The use of HRMAS NMR spectroscopy to study the <Emphasis Type="Italic">in vivo</Emphasis> intra–cellular carbon/nitrogen ratio of <Emphasis Type="Italic">Solieria chordalis</Emphasis> (Rhodophyta)

The red alga Solieria chordalis (J. Agardh) C. Agardh (Rhodophyta) was used as a model to investigate the effects of changes in seawater salinity on the carbon/nitrogen ratio. Carbohydrates and nitrogenous metabolites are major components of this alga and their metabolisms are intimately linked. Previous publications have provided a solid database for these two primary metabolic pathways from experiments and observations in situ. Storage products (e.g. floridean starch), cell wall polysaccharides (carrageenan) and low molecular weight carbohydrates such as floridoside and digeneaside are major compounds constituting the pool of available carbon. Compounds such as amino acids and peptides, constitute the pool of nitrogen. This study focuses on the intracellular C/N ratio inside the pool of low molecular weight compounds. This C/N ratio can be defined as the balance between carbohydrates and amino acids. High–resolution magic angle spinning nuclear magnetic resonance spectroscopy (HRMAS NMR) provides a powerful approach for in vivo analysis of the pool of intracellular organic compounds. These in vivo results were complimented with quantitative data obtained from high performance liquid chromatography (HPLC). In vivo and in vitro experimental analyses provided a intracellular molecular balance and defined the C/N ratio. In order to study the effect of salt stress on the carbon/nitrogen ratio, S. chordalis was cultured under controlled conditions. Effects of hyposalinity and hypersalinity stresses (low 22 ‰ and high 50 ‰ salinity) were tested. Both HPLC and NMR data, obtained on stressed and unstressed algae, generated insights into variations of carbonated and nitrogenous metabolites, involving changes of the C/N ratios, and demonstrated the adaptive responses of the seaweed. 19th International Seaweed Symposium KOBE JAPAN.     

Woodrat (<Emphasis Type="Italic">Neotoma</Emphasis>) herbivores maintain nitrogen balance on a low-nitrogen,high-phenolic forage, <Emphasis Type="Italic">Juniperus monosperma</Emphasis>

The acquisition of adequate quantities of nitrogen is a challenge for herbivorous vertebrates because many plants are in low nitrogen and contain secondary metabolites that reduce nitrogen digestibility. To investigate whether herbivores maintain nitrogen balance on plant diets low in nitrogen and high in secondary compounds, we studied the effect of juniper (Juniperus monosperma) ingestion on the nitrogen balance of two species of herbivorous woodrats (Neotoma stephensi and N. albigula). These woodrat species feed on the foliage of juniper: N. stephensi is a juniper specialist, whereas N. albigula is a generalist that incorporates some juniper in its diet. Based on the nitrogen contents of the natural diets of these woodrats, we predicted that the generalist would be in negative nitrogen balance on a juniper diet whereas the specialist would not be affected. We found that both species of woodrat had low-nitrogen requirements (334.2 mg N/kg^0.75/day) and that a diet of 50% juniper did not result in negative nitrogen balance for either species. However, excretion patterns of nitrogen were altered; on the 50% juniper diet, fecal nitrogen losses increased ~38% and urinary nitrogen losses were half that of the control diet. The results suggest that absorption and detoxification of juniper secondary compounds may be more important for restricting juniper intake by the generalist than nitrogen imbalance.     

Nitrogen attenuation in the Connecticut River,northeastern USA; a comparison of mass balance and N<Subscript>2</Subscript> production modeling approaches

Two methods were used to measure in-stream nitrogen loss in the Connecticut River during studies conducted in April and August 2005. A mass balance on nitrogen inputs and output for two study reaches (55 and 66 km), at spring high flow and at summer low flow, was computed on the basis of total nitrogen concentrations and measured river discharges in the Connecticut River and its tributaries. In a 10.3 km subreach of the northern 66 km reach, concentrations of dissolved N₂ were also measured during summer low flow and compared to modeled N₂ concentrations (based on temperature and atmospheric gas exchange rates) to determine the measured “excess” N₂ that indicates denitrification. Mass balance results showed no in-stream nitrogen loss in either reach during April 2005, and no nitrogen loss in the southern 55 km study reach during August 2005. In the northern 66 km reach during August 2005, however, nitrogen output was 18% less than the total nitrogen inputs to the reach. N₂ sampling results gave an estimated rate of N₂ production that would remove 3.3% of the nitrogen load in the river over the 10.3 km northern sub-reach. The nitrogen losses measured in the northern reach in August 2005 may represent an approximate upper limit for nitrogen attenuation in the Connecticut River because denitrification processes are most active during warm summer temperatures and because the study was performed during the annual low-flow period when total nitrogen loads are small.     

