Heat transfer study and optimization of nanofluid triangular cavity with a pentagonal barrier by finite element approach and RSM

Nowadays, several engineering applications and academic investigations have demonstrated the significance of heat transfers in general and mixed convection heat transfer (MCHT) in particular in cavities containing obstacles. This study's main goal is to analyze the MCHT of a nanofluid in a triangular cavity with a pentagonal barrier using magneto hydrodynamics (MHD). The cavity's-oriented walls are continuous cold temperature, whereas the bottom wall of the triangle and all pentagonal obstacle walls are kept at a constant high temperature. For solving governing equations, we utilized the Galerkin's finite element approach. Four dimensionless factors, Richardson number (0.01 ≤ Ri ≤ 5), Reynolds number (10 ≤ Re ≤ 50), Buoyancy ratio (0.01 ≤ Br ≤ 10) and Hartmann number (0 ≤ Ha ≤20) are examined for their effects on streamlines, isotherms, concentration, velocity, and the Nusselt number. Also, with the help of Taguchi method and Response Surface Method (RSM) the optimization of the studied dimensionless parameters has been done. The optimum values of Ri, Re, Ha and Br are obtained 4.95, 30.49,18.35 and 0.05 respectively. Ultimately, a correlation has been extracted for obtaining the optimum average Nusselt number (Nu) in mentioned cavity.

X-ray tube with artificial neural network model as a promising alternative for radioisotope source in radiation based two phase flowmeters

In this paper, X-ray tube is introduced as a potential alternative for radioisotope sources used in radiation based liquid-gas two-phase flowmeters. X-ray tubes have lots of advantages over the radioisotope sources such as having an adjustable emitting photon's energy, being safer from point of view of radiation health physics during the transportation of the source, having ability to generate a high flux photon beam, and etc. The proposed radiation based system in this study composes an X-ray tube with a tube voltage of 150 kV and a 2.5 mm aluminum filter as the radiation source and one sodium iodide crystal as the photon detector. A pipe was positioned between the X-ray tube and the detector. Two main flow regimes of annular and stratified with different void fractions were modelled inside the pipe. Artificial neural network model of multi-layer perceptron (MLP) was also used in this study for analyzing the obtained data. The output spectrum of sodium iodide detector with 150 samples was applied as the input of multi-layer perceptron network and void fraction was considered as its output. The root mean squared error of proposed measuring system was 4.13 which shows the X-ray tube can be implemented as a promising alternative for radioisotope in radiation based two phase flow meters.

Capsular serotype and antibiotic resistance of group B streptococci isolated from pregnant women in Ardabil, Iran

BACKGROUND AND OBJECTIVES

Group B Streptococci (GBS) is a major cause of neonatal and maternal infections. The aim of this study was to determine the serotype distribution and antibiotic resistance profile of GBS strains isolated from pregnant women in Ardabil.

MATERIALS AND METHODS

Antibiotic resistance of 56 GBS isolates was investigated using E-test strips and disk-diffusion method. Serotyping was performed using capsular antiserum.

RESULTS

The results of MIC tests showed all isolates were susceptible to ampicillin, vancomycin and penicillin. One isolate (1.7%) showed reduced susceptibility pattern to penicillin (MIC; 0.25 µg/ml). There were 3 (5.3%) isolates semi-sensitive (0.25-1 µg/ml) to erythromycin (2; 0.5 µg/ml and 1; 0.38 µg/ml) and 2 (3.5%) isolates to clindamycin (1; 0.5 µg/ml, 1; 0.38 µg/ml). Additionally, 2 (3.5%) isolates were resistant to clindamycin (1; 16 µg/ml, 1; 2 µg/ml). According to the disk diffusion test, 47 (83.9%), 8 (14.2%) and 7 (12.5%) isolates were resistant to Co-trimoxazole, ciprofloxacin and ceftriaxone respectively. Serotypes V (19.6%), II (12.5%) and IV (12.5%) were the most frequent followed by serotypes III (10.7%) and VI (10.7%), Ib (8.9%), Ia (7/1%), VII (5/3%) and VIII (5/3%); 7.1% of strains were nontypeable.

