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Background: Data from empirical investigations on the feasibility and acceptability of using sit-stand desks in an office-based setting in low- and middle-income settings are limited. Objectives: To explore the perceptions of South African office workers towards using height-adjustable sit-stand desks to reduce sitting time during vocational hours. Methods: Self-reported sedentary behaviour and in-depth, semi-structured interviews were conducted in December 2020. Thematic content analysis approach was used to develop themes. Results: Eleven office workers with a work-time sitting time of 8 (6-8) hours were interviewed (age 40.5 ± 12.6 years), most (91%) were female. The main themes emerged and included: overall impressions of the height-adjustable sit-stand desks; enablers versus barriers to using the desk and readiness to continue using sit-stand desks. Conclusion: The findings of this research add to the evidence on environmental workstation modifications for reducing sedentary behaviour. Further investigations on the efficacy of sit-stand desks are recommended in South African university office workers.

Our objective was to describe patterns and predictors of sedentary behavior (sitting time) over 10 years among a large Canadian cohort. Data are from the Canadian Multicentre Osteoporosis Study, a prospective study of women and men randomly selected from the general population. Respondents reported socio-demographics, lifestyle behaviors and health outcomes in interviewer-administered questionnaires; weight and height were measured. Baseline data were collected between 1995 and 1997 (n = 9418; participation rate = 42%), and at 5- (n = 7648) and 10-year follow-ups (n = 5567). Total sitting time was summed across domain-specific questions at three time points and dichotomized into "low" (≤ 7 h/day) and "high" (> 7 h/day), based on recent meta-analytic evidence on time sitting and all-cause mortality. Ten-year sitting patterns were classified as "consistently high", "consistently low", "increased", "decreased", and "mixed". Predictors of sedentary behavior patterns were explored using chi-square tests, ANOVA and logistic regression. At baseline (mean age = 62.1 years ± 13.4) average sitting was 6.9 h/day; it was 7.0 at 5- and 10-year follow-ups (p for trend = 0.12). Overall 23% reported consistently high sitting time, 22% consistently low sitting, 14% decreased sitting, 17% increased sitting with 24% mixed patterns. Consistently high sitters were more likely to be men, university educated, full-time employed, obese, and to report consistently low physical activity levels. This is one of the first population-based studies to explore patterns of sedentary behavior (multi-domain sitting) within men and women over years. Risk classification of sitting among many adults changed during follow-up. Thus, studies of sitting and health would benefit from multiple measures of sitting over time.

Issue addressed This study examines how sedentary behaviour (too much sitting) was covered as a health issue by Australian newspapers and how physical activity was framed within this newspaper coverage. Methods Articles featuring sedentary behaviour published in Australian newspapers between 2000 and 2012 were analysed for content and framing. Main outcome measures were volume, number and content of newspaper articles; framing and types of sedentary behaviour; responsibility for the problem of and solutions to high levels of sedentary behaviour; and physical activity mentions and how it was framed within sedentary behaviour coverage. Results Out of 48 articles, prolonged sitting was framed as bad for health (52%) and specifically as health compromising for office workers (25%). Adults who sat a lot were framed as 'easy targets' for ill health (21% of headlines led with 'sitting ducks' or 'sitting targets'). Prolonged sitting was framed as an issue of individual responsibility (>90%) with less mention of environmental and sociocultural contributors. Thirty-six of 48 articles mentioned physical activity; 39% stated that being physically active does not matter if a person sits for prolonged periods of time or that the benefits of physical activity are undone by too much sitting. Conclusions News coverage should reflect the full socio-ecological model of sedentary behaviour and continually reinforce the independent and well-established benefits of health-enhancing physical activity alongside the need to limit prolonged sitting. So what? It is important that the entire 'move more, sit less, every day!' message is communicated by news media.

