Self-stabilization of neuronal networks

Between the extreme views concerning ontogenesis (genetic vs. environmental determination), we use a moderate approach: a somehow pre-established neuronal model network reacts to activity deviations (reflecting input to be compensated), and stabilizes itself during a complex feed-back process. Morphogenesis is based on an algorithm formalizing the compensation theory of synaptogenesis (Wolff and Wagner 1983). This algorithm is applied to randomly connected McCulloch-Pitts networks that are able to maintain oscillations of their activity patterns over time. The algorithm can lead to networks which are morphogenetically stable but preserve self-maintained oscillations in activity. This is in contrast to most of the current models of synaptogenesis and synaptic modification based on Hebbian rules of plasticity. Hebbian networks are morphogenetically unstable without additional assumptions. The effects of compensation on structural and functional properties of the networks are described. It is concluded that the compensation theory of synaptogenesis can account for the development of morphogenetically stable neuronal networks out of randomly connected networks via selective stabilization and elimination of synapses.The logic of the compensation algorithm is based on experimental results. The present paper shows that the compensation theory can not only predict the behavior of synaptic populations (Wagner and Wolff, in preparation), but it can also describe the behavior of neurons interconnected in a network, with the resulting additional system properties. The neuronal interactions-leading to equilibrium in certain cases-are a self-organizing process in the sense that all decisions are performed on the individual cell level without knowing the overall network situation or goal.     

Temperature compensation through systems biology

Temperature has a strong influence on most individual biochemical reactions. Despite this, many organisms have the remarkable ability to keep certain physiological fluxes approximately constant over an extended temperature range. In this study, we show how temperature compensation can be considered as a pathway phenomenon rather than the result of a single-enzyme property. Using metabolic control analysis, it is possible to identify reaction networks that exhibit temperature compensation. Because most activation enthalpies are positive, temperature compensation of a flux can occur when certain control coefficients are negative. This can be achieved in networks with branching reactions or if the first irreversible reaction is regulated by a feedback loop. Hierarchical control analysis shows that networks that are dynamic through regulated gene expression or signal transduction may offer additional possibilities to bring the apparent activation enthalpies close to zero and lead to temperature compensation. A calorimetric experiment with yeast provides evidence that such a dynamic temperature adaptation can actually occur.     

Eye tracking using artificial neural networks for human computer interaction

This paper describes an ongoing project that has the aim to develop a low cost application to replace a computer mouse for people with physical impairment. The application is based on an eye tracking algorithm and assumes that the camera and the head position are fixed. Color tracking and template matching methods are used for pupil detection. Calibration is provided by neural networks as well as by parametric interpolation methods. Neural networks use back-propagation for learning and bipolar sigmoid function is chosen as the activation function. The user's eye is scanned with a simple web camera with backlight compensation which is attached to a head fixation device. Neural networks significantly outperform parametric interpolation techniques: 1) the calibration procedure is faster as they require less calibration marks and 2) cursor control is more precise. The system in its current stage of development is able to distinguish regions at least on the level of desktop icons. The main limitation of the proposed method is the lack of head-pose invariance and its relative sensitivity to illumination (especially to incidental pupil reflections).     

基于生态系统服务价值的区域生态补偿——以山东省为例

区域生态补偿是协调区域发展的重要机制,但区域补偿的依据一直存在争议。综合考虑区域的生态系统服务价值和经济发展水平,提出了生态补偿优先级(ecological compensation priority sequence,ECPS)作为区域间补偿的重要依据。对山东省不同生态区和不同县市的生态系统服务价值和生态补偿优先级进行了计算,从生态区、市和县3个空间尺度分析了山东省开展区域生态补偿的优先领域和补偿机制。结果表明:山东省生态区中处于西部地区的鲁西南平原湖区生态区应优先获得补偿,偏东部的鲁东丘陵生态区和鲁中南山地丘陵生态区应优先支付补偿;在山东省17地级市中菏泽市应优先获得补偿;对青岛、济南、菏泽和东营4个典型市中的各县区进行生态补偿优先级核算,4个城市中补偿优先级最低的均为市区,说明市区是生态系统服务的输入和受益地区,而周围县市的补偿优先级较高,是"生态输出"地区,应该得到区域生态补偿,其中东营河口区补偿优先级最高,为典型的高"生态输出"、经济欠发达的地区,应优先享受区域生态补偿。本研究提出的生态补偿优先级为开展区域生态补偿提供了较为简单可靠的指标,可为山东或其他地区的区域生态补偿提供科学依据。     

