On the Ionization of Luminous WMAP Sources in the Galaxy : Constraints from He Recombination Line Observations with the GBT

The Wilkinson Microwave Anisotropy Probe (WMAP) free-free foreground emission map is used to identify diffuse ionized regions (DIR) in the Galaxy (Rahman & Murray 2010). It has been found that the 18 most luminous WMAP sources produce more than half of the total ionizing luminosity of the Galaxy. We observed radio recombination lines (RRLs) toward the luminous WMAP source G49.75-0.45 with the Green Bank Telescope near 1.4 GHz. Hydrogen RRL is detected toward the source but no helium line is detected, implying that n_He+/n_H+ < 0.024. This limit puts severe constraint on the ionizing spectrum. The total ionizing luminosity of G49 (3.05 x 10^51 s^-1) is ~ 2.8 times the luminosity of all radio HII regions within this DIR and this is generally the case for other WMAP sources. Murray & Rahman (2010) propose that the additional ionization is due to massive clusters (~ 7.5 x10^3 Msun for G49) embedded in the WMAP sources. Such clusters should produce enough photons with energy \geq 24.6 eV to fully ionize helium in the DIR. Our observations rule out a simple model with G49 ionized by a massive cluster. We also considered 'leaky' HII region models for the ionization of the DIR, suggested by Lockman and Anantharamaiah, but these models also cannot explain our observations. We estimate that the helium ionizing photons need to be attenuated by > ~10 times to explain the observations. If selective absorption of He- ionizing photons by dust is causing this additional attenuation, then the ratio of dust absorption cross sections for He- and H- ionizing photons should be > ~6.Comment: Accepted for publication in the ApJ; 14 pages, 3 figure

A compact steep spectrum radio source in NGC1977

A compact steep spectrum radio source (J0535-0452) is located in the sky coincident with a bright optical rim in the HII region NGC1977. J0535-0452 is observed to be $\leq 100$ mas in angular size at 8.44 GHz. The spectrum for the radio source is steep and straight with a spectral index of -1.3 between 330 and 8440 MHz. No 2 \mu m IR counter part for the source is detected. These characteristics indicate that the source may be either a rare high redshift radio galaxy or a millisecond pulsar (MSP). Here we investigate whether the steep spectrum source is a millisecond pulsar.The optical rim is believed to be the interface between the HII region and the adjacent molecular cloud. If the compact source is a millisecond pulsar, it would have eluded detection in previous pulsar surveys because of the extreme scattering due to the HII region--molecular cloud interface. The limits obtained on the angular broadening along with the distance to the scattering screen are used to estimate the pulse broadening. The pulse broadening is shown to be less than a few msec at frequencies \gtsim 5 GHz. We therefore searched for pulsed emission from J0535-0452 at 14.8 and 4.8 GHz with the Green Bank Telescope (GBT). No pulsed emission is detected to 55 and 30 \mu Jy level at 4.8 and 14.8 GHz. Based on the parameter space explored by our pulsar search algorithm, we conclude that, if J0535-0452 is a pulsar, then it could only be a binary MSP of orbital period \ltsim 5 hrs.Comment: Accepted for publication in A&A (3pages, 1 fig

Dams and Special Structures

Rain vibration of cables is becoming a matter of great concern recently in Japan for design and construction of cables-stayed- bridges. The features of rain vibration are the strong influence of rain on wind-induced oscillation of cable. The cables in cable-stayed bridges, which are stable with respect to wind acting in dry condition, became very unstable with rain, and large amplitude oscillation of cable could be developed under low speed wind around10m/s. for the first time this phenomena have been seen in the bridge Meiko-Nishi (Japan) and after in the others cable-stayed bridges as: Aratsu, Higashi - Kobe (Japan), Domitz (Germany), Erasmus (Holland) est. Many analytical and experimental investigations have been made for known the influence of different factors that produce this phenomenon in much country, especially in this country that is attacked by this phenomenon as: Japan, Germany, Holland, France EST. The reason of this seminar work is to make UN representation to this phenomenon, to represent same some analytical and experimental investigation made by different authors and conclusion yielding from this investigation. Here are presented first the response of cables on the excitation by the wind and after are compared with the response under the couplet excitation &lt;&lt; Rain-Wind &gt;&gt;The principal parameters that give a grate influence in this phenomenon can be classified in two groups. First the group of the situation of cable were included: the orientation of cable, wind speed, reins intensity. In second group named cables properties were are included natural periods, damping ratio and property of the surface of cables. We point here the fact that even many investigation are made this phenomenon is not well known, the reason for this is the fact that the excitation couplet Rain - Wind is very comple

A survey of Radio Recombination Lines using Ooty Radio Telescope at 328 MHz in the Inner Galaxy

