Search

International audience; Multi-anvil and laser-heated diamond anvil methods areused to subject Ge and Si mixtures to pressures and temperaturesof between 12 and 17 GPa and 1500 – 1800 K, respectively.Synchrotron angle dispersive X-ray diffraction, precession electrondiffraction and chemical analysis using electron microscopy, revealrecovery at ambient pressure of hexagonal Ge-Si solid solutions(P63/mmc). Taken together, the multi-anvil and diamond anvil resultsreveal that hexagonal solid solutions can be prepared for all Ge-Sicompositions. This hexagonal class of solid solutions constitutes asignificant expansion of the bulk Ge-Si solid solution family, and is ofactive interest for optoelectronic applications.

Angewandte Chemie / International edition 60(16), 9009 - 9014 (2021). doi:10.1002/anie.202016179, The cubic diamond (Fd-3m) group IVA element Si has been the material driver of the electronics industry since its inception. We report synthesis of a new cubic (Im-3m) group IVA material, a GeSn solid solution, upon heating Ge and Sn at pressures from 13 to 28 GPa using double-sided diamond anvil laser-heating and large volume press methods. Both methods were coupled with in-situ angle dispersive X-ray diffraction characterization. The new material substantially enriches the seminal group IVA alloy materials landscape by introducing an eightfold coordinated cubic symmetry, which markedly expands on the conventional tetrahedrally coordinated cubic one. This cubic solid solution is formed, despite Ge never adopting the Im-3m symmetry, melting inhibiting subsequent Im-3m formation and reactant Ge and Sn having unlike crystal structures and atomic radii at all these pressures. This is hence achieved without adherence to conventional formation criteria and routes to synthesis. This advance creates fertile avenues for new materials development., Published by Wiley-VCH, Weinheim

Journal of the American Chemical Society 143(21), 7920 - 7924 (2021). doi:10.1021/jacs.1c03765, Ge and Sn are unreactive at ambient conditions. Their significant promise for optoelectronic applications is thus largely confined to thin film investigations. We sought to remove barriers to reactivity here by accessing a unique pressure, 10 GPa, where the two elements can adopt the same crystal structure (tetragonal, $I4_1$/$amd$) and exhibit compatible atomic radii. The route to GeSn solid solution, however, even under these directed conditions, is different. Reaction upon heating at 10 GPa occurs between unlike crystal structures (Ge, $Fd3m$ and Sn, $I$4/$mmm$), which also have highly incompatible atomic radii. They should not react, but they do. A reconstructive transformation of $I$4/$mmm$ into the $I$4$_1$/$amd$ solid solution then follows. The new tetragonal GeSn solid solution ($I$4$_1$/$amda$ = 5.280(1) Å, c = 2.915(1) Å, Z = 4 at 9.9 GPa and 298 K) also constitutes the structural and electronic bridge between 4-fold and newly prepared 8-fold coordinated alloy cubic symmetries. Furthermore, using this high-pressure route, bulk cubic diamond-structured GeSn alloys can now be obtained at ambient pressure. The findings here remove confining conventional criteria on routes to synthesis. This opens innovative avenues to advanced materials development., Published by American Chemical Society, Washington, DC

A comprehensive study of sillenite Bi12SiO20 single-crystal properties, including elastic stiffness and piezoelectric coefficients, dielectric permittivity, thermal expansion and molar heat capacity, is presented. Brillouin-interferometry measurements (up to 27 GPa), which were performed at high pressures for the first time, and ab initio calculations based on density functional theory (up to 50 GPa) show the stability of the sillenite structure in the investigated pressure range, in agreement with previous studies. Elastic stiffness coefficients c 11 and c 12 are found to increase continuously with pressure while c 44 increases slightly for lower pressures and remains nearly constant above 15 GPa. Heat-capacity measurements were performed with a quasi-adiabatic calorimeter employing the relaxation method between 2 K and 395 K. No phase transition could be observed in this temperature interval. Standard molar entropy, enthalpy change and Debye temperature are extracted from the data. The results are found to be roughly half of the previous values reported in the literature. The discrepancy is attributed to the overestimation of the Debye temperature which was extracted from high-temperature data. Additionally, Debye temperatures obtained from mean sound velocities derived by Voigt-Reuss averaging are in agreement with our heat-capacity results. Finally, a complete set of electromechanical coefficients was deduced from the application of resonant ultrasound spectroscopy between 103 K and 733 K. No discontinuities in the temperature dependence of the coefficients are observed. High-temperature (up to 1100 K) resonant ultrasound spectra recorded for Bi12 MO20 crystals revealed strong and reversible acoustic dissipation effects at 870 K, 960 K and 550 K for M = Si, Ge and Ti, respectively. Resonances with small contributions from the elastic shear stiffness c 44 and the piezoelectric stress coefficient e 123 are almost unaffected by this dissipation.

Using optical absorption and Raman spectroscopic measurements, in conjunction with the first-principles calculations, a pressure-induced high-spin (HS)-to-low-spin (LS) state electronic transition of Fe2+ (M2-octahedral site) was resolved around 76-80GPa in a natural triphylite-lithiophilite sample with chemical composition (LiFe0.7082+Mn0.292PO4)-Li-M1-Fe-M2 (theoretical composition (LiFe0.52+Mn0.5PO4)-Li-M1-Fe-M2). The optical absorption spectra at ambient conditions consist of a broad doublet band with two constituents (1) (similar to 9330cm(-1)) and (2) (similar to 7110cm(-1)), resulting from the electronic spin-allowed transition (T2gEg)-T-5-E-5 of octahedral (HSFe2+)-Fe-M2. Both (1) and (2) bands shift non-linearly with pressure to higher energies up to similar to 55GPa. In the optical absorption spectrum measured at similar to 81GPa, the aforementioned HS-related bands disappear, whereas a new broadband with an intensity maximum close to 16,360cm(-1) appears, superimposed on the tail of the high-energy ligand-to-metal O2-Fe2+ charge-transfer absorption edge. We assign this new band to the electronic spin-allowed dd-transition (1)A(1g)(1)T(1g) of LS Fe2+ in octahedral coordination. The high-pressure Raman spectra evidence the Fe2+ HS-to-LS transition mainly from the abrupt shift of the P-O symmetric stretching modes to lower frequencies at similar to 76GPa, the highest pressure achieved in the Raman spectroscopic experiments. Calculations indicated that the presence of Mn-M2(2+) simply shifts the isostructural HS-to-LS transition to higher pressures compared to the triphylite Fe-M2(2+) end-member, in qualitative agreement with our experimental observations.

