Cellular Structures of Carbon Nanotubes in a Polymer Matrix Improve Properties Relative to Composites with Dispersed Nanotubes

A new processing method has been developed to combine a polymer and single wall carbon nanotubes (SWCNTs) to form electrically conductive composites with desirable rheological and mechanical properties. The process involves coating polystyrene (PS) pellets with SWCNTs and then hot pressing to make a contiguous, cellular SWCNT structure. By this method, the electrical percolation threshold decreases and the electrical conductivity increases significantly as compared to composites with a well-dispersed SWCNTs. For example, a SWCNT / PS composite with 0.5 wt% nanotubes and made by this coated particle process (CPP) has an electrical conductivity of ~ 3 x 10-4 S/cm, while a well-dispersed composite made by a coagulation method with the same SWCNT amount has an electrical conductivity of only ~ 10-8 S/cm. The rheological properties of the composite with a macroscopic cellular SWCNT structure are comparable to PS, while the well-dispersed composite exhibits a solid-like behavior, indicating that composites made by this new CPP method are more processable. In addition, the mechanical properties of the CPP-made composite decrease only slightly, as compared with PS. Relative to the common appoach of seeking better dispersion, this new fabrication method provides an important alternative means to higher electrical conductivity in SWCNT / polymer composites. Our straightforward particle coating and pressing method avoids organic solvents and is suitable for large-scale, inexpensive processing using a wide variety of polymer and nanoparticles

Insect visual sensitivity to long wavelengths enhances colour contrast of insects against vegetation

The sensitivity of animal photoreceptors to different wavelengths of light strongly influence the perceived visual contrast of objects in the environment. Outside of the human visual wavelength range, ultraviolet sensitivity in many species provides important and behaviourally relevant visual contrast between objects. However, at the opposite end of the spectrum, the potential advantage of red sensitivity remains unclear. We investigated the potential benefit of long wavelength sensitivity by modelling the visual contrast of a wide range of jewel beetle colours against flowers and leaves of their host plants to hypothetical insect visual systems. We find that the presence of a long wavelength sensitive photoreceptor increases estimated colour contrast, particularly of beetles against leaves. Moreover, under our model parameters, a trichromatic visual system with ultraviolet (λ(max) = 355 nm), short (λ(max) = 445 nm) and long (λ(max) = 600 nm) wavelength photoreceptors performed as well as a tetrachromatic visual system, which had an additional medium wavelength photoreceptor (λ(max) = 530 nm). When we varied λ(max) for the long wavelength sensitive receptor in a tetrachromatic system, contrast values between beetles, flowers and leaves were all enhanced with increasing λ(max) from 580 nm to at least 640 nm. These results suggest a potential advantage of red sensitivity in visual discrimination of insect colours against vegetation and highlight the potential adaptive value of long wavelength sensitivity in insects

The genomic diversification of grapevine clones.

BACKGROUND:Vegetatively propagated clones accumulate somatic mutations. The purpose of this study was to better appreciate clone diversity and involved defining the nature of somatic mutations throughout the genome. Fifteen Zinfandel winegrape clone genomes were sequenced and compared to one another using a highly contiguous genome reference produced from one of the clones, Zinfandel 03. RESULTS:Though most heterozygous variants were shared, somatic mutations accumulated in individual and subsets of clones. Overall, heterozygous mutations were most frequent in intergenic space and more frequent in introns than exons. A significantly larger percentage of CpG, CHG, and CHH sites in repetitive intergenic space experienced transition mutations than in genic and non-repetitive intergenic spaces, likely because of higher levels of methylation in the region and because methylated cytosines often spontaneously deaminate. Of the minority of mutations that occurred in exons, larger proportions of these were putatively deleterious when they occurred in relatively few clones. CONCLUSIONS:These data support three major conclusions. First, repetitive intergenic space is a major driver of clone genome diversification. Second, clones accumulate putatively deleterious mutations. Third, the data suggest selection against deleterious variants in coding regions or some mechanism by which mutations are less frequent in coding than noncoding regions of the genome