A survey of radio recombination lines in the Galactic plane with longitude $-32^o < l < +80^o$ and latitude $b<\pm3^o$ using Ooty Radio Telescope(ORT) at 328 MHz has been reported. ORT observations were made using a New Digital Backend(NDB) augmented to it recently. With NDB ORT had a beam of $2^o.3 \times 2^o.2 sec(\delta)$ and a passband of $\sim$1 MHz in the spectral line mode. The above mentioned Galactic region was divided into $\sim 2^o \times 2^o$ patches with the ORT beam pointed to the center. The ORT observations form a study of distribution of extended low-density warm-ionized medium(ELDWIM) in the inner Galaxy using H271$\alpha$ RL. By obtaining kinematical distances using $V_{LSR}$ of the H271$\alpha$ RLs the distribution of ELDWIM clouds within the inner Galaxy has been deduced for the region given above.Comment: 28 pages, Published in The Astronomical Journal with minor difference

Carbon Recombination Lines toward the Riegel-Crutcher Cloud and other Cold HI Regions in the inner Galaxy

We report here, for the first time, the association of low frequency CRRL with \HI\ self-absorbing clouds in the inner Galaxy and that the CRRLs from the innermost $\sim 10^{\circ}$ of the Galaxy arise in the Riegel-Crutcher (R-C) cloud. The R-C cloud is amongst the most well known of \HI\ self-absorbing (HISA) regions located at a distance of about 125 pc in the Galactic centre direction. Taking the R-C cloud as an example, we demonstrate that the physical properties of the HISA can be constrained by combining multi-frequency CRRL and \HI\ observations. The derived physical properties of the HISA cloud are used to determine the cooling and heating rates. The dominant cooling process is emission of the \CII\ 158 \mum line whereas dominant heating process in the cloud interior is photoelectric emission. Constraints on the FUV flux (G0 $\sim$ 4 to 7) falling on the R-C cloud are obtained by assuming thermal balance between the dominant heating and cooling processes. The H$_2$ formation rate per unit volume in the cloud interior is $\sim$ 10$^{-10}$ -- 10$^{-12}$ s$^{-1}$ \cmthree, which far exceeds the H$_2$ dissociation rate per unit volume. We conclude that the self-absorbing cold \HI\ gas in the R-C cloud may be in the process of converting to the molecular form. The cold \HI\ gas observed as HISA features are ubiquitous in the inner Galaxy and form an important part of the ISM. Our analysis shows that combining CRRL and \HI\ data can give important insight into the nature of these cold gas. We also estimate the integration times required to image the CRRL forming region with the upcoming SKA pathfinders. Imaging with the MWA telescope is feasible with reasonable observing times.Comment: 11 pages, 4 figures, 5 tables, accepted by MNRA

Helium Ionization in the Diffuse Ionized Gas surrounding UCHII regions

We present measurements of the singly ionized helium to hydrogen ratio ($n_{He^+}/n_{H^+}$) toward diffuse gas surrounding three Ultra-Compact HII (UCHII ) regions: G10.15-0.34, G23.46-0.20 \& G29.96-0.02. We observe radio recombination lines (RRLs) of hydrogen and helium near 5 GHz using the GBT to measure the $n_{He^+}/n_{H^+}$ ratio. The measurements are motivated by the low helium ionization observed in the warm ionized medium (WIM) and in the inner Galaxy diffuse ionized regions (DIR). Our data indicate that the helium is not uniformly ionized in the three observed sources. Helium lines are not detected toward a few observed positions in sources G10.15-0.34 \& G23.46-0.20 and the upper limits of the $n_{He^+}/n_{H^+}$ ratio obtained are 0.03 and 0.05 respectively. The selected sources harbor stars of type O6 or hotter as indicated by helium line detection toward the bright radio continuum emission from the sources with mean $n_{He^+}/n_{H^+}$ value 0.06$\pm$0.02. Our data thus show that helium in diffuse gas located a few pc away from the young massive stars embedded in the observed regions is not fully ionized.We investigate the origin of the non-uniform helium ionization and rule out the possibilities : (a) that the helium is doubly ionized in the observed regions and (b) that the low $n_{He^+}/n_{H^+}$ values are due to additional hydrogen ionizing radiation produced by accreting low-mass stars (Smith 2014). We find that selective absorption of ionizing photons by dust can result in low helium ionization but needs further investigation to develop a self-consistent model for dust in HII regions.Comment: 43 pages, 11 figures, 5 tables accepted to Ap

Dependence of carbon dioxide hydrogenation on the structure of zirconia-based rhodium catalyst

