Numerical and experimental analysis of labyrinth seals with rhomboidal cells

The labyrinth seals are devices commonly used in turbomachinery to reduce hot gas leakages through engine clearances, which adversely affect the gas turbine performance. For this reason, in the last decades, many in-depth analyses and optimization studies were carried out on this topic using experimental, analytical and numerical approaches. In this work, an innovative rhomboidal pattern is presented, obtained through Computational Fluid Dynamics (CFD) simulations, which is more dissipative than commonly used honeycomb cells. The experiments, performed using a Test Article that reproduces a stage and the next stator of a real low-pressure turbine suitably scaled, allowed to validate the numerical results in a situation that closely approximates the real one of use. The results obtained show that the leakages flow fraction of the total mass flow rate that bypasses the blade, which is 29.4% using a honeycomb pattern, is reduced to 27% with rhomboidal cells. The experimental results also made it possible to verify that the new pattern also behaves well from a thermal point of view, giving rise to temperature differences with respect to the honeycomb of less than 1%

El ensayo Micro Deval. Sus características y ámbitos de aplicación

En este documento se presentan los aspectos más relevantes del proceso de implementación del ensayo Micro Deval, contemplado por la Norma ASTM D 6928, “Standard test method for resistance of coarse aggregate to degradation by abrasion in the Micro-Deval apparatus”, en los laboratorios de Suelos y Pavimentos del Centro de Estudios Geotécnicos de la Escuela Colombiana de Ingeniería. En el proceso de implementación se evaluaron las principales características, ventajas y limitaciones del ensayo, los factores que afectan sus resultados, las correlaciones con otros ensayos relacionados con la dureza y con la durabilidad de los agregados, en especial con el ensayo de Desgaste Los Ángeles, y las correlaciones del ensayo con el comportamiento en servicio de los pavimentos, obtenidas en diferentes ambientes por diversos autores. Estos aspectos se tratan en este documento y se dejan para otro documento los resultados encontrados, al aplicar el ensayo Micro Deval, sobre agregados provenientes principalmente de fuentes de la ciudad de Bogotá. Se concluye en general que el Ensayo Micro Deval tiene gran aceptación, es simple, consume poco tiempo, tiene buena repetibilidad, reproducibilidad y comprobada correlación con el comportamiento en servicio de los agregados, ya se usen para la conformación de capas granulares o para la elaboración de mezclas asfálticas.This report shows the most relevant aspects of the implementation of the Micro Deval test, according to ASTM D 6928, “Standard test method for resistance of coarse aggregate to degradation by abrasion in the Micro-Deval apparatus”, at the Escuela Colombiana de Ingeniería Soils and Pavements Laboratory. During the implementation process the main characteristics, advantages, weaknesses, limiting factors of the test were evaluated, as well as correlations with other tests related to hardness and durability of aggregates, particularly the Los Angeles test and correlations with pavements in-service performance in different environments according to different authors. It is concluded that the Micro-Deval test is a widely accepted test, simple, no time consuming, has good repeatability, reproducibility and shows good correlation with aggregates in-service performance, either for granular bases or asphalt mixes. As other studies have shown, the Micro-Deval results had no correlation with the Los Angeles and aggregates absorption results