We have conducted high pressure far-infrared absorbance and Raman spectroscopic investigations on a natural iron-free dolomite sample up to 40 GPa. Comparison between the present observations and literature results unraveled the effect of hydrostatic conditions on the high pressure dolomite polymorph adopted close to 40 GPa, i.e. the triclinic Dol-IIIc modification. In particular, non-hydrostatic conditions impose structural disorder at these pressures, whereas hydrostatic conditions allow the detection of an ordered Dol-IIIc vibrational response. Hence, hydrostatic conditions appear to be a key ingredient for modeling carbon subduction at lower mantle conditions. Our complementary first-principles calculations verified the far-infrared vibrational response of the ambient- and high pressure dolomite phases.

The high-pressure phase behavior of strontianite (SrCO3) was both experimentally and theoretically investigated by Raman spectroscopy up to 78 GPa in a diamond anvil cell and density functional theory-based calculations. Our study shows a phase transition between 23.7 and 26.8 GPa during compression from space group Pmcn to post-aragonite SrCO3, which is accompanied by significant changes in the vibrational spectrum. The excellent agreement between the observed and computed Raman frequencies and intensities implies that the high-pressure polymorph has space group Pmmn and contributes to resolving an existing disagreement concerning the correct space group symmetry of this high-pressure polymorph. It is shown that the transition pressure from the aragonite to a post-aragonite phase increases linearly with decreasing cation radius for (Ca, Sr, Ba, Pb) carbonates.

Alloy and nitride solid solutions are prominent for structural, energy and information processing applications. There are frequently however barriers to making them. We remove barriers to reactivity here using pressure with a new synthetic approach. We target pressures where the reasons for cubic endmember nitride instability can become the driving force for cubic nitride solid solution stability. Using this approach we form a novel rocksalt Mg$_{0.4}$Fe$_{0.6}$N solid solution at between 15 and 23 GPa and up to 2500 K. This is a system where, neither an alloy nor a nitride solid solution form at ambient conditions and bulk MgN and FeN endmembers do not form, either at ambient or at high pressure. The new nitride is formed, by removing endmember lattice mismatch with pressure, allowing a stabilizing redistribution of valence electrons upon heating. This approach can be employed for a range of normally unreactive systems. Mg, Fe and enhanced nitrogen presence, may also indicate a richer reaction chemistry in our planets interior.

Angle-dispersive X-ray diffraction and microfluorescence together with precession electron diffraction (PED) and scanning electron microscopy measurements on iron nitride prepared at 15 GPa and 1800 K from iron and sodium azide starting materials reveal synthesis of both hexagonal P6322 and trigonal P312 Fe3N1+x modifications (a = 4.745 (1) A, c = 4.403 (1) A, Z = 2). Nitrogen access to vacant interstitial sites, repulsions between nitrogen ions and metal nitride thermal stability are the factors relating iron nitride-phase relations to those of other early (Hf, Zr, Ti)-N and late (Ni-N) transition metal nitrides subjected to similar pressure and temperature conditions. Here, Fe3N1+x can accommodate pressure and x variability by situating nitrogen in a broader range of interstitial crystallographic sites in the intimately related hexagonal and trigonal crystal structures.

A novel rock salt Mg0.4Fe0.6N solid solution is obtained by hot pressing a 70:30 at.% mixture of Fe and Mg together with NaN3 (MgO capsule in multianvil cell, 15 GPa, 1800 K, 1 min).

The single crystal elastic constants Cij and the shear and adiabatic bulk modulus of a natural portlandite (Ca(OH)2) crystal were determined by Brillouin spectroscopy at ambient conditions. The elastic constants, expressed in GPa, are: C11 = 102.0(± 2.0), C12 = 32.1(± 1.0), C13 = 8.4(± 0.4), C14 = 4.5(± 0.2), C33 = 33.6(± 0.7), C44 = 12.0(± 0.3), C66 = (C11–C12)/2 = 35.0(± 1.1), where the numbers in parentheses are 1σ standard deviations. The Reuss bounds of the adiabatic bulk and shear moduli are K0S = 26.0(± 0.3) GPa and G0 = 17.5(± 0.4) GPa, respectively, while the Voigt bounds of these moduli are K0S = 37.3(± 0.4) GPa and G0 = 24.4(± 0.3) GPa. The Reuss and Voigt bounds for the aggregate Young's modulus are 42.8(± 1.0) GPa and 60.0(± 0.8) GPa respectively, while the aggregate Poisson's ratio is equal to 0.23(± 0.01). Portlandite exhibits both large compressional elastic anisotropy with C11/C33 = 3.03(± 0.09) equivalent to that of the isostructural hydroxide brucite (Mg(OH)2), and large shear anisotropy with C66/C44 = 2.92(± 0.12) which is 11% larger than brucite. The comparison between the bulk modulus of portlandite and that of lime (CaO) confirms a systematic linear relationship between the bulk moduli of brucite-type simple hydroxides and the corresponding NaCl-type oxides.

