Search

A previously undescribed small lenticular (~5 × 5 × 5 m) pegmatite, located near Wellington Lake in the NW part of the 1.08 Ga ‘A-type’ (anorogenic) ferroan Pikes Peak granite batholith, ~15 km SW of the South Platte pegmatite district in central Colorado, is concentrically zoned around a mostly monomineralic quartz core with interconnected miarolitic cavities. Major constituents of the Wellington Lake pegmatite are quartz, perthitic microcline, albite (variety cleavelandite), hematite, and biotite. Accessory minerals include fluocerite, bastnäsite, columbite, zircon (var. ‘cyrtolite’), thorite, and secondary U phases. Fluorite is conspicuously absent, although it is a common phase in the South Platte district NYF-type pegmatites, which are rich in niobium (Nb), yttrium (Y), fluorine (F), and heavy rare-earth elements (HREE). Notable for the Wellington Lake pegmatite are a small quantity of well-developed tabular crystals of fluocerite that reach up to 4 cm in diameter, with sub-mm epitaxial bastnäsite overgrowths, suggesting formation from F- and CO2-bearing solutions rich in light rare-earth elements (LREE), with decreasing a(F-)/a(CO32-) during the last crystallization phase. An Nd-isotope value of εNd1.08Ga = -1.6 for the fluocerite is within the range of εNd1.08Ga = -0.2 to -2.7 of the host coarse-grained, pink K-series Pikes Peak Granite (PPG), indicating that REE and other pegmatite constituents derived from the parental PPG magma. A calculation of total pegmatite composition based on whole-rock chemistry and volume estimates of the different pegmatite zones reveals an overall composition similar to the PPG with respect to Si, Al, Na, and K. Yet the pegmatite is depleted in Fe, Mg, Ca, Ti, Mn, and P, the high-field-strength elements (HFSE; Zr, Hf, Nb, Y, Th), and, most significantly, total REE compared to the PPG. Despite containing the LREE minerals fluocerite and bastnäsite, the lack of a net overall REE enrichment of the pegmatite compared to the PPG reflects the large amount of REE-poor silicate minerals forming the wall, intermediate, and core zones of the pegmatite. The calculated total pegmatite composition suggests that the pegmatite formed by the separation from the PPG magma of an F-poor H2O-saturated silicate melt depleted in REE and HFSE compared to the F-rich melts, which formed the NYF-type HREE-rich (LaN/YbN < 1) pegmatites in the South Platte district. Homogenization temperatures of < 500°C for possibly primary fluid inclusions in large quartz crystals from the core of the Wellington Lake pegmatite are consistent with recent models of pegmatite petrogenesis leading to nucleation controlled mega-crystal growth resulting from supercooling.

We develop the capacity region for the bosonic broadcast channel in the presence of thermal noise and photon loss due to the environment. The bosonic channel is a quantum-mechanical description of many practical communication links such as optical, microwave, and radiofrequency. We employ our results to find the capacity region for quantum-secure covert broadcast over such channels and show that time-division is optimal as in the classical covert broadcast scenario. We rely on a strong minimum entropy output conjecture, a direct result of the entropy photon-number inequality (EPnI) conjecture.

Beryl from Xuebaoding, Sichuan Province, western China is known for its unusual tabular habit and W–Sn–Be paragenesis in a greisen-type deposit. The crystals are typically colourless transparent to pale blue, often with screw dislocations of hexagonal symmetry on the (0001) crystal faces. Combining electron microprobe analyses and laser ablation inductively coupled plasma mass spectrometry with single-crystal X-ray diffraction (XRD), correlated with Raman and micro-infrared (IR) spectroscopy and imaging, the crystal chemical characteristics are determined. The contents of Na+ (0.24–0.38 atoms per formula unit (apfu)) and Li+ up to 0.38 apfu are at the high end compared to beryl from other localities worldwide. Li+ substitution for Be2+ on the tetrahedral (T2) site is predominantly charge balanced by Na+ on the smaller channel (C2) site, with Na+ ranging from 91.5% to 99.7% (apfu) of the sum of all other alkali elements. Cs+ and minor Rb+ and K+ primarily charge balance the minor M2+ substitution for Al3+ at the A site; all iron at the A site is suggested to be trivalent. The a axis ranges from 9.2161(2) to 9.2171(4) Å, with unit-cell volume from 678.03(3) to 678.48(7) Å3. The c/a ratio of 1.0002–1.0005 is characteristic for T2-type beryl with unit-cell parameters controlled primarily by Be2+ substitution. Transmission micro-IR vibrational spectroscopy and imaging identifies coordination of one or two water molecules to Na+ (type IIs and type IId, respectively) as well as alkali free water (type I). Based on IR absorption cross section and XRD a C1 site water content of 0.4–0.5 apfu is derived, i.e. close to 50% site occupancy. Secondary crystal phases with a decrease in Fe and Mg, yet increase in Na, suggest early crystallisation of aquamarine, with goshenite being late. With similar crystal chemistry to beryl of columnar habit from other localities worldwide, the tabular habit of Xuebaoding beryl seems to be unrelated to chemical composition and alkali content., Mineralogical Magazine, 85 (2)

Correlative hyperspectral Raman imaging with high spatial and spectral resolution, precision with peak position and linewidth analysis, and from the μm to mm scale, provides new insight into structural characteristics in dentin and enamel. We determine variations in degree of crystallinity, both locally across the dentin–enamel junction, and with distinct long‐range spatial variations. We identify a correlation of spectral peak position and linewidth as a measure of crystal lattice disorder across tubules, dentin, dentin–enamel junction, and enamel.

