bluuebunny/crossref_metadata_2025_split huggingface dataset:
Using GEMANOVA to explore the pattern generating properties of the Delta‐Notch model
Authors: Isaeva Julia , Sæbø Solve , Wyller John Andreas , Liland Kristian Hovde , Faergestad Ellen Mosleth , Bro Rasmus , Martens Harald 
Published: October 2010

AbstractIn the area of systems biology, increasingly complex models are developed to approximate biological processes. The complexity makes it difficult to derive the properties of such models analytically. An alternative to analytical considerations is to use multivariate statistical methods to reveal essential properties of the models. In this paper it is shown how the properties of a relatively complex mathematical model for describing cell‐pattern development, the Delta‐Notch model, can be explored by means of statistical analyses of data generated from the model. ANOVA is a well‐known and one of the most commonly used methods for analyzing data from designed experiments, but it turns out that it is not always appropriate for finding and exploring higher‐order interactions. For this purpose a multiplicative alternative—GEMANOVA—was used in the present paper for studying the Delta‐Notch model, for which the properties depend on higher order interactions between the model parameters. It is shown here how a forward selection strategy combined with bootstrapping can be used to identify GEMANOVA models with reasonable fit to the data, and it is demonstrated how new insight about the Delta‐Notch model can be gained from interpreting the GEMANOVA output. Copyright © 2010 John Wiley & Sons, Ltd.
Neutralization of a sec‐Ammonium Group Unusually Stabilized by the “Rotaxane Effect”: Synthesis, Structure, and Dynamic Nature of a “Free” sec‐Amine/Crown Ether‐Type Rotaxane
Authors: Nakazono Kazuko , Takata Toshikazu 
Published: October 2010

AbstractA fifteen‐year riddle has been settled: neutralization, the most popular chemical event, of a crown ether/sec‐ammonium salt‐type rotaxane has been achieved and a completely nonionic crown ether/sec‐amine‐type rotaxane isolated. A [2]rotaxane was prepared as a typical substrate from a mixture of dibenzo[24]crown‐8 ether (DB24C8) and sec‐ammonium hexafluorophosphate (PF6) with a terminal hydroxy group through end‐capping with 3,5‐dimethylbenzoic anhydride in the presence of tributylphosphane as a catalyst in 90 % yield. A couple of approaches to the neutralization of the ammonium rotaxane were investigated to isolate the free sec‐amine‐type rotaxane by decreasing the degree of thermodynamic and kinetic stabilities. One approach was the counteranion‐exchange method in which the soft counterion PF6− was replaced with the fluoride anion by mixing with tetrabutylammonium fluoride, thus decreasing the cationic character of the ammonium moiety. Subsequent simple washing with a base allowed us to isolate the free sec‐amine‐type rotaxane in a quantitative yield. The other approach was a synthesis based on a protection/deprotection protocol. The acylation of the sec‐ammonium moiety with 2,2,2‐trichloroethyl chloroformate gave an N‐carbamated rotaxane that could be deprotected by treating with zinc in acetic acid to afford the corresponding free sec‐amine‐type rotaxane in a quantitative yield. The structure of the free sec‐amine‐type rotaxane was fully confirmed by spectral and analytical data. The generality of the counteranion‐exchange method was also confirmed through the neutralization of a bisammonium‐type [3]rotaxane. The mechanism was studied from the proposed potential‐energy diagram of the rotaxanes with special emphasis on the role of the PF6− counterion.
Crystallization‐Controlled Dynamic Self‐Assembly and an On/Off Switch for Equilibration Using Boronic Ester Formation
Authors: Takahagi Hiroki , Iwasawa Nobuharu 
Published: October 2010