The pressure dependence of the sound velocities, single-crystal elastic constants, and shear and adiabatic bulk moduli of a natural gahnite (ZnAl2O4) spinel have been determined to ~9 GPa by gigahertz ultrasonic interferometry in a diamond anvil cell. The elastic constants of gahnite are (in GPa): C11 = 290(3), C12 = 169(4), and C44 = 146(2). The elastic constants C11 and C12 have similar pressure derivatives of 4.48(10) and 5.0(8), while the pressure derivative of C44 is 1.47(3). In contrast to magnetite, gahnite does not exhibit C44 mode softening over the experimental pressure range. The adiabatic bulk modulus KS0 is 209(5) GPa, with pressure derivative KS' = 4.8(3), and the shear modulus G0 = 104(3) GPa, with G' = 0.5(2). Gahnite, along with chromite (FeCr2O4) and hercynite (FeAl2O4) are the least compressible of the naturally occurring oxide spinels. Evaluation of Birch’s Law for isostructural minerals indicates that spinels containing transition metals on both the [4] A and [6] B sites

Sunspots appear on the Sun in two bands on either side of the equator that drift toward lower latitudes as each sunspot cycle progresses. We examine the drift of the centroid of the sunspot area toward the equator in each hemisphere from 1874 to 2002 and find that the drift rate slows as the centroid approaches the equator. We compare the drift rate at sunspot cycle maximum with the period of each cycle for each hemisphere and find a highly significant anticorrelation: hemispheres with faster drift rates have shorter periods. These observations are consistent with a meridional counterflow deep within the Sun as the primary driver of the migration toward the equator and the period associated with the sunspot cycle. We also find that the drift rate at maximum is significantly correlated with the amplitude of the following cycle, a prediction of dynamo models that employ a deep meridional flow toward the equator. Our results indicate an amplitude of about 1.2 m s 1 for the meridional flow velocity at the base of the solar convection zone.

A new method of generating shear waves with near-optical wavelength has been developed for gigahertz ultrasonic interferometry. The new acoustic technique features a P-to-S conversion upon reflection inside an MgO buffer rod, and is used first to determine the full set of ambient P–T elastic constants (cij) of magnesiowustite—(Mg, Fe)O. In addition, P-wave travel times have been measured in olivine to 250oC at ~ 2.5 GPa in a resistance-heated ultrasonic diamond anvil cell, demonstrating that acoustic coupling can be maintained at high temperature in a hydrostatic (alcohol) pressure medium. The new methodology brings us closer to obtaining a complete travel-time equation of state for single-crystal samples.

We examine the "Group" sunspot numbers constructed by Hoyt and Schatten to determine their utility in characterizing the solar activity cycle. We compare smoothed monthly Group Sunspot Numbers to Zurich (International) Sunspot Numbers, 10.7-cm radio flux, and total sunspot area. We find that the Zurich numbers follow the 10.7-cm radio flux and total sunspot area measurements slightly better than the Group numbers. We examine several significant characteristics of the sunspot cycle using both Group numbers and Zurich numbers. We find that the "Waldmeier Effect" - the anti-correlation between cycle amplitude and the elapsed time between minimum and maximum of a cycle - is much more apparent in the Zurich numbers. The "Amplitude-Period Effect" the anti-correlation between cycle amplitude and the length of the previous cycle from minimum to minimum - is also much more apparent in the Zurich numbers. The "Amplitude-Minimum Effect" - the correlation between cycle amplitude and the activity level at the previous (onset) minimum is equally apparent in both the Zurich numbers and the Group numbers. The "Even-Odd Effect" - in which odd-numbered cycles are larger than their even-numbered precursors - is somewhat stronger in the Group numbers but with a tighter relationship in the Zurich numbers. The "Secular Trend" - the increase in cycle amplitudes since the Maunder Minimum - is much stronger in Group numbers. After removing this trend we find little evidence for multi-cycle periodicities like the 80 year Gleissberg cycle or the two- and three-cycle periodicities. We also find little evidence for a correlation between the amplitude of a cycle and its period or for a bimodal distribution of cycle periods. We conclude that the Group numbers are most useful for extending the sunspot cycle data further back in time and thereby adding more cycles and improving the statistics. However, the Zurich numbers are more useful for characterizing the on-going levels of solar activity.

High-pressure and -temperature experiments on Ge and Si mixtures to 17 GPa and 1500 K allow us to obtain extended Ge Si solid solutions with cubic (Ia (3) over bar) and tetragonal (P4(3)2(1)2) crystal symmetries at ambient pressure. The cubic modification can be obtained with up to 77 atom % Ge and the tetragonal modification for Ge concentrations above that. Together with Hume-Rothery criteria, melting point convergence is employed here as a favored attribute for solid solution formation. These compositionally tunable alloys are of growing interest for advanced transport and optoelectronic applications. Furthermore, the work illustrates the significance of employing precession electron diffraction for mapping new materials landscapes resulting from tailored high-pressure and -temperature syntheses.

Ultrasonic interferometry at near-gigahertz frequencies is used to investigate longitudinal sound wave velocities parallel to [100] and [111] and the elastic constant c11 for high quality single crystals of magnesiowustite (Mg,Fe)O. The measurements were made at room pressure and temperature on samples spanning the full compositional range from periclase (MgO) to wustite (Fe1-xO). A strong P-wave anisotropy of ∼10% was measured for periclase, increasing about 1% for Mg0.94Fe0.06O then decreasing linearly to ∼0% for wustite. The elastic modulus c11 of magnesiowustite decreases linearly with iron content by −0.72(3) GPa/mol% FeO with the exception of a sharp increase for pure periclase. Thus, the addition of a small amount of iron to periclase has a major effect on its elastic behavior. This observation indicates that the use of a simple interpolation of elastic constant data between periclase and wustite [Jackson, 1998] may yield erroneous predictions for lower mantle compositions based on seismic data.

