Characterization of a 1D-imaging high-energy x-ray backlighter driven by the National Ignition Facility Advanced Radiographic Capability laser.

Plastic deformation of samples compressed to Mbar pressures at high strain rates at the National Ignition Facility (NIF) forms the basis of ongoing material strength experiments in conditions relevant to meteor impacts, geophysics, armor development, and inertial confinement fusion. Hard x-ray radiography is the primary means of measuring the evolution of these samples, typically employing a slit-collimated high-Z microdot driven by the NIF laser to generate >40 keV x rays [E. Gumbrell et al., Rev. Sci. Instrum. 89, 10G118 (2018) and C. M. Huntington et al., Rev. Sci. Instrum. 89, 10G121 (2018)]. Alternatively, a dysprosium "micro-flag" target driven by the Advanced Radiographic Capability laser (∼2 kJ, 10 ps) can deliver significantly higher spatiotemporal resolution [M. P. Hill et al., Rev. Sci. Instrum. 92, 033535 (2021)], especially in high-opacity samples. Initial experiments revealed problematic brightness and spectral gradients from this source, but by radiographing a set of diamond-turned, 105 µm-thick Pb test objects and supported by simulations using the 3D Monte Carlo code GEANT4, these geometry-dependent gradients across the field of view are quantified and mitigation strategies are assessed. In addition to significantly enhancing the modulation transfer function compared to the existing system, image stacking from multiple layers of image plate is shown to almost double the signal to noise ratio that will reduce uncertainties in future dynamic strength experiments.

HELLP syndrome: laboratory parameters and clinical course in four patients treated with plasma exchange.

We report our apheresis department's experience with four patients with HELLP (hemolysis, elevated liver enzymes, low platelets) syndrome. The average age of the patients was 23.25 years (range 19-27). Three were in their second pregnancy while one was a primigravida. All had symptoms of pre-eclampsia prior to delivery. All experienced the syndrome postpartum. Plasma exchange was instituted an average of 3.25 days postpartum (range 1.08-7.33 days). All underwent plasmapheresis with fresh frozen plasma replacement. The average number of plasma exchange treatments was four (range 1-8). The first laboratory parameter to reach its peak/nadir was the aspartate aminotransferase (AST), followed by the lactate dehydrogenase (LDH) enzyme level, followed by the hemoglobin (HGB) level, and, finally, the platelet count (PLT). The AST was the first parameter to peak and the first to normalize. In the three cases in which more than one plasmapheresis procedure was performed, plasmapheresis was required for an average of 98 hours (range 39-206 hours) after a normal AST level was obtained in order to achieve a self-sustaining platelet count of > or = 100 x 10(9)/L. No additional exchanges were required to maintain the PLT once a PLT of over 100 x 10(9)/L was attained. The laboratory values normalized in the following order: AST, HGB, PLT, and LDH. Three patients were discharged anemic. One was discharged with a normal LDH level. By our experience, awaiting normal LDH levels as an indicator for cessation of plasma exchange therapy would mean subjecting the patients to many unnecessary procedures.(ABSTRACT TRUNCATED AT 250 WORDS)

A compressive strength study of complete ceramic crowns. Part II.

The original study by this group compared the crushing strength of Cerestore crowns with porcelain-fused-to-metal crowns and porcelain jackets. Since that time, two porcelains, Dicor and Renaissance, have become available. This study compares Cerestore, Dicor, and Renaissance crowns using a porcelain-fused-to-metal crown as a standard for the type of crown with maximum strength that is currently available and an all-porcelain crown to represent the porcelain with the least strength. All of the methods used in the first study were used again. The results demonstrated that these new porcelains have strengths that make them questionable for routine use in every posterior crown situation.

A compressive strength study of an all-ceramic crown.

Eighteen crowns were subjected to the same occlusal loading. The porcelain-fused-to-metal crown was more than twice as resistant to the load than the Cerestore crown and almost four times stronger than the porcelain crown. These tests show that porcelain fused to metal has demonstrated its capability as a strong posterior restoration. The Cerestore crown, though superior to the porcelain crown, is significantly less resistant to fracture than the porcelain-fused-to-metal restoration.