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Images of the 30 June 1973 total eclipse were combined with radio scattering and scintillation measurements to show fine ray- like structures within coronal holes. These structures are three orders of magnitude smaller than the smallest filamentary structure seen before.
Electronic heat-transfer devices of a proposed type would exploit some of the quantum-wire-like, pseudo-superconducting properties of single-wall carbon nanotubes or, optionally, room-temperature-superconducting polymers (RTSPs). The devices are denoted thermo-electron ballistic (TEB) coolers or heaters because one of the properties that they exploit is the totally or nearly ballistic (dissipation or scattering free) transport of electrons. This property is observed in RTSPs and carbon nanotubes that are free of material and geometric defects, except under conditions in which oscillatory electron motions become coupled with vibrations of the nanotubes. Another relevant property is the high number density of electrons passing through carbon nanotubes -- sufficient to sustain electron current densities as large as 100 MA/square cm. The combination of ballistic motion and large current density should make it possible for TEB devices to operate at low applied potentials while pumping heat at rates several orders of magnitude greater than those of thermoelectric devices. It may also enable them to operate with efficiency close to the Carnot limit. In addition, the proposed TEB devices are expected to operate over a wider temperature range
We aim to acquire measurements of the structure and dynamics of certain liquid-fluid interfaces using an ensemble of techniques in collaboration: (1) Total internal reflection (TIR) Surface light scattering spectroscopy (SLSS), (2) Brewster angle microscopy (BAM), and (3) Drop-shape analysis. SLSS and BAM can be done on a shared interfacial footprint. Results using a 50-50 mixture of pentane-isohexane, which extends the range of NASA's Confined Vapor Bubble (CVB) experiment, yield surface tension results that differ from the expected Langmuir Fit. These results were confirmed using both the SLSS and drop-shape analysis approaches.
Polar stratospheric clouds (PSCs) play a crucial role in the springtime chemical depletion of ozone at high latitudes. PSC particles (primarily supercooled ternary solution, or STS droplets) provide sites for heterogeneous chemical reactions that transform stable chlorine and bromine reservoir species into highly reactive ozone-destructive forms. Furthermore, large nitric acid trihydrate (NAT) PSC particles can irreversibly redistribute odd nitrogen through gravitational sedimentation (a process commonly known as denitrification), which prolongs the ozone depletion process by slowing the reformation of the stable chlorine reservoirs. Spaceborne observations from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite are providing a rich new dataset for studying PSCs. CALIPSO is an excellent platform for studying polar processes with CALIOP acquiring, on average, over 300,000 backscatter profiles daily at latitudes between 55o and 82o in both hemispheres. PSCs are detected in the CALIOP backscatter profiles using a successive horizontal averaging scheme that enables detection of strongly scattering PSCs (e.g., ice) at the finest possible spatial resolution (5 km), while enhancing the detection of very tenuous PSCs (e.g., low number density NAT) at larger spatial scales (up to 135 km). CALIOP PSCs are separated into composition classes (STS; liquid/NAT mixtures; and ice) based on the ensemble 532-nm scattering ratio (the ratio of total-to-molecular backscatter) and 532-nm particulate depolarization ratio (which is sensitive to the presence of non-spherical, i.e. NAT and ice particles). In this paper, we will provide an overview of the CALIOP PSC detection and composition classification algorithm and then examine the vertical and spatial distribution of PSCs in the Arctic and Antarctic on vortex-wide scales for entire PSC seasons over the more than nine-year data record from 2006- 2015.
Polar stratospheric clouds (PSCs) play a crucial role in the springtime chemical depletion of ozone at high latitudes. PSC particles (primarily supercooled ternary solution, or STS droplets) provide sites for heterogeneous chemical reactions that transform stable chlorine and bromine reservoir species into highly reactive ozone-destructive forms. Furthermore, large nitric acid trihydrate (NAT) PSC particles can irreversibly redistribute odd nitrogen through gravitational sedimentation (a process commonly known as denitrification), which prolongs the ozone depletion process by slowing the reformation of the stable chlorine reservoirs. Spaceborne observations from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite are providing a rich new dataset for studying PSCs. CALIPSO is an excellent platform for studying polar processes with CALIOP acquiring, on average, over 300,000 backscatter profiles daily at latitudes between 55o and 82o in both hemispheres. PSCs are detected in the CALIOP backscatter profiles using a successive horizontal averaging scheme that enables detection of strongly scattering PSCs (e.g., ice) at the finest possible spatial resolution (5 km), while enhancing the detection of very tenuous PSCs (e.g., low number density NAT) at larger spatial scales (up to 135 km). CALIOP PSCs are separated into composition classes (STS; liquid/NAT mixtures; and ice) based on the ensemble 532-nm scattering ratio (the ratio of total-to-molecular backscatter) and 532-nm particulate depolarization ratio (which is sensitive to the presence of non-spherical, i.e. NAT and ice particles). In this paper, we will provide an overview of the CALIOP PSC detection and composition classification algorithm and then examine the vertical and spatial distribution of PSCs in the Arctic and Antarctic on vortex-wide scales for entire PSC seasons over the more than nine-year data record from 2006- 2015.
