Doublet Components Research Articles

Iron-oxide aerogel and xerogel catalyst formulations: Characterization by 57Fe Mössbauer and XAFS spectroscopies

Iron in various iron-oxide aerogel and xerogel catalyst formulations (> or =85% Fe(2)O(3); < or =10% K, Co, Cu, or Pd) developed for possible use in Fischer-Tropsch synthesis (FTS) or the water-gas-shift (WGS) reaction has been examined by (57)Fe Mössbauer spectroscopy. The seventeen samples consisted of both as-prepared and calcined aerogels and xerogels and their products after use as catalysts for FTS or the WGS reaction. Complementary XAFS spectra were obtained on the occurrence of the secondary elements in some of the same materials. A broad, slightly asymmetric, two-peak Mössbauer spectrum was obtained from the different as-prepared and calcined catalyst formulations in the majority of cases. Such spectra could only be satisfactorily fit with three quadrupole doublet components, but no systematic trends in the isomer shift and quadrupole splitting parameters and area ratios of the individual components could be discerned that reflected variations in the composition or preparation of the aerogel or xerogel materials. However, significant reductions were noted in the Mössbauer effective thickness (recoilless absorption effect per unit mass of iron) parameter, chi(eff)/g, determined at room temperature, for aerogels and xerogels compared to bulk iron oxides, reflecting the openness and lack of rigidity of the aerogel and xerogel structures. Mössbauer measurements for two aerogels over the range from 15 to 292K confirmed the greatly diminished nature of this parameter at room temperature. Major increases in the effective thickness parameter were observed when the open structure of the aerogel or xerogel collapsed during calcination resulting in the formation of iron oxides (hematite, spinel ferrite). Similar structural changes were indicated by increases in this parameter after use of iron-oxide aerogels as catalysts for FTS or the WGS reaction, during which the iron-oxide aerogel was converted to a mixture of nonstoichiometric magnetite and the Hägg carbide, chi-Fe(5)C(2), or nonstoichiometric magnetite, respectively.

Polaronic and charge ordering effects in Pr 0.5 Sr 0.5 Mn 1− x Fe x O 3

In this work we report the results of X-ray diffraction and Mossbauer spectroscopy for the systems Pr0.5Sr0.5Mn1 − x Fe x O3 (with x = 0.05, 0.10, 0.15, 0.20, 0.25, 0.30). XRD patterns indicated that all samples were single phase with slightly distorted orthorhombic symmetry. Room temperature Mossbauer spectra are all quadrupole split, indicating paramagnetic relaxation of the Fe moment for all values of Fe concentrations. The spectra are fitted with two doublet components associated with Fe3 + ions in octahedral sites with different distortions. Mossbauer spectra recorded at liquid nitrogen temperature for this system also indicate paramagnetic relaxation of the Fe moments down to liquid nitrogen temperature (LNT). In these spectra a third quadrupole component with quadrupole splitting close to zero develops. This component is associated with the delocalization of the charge carriers and the consequent disappearance of lattice distortions produced by the polaronic effect at room temperature. The component with the high quadrupole splitting (0.81 to 1.07 mm/s) results from Jahn–Teller distortion as a consequence of charge ordering transition at low temperature.

Structural characterization of metal–metal bonded polymer [Ru(L)(CO)2]n (L = 2,2′-bipyridine) in the solid state using high-resolution NMR and DFT chemical shift calculations

