262 research outputs found
Sleep patterns of Japanese preschool children and their parents: implications for co-sleeping
Abstract Aim The aim of this study was to investigate the direct relationship of sleep schedule and sleep quality variables between healthy preschool children and their parents, focusing on the influence of the difference in bedtime between each other. Methods Forty-seven Japanese 5-year-old children and their primary parent were studied. The parents completed questionnaires including the Epworth Sleepiness Scale and Pittsburgh Sleep Quality Index. The children wore an actigraph for one week. Results Although sleep patterns of children were generally independent of their parents, late sleep end time and bedtime of children were associated with parents' late sleep end time on weekends. For 87% of children and parents who shared a bedroom, sleep quality was negatively affected by a shorter difference in bedtimes between child and parent, but not by co-sleeping. Conclusion Sleep behaviours of parents can influence those of their children. For parents and children who share a bedroom, the timing of bedtime rather than co-sleeping may be a key factor in modulating sleep patterns. Trying to get children asleep and subsequently falling asleep at a similar time may disturb parents' sleep quality, which may subsequently affect that of their children
Magnetic order in CaFe1-xCoxAsF (x = 0, 0.06, 0.12) superconductor compounds
A Neutron Powder Diffraction (NPD) experiment has been performed to
investigate the structural phase transition and magnetic order in CaFe1-xCoxAsF
superconductor compounds (x = 0, 0.06, 0.12). The parent compound CaFeAsF
undergoes a tetragonal to orthorhombic phase transition at 134(3) K, while the
magnetic order in form of a spin-density wave (SDW) sets in at 114(3) K. The
antiferromagnetic structure of the parent compound has been determined with a
unique propagation vector k = (1,0,1) and the Fe saturation moment of 0.49(5)uB
aligned along the long a-axis. With increasing Co doping, the long range
antiferromagnetic order has been observed to coexist with superconductivity in
the orthorhombic phase of the underdoped CaFe0.94Co0.06AsF with a reduced Fe
moment (0.15(5)uB). Magnetic order is completely suppressed in optimally doped
CaFe0.88Co0.12AsF. We argue that the coexistence of SDW and superconductivity
might be related to mesoscopic phase separation.Comment: 4pages, 4figure
Homogeneous coexistence of SDW and SC states in CaFe(1-x)Co(x)AsF studied by nuclear magnetic resonance
We investigated the homogeneous coexistence of spin-density-wave (SDW) and
superconducting (SC) states via 75As-nuclear magnetic resonance (NMR) in
CaFe(1-x)Co(x)AsF and found that the electronic and magnetic properties of this
compound are intermediate between those of LaFeAsO(1-x)F(x) and
Ba(Fe(1-x)Co(x))2As2. For 6% Co-doped samples, the paramagnetic spectral weight
completely disappears in the crossover regime between the SDW and SC phases
followed by the anomalous behavior of relaxation rate (1/T1), implying that the
two phases are not segregated. The 59Co-NMR spectra show that spin moments are
not commensurate but spatially modulated. These experimental results suggest
that incommensurate SDW (IC-SDW) and SC states are compatible in this compound.Comment: 5 pages, 4 figure
Neutron diffraction study on phase transition and thermal expansion of SrFeAsF
The magnetic ordering and crystal structure of iron pnictide SrFeAsF was
investigated by using neutron powder diffraction method. With decreasing
temperature, the tetragonal to orthorhombic phase transition is found at 180 K,
while the paramagnetic to antiferromagnetic phase transition set in at 133 K.
Similar to the parent compound of other iron pnictide system, the striped Fe
magnetism is confirmed in antiferromagnetic phase and the Fe moment of 0.58(6)
uB aligned along long a axis. The thermal expansion of orthorhombic phase of
SrFeAsF is also investigated. Based on the Grueneisen approximation and Debye
approximation for internal energy, the volume of SrFeAsF can be well fitted
with Debye temperature of 347(5) K. The experimental atomic displacement
parameters for different crystallographic sites in SrFeAsF are analyzed with
Debye model. The results suggested that the expansion of FeAs layers plays an
important role in determining the thermal expansion coefficient.Comment: 4 pages, 3 figure
Comparison of crystal structures and effects of Co substitution in a new member of Fe-1111 superconductor family AeFeAsF(Ae = Ca and Sr): a possible candidate for higher Tc superconductor
We refined crystal structures of newly found members of the Fe-1111
superconductor family, CaFe\_{1-x}Co\_{x}AsF and SrFe\_{1-x}Co\_{x}AsF (x = 0,
0.06, 0.12) by powder synchrotron X-ray diffraction analysis. The tetragonal to
orthorhombic phase transitions were observed at ~120 K for unsubstituted
CaFeAsF and at ~180 K for unsubstituted SrFeAsF, the transition temperatures
agreeing with kinks observed in temperature-dependent resistivity curves.
