331 research outputs found
Quantitative detection of atropine-delayed gastric emptying in the horse by the <sup>13</sup>C-octanoic acid breath test
The <sup>13</sup>C-octanoic acid breath test has been correlated significantly to radioscintigraphy for measurement of gastric emptying indices in healthy horses. The objective of this study was to investigate the validity of the test for measurement of equine delayed gastric emptying, prior to its potential clinical application for this purpose. A model of atropine- induced gastroparesis was used. Gastric emptying rate was measured twice in 8 horses using concurrent radioscintigraphy and/or breath test after treatment i.v. with either atropine (0.035 mg/kg bwt) or saline in randomised order. Analysis of both data sets demonstrated that the atropine treatment had caused a significant delay in gastric emptying rate. Paired breath test data showed an atropine-induced delay in gastric half-emptying time t(1/2)), with no overlap in the 99% Cl range (P<0.001). Significant correlations were found between scintigraphy and <sup>13</sup>C-octanoic acid breath test for calculation of both t(1/2) (P<0.01) and lag phase duration (P<0.05) in the atropine-delayed emptying results. The mean (s.d.) bias in breath test t(1/2) when compared with scintigraphy was 1.78 (0.58) h. The results demonstrated that the <sup>13</sup>C-octanoic acid breath test was an effective diagnostic modality for the measurement of equine delayed gastric emptying. The technique offers advantages to existing methods for clinical investigation, as it is noninvasive, not radioactive, quantitative and requires minimal equipment or training to perform
Validation of the <sup>13</sup>C-octanoic acid breath test for measurement of equine gastric emptying rate of solids using radioscintigraphy
Reasons for performing study: Disordered gastric motility may be a significant factor in the pathogenesis of many equine conditions. Although tests for liquid phase emptying rate have been validated in the horse, there are no effective tests for solid phase emptying measurement that can be performed routinely in the field.
Objectives: The objective of this study was the assessment of a novel stable isotope technique, the <sup>13</sup>C-octane acid breath test (<sup>13</sup> C-OABT), for the measurement of gastric emptying of solid ingesta, by direct comparison with the optimum method of gastric scintigraphy.
Methods: To facilitate dual measurement of gastric emptying, a test meal was used containing baked egg yolk labelled with both <sup>13</sup>C-octanoic acid and (99m)technetium sulphur colloid. Simultaneous, serial lateral gastric scintigraphs and expiratory breath samples were obtained in 12 healthy horses after voluntary ingestion of the test meal. Analysis of breath (CO2)-C-13:(CO2)-C-12 ratio was performed by continuous flow isotope ratio mass spectrometry. Power regression was used to determine the gastric emptying coefficient, the gastric half-emptying time (t(1/2)) and duration of the lag phase (t(lag)).
Results: Significant correlations (P < 0.001) were found between the 2 techniques for measurement of both t(1/2) and t(lag). In addition, scintigraphic left t(1/2) was correlated significantly to breath test gastric emptying coefficient (P < 0.001).
Conclusions: It was concluded that the <sup>13</sup>C-octanoic acid breath test is a reliable diagnostic procedure to measure gastric emptying rate of solids in the horse.
Potential relevance: Being safe, noninvasive and easy to perform, this test has potential value as; both sensitive diagnostic modality and humane research tool for motility studies
Selection models with monotone weight functions in meta analysis
Publication bias, the fact that studies identified for inclusion in a meta
analysis do not represent all studies on the topic of interest, is commonly
recognized as a threat to the validity of the results of a meta analysis. One
way to explicitly model publication bias is via selection models or weighted
probability distributions. We adopt the nonparametric approach initially
introduced by Dear (1992) but impose that the weight function is monotonely
non-increasing as a function of the -value. Since in meta analysis one
typically only has few studies or "observations", regularization of the
estimation problem seems sensible. In addition, virtually all parametric weight
functions proposed so far in the literature are in fact decreasing. We discuss
how to estimate a decreasing weight function in the above model and illustrate
the new methodology on two well-known examples. The new approach potentially
offers more insight in the selection process than other methods and is more
flexible than parametric approaches. Some basic properties of the
log-likelihood function and computation of a -value quantifying the evidence
against the null hypothesis of a constant weight function are indicated. In
addition, we provide an approximate selection bias adjusted profile likelihood
confidence interval for the treatment effect. The corresponding software and
the datasets used to illustrate it are provided as the R package selectMeta.
