Density dependence of the pairing interaction and pairing correlation in unstable nuclei

This work aims at a global assessment of the effect of the density dependence of the zero-range pairing interaction. Systematic Skyrme-Hartree-Fock-Bogoliubov calculations with the volume, surface and mixed pairing forces are carried out to study the pairing gaps in even-even nuclei over the whole nuclear chart. Calculations are also done in coordinate representation for unstable semi-magic even-even nuclei. The calculated pairing gaps are compared with empirical values from four different odd-even staggering formulae. Calculations with the three pairing interactions are comparable for most nuclei close to $\beta$-stability line. However, the surface interaction calculations predict neutron pairing gaps in neutron-rich nuclei that are significantly stronger than those given by the mixed and volume pairing. On the other hand, calculations with volume and mixed pairing forces show noticeable reduction of neutron pairing gaps in nuclei far from the stability.Comment: 9 pages, 10 figures, 3 tables, printer-friendl

Effect of asymmetry in the restoring force of the "click" mechanism in insect flight

The aim of this paper is to examine the effect of asymmetry in the force-deflection characteristics of an insect flight mechanism on its nonlinear dynamics. An improved simplified model for insect flight mechanism is suggested and numerical methods are used to study its dynamics. The range at which the mechanism may operate is identified. The asymmetry can lead to differences in the velocity in the upward and downward movements which can be beneficial for the insect flight

Mutual interaction of salinity and dietary protein level on growth, survival and body composition of narrow clawed cray fish (Astacus leptodactylus)

In this study Astacus leptodactylus were tested for 8 week with three practical diets containing three crude protein (30, 35 and 40%) and isoenergetic level (370kcal/100 g) in fresh water and brackish water of Caspian Sea. In this test, 6 treatments were used with three replicates in 18 fiberglass tank (110 liter). Each tank had 5 narrow clawed Cray fish (mean (±SD) individual weight=17±2.3g) and totally 90 clawed Cray fish were stocking. Result indicates mean weight of Cray fish in fresh water and brackish water were 14.82 and 12.73, respectively, that were significantly different. The highest survival occurred in interaction between protein (30%) and salinity (0) (95.55%) and lowest survival occurred in protein 40 – salinity (12) that were significantly different. The highest specific growth rate (SGR), weight gain (WG), Protein Efficiency Ratio (PER), Net Protein Utilization (NPU) and lowest Feed Conversion Ratio (FCR), demonstrated that dietary (protein 30% and fresh water) which had no significantly differences. Result of this study showed that the highest protein of body composition were in practical diet containing 30% protein and 0 salinity (freshwater) that were significantly different with other treatment

A study of professional radiation hazards in CT scan and nuclear medicine workers using GTG-banding and solid stain

Background: CT scan and nuclear medicine exams deliver a great part of medical exposures. This study examined professional radiation hazards in CT scan and nuclear medicine workers. Methods: In a cross sectional study 30 occupationally exposed workers and 7 controls (all from personnel of a laboratory) were selected. Physical dosimetry was performed for exposed workers. Blood samples were obtained from the experimental and control groups. Three culture mediums for each one were prepared in due to routine chromosome analysis using G-banding and solid stain. Results: There were significant increased incidence of chromatid gap (ctg) and chromatid break (ctb) with mean±SD frequencies of 3±0.84 and 3.1±1.40 per 100 cells respectively in the nuclear medicine workers versus controls with mean±SD frequencies of 1.9±0.69 and 1.3±0.84 for ctg and ctb, respectively. Chromosome gaps (chrg) were higher significantly in the nuclear medicine population (2.47±0.91) than in controls (1.4±0.9) (p< 0.05). In CT scan group the ctg and ctb were increased with a mean±SD frequency of 2.7±0.79 and 2.6±0.91 per 100 cells respectively compared with control group. The mean±SD frequencies of the chrb were 2.0±0.75 and 0.86±0.690 per 100 cells for exposed workers and control group, respectively. Conclusion: This study showed chromosome aberrations in peripheral lymphocytes using solid stain method are reasonable biomarker reflecting personnel radiation damage

Age-dependent dynamic electrophysiological field potential behavior of atrioventricular node during experimental AF in rabbit

Introduction: Electrophysiological studies have demonstrated a relationship between aging and atrioventricular (AV) nodal conduction and refractoriness. The aim of the present study was to determine the effects of nodal aging on dynamic AV nodal field potential recording during atrial fibrillation (AF) in rabbit. Methods: Two groups of male New Zealand rabbits (neonatal 2-week-olds and adult 12-week-olds, n=14 each group) were used in this study. Field potential recordings were executed by silver electrodes with a diameter of 100 μM. Pre-defined stimulation protocols of AF, zone of concealment (ZOC) and concealed conduction for determination of the electrophysiological properties of the AV-node were separately applied in each group. Results: Results of the study showed that mean ventricular rate (HH) during atrial fibrillation was smaller in the neonatal compared to the adult group (229.1 ± 8.3 versus 198.6 ± 13.1 msec, respectively). Also ventricular distribution conduction pattern showed two peaks in the adult and one peak in the neonatal group. Analyzing the zone of concealment in different rates and after concealed beat indicated that the zone of concealment in neonates were significantly smaller compared with adult rabbits and increasing zone of concealment, which is accompanied with increasing ventricular rate is abrogated in the neonatal group (5 ± 3.3, 12.2 ± 6.3 msec). Conclusion: The results of this study showed that the electrophysiological protective dynamic behavior of the AV node during atrial fibrillation is smaller in neonates compared to adults. Narrower zone of concealment, abrogation rate dependent trend of the zone of concealment and shorter nodal refractoriness can account for the specific nodal electrophysiological properties of neonatal rabbits

Effect of nitric oxide modulation on the basic and rate-dependent electrophysiological properties of AV-node in the isolated heart of rabbit: The role of adrenergic and cholinergic receptors

Introduction: Recent studies showed that nitrergic system have specific modulatory effects on electrophysiological properties of atrioventricular (AV) node. The aim of this study was to determine the effects of nitric oxide (NO) on the electrophysiological properties of isolated rabbit AV node and to investigate the role of adrenergic and cholinergic receptors in the mechanism of its action. Methods: In our laboratory, an experimental model of isolated double-perfused AV-node of rabbits weighing 1.5-2 kg was used. Specific experimental protocols of recovery, Facilitation, Fatigue and Wenckbach were applied in both control and in the presence of the drug. A total number of 35 rabbits were divided randomly into the following groups (n=7): 1) L-Arg (NO donor) (250, 750 and 1000 μmol), 2) L- NAME, a NO synthesis inhibitor (25, 50 and 100 μmol), 3) L-Arg + L- NAME, 4) Nadolol (1 μmol), 5) Atropine (3 μmol). All data were shown as mean ± SE. The level of statistical significance was set at p<0.05. Results: Our results revealed the depressant effect of L-Arg on the basic and rate-dependent electrophysiological properties of AV-node. L- NAME did not deteriorate the effects of L-Arg on the basic and rate-dependent properties, nevertheless, at high concentration (100 μmol) it had a direct inhibitory effect on the AV-node. Nadolol and atropine could prevent the effects of NO on the basic nodal characteristics and the fatigue phenomenon, respectively. Conclusion: Nitergic system can affect basic and rate-dependent electrophysiological properties of the AV-node through adrenergic and cholinergic receptors