Qs Values Research Articles

A high-resolution, calibrated airborne radiometric dataset applied to the estimation of crustal heat production in the Archaean northern Pilbara Craton, Western Australia

In stable cratonised crust, the measured surface heat flow ( qs) approximates the sum of the “deep” heat flux due to mantle convection (qm), and the heat flow contribution of predominantly “shallow” crust-hosted radiogenic heat production ( qc). Archaean terrains worldwide are characterised by low and relatively uniform qs values (30–50 mW m −2 ), and the common concentration of the heat-producing elements (HPEs) K, Th and U in the upper crust means that accurate estimates of HPE abundances in the major lithological units exposed are critical to the meaningful estimation of qc. However, unit-scale geochemical datasets used for this purpose are often small and/or unevenly spatially distributed, and considerable scope exists for “average” heat production determinations that are not representative of the exposure. This study evaluates the potential of a high-resolution (400 m flight line spacing) calibrated airborne radiometric dataset to provide reasonable area-averaged heat production estimates for major Archaean granitoid complexes within the well-exposed southern East Pilbara Granite–Greenstone Terrane (EPGGT) of Western Australia. Using the available geochemical data as ground control, we show that the overall spatial and attribute accuracy of the radiometric data is high within felsic rocks for all HPEs, with 20–40% of all site comparisons yielding geochemical and radiometric values within 5% of each other. Departures from this trend are principally attributable to: (1) K depletion of the surface layer sampled by gamma-ray spectrometry, due to the mobility of K in weathering environments, and (2) U enrichment or depletion in the surface layer reflecting disequilibrium in the 238 U decay chain affecting the gamma-ray response. However, both trends proved systematic and correctable at the scale of individual granitoid complexes, and we derive area-averaged heat production (H) estimates in the range 1.5–3.0 Wm −3 for the volumetrically dominant pre-2.9 Ga EPGGT granites, rising to H = 4.0–6.5 Wm −3 for small, late-stage (c. 2.85 Ga) plutons. Integration of these data with independent geophysical and geochemical constraints on upper crustal structure in the EPGGT suggests that observed heat flow in the East Pilbara ( qs = 35–50 mW m −2 ) comprises qm = 10–15 mW m −2 and qc = 25–40 mW m −2 , and this latter range shows considerable overlap with qc values deduced for many Proterozoic crustal segments worldwide. This implies that HPE abundance alone does not exert primary control on the preservation of Archaean crust, and it is likely that geologic processes that concentrate HPEs in the uppermost crust play an important role in cooling and strengthening the upper lithosphere, thereby increasing its thermal and mechanical resistance to subsequent reworking. © 2003 Elsevier B.V. All rights reserved.

On-line mixed hemodiafiltration with a feedback for ultrafiltration control: Effect on middle-molecule removal

Increased middle-molecular uremic toxin removal seems to favorably influence survival in dialysis patients. The aim of this study was to verify if, in on-line mixed hemodiafiltration, solute removal by convection may be enhanced by forcing the ultrafiltration rate (QUF) and optimizing the infusion technique in order to achieve the highest possible filtration fraction (FF). Removal of beta2-microglobulin (beta2-m), urea, creatinine, and phosphate were compared in 20 patients randomly submitted to one dialysis session (A), one postdilution hemodiafiltration session (B), and three sessions of mixed hemodiafiltration (C, D, and E) at different infusion rates (QS). In mixed hemodiafiltration, a newly developed feedback system automatically maintained the transmembrane pressure (TMP) within its highest range of safety (250 to 300 mm Hg) at constant QUF, while ensuring the maximum FF by splitting infusion between pre- and postdilution. A mean QS of 134 +/- 20 mL/min (mean FF = 0.65) was attained in post-HDF, and up to 307 +/- 41 mL/min (mean FF = 0.69) in mixed hemodiafiltration. The mean dialysate clearances (KDQ) for all tested solutes and urea eKt/V were significantly higher in all hemodiafiltration sessions than in dialysis. Only in the case of urea did the infusion mode have no significant effect. KDQ for beta2-m was maximal in session D and significantly higher than in session B (90.2 +/- 11 mL/min vs. 77.5 +/- 11 mL/min; P = 0.02). KDQ for beta2-m significantly correlated with QS and the plasma water flow rate (QPW). The highest KDQ for beta2-m was found at values of QS approximately QPW. Beyond this value KDQ decreased. The mixed infusion mode in hemodiafiltration, controlled by the TMP-ultrafiltration feedback, seems to improve the efficiency of hemodiafiltration by fully exploiting the convective mechanism of solute removal. The feedback automatically adjusted the infusion rate and site to the maximum FF taking into account flow conditions, internal pressures, and hydraulic permeability of the dialyzer and their complex interactions.

