Ion-beam machining of millimeter scale optics

An ion-beam microcontouring process is developed and implemented for figuring millimeter scale optics. Ion figuring is a noncontact machining technique in which a beam of high-energy ions is directed toward a target substrate to remove material in a predetermined and controlled fashion. Owing to this noncontact mode of material removal, problems associated with tool wear and edge effects, which are common in conventional machining processes, are avoided. Ion-beam figuring is presented as an alternative for the final figuring of small (<1-mm) optical components. The depth of the material removed by an ion beam is a convolution between the ion-beam shape and an ion-beam dwell function, defined over a two-dimensional area of interest. Therefore determination of the beam dwell function from a desired material removal map and a known steady beam shape is a deconvolution process. A wavelet-based algorithm has been developed to model the deconvolution process in which the desired removal contours and ion-beam shapes are synthesized numerically as wavelet expansions. We then mathematically combined these expansions to compute the dwell function or the tool path for controlling the figuring process. Various models have been developed to test the stability of the algorithm and to understand the critical parameters of the figuring process. The figuring system primarily consists of a duo-plasmatron ion source that ionizes argon to generate a focused (~200-mum FWHM) ion beam. This beam is rastered over the removal surface with a perpendicular set of electrostatic plates controlled by a computer guidance system. Experimental confirmation of ion figuring is demonstrated by machining a one-dimensional sinusoidal depth profile in a prepolished silicon substrate. This profile was figured to within a rms error of 25 nm in one iteration.     

Vacuum flashover on diamond-like carbon-coated insulators

Thin coatings of diamond-like carbon (DLC) were applied to cylindrical alumina and high temperature polyimide insulator samples. The coated insulators and uncoated controls were tested for resistance to surface flashover in vacuum under a dc voltage gradient. The DLC-coated insulators had significantly higher flashover potential than the controls and showed no visible tracking on their surface, even after multiple discharges. DLC coatings, applied at temperatures <350°C, show promise for improving the performance of HV vacuum feedthroughs, switches, and in other applications     

Lumped-element model for computing the equilibrium chargedistribution along a moving web

A lumped-element model has been used to explain charge conduction and convection in stationary and moving web systems. Incremental sectors of the web are assigned conductance and capacitance, and their individual potentials are computed. Ordinary circuit equations are used to determine the evolution of the charge distribution. The simulation method provides physical insight into the means by which charges are concentrated or rarified at points of geometrical transition, such as the peeling point between a web and a roller. Results compare favorably with the analytical solutions of other authors     

Large scale identification of genes involved in cell surface biosynthesis and architecture in Saccharomyces cerevisiae

The sequenced yeast genome offers a unique resource for the analysis of eukaryotic cell function and enables genome-wide screens for genes involved in cellular processes. We have identified genes involved in cell surface assembly by screening transposon-mutagenized cells for altered sensitivity to calcofluor white, followed by supplementary screens to further characterize mutant phenotypes. The mutated genes were directly retrieved from genomic DNA and then matched uniquely to a gene in the yeast genome database. Eighty-two genes with apparent perturbation of the cell surface were identified, with mutations in 65 of them displaying at least one further cell surface phenotype in addition to their modified sensitivity to calcofluor. Fifty of these genes were previously known, 17 encoded proteins whose function could be anticipated through sequence homology or previously recognized phenotypes and 15 genes had no previously known phenotype.     

Location of a high affinity Zn2+ binding site in the channel of alpha1beta1 gamma-aminobutyric acidA receptors

Zn2+ inhibits currents through gamma-aminobutyric acid (GABA)A receptors. Its affinity depends on the subunit composition; alpha1beta1 receptors are inhibited with high affinity (IC50 = 0.54 micro M). We sought to identify the residues that form this high affinity Zn2+ binding site. beta1His267 aligns with alpha1Ser272, a residue near the extracellular end of the M2 membrane-spanning segment that we previously demonstrated to be exposed in the channel. The Zn2+ affinity of alpha1beta1 H267S was reduced by 300-fold (IC50 = 161 micro M). Addition of a histidine at the aligned position in alpha1 creates a receptor, alpha1S272Hbeta1, that should have five channel-lining histidines; the Zn2+ affinity was increased 20-fold (IC50 = 0.025 micro M). Shifting the position of the histidine from the beta1 subunit to the aligned position in alpha1 with the two mutants alpha1S272Hbeta1H267S reduced the affinity (IC50 = 26 micro M) compared with wild-type. We infer that the high affinity Zn2+ binding site involves beta1His267 from at least two subunits. For two histidines to interact with a Zn2+ ion, the alpha carbons must be separated by <13 A. This limits the separation of the subunits and provides a constraint on the possible quaternary structures of the channel. The ability of a divalent cation to penetrate from the extracellular end of the channel to beta1His267 implies that the charge-selectivity filter, the structure that discriminates between anions and cations, is located at a more cytoplasmic position than beta1His267; this is consistent with our previous work that showed that positively charged sulfhydryl-specific reagents reacted with an engineered cysteine residue as cytoplasmic as alpha1T261C.     

