Evaluating volatility dynamics and the forecasting ability of Markov switching models

This paper uses Markov switching models to capture volatility dynamics in exchange rates and to evaluate their forecasting ability. We identify that increased volatilities in four euro‐based exchange rates are due to underlying structural changes. Also, we find that currencies are closely related to each other, especially in high‐volatility periods, where cross‐correlations increase significantly. Using Markov switching Monte Carlo approach we provide evidence in favour of Markov switching models, rejecting random walk hypothesis. Testing in‐sample and out‐of‐sample Markov trading rules based on Dueker and Neely (Journal of Banking and Finance, 2007) we find that using econometric methodology is able to forecast accurately exchange rate movements. When applied to the Euro/US dollar and the euro/British pound daily returns data, the model provides exceptional out‐of‐sample returns. However, when applied to the euro/Brazilian real and the euro/Mexican peso, the model loses power. Higher volatility exercised in the Latin American currencies seems to be a critical factor for this failure. Copyright © 2009 John Wiley & Sons, Ltd.     

Aurora A kinase (AURKA) in normal and pathological cell division

Temporally and spatially controlled activation of the Aurora A kinase (AURKA) regulates centrosome maturation, entry into mitosis, formation and function of the bipolar spindle, and cytokinesis. Genetic amplification and mRNA and protein overexpression of Aurora A are common in many types of solid tumor, and associated with aneuploidy, supernumerary centrosomes, defective mitotic spindles, and resistance to apoptosis. These properties have led Aurora A to be considered a high-value target for development of cancer therapeutics, with multiple agents currently in early-phase clinical trials. More recently, identification of additional, non-mitotic functions and means of activation of Aurora A during interphase neurite elongation and ciliary resorption have significantly expanded our understanding of its function, and may offer insights into the clinical performance of Aurora A inhibitors. Here we review the mitotic and non-mitotic functions of Aurora A, discuss Aurora A regulation in the context of protein structural information, and evaluate progress in understanding and inhibiting Aurora A in cancer.     

Variations in Ca and Mg contents inArbacia eggs as a result of fertilization

Zusammenfassung Es werden die Veränderungen im Ca- und Mg-Gehalt der Eier vonArbacia pust. während der ersten Stunde nach der Befruchtung untersucht. Es wird ein Ca- und Mg-Verlust mit Höhepunkt eine halbe Stunde nach der Befruchtung festgestellt.     

Testing the genetics underlying the co-evolution of mate choice and ornament in the wild

One of the most debated questions in evolutionary biology is whether female choice of males with exaggerated sexual displays can evolve as a correlated response to selection acting on genes coding for male attractiveness or high overall viability. To date, empirical studies have provided support for parts of this scenario, but evidence for all key genetic components in a natural population is lacking. Here we use animal-model quantitative genetic analysis on data from over 8,500 collared flycatchers (Ficedula albicollis) followed for 24 years to quantify all of the key genetic requirements of both fisherian and 'good-genes' models on sexual selection in the wild. We found significant additive genetic variances of all the main components: male ornament (forehead patch size), female mate choice for this ornament, male fitness and female fitness. However, when the necessary genetic correlations between these components were taken into account, the estimated strength of indirect sexual selection on female mate choice was negligible. Our results show that the combined effect of environmental influences on several components reduces the potential for indirect sexual selection in the wild. This study provides insight into the field of sexual selection by showing that genes coding for mate choice for an ornament probably evolve by their own pathways instead of 'hitchhiking' with genes coding for the ornament.     

Structure and function of a membrane component SecDF that enhances protein export

Protein translocation across the bacterial membrane, mediated by the secretory translocon SecYEG and the SecA ATPase, is enhanced by proton motive force and membrane-integrated SecDF, which associates with SecYEG. The role of SecDF has remained unclear, although it is proposed to function in later stages of translocation as well as in membrane protein biogenesis. Here, we determined the crystal structure of Thermus thermophilus SecDF at 3.3?? resolution, revealing a pseudo-symmetrical, 12-helix transmembrane domain belonging to the RND superfamily and two major periplasmic domains, P1 and P4. Higher-resolution analysis of the periplasmic domains suggested that P1, which binds an unfolded protein, undergoes functionally important conformational changes. In vitro analyses identified an ATP-independent step of protein translocation that requires both SecDF and proton motive force. Electrophysiological analyses revealed that SecDF conducts protons in a manner dependent on pH and the presence of an unfolded protein, with conserved Asp and Arg residues at the transmembrane interface between SecD and SecF playing essential roles in the movements of protons and preproteins. Therefore, we propose that SecDF functions as a membrane-integrated chaperone, powered by proton motive force, to achieve ATP-independent protein translocation.     

