56,582 research outputs found
Interstitials in tetrahedrally close-packed phases: C, N, O, and F in ?-tungsten from first principles
No full textSeveral tetrahedrally close-packed (tcp) phases, such as ?-W, ?-Ta, and ?-U, are believed to be stabilized by impurities. Here we analyze the various ways in which impurities can be dissolved in tcp structures paying special attention to interstitial configurations in the ?-W (A15) structure. We find that at most there are only seven interstitial positions possible. Through ab initio calculations we show that common impurities such as C, N, O, and F, dissolve interstitially in ?-W and that N, O, and F interstitials prefer the same position in the ?-W (A15) structure.Materials Science and EngineeringMechanical, Maritime and Materials Engineerin
The legacy of sperm banking: how fertility monitoring and disposal of sperm are linked with views of cancer treatment
No full textBackground: sperm banking is recommended for all men before cancer treatment, which carries a risk of long-term gonadal damage. However, relatively few men take up the offer. Among them, few attend for fertility monitoring or agree to sperm disposal where fertility recovers. Sperm banks are therefore burdened by long-term storage of samples that may not be needed for conception, with implications for healthcare resources. The aims here were to determine the views of men regarding personal benefits of sperm banking, and the advantages and disadvantages of fertility monitoring and disposal in the longer term.Methods: semi-structured interviews were conducted with 19 men who were diagnosed with cancer and had banked sperm at least 5 years previously. Men were asked to recall their experiences from diagnosis to the present time, focusing on the consequences for their fertility. Interviews were transcribed and analysed using Interpretative Phenomenological Analysis.Results: results are discussed in relation to decisions surrounding banking sperm, fertility monitoring and attitudes to disposal of banked sperm. Complex attitudes were identified, with men's views reflecting their understanding of their current and future fertility and the possible trajectory of cancer itself. Men are overwhelmed by information on diagnosis and fail to understand the implications of cancer treatment for their future fertility.Conclusions: in diagnosis, men are given large amounts of information about cancer and treatment but fail to understand the longer-term implications of sperm banking. These implications need to be specifically addressed at subsequent appointments in order to optimize fertility monitoring and timely disposal of sperm sample
Close-ups of the preserved gastroliths within IGVR 9105.
No full textA) G1. B) G2. C) G3. D) G4. E) G5. F) From the left G6 and G7. G) G8. H) G9. I) G10. Scale bars: A,C,E,F,H 2) cm; B,G,I) 1 cm.</p
Substrate Conformation Masquerades Two different Oxidants in Aromatic C-H and C-F bond activation by Heme-dependent Tyrosine Hydroxylase
No full textA recently discovered heme-dependent enzyme TyrH offers a green approach for functionalizing the high-strength C-H and C-F bonds in aromatic compounds. However, there is ambiguity regarding the nature of intermediates (Cpd 0 or Cpd I) involved in activating these bonds. Herein, using comprehensive MD Simulations and hybrid QM/MM calculations, we reveal that it is Compound I (Cpd I) that acts as the primary oxidant involved in the functionalization of both the C-F and C-H bonds. Our study shows that the His88 close to the catalytic site acts as a modulator of aromaticity and is essential to initiate the C-H and C-F bond activation. The reaction proceeds via the proton abstraction from the 4-OH group of the substrate by His88, which is coupled with an electron transfer to form a single-electron reduced Cpd I-like intermediate. This species then inserts the oxygen atom into the sp3 hybridized C-H and C-F bond of the substrate. Interestingly, our mechanistic study shows that the two different conformations of the substrate are actually responsible for the C-F and C-H functionalization, which masquerades as two different characters of oxidants involved in the reaction
An Optimization Method for solutions of Close Eclipsing Binaries
No full textIn this paper we show the performances of the Controlled Random Search of Price (1976) in light curve solution of dose eclipsing binaries, in connection with WilsonDevinney model for light curve synthesis ( 1971), comparing it with other existing procedures. Examples of solved systems demonstrate the power and reliability of this technique, in particular when applied to simultaneuos solution of light and radia! velocity curves for eccentric binary systems
New thermoelastic parameters of natural C2/c omphacite
No full textThe compressibility at room temperature and the thermal expansion at room pressure of two disordered crystals (space group C2/c) obtained by annealing a natural omphacite sample (space group P2/n) of composition close to Jd 56Di 44 and Jd 55Di 45, respectively, have been studied by single-crystal X-ray diffraction. Using a Birch-Murnaghan equation of state truncated at the third order [BM3-EoS], we have obtained the following coefficients: V 0 = 421.04(7) Å 3, K T0 = 119(2) GPa, K′ = 5.7(6). A parameterized form of the BM3 EoS was used to determine the axial moduli of a, b and c. The anisotropy scheme is β c ≤ β a ≤ β b, with an anisotropy ratio 1.05:1.00:1.07. A fitting of the lattice variation as a function of temperature, allowing for linear dependency of the thermal expansion coefficient on the temperature, yielded α V(1bar,303K) = 2.64(2) × 10 -5 K -1 and an axial thermal expansion anisotropy of α b ≫ α a > α c. Comparison of our results with available data on compressibility and thermal expansion shows that while a reasonable ideal behaviour can be proposed for the compressibility of clinopyroxenes in the jadeite-diopside binary join [K T0 as a function of Jd molar %: K T0 = 106(1) GPa + 0.28(2) × Jd (mol%)], the available data have not sufficient quality to extract the behaviour of thermal expansion for the same binary join in terms of composition
