Convergence of the Best Linear Predictor of a Weakly Stationary Random Field

Journal of Fourier Analysis and Applications - Suppose that $$\{X_{m,n}\}_{(m,n)\in \mathbb {Z}^2}$$ is a centered, weakly stationary random field with spectral density function W. Let $$X'$$...     

Direct Observation of an Oxepin from a Bacterial Cytochrome P450‐Catalyzed Oxidation

The cytochromes P450 are hemoproteins that catalyze a range of oxidative C?H functionalization reactions, including aliphatic and aromatic hydroxylation. These transformations are important in a range of biological contexts, including biosynthesis and xenobiotic biodegradation. Much work has been carried out on the mechanism of aliphatic hydroxylation, implicating hydrogen atom abstraction, but aromatic hydroxylation is postulated to proceed differently. One mechanism invokes as the key intermediate an arene oxide (and/or its oxepin tautomer). Conclusive isolation of this intermediate has remained elusive and, currently, direct formation of phenols from a Meisenheimer intermediate is believed to be favored. We report here the identification of a P450 [P450_cam (CYP101A1) and P450_cin (CYP176A1)]‐generated arene oxide as a product of in vitro oxidation of tert‐butylbenzene. Computations (CBS‐QB3) predict that the arene oxide and oxepin have similar stabilities to other arene oxides/oxepins implicated (but not detected) in P450‐mediated transformations, suggesting that arene oxides can be unstable terminal products of P450‐catalyzed aromatic oxidation that can explain the origin of some observed metabolites.     

Anecdotal History of Styrene and Polystyrene

A formal history of styrene and polystyrene from 1839 through 1952 appears in the Styrene monograph edited by Boundy and writer but now out of print. Updating of the story by several teams of Dow writers appeared in the Kirk-Othmer Encyclopedia, the Encyclopedia of Polymer Science and Technology, and the SPE Award address of Amos. We propose a more personalized history written from the perspective of one whose 40-year professional career was involved in scientific and technological aspects of the subject. We view this history as a complex interplay of science, technology, industrial activity, management decisions, legal and patent activities, people, and the vagaries of World War II. Germany had an early industrial lead prior to 1941 with a monomer process and mass polymerization techniques. Original work on styrene-butadiene elastomers was another first. Germany also had a scientific lead as academic scientists such as Staudinger, Kern, Schulz, Jenckel, and Ueberreiter became involved in the chemistry and physics of styrene and polystyrene (PS). Mark was first in industry and then in the university. Several United States companies were active with styrene and PS, also prior to 1941. Involvement of the United States in World War II lead to a government decision to produce SBR. This catapulted styrene into a major synthetic chemical. The lead passed from Germany to the United States, especially with the large excess capacity for monomer after 1945. Management decisions encouraged diverse large-scale polymer uses for styrene, aided by the low price for the monomer. Through a bizarre series of events (war, people, and legal action), proprietary industrial knowledge in both Germany and the United States had diffused into the domain of public knowledge. Styrene and PS now face the problems of any petrochemical product.     

History of the Development and Growth of Thermosetting Polymers

Fibrous proteins are cross-linked through the disulfide linkages of cystine; animal and vegetable proteins can be cross-linked by the reaction of tannic acid, chromic acid, or formaldehyde; and natural rubber can be vulcanized by heating with sulfur. However, most thermosetting polymers are synthetic polymers. These include saturated polyesters (Glyptals) synthesized by Smith in 1901, phenolic plastics produced by Baekeland in 1907, urea and melamine plastics produced by John and Henkel in 1918 and 1935, alkyds patented by Kienle in 1933, glycol maleates patented by Ellis in 1937, and epoxy resins patented by Schlack in 1933. Many of these developments were made prior to the advent of commercial synthetic thermoplastics. However, because their fabrication is more labor intensive than that of thermoplastics, thermosetting plastics now account for less than 20% of all plastics produced. Nevertheless, over 2.5 million tons of these thermosets are produced annually and the use of these cross-linked plastics continues to grow.     

Chemoproteomic Discovery of AADACL1 as a Regulator of Human Platelet Activation

1. Download : Download high-res image (288KB)
2. Download : Download full-size image

     

Stereospecific Synthesis and Acylation of cis 1-Halo 2-Trimethylsilyl Ethylenes

Several routes to 1-halo 2-trimethylsilyl ethylenes have been previously proposed ^1-6: from ethyn7yltrimethylilane (addition of HBr^1,2), ethyltrichlorosilane (addition H by C1, followed by dehydrohalogenation and further methylation of th Si-C1 bonds)³ or by other ways ^4,5, especially by reaction of (2-trimethylsilyl) vinyl lithium with dibromoethane⁶.     

Photosynthetic Electron Transport in an Anoxygenic Photosynthetic Bacterium Afifella (Rhodopseudomonas) marina Measured Using PAM Fluorometry

Blue diode‐based pulse amplitude modulation (PAM) technology can be used to measure the photosynthetic electron transport rate (ETR) in a purple nonsulfur anoxygenic photobacterium, Afifella (Rhodopseudomonas) marina. Rhodopseudomonads have a reaction center light harvesting antenna complex containing an RC‐2 type bacteriochlorophyll a protein (BChl a RC‐2‐LH1) which has a blue absorption peak and variable fluorescence similar to PSII. Absorptance of cells filtered onto glass fiber disks was measured using a blue–diode‐based absorptance meter (Blue‐RAT) so that absolute ETR could be calculated from PAM experiments. Maximum quantum yield (Y) was ≈0.6, decreasing exponentially as irradiance increased. ETR vs irradiance (P vs E) curves fitted the waiting‐in‐line model (ETR = (ETR_max × E/E_opt) × exp(1 ? E/E_opt)). Maximum ETR (ETR_max) was ≈1000–2000 μmol e^? mg^?1 BChl a h^?1. Fe²⁺, bisulfite and thiosulfate act as photosynthetic electron donors. Optimum irradiance was ≈100 μmol m^?2 s^?1 PPFD even in Afifella grown in sunlight. Quantum efficiencies (α) were ≈0.3–0.4 mol e^? mol hλ^?1; or ≈11.8 ± 2.9 mol e^? mol hλ^?1 m² μg^?1 BChl a). An underlying layer of Afifella in a constructed algal/photosynthetic bacterial mat has little effect on the measured ETR of the overlying oxyphotoautotroph (Chlorella).     

A Lewis Acid-Catalyzed Procedure for the Conversion of 2-Methoxyethoxymethyl Ethers to Carboxylic Esters

A procedure for the conversion of 2-methoxy-ethoxymethyl (MEM) ethers to carboxylic esters employed ferric chloride (0.4 equivalents) and a carboxylic anhydride (14 equivalents) and exhibited selectivity for the MEM ether functionality in the presence of benzyl ethers.     

Synthesis of isoindolinones via inverse-electron demand Diels–Alder cycloadditions

A new synthetic method has been developed for the synthesis of 2,4,5-substituted isoindolinones by means of intramolecular inverse-electron demand Diels–Alder cycloaddition reactions of substituted pyridazines. By taking advantage of the inherent reactivity of an intermediate chloropyridazine, a diverse set of analogues were prepared from common reagents and intermediates.