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41.
Lifetimes of high spin states up to {
}=22+ in the yrast positive parity bands have been measured to investigate the shape evolution with increasing spin in 72, 74Se. The Q
t values derived from these measurements indicate that prolate shape stabilizes for 72Se, while a triaxial shape develops for 74Se at higher spins. Comparison of the observed trend in Q
t with spin for 72, 74Se with that of the corresponding kryptones isotones emphasizes the stability provided by N=38 prolate shell gap even at high rotational frequency. 相似文献
42.
Biologic conversion of inexpensive and abundant sources of cellulosic biomass offers a low-cost route to production of fuels
and commodity chemicals that can provide unparalleled environmental, economic, and strategic benefits. However, low-cost,
high-yiel technologies are needed to recover sugars from the hemicellulose fraction of biomass and to prepare the remaining
cellulose fraction for subsequent hydrolysis. Uncatalyzed hemicellulose hydrolysis in flow-through systems offers a number
of important advantages for removal of hemicellulose sugars, and it is believed that oligomers could play an important role
in explaining why the performance of flow-through systems differs from uncatalyzed steam explosion approaches. Thus, an effort
is under way to study oligomer formation kinetics, and a small batch reactor is being applied to capture these important intermediates
in a closed system that facilitates material balance closure for varying reaction conditions. In this article, heat transfer
for batch tubes is analyzed to derive temperature profiles for different tube diameters and assess the impact on xylan conversion.
It was found that the tube diameter must be <0.5 in, for xylan hydrolysis to follow the kinetics expected for a uniform temperature
system at typical operating conditions. 相似文献
43.
The projected cost of ethanol production, from cellulosic biomass has been reduced by almost a factor of four over the last
20 yr. Thus, it is now competitive for blending with gasoline, and several companies are working to build the first plants.
However, technology development faced challenges at all levels. Because the benefits of bioethanol were not well understood,
it was imperative to clarify and differentiate its attributes. Process engineering was invaluable in focusing on promising
opportunities for improvements, particularly in light of budget reductions, and in tracking progress toward a competitive
goal. Now it is vital for one or more commercial projects to besuccessful, and improving our understanding of process fundamentals
will reduce the time and costs for commercialization. Additionally, the cost of bioethanol, must be cut further to be competitive
as a pure fuel in the open market, and aggressive technology advances are required to meet this target. 相似文献
44.
45.
Because pretreatment of biomass with hot water only in differential flow systems offers very digestible cellulose and potentially
less inhibition by liquid hydrolysate, solids and liquid hydrolysate from bagasse pretreated with hot water were fed to a
batch cellulase production system using the Rut C30 strain of Trichoderma reesei to determine the suitability of these substrates for cellulase production. The organism was found to be sensitive to inhibitors
in the liquid hydrolysate but could be adapted to improve its tolerance. In addition, filtering of the material reduced inhibitory
effects. The organism was also sensitive to some component in the solids, and they had to be washed heavily to achieve good
growth and cellulase production rates. Even then, a lag was found before enzyme production would commence on pretreated solids
whereas no such lag was experienced with Solka Floc. However, once enzyme production began, as high and even somewhat greater
cellulase productivities were realized with washed pretreated solids. Adding lignin to Solka Floc delayed enzyme production,
suggesting that lignin or other materials in the lignin solids could cause the lag observed for pretreated bagasse, but more
studies are needed to resolve the actual reason for this delay. 相似文献
46.
Lynd Lee R. Elamder Richard T. Wyman Charles E. 《Applied biochemistry and biotechnology》1996,57(1):741-761
Applied Biochemistry and Biotechnology - Analysis is undertaken motivated by the question: “What are the likely features and cost of a facility producing ethanol from cellulosic biomass at a... 相似文献
47.
St-Jacques AD Wyman IW Macartney DH 《Chemical communications (Cambridge, England)》2008,(40):4936-4938
Cucurbit[7]uril binds, with considerable size selectivity, NR(4)(+), PR(4)(+), and SR(3)(+) cations (R=Me, Et, (n)Pr, (n)Bu), with the smaller guests inside its cavity, rather than at the carbonyl-lined portals. 相似文献
48.
The host-guest stability constants for the inclusion of a series of small neutral polar organic guests in cucurbit[7]uril (CB[7]) have been determined in aqueous solution by (1)H NMR titrations. The dependence of the stability constant on the nature of the guests indicates that hydrophobic and dipole-quadrupole interactions are responsible for the binding. The complexation-induced chemical shift changes in the guest proton resonances, coupled with energy-minimization calculations, suggest that the guests are located such that their dipole moment is aligned perpendicular with the quadrupole moment of the CB[7] host. The stability constants for acetone and acetophenone decrease in the presence of Na(+) or K(+) cations as a result of cation capping of the CB[7] portals. 相似文献
49.
50.
KM Clauwaert Van Bocxlaer JF HJ Major JA Claereboudt WE Lambert Van den Eeckhout EM Van Peteghem CH De Leenheer AP 《Rapid communications in mass spectrometry : RCM》1999,13(14):1540-1545
This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd. 相似文献