596 research outputs found
Optical properties of the Ti surface structured by femtosecond laser beam
Wavelength-scaled periodic ripples formed on the Ti surface under the action
of femtosecond laser irradiation have been investigated. The ripples were oriented in
parallel to the incident light polarization. After initial formation of ripples, the following
laser induced chemical transformation of metallic Ti into dielectric compound was
established using the Raman scattering data. Weak Wood’s anomaly in the spectra on
light diffracted by the structured Ti surface testifies the minor plasmonic activity
PRUSSIC I - a JVLA survey of HCN/HCO+/HNC (1-0) emission in z3 dusty galaxies: Low dense-gas fractions in high-redshift star-forming galaxies
Dusty star-forming galaxies (DSFGs) at redshift z1 are among the most
vigorously star-forming galaxies in the Universe. However, their dense
(10 cm ) gas phase - typically traced by HCN(1-0) - remains
almost entirely unexplored: only two DSFGs have been detected in HCN(1-0) to
date. We present results of a JVLA survey of the J=1-0 transition of HCN, HCO+,
and HNC(1-0) in six strongly lensed DSFGs at z = 2.5 - 3.3, effectively
doubling the number of DSFGs with deep observations of these lines. We detect
HCN(1-0) emission in one source (J1202+5354, 4.4), with a tentative
HCO+ (1-0) detection in another (J1609+6045, 3.3). Spectral stacking
yields strict upper limits on the HCN/FIR (3.610) and
HCN/CO(1-0) ratios (0.045). The inferred HCN/FIR ratios (a proxy for the
star-formation efficiency) are consistent with those in z0 FIR-luminous
starbursts. However, the HCN/CO ratios - a proxy for the dense-gas fraction -
are a factor of a few lower than suggested by the two previous DSFG detections.
Our results imply that most DSFGs have low dense-gas fractions. A comparison
with Krumholz & Thompson (2007) models of star-forming galaxies indicates that
the bulk of gas in DSFGs is at lower densities (10 cm ),
similar to "normal" star-forming galaxies, rather than ultraluminous
starbursts.Comment: Submitted to A&A 28th April 2022, accepted 19th July 202
The influence of abiotic factors on the bloom-forming alga Ulva flexuosa (Ulvaceae, Chlorophyta): possibilities for the control of the green tides in freshwater ecosystems
In vitro activity of daptomycin, linezolid and rifampicin on Staphylococcus epidermidis biofilms
Owing to their massive use, Staphylococcus
epidermidis has recently developed significant resistance to
several antibiotics, and became one of the leading causes of
hospital-acquired infections. Current antibiotics are typically
ineffective in the eradication of bacteria in biofilmassociated
persistent infections. Accordingly, the paucity
of effective treatment against cells in this mode of growth
is a key factor that potentiates the need for new agents
active in the prevention or eradication of biofilms. Daptomycin
and linezolid belong to the novel antibiotic therapies
that are active against gram-positive cocci. On the other
hand, rifampicin has been shown to be one of the most
potent, prevalent antibiotics against S. epidermidis biofilms.
Therefore, the main aim of this study was to study
the susceptibility of S. epidermidis biofilm cells to the two
newer antimicrobial agents previously mentioned, and
compare the results obtained with the antimicrobial effect
of rifampicin, widely used in the prevention/treatment of
indwelling medical device infections. To this end the in
vitro activities of daptomycin, linezolid, and rifampicin on
S. epidermidis biofilms were accessed, using these antibiotics
at MIC and peak serum concentrations. The results
demonstrated that at MIC concentration, rifampicin was the
most effective antibiotic tested. At peak serum concentration,
both strains demonstrated similar susceptibility to
rifampicin and daptomycin, with colony-forming units
(CFUs) reductions of approximately 3–4 log10, with a
slightly lower response to linezolid, which was also more
strain dependent. However, considering all the parameters
studied, daptomycin was considered the most effective
antibiotic tested, demonstrating an excellent in vitro
activity against S. epidermidis biofilm cells. In conclusion,
this antibiotic can be strongly considered as an acceptable
therapeutic option for S. epidermidis biofilm-associated
infections and can represent a potential alternative to rifampicin
in serious infections where rifampicin resistance
becomes prevalent.Bruna Leite acknowledges the financial support from ISAC/Program Erasmus Munds External Cooperation and the IBB-Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, University of Minho, Campus of Gualtar. Fernanda Gomes and Pilar Teixeira fully acknowledge the financial support from Fundacao para a Ciencia e Tecnologia (FCT) through the grants SFRH/BD/32126/2006 and SFRH/BPD/26803/2006, respectively
Analysis of ground reaction force and electromyographic activity of the gastrocnemius muscle during double support
O documento em anexo encontra-se na versão post-print (versão corrigida pelo editor).Purpose: Mechanisms associated with energy expenditure during gait have been extensively researched and studied. According to the double-inverted pendulum model energy expenditure is higher during double support, as lower limbs need to work to redirect the centre of mass velocity. This study looks into how the ground reaction force (GRF) of one limb affects the muscle activity required by the medial gastrocnemius (MG) of the contralateral limb during step-to-step transition. Methods: Thirty-five subjects were monitored as to the MG electromyographic activity (EMGa) of one limb and the GRF of the contralateral limb during double support. Results: After determination of the Pearson correlation coefficient (r), a moderate correlation was observed between the MG EMGa of the dominant leg and the vertical (Fz) and anteroposterior (Fy) components of GRF of the non-dominant leg (r=0.797, p<0.0001; r=-0.807, p<0.0001) and a weak and moderate correlation was observed between the MG EMGa of the non-dominant leg and the Fz and Fy of the dominant leg, respectively (r=0.442, p=0.018; r=-0.684 p<0.0001). Conclusions: The results obtained suggest that during double support, GRF is
