bluuebunny/crossref_metadata_2025 huggingface dataset:
Cytocompatibility and haemocompatibility of Zr, ZrC and ZrCN films
Authors: Xue X Y , Chu C L , Yin L H , Pu Y P , Chu P K
Published: March 2012

The cytocompatibility and haemocompatibility of three zirconium based films, i.e. Zr, ZrC and ZrCN, deposited on NiTi shape memory alloy by magnetron sputtering are investigated and compared to those of electropolished NiTi shape memory alloy. The Zr(C,N) series films have deteriorated wettability but have positive effects on the blood compatibility and cytocompatibility of NiTi. Better haemolysis resistance and thromboresistant properties are observed. There are more living cells on the Zr(C,N) series films, and the cells show a higher relative growth rate value than those on the electropolished NiTi. The Zr(C,N) series films act as barrier layers and promote the proliferation of fibroblasts by blocking the leaching of toxic nickel ions from NiTi.
New electroless copper plating bath using sodium hypophosphite as reductant
Authors: Yuan X L , Gao J , Yang Z F , Wang Z X , Wang Z L
Published: March 2012

In this paper, a new environment friendly electroless plating bath using sodium hypophosphite as reductant and nitrilotriacetic acid as complexing agent was investigated under the acid condition. The effects of bath temperature, pH, CuSO4.5H2O concentration, nitrilotriacetic acid concentration and NaH2PO2.H2O concentration upon the deposition rate and the bath stability were studied. The electrochemical results indicated that the deposition rate of the electroless copper increased with the decrease in the pH, and it reached 2·4 μm h−1 when the bath pH was 6·0. The as deposited Cu films were characterised by energy dispersive X-ray analyser, X-ray diffraction, atomic force microscopy and resistivity measurement. The quality of the Cu films were improved by the addition of a surfactant PEG-600, and a uniform copper film with a low resistivity (2·60 μΩ cm) was obtained, which was able to be used as seed layer for electroplating Cu.
High temperature sulphidation of HVOF sprayed CeO2 modified NiCrAlY coatings in H2/H2S atmospheres
Authors: Wang Y , Sun X G , He J Q , Chen S F , Wang L , Wang Z
Published: March 2012

High temperature sulphidation is one of the most deleterious forms of surface degradation. In the present work, the high temperature sulphidation behaviours of high velocity oxyfuel sprayed NiCrAlY and NiCrAlYCe coatings on high pressure steels in H2–H2S mixtures were investigated. Results showed that the NiCrAlYCe coating provided much better sulphidation resistance than the NiCrAlY coating in the given environment. After adding minor CeO2, the outer layer of scales became compact and showed good adhesion, which decreased the sulphur vapour pressure inside the scale and promoted the formation of more protective inner layer of sulphospinels (Cr, Ni)Al2S2.
Microstructure characteristics and corrosion resistance of Ni–Co alloy coating prepared on AZ91D magnesium alloy
Authors: Yang X K , Mu X L , Xu Z Q , Li J N , Zhu L , Zhang S Y , Li Ch , Wen B W
Published: March 2012

In this article, a protective Ni–Co alloy coating was prepared on AZ91D magnesium alloy which was pretreated with electroless plating. The surface morphologies, microstructure and chemical composition of the coatings were studied using environmental scanning electron microscope, X-ray diffraction and energy dispersive spectroscopy respectively. The surface morphologies and microstructure analysis showed that the Ni–Co alloy coating possessed cone shaped grain congeries and formed face centred cubic solid solution. The energy dispersive spectroscopy analysis revealed that the content of cobalt element in the alloy coating was ∼31 wt-%. Potentiodynamic polarisation curves and electrochemical impedance spectroscopy were employed to investigate the corrosion resistance of different corrosive systems in neutral 3·5 wt-%NaCl and 0·5 mol L–1 Na2SO4 solutions, which were chosen to simulate the effects of marine and industrial environments respectively. The results showed that the corrosion resistance of the AZ91D magnesium alloy was obviously improved by the Ni–Co alloy coating.
Effects of plasma nitriding on properties of electroless Ni–B coating
Authors: Ahmadkhaniha D , Mahboubi F
Published: March 2012

In this study, the properties of nitrided electroless Ni–B coating prepared by conventional plasma nitriding (CPN), were compared with those of annealed one. For this purpose, electroless Ni–B coatings were deposited from an alkaline bath on AISI 4140 substrates. Then some of the prepared coatings were annealed under controlled atmosphere and the other ones were plasma nitrided at the same conditions. Microstructure, morphology, microhardness and wear resistance of the coatings were evaluated. Based on the results, under the experimental conditions, plasma nitriding increases surface roughness; meanwhile, it improves wear resistance and microhardness of the coatings. The sputtering of iron atoms during CPN process could be the main reason for these results.
Economical deposition of Ni high cerium oxide nanocomposite coatings
Authors: Hasannejad H , Shahrabi T
Published: March 2012

Ni high cerium oxide nanocomposite coatings were prepared by electrodeposition process using inexpensive and particle free aqueous baths containing NiCl2.6H2O and CeCl3.7H2O salts. Scanning electron microscopy, atomic force microscopy, EDAX and X-ray diffraction studies showed the possibility of deposition of nickel containing 35% cerium oxide composite coating. Electrochemical impedance spectroscopy and potentiodynamic data indicated that the presence of cerium oxide in the Ni deposit led to an increase in electrocatalytic activity in hydrogen evolution.
Mechanical and corrosion properties of Ta–Mo coatings by heating processes
Authors: Ji X , Mi Y M , Zhou X Y , Zhang C M
Published: March 2012

