Syntheses and structural characterization of zirconium-tin and zirconium-lead binary and ternary systems

The binary zirconium-tin system was reinvestigated. The A15 phase appears to be a line phase with a Zr[subscript]4Sn composition. This phase is extremely unstable with oxygen contamination. The Zr[subscript]5Sn[subscript]3 (Mn[subscript]5Si[subscript]3-type) and Zr[subscript]5Sn[subscript]4 (Ti[subscript]5Ga[subscript]4-type) compounds are line phases below 1000°C, the latter being a self-interstitial phase of the former. ZrSn[subscript]2 is the tin-richest phase. There is an one-phase region between these phases with partial self-interstitials at high temperatures. The zirconium-lead system behaves similarly: there are an A15 phase with a Zr[subscript]~5.8Pb composition, Zr[subscript]5Pb[subscript]3 (Mn[subscript]5Si[subscript]3-type) and Zr[subscript]5Pb[subscript]4 (Ti[subscript]5Ga[subscript]4-type) compounds, and a high temperature solid solution between Zr[subscript]5Pb[subscript]\u3e3.5 and Zr[subscript]5Pb[subscript]4 from below 1000°C; however, the ZrSn[subscript]2 analogue is not formed;The Mn[subscript]5Si[subscript]3-type phases in these systems can accommodate third elements interstitially to form stoichiometric compounds Zr[subscript]5Sn[subscript]3Z (Z = B, C, N, O, Al, Si, P, S, Cu, Zn, Ga, Ge, As and Se) and Zr[subscript]5Pb[subscript]3Z (Z = Al, Si, P, S, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Ag, Cd, In, Sn, Sb and Te) as well as their self-interstitial derivatives. The stoichiometric nature of most of the interstitial phases was confirmed by structure analyses of single crystals for Z = C, O, and Ge in Zr[subscript]5Sn[subscript]3Z and Z=Zn and Pb in Zr[subscript]5Pb[subscript]3Z and of powder for Zr[subscript]5Sn[subscript]3Ga as well as by synthetic considerations. The crystal structures show strong zirconium-interstitial interactions. A substoichiometric interstitial phase also exists for Zr[subscript]5Sn[subscript]3S[subscript] x (0.5 ≤ x ≤ 1.0). Vapor phase transport reactions for Z = Al, Zn, and Pb in Zr[subscript]5Pb[subscript]3Z were successful with the transporting agent ZrCl[subscript]4;The systems Zr-Sn-T, T = Fe, Co and Ni, did not produce stoichiometric interstitial phases Zr[subscript]5Sn[subscript]3T. Instead, the interstitial phases for these elements are formed only with excess tin that partially occupies the interstitial site together with a T element. Reducing the amount of tin in these systems yields two new phases; Zr[subscript]5Sn[subscript] 2 + xFe[subscript] 1 - x (0 ≤ x ≤ 0.28) (W[subscript]5Si[subscript]3-type) and Zr[subscript]6Sn[subscript]2Fe (Zr[subscript]6Al[subscript]2Co-type) as characterized by X-ray single crystal analyses. A cobalt analogue for the latter was also synthesized. ftn*DOE Report IS-T-1505. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy

The Light and Period Variations of the Eclipsing Binary BX Draconis

New CCD photometric observations of BX Dra were obtained for 26 nights from 2009 April to 2010 June. The long-term photometric behaviors of the system are presented from detailed studies of the period and light variations, based on the historical data and our new observations. All available light curves display total eclipses at secondary minima and inverse O'Connell effects with Max I fainter than Max II, which are satisfactorily modeled by adding the slightly time-varying hot spot on the primary star. A total of 87 times of minimum light spanning over about 74 yrs, including our 22 timing measurements, were used for ephemeris computations. Detailed analysis of the O-C diagram showed that the orbital period has changed in combinations with an upward parabola and a sinusoidal variation. The continuous period increase with a rate of +5.65 \times 10^-7 d yr^-1 is consistent with that calculated from the Wilson-Devinney synthesis code. It can be interpreted as a mass transfer from the secondary to the primary star at a rate of 2.74 \times 10^-7 M\odot yr^-1, which is one of the largest rates for contact systems. The most likely explanation of the sinusoidal variation with a period of 30.2 yrs and a semi-amplitude of 0.0062 d is a light-traveltime effect due to the existence of a circumbinary object. We suggest that BX Dra is probably a triple system, consisting of a primary star with a spectral type of F0, its secondary component of spectral type F1-2, and an unseen circumbinary object with a minimum mass of M3 = 0.23 M\odot.Comment: 24 pages, including 5 figures and 9 tables, accepted for publication in PAS

Conventional Vickers and true instrumented indentation hardness determined by instrumented indentation tests

