Seasonal variations and sources of mass and chemical composition for PM10 aerosol in Hangzhou,China

Aerosol observation was conducted for four seasons from September 2001 to August 2002 at five sampling sites in Hangzhou, South China, on PM10 mass, 22 elements (Na, Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Br, Cd, Ba, and Pb), 5 major ions (F-, Cl-, NO3-, SO42-, and NH4+), and organic and elemental carbon (OC and EC), showing that PM10 mass ranged from 46.7 to 270.8 μg/m3, with an annual average of 119.2 μg/m3. Na, AI, Si, S. K, Ca, and Fe were the most abundant elements in PM10, most ors being in the form of SO42-. SO42-, NO4-, and NH4+ were the major ions, which contributed to about 20%; of the PM10 mass. The mean seasonal concentrations for SO42- , averaged over all sites, were found to be 18.0, 18.5, 24.Z and 21.4 μg/m3. for spring, summer, autumn, and winter, respectively, while the corresponding Ioadings for NO3- were 72, 4.7, 7.1, and 11.2μg/m3. and for NH4+ were 6.0, 5.9, 8.2. and 9.3 μg/m3, in the form mostly of NH4NO3 in spring, autumn, and winter, and mostly of (NH4)2SO4 in summer. The low NO3-/SO42- ratio found indicates coal combustion as the major source throughout the year. The mean annual concentrations of OC and EC in PM10 were found to be 21A, and 4.1 μg/m3, respectively. Material balance calculation indicated that fugitive dust, the secondary aerosol, and carbonaceous matter were the most abundant species in PM10 for the four seasons, as is characteristic for cities in South China.     

Controlling the spontaneous emission of a superconducting transmon qubit

We present a detailed characterization of coherence in seven transmon qubits in a circuit QED architecture. We find that spontaneous emission rates are strongly influenced by far off-resonant modes of the cavity and can be understood within a semiclassical circuit model. A careful analysis of the spontaneous qubit decay into a microwave transmission-line cavity can accurately predict the qubit lifetimes over 2 orders of magnitude in time and more than an octave in frequency. Coherence times T1 and T_{2};{*} of more than a microsecond are reproducibly demonstrated.     

Proximal magnetometry in thin films using betaNMR

Low energy ion implantation of hyperpolarized radioactive magnetic resonance probes allows the NMR study of thin film heterostructures by enabling depth-resolved measurements on a nanometer lengthscale. By stopping the probe ions in a layer adjacent to a layer of interest, it is possible to study magnetic fields proximally. Here we show that, in the simplest case of a uniformly magnetized layer, this yields an unperturbed in situ frequency reference. We also discuss demagnetization contributions to measured shifts for this case. With a simple illustrative calculation, we show how a nonuniformly magnetized layer causes a strongly depth-dependent line broadening in an adjacent layer. We then give some experimental examples of resonance line broadening in heterostructures.     

The separation and isolation of gold by selective extraction and transport through a polyurethane ether-type membrane

The separation and isolation of gold(III) by selective extraction and transport through a ether-type polyurethane membrane was studied. Gold was found to be extracted into the membrane in strongly acidic solutions of HCl and HBr as the HAuBr(4) and HAuCl(4) complexes. Once extracted, the HAuCl(4) and HAuBr(4) complexes diffuse through the membrane and are recovered quantitatively in a receiving cell solution. This phenomenon was studied for the separation of a variety of binary metal solutions as well as for the separation of gold from a solution of gold ore. The preconcentration of gold was also achieved by adjusting the starting and receiving cell solution volumes.     

Design of novel antibiotics that bind to the ribosomal acyltransfer site

The structure of neamine bound to the A site of the bacterial ribosomal RNA was used in the design of novel aminoglycosides. The design took into account stereo and electronic contributions to interactions between RNA and aminoglycosides, as well as a random search of 273 000 compounds from the Cambridge structural database and the National Cancer Institute 3-D database that would fit in the ribosomal aminoglycoside-binding pocket. A total of seven compounds were designed and subsequently synthesized, with the expectation that they would bind to the A-site RNA. Indeed, all synthetic compounds were found to bind to the target RNA comparably to the parent antibiotic neamine, with dissociation constants in the lower micromolar range. The synthetic compounds were evaluated for antibacterial activity against a set of important pathogenic bacteria. These designer antibiotics showed considerably enhanced antibacterial activities against these pathogens, including organisms that hyperexpressed resistance enzymes to aminoglycosides. Furthermore, analyses of four of the synthetic compounds with two important purified resistance enzymes for aminoglycosides indicated that the compounds were very poor substrates; hence the activity of these synthetic antibiotics does not appear to be compromised by the existing resistance mechanisms, as supported by both in vivo and in vitro experiments. The design principles disclosed herein hold the promise of the generation of a large series of designer antibiotics uncompromised by the existing mechanisms of resistance.     

Studies on intramolecular Diels-Alder reactions of furo[3,4-c]pyridines in the synthesis of conformationally restricted analogues of nicotine and anabasine

En route to conformationally restricted analogues of nicotine and anabasine, a novel synthetic route to bridged anabasines is described that hinges on a domino intramolecular [4 + 2]-cycloaddition/ring opening-elimination sequence of 3-amino-substituted furo[3,4-c]pyridines. Extension of this route to bridged nicotines, however, proved abortive, even when the dienophile tether is activated by a p-tolylsulfonyl group or when the diene moiety is activated by an electron-releasing methoxy substituent. A detailed density functional theoretical study (B3LYP/6-31+G) was undertaken to provide insight into the factors that facilitate an intramolecular Diels-Alder reaction in the former case.     

Synthesis and reactions of a stable o-quinoid 10-pi-electron system, Furo

Methyl 4,6-dichloro-3-(diethylamino)furo[3, 4-c]pyridine-1-carboxylate (6), an intermediate in the Hamaguchi-Ibata reaction involving the Rh(II)-catalyzed intramolecular reaction of a diazo group with the carbonyl of an adjacent amido group, has been isolated and characterized. PM3 calculations reveal the heat of formation (DeltaH(f)) of this remarkably stable molecule to be -77.7 kcal/mol. Compound 6 undergoes a facile Diels-Alder cycloaddition with a variety of dienophiles to give polysubstituted isoquinoline derivatives via ring opening of initially formed cycloadducts. In each case the cycloaddition proceeds with high regioselectivity, with the electron-withdrawing group located ortho to the amino group. The most favorable FMO interaction is between the HOMO of the azaisobenzofuran 6 and the LUMO of the dienophile. The atomic coefficient at the ester carbon of the azaisobenzofuran 6 is larger than the amino center, and this nicely accommodates the observed regioselectivity.     

The extraction of uranium by amidoximated orlon

The nitrile groups in polyacrylonitrile (Orlontrade mark) fabric were converted to amidoxime groups to produce an amidoximated orlon fabric. The amidoximated fabric was evaluated for its ability to extract uranium from aqueous solution with a wide range of temperature and pH values. The conversion of nitrile groups to amidoxime groups was simple and relatively inexpensive. In general, the modified orlon fabric showed superior extractability of uranium at all temperatures and pH values tested when compared to untreated Orlontrade mark fabric.     

Hydrophobic interaction and hydrogen bonding cooperatively confer a vancomycin hydrogel: a potential candidate for biomaterials

Antibiotic hydrogels based on a vancomycin (Van) derivative, formed by self-assembling Van-pyrene (1) in water, using the pi-pi interaction of pyrene moieties and hydrogen bonding of Vans, promise a new way to make novel biomaterials.