Photocatalytic performance of nanocrystalline Bi5Ti3FeO15 layered perovskite under visible light

Nanocrystalline Bi5Ti3FeO15 layered perovskite exhibiting Aurivillius phase was synthesized by polymerized complex (PC) method and investigated for its physico-chemical as well as optical properties. The crystallization of Bi5Ti3FeO15 synthesized by PC method was found to occur in the temperature range of 800-1050 degress C, whereas the single crystalline Bi5Ti3FeO15 formed at 1030 degrees C by solid state reaction (SSR) method. The observation of highly pure phase and such lower crystallization temperature in Bi5Ti3FeO15 prepared by PC method, is in total contrast to that observed in Bi5Ti3FeO15 prepared by the conventional solid-state reaction (SSR) method. The band gap of nanocrystalline Bi5Ti3FeO15 determined from UV-Vis diffusion reflectance spectrometer was 2.38 eV (525 nm). The photocatalytic activity of Pt/Bi5Ti3FeO15 prepared by PC method was investigated with the photodecomposition of isopropyl alcohol (IPA) and hydrogen production from water-methanol mixed solution under visible light (lambda > or = 420 nm). The respective activities for PC sample were higher than that of Pt/Bi5Ti3FeO15 prepared by SSR as well as Pt/TiO(2-x)N(x).     

Experimental and theoretical evaluation of microbubble behavior: effect of transmitted phase and bubble size

Ultrasound contrast agents provide new opportunities to image vascular volume and flow rate directly. To accomplish this goal, new pulse sequences can be developed to detect specifically the presence of a microbubble or group of microbubbles. We consider a new scheme to detect the presence of contrast agents in the body by examining the effect of transmitted phase on the received echoes from single bubbles. In this study, three tools are uniquely combined to aid in the understanding of the effects of transmission parameters and bubble radius on the received echo. These tools allow for optical measurement of radial oscillations of single bubbles during insonation, acoustical study of echoes from single contrast agent bubbles, and the comparison of these experimental observations with theoretical predictions. A modified Herring equation with shell terms is solved for the time-dependent bubble radius and wall velocity, and these outputs are used to formulate the predicted echo from a single encapsulated bubble. The model is validated by direct comparison of the predicted radial oscillations with those measured optically. The transient bubble response is evaluated with a transducer excitation consisting of one-cycle pulses with a center frequency of 2.4-MHz. The experimental and theoretical results are in good agreement and predict that the transmission of two pulses with opposite polarity will yield similar time domain echoes with the first significant portion of the echo generated when the rarefactional half-cycle reaches the bubble.     

In vitro behavior of osteoblast-like cells on PLLA films with a biomimetic apatite or apatite/collagen composite coating

To investigate the methods to improve the cell–material interaction of devices or tissue engineering scaffolds made of poly(l-lactic acid) (PLLA) polymer, apatite and apatite/collagen composite coatings were formed on PLLA films within 24 h through accelerated biomimetic processes. In vitro investigation using Saos-2 osteoblast-like cells through cell culture was conducted to assess the biological performance of these biomimetic coatings. The cell morphology on three types of surfaces, viz., PLLA film, PLLA film with the apatite coating, and PLLA film with the apatite/collagen composite coating, was studied using scanning electron microscopy (SEM). Cell viability was estimated using the MTT assay. The differentiated cell function was assessed by measuring the alkaline phosphatase (ALP) activity. The results obtained indicated that the biomimetic apatite and apatite/collagen composite coatings could significantly enhance the proliferation and differentiation of osteoblast-like cells. The apatite/collagen composite coating appears to be promising for the surface modification of PLLA-based devices with much improved interactions with osteoblastic cells.     

Alkylamine odors from degradation of flocculant polymers in sludges

The cationic organic polymers used to enhance thickening and dewatering processes are potential sources of strong odors. These polymers vary in chemical structure, and some may be more susceptible to biotic or abiotic degradation than others. The product organic amines will be volatilized most noticeably at high pH, as in lime addition. These possibilities were examined using several structural types of polymers combined with anaerobically digested sludge. Two commonly used polymers gave significant production of trimethylamine (TMA), which was released upon lime addition. Their structures were correlated with reactions that yield TMA. An initial ester hydrolysis step appears to be biologically mediated, but subsequent steps can occur due to alkaline conditions. An alternative cationic polymer structure did not generate TMA but required a much higher dose to effect sufficient conditioning of the sludge. The acrylamide-based polymers were shown to be the predominant source of TMA in limed sludges.     

Optical and chemical characteristics of the atmospheric aerosol in four towns in southern Poland

The absorption coefficient a(p) [m(-1)] as well as the mass absorption coefficient sigma(p) [m(2)/g] has been estimated for PM10 and PM2.5 in four towns located in southern Poland, based on the assumption that the reflectance of aerosol-laden filters is a good proxy for the absorptivity of aerosols. The optical properties of the airborne particles were also compared with their surface composition obtained by photoelectron spectroscopy (XPS). It was found that coarse particles, which constituted 20-30% of PM10, exhibited insignificant contribution to the absorption. The most absorptive aerosols were found in the towns located in Upper Silesia, a highly industrialized area. This reflects both the relative content of carbon in PM2.5 and the mass concentration of the fine mode. It was found that oxides and sulfates play an important role in promoting the reflectance of light from aerosols in the winter. These results support the suggestion that the revision of existing air quality standards for particulate pollution is needed.     

