218 research outputs found
Chemotaxis Study Using Optical Tweezers To Observe The Strength And Directionality Of Forces Of Leishmania Amazonensis
The displacements of a dielectric microspheres trapped by an optical tweezers (OT) can be used as a force transducer for mechanical measurements in life sciences. This system can measure forces on the 50 femto Newtons to 200 pico Newtons range, of the same order of magnitude of a typical forces induced by flagellar motion. The process in which living microorganisms search for food and run away from poison chemicals is known is chemotaxy. Optical tweezers can be used to obtain a better understanding of chemotaxy by observing the force response of the microorganism when placed in a gradient of attractors and or repelling chemicals. This report shows such observations for the protozoa Leishmania amazomenzis, responsible for the leishmaniasis, a serious tropical disease. We used a quadrant detector to monitor the movement of the protozoa for different chemicals gradient. This way we have been able to observe both the force strength and its directionality. The characterization of the chemotaxis of these parasites can help to understand the infection mechanics and improve the diagnosis and the treatments employed for this disease.6326Law, A.M.J., Aitken, M.D., Continuous-flow capillary assay for measuring bacterial chemotaxi (2005) Applied and Environmental Microbiology, 71 (6), pp. 3137-3143Khan, S., Jain, S., Reid, G.P., Trentham, D.R., The fast tumble signal in bacterial chemotaxis (2004) Biophysical Journal, 86 (6), pp. 4049-4058Neuman, K.C., Chadd, E.H., Liou, G.F., Bergman, K., Block, S.M., Characterization of photodamage to Escherichia coli in optical traps (1999) Biophysical Journal, 77 (5), pp. 2856-2863Who, World Health Organization, 2001Gontijo, B., Carvalho, M.L.R., Leishmaniose tegumentar Americana (2003) Revista da Sociedade Brasileira de Medicina Tropical, 36 (1), pp. 71-80Handman, E., Cell biology of Leishmania (2000) Advances in Parasitology, 44, pp. 1-39Rice, S.E., Purcell, T.J., Spudich, J.A., Building and using optical traps to study properties of molecular motors (2003) Biophotonics, PT B, 361, pp. 112-133Rohrbach, A., Stelzer, E.H.K., Three-dimensional position detection of optically trapped dielectric particles (2002) Journal of Applied Physics, 91 (8), pp. 5474-5488Gittes, F., Schmidt, C.F., Interference model for back-focal-plane displacement detection in optical tweezers (1998) Optics Letters, 23 (1), pp. 7-9Allersma, M.W., Gittes, F., DeCastro, M.J., Stewart, R.J., Schmidt, C.F., Two-dimensional tracking of ncd motiliry by back focal plane interferometry (1998) Biophysical Journal, 74 (2), pp. 1074-108
Modeling the Subsurface Structure of Sunspots
While sunspots are easily observed at the solar surface, determining their
subsurface structure is not trivial. There are two main hypotheses for the
subsurface structure of sunspots: the monolithic model and the cluster model.
Local helioseismology is the only means by which we can investigate
subphotospheric structure. However, as current linear inversion techniques do
not yet allow helioseismology to probe the internal structure with sufficient
confidence to distinguish between the monolith and cluster models, the
development of physically realistic sunspot models are a priority for
helioseismologists. This is because they are not only important indicators of
the variety of physical effects that may influence helioseismic inferences in
active regions, but they also enable detailed assessments of the validity of
helioseismic interpretations through numerical forward modeling. In this paper,
we provide a critical review of the existing sunspot models and an overview of
numerical methods employed to model wave propagation through model sunspots. We
then carry out an helioseismic analysis of the sunspot in Active Region 9787
and address the serious inconsistencies uncovered by
\citeauthor{gizonetal2009}~(\citeyear{gizonetal2009,gizonetal2009a}). We find
that this sunspot is most probably associated with a shallow, positive
wave-speed perturbation (unlike the traditional two-layer model) and that
travel-time measurements are consistent with a horizontal outflow in the
surrounding moat.Comment: 73 pages, 19 figures, accepted by Solar Physic
Organic nitrate aerosol formation via NO³ + biogenic volatile organic compounds in the southeastern United States
Gas- and aerosol-phase measurements of oxidants, biogenic volatile organic compounds (BVOCs) and organic nitrates made during the Southern Oxidant and Aerosol Study (SOAS campaign, Summer 2013) in central Alabama show that a nitrate radical (NO₃) reaction with monoterpenes leads to significant secondary aerosol formation. Cumulative losses of NO₃ to terpenes are correlated with increase in gasand aerosol-organic nitrate concentrations made during the campaign. Correlation of NO₃ radical consumption to organic nitrate aerosol formation as measured by aerosol mass spectrometry and thermal dissociation laser-induced fluorescence suggests a molar yield of aerosol-phase monoterpene nitrates of 23–44 %. Compounds observed via chemical ionization mass spectrometry (CIMS) are correlated to predicted nitrate loss to BVOCs and show C₁₀H₁₇NO₅, likely a hydroperoxy nitrate, is a major nitrate-oxidized terpene product being incorporated into aerosols. The comparable isoprene product C₅H₉NO₅ was observed to contribute less than 1% of the total organic nitrate in the aerosol phase and correlations show that it is principally a gas-phase product from nitrate oxidation of isoprene. Organic nitrates comprise between 30 and 45% of the NOy budget during SOAS. Inorganic nitrates were also monitored and showed that during incidents of increased coarse-mode mineral dust, HNO₃ uptake produced nitrate aerosol mass loading at a rate comparable to that of organic nitrate produced via NO₃ CBVOCs
Adolescência: ações e percepção dos médicos e enfermeiros do Programa Saúde da Família
Effects of Effective Dendrite Size on Dynamic Tensile Properties of Ti-Based Amorphous Matrix Composites
Estratégia de coalimentação na sobrevivência e no crescimento de larvas de Betta splendens durante a transição alimentar
Seleção de materiais e revestimentos para o controle de incrustações do mexilhão dourado na Usina Hidrelétrica de Ibitinga (SP, Brasil)
Test of Lorentz and CPT violation with Short Baseline Neutrino Oscillation Excesses
The sidereal time dependence of MiniBooNE electron neutrino and anti-electron
neutrino appearance data are analyzed to search for evidence of Lorentz and CPT
violation. An unbinned Kolmogorov-Smirnov test shows both the electron neutrino
and anti-electron neutrino appearance data are compatible with the null
sidereal variation hypothesis to more than 5%. Using an unbinned likelihood fit
with a Lorentz-violating oscillation model derived from the Standard Model
Extension (SME) to describe any excess events over background, we find that the
electron neutrino appearance data prefer a sidereal time-independent solution,
and the anti-electron neutrino appearance data slightly prefer a sidereal
time-dependent solution. Limits of order 10E-20 GeV are placed on combinations
of SME coefficients. These limits give the best limits on certain SME
coefficients for muon neutrino to electron neutrino and anti-muon neutrino to
anti-electron neutrino oscillations. The fit values and limits of combinations
of SME coefficients are provided.Comment: 14 pages, 3 figures, and 2 tables, submitted to Physics Letters
Teaching at primary healthcare services within the Brazilian national health system (SUS) in Brazilian healthcare professionals' training
Divergência genética de milho transgênico em relação à produtividade de grãos e à qualidade nutricional
- …