草地生态系统中土壤氮素矿化影响因素的研究进展

氮素是各种植物生长和发育所需的大量营养元素之一,也是牧草从土壤吸收最多的矿质元素．土壤中的氮大部分以有机态形式存在,而植物可以直接吸收利用的是无机态氮．这些有机态氮在土壤动物和微生物的作用下。由难以被植物直接吸收利用的有机态转化为可被植物直接吸收利用的无机态的过程就是土壤氮的矿化．氮素矿化受多种因子的影响,这些因子可以归结为生物因子和非生物因子．生物因子包括：土壤动物、土壤微生物和植物种类．土壤动物可以促进土壤有机质的矿化;土壤微生物种类、结构及功能与氮的分解、矿化有密切的关系;不同的植物种类对土壤氮素的矿化作用是不相同的,一般来说。有豆科植物生长的土壤比其它种类土氮素矿化的作用大．非生物因素一般可以分为环境因子和人类活动干扰．环境因子中土壤温度和含水量对土壤氮素矿化的影响是国内外众多科学家研究的方向．尽管如此,在此方面的研究还没有取得一致意见,仍然需要进行这方面的研究,而在其他诸如：不同的土壤质地与土壤类型方面,研究报道的结论也很不一致,草地生态系统中人类活动对土壤氮素矿化的影响主要包括,不同强度的放牧,割草以及施肥、火烧强度等．非生物因子对氮素矿化的影响非常直接和明显,尤其是人类活动．本文综述了近年来影响草地生态系统土壤氮素矿化有关因素的一些进展．     

Review of sorption and diffusion of lipophilic molecules in cuticular waxes and the effects of accelerators on solute mobilities

Many agrochemicals are applied to the leaf surfaces of crop plants. Systemic chemicals have to penetrate through the cuticle, which forms an effective transport barrier. The barrier properties of cuticles are mainly due to the cuticular waxes deposited as partially crystalline aggregates on the outer surfaces of leaves. Substances increasing the mobilities of agrochemicals in cuticular waxes are called accelerators and it is shown that they act as plasticizers when absorbed by cuticular waxes. They decrease the barrier properties of the waxes and thus increase the mobilities of the agrochemicals through them. In order to analyse the efficiency of different accelerators, the sorption and mobility of both agrochemicals and accelerators within cuticular waxes was measured. Such information was used to establish correlations between the internal concentrations of accelerators and their mobility-enhancing effects on agrochemicals in the cuticle. This, in turn, allowed the determination and comparison of the intrinsic effects of different accelerators and to rationalize the effect of accelerators on the cuticular permeability of agrochemicals. Results describing the sorption (partition coefficients) and mobility (diffusion coefficients) of lipophilic organic molecules in reconstituted cuticular waxes from different plant species, and the effect of two different classes of accelerators (alcohol ethoxylates and n-alkyl esters), on the mobility of organic molecules are presented and discussed.     

Radiation Protection in Canada: Part II. * The Role of the Radiation Protection Division in Safeguarding the Health of Radiation Workers

The current status of radiation protection in Canada is discussed in the second of a three-part series and particular emphasis is placed on the role of the Radiation Protection Division of the Department of National Health and Welfare. Administrative and operational control procedures have been developed, involving prior approval of health safeguards in the radioisotope user''s facilities and techniques, and systematic monitoring and inspection. Where necessary, a medical follow-up of accidents and excessive radiation exposures is carried out. In 1963 more than 1600 radioisotope licences were issued. Filmmonitoring service was provided to about 15,500 isotope and x-ray workers. Semiautomatic handling procedures have been developed to meet the increasing demand for film-monitoring services.Monitoring and inspection services have been provided for x-ray workers, and a committee has been formed to develop administrative procedures for health and safety control in x-ray work. Committees have also been set up to review the health and safety aspects of the operation of nuclear reactors and particle accelerators.     

Developments in pre-treatment methods to improve anaerobic digestion of sewage sludge

During wastewater treatment, most organic matter is transferred to a solid phase commonly known as sludge or biosolids. The high cost of sludge management and the growing interest in alternative energy sources have prompted proposals for different strategies to optimize biogas production during anaerobic sludge treatment. Because of the high solid content and complex structure of sludge-derived organic matter, methane production during digestion is limited at the hydrolysis step. Therefore, large digester volume and long retention times of over 20 days are necessary to achieve adequate stabilization. Pre-treatments can be used to hydrolyze sludge and consequently improve biogas production, solids removal and sludge quality after digestion. This paper reviews the main pre-treatment processes, with emphasis on the most recent developments. An overview of the different technologies is presented, discussing their effects on sludge properties and anaerobic digestion. Future challenges and concerns related to pre-treatment assessment and implementation are also addressed.     

