Fission yeast Stn1 is crucial for semi-conservative replication at telomeres and subtelomeres

The CST complex is a phylogenetically conserved protein complex consisting of CTC1/Cdc13, Stn1 and Ten1 that protects telomeres on linear chromosomes. Deletion of the fission yeast homologs stn1 and ten1 results in complete telomere loss; however, the precise function of Stn1 is still largely unknown. Here, we have isolated a high-temperature sensitive stn1 allele (termed stn1-1). stn1-1 cells abruptly lost telomeric sequence almost completely at the restrictive temperature. The loss of chromosomal DNA happened without gradual telomere shortening, and extended to 30 kb from the ends of chromosomes. We found transient and modest single-stranded G-strand exposure, but did not find any evidence of checkpoint activation in stn1-1 at the restrictive temperature. When we probed neutral-neutral 2D gels for subtelomere regions, we found no Y-arc-shaped replication intermediates in cycling cells. We conclude that the loss of telomere and subtelomere DNAs in stn1-1 cells at the restrictive temperature is caused by very frequent replication fork collapses specifically in subtelomere regions. Furthermore, we identified two independent suppressor mutants of the high-temperature sensitivity of stn1-1: a multi-copy form of pmt3 and a deletion of rif1. Collectively, we propose that fission yeast Stn1 primarily safeguards the semi-conservative DNA replication at telomeres and subtelomeres

The evolution of cutting forces during slot milling of unidirectional carbon fiber reinforced polymer (UD-CFRP) composites

Cutting forces generated during traditional machining of fiber reinforced polymer composites play an important role in determining machined surface quality. The cutting force signals also provide a live indicator of the dynamic behavior of the chip formation process. Cutting forces in machining FRPs are dependent primarily on the instantaneous fiber cutting angle, chip thickness, cutting edge geometry and the current state of cutting edge wear. In this study, effects of the cutting edge rake angle and tool wear on cutting force evolution during slot milling of unidirectional carbon fiber reinforced polymer (UD-CFRP) composite was investigated. The cutting forces were measured in the feed and normal directions and then transformed to the tangential and radial directions of the tool path. A simplified cutting force model consisting of a shearing region and a pressing was used to determine the shearing and friction force components. This allowed determination of the friction coefficient on the clearance face of the tool. It was found that the friction coefficient varied significantly with rake angle and fiber cutting angle. The effect of rake angle on cutting forces is more discernable in the shearing region with positive rake angle tool providing the most efficient cutting. Furthermore, correlations were found between machining damage and the magnitude and orientation of the resultant shearing force

Varying CFRP workpiece temperature during slotting : effects on surface metrics, cutting forces and chip geometry

Carbon fibre reinforced thermoset polymer (CFRP) components are typically edge trimmed using a milling process to achieve final part shape. During this process the material is subject to significant heating at the tool-workpiece interface. Damage due to heating is fibre orientation specific; for some orientations it can lead to matrix smearing, potentially hiding defects and for others it can increase pullout. Understanding these relationships is critical to attaining higher throughput by edge milling. For the first time this study focuses on active heating of the CFRP rather than passive measurement, through use of a thermocouple controlled system to heat a CFRP workpiece material from room temperature (RT) up to 110 °C prior to machining. Differences in cutting mechanisms for fibres oriented at 0, 45, 90 and -45° are observed with scanning electron microscopy (SEM), and quantified with using focus variation with an increase of 89.9% Sa reported between RT and 110°C CFRP panel pre-heating. Relationships to cutting forces through dynamometer readings and tool temperature through infra-red (IR) measurements are also made with a novel optical method to measure cut chips presented. Results show an increase in chip length and width for increasing cutting temperature from RT to 110°C (3.39 and 0.79 µm for length and width, respectively). This work improves current understandings of how the cutting mechanism changes with increased temperature and suggests how improved milling throughput can be achieved

Epifluorescent microscopy of edge-trimmed carbon fibre-reinforced polymers : an alternative to computed tomography scanning

X-Ray computed tomography (XCT) can be used to detect edge-milled carbon fibre-reinforced polymer (CFRP) defects. Significantly this method is able to show subsurface defects that cannot be captured by traditional methods such as stylus-based or more novel areal methods of surface quality measurement. While useful, this method can be prohibitive due to high equipment cost, scanning time and image resolution. XCT can often produce artefacts which falsely predict damage or obscure damage and depending on machine X-ray power often cannot resolve damage to fibre diameter which is critical when observing milled quality of the surface/subsurface. This study utilises epifluorescent (EF) optical microscopy to provide high-quality optical images as an alternative to XCT to observe through-depth damage of CFRP materials. The method of computing the novel damage criteria is presented, as well as the validation of the method which compares EF to XCT. Subsurface damage of fabric and unidirectional (UD) materials in 0°, 45°, 90° and −45° orientations to the cutting edge is observed to demonstrate typical defects. A novel metric resulting from the EF method provides a total area of damage when compared to a theoretically straight cut across the face of the edge-milled CFRP. The method shows that different subsurface damage exists for different fibre orientations to the cutting edge, highlighting the clear need for through-depth analysis of machined edges. In addition, the method is shown to be a suitable alternative to XCT with scope for further development of industrial aerospace and automotive quality control of machined CFRP parts

List of New Names of Plant Pathogenic Bacteria (2008-2010)

