1→2)]‐β‐D‐glucopyranosyl}echinocystic acid 28‐O‐β‐D‐glucopyranosyl ester (3) on the basis of spectral analyses, including MS, 1H‐NMR, 13C‐NMR, DEPT, HSQC, HMBC, NOESY, and HSQC‐TOCSY experiments. All isolates obtained were evaluated for their cytotoxic activities against three human tumor cell lines (HepG2, SKOV3, and A549). Compound 3 showed significant cytotoxicity against A549 cell line (IC50 9.9±1.5 μM).
Antitumor Effect of the Essential Oil from Leaves of Guatteria pogonopus (Annonaceae)
Authors: do N. Fontes José Eraldo , Ferraz Rosana P. C. , Britto Anny C. S. , Carvalho Adriana A. , Moraes Manoel O. , Pessoa Claudia , Costa Emmanoel V. , Bezerra Daniel P. 
Published: April 2013

AbstractGuatteria pogonopus Martius, a plant belonging to the Annonaceae family, is found in the remaining Brazilian Atlantic Forest. In this study, the chemical composition and antitumor effects of the essential oil isolated from leaves of G. pogonopus was investigated. The chemical composition of the oil was determined by GC‐FID and GC/MS analyses. The in vitro cytotoxicity was evaluated against three different tumor cell lines (OVCAR‐8, NCI‐H358M, and PC‐3M), and the in vivo antitumor activity was tested in mice bearing sarcoma 180 tumor. A total of 29 compounds was identified and quantified in the oil. The major compounds were γ‐patchoulene (13.55%), (E)‐caryophyllene (11.36%), β‐pinene (10.37%), germacrene D (6.72%), bicyclogermacrene (5.97%), α‐pinene (5.33%), and germacrene B (4.69%). The essential oil, but neither (E)‐caryophyllene nor β‐pinene, displayed in vitro cytotoxicity against all three tumor cell lines tested. The obtained average IC50 values ranged from 3.8 to 20.8 μg/ml. The lowest and highest values were obtained against the NCI‐H358M and the OVCAR‐8 cell lines, respectively. The in vivo tumor‐growth‐inhibition rates in the tumor‐bearing mice treated with essential oil (50 and 100 mg/kg/d) were 25.3 and 42.6%, respectively. Hence, the essential oil showed significant in vitro and in vivo antitumor activity.
Chemotaxonomic Implications of the n‐Alkane Composition and the Nonacosan‐10‐ol Content in Picea omorika, Pinus heldreichii, and Pinus peuce
Authors: Nikolić Biljana , Tešević Vele , Bojović Srdjan , Marin Petar D. 
Published: April 2013

AbstractThe n‐alkane composition and the nonacosan‐10‐ol content in the needle cuticular waxes of Serbian spruce (Picea omorika), Bosnian pine (Pinus heldreichii), and Macedonian pine (Pinus peuce) were compared. The amount of nonacosan‐10‐ol in the needle waxes of P. omorika was higher than those in P. heldreichii and P. peuce. The range of n‐alkanes was also wider in P. omorika (C18–C35) than in P. heldreichii and P. peuce (C18–C33). The dominant n‐alkanes were C29 in the needle waxes of P. omorika, C23, C27, and C25 in those of P. heldreichii, and C29, C25, C27, and C23 in those of P. peuce. The waxes of P. omorika contained higher amounts of n‐alkanes C29, C31, and C33, while those of P. heldreichii and P. peuce had higher contents of n‐alkanes C21, C22, C23, C24, and C26. The principal component analysis of the contents of nine n‐alkanes showed a clear separation of the Serbian spruce populations from those of the two investigated pine species, which partially overlapped. The separation of the species was due to high contents of the n‐alkanes C29 and C31 (P. omorika), C19, C20, C21, C22, C23, and C24 (P. heldreichii), and C28 (P. peuce). Cluster analysis also showed a clear separation between the P. omorika populations on one side and the P. heldreichii and P. peuce populations on the other side. The n‐alkane and terpene compositions are discussed in the light of their usefulness in chemotaxonomy as well as with regard to the biogeography and phylogeny of these rare and endemic conifers.
Synthesis and Evaluation of Biphenyl Compounds as Kinesin Spindle Protein Inhibitors
Authors: Holland Jason P. , Kang Albert , Cohrs Susan , Selivanova Svetlana V. , Milicevic Sephton Selena , Betzel Thomas , Frey Daniel , Wieser Mara , Jaussi Rolf , Kammerer Richard A. , Schibli Roger , Fischer Eliane 
Published: April 2013

