Temperature-Driven Self-Doping in Magnetite.

Magnetite is one of the most fascinating materials exhibiting the enigmatic first-order Verwey transition which is conventionally manipulated through chemical doping. Here, we show that heating magnetite results in a spontaneous charge reordering and, consequently, a hole self-doping effect at the octahedral sublattice. Core-level x-ray spectroscopy measurements combined with theory uncovers that there are three regimes of self-doping that map the temperature dependence of the electrical conductivity and magnetism up to the Curie temperature. Our results provide an elegant analogy between the effect of chemical doping and temperature-driven self-doping on trimerons in magnetite.

Noncollinear Ordering of the Orbital Magnetic Moments in Magnetite.

The magnitude of the orbital magnetic moment and its role as a trigger of the Verwey transition in the prototypical Mott insulator, magnetite, remain contentious. Using 1s2p resonant inelastic x-ray scattering angle distribution (RIXS-AD), we prove the existence of noncollinear orbital magnetic ordering and infer the presence of dynamical distortion creating a polaronic precursor for the metal to insulator transition. These conclusions are based on a subtle angular shift of the RIXS-AD spectral intensity as a function of the magnetic field orientation. Theoretical simulations show that these results are only consistent with noncollinear magnetic orbital ordering. To further support these claims we perform Fe K-edge x-ray magnetic circular dichroism in order to quantify the Fe average orbital magnetic moment.

Influence of the nature and environment of manganese in Mn-BEA zeolites on NO conversion in selective catalytic reduction with ammonia.

Manganese-containing BEA zeolites, MnxSiBEA (x = 1-4 wt%) and Mn(I.E.)AlBEA, were prepared by a two-step post-synthesis method and a conventional wet ion-exchange, respectively, and applied as catalysts in the selective catalytic reduction of NO with ammonia (NH3-SCR). The physicochemical analysis of zeolite properties by high-energy-resolution fluorescence-detected XANES (HERFD-XANES) and X-ray emission spectroscopy (XES) uncovered that the coordination, geometry and oxidation state of Mn species are strongly related to the preparation method. Additionally, the study of catalyst acidity by FTIR spectroscopy with CO and pyridine probe molecules provided important insight into the number and type of acidic centres present on the catalyst surface. The catalytic results revealed that NO conversion depended on the state and content of Mn. The zeolites obtained by the two-step post-synthesis method and with a low Mn content were very active in the medium temperature range (NO conversion ∼100%) with simultaneous high selectivity to N2 due to the presence of isolated, framework Mn(iii) and Mn(ii) species. The N2O formation was especially high in the case of catalysts containing extra-framework polynuclear Mn species and negligible in the case of Mn(I.E.)AlBEA containing predominantly isolated, extra-framework Mn(ii) species.

X-ray spectroscopic study of solvent effects on the ferrous and ferric hexacyanide anions.

We present an Fe Kα resonant inelastic X-ray scattering (RIXS) and X-ray emission (XES) study of ferrous and ferric hexacyanide dissolved in water and ethylene glycol. We observe that transitions below the absorption edge show that the solvent has a distinct effect on the valence electronic structure. In addition, both the RIXS and XES spectra show a stabilization of the 2p levels when dissolved in water. Using molecular dynamics simulations, we propose that this effect arises from the hydrogen-bonding interactions between the complex and nearby solvent molecules. This withdraws electron density from the ligands, stabilizing the complex but also causing a slight increase in π-backbonding.

Chemical state of complex uranium oxides.

We report here the first direct observation of U(V) in uranium binary oxides and analyze the gradual conversion of the U oxidation state in the mixed uranium systems. Our finding clarifies previous contradicting results and provides important input for the geological disposal of spent fuel, recycling applications, and chemistry of uranium species.

Single impurity Anderson model versus density functional theory for describing Ce L3 x-ray absorption spectra of CeFe2: resolution of a recent controversy.

We resolved a recent controversy on the structure of the Ce L(3) x-ray absorption spectra (XAS) of CeFe(2); i.e., which of the single impurity Anderson model (SIAM) and the first-principles band calculations based on the density-functional theory (DFT) describes more appropriately the Ce 4f states and their contribution to the Ce L(3) XAS? For this purpose, we examined the core-hole effect in Ce L(3) XAS as an application of our new method taking advantage of resonant x-ray emission spectroscopy. Our result clearly shows that the Ce L(3) XAS structure is caused by the mixed valence 4f character revealed by the core-hole potential effect as indicated by SIAM, but denies the possibility that the L(3) XAS structure is caused by the 5d band structure with a very small core-hole effect as predicted by band calculations based on DFT.

