638 research outputs found
Detectability of Glycine in Solar-type System Precursors
Glycine (NH2CH2COOH) is the simplest amino acid relevant for life. Its
detection in the interstellar medium is key to understand the formation
mechanisms of pre-biotic molecules and their subsequent delivery onto planetary
systems. Glycine has extensively been searched for toward hot molecular cores,
although these studies did not yield any firm detection. In contrast to hot
cores, low-mass star forming regions, and in particular their earliest stages
represented by cold pre-stellar cores, may be better suited for the detection
of glycine as well as more relevant for the study of pre-biotic chemistry in
young Solar System analogs. We present 1D spherically symmetric radiative
transfer calculations of the glycine emission expected to arise from the
low-mass pre-stellar core L1544. Water vapour has recently been reported toward
this core, indicating that a small fraction of the grain mantles in L1544
(~0.5%) has been injected into the gas phase. Assuming that glycine is
photo-desorbed together with water in L1544, and considering a solid abundance
of glycine on ices of ~1E-4 with respect to water, our calculations reveal that
several glycine lines between 67 GHz and 80 GHz have peak intensities larger
than 10 mK. These results show for the first time that glycine could reach
detectable levels in cold objects such as L1544. This opens up the possibility
to detect glycine, and other pre-biotic species, at the coldest and earliest
stages in the formation of Solar-type systems with near-future instrumentation
such as the Band 2 receivers of ALMA.Comment: 5 pages, 2 figures, 1 tables. Accepted for publication in ApJ Letter
Latent Tuberculosis Infection among Healthcare Students and Postgraduates in a Mediterranean Italian Area: What Correlation with Work Exposure?
Background: Tuberculosis screening is part of the standard protocol for evaluating the risk of infection in healthcare workers. The aim of this study was to evaluate the prevalence of latent tuberculosis infection (LTBI) among students attending various healthcare profession degree courses and postgraduate medical courses at the School of Medicine of the University of Palermo, Italy, and assess the possible professional origin of infection. Methods: In total, 2946 students (2082 undergraduates and 864 postgraduates) took part in a screening program for LTBI between January 2014 to April 2019 using the tuberculin skin test (TST). Students with a positive TST result underwent a Quantiferon-TB test (QFT). Results: Among the 2082 undergraduates, 23 (1.1%) had a positiveTST;theresultwasconfirmedwithQFTfor13(0.62%)ofthem. Amongthe864postgraduate students,24(2.78%)hadapositiveTSTandonly18(2.08%)showedapositiveQTF.Latenttuberculosis infectionsweresignificantlymorefrequentamongpostgraduatesthanundergraduates(2.08% > 0.62%, p < 0.0001). There was a higher number of subjects previously vaccinated for TB (18.87% > 0.24%, p < 0.0001), and of vaccinated subjects found positive for TST and QTF (66.67% > 7.69%, p = 0.001) in the postgraduate group. Conclusion: Latent TB is relatively low among medical school students in our geographic area. Nevertheless, this infectious disease must be regarded as a re-emerging biohazard for which preventive strategies are required to limit the risk of infection, especially among exposed workers
Codon and Reverse Codon: A Theoretical Approach to Reinterpret the Genetic Code Table
The genetic code table represents a fundamental scheme to translate a genetic code into a sequence of amino acids and, therefore, the possibility of operating the synthesis of all the proteins necessary for the life of organisms. Unfortunately, the various biological mechanisms are not fully clear. Hence, in this report, we analyzed the genetic code table and the amino acids codified by codons with an original theoretical and statistical approach based on the concept of permutations. We found an interesting reinterpretation of many codons, as reverse codons, which could help clarify some as-yet-unknown aspects in the field of protein folding
The dynamical properties of dense filaments in the infrared dark cloud G035.39-00.33
Infrared Dark Clouds (IRDCs) are unique laboratories to study the initial
conditions of high-mass star and star cluster formation. We present
