Average Release Rate Research Articles

Preparation and characterization of polybenzoxazine foam with flame retardancy

Polybenzoxazine foam was successfully prepared using phenolic resin as modifier and catalyst. The structural properties, curing behavior, thermal stability, cellular structure, mechanical properties and flame retardancy properties of the foam were characterized by Fourier transform infrared (FTIR) spectrometry, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), compression tests, limiting oxygen index (LOI) tests and cone calorimetry test, respectively. The experimental results indicated that both phenolic resin and imidazole catalyzed the curing process of benzoxazine and that the curing temperature decreased obviously. The polybenzoxazine foam loaded with different contents of phenolic resin showed an isotropic cellular structure with relative densities ranging from 116 to 185 kg/m3, and the compressive strength and compressive modulus could reach as high as 0.512 and 7.21 MPa, respectively. In addition, the cone calorimeter test results showed that the average heat release rate (av‐HRR), total heat release (THR) and total smoke production (TSP) of PBZ‐7.5 reduced, which indicated that the polybenzoxazine has satisfactory flame retardancy with the addition of phenolic resin.

Municipal solid waste incineration fly ash exposed to carbonation and acid rain corrosion scenarios: Release behavior, environmental risk, and dissolution mechanism of toxic metals

This study investigated the leaching behavior, environmental risk, and dissolution mechanism of toxic metals (TMs) in solidified/stabilized municipal solid waste incineration fly ash (MSWI FA) exposed to alternative “carbonation + acid rain corrosion” disposal scenarios. The content of TMs (mg/kg) showed a trend of Zn (12,187.10 ± 168.60) > Pb (3374.43 ± 66.12) > Cu (1055.14 ± 32.52) > Cr (127.95 ± 8.12) > Cd (119.05 ± 6.26) > Ni (49.50 ± 3.20). Initial leaching of CO2-saturated water (CSW) and replacement of simulated acid rain (SAR) increased the environmental risk of leached TMs. The results of “average release rate” (mg/(kg·d)) of TMs indicated that Zn (0.8307)/Cu (0.0278)/Cd (0.0109) and Cu (0.0581)/Cr (0.001176)/Ni (0.004339) in phosphoric acid stabilized FA and Pb (0.0753)/Cr (0.001921)/Ni (0.00111) and Pb (0.0656)/Zn (1.0560)/Cd (0.0050) in Portland cement solidified FA were the key “problem TMs” during carbonation and acid rain corrosion, respectively. CSW leaching increased the independent environmental risk of most TMs in residual FA (especially Zn/Cd) due to the increased carbonate-bound fraction. Compared with independent carbonation, alternative “carbonation + acid rain corrosion” contributed to a higher comprehensive environmental risk for TMs in residual FA. CSW leaching system was an indirect carbonation based on CO2-water and FA matrix, in which “nucleation and dissolution” of carbonates and “immobilization and dissolution” of TMs coexisted. The dissolution mechanism of TMs was mainly controlled by reaction equilibrium of nucleation and dissolution of carbonates containing TMs. Dissolution and nucleation were the dominant mechanism in the early and later periods of CSW leaching, respectively. Carbonate layer dissolution, H+ corrosion/displacement, and counter-ion effect (SO42− > NO3− > Cl−) were the main mechanisms affecting TM dissolution during SAR leaching.

Effect of type of organic modifier on the clay layered-based nanocomposites flammability and toxic gases emission