The metal bonded ruthenium polymer [Ru(0)(bpy)(CO)(2)](n) (bpy = 2,2'-bipyridine) is known to be a very promising and efficient solid material for catalysis applications, such as carbon dioxide electroreduction in pure aqueous media and the water-gas shift reaction. It also exhibits potential application for molecular electronics as a conductive molecular wire. The insolubility and relative air-sensitivity of [Ru(0)(bpy)(CO)(2)](n) as well as the lack of monocrystals make its structural characterization very challenging. A first approach to determine the structure of this polymer has been obtained by ab initio X-ray powder diffraction, based on the known X-ray structure of [Ru(CO)(4)](n). In order to refine this structure, a non-conventional solid-state NMR study was performed. The results of this study are presented here. The comparison of high-resolution solid-state (13)C NMR spectra of the polymer with those of the corresponding monomeric [Ru(bpy)(CO)(2)Cl(2)] or dimeric [Ru(bpy)(CO)(2)Cl](2) precursor complexes has shown a clear shift and splitting of carbonyl ligand resonances, which turns out to be linearly correlated with the redox state of the Ru (ii, i or 0, respectively). Bipyridine resonances are also affected but in a non-trivial way. Finally, in the case of the dimer, it was found that the CO peak splitting (2.7 ppm) contains structural information, e.g. the ligand staggering angle. Based on DFT chemical shift calculations on corresponding model molecules (n = 1-2), all the described experimental observations could be reproduced. Moreover, upon extending these calculations to models of increasing length (n = 3-5), it turns out that information about the staggering angle between successive ligands is actually retained in the CO NMR computed peak splitting. Turning back to experiments, the CO broad signal measured for the wire could be decomposed into a major component (at 214.9 ppm) assigned to the internal CO ligands, and a minor doublet component (216.9 and 218.1 ppm) whose splitting (2.8 ppm) contains the staggering angle information. Finally, from the relative integrals of these three components, expected to be in the ratio 1 : 1 : n-2, it was possible to tentatively estimate the length n of the polymetallic wire (n = 7).

Pressure-induced line mixing in the ν4 band of NH 3 perturbed by O 2 and self-perturbed

Pressure-induced line-mixing parameters of 231 rovibrational transitions of several branches in the ν 4 band of ammonia perturbed by O 2 have been measured at room temperature (295 K) using a high-resolution Fourier transform spectrometer. The line-mixing parameters were obtained using the method of multi-spectrum fitting to the measured shapes of the lines, including the interference effects caused by the line overlaps. The largest amounts of coupling are observed between the symmetric and asymmetric components of inversion doublets mainly in the PP branch of the ν 4 band. The line-mixing parameters are both positive and negative and are much greater for self-broadening than for O 2-broadening. The estimated error is around 15% and widely depends on the quality of spectral lines. In order to predict these line-mixing parameters, we have calculated state-to-state cross sections for NH 3 perturbed by O 2- and self-perturbed using a semiclassical model. The predicted values are in reasonable agreement with the measurements for O 2- and self-broadening. This calculation illustrates that the state-to-state cross section contributions to the line-mixing parameters mainly arises from the energy transfer between symmetric and asymmetric components of the inversion doublets. An examination of these cross sections shows a pronounced J and K quantum number dependence.

Spectroscopic and theoretical studies of some N-methoxy- N-methyl-2-[(4′-substituted) phenylsulfonyl]propanamides

The analysis of the IR carbonyl band of the N-methoxy- N-methyl-2-[(4′-substituted)phenylsulfonyl]propanamides Y-PhSO 2CH(Me)C(O)N(OMe)Me (Y = OMe 1, Me 2, H 3, Cl 4, NO 2 5), supported by HF/6-31G(d,p) calculations of 3, indicated the existence of two gauche conformers ( g 1 and g 2), the g 1 conformer being the most stable and the least polar one (in gas phase and in solution). Both conformers are present in solution of the non polar solvent (CCl 4) for 1– 5 and in solution of the more polar solvents (CHCl 3) for 1, 4, 5 and (CH 2Cl 2) for 5, while only the g 1 conformer is present in solution of the most polar solvent (CH 3CN) for 1– 5. The g 1 and g 2 conformers correspond to the enantiomeric pairs of diastereomers ( diast 1 and diast 2) whose relative configurations are [C(3) RN R]/[C(3) SN S] and [C(3) RN S]/[C(3) SN R], respectively. The computed carbonyl frequencies for g 1 ( diast 1) and g 2 ( diast 2) stereoisomers of 3 match well the experimental values. The NBO analysis, for 3 shows the important role of the orbital interactions in conformer stabilization and the overall balance of these interactions corroborates that the g 1 conformer is more stable than the g 2 one. The observed abnormal solvent effect on the relative intensities of the carbonyl doublet components is attributed to the molecular crowding in the g 2 conformer which hinders its solvation in comparison to the g 1 conformer ( diast 1). X-ray single crystal analysis performed for 3 shows the existence of two g 2 a and g 1 b conformers of diastereomers ( diast 2 a and diast 1 b ) whose absolute configurations are [C(3) RN S] and [C(3) RN R], respectively. The larger population and, thus, the larger stabilization of the g 2 a conformer over the g 1 b form in the crystals may be associated with a larger energy gain deriving from dipole moment coupling in the former conformer along with a series of C H…O electrostatic and hydrogen bond interactions.

