Evidence for an Additional Heat Source in the Warm Ionized Medium of Galaxies

Spatial variations of the [S II]/H-Alpha and [N II]/H-Alpha line intensity ratios observed in the gaseous halo of the Milky Way and other galaxies are inconsistent with pure photoionization models. They appear to require a supplemental heating mechanism that increases the electron temperature at low densities n_e. This would imply that in addition to photoionization, which has a heating rate per unit volume proportional to n_e^2, there is another source of heat with a rate per unit volume proportional to a lower power of n_e. One possible mechanism is the dissipation of interstellar plasma turbulence, which according to Minter & Spangler (1997) heats the ionized interstellar medium in the Milky Way at a rate ~ 1x10^-25 n_e ergs cm^-3 s^-1. If such a source were present, it would dominate over photoionization heating in regions where n_e < 0.1 cm^-3, producing the observed increases in the [S II]/H-Alpha and [N II]/H-Alpha intensity ratios at large distances from the galactic midplane, as well as accounting for the constancy of [S II]/[N II], which is not explained by pure photoionization. Other supplemental heating sources, such as magnetic reconnection, cosmic rays, or photoelectric emission from small grains, could also account for these observations, provided they supply to the warm ionized medium ~ 10^-5 ergs s^-1 per cm^2 of Galactic disk.Comment: 10 pages, 1 figur

FUSE Detection of Galactic OVI Emission in the Halo above the Perseus Arm

Background observations obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) toward l=95.4, b=36.1 show OVI 1032,1038 in emission. This sight line probes a region of stronger-than-average soft X-ray emission in the direction of high-velocity cloud Complex C above a part of the disk where Halpha filaments rise into the halo. The OVI intensities, 1600+/-300 ph/s/cm^2/sr (1032A) and 800+/-300 ph/s/cm^2/sr (1038A), are the lowest detected in emission in the Milky Way to date. A second sight line nearby (l=99.3, b=43.3) also shows OVI 1032 emission, but with too low a signal-to-noise ratio to obtain reliable measurements. The measured intensities, velocities, and FWHMs of the OVI doublet and the CII* line at 1037A are consistent with a model in which the observed emission is produced in the Galactic halo by hot gas ejected by supernovae in the Perseus arm. An association of the observed gas with Complex C appears unlikely.Comment: accepted for publication in ApJL, 11 pages including 3 figure

WHAM Observations of H-Alpha, [S II], and [N II] toward the Orion and Perseus Arms: Probing the Physical Conditions of the Warm Ionized Medium

A large portion of the Galaxy (l = 123 deg to 164 deg, b = -6 deg to -35 deg), which samples regions of the Local (Orion) spiral arm and the more distant Perseus arm, has been mapped with the Wisconsin H-Alpha Mapper (WHAM) in the H-Alpha, [S II] 6716, and [N II] 6583 lines. Several trends noticed in emission-line investigations of diffuse gas in other galaxies are confirmed in the Milky Way and extended to much fainter emission. We find that the [S II]/H-Alpha and [N II]/H-Alpha ratios increase as absolute H-Alpha intensities decrease. For the more distant Perseus arm emission, the increase in these ratios is a strong function of Galactic latitude and thus, of height above the Galactic plane. The [S II]/[N II] ratio is relatively independent of H-Alpha intensity. Scatter in this ratio appears to be physically significant, and maps of it suggest regions with similar ratios are spatially correlated. The Perseus arm [S II]/[N II] ratio is systematically lower than Local emission by 10%-20%. With [S II]/[N II] fairly constant over a large range of H-Alpha intensities, the increase of [S II]/H-Alpha and [N II]/H-Alpha with |z| seems to reflect an increase in temperature. Such an interpretation allows us to estimate the temperature and ionization conditions in our large sample of observations. We find that WIM temperatures range from 6,000 K to 9,000 K with temperature increasing from bright to faint H-Alpha emission (low to high [S II]/H-Alpha and [N II]/H-Alpha) respectively. Changes in [S II]/[N II] appear to reflect changes in the local ionization conditions (e.g. the S+/S++ ratio). We also measure the electron scale height in the Perseus arm to be 1.0+/-0.1 kpc, confirming earlier, less accurate determinations.Comment: 28 pages, 10 figures. Figures 2 and 3 are full color--GIFs provided here, original PS figures at link below. Accepted for publication in ApJ. More information about the WHAM project can be found at http://www.astro.wisc.edu/wham/ . REVISION: Figure 6, bottom panel now contains the proper points. No other changes have been mad

Observation of electronic and atomic shell effects in gold nanowires

The formation of gold nanowires in vacuum at room temperature reveals a periodic spectrum of exceptionally stable diameters. This is identified as shell structure similar to that which was recently discovered for alkali metals at low temperatures. The gold nanowires present two competing `magic' series of stable diameters, one governed by electronic structure and the other by the atomic packing.Comment: 4 pages, 4 figure

Investigation of the μ- and κ-opioid receptor activation by eight new synthetic opioids using the [35^{35}S]-GTPγS assay: U-47700, isopropyl U-47700, U-49900, U-47931E, N-methyl U-47931E, U-51754, U-48520, and U-48800