Polar stratospheric clouds (PSCs) play a crucial role in the springtime chemical depletion of ozone at high latitudes. PSC particles (primarily supercooled ternary solution, or STS droplets) provide sites for heterogeneous chemical reactions that transform stable chlorine and bromine reservoir species into highly reactive ozone-destructive forms. Furthermore, large nitric acid trihydrate (NAT) PSC particles can irreversibly redistribute odd nitrogen through gravitational sedimentation (a process commonly known as denitrification), which prolongs the ozone depletion process by slowing the reformation of the stable chlorine reservoirs. Spaceborne observations from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite are providing a rich new dataset for studying PSCs. CALIPSO is an excellent platform for studying polar processes with CALIOP acquiring, on average, over 300,000 backscatter profiles daily at latitudes between 55o and 82o in both hemispheres. PSCs are detected in the CALIOP backscatter profiles using a successive horizontal averaging scheme that enables detection of strongly scattering PSCs (e.g., ice) at the finest possible spatial resolution (5 km), while enhancing the detection of very tenuous PSCs (e.g., low number density NAT) at larger spatial scales (up to 135 km). CALIOP PSCs are separated into composition classes (STS; liquid/NAT mixtures; and ice) based on the ensemble 532-nm scattering ratio (the ratio of total-to-molecular backscatter) and 532-nm particulate depolarization ratio (which is sensitive to the presence of non-spherical, i.e. NAT and ice particles). In this paper, we will provide an overview of the CALIOP PSC detection and composition classification algorithm and then examine the vertical and spatial distribution of PSCs in the Arctic and Antarctic on vortex-wide scales for entire PSC seasons over the more than eight-year data record.
Polar stratospheric clouds (PSCs) play a crucial role in the springtime chemical depletion of ozone at high latitudes. PSC particles (primarily supercooled ternary solution, or STS droplets) provide sites for heterogeneous chemical reactions that transform stable chlorine and bromine reservoir species into highly reactive ozone-destructive forms. Furthermore, large nitric acid trihydrate (NAT) PSC particles can irreversibly redistribute odd nitrogen through gravitational sedimentation (a process commonly known as denitrification), which prolongs the ozone depletion process by slowing the reformation of the stable chlorine reservoirs. Spaceborne observations from the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) lidar on the CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) satellite are providing a rich new dataset for studying PSCs. CALIPSO is an excellent platform for studying polar processes with CALIOP acquiring, on average, over 300,000 backscatter profiles daily at latitudes between 55o and 82o in both hemispheres. PSCs are detected in the CALIOP backscatter profiles using a successive horizontal averaging scheme that enables detection of strongly scattering PSCs (e.g., ice) at the finest possible spatial resolution (5 km), while enhancing the detection of very tenuous PSCs (e.g., low number density NAT) at larger spatial scales (up to 135 km). CALIOP PSCs are separated into composition classes (STS; liquid/NAT mixtures; and ice) based on the ensemble 532-nm scattering ratio (the ratio of total-to-molecular backscatter) and 532-nm particulate depolarization ratio (which is sensitive to the presence of non-spherical, i.e. NAT and ice particles). In this paper, we will provide an overview of the CALIOP PSC detection and composition classification algorithm and then examine the vertical and spatial distribution of PSCs in the Arctic and Antarctic on vortex-wide scales for entire PSC seasons over the more than eight-year data record.
The reaction mechanisms for neutrino interactions with an {sup 40}Ar nucleus with the LBNF flux are calculated with the Giessen-Boltzmann-Uehling-Uhlenbeck (GiBUU) transport-theoretical implementation of these interactions. Quasielastic scattering, many-body effects, pion production and absorption and Deep Inelastic Scattering are discussed; they all play a role at the LBNF energies and are experimentally entangled with each other. Quasielastic scattering makes up for only about 1/3 of the total cross section whereas pion production channels make up about 2/3 of the total. This underlines the need for a consistent description of the neutrino-nucleus reaction that treats all channels on an equal, consistent footing. The results discussed here can also serve as useful guideposts for the Intermediate Neutrino Program.
