Tantalum strength at extreme strain rates from impact-driven Richtmyer-Meshkov instabilities.

Recently, Richtmyer-Meshkov instability (RMI) experiments driven by high explosives and fielded with perturbations on a free surface have been used to study strength at extreme strain rates and near zero pressure. The RMI experiments reported here used impact loading, which is experimentally simpler, more accurate to analyze, and which also allows the exploration of a wider range of conditions. Three experiments were performed on tantalum at shock stresses from 20 to 34 GPa, with six different perturbation sizes at each shock level, making this the most comprehensive set of strength-focused RMI experiments reported to date on any material. The resulting estimated average strengths of 1200-1400 MPa at strain rates of 10^{7}/s exceeded, by 40% or more, a common power law extrapolation from data at strain rates below 10^{4}/s. Taken together with other data in the literature that show much higher strength at simultaneous high rates and high pressure, these RMI data isolated effects and indicated that, in the range of conditions examined, the pressure effects are more significant than rate effects.

Laser-plasmas in the relativistic-transparency regime: Science and applications.

Laser-plasma interactions in the novel regime of relativistically induced transparency (RIT) have been harnessed to generate intense ion beams efficiently with average energies exceeding 10 MeV/nucleon (>100 MeV for protons) at "table-top" scales in experiments at the LANL Trident Laser. By further optimization of the laser and target, the RIT regime has been extended into a self-organized plasma mode. This mode yields an ion beam with much narrower energy spread while maintaining high ion energy and conversion efficiency. This mode involves self-generation of persistent high magnetic fields (∼104 T, according to particle-in-cell simulations of the experiments) at the rear-side of the plasma. These magnetic fields trap the laser-heated multi-MeV electrons, which generate a high localized electrostatic field (∼0.1 T V/m). After the laser exits the plasma, this electric field acts on a highly structured ion-beam distribution in phase space to reduce the energy spread, thus separating acceleration and energy-spread reduction. Thus, ion beams with narrow energy peaks at up to 18 MeV/nucleon are generated reproducibly with high efficiency (≈5%). The experimental demonstration has been done with 0.12 PW, high-contrast, 0.6 ps Gaussian 1.053 µm laser pulses irradiating planar foils up to 250 nm thick at 2-8 × 1020 W/cm2. These ion beams with co-propagating electrons have been used on Trident for uniform volumetric isochoric heating to generate and study warm-dense matter at high densities. These beam plasmas have been directed also at a thick Ta disk to generate a directed, intense point-like Bremsstrahlung source of photons peaked at ∼2 MeV and used it for point projection radiography of thick high density objects. In addition, prior work on the intense neutron beam driven by an intense deuterium beam generated in the RIT regime has been extended. Neutron spectral control by means of a flexible converter-disk design has been demonstrated, and the neutron beam has been used for point-projection imaging of thick objects. The plans and prospects for further improvements and applications are also discussed.

Ozena in Immigrants of Differing Backgrounds.

Ozena, or atrophic rhinitis, is a chronic nasal process seen in Africa, India, and the Middle East. It is marked by the triad of fetid nasal discharge, crusting, and atrophy, and is often associated with Klebsiella infection. We present cases of ozena with nasal Klebsiella in three unrelated patients, including two east African children and one Saudi adult. All three patients grew Klebsiella species in culture and required prolonged treatment with multiple methodologies, including antibiotics, saline rinses, and surgical debridement. They differed greatly in time from presentation to diagnosis, and demonstrated various stages of the disease process. Ozena is rarely seen in the United States, and when it is seen, it is often misdiagnosed. Lack of prompt, adequate treatment can lead to long-term sequelae such as obliteration of nasal architecture, anosmia, sinus and skull base destruction, and social disenfranchisement due to the extreme foul smell of the nasal discharge. Clinicians should maintain a high index of suspicion for primary atrophic rhinitis when presented with its classic symptoms. Culture-directed and prolonged therapy with appropriate follow-up is a necessary component of a successful treatment plan.

Loss of two introns from the Magnolia tripetala mitochondrial cox2 gene implicates horizontal gene transfer and gene conversion as a novel mechanism of intron loss.

Intron loss is often thought to occur through retroprocessing, which is the reverse transcription and genomic integration of a spliced transcript. In plant mitochondria, several unambiguous examples of retroprocessing are supported by the parallel loss of an intron and numerous adjacent RNA edit sites, but in most cases, the evidence for intron loss via retroprocessing is weak or lacking entirely. To evaluate mechanisms of intron loss, we designed a polymerase chain reaction (PCR)-based assay to detect recent intron losses from the mitochondrial cox2 gene within genus Magnolia, which was previously suggested to have variability in cox2 intron content. Our assay showed that all 22 examined species have a cox2 gene with two introns. However, one species, Magnolia tripetala, contains an additional cox2 gene that lacks both introns. Quantitative PCR showed that both M. tripetala cox2 genes are present in the mitochondrial genome. Although the intronless gene has lost several ancestral RNA edit sites, their distribution is inconsistent with retroprocessing models. Instead, phylogenetic and gene conversion analyses indicate that the intronless gene was horizontally acquired from a eudicot and then underwent gene conversion with the native intron-containing gene. The models are presented to summarize the roles of horizontal gene transfer and gene conversion as a novel mechanism of intron loss.

