bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis and Characterization of Novel Titanium, Germanium, and Tin Silazane Complexes Bearing a Cyclohexasilazanetriido Ligand
Authors: Lehnert Christian , Wagler Jörg , Kroke Edwin , Roewer Gerhard 
Published: February 2007

AbstractNovel heterometallic silazane complexes were synthesized by the reaction of 1‐lithio‐2,2,4,4,6,6‐hexamethylcyclotrisilazane Li(HMCTS)H2 with the tetrachloride salts of titanium and germanium as well as by the reaction of 1,1,3,3,5,5‐hexamethylcyclotrisilazane H3(HMCTS) with tin tetrachloride and excess triethylamine. The products [H3(DMCHS)TiCl] (1), [H3(DMCHS)GeCl] (2), and [H3(DMCHS)SnCl] (3) {H3(DMCHS) = 2,2,4,4,6,6,8,8,10,10,12,12‐dodecamethylcyclohexasilazane‐1,5,9‐triido} were characterized by 1H‐, 13C‐, 14N‐, and 29Si NMR spectroscopy, elemental analyses and single‐crystal X‐ray structure analyses. The complexes have a surprising and interesting structure, that of a new dodecamethylcyclohexasilazane system with the Ti, Ge, or Sn atom in the center. These metal atoms are coordinated by one chlorine atom and three nitrogen atoms. The metal centers are part of three six‐membered hetero‐silazane rings. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Synthesis and Conformational Analysis of Constrained β‐Turn Mimetics Incorporating a Bicyclic Turn Inducer by Use of the Petasis Three‐Component Reaction on Solid Phase
Authors: Danieli Elisa , Trabocchi Andrea , Menchi Gloria , Guarna Antonio 
Published: February 2007

AbstractA new set of β‐turn mimetics incorporating a bicyclic turn inducer was achieved by use of the solid‐phase Petasis reaction in a stereoselective fashion. The stereoselectivity of the reaction turned out to be dependent on the side chain of the amino acid preceding the reverse turn inducer. The β‐turn mimetics were stabilized by strong intramolecular 10‐membered ring hydrogen bonds, detected by conformational analysis by NMR and molecular modelling, whilst the turn type was controlled by the final amine component. Use of arylboronic acids provided access to chemical diversity at position i + 1, whilst the versatility of the HMBA resin allowed additional diversification to be introduced at the cleavage stage, thus providing a tool for the generation of libraries of β‐turn mimetics as privileged structures in combinatorial chemistry.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Does the Planar Aromatic Phosphorus Analogue of Pyridone Exist?
Authors: Li Wei‐Qi , Tian Wei Quan , Feng Ji‐Kang , Liu Zi‐Zhong 
Published: February 2007

AbstractDensity functional calculations show that the minimum of meta‐phosphanyl ketone on the potential energy surface is a planar conformation. The minima of ortho‐phosphanyl ketone and para‐phosphanyl ketone have nonplanar structures. However, according to the sum of the bonding angles about the tricoordinated phosphorus atom, the degree of planarity of the ortho‐ and para‐phosphanyl ketones is higher than that of the known phosphole and PH3. Thenucleus‐independent chemical shifts and other electronic properties show that the planar phosphorus analogues of pyridone are π aromatic. The position of the carbonyl group relative to the tricoordinate phosphorus atom affects the delocalization of the phosphorus lone pair of electrons and the aromaticity of the molecule. Introduction of a σ‐donor, π‐acceptor, and bulky substituents at the phosphorus atom can decrease the pyramidal character efficiently. We predict that planar aromatic phosphanyl ketones do exist.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Dynamic Rotational Oscillation of Cerium(IV) Bis(porphyrinate) and Its Control by Diamine Guest Binding with Positive Homotropic Allosterism
Authors: Ikeda Masato , Kubo Yohei , Yamashita Kousei , Ikeda Tomohiro , Takeuchi Masayuki , Shinkai Seiji 
Published: February 2007