Thalénite-(Y), ideally Y3Si3O10F, is a heavy-rare-earth-rich silicate phase occurring in granite pegmatites that may help to illustrate rare-earth element (REE) chemistry and behaviour in natural systems. The crystal structure and mineral chemistry of thalénite-(Y) were analysed by electron microprobe analysis, X-ray diffraction and micro-Raman spectroscopy from a new locality in the peralkaline granite of the Golden Horn batholith, Okanogan County, Washington State, USA, in comparison with new analyses from the White Cloud pegmatite in the Pikes Peak batholith, Colorado, USA. The Golden Horn thalénite-(Y) occurs as late-stage sub-millimetre euhedral bladed transparent crystals in small miarolitic cavities in an arfvedsonite-bearing biotite granite. It exhibits growth zoning with distinct heavy-rare-earth element (HREE) vs. light-rare-earth element (LREE) enriched zones. The White Cloud thalénite-(Y) occurs in two distinct anhedral and botryoidal crystal habits of mostly homogenous composition. In addition, minor secondary thalénite-(Y) is recognized by its distinct Yb-rich composition (up to 0.8 atoms per formula unit (apfu) Yb). Single-crystal X-ray diffraction analysis and structure refinement reveals Y-site ordering with preferential HREE occupation of Y2 vs. Y1 and Y3 REE sites. Chondrite normalization shows continuous enrichment of HREE in White Cloud thalénite-(Y), in contrast to Golden Horn thalénite-(Y) with a slight depletion of the heaviest REE (Tm, Yb and Lu). The results suggest a hydrothermal origin of the Golden Horn miarolitic thalénite-(Y), compared to a combination of both primary magmatic followed by hydrothermal processes responsible for the multiple generations over a range of spatial scales in White Cloud thalénite-(Y).

Juno swoops around giant Jupiter Jupiter is the largest and most massive planet in our solar system. NASA's Juno spacecraft arrived at Jupiter on 4 July 2016 and made its first close pass on 27 August 2016. Bolton et al. present results from Juno's flight just above the cloud tops, including images of weather in the polar regions and measurements of the magnetic and gravitational fields. Juno also used microwaves to peer below the visible surface, spotting gas welling up from the deep interior. Connerney et al. measured Jupiter's aurorae and plasma environment, both as Juno approached the planet and during its first close orbit. Science , this issue p. 821 , p. 826

The combination of the Doppler data from the first two Juno science orbits provides an improved estimate of the gravity field of Jupiter, crucial for interior modeling of giant planets. The low-degree spherical harmonic coefficients, especially J4 and J6, are determined with accuracies better than previously published by a factor of 5 or more. In addition, the independent estimates of the Jovian gravity field, obtained by the orbits separately, agree within uncertainties, pointing to a good stability of the solution. The degree 2 sectoral and tesseral coefficients, C2,1, S2,1, C2,2, and S2,2, were determined to be statistically zero as expected for a fluid planet in equilibrium.

A new method has been applied to the determination of neutron nonelastic cross sections for iron 56 Fe and lead 208 Pb for energies between 5 and 26 MeV. These data have estimated errors of only a few percent and do not suffer from the ambiguities encountered in earlier nonelastic data. We attempt to fit these high-precision data using both a semiclassical single phase shift model (nuclear Ramsauer model) as well as a recent global optical model that well reproduces a wide body of neutron scattering observables. At the 5% uncertainty level, both models produce satisfactory fits. However, neither model gives satisfactory fits to these new precise data. We conclude that fitting precise data, i.e., data with errors of ∼2% or less, may require a nuclear mass dependence of radii that reflects structure effects such as shell closures.

The General Insurance Premium Rating Issues Working Party (GRIP) was established by the General Insurance Board of the Faculty and Institute of Actuaries in 2005 to review actuarial involvement in premium rating issues, pricing being one of the key areas in which actuaries work.GRIP published a full report in January 2007, which is available at www.actuaries.org.uk/grip. This short paper summarises the recommendations of that full report. Further background, discussion and the rationale for these recommendations are set out in more detail in the full report.

The nuclear Ramsauer model is a semi‐classical, analytic approximation to nucleon‐nucleus scattering that reproduces total cross‐section data at the 1% level for A > 40, En = 5–60 MeV with 7–10 parameters. A quick overview of the model is given, demonstrating the model’s utility in nuclear data evaluation. The Ramsauer model predictions for reaction cross section, elastic cross section, and elastic scattering angular distributions are considered. In a recent paper it has been shown that the nuclear Ramsauer model does not do well in predicting details of the angular distribution of neutron elastic scattering for incident energies of less than 60 MeV for 208Pb. However, in this contribution it is demonstrated that the default angular bin dispersion most widely used in Monte Carlo transport codes is such that the observed differences in angular shapes are on too fine a scale to affect transport calculations. Simple studies indicate that 512–2048 bins are necessary to achieve the dispersion required for calc...

