The effect of temperature on development and behavior of relict leopard frog tadpoles (Rana onca)

Relict Leopard frogs (Rana onca) are found in thermal springs with water temperatures in excess of 30°C at the source but it\u27s unknown whether tadpoles require reintroduction sites with specific thermal conditions for development. Tadpole survivorship at 20, 25 and 30°C was 84, 93.8, and 66%, respectively, while none survived at 35°C. Time to metamorphosis was significantly shorter for 25°C acclimation group (62+/-8 days) followed by the 30° (106+/-51 days) and 20°C (260+/-47 days) acclimation groups. Development was arrested in the 15°C acclimated group and survivorship declined to 63.8% after 191 days. However, 80% of the surviving larvae completed metamorphosis after temperature was increased to 25°C. When placed in a thermal gradient, larvae selected temperatures closest to their acclimation temperature. Maximum burst speed was greatest at 25°C for all but not the 30°C acclimation groups. Thus, reintroduction sites require water temperatures between 20° and 30°C during most of the year

The application of a non-Newtonian rheological equation to low-density polyethylene

A generalized non-Newtonian equation describing the rheology of molten thermoplastics is verified for low-density polyethylenes. The equation is extended to account for both rheological temperature dependency and polyethylene molecular weight dependency. The prediction of the rheology of new polyethylenes without additional experimentation is thus possible

Réflexions critiques sur l'avènement de l'union civile boiteuse en droit international privé québécois

[À l'origine dans / Was originally part of : Fac. Droit - Coll. facultaire - Droit international][À l'origine dans / Was originally part of : Fac. Droit - Coll. facultaire - Droit privé - Famille et personnes

Predicting Future Sources of Mass Toxic Tort Litigation

The authors describe the efforts of an expert working group to identify potential sources, over the next five to ten years, of future mass litigation and report on the group\u27s consensus conclusions

International Portfolio Diversification: Short-Term Financial Assets and Gold

Using a continuous-time finance-theoretic framework, this paper presents the optimal portfolio rule of an international investor who consumes N national composite goods and who holds N domestic-currency-denominated assets with known nominal interest rates in an environment where prices of goods, assets and exchange rates follow geometric Brownian motion. It is shown that the currency portfolio rule described in Macedo (1982a) is applicable to the case where there are N assets with a known price and one asset, gold, with a random rice in terms of the numeraire. Under these assumptions, it is found that the optimal portfolio of an investor consuming goods from all major industrialized countries (according to their weight in total trade) would be dominated in March 1981 by long positions in U.S. dollars (25%), yen (17%), D. marks (16%), French francs (15%) and pounds sterling (10%). An investor consuming only U.S. goods, by contrast, would hold 96% of his optimal portfolio in U.S. dollars. Because of the covariance of exchange rates and gold, the exclusion of the latter generates substantial reshuffling. The analysis of the evolution of portfolios over time shows that shares changed dramatically at the beginning of the period and did not begin to approach their March 1981 values until the end of 1975. In the case of the yen and the pound there were oscillations throughout the period. With respect to the dollar share in the optimal portfolio of the U.S. and international investor, it is found that, in the period between late 1974 and mid-1976, a period in which the dollar is considered to have been "strong", a large decline in its optimal share took place.

US News and World Report Cancer Hospital Rankings: Do They Reflect Measures of Research Productivity?

Context: Prior research has faulted the US News and World Report hospital specialty rankings for excessive reliance on reputation, a subjective measure of a hospital's performance.Objective: To determine whether and to what extent reputation correlates with objective measures of research productivity among cancer hospitals.Design: A retrospective observational study.Setting: Automated search of NIH Reporter, BioEntrez, BioMedline and Clinicaltrials.gov databases.Participants: The 50 highest ranked cancer hospitals in 2013's US News and World Report Rankings.Exposure: We ascertained the number of NCI funded grants, and the cumulative funds received by each cancer center. Additionally, we identified the number of phase I, phase II, and phase III studies published and indexed in MEDLINE, and registered at clinicaltrials.gov. All counts were over the preceding 5 years. For published articles, we summed the impact factor of the journals in which they appeared. Trials were attributed to centers on the basis of the affiliation of the lead author or study principal investigator.Main Outcome: Correlation coefficients from simple and multiple linear regressions for measures of research productivity and a center's reputation.Results: All measures of research productivity demonstrated robust correlation with reputation (mean r-squared  = 0.65, median r-squared = 0.68, minimum r-squared = .41, maximum r-squared = 0.80). A multivariable model showed that 93% of the variation in reputation is explained by objective measures.Conclusion: Contrary to prior criticism, the majority of reputation, used in US News and World Rankings, can be explained by objective measures of research productivity among cancer hospitals.</p

