2,651 research outputs found
Solar and atmospheric neutrino oscillations with three flavours
We analyze the solar and the atmospheric neutrino problems in the context of
three flavour neutrino oscillations. We assume a mass hierarchy in the vacuum
mass eigenvalues , but make no approximation
regarding the magnitudes of the mixing angles. We find that there are small but
continuous bands in the parameter space where the constraints imposed by the
current measurements of , and Kamiokande
experiments are satisfied at level. The allowed parameter space
increases dramatically if the error bars are enlarged to . The
electron neutrino survival probability has different energy dependence in
different regions of the parameter space. Measurement of the recoil electron
energy spectrum in detectors that use scattering may distinguish
between some of the allowed regions of parameter space. Finally we use the
results for the parameter space admitted by the solar neutrinos as an input for
the atmospheric neutrino problem and show that there exists a substantial
region of parameter space in which both problems can be solved.Comment: 25 pages plus eight figures. Uses Revtex. Postcript files for figures
sent separately as a uuencoded fil
A Process for Co-Designing Educational Technology Systems for Refugee Children
There is a growing interest in the potential for technology to facilitate emergency education of refugee children. However, designing in this space requires knowledge of the displaced population and the contextual dynamics surrounding it. Design should therefore be informed by both existing research across relevant disciplines, and from the practical experience of those who are on the ground facing the problem in real life. This paper describes a process for designing appropriate technology for these settings. The process draws on literature from emergency education, student engagement and motivation, educational technology, and participatory design. We emphasise a thorough understanding of the problem definition, the nature of the emergency, and of socio-cultural aspects that can inform the design process. We describe how this process was implemented leading to the design of a digital learning space for children living in a refugee camp in Greece. This drew on involving different groups of participants such as social-workers, parents, and children
Common Origin for the Solar and Atmospheric Neutrino Deficits
Some typos corrected, slightly different abstract, same plots, results and
conclusions.Comment: 14 Latex pages, 3 figures attached as postscript files, IFP-472-UNC,
PRL-TH-93/1
Solar Neutrinos with Three Flavor Mixings
The recent 71Ga solar neutrino observation is combined with the 37Cl and
Kamiokande-II observations in an analysis for neutrino masses and mixings. The
allowed parameter region is found for matter enhanced mixings among all three
neutrino flavors. Distortions of the solar neutrino spectrum unique to three
flavors are possible and may be observed in continuing and next generation
experiments.Comment: August 1992 (Revised) PURD-TH-92-
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Word frequency and trends in the development of French vocabulary in lower intermediate students during Year 12 in English schools
Order/disorder phase transition in cordierite and its possible relationship to the development of symplectite reaction textures in granulites
Based on a consistent set of empirical interatomic potentials, static structure energy calculations of various Al/Si configurations in the supercell of Mg-cordierite and Monte Carlo simulations the phase transition between the orthorhombic and hexagonal modifications of cordierite (Crd) is predicted at 1623 K. The temperature dependences of the enthalpy, entropy, and free energy of the Al/Si disorder were calculated using the method of thermodynamic integration. The simulations suggest that the commonly observed crystallization of cordierite in the disordered hexagonal form could be related to a tendency of Al to occupy T1 site, which is driven by local charge balance. The increase in the Al fraction in the T1 site over the ratio of 2/3(T1): 1/3(T2), that characterizes the ordered state, precludes formation of the domains of the orthorhombic phase. This intrinsic tendency to the crystallization of the metastable hexagonal phase could have significantly postponed the formation of the association of orthorhombic cordierite and orthopyroxene over the association of quartz and garnet in metapelites subjected to granulite facies metamorphism. The textures of local metasomatic replacement (the formation of Crd + Opx or Spr + Crd symplectites between the grains of garnet and quartz) indicate the thermodynamic instability of the association of Qtz + Grt at the moment of the metasomatic reaction. This instability could have been caused by the difficulty of equilibrium nucleation of orthorhombic cordierite
