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71.
72.
Glucosamine sulfate was prepared from glucosamine hydrochloride that was produced by acidic hydrolysis of chitin by ion-exchange method. Optical rotation and elemental analysis characterized the degree of its purity. In addition, the antioxidant potency of chitosan derivative-glucosamine sulfate was investigated in various established in vitro systems, such as superoxide (O-2)/hydroxyl (·OH) radicals scavenging, reducing power, iron ion chelating. The following results are obtained: first, glucosamine sulfa... 相似文献
73.
Estimation of loads derived from shipping water events in naval and offshore structures is of importance to improve their structural design or to predict changes in their dynamics. For the case of vertical loads on deck of a fixed structure, it is possible to estimate analytically their evolution in time by considering the distribution of shipping water elevations. However, the classical approach to estimate this distribution (i.e., dam-break method) tends to overestimate the amount of water on deck and does not follow the generated decay trends observed experimentally. In the present work, the time evolution of the vertical loads due to shipping water events was studied analytically and experimentally. The validation of the use of a convolution model to estimate the time evolution of vertical loads is presented, aiming to improve the results obtained with classical approaches. A systematic experimental study has been conducted using the wet dam-break method to generate isolated shipping water events, measuring the slow-varying vertical loads on a rectangular fixed structure. A force balance and a high-speed camera have been used at the same sampling rate to monitor the vertical loads and the shipping water evolution on the deck. Results demonstrated that the use of the convolution model improved the representation of the time series of loads compared with the traditional dam-break approach. With this new method, it was possible to capture the peaks and the decay tendencies observed in the experimental data in an approximated way. 相似文献
74.
Gi-Hoon Hong Young-Ill Kim Mark Baskaran Suk-Hyun Kim Chang-Soo Chung 《Journal of Oceanography》2008,64(2):277-292
The distribution of the natural radionuclide 210Po in the water column along a horizontal transect of the continental shelf, slope and deep basin regions of the East Sea
(Sea of Japan), a marginal sea of the Northwest Pacific Ocean, was investigated, and its behavior is described here. The settling
fluxes of particulate 210Po in the deep basin along with 210Pb, 234Th and biogenic matter were also determined. 210Po inventories in the water column were observed to decrease from winter to summer in all stations, probably due to increased
influx of 210Po-poor Kuroshio Water of the Northwest Pacific Ocean during summer. Vertical profiles of dissolved and particulate 210Po along with the settling fluxes of particulate 210Po in the deep basin station have enabled us to evaluate temporal variations and residence times of 210Po. In the slope and basin, activities of dissolved 210Po generally decreased from the surface to the bottom water, with maximum activity just below the subsurface chlorophyll a maximum at 50–75 m depth in spring and summer. These subsurface peaks of dissolved 210Po activity were attributed to the release of 210Po from the decomposition of 210Po-laden biogenic particulate organic matter. In the deep basin, despite the decrease in total mass flux, the sinking flux
of particulate 210Po was higher in the deeper trap (2000 m) than in the shallower one (1000 m), probably due to scavenging of dissolved 210Po from the water column during particle descent and/or break-down of 210Po-depleted particulate matter between 1,000 m and 2,000 m depths. In general, the ratios of the particulate phase to the
dissolved phase of 210Po (Kd) increased with depth in the slope and basin stations. 210Po removal from the water column appears to depend on the primary productivity in the upper waters. There is an inverse relationship
between Kd and suspended particulate matter (SPM) concentration in the water column. From the 210Po activity/chlorophyll a concentration ratios, it appears that sinking particles arriving at 1000 m depth were similar to those in the surface waters. 相似文献
75.
利用NCEP 1°×1°的6 h再分析资料和常规气象观测资料,对2012年7月21日发生在北京地区的一次大暴雨天气过程进行非地转湿Q矢量(Q*)和湿位涡等物理量诊断分析,研究暴雨期间Q*散度、锋生函数和湿位涡的时空分布特征,以及它们与强降水之间的关系。结果表明,Q*在850 hPa高度层上对暴雨表现出良好的诊断特性,冷、暖气流的汇聚加强了锋生作用,强锋生中心出现几小时后即出现暴雨。暴雨区位于Q*辐合区内,Q*散度对6 h后暴雨的落区有很好的指示意义。暴雨落区基本位于MPV1正、负值交界处的等值线密集带上以及MPV2负值区内。暴雨区上空,从近地面到对流层低层的对流性不稳定与条件性对称不稳定同时存在,两者共同作用,这很可能是此次暴雨的中尺度对流系统发生发展的重要条件之一。 相似文献
76.