Two-Timescale Learning Using Idiotypic Behaviour Mediation For A Navigating Mobile Robot

A combined Short-Term Learning (STL) and Long-Term Learning (LTL) approach to solving mobile-robot navigation problems is presented and tested in both the real and virtual domains. The LTL phase consists of rapid simulations that use a Genetic Algorithm to derive diverse sets of behaviours, encoded as variable sets of attributes, and the STL phase is an idiotypic Artificial Immune System. Results from the LTL phase show that sets of behaviours develop very rapidly, and significantly greater diversity is obtained when multiple autonomous populations are used, rather than a single one. The architecture is assessed under various scenarios, including removal of the LTL phase and switching off the idiotypic mechanism in the STL phase. The comparisons provide substantial evidence that the best option is the inclusion of both the LTL phase and the idiotypic system. In addition, this paper shows that structurally different environments can be used for the two phases without compromising transferability.Comment: 40 pages, 12 tables, Journal of Applied Soft Computin

Latent stem and progenitor cells in the hippocampus are activated by neural excitation

The regulated production of neurons in the hippocampus throughout life underpins important brain functions such as learning and memory. Surprisingly, however, studies have so far failed to identify a resident hippocampal stem cell capable of providing the renewable source of these neurons. Here, we report that depolarizing levels of KCl produce a threefold increase in the number of neurospheres generated from the adult mouse hippocampus. Most interestingly, however, depolarizing levels of KCl led to the emergence of a small subpopulation of precursors (approximately eight per hippocampus) with the capacity to generate very large neurospheres (>250 µm in diameter). Many of these contained cells that displayed the cardinal properties of stem cells: multipotentiality and self-renewal. In contrast, the same conditions led to the opposite effect in the other main neurogenic region of the brain, the subventricular zone, in which neurosphere numbers decreased by ~40% in response to depolarizing levels of KCl. Most importantly, we also show that the latent hippocampal progenitor population can be activated in vivo in response to prolonged neural activity found in status epilepticus. This work provides the first direct evidence of a latent precursor and stem cell population in the adult hippocampus, which is able to be activated by neural activity. Because the latent population is also demonstrated to reside in the aged animal, defining the precise mechanisms that underlie its activation may provide a means to combat the cognitive deficits associated with a decline in neurogenesis

A psychologically informed, audiologist-delivered, manualised intervention for tinnitus:protocol for a randomised controlled feasibility trial (Tin Man study)

Background: Chronic tinnitus is a common incurable condition often associated with depression, anxiety, insomnia and reduced quality of life. Within National Health Service (NHS) audiology in the United Kingdom (UK), no standard protocol currently exists for the treatment of tinnitus. Counselling is only available in less than half of audiology departments, and there is no agreed standard for what constitutes tinnitus counselling. There is substantial evidence from systematic reviews for the clinical benefit of cognitive behaviour therapy (CBT) for tinnitus delivered by clinical psychologists or psychiatrists, but no studies have sufficiently evidenced the NHS model of tinnitus care where management is increasingly being delivered by audiology professionals. In a pilot randomised controlled trial (RCT), this study aims to evaluate the feasibility of comparing a psychologically informed guidance manual developed to support audiologist management of tinnitus with usual treatment. Methods/design: Phase 1 consisted of three development stages: (1) a scoping review to generate a comprehensive set of tinnitus counselling components, (2) a Delphi survey involving expert patients (n = 18) and clinicians (n = 21) to establish consensus on the essential core attributes of tinnitus counselling, and (3) incorporation of these elements into a manualised care protocol. In phase 2, following training in a dedicated workshop, the manualised intervention will be delivered by three experienced audiologists across three different sites. Patients (n = 30) will be randomly allocated to receive either (1) psychologically informed management from an audiologist trained to deliver the manualised intervention or (2) treatment as usual (TAU) from an audiologist who has not received this training. Quantitative outcome measures will be administered at baseline, discharge and 6-month follow-up. Qualitative interviews with participating patients and clinicians will be conducted to gather perspectives on the feasibility and acceptability of the manualised intervention. Discussion: The feasibility of proceeding to a definitive RCT will be assessed via compliance with the manual, willingness to be randomised, number of eligible participants, rate of recruitment, retention and collection of quantitative outcome measures. This research offers an important first step to an evidence-based, standardised and accessible approach to tinnitus care

