Geostationary payload concepts for personal satellite communications

This paper reviews candidate satellite payload architectures for systems providing world-wide communication services to mobile users equipped with hand-held terminals based on large geostationary satellites. There are a number of problems related to the payload architecture, on-board routing and beamforming, and the design of the S-band Tx and L-band Rx antenna and front ends. A number of solutions are outlined, based on trade-offs with respect to the most significant performance parameters such as capacity, G/T, flexibility of routing traffic to beams and re-configuration of the spot-beam coverage, and payload mass and power. Candidate antenna and front-end configurations were studied, in particular direct radiating arrays, arrays magnified by a reflector and active focused reflectors with overlapping feed clusters for both transmit (multimax) and receive (beam synthesis). Regarding the on-board routing and beamforming sub-systems, analog techniques based on banks of SAW filters, FET or CMOS switches and cross-bar fixed and variable beamforming are compared with a hybrid analog/digital approach based on Chirp Fourier Transform (CFT) demultiplexer combined with digital beamforming or a fully digital processor implementation, also based on CFT demultiplexing

L'ensenyament de la Salut Pública a Catalunya

Un dels aspectes clau de la política sanitària és el dels recursos humans. Pel seu cost, però també per la naturalesa mateixa dels serveis de salut, on la majoria d¡activitats s'han de fer de manera personalitzada. I encara és més important la qüestió si tenim en compte la necessitat d'un canvi substancial en les orientacions tradicionals, com demana l'OMS quan reformula els objectius per assolir la 'salut per a tothom l'any 2000'. [...

Quantifying deformation processes in the SE Pyrenees using U-Pb dating of fracture-filling calcites

It is difficult to quantify the timing of the deformation processes in brittle fold-thrust belts because minerals suitable for dating and well-preserved growth strata sediments are scarce or absent. Here, we quantify the duration of thrust sheet emplacement and shortening rates in the SE Pyrenean thrust sequence using U-Pb dating of fracture-filling calcites. The obtained U-Pb dates reveal a minimum duration for the emplacement of each thrust unit (18.7 Ma for the Bóixols-Upper Pedraforca, 11.6 Ma for the Lower Pedraforca and 14.3 Ma for the Cadí thrust sheets) and show that piggy-back thrusting was accompanied by post-emplacement deformation of the upper thrust sheets above the lower sheets during their south-directed tectonic transport. We calculated shortening rates of 0.6, 3.1 and 1.1 mm a−1 from the older to younger emplaced thrust sheets. Our results also reveal the formation of local normal faults during the late Oligocene as a result of the late stages of compression and exhumation in the SE Pyrenees. We observed that temperatures >110 °C could be a limiting factor when applying the U-Pb dating method

The contact uranium prospect, Kiggavik project, Nunavut (CVanada): Tectonic history, structural constrains and timing of mineralization

Uranium mineralization in the Kiggavik area, on the eastern border of the Thelon basin (Nunavut, Canada), hosts significant uranium resources within the basement and its understanding is critical to comprehending the genesis of unconformity-related deposits' structural controls and therefore exploration of these types of deposits in this prospective district. This article deciphers the complex multiphase fracture network associated with uranium mineralization of the most recently discovered, basement-hosted prospect in the Kiggavik area, named Contact. The Contact prospect is located along the Andrew Lake Fault (ALF), a major NE-SW fault corridor in the area. This study combines field work, drillcore logging, sampling, and macro- to micro- petro-structural analyses. Key results from this study highlight that the NE-trending ALF, along with the ENE-trending Thelon (TF) and Judge Sissons (JSF) faults, formed early during intracratonic rifting and deposition of the Baker Lake and Wharton groups (ca. 1850-1750 Ma) in response to the Thelon and Trans-Hudsonian orogeny. The ALF was affected by a strong silicification-brecciation event that likely developed at ca. 1750 Ma, and partitioned later deformation and fluid circulation. In the Contact prospect, the ALF was reactivated multiple times and mineralized in three stages with distinctive secondary fracture patterns, alteration, and mineralization types. Ten fracture stages have been identified at the Contact prospect, f1-f10. The first stage of mineralization, coeval with f5, is related to fluids of unconstrained origin that circulated through E-W faults in the area that locally re-activated quartz veins of the brecciation event at the intersection with the ALF. Mineralization at this stage is polymetallic and associated with weak clay alteration. The second stage of uranium mineralization occurred coeval with transtensional reactivation of the NE-SW trending ALF (f6c) and in relation to circulation of oxidizing basinal brines within the fault zone. Mineralization at this stage is monometallic and associated with illite and sudoite alteration. Later reactivation of the inherited fracture network (f8) led to strong illitization and bleaching of the host rock, with local reworking of the ore body. Finally, reactivation of the fracture network during f9 and 10 lead to circulation of meteoric fluids that remobilized mineralization in a third stage of uranium re-concentration along redox fronts, with strong illitization and bleaching of the host rock. Unlike the classic unconformity-related uranium deposits in the Athabasca Basin where clay alteration halos occur around the ore bodies related to mineralizing processes, in the Contact prospect the strongest clay alteration event (f8) postdates both main stages of mineralization. Along with uranium remobilization, the basement-hosted Contact prospect is likely a relict of what was once a larger deposit