Cation distribution in calcic amphiboles from the Nuggihalli Greenstone belt, S. India and its geological significance

Amphiboles from Nuggihalli schist belt are analyzed and found to be mainly magnesio-hornblende, ferro-hornblende and actinolitic hornblende. Mossbauer study of actinolitic hornblende shows presence of iron in the Ml, M2, M3 and M4 sites. A lower QS value (1.66 mm/s) at M4 site for Fe 2 + indicates a faster rate of crystallization of the studied sample whereas Fe 3 + /Fe 2 + ratio (0.14) indicates that the amphiboles were formed in an oxidizing environment (high fO 2 ). Based on plagioclase-amphibole geothermometry, equilibration temperature of meta-anorthosite is seen to range between 648 °C (921 K) and 704 °C (977K). The amphibolite is found to be equilibrated in a water rich environment (X H 2 O ranging from 0.81 to 0.89). Considering the pressures as 5 and 7kbar, and the amphibolite subassemblages such as, calcite-rutile-quartz and epidote-plagioclase-calcite, in the T-X C O 2 section (derived from THERMOCALC program) the invariant points are seen to be at (i) X C O 2 = 0.11, T = 493 °C and (ii) X C O 2 = 0.19, T = 562 °C at the respective pressures. The calculated M2-M4 distribution coefficient (K D ) in Nuggihalli actinolitic hornblende is found to be 0.0034, which corresponds to a temperature of equilibration at around 435 °C.

Metallacumulenylidene complexes in the [(η 5-C 5Me 5)(η 2-dppe)Fe(=C(=C) nR 2)]X ( n = 0, 1, 2) series: investigations of the iron-carbon bonding by Mössbauer spectroscopy and X-ray analyses

The synthesis of the iron allenylidene complexes [(η 5-C 5Me 5)(η 2-dppe)Fe(=C=C=C(Ph)Ph)][X] ( 5a, X = PF 6, 95%; 5b, X = BPh 4, 91%; dppe = 1,2-bis(diphenylphosphino)ethane) was achieved by reacting the complex (η 5-C 5Me 5)(η 2-dppe)FeCl ( 10) with 1 equiv of 1,1-diphenyl-prop-2-yn-1-ol in methanol in the presence of KPF 6 or NaBPh 4. Surprisingly, when the reaction was carried out in the presence of the tetraphenylborate anion, the final product contained both 5b and the hydroxyvinylidene [(η 5-C 5Me 5)(η 2-dppe)Fe(=C=C(H)C(OH)(Ph) 2)][BPh 4] ( 14b) in the 1:1 ratio. Further treatment of the mixture with Amberlyst 15 in methanol provided the allenylidene 5b as a pure sample. The allenylidene complexes [(η 5-C 5Me 5)(η 2-dppe)Fe(=C=C=C(Me)Ph)][PF 6] ( 6) and [(η 5-C 5Me 5)(η 2-dppe)Fe(=C=C=C(Me)Et)][PF 6] ( 7) were prepared according to the same procedure and they were isolated as purple powders in 90% yield. The X-ray crystal structures were determined for the vinylidene complexes [(η 5-C 5Me 5)(η 2-dppe)Fe(=C=CH 2)][PF 6] ( 3) and [(η 5-C 5Me 5)(η 2-dppe)Fe(=C=C(Ph)H)][PF 6] ( 4), and the allenylidene derivative 5a. In the homogeneous series of complexes [(η 5-C 5Me 5)(η 2-dppe)Fe(=(C) n (R)R’)][PF 6], ( n = 1, R = H, R′ = Me, X = PF 6, 1; n =1, R = H, R’ = OMe, X = PF 6, 2a; n = 1, R = H, R’ = OMe, X = CF 3OSO 2, 2b; n = 2, R = R′ = H, X = PF 6, 3; n = 2, R = H, R′ = Ph, X = PF 6, 4; n = 3, R = R′ = Ph, X = PF 6, 5a; n = 3, R = R′ = Ph, X = BPh 4, 5b; n = 3, R = Me, R′ = Ph, X = PF 6, 6; n = 3, R = Me, R′ = Et, X = PF 6, 7; n = 3, R = Me, R′ = OMe, X = BPh 4, 8), an empiric relationship between the Mössbauer parameters, δ and QS, was found. This observation would indicate that the positive charge on the iron nucleus decreases with the Fe=C bond order. Moreover, in this series of iron cumulenylidene derivatives, comparison of the variation of the metal–carbon bond distances determined by X-ray analyses with the Mössbauer QS values allows the observation of a linear correlation ( R = 0.99). To cite this article: G. Argouarch et al., C. R. Chimie 6 (2003).