构建森林生态补偿机制的关键问题

构建森林生态补偿机制的关键问题主要有三个方面:利益相关者的界定、补偿金额的确定及补偿方式。目前存在的较大争议是森林生态效益货币化计量结果与实际补偿额度之间有巨大差异,一方面森林经营者认为补偿额远远不能满足投入需求,应以生态效益产出为补偿金额的计算依据;另一方面,森林生态效益的很大部分来自自然投入,不能以货币化的形势简单计量。森林生态补偿的国际案例表明:世界各国因森林资源产权制度不同,其森林生态补偿机制有所差异,私有林偏重于市场补偿机制,公有林则偏重于政府主导的补偿机制。森林生态补偿资金主要来自森林生态系统服务用户付费、政府代表受益方付费及国际组织捐赠;在补偿方式上,以政府投资为主,以用户付费和基于市场的认证授权交易为辅。借鉴国际经验,结合我国森林生态效益补偿现状,森林经营者是生态系统服务供给方是确定的,而森林生态系统服务获取方的确定则非常困难。因此,政府主导和第三方介入应是解决森林生态补偿资金来源和补偿的主要方式,受损方及其受损成本是森林生态补偿金额的计算依据。     

地下水生态补偿标准核算模型

地下水是水资源的重要组成部分,在维持生产生活、推动社会经济发展方面具有重要作用。地下水生态补偿有助于促进地下水资源合理开发利用,但是国内外关于此方面尤其是补偿标准的研究非常缺乏。本研究提出由基础、奖惩、科技和风险补偿构成的地下水生态补偿标准核算模型,综合考虑气候条件和经济水平,明确补偿优先等级,并将模型应用于山西省11个市,核算其地下水生态补偿标准。结果表明: 基础补偿在总补偿中占比最大,且非市场价值占比在60%以上,说明地下水具有较高的调节服务价值;2008—2017年,各市发展系数有明显提高,说明区域经济水平提升,补偿能力有所增强;补偿优先等级受地下水非市场价值及区域经济水平的影响,各地补偿优先等级差异明显,需要尽快落实各地的地下水生态补偿工作。同时,建议尽快完善地下水风险补偿制度,设立地下水生态科技补偿专项资金,建立长期有效的地下水生态补偿机制。     

中国矿产资源开发区生态补偿研究进展

矿产资源开发区生态补偿是调整利益相关者因资源开采引发的环境利益和经济利益分配不均,并对矿产资源开发造成的外部成本内部化的制度安排。从矿产资源开发区生态补偿的理论研究、生态补偿机制、生态补偿标准,以及多学科交叉研究四方面对我国生态补偿相关研究进行了总结分析。从中发现:我国矿产资源开发区生态补偿仍以政府主导;矿产资源开发区生态补偿机制有待完善,在补偿主体、客体、途径、期限、内容等研究结论仍不明晰;现有补偿主要以经济补偿为主,补偿模式单一、补偿资金不足;生态补偿标准评估方法各有侧重点,尚未形成系统完善的矿产资源开发区生态补偿标准评估方法。今后应加强以下研究:强化生态补偿的理论研究,从市场产权交易和政府监督出发,构建科学生态补偿机制,结合区域自然、社会、经济特征,确定生态补偿标准;科学合理评估矿产资源开发造成的生态服务价值损益;结合生态补偿理论研究,采用多学科交叉分析,根据矿产资源开发阶段,构建矿产资源开发区生态补偿框架体系,明确生态补偿主客体、标准、方式、期限等;提炼矿产资源开发区生态补偿类型与模式,并构建矿产资源开发区生态补偿长效机制。     

主体功能区视角下的生态补偿研究——以湖北省为例

合理界定区域生态补偿主客体,确定生态补偿优先级是构建区域生态补偿机制的核心内容。从主体功能区视角出发,在测算湖北省生态系统服务价值的基础上,界定生态受偿与补偿支付主体,确定生态受偿与补偿支付等级与次序。结果表明：（1）湖北省生态系统服务总价值、市场价值和非市场价值在空间分布上具有相似性,总体呈现出"西部高,东中低"的格局,高值区多集中于重点生态功能区和农产品主产区,低值区多集中于重点开发区;（2）30个重点生态功能区的生态受偿等级总体分为五级,呈现出"西高东低"的空间分布格局,房县为第一生态受偿区;（3）29个农产品主产区生态受偿优先级总体分为五级,随县为生态受偿一级区域;（4）30个重点开发区的补偿支付等级总体分为五级,呈现出"东先西后"的空间分布格局,在生态补偿支付实践中,国家层面重点开发区应先于省级层面重点开发区。     

