Copper (Cu) is increasingly important as the global economy becomes more reliant on renewable energy sources. The Mount Isa Inlier, NW Queensland, is one of Australia's most important metallogenic ...provinces, hosting several deposits of Cu, Pb, Zn, Ag and U, including the famous world-class Mount Isa deposit. The Mount Isa Cu-Pb-Zn-Ag deposit is the second largest producer of Cu in Australia, yet the formation, geometry and timing of the mineralisation is still debated. One reason for this lack of consensus is that Mount Isa has undergone a long and complex deformation history with north-south shortening (D1), east-west shortening (D2), top to the east shear (D3), ENE-WSW shortening (D4a), WNW-ESE shortening (D4b), and east-west shortening (D5a and D5b). Recent studies at Mount Isa have suggested that Cu mineralisation initiated in D4a and proceeded through to the main Cu mineralisation in D4b, where the orebodies have a strong structural control on their geometries. Foliation boudinage structures, which form in anisotropic and homogeneous rocks, have been identified in the Mount Isa Cu orebodies. Confusions in terminology that exist in the foliation boudinage literature have required a detailed review of the literature leading to a synthesis of current ideas. The formation and development of foliation boudinage structures have previously been modelled in 2-dimensions through analogue and computer techniques. However, no previous studies have investigated the formation and evolution of natural foliation boudinage structures in 3-dimensions. This study combines structural observations, kinematic analysis, petrography, and 3-dimensional modelling of foliation boudinage structures using computerised tomography (CT) and serial sectioning, to constrain their timing and importance in the mineralisation at Mount Isa and to infer the processes involved in their evolution. Small scale foliation boudinage structures were sampled in drill core proximal to the Mount Isa Cu deposit and their orientations were recorded. Most drillholes analysed at Mount Isa were unoriented, however, foliation boudinage structures have been reoriented using new methods developed in this study. Desurveying methods were first compared to find the most precise method for plotting the drillhole pathway using examples from Mount Isa. New computer code was developed to determine the orientations and positions of drillholes along their entire length using the existing desurveying methods. The drillhole survey measurements given by the computer codes allow the original orientations of the foliation boudinage structures to be determined. Foliation boudinage structures occur most commonly in the unaltered Urquhart Shale where the anisotropy and homogeneity provided by the shale layering is intact. Detailed petrographic analysis of the foliation boudinage structures has identified that an initial rim of quartz and dolomite was followed by infill and replacement by later sulphides. The dominant sulphides in the foliation boudinage structures are pyrrhotite and minor chalcopyrite, both associated with the Cu mineralisation at Mount Isa. The paragenesis of the foliation boudinage structures is consistent with the established paragenesis of the main Cu mineralisation. The foliation boudinage structures plunge gently to the north and south as a result of approximately layer-normal shortening and layer-parallel extension of the steeply west-dipping Urquhart Shale. North-plunging structures formed by ENE-WSW dextral-reverse shortening during the D4a deformation event and the south-plunging structures formed by WNW-ESE sinistral-reverse shortening during the D4b deformation event. Electron Backscatter Diffraction (EBSD), combined with 2-dimensional and 3-dimensional strain analyses show that the ore-related sulphide mineral infills of foliation boudinage structures at Mount Isa have undergone significant intracrystalline deformation. Pyrrhotite grains show well-developed grain shape and crystallographic preferred orientations, with c-axes normal to the shale layers. The strain ellipsoid shows a change from plane to flattening strain, indicating a progressive deformation during foliation boudinage. Previous studies have suggested that the foliation boudinage structures remain as fluid filled voids throughout their development. However, strain of the pyrrhotite infill, which has a low strength under the conditions of deformation, indicate that the voids were mostly filled during the final stages of foliation boudinage. 