Separation of Source, Propagation and Site Effects from S Waves¶of Local Earthquakes in Bursa Region, Northwestern Turkey

— We have used micro-earthquake recordings (M= 1.8–4.1) of local events in the distance range of 5–60 km in order to quantify the attenuation and site effects in the vicinity of the Bursa city, Marmara region, Turkey. The data set consists of 120 three-component recorded accelograms from 69 earthquakes, recorded at six stations. Each station is deployed on different geologic units, such as massive limestone, slope deposit and Quaternary young sediments, in the framework of the Marmara Poly-Project.¶In this study a nonparametric inversion method was applied to acceleration records from the Bursa region to estimate source, site and path effects using a two-step inversion. At the first step, we determined attenuation functions by analyzing the distance dependence of the spectral amplitudes and retrieved values of Q s (f) = 46.59f 0.67. At the second step, the corrected S-waves spectral records for the attenuation function, including the geometrical spreading effect, were inverted to separate source and site response for 21 different frequencies selected between 0.5 and ∼25 Hz. The near-surface attenuation, κ value, was also estimated by using the model proposed by Anderson and Hough (1984) at each site. We observed that κ0 is smaller for stations located on rock site (Igdιr, SIGD, κ0∼0.004) compared to the one that is located on Neogene sediment (Cukurca, SCKR, κ0∼0.018).¶Site amplifications from inversion showed that the station located within the Bursa basin, Cukurca (SCKR), is the most important site with about 4.0 amplification value at 1.8 Hz. Demirtas (SDEM) amplifies the spectral amplitudes about 3.0 times at 2.0 Hz, SHMK about 3.5 times between 2.5 and 3.5 Hz and SHMT nearly reaching 3.5 times between 1.5 and 4.0 Hz. However, stations located on the Uludag Mountain Massif (SKAY and SIGD), which correspond to a deep limestone geological unit, have the smallest amplification, that values between 0.6 and 1.4.

The fermentation of mixtures of D‐glucose and D‐xylose by Candida shehatae, Pichia stipitis or Pachysolen tannophilus to produce ethanol

AbstractThe fermentation of mixtures of D‐glucose and D‐xylose by three non‐traditional yeasts: Candida shehatae (ATCC 34887), Pachysolen tannophilus (ATCC 32691) and Pichia stipitis (ATCC 58376) have been studied to determine the optimal strain and initial culture conditions for the efficient production of ethanol. The comparison was made on the basis of maximum specific growth rate (µm), biomass productivity, the specific rates of total substrate consumption (qs) and ethanol production (qE) and the overall yields of ethanol and xylitol. All the experiments were performed in stirred‐tank batch reactors at a temperature of 30 °C. The initial pH of the culture medium was 4.5. The highest values of µm (above 0.5 h−1) were obtained with P stipitis in cultures containing high concentrations of D‐xylose. All three yeasts consumed the two monosaccharides in sequence, beginning with D‐glucose. The values of qs diminished during the course of each experiment with all of the yeasts. The highest values of the specific rates of total substrate consumption and ethanol production were obtained with C shehatae (for t = 10 h, qs and qE were above 5 g g−1 h−1 and 2 g g−1 h−1, respectively), although the highest overall ethanol yields were fairly similar with all three yeasts, at around 0.4 g g−1.© 2002 Society of Chemical Industry

Unexpected Values of Qs in the Unconsolidated Sediments of the Mississippi Embayment

