The prevalence and morphometric features of mastoid emissary vein on multidetector computed tomography

Background: The aim of the study was to evaluate the prevalence and morphometric features of mastoid emissary vein (MEV) on multidetector computed tomography (MDCT) scans, emphasize its clinical significance and review its surgical implications. Materials and methods: Cranial and temporal bone MDCTs of 248 patients (496 sides) were analysed by 2 radiologists. Mastoid foramen (MF) was defined on the 3 dimensional volume rendered (3DVR) images. The MF and mastoid emissary canal (MEC) were investigated in axial thin slices and the diameters of the largest MF and MEC were measured. Mean diameters of MF and MEC were determined. The number of the mastoid foramina was noted. Differences in MF prevalence by sex and side were evaluated. Results: The overall prevalence of MEC was 92.3%. It was observed in 91.5% of women and 93.3% of men. MEC was present on the right side in 84.7% and on the left side in 82.3% of temporal bones. The mean diameter of MF was 1.92 ± ± 1.02 mm on the right and 1.84 ± 0.98 mm on the left. In both sides the number of the MF’s changed from absent to triple. The mean diameter of MEC was 1.58 ± 0.86 mm on the right and 1.48 ± 0.79 mm on the left side. The mean diameter of MEC was significantly larger in men. No significant correlation was detected between age and the MEC diameter. Conclusions: The preoperative detection of mastoid emissary veins is necessary. The radiologists should be familiar with their clinical significance and variant appearances and report them accurately. Knowledge of their morphology and surgical implications by the surgeons will make them aware to avoid unexpected and fatal complications while operating in the suboccipital and mastoid area. MDCT is a reliable diagnostic tool for imaging the MEC and MF.

Phase and frequency entrainment in locally coupled phase oscillators with repulsive interactions

Recent experiments in one and two-dimensional microfluidic arrays of droplets containing Belousov -Zhabotinsky reactants show a rich variety of spatial patterns [J. Phys. Chem. Lett. 1, 1241-1246 (2010)]. The dominant coupling between these droplets is inhibitory. Motivated by this experimental system, we study repulsively coupled Kuramoto oscillators with nearest neighbor interactions, on a linear chain as well as a ring in one dimension, and on a triangular lattice in two dimensions. In one dimension, we show using linear stability analysis as well as numerical study, that the stable phase patterns depend on the geometry of the lattice. We show that a transition to the ordered state does not exist in the thermodynamic limit. In two dimensions, we show that the geometry of the lattice constrains the phase difference between two neighbouring oscillators to 120 degrees. We report the existence of domains with either clockwise or anti-clockwise helicity, leading to defects in the lattice. We study the time dependence of these domains and show that at large coupling strengths, the domains freeze due to frequency synchronization. Signatures of the above phenomena can be seen in the spatial correlation functions.Comment: 9 pages, 12 figure

Monitoring of yeast metabolism with calorimetry

A system for calorimetric measurements is established in a 1500 L pilot bioreactor. Saccharomyces cerevisiae, baker’s yeast has three metabolic pathways: 1) purely oxidative, glucose consuming; 2) purely reductive, glucose consuming and ethanol producing and 3) purely oxidative, ethanol consuming. Designing experiments to lead the yeast to a single pathway, the accuracy of the calorimetric measurements are verified. Using on-line data of microbial heat production and substrate consumption, the combustion enthalpies of glucose and ethanol in purely oxidative (aerobic) fed batch fermentations are determined as 15900 and 29000 kJ/kg respectively, Combustion enthalpy of glucose in purely reductive (anaerobic) environment is determined as 511 kJ/kg. These values are in good corresponding with literature data. It is now possible to determine the fraction of substrate uptake utilized for energy (catabolism, k) and biosynthesis (anabolism, a) metabolisms on-line. In oxidative (aerobic) fermentations we determined kSox=0.45 for glucose, kEox=0.63 for ethanol and in reductive (anaerobic) fermentations kSred=0.96 for glucose; the anabolism factors are aSox=0.55, aEox=0.37 and aSred=0.04 respectively. The single pathways can occur together so that an experiment is designed with changing environmental conditions to prove the overall calorimetric model. The result is that measured and the calculated microbial heat energy rates are in good accordance. Calorimetric measurements can be used to monitor yeast metabolism on-line, for advanced control strategies or, to predict fermentations or for designing heat exchanger or bioreactor systems

