The Impact of Vein Mechanical Compliance on Arteriovenous Fistula Outcomes

© 2016 Elsevier Inc. Background Arteriovenous fistulae (AVFs) are the preferred access for hemodialysis but suffer a high early failure rate. The aim of this study was to determine how venous distensibility, as measured in vitro, relates to early outcomes of AVF formed with the sampled vein. Methods Ethical approval was obtained for all aspects of this study. During AVF formation a circumferential segment of the target vein was sampled. Mechanical stress testing of the venous segments was undertaken using a dynamic mechanical analyzer, with progressive stress loading at 2 N/min to a maximum of 10 N or until sample disruption. Stress-strain curves were obtained for vein samples and Young's modulus (YM) calculated. Duplex assessment of the fistulae was undertaken at 30 days. Results Thirty patients consented to participate with 29 samples obtained for analysis. Statistical comparison of YM demonstrated no relationship with common cardiovascular risk factors or dialysis status. Subject age greater than 65 was the only patient factor which showed a significant difference in YM (P = 0.05). Furthermore, a negative correlation was confirmed between age and YM (Pearson's r = -0.465, P < 0.05). Nine of the 29 subjects suffered an early AVF failure. Mann-Whitney U testing for differences in distribution reported that YM was significantly higher in those fistulas which failed (P < 0.005). Conclusions Reduced venous compliance appears to result in higher failure rates of AVFs. With the advancement of clinical tools such as speckle tracing ultrasound identification of vessel compliance in vivo may produce valuable additional information for clinicians planning AVF surgery

Measurement of hydrogen depth distribution by resonant nuclear reactions

The resonance at E (19F) =6.42 MeV in the reaction 1H(19F,alphagamma)16O has been explored as a potentially useful method for the quantitative determination of hydrogen concentration as a function of depth in a solid substrate. The relative merits of this resonance, the 16.44-MeV resonance in the same reaction, and the 6.39-MeV resonance in the reaction 1H(15N,alphagamma)12C are discussed

Current-spin coupling for ferromagnetic domain walls in fine wires

The coupling between a current and a domain wall is examined. In the presence of a finite current and the absence of a potential which breaks the translational symmetry, there is a perfect transfer of angular momentum from the conduction electrons to the wall. As a result, the ground state is in uniform motion. This remains the case when relaxation is accounted for. This is described by, appropriately modified, Landau-Lifshitz-Gilbert equations.Comment: 4 pqges, no figure

The screwworm eradication data system archives

The archives accumulated during 1 year of operation of the Satellite Temperature-Monitoring System during development of the Screwworm Eradication Data System are reported. Brief descriptions of all the kinds of tapes, as well as their potential uses, are presented. Reference is made to other documents that explain the generation of these data

Massive quark scattering at strong coupling from AdS/CFT

We extend the analysis of Alday and Maldacena for obtaining gluon scattering amplitudes at strong coupling to include external massive quark states. Our quarks are actually the N=2 hypermultiplets which arise when D7-brane probes are included in the AdS_5 x S^5 geometry. We work in the quenched approximation, treating the N=2 matter multiplets as external sources coupled to the N=4 SYM fields. We first derive appropriate massive-particle boundary conditions for the string scattering worldsheets. We then find an exact worldsheet which corresponds to the scattering of two massive quarks and two massless gluons and extract from this the associated scattering amplitude. We also find the worldsheet and amplitude for the scattering of four massive quarks. Our worldsheet solutions reduce to the four massless gluon solution of Alday and Maldacena in the limit of zero quark mass. The amplitudes we compute can also be interpreted in terms of 2-2 scattering involving gluons and massive W-bosons.Comment: 46 pages, 11 figures, v4: additional comments added to intr

Analysis of the total 12C(α,γ)16O cross section based on available angular distributions and other primary data

Because a knowledge of the 12C/16O ratio is crucial to the understanding of the later evolution of massive stars, new R- and K-matrix fits have been completed using the available angular distribution data from radiative α capture and elastic α scattering on 12C. Estimates of the total 12C(α,γ)16O rate at stellar energies are reported. In contrast with previous work, the analyses generally involve R- and K-matrix fits directly to the primary data, i.e., the energy- and angle-dependent differential yields, with all relevant partial waves fitted simultaneously (referred to here as surface fits). It is shown that, while the E1 part of the reaction is well constrained by a recent experiment on the β-delayed α-particle decay of 16N, only upper limits can be placed on the E2 ground state cross section factor which we take conservatively as SE2(300)<140 keV b. Simulations were then carried out to explore what kind of new data could lead to better restrictions on SE2(300). We find that improved elastic scattering data may be the best short-term candidate for such restrictions while significantly improving S(300) with new radiative capture data may require a longer-term effort. Theoretical models and estimates from α-transfer reactions for the E2 part of 12C(α,γ)16O are then discussed for comparison with the R- and K-matrix fits of the present work