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1.
Summary In this paper, we consider the following problem: given a layered network including a set of messages, each of which must be transmitted from a source to a sink node, what is the sequence of moves from one node to another which minimizes the total completion time? We first show that the general problem is NP-complete for both fixed and variable path routing (thus the scheduling problem for more realistic networks with cycles must be considered computationally intractable). We then consider several restrictions which admit polynomia time algorithms.Most of this work was done while this author was at the Department of Mathematics, University of Rome La Sapienza 相似文献
2.
Lithium orthosilicate reduction was examined by Temperature Programmed Reaction (TPR) and Temperature Programmed Desorption (TPD) methods performed in He (or Ar) + H2 purge gas flowing through pebble bed specimens. The parameters governing the kinetics and the steady-state of the reduction process to Li4SiO4−x were determined at 800°C. The level x of the O-vacancy concentration at steady-state (of the order of 1.5×10−3 mole fraction) was found to be compatible with the impurities content in the specimens. Pebble pre-annealing treatments were found to affect the microstructure and the reduction mechanism. Post-irradiation tritium release by TPD tests were performed on both stoichiometric and reduced pebbles with similar results. Tritium release properties of this breeder system seem to be independent from the material reduction state (x). 相似文献
3.
Lukas Spree Fupin Liu Volker Neu Marco Rosenkranz Georgios Velkos Yaofeng Wang Sandra Schiemenz Jan Dreiser Pierluigi Gargiani Manuel Valvidares Chia-Hsiang Chen Bernd Büchner Stanislav M. Avdoshenko Alexey A. Popov 《Advanced functional materials》2021,31(48):2105516
The chemical functionalization of fullerene single molecule magnet Tb2@C80(CH2Ph) enables the facile preparation of robust monolayers on graphene and highly oriented pyrolytic graphite from solution without impairing their magnetic properties. Monolayers of endohedral fullerene functionalized with pyrene exhibit magnetic bistability up to a temperature of 28 K. The use of pyrene terminated linker molecules opens the way to devise integration of spin carrying units encapsulated by fullerene cages on graphitic substrates, be it single-molecule magnets or qubit candidates. 相似文献
4.
Santolo Daliento Vincenzo d'Alessandro Pierluigi Guerriero Orlando Tari 《Progress in Photovoltaics: Research and Applications》2015,23(2):194-200
In this paper, the selective illumination approach is adopted to separately extract the shunt resistance of the individual subcells belonging to a tandem cell. The method relies on simple theoretical considerations and is based on the measurement of the current–voltage characteristic of the tandem cell by alternately keeping one of the subcells under dark conditions. Numerical simulations are employed to support the reliability of the technique, which is experimentally tested on micromorph devices deposited onto glass covered by a V‐shaped transparent conducting oxide and subject to different thermal treatments. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
5.
Mariela Torres Marcela Martínez Pierluigi Pierantozzi María Albanese Agustín Nasjleti Damián Maestri 《Journal of the American Oil Chemists' Society》2011,88(6):755-762
Oil blending was conducted to study the effects of changes in fatty acid composition (FAC), tocopherols and total phenol content
(TPC) on oxidative stability of virgin olive oil (VOO):walnut oil (WO) blends. The measurement of the antioxidant activity
of bioactive components present in the parent oils and blends was achieved by their ability to scavenge the free stable 2,2-diphenyl-1-picrylhydrazyl
radical (DPPH·). The highest percentage of DPPH· inhibition was found for pure VOO, and the lowest one for pure WO. EC50 values obtained from the DPPH assay correlated significantly and inversely with TPC. The generation of volatile flavor components
in VOO indicated the predominance of C6 compounds produced through biochemical (enzymatic) pathways, whereas WO showed increased concentrations of medium chain (C7–C11) aldehydes produced through chemical (oxidative) pathways. The results obtained confirm the importance of VOO phenolics in
providing protection against oxidation in VOO and VOO/WO blends. However, considering the impact of FAC and the content of
endogenous antioxidant substances mentioned previously on the oxidative stability of the oils analyzed, the effect of an elevated
unsaturation level (WO) prevails over a high amount of such bioactive components (VOO). 相似文献
6.
Righi V Di Nunzio M Danesi F Schenetti L Mucci A Boschetti E Biagi P Bonora S Tugnoli V Bordoni A 《Lipids》2011,46(7):627-636
It is well recognized that a high dietary intake of long-chain polyunsaturated fatty acids (LC-PUFA) has profound benefits
on health and prevention of chronic diseases. In particular, in recent years there has been a dramatic surge of interest in
the health effects of n-3 LC-PUFA derived from fish, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids. Notwithstanding,
the metabolic fate and the effects of these fatty acids once inside the cell has seldom been comprehensively investigated.
Using cultured neonatal rat cardiomyocytes as model system we have investigated for the first time, by means of high-resolution
magic-angle spinning nuclear magnetic resonance (HR-MAS NMR) spectroscopy in combination with gas chromatography (GC), the
modification occurring in the cell lipid environment after EPA and DHA supplementation. The most important difference between
control and n-3 LC-PUFA-supplemented cardiomyocytes highlighted by HR-MAS NMR spectroscopy is the increase of signals from
mobile lipids, identified as triacylglycerols (TAG). The observed increase of mobile TAG is a metabolic response to n-3 LC-PUFA
supplementation, which leads to an increased lipid storage. The sequestration of mobile lipids in lipid bodies provides a
deposit of stored energy that can be accessed in a regulated fashion according to metabolic need. Interestingly, while n-3
LC-PUFA supplementation to neonatal rat cardiomyocytes causes a huge variation in the cell lipid environment, it does not
induce detectable modifications in water-soluble metabolites, suggesting negligible interference with normal metabolic processes. 相似文献
7.