We evaluate Vickers hardness and true instrumented indentation test (IIT) hardness of 24 metals over a wide range of mechanical properties using just IIT parameters by taking into account the real contact morphology beneath the Vickers indenter. Correlating the conventional Vickers hardness, indentation contact morphology, and IIT parameters for the 24 metals reveals relationships between contact depths and apparent material properties. We report the conventional Vickers and true IIT hardnesses measured only from IIT contact depths; these agree well with directly measured hardnesses within ±6% for Vickers hardness and ±10% for true IIT hardness

Haptic Stylus and Empirical Studies on Braille, Button, and Texture Display

This paper presents a haptic stylus interface with a built-in compact tactile display module and an impact module as well as empirical studies on Braille, button, and texture display. We describe preliminary evaluations verifying the tactile display's performance indicating that it can satisfactorily represent Braille numbers for both the normal and the blind. In order to prove haptic feedback capability of the stylus, an experiment providing impact feedback mimicking the click of a button has been conducted. Since the developed device is small enough to be attached to a force feedback device, its applicability to combined force and tactile feedback display in a pen-held haptic device is also investigated. The handle of pen-held haptic interface was replaced by the pen-like interface to add tactile feedback capability to the device. Since the system provides combination of force, tactile and impact feedback, three haptic representation methods for texture display have been compared on surface with 3 texture groups which differ in direction, groove width, and shape. In addition, we evaluate its capacity to support touch screen operations by providing tactile sensations when a user rubs against an image displayed on a monitor

The coordination dynamics of bimanual circle drawing as a function of scaling movement amplitude

The purpose of this study was to investigate the influence of amplitude scaling on bimanual coordination in a circle drawing task. Eleven right-handed subjects traced the perimeter of 5 circles measuring 3, 6, 9, 12, and 15 cm in diameter under the following coordination conditions: (1) both hands move inward together (symmetric coordination pattern), and (2) both hands move counterclockwise together (asymmetric coordination pattern). In a set of self-paced trials, subjects traced each circle separately at a preferred frequency and separately for each coordination pattern. Although subjects matched the required amplitude of the target circles quite well, radial amplitude variability increased with increasing circle diameter. No transitions or movement reversals were observed in the self-paced trials, and the symmetric pattern was more stable than the asymmetric pattern. In a set of amplitude scaling trials, subjects continuously traced the 5 circles from small (3 cm) to big (15 cm) (SB) and from big to small (BS) at two fixed pacing frequencies (1.25 Hz and 1.5 Hz). Observed cycling frequency decreased with increasing circle diameter, and observed radial amplitude was most accurate when tracing the 9 cm diameter circle, with larger than required amplitude when tracing the 3 cm and 6 cm diameter circles, and smaller than required amplitude when tracing the 12 cm and 15 cm diameter circles. Radial amplitude variability also increased with increasing circle diameter in the amplitude scaling trials. The symmetric coordination pattern was more stable than the symmetric coordination pattern. Transitions from the asymmetric to symmetric coordination pattern as well as movement reversals were observed in both scaling directions. No transitions occurred while producing the symmetric pattern in any scaling direction or pacing frequency condition. The results show that amplitude scaling influenced the spatiotemporal aspects of bimanual circle drawing. Moreover, amplitude scaling induced more transitions than previous research that scaled movement frequency as a control parameter in bimanual circle drawing tasks

The coordination dynamics of control and learning in a visuomotor tracking task

Two experiments were designed to examine the influence of the strength of perceptionaction coupling on the control and learning of a visuomotor tracking pattern. Participants produced rhythmic elbow flexion-extension motions to learn a visually defined 90° relative phase tracking pattern with an external sinusoidal signal which was set at 0.8 Hz with 8 cycles in a trial. Day 1 and Day 2 practice sessions consisted of a total of 72 practice trials. There were two visuomotor congruency groups, a congruent group with visual feedback representing the elbow’s rotation and an incongruent group with feedback representing the elbow’s rotation transformed by 180°. Before Day 1 practice (pre-practice) and 24 hours after Day 2 practice (post-practice), participants produced 0°, 45°, 90°, 135°, and 180° relative phase tracking patterns either with or without tracking feedback. The external signal and the limb’s feedback were provided in the same workspace in Experiment 1, while both signals were provided in a separate workspace in Experiment 2. The pre-practice results demonstrated that the 0° relative phase pattern was the most accurate and stable pattern, whereas the 90° and 135° relative phase patterns were less accurate and more variable. The incongruent group produced a more accurate and less variable 180° relative phase pattern compared to the congruent group. Practice led to a decrease in phase error and variability toward the required 90° relative phase pattern in both experiments. The congruent group produced more accurate tracking and less variable elbow amplitude compared to the incongruent group in the separate workspace, whereas no such congruency effects were found in the same workspace during practice. The post-practice results showed overall improvements in phase accuracy and stability in most relative phase patterns with practice. Overall deterioration in tracking performance was found when tracking without feedback in the pre- and post-practice sessions. These findings demonstrated that the perception-action coupling strength was modified by feedback, visuomotor mapping, perceptual pattern, and workspace framework. The differential strength of perception-action impacted the learning of the required visuomotor tracking pattern as well as the production of tracking accuracy and stability differentially among the other tracking patterns