3-dimensional modelling of foliation boudinage structures suggest a model of propagation along their long-axes, with the oldest sections, greatest displacements, and most complex mineral phase boundaries in the central part of the structure, in a similar fashion to faults. Stages identified in the evolution of foliation boudinage structures at Mount Isa, are: 1) dolomite replacement of unaltered shale, 2) fracture and cleavage development, 3) exploitation of existing discontinuities by the developing structures during shortening, 4) silica-dolomite infill and 5) final infill with ore related sulphides. As the foliation boudinage structures at Mount Isa exploit existing discontinuities, fluid pressures during foliation boudinage are likely to be lower than during other types of foliation boudinage developed within undeformed host rocks. This study, along with recent studies at Mount Isa, contrast to previous ideas about the Cu orebodies, and enable an improved explanation for their geometries, kinematics, and timing. This study supports the most recent ideas that the structural controls on the Mount Isa Cu orebodies resulted from epigenetic mineralisation at the time of ENE-WSW and WNW-ESE shortening of the Urquhart Shale during D4 deformation. This relatively late timing of foliation boudinage and Cu mineralisation in the deformation sequence is in contrast to the syngenetic and early timing of Cu mineralisation proposed by some previous authors. The strain and kinematics expected in both D4a and D4b are recorded in the formation and evolution of foliation boudinage structures at Mount Isa. The drill core scale structures proximal to the Cu orebodies may be used as a tool for vectoring towards mineralisation at the Mount Isa deposit. Foliation boudinage structures likely impart a structural control on the Cu mineralisation at the scale of the orebodies and may control the geometries of other deposits in similar rock types.
In the first part of this thesis we study string corrections to one-loop amplitudes of single-particle half-BPS operators Op in AdS₅ × S⁵. The tree-level correlators (dual to AdS scattering ...amplitudes via the AdS/CFT correspondence) in supergravity enjoy an accidental 10d conformal symmetry. Consequently, one observes a partial degeneracy in the spectrum of anomalous dimensions of double-trace operators and at the same time equality of many different correlators for different external charges pᵢ=1,2,3,4. The one-loop contribution is expected to lift such bonus properties, and its precise form can be predicted from tree-level data and consistency with the operator product expansion. Here we present a closed-form Mellin space formula for ⟨Op₁ Op₂ Op₃ Op₄ ⟩ at order λ⁻³/² in the expansion around large λ valid for arbitrary external charges pᵢ. Our formula makes explicit the lifting of the bonus degeneracy among different correlators through a feature we refer to as 'sphere splitting'. While tree-level Mellin amplitudes come with a single crossing symmetric kernel, which defines the pole structure of the AdS₅ × S⁵ amplitude, our one-loop amplitude naturally splits the S⁵ part into two separate contributions. The amplitude also exhibits a remarkable consistency with the corresponding flat space IIB amplitude through the large p limit. In the second part of this thesis we study the relation between the branch cut structure of scattering amplitudes in planar N = 4 SYM and Grassmannian cluster algebras using the novel language of Gröbner theory. We detail how to extract the familiar A-coordinates and their respective adjacency conditions from the Gröbner fan of the Plücker ideal. Having established this connection we apply similar techniques to the case of non dual conformal invariant five-point kinematics where we extract the full non-planar symbol alphabet relevant for the construction of five-point integrals/amplitudes. Finally, we continue to study the connection between cluster algebras and scattering amplitudes by considering the family of partial flag cluster algebras F (2, 4, n) in order to extract information on the symbol alphabet for amplitudes with five-point and six-point non dual conformal invariant kinematics.
We present a detailed study of the nuclear star clusters (NSCs) and massive black holes (BHs) of four of the nearest low-mass early-type galaxies: M32, NGC 205, NGC 5102, and NGC 5206. We measure the ...dynamical masses of both the BHs and NSCs in these galaxies using Gemini/NIFS or VLT/SINFONI stellar kinematics, Hubble Space Telescope (HST) imaging, and Jeans anisotropic models. We detect massive BHs in M32, NGC 5102, and NGC 5206, while in NGC 205, we find only an upper limit. These BH mass estimates are consistent with previous measurements in M32 and NGC 205, while those in NGC 5102 and NGC 5206 are estimated for the first time and both found to be <106 M . This adds to just a handful of galaxies with dynamically measured sub-million M central BHs. Combining these BH detections with our recent work on NGC 404's BH, we find that 80% (4/5) of nearby, low-mass ( M ; km s−1) early-type galaxies host BHs. Such a high occupation fraction suggests that the BH seeds formed in the early epoch of cosmic assembly likely resulted in abundant seeds, favoring a low-mass seed mechanism of the remnants, most likely from the first generation of massive stars. We find dynamical masses of the NSCs ranging from 2 to 73 × 106 M and compare these masses to scaling relations for NSCs based primarily on photometric mass estimates. Color gradients suggest that younger stellar populations lie at the centers of the NSCs in three of the four galaxies (NGC 205, NGC 5102, and NGC 5206), while the morphology of two are complex and best fit with multiple morphological components (NGC 5102 and NGC 5206). The NSC kinematics show they are rotating, especially in M32 and NGC 5102 ( ).