Effect of plant and artificial aeration on solids accumulation and biological activities in constructed wetlands

In constructed wetlands, solids accumulation may have two consequences with opposing effects on treatment efficiency: it decreases the longevity by reducing void space and it enhances biological activity by favoring biofilm development. The goal of our study was to estimate the effect of plants (presence and species) and artificial aeration on solids accumulation (volatile and inorganic). The horizontal and vertical distribution of solids was sampled using solids traps in 12 constructed wetland mesocosms (5 years old). Microbial density and activity were estimated in the biological fraction of the sampled solids. The effect of plant presence reduced accumulated solids by 26% and sulphide content by 50% sulphide content. There was more solids accumulation in Typha angustifolia units than in Phragmites australis. Also, T. angustifolia generated more biological activities at the surface and close to the inlet while conditions were more homogeneous throughout P. australis units. Aeration (1) stimulated biofilm development at the inlet of planted beds, (2) seemed to reduce mineral matter accumulation and (3) generated the same pattern of activities in planted beds enabling to reach a total nitrogen removal rate of up to 0.65 g N m^?2 d^?1.     

Dispersions in hydrocarbon fermentation. A retrospective study

A nondimensionalized plot, obtained by normalizing the drop-size distribution in the hydrocarbon phase using the Sauter mean diameter, shows a tendency towards self-preservation of the distribution. Changes of distribution in time during the course of fermentation, initial dispersed phase fraction, speed of rotation, and reactor size were taken into account. Using this self-preserving property, an empirical (single parameter) equation has been proposed for drop-size distribution. Data, available from the literature, are presented for non-biological and biological systems (gas-oil, n-hexadecane, and n-hexadecane dissolved in dewaxed gas oil as dispersed phases). The parameter, Sauter mean diameter, has been correlated with the operating conditions, and a critical review presented. Cell density was found to have significant effect on Sauter mean diameter. This effect has also been empirically explained. The possibilities of using generalized distribution in predicting the performance of fermenters is outlined.     

Use of molecular markers in breeding for soluble solids content in tomato — a re-examination

Summbary Through earlier breeding efforts, portions of the genome of the wild species Lycopersicon chmielewskii have been introgressed into the cultivated tomato (Rick 1974). These introgressed chromosomal segments have been reported to increase soluble solids in fruit of certain tomato varieties (Rick 1974). Recently, two of the introgressed segments have been identified with RFLP markers and tested for effects on soluble solids in a single F2 population (Osborn et al. 1987). Based on results from that experiment, it was determined that one of the detected segments contains gene(s) controlling soluble solids and concluded that tomato varieties could be improved for this character by indirect selection for the linked RFLP marker (Osborn et al. 1987). In this report, we have independently tested the association between RFLP and isozyme markers and genes controlling soluble solids and other characters in the above described material. These experiments differ from the previous ones in that a set of 132 molecular markers (isozymes and DNA clones) of known chromosomal position have been used. Three introgressed chromosomal segments from L. chmielewskii have been identified using these markers. They map to the middle and the end of chromosome 7 (> 40 cM apart) and to the end of chromosome 10. The effects of these segments on soluble solids and other horticultural characters were tested in crosses with three different cultivars over a period of two years. Two of the three segments were found to increase soluble solids, however the effect of one of these was dependent on genetic background. Both segments were found to be associated with deleterious characters including increase in fruit pH, lower yield and small fruit. These results confirm the utility of molecular markers for detecting genes underlying quantitative variation but demonstrate the danger in establishing breeding programs around such linkages until the effects of the quantitative genes have been tested in a variety of genetic backgrounds and for associated effects on other characters of agronomic importance.     

Genetic analyses of correlated solids, flavor, and health-enhancing traits in onion (Allium cepa L.)