Sulfur-metal orbital hybridization in sulfur-bearing compounds studied by X-ray emission spectroscopy.

The electronic structure and ligand environment of sulfur was investigated in various sulfur-containing compounds with different structures and chemical states by using X-ray emission spectroscopy (XES). Calculations were performed using density functional theory (DFT) as implemented in the StoBe code. The sulfur chemical state and atomic environment is discussed in terms of the molecular orbitals and partial charges that are obtained from the calculations. The main spectral features can be modeled using our calculational approach. The sensitivity of the Kbeta emission to the cation and the local symmetry is discussed.

Intramolecular Hgπ interactions of d-character with non-bridging atoms in mercury-aryl complexes.

Mercury 5d-orbitals are involved in intramolecular π-interactions with carbon and sulfur nearest and next-nearest neighbors in mercury-aryl complexes. This unexpected character of the electron cloud of mercury was revealed by high energy-resolution XANES spectroscopy readily interpreted in terms of a final-state local (l,m)-projected density of states (DOS).

Spatial imaging of carbon reactivity centers in Pd/C catalytic systems.

Gaining insight into Pd/C catalytic systems aimed at locating reactive centers on carbon surfaces, revealing their properties and estimating the number of reactive centers presents a challenging problem. In the present study state-of-the-art experimental techniques involving ultra high resolution SEM/STEM microscopy (1 Å resolution), high brilliance X-ray absorption spectroscopy and theoretical calculations on truly nanoscale systems were utilized to reveal the role of carbon centers in the formation and nature of Pd/C catalytic materials. Generation of Pd clusters in solution from the easily available Pd2dba3 precursor and the unique reactivity of the Pd clusters opened an excellent opportunity to develop an efficient procedure for the imaging of a carbon surface. Defect sites and reactivity centers of a carbon surface were mapped in three-dimensional space with high resolution and excellent contrast using a user-friendly nanoscale imaging procedure. The proposed imaging approach takes advantage of the specific interactions of reactive carbon centers with Pd clusters, which allows spatial information about chemical reactivity across the Pd/C system to be obtained using a microscopy technique. Mapping the reactivity centers with Pd markers provided unique information about the reactivity of the graphene layers and showed that >2000 reactive centers can be located per 1 µm2 of the surface area of the carbon material. A computational study at a PBE-D3-GPW level differentiated the relative affinity of the Pd2 species to the reactive centers of graphene. These findings emphasized the spatial complexity of the carbon material at the nanoscale and indicated the importance of the surface defect nature, which exhibited substantial gradients and variations across the surface area. The findings show the crucial role of the structure of the carbon support, which governs the formation of Pd/C systems and their catalytic activity.

Oxytocin concentrations in peripheral blood during the oestrous cycle and after ovariectomy in two breeds of sheep with low and high fecundity.

Oxytocin was measured radioimmunologically during the oestrous cycle in six ewes of each of two local Moroccan breeds of sheep. Concentrations in both breeds approached the lower limit of the assay (3 pg/ml) from 2 days before oestrus, throughout heat and ovulation until day 2 of the cycle. Oxytocin concentrations then increased in both breeds, the resulting highest levels on days 5-7 were, on average, between 30 and 60 pg/ml in the D'man sheep and 13-31 pg/ml in the Timhadite breed. Oxytocin levels then decreased to about 7 pg/ml in the D'man and about 4-5 pg/ml in the Timhadite breed on days 14-15. After ovariectomy oxytocin concentrations remained at about the limit of detection for a further 19-20 days in both breeds.

Comparative pharmacokinetics of new quinolones.

The pharmacokinetic properties of the new quinolones are characterised by a high volume of distribution, long biological half-life, low serum protein binding, elimination mainly by the kidneys, high total and renal clearances, limited biotransformation and a moderate to excellent bioavailability after oral administration. However, each quinolone derivative (ciprofloxacin, enoxacin, norfloxacin, ofloxacin and pefloxacin) possesses individual pharmacokinetic characteristics, which should be considered in the treatment of patients, especially when liver and/or renal dysfunction exists.

Variation in hormonal feedback and reproductive performance in adult rams of different genotypes.

