Unravelling quantum carpets: a travelling wave approach

Quantum carpets are generic spacetime patterns formed in the probability distributions P(x,t) of one-dimensional quantum particles, first discovered in 1995. For the case of an infinite square well potential, these patterns are shown to have a detailed quantitative explanation in terms of a travelling-wave decomposition of P(x,t). Each wave directly yields the time-averaged structure of P(x,t) along the (quantised)spacetime direction in which the wave propagates. The decomposition leads to new predictions of locations, widths depths and shapes of carpet structures, and results are also applicable to light diffracted by a periodic grating and to the quantum rotator. A simple connection between the waves and the Wigner function of the initial state of the particle is demonstrated, and some results for more general potentials are given.Comment: Latex, 26 pages + 6 figures, submitted to J. Phys. A (connections with prior literature clarified

The epidemiology of observed temperament: Factor structure and demographic group differences

This study investigated the factor structure of observational indicators of children’s temperament that were collected across the first three years of life in the Family Life Project (N = 1205) sample. A four-factor model (activity level, fear, anger, regulation), which corresponded broadly to Rothbart’s distinction between reactivity and regulation, provided an acceptable fit the observed data. Tests of measurement invariance demonstrated that a majority of the observational indicators exhibited comparable measurement properties for male vs. female, black vs. white, and poor vs. not-poor children, which improved the generalizability of these results. Unadjusted demographic group comparisons revealed small to moderate sized differences (Cohen ds = |.23 – .42|) in temperamental reactivity and moderate to large sized differences (Cohen ds = −.64 – −.97) in regulation. Collectively, demographic variables explained more of the variation in regulation (R2 = .25) than in reactivity (R2 = .02 – .06). Follow-up analyses demonstrated that race differences were substantially diminished in magnitude and better accounted for by poverty. These results help to validate the distinction between temperamental reactivity and regulation using observational indicators

Agree or agree to disagree? Assessing the convergence between parents and observers on infant temperament

The assessment of infant temperament has been typically accomplished with parent questionnaires. When compared with temperament behaviours observed in the laboratory, parents and observers generally do not agree, leading some researchers to question the validity of parent report. This paper reports on a representative sample of infants whose families resided in non-metropolitan counties and whose temperament was measured in three ways: (1) standard parent report (Infant Behavior Questionnaire); (2) observer ratings across two lengthy home visits; and (3) observer coding of second-by-second reactions to specific emotion-eliciting tasks. In order to account for both trait and method variance, structural equation modelling was applied to a sample of 955 infants (M age = 7.3 months) using variables from the three methods that reflected the dimensions of positivity and negativity. Although models based solely on method factors and trait factors fit the data well, results indicated that a model that included method and trait factors provided the best fit. Results also indicated that parents and observers (either across the home visit or to specific tasks) converge, to a degree, on ratings of the positivity dimension but diverge on the negativity dimension

Interparental aggression, attention skills, and early childhood behavior problems

The current study explored longitudinal associations between interparental aggression, the development of child attention skills, and early childhood behavior problems in a diverse sample of 636 families living in predominately low-income, nonmetropolitan communities. The results of latent-variable, cross-lagged longitudinal models revealed that maternal-reported interparental aggression in infancy predicted reduced observed attention skills in toddlerhood; no association was observed, however, between attention in infancy and interparental aggression during the toddler years. Further, reduced toddler attention and high interparental aggression were both associated with increased risk for attention-deficit/hyperactivity disorder symptoms and conduct problems at 3 years of age. Processes largely operated in similar ways regardless of child gender or low-income status, although a few differences were observed. Overall, the results suggest that interparental aggression undermines attention development, putting children’s early behavioral adjustment at risk

Greater fear reactivity and psychophysiological hyperactivity among infants with later conduct problems and callous-unemotional traits

Approximately one-third of children who meet criteria for conduct problems (CP) are also characterized by elevated callous-unemotional (CU) traits. This subgroup is at elevated risk for more pervasive and extreme levels of later antisocial behavior and has been characterized by a fearlessness temperament and blunted stress psychophysiology at older ages. The objective of this study is to examine group differences in fear reactivity and stress psychophysiology in infancy among children classified as having CP with CU (CP+CU), CP without CU (CP-only), or no CP in later childhood

Noninvasive 3D Field Mapping of Complex Static Electric Fields

Many upcoming experiments in antimatter research require low-energy antiproton beams. With a kinetic energy in the order of 100 keV, the standard magnetic components to control and focus the beams become less effective. Therefore, electrostatic components are being developed and installed in transfer lines and storage rings. However, there is no equipment available to precisely map and check the electric field generated by these elements. Instead, one has to trust in simulations and, therefore, depend on tight fabrication tolerances. Here we present, for the first time, a noninvasive way to experimentally probe the electrostatic field in a 3D volume with a microsensor. Using the example of an electrostatic quadrupole focusing component, we find excellent agreement between a simulated and real field. Furthermore, it is shown that the spatial resolution of the probe is limited by the electric field curvature which is almost zero for the quadrupole. With a sensor resolution of 61V/m/√Hz, the field deviation due to a noncompliance with the tolerances can be resolved. We anticipate that this compact and practical field strength probe will be relevant also for other scientific and technological disciplines such as atmospheric electricity or safeguarding near power infrastructure

MEMS cantilever based magnetic field gradient sensor

This paper describes major contributions to a MEMS magnetic field gradient sensor. An H-shaped structure supported by four arms with two circuit paths on the surface is designed for measuring two components of the magnetic flux density and one component of the gradient. The structure is produced from silicon wafers by a dry etching process. The gold leads on the surface carry the alternating current which interacts with the magnetic field component perpendicular to the direction of the current. If the excitation frequency is near to a mechanical resonance, vibrations with an amplitude within the range of 1–103 nm are expected. Both theoretical (simulations and analytic calculations) and experimental analysis have been carried out to optimize the structures for different strength of the magnetic gradient. In the same way the impact of the coupling structure on the resonance frequency and of different operating modes to simultaneously measure two components of the flux density were tested. For measuring the local gradient of the flux density the structure was operated at the first symmetrical and the first anti-symmetrical mode. Depending on the design, flux densities of approximately 2.5 µT and gradients starting from 1 µT mm−1 can be measured

Temperature dependency of silicon structures for magnetic field gradient sensing

This work describes the temperature dependence of two sensors for magnetic field gradient sensors and demonstrates a structure to compensate for the drift of resonance frequency over a wide temperature range. The temperature effect of the sensing element is based on internal stresses induced by the thermal expansion of material, therefore FEM is used to determine the change of the eigenvalues of the sensing structure. The experimental setup utilizes a Helmholtz coil system to generate the magnetic field and to excite the MEMS structure with Lorentz forces. The MEMS structure is placed on a plate heated with resistors and cooled by a Peltier element to control the plate temperature. In the second part, we describe how one can exploit temperature sensitivity for temperature measurements and we show the opportunity to include the temperature effect to increase the sensitivity of single-crystal silicon made flux density gradient sensors