Seismic shear anisotropy in the lowermost mantle most likely results from elastic shear anisotropy and lattice preferred orientation of its constituent minerals, including perovskite, post-perovskite, and ferropericlase. Measurements of the elastic shear anisotropy of single-crystal (Mg 0.9 Fe 0.1 )O up to 69 gigapascals (GPa) show that it increased considerably across the pressure-induced spin transition of iron between 40 and 60 GPa. Increasing iron content further enhances the anisotropy. This leads to at least 50% stronger elastic shear anisotropy of (Mg,Fe)O in the lowermost mantle compared to MgO, which is typically used in geodynamic modeling. Our results imply that ferropericlase is the dominant cause of seismic shear anisotropy in the lower mantle.

A number of techniques currently in use for predicting solar activity on a solar cycle timescale are tested with historical data. Some techniques, e.g., regression and curve fitting, work well as solar activity approaches maximum and provide a month-by-month description of future activity, while others, e.g., geomagnetic precursors, work well near solar minimum but only provide an estimate of the amplitude of the cycle. A synthesis of different techniques is shown to provide a more accurate and useful forecast of solar cycle activity levels. A combination of two uncorrelated geomagnetic precursor techniques provides a more accurate prediction for the amplitude of a solar activity cycle at a time well before activity minimum. This combined precursor method gives a smoothed sunspot number maximum of 154 ± 21 at the 95% level of confidence for the next cycle maximum. A mathematical function dependent on the time of cycle initiation and the cycle amplitude is used to describe the level of solar activity month by month for the next cycle. As the time of cycle maximum approaches a better estimate of the cycle activity is obtained by including the fit between previous activity levels and this function. This Combined Solar Cycle Activity Forecast gives, as of January 1999, a smoothed sunspot maximum of 146 ± 20 at the 95% level of confidence for the next cycle maximum.

We have analyzed an active region which was observed in H.alpha (Multichannel Subtractive Double Pass Spectrograph), in UV lines (SMM/UVSP), and in X-rays (SMM/HXIS). In this active region there were only a few subflares and many small bright points visible in UV and in X-rays. Using an extrapolation based on the Fourier transform, we have computed magnetic field lines connecting different photospheric magnetic polarities from ground-based magnetograms. Along the magnetic inversion lines we find two different zones: (1) a high-shear region (> 70 deg) where subflares occur, and (2) a low-shear region along the magnetic inversion line where UV bright points are observed. In these latter regions the magnetic topology is complex with a mixture of polarities. According to the velocity field observed in the Si IV lamda.1402 line and the extrapolation of the magnetic field, we notice that each UV bright point is consistent with emission from low-rising loops with downflows at both ends. We notice some hard X-ray emissions above the bright-point regions with temperatures up to 8 x 10(exp 6) K, which suggests some induced reconnection due to continuous emergence of new flux. This reconnection is also enhanced by neighboring subflares.

On the basis of the lowest observed smoothed monthly mean sunspot number, cycle 23 appears to have conventionally begun in May 1996, in conjunction with the first appearance of a new cycle, high-latitude spot-group. Such behavior, however, is considered rather unusual, since, previously (based upon the data- available cycles 12-22), the first appearance of a new cycle, high-latitude spot- group has always preceded conventional onset by at least 3 months. Furthermore, accepting May 1996 as the official start for cycle 23 poses a dilemma regarding its projected size and timing of maximum amplitude. Specifically, from the max-min and amplitude-period relationships we infer that cycle 23 should be above average in size and a fast riser, with maximum amplitude occurring before May 2000 (being in agreement with projections for cycle 23 based on precursor information), yet from its initial languid rate of rise (during the first 6 months of the cycle) we infer that it should be below average in size and a slow riser, with maximum amplitude occurring after May 2000. The dilemma vanishes, however, when we use a slightly later-occurring onset. For example, using August 1996, a date associated with a local secondary minimum prior to the rapid rise that began shortly thereafter (in early 1997), we infer that cycle 23's rate of rise is above that for the mean of cycles 1-22, the mean of cycles 10-22 (the modern era cycles), the mean of the modern era'fast risers,' and the largest of the modern era 'slow risers' (i.e., cycle 20), thereby, suggesting that cycle 23 will be both fast-rising and above average in size, peaking before August 2000. Additionally, presuming cycle 23 to be a well- behaved fast-rising cycle (regardless of whichever onset date is used), we also infer that its maximum amplitude likely will measure about 144.0 q+/- 28.8 (from the general behavior found for the bulk of modern era fast risers; i.e., 5 of 7 have had their maximum amplitude to lie within 20% of the mean curve for modern era fast risers). It is apparent, then, that sunspot number growth during 1998 will prove crucial for correctly establishing the size and shape of cycle 23.

The first occurrence of a high-latitude, new cycle spot group for cycle 23 was in May 1996, in conjunction with a minimum in the smoothed monthly mean sunspot number. Since then, new cycle spot groups have become more predominant, and the smoothed monthly mean sunspot number has slowly risen. Such behavior indicates that new cycle 23 probably had its minimum annual average sunspot number, R(min), equal to 8.7, in 1996. Because this value is larger than the average for R(min), cycle 23 is expected to have a maximum amplitude, R(max), that, likewise, will be larger than average, suggesting further that it probably will be both fast rising (i.e., peaking before May 2000) and of shorter than average length (i.e., ending before May 2007). Another parameter well correlated with R(max) is the minimum amplitude of the aa geomagnetic index, aa(mm), which usually occurs either in the year of R(min) occurrence or, more often, in the following year. For 1996 the annual average of aa measured 18.6. Presuming this value to be aa(min) for cycle 23, we calculate cycle 23's R(max) to be about 171.0 ± 17.6 (i.e., the 90% prediction interval), based on the stronger (r = 0.98) bivariate fit of R(max) versus both R(min) and aa(min). Comparison of this estimate with others, using various combinations of parameters, yields an overlap in the prediction intervals for R(max) of about 168 ± 15, a range that is within the consensus recently reported by Joselyn et al. [1997] (= 160 ± 30). Thus this study supports the view that cycle 23 will have an R(max) that will be larger than average but smaller than was seen for cycle 19, the largest cycle on record with R(max) = 190.2.

