Context.
With an estimated diameter in the 320–350 km range, (704) Interamnia is the fifth largest main belt asteroid and one of the few bodies that fills the gap in size between the four largest ...bodies with
D
> 400 km (Ceres, Vesta, Pallas and Hygiea) and the numerous smaller bodies with diameter ≤200 km. However, despite its large size, little is known about the shape and spin state of Interamnia and, therefore, about its bulk composition and past collisional evolution.
Aims.
We aimed to test at what size and mass the shape of a small body departs from a nearly ellipsoidal equilibrium shape (as observed in the case of the four largest asteroids) to an irregular shape as routinely observed in the case of smaller (
D
≤ 200 km) bodies.
Methods.
We observed Interamnia as part of our ESO VLT/SPHERE large program (ID: 199.C-0074) at thirteen different epochs. In addition, several new optical lightcurves were recorded. These data, along with stellar occultation data from the literature, were fed to the All-Data Asteroid Modeling algorithm to reconstruct the 3D-shape model of Interamnia and to determine its spin state.
Results.
Interamnia’s volume-equivalent diameter of 332 ± 6 km implies a bulk density of
ρ
= 1.98 ± 0.68 g cm
−3
, which suggests that Interamnia – like Ceres and Hygiea – contains a high fraction of water ice, consistent with the paucity of apparent craters. Our observations reveal a shape that can be well approximated by an ellipsoid, and that is compatible with a fluid hydrostatic equilibrium at the 2
σ
level.
Conclusions.
The rather regular shape of Interamnia implies that the size and mass limit, under which the shapes of minor bodies with a high amount of water ice in the subsurface become irregular, has to be searched among smaller (
D
≤ 300 km) less massive (
m
≤ 3 × 10
19
kg) bodies.
•Ag 3d5/2 binding energy for Ag(II)SO4 is as large as 370.1eV.•This is the largest value ever measured for a silver (II) compound.•Large shift is connected with the extreme oxidizing nature of Ag(II) ...species.•Ag(I)2S2O7 exhibits both positive and negative shifts with respect to metallic Ag.•Two distinct Ag(I) sites are responsible for large BE difference of 3.6eV.
Anomalous chemical shifts, i.e. cases when binding energy decreases with the increase of the oxidation state, have been well-documented for selected compounds of silver, and well understood based on analysis of initial- and final-state effects in the XPS spectra. Here we report two examples of even more exotic behaviour of chemical shifts for two silver compounds. The first one is Ag2S2O7 which exhibits both positive and negative substantial shifts with respect to metallic Ag for two distinct Ag(I) sites in its crystal structure, which differ by as much as 3.6eV. Another is AgSO4, a rare example of oxo silver (II) salt, which exhibits “normal” chemical shift but the Ag 3d5/2 binding energy takes the largest value measured for a silver (II) compound (370.1eV). This property is connected predominantly with the extremely strongly oxidizing nature of Ag(II) species.
ABSTRACT
High angular resolution disc-resolved images of (7) Iris collected by VLT/SPHERE instrument are allowed for the detailed shape modelling of this large asteroid revealing its surface ...features. If (7) Iris did not suffer any events catastrophic enough to disrupt the body (which is very likely) by studying its topography, we might get insights into the early Solar system’s collisional history. When it comes to internal structure and composition, thoroughly assessing the volume and density uncertainties is necessary. In this work, we propose a method of uncertainty calculation of asteroid shape models based on light curve and adaptive optics (AO) images. We apply this method on four models of (7) Iris produced from independent Shaping Asteroids using Genetic Evolution and All-Data Asteroid Modelling inversion techniques and multiresolution photoclinometry by deformation. Obtained diameter uncertainties stem from both the observations from which the models were scaled and the models themselves. We show that despite the availability of high-resolution AO images, the volume and density of (7) Iris have substantial error bars that were underestimated in the previous studies.
Context. The shapes and spin states of asteroids observed with photometric techniques can be reconstructed using the lightcurve inversion method. The resultant models can then be confirmed or ...exploited further by other techniques, such as adaptive optics, radar, thermal infrared, stellar occultations, or space probe imaging. Aims. During our ongoing work to increase the set of asteroids with known spin and shape parameters, there appeared a need for displaying the model plane-of-sky orientations for specific epochs to compare models from different techniques. It would also be instructive to be able to track how the complex lightcurves are produced by various asteroid shapes. Methods. Basing our analysis on an extensive photometric observational dataset, we obtained eight asteroid models with the convex lightcurve inversion method. To enable comparison of the photometric models with those from other observing/modelling techniques, we created an on-line service where we allow the inversion models to be orientated interactively. Results. Our sample of objects is quite representative, containing both relatively fast and slow rotators with highly and lowly inclined spin axes. With this work, we increase the sample of asteroid spin and shape models based on disk-integrated photometry to over 200. Three of the shape models obtained here are confirmed by the stellar occultation data; this also allowed independent determinations of their sizes to be made. Conclusions. The ISAM service can be widely exploited for past and future asteroid observations with various, complementary techniques and for asteroid dimension determination.
