3,246 research outputs found
A study of the merits of filmstrip-oriented reading instruction as opposed to teacher-developed instruction at the secondary level
Educators have been exhorted to experiment with different techniques to discover ways of teaching reading more effectively and have been censured for their negligence in not making greater use of visual media. Yet, at the same time, teachers have been warned to wait and see , and not to accept exaggerated claims because the effectiveness of mechanical aids in teaching reading is still considered controversial by many authorities. The aim of this experimental study was to determine the value of direct teaching of reading skills through a commercially prepared filmstrip program, Tachist-O-Filmstrips , as opposed to a teacher-developed instructional program at the secondary level. Specific objectives centered about the comparative values of the two programs in their effects on: 1. General reading achievement 2. Vocabulary growth - both recognition and meaning 3. Comprehension accuracy 4. Rate of reading 5. Interest in reading
Associations between objectively measured physical activity and later mental health outcomes in children: findings from the UK Millennium Cohort Study.
BACKGROUND: The beneficial effect of physical activity (PA) on mental health in adults is well established, but less is known about this relationship in children. We examine associations between objectively measured sedentary time, PA and mental health in 11-year-olds from the UK Millennium Cohort Study (MCS). METHODS: Longitudinal data from MCS sweeps 4 (age 7) and 5 (age 11) were used (n=6153). Accelerometer data were collected at MCS4, and mental health was measured at MCS4 and MCS5 using subscales (peer, emotional, conduct, hyperactivity) of the Strengths and Difficulties Questionnaire (SDQ). Associations between mean daily PA minutes at different intensities (sedentary, light, moderate-to-vigorous) at MCS4 and SDQ outcomes at MCS5 (score range 0-10) were estimated using multiple linear regression models, adjusting for SDQ at MCS4 and individual and family characteristics, and stratified by gender. RESULTS: In fully adjusted models, increased PA at MCS4 was associated with fewer peer problems in boys and girls at MCS5. For each additional 15 min in moderate-to-vigorous physical activity (MVPA), peer problems decreased -0.077 points (95% CI -0.133 to -0.022) in boys. For girls, light PA was associated with decreased peer problems (-0.071 points/30 min, 95% CI -0.130 to -0.013). Greater sedentary time was associated with more peer problems and fewer hyperactivity symptoms in boys and girls. Increased MVPA was associated with more conduct and hyperactivity problems in boys and more hyperactivity in girls. CONCLUSIONS: Increased sedentary time is associated with more peer problems in children, and PA, generally, is beneficial for peer relations in children aged 11
Equivalent qubit dynamics under classical and quantum noise
We study the dynamics of quantum systems under classical and quantum noise,
focusing on decoherence in qubit systems. Classical noise is described by a
random process leading to a stochastic temporal evolution of a closed quantum
system, whereas quantum noise originates from the coupling of the microscopic
quantum system to its macroscopic environment. We derive deterministic master
equations describing the average evolution of the quantum system under
classical continuous-time Markovian noise and two sets of master equations
under quantum noise. Strikingly, these three equations of motion are shown to
be equivalent in the case of classical random telegraph noise and proper
quantum environments. Hence fully quantum-mechanical models within the Born
approximation can be mapped to a quantum system under classical noise.
