Heat transfer in separated flows on the pressure side of turbine blades

Heat transfer in separated flows on the pressure side of a typical high lift turbine profile is numerically investigated by means of an in-house CFD code. The numerical code was first validated on attached flows in turbine blades. To obtain flow separation cases, the profile is subject to large negative incidences so that a separation bubble is obtained at the pressure side. The numerical results are compared to available experimental data for code validation. It is shown how local minima and maxima values of the heat transfer coefficient are related to the separation and reattachment points, where the velocity component perpendicular to the wall is shown to have a significant effect on the heat transfe

Genetic Ablation of Bcl-x Attenuates Invasiveness without Affecting Apoptosis or Tumor Growth in a Mouse Model of Pancreatic Neuroendocrine Cancer

Tumor cell death is modulated by an intrinsic cell death pathway controlled by the pro- and anti-apoptotic members of the Bcl-2 family. Up-regulation of anti-apoptotic Bcl-2 family members has been shown to suppress cell death in pre-clinical models of human cancer and is implicated in human tumor progression. Previous gain-of-function studies in the RIP1-Tag2 model of pancreatic islet carcinogenesis, involving uniform or focal/temporal over-expression of Bcl-xL, demonstrated accelerated tumor formation and growth. To specifically assess the role of endogenous Bcl-x in regulating apoptosis and tumor progression in this model, we engineered a pancreatic β-cell-specific knockout of both alleles of Bcl-x using the Cre-LoxP system of homologous recombination. Surprisingly, there was no appreciable effect on tumor cell apoptosis rates or on tumor growth in the Bcl-x knockout mice. Other anti-apoptotic Bcl-2 family members were expressed but not substantively altered at the mRNA level in the Bcl-x-null tumors, suggestive of redundancy without compensatory transcriptional up-regulation. Interestingly, the incidence of invasive carcinomas was reduced, and tumor cells lacking Bcl-x were impaired in invasion in a two-chamber trans-well assay under conditions mimicking hypoxia. Thus, while the function of Bcl-x in suppressing apoptosis and thereby promoting tumor growth is evidently redundant, genetic ablation implicates Bcl-x in selectively facilitating invasion, consistent with a recent report documenting a pro-invasive capability of Bcl-xL upon exogenous over-expression

Elevated Expression of Stromal Palladin Predicts Poor Clinical Outcome in Renal Cell Carcinoma

The role that stromal renal cell carcinoma (RCC) plays in support of tumor progression is unclear. Here we sought to determine the predictive value on patient survival of several markers of stromal activation and the feasibility of a fibroblast-derived extracellular matrix (ECM) based three-dimensional (3D) culture stemming from clinical specimens to recapitulate stromal behavior in vitro. The clinical relevance of selected stromal markers was assessed using a well annotated tumor microarray where stromal-marker levels of expression were evaluated and compared to patient outcomes. Also, an in vitro 3D system derived from fibroblasts harvested from patient matched normal kidney, primary RCC and metastatic tumors was employed to evaluate levels and localizations of known stromal markers such as the actin binding proteins palladin, alpha-smooth muscle actin (α-SMA), fibronectin and its spliced form EDA. Results suggested that RCCs exhibiting high levels of stromal palladin correlate with a poor prognosis, as demonstrated by overall survival time. Conversely, cases of RCCs where stroma presents low levels of palladin expression indicate increased survival times and, hence, better outcomes. Fibroblast-derived 3D cultures, which facilitate the categorization of stromal RCCs into discrete progressive stromal stages, also show increased levels of expression and stress fiber localization of α-SMA and palladin, as well as topographical organization of fibronectin and its splice variant EDA. These observations are concordant with expression levels of these markers in vivo. The study proposes that palladin constitutes a useful marker of poor prognosis in non-metastatic RCCs, while in vitro 3D cultures accurately represent the specific patient's tumor-associated stromal compartment. Our observations support the belief that stromal palladin assessments have clinical relevance thus validating the use of these 3D cultures to study both progressive RCC-associated stroma and stroma-dependent mechanisms affecting tumorigenesis. The clinical value of assessing RCC stromal activation merits further study