In this research, substrate heating process has been used for the production of Ta–Mo high temperature protective coatings. The microstructures of the alloy coatings have been studied through X-ray diffraction and scanning electron microscopy. Mechanical and corrosion properties of different alloys have been investigated in both low and high temperature heating processes. Substrate heating processes (from 250 to 550°C) were expected to produce partially recrystallised and fully recrystallised microstructures. Higher heating temperature results in recrystallised microstructures, but adversely affects the density of atoms Vt and bond energy G. The behaviour of low and high temperature heating processes on corrosion and mechanical properties of Ta–Mo nanostructured coatings was studied.
Co–W films prepared from electroplating baths with different complexing agents
Authors: Wei G Y , Lou J W , Ge H L , Yu Y D , Jiang L , Sun L X
Published: March 2012

The influence of different complexing agents with hydroxycarboxylic acid group on the electrodeposited Co–W thin films has been investigated. Comparison between the polarisation curves shows that the negative shift on the electrodeposition potential increased in the following order: no complexing agent, tartrate, malate, gluconate and citrate. The particular shapes of the j– t transients indicate that a nucleation and growth process was involved for the Co–W electrodeposition in the presence of complexing agents investigated. The reduced current transients follow the instantaneous nucleation model for all four complexing agents at the initial stages. Surface morphology, phase composition and magnetic properties were observed by means of field emission SEM, X-ray diffraction and vibrating sample magnetometer respectively. It has been found out that surface morphology and phase composition were markedly affected by the nature of the complexing agents. In the absence of complexing agents and in the presence of citrate, reflections of Co7W6, Co (1 0 0) and Co (0 0 2) appeared simultaneously. For the deposits obtained from solutions containing malate, there are two main peaks: Co7W6 and Co (0 0 2). In the case of tartrate, two peaks of Co are observed: Co (0 0 2) and Co (1 0 0). Reflections of Co (0 0 2) appeared for the deposits prepared from gluconate baths. Co–W magnetic thin films presented good soft magnetic properties ( Hc = 2 Oe, Ms = 1403 emu cm−3) compared with pure cobalt thin films (1370 emu cm−3) when 0··3 mol L−1 citrate was used as complexing agent.
Microstructure and wear behaviour of laser clad NiCrBSi+Ta composite coating
Authors: Yu T , Deng Q L , Zheng J F , Dong G , Yang J G
Published: March 2012

Ta was added to laser clad NiCrBSi coating to improve wear resistance. In situ synthesised TaC particles of nearly equiaxed shape were uniformly dispersed in the coating. The colony that contained acicular Cr rich boride or carbide grew radially around the TaC particle and had a strong bond with the particle. The TaC particles had good bonds with the matrix, and tended to be crushed and impressed into the matrix instead of being pulled out from the wear surface during the wear process. The NiCrBSi+Ta coating exhibited higher fracture toughness, and higher abrasive and adhesive wear resistance than the NiCrBSi coating. The primary wear mechanism of the NiCrBSi+Ta coating was abrasion combined with the oxidation process under all test conditions while the main wear mechanism of the NiCrBSi coating was abrasion and microflaking under a low load (30 N), and adhesion and oxidation under a high load (75 N).
Neonatal lymph node stromal cells drive myelodendritic lineage cells into a distinct population of CX3CR1+CD11b+F4/80+ regulatory macrophages in mice
Authors: Zhang Xiangyue , Yu Songfeng , Hoffmann Katharina , Yu Kai , Förster Reinhold
Published: March 2012

Beyond providing a scaffold for immune cells, recent studies indicate that lymph node stromal cells provide potent regulatory capacities that affect the quality of adaptive immune responses. In this study, we provide evidence that neonatal lymph node stromal cells (nnLNSCs) consistently promote the differentiation of macrophage dendritic cell progenitors as well as mature and immature dendritic cells into a distinct population of CX3CR1+ CD11b+F4/80+ regulatory macrophages (regMΦ). These cells possess remarkably low levels of T cell costimulatory molecules as well as MHC class II molecules. regMΦ do not interfere with early T-cell activation but, via nitric oxide secretion, efficiently suppress T-cell proliferation. Furthermore, CD4+ T cells proliferating in the presence of regMΦ gain immunosuppressive capacity and MΦ isolated from day 3 nnLNs are T-cell immunosuppressive. Adoptive transfer of antigen-loaded regMΦ induce a profound antigen-specific immune suppression in vivo. Together our data show that nnLNSCs skew the differentiation of dendritic cells and their progenitors toward regMΦ, thus revealing a novel mechanism for local immune regulation.
Human NK cells at early stages of differentiation produce CXCL8 and express CD161 molecule that functions as an activating receptor
Authors: Montaldo Elisa , Vitale Chiara , Cottalasso Francesca , Conte Romana , Glatzer Timor , Ambrosini Paolo , Moretta Lorenzo , Mingari Maria Cristina
Published: March 2012

