Evidence for repeated acquisition and loss of complex body-form characters in an insular clade of Southeast Asian semi-fossorial skinks

Evolutionary simplification, or loss of complex characters, is a major theme in studies of body-form evolution. The apparently infrequent evolutionary reacquisition of complex characters has led to the assertion (Dollo's Law) that once lost, complex characters may be impossible to re-evolve, at least via the exact same evolutionary process. Here, we provide one of the most comprehensive, fine-scale analyses of squamate body-form evolution to date, introducing a new model system of closely related, morphologically variable, lizards. Our phylogenetic results support independent instances of complete limb loss as well as multiple instances of digit and external ear opening loss and re-acquisition. Even more striking, we find strong statistical support for the re-acquisition of a pentadactyl body form from a digit-reduced ancestor. Our study reveals that species of the genus Brachymeles exemplify regions of morphospace (body plans) previously undocumented in squamates. Our findings have broad, general implications for body-form evolution in burrowing vertebrates: whatever constraints have shaped trends in morphological evolution among other squamate groups (excluding Bipes) have been lost in this one exemplary clade. The results of our study join a nascent body of literature showing strong statistical support for character loss, followed by evolutionary re-acquisition of complex structures associated with a generalized pentadactyl body form.     

What can we learn from Einstein and Arrhenius about the optimal flow of our blood?

Background

The oxygen flow in humans and other higher animals depends on the erythrocyte-to-blood volume ratio, the hematocrit. Since it is physiologically favourable when the flow of oxygen transport is maximum it can be assumed that this situation has been achieved during evolution. If the hematocrit was too low, too few erythrocytes could transport oxygen. If it was too high, the blood would be very viscous, so that oxygen supply would again be reduced.

Methods

The theoretical optimal hematocrit can be calculated by considering the dependence of blood viscosity on the hematocrit. Different approaches to expressing this dependence have been proposed in the literature. Here, we discuss early approaches in hydrodynamics proposed by Einstein and Arrhenius and show that especially the Arrhenius equation is very appropriate for this purpose.

Results & conclusions

We show that despite considerable simplifications such as neglecting the deformation, orientation and aggregation of erythrocytes, realistic hematocrit values of about 40% can be derived based on optimality considerations. Also the prediction that the ratio between the viscosities of the blood and blood plasma at high shear rates nearly equals Euler's constant (2.718) is in good agreement with observed values. Finally, we discuss possible extensions of the theory. For example, we derive the theoretical optimal hematocrit for persevering divers among marine mammals to be 65%, in excellent agreement with the values observed in several species.

General significance

These considerations are very important for human and animal physiology since oxygen transport is an important factor for medicine and physical performance.     

卫生信息化背景下电子健康档案建设的法律思考

在卫生信息化日快速发展的背景下, 电子健康档案日益被重视并开始逐步推广,但是其中存在的法律问题也同时显现。在分析我国电子健康档案信息安全的基础上,对电子健康档案的法律地位、患者的隐私权、医师注意义务以及政府的公共行政权利等方面进行了探讨。     

不同海拔梯度高寒草地地下生物量与环境因子的关系

以新疆天山南坡的巴音布鲁克高寒草地为对象, 研究了不同海拔梯度高寒草地地下生物量的变化及其与环境因子的关系.结果表明: 随着海拔的升高, 高寒草原、高寒草原化草甸和高寒草甸的地下生物量逐渐增大, 二者呈极显著正相关( P<0.01 ).地下生物量从表层至底层逐渐递减,呈“T”形分布.高寒草原、高寒草原化草甸和高寒草甸0～10 cm土层的地下生物量分别占总地下生物量的68.1%、84.1%和86.7%.地下生物量与大气温度呈极显著负相关, 与相对湿度和土壤含水量呈极显著正相关(P<0.01 ), 而与有机质、速效氮和pH等无显著相关.     

