High Loss Region Research Articles

Atomic Resolution Energy-Filtered HREM at High-Loss Region Using Cs- and Cc-Corrected TEM

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.

Experimental Study of Effects of Grooved Tip Clearances on the Flow Field in a Compressor Cascade Passage

This paper presents an experimental investigation of effects of grooved tip clearances on the flow field of a compressor cascade. The tests were performed in a low-speed large-scale cascade, respectively, with two tip-clearance configurations, including the flat tip and the grooved tip with a chordwise channel on the blade top. The flow field at 10% chord downstream from the cascade trailing edge was measured at four incidence angles using a mini five-hole pressure probe. The static pressure distribution was measured on the tip endwall. The results show that the pressure gradient from the pressure side to the suction side on the blade tip is reduced due to the existence of the channel. As a result, the leakage flow is weakened. The high-blockage and high-loss region caused by the leakage flow is narrower with the grooved tip. In the meantime, the leakage flow migrates to lower span-wise position. The combined result is that the flow capacity in the tip region is improved at the incidence angles of 0 deg and 5 deg with the grooved tip. However, the loss is slightly greater than that with the flat tip at all the incidence angles.

Investigation of the Tip Clearance Flow in a Compressor Cascade Using a Novel Laser Measurement Technique With High Temporal Resolution

The understanding of the tip clearance flow in axial compressors is a key issue for developing new compressors with enhanced efficiency and reduced noise for instance. However, necessary flow measurements in the blade tip region and within the tip clearance are challenging due to the small gap width. The application of a novel optical measurement technique named Doppler global velocimetry with laser frequency modulation is presented, which provides velocity field measurements of all three velocity components nonintrusively in the tip clearance flow of a linear cascade at near stall conditions. These array measurements have a high temporal resolution enabling turbulence analysis such as the evaluation of velocity standard deviations and turbulence spectra up to several kilohertz. Conventional pneumatic and hot-wire measurements in planes at the inlet and the outlet as well as on the blade surface were taken to complete the flow pattern and validate the data of the Doppler global velocimetry. Wake measurements identified a strong flow separation in the rear suction side dominating the transient character of the cascade flow. Towards the endwall this high loss region is reduced by the clearance flow and the resulting vortex, which is obviously not affected by the profile separation and the pulsating blockage frequency. Inside the blade passage and the tip clearance the Doppler global velocimetry measurements allowed a spatial assignment of the origin of the tip leakage flow and the downstream developing vortex. In addition, the tip clearance vortex could be resolved and identified successfully as the most dominant turbulence generating effect in the near endwall region at this high loading operating point of the blading.

Structure of diamondlike carbon films deposited by femtosecond and nanosecond pulsed laser ablation

The characterization of diamondlike carbon (DLC) films is a challenging subject, considering the diversity of carbon-based nanostructures depending on the deposition process. We propose to combine multiwavelength (MW) Raman spectroscopy and electron energy-loss spectroscopy (EELS) to probe the structural disorder and the carbon hybridizations of DLC films deposited by pulsed laser ablation performed either with a nanosecond laser (film labeled ns-DLC), either with a femtosecond laser (film labeled fs-DLC). Such deposition methods allow to reach a rather high carbon sp3 hybridization but with some significant differences in terms of structural disorder and carbonaceous chain configurations. MW Raman investigations, both in the UV and visible range, is a popular and nondestructive way to probe the structural disorder and the carbon hybridizations. EELS allows the determination of the carbon plasmon energy in the low-loss energy region of the spectra, as well as the fine structure of the ionization threshold in the high-loss energy region. The paper shows that the combination of MW Raman and EELS is a powerful way to elucidate the nanostructure of DLC films. Complementary nanoindentation investigations allow to correlate the analytical results with the mechanical properties of the films. The ns-DLC film presents a stronger sp3-bonded C character (74%–85%) with a significant content of sp2 chains, whereas the fs-DLC contains less sp3 bonds (35%–50%) with a significant content of sp2-bonded C rings. The ns-DLC film exhibits a higher proportion of disordered sp2 C mainly in the form of chains. Comparatively, the fs-DLC exhibits a predominance of more ordered sp2 C structures in the form of graphitic aggregates whose size has been estimated near three aromatic rings. The film characteristics are in agreement with their mechanical properties. We also propose a correlation between the nanostructure and composition of the films with the deposition mechanisms. The difference in kinetic energy distribution in the plasma plume, together with an absence of interaction between the plasma plume and the femtosecond laser, are responsible for the observed differences in sp3 C content and sp2 C configuration ranging between a predominance of more ordered sp2 rings in the fs-DLC film and a predominance of sp2 chains in the ns-DLC film. These results are consistent with the mechanisms of subplantation occurring during DLC deposition