associated with the EMGa of the contralateral MG and that there is an increased dependence between the GRF of the non-dominant leg and the EMGa of the dominant MG
Toward an internally consistent astronomical distance scale
Accurate astronomical distance determination is crucial for all fields in
astrophysics, from Galactic to cosmological scales. Despite, or perhaps because
of, significant efforts to determine accurate distances, using a wide range of
methods, tracers, and techniques, an internally consistent astronomical
distance framework has not yet been established. We review current efforts to
homogenize the Local Group's distance framework, with particular emphasis on
the potential of RR Lyrae stars as distance indicators, and attempt to extend
this in an internally consistent manner to cosmological distances. Calibration
based on Type Ia supernovae and distance determinations based on gravitational
lensing represent particularly promising approaches. We provide a positive
outlook to improvements to the status quo expected from future surveys,
missions, and facilities. Astronomical distance determination has clearly
reached maturity and near-consistency.Comment: Review article, 59 pages (4 figures); Space Science Reviews, in press
(chapter 8 of a special collection resulting from the May 2016 ISSI-BJ
workshop on Astronomical Distance Determination in the Space Age
Opinion dynamics: models, extensions and external effects
Recently, social phenomena have received a lot of attention not only from
social scientists, but also from physicists, mathematicians and computer
scientists, in the emerging interdisciplinary field of complex system science.
Opinion dynamics is one of the processes studied, since opinions are the
drivers of human behaviour, and play a crucial role in many global challenges
that our complex world and societies are facing: global financial crises,
global pandemics, growth of cities, urbanisation and migration patterns, and
last but not least important, climate change and environmental sustainability
and protection. Opinion formation is a complex process affected by the
interplay of different elements, including the individual predisposition, the
influence of positive and negative peer interaction (social networks playing a
crucial role in this respect), the information each individual is exposed to,
and many others. Several models inspired from those in use in physics have been
developed to encompass many of these elements, and to allow for the
identification of the mechanisms involved in the opinion formation process and
the understanding of their role, with the practical aim of simulating opinion
formation and spreading under various conditions. These modelling schemes range
from binary simple models such as the voter model, to multi-dimensional
continuous approaches. Here, we provide a review of recent methods, focusing on
models employing both peer interaction and external information, and
emphasising the role that less studied mechanisms, such as disagreement, has in
driving the opinion dynamics. [...]Comment: 42 pages, 6 figure
The ALMA REBELS Survey: Discovery of a massive, highly star-forming and morphologically complex ULIRG at
We present Atacama Large Millimeter/Submillimeter Array (ALMA) [CII] and
continuum observations of REBELS-25, a massive,
morphologically complex ultra-luminous infrared galaxy (ULIRG; L) at , spectroscopically
confirmed by the Reionization Era Bright Emission Line Survey (REBELS) ALMA
Large Programme. REBELS-25 has a significant stellar mass of
M. From dust-continuum and ultraviolet
observations, we determine a total obscured + unobscured star formation rate of
SFR M yr. This is about four times the SFR
estimated from an extrapolated main-sequence. We also infer a [CII]-based
molecular gas mass of ,
implying a molecular gas depletion time of Gyr. We observe a [CII] velocity gradient consistent
with disc rotation, but given the current resolution we cannot rule out a more
complex velocity structure such as a merger. The spectrum exhibits excess [CII]
emission at large positive velocities ( km s), which we
interpret as either a merging companion or an outflow. In the outflow scenario,
we derive a lower limit of the mass outflow rate of 200 M yr,
which is consistent with expectations for a star formation-driven outflow.
Given its large stellar mass, SFR and molecular gas reservoir Myr
after the Big Bang, we explore the future evolution of REBELS-25. Considering a
simple, conservative model assuming an exponentially declining star formation
history, constant star formation efficiency, and no additional gas inflow, we
find that REBELS-25 has the potential to evolve into a galaxy consistent with
the properties of high-mass quiescent galaxies recently observed at .Comment: Accepted for publication in MNRAS. 21 pages, 8 figure
New trends in the economic systems management in the context of modern global challenges
New trends in the economic systems management in the context of modern global challenges: collective monograph / scientific edited by M. Bezpartochnyi, in 2 Vol. // VUZF University of Finance, Business and Entrepreneurship. – Sofia: VUZF Publishing House “St. Grigorii Bogoslov”, 2020. – Vol. 1. – 309 p
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