INTRODUCTION: Population aging is associated with a rising burden of non-communicable disease, profoundly impacting health policy and practice. Adopting and adhering to healthy lifestyles in middle or older age can protect against morbidity and mortality. Retirement brings opportunities to reconfigure habitual lifestyles and establish new routines. This study examines the longitudinal association between retirement and a range of lifestyle risk behaviors among a large population-based sample of Australian adults. METHODS: Study sample included working adults aged ≥45 years at baseline (2006-2009, N=23,478-26,895). Lifestyle behaviors, including smoking, alcohol use, physical activity, diet, sedentary behavior, and sleep, were measured at both baseline and follow-up (2010). Logistic regression models estimated the odds of having each risk factor at follow-up and multiple linear regression models calculated the change in the total number of risk factors, adjusted for baseline risk and other covariates. Sociodemographic characteristics and reasons for retirement were tested as potential effect modifiers. RESULTS: During the 3.3-year follow-up, about 11% of respondents retired. Retirement was associated significantly with reduced odds of smoking (AOR=0.74); physical inactivity (AOR=0.73); excessive sitting (AOR=0.34); and at-risk sleep patterns (AOR=0.82). There was no significant association between retirement and alcohol use or fruit and vegetable consumption. Change in the total number of lifestyle risk factors differed significantly by reason for retirement. CONCLUSIONS: In a large population-based Australian cohort, retirement was associated with positive lifestyle changes. Health professionals and policymakers should consider developing special programs for retirees to capitalize on the healthy transitions through retirement.

The quantum theory of nonlinear effects for optical transitions of electrons in quasi-zero dimensional (Q0D) quantum dots fabricated from n-type III–V compound semiconductor materials such as n-type GaAs has been studied due to the nonparabolicity of energy band structures. We use the effective mass approximation for carriers in the quantum dots. Most realistic quantum dot systems contain the box with a thickness c and the lateral width (a,b). Using the time-independent perturbation theory, the first order correction of the eigenfunctions and eigenvalues for the system has been calculated. And the free-carrier absorption coefficient may be calculated for Q0D quantum dots from n-type GaAs where the polar optical phonon scattering is dominant. Our results show that the free-carrier absorption coefficient in Q0D quantum dots increases quite rapidly with increasing temperature in the region of low temperatures. When temperatures are larger than 100 K, the free-carrier absorption coefficient increases slowly with temperature. This shows that the nonlinear property of energy band structures due to the nonparabolicity plays an important role in low temperatures. The discussion about the dot size effect of the quantum confinement region in n-type GaAs quantum dots has also been given.

The impurity-limited mobility of semiconducting thin wires for the nonparabolic band structure of electrons in n-type gallium arsenide has been investigated by scattering from ionized impurities or from the uniform distribution of remote impurities. Results are shown that the impurity-limited mobility due to scattering from background impurities increases monotonically and slowly with increasing temperature, while the impurity-limited mobility due to scattering from remote impurities increases rapidly with temperature. It is also shown that the mobility for both types of impurities decreases with increasing wire radius. However, for scattering from remote impurities, the mobility appears slowly decreasing with the wire radius at higher temperatures.

The free-carrier absorption in n-type InSb films has been investigated for carriers confined in quasi-two-dimensional (2D) semiconductors with the nonparabolic energy band of electrons. We discuss the effect of phonon scattering on the free-carrier absorption coefficient (~) for both deformation-potential coupling and piezoelectric coupling. ~ is found to depend on the photon polarization relative to the direction normal to the quasi-2D structure, the photon frequency, the film thickness, and the temperature. ~ could be complex due to the interaction between photons, phonons, and electrons. (i) When the acoustic phonon scattering is dominant, ~ increases with decreasing the film thickness for phonons polarized parallel or perpendicular to the layer plane. It is also shown that ~t increases with decreasing photon frequency and increasing temperature for photons polarized parallel to the layer plane, while for photons polarized perpendicular to the layer plane the ct temperature-dependence is more complicated. (ii) If the piezoelectric scattering is dominant, ~ is also decreasing with increasing the film thickness for photons polarized parallel or perpendicular to the layer plane. But ct decreases with increasing temperature for photons polarized perpendicular to the layer plane. Moreover, numerical results for the parallel polarization are much smaller than those for the perpendicular polarization.