AbstractMacrocyclic boronic esters of different sizes can be prepared selectively from the same starting diboronic acid and 1,2‐diol by means of an interesting dynamic self‐assembly phenomena. More specifically, two kinds of macrocyclic boronic esters could be formed diastereoselectively and nearly quantitatively under neutral conditions by the addition of an appropriate guest molecule that acts as a template. Although a mixture of tetrol 1 and di(boronic acid) 2 in methanol gave only insoluble polymeric boronic esters, a soluble macrocyclic boronic ester, homo‐[2+2], was obtained selectively in the presence of toluene as a guest molecule. Furthermore, when benzene was employed as a guest molecule, the selective formation of another macrocyclic boronic ester, hetero‐[3+3], occurred. Interestingly, each of these macrocycles could be converted into the other in the presence of methanol and the appropriate guest molecule; however, under aprotic conditions, guest molecules encaged by the macrocyclic boronic ester could be exchanged without affecting its structure. Thus the presence or absence of a protic solvent could be used as a regulator to switch on or off the dynamic equilibrium of the system. In addition, investigation of the effect of reaction time, direct observation of the reaction mixture by NMR spectroscopy, and carrying out the reaction using optically active tetrol suggested that precipitation plays an essentially important role in the selective formation of the macrocyclic boronic esters. Thus, although both of [2+2] and [3+3] were present as solutes in the reaction mixture, the type of added guest molecule induced the selective precipitation of only one form of macrocyclic boronic ester, hence displacing the equilibrium of the system.
Organocatalysts for the Controlled “Immortal” Ring‐Opening Polymerization of Six‐Membered‐Ring Cyclic Carbonates: A Metal‐Free, Green Process
Authors: Helou Marion , Miserque Olivier , Brusson Jean‐Michel , Carpentier Jean‐François , Guillaume Sophie M. 
Published: October 2010

AbstractSix‐membered cyclic carbonates, namely trimethylene carbonate (TMC), 3,3‐dimethoxytrimethylene carbonate (DMTMC) and 3‐benzyloxytrimethylene carbonate (BTMC), undergo controlled “immortal” ring‐opening polymerization (iROP) under mild conditions (bulk, 60–150 °C), by using organocatalysts, including an amine [4‐N,N‐dimethylaminopyridine (DMAP)], a guanidine [1,5,7‐triazabicyclo‐[4.4.0]dec‐5‐ene (TBD)], or a phosphazene [2‐tert‐butylimino‐2‐diethylamino‐1,3‐dimethylperhydro‐1,3,2‐diazaphosphorine (BEMP)], in the presence of an alcohol [benzyl alcohol (BnOH), 1,3‐propanediol (PPD), glycerol (GLY)] that acts as both a co‐initiator and a chain‐transfer agent. Remarkably, such organocatalysts remain highly active in the iROP of technical‐grade, unpurified TMC. Under optimized conditions, as much as 100 000 equivalents of TMC were fully converted by as little as 10 ppm of BEMP with the simultaneous growth of as many as 200 polymer chains, allowing the preparation of high molar mass poly(trimethylene carbonate)s (up to 45 800 g mol−1). These catalyst systems enable among the highest activities (TOF=55 800 h−1) and productivities (TON=95 000) ever reported for the ROP of TMC.
X‐ray Fluorescence Investigation of Ordered Intermetallic Phases as Electrocatalysts towards the Oxidation of Small Organic Molecules
Authors: Liu Yi , Lowe Michael A. , Finkelstein Ken D. , Dale Darren S. , DiSalvo Francis J. , Abruña Héctor D. 
Published: October 2010

