320 research outputs found
Momentum-resolved study of the saturation intensity in multiple ionization
We present a momentum-resolved study of strong field multiple ionization of
ionic targets. Using a deconvolution method we are able to reconstruct the
electron momenta from the ion momentum distributions after multiple ionization
up to four sequential ionization steps. This technique allows an accurate
determination of the saturation intensity as well as of the electron release
times during the laser pulse. The measured results are discussed in comparison
to typically used models of over-the-barrier ionization and tunnel ionization
Natural history of Plasmodium odocoilei malaria infection in farmed white-tailed deer
ABSTRACT White-tailed deer (Odocoileus virginianus), an ecologically and economically important species, are the most widely distributed large animals in North America. A recent study indicated that up to 25% of all white-tailed deer may be infected with Plasmodium odocoilei, a malaria parasite belonging to the distinct clade of ungulate-infecting Plasmodium spp. Because the clinical impact of P. odocoilei on deer health and survival is unknown, we undertook a retrospective longitudinal study of farmed Floridian O. virginianus fawns. We found that a substantial proportion (21%) of fawns acquire malaria infection during the first 8 months of life. Some animals naturally clear P. odocoilei infection, while other animals remain persistently positive. Importantly, we found that animals that acquire malaria parasites very early in life have poor survival compared to animals that remain uninfected. Our report thus provides the first evidence of a clinically significant impact of malaria infection in young deer. IMPORTANCE Malaria parasites of the genus Plasmodium are known to infect a variety of vertebrate hosts, including ungulates (hoofed mammals). A recent study found that up to a quarter of white-tailed deer (Odocoileus virginianus) in North America are infected with the parasite Plasmodium odocoilei. In addition to occupying an important ecological niche, white-tailed deer are popular game animals and deer farming represents a rapidly growing industry. However, the effect of P. odocoilei infection in this ecologically and economically important ungulate species is unknown. Our work is significant because (i) we identified a high prevalence of P. odocoilei in farmed deer and (ii) we found evidence for both cleared and persistent infection, as well as an association with decreased survival of young fawns
Above threshold ionization by few-cycle spatially inhomogeneous fields
We present theoretical studies of above threshold ionization (ATI) produced
by spatially inhomogeneous fields. This kind of field appears as a result of
the illumination of plasmonic nanostructures and metal nanoparticles with a
short laser pulse. We use the time-dependent Schr\"odinger equation (TDSE) in
reduced dimensions to understand and characterize the ATI features in these
fields. It is demonstrated that the inhomogeneity of the laser electric field
plays an important role in the ATI process and it produces appreciable
modifications to the energy-resolved photoelectron spectra. In fact, our
numerical simulations reveal that high energy electrons can be generated.
Specifically, using a linear approximation for the spatial dependence of the
enhanced plasmonic field and with a near infrared laser with intensities in the
mid- 10^{14} W/cm^{2} range, we show it is possible to drive electrons with
energies in the near-keV regime. Furthermore, we study how the carrier envelope
phase influences the emission of ATI photoelectrons for few-cycle pulses. Our
quantum mechanical calculations are supported by their classical counterparts
Coherent control at its most fundamental: CEP-dependent electron localization in photodissoziation of a H2+ molecular ion beam target
Measurements and calculations of the absolute carrier-envelope phase (CEP)
effects in the photodissociation of the simplest molecule, H2+, with a 4.5-fs
Ti:Sapphire laser pulse at intensities up to (4 +- 2)x10^14 Watt/cm^2 are
presented. Localization of the electron with respect to the two nuclei (during
the dissociation process) is controlled via the CEP of the ultra-short laser
pulses. In contrast to previous CEP-dependent experiments with neutral
molecules, the dissociation of the molecular ions is not preceded by a
photoionization process, which strongly influences the CEP dependence.
Kinematically complete data is obtained by time- and position-resolved
coincidence detection. The phase dependence is determined by a single-shot
phase measurement correlated to the detection of the dissoziation fragments.
The experimental results show quantitative agreement with ab inito 3D-TDSE
calculations that include nuclear vibration and rotation.Comment: new version includes minore changes and adding the supp_material.pd
Momentum distributions of sequential ionization generated by an intense laser pulse
Journals published by the American Physical Society can be found at http://publish.aps.org/The relative yield and momentum distributions of all multiply charged atomic ions generated by a short (30 fs) intense (10(14)-5 x 10(18) W/cm(2)) laser pulse are investigated using a Monte Carlo simulation. We predict a substantial shift in the maximum (centroid) of the ion-momentum distribution along the laser polarization as a function of the absolute phase. This effect should be experimentally detectable with currently available laser systems even for relatively long pulses, such as 25-30 fs. In addition to the numerical results, we present semianalytical scaling for the position of the maximum
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Bioluminescent reporters for catabolic gene expression and pollutant bioavailability
The application of visualized catabolic nah-gene expression using a luxCDABE gene fusion provides a valuable method to measure quantitatively and specifically naphthalene and salicylate bioavailability. It has been demonstrated that the physiological state of the test culture together with the intrinsic regulation mechanisms of the naphthalene degradation pathway as well as the physiological aspects of the lux gene fusion have to be taken into account. The method presented provides a high potential for in situ bioprocess monitoring. In addition, the results obtained with immobilized cells provide a basis for the development of biosensors for environmental applications in specific pollutant monitoring in waste streams and soil slurry systems but, as a general method, also for more conventional biotechnological process control. 8 refs., 2 figs., 1 tab
Precise, real-time, single-shot carrier-envelope phase measurement in the multi-cycle regime
Polarization gating is used to extend a real-time, single-shot, carrier-envelope phase (CEP) measurement, based on high-energy above-threshold ionization in xenon, to the multi-cycle regime. The single-shot CEP precisions achieved are better than 175 and 350 mrad for pulse durations up to 10 fs and 12.5 fs, respectively, while only 130 mu J of pulse energy are required. This opens the door to study and control of CEP-dependent phenomena in ultra-intense laser-matter interaction using optical parametric chirped pulse amplifier based tera- and petawatt class lasers
Carrier–envelope phase effect in the yield of sequential ionization by an intense few-cycle laser pulse
High-power ytterbium-doped fiber laser delivering few-cycle, carrier-envelope phase-stable 100 µJ pulses at 100 kHz
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