Well dispersed polyethylene (PE) nanocomposites were developed. Montmorillonite (MMT) as aluminosilicate clay layers was modified using organic silanes of different side chains. The MMT was grafted using 3-(trimethoxysilyl)propylamine, N-[3-(trimethoxysilyl)propyl]ethylenediamine, and trimethoxyvinylsilane. The modification process of MMT using organic different silanes was elucidated using microscopic, thermogravimetric, spectroscopic, and X-ray diffraction tools. Then, the developed organoclays were dispersed uniformly in PE matrix producing well exfoliated and dispersed polymer nanocomposites. The mass loadings of dispersed organoclay were varied and the impact of organic silane structure was studied. Thermal stability and flammability properties of the developed polymer nanocomposites were evaluated. The peak heat release rate and average heat release rate were reduced by 48% and 61%, respectively compared to virgin polymer. Also, the average mass loss rate was significantly reduced by 50%. This is in addition to reduction in emission of carbon monoxide (CO) and carbon dioxide (CO2) by 45% and 56%, respectively. The effect of side chain of organosilane on the performance of modified clay layers was studied. The toxicity of gases evolved during combustion process of PE and their polymer nanocomposites were evaluated using Fourier transform infrared connected to cone calorimeter. Additionally, the influence of organic silane on the pyrolysis and toxic gases emission was further studied.

Releasing control of nitrogen and phosphorus from contaminated sediment covered with aluminum-zirconium modified zeolite

In this paper, aluminum and zirconium based metal compounds were used to modify natural zeolite to produce Al-Zr modified zeolite (AZMZ). The adsorption performance, micro morphology and releasing control effect of AZMZ on nitrogen and phosphorus from sediment were tested. Test results show that the adsorption performance of natural zeolites on ammonia nitrogen and phosphate in water was significantly improved after Al-Zr modification. The adsorption model is chemical adsorption, and follows the quasi second-order kinetic equation and Langmuir model. The saturated adsorption capacity of 0.5 to 1.0 mm size of AZMZ for ammonia nitrogen and phosphate in water is 8.40 mg/g and 3.10 mg/g respectively. AZMZ has the potential to be used as in-situ covering materials to control the release of nitrogen and phosphorus from sediment. The average release rate was resduced by the increasing thickness of AZMZ. When the covering thickness of AZMZ reaches 0.5 cm, the releasing rate of nitrogen and phosphorus in the sediment can be effectively controlled. When the AZMZ thickness reaches 1.0 cm, the releasing reduction rate of nitrogen and phosphorus in the sediment are 89.1% and 75.3% respectively.

Influence of intake air temperature control on characteristics of a Homogeneous Charge Compression Ignition engine for hydrogen-enriched kerosene-dimethyl ether usage

In this study, the high-speed of 2000 rpm and low-speed of 1000 rpm behaviors on the HCCI test engine at full load were examined experimentally by controlling the intake air temperature. The tests were carried out at 0.90 equivalence ratio for hydrogen-enriched kerosene-dimethyl ether mixture. In order to expand the usage of HCCI engines in daily life, their problems encountered at high loads and high speeds need to be solved. The main reason of these problems is the control of the start of combustion since there is no external combustion system in HCCI engines.The experimental results show that the intake air temperature directly affects engine performance and emissions. The intake air temperature control was led to shorter flame development time and better combustion stability. The in-cylinder pressure at 1000 rpm for 373 K is overall 6.82% and 4.07% higher than the 273 K and 298 K. The average heat release rate curve trends at 1000 rpm are overall 45.68% higher than 2000 rpm. The brake specific fuel consumption for 2000 rpm is about 5.29% higher than 1000 rpm. The differences between the two NOx trends are 35.4% maximum and 11.03% minimum for 1000 rpm and 2000 rpm. At high engine speed, the HC formation drops linearly from 488 ppm to 339 ppm with increasing air temperature. Also, the soot formation decreased with a slope of 1.58 times higher than 1000 rpm. Overall, the increase in intake air temperature at the tests positively affected in-cylinder pressure, CO, HC and soot.