Performance evaluation of mixed convection in an inclined square channel with uniform temperature walls

Numerical analyses were performed for the effect of inclined angle on the mixing flow in a square channel with uniform temperature walls ( T w = 30 °C) and inlet temperature ( T 0 = 10 °C). Three-dimensional governing equations were solved numerically for Re = 100, Pr = 0.72 and various inclined angles (from −90° to 90°). Three-dimensional behavior of fluid in a channel was examined for each angle. Thermal performance was evaluated using the relationship between Nusselt number ratio and pressure loss ratio with and without buoyancy induced flow as a parameter of inclined angles. High heat transfer and low pressure loss region was from −15° to −60° in thermal performance using mean Nusselt number ratio.

Measured and non-free vortex design results of axial flow fans

The research is about the determination of developing flow pattern in the axial flow fan impeller. A measuring method and a sizing method of axial flow fans used in a research project have been studied. In this way it has been determined the spatial distribution of static pressure directly behind the impeller as well as the spatial distribution and direction of total pressure in a fixed system to the blade channel. There is an opportunity to identify the high loss region in the impeller: to determine the pressure loss and the hydraulic efficiency at each point. The article shows the results of comparison between the measurement data and the sizing results in the case of one in the agricultural-field utilized cooling fan. The impeller was designed by the help of the fore slanted blades in circumference direction as well as the non-free vortex theory. The basic theories of the design method of the blades and the realization of measurement results are analyzed, too.

Analysis of genotype polymorphism of tumor-related genes harbored in chromosome arm 1p and 8p in hepatocellular carcinoma patients by cSNP chip

The majority of single nucleotide polymorphisms (SNPs) found in the coding region (cSNPs) are single base substitutions that may or may not lead to amino acid substitutions, most of which are related to diseases. Some cSNPs may prove useful for their potential links to functional cSNPs via linkage disequilibrium mapping. We have selected 48 cSNPs located in the coding regions of 25 genes to construct the cSNP chip. These genes are harbored in the high frequency loss regions of the chromosome 1p and 8p and related with apoptosis, cell cycles, signal transduction, oncogene, tumor suppressor genes and so on. All of the cSNPs can lead to amino acid substitutions except TP73 (rs1801174). The PCR products amplified from 31 hepatocellular carcinoma (HCC) specimens were labeled with Dig-dUTP and then hybridized with the cSNP chips. The results showed that there was no hybridization signal when there was more than one site of mutation in the amplification sequence, indicating that the cSNP chip had a high sensitivity. The statistic data of the SNP (MT, homozygous and HT, heterozygous) in the HCC patients with different phenotypes (HBV+/−, differentiation stage, family history positive or negative, tumor size) indicated that the number of MT was distinctly different between patients with positive HBV and negative HBV. The MT and HT numbers of all the 48 cSNPs were significantly different between low differentiation and high differentiation HCC patients. The numbers of MT and HT were not different between positived and negative family history groups and between tumor size >3 cm and ⩽ 3 cm groups. The study results provided useful information for understanding the molecular mechanisms of HCC development.