Benefit to N<Subscript>2</Subscript>-fixing alder of extending growth period at the cost of leaf nitrogen loss without resorption

This study examines the adaptive role of not resorbing N in N₂-fixing deciduous trees in terms of their energy balance. The autumnal growth of N₂-fixing Alnus firma Sieb. et Zucc. (alder) was compared with that of the non-N₂-fixing Morus bombycis Koizumi (mulberry), which resorbs leaf N. The freezing resistance of leaves of both species was –2°C. Mulberry seedlings lost their photosynthetic ability in mid-October, although the minimum temperature was still above 0°C. Thereafter, their leaves turned yellow and were gradually shed. In contrast, seedlings of the alder maintained their photosynthetic ability until mid-November, when the minimum temperature fell to the freezing resistance limit. Thereafter, their leaves were shed quickly without an autumn tint. The mulberry resorbed 48.9% of leaf N, whereas the alder resorbed hardly any. These results show that, compared with the mulberry tree, the alder extended its growth period for 1 month in return for losing leaf N without resorption. The amount of energy assimilated by the alder in the extended growth period was about six times that required for compensating for the nitrogen loss, if the compensation is dependent only on the tree's own nitrogen fixation. This surplus energy balance has probably allowed N₂-fixing deciduous trees to evolve their non-N-resorbing trait.     

Dynamic data replacement and adaptive scheduling policies in spark

Improper data replacement and inappropriate selection of job scheduling policy are important reasons for the degradation of Spark system operation speed, which directly causes the performance degradation of Spark parallel computing. In this paper, we analyze the existing caching mechanism of Spark and find that there is still more room for optimization of the existing caching policy. For the task structure analysis, the key information of Spark tasks is taken out to obtain the data and memory usage during the task runtime, and based on this, an RDD weight calculation method is proposed, which integrates various factors affecting the RDD usage and establishes an RDD weight model. Based on this model, a minimum weight replacement algorithm based on RDD structure analyzing is proposed. The algorithm ensure that the relatively more valuable data in the data replacement process can be cached into memory. In addition, the default job scheduling algorithm of the Spark framework considers a single factor, which cannot form effective scheduling for jobs and causes a waste of cluster resources. In this paper, an adaptive job scheduling policy based on job classification is proposed to solve the above problem. The policy can classify job types and schedule resources more effectively for different types of jobs. The experimental results show that the proposed dynamic data replacement algorithm effectively improves Spark's memory utilization. The proposed job classification-based adaptive job scheduling algorithm effectively improves the system resource utilization and shortens the job completion time.

     

Evaluation of the diversity of nitrogen-fixing bacteria in soybean rhizosphere by <Emphasis Type="Italic">nifH</Emphasis> gene analysis

Biological nitrogen fixation plays an important role in the nitrogen balance of agricultural ecosystems and provides an essential part of nitrogen nutrition for plants, even in conditions of intensive fertilization. The main agrobiotechnological method for soybean cultivation (Glycine max (L.) Merril) is an application of microbial preparations based on Bradyrhizobium japonicum. Successful inoculation strongly depends on the interactions between the introduced microorganism and the aboriginal rhizosphere microorganisms. To evaluate the composition of diazotrophic communities, a study of the diversity of the molecular marker for nitrogen fixation, the nifH gene, in the samples of soybean rhizosphere soil was carried out. Experiments were performed in the variants when soybean was cultivated without inoculation and after adding bacterial preparations, as well as in enrichment cultures of diazotrophs. The revealed diazotrophic microorganisms demonstrated low level of similarity to the known microorganisms (74–95% identity by nucleotides), and were identified as species of the phyla Firmicutes and Proteobacteria. In the composition of nitrogen-fixing communities in the rhizosphere soil, the microorganisms of the genera Clostridium, Paenibacillus, and Spirochaeta were shown to prevail.     

