Singular-value decomposition of solution operators to model evolution equations

We consider evolution equations generated by quadratic operators admitting a decomposition in creation-annihilation operators without usual ellipticity-type hypotheses; this class includes hypocoercive model operators. We identify the singular value decomposition of their solution operators with the evolution generated by an operator of harmonic oscillator type, and in doing so derive exact characterizations of return to equilibrium and regularization for any complex time.Comment: 10 pages, 1 figur

On ergodic operator means in Banach spaces

We consider a large class of operator means and prove that a number of ergodic theorems, as well as growth estimates known for particular cases, continue to hold in the general context under fairly mild regularity conditions. The methods developed in the paper not only yield a new approach based on a general point of view, but also lead to results that are new, even in the context of the classical Cesaro means

Seizure Disorders in Goats and Sheep.

BackgroundGoats and sheep are more likely to be presented for examination for seizures than are cattle, possibly as a consequence of their relatively smaller body size. Currently, no reports describing seizure disorders in goats and sheep are available.ObjectivesTo describe clinical features and treatment outcomes of sheep and goats presented for seizures.AnimalsA total of 59 goats and 21 sheep presented for seizures.MethodsRetrospective study. Medical records from 1994 to 2014 at the Veterinary Medical Teaching Hospital, University of California, Davis, were reviewed. Descriptive statistics were used to summarize data. Logistic regression was performed to determine whether variables were associated with mortality.ResultsThe majority of seizures in goats and sheep had structural or metabolic causes. Polioencephalomalacia (PEM) secondary to ruminal lactic acidosis or PEM of undetermined cause was the most frequently diagnosed cause of seizures in goats and sheep. The proportions of mortality in goats and sheep were 49.2 and 42.9%, respectively. Age increased the odds mortality (odds ratio [OR], 1.51; 95% confidence interval [CI], 1.07, 2.14) in goats. Goats with structural or metabolic causes of seizures had higher odds for mortality (OR, 37.48; 95% CI, 1.12, 99.10) than those with unknown causes. Age and etiological diagnosis were not significant (P > .05) predictors of mortality in affected sheep.Conclusions and clinical relevanceSeizure disorders in goats and sheep are associated with high mortality, despite treatment. Current treatment in goats and sheep with seizures warrants further investigation to determine whether treatments are beneficial or detrimental to survival

The Returns to Temporary Migration to the United States: Evidence from the Mexican Urban Employment Survey

Mexican migration to the United States has been a very important issue throughout the twentieth century, and its relevance has reached unprecedented levels during the last two decades. Even though there is a huge body of literature that analyses many different aspects of this phenomenon, the economic performance of migrants with respect to the Mexican labour markets has received very little attention. This paper aims at filling this gap by presenting new evidence on the effect that migration to the United States has on labour market outcomes of Mexican workers. It uses data from the Mexican National Survey of Urban Labour (ENEU) for the period 1994-2002. Among other advantages, the panel structure of the survey is ideal for minimizing the problems of self-selection bias that are common in most of the alternative data sources. Fixed-effects estimation indicates that Mexican workers that migrate temporarily to the United States obtain significantly higher earnings in the U.S. labour market than in the Mexican one during the period of migration. They also tend to work longer hours and face a generally higher likelihood of non employment during the period of return migration. Finally, the gains from temporary migration are lower for more skilled workers and for those migrating from the most distant regions in Mexico, relative to the United States.temporary migration, real wages, labour supply