The effects of genetic, pre-harvest (season of harvest, spear diameter, spear portion and spear tip color) and post-harvest factors (storage and domestic preparation practices, e.g., peeling and cooking) on total phenolic, flavonoid and ascorbic acid content of white asparagus spears and their correlation with antioxidant capacity (DPPH and FRAP) were studied. Results showed that genetic material was important for the total phenolic content but not season of harvest, spear diameter or storage. Violet spear tips and apical spear portions showed the largest amount of total phenolics. Peeling did not affect total phenolics in fresh asparagus, whereas it reduced their content in stored asparagus, while cooking resulted in an increase in both fresh and stored asparagus. However, the soluble extract of total phenolics and flavonoids were minor and the missing significance of phenolics and flavonoids in antioxidant capacity of white asparagus spears depends on these small amounts. 相似文献
US and international government efforts to equip major seaports with large area neutron detectors, aimed to intercept the smuggling of nuclear materials, have precipitated a critical shortage of 3He gas. It is estimated that the annual demand of 3He for US security applications alone is more than the worldwide supply. This is strongly limiting the prospects of neutron science, safeguards, and other applications that rely heavily on 3He-based detectors. Clearly, alternate neutron detection technologies that can support large sensitive areas, and have low gamma sensitivity and low cost must be developed.We propose a low-cost technology based on long copper tubes (straws), coated on the inside with a thin layer of 10B-enriched boron carbide (10B4C). In addition to the high abundance of boron on Earth and low cost of 10B enrichment, the boron-coated straw (BCS) detector offers distinct advantages over conventional 3He-based detectors, and alternate technologies such as 10BF3 tubes and 10B-coated rigid tubes. These include better distribution inside moderator assemblies, many-times faster electronic signals, no pressurization, improved gamma-ray rejection, no toxic or flammable gases, and ease of serviceability.We present the performance of BCS detectors dispersed in a solid plastic moderator to address the need for portal monitoring. The design adopts the outer dimensions of currently deployed 3He-based monitors, but takes advantage of the small BCS diameter to achieve a more uniform distribution of neutron converter throughout the moderating material. We show that approximately 63 BCS detectors, each 205 cm long, distributed inside the moderator, can match or exceed the detection efficiency of typical monitors fitted with a 5 cm diameter 3He tube, 187 cm long, pressurized to 3 atm. 相似文献
A simple and fast method for the TMS derivatization of phenolic acids in a closed vial using microwave irradiation followed by GC/MS analysis is proposed. A full factorial design was used to investigate the effects of two independent variables, namely, time and power of microwave irradiation, on the yield of silylation reaction. The optimal conditions were tested against the classical heating derivatization procedure. No significant differences were found between the classical heating and microwave-assisted derivatization. Chromatographic separation of the nine phenolic acids examined was achieved in 16 min. The mass spectral fragmentation patterns of the derivatives obtained by the proposed method were identical to those from the classical heating. Four different batches of brewer’s spent grain were extracted and analyzed for the total phenolic acid content. Significant differences between the batches of spent grains were found for all analytes. The total phenolic acid content varied between 2688 and 4884 μg/g. 相似文献
The objectives of the present study were (a) to produce gluten-free bread, fortified with iron (GFB-Fe), using selected iron compounds (ferric pyrophosphate, ferric pyrophosphate with emulsifiers, NaFeEDTA, electrolytic iron, ferrous gluconate, ferrous lactate and ferrous sulphate) (b) to test sensory characteristics of the GFB-Fe (feel-mouth texture, crumb colour, aroma and taste) (c) to compare iron dialyzability of various iron compounds in GFB-Fe. The most acceptable products were those fortified with ferric pyrophosphate with emulsifiers and ferric pyrophosphate. Ferrous dialyzable iron (ferrous iron with molecular weight lower than 8000 Da, an index for prediction of iron bioavailability) was measured under simulated gastrointestinal conditions. Ferrous dialyzable iron in GFB-Fe fortified with ferric pyrophosphate with emulsifiers, NaFeEDTA, ferrous bis-glycinate, ferrous gluconate or ferrous sulphate was higher than that in GFB-Fe fortified with electrolytic iron, ferrous lactate or ferric pyrophosphate (P < 0.05). These results are promising for the development of GFB-Fe products in the future. 相似文献
Communication networks, whether they are wired or wireless, have traditionally been assumed to be connected at least most
of the time. However, emerging applications such as emergency response, special operations, smart environments, VANETs, etc.
coupled with node heterogeneity and volatile links (e.g. due to wireless propagation phenomena and node mobility) will likely
change the typical conditions under which networks operate. In fact, in such scenarios, networks may be mostly disconnected,
i.e., most of the time, end-to-end paths connecting every node pair do not exist. To cope with frequent, long-lived disconnections,
opportunistic routing techniques have been proposed in which, at every hop, a node decides whether it should forward or store-and-carry a message.