Commercial fish oils and foods containing fish may contain trans and/or isomerized fatty acids (FA) produced during processing or as part of prepared foods. The current American Oil Chemists’
Society (AOCS) official method for marine oils (method Ce 1i-07) is based on separation by use of poly(ethylene glycol) (PEG)
columns, for example Supelcowax-10 or equivalent, which do not resolve most unsaturated FA geometric isomers. Highly polar
100-m cyanopropyl siloxane (CPS) columns, for example SP-2560 and CP Sil 88 are recommended for separation of geometric FA
isomers. Complementary separations were achieved by use of two different elution temperature programs with the same CPS column.
This study is the first direct comparison of the separations achieved by use of 30-m Supelcowax-10 and 100-m SP-2560 columns
for fatty acid methyl esters (FAME) prepared from the same fish oil and fish muscle sample. To simplify the identification
of the FA in these fish samples, FA were fractionated on the basis of the number and type of double bonds by silver-ion solid-phase
extraction (Ag+-SPE) before GC analysis. The results showed that a combination of the three GC separations was necessary to resolve and identify
most of the unsaturated FA, FA isomers, and other components of fish products, for example phytanic and phytenic acids. Equivalent
chain length (ECL) values of most FAME in fish were calculated from the separations achieved by use of both GC columns; the
values obtained were shown to be consistent with previously reported values for the Supelcowax-10 column. ECL values were
also calculated for the FA separated on the SP-2560 column. The calculated ECL values were equally valid under isothermal
and temperature-programmed elution GC conditions, and were valuable for confirmation of the identity of several unsaturated
FAME in the fish samples. When analyzing commercially prepared fish foods, deodorized marine oils, or foods fortified with
marine oils it is strongly recommended that quantitative data acquired by use of PEG columns is complemented with data obtained
from separations using highly polar CPS columns. 相似文献
8.
Whitehill JG Opiyo SO Koch JL Herms DA Cipollini DF Bonello P 《Journal of chemical ecology》2012,38(5):499-511
The emerald ash borer (Agrilus planipennis, EAB) is an invasive wood-borer indigenous to Asia and is responsible for widespread ash (Fraxinus spp.) mortality in the U.S. and Canada. Resistance and susceptibility to EAB varies among Fraxinus spp., which is a result of their co-evolutionary history with the pest. We characterized constitutive phenolic profiles and lignin levels in the phloem of green, white, black, blue, European, and Manchurian ash. Phloem was sampled twice during the growing season, coinciding with phenology of early and late instar EAB. We identified 66 metabolites that displayed a pattern of variation, which corresponded strongly with phylogeny. Previously identified lignans and lignan derivatives were confirmed to be unique to Manchurian ash, and may contribute to its high level of resistance to EAB. Other compounds that had been considered unique to Manchurian ash, including hydroxycoumarins and the phenylethanoids calceolarioside A and B, were detected in closely related, but susceptible species, and thus are unlikely to contribute to EAB resistance of Manchurian ash. The distinct phenolic profile of blue ash may contribute to its relatively high resistance to EAB. 相似文献
9.
Pierluigi Guerrini De LucaClaudio Scali 《Chemical engineering science》2002,57(11):2077-2087
Applicability of different temperature oscillation calorimetry algorithms, previously proposed in the literature, for the evaluation of the heat transfer coefficient during the course of the reaction, is analysed by referring to the experimental data from a methyl methacrylate polymerisation reactor.Results are coincident in the nominal case (no errors on data), while differences appear in the elaboration of real data. The effect of uncertainty in the experimental data has been simulated in terms of error on the amplitude and on the phase of reactor and jacket temperature profiles.This approach allows to indicate algorithms having the best robustness properties and to give an explanation of phase errors in terms of a lumped parameter which accounts for different phenomena, not included in the basic hypotheses of the method. Based on this observation, a procedure to eliminate this source of errors from experimental data is proposed for the more general algorithm presented to handle oscillating temperature profiles generated by different techniques. 相似文献
10.
In studies of feeding by the bark beetle, Ips paraconfusus, two pine stilbenes (pinosylvin and pinosylvin methyl ether), ferulic acid glucoside, and enantiomers of the four most common sugars present in ponderosa pine phloem (sucrose, glucose, fructose, and raffinose) did not stimulate or reduce male feeding when assayed on wet -cellulose with or without stimulatory phloem extractives present. When allowed to feed on wet -cellulose containing sequential extracts (hexane, methanol, and water) of ponderosa pine phloem, methanol and water extractives stimulated feeding, but hexane extractives did not. Males confined in wet -cellulose containing aqueous or organic extracts of culture broths derived from phloem tissue and containing the root pathogen, Heterobasidion annosum, ingested less substrate than beetles confined to control preparations. In an assay using logs from uninoculated ponderosa pines, the mean lengths of phloem in the digestive tracts increased as time spent feeding increased. Males confined to the phloem of basal logs cut from ponderosa pines artificially inoculated with H. annosum ingested significantly less phloem than beetles in logs cut from trees that were (combined) mock-inoculated or uninoculated and did not contain the pathogen. However, individual pathogen-containing treatments were not significantly different from uninoculated controls. It was concluded that altered feeding rates are not a major factor which may explain why diseased ponderosa pines are colonized by I. paraconfusus. 相似文献