Recently cross section differences among the isotopes 182, 184, 186W have been measured as part of a study of total cross sections in the 5–560 MeV energy range.1) These measurements show oscillations up to 150 mb between 5 and 100 MeV. Spherical and deformed phenomenological optical potentials with typical radial and isospin dependences show very small oscillations, in disagreement with the data. In a simple Ramsauer model, 2–4) this discrepancy can be traced to a cancellation between radial and isospin effects. Understanding this problem requires a more detailed model that incorporates a realistic description of the neutron and proton density distributions. This has been done with results of Hartree-Fock-Bogolyubov calculations using the Gogny force, together with a microscopic folding model employing a modification5,6) of the JLM potential as an effective interaction. This treatment yields a satisfactory interpretation of the observed total cross section differences.

The equivalence principle can be tested using accurate tracking of the Moon, planets, and interplanetary spacecraft. Tests with solar system bodies probe the dependence of the equivalence principle on self-energy. Analysis of lunar laser ranges yields the difference in the ratio of the gravitational and inertial masses for the Earth and Moon of ({-0.7}?1.5)?10-13. In conjunction with laboratory tests of the equivalence principle and spacecraft and VLBI tests of PPN ?, one derives |?-1|?0.0005. Planetary tests are feasible, in particular tests using Mars. Improvements in Doppler accuracies under development may allow tests with interplanetary spacecraft.

Polypurine tracts are important elements of eukaryotic promoters. They are believed to somehow destabilize chromatin, but the mechanism of their action is not known. We show that incorporating an A(16) element at an end of the nucleosomal DNA and further inward destabilizes histone-DNA interactions by 0.1 +/- 0.03 and 0.35 +/- 0.04 kcal mol(-1), respectively, and is accompanied by 1.5- +/- 0.1-fold and 1.7- +/- 0.1-fold increases in position-averaged equilibrium accessibility of nucleosomal DNA target sites. These effects are comparable in magnitude to effects of A(16) elements that correlate with transcription in vivo, suggesting that our system may capture most of their physiological role. These results point to two distinct but interrelated models for the mechanism of action of polypurine tract promoter elements in vivo. Given a nucleosome positioned over a promoter region, the presence of a polypurine tract in that nucleosome's DNA decreases the stability of the DNA wrapping, increasing the equilibrium accessibility of other DNA target sites buried inside that nucleosome. Alternatively (if nucleosomes are freely mobile), the presence of a polypurine tract provides a free energy bias for the nucleosome to move to alternative locations, thereby changing the equilibrium accessibilities of other nearby DNA target sites.

Posttranslational acetylation of the conserved core histone N-terminal tail domains is linked to gene activation, but the molecular mechanisms involved are not known. In an earlier study we showed that removing the tail domains altogether by trypsin proteolysis (which leaves nucleosomes nevertheless intact) leads to 1.5 to 14-fold increases in the dynamic equilibrium accessibility of nucleosomal DNA target sites. These observations suggested that, by modestly increasing the equilibrium accessibility of buried DNA target sites, histone acetylation could result in an increased occupancy by regulatory proteins, ultimately increasing the probability of transcription initiation. Here, we extend these observations to a more natural system involving intact but hyperacetylated nucleosomes. We find that histone hyperacetylation leads to 1.1 to 1.8-fold increases in position-dependent equilibrium constants for exposure of nucleosomal DNA target sites, with an average increase of 1.4(+/-0.1)-fold. The mechanistic and biological implications of these results are discussed.

A recent paper discussed fits of the nuclear Ramsauer model to total neutron cross sections for mass numbers A > 40 and for neutron energies between 6 and 60 MeV. These results are extended to nuclei of mass

We have previously shown that nucleosomes are conformationally dynamic: DNA sequences that in the time-average are buried inside nucleosomes are nevertheless transiently accessible, even to large proteins (or any other macromolecule). We refer to this dynamic behavior as “site exposure”. Here we show that: (i) the equilibrium constants describing this dynamic site exposure decrease progressively from either end of the nucleosomal DNA in toward the middle; and (ii) these position-dependent equilibrium constants are strongly dependent on the nucleosomal DNA sequence. The progressive decrease in equilibrium constant with distance inside the nucleosome supports the hypothesis that access to sites internal to a nucleosome is provided by progressive (transient) release of DNA from the octamer surface, starting from one end of the nucleosomal DNA. The dependence on genomic DNA sequence implies that a specific genomic DNA sequence could be a major determinant of target site occupancies achieved by regulatory proteins in vivo , by either governing the time-averaged accessibility for a given nucleosome position, or biasing the time-averaged positioning (of mobile nucleosomes), which in turn is a major determinant of site accessibility.