We studied the attenuation of shear waves at three sites in the Mississippi embayment using data recorded in boreholes drilled to depths of up to 60 m. The source was a highly repeatable compressed-air-driven hammer. To estimate attenuation we used a spectral ratio technique for fixed depth and variable frequency. The best-fit line for each depth z gives a measure of the cumulative attenuation, indicated by α( z ). Then we fit a straight line to α( z ) for a range of values of z . The slope of this line gives an estimate of the average attenuation per distance and was used to determine an average Q s. For one of the sites (Newport, northeastern Arkansas), Q s ranges between 34 (1.5 m ≤ z ≤ 44.2 m) and 44 (1.5 m ≤ z ≤ 51.8 m). These values are significantly higher than the more typical value of about 10 determined for unconsolidated sediments by other authors. In addition, these high values correspond to sediments with low average shear-wave velocity (about 300 m/sec). In contrast, average Q s and velocity for sediments in Shelby Forest (near Memphis, Tennessee) are 22 and 348 m/sec (22.6 m ≤ z ≤ 60.1 m), respectively. Therefore, these results go against the conventional wisdom that low velocity implies low Q . For the third site (Marked Tree, northeastern Arkansas), average Q s and velocity are 18 and 251 m/sec (9.8 m ≤ z ≤ 33.6 m), respectively. This site is about 75 km from Newport, and the differences in attenuation appear related to differences in lithology. Manuscript received 5 April 2001.

An attenuation study using earthquakes from the 1997 Umbria-Marche sequence

We studied spatial and temporal characteristics of seismic attenuation inCentral Italy using S- and coda- waves recorded by the MarchesanSeismograph Network from earthquakes located in the epicentral area ofthe 1997 Umbria-Marche sequence. The amplitude decay of the S waveswith distance was defined calculating empirical attenuation functions at 15frequencies between 1 and 25 Hz. We analyzed separately foreshocks andaftershocks and we found the same attenuation functions, suggesting thatthe possible temporal variations could be confined in a small area. Thefrequency dependence of QS was approximated by the equation QS=18 · f2.0between 1 and 10 Hz. At higher frequencies (10–25 Hz), the frequencydependence of Qs weakens, having an average value of QS=990. We also estimated Q from coda waves (QC) using the single-scattering models of Aki andChouet (1975) and Sato (1977). We found that QC=77 · f0.6, (between 2 and 20Hz) at the western side of the mountain chain, using either foreshocks oraftershocks. This relation is consistent with previous estimates of QCreported for the Central Apennines. For a volume sampling the Colfioritobasin, the Apennines and the Marche region we found that QC=55 · f0.8,indicating highattenuation below the mountain belt. To detect small temporal changes ofQ, we calculated spectral ratios of 5 temporal doublets located in theepicentral area and recorded at the closest station. We found temporalchanges of Q that vary from 27% to 56%, depending on the locationof the doublets. This variability suggests that the temporal change ofattenuation may depend on the spatial variation of Q and perhaps on thespatial distribution of tectonic stress in the epicentral area.

Quarkonium suppression as a probe of a saturated gluon plasma?

A dense parton system is expected to be formed in the early stage of relativistic heavy-ion collisions at RHIC energies and above. The probability of a quark–gluon plasma production and the resulting strength of its signatures depends strongly on the initial conditions associated to the distributions of partons in the nuclear wave functions. At very high energies, the growth of parton distributions should saturate, possibly forming a Color Glass Condensate, which is characterized by a bulk momentum scale Qs. As a direct consequence, the possible signatures of the QGP should be Qs-dependent if the saturation scenario is valid for RHIC and LHC. In this Letter we assume the saturation scenario for the QGP formation and estimate the saturation scale dependence of quarkonium suppression. We conclude that, if this scenario is valid, the ϒ suppression only occurs at large values of Qs.

