bluuebunny/crossref_metadata_2025_split huggingface dataset:
A necessary and sufficient condition for the nirenberg problem
Authors: Chen Wenxiong , Li Congming 
Published: April 2007

AbstractWe seek metrics conformal to the standard ones on Sn having prescribed Gaussian curvature in case n = 2 (the Nirenberg Problem), or prescribed scalar curvature for n ≧ 3 (the Kazdan‐Warner problem). There are well‐known Kazdan‐Warner and Bourguignon‐Ezin necessary conditions for a function R(x) to be the scalar curvature of some conformally related metric. Are those necessary conditions also sufficient? This problem has been open for many years.In a previous paper, we answered the question negatively by providing a family of counter examples.In this paper, we obtain much stronger results. We show that, in all dimensions, if R(x) is rotationally symmetric and monotone in the region where it is positive, then the problem has no solution at all. It follows that, on S2, for a non‐degenerate, rotationally symmetric function R(θ), a necessary and sufficient condition for the problem to have a solution is that Rθ changes signs in the region where it is positive. This condition, however, is still not sufficient to guarantee the existence of a rotationally symmetric solution, as will be shown in this paper. We also consider similar necessary conditions for non‐symmetric functions. ©1995 John Wiley & Sons, Inc.
An existence and uniqueness result of a nonlinear two‐dimensional elliptic boundary value problem
Authors: Gamba Irene M. 
Published: April 2007

AbstractWe consider a boundary value problem for the generalized two‐dimensional flow equation Δφ = Δφ · h for h a Cα vector field, where the speed is prescribed on a part of the boundary. By using Bers theory combined with elliptic operator theory in nonsmooth domains, we show existence and uniqueness of a C2,α solution with nonvanishing gradient, and we find positive lower and upper bounds for |Δφ| along with C2,α estimates of φ, in terms of the Cα and L∞ norms of h. ©1995 John Wiley & Sons, Inc.
Entropy flux‐splittings for hyperbolic conservation laws part I: General framework
Authors: Chen Gui‐Qiang , Lefloch Philippe G. 
Published: April 2007

AbstractA general framework is proposed for the derivation and analysis of flux‐splittings and the corresponding flux‐splitting schemes for systems of conservation laws endowed with a strictly convex entropy. The approach leads to several new properties of the existing flux‐splittings and to a method for the construction of entropy flux‐splittings for general situations. A large family of genuine entropy flux‐splittings is derived for several significant examples: the scalar conservation laws, the p‐system, and the Euler system of isentropic gas dynamics. In particular, for the isentropic Euler system, we obtain a family of splittings that satisfy the entropy inequality associated with the mechanical energy. For this system, it is proved that there exists a unique genuine entropy flux‐splitting that satisfies all of the entropy inequalities, which is also the unique diagonalizable splitting. This splitting can be also derived by the so‐called kinetic formulation. Simple and useful difference schemes are derived from the flux‐splittings for hyperbolic systems. Such entropy flux‐splitting schemes are shown to satisfy a discrete cell entropy inequality. For the diagonalizable splitting schemes, an a priori L∞ estimate is provided by applying the principle of bounded invariant regions. The convergence of entropy flux‐splitting schemes is proved for the 2 × 2 systems of conservation laws and the isentropic Euler system. ©1995 John Wiley & Sons, Inc.
Program derivation with verified transformations — a case study
Authors: Keller J. P. , Paige R. 
Published: April 2007

AbstractA program development methodology based on verified program transformations is described and illustrated through derivations of a high level bisimulation algorithm and an improved minimum‐state DFA algorithm. Certain doubts that were raised about the correctness of an initial paper‐and‐pencil derivation of the DFA minimization algorithm were laid to rest by machine‐checked formal proofs of the most difficult derivational steps. Although the protracted labor involved in designing and checking these proofs was almost overwhelming, the expense was somewhat offset by a successful reuse of major portions of these proofs. In particular, the DFA minimization algorithm is obtained by specializing and then extending the last step in the derivation of the high level bisimulation algorithm.Our experience suggests that a major focus of future research should be aimed towards improving the technology of machine checkable proofs — their construction, presentation, and reuse. This paper demonstrates the importance of such a technology to the verification of programs and program transformations. We believe that the utility of transformational systems to program development will ultimately rest on a practical program correctness technology. © 1996 John Wiley & Sons, Inc.
Synthesis of reversible logic for nanoelectronic circuits
Authors: De Vos Alexis , Van Rentergem Yvan 
Published: April 2007