Mixing by Swimming Algae

In this fluid dynamics video, we demonstrate the microscale mixing enhancement of passive tracer particles in suspensions of swimming microalgae, Chlamydomonas reinhardtii. These biflagellated, single-celled eukaryotes (10 micron diameter) swim with a "breaststroke" pulling motion of their flagella at speeds of about 100 microns/s and exhibit heterogeneous trajectory shapes. Fluorescent tracer particles (2 micron diameter) allowed us to quantify the enhanced mixing caused by the swimmers, which is relevant to suspension feeding and biogenic mixing. Without swimmers present, tracer particles diffuse slowly due solely to Brownian motion. As the swimmer concentration is increased, the probability density functions (PDFs) of tracer displacements develop strong exponential tails, and the Gaussian core broadens. High-speed imaging (500 Hz) of tracer-swimmer interactions demonstrates the importance of flagellar beating in creating oscillatory flows that exceed Brownian motion out to about 5 cell radii from the swimmers. Finally, we also show evidence of possible cooperative motion and synchronization between swimming algal cells.Comment: 1 page, APS-DFD 2009 Gallery of Fluid Motio

Results at 24 months from the prospective, randomized, multicenter Investigational Device Exemption trial of ProDisc-C versus anterior cervical discectomy and fusion with 4-year follow-up and continued access patients.

BackgroundCervical total disk replacement (TDR) is intended to address pain and preserve motion between vertebral bodies in patients with symptomatic cervical disk disease. Two-year follow-up for the ProDisc-C (Synthes USA Products, LLC, West Chester, Pennsylvania) TDR clinical trial showed non-inferiority versus anterior cervical discectomy and fusion (ACDF), showing superiority in many clinical outcomes. We present the 4-year interim follow-up results.MethodsPatients were randomized (1:1) to ProDisc-C (PDC-R) or ACDF. Patients were assessed preoperatively, and postoperatively at 6 weeks and 3, 6, 12, 18, 24, 36, and 48 months. After the randomized portion, continued access (CA) patients also underwent ProDisc-C implantation, with follow-up visits up to 24 months. Evaluations included Neck Disability Index (NDI), Visual Analog Scale (VAS) for pain/satisfaction, and radiographic and physical/neurologic examinations.ResultsRandomized patients (103 PDC-R and 106 ACDF) and 136 CA patients were treated at 13 sites. VAS pain and NDI score improvements from baseline were significant for all patients (P &lt; .0001) but did not differ among groups. VAS satisfaction was higher at all time points for PDC-R versus ACDF patients (P = .0499 at 48 months). The percentage of patients who responded yes to surgery again was 85.6% at 24 months and 88.9% at 48 months in the PDC-R group, 80.9% at 24 months and 81.0% at 48 months in the ACDF group, and 86.3% at 24 months in the CA group. Five PDC-R patients (48 months) and no CA patients (24 months) had index-level bridging bone. By 48 months, approximately 4-fold more ACDF patients required secondary surgery (3 of 103 PDC-R patients [2.9%] vs 12 of 106 ACDF patients [11.3%], P = .0292). Of these, 6 ACDF patients (5.6%) required procedures at adjacent levels. Three CA patients required secondary procedures (24 months).ConclusionsOur 4-year data support that ProDisc-C TDR and ACDF are viable surgical options for symptomatic cervical disk disease. Although ACDF patients may be at higher risk for additional surgical intervention, patients in both groups show good clinical results at longer-term follow-up