Validation of a new hand-held electronic data capture method for continuous monitoring of subjective appetite sensations

Background When large scale trials are investigating the effects of interventions on appetite, it is paramount to efficiently monitor large amounts of human data. The original hand-held Electronic Appetite Ratings System (EARS) was designed to facilitate the administering and data management of visual analogue scales (VAS) of subjective appetite sensations. The purpose of this study was to validate a novel hand-held method (EARS II (HP® iPAQ)) against the standard Pen and Paper (P&P) method and the previously validated EARS. Methods Twelve participants (5 male, 7 female, aged 18-40) were involved in a fully repeated measures design. Participants were randomly assigned in a crossover design, to either high fat (>48% fat) or low fat (<28% fat) meal days, one week apart and completed ratings using the three data capture methods ordered according to Latin Square. The first set of appetite sensations was completed in a fasted state, immediately before a fixed breakfast. Thereafter, appetite sensations were completed every thirty minutes for 4h. An ad libitum lunch was provided immediately before completing a final set of appetite sensations. Results Repeated measures ANOVAs were conducted for ratings of hunger, fullness and desire to eat. There were no significant differences between P&P compared with either EARS or EARS II (p > 0.05). Correlation coefficients between P&P and EARS II, controlling for age and gender, were performed on Area Under the Curve ratings. R2 for Hunger (0.89), Fullness (0.96) and Desire to Eat (0.95) were statistically significant (p < 0.05). Conclusions EARS II was sensitive to the impact of a meal and recovery of appetite during the postprandial period and is therefore an effective device for monitoring appetite sensations. This study provides evidence and support for further validation of the novel EARS II method for monitoring appetite sensations during large scale studies. The added versatility means that future uses of the system provides the potential to monitor a range of other behavioural and physiological measures often important in clinical and free living trials.

Preliminary design of a tensile-strained p-type Si/SiGe quantum well infrared photodetector

Considering tensile-strained p-type Si/Si1-yGey quantum wells grown on a relaxed Si1-xGex ( 0 0 1) virtual substrate ( y < x), the hole subband structure and the effective masses of the first bound hole state in the quantum wells are calculated by using the 6 x 6 k center dot p method. Designs for tensile-strained p-type quantum well infrared photodetectors ( QWIPs) based on the bound-to-quasi-bound transitions are discussed, which are expected to retain the ability of coupling normally incident infrared radiation without any grating couplers, have lower dark current than n-type QWIPs and also have a larger absorption coefficient and better transport characteristics than normal unstrained or compressive-strained p-type QWIPs.

Influence of N doping on the Rashba coefficient, semiconductor-metal transition, and electron effective mass in InSb1-xNx nanowires: Ten-band k center dot p model

The electronic structures of InSb1-xNx nanowires are investigated using the ten-band k center dot p method. It is found that nitrogen increases the Rashba coefficient of the nanowires dramatically. For thick nanowires, the Rashba coefficient may increase by more than 20 times. The semiconductor-metal transition occurs more easily in InSb1-xNx nanowires than in InSb nanowires. The electronic structure of InSb1-xNx nanowires is very different from that of the bulk material. For fixed x the bulk material is a semimetal, while the nanowires are metal-like. In InSb1-xNx bulk material and thick nanowires, an interesting decrease of electron effective mass is observed near k=0 which is induced by the nitrogen, but this phenomenon disappears in thin nanowires.

Factors influencing the dissolution of phosphate rock in a range of high P-fixing soils from Cameroon

A laboratory incubation experiment was conducted to evaluate the soil factors that influence the dissolution of two phosphate rocks (PRs) of different reactivity (Gafsa, GPR, reactive PR; and Togo-Hahotoe, HPR, low reactivity PR) in seven agricultural soils from Cameroon having variable phosphorus (P)- sorption capacities, organic carbon (C) contents, and exchangeable acidities. Ground PR was mixed with the soils at a rate of 500 mg P kg 21 soil and incubated at 30 degrees C for 85 days. Dissolution of the PRs was determined at various intervals using the Delta NaOH-P method ( the difference of the amount of P extracted by 0.5 M NaOH between the PR-treated soils and the control). Between 4 and 27% of HPR and 33 and 50% of GPR were dissolved in the soils. Calcium (Ca) saturation of cation exchange sites and proton supply strongly affected PR dissolution in these soils. Acid soils with pH-(H2O), < 5 (NKL, ODJ, NSM, MTF) dissolved more phosphate rock than those with pH-(H2O) > 5 (DSC, FGT, BAF). However, the lack of a sufficient Ca sink in the former constrained the dissolution of both PRs. The dissolution of GPR in the slightly acidic soils was limited by increase in Ca saturation and that of HPR was constrained by limited supply in protons. Generally, the dissolution of GPR was higher than that of HPR for each soil. The kinetics of dissolution of PR in the soils was best described by the power function equation P At B. More efficient use of PR in these soils can be achieved by raising the soil cation exchange capacity, thereby increasing the Ca sink size. This could be done by amending such soils with organic materials.

