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GLOSTAR: Radio Source Catalog I. 28 degrees < l < 36 degrees and vertical bar b vertical bar < 1 degrees
No full textContext. Radio continuum surveys of the Galactic plane are an excellent way to identify different source populations such as planetary nebulae, H II regions, and radio stars and characterize their statistical properties. The Global View of Star Formation in the Milky Way (GLOSTAR) survey will study the star formation in the Galactic plane between -2 degrees < l < 85 degrees and vertical bar b vertical bar < 1 degrees with unprecedented sensitivity in both flux density (similar to 40 mu Jy beam(-1)) and range ofangular scales (similar to 1 `'.5 to the largest radio structures in the Galaxy). Aims. In this paper we present the first results obtained from a radio continuum map of a 16-square-degree-sized region of the Galactic plane centered on l = 32 degrees and b = 0 degrees (28 degrees < l < 36 degrees and vertical bar b vertical bar < 1 degrees). This map has a resolution of 18 `' and a sensitivity of similar to 60-150 mu Jy beam(-1). Methods. We present data acquired in 40 h of observations with the VLA in D-configuration. Two 1 GHz wide sub-bands were observed simultaneously and they were centered at 4.7 and 6.9 GHz. These data were calibrated and imaged using the Obit software package. The source extraction was performed using the BLOBCAT software package and verified through a combination of visual inspection and cross-matching with other radio and mid-infrared surveys. Results. The final catalog consists of 1575 discrete radio sources and 27 large scale structures (including W43 and W44). By cross-matching with other catalogs and calculating the spectral indices (S(nu) alpha nu(alpha)), we have classified 231 continuum sources as H II regions, 37 as ionization fronts, and 46 as planetary nebulae. The longitude and latitude distribution and negative spectral indices are all consistent with the vast majority of the unclassified sources being extragalactic background sources. Conclusions. We present a catalog of 1575 radio continuum sources and discuss their physical properties, emission nature, and relation to previously reported data. These first GLOSTAR results have increased the number of reliable H II regions in this part of the Galaxy by a factor of four
Multimodal Ion Sensing by Structurally Simple Pyridine-End Oligo p-Phenylenevinylenes for Sustainable Detection of Toxic Industrial Waste
No full textEnvironmental pollution induced by toxic metal ions and harmful chemicals mainly from industrial waste poses a significant threat which urges for their rapid detection before release into the ecosystem above the permissible level. Optical sensors are inexpensive, simple, yet efficient in sensing such toxicants. Herein, we show that structurally simple pi-conjugated pyridine-end p-phenylenevinylene oligomers can selectively sense toxic metal ions and anions in solution, supramolecular gels, as well as in solid support. Interaction of Hg2+ at nanomolar concentrations with the linear pyridine-ends via two-site coordination was clearly seen from ``naked eye'' color changes and fluorometric investigations. The sensitivity as well as selectivity of the oligomers toward Hg2+ was found to be greatly affected by the extent of aromatic conjugation and pK(a) of the end-pyridine functionalities. Interestingly, one of the oligomers (3) containing an isoniazid moiety renders visual color changes with both Hg2+ and CN- ions through two different binding sites involving two nonidentical sensing pathways which enable this probe for the detection of multiple analytes at the same time. Moreover, these ions (Hg2+/CM-) showed remarkable tuning of the supramolecular assembly (molecular gels) of 3, depicting reversible sol gel transformation on complementary addition of Hg2+/CN- in proper stoichiometry which could be useful in scavenging toxic ions from industrial wastes. In addition, the low-cost, reusable paper discs coated with the probe molecules show rapid, onsite detection of toxic ions even from the contaminated water samples. Therefore, this highly efficient multimodal sensing of toxic ions by easy-to-synthesize molecular probes could inspire the design of new sensors with varying chromophores for the color-tunable sensing of toxic ions
Observed differences between near-surface air and skin temperatures using satellite and ground-based data