Design of a circular cascaded arc torch array for plasma spray

A new concept has been verified for a plasma spray electrode system that improves plasma plume uniformity over that of a single arc torch. A six-electrode, circular, arc-cascade discharge was formed by mounting seven tungsten-rod electrodes radially around a stream of argon gas. To maintain the plasma plume, the cascade-arc discharge was repetitively triggered using a cascaded high-voltage spark initiated by a secondary spark gap. The typical cascade arc voltage and current were 130 V and 20 A. Results show that the cascaded arc array system can create a ring-shaped plasma plume having near-uniform electrical energy in the circular direction. This feature suggests that the configuration may have future use in plasma torch systems requiring uniform circular symmetry. In such a system, spray particles can be injected into the center of the plasma ring. At the same time, such an arrangement also could provide a lower-cost alternative to systems that use multiple two-electrode plasma torches arranged in a circular configuration. In the latter system, each two-electrode plasma torch is fed by a separate power supply.     

Localization of speech parameters by brain scan

Speech was studied in 18 patients who had a positive radioisotope brain scan within the left hemisphere and a history of a single stroke. Seventeen patients had definite language impariment. In most cases of either fluent or nonfluent aphasia, the center of the scan was behind the central sulcus. Patients with perisylvian involvement were much more likely to have severe comprehension deficit than those without such involvement. Those patients with the most severely decreased fluency were significantly more likely than those more fluent to have markedly decreased comprehension. In an occasional patient, involvement of fluency and comprehension was divergent, suggesting that these processes may be differentially affected.     

CD73/Adenosine Pathway Involvement in the Interaction of Non-Small Cell Lung Cancer Stem Cells and Bone Cells in the Pre-Metastatic Niche

Adenosinergic signaling is an important regulator of tissue homeostasis and extracellular accumulation of adenosine (Ado) and is associated with different pathologies, such as cancer. In non-small-cell lung cancer (NSCLC), a subset of CD133/CXCR4+ cancer stem cell (CSCs) has been demonstrated to initiate bone metastases. Here we investigated how NSCLC CSCs interact with osteoclasts (OCs) and osteoblasts (OBs) by modulating Ado production and OC activity. We proved that CSC-spheres, generated in vitro from NSCLC cell lines, express CD38, PC-1, and CD73, enzymes of the non-canonical adenosinergic pathway, produce high level of Ado, and down-regulate A1R and A3R inhibitory receptors, while expressing A2AR and A2BR. To address the Ado role and modulation of the in-bone pre-metastatic niche, we performed co-cultures of CSC-spheres with OCs and OBs cells. Firstly, we verified that active OCs do not activate non-canonical the adenosinergic pathway, conversely to OBs. OCs co-cultured with CSC-spheres increase Ado production that is related to the OC resorption activity and contributes to T-cell suppression. Finally, we proved the efficacy of anti-CD73 agents in blocking NSCLC cell migration. Overall, we assessed the importance of adenosinergic signaling in the interaction between CSCs and OCs at the pre-metastatic niche, with therapeutic implications related to Ado production.     

Immunohistochemical analysis of insulin-like growth factor-binding proteins -1, -2, and -3 in implantation sites of the mouse

PURPOSE: Our purpose was to analyze potential interactions between the embryo and the maternal endometrial interface in vivo by analyzing immunolocalization of insulin-like growth factor-binding proteins (IGFBPs) -1, -2, and -3 in implantation sites of the mouse. METHODS: Six-week-old B6D2F1 female mice underwent superovulation followed by mating and sacrifice at timed intervals. Formalin-fixed paraffin-embedded tissue was used for avidin-biotin immunocytochemical localization of IGFBPs utilizing standard methodology. RESULTS: Immunostaining at 1.5 days post coitum revealed light staining in the epithelial glandular cells and faint staining in decidual stroma for both IGFBP-1 and IGFBP-2. At 7.5-10.5 days post coitum, there was moderate-dense immunostaining in the decidualized stromal cells at the implantation site for all three IGFBPs, whereas light immunostaining was seen in nonimplantation site decidua. CONCLUSIONS: Compartmentalization of immunostaining for IGFBP-1, -2, and -3 within decidualized stroma suggests that these proteins may be regulated by trophoblastic and/or embryonic signals.