Effects of bleaching on the sensitivity to dose of the infrared-stimulated luminescence of potassium-rich feldspars from Ynyslas, Wales

Reduction of the luminescence signal to a residual level before irradiation is an inherent part of the regeneration method of equivalent dose (ED) determination, but is likely to lead to changes in the sensitivity of the dosimeter. Sensitivity changes caused by different methods of reduction of the infrared- stimulated luminescence (IRSL) signal have been investigated by subjecting potassium-rich feldspars extracted from modern dune sand from Ynyslas, on the Dyfi Estuary in Wales, to repeated cycles of removal of the luminescence signal and beta irradiation. The methods used to remove the signal were exposure to natural sunlight, a solar simulator and infrared-emitting diodes with a wavelength of 880Δ 80 nm and heating to 450°C.     

Comparative extreme ultraviolet emission measurements for lithium and tin laser plasmas

Detailed spectroscopic studies on extreme UV emission from laser plasmas using tin and lithium planar solid targets were completed. At 13.5 nm, the best conversion efficiency (CE) for lithium was found to be 2.2% at intensities near 7 x 10(10) W/cm(2). The highest CE measured for tin was near 5.0% at an intensity close to 1 x 10(11) W/cm(2).     

Freezing-off in disc cavities

A semi-quantitative analysis is presented of freezing-off in a disc cavity during the injection moulding of thermoplastics. A criterion is obtained which enables the occurrence of freezing-off to be predicted, at least crudely. The form of the criterion is found to depend on the direction of flow (radially outward or inward) in the disc.     

Injection moulding of thermoplastics. I. Freezing-off at gates

The injection moulding of thermoplastics involves, during mould filling, flow of a hot molten polymer into a mould network, the walls of which are so cold that the polymer freezes on them. During the constant pressure drop part of the filling stage, but not during the preceding constant flow-rate part, freezing-off, that is premature blockage of the mould network by frozen polymer, is possible. A semi-quantitative analysis of such freezing-off at a gate is presented here. The length-scales and time-scales of all the relevant physical processes occurring during freezing-off are identified and a criterion is obtained which enables the occurrence of freezing-off to be predicted, at least crudely. a _j constant - b _jk constant - Br Brinkman number - Br ₀ initial Brinkman number - Gz Graetz number - Gz ₀ initial Graetz number - h _c half-height of flat cavity - h _g half-height of flat gate - h _g ^* half-height of polymer melt region in flat gate - L _c length of cavity - L _f filled length - L _g length of gate - m viscosity shear-rate exponent - P pressure drop - Q volumetric flow-rate - r radial coordinate in round gate and cavity - R _c radius of round cavity - R _g radius of round gate - R _g ^* radius of polymer melt region in round gate - Sf Stefan number - t time - t _f freeze-off time - T temperature - T _i inlet polymer melt temperature - T _m melting temperature of polymer - T _w gate wall temperature - u _r radial velocity in round gate - u _x axial velocity in flat gate - u _y transverse velocity in flat gate - u _z axial velocity in round gate - w _c width of flat channel - w _g width of flat gate - x axial coordinate in flat gate and cavity - y transverse coordinate in flat gate and cavity - z axial coordinate in round gate and cavity - thermal conductivity of molten polymer - thermal conductivity of frozen polymer - heat capacity of molten polymer - heat capacity of frozen polymer - _h ratio of half-height of flat gate to that of flat cavity - _R ratio of radius of round gate to that of round cavity - _w ratio of width of flat gate to that of flat cavity - dimensionless axial coordinate in round gate and cavity - dimensionless transverse coordinate in flat gate and cavity - ^* dimensionless half-height of polymer melt region in flat gate - dimensionless temperature - _i dimensionless inlet temperature - _j j-th term in power series expansion of dimensionless temperature - thermal diffusivity ratio - dimensionless filled length - latent heat of fusion of polymer - µ viscosity - µ ₀ unit shear-rate viscosity - v _j j-th eigenvalue - j-th zero of zeroth-order Bessel function of first kind - dimensionless axial coordinate in flat gate and cavity - _c dimensionless pressure drop in cavity - _g dimensionless pressure drop in gate - density of molten polymer - density of frozen polymer - dimensionless radial coordinate in round gate and cavity - ^* dimensionless radius of polymer melt region in round gate - dimensionless time - _f dimensionless freeze-off time - ₀ dimensionless time at start of final phase of freezing-off - rescaled dimensionless time - rescaled dimensionless freeze-off time - rescaled dimensionless time at start of final phase of freezing-off - dimensionless similarity variable - dummy variable - scaled dimensionless axial coordinate in gate     

A Districtwide Study of Automaticity When Included in Concept‐Based Elementary School Mathematics Instruction

While conceptual understanding of properties, operations, and the base‐ten number system is certainly associated with the ability to access math facts fluently, the role of math fact memorization to promote conceptual understanding remains contested. In order to gain insight into this question, this study looks at the results when one of three elementary schools in a school district implements mandatory automaticity drills for 10 minutes each day while the remaining two elementary schools, with the same curriculum and very similar demographics, do not. This study looks at (a) the impact that schoolwide implementation of automaticity drills has on schoolwide computational math skills as measured by the ITBS and (b) the relationship between automaticity and conceptual understanding as measured by statewide standardized testing. The results suggest that while there may be an association between automaticity and higher performance on standardized tests, caution should be taken before assuming there are benefits to promoting automaticity drills. These results are consistent with those that support a process‐driven approach to automaticity based on familiarity with properties and strategies associated with the base‐ten number system; they are not consistent with those that support an answer‐driven approach to automaticity based on memorization of answers.     