Human natural killer (NK) cell development is a step-by-step process characterized by phenotypically identified stages. CD161 is a marker informative of the NK cell lineage commitment, whereas CD56, CD117, and CD94/NKG2A contribute to define discrete differentiation stages. In cells undergoing in vitro differentiation from CD34+ umbilical cord blood (UCB) progenitors, LFA-1 expression allowed to discriminate between immature noncytolytic CD161+CD56+LFA-1− and more differentiated cytolytic CD161+CD56+LFA-1+ NK cells. CD161+CD56+LFA-1− NK cells produce large amounts of CXCL8 after phorbol myristate acetate (PMA) or cytokine treatment. Remarkably, CXCL8 mRNA expression was also detected in fresh stage III immature NK cells isolated from tonsils and these cells expressed CXCL8 protein on PMA stimulation. Within in vitro UCB-derived CD161+CD56+LFA-1− NK cells, CXCL8 release was also induced on antibody-mediated cross-linking of NKp44 and CD161. Such unexpected activating function of CD161 was confined to the CD161+CD56+LFA-1− subset, because it did not induce cytokine release or CD107a expression in CD161+CD56+LFA-1+ cells or in mature peripheral blood NK cells. Anti-CXCL8 neutralizing antibody induced a partial inhibition of NK cell differentiation, which suggests a regulatory role of CXCL8 during early NK cell differentiation. Altogether, these data provide novel information that may offer clues to optimize NK cell maturation in hematopoietic stem cell transplantation.
Dendritic cells and regulation of graft-versus-host disease and graft-versus-leukemia activity
Authors: Stenger Elizabeth O. , Turnquist Hēth R. , Mapara Markus Y. , Thomson Angus W.
Published: March 2012

Hematopoietic stem cell transplantation is the only curative treatment for many malignant hematologic diseases, with an often critical graft-versus-leukemia effect. Despite peritransplant prophylaxis, GVHD remains a significant cause of posthematopoietic stem cell transplantation morbidity and mortality. Traditional therapies have targeted T cells, yet immunostimulatory dendritic cells (DCs) are critical in the pathogenesis of GVHD. Furthermore, DCs also have tolerogenic properties. Monitoring of DC characteristics may be predictive of outcome, and therapies that target DCs are innovative and promising. DCs may be targeted in vivo or tolerogenic (tol) DCs may be generated in vitro and given in the peritransplant period. Other cellular therapies, notably regulatory T cells (Treg) and mesenchymal stem cells, mediate important effects through DCs and show promise for the prevention and treatment of GVHD in early human studies. Therapies are likely to be more effective if they have synergistic effects or target both DCs and T cells in vivo, such as tolDCs or Treg. Given the effectiveness of tolDCs in experimental models of GVHD and their safety in early human studies for type 1 diabetes, it is crucial that tolDCs be investigated in the prevention and treatment of human GVHD while ensuring conservation of graft-versus-leukemia effects.
Antitumor activities of ATP-competitive inhibitors of mTOR in colon cancer cells
Authors: Blaser Benjamin , Waselle Laurent , Dormond-Meuwly Anne , Dufour Marc , Roulin Didier , Demartines Nicolas , Dormond Olivier
Published: March 2012

Background

The mammalian target of rapamycin (mTOR) is frequently activated in colon cancers due to mutations in the phosphatidylinositol 3-kinase (PI3K) pathway. Targeting mTOR with allosteric inhibitors of mTOR such as rapamycin reduces colon cancer progression in several experimental models. Recently, a new class of mTOR inhibitors that act as ATP-competitive inhibitors of mTOR, has been developed. The effectiveness of these drugs in colon cancer cells has however not been fully characterized.

Methods

LS174T, SW480 and DLD-1 colon cancer cell lines were treated with PP242 an ATP-competitive inhibitor of mTOR, NVP-BEZ235, a dual PI3K/mTOR inhibitor or rapamycin. Tumor cell growth, proliferation and survival were assessed by MTS assay, 5-bromo-2'-deoxyuridine (BrDU) incorporation or by quantification of DNA fragmentation respectively. In vivo, the anticancer activity of mTOR inhibitors was evaluated on nude mice bearing colon cancer xenografts.

Results

PP242 and NVP-BEZ235 reduced the growth, proliferation and survival of LS174T and DLD-1 colon cancer cells more efficiently than rapamycin. Similarly, PP242 and NVP-BEZ235 also decreased significantly the proliferation and survival of SW480 cells which were resistant to the effects of rapamycin. In vivo, PP242 and NVP-BEZ235 reduced the growth of xenografts generated from LS174T and SW480 cells. Finally, we also observed that the efficacy of ATP-competitive inhibitors of mTOR was enhanced by U0126, a MEK inhibitor.

Conclusions

Taken together, these results show that ATP-competitive inhibitors of mTOR are effective in blocking colon cancer cell growth in vitro and in vivo and thus represent a therapeutic option in colon cancer either alone or in combination with MEK inhibitors.
Proteomic analysis of soybean defense response induced by cotton worm (prodenia litura, fabricius) feeding
Authors: Fan Rui , Wang Hui , Wang Yongli , Yu Deyue
Published: March 2012

Background

Cotton worm is one of the main insects of soybean in southern China. Plants may acquire defense mechanisms that confer protection from predation by herbivores. Induced responses can lead to increased resistance against herbivores in many species. This study focuses on searching changed proteins in soybean defense response induced by cotton worm feeding.

Results

Ten protein spots that are changed in abundance in response to cotton worm feeding were identified by Two-dimensional gel electrophoresis (2-DE). A total of 11 unique proteins from these spots were identified by MALDI-TOF MS. The mRNA and protein relative expression levels of most changed proteins were up-regulated. These proteins were mainly involved in physiological processes, including active oxygen removal, defense signal transduction, and metabolism regulation.

