A Stepwise Planned Approach to the Solution of Hilbert's Sixth Problem. III : Measurements and von Neumann Projection/Collapse Rule

Supmech, the universal mechanics developed in the previous two papers, accommodates both quantum and classical mechanics as subdisciplines (a brief outline is included for completeness); this feature facilitates, in a supmech based treatment of quantum measurements, an unambiguous treatment of the apparatus as a quantum system approximated well by a classical one. Taking explicitly into consideration the fact that observations on the apparatus are made when it has `settled down after the measurement interaction' and are restricted to macroscopically distinguishable pointer readings, the unwanted superpositions of (system + apparatus) states are shown to be suppressed; this provides a genuinely physics based justification for the (traditionally \emph{postulated}) von Neumann projection/collapse rule. The decoherence mechanism brought into play by the stated observational constraints is free from the objections against the traditional decoherence program.Comment: 29 pages; one section and two references added; results unchange

Levi problem and semistable quotients

A complex space $X$ is in class ${\mathcal Q}_G$ if it is a semistable quotient of the complement to an analytic subset of a Stein manifold by a holomorphic action of a reductive complex Lie group $G$. It is shown that every pseudoconvex unramified domain over $X$ is also in ${\mathcal Q}_G$.Comment: Version 2 - minor edits; 8 page

On hyperbolicity of SU(2)-equivariant, punctured disc bundles over the complex affine quadric

Given a holomorphic line bundle over the complex affine quadric $Q^2$, we investigate its Stein, SU(2)-equivariant disc bundles. Up to equivariant biholomorphism, these are all contained in a maximal one, say $\Omega_{max}$. By removing the zero section to $\Omega_{max}$ one obtains the unique Stein, SU(2)-equivariant, punctured disc bundle over $Q^2$ which contains entire curves. All other such punctured disc bundles are shown to be Kobayashi hyperbolic.Comment: 15 pages, v2: minor changes, to appear in Transformation Group

Polarised epithelial monolayers of the gastric mucosa reveal insights into mucosal homeostasis and defence against infection

Objective Helicobacter pylori causes life-long colonisation of the gastric mucosa, leading to chronic inflammation with increased risk of gastric cancer. Research on the pathogenesis of this infection would strongly benefit from an authentic human in vitro model. Design Antrum-derived gastric glands from surgery specimens served to establish polarised epithelial monolayers via a transient air–liquid interface culture stage to study cross-talk with H. pylori and the adjacent stroma. Results The resulting ‘mucosoid cultures’, so named because they recapitulate key characteristics of the gastric mucosa, represent normal stem cell-driven cultures that can be passaged for months. These highly polarised columnar epithelial layers encompass the various gastric antral cell types and secrete mucus at the apical surface. By default, they differentiate towards a foveolar, MUC5AC-producing phenotype, whereas Wnt signalling stimulates proliferation of MUC6-producing cells and preserves stemness—reminiscent of the gland base. Stromal cells from the lamina propria secrete Wnt inhibitors, antagonising stem-cell niche signalling and inducing differentiation. On infection with H. pylori, a strong inflammatory response is induced preferentially in the undifferentiated basal cell phenotype. Infection of cultures for several weeks produces foci of viable bacteria and a persistent inflammatory condition, while the secreted mucus establishes a barrier that only few bacteria manage to overcome. Conclusion Gastric mucosoid cultures faithfully reproduce the features of normal human gastric epithelium, enabling new approaches for investigating the interaction of H. pylori with the epithelial surface and the cross-talk with the basolateral stromal compartment. Our observations provide striking insights in the regulatory circuits of inflammation and defence.</p

Pseudoconvex domains spread over complex homogeneous manifolds

Using the concept of inner integral curves defined by Hirschowitz we generalize a recent result by Kim, Levenberg and Yamaguchi concerning the obstruction of a pseudoconvex domain spread over a complex homogeneous manifold to be Stein. This is then applied to study the holomorphic reduction of pseudoconvex complex homogeneous manifolds X=G/H. Under the assumption that G is solvable or reductive we prove that X is the total space of a G-equivariant holomorphic fiber bundle over a Stein manifold such that all holomorphic functions on the fiber are constant.Comment: 21 page

Terahertz spectroscopy of N18^{18}O and isotopic invariant fit of several nitric oxide isotopologs

A tunable far-infrared laser sideband spectrometer was used to investigate a nitric oxide sample enriched in 18O between 0.99 and 4.75 THz. Regular, electric dipole transitions were recorded between 0.99 and 2.52 THz, while magnetic dipole transitions between the 2Pi(1/2) and 2Pi(3/2) spin-ladders were recorded between 3.71 and 4.75 THz. These data were combined with lower frequency data of N(18)$O (unlabeled atoms refer to (14)N and (16)O, respectively), with rotational data of NO, (15)NO, N(17)O, and (15)N(18)O, and with heterodyne infrared data of NO to be subjected to one isotopic invariant fit. Rotational, fine and hyperfine structure parameters were determined along with vibrational, rotational, and Born-Oppenheimer breakdown corrections. The resulting spectroscopic parameters permit prediction of rotational spectra suitable for the identification of various nitric oxide isotopologs especially in the interstellar medium by means of rotational spectroscopy.Comment: 8 pages, 1 figure; part of the Marilyn Jacox special issue of the Journal of Molecular Spectroscopy, in pres

Distance perception in a natural outdoor setting: is there a developmental trend to overconstancy?