First-principles quantum dynamics in interacting Bose gases: I. The positive P representation

The performance of the positive P phase-space representation for exact many- body quantum dynamics is investigated. Gases of interacting bosons are considered, where the full quantum equations to simulate are of a Gross-Pitaevskii form with added Gaussian noise. This method gives tractable simulations of many-body systems because the number of variables scales linearly with the spatial lattice size. An expression for the useful simulation time is obtained, and checked in numerical simulations. The dynamics of first-, second- and third-order spatial correlations are calculated for a uniform interacting 1D Bose gas subjected to a change in scattering length. Propagation of correlations is seen. A comparison is made with other recent methods. The positive P method is particularly well suited to open systems as no conservation laws are hard-wired into the calculation. It also differs from most other recent approaches in that there is no truncation of any kind.

Study of valence intersubband absorption in tensile strained Si/SiGe quantum wells

The hole subband structures and effective masses of tensile strained Si/Si1-yGey quantum wells are calculated by using the 6x6 k.p method. The results show that when the tensile strain is induced in the quantum well, the light-hole state becomes the ground state, and the light hole effective masses in the growth direction are strongly reduced while the in-plane effective masses are considerable. Quantitative calculation of the valence intersubband transition between two light hole states in a 7nm tensile strained Si/Si0.55Ge0.45 quantum well grown on a relaxed Si0.5Ge0.5 (100) substrates shows a large absorption coefficient of 8400 cm(-1).

Rashba spin splitting of the minibands of coupled InAs/GaAs pyramid quantum dots

The Rashba spin splitting of the minibands of coupled InAs/GaAs pyramid quantum dots is investigated using the k center dot p method and valence force field model. The Rashba splitting of the two dimensional miniband in the lateral directions is found due to the structure inversion asymmetry in the vertical direction while the miniband in the vertical direction has no Rashba spin splitting. As the space between dots increases, the Rashba coefficients decrease and the conduction-band effective mass increases. This Rashba spin splitting of the minibands will significantly affect the spin transport properties between quantum dots. (C) 2008 American Institute of Physics.

Highly anisotropic and electric field tunable Zeeman splittings in Mn-doped CdS nanowires

The electronic structure, Zeeman splitting, and g factor of Mn-doped CdS nanowires are studied using the k center dot p method and the mean field model. It is found that the Zeeman splittings of the hole ground states can be highly anisotropic, and so can their g factors. The hole ground states vary a lot with the radius. For thin wire, g(z) (g factor when B is along the z direction or the wire direction) is a little smaller than g(x). For thick wire, g(z) is mcuh larger than g(x) at small magnetic field, and the anisotropic factor g(z)/g(x) decreases as B increases. A small transverse electric field can change the Zeeman splitting dramatically, so tune the g(x) from nearly 0 to 70, in thick wire. The anisotropic factor decreases rapidly as the electric field increases. On the other hand, the Zeeman splittings of the electron ground states are always isotropic.

Room-temperature highly anisotropic ferromagnetism and uniaxial spin amplification in (In,Mn)As quantum dots

The hole-mediated ferromagnetism in (In,Mn)As quantum dots is investigated using the k center dot p method and the mean field model. It is found that the (In,Mn)As quantum dot can be ferromagnetic at room temperature when there is one hole in the dot. For the spherical quantum dots, the Curie temperature decreases as the diameter increases, and increases as the effective composition of magnetic ions increases. It is interesting to find that the (In,Mn)As oblate quantum dot has highly anisotropic Zeeman splitting and ferromagnetism due to the spin-orbit coupling effect, which can be used as an uniaxial spin amplifier. (c) 2008 American Institute of Physics.