AbstractThe composition of ordered intermetallic nanoparticles (PtBi and PtPb) has been quantitatively studied by in situ X‐ray fluorescence (XRF) during active electrochemical control in solutions of supporting electrolyte and small organic molecules (SOMs). Because the Pt Lβ1,2 lines and the Bi Lα1,2 lines are only separated by 200 eV, an energy‐dispersive detector and a multiple‐channel analyzer (MCA) were used to record the major fluorescent emission lines from these two elements. The molar ratios of platinum to the less‐noble elements (Bi, Pb) in the nanoparticles dramatically changed as a function of the applied upper limit potentials (Eulp) in cyclic voltammetric (CV) characterization. Similar to previous investigations for bulk intermetallic surfaces, the less‐noble elements leached out from the surfaces of the intermetallic nanoparticles. For PtBi nanoparticles, the ratios of fluorescence intensities of Pt/Bi in the samples were 0.42, 0.96, and 1.36 for Eulp=+0.40, +0.80, and 1.20 V, respectively, while cycling the potential from −0.20 V to the Eulp value for 10 cycles. The leaching‐out process of the less‐noble elements occurred at more negative Eulp values than expected. After cycling to relatively positive Eulp values, nonuniform PtM (M=Bi of Pb) nanoparticles formed with a Pt‐rich shell and intermetallic PtM core. When the supporting solutions contained active fuel molecules in addition to the intermetallic nanoparticles (formic acid for PtBi, formic acid and methanol for PtPb), kinetic stabilization effects were observed for Eulp=+0.80 V, in a way similar to the response of the bulk materials. It was of great importance to quantitatively explore the change in composition and structure of the intermetallic nanoparticles under active electrochemical control. More importantly, this approach represents a simple, universal, and multifunctional method for the study of multi‐element nanoparticles as electrocatalysts. This is, to our knowledge, the first report of nondestructive, quantitative characterization of bimetallic or multi‐elemental nanoparticles electrocatalysts under active electrochemical control.
Short‐Peptide‐Based Hydrogel: A Template for the In Situ Synthesis of Fluorescent Silver Nanoclusters by Using Sunlight
Authors: Adhikari Bimalendu , Banerjee Arindam 
Published: October 2010

AbstractN‐terminally Fmoc‐protected dipeptide, Fmoc‐Val‐Asp‐OH, forms a transparent, stable hydrogel with a minimum gelation concentration of 0.2 % w/v. The gelation property of the hydrogel was investigated by using methods such as transmission electron microscopy, field‐emission scanning electron microscopy, atomic force microscopy and Fourier transform infrared spectroscopy. The silver‐ion‐encapsulating hydrogel can efficiently and spontaneously produce fluorescent silver nanoclusters under sunlight at physiological pH (7.46) by using a green chemistry approach. Interestingly, in the absence of any conventional reducing agent but in the presence of sunlight, silver ions were reduced by the carboxylate group of a gelator peptide that contains an aspartic acid residue. These clusters were investigated by using UV/Vis spectroscopy, photoluminescence spectroscopy, high‐resolution transmission electron microscopy (HR‐TEM), atomic force microscopy (AFM) and X‐ray diffraction (XRD) studies. Mass spectrometric analysis shows the presence of a few atoms in nanoclusters containing only Ag2. The reported fluorescent Ag nanoclusters show excellent optical properties, including a very narrow emission profile and large Stokes shift (>100 nm). The reported fluorescent Ag nanoclusters within hydrogel are very stable even after 6 months storage in the dark at 4 °C. The as‐prepared hydrogel–nanocluster conjugate could have applications in antibacterial preparations, bioimaging and other purposes.
Double‐CO32− Centered [CoII5] Wheel and Modeling of Its Magnetic Properties
Authors: Sarkar Mrinal , Aromí Guillem , Cano Joan , Bertolasi Valerio , Ray Debashis 
Published: October 2010

