Discovery of 6.035GHz Hydroxyl Maser Flares in IRAS18566+0408

We report the discovery of 6.035GHz hydroxyl (OH) maser flares toward the massive star forming region IRAS18566+0408 (G37.55+0.20), which is the only region known to show periodic formaldehyde (4.8 GHz H2CO) and methanol (6.7 GHz CH3OH) maser flares. The observations were conducted between October 2008 and January 2010 with the 305m Arecibo Telescope in Puerto Rico. We detected two flare events, one in March 2009, and one in September to November 2009. The OH maser flares are not simultaneous with the H2CO flares, but may be correlated with CH3OH flares from a component at corresponding velocities. A possible correlated variability of OH and CH3OH masers in IRAS18566+0408 is consistent with a common excitation mechanism (IR pumping) as predicted by theory.Comment: Accepted for publication in the Astrophysical Journa

Collisional Methods with Applications to Charged Particle Beams

Accurate and efficient computational methods are essential to study the dynamics of charged particle beams. Most of the available numerical methods in beam physics are based on the collisionless model which is sufficient for applications that does not depend on Coulomb collisions of the simultaneously interacting particles. However, the development of collisional numerical methods has become greatly important in recent years for applications where collisions play an important role such as the electron cooling of high energy hadron beams. While collisional methods can provide very accurate simulations, their algorithms are very complex, and they face efficiency challenges. In this work, we present our development of new collisional numerical methods which are the first methods that can provide an accurate microscopic description of beam dynamics with high computational efficiency. The first method is the Simo` integrator which solves the N-body problem of beams by direct integration of the particles\u27 equations of motion in the presence of external electromagnetic fields. Its development included very unique techniques to obtain accuracy while resolving all the efficiency challenges known to N-body integrators. Consequently, the Simo` integrator is the first large-scale collisional numerical method in beam physics that is accurate up to machine precision with a relatively high efficiency. Then, we incorporate the Simo` integrator to model collisions into our other collisional method referred to as the Particles\u27 High-Order Adaptive Dynamics (PHAD). PHAD employs an advanced version of the fast multipole method (FMM) along with Strang splitting method, and the addition of the Simo` integrator makes PHAD the first most efficient, numerically symplectic, collisional method in beam physics. For an enhanced performance, the algorithms of both the Simo` integrator and PHAD were fully parallelized on a large-scale high-performance hybrid cluster. We present simulations performed by our codes of three complicated beam dynamics problems. One application is for the electron cooling of ion beams to which our simulations demonstrate and give the first insight of the microscopic description of electron cooling with accurate prediction of cooling time. The other application illustrates density modulations of electron beams due to ions from a collisional picture of the dynamics and provide conditions to obtain a strong modulation signal necessary for variants of coherent electron cooling systems. The last application considers microscopic simulations of the relaxation of certain beam perturbations which illustrates finite N effects in contrast to the kinetic limit of the collisionless methods, and the resulted relaxation times are important for applications like the beam echo

Collisional methods with applications to charged particle beams

In this work, we present our development of new collisional numerical methods which are the first methods that can provide an accurate microscopic description of beam dynamics with high computational efficiency. The first method is the Simò integrator which solves the N-body problem of beams by direct integration of the particles\u27 equations of motion in the presence of external electromagnetic fields. Its development included very unique techniques to obtain accuracy while resolving all the efficiency challenges known to N-body integrators. Consequently, the Simò integrator is the first large-scale collisional numerical method in beam physics that is accurate up to machine precision with a relatively high efficiency. Then, we incorporate the Simò integrator to model collisions into our other collisional method referred to as the Particles\u27 High-Order Adaptive Dynamics (PHAD). PHAD employs an advanced version of the fast multipole method (FMM) along with Strang splitting method, and the addition of the Simò integrator makes PHAD the first most efficient, numerically symplectic, collisional method in beam physics. For an enhanced performance, the algorithms of both the Simò integrator and PHAD were fully parallelized on a large-scale high-performance hybrid cluster. We present simulations performed by our codes of three complicated beam dynamics problems. One application is for the electron cooling of ion beams to which our simulations demonstrate and give the first insight of the microscopic description of electron cooling with accurate prediction of cooling time. The other application illustrates density modulations of electron beams due to ions from a collisional picture of the dynamics and provide conditions to obtain a strong modulation signal necessary for variants of coherent electron cooling systems. The last application considers microscopic simulations of the relaxation of certain beam perturbations which illustrates finite N effects in contrast to the kinetic limit of the collisionless methods, and the resulted relaxation times are important for applications like the beam echo