Time-averaging within the excited state of the nitrogen-vacancy centre in diamond

The emission intensity of diamond samples containing negatively charged nitrogen-vacancy centres are measured as a function of magnetic field along the ⟨111⟩ direction for various temperatures. At low temperatures the responses are sample and stress dependent and can be modelled in terms of the previous understanding of the 3E excited state fine structure which is strain dependent. At room temperature the responses are largely sample and stress independent, and modelling involves invoking a strain independent excited state with a single zero field spin-level splitting of 1.42 GHz. The change in behaviour is attributed to a temperature dependent averaging process over the components of the excited state orbital doublet. It decouples orbit and spin and at high temperature the spin levels become independent of any orbit splitting. One significant implication of this averaging is that it simplifies the development of room temperature applications.

Fluorination of perovskite-related phases of compositionSrFe1−xSnxO3−δ

Perovskite-related compounds of compositionSrFe1−xSnxO3−δ (x = 0.31,0.54) have been prepared. X-ray powder diffraction shows that the materials adopt orthorhombicunit cells. The lattice parameters increase with the incorporation of increasing amounts oftin, which is shown by x-ray absorption near edge structure investigation to be present asSn4+.57Fe Mössbauer spectroscopy indicates that iron in these phases is present asFe5+ andFe3+ and that the materials adopt the compositionsSrFe0.69Sn0.31O2.94 andSrFe0.46Sn0.54O2.88. We propose that thedisproportionation of Fe4+ in SrFeO3−δ to Fe5+ and Fe3+ in SrFe1−xSnxO3−δ is driven by the reduction of local lattice strain.The materials have been fluorinated by reaction with poly(vinylidene fluoride) to give products ofcomposition SrFe0.69Sn0.31O2.31F0.69 and SrFe0.46Sn0.54O2.54F0.46. The increased iron to oxygen or fluorine distances as revealed by theextended x-ray absorption fine structure are associated with the reduction ofFe5+ toFe3+ as evidencedby 57Fe Mössbauerspectroscopy. The 57Fe Mössbauer spectra recorded from the fluorinated materials at low temperature show the coexistenceof magnetic sextet and non-magnetic doublet components corresponding to networks ofFe3+ coupled throughoxide ions. The Sn4+ ions disrupt the coupling and the size of the networks. The magnetic susceptibilitymeasurements and Mössbauer spectra recorded between 4.2 and 300 K are usedto model the magnetic properties of these materials, with the larger networksappearing to possess random spin orientations consistent with spin glass-typematerials.

