bluuebunny/crossref_metadata_2025_split huggingface dataset:
Steric effects on the dialkyl substituted X2C2Si silylenes: A theoretical study
Authors: Kassaee M. Z. , Musavi S. M. , Soleimani‐Amiri S. , Ghambarian M. 
Published: October 2006

AbstractWith the aim of recognizing the steric effects on the silylenic H2C2Si structures, ab initio and DFT calculations are carried out on 24 structures of X2C2Si (where X is hydrogen (H), methyl (Me), isopropyl (i‐pro), and tert‐butyl (tert‐Bu)). These species are at either triplet (t) or singlet (s) states. They are confined to the following three sets of structures (1X, 2X and 3X). Structures 1X include silacyclopropenylidenes (1s‐H and 1t‐H) and their 2,3‐disubstituted derivatives (1t‐Me, 1s‐Me; 1t‐i‐pro, 1s‐i‐pro; 1t‐tert‐Bu, 1s‐tert‐Bu). Structures 2X include vinylidenesilylenes (2s‐H and 2t‐H) and their 3,3‐disubstituted derivatives (2t‐Me, 2s‐Me; 2t‐i‐pro, 2s‐i‐pro; 2t‐tert‐Bu, 2s‐tert‐Bu). Structures 3X include ethynylsilylenes (3s‐H and 3t‐H) and their 1,3‐disubstituted derivatives (3t‐Me, 3s‐Me; 3t‐i‐pro, 3s‐i‐pro; 3t‐tert‐Bu, 3s‐tert‐Bu). Singlet–triplet energy separations (Δ Es‐t, X) and relative energies for the above structures are acquired at HF/6‐31G*, B1LYP/6‐31G*, B3LYP/6‐31G*, MP2/6‐31G*, HF/6‐31G**, B1LYP/6‐31G**, B3LYP/6‐31G**, and MP2/6‐31G** levels of theory. The highest Δ Es‐t, X is encountered for 1X. All singlet states of X2C2Si, are more stable than their corresponding triplet states. Linear correlations are found between the LUMO–HOMO energy gaps of the singlet 1s‐X and 2s‐X with their corresponding singlet–triplet energy separations calculated at B3LYP/6‐31G**. The seven structures 2s‐Me, 2t‐Me, 3s‐Me, 1t‐Me, 1s‐Me, 1s‐tert‐Bu, and 3t‐tert‐Bu do not appear to be real isomers. Different stability orders are obtained as a function of the substituents (X). The order of stability for six isomers of H2C2Si is 1s‐H > 2s‐H > 3s‐H > 2t‐H > 3t‐H > 1t‐H. Replacing hydrogen atoms by methyl group (X = Me) presents a new stability order: 1s‐Me > 3s‐Me > 2s‐Me > 3t‐Me > 2t‐Me > 1t‐Me; and for (i‐pro)2C2Si is 1s‐i‐pro > 2s‐i‐pro ≈ 3s‐i‐pro > 3t‐i‐pro ≈ 2t‐i‐pro > 1t‐i‐pro. Using the larger tert‐butyl group as a substituent (X), yet it offers a more different stability order for six structures of (tert‐Bu)2C2Si: 1s‐tert‐Bu > 3s‐tert‐Bu > 2s‐tert‐Bu > 3t‐tert‐Bu > 1t‐tert‐Bu > 2t‐tert‐Bu. Among eight levels employed, B3LYP/6‐31G** appears as the method of choice. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:619–633, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20204
Synthesis and thermal stability of S‐trimethylsilyl esters of tetracoordinated phosphorus amidothioacids
Authors: Nizamov Il'yas S. , Bolshakova Olga V. , Al'metkina Lyubov A. , Nizamov Il'nar D. , Sergeenko Gulnur G. , Frolova Liliya V. , Krivolapov Dmitry B. , Batyeva Elvira S. , Litvinov Igor A. 
Published: October 2006

