Machine learning for detection of 3D features using sparse x-ray tomographic reconstruction.

In many inertial confinement fusion (ICF) experiments, the neutron yield and other parameters cannot be completely accounted for with one and two dimensional models. This discrepancy suggests that there are three dimensional effects that may be significant. Sources of these effects include defects in the shells and defects in shell interfaces, the fill tube of the capsule, and the joint feature in double shell targets. Due to their ability to penetrate materials, x rays are used to capture the internal structure of objects. Methods such as computational tomography use x-ray radiographs from hundreds of projections, in order to reconstruct a three dimensional model of the object. In experimental environments, such as the National Ignition Facility and Omega-60, the availability of these views is scarce, and in many cases only consists of a single line of sight. Mathematical reconstruction of a 3D object from sparse views is an ill-posed inverse problem. These types of problems are typically solved by utilizing prior information. Neural networks have been used for the task of 3D reconstruction as they are capable of encoding and leveraging this prior information. We utilize half a dozen, different convolutional neural networks to produce different 3D representations of ICF implosions from the experimental data. Deep supervision is utilized to train a neural network to produce high-resolution reconstructions. These representations are used to track 3D features of the capsules, such as the ablator, inner shell, and the joint between shell hemispheres. Machine learning, supplemented by different priors, is a promising method for 3D reconstructions in ICF and x-ray radiography, in general.

Use of computer vision for analysis of image datasets from high temperature plasma experiments.

Great strides have been made in improving the quality of x-ray radiographs in high energy density plasma experiments, enabled in part by innovations in engineering and manufacturing of integrated circuits and materials. As a consequence, the radiographs of today are filled with a great deal of detail, but few of these features are extracted in a systematic way. Analysis techniques familiar to plasma physicists tend toward brittle 1D lineout or Fourier transform type analyses. The techniques applied to process our data have not kept pace with improvements in the quality of our data. Fortunately, the field of computer vision has a wealth of tools to offer, which have been widely used in industrial imaging and, more recently, adopted in biological imaging. We demonstrate the application of computer vision techniques to the analysis of x-ray radiographs from high energy density plasma experiments, as well as give a brief tutorial on the computer vision techniques themselves. These tools robustly extract 2D contours of shocks, boundaries of inhomogeneities, and secondary flows, thereby allowing for increased automation of analysis, as well as direct and quantitative comparisons with simulations.

Soft x-ray spectrum unfold of K-edge filtered x-ray diode arrays using cubic splines.

Cubic spline interpolation is able to recover temporally and spectrally resolved soft x-ray fluxes from an array of K-edge filtered x-ray diodes without the need for a priori assumptions about the spectrum or the geometry of the emitting volume. The mathematics of the cubic spline interpolation is discussed in detail. The analytic nature of the cubic spline solution allows for analytical error propagation, and the method of calculating the error for radiation temperature, spectral power, and confidence intervals of the unfolded spectrally resolved flux is explained. An unfold of a blackbody model demonstrates the accuracy of the cubic spline unfold. Tests of cubic spline performance using spectrally convolved detailed atomic model simulation results have been performed to measure the method's ability to conserve spectral power to within a factor of 2 or better in line-dominated regimes. The unfold is also demonstrated to work when information from the x-ray diode array is limited due to high signal-to-noise ratios or the lack of signal due to over-attenuation or over-filtration of the x-ray diode signal. The robustness of the unfold with respect to background subtraction and raw signal processing, signal alignment between diode traces, limited signal information, and initial conditions is discussed. Results from an example analysis of a halfraum drive are presented to demonstrate the capabilities of the unfold in comparison with previously established methods.

Reply to 'Thomson scattering in inhomogeneous plasmas: The Role of the Fluctuation-Dissipation Theorem'.