Proton Energy Straggling Measurement in Metal Foils by Using a Si(Li) Detector

Measurements of energy loss and transmitted energy straggling were performed using a Si(Li) detector for 28.6 MeV protons incident on thin foil targets of Al, Cu and Au in air. The straggling widths were studied as functions of the target thickness and the target species. The initial proton beam energy from the MC-50 cyclotron was 45 MeV and it was decreased to 28.6 MeV by passing it through a 2-mm-thick Al window, 34.5 cm of air, a 2-mm-thick Al degrader and 144.5 cm of air. This 28.6 MeV proton beam was incident on Al, Cu and Au foils of various thicknesses installed in front of a Si(Li) detector. As a result, the energy loss strongly depended on the target thickness and species and the transmitted energy straggling was not related to the target species. Compared with the calculated results based on a simple Bohr's expression, the measured values agreed with the calculated ones in the low energy loss region less than 60 % of the incident proton beam energy. In the high-loss region, there was big mismatch of more than 25 %.

Mode Interactions and Sound Power Transmission Loss of Expansion Chambers

The mode interactions and the sound transmission loss across the expansion chambers with and without tapered sections are studied by the finite element method in the present investigation. Results from chambers with symmetrical inlet and outlet suggest lower sound power transmission loss at frequencies below that of the first symmetrical transverse chamber mode when the tapered section angle is reduced. Weak sound power transmission loss is also observed for this chamber type at frequency higher than that of the first symmetrical duct mode. Numerous high and low sound power transmission loss regions are observed between these two eigenfrequencies. Higher plane wave power transmission loss can be found at smaller tapered section angle only if one of the chamber endings is not tapered. Such chamber bears important industrial application.

Study of the order–disorder transition and martensitic transformation in a Cu–Al–Be alloy by EELS

Changes in 3d states occupancy associated with order–disorder transition and martensitic transformation in a Cu–Al–Be alloy was investigated by electron energy loss spectroscopy (EELS) in both high energy and low energy loss regions. From the high energy loss region, the Cu L 2,3 white-line intensities, which reflect the unoccupied density of states in 3d bands, was measured for three states of the alloy: disordered austenite, ordered austenite and martensite. It was found that the white-line intensity remains the same during order–disorder transition but appears slightly smaller in martensite, indicating that some electrons left Cu 3d bands or some hybridization took place during phase transformation. From the low energy loss region, the optical joint density of states (OJDS) was obtained by Kramers–Kronig analysis. As maxima observed in the OJDS spectra are assigned to interband transitions, these spectra can be used to probe changes in the electronic band structure. The analysis shows that during the martensitic transformation, the peaks positions and relative intensities in the OJDS spectra undergoes noticeable changes, which are associated with interband transitions.

Whole-Genome Allelotyping Identified Distinct Loss-of-Heterozygosity Patterns in Mucinous Ovarian and Appendiceal Carcinomas

Mucinous adenocarcinoma of the ovary is one of the common histologic types of ovarian cancer. Its pathogenesis is largely unknown. In addition, the differential diagnosis of metastatic mucinous carcinomas to the ovaries, particularly those originating from the appendix, remains challenging. The purpose of this study is to identify molecular biomarkers for mucinous ovarian adenocarcinoma and compare them with those of appendiceal origin. Genome-wide loss-of-heterozygosity (LOH) analysis was done on DNA isolated from 28 microdissected primary mucinous ovarian carcinomas and five appendiceal adenocarcinomas. Markers from high-loss regions were selected for further analysis on a total of 32 ovarian and 14 appendiceal cancers. High levels of LOH rates (>40%) were detected on chromosome arms 9p, 17p, and 21q in mucinous ovarian carcinoma cases. The frequency of allelic loss was similar between high-grade and low-grade mucinous ovarian carcinoma cases but was significantly higher in ovarian versus appendiceal cases. In addition, LOH rates on five chromosomal loci were statistically different between ovarian and appendiceal carcinomas. A high frequency of LOH can be found in mucinous ovarian adenocarcinomas independent of grade. Despite histologic similarities between mucinous ovarian carcinomas and metastatic appendiceal carcinomas, they have distinct LOH profiles, which may be used for distinguishing the two diseases.