AbstractS‐(Diethylamino)dimethylsilyl bis(diethylamido)dithiophosphate 3 was obtained by the reaction of tetraphosphorus decasulfide 1 with bis(diethylamino)dimethylsilane 2a. The reactions of Lawesson's reagent 5 with 2a and the alkyl homologues of Davy's reagent 8a,b with trimethyl(diethylamino)silane 6 were studied. On the basis of these reactions, methods of synthesizing S‐(diethylamino)dimethylsilyl or S‐(diethylamino)diphenylsilyl 4‐methoxyphenyl (diethylamido)dithiophosphonates 7a and 7b and S‐trimethylsilyl S‐alkyl(diethylamido)trithiophosphates 9a,b are described. The optimal reaction conditions and thermal stability of S‐trimethylsilyl S‐ethyl(diethylamido)trithiophosphate 9a were defined by differential thermal analyses. Compound 9a have been decomposed to form 2,4‐bis(diethylamido)‐1,3,2,4‐dithiadiphosphetane‐2,4‐disulfide 10 which structure was established by X‐ray single crystal diffraction. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:670–675, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20231
Microwave‐assisted solid‐phase synthesis of 2,4,5‐triaryl imidazoles in solventless system: An improved protocol
Authors: Oskooie Hossein A. , Alimohammadi Zahra , Heravi Majid M. 
Published: October 2006

AbstractThe solventless microwave‐assisted synthesis of 2,4,5‐triaryl imidazoles from 1,2‐diphenylethandione or 2‐hydroxy‐1,2‐diphenylethanone in the presence of NH4OAc/NaHSO4 supported onto silica gel under microwave irradiation is reported. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:699–702, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20237
Syntheses of symmetric and unsymmetric 2,6‐bis(phosphino)phenols
Authors: Beganskiene Aldona , Nikishkin Nicolai I. , Luck Rudy L. , Urnezius Eugenijus 
Published: October 2006

AbstractCompounds bearing the structural motif of 2,6‐bis(phosphino)phenol have been synthesized via two general methods. Double lithium‐halogen exchange occurred in low‐temperature reactions of O‐protected (by methyl‐ or tetrahydropyranyl groups) 2,6‐dibromo‐4‐methylphenol derivatives with BuLi (2 equivalents); quenching the reaction mixtures with chlorophosphines ClPR2 (R = Ph, iPr) and corresponding O‐deprotection yielded symmetrically substituted 2,6‐bis(phosphino)phenols. Sequential incorporation of PR2 functionalities was accomplished via single lithium‐halogen exchange (1 eq. of BuLi) of tetrahydropyranyl‐protected 2,6‐dibromo‐4‐methylphenol followed by ClPR2 quenches, thus enabling the syntheses of unsymmetric 2,6‐bis(phosphino)phenols. Such compounds were also obtained via sequential ortho‐lithiations of tetrahydropyranyl‐protected 4‐tert‐but ylphenol, followed by ClPR2 quenches. All of the new compounds have been characterized by spectrometric methods (1H and 31P NMR, and mass spectrometry). In addition, two of the compounds, 1‐(diphenylphosphino)‐3‐(diphenylphosphoryl)‐2‐methoxy‐5‐methylbenzene (3a‐ox) and 1,3‐bis(diphenylphosphino)‐2‐methoxy‐5‐methylbenzene (6a) have also been characterized via single crystal X‐ray diffraction experiments. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:656–663, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20251
Soluble poly(ethylene glycol) supported efficient synthesis of 2,5‐disubstituted 1,3,4‐oxadiazoles and 1,3,4‐thiadiazoles
Authors: Li Zheng , Yang Jingya , Wang Junke , Wang Xicun 
Published: October 2006

AbstractAn efficient soluble poly(ethylene glycol) (PEG) supported liquid‐phase parallel synthetic method for 2,5‐disubstituted 1,3,4‐oxadiazoles and 1,3,4‐thiadiazoles is described. 2‐Aryl‐5‐(4′‐methoxycarbonylphenoxymethyl)‐1,3,4‐oxadiazoles and 2‐aryloxymethyl‐5‐(4′‐methoxycarbonylphenoxyacetamido)‐1,3,4‐thiadiazoles are synthesized in high yield and high purity using this polymer supported strategy. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:664–669, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20253
Lawesson's reagent for direct thionation of hydroxamic acids: Substituent effects on LR reactivity
Authors: Przychodzeń Witold 
Published: October 2006

