Interactions between force and timing control of repeated actions

Variability is an inherent component in movement and provides an insight into control processes involved in producing motor responses. This thesis investigates the interactions between force and timing processes in the production of repetitive actions from an information processing perspective. Force-time interactions are examined in steady state sequences, sequences with step changes, and steady state sequences with a secondary visual search task as an attentional load. The account of control in normal healthy participants is then applied to describe behaviour of patients with cerebrovascular accidents (CVAs) in two case studies. Interaction was found to be present in variability measures and was quantified using cross-correlation analysis. Overall, results demonstrated that one locus of force-time interaction is at a cognitive level where motor responses are organised for execution. Corresponding changes in magnitude of dependence according to availability of attentional resources and task prioritisation supported this observation. Dependence patterns in patients with CVAs reflected loss of control when task difficulty increased. Finally, based on the findings, a conceptual model describing the interaction is proposed towards the development of a formal model for simulation studies

Modelling single-person and multi-person event-based synchronisation

A linear phase correction model has been shown to accurately reflect the corrective processes involved in synchronising motor actions to an external rhythmic cue. The model originated from studies of finger tapping to an isochronous metronome beat and is based on the time series of asynchronies between the metronome and corresponding finger tap onsets, along with their associated intervals. Over recent years the model has evolved and been applied to more complex scenarios, including phase perturbed cues, tempo variations and, most recently, timing within groups. Here, we review the studies that have contributed to the development of the linear phase correction model and the associated findings related to human timing performance. The review provides a background to the studies examining single-person timing to simple metronome cues. We then further expand on the more complex analyses of motor timing to phase and tempo shifted cues. Finally, recent studies investigating inter-personal synchronisation between groups of two or more individuals are discussed, along with a brief overview on the implications of these studies for social interactions. We conclude with a discussion on future areas of research that will be important for understanding corrective timing processes between people

Classification of entomological origin of honey based on its physicochemical and antioxidant properties

Physicochemical and antioxidant properties of raw honeys from Malaysia were used as markers for determining its entomological source of bee species of Apis dorsata, Apis mellifera, Apis cerana, or Heterotrigona itama. Physicochemical properties of moisture content, water activity, specific gravity, viscosity, pH, free acidity, electrical conductivity, colour (L*, a* and b*), colour intensity, and antioxidant properties including the DPPH free radical scavenging activity power (1/IC50), ascorbic acid equivalent antioxidant content (AEAC), ferric ion reducing antioxidant power (FRAP), and total phenolic content (TPC) were measured and analysed. Honeys were classified into two major groups of those from honey bees (Apis spp.) and Trigona stingless bees (Heterotrigona itama) from its physicochemical and antioxidant properties using hierarchical cluster and principal component analyses. The Kelulut honey produced by stingless bees, Heterotrigona itama was differentiable from honeys from the regular honey bee species, the Apis spp. with characteristics of high moisture content of 33.24 g/100 g, free acidity of 136.8 meq/kg, colour intensity of 990.3 mAU, AEAC of 26.64 mg/100 g, and FRAP of 41.95 mg AAE/100 g. Honey classification by its entomological origin helps in honey identification and it reduces honey fraudulence

Structural Modeling and Biochemical Characterization of Recombinant KPN_02809, a Zinc-Dependent Metalloprotease from Klebsiella pneumoniae MGH 78578

Klebsiella pneumoniae is a Gram-negative, cylindrical rod shaped opportunistic pathogen that is found in the environment as well as existing as a normal flora in mammalian mucosal surfaces such as the mouth, skin, and intestines. Clinically it is the most important member of the family of Enterobacteriaceae that causes neonatal sepsis and nosocomial infections. In this work, a combination of protein sequence analysis, structural modeling and molecular docking simulation approaches were employed to provide an understanding of the possible functions and characteristics of a hypothetical protein (KPN_02809) from K. pneumoniae MGH 78578. The computational analyses showed that this protein was a metalloprotease with zinc binding motif, HEXXH. To verify this result, a ypfJ gene which encodes for this hypothetical protein was cloned from K. pneumoniae MGH 78578 and the protein was overexpressed in Escherichia coli BL21 (DE3). The purified protein was about 32 kDa and showed maximum protease activity at 30 °C and pH 8.0. The enzyme activity was inhibited by metalloprotease inhibitors such as EDTA, 1,10-phenanthroline and reducing agent, 1,4-dithiothreitol (DTT). Each molecule of KPN_02809 protein was also shown to bind one zinc ion. Hence, for the first time, we experimentally confirmed that KPN_02809 is an active enzyme with zinc metalloprotease activity

an observational study

Objective This study aimed to investigate total and device-specific screen viewing (SV) and its determinants in children aged 2 years and below. Design Cross-sectional study conducted in February 2014. Setting Well-child clinics in Singapore national polyclinics. Participants Parents of children (Singapore citizens or permanent residents) aged 2 years and below were enrolled during routine clinic visits. Out of 794 eligible parent–child dyads, 725 (91.3%) provided informed consent and were included in the analysis. Main outcome measures Device-specific information on SV and determinants was ascertained using interviewer-administered survey questionnaires. The prevalence and duration of aggregate and device-specific SV were reported. Associations with potential determinants were investigated using multiple logistic regression analysis. A p value less than 0.05 was considered statistically significant. Results The prevalence of daily SV and SV ≥2 h/day constituted 53.5% and 16.3%, respectively. The majority of children aged 18–24 months (88.2%) engaged in daily SV. TVs and mobile devices were the most commonly used screen devices, followed by computers and video consoles. In multivariable analysis, younger child age, Chinese ethnicity and setting rules on time of SV were strongly and consistently associated with lower levels of any SV and SV ≥2 h/day. Parental knowledge of SV recommendations and less parental SV were additionally associated with lower levels of SV ≥2 h/day. The number of screen devices was not associated with children's SV. Conclusions In contrast to recommendations, SV prevalence in children aged less than 2 years is high and appears to increase steadily across age groups. TVs and mobile devices are most frequently used. Improving parental knowledge of SV recommendations, reducing parental SV and especially the implementation of strict rules on SV time could be successful strategies to reduce SV in young children

Spawning rings of exceptional points out of Dirac cones

The Dirac cone underlies many unique electronic properties of graphene and topological insulators, and its band structure--two conical bands touching at a single point--has also been realized for photons in waveguide arrays, atoms in optical lattices, and through accidental degeneracy. Deformations of the Dirac cone often reveal intriguing properties; an example is the quantum Hall effect, where a constant magnetic field breaks the Dirac cone into isolated Landau levels. A seemingly unrelated phenomenon is the exceptional point, also known as the parity-time symmetry breaking point, where two resonances coincide in both their positions and widths. Exceptional points lead to counter-intuitive phenomena such as loss-induced transparency, unidirectional transmission or reflection, and lasers with reversed pump dependence or single-mode operation. These two fields of research are in fact connected: here we discover the ability of a Dirac cone to evolve into a ring of exceptional points, which we call an "exceptional ring." We experimentally demonstrate this concept in a photonic crystal slab. Angle-resolved reflection measurements of the photonic crystal slab reveal that the peaks of reflectivity follow the conical band structure of a Dirac cone from accidental degeneracy, whereas the complex eigenvalues of the system are deformed into a two-dimensional flat band enclosed by an exceptional ring. This deformation arises from the dissimilar radiation rates of dipole and quadrupole resonances, which play a role analogous to the loss and gain in parity-time symmetric systems. Our results indicate that the radiation that exists in any open system can fundamentally alter its physical properties in ways previously expected only in the presence of material loss and gain