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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

MOV10 inhibits replication of porcine reproductive and respiratory syndrome virus by retaining viral nucleocapsid protein in the cytoplasm of Marc-145 cells

Highlights: • Porcine reproductive and respiratory syndrome (PRRS) affects industrial pig farming. • N protein is the main protein of PRRS virus (PRRSV) in infected cells which is important for PRRSV replication. • Moloney leukemia virus 10 protein (MOV10) is a new host restriction factor of PRRSV. • MOV10 interacts with PRRSV N protein and inhibits PRRSV replication in vitro. • MOV10 inhibits nuclear entry of N protein, thus impairing viral life cycle. Porcine reproductive and respiratory syndrome virus (PRRSV) has been a major threat to global industrial pig farming ever since its emergence in the late 1980s. Identification of sustainable and effective control measures against PRRSV transmission is a pressing problem. The nucleocapsid (N) protein of PRRSV is specifically localized in the cytoplasm and nucleus of virus-infected cells which is important for PRRSV replication. In the current study, a new host restricted factor, Moloney leukemia virus 10-like protein (MOV10), was identified as an inhibitor of PRRSV replication. N protein levels and viral replication were significantly reduced in Marc-145 cells stably overexpressing MOV10 compared with those in wild-type Marc-145 cells. Adsorption experiments revealed that MOV10 did not affect the attachment and internalization of PRRSV. Co-immunoprecipitation and immunofluorescence co-localization analyses showed that MOV10 interacted and co-localized with the PRRSV N protein in the cytoplasm. Notably, MOV10 affected the distribution of N protein in the cytoplasm and nucleus, leading to the retention of N protein in the former. Taken together, these findings demonstrate for the first time that MOV10 inhibits PRRSV replication by restricting the nuclear import of N protein. These observations have great implications for the development of anti-PRRSV drugs and provide new insight into the role of N protein in PRRSV biology.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Commissioning of small field size radiosurgery cones in a 6-MV flattening filter-free beam

This study aimed to describe the commissioning of small field size radiosurgery cones in a 6-MV flattening filter free (FFF) beam and report our measured values. Four radiosurgery cones of diameters 5, 10, 12.5, and 15 mm supplied by Elekta Medical were commissioned in a 6-MV FFF beam from an Elekta Versa linear accelerator. The extraction of a reference signal for measuring small fields in scanning mode is challenging. A transmission chamber was attached to the lower part of the collimators and used for percentage depth dose (PDD) and profile measurements in scanning mode with a stereotactic diode. Tissue-maximum ratios (TMR) and output factors (OF) for all collimators were measured with a stereotactic diode (IBA). TMR and the OF for the largest collimator were also acquired on a polystyrene phantom with a microionization chamber of 0.016 cm{sup 3} volume (PTW Freiburg PinPoint 3D). Measured TMR with diode and PinPoint microionization chamber agreed very well with differences smaller than 1% for depths below 20 cm, except for the smaller collimator, for which differences were always smaller than 2%. Calculated TMR were significantly different (up to 7%) from measured TMR. OF measured with diode and chamber showed a difference of 3.5%. The use of a transmission chamber allowed the measurement of the small-field dosimetric properties with a simple setup. The commissioning of radiosurgery cones in FFF beams has been performed with essentially the same procedures and recommended detectors used with flattened beams. Good agreement was found between TMR measurements acquired with the IBA stereotactic diode and the PinPoint 3D microionization chamber. The transmission chamber overcomes the problem of extracting a reference signal and is of great help for small-field commissioning.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Hybrid proton acceleration scheme using relativistic intense laser light

Ion acceleration phenomena at relativistic intense laser interaction with thin foil targets are studied to find an efficient laser-target interaction concept at the conditions, where neither the ponderomotive pressure of the laser light nor the hot electron pressure is negligible. Particle in cell simulations and the analytical model are allowing to predict optimum laser-target parameters and suggesting a significant increase of proton energy if a hybrid proton acceleration scheme is used. In the proposed scenario, the laser polarisation is changed during the acceleration process: First with circularly polarised laser light the target is accelerated as a whole by the ponderamotive pressure, and then with linearly polarised laser light the electrons are heated which additionally increases the accelerating field. The calculations are in good agreement with experimental findings.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Group velocity dispersion and relativistic effects on the wakefield induced by chirped laser pulse in parabolic plasma channel