Two recent measurement programs have yielded an extensive body of neutron total cross-section data for a number of targets at energies up to 500 MeV. Recently, it has been shown that the simple Ram...

The simple nuclear Ramsauer model has been used successfully to fit neutron total cross sections for more than four decades but has not been widely used because the foundations of the model seem so...

The influence of the negative neighboring group has been quantified kinetically using hydrocarbon monomers containing oxygen and sulfur. Rate constants were determined for the ADMET polymerization of bis(4-pentenyl) ether (3), bis(5-hexenyl) ether (4), bis(4-pentenyl) sulfide (5), and bis(5-hexenyl) sulfide (6) using both Schrock's catalyst Mo(CHCMe2Ph)(N-2,6-C6H3-i-Pr2)(OCMe(CF3)2)2 [Mo] and Grubbs' phenyl version of the ruthenium metathesis catalyst RuCl2(CHPh)(PCy3)2 [Ru]. Both catalysts experience the effect of functional group presence. Further, a pure hydrocarbon version of the negative neighboring group effect has also been demonstrated using the monomer 1,5-hexadiene. In this case, [Mo] catalysis produces linear 1,4-polybutadiene in a reaction that exhibits a typical ADMET rate constant and activation energy. On the other hand, [Ru] catalysis leads principally to the formation of cyclic compounds rather than linear polymers. This change in mechanism for [Ru] catalysis can be attributed to multiple...

Segmented oligomers consisting of polyoctenylene hard segments and unsaturated polytetrahydrofuran soft segments were prepared using acyclic diene metathesis (ADMET) copolymerization techniques. These are the first such segmented materials prepared via metathesis chemistry. Two different molecular weight α,ω-poly(tetrahydrofuran)diene soft segment monomers of the structure [CH2CH(CH2)4[O(CH2)4]-nO(CH2)4CHCH2] (1) were synthesized by the cationic living polymerization of tetrahydrofuran (THF). Trifluoromethanesulfonic anhydride, (CF3SO2)2O (triflic anhydride) (2), was employed as the initiator, followed by in situ bis-functionalization with 5-hexen-1-ol, [CH2=CH(CH2)4OH] (3), to yield soft segment dienes with vinyl end groups. The functionality of these soft segment monomers was approximately 1.9. These telechelic monomers possessed sufficient functionality to be homopolymerized or copolymerized with 1,9-decadiene (4) to generate well phase separated, segmented oligomers exhibiting hard segment/soft segment thermal behavior. The segmented copolymers were characterized by 1H-NMR, 13C-NMR, and IR spectroscopy, elemental analysis, and TGA and DSC analysis. Average molecular weights were determined by gel permeation chromatography (GPC) and end-group analysis. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3441–3449, 1997

The zero degree (p,n) cross sections for a wide variety of targets and energies show an inverted angular shape for the differential cross section (the zero degree cross section has a minimum), which is correlated with the minimum observed in the neutron total cross section. Ramsauer calculations do not reproduce this correlation without the addition of a surface contribution. The existence of a zero degree (p,n) minimum can be thought of as a Ramsauer effect in angular momentum space (i.e., kR). We show that the existence of this inverted angular distribution also implies a rapid variation of the forward scattering amplitude with energy. We conjecture that the detailed description of the forward angle quasielastic (p,n) cross sections at these minima is extremely sensitive to the details of the nuclear surface. {copyright} {ital 1997} {ital The American Physical Society}

Development of an interactive display for the Smithsonian Institution's How Things Fly gallery illustrating fundamental aerodynamic principles associated with flight is described. Results from Reynolds-average Navier-Stokes simulations of various airfoil geometries and flight conditions are presented in a graphics-based interactive display implemented on an Intel 486/Pentium-class personal computer. This interactive display is one mechanism used to demonstrate basic aerodynamic principles to museum visitors in this new gallery within the National Air and Space Museum. © 1997 John Wiley & Sons, Inc. Comput. Appl Eng Educ 5: 13–20, 1997

Cross sections for the (p,n) reaction on targets of $^{90}\mathrm{Zr}$ and $^{92}\mathrm{Zr}$ have been measured at 26 MeV. Our resolution for these measurements was better than 200 keV and allowed the observation of numerous ${1}^{+}$ states in $^{92}\mathrm{Nb}$ below 7 MeV excitation. Our analysis is focused on states below the primary Gamow-Teller state and shows a fragmentation of the Gamow-Teller strength that is only partially accounted for by three different model calculations: a quasiparticle model, a shell model, and a random-phase approximation calculation. All three models yield predictions which include appreciable strength between 3 and 7 MeV excitation, but fail to describe our experimental results in detail. \textcopyright{} 1996 The American Physical Society.

The reflection of a normal shock wave from the end wall of a two‐dimensional channel has been numerically simulated to investigate the unsteady, viscous interaction aspects of shock bifurcation. The numerical simulation implements a data‐parallel version of the Flux‐Corrected Transport algorithm that has been coupled to the viscous transport terms of the Navier–Stokes equations. All numerical simulations were performed on the Connection Machine, the CM‐5. The results indicate that the shear layer in the bifurcation zone is unstable, and the large and small scale vortices lead to complex flow patterns. In addition, the high‐speed, essentially inviscid flow, which is adjacent to the shear layer, is deflected over this region. As a result, weak shock and expansions waves are generated and a reattachment shock is formed at the trailing edge of the interaction region. The impact of heat transfer, Reynolds number, and incident shock strength on the viscous interaction is also investigated. Heat transfer to the ...

