The formation of massive primordial stars in the presence of moderate UV backgrounds

Radiative feedback from populations II stars played a vital role in early structure formation. Particularly, photons below the Lyman limit can escape the star forming regions and produce a background ultraviolet (UV) flux which consequently may influence the pristine halos far away from the radiation sources. These photons can quench the formation of molecular hydrogen by photo-detachment of $\rm H^{-}$. In this study, we explore the impact of such UV radiation on fragmentation in massive primordial halos of a few times $\rm 10^{7}$~M${_\odot}$. To accomplish this goal, we perform high resolution cosmological simulations for two distinct halos and vary the strength of the impinging background UV field in units of $\rm J_{21}$. We further make use of sink particles to follow the evolution for 10,000 years after reaching the maximum refinement level. No vigorous fragmentation is observed in UV illuminated halos while the accretion rate changes according to the thermal properties. Our findings show that a few 100-10, 000 solar mass protostars are formed when halos are irradiated by $\rm J_{21}=10-500$ at $\rm z>10$ and suggest a strong relation between the strength of UV flux and mass of a protostar. This mode of star formation is quite different from minihalos, as higher accretion rates of about $\rm 0.01-0.1$ M$_{\odot}$/yr are observed by the end of our simulations. The resulting massive stars are the potential cradles for the formation of intermediate mass black holes at earlier cosmic times and contribute to the formation of a global X-ray background.Comment: Submitted to APJ, comments are welcome. High resolution copy is available at http://www.astro.physik.uni-goettingen.de/~mlatif/IMBHs_apj.pd

A Normal-Mode Approach to Jovian Atmospheric Dynamics

We propose a nonlinear, quasi-geostrophic, baroclinic model of Jovian atmospheric dynamics, in which vertical variations of velocity are represented by a truncated sum over a complete set of orthogonal functions obtained by a separation of variables of the linearized quasi-geostrophic potential vorticity equation. A set of equations for the time variation of the mode amplitudes in the nonlinear case is then derived. We show that for a planet with a neutrally stable, fluid interior instead of a solid lower boundary, the baroclinic mode represents motions in the interior, and is not affected by the baroclinic modes. One consequence of this is that a normal-mode model with one baroclinic mode is dynamically equivalent to a one layer model with solid lower topography. We also show that for motions in Jupiter's cloudy lower troposphere, the stratosphere behaves nearly as a rigid lid, so that the normal-mode model is applicable to Jupiter. We test the accuracy of the normal-mode model for Jupiter using two simple problem forced, vertically propagating Rossby waves, using two and three baroclinic modes and baroclinic instability, using two baroclinic modes. We find that the normal-road model provide qualitatively correct results, even with only a very limited number of vertical degrees of freedom

Dark-matter halo mergers as a fertile environment for low-mass Population III star formation

While Population III stars are typically thought to be massive, pathways towards lower-mass Pop III stars may exist when the cooling of the gas is particularly enhanced. A possible route is enhanced HD cooling during the merging of dark-matter halos. The mergers can lead to a high ionization degree catalysing the formation of HD molecules and may cool the gas down to the cosmic microwave background (CMB) temperature. In this paper, we investigate the merging of mini-halos with masses of a few 10$^5$ M$_\odot$ and explore the feasibility of this scenario. We have performed three-dimensional cosmological hydrodynamics calculations with the ENZO code, solving the thermal and chemical evolution of the gas by employing the astrochemistry package KROME. Our results show that the HD abundance is increased by two orders of magnitude compared to the no-merging case and the halo cools down to $\sim$60 K triggering fragmentation. Based on Jeans estimates the expected stellar masses are about 10 M$_\odot$. Our findings show that the merging scenario is a potential pathway for the formation of low-mass stars.Comment: Submitted to MNRA

Ion beam effect on Ge-Se chalcogenide glass films: Non-volatile memory array formation, structural changes and device performance

