Analysis of a variational model for nematic shells

We analyze an elastic surface energy which was recently introduced by G. Napoli and L.Vergori to model thin films of nematic liquid crystals. We show how a novel approach that takes into account also the extrinsic properties of the surfaces coated by the liquid crystal leads to considerable differences with respect to the classical intrinsic energy. Our results concern three connected aspects: i) using methods of the calculus of variations, we establish a relation between the existence of minimizers and the topology of the surface; ii) we prove, by a Ginzburg-Landau approximation, the well-posedness of the gradient flow of the energy; iii) in the case of a parametrized axisymmetric torus we obtain a stronger characterization of global and local minimizers, which we supplement with numerical experiments.Comment: Revised version. Includes referee's comments. Some proofs are changed. To appear on Mathematical Models and Methods in Applied Sciences (M3AS

Equilibrium configurations of nematic liquid crystals on a torus

The topology and the geometry of a surface play a fundamental role in determining the equilibrium configurations of thin films of liquid crystals. We propose here a theoretical analysis of a recently introduced surface Frank energy, in the case of two-dimensional nematic liquid crystals coating a toroidal particle. Our aim is to show how a different modeling of the effect of extrinsic curvature acts as a selection principle among equilibria of the classical energy, and how new configurations emerge. In particular, our analysis predicts the existence of new stable equilibria with complex windings.Comment: 9 pages, 6 figures. This version is to appear on Phys. Rev.

RECURSIVE PATH FOLLOWING IN LOG POLAR SPACE FOR AUTONOMOUS LEAF CONTOUR EXTRACTION

Use of image segmentation has caused agriculture advancement in species identification, chlorophyll measurements, plant growth and disease detection. Most methods require some level of manual segmentation as autonomous image segmentation is a difficult task. Methods with the highest segmentation precision use a priori knowledge obtained from user input which is time consuming and subjective. This research focuses on providing current segmentation methods a pre-processing model that autonomously extracts an internal and external contour of the leaf. The model converts the uniform Cartesian images to non-uniformly sampled images in log polar space. A recursive path following algorithm was designed to map out the leaf’s edge boundary. This boundary is shifted inward and outward to create two contours; one that lies within the foreground and one within the background. The image database consists of 918 leaves from multiple plants and different background mediums. The model successfully created contours for 714 of the leaves. Results of the autonomously created contours being used in lieu of user-input contours for a current segmentation algorithm are presented

FEDSM2003-45024 WAVELET ANALYSIS OF SPACE-VARYING INTERMITTENT WALL PRESSURE FIELD OF TRANSITIONAL BOUNDARY LAYER

ABSTRACT Measurements of the space-time fluctuating wall pressure field across the transition region of a flat plate zero pressure gradient boundary layer have been performed in an anechoic wind tunnel with a 64-element linear array of sub-miniature hearing-aid microphones (d + = 15). Wavelet transforms are being used to quantify the structure and nonhomogeneous wavenumber-frequency spectral content of the field. The results illustrate that the fluctuations within the turbulent spots scale with those which exists in a fully developed turbulent boundary layer consistent with previous findings. The spectral contributions due to a second much larger length/time scale associated with the mean spacing between spots (e.g., turbulent spot wavepacket pulse trains) is under investigation. Based on an analysis of sinusoidal pulse train signals and consideration of the well established bursting frequency in turbulent boundary layers, it is conjectured here that the turbulent spot wavepacket pulse trains should produce a statistical distribution of energy about the mean fundamental pulse train frequency

RECENZJE

Comparative Constitutional Law in Asia, red. R. Dixon, T. Ginsburg, Edward Edgar Publishing Limited, Northampton 2014, ss. 353 (Anna Michalak)Huang Lihai, Kto biega jeszcze szybciej niż błyskawica, przeł. Wu Lan,Wydawnictwo Uniwersytetu Gdańskiego–Flower City Publishing House, Gdańsk–Kanton 2015, ss. 222 (Tomasz Snarski

Effective pain reduction during bone marrow biopsy and aspiration – Technique over experience

Background: Bone marrow biopsy and aspiration (BMBA) is a diagnostic procedure within the field of internal medicine. The intensity of the pain felt by the patients often goes unrecognized by the medical staff. No extant studies have addressed pain intensity experienced during each particular step of a BMBA. Objectives: The aim was to analyze the pain intensity and explore the extent to which the technique applied by the doctor performing the biopsy influences the pain level. Methods: A survey comprising 17 questions was created and it addressed characteristics of the patients, previous experience and pain intensity on each step of the procedure. Results: 125 patients were enrolled into the study. Age (p=0.009), gender (p=0.02), pain during previous biopsies (