Regulation of Autoimmune Germinal Center Reaction by Tfh Cells and Application of Tfr-like Cells for the Treatment of Autoimmune B Cell Responses

Excessive follicular helper T (Tfh) cell responses to self-antigens are associated with antibody-mediated autoimmune diseases in humans including systemic lupus erythematosus (SLE). Numeral and functional aberrations of T regulatory T (Treg) cells are common in patients with autoimmune diseases. Although different types of immunosuppressive agents have been used clinically to treat antibody-mediated autoimmune diseases, they generally have side effects due to the lack of target-specificity. To minimalize the adverse effects, there is a need to develop target-specific therapeutics which specifically control auto-reactive B cell responses and auto-reactive Tfh cell responses. Recent studies unveiled that Foxp3+ Treg cells expressing CXCR5 can migrate into the germinal center (GC) zone where they specifically suppress GC reactions in vivo, presumably by directly suppressing B cells and/or Tfh cells. These CXCR5+ Foxp3+ Treg cells are termed as follicular regulatory T (Tfr) cells. Due to their ability to specifically suppress Tfh cell and GC B cell responses, use of Tfr cells may be a promising target-specific therapy for the treatment of autoantibody-mediated autoimmune diseases. To evaluate the role of Tfr cells in autoantibody-mediated autoimmune diseases, we employed a BXD2 mouse model of spontaneous autoimmune lupus. Immune balance between Tfh and Tfr cell responses is crucial for the prevention of self-destructive antibody generation. However, the contribution of Tfh cells and Tfr cells to auto-reactive B cell responses in the BXD2 strain had not been evaluated. Therefore, we examined Tfh, Tfr and other relevant immune cellular responses in this autoimmune strain. We found no differences in both the frequency of Th17 cells and the levels of IL-17 in the circulation between wild-type and BXD2 mice. By contrast, the frequency of Tfh cells was significantly increased, and the numbers of Tfh cells were positively correlated with the levels of autoantibodies. In addition, we observed that IL-21-producing Tfh cells, but not IL-17-producing Th17 cells, efficiently promoted the production of IgG from BXD2 B cells in vitro. These results supported the role of Tfh cells in the development of auto-reactive B cell responses. In addition, the frequency of Tfr cells was reduced in BXD2 mice. Therefore, imbalance between Tfh cells and Tfr cells in BXD2 mice likely caused the self-destructive antibody generation, thereby providing additional support that Tfr cell-based immunotherapy may ameliorate antibody-mediated autoimmunity. Unfortunately, sufficient numbers of Tfr cells that will be required for immunotherapy will be difficult to obtain since they are only found in low frequency in vivo. To address this problem, we employed retroviral transduction of CXCR5 onto Foxp3+ Treg cells, which are more abundant and less difficult to purify than Tfr cells. We termed these engineered CXCR5 overexpressing Foxp3+ Treg cells as eTfr cells. We demonstrated that transduction of CXCR5 in the eTfr cells did not affect the expression of other genes important for Treg or Tfh cell function. Furthermore, eTFr cells migrated in response to CXCL13 and had T cell suppressive capacity in vitro, demonstrating that eTfr cells maintained critical Tfr cell-like properties in vitro and were potentially a cell source for Tfr cell-based immunotherapy. To test the therapeutic potential of the eTfr cells, we performed in vivo adoptive co-transfer experiments using TCRβ-deficient mice. Unfortunately, the results from these in vivo investigations were inconclusive, indicating the further refinement of the model system will be required to determine the viability of the eTfr therapeutic approach for the autoantibody-mediated autoimmune disease. In summary, we demonstrated that imbalance between Tfh cell and Tfr cells and IL-21, produced by Tfh cells, lead to auto-reactive GC B cell responses in BXD2 mice, suggesting that similar imbalances may have relevance in human autoantibody-mediated autoimmune diseases. Moreover, eTfr cells can migrate in response to CXCL13 and suppress T cell responses in vitro, supporting the possibility that eTfr cells may provide a novel immunotherapeutic approach for the treatment of antibody-mediated autoimmune disorders

Behavior of Connections Between SHS Columns & W-section Beams

Connections between SHS (Square Hollow Section) columns and W-section beams are generally fabricated by welding with or without endplates in the factory. These welded connections possess some finite degree of rotational stiffness which falls between fully rigid and ideally pinned joints. The influence of partially restrained connections on structural response not only changes the moment distribution but also increases frame drift. In this paper, a series of connection tests joining SHS column and W-section beam were executed and the test results compared with theoretical values. A method to utilize nonlinear moment-rotation relations of beam-to-column connections in steel framed structures is proposed. For the problem of contact in endplate-type connections, a simple and efficient method is also introduced