AbstractTo explore the generality and scope of direct thionation of hydroxamic acids (HAs), the reaction of various structurally diverse HAs with Lawesson's reagent was investigated. The yield of thiohydroxamic acid (THAs) is poor when HAs possess bulky acyl and/or N‐substituents, acidic α‐hydrogen atoms, or an N‐phenyl ring. THAs yields were correlated with Brown sigma parameter. The relative rates of two subsequent processes k and k were also measured. Correlation was also found for methine proton chemical shifts of N‐isopropyl benzothiohydroxamic acids. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:676–684, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20259
One‐pot synthesis of aryl and heteroaroyl‐substituted hydroxypyrazolines from the reactions of β‐alkoxyvinyl trichloromethyl ketones with heteroarylhydrazides
Authors: Bonacorso Helio G. , Oliveira Marli R. , Costa Michelle B. , Drekener Roberta L. , Silva Letícia B. da , Zanatta Nilo , Martins Marcos A. P. 
Published: October 2006

AbstractThe one‐step regiospecific synthesis of a novel series of 10 trichloromethyl‐, aryl‐, and heteroaroyl‐substituted 5‐hydroxy‐2‐pyrazolines affords 1‐(2‐thenoyl)‐, 1‐(2‐furoyl)‐, and 1‐(isonicotinoyl)‐3‐aryl‐5‐hydroxy‐5‐trichloromethyl‐4,5‐dihydro‐1H‐pyrazoles in 63–92% yields from the cyclocondensation reactions of 1,1,1‐trichloro‐4‐methoxy‐4‐aryl‐3‐buten‐2‐ones (where aryl substituents are –C6H5, 4‐CH3C6H4, 4‐OCH3C6H4, 4‐FC6H4, 4‐ClC6H4, 4‐BrC6H4) with 2‐thiophenecarboxylic hydrazide, furoic hydrazide, and isonicotinic acid hydrazide, respectively. Dehydration reaction of two 2‐pyrazolines with P2O5 furnished the corresponding 1H‐pyrazoles in low yields (21–29%). © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:685–691, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20261
Restoring theta‐like rhythmicity in rats restores initial learning in the Morris water maze
Authors: McNaughton Neil , Ruan Ming , Woodnorth Mary‐Anne 
Published: October 2006

AbstractNeural activity often becomes rhythmic during mental processing. But there has been no direct proof that rhythmicity, per se, is important for mental function. We assessed this issue in relation to the contribution of hippocampal theta‐frequency rhythmicity to learning in the Morris water maze by blocking theta (and other septal inputs to the hippocampus) and then using electrical stimulation to restore rhythmicity. We injected tetracaine into the medial septal area, and so blocked septal input to the hippocampus in rats throughout 16 consecutive trials in a Morris water maze. Rats with no hippocampal theta also showed no initial learning in the maze. Theta rhythmicity in the supramammillary area remained after septal blockade, and we used this to trigger electrical stimulation of the fornix superior. This substantially restored hippocampal theta‐like rhythmicity throughout training at a normal frequency but with abnormal wave forms. This treatment applied throughout training substantially restored initial learning. Fixed frequency (7.7 Hz) stimulation produced rhythmic activity and a brief improvement in learning. Irregular stimulation with an average frequency of 7.7 Hz produced little rhythmicity and little improvement in learning. These results demonstrate that brain rhythmicity, per se, can be important for mental processing even when the detailed information originally carried by neurons is lost and when the reinstated pattern of population firing is not normal. The results suggest that the precise frequency of rhythmicity may be important for hippocampal function. Functional rhythmicity needs, therefore, to be included in neural models of cognitive processing. The success of our procedure also suggests that simple alterations of rhythmicity could be used to ameliorate deficits in learning and memory. © 2006 Wiley‐Liss, Inc.
Pathway specificity of dendritic spine morphology in identified synapses onto rat hippocampal CA1 neurons in organotypic slices
Authors: De Simoni Anna , Edwards Frances A. 
Published: October 2006

