3,851 research outputs found
Introduction to Hemodynamic Forces Analysis: Moving Into the New Frontier of Cardiac Deformation Analysis
Theoretical predictions for vehicular headways and their clusters
This article presents a derivation of analytical predictions for steady-state
distributions of netto time gaps among clusters of vehicles moving inside a
traffic stream. Using the thermodynamic socio-physical traffic model with
short-ranged repulsion between particles (originally introduced in [Physica A
\textbf{333} (2004) 370]) we firstly derive the time-clearance distribution in
the model. Consecutively, the statistical distributions for the so-called time
multi-clearances are calculated by means of theory of functional convolutions.
Moreover, all the theoretical surmises used during the above-mentioned
calculations are proven by the statistical analysis of traffic data. The
mathematical predictions acquired in this paper are thoroughly compared with
relevant empirical quantities and discussed in the context of three-phase
traffic theory.Comment: 23 pages, 10 figure
Q1549-C25: A Clean Source of Lyman-Continuum Emission at
We present observations of Q1549-C25, an ~L* star-forming galaxy at z=3.15
for which Lyman-continuum (LyC) radiation is significantly detected in deep
Keck/LRIS spectroscopy. We find no evidence for contamination from a
lower-redshift interloper close to the line of sight in the high
signal-to-noise spectrum of Q1549-C25. Furthermore, the morphology of Q1549-C25
in V_606, J_125, and H_160 Hubble Space Telescope (HST) imaging reveals that
the object consists of a single, isolated component within 1". In combination,
these data indicate Q1549-C25 as a clean spectroscopic detection of LyC
radiation, only the second such object discovered to date at z~3. We model the
spectral energy distribution (SED) of Q1549-C25, finding evidence for
negligible dust extinction, an age (assuming continuous star formation) of ~1
Gyr, and a stellar mass of M_*=7.9x10^9 M_sun. Although it is not possible to
derive strong constraints on the absolute escape fraction of LyC emission,
f_esc(LyC), from a single object, we use simulations of intergalactic and
circumgalactic absorption to infer f_esc(LyC)>=0.51 at 95% confidence. The
combination of deep Keck/LRIS spectroscopy and HST imaging is required to
assemble a larger sample of objects like Q1549-C25, and obtain robust
constraints on the average f_esc(LyC) at z~3 and beyond.Comment: 6 pages, 5 figures, accepted to ApJ Letter
Gastrointestinal nematodes and anthelmintic resistance in Danish goat herds
The prevalence of gastrointestinal parasites in Danish goats and the presence of anthelmintic resistance (AR) in 10 selected herds were investigated during AprilâSeptember 2012. All Danish herds (n = 137) with 10 or more adult goats were invited to participate, and of these 27 herds met the inclusion criterion of more than 10 young kids never treated with anthelmintics. Questionnaire data on management were collected, and faecal samples from 252 kids were analysed by the McMaster technique. From all herds with a mean faecal egg count (FEC) above 300 eggs per g of faeces, pooled samples were stained with peanut agglutinin (PNA) for specific detection of Haemonchus contortus. Strongyle eggs were detected with an individual prevalence of 69%, including Nematodirus battus (3.6%) and other Nematodirus species (15.0%). Eimeria spp. were observed in 99.6% of the kids. H. contortus was found in 11 of 12 (92%) tested herds. Anthelmintics were used in 89% of the herds with mean treatment frequencies of 0.96 and 0.89 treatments per year for kids and adults, respectively. In 2011, new animals were introduced into 44% of the herds of which 25% practised quarantine anthelmintic treatments. In 10 herds the presence of AR was analysed by egg hatch assay and FEC reduction tests using ivermectin (0.3 mg/kg) or fenbendazole (10.0 mg/kg). AR against both fenbendazole and ivermectin was detected in seven herds; AR against fenbendazole in one herd, and AR against ivermectin in another herd. In conclusion, resistance to the most commonly used anthelmintics is widespread in larger goat herds throughout Denmark
A zone of preferential ion heating extends tens of solar radii from Sun
The extreme temperatures and non-thermal nature of the solar corona and solar
wind arise from an unidentified physical mechanism that preferentially heats
certain ion species relative to others. Spectroscopic indicators of unequal
temperatures commence within a fraction of a solar radius above the surface of
the Sun, but the outer reach of this mechanism has yet to be determined. Here
we present an empirical procedure for combining interplanetary solar wind
measurements and a modeled energy equation including Coulomb relaxation to
solve for the typical outer boundary of this zone of preferential heating.