Self-broadening, self-shift and self-mixing in the ν2, 2 ν2 and ν4 bands of NH 3

Using Fourier-transform spectra (Bruker IFS 120 HR, resolution ≈0.004 cm −1) of NH 3 in nine branches of the ν 2, 2 ν 2 and ν 4 bands, self-broadening and self-shift as well as self-mixing coefficients have been determined at room temperature ( T=295 K) for more than 350 rovibrational lines located in the spectral range 1000–1800 cm −1. A non-linear least-squares multispectrum fitting procedure, including line mixing effects, has been used to retrieve successively the line parameters from 11 experimental spectra recorded at different pressures of pure NH 3. The accuracies of self-broadening coefficients are estimated to be better than 2% for most lines. The mean accuracies of line-mixing and line-shift data are estimated to be about 15% and 25%, respectively. The results are compared with previous measurements and with values calculated using a semiclassical model based upon the Robert–Bonamy formalism that reproduces rather well the systematic experimental J and K quantum number dependencies of the self-broadening coefficients. The results concerning line mixing demonstrate a large amount of coupling between the symmetric and asymmetric components of inversion doublets mainly in the ν 4 band. The line mixing parameters are both positive and negative. More than two thirds of the lines studied here have a positive shift coefficient. However, for most of them the shift coefficients are negative in the 2 ν 2 band. They are positive for the R branch of the ν 2 band and for the P R and R P branches of the ν 4 band. For the other branches they are both positive and negative. Some components of inversion doublets illustrate a correlation between line mixing and shift phenomena demonstrated by a quadratic pressure dependence of line position.

AEGIS: THE NATURE OF THE HOST GALAXIES OF LOW-IONIZATION OUTFLOWS ATz&lt; 0.6

We report on a S/N-limited search for low-ionization gas outflows in the spectra of the 0.11 < z < 0.54 objects in the EGS portion of the DEEP2 survey. Doppler shifts from the host galaxy redshifts are systematically searched for in the Na I 5890,96 doublet (Na D). Although the spectral resolution and S/N limit us to study the interstellar gas kinematics from fitting a single doublet component to each observed Na D profile, the typical outflow often seen in local luminous-infrared galaxies (LIRGs) should be detected at >~ 6 sigma in absorption equivalent width down to the survey limiting S/N (~ 5 per pixel) in the continuum around Na D. The detection rate of LIRG-like outflow clearly shows an increasing trend with star-forming activity and infrared luminosity. However, by virtue of not selecting our sample on star formation, we also find a majority of outflows in galaxies on the red sequence in the rest-frame (U-B, M_B) color-magnitude diagram. Most of these red-sequence outflows are of early-type morphology and show the sign of recent star formation in their UV-optical colors; some show enhanced Balmer H-beta absorption lines indicative of poststarburst as well as high dust extinction. These findings demonstrate that outflows outlive starbursts and suggest that galactic-scale outflows play a role in quenching star formation in the host galaxies on their way to the red sequence. The fate of relic winds, as well as the observational constraints on gaseous feedback models, may be studied in galaxies during their poststarburst phase. We also note the presence of inflow candidates in red, early-type galaxies, some with signs of AGNs/LINERs but little evidence for star formation.

Neutrinos from Inert Doublet dark matter

We investigate the signatures of neutrinos produced in theannihilation of WIMP dark matter in the Earth, the Sun and at theGalactic centre within the framework of the Inert Doublet Model andextensions. We consider a dark matter candidate, that we take to beone of the neutral components of an extra Higgs doublet, in threedistinct mass ranges, which have all been shown previously to beconsistent with both WMAP abundance and direct detection experimentsexclusion limits. Specifically, we consider a light WIMP with massbetween 4 and 8 GeV (low), a WIMP with mass around 60-70 GeV(middle) and a heavy WIMP with mass above 500 GeV (high). In thefirst case, we show that capture in the Sun may be constrained usingSuper-Kamiokande data. In the last two cases, we argue that indirectdetection through neutrinos is challenging but not altogetherexcluded. For middle masses, we try to make the most benefit of theproximity of the so-called 'iron resonance' that might enhance thecapture of the dark matter candidate by the Earth. The signal fromthe Earth is further enhanced if light right-handed Majorananeutrinos are introduced, in which case the scalar dark mattercandidate may annihilate into pairs of mono-energetic neutrinos. Inthe case of high masses, detection of neutrinos from the Galacticcentre might be possible, provided the dark matter abundance issubstantially boosted.