X-ray-diffraction measurements show that ${\mathrm{Rb}}_{2}$${\mathrm{ZnBr}}_{4}$,${\mathrm{nK}}_{2}$${\mathrm{ZnCl}}_{4}$, and ${\mathrm{Rb}}_{2}$${\mathrm{ZnCl}}_{4}$ become amorphous at pressures exceeding 10 GPa. In contrast, their ${\mathrm{Cs}}_{2}$${\mathrm{ZnCl}}_{4}$ and ${\mathrm{K}}_{2}$${\mathrm{SeO}}_{4}$ isomorphs undergo crystal-crystal phase transitions and do not amorphize at the highest pressures measured \ensuremath{\sim}60 GPa. This indicates that the tendency of ${\mathrm{A}}_{2}$${\mathrm{BX}}_{4}$ molecular ionic solids to amorphize upon compression depends predominantly on the ratio of the size of the anionic tetrahedral ${\mathrm{BX}}_{4}$ groups to that of the interstitial A cations. This criterion is also consistent with the incommensurate phase behavior exhibited by several of these solids at ambient pressure.

The pressure dependence of single-crystal elastic moduli of a natural Mn-rich franklinite, (Mn 0.40 Fe 2+ 0.16 Zn 0.37 Mg 0.03 )(Fe 3+ 1.94 Al 0.08 )O 4 , has been determined by GHz-ultrasonic interferometry in a diamond-anvil cell to 9.8 GPa. The room-pressure elastic constants of franklinite are C 11 = 244(3) GPa, C 12 = 142(4) GPa, and C 44 = 77(2) GPa. Linear pressure derivatives of C 11 and C 12 are 4.3(3) and 3.8(3), respectively, whereas the C 44 modulus exhibits softening, fitted in the P ≤ 10 GPa pressure range to C 44 = 77(2) + 0.29(2) P – 0.018(2) P 2 GPa. The average of Hashin-Shtrikman bounds on the adiabatic bulk modulus ( K S0 ) of franklinite is 175(3) GPa, with pressure derivative K S ′ = 4.3(3), and the shear modulus G 0 = 66(2) GPa with G ′ = 0.09(3). The isothermal compressibility of franklinite was determined from a separate high-pressure, single-crystal X-ray diffraction experiment to 7.8 GPa, yielding K T0 = 173.5(7) GPa fitted with a fixed pressure derivative of K T ′ = 4. When K ′ is fixed to the ultrasonic value of 4.3, we obtain K T0 = 172.2(7) GPa. In contrast to iron-free gahnite (ZnAl 2 O 4 ), franklinite exhibits pressure-induced mode softening of C 44 similar to magnetite (Fe 3 O 4 ). Between end-member compositions ZnFe 2 O 4 (franklinite) and MnFe 2 O 4 (jacobsite), the bulk modulus decreases linearly with increasing %Mn, however we observe non-linear behavior in other elastic moduli, especially C 44 , which displays a pronounced negative anomaly for the mid-range Mn composition. Applying Birch’s law to AB 2 O 4 -type spinels reveals that oxide spinels containing transition metals on both A and B sites follow a distinct trend from other spinels.

The decline of cycle 22 is shown to be consistent with the notion that it will have a period

Patients with severe mental illness are at high risk for metabolic and cardiac disorders. Thus, monitoring of cardiovascular risks is imperative and schedules for screening for lipids, glucose, body mass index (BMI), waist-hip ratio and blood pressure have been developed. We intended to analyze screening for metabolic disorders in German patients with schizophrenia spectrum disorders in routine psychiatric care. We included 674 patients with any F2 diagnosis in out- and inpatient settings and analyzed metabolic screening procedures as practiced under conditions of usual care. Except BMI (54 %), all other values were documented only in a minority of patients: waist circumference (23 %), cholesterol (28 %), fasting glucose (19 %), triglycerides (25 %) and blood pressure (37 %). We found evidence for less than perfect quality of blood pressure measures. The group of patients who met the individual metabolic syndrome ATP III criteria was comparable to the US CATIE trial. We conclude that frequency and quality of metabolic monitoring in German in- and outpatients settings are not in accordance with the respective recommendations. Similar to previous reports we found evidence for a high prevalence of metabolic disturbances in German patients with schizophrenia spectrum disorders.

The temporal behavior of a sunspot cycle, as described by the International sunspot numbers, can be represented by a simple function with four parameters: starting time, amplitude, rise time, and asymmetry. Of these, the parameter that governs the asymmetry between the rise to maximum and the fall to minimum is found to vary little from cycle to cycle and can be fixed at a single value for all cycles. A close relationship is found between rise time and amplitude which allows for a representation of each cycle by a function containing only two parameters: the starting time and the amplitude. These parameters are determined for the previous 22 sunspot cycles and examined for any predictable behavior. A weak correlation is found between the amplitude accurate to within about 30% right at the start of the cycle. As the cycle progresses, the amplitude can be better determined to within 20% at 30 months and to within 10% at 42 months into the cycle, thereby providing a good prediction both for the timing and size of sunspot maximum and for the behavior of the remaining 7-12 years of the cycle.

