Twist-bend nematic phase in cyanobiphenyls and difluoroterphenyls bimesogens

The paper reviews assignment of the low-temperature nematic phase observed in simple bimesogenic or dimeric systems based on cyanobiphenyls and difluoroterphenyls to the twist-bend nematic phase, NTB, using a range of experimental techniques. These include DSC, X-rays, Polarising Microscopy, electro-optics, birefringence and measurements of the electroclinic effect arising from flexoelectricity. An emphasis is laid on the observations of the chiral domains of opposite handedness at zero field in an otherwise achiral liquid crystalline system in this phase. These observations are a direct consequence of the structure of the twist-bend phase predicted by Ivan Dozov for achiral bent core molecules. The paper reviews the electro-optic phenomena and the observed electroclinic effect and how these observations assign it as the NTB phase. Results of the nanoscale helical pitch measurements using freeze-fracture microscopy are reviewed and discussed briefly. Results of the measurements of elastic constants especially close to the N–NTB transition are also reviewed

Origin of Superconductivity in Boron-doped Diamond

Superconductivity of boron-doped diamond, reported recently at T_c=4 K, is investigated exploiting its electronic and vibrational analogies to MgB2. The deformation potential of the hole states arising from the C-C bond stretch mode is 60% larger than the corresponding quantity in MgB2 that drives its high Tc, leading to very large electron-phonon matrix elements. The calculated coupling strength \lambda ~ 0.5 leads to T_c in the 5-10 K range and makes phonon coupling the likely mechanism. Higher doping should increase T_c somewhat, but effects of three dimensionality primarily on the density of states keep doped diamond from having a T_c closer to that of MgB2.Comment: Four pages with two embedded figures, corrected fig1. (To appear in Physical Review Letters(2004)

The cestode parasite Grillotia Angeli as a biological tag for mackerel in the eastern North Atlantic

The trypanorhynch cestode Grillotia angeli Dollfus, 1969, infects mackerel Scomber scombrus L. up to the age of two years and survives thereafter as an encvsted plerocercus for as long as the mackerel lives. In the eastern North Atlantic infection can only take ilace in and to the south of ICES sub-area VII, ie to the south and west of Britain and Ireland. In year classes 1977 and earlier, 13.8% of mackerel which originated from nursery grounds in sub-area VII were infected with -G. angeli; in yLar classes 1978 and later, prevalence decreased to 1.2%. Data from year elasses 1977 and earlier indicate that: (1) mackerel caught off the north coast of Spain (sub-area VIII) and off Portugal (sub-area IX) were of dif ferent nursery origin from those caught further north; (2) mackerel caught in the southern North Sea (Division IVc) were predominately of southwestern origin; (3) to the northwest of Scotland (Division VIa north of 58ON) the proportions of mackerel of southwestern origin decreased from approximately 50% in September to 10% in January-February, then increased to >50% in March-April; (4) approximately 30% of all rnackerel caught in the Norwegian Sea (Division IIa) and the northern North Sea (Division IVa) were of southwestern origin. Brevalence data from different areas suggest that mackerel of year classes 1978 and later from southwestern nursery grounds have been migrating into northern areas in greater numbers than earlier year classes

The stabilisation of the Nx phase in mixtures

The phase behaviour of mixtures between two symmetric dimers, CBC9CB and the ether-linked analogue CBOC9OCB was investigated by Polarizing Optical Microscopy (POM), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) studies. The dimeric constituents are fully miscible and the construction of a temperature-composition phase diagram reveals a surprising amplification of the stability of the Nx phase in compositions of up to 37 wt% of CBOC9OCB in CBC9CB. The origin for this enhancement of stability is discussed and an explanation based on chiral recognition is developed

Precise Tight-binding Description of the Band Structure of MgB2

We present a careful recasting of first-principles band structure calculations for MgB2 in a non-orthogonal sp-tight-binding (TB) basis. Our TB results almost exactly reproduce our full potential linearized augmented plane wave results for the energy bands, the densities of states and the total energies. Our procedure generates transferable Slater-Koster parameters which should be useful for other studies of this important material.Comment: REVTEX, 2 Encapsulated PostScript Figure

Positron annihilation induced Auger electron spectroscopy

Recently, Weiss et al. have demonstrated that it is possible to excite Auger transitions by annihilating core electrons using a low energy (less than 30eV) beam of positrons. This mechanism makes possible a new electron spectroscopy, Positron annihilation induced Auger Electron Spectroscopy (PAES). The probability of exciting an Auger transition is proportional to the overlap of the positron wavefunction with atomic core levels. Since the Auger electron energy provides a signature of the atomic species making the transition, PAES makes it possible to determine the overlap of the positron wavefunction with a particular element. PAES may therefore provide a means of detecting positron-atom complexes. Measurements of PAES intensities from clean and adsorbate covered Cu surfaces are presented which indicate that approx. 5 percent of positrons injected into CU at 25eV produce core annihilations that result in Auger transitions

Noninvasive Measurement of Dissipation in Colloidal Systems

According to Harada and Sasa [Phys. Rev. Lett. 95, 130602 (2005)], heat production generated in a non-equilibrium steady state can be inferred from measuring response and correlation functions. In many colloidal systems, however, it is a nontrivial task to determine response functions, whereas details about spatial steady state trajectories are easily accessible. Using a simple conditional averaging procedure, we show how this fact can be exploited to reliably evaluate average heat production. We test this method using Brownian dynamics simulations, and apply it to experimental data of an interacting driven colloidal system

Introducing zanadio: A digitalized, multimodal program to treat obesity

While the prevalence of overweight and obesity has been increasing annually, the accessibility of on-site treatment programs is not rising correspondingly. Digital, evidence-based obesity treatment programs could potentially alleviate this situation. The application zanadio has been developed to enable patients with obesity (BMI 30-45 kg/m2) to participate in a digital, multimodal weight reduction program based on current treatment guidelines. This article is divided into two parts: (I) it introduces zanadio, its aims and therapeutic concept, and (II) provides a first impression and demographic data on more than 11,000 patients from across the country who have used zanadio within the last 16 months, which demonstrates the demand for a digital obesity treatment. zanadio has the potential to partially close the current gap in obesity care. Future work should focus on identifying predictors of successful weight loss to further individualize digital obesity treatment, and an important next step would be to prevent obesity, i.e., to start the treatment at lower BMI levels, and to invent digital treatment programs for children and adolescents

Thermal optical non-linearity of nematic mesophase enhanced by gold nanoparticles – an experimental and numerical investigation

In this work the mechanisms leading to the enhancement of optical nonlinearity of nematic liquid crystalline material through localized heating by doping the liquid crystals (LCs) with gold nanoparticles (GNPs) are investigated. We present some experimental and theoretical results on the effect of voltage and nanoparticle concentration on the nonlinear response of GNP-LC suspensions. The optical nonlinearity of these systems is characterized by diffraction measurements and the second order nonlinear refractive index, n 2 , is used to compare systems with different configurations and operating conditions. A theoretical model based on heat diffusion that takes into account the intensity and finite size of the incident beam, the nanoparticle concentration dependent absorbance of GNP doped LC systems and the presence of bounding substrates is developed and validated. We use the model to discuss the possibilities of further enhancing the optical nonlinearity