The role of domain redundancy in genetic robustness against null mutations

A key question in molecular genetics is why severe gene mutations often do not result in a detectable abnormal phenotype. Alternative networks are known to be a gene compensation mechanism. Gene redundancy, i.e. the presence of a duplicate gene (or paralog) elsewhere in the genome, also underpins many cases of gene dispensability. Here, we investigated the role of partial duplicate genes on dispensability, where a partial duplicate is defined as a gene that has no paralog but which codes for a protein made of domains, each of which belongs to at least another protein. The rationale behind this investigation is that, as a partial duplicate codes for a domain redundant protein, we hypothesised that its deletion might have a less severe phenotypic effect than the deletion of other genes. This prompted us to (re)address the topic of gene dispensability by focusing on domain redundancy rather than on gene redundancy. Using fitness data of single-gene deletion mutants of Saccharomyces cerevisiae, we will show that domain redundancy is a compensation mechanism, the strength of which is lower than that of gene redundancy. Finally, we shall discuss the molecular basis of this new compensation mechanism.     

Fibrillins can co-assemble in fibrils,but fibrillin fibril composition displays cell-specific differences

Fibrillins are microfibril-forming extracellular matrix macromolecules that modulate skeletal development. In humans, mutations in fibrillins result in long bone overgrowth as well as other distinct phenotypes. Whether fibrillins form independent microfibrillar networks or can co-polymerize, forming a single microfibril, is not known. However, this knowledge is required to determine whether phenotypes arise because of loss of singular or composite functions of fibrillins. Immunolocalization experiments using tissues and de novo matrices elaborated by cultured cells demonstrated that both fibrillins can be present in the same individual microfibril in certain tissues and that both fibrillins can co-polymerize in fibroblast cultures. These studies suggest that the molecular information directing fibrillin fibril formation may be similar in both fibrillins. Furthermore, these studies provide a molecular basis for compensation of one fibrillin by the other during fetal life. In postnatal tissues, fibrillin-2 antibodies demonstrated exuberant staining in only one location: peripheral nerves. This surprising finding implicates distinct functions for fibrillin-2 in peripheral nerves, because a unique feature in humans and in mice mutant for fibrillin-2 is joint contractures that resolve over time.     

Adaptive temperature compensation in circadian oscillations

A temperature independent period and temperature entrainment are two defining features of circadian oscillators. A default model of distributed temperature compensation satisfies these basic facts yet is not easily reconciled with other properties of circadian clocks, such as many mutants with altered but temperature compensated periods. The default model also suggests that the shape of the circadian limit cycle and the associated phase response curves (PRC) will vary since the average concentrations of clock proteins change with temperature. We propose an alternative class of models where the twin properties of a fixed period and entrainment are structural and arise from an underlying adaptive system that buffers temperature changes. These models are distinguished by a PRC whose shape is temperature independent and orbits whose extrema are temperature independent. They are readily evolved by local, hill climbing, optimization of gene networks for a common quality measure of biological clocks, phase anticipation. Interestingly a standard realization of the Goodwin model for temperature compensation displays properties of adaptive rather than distributed temperature compensation.     

Functional compensation between hematopoietic stem cell clones in vivo

In most organ systems, regeneration is a coordinated effort that involves many stem cells, but little is known about whether and how individual stem cells compensate for the differentiation deficiencies of other stem cells. Functional compensation is critically important during disease progression and treatment. Here, we show how individual hematopoietic stem cell (HSC) clones heterogeneously compensate for the lymphopoietic deficiencies of other HSCs in a mouse. This compensation rescues the overall blood supply and influences blood cell types outside of the deficient lineages in distinct patterns. We find that highly differentiating HSC clones expand their cell numbers at specific differentiation stages to compensate for the deficiencies of other HSCs. Some of these clones continue to expand after transplantation into secondary recipients. In addition, lymphopoietic compensation involves gene expression changes in HSCs that are characterized by increased lymphoid priming, decreased myeloid priming, and HSC self‐renewal. Our data illustrate how HSC clones coordinate to maintain the overall blood supply. Exploiting the innate compensation capacity of stem cell networks may improve the prognosis and treatment of many diseases.     