The Effect of Helium Sedimentation on Galaxy Cluster Masses and Scaling Relations

Recent theoretical studies predict that the inner regions of galaxy clusters may have an enhanced helium abundance due to sedimentation over the cluster lifetime. If sedimentation is not suppressed (e.g., by tangled magnetic fields), this may significantly affect the cluster mass estimates. We use Chandra X-ray observations of eight relaxed galaxy clusters to investigate the upper limits to the effect of helium sedimentation on the measurement of cluster masses and the best-fit slopes of the Y_X - M_500 and Y_X - M_2500 scaling relations. We calculated gas mass and total mass in two limiting cases: a uniform, un-enhanced abundance distribution and a radial distribution from numerical simulations of helium sedimentation on a timescale of 11 Gyrs. The assumed helium sedimentation model, on average, produces a negligible increase in the gas mass inferred within large radii (r < r500) (1.3 +/- 1.2 per cent) and a (10.2 +/- 5.5) per cent mean decrease in the total mass inferred within r < r500. Significantly stronger effects in the gas mass (10.5 +/- 0.8 per cent) and total mass (25.1 +/- 1.1 per cent) are seen at small radii owing to a larger variance in helium abundance in the inner region, r < 0.1 r500. We find that the slope of the Y_X -M_500 scaling relation is not significantly affected by helium sedimentation.Comment: 11 pages, accepted for publication in Astronomy and Astrophysic

Segregation of Polymers in Confined Spaces

We investigate the motion of two overlapping polymers with self-avoidance confined in a narrow 2d box. A statistical model is constructed using blob free-energy arguments. We find spontaneous segregation under the condition: $L > R_{//}$, and mixing under $L < R_{//}$, where L is the length of the box, and $R_{//}$ the polymer extension in an infinite slit. Segregation time scales are determined by solving a mean first-passage time problem, and by performing Monte Carlo simulations. Predictions of the two methods show good agreement. Our results may elucidate a driving force for chromosomes segregation in bacteria

The process of crack propagation during rotary percussion drilling of hard rocks

Rotary percussion drilling determines the possibility of reducing waste and intrusion of foreign objects into the solution. It reduces drilling costs and increases the processing speed of the resulting product, and also contributes to the high-quality result at the beginning of the drilling string project design. Reducing the number of cracks decreases the amount of rock used and improves the quality of the resulting product. The novelty of the study lies in development and practical application of fibreglass drilling strings that provide reduced energy consumption for drilling and increased elasticity. The authors show that the use of such strings makes possible to shorten the time of field development and increase the yield in difficult geological conditions. Establishment of strings made of polymeric materials and composite structures can significantly reduce the number of cracks in hard rocks. This determines the conditions for the environmental friendliness of the entire production process, the gradual reduction of waste rock usage and increase in the secondary use of oil production materials

Modeling the Transition between Localized and Extended Deposition in Flow Networks through Packings of Glass Beads

We use a theoretical model to explore how fluid dynamics, in particular, the pressure gradient and wall shear stress in a channel, affect the deposition of particles flowing in a microfluidic network. Experiments on transport of colloidal particles in pressure-driven systems of packed beads have shown that at lower pressure drop, particles deposit locally at the inlet, while at higher pressure drop, they deposit uniformly along the direction of flow. We develop a mathematical model and use agent-based simulations to capture these essential qualitative features observed in experiments. We explore the deposition profile over a two-dimensional phase diagram defined in terms of the pressure and shear stress threshold, and show that two distinct phases exist. We explain this apparent phase transition by drawing an analogy to simple one-dimensional models of aggregation in which the phase transition is calculated analytically.Comment: 9 pages, 6 figures including Supplemental Materia

Jamming as a critical phenomenon : A field theory of zero-temperature grain packings

Peer reviewedPublisher PD

Dynamics in the Metabasin Space of a Lennard-Jones Glass Former: Connectivity and Transition Rates

Using simulations, we construct the effective dynamics in metabasin space for a Lennard-Jones glass-former. Metabasins are identified via a scheme that measures transition rates between inherent structures, and generates clusters of inherent structures by drawing in branches that have the largest transition rates. The effective dynamics is shown to be Markovian but differs significantly from the simplest trap models. We specifically show that retaining information about the connectivity in metabasin space is crucial for reproducing the slow dynamics observed in this system.Comment: 8 pages, 10 figures. References add. A typo correcte