Universality in molecular halo clusters

Ground state of weakly bound dimers and trimers with a radius extending well into the classically forbidden region is explored, with the goal to test the predicted universality of quantum halo states. The focus of the study are molecules consisting of T$\downarrow$, D$\downarrow$, $^3$He, $^4$He and alkali atoms, where interaction between particles is much better known than in the case of nuclei, which are traditional examples of quantum halos. The study of realistic systems is supplemented by model calculations in order to analyze how low-energy properties depend on the interaction potential. The use of variational and diffusion Monte Carlo methods enabled very precise calculation of both size and binding energy of the trimers. In the quantum halo regime, and for large values of scaled binding energies, all clusters follow almost the same universal line. As the scaled binding energy decreases, Borromean states separate from tango trimers.Comment: 5 pages, 3 figures, accepted for publication in Phys. Rev. Let

Električna vodljivost, Hallov koeficijent i termoelektrična snaga ikosaedarskih i-Al 62Cu25.5Fe12.5 i i-Al63Cu25Fe12 kvazikristala

The electrical conductivity, Hall coefficient and thermoelectric power of icosahedral i-Al62Cu25.5Fe12.5 quasicrystal samples in the temperature range 2 K - 340 K are measured, and comparison with icosahedral i-Al63Cu25Fe12 quasicrystal samples is made. We have analysed the temperature dependence of the conductivity below 70 K and the results of this analysis are consistent with the predictions of the weak-localisation and the electron-electron interaction theories. The temperature dependence of the electrical conductivity, Hall coefficient and thermoelectric power above 40 K are consistently explained by a two-band model. Although the overlapping of the valence and conduction bands at Fermi level is responsible for the coexistence of both types of carriers, and it enables us to describe quasicrystals as semi-metals, the temperature variation of the electrical conductivity is determined by that of carrier density which makes the situation essentially the same as that in normal semiconductors.Mjerili smo električnu vodljivost, Hallov koeficijent i termoelektričnu snagu uzorka ikosaedarskog kvazikristala i-Al62Cu25.5Fe12.5 u području temperature 2 K – 340 K i usporedili s uzorkom ikosaedarskog kvazikristala i-Al62Cu25.5Fe12.5. Analizirali smo temperaturnu ovisnost električne vodljivosti ispod 70 K i ustanovili da su rezultati u skladu s predviđanjima teorija slabe lokalizacije i međudjelovanja elektronelektron. Ovisnost električne vodljivosti, Hallovog koeficijenta i termoelektrične snage o temperaturi iznad 40 K uspješno se objašnjava modelom dviju vrpci. Iako je predodžba o preklapanju valentne i vodljive vrpce na Fermijevoj razini odgovorna za istovremeno postojanje dviju vrsta nositelja i za opis kvazikristala kao polumetala, temperaturna ovisnost električne vodljivosti je, kao i kod normalnih poluvodiča, određena promjenom gustoće nositelja

Električna vodljivost, Hallov koeficijent i termoelektrična snaga ikosaedarskih i-Al 62Cu25.5Fe12.5 i i-Al63Cu25Fe12 kvazikristala