The excitation of wake field plasma waves by a short laser pulse propagating through a parabolic plasma channel is studied. The laser pulse is assumed to be initially chirped. In this regard, the effects of initial and induced chirp on the plasma wake field as well as the laser pulse parameters are investigated. The group velocity dispersion and nonlinear relativistic effects were taken into account to evaluate the excited wake field in two dimension using source dependent expansion method. Positive, negative, and un-chirped laser pulses were employed in numerical code to evaluate the effectiveness of the initial chirp on 2-D wake field excitation. Numerical results showed that for laser irradiances exceeding 10{sup 18}W/cm{sup 2}, an intense laser pulse with initial positive chirp generates larger wake field compared to negatively and un-chirped pulses.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Mitigation of two-plasmon decay in direct-drive inertial confinement fusion through the manipulation of ion-acoustic and Langmuir wave damping

The extended Zakharov model of the two-plasmon decay instability in an inhomogeneous plasma [D. F. DuBois et al., Phys. Rev. Lett. 74, 3983 (1995); D. A. Russell and D. F. DuBois, Phys. Rev. Lett. 86, 428 (2001)] is further generalized to include the evolution of the electron distribution function in the quasi-linear approximation [cf., e.g., K. Y. Sanbonmatsu et al. Phys. Plasmas 7, 2824 (2000); D. A. Russell et al., paper presented at the Workshop on SRS/SBS Saturation, Wente Vineyards, Livermore, CA, 2–5 April 2002]. This makes it possible to investigate anomalous absorption of laser light and hot electron production due to the two-plasmon decay instability of multiple overlapping electromagnetic waves. Scalings of hot-electron production in the (stationary) nonlinearly saturated regime relevant to recent experiments [B. Yaakobi et al., Phys. Plasmas 19, 012704 (2012); D. H. Froula et al., Phys. Rev. Lett. 108, 165003 (2012)] have been obtained. They indicate a sensitivity to ion-acoustic wave (IAW) damping and to the collisional absorption of Langmuir waves. Such a sensitivity might be exploited in inertial confinement fusion target design by the use of mid-Z ablators.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Tailoring femtosecond laser pulse filamentation using plasma photonic lattices

We demonstrate experimentally that by using transient plasma photonic lattices, the attributes of intense femtosecond laser filaments, such as peak intensity and length, can be dynamically controlled. The extended plasma lattice structure is generated using two co-propagating non-diffracting intense Bessel beams in water. The use of such transient lattice structures to control the competition between linear and nonlinear effects involved in filamentation opens the way for extensive control of the filamentation process.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Self-focusing of a Gaussian electromagnetic beam in a multi-ions plasma

In this paper, the authors have developed a formulation for the dependence of electron and ion densities on the irradiance of an electromagnetic beam in a plasma with multiply charged ions, corresponding to collisional, ponderomotive, and relativistic-ponderomotive nonlinearities and different electron/ion temperatures; consequently, the corresponding expressions for the electron density modification in the presence of an electromagnetic (em) field have been derived. Paraxial approach in the vicinity of intensity maximum has been adopted to analyze the propagation characteristics of an em beam in such plasmas; on the basis of this analysis, critical curves and self-focusing curves have been computed numerically and graphically illustrated. For a numerical appreciation of the analysis, we have specifically carried out the computations for the simultaneous presence of singly and doubly charged ions in the plasma. As an important outcome, it is seen that the nonlinear effects (and hence self-focusing) get suppressed in the presence of multiply ionized ions; the conditions for the three modes of em-beam propagation viz. oscillatory focusing/defocusing and steady divergence have been discussed.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Turning point temperature and competition between relativistic and ponderomotive effects in self-focusing of laser beam in plasma

The propagation characters of Gaussian laser beam in collisionless plasma are investigated by considering the ponderomotive and relativistic nonlinearities. The second-order differential equation of dimensionless beam width parameter is solved numerically, taking into account the effect of electron temperature. The results show that the ponderomotive force does not facilitate the relativistic self-focusing in all intensity ranges. In fact, there exists a certain intensity value that, if below this value, the ponderomotive nonlinearity can contribute to the relativistic self-focusing, or obstruct it, if above. It is also indicated that there is a temperature interval in which self-focusing can occur, while the beam diverges outside of this region. In addition, the results represent the existence of a “turning point temperature” in the mentioned interval that the self-focusing has the strongest power. The value of the turning point is dependent on laser intensity in which higher intensities result in higher turning point.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Effect of laser beam filamentation on coexisting stimulated Raman and Brillouin scattering

This paper presents the study of stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS) when both of these processes are coexisting and pump laser beam initial power is more than filamentation threshold. On account of the ponderomotive nonlinearity, the pump laser beam gets filamented, and both the scattering processes (SRS and SBS) get affected. Simultaneous presence of SRS and SBS (five wave interaction case) also affect the pump filamentation process due to pump depletion. Both the scattering processes (SRS and SBS) are enhanced due to filamentation of laser beam. Results are also compared with the three wave interaction case (either SRS or SBS) with and without filamentation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Numerical investigation of electron self-injection in the nonlinear bubble regime

