Mode Confinement in Photonic Quasi-Crystal Point-Defect Cavities for Particle Accelerators

In this Letter, we present a study of the confinement properties of point-defect resonators in finite-size photonic-bandgap structures composed of aperiodic arrangements of dielectric rods, with special emphasis on their use for the design of cavities for particle accelerators. Specifically, for representative geometries, we study the properties of the fundamental mode (as a function of the filling fraction, structure size, and losses) via 2-D and 3-D full-wave numerical simulations, as well as microwave measurements at room temperature. Results indicate that, for reduced-size structures, aperiodic geometries exhibit superior confinement properties by comparison with periodic ones.Comment: 4 pages, 4 figures, accepted for publication in Applied Physics Letter

Future directions for online incivility research

This chapter makes a normative argument that incivility scholars should shift directions in exploring aversive online communication. Specifically, it is vital for scholars to consider various subsets of incivility (e.g., profanity or hate speech), rather than treat incivility as a monolith and to acknowledge that different types are not equally damaging to democracy or interpersonal relations. Furthermore, this chapter calls for more attention to how incivility of all types hurts those from marginalized groups and how and why those with less societal power are more frequent targets of toxicity, as well as how to protect them. It also proposes that the role of online platforms, like Facebook, WeChat, and WhatsApp, be integorrated more fully in regard to incivility and that incivility be studied in concert with other types of problematic speech, such as misinformation and disinformation

La incorporación de la sociología de las ciencias en la formación docente : una deuda pendiente

Si lo que se pretende es mejorar la enseñanza aprendizaje de las ciencias en los contextos escolares es importante comenzar por reflexionar acerca de la formación que reciben los futuros docentes en las materias curriculares. Este análisis no sólo requiere considerar los contenidos disciplinares sino también aspectos epistemológicos y sociológicos. Sin embargo estos últimos ha sido menos tenidos en cuenta siendo que, a partir de mediados del siglo XX, la sociología de las ciencias conforma una disciplina con un amplio desarrollo. Así es que los futuros maestros pueden reconocer autores y corrientes psicológicas y epistemológicas que inciden en la curricula, sin embargo difícilmente sepan que es el “ethos mertoniano”, el programa fuerte o los aportes de Latour. En ese trabajo reseñaremos algunos conceptos estructurantes de la sociología de las ciencias

Elaboración de estándares para evaluar una competencia : un ejemplo aplicado a la interpretación de las fórmulas químicas

La evaluación por competencias es entendida como la capacidad de realización situada y afectada por el contexto en el que se desenvuelve el sujeto. Este enfoque requiere modificar concepciones y prácticas muy arraigadas. Al cursar Química, una competencia que los alumnos deben alcanzar se refiere al aprendizaje y la comprensión del lenguaje de la Química. En este dominio, una fórmula química emplea para su escritura dos sistemas de símbolos, el alfabeto y los números arábigos, pero siguiendo reglas diferentes al del uso en la vida cotidiana (comunicación verbal y matemática). En este trabajo nos proponemos reconocer algunos de los significados que las fórmulas tienen para los alumnos que inician el cursado de la asignatura, esto nos permitirá identificar estándares que ayudarán a definir en que nivel de competencia respecto del lenguaje químico se encuentran los alumnos

Hybrid photonic-bandgap accelerating cavities

In a recent investigation, we studied two-dimensional point-defected photonic bandgap cavities composed of dielectric rods arranged according to various representative periodic and aperiodic lattices, with special emphasis on possible applications to particle acceleration (along the longitudinal axis). In this paper, we present a new study aimed at highlighting the possible advantages of using hybrid structures based on the above dielectric configurations, but featuring metallic rods in the outermost regions, for the design of extremely-high quality factor, bandgap-based, accelerating resonators. In this framework, we consider diverse configurations, with different (periodic and aperiodic) lattice geometries, sizes, and dielectric/metal fractions. Moreover, we also explore possible improvements attainable via the use of superconducting plates to confine the electromagnetic field in the longitudinal direction. Results from our comparative studies, based on numerical full-wave simulations backed by experimental validations (at room and cryogenic temperatures) in the microwave region, identify the candidate parametric configurations capable of yielding the highest quality factor.Comment: 13 pages, 5 figures, 3 tables. One figure and one reference added; minor changes in the tex

A Framework for the Maintenance and Evolution of ePolicy-guided Web Applications

In this paper we present an “ePolicy framework” that can be used to develop transactional-based ePolicy-guided Web applications. This framework incorporates a non-proprietary component based architecture, a well-defined standards-based user interface, a structured representation of ePolicies, ePolicy operations and user input data, and incorporates a maintenance management component. Each component is self-contained and can therefore be independently maintained. ePolicies and associated ePolicy operations are not embedded in the system software but are stored centrally in an external store (Policy Repository) and are dynamically loaded as required. Executable code (marshalled from XML) is automatically generated from the ePolicies and the ePolicy operations and used in policy-guided evaluation. The Policy Repository, accessible by suitably privileged components, removes ePolicy duplication and from a maintenance perspective, this approach reduces the possibility of errors being introduced by data duplication. Updates to ePolicies are seamlessly applied the next time an ePolicy is loaded. ePolicies are represented in a standard uniform format and as all components use this uniform format, maintainers do not need to understand or handle multiple data formats. They are represented using a policy hierarchy composed of three layers: meta-ePolicies, ePolicy-groups and ePolicies. Each of the components is designed using Object-Oriented principles. Our ePolicy framework will work in a centralized or distributed environment. We believe that using our framework to develop ePolicy-guided evaluation systems will reduce data maintenance and expedite software evolution

Sulfur-containing histidine compounds inhibit γ-glutamyl transpeptidase activity in human cancer cells

γ-Glutamyl transpeptidase (GGT) is an enzyme located on the surface of cellular membranes and involved in GSH metabolism and maintenance of redox homeostasis. High GGT expression on tumor cells is associated with increased cell proliferation and resistance against chemotherapy. GGT inhibitors evaluated so far in clinical trials are too toxic for human use. In this study, using enzyme kinetics analyses, we demonstrate that ovothiols, 5(Nπ)-methyl thiohistidines of marine origin, act as noncompetitive inhibitors of GGT, with an apparent Ki of 21 μM, when we fixed the concentrations of the donor substrate. We found that these compounds are more potent than the known GGT inhibitor 6-diazo-5-oxo-L-norleucine and are not toxic toward human embryonic cells. In particular, cellular process-specific fluorescence-based assays revealed that ovothiols induce a mixed cell-death phenotype of apoptosis and autophagy in GGT-overexpressing cell lines, including human liver cancer and chronic B leukemic cells. The findings of our study provide the basis for further development of 5-thiohistidines as therapeutics for GGT-positive tumors and highlight that GGT inhibition is involved in autophagy