The electrical conductivity, Hall coefficient and thermoelectric power of icosahedral i-Al62Cu25.5Fe12.5 quasicrystal samples in the temperature range 2 K - 340 K are measured, and comparison with icosahedral i-Al63Cu25Fe12 quasicrystal samples is made. We have analysed the temperature dependence of the conductivity below 70 K and the results of this analysis are consistent with the predictions of the weak-localisation and the electron-electron interaction theories. The temperature dependence of the electrical conductivity, Hall coefficient and thermoelectric power above 40 K are consistently explained by a two-band model. Although the overlapping of the valence and conduction bands at Fermi level is responsible for the coexistence of both types of carriers, and it enables us to describe quasicrystals as semi-metals, the temperature variation of the electrical conductivity is determined by that of carrier density which makes the situation essentially the same as that in normal semiconductors.Mjerili smo električnu vodljivost, Hallov koeficijent i termoelektričnu snagu uzorka ikosaedarskog kvazikristala i-Al62Cu25.5Fe12.5 u području temperature 2 K – 340 K i usporedili s uzorkom ikosaedarskog kvazikristala i-Al62Cu25.5Fe12.5. Analizirali smo temperaturnu ovisnost električne vodljivosti ispod 70 K i ustanovili da su rezultati u skladu s predviđanjima teorija slabe lokalizacije i međudjelovanja elektronelektron. Ovisnost električne vodljivosti, Hallovog koeficijenta i termoelektrične snage o temperaturi iznad 40 K uspješno se objašnjava modelom dviju vrpci. Iako je predodžba o preklapanju valentne i vodljive vrpce na Fermijevoj razini odgovorna za istovremeno postojanje dviju vrsta nositelja i za opis kvazikristala kao polumetala, temperaturna ovisnost električne vodljivosti je, kao i kod normalnih poluvodiča, određena promjenom gustoće nositelja

Spin-polarized hydrogen and its isotopes: a rich class of quantum phases (Review Article)

We review the recent activity in the theoretical description of spin-polarized atomic hydrogen and its isotopes at very low temperatures. Spin-polarized hydrogen is the only system in nature that remains stable in the gas phase even in the zero temperature limit due to its small mass and weak interatomic interaction. Hydrogen and its heavier isotope tritium are bosons, the heavier mass of tritium producing a self-bound (liquid) system at zero temperature. The other isotope, deuterium, is a fermion with nuclear spin one making possible the study of three different quantum systems depending on the population of the three degenerate spin states. From the theoretical point of view, spin-polarized hydrogen is specially appealing because its interatomic potential is very accurately known making possible its precise quantum many-body study. The experimental study of atomic hydrogen has been very difficult due to its high recombination rate, but it finally led to its Bose–Einstein condensate state in 1998. Degeneracy has also been observed in thin films of hydrogen adsorbed on the ⁴He surface allowing for thepossibility of observing the Berezinskii–Kosterlitz–Thouless superfluid transition

Associating Air Pollution with Cytokinesis-Block Micronucleus Assay Parameters in Lymphocytes of the General Population in Zagreb (Croatia).

Air pollution is recognized as one of the most serious public health issues worldwide and was declared to be a leading environmental cause of cancer deaths. At the same time, the cytokinesis-block micronucleus (CBMN) assay serves as a cancer predictive method that is extensively used in human biomonitoring for populations exposed to environmental contamination. The objective of this cross-sectional study is two-fold: to evaluate genomic instability in a sample (N = 130) of healthy, general population residents from Zagreb (Croatia), chronically exposed to different levels of air pollution, and to relate them to air pollution levels in the period from 2011 to 2015. Measured frequencies of CBMN assay parameters were in agreement with the baseline data for the general population of Croatia. Air pollution exposure was based on four factors obtained from a factor analysis of all exposure data obtained for the examined period. Based on the statistical results, we did not observe a significant positive association between any of the CBMN assay parameters tested and measured air pollution parameters for designated time windows, except for benzo(a)pyrene (B[a]P) that showed significant negative association. Our results show that measured air pollution parameters are largely below the regulatory limits, except for B[a]P, and as such, they do not affect CBMN assay parameters' frequency. Nevertheless, as air pollution is identified as a major health threat, it is necessary to conduct prospective studies investigating the effect of air pollution on genome integrity and human health

Air Pollution and Primary DNA Damage among Zagreb (Croatia) Residents: A Cross-Sectional Study.