AIMS: To determine if Butyrivibrio fibrisolvens strain 3071 is able to use fructose polymers for growth and to identify the enzymes involved in their digestion. METHODS AND RESULTS: Strain 3071 ...utilized 97, 89, 85 and 60% of sucrose, timothy grass fructan, inulin oligosaccharides and inulin, respectively, in the growth medium. A cell extract from timothy grass fructan‐grown bacteria was used for identification of fructanolytic enzymes by anion exchange chromatography, gel filtration, zymography and thin‐layer chromatography. The bacterium synthesizes a specific endolevanase and a nonspecific β‐fructofuranosidase. Both enzymes occurred in two forms differing in molecular weight. The β‐fructofuranosidase was not able to digest long‐chain inulin or timothy grass fructan, but degraded inulin oligosaccharides and sucrose. Addition of 1,4‐dithioerythritol to an enzyme solution did not affect the activity of endolevanase(s), but increased the ability of β‐fructofuranosidase to digest sucrose. The digestion of timothy grass fructan by endolevanase(s) was described by Michaelis–Menten kinetics in which Kₘ = 2·82 g l⁻¹ and Vₘₐₓ = 4·01 μmoles reducing sugar equivalents × mg⁻¹ × min⁻¹. CONCLUSION: Strain 3071 synthesizes enzymes enabling it to use grass fructans for growth. SIGNIFICANCE AND IMPACT OF THE STUDY: Butyrivibrio fibrisolvens strain 3071 can be considered a member of the rumen fructanolytic guild.
Asteroids' spin axis distribution Marciniak, A.; Michałowski, T.
Astronomy and astrophysics (Berlin),
03/2010, Letnik:
512
Journal Article
Recenzirano
Odprti dostop
Analysing the database of asteroid models from inversion techniques (DAMIT), we found that the spin axis of asteroids do not avoid the ecliptic plane, which had been widely understood since the early ...days of asteroid physical studies. Previously observed depopulation was probably caused by the EAM methods bias, which is absent if the asteroid shapes are modelled as more complex rather than triaxial ellipsoids.
Aims. Asteroid (1862) Apollo is one of two asteroids in which the YORP effect was detected. We carried out new photometric observations of Apollo in April 2007 to enlarge the time line and to derive ...a more precise shape and spin state model. We also observed another YORP-candidate, asteroid (25143) Itokawa, in December 2006 and January 2007 to obtain a longer time line. An estimation of the YORP strength on Itokawa based on its precise shape model from the Hayabusa mission predicted the deceleration to be already observable during the 2007 apparition. Methods. We used the lightcurve inversion method to model the shape and spin state of Apollo. For Itokawa, the shape and pole direction are known to a high degree of accuracy from the Hayabusa mission, so we used a modified version of lightcurve inversion with only two free parameters – the rotation period and its linear change in time. Results. The new model of Apollo confirms earlier results. The observed acceleration of Apollo's rotation rate is $(5.5 \pm 1.2) \times 10^{-8}\,\mathrm{rad\,d}^{-2}$, which is in agreement with the theoretically predicted value. For Itokawa, the theoretical YORP value is sensitive to the resolution of the shape model and lies in the range from -2 to $-3\times 10^{-7}\,\mathrm{rad\,d}^{-2}$. This is inconsistent with results of lightcurve inversion that place an upper limit to the change of Itokawa's rotation rate ∼$1.5 \times 10^{-7}\,\mathrm{rad}\,\mathrm{d}^{-2}$.
Murein polysaccharides may contribute to a considerable part of the dry matter of bacterial cells. Their utilization by protozoa inhabiting the rumen is, however, poorly recognized. The objective of ...this study was to examine the ability of three species of ciliates, i.e.,
Eudiplodinium maggii
,
Diploplastron affine
, and
Entodinium caudatum
of digest, and ferment these saccharides. The cultivation experiments showed that the enrichment of growth medium with bacterial cell wall β-glycans increased the ciliate number (
p
< 0.05). A statistically significant increase (
p
< 0.01) was followed by a continuous decrease (
p
< 0.01) in the percentage of individuals containing β-glycans particles after 4- and 24-h incubation of ciliates with this substrate, respectively. The enzymatic experiments confirmed the ability of the examined protozoa to digest murein.
E. caudatum
exhibited the highest activity (8.2 unit (U)/mg protein per min), and
E. maggii
, the lowest (3.0 U/mg protein per min). The production rates of volatile fatty acids by starved and fed ciliate species were 0.7 and 1.6 (
E. caudatum
) pmol/ciliate cell per h, 30.5 and 42.5 (
E. maggii
) pmol/ciliate cell per h, and 8.3 and 19.2 (
D. affine
) pmol/ciliate cell per h (
p
< 0.05).
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