The conductive bridge non-volatile memory technology is an emerging way to replace traditional charge based memory devices for future neural networks and configurable logic applications. An array of the memory devices that fulfills logic operations must be developed for implementing such architectures. A scheme to fabricate these arrays, using ion bombardment through a mask, has been suggested and advanced by us. Performance of the memory devices is studied, based on the formation of vias and damage accumulation due to the interactions of Ar+ ions with GexSe1-x (x=0.2, 0.3 and 0.4) chalcogenide glasses as a function of the ion energy and dose dependence. Blanket films and devices were created to study the structural changes, surface roughness, and device performance. Raman Spectroscopy, Atomic Force Microscopy (AFM), Energy Dispersive X-Ray Spectroscopy (EDS) and electrical measurements expound the Ar+ ions behavior on thin films of GexSe1-x system. Raman studies show that there is a decrease in area ratio between edge-shared to corner-shared structural units, revealing occurrence of structural reorganization within the system as a result of ion/film interaction. AFM results demonstrate a tendency in surface roughness improvement with increased Ge concentration, after ion bombardment. EDS results reveal a compositional change in the vias, with a clear tendency of greater interaction between ions and the Ge atoms, as evidenced by greater compositional changes in the Ge rich films

A UV flux constraint on the formation of direct collapse black holes

The ability of metal free gas to cool by molecular hydrogen in primordial halos is strongly associated with the strength of ultraviolet (UV) flux produced by the stellar populations in the first galaxies. Depending on the stellar spectrum, these UV photons can either dissociate $\rm H_{2}$ molecules directly or indirectly by photo-detachment of $\rm H^{-}$ as the latter provides the main pathway for $\rm H_{2}$ formation in the early universe. In this study, we aim to determine the critical strength of the UV flux above which the formation of molecular hydrogen remains suppressed for a sample of five distinct halos at $z>10$ by employing a higher order chemical solver and a Jeans resolution of 32 cells. We presume that such flux is emitted by PopII stars implying atmospheric temperatures of $\rm 10^{4}$~K. We performed three-dimensional cosmological simulations and varied the strength of the UV flux below the Lyman limit in units of $\rm J_{21}$. Our findings show that the value of $\rm J_{21}^{crit}$ varies from halo to halo and is sensitive to the local thermal conditions of the gas. For the simulated halos it varies from 400-700 with the exception of one halo where $\rm J_{21}^{crit} \geq 1500$. This has important implications for the formation of direct collapse black holes and their estimated population at z > 6. It reduces the number density of direct collapse black holes by almost three orders of magnitude compared to the previous estimates.Comment: 10 pages, 6 figures, matches the accepted version to ber published in MNRAS, higher resolution version is available at http://www.astro.physik.uni-goettingen.de/~mlatif/Jcrit.pd

Strategi Pengembangan Pariwisata Pantai di Kota Ternate, Provinsi Maluku Utara

The city of Ternate has great potential in the field of tourism, with a strategic geographicallocation has a high level of tourist visits both local and foreign tourists, has a variety of touristobjects and attractions and has the characteristics of the city as a coastal city (waterfront city).However, currently the tourism potential along the coast of Ternate City has not been maximallyexplored. This study aims to 1) analyze beach tourism objects that have developed, those that havethe potential to be developed and those that have less potential to be developed; 2) analyze thefactors that attract tourists; 3) analyze the strategy of developing tourism objects. several methodsused include Multi-Criteria Evaluation (MCE), binary logistic regression, and AWOT combinedAnalytic Hierarchy Process (AHP) and Strenghts, Weakness, Opportunities, and Threats (SWOT).Based on the results of the assessment of physical parameters and institutional, socio-cultural andeconomic parameters, Of the nine identified beach tourism objects, five of them have beendeveloped, two tourism objects are included in the category of tourism objects that have thepotential to be developed and the other two have less potential to be developed. Factors drivingand attracting tourist interest in beach tourism objects in Ternate City consist of, Age; Visitfrequency; one-time visit fee and facilities. The priority strategy for developing beach tourismobjects in Ternate City consists of: developing tourism objects by taking advantage of theiruniqueness and increasing promotion; program upgrade community based tourism, improvemaintenance event-event related to tourism, improvement of accommodation facilities;development of the tourism sector as a leading sector, reinforces existing regulations in terms oflicensing of C minerals in tourist areas