Oxidation Experiment of Natural Megacrystal Clinopyroxene: Implications for Assignment of Mössbauer Spectra

AbstractThe Mössbauer spectra of natural megacrystal clinopyroxene are usually fitted by 4 sets of symmetric doublets, A‐A', B‐B', C‐C' and D‐D', respectively, in terms of increasing Qs value in literature. But the assignments of those doublets are quite different, except the D‐D' doublet assigned to Fe3+at the lattice site M***1 in previous papers. Particularly, the assignment and interpretation of the C‐C' doublet are diverse.The oxidation experiments of natural megacrystal clinopyroxene collected from the Hannuoba basalt, North China, were performed under controlled conditions of temperature at 1000°C and oxygen fugacity of FMQ buffer in 1, 2, ***3 and 5 days respectively. The oxidized samples were then measured by X‐ray diffraction spectrometry and Mössbauer spectrometry. The oxidation of clinopyroxene is characterized by Fe2+ → Fe3+at M1 under the subsolidus conditions, which is consistent with the increase of the area of the D‐D' doublet when the heating time increases. Accordingly, the area of the A‐A' and B‐B' doublets decreases with the increasing heating time. However, the area of C‐C' keeps almost constant.Therefore, the 4 sets of doublets can be assigned correctly as follows: A‐A' doublet to Fe+2at M1, B‐B' Fe2+at M1, C‐C' Fe2+at M2, and D‐D' Fe3+at M1. The M1 site splitting is due to the NNN (Next Nearest Neighbour) effect of the M2 site. The amount of Fe3+at the tetrohedral site of megacrystal clinopyroxene is negligible according to this study.

Preliminary laboratory investigations into the attenuation of compressional and shear waves on near‐surface marine sediments

The attenuation of compressional and shear waves (Qp and Qs) has been studied by several authors but most of these investigations were performed on deep buried reservoir sandstones in order to distinguish between gas and condensate reservoirs and water‐saturated sandstones. We present a preliminary investigation into the use of seismic wave attenuation as a measure of the geotechnical parameters of the near‐surface marine sediments, a little‐studied geological setting. A 6.9 m‐long gravity core was taken from the continental slope of the Barents Sea at a water depth of 2227 m. The core was primarily composed of brown to olive‐grey clayey mud, having a high content of foraminifers and being locally bioturbated. The values of Qp and Qs were determined using the rise‐time method at 19 and 18 different points of the core, respectively, and they were correlated with geotechnical parameters such as wet bulk density, porosity, water content, shear strength and C/P ratio (the ratio of shear strength to overburden pressure). The calculated correlation coefficients for all correlations ranged from −0.39 to 0.41, suggesting that the attenuation characteristics of seismic waves could not be used to derive geotechnical parameters of marine sediments. However, with such a small data set it is difficult to determine clearly whether attenuation is primarily a frequency‐dependent parameter and consequently not related to sediment properties, or whether the limited number of data points is the main factor responsible for the low correlation coefficients observed. Moreover, several different methods are available for the computation of the quality factor Q, and the rise‐time method may not be the most appropriate means of determining the attenuation on near‐surface marine sediments.

Preparation and spectroscopic studies of diorganotin(IV) complexes with adenosine and related compounds

Nine complexes of adenosine and related compounds (adenosine-5'-monophosphate, adenosine-5'-triphosphate, 1-methyl-adenosine, pyridoxal-5-phosphate and β-nicotinamide-adenine-dinucleotide-phosphoric acid) with di-n-butyltin(IV) oxide and/or di-n-butytin(IV) dichloride were prepared in the solid state. The compositions of the complexes were determined by standard analytical methods. It was found that the complexes contain organotin(IV) moiety and the ligand in a ratio of 1:1 or 2:1. The FTIR spectra demonstrated that di-n-butyltin(IV) oxide reacts with the D-ribose moiety of the ligands, while di-n-butyltin(IV) dichloride is co-ordinated to the deprotonated phosphate group. The basic part of the ligands does not participate directly in complex formation. Comparison of the experimental Mossbauer QS values with those calculated on the basis of the PQS concept revealed that the organotin(IV) moiety has trigonal-bipyramidal, octahedral and in some cases tetrahedral geometry also. Some of the complexes contain the organotin(IV) cation in two different surroundings.

Distributions of the hyperfine interaction parameters in (Er 1− xSm x) 2Fe 14B as seen by Mössbauer spectroscopy

The distributions of the hyperfine interaction parameters, caused by substitution of Sm for Er in the (Er 1− x Sm x ) 2Fe 14B system, were studied by Mössbauer spectroscopy both at room and liquid nitrogen temperatures. It was proved that the random distribution of the rare earth atoms over their crystal sites and the additive contribution of the Sm atoms to the values of the hyperfine interaction parameters at the iron crystal sites lead to a linear dependence of the average values of the 57Fe hyperfine magnetic field, isomer shift and quadrupole interaction on the Sm concentration in the present compounds. From these linear relations, the contributions Δ H , Δ IS and Δ QS to the values of the hyperfine magnetic field, isomer shift and quadrupole interaction, caused by the presence of the Sm atom in the nearest neighbour shell of the Fe crystal sites, were derived. No distinct correlations were found between the Δ H , Δ IS and Δ QS values and those of the nearest neighbours and/or their distances from the Fe crystal sites.

