bluuebunny/crossref_metadata_2025_split huggingface dataset:
Global and local linear buckling behavior of a chiral cellular structure
Authors: Spadoni A. , Ruzzene M. , Scarpa F. 
Published: February 2005

AbstractThis paper investigates the flat‐wise compression behavior of an innovative cellular structure configuration. The considered layout has a hexagonal chiral geometry featuring cylinders, or nodes, joined by ligaments, or ribs. The resulting assembly is characterized by a number of interesting properties that can be exploited for the design of alternative honeycombs or cellular topologies to be used in sandwich construction. The flat‐wise strength of the chiral geometry is investigated through classical analytical formulas for the linear buckling of thin plates and shells and a bifurcation analysis performed on a Finite Element model. The analytical expressions predict the global buckling behavior and the resulting critical loads, and can be directly compared with the results obtained from the Finite Element analysis. In addition, the Finite Element model predicts local buckling modes, which should be considered to evaluate the possible development of localized plasticity. A sensitivity study is performed to evaluate the influence of the geometry of the chiral structure on its buckling strength. The study shows that the considered topology can offer great design flexibility, whereby several parameters can be selected and modified to improve the flat‐wise performance. The comparison with traditional, hexagonal centro‐symmetric structural configurations concludes the paper and demonstrates the enhanced performance and the potentials of chiral noncentro‐symmetric designs. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Monte Carlo simulation of two‐dimensional hard body systems with extreme values of the Poisson's ratio
Authors: Tretiakov K. V. , Wojciechowski K. W. 
Published: February 2005

AbstractMonte Carlo computer simulations with variable shape of the periodic box were performed for a few two‐dimensional, hard‐body models showing elastically isotropic solid phases. Two examples of homo‐molecular (i.e. consisting of identical molecules) systems of anisotropic molecules are discussed which form unusual solid phases, showing negative Poisson's ratio and know as auxetic ones, at densities and pressures higher than the elastically isotropic solid phases. Sharp extremes of the Poisson's ratio were observed for both systems at freezing of the orientational degrees of freedom of the molecules: a minimum was observed for the system for which the auxetic phase with frozen rotation is isotropic and a maximum was found for the other system. This indicates that isotropic auxetic phases can have auxetic precursors with much more negative Poisson's ratios than those characterizing the auxetic phases themselves. An example of a hetero‐molecular (i.e. mixture consisting of different molecules), elastically isotropic system is also discussed – the polydisperse hard disc system. The simulations revealed a maximum of the Poisson's ratio in the close packing limit at any nonzero polydispersity. Although no manifestation of any auxetic behaviour has been found in this system, the obtained results indicate other unusual effect – a jump (discontinuity) of the Poisson's ratio at close packing when the polydispersity tends to zero. The results obtained in this work demonstrate that the Poisson's ratio can play the role of a sensitive indicator of (at least) some structural changes in solids. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Design of auxetic polymer self‐assemblies
Authors: Wei Gaoyuan 
Published: February 2005

AbstractAlternating copolymers having a double‐arrow‐like “hard” block and a spring‐like “soft” segment have been designed which can in principle self‐assembly into two‐dimensional supramolecular networks. Molecular‐mechanics calculations show that such self‐assemblies can be auxetic when the lengths of the block and the segment are carefully chosen, with one metastable supermolecule having one of its six Poisson ratios as negatively large as –11.86. The underlying principle of designing such auxetic self‐assembly of copolymers with specified architecture is also given as are the deciding factors such as the packing geometry and the associated lattice energy in achieving the auxeticity. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Liquids at negative pressure
Authors: Xiao C. , Heyes D. M. , Powles J. G. 
Published: February 2005

