Far-infrared spectra of lateral quantum dot molecules

We study effects of electron-electron interactions and confinement potential on the magneto-optical absorption spectrum in the far-infrared range of lateral quantum dot molecules. We calculate far-infrared (FIR) spectra for three different quantum dot molecule confinement potentials. We use accurate exact diagonalization technique for two interacting electrons and calculate dipole-transitions between two-body levels with perturbation theory. We conclude that the two-electron FIR spectra directly reflect the symmetry of the confinement potential and interactions cause only small shifts in the spectra. These predictions could be tested in experiments with nonparabolic quantum dots by changing the number of confined electrons. We also calculate FIR spectra for up to six noninteracting electrons and observe some additional features in the spectrum.Comment: For better quality Figs download manuscript from http://www.fyslab.hut.fi/~mma/FIR/Helle_qdmfir.ps.g

Search for grain growth towards the center of L1544

In dense and cold molecular clouds dust grains are surrounded by thick icy mantles. It is however not clear if dust growth and coagulation take place before the switch-on of a protostar. This is an important issue, as the presence of large grains may affect the chemical structure of dense cloud cores, including the dynamically important ionization fraction, and the future evolution of solids in protoplanetary disks. To study this further, we focus on L1544, one of the most centrally concentrated pre-stellar cores on the verge of star formation, and with a well-known physical structure. We observed L1544 at 1.2 and 2 mm using NIKA, a new receiver at the IRAM 30 m telescope, and we used data from the Herschel Space Observatory archive. We find no evidence of grain growth towards the center of L1544 at the available angular resolution. Therefore, we conclude that single dish observations do not allow us to investigate grain growth toward the pre-stellar core L1544 and high sensitivity interferometer observations are needed. We predict that dust grains can grow to 200 $\mu$m in size toward the central ~300 au of L1544. This will imply a dust opacity change by a factor of ~2.5 at 1.2 mm, which can be detected using the Atacama Large Millimeter and submillimeter Array (ALMA) at different wavelengths and with an angular resolution of 2".Comment: 12 pages, 14 figures. Accepted for publication in A&

Two-electron lateral quantum-dot molecules in a magnetic field

Laterally coupled quantum dot molecules are studied using exact diagonalization techniques. We examine the two-electron singlet-triplet energy difference as a function of magnetic field strength and investigate the magnetization and vortex formation of two- and four-minima lateral quantum dot molecules. Special attention is paid to the analysis of how the distorted symmetry affects the properties of quantum-dot molecules.Comment: 18 pages, 26 figure

Millimeter and Submillimeter Survey of the R Corona Australis Region

Using a combination of data from the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO), the Arizona Radio Observatory Kitt Peak 12m telescope and the Arizona Radio Observatory 10m Heinrich Hertz Telescope, we have studied the most active part of the R CrA molecular cloud in multiple transitions of Carbon Monoxide, HCO$^+$ and 870\micron continuum emission. Since R CrA is nearby (130 pc), we are able to obtain physical spatial resolution as high as 0.01pc over an area of 0.16 pc$^2$, with velocity resolution finer than 1 km/s. Mass estimates of the protostar driving the mm-wave emission derived from HCO$^+$, dust continuum emission and kinematic techniques point to a young, deeply embedded protostar of $\sim$0.5-0.75 M$_\odot$, with a gaseous envelope of similar mass. A molecular outflow is driven by this source that also contains at least 0.8 M$_\odot$ of molecular gas with $\sim$0.5 L$_\odot$ of mechanical luminosity. HCO$^+$ lines show the kinematic signature of infall motions as well as bulk rotation. The source is most likely a Class 0 protostellar object not yet visible at near-IR wavelengths. With the combination of spatial and spectral resolution in our data set, we are able to disentangle the effects of infall, rotation and outflow towards this young object.Comment: 29 pages, 9 figures. Accepted for publication in the Astrophysical Journa

C18O (3-2) observations of the Cometary Globule CG 12: a cold core and a C18O hot spot

The feasibility of observing the C18O (3-2) spectral line in cold clouds with the APEX telescope has been tested. As the line at 329.330 GHz lies in the wing of a strong atmospheric H2O absorption it can be observed only at high altitude observatories. Using the three lowest rotational levels instead of only two helps to narrow down the physical properties of dark clouds and globules. The centres of two C18O maxima in the high latitude low mass star forming region CG 12 were mapped in C18O (3-2) and the data were analyzed together with spectral line data from the SEST. The T_MB(3-2)/T_MB(2-1) ratio in the northern C18O maximum, CG 12 N, is 0.8, and in the southern maximum, CG 12 S, ~2. CG 12 N is modelled as a 120'' diameter (0.4pc) cold core with a mass of 27 Msun. A small size maximum with a narrow, 0.8 kms-1, C18O (3-2) spectral line with a peak temperature of T_MB ~11 K was detected in CG 12 S. This maximum is modelled as a 60'' to 80'' diameter (~0.2pc) hot (80 K < Tex < 200 K) ~1.6 Msun clump. The source lies on the axis of a highly collimated bipolar molecular outflow near its driving source. This is the first detection of such a compact, warm object in a low mass star forming region.Comment: APEX A&A special issue, accepte

Glutathione s-transferase omega in the lung and sputum supernatants of COPD patients