AbstractKinesin spindle protein (KSP), an ATP‐dependent motor protein, plays an essential role in bipolar spindle formation during the mitotic phase (M phase) of the normal cell cycle. KSP has emerged as a novel target for antimitotic anticancer drug development. In this work, we synthesized a range of new biphenyl compounds and investigated their properties in vitro as potential antimitotic agents targeting KSP expression. Antiproliferation (MTT (=3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐2H‐tetrazolium bromide)) assays, combined with fluorescence‐assisted cell sorting (FACS) and Western blot studies analyzing cell‐cycle arrest confirmed the mechanism and potency of these biphenyl compounds in a range of human cancer cell lines. Structural variants revealed that functionalization of biphenyl compounds with bulky aliphatic or aromatic groups led to a loss of activity. However, replacement of the urea group with a thiourea led to an increase in antiproliferative activity in selected cell lines. Further studies using confocal fluorescence microscopy confirmed that the most potent biphenyl derivative identified thus far, compound 7, exerts its pharmacologic effect specifically in the M phase and induces monoaster formation. These studies confirm that chemical scope remains for improving the potency and treatment efficacy of antimitotic KSP inhibition in this class of biphenyl compounds.
Proton Hopping: A Proposed Mechanism for Myelinated Axon Nerve Impulses
Authors: Kier Lemont B. , Tombes Robert M. 
Published: April 2013

AbstractMyelinated axon nerve impulses travel 100 times more rapidly than impulses in non‐myelinated axons. Increased speed is currently believed to be due to ‘hopping’ or ‘saltatory propagation’ along the axon, but the mechanism by which impulses flow has never been adequately explained. We have used modeling approaches to simulate a role for proton hopping in the space between the plasma membrane and myelin sheath as the mechanism of nerve action‐potential flow.
On the Pathways of Biologically Relevant Diatomic Gases through Proteins. Dioxygen and Heme Oxygenase from the Perspective of Molecular Dynamics
Authors: Pietra Francesco 
Published: April 2013

AbstractThis work deals with dioxygen (O2) binding sites and pathways through inducible human heme oxygenase (HO‐1). The experimentally known distal binding site 1, and sites 2–3 above it, could be reproduced by means of non‐deterministic random‐acceleration molecular‐dynamics (RAMD) simulations. In addition, RAMD revealed the proximal binding site 5, a deeply‐seated binding site 4, which lies behind heme, as well as a few gates communicating with the external medium. In getting from site 1 to the main gate, which lies on the protein front opposed to site 4, O2 follows chiefly the shortest direct pathway. Less frequently, O2 visits intermediate sites 2, 4, or 5 along longer pathways. A similarity between HO‐1, myoglobin, and cytoglobin in using, for diatomic gas delivery, the direct shortest pathway from the heme center to the surrounding medium, is emphasized. Otherwise, comparing other proteins and diatomic gases, each system reveals its peculiarities as to sites, gates, and pathways. Thus, relating these properties to the physiological functions of the proteins remains in general a challenge for future studies.
Congruence of Phytochemical and Morphological Profiles along an Altitudinal Gradient in Origanum vulgare ssp. vulgare from Venetian Region (NE Italy)
Authors: Giuliani Claudia , Maggi Filippo , Papa Fabrizio , Maleci Bini Laura 
Published: April 2013

