Detecting macroeconomic phases in the Dow Jones Industrial Average time series

In this paper, we perform statistical segmentation and clustering analysis of the Dow Jones Industrial Average (DJI) time series between January 1997 and August 2008. Modeling the index movements and log-index movements as stationary Gaussian processes, we find a total of 116 and 119 statistically stationary segments respectively. These can then be grouped into between five and seven clusters, each representing a different macroeconomic phase. The macroeconomic phases are distinguished primarily by their volatilities. We find that the US economy, as measured by the DJI, spends most of its time in a low-volatility phase and a high-volatility phase. The former can be roughly associated with economic expansion, while the latter contains the economic contraction phase in the standard economic cycle. Both phases are interrupted by a moderate-volatility market correction phase, but extremely-high-volatility market crashes are found mostly within the high-volatility phase. From the temporal distribution of various phases, we see a high-volatility phase from mid-1998 to mid-2003, and another starting mid-2007 (the current global financial crisis). Transitions from the low-volatility phase to the high-volatility phase are preceded by a series of precursor shocks, whereas the transition from the high-volatility phase to the low-volatility phase is preceded by a series of inverted shocks. The time scale for both types of transitions is about a year. We also identify the July 1997 Asian Financial Crisis to be the trigger for the mid-1998 transition, and an unnamed May 2006 market event related to corrections in the Chinese markets to be the trigger for the mid-2007 transition.     

Sulfated silica-titania aerogel as a bifunctional oxidative and acidic catalyst in the synthesis of diols

Sulfated silica-titania aerogel (SO₄/ST) catalyst was prepared by direct synthesis and modified with H₂SO₄ by wet impregnation method. Brønsted acid sites were generated after sulfation of the silica-titania aerogel with a pKa of −14.52. Consecutive transformation of 1-octene, catalyzed by sulfated silica-titania aerogel using aqueous hydrogen peroxide as oxidant shows high activity towards 1,2-octanediol through the formation of 1,2-epoxyoctane. The formation of 1,2-octanediol is enabled by the co-existence of sulfated Ti species with Brønsted acid sites in the SO₄/ST system. Sulfated silica-titania aerogel catalyst produced 1,2-octanediol (326 μmol) with selectivity of 63%. In contrast, no diol was produced when silica-titania aerogel was used.     

Structure-activity relationships for a new family of sulfonylurea herbicides

Summary Acetohydroxyacid synthase (AHAS; EC 2.2.1.6) catalyzes the first common step in branched-chain amino acid biosynthesis. The enzyme is inhibited by several chemical classes of compounds and this inhibition is the basis of action of the sulfonylurea and imidazolinone herbicides. The commercial sulfonylureas contain a pyrimidine or a triazine ring that is substituted at both meta positions, thus obeying the initial rules proposed by Levitt. Here we assess the activity of 69 monosubstituted sulfonylurea analogs and related compounds as inhibitors of pure recombinant Arabidopsis thaliana AHAS and show that disubstitution is not absolutely essential as exemplified by our novel herbicide, monosulfuron (2-nitro-N-(4′-methyl-pyrimidin−2′-yl) phenyl-sulfonylurea), which has a pyrimidine ring with a single meta substituent. A subset of these compounds was tested for herbicidal activity and it was shown that their effect in vivo correlates well with their potency in vitro as AHAS inhibitors. Three-dimensional quantitative structure–activity relationships were developed using comparative molecular field analysis and comparative molecular similarity indices analysis. For the latter, the best result was obtained when steric, electrostatic, hydrophobic and H-bond acceptor factors were taken into consideration. The resulting fields were mapped on to the published crystal structure of the yeast enzyme and it was shown that the steric and hydrophobic fields are in good agreement with sulfonylurea-AHAS interaction geometry.     