The process of electron self-injection in the nonlinear bubble wake generated by a short and intense laser pulse propagating in a uniform underdense plasma is studied by means of fully self-consistent particle-in-cell simulations and test-particle simulations. We consider a wake generated by a non-evolving laser driver traveling with a prescribed velocity, which then sets the structure and the velocity of the wake, so the injection dynamics is decoupled from driver evolution, but a realistic structure for the wakefield is retained. We show that a threshold for self-injection into a non-evolving bubble wake exists, and we characterize the dependence of the self-injection threshold on laser intensity, wake velocity, and plasma temperature for a range of parameters of interest for current and future laser-plasma accelerators.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Intense terahertz emission from relativistic circularly polarized laser pulses interaction with overdense plasmas

During the interaction of a relativistic circularly polarized laser pulse with an overdense plasma target, the longitudinal motion of bunches of electrons under the action of light pressure and electrostatic restore force can emit intense terahertz (THz) pulses. This mechanism allows high pump laser intensity and large electron number participating in the emission. Two-dimensional particle-in-cell simulations are carried out to investigate the THz emission. The results suggest that such a source can produce remarkably intense THz pulses with energy of several mJ/sr and power of tens of gigawatts, which could find applications in nonlinear studies and relativistic laser-plasma interaction diagnostics.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2014

Nonlinear optical localization in embedded chalcogenide waveguide arrays

We report the nonlinear optical localization in an embedded waveguide array fabricated in chalcogenide glass. The array, which consists of seven waveguides with circularly symmetric cross sections, is realized by ultrafast laser writing. Light propagation in the chalcogenide waveguide array is studied with near infrared laser pulses centered at 1040 nm. The peak intensity required for nonlinear localization for the 1-cm long waveguide array was 35.1 GW/cm{sup 2}, using 10-nJ pulses with 300-fs pulse width, which is 70 times lower than that reported in fused silica waveguide arrays and with over 7 times shorter interaction distance. Results reported in this paper demonstrated that ultrafast laser writing is a viable tool to produce 3D all-optical switching waveguide circuits in chalcogenide glass.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Carbon nanotube biconvex microcavities

Developing highly efficient microcavities with predictive narrow-band resonance frequencies using the least amount of material will allow the applications in nonlinear photonic devices. We have developed a microcavity array that comprised multi-walled carbon nanotubes (MWCNT) organized in a biconvex pattern. The finite element model allowed designing microcavity arrays with predictive transmission properties and assessing the effects of the microarray geometry. The microcavity array demonstrated negative index and produced high Q factors. 2–3 μm tall MWCNTs were patterned as biconvex microcavities, which were separated by 10 μm in an array. The microcavity was iridescent and had optical control over the diffracted elliptical patterns with a far-field pattern, whose properties were predicted by the model. It is anticipated that the MWCNT biconvex microcavities will have implications for the development of highly efficient lenses, metamaterial antennas, and photonic circuits.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Generation of a broad IR spectrum and N-soliton compression in a longitudinally inhomogeneous dispersion-shifted fibre

The propagation of N-soliton pulses in an optical fibre with slowly decreasing, shifted anomalous dispersion has been studied experimentally and theoretically. Using a generalised nonlinear Schrödinger equation, we have constructed an adequate numerical model for light propagation in such fibre. Using numerical simulation, we have shown that the use of dispersion-decreasing fibres ensures higher average dispersive radiation intensity and better uniformity of the supercontinuum spectrum. A reduction in the third-order dispersion of such fibres enables supercontinuum generation with a bandwidth exceeding that in homogeneous fibres by several hundred nanometres even in the case of a medium-power subpicosecond source. (nonlinear optical phenomena)

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

An infinite set of Ward identities for adiabatic modes in cosmology

We show that the correlation functions of any single-field cosmological model with constant growing-modes are constrained by an infinite number of novel consistency relations, which relate N+1-point correlation functions with a soft-momentum scalar or tensor mode to a symmetry transformation on N-point correlation functions of hard-momentum modes. We derive these consistency relations from Ward identities for an infinite tower of non-linearly realized global symmetries governing scalar and tensor perturbations. These symmetries can be labeled by an integer n. At each order n, the consistency relations constrain — completely for n = 0,1, and partially for n ≥ 2 — the q{sup n} behavior of the soft limits. The identities at n = 0 recover Maldacena's original consistency relations for a soft scalar and tensor mode, n = 1 gives the recently-discovered conformal consistency relations, and the identities for n ≥ 2 are new. As a check, we verify directly that the n = 2 identity is satisfied by known correlation functions in slow-roll inflation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

