Enhancement of perfluoropolyether boundary lubrication performance: I. Preliminary results

A ball bearing simulator operating under starved conditions was used to evaluate the boundary lubrication performance of a perfluoropolyether (PFPE) Krytox 143 AB. Several approaches to enhance boundary lubrication were studied. These included: (1) soluble boundary additives, (2) bearing surface modifications, (3) 'run-in' surface films, and (4) ceramic bearing components. In addition, results were compared with two non-perfluorinated liquid lubricant formulations. Based on these preliminary tests, the following tentative conclusions can be made: (1) substantial improvements in boundary lubrication performance were observed with a beta-diketone boundary additive and a tricresyl phosphate (TCP) liquid surface pretreatment; (2) the use of rough Si3N4 balls (Ra = 40 micro-in) also provided substantial improvement but with concomitant abrasive wear; (3) marginal improvements were seen with two boundary additives (a phosphine and a phosphatriazine) and a neat (100%) fluid (a carboxylic acid terminated PFPE); and surface pretreatments with a synthetic hydrocarbon, a PTFE coating, and TiC coated 440C and smooth Si3N4 balls (R(sub a) less than 1 micro-in); and (4) two non-PFPE lubricant formulations (a PAO and a synthetic hydrocarbon) yielded substantial improvements

Reversible binding of platelet-derived growth factor-AA, -AB, and -BB isoforms to a similar site on the "slow" and "fast" conformations of alpha 2-macroglobulin.

The mechanism by which the platelet-derived growth factor (PDGF)-binding protein, alpha 2-macroglobulin (alpha 2M), modulates PDGF bioactivity is unknown, but could involve reversible PDGF-alpha 2M binding. Herein we report that greater than 70% of 125I-PDGF-BB or -AB complexed to alpha 2M was dissociated by SDS-denaturation followed by SDS-polyacrylamide gel electrophoresis, i.e. most of the binding was noncovalent. Reduction of the PDGF.alpha 2M complex following denaturation dissociated the cytokine from alpha 2M by greater than 90%, suggesting covalent disulfide bond formation. Approximately 50% of the growth factor was dissociated by lowering the pH from 7.5 to 4.0. 125I-PDGF-BB bound alpha 2M in a time-dependent manner (t1/2 = approximately 1 h), reaching equilibrium after 4 h. The 125I-PDGF.BB/alpha 2M complex dissociated more slowly (t1/2 = approximately 2.5 h). "Slow" and "fast" alpha 2M bound nearly equal amounts of PDGF-AB or -BB. Trypsin treatment converted PDGF-BB/alpha 2M complex to the fast conformation but did not release bound 125I-PDGF-BB. All PDGF-isoforms (AA, -AB, and -BB) competed for binding with 125I-PDGF-BB binding to slow alpha 2M and fast alpha 2M-methylamine by 65-80%. Other cytokines that bind alpha 2M (transforming growth factor-beta 1 and -beta 2, tumor necrosis factor-alpha, basic fibroblast growth factor, interleukin -1 beta, and -6) did not compete for 125I-PDGF-BB binding slow alpha 2M, but transforming growth factor-beta 1 and basic fibroblast growth factor inhibited 125I-PDGF-BB binding alpha 2M-methylamine by 30-50%. The reversible nature of the PDGF.alpha 2M complex could allow for targeted PDGF release near mesenchymal cells which possess PDGF receptors

The Current State of Performance Appraisal Research and Practice: Concerns, Directions, and Implications

On the surface, it is not readily apparent how some performance appraisal research issues inform performance appraisal practice. Because performance appraisal is an applied topic, it is useful to periodically consider the current state of performance research and its relation to performance appraisal practice. This review examines the performance appraisal literature published in both academic and practitioner outlets between 1985 and 1990, briefly discusses the current state of performance appraisal practice, highlights the juxtaposition of research and practice, and suggests directions for further research

A bibliometric review of financial market integration literature

We undertake a meta-literature review on the topic of financial market integration (FMI), covering 260 articles from 1981 to 2021. Our review consists of quantitative analysis of bibliometric citations concomitant with qualitative analysis of content, towards a goal of identifying primary research streams and proposing directions for future research. We identify five research groups: (1) portfolio diversification with financial market integration; (2) general equity market integration; (3) financial market linkage with respect to crises and events; (4) time-varying financial market integration; and (5) co-movements and spillovers between commodities and financial markets; as well as present a wide array of future research directions. We conduct an extensive review of FMI literature, answering several questions: (1) What is the domain of FMI research?; (2) What are the influential aspects of top journals and authors, and the characteristics of the most studied topics?; (3) What are the past and current key research streams in FMI literature?; and (4) What are the substantial future relevant research questions to explore regarding FMI? Given the ongoing attention on financial market integration by both academicians and policy makers, our results should be of great interest