Leptonic decay constants f(K), f(D), and f(Ds) with N-f=2+1+1 twisted-mass lattice QCD
No full textWe present a lattice QCD calculation of the pseudoscalar decay constants f(K), f(D) and f(Ds) performed using the gauge configurations produced by the European Twisted Mass Collaboration with N-f = 2 + 1 + 1 dynamical quarks, which include in the sea, besides two light mass degenerate quarks, also the strange and charm quarks with masses close to their values in the real world. The simulations are based on a unitary setup for the two light mass-degenerate quarks and on a mixed action approach for the strange and charm quarks. We use data simulated at three different values of the lattice spacing in the range 0.06-0.09 fm and at pion masses in the range 210-450 MeV. Our main results are f(K+)/f(pi+) = 1.184(16), f(K+) = 154.4(2.0) MeV, which incorporate the leading strong isospin breaking correction due to the up and down quark mass difference, and f(K) = 155.0(1.9) MeV, f(D) = 207.4(3.8) MeV, f(Ds) = 247.2(4.1) MeV, f(Ds)/f(D) = 1.192(22) and (f(Ds)/f(D))/(f(K)/f(pi)) = 1.003(14) obtained in the isospin symmetric limit of QCD. Combined with the experimental measurements of the leptonic decay rates of kaon, pion, D and D-s mesons our results lead to the following determination of the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements: vertical bar V-us vertical bar = 0.2269(29), vertical bar V-cd vertical bar = 0.2221(67) and vertical bar V-cs vertical bar = 1.014(24). Using the latest value of vertical bar V-ud vertical bar from superallowed nuclear beta decays the unitarity of the first row of the CKM matrix is fulfilled at the per mill level
Logarithmic variance profiles and the corresponding f-1 spectra of temperature fluctuations in turbulent Rayleigh-Bénard convection
No full textWe report experimental results for the temperature variance 2(z) and the corresponding frequency spectra P(f) in turbulent Rayleigh-Bénard convection (RBC) in a cylindrical sample of aspect ratioT= D/L = 1:00 (D = 1:12 m is the diameter and L = 1:12 m the height). The measurements were conducted in the Rayleigh-number range 1011 < Ra < 1:35 1014 and Pr ' 0:8. For Ra = 1:35x1014, 2(z) could be described well by a logarithmic dependence on the vertical position z in a range of z 1 < z < z 2 with z 1 ' 70 and z 2 = 0:1L. Here L=(2Nu) is the thickness of a thin thermal sublayer adjacent to the horizontal plate where the heat flux (denoted by the Nusselt number Nu) is carried mostly by thermal diffusion. In the log layer, we found that the temperature spectra had a significant frequency range over which P(f) f with close to 1. As Ra decreased, increased so that the log layer became thinner. At Ra = 2:05 1011, z 2 < z 1 and therefore there was no range for a log layer. Correspondingly, the temperature spectrum near the horizontal plate did not have the f1 scaling form either
Kepler-14b: A Massive Hot Jupiter Transiting an F Star in a Close Visual Binary
No full textWe present the discovery of a hot Jupiter transiting an F star in a close visual (0[" over .]3 sky projected angular separation) binary system. The dilution of the host star's light by the nearly equal magnitude stellar companion (~0.5 mag fainter) significantly affects the derived planetary parameters, and if left uncorrected, leads to an underestimate of the radius and mass of the planet by 10% and 60%, respectively. Other published exoplanets, which have not been observed with high-resolution imaging, could similarly have unresolved stellar companions and thus have incorrectly derived planetary parameters. Kepler-14b (KOI-98) has a period of P = 6.790 days and, correcting for the dilution, has a mass of M[subscript p] = 8.40[superscript +0.35] [subscript – 0.34] M [subscript J] and a radius of R[subscript p] = 1.136[superscript +0.073] [subscript – 0.054] R [subscript J], yielding a mean density of ρ [subscript p] = 7.1 ± 1.1 g cm[superscript –3]
Alkaline earth metal organoamide complexes displaying close Ae-F(C) (Ae = Ca, Mg) interactions
No full textProtolysis of [Ca{N(SiMe(3))₂)(thf)₂] (thf = tetrahydrofuran) with the N,N-dialkyl-N′-2,3,5,6-tetrafluorophenylethane-1,2-diamines, p-HC₆F₄N(CH₂)₂NR₂ (LᴿH; R = Me or Et), yields [Ca(p-HC₆F₄N(CH₂)₂NR₂ (L(thf)₂], whilst protolysis of di-n-butylmagnesium by the same amines yields [Mg(p-HC₆F₄N(CH₂)₂NR₂ complexes. X-Ray crystal structures show that the calcium derivatives contain eight-coordinate calcium atoms, with tridentate (N,N′,o-F) coordination of the organoamide ligands and cisoid thf donors. It is noteworthy that the Ca–F(C) bond lengths are shorter than the Ca–NR₂ bond lengths. By contrast, magnesium forms centrosymmetric, six-coordinate, homoleptic complexes, in which the Mg–NR₂ bond lengths are shorter than the Mg–F(C) bond lengths. 19F{1H} NMR spectra of the R = Me complexes support retention of Ae–F(C) linkages in solution at low temperatures. Heating the complexes for a prolonged period in C₆D₆ at 80°C showed no evidence of C–F activation reactions
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