CONCLUSIONS

In this study, most isolates were sensitive to common antibiotics, but increased resistance to other antibiotics indicates the importance of monitoring of antibiotic resistance in group B streptococci over time.

Conformational aspects of HIV-1 integrase inhibition by a peptide derived from the enzyme central domain and by antibodies raised against this peptide

Monospecific antibodies were raised against a synthetic peptide K159 (SQGVVESMNKELKKIIGQVRDQAEHLKTA) reproducing the segment 147-175 of HIV-1 integrase (IN). Synthesis of substituted and truncated analogs of K159 led us to identify the functional epitope reacting with antibodies within the C-terminal portion 163-175 of K159. Conformational studies combining secondary structure predictions, CD and NMR spectroscopy together with ELISA assays, showed that the greater is the propensity of the epitope for helix formation the higher is the recognition by anti-K159. Both the antibodies and the antigenic peptide K159 exhibited inhibitory activities against IN. In contrast, neither P159, a Pro-containing analog of K159 that presents a kink around proline but with intact epitope conformation, nor the truncated analogs encompassing the epitope, were inhibitors of IN. While the activity of antibodies is restricted to recognition of the sole epitope portion, that of the antigenic K159 likely requires interactions of the peptide with the whole 147-175 segment in the protein [Sourgen F., Maroun, R.G., Frère, V., Bouziane, A., Auclair, C., Troalen, F. & Fermandjian, S. (1996) Eur. J. Biochem. 240, 765-773]. Actually, of all tested peptides only K159 was found to fulfill condition of minimal number of helical heptads to achieve the formation of a stable coiled-coil structure with the IN 147-175 segment. The binding of antibodies and of the antigenic peptide to this segment of IN hampers the binding of IN to its DNA substrates in filter-binding assays. This appears to be the main effect leading to inhibition of integration. Quantitative analysis of filter-binding assay curves indicates that two antibody molecules react with IN implying that the enzyme is dimeric within these experimental conditions. Together, present data provide an insight into the structure-function relationship for the 147-175 peptide domain of the enzyme. They also strongly suggest that the functional enzyme is dimeric. Results could help to assess models for binding of peptide fragments to IN and to develop stronger inhibitors. Moreover, K159 antibodies when expressed in vivo might exhibit useful inhibitory properties.

Signal standardization of the secondary ion mass spectrometry (SIMS) microscope for quantification of halogens and calcium in biological applications

The secondary ion mass spectrometry (SIMS) microscope is able to map chemical elements in tissue sections. Although absolute quantification of an element remains difficult, a relative quantitative approach is possible for soft tissue by using carbon (12C) as an internal reference present at large homogeneous and constant concentration in specimen and embedding resin. In this study, this approach is used to standardize the signal of an SIMS microscope for the quantification of halogens (9F-, 35Cl- and 79Br-) and calcium (40Ca+). Standard preparation was determined based on homogeneity and stability criteria by molecular incorporation (halogens) or mixing (calcium) in methacrylate resin. Standard measurements were performed by depth analysis on areas of 8 microns (halogens) and 150 microns (calcium) in diameter for 10-30 min, under Cs+ (halogens) or Ox+ (calcium) bombardment. Results obtained from 100-120 measurements for each standard dilution show that the relationship between the signal intensity measured and the elemental concentration (micrograms/mg of wet tissue or mM) is linear in the range of biological concentrations. This quantitative approach was applied firstly to bromine of the 5-bromo-2'-deoxyuridine (BrdU) used as nuclear marker of rat hepatocytes in proliferation. The second model concerns depletion of calcium concentration in cortical compartment in Paramecium tetraurelia during exocytosis. Then signal standardization in SIMS microscopy allows us to correlate quantitative results with those obtained from other methods.