生态补偿的机理与准则

分析国内外生态补偿实践和理论研究的基础上,从可持续发展角度探讨生态补偿的基本内涵;通过对生态系统自组织与反馈、恢复机制的剖析,提出了生态补偿应遵循的基本准则;结合国情,探讨了生态补偿亟待解决的实践困惑和应对策略。     

赣西地区生态系统服务价值与生态补偿策略

生态补偿是解决区域生态保护与经济发展诸多矛盾的一项重要措施。基于土地利用变化,采用当量因子计算方法,对赣西地区2002-2016年的生态系统服务价值时空变化特征进行了分析。综合考虑区域自然、经济发展水平,测算了区域内各县（市、区）生态补偿优先级和生态补偿额度,探讨了区域生态补偿策略。研究结果表明：（1）赣西地区林地的生态系统服务价值最高,占总价值比例的80.39%,水源涵养、土壤保持、气体调节等是生态系统内的主要服务类型,三者占到总比例的51.18%,但从整个区域来看,总的生态系统服务价值和生态系统各单项服务价值均呈不同程度降低趋势。从县域单元看,生态系统服务价值相对较低的分别是渝水区、樟树市、丰城市和高安市;相对较高的主要分布在铜鼓县、宜丰县、奉新县和靖安县;生态系统服务价值下降率最高的是安源区、袁州区和渝水区。（2）赣西地区理论生态补偿总额度为3.9262亿元,占总GDP的0.13%,林地生态系统的补偿额为3.1820亿元,占总补偿的81.04%。从县域单元看,铜鼓、靖安和宜丰县为优先补偿顺序的前三位,补偿额度分别为0.9622,0.6822和0.4735亿元,占总补偿额度的53.94%,处于后三位的分别是安源区、樟树市和上高县,占总补偿额度的1.66%。测算出的补偿顺序与理论补偿额度,与县区统计数据资料部分印证,这表明该研究具有一定的科学性和合理性。补偿资金占GDP值比重低,对地方财政压力小,在保护区域生态环境与可持续发展的具体实践中,具有一定的可操作性。     

Global research trends and gaps in ecological compensation studies from 1990 to 2020: A scientometric review

Ecosystems are facing severe destruction and threats due to unreasonable human utilization. Repairing damage to nature and protect biodiversity through ecological compensation will be an inevitable measure for achieving sustainable development. To explore the current research hotspots and future research directions of ecological compensation, this paper tries to search the WoS Core Collection and collects 685 ecological compensation papers published between 1990 and 2020. R language and CiteSpace software were applied in this paper. It is found that: (1) The number of articles has gone through the initial explorations, fluctuating growth, and rapid development of the field from 1990 to 2020. Only 7.5% of authors have published more than two papers. (2) Regarding the production of papers, the top 3 countries are the US, China, and the UK. At present, the majority of countries focus on independent research, and international cooperation is gradually strengthening. (3) The current research hotpots mainly invlove biodiversity and sustainable development, ecological compensation for forests and water resources, China's Grain-to-Green Project, poverty reduction, livelihood issues, public participation willingness and equity issues, indicating that ecological compensation is a rapidly emerging interdisciplinary academic field. (4) The results reveal several research directions in the future: strengthening theoretical research, resolving issues pertaining to the complex relationships among stakeholders, encouraging a transformation from qualitative to quantitative research, increasing the focus of ecological compensation models on local conditions, and applying more scientific models and high-tech tools in effect evaluation.     

湿地保护区周边农户生态补偿意愿比较

湿地生态补偿研究一直是国内外学者们研究的热点和难点。运用问卷调查方法和统计学的多元回归模型,分析湿地保护区周边生态补偿机制中微观经济主体-农户的行为与选择的问题,确定农户的生态补偿意愿值,及影响农户生态补偿意愿的主要影响因素并做比较分析。以陕西朱鹮国家级自然保护区为例,应用条件价值法(CVM),计量了2008年和2011年朱鹮保护区周边社区农户的绿色水稻生态补偿意愿值,分别为:3560.56元/hm2和3679.83元/hm2;Logistic回归模型分析的结果表明,同时影响农户2008年和2011年生态补偿意愿的相同因素是水田面积占耕地总面积比重,另外影响显著的因素主要是家庭年均收入、是否有非农收入、农户生产区距离朱鹮保护区核心区的远近、水稻田由于保护朱鹮减产是否严重。研究结果表明:应以政府为主导,加大湿地生态补偿的力度并建立生态补偿的长效机制。对推进和落实我国湿地生态经济补偿机制,特别是为陕西朱鹮湿地保护区生态经济补偿机制的完善具有参考价值。     