AbstractPlants of Origanum vulgare L. ssp. vulgare from the Veneto region (NE Italy) were selected to study the variability of the essential‐oil composition from leaves and inflorescences throughout an elevation gradient. We investigated also the morphology of non‐glandular and glandular trichomes, their distribution on the vegetative and reproductive organs, as well as the histochemistry of the secreted products, with special focus on the terpenoidic fraction.Since glandular trichomes are prerequisite for the essential‐oil synthesis, the second objective was to establish whether its production is related to glandular hair number, and density. Essential‐oil contents decline with increasing altitude, and the micromorphological observations revealed a decrease in trichome density along the same direction. Moreover, GC/MS analysis together with principal component analysis (PCA) showed that the three investigated populations were significantly different in chemical composition. Therefore, an important interpopulation variability for low‐, mid‐, and high‐altitude sites was established, suggesting the likely occurrence of different biotypes associated with altitudinal levels.Hence, the involvement of abiotic factors such as temperature and drought in the chemical polymorphism of O. vulgare associated with elevation is briefly discussed.
Imidazolium‐Based Organic–Inorganic Hybrid Silica as a Functional Platform Dramatically Boosts Chiral Organometallics Performance in Asymmetric Catalysis
Authors: Xia Daquan , Cheng Tanyu , Xiao Wei , Liu Ketang , Wang Zhaoliang , Liu Guohua , Li Hexing , Wang Wei 
Published: April 2013

AbstractPhase‐transfer featured, imidazolium‐based, organic‐inorganic hybrid silica represents a novel functionalized platform with particularly attractive features in asymmetric catalysis. Herein, we report a chiral organorhodium‐functionalized heterogeneous catalyst. As demonstrated in the studies, it displays comparable or higher catalytic activity and enantioselectivity than its homogeneous counterpart in asymmetric transformations. The superior catalytic performance is attributed to the synergistic effect of the salient imidazolium phase‐transfer character and the confined chiral organorhodium catalytic nature in addition to the merits of mesoporous silica. Furthermore, it is more robust than other silica‐derived heterogeneous systems and can be conveniently recovered and reused at least 10 times without loss of its catalytic efficiency. These features render the catalyst particularly attractive in practice of organic synthesis. The outcomes from the study clearly show that the strategy described here offers a general approach to immobilization of chiral ligand‐derived silane onto the phase‐transfer featured imidazolium‐based organic‐inorganic hybrid silica materials with significant improving catalyst efficiency.
Epoxide Opening versus Silica Condensation during Sol–Gel Hybrid Biomaterial Synthesis
Authors: Gabrielli Luca , Russo Laura , Poveda Ana , Jones Julian R. , Nicotra Francesco , Jiménez‐Barbero Jesús , Cipolla Laura 
Published: April 2013

AbstractHybrid organic–inorganic solids represent an important class of engineering materials, usually prepared by sol–gel processes by cross‐reaction between organic and inorganic precursors. The choice of the two components and control of the reaction conditions (especially pH value) allow the synthesis of hybrid materials with novel properties and functionalities. 3‐Glycidoxypropyltrimethoxysilane (GPTMS) is one of the most commonly used organic silanes for hybrid‐material fabrication. Herein, the reactivity of GPTMS in water at different pH values (pH 2–11) was deeply investigated for the first time by solution‐state multinuclear NMR spectroscopic and mass spectrometric analysis. The extent of the different and competing reactions that take place as a function of the pH value was elucidated. The NMR spectroscopic and mass spectrometric data clearly indicate that the pH value determines the kinetics of epoxide hydrolysis versus silicon condensation. Under slighly acidic conditions, the epoxy‐ring hydrolysis is kinetically more favourable than the formation of the silica network. In contrast, under basic conditions, silicon condensation is the main reaction that takes place. Full characterisation of the formed intermediates was carried out by using NMR spectroscopic and mass spectrometric analysis. These results indicate that strict control of the pH values allows tuning of the reactivity of the organic and inorganic moities, thus laying the foundations for the design and synthesis of sol–gel hybrid biomaterials with tuneable properties.
Highly Regioselective Organocatalyzed Synthesis of Pyrazoles from Diazoacetates and Carbonyl Compounds
Authors: Wang Lei , Huang Jiayao , Gong Xiaojie , Wang Jian 
Published: April 2013

