Mechanical Toy Research Articles

Quantum cosmological backreactions. II. Purely homogeneous quantum cosmology

This is the second paper in a series of four in which we use space adiabatic methods in order to incorporate backreactions among the homogeneous and between the homogeneous and inhomogeneous degrees of freedom in quantum cosmological perturbation theory. The purpose of the present paper is twofold. On the one hand, it illustrates the formalism of space adiabatic perturbation theory (SAPT) for two simple quantum mechanical toy models. On the other, it proves the main point, namely that backreactions lead to additional correction terms in effective Hamiltonians that one would otherwise neglect in a crude Born-Oppenheimer approximation. The first model that we consider is a harmonic oscillator coupled to an anharmonic oscillator. We chose it because it displays many similarities with the more interesting second model describing the coupling between an inflaton and gravity restricted to the purely homogeneous and isotropic sector. These results have potential phenomenological consequences in particular for quantum cosmological theories describing big bounces such as Loop Quantum Cosmology (LQC).

Cord serum brain-derived neurotrophic factor levels at birth associate with temperament outcomes at one year

Altered serum levels of brain-derived neurotrophic factor (BDNF) are consistently linked with neurological disorders. BDNF is also increasingly implicated in the pathogenesis of neurodevelopmental disorders, particularly those found more frequently in males. At birth, male infants naturally have significantly lower serum BDNF levels (∼10–20% lower than females), which may render them more vulnerable to neurodevelopmental disorders. We previously characterized serum BDNF levels in mothers and their newborn infants as part of the Grown in Wales Study. Here, we analyzed whether cord serum BDNF levels at birth correlate with sex-specific outcomes at one year. The Bayley Scale of Infant Development, Third Edition (BSID-III) and Laboratory Temperament Assessment Battery (Lab-TAB) tasks were used to assess infant behavior and neurodevelopment at 12–14 months (mean ± SD: 13.3 ± 1.6 months; 46% male; n = 56). We found no relationship between serum BDNF levels at birth and BSID-III neurodevelopmental outcomes (cognitive or language), nor with infant behaviors in the Lab-TAB unpredictable mechanical toy or maternal separation tasks. In the sustained attention task, there was a significant positive relationship between serum BDNF and infant negative affect (B = 0.06, p = 0.018) and, for boys only, between serum BDNF and intensity of facial interest (B = 0.03, p = 0.005). However, only the latter remained after correction for multiple testing. This sex-specific association between cord serum BDNF and a parameter of attention at 12–14 months provides some support for the hypothesis that reduced serum BDNF levels at birth are linked to an increased risk for neurodevelopmental disorders.

Gyroscopes and the Chemical Literature, 2002-2020: Approaches to a Nascent Family of Molecular Devices.

Research directed toward the goal of molecular gyroscopes since the coverage of a previous review (2002) is described. Such species are a subclass of molecular rotors, which are comprised of rotators and stators. Major categories include (1) systems in which a rotator is embedded in a cage-like stator reminiscent of mechanical toy gyroscopes and (2) molecules that have been engineered to crystallize with parallel rotators and voids or other features that enable the rotator to rotate in the solid state (amphidynamic crystals). Particular attention is given to structural data and strategies for the minimization of rotational barriers. Synthetic routes are also described. Some allied types of molecules and supramolecular assemblies are also treated.

Animal presence modulates frontal brain activity of patients in a minimally conscious state: A pilot study

ABSTRACT Integrating animals into therapy is applied increasingly in patients in a minimally conscious state (MCS). This pilot study investigates the effect of animal presence on frontal brain activity in MCS patients compared to healthy subjects. O2HB, HHb and tHb of two MCS patients and two healthy adults was measured in frontal cortex using functional near-infrared spectroscopy during three sessions with a live animal and three sessions with a mechanical toy animal present. Each session had five phases: (1) baseline, (2) watching animal, (3) passive contact, (4) active contact, (5) neutral. Data were descriptively analysed. All participants showed the largest hemodynamic response during direct contact with the live or toy animal compared to “baseline” and “watching.” During active contact, three of the four participants showed a stronger response when stroking the live compared to the toy animal. All participants showed an inverted signal with higher HHb than O2Hb concentrations while stroking the live or toy animal. Animal contact leads to a neurovascular reaction in both MCS patients and healthy subjects, indicating elevated neural activity in the frontal cortex. We conclude that while a toy animal can elicit attention processes, active contact to a living animal is combined with emotional processes.

A mechanical toy model linking cell-substrate adhesion to multiple cellular migratory responses.