Applied to two decades of observations by the Wind spacecraft, our results are
consistent with preferential heating being active in a zone extending from the
transition region in the lower corona to an outer boundary 20-40 solar radii
from the Sun, producing a steady state super-mass-proportional
-to-proton temperature ratio of . Preferential ion heating
continues far beyond the transition region and is important for the evolution
of both the outer corona and the solar wind. The outer boundary of this zone is
well below the orbits of spacecraft at 1 AU and even closer missions such as
Helios and MESSENGER, meaning it is likely that no existing mission has
directly observed intense preferential heating, just residual signatures. We
predict that {Parker Solar Probe} will be the first spacecraft with a perihelia
sufficiently close to the Sun to pass through the outer boundary, enter the
zone of preferential heating, and directly observe the physical mechanism in
action.Comment: 11 pages, 7 figures, accepted for publication in the Astrophysical
Journal on 1 August 201
Computing generalized inverses using LU factorization of matrix product
An algorithm for computing {2, 3}, {2, 4}, {1, 2, 3}, {1, 2, 4} -inverses and
the Moore-Penrose inverse of a given rational matrix A is established. Classes
A(2, 3)s and A(2, 4)s are characterized in terms of matrix products (R*A)+R*
and T*(AT*)+, where R and T are rational matrices with appropriate dimensions
and corresponding rank. The proposed algorithm is based on these general
representations and the Cholesky factorization of symmetric positive matrices.
The algorithm is implemented in programming languages MATHEMATICA and DELPHI,
and illustrated via examples. Numerical results of the algorithm, corresponding
to the Moore-Penrose inverse, are compared with corresponding results obtained
by several known methods for computing the Moore-Penrose inverse
Night MattersâWhy the Interdisciplinary Field of âNight Studiesâ Is Needed
The night has historically been neglected in both disciplinary and interdisciplinary research. To some extent, this is not surprising, given the diurnal bias of human researchers and the difficulty of performing work at night. The night is, however, a critical element of biological, chemical, physical, and social systems on Earth. Moreover, research into social issues such as inequality, demographic changes, and the transition to a sustainable economy will be compromised if the night is not considered. Recent years, however, have seen a surge in research into the night. We argue that ânight studiesâ is on the cusp of coming into its own as an interdisciplinary field, and that when it does, the field will consider questions that disciplinary researchers have not yet thought to ask
A method to define the priority for maintenance and repair works of Italian motorway tunnels
The construction of motorways in Italy dates back to 1921 and still lasts today. Along
them there is a large number of tunnels, many of which have been in service for more than 50
years and have experienced various levels of decay due to aging. An extensive assessment and
inspection plan is taking place finalized to highlight situations where maintenance and repair
works are needed to guarantee the continuation of service in safe conditions and functionality.
Due to the number of tunnels, the need arises to classify them and define priorities for
intervention on the basis of a first assessment and of a robust and scientific-based tool to orientate
the investments. This paper describes the methodology that was developed by the Authors for
this purpose, assessing the attention level of every tunnel. The method relies on a quantitative
approach that allows quantifying the risk based on five risk factors composed of a number of
relevant parameters. Their relative interaction, which guided the scores assigned to each
parameter, was assessed by applying the Rock Engineering System [2]. A number of examples
of existing tunnels are shown to illustrate the application of the method and to draw conclusions
about its validity and reliability
Frugal Clay Press for Nicaragua: Design of a Human-Powered Clay Brick Press for Rural Application
This team was connected to a brick-making social entrepreneurship in Ciudad DarĂo, Nicaragua. Travel to Nicaragua in March of 2018 determined that the entrepreneurship wanted a manual brick press to increase the mechanical properties of bricks while decreasing the time needed for the bricks to dry before being baked. Fabrication of a semi-functional beta prototype was completed in May of 2018. Prototype operational tests showed that one cycle of brick compression and retrieval took roughly 3.5 minutes to produce a single double-sized brick. Water absorptivity tests determined that compressed bricks of red art clay experienced a percent absorptivity of 20.5%, with non-compressed bricks formed in Nicaragua having an absorptivity of 35.0%. Finally, the ultimate compressive strength of bricks produced using the prototype averaged to 1,640 psi, as compared to 822 psi of the Nicaraguan brick. Insufficient data was collected to confirm the safety and effectiveness of the design. Several mechanical errors in clay compression and subsystem interferences merit further redesign. Recommendations for design iterations are included for future design teams to finalize and deploy the device
Detection of Eight Cannabinoids and One Tracer in Wastewater and River Water by SPE-UPLCâESI-MS/MS
The consumption of illicit drugs represents a global social and economic problem. Using suitable analytical methods, monitoring, and detection of different illegal drugs residues and their metabolites in wastewater samples can help combat this problem. Our article defines a method to develop, validate, and practically applicate a rapid and robust analytical process for the evaluation of six naturally occurring cannabinoids (CBG, CBD, CBDV, CBN, THC, THCV), two cannabinoids in acidic form (CBDA, THCA-A), and the major cannabis-related human metabolite (THC-COOH). After SPE offline enrichment, we used a UPLCâESI-MS/MS system, which permitted the determination of several by-products. Studied matrices were samples of different origins: (i) effluent water from a wastewater treatment plant in the Porto urban area; (ii) environmental water from Febros River, the last left-bank tributary of the Douro River. The multi-residue approach was substantiated and successfully employed to analyze the water samples collected in the above locations. The rapid and precise quantification of nine different cannabinoids in different water samples occurred within nine minutes at the ng Lâ1 level. The appearance of dozens of ng Lâ1 of some cannabis secondary metabolites, such as CBD, CBDA, CBN, THCA-A, indicates this plant speciesâ widespread usage among the general population in the considered area
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