Missing Gamow-Teller strength in mass 42

The reaction ⁴²Ca(p,n)⁴²Sc at E_p = 160 MeV is used to measure the Gamow-Teller (GT) strength function. Normalization of the dominant peak in the (p,n) spectrum to B(GT) determined from the analogous transition in the beta decay of ⁴²Ti renders the strength function absolute, and the total measured stregth is about half of the minimum value required for a T = 1 nucleus. Shell model calculations are presented which reproduce the shape of the strength function, but overpredict the absolute measured strength by about a factor of two. Evidently the missing strength has been moved out of the region of nucleon particle-hole excitations, and quenching, due possibly to Δ₃₃ coupling, is indicated. Symmetry implications of an observed strong suppression of the T_> component of the GT strength are discussed.     

Excitability in a quantum dot semiconductor laser with optical injection

We experimentally analyze the dynamics of a quantum dot semiconductor laser operating under optical injection. We observe the appearance of single- and double-pulse excitability at one boundary of the locking region. Theoretical considerations show that these pulses are related to a saddle-node bifurcation on a limit cycle as in the Adler equation. The double pulses are related to a period-doubling bifurcation and occur on the same homoclinic curve as the single pulses.     

Changes in the heavy metal contents of soil from the Park Grass Experiment at Rothamsted Experimental Station

The classical Rothamsted Experiments allow to contribute to current research. The heavy metal content of soil and hay samples have been measured with ICP-AES from a control and a fertilized plot of the Park Grass Experiment. Today a difference of 1.2 can be observed in the pH levels of the control and fertilized plots; the pH level of the control plot has decreased about 1.0, that of the fertilized plot about 2.2 as a result of 150 years of acid deposition and fertilization. The changes in the pH levels has caused many changes in the heavy metal content of the top layer of the soil. Using different extraction methods (e.g., ammonium acetate, EDTA, and sequential analysis), the heavy metal content of different fractions have been estimated. In the control plot, the Zn, Cd and Pb content increased. In the fertilized plot, the Pb and Cd contents have also increased because of atmospheric deposition and small amounts of lead in the fertilizer. The available form of Cd and Pb increased in both the control and the fertilized plots.     

Banana‐shaped dopants for flexoelectric nematic mixtures

The synthesis is reported of new meta‐substituted quaterphenyls and several related dimers as dopants for nematic mixtures with flexoelectric properties. The number and nature of the terminal substituents is varied from apolar with a small dipole moment to polar with a strong dipole moment. The number of methylene units in the flexible aliphatic spacer between the polyfluorinated aromatic groups of the dimers is also varied. Dimers capable of banana‐shaped conformers induce an increase in the flexoelectric coefficients of mixtures containing them and reduce the clearing point to a small extent.     

Rod-shaped dopants for flexoelectric nematic mixtures

We report the synthesis and liquid crystalline behaviour of two series of para-substituted terphenyls as dopants with a rigid rod-like shape, rather than a wedge-, pear- or banana-shape, for guest–host nematic mixtures with flexoelectric properties. One series of liquid crystalline dopants is of low-to-strongly negative dielectric anisotropy and the other is of low-to-strongly positive dielectric anisotropy. The usefulness of apolar and polar rod-like dopants as components of flexoelectric nematic mixtures of positive dielectric anisotropy for use in LCDs is investigated in general and the dependence of the flexoelectric properties of the doped nematic mixtures on the polarity of the dopants is studied in particular. The correlation between the concentration of the dopant and the magnitude of the flexoelastic ratio of several guest–host nematic mixtures is investigated.     

New approaches to the microscopic imaging of Trypanosoma brucei.

Protozoan parasites are fearsome pathogens responsible for a substantial proportion of human mortality, morbidity, and economic hardship. The principal disease agents are members of the orders Apicomplexa (Plasmodium, Toxoplasma, Eimeria) and Kinetoplastida (Trypanosomes, Leishmania). The majority of humans are at risk from infection from one or more of these organisms, with profound effects on the economy, social structure and quality of life in endemic areas; Plasmodium itself accounts for over one million deaths per annum, and an estimated 4 x 10(7) disability-adjusted life years (DALYs), whereas the Kinetoplastida are responsible for over 100,000 deaths per annum and 4 x 10(6) DALYs. Current control strategies are failing due to drug resistance and inadequate implementation of existing public health strategies. Trypanosoma brucei, the African Trypanosome, has emerged as a favored model system for the study of basic cell biology in Kinetoplastida, because of several recent technical advances (transfection, inducible expression systems, and RNA interference), and these advantages, together with genome sequencing efforts are widely anticipated to provide new strategies of therapeutic intervention. Here we describe a suite of methods that have been developed for the microscopic analysis of T. brucei at the light and ultrastructural levels, an essential component of analysis of gene function and hence identification of therapeutic targets.     

The Effectiveness of Communication at Meetings: A Case Study

Meetings occupy over 30 per cent of the time of an executive and existing training in meeting behaviour was not considered to be effective. Methods used to analyse communication at meetings are described. A group of observers has been trained to assist chairmen in improving the usefulness of their meetings. Reductions of 20 per cent in the number of meetings and of 30 per cent in their duration have been achieved. Standard practices for meetings have been established. Training should be given to coherent groups in the organization rather than to individuals if changes in behaviour patterns are desired.     

Nematogenic laterally fluorinated biphenyls with polar terminal groups

Abstract

The physical properties are reported for a series of positive dielectric anisotropy (δε) alkylbiphenyls possessing a halogen-containing terminal group and incorporating varying degrees of lateral fluorination. The nematic range and dielectric and optical anisotropies can be varied by the appropriate choice of terminal group and extent of lateral substitution. These materials possess greater stability than the corresponding cyano compounds and are suitable for use in applications that require high stability.     

Transport of charged Aerosol OT inverse micelles in nonpolar liquids

Surfactants such as Aerosol OT (AOT) are commonly used to stabilize and electrically charge nonpolar colloids in devices such as electronic ink displays. The electrical behavior of such devices is strongly influenced by the presence of charged inverse micelles, formed by excess surfactant that does not cover the particles. The presence of charged inverse micelles results in increased conductivity of the solution, affecting both the energy consumption of the device and its switching characteristics. In this work, we use transient current measurements to investigate the electrical properties of suspensions of the surfactant Aerosol OT in dodecane. No particles are added, to isolate the effect of excess surfactant. The measured currents upon application of a voltage step are found to be exponentially decaying, and can be described by an analytical model based on an equivalent electric circuit. This behavior is physically interpreted, first by the high generation rate of charged inverse micelles giving the suspension resistor like properties, and second by the buildup of layers of charged inverse micelles at both electrodes, acting as capacitors. The model explains the measurements over a large range of surfactant concentrations, applied voltages, and device thicknesses.