Hole-mediated electric field tunable high Curie temperature in Mn-doped wurtzite ZnO nanowires

The hole-mediated Curie temperature in Mn-doped wurtzite ZnO nanowires is investigated using the k center dot p method and mean field model. The Curie temperature T-C as a function of the hole density has many peaks for small Mn concentration (x(eff)) due to the density of states of one-dimensional quantum wires. The peaks of T-C are merged by the carriers' thermal distribution when x(eff) is large. High Curie temperature T-C > 400 K is found in (Zn,Mn)O nanowires. A transverse electric field changes the Curie temperature a lot. (Zn,Mn)O nanowires can be tuned from ferromagnetic to paramagnetic by a transverse electric field at room temperature. (c) 2007 American Institute of Physics.

Electronic structure and optical gain of truncated InAs1-xNx/GaAs quantum dots

The shape of truncated square-based pyramid quantum dots (QDs) is similar to that of real QDs in experiments. The electronic band structures and optical gain of InAs1-xNx/GaAs QDs are calculated by using the 10-band k.p model, and the strain is calculated by the valence force field (VFF) method. When the top part of the QD is truncated, greater truncation corresponds to a flatter shape of the QD. The truncation changes the strain distribution and the confinement in the z direction. A flatter QD has a greater C1-HH1 transition energy, greater transition matrix element, less detrimental effect of higher excited transition, and higher saturation gain and differential gain. The trade-off between these properties must be considered. From our results, a truncated QD with half of its top part removed has better overall performance. This can provide guidance to growing QDs in experiments in which the proper growing conditions can be controlled to achieve required properties. (C) 2009 Elsevier Ltd. All rights reserved.

Highly anisotropic Zeeman splittings of wurtzite Cd1-xMnxSe quantum dots

The electronic structure and Zeeman splittings of wurtzite Cd1-xMnxSe quantum spheres are studied using the k center dot p method and mean-field model. It is interesting to find that the Zeeman splittings of some hole states in quantum spheres are highly anisotropic due to the spin-orbit coupling and wurtzite crystal structure. The anisotropy of the Zeeman splittings of hole ground states in large dots is large, while that in small dot is small because the hole ground states vary with radius. An external electrical field can change the Zeeman splitting significantly, and tune the g factor from nearly 0 to about 100.

Energy band design for Si/SiGe quantum cascade laser

This paper introduces in detail the working principle of Si/SiGe Quantum cascade laser(QCL). Appropriate parameters are used to calculate the hole subband structure of Si/Si1-xGex quantum well using a six-band k center dot p method. The dispersion relation and energy band for different layer thickness and compositions are investigated. Meanwhile, the energy separations between hole subbands in Si/Si1-xGex/Si quantum wells are also analyzed. Finally the calculated results are used for the Si/SiGe QCL design, which will be beneficial to the structure optimization of Si/SiGe QCL.

Comparative study for colloidal quantum dot conduction band state calculations

By comparing the results of some well-controlled calculation methods, we analyze the relative importance of bulk band structure, multi-bulk-band coupling, and boundary conditions in determining colloidal quantum dot conduction band eigenenergies. We find that while the bulk band structure and correct boundary conditions are important, the effects of multi-bulk-band coupling are small.

Electronic structures of wurtzite ZnO and ZnO/MgZnO quantum well

The band structures of wurtzite ZnO are calculated using the empirical pseudopotential method (EPM). The 8 parameters of the Zn and O atom pesudopotential form factors with Schluter's formula are obtained. The effective mass parameters are extracted by using k.p Hamiltonian to fit the EPM results. The calculated band edge energies (E-g, E-A, E-B, and E-C) at Gamma point are in good agreement with experimental results. The ordering of ZnO at the top of valence band is found to be A(Gamma(7))-B(Gamma(9))-C(Gamma(7)) due to a negative spin-orbit (SO) splitting. Based on the band parameters obtained, the valence hole subbands of wurzite ZnO/MgxZn1-xO tensile-strained quantum wells (QWs) with different well widths and Mg compositions are calculated using 6-band k.p method. (c) 2005 Elsevier B.V. All rights reserved.