Release Model of Water-soluble Chitosan Nanoparticles for Protein Delivery

[Objective] The experiment aimed to explore release rule of water-soluble chitosan (WSC) in vitro. [Method]The bovine serum albumin(BSA) was taken as a model protein drug and some existing release models such as Kinetics model, Gompertz model, Weibull model, Higuchi model and Logistic model were used to fit the BSA release profile from WSC carriers. [Result] Except Higuchi model and Logistic model, other models could fit BSA release profile better. [Conclusion] Gompertz two-order kinetics model could fit the release of WSC nano-particles better and model parameters had practical physical meaning.

The stress release model and results from modelling features of some seismic regions in China

The stress release model is a stochastic point process model developed from the theory of elastic rebound. It can be used to analyse, simulate or predict the seismicity in a certain seismic region. This paper first gives a brief representation of the theory of the stress release model and the method of how to use it to analyse earthquake data, then this model is to fit the earthquake data in North China, Southwest China and Taiwan. The results show that the stress release model fits to the data better than the Poisson model. The different features of stress accumulation and release in these regions imply that the seismic activity is essentially different among these regions.

The principle of coupled stress release model and its application

oupled stress release model is proposed in the paper considering the interaction between different parts based on stress release model by VereJones, and is used to historical earthquake data from North China. The results by this model are compared with the results by original stress release model using AIC criterion. The results show that coupled stress release model is better than original model.

Tuning alginate-bentonite microcapsule size and structure for the regulated release of P.putida Rs-198

In this study, different sizes of microcapsules with alginate and bentonite as natural macromolecular materials were prepared to investigate the release property of Pseudomonas putida Rs-198. The characteristics of three microcapsules were evaluated by SEM, FTIR, TG-DSC, XRD and wall thickness. The sizes of three microcapsules(MA, MB, and MC) were 1270.50, 831.79 and 42.52 μm, respectively. First, the encapsulation efficiency of three MA, MB, and MC microcapsules were 82.20%, 90.41%, and 85.84%, respectively.Second, the contact angles of MA and MB samples were similar, while smaller microcapsules MC have higher contact angle(85.05°), indicating poor hydrophilia and decreasing the swelling degrees. Third,the release cumulant of Rs-198 and macromolecule BSA linear stage was fitted to self-established mathematic model. Results show that the microcapsule size had a considerably positive effect on release detail. The large microcapsule possessed strong leak-tightness for Rs-198 as a slow-release microbial agent. Furthermore, the porosity of microcapsules determined their swelling and release and may affect bacterial growth and survival. In conclusion, the Rs-198 microcapsule with different sizes will be pertinently selected based on the characteristics of agricultural production requirements.

Improved stress release model: Application to the study of earthquake prediction in Taiwan Region

Stress release model used to be applied to seismicity study of large historical earthquakes in a space of large scale. In this paper, we improve the stress release model, and discuss whether the stress release model is still applicable or not in the case of smaller spatio-temporal scale and weaker earthquakes. As an example of testing the model, we have analyzed the M greater than or equal 6 earthquakes in recent about 100 years. The result shows that the stress release model is still applicable. The earthquake conditional probability intensity in Taiwan Region is calculated with the improved stress release model. We see that accuracy of earthquake occurrence time predicted by the improved stress release model is higher than that by Poisson model in the test of retrospect earthquake prediction.

pH-sensitive KHA/CMC-Fe^(3+)@CS hydrogel loading and the drug release properties of riboflavin

To improve drug utilization,reduce the drug administration frequency,increase the release time,and reduce the drug side effects in the human body,we prepared(KHA/CMC-Fe^(3+))@CS hydrogel spheres using green and natural potassium humate(KHA),carboxymethyl cellulose(CMC),and chitosan(CS)as raw materials and Fe3+as a crosslinking agent,and loaded them with riboflavin for drug sustainedrelease study using the drop ball method.The tests with FTIR,SEM,TG,and X-ray diffractometer showed that the coordination among KHA,CMC,and Fe^(3+)formed a three-dimensional network structure,where cs was encapsulated on the surface of the hydrogel spheres via noncovalent bonding,resulting in good thermal stability.The stability,drug loading,swelling,and in vitro release of the(KHA/CMC-Fe^(3+))@CS hydrogel spheres were investigated.The results showed that the hydrogel spheres were significantly pH-sensitive,with 11.16 g/g higher swelling in an alkaline environment(pH=7.4)than that in an acidic environment(pH=1.2).The swelling and drug release process of the hydrogel spheres were analyzed using mathematical models,concluding that the hydrogel swelling follows Schott second-order swelling kinetics,and the drug release mechanism was Fickian delivery mode.