Adult Moroccan rams of two different genotypes were compared on the basis of seasonality, fertility and sensitivity to gonadal feedback on the pituitary and hypothalamus. One breed with less seasonal breeding and high fertility, D'Man and one with less fertility and marked seasonal variation in breeding behaviour, Bnihsen. Four animals in each genotype were hemicastrated and 9 mo later castrated, to examine the effect of hormonal control on the hypothalamo-hypophyseal feedback system. Nine months after hemicastration the D'Man breed showed higher gonadotrophine values (LH, FSH). The remaining testicule in turn produced more estradiol-17beta but less testosterone in these rams. The testosterone production was increased in the Bnihsen rams following castration. After castration the FSH values increased rapidly in all animals with higher values for the D'Man rams. LH-release was faster in the hemicastrated rams than in controls. This is the first report on differences for hormonal feedback-systems in adult rams from different genotypes. The hormonal feedback-system is less sensitive for adult rams from breeds with higher fertility and nonseasonaly. In addition to that it was found that a difference seems to exist in the regulation for the release of FSH and LH.

Variation in hormonal feedback and reproductive performance in rams of different genotypes from birth through puberty.

Comparative experiments were carried out for elucidate the mechanisms that establish and control sexual behaviour of rams. Fifty-four ram lambs 2 to 24 wk of age were used for each of two genotypes and their crosses. The genotypes examined were the highly fertile nonseasonal D'Man breed and the low fertile seasonal Timahdite breed as well as the crossbreed of these two genotypes. Morphological, spermatological, ethological and endocrine parameters were compared. There seems to be a breed-dependent difference in the luteinizing hormone (LH) releasing pattern after gonadotropin releasing hormone (GnRH) stimulation at a specific prepubertal time period. This in turn reflects a breed-dependent difference in behavioral response in similar stages of physical maturation. The difference in behaviour is much more marked than the difference in physical characteristics.

Morphological and functional characteristics of the dominant follicle and corpus luteum in cattle and their influence on ovarian function.

Predicting the functional activity of a dominant follicle (DF) and corpus luteum (CL) might be important before starting a superovulation regime or a synchronization program. The DF and CL were characterized morphologically by using ultrasonography and were characterized functionally by estimating the estradiol-17beta/progesterone (E2/P4) ratio. Their influence on ovarian function was estimated through their ability to ovulate at different stages of development in response to PGF2alpha-application. A total of 47 Holstein Friesian (35 cows and 12 heifers) were used in two experiments. In Experiment 1, 25 animals were examined by daily transrectal palpation and ultrasonography to follow the morphological development of the DF. The status of the DF was categorized into 3 groups (A1, B1, C1). The A1 group (n=7) contained animals with DF in the growing phase or in early static growth phase for less than 3 days. Group B1 (n=13) included animals with DF in static growth phase for 3 to 4 days, while Group C1 (n=5) comprised animals with DF keeping a plateau for more than 4 days or animals with DF in the regression phase. The DF were aspirated transvaginally and the follicular fluid (FF) was analyzed for E2 and P4. In Experiment 2, 22 animals were included. As in Experiment 1, the animals were classified into three groups (A2, n=10; B2, n=5; C2, n=7). They were treated by a single dose of PGF2alpha (25 mg, i.m.) between Days 8 and 12 of the cycle. Results showed that luteolyses occurred in all animals. The DF, which were in growing or in early static growth phase < 3 days were always E2-dominant (E2 > P4) and ovulated after PGF2alpha-application in 6/8 of cases and persisted in 2 (Group A2). The DF persisting > 4 days or that had been in regression were always P4-dominant. This type of DF regressed after PGF2alpha-application (Group C2). The DF in early static growth phase for 3 to 4 days in 5/13 cases were E2-dominant and in 8/13 cases were P4-dominant. This type of DF ovulated in 3/5 cases and regressed in 2/5 cases after PGF2alpha-application (Group B2). These results suggest that the DF is morphologically and functionally defined as long as the DF is in the growing or early static growth phase (A1, A2) for at least 2 days or if the DF is in regression (C1, C2). However, when the DF is in the static growth phase for 3 or 4 days (B1, B2), their morphological and functional characteristics are different. The CL controlls ovulation in the A and C groups and plays an abettor's roll in the B-group.

Induction of oestrus in Saanen goats at early breeding season by intravaginal progesterone sponges (MAP) or by prostaglandin F(2)alpha injections. Effect on different age groups.