Effects of Reynolds Number and Freestream Turbulence on Turbine Tip Clearance Flow

Tip clearance losses represent a major efficiency penalty of turbine blades. This paper describes the effect of tip clearance on the aerodynamic characteristics of an unshrouded axial-flow turbine cascade under very low Reynolds number conditions. The Reynolds number based on the true chord length and exit velocity of the turbine cascade was varied from 4.4×104 to 26.6×104 by changing the velocity of fluid flow. The freestream turbulence intensity was varied between 0.5% and 4.1% by modifying turbulence generation sheet settings. Three-dimensional flow fields at the exit of the turbine cascade were measured both with and without tip clearance using a five-hole pressure probe. Tip leakage flow generated a large high total pressure loss region. Variations in the Reynolds number and freestream turbulence intensity changed the distributions of three-dimensional flow, but had no effect on the mass-averaged tip clearance loss of the turbine cascade.

ANALYSIS OF ANDROGEN REGULATED HOMEOBOX GENE NKX3.1 DURING PROSTATE CARCINOGENESIS

NKX3.1 is an androgen regulated gene that is largely specific to the prostate for expression and it is predicted to encode a homeobox protein. Null alleles of NKX3.1 in mice results in impaired prostate development as well as hyperplasia and dysplasia of the prostate. In addition, the NKX3.1 gene maps to a region of high loss of heterozygosity in prostate cancer in humans, suggesting that NKX3.1 might have a direct role in prostate carcinogenesis, possibly functioning as a tumor suppressor protein. Previous studies of the levels of NKX3.1 mRNA or protein in prostate cancer specimens have resulted in conflicting findings. To resolve this issue we assessed NKX3.1 expression by mRNA in situ analysis and immunohistochemistry on the same prostate cancer tissue arrays. Data showed that NKX3.1 mRNA and protein levels in prostate cancer specimens are correlated, suggesting that most regulation is at the transcriptional level. There was no correlation of NKX3.1 expression levels with tumor grade or clinical stage. In general there was a suggestion that worse clinical features at surgery were associated with lower IHC stain scores. In particular, extracapsular extension but not seminal vesicle invasion inversely correlated with NKX3.1 expression. Together these data suggest that NKX3.1 does not function as a typical tumor suppressor protein in prostate cancer but it may still have important regulatory roles during prostate cancer progression.

Flow Characteristics in a Transonic Ultra-Low-Aspect-Ratio Axial Turbine Vane

Low-aspect-ratio (Low AR) nozzle guide vane (NGV) has been rarely adopted in conventional turbine component because of a low performance as predicted by one-dimensional loss model. The reason is that performance deterioration becomes especially large by the increase of secondary flow due to the low AR. On the other hand, there are some considerable benefits by adopting the low AR NGV. For example, by decreasing the number of the NGV, it leads to no resonance of rotor blade (RB) due to the number of NGV and low cost. Therefore HONDA R&D has developed a unique single stage HPT characterized by ultra-low AR (span height/axial chord=0.30) NGV in order to attain no resonance of RB and low cost, forming a part of the development for a small turbo fan engine. In the development stage, an unconventional phenomenon of high loss region has been observed around the center between blade to blade near the hub wall at NGV exit. The high loss region significantly influences on the turbine stage performance. This paper presents the special phenomenon of the high loss region and clarifies the reason using various CFD analyses, including rig test results and some techniques for high performance turbine component. The main reason of the high loss region is due to an axial cavity below hub wall between NGV and RB. Also, fillet R of NGV at the trailing edge on hub wall significantly increases the loss.

Performance Evaluation of Mixed Convection in an Inclined Square Channel with Uniform Temperature Walls

Abstract Numerical analyses were performed for the effect of inclined angle on the mixing flow in a square channel with uniform temperature walls (Tw = 30 °C) and inlet temperature (T0 = 10 °C). Three-dimensional governing equations were solved numerically for Re = 100, Pr = 0.72 and various inclined angles (from −90° to 90°). Three-dimensional behavior of fluid in a channel was examined for each angle. Thermal performance was evaluated using the relationship between Nusselt number ratio and pressure loss ratio with and without buoyancy induced flow as a parameter of inclined angles. High heat transfer and low pressure loss region was from −15° to −60° in thermal performance using mean Nusselt number ratio.