The National Ignition Facility neutron imaging system.

The National Ignition Facility (NIF) is scheduled to begin deuterium-tritium (DT) shots possibly in the next several years. One of the important diagnostics in understanding capsule behavior and to guide changes in Hohlraum illumination, capsule design, and geometry will be neutron imaging of both the primary 14 MeV neutrons and the lower-energy downscattered neutrons in the 6-13 MeV range. The neutron imaging system (NIS) described here, which we are currently building for use on NIF, uses a precisely aligned set of apertures near the target to form the neutron images on a segmented scintillator. The images are recorded on a gated, intensified charge coupled device. Although the aperture set may be as close as 20 cm to the target, the imaging camera system will be located at a distance of 28 m from the target. At 28 m the camera system is outside the NIF building. Because of the distance and shielding, the imager will be able to obtain images with little background noise. The imager will be capable of imaging downscattered neutrons from failed capsules with yields Y(n)>10(14) neutrons. The shielding will also permit the NIS to function at neutron yields >10(18), which is in contrast to most other diagnostics that may not work at high neutron yields. The following describes the current NIF NIS design and compares the predicted performance with the NIF specifications that must be satisfied to generate images that can be interpreted to understand results of a particular shot. The current design, including the aperture, scintillator, camera system, and reconstruction methods, is briefly described. System modeling of the existing Omega NIS and comparison with the Omega data that guided the NIF design based on our Omega results is described. We will show NIS model calculations of the expected NIF images based on component evaluations at Omega. We will also compare the calculated NIF input images with those unfolded from the NIS images generated from our NIS numerical modeling code.

Mirror-image reversal of coronal computed tomography scans.

OBJECTIVES/HYPOTHESIS: Mirror-image reversal of coronal computed tomography (CT) scans can be a significant problem in patient care, potentially leading to wrong-sided surgery and malpractice suits. There is no literature describing the problem of mirror-image reversal of coronal CT scans. Generally, medical errors are not widely published: however, with the emphasis on reduction of errors in medicine, this topic should be openly discussed. STUDY DESIGN: Retrospective review of patient care and an assessment of current methods. METHODS: Two cases of mirror-image reversal of coronal CT scans were reviewed, and the authors found that each case represented a different type of error. In the first case, the error was recognized in the operating room. The second case resulted in wrong-sided surgery, and a lawsuit was filed. These two separate occurrences led to a review of the methods for determining right versus left side for orienting and labeling of CT scans. Orientation of coronal scans depends on whether the patient is prone or supine. Thus, technician input is required. If a labeling mistake is made, radiologists may not readily catch the mistake because of the symmetry of the head and neck anatomy. RESULTS: A review of the markings on each scan should provide the otolaryngologist with enough information to determine whether the scan is mislabeled. CONCLUSION: The incidence of mislabeled coronal CT scans is unknown. This error can result in inappropriate patient care and lawsuits for wrong-sided surgery. Awareness of the potential problem and open discussion of interpretation and prevention are necessary.

Subglottic laryngeal paraganglioma.

OBJECTIVES: To review the clinical and pathological picture of laryngeal paragangliomas and compare laryngeal paragangliomas with the three other types of laryngeal neuroendocrine neoplasms. STUDY DESIGN: The study presents a case review of a patient with a subglottic laryngeal paraganglioma treated at our institution, with a literature review of the laryngeal neuroendocrine neoplasms. Included is a review of all four neuroendocrine neoplasms, taking a close look at a comparison between laryngeal paragangliomas and atypical carcinoids tumors. All cases of subglottic laryngeal paragangliomas reported in the literature were also compiled and tabulated. METHODS: The patient's record was reviewed for age, symptomatology, workup, and surgical procedures performed. RESULTS: The patient was disease free 36 months after undergoing a tracheostomy for airway control, followed by a cricoid split for complete excision of the tumor. CONCLUSIONS: It is important to differentiate among the four laryngeal neuroendocrine neoplasms, especially between atypical carcinoids and paragangliomas. Each tumor requires different treatments, with the former requiring a more aggressive approach. Paragangliomas must be completely excised to prevent their recurrence, and this approach should be considered a curative treatment. In addition, the immunohistochemical battery is of paramount importance in obtaining the correct pathological diagnosis.