More than eight million premature deaths annually can be attributed to air pollution, with 99% of the world's population residing in areas below recommended air quality standards. Hence, the present study aimed to examine the association between primary DNA damage and air pollution data among 123 participants enrolled between 2011 and 2015 in Zagreb, Croatia. While most measured air pollutants adhered to regulatory limits, benzo[a]pyrene concentrations bound to PM <sub>10</sub> exceeded them. Factorial analysis narrowed down air pollution data to four exposure factors (particulate matter, two metal factors, and other pollutants). Despite the absence of significant positive associations between modeled air pollution exposure factors and comet assay descriptors (tail length, tail intensity, tail moment, and highly damaged nuclei), the critical health implications of air pollution warrant further investigations, particularly with biomarkers of exposure and different biomarkers of effect in populations facing air pollution exposure

Wide-field CO isotopologue emission and the CO-to-H2_2 factor across the nearby spiral galaxy M101

Carbon monoxide (CO) emission is the most widely used tracer of the bulk molecular gas in the interstellar medium (ISM) in extragalactic studies. The CO-to-H$_2$ conversion factor, $\alpha_{\rm CO}$, links the observed CO emission to the total molecular gas mass. However, no single prescription perfectly describes the variation of $\alpha_{\rm CO}$ across all environments across galaxies as a function of metallicity, molecular gas opacity, line excitation, and other factors. Using resolved spectral line observations of CO and its isotopologues, we can constrain the molecular gas conditions and link them to a variation in the conversion factor. We present new IRAM 30-m 1mm and 3mm line observations of $^{12}$CO, $^{13}$CO, and C$^{18}$O} across the nearby galaxy M101. Based on the CO isotopologue line ratios, we find that selective nucleosynthesis and opacity changes are the main drivers of the variation in the line emission across the galaxy. Furthermore, we estimated $\alpha_{\rm CO(1-0)}$ using different approaches, including (i) the dust mass surface density derived from far-IR emission as an independent tracer of the total gas surface density and (ii) LTE-based measurements using the optically thin $^{13}$CO(1-0) intensity. We find an average value of $\alpha_{\rm CO}=4.4{\pm}0.9\rm\,M_\odot\,pc^{-2}(K\,km\,s^{-1})^{-1}$ across the galaxy, with a decrease by a factor of 10 toward the 2 kpc central region. In contrast, we find LTE-based values are lower by a factor of 2-3 across the disk relative to the dust-based result. Accounting for $\alpha_{\rm CO}$ variations, we found significantly reduced molecular gas depletion time by a factor 10 in the galaxy's center. In conclusion, our result suggests implications for commonly derived scaling relations, such as an underestimation of the slope of the Kennicutt Schmidt law, if $\alpha_{\rm CO}$ variations are not accounted for.Comment: Accepted for publication in A&A, 25 pages, 15 figure

A constant N2_2H+^+(1-0)-to-HCN(1-0) ratio on kiloparsec scales

Nitrogen hydrides such as NH$_3$ and N$_2$H$^+$ are widely used by Galactic observers to trace the cold dense regions of the interstellar medium. In external galaxies, because of limited sensitivity, HCN has become the most common tracer of dense gas over large parts of galaxies. We provide the first systematic measurements of N$_2$H$^+$(1-0) across different environments of an external spiral galaxy, NGC6946. We find a strong correlation ($r>0.98,p<0.01$) between the HCN(1-0) and N$_2$H$^+$(1-0) intensities across the inner $\sim8\mathrm{kpc}$ of the galaxy, at kiloparsec scales. This correlation is equally strong between the ratios N$_2$H$^+$(1-0)/CO(1-0) and HCN(1-0)/CO(1-0), tracers of dense gas fractions ($f_\mathrm{dense}$). We measure an average intensity ratio of N$_2$H$^+$(1-0)/HCN(1-0)$=0.15\pm0.02$ over our set of five IRAM-30m pointings. These trends are further supported by existing measurements for Galactic and extragalactic sources. This narrow distribution in the average ratio suggests that the observed systematic trends found in kiloparsec-scale extragalactic studies of $f_\mathrm{dense}$ and the efficiency of dense gas (SFE$_\mathrm{dense}$) would not change if we employed N$_2$H$^+$(1-0) as a more direct tracer of dense gas. At kiloparsec scales our results indicate that the HCN(1-0) emission can be used to predict the expected N$_2$H$^+$(1-0) over those regions. Our results suggest that, even if HCN(1-0) and N$_2$H$^+$(1-0) trace different density regimes within molecular clouds, subcloud differences average out at kiloparsec scales, yielding the two tracers proportional to each other.Comment: Accepted for publication in Astronomy & Astrophysic

