46 research outputs found

    Investigating the origins of fluctuation forces on plates immersed in turbulent flows

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    A net force can arise on objects which lie in systems with complex energy partitions, even if the system is on average stationary. These forces are usually called fluctuation forces, as they arise due to the objects modifying the character of the fluctuations within the system. We continue the investigation of Spandan \emph{et al.}, \textit{Sci. Adv., 6(14), eaba0461} (2020), who found an attractive fluctuation force between two parallel square plates in homogeneous isotropic turbulence (HIT). We conduct simulations which systematically vary the plate size and Reynolds number. At Reλ=100Re_\lambda=100 small plates show a monotonic force dependence, with a maximum force for the smallest plate separations, while medium and large plates show a non-monotonic behaviour of the force with maximum attractive force at intermediate separations. We find that energy-related statistics cannot explain the dependence on plate separation of the force, but that statistics related to vorticity do show qualitative variations around the plate separation corresponding to the maximum force. This suggests that the role of plates in affecting intense vorticity structures is critical to the behaviour of the force. By decreasing ReλRe_\lambda, we show that removing vortex stretching decreases the attractive force, but does not completely eliminate it, and find that the local maximum at intermediate distances becomes a local minimum. This confirms that the attractive force is related to vorticity, while suggesting that a second mechanism is present -- supporting the proposal for a two-fold origin from earlier work: the plates both restrict the presence of energy structures in the slit and pack intense vortical structures which stretch each other causing the pressure to drop

    Assessment of folate receptor-β expression in human neoplastic tissues

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    Over-expression of folate receptor alpha on cancer cells has been frequently exploited for delivery of folate-targeted imaging and therapeutic agents to tumors. Because limited information exists on expression of the beta isoform of the folate receptor in human cancers (FR-β), we have evaluated the immunohistochemical staining pattern of FR-β in 992 tumor sections from 20 different human cancer types using a new anti-human FR-β monoclonal antibody. FR-β expression was shown to be more pronounced in cells within the stroma, primarily macrophages and macrophage-like cells than cancer cells in every cancer type studied. Moreover, FR-β expression in both cancer and stromal cells was found to be statistically more prominent in females than males. A significant positive correlation was also observed between FR-β expression on stromal cells and both the stage of the cancer and the presence of lymph node metastases. Based on these data we conclude FR-β may constitute a good target for specific delivery of therapeutic agents to activated macrophages and that accumulation of FR-β positive macrophages in the stroma could serve as a useful indicator of a tumor's metastatic potential

    Diabetes reduces bone marrow and circulating porcine endothelial progenitor cells, an effect ameliorated by atorvastatin and independent of cholesterol

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    Bone marrow derived endothelial progenitor cells (EPCs) are early precursors of mature endothelial cells which replenish aging and damaged endothelial cells. The authors studied a diabetic swine model to determine if induction of DM adversely affects either bone marrow or circulating EPCs and whether a HMG-CoA reductase inhibitor (statin) improves development and recruitment of EPCs in the absence of cholesterol lowering. Streptozotocin was administered to Yorkshire pigs to induce DM. One month after induction, diabetic pigs were treated with atorvastatin (statin, n = 10), ezetimibe (n = 10) or untreated (n = 10) and evaluated for number of bone marrow and circulating EPCs and femoral artery endothelial function. There was no effect of either medication on cholesterol level. One month after induction of DM prior to administration of drugs, the number of bone marrow and circulating EPCs significantly decreased (P < 0.0001) compared to baseline. Three months after DM induction, the mean proportion of circulating EPCs significantly increased in the atorvastatin group, but not in the control or ezetimibe groups. The control group showed progressive reduction in percentage of flow mediated vasodilatation (no dilatation at 3 months) whereas the atorvastatin group and ezetimibe exhibited vasodilatation, 6% and 4% respectively. DM results in significant impairment of bone marrow and circulating EPCs as well as endothelial function. The effect is ameliorated, in part, by atorvastatin independent of its cholesterol lowering effect. These data suggest a model wherein accelerated atherosclerosis seen with DM may, in part, result from reduction in EPCs which may be ameliorated by treatment with a statin

    Recruitment for a Hospital-Based Pragmatic Clinical Trial using Volunteer Nurses and Students