AbstractWe have synthesized a porphyrin oscillator (1) composed of cerium(IV) bis(porphyrinate) bearing four peripheral zinc(II) porphyrinates. The rotational oscillation frequency of the porphyrin was evaluated in solution with and without the presence of diamine guest 2 by variable temperature NMR spectroscopy. The results established that the rotational frequency can be controlled by added guest utilizing positive homotropic allosterism. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Synthesis of Heterocyclic Systems by Transition‐Metal‐Catalyzed Cyclization‐Migration Reactions – A Diversity‐Oriented Strategy for the Construction of Spirocyclic 3(2H)‐Furanones and 3‐Pyrrolones
Authors: Binder Jörg T. , Crone Benedikt , Kirsch Stefan F. , Liébert Clémence , Menz Helge 
Published: February 2007

AbstractTwo platinum(II)‐catalyzed heterocyclization‐migration reactions that provide five‐membered heterocycle products are described. With 5 mol‐% of PtCl2 as a catalyst, 2‐alkynyl‐2‐hydroxy carbonyl compounds 1 are converted into 3(2H)‐furanones 2 at 80 °C in moderate to excellent yields under very mild reaction conditions. The reaction is proposed to proceed through an oxonium ion intermediate B, which triggers a stereospecific 1,2‐shift analogous to an α‐ketol rearrangement. When exploited in a different manner, the 2‐alkynyl‐2‐hydroxy carbonyl compounds 1 afford 3‐pyrrolones 3 in 33–81 % yield. For this purpose, the starting compounds 1 are treated with primary amines in the presence of 5 mol‐% of PtCl2 at 100 °C in a convenient one‐pot process. These cyclization‐migration reactions give novel access to 3(2H)‐furanones and 3‐pyrrolones in which the 2‐position bears aryl or alkyl substituents. Synthetically challenging spirocyclic compounds can be prepared in this fashion by ring contraction. Studies that define the scope and limitations of the cyclization‐migration synthesis of heterocyclic systems are also described. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Ionic Liquids Modify the Performance of Carbon Based Potentiometric Sensors
Authors: Safavi Afsaneh , Maleki Norouz , Honarasa Fatemeh , Tajabadi Fariba , Sedaghatpour Fatemeh 
Published: February 2007

AbstractA new type of potentiometric sensor based on a recently constructed carbon ionic liquid electrode (CILE) is described. Two kinds of ionic liquids, i.e., N‐octylpyridinium hexafluorophosphate (OPFP) and 1‐butyl‐3‐methylimidazoluim hexafluorophosphate (BMFP) were tested as binder for construction of the carbon composite electrode. The characteristics of these electrodes as potentiometric sensors were evaluated and compared with those of the traditional carbon paste electrode (CPE). The results indicate that potentiometric sensors constructed with ionic liquid show an increase in performance in terms of Nernstian slope, selectivity, response time, and response stability compared to CPE.
Electroanalysis of Ethanol with a Glass Carbon Electrode Comodified with Liver Tissue Homogenate and Carbon Nanotubes
Authors: Chen Jing , Chen Guifang , Li Dong , Jia Jianbo , Li Genxi 
Published: February 2007

AbstractLiver tissue homogenate and carbon nanotubes (CNTs) are comodified on a glass carbon electrode for electroanalysis of ethanol. Alcohol dehydrogenase, which is rich in liver tissue, can catalyze the oxidation of ethanol. Experimental results reveal that the catalytic peak current of ethanol is linear with ethanol concentration in the range of 2×10−8–7×10−7 mol/L. The limit of detection is 5×10−9 mol/L. The relative standard deviation for six determinations of a 0.5 μM ethanol sample is 4.0%. The optimal condition of the electrode modification has been obtained, and the best operating temperature has been known as 30 °C. The stability of the modified electrode can also be reasonably satisfactory.
Amperometric L‐Lactate Biosensor Based on Gold Nanoparticles
Authors: Jena Bikash Kumar , Raj C. Retna 
Published: February 2007