Ovulation inhibition with a new vaginal ring containing trimegestone

ObjectivesThe primary objective was to determine the lowest trimegestone (TMG) dose, administered via a vaginal ring, that effectively inhibited ovulation. Study designSingle-centre, open-label, single-dose, parallel-group clinical trial with adaptive design. Eighty healthy female volunteers with proven ovulatory cycles were allocated to treatment with a vaginal ring during 28 days, with an average daily release rate of either 46 µg, 94 µg, 147 µg, or 184 µg TMG (20 women/group). Ultrasound measurements of follicular growth and endometrial thickness, and blood sampling for follicle-stimulating hormone, luteinizing hormone, estradiol and progesterone determinations were performed every 3rd (±1) day from treatment day 4 (±1) until day 28 (±1), and in a follow-up phase after ring removal, until study day 39 (±1). Trimegestone concentrations were measured at each visit in the treatment phase. ResultsMean age and body mass index were 28.8 years and 23.15 kg/m2. One subject in the lowest dose group (46 µg/day) ovulated, no ovulations were seen in the higher dose groups. The degree of ovarian suppression increased with the dose. Median estradiol levels were 119, 36.5, 33.2 and 27.2 pg/mL in the 46, 94, 147 and 184 µg/day groups, respectively. Ovarian activity was resumed in the follow-up phase. Plasma TMG levels gradually declined over the treatment period and showed dose proportionality. The study treatment was safe and well tolerated. ConclusionThe release rate of 94 µg TMG per day was the lowest effective dose for ovulation inhibition. The study results justify further development of the TMG-ring as progestogen-only contraceptive. ImplicationsThe vaginal ring releasing TMG seems to be an effective new progestogen-only contraceptive preparation, having the advantage of once-a-month vaginal insertion.

Development of a pyrolysis model for an intumescent flame retardant system: Poly(lactic acid) blended with melamine and ammonium polyphosphate

A pyrolysis model capable of predicting materials' fire behavior as a function of concentration was developed for an intumescent flame retardant system: poly(lactic acid) (PLA) blended with melamine (MEL) and ammonium polyphosphate (APP). The model was developed through inverse analysis of data obtained from bench-scale pyrolysis experiments wherein a 0.07-m-diameter disk-shaped sample was exposed to well-defined radiant heating in an anaerobic environment. Sample back surface temperature, sample shape profile and burning rate were measured simultaneously. A numerical pyrolysis modeling framework, ThermaKin2Ds, and a previously developed semi-global thermal decomposition reaction mechanism were employed in the inverse analysis to determine material properties that define the heat and mass transport inside the pyrolyzing solids. The final pyrolysis model was found to predict materials' fire behavior for a variety of thermal exposures and material compositions. The model construction process revealed that a reduction in gas transfer coefficients helped to reproduce certain features of the burning rates profiles. Idealized cone calorimetry scenarios were simulated to study the influence of additives on materials’ fire behavior, and the results demonstrated that the blend with 5 wt% MEL and 25 wt% APP was found to be the most effective system with a 69% reduction in the average heat release rate comparing to that of PLA. A similar significant reduction has been reported in the literature, supporting the accuracy of this model. This work demonstrates a methodology that enables intelligent design of intumescent flame retardant materials tailored for specific applications, where low flammability is required.

Copper-Based Metal-Organic Framework as a Controllable Nitric Oxide-Releasing Vehicle for Enhanced Diabetic Wound Healing.

Chronic wounds are one of the most serious complications of diabetes mellitus. Even though utilizing nitric oxide (NO) as a gas medicine to repair diabetic wounds presents a promising strategy, controlling the NO release behavior in the affected area, which is vital for NO-based therapy, still remains a significant challenge. In this work, a copper-based metal-organic framework, namely, HKUST-1, has been introduced as a NO-loading vehicle, and a NO sustained release system with the core-shell structure has been designed through the electrospinning method. The results show that the NO is quantificationally and stably loaded in the HKUST-1 particles, and the NO-loaded HKUST-1 particles are well incorporated into the core layer of the coaxial nanofiber. Therefore, NO can be controllably released with an average release rate of 1.74 nmol L-1 h-1 for more than 14 days. Moreover, the additional copper ions released from the degradable HKUST-1 play a synergistic role with NO to promote endothelial cell growth and significantly improve the angiogenesis, collagen deposition as well as anti-inflammatory property in the wound bed, which eventually accelerate the diabetic wound healing. These results suggest that such a copper-based metal-organic framework material as a controllable NO-releasing vehicle is a highly efficient therapy for diabetic wounds.