Conclusion

This is the first proteomic analysis of the soybean defense response induced by cotton worm. The differentially expressed proteins could work together to play a major role in the induced defense response. PAL and SAMS were up-regulated at both the protein and mRNA levels. These genes can be strongest candidates for further functional research.
Serous cystadenocarcinoma of the pancreas: report of a case and management reflections
Authors: Bramis K , Petrou A , Papalambros A , Manzelli A , Mantonakis E , Brennan N , Felekouras E
Published: March 2012

Background

Serous adenomas represent 1-2% of pancreatic neoplasms and typically are asymptomatic not requiring any treatment and simple observation is the option of choice. Although, they carry a realistic risk of malignancy despite the general view that they never become malignant. We report a case, which, according to our best knowledge is the 27th case reported in the literature.

Methods

We reviewed the literature by performing a search in Pub Med and Medline.

Results

A 86-year old patient known to have a serous cystadenoma of the pancreas treated conservatively through a close clinical and radiological follow up which was unattended for 4 years ending up to our emergency department suffering an acute abdomen. Exploratory laparotomy revealed a perforated prepyloric ulcer which was treated accordingly. Patient died some weeks later due to severe medical co morbidities.

Conclusion

Serous cystic neoplasms of the pancreas carry a realistic risk of malignancy despite the general view that they never become malignant. In our opinion the treatment strategy of serous cystic neoplasms of the pancreas should be aggressive even in cases of remote metastases since prognosis of the disease is satisfactory
Preparation and characterization of ZnO microcantilever for nanoactuation
Authors: Wang Peihong , Du Hejun , Shen Shengnan , Zhang Mingsheng , Liu Bo
Published: March 2012

Zinc oxide [ZnO] thin films are deposited using a radiofrequency magnetron sputtering method under room temperature. Its crystalline quality, surface morphology, and composition purity are characterized by X-ray diffraction [XRD], atomic force microscopy [AFM], field-emission scanning electron microscopy [FE-SEM], and energy-dispersive X-ray spectroscopy [EDS]. XRD pattern of the ZnO thin film shows that it has a high c-axis-preferring orientation, which is confirmed by a FE-SEM cross-sectional image of the film. The EDS analysis indicates that only Zn and O elements are contained in the ZnO film. The AFM image shows that the film's surface is very smooth and dense, and the surface roughness is 5.899 nm. The microcantilever (Au/Ti/ZnO/Au/Ti/SiO2/Si) based on the ZnO thin film is fabricated by micromachining techniques. The dynamic characterizations of the cantilever using a laser Doppler vibrometer show that the amplitude of the cantilever tip is linear with the driving voltage, and the amplitude of this microcantilever's tip increased from 2.1 to 13.6 nm when the driving voltage increased from 0.05 to 0.3 Vrms. The calculated transverse piezoelectric constant d
31 of the ZnO thin film is -3.27 pC/N. This d
31 is high compared with other published results. This ZnO thin film will be used in smart slider in hard disk drives to do nanoactuation in the future.
Polyamide 66 microspheres metallised with in situ synthesised gold nanoparticles for a catalytic application
Authors: Cheval Nicolas , Gindy Nabil , Flowkes Clifford , Fahmi Amir
Published: March 2012

A simple concept is proposed to metallise polyamide 66 (PA66) spherulite structures with in situ synthesised gold nanoparticles (Au NPs) using a wet chemical method. This cost-effective approach, applied to produce a PA66/Au NP hybrid material, offers the advantages of controlling the nanoparticle size, the size distribution and the organic-inorganic interactions. These are the key factors that have to be controlled to construct consistent Au nanostructures which are essential for producing the catalytic activities of interest. The hybrid materials obtained are characterised by means of scanning electron microscopy, transmission electron microscopy, attenuated total reflection-Fourier transform infrared spectrometry and X-ray diffraction spectrometry. The results show that PA66 microspheres obtained via the crystallisation process are coated with Au NPs of 13 nm in size. It was found that controlling the metal coordination is the key parameter to template the Au NPs on the spherulite surfaces. The preparation processes and the key factors leading to the formation of PA66 spherulites coated with Au NPs are discussed. Moreover, the efficiency of the coated spherulites as a potential catalyst is proved by demonstrating the reduction of methylene blue via UV-visible spectrometry.
MSNS: mobile sensor network simulator for area coverage and obstacle avoidance based on GML
Authors: Jeong Young-Sik , Han Youn-Hee , Park James J , Lee SooYoung
Published: March 2012

A mobile sensor network is a distributed collection of sensors, each of which has sensing, computation, communication, and locomotion capabilities. In particular, locomotion facilitates the ability to self-deployment. In such a network of self-deployable mobile sensors, it is difficult to evaluate the effectiveness of mobile sensor network deployment in a given target area because we cannot predict the coverage rate for the target area. The coverage rate will be changed due to the number of sensor required in the target area, connectivity degree to be maintained and unknown obstacles. In this article, we develop mobile sensor network simulator (MSNS) in order to visualize (1) coverage secured by mobile sensors and (2) avoidance of obstacle objects (building, road and wall, and so on) on the real map drawn by GML (Geography Markup Language). From a user, MSNS receives the number of mobile sensor nodes, connectivity degree, sensor node's sensing range, communication range, and supersonic wave range. And then it visualizes the location information of sensor nodes, connectivity degree, and sensing coverage, all of which change with simulation time. Thereby we can estimate how many nodes are required in a given target area, and also calculate coverage rate of the target area in advance to the real deployment of mobile sensors.
Molecular alterations of isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) metabolic genes and additional genetic mutations in newly diagnosed acute myeloid leukemia patients
Authors: Chotirat Sadudee , Thongnoppakhun Wanna , Promsuwicha Orathai , Boonthimat Chetsada , Auewarakul Chirayu U
Published: March 2012

Background

Isocitrate dehydrogenase 1 and 2 (IDH1 and IDH2) metabolic genes encode cytosolic and mitochondrial enzymes that catalyze the conversion of isocitrate to α-ketoglutarate. Acquired somatic mutations of IDH1 and IDH2 have recently been reported in some types of brain tumors and a small proportion of acute myeloid leukemia (AML) cases.