More is less: agricultural impacts on the N cycle in Argentina

Human impact on nitrogen cycling, in particular the introduction of reactive nitrogen in terrestrial and aquatic ecosystems, can be examined at multiple scales, from the global impact on atmospheric chemistry to the impact of human activities on soil organic matter and fertility at the scale of square meters. Nevertheless, anthropogenic loading of nitrogen cycling in natural and managed ecosystems can be seen most directly at the regional scale, where concentrated human activity results in disruption of the nitrogen balance, with consequences for biogeochemical cycling and their interactions. Differences in land-use and agricultural practices between North and South America, and the importance of economic drivers that determine the fate of new reactive nitrogen demonstrate a contrasting picture of human impact on N cycling when the consequences are considered at the global vs. the regional scale. In particular, in the Pampa region of Argentina, the central agricultural zone of the country, the expansion of soybean cultivation in the last 20 years and the use of synthetic fertilizers have resulted in an influx of reactive nitrogen into these systems, with unexpected consequences for the nitrogen balance. A mass balance of nitrogen for soybean demonstrates that increased nitrogen inputs from biological fixation do not compensate for losses due to seed export, such that most areas under soybean cultivation are currently experiencing a substantive net loss of nitrogen. In addition, other crops that are currently being fertilized still show a net loss of nitrogen also due to the effect of primary exports from these agroecosystems. These simple models demonstrate that socioeconomic factors in large part drive the contrasting effects of anthropogenic impact on nitrogen cycling at global vs. regional scales. The future impact on nitrogen cycling in the Americas requires an integration of both ecological factors and socioeconomic drivers that will ultimately determine human disruption of the nitrogen cycle.     

Carbon/Nitrogen Imbalance Associated with Drought-Induced Leaf Senescence in Sorghum bicolor

Drought stress triggers mature leaf senescence, which supports plant survival and remobilization of nutrients; yet leaf senescence also critically decreases post-drought crop yield. Drought generally results in carbon/nitrogen imbalance, which is reflected in the increased carbon:nitrogen (C:N) ratio in mature leaves, and which has been shown to be involved in inducing leaf senescence under normal growth conditions. Yet the involvement of the carbon/nitrogen balance in regulation of drought-induced leaf senescence is unclear. To investigate the role of carbon/nitrogen balance in drought-induced senescence, sorghum seedlings were subjected to a gradual soil drought treatment. Leaf senescence symptoms and the C:N ratio, which was indicated by the ratio of non-structural carbohydrate to total N content, were monitored during drought progression. In this study, leaf senescence developed about 12 days after the start of drought treatment, as indicated by various senescence symptoms including decreasing photosynthesis, photosystem II photochemistry efficiency (Fv/Fm) and chlorophyll content, and by the differential expression of senescence marker genes. The C:N ratio was significantly enhanced 10 to 12 days into drought treatment. Leaf senescence occurred in the older (lower) leaves, which had higher C:N ratios, but not in the younger (upper) leaves, which had lower C:N ratios. In addition, a detached leaf assay was conducted to investigate the effect of carbon/nitrogen availability on drought-induced senescence. Exogenous application of excess sugar combined with limited nitrogen promoted drought-induced leaf senescence. Thus our results suggest that the carbon/nitrogen balance may be involved in the regulation of drought-induced leaf senescence.     

A genetic algorithm with adaptive mutations and family competition for training neural networks

In this paper, we present a new evolutionary technique to train three general neural networks. Based on family competition principles and adaptive rules, the proposed approach integrates decreasing-based mutations and self-adaptive mutations to collaborate with each other. Different mutations act as global and local strategies respectively to balance the trade-off between solution quality and convergence speed. Our algorithm is then applied to three different task domains: Boolean functions, regular language recognition, and artificial ant problems. Experimental results indicate that the proposed algorithm is very competitive with comparable evolutionary algorithms. We also discuss the search power of our proposed approach.     

Wind power prediction based on neural network with optimization of adaptive multi-group salp swarm algorithm

Salp swarm algorithm (SSA) is a swarm intelligence algorithm inspired by the swarm behavior of salps in oceans. In this paper, a adaptive multi-group salp swarm algorithm (AMSSA) with three new communication strategies is presented. Adaptive multi-group mechanism is to evenly divide the initial population into several subgroups, and then exchange information among subgroups after each adaptive iteration. Communication strategy is also an important part of adaptive multi-group mechanism. This paper proposes three new communication strategies and focuses on promoting the performance of SSA. These measures significantly improve the cooperative ability of SSA, accelerate convergence speed, and avoid easily falling into local optimum. And the benchmark functions confirm that AMSSA is better than the original SSA in exploration and exploitation. In addition, AMSSA is combined with prediction of wind power based on back propagation (AMSSA-BP) neural network. The simulation results show that the AMSSA-BP neural network prediction model can achieve a better prediction effect of wind power.