The die swell phenomenon

Summary A polymer melt or solution undergoes an increase in its cross-section when it is forced out of an orifice into air. The normal stress effects and elastic effects shown by these materials are frequently invoked to explain this die swell phenomenon. These explanations are here discussed and criticised. The analogous situation for a Newtonian jet is also discussed and the solution to a related problem of two-dimensional lowReynolds number flow is given.

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Zusammenfassung Kunststoffschmelzen oder -lösungen zeigen nach dem Austritt aus einer Mündung in Luft eine Aufweitung des Querschnitts. Häufig wird dieses Schwell-Phänomen als Folge von Normalspannungen und Elastizität erklärt. Erklärungen dieser Art werden hier kritisch untersucht.Ebenso wird der entsprechende Fall einer Newtonschen Düsenströmung diskutiert. Für das verwandte Problem einer zweidimensionalen Strömung bei niedrigerReynolds-Zahl wird die Lösung gegeben.

     

1,2-diphosphaacenaphthene 1,2-dications: synthetic, stereochemical and computational study of the stabilising role of naphthalene-1,8-diyl backbone

Syntheses and full characterisation data (including single crystal diffraction) of three 1,2‐diphosphonium dicationic species with the naphthalene‐1,8‐diyl (Nap) backbone are reported. The oxidation of Nap[P(NMe₂)₂]₂ with P₂I₄ to its 1,2‐dication was achieved. meso‐ and rac‐forms of “all carbon” 1,2‐diphosphonium dications were obtained in good yields and purity by double alkylation of the parent diphosphine (1,2‐diphenyl‐1,2‐diphosphaacenaphthene) with methyl triflate or trimethyloxonium tetrafluoroborate. Each methylating reagent produces one of the rac‐ or meso‐forms of the dication diastereospecifically. Structural parameters of the new dications are discussed with respect to other phosphorus 1,2‐dications. DFT (B3LYP) computations revealed the significant role of the naphthalene backbone in stabilisation of the dicationic motif and helped to assess the energy cost of the steric clash of a variety of groups attached to the peri‐positions of naphthalene. The synthesis and single crystal X‐ray data of the extremely crowded Nap[P(?Se)(OiPr)₂]₂ are discussed, and are contrasted with the unsuccessful synthesis of Nap(PtBu₂)₂ from NapLi₂ and ClPtBu₂.     

Self-organization of amphiphilic liquid-crystalline dendrimers in bulk and at the interface

A comparative analysis of the structure and phase behavior of synthesized carbosilane amphiphilic LC dendrimers of the third generation containing mesogenic phenyl and oligo(ethylene glycol) fragments is performed. When phenol groups are replaced with oligo(ethylene glycol) moieties, the temperature interval of the existence of the LC phase in the mesogen-containing dendrimers decreases. The chemical nature of hydrophilic terminal groups is found to control the organization of dendrimers in the smectic mesophase. Structural models for their packing are proposed. Amphiphilic dendrimers are shown to form stable Langmuir films at the water/air interface. Surface-pressure-surface area-isotherms are constructed. The effect of the chemical nature of hydrophilic groups on the formation of a monolayer at the interface and on the packing density of dendrimer molecules in the monolayer is discussed.     

Microproteomic analysis of 10,000 laser captured microdissected breast tumor cells using short-range sodium dodecyl sulfate-polyacrylamide gel electrophoresis and porous layer open tubular liquid chromatography tandem mass spectrometry

Precise proteomic profiling of limited levels of disease tissue represents an extremely challenging task. Here, we present an effective and reproducible microproteomic workflow for sample sizes of only 10,000 cells that integrates selective sample procurement via laser capture microdissection (LCM), sample clean-up and protein level fractionation using short-range SDS-PAGE, followed by ultrasensitive LC-MS/MS analysis using a 10 μm i.d. porous layer open tubular (PLOT) column. With 10,000 LCM captured mouse hepatocytes for method development and performance assessment, only 10% of the in-gel digest, equivalent to ～1000 cells, was needed per LC-MS/MS analysis. The optimized workflow was applied to the differential proteomic analysis of 10,000 LCM collected primary and metastatic breast cancer cells from the same patient. More than 1100 proteins were identified from each injection with >1700 proteins identified from three LCM samples of 10,000 cells from the same patient (1123 with at least two unique peptides). Label free quantitation (spectral counting) was performed to identify differential protein expression between the primary and metastatic cell populations. Informatics analysis of the resulting data indicated that vesicular transport and extracellular remodeling processes were significantly altered between the two cell types. The ability to extract meaningful biological information from limited, but highly informative cell populations demonstrates the significant benefits of the described microproteomic workflow.