528 research outputs found
Genetic Complementation to Identify DNA Elements That Influence Complement Resistance in Leishmania chagasi
Past studies showed that Leishmania spp. promastigotes exhibit differential sensitivity to complement mediated lysis (CML) during development in vitro and in vivo. Leishmania chagasi promastigotes in cultures during logarithmic and stationary growth phases are CML-sensitive or CML-resistant when exposed to human serum, respectively, but only in cultures recently initiated with parasites from infected animals; serially passaged cultures become constitutively CML-sensitive regardless of growth phase. Building on these observations, a genetic screen was conducted to identify novel complement resistance factors of L. chagasi. A cosmid library containing genomic DNA was transfected into a promastigote line previously subjected to \u3e50 serial passages. Selection with human serum for CML resistance yielded 12 transfectant clones. Cosmids isolated from 7 of these clones conferred CML resistance when transfected into an independent, high-passage promastigote culture; at 12% human serum, the mean survival of transfectants was 37% (±11.6%), and that of control transfectants was about 1%. Inserts within the 7 cosmids were unique. Determination of the complete DNA sequence for 1 cosmid indicated that its 32-kilobase insert was 89% identical (overall) to a 31-kilobase region of Leishmania major chromosome 36, which is predicted to encode 6 genes, all of which encode hypothetical proteins
Impact of aftertreatment devices on primary emissions and secondary organic aerosol formation potential from in-use diesel vehicles: results from smog chamber experiments
Diesel particulate matter (DPM) is a significant source of aerosol in urban
areas and has been linked to adverse health effects. Although newer European
directives have introduced increasingly stringent standards for primary PM
emissions, gaseous organics emitted from diesel cars can still lead to large
amounts of secondary organic aerosol (SOA) in the atmosphere. Here we
present results from smog chamber investigations characterizing the primary
organic aerosol (POA) and the corresponding SOA formation at atmospherically
relevant concentrations for three in-use diesel vehicles with different
exhaust aftertreatment systems. One vehicle lacked exhaust aftertreatment
devices, one vehicle was equipped with a diesel oxidation catalyst (DOC) and
the third vehicle used both a DOC and diesel particulate filter (DPF). The
experiments presented here were obtained from the vehicles at conditions
representative of idle mode, and for one car in addition at a speed of 60 km/h.
An Aerodyne high-resolution time-of-flight aerosol mass spectrometer
(HR-ToF-AMS) was used to measure the organic aerosol (OA) concentration and
to obtain information on the chemical composition. For the conditions
explored in this paper, primary aerosols from vehicles without a particulate
filter consisted mainly of black carbon (BC) with a low fraction of organic
matter (OM, OM/BC < 0.5), while the subsequent aging by photooxidation
resulted in a consistent production of SOA only for the vehicles without a
DOC and with a deactivated DOC. After 5 h of aging ~80% of the
total organic aerosol was on average secondary and the estimated "emission
factor" for SOA was 0.23–0.56 g/kg fuel burned. In presence of both a DOC
and a DPF, only 0.01 g SOA per kg fuel burned was produced within 5 h
after lights on. The mass spectra indicate that POA was mostly a
non-oxidized OA with an oxygen to carbon atomic ratio (O/C) ranging from
0.10 to 0.19. Five hours of oxidation led to a more oxidized OA with an O/C
range of 0.21 to 0.37
Anomalous asymmetry of magnetoresistance in NbSe single crystals
A pronounced asymmetry of magnetoresistance with respect to the magnetic
field direction is observed for NbSe crystals placed in a magnetic field
perpendicular to their conducting planes. It is shown that the effect persists
in a wide temperature range and manifests itself starting from a certain
magnetic induction value , which at K corresponds to the
transition to the quantum limit, i.to the state where the Landay level
splitting exceeds the temperature.Comment: 4 pages, 6 figures, to be appeared in JETP Let
Integrating DGSs and GATPs in an Adaptative and Collaborative Blended-Learning Web-Environment
The area of geometry with its very strong and appealing visual contents and
its also strong and appealing connection between the visual content and its
formal specification, is an area where computational tools can enhance, in a
significant way, the learning environments.
The dynamic geometry software systems (DGSs) can be used to explore the
visual contents of geometry. This already mature tools allows an easy
construction of geometric figures build from free objects and elementary
constructions. The geometric automated theorem provers (GATPs) allows formal
deductive reasoning about geometric constructions, extending the reasoning via
concrete instances in a given model to formal deductive reasoning in a
geometric theory.
An adaptative and collaborative blended-learning environment where the DGS
and GATP features could be fully explored would be, in our opinion a very rich
and challenging learning environment for teachers and students.
