Promotion of Plasma-Induced Deuterium Uptake in Ruthenium Films by Monolayer-Thick Tin Layers

Surface impurities can have a significant influence on hydrogen uptake of materials. Examples such as the hydrogen spillover effect demonstrate that even very small surface impurity quantities can lead to order-of-magnitude changes in the total amount of hydrogen taken up by a material. In this work, we report the first experimental demonstration of promoted deuterium uptake in Ru thin films by Sn. Deuterium plasma exposures were carried out for Ru-capped targets covered by Sn up to a few atoms in thickness. After the exposure, the residual Sn content and the deuterium retention were measured to quantify the Sn etching and the deuterium uptake, respectively. By increasing the amount of Sn from zero to one atomic layer on Ru, we found after the exposure that the Sn content stays unchanged while the deuterium uptake rate severely increases with the Sn content by 2-3 orders of magnitude. These results can be understood by simulations using a reaction-diffusion model with multiple surface species and the lateral surface migration of deuterium. By contrast, as the as-deposited Sn content goes above one atomic layer, Sn removal takes place, and the deuterium uptake rate decreases with the as-deposited Sn content. Possible explanations are proposed by considering the interplay between Sn etching and deuterium uptake. In all, this work provides insights into interactions between multiple surface species in relation to plasma-induced hydrogen uptake. By further development, this could eventually lead to a potential mitigation method to circumvent the promoted hydrogen uptake in Ru-capped films.

Atomistic simulations of graphite etching at realistic time scales

Hydrogen-graphite interactions are relevant to a wide variety of applications, ranging from astrophysics to fusion devices and nano-electronics. In order to shed light on these interactions, atomistic simulation using Molecular Dynamics (MD) has been shown to be an invaluable tool. It suffers, however, from severe time-scale limitations. In this work we apply the recently developed Collective Variable-Driven Hyperdynamics (CVHD) method to hydrogen etching of graphite for varying inter-impact times up to a realistic value of 1 ms, which corresponds to a flux of ∼1020 m-2 s-1. The results show that the erosion yield, hydrogen surface coverage and species distribution are significantly affected by the time between impacts. This can be explained by the higher probability of C-C bond breaking due to the prolonged exposure to thermal stress and the subsequent transition from ion- to thermal-induced etching. This latter regime of thermal-induced etching - chemical erosion - is here accessed for the first time using atomistic simulations. In conclusion, this study demonstrates that accounting for long time-scales significantly affects ion bombardment simulations and should not be neglected in a wide range of conditions, in contrast to what is typically assumed.

Oscillatory vapour shielding of liquid metal walls in nuclear fusion devices

Providing an efficacious plasma facing surface between the extreme plasma heat exhaust and the structural materials of nuclear fusion devices is a major challenge on the road to electricity production by fusion power plants. The performance of solid plasma facing surfaces may become critically reduced over time due to progressing damage accumulation. Liquid metals, however, are now gaining interest in solving the challenge of extreme heat flux hitting the reactor walls. A key advantage of liquid metals is the use of vapour shielding to reduce the plasma exhaust. Here we demonstrate that this phenomenon is oscillatory by nature. The dynamics of a Sn vapour cloud are investigated by exposing liquid Sn targets to H and He plasmas at heat fluxes greater than 5 MW m⁻². The observations indicate the presence of a dynamic equilibrium between the plasma and liquid target ruled by recombinatory processes in the plasma, leading to an approximately stable surface temperature.

Vapour shielding is one of the interesting mechanisms for reducing the heat load to plasma facing components in fusion reactors. Here the authors report on the observation of a dynamic equilibrium between the plasma and the divertor liquid Sn surface leading to an overall stable surface temperature.