HCN emission from translucent gas and UV-illuminated cloud edges revealed by wide-field IRAM 30m maps of Orion B GMC: Revisiting its role as tracer of the dense gas reservoir for star formation

We present 5 deg^2 (~250 pc^2) HCN, HNC, HCO+, and CO J=1-0 maps of the Orion B GMC, complemented with existing wide-field [CI] 492 GHz maps, as well as new pointed observations of rotationally excited HCN, HNC, H13CN, and HN13C lines. We detect anomalous HCN J=1-0 hyperfine structure line emission almost everywhere in the cloud. About 70% of the total HCN J=1-0 luminosity arises from gas at A_V < 8 mag. The HCN/CO J=1-0 line intensity ratio shows a bimodal behavior with an inflection point at A_V < 3 mag typical of translucent gas and UV-illuminated cloud edges. We find that most of the HCN J=1-0 emission arises from extended gas with n(H2) < 10^4 cm^-3, even lower density gas if the ionization fraction is > 10^-5 and electron excitation dominates. This result explains the low-A_V branch of the HCN/CO J=1-0 intensity ratio distribution. Indeed, the highest HCN/CO ratios (~0.1) at A_V < 3 mag correspond to regions of high [CI] 492 GHz/CO J=1-0 intensity ratios (>1) characteristic of low-density PDRs. Enhanced FUV radiation favors the formation and excitation of HCN on large scales, not only in dense star-forming clumps. The low surface brightness HCN and HCO+ J=1-0 emission scale with I_FIR (a proxy of the stellar FUV radiation field) in a similar way. Together with CO J=1-0, these lines respond to increasing I_FIR up to G0~20. On the other hand, the bright HCN J=1-0 emission from dense gas in star-forming clumps weakly responds to I_FIR once the FUV radiation field becomes too intense (G0>1500). The different power law scalings (produced by different chemistries, densities, and line excitation regimes) in a single but spatially resolved GMC resemble the variety of Kennicutt-Schmidt law indexes found in galaxy averages. As a corollary for extragalactic studies, we conclude that high HCN/CO J=1-0 line intensity ratios do not always imply the presence of dense gas.Comment: accepted for publication in A&A. 24 pages, 18 figures, plus Appendix. Abridged Abstract. English language not edite

Comparing the pre-SNe feedback and environmental pressures for 6000 HII regions across 19 nearby spiral galaxies

The feedback from young stars (i.e. pre-supernova) is thought to play a crucial role in molecular cloud destruction. In this paper, we assess the feedback mechanisms acting within a sample of 5810 HII regions identified from the PHANGS-MUSE survey of 19 nearby ($1$, and expanding, yet there is a small sample of compact HII regions with $P_\mathrm{tot,max}/P_\mathrm{de} < 1$ ($\sim$1% of the sample). These mostly reside in galaxy centres ($R_\mathrm{gal}<1$kpc), or, specifically, environments of high gas surface density; log($\Sigma_\mathrm{gas}/\mathrm{M_\odot} \mathrm{pc}^{-2}$)$\sim$2.5 (measured on kpc-scales). Lastly, we compare to a sample of literature measurements for $P_\mathrm{therm}$ and $P_\mathrm{rad}$ to investigate how dominant pressure term transitions over around 5dex in spatial dynamic range and 10 dex in pressure