The intra- and extracellular distribution and relative density of lamellar bodies (LBs) were determined by electron microscopy in synovial biopsies from 20 non-rheumatoid arthritis (RA) patients. LBs were found on the synovial surface, in intimal cells, throughout intimal matrix, in blood vessel walls, in endothelial cytoplasm and within vascular lumena. Lamellar profiles were observed in type B synoviocytes within rough endoplasmic reticulum (RER), in association with the Golgi apparatus, and embedded in electron dense matrix (projection cores) in multivesicular bodies. Exocytotic release of mature LBs into intimal matrix was observed. In type A synoviocytes the outer lamellae of LBs were frequently found in contiguity with the limiting membrane of lysosomes. An in vitro investigation of the ultrastructural features of LB formation in cultured type B synoviocytes (from 3 non-RA patients) gave results similar to those obtained in biopsies. These studies provide ultrastructural evidence of synoviocyte activity in secreting and degrading phospholipid lubricant in a sophisticated system whose function and pathological derangements are largely unknown.

Objective. Because there is no evidence for the effectiveness of antibiotic prophylaxis in children with neurogenic bladder, the value of once-daily nitrofurantoin macrocrystals was assessed in a selected population with neurogenic bladder due to meningomyelocele. Methods and trial population. Children with significant urinary tract abnormalities other than neurogenic bladder were excluded. A urinary tract "infection" was defined as ≥108 colony forming units of bacteria/L of urine together with pyuria of ≥50 x 106 leukocytes/L, and/or symptoms consistent with an urinary tract infection. Fifty-six children participated in a 24-week double-blinded, placebo-controlled cross-over study. The infeclion status was assessed at two weekly intervals or if relevant clinical manifestations occurred. Results. For the whole trial the average percentage of "infections" per urine sample for each patient was reduced from 39% on placebo to 19% on single daily dose prophylaxis (P < .0003). For the first 12 weeks of the trial corresponding figures were 45% on placebo and 22% on prophylaxis (P < .0018). There was evidence for a marked carryover protective effect of nitrofurantoin into the placebo arm of the trial. Conclusion. Nitrofurantoin is an effective prophylactic agent during a 3-month period. Long-term studies are needed to confirm the reasonable expectation of a beneficial effect on urinary tract damage.

Differential cross sections for the ([ital p],[ital n]) reaction to the ground-state and excited-state analogs of [sup 105]Pd have been measured at a proton bombarding energy of 26 MeV. Both the magnitude and the angular distribution of the cross sections for the analog states are found to follow the same general trend observed for the even-even palladium isotopes. Contributions to the analog transition on odd-[ital A] targets from spin-flip, higher multipoles, collective admixtures, and multistep processes are calculated and are found to be of order 1/([ital N][minus][ital Z]) or smaller, as compared to the ([ital N][minus][ital Z]) scaling expected for the Fermi transition. This is in agreement with our experimental data which show that the analog cross section scales as ([ital N][minus][ital Z]) relative to the neighboring nuclei. Among the excited analog states within the first MeV of excitation, the levels at 0.44 and 0.78 MeV were the most strongly populated. This is consistent with a two-step mechanism involving inelastic scattering and charge exchange, since these two states are also known to have the largest [ital B]([ital E]2) values. Although the small predicted magnitude of the additional contributions for nonzero spin targets agrees nicely with the present measurements for [supmore » 105]Pd, it leaves the puzzle as to why cross sections for odd isotopes for titanium and molybdenum measured in previous work were found to be larger than corresponding cross sections for adjacent even isotopes.« less

In a recent report Navratil et al. evaluated the angle-integrated cross section and the angular distribution for 14-MeV n+T elastic scattering by inferring these cross sections from accurately measured p+3He angular distributions. This evaluation used a combination of two theoretical treatments, based on the no-core shell model and resonating-group method (NCSM/RGM) and on the R-matrix formalism, to connect the two charge-symmetric reactions n+T and p+{sup 3}He. In this report we extend this treatment to cover the neutron incident energy range 6-14 MeV. To do this, we evaluate angle-dependent correction factors for the NCSM/RGM calculations so that they agree with the p+{sup 3}He data near 6 MeV, and using the results found earlier near 14 MeV we interpolate these correction factors to obtain correction factors throughout the 6-14 MeV energy range. The agreement between the corrected NCSM/RGM and R-Matrix values for the integral elastic cross sections is excellent ({+-}1%), and these are in very good agreement with total cross section experiments. This result can be attributed to the nearly constant correction factors at forward angles, and to the evidently satisfactory physics content of the two calculations. The difference in angular shape, obtained by comparing values of the scattering probability distribution P({mu}) vs. {mu}(the cosine of the c.m. scattering angle), is about {+-}4% and appears to be related to differences in the two theoretical calculations. Averaging the calculations yields P({mu}) values with errors of {+-}2 1/2 % or less. These averaged values, along with the corresponding quantities for the differential cross sections, will form the basis of a new evaluation of n+T elastic scattering. Computer files of the results discussed in this report will be supplied upon request.

