Simulation of optical interstellar scintillation

Stars twinkle because their light propagates through the atmosphere. The same phenomenon is expected on a longer time scale when the light of remote stars crosses an interstellar turbulent molecular cloud, but it has never been observed at optical wavelengths. The aim of the study described in this paper is to fully simulate the scintillation process, starting from the molecular cloud description as a fractal object, ending with the simulations of fluctuating stellar light curves. Fast Fourier transforms are first used to simulate fractal clouds. Then, the illumination pattern resulting from the crossing of background star light through these refractive clouds is calculated from a Fresnel integral that also uses fast Fourier transform techniques. Regularisation procedure and computing limitations are discussed, along with the effect of spatial and temporal coherency (source size and wavelength passband). We quantify the expected modulation index of stellar light curves as a function of the turbulence strength --characterised by the diffraction radius $R_{diff}$-- and the projected source size, introduce the timing aspects, and establish connections between the light curve observables and the refractive cloud. We extend our discussion to clouds with different structure functions from Kolmogorov-type turbulence. Our study confirms that current telescopes of ~4m with fast-readout, wide-field detectors have the capability of discovering the first interstellar optical scintillation effects. We also show that this effect should be unambiguously distinguished from any other type of variability through the observation of desynchronised light curves, simultaneously measured by two distant telescopes.Comment: 11 pages, 11 figures, accepted for publication in Astronomy and Astrophysic

Micromorphological, anatomical and molecular study of Hedera species (Araliaceae) in Iran

Hedera, with 12 extant species, is a genus of evergreen climbers native to Europe, north Africa, and south Asia. In this study, the micromorphological, anatomical structure and molecular evidences of 11 populations from two species of Hedera (H. helix and H. pastuchovii) have been considered to evaluate the relationships in Hedera. In total, seven quantitative and qualitative characters of pollen were selected and measured. Based on this study, the anticlinal wall and surface sculpturing of seed support for separation of two species of Hedera. Micromorphology of epidermis illustrated two types of epidermal cells: puzzle-shaped and polygonal cells. Using nuclear (nrDNA ITS) marker, we reconstructed phylogenetic relationships within two species of Hedera. This data set was analyzed by phylogenetic methods including Bayesian inference, maximum likelihood, and maximum parsimony. In phylogenetic analyses, all members of two species formed a well-supported clade (PP = 1; ML/BS = 100/100) and divided into two major clades (A and B). Neighbor Net diagram demonstrated separation of the studied populations. The results showed that these taxa differ in taxonomically important micromorphological, anatomical and molecular characteristics and these data provide reliable evidence for separation of these two species

Molecular basis of antibiotic multiresistance transfer in Staphylococcus aureus

Multidrug-resistant Staphylococcus aureus infections pose a significant threat to human health. Antibiotic resistance is most commonly propagated by conjugative plasmids like pLW1043, the first vancomycin-resistant S. aureus vector identified in humans. We present the molecular basis for resistance transmission by the nicking enzyme in S. aureus (NES), which is essential for conjugative transfer. NES initiates and terminates the transfer of plasmids that variously confer resistance to a range of drugs, including vancomycin, gentamicin, and mupirocin. The NES N-terminal relaxase–DNA complex crystal structure reveals unique protein–DNA contacts essential in vitro and for conjugation in S. aureus. Using this structural information, we designed a DNA minor groove-targeted polyamide that inhibits NES with low micromolar efficacy. The crystal structure of the 341-residue C-terminal region outlines a unique architecture; in vitro and cell-based studies further establish that it is essential for conjugation and regulates the activity of the N-terminal relaxase. This conclusion is supported by a small-angle X-ray scattering structure of a full-length, 665-residue NES–DNA complex. Together, these data reveal the structural basis for antibiotic multiresistance acquisition by S. aureus and suggest novel strategies for therapeutic intervention

The mechanism and control of DNA transfer by the conjugative relaxase of resistance plasmid pCU1

Bacteria expand their genetic diversity, spread antibiotic resistance genes, and obtain virulence factors through the highly coordinated process of conjugative plasmid transfer (CPT). A plasmid-encoded relaxase enzyme initiates and terminates CPT by nicking and religating the transferred plasmid in a sequence-specific manner. We solved the 2.3 Å crystal structure of the relaxase responsible for the spread of the resistance plasmid pCU1 and determined its DNA binding and nicking capabilities. The overall fold of the pCU1 relaxase is similar to that of the F plasmid and plasmid R388 relaxases. However, in the pCU1 structure, the conserved tyrosine residues (Y18,19,26,27) that are required for DNA nicking and religation were displaced up to 14 Å out of the relaxase active site, revealing a high degree of mobility in this region of the enzyme. In spite of this flexibility, the tyrosines still cleaved the nic site of the plasmid’s origin of transfer, and did so in a sequence-specific, metal-dependent manner. Unexpectedly, the pCU1 relaxase lacked the sequence-specific DNA binding previously reported for the homologous F and R388 relaxase enzymes, despite its high sequence and structural similarity with both proteins. In summary, our work outlines novel structural and functional aspects of the relaxase-mediated conjugative transfer of plasmid pCU1

