455 research outputs found
Radio Monitoring Campaigns of Six Strongly Lensed Quasars
We observed six strongly lensed, radio-loud quasars (MG 0414+0534, CLASS
B0712+472, JVAS B1030+074, CLASS B1127+385, CLASS B1152+199, and JVAS
B1938+666) in order to identify systems suitable for measuring cosmological
parameters using time delays between their multiple images. These systems are
in standard two and four image configurations, with B1938 having a faint
secondary pair of images. Two separate monitoring campaigns were carried out
using the VLA and upgraded JVLA. Lightcurves were extracted for each individual
lensed image and analyzed for signs of intrinsic variability. While it was not
possible to measure time delays from these data, -based and structure
function tests found evidence for variability in a majority of the lightcurves.
B0712 and B1030 had particularly strong variations, exhibiting linear flux
trends. These results show that most of these systems should be targeted with
followup monitoring campaigns, especially B0712 and B1030.Comment: Submitted to MNRA
The plight of the sense-making ape
This is a selective review of the published literature on object-choice tasks, where participants use directional cues to find hidden objects. This literature comprises the efforts of researchers to make sense of the sense-making capacities of our nearest living relatives. This chapter is written to highlight some nonsensical conclusions that frequently emerge from this research. The data suggest that when apes are given approximately the same sense-making opportunities as we provide our children, then they will easily make sense of our social signals. The ubiquity of nonsensical contemporary scientific claims to the effect that humans are essentially--or inherently--more capable than other great apes in the understanding of simple directional cues is, itself, a testament to the power of preconceived ideas on human perception
Are chimpanzees really so poor at understanding imperative pointing? Some new data and an alternative view of canine and ape social cognition
There is considerable interest in comparative research on different species’ abilities to respond to human communicative cues such as gaze and pointing. It has been reported that some canines perform significantly better than monkeys and apes on tasks requiring the comprehension of either declarative or imperative pointing and these differences have been attributed to domestication in dogs. Here we tested a sample of chimpanzees on a task requiring comprehension of an imperative request and show that, though there are considerable individual differences, the performance by the apes rival those reported in pet dogs. We suggest that small differences in methodology can have a pronounced influence on performance on these types of tasks. We further suggest that basic differences in subject sampling, subject recruitment and rearing experiences have resulted in a skewed representation of canine abilities compared to those of monkeys and apes
The mismeasure of ape social cognition
In his classic analysis, The Mismeasure of Man, Gould (1981) demolished the idea that intelligence was an inherent, genetic trait of different human groups by emphasizing, among other things, (a) its sensitivity to environmental input, (b) the incommensurate pre-test preparation of different human groups, and (c) the inadequacy of the testing contexts, in many cases. According to Gould, the root cause of these oversights was confirmation bias by psychometricians, an unwarranted commitment to the idea that intelligence was a fixed, immutable quality of people. By virtue of a similar, systemic interpretive bias, in the last two decades, numerous contemporary researchers in comparative psychology have claimed human superiority over apes in social intelligence, based on two-group comparisons between postindustrial, Western Europeans and captive apes, where the apes have been isolated from European styles of social interaction, and tested with radically different procedures. Moreover, direct comparisons of humans with apes suffer from pervasive lapses in argumentation: Research designs in wide contemporary use are inherently mute about the underlying psychological causes of overt behavior. Here we analyze these problems and offer a more fruitful approach to the comparative study of social intelligence, which focuses on specific individual learning histories in specific ecological circumstances
A Random Matrix Approach to Language Acquisition
Since language is tied to cognition, we expect the linguistic structures to
reflect patterns we encounter in nature and analyzed by physics. Within this
realm we investigate the process of protolanguage acquisition, using analytical
and tractable methods developed within physics. A protolanguage is a mapping
between sounds and objects (or concepts) of the perceived world. This mapping
is represented by a matrix and the linguistic interaction among individuals is
described by a random matrix model. There are two essential parameters in our
approach. The strength of the linguistic interaction , which following
Chomsky's tradition, we consider as a genetically determined ability, and the
number of employed sounds (the lexicon size). Our model of linguistic
interaction is analytically studied using methods of statistical physics and
simulated by Monte Carlo techniques. The analysis reveals an intricate
relationship between the innate propensity for language acquisition and
the lexicon size , . Thus a small increase of the
genetically determined may lead to an incredible lexical explosion. Our
approximate scheme offers an explanation for the biological affinity of
different species and their simultaneous linguistic disparity.Comment: 16 pages, 4 figures. Submitted to JSTA
Understanding language evolution : beyond Pan-centrism
