Extending the Role of Computational Fluid Dynamics in Screw Machines

Previous publications show that computational fluid dynamics (CFD) can be readily used for the flow prediction and analysis of screw compressors. Several case studies are presented in this article to show the scope and applicability of such methods. These include solid–fluid interaction in screw compressors, prediction of flow generated noise in screw machines, cavitation modelling in gear pumps, and flow in multiphase pumps for oil and gas industry. Numerical grids for all these cases were generated by the authors using an in-house grid generator, while the CFD calculations were performed with a variety of commercially available CFD codes. In order to validate the accuracy of the CFD calculations, an extended test programme was carried out using laser Doppler velocimetry to measure the mean and fluctuating velocity distribution in screw compressor flow domains. The measurement results are then compared with the CFD simulations. The results confirm the viability of the developed techniques. It is shown in this publication that the flexibility of the developed method creates further opportunities for a broader use of CFD for analysis of twin screw machines in a range of new applications

A 3 tesla magnetic resonance imaging volumetric analysis of the hippocampal formation: dependence on handedness and age

Background: The hippocampal formation (HF) is one of the most important parts of the brain in the magnetic resonance imaging (MRI) volumetric analysis in various domains, but not completely from all aspects, including the handedness. The aim of our study was to evaluate the possible differences in the volume of the right and left HF among the healthy right-handed and left-handed subjects, and to determine whether the volume differences are age related. Materials and methods: The MRI of this prospective study was performed using T1 fast field echo (FFE) sequence. The 124 subsequent coronal slices (thickness 1.5 mm) were performed in each participant. The obtained HF volumes were normalised and statistically compared. Volunteers comprised 30 persons aged 22.0 years, 12 of whom were the left-handed, and 30 persons aged 75.2 years on average, 9 of whom were the left-handed. Results: The right and left HF volumes averaged 2.986 cm3 and 2.858 cm3 in the right-handed, and 2.879 cm3 and 3.020 cm3 in the left-handed young volunteers, as well as 2.728 cm3 and 2.650 cm3 in the right-handed, and 2.617 cm3 and 2.780 cm3 in the left-handed elderly persons. The HF volume ratios in the young left-handed participants showed a significant left-greater-than-right asymmetry. A significant difference was also noticed within the right-to-left volume ratios of the right- and left-handed young and elderly participants. The latter reduction in the HF volume within the aged group can be interpreted as a slight atrophy of the HF. Conclusions: There is a significant difference in the volumes of the left and right HF of the left-handed young participants. The age related HF volume differences were proven between the groups of the young and elderly volunteers. The obtained data should be included into the future MRI studies of the HF volumes in various clinical domains.

Analytical Grid Generation for accurate representation of clearances in CFD for Screw Machines

One of the major factors affecting the performance prediction of twin screw compressors by use of computational fluid dynamics (CFD) is the accuracy with which the leakage gaps are captured by the discretization methods. The accuracy of mapping leakage flows can be improved by increasing the number of grid points on the profile. However, this method faces limitations when it comes to the complex deforming domains of a twin screw compressor because the computational time increases tremendously. In order to address this problem, an analytical grid distribution procedure is formulated that can independently refine the region of high importance for leakage flows in the interlobe space. This paper describes the procedure of analytical grid generation with the refined mesh in the interlobe area and presents a test case to show the influence of the mesh refinement in that area on the performance prediction. It is shown that by using this method, the flow domains in the vicinity of the interlobe gap and the blowhole area are refined which improves accuracy of leakage flow predictions

Fisher zeros of the Q-state Potts model in the complex temperature plane for nonzero external magnetic field

The microcanonical transfer matrix is used to study the distribution of the Fisher zeros of the $Q>2$ Potts models in the complex temperature plane with nonzero external magnetic field $H_q$. Unlike the Ising model for $H_q\ne0$ which has only a non-physical critical point (the Fisher edge singularity), the $Q>2$ Potts models have physical critical points for $H_q<0$ as well as the Fisher edge singularities for $H_q>0$. For $H_q<0$ the cross-over of the Fisher zeros of the $Q$-state Potts model into those of the ($Q-1$)-state Potts model is discussed, and the critical line of the three-state Potts ferromagnet is determined. For $H_q>0$ we investigate the edge singularity for finite lattices and compare our results with high-field, low-temperature series expansion of Enting. For $3\le Q\le6$ we find that the specific heat, magnetization, susceptibility, and the density of zeros diverge at the Fisher edge singularity with exponents $\alpha_e$, $\beta_e$, and $\gamma_e$ which satisfy the scaling law $\alpha_e+2\beta_e+\gamma_e=2$.Comment: 24 pages, 7 figures, RevTeX, submitted to Physical Review