Panagiotis T. Nastos Dimitrios Alexakis Helen A. Kanellopoulou Akindinos E. Kelepertsis 《Journal of Atmospheric Chemistry》2007,58(2):167-179
The goal of this study is to determine the chemical composition of rain, in the wider region of Athens, Greece for the time
period 1st September 2001 to 31st August 2002. Two model automatic rain samplers were installed in the Meteorological Station
of Laboratory of Climatology (latitude: 37° 58′ N, longitude: 23° 47′ E) inside the Athens University Campus and in a site
at Heraklio Attica, a northern suburb of Athens (latitude: 38° 03′ N, longitude: 23° 45′ E). The concentrations (μeq l−1) of the major cations (H+, Na+, K+, Ca2+ and Mg2+) and anions (Cl−, , και ), as well as pH and conductivity of rain in 39 total samples were determined. The figures of pH range from 6.4 to 8.4 and
conductivity from 8 to 207 μS cm−1. The analysis showed that Ca2+ ions are abundant within all examined samples, while and present the highest concentrations from the anions. In order to find out the origin of the air masses, the air mass back
trajectories were calculated. Five sectors of the origin of air masses were revealed: the North, the South, the Local, the
West and the East sector. Multivariate methods included Factor Analysis and Discriminant Analysis were applied to the examined
ion concentrations and three main factors were extracted, which discriminated the ions according to their origin. The first
group of ions is interpreted as the result of the anthropogenic activity, the second group represents the acidity–alkalinity
independently of their source and the third one the marine influence. 相似文献
77.
气候变化导致全球热浪灾害事件频发。湿球黑球温度综合考虑了温度和湿度协同作用,相较于单独的温度指标更能表征热浪对人类社会的影响。基于该指数定义热浪,利用CMIP5多模式温度和相对湿度模拟数据以及SSP3人口数据,量化并分析了未来全球及区域尺度热浪的人口暴露度变化以及造成暴露度变化的各因素的贡献率。结果表明:(1)过去(1986—2005年)暴露度的分布主要受人口分布的影响,印度次大陆以及中国东部、东南沿海地区是暴露度高值区,未来(2081—2100年)热带地区暴露度的增加尤为明显;(2)全球区域间暴露度变化差异显著,未来南亚地区平均暴露度的增幅最大,接近3×104万人·d,而澳大利亚北部、亚洲北部、加拿大地区平均暴露度的增幅不足100万人·d;(3)气候和人口因素共同作用是造成绝大多数热带地区暴露度变化的最主要原因,而对于中高纬度地区来说,气候要素的贡献率最大;(4)气候和人口因素共同作用对全球暴露度变化的贡献占据主导地位。 相似文献
78.
INTRODUCTIONIthaslongbeenknownthatfatsundergoslowautoxidationduringstorage;andthatantioxidantswhichscavengefreeradicalsexistingduringtheinitialstageorearlypropagationstageoflipidoxida tioncanpreventrancidity ,soantioxidantsareoftenusedasfoodadditivescapableofdelaying ,re tardingorpreventingtherancidityinlipidsduetooxidation .Inthissense ,anidealantioxidantshouldhavethefollowingcharacteristics:safeinuse ,noodor,flavororcolor,effectiveatlowcon centration ,easytoincorporateandavailableatlowco… 相似文献
79.
Ozone chemistry processes are analyzed during a cumulus cloud process with the model(1CCCM)described in Part Ⅰ.The simulation results show that entire cumulus cloud process can bewell described with the development of vertical velocities and liquid water content which are the twomost outstanding features of cumulus clouds.Ozone chemistry is strongly influenced by cumulusclouds.NO_x can be transported upwards above 4 km in the first 20 minutes of the convection eventand form a relative higher concentration area which enhances the production of ozone.Two areas ap-pear during the convection event:area of net ozone production and area of net ozone depletion.Thearea of ozone depletion coincides with the area of liquid water within cloud.Results show that theaqueous phase(cloud water and rainwater)can alter gas ozone level through two ways:one is scav-enging free radicals(HO_2)from the gas phase and thereby inhibiting the reactions of transformationto NO_2 from NO,which results in reduction of the gas source of ozone;the other is aqueous phasechemical reactions which consume ozone in the aqueous phase.Calculations reveal that the reaction O_3+OH→HO_2 is the main pathway of ozone depletion in gas phase during the process of cumulusclouds. 相似文献
80.