International audience; In response to ESA's Call for proposals of 5 March 2007 of the COSMIC VISION 2015-2025 plan of the ESA science programme, we propose a M-class satellite mission to test of the Equivalence Principle in the quantum domain by investigating the extended free fall of matter waves instead of macroscopic bodies as in the case of GAUGE, MICROSCOPE or STEP. The satellite, called Matter Wave Explorer of Gravity, will carry an experiment to test gravity, namely the measurement of the equal rate of free fall with various isotopes of distinct atomic species with precision cold atom interferometry in the vicinity of the earth. This will allow for a first quantum test the Equivalence Principle with spin polarised particles and with pure fermionic and bosonic atomic ensembles. Due to the space conditions, the free fall of Rubidium and Potassium isotopes will be compared with a maximum accelerational sensitivity of 5*10 − 16 m/s2 corresponding to an accuracy of the test of the Equivalence Principle of 1 part in 1016. Besides the primary scientific goal, the quantum test of the Equivalence Principle, the mission can be extended to provide additional information about the gravitational field of the earth or for testing theories of fundamental processes of decoherence which are investigated by various theory groups in the context of quantum gravity phenomenology. In this proposal we present in detail the mission objectives and the technical aspects of the proposed mission.

This paper presents an analysis and reconstruction of a real-world, high-speed yaw and rollover of a sport utility vehicle that occurred on paved and unpaved surfaces with uneven topography. A law enforcement videotape of the crash, along with detailed inspection and measurement of the subject vehicle and accident site, enabled quantitative analysis of the event. The physical evidence was correlated with video images of the real-world rollover to obtain detailed information of the rollover mechanics throughout the sequence. The initial speed of the vehicle was 79 mph and its speed at overturn was 54 mph. The vehicle rolled six revolutions. The average roll rate for the entire sequence was more than 300 degrees/second, with peak values approaching 540 degrees/second. The rollover deceleration was found to be non-uniform during the sequence, and ranged from approximately 0.6 g to 0.2 g. Comparison with analytical results obtained from a reconstruction approach using typical values of constant deceleration indicates reasonably close agreement for overturn speed and average roll rate.

The simple nuclear Ramsauer model is extended to include explicitly the isovector potential. This model predicts large differences between proton and neutron total nuclear cross sections. When this model is applied to isotope/isotone total neutron cross section differences, it gives a good description of the measured data in the mass 140 region. Non-isospin-dependent differences in the isotopic imaginary potential are observed which totally obscure the contribution from the isovector imaginary potential. Additional measurements further from closed nuclear shells may yield useful information on the isovector imaginary potential.

A rationale for, and data from, a trial of a theory of item generation by algorithms whose origins are cognitive models of task performance are presented. Since Spearman (1904), intelligence has been operationally defined and assessed in human subjects by administering identical test items whose content and order have been fixed only after empirical iterations. In our approach, intelligence is ostensively defined by theoretically determined algorithms used for item construction and presentation. Knowledge of what cognitive factors limit human performance makes it possible to vary within tightly specified parameters those features of the tasks that contribute to difficulty, which we call radicals, to let those components of the tasks that do not contribute to difficulty vary randomly, and to counterbalance aspects of answer production that might induce biases of response. Empirical data are based on the generation of five different short tests demanding only functional literacy as a prerequisite for their execution. Four parallel forms of each test were administered to young male Army recruits whose scores were collated with their Army Entrance Test results, which were not previously known to us. Results show that the parallel, algorithm-generated item sets are statistically invariant, which item generation theory demands; and that the individual tests differentially predict Army Entrance Test scores. We conclude that IQ test performances are parsimoniously explained by individual differences in encoding, comparison and reconstructive memory processes.

[1] A close flyby of Saturn's satellite Rhea by the Cassini spacecraft on 26 November 2005 can be used to infer its mass and quadrupole gravity moments. From these data we derive a mean density of 1233 ± 5 kg m−3 for Rhea and an axial moment of inertia consistent with an undifferentiated interior. The small density implies an interior made up of about 25% rock-metal and 75% water ice by mass. The moment of inertia implies a homogeneous mix of these constituents with some compression of the ice and the transition from ice I to ice II at depth.

Experimental values for r.m.s. charge density radii show deviations from a simple A 1/3 dependence of several percent for statically deformed nuclei and around shell closures. These data, for both stable nuclei and nuclei away from the valley of stability, are well described by Hartree-Fock-Bogolyubov calculations carried out at Bruy` eres- le-ChBy using the neutron and proton r.m.s. radii from these same HFB calculations in conjunction with a folding model to produce an optical potential, we can then predict the expected results from neutron scattering experiments. We have made a detailed study of this procedure in the A = 40-70 mass range. The calculated 14-MeV neutron nonelastic and total cross sections show deviations of several percent from a smooth dependence on A. We conclude that using mean field - folding model calculations is useful for estimating neutron cross sections on nuclei both on and away from the valley of stability.