Design and characterization of a prototype divertor viewing infrared video bolometer for NSTX-U

The InfraRed Video Bolometer (IRVB) is a powerful tool to measure radiated power in magnetically confined plasmas due to its ability to obtain 2D images of plasma emission using a technique that is compatible with the fusion nuclear environment. A prototype IRVB has been developed and installed on NSTX-U to view the lower divertor. The IRVB is a pinhole camera which images radiation from the plasma onto a 2.5 μm thick, 9 × 7 cm² Pt foil and monitors the resulting spatio-temporal temperature evolution using an IR camera. The power flux incident on the foil is calculated by solving the 2D+time heat diffusion equation, using the foil's calibrated thermal properties. An optimized, high frame rate IRVB, is quantitatively compared to results from a resistive bolometer on the bench using a modulated 405 nm laser beam with variable power density and square wave modulation from 0.2 Hz to 250 Hz. The design of the NSTX-U system and benchtop characterization are presented where signal-to-noise ratios are assessed using three different IR cameras: FLIR A655sc, FLIR A6751sc, and SBF-161. The sensitivity of the IRVB equipped with the SBF-161 camera is found to be high enough to measure radiation features in the NSTX-U lower divertor as estimated using SOLPS modeling. The optimized IRVB has a frame rate up to 50 Hz, high enough to distinguish radiation during edge-localized-modes (ELMs) from that between ELMs.

Self-Regulated Plasma Heat Flux Mitigation Due to Liquid Sn Vapor Shielding

A steady-state high-flux H or He plasma beam was balanced against the pressure of a Sn vapor cloud for the first time, resulting in a self-regulated heat flux intensity near the liquid surface. A temperature response of the liquid surface characterized by a decoupling from the received heating power and significant cooling of the plasma in the neutral Sn cloud were observed. The plasma heat flux impinging on the target was found to be mitigated, as heat was partially dissipated by volumetric processes in the vapor cloud rather than wholly by surface effects. These results motivate further exploration of liquid metal solutions to the critical challenge of heat and particle flux handling in fusion power plants.

Insulin receptor activation in solitary fibrous tumours

Solitary fibrous tumours (SFTs) are known to overexpress insulin-like growth factor 2 (IGF-2). The down-stream oncogenic pathways of IGF-2, however, are not clear. Here we report uniform activation of the insulin receptor (IR) pathway in SFTs, which are mesenchymal tumours frequently associated with hypoglycaemia. Whereas the IR and its downstream signalling pathways were constitutively activated in SFTs, insulin-like growth factor 1 receptor (IGF-1R) was not expressed in these tumours. We also find that SFT cells secrete IGF-2 and proliferate in serum-free medium, consistent with an IGF-2/IR autocrine loop. The aetiological relevance of IGF-2 is supported by expression of IR-A, the IR isoform with high affinity for IGF-2, in all SFTs. Our studies suggest that IR activation plays an oncogenic role in SFTs.

Cattle lack vascular receptors for Escherichia coli O157:H7 Shiga toxins

Escherichia coli O157:H7 causes Shiga toxin (Stx)-mediated vascular damage, resulting in hemorrhagic colitis and the hemolytic uremic syndrome in humans. These infections are often foodborne, and healthy carrier cattle are a major reservoir of E. coli O157:H7. We were interested in knowing why cattle are tolerant to infection with E. coli O157:H7. Cattle tissues were examined for the Stx receptor globotriaosylceramide (Gb(3)), for receptivity to Stx binding in vitro, and for susceptibility to the enterotoxic effects of Stx in vivo. TLC was used to detect Gb(3) in tissues from a newborn calf. Gb(3) was detected by TLC in kidney and brain, but not in the gastrointestinal tract. Immunohistochemistry was used to define binding of Stx1 and Stx2 overlaid onto sections from cattle tissues. Stx1 and Stx2 bound to selected tubules in the cortex of the kidney of both newborn calves (n = 3) and adult cattle (n = 3). Stx did not bind to blood vessels in any of the six gastrointestinal and five extraintestinal organs examined. The lack of Gb(3) and of Stx receptivity in the gastrointestinal tract raised questions about the toxicity of Stx in bovine intestine. We found that neither viable E. coli O157:H7 nor Stx-containing bacterial extracts were enterotoxic (caused fluid accumulation) in ligated ileal loops in newborn calves. The lack of vascular receptors for Stx provides insight into why cattle are tolerant reservoir hosts for E. coli O157:H7.