Caracterización de agregados pétreos con el ensayo Micro Deval

En este documento se presentan los aspectos más relevantes del proceso de implementación del ensayo Micro Deval, contemplado por la Norma ASTM D 6928, “Standard test method for resistance of coarse aggregate to degradation by abrasion in the Micro-Deval apparatus”, en los laboratorios de Suelos y Pavimentos del Centro de Estudios Geotécnicos de la Escuela Colombiana de Ingeniería. En esta segunda parte se incluyen los resultados obtenidos de los ensayos Micro Deval y de Desgaste Los Ángeles y sus variantes (100 rev. y en húmedo 500 rev.) realizados sobre 15 muestras de agregados, utilizados en la ciudad de Bogotá principalmente para la elaboración de mezclas asfálticas. Igualmente, se incluye el análisis de estos resultados junto con unas conclusiones preliminares, así como algunas recomendaciones derivadas de este proceso. Como se ha mostrado en otros estudios, sobre los materiales analizados en el presente no se evidenció una adecuada correlación con el ensayo de Desgaste Los Ángeles, ni con la absorción de los agregados. Sin embargo, las líneas de tendencia muestran un incremento en las pérdidas medidas con el ensayo de Desgaste Los Ángeles y en la absorción con el aumento en las pérdidas en el Micro Deval. Del análisis de los resultados encontrados también se concluye que si se tienen en cuenta los requisitos del agregado grueso para mezclas asfálticas en caliente, fijados por el IDU en las Especificaciones ET-2005, para tránsitos pesados (tipo T4 –T5) y capas de rodadura, el ensayo de Desgate Los Ángeles resulta ser más conservador que el Ensayo Micro Deval. Se recomienda continuar evaluando fuentes de materiales para seguir ajustando las respectivas especificaciones a las condiciones imperantes en nuestro medio.This report shows the most relevant aspects of the implementation of the Micro Deval test, according to ASTM D 6928, “Standard test method for resistance of coarse aggregate to degradation by abrasion in the Micro-Deval apparatus”, at the Escuela Colombiana de Ingeniería Soils and Pavements Laboratory. Micro-Deval and Los Angeles tests results in 15 samples of aggregates used in Bogotá, principally for asphalt mixes, are shown as well as the analyses of these results along with preliminary conclusions and recommendations. As other studies have shown, the Micro-Deval results had no correlation with the Los Angeles and aggregates absorption results. The trend lines do, however, show increasing Los Angeles Abrasion and absorption results with the increasing Micro Deval results. From the analysis of the materials results used in this investigation, it can be concluded that the Los Angeles test is more conservative than Micro-Deval test, for coarse aggregate used in hot asphalt mixes under IDU high volume of traffic (types T4 – T5) and surface courses, according the Specifications IDU ET-2005. It is recommended to evaluate more aggregate sources to continue adjusting specifications to our particular conditions

Superradiance mediated by Graphene Surface Plasmons

We demonstrate that the interaction between two emitters can be controlled by means of the efficient excitation of surface plasmon modes in graphene. We consider graphene surface plasmons supported by either two-dimensional graphene sheets or one-dimensional graphene ribbons, showing in both cases that the coupling between the emitters can be strongly enhanced or suppressed. The super- and subradiant regimes are investigated in the reflection and transmission configurations. Importantly, the length scale of the coupling between emitters, which in vacuum is fixed by the free space wavelength, is now determined by the wavelength of the graphene surface plasmons that can be extremely short and be tuned at will via a gate voltage

A nucleotide insertion and frameshift cause albumin Kénitra, an extended and O-glycosylated mutant of human serum albumin with two additional disulfide bridges

Albumin Kenitra is a new type of genetic variant of human serum albumin that has been found in two members of a family of Sephardic Jews from Kenitra (Morocco). The slow-migrating variant and the normal protein were isolated by anion-exchange chromatography and, after treatment with CNBr, the digests were analyzed by two-dimensional electrophoresis in a polyacrylamide gel. The CNBr peptides of the variant were purified by reverse-phase high performance liquid chromatography and submitted to sequence analysis. Albumin Kenitra is peculiar because it has an elongated polypeptide chain, 601 residues instead of 585, and its sequence is modified beginning from residue 575. DNA structural studies showed that the variant is caused by a single-base insertion, an adenine at nucleotide position 15 970 in the genomic sequence, which leads to a frameshift with the subsequent translation to the first termination codon of exon 15. Mass spectrometric analyses revealed that the four additional cysteine residues of the variant form two new S-S bridges and showed that albumin Kenitra is partially O-glycosylated by a monosialylated HexHexNAc structure. This oligosaccharide chain has been located to Thr596 by amino-acid sequence analysis of the tryptic fragment 592-59

Fibroblasts from patients with Diamond-Blackfan anaemia show abnormal expression of genes involved in protein synthesis, amino acid metabolism and cancer

Background: Diamond-Blackfan anaemia (DBA) is a rare inherited red cell hypoplasia characterised by a defect in the maturation of erythroid progenitors and in some cases associated with malformations. Patients have an increased risk of solid tumors. Mutations have been found in several ribosomal protein (RP) genes, i.e RPS19, RPS24, RPS17, RPL5, RPL11, RPL35A. Studies in haematopoietic progenitors from patients show that haplo-insufficiency of an RP impairs rRNA processing and ribosome biogenesis. DBA lymphocytes show reduced protein synthesis and fibroblasts display abnormal rRNA processing and impaired proliferation. Results: To evaluate the involvement of non-haematopoietic tissues in DBA, we have analysed global gene expression in fibroblasts from DBA patients compared to healthy controls. Microarray expression profiling using Affymetrix GeneChip Human Genome U133A 2.0 Arrays revealed that 421 genes are differentially expressed in DBA patient fibroblasts. These genes include a large cluster of ribosomal proteins and factors involved in protein synthesis and amino acid metabolism, as well as genes associated to cell death, cancer and tissue development. Conclusion: This analysis reports for the first time an abnormal gene expression profile in a non-haematopoietic cell type in DBA. These data support the hypothesis that DBA may be due to a defect in general or specific protein synthesis. \ua9 2009 Avondo et al; licensee BioMed Central Ltd