We performed high-pressure synchrotron x-ray diffraction experiments on nanocrystalline (nc-) MgO compressed both under quasi-hydrostatic and non-hydrostatic conditions in a diamond-anvil cell. Data obtained under hydrostatic conditions show that nc-MgO (average crystallite size of 20 nm) is 8-9% more compressible than “bulk” MgO. Analysis of our results collected under non-hydrostatic conditions yields a bulk modulus that is about 27% larger than the one derived from the quasi-hydrostatic compression experiments. Thus, the apparent bulk modulus strongly depends on the experimental stress conditions.

The elasticity of minerals is central to our understanding of the structure and properties of the Earth, and other planets. In the last half-century, and in particular within the last 15 years, there have been many new developments in the experimental methods used to determine the elastic properties of minerals. Not only have new techniques become available, but the pressure and temperature ranges over which they can be applied have been greatly extended and the precision and accuracy of the results have been significantly improved. Given these rapid advances in measurement techniques we provide a brief guide to the theory of the elasticity of minerals, and we review and compare the physical principles and the capabilities of the experimental techniques now available.

Ferropericlase is the second most abundant mineral in Earth's lower mantle and knowledge of its elastic properties at relevant conditions is needed to adequately interpret seismic observations in terms of the mineralogy and thermal state of the deep Earth. Here, we report the complete elastic tensor of (Mg{sub 0.9}Fe{sub 0.1})O ferropericlase to 81.2 GPa at room temperature measured by Brillouin spectroscopy and X-ray diffraction in the diamond-anvil cell. Our data indicate that the spin transition of iron between 45 and 63 GPa dramatically affects the longitudinal and off-diagonal elements of the elastic stiffness tensor c{sub 11} and c{sub 12}, whereas it leaves the shear constant c{sub 44} almost unaffected. Based on our results, the spin transition markedly changes the pressure (and temperature) dependence of the compressional and bulk sound velocities and must be taken into account in any attempt to match average radial seismic velocity profiles with mineral physics observations. The different pressure dependence of compressional (and bulk) and shear sound velocities across the high-spin to low-spin (HS-LS) transition implies that the spin transition might be best observed in the v{sub p}/v{sub s} ratio and its pressure (and temperature) derivative. We also point out the possibility that the spin transitionmore » leads to an anti-correlated temperature dependence of shear and compressional wave speeds in certain pressure-temperature regimes in Earth's lower mantle.« less

The single-crystal elastic moduli of (Mg 0.987 ,Fe 0.013 )O were measured by Brillouin spectroscopy in a diamond-anvil cell at high pressures to 9 GPa at room temperature. The ambient-pressure single-crystal elastic moduli are (1) C 11 = 291.2(3.0) GPa; (2) C 12 = 96.1(2.0) GPa; and (3) C 44 = 151.9(2.0) GPa. From the single-crystal moduli, the aggregate elastic moduli are calculated to be adiabatic bulk modulus K S0 = 161.1(3.0) GPa, the Voigt bound of the shear modulus is G V = 130.0(2.0), and the Reuss bound G R = 124.2(2.0) GPa, giving a Voigt-Reuss-Hill average G = 127.1(2.0) GPa. We find that the addition of 1.3 mol% of Fe has a surprisingly large effect on the aggregate shear modulus, decreasing the room-pressure value by 2.4% as compared to Brillouin data for periclase (MgO) measured with the same technique. The adiabatic bulk modulus also decreases by 1.3%, although this decrease is within the mutual uncertainties of the measurements. Our results confirm significant non-linearity in single-crystal elastic moduli C 11 and C 44 and the aggregate shear modulus G of magnesiowustite in the Mg-rich end. The pressure derivative of the bulk modulus K S ′ = 4.2(2), as determined by a third-order finite-strain fit, is about 9% higher than the Brillouin results for the MgO end-member, whereas the pressure dependence of the shear modulus G ′ = 2.3(1) is found to be identical to that of periclase. The measurements demonstrate that even a small amount of Fe (1.3 mol%) has a measurable effect on the elastic properties of MgO-FeO solid solutions.

The photometric variability of the Ap star HD 10783 = UZ Psc is discussed. New UBV photometry, obtained between late 1965 and early 1969, is presented and it is combined with existing published photometry to derive an improved ephemeris for times of maximum brightness: 2439758.00 + 4d.1328 n. It is concluded that the results are not very sensitive to the small shifts applied to the blue photometry.

Advances in the generation and transmission of very high frequency ultrasonic signals make it practical to measure elastic properties in single crystals small enough to be subjected to high pressures and temperatures in a new diamond anvil cell designed for simultaneous ultrasonic and x-ray diffraction measurements up to 5 GPa and 400°C. In addition to providing a new accurate method for measuring elastic properties this technique can provide simultaneous equations of state which can be used to produce a new primary pressure scale. Preliminary measurements on MgO show the feasibility of this new technique.

The single-crystal elastic properties of high-spin (Mg_(0.94)Fe_(0.06))O ferropericlase were measured by Brillouin spectroscopy on a sample compressed to 20 GPa with diamond anvil cells using methanol-ethanol-water as a pressure-transmitting medium. At room pressure, the adiabatic bulk (K_0S) and shear (μ_0S) moduli are K_0S = 163 ± 3 GPa and μ_0S = 121 ± 2 GPa, in excellent agreement with ultrasonic results from the same bulk sample (Jacobsen et al., 2002). A fit to all our high-pressure Brillouin data using a third-order finite-strain equation of state yields the following pressure derivatives of the adiabatic bulk and shear moduli: K′_0S = 3.9 ± 0.2 and μ′_0S = 2.1 ± 0.1. Within the uncertainties, we find that K_0S and K′_0S of (Mg_0.94)Fe_(0.06))O are unchanged from MgO. However, μ_0S and μ′_0S of (Mg_(0.94)Fe_(0.06))O are reduced by 8% and 11%, respectively. The aggregate compressional (VP) and shear (VS) wave velocities are reduced by 4% and 6%, respectively, as compared to MgO. The pressure dependence of the single-crystal elastic moduli and aggregate sound velocities is linear within the investigated pressure range. The elastic anisotropy of (Mg_(0.94)Fe_(0.06))O is about 10% greater than that of MgO at ambient conditions. At the highest pressure obtained here, the elastic anisotropy of (Mg_(0.94)Fe_(0.06))O is close to zero. On the basis of our measurements and earlier ultrasonic measurements, we find that the pressure derivatives of shear moduli obtained at room pressure for low iron concentrations (