Flame‐retardant properties and synergistic effect of ammonium polyphosphate/aluminum hydroxide/mica/silicone rubber composites

SummaryThe flammability behaviors of ammonium polyphosphate/aluminum hydroxide/mica/silicone rubber (APP/Al[OH]3/mica/SiR) ceramifying composites containing APP, Al[OH]3, and mica are investigated by cone calorimeter test. The thermal degradation and the synergistic effect of APP/Al(OH)3/mica/SiR composites are investigated by thermal gravimetric analysis, X‐ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and X‐ray photoelectron spectroscopy. APP/Al(OH)3/mica/SiR composites with 25 wt% of APP, 20 wt% of Al(OH)3, 25 wt% of mica, and 30 wt% SiR presents a much lower total heat release, the value of peak heat release rate (PHRR), the maximum average heat release rate, the longest time to ignition, and time to the PHRR (tPHRR), compared with the flame‐retardant properties from composites with filler of APP and mica or APP and Al(OH)3 alone. The results indicate that there is an excellent synergism in APP, Al(OH)3, and mica, which endows APP/Al(OH)3/mica/SiR composites with both good flame retardancy and fire prevention. The study on the synergism effect between fire prevention and flame retardancy of APP/Al(OH)3/mica/SiR composites indicates that compounds containing P‐O‐Al are formed due to the reaction between APP and Al(OH)3 during combustion in the early stage and a coherent, dense, and sealed structure is formed due to the reaction in mica, phosphates, and the thermal decomposition products of SiR during combustion in the later stage.

Joint‐aggregation intumescent flame‐retardant effect of ammonium polyphosphate and charring agent in polypropylene

AbstractIn order to explore the structure mode of intumescent flame retardants (IFRs) with higher efficiency, IFR particles with joint‐aggregation structure (@IFR) were obtained through the treatment of ammonium polyphosphate (APP) and a charring agent (PT‐Cluster) in their aqueous solution. Then, the joint‐aggregation IFR effect was researched using its application in polypropylene. In case of 20 wt% IFR loading, the limiting oxygen index (LOI) value of @IFR/PP was 1.1% higher than that of 15APP/5PT‐Cluster/PP mixture, and a 1.6 mm‐thick @IFR/PP composite passed the UL 94 V‐2 rating test, while 15APP/5PT‐Cluster/PP demonstrated no flame‐retardant rating in UL 94 vertical burning tests. In a cone calorimeter test, @IFR also had a better inhibition effect on heat release. The average heat release rate (av‐HRR) value during 0 to 120 seconds of @IFR/PP was only 41 kW m−2, which was 33.9% lower than that of the 15APP/5PT‐Cluster/PP. Furthermore, the peak heat release rate (pk‐HRR) of @IFR/PP was 20.5% lower than that of 15APP/5PT‐Cluster/PP, and the time to pk‐HRR of @IFR/PP was 710 seconds, while that of 15APP/5PT‐Cluster/PP was 580 seconds. The better inhibition effect on HRR and the delay of time to pk‐HRR were caused by the joint‐aggregated structure of @IFR, which can rapidly react to form stable and efficient char layers. This kind of join‐aggregation IFR effect has great significance in suppressing the spread of fire in reality. In addition, @IFR also increased the mechanical properties of PP composites slightly compared with the APP/PT‐Cluster mixture.

Using Time-Series Videos to Quantify Methane Bubbles Flux from Natural Cold Seeps in the South China Sea

Natural cold seeps are an important source of methane and other greenhouse gases to the ocean and atmosphere in the marine environment. Accurate quantification of methane bubble fluxes from cold seeps is vital for evaluating their influence on the global methane budget and climate change. We quantified the flux of gas bubbles released from two natural cold seep sites in the South China Sea: one seep vent in the Haima cold seeps (1400 m depth) and three seep vents at Site F (1200 m depth). We determined bubble diameter, size distribution, and bubble release rate using image processing techniques and a semiautomatic bubble-counting algorithm. The bubble size distributions fit well to log-normal distribution, with median bubble diameters between 2.54 mm and 6.17 mm. The average bubble diameters and release rates (4.8–26.1 bubbles s−1) in Site F was lower than that in Haima cold seeps (22.6 bubbles s−1), which may be attributed to a variety of factors such as the nature of the gas reservoir, hydrostatic pressure, migration pathways in the sediments, and pore size. The methane fluxes emitted at Haima cold seeps (12.6 L h−1) and at Site F (4.9 L h−1) indicate that the Haima and Site F cold seeps in the South China Sea may be a source of methane to the ocean. However, temporal variations in the bubble release rate and the geochemical characteristics of the seeps were not constrained in this study due to the short observational time interval.

