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We report on an experimental observation of the streaking of betatron x rays in a curved laser wakefield accelerator. The streaking of the betatron x rays was realized by launching a laser pulse into a plasma with a transverse density gradient. By controlling the plasma density and the density gradient, we realized the steering of the laser driver, electron beam, and betatron x rays simultaneously. Moreover, we observed an energy-angle correlation of the streaked betatron x rays and utilized it in diagnosing the electron acceleration process in a single-shot mode. Our work could also find applications in advanced control of laser beam and particle propagation. More importantly, the angular streaked betatron x ray has an intrinsic spatiotemporal correlation, which makes it a promising tool for single-shot pump-probe applications.
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The creation and disruption of inertially collimated plasma flows are investigated through experiment, simulation, and analytical modeling. Supersonic plasma jets are generated by laser-irradiated plastic cones and characterized by optical interferometry measurements. Targets are magnetized with a tunable B field with strengths of up to 5 T directed along the axis of jet propagation. These experiments demonstrate a hitherto unobserved phenomenon in the laboratory, the magnetic disruption of inertially confined plasma jets. This occurs due to flux compression on axis during jet formation and can be described using a Lagrangian-cylinder model of plasma evolution implementing finite resistivity. The basic physical mechanisms driving the dynamics of these systems are described by this model and then compared with two-dimensional radiation-magnetohydrodynamic simulations. Experimental, computational, and analytical results discussed herein suggest that contemporary models underestimate the electrical conductivity necessary to drive the amount of flux compression needed to explain observations of jet disruption.
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We report the first observation, in a supersonic flow, of the evolution of the Kelvin-Helmholtz instability from a single-mode initial condition. To obtain these data, we used a novel experimental system to produce a steady shock wave of unprecedented duration in a laser-driven experiment. The shocked, flowing material creates a shear layer between two plasmas at high energy density. We measured the resulting interface structure using radiography. Hydrodynamic simulations reproduce the large-scale structures very well and the medium-scale structures fairly well, and imply that we observed the expected reduction in growth rate for supersonic shear flow.
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Talbot-Lau x-ray interferometry is a refraction-based diagnostic that can map electron density gradients through phase-contrast methods. The Talbot-Lau x-ray deflectometry (TXD) diagnostics have been deployed in several high energy density experiments. To improve diagnostic performance, a monochromatic TXD was implemented on the Multi-Tera Watt (MTW) laser using 8 keV multilayer mirrors (Δθ/θ = 4.5%-5.6%). Copper foil and wire targets were irradiated at 1014-1015 W/cm2. Laser pulse length (â¼10 to 80 ps) and backlighter target configurations were explored in the context of Moiré fringe contrast and spatial resolution. Foil and wire targets delivered increased contrast <30%. The best spatial resolution (<6 µm) was measured for foils irradiated 80° from the surface. Further TXD diagnostic capability enhancement was achieved through the development of advanced data postprocessing tools. The Talbot Interferometry Analysis (TIA) code enabled x-ray refraction measurements from the MTW monochromatic TXD. Additionally, phase, attenuation, and dark-field maps of an ablating x-pinch load were retrieved through TXD. The images show a dense wire core of â¼60 µm diameter surrounded by low-density material of â¼40 µm thickness with an outer diameter ratio of â¼2.3. Attenuation at 8 keV was measured at â¼20% for the dense core and â¼10% for the low-density material. Instrumental and experimental limitations for monochromatic TXD diagnostics are presented. Enhanced postprocessing capabilities enabled by TIA are demonstrated in the context of high-intensity laser and pulsed power experimental data analysis. Significant advances in TXD diagnostic capabilities are presented. These results inform future diagnostic technique upgrades that will improve the accuracy of plasma characterization through TXD.
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Talbot-Lau x-ray interferometry has been implemented to map electron density gradients in High Energy Density Physics (HEDP) experiments. X-ray backlighter targets have been evaluated for Talbot-Lau X-ray Deflectometry (TXD). Cu foils, wires, and sphere targets have been irradiated by 10-150 J, 8-30 ps laser pulses, while two pulsed-power generators (â¼350 kA, 350 ns and â¼200 kA, 150 ns) have driven Cu wire, hybrid, and laser-cut x-pinches. A plasma ablation front generated by the Omega EP laser was imaged for the first time through TXD for densities >1023 cm-3. Backlighter optimization in combination with x-ray CCD, image plates, and x-ray film has been assessed in terms of spatial resolution and interferometer contrast for accurate plasma characterization through TXD in pulsed-power and high-intensity laser environments. The results obtained thus far demonstrate the potential of TXD as a powerful diagnostic for HEDP.