Cancer is one of the most significant health care problems today. It is estimated that 1 in 2 men and women will be diagnosed with some form of cancer in their lifetime. Nearly two thirds of cancer patients will receive radiation therapy at some point in their care and the vast majority of these radiotherapy treatments will be performed with megavoltage photon therapy. Photon treatment techniques typically devote considerable attention to limiting the exposure of healthy tissues outside of the intended treatment volume. Nonetheless, small levels of unwanted stray radiation are incident upon the patient's whole body, which can increase the risk for numerous late effects, including second malignancies. When one considers that second cancers account for approximately 15% of all cancers and that it is projected that by the year 2020, there will be almost 20 million cancer survivors in the United States and four million in the UK, the need for improved accuracy in stray dose calculations appears likely to increase dramatically. Despite the obvious benefits this capability would afford, contemporary commercial treatment planning systems (TPSs) lack the ability to accurately predict stray dose outside the treatment field, e.g., beyond the 5% isodose surface. Thus, there is a large, variable, and systematic underestimation of stray radiation exposures by commonly used clinical TPSs for photon therapy. To overcome this problem, in a companion paper we proposed a simple, physics-based analytical model that calculates the total therapeutic and stray dose from photon treatment fields. The purpose of this work was to evaluate the accuracy of the basic physics in the analytical absorbed dose model for several simple treatment fields. We assessed the performance of the basic physics in an analytical model that calculates the total absorbed dose deposited by primary, leakage, and scattered photons both inside and outside of square treatment fields of 6 MV photon conventional radiotherapy. The assessment was accomplished by comparing model predictions of total dose with measured dose profiles in a water-phantom. The major finding of this study is that the physics-based model performed well, predicting dose in water within 11.5% dose difference or 5 mm distance to agreement with measured values in the therapeutic region and within 1.1 mGy/Gy or 0.5 mm distance to agreement with measured values in the out-of-field region at 90% of the locations considered. Contemporary external-beam photon TPSs do not include the capability to accurately predict the absorbed dose beyond a few centimeters outside of the treatment field. Our work suggests that it is feasible to improve dosimetric accuracy in the out-of-field region using a simple and computationally fast, physics-based analytical algorithm. This is demonstrated by the measured absorbed dose as well as the corresponding values calculated by two contemporary commercial TPSs (Pinnacle, Philips Health care, Andover, MA and Eclipse, Varian Medical Systems, Inc., Palo Alto, CA) and the analytical model considered in this work. It is apparent that both TPSs underestimated the absorbed dose by greater than 3 mGy/Gy at locations outside of the 0.5% relative dose level. In contrast, the analytical model evaluated in this work calculated absorbed dose in the same region within 0.4 mGy/Gy of measured values. The physics-based analytical dose model could prove useful in a number of different applications. The accurate knowledge of absorbed dose deposited outside of the treatment field is especially important for predicting radiation late effects, such as second cancer, fertility complications, and cardiac toxicity. It may also facilitate predictions of the effects of in utero exposure. We conclude that it is possible to accurately calculate the therapeutic and stray absorbed dose from a conventional radiotherapy treatment field of 6 MV photons using a physics-based analytical model. This was demonstrated by the agreement between measured and calculated doses in water within 11.5% relative dose difference or 5 mm distance to agreement in the therapeutic region, and within 1.1 mGy/Gy absolute dose difference or 0.5 mm distance to agreement in the out-of-field region at 90% of positions for all of the fields considered in this work. This is also illustrated by Figure 4 which plots dose values from analytical model predictions and measurements at five representative irradiation conditions and shows that the analytical model agreement is good in all cases. Furthermore, the model validated in this work evidently can predict dose values with better accuracy at out-of-field locations than contemporary TPSs. This and previous works, taken together, suggest that analytical physics-based models will offer advantages over TPSs or Monte Carlo models for whole-body dose calculations for several radiotherapy applications.