Mesoderm and ectoderm lineages in the crustacean Parhyale hawaiensis display intra-germ layer compensation

In Parhyale hawaiensis, the first three divisions are holoblastic and asymmetric, resulting in an embryo comprised of eight cells—four macromeres and four micromeres. Lineage studies performed at this stage demonstrate that the progeny of each cell contribute to specific portions of different germ layers. However, it is not known if this lineage pattern means a given blastomere is committed to its specific fate, indicative of mosaic development, or if regulation can occur between blastomere progeny so that the loss of a blastomere could be compensated for during development. Furthermore, if compensation occurs, what would be the source of such replacement? To investigate these possibilities, we performed ablation experiments at the eight-cell stage. We find that loss of blastomeres results in compensation. To determine the compensation pattern, we combined ablation and cell lineage tracing to reveal that progeny of mesoderm and ectoderm producing blastomeres display intra-germ layer compensation. Furthermore, by ablating lineages later in development, we identify a key interval between gastrulation and germband elongation after which compensation no longer occurs. Our results suggest that Parhyale possesses a mechanism to assess the status of mesoderm and ectoderm formation and alter development to replace the missing portions of these lineages.     

基于外溢生态系统服务价值的区域生态补偿机制研究

由于不同的区域存在着资源分配、经济发展的不平等性,区域间的生态补偿日益受到关注。但区域生态补偿的依据一直存在争议,中国尚没有完善的区域综合生态补偿机制。提出了一种生态系统服务外溢理论,以扣除当地生态服务使用量后外溢的生态价值作为生态补偿依据,建立了区域综合生态补偿框架,同时考虑区域生态服务外溢占用情况和经济发展水平,有针对性地制定了9种补偿方案。由于生态系统服务具有流动性,生态补偿的受偿方和补偿方并非一一对应的关系,所以各行政区域之间进行补偿资金的。横向转移需要在全省或全国层面进行统筹和保障,最后统筹结果的少量盈缺再由中央财政或地方政府通过纵向转移支付辅助调平。构建了生态补偿模型和方案,针对现有生态系统服务价值评估结果,利用综合生态补偿机制分别分析了2015年长江流域上海、江西、四川等6个典型地区的生态补偿支付方案。结果表示需要接受生态补偿的地区有青海、四川、湖南和江西,应分别得到横向转移支付资金32.26亿元、153.3亿元、59.08亿元、67.1亿元;需要提供生态补偿的地区有浙江、上海,应该分别支付横向转移支付资金1.97亿元和47.31亿元。建立的补偿框架提高了各区域的参与度,对促进生态建设、统筹区域的协调发展、体现社会公平性有重要意义。     

X-marks the spot: X-chromosome identification during dosage compensation

Dosage compensation is the essential process that equalizes the dosage of X-linked genes between the sexes in heterogametic species. Because all of the genes along the length of a single chromosome are co-regulated, dosage compensation serves as a model system for understanding how domains of coordinate gene regulation are established. Dosage compensation has been best studied in mammals, flies and worms. Although dosage compensation systems are seemingly diverse across species, there are key shared principles of nucleation and spreading that are critical for accurate targeting of the dosage compensation complex to the X-chromosome(s). We will highlight the mechanisms by which long non-coding RNAs function together with DNA sequence elements to tether dosage compensation complexes to the X-chromosome. This article is part of a Special Issue entitled: Chromatin and epigenetic regulation of animal development.     

Real-time tumor tracking with an artificial neural networks-based method: A feasibility study

The purpose of this study was to develop and assess the performance of a tumor tracking method designed for application in radiation therapy. This motion compensation strategy is currently applied clinically only in conventional photon radiotherapy but not in particle therapy, as greater accuracy in dose delivery is required.We proposed a tracking method that exploits artificial neural networks to estimate the internal tumor trajectory as a function of external surrogate signals. The developed algorithm was tested by means of a retrospective clinical data analysis in 20 patients, who were treated with state of the art infra-red motion tracking for photon radiotherapy, which is used as a benchmark. Integration into a hardware platform for motion tracking in particle therapy was performed and then tested on a moving phantom, specifically developed for this purpose.Clinical data show that a median tracking error reduction up to 0.7 mm can be achieved with respect to state of the art technologies. The phantom study demonstrates that a real-time tumor position estimation is feasible when the external signals are acquired at 60 Hz.The results of this work show that neural networks can be considered a valuable tool for the implementation of high accuracy real-time tumor tracking methodologies.