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Magnetized Liner Inertial Fusion (MagLIF) at Sandia National Laboratories involves a laser preheating stage where a few-ns laser pulse passes through a few-micron-thick plastic window to preheat gaseous fusion fuel contained within the MagLIF target. Interactions with this window reduce heating efficiency and mix window and target materials into the fuel. A recently proposed idea called "Laser Gate" involves removing the window well before the preheating laser is applied. In this article, we present experimental proof-of-principle results for a pulsed-power implementation of Laser Gate, where a thin current-carrying wire weakens the perimeter of the window, allowing the fuel pressure to push the window open and away from the preheating laser path. For this effort, transparent targets were fabricated and a test facility capable of studying this version of Laser Gate was developed. A 12-frame bright-field laser schlieren/shadowgraphy imaging system captured the window opening dynamics on microsecond timescales. The images reveal that the window remains largely intact as it opens and detaches from the target. A column of escaping pressurized gas appears to prevent the detached window from inadvertently moving into the preheating laser path.
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Energy-transport effects can alter the structure that develops as a supernova evolves into a supernova remnant. The Rayleigh-Taylor instability is thought to produce structure at the interface between the stellar ejecta and the circumstellar matter, based on simple models and hydrodynamic simulations. Here we report experimental results from the National Ignition Facility to explore how large energy fluxes, which are present in supernovae, affect this structure. We observed a reduction in Rayleigh-Taylor growth. In analyzing the comparison with supernova SN1993J, a Type II supernova, we found that the energy fluxes produced by heat conduction appear to be larger than the radiative energy fluxes, and large enough to have dramatic consequences. No reported astrophysical simulations have included radiation and heat conduction self-consistently in modeling supernova remnants and these dynamics should be noted in the understanding of young supernova remnants.
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The coherent elastic scattering of neutrinos off nuclei has eluded detection for four decades, even though its predicted cross section is by far the largest of all low-energy neutrino couplings. This mode of interaction offers new opportunities to study neutrino properties and leads to a miniaturization of detector size, with potential technological applications. We observed this process at a 6.7σ confidence level, using a low-background, 14.6-kilogram CsI[Na] scintillator exposed to the neutrino emissions from the Spallation Neutron Source at Oak Ridge National Laboratory. Characteristic signatures in energy and time, predicted by the standard model for this process, were observed in high signal-to-background conditions. Improved constraints on nonstandard neutrino interactions with quarks are derived from this initial data set.
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BACKGROUND: In randomized trials, screening mammography has led to decreased mortality from breast cancer. However, the low positive predictive value of mammography (i.e., the proportion of patients with a positive test result who actually have breast cancer) results in a large number of unnecessary biopsies. We determined whether scintimammography with technetium-99m-sestamibi is a useful supplemental diagnostic tool for women with nonpalpable breast abnormalities identified by conventional mammography. METHODS: Scintimammography was performed preoperatively on 70 women who were 31-66 years of age (mean age and median age = 51 years). These women had nonpalpable breast abnormalities identified by conventional mammography; subsequently, a needle-localization excisional biopsy of each suspicious lesion was performed. Scintimammographic images were interpreted independently by two nuclear medicine physicians who were blinded to all clinical and pathologic data, and an interobserver variation analysis was performed. RESULTS: Interobserver variation analysis of the scintimammographic findings showed an agreement for breast diagnosis of 97% and a kappa coefficient of 0.90. Comparison of scintimammographic findings and histopathologic results revealed that the sensitivity (proportion of patients with breast cancer who had a positive test result), the specificity (proportion of patients without breast cancer who had a negative test result), the positive predictive value and the negative predictive value (proportion of patients with a negative test result who actually did not have breast cancer) of scintimammography were 56% (95% confidence interval [CI] = 23%-85%), 87% (95% CI = 75%-94%), 38% (95% CI = 15%-68%), and 93% (95% CI = 82%-98%), respectively. Four of nine breast cancers were not detected by scintimammography. CONCLUSION: Because of excellent interobserver agreement, scintimammography provides an objective way of detecting primary breast carcinoma. In view of its low sensitivity and positive predictive value, however, scintimammography is not currently recommended as a screening test in patients with nonpalpable positive mammographic findings.