AbstractA novel amperometric biosensor for the sensing of L‐lactate is developed using L‐lactate dehydrogenase (LDH) and hydroxylamine enlarged gold nanoparticles (GNPs). LDH and GNPs have been integrated with the sol–gel 3‐D silicate network derived from 3‐(mercaptopropyl)trimethoxysilane (MPTS). The biosensing of L‐lactate is based on the electrocatalytic determination of enzymatically generated NADH by GNPs of the integrated assembly. The GNPs on the network efficiently catalyze the oxidation of NADH at −0.065 V, which is ca. 915 mV less positive than on the bulk Au electrode. The biosensor was characterized in terms of the effects of enzyme loading, solution pH, and cofactor concentration. The integrated biosensor was successfully utilized for the amperometric sensing of L‐lactate and it shows excellent sensitivity with a detection limit of 100 nM. The common interfering electroactive compounds in the biological system do not interfere the amperometric measurement of L‐lactate. This biosensor linearly responds to L‐lactate in the range of 0–0.8 mM and the sensitivity of the electrode was 0.446 nA/nM. Excellent reproducibility, long time storage and operational stability have been achieved.
Cyclic Voltammetric Studies of a Pyrolytic Carbon Film Electrode and the Effect of Laser Irradiation
Authors: Hadi M. , Rouhollahi A. , Taidy F. , Yousefi M. 
Published: February 2007

AbstractThe effects of laser irradiation with a small N2 laser on the reactivation of a pyrolytic carbon (PC) film electrode were investigated. Cyclic voltammetry, Raman spectroscopy and scanning electron microscopy (SEM) were used to characterize the electrode. The electrode response decayed during the solution exposure but could be restored to a good performance via this reactivation method. It was found that the effect of laser to promote electron transfer was desorption the physisorbed impurities to exposure more active sites on the surface. Also, the electrochemical results were compared to the results of organic solvent washing and anodization.
Enhanced Microchip Electrophoresis of Neurotransmitters on Glucose Oxidase Modified Poly(dimethylsiloxane) Microfluidic Devices
Authors: Wang Ai‐Jun , Xu Jing‐Juan , Chen Hong‐Yuan 
Published: February 2007

AbstractIn this paper, glucose oxidase (GOx) was employed to construct a functional film on the poly(dimethylsiloxane) (PDMS) microfluidic channel surface and apply to perform electrophoresis coupled with in‐channel electrochemical detection. The film was formed by sequentially immobilizing poly(diallyldimethylammonium chloride) (PDDA) and GOx to the microfluidic channel surface via layer‐by‐layer (LBL) assembly. A group of neurotransmitters (5‐hydroxytryptamine, 5‐HT; dopamine, DA; epinephrine, EP; dobuamine, DBA) as a group of separation model was used to evaluate the effect of the functional PDMS microfluidic devices. Electroosmotic flow (EOF) in the modified PDMS microchannel was well suppressed compared with that in the native one. Experimental conditions were optimized in detail. As expected, these analytes were efficiently separated within 110 s in a 3.7 cm long separation channel and successfully detected at a single carbon fiber electrode. Good performances were attributed to the decreased EOF and the interactions of analytes with the immobilized GOx on the PDMS surface. The theoretical plate numbers were 2.19×105, 1.89×105, 1.76×105, and 1.51×105 N/m at the separation voltage of 1000 V with the detection limits of 1.6, 2.0, 2.5 and 6.8 μM (S/N=3) for DA, 5‐HT, EP and DBA, respectively. In addition, the modified PDMS channels had long‐term stability and excellent reproducibility.
Simultaneous Determination of Quinoline and Pyridine Compounds in Gasoline and Diesel by Differential Pulse Voltammetry
Authors: Okumura Leonardo L. , Stradiotto Nelson R. 
Published: February 2007

