Measurement of D0-->pilnu(Klnu) form factors and absolute branching fractions

Using a 282 fb-1 data sample collected by the Belle experiment at the KEKB e+e- collider, we study D0 decays to K-l+nu and pi-l+nu final states. The D0 flavor and momentum are tagged through a full reconstruction of the recoiling charm meson and additional mesons from fragmentation. The reconstruction method provides very good resolution in neutrino momentum and in q2=(pl+pnu)2. Normalizing to the total number of D0 tags, we measure the absolute branching fractions to be B(D0-->Klnu)=(3.45+/-0.07stat+/-0.20syst)% and B(D0-->pilnu)=(0.255+/-0.019stat+/-0.016syst)% and the semileptonic form factors (within the modified pole model) f+K(0)=0.695+/-0.007stat+/-0.022syst and f+pi(0)=0.624+/-0.020stat+/-0.030syst.     

Field-free alignment of molecules observed with high-order harmonic generation

High-order harmonic generation is demonstrated to provide a sensitive way for an extensive study of dynamic processes in the field-free alignment of strong-field-induced molecular rotational wave packets. The time-dependent harmonic signal observed from field-free-aligned N2, O2, and CO2 has been found to include two sets of beat frequency for pairs of coherently populated rotational states. One of them is the well-known frequency component characterizing the field-free alignment of molecules, and the other is ascribed to the beat that arises from coherence embedded in the wave packet. We discuss the effect of each frequency component on the revival signal observed with the harmonic generation.     

Testing performance of the improved pinhole collimator and its application to small animals

Testing performance of the improved pinhole collimator of 1.5 mm aperture attached to the gamma camera was carried out with three kinds of radionuclides, 99mTc, 67Ga and 131I, using a hand-made phantom. The results obtained in this experiment were compared to those obtained with a human pinhole collimator of 4 mm aperture. Those were nearly understood by taking account of the effective aperture of a pinhole collimator for each effective photon energy. And all scintigrams obtained from rats with various scintigraphy showed high resolution images.     

THE CHLOROPHYLL a AGGREGATE ABSORBING NEAR 685 nm IS SELECTIVELY FORMED IN AQUEOUS TETRAHYDROFURAN*

An aqueous solution of 2–12% (vol/vol) tetrahydrofuran (THF) induced the selective aggregation of chlorophyll a (Chl a) to form a novel species, A-685, absorbing near 685 nm. The formation of A-685 was closely correlated with a decrease in water activity of the solution. A Raman spectrum of the Chl a species formed in the presence of 6% THF suggests a unique interaction among Chl a, solvent THF and water molecules to give a stacked aggregate (Chl a.THF.H₂O.THF.Chl a). The circular dichroic spectrum of the Chl a species formed in the 6% THF aqueous solution showed an intense signal that had negative and positive wings with about 100-fold larger molar ellipticity for the A-685 than for monomer. However, Chl a', the C10 epimer of Chl a, and chlorophyllide, with a phytyl chain replaced by an ethyl group, did not form A-685 in 6% THF. These clearly indicate that 10-methylcarboxylate and the phytyl chain have a significant role in stabilizing A-685. A possible structure for A-685 is proposed as a novel in vitro model for the P-680 Chl a dimer.     

INTERCONVERSION OF BACTERIOCHLOROPHYLL c AGGREGATES IN SOLID FILMS UPON ORGANIC VAPOR TREATMENT

Bacteriochlorophyll c (BChl c) solid films were prepared from a carbon tetrachloride solution on CaF₂ plates as artificial aggregates. Effects of organic vapor such as acetone and tetrahydrofuran (THF) on the BChl c films were studied by absorption and Fourier-transform infrared spectroscopy. Two major homologs (R[E,E]BChl c_F and R[P,E]BChl c_F) and one minor homolog (S[I,E]BChl c) isolated from the green photosynthetic bacterium Chlorobium limicola strain 6230 were examined for the experiments. The BChl c polymeric aggregates absorbing at739–753 nm similar to those in the chlorosome were induced for all homologs upon the treatment of BChl c solid film with acetone vapor. The 13¹-keto C=O stretching band in the R[E,E]BChl c_F solid film showed a downward shift from 1651 cm^?1to 1643 cm^?1 with a concomitant shift of the 3¹-OH stretching bands from 3337 and 3238 cm^?1 to 3163 cm^?1. It was suggested that the lower aggregates brought about by Mg…O=C(13¹) and (3¹)O…O=C(13¹) bonds were transformed into the higher aggregates strongly hydrogen-bonded in a Mg…(3¹)O-H…O=C(13^l) interaction. They were transformed to a monomer-like form absorbing at 667 nm upon exposure to THF vapor and were reversibly converted to the higher aggregates upon removal of THF molecules in vacuo.     