Study on Side-Jet Injection Near a Duct Entry With Various Injection Angles

Turbulent flowfields resulting from an oblique jet injecting from a rectangular side-inlet duct into a rectangular main duct with an aspect ratio 3.75 without a forced crossflow are presented in terms of laser-Doppler velocimetry measurements. The main focuses are the effects of the side-jet angle (θ) and side-jet flow rate (Qs) on the mass entrainment upstream of side-jet port and the flowfield in the rectangular duct. The side-inlet angles investigated were 30, 45, and 60 deg and Reynolds numbers based on the air density, rectangular duct height and bulk mean velocity were in the range of 7.1 × 103 to 3.6 × 104 corresponding to Qs values of 1 × 103 to 5 × 103 L/min. The present study suggests the presence of a critical side-injection angle θc (30 ≤ θc ≤ 45 deg) above which a recirculation zone appears in the rectangular duct, whereas below which the recirculation zone is absent. For the more tangential angle (θ = 30 deg), almost as much fluid is entrained into the main duct as was injected from the side jet. The mean flow field in the rectangular duct is found to be a weak function of the Reynolds-number for the range of Qs investigated. In addition, a simple linear correlation between the mass entrainment upstream of the side-jet port and side-injection angle is obtained. Complementary flow visualizations and numerical computations with an algebraic Reynolds stress model were also performed. The discrepancies between measured and computed results are documented.

A quadrupole ion trap/time-of-flight mass spectrometer with a parabolic reflectron.

A matrix-assisted laser desorption/ionization-quadrupole ion trap/reflectron time-of-flight (MALDI-QIT/reTOF) mass spectrometer design and its operation in both normal and tandem mass spectrometric modes are described. A parabolic reflectron was found to be capable of providing mass resolution of 5000 for an initial ion energy distribution ranging over a 50% energy interval of the entire reflectron energy range. The sensitivity, ion isolation and fragmentation efficiency in the MALDI-QIT/reTOF instrument were close to those observed in the MALDI/QIT mass spectrometer. The mass resolution was shown to depend on the extraction field potentials, the r.f. trapping voltage amplitude and the phase of shutting down the r.f. voltage before extraction. At values of qs < 0.3-0.4 the mass resolution does not depend on the ion mass, is in a range of 1000-1400 and is governed by the extraction voltages and the ion temperature before extraction, the latter shown to be in the range 1180-1690 K. The variation of the mass resolution for ions at values of qs > 0.4 is irregular but normally it is lower than that for ions having lower qs values. Mass spectral line positions shifted when the trapping voltage before extraction was varied. The line shifts were larger for lower mass ions and were comparable to the line widths in the case of very low masses.

The effect of organic oxidants on the oxidation of the Fe(II) ferrocenyl acetylide diphosphine complex. A clear linearity of the Mössbauer parameter in the Fe(III)–Fe(II) species dependent on the organic oxidant

The Fe(II) ferrocenylacetylide complex, [(η-Cp)(dppe)FeCCFc], was oxidized by various organic oxidants. The stability of the one-electron oxidized species depended on the oxidants. The oxidized complexes exhibited an intervalence transfer band at ∼1600 nm, suggesting that these are highly electron-delocalized mixed-valence complexes. The IR spectra ( ν CC=1956–1976 cm −1) and the Mössbauer spectra (QS=2.17–2.48 and 1.03–1.46 mm s −1) support the above suggestion. There is a linear relationship between the QS values of the Fc and the (η-Cp)(dppe)Fe sites in the oxidized species.

Glucose metabolism in the yeast Schwanniomyces castellii: role of phosphorylation site I and an alternative respiratory pathway.