The objective of this IOP was to evaluate the performances of the new Leosphere R-MAN 510 lidar procured by the Australian Bureau of Meteorology, by testing it against the MPL and Raman lidars at the Darwin ARM site. This lidar is an eye-safe (355 nm), turn-key mini Raman lidar, which allows for the detection of aerosols and cloud properties, and the retrieval of particulate extinction profiles. To do so, the R-MAN 510 lidar has been operated at the Darwin ARM site, next to the MPL, Raman lidar, and Vaisala ceilometer for three months (from 20 January 2013 to 20 April 2013) in order to collect a good sample for statistical comparisons. The comparisons with the Raman lidar were not performed, since the Raman lidar attenuated backscatter and depolarization ratio product was not available. A new product has just been delivered to the ARM archive as a value-added product, hence this study will continue. Nevertheless we have developed software to match the different space and time resolutions of the other lidars and project the data onto a common grid to permit detailed comparison of the instruments’ performance and an enhanced analysis of clouds and aerosols through the use of composite data products, like the ratios of attenuated backscatters, attenuated scattering ratios and depolarization ratios. Comparisons between the MPL and R-MAN510 lidar data exhibit large differences in total attenuated backscatter at 355 and 532 nm, attenuated scattering ratios, and aerosol volume depolarization ratios. Differences in attenuated backscatter result mainly from the different relative contributions of scattering from molecules and particles at the different wavelengths, but there are some intriguing differences that will require further investigations. The differences in volume depolarization ratios are due to the much larger contribution of molecular returns to the volume depolarization ratio (5 times larger at 355 nm than at 532 nm). The R-MAN510 lidar is also found to be much less sensitive to daylight solar background illumination, which is greater at the visible wavelength than in the UV.
Consideration is given to a model of gamma-ray burst sources based on repeated Compton scatterings of soft photons by relativistic nonthermal electrons. Relativistic electrons which are continuously produced in the source radiate the total power L supplied to them. Higher order Compton scatterings, which occur when L(soft) is much less than L make the model distinct. The spectrum having an X-ray energy index of about one results from the superposition of the spectral components from several orders of Compton scattering; the change of the slope at several hundred keV arises from the Klein-Nishina decline of the scattering cross section.
High-dispersion IUE spectra have been obtained of HD 38087, a star associated with reflection nebulosity where 2175 A scattering has previously been observed. The presence of 2175 A in emission implies unusually large grains, an attempt was made to see how these unusual grains may have affected the depletions of gas-phase elements onto dust in the line of sight. Even though the observed scattering region constitutes only a fraction of the total column density of dust, it is expected that the present line-of-sight analysis provides useful information on the gas and dust in the scattering nebulosity. Somewhat larger overall depletions than normal are found, and it is found that the depletions of certain elements (manganese and zinc) are enhanced relative to the normal pattern of element-to-element depletions, suggesting that grain growth has occurred with some elements sticking to grains preferentially. The molecular fraction in the line of sight is low, in accord with similar lines of sight having low far-ultraviolet extinction and large depletions.
Pores within organic matter (OM) are a significant contributor to the total pore system in gas shales. These pores contribute most of the storage capacity in gas shales. Here we present a novel approach to characterize the OM pore structure (including the porosity, specific surface area, pore size distribution, and water accessibility) in Marcellus shale. By using ultrasmall and small-angle neutron scattering, and by exploiting the contrast matching of the shale matrix with suitable mixtures of deuterated and protonated water, both total and water-accessible porosity were measured on centimeter-sized samples from two boreholes from the nanometer to micrometer scale with good statistical coverage. Samples were also measured after combustion at 450 °C. Analysis of scattering data from these procedures allowed quantification of OM porosity and water accessibility. OM hosts 24–47% of the total porosity for both organic-rich and -poor samples. This porosity occupies as much as 29% of the OM volume. In contrast to the current paradigm in the literature that OM porosity is organophilic and therefore not likely to contain water, our results demonstrate that OM pores with widths >20 nm exhibit the characteristics of water accessibility. In conclusion, our approach reveals the complex structure and wetting behavior of the OM porosity at scales that are hard to interrogate using other techniques.