Track formation in germanium crystals irradiated with superhigh-energy ions

Damage production was studied in 710MeV Bi and 1.3GeV U ions irradiated single-crystalline germanium by means of transmission electron microscopy and selective chemical etching. The formation of discontinuous tracks was registered in the depth region of high electronic energy loss of the incident ions. The observed features of discontinuous track formation in Ge are described within the fluctuation model of track formation.

Numerical Simulation on the Flow Field in a Turbine Stage with Upstream Flow Injection from the Outer Casing: Effects of the Injection Angle.

Flow injection is being used in steam turbines for some combined or geothermal plants in order to increase its total thermal efficiency. It can be easily imagined, however, that such a flow injection is accompanied by additional aerodynamic loss due to the flow mixing or the change in local flow angle. Preliminary three-dimensional steady numerical simulations are conducted for the flow field inside the chamber from which the secondary flow is injected. The results showed a small variation of the flow velocity at the injection slot and provided useful information concerning the magnitude of the pitchwise variation of the injection angle. Further numerical simulations in a turbine stage were then performed by prescribing different injection angle distribution at the injection slot. The turbine stage computations revealed the existence of a high loss region generated from the interaction of the injected flow and the passage vortex near the tip of the nozzle vanes. It was found that injection angles orientated to the suction side of the stator provided lower loss values, while cases where flow was injected to the pressure side minimized the flow angle deviation.

A dynamical analysis on V-shaped solid laser resonator and the improved one

We have analyzed the dynamics of the general V-shaped solid laser resonator in detail and pointed out its advantage and shortcoming. Its crucial shortcoming is the appearance of a high-loss region when the dynamics factor approaches 1ft≈1l1-f, and in this case the laser cannot run. In order to overcome this weakness, we have introduced a kind of improved V-shaped resonator proposed by Liu Jun-hai, and based on this we put forward an improved more compact V-shaped resonator.

Loss of heterozygosity and heterogeneity of its appearance and persisting in the course of acute myeloid leukemia and myelodysplastic syndromes

Screening for loss of heterozygosity (LOH) of the panel of 18 highly polymorphic microsatellite markers, especially from the region 11p15, was carried out on 154 samples from 26 patients with acute myeloid leukemia and eight with myelodysplastic syndromes (MDS). LOH was detected at the majority (72%) of the loci tested: 47% of informative patients displayed LOH for at least one of the microsatellite locus from the region 11p15 and 23.5% of patients displayed LOH among the other markers tested within the study. A longitudinal follow-up of patients showed a remarkable heterogeneity of LOH appearance and its persistance during the course of the disease suggesting an intratumor clonal heterogeneity, or alternatively, presence of LOH in more than one cell clone. The data revealed two regions of high loss of one allele in 11p15.5, defined by markers D11S1363 and D11S1338, indicating that LOH at the subtelomeric region of the short arm of chromosome 11 is a much common event in hematological malignancies than it was previously reported.

Neuropathological and Histochemical Changes in a Multiple Mitochondrial DNA Deletion Disorder

The identification of cytochrome c oxidase (COX)-deficient/succinate dehydrogenase (SDH)- positive cells using sequential histochemistry has proved important in the identification of cells with high mitochondrial DNA (mtDNA) mutant load. We demonstrate large numbers of COX-deficient/SDH-positive neurons in a mosaic pattern throughout the CNS of a patient with a multiple mtDNA deletion disorder. This patient had prominent central and peripheral nervous system involvement with marked cerebellar ataxia, a parkinsonian extra-pyramidal movement disorder, external ophthalmoplegia, dysphagia, and a severe peripheral neuropathy. There was degeneration of myelin tracts in the cerebellum and dorsal spinal columns, diffuse astrocytosis, and selective neuronal degeneration particularly in the midbrain and cerebral microvacuolation. The proportional distribution of the COX-deficient neurons did not always correlate directly with the degree of neuropathological damage with regions of high neuronal loss having relatively low proportions of these cells. Other clinically affected CNS regions have high levels of COX-deficient neurons without significant cell loss. The role of these COX-deficient neurons in causing neuronal degeneration and clinical symptoms is discussed.