545 research outputs found
Response variability in balanced cortical networks
We study the spike statistics of neurons in a network with dynamically
balanced excitation and inhibition. Our model, intended to represent a generic
cortical column, comprises randomly connected excitatory and inhibitory leaky
integrate-and-fire neurons, driven by excitatory input from an external
population. The high connectivity permits a mean-field description in which
synaptic currents can be treated as Gaussian noise, the mean and
autocorrelation function of which are calculated self-consistently from the
firing statistics of single model neurons. Within this description, we find
that the irregularity of spike trains is controlled mainly by the strength of
the synapses relative to the difference between the firing threshold and the
post-firing reset level of the membrane potential. For moderately strong
synapses we find spike statistics very similar to those observed in primary
visual cortex.Comment: 22 pages, 7 figures, submitted to Neural Computatio
A guide for building fit-for-purpose land administration systems in less developed countries:capacity development, change management and project delivery
Effect of holding office on the behavior of politicians
Does being elected to political office change an individual’s behavior? Some scholars and policymakers assert that elected officials are inherently different from nonpoliticians, whereas others argue that political institutions or the culture of politics inculcate certain behaviors. We identify the effect of holding office on behavior. We recruit in-office and out-of-office politicians in Zambia to participate in behavioral games that measure reciprocity, a behavioral trait that underpins various interactions in the political arena from bribery to lobbying to legislative bargaining. We find that holding elected office causes an increase in reciprocity. The policy implication of this finding is that political institutions, culture, and incentive structures can be designed to shape the behavior and choices of society’s leaders
Occurrence of <em>Cryptosporidium</em> spp. oocysts in low quality water and on vegetables irrigated with low quality water in Kumasi, Ghana
A DNA-binding activity in BPV initiator protein E1 required for melting duplex ori DNA but not processive helicase activity initiated on partially single-stranded DNA
The papillomavirus replication protein E1 assembles on the viral origin of replication (ori) as a series of complexes. It has been proposed that the ori DNA is first melted by a head-to-tail double trimer of E1 that evolves into two hexamers that encircle and unwind DNA bi-directionally. Here the role of a conserved lysine residue in the smaller tier or collar of the E1 helicase domain in ori processing is described. Unlike the residues of the AAA+ domain DNA-binding segments (β-hairpin and hydrophobic loop; larger tier), this residue functions in the initial melting of duplex ori DNA but not in the processive DNA unwinding of partially single-stranded test substrates. These data therefore define a new DNA-binding related activity in the E1 protein and demonstrate that separate functional elements for DNA melting and helicase activity can be distinguished. New insights into the mechanism of ori melting are elaborated, suggesting the coordinated involvement of rigid and flexible DNA-binding components in E1
Gastrointestinal parasites of cats in Denmark assessed by necropsy and concentration McMaster technique
Detection and molecular characterisation of Cryptosporidium parvum in British European hedgehogs (Erinaceus europaeus)
Surveillance was conducted for the occurrence of protozoan parasites of the genus Cryptosporidium in European hedgehogs (Erinaceus europaeus) in Great Britain. In total, 108 voided faecal samples were collected from hedgehogs newly admitted to eight wildlife casualty treatment and rehabilitation centres. Terminal large intestinal (LI) contents from three hedgehog carcasses were also analysed. Information on host and location variables, including faecal appearance, body weight, and apparent health status, was compiled. Polymerase Chain Reaction (PCR) targeting the 18S ribosomal RNA gene, confirmed by sequencing, revealed an 8% (9/111) occurrence of Cryptosporidium parvum in faeces or LI contents, with no significant association between the host or location variables and infection. Archived small intestinal (SI) tissue from a hedgehog with histological evidence of cryptosporidiosis was also positive for C. parvum by PCR and sequence analysis of the 18S rRNA gene. No other Cryptosporidium species were detected. PCR and sequencing of the glycoprotein 60 gene identified three known zoonotic C. parvum subtypes not previously found in hedgehogs: IIdA17G1 (n=4), IIdA19G1 (n=1) and IIdA24G1 (n=1). These subtypes are also known to infect livestock. Another faecal sample contained C. parvum IIcA5G3j which has been found previously in hedgehogs, and for which there is one published report in a human, but is not known to affect livestock. The presence of zoonotic subtypes of C. parvum in British hedgehogs highlights a potential public health concern. Further research is needed to better understand the epidemiology and potential impacts of Cryptosporidium infection in hedgehogs
Evaluation of feed safety aspects in feeding organic layers with fresh house fly larvae (Musca domestica) reared in poultry manure
The nature of the phosphate complex of sulphite oxidase from electron-paramagnetic-resonance studies
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