Twenty-one maiden and 29 pluriparous milking Ankara Saanen goats received either two i.m. injections of PGF(2)alpha (n=25) or intravaginal MAP sponges (n=25) early in November at the start of the breeding season. About twice as many pluriparous goats as maiden goats exhibited estrus after either treatment (87% vs. 47%). Breeding after this induced estrus caused pregnancies in 62% of the pluriparous goats, but only in 24% of the maiden animals. Maximal concentrations of progesterone were reached 11 days after the start of the MAP treatment. Progesterone declined to basal levels two to four days after sponge withdrawal. A significant slower progesterone increase also resulting in lower maximal concentrations could be observed in maiden goats. Luteolysis was evident in all animals within 24 h after PGF(2)alpha injection. Nine goats (six maiden and three pluriparous) did not exhibit Heat after the second injection and showed only a slow increase of progesterone. It seems that noncyclic animals are less sensitive to MAP treatment than to the first PGF(2)alpha injection. Goats at the beginning of the breeding season may react after a premature interruption of corpus luteum function (after second PGF(2)alpha injection) with delayed or inadequate follicular function.

[Feasibility of detecting steroid hormones in cattle feces for monitoring ovarian function]. / Zur Aussagefähigkeit von Steroidhormonen im Kot von Rindern für deren Ovarfunktionen.

Faecal material from four non pregnant cows was withdrawn in two-day intervalls during a four-week period. At the same time bloodsamples were taken to monitor the ovarian function. Clinical and ultrasonographical examinations were recorded in parallel. To look for the stability of the faecal steroid analogues for P4 (Progesterone) and E2 (Estradiol-17 beta) faecal material was stored at 37 degrees C and samples from that analyzed in two-day intervals. The P4 (Progesterone)-analogues values in the faeces showed good correlation to cycling ovarian functions as monitored by bloodlevels from P4, clinical examination and ultrasonography. In contrast the E2-analogues values showed no cycling pattern. One cow however showed ovarian cysts which was monitored in the P4 values for blood and faeces. Concerning the stability of the steroid analogues it could be demonstrated that the P4-values show a steady decrease with minimum values of 20 ng/g dry material. During the first four days after sampling reliable values for clinical interpretations can be found. The concentrations for E2 are very inconstant and so far not of interest. The investigation shows that the faecal steroid P4 can be used for monitoring ovarian function. It has to be analyzed within four days after sampling when stored at room temperature.

[Some parameters in reproduction of a Maroccain sheep breed (race d'Man) (author's transl)]. / Einige Parameter zur Reproduktion einer marokkanischen Schafrasse (race d'Man).

The importance of the sheep in Marocco was shown with help of statistical data. As there exist very few scientific work on sheep reproduction in this country, we began to work on local breeds with the race d'Man. The breed is asaisonal and is able to lamb 2 times within 13 months, with mostly 2 or more youngs (1,8 lambs per partum). The delay of gestation was found with 150 days, the duration of a cycle 17 days. The libido shown by the rams is violent. They easily accepted an other male as phantome for the collection of sperm with the easily accepted artificial vagina. The gonads are ovoid formed and are early developed. Remarkable is the tail of the epididymis which is covered in a pocketlike formed structure of the distal scrotum. Its volume is remarkable. Concerning the characteristics of the sperm there is no difference with other breeds. Therefore the conclusion seems reasonable that this apparent development of the epididmymis tail is an organ for thermoregulation for the sperm as the breeds origin are the oasis of the Sahara. The early onset of puberty as well as the violent sexual interest and the high rate of reproduction and asaisonal behavior could be a reference to a "primitive breed".

Separation of two-electron photoexcited atomic processes near the inner-shell threshold.

By means of a high resolution resonant inelastic x-ray scattering spectroscopy, we have for the first time separated spectral features pertaining to different two-electron atomic processes in the vicinity of an inner-shell threshold. Contributions of shakeoff, shakeup, and resonant 1s3p double excitations were extracted from the Ar KM-M{2,3}M x-ray satellite line intensity measured as a function of photon energy from [1s3p] double excitation threshold to saturation. The isolated [1s3p]nln'l' excitation spectrum is critically compared to the outcome of the multiconfiguration Dirac-Fock model with relaxation.

Spin-orbit mediated interference in the radiative and nonradiative channels of the La 4d core resonances.

Symmetrical fluorescence yield profiles and asymmetrical electron yield profiles of the preresonances at the La N_{IV,V} x-ray absorption edge are experimentally observed in LaPO_{4} nanoparticles. Theoretical studies show that they are caused by interference effects. The spin-orbit interaction and the giant resonance produce symmetry entangled intermediate states that activate coherent scattering and alter the spectral distribution of the oscillator strength. The scattering amplitudes of the electron and fluorescence decays are further modified by the spin-orbit coupling in the final 5p;{5}epsilonl and 5p;{5}4f;{1} states.