AbstractReversible logic circuits can be synthesized hierarchically by dividing them into smaller, more manageable blocks. As all reversible circuits of a certain width w form a group, this problem relates to the partitioning of a group into (double) cosets. In this article, we propose three different strategies for the synthesis of reversible circuits, all based on group theory. We will compare these different methods and will determine which is the most efficient. Copyright © 2007 John Wiley & Sons, Ltd.
Type I collagen is a genetic modifier of matrix metalloproteinase 2 in murine skeletal development
Authors: Egeblad Mikala , Shen H.‐C. Jennifer , Behonick Danielle J. , Wilmes Lisa , Eichten Alexandra , Korets Lidiya V. , Kheradmand Farrah , Werb Zena , Coussens Lisa M. 
Published: April 2007

AbstractRecessive inactivating mutations in human matrix metalloproteinase 2 (MMP2, gelatinase A) are associated with syndromes that include abnormal facial appearance, short stature, and severe bone loss. Mmp2−/− mice have only mild aspects of these abnormalities, suggesting that MMP2 function is redundant during skeletal development in the mouse. Here, we report that Mmp2−/− mice with additional mutations that render type I collagen resistant to collagenase‐mediated cleavage to TCA and TCB fragments (Col1a1r/r mice) have severe developmental defects resembling those observed in MMP2‐null humans. Composite Mmp2−/−;Col1a1r/r mice were born in expected Mendelian ratios but were half the size of wild‐type, Mmp2−/−, and Col1a1r/r mice and failed to thrive. Furthermore, composite Mmp2−/−;Col1a1r/r animals had very abnormal craniofacial features with shorter snouts, bulging skulls, incompletely developed calvarial bones and unclosed cranial sutures. In addition, trabecular bone mass was reduced concomitant with increased numbers of bone‐resorbing osteoclasts and osteopenia. In vitro, MMP2 had a unique ability among the collagenolytic MMPs to degrade mutant collagen, offering a possible explanation for the genetic interaction between Mmp2 and Col1a1r. Thus, because mutations in the type I collagen gene alter the phenotype of mice with null mutations in Mmp2, we conclude that type I collagen is an important modifier gene for Mmp2. Developmental Dynamics 236:1683–1693, 2007. © 2007 Wiley‐Liss, Inc.
Cre‐conditional expression of constitutively active Notch1 in transgenic mice
Authors: Liu Ju , Lobe Corrinne G. 
Published: April 2007

AbstractThe Notch signaling pathway plays a critical role during mammalian development. To bypass embryonic lethality associated with constitutive Notch1 signaling, we created transgenic mice with a floxed β‐geo/stop signal between a cytomegalo virus promoter and the constitutively active intracellular domain of Notch1 (IC‐Notch1). IC‐Notch1 is activated upon introduction of Cre recombinase and it is coexpressed with an enhanced green fluorescent protein or human placental alkaline phosphatase reporter. We created three IC‐Notch1 transgenic mouse lines and crossed them to a general Cre deletor mouse line, pCX‐Cre. The double transgenic IC‐Notch1/pCX‐Cre embryos have widespread expression of IC‐Notch1 and reporters and die before 10.5 days of gestation. Morphological and histological analysis of the double transgenic embryos indicated growth arrest and various developmental defects, including lack of neural tube closure, disorganized somites, and disrupted vasculature. The conditional IC‐Notch1 expressing transgenic mice provide a unique tool to investigate the Notch pathway using tissue‐specific Cre mice and inducible Cre systems. genesis 45:259–265, 2007. © 2007 Wiley‐Liss, Inc.
Synthesis and Reactions of Polynuclear Polyhydrido Rare Earth Metal Complexes Containing “(C5Me4SiMe3)LnH2” Units: A New Frontier in Rare Earth Metal Hydride Chemistry
Authors: Hou Zhaomin , Nishiura Masayoshi , Shima Takanori 
Published: April 2007

