818 research outputs found
Nonlinear localized modes in dipolar Bose-Einstein condensates in optical lattices
The modulational instability and discrete matter wave solitons in dipolar
BEC, loaded into a deep optical lattice, are investigated analytically and
numerically. The process of modulational instability of nonlinear plane matter
waves in a dipolar nonlinear lattice is studied and the regions of instability
are established. The existence and stability of bulk discrete solitons are
analyzed analytically and confirmed by numerical simulations. In a marked
contrast with the usual DNLS behavior (no dipolar interactions), we found a
region where the two fundamental modes are simultaneously unstable allowing
enhanced mobility across the lattice for large norm values. To study the
existence and properties of surface discrete solitons, an analysis of the dimer
configuration is performed. The properties of symmetric and antisymmetric modes
including the stability diagrams and bifurcations are investigated in closed
form. For the case of a bulk medium, properties of fundamental on-site and
inter-site localized modes are analyzed. On-site and inter-site surface
localized modes are studied finding that they do not exist when nonlocal
interactions predominate with respect to local ones.Comment: 12 pages, 13 figure
Coexistence of Non-Conventional Condensates in Two-Level Bose Atom System
In the framework of the Bogolyubov approximation and using the Bogolyubov
inequalities we give a simple proof of the coexistence of two non-conventional
Bose-Einstein condensates in the case of some superstable Bose system whose
atoms have an internal two-level structure and their energy operators in the
second quantized form depend on the number operators only.Comment: 17 page
Dinuclear organotin building blocks and their conversion into a tetranuclear macrocycle containing Sn-O-Sn linkages
Six dinuclear organotin building blocks of general composition RR′R′′SnCH2Si(CH3)2−biphenyl−Si(CH3)2CH2SnR′′R′R, in which the tin atoms are separated by a p,p′-biphenylene bridge and carry different substituents [BD1 with R, R′=CH2Si(CH3)3, R′′=Ph; BD2 with R, R′=CH2Si(CH3)3, R′′=Cl; BD3, with R, R′=CH2Si(CH3)3, R′′=I; BD4 with R=CH2Si(CH3)2(C5H4FeCp), R′, R′′=Ph; BD5 with R=CH2Si(CH3)2(C5H4FeCp), R′=Ph, R”=Cl; BD6 with R=CH2Si(CH3)2(C5H4FeCp), R′=Ph, R′′=I], were synthesized and characterized by spectroscopic and spectrometric methods. Furthermore, the crystal and molecular structures of BD2 were determined by single-crystal X-ray diffraction (SCXRD) analysis, revealing the formation of molecular strands through intermolecular Cl→Sn contacts. The 1D coordination polymer [BD2]n comprises macrocyclic rings of composition [BD2]2 that motivated the generation of a related molecular macrocyclic structure by reaction of BD2 with silver (I) oxide in a 2 : 2 stoichiometry. The [2+2] macrocyclization yielded the 30-membered tetra-nuclear ring structure M1, viz., {[R2SnCH2Si(CH3)2−biphenyl−(CH3)2SiCH2SnR2](μ-O)}2, in which two BD2 dinuclear building blocks are linked through two covalent Sn−O−Sn moieties. Examination by DFT calculations at the B3LYP/def2svp and B3LYP/6-31G*(C,H,O,Si)/LanL2DZ(Sn) levels of theory gave energy minima for molecular conformers of M1 carrying the Sn−O−Sn and p,p′-biphenylene bridges in syn- or anti-orientation
Molecular cage assembly by Sn-O-Sn bridging of di-, tri- and tetranuclear organotin tectons: extending the spacing in double ladder structures
Hydrolysis reactions of di- and trinuclear organotin halides yielded large novel cage compounds containing Sn−O−Sn bridges. The molecular structures of two octanuclear tetraorganodistannoxanes showing double-ladder motifs, viz., [{Me3SiCH2(Cl)SnCH2YCH2Sn(OH)CH2SiMe3}2(μ-O)2]2 [1, Y=p-(Me)2SiC6H4-C6H4Si(Me)2] and [{Me3SiCH2(I)SnCH2YCH2Sn(OH)CH2SiMe3}2(μ-O)2]2⋅0.48 I2 [2⋅0.48 I2, Y=p-(Me)2SiC6H4-C6H4Si(Me)2], and the hexanuclear cage-compound 1,3,6-C6H3(p-C6H4Si(Me)2CH2Sn(R)2OSn(R)2CH2Si(Me)2C6H4-p)3C6H3-1,3,6 (3, R=CH2SiMe3) are reported. Of these, the co-crystal 2⋅0.48 I2 exhibits the largest spacing of 16.7 Å reported to date for distannoxane-based double ladders. DFT calculations for the hexanuclear cage and a related octanuclear congener accompany the experimental work
Contribution to van der Waerden's conjecture
AbstractIn this paper, we give two different elementary proofs for the inequality which states that the permanent of doubly stochastic matrices is greater than or equal to (n!/nn). This inequality was proved earlier by the author, and independently by Egorychev and Falikman
Identification and multi-environment validation of resistance to rust (Uromyces viciae-fabae) in Vicia faba
A germplasm collection of 484 accessions of Vicia faba was screened for resistance to rust (Uromyces viciae-fabae) under field conditions. Accessions varied in the levels of rust infection, although no complete resistance was identified. Stability of resistance of the 39 most-resistant accessions was tested in a multi-location experiment in Austria, Egypt, Tunisia, United Kingdom and Spain over three additional field seasons. Genotype×environment interaction accounted for 43% of the sum of squares of the multi-environment evaluation, revealing instability of the phenotypic expression across environments. This might hamper the efficiency of selection suggesting the need for selection in different environments. Three possible mega-environments were discerned in the studied area, Mediterranean (Spain, Tunisia and Egypt), Oceanic (UK) and Continental (Austria). Córdoba (Spain) and Kafr El-Sheik (Egypt) showed as ideal environments for rust resistance screenings within Mediterranean environment. Several accessions (300, 303, 311, 313, 720, 1196 and 1271) were grouped