Although the transition temperature decreases, the structural phase transitions
were observed below 100 K in both samples of x = 0.06, and finally they were
suppressed in the doping level of x = 0.12. The refined structures reveal that
distortions of the FeAs4 tetrahedron from the regular tetrahedron likely
originate from mismatches in atomic radii among the constituent elements. In
this system, the enlarged FeAs4 tetrahedron resulting from larger radius of Sr
than that of Ca is flattened along a-b plane, whereas the smaller radius of Ca
makes the tetrahedron closer to regular one, and their characteristic shapes
are further enhanced by Co substitution. These results suggest that the CaFeAsF
compound is a promising candidate for higher-Tc superconductor.Comment: 17 pages, 8 figures, 2 tables, Supplementary information is included
at the end of the documen
Effects of magnetic doping and temperature dependence on phonon dynamics in CaFe\_{1-x}Co\_{x}AsF compounds (x = 0, 0.06, 0.12)
We report detailed measurements of composition as well as temperature
dependence of the phonon density-of-states in a new series of FeAs compounds
with composition CaFe1\_{1-x}Co\_{x}AsF (x = 0, 0.06, 0.12). The composition as
well as temperature dependence of phonon spectra for CaFe\_{1-x}Co\_{x}AsF (x =
0, 0.06, 0.12) compounds have been measured using time of flight IN4C and IN6
spectrometers at ILL, France. The comparison of phonon spectra at 300 K in
these compounds shows that acoustic phonon modes up to 12 meV harden in the
doped compounds in comparison to the parent CaFeAsF. While intermediate energy
phonon modes from 15 meV to 25 meV are also found to shift towards high
energies only in the 12 % Co doped CaFeAsF compound. The experimental results
for CaFe\_{1-x}Co\_{x}AsF (x = 0, 0.06, 0.12) are quite different from our
previous phonon studies on parent and superconducting MFe2As2 (M=Ba, Ca, Sr)
where low-energy acoustic phonon modes do not react with doping, while the
phonon spectra in the intermediate range from 15 to 25 K are found to soften in
these compounds. We argue that stronger spin phonon interaction play an
important role for the emergence of superconductivity in these compounds. The
lattice dynamics of CaFe\_{1-x}Co\_{x}AsF (x = 0, 0.06, 0.12) compounds is also
investigated using the ab-initio as well as shell model phonon calculations. We
show that the nature of the interaction between the Ca and the Fe-As layers in
CaFeAsF compounds is quite different compared with our previous studies on
CaFe2As2.Comment: 19 pages, 5 figure
Phonon spectra in CaFe2As2 and Ca0.6Na0.4Fe2As2: Measurement of the pressure and temperature dependence and comparison with ab-initio and shell model calculations
We report the pressure and temperature dependence of the phonon
density-of-states in superconducting Ca0.6Na0.4Fe2As2 (Tc=21 K) and the parent
compound CaFe2As2, using inelastic neutron scattering. We observe no
significant change in the phonon spectrum for Ca0.6Na0.4Fe2As2 at 295 K up to
pressures of 5 kbar. The phonon spectrum for CaFe2As2 shows softening of the
low-energy modes by about 1 meV when decreasing the temperature from 300 K to
180 K. There is no appreciable change in the phonon density of states across
the structural and anti-ferromagnetic phase transition at 172 K. These results,
combined with our earlier temperature dependent phonon density of states
measurements for Ca0.6Na0.4Fe2As2, indicate that the softening of low-energy
phonon modes in these compounds may be due to the interaction of phonons with
electron or short-range spin fluctuations in the normal state of the
superconducting compound as well as in the parent compound. The phonon spectra
are analyzed with ab-initio and empirical model calculations giving partial
densities of states and dispersion relations.Comment: 14 pages, 6 figure
Magnetic Lattice Dynamics of the Oxygen-Free FeAs Pnictides: How Sensitive are Phonons to Magnetic Ordering?
To shed light on the role of magnetism on the superconducting mechanism of
the oxygen-free FeAs pnictides, we investigate the effect of magnetic ordering
on phonon dynamics in the low-temperature orthorhombic parent compounds, which
present a spin-density wave. The study covers both the 122 (AFe2As2; A=Ca, Sr,
Ba) and 1111 (AFeAsF; A=Ca, Sr) phases. We extend our recent work on the Ca
(122 and 1111) and Ba (122) cases by treating computationally and
experimentally the 122 and 1111 Sr compounds. The effect of magnetic ordering
is investigated through detailed non-magnetic and magnetic lattice dynamical
calculations. The comparison of the experimental and calculated phonon spectra
shows that the magnetic interactions/ordering have to be included in order to
reproduce well the measured density of states. This highlights a
spin-correlated phonon behavior which is more pronounced than the apparently
weak electron-phonon coupling estimated in these materials. Furthermore, there
is no noticeable difference between phonon spectra of the 122 Ba and Sr,
whereas there are substantial differences when comparing these to CaFe2As2
originating from different aspects of structure and bonding
Improving design education at Kanazawa Intitute of Technology
A Task Force made up of a multicultural group of visiting professors at KIT, worked together with Japanese counterparts to develop materials to Improve Design Education At Kanazawa Institute of Technology (IDEA-KIT), Japan. The IDEA-KIT Task Force decided to use the Design Engineering Process that we teach to address the problem related to improving design education. The Task Force mission was to identify problems and needs in Engineering Design Education (EDE), to develop design specifications for educational materials to meet these needs, to generate a large number of concepts for ways to satisfy the design specifications, and select the best and most feasible ones for development to a level appropriate for classroom use in the autumn quarter of 1999. To facilitate implementation at KIT, all materials developed were to be modular, easy to use for both the faculty and students, and provide guidance in managing courses and standardising practices.As with any new programme, there were significant challenges in developing and implementing the EDE programme at KIT. While some challenges were anticipated, most did not show their true difficulty until experience in running the programme was available
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