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Search Results: 1 - 10 of 228011 matches for " R. Nicholas Laribee "
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The Ccr4-Not Complex Interacts with the mRNA Export Machinery
Shana C. Kerr,Nowel Azzouz,Stephen M. Fuchs,Martine A. Collart,Brian D. Strahl,Anita H. Corbett,R. Nicholas Laribee
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0018302
Abstract: The Ccr4-Not complex is a key eukaryotic regulator of gene transcription and cytoplasmic mRNA degradation. Whether this complex also affects aspects of post-transcriptional gene regulation, such as mRNA export, remains largely unexplored. Human Caf1 (hCaf1), a Ccr4-Not complex member, interacts with and regulates the arginine methyltransferase PRMT1, whose targets include RNA binding proteins involved in mRNA export. However, the functional significance of this regulation is poorly understood.
Do Auditory Temporal Discrimination Tasks Measure Temporal Resolution of the CNS?  [PDF]
Ian T. Zajac, Nicholas R. Burns
Psychology (PSYCH) , 2011, DOI: 10.4236/psych.2011.27114
Abstract: Rammsayer & Brandler (2002) have proposed that auditory temporal discrimination tasks provide a measure of temporal resolution of the CNS which is argued to be partly responsible for higher order cognitive functioning. We report on two studies designed to elicit the nature of the functions underpinning these auditory tasks. Study 1 assessed whether temporal generalisation (TG) might be better considered as a measure of working memory rather than of temporal resolution of the CNS. In N = 66 undergraduates TG did not predict speed of processing tasks; however, there was evidence of a relationship between TG and working memory. Study 2 reanalyzed pre- viously published data on temporal discrimination tasks and showed that the relationship between auditory tem- poral tasks and intelligence reflects memory functions and processing speed. Auditory temporal discrimination tasks are confounded by speed and memory and should not be considered as measures of temporal resolution of the CNS.
Accurately Measuring Inspection Time with Computers  [PDF]
A. Kym Preiss, Nicholas R. Burns
International Journal of Intelligence Science (IJIS) , 2012, DOI: 10.4236/ijis.2012.24013
Abstract: Accurately measuring inspection time (IT) with computers requires several considerations. They are: 1) Screen redraw period; 2) Synchronous and timely image presentation; 3) Stimulus duration timing; 4) Image scale invariance; 5) Stan dardized presentation format (of which image scale invariance is a part). The first consideration dictates a minimum duration available for measuring IT. The second and third are necessary for accurate stimulus duration. The fourth is necessary to provide scale invariant images, that is, images with the same visual angle at a given viewing distance on any computer. And the fifth ensures that participants everywhere respond to the same task. Our computer program em bodies these elements and we make it freely available to any interested party. Data to establish validity and reliability are presented, and normative data on 2518 participants aged 6 to 92 years are available.
The Role of Protein Kinase Cη in T Cell Biology
Nicholas R. J. Gascoigne
Frontiers in Immunology , 2012, DOI: 10.3389/fimmu.2012.00177
Abstract: Protein kinase Cη (PKCη) is a member of the novel PKC subfamily, which also includes δ, ε, and θ isoforms. Compared to the other novel PKCs, the function of PKCη in the immune system is largely unknown. Several studies have started to reveal the role of PKCη, particularly in T cells. PKCη is highly expressed in T cells, and is upregulated during thymocyte positive selection. Interestingly, like the θ isoform, PKCη is also recruited to the immunological synapse that is formed between a T cell and an antigen-presenting cell. However, unlike PKCθ, which becomes concentrated to the central region of the synapse, PKCη remains in a diffuse pattern over the whole area of the synapse, suggesting distinctive roles of these two isoforms in signal transduction. Although PKCη is dispensable for thymocyte development, further analysis of PKCη- or PKCθ-deficient and double-knockout mice revealed the redundancy of these two isoforms in thymocyte development. In contrast, PKCη rather than PKCθ, plays an important role for T cell homeostatic proliferation, which requires recognition of self-antigen. Another piece of evidence demonstrating that PKCη and PKCθ have isoform-specific as well as redundant roles come from the analysis of CD4 to CD8 T cell ratios in the periphery of these knockout mice. Deficiency in PKCη or PKCθ had opposing effects as PKCη knockout mice had a higher ratio of CD4 to CD8 T cells compared to that of wild-type mice, whereas PKCθ-deficient mice had a lower ratio. Biochemical studies showed that calcium flux and NFκB translocation is impaired in PKCη-deficient T cells upon TCR crosslinking stimulation, a character shared with PKCθ-deficient T cells. However, unlike the case with PKCθ, the mechanistic study of PKCη is at early stage and the signaling pathways involving PKCη, at least in T cells, are essentially unknown. In this review, we will cover the topics mentioned above as well as provide some perspectives for further investigations regarding PKCη.
The critical surface fugacity of self-avoiding walks on a rotated honeycomb lattice
Nicholas R. Beaton
Mathematics , 2012,
Abstract: In a recent paper by Beaton et al, it was proved that a model of self-avoiding walks on the honeycomb lattice, interacting with an impenetrable surface, undergoes an adsorption phase transition when the surface fugacity is $1+\sqrt{2}$. Their proof used a generalisation of an identity obtained by Duminil-Copin and Smirnov, and confirmed a conjecture of Batchelor and Yung. We consider a similar model of self-avoiding walk adsorption on the honeycomb lattice, but with the lattice rotated by $\pi/2$. For this model there also exists a conjecture for the critical surface fugacity, made in 1998 by Batchelor, Bennett-Wood and Owczarek. Using similar methods to Beaton et al, we prove that this is indeed the critical fugacity.