AbstractThe output of the hippocampus is largely determined by interaction of the three excitatory pathways that impinge on CA1 pyramidal neurons. These synapses, formed by axons of: (1) CA3 pyramidal neurons; (2) neurons of the entorhinal cortex (EC); and (3) neighboring CA1 neurons, are all potentially plastic. Here, we take advantage of the accessibility of the organotypic slice preparation to identify the type of spines with which each of these pathways forms synapses, at different developmental stages. Recent reports have shown that morphology of dendritic spines is activity‐dependent with large mushroom spines being thought to represent stronger synaptic connections than thin or stubby spines. Although in a wide range of preparations, mushroom spines represent only 15% of spines across the whole dendritic tree, we find that this proportion is highly pathway specific. Thus in organotypic slices, the axons of CA3 neurons form synapses with mushroom spines on CA1 neurons in ∼50% of cases, whereas this spine type is rare (<10%) in either of the other two pathways. This high proportion of mushroom spines only occurs after spontaneous excitatory activity in the CA1 cells increases over the second week in vitro. Previous studies suggest that pathway specificity also occurs in vivo. In tissue fixed in vivo, it is the synapses of distal apical dendrites thought to be formed by axons originating in the EC that are richer in mushroom spines. Hence, contrary to previous suggestions, the proportion of mushroom spines is clearly not an intrinsic property of the pathway but rather a characteristic dependent on the environment. We suggest that this is most likely a result of the previous activity of the synapses. The fact that, despite the large differences in pathway specificity between preparations, the overall proportion of different spine types remains unchanged, suggests a strong influence of homeostasis across the network. © 2006 Wiley‐Liss, Inc.
Discovery of deregulation of zinc homeostasis and its associated genes in esophageal squamous cell carcinoma using cDNA microarray
Authors: Kumar Anupam , Chatopadhyay Tusharkant , Raziuddin Mohamad , Ralhan Ranju 
Published: October 2006

AbstractEsophageal squamous cell carcinoma (ESCC) in the Indian population is associated with poor nutritional status, low socioeconomic conditions, bidi smoking and consumption of smokeless tobacco products, besides alcohol drinking and cigarette smoking. To determine the impact of these risk factors on molecular pathogenesis of ESCC, we determined global gene expression profiles of 7 paired samples of ESCC and histologically confirmed nonmalignant esophageal tissues using 19.1K cDNA microarrays. The most salient finding was identification of 19 differentially expressed genes encoding zinc binding or modulating proteins associated with transcriptional regulation, ubiquitin–protein degradation and maintenance of zinc homeostasis. Validation of differential expression of a subset of genes by real‐time quantitative RT‐PCR (real‐time QRT‐PCR) in clinical specimens of ESCC, esophageal dysplasia and histologically nonmalignant esophageal tissues and immunohistochemical analysis using tissue microarrays confirmed the microarray data and demonstrated upregulation of zinc finger proteins, cellular modulator of immune recognition (c‐MIR), snail homolog 2 (SLUG), zinc transporter, ZnT7 and downregulation of zinc metabolizing protein, metallothionein MT1G. We also observed upregulation of mitogen activated protein kinase kinase kinase 3 (MAP3K3/MEKK3), a kinase anchor protein 13 (AKAP13) and transglutaminase2 (TG2). Interestingly, we found upregulation of ZnT7 transcripts in ESCC cells (TE13) grown in zinc deficient condition. In conclusion, our data suggest deregulation of genes associated with zinc homeostasis in ESCC. © 2006 Wiley‐Liss, Inc.
Aromaticity in linear polyacenes: Generalized population analysis and molecular quantum similarity approach
Authors: Bultinck Patrick , Ponec Robert , Carbó‐Dorca Ramon 
Published: October 2006