Furthermore, we apply the derived equations together with pulse optimization
techniques to achieve high-fidelity one-qubit operations under random telegraph
noise, and hence fight decoherence in these systems of great practical
interest.Comment: 5 pages, 2 figures; converted to PRA format, added Fig. 2, corrected
typo
General criteria for the stability of uniaxially ordered states of Incommensurate-Commensurate Systems
Reconsidering the variational procedure for uniaxial systems modeled by
continuous free energy functionals, we derive new general conditions for
thermodynamic extrema. The utility of these conditions is briefly illustrated
on the models for the classes I and II of incommensurate-commensurate systems.Comment: 5 pages, to be published in Phys. Rev. Let
Berenstein-Zelevinsky triangles, elementary couplings and fusion rules
We present a general scheme for describing su(N)_k fusion rules in terms of
elementary couplings, using Berenstein-Zelevinsky triangles. A fusion coupling
is characterized by its corresponding tensor product coupling (i.e. its
Berenstein-Zelevinsky triangle) and the threshold level at which it first
appears. We show that a closed expression for this threshold level is encoded
in the Berenstein-Zelevinsky triangle and an explicit method to calculate it is
presented. In this way a complete solution of su(4)_k fusion rules is obtained.Comment: 14 page
Lie group weight multiplicities from conformal field theory
Dominant weight multiplicities of simple Lie groups are expressed in terms of
the modular matrices of Wess-Zumino-Witten conformal field theories, and
related objects. Symmetries of the modular matrices give rise to new relations
among multiplicities. At least for some Lie groups, these new relations are
strong enough to completely fix all multiplicities.Comment: 12 pages, Plain TeX, no figure
Coupling of the lattice and superlattice deformations and hysteresis in thermal expansion for the quasi one-dimensional conductor TaS
An original interferometer-based setup for measurements of length of
needle-like samples is developed, and thermal expansion of o-TaS crystals
is studied. Below the Peierls transition the temperature hysteresis of length
is observed, the width of the hysteresis loop being up to . The behavior of the loop is anomalous: the length changes so
that it is in front of its equilibrium value. The hysteresis loop couples with
that of conductivity. The sign and the value of the length hysteresis are
consistent with the strain dependence of the charge-density waves (CDW) wave
vector. With lowering temperature down to 100 K the CDW elastic modulus grows
achieving a value comparable with the lattice Young modulus. Our results could
be helpful in consideration of different systems with intrinsic
superstructures.Comment: 4 pages, 3 figures. Phys. Rev. Lett., accepted for publicatio
Strategy for Enhancing Ultrahigh-Molecular-Weight Block Copolymer Chain Mobility to Access Large Period Sizes (>100 nm)
Assembling ultrahigh-molecular-weight (UHMW) block copolymers (BCPs) in rapid time scales is perceived as a grand challenge in polymer science due to slow kinetics. Through surface engineering and identifying a nonvolatile solvent (propylene glycol methyl ether acetate, PGMEA), we showcase the impressive ability of a series of lamellar poly(styrene)-block-poly(2-vinylpyridine) (PS-b-P2VP) BCPs to self-assemble directly after spin-coating. In particular, we show the formation of large-period (≈111 nm) lamellar structures from a neat UHMW PS-b-P2VP BCP. The significant influence of solvent–polymer solubility parameters are explored to enhance the polymer chain mobility. After optimization using solvent vapor annealing, increased feature order of ultralarge-period PS-b-P2VP BCP patterns in 1 h is achieved. Isolated metallic and dielectric features are also demonstrated to exemplify the promise that large BCP periods offer for functional applications. The methods described in this article center on industry-compatible patterning schemes, solvents, and deposition techniques. Thus, our straightforward UHMW BCP strategy potentially paves a viable and practical path forward for large-scale integration in various sectors, e.g., photonic band gaps, polarizers, and membranes that demand ultralarge period sizes
Progress Towards a Multi-Modal Capsule Endoscopy Device Featuring Microultrasound Imaging
Current clinical standards for endoscopy in the gastrointestinal (GI) tract combine high definition optics and ultrasound imaging to view the lumen superficially and through its thickness. However, these instruments are limited to the length of an endoscope and the only clinically available, autonomous devices able to travel the full length of the GI tract easily offer only video capsule endoscopy (VCE). Our work seeks to overcome this limitation with a device (“Sonopill”) for multimodal capsule endoscopy, providing optical and microultrasound (μUS) imaging and supporting sensors1.
μUS transducers have been developed with multiple piezoelectric materials operating across a range of centre frequencies to study viability in the GI tract. Because of the combined constraints of μUS imaging and the low power / heat tolerance of autonomous devices, a hybrid approach has been taken to the transducer design, with separate transmit and receive arrays allowing multiple manufacturing approaches to maximise system efficiency. To explore these approaches fully, prototype devices have been developed with PVDF, high-frequency PZT and PMN-PT composites, and piezoelectric micromachined ultrasonic transducer arrays. Test capsules have been developed using 3D printing to investigate issues including power consumption, heat generation / dissipation, acoustic coupling, signal strength and capsule integrity. Because of the high functional density of the electronics in our proposed system, application specific integrated circuits (ASICs) have been developed to realise the ultrasound transmit and receive circuitry along with white-light and autofluorescence imaging with single-photon avalanche detectors (SPADs).
The ultrasound ASIC has been developed and the SPAD electronics and optical subsystem have been validated experimentally. The functionality of various transducer materials has been examined as a function of frequency and ultrasound transducers have been developed to operate at centre frequencies in the range 15 - 50 MHz. Ex vivo testing of porcine tissue has been performed, generating images of interest to the clinical community, demonstrating the viability of the Sonopill concept
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