Modeling Temperature Variations in MILD Combustion Using MuSt-FGM

The energy demand in the world is ever increasing, and for some applications combustion is still the only reliable source, and will remain as such in the foreseeable future. To be able to mitigate the environmental effects of combustion, we need to move to cleaner technologies. Moderate or intense low oxygen dilution (MILD) combustion is one of these technologies, which offer less harmful emissions, especially nitric oxide and nitrogen dioxide (NOx). It is achieved by the recirculation of the flue gases into the fresh reactants, reducing the oxygen content, and thereby causing the oxidation reactions to occur at a milder pace, as the acronym suggests. This results in a flameless combustion process and reduces the harmful emissions to negligible amounts. To assist in the design and development of combustors that work in the MILD regime, reliable and efficient models are required. In this study, modeling of the effects of temperature variation in the oxidizer of a MILD combustion case is tackled. The turbulent scales are fully resolved by performing direct numerical simulations (DNS), and chemistry is modeled using multistage flamelet generated manifolds (MuSt-FGM). In order to model the temperature variations, a passive scalar which is created by normalizing the initial temperature in the oxidizer is defined as a new control variable. During flamelet creation, it was observed that not all the compositions are autoigniting. Several approaches are proposed to solve this issue. The results from these cases are compared against the ones performed using detailed chemistry. With the best performing approach, the ignition delay is predicted fairly well, but the average heat release rate is over-predicted. Some possible causes of this mismatch are also given in the discussion.

Flame Retardancy of High-Density Polyethylene Composites with P,N-Doped Cellulose Fibrils.

To derive P,N-doped cellulose fibrils, phosphoric acid and aqueous ammonia were placed in a one-pot reaction, and the phosphate groups and ammonium phosphates were successfully introduced into the cellulose surface. The obtained P,N-doped cellulose fibrils with high liberation were thereafter incorporated into a high-density polyethylene (HDPE) matrix to improve the flame retardancy of HDPE composites, and they had a significant improvement on flame retardancy of HDPE composites. In particular, 7 wt % P,N-doped cellulose fibrils considerably reduced the average and peak heat release rate (HRR) by 29.6% and 72.9%, respectively, and increased the limited oxygen index (LOI) by 30.5%. The presence of phosphate groups and ammonium phosphates within P,N-doped cellulose fibrils was found to promote the thermal degradation of HDPE composites at a lower temperature (i.e., 240 °C). The released acid catalyzed the dehydration of cellulose to form an aromatic carbonaceous structure with a higher crystalline orientation, which improves the flame retardancy of HDPE composites.

Bioactive ophiopogonin release form bioglass-collagen-phosphatidylserine scaffolds to enhance bone repair in vitro

The goal of this study is to construct bone scaffolds with neuroregulatory function. The scaffolds were prepared using bioglass (BG) powder, collagen (COL) solution, phosphatidylserine (PS) and ophiopogonin loaded COL microspheres as the main components. Combinatorial processing techniques involving chemical-crosslinking and freeze-drying were used. The resultant scaffold constructs were characterized in terms of their morphology, drug release kinetics, pharmacological and biological activities for osteoblast and neurocyte. The microporphology observation showed that the scaffolds had highly interconnected pores, favorable drug release kinetics in view of low initial release and slow average release rate. Moreover, cell studies showed that the involvement of ophiopogonin contributed to the proliferation and mineralization of MC3T3-E1 cells, and the neurite outgrowth of neuron. The drug-loaded composite scaffolds may therefore be a potential replacement in bone-tissue engineering.