AbstractThe presence of trace basic organonitrogen compounds such as quinoline and pyridine in derivative petroleum fuels plays an important role in maintaining the engines of vehicles. However, these substances can contaminate the environment and so must be controlled because most of them are potentially carcinogenic and mutagenic. For these reasons, a reliable and sensitive method was developed for the determination of basic nitrogen compounds in fuel samples such as gasoline and diesel. This method utilizes preconcentration on an ion–exchange resin (Amberlyte IR–120 H) followed by differential pulse voltammetry (DPV) on a glassy carbon electrode. The electrochemical behavior of quinoline and pyridine as studied by cyclic voltammetry (CV) suggests that their reduction occurs via a reversible electron transfer followed by an irreversible chemical reaction. Very well resolved diffusion‐controlled voltammetric peaks were obtained in dimethylformamide (DMF) with tetrabutylammonium tetrafluoroborate (TBAF4 0.1 mol L−1) for quinoline (−1.95 V) and pyridine (−2.52 V) vs. Ag|AgCl|KClsat reference electrode. The proposed DPV method displayed a good linear response from 0.10 to 300 mg L−1 and a limit of detection (LOD) of 5.05 and 0.25 μg L−1 for quinoline and pyridine, respectively. Using the method of standard additions, the simultaneous determination of quinoline and pyridine in gasoline samples yielded 25.0±0.3 and 33.0±0.7 mg L−1 and in diesel samples yielded 80.3±0.2 and 131±0.4 mg L−1, respectively. Spike recoveries were 94.4±0.3% and 101±0.5% for quinoline and pyridine, respectively, in the fuel determinations. This proposed method was also compared with UV‐vis spectrophotometric measurements. Results obtained for the two methods agreed well based on F and t student's tests.
Sequences with low total squared asynchronous correlation for chip‐unaligned CDMA systems
Authors: Vanhaverbeke Frederik , Moeneclaey Marc 
Published: February 2007

AbstractWe examine some properties of Chip‐unaligned (Cu) CDMA systems with sequences that are obtained by means of an eigen update algorithm. We briefly refer to these systems as ‘Cu systems with low total squared asynchronous correlation (TSAC)’. The notion of TS(A)C, which is well‐known for Chip‐aligned (Ca) systems, is extended to the Cu case. It is found that the TSAC of Cu systems with low TSAC is a non‐sensitive function of the time shift set of the Cu system, but it is strongly dependent on the chip pulse. Similar to the Ca case, for high channel loads, the TSAC of some Cu systems with low TSAC appears to be proportional to the channel load and the number of users in the system, while the equally good property is valid. An examination of the maximum common signal to interference and noise ratio (SINR) target level κmax indicates that particular types of Cu systems with low TSAC allow for a significantly higher value of κmax than achievable in Ca systems. Copyright © 2007 John Wiley & Sons, Ltd.
Optimal prediction with nonstationary ARFIMA model
Authors: Boutahar Mohamed 
Published: February 2007

AbstractWe propose two methods to predict nonstationary long‐memory time series. In the first one we estimate the long‐range dependent parameterdby using tapered data; we then take the nonstationary fractional filter to obtain stationary and short‐memory time series. In the second method, we take successive differences to obtain a stationary but possibly long‐memory time series. For the two methods the forecasts are based on those obtained from the stationary components.  Copyright © 2007 John Wiley & Sons, Ltd.
Traditional versus unobserved components methods to forecast quarterly national account aggregates
Authors: Marrero Gustavo A. 
Published: February 2007