Seismicity research in the subregions of Chinese mainland using strain accumulating and releasing model based on G-R relation

According to the deficiency of the strain accumulating and releasing curves and the previous models, the strain-accumulating rate of the strain accumulating and releasing model has been deduced based on the G-R relation and the empirical formula between energy release and earthquake magnitude, where the strain-accumulating rate is relative independent of the strain-releasing rate. Five typical areas in Chinese mainland are selected on the basis of the hypothesis on active tectonic block, and small earthquakes from 1970 are imported to calculate the annual strain-accumulating rates considering the completeness of historical seismic data. Having introduced the strain-accumulating rates into the amended model, present strain phases are got. According to the present stages in their own cycles, the future earthquake tendency of each sub-region is discussed.

A micromechanical damage model for rocks and concretes under triaxial compression

Based on analysis of deformation in an infinite isotropic elastic matrix containing an embedded elliptic crack, subject to far field triaxial compressive stress, the energy release rate and a mixed fracture criterion are obtained by using an energy balance approach. The additional compliance tensor induced by a single closed elliptic microcrack in a representative volume element and its in-plane growth is derived. The additional compliance tensor induced by the kinked growth of the elliptic microcrack is also obtained. The effect of the microcracks, randomly distributed both in geometric characteristics and orientations, is analyzed with the Taylor＇s scheme by introducing an appropriate probability density function. A micromechanical damage model for rocks and concretes under triaxial compression is obtained and experimentally verified.

The estimation of yearly probability gain for seismic statistical model

Based on the calculation method of information gain in the stochastic process presented by Vere-Jones, the rela tion between information gain and probability gain is studied, which is very common in earthquake prediction, and the yearly probability gain for seismic statistical model is proposed. The method is applied to the non stationary Poisson model with whole-process exponential increase and stress release model. In addition, the prediction method of stress release model is obtained based on the inverse function simulation method of stochastic variable.

Experimental modeling of polymer latex spray coating for producing controlled-release urea

Spray coating of polymer latex onto fertilizer particles in a fiuidized bed for producing controlled-release urea is an environment friendly technology as it does not need any toxic organic solvent. Since the spray coating process in a fluidized bed occurs in the presence of particle collisions, the coating of the particles is random, intermittent and multiple, thus making it difficult to investigate the film formation process. In this paper, an experimental model apparatus was designed and used to investigate the effects of the key factors in the spray coating process. This apparatus reasonably simplified the complex process to avoid particle collisions and randomness in the coating. The intermittent coating in the fluidized bed was modeled by periodic coating and dewatering in the experimental apparatus. A large area film was obtained, and the film permeability was measured. The effects of atomizing gas flow rate, spray rate of latex, solid content of latex and gas temperature on film structure and film permeability were investigated. It was found that water transfer played a dominant role in the spray coating process.

Modeling iron release from cast iron pipes in an urban water distribution system caused by source water switch

Significant iron release from cast iron pipes in water distribution systems(WDSs),which usually occurs during the source water switch period,is a great concern of water utilities because of the potential occurrence of"red water"and customer complaints.This study developed a new method which combined in-situ water stagnation experiments with mathematical models and numerical simulations to predict the iron release caused by source water switch.In-situ water stagnation experiments were conducted to determine the total iron accumulation in nine cast iron pipes in-service in Beijing when switching the local water to tre ated Danjiangkou Reservior water.Results showe d that the difference in the concentration increment of total iron in 24 hr(ΔCITI,24),i.e.short-term iron release,caused by source water switch was mainly dependent on the difference in the key quality parameters(pH,hardness,nitrate,Larson Ratio and dissolved oxygen(DO))between the two source waters.The iron release rate(RFe)after switch,i.e.long-term iron release,was closely related to the pipe properties as well as the DO and total residual chlorine(TRC)concentrations.Mathematical models ofΔCITI,24 and RFe were developed to quantitatively reveal the relationship between iron release and the key quality parameters.The RFe model could successfully combine with EPANET-MSX,a numerical simulator of water quality for WDSs to extend the iron release modeling from pipe level to network level.The new method is applicable to predicting iron release during source water switch,thus facilitating water utilities to take preventive actions to avoid"red water".