Event-Triggered H∞ Filter Design of T-S Fuzzy Systems Subject to Hybrid Attacks and Sensor Saturation

This paper addresses the problem of event-triggered $H_\infty $ filter design for nonlinear systems under both hybrid attacks and sensor saturation. A novel event-triggered mechanism (ETM) is proposed to reduce the number of transmission data per unit time, thereby improving the network QoS and taking the control performance into account. Considering that the deception attack may deteriorate the control performance, ETM is designed to be sensitive to deception attacks, that is, the average data release rate during the deception attack is higher than other periods. Consequently, the control performance can be improved. Moreover, the proposed ETM can reduce the occurrence of erroneous triggering events that are aroused by abnormal abrupt variation. In addition, the denial-of-service (DoS) attack is considered as well. A switching filtering error model is established based on the fact of each period of DoS attack being classified as active period and sleeping period. In addition, the problem of measurement saturation is concerned in filter design. By using Lyapunov-Krasovskii stability theory, sufficient conditions are obtained to guarantee the stability of the fuzzy filtering error system. The effectiveness of filter design methods is finally verified by a simulation example.

Effects of algal-detritus accumulation on the mineralization characteristics of lake sediment

蓝藻水华暴发形成的大量有机碎屑，沉降到沉积物表面，影响沉积物有机质矿化，进而影响碳氮磷循环.本实验选择于桥水库湖心区作为沉积物采样点，通过设置不同密度藻屑添加组（×1倍组和×20倍组）及空白对照组，研究藻屑堆积对沉积物矿化特征的影响及其环境效应，为蓝藻水华影响下的饮用水环境修复和科学管理提供一定的理论依据.结果表明：（1）藻屑添加降低了上覆水pH值，改变了沉积物生物酶活性.藻屑添加密度越大，上覆水pH值越低、波动越大，反映了培养过程异养微生物活性的变化.×1倍组的转化酶活性较高；×20倍组蛋白酶活性和碱性磷酸酶活性较高.（2）藻屑添加对沉积物的矿化途径和沉积物产物的释放速率产生了显著影响.藻屑添加密度越大，有机质矿化速率越大.其中，×1倍组主要增强好氧矿化，释放CO₂；×20倍组主要增强厌氧产甲烷矿化，释放CH₄.（3）不同密度的藻屑添加组，其氮磷扩散、释放通量存在明显差别.×1倍组以沉积物吸附为主，其上覆水NH₄⁺和PO₄^3-平均释放速率与对照组差异较小；×20倍组的NH₄⁺在第0~10天以沉积物吸附为主，之后和PO₄^3-均以向上覆水中释放为主，其NH₄⁺和PO₄^3-平均释放速率（分别为0.223）和0.075 mg/（L·d））明显大于其他实验组.因此，大量蓝藻堆积明显促进沉积物的碳氮磷矿化，释放大量CO₂、CH₄和氮磷营养盐至上覆水中，对湖泊水环境造成污染，为蓝藻的生长繁殖作贡献.;A large amount of organic algal-detritus after cyanobacterial bloom settled on the surface of the sediment, which has an effect on the mineralization characteristic of sedimentary organic matter, and then the biogeochemical cycle of carbon, nitrogen, and phosphorus. In this study, the central area of Yuqiao Reservoir was selected as the sediment sampling point. By the addition treatments of different densities of algal-detritus (×1 and×20 treatments) and blank controls, the effects of algal-detritus accumulation on the mineralization and their environmental effects were studied to provide some theoretical basis for drinking water environmental restoration and scientific management under the influence of cyanobacteria bloom. The results showed that the addition of algal-detritus lowered the pH value of overlying water and changed the activity of biological enzymes in the sediments. The higher the density of algal-detritus, the lower the pH value of the overlying water and the greater the fluctuation were. The×1 treatment had higher invertase activity, meanwhile the×20 treatment had higher protease activity and alkaline phosphatase activity. Secondly, the addition of algal-detritus had a significant effect on sedimentary mineralization pathways and release rates of mineralization products. The higher the density of algal-detritus, the greater the mineralization rate of sedimentary organic matter was. Moreover, the×1 treatment mainly enhanced aerobic mineralization with the increasing release of CO₂; the×20 treatment mainly enhanced anaerobic methanogens mineralization with the increasing release of CH₄. Thirdly, the diffusion and release fluxes of nitrogen and phosphorus were significantly different in algal-detritus addition treatments with different densities. Sediment adsorption was dominated in the×1 treatment, in which the average release rates of NH₄⁺ and PO₄^3- in overlying water differed slightly from the blank controls. In the×20 treatment, the flux of NH₄⁺ showed the tendency of sediment adsorption in the initial ten days and transferred to releasing potential in the remained time, while the releasing flux of PO₄^3- to overlying water was existed during the whole incubation period. The average release rates of NH₄⁺ and PO₄^3- in the×20 treatment (0.223 mg/(L·d) and 0.075 mg/(L·d), respectively) were significantly higher than those of the other treatments. In general, the accumulation of high density of algal-detritus promotes the mineralization of organic carbon, nitrogen, and phosphorus, releasing a large amount of CO₂, CH₄, and nutrients to the overlying water, which decreases water quality and contributes to the growth and reproduction of cyanobacteria.

