A Reverse Monte Carlo study of H+D Lyman alpha absorption from QSO spectra

A new method based on a Reverse Monte Carlo [RMC] technique and aimed at the inverse problem in the analysis of interstellar (intergalactic) absorption lines is presented. The line formation process in chaotic media with a finite correlation length $(l > 0)$ of the stochastic velocity field (mesoturbulence) is considered. This generalizes the standard assumption of completely uncorrelated bulk motions $(l \equiv 0)$ in the microturbulent approximation which is used for the data analysis up-to-now. It is shown that the RMC method allows to estimate from an observed spectrum the proper physical parameters of the absorbing gas and simultaneously an appropriate structure of the velocity field parallel to the line-of-sight. The application to the analysis of the H+D Ly$\alpha$ profile is demonstrated using Burles & Tytler [B&T] data for QSO 1009+2956 where the DI Ly$\alpha$ line is seen at $z_a = 2.504$. The results obtained favor a low D/H ratio in this absorption system, although our upper limit for the hydrogen isotopic ratio of about $4.5\times10^{-5}$ is slightly higher than that of B&T (D/H = $3.0^{+0.6}_{-0.5} \times 10^{-5}$). We also show that the D/H and N(HI) values are, in general, correlated, i.e. the derived D-abundance may be badly dependent on the assumed hydrogen column density. The corresponding confidence regions for an arbitrary and a fixed stochastic velocity field distribution are calculated.Comment: 6 pages, LaTeX, 2 Postscript figures, to appear in "The Primordial Nuclei and Their Galactic Evolution", eds. N. Prantzos, M. Tosi, R. von Steiger (Kluwer: Dordrecht

Capital flows and credit booms in emerging market economies?

Private capital began flowing back to emerging market economies (EMEs) in 2002 and continued to mid-2006. In parallel, most of these countries also witnessed rapid growth in bank credit to the private sector (BCPS). This paper seeks to determine whether this strong credit expansion reflects financial deepening or excess liquidity. In the first case, this phenomenon forms part of an economic catch-up process. In the second, the main emphasis is on the potential weakness of domestic banking systems and increased macroeconomic vulnerabilities of the concerned countries. Capital inflows tend to exacerbate these risks, such that they often coincide with credit booms. Depending on the observation period and the sample of emerging countries, between 40% and 60% of credit booms took place at a time when capital inflows were high. However, the linkage between credit booms and banking and financial crises is weaker, insofar as only 6%-20% of credit booms lead to a crisis. To explore the role of capital inflows in the observed credit expansion in EMEs, this article presents an econometric analysis of a 27-country sample over the last four years. A two-stage approach is taken: first, countries that have experienced excessive growth in bank credit to the private sector are identifi ed; second, the causality relationship between capital inflows and bank credit in these countries is examined. The main findings suggest that of the 27 EMEs, which on the whole recorded strong capital inflows over the last four years, just nine experienced a credit boom. Moreover, there does not appear to be a clear-cut causality relationship between capital inflows and BCPS. It is therefore difficult to draw general conclusions as regards financial stability. In some countries, a combination of substantial capital infl ows and credit booms may generate risks of instability if the external financing causes profound macroeconomic and financial imbalances. In other countries, massive capital infl ows and rapid credit growth may be linked to a healthier process of financial deepening.

Recent developments in monetary and financial integration in Asia.

Asia’s share of world trade has expanded constantly over the last two decades. This increase reflects, inter alia, the considerable strengthening of trade links between the countries of the region, fostered by the vertical specialisation of the Asian economies. In the 1980s, the most advanced economies in the region, e.g. Japan, relocated the most labour-intensive stages of their production processes to the newly-industrialised Asian economies like South Korea and Singapore and then, in the 1990s, to emerging Asia, i.e. Indonesia, Malaysia, the Philippines and Thailand. The emergence of China has also given signifi cant impetus to regional trade integration. Surging intra-regional direct investment fl ows have accompanied and shored up trade fl ows, however, portfolio investment fl ows and cross-border bank loans have remained limited. Given that production processes within the region are complementary and that the final destination for exports is outside the region, the lack of a regional exchange rate arrangement in Asia does not appear to be a concern in the short term. Indeed, the regional integration initiatives adopted in Asia in the aftermath of the 1997-1998 financial crisis aim to build further resilience to fi nancial market turbulence. Firstly, deeper and more liquid local bond markets should make it possible to reduce the double financial mismatch, i.e. the currency mismatch and maturity mismatch, which largely sustained the crisis. In this regard, the ASEAN+3 Asian Bond Market Initiative examines the supply-side issues while the Asian Bond Funds initiative of the Executives’ Meeting of East Asia-Pacifi c Central Banks (EMEAP) deals with demand-side issues via the pooling of resources to buy bonds issued by member countries. Secondly, the Chiang Mai Initiative, which consists in a network of currency swap arrangements between the central banks of the ASEAN+3 member states, provides these countries with a regional fi nancial assistance mechanism in the event of a liquidity crisis. The Asian vertical model of production appears to have reached its limit and is evolving towards a more “horizontal” model in terms of both production (substitutability of production processes as a result of the shift towards higher value-added activities) and consumption (expansion of the regional market linked to the growth potential of domestic Chinese demand). Regional monetary co-operation could therefore aim in the future at curbing intra-regional exchange rate fl uctuations in order to promote trade and investment within the region.

The emerging role of 5-hydroxymethylcytosine in neurodegenerative diseases

Copyright © 2014 Al-Mahdawi, Anjomani Virmouni and Pook. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.This article has been made available through the Brunel Open Access Publishing Fund.DNA methylation primarily occurs within human cells as a 5-methylcytosine (5mC) modification of the cytosine bases in CpG dinucleotides. 5mC has proven to be an important epigenetic mark that is involved in the control of gene transcription for processes such as development and differentiation. However, recent studies have identified an alternative modification, 5-hydroxymethylcytosine (5hmC), which is formed by oxidation of 5mC by ten-eleven translocation (TET) enzymes. The overall levels of 5hmC in the mammalian genome are approximately 10% of 5mC levels, although higher levels have been detected in tissues of the central nervous system (CNS). The functions of 5hmC are not yet fully known, but evidence suggests that 5hmC may be both an intermediate product during the removal of 5mC by passive or active demethylation processes and also an epigenetic modification in its own right, regulating chromatin or transcriptional factors involved in processes such as neurodevelopment or environmental stress response. This review highlights our current understanding of the role that 5hmC plays in neurodegenerative diseases, including Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), fragile X-associated tremor/ataxia syndrome (FXTAS), Friedreich ataxia (FRDA), Huntington's disease (HD), and Parkinson's disease (PD).Sara Anjomani Virmouni was supported by funding to Mark A. Pook from the Friedreich’s Ataxia Research Alliance(FARA)