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Neoplasias de la Mama/diagnóstico por imagen , Mamografía/métodos , Tecnecio Tc 99m Sestamibi , Adulto , Anciano , Biopsia , Neoplasias de la Mama/patología , Carcinoma Ductal de Mama/diagnóstico por imagen , Carcinoma Ductal de Mama/patología , Carcinoma Intraductal no Infiltrante/diagnóstico por imagen , Carcinoma Intraductal no Infiltrante/patología , Estudios de Evaluación como Asunto , Reacciones Falso Negativas , Femenino , Humanos , Tamizaje Masivo , Persona de Mediana Edad , Variaciones Dependientes del Observador , Palpación , Valor Predictivo de las Pruebas , Cintigrafía , Estudios Retrospectivos , Sensibilidad y Especificidad , Método Simple CiegoRESUMEN
Soft x-ray emission from laser irradiated gold foils was measured at the Omega-60 laser system using the Dante photodiode array. The foils were heated with 2 kJ, 6 ns laser pulses and foil thicknesses were varied between 0.5, 1.0, and 2.0 µm. Initial Dante analysis indicates peak emission temperatures of roughly 100 eV and 80 eV for the 0.5 µm and 1.0 µm thick foils, respectively, with little measurable emission from the 2.0 µm foils.
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Experiments were performed to mitigate the hard x-ray background commonly observed in backlit pinhole imagers. The material of the scaffold holding the primary backlighter foil was varied to reduce the laser-plasma instabilities responsible for hot electrons and resulting hard x-ray background. Radiographic measurements with image plates showed a factor of >25 decrease in x-rays between 30 and 67 keV when going from a plastic to Al or V scaffold. A potential design using V scaffold offers a signal-to-background ratio of 6:1, a factor of 2 greater than using the bare plastic scaffold.
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Talbot-Lau X-ray deflectometry (TXD) has been developed as an electron density diagnostic for High Energy Density (HED) plasmas. The technique can deliver x-ray refraction, attenuation, elemental composition, and scatter information from a single Moiré image. An 8 keV Talbot-Lau interferometer was deployed using laser and x-pinch backlighters. Grating survival and electron density mapping were demonstrated for 25-29 J, 8-30 ps laser pulses using copper foil targets. Moiré pattern formation and grating survival were also observed using a copper x-pinch driven at 400 kA, â¼1 kA/ns. These results demonstrate the potential of TXD as an electron density diagnostic for HED plasmas.
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Ultra-intense short pulse lasers incident on solid targets (e.g., thin Au foils) produce well collimated, broad-spectrum proton beams. These proton beams can be used to characterize magnetic fields, electric fields, and density gradients in high energy-density systems. The LLNL-Imaging Proton Spectrometer (L-IPS) was designed and built [H. Chen et al., Rev. Sci. Instrum. 81, 10D314 (2010)] for use with such laser produced proton beams. The L-IPS has an energy range of 50 keV-40 MeV with a resolving power (E/dE) of about 275 at 1 MeV and 21 at 20 MeV, as well as a single spatial imaging axis. In order to better characterize the dispersion and imaging capability of this diagnostic, a 3D finite element analysis solver is used to calculate the magnetic field of the L-IPS. Particle trajectories are then obtained via numerical integration to determine the dispersion relation of the L-IPS in both energy and angular space.
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Regional transcutaneous oximetry is a new, noninvasive diagnostic technique for the investigation of peripheral vascular disease (PVD) that uses differences in limb and trunk transcutaneous PO2 to assess the adequacy of local perfusion. The application of such measurements would be of great importance in diabetes, in which limb ischemia is commonly difficult to assess. A group of diabetic subjects with symptomatic PVD was studied with regional oximetry, Doppler-assisted blood pressure measurements, and arteriography. Doppler studies correlated poorly to symptom grade and angiographic data, while oximetry clearly demonstrated limb hypoxia under the functional conditions appropriate to the patients' clinical symptomatology. The superiority of oximetry to Doppler studies was highly significant (X2 = 12.64, P less than 0.001). Regional transcutaneous oximetry should therefore be the noninvasive diagnostic test of choice in the initial evaluation of the diabetic limb for PVD. Because of its dependence on the adequacy of local oxygenation, transcutaneous oximetry is a powerful tool for investigation of the pathophysiology of PVD and will, in the future, have wide-ranging applications to the diagnosis and therapy of PVD.
