Poly (vinyl alcohol) (PVA) and its derivatives,the excellent water-soluble polymers,have attracted more and more attention,as they show the usability in many processes,as well as possess the promise of degradation in the presence of some specific microbials.In the present paper,the recent advances in the biodegradation of PVA and its derivatives,including the mechanism,influential factors,evaluation method and degradation environment etc,have been reviewed.Moreover,the latest development of PVA-based blendsPcomposites and their biodegradation is also introduced in the present article.

This paper reviews the progress of work on the K/T boundary and dinosaurs extinction hypotheses,and concludes that,on the one hand,many achievements were acquired,but on the other hand,most of work in the past focused on evidence of the catastrophic environment.Only very few scientists who noted that Co 、Cr 、Ni 、Mn、V etc,contents of which display obvious changes,also are bio-necessary trace elements,and others,such as REE、Pb、Sr etc,may be very important for normal physiological functions of biology have realized that there may be affinity between the change of contents of some elements across the K/T boundary and dinosaurs extinction,so more systemic research should be done.In the future,we should strengthen such studies as the effects of elements on biology and so on.

A computational fluid dynamic study,based on 2-D incompressible Navier-Stokes Equations,is presented to investigate the aerodynamics effects of time-changing wing flexible deformation in its flapping.Two elementary motions of the wing flapping,i.e. accelerated translation and non-uniform rotation,are studied,in which both the flexible and rigid wing cases are compared.It is revealed that in comparison of the rigid wing case,the wing deformation acceleration in the flexible wing case leads to the added inertial effect,which causes a lot of change in instantaneous aerodynamic performance of the wing.With regard to the time-averaged one,the flexibility effect is much less.

The interferometric solar image reconstruction is the last and the most important method to get the highresolution image.The Skilling-Bryan maximum entropy method featured in convergence rate is one of the predominant methods in astronomy image proceeding.The proposed method innovated in search directions of SB combines the speed with exactness harmoniously as a result of the error adjustment.Finally the simulations were conducted with both methods of interferometric solar image reconstruction in national astronomical observatories.Results showed the superiority of the improved method in resolution and counterbalance in computing time.Its stability was also testified with various examples.

This paper introduces the development of RS232 communication driver under EPICS based on Linux platform.The work is based on the control system of BEPCII experimental electron gun.OMRON CQM1 PLC is taken as the example device.Its EPICS driver is analyzed in detail,including the driver's hierarchical structure and particular implementation codes.The plan of developing EPICS device support programs of other devices based on this universal serial port communicat ion driver is in progress.

α-linolenic acid and α-linoleate ethylester were sampled in glass bottles charged with air and nitrogen and were irradiated with ⁶⁰Co at different dose levels.Peroxide values of the samples were determined every two days.The results showed that the irradiat ion dose and t ime have great effects on the peroxide value of the linolenic acid.Relationships between the peroxide value and reaction mechanism under the γ-irradiation were discussed.

Inhibitory activity and character of black tea extract and theaflavins are measured through inhibition kinetics.Based on the kinetics data,both of them are proved to be effective inhibitors of β-ketoacyl reductase of type I fatty acid synthase (KR),which exists in animals and β-ketoacyl reductase of type II fatty acid synthase (FabG),which exists in bacteria.The two inhibitors exhibit potent reversible and irreversible inhibitory activity on KR and FabG and are competitive inhibitors against NADPH,which is one of substrates of KR and FabG.The presence of NADPH clearly prevents the inactivation of KR and FabG by those two inhibitors.This shows that the inhibitors might act on NADPH binding site of KR and FabG.The consistent inhibitory character of two inhibitors suggests that these two β-ketoacyl reductases with different evaluation degrees possess similar active sites.The homology analysis of amino acid sequence shows that there exists one highly homologous region which may be responsible for the formation of active site located in KR and FabG.Therefore,the conformation of the active site in KR can be understood through the study of FabG.These two inhibitors are promising for practical application because of their potent inhibitory activity and rich sources.

LSM is the access control framework for Linux system.In the ANSHENG secure operating system V4.0,a secure auditing system based on the extended Linux Security Modules was introduced.Compared with the secure auditing system of ANSHENG secure operating system V2.0,the LSM based auditing system has a better performance.Last,the auditing system developed a method to detect covered channels in our ANSHENG secure operating system V4.0.

By analyzing the precipitation and largescale circumfluence during the period of Meiyu in 2003,the moist potential vorticity (MPV),including the mass forcing,is used to suggest that the intensive rainfall in torrential rain system can cause anomaly of the MPV.The data diagnoses manifest that the anomaly of the MPV and the precipitation have better accordance during the period of heavyMeiyu over Changjiang river basin and Huanghe river basin in 2003.We can forecast the possible distribution and movement direction of the torrential rain system according to the impermeability of the MPV.The anomaly induced by both heat and mass forcings in the torrential rain system will be a good dynamical tracer for tracking the torrential rain region.

Based on the land price system and land price special distribution rules,concerning shortcomings of current land price thematic maps,the urban land price equiprice line map and the method of drawing an urban land equiprice line map were introduced.Based on the investigation of Hohhot's land price,the urban land equiprice line maps of Hohhot commercial,residential and industrial lands,were drawn with satisfactory results.Finally,some problems are raised over drawing the urban land equiprice line map.