BOLD Coupling between Lesioned and Healthy Brain Is Associated with Glioma Patients’ Recovery

Predicting functional outcomes after surgery and early adjuvant treatment is difficult due to the complex, extended, interlocking brain networks that underpin cognition. The aim of this study was to test glioma functional interactions with the rest of the brain, thereby identifying the risk factors of cognitive recovery or deterioration. Seventeen patients with diffuse non-enhancing glioma (aged 22–56 years) were longitudinally MRI scanned and cognitively assessed before and after surgery and during a 12-month recovery period (55 MRI scans in total after exclusions). We initially found, and then replicated in an independent dataset, that the spatial correlation pattern between regional and global BOLD signals (also known as global signal topography) was associated with tumour occurrence. We then estimated the coupling between the BOLD signal from within the tumour and the signal extracted from different brain tissues. We observed that the normative global signal topography is reorganised in glioma patients during the recovery period. Moreover, we found that the BOLD signal within the tumour and lesioned brain was coupled with the global signal and that this coupling was associated with cognitive recovery. Nevertheless, patients did not show any apparent disruption of functional connectivity within canonical functional networks. Understanding how tumour infiltration and coupling are related to patients’ recovery represents a major step forward in prognostic development.Consejeria de Economia, Innovacion, Ciencia y Empleo.Junta de Andalucia CV20-45250; A-TIC-080-UGR18; B-TIC-586-UGR20; P20-0052

Fluid Dynamics in a Thrust Fault Inferred from Petrology and Geochemistry of Calcite Veins: An Example from the Southern Pyrenees

Petrographic and geochemical analyses (δ18O, δ13C, 87Sr/86Sr, clumped isotopes, and elemental composition) coupled with field structural data of synkinematic calcite veins, fault rocks, and host rocks are used to reconstruct the episodic evolution of an outstanding exposed thrust zone in the Southern Pyrenees and to evaluate the fault behavior as a conduit or barrier to fluid migration. The selected thrust displaces the steeply dipping southern limb of the Sant Corneli-Bóixols anticline, juxtaposing a Cenomanian-Turonian carbonate unit against a Coniacian carbonate sequence. Successive deformation events are recorded by distinct fracture systems and related calcite veins, highlighting (i) an episodic evolution of the thrust zone, resulting from an upward migration of the fault tip (process zone development) before growth of the fault (thrust slip plane propagation), and (ii) compartmentalization of the thrust fault zone, leading to different structural and fluid flow histories in the footwall and hanging wall. Fractures within the footwall comprise three systematically oriented fracture sets (F1, F2, and F3), each sealed by a separate generation calcite cement, and a randomly oriented fracture system (mosaic to chaotic breccia), cemented by the same cements as fracture sets F1 and F2. The formation of fractures F1 and F2 and the mosaic to chaotic breccia is consistent with dilatant fracturing within the process zone (around the fault tip) during initial fault growth, whereas the formation of the latest fracture system points to hybrid shear-dilational failure during propagation of the fault. The continuous formation of different fracture systems and related calcite cementation phases evidences that the structural permeability in the footwall was transient and that the fluid pathways and regime evolved due to successive events of fracture opening and calcite cementation. Clumped isotopes evidence a progressive increase in precipitation temperatures from around 50°C to 117°C approximately, interpreted as burial increase linked to thrust sheet emplacement. During this period, the source of fluid changed from meteoric fluids to evolved meteoric fluids due to the water-rock interaction at increasing depths and temperatures. Contrary to the footwall, within the hanging wall, only randomly oriented fractures are recognized and the resulting crackle proto-breccia is sealed by a later and different calcite cement, which is also observed in the main fault plane and in the fault core. This cement precipitated from formation fluids, at around 95°C, that circulated along the fault core and in the hanging wall block, again supporting the interpretation of compartmentalization of the thrust structure. The integration of these data reveals that the studied thrust fault acted as a transverse barrier, dividing the thrust zone into two separate fluid compartments, and a longitudinal drain for migration of fluids. This study also highlights the similarity in deformation processes and mechanisms linked to the evolution of fault zones in compressional and extensional regimes involving carbonate rocks

Geochemical and mineralogical signature of fault zones in Archean basement rocks: characterizing a multi-episodic history of fluid-rock interactions