植物异黄酮合酶研究进展

植物异黄酮是一类具有增强植物抗病、诱导根瘤形成以及预防激素相关肿瘤发生、缓解女性更年期综合症的活性次生代谢产物,其合成关键酶是异黄酮合酶(IFS)。介绍了IFS的催化机理、基因克隆与表达调控的研究进展,讨论了开展IFS代谢工程研究对提高植物抗病虫害能力和改善农作物营养保健功效的意义。     

On a mathematical theory of embolism

A theory of embolism based on an optimization model of blood flow is proposed and used to explain the topographic distribution of emboli in arterial trees.     

A Thermodynamic Perspective on Natural Selection

A novel thermodynamic perspective on natural selection is presented. In the case that life continuity is optimized in an ideal system, where relatively constant and homogeneous selective pressures favour a given competing species, natural selection leads that system to a stationary state of maximum genotypic uniformity of life and maximum sustainable consumption of available energy by life (competitive equilibrium). Structurally and functionally, this optimizing tendency towards competitive equilibrium looks similar to the optimizing tendency towards thermodynamic equilibrium of classical thermodynamics (maximum energetic uniformity and maximum degradation of available energy). The principle of competitive exclusion may thus be conceptually viewed as an ecological manifestation of the second law of (classical) thermodynamics. On the other hand, the novel thermodynamic perspective on natural selection is discussed with regard to the open and nonequilibrium system of nature, where selective pressures vary in space and time. In this case, natural selection can induce diversity instead of uniformity, though an optimizing tendendcy towards maximum sustainable consumption of resources (optimization of life continuity) always remains. Overall, it is concluded that the action of natural selection favours the maximization of the sustainable consumption of energy at the level of individual organism.     

Radiomics software for breast imaging optimization and simulation studies

Background and ObjectiveThe development, control and optimisation of new x-ray breast imaging modalities could benefit from a quantitative assessment of the resulting image textures. The aim of this work was to develop a software tool for routine radiomics applications in breast imaging, which will also be available upon request.MethodsThe tool (developed in MATLAB) allows image reading, selection of Regions of Interest (ROI), analysis and comparison. Requirements towards the tool also included convenient handling of common medical and simulated images, building and providing a library of commonly applied algorithms and a friendly graphical user interface. Initial set of features and analyses have been selected after a literature search. Being open, the tool can be extended, if necessary.ResultsThe tool allows semi-automatic extracting of ROIs, calculating and processing a total of 23 different metrics or features in 2D images and/or in 3D image volumes. Computations of the features were verified against computations with other software packages performed with test images. Two case studies illustrate the applicability of the tool – (i) features on a series of 2D ‘left’ and ‘right’ CC mammograms acquired on a Siemens Inspiration system were computed and compared, and (ii) evaluation of the suitability of newly proposed and developed breast phantoms for x-ray-based imaging based on reference values from clinical mammography images. Obtained results could steer the further development of the physical breast phantoms.ConclusionsA new image analysis toolbox was realized and can now be used in a multitude of radiomics applications, on both clinical and test images.     

Chebanov law and Vakar formula in mathematical models of complex systems

Ecological models written in a mathematical language L(M) or model language, with a given style or methodology can be considered as a text. It is possible to apply statistical linguistic laws and the experimental results demonstrate that the behaviour of a mathematical model is the same of any literary text of any natural language. A text has the following characteristics: (a) the variables, its transformed functions and parameters are the lexic units or LUN of ecological models; (b) the syllables are constituted by a LUN, or a chain of them, separated by operating or ordering LUNs; (c) the flow equations are words; and (d) the distribution of words (LUM and CLUN) according to their lengths is based on a Poisson distribution, the Chebanov's law. It is founded on Vakar's formula, that is calculated likewise the linguistic entropy for L(M). We will apply these ideas over practical examples using MARIOLA model. In this paper it will be studied the problem of the lengths of the simple lexic units composed lexic units and words of text models, expressing these lengths in number of the primitive symbols, and syllables. The use of these linguistic laws renders it possible to indicate the degree of information given by an ecological model.