Variability monitoring of the hydroxyl maser emission in G12.889+0.489

Through a series of observations with the Australia Telescope Compact Array we have monitored the variability of ground-state hydroxyl maser emission from G12.889+0.489 in all four Stokes polarisation products. These observations were motivated by the known periodicity in the associated 6.7-GHz methanol maser emission. A total of 27 epochs of observations were made over 16 months. No emission was seen from either the 1612 or 1720 MHz satellite line transitions (to a typical five sigma upper limit of 0.2 Jy). The peak flux densities of the 1665 and 1667 MHz emission were observed to vary at a level of ~20% (with the exception of one epoch which dropped by <40%). There was no distinct flaring activity at any epoch, but there was a weak indication of periodic variability, with a period and phase of minimum emission similar to that of methanol. There is no significant variation in the polarised properties of the hydroxyl, with Stokes Q and U flux densities varying in accord with the Stokes I intensity (linear polarisation, P, varying by <20%) and the right and left circularly polarised components varying by <33% at 1665-MHz and <38% at 1667-MHz. These observations are the first monitoring observations of the hydroxyl maser emission from G12.889+0.489.Comment: 7 pages, 6 figures, accepted for publication in MNRA

The Effect of the Surface Roughness of Porcelain on the Adhesion of Oral Streptococcus mutans

Aim: Dental plaque has a harmful influence on periodontal tissue. When a porcelain restoration is fabricated and refinishing of the glazed surface is inevitable, the increase in surface roughness facilitates the adhesion of plaque and its components. The aim of this in vitro study was to evaluate the effect of surface roughness of glazed or polished porcelain on the adhesion of oral Streptococcus mutans

Hydrogen sulfide removal from biogas using a salak fruit seeds packed bed reactor with sulfur oxidizing bacteria as biofilm

A packed bed reactor was evaluated for hydrogen sulfide (H2S) removal by sulfur-oxidizing bacteria attached as a biofilm on salak fruit seeds (SFS). The bacteria were isolated from the sludge of the wastewater of a biogas plant. The promising isolate from the previous work was used in a biofilter, and its capacity to remove H2S was evaluated at effects of time of operation, effects of biogas flow rate, effects of axial distance, and packing material. Obtained results showed that isolate attached to SFS in an 80 cm height and 8 cm inside diameter biofilter column could decrease H2S in biogas from 142.48 ppm to 4.06 ppm (97.15% removal efficiency) for a biogas flow rate of 8550 g m3 h1 corresponding to a residence time of 4 h. Simple kinetic models of sulfide removal and bacterial growth was proposed to describe the operation of the biofilter. The radial H2S concentration gradient in the flowing gas is to be neglected so is the H2S concentration in the biofilm at certain axial distance. Meanwhile, the rate of H2S degradation was approximated by Monod type equation. The obtained simultaneous ordinary differential equations solved by Runge-Kutta method. Comparing the calculated results and the experimental data, it can be concluded that model proposed can sufficiently describe the performance of the H2S removal. The suitable values of the parameters are as follows: max = 0.0000007 (s1), KS = 0.0000039 (g cm3), kG = 0.0086 (cm s1), HS = 0.9 ((g cm3)/(g cm3)), and Yx/s = 10.Directorate General of Higher Educations of Indonesia - scholarship of doctorate program (BPPDN) at Gadjah Mada University ; Hibah Bersaing 2015 and Sandwich-Like program 201

3-Benzyl-8-meth­oxy-2-sulfanyl­idene-1,2,3,4-tetra­hydro­quinazolin-4-one

The tetra­hydro­quinazole fused-ring system of the title compound, C16H14N2O2S, is roughly planar (r.m.s. deviation = 0.039 Å); the phenyl ring of the benzyl substituent is aligned at 78.1 (1)° with respect to the mean plane of the fused-ring system. In the crystal, two mol­ecules are linked by a pair of N—H⋯S hydrogen bonds about a center of inversion, generating a dimer

5-Chloro-2-methyl­sulfonyl-1,2,4-triazolo[1,5-a]quinazoline

The triazoloquinazole fused-ring system of the title compound, C10H7ClN4O2S, is essentially planar (r.m.s. deviation = 0.009 Å). In the methyl­sulfonyl substituent, the two S—O bonds are of equal length [1.402 (2) Å]. In the crystal, adjacent mol­ecules inter­act weakly through Cl⋯N contacts [ca 3.197 (2) Å]

3-(Prop-2-en-1-yl)-2-sulfanyl­idene-1,2,3,4-tetra­hydro­quinazolin-4-one

The tetra­hydro­quinazoline fused-ring system of the title compound, C11H10N2OS, is approximately planar (r.m.s. deviation = 0.019 Å). In the crystal, adjacent mol­ecules are linked by N—H⋯O hydrogen bonds, forming a chain running along the b axis