East of the Paleoproterozoic Thelon basin (Nunavut, Canada), unconformity-related uranium deposits of the Kiggavik area, explored by AREVA, are hosted within Archean basement rocks (mainly gneisses and various magmatic intrusives). The study focuses on the Contact prospect, located along the NE-trending Andrew Lake fault and hosted within Archean granitic gneiss. There, the fracture network evolved in a brittle style from ca. 1830 Ma to ca. 1300 Ma for the main fracturing events. The successive fracturing events were associated with circulation of various fluids that interacted with host rocks and fault rocks and caused alteration of the protolith while precipitating new minerals, thus changing the elemental signature of the rock and giving each event a characteristic geochemical signature. AREVA possesses a vast dataset of systematic geochemical analyses (1519 samples in the dataset of the Contact prospect) which, along with newly conducted mineral characterization (microscopy, SEM, microprobe) and fluid inclusions study (microthermometry, Raman spectroscopy, LA-ICP MS) allowed characterizing the geochemical signature of selected fault zones, hence of the fluids that traveled through them at the time of each fracturing event. Four major fracturing events were geochemically characterized: one occurring at ca. 1750 Ma before the emplacement of the Paleoproterozoic Thelon basin infill (1667-1540 Ma), and three occurring after (between 1540 and 1267 Ma). The first main fracturing event is characterized by circulation of Si-rich fluids likely of igneous origin that silicified the Andrew Lake fault system. Vapor-only fluid inclusions displaying low-salinity and high entrapment temperature are representative of the mosaic quartz breccia that sealed fault zones during this event. The fracturing events and associated fluid circulations occurring after this silicifying event were compartmentalized by a large quartz breccia zone. Fault zones of the second fracturing event are relatively narrow ( to 50m) with moderate enrichment in the same elements, except for Fe, Mo, V and Se; they also display a higher content in non-mobile elements (Al and Ti) as a result of the loss of mobile elements during argillization. The fluids that circulated during these two fracturing events were oxidizing, sodic-calcic basinal brines of low temperatures (∼200 ◦C), enriched in uranium. The fourth fracturing event is characterized by fault zones that drove reduced, likely acidic and hot fluids (∼300 ◦C), that caused complete destabilization of iron oxides and also illitization of the host rock. This kind of analysis sheds light on the complexity of the fluid circulation events that may have occurred in impermeable basement rocks, and provides a powerful tool to decipher fluid-fault interactions and to potentially distinguish successive fault zones in cores by their geochemical signature

Geochronological and geochemical data from fracture-filling calcites from the Lower Pedraforca thrust sheet (SE Pyrenees)

U-Pb dating using laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS), δ13 C, δ18 O, clumped isotopes and 87 Sr/ 86 Sr analysis, and electron microprobe have been applied to fracture-filling calcites and host carbonates from the Lower Pedraforca thrust sheet, in the SE Pyrenees. These data are used to determine the type and origin of migrat- ing fluids, the evolution of the palaeohydrological system and timing of fracturing during the emplacement of this thrust sheet, as described in the article 'From hydroplastic to brit- tle deformation: controls on fluid flow in fold and thrust belts. Insights from the Lower Pedraforca thrust sheet (SE Pyrenees)'-Marine and Petroleum Geology (2020). The in- tegration of these data is also used to compare the fluid flow evolution of the Southern Pyrenees with that of other oro- gens worldwide and to generate a fluid flow model in fold and thrust belts. At a more local scale, the U-Pb dataset pro- vides new absolute ages recording the deformation in the Lower Pedraforca thrust sheet, which was previously dated by means of indirect methods such as biostratigraphy of ma- rine sediments and magnetostratigraphy of continental de- posits

Multiple fluid flow events from salt-related rifting to basin inversion (Upper Pedraforca thrust sheet, SE Pyrenees)

Fault-related dolomitisation is responsible for the development of numerous hydrocarbon reservoirs hosted in diagenetically-altered carbonates and is therefore critical to hydrocarbon exploration, subsurface storage (i.e. CO2), the formation of associated mineralisation (i.e. MVT-deposits) and for understanding the key controls on subsurface fluid flow. Multiple dolomitised outcrop analogues have been characterised in recent years, but uncertainty still remains as to the controls on dolomitisation in terms of dolostone geobody size and geometries, their distribution and how they impact reservoir quality. Late Tithonian shallow-marine carbonates at Serra Esparreguera in the Maestrat Basin (E. Spain) were partially dolomitised on the seismic scale, resulting in a spectrum of geobodies with varying degrees of spatial connectivity. Dolostone predominantly replaces Polpís Fm wackestones and packstones, and bioclastic grainstones of the Bovalar Fm. Dolostone geobodies transition through vertical stratigraphy from being massive and spatially extensive to localised stratabound bodies as textural heterogeneity increases. Irregular dolostone geometries occur in the Polpís Fm, which is texturally homogenous relative to the overlying Bovalar Fm, cross-cutting bedding in areas with high abundance of faults. Faults occur adjacent to dolostone and constrain its lateral extent across the outcrop. Dolomitisation fronts are typically sharp with morphologies affected by small-scale faults and bedding-parallel stylolites. Dolomitisation occurred under burial conditions and dolostones were later overprinted by phases of calcite and saddle dolomite cementation. The spatial distribution of dolostone is strongly influenced by the depositional heterogeneity and faults, while smaller structures (i.e. metre-scale fractures and stylolites) and bedding surfaces controlled the dolomitisation front geometry. Dolostone geobodies at Serra Esparreguera provide new insights into the structural, depositional and diagenetic controls on dolomitisation at a seismic scale, which can be used as a predictive guide to improve the understanding of carbonate reservoirs with complex paragenetic histories