Laser Alloying Advantages by Dry Coating Metallic Powder Mixtures with SiOx Nanoparticles.

Up to now, minimizing segregation of free-flowing, microscale metal powder mixtures driven by different mass density is an open challenge. In this work, effects of particle size variation on homogeneity of Al-Cu mixtures, with a density ratio of 3.3, are examined. Dry coating Al particles with 0.3 wt% fumed silica SiOx nanoparticles significantly decreases interparticle attraction. This enlarges the range of free-flowing Al particle sizes to < 20 µm. Powder mixture homogeneity is examined optically in vibrated bulk powder and thinly spread layers. From various powder mixtures, solid samples are built layer by layer with the Additive Manufacturing (3D printing) technology Laser Beam Melting in metal powder bed (LBM). Chemical homogeneity of solids is evaluated via energy-dispersive X-ray spectroscopy, backscattered electron microscopy, metallographic analysis and tensile tests. Persistent homogeneity of Al-Cu powder mixtures and LBM solids is found only with particles < 20 µm dry coated with SiOx nanoparticles. Observed segregation phenomena are explained with a decrease in particle mobility at increasing local concentration and the decreasing effectiveness of mass in smaller particles. The main effects are based on geometry, so they are expected to be transferrable to other nanoparticles, alloying components and powder bed technologies, e.g., binder jetting.

Determination of laser beam focus position based on secondary speckles pattern analysis.

Proper positioning of a laser beam focus is a universal problem for various applications that does not have a universal solution. Quite often the taken approach relies on some sort of a calibration and temporal stability of the laser and the optical train. While such an approach can be suitable for a large number of applications its applicability becomes limited in the cases where the laser beam properties uncontrollably change with time. The latter can occur due to the thermal effects, for example. In those cases, the laser focus positioning method should include direct analysis of the laser beam properties. In this contribution we present a simple optical method based on the secondary speckles pattern analysis suitable for determination of the absolute focal spot position. The method does not require any a priori knowledge of the laser beam properties and is suitable for various diffuse or partially diffuse surfaces of interest.

Measuring adherence in a community-based elderly population.

OBJECTIVE: To examine the reliability and validity of the Medication Adherence Individual Review-Screening Tool (MedAdhIR-ST) for assessing medication adherence in a community-dwelling elderly population. DESIGN: A prospective, observational pilot study comparing the reliability and validity of the MedAdhIR-ST and the Medication Adherence Questionnaire (MAQ). SETTING: Independent senior-housing apartments and senior centers in Wake County, North Carolina. PARTICIPANTS: Eligible subjects included individuals 60 years of age or older who were living in the community and managing their own medication regimens. INTERVENTIONS: Each subject was asked to participate in two assessment visits, two weeks (+/- 3 days) apart, in which the questions of the MedAdhIR-ST and MAQ were administered. MAIN OUTCOME MEASURE: Medication adherence. RESULTS: Both tools showed moderate-to-high test/retest reliability in the study population (correlation coefficient of 0.632 for MAQ, and 0.699 for MedAdhIR-ST), and moderate internal consistency (Cronbach's a of 0.551 and 0.584, respectively). Moderate concordance in the ability to assess adherence was observed between MedAdhIR-ST and MAQ (positive correlation coefficient of 0.450). When compared with refill records, MedAdhIR-ST was slightly more sensitive (67% vs. 43%) and specific (60% vs. 50%) for detecting adherence and nonadherence, respectively, compared with MAQ. Exploratory factor analysis indicated that MedAdhIR-ST is multidimensional. CONCLUSION: MedAdhIR-ST appears to be a reliable and valid tool for screening nonadherence in a community-dwelling elderly population.

Rapid identification and sorting of viable virus-reactive CD4(+) and CD8(+) T cells based on antigen-triggered CD137 expression.

Current methods for the detection and isolation of antigen-specific CD4(+) and CD8(+) T cells require the availability of peptide/MHC multimers or are restricted to cells that produce cytokines after antigen contact. Here we show that de novo cell surface expression of the TNF-receptor family member CD137 (4-1BB) identifies recently activated, but not resting, human CD4(+) and CD8(+) memory T cells. Maximum CD137 expression level is uniformly observed in both T-cell subsets at 24h after stimulation with antigen. In experiments with CMV and EBV-reactive T cells, we confirmed the specificity of CD137 expression by co-staining with peptide/HLA tetramers. Substantial proportions of CD137(+) T cells did not produce IFN-gamma, suggesting that CD137 detects a broader repertoire of antigen-specific T cells. Activated CD137(+) T cells could be easily purified by MACS and expanded in vitro thereafter. This CD137-based enrichment method was capable of isolating 2-fold higher numbers of anti-viral CD4(+) and CD8(+) T cells compared to the IFN-gamma secretion assay. In conclusion, antigen-triggered CD137 expression allows the rapid detection and sorting of virus-reactive CD4(+) and CD8(+) T cells. The CD137 assay is most attractive for the simultaneous targeting of anti-viral T helper and effector cells in monitoring studies and adoptive immunotherapy trials.