During cell migration, forces applied to a cell from its environment influence the motion. When the cell is placed on a substrate, such a force is provided by the cell-substrate adhesion. Modulation of adhesivity, often performed by the modulation of the substrate stiffness, tends to cause common responses for cell spreading, cell speed, persistence, and random motility coefficient. Although the reasons for the response of cell spreading and cell speed have been suggested, other responses are not well understood. In this study, we develop a simple toy model for cell migration driven by the relation of two forces: the adhesive force and the plasma membrane tension. The simplicity of the model allows us to perform the calculation not only numerically but also analytically, and the analysis provides formulas directly relating the adhesivity to cell spreading, persistence, and the random motility coefficient. Accordingly, the results offer a unified picture on the causal relations between those multiple cellular responses. In addition, cellular properties that would influence the migratory behavior are suggested.

Gendered Packaging of a STEM Toy Influences Children's Play, Mechanical Learning, and Mothers’ Play Guidance

To study effects of the gender-packaging of science, technology, engineering, and mathematics (STEM) toys, mother-child dyads (31 daughters; 30 sons; M=5.2years) were randomly assigned to play with a mechanical toy packaged for girls (GoldieBlox) or boys (BobbyBlox). When familiarizing themselves with the toy to prepare for play, mothers given BobbyBlox built more with toy pieces than did mothers given GoldieBlox. During dyadic play, mothers with sons built more; mothers with daughters read the toy's narrative instructions more. Children's independent play likewise varied with game packaging. Girls learned the mechanical belt-drive principle better from playing with BobbyBlox; boys learned the principle better from playing with GoldieBlox. Implications for gender-schema theories, STEM interventions, and toy marketing are discussed.

Physics of the mechanical toy Gee-Haw Whammy Diddle

Gee-Haw Whammy Diddle is a seemingly simple mechanical toy consisting of a wooden stick and a second stick that is made up of a series of notches with a propeller at its end. When the wooden stick is pulled over the notches, the propeller starts to rotate. Despite its simplicity, physical principles governing the motion of the stick and the propeller are rather complicated and interesting. Here we provide a thorough analysis of the system and parameters influencing the motion. We show that contrary to the results published on this topic so far, neither elliptic motion of the stick nor frequency synchronization is needed for starting a stable motion of the propeller.

Spectral analysis of gravitational waves from binary neutron star merger remnants

In this work we analyze the gravitational wave signal from hypermassive neutron stars formed after the merger of binary neutron star systems, focusing on its spectral features. The gravitational wave signals are extracted from numerical relativity simulations of models already considered by De Pietri et al. [Phys. Rev. D 93, 064047 (2016)], Maione et al. [Classical Quantum Gravity 33, 175009 (2016)], and Feo et al. [Classical Quantum Gravity 34, 034001 (2017)], and allow us to study the effect of the total baryonic mass of such systems (from $2.4{M}_{\ensuremath{\bigodot}}$ to $3{M}_{\ensuremath{\bigodot}}$), the mass ratio (up to $q=0.77$), and the neutron star equation of state, in both equal and highly unequal mass binaries. We use the peaks we find in the gravitational spectrum as an independent test of already published hypotheses of their physical origin and empirical relations linking them with the characteristics of the merging neutron stars. In particular, we highlight the effects of the mass ratio, which in the past was often neglected. We also analyze the temporal evolution of the emission frequencies. Finally, we introduce a modern variant of Prony's method to analyze the gravitational wave postmerger emission as a sum of complex exponentials, trying to overcome some drawbacks of both Fourier spectra and least-squares fitting. Overall, the spectral properties of the postmerger signal observed in our simulation are in agreement with those proposed by other groups. More specifically, we find that the analysis of Bauswein and Stergioulas [Phys. Rev. D 91, 124056 (2015)] is particularly effective for binaries with very low masses or with a small mass ratio and that the mechanical toy model of Takami et al. [Phys. Rev. D 91, 064001 (2015)] provides a comprehensive and accurate description of the early stages of the postmerger.

Simulating interaction: Using gaze-contingent eye-tracking to measure the reward value of social signals in toddlers with and without autism

Several accounts have been proposed to explain difficulties with social interaction in autism spectrum disorder (ASD), amongst which atypical social orienting, decreased social motivation or difficulties with understanding the regularities driving social interaction. This study uses gaze-contingent eye-tracking to tease apart these accounts by measuring reward related behaviours in response to different social videos. Toddlers at high or low familial risk for ASD took part in this study at age 2 and were categorised at age 3 as low risk controls (LR), high-risk with no ASD diagnosis (HR-no ASD), or with a diagnosis of ASD (HR-ASD). When the on-demand social interaction was predictable, all groups, including the HR-ASD group, looked longer and smiled more towards a person greeting them compared to a mechanical Toy (Condition 1) and also smiled more towards a communicative over a non-communicative person (Condition 2). However, all groups, except the HR-ASD group, selectively oriented towards a person addressing the child in different ways over an invariant social interaction (Condition 3). These findings suggest that social interaction is intrinsically rewarding for individuals with ASD, but the extent to which it is sought may be modulated by the specific variability of naturalistic social interaction.