Characteristics and significance of nitrogen, phosphorus and oxygen transportation at the sediment-water interface in east Lake Chaohu

以东巢湖近城市湖湾沉积物为研究对象，在沉积物氮、磷营养盐分析的基础上，采用沉积物柱状芯样静态释放模拟法定量评估研究区域沉积物-水界面氨氮、溶解性活性磷酸盐营养盐释放潜力，利用微电极非损伤测定技术获得沉积物-水微界面溶解氧（DO）剖面分布及微界面DO消耗和扩散特征.结果表明：东巢湖近城市湖湾沉积物氮、磷污染物蓄积量较高，受TN、TP污染程度较重.沉积物内源氨氮、磷酸盐释放明显，平均释放速率分别达到32.44 mg/（m²·d）和1.25 mg/（m²·d），区域内沉积物已成为水柱中氮、磷营养盐的污染源.研究区域上覆水体处于好氧状态，沉积物-水微界面平均DO穿透深度（OPD）达到5.3 mm，平均DO扩散通量为4.56 mmol/（m²·d），表现出良好的DO扩散能力.沉积物内源氨氮和磷酸盐释放能力与表层沉积物TN/TP物质含量及沉积物-水微界面DO穿透深度有关，在沉积物氮、磷污染较重的情况下，DO穿透深度越低越有利于氮、磷污染物从沉积物向上覆水体释放.;A comprehensive study of transportation features of nitrogen, phosphorous and dissolve oxygen at the sediment-water interface was carried out in near city areas of east Lake Chaohu. Based on the investigation of sediment nutrients analysis and nutrients release incubation experiments, the release potential and release rates of ammonia nitrogen (NH₃-N) and soluble reactive phosphorous (SRP) of different sediments were estimated. The distribution characteristics, diffusion fluxes, and consumption rates of dissolved oxygen (DO) at the sediment-water interface of different sediments were studied by using a non-invasive microelectrode analysis system. The results showed the surface sediments in the near city areas of east Lake Chaohu were in severe nitrogen and phosphorous pollution with high total nitrogen (TN) and total phosphorus (TP) loadings. Typical internal releases of NH₃-N and SRP were observed from all sediments with the average release rates of 32.44 mg/(m²·d) and 1.25 mg/(m²·d), respectively. The sediments play the role of pollution source rather than the sink for NH₃-N and SRP in the study area. Results also showed that all overlying water were at aerobic condition. The average oxygen penetration depth (OPD) and oxygen diffusion flux at sediment-water micro-interfaces reached 5.3 mm and 4.56 mmol/(m²·d) respectively, indicating good DO diffusion ability from the boundary layer to the sediment. The internal release intensity of NH₃-N and SRP are influenced by TN/TP contents of the surface sediment as well as the OPD at the sediment-water interface. The release of NH₃-N and SRP from sediments could be benefited from the high nitrogen and phosphorous loadings and low OPD and contribute to the eutrophication of the lake.