In 2009, new synthetic opioids appeared on the new psychoactive substances market. This class of new psychoactive substances generally poses a health risk due to the high affinity and potency of most of these compounds for the opioid receptors. It is known that overdoses can lead to respiratory depression and result in death. However, for many new synthetic opioids, data on toxicological and toxicokinetic properties are scarce. In the present study, eight U-opioids were investigated for their structure activity relationships at the μ- and κ-opioid receptors using a [$^{35}$S]-GTPγS assay. The potencies of the investigated U-opioids were lower than those of the reference compounds (μ-opioid receptor: hydromorphone, fentanyl; κ-opioid receptor: U-69593, U-50488). At the μ-opioid receptor, U-47700 showed the highest potency with an EC$_{50}$ value of 111 nM, and at the κ-opioid receptor, U-51754 was found to be the most potent compound with an EC$_{50}$ value of 120 nM. The following structural features were advantageous for activating the μ-opioid receptor: two chlorine substituents in 3,4-position at the aromatic ring, the absence of the methylene group between the amide group and the aromatic ring, a methyl group at the amide nitrogen, and/or a dimethylamine residue at the amine nitrogen of the cyclohexane ring. Further, the following structural features were beneficial for κ-opioid receptor activation: a methylene group between the amide group and the aromatic ring, a pyrrolidine residue at the amine nitrogen of the cyclohexane ring, a methyl group at the amide nitrogen, and/or a chlorine substitution at the 3,4-position of the aromatic ring

Multi-element fingerprinting of waters to evaluate connectivity among depressional wetlands

Establishing the connectivity among depressional wetlands is important for their proper management, conservation and restoration. In this study, the concentrations of 38 elements in surface water and porewater of depressional wetlands were investigated to determine chemical and hydrological connectivity of three hydrological types: recharge, flow-through, and discharge, in the Prairie Pothole Region of North America. Most element concentrations of porewater varied significantly by wetland hydrologic type (p \u3c 0.05), and increased along a recharge to discharge hydrologic gradient. Significant spatial variation of element concentrations in surface water was observed in discharge wetlands. Generally, higher element concentrations occurred in natural wetlands compared to wetlands with known disturbances (previous drainage and grazing). Electrical conductivity explained 42.3% and 30.5% of the variation of all element concentrations in porewater and surface water. Non-metric multidimensional scaling analysis showed that the similarity decreased from recharge to flowthrough to discharge wetland in each sampling site. Cluster analysis confirmed that element compositions in porewater of interconnected wetlands were more similar to each other than to those of wetlands located farther away. Porewater and surface water in a restored wetland showed similar multi-element characteristics to natural wetlands. In contrast, depressional wetlands connected by seeps along a deactivated drain-tile path and a grazed wetland showed distinctly different multi-element characteristics compared to other wetlands sampled. Our findings confirm that the multi-element fingerprinting method can be useful for assessing hydro-chemical connectivity across the landscape, and indicate that element concentrations are not only affected by land use, but also by hydrological characteristics

Emergence of quasiparticle Bloch states in artificial crystals crafted atom-by-atom

The interaction of electrons with a periodic potential of atoms in crystalline solids gives rise to band structure. The band structure of existing materials can be measured by photoemission spectroscopy and accurately understood in terms of the tight-binding model, however not many experimental approaches exist that allow to tailor artificial crystal lattices using a bottom-up approach. The ability to engineer and study atomically crafted designer materials by scanning tunnelling microscopy and spectroscopy (STM/STS) helps to understand the emergence of material properties. Here, we use atom manipulation of individual vacancies in a chlorine monolayer on Cu(100) to construct one- and two-dimensional structures of various densities and sizes. Local STS measurements reveal the emergence of quasiparticle bands, evidenced by standing Bloch waves, with tuneable dispersion. The experimental data are understood in terms of a tight-binding model combined with an additional broadening term that allows an estimation of the coupling to the underlying substrate.Comment: 7 figures, 12 pages, main text and supplementary materia

Surface plasmon resonance biosensors for highly sensitive detection in real samples

In this work we summarize the main results obtained with the portable surface plasmon resonance (SPR) device developed in our group (commercialised by SENSIA, SL, Spain), highlighting its applicability for the real-time detection of extremely low concentrations of toxic pesticides in environmental water samples. In addition, we show applications in clinical diagnosis as, on the one hand, the real-time and label-free detection of DNA hybridization and single point mutations at the gene BRCA-1, related to the predisposition in women to develop an inherited breast cancer and, on the other hand, the analysis of protein biomarkers in biological samples (urine, serum) for early detection of diseases. Despite the large number of applications already proven, the SPR technology has two main drawbacks: (i) not enough sensitivity for some specific applications (where pM-fM or single-molecule detection are needed) (ii) low multiplexing capabilities. In order solve such drawbacks, we work in several alternative configurations as the Magneto-optical Surface Plasmon Resonance sensor (MOSPR) based on a combination of magnetooptical and ferromagnetic materials, to improve the SPR sensitivity, or the Localized Surface Plasmon Resonance (LSPR) based on nanostructures (nanoparticles, nanoholes,...), for higher multiplexing capabilities