Response to Comment on "Insulator-metal transition in dense fluid deuterium".

In their comment, Desjarlais et al claim that a small temperature drop occurs after isentropic compression of fluid deuterium through the first-order insulator-metal transition. We show that their calculations do not correspond to the experimental thermodynamic path, and that thermodynamic integrations with parameters from first-principles calculations produce results in agreement with our original estimate of the temperature drop.

Insulator-metal transition in dense fluid deuterium.

Dense fluid metallic hydrogen occupies the interiors of Jupiter, Saturn, and many extrasolar planets, where pressures reach millions of atmospheres. Planetary structure models must describe accurately the transition from the outer molecular envelopes to the interior metallic regions. We report optical measurements of dynamically compressed fluid deuterium to 600 gigapascals (GPa) that reveal an increasing refractive index, the onset of absorption of visible light near 150 GPa, and a transition to metal-like reflectivity (exceeding 30%) near 200 GPa, all at temperatures below 2000 kelvin. Our measurements and analysis address existing discrepancies between static and dynamic experiments for the insulator-metal transition in dense fluid hydrogen isotopes. They also provide new benchmarks for the theoretical calculations used to construct planetary models.

Posterior C1C2 harms fusion with 3D surgical navigation.

Several types of atlantoaxial instability can justify surgical fixation. The instrumented fusion procedure described by Harms with screw fixation of the C1 lateral masses and C2 pedicles is a demanding technique that provides lasting stabilization. However, it has been associated with nerve and vascular complications due to the local anatomical configuration. Surgical navigation systems can help improve the procedure's accuracy. We describe a series of 11 cases of C1C2 Harms fusion performed with surgical navigation and intraoperative 3D imaging checks. All procedures were carried out completely with satisfactory implant placement. There were no adverse events related to the procedure during the peri-operative period. No cortical breach was detected using cone-beam CT at the end of the procedure. The technical challenges and risks associated with C1C2 Harms fusion have led to the use of 3D intraoperative imaging systems, when available.

Endopelvic Approach for Iliac Crest Bone Harvesting.

BACKGROUND: The anterior approach to lumbar spine surgery has grown in popularity in the past few years; spinal fusion of the last 2 lumbar levels is often required. Although alternatives to bone grafting are available, including recombinant human bone morphogenetic protein 2 or bone substitutes, only cancellous autologous bone has all the required factors for bone growth. To avoid the use of bone substitutes, remote iliac crest bone harvesting remains the gold standard. However, this technique may lead to some unfavorable outcomes. CASE DESCRIPTION: The patient was a 46-year-old man with severe back and left leg pain. Magnetic resonance imaging showed an inflammatory discopathy of L5-S1 associated with a left posterior lateral herniated disc. Conservative treatment failed, and surgical treatment of the lumbar disk disease and the herniated disc was scheduled. A novel iliac crest bone harvesting method was performed during the retroperitoneal approach to the anterior lumbar interbody fusion. The patient's postoperative course was uneventful. There were no adverse outcomes related to the bone donor site. CONCLUSIONS: This is the first in vivo report of endopelvic iliac crest bone harvesting. This technique allows bone graft harvesting to be performed with the same retroperitoneal approach used for anterior lumbar interbody fusion. It avoids many common complications associated with the remote approach to the iliac crest.

CT analysis of C2 pedicles morphology and considerations of useful parameters for screwing.