Catalytic CO2 conversion into value added products has been one of the major study due to high energy demand and increasing atmospheric CO2 concentration. A catalytic reaction itself fulfills the Principles of Green Chemistry, but finding a catalyst for CO2 conversion at optimal temperature and atmospheric has been a greatest challenge. Studies have shown the structure of the catalyst is vital in CO2 hydrogenation for the product selectivity and reaction conditions. Support plays an important role in a reaction; where ordered struc-ture, high surface area and active sites are of high concern for a promising catalyst. This thesis has been made to study the rely of CO2 hydrogenation on the structure of the cata-lyst. Support monoclinic zirconia nanorods (ZrO2 NRs) were prepared via hydrothermal synthe-sis and Rhodium (0.5 and 2 wt%) was loaded via wet impregnation. Activity tests were con-ducted for carbon dioxide hydrogenation under atmospheric pressure and at 200 °C. The performance of the catalyst was compared with Rh loaded catalyst on commercial mono-clinic zirconia support (com ZrO2). During the experiment, the effect of parameters such as the Rhodium content and WHSV on the performance of the catalysts were compared. 200 mg of catalyst was tested in CO2 hydrogenation, which was carried out for 4 h with WHSV 1500 h-1 to 6000 h-1. Catalyst was diluted with SiC for the higher loading of Rhodium. Catalyst prepared 0.5 wt% Rh in com ZrO2 support resulted higher conversion and CH4 se-lectivity (C = 5.23 %, SCH4=64.9 %) than with ZrO2 NRs (C = 4.7 %, SCH4=36.9 %) . With 2 wt% Rh, CH4 selectivity increased for com ZrO2 supported catalyst (SCH4=75.7 %). From the sorp-tion experiments, the Rhodium particles were bigger in size on ZrO2 NRs than on com ZrO2 which could have resulted less conversion and CH4 selectivity. An interesting result, with the formation of small amounts of higher alkanes (ethane, propane) during hydrogenation, was observed. The conversion and selectivity of ZrO2 NRs supported catalyst could not result better than com ZrO2 supported catalyst. The capping agent, NaOL, was found to be occupying the active sites on the ZrO2 NRs support and thorough removal of it could result better conversion. Nevertheless, the conversion and selectivity of zirconia-based Rhodium catalyst in CO2 hydrogenation at low temperature and atmospheric pressure could open up a promising objective for the future research

Quenched Random Disorder Studies In Liquid Crystal + Aerosil Dispersions

This thesis presents a series of studies of quenched random disorder (QRD) on liquid crystals. We have used high-resolution AC-Calorimetry, high-resolution X-Ray Diffraction (XRD), X-Ray Intensity Fluctuation Spectroscopy (XIFS), Turbidity, Integrated Low-Angle Light Scattering (ILALS), as well as Polarizing Microscopy to characterize the effects of a nano-colloidal dispersions of aerosils in the phase transitions of several liquid crystals. The aerosil ($SIL$) is made of 70~AA~ diameter SiO$_{2}$ particles coated with hydroxyl (-OH) groups. The coating allows the $SIL$ particles to hydrogen-bond together, to form a very low density gel in an organic solvent. This provides the quenched random disorder. The liquid crystals of interest are: octyloxycyanobiphenyl ($8OCB$), 4-extit{n}-pentylphenylthiol-4\u27-extit{n}-octyloxybenzoate (ar{8}$S5), 4\u27-transbutyl-4-cyano-4-heptyl-bicyclohexane ($CCN47$), and octylcyanobiphenyl ($8CB$). Studies have been carried out as a function of aerosil concentration and temperature spanning the following phase transitions, Isotropic to Nematic (emph{I-N}), nematic to smectic-emph{A} (emph{N-SmA}), smectic-emph{A} to smectic-emph{C} (emph{SmA-SmC}), and crystallization

Hydrogen 2p--2s transition: signals from the epochs of recombination and reionization

We propose a method to study the epoch of reionization based on the possible observation of 2p--2s fine structure lines from the neutral hydrogen outside the cosmological H {\sc ii} regions enveloping QSOs and other ionizing sources in the reionization era. We show that for parameters typical of luminous sources observed at $z \simeq 6.3$ the strength of this signal, which is proportional to the H {\sc i} fraction, has a brightness temperature $\simeq 20 \mu K$ for a fully neutral medium. The fine structure line from this redshift is observable at $\nu \simeq 1 \rm GHz$ and we discuss prospects for the detection with several operational and future radio telescopes. We also compute the characteristics of this signal from the epoch of recombination: the peak brightness is expected to be $\simeq 100 \mu K$; this signal appears in the frequency range 5-10 MHz. The signal from the recombination era is nearly impossible to detect owing to the extreme brightness of the Galactic emission at these frequencies.Comment: 17 pages, 1 figure, to appear in Ap