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    BACKGROUND/AIMS: Recruitment of subjects is critical to the success of any clinical trial, but achieving this goal can be a challenging endeavor. Volunteer nurse and student enrollers are potentially an important source of recruiters for hospital-based trials; however, little is known of either the efficacy or cost of these types of enrollers. We assessed volunteer clinical nurses and health science students in their rates of enrolling family members in a hospital-based, pragmatic clinical trial of cardiopulmonary resuscitation education, and their ability to achieve target recruitment goals. We hypothesized that students would have a higher enrollment rate and are more cost-effective compared to nurses. METHODS: Volunteer nurses and student enrollers were recruited from eight institutions. Participating nurses were primarily bedside nurses or nurse educators while students were pre-medical, pre-nursing, and pre-health students at local universities. We recorded the frequency of enrollees recruited into the clinical trial by each enroller. Enrollers\u27 impressions of recruitment were assessed using mixed-methods surveys. Cost was estimated based on enrollment data. Overall enrollment data were analyzed using descriptive statistics and generalized estimating equations. RESULTS: From February 2012 to November 2014, 260 hospital personnel (167 nurses and 93 students) enrolled 1493 cardiac patients\u27 family members, achieving target recruitment goals. Of those recruited, 822 (55%) were by nurses, while 671 (45%) were by students. Overall, students enrolled 5.44 (95% confidence interval (CI): 2.88, 10.27) more subjects per month than nurses (p \u3c 0.01). After consenting to participate in recruitment, students had a 2.85 (95% CI: 1.09, 7.43) increased chance of enrolling at least one family member (p = 0.03). Among those who enrolled at least one subject, nurses enrolled a mean of 0.51(95% CI: 0.42, 0.59) subjects monthly, while students enrolled 1.63 (95% CI: 1.37, 1.90) per month (p \u3c 0.01). Of 198 surveyed hospital personnel (127 nurses, 71 students), 168/198 (85%) felt confident conducting enrollment. The variable cost per enrollee recruited was 25.38persubjectfornursesand25.38 per subject for nurses and 23.30 per subject for students. CONCLUSIONS: Overall, volunteer students enrolled more subjects per month at a lower cost than nurses. This work suggests that recruitment goals for a pragmatic clinical trial can be successfully obtained using both nurses and students

    Validation of Diffuse Correlation Spectroscopic Measurement of Cerebral Blood Flow Using Phase-Encoded Velocity Mapping Magnetic Resonance Imaging

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    Diffuse correlation spectroscopy (DCS) is a novel optical technique that appears to be an excellent tool for assessing cerebral blood flow in a continuous and non-invasive manner at the bedside. We present new clinical validation of the DCS methodology by demonstrating strong agreement between DCS indices of relative cerebral blood flow and indices based on phase-encoded velocity mapping magnetic resonance imaging (VENC MRI) of relative blood flow in the jugular veins and superior vena cava. Data were acquired from 46 children with single ventricle cardiac lesions during a hypercapnia intervention. Significant increases in cerebral blood flow, measured both by DCS and by VENC MRI, as well as significant increases in oxyhemoglobin concentration, and total hemoglobin concentration, were observed during hypercapnia. Comparison of blood flow changes measured by VENC MRI in the jugular veins and by DCS revealed a strong linear relationship, R = 0.88, p \u3c 0.001, slope = 0.91 ± 0.07. Similar correlations were observed between DCS and VENC MRI in the superior vena cava, R = 0.77, slope = 0.99 ± 0.12, p \u3c 0.001. The relationship between VENC MRI in the aorta and DCS, a negative control, was weakly correlated, R = 0.46, slope = 1.77 ± 0.45, p \u3c 0.001

    On the Use of Variance per Genotype as a Tool to Identify Quantitative Trait Interaction Effects: A Report from the Women's Genome Health Study

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    Testing for genetic effects on mean values of a quantitative trait has been a very successful strategy. However, most studies to date have not explored genetic effects on the variance of quantitative traits as a relevant consequence of genetic variation. In this report, we demonstrate that, under plausible scenarios of genetic interaction, the variance of a quantitative trait is expected to differ among the three possible genotypes of a biallelic SNP. Leveraging this observation with Levene's test of equality of variance, we propose a novel method to prioritize SNPs for subsequent gene–gene and gene–environment testing. This method has the advantageous characteristic that the interacting covariate need not be known or measured for a SNP to be prioritized. Using simulations, we show that this method has increased power over exhaustive search under certain conditions. We further investigate the utility of variance per genotype by examining data from the Women's Genome Health Study. Using this dataset, we identify new interactions between the LEPR SNP rs12753193 and body mass index in the prediction of C-reactive protein levels, between the ICAM1 SNP rs1799969 and smoking in the prediction of soluble ICAM-1 levels, and between the PNPLA3 SNP rs738409 and body mass index in the prediction of soluble ICAM-1 levels. These results demonstrate the utility of our approach and provide novel genetic insight into the relationship among obesity, smoking, and inflammation