No full textAccurate estimates of long-term land surface temperature (T-s) and near-surface air temperature (T-a) at finer spatio-temporal resolutions are crucial for surface energy budget studies, for environmental applications, for land surface model data assimilation, and for climate change assessment and its associated impacts. The Atmospheric Infrared Sounder (AIRS) and Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the Aqua satellite provide a unique opportunity to estimate both temperatures twice daily at the global scale. In this study, differences between T-a and T-s were assessed locally over regions of North America from 2009 to 2013 using ground-based observations covering a wide range of geographical, topographical, and land cover types. The differences between T-a and T-s during non-precipitating conditions are generally 2-3 times larger than precipitating conditions. However, these differences show noticeable diurnal and seasonal variations. The differences between T-a and T-s were also investigated at the global scale using the AIRS estimates under clear-sky conditions for the period 2003-2015. The tropical regions showed about 5-20 degrees C warmer T-s than T-a during the day-time, whereas opposite characteristics (about 2-5 degrees C cooler T-s than T-a) are found over most parts of the globe during the night-time. Additionally, T-s estimates from the AIRS and the MODIS sensors were inter-compared. Although large-scale features of T-s were essentially similar for both sensors, considerable differences in magnitudes were observed (>6 degrees C over mountainous regions). Finally, T-a and T-s estimates from the AIRS and MODIS sensors were validated against ground-based observations for the period of 2009-2013. The error characteristics notably varied with ground stations and no clear evidence of their dependency on land cover types or elevation was detected. However, the MODIS-derived T-s estimates generally showed larger biases and higher errors compared to the AIRS-derived estimates. The biases and errors increased steadily when the spatial resolution of the MODIS estimates changed from finer to coarser. These results suggest that representativeness error should be properly accounted for when validating satellite-based temperature estimates with point observations
Dynamics of linear molecules in water: Translation-rotation coupling in jump motion driven diffusion
No full textWe study by computer simulations, and by theory, the coupled rotational and translational dynamics of three important linear diatomic molecules, namely, carbon monoxide (CO), nitric oxide (NO), and cyanide ion (CN-) in water. Translational diffusion of these molecules is found to be strongly coupled to their own rotational dynamics which, in turn, are coupled to similar motions of the surrounding water. In particular, we find that coupled orientational jump motions play an important role in all three cases. While CO and NO show similar features, CN- exhibits certain differences. Our results agree well with the known experimental values of the diffusion coefficient. We examined the validity of hydrodynamic predictions and found them to be inadequate, particularly for rotational diffusion. A mode coupling theory approach is developed and applied to understand the complexity of translation-rotation coupling
Effect of Mechanical Mixing in Dissimilar Friction Stir Welding of Aluminum to Titanium with Zinc Interlayer
No full textWelding of aluminum (Al) and titanium (Ti) is difficult and challenging due to their differences in chemical and physical properties, and the evolution of brittle intermetallic compounds. Formation of critical intermetallics can be minimized by using an interlayer material, which leads to ternary mechanical mixing in the weld nugget. In the present investigation, a zinc (Zn) interlayer has been used during friction stir welding (FSW) of Al-Ti. It has been found that tool offset position is one of the important parameters in controlling the amount of ternary mechanical mixing of materials. The mechanical mixing of Zn with Al and Ti alters the phase evolution and restricts the formation of the brittle Al3Ti intermetallic compound. The optimum tool offset exhibits a homogeneous mechanical mixing and inhibits the formation of brittle intermetallic compounds, which leads to a substantial increment in the mechanical properties of the weld
Fuel drop impact on heated solid surface in film evaporation regime