     

乳酸菌对肠免疫调节功能研究进展

乳酸菌作为益生菌是人体肠道中的重要生理菌群,对维持肠道的微生态平衡,缓解过敏,抑制肠道炎症反应等免疫调节方面有重要作用。本文综述了乳酸菌对肠免疫系统的调节作用,主要从调节先天性免疫和获得性免疫系统角度出发,讨论相关研究进展,并对乳酸菌在免疫调节方面的应用前景作了展望。     

<Emphasis Type="Italic">Argiope bruennichi</Emphasis> shows a drinking-like behaviour in web hub decorations (Araneae,Araneidae)

As stationary predators, araneid spiders that lack protective retreats are especially vulnerable to abiotic influences. Species of the genus Argiope permanently remain at the hub of their orb webs and are thereby exposed to desiccating circumstances. Like other land arthropods, spiders must balance their hygric status. Beside desiccation avoidance behaviours, they can manage this balance by water gain through either liquefied prey items or direct ingestions of free water. Drinking-like behaviours are sparely documented for Araneids. We observed Argiope bruennichi ingesting accumulated water droplets from the silk-overstitched web hub, a part of the web decoration, and subsequently tested whether this behaviour is a regular feature of this species. In 50% of our observations, spiders that had been sprayed with water actively searched the hub decoration for water droplets and ingested them. The behavioural elements were very stereotypic among the tested individuals. Significantly, A. bruennichi females only searched the covered web hubs for water, even though the entire web was moistened. These data suggest that hub decorations of A. bruennichi might have an adaptive significance by helping to maintain a balance of water metabolism, adding yet another element to the spirited debate about the functional significance of web decorations.     

New appreciation of nitrogen balance obtained from Japanese navy data.

In 1943, one of the authors (Miura) worked on the nutritional study of Japanese navy sailors. Fortunately the raw data of this study were conserved in secret in the private file of Miura. Recently, another author (Hashimoto) was seeking the data concerning nitrogen balance of Japanese people. Miura, recalling the remaining of the old data; he picked up the records of nitrogen metabolism of three sailors (A, B and C). Subject A, 34 years old, showed a net nitrogen balance of 77 g of protein per day; whereas subject B, 20 years old and subject C, 15 years old showed positive nitrogen balance. The authors remarked the relationship between unabsorbed nitrogen and nitrogen balance: The unabsorbed ratio of food nitrogen was the greatest in A (29%), but in B (22%) and C (19%) showed rather low ratio. Recent study using tracers, revealed that some amino acids, especially unabsorbed leucine in the intestine, might act as regulators of nitrogen balance in adults.     

MIMO adaptive linearizing control of fed-batch amino acids simultaneous production

A new approach for modelling of fed batch amino acids simultaneous production is proposed. A MIMO adaptive non-linear control algorithm is designed to regulate the sugar concentration and the nitrogen concentration. A control scheme is chosen for practical implementation.     

Respiration and nitrogen and carbohydrate contents in perennial rhizome-forming plants as related to realization of different adaptive strategies

Accumulation of biomass, the respiration rate, and the contents of total nitrogen and nonstructural carbohydrates were studied for 14 perennial long-rhizome-forming species differing in the type of adaptive strategy. Fast-growing species with well expressed competitive-ruderal properties (CR plants) were characterized by a higher productivity, a better nitrogen status, and more intense respiration than slowly growing stress-tolerant species (S plants). The proportion of rhizomes in the weight of the whole plant varied from 30 to 70% and was higher in S species. In CR species, the respiration rate measured in rhizomes at 20°C was equal on the average to 1 mg CO₂/(g dry wt h), which was threefold higher than in S species. In S species, a considerable amount of nitrogen (50%) was present in rhizomes, whereas in CR species, most part of nitrogen (70–80%) was localized in the aboveground organs. The correlation analysis revealed a direct dependence (r = 0.75) between the respiration rate and nitrogen content in leaves; in the rhizomes the correlation between these indices was low (r = 0.39). The content of carbohydrates in the leaves and sink organs, rhizomes, was determined by the type of plant ecological strategy and life duration of their photosynthesizing organs (summergreen, evergreen species). In general, the results obtained demonstrated a close relation between adaptive strategy, ecological confinement, the rhythm of seasonal development, and physiological properties of long-rhizome-forming plants.     