Methods

Two-hundred and thirty newly diagnosed AML patients were analyzed for the presence of IDH1 and IDH2 heterozygous mutations by polymerase chain reaction-denaturing high performance liquid chromatography (PCR-DHPLC) followed by direct sequencing. Clinical and biological characteristics were analyzed and correlated to the IDH mutational status. Coexisting mutations such as FLT3, PML- RARA, RAS, AML1, and NPM1 mutations were additionally explored.

Results

The prevalence of IDH1 and IDH2 mutations was 8.7% (20/230) and 10.4% (24/230), respectively. Six missense mutations were identified among IDH1-mutated cases; p.R132H (n = 8), p.R132C (n = 6), p.R132S (n = 2), p.R132G (n = 2), p.R132L (n = 1), and p.I99M (n = 1). Two missense mutations were found in IDH2-mutated cases; p.R140Q (n = 20) and p.R172K (n = 4). No patients had dual IDH1 and IDH2 mutations. About 18% of AML with normal cytogenetics and 31% of acute promyelocytic leukemia had IDH mutations. Half of the IDH-mutated cohort had normal karyotype and the major FAB subtype was AML-M2. Interestingly, IDH1- and IDH2-mutated cases predominantly had NPM1 mutations (60-74%) as compared to the wild type (P < 0.001). Very few IDH-mutated cases had FLT3 and/or RAS abnormalities and none of them had AML1 mutations. Older age and higher median platelet counts were significantly associated with IDH2 mutations although the clinical impact of either IDH1 or IDH2 mutations on patients' overall survival could not be observed.

Conclusion

Overall, 19% of newly diagnosed AML patients had alterations of IDH genes. No patients concurrently carried both IDH1 and IDH2 mutations suggesting that these mutations were mutually exclusive. NPM1 mutation appears as a major coexisting genetic mutation in IDH-mutated patients. Our present data failed to support the prognostic relevance of IDH mutations although alterations of these metabolic genes potentially have an important role in leukemia development.
Unified geophysical and geological 3D Earth models
Authors: Lelièvre Peter , Carter-McAuslan Angela , Farquharson Colin , Hurich Charles
Published: March 2012

Three-dimensional geological Earth models typically comprise wireframe surfaces of connected triangles that represent geological contacts. In contrast, Earth models used by most current 3D geophysical numerical modeling and inversion methods are built on rectilinear meshes. This is because the mathematics for computing data responses are simpler on rectilinear meshes. In such a model, the relevant physical properties are uniform within each brick-like cell but possibly different from one cell to the next, producing a pixellated representation of the Earth. In principle, arbitrary spatial variations can be represented if a sufficiently fine discretization is used. However, no matter how fine the discretization of the rectilinear mesh, such a mesh is always incompatible with geological models comprising wireframe surfaces. Also, because the computational resources required by 3D numerical modeling and inversion methods increase dramatically as the discretization of a model is refined, it is never really possible to achieve as fine a discretization as one would like. This exacerbates the mismatch between models that comprise wireframe surfaces and those built on rectilinear meshes. To address this incompatibility, we are using unstructured tetrahedral meshes to specify 3D geophysical Earth models. We hope that working with unstructured meshes will facilitate the construction of common Earth models consistent with both the geological and geophysical data available.
How to make better use of physical properties in mineral exploration: The exploration site measurement
Authors: Smith Richard , Shore Mark , Rainsford Desmond
Published: March 2012

In recent years, there has been a growing awareness that a better understanding of physical property information is required in mineral exploration. As a consequence, there has been a strong push to collect more data and to use these data more intelligently. There are a multiplicity of reasons behind this impetus: geophysicists want more information about physical property data to enable better surveys to be planned and better interpretations to come from the data acquired and geologists want physical properties to provide addition information about the geology that might allow them to see variations in rocks that are not easy to see using traditional or more expensive methods (hand specimen examination, thin sections, lithogeochemistry, assays, etc.). If a hole is drilled on a geophysical target, then a physical property measurement of the core or the rocks surrounding the core can confirm if the target was intercepted and provides data that can be used to model the target response.
Pareto Lévy Measures and Multivariate Regular Variation
Authors: Eder Irmingard , Klüppelberg Claudia
Published: March 2012