Assessment of Pesticide Residues in Some Fruits Using Gas Chromatography Coupled with Micro Electron Capture Detector

A very sensitive analytical method for the determination of 26 pesticides in some fruits based on solid phase extraction (SPE) cleanup was developed using gas chromatography (GC) coupled with micro electron capture detector (μECD). The identity of the pesticides was confirmed by gas chromatography mass spectroscopy (GC-MS) using selected ion monitoring (SIM) mode. Ethyl acetate was used as a solvent for the extraction of pesticide residues with assistance of sonication. For cleanup an octadecyl, C18 SPE column was used. A linear response of μECD was observed for all pesticides with good correlation coefficients (>0.9992). Proposed method was successfully applied for the determination of pesticide residues in the orange, apple, and grape fruits. Average recoveries achieved for all of the pesticides at fortification levels of 0.05, 1.0 and 2.0 μg g-1 in analyzed fruits were above 90% with relative standard deviations (RSD) less than

Microstructure of the juvenile sheep aortic valve hinge region and the trilamellar sliding hypothesis.

Background: The aortic valve mechanism performs extremely sophisticated functions which depend on the microstructure of its component parts. The hinge mechanism of the aortic leaflets plays a crucial part in the overall function. However, the detailed microstructure and its relation to function has not been adequately studied. Methods: The aortic roots of juvenile sheep were fixed under physiologic pressure. Sections through all three sinuses were then performed to illustrate the microstructure of the hinge mechanism in different regions of the aortic root. Results: The hinge region in the different sinuses showed unique microstructure with a trilamellar topology with a dominant core consisting of glycosaminoglycans. The exact arrangement of the trilamellar structures varies around the aortic sinuses, which could have functional implications. These features allow the hinge to perform its complex functions through what we have described as "the trilamellar sliding hypothesis". Conclusion: The microstructure of the hinge mechanism is unique and enables it to perform it sophisticated functions

Influence of meteorological variables on suburban atmospheric pm2.5 in the southern region of peninsular Malaysia

Air pollution is a crucial contributor to premature mortality and health problems. The excessive inhalation of fine particulate matter (PM2.5) is strongly associated with adverse health effects due to its capability to penetrate deep into the human respiratory system. This study aimed to analyze the seasonal cycles of 24 h average PM2.5 mass concentrations in a suburban area in the southern region of Peninsular Malaysia. The meteorological variables and PM2.5 data were obtained via a Grimm Environmental Dust Monitor from August 2017 until January 2018. The maximum 24 h mass concentration was 44.6 µg m–3, with a mean value of 21.85 µg m–3, which was observed during the southwest monsoon . 43.33% and 8.33% of the daily concentrations exceeded the 24 h World Health Organization Guideline and Malaysian Ambient Air Quality Standard, respectively. The variation in the PM2.5 mass ranged between 0.53 and 0.90 times of the PM10 mass, indicating that the PM2.5 consistently contributed 52–92% of the PM10 mass concentration. During the monsoon seasons, the ambient temperature exhibited a significant positive correlation (p < 0.05) with the PM2.5 mass concentration (r = 0.425–0.541), whereas the wind speed (r = –0.23 to –0.0127) and the relative humidity (r = –0.472 to –0.271) displayed strong negative correlations with it. Additionally, the rainfall was weakly correlated with the mass concentration. The presence of northeasterly wind at the study site suggests that the PM2.5 originated from sources to the northeast, which are influenced by anthropogenic activities and high traffic