Utilization of urea by leaves of bromeliad <Emphasis Type="Italic">Vriesea gigantea</Emphasis> under water deficit: much more than a nitrogen source

Vriesea gigantea Gaudichaud is an epiphytic bromeliad with a high capacity to take up urea. In plants, urea is hydrolyzed by urease into ammonium and CO₂, providing nitrogen to the plant. Most studies of urea nutrition have focused only on nitrogen metabolism, whereas scarce attention has been given to CO₂ assimilation. Therefore, this study attempted to investigate whether urea could play an important role as a carbon source, which could be of a significant importance under water deficit conditions because of the limitation in atmospheric CO₂ influx into the leaves due to stomatal closure. In this study, detached leaves of V. gigantea were exposed to water deficit and supplied with urea. The most photosynthetic parts of the leaf (mainly the apical leaf portion) showed higher urease activities and CO₂ buildup near chloroplasts, particularly during the nighttime under water deficit conditions when compared to urea application without the water deficit. Moreover, part of the CO₂ generated from urea hydrolysis was fixed into malate, probably via phosphoenolpyruvate carboxylase. Therefore, urea may contribute to the carbon balance of plants under water deficit conditions. Our data suggest that, besides being a source of nitrogen, urea might also be an important carbon source during CO₂-limited conditions in leaves of epiphytic bromeliads.     

Differences in response to simulated herbivory between <Emphasis Type="Italic">Quercus crispula</Emphasis> and <Emphasis Type="Italic">Quercus dentata</Emphasis>

To evaluate the responses of Quercus crispula and Quercus dentata to herbivory, their leaves were subjected to simulated herbivory in early spring and examined for the subsequent changes in leaf traits and attacks by chewing herbivores in mid summer. In Quercus crispula, nitrogen content per area was higher in artificially damaged leaves than in control leaves. This species is assumed to increase the photosynthetic rate per area by increasing nitrogen content per area to compensate leaf area loss. In Quercus dentata, nitrogen content per area did not differ between artificially damaged and control leaves, while nitrogen content per mass was slightly lower in artificially damaged leaves. The difference in their responses can be attributable to the difference in the architecture of their leaves and/or the severeness of herbivory. The development of leaf area from early spring to mid summer was larger in artificially damaged leaves than in control leaves in both species, suggesting the compensatory response to leaf area loss. Leaf dry mass per unit area was also larger in artificially damaged leaves in both species, but the adaptive significance of this change is not clear. In spite of such changes in leaf traits, no difference was detected in the degree of damage by chewing herbivores between artificially damaged and controlled leaves in both species.     

Nitrogen Depletion and Redistribution by Free‐Ranging Cattle in the Restoration Process of Mosaic Landscapes: The Role of Foraging Strategy and Habitat Proportion

In a mosaic landscape in N‐Belgium (W‐Europe), consisting of forest, grassland, and wooded pasture on former agricultural land, we assessed nitrogen redistribution by free‐ranging cattle (±0.2 animal units ha^?1 yr^?1). We examined if the spatial redistribution of nitrogen among habitats by cattle could restore nutrient‐poor conditions in preferred foraging habitats, and conversely whether such translocation could lead to extreme eutrophication in preferred resting habitats. We used nitrogen content of different diet classes, habitat use, foraging and defecation behavior, weight gain, and nitrogen losses in the actual situation to explore four different habitat proportion scenarios and two different foraging strategies to calculate a net nitrogen balance per habitat. An atmospheric deposition of 30 kg N ha^?1 yr^?1 with varying interception factors according to the habitat types was included in an integrated nitrogen balance. All scenarios showed a net nitrogen transport from grassland and wooded pasture to forest habitat. We found that nitrogen redistribution strongly depends on habitat proportion. Nitrogen losses from preferred grassland habitat can be high, given its proportion is small. Depletion is only to be expected at excretion‐free areas and probably is of minor importance to trigger the establishment of woody species. In general, nitrogen transported by cattle was much lower than input by atmospheric deposition, but grazing can compensate for high N inputs in excretion‐free areas and maintain grassland types that support critical loads of 20–25 kg N ha^?1 yr^?1. In none of the scenarios, N transport by cattle resulted in the exceeding of critical nitrogen loads to vulnerable forest ground vegetation.