Free-carrier absorption in n-type GaAs films has been investigated for the case where the free carriers are confined in a quasi-two-dimensional semiconducting structure with a non-parabolic energy band of electrons. It is assumed that the carriers in semiconductors are scattered by acoustic phonons via firstly the deformation-potential coupling and secondly the piezoelectric coupling. Results show that the free-carrier absorption coefficient depends upon the polarization of the electromagnetic radiation relative to the direction normal to the quasi-two-dimensional structure, the film thickness, the photon frequency and the temperature of the semiconductors. The free-carrier absorption coefficient could be complex owing to the interaction of photons, phonons and conduction electrons in piezoelectric semiconductors. Firstly, when the deformation-potential coupling is dominant, the absorption coefficient increases with decreasing photon frequency and increasing temperature for the radiation field polarized parallel and perpendicular to the layer plane. It is also shown that the absorption coefficient increases with decreasing film thickness. Secondly, when the piezoelectric scattering is dominant, the absorption coefficient increases with decreasing photon frequency and decreasing film thickness for the radiation field polarized parallel and perpendicular to the layer plane. However, the absorption coefficient increases with increasing temperature for the radiation field polarized parallel to the layer plane while, for the radiation field polarized perpendicular to the layer plane, the absorption coefficient increases with decreasing temperature.

A systolic algorithm for solving the 0/1-knapsack problems with n items is presented. The computational model used is a tree structure which consists of 2" identical processing elements (PEs). Each PE executes the same program at any time step. The time complexity varies from n to 3n — 2 steps which includes all the input/output data communication time. The design process and the correctness verification of this algorithm are considered in detail.

The effect of nonpolar optical phonon scattering on the free-carrier absorption in n-type semiconductors such as germanium has been investigated quantum mechanically in quantizing magnetic fields. It is assumed that the energy band of electrons in semiconductors is nonparabolic and the dominant scattering mechanism for electrons in solids is that of nonpolar optical phonon scattering. When the radiation field is polarized parallel to the magnetic field, the absorption coefficient will be of complex value due to the interaction of the radiation field and the optical phonon field with electrons in semiconductors. Results show that real and imaginary parts of the absorption coefficient oscillate quite considerably with the magnetic field in the high fields for the heavily doped n-type Ge. Both real and imaginary parts of the absorption coefficient appear as positive and negative values when changing the magnetic field. In low magnetic fields, the imaginary part of the absorption coefficient disappears. However, if the density of electrons increases, the imaginary part of the absorption coefficient will increase with the magnetic field in low fields. Moreover, it is also shown that the amplitudes of oscillations for the real and imaginary parts of the absorption coefficient do not vary in a regular trend with the density of electrons.

The effect of nonpolar optical phononscattering on the free‐carrier absorption in n‐type semiconductors such as germanium has been investigated quantum mechanically in quantizing magnetic fields. It is assumed that the energy band structure of electrons in semiconductors is nonparabolic and the dominant scattering mechanism for conduction electrons is of the nonpolar optical phononscattering. When the radiation is polarized parallel to a dc magnetic fieldB, the absorption coefficient appears to be of a complex value due to the interaction between the radiation field and the optical phonon field in nondegenerate semiconductors. Results show that the real part of the absorption coefficient oscillates with the magnetic field in the high‐field region, and imaginary part of the absorption coefficient appears with a few extremum points (peaks and dips) in high magnetic fields. These are different from those of the acoustic phononscattering in III–V compound semiconductors such as InSb or GaAs, in which the absorption coefficient oscillates with the magnetic field in lower magnetic fields and then increases monotonically with the field.

Free-carrier absorption in degenerate semiconductors such as n-type InSb has been investigated in quantizing magnetic fields at a very low temperature limit. It is assumed that the energy band of electrons in semiconductors is nonparabolic and the dominant scattering mechanism for electrons is the acoustic phonon scattering via the deformation potential coupling. Numerical results show that both real and imaginary parts of the absorption coefficient in degenerate semiconductors oscillate quite considerably with the magnetic field from the lower-field up to a higher-field region and some discontinuous points can be observed there. This is different from the numerical results shown in nondegenerate semiconductors.

Given n items, a parallel algorithm for generating all the n! permutations is presented. The computational model used is a linear array which consists of n identical processing elements with a simple structure. One permutation is produced at each other time step. The elapsed time to produce a permutation is independent of the integer n. The basic idea used is the iterative method and the exchange of two consecutive components in an existing permutation. The design procedures of this algorithm are considered in detail. The ranking and unranking functions of the required permutations are also discussed.

Given n elements and an arbitrary integer m for m ⩽ n, a systolic algorithm for generating all r -subsets (subsets containing r elements) with 1 ⩽ r ⩽ m in lexicographic order is presented. The computational model used is a linear systolic array consisting of m identical processing elements with a simple structure. One subset is produced at a time step. The elapsed time within a time step is independent of integers r , n and m . The design process of systolic array and the verification of systolic algorithm are considered in detail.

