Mechanisms of spindle positioning.

Accurate positioning of spindles is essential for asymmetric mitotic and meiotic cell divisions that are crucial for animal development and oocyte maturation, respectively. The predominant model for spindle positioning, termed "cortical pulling," involves attachment of the microtubule-based motor cytoplasmic dynein to the cortex, where it exerts a pulling force on microtubules that extend from the spindle poles to the cell cortex, thereby displacing the spindle. Recent studies have addressed important details of the cortical pulling mechanism and have revealed alternative mechanisms that may be used when microtubules do not extend from the spindle to the cortex

Divestment and Climate Change

In January of 2016, a number of Laurier faculty signed a letter (hereafter “The Letter”) urging the University to divest from fossil fuel companies in all endowment funds and the employee pension.1 This research note addresses a number of issues related to the divestment strategy—in particular, the stranded asset thesis, financial strategy alternatives, implementation challenges and the financial effects of divestment strategies. This note does not consider alternative strategies for decarbonizing the economy. The Letter itself does not explain why divestment is superior to alternatives like promoting research into clean energy generation, renewable energy sources, climate science, and environmental economics. The Letter articulates two goals. The first part of The Letter argues that, “Sooner or later, the world is going to get serious about regulating carbon emissions and when it does assets will likely be stranded.” This argument supports a risk management goal: that portfolio managers should hedge the risk of stranded assets. The second goal, articulated later in The Letter, is more revolutionary. In particular, that “the present generation…have a duty to help decarbonize the global economy as rapidly as possible.” Establishing the goal is important because the goal informs the optimal financial strategy. If the goal is to hedge stranded asset risk, then the best risk management strategies are: 1) diversification; or 2) portfolio reweighting. If the goal is to decarbonize the economy, then diversification and reweighting will have little effect. The financial strategy with the most potential to influence corporate behavior is full divestment. The remainder of this note is organized as follows. The second section defines the stranded asset thesis and contrasts it to another thesis. The third section defines two alternative financial strategies: divestment and reweighting. The fourth section discusses the challenge of using GHG emissions data to implement divestment or reweighting. The fifth section presents the financial theory of divestment and empirical evidence on the impact of divestment on risk and return. The sixth section concludes

Development of rapid, automated diagnostics for infectious disease: advances and challenges

The last 2 years has seen an exponential rise in the amount of research funding made available for the development of rapid diagnostic devices for infectious agents of medical importance. This review reports on several such projects. These highlight the development of fully automated devices for rapid diagnostics, ranging from fully automated real-time PCR-based detection methods to fully automated PCR- and array-based machines for the detection and typing of influenza. This review will also highlight the importance of refocusing work on classical immunoassay techniques, showing how biosensor-based immunoassays can greatly enhance existing assays and at a much reduced cost to molecular-based methods

A simple one-dimensional model for the explanation and analysis of GaAs MESFET behavior

The explanation of GaAs metal-semiconductor field effect transistor (MESFET) operation often involves the use of simplistic analytical formulae, which serve to obscure the more subtle physics of device action. The authors consider here a simple one-dimensional (1-D) model for GaAs MESFETs, which avoids more confusing numerical modeling schemes, yet still facilitates an analysis of the physical functionality of the device. The model takes into account current saturation due to either velocity saturation or channel pinch-off, the modulation of effective gate length and the series resistance of the regions beyond the gate. The results of the model have been compared to experimental data readily obtained from the literature, and the agreement has been shown to be goo

FORTRAN program for computing coordinates of circular-arc, single and tandem, turbine and compressor, blade sections on a plane

Coordinates for circular arc blade section of aircraft high speed compressor gas turbines were computed using FORTRAN 4 program. Aerodynamic configurations studied include single segment airfoils, airfoils with slots, and mutiple segment tandem arranged airfoil

Novel nonalloyed thermally stable Pd/Sn and Pd/Sn/Au ohmic contacts for the fabrication of GaAs MESFETs

GaAs metal-semiconductor field-effect transistors (MESFETs) have been fabricated utilizing thermally stable Pd/Sn and Pd/Sn/Au ohmic contacts for the first time. MESFETs with Pd/Ge ohmic contacts are fabricated for comparison. The thermal stability of the Pd/Sn, Pd/Ge and Pd/Sn/Au ohmic contacts is also presente

A casein kinase 1 prevents expulsion of the oocyte meiotic spindle into a polar body by regulating cortical contractility.

During female meiosis, haploid eggs are generated from diploid oocytes. This reduction in chromosome number occurs through two highly asymmetric cell divisions, resulting in one large egg and two small polar bodies. Unlike mitosis, where an actomyosin contractile ring forms between the sets of segregating chromosomes, the meiotic contractile ring forms on the cortex adjacent to one spindle pole, then ingresses down the length of the spindle to position itself at the exact midpoint between the two sets of segregating chromosomes. Depletion of casein kinase 1 gamma (CSNK-1) in Caenorhabditis elegans led to the formation of large polar bodies that contain all maternal DNA, because the contractile ring ingressed past the spindle midpoint. Depletion of CSNK-1 also resulted in the formation of deep membrane invaginations during meiosis, suggesting an effect on cortical myosin. Both myosin and anillin assemble into dynamic rho-dependent cortical patches that rapidly disassemble in wild-type embryos. CSNK-1 was required for disassembly of both myosin patches and anillin patches. Disassembly of anillin patches was myosin independent, suggesting that CSNK-1 prevents expulsion of the entire meiotic spindle into a polar body by negatively regulating the rho pathway rather than through direct inhibition of myosin

Modified bubble level senses pitch and roll angles over wide range

Bubble level sensor with fiber-optic field flattener is simple, rugged, small, and impervious to temperature and vibration effects. Pitch angles from -15 deg to +40 deg and roll angles of +30 deg are determined within 0.5 deg

A novel chromosome segregation mechanism during female meiosis.

In a wide range of eukaryotes, chromosome segregation occurs through anaphase A, in which chromosomes move toward stationary spindle poles, anaphase B, in which chromosomes move at the same velocity as outwardly moving spindle poles, or both. In contrast, Caenorhabditis elegans female meiotic spindles initially shorten in the pole-to-pole axis such that spindle poles contact the outer kinetochore before the start of anaphase chromosome separation. Once the spindle pole-to-kinetochore contact has been made, the homologues of a 4-μm-long bivalent begin to separate. The spindle shortens an additional 0.5 μm until the chromosomes are embedded in the spindle poles. Chromosomes then separate at the same velocity as the spindle poles in an anaphase B-like movement. We conclude that the majority of meiotic chromosome movement is caused by shortening of the spindle to bring poles in contact with the chromosomes, followed by separation of chromosome-bound poles by outward sliding