In a comment on our article "Theory of Thomson scattering in inhomogeneous media", V. V. Belyi asserts that there is an inconsistency in our method of applying gradient effects via the dielectric superposition principle, in violation of the fluctuation-dissipation theorem; and that his Klimontovich-Langevin formulation would be more appropriate to our application. While we agree that a generalization, along the lines of Belyi's work, would be required for strongly coupled systems, for the weakly coupled systems which we considered, these corrections are not necessary and our approach is still appropriate.Replying to: V. Belyi, Sci. Rep. 8 (2018); https://doi.org/10.1038/s41598-018-25319-6 .

Theory of Thomson scattering in inhomogeneous media.

Thomson scattering of laser light is one of the most fundamental diagnostics of plasma density, temperature and magnetic fields. It relies on the assumption that the properties in the probed volume are homogeneous and constant during the probing time. On the other hand, laboratory plasmas are seldom uniform and homogeneous on the temporal and spatial dimensions over which data is collected. This is particularly true for laser-produced high-energy-density matter, which often exhibits steep gradients in temperature, density and pressure, on a scale determined by the laser focus. Here, we discuss the modification of the cross section for Thomson scattering in fully-ionized media exhibiting steep spatial inhomogeneities and/or fast temporal fluctuations. We show that the predicted Thomson scattering spectra are greatly altered compared to the uniform case, and may lead to violations of detailed balance. Therefore, careful interpretation of the spectra is necessary for spatially or temporally inhomogeneous systems.

Density functional theory investigations of NiN2S2 reactivity as a function of nitrogen donor type and N-H...S hydrogen bonding inspired by nickel-containing superoxide dismutase.

Density functional theory calculations on a series of six square-planar NiN2S2 complexes have been performed. The nitrogen donor type was varied from diamino in Ni(bme-dmed), 1, to amino-amido in [Ni(mama)]-, 2, to diamido in [Ni(ema)]2-, 3. The sulfur-oxygenated derivative Ni(bme-O2-dmed), 4, and hydrogen-bonded derivatives (5 and 6) of 2 and 3 were also studied. Full geometric optimization and subsequent population analyses were performed using the 6-311g(d,p) basis set. The frontier molecular orbitals for all complexes contain significant nickel and sulfur character. Molecular electrostatic potentials show that amido nitrogen donors increase electron density at nickel relative to sulfur. Sulfur modification further shifts electron density away from the ligand towards the metal. It is proposed that the nitrogen donor type and sulfur modification may regulate sulfur-site reactivity in nickel-containing superoxide dismutase.

Quantum chemical modeling of Co--C bond activation in B(12)-dependent enzymes.

Recent progress in computational modeling of the catalytic activation of cobalt-carbon bond cleavage shows that quantum chemical calculations could be an important part of coenzyme B(12) research. Particular emphasis has been placed on density functional theory, which is now emerging as a powerful tool to elucidate the electronic structure and spectroscopic properties of the active sites of metalloenzymes.

Laparoscopic partial nephrectomy and wedge resection for the treatment of renal malignancy.

The widespread use of abdominal ultrasonography, CT, and MRI has led to an increase in the number of incidentally detected renal masses, some of which are malignant. Numerous studies suggest that partial nephrectomy or wedge resection of these lesions yield cure rates similar to those obtained with radical surgery. Laparoscopic nephron-sparing surgery is one of the more challenging minimally invasive surgical techniques, and its use is largely restricted to specialized medical centers. The techniques and available results are described.

Morbid obesity and the prone position: a case report.

An improperly positioned prone patient can experience serious impairment of cardiopulmonary function. However, with appropriate preparation, even an extremely obese patient can safely tolerate the prone position.

Laparoscopic repair of incisional and parastomal hernias after major genitourinary or abdominal surgery.