AbstractWe have further explored the final stages of the collapse of an unstable cavity or bubble using the Molecular Dynamics computer simulation technique. A nanometre sized spherical volume of molecules was removed from a bulk Lennard–Jones liquid, which being mechanically and thermodynamically unstable, proceeded to collapse. The molecules with the highest kinetic energy were the first to enter the initially empty cavity. The temperature of individual molecules inside the cavity, while the density was still typical of a gas, could reach at least an order of magnitude larger than that of the surrounding liquid, e.g., equivalent to 6,000 K for water, which is not unreasonable for the sonoluminescence effect to be seen. During the filling in of the cavity, the average temperature decreased, as the contents thermally equilibrated with the surrounding liquid. The bubble partially filled in, and then proceeded to partially empty again, and so on in an oscillatory manner, with ever decreasing amplitude towards the final uniform liquid state. This ‘recoil’ effect is predicted by classical hydrodynamic treatments and has been observed in experiment for much larger bubbles. The temperature, density and normal pressure component were resolved as a function of radius from the centre of the bubble at selected times during the collapsing process. The simulations support the view that MD can provide a realistic representation of the final stages of cavity collapse. It does not make assumptions about equation of state and transport coefficients as would be required for a comparable solution of the Navier–Stokes hydrodynamics equations, and is therefore an especially appropriate description for the final stages of the collapse. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Toward molecular auxetics: Main chain liquid crystalline polymers consisting of laterally attached para‐quaterphenyls
Authors: He Chaobin , Liu Puwei , McMullan Philip J. , Griffin Anselm C. 
Published: February 2005

AbstractPolymers containing para‐quaterphenyl rods laterally attached to the polymer main chain have been synthesized. The molecular design choices which led to use of the quaterphenyl rod to achieve auxetic response will be discussed. Preparative chemistry of the monomers will be described along with the details of the polymerization reaction. Both polyethers and polyesters were prepared. The length of the flexible alkyl main chains which link the rods plays an important role in determining whether the resulting polymers will exhibit liquid crystallinity. Polymers with longer alkyl links exhibit nematic liquid crystallinity and the rods appear to have their long axes oriented roughly parallel and along the main chain direction. X‐ray scattering experiments were performed on the polymers both in the quiescent (unstretched) and the stretched states. Results from these experiments suggest that, under tensile strain, site connectivity driven rod‐reorientation occurs in these materials giving rise to an increase in the interchain distance for these polymers. This increase in the interchain separation is consistent with our concept of a molecular level auxetic mechanism for this type of designed polymer. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Al‐based systems with unusual mechanical and transport properties
Authors: Müllerová K. , Kovácik J. , Simancík F. , Švec P. 
Published: February 2005

AbstractAddition of selected transition‐metal elements into aluminum matrix is known to yield systems that exhibit unique structural arrangements and mechanical properties, especially high yield strength obtained after suitable heat treatment. These lightweight systems are known to be compactable from ribbon shape prepared by rapid quenching of the melt into bulk form, yielding physically and technically attractive materials. The combination of knowledge about formation of aluminum‐based foams with the physics of rapid quenching and compaction is shown as a possible route for approaching the preparation of lightweight materials with potentially auxetic behavior. Enhancement of this property is discussed briefly in terms of tailoring the network or cell‐pore structure of different dimensions, ranging from millimeters down to nanoscale and sub‐nanoscale atomic ordering. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Decomposition of protonated noradrenaline and normetanephrine assisted by NH2 migration studied by electrospray tandem mass spectrometry and molecular orbital calculations
Authors: Rogalewicz Françoise , Bourcier Sophie , Hoppilliard Yannik 
Published: February 2005