A second-generation high-frequency acoustic interferometer has been developed for high-pressure and high-temperature elasticity measurements in the diamond anvil cell. The instrument measures single-crystal compressional and shear-wave travel times, which are converted to sound velocities and elastic moduli for direct application to problems in geophysics. The second-order elastic constants (cij) of several iron-bearing oxide minerals has been measured under hydrostatic pressures to ~10 GPa. Pressure-induced c44 mode softening is observed in magnetite (Fe3O4), wustite (Fe0.95O) and in iron-rich magnesiowustite-(Mg, Fe)O, indicating that strong magnetoelastic coupling is common among these iron-rich oxides well ahead of known structural phase transitions. In (Mg, Fe)O, the pressure derivative of c44 is highly sensitive to composition and switches sign between 1.2 ± 0.2 at 25 mol% FeO to −0.96 ± 0.3 at 75 mol% FeO, and is about zero for (Mg, Fe)O containing 50 mol% FeO. In wustite, a discontinuity in the pressure derivatives c11 and C12 at ~5 GPa is interpreted to result from the onset of magnetic ordering, implying that a partially ordered but still cubic phase of FeO exists between ~5 GPa and where the rhombohedral distortion occurs at ~17 GPa.

The complete elastic tensor of Fe0.94O (wüstite) has been determined to 10 GPa using acoustic interferometry at GHz frequencies inside a diamond-anvil cell. The soft mode (C44) elastic constant of FeO is reduced by 20% over the experimental pressure range. An unusual discontinuity in the pressure derivatives of C11 and C12 at 4.7+/-0.2 GPa corresponds to the pressure at which the onset of a magnetic ordering transition is observed by high-pressure Mössbauer spectroscopy and neutron powder diffraction. Our new results combined with literature structural high P-T data suggest that there is a magnetic, although still cubic, phase of FeO between approximately 5 and approximately 17 GPa.

The emerging picture of Earth's deep interior from seismic tomography indicates more complexity than previously thought. The presence of lateral anisotropy and heterogeneity in Earth's mantle highlights the need for fully anisotropic elasticity data from mineral physics. A breakthrough in high-frequency (gigahertz) ultrasound has resulted in transmission of pure-mode elastic shear waves into a high-pressure diamond-anvil cell using a P-to-S elastic-wave conversion. The full elastic tensor ( c ij ) of high-pressure minerals or metals can be measured at extreme conditions without optical constraints. Here we report the effects of pressure and composition on shear-wave velocities in the major lower-mantle oxide, magnesiowüstite-(Mg,Fe)O. Magnesiowüstite containing more than ≈50% iron exhibits pressure-induced c 44 shear-mode softening, indicating an instability in the rocksalt structure. The oxide closer to expected lower-mantle compositions (≈20% iron) shows increasing shear velocities more similar to MgO, indicating that it also should have a wide pressure-stability field. A complete sign reversal in the c 44 pressure derivative points to a change in the topology of the (Mg,Fe)O phase diagram at ≈50–60% iron. The relative stability of Mg-rich (Mg,Fe)O and the strong compositional dependence of shear-wave velocities (and ∂ c 44 /∂ P ) in (Mg,Fe)O implies that seismic heterogeneity in Earth's lower mantle may result from compositional variations rather than phase changes in (Mg,Fe)O.

investigated Fe 3+ -bearing (Mg,Fe)O single crystals prepared by interdiffusion having Fe/(Fe + Mg) = 0.06, 015, 0.24, 0.27, 0.37, 0.53, 0.56, 0.75, and 0.79, with ferric iron contents ranging from � 1 to 12% of the total Fe. The elastic constants (c11, c12, c44) are determined from compressional and shear wave velocities in the (100) and (111) propagation directions in the range of 0.5-1.2 GHz. The c11 and c44 elastic constants soften from periclase to wustite, whereas the c12 elastic constant increases. The rate of change in the elastic constants with composition (@cij/@x) is greatest between MgO and (Mg,Fe)O with � 25 mol % FeO implying that substitution of Fe into periclase has a greater effect on the elastic properties than adding Mg to wustite. The elastic anisotropy of (Mg,Fe)O has rather unusual behavior, being essentially constant for the range 0-25 mol % FeO but then decreases linearly with Fe content such that wustite is elastically isotropic. The elastic properties of (Mg,Fe)O having similar total Fe but varying Fe 3+ contents are identical within uncertainty. The isothermal compressibility of samples with Fe/(Fe + Mg) = 0.27, 0.56, and 0.75 is determined by single-crystal X-ray diffraction in a diamond anvil cell to � 9 GPa. For these samples, K0T = 158.4(4), 155.8(9), and 151.3(6) GPa with @KT/@P = 5.5(1), 5.5(1), and 5.6(2), respectively (where values in parentheses indicate standard deviations). The deviation of @KT/@P from 4.0 corresponds to a difference in calculated density of about one percent for ferropericlase (Mg0.8Fe0.2)O at 30 GPa from the value predicted by second-order truncation of the Birch- Murnaghan equation of state. INDEX TERMS: 3620 Mineralogy and Petrology: Crystal chemistry; 3909 Mineral Physics: Elasticity and anelasticity; 3919 Mineral Physics: Equations of state; 3924 Mineral Physics: High-pressure behavior; KEYWORDS: magnesiowustite, elastic constants, ultrasonics, crystal chemistry, bulk moduli