The free-carrier absorption in n-type InSb films has been studied for quantum well structures fabricated from III–V semiconducting materials where the polar optical phonon scattering is predominant. We consider here two special cases: the electromagnetic radiation is polarized parallel to the layer plane and perpendicular to the layer plane separately. The energy band of electrons in semiconductors is assumed to be nonparabolic. Results show that when the electromagnetic radiation is polarized parallel to the layer plane, the free-carrier absorption coefficient is independent of temperature in a small quantum well region such as d

We present a systolic algorithm to generate all the n! permutations of n given items. The computational model used is a linear systolic array consisting of n identical PEs. This algorithm requires n! time steps to solve this problem. Since any PE is identical and executes the same program, it is suitable for VLSI implementation. The correctness of the algorithm is proved. We also consider the ranking and unranking functions of permutations in this parallel algorithm

A linear systolic array for generating all combinations of m items (m is given) out of n given items in lexicographic order is presented. Each processing element of the systolic array performs two simple if-then-else statements. It takes 2 ∗ n C m + (m − 1) time steps to generate all nCm combinations, where m is the number of processing elements. The correctness proof of this algorithm is also given. Due to its simplicity, regularity and local interconnection, the array is suitable for VLSI implementation.

The free-carrier absorption has been studied for quantum well structures fabricated from III–V semiconductors such as n-type InSb films when the acoustic phonon scattering is dominant. The energy band of carriers in semiconductors is assumed to be nonparabolic. The scattering mechanisms of phonons with carriers in semiconductors are considered for the deformation-potential coupling and the piezoelectric coupling separately. Results show that the free-carrier absorption coefficient in n-type InSb films depend upon the polarization of the radiation field relative to the direction normal to the quantum well structures, the photon frequency, the film thickness and the temperature. It is also found that the free-carrier absorption coefficient could be complex due to the interaction of the radiation field and the photon field with carriers in semiconductors. Thus, the index of refraction of semiconducting films could be change due to this carrier-phonon-photon interaction.

Effect of the nonparabolicity on free‐carrier absorption in nondegenerate semiconductors has been investigated at quantizing magnetic fields. The dominant scattering mechanism for electrons is assumed to be of the acoustic phonon scattering via the deformation‐potential coupling. When the radiation is polarized parallel to a magnetic field, the absorption coefficient oscillates with the magnetic field in lower fields and then increases monotonically with the field. These oscillations of the abosrption coefficient with the magnetic field will be diminished with decreasing temperature and depend on the band gap of semiconductors.

A quantum theory for the free-carrier absorption of semiconductors to take into account the nonpolar optical phonon scattering in a semiconductor such as germanium has been studied for electrons in a parabolic energy band [1]. In quantizing magnetic fields, different scattering mechanisms give rise to different magnetic-field dependences of the scattering rates [2]. In the present work, we shall study the effect of nonpolar optical phonon scattering on the free-carrier absorption with a nonparabolic energy band of n-type nondegenerate semiconductors such as germanium.

Free-carrier absorption in n-type GaAs in quantizing magnetic fields has been investigated quantum mechanically. It is assumed that the energy band of electrons in semiconductors is nonparabolic and the dominant scattering mechanism for electrons is acoustic-phonon scattering via deformation-potential coupling. When the radiation field is polarized parallel to the magnetic field, the free-carrier absorption coefficient assumes a complex value due to the ac radiation and phonon fields. Our results show that the real part of the absorption coefficient and the imaginary part of the absorption coefficient oscillate with the magnetic field. However, at very low temperatures, oscillations in the imaginary part are diminished and its value decreases rapidly with increasing magnetic field.

Hot-electron transport in n-type GaAs has been investigated in the crossed applied OC electric field and DC magnetic field. The energy band structure of conduction electrons is taken to be a non-parabolic band and the dominant interaction between hot electrons and lattices is assumed to be the deformation- potential coupling. Results show that the dissipative current density increases nonlinearly with the applied electric field owing to the non-parabolic band structure of electrons in semiconductors. In the lower electric field region, the dependence of the current density on temperature does not appear to follow a regular trend. It is also shown that the current density depends strongly on the magnetic field