Environmental stress and recovery: the geochemical record of human disturbance in New Bedford Harbor and Apponagansett Bay,Massachusetts (USA)

Sediments record the history of contamination to estuaries. Analysis of the concentrations of toxic organic compounds, contaminant and crustal metals, organic carbon content and isotopic composition in sediment cores from two estuarine systems in Buzzards Bay allowed reconstruction of human impacts over 350 years. Vertical distributions of the contaminants correlate with changes in the nature of watershed/estuarine activities. All contaminants were highly enriched (tens to hundreds times background) in modern New Bedford Harbor sediments. Enrichment began around the turn of the 20th century for all but PCBs, which were first synthesized in the 1930s. An increase in organic carbon content and a shift of carbon isotopes toward a more terrestrial signature illustrates increasing anthropogenic impact in New Bedford as population grew along with the industrial base. Institution of environmental protection measures in the late 20th century was reflected in decreased, although still substantially elevated, concentrations of contaminants. A lack of industrial development in Apponagansett Bay resulted in much lower concentrations of the same indicators, although specific contaminants related to the early whaling industry increased significantly above background as early as the late 18th century. The similarity of indicators in older portions of cores from NBH and unimpacted Apponagansett Bay demonstrates that cores can be used to establish reference conditions as successfully as using separate sites judged a priori to represent the reference state. The historical reconstruction approach provides the basis for establishing relationships between environmental stressors and factors that drive the stressors, as well as a framework for the assessment of ecological response(s) to environmental stressors over a range of time and/or exposure scales.     

基于非线性直接优化方法的发电机励磁系统参数辨识

励磁模型的准确程度对于电力系统仿真的准确性有显著影响。提出了一种新的、工程中容易实现的方法,即利用非线性直接优化法辨识微分方程形式的励磁模型参数。首先利用Matlab仿真与传统的最小二乘法比较验证算法有效性。然后利用动态信号记录装置,根据模型结构获得各个环节的时域内发电机阶跃试验数据,对1台300 MW汽轮发电机组的励磁系统分别进行分环节参数辨识和整体辨识。利用电力系统分析综合程序(power system analysis software package,PSASP)的用户自定义模型功能建立励磁模型进行相同的阶跃仿真,结果验证了辨识参数在电力系统仿真中的有效性。     

Assessing homeland chemical hazards outside the military gates: industrial hazard threat assessments for department of defense installations

As part of comprehensive joint medical surveillance measures outlined by the Department of Defense, the US Army Center for Health Promotion and Preventive Medicine (USACHPPM) is beginning to assess environmental health threats to continental US military installations. A common theme in comprehensive joint medical surveillance, in support of Force Health Protection, is the identification and assessment of potential environmental health hazards, and the evaluation and documentation of actual exposures in both a continental US and outside a continental US setting. For the continental US assessments, the USACHPPM has utilized the US Environmental Protection Agency (EPA) database for risk management plans in accordance with Public Law 106-40, and the toxic release inventory database, in a state-of the art geographic information systems based program, termed the Consequence Assessment and Management Tool Set, or CATS, for assessing homeland industrial chemical hazards outside the military gates. As an example, the US EPA toxic release inventory and risk management plans databases are queried to determine the types and locations of industries surrounding a continental US military installation. Contaminants of concern are then ranked with respect to known toxicological and physical hazards, where they are then subject to applicable downwind hazard simulations using applicable meteorological and climatological data sets. The composite downwind hazard areas are mapped in relation to emergency response planning guidelines (ERPG), which were developed by the American Industrial Hygiene Association to assist emergency response personnel planning for catastrophic chemical releases. In addition, other geographic referenced data such as transportation routes, satellite imagery and population data are included in the operational, equipment, and morale risk assessment and management process. These techniques have been developed to assist military medical planners and operations personnel in determining the industrial hazards, vulnerability assessments and health risk assessments to continental United States military installations. These techniques and procedures support the Department of Defense Force Protection measures, which provides awareness of a terrorism threat, appropriate measures to prevent terrorist attacks and mitigate terrorism's effects in the event that preventive measures are ineffective.     

Molecular inflammation hypothesis of aging based on the anti-aging mechanism of calorie restriction

Accumulating evidence strongly suggests that oxidative stress underlies aging processes. Research provides consistent evidence that calorie restriction (CR) reduces age-related oxidative stress and has anti-inflammatory properties. However, information is lacking on the molecular mechanism that would better define the interrelation of reactive oxygen species and nitrogen species and the pro-inflammatory states of the aging process. In this review, the biochemical and molecular bases of the inflammatory process in the aging process are analyzed to delineate the molecular inflammation hypothesis of aging. The key players involved in the proposed hypothesis are the age-related upregulation of NF-kappa B, IL-1 beta, IL-6, TNFalpha, cyclooxygenase-2, and inducible NO synthase, all of which are attenuated by CR. Furthermore, age-related NF kappa B activation is associated with phosphorylation by I kappa B kinase/NIK and MAPKs, while CR blocked these activation processes. The modulation of these factors provides molecular insights of the anti-inflammatory action of CR in relation to the aging process. Based on available finding and our recent supporting evidence, we prefer to use "molecular inflammation" to emphasize the importance of the molecular reaction mechanisms and their aberrance, predisposing to fully expressed chronic inflammatory phenomena. It was further proposed that CR's major force of the regulation of redox-sensitive inflammation may well be its life-prolonging action.