P-wave velocities in periclase were determined up to 4.4 GPa and 207°C using a GHz ultrasonic interferometer and a resistance-heated diamond anvil cell. The samples were disks of synthetic periclase single crystal cut parallel to the (100) plane with dimensions of 300 μm in diameter and 46 μm in thickness. A 250-μm-thick tungsten-tantalum alloy as well as rhenium foils were used as gaskets. The signal was introduced through a buffer rod which was directly coupled to one of the diamond anvils by means of force applied to the buffer rod. The sample was coupled to one of the diamond anvils by means of normal force applied from the pressure medium, which was a fine-grain potassium bromide powder. The pressures in room temperature runs were determined by ruby fluorescence. Least squares fitting to the elastic constants derived from our experimental data yield c 11 (GPa) = 296.8(±0.7) + 10.9(±0.9) × P (GPa). The results are in good agreement with previous determinations using ultrasonic interferometry on larger samples at lower frequencies and at lower pressures. The ultrasonic signals obtained in the high-temperature runs showed no deterioration in quality, and we were able to obtain travel-time data. By extrapolating the results from earlier work, we were able to estimate the pressure in the sample chamber while at high temperatures using the travel-time data.

Between 1975 and 1989 we carried out a total of 567 resections of the colon and rectum and performed a uni- or bilateral ovarectomy in 53 (9.3%) cases. Histopathological findings in the case of 41 (7.2%) patients were unremarkable whereas 8 cases (1.4%) revealed metastases of the colorectal cancer. In the case of 4 patients (0.7%) synchronous ovarian cancer occurred. According to the TNM-scheme primary tumors included T2 in 2 cases, T3 in 5 and T4 in 1 of the cases. Reported figures of ovarian metastases in colorectal cancer vary between 2.0 and 10.3%, we found 2.1% in our series. Prophylactic ovarectomy even in premenopausal patients is indicated if one or both ovaries show pathological findings on laparotomy since infiltrative growth of the tumor can be proved only histologically. In addition we performed bilateral oophorectomy on postmenopausal women as a method of preventing occurrence of other ovarian tumors.

Im Jahre 1980 beschrieben Knight u. Griffen eine Technik fur die Resektionen am Rektum unter Anwendung der Klammernahtgerate EEA und TA-55. 1983 legten Cohen et al. erstmals einen Ergebnisbericht uber 26 Patienten vor, die sie in der von Knight und Griffen angegebenen Technik operiert hatten. Ihre Arbeit trug den Titel “Double stapling technic for low anterior resection”, womit diese spezielle Anastomosentechnik ihren zutreffenden und bis heute gebrauchlichen Namen erhielt.

We have studied SMM Hard X-ray Imaging Spectrometer (HXIS) and Ultraviolet Spectrometer and Polarimeter (UVSP) observations of a flare on April 10, 1980, where both instruments simultaneously imaged a hard X-ray footpoint area. The UVSP recorded the emission in the NV line at 1238.8 A, with a spatial resolution of 3″ and a temporal resolution of 10 seconds. While the overall footpoint area as seen in the hard X-ray images (16–30 keV) is of the order of two HXIS (8″)2 pixels (6 x 1017 cm2), the UV observations show evidence of smaller scale structure (≈ 5 X 1016 cm2) for individual peaks throughout the duration of the hard X-ray burst. The ultraviolet peaks are also characterized by redshifts in the line, which is formed at the 105 K level within the transition region.

High‐frequency acoustic interferometry is widely used to penetrate a medium and measure the reflection signature, which can reveal details about the inner structure of the medium. It is a very helpful and one of the most accurate techniques for determination elastic properties of different materials being capable to measure sound wave velocities in very small samples under high pressures. The ultrasonic interferometry system operating at 0.6‐2.1 gigahertz (GHz) frequencies was developed in the Bavarian Geoinstitute of the University of Bayreuth for in situ high pressure and temperature experiments. High pressures are reached by using diamond anvil cell, and a Pt‐resistive heater allows reaching high temperatures. The experimental setup is equipped with a laser system, which allows measuring a shift of ruby fluorescence line at every given temperature.

An error was made in entering the data used in Figure 6. This changes the results concerning the length of the time lag between the variations in the meridional flow speed and those in the cycle amplitude. The final paragraph on page 667 should read: ‘‘Finally, we study the relationship between the drift velocities and the amplitudes of the hemisphere/cycles. In Figure 5 we compare the drift velocity at the maximum of the cycle to the amplitude of that cycle for that hemisphere. There is a positive (0.5) and significant (95%) correlation between the two. However, an even stronger relationship is found between the drift velocity and the amplitude of the N þ 2 cycle. The correlation is stronger (0.7) and more significant (99%), as shown in Figure 6. This relationship is suggestive of a ‘‘memory’’ in the solar cycle, again a property of dynamo models that use meridional circulation. Indeed, the two-cycle lag is precisely the relationship found by Charbonneau & Dikpati (ApJ, 543, 1027 [2000]). This behavior is, however, more difficult to interpret, and we elaborate on this in the next section. In either case, these correlations only explain part of the variance in cycle amplitude (25% for the current cycle and 50% for the N þ 2 cycle). Obviously, other mechanisms, such as variations in the gradient in the rotation rate, also contribute to the cycle amplitude variations. Our investigation of possible connections between drift rates and the amplitudes of the N þ 1 and N þ 3 cycles gives no significant correlations at these alternative time lags.’’ The revised Figure 6 and its caption are given below.