AbstractA series of tetranuclear octahydrido rare earth metal complexes of general formula [(C5Me4SiMe3)Ln(μ‐H)2]4(THF)n (Ln = Sc, Y, Gd, Dy, Ho, Er, Tm, Lu; n = 0, 1, or 2) that contain C5Me4SiMe3 as an ancillary ligand have been prepared and structurally characterized. These hydride clusters are soluble in common organic solvents such as THF, toluene, and hexane, and maintain their tetranuclear framework in solution. Such polynuclear polyhydrido complexes exhibit extremely high and unique reactivity toward a variety of unsaturated substrates including CO, CO2, and nitriles. The reaction of these neutral polyhydrides with one equivalent of [Ph3C][B(C6F5)4] affords the corresponding cationic hydride clusters [(C5Me4SiMe3)4Ln4H7(THF)n][B(C6F5)4], which can act as catalysts for the syndiospecific polymerization of styrene and regio‐ and stereospecific cis‐1,4‐polymerization of 1,3‐cyclohexadiene. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Synthesis and Functionalization of Germanium Triphenylcorrolate: The First Example of a Partially Brominated Corrole
Authors: Nardis Sara , Mandoj Federica , Paolesse Roberto , Fronczek Frank R. , Smith Kevin M. , Prodi Luca , Montalti Marco , Battistini Gionata 
Published: April 2007

AbstractGe complexes of 5,10,15‐triphenylcorrole were prepared in refluxing dry DMF using GeCl4 as the source of Ge. Chromatographic separation of the crude reaction mixture afforded the μ‐oxo dimer 1 and the methoxy derivative 2a. The corresponding chloride 2b can be obtained by treatment of 1 or 2a with HCl. The reaction of 2a with Br2 in CHCl3/py afforded the hexabromo derivative 3 as the main product, giving the first indication of the regioselective substitution of pyrroles B and C on the corrole ring. The fully brominated open‐chain tetrapyrrole 4 was also characterized as a reaction by‐product. Different partially brominated Ge complexes 5 and 6 have been obtained by variation of reaction conditions, while the heptabromo derivative was obtained in a mixture with the corresponding fully brominated Gecorrole. Photophysical characterization of Ge corrolates confirmed the high fluorescence quantum yield of such complexes, and also led to the first observation of phosphorescence emissions from corrole complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Chemistry of floral scents in four Licuala species (Arecaceae)
Authors: Meekijjaroenroj Aroonrat , Bessière Jean‐Marie , Anstett Marie‐Charlotte 
Published: April 2007

AbstractFloral fragrances are known to attract pollinators. Resemblances in the chemistry of floral scents may associate a group of plants to the same array of pollinators and/or mirror the systematics of related species. In this study, floral volatiles were extracted and all compounds identified from four Licuala palms: L. grandis, L. mattanensis, L. spinosa and L. lauterbachii. A typical emission of isoprenoid compounds in the four species was revealed. However, each species was characterized by a different chemical composition of the floral bouquet. The relative importance of similarity and diversity found in floral scent chemistry for pollination and systematics is discussed. Copyright © 2007 John Wiley & Sons, Ltd.
BILU implicit multiblock Euler/Navier–Stokes simulation for rotor tip vortex and wake convection
Authors: Zhong Bowen , Shaw Scott , Qin Ning 
Published: April 2007

AbstractIn this paper, a block incomplete lower–upper (BILU) decomposition method is incorporated with a multiblock three‐dimensional Euler/Navier–Stokes solver for simulation of hovering rotor tip vortices and rotor wake convection. Results of both Euler and Navier–Stokes simulations are obtained and compared with experimental observations. The comparisons include surface pressure distributions and tip vortex trajectories. The comparisons suggest that resolution of the boundary layer is important for the accurate evaluation of the blade surface loading, but is less so for the correct prediction of the vortex trajectory. Numerical tests show that, using Courant–Friedrichs–Lewy (CFL) number of 10 or 30 with the developed BILU implicit scheme can be 6–7 times faster than an explicit scheme. The importance of solution acceleration schemes that increase the permitted time‐step is illustrated by comparing the evolving wake structures at different stages of the calculation. In contrast to fixed wing simulations, the extent of the wake structures is shown to require resolution of large physical time. This observation explains the poor performance that is obtained when employing convergence acceleration strategies originally intended for solution of equilibrium problems, such as the multigrid methods. Copyright © 2007 John Wiley & Sons, Ltd.
Effect of the Anodic Diffusion Layer on the Performance of Liquid Fuel Cells
Authors: Xie F. , Chen C. , Meng H. , Shen P. K. 
Published: April 2007