BACKGROUND AND PURPOSE: Abdominal wall or parastomal hernias following major genitourinary or abdominal surgery are a significant surgical problem. Open surgical repair is difficult because of adhesion formation and poor definition of the hernia fascial edges. Laparoscopic intervention has allowed effective correction of these abdominal wall hernias. PATIENTS AND METHODS: From November 1997 to June 2000, 14 male and 3 female patients underwent laparoscopic abdominal wall herniorrhaphy at our institution. Of these, 13 patients received incisional and 4 parastomal hernia repair. All hernia defects were repaired using a measured piece of Gore-Tex DualMesh. A retrospective review of each patient's history and operative characteristics was undertaken. RESULTS: All repairs were successful. No patient required conversion to an open procedure, and there were no intraoperative complications. The average operative time was 4 (range 2.5-6.5) and 4.3 (range 3.75-5.5) hours in the incisional and parastomal group, respectively. The average hospital stay was 4.9 days (range 2-12) for the incisional group and 3.8 (range 3-4) days for the parastomal group. To date, two patients experienced a recurrence of incisional hernias, at 5 and 8 months postoperatively. No recurrences have developed in the parastomal hernia repairs at 2 to 33 months. CONCLUSION: Laparoscopic repair of abdominal wall incisional or parastomal hernias provides an excellent anatomic correction of such defects. Adhesions are lysed under magnified laparoscopic vision, and the true limits of the fascial defects are clearly identified. The DualMesh is easy to work with and has yielded excellent results. A comparison with open repair with respect to perioperative factors and long-term success is currently under way.

Is the CO adduct of myoglobin bent, and does it matter?

Early reports of a severely bent CO adduct in myoglobin inspired the idea that heme proteins discriminate against CO, relative to O(2), via steric hindrance imposed by a distal histidine residue. Recent results showing that the bound CO is only slightly distorted do not by themselves overthrow the steric hypothesis, because the steric energy could be stored in displacements of the protein. However, experimental data on site-directed mutants show that the main determinant of ligand affinity changes is the polarity of the binding pocket and that H-bonding by the distal histidine accounts for about 85% of the O(2)/CO discrimination while steric hindrance accounts for the remaining 15%.

Laparoscopic management of bladder pheochromocytoma.

Pheochromocytoma primarily involving the bladder is an uncommon pathologic finding. Patients may present with transient hypertension associated with palpitations and diaphoresis on micturition. A case of bladder pheochromocytoma treated by laparoscopic partial cystectomy is presented. The management principles of bladder pheochromocytoma for our specific case are discussed. Successful treatment requires that the correct diagnosis and tumor location be made in conjunction with the obligatory preoperative preparation of the patient.

Laparoscopic partial nephrectomy and wedge resection.

Partial nephrectomy is a more challenging operation than radical or simple nephrectomy, primarily because of the risk of complications such as bleeding. This problem is even more troublesome with minimally invasive approaches because of the dearth of effective hemostatic instruments and supplies. The location of the lesion determines whether a transperitoneal or a retroperitoneal route will be employed. Centrally located or anterior renal lesions generally are approached transperitoneally whereas peripheral lateral or posterior lesions are accessed by retroperitoneoscopy. The Harmonic Scalpel with slow cutting and high coagulation settings is useful for incising the renal capsule and parenchyma. The argon beam coagulator is helpful to stop any persistent bleeding. The few reported series of laparoscopic partial nephrectomy indicate considerably longer operative times than are needed for open surgery and hospitalization of upwards of 5 days, largely to monitor drainage and urine leakage. It is hoped that this advanced laparoscopic technique will become more user friendly with further developments in techniques and instrumentation to provide patients with the expected benefits of minimally invasive surgery.

Laparoscopic lymph node dissection: pelvic and retroperitoneal.

The application of laparoscopic procedures to the field of urology continues to expand at a rapid rate. The initial animal studies performed in the late 1980s were brought into the clinical arena by 1990. The first widely accepted procedure was laparoscopic pelvic lymph node dissection for the staging of prostate cancer. Since that time, numerous laparoscopic procedures have been developed and accepted. Herein we discuss laparoscopic pelvic lymph node dissection for the staging evaluation of cancer of the prostate with possible applications to the bladder, urethra, and penis. The technique of laparoscopic retroperitoneal lymph node dissection has been used for cancer of the testes and will also be described. The indications and a brief review of the postoperative results will also be discussed for each malignancy.