Gut contents of silver carp, Hypophthalmichthys molitrix, and the disruption of a centric diatom, Cyclotella, on passage through the esophagus and intestine

The digestibility of algae by stomachless filter-feeding fish has been debated for decades. Results from gut contents and digestive enzyme analysis suggest poor utilization, while the measurement of food assimilation using radiolabeled isotope techniques indicate reasonable assimilation efficiency. Phytoplankton in the gut contents of the planktivorous filter-feeding silver carp were studied during March-May. The fish were cultured in a large net cage in a shallow, hypertrophic subtropical Chinese lake, Lake Donghu. In terms of biomass, the dominant phytoplankton in the fore-gut contents were Cyclotella (average 77.8%, range 69.7-93.5%) and Cryptomonas (average 9.57%, range 0-20.4%). The Ivlev's electivity index E of silver carp was much higher for Cyclotella (1.54) than for Cryptomonas (0.56). The majority of the phytoplankton found in the intestines of silver carp were 8-20 mu m, but they were also able to collect particles as small as 4.5-10 mu m, smaller than their filtering net meshes, suggesting that the secretion of mucus may play an important role in collecting such small particles. We conclude that disruption of cell walls is principally by the pharyngeal teeth, explaining previous contradictory conclusions. (C) 1999 Elsevier Science B.V. All rights reserved.

Structure and magnetic property of (Ga,Cr)As films with different Cr contents

We report variations in structure and magnetic property of (Ga,Cr) As films with increasing Cr content x. Due to phase segregation, a tendency towards inhomogeneous distribution with increasing x is confirmed. Barkhausen-like magnetization and large remanent magnetic moment were also clearly observed in the samples with x<5.3%. However, spin-glass-like behaviors were observed in both dc and ac magnetic measurements, which might originate from the competition between magnetic nucleation and frustration of long ferromagnetic order in this inhomogeneous system. All the samples exhibit characteristics of variable-range hopping conductivity at temperature below 150 K. Typical magnetic circular dichroism structure was observed in the sample with x=7.9%.

Electron transport properties of MM-HEMT with varied channel indium contents

Transport properties of two-dimensional electron gas (2DEG) are crucial to metamorphic high-electron-mobility transistors (MM-HEMT). We have investigated the variations of subband electron mobility and concentration versus temperature from Shubnikov-de Hass oscillations., and variable temperature Hall measurements. The results indicate that the electrical performance is the best when the In content is 0.65 in the channel for MM-HEMT. When the In content exceeds 0.65, a large lattice mismatch will cause dislocations and result in the decrease of mobility and the fall of performance in materials and devices.

Mineral and chemical composition and some trace element contents in coals and coal ashes from Huaibei coal field, China

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聚乙二醇模拟干旱对甜高粱幼苗丙二醛、脯氨酸含量的影响；Effects of Drought Stress Simulated by PEG on Malonaldehyde and Proline Contents of Sweet Sorghum Seedlings

以甜高粱品种KFJT-CK及经过碳离子辐照选育出的早熟突变株KFJT-1为材料,用浓度分别为5%,10%和15%的聚乙二醇(PEG)6000模拟干旱对其进行胁迫处理,测定丙二醛(MDA)及脯氨酸(Pro)的含量。随着胁迫时间的延长和胁迫程度的增加,MDA含量持续升高;Pro含量在5%和10%PEG胁迫下持续升高,在15%PEG胁迫下先升高后降低。表明碳离子辐照可能使甜高粱膜脂过氧化特性发生改变,影响Pro的表达。为进一步研究碳离子束辐照对甜高粱的耐旱生理提供一定的基础,并为下一步的育种工作提供有用的参考。

A study of NiZnCu-ferrite/SiO2 nanocomposites with different ferrite contents synthesized by sol-gel method

Ni0.65Zn0.35Cu0.1Fe1.9O4/SiO2 nanocomposites with different weight percentages of NiZnCu-ferrite dispersed in silica matrix were successfully fabricated by the sol-gel method using tetraethylorthosilicate (TEOS) as a precursor of silica, and metal nitrates as precursors of NiZnCu ferrite. The thermal decomposition process of the dried gel was studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The obtained Ni0.65Zn0.35Cu0.1Fe1.9O4/SiO2 nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), scanning electron microscope (SEM), Mossbauer spectroscopy and vibrating sample magnetometry (VSM). The formation of stoichiometric NiZnCu-ferrite dispersed in silica matrix is confirmed when the weight percentage of ferrite is not more than 30%. Samples with higher ferrite content have small amount of alpha-Fe2O3. The transition from the paramagnetic to the ferromagnetic state is observed as the ferrite content increases from 20 to 90wt%.

Major, minor and trace-elemental contents analysis in northeast soybeans by ICP-AES

Major, minor and trace elemental contents in northeast China soybeans were determined by using inductively, coupled plasma atomic emission spectrometry (ICP-AES). Three different sample digestion methods including two wet digestions, HNO3-HClO4 and HNO3-H2SO4 and a dry ash method were compared. Owing to the high oil content in soybeans, long time is needed and access acid should be added, with mixed acid digestion methods, which may result in higher sample blank. Therefore, the dry ask method would be more proper for the pre-treatment of soybean samples. Potassium and phosphorus are major elements in soybeans, so the effect of potassium and phosphorus on the other elements was investigated. Results showed that the potassium and phosphorus did not affect the determination. of other trace elements. There are not significant differences in trace elemental contents for the eleven northeast China soybeans.