Controlling trapping potentials and stray electric fields in a microfabricated ion trap through design and compensation
Recent advances in quantum information processing with trapped ions have
demonstrated the need for new ion trap architectures capable of holding and
manipulating chains of many (>10) ions. Here we present the design and detailed
characterization of a new linear trap, microfabricated with scalable
complementary metal-oxide-semiconductor (CMOS) techniques, that is well-suited
to this challenge. Forty-four individually controlled DC electrodes provide the
many degrees of freedom required to construct anharmonic potential wells,
shuttle ions, merge and split ion chains, precisely tune secular mode
frequencies, and adjust the orientation of trap axes. Microfabricated
capacitors on DC electrodes suppress radio-frequency pickup and excess
micromotion, while a top-level ground layer simplifies modeling of electric
fields and protects trap structures underneath. A localized aperture in the
substrate provides access to the trapping region from an oven below, permitting
deterministic loading of particular isotopic/elemental sequences via
species-selective photoionization. The shapes of the aperture and
radio-frequency electrodes are optimized to minimize perturbation of the
trapping pseudopotential. Laboratory experiments verify simulated potentials
and characterize trapping lifetimes, stray electric fields, and ion heating
rates, while measurement and cancellation of spatially-varying stray electric
fields permits the formation of nearly-equally spaced ion chains.Comment: 17 pages (including references), 7 figure
Constraints on Three-Neutrino Mixing from Atmospheric and Reactor Data
Observations of atmospheric neutrinos are usually analyzed using the
simplifying approximation that either or
two-flavor mixing is relevant. Here we
instead consider the data using the simplifying approximation that only one
neutrino mass scale is relevant. This approximation is the minimal three-flavor
notation that includes the two relevant two-flavor approximations. The
constraints in the parameter space orthogonal to the usual, two-flavor analyses
are studied.Comment: 15 pages, preprint IUHET-26
The duality of ocean acidification as a resource and a stressor
Ecologically dominant species often define ecosystem states, but as human disturbances intensify, their subordinate counterparts increasingly displace them. We consider the duality of disturbance by examining how environmental drivers can simultaneously act as a stressor to dominant species and as a resource to subordinates. Using a model ecosystem, we demonstrate that CO2-driven interactions between species can account for such reversals in dominance; i.e., the displacement of dominants (kelp forests) by subordinates (turf algae). We established that CO2 enrichment had a direct positive effect on productivity of turfs, but a negligible effect on kelp. CO2 enrichment further suppressed the abundance and feeding rate of the primary grazer of turfs (sea urchins), but had an opposite effect on the minor grazer (gastropods). Thus, boosted production of subordinate producers, exacerbated by a net reduction in its consumption by primary grazers, accounts for community change (i.e., turf displacing kelp). Ecosystem collapse, therefore, is more likely when resource enrichment alters competitive dominance of producers, and consumers fail to compensate. By recognizing such duality in the responses of interacting species to disturbance, which may stabilize or exacerbate change, we can begin to understand how intensifying human disturbances determine whether or not ecosystems undergo phase shifts
Emphysematous cholecystitis: a case report
A 65-year-old Greek man with a history of diabetes mellitus and hypertension was admitted because of right upper quadrant pain, nausea and palpable right quadrant mass. On admission the patient was febrile (38.8°C) with a total bilirubin level of 1.99 mg/dl (direct 0.59 mg/dl); SGOT 1.26 mg/dl; Na 135 mmol/l and K 2.9 mmol/l. The white blood count was 15200/μl with 92.2% neutrophiles. Axial sections of single slice CT imaging (section thickness 10 mm), revealed emphysematous cholecystitis with thickening of gallbladder wall and wall enhancement after iv contrast enhancement, as well as, dilatation of the gallbladder with multiple gallstones precipitate and intraluminal air. The patient underwent subtotal cholecystectomy and a cholecystostomy was placed. The culture of the bile showed positivity to toxin A of Clostridium Difficile and to Escherichia Coli. The postoperative course of the patient was uneventful
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