Observing CMB polarisation through ice

Ice crystal clouds in the upper troposphere can generate polarisation signals at the uK level. This signal can seriously affect very sensitive ground based searches for E- and B-mode of Cosmic Microwave Background polarisation. In this paper we estimate this effect within the ClOVER experiment observing bands (97, 150 and 220 GHz) for the selected observing site (Llano de Chajnantor, Atacama desert, Chile). The results show that the polarisation signal from the clouds can be of the order of or even bigger than the CMB expected polarisation. Climatological data suggest that this signal is fairly constant over the whole year in Antarctica. On the other hand the stronger seasonal variability in Atacama allows for a 50% of clean observations during the dry season.Comment: 7 Pages, 4 figure

Millimeter and sub-millimeter atmospheric performance at Dome C combining radiosoundings and ATM synthetic spectra

The reliability of astronomical observations at millimeter and sub-millimeter wavelengths closely depends on a low vertical content of water vapor as well as on high atmospheric emission stability. Although Concordia station at Dome C (Antarctica) enjoys good observing conditions in this atmospheric spectral windows, as shown by preliminary site-testing campaigns at different bands and in, not always, time overlapped periods, a dedicated instrument able to continuously determine atmospheric performance for a wide spectral range is not yet planned. In the absence of such measurements, in this paper we suggest a semi-empirical approach to perform an analysis of atmospheric transmission and emission at Dome C to compare the performance for 7 photometric bands ranging from 100 GHz to 2 THz. Radiosoundings data provided by the Routine Meteorological Observations (RMO) Research Project at Concordia station are corrected by temperature and humidity errors and dry biases and then employed to feed ATM (Atmospheric Transmission at Microwaves) code to generate synthetic spectra in the wide spectral range from 100 GHz to 2 THz. To quantify the atmospheric contribution in millimeter and sub-millimeter observations we are considering several photometric bands in which atmospheric quantities are integrated. The observational capabilities of this site at all the selected spectral bands are analyzed considering monthly averaged transmissions joined to the corresponding fluctuations. Transmission and pwv statistics at Dome C derived by our semi-empirical approach are consistent with previous works. It is evident the decreasing of the performance at high frequencies. We propose to introduce a new parameter to compare the quality of a site at different spectral bands, in terms of high transmission and emission stability, the Site Photometric Quality Factor.Comment: accepted to MNRAS with minor revision

A Search for Propylene Oxide and Glycine in Sagittarius B2 (LMH) and Orion

We have used the Mopra Telescope to search for glycine and the simple chiral molecule propylene oxide in the Sgr B2 (LMH) and Orion KL, in the 3-mm band. We have not detected either species, but have been able to put sensitive upper limits on the abundances of both molecules. The 3-sigma upper limits derived for glycine conformer I are 3.7 x 10^{14} cm^{-2} in both Orion-KL and Sgr B2 (LMH), comparable to the reported detections of conformer I by Kuan et al. However, as our values are 3-sigma upper limits rather than detections we conclude that this weighs against confirming the detection of Kuan et al. We find upper limits for the glycine II column density of 7.7 x 10^{12} cm^{-2} in both Orion-KL and Sgr B2 (LMH), in agreement with the results of Combes et al. The results presented here show that glycine conformer II is not present in the extended gas at the levels detected by Kuan et al. for conformer I. Our ATCA results (Jones et al.) have ruled out the detection of glycine (both conformers I and II) in the compact hot core of the LMH at the levels reported, so we conclude that it is unlikely that Kuan et al. have detected glycine in either Sgr B2 or Orion-KL. We find upper limits for propylene oxide abundance of 3.0 x 10^{14} cm^{-2} in Orion-KL and 6.7 x 10^{14} cm^{-2} in Sgr B2 (LMH). We have detected fourteen features in Sgr B2 and four features in Orion-KL which have not previously been reported in the ISM, but have not be able to plausibly assign these transitions to any carrier.Comment: 12 pages, 3 figures. Accepted by MNRAS 12th January 200

Feasibility of a Nutrition Training Program on Improving Self-Efficacy and Life Skill Development for Adolescents with Sickle Cell Disease

Adolescents with sickle cell disease (SCD) are at risk for growth and nutritionaldeficiencies due to poor dietary intake. Presently, no efficacious behavioral intervention exists to address the nutritional need in SCD management. The Good Nutrition 4Me Living with SCD program is a multi-component intervention, developed to improve knowledge base and the dietary habits of adolescents living with SCD. This report reviews the outcomes for 5 adolescents that participated in this 5-week program. Dietary intake was monitored daily via text messaging and progress with goals was reviewed weekly in the group sessions. Parents were also updated on their adolescent’s progress with dietary goals during a family session in the home setting. Resulted indicated promising effects across participants, with trends towards improvement in knowledge about nutritional recommendations and dietary intake. The Good Nutrition 4Me Living with SCD program was viewed as feasible and palatable, as all evaluable families completed the intervention and one-month follow-up activities