Language does not fossilize but this does not mean that the language's evolutionary timeline is lost forever. Great apes provide a window back in time on our last prelinguistic ancestor's communication and cognition. Phylogeny and cladistics implicitly conjure Pan (chimpanzees, bonobos) as a superior (often the only) model for language evolution compared with earlier diverging lineages, Gorilla and Pongo (orangutans). Here, in reviewing the literature, it is shown that Pan do not surpass other great apes along genetic, cognitive, ecologic, or vocal traits that are putatively paramount for language onset and evolution. Instead, revived herein is the idea that only by abandoning single-species models and learning about the variation among great apes, there might be a chance to retrieve lost fragments of the evolutionary timeline of language.PostprintPeer reviewe
Neuroacanthocytosis associated with a defect of the 4.1R membrane protein
BACKGROUND: Neuroacanthocytosis (NA) denotes a heterogeneous group of diseases that are characterized by nervous system abnormalities in association with acanthocytosis in the patients' blood. The 4.1R protein of the erythrocyte membrane is critical for the membrane-associated cytoskeleton structure and in central neurons it regulates the stabilization of AMPA receptors on the neuronal surface at the postsynaptic density. We report clinical, biochemical, and genetic features in four patients from four unrelated families with NA in order to explain the cause of morphological abnormalities and the relationship with neurodegenerative processes. CASE PRESENTATION: All patients were characterised by atypical NA with a novel alteration of the erythrocyte membrane: a 4.1R protein deficiency. The 4.1R protein content was significantly lower in patients (3.40 ± 0.42) than in controls (4.41 ± 0.40, P < 0.0001), reflecting weakened interactions of the cytoskeleton with the membrane. In patients IV:1 (RM23), IV:3 (RM15), and IV:6 (RM16) the 4.1 deficiency seemed to affect the horizontal interactions of spectrin and an impairment of the dimer self-association into tetramers was detected. In patient IV:1 (RM16) the 4.1 deficiency seemed to affect the skeletal attachment to membrane and the protein band 3 was partially reduced. CONCLUSION: A decreased expression pattern of the 4.1R protein was observed in the erythrocytes from patients with atypical NA, which might reflect the expression pattern in the central nervous system, especially basal ganglia, and might lead to dysfunction of AMPA-mediated glutamate transmission
Microbial Communication, Cooperation and Cheating: Quorum Sensing Drives the Evolution of Cooperation in Bacteria
An increasing body of empirical evidence suggests that cooperation among clone-mates is common in bacteria. Bacterial cooperation may take the form of the excretion of “public goods”: exoproducts such as virulence factors, exoenzymes or components of the matrix in biofilms, to yield significant benefit for individuals joining in the common effort of producing them. Supposedly in order to spare unnecessary costs when the population is too sparse to supply the sufficient exoproduct level, many bacteria have evolved a simple chemical communication system called quorum sensing (QS), to “measure” the population density of clone-mates in their close neighborhood. Cooperation genes are expressed only above a threshold rate of QS signal molecule re-capture, i.e., above the local quorum of cooperators. The cooperative population is exposed to exploitation by cheaters, i.e., mutants who contribute less or nil to the effort but fully enjoy the benefits of cooperation. The communication system is also vulnerable to a different type of cheaters (“Liars”) who may produce the QS signal but not the exoproduct, thus ruining the reliability of the signal. Since there is no reason to assume that such cheaters cannot evolve and invade the populations of honestly signaling cooperators, the empirical fact of the existence of both bacterial cooperation and the associated QS communication system seems puzzling. Using a stochastic cellular automaton approach and allowing mutations in an initially non-cooperating, non-communicating strain we show that both cooperation and the associated communication system can evolve, spread and remain persistent. The QS genes help cooperative behavior to invade the population, and vice versa; cooperation and communication might have evolved synergistically in bacteria. Moreover, in good agreement with the empirical data recently available, this synergism opens up a remarkably rich repertoire of social interactions in which cheating and exploitation are commonplace
HIV-1 Tat protein directly induces mitochondrial membrane permeabilization and inactivates cytochrome c oxidase
The Trans-activator protein (Tat) of human immunodeficiency virus (HIV)
is a pleiotropic protein involved in different aspects of AIDS pathogenesis. As
a number of viral proteins Tat is suspected to disturb mitochondrial function.
We prepared pure synthetic full-length Tat by native chemical ligation (NCL),
and Tat peptides, to evaluate their direct effects on isolated mitochondria.
Submicromolar doses of synthetic Tat cause a rapid dissipation of the
mitochondrial transmembrane potential (ΔΨm) as well as
cytochrome c release in mitochondria isolated from mouse liver, heart,
and brain. Accordingly, Tat decreases substrate oxidation by mitochondria
isolated from these tissues, with oxygen uptake being initially restored by
adding cytochrome c. The anion-channel inhibitor
4,4′-diisothiocyanostilbene-2,2′-disulfonic acid (DIDS) protects
isolated mitochondria against Tat-induced mitochondrial membrane
permeabilization (MMP), whereas ruthenium red, a ryanodine receptor blocker,
does not. Pharmacologic inhibitors of the permeability transition pore,
Bax/Bak inhibitors, and recombinant Bcl-2 and Bcl-XL proteins do not reduce
Tat-induced MMP. We finally observed that Tat inhibits cytochrome c
oxidase (COX) activity in disrupted mitochondria isolated from liver, heart, and
brain of both mouse and human samples, making it the first described viral
protein to be a potential COX inhibitor
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