high-sensitivity and high-angular resolution IRAM PdBI observations of N2H+
(1-0) towards IRDC G035.39-00.33. It is found that G035.39-00.33 is a highly
complex environment, consisting of several mildly supersonic filaments
(sigma_NT/c_s ~1.5), separated in velocity by <1 km s^-1 . Where multiple
spectral components are evident, moment analysis overestimates the non-thermal
contribution to the line-width by a factor ~2. Large-scale velocity gradients
evident in previous single-dish maps may be explained by the presence of
substructure now evident in the interferometric maps. Whilst global velocity
gradients are small (<0.7 km s^-1 pc^-1), there is evidence for dynamic
processes on local scales (~1.5-2.5 km s^-1 pc^-1 ). Systematic trends in
velocity gradient are observed towards several continuum peaks. This suggests
that the kinematics are influenced by dense (and in some cases, starless)
cores. These trends are interpreted as either infalling material, with
accretion rates ~(7 \pm 4)x10^-5 M_sun yr^-1 , or expanding shells with
momentum ~24 \pm 12 M_sun km s^-1 . These observations highlight the importance
of high-sensitivity and high-spectral resolution data in disentangling the
complex kinematic and physical structure of massive star forming regions.Comment: 25 pages, 23 figures, accepted for publication in MNRA
Regenerative medicine: shedding light into the link between aging and cancer
The evidence linking aging and cancer is overwhelming. Findings emerging from the field of regenerative medicine reinforce the notion that aging and cancer are profoundly interrelated in their pathogenetic pathways. We discuss evidence to indicate that age-associated alterations in the tissue microenvironment contribute to the emergence of a neoplastic-prone tissue landscape, which is able to support the selective growth of pre-neoplastic cell populations. Interestingly, tissue contexts that are able to select for the growth of pre-neoplastic cells, including the aged liver microenvironment, are also supportive for the clonal expansion of normal, homotypic, transplanted cells. This suggests that the growth of normal and pre-neoplastic cells is possibly driven by similar mechanisms, implying that strategies based on principles of regenerative medicine might be applicable to modulate neoplastic disease
A Virialized Filamentary Infrared Dark Cloud
The initial conditions of massive star and star cluster formation are
expected to be cold, dense and high column density regions of the interstellar
medium, which can reveal themselves via near, mid and even far-infrared
absorption as Infrared Dark Clouds (IRDCs). Elucidating the dynamical state of
IRDCs thus constrains theoretical models of these complex processes. In
particular, it is important to assess whether IRDCs have reached virial
equilibrium, where the internal pressure balances that due to the
self-gravitating weight of the cloud plus the pressure of the external
environmental. We study this question for the filamentary IRDC G035.39-00.33 by
deriving mass from combined NIR & MIR extinction maps and velocity dispersion
from C18O (1-0) & (2-1) line emission. In contrast to our previous moderately
super-virial results based on 13CO emission and MIR-only extinction mapping,
with improved mass measurements we now find that the filament is consistent
with being in virial equilibrium, at least in its central parsec-wide region
where ~1000 M_Sun snakes along several parsecs. This equilibrium state does not
require large-scale net support or confinement by magnetic fields.Comment: 4 pages, 2 figures, Accepted to ApJ
Chemically modified β-cyclodextrins useful in developing biosensors of agricultural and food relevance
β-cyclodextrin (β-CD), a natural, non-toxic cycloeptaamilose macrocycle, is a useful biomatrix for immobilizing enzymes on a biosensor surface because of the affinity of its cavity for hydrophobic guest molecules (e.g., aminoacids). In this work β-CD has been successfully modified with different poly-carboxylic acids (PCAs) including 1,2,3,4-butanetetracarboxylic acid. Time activation, pH, pressure and stoichiometry were optimized in order to achieve selected substitutions on the
macrocycle hydroxy groups. The modified β-CDs, prepared under mild conditions, are completely water-soluble and could be grafted on a biosensor surface
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