We consider regular variation of a Lévy processX:= (Xt)t≥0inwith Lévy measure Π, emphasizing the dependence between jumps of its components. By transforming the one-dimensional marginal Lévy measures to those of a standard 1-stable Lévy process, we decouple the marginal Lévy measures from the dependence structure. The dependence between the jumps is modeled by a so-calledPareto Lévy measure, which is a natural standardization in the context of regular variation. We characterize multivariate regularly variation ofXby its one-dimensional marginal Lévy measures and the Pareto Lévy measure. Moreover, we define upper and lower tail dependence coefficients for the Lévy measure, which also apply to the multivariate distributions of the process. Finally, we present graphical tools to visualize the dependence structure in terms of the spectral density and the tail integral for homogeneous and nonhomogeneous Pareto Lévy measures.
Numerical Methods for the Exit Time of a Piecewise-Deterministic Markov Process
Authors: Brandejsky Adrien , De Saporta Benoîte , Dufour François
Published: March 2012

We present a numerical method to compute the survival function and the moments of the exit time for a piecewise-deterministic Markov process (PDMP). Our approach is based on the quantization of an underlying discrete-time Markov chain related to the PDMP. The approximation we propose is easily computable and is even flexible with respect to the exit time we consider. We prove the convergence of the algorithm and obtain bounds for the rate of convergence in the case of the moments. We give an academic example and a model from the reliability field to illustrate the results of the paper.
Phase-Type Distributions and Optimal Stopping for Autoregressive Processes
Authors: Christensen Sören
Published: March 2012

Autoregressive processes are intensively studied in statistics and other fields of applied stochastics. For many applications, the overshoot and the threshold time are of special interest. When the upward innovations are in the class of phase-type distributions, we determine the joint distribution of these two quantities and apply this result to problems of optimal stopping. Using a principle of continuous fit, this leads to explicit solutions.
Continuous, Discrete, and Conditional Scan Statistics
Authors: Fu James C. , Wu Tung-Lung , Lou W.Y. Wendy
Published: March 2012

The distributions for continuous, discrete, and conditional discrete scan statistics are studied. The approach of finite Markov chain imbedding, which has been applied to random permutations as well as to runs and patterns, is extended to compute the distribution of the conditional discrete scan statistic, defined from a sequence of Bernoulli trials. It is shown that the distribution of the continuous scan statistic induced by a Poisson process defined on (0, 1] is a limiting distribution of weighted distributions of conditional discrete scan statistics. Comparisons of rates of convergence as well as numerical comparisons of various bounds and approximations are provided to illustrate the theoretical results.
Binary Trees, Exploration Processes, and an Extended Ray-Knight Theorem
Authors: Ba Mamadou , Pardoux Etienne , Sow Ahmadou Bamba
Published: March 2012

We study the bijection between binary Galton-Watson trees in continuous time and their exploration process, both in the subcritical and in the supercritical cases. We then take the limit over renormalized quantities, as the size of the population tends to ∞. We thus deduce Delmas' generalization of the second Ray-Knight theorem.
Spectral Theory for Weakly Reversible Markov Chains
Authors: Wübker Achim
Published: March 2012

The theory of L2-spectral gaps for reversible Markov chains has been studied by many authors. In this paper we consider positive recurrent general state space Markov chains with stationary transition probabilities. Replacing the assumption of reversibility with a weaker assumption, we still obtain a simple necessary and sufficient condition for the spectral gap property of the associated Markov operator in terms of the isoperimetric constant. We show that this result can be applied to a large class of Markov chains, including those that are related to positive recurrent finite-range random walks on Z.
Juggler's Exclusion Process
Authors: Leskelä Lasse , Varpanen Harri
Published: March 2012

Juggler's exclusion process describes a system of particles on the positive integers where particles drift down to zero at unit speed. After a particle hits zero, it jumps into a randomly chosen unoccupied site. We model the system as a set-valued Markov process and show that the process is ergodic if the family of jump height distributions is uniformly integrable. In a special case where the particles jump according to a set-avoiding memoryless distribution, the process reaches its equilibrium in finite nonrandom time, and the equilibrium distribution can be represented as a Gibbs measure conforming to a linear gravitational potential.
Context-dependent function of a conserved translational regulatory module
Authors: Liu Qinwen , Stumpf Craig , Thomas Cristel , Wickens Marvin , Haag Eric S.
Published: March 2012

The modification of transcriptional regulation is a well-documented evolutionary mechanism in both plants and animals, but post-transcriptional controls have received less attention. The derived hermaphrodite of C. elegans has regulated spermatogenesis in an otherwise female body. The PUF family RNA-binding proteins FBF-1 and FBF-2 limit XX spermatogenesis by repressing the male-promoting proteins FEM-3 and GLD-1. Here, we examine the function of PUF homologs from other Caenorhabditis species, with emphasis on C. briggsae, which evolved selfing convergently. C. briggsae lacks a bona fide fbf-1/2 ortholog, but two members of the related PUF-2 subfamily, Cbr-puf-2 and Cbr-puf-1.2, do have a redundant germline sex determination role. Surprisingly, this is to promote, rather than limit, hermaphrodite spermatogenesis. We provide genetic, molecular and biochemical evidence that Cbr-puf-2 and Cbr-puf-1.2 repress Cbr-gld-1 by a conserved mechanism. However, Cbr-gld-1 acts to limit, rather than promote, XX spermatogenesis. As with gld-1, no sex determination function for fbf or puf-2 orthologs is observed in gonochoristic Caenorhabditis. These results indicate that PUF family genes were co-opted for sex determination in each hermaphrodite via their long-standing association with gld-1, and that their precise sex-determining roles depend on the species-specific context in which they act. Finally, we document non-redundant roles for Cbr-puf-2 in embryonic and early larval development, the latter role being essential. Thus, recently duplicated PUF paralogs have already acquired distinct functions.
A hindbrain-repressive Wnt3a/Meis3/Tsh1 circuit promotes neuronal differentiation and coordinates tissue maturation
Authors: Elkouby Yaniv M. , Polevoy Hanna , Gutkovich Yoni E. , Michaelov Ariel , Frank Dale
Published: March 2012