AbstractA general, organocatalytic inverse‐electron‐demand [3+2] cycloaddition reaction between a range of carbonyl compounds and diazoacetates has been developed. This reaction is catalyzed by secondary amines as a “green promoter” to generate substituted pyrazoles with high levels of regioselectivity. It is noteworthy that this [3+2] cycloaddition reaction proceeds efficiently at room temperature with a simple and inexpensive catalyst. Considering the large variety and ready availability of the starting materials (e.g. ketones, β‐ketoesters, β‐diketones, and aldehydes), as well as the operational simplicity of this process, a convenient, practical, and highly modular pyrazole synthesis has been developed. We believe that this work will arouse more research interest in the organocatalytic synthesis of other biologically active heterocycles. Such studies are currently underway in our laboratory.
Ball‐Milling‐Induced Amorphization of Zeolitic Imidazolate Frameworks (ZIFs) for the Irreversible Trapping of Iodine
Authors: Bennett Thomas D. , Saines Paul J. , Keen David A. , Tan Jin‐Chong , Cheetham Anthony K. 
Published: April 2013

AbstractThe I2‐sorption and ‐retention properties of several existing zeolitic imidazolate frameworks (ZIF‐4, ‐8, ‐69) and a novel framework, ZIF‐mnIm ([Zn(mnIm)2]; mnIm=4‐methyl‐5‐nitroimidazolate), have been characterised using microanalysis, thermogravimetric analysis and X‐ray diffraction. The topologically identical ZIF‐8 ([Zn(mIm)2]; mIm=2‐methylimidazolate) and ZIF‐mnIm display similar sorption abilities, though strikingly different guest‐retention behaviour upon heating. We discover that this guest retention is greatly enhanced upon facile amorphisation by ball milling, particularly in the case of ZIF‐mnIm, for which I2 loss is retarded by as much as 200 °C. It is anticipated that this general approach should be applicable to the wide range of available metal–organic framework‐type materials for the permanent storage of harmful guest species.
Multi‐faceted Reactivity of Alkyltellurophenols Towards Peroxyl Radicals: Catalytic Antioxidant Versus Thiol‐Depletion Effect
Authors: Amorati Riccardo , Valgimigli Luca , Dinér Peter , Bakhtiari Khadijeh , Saeedi Mina , Engman Lars 
Published: April 2013

AbstractHydroxyaryl alkyl tellurides are effective antioxidants both in organic solution and aqueous biphasic systems. They react by an unconventional mechanism with ROO. radicals with rate constants as high as 107 M−1 s−1 at 303 K, outperforming common phenols. The reactions proceed by oxygen atom transfer to tellurium followed by hydrogen atom transfer to the resulting RO. radical from the phenolic OH. The reaction rates do not reflect the electronic properties of the ring substituents and, because the reactions occur in a solvent cage, quenching is more efficient when the OH and TeR groups have an ortho arrangement. In the presence of thiols, hydroxyaryl alkyl tellurides act as catalytic antioxidants towards both hydroperoxides (mimicking the glutathione peroxidases) and peroxyl radicals. The high efficiency of the quenching of the peroxyl radicals and hydroperoxides could be advantageous under normal cellular conditions, but pro‐oxidative (thiol depletion) when thiol concentrations are low.
Design, Synthesis, and Antibacterial Activity of Demethylvancomycin Analogues against Drug‐Resistant Bacteria
Authors: Chang Jun , Zhang Si‐Ji , Jiang Yong‐Wei , Xu Liang , Yu Jian‐Ming , Zhou Wen‐Jiang , Sun Xun 
Published: April 2013

AbstractFive novel N‐substituted demethylvancomycin derivatives were rationally designed and synthesized by using a structure‐based approach. The in vitro antibacterial activities against methicillin‐resistant Staphylococcus aureus (MRSA), gentamicin‐resistant Enterococcus faecalis (GRE), methicillin‐resistant Streptococcus pneumoniae (MRS), and vancomycin‐resistant Enterococcus faecalis (VRE) were evaluated. One of the compounds, N‐(6‐phenylheptyl)demethylvancomycin (12 a), was found to exhibit more potent antibacterial activity than vancomycin and demethylvancomycin. Compound 12 a was also found to be ∼18‐fold more efficacious than vancomycin against MRSA; however, the two compounds were found to have similar efficacy against MRS. Furthermore, compound 12 a exhibited a favorable pharmacokinetic profile with a half‐life of 5.11±0.52 h, which is longer than that of vancomycin (4.3±1.9 h). These results suggest that 12 a is a promising antibacterial drug candidate for further preclinical evaluation.