No full textThis study reports an experimental investigation on the dynamics of impacting hydrocarbon fuel drops on a heated stainless steel surface in the film evaporation regime. The analysis is focused on the description of maximum spreading diameter of the impacting fuel drops on the heated surface kept at different temperatures below the boiling point of the fuel. By considering four different fuels of varying physical properties and fuel drops with impact velocity in the range 0.6 - 3.5 m/sec, the study explores a wide range of Weber number (30 - 902), Reynolds number (372 - 13457) and Ohnesorge number (0.0022 - 0.0151). The drop morphology and spreading dynamics on the heated surface are quantified by studying high speed videos of drop impact captured during experiments. Data analysis suggests that, in addition to Weber number and surface temperature, dynamic viscosity of the fuel also plays a role in determining the quantified trends of maximum spreading diameter. Existing theoretical models for the prediction of maximum diameter on unheated flat surfaces can be extended for drop impact on heated surfaces in the film evaporation regime by using surface temperature dependent fuel viscosity. With the support of the present experimental data, an empirical model involving an explicit surface temperature term is proposed for the prediction of maximum diameter on a heated surface in the film evaporation regime
Experimental studies on structure of airblast spray in crossflow
No full textThe present investigation is focused on experimental studies on the structure of airblast spray in crossflow. Atomizer is at a higher pressure than ambient and the airblast gas is expected to exhibit features generally found in under-expanded gas jets. High-speed images are captured using shadowgraphy technique. Certain wave-like structures observed in the near-nozzle region are attributed to shock-vortex interactions, generally observed in under-expanded gas jets. Proper Orthogonal Decomposition (POD) analysis has been carried out using these images. POD mode shapes clearly show signatures of shock-vortex oscillations and frequencies close to the screeching frequency observed in under-expanded jets. The POD modes are compared for different conditions and the significance of dynamic structures and their temporal behavior is discussed. Finally, a regime map is also proposed to characterize spray behavior in crossflow
Boron-Catalyzed C-C Functionalization of Allyl Alcohols
No full textTris(pentafluorophenyl)borane-catalyzed C-C bond functionalization of arylallyl alcohols using donor-acceptor carbenes is presented. The allylic hydroxyl group is found to assist the product formation by neighboring group participation providing a clue towards mechanistic understanding. This method can also be employed to effect homologation of allyl alcohols to homoallyl alcohols. Overall, this metal-free transformation presents a novel disconnection strategy towards carbon-carbon bond scission and formation
The role of cross-correlation between precipitation and temperature in basin-scale simulations of hydrologic variables
No full textUncertainty in climate forcings causes significant uncertainty in estimating streamflow and other land-surface fluxes in hydrologic model simulations. Earlier studies primarily analyzed the importance of reproducing cross-correlation between precipitation and temperature (P-T cross-correlation) using various downscaling and weather generator schemes, leaving out how such biased estimates of P-T cross-correlation impact streamflow simulation and other hydrologic variables. The current study investigates the impacts of biased P-T cross-correlation on hydrologic variables using a fully coupled hydrologic model (Penn-state Integrated Hydrologic Model, PIHM). For this purpose, a synthetic weather generator was developed to generate multiple realizations of daily climate forcings for a specified P-T cross-correlation. Then, we analyzed how reproducing/neglecting P-T cross-correlation in climate forcings affect the accuracy of a hydrologic simulation. A total of 50 synthetic data sets of daily climate forcings with different P-T cross-correlation were forced into to estimate streamflow, soil moisture, and groundwater level under humid (Haw River basin in NC, USA) and arid (Lower Verde River basin in AZ, USA) hydroclimate settings. Results show that climate forcings reproducing the P-T cross-correlation yield lesser root mean square errors in simulated hydrologic variables (primarily on the sub-surface variables) as compared to climate forcings that neglect the P-T cross-correlation. Impacts of P-T cross-correlation on hydrologic simulations were remarkable to low flow and sub-surface variables whereas less significant to flow variables that exhibit higher variability. We found that hydrologic variables with lower internal variability (for example: groundwater and soil-moisture depth) are susceptible to the bias in P-T cross-correlation. These findings have potential implications in using univariate linear downscaling techniques to bias-correct GCM forcings, since univariate linear bias-correction techniques reproduce the GCM estimated P-T cross-correlation without correcting the bias in P-T cross-correlation