AbstractA high‐spin CoII cluster with a rare pentagonal molecular structure and formula [Co5(CO3)2(bpp)5]ClO4 (1; Hbpp is 2,6‐bis(phenyliminomethyl)‐4‐methylphenolate) has been synthesized and characterized by single‐crystal X‐ray diffraction. This topology arises from fusing five [Co2(bpp)] moieties in a cyclic manner around two CO32− central ligands, resulting in propeller‐like configuration. The irregular coordination of the carbonate ions to the metal centers results in a combination of coordination numbers (CNs) of the CoII ions of five and six. The bulk magnetization of this complicated magnetically exchanged system has been modeled successfully by employing a matrix diagonalization technique. For this, the combination of S=3/2 ions (CN=5) with ions exhibiting strong spin‐orbit coupling (CN=6) has been considered and a perturbative approach to handle the data in the whole studied range of temperatures (2–300 K) yielding parameters of g and D (for the five‐coordinate CoII ions), of A, κ, λ, and Δ (for the metals with spin‐orbit coupling) and of the exchange constants J. The agreement with results from DFT calculations, also presented here, is remarkable.
Cyclopropylamines fromN,N‐Dialkylcarboxamides and Grignard Reagents in the Presence of Titanium Tetraisopropoxide or Methyltitanium Triisopropoxide
Authors: de Meijere Armin , Chaplinski Vladimir , Winsel Harald , Kordes Markus , Stecker Björn , Gazizova Vesta , Savchenko Andrei I. , Boese Roland , Schill (née Brackmann) Farina 
Published: October 2010

AbstractThirty‐three differentN,N‐dialkyl‐ andN‐alkyl‐N‐phosphorylalkyl‐substituted carboxamides9–17were treated with unsubstituted as well as with 2‐alkyl‐, 2,2‐dialkyl‐, and 3‐alkenyl‐substituted ethylmagnesium bromides6in the presence of stoichiometric amounts of titanium tetraisopropoxide or methyltitanium triisopropoxide to furnish substituted cyclopropylamines20–25in 20–98 % yield, depending on the substituents with no (1:1) to excellent (>25:1) diastereoselectivities. Generally higher yields (up to 98 %) of the cyclopropylamines20–28without loss of the diastereoselectivity were obtained with methyltitanium triisopropoxide as the titanium mediator. Under these conditions, even dioxolane‐protected ketones and halogen‐substituted and chiral as well as achiral alkyloxyalkyl‐substituted carboxamides could be converted to the correspondingly substituted cyclopropylamines with unsubstituted as well as phenyl‐ and a variety of alkyl‐substituted ethylmagnesium bromides in addition to numerous heteroatom‐containing (e.g., halogen‐, trityloxy‐, tetrahydropyranyloxy‐substituted) Grignard reagents (62 examples altogether). The transformation ofN,N‐diformylalkylamines54with ethylmagnesium bromide in the presence of methyltitanium triisopropoxide toN,N‐dicyclopropyl‐N‐alkylamines55can be brought about in up to 82 % yield (6 examples). An asymmetric variant of the titanium‐mediated cyclopropanation ofN,N‐dialkylcarboxamides has been developed by applying chiral titanium mediators generated from stoichiometric amounts of titanium tetraisopropoxide and chiral diamino or diol ligands, respectively. The most efficient chiral mediators turned out to be titanium bistaddolates that provided the corresponding cyclopropylamines with enantiomeric excesses (ee) of up to 84 %. Evaluation of several silyl‐based additives revealed that the reaction can also efficiently be carried out with substoichiometric amounts (down to 25 mol %) of the titanium reagent, as long as 2‐aryl‐ or 2‐ethenyl‐substituted ethylmagnesium halides are used and a concomitant slight decrease in yields is accepted. The newly developed methodology was successfully applied for the preparation of analogues with cyclopropylamine moieties of known drugs and natural products such as the nicotine metabolite (S)‐Cotinine as well as the insecticides Dinotefuran and Imidacloprid.
Smart Macrocyclic Molecules: Induced Fit and Ultrafast Self‐Sorting Inclusion Behavior through Dynamic Covalent Chemistry
Authors: Han Ji‐Min , Pan Jin‐Long , Lei Ting , Liu Chenjiang , Pei Jian 
Published: October 2010