Entangled spins and ghost-spins

We study patterns of quantum entanglement in systems of spins and ghost-spins regarding them as simple quantum mechanical toy models for theories containing negative norm states. We define a single ghost-spin as in [20] as a 2-state spin variable with an indefinite inner product in the state space. We find that whenever the spin sector is disentangled from the ghost-spin sector (both of which could be entangled within themselves), the reduced density matrix obtained by tracing over all the ghost-spins gives rise to positive entanglement entropy for positive norm states, while negative norm states have an entanglement entropy with a negative real part and a constant imaginary part. However when the spins are entangled with the ghost-spins, there are new entanglement patterns in general. For systems where the number of ghost-spins is even, it is possible to find subsectors of the Hilbert space where positive norm states always lead to positive entanglement entropy after tracing over the ghost-spins. With an odd number of ghost-spins however, we find that there always exist positive norm states with negative real part for entanglement entropy after tracing over the ghost-spins.

EXPANDING ENGINEERING DESIGN WITH MINI PROJECTS – THEORY OF MECHANISMS A PILOT COURSE

In order to expand the instruction ofengineering design in courses that are predominantlyengineering science, the Chair in Design Engineering ofthe University of Victoria has launched a program tointroduce design mini-projects. The development andmanagement of these projects is conducted by the courseinstructor in collaboration with a Design TeachingAssistant. The first design mini-project has beendeveloped for Theory of Mechanisms, a third-year corecoursein Mechanical Engineering. The course isprimarily theoretical and includes four laboratoryprojects that are based on deterministic problems. Inorder to establish an appropriate project, a list oflearning objectives that complements the theoreticalcontent of the course and exposes students to anengineering design problem has been identified. Theproject consists in designing and building an automatonfor young children – a mechanical toy operated by a handcrank. Overall the project was successful, studentsrapidly embraced it, the submitted prototypes generallymet or exceeded our expectations, and the learningobjectives were achieved.

On History and Policy: Time in the Age of Neoliberalism

It is often said that history matters, but these words are usually little more than a hollow statement. In the aftermath of the Great Recession, the view that the economy is a mechanical toy that can be fixed using a few simple tools has continued to be held by economists and policy makers and echoed by the media. The essay addresses the origins of this unfortunate belief, inherent to neoliberalism, and what can be done to bring time back into public discourse.

Spectral properties of the post-merger gravitational-wave signal from binary neutron stars

Extending previous work by a number of authors, we have recently presented a new approach in which the detection of gravitational waves from merging neutron star binaries can be used to determine the equation of state of matter at nuclear density and hence the structure of neutron stars. In particular, after performing a large number of numerical-relativity simulations of binaries with nuclear equations of state, we have found that the post-merger emission is characterized by two distinct and robust spectral features. While the high-frequency peak was already shown to be associated with the oscillations of the hypermassive neutron star produced by the merger and to depend on the equation of state, we have highlighted that the low-frequency peak is related to the merger process and to the total compactness of the stars in the binary. This relation is essentially universal and provides a powerful tool to set tight constraints on the equation of state. We here provide additional information on the extensive analysis performed, illustrating the methods used, the tests considered, as well as the robustness of the results. We also discuss additional relations that can be deduced when exploring the data and how these correlate with various properties of the binary. Finally, we present a simple mechanical toy model that explains the main spectral features of the post-merger signal and can even reproduce analytically the complex waveforms emitted right after the merger.

“I love the cute caterpillar!” autistic children's production of internal state language across contexts and relations to Joint Attention and theory of mind

Research on internal state language in autistic children reveals an uneven pattern. While some studies show that high-ability autistic children are impaired across a broad range of internal state term categories (e.g., desires, emotions and cognitive terms), other research shows that autistic children are more selectively impaired in their talk about cognitive states. Finally, some studies even demonstrate no impairments. The different findings have largely been explained by context effects. However, to date, studies have yet to compare the same children across different contexts to corroborate this interpretation. Further, studies involving contexts where autistic children's reactivity is actively triggered by providing clear joint attention cues or by exploiting autistic children's intense interest in objects are lacking. Thus, this study tested internal state language from different categories across three different contexts (narrative context, motivating mechanical toy context, elicited interactive joint attention context) and related it to joint attention skills and children's theory of mind. Results revealed that deficits in autistic children's internal state language were highly specific and relation to theory of mind varied by context. In sum, this research suggests that both theorists and practitioners need to take into account context when studying or promoting autistic individuals’ psychological comprehension.

