Perfectfit @ work : Effectiveness of blended web-based workplace health promotion programs

Cardiovascular disease (CVD) is the leading cause of death throughout the world, and is associated with morbidity and decreased employability. The prevalence of CVD and of people at risk for CVD (e.g. obesity, diabetes or hypertension) has been increasing. A healthy lifestyle is important in the prevention of CVD. Thus, effective preventive health initiatives aimed at a healthy lifestyle to decrease cardiovascular risks are beneficial to health and would improve sustainable employability of workers. In this thesis, the association between CVD and exit from paid employment was investigated, followed by intervention-studies on two ‘blended’ workplace health promotion programs, a combination of eHealth and motivational interviewing. We found positive changes in health behavior and health outcomes in both health programs. These findings show that blended workplace health promotion programs are promising in improving health and employability in employees at increased cardiovascular risk. Recommendations for future practice and research are made

Design and baseline characteristics of the PerfectFit study: A multicenter cluster-randomized trial of a lifestyle intervention in employees with increased cardiovascular risk

Background: The prevalence of unhealthy lifestyles and preventable chronic diseases is high. They lead to disabilities and sickness absence, which might be reduced if health promotion measures were applied. Therefore, we developed the PerfectFit health promotion intervention with a "blended care"-approach, which consists of a web-based health risk assessment (HRA) including tailored and personalized advice, followed by motivational interviewing (MI). We hypothesize that adding MI to a web-based HRA leads to better health outcomes. The objective is to describe the design and baseline characteristics of the PerfectFit study, which is being conducted among employees with high cardiovascular risk in the military workforce, the police organization and an academic hospital. Methods: PerfectFit is a cluster randomized controlled trial, consisting of two arms. Based on cardiovascular risk profiling, done between 2012 and 2014, we included employees based on one or more risk factors and motivation to participate. One arm is the 'limited' health program (control) that consists of: (a) an HRA as a decision aid for lifestyle changes, including tailored and personalized advice, and pros and cons of the options, and (b) a newsletter every 3 months. The other arm is the 'extensive' program (intervention), which is additionally offered MI-sessions by trained occupational physicians, 4 face-to-face and 3 by telephone, and is offered more choices of health promotion activities in the HRA. During the follow-up period, participants choose the health promotion activities they personally prefer. After six and twelve months, outcomes will be assessed by online questionnaires. After twelve months the cardiovascular risk profiling will be repeated. The primary outcome is self-reported general health. Secondary outcomes are self-reported work ability, CVD-risk score, sickness absence, productivity loss at work, participation in health promotion activities, changes in lifestyle (smoking, alcohol consumption, physical activity, stress management) and body mass index. Furthermore, a process evaluation and an economic analysis will be performed. Discussion: Additional coaching using MI is expected to be a key factor for success of the web-based HRA in employees with increased cardiovascular risk. This "blended care"-approach may be an essential strategy for effective health promotion activities. Trial registration: Dutch Trial Register by registration number NTR4894, 14/11/2014

Quantum Pumping in the Magnetic Field: Role of Discrete Symmetries

We consider an effect of the discrete spatial symmetries and magnetic field on the adiabatic charge pumping in mesoscopic systems. In general case, there is no symmetry of the pumped charge with respect to the inversion of magnetic field Q(B) \neq Q(-B). We find that the reflection symmetries give rise to relations Q(B)=Q(-B) or Q(B)=-Q(-B) depending on the orientation of the reflection axis. In presence of the center of inversion, Q(B) = 0. Additional symmetries may arise in the case of bilinear pumping.Comment: 4 page

Kondo effect induced by a magnetic field

We study peculiarities of transport through a Coulomb blockade system tuned to the vicinity of the spin transition in its ground state. Such transitions can be induced in practice by application of a magnetic field. Tunneling of electrons between the dot and leads mixes the states belonging to the ground state manifold of the dot. Remarkably, both the orbital and spin degrees of freedom of the electrons are engaged in the mixing at the singlet-triplet transition point. We present a model which provides an adequate theoretical description of recent experiments with semiconductor quantum dots and carbon nanotubes

