p-sd Shell gap reduction in neutron-rich systems and cross-shell excitations in 20 O

Excited states in 20O were populated in the reaction 10Be(14C,alpha) at Florida State University (FSU). Charged particles were detected with a particle telescope consisting of 4 annularly segmented Si surface barrier detectors and gamma radiation was detected with the FSU gamma detector array. Five new states were observed below 6 MeV from the alpha-gamma and alpha-gamma-gamma coincidence data. Shell model calculations suggest that most of the newly observed states are core-excited 1p-1h excitations across the N=Z=8 shell gap. Comparisons between experimental data and calculations for the neutron-rich O and F isotopes imply a steady reduction of the p-sd shell gap as neutrons are added.     

A definitive synthesis of D-myo-inositol 1,4,5,6-tetrakisphosphate and its enantiomer D-myo-inositol 3,4,5,6-tetrakisphosphate from a novel butane-2,3-diacetal-protected inositol

New and rapid syntheses of the enantiomeric intracellular signalling molecules d-myo-inositol 1,4,5,6-tetrakisphosphate (1 a) and D-myo-inositol 3,4,5,6-tetrakisphosphate (1 b) are described. The synthetic strategy employs the novel butane-2,3-diacetal-protected (BDA-protected) myo-inositol (+/-)-3 ab, directly accessible from myo-inositol on a large scale, and an optical resolution with diastereoisomeric (R)-(-)-acetylmandelate esters. The X-ray crystal structure of (+/-)-4, an unusual side product of acid-catalysed reaction of myo-inositol with butanedione is also presented, and the absolute configurations of 1 a and 1 b are definitively assigned by conversion of key precursors into (+)-bornesitol and L-iditol hexaacetate, respectively. Biological activity of synthetic 1 b was confirmed in comparison with the natural polyphosphate.     

Formation of para-quinomethanes via 4-aminobutylcatechol oxidation and ortho-quinone tautomerism

Enzymatic and chemical oxidation of 4-(4-N,N-dialkylaminobutyl)catechols leads to formation of 1,1-dialkyl-pyrrolidinium salts in good yield. It is proposed that these products are formed by tautomerism of the initially formed ortho-quinones to para-quinomethanes. The corresponding secondary amines do not form para-quinomethanes but cyclise giving tetrahydro-1H-benzo[b]azepine-7,8-diones. The failure of the dialkylaminobutyl derivatives to cyclise to bicyclic betaines, in a manner analogous to lower homologues and monoalkylaminobutyl derivatives, is attributed to steric hindrance. This proposal is supported by evidence that the sterically hindered N-tert-butylaminobutyl derivative, in contrast to other secondary amines, does not cyclise but gives a para-quinomethane-derived product. Based on pulse radiolysis and spectrophotometric evidence, para-quinomethane formation appears to be much slower than cyclisation and only occurs when cyclisation is unfavourable. The ortho-quinones formed from 5-aminopentylcatechols neither cyclise nor tautomerise suggesting that the chain length in these derivatives is too long for both cyclisation and intramolecular deprotonation.     

Improved branching ratio measurement for the decay K(0)(L) --> &mgr;(+)&mgr;(-)

We report results from Experiment 871, performed at the BNL AGS, of a measurement of the branching ratio K(0)(L)-->&mgr;(+)&mgr;(-) with respect to the CP-violating mode K(0)(L)-->pi(+)pi(-). This experiment detected over 6200 candidate &mgr;(+)&mgr;(-) events, a factor of 6 more than that seen in all previous measurements combined. The resulting branching ratio gamma(K(0)(L)-->&mgr;(+)&mgr;(-))/gamma(K(0)(L)-->pi(+)pi(-)) = (3. 474+/-0.057)x10(-6) leads to a branching fraction B(K(0)(L)-->&mgr;(+)&mgr;(-)) = (7.18+/-0.17)x10(-9), which is consistent with the current world average, and reduces the uncertainty in this decay mode by a factor of 3.     

Preliminary estimate of the cost of ethanol production for ssf technology

The Solar Energy Research Institute (SERI) recently completed a detailed engineering and economic analysis of the simultaneous saccharification and fermentation (SSF) based wood-to-ethanol process. The reference-case design was based on a plant capacity of 1920 dry t/d and a wood cost of $42/dry t. For this case, the preliminary estimate of the production cost of the ethanol product is about $1.22/gal. The combined effects of optimizing SSF enzyme loading, increasing plant capacity to 10,000 dry t/d, and reducing wood cost to $34/dry t are to reduce the preliminary estimate of the production cost to about $0.95/gal. Other technological improvements may further reduce the production cost. Certain technical assumptions, inherent in the analysis, are being investigated further.