Tensin3 Is a Negative Regulator of Cell Migration and All Four Tensin Family Members Are Downregulated in Human Kidney Cancer

BACKGROUND: The Tensin family of intracellular proteins (Tensin1, -2, -3 and -4) are thought to act as links between the extracellular matrix and the cytoskeleton, and thereby mediate signaling for cell shape and motility. Dysregulation of Tensin expression has previously been implicated in human cancer. Here, we have for the first time evaluated the significance of all four Tensins in a study of human renal cell carcinoma (RCC), as well as probed the biological function of Tensin3. PRINCIPAL FINDINGS: Expression of Tensin2 and Tensin3 at mRNA and protein levels was largely absent in a panel of diverse human cancer cell lines. Quantitative RT-PCR analysis revealed mRNA expression of all four Tensin genes to be significantly downregulated in human kidney tumors (50-100% reduction versus normal kidney cortex; P<0.001). Furthermore, the mRNA expressions of Tensins mostly correlated positively with each other and negatively with tumor grade, but not tumor size. Immunohistochemical analysis revealed Tensin3 to be present in the cytoplasm of tubular epithelium in normal human kidney sections, whilst expression was weaker or absent in 41% of kidney tumors. A subset of tumor sections showed a preferential plasma membrane expression of Tensin3, which in clear cell RCC patients was correlated with longer survival. Stable expression of Tensin3 in HEK 293 cells markedly inhibited both cell migration and matrix invasion, a function independent of putative phosphatase activity in Tensin3. Conversely, siRNA knockdown of endogenous Tensin3 in human cancer cells significantly increased their migration. CONCLUSIONS: Our findings indicate that the Tensins may represent a novel group of metastasis suppressors in the kidney, the loss of which leads to greater tumor cell motility and consequent metastasis. Moreover, tumorigenesis in the human kidney may be facilitated by a general downregulation of Tensins. Therefore, anti-metastatic therapies may benefit from restoring or preserving Tensin expression in primary tumors

A Biobrick Library for Cloning Custom Eukaryotic Plasmids

Researchers often require customised variations of plasmids that are not commercially available. Here we demonstrate the applicability and versatility of standard synthetic biological parts (biobricks) to build custom plasmids. For this purpose we have built a collection of 52 parts that include multiple cloning sites (MCS) and common protein tags, protein reporters and selection markers, amongst others. Importantly, most of the parts are designed in a format to allow fusions that maintain the reading frame. We illustrate the collection by building several model contructs, including concatemers of protein binding-site motifs, and a variety of plasmids for eukaryotic stable cloning and chromosomal insertion. For example, in 3 biobrick iterations, we make a cerulean-reporter plasmid for cloning fluorescent protein fusions. Furthermore, we use the collection to implement a recombinase-mediated DNA insertion (RMDI), allowing chromosomal site-directed exchange of genes. By making one recipient stable cell line, many standardised cell lines can subsequently be generated, by fluorescent fusion-gene exchange. We propose that this biobrick collection may be distributed peer-to-peer as a stand-alone library, in addition to its distribution through the Registry of Standard Biological Parts (http://partsregistry.org/)