Single-ion quantum lock-in amplifier

Quantum metrology uses tools from quantum information science to improve measurement signal-to-noise ratios. The challenge is to increase sensitivity while reducing susceptibility to noise, tasks that are often in conflict. Lock-in measurement is a detection scheme designed to overcome this difficulty by spectrally separating signal from noise. Here we report on the implementation of a quantum analogue to the classical lock-in amplifier. All the lock-in operations--modulation, detection and mixing--are performed through the application of non-commuting quantum operators to the electronic spin state of a single, trapped Sr(+) ion. We significantly increase its sensitivity to external fields while extending phase coherence by three orders of magnitude, to more than one second. Using this technique, we measure frequency shifts with a sensitivity of 0.42 Hz Hz(-1/2) (corresponding to a magnetic field measurement sensitivity of 15 pT Hz(-1/2)), obtaining an uncertainty of less than 10 mHz (350 fT) after 3,720 seconds of averaging. These sensitivities are limited by quantum projection noise and improve on other single-spin probe technologies by two orders of magnitude. Our reported sensitivity is sufficient for the measurement of parity non-conservation, as well as the detection of the magnetic field of a single electronic spin one micrometre from an ion detector with nanometre resolution. As a first application, we perform light shift spectroscopy of a narrow optical quadrupole transition. Finally, we emphasize that the quantum lock-in technique is generic and can potentially enhance the sensitivity of any quantum sensor.     

Lyn is a redox sensor that mediates leukocyte wound attraction in vivo

Tissue wounding induces the rapid recruitment of leukocytes. Wounds and tumours--a type of 'unhealed wound'--generate hydrogen peroxide (H(2)O(2)) through an NADPH oxidase (NOX). This extracellular H(2)O(2) mediates recruitment of leukocytes, particularly the first responders of innate immunity, neutrophils, to injured tissue. However, the sensor that neutrophils use to detect the redox state at wounds is unknown. Here we identify the Src family kinase (SFK) Lyn as a redox sensor that mediates initial neutrophil recruitment to wounds in zebrafish larvae. Lyn activation in neutrophils is dependent on wound-derived H(2)O(2) after tissue injury, and inhibition of Lyn attenuates neutrophil wound recruitment. Inhibition of SFKs also disrupted H(2)O(2)-mediated chemotaxis of primary human neutrophils. In vitro analysis identified a single cysteine residue, C466, as being responsible for direct oxidation-mediated activation of Lyn. Furthermore, transgenic-tissue-specific reconstitution with wild-type Lyn and a cysteine mutant revealed that Lyn C466 is important for the neutrophil wound response and downstream signalling in vivo. This is the first identification, to our knowledge, of a physiological redox sensor that mediates leukocyte wound attraction in multicellular organisms.     

Endonuclease G is a novel determinant of cardiac hypertrophy and mitochondrial function

Left ventricular mass (LVM) is a highly heritable trait and an independent risk factor for all-cause mortality. So far, genome-wide association studies have not identified the genetic factors that underlie LVM variation, and the regulatory mechanisms for blood-pressure-independent cardiac hypertrophy remain poorly understood. Unbiased systems genetics approaches in the rat now provide a powerful complementary tool to genome-wide association studies, and we applied integrative genomics to dissect a highly replicated, blood-pressure-independent LVM locus on rat chromosome 3p. Here we identified endonuclease G (Endog), which previously was implicated in apoptosis but not hypertrophy, as the gene at the locus, and we found a loss-of-function mutation in Endog that is associated with increased LVM and impaired cardiac function. Inhibition of Endog in cultured cardiomyocytes resulted in an increase in cell size and hypertrophic biomarkers in the absence of pro-hypertrophic stimulation. Genome-wide network analysis unexpectedly implicated ENDOG in fundamental mitochondrial processes that are unrelated to apoptosis. We showed direct regulation of ENDOG by ERR-α and PGC1α (which are master regulators of mitochondrial and cardiac function), interaction of ENDOG with the mitochondrial genome and ENDOG-mediated regulation of mitochondrial mass. At baseline, the Endog-deleted mouse heart had depleted mitochondria, mitochondrial dysfunction and elevated levels of reactive oxygen species, which were associated with enlarged and steatotic cardiomyocytes. Our study has further established the link between mitochondrial dysfunction, reactive oxygen species and heart disease and has uncovered a role for Endog in maladaptive cardiac hypertrophy.     

唐宋文人审美情趣的嬗变——论山水画的兴起发展

唐宋作为中国文化发展的又一鼎盛与重要转折时期,其绘画也是瑰丽多姿。而文人是社会意识的代表,他们所体现出来的审美追求,最为充分地表现中国绘画的社会主流审美情趣。中国的艺术精神,可说由唐代水墨淡彩山水的出现而完成了它自身性格所要求的形式,才完成了文人进入绘画主流审美意识的舞台。随着社会思潮的不断变迁,山水画取代了人物画却在其后不远的北宋时代迎来了它的高峰。