AbstractA family of macrocycles with oligo(ethylene glycol) chains, 4O, 5O, and 6O, was developed to construct a series of new incorporated macrocycles through dynamic covalent chemistry. These flexible macrocycles exhibited excellent “self‐sorting” abilities with diamine compounds, which depended on the “induced‐fit” rule. For instance, the host macrocycles underwent conformational modulation to accommodate the diamine guests, affording [1+1] intramolecular addition compounds regardless of the flexibility of the diamine. These macrocycles folded themselves to fit various diamines with different chain length through modulation of the flexible polyether chain, and afforded intramolecular condensation products. However, if the chain of the diamine was too long and rigid, oligomers or polymers were obtained from the mixture of the macromolecule and the diamine. All results demonstrated that inclusion compounds involving conformationally suitable aromatic diamines were thermodynamically favorable candidates in the mixture due to the restriction of the macrocycle size. Furthermore, kinetic and thermodynamic studies of self‐sorting behaviors of both mixed 4O–5O and 4O–6O systems were investigated in detail. Finally, theoretical calculations were also employed to further understand such self‐sorting behavior, and indicated that the large enthalpy change of H2NArArNH2@4O is the driving force for the sorting behavior. Our system may provide a model to further understand the principle of biomolecules with high specificity due only to their conformational self‐adjusting ability.
Development of Versatile and Silver‐Free Protocols for Gold(I) Catalysis
Authors: Gaillard Sylvain , Bosson Johann , Ramón Rubén S. , Nun Pierrick , Slawin Alexandra M. Z. , Nolan Steven P. 
Published: October 2010

AbstractThe use of a versatileN‐heterocyclic carbene (NHC) gold(I) hydroxide precatalyst, [Au(OH)(IPr)], (IPr=N,N′‐bis(2,6‐diisopropylphenyl)imidazol‐2‐ylidene) permits the in situ generation of the [Au(IPr)]+ion by simple addition of a Brønsted acid. This cationic entity is believed to be the active species in numerous catalytic reactions.1H NMR studies in several solvent media of the in situ generation of this [Au(IPr)]+ion also reveal the formation of a dinuclear gold hydroxide intermediate [{Au(IPr)}2(μ‐OH)], which is fully characterized and was tested in gold(I) catalysis.
Bulk and Surface Structure and High‐Temperature Thermoelectric Properties of Inverse Clathrate‐III in the Si‐P‐Te System
Authors: Zaikina Julia V. , Mori Takao , Kovnir Kirill , Teschner Detre , Senyshyn Anatoliy , Schwarz Ulrich , Grin Yuri , Shevelkov Andrei V. 
Published: October 2010

AbstractThe creation of thermoelectric materials for waste heat recovery and direct solar energy conversion is a challenge that forces the development of compounds that combine appreciable thermoelectric figure‐of‐merit with high thermal and chemical stability. Here we propose a new candidate for high‐temperature thermoelectric materials, the type‐III Si172−xPxTey cationic clathrate, in which the framework is composed of partially ordered silicon and phosphorus atoms, whereas tellurium atoms occupy guest positions. We show that the utmost stability of this clathrate (up to 1500 K) in air is ensured by the formation of a nanosized layer of phosphorus‐doped silica on the surface, which prevents further oxidation and degradation. As‐cast (non‐optimized) Si‐P‐Te clathrates display rather high values of the thermoelectric figure‐of‐merit (ZT=0.24–0.36) in the temperature range of 700–1100 K. These ZT values are comparable to the best values achieved for the properly doped transition‐metal‐oxide materials. The methods of the thermoelectric efficiency optimization are discussed.
Asymmetric reduction of β‐ketoesters and chiral β‐iminoesters: Impact of a α‐quaternary stereocenter
Authors: Almahli Hadia , Hendra Frédéric , Troufflard Claire , Cavé Christian , Joseph Delphine , Delarue‐Cochin Sandrine 
Published: October 2010