AbstractNovel diffusion layers for liquid direct methanol fuel cells (DMFCs) are designed and fabricated. The factors affecting the performance of DMFCs are determined. The results demonstrate that the diffusion layers made by micrometer scale particles and a hydrophilic binder can reduce the liquid sealing effect and increase the mass transfer property. The performance of DMFCs made using novel diffusion layers is greatly improved. The porous structure of such diffusion layers may improve the channels therein, which allows liquid methanol to diffuse in and gaseous CO2 to diffuse out easily. Higher methanol concentrations can be used due to the formation of a larger three‐phase interfacial area.
Neuroimaging endophenotypes: Strategies for finding genes influencing brain structure and function
Authors: Glahn David C. , Thompson Paul M. , Blangero John 
Published: April 2007

AbstractIt is vitally important to identify the genetic determinants of complex brain‐related disorders such as autism, dementia, mood disorders, and schizophrenia. However, the search for genes predisposing individuals to these illnesses has been hampered by their genetic and phenotypic complexity and by reliance upon phenomenologically based qualitative diagnostic systems. Neuroimaging endophenotypes are quantitative indicators of brain structure or function that index genetic liability for an illness. These indices will significantly improve gene discovery and help us to understand the functional consequences of specific genes at the level of systems neuroscience. Here, we review the feasibility of using neuroanatomic and neuropsychological measures as endophenotypes for brain‐related disorders. Specifically, we examine specific indices of brain structure or function that are genetically influenced and associated with neurological and psychiatric illness. In addition, we review genetic approaches that capitalize on the use of quantitative traits, including those derived from brain images. Hum Brain Mapp, 2007. © 2007 Wiley‐Liss, Inc.
An empirical analysis of nonstationarity in a panel of interest rates with factors
Authors: Moon Hyungsik Roger , Perron Benoit 
Published: April 2007

AbstractThis paper studies nonstationarities in a panel of Canadian and US interest rates of different maturities and risk. We focus on methods which model the cross‐sectional dependence within the panel as a linear dynamic factor model, and decompose our data into common and idiosyncratic components that we analyze in turn. Our results suggest the presence of a single nonstationary factor in our panel. Since some of the idiosyncratic components are stationary, we conclude that these series are cointegrated. Finally, the dominant factors can be interpreted as level and slope factors as in the term structure literature. Copyright © 2007 John Wiley & Sons, Ltd.
Heterogeneity and cross section dependence in panel data models: theory and applications introduction
Authors: Baltagi Badi H. , Hashem Pesaran M. 
Published: April 2007

AbstractThe papers included in this special issue are primarily concerned with the problem of cross section dependence and heterogeneity in the analysis of panel data models and their relevance in applied econometric research. Cross section dependence can arise due to spatial or spill over effects, or could be due to unobserved (or unobservable) common factors. Much of the recent research on non‐stationary panel data have focussed on this problem. It was clear that the first generation panel unit root and cointegration tests developed in the 1990's, which assumed cross‐sectional independence, are inadequate and could lead to significant size distortions in the presence of neglected cross‐section dependence. Second generation panel unit root and cointegration tests that take account of possible cross‐section dependence in the data have been developed, see the recent surveys by Choi (2006) and Breitung and Pesaran (2007). The papers by Baltagi, Bresson and Pirotte, Choi and Chue, Kapetanios, and Pesaran in this special issue are further contributions to this literature. The papers by Fachin, and Moon and Perron are empirical studies in this area. Controlling for heterogeneity has also been an important concern for empirical researchers with panel data methods promising better handle on heterogeneity than cross‐section data methods. The papers by Hsiao, Shen, Wang and Weeks, Pedroni and Serlenga and Shin are empirical contributions to this area. Copyright © 2007 John Wiley & Sons, Ltd.
The murine ortholog of the SHP‐2 binding molecule, PZR accelerates cell migration on fibronectin and is expressed in early embryo formation
Authors: Roubelakis Maria G. , Martin‐Rendon Enca , Tsaknakis Grigorios , Stavropoulos Athanassios , Watt Suzanne M. 
Published: April 2007

