Killing spinors in supergravity with 4-fluxes

We study the spinorial Killing equation of supergravity involving a torsion 3-form \T as well as a flux 4-form \F. In dimension seven, we construct explicit families of compact solutions out of 3-Sasakian geometries, nearly parallel \G_2-geometries and on the homogeneous Aloff-Wallach space. The constraint \F \cdot \Psi = 0 defines a non empty subfamily of solutions. We investigate the constraint \T \cdot \Psi = 0, too, and show that it singles out a very special choice of numerical parameters in the Killing equation, which can also be justified geometrically

Non-invasive monitoring of renal transplant recipients: Urinary excretion of soluble adhesion molecules and of the complement-split product C4d

Background: The number of inducible adhesion molecules known to be involved in cell-mediated allograft rejection is still increasing. In addition, recent data describe complement activation during acute humoral allograft rejection. The aim of this study was to assess whether specific molecules from either pathway are excreted into urine and whether they can provide useful diagnostic tools for the monitoring of renal transplant recipients. Methods: Urinary concentrations of soluble adhesion molecules (sICAM-1, sVCAM-1) and of the complement degradation product C4d were determined by standardized ELISA technique in 75 recipients of renal allografts and 29 healthy controls. Patient samples were assigned to four categories according to clinical criteria: group 1: acute steroid-sensitive rejection (ASSR, n=14), group 2: acute steroid-resistant rejection (ASRR, n=12), group 3: chronic allograft dysfunction (CAD, n=20) and group 4: stable graft function (SGF, n=29). Results: All patients with rejection episodes (groups 1-3) had significantly higher values of urinary sC4d compared with healthy controls and patients with stable graft function (p<0.05). The urinary levels of sVCAM-1 were significantly higher in group 2 (ASRR) compared with all other groups (p<0.001). Uniformly low amounts of s-VCAM-1 and complement-split product C4d were excreted by healthy controls (group 0). In contrast, urinary sICAM-1 concentration in healthy controls was almost as high as in group 2 (ASRR) whereas patients with a stable functioning graft (group 4) excreted significantly less sICAM-1 (p<0.05). Conclusion: The evaluation of sVCAM-1 and sC4d excretion in urine can provide a valuable tool with regard to the severity and type of allograft rejection. With respect to long-term allograft survival, serial measurements of these markers should have the potential to detect rejection episodes and prompt immediate treatment. Copyright (C) 2003 S. Karger AG, Basel

An Approximation for the rp-Process

Hot (explosive) hydrogen burning or the Rapid Proton Capture Process (rp-process) occurs in a number of astrophysical environments. Novae and X-ray bursts are the most prominent ones, but accretion disks around black holes and other sites are candidates as well. The expensive and often multidimensional hydro calculations for such events require an accurate prediction of the thermonuclear energy generation, while avoiding full nucleosynthesis network calculations. In the present investigation we present an approximation scheme applicable in a temperature range which covers the whole range of all presently known astrophysical sites. It is based on the concept of slowly varying hydrogen and helium abundances and assumes a kind of local steady flow by requiring that all reactions entering and leaving a nucleus add up to a zero flux. This scheme can adapt itself automatically and covers situations at low temperatures, characterized by a steady flow of reactions, as well as high temperature regimes where a $(p,\gamma)-(\gamma,p)$-equilibrium is established. In addition to a gain of a factor of 15 in computational speed over a full network calculation, and an energy generation accurate to more than 15 %, this scheme also allows to predict correctly individual isotopic abundances. Thus, it delivers all features of a full network at a highly reduced cost and can easily be implemented in hydro calculations.Comment: 18 pages, LaTeX using astrobib and aas2pp4, includes PostScript figures; Astrophysical Journal, in press. PostScript source also available at http://quasar.physik.unibas.ch/preps.htm

Hadamard states from null infinity

Free field theories on a four dimensional, globally hyperbolic spacetime, whose dynamics is ruled by a Green hyperbolic partial differential operator, can be quantized following the algebraic approach. It consists of a two-step procedure: In the first part one identifies the observables of the underlying physical system collecting them in a *-algebra which encodes their relational and structural properties. In the second step one must identify a quantum state, that is a positive, normalized linear functional on the *-algebra out of which one recovers the interpretation proper of quantum mechanical theories via the so-called Gelfand-Naimark-Segal theorem. In between the plethora of possible states, only few of them are considered physically acceptable and they are all characterized by the so-called Hadamard condition, a constraint on the singular structure of the associated two-point function. Goal of this paper is to outline a construction scheme for these states which can be applied whenever the underlying background possesses a null (conformal) boundary. We discuss in particular the examples of a real, massless conformally coupled scalar field and of linearized gravity on a globally hyperbolic and asymptotically flat spacetime.Comment: 23 pages, submitted to the Proceedings of the conference "Quantum Mathematical Physics", held in Regensburg from the 29th of September to the 02nd of October 201