Organoruthenium Antagonists of Human A3 Adenosine Receptors

Human A₃ adenosine receptor (hA₃AR) is a membrane‐bound G protein‐coupled receptor implicated in a number of severe pathological conditions, including cancer, in which it acts as a potential therapeutic target. To derive structure–activity relationships on pyrazolo–triazolo–pyrimidine (PTP)‐based A₃AR antagonists, we developed a new class of organometallic inhibitors through replacement of the triazolo moiety with an organoruthenium fragment. The objective was to introduce by design structural diversity into the PTP scaffold in order to tune their binding efficacy toward the target receptor. These novel organoruthenium antagonists displayed good aquatic stability and moderate binding affinity toward the hA₃ receptor in the low micromolar range. The assembly of these complexes through a template‐driven approach with selective ligand replacement at the metal center to control their steric and receptor‐binding properties is discussed.     

Application of chalcone-based dithiocarbamate derivative incorporated sol–gel for the removal of Hg (II) ion from water

Journal of Sol-Gel Science and Technology - This study demonstrated the application of chalcone-based dithiocarbamate derivative as metal capturing ligand for the removal of mercury ion (Hg2+) in...     

Pure Blue‐Light Emissive Poly(oligofluorenes) with Bifunctional POSS in the Main Chain

Emission of conjugated polymers is known to undergo bathochromic shift from solution to film formation due to π–π stacking in the solid state. In this report, a series of pearl‐necklace‐like hybrid polymers is designed via the hydrosilylation condensation between bifunctional polyhedral oligomeric silsesquioxanes ( B‐POSS ) and oligofluorene segments. Optoelectronic analyses unequivocally show that the presence of these interconnecting B‐POSS can effectively reduce red‐shift in photoluminescence and electroluminescence during film formation. These hybrid poly(oligofluorenes) display stable blue emission with high color purity. Thermal analyses also indicate that they are vitrified polymers with high glass transition temperature (up to 125 °C). We believe that this strategy can be extended to other conjugated systems to control color purity in electroactive materials and holds promise as new emissive materials for various applications.

     

Single sensor for multiple analytes: fluorogenic detection of Al3+ in aqueous media and AcO− in organic media

A simple novel receptor, designed to have a combination of both oxygen and nitrogen-binding sites for metal ion and hydrogen bond donor sites for anion, was synthesised. The receptor has been explored for the selective detection of cation Al³⁺ over the other interfering metal ions and anion AcO^?  against a range of physiologically relevant anions in the fluorescence spectroscopy. The receptor shows a different response to aluminium and acetate in the emission spectra. The binding isotherm and detection limit demonstrate that the receptor is an excellent fluorometric probe for Al³⁺ and AcO^? .     

Correlative studies in optical reflectance measurements of cerebral blood oxygenation

A numerical study is made of correlation development for measuring cerebral blood oxygen saturation (StO) noninvasively using optical reflectance ratio of dual wavelengths. The Monte Carlo (MC) method was used for simulating reflectance measurements in a model neck tissue, where the cerebral blood oxygenation was monitored through the blood flows in the common carotid artery (CCA) and jugular vein. Reflectance ratios between two wavelengths at 633 and 800 nm were obtained under different blood vessel conditions. The results revealed a quantifiable correlation between the reflectance ratio and the cerebral StO level. Correlations for each of the blood vessel parameters such as the location, size, and hemoglobin concentration of the CCA or jugular vein (JV) were developed.     

Excited states and multi-exciton complexes in single CdTe quantum dots

We present an optical study of excited states in single CdTe quantum dot (QDs). Using micro-photoluminescence excitation spectroscopy, absorption up to two confined excited levels have been observed in some dots. Power-dependent micro-photoluminescence is then used to study the occupation of excited states. The emission pattern is characteristic of the increase of the exciton number in the QD (shell-filling). A clear identification of the different multi-exciton complexes has been obtained in a highly symmetric dot. The evolution of the different multi-exciton intensities can then be reproduced by solving the rate equations for multi-exciton state occupancy and the fit by this simple model provides an estimate of the radiative lifetime of the different multi-exciton complexes.