Scaling Of The Coulomb Energy Due To Quantum Fluctuations In The Charge Of A Quantum Dot

The charging energy of a quantum dot is measured through the effect of its potential on the conductance of a second dot. This technique allows a measurement of the scaling of the dot's charging energy with the conductance of the tunnel barriers leading to the dot. We find that the charging energy scales quadratically with the reflection probability of the barriers. In a second experiment we study the transition from a single to a double-dot which exhibits a scaling behavior linear in the reflection probability. The observed power-laws agree with a recent theory.Comment: 5 pages, uuencoded and compressed postscript file, with figure

Quantized adiabatic charge pumping and resonant transmission

Adiabatically pumped charge, carried by non-interacting electrons through a quantum dot in a turnstile geometry, is studied as function of the strength of the two modulating potentials (related to the conductances of the two point-contacts to the leads) and of the phase shift between them. It is shown that the magnitude and sign of the pumped charge are determined by the relative position and orientation of the closed contour traversed by the system in the parameter plane, and the transmission peaks (or resonances) in that plane. Integer values (in units of the electronic charge $e$) of the pumped charge (per modulation period) are achieved when a transmission peak falls inside the pumping contour. The integer value is given by the winding number of the pumping contour: double winding in the same direction gives a charge of 2, while winding around two opposite branches of the transmission peaks or winding in opposite directions can give a charge close to zero.Comment: 7 pages, 12 figure

Pumped current and voltage for an adiabatic quantum pump

We consider adiabatic pumping of electrons through a quantum dot. There are two ways to operate the pump: to create a dc current ${\bar I}$ or to create a dc voltage ${\bar V}$. We demonstrate that, for very slow pumping, ${\bar I}$ and ${\bar V}$ are not simply related via the dc conductance $G$ as $\bar I = \bar V G$. For the case of a chaotic quantum dot, we consider the statistical distribution of ${\bar V} G - {\bar I}$. Results are presented for the limiting cases of a dot with single channel and with multichannel point contacts.Comment: 6 pages, 4 figure

Acoustoelectric pumping through a ballistic point contact in the presence of magnetic fields

The acoustoelectric current, J, induced in a ballistic point contact (PC) by a surface acoustic wave is calculated in the presence of a perpendicular magnetic field, B. It is found that the dependence of the current on the Fermi energy in the terminals is strongly correlated with that of the PC conductance: J is small at the conductance plateaus, and is large at the steps. Like the conductance, the acoustoelectric current has the same functional behavior as in the absence of the field, but with renormalized energy scales, which depend on the strength of the magnetic field, | B|.Comment: 7 page

Oscillations of the magnetic polarization in a Kondo impurity at finite magnetic fields

The electronic properties of a Kondo impurity are investigated in a magnetic field using linear response theory. The distribution of electrical charge and magnetic polarization are calculated in real space. The (small) magnetic field does not change the charge distribution. However, it unmasks the Kondo cloud. The (equal) weight of the d-electron components with their magnetic moment up and down is shifted and the compensating s-electron clouds don't cancel any longer (a requirement for an experimental detection of the Kondo cloud). In addition to the net magnetic polarization of the conduction electrons an oscillating magnetic polarization with a period of half the Fermi wave length is observed. However, this oscillating magnetic polarization does not show the long range behavior of Rudermann-Kittel-Kasuya-Yosida oscillations because the oscillations don't extend beyond the Kondo radius. They represent an internal electronic structure of the Kondo impurity in a magnetic field. PACS: 75.20.Hr, 71.23.An, 71.27.+

Effect of inelastic scattering on parametric pumping

Pumping of charge in phase-coherent mesoscopic systems due to the out-of-phase modulation of two parameters has recently found considerable interest. We investigate the effect of inelastic processes on the adiabatically pumped current through a two terminal mesoscopic sample. We find that the loss of coherence does not suppress the pumped charge but rather an additional physical mechanism for an incoherent pump effect comes into play. In a fully phase incoherent system the pump effect is similar to a rectification effect