Equilibrium configurations of two charged masses in General Relativity

An asymptotically flat static solution of Einstein-Maxwell equations which describes the field of two non-extreme Reissner - Nordstr\"om sources in equilibrium is presented. It is expressed in terms of physical parameters of the sources (their masses, charges and separating distance). Very simple analytical forms were found for the solution as well as for the equilibrium condition which guarantees the absence of any struts on the symmetry axis. This condition shows that the equilibrium is not possible for two black holes or for two naked singularities. However, in the case when one of the sources is a black hole and another one is a naked singularity, the equilibrium is possible at some distance separating the sources. It is interesting that for appropriately chosen parameters even a Schwarzschild black hole together with a naked singularity can be "suspended" freely in the superposition of their fields.Comment: 4 pages; accepted for publication in Phys. Rev.

Long memory dynamics in a discrete-time real business cycle DSGE model and a continuous-time macro-financial model

Long memory refers to a property of a stationary stochastic process or a time series. More specifically, a stationary time series is called a long memory process if its autocorrelation function (ACF) decays very slowly to zero. Indeed, the convergence is so slow that the sum of the ACF’s absolute values diverges. In contrast, traditional time series models such as ARMA processes are so-called short memory processes as their ACF decays rapidly, such that these processes permit only a limited dependency structure. This dissertation is motivated by the following observation. In the 1960s, Mandelbrot initiated research on long memory processes. After the work of Hosking, Granger, and Joyeux in the early 1980s, who developed a class of long memory processes (the so-called ARFIMA processes), there is increasing empirical evidence that many macroeconomic time series can be well-described by long memory processes. Moreover, some theoretical explanations exist for the presence of long memory in (macro)economic time series. For instance, the aggregation of microdata can induce long memory in macro data. On the other hand, stochastic models build a cornerstone in modern macroeconomics to explain macroeconomic relationships, analyze counterfactual scenarios, or make forecasts. Two representative types of stochastic models are the discrete-time dynamic stochastic general equilibrium (DSGE) models and the continuous-time macro-financial models. Both types of these models use exogenous stochastic processes to describe the dynamics of the model’s variables. However, the exogenous stochastic processes often assumed for modeling are predominantly short memory processes. This becomes evident for DSGE models, in which technology shocks, monetary policy shocks, preference shocks, etc., are described by first-order autoregressive processes (AR(1) processes). However, since DSGE models are typically estimated with macro data, it may be appropriate to use a long memory process instead of a short memory process in a DSGE model.This dissertation aims to contribute to the integration of these two strands of the literature by introducing long memory dynamics in a DSGE and a macro-financial model. Before Chapter 4 and Chapter 5 introduce long memory into these two types of models, Chapter 2 introduces the mathematical framework and the discrete-time and continuous-time long memory processes that will later be used for modeling purposes. Chapter 3 gives an overview of long memory in economic and econometric research and underlines the relevance of long memory. Chapter 4 considers a real business cycle (RBC) model extended by long memory in the exogenous technology shock. In order to ensure that this is a true generalization of the existing model, the class of so-called ARFIMA processes is used. More precisely, the assumption of an exogenous AR(1) technology shock is replaced with an exogenous long memory ARFIMA(1, d, 0) process. Compared to the former, the latter has an additional parameter d that specifies the ACF’s decay rate and controls the strength of the long memory in the process. Setting this parameter to zero returns the well-known standard model (the AR(1) process) as a special case. However, the derivation of the solution of such a model is not trivial. If one considers a higher-order ARMA process instead of an AR(1) process, this can be done quite easily by expanding the model’s state space. For ARFIMA processes, this procedure does not work since they do not have such a finite-dimensional state space representation. Thus, Chapter 4 focuses on the solvability of such a long memory DSGE model. It turns out that the solution method of Klein (2000) can be extended to such models. This opens the possibility of analyzing the responses of the model’s variables to different specifications of the exogenous shocks using impulse-response functions (IRF). In addition, besides pure short and long memory processes, mixed processes, as well as so-called trend shocks with a permanent character, are considered and contrasted with each other. It turns out that the model’s responses to pure long memory shocks do not differ qualitatively from pure short memory AR(1) shocks. At first glance, this seems surprising from a model perspective. One might have expected an infinitely-lived representative agent with rational expectations to account for the long-lasting shock effects in his intertemporal consumption and labor supply decision. That this is not the case can be explained by the fact that the household in the model discounts its expected utility at an exponential rate. Thus, the shock effects in later periods have little impact on his consumption and labor supply decisions immediately after the time of shock occurrence. However, it is also shown that the model’s responses in the mixed short and long memory cases differ significantly from the responses in the corresponding pure cases. It is shown that the effect of the shock in the period after its occurrence is equal to the sum of the two memory parameters. Thus, long memory not only affects the model in the long term but can also affect model dynamics in the short term. Finally, the model responses are compared with those of a permanent growth shock. It is illustrated that the model’s responses to shocks with high short and long memory parameters are similar to those of a trend shock in the short run. In the long run, the economy reaches a new balanced growth path in response to the growth shock, whereas, in the mixed short and long memory case, it slowly returns to its old steady state. In Chapter 5, a continuous-time macro-financial model is extended to allow for long memory in the economy’s aggregate output growth rates. For modeling purposes, the Brownian motion assumed in the reference model is replaced with an approximation of a fractional Brownian motion. This replacement allows the exogenous shock to be split into a drift and volatility effect and the model to be solved using existing solution methods. It turns out that the evolution of the wealth distribution between the two agents in the model, which serves as a state variable, depends only on the volatility effect. In particular, the presence of long memory slows down the convergence of the state variable toward its steady state value. Moreover, the evolution of the aggregate wealth can be decoupled to some extent from the evolution of the wealth distribution and, thus, from the evolution of the state variable. While both models considered in this thesis can be solved given the more general long memory dynamics, the price for introducing long memory this way seems high. For example, estimating a long memory DSGE model is difficult because the associated DSGE model no longer has a finite-dimensional state space representation, which is typically used for estimating DSGE models. In the continuous-time model, the outlined decoupling of an economy’s total wealth from wealth distribution allows for more sophisticated modeling. However, this feature seems to contradict the general model structure of this kind of models. Generally, in this model category, all variables can be expressed as functions of the underlying state variables. This no longer holds true in the model under consideration, so generalizations to more complex models appear difficult