Many light Higgs bosons in the next-to-minimal supersymmetric model

The next-to-minimal supersymmetric model with a light doubletlike CP-odd Higgs boson and small tan{beta} can satisfy all experimental limits on Higgs bosons even with light superpartners. In these scenarios, the two lightest CP-even Higgs bosons, h{sub 1} and h{sub 2}, and the charged Higgs boson, h{sup +}, can all be light enough to be produced at CERN LEP and yet have decays that have not been looked for or are poorly constrained by existing collider experiments. The channel h{sub 1}{yields}a{sub 1}a{sub 1} with a{sub 1}{yields}{tau}{sup +}{tau}{sup -} or 2j is still awaiting LEP constraints for m{sub h{sub 1}}>86 or 82 GeV, respectively. LEP data may also contain e{sup +}e{sup -}{yields}h{sub 2}a{sub 1} events where h{sub 2}{yields}Za{sub 1} is the dominant decay, a channel that was never examined. Decays of the charged Higgs bosons are often dominated by H{sup {+-}}{yields}W{sup {+-}}{sup (}*{sup )}a{sub 1} with a{sub 1}{yields}gg, cc, and {tau}{sup +}{tau}{sup -}. This is a channel that has so far been ignored in the search for t{yields}h{sup +}b decays at the Tevatron. A specialized analysis might reveal a signal. The light a{sub 1} might be within the reach of B factories via {upsilon}{yields}{gamma}a{sub 1} decays. We study typical mass ranges and more » branching ratios of Higgs bosons in this scenario and compare these scenarios where the a{sub 1} has a large doublet component to the more general scenarios with arbitrary singlet component for the a{sub 1}. « less

Influence of Mn-for-Fe substitution on structural properties of synthetic goethite

In order to study the effect of alloying elements, such as manganese, on the properties of the rust on weathering steels, a series of Mn-goethite samples containing different amounts of Mn were synthesized from ferrihydrite in alkaline media. The samples were characterized by X-ray diffraction (XRD) and Mossbauer spectroscopy. The cell parameters calculated from the XRD patterns showed clearly that the a- and c-parameters decrease while the b-parameter increases with increasing Mn concentration, indicating that the octahedra of the goethite structure become distorted by an incorporation of Mn (Jahn–Teller-effect). Mossbauer spectra of the samples were recorded at room temperature (RT) and at 80 K. The quadrupole shift values gradually decrease with increasing Mn substitution in the goethite structure. It has been observed that the magnetic hyperfine field values of maximum probability are reduced with increasing Mn in the samples. No doublet component was observed in the RT MS spectra suggesting that no effects of superparamagnetim resulting from smaller particles are present.

Hyperfine interactions in szomolnokite (FeSO 4·H 2O)

The temperature dependencies of the ferrous Mössbauer parameters for synthetic szomolnokite are determined in the range between 4 and 450 K. A magnetic order-disorder transition is observed at 29.6 ± 0.5 K. The Mössbauer spectra in the paramagnetic region are well fitted by the superposition of a Fe 2+ distributed quadrupole component and a small ferric doublet component. The spectra in the magnetic region are typically for Fe 2+, showing up to eight absorption lines. They are analyzed from diagonalization of the full nuclear-interaction hamiltonian. The saturation value of the hyperfine field is 32.5 T. For temperatures below 29 K, the adjusted value for the asymmetry parameter of the EFG is η ≈ 0.63 and for the quadrupole splitting Δ E Q ≈ 3.08 mm/s. These values are in line with those measured at temperatures in the paramagnetic regime. The temperature dependence of the quadrupole splitting is interpreted within the ferrous 5D orbital energy level scheme by a crystal field calculation based on the point symmetry of the Fe 2+ site in szomolnokite. It is found that the high asymmetry of the EFG is caused by the presence of the H 2O groups in the structure. The variation of the hyperfine field with temperature is interpreted within the molecular field approximation, however, taking exchange magnetostriction into account. From the temperature dependence of the isomer shift the characteristic Mössbauer temperature Θ M is determined to be 425 K, from which the Mössbauer fraction at room temperature is estimated to be 0.79.

