A topographical analysis of hippocampal field connectivity

The intrinsic connectivity of the hippocampus in the rat was studied using the retrograde tracers Fast Blue and rhodamine microspheres. In an initial double-labelling study the bilateral labelling within the CA3 field was observed following injection of the two dyes into homologous regions in the two CA1 fields. The labelling in the contralateral CA3 field was found to be identical both in distribution and in density to that observed in ipsilateral CAS, suggesting that the CAS-CA1 projection is bilaterally symmetrical. The observation that nearly 100% of backfilled cells were double-labelled indicates that homologous regions in the two CA1 fields receive information from the same cells in CAS, which indicates that the two CA1 fields act as one functional unit. Evidence for the existence of a sparse association/commissural system within CA1 was provided by the presence of a small number of labelled cells in the contralateral CA1 field. The topographic organization of the CAS-CA1 projection was studied following a series of injections of the two dyes into different locations across the extent of the CA1 field. In this experiment a new technique for the injections of tracers into the hippocampus was introduced, in which a microelectrode positioned adjacent to the tip of the injection pipette was used to record neuronal activity during the operation. This allowed the complex spike firing of hippocampal cells to be used as a marker for the dorsoventral location of the injection, thus greatly improving the accuracy of the injections. An analysis of the labelling in the extended hippocampus reveals that projections to CA1 arise from bands of cells organized diagonally across the CAS field. The CAS-CA1 projection was topographically organized in the septotemporal plane, with progressively more temporal parts of CA1 receiving inputs from bands located more temporally in CA3, Further analysis showed that cells positioned along a diagonal axis in CA1 were found to receive fibres from the same band of cells in CA3, and that this "CA1 axis" is similar to the axis of the diagonal bands in CAB. It therefore appears that the CA3-CA1 projection is organized in a diagonal fashion across the septotemporal length of the hippocampus both in terms of projecting and recipient cells. A number of injections was also placed into the CA3 field in order to study the CA3 association projection. In these cases the pattern of labelling in the CA3 field in the extended hippocampus was organized parallel to the septotemporal axis, and was topographically organized such that any given region in CA3 preferentially received fibres from cells located along the Scime transverse segment of CA3. These findings support the notion that the CA3 association pathway interconnects cells spread over a large fraction of the septotemporal extent of CAS. Preliminary data concerning the organization of the projection from the dentate gyrus to CA3 were collected following an injection of biocytin into the dentate gyrus. Additional data was taken from 3 animals in which rhodamine microspheres were found to be transported anterogradely along the mossy fibres in a previously unreported fashion. In all cases the projection was organized orthogonal to the septotemporal axis for most of the its length, with a shift in trajectory in proximal CA3 in the temporal direction. These results show that these three intrahippocampal pathways are angled with respect to each other, thus forming a lattice framework of connections similar to the "crossing fibre arrays" described by Tamamaki and Nojyo (1991a). Each pathway displays a specific directionality which, in contrast to the original lamellar hypothesis, allows the spread of information across all parts of the hippocampus. (Abstract shortened by ProQuest.

Key emerging issues in frontotemporal dementia.

Frontotemporal dementia (FTD) encompasses the syndromes of behavioural variant FTD (bvFTD) and primary progressive aphasia (PPA) and refers to those neurodegenerative diseases characterised by predominant pathological involvement of the frontal and temporal lobes. Recent years have witnessed major advances in the clinical characterisation of FTD, reflected in the publication of updated diagnostic criteria for bvFTD and PPA, and the discovery of new pathogenic mutations has added to the understanding of genotype-phenotype interactions and of disease mechanisms. Emerging results from longitudinal studies of familial FTD show that imaging and cognitive changes occur years before symptom onset and such studies may yield biomarkers of early disease that in turn will facilitate earlier diagnosis. The hope and (guarded) expectation is that these advances may together herald the beginning of the end of the chapter in which FTD is considered an inexorably progressive and untreatable condition.Dr Chan is funded by the Cambridge NIHR Biomedical Research Centre and receives grant income from the UK Medical Research Council, Technology Strategy Board and the Cambridge Isaac Newton Trust.This is the author accepted manuscript. The final version is available from Springer via http://dx.doi.org/10.1007/s00415-015-7880-

Performance of a parallel code for the Euler equations on hypercube computers

The performance of hypercubes were evaluated on a computational fluid dynamics problem and the parallel environment issues were considered that must be addressed, such as algorithm changes, implementation choices, programming effort, and programming environment. The evaluation focuses on a widely used fluid dynamics code, FLO52, which solves the two dimensional steady Euler equations describing flow around the airfoil. The code development experience is described, including interacting with the operating system, utilizing the message-passing communication system, and code modifications necessary to increase parallel efficiency. Results from two hypercube parallel computers (a 16-node iPSC/2, and a 512-node NCUBE/ten) are discussed and compared. In addition, a mathematical model of the execution time was developed as a function of several machine and algorithm parameters. This model accurately predicts the actual run times obtained and is used to explore the performance of the code in interesting but yet physically realizable regions of the parameter space. Based on this model, predictions about future hypercubes are made

Stratigraphy and chronology of the Stent tephra, a c. 4000 year old distal silicic tephra from Taupo Volcanic Centre, New Zealand.