In this text we will describe the Web Geometry Laboratory a Web environment
incorporating a DGS and a repository of geometric problems, that can be used in
a synchronous and asynchronous fashion and with some adaptative and
collaborative features.
As future work we want to enhance the adaptative and collaborative aspects of
the environment and also to incorporate a GATP, constructing a dynamic and
individualised learning environment for geometry.Comment: In Proceedings THedu'11, arXiv:1202.453
The Use of Heart Rate Variability in Esports: A Systematic Review
Heart rate variability (HRV) is a psychophysiological measure of particular interest in esports due to its potential to monitor player self-regulation. This study aimed to systematically review the utilisation of HRV in esports. Consideration was given to the methodological and theoretical underpinnings of previous works to provide recommendations for future research. The protocol was made available on the Open Science Framework. Inclusion criteria were empirical studies, examining HRV in esports, using esports players, published in English. Exclusion criteria were non-peer-reviewed studies, populations with pre-existing clinical illness other than Internet Gaming Disorder (IGD), opinion pieces or review papers. In November 2022 a search of Web of Science, PubMed, and EBSCOHost identified seven studies using HRV in esports. Risk of bias was assessed using the Mixed Methods Appraisal Tool. Narrative review identified two primary uses of HRV in esports; stress response and IGD. A lack of theoretical and methodological underpinning was identified as a major limitation of current literature. Further investigation is necessary before making recommendations regarding the use of HRV in esports. Future research should employ sound theoretical underpinning such as the use of vagally mediated HRV and the robust application of supporting methodological guidelines when investigating HRV in esports
Dating of the hominid (Homo neanderthalensis) remains accumulation from El Sidrón Cave (Piloña, Asturias, North Spain): an example of a multi-methodological approach to the dating of Upper Pleistocene sites.
The age of Neanderthal remains and associated sediments from El Sidrón cave has been obtained through different dating methods (14CAMS, U/TH, OSL, ESR and AAR) and samples (charcoal debris, bone, tooth dentine, stalagmitic flowstone, carbonate-rich sediments, sedi- mentary quartz grains, tooth enamel and land snail shells). Detrital Th contamination ren- dered Th/U dating analyses of flowstone unreliable. Recent 14C contamination produced spurious age-values from charcoal samples as well as from inadequately pretreated tooth samples. Most consistent 14C dates are grouped into two series: one between 35 and 40 ka and the other between 48 and 49 ka. Most ESR and AAR samples yielded concordant ages, ranging between 39 and 45 ka; OSL dating results permitted adequate bracketing of the sedimentary layer that contained the human remains. Our results emphasize the value of multi-dating approaches for the establishment of reliable chronologies of human remains
Dating of the hominid (homo neanderthalensis) remains accumulation from el sidrón cave (piloña, asturias, north spain): An example of a multi-methodological approach to the dating of upper pleistocene sites
The age of Neanderthal remains and associated sediments from El Sidrón cave has been obtained through different dating methods (14CAMS, U/TH, OSL, ESR and AAR) and samples (charcoal debris, bone, tooth dentine, stalagmitic flowstone, carbonate-rich sedi
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Soot reference materials for instrument calibration and intercomparisons: A workshop summary with recommendations
Soot, which is produced from biomass burning and the incomplete combustion of fossil and biomass fuels, has been linked to regional and global climate change and to negative health problems. Scientists measure the properties of soot using a variety of methods in order to quantify source emissions and understand its atmospheric chemistry, reactivity under emission conditions, interaction with solar radiation, influence on clouds, and health impacts. A major obstacle currently limiting progress is the absence of established standards or reference materials for calibrating the many instruments used to measure the various properties of soot.
The current state of availability and practicability of soot standard reference materials (SRMs) was reviewed by a group of 50 international experts during a workshop in June of 2011. The workshop was convened to summarize the current knowledge on soot measurement techniques, identify the measurement uncertainties and limitations related to the lack of soot SRMs, and identify attributes of SRMs that, if developed, would reduce measurement uncertainties. The workshop established that suitable SRMs are available for calibrating some, but not all, measurement methods. The community of users of the single-particle soot-photometer (SP2), an instrument using laser-induced incandescence, identified a suitable SRM, fullerene soot, but users of instruments that measure light absorption by soot collected on filters did not. Similarly, those who use thermal optical analysis (TOA) to analyze the organic and elemental carbon components of soot were not satisfied with current SRMs. The workshop, and subsequent, interactive discussions, produced a number of recommendations for the development of new SRMs, and their implementation, that would be suitable for the different soot measurement methods
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