Plant RuBisCo assembly in E. coli with five chloroplast chaperones including BSD2

Plant RuBisCo, a complex of eight large and eight small subunits, catalyzes the fixation of CO2 in photosynthesis. The low catalytic efficiency of RuBisCo provides strong motivation to reengineer the enzyme with the goal of increasing crop yields. However, genetic manipulation has been hampered by the failure to express plant RuBisCo in a bacterial host. We achieved the functional expression of Arabidopsis thaliana RuBisCo in Escherichia coli by coexpressing multiple chloroplast chaperones. These include the chaperonins Cpn60/Cpn20, RuBisCo accumulation factors 1 and 2, RbcX, and bundle-sheath defective-2 (BSD2). Our structural and functional analysis revealed the role of BSD2 in stabilizing an end-state assembly intermediate of eight RuBisCo large subunits until the small subunits become available. The ability to produce plant RuBisCo recombinantly will facilitate efforts to improve the enzyme through mutagenesis

Zur Maltechnik Caspar David Friedrichs. Untersuchungen der Gemälde in den Beständen der Stiftung Preußische Schlösser und Gärten Berlin-Brandenburg und des Niedersächsischen Landesmuseums Hannover

Die insgesamt 14 Gemälde Caspar David Friedrichs in den Sammlungen der Stiftung Preußische Schlösser und Gärten Berlin-Brandenburg und des Landesmuseums in Hannover wurden anlässlich des 250. Geburtsjubiläums des Künstlers von einem interdisziplinären Team kunsttechnologisch untersucht. Strahlentechnische Aufnahmen, eine Bildträger-Untersuchung mittels künstlicher Intelligenz, die Bestimmung von Malmaterialien mithilfe spektroskopischer Verfahren und nicht zuletzt eine genaue Analyse des Werkprozesses führten zu neuen Einsichten, die auch über das bisherige Wissen zur Maltechnik Friedrichs hinausgehen. So sprechen die Befunde dafür, dass der Künstler einen eigenen Vorrat an grundierten Leinwänden nutzte und selbst auf Keilrahmen aufspannte. Die Herstellungsspuren des verwendeten Malertuchs ließen sich mit den Werkzeugen und Techniken der sächsischen Wachstuchfabrikation in Verbindung bringen. Für die Bildkompositionen stellte sich Friedrich passende Vergrößerungen seiner zeichnerischen Studien her und nutzte dazu offensichtlich einen Pantographen, wie anhand kleiner ganzer Zahlenverhältnisse in den Größenstufen hier erstmalig erkannt werden konnte. Auch sogenannte Kartons für die Übertragung einer fertigen Komposition auf den Malgrund müssen laut der Untersuchungsergebnisse angenommen werden. Das hierin zum Ausdruck kommende Streben nach einer authentischen Darstellung von einmal Gesehenem findet sich auch in der malerischen Ausführung. Mit einer fein abgestimmten Pigmentpalette, in der farbstarke Eisenoxidpigmente, Smalte und Kobaltblau eine besondere Rolle spielen und deren Mischgrüns der Künstler hier durch das selten nachzuweisende Rinmans Grün und ein Kupfergrün ergänzte, erreichte er besondere Farbwirkungen und naturgetreue Wiedergaben. Wie er dabei versiert die Möglichkeiten der Ölmalerei nutzte, beispielsweise die noch nicht getrocknete Farbe modellierte, gehört zu dem Repertoire an besonderen Techniken, das anhand der Untersuchungsergebnisse für die aus allen Werkphasen stammenden Gemälde deutlich wird