AbstractThe relative aromaticity of benzenoid rings in the linear polyacenes is investigated using two novel aromaticity approaches. According to the first, the aromaticity of individual benzene rings was gauged by the values of six‐center bond indices (SCI) calculated within the so‐called Generalized Population Analysis (GPA). In the second approach, the same goal is addressed using the theory of Molecular Quantum Similarity (MQS). Both independent approaches are found to correlate very well, and both point toward decreasing aromaticity in any linear polyacenes upon going from the outer to inner rings. © 2006 Wiley Periodicals, Inc. J Comput Chem, 2007
Bond order and valence indices: A personal account
Authors: Mayer I. 
Published: October 2006

AbstractThe paper accounts for the author's activity in developing bond order and valence indices since the early 80s. These indices represent an important conceptual link between the physical description of molecules as systems of electrons and nuclei and the chemical picture of molecules consisting of atoms kept together by bonds. They are also useful for a systematization and interpretation of the results obtained in the quantum chemical calculations, by permitting to extract from the wave function different pieces of information that may be assigned chemical significance. In some cases they can have some predictive power, too. Historically, the prototypes of such indices were introduced in the semiempirical quantum chemistry; the most important developments were Coulson'scharge–bond order matrixin the simple Hückel theory and the Wiberg index in the CNDO framework. (Valence indices were also introduced in the semiempirical theory.) The definition of theab initiobond order index emerged from the asymptotic term of the exchange energy component of the partitioning performed in the framework of the author's so‐called “chemical Hamiltonian approach” using a “mixed” second quantization formalism for overlapping basis sets. They can also be introduced by studying the exchange part of the two‐particle density (or of the second‐order density matrix). Some properties of the bond order indices are discussed and the author's (until now unpublished) proof is also presented, showing the sufficient conditions under which the bond order index of a homonuclear diatomics is equal to the “chemist's bond order,” i.e., the half of the difference between the number of electrons occupying bonding and antibonding orbitals. Theab initiovalence indices are also introduced and discussed, and it is stressed that for correlated wave function the same “exchange only” definition of the bond order and valence indices should be used, which was introduced for the SCF case. The recent concept of the “atomic decomposition of identity” is also discussed and it is utilized for introducing bond orders and valences in the framework of the “3D analysis,” when atoms are defined not by their basis orbitals but as regions of the three‐dimensional (3D) physical space. Two versions of the 3D analysis are considered—the AIM (atoms in molecules)‐type decomposing the space into disjunct atomic domains and the “fuzzy atoms” scheme in which there are no sharp boundaries between the atoms but they exhibit a continuous transition from one to another. © 2006 Wiley Periodicals, Inc. J Comput Chem, 2007
Gluteal muscle attachment during proximal femoral reconstruction in a canine model
Authors: Pluhar G. Elizabeth , Manley Paul A. , Heiner John P. , Vanderby Ray , Markel Mark D. 
Published: October 2006

AbstractIn this 18 month in vivo canine study we compared three methods of attaching the gluteal muscles to the proximal femur during hip reconstruction with an allograft‐prosthesis composite (APC). All three methods are commonly practiced in human hip revision surgery and data on their effectiveness in dogs is directly relevant to human treatment. The methods compared were host gluteal tendon sutured to allograft tendon, host greater trochanter apposed to allograft using a cable grip system, and host cortical bone shells around the allograft secured with cerclage wires. For each method, we assessed changes in allograft‐host bone fusion, weight bearing, gluteal muscle mass, and structural properties through qualitative radiography, gait analysis, histology, and biomechanical testing. Hip reconstruction using the WRAP method resulted in the greatest limb use with complete resolution of gluteal muscle atrophy 18 months after surgery. This method yielded a stronger, more stable hip joint that allowed for more normal limb function. These hips had the more rapid rate of bony union at the host bone‐allograft junction and little resorption of the graft. The increased limb use and resultant larger gluteal muscle mass conferred to the WRAP hip composites the greatest tensile strength and stiffness when tested 18 months after reconstruction. There was a large amount of new bone formation on the periosteal surface where the WRAP reconstructions had an overlay of live bone that resulted in a more rapid union and increased cortical width at the level of the osteotomy. New bone also penetrated into the allograft a greater distance from the osteotomy in the WRAP group. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 25:208–220, 2007
Use of Nitrogen as a Blowing Agent for the Production of Fine‐Celled High‐Density Polyethylene Foams
Authors: Lee John W. S. , Park Chul B. 
Published: October 2006