A link between the ice nucleation activity and the biogeochemistry of seawater

Emissions of ice-nucleating particles (INPs) from sea spray can impact climate and precipitation by changing cloud formation, precipitation, and albedo. However, the relationship between seawater biogeochemistry and the ice nucleation activity of sea spray aerosols remains unclarified. Here, we demonstrate a link between the biological productivity in seawater and the ice nucleation activity of sea spray aerosol under conditions relevant to cirrus and mixed-phase cloud formation. We show for the first time that aerosol particles generated from both subsurface and microlayer seawater from the highly productive eastern tropical North Pacific Ocean are effective INPs in the deposition and immersion freezing modes. Seawater particles of composition similar to subsurface waters of highly productive regions may therefore be an unrealized source of effective INPs. In contrast, the subsurface water from the less productive Florida Straits produced less effective immersion mode INPs and ineffective depositional mode INPs. These results indicate that the regional biogeochemistry of seawater can strongly affect the ice nucleation activity of sea spray aerosol

Bearing strength of commercial cross-banded compreg under aircraft bolts

Information reviewed and reaffirmed March 1956 and 1962

Bolt-bearing strength of laboratory-made cross-banded yellow birch compreg under aircraft bolts

This report is one of a series issued in cooperation with the Army-Navy-Civil Committee on Aircraft Design Criteria under the supervision of the Aeronautical Boar

Clinical actionability of comprehensive genomic profiling for management of rare or refractory cancers

Background. The frequency with which targeted tumor sequencing results will lead to implemented change in care is unclear. Prospective assessment of the feasibility and limitations of using genomic sequencing is critically important. Methods. A prospective clinical study was conducted on 100 patients with diverse-histology, rare, or poor-prognosis cancers to evaluate the clinical actionability of a Clinical Laboratory Improvement Amendments (CLIA)-certified, comprehensive genomic profiling assay (FoundationOne), using formalin-fixed, paraffin-embedded tumors. The primary objectives were to assess utility, feasibility, and limitations of genomic sequencing for genomically guided therapy or other clinical purpose in the setting of a multidisciplinary molecular tumor board. Results. Of the tumors from the 92 patients with sufficient tissue, 88 (96%) had at least one genomic alteration (average 3.6, range 0–10). Commonly altered pathways included p53 (46%), RAS/RAF/MAPK (rat sarcoma; rapidly accelerated fibrosarcoma; mitogen-activated protein kinase) (45%), receptor tyrosine kinases/ligand (44%), PI3K/AKT/mTOR (phosphatidylinositol-4,5-bisphosphate 3-kinase; protein kinase B; mammalian target of rapamycin) (35%), transcription factors/regulators (31%), and cell cycle regulators (30%). Many low frequency but potentially actionable alterations were identified in diverse histologies. Use of comprehensive profiling led to implementable clinical action in 35% of tumors with genomic alterations, including genomically guided therapy, diagnostic modification, and trigger for germline genetic testing. Conclusion. Use of targeted next-generation sequencing in the setting of an institutional molecular tumor board led to implementable clinical action in more than one third of patients with rare and poor-prognosis cancers. Major barriers to implementation of genomically guided therapy were clinical status of the patient and drug access. Early and serial sequencing in the clinical course and expanded access to genomically guided early-phase clinical trials and targeted agents may increase actionability. Implications for Practice: Identification of key factors that facilitate use of genomic tumor testing results and implementation of genomically guided therapy may lead to enhanced benefit for patients with rare or difficult to treat cancers. Clinical use of a targeted next-generation sequencing assay in the setting of an institutional molecular tumor board led to implementable clinical action in over one third of patients with rare and poor prognosis cancers. The major barriers to implementation of genomically guided therapy were clinical status of the patient and drug access both on trial and off label. Approaches to increase actionability include early and serial sequencing in the clinical course and expanded access to genomically guided early phase clinical trials and targeted agents

Stories and Statistics: A Mixed Picture of Gender Equity in Mathematics

The goal of this chapter is to gain a better understanding of the experiences of mathematics anxiety that some women elementary preservice teachers encounter while learning mathematics during their own K-12 years. Specifically, this chapter is an analysis of the personal well-remembered events (WREs) told and recorded by women during their preservice teaching professional sequence. These narrative writings provide a powerful voice for the degree to which mathematics anxiety shape preservice teachers’ beliefs on what it means to learn mathematics. This intersection of teacher knowledge is important, as these are women who are on the professional track to teach mathematics. The focused analysis for this chapter is aimed at ways in which teacher preparation programs could broaden current views of women who have anxiety and confidence issues in mathematics