DARK MATTER CANDIDATE IN A HEAVY HIGGS MODEL: DIRECT DETECTION RATES

We investigate direct detection rates for Dark Matter candidates arise in a SU (2)L× U (1)Y with an additional doublet Higgs proposed by Barbieri, Hall and Rychkov. We refer to this model as "Heavy Higgs Model". The Standard Model Higgs mass comes out from this model is very heavy, so there is very slim chance that there is no Higgs boson mass below 200 GeV. The additional Higgs boson develops neither any VEV due to the choice of coefficient of the scalar potential of the model nor it has any coupling with fermions due to the incorporation of a discrete parity symmetry. Thus, the neutral components of the extra doublet are stable and can be considered as probable candidate of Cold Dark Matter. We have made calculations for three different types of Dark Matter experiments, namely, 76 Ge (like GENIUS), DAMA (NaI) and XENON (131 Xe ). Also demonstrated the annual variation of Dark Matter detection in case of all three

Infrared Absorption Spectra in the Hydroxyl Stretching Regions of Gaseous Tropolone OHO Isotopomers

Abstract Fourier transform infrared (FTIR) absorption spectra in the 2000 to 3500 cm–1 range are reported for the gaseous 16 O, 16 O- and 18 O, 18 O-isotopomers of tropolone[OH(OD)] at 25 oC. The spectral doublet component separations are near 20 and 19 cm–1 for 16 O, 16 O- and 18 O, 18 O-Tp(OH), respectively, and near 7 and 6.5 cm–1 for 16 O, 16 O- and 18 O, 18 O-Tp(OD). The spectra suggest the tautomerization tunneling mechanisms in these states are complex multidimensional processes including the participation of IVR. In general, the OHO isotope effects demonstrate a mixing of O atom displacement coordinates into the intramolecular dynamics for most of the vibrational states observed in the fundamental CH/OH(OD) stretching regions.

Charged Higgs bosons in the next-to MSSM (NMSSM)

The charged Higgs boson decays H±→W±A1 and H±→W±Hi are studied in the framework of the next-to-minimal supersymmetric standard model (NMSSM). It is found that the decay rate for H±→W±A1 can exceed the rates for the τ±ν and tb channels both below and above the top–bottom threshold. The dominance of H±→W±A1 is most readily achieved when A1 has a large doublet component and small mass. We also study the production process pp→H±A1 at the LHC followed by the decay H±→W±A1, which leads to the signature W±A1A1. We suggest that pp→H±A1 is a promising discovery channel for a light charged Higgs boson in the NMSSM with small or moderate tanβ and dominant decay mode H±→W±A1. This W±A1A1 signature can also arise from the Higgsstrahlung process pp→W±H1 followed by the decay H1→A1A1. It is shown that there exist regions of parameter space where these processes can have comparable cross sections and we suggest that their respective signals can be distinguished at the LHC by using appropriate reconstruction methods.

The Paschen-Back effect in the Li I 6708 Å line and the presence of lithium in cool magnetic Ap stars

A number of cool magnetic Ap stars show a prominent feature at lambda 6708 A. Its identification with Li I remains controversial due to a poor knowledge of the spectra of rare-earth elements that are strongly enhanced in peculiar stars and can potentially provide an alternative identification. We suggest to investigate the 6708 line in Ap stars with strong magnetic fields. In these objects the magnetic broadening and splitting provides an additional powerful criterium for line identification, allowing to use the whole line profile instead of a mere coincidence of the observed and predicted wavelength. Due to a small separation of the Li I doublet components, their magnetic splitting pattern deviates from the one expected for the Zeeman effect even in relatively weak fields. We carry out detailed calculations of the transition between the Zeeman and Paschen-Back regimes in the magnetic splitting of the Li I line and compute polarized synthetic spectra for the range of field strength expected in Ap stars. Theoretical spectral synthesis is compared with the high-resolution observations of cool Ap stars HD 116114, HD 166473 and HD 154708, which have a mean field strength of 6.4, 8.6 and 24.5 kG, respectively, and show a strong 6708 A line. High-resolution spectra for the 6708 A region are analysed for 17 magnetic Ap stars. The presence of the 6708 A line is confirmed in 9 stars and reported for the first time in 6 stars. We demonstrate that the observed profiles of the 6708 A line in the strong field stars HD 116114, HD 166473 and HD 154708 correspond rather well to the theoretical calculations assuming the Li I identification. Inclusion of the Paschen-Back effect improves the agreement with observations, especially for HD 154708. Results of our study confirm the Li I identification proposed for the 6708 A line in cool Ap stars.