Gaia Data Release 3 de Laverny, P.; Spagna, A.; Vallenari, A. ...
Astronomy and astrophysics (Berlin),
06/2023, Letnik:
674
Journal Article, Web Resource
Recenzirano
Odprti dostop
Context.
The motion of stars has been used to reveal details of the complex history of the Milky Way, in constant interaction with its environment. Nevertheless, to reconstruct the Galactic history ...puzzle in its entirety, the chemo-physical characterisation of stars is essential. Previous
Gaia
data releases were supported by a smaller, heterogeneous, and spatially biased mixture of chemical data from ground-based observations.
Aims.
Gaia
Data Release 3 opens a new era of all-sky spectral analysis of stellar populations thanks to the nearly 5.6 million stars observed by the Radial Velocity Spectrometer (RVS) and parametrised by the GSP-Spec module. In this work, we aim to demonstrate the scientific quality of
Gaia
’s Milky Way chemical cartography through a chemo-dynamical analysis of disc and halo populations.
Methods.
Stellar atmospheric parameters and chemical abundances provided by
Gaia
DR3 spectroscopy are combined with DR3 radial velocities and EDR3 astrometry to analyse the relationships between chemistry and Milky Way structure, stellar kinematics, and orbital parameters.
Results.
The all-sky
Gaia
chemical cartography allows a powerful and precise chemo-dynamical view of the Milky Way with unprecedented spatial coverage and statistical robustness. First, it reveals the strong vertical symmetry of the Galaxy and the flared structure of the disc. Second, the observed kinematic disturbances of the disc – seen as phase space correlations – and kinematic or orbital substructures are associated with chemical patterns that favour stars with enhanced metallicities and lower
α
/Fe abundance ratios compared to the median values in the radial distributions. This is detected both for young objects that trace the spiral arms and older populations. Several
α
, iron-peak elements and at least one heavy element trace the thin and thick disc properties in the solar cylinder. Third, young disc stars show a recent chemical impoverishment in several elements. Fourth, the largest chemo-dynamical sample of open clusters analysed so far shows a steepening of the radial metallicity gradient with age, which is also observed in the young field population. Finally, the
Gaia
chemical data have the required coverage and precision to unveil galaxy accretion debris and heated disc stars on halo orbits through their
α
/Fe ratio, and to allow the study of the chemo-dynamical properties of globular clusters.
Conclusions.
Gaia
DR3 chemo-dynamical diagnostics open new horizons before the era of ground-based wide-field spectroscopic surveys. They unveil a complex Milky Way that is the outcome of an eventful evolution, shaping it to the present day.
Footwear Science The influence of variations in heel and forefoot midsole stiffness on sagittal plane kinematics and joint moments at the knee and ankle
Elastomer-based soft-continuum robots with an extensible backbone exhibit high flexibility. These manipulators might show nonlinear kinematic behaviors due to, for example, the material ...hyperelasticity and means of actuation. Formulating a reliable kinematic model for an effective inverse kinematics control strategy is challenging, but is paramount for allowing effective manoeuvrability and controllability. In this article, we devise a kinematic modeling and control method for pneumatic-driven soft-continuum robots (up to 100% elongation ratio). The method is based on the Cosserat rod model including a pressure-dependent dynamic modulus. The kinematic model and control strategy are then expressed as nonlinear least-squares optimization problems. Hence, various inverse kinematics control modes can be achieved for a multisegment robot, e.g., tip position and orientation control of the overall robot or tip position control of each segment. Simulations and experiments are both conducted to validate the proposed method. The results highlight the high fidelity of the modeling technique and the effectiveness of the proposed inverse kinematics controller. In particular, the modeling and trajectory control errors for a two-segment robot are smaller than 4.5 mm, i.e., 5% of the robot's overall length.