The critical pulling force for self-avoiding walks
Nicholas R. Beaton
Mathematics , 2014, DOI: 10.1088/1751-8113/48/16/16FT03
Abstract: Self-avoiding walks are a simple and well-known model of long, flexible polymers in a good solvent. Polymers being pulled away from a surface by an external agent can be modelled with self-avoiding walks in a half-space, with a Boltzmann weight $y = e^f$ associated with the pulling force. This model is known to have a critical point at a certain value $y_c$ of this Boltzmann weight, which is the location of a transition between the so-called free and ballistic phases. The value $y_c=1$ has been conjectured by several authors using numerical estimates. We provide a relatively simple proof of this result, and show that further properties of the free energy of this system can be determined by re-interpreting existing results about the two-point function of self-avoiding walks.
Adsorption of self-avoiding walks at a defect
Nicholas R. Beaton
Mathematics , 2014,
Abstract: We consider the model of self-avoiding walks on the $d$-dimensional hypercubic lattice interacting with a $d^*$-dimensional defect, where $1\leq d^*
Litter Decomposition and Soluble Carbon, Nitrogen, and Phosphorus Release in a Forest Ecosystem  [PDF]
Maria L. Silveira, Konda R. Reddy, Nicholas B. Comerford
Open Journal of Soil Science (OJSS) , 2011, DOI: 10.4236/ojss.2011.13012
Abstract: Litter is an important source of easily mineralizable C, N, and P for microbial metabolism in forest ecosystems; however, its decomposition is dependent upon a variety of biotic and abiotic factors, including litter chemical composition and plant specie, soil properties, and climate. We investigated C, N, and P mineralization patterns of pine litter, oak and a mixture of various species commonly found in wetland landscape position. Litter species were incubated (alone and with soils) under laboratory conditions in the dark for 120 days. Samples were leached weekly and the leachates were analyzed for pH, E4:E6 ratio, dissolved organic carbon (DOC), total N, NO3, NH4, soluble reactive P, and total P. CO2 effluxes during the 120-d incubation period were measure using NaOH traps. Carbon loss was calculated as the sum of DOC and CO2 effluxes. Results indicated that patterns of C and N release varied with litter species and soil type. Mix species treatment resulted in larger DOC and N pulses compared to pine and oak treatments. The majority of the DOC, N, and P leached was retained by the soils. When litters were added to the soils, a greater proportion of the C was lost as CO2, while litter incubated alone lost more C as DOC. This result demonstrated the importance of the soil microbial community affecting the patterns of litter mineralization. Total N concentration and C:N ratio of the litter species were significantly correlated to C loss.
Do Purpose-Designed Auditory Tasks Measure General Speediness?  [PDF]
Ian T. Zajac, Nicholas R. Burns, Ted Nettelbeck
International Journal of Intelligence Science (IJIS) , 2012, DOI: 10.4236/ijis.2012.22004
Abstract: This study was concerned with the measurement of General Speediness (Gs) using the auditory modality. Existing as well as purpose-developed auditory tasks that maintained the cognitive requirements of established visually presented Gs marker tests were completed by N = 80 university undergraduates. Analyses supported the results of our previous work [1] and auditory and visual tasks combined to define latent RT and Gs factors. Moreover, the analysis did not support the presence of modality-specific speed factors. Overall, this study provides further evidence suggesting that auditory tasks might successfully measure existing broad abilities defined in intelligence theories (i.e., Gf, Gc, etc.) provided they maintain the same cognitive requirements as existing visual measures of such constructs.
Activin-Directed Differentiation of Human Embryonic Stem Cells Differentially Modulates Alveolar Epithelial Wound Repair via Paracrine Mechanism  [PDF]
Khondoker M. Akram, Monica A. Spiteri, Nicholas R. Forsyth
Stem Cell Discovery (SCD) , 2014, DOI: 10.4236/scd.2014.43008

Differentiated embryonic stem cells (ESC) can ameliorate lung inflammation and fibrosis in animal lung injury models; therefore, ESC, or their products, could be candidates for regenerative therapy for incurable lung diseases, such as idiopathic pulmonary fibrosis (IPF). In this study, we have investigated the paracrine effect of differentiated and undifferentiated human ESC on alveolar epithelial cell (AEC) wound repair. hESC line, SHEF-2 cells were differentiated with Activin treatment for 22 days in an embryoid body (EB) suspension culture. Conditioned media (CM) which contain cell secretory factors were collected at different time points of differentiation. CM were then tested onin vitro wound repair model with human type II AEC line, A549 cells (AEC). Our study demonstrated that CM originated from undifferentiated hESC significantly inhibited AEC wound repair when compared to the control. Whereas, CM originated from Activin-directed hESC differentiated cell population demonstrated a differential reparative effect on AEC wound repair model. CM obtained from Day-11 of differentiation significantly enhanced AEC wound repair in comparison to CM collected from pre- and post-Day-11 of differentiation. Day-11 CM enhanced AEC wound repair through significant stimulation of cell migration and cell proliferation. RT-PCR and immunocytochemistry confirmed that Day-11 CM was originated form a mixed population of endodermal/mesodermal differentiated hESC. This report suggests a putative paracrine-mediated epithelial injury healing mechanism by hESC secreted products, which is valuable in the development of novel stem cell-based therapeutic strategies.

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