Exciton states and optical properties of CdSe nanocrystals

The optical spectra of CdSe nanocrystals up to 55 A in diameter are analyzed in a wide range of energies from the fine structure of the low-energy excitations to the so-called high-energy transitions. We apply a symmetry-based method in two steps. First we take the tight-binding (TB) parameters from the bulk sp^{3}s^{*} TB model, extended to include the spin-orbit interaction. The full single-particle spectra are obtained from an exact diagonalization by using a group-theoretical treatment. The electron-hole interaction is next introduced: Both the Coulomb (direct) and exchange terms are considered. The high-energy excitonic transitions are studied by computing the electric dipole transition probabilities between single-particle states, while the transition energies are obtained by taking into account the Coulomb interaction. The fine structure of the lowest excitonic states is analyzed by including the electron-hole exchange interaction and the wurtzite crystal-field terms in the exciton Hamiltonian. The latter is diagonalized in the single electron-hole pair excitation subspace of progressively increasing size until convergence. The peaks in the theoretical transition spectra are then used to deduce the resonant and nonresonant Stokes shifts, which are compared with their measured values in photoluminescence experiments. We find that the final results depend on the crystal-field term, the relative size of the surface and the degree of saturation of the dangling bonds. The results show a satisfactory agreement with the available experimental data.Comment: Revtex, 24 pages, 7 Postscript figure

The Conserved Candida albicans CA3427 Gene Product Defines a New Family of Proteins Exhibiting the Generic Periplasmic Binding Protein Structural Fold

Nosocomial diseases due to Candida albicans infections are in constant rise in hospitals, where they cause serious complications to already fragile intensive care patients. Antifungal drug resistance is fast becoming a serious issue due to the emergence of strains resistant to currently available antifungal agents. Thus the urgency to identify new potential protein targets, the function and structure of which may guide the development of new antifungal drugs. In this context, we initiated a comparative genomics study in search of promising protein coding genes among the most conserved ones in reference fungal genomes. The CA3427 gene was selected on the basis of its presence among pathogenic fungi contrasting with its absence in the non pathogenic Saccharomyces cerevisiae. We report the crystal 3D-structure of the Candida albicans CA3427 protein at 2.1 Å resolution. The combined analysis of its sequence and structure reveals a structural fold originally associated with periplasmic binding proteins. The CA3427 structure highlights a binding site located between the two protein domains, corresponding to a sequence segment conserved among fungi. Two crystal forms of CA3427 were found, suggesting that the presence or absence of a ligand at the proposed binding site might trigger a “Venus flytrap” motion, coupled to the previously described activity of bacterial periplasmic binding proteins. The conserved binding site defines a new subfamily of periplasmic binding proteins also found in many bacteria of the bacteroidetes division, in a choanoflagellate (a free-living unicellular and colonial flagellate eukaryote) and in a placozoan (the closest multicellular relative of animals). A phylogenetic analysis suggests that this gene family originated in bacteria before its horizontal transfer to an ancestral eukaryote prior to the radiation of fungi. It was then lost by the Saccharomycetales which include Saccharomyces cerevisiae

Genome-Wide Patterns of Gene Expression during Aging in the African Malaria Vector Anopheles gambiae

The primary means of reducing malaria transmission is through reduction in longevity in days of the adult female stage of the Anopheles vector. However, assessing chronological age is limited to crude physiologic methods which categorize the females binomially as either very young (nulliparous) or not very young (parous). Yet the epidemiologically relevant reduction in life span falls within the latter category. Age-grading methods that delineate chronological age, using accurate molecular surrogates based upon gene expression profiles, will allow quantification of the longevity-reducing effects of vector control tools aimed at the adult, female mosquito. In this study, microarray analyses of gene expression profiles in the African malaria vector Anopheles gambiae were conducted during natural senescence of females in laboratory conditions. Results showed that detoxification-related and stress-responsive genes were up-regulated as mosquitoes aged. A total of 276 transcripts had age-dependent expression, independently of blood feeding and egg laying events. Expression of 112 (40.6%) of these transcripts increased or decreased monotonically with increasing chronologic age. Seven candidate genes for practical age assessment were tested by quantitative gene amplification in the An. gambiae G3 strain in a laboratory experiment and the Mbita strain in field enclosures set up in western Kenya under conditions closely resembling natural ones. Results were similar between experiments, indicating that senescence is marked by changes in gene expression and that chronological age can be gauged accurately and repeatedly with this method. These results indicate that the method may be suitable for accurate gauging of the age in days of field-caught, female An. gambiae