Despite a growing number of such proposals, there still exists little consensus on the most suitable routing algorithm(s)
in this context. One of the reasons is the large diversity of emerging wireless applications and networks exhibiting such
“episodic” connectivity. These networks often have very different characteristics and requirements, making it very difficult,
if not impossible, to design a routing solution that fits all. In this paper, we first break up existing routing strategies
into a small number of common and tunable routing modules (e.g. message replication, coding, etc.), and then show how and when a given routing module should be used, depending on the set of network characteristics exhibited by the wireless application. We further attempt to create a taxonomy for intermittently connected networks. We
try to identify generic network characteristics that are relevant to the routing process (e.g., network density, node heterogeneity, mobility patterns) and dissect different
“challenged” wireless networks or applications based on these characteristics. Our goal is to identify a set of useful design guidelines that will enable one to choose an appropriate routing protocol for the application or network in hand. Finally, to demonstrate
the utility of our approach, we take up some case studies of challenged wireless networks, and validate some of our routing
design principles using simulations. 相似文献
The synthesis of silver nanoparticles attached on the surface of a hollow cornet‐like polymer matrix which served as a reductant and host matrix is described. This hybrid organic/inorganic macromolecular matrix is exhibiting anion‐exchange properties, porous structure and hollow morphologies, and absorptions in the visible light region. Due to the anion‐exchange property and the 3D orientation of the macromolecular chains the material is defining a new functional organic/inorganic hybrid. For the synthesis of nanoparticles, no other reducing agents were used and silver nanoparticles with a mean diameter of less than 20 nm were attached on the surface of the polymer, thus inheriting the composite with high antibacterial activity tested in bacterial strains and yeasts.
This paper presents a model to evaluate the impact of substrate noise on a CMOS regenerative comparator and moreover to predict
the resulting performance degradation of a flash analog-to-digital (A/D) converter. The proposed approach initially relates
substrate noise to the induced timing uncertainty of the comparator by means of an analytical linear model. In particular,
the analysis first focuses on analyzing and expressing the resulting non-uniform sampling distortion in regenerative comparators
in the presence of a deterministic ground bounce. Two sources of distortion are identified and evaluated: the input-dependent
and the substrate noise-dependent one. For each error contributor, the analysis investigates two cases of timing error, based
on the frequency correlation of the interfering signal with the sampling clock. The properties (number and power of distortion
tones) of the sampling error spectrum are found to be highly dependent on the spectral content of the interfering signal and
the sampling clock, while the model captures accurately the induced distortion. Subsequently, the linear model is extended
to estimate the degradation of flash A/D converters and is utilized to predict the performance of practical flash and time-interleaved
converters in the presence of substrate noise. 相似文献
The tocopherol (Tp) and tocotrienol (Tt) compositions of raw Greek olive fruit pericarp were determined by high-performance liquid chromatography. The following four types of fruit collected from three main varieties of olive trees were analysed: ‘Conservolea’ (green), ‘Halkidiki’ (green), ‘Conservolea’ (black) and ‘Calamon’ (black). α-Tp was found to be the predominant Tp in all types. The variety and stage of maturity influenced the Tp and Tt composition. β-Tp and α-Tt were found only in trace quantities in green olives. The same was true for α-Tp in all types and γ-Tp in ‘Conservolea’ (green). The calculated α-Tp equivalents (Tp and Tt compositions expressed as α-Tp according to their relative biological activities) were 21·6, 29·7, 36·8 and 39·4 μg g?1 pericarp or 138, 132, 189 and 196 μg g?1 lipid for ‘Conservolea’ (green), ‘Halkidiki’ (green), ‘Conservolea’ (black) and ‘Calamon’ (black), respectively. 相似文献