During development, early inducing programs must later be counterbalanced for coordinated tissue maturation. In Xenopus laevis embryos, activation of the Meis3 transcription factor by a mesodermal Wnt3a signal lies at the core of the hindbrain developmental program. We now identify a hindbrain restricting circuit, surprisingly comprising the hindbrain inducers Wnt3a and Meis3, and Tsh1 protein. Functional and biochemical analyses show that upon Tsh1 induction by strong Wnt3a/Meis3 feedback loop activity, the Meis3-Tsh1 transcription complex represses the Meis3 promoter, allowing cell cycle exit and neuron differentiation. Meis3 protein exhibits a conserved dual-role in hindbrain development, both inducing neural progenitors and maintaining their proliferative state. In this regulatory circuit, the Tsh1 co-repressor controls transcription factor gene expression that modulates cell cycle exit, morphogenesis and differentiation, thus coordinating neural tissue maturation. This newly identified Wnt/Meis/Tsh circuit could play an important role in diverse developmental and disease processes.
Somatic small RNA pathways promote the mitotic events of megagametogenesis during female reproductive development in Arabidopsis
Authors: Tucker Matthew R. , Okada Takashi , Hu Yingkao , Scholefield Andrew , Taylor Jennifer M. , Koltunow Anna M. G.
Published: March 2012

Female gamete development in Arabidopsis ovules comprises two phases. During megasporogenesis, a somatic ovule cell differentiates into a megaspore mother cell and undergoes meiosis to produce four haploid megaspores, three of which degrade. The surviving functional megaspore participates in megagametogenesis, undergoing syncytial mitosis and cellular differentiation to produce a multicellular female gametophyte containing the egg and central cell, progenitors of the embryo and endosperm of the seed. The transition between megasporogenesis and megagametogenesis is poorly characterised, partly owing to the inaccessibility of reproductive cells within the ovule. Here, laser capture microdissection was used to identify genes expressed in and/or around developing megaspores during the transition to megagametogenesis. ARGONAUTE5 (AGO5), a putative effector of small RNA (sRNA) silencing pathways, was found to be expressed around reproductive cells during megasporogenesis, and a novel semi-dominant ago5-4 insertion allele showed defects in the initiation of megagametogenesis. Expression of a viral RNAi suppressor, P1/Hc-Pro, driven by the WUSCHEL and AGO5 promoters in somatic cells flanking the megaspores resulted in a similar phenotype. This indicates that sRNA-dependent pathways acting in somatic ovule tissues promote the initiation of megagametogenesis in the functional megaspore. Notably, these pathways are independent of AGO9, which functions in somatic epidermal ovule cells to inhibit the formation of multiple megaspore-like cells. Therefore, one somatic sRNA pathway involving AGO9 restricts reproductive development to the functional megaspore and a second pathway, inhibited by ago5-4 and P1/Hc-Pro, promotes megagametogenesis.
Role of shear-stress-induced VEGF expression in endothelial cell survival
Authors: dela Paz Nathaniel G. , Walshe Tony E. , Leach Lyndsay L. , Saint-Geniez Magali , D'Amore Patricia A.
Published: March 2012

Vascular endothelial growth factor (VEGF) plays a crucial role in developmental and pathological angiogenesis. Expression of VEGF in quiescent adult tissue suggests a potential role in the maintenance of mature blood vessels. We demonstrate, using a Vegf–lacZ reporter mouse model, that VEGF is expressed by arterial but not by venous or capillary endothelial cells (ECs) in vivo. Using an in vitro model, we show that arterial shear stress of human umbilical vein ECs (HUVECs) decreases apoptosis and increases VEGF expression, which is mediated by the induction of Krüppel-like factor 2 (KLF2). Additionally, shear stress stimulates the expression of VEGF receptor 2 (VEGFR2) and is associated with its activation. Knockdown of VEGF in shear stressed HUVECs blocks the protective effect of shear stress, resulting in EC apoptosis equivalent to that in control ECs cultured under static conditions. Similarly, treatment of ECs subjected to arterial shear stress with the VEGF receptor tyrosine kinase inhibitor SU1498, or VEGFR2 neutralizing antiserum, led to increased apoptosis, demonstrating that the mechanoprotection from increased shear is mediated by VEGFR2. Taken together, these studies suggest that arterial flow induces VEGF–VEGFR2 autocrine–juxtacrine signaling, which is a previously unidentified mechanism for vascular EC survival in adult arterial blood vessels.
In vivo fluorescence resonance energy transfer imaging reveals differential activation of Rho-family GTPases in glioblastoma cell invasion
Authors: Hirata Eishu , Yukinaga Hiroko , Kamioka Yuji , Arakawa Yoshiki , Miyamoto Susumu , Okada Takaharu , Sahai Erik , Matsuda Michiyuki
Published: March 2012