AbstractSummary:While many experiments have been performed to examine the effects of administering CO2as a blowing agent in the foaming process, very few studies have investigated the use of N2for this purpose. In this study, foaming experiments were conducted in extrusion using HDPE as a polymeric material and N2as a blowing agent. Talc was used as a nucleating agent, and three different pressure‐drop rates were applied to study the effects of pressure‐drop rates on HDPE foams. The experimental results revealed that the void fraction of high‐density foams blown with N2was not affected by the die temperature, contrasting the situation in low‐density foams. Surprisingly, it was the cell density which determined the void fraction of high‐density foams. It was also found that the use of talc significantly increased the cell density and the void fraction of the foams and minimized the role played by the pressure‐drop rate in cell nucleation.Effect of N2content on the cell density of HDPE foams.magnified imageEffect of N2content on the cell density of HDPE foams.
Terminal latency index in neuropathy with antibodies against myelin‐associated glycoproteins
Authors: Lupu Vitalie D. , Mora Carlos A. , Dambrosia Jim , Meer Jacob , Dalakas Marinos , Floeter Mary Kay 
Published: October 2006

AbstractNeuropathy with antibodies against myelin‐associated glycoproteins (MAG/SGPG‐N) and hereditary sensorimotor neuropathy type 1 (HMSN1) are characterized by chronic demyelination with little conduction block. Electrodiagnostic studies suggest that in HMSN1 conduction slowing occurs uniformly along the nerve, whereas in MAG/SGPG‐N it is predominantly distal. Some but not all previous reports have shown that the terminal latency index (TLI) was useful to distinguish MAG/SGPG‐N from chronic idiopathic demyelinating polyneuropathy. We compared median TLI from 21 patients with MAG/SGPG‐N with those obtained from 26 patients with HMSN1, 20 with HMSN2, and 12 healthy volunteers. All patients with TLI <0.26 had MAG/SGPG‐N, and all patients with TLI ≥0.32 had HMSN1. In the remaining patients with intermediate TLI values, ulnar distal motor latency (DML) aided in differentiation between MAG/SGPG‐N and HMSN1 with an overall sensitivity of 100% and specificity of 98%. In conclusion, median TLI in combination with ulnar DML can further guide the demyelinating neuropathy evaluation toward hereditary or autoimmune causes. Muscle Nerve, 2006
Sensory conduction study of the infrapatellar branch of the saphenous nerve
Authors: Bademki̇ran Fi̇kret , Obay Basra , Aydogdu Ibrahi̇m , Erteki̇n Cumhur 
Published: October 2006

AbstractAlthough neuropathies of the infrapatellar nerve (infrapatellar branch of the saphenous nerve, IPBSN) have been reported clinically, no electrophysiological method has been defined to evaluate IPBSN conduction. We therefore studied a total of 60 saphenous nerves and 60 IPBSNs from 36 volunteers. The IPBSN was stimulated medially with a surface electrode 2 cm below the patella. The response was recorded with a needle electrode located close to the nerve 1 cm lateral to the femoral artery in the inguinal region. Sensory nerve action potentials were obtained from each subject; mean latency of the first positive peak was 8.1 ± 0.9 ms, conduction velocity was 54 ± 4.4 m/s, and response amplitude was 1.3 ± 1.1 μV. The method that we describe may be an easy and useful electrophysiological test for neuropathies of the IPBSN. Muscle Nerve, 2006