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Diabetes Mellitus/fisiopatología , Angiopatías Diabéticas/diagnóstico , Pie/irrigación sanguínea , Anciano , Angiografía/métodos , Presión Sanguínea , Femenino , Humanos , Masculino , Persona de Mediana Edad , Oximetría/métodos , Flujo Sanguíneo Regional , UltrasonografíaRESUMEN
Oncolytic adenoviruses, such as Delta-24-RGD (Δ24RGD), are replication-competent viruses that are genetically engineered to induce selective cancer cell lysis. In cancer cells, Δ24RGD induces massive autophagy, which is required for efficient cell lysis and adenoviral spread. Understanding the cellular mechanisms underlying the regulation of autophagy in cells treated with oncolytic adenoviruses may provide new avenues to improve the therapeutic effect. In this work, we showed that cancer cells infected with Δ24RGDundergo autophagy despite the concurrent activation of the AKT/mTOR pathway. Moreover, adenovirus replication induced sustained activation of JNK proteins in vitro. ERK1/2 phosphorylation remained unchanged during adenoviral infection, suggesting specificity of JNK activation. Using genetic ablation and pharmacological inactivation of JNK, we unequivocally demonstrated that cells infected with Δ24RGD required JNK activation. Thus, genetic co-ablation of JNK1 and JNK2 genes or inhibition of JNK kinase function rendered Δ24RGD-treated cells resistant to autophagy. Accordingly, JNK activation induced phosphorylation of Bcl-2 and prevented the formation of Bcl-2/Beclin 1 autophagy suppressor complexes. Using an orthotopic model of human glioma xenograft, we showed that treatment with Δ24RGD induced phosphorylation and nuclear translocation of JNK, as well as phosphorylation of Bcl-2. Collectively, our data identified JNK proteins as an essential mechanistic link between Δ24RGD infection and autophagy in cancer cells. Activation of JNK without inactivation of the AKT/mTOR pathway constitutes a distinct molecular signature of autophagy regulation that differentiates Δ24RGD adenovirus from the mechanism used by other oncolytic viruses to induce autophagy and provides a new rationale for the combination of oncolytic viruses and chemotherapy.
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Adenoviridae/fisiología , Autofagia , Proteínas Quinasas JNK Activadas por Mitógenos/fisiología , Virus Oncolíticos/fisiología , Línea Celular , Humanos , Viroterapia Oncolítica , Transducción de SeñalRESUMEN
UNLABELLED: Scintimammography with 99mTc-sestamibi can be used as a complementary technique to improve the mammogram's sensitivity and specificity for detection of breast carcinoma. We have observed in some patients focal areas of increased 99mTc-sestamibi uptake with no corresponding abnormalities on physical examination or mammogram. A phantom device and a special needle were designed to stereotactically localize these lesions before biopsy. METHODS: After intravenous injection of 30 mCI (1110 MBq) of 99m Tc-sestamibi, a prone lateral image of the abnormal breast was obtained. With the patient in the prone position, the breast was compressed with two fenestrated plates in the prone position. The x and y coordinates of the abnormal hot spot of the breast were determined. The z coordinate of focal 99mTc-sestamibi uptake was determined by advancing a localizer needle through a selected predetermined hole of the fenestrated plate using real-time visualization on the persistence monitor. The tip of the opturator inside the needle is welded with 57Co to determine the depth of the hot spot in the breast. RESULTS: Three women, all of whom had normal mammogram and breast physical examinations, were studied using 99mTc-sestamibi prone breast imaging. Pre-excisional biopsy needle localization of abnormal focal uptake was performed. Two women demonstrated infiltrative ductal carcinoma, and the third had proliferative fibrocystic disease of the breast. CONCLUSION: Our initial experience demonstrates that nuclear medicine guided stereotactic needle biopsy of the breast in patients with positive scintimammograms is technically feasible. In the future, this technology will enable us to detect breast carcinoma in the absence of clear-cut clinical and mammographic findings.
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Biopsia con Aguja/métodos , Mama/diagnóstico por imagen , Mama/patología , Mamografía , Técnicas Estereotáxicas , Adulto , Biopsia con Aguja/instrumentación , Femenino , Humanos , Persona de Mediana Edad , Fantasmas de Imagen , Cintigrafía , Radiofármacos , Sensibilidad y Especificidad , Tecnecio Tc 99m SestamibiRESUMEN
To determine the immediate effect of running and interrupted suture on anastomotic compliance, catheters were positioned in both femoral arteries of ten dogs for pressure measurement and introduction of an electromagnetic rheoangiometry loop probe. Changes in the area of the loop allowed simultaneous determination of the static and pulsatile internal diameter of the vessel when the loop was in an externally induced magnetic field. After dynamic diameter compliance (Cd) of the undisturbed femoral arteries was obtained, they were exposed, stripped of their adventitia, and divided. They were subsequently anastomosed with 6-0 polypropylene suture using a running anastomosis for one femoral artery and an interrupted anastomosis for the other; Cd was then measured 1 cm proximal to the anastomoses, at the anastomoses, and 1 cm distal to the anastomoses. The Cd significantly decreased with both running and interrupted anastomoses; running anastomoses showed significantly greater decrease in compliance than did interrupted.