as moderately to highly resistant in the three defined mega-environments. These accessions showed clear differences both in terms of reduced disease severity and high stability, which make them good candidates for international faba bean breeding programmes. Concerning each mega-environment, accessions 300 and 311 were the most resistant and stable ones across the Mediterranean one, followed by accessions 720, 1022, 1272, 1320 and BPL261. On the contrary other accessions (313, 452, 481 and 1196) were the most resistant in Oceanic and Continental environments. However, 452 and 481 were susceptible in the Mediterranean mega-environment. This contrasting performance across the environments was also supported by contradictory performance of the checks BPL261 and Baraca in Oceanic and Continental environments, suggesting differential virulence in rust populations, which deserves further attention.Published versio
Outcome of Antifungal Combination Therapy for Invasive Mold Infections in Hematological Patients is Independent of the Chosen Combination
Invasive mold infection (IMI) remains a major cause of mortality in high-risk hematological patients. The aim of this multicenter retrospective, observational study was to evaluate antifungal combination therapy (ACT) for proven and probable IMI in hematological patients. We analyzed 61 consecutive cases of proven (n=25) and probable (n=36) IMI treated with ACT collected from eight Spanish hospitals from January 2005 to December 2009. Causal pathogens were: Aspergillus spp (n=49), Zygomycetes (n=6), Fusarium spp (n=3), and Scedosporium spp (n=3). Patients were classified in three groups according to the antifungal combination employed: Group A, liposomal amphotericin B (L-AmB) plus caspofungin (n=20); Group B, LAmB plus a triazole (n=20), and Group C, voriconazole plus a candin (n=21). ACT was well tolerated with minimal adverse effects. Thirty-eight patients (62%) achieved a favorable response (35 complete). End of treatment and 12-week survival rates were 62% and 57% respectively, without statistical differences among groups. Granulocyte recovery was significantly related to favorable response and survival (p<0.001) in multivariate analysis. Our results suggest that comparable outcomes can be achieved with ACT in high risk hematological patients with proven or probable IMI, whatever the combination of antifungal agents used
Characterization of the Anderson metal-insulator transition for non ergodic operators and application
We study the Anderson metal-insulator transition for non ergodic random
Schr\"odinger operators in both annealed and quenched regimes, based on a
dynamical approach of localization, improving known results for ergodic
operators into this more general setting. In the procedure, we reformulate the
Bootstrap Multiscale Analysis of Germinet and Klein to fit the non ergodic
setting. We obtain uniform Wegner Estimates needed to perform this adapted
Multiscale Analysis in the case of Delone-Anderson type potentials, that is,
Anderson potentials modeling aperiodic solids, where the impurities lie on a
Delone set rather than a lattice, yielding a break of ergodicity. As an
application we study the Landau operator with a Delone-Anderson potential and
show the existence of a mobility edge between regions of dynamical localization
and dynamical delocalization.Comment: 36 pages, 1 figure. Changes in v2: corrected typos, Theorem 5.1
slightly modifie
Pesquisa de validação da percepção Exame Nacional de Enfermagem do Chile
Investigación descriptiva cuantitativa y cualitativa. Objetivo: validar encuesta de percepción de los egresados de Enfermería en Chile, respecto al Examen Nacional de Enfermería. Metodología: lo cualitativo consideró el método Delphi participando expertos en la disciplina de enfermería y del área educación y evaluación. Para lo cuantitativo se utilizó el análisis de alfa de Cronbach, usando el sistema SPSS. Resultados: El K obtenido por los expertos estuvo entre el 0,95 a 1 lo que determinó que todos tenían un alto grado de competencia en el tema sobre el cual se les consultó. Los expertos vincularon los objetivos propuestos con cada uno de los 21 ítems de la encuesta. En 8 de ellos el 100% de los expertos coincidió con lo plateado por la Comisión del Examen Nacional de Enfermería, en 10 de los ítems un 80%, en 2 de los ítems un 50% y en 1 ítem un 33%. El alpha de Cronbach obtenido fue de 0,97, lo que demuestra un alto grado de consistencia interna del instrumento. Conclusiones: Se valida la encuesta de opinión, cumpliendo de manera rigurosa y lógica con todas sus etapas, demostrando su validez y confiabilidad.Quantitative and qualitative descriptive research. Objective: to validate the survey on the perception of nursing graduates in Chile, regarding the National Exam taken and applied. Methodology: qualitative, using the Delphi method with experts in the areas of nursing, education, and evaluation; and quantitative, using Cronbach's alpha analysis with the SPSS system. Results: The K was between 0.95 to 1, which suggests that all of the experts had a high degree of competence in the opinion topic. The objectives proposed in the 21-item survey were linked. In 8 items 100% of the experts stated their agreement with the aspects raised by the National Nursing Exam Commission; in 10 items 80%, in 2 items 50% and in 1 item 33%. Cronbach's alpha method estimated the internal consistency reliability of the instrument to be 0.97, demonstrating a high degree of internal consistency among the items analyzed. Conclusions: to validate an instrument it is necessary to rigorously complete each step with a sequence that allows one to account for validity and reliability
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