A psychologically informed, audiologist-delivered, manualised intervention for tinnitus:protocol for a randomised controlled feasibility trial (Tin Man study)

Background: Chronic tinnitus is a common incurable condition often associated with depression, anxiety, insomnia and reduced quality of life. Within National Health Service (NHS) audiology in the United Kingdom (UK), no standard protocol currently exists for the treatment of tinnitus. Counselling is only available in less than half of audiology departments, and there is no agreed standard for what constitutes tinnitus counselling. There is substantial evidence from systematic reviews for the clinical benefit of cognitive behaviour therapy (CBT) for tinnitus delivered by clinical psychologists or psychiatrists, but no studies have sufficiently evidenced the NHS model of tinnitus care where management is increasingly being delivered by audiology professionals. In a pilot randomised controlled trial (RCT), this study aims to evaluate the feasibility of comparing a psychologically informed guidance manual developed to support audiologist management of tinnitus with usual treatment. Methods/design: Phase 1 consisted of three development stages: (1) a scoping review to generate a comprehensive set of tinnitus counselling components, (2) a Delphi survey involving expert patients (n = 18) and clinicians (n = 21) to establish consensus on the essential core attributes of tinnitus counselling, and (3) incorporation of these elements into a manualised care protocol. In phase 2, following training in a dedicated workshop, the manualised intervention will be delivered by three experienced audiologists across three different sites. Patients (n = 30) will be randomly allocated to receive either (1) psychologically informed management from an audiologist trained to deliver the manualised intervention or (2) treatment as usual (TAU) from an audiologist who has not received this training. Quantitative outcome measures will be administered at baseline, discharge and 6-month follow-up. Qualitative interviews with participating patients and clinicians will be conducted to gather perspectives on the feasibility and acceptability of the manualised intervention. Discussion: The feasibility of proceeding to a definitive RCT will be assessed via compliance with the manual, willingness to be randomised, number of eligible participants, rate of recruitment, retention and collection of quantitative outcome measures. This research offers an important first step to an evidence-based, standardised and accessible approach to tinnitus care

Relations between matrix metalloproteinase (MMP) activity, type I collagen accumulation, and glomerular sclerosis in the oim mouse [abstract]

Abstract only availableFaculty Mentor: Dr. Charlotte Phillips, BiochemistryA novel type I collagen glomerulopathy was identified in oim mice [pro2(I) collagen (COL1A2 deficient)], which synthesize exclusively homotrimeric type I collagen, [1(I)3]. Type I collagen exists predominantly as a heterotrimer [1(I)2 2(I)], although the homotrimeric form is present in small amounts in skin, embryologic tissues and would healing. However, the functional role of this homotrimer is unknown. In the oim mouse kidney the homotrimer accumulates in the glomeruli. Under normal physiologic conditions type I collagen is not present in the glomeruli; its accumulation is pathologic. In the following study we use an innovative perfusion technique that utilizes magnetic beads to isolate the glomeruli from surrounding tissue to investigate whether the accumulation of homotrimer is a result of either increased synthesis or a decreased degradative function of glomerular MMPs. We demonstrate through RT-PCR amplification that wild type and oim glomerular cells do, in fact, produce transcripts for MMP-1, MMP-2, MMP-9, and MMP-13. Furthermore, preliminary studies from collagen gel zymography suggest that glomerular MMPs cleave heterotrimeric type I collagen preferentially