Onion possesses organosulfur compounds and carbohydrates that provide unique flavor and health-enhancing characteristics. Significant phenotypic correlations have been reported among soluble solids content (SSC), total dry matter, pungency, and onion-induced in vitro antiplatelet activity. A genetic map and segregating F3M families derived from a cross between two inbred populations were used to identify and estimate the effects of quantitative trait loci (QTLs) controlling these traits at 30 and 90 days postharvest. In vitro antiplatelet activities among different onion populations were consistent across six human blood donors. Most of the populations showed in vitro antiplatelet activities; however, for some donors, one of the parental lines and two F3M families had pro-aggregatory effects under our experimental conditions. SSC, dry matter, pungency, and in vitro antiplatelet activity showed significant positive phenotypic and genetic correlations. A chromosome region on linkage group E accounted for a significant amount of the phenotypic variation for all of these traits. The correlations among these traits may be due to linkage or pleiotropy of genes controlling solids content. Our results indicate that it will be difficult to develop onion populations with lower pungency and high in vitro antiplatelet activity; however, the strong genetic and phenotypic correlations between high in vitro antiplatelet activity and high SSC are beneficial for the health functionality of onion.     

Physical and Chemical Studies of Lago Tupé; a Central Amazonian Black Water “Ria Lake”

Lago Tupé, a Central Amazonian dystrophic black water “Ria lake” (blocked valley lake), lateral to the Rio Negro, was studied at all depths for a year. Physical and chemical results of that study are presented here as a prelude to the microbiological studies. The lake's origin and morphology are discussed. Results concerned with thermal properties, suspended matter and dissolved solids are presented, in addition to results on ionic composition, alkalinity, hardness, pH and dissolved oxygen. Nutrient studies include section of phosphate and nitrogen and conclude with silicate results.     

Assessment of characteristics and biological treatment technologies of Jordanian wastewater

Demand for wastewater treatment facilities will increase as Jordan's population grows. In addition, currently available systems of treatment desperately need upgrades in capacity or supplementary systems; especially in the Amman-Zarqa region. Overall; based on the current wastewater flow rates; approximately 85% of the collected sewerage is treated in stabilization ponds, 10% in trickling filters, and 5% in activated sludge systems. This study was carried out to analyze and identify the properties of Jordanian wastewater; compare it to the common characteristics internationally known; and couple that with a proposal of an appropriate treatment technology. Five treatment plants were selected to achieve the objectives of this study; the flow rate of which constitutes approximately 80% of the total treated wastewater in Jordan, based on the design capacity. The study concluded that the wastewater generated in Jordan is classified as strong in terms of total dissolved solids content, total suspended solids content, and chemical and biochemical oxygen demands (COD and BOD). The efficiency of the selected technologies in removing dissolved solids from wastewater was low while it was reasonably high in terms of suspended solids removal. The technology achieving highest percent removals of BOD and solids was that of activated sludge and its modifications. Based on the factors considered in evaluating and selecting unit operations and processes, the activated sludge and its modifications are probably the process technology that should be used in treating Jordanian domestic wastewaters.     

Diurnal variation of biological and non-biological particles in the atmosphere of Córdoba, Spain

In this work, the daily distribution of biological and non-biological particles in the atmosphere of the city of Córdoba, Spain, is analysed in order to know at what time of day the concentrations of solid suspended particles in the air is maximum. This knowledge can be useful for all those people who suffer of respiratory diseases and can help them to plan their outdoors activities. The concentrations of non-biological material have been estimated by using spectrophotometrical techniques. With this method, the amount of non-biological material is expressed in percentage of light absorbance in values oscillating from 0.00: absence of particles to 1.00: extreme presence of particles. As the absorption of light depends on the colour of the particle, it is also possible to distinguish dark particles (soot, diesel exhaust particles, sand) from hyaline or light coloured ones (pollen grains and several fungal spores types). The results have shown that the maximum peaks of material are achieved early in the mornings and late in the evenings. Aerobiological methodology has been used when dealing with material of biological origin. In this latter case, pollen grains and fungal spores have been differentiated from the rest of solid material. Due to their importance as agents causing pollen allergy in the area and the high percentage that they represent with respect to the total pollen spectrum, Olea europaea and grass pollen types have been differentiated from the rest of pollen types. The results show that the peaks of non-biological particles in the air throughout the day are related to the activities carried out by men in the city: commercial and working hours or social activities in the different seasons of the year. As regards the biological material, the pattern of fungal spores is clearly influenced by the climatic characteristics of the area, presenting the maximum concentrations in the late afternoon. The pollen grains follow a pattern coinciding with the diurnal maximum temperatures and sunshine hours. The values of the curve oscillate from 200 grains/m3 of air in night hours to maximum over 1000 grains/m3 at midday. The diurnal variation of Olea europaea is quite similar to this general pattern, presenting the maximum concentrations of pollen grains at central hours of day. The grasses show some differences due to the high number of species included in this family.     