AbstractWe aim to assess the ability of two alternative forecasting procedures to predict quarterly national account (QNA) aggregates. The application of Box–Jenkins techniques to observed data constitutes the basis of traditional ARIMA and transfer function methods (BJ methods). The alternative procedure exploits the information of unobserved high‐ and low‐frequency components of time series (UC methods). An informal examination of empirical evidence suggests that the relationships between QNA aggregates and coincident indicators are often clearly different for diverse frequencies. Under these circumstances, a Monte Carlo experiment shows that UC methods significantly improve the forecasting accuracy of BJ procedures if coincident indicators play an important role in such predictions. Otherwise (i.e., under univariate procedures), BJ methods tend to be more accurate than the UC alternative, although the differences are small. We illustrate these findings with several applications from the Spanish economy with regard to industrial production, private consumption, business investment and exports.  Copyright © 2007 John Wiley & Sons, Ltd.
On estimating contemporaneous quarterly regional GDP
Authors: Pavía‐Miralles Jose Manuel , Cabrer‐Borrás Bernardí 
Published: February 2007

AbstractSubnational regional jurisdictions rarely have at their disposal a reasonable array of timely statistics to monitor their economic condition. In light of this, we develop a procedure that simultaneously estimates a quarterly time series for all regions of a country based upon quarterly national and annual regional data. While other such techniques exist, we suggest a temporal error structure that eliminates possible spurious jumps. Using our approach, regional analysts should now be able to distribute national growth among regions as soon as quarterly national figures are released. In a Spanish application, we detail some practicalities of the process and show that our proposal produces better estimates than the uniregional methods often used.  Copyright © 2007 John Wiley & Sons. Ltd.
Shunting and hyperpolarizing GABAergic inhibition in the high‐potassium model of ictogenesis in the developing rat hippocampus
Authors: Isaev Dmytro , Isaeva Elena , Khazipov Rustem , Holmes Gregory L. 
Published: February 2007

AbstractOntogenesis of GABAergic signaling may play an important role in developmental changes in seizure susceptibility in the high‐potassium model of ictogenesis in vitro. The age‐dependent effects of [K+]o on the reversal potential of the GABA(A)‐mediated responses and membrane potential in hippocampal slices in vitro were compared with the effect of GABA(A)‐receptors antagonists and GABA(A) modulators on high‐potassium induced seizures in the CA3 pyramidal layer of rat hippocampus in vivo. GABA(A) responses were depolarizing at P8–12 and hyperpolarizing at P17–21. In P8–12 rats, GABA(A) responses switch their polarity from depolarizing to hyperpolarizing upon elevation of extracellular potassium. At ∼10 mM [K+]o, activation of GABA(A) receptors produced an isoelectric, purely shunting response characterized by no changes in the membrane potential but an increase in the membrane conductance. In P17–21 rats, the hyperpolarizing GABA(A) driving force progressively increased with elevation of [K+]o. In P8–12 rats in vivo, GABA(A)‐receptor antagonists did not affect the occurrence of ictal discharges induced by intrahippocampal injection of 10 mM [K+]o, but significantly increased seizure duration. Diazepam and isoguvacine completely prevented seizures induced by 10 mM [K+]o. In P17–21 rats, GABA(A)‐receptor antagonists strongly increased the occurrence of ictal activity induced both by 10 mM [K+]o. Taken together, these results suggest that anticonvulsive effects of GABA are because of the combination of shunting and hyperpolarizing actions of GABA. Although shunting GABA is already efficient in the young age group, a developmental increase in the hyperpolarizing GABA(A) driving force likely contributes to the increase in the GABAergic control of seizures upon maturation. © 2007 Wiley‐Liss, Inc.
NY‐ESO‐1 protein expression in primary breast carcinoma and metastases—correlation with CD8+ T‐cell and CD79a+ plasmacytic/B‐cell infiltration
Authors: Theurillat Jean‐Philippe , Ingold Fabienne , Frei Claudia , Zippelius Alfred , Varga Zsuzsanna , Seifert Burkhardt , Chen Yao‐Tseng , Jäger Dirk , Knuth Alexander , Moch Holger 
Published: February 2007