     

Laser-hole boring into overdense plasmas measured with soft X-Ray laser probing

A laser self-focused channel formation into overdense plasmas was observed using a soft x-ray laser probe system with a grid image refractometry (GIR) technique. 1.053 &mgr;m laser light with a 100 ps pulse duration was focused onto a preformed plasma at an intensity of 2x10(17) W/cm (2). Cross sections of the channel were obtained which show a 30 &mgr;m diameter in overdense plasmas. The channel width in the overdense region was kept narrow as a result of self-focusing. Conically diverging density ridges were also observed along the channel, indicating a Mach cone created by a shock wave due to the supersonic propagation of the channel front.     

Reduced occupancy of the deeply bound 0d(5/2) neutron state in 32Ar

The 9Be(32Ar, 31Ar)X reaction, leading to the 5/2+ ground state of a nucleus at the proton drip line, has a cross section of 10.4(13) mb at a beam energy of 65.1 MeV/nucleon. This translates into a spectroscopic factor that is only 24(3)% of that predicted by the many-body shell-model theory. We introduce refinements to the eikonal reaction theory used to extract the spectroscopic factor to clarify that this very strong reduction represents an effect of nuclear structure. We suggest that it reflects correlation effects linked to the high neutron separation energy (22.0 MeV) for this state.     

Structural and electronic properties of graphite layers grown on SiC(0 0 0 1)

Photoelectron spectroscopy, low-energy electron diffraction, and scanning probe microscopy were used to investigate the electronic and structural properties of graphite layers grown by solid state graphitization of SiC(0 0 0 1) surfaces. The process leads to well-ordered graphite layers which are rotated against the substrate lattice by 30°. On on-axis 6H-SiC(0 0 0 1) substrates we observe graphitic layers with up to several 100 nm wide terraces. ARUPS spectra of the graphite layers grown on on-axis 6H-SiC(0 0 0 1) surfaces are indicative of a well-developed band structure. For the graphite/n-type 6H-SiC(0 0 0 1) layer system we observe a Schottky barrier height of ?_B,n = 0.3 ± 0.1 eV. ARUPS spectra of graphite layers grown on 8° off-axis oriented 4H-SiC(0 0 0 1) show unique replicas which are explained by a carpet-like growth mode combined with a step bunching of the substrate.     

A single extraction method for the analysis by liquid chromatography/tandem mass spectrometry of fumonisins and biomarkers of disrupted sphingolipid metabolism in tissues of maize seedlings

The fungus Fusarium verticillioides is a pathogen of many plants and produces fumonisins. In addition to their well-studied animal toxicoses, these toxins contribute to the development of maize seedling disease in susceptible maize varieties. Fumonisin disruption of sphingolipid biosynthesis occurs during pathogenesis. An extraction method was developed for the simultaneous analysis of fumonisins B₁ (FB₁), B₂ (FB₂) and B₃ (FB₃), free sphingoid bases and sphingoid base 1-phosphates in maize tissues by liquid chromatography/linear ion trap tandem mass spectrometry. The method involved a single extraction using 1:1 acetonitrile:water + 5% formic acid (1 ml per 10 mg tissue). Mean recoveries ranged from approximately 50 to 99 percent, and limits of detection ranged from 10 fg μl⁻¹ to 6900 fg μl⁻¹. To test the efficacy of the method, seeds of a susceptible maize line were inoculated with a pathogenic, fumonisin-producing strain of F. verticillioides. The seedlings were then harvested, and fumonisin content, as well as sphingoid bases and their 1-phosphates, were measured in the leaf and root tissues. Fumonisin accumulation was significantly greater in leaf one compared to leaves two and three. While FB₁, FB₂, and FB₃ were detected in root tissues, FB₁ was preferentially accumulated in leaf tissues. Accumulation of sphingoid bases and their 1-phosphates was evident in roots and leaves of seedlings grown from inoculated seed, with the level of accumulation being similar in leaves 1, 2 and 3. The method developed was effective, fast, and sensitive for use in simultaneously measuring fumonisin in tissues and their effects on sphingolipid metabolite biomarkers of disease. The method should be useful for screening maize cultivars for susceptibility to F. verticillioides-induced seedling diseases. Figure Lesion with chromatography