The status of medical physics in radiotherapy in China

PurposeTo present an overview of the status of medical physics in radiotherapy in China, including facilities and devices, occupation, education, research, etc.Materials and methodsThe information about medical physics in clinics was obtained from the 9-th nationwide survey conducted by the China Society for Radiation Oncology in 2019. The data of medical physics in education and research was collected from the publications of the official and professional organizations.ResultsBy 2019, there were 1463 hospitals or institutes registered to practice radiotherapy and the number of accelerators per million population was 1.5. There were 4172 medical physicists working in clinics of radiation oncology. The ratio between the numbers of radiation oncologists and medical physicists is 3.51. Approximately, 95% of medical physicists have an undergraduate or graduate degrees in nuclear physics and biomedical engineering. 86% of medical physicists have certificates issued by the Chinese Society of Medical Physics. There has been a fast growth of publications by authors from mainland of China in the top international medical physics and radiotherapy journals since 2018.ConclusionsDemand for medical physicists in radiotherapy increased quickly in the past decade. The distribution of radiotherapy facilities in China became more balanced. High quality continuing education and training programs for medical physicists are deficient in most areas. The role of medical physicists in the clinic has not been clearly defined and their contributions have not been fully recognized by the community.     

Effect of Increasing Total Solids Contents on Anaerobic Digestion of Food Waste under Mesophilic Conditions: Performance and Microbial Characteristics Analysis

The total solids content of feedstocks affects the performances of anaerobic digestion and the change of total solids content will lead the change of microbial morphology in systems. In order to increase the efficiency of anaerobic digestion, it is necessary to understand the role of the total solids content on the behavior of the microbial communities involved in anaerobic digestion of organic matter from wet to dry technology. The performances of mesophilic anaerobic digestion of food waste with different total solids contents from 5% to 20% were compared and the microbial communities in reactors were investigated using 454 pyrosequencing technology. Three stable anaerobic digestion processes were achieved for food waste biodegradation and methane generation. Better performances mainly including volatile solids reduction and methane yield were obtained in the reactors with higher total solids content. Pyrosequencing results revealed significant shifts in bacterial community with increasing total solids contents. The proportion of phylum Chloroflexi decreased obviously with increasing total solids contents while other functional bacteria showed increasing trend. Methanosarcina absolutely dominated in archaeal communities in three reactors and the relative abundance of this group showed increasing trend with increasing total solids contents. These results revealed the effects of the total solids content on the performance parameters and the behavior of the microbial communities involved in the anaerobic digestion of food waste from wet to dry technologies.     

A Two-Stage Procedure for the Removal of Batch Effects in Microarray Studies

The presence of different batches is routinely observed in microarray studies and is well known that non-biological variability potentially confounding biological differences is commonly related to such batches. The removal of these undesired effects for a non-biased inference is often accomplished either with normalization methods that do not take into account all the available information, or with models that rely on strong parametric assumptions. We have developed a new method for the batch effects removal, named ber, which is based on a two-stage procedure for the estimation of location and scale parameters. Batch effects and biological differences are estimated using a regression approach and bagging, therefore mild distributional assumptions are required. We have compared ber with other commonly employed methods and we have shown that ber can bring to a higher power in detecting differentially expressed genes. The application of ber to a real microarray study led to interpretable biological results. The method is implemented in the R package ber, available through CRAN repository.     

Use of native aquatic macrophytes in the reduction of organic matter from dairy effluents

Considering the diversity and the unexplored potential of regional aquatic flora, this study aimed to identify and analyze the potential of native aquatic macrophytes to reduce the organic matter of dairy wastewater (DW) using experimental constructed wetlands. The dairy wastewater (DW) had an average chemical oxygen demand (COD) of 7414.63 mg/L and then was diluted to 3133.16 mg/L (D1) and to 2506.53 mg/L (D2). Total solids, COD, temperature, and pH analyses were performed, and the biochemical oxygen demand (BOD) was estimated from the COD values. The best performance in the reduction of the organic matter was observed for Polygonum sp. (87.5% COD and 79.6% BOD) and Eichhornia paniculata (90% COD and 83.7% BOD) at dilution D1, on the 8th day of the experiment. However, the highest total solids removal was observed for Polygonum sp. (32.2%), on the 4th day, at dilution D2. The total solid (TS) concentration has also increased starting from the 8th day of the experiment was observed which may have been due to the development of mosquito larvae and their mechanical removal by sieving, thus changing the steady state of the experimental systems. The macrophytes Polygonum sp. and E. paniculata were considered suitable for the reduction of organic matter of DW using constructed wetlands.     