Mirror-imaged doublets of Tetmemena pustulata: Implications for the development of left–right asymmetry

Ciliated protozoa possess cellular axes reflected in the arrangement of their ciliature. Upon transverse fission, daughter cells develop an identical ciliary pattern, ensuring perpetuation of the cellular phenotype. Experimentally manipulated cells can be induced to form atypical phenotypes, capable of intraclonal propagation and regeneration after encystment. One such phenotype in the ciliate Tetmemena pustulata (formerly Stylonychia pustulata) is the mirror-imaged doublet. These cells possess two distinct sets of ciliature, juxtaposed on the surfaces in mirror image symmetry, with a common anterior–posterior axis. We have examined whether individual ciliary components of Tetmemena mirror-image doublets are mirror imaged. Ultrastructural analysis indicates that despite global mirror imaging of the ciliature, detailed organization of the membranelles is reversed in the mirror-image oral apparatus (OA), such that the ciliary effective stroke propels food away from the OA. Assembly of compound ciliary structures of both OAs starts out identically, but as the structures associated with the mirror-image OA continue to form, the new set of membranelles undergoes a 180° planar rotation on the ventral surface relative to the same structures in the typical OA. The overall symmetry of the OA thus appears to be separable from the more localized assembly of individual basal bodies. True mirror imagery of the membranelles would require new enantiomorphic forms of the individual ciliary components, particularly the basal bodies, which is never observed. These observations suggest a mechanistic hypothesis with implications for the development of left–right asymmetry not only in ciliates, but perhaps also in development of left–right asymmetry in general.

Dipolar cross-relaxation modulates signal amplitudes in the 1H NMR spectrum of hyperpolarized [ 13C]formate

The asymmetry in the doublet of a spin coupled to hyperpolarized 13C has been used previously to measure the initial polarization of 13C. We tested the hypothesis that a single observation of the 1H NMR spectrum of hyperpolarized 13C formate monitors 13C polarization. Depending on the microwave frequency during the polarization process, in-phase or out-of-phase doublets were observed in the 1H NMR spectrum. Even in this simple two-spin system, 13C polarization was not reflected in the relative area of the J CH doublet components due to strong heteronuclear cross-relaxation. The Solomon equations were used to model the proton signal as a function of time after polarization and to estimate 13C polarization from the 1H NMR spectra.

Multivariate analysis in provenance studies: Cerrillos obsidians case, Peru

We present the preliminary results of a provenance study of obsidians samples from Cerrillos (ca. 800–100 b.c.) using Mossbauer Spectroscopy. The Cerrillos archaeological site, located in the Upper Ica Valley, Peru, is the only Paracas ceremonial center excavated so far. The archaeological data collected suggest the existence of a complex social and economic organization on the south coast of Peru. Provenance research of obsidian provides valuable information about the selection of lithic resources by our ancestors and eventually about the existence of communication routes and exchange networks. We characterized 18 obsidian artifacts samples by Mossbauer spectroscopy from Cerrillos. The spectra, recorded at room temperature using different velocities, are mainly composed of broad asymmetric doublets due to the superposition of at least two quadrupole doublets corresponding to Fe2+ in two different sites (species A and B), one weak Fe3+ doublet (specie C) and magnetic components associated to the presence of small particles of magnetite. Multivariate statistical analysis of the Mossbauer data (hyperfine parameters) allows to defined two main groups of obsidians, reflecting different geographical origins.