AbstractThe human P zero‐related protein (hPZR) has a unique function in regulating cell migration. This activity is dependent on both its cytoplasmic immunoreceptor tyrosine inhibitory motif (ITIM) and its interaction with the tyrosine protein phosphatase, src homology phosphatase‐2 (SHP‐2). Here, using in silico and cDNA cloning approaches, we identify the murine ITIM‐containing hPZR ortholog, mPZR, together with its ITIM‐less isoform, mPZRb. We demonstrate that, like hPZR, these type 1 integral murine transmembrane isoforms are derived by differential splicing from a single gene transcription unit on mouse chromosome 1, and differ only in the sequence of their cytoplasmic domains. Importantly, mPZR mimicks hPZR functionally by accelerating SHP‐2‐mediated cell migration on fibronectin. Interestingly, we further demonstrate that although neither mPZR nor mPZRb is expressed in murine pluripotent embryonic stem cells, they first appear at approximately day 3 of blastocyst formation in vivo and of embryoid body formation in vitro. These studies thus provide the basis for defining the function of the mPZR isoforms in vivo, particularly with respect to their roles in regulating SHP‐2‐dependent cell migration during development. J. Cell. Biochem. 102: 955–969, 2007. © 2007 Wiley‐Liss, Inc.
Identification of genetic networks involved in the cell growth arrest and differentiation of a rat astrocyte cell line RCG‐12
Authors: Takasaki Ichiro , Takarada Satoko , Fukuchi Mamoru , Yasuda Makoto , Tsuda Masaaki , Tabuchi Yoshiaki 
Published: April 2007

AbstractThe purpose of the present study is to establish and characterize a conditionally immortalized astrocyte cell line and to clarify the genetic networks responsible for the cell growth arrest and differentiation. A conditionally immortalized astrocyte cell line, RCG‐12, was established by infecting primary cultured rat cortical glia cells with a temperature‐sensitive simian virus 40 large T‐antigen. At a permissive temperature of 33°C, the large T‐antigen was expressed and cells grew continuously. On the other hand, the down‐regulation of T‐antigen at a non‐permissive temperature of 39°C led to growth arrest and differentiation. The cells expressed astrocyte‐expressed genes such as glial fibrillary acidic protein. Interestingly, the differentiated condition induced by the non‐permissive temperature significantly elevated the expression levels of several astrocyte‐expressed genes. To identify the detailed mechanisms by which non‐permissive temperature‐induced cell growth arrest and differentiation, we performed high‐density oligonucleotide microarray analysis and found that 556 out of 15,923 probe sets were differentially expressed 2.0‐fold. A computational gene network analysis revealed that a genetic network containing up‐regulated genes such as RB, NOTCH1, and CDKN1A was associated with the cellular growth and proliferation, and that a genetic network containing down‐regulated genes such as MYC, CCNB1, and IGF1 was associated with the cell cycle. The established cell line RCG‐12 retains some characteristics of astrocytes and should provide an excellent model for studies of astrocyte biology. The present results will also provide a basis for understanding the detailed molecular mechanisms of the growth arrest and differentiation of astrocytes. J. Cell. Biochem. 102: 1472–1485, 2007. © 2007 Wiley‐Liss, Inc.
Esterases and putative lipases from tropical isolates of Aureobasidium pullulans
Authors: Kudanga Tukayi , Mwenje Eddie , Mandivenga Faith , Read John S. 
Published: April 2007

AbstractEsterases and lipases have been studied in a number of fungi, though very little is known about esterases from Aureobasidium pullulans especially from the African tropics. In this study, forty‐two Zimbabwean isolates were screened for lipase activity on tributyrin agar. Extracellular esterase activities of seven selected isolates were studied under varying conditions using para ‐nitrophenol acetate as substrate. Twenty isolates (48%) showed lipolytic activity; sixteen showed negative results for lipase activity while the rest showed weak activities. Esterase activities in broth cultures ranged from 0.011–0.223 mmol/μg protein/min while activities ranged from 1.5–12.8 U/ml under solid state fermentation. The esterases were optimally active at pH 7.6–8.0, showed a temperature optimum of 35 °C and retained more than 50% activity at temperatures up to 60 °C and at pH 4.0–7.0 after 150 min. Enzyme production was optimal after 5–6 days with diammonium hydrogen phosphate as nitrogen source. Isolates showed variations in preference for carbon source for esterase production. The A. pullulans esterases differed from most fungal esterases in that they are optimally active in alkaline conditions and are active over a broad pH range. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)