Thermal diffusivity measurements of metastable austenite during continuous cooling

The thermal diffusivity of the metastable undercooled austenite is relevant for the quantitative analysis of the carbon and low-alloy steel quench. The standard laser-flash method requires prior thermal equilibrium between the sample and the furnace, which may not be possible to achieve without allowing the metastable phase to transform. Nevertheless, depending upon the steel's hardenability, the thermal transient due to a laser pulse may be much shorter than a cooling transient sufficiently steep to prevent the transformation of the austenite. In one such case, flash measurements were performed during continuous sample cooling and the thermal diffusivity of the metastable austenite was determined by using an extension of the standard analytical model. The adopted analytical model and data reduction procedure are described and the limitations and uncertainties of this method are discussed, also with the aid of a non-linear numerical simulation. The measured thermal diffusivity of the under cooled low-alloy austenite decreases linearly from 5.4•10−6 m2 s−1 at 1133 K to 4.3•10−6 m2 s−1 at 755 K; this trend is in broad agreement with one previous set of measurements upon a low-alloy undercooled austenite and with a large number of previous standard measurements upon stable (high-alloy) austenitic stainless steels

Analysis of epidermal growth factor receptor expression as a predictive factor for response to gefitinib (‘Iressa’, ZD1839) in non-small-cell lung cancer

Gefitinib ('Iressa', ZD1839) is an orally active epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor that has demonstrated antitumour activity and favourable tolerability in Phase II studies. We investigated whether EGFR expression levels could predict for response to gefitinib in patients with advanced non-small-cell lung cancer (NSCLC), who received gefitinib (250 mg day(-1)) as part of a worldwide compassionate-use programme. Tissue samples were analysed by immunohistochemistry to assess membrane EGFR immunoreactivity. Of 147 patients enrolled in our institution, 50 patients were evaluable for assessment of both clinical response and EGFR expression. The objective tumour response rate was 10% and disease control was achieved in 50% of patients. Although high EGFR expression was more common in squamous-cell carcinomas than adenocarcinomas, all objective responses were observed in patients with adenocarcinoma. Response and disease control with gefitinib were not associated with high EGFR expression. Overall, median survival was 4 months, and the 1-year survival rate was 18%. Strong EGFR staining correlated with shorter survival time for all patients. Gefitinib demonstrated promising clinical activity in this group of patients with NSCLC. These results have also shown that EGFR expression is not a significant predictive factor for response to gefitinib

ERMP1, a novel potential oncogene involved in UPR and oxidative stress defense, is highly expressed in human cancer

Endoplasmic reticulum (ER) stress and unfolded protein response (UPR) are highly activated in cancer and involved in tumorigenesis and resistance to anti-cancer therapy. UPR is becoming a promising target of anti-cancer therapies. Thus, the identification of UPR components that are highly expressed in cancer could offer new therapeutic opportunity. In this study, we demonstrate that Endoplasmic Reticulum Metallo Protease 1 (ERMP1) is broadly expressed in a high percentage of breast, colo-rectal, lung, and ovary cancers, regardless of their stage and grade. Moreover, we show that loss of ERMP1 expression significantly hampers proliferation, migration and invasiveness of cancer cells. Furthermore, we show that this protein is an important player in the UPR and defense against oxidative stress. ERMP1 expression is strongly affected by reticular stress induced by thapsigargin and other oxidative stresses. ERMP1 silencing during reticular stress impairs the activation of PERK, a key sensor of the UPR activation. Loss of ERMP1 also prevents the expression of GRP78/BiP, a UPR stress marker involved in the activation of the survival pathway. Finally, ERMP1 silencing in cells exposed to hypoxia leads to inhibition of the Nrf2-mediated anti-oxidant response and to reduction of accumulation of HIF-1, the master transcription factor instructing cells to respond to hypoxic stress. Our results suggest that ERMP1 could act as a molecular starter to the survival response induced by extracellular stresses. Moreover, they provide the rationale for the design of ERMP1-targeting drugs that could act by inhibiting the UPR initial adaptive response of cancer cells and impair cell survival