AbstractAs part of a research program on neurotransmitters in a biological fluid, the fragmentations characterising catecholamines protonated under electrospray ionisation (ESI) conditions, under low collision energy in a triple‐quadrupole mass spectrometer, were investigated. The decompositions of protonated noradrenaline (VH) and normetanephrine (VIH) were studied. Both precursor ions eliminate first H2O at very low collision energy, and the fragmentations of [MH–H2O]+ occur at higher collision energy. The breakdown graphs of [MH–H2O]+ ions, with collision energy varying from 0–40 eV in the laboratory frame, are presented. [VIH–H2O]+ ions lose competitively NH3 and CH3OH. For [VH–H2O]+ the loss of NH3 is dominant while H2O is eliminated at very low abundance at all collision energies. All of these secondary fragmentations are followed at higher collision energies by elimination of CO. These fragmentations are interpreted by means of ab initio calculations up to the B3LYP/6‐311+G(2d,2p) level of theory. The elimination of H2O requires first the isomerisation of N‐protonated forms, chosen as energy references, to O‐protonated forms. The isomerisation barriers are calculated to be lower than 81 kJ/mol above the N‐protonated forms. The elimination of NH3 from [MH–H2O]+ requires first the migration, via a cyclisation, of the amine function from the linear chain to the aromatic ring in order to prevent the formation of unstable disubstituted carbocations in the ring. The barriers associated with the loss of NH3 are located 220 and 233 kJ/mol above VH and 219 kJ/mol above VIH. The energy barrier for the loss of ROH is located 236 and 228 kJ/mol above VH and VIH, respectively. The absence of ions corresponding to [VH–2H2O]+ is due to a parasitic mechanism with an activation barrier lower than 236 kJ/mol that leads to a stable species unable to fragment, thus preventing the second loss of H2O. Losses of CO following the secondary fragmentations involve activation barriers higher than 330 kJ/mol. Copyright © 2005 John Wiley & Sons, Ltd.
Determination of amphetamine, methamphetamine, 3,4‐methylenedioxyamphetamine, 3,4‐methylenedioxyethylamphetamine, and 3,4‐methylenedioxymethamphetamine in urine by online solid‐phase extraction and ion‐pairing liquid chromatography with detection by electrospray tandem mass spectrometry
Authors: Wu Ti‐Yu , Fuh Ming‐Ren 
Published: February 2005

AbstractA method using an online solid‐phase extraction (SPE) and ion‐pairing liquid chromatography with electrospray tandem mass spectrometry (LC/ES‐MS/MS) was developed for determination of amphetamine (Amp), methamphetamine (mAmp), 3,4‐methylenedioxyamphetamine (MDA), 3,4‐methylenedioxyethylamphetamine (MDEA), and 3,4‐methylenedioxymethamphetamine (MDMA) in urine samples. A SPE cartridge column with both hydrophilic and lipophilic functions was utilized for online extraction. A reversed‐phase C18 LC column was employed for LC separation and MS/MS was used for detection. Trifluoroacetic acid was added to the mobile phase as an ion‐pairing reagent. This method was fully automated and the extraction and analysis procedures were controlled by a six‐port switch valve. Recoveries ranging from 85–101% were measured. Good linear ranges (10–500 ng/mL) for Amp and mAmp were determined. For MDA, MDMA and MDEA, dual linear ranges were obtained from 5–100 and 100–500 ng/mL, respectively. The detection limit of each analytical compound, based on a signal‐to‐noise ratio of 3, ranged from 1–3 ng/mL. The applicability of this newly developed method was examined by analyzing several urine samples from drug users. Good agreement was obtained between the results from this method and a literature GC/MS method. Copyright © 2005 John Wiley & Sons, Ltd.
The use of the propensity score for estimating treatment effects: administrative versus clinical data
Authors: Austin Peter C. , Mamdani Muhammad M. , Stukel Therese A. , Anderson Geoffrey M. , Tu Jack V. 
Published: February 2005