Congenital mesoblastic nephroma t(12;15) is associated with ETV6-NTRK3 gene fusion: cytogenetic and molecular relationship to congenital (infantile) fibrosarcoma

Morphological, cytogenetic, and biological evidence supports a relationship between congenital (infantile) fibrosarcoma (CFS) and congenital mesoblastic nephroma (CMN). These tumors have a very similar histological appearance, and they are both associated with polysomies for chromosomes 8, 11, 17, and 20. Recently, CFS was shown to contain a novel t(12; 15)(p13;q25) translocation resulting in ETV6-NTRK3 gene fusion. The aims of this study were to determine whether congenital mesoblastic nephroma contains the t(12;15)(p13;q25) translocation and ETV6-NTRK3 gene fusion and whether ETV6-NTRK3 fusions, in CMN and CFS, antedate acquisition of nonrandom chromosome polysomies. To address these aims, we evaluated 1) ETV6-NTRK3 fusion transcripts by reverse transcriptase polymerase chain reaction and sequence analysis, 2) genomic ETV6-region chromosomal rearrangement by fluorescence in situ hybridization, and 3) chromosomal polysomies by karyotyping and fluorescence in situ hybridization. We report ETV6-NTRK3 fusion transcripts and/or ETV6-region rearrangement in five of six CMNs and in five of five CFSs. The ETV6-NTRK3 fusion transcripts and/or ETV-region chromosome rearrangements were demonstrated in two CMNs and one CFS that lacked chromosome polysomies. These findings demonstrate that t(12;15) translocation, and the associated ETV6-NTRK3 fusion, can antedate acquisition of chromosome polysomies in CMN and CFS. CMN and CFS are pathogenetically related, and it is likely that they represent a single neoplastic entity, arising in either renal or soft tissue locations.

Subtracted, unique-sequence, in situ hybridization: experimental and diagnostic applications

Nonrandom chromosomal aberrations, particularly in cancer, identify pathogenic biological pathways and, in some cases, have clinical relevance as diagnostic or prognostic markers. Fluorescence and colorimetric in situ hybridization methods facilitate identification of numerical and structural chromosome abnormalities. We report the development of robust, unique-sequence in situ hybridization probes that have several novel features: 1) they are constructed from multimegabase contigs of yeast artificial chromosome (YAC) clones; 2) they are in the form of adapter-ligated, short-fragment, DNA libraries that may be amplified by polymerase chain reaction; and 3) they have had repetitive sequences (eg, Alu and LINE elements) quantitatively removed by subtractive hybridization. These subtracted probes are labeled conveniently, and the fluorescence or colorimetric detection signals are extremely bright. Moreover, they constitute a stable resource that may be amplified through at least four rounds of polymerase chain reaction without diminishing signal intensity. We demonstrate applications of subtracted probes for the MYC and EWS oncogene regions, including 1) characterization of a novel EWS-region translocation in Ewing's sarcoma, 2) identification of chromosomal translocations in paraffin sections, and 3) identification of chromosomal translocations by conventional bright-field microscopy.

Retention of oncogenicity by a Marek's disease virus mutant lacking six unique short region genes

We previously reported the construction of Marek's disease virus (MDV) strains having mutations in various genes that map to the unique short (US) region of the viral genome (J.L. Cantello, A.S. Anderson, A. Francesconi, and R.W. Morgan, J. Virol. 65:1584-1588, 1991; M.S. Parcells, A.S. Anderson, and R.W. Morgan, Virus Genes 9:5-13, 1994; M.S. Parcells, A.S. Anderson, and R.W. Morgan, J. Virol. 68:8239-8253, 1994). These strains were constructed by using a high-passage-level serotype 1 MDV strain which grew well in chicken embryo fibroblasts. Despite the growth of the parent and mutant viruses in cell culture, in vivo studies were limited by poor growth of these strains in chickens. One of the mutants studied lacked 4.5 kbp of US region DNA and contained the lacZ gene of Escherichia coli inserted at the site of the deletion. The deletion removed MDV homologs to the US1, US2, and US10 genes of herpes simplex virus type 1 as well as three MDV-specific open reading frames. We now report the construction of a mutant MDV containing a similar deletion in the US region of the highly oncogenic RB1B strain. This mutant, RB1B delta 4.5lac, had a growth impairment in established chicken embryo fibroblasts similar to that described previously for MDVs lacking a functional US1 gene. In chickens, RB1B delta 4.5lac showed decreased early cytolytic infection, mortality, tumor incidence, and horizontal transmission. Several lymphoblastoid cell lines were established from RB1B delta 4.5lac-induced tumors, and virus reactivated from these cell lines was LacZ+. These results indicate that the deleted genes are nonessential for the transformation of chicken T cells or for the establishment and maintenance of latency. On the basis of the growth impairment observed for RB1B delta 4.5lac in cell culture and in vivo, we conclude that deletion of these genes affects the lytic replication of MDV. This is the first MDV mutant constructed in the RB1B oncogenic strain, and the methodology described herein provides for the direct examination of MDV-encoded determinants of oncogenicity.