Measuring Racial Discrimination in Bail Decisions

We develop new quasi-experimental tools to measure racial discrimination, due to either racial bias or statistical discrimination, in the context of bail decisions. We show that the omitted variables bias in observational release rate comparisons can be purged by using the quasi-random assignment of judges to estimate average race-specific misconduct risk. We find that approximately two-thirds of the average release rate disparity between white and Black defendants in New York City is due to racial discrimination. We then develop a hierarchical marginal treatment effects model to study the drivers of discrimination, finding evidence of both racial bias and statistical discrimination. Outcome-based tests of racial bias therefore omit an important source of racial discrimination in bail decisions, and cannot be used to rule out all possible violations of U.S. anti-discrimination law.

Tris (2-aminoethyl) Amine Functionalized Nanoporous Silica SBA-15 as a Potential Drug Carrier for Citalopram

Introduction: Ordered nanoporous silica such as SBA-15 has a great potential for application in controlled drug release systems. Chemical modification of the silanol groups of SBA-15 allows better control over drug loading and release. Therefore, tris(2-aminoethyl) amine-functionalized mesoporous silica SBA-15 was evaluated as a potential carrier for the delivery of citalopram. Methods: Tris (2-aminoethyl) amine-functionalized SBA-15 was synthesized and characterized by various methods. Citalopram was loaded on the functionalized SBA-15 and drug release into simulated body fluid (SBF) solution and phosphate buffers was investigated. Results: The optimal condition for loading of the citalopram was obtained at pH = 9 after stirring for 5 minutes. The release profile of citalopram was monitored in phosphate buffers with three different pH values of 5, 7, and 8. A faster release rate at lower pH value was observed, suggesting a weaker interaction because of the protonation of the amino group of the functionalized SBA15. The average release rate of citalopram from each gram of functionalized SBA-15 was 12 µg h-1 in the SBF. Conclusion: The results showed that loading amount and release rate of citalopram depended on pH value and the release process showed a very slow release pattern. Therefore, tris (2-aminoethyl) amine-functionalized SBA-15 is a suitable carrier for controlled release of citalopram and has a great potential for disease therapy.

The synergistic effects of SrF2 nanoparticles, YSZ nanoparticles, and poly-ε-l-lysin on physicomechanical, ion release, and antibacterial-cellular behavior of the flowable dental composites

Resin-based pit-and-fissure sealants (flowable resin composites) were formulated using bisphenol-A-glycerolatedimethacrylate (Bis-GMA)-triethylene glycol dimethacrylate-(TEGDMA)-diurethanedimethacrylate (UDMA) mixed monomers and multiple fillers, including synthetic strontium fluoride (SrF2) nanoparticles as a fluoride-releasing and antibacterial agent, yttria-stabilized zirconia (YSZ) nanoparticles as an auxiliary filler, and poly-ε-l-lysin (ε-PL) as an auxiliary antibacterial agent. Based on the physical, mechanical and initial antibacterial properties, the formulated nano-sealant containing 5wt% SrF2, 5wt% YSZ and 0.5wt% ε-PL was selected as the optimal specimen and examined for ion release and cytotoxicity. The results showed an average release rate of 0.87μg·cm-2·day-1 in the aqueous medium (pH6.9) and 1.58μg·cm-2·day-1 in acidic medium (pH4.0). The maximum cytotoxicity of 20% toward human bone marrow mesenchymal stem cells (hMSCs) was observed according to the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) cytotoxicity assay and acridine orange staining test. A synergy between SrF2 nanoparticles and ε-PL exhibited a better antibacterial activity in terms of colony reduction compared to the other samples. However, the inclusion of SrF2 and ε-PL caused mechanically weakening of the sealants that was partly compensated by incorporation of YSZ nanoparticles (up to 10wt%).