Selective effects of explanation on learning during early childhood

Two studies examined the specificity of effects of explanation on learning by prompting 3- to 6-year-old children to explain a mechanical toy and comparing what they learned about the toy’s causal and non-causal properties with children who only observed the toy, both with and without accompanying verbalization. In Study 1, children were experimentally assigned to either explain or observe the mechanical toy. In Study 2, children were classified according to whether the content of their response to an undirected prompt involved explanation. Dependent measures included whether children understood the toy’s functional–mechanical relationships, remembered perceptual features of the toy, effectively reconstructed the toy, and (for Study 2) generalized the function of the toy when constructing a new one. Results demonstrate that across age groups, explanation promotes causal learning and generalization but does not improve (and in younger children can even impair) memory for causally irrelevant perceptual details.

Exploring the Clapeyron Equation and the Phase Rule Using a Mechanical Drawing Toy

The equilibrium between phases is a key concept from the introductory physical chemistry curriculum. Phase diagrams display which phase is the most stable at a given temperature and pressure. If more than one phase has the lowest Gibbs energy, then those phases are in equilibrium under those conditions. An activity designed to demonstrate the phase rule and to encourage deeper understanding of the Clapeyron equation is presented. This activity uses a mechanical drawing toy (such as an Etch A Sketch) with horizontal and vertical dials that can be adapted to explore mathematical relationships in a graphical situation. This activity is designed primarily for students taking second- or third-year physical chemistry, although some aspects of the activity would be appropriate for first-year general chemistry.

A Toy Robot via Cam Design as a Balance Module of Gravity Shifting

This study presents a brand new concept in contrast to that of the conventional mechanical toy robots on the market. Conventional toy robots rely mainly on a large sole area to reduce wobble during walking. In this study walking stability is realized not by large sole areas but by a cam designed to automatically shift the center of gravity during walking. The biped toy robot proposed is driven by a single motor. As soon as the robot takes a forwards step, the center of gravity is changed by the cam module, and under the action of gravity, the trunk moves automatically to shift the center of gravity. Both walking and shifting the center of gravity is done by one motor. It was a goal of this study to develop a new type of walking toy robot by modifying traditional toy design. Experiment and simulation revealed that the rotation speed of the crank influences the walking of the biped toy robot, and the crank length influences both the length and height of the stride. In addition, counterbalance of the robot while walking is affected by the location of the center of gravity of the trunk and the distance between the feet. It became clear that the stability of the walking robot was determined by many factors, and difficulties may arise if any of these factors is changed.

Qubit models of black hole evaporation

Recently, several simple quantum mechanical toy models of black hole evaporation have appeared in the literature attempting to illuminate the black hole information paradox. We present a general class of models that is large enough to describe both unitary and nonunitary evaporation, and study a few specific examples to clarify some potential confusions regarding recent results. We also generalize Mathur’s bound on small corrections to black hole dynamics. Conclusions are then drawn about the requirements for unitary evaporation of black holes in this class of models. We present a one-parameter family of models that continuously deforms nonunitary Hawking evaporation into a unitary process. The required deformation is large.

Motion-guided mechanical toy modeling

We introduce a new method to synthesize mechanical toys solely from the motion of their features. The designer specifies the geometry and a time-varying rotation and translation of each rigid feature component. Our algorithm automatically generates a mechanism assembly located in a box below the feature base that produces the specified motion. Parts in the assembly are selected from a parameterized set including belt-pulleys, gears, crank-sliders, quick-returns, and various cams (snail, ellipse, and double-ellipse). Positions and parameters for these parts are optimized to generate the specified motion, minimize a simple measure of complexity, and yield a well-distributed layout of parts over the driving axes. Our solution uses a special initialization procedure followed by simulated annealing to efficiently search the complex configuration space for an optimal assembly.

On the role of spectral markers and stability in spine models

We considered various stability issues related to biomechanical models of the spine, taking as our point of departure the scalar quantities proposed in Howarth et al. (2004). We discussed their significance and applicability by considering some mechanical toy models. In particular, we analysed the relevance of the behaviour of some of these measurements, namely, the determinant of the Hessian matrix and other quantities containing information of a similar spectral nature, and the role they may play in this type of studies. We showed that although in some cases these markers contain information about the load acting on the subject, this information may also be masked and not be detectable from these indexes.These models also allowed us to see how a system with these characteristics may become highly sensitive even to small load changes, and prompted us to put forward the hypothesis that trying to preserve stability at all costs might, under some circumstances, be an actual cause for system damage.