Five classification methods which are MLC (Maximum Likelihood Classifier),Parzen window,CART decision tree,BP neural network and Fuzzy ARTMAP neural network are selected to map the land cover of Huabei Area in China using MODIS 250m data.The results show that Parzen window performs best in the five classifiers.And CART and BP have satisfactory accuracy whereas Fuzzy ARTMAP has unexpected bad accuracy in comparison with MLC.CART decision tree has better flexibility and robustness.However,it pursues high accuracy at the cost of the sample size.BP neural network has high accuracy but requires high-quality samples and it is hard to define its net structure parameters.The results also show the classification accuracy difference caused by the size of training samples on MLC,Parzen window and Fuzzy ARTMAP,CART and BP are below 5%,5%～10% and above 10%,respectively.

Convection features in a thin liquid layerwith heating sources is studied in the present paper.Pimputakar and Ostrach gave the thickness equation and flow field of the liquid layer,in the case of a single heating source.This paper examines the variety of the flow image in a thin liquid layer with multiple heating sources,depending on the parameters,especially the distance of the heating sources.The bifurcation phenomenon in the convection is discussed in detail.

This experiment simulated the sediment resuspension caused by shaking through variable speed reciprocal shaker (HY-4) under the room temperature,and studied the change of nitrogen concentration.In the experiment,the concentration of NH₄⁺-N in water was found to have a negative relation with the increasing ratios between the mass of sediment and the volume of seawater.About 6h later,the concentration in water with shaking rate of 60rPmin decreased to the lowest of the three rates.The concentration in water with shaking rate of 120rPmin increased to the highest.When the shaking velocity was low,the concentration of NH₄⁺-N in the sea water had a positive relation with the concentration of suspended particulate materials.When the shaking velocity was high,the concentration of NH₄⁺-N in the sea water had a negative relation with the concentration of suspended particulate materials.Itps mainly because that when the concentration of the suspended particulate materials is lower,the release is dominated,so the concentration of NH₄⁺-N had a positive relation with the concentration of suspended particulate materials.When the concentration of the suspended particulate is higher,the absorption is dominated,so the concentration of NH₄⁺-N has a negative relation with the concentration of suspended particulate materials.In the course of the resuspension,the fine grain sediment in the chosen sea water had the most contribution to NH₄⁺-N of the sea water,with the medium and coarse grain sediment as the second and third contributors.The concentration of NO₃^--N in water had a negative relation with mixture ratios and shaking velocities.The coarse sediment had a similar trend with the fine sediment.The medium grain sediment of the chosen sea area had more contribution to sea water than the coarse and fine sediment.At the beginning of each experiment,the concentration of NH₄⁺-N was high.It showed that the NH₄⁺-N in the sediment had a large release at the beginning.It is because that in the process of freeze-dried,NH₄⁺-N in pore water was adsorbed on the sediment surface,and the force of combination was delicacy.Nitrogen has different forms in sediments,which represent different geochemical characters and has different effects in the cycle in the sediments.So itps necessary to study the effect of resuspension on the concentration of different forms nitrogen in the sediments.In this experiment,KCl 、HAc-NaAc 、NaOH were separately used to extract sequentially ion-exchange form,carbonate form,and their concentrations were measured.NO₃^--N、NH₄⁺-N mainly came from ion-exchange form,carbonate form nitrogen,and the contribution of iron-manganese form nitrogen was less.

Two MACs which are based on tweakable block ciphers are constructed:TXOR and PMAC.Then their corresponding stateful,randonmized,and determined algorithms are studied respectively and the concrete security bounds are given.

An improved identity-based encryption (RS-PKC) is proposed to solve the problems of key escorw and revocation about ID-Based encryption.The scheme has adaptively chosen ciphertext security in the random oracle model.The construction of RS-PKC is presented and the security can be reducted to the computational Bilinear Diffie-Hellman assumption.

The temperature decline of production wells is a potential problem induced by reinjection.At Laugaland,in order to assess and predict the temperature changes result ing from reinjection,a tracer test was carried out as an effective tool for quantitat ively studying the hydraulic connection between production and injection wells.The analysis of the tracer test data indicates that the connection between the injection well GN-1 and production well LWN-4 is fairly direct.Based on the tracer test,the reinject ion-induced temperature decline of the production well LWN-4 was predicted under different hypotheses and production-reinjection scenarios.The calculated temperature decline is,however,a few degrees greater than the actual cooling observed.The discrepancy is mainly attributed to a drastic change in flow conditions because of reduced production since reinjection started.In addition,the major earthquakes in 2000 may also have influenced the flow-pattern in the reservoir at Laugaland.

Changes of microenvironment and micellar properties of poly (ethylene oxide)2poly (propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) block copolymers were investigated on the molecular level.The Fourier transform infrared (FTIR) results showed that quantitative information of micelle structure of PEO-PPO-PEO block copolymer based on the effect of temperature,solvent and composition.Effects of alkali halide salts and aliphatic alcohol upon the thermally induced controlled aggregation of PEO-PPO-PEO block copolymers have been examined by fluorescence spectrum.There is a competition between ether oxygen atoms of the polymer and the ions for available water of hydration,which indirectly weakens the interaction of polymer with water and results in a decrease in the solubility of polymer in water.The extraction capacity of hydrogel is enhanced dramatically by encapsulating PEO-PPO-PEO block copolymers.The alginate hydrogel can be reused through a process of drying,reverse-extraction and regeneration.

Template-synthesis is a simple but effective method to construct hierarchical structures on meso-scale.This work involves the preparation of composite particles and their self-assembly,and the preparation of one-dimensional fibers and their self-assembly.The preparation of hollow particles with tunable cavity in the range of whole particle radius is emphasized.The particles have potential applications in many areas such as in catalysis,controlled delivery,artificial cells,light fillers,low dielectric constant materials and photonic crystals materials.