Two-photon excitation microscopy was used to visualized two different modes of invasion at perivascular and intraparenchymal regions of rat C6 glioblastoma cells that were orthotopically implanted into rat brains. Probes based on the principle of Förster resonance energy transfer (FRET) further revealed that glioblastoma cells penetrating the brain parenchyma showed higher Rac1 and Cdc42 activities and lower RhoA activity than those advancing in the perivascular regions. This spatial regulation of Rho-family GTPase activities was recapitulated in three-dimensional spheroid invasion assays with rat and human glioblastoma cells, in which multipod glioblastoma cells that invaded the gels and led the other glioblastoma cells exhibited higher Rac1 and Cdc42 activities than the trailing glioblastoma cells. We also studied the Cdc42-specific guanine nucleotide exchange factor Zizimin1 (also known as DOCK9) as a possible contributor to this spatially controlled activation of Rho-family GTPases, because it is known to play an essential role in the extension of neurites. We found that shRNA-mediated knockdown of Zizimin1 inhibited formation of pseudopodia and concomitant invasion of glioblastoma cells both under a 3D culture condition and in vivo. Our results suggest that the difference in the activity balance of Rac1 and Cdc42 versus RhoA determines the mode of glioblastoma invasion and that Zizimin1 contributes to the invasiveness of glioblastoma cells with high Rac1 and Cdc42 activities.
The HIF1 target geneNOX2promotes angiogenesis through urotensin-II
Authors: Diebold Isabel , Petry Andreas , Sabrane Karim , Djordjevic Talija , Hess John , Görlach Agnes
Published: March 2012

Urotensin-II (U-II) has been considered as one of the most potent vasoactive peptides, although its physiological and pathophysiological role is still not finally resolved. Recent evidence suggests that it promotes angiogenic responses in endothelial cells, although the underlying signalling mechanisms are unclear. Reactive oxygen species derived from NADPH oxidases are major signalling molecules in the vasculature. Because NOX2 is functional in endothelial cells, we investigated the role of the NOX2-containing NADPH oxidase in U-II-induced angiogenesis and elucidated a possible contribution of hypoxia-inducible factor-1 (HIF-1), the master regulator of hypoxic angiogenesis, in the response to U-II. We found that U-II increases angiogenesis in vitro and in vivo, and these responses were prevented by antioxidants, NOX2 knockdown and in Nox2−/− mice. In addition, U-II-induced angiogenesis was dependent on HIF-1. Interestingly, U-II increased NOX2 transcription involving HIF-1, and chromatin immunoprecipitation confirmed NOX2 as a target gene of HIF-1. In support, NOX2 levels were greatly diminished in U-II-stimulated isolated vessels derived from mice deficient in endothelial HIF-1. Conversely, reactive oxygen species derived from NOX2 were required for U-II activation of HIF and upregulation of HIF-1. In line with this, U-II-induced upregulation of HIF-1 was absent in Nox2−/− vessels. Collectively, these findings identified HIF-1 and NOX2 as partners acting in concert to promote angiogenesis in response to U-II. Because U-II has been found to be elevated in cardiovascular disorders and in tumour tissues, this feed-forward mechanism could be an interesting anti-angiogenic therapeutic option in these disorders.
Mitogen-activated protein kinase (MAPK/ERK) regulates adenomatous polyposis coli during growth-factor-induced cell extension
Authors: Caro-Gonzalez Hector Y. , Nejsum Lene N. , Siemers Kathleen A. , Shaler Thomas A. , Nelson W. James , Barth Angela I. M.
Published: March 2012

Regulation of the microtubule- and actin-binding protein adenomatous polyposis coli (APC) is crucial for the formation of cell extensions in many cell types. This process requires inhibition of glycogen synthase kinase-3β (GSK-3β), which otherwise phosphorylates APC and decreases APC-mediated microtubule bundling. Although it is assumed, therefore, that APC phosphorylation is decreased during initiation of cell extensions, the phosphorylation state of APC has never been analyzed directly. We show here that NGF- and EGF-induced initial cell extensions result in APC phosphorylation by the MAPK/ERK pathway, which, in parallel with inhibition of GSK-3β, promotes localization of APC to the tip of cell extensions. Whereas GSK-3β inhibition promotes APC binding and stabilization of microtubules, we show that phosphorylation by ERK inhibits the interaction of APC with F-actin, and APC-mediated F-actin bundling, but not APC-mediated microtubule bundling, in vitro. These results identify a previously unknown APC regulatory pathway during growth-factor-induced cell extension, and indicate that the GSK-3β and ERK pathways act in parallel to regulate interactions between APC and the cytoskeleton during the formation of cell extensions.
TGF-β-induced activation of mTOR complex 2 drives epithelial–mesenchymal transition and cell invasion
Authors: Lamouille Samy , Connolly Erin , Smyth James W. , Akhurst Rosemary J. , Derynck Rik
Published: March 2012

In cancer progression, carcinoma cells gain invasive behavior through a loss of epithelial characteristics and acquisition of mesenchymal properties, a process that can lead to epithelial–mesenchymal transition (EMT). TGF-β is a potent inducer of EMT, and increased TGF-β signaling in cancer cells is thought to drive cancer-associated EMT. Here, we examine the physiological requirement for mTOR complex 2 (mTORC2) in cells undergoing EMT. TGF-β rapidly induces mTORC2 kinase activity in cells undergoing EMT, and controls epithelial cell progression through EMT. By regulating EMT-associated cytoskeletal changes and gene expression, mTORC2 is required for cell migration and invasion. Furthermore, inactivation of mTORC2 prevents cancer cell dissemination in vivo. Our results suggest that the mTORC2 pathway is an essential downstream branch of TGF-β signaling, and represents a responsive target to inhibit EMT and prevent cancer cell invasion and metastasis.