AbstractNY‐ESO‐1 is a cancer testis antigen expressed in various malignancies and testicular germ cells. Because of its capacity to induce specific humoral and cellular immunity in patients with NY‐ESO‐1‐positive carcinomas, it represents a promising target for cancer immunotherapy. In breast cancer, NY‐ESO‐1‐mRNA was reported in up to 42%, but protein expression has not been determined to larger extent. In the present tissue microarray‐based study, primary breast cancers (n = 1,444), in situ lesion (n = 148), recurrences (n = 88), lymph node (n = 525) and distant metastases (n = 91) were studied for NY‐ESO‐1 expression by immunohistochemistry. NY‐ESO‐1‐protein expression was compared with mRNA expression by real‐time PCR. NY‐ESO‐1‐protein was detected in 3.1% (4/128) in situ lesions and in 2.1% (28/1355) invasive breast cancer. There were 1.8% (9/493) NY‐ESO‐1‐positive lymph node and 5.1% (4/78) positive distant metastases. NY‐ESO‐1 was more frequently expressed in grade 3 (4.9%) than in grade 2 (0.8%) and grade 1 (0.5%) carcinomas (p < 0.0001). Presence of tumor‐infiltrating CD8+ T‐cells correlated with NY‐ESO‐1 (p < 0.0001) on the tissue microarray. On randomly selected large sections, 4 out of 9 NY‐ESO‐1‐positive tumors displayed a brisk infiltrate of CD79a+ plasmocytes/B‐cells, but none of 10 NY‐ESO‐1‐negative tumors (p < 0.05). NY‐ESO‐1‐mRNA expression was detected in frozen samples of NY‐ESO‐1‐protein positive (n = 6) and negative breast cancers (n = 8) and in normal testis. Comparison between mRNA and protein expression revealed that only breast cancers with NY‐ESO‐1‐mRNA levels comparable or higher than testis expressed NY‐ESO‐1‐protein. These findings suggest that NY‐ESO‐1‐positive breast cancers represent a small subset of poorly differentiated tumors with evidence of cellular and humoral immune response. © 2007 Wiley‐Liss, Inc.
Intratumoral injection of dendritic cells in combination with local hyperthermia induces systemic antitumor effect in patients with advanced melanoma
Authors: Guo Jun , Zhu Jun , Sheng Xinan , Wang Xiaopei , Qu Li , Han Yan , Liu Yuexiang , Zhang Hui , Huo Ling , Zhang Shuhui , Lin Baohe , Yang Zhi 
Published: February 2007

AbstractDendritic cells (DC) are potent antigen‐presenting cells that can present tumor antigens chaperoned by heat shock proteins (HSPs), while local hyperthermia (LHT) can increase the expression of HSPs. In this study, we determine if intratumoral injection of immature DC after LHT (LHT+IT‐DC) induces systemic antitumor immunity in patients with advanced melanoma, and investigate the potential immunological mechanisms involved in the treatments. Patients were randomly assigned to intratumoral administration of autologous immature DC triweekly, with (LHT+IT‐DC, arm A, n = 9) or without (IT‐DC, arm B, n = 9) LHT. Our results showed that there were no grade 3/4 toxicities. The time to progress (TTP) of arm A was 5 months, significantly longer than that in arm B (2 months, p < 0.05). However, the overall survival time had no statistical difference (13 months vs. 6 months, p > 0.05) between the 2 groups. Our ELISPOT assay showed a significantly increased melanoma‐specific IFN‐γ production in arm A, suggesting that LHT+IT‐DC was more effective in the induction of cytotoxic T lymphocytes (CTL) than IT‐DC alone. Furthermore, we detected an increased HSPs expression 4 hr after the first LHT, an enhanced Th1/Th2 chemokines production 24 hr after the first LHT+IT‐DC treatment, a promoted migration of DC to afferent lymph nodes, and a decreased infiltration of regulatory T cells (CD4+CD25+) and an increased infiltration of active CTL (CD8+CD28+) 48 hr after the third DC injection in arm A patients. Therefore, LHT+IT‐DC can induce effective specific antitumor immunity and facilitate a Th1‐polarized immune response in patients with advanced melanoma. © 2007 Wiley‐Liss, Inc.