Successive electron transfer reaction of the lithium salt of 5-methyl-5,10-dihydrophenazine anion with 4-nitrophenethyl bromide via 4-nitrostyrene

The reaction of lithium salt of 5-methyl-5,10-dihydrophenazine anion with 4-nitrophenethyl bromide in 1,2-dimethoxyethane gave unexpected compounds, 1,2-bis[5-(10-methyl-5,10-dihydrophenazinyl)]-1-(4-nitrophenyl)ethane and 1,4-bis(4-nitrophenyl)-1,4-bis[5-(10-methyl-5,10-dihydrophenazinyl)]butane, while the reaction in dimethyl sulfoxide brought about the formation of 5-methyl-10-(4-nitrophenethyl)-5,10-dihydrophenazine. The successive electron transfer mechanism is proposed for the former reaction via 4-nitrostyrene.     

The Effects of pH and Ionic Strength on the Aggregation of Bacteriochlorophyll c in Aqueous Organic Media: The Possibility of Two Kinds of Aggregates

The aggregation behavior of two homologs of bacteriochlorophyll c (BChl c) in various media was investigated for the effects of pH and salt, and the corresponding structures were analyzed by Fourier transform (FT)-IR spectroscopy. R-[P, E] BChl c_F (3¹-R-form of BChl c with a propyl group at the C-8 position and an ethyl group at the C-12 position) and R-[E, E] BChl c_F (3¹-R-form of BChl c with two ethyl groups at positions C-8 and C-12) were isolated from the green sulfur bacterium Chloro-bium limicola. Aggregates of each homolog showed a pH-dependent shift of the absorption maximum; at low pH, the peak moved to the red. This tendency was also revealed by circular dichroic spectra. A similar red shift of the peak was also induced by a high concentration of salt (NaCl) or buffer for both homologs. The FT-IR spectrum indicates that at low pH, both homologs formed a rather amorphous aggregate. On the other hand, a regular structure of R-[P, E] BChl c_F was indicated in an acetone-water mixture. This structure was stabilized by a triangular interaction among three pigment molecules through the Mg-OH (3>) O = C (13¹) linkage. This structure was not found for R-[E, E] BChl c_F. These results indicate that the replacement of the side chain at the C-8 position on the macrocycle induces a change in aggregation behavior. A possible heterogeneity of the in vivo rod structure of chlorosomes in green sulfur bacteria is discussed based on the above results.     

Enhancement of extreme ultraviolet radiations from a laser-produced plasma using copper–tungsten alloy

Continuous extreme ultraviolet (EUV) emission intensity from a laser-produced plasma in the wavelength between 40 and 200 nm for a copper–tungsten alloy target was observed to be 1.3 times higher than that for a tungsten target. Using the alloy target, low-opacity regions of one material were filled with high-opacity regions of another material. This opacity effect resulted in the increase of a calculated Rosseland mean opacity compared with either of the constituents, which may explain the increase of the EUV emission intensity.     

Uroleuconaphins A2a, A2b, B2a, and B2b: four yellowish pigments from the aphid Uroleucon nigrotuberculatum (Olive)

Four novel yellowish pigments, uroleuconaphins A_2a, A_2b (3a, 3b), and B_2a, B_2b (4a, 4b), were isolated from the aphid Uroleucon nigrotuberculatum (Olive). Their structures were established by detailed analyses of 1D and 2D NMR spectra and mechanistic consideration of the interconversion between 3 (or 4) and uroleuconaphin A₁ (1) (or B₁ (2)).     

A facile and practical method of preparing optically active α-monosubstituted cycloalkanones by thermodynamically controlled deracemization

Racemic 2-monosubstituted cycloalkanones were converted to R-isomers when TADDOLs (e.g., 1a, b) were used as host molecules in alkaline aqueous MeOH. The efficiency of this thermodynamically controlled deracemization was strongly influenced by the mixture ratio of the solvent, H₂O/MeOH. Based on this finding, an improved method of preparing (R)-2-monosubstituted cycloalkanones with higher optical purity was developed. For example, (R)-2-(4-methylbenzyl)cyclohexanone (5) was obtained in 85% yield with 98% ee, when a 1:1 mixture of H₂O/MeOH was used as the solvent in the presence of 1a.