In 2010 the International Society of Plant Pathology Committee on the Taxonomy of Plant Pathogenic Bacteria published the Comprehensive List of Names of Plant Pathogenic Bacteria, 1980-2007 to provide an authoritative register of names of plant pathogens. In this manuscript we update the list of names by cataloguing names published from 2008 to 2010. We provide those names that have been validly and effectively published in this time frame, the proposed names that we judged to be invalid and names published earlier that did not make the previous lists. We also discuss problems that arise in the naming of strains that fall into the status Candidatus and nomenclatural problems in the genus Xanthomonas

Effects of tool coating and tool wear on the surface quality and flexural strength of slotted CFRP

Machining of carbon fibre reinforced polymer (CFRP) is abrasive and causes significant tool wear. The effect of tool wear on static flexural strength is investigated, using edge trimming with uncoated carbide and chemical vapour deposition (CVD) diamond coated burr style tools. Edge rounding (ER) criteria along with flank wear are used to observe tool degradation with ER shown to preferentially wear allowing the tool to become cyclically sharper and duller, corresponding to fluctuating dynamometer readings, a novelty for CFRP machining. Areal surface metrics degraded for an uncoated tool due to changes in cutting mechanism, whilst for up to 16.2 m of linear traverse, the coated tool showed limited changes. Tool wear, caused by edge trimming 7.2 m of CFRP, using an uncoated carbide tool, provided a flexural strength reduction of up to 10.5 %, directly linking tool wear to reduced mechanical strength

List of New Names of Plant Pathogenic Bacteria (2011-2012)

The International Society of Plant Pathology Committee on the Taxonomy of Plant Pathogenic Bacteria has responsibility to evaluate the names of newly proposed pathovars for adherence to the International Standards for Naming Pathovars of Phytopathogenic Bacteria. Currently, the Comprehensive List of Names and the List of New Names of Plant Pathogenic Bacteria provide the authoritative register of names of bacterial plant pathogens. In this manuscript we up-date the list of names by cataloguing and evaluating names of plant pathogenic bacteria published in 2011 and 2012. We provide those names that have been validly and effectively published in this time frame, the proposed names that we judged to be invalid, and names published earlier that did not make the previous lists

Intrinsic pinning property of FeSe0.5Te0.5

The intrinsic pinning properties of FeSe0.5Te0.5, which is the superconductor with Tc of about 14 K, were studied by the analysis of magnetization curves by the extended critical state model. In the magnetization measurements by SQUID magnetometer, the external magnetic fields were applied parallel and perpendicular to c-axis of the sample. The critical current density Jc's under the perpendicular field of 1 T were estimated by using the Kimishima model as about 1.6 x 10^4, 8.8 x 10^3, 4.1 x 10^3, and 1.5 x 10^3 A/cm2 at 5, 7, 9, and 11 K, respectively, and the temperature dependence of Jc could be fitted with the exponential law of Jc(0)xexp(-{\alpha}T /Tc) up to 9 K and power law of Jc(0)x(1-T / Tc)n near Tc.Comment: 19 pages, 7 figure

Effects of machine stiffness and cutting tool design on the surface quality and flexural strength of edge trimmed carbon fibre reinforced polymers

A 22 full factorial design of experiment is used to investigate the effects of two machining platforms (5-axis elevated gantry versus 6-axis articulated robotic system) and two cutting tool designs (burr versus herringbone) on surface metrics and flexural strength of a 14 ply T300 2x2 carbon fibre reinforced polymer. A range of areal metrics were considered to characterise the surface with Sal and Stdi best able to represent differences due to the choice of robotic system or overhead gantry. The robotic system produces coupons with flexural strengths up to 26% higher than the overhead gantry. The choice of tool has a less significant effect however machine-tool interactions do play a role in the flexural strength. Analysis using scanning electron microscopy shows that defects may be obscured by smeared matrix which may contribute to overall flexural strength differences

Monte Carlo simulations of membrane signal transduction events: Effect of receptor blockers on G-protein activation

Cells have evolved elaborate strategies for sensing, responding to, and interacting with their environment. In many systems, interaction of cell surface receptors with extracellular ligand can activate cellular signal transduction pathways leading to G-protein activation and calcium mobilization. In BC 3 H1 smooth muscle-like cells, we find that the speed of calcium mobilization as well as the fraction of cells which mobilize calcium following phenylephrine stimulation is dependent upon receptor occupation. To determine whether receptor inactivation affects calcium mobilization, we use the receptor antagonist prazosin to block a fraction of cell surface receptors prior to phenylephrine stimulation. For cases of equal receptor occupation by agonist, cells with inactivated or blocked receptors show diminished calcium mobilization following phenylephrine stimulation as compared to cells without inactivated receptors. Ligand/receptor binding and two-dimensional diffusion of receptors and G-proteins in the cell membrane are studied using a Monte Carlo model. The model is used to determine if receptor inactivation affects G-protein activation and thus the following signaling events for cases of equal equilibrium receptor occupation by agonist. The model predicts that receptor inactivation by antagonist binding results in lower G-protein activation not only by reducing the number of receptors able to bind agonist but also by restricting the movement of agonist among free receptors. The latter process is important to increasing the access of bound receptors to G-proteins.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43997/1/10439_2006_Article_BF00000009.pd