This enables full reproducibility of the results in this paper.Comment: 15 pages, 2 figures. Some minor changes according to reviewer
comment
Tuning the properties of a UV-polymerized, cross-linked solid polymer electrolyte for lithium batteries
Lithium metal anodes have been pursued for decades as a way to significantly increase the energy density of lithium-ion batteries. However, safety risks caused by flammable liquid electrolytes and short circuits due to lithium dendrite formation during cell cycling have so far prevented the use of lithium metal in commercial batteries. Solid polymer electrolytes (SPEs) offer a potential solution if their mechanical properties and ionic conductivity can be simultaneously engineered. Here, we introduce a family of SPEs that are scalable and easy to prepare with a photopolymerization process, synthesized from amphiphilic acrylic polymer conetworks based on poly(ethylene glycol), 2-hydroxy-ethylacrylate, norbornyl acrylate, and either lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) or a single-ion polymethacrylate as lithium-ion source. Several conetworks were synthesized and cycled, and their ionic conductivity, mechanical properties, and lithium transference number were characterized. A single-ion-conducting polymer electrolyte shows the best compromise between the different properties and extends the calendar life of the cell
Single-Ion Conducting Polymer Nanoparticles as Functional Fillers for Solid Electrolytes in Lithium Metal Batteries
[EN]Composite solid electrolytes including inorganic nanoparticles or nanofibers which improve the performance of polymer electrolytes due to their superior mechanical, ionic conductivity, or lithium transference number are actively being researched for applications in lithium metal batteries. However, inorganic nanoparticles present limitations such as tedious surface functionalization and agglomeration issues and poor homogeneity at high concentrations in polymer matrixes. In this work, we report on polymer nanoparticles with a lithium sulfonamide surface functionality (LiPNP) for application as electrolytes in lithium metal batteries. The particles are prepared by semibatch emulsion polymerization, an easily up-scalable technique. LiPNPs are used to prepare two different families of particle-reinforced solid electrolytes. When mixed with poly(ethylene oxide) and lithium bis(trifluoromethane)sulfonimide (LiTFSI/PEO), the particles invoke a significant stiffening effect (E' > 106 Pa vs 105 Pa at 80 °C) while the membranes retain high ionic conductivity (sigma = 6.6 * 10-4 S cm-1). Preliminary testing in LiFePO4 lithium metal cells showed promising performance of the PEO nanocomposite electrolytes. By mixing the particles with propylene carbonate without any additional salt, we obtain true single-ion conducting gel electrolytes, as the lithium sulfonamide surface functionalities are the only sources of lithium ions in the system. The gel electrolytes are mechanically robust (up to G' = 106 Pa) and show ionic conductivity up to 10-4 S cm-1. Finally, the PC nanocomposite electrolytes were tested in symmetrical lithium cells. Our findings suggest that all-polymer nanoparticles could represent a new building block material for solid-state lithium metal battery applications.L.P. has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska–Curie grant agreement no. 797295. P.S. has been funded by the SNSF (Swiss National Science Foundation) under project number P2FRP2_191846. J.R.L. and D.M. acknowledge the funding by the Basque Government (IT99-16). V.B. acknowledges support from the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract no. DE-AC05-00OR22725. A.S. acknowledges financial support for dielectric measurements and data discussions by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division
Task-Specific Phosphonium Iongels by Fast UV-Photopolymerization for Solid-State Sodium Metal Batteries
Sodium metal batteries are an emerging technology that shows promise in terms of materials availability with respect to lithium batteries. Solid electrolytes are needed to tackle the safety issues related to sodium metal. In this work, a simple method to prepare a mechanically robust and efficient soft solid electrolyte for sodium batteries is demonstrated. A task-specific iongel electrolyte was prepared by combining in a simple process the excellent performance of sodium metal electrodes of an ionic liquid electrolyte and the mechanical properties of polymers. The iongel was synthesized by fast (<1 min) UV photopolymerization of poly(ethylene glycol) diacrylate (PEGDA) in the presence of a saturated 42%mol solution of sodium bis(fluorosulfonyl)imide (NaFSI) in trimethyl iso-butyl phosphonium bis(fluorosulfonyl)imide (P111i4FSI). The resulting soft solid electrolytes showed high ionic conductivity at room temperature (≥10−3 S cm−1) and tunable storage modulus (104–107 Pa). Iongel with the best ionic conductivity and good mechanical properties (Iongel10) showed excellent battery performance: Na/iongel/NaFePO4 full cells delivered a high specific capacity of 140 mAh g−1 at 0.1 C and 120 mAh g−1 at 1 C with good capacity retention after 30 cycles.L.P. has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska–Curie grant agreement No. 797295. P.S. has been funded by the SNSF (Swiss National Science Foundation) under project number P2FRP2_191846. D.M., M.G., and A.F.A. acknowledge the funding by the Basque Government through Elkartek KK-2020/00078 and Agencia Estatal de Investigación (PLEC2021-007929). D.M. and M.G. also acknowledge the funding by Agencia Estatal de Investigación (PID2020-119026GB-100 and PID2019-107468RB-C22), respectively. A.P.S. acknowledges financial support for dielectric measurements and data discussions by NSF (award CHE-2102425)
Has the CSR engagement of electrical companies had an effect on their performance? A closer look at the environment
Even though electrical companies attain a top ranking in the publication of CSR reports, they are often accused of 'green‐washing' due to their bad environmental reputation. The current economic crisis is testing their real CSR commitment more than ever, especially when this goes beyond its economic consequences.
Based on a worldwide sample of electrical companies, we are going to study why companies are being socially responsible. We wish to know if it is due to the impact on the firms' performance or whether there are other motives (legitimation, improving their reputation) that lead companies to carry out these practices. We will also consider if it changes across the kind of CSR action considered.
The results show that there is an economic justification beyond the socially responsible behaviour of the electrical companies. Additionally, most kinds of CSR action (community, diversity, corporate governance, product responsibility) are also carried out looking for economic rewards. However, the CSR actions oriented to the environment are mainly motivated by their need to improve their image and reverse their negative impact
Cyclophosphamide and human organ transplantation.
Cyclophosphamide, a drug that has not previously had an important role in whole-organ transplantation, was given as a primary immunosuppressant to one liver and eleven kidney recipients, in combination with prednisone and horse antilymphocyte globulin. One of the patients died despite good renal-graft function. Two kidneys from a common cadaveric donor failed. The other nine patients have excellent function of their homografts after 2-3 months. Cyclophosphamide was substituted for azathioprine in one hepatic and five renal recipients who were suspected of having liver toxicity from azathioprine 3 months to almost 8 years post-transplantation. Graft function was maintained after this change, and the evidence of liver injury subsided. © 1971
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