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Arterias/cirugía , Técnicas de Sutura , Procedimientos Quirúrgicos Vasculares/métodos , Animales , Cateterismo , Adaptabilidad , Perros , Campos Electromagnéticos , Arteria Femoral/cirugíaRESUMEN
Transcutaneous oxygen tension Ptco2 is directly related to skin oxygen delivery. Regional transcutaneous oximetry ( RTO ) compares peripheral and truncal (Ptco2), yielding a regional perfusion index indicative of local limb perfusion. The relative diagnostic values of RTO , Doppler ankle-brachial pressure ratio (ABR), pulse volume recording (PVR), and toe pulse reappearance time (PRT/2) were studied in 64 limbs of patients with diabetes. These limbs were clinically classifiable into claudication, rest pain, and gangrene groups. Regional transcutaneous oximetry had a higher diagnostic accuracy than ABR (X2 = 27.47, P less than .001), PVR (X2 = 7.54, P less than .01), and PRT/2 (X2 = 10.99, P less than .001). Regional transcutaneous oximetry was universally applicable and the degree of hypoxia observed correlated with clinical symptoms. Significant hypoxia predicted large-vessel angiographic lesions, many of which were reconstructible . Regional transcutaneous oximetry should be the initial noninvasive test in diabetic peripheral vascular disease.
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Diabetes Mellitus/diagnóstico , Oximetría , Anciano , Diabetes Mellitus/fisiopatología , Extremidades/irrigación sanguínea , Femenino , Humanos , Isquemia/diagnóstico , Isquemia/fisiopatología , Masculino , Persona de Mediana EdadRESUMEN
We investigated the histologic and biochemical effects of carbon dioxide and neodymium (Nd)-YAG laser welding on the healing of venotomies. Ten canine femoral venotomies 2 cm in length were approximated and welded with 10 600-nm wavelength, 1-W power over 20 to 25 s for CO2 laser, and 1060-nm wavelength, 1-W power over 30 to 40 s for Nd-YAG laser. On removal at one to three weeks, all veins (4/4 welded by CO2 and 6/6 by Nd-YAG) were patent without hematomas. Histologic and biochemical analyses of the venous tissues demonstrated active healing at the venotomy sites. We conclude that the CO2 and Nd-YAG lasers can be used successfully to weld venotomies and may provide an alternative to conventional suture techniques for repair of vascular lesions.
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Terapia por Láser , Venas/cirugía , Animales , Dióxido de Carbono , Perros , Estudios de Evaluación como Asunto , Humanos , Venas/anatomía & histología , Cicatrización de HeridasRESUMEN
Transection of the common bile duct (CBD) secondary to iatrogenic or civilian trauma is a devastating injury associated with a high incidence of complications, especially biliary fistula and stricture formation. We evaluated the efficacy of Fibrin Sealant--a biologic adhesive containing highly concentrated human fibrinogen--in primary end-to-end anastomosis of the transected CBD in ten adult mongrel dogs. Postoperative T-tube stents in the CBD anastomosis and abdominal drainage were not used. Only two absorbable sutures were used for each CBD anastomosis. The dogs were reexplored postoperatively at intervals varying from one week to nine months; cholangiography was performed at postoperative intervals varying from one to six months. Examination of CBD specimens harvested one month or more after surgery revealed complete healing and no signs of previous injury. Histologic examination disclosed well-healed ductal tissue, without a significant inflammatory response. One dog had an anastomotic leak, and two had moderate narrowing of the CBD anastomosis. Our experience in experimental CBD anastomosis indicates that Fibrin Sealant helps seal biliary anastomoses against leakage; controls bleeding from cut edges of bile duct segments; has good systemic and local compatibility; may promote bile duct wound healing; and significantly reduces the number of sutures needed for primary repair, thereby decreasing the potential for anastomotic ischemia, mucosal damage, and biliary stricture formation.