Tephrostratigraphic and chronologic studies in two areas of the North Island have identified a previously unrecorded, thin, distal silicic tephra derived from the Taupo Volcanic Centre. In Taranaki, three radiocarbon ages of the uncorrelated tephra are consistent with the independent radiocarbon chronology obtained from enveloping Egmontsourced tephras. In western Bay of Plenty, where the uncorrelated tephra is also directly dated, it is overlain by Whakaipo Tephra (c. 2.7 ka) and underlain by Hinemaiaia Tephra (c. 4.5 ka). From these sites in Taranaki and western Bay of Plenty, seven radiocarbon dates obtained on the uncorrelated silicic tephra yield an error-weighted mean age of 3970 ±31 conventional radiocarbon years B.P. The ages on the uncorrelated tephra (informally referred to as Stent tephra) from both areas are statistically identical but significantly different from those on both Waimihia and Hinemaiaia Tephras. occurrence of Stent tephra in Taranaki, c. 160 km upwind from the postulated source area, and in western Bay of Plenty, suggests that it represents the product of a moderately large plinian eruption. Until recently, its validity as a discrete eruptive event had been problematical, because a near-source equivalent deposit between Waimihia and Hinemaiaia Tephras was not recognised in the Taupo area. However, a revised stratigraphy proposed by C. J. N. Wilson in 1993 for eastern sectors of the Taupo area shows that multiple tephra layers were erupted from Taupo volcano between c. 3.9 and 5.2 ka. Of these newly recognised layers, unit-g--the product of a moderately large eruption (>0.15 km3) at c. 4.0 ka--is tentatively correlated with Stent tephra. Other eruptive units recognised by Wilson are either too old or too small in volume to be considered as likely correlatives

Using hexamers to predict cis-regulatory motifs in Drosophila

BACKGROUND: Cis-regulatory modules (CRMs) are short stretches of DNA that help regulate gene expression in higher eukaryotes. They have been found up to 1 megabase away from the genes they regulate and can be located upstream, downstream, and even within their target genes. Due to the difficulty of finding CRMs using biological and computational techniques, even well-studied regulatory systems may contain CRMs that have not yet been discovered. RESULTS: We present a simple, efficient method (HexDiff) based only on hexamer frequencies of known CRMs and non-CRM sequence to predict novel CRMs in regulatory systems. On a data set of 16 gap and pair-rule genes containing 52 known CRMs, predictions made by HexDiff had a higher correlation with the known CRMs than several existing CRM prediction algorithms: Ahab, Cluster Buster, MSCAN, MCAST, and LWF. After combining the results of the different algorithms, 10 putative CRMs were identified and are strong candidates for future study. The hexamers used by HexDiff to distinguish between CRMs and non-CRM sequence were also analyzed and were shown to be enriched in regulatory elements. CONCLUSION: HexDiff provides an efficient and effective means for finding new CRMs based on known CRMs, rather than known binding sites

Analysis of the Tuning Sensitivity of Silicon-on-Insulator Optical Ring Resonators

High-quality-factor optical ring resonators have recently been fabricated in thin silicon-on-insulator (SOI). Practical applications of such devices will require careful tuning of the precise location of the resonance peaks. In particular, one often wants to maximize the resonance shift due to the presence of an active component and minimize the resonance shift due to temperature changes. This paper presents a semianalytic formalism that allows the prediction of such resonance shifts from the waveguide geometry. This paper also presents the results of experiments that show the tuning behavior of several ring resonators and find that the proposed semianalytic formalism agrees with the observed behavior

Enhancing the capacity of oxygen carriers for selective oxidations through phase cooperation: Bismuth oxide and ceria-zirconia

Interfacing selective catalysts with oxygen carriers enhances capacity without affecting the surface chemistry, simplifying the design of selective oxygen carriers.</p

Implementing Knowledge Management

The growing reliance on intellectual assets to gain competitive advantage has necessitated the development and implementation of knowledge management systems in order to collect, organize and transfer all of the knowledge accumulated by modern organizations.&nbsp; This study is presented as a consolidation of previous research performed in this area, and integrates this work with a meta-analysis of two real life case studies.&nbsp; The corresponding results suggest that the tacit/explicit dimension of knowledge is a strong indicator of the type of knowledge management strategy a given company should follow

Corporate Ethics: China vs. USA

Fairness is one of the basic aspects of business exchange.  Ethics are principles used to establish fairness.  This study will look at background and origins for different American and Chinese ethical beliefs.  It is important for U.S. and Chinese firms to understand each other’s cultural perspectives, especially as the Chinese market opens up.  Methods to resolve ethical conflict will be reviewed.  Business agents from both cultures can relate and deal with each other if they have the knowledge, skills, and patience to do so.  This study builds on prior research that suggests that younger Chinese are more concerned with profit than with abiding by regulations or adhering to corporate ethics.  The major argument of this study is that future Chinese business leaders, born after China’s one-child policy was implemented in 1979, will be primarily concerned with self-interest and making decisions that will benefit them individually.  Guanxi (interpersonal connections or human relationships), corporate ethics and social responsibility (CESR) beliefs will be reduced in importance and influence.  American managers should incorporate this information when formulating a “China strategy”