SU-F-T-582: Small Field Dosimetry in Radiosurgery Collimators with a Stealth Chamber

Purpose: The extraction of a reference signal for measuring small fields in scanning mode can be problematic. In this work we describe the use of a transmission chamber in small field dosimetry for radiosurgery collimators and compare TMR curves obtained with stereotactic diode and microionization chamber. Methods: Four radiosurgery cones of diameters 5, 10, 12.5, and 15mm supplied by Elekta Medical were commissioned in a 6MV FFF beam from an Elekta Versa linac. A transmission chamber manufactured by IBA (Stealth chamber) was attached to the lower part of the collimators and used for PDD and profile measurements in scanning mode with a Scanditronix stereotactic diode. It was also used for centering the stereotactic diode in the water tank to measure TMR and output factors, by integrating the signal. TMR measurements for all collimators and the OF for the largest collimator were also acquired on a polystyrene PTW 29672 phantom with a PTW PinPoint 3D chamber 0.016 cm3 volume. Results: Measured TMR with diode and microionization chamber agreed very well with differences larger than 1% only for depths above 15cm, except the smaller collimator, for which differences were always smaller than 2%. Calculated TMR were significantly different (up to 7%) from measured TMR. The differences are attributed to the change in response of the diode with depth, because the effective field aperture varies with depth. Furthermore, neglecting the ratio of phantom-scatter factors in the conversion formula also contributes to this difference. OF measured with diode and chamber showed a difference of 3.5%. Conclusion: The transmission chamber overcomes the problem of extracting a reference signal and is of great help for small field commissioning. Calculating TMR from PDD is strongly discouraged. Good agreement was found when comparing measurements of TMR with stereotactic diode in water with measurements with microionization chamber in polystyrene.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2023

Online Monitoring of Medium Voltage Cable Systems with Spread Spectrum Time Domain and Frequency Domain Reflectometry

In-service failures of wave energy convertor (WEC) cable systems can have a significant cost and power availability impact. Close parallel research 2019 data showed > 1B£ and 9 Terra-Watt-Hours associated with global off-shore wind (OSW) cable failures (Strang-Moran 2020). OSW is a closely related technology but currently is significantly cheaper than WEC technology. For wave energy to compete, the problem of reliable cable transmission must be mitigated. This project develops isolation technology to allow online high frequency reflectometry testing of medium voltage cables (1 to 10 kV and higher) without arcing or damage to the test instrument. Online spread spectrum time domain reflectometry (SSTDR) testing has been established for low voltage cable systems in the aircraft and rail industry and the ability to detect and locate cable flaws of interest is well understood. Extending reflectometry testing to medium voltage systems could enable detection of cable damage before failures occur thereby allowing repair and replacement of damaged cable segments to be scheduled and managed. The seedling project succeeded to pass and receive high frequency SSTDR signals onto a cable up to 1 kV using a parallel trace isolation circuit board that can be connected onto the test cable. The approach used a novel circuit design for which an invention disclosure has been filed. A proposed sapling project would extend the technology toward the higher operating voltages used by WEC systems, thereby enabling online SSTDR cable monitoring. The goal of the seedling project was to extend the capability of the ARENA cable/motor test bed to address medium voltages and to develop a high pass filter isolation architecture to protect the reflectometry instrument from the low frequency (DC – 60 Hz) line voltage while allowing the high frequency diagnostic signal to pass to and from the test instrument to the live line. Initial efforts focused on passive LCR filter circuits to reduce 60 Hz levels below 10 volts from a 10 kV line while allowing the MHz high frequency chirps to pass onto the cables and for mV signals to be detected. We discovered that the parasitic loss behavior of real high voltage components precluded this approach from working. An alternate approach was adapted for the electric field to couple between two parallel traces on a printed circuit board much like a radio-frequency coupler. The challenge here was and is to have the parallel traces close enough to each other to effectively pass the high frequency chirp onto the live line and receive any reflected signal from any encountered impedance change along the cable. This reflected signal will be in the mV range. The traces however must be far enough apart to not allow arcing on the board. A design with 3 mm spacing was determined to allow the high frequency signal to pass onto the live line and receive the mV signal back into the instrument while reducing the 60 Hz voltage amplitude by >80 dB (more than a factor of 10,000) without allowing arcing from across the parallel traces. This was confirmed by simulation and test.

16 TIDAL AND WAVE POWER↗