Glucose metabolism in a Crabtree-negative yeast, Schwanniomyces castellii, and a cytochrome b-deficient mutant of this strain was investigated in chemostat culture. The wild-type and mutant strains exhibited the same behavior. Oxidative metabolism was observed when the substrate uptake rate (qS) was low. Fermentative metabolites were excreted when the qS value was higher than 0.40 g.g-1.h-1, indicating the occurrence of a respirofermentative metabolism; however, the respiratory quotient (RQ) remained near 1. When fermentation occurred, the cytochrome pathway was repressed but not the salicylhydroxamic acid (SHAM)-sensitive pathway. The presence of an alternative SHAM-sensitive respiratory pathway and the presence of phosphorylation site I in all metabolic conditions explained the RQ value of 1 and accounted for high biomass yields in oxidative metabolism conditions (0.62 g.g-1 for the wild-type strain and 0.31 g.g-1 for the cytochrome b-deficient mutant strain).

Iron Distribution in High P-T Garnets from Sittampundi Granulites, and its Geochemical Implications

Garnets from high P—T granulite field of Sittampundi, Tamil Nadu were investigated by 57Fe Mössbauer spectroscopy. The room temperature (298 K) three-band spectra, which have been splitted to two doublets, reveal Fe2+ ions to be exclusively located at dodecahedral site (IS = 1.303–1.389 mm/s; QS = 3.423–3.822 mm/s) and Fe3+ at tetrahedral site (IS = 0.0060.163 mm/s; QS = 0.520–0.663 mm/s). The Fe3+/∑Fe ratios vary between 0.073 and 0.150, which indicate its formation at high P—T field. The high values of QS of tetrahedral Fe3+ suggest that the occupied site is very regular with little distortion. The fairly broad line-width (FWHM, 0.455–0.596 mm/s) of Fe3+ doublet may arise from a substitution of some tetrahedral Si by (OH)− group. The strong partition and ordering of Fe2+ and Fe3+ in dodecahedral and tetrahedral sites, having octahedral sites totally free from iron, suggest in a strong measure of slow cooling and recrystallization of garnet through decompression. The presence of tetrahedral Fe3+ strongly depicts the existence of octahedral Si, amounting to an excess of saturation value for tetrahedral sites by Si + Fe3+ ions together at these sites.

Influence of roasting on the water sorption isotherms of nuts / Influencia del tueste sobre las isotermas de sorción de agua de diferentes frutos secos

This work studies the influence of the roasting process on sorption isotherms of almond, hazelnut and peanut over the normal range of storage temperatures (5, 25 and 45 °C) The results obtained showed that water sorption properties of unroasted nuts are affected by fat content. The mono layer moisture content and water affinity (sorption heat, Qs) increased when the nut fat content decreased. After roasting, a more homogeneous water affinity was observed for the different products, although fat content still affected the monolayer capacity. Also, roasting reduced mono layer moisture content and Qs values in each sample and made the moisturizing process less spontaneous (decreasing the thermodynamic driving force). These results are consistent with an increase of the hydrophobicity of the cellular components of nuts due to the enhancement of lipid interactions. The water binding properties of active points in the roasted products were reduced and, hence, some water sorption active points disappeared.

Local stability criterion for stars and gas in a galactic disc

We obtain the criterion for local stability against axisymmetric perturbations in gravitationally coupled stars and gas in a galactic disc. The stars and gas are treated as two isothermal fluids, with the random velocity dispersion being higher in stars than in gas. The aim is to obtain a quantitative measure of the mutual destabilizing effect of the two components on each other. The problem is phrased in terms of a complete set of three dimensionless parameters: Qs and Qg the standard Q parameters for local stability for stars alone and gas alone, respectively, and ε, the gas mass fraction in the disc. The results for Qs−g, the two-fluid local stability parameter, and ls−g, the dimensionless wavelength at which it is hardest to stabilize the two-fluid system, are obtained seminumerically as a function of Qs, Qg and ε and are presented as contour plots. The Qs−g values are lower than the one-fluid Qs or Qg values, especially for high gas fractions (ε ≥ 0.15), indicating that the star-gas disc is more unstable than either constituent fluid by itself. ls−g shows a bimodal distribution for low gas fractions (ε ≤ 0.1 ) — that is, for low Qs values ls−g is in the stellar regime of high wavelengths, and vice versa. In contrast, for high gas fractions (ε ≥ 0.15), the variation is smooth. Some applications of these results for the theoretical studies of stability and evolution of galaxies are discussed.