INTRODUCTION: Surgery of cervical spine steadily requires realizing posterior osteosynthesis. The anchoring of instrumentation in C2 steadily constitutes an important stake of prognosis. Pedicle screwing is one of the best options and remains associated with a low morbidity. The aim of this CT study is to provide, from a wide population, the descriptive anatomical parameters of C2 pedicles. The data enable this analysis of feasibility of C2 pedicles screwing. MATERIALS AND METHODS: A continuous and retrospective series have explored 100 CT scans of the cervical spine without finding C2 fracture. The software OSIRIX v5.0.2 has been used. The dimensions of the pedicles in C2 as length, diameter, and distance from the vertebral foramens have been measured from the preset posterior entry point. Their orientation has been described in the axial and sagittal plan by the pedicle transverse angle, the sagittal angle and the pedicle-lamina angle used as a visible mark during the procedure. At least, the feasibility of pedicle screwing has been evaluated using a diameter criterion higher than 4 mm. RESULTS: The dimensions analysis of 200 studied pedicles has found an average length as 26.18 mm, an average diameter as 5.18 mm and an average distance between the entry point and the vertebral foramen as 9.06 mm. Their orientations have an average PTA as 36.6° and a SA as 25.8°. The average of the PLA was 81.3. The screwing feasibility has been evaluated as 92.5 % in the whole series. CONCLUSION: These morphological data come from a large series give some help for the C2 pedicle screwing preoperative planning. These lean on 3D measures but also on accessible mark during the procedure and despite the difference of the patient orientation. A CT preoperative planning of the pedicle screwing remains essential because more than 7 % of the pedicles have a diameter lower than 4 mm.

Hydrodynamic study of plasma amplifiers for soft-x-ray lasers: a transition in hydrodynamic behavior for plasma columns with widths ranging from 20 µm to 2 mm.

Plasma-based seeded soft-x-ray lasers have the potential to generate high energy and highly coherent short pulse beams. Due to their high density, plasmas created by the interaction of an intense laser with a solid target should store the highest amount of energy density among all plasma amplifiers. Our previous numerical work with a two-dimensional (2D) adaptive mesh refinement hydrodynamic code demonstrated that careful tailoring of plasma shapes leads to a dramatic enhancement of both soft-x-ray laser output energy and pumping efficiency. Benchmarking of our 2D hydrodynamic code in previous experiments demonstrated a high level of confidence, allowing us to perform a full study with the aim of the way for 10-100 µJ seeded soft-x-ray lasers. In this paper, we describe in detail the mechanisms that drive the hydrodynamics of plasma columns. We observed transitions between narrow plasmas, where very strong bidimensional flow prevents them from storing energy, to large plasmas that store a high amount of energy. Millimeter-sized plasmas are outstanding amplifiers, but they have the limitation of transverse lasing. In this paper, we provide a preliminary solution to this problem.

Characterization of the preformed plasma for high-intensity laser-plasma interaction.

The interaction of a very intense, very short laser pulse is modified by the presence of a preformed plasma prior to the main short pulse. The preformed plasma is created by a small prepulse interacting with the target prior to the main pulse. The prepulse has been monitored using a water-cell-protected fast photodiode allowing on every shot a high dynamic measurement of the pulse profile. Simultaneously we have used time-resolved interferometry to look at the preformed plasma on a 300 TW, 700 fs laser. The two-dimensional density maps obtained have been compared with two-dimensional hydrodynamic simulations.

Density measurement of shock compressed foam using two-dimensional x-ray radiography.

We have used spherically bent quartz crystal to image a laser-generated shock in a foam medium. The foam targets had a density of 0.16 g/cm(3) and thickness of 150 microm, an aluminum/copper pusher drove the shock. The experiment was performed at the Titan facility at Lawrence Livermore National Laboratory using a 2 ns, 250 J laser pulse to compress the foam target, and a short pulse (10 ps, 350 J) to generate a bright Ti K alpha x-ray source at 4.5 keV to radiograph the shocked target. The crystal used gives a high resolution (approximately 20 microm) monochromatic image of the shock compressed foam.

Hartmann wave-front measurement at 13.4 nm with lambdaEUV/120 accuracy.

We report, for the first time to our knowledge, experimental demonstration of wave-front analysis via the Hartmann technique in the extreme ultraviolet range. The reference wave front needed to calibrate the sensor was generated by spatially filtering a focused undulator beam with 1.7- and 0.6-microm-diameter pinholes. To fully characterize the sensor, accuracy and sensitivity measurements were performed. The incident beam's wavelength was varied from 7 to 25 nm. Measurements of accuracy better than lambdaEUV/120 (0.11 nm) were obtained at lambdaEUV = 13.4 nm. The aberrations introduced by an additional thin mirror, as well as wave front of the spatially unfiltered incident beam, were also measured.