The main purpose of the present study was to investigate whether in natural environment, using very large physical distances, there is a trend to overconstancy for distance estimates during development. One hundred and twenty-nine children aged 5 to 13 years old and twenty-one adults (in a control group), participated as observers. The observer’s task was to bisect egocentric distances, ranging from 1.0 to 296.0 m, presented in a large open field. The analyses focused on two parameters, constant errors and variable errors, such as measuring accuracy and precision, respectively. A third analysis focused on the developmental pattern of shifts in constancy as a function of age and range of distances. Constant error analysis showed that there are two relevant parameters for accuracy, age, and range of distances. For short distances, there are three developmental stages: 5-7 years, when children have unstable responses, 7-11, underconstancy, and 13 to adulthood, when accuracy is reached. For large distances, there is a two-stage development: 5-11 years, with severe underconstancy, and beyond this age, with mild underconstancy. Variable errors analyses indicate that precision is noted for 7 year-old children, independently of the range of distances. The constancy analyses indicated that there is a shift from constancy (or slightly overconstancy) to underconstancy as a function of physical distance for all age groups. The age difference is noted in the magnitude of underconstancy that occurs in larger distances, where adults presented lower levels of underconstancy than children. The present data were interpreted as due to a developmental change in cognitive processing rather than to changes in visual space perception.El principal objetivo de este estudio fue investigar si en un medio natural, empleando distancias físicas muy grandes, hay una tendencia a sobre-constancia para las estimaciones de distancias durante el desarrollo evolutivo. Participaron como observadores 129 niños de edades entre 5 y 13 años y 21 adultos (en un grupo control). La tarea de los observadores consistió en biseccionar unas distancias egocéntricas, que variaban entre 1,0 y 296,0 m, presentadas en un gran campo abierto. El análisis se centró en dos parámetros, error constante y error variable, de la exactitud y precisión de medida, respectivamente. Un tercer análisis se centró en el patrón evolutivo de cambios en la constancia en función de la edad y el rango de distancias. El análisis de los errores constantes mostró que hay dos parámetros relevantes para la precisión, edad y rango de distancias. Para distancias cortas, hay tres fases evolutivas: 5-7 años, cuando los niños dan respuestas inestables, 7-11, infra-constancia, y 13 años hasta la adultez, cuando alcanzan la exactitud (constancia). Para las distancias largas, hay un desarrollo de dos fases: 5-11 años, con infra-constancia severa, y más allá de esta edad, con ligera infraconstancia. El análisis del error variable indica que se alcanza precisión a partir de 7 años, con independencia del rango de distancias. En análisis de la constancia indica que existe un cambio desde la constancia (o una ligera sobre-constancia) a infra-constancia en función de la distancia física para todos los grupos de edad. La diferencia de edad se nota en la magnitud de la infra-constancia que ocurre en las distancias más largas, donde los adultos presentaban niveles menores de infra-constancia que los niños. Estos datos se interpretan como debidos a un cambio evolutivo en el procesamiento cognitivo más que a cambios en la percepción visual del espacio

One-Dimensional and Multi-Dimensional Studies of the Exocentric Distance Estimates in Frontoparallel Plane, Virtual Space, and Outdoor Open Field

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Effects of anisotropy in geostrophic turbulence

The Boussinesq model of convection in a flat layer with heating from below is considered. We analyze the effects of anisotropy caused by rapid rotation in physical and wave spaces and demonstrate the suppression of energy transfer by rotation. We also examine the structure of the wave triangle in nonlinear interaction. The range of parameters is adapted to the models of convection in the geodynamo

Implementation of higher-order absorbing boundary conditions for the Einstein equations

We present an implementation of absorbing boundary conditions for the Einstein equations based on the recent work of Buchman and Sarbach. In this paper, we assume that spacetime may be linearized about Minkowski space close to the outer boundary, which is taken to be a coordinate sphere. We reformulate the boundary conditions as conditions on the gauge-invariant Regge-Wheeler-Zerilli scalars. Higher-order radial derivatives are eliminated by rewriting the boundary conditions as a system of ODEs for a set of auxiliary variables intrinsic to the boundary. From these we construct boundary data for a set of well-posed constraint-preserving boundary conditions for the Einstein equations in a first-order generalized harmonic formulation. This construction has direct applications to outer boundary conditions in simulations of isolated systems (e.g., binary black holes) as well as to the problem of Cauchy-perturbative matching. As a test problem for our numerical implementation, we consider linearized multipolar gravitational waves in TT gauge, with angular momentum numbers l=2 (Teukolsky waves), 3 and 4. We demonstrate that the perfectly absorbing boundary condition B_L of order L=l yields no spurious reflections to linear order in perturbation theory. This is in contrast to the lower-order absorbing boundary conditions B_L with L<l, which include the widely used freezing-Psi_0 boundary condition that imposes the vanishing of the Newman-Penrose scalar Psi_0.Comment: 25 pages, 9 figures. Minor clarifications. Final version to appear in Class. Quantum Grav