Restoration of urban green environments based on the theories of vegetation ecology

Modern cities and industrial areas are standardized, built of non-biological materials such as iron, cement and petrochemicals. The most desirable life for citizens should be both mentally and physically sound, which are the basis of existence for all lives. A multistratal forest is estimated to have 25–30 times the green surface area monostratal grass. With underground organic compounds, multistratal forests also contribute to the reduction of CO₂. Building facilities can be completed in short term with economic backing. But it takes biological time to regenerate a multistratal forest using living green construction materials. It is urgent to start the restoration and reconstruction of native green environments immediately. To form green environments of multistructure using plants, it is necessary to systematize the data from field investigations and to follow the scientific scenario based on potential natural vegetation. We propose the restoration of native forests, which function as disaster-prevention and environmental-preservation forests in urban and pre-urban areas. Native forests grow well with no management. With the ecological technique 600 sites have been successfully revegetated in the Japanese Archipelago, in Malaysia, Melaka, Kuala Lumpur, and Bangkok in Southeast Asia, and in Belem, Brazil, and Concepcion, Chile in South America.     

The effect of oligonucleotide microarray data pre-processing on the analysis of patient-cohort studies

Background  

Intensity values measured by Affymetrix microarrays have to be both normalized, to be able to compare different microarrays by removing non-biological variation, and summarized, generating the final probe set expression values. Various pre-processing techniques, such as dChip, GCRMA, RMA and MAS have been developed for this purpose. This study assesses the effect of applying different pre-processing methods on the results of analyses of large Affymetrix datasets. By focusing on practical applications of microarray-based research, this study provides insight into the relevance of pre-processing procedures to biology-oriented researchers.     

Calculation of the release of total organic matter and total mineral using the hydrodynamic equations applied to palm oil mill effluent treatment by cascaded anaerobic ponds

Anaerobic treatment processes to remove organic matter from palm oil mill effluent (POME) have been used widely in Malaysia. Still the amounts of total organic and total mineral released from POME that may cause degradation of the receiving environment need to be verified. This paper proposes the use of the hydrodynamic equations to estimate performance of the cascaded anaerobic ponds (CAP) and to calculate amounts of total organic matter and total mineral released from POME. The CAP efficiencies to remove biochemical oxygen demands, chemical oxygen demands, total solids and volatile solids (VS) as high as 94.5, 93.6, 96.3 and 98.2 %, respectively, are estimated. The amounts of total organic matter and total mineral as high as 538 kg VS/day and 895 kg FS/day, respectively, released from POME to the receiving water are calculated. The implication of the proposed hydrodynamic equations contributes to more versatile environmental assessment techniques, sometimes replacing laboratory analysis.     

Biomineralization of Weathered Rock Rinds: Examples from the Lower Afroalpine Zone on Mount Kenya

Rock rinds have been used for half a century to date glacial deposits and recently inroads have been developed to use nuclides to provide absolute ages of weathering rinds in pebble clasts. Although maximum and minimum rind thicknesses have helped to elucidate time since deposition and allowed stratigraphic division of deposits at glacial rank, little has been done to investigate the wealth of mineral degradation, growth of alteration products and biomineralization that occur in these weathered crusts. In some cases the mass of microbe-mineral intergrowth is nearly present on a 50%/50% basis, with the biotic mass intergrown with mineral matter to such an extent that it probably controls pH and redox phenomena that act as accelerators in the weathering process. Assuming weathering time spans of 2 × 10⁶ years or more for a complete cycle, eventual clast decomposition is the end product. Here we present evidence of microbe-clast intergrowth from selected sites of Pleistocene age (～70 ka to 2.0 Ma) in the lower Afroalpine of Mt. Kenya and hypothesize about its role in rock decomposition and fossilization of biotic end-members.