Wick’s limit is an inequality that relates the zero‐degree differential elastic scattering cross section to the total cross section. The deviation of Wick’s limit from an exact equality is small over a wide range of incident energies and target masses. Under these circumstances we show that Wick’s limit can be used to correlate the uncertainties in the two terms of the reaction (nonelastic) cross section expressed as the difference between the total and angle‐integrated elastic cross sections. When suitable elastic angular distributions are available, we show that the reaction cross section may be obtained with small errors (typically 1.5–3%). Examples are shown for 208Pb, 54–56Fe, 232Th, and 238U.

We construct an analytic model to demonstrate qualitatively the correspondence between the measured neutron total cross section and the regions where Wick's limit is actually an equality. This model does not give sufficiently accurate quantitative results, so we extend our calculations by using the nuclear optical model with both local and global parameters. We then demonstrate how Wick's limit can be used to give useful reaction cross-section information.

To test the efficacy of treatment for unilateral visual loss detected by preschool vision screening and the extent to which effectiveness varies with initial severity.Randomised controlled trial of full treatment with glasses and patching, if required, compared with glasses only or no treatment. Masked assessment of best corrected acuity after one year of follow up.Eight UK eye departments.177 children aged 3-5 years with mild to moderate unilateral impairment of acuity (6/9 to 6/36) detected by screening.Children in the full and glasses treatment groups had incrementally better visual acuity at follow up than children who received no treatment, but the mean treatment effect between full and no treatment was equivalent to only one line on a Snellen chart (0.11 log units; 95% confidence interval 0.050 to 0.171; P0.0001). The effects of treatment depended on initial acuity: full treatment showed a substantial effect in the moderate acuity group (6/36 to 6/18 at recruitment) and no significant effect in the mild acuity group (6/9 to 6/12 at recruitment) (P = 0.006 for linear regression interaction term). For 64 children with moderate acuity loss the treatment effect was 0.20 log units, equivalent to one to two lines on a Snellen chart. When all children had received treatment, six months after the end of the trial, there was no significant difference in acuity between the groups.Treatment is worth while in children with the poorest acuity, but in children with mild (6/9 to 6/12) unilateral acuity loss there was little benefit. Delay in treatment until the age of 5 did not seem to influence effectiveness.

Intrinsic nucleosome dynamics termed "site exposure" provides spontaneous and cooperative access to buried regions of nucleosomal DNA in vitro. Two different mechanisms for site exposure have been proposed, one based on nucleosome translocation, the other on dynamic nucleosome conformational changes in which a stretch of the nucleosomal DNA is transiently released off the histone surface. Here we report on three experiments that distinguish between these mechanisms. One experiment investigates the effects on the accessibilities of restriction enzyme target sites inside nucleosomes when extra DNA (onto which the nucleosome may move at low energetic cost) is appended onto one end. The other two experiments test directly for nucleosome mobility under the conditions used to probe accessibility to restriction enzymes: one on a selected nonnatural nucleosome positioning sequence, the other on the well-studied 5S rRNA gene nucleosome positioning sequence. We find from all three assays that restriction enzymes gain access to sites throughout the entire length of the nucleosomal DNA without contribution from nucleosome translocation. We conclude that site exposure in nucleosomes in vitro occurs via a nucleosome conformational change that leads to transient release of a stretch of DNA from the histone surface, most likely involving progressive uncoiling from an end. Recapture at a distal site along DNA that has partially uncoiled would result in looped structures which are believed to contribute to RNA polymerase elongation and may contribute to spontaneous or ATP-driven nucleosome mobility. Transient open states may facilitate the initial entry of transcription factors and enzymes in vivo.

Patients with reconstruction of craniofacial or intraoral defects experience a profound impact on their quality of life (QOL). This impact on QOL is influenced by the patients' medical conditions and the treatment interventions. Instruments to measure general QOL have been available for many years. A major criticism of QOL instruments is that too often the questions are not specific to the particular problems of a disease or condition. A search of the literature regarding QOL measurement for patients with maxillofacial implant-supported prostheses produced a short list of instruments, none of which were sufficiently developed or suited to the patients involved in reconstructive treatment. This study was designed to develop pretreatment and posttreatment questionnaires for measuring QOL for patients with reconstruction of a craniofacial defect and patients with reconstruction of loss of specific intraoral structures utilizing an implant-supported prosthesis (e.g., severe resorption of the maxilla or mandible or both). The goal was to develop brief, targeted instruments for this specific patient population. The produced instruments were sensitive and easy to administer and score, and no disruption of clinical care occurred with the administration of the questionnaires. The instruments were used with equal success both in face-to-face interviews and via mail.

