Gram-positive anaerobe <i>cocci </i>(GPAC) are underrepresented in the microbiome of filaggrin-deficient human skin

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Isolation of chromosome clusters from metaphase-arrested HeLa cells

We have developed a simplified approach for the isolation of metaphase chromosomes from HeLa cells. In this method, all the chromosomes from a cell remain together in a bundle which we call a “metaphase chromosome cluster”. Cells are arrested to 90–95% in metaphase, collected by centrifugation, extracted with non-ionic detergent in a low ionic strength buffer at neutral pH, and homogenised to strip away the cytoskeleton. The chromosome clusters which are released can then be isolated in a crude state by pelleting or they can be purified away from nearly all the interphase nuclei and cytoplasmic debris by banding in a Percoll TM density gradient. — This procedure has the advantages that it is quick and easy, metaphase chromatin is recovered in high yield, and Ca ++ is not needed to stabilise the chromosomes. Although the method does not yield individual chromosomes, it is nevertheless very useful for both structural and biochemical studies of mitotic chromatin. The chromosome clusters also make possible biochemical and structural studies of what holds the different chromosomes together. Such information could be useful in improving chromosome isolation procedures and for understanding suprachromosomal organisation of the nucleus.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47359/1/412_2004_Article_BF00327351.pd

Analysis and effect of large synchronous motors on power systems

Thesis (M. Ing. (Electrical Engineering))--North-West University, Potchefstroom Campus, 2005.Large synchronous machines are frequently utilised in industry and have several advantages and disadvantages. Although a synchronous motor is more efficient than an induction motor, it is also far more complex and sensitive in terms of starting and voltage dips respectively. It is therefore important to understand the impact and sensitivities of a synchronous motor. The impact that a large synchronous motor has on a power system network can be significant. The impact of the quality of supply of the power system on a large synchronous motor can also impact negatively on the operational availability of the motor and should be well understood. A synchronous motor will be installed in a production facility and as such, this investigation is in the form of a case study. This document entails the detailed study, modelling and simulation of the impact of a large low-speed synchronous motor on a power system network, as well as the impact of the power system network on the motor (in terms of voltage dips). Detailed machine and system parameters were gathered from the motor supplier and utility. The effect that the motor has on the network and the effect of the network on the motor were analysed with detailed actual system and motor data. These analyses included load flows, short circuits, motor starting and a transient stability. A comparison of the supplier-suggested stability limits was made with the outcome of an undervoltage stability study. The study revealed that the supplier was over-pessimistic about the voltage dip ride-through capability. Graph 3.28: Voltage dip scatter plot indicating different tripping areas indicates a significant improvement from what was initially offered by the supplier. The dip ride-through capability was increased almost threefold after the interaction of the motor with the power system was studied in detail. This increased dip ride-through capability will have a significant impact on the plant performance. This however must be achieved without any damage to the motor or the associated equipment of this machine. Proper control with a thorough understanding of the synchronous motor's behaviour will lead to an increase in the machine's operational availability (on-line time for a continuous process)Master

Conceptual combination with PUNC

Noun-noun compounds play a key role in the growth of language. In this article we present a system for producing and understanding noun-noun compounds (PUNC). PUNC is based on the Constraint theory of conceptual combination and the C-3 model. The new model incorporates the primary constraints of the Constraint theory in an integrated fashion, creating a cognitively plausible mechanism of interpreting noun-noun phrases. It also tries to overcome algorithmic limitations of the C-3 model in being more efficient in its computational complexity, and deal with a wider span of empirical phenomena, such as dimensions of word familiarity. We detail the model, including knowledge representation and interpretation production mechanisms. We show that by integrating the constraints of the Constraint theory of conceptual combination and prioritizing the knowledge available within a concept's representation, PUNC can not only generate interpretations that reflect those produced by people, but also mirror the differences in processing times for understanding familiar, similar and novel word combinations