AbstractThere is an increasing interest in using administrative data to estimate the treatment effects of interventions. While administrative data are relatively inexpensive to obtain and provide population coverage, they are frequently characterized by lack of clinical detail, often leading to problematic confounding when they are used to conduct observational research. Propensity score methods are increasingly being used to address confounding in estimating the effects of interventions in such studies. Using data on patients discharged from hospital for whom both administrative data and detailed clinical data obtained from chart reviews were available, we examined the degree to which stratifying on the quintiles of propensity scores derived from administrative data was able to balance patient characteristics measured in clinical data. We also determined the extent to which measures of treatment effect obtained using propensity score methods were similar to those obtained using traditional regression methods. As a test case, we examined the treatment effects of ASA and beta‐blockers following acute myocardial infarction. We demonstrated that propensity scores developed using administrative data do not necessarily balance patient characteristics contained in clinical data. Furthermore, measures of treatment effectiveness were attenuated when obtained using clinical data compared to when administrative data were used. Copyright © 2005 John Wiley & Sons, Ltd.
Repeat Pulmonary Resection for Isolated Recurrent Lung Metastases Yields Results Comparable to Those after First Pulmonary Resection in Colorectal Cancer
Authors: Ogata Yutaka , Matono Keiko , Hayashi Akihiro , Takamor Shinzo , Miwa Keisuke , Sasatomi Teruo , Ishibashi Nobuya , Shida Seiichiro , Shirouzu Kazuo 
Published: February 2005

AbstractPulmonary resection for colorectal metastases is well accepted. However, the main cause of death after pulmonary resection is recurrence in the lung. The aim of this study was to clarify whether a repeat pulmonary resection was warranted in patients with recurrent lung metastases. The records of 76 patients undergoing initial pulmonary resection, including 14 patients undergoing a repeat operation for lung metastases, were reviewed for survival, operative morbidity, and mortality. Overall, pulmonary resection was performed 96 times in this group of patients. The operative mortality was 0%, morbidity involved only one case of major postoperative hemorrhage associated with the first operation. The cumulative 5‐year survival rate for the 76 patients was 32%. After the second pulmonary operation, recurrence was identified in 79% (11 of 14) of the patients. In 10 patients with isolated lung recurrence after a first pulmonary resection, who showed no extrapulmonary disease before or at the time of first thoracotomy, the 3‐year, and 5‐year‐survival rate after the second pulmonary resection was 67%, and 33%, respectively, comparing favorably with the survival rate in those who underwent primary pulmonary resection. In contrast, all 4 patients with extrapulmonary disease before or at the time of thoracotomy had poor prognosis. Repeat pulmonary operation for isolated recurrent colorectal metastases to the lung yielded results comparable to those after the first pulmonary resection in terms of operative mortality and survival in the absence of hilar/mediastinal lymph node or extrathoracic involvement.
Somatostatin, Somatostatin Receptors, and Pancreatic Cancer
Authors: Li Min , Fisher William E. , Kim Hee Joon , Wang Xiaoping , Brunicardi Charles F. , Chen Changyi , Yao Qizhi 
Published: February 2005

AbstractSomatostatin may play an important role in the regulation of cancer growth including pancreatic cancer by interaction with somatostatin receptors (SSTRs) on the cell surface. Five SSTRs were cloned, and the function of these SSTRs is addressed in this review. SSTR‐2, SSTR‐5, and SSTR‐1 are thought to play major roles in inhibiting pancreatic cancer growth both in vitro and in vivo. SSTR‐3 may be involved in mediating apoptosis, but the role of SSTR‐4 is not clear. In most pancreatic cancers, functional SSTRs are absent. Reintroduction of SSTR genes has been shown to inhibit pancreatic cancer growth in cell cultures and animal models.
Role of Proteases in Pancreatic Carcinoma
Authors: Patten Lane C. , Berger David H. 
Published: February 2005

AbstractProteases play an important role in cancer invasion and metastasis. In this review we specifically discuss the role of these proteases in pancreatic carcinoma. Serine proteases and matrix metalloproteinases are the focus of intense research, as they appear to be related to the process of tumor progression. We discuss the diagnostic and prognostic value of these two groups of proteases. Lastly, we report on the current and recent clinical trials focusing on inhibition of these proteases.
Abrogation of Transforming Growth Factor‐β Signaling in Pancreatic Cancer
Authors: Lin Xia , Feng Xin‐Hua 
Published: February 2005