Study of the anticancer properties of methyl- and phenyl-substituted carbon- and silicon-bridged ansa-titanocene complexes

The previously known complexes {[}Ti\{(Me2CMe2C)(eta(5)-C5H4)(2)\}Cl-2] (1), {[}Ti\{Me2C(eta(5)-C5H4)(2)\}Cl-2] (2), {[}Ti \{Me2Si(eta(5)-C5H4)(2)\}Cl-2] (4), {[}Ti\{MePhSi(eta(5)-C5H4)(2)\}Cl-2] (5) and {[}Ti\{MePhSi(eta(5)-C5Me4)(2)\}Cl-2] (6) have been prepared following reported procedures. The novel complex {[}Ti\{MePhC(eta(5)-C5H4)(2)\}Cl-2] (3) has been prepared and characterized. The cytotoxic activity of 1-6 has been tested after 72 h on melanoma A375 and B16, prostate cancer DU145 and LNCaP and colon cancer HCT116, SW620 and CT26CL25 cell lines observing a high cytotoxic activity of complexes 1 and 6 compared to the reference compound ({[}Ti(eta(5)-C5H5)(2)\}Cl-2]). 1 and 6 have also been tested against primary normal mouse keratinocytes and lung fibroblasts. While viability of both type of primary cells was significantly less affected by 1 in comparison to the reference compound {[}Ti(eta(5)-C5H5)(2)Cl-2], compound 6 was completely nontoxic for nonmalignant cells, indicating a potential selectivity of this compound towards cancer cell lines. In addition CFSE staining, cell cycle analysis, AnnexinV-FITC/PI staining, detection of caspase activity and mitochondrial potential showed that 1 and 6 were acting through inhibition of proliferation and subsequent induction of mitochondrial dependent apoptosis in colon cancer cell lines, HCT116 and SW620, which express low sensitivity to cisplatin. Compound 6 was found to be the leading drug in this group since it shows the fastest and most selective anticancer profile. (C) 2013 Elsevier B.V. All rights reserved.Ministerio de Educacion y Ciencia, Spain {[}CTQ-2011-24346, CTQ-2012-30762]; Ministry of Science and Technological Development of the Republic of Serbia {[}173013]; Grant Agency of the Czech Republic {[}P207/12/2368

Modulatory in vitro effects of interleukin-1 receptor antagonist (IL-1Ra) or antisense oligonucleotide to interleukin-1 beta converting enzyme (ICE) on acute myeloid leukaemia (AML) cell growth

We investigated the effects of interleukin-1 receptor antagonist (IL-1Ra) on the spontaneous proliferation and AML colony forming unit (CFU-AML) formation of bone marrow and peripheral blood cells in 50 acute myeloid leukaemia (AML) patients. Exposure to IL-1Ra (10 mu g/ml) caused either decreased, unaltered or increased AML cell proliferation, as well as of CFU-AML colony formation, depending on the individual patient, but the inhibitory effects were dominant. To evaluate the involvement of IL-1 beta converting enzyme (ICE) in the autonomous AML cell growth, the effects of an antisense oligonucleotide on ICE were examined in 19 of these patients. In a majority of patients, antisense ICE suppressed both AML cell proliferation and CFU-AML although a stimulatory effect was sometimes evident. The proportion of AML patients with suppression obtained by antisense ICE was higher than with IL-1Ra, suggesting the involvement of additional ICE-dependent cytokine(s) in AML cell growth besides IL-1. The presence of IL-1Ra or antisense ICE also suppressed the endogenous IL-1 beta production of AML cells, at both the level of pro-IL-1 beta and mature IL-1 beta. Although inhibition by IL-1Ra or antisense ICE on growth parameters of AML cells in vitro prevailed, indicating the importance of IL-1 activity in autonomous AML cell growth, stimulatory effects on the cells of some patients suggest that AML is a heterogenous disorder regarding IL-1 beta regulation.nul

A Class of Selective CIC FIR Filter Functions

A new class of modified selective multiplerless Cascaded-Integrator-Comb (CIC) finite impulse response (FIR) filter functions with application in modern communication systems, which have superior performances compared to the classical CIC filter functions are presented here. A few design examples that illustrate the properties of the proposed filter class are also presented. Novel filter functions have a minimum attenuation of 166.52 dB, 258.56 dB and 350.46 dB, respectively. The achieved improvements versus classical CIC filters are 29.84 dB, 34.90 dB and 39.82 dB, respectively