BACKGROUND: The major contribution to oxidant related lung damage in COPD is from the oxidant/antioxidant imbalance and possibly impaired antioxidant defence. Glutathione (GSH) is one of the most important antioxidants in human lung and lung secretions, but the mechanisms participating in its homeostasis are partly unclear. Glutathione-S-transferase omega (GSTO) is a recently characterized cysteine containing enzyme with the capability to bind and release GSH in vitro. GSTO has not been investigated in human lung or lung diseases. METHODS: GSTO1-1 was investigated by immunohistochemistry and Western blot analysis in 72 lung tissue specimens and 40 sputum specimens from non-smokers, smokers and COPD, in bronchoalveolar lavage fluid and in plasma from healthy non-smokers and smokers. It was also examined in human monocytes and bronchial epithelial cells and their culture mediums in vitro. RESULTS: GSTO1-1 was mainly expressed in alveolar macrophages, but it was also found in airway and alveolar epithelium and in extracellular fluids including sputum supernatants, bronchoalveolar lavage fluid, plasma and cell culture mediums. The levels of GSTO1-1 were significantly lower in the sputum supernatants (p = 0.023) and lung homogenates (p = 0.003) of COPD patients than in nonsmokers. CONCLUSION: GSTO1-1 is abundant in the alveolar macrophages, but it is also present in extracellular fluids and in airway secretions, the levels being decreased in COPD. The clinical significance of GSTO1-1 and its role in regulating GSH homeostasis in airway secretions, however, needs further investigations

Electronic structure of rectangular quantum dots

We study the ground state properties of rectangular quantum dots by using the spin-density-functional theory and quantum Monte Carlo methods. The dot geometry is determined by an infinite hard-wall potential to enable comparison to manufactured, rectangular-shaped quantum dots. We show that the electronic structure is very sensitive to the deformation, and at realistic sizes the non-interacting picture determines the general behavior. However, close to the degenerate points where Hund's rule applies, we find spin-density-wave-like solutions bracketing the partially polarized states. In the quasi-one-dimensional limit we find permanent charge-density waves, and at a sufficiently large deformation or low density, there are strongly localized stable states with a broken spin-symmetry.Comment: 8 pages, 9 figures, submitted to PR

Genotyping of clinically relevant human adenoviruses by array-in-well hybridization assay

AbstractA robust oligonucleotide array-in-well hybridization assay using novel up-converting phosphor reporter technology was applied for genotyping clinically relevant human adenovirus types. A total of 231 adenovirus-positive respiratory, ocular swab, stool and other specimens from 219 patients collected between April 2010 and April 2011 were included in the study. After a real-time PCR amplification targeting the adenovirus hexon gene, the array-in-well assay identified the presence of B03 (n = 122; 57.5% of patients), E04 (29; 13.7%), C02 (21; 9.9%), D37 (14; 6.6%), C01 (12; 5.7%), C05 (5; 2.4%), D19 (4; 1.9%), C06 (2; 0.9%), D08 (1; 0.5%), A31 (1; 0.5%) and F41 (1; 0.5%) genotypes among the clinical sample panel. The typing result was obtained for all specimens that could be amplified (n = 223; 97%), and specificity of the typing was confirmed by sequencing specimens representing each of the different genotypes. No hybridization signal was obtained in adenovirus-negative specimens or specimens with other viruses (n = 30). The array-in-well hybridization assay has great potential as a rapid and multiplex platform for the typing of clinically relevant human adenovirus genotypes in different specimen types

Scaling in the correlation energies of two-dimensional artificial atoms

We find an unexpected scaling in the correlation energy of artificial atoms, i.e., harmonically confined two-dimensional quantum dots. The scaling relation is found through extensive numerical examinations including Hartree-Fock, variational quantum Monte Carlo, density-functional, and full configuration-interaction calculations. We show that the correlation energy, i.e., the true ground-state total energy subtracted by the Hartree-Fock total energy, follows a simple function of the Coulomb energy, confimenent strength and, the number of electrons. We find an analytic expression for this function, as well as for the correlation energy per particle and for the ratio between the correlation and total energies. Our tests for independent diffusion Monte Carlo and coupled-cluster results for quantum dots -- including open-shell data -- confirm the generality of the obtained scaling. As the scaling is also well applicable to $\gtrsim$ 100 electrons, our results give interesting prospects for the development of correlation functionals within density-functional theory.Comment: Accepted to Journal of Physics: Condensed Matte

Detection of H2D+ in a massive prestellar core in Orion B

Aims. The purpose of this study is to examine the prediction that the deuterated H3+ ion, H2D+, can be found exclusively in the coldest regions of molecular cloud cores. This is also a feasibility study for the detection of the ground-state line of ortho-H2D+ at 372 GHz with APEX. Methods. The 1(10)-1(11) transition of H2D+ at 372 GHz was searched towards selected positions in the massive star forming cloud OriB9, in the dark cloud L183, and in the low- to intermediate mass star-forming cloud R CrA. Results. The line was detected in cold, prestellar cores in the regions of OriB9 and L183, but only upper limits were obtained towards other locations which either have elevated temperatures or contain a newly born star. The H2D+ detection towards OriB9 is the first one in a massive star-forming region. The fractional ortho-H2D+ abundances (relative to H2) are estimated to be about 1.0E-10 in two cold cores in OriB9, and 3.0E-10 in the cold core of L183. Conclusions. The H2D+ detection in OriB9 shows that also massive star forming regions contain very cold prestellar cores which probably have reached matured chemical composition characterized, e.g., by a high degree of deuterium fractionation. Besides as a tracer of the interior parts of prestellar cores, H2D+ may therefore be used to put contraints on the timescales related to massive star formation