23,937 research outputs found
Apparatus for measuring thermal conductivity Patent
Development of apparatus for measuring thermal conductivit
Structure, bonding and morphology of hydrothermally synthesised xonotlite
The authors have systematically investigated the role of synthesis conditions upon the structure and morphology of xonotlite. Starting with a mechanochemically prepared, semicrystalline phase with Ca/Si=1, the authors have prepared a series of xonotlite samples hydrothermally, at temperatures between 200 and 250 degrees C. Analysis in each case was by X-ray photoelectron spectroscopy, environmental scanning electron microscopy and X-ray diffraction. The authors’ use of a much lower water/solid ratio has indirectly confirmed the ‘through solution’ mechanism of xonotlite formation, where silicate dissolution is a key precursor of xonotlite formation. Concerning the role of temperature, too low a temperature (~200 degrees C) fails to yield xonotlite or leads to increased number of structural defects in the silicate chains of xonotlite and too high a temperature (>250 degrees C) leads to degradation of the xonotlite structure, through leaching of interchain calcium. Synthesis duration meanwhile leads to increased silicate polymerisation due to diminishing of the defects in the silicate chains and more perfect crystal morphologies
Progression and assessment in foreign languages at Key Stage 2
The teaching of primary languages has been increasing steadily, in response to the future entitlement for all Key Stage 2 (KS2) pupils aged 7-11 to learn a foreign language by 2010. However, there remain concerns about progression both within KS2 and through to secondary school and about how learners' progress is assessed. This paper presents findings on the issues of progression and assessment taken from case studies which formed part of a project funded by the then Department for Education and Skills (DfES), now the Department for Children, Schools and Families (DCSF). This project set out to evaluate 19 local authority (LA) Pathfinders in England that were piloting the introduction of foreign language learning at KS2 between 2003 and 2005. Findings revealed that there was inconsistency between schools, even within each LA Pathfinder, in the use of schemes of work and that assessment was generally underdeveloped in the majority of the Pathfinders. In order to set these findings in context, this paper examines the issues of progression and assessment in foreign language learning in England. Finally, it investigates the challenges English primary schools face in terms of progression and assessment in the light of the new entitlement and discusses implications for the future. Managing progression, both within KS2 and through to secondary school at KS3 (ages 11-14), is one of the key factors in determining the overall success of starting languages in primary school
Infinite barbarians
This paper discusses an infinite regress that looms behind a certain kind of historical explanation. The movement of one barbarian group is often explained by the movement of others, but those movements in turn call for an explanation. While their explanation can again be the movement of yet another group of barbarians, if this sort of explanation does not stop somewhere we are left with an infinite regress of barbarians. While that regress would be vicious, it cannot be accommodated by several general views about what viciousness in infinite regresses amounts to. This example is additional evidence that we should prefer a pluralist approach to infinite regresses
The nature of a broad line radio galaxy: Simultaneous RXTE and Chandra HETG observations of 3C 382
We present the results from simultaneous chandra and rxte observations of the
X-ray bright Broad-Line Radio Galaxy (BLRG) 3C 382. The long (120 ks) exposure
with chandra HETG allows a detailed study of the soft X-ray continuum and of
the narrow component of the Fe Kalpha line. The rxte PCA data are used to put
an upper limit on the broad line component and constrain the hard X-ray
continuum. A strong soft excess below 1 keV is observed in the time-averaged
HETG spectrum, which can be parameterized with a steep power law or a thermal
model. The flux variability at low energies indicates that the origin of the
soft excess cannot be entirely ascribed to the circumnuclear diffuse emission,
detected by chandra on scales of 20-30 arcsec (22-33 kpc). A narrow (sigma<90
eV) Fe Kalpha line (with EW< 100 eV) is observed by the chandra HEG. Similar
values for the line parameters are measured by the rxte PCA, suggesting that
the contribution from a broad line component is negligible. The fact that the
exposure is split into two observations taken three days apart allows us to
investigate the spectral and temporal evolution of the source on different
timescales. Significant flux variability associated with spectral changes is
observed on timescales of hours and days. The spectral variability is similar
to that observed in radio-quiet AGN ruling out a jet-dominated origin of the
X-rays.Comment: 19 pages, 10 figures, 3 tables, accepted for publication in Ap
Low- and high-frequency noise from coherent two-level systems
Recent experiments indicate a connection between the low- and high-frequency
noise affecting superconducting quantum systems. We explore the possibilities
that both noises can be produced by one ensemble of microscopic modes, made up,
e.g., by sufficiently coherent two-level systems (TLS). This implies a relation
between the noise power in different frequency domains, which depends on the
distribution of the parameters of the TLSs. We show that a distribution,
natural for tunneling TLSs, with a log-uniform distribution in the tunnel
splitting and linear distribution in the bias, accounts for experimental
observations.Comment: minor corrections, references adde
Risk of cancer following primary total hip replacement or primary resurfacing arthroplasty of the hip : A retrospective cohort study in Scotland
Acknowledgements: We are grateful to Lee Barnsdale, Doug Clark, and Richard Dobbie for advice and assistance with data preparation before analysis, and to the three anonymous referees for their helpful comments and suggestions.Peer reviewedPublisher PD
Integrity bases for local invariants of composite quantum systems
Unitary group branchings appropriate to the calculation of local invariants
of density matrices of composite quantum systems are formulated using the
method of -function plethysms. From this, the generating function for the
number of invariants at each degree in the density matrix can be computed. For
the case of two two-level systems the generating function is . Factorisation of such series leads
in principle to the identification of an integrity basis of algebraically
independent invariants. This note replaces Appendix B of our paper\cite{us} J
Phys {\bf A33} (2000) 1895-1914 (\texttt{quant-ph/0001076}) which is incorrect.Comment: Latex, 4 pages, correcting Appendix B of quant-ph/0001076 Error in
corrected and conclusions modified accordingl
Dephasing in Metals by Two-Level Systems in the 2-Channel-Kondo Regime
We point out a novel, non-universal contribution to the dephasing rate
1/\tau_\phi \equiv \gamma_\phi of conduction electrons in metallic systems:
scattering off non-magnetic two-level systems (TLSs) having almost degenerate
Kondo ground states. In the regime \Delta_{ren} < T < T_K (\Delta_{ren} =
renormalized level splitting, T_K = Kondo temperature), such TLSs exhibit
non-Fermi-liquid physics that can cause \gamma_\phi, which generally decreases
with decreasing T, to seemingly saturate in a limited temperature range before
vanishing for T \to 0. This could explain the saturation of dephasing recently
observed in gold wires [Mohanty et al. Phys. Rev. Lett. 78, 3366 (1997)].Comment: Final published version, including minor improvements suggested by
referees. 4 pages, Revtex, 1 figur
Magnetoresistance of proximity coupled Au wires
We report measurements of the magnetoresistance (MR) of narrow Au wires
coupled to a superconducting Al contact on one end, and a normal Au contact on
the other. The MR at low magnetic field is quadratic in , with a
characteristic field scale determined by phase coherent paths which
encompass not only the wire, but also the two contacts. is essentially
temperature independent at low temperatures, indicating that the area of the
phase coherent paths is not determined by the superconducting coherence length
in the normal metal, which is strongly temperature dependent at low
temperatures. We identify the relevant length scale as a combination of the
electron phase coherence length in the normal metal and the coherence
length in the superconductor
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