Establishment of gene bank of inland water fish species

Genetic knowledge helps to protect biodiversity and optimal harvest resources by several ways. This knowledge can help to reduce the risk of extinction to those populations that have high genetic diversity or diminished by detected them. Also, studies of population genetics can present guidelines for improving the structure of the population and understanding the biology of species. One of the most important applications of DNA database is detecting species, fishing offense, diagnose of anemia and genetic classification of animals. DNA bank has helped to identify the species that are hunted and were discovered only parts of their meat and texture. Optimal Storage of aquatic genetic resources and the conservation of biological diversity, as the national capital by using biotechnology methods are the most important goals of gene bank and database reserves of the country creation. Collecting biological specimens of aquatic species, preparation and long-term maintenance of them, genetic registration of endangered and threatened species and the use of biotechnology techniques for the protection, conservation and management of aquatic genetic resources is one of the other functions of the gene bank. Gene bank of inland waters of Iran (Gorgan) is planned and implemented to identify, collect, maintain and protect species at the level of genes, cells, tissues and live fish research and commercial exploitation. Despite the predicted projected funding for this project, unfortunately funding sources have been considered, does not allocated. Therefore some parts of the aims of this project has been organized by Golestan province credits to build molecular laboratory and aquaculture pond in Alang farm and exploitation of potential Gharasou station and Sijoval center restocking and the conditions for the bulk of the project goals is provided. Some parts like tissue culture laboratory and bioinformatics as well as parts and equipment related to the freezing of sperm and embryo development are the items that should be considered in the development of the this bank

Ion-molecule and ion-surface collisions in hybrid and multiquadrupole mass spectrometers

Ion/molecule and ion/surface collisions are two major methods by which gas phase ions are characterized in tandem mass spectrometry. This work deals with developing novel instrumentation and applications in these areas. The stability of polyatomic ions upon collision with a surface was studied in a hybrid BQ (B = magnet, Q = quadrupole) mass spectrometer. Even-electron ions were generally found to reflect more readily than those with odd number of electrons. Reflection of an ion was also influenced by its degree of unsaturation and origin. A hybrid BQQ mass spectrometer was built to study dissociative charge exchange (DCE) of various ions with polyatomic neutrals. Products were collected at 90\sp\circ with respect to the primary ion beam and the internal energy deposited in the target was shown to depend principally on the recombination energy of the reactant ion and the ionization energy of the target. The extent of fragmentation in the DCE spectra, in several cases, demonstrated strong dependance on the kinetic energy of the projectile ions. Three C\sb6H\sb6 isomers, benzene, 1,5-hexadiyne and 2,4-hexadiyne, were distinguished via the DCE method. Collisions between ions generated from dihalomethanes CH\sb2X\sb2 (where X = I, Br, or Cl) and a variety of targets were studied. Gaseous hydrocarbon targets were examined in a triple quadrupole mass spectrometer and solid targets in an orthogonal QQ mass spectrometer. Competition between charge exchange (CE), DCE, collision-induced dissociation (CID), surface-induced dissociation (SID) and sputtering of the surface adsorbates was examined. CE and DCE were favored at lower collision energies, and CID at either higher collision energies or when the CE reaction was endothermic or only slightly exothermic. In general, collisions of odd-electron incident ions with the surface favored hydrogen atom abstraction, neutralization and fragmentation, as opposed to reflection favored by even-electron projectiles. Sputtering of the surface adsorbates showed little dependence on the kinetic energy of the projectile ions. CE of C\sb3F\sb6 by a variety of atomic and molecular ions were used to characterize the energetics associated with formation of C\sb3F\sb6\sp{+.}. The internal energy of the nascent C\sb3F\sb6\sp{+.} ion, assessed by observing the degree to which it fragmented, increased with the recombination energy of the CE reagent

Identifying the predictors of turnover intention based on nurse managers’ toxic leadership behaviors among nurses in Iran: a cross-sectional correlational study

Abstract Background Unfavorable leadership practices are a growing concern in the field of healthcare and nursing that have adverse consequences on nurses’ career outcomes. One of the undesirable leadership styles is the toxic leadership style. Considering the importance of nursing managers’ leadership style and its impact on nurses’ performance and the scarcity of studies in this field, the present study was conducted to determine toxic leadership behaviors in nursing managers and their relationship with the turnover intention among nurses. Methods A multicenter cross-sectional correlational study. This study involved 551 nurses from 5 educational-medical centers in Ardabil province, north-western Iran. Three self-report scales, including The demographic and occupational information form, the Toxic Leadership Behaviors of Nurse Managers Scale (ToxBH-NM), and the turnover intention questionnaire were adopted for assessment purposes in this study. Data were analyzed using SPSS (Version 22) software using descriptive statistics, Pearson correlation coefficient test, t-test, ANOVA test, and multiple linear regression analysis. Results Overall, 551 nurses participated in this research. There was a significantly positive relationship between Turnover intention and Toxic leadership behavior Subscales (r = 0.475, p < 0.001). Furthermore, multiple linear regression analysis showed Toxic leadership behavior Subscales (Intemperate behavior, Narcissistic behavior, Self-promoting behavior, and Humiliating behavior), Hospital, unit, Age, and Marital status predict Turnover intention when other variables are controlled. Conclusion A leader who directly and indirectly adopts toxic behavior toward their employees destructively affects both individuals and organizations. Nurses who work for a manager exhibiting toxic leadership behaviors demonstrated higher turnover intention