AbstractDiastereomeric reduction of nonactivated, hindered β‐keto and chiral β‐iminoesters are described. The influence of a α‐stereocontrolled center on the efficiency and stereoselectivity of the reduction was studied. Reaction conditions were optimized to synthesize β‐hydroxy‐ and β‐aminoesters in good yields. In the case of chiral β‐iminoesters, influence of matched/mismatched diastereomeric pairs has been assessed. Chirality, 2011. © 2010 Wiley‐Liss, Inc.
A reverse phase HPLC method for the separation of two stereo isomers of 2‐[4‐(methylsulfonyl)phenyl]‐3‐(3(r)‐oxocyclopentyl)propanoic acid
Authors: Davadra Prakash M. , Patel Timir K. , Chauhan Jignesh C. , Kharul Rajendra K. , Pandey Bipin , Jain Mukul R. , Bapodra Atul H. 
Published: October 2010

AbstractThis study describes successful method development and separation of two stereo isomers of 2‐[4‐(methylsulfonyl)phenyl]‐3‐(3(R)‐oxocyclopentyl)propanoic acid by reverse phase high‐performance liquid chromatography. Baseline resolution was achieved on a J'sphere‐ODS‐H80 (150 mm × 4.6 mm, 4 μm) column using mobile phase consisting of 0.05% triflouroacetic acid in water‐acetonitrile (85:15, v/v) at a flow rate of 1.0 ml/min. The detection was carried out at 228 nm. The title compound, in turn, can be obtained by C‐alkylation of methyl 2‐[4‐(methylthio)phenyl]acetate with 2(S)‐iodomethyl‐8,8‐dimethyl‐6,10‐dioxaspiro[4.5]decane followed by consecutive hydrolysis and oxidation. The partially validated analytical method (system suitability, peak homogeneity, linearity, precision, robustness, and solution stability) has limit of detection and limit of quantification, 0.15 and 0.50 μg/ml respectively. Alternatively, the new method is being routinely utilized to monitor epimerization of α‐carbon of the propanoic acid in the title compound by crystallization‐induced dynamic resolution. Chirality, 2011. © 2010 Wiley‐Liss, Inc.
The effects of body mass index on complications and survival outcomes in patients with cervical carcinoma undergoing curative chemoradiation therapy
Authors: Kizer Nora T. , Thaker Premal H. , Gao Feng , Zighelboim Israel , Powell Matthew A. , Rader Janet S. , Mutch David G. , Grigsby Perry W. 
Published: October 2010

AbstractBACKGROUND:The effect of body mass index (BMI) on treatment outcomes for patients with locally advanced cervical carcinoma who receive definitive chemoradiation is unclear.METHODS:The cohort in this study included all patients with cervical carcinoma (n = 404) who had stage IB1 disease and positive lymph nodes or stage ≥IB2 disease and received treatment at the authors' facility between January 1998 and January 2008. The mean follow‐up was 47.2 months. BMI was calculated using the National Institute of Health online calculator. BMI categories were created according to the World Health Organization classification system. Primary outcomes were overall survival, disease‐free survival, and complication rate. Univariate and multivariate analyses were performed. Kaplan‐Meier survival curves were generated and compared using Cox proportional hazard models.RESULTS:On multivariate analysis, compared with normal weight (BMI 18.5‐24.9 kg/m2), a BMI <18.5 kg/m2 was associated with decreased overall survival (hazard ratio, 2.37; 95% confidence interval, 1.28‐4.38; P < .01). The 5‐year overall survival rate was 33%, 60%, and 68% for a of BMI <18.5 kg/m2, a BMI from 18.5 kg/m2 to 24.9 kg/m2, and a BMI >24.9 kg/m2, respectively. A BMI <18.5 kg/m2 was associated with increased risk of grade 3 or 4 complications compared with a BMI >24.9 kg/m2 (radiation enteritis: 16.7% vs 13.6%, respectively; P = .03; fistula: 11.1% vs 8.8%, respectively; P = .05; bowel obstruction: 33.3% vs 4.4%, respectively; P < .001; lymphedema: 5.6% vs 1.2%, respectively; P = .02).CONCLUSIONS:Underweight patients (BMI <18.5 kg/m2) with locally advanced cervical cancer had diminished overall survival and more complications than normal weight and obese patients. Cancer 2011. © 2010 American Cancer Society.