Malignant histiocytosis: a clinical, histologic, and immunohistochemical study of 20 cases

To better characterize the diagnostic criteria and clinical behavior of malignant histiocytosis, 20 patients treated at the Mayo Clinic during a 25-year period were studied. A wide spectrum of cytologic differentiation was observed, with cells ranging from bland to highly anaplastic; hemophagocytosis was prominent only in conjunction with a bland histologic appearance. In surgical specimens, the diagnosis of malignant histiocytosis necessitated the use of immunoperoxidase methods for lysozyme, immunoglobulin light chain, and alpha-antitrypsin content, as well as cytochemical stains for acid phosphatase and nonspecific esterase. All autopsies showed that organ involvement had varied somewhat from that reported earlier. The correct diagnosis of malignant histiocytosis was made prior to death in only ten of the 20 cases. The mean survival in the 17 fatal cases was 7.6 months; three of the seven patients treated by aggressive chemotherapy achieved complete remission. Relatively longer survival was correlated with initial confinement to the skin and the absence of cytopenia or liver function abnormalities. Three patients with pulmonary involvement from malignant histiocytosis had apparent inappropriate antidiuretic hormone secretion in the absence of central nervous system disease. The accelerated clinical progression of malignant histiocytosis and its response to current chemotherapeutic regimens make rapid diagnosis and familiarity with the pathologic variations seen in this disorder imperative. Routine utilization of special light-microscopic and immunohistochemical stains is mandatory.

Use of imprints for monoclonal antibody studies: suitability of air-dried preparations from lymphoid tissues with an immunohistochemical method

Air-dried imprint preparations are conveniently produced from human lymphoid samples without the special methods required for snap-freezing tissues or rendering them into suspensions. T-cells, T-cell subsets (helper and suppressor), and HLA-DR-positive cells (B-lymphocytes, monocytic-histiocytic cells) can be identified in such imprints by the use of commercially obtained mouse hybridoma antibodies with a simple two-step immunoperoxidase method. Direct nuclear morphologic correlation with surface determinants is achieved by this method. Immunoreactivity is retained only eight to 10 days in such air-dried preparations, and attempts to prolong reactivity have been unsuccessful so far.

Immunoglobulin light chain staining of lymph node biopsies: an interlaboratory comparison

In recent years, the demonstration of cell surface or cytoplasmic monoclonal immunoglobulin kappa or lambda light chains in lymphoid tissues has been considered evidence of their B-cell origin. In an effort to evaluate the reproducibility of results among various laboratories performing immunoperoxidase immunostaining of lymph node specimens, 12 lymph node biopsies were similarly fixed and processed, and serial sections submitted to four laboratories for staining by the unlabelled antibody (peroxidase-antiperoxidase conjugate) technique. Seven of these were malignant lymphomas four were negative, and one was metastatic carcinoma. Participants were not told the diagnosis and were asked to evaluate each specimen for the presence of monoclonal light chain staining. While the overall agreement in results were good, one of four laboratories differed from the other three in four out of the 12 cases. The significance of this finding and its implications are discussed.

Physician extenders in walk-in clinics: a prospective evaluation of the AMOSIST program

The Automated Military Outpatient System (AMOS) Project was developed to improve the ambulatory care of patients with episodic and chronic illnesses. During the development of its episodic care component, the relative frequency of problems treated by the walk-in clinic staff was analyzed and showed a high volume of acute minor illnesses. A simple, conservative triage system run by non-professionals was developed to screen patients to a clinic for benign, self-limited illnesses run by physician-extenders. This group, the equivalent of civilian licensed practical nurses and nurses' aides, was trained in a task-oriented fashion to treat 44 common minor illnesses. Clinical algorithms for these illnesses were developed and used as training tools, memory aids, and auditing instruments. This program is now operating in 26 US Army hospitals and caring for some 44,000 patients a month in the continetal United States. We report the results of a prospective audit of the corpsmen and a study of the patient attitude and acceptance of the program.