SciCombinator

Discover the most talked about and latest scientific content & concepts.

Concept: Natural number

249

Human infants in the first year of life possess an intuitive sense of number. This preverbal number sense may serve as a developmental building block for the uniquely human capacity for mathematics. In support of this idea, several studies have demonstrated that nonverbal number sense is correlated with mathematical abilities in children and adults. However, there has been no direct evidence that infant numerical abilities are related to mathematical abilities later in childhood. Here, we provide evidence that preverbal number sense in infancy predicts mathematical abilities in preschool-aged children. Numerical preference scores at 6 months of age correlated with both standardized math test scores and nonsymbolic number comparison scores at 3.5 years of age, suggesting that preverbal number sense facilitates the acquisition of numerical symbols and mathematical abilities. This relationship held even after controlling for general intelligence, indicating that preverbal number sense imparts a unique contribution to mathematical ability. These results validate the many prior studies purporting to show number sense in infancy and support the hypothesis that mathematics is built upon an intuitive sense of number that predates language.

Concepts: Infant, Mathematics, Number, Real number, Set theory, Natural number, Infinity, Arithmetic

136

Endogenous retrovirus (ERV) sequences provide a rich source of information about the long-term interactions between retroviruses and their hosts. However, most ERVs are derived from a subset of retrovirus groups, while ERVs derived from certain other groups remain extremely rare. In particular, only a single ERV sequence has been identified that shows evidence of being related to an ancient Deltaretrovirus, despite the large number of vertebrate genome sequences now available. In this report, we identify a second example of an ERV sequence putatively derived from a past deltaretroviral infection, in the genomes of several species of horseshoe bats (Rhinolophidae). This sequence represents a fragment of viral genome derived from a single integration. The time of the integration was estimated to be 11-19 million years ago. This finding, together with the previously identified endogenous Deltaretrovirus in long-fingered bats (Miniopteridae), suggest a close association of bats with ancient deltaretroviruses.

Concepts: HIV, DNA, Mathematics, RNA virus, Natural number, Retrovirus, Endogenous retrovirus, Retroviruses

37

We examine the temporal evolution of digital communication activity relating to the American anti-capitalist movement Occupy Wall Street. Using a high-volume sample from the microblogging site Twitter, we investigate changes in Occupy participant engagement, interests, and social connectivity over a fifteen month period starting three months prior to the movement’s first protest action. The results of this analysis indicate that, on Twitter, the Occupy movement tended to elicit participation from a set of highly interconnected users with pre-existing interests in domestic politics and foreign social movements. These users, while highly vocal in the months immediately following the birth of the movement, appear to have lost interest in Occupy related communication over the remainder of the study period.

Concepts: Sociology, Natural number, Integer, Remainder, Social movement, Twitter, ASCII, Activism

29

Tissues are complex milieus consisting of numerous cell types. Several recent methods have attempted to enumerate cell subsets from transcriptomes. However, the available methods have used limited sources for training and give only a partial portrayal of the full cellular landscape. Here we present xCell, a novel gene signature-based method, and use it to infer 64 immune and stromal cell types. We harmonized 1822 pure human cell type transcriptomes from various sources and employed a curve fitting approach for linear comparison of cell types and introduced a novel spillover compensation technique for separating them. Using extensive in silico analyses and comparison to cytometry immunophenotyping, we show that xCell outperforms other methods. xCell is available at http://xCell.ucsf.edu/ .

Concepts: Cell, Cellular differentiation, Cell type, Natural number

27

We report the enantiospecific total synthesis of (+)-tubingensin A. Our synthesis features an aryne cyclization to efficiently introduce the vicinal quaternary stereocenters of the natural product and proceeds in only 9 steps (longest linear sequence) from known compounds.

Concepts: Total synthesis, Paclitaxel total synthesis, Natural number, Isomorphism, Integer, Partially ordered set, Ordinal number, Well-order

27

Given a set of points on the plane and an assignment of values to them, an optimal linear partition is a division of the set into two subsets which are separated by a straight line and maximally contrast with each other in the values assigned to their points. We present a method for inspecting and rating all linear partitions of a finite set, and a package of three functions in the R language for executing the computations. One function is for finding the optimal linear partitions and corresponding separating lines, another for graphically representing the results, and a third for testing how well the data comply with the linear separability condition. We illustrate the method on possible data from a psychophysical experiment (concerning the size-weight illusion) and compare its performance with that of linear discriminant analysis and multiple logistic regression, adapted to dividing linearly a set of points on the plane.

Concepts: Logistic regression, Set theory, Natural number, Linear equation, Line, Empty set, Bijection, Basic concepts in set theory

27

We report a detailed binding study addressing both the thermodynamics and kinetics of binding of a large set of guest molecules - with widely varying properties - to a water-soluble metal-organic M4L6 host. The effects of different guest properties upon binding strength and kinetics are elucidated by a systematic analysis of the binding data through principal component analysis, thus allowing for structure-property relationships to be determined. These insights allowed us to design more complex encapsulation sequences, in which multiple guests, added simultaneously, are bound and released by the host in a time-dependent manner, thus allowing multiple states of the system to be accessed sequentially. Moreover, by inclusion of the pH-sensitive guest pyridine we were able to further extend our control over binding by creating a reversible pH-controlled three-guest sequential binding cycle.

Concepts: Series, Mathematical analysis, Sequence, Principal component analysis, Natural number, Set, Real analysis, Limit of a sequence

25

Number is a complex category, as with the word"number" we may refer to different entities. First, it is a perceptual property that characterizes any set of individual items, namely its cardinality. The ability to extract the (approximate) cardinality of sets is almost universal in the animal domain and present in humans since birth. In primates, posterior parietal cortex seems to be a crucial site for this ability, even if the degree of selectivity of numerical representations in parietal cortex reported to date appears much lower compared to that of other semantic categories in the ventral stream. Number can also be intended as a mathematical object, which we humans use to count, measure, and order: a (verbal or visual) symbol that stands for the cardinality of a set, the intensity of a continuous quantity or the position of an item on a list. Evidence points to a convergence towards parietal cortex for the semantic coding of numerical symbols and to the bilateral occipitotemporal cortex for the shape coding of Arabic digits and other number symbols.

Concepts: Mathematics, Function, Cerebrum, Number, Real number, Natural number, Parietal lobe, Category theory

25

Despite recent discoveries of germline and somatic mutations in melanoma, naevus count remains the most important risk factor for melanoma. Counting naevi on the whole body is time consuming. In order to identify patients at risk for melanoma, many studies have used naevus count on selected body sites as a proxy for total body naevus count.

Concepts: Natural selection, Statistics, Natural number, Dysplastic nevus, Ordinal number

25

In this paper, the stability problem is studied for a class of stochastic neural networks (NNs) with local impulsive effects. The impulsive effects considered can be not only nonidentical in different dimensions of the system state but also various at distinct impulsive instants. Hence, the impulses here can encompass several typical impulses in NNs. The aim of this paper is to derive stability criteria such that stochastic NNs with local impulsive effects are exponentially stable in mean square. By means of the mathematical induction method, several easy-to-check conditions are obtained to ensure the mean square stability of NNs. Three examples are given to show the effectiveness of the proposed stability criterion.

Concepts: Effect, Dimension, Arithmetic mean, Natural number, Neural network, Cauchy distribution, Mathematical logic, Mathematical proof