AbstractTransforming growth factor‐β (TGFβ) functions as a growth inhibitor for many cell types by inhibiting cell cycle progression. Loss of TGFβ responsiveness can lead to deregulated cell proliferation and ultimately tumor progression. For example, the TGFβ signaling pathway is a frequent target for inactivation in pancreatic cancer. Functional connection between the potent growth inhibitory activity of TGFβ and the tumor suppressor activity of Smads has been well documented. Smads directly modulate transcription of the genes involved in cell cycle progression in response to TGFβ, and that abrogation of this regulation leads to tumor progression. In this review, we summarize recent research progress on TGFβ signaling and pancreatic cancer.
Effects of number of flowers per raceme and number of racemes per plant on bumblebee visits and female reproductive success in Salvia nipponica (Labiatae)
Authors: Miyake Yasuko C. , Sakai Satoki 
Published: February 2005

AbstractWe studied the adaptive arrangement of raceme flowers in dense and sparse habitats of Salvia nipponica. We recorded bumblebee visits and collected mature seeds to estimate outcrossing rates from allozyme genotypes. To examine the resource investment in flowering stalks, we measured their length and dry mass. We found that a greater number of open flowers in a raceme enhanced bumblebee visits and successive probings in both density plots. However, greater height of a raceme did not enhance these in plots of either density. In the high‐density plot, both a greater mean number of open flowers in a raceme and a greater number of flowering racemes on a plant enhanced bumblebee visits, successive probings, and also enhanced outcrossing rate in spite of an increase in successive probings. Although the number of flowers per raceme had a greater positive effect on seed‐to‐ovule ratios than did the number of racemes, the number of flowers per raceme may be constrained because a longer flowering stalk needs greater buckling strength. Hence, it may be advantageous for plants in high‐density plots to increase both number of flowers per raceme and number of racemes. In the low‐density plot, a greater number of flowering racemes on a plant enhanced pollinator visits, but a greater mean number of open flowers in a raceme did not. Hence, it may be advantageous for plants to increase the number of racemes while keeping the numbers of flowers per raceme small. Thus, the adaptive number of flowers per raceme and number of racemes per plant may differ between high‐ and low‐density plots.
Characterization of the interactions between stromal and haematopoietic progenitor cells in expansion cell culture models
Authors: Bilko N.M. , Votyakova I.A. , Vasylovska S.V. , Bilko D.I. 
Published: February 2005

AbstractDevelopment of the long‐term culture models of haematopoietic stem cells (HSCs) is one of the important tasks in modern biotechnology. It has been suggested that stromal presence is important for haematopoiesis in vitro and in vivo, but the question remains: whether diffusible factors produced by stromal cells are sufficient for the regeneration of primitive and definitive haematopoietic cells, or direct cell‐to‐cell contacts of the cultured material with underlying stromal base would be required. During present studies, influence of various feeder layers and feeder layer conditioned media on proliferative, differentiative and clonogenic activity of human AC133+ derived from human umbilical cord blood was investigated. Cell extracts for feeder layers were prepared from 4–6 weeks old human embryos and co‐cultured feeder cells. Effects of the conditioned media were also determined. Culture and feeder layer media were additionally supplemented with commonly implemented factors such as GM‐CSF, IL‐3 and LIF. Estimation of morpho‐functional properties of AC133+ cultivated suspension cultures was performed in subculture experiments using semisolid agar culture conditions. Multipotential CFU‐MIX (CFU‐GEMM) and unipotential progenitor cells CFU‐GM, BFU‐E and CFU‐E were observed and analyzed. Our data suggest that haematopoiesis can be sustained for prolonged cultivation periods in the presence of feeder layer cells or conditioned media supported culture models. Prolonged support of primitive haematopoietic cells and their clonogenic capacity and functional characteristics in feeder layer positive cultures, indicates that diffusible factors are sufficient for haematopoiesis and suggests that direct cell‐to‐cell contacts may not be exclusively required for successful long‐term in vitro haematopoiesis.