A Systematic Study of Disaster Risk in Brunei Darussalam and Options for Vulnerability-Based Disaster Risk Reduction

This systematic study of disaster risk and disaster management efforts in Brunei Darussalam uncovers the reasons why floods and landslides in particular continue to inflict significant social,economic,and psychological toll.Vulnerability to the impacts of hydro-meteorological hazards continue to rise despite international awareness and improved disaster governance and information,and regardless of the vast financial and material resources spent on structural and nonstructural measures for disaster relief and community awareness.Our premise is that,a poor diagnosis of the disaster risk issue is at the root of the disaster risk dilemma in Brunei Darussalam.We conducted our vulnerability-centered disaster risk assessment based largely on the Pressure and Release(PAR) Model proposed by Wisner et al.Our research results reveal that:(1)Hazard-risk in Brunei is high due to the impact of global climate change,the country's local geography,and Brunei's relative location in the Asia–Pacific Region.Limited reporting of localized disasters to international databases however fuels the misperception of low disaster risk in Brunei;(2) High community vulnerability and disaster risk is due to limited knowledge,awareness,and motivation among the general population,which prevents effective mitigation and adaptation to low magnitude but recurrent hazardous events;and(3) Partial incorporation of disasterrisk reduction into governance structures and development plans contributes to heightened disaster risks.Integrated frameworks are proposed that can minimize social vulnerability,reduce disaster risk,and enhance community resilience and adaptive capacity as part of a strengthened governance mechanism.Coupled with improvements in preparedness,response,recovery,and reconstruction promoted by the National Disaster Management Centre(NDMC),vulnerability and disaster risk can be minimized,and a more inclusive and sustainable growth can be generated.

Application and discussion of statistical seismology in probabilistic seismic hazard assessment studies

Earthquakes are one of the natural disasters that pose a major threat to human lives and property. Earthquake prediction propels the construction and development of modern seismology;however, current deterministic earthquake prediction is limited by numerous difficulties. Identifying the temporal and spatial statistical characteristics of earthquake occurrences and constructing earthquake risk statistical prediction models have become significant;particularly for evaluating earthquake risks and addressing seismic planning requirements such as the design of cities and lifeline projects based on the obtained insight. Since the 21 st century, the occurrence of a series of strong earthquakes represented by the Wenchuan M8 earthquake in 2008 in certain low-risk prediction areas has caused seismologists to reflect on traditional seismic hazard assessment globally. This article briefly reviews the development of statistical seismology, emphatically analyzes the research results and existing problems of statistical seismology in seismic hazard assessment, and discusses the direction of its development. The analysis shows that the seismic hazard assessment based on modern earthquake catalogues in most regions should be effective. Particularly, the application of seismic hazard assessment based on ETAS(epidemic type aftershock sequence)should be the easiest and most effective method for the compilation of seismic hazard maps in large urban agglomeration areas and low seismic hazard areas with thick sedimentary zones.

Nontarget screening using passive air and water sampling with a level Ⅱ fugacity model to identify unregulated environmental contaminants

It is thought that there are many unregulated anthropogenic chemicals in the environment.For risk assessment of chemicals, it is essential to estimate the predicted environmental concentrations. As an effort of identifying residual organic contaminants in air and water in Korea, nontarget screening using two-dimensional gas chromatography time-of-flight mass spectrometry（GC × GC-TOFMS） was conducted at 10 sites using polyurethane foam passive air sampler and at 6 sites using polydimethyl siloxane（PDMS） passive water sampler in three different seasons in 2014. More than 600 chemical peaks were identified satisfying the identification criteria in air and water samples, respectively, providing a list for further investigation. Chemical substances with reported national emission rates in2014（n = 149） were also screened for potential existence in the environment using a level Ⅱ fugacity model. Most of chemical substances classified as not detectable were not identified with detection frequency greater than 20% by nontarget screening, indicating that a simple equilibrium model has a strong potential to be used to exclude chemicals that are not likely to remain in the environment after emissions from targeted monitoring.

Konjac glucomannan and xanthan gum as compression coat for colonic drug delivery:experimental and theoretical evaluations

Compression coated tablets for oral colon specific delivery systems were developed with a mixture polysaccharide of konjac glucomannan(KGM)and xanthan gum(XG)as the compression coat.Diffusion of cimetidine from compression coated tablets was investigated by release experiment in Vitro.0.22U/mLβ-mannanase was applied in the mimic colon solution.The structure of the mixture polysaccharide was studied by an atomic force microscope(AFM).The experimental results indicate that a KGM70 tablet with a 0.4 g coat is of good design,due to a less than 5%drug loss in the mimic upper gastrointestinal solution by the synergistic interaction between XG and KGM,and due to about 50%cumulative release in the mimic colon solution by degradation after 24 hours.The release mechanism and model are discussed based on different periods of drug release including the delay of the drug,the constant release without an enzyme and the delay of degradation.Under hydrolysis byβ-mannanase,drug release from the tablet with KGM coat shows an exponential increase,while that from the dosage with the mixture polysaccharide coat is an approximately zero-order process in which the constant release rate relates to the release velocity of a non-degraded system,the content of KGM within the coat and the average molecular weight ratio of KGM to XG.It was found that XG was the framework of the polysaccharide mixtures by AFM,which is similar to the analysis results from experiments on drug release.