Single particle orientation and rotational tracking (SPORT) has recently become a powerful optical microscopy tool that can expose many molecular motions. Unfortunately, there is not yet a single microscopy technique that can decipher all particle motions in all environmental conditions, thus there are limitations to current technologies. Within, the two powerful microscopy tools of total internal reflection and interferometry are advanced to determine the position, orientation, and optical properties of metallic nanoparticles in a variety of environments. Total internal reflection is an optical phenomenon that has been applied to microscopy to produce either fluorescent or scattered light. The non-invasive far-field imaging technique is coupled with a near-field illumination scheme that allows for better axial resolution than confocal microscopy and epi-fluorescence microscopy. By controlling the incident illumination angle using total internal reflection fluorescence (TIRF) microscopy, a new type of imaging probe called “non-blinking” quantum dots (NBQDs) were super-localized in the axial direction to sub-10-nm precision. These particles were also used to study the rotational motion of microtubules being propelled by the motor protein kinesin across the substrate surface. The same instrument was modified to function under total internal reflection scattering (TIRS) microscopy to study metallic anisotropic nanoparticles and their dynamic interactions with synthetic lipid bilayers. Utilizing two illumination lasers with opposite polarization directions at wavelengths corresponding to the short and long axis surface plasmon resonance (SPR) of the nanoparticles, both the in-plane and out-of-plane movements of many particles could be tracked simultaneously. When combined with Gaussian point spread function (PSF) fitting for particle super-localization, the binding status and rotational movement could be resolved without degeneracy. TIRS microscopy was also used to find the 3D orientation of stationary metallic anisotropic nanoparticles utilizing only long-axis SPR enhancement. The polarization direction of the illuminating light was rotated causing the relative intensity of p-polarized and s-polarized light within the evanescent field to change. The interaction of the evanescent field with the particles is dependent on the orientation of the particle producing an intensity curve. This curve and the in-plane angle can be compared with simulations to accurately determine the 3D orientation. Differential interference contrast (DIC) microscopy is another non-invasive far-field technique based upon interferometry that does not rely on staining or other contrast enhancing techniques. In addition, high numerical aperture condensers and objectives can be used to give a very narrow depth of field allowing for the optical tomography of samples, which makes it an ideal candidate to study biological systems. DIC microscopy has also proven itself in determining the orientation of gold nanorods in both engineered environments and within cells. Many types of nanoparticles and nanostructures have been synthesized using lithographic techniques on silicon wafer substrates. Traditionally, reflective mode DIC microscopes have been developed and applied to the topographical study of reflective substrates and the imaging of chips on silicon wafers. Herein, a laser-illuminated reflected-mode DIC was developed for studying nanoparticles on reflective surfaces.
We plan to have two independent polarimetry systems at MESA based on totally different physical processes. A first one tries to minimize the systematic uncertainties in double polarized Mo/ller scattering, which is to be achieved by stored hydrogen atoms in an atomic trap (Hydro-Mo/ller-Polarimeter). The other one relies on the equality of polarizing and analyzing power which allows to measure the effective analyzing power of a polarimeter with very high accuracy. Since the status of Hydro-Mo/ller is presented in a separate paper we concentrate on the double scattering polarimeter in this article.
We consider the creation of kink-antikink pairs of a scalar field ϕ by the scattering of classical wave packets of a second scalar field ψ when there are no direct interactions between ϕ and ψ . The creation becomes possible only due to a quantum field that interacts with both ϕ and ψ . We scan parameter space and find it favorable for kink production when the initial wave packets have large total energy and wide spatial extent but scatter at low velocities. Published by the American Physical Society 2024
Here we present quantitative measurements of total electron numbers in laser-induced air breakdown at pressures ranging from atmospheric to 40 bar{sub g} by 10 ns and 100 ps laser pulses. A quantifiable definition for the laser-induced breakdown threshold is identified by a sharp increase in the measurable total electron numbers via dielectric-calibrated coherent microwave scattering. For the 10 ns laser pulse, the threshold of laser-induced breakdown in atmospheric air is defined as the total electron number of ∼10{sup 6}. This breakdown threshold decreases with an increase of pressure and laser photon energy (shorter wavelength), which is consistent with the theory of initial multiphoton ionization and subsequent avalanche processes. For the 100 ps laser pulse cases, a clear threshold is not present and only marginal pressure effects can be observed, which is due to the short pulse duration leading to stronger multiphoton ionization and minimal collisional avalanche ionization.
Diffusion thermopower S{sub d} is investigated, theoretically, as a function of temperature, T and electron concentration, n{sub s} in a n-type monolayer molebdenum disulfide (MoS{sub 2}). Electron scattering due to unscreened deformation potential (DP) coupling of TA phonons, screened DP coupling of LA phonons, and screened piezoelectric (PE) coupling of LA and TA phonons is considered. Total S{sub d} is dominated by electron scattering by TA phonons via unscreened DP coupling. S{sub d} is found to increase (decrease) with increasing T (n{sub s}). At low T and for high n{sub s}, S{sub d} ∼ T and n{sub s}{sup −1} as found from the Mott formula. At a given T and for given ns, S{sub d} in MoS{sub 2} is much larger than that in GaAs, due to the larger electron effective mass in the former.