Context.
Stellar dynamic-based black hole mass measurements of M 87 are twice that determined via ionized gas kinematics; the former are closer to the mass estimated from the diameter of the ...gravitationally lensed ring around the black hole.
Aims.
Using a deeper and more comprehensive ionized gas kinematic data set, we aim to better constrain the complex morphology and kinematics of the nuclear ionized gas and thus gain insights into the reasons behind the disagreement between the mass measurements.
Methods.
We use new narrow field mode with adaptive optics and wide field mode integral field spectroscopic data from the Multi Unit Spectroscopic Explorer instrument on the Very Large Telescope to model the morphology and kinematics of multiple ionized gas emission lines (primarily H
α
+N II
λλ
6548,6583 and O I
λ
6300) in the nucleus of M 87. We used
Kinemetry
to fit the position angle, inclination, and velocities of the subarcsecond ionized gas disk. We used
KinMSpy
to create simulated datacubes across a range of black hole masses and disk inclinations, and parameterized the differences of the resulting residual (observed minus simulated) velocity maps, in order to obtain the best-fit model.
Results.
The new deep data set reveals complexities in the nuclear ionized gas kinematics that were not seen in earlier sparse and shallower
Hubble
Space Telescope spectroscopy. Several ionized gas filaments, some with high flow velocities, can be traced down into the projected sphere of influence. However, not all truly pass close to the black hole. Additionally, we find evidence of a partially filled biconical outflow, aligned with the jet, with radial velocities of up to 400 km s
−1
. The subarcsecond rotating ionized gas “disk” is well resolved in our datacubes. The velocity isophotes of this disk are twisted, and the position angle of the innermost gas disk (≲5 pc) tends toward a value perpendicular to the radio jet axis. The complexity of the nuclear morphology and kinematics (the mix of a warped disk with spiral arms, large linewidths, strong outflows, and filaments crossing the black hole in projection) precludes the measurement of an accurate black hole mass from the ionized gas kinematics. Two results, each relatively weak but together more convincing, support a high-mass black hole (∼6.0 × 10
9
M
⊙
) in a low-inclination disk (
i
∼ 25°) rather than a low-mass black hole (∼3.5 × 10
9
M
⊙
) in a
i
= 42° disk: (a)
Kinemetry
fits to the subarcsecond disk support inclinations of ∼20°–25° rather than 42°; and (b) velocity residual (observed minus simulated) maps with slightly smaller residuals are found for the former case. The specific (sub-Keplerian) radiatively inefficient accretion flow (RIAF) model previously proposed to reconcile the mass measurement discrepancy was also tested: the sub-Keplerian factor used in this model is not sufficiently small to make a high-mass black hole in a RIAF inflow masquerade as a low-mass black hole in a Keplerian inflow. In general, Keplerian disk models perform significantly better than the RIAF model when fitting the subarcsecond ionized gas disk.
Conclusions.
A disk inclination close to 25° for the nuclear gas disk (rather than the previously posited 42°) and the warp in the subarcsecond ionized gas disk help reconcile the contradictory nature of key earlier results: (a) the mass discrepancy between stellar and ionized gas black hole masses (our results support the former) and (b) the misorientation between the axes of the ionized gas disk and the jet (we find them to be aligned in both two and three dimensions). Furthermore, we identify a previously unknown 400 km s
−1
(partially filled) biconical outflow along the (three-dimensional) jet axis and show that the velocities of the two largest ionized gas filaments at 8″–30″ nuclear distances can be explained primarily by rotation in the extension of the nuclear ionized gas disk (inclination ∼25°).
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