Introducing the novel concept of cumulative concentration roses for studying the transport of ultrafine particles from an airport to adjacent residential areas

Airports are often surrounded by urban residential areas, which is both a motivation and challenge for studying their potential impact on local air quality. Airports are a relevant source of ultrafine particles (UFPs), which can pose a risk to human health due to their small size (particle diameter Dp≤100 nm). However, in urban environments, UFPs originate from a multitude of biogenic and anthropogenic sources. Here, we investigate UFPs in close proximity to an airport to disentangle their impact on local air quality from other urban sources. We present observations and analyses of airborne UFP concentrations and size distributions determined at two sites in close proximity to Munich Airport. Therefore, two novel measurement stations were established north and south of the airport but were neither situated on the axis of prevailing wind directions nor impacted by fly overs. This set-up allowed us to explore a mainly advection-driven distribution of UFPs into the most populated adjacent residential areas. The observation period covered a full year from August 2021 to July 2022. We analysed the data set in three steps. (1) First, we derived UFP concentration roses using the wind data as reported at 10 m height at the airport to represent the local wind field. An increase in particle number concentrations and a shift of the modal maximum towards smaller mobility diameters became evident for wind directions, including those approaching from the airport. During the airport's operation hours during the daytime, median particle number concentrations were 2.2- and 1.6-fold compared to nighttime at the northern station and the southern station. However, our data had a high variability, and the direction-based analysis was uncertain due to other potential UFP sources in the surroundings and the assumption of a homogeneous, local wind field. (2) Next, we derived concentration roses employing the airflow observations from the two measuring stations at 5.3 m height. While the annual concentration rose in principle yielded the same conclusions as the first analysis step, a significant seasonal and diurnal variability of UFPs and wind became evident. The influencing factors were likely other urban local UFP sources, an increased surface roughness due to green vegetation, and the atmospheric boundary layer development. (3) In order to assess the possible advection of UFPs from the direction of Munich Airport relative to all other directions over the course of the year, we calculated cumulative concentration roses with both local- and site-scale wind data. Under the assumption of a homogeneous local wind field, the fraction of all UFPs sampled in airflows approaching from the airport's direction was 21 % (N322) and 40 % (S229). Considering a local background, the range of UFP advection from Munich Airport to the adjacent residential areas was up to 10 % in the north and 14 % in the south. It has to be noted that these values highlight the relative magnitude of the maximum impact of the airport on local air quality as they do not distinguish between UFP sources from the airport and other measuring sites. Additionally, they integrate over a time period during which the airport did not reach its full capacity compared to pre-COVID-19 times.</p

The Cauchy problem on a characteristic cone for the Einstein equations in arbitrary dimensions

We derive explicit formulae for a set of constraints for the Einstein equations on a null hypersurface, in arbitrary dimensions. We solve these constraints and show that they provide necessary and sufficient conditions so that a spacetime solution of the Cauchy problem on a characteristic cone for the hyperbolic system of the reduced Einstein equations in wave-map gauge also satisfies the full Einstein equations. We prove a geometric uniqueness theorem for this Cauchy problem in the vacuum case.Comment: 83 pages, 1 figur

Unsupervised Meta-Analysis on Diverse Gene Expression Datasets Allows Insight into Gene Function and Regulation

Over the past years, microarray databases have increased rapidly in size. While they offer a wealth of data, it remains challenging to integrate data arising from different studies. Here we propose an unsupervised approach of a large-scale meta-analysis on Arabidopsis thaliana whole genome expression datasets to gain additional insights into the function and regulation of genes. Applying kernel principal component analysis and hierarchical clustering, we found three major groups of experimental contrasts sharing a common biological trait. Genes associated to two of these clusters are known to play an important role in indole-3-acetic acid (IAA) mediated plant growth and development or pathogen defense. Novel functions could be assigned to genes including a cluster of serine/threonine kinases that carry two uncharacterized domains (DUF26) in their receptor part implicated in host defense. With the approach shown here, hidden interrelations between genes regulated under different conditions can be unraveled

Spatio-temporal dynamics of bumblebees foraging under predation risk

We analyze 3D flight paths of bumblebees searching for nectar in a laboratory experiment with and without predation risk from artificial spiders. For the flight velocities we find mixed probability distributions reflecting the access to the food sources while the threat posed by the spiders shows up only in the velocity correlations. The bumblebees thus adjust their flight patterns spatially to the environment and temporally to predation risk. Key information on response to environmental changes is contained in temporal correlation functions, as we explain by a simple emergent model.Comment: Accepted for publication in PR