730 research outputs found
Computing semiparametric bounds on the expected payments of insurance instruments via column generation
It has been recently shown that numerical semiparametric bounds on the
expected payoff of fi- nancial or actuarial instruments can be computed using
semidefinite programming. However, this approach has practical limitations.
Here we use column generation, a classical optimization technique, to address
these limitations. From column generation, it follows that practical univari-
ate semiparametric bounds can be found by solving a series of linear programs.
In addition to moment information, the column generation approach allows the
inclusion of extra information about the random variable; for instance,
unimodality and continuity, as well as the construction of corresponding
worst/best-case distributions in a simple way
Copositive certificates of non-negativity for polynomials on semialgebraic sets
A certificate of non-negativity is a way to write a given function so that
its non-negativity becomes evident. Certificates of non-negativity are
fundamental tools in optimization, and they underlie powerful algorithmic
techniques for various types of optimization problems. We propose certificates
of non-negativity of polynomials based on copositive polynomials. The
certificates we obtain are valid for generic semialgebraic sets and have a
fixed small degree, while commonly used sums-of-squares (SOS) certificates are
guaranteed to be valid only for compact semialgebraic sets and could have large
degree. Optimization over the cone of copositive polynomials is not tractable,
but this cone has been well studied. The main benefit of our copositive
certificates of non-negativity is their ability to translate results known
exclusively for copositive polynomials to more general semialgebraic sets. In
particular, we show how to use copositive polynomials to construct structured
(e.g., sparse) certificates of non-negativity, even for unstructured
semialgebraic sets. Last but not least, copositive certificates can be used to
obtain not only hierarchies of tractable lower bounds, but also hierarchies of
tractable upper bounds for polynomial optimization problems.Comment: 27 pages, 1 figur
Generation of Multivirus-specific T Cells to Prevent/treat Viral Infections after Allogeneic Hematopoietic Stem Cell Transplant
Viral infections cause morbidity and mortality in allogeneic hematopoietic stem cell transplant (HSCT) recipients. We and others have successfully generated and infused T-cells specific for Epstein Barr virus (EBV), cytomegalovirus (CMV) and Adenovirus (Adv) using monocytes and EBV-transformed lymphoblastoid cell (EBV-LCL) gene-modified with an adenovirus vector as antigen presenting cells (APCs). As few as 2x105/kg trivirus-specific cytotoxic T lymphocytes (CTL) proliferated by several logs after infusion and appeared to prevent and treat even severe viral disease resistant to other available therapies. The broader implementation of this encouraging approach is limited by high production costs, complexity of manufacture and the prolonged time (4-6 weeks for EBV-LCL generation, and 4-8 weeks for CTL manufacture – total 10-14 weeks) for preparation. To overcome these limitations we have developed a new, GMP-compliant CTL production protocol. First, in place of adenovectors to stimulate T-cells we use dendritic cells (DCs) nucleofected with DNA plasmids encoding LMP2, EBNA1 and BZLF1 (EBV), Hexon and Penton (Adv), and pp65 and IE1 (CMV) as antigen-presenting cells. These APCs reactivate T cells specific for all the stimulating antigens. Second, culture of activated T-cells in the presence of IL-4 (1,000U/ml) and IL-7 (10ng/ml) increases and sustains the repertoire and frequency of specific T cells in our lines. Third, we have used a new, gas permeable culture device (G-Rex) that promotes the expansion and survival of large cell numbers after a single stimulation, thus removing the requirement for EBV-LCLs and reducing technician intervention. By implementing these changes we can now produce multispecific CTL targeting EBV, CMV, and Adv at a cost per 106 cells that is reduced by >90%, and in just 10 days rather than 10 weeks using an approach that may be extended to additional protective viral antigens. Our FDA-approved approach should be of value for prophylactic and treatment applications for high risk allogeneic HSCT recipients
Euphorbia paniculata Desf. subsp. paniculata en el sureste ibérico
Euphorbia paniculata Desf. subsp. paniculata in SE SpainPalabras clave. Euphorbia, Corología, Murcia, Almeria, España.Keywords. Euphorbia, Chorology, Murcia, Almeria, Spain
Caracterización y evaluación de la variabilidad de doce colectas de Phaseolus vulgaris tipo reventon procedente de la provincia de Santiago de Chuco (Perú)
Se realizaron doce colectas de “ñuña” en la sierra de Santiago de Chuco, La Libertad (Perú) a fin de evaluar la variación morfológica y cuantitativa de sus granos, así como el comportamiento de sus cultivos bajo condiciones de costa norte de la Provincia de Trujillo (Perú). Se encontró gran variación morfológica respecto a la forma, brillo y color de los granos entre las colectas, alta variación para los caracteres asociados con el rendimiento y la calidad de los granos donde las entradas que presentaron mayor peso de 100 granos secos fueron SUNT 01 con 53.20 g, SUNT 03 con 58.50 g ,SUNT 05 con 70.90 g y SUNT 08 con 66.00 g . Los mejores volúmenes, porcentaje de expansión y textura de los granos tostados lo presentaron las entradas SUNT 02, SUNT03, SUNT 05 y SUNT 11, siendo las entradas más sobresalientes para los caracteres antes mencionados SUNT 03 Y SUNT 05. Respecto al comportamiento fenotípico, las colectas cultivadas bajo condiciones agroecológicas de costa norte fueron las entradas SUNT01, SUNT 02, SUNT 05 y SUNT 11, las que desarrollaron mejor bajo estas condiciones.Palabras clave: Variación morfológica, germoplasma, Phaseolus vulgari
First detection in Europe of the metallo-β-lactamase IMP-15 in clinical strains of Pseudomonas putida and Pseudomonas aeruginosa
AbstractIn a prospective study (2009–2011) in healthcare institutions from the Canary Islands (Spain), 6 out of 298 carbapenem non-susceptible Pseudomonas aeruginosa isolates produced a metallo-β-lactamase: four IMP-15, two VIM-2 (including one IMP-15-positive isolate) and one VIM-1. Multilocus sequence typing identified the single VIM-1-producing isolate as clone ST111 and two IMP-15-producing isolates as ST606, but, strikingly, bacterial re-identification revealed that the other three isolates (producing IMP-15 and/or VIM-2) were actually Pseudomonas putida. Further retrospective analysis revealed a very high prevalence (close to 50%) of carbapenem resistance in this environmental species. Hence, we report the simultaneous emergence in hospitals on the Canary Islands of P. putida and P. aeruginosa strains producing IMP-15, a metallo-β-lactamase not previously detected in Europe, and suggest an underestimated role of P. putida as a nosocomial reservoir of worrying transferable resistance determinants
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