Recently, new cross section measurements by the GEANIE collaboration have been published for {sup 239}Pu(n, 2n{gamma}) [Ber00] and {sup 235}U(n, 2n{gamma}) [You00] from threshold to 20 MeV. When combined with nuclear reaction calculations [Che00, Cha99, Cha01], these measurements provide the most accurate information available on the shape and magnitude of the {sup 239}Pu(n, 2n) cross section for incident neutron energies, E{sub n} {approx}< 14 MeV. This new data has prompted a re-evaluation of the {sup 239}Pu(n, 2n) {sup 238}Pu reaction cross section considering all available experimental data. The data prior to the measurement of Bernstein et al. [Ber00] is illustrated in Figure 1a. These data sets were considered by previous evaluations [ENDL] of the {sup 239}Pu(n, 2n) cross section. The most precise experiment was an activation measurement done by Lougheed et al. [Lou00] for incident neutron energies, E{sub n}, between 13-15 MeV. In addition, there were two neutron-counting experiments, one by Mather et al. [Mat72] and one by Frehaut et al. [Fre85]. These two measurements cover a wide incident neutron range, with data points from threshold to E{sub n} {approx} 14 MeV. The available data sets are in poor agreement with each other and in some cases do not meetmore » basic expectations. These experiments will be reviewed in detail. The new contributions to this evaluation are (1) the GEANIE data coupled with reaction modeling, illustrated in Figure 1b, and (2) the systematic use of other nuclear data in order to put constraints on the shape and magnitude of the {sup 239}Pu(n, 2n) cross section. The approach of this evaluation has been to use consistency arguments supported by nuclear data to resolve the measurement differences, with the goal of providing: (1) A comprehensive picture of our knowledge on the {sup 239}Pu(n, 2n) cross section; and (2) A new evaluation including the best possible estimate of the cross section and a one-sigma estimate the uncertainties. This paper is organized in the following fashion: Section 2: Evaluation of {sup 239}Pu(n, 2n) measurements--Measurements of the {sup 239}Pu(n, 2n) cross section are evaluated for reliability (systematic uncertainties) and for renormalization possibilities. Section 3: Consistency with other experimental data--Experimental data and nuclear data evaluations for non-elastic, inelastic, fission, (n, 2n), and neutron production cross sections are reviewed in the context of unitarity and other constraints. Conclusions with regard to the shape and magnitude of the {sup 239}Pu(n, 2n) cross section are drawn. Section 4: Recommended {sup 239}Pu(n, 2n) cross section and uncertainties--The results of Section 2 and 3 are combined to provide an overall ''best'' data set with evaluated uncertainties. The recommended {sup 239}Pu(n, 2n) cross sections and relative uncertainties are given in tabular format and compared with other evaluations.« less

Pulse-width modulation (PWM) was investigated as a means of metering and distributing anhydrous ammonia fertilizer. A multipoint system having one PWM valve for each knife was developed and tested for lateral distribution and flow characteristics. The PWM manifold was designed to promote cooling of the incoming ammonia, to ensure that liquid ammonia was fed to the PWM valves at all times. The flow from each PWM valve was determined by a dynamic water absorption method. Valve duty cycles ranging from 3% to 90% were tested. Lateral coefficients of variation were less than 10%, provided that the PWM valve duty cycle was 10% or higher. Ammonia flow was a function of duty cycle and pressure drop across the valves. The valve flow model indicates that a turn-down ratio of 50:1 is feasible, which will allow a single valve design to meet a wide range of fertilizer application rates.

Using existing experimental data for neutron-induced total, elastic, inelastic, reaction and fission cross sections, as well as results from nuclear model calculations and evaluations from nuclear reaction data libraries, we derived an estimate for the cross sections for the {sup 235}U(n,2n) and {sup 239}Pu(n,2n) reactions for the neutron energy range from threshold to approximately 12 MeV. In effect, our approach is based on subtracting the fission and inelastic cross sections from the total reaction cross section where the difference is expected to yield the (n,2n) cross section. In addition to this subtraction approach, a ratio method and a differential method have also been explored. For {sup 235}U(n,2n), as a test case, we arrive at a cross section consistent with previous measurements, and for {sup 239}Pu(n,2n) we obtain a peak value of 400 {+-} 60 mb for the incident neutron energy range of 10 {le} E{sub n} {le} 12 MeV.

We have previously shown that nucleosomes are conformationally dynamic: DNA sequences that in the time-average are buried inside nucleosomes are nevertheless transiently accessible, even to large proteins (or any other macromolecule). We refer to this dynamic behavior as "site exposure". Here we show that: (i) the equilibrium constants describing this dynamic site exposure decrease progressively from either end of the nucleosomal DNA in toward the middle; and (ii) these position-dependent equilibrium constants are strongly dependent on the nucleosomal DNA sequence. The progressive decrease in equilibrium constant with distance inside the nucleosome supports the hypothesis that access to sites internal to a nucleosome is provided by progressive (transient) release of DNA from the octamer surface, starting from one end of the nucleosomal DNA. The dependence on genomic DNA sequence implies that a specific genomic DNA sequence could be a major determinant of target site occupancies achieved by regulatory proteins in vivo, by either governing the time-averaged accessibility for a given nucleosome position, or biasing the time-averaged positioning (of mobile nucleosomes), which in turn is a major determinant of site accessibility.