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International audience; An approach based on the use of a macromolecular coupling agent and the aim to improve the interfacial adhesion between piezoelectric ceramics and piezoelectric polymer matrix in piezoelectric composites is presented. Poly(methyl methacrylate) (PMMA) bearing a catechol moiety was used as a macromolecular coupling agent, as it is known to be miscible to piezoelectric fluoropolymers and catechol groups can strongly bind to a large variety of surfaces. Thus, entanglement between the PMMA chains and the amorphous segments of the fluoropolymer would ensure the desired interfacial adhesion. Well-defined PMMA was synthesized via RAFT polymerization using 2-cyano-2-propyl dodecyl trithiocarbonate as a chain-transfer agent. The PMMA ω-chain end was then functionalized with a catechol group via a one-pot aminolysis/thia-Michael addition procedure using a dopamine acrylamide (DA) derivative as a Michael acceptor. The presence of the catechol moiety at the chain end of PMMA was controlled by 1H NMR and cyclic voltammetry measurements. The resulting PMMA-DA was then grafted onto the surface of a lead-free piezoelectric ceramic film (i.e., a thin film of H2O2-activated (Bi0.5Na0.5)TiO3 (BNT) with a large contact area). The increase of the water contact angle confirmed the efficiency of the grafting. A commercial piezoelectric copolymer P(VDF-co-TrFE) was then spin-coated onto the modified BNT surface to form a bilayer composite. The composite cross section prepared by cryofracture was examined by scanning electron microscopy and revealed that the ceramic/polymer interface of the BNT-PMMA/P(VDF-co-TrFE) bilayer composite exhibits a much better cohesion than its counterpart composite prepared from nonmodified BNT. Moreover, the grazing incidence wide-angle X-ray scattering confirmed that the copolymer crystal structure was not impacted by the presence of the PMMA-DA coupling agent. A strong piezoelectric response was locally detected by piezoresponse force microscopy. This study highlights the potential of PMMA-DA as a macromolecular coupling agent to improve the ceramic/polymer interface in piezoelectric composite materials.

Objective: The corrosion behavior of titanium alloy (NiTi) orthodontic wires shows a high resistance to corrosion in various solutions, such as Ringer's solution, artificial saliva, sodium chloride solution, and others. In these different liquids, NiTi corrosion resistance is higher than that of stainless steel or cobalt-based alloys. These research studies the behavior of the nickel-titanium Orthodontics archwires in the mouth by three methods. Methods: The first testing was the SEM that can perform EPMA (Electro Probing Micro Analysis), microanalysis X, and local and quantitative elementary analysis, and the examination of NiTi are observed in two ways: cross sectional and surface examination. The second one was the electrochemical analysis performed by immersion in an artificial saliva solution consisting of lactic acid at 0.1 moles per liter and sodium chloride at 0.1 mole per liter: Two types of NiTi orthodontic arches were tested. The first ones are from the manufacturer Ortho Classic and were used in the mouth for 4-6 weeks. The second arches are from the manufacturer AZ Dent and were new. The last test was the TEM cartography that shows the atoms and their dispersion on the surface of the wire. Results: The results showed that the presence of corrosion cells in the artificial saliva proved that the NiTi orthodontic archwires were able to initiate the process of corrosion in the mouth, particularly at the point of friction in contact with the braces (Ti6Al4V). Conclusion: The results obtained by the MET on thin sections of orthodontic arches prepared by the FIB method revealed the presence of double or multiple layers of titanium oxide and N-oxide plus aluminum.

International audience; Mesoporous silica (MPS) carriers are considered as a promising strategy to increase the solubility of poorly soluble drugs and to stabilize the amorphous drug delivery system. The development by the authors of a solvent-free method (milling-assisted loading, MAL) made it possible to manipulate the physical state of the drug within the pores. The present study focuses on the effects of the milling intensity and the pore architecture (chemical surface) on the physical state of the confined drug and its release profile. Ibuprofen (IBP) and SBA-15 were used as the model drug and the MPS carrier, respectively. It was found that decreasing the milling intensity promotes nanocrystallization of confined IBP. Scanning electron microscopy and low-frequency Raman spectroscopy investigations converged into a bimodal description of the size distribution of particles, by decreasing the milling intensity. The chemical modification of the pore surface with 3-aminopropyltriethoxisylane also significantly promoted nanocrystallization, regardless of the milling intensity. Combined analyses of drug release profiles obtained on composites prepared from unmodified and modified SBA-15 with various milling intensities showed that the particle size of composites has the greatest influence on the drug release profile. Tuning drug concentration, milling intensity, and chemical surface make it possible to easily customize drug delivery.

Biofilms consist of microbial communities enclosed in a self-produced extracellular matrix which is mainly responsible of biofilm virulence. Targeting this matrix could be an effective strategy to control biofilms. In this work, we examined the efficacy of two proteolytic enzymes, pepsin and trypsin, to degrade P. aeruginosa and E. faecalis biofilms and their synergistic effect when combined with carvacrol. The minimum dispersive concentrations (MDCs) and the contact times of enzymes, as well as the minimal inhibitory concentrations (MICs) and contact times of carvacrol, were determined against biofilms grown on polystyrene surfaces. For biofilms grown on stainless steel surfaces, the combined pepsin or trypsin with carvacrol treatment showed more significant reduction of both biofilms compared with carvacrol treatment alone. This reduction was more substantial after sequential treatment of both enzymes, followed by carvacrol with the greatest reduction of 4.7 log CFU mL−1 (p < 0.05) for P. aeruginosa biofilm and 3.3 log CFU mL−1 (p < 0.05) for E. faecalis biofilm. Such improved efficiency was also obvious in the epifluorescence microscopy analysis. These findings demonstrate that the combined effect of the protease-dispersing activity and the carvacrol antimicrobial activity could be a prospective approach for controlling P. aeruginosa and E. faecalis biofilms. This work was supported by the University of Lille, CNRS, INRAE, Centrale Lille, UMET-Unité Matériaux et Transformations under Grant [UMR 8207].

The biofilm lifestyle plays a major role in the resistance and virulence of

In food industries, microbial contaminations are difficult to control due to the recurrent formation of biofilms that hinders antimicrobials penetration and efficiency. An understanding of Salmonella Enteritidis biofilms behavior under flow conditions is a key to develop efficient preventive and control strategies. S. Enteritidis biofilms displayed 5.96, 6.28 and 6.80 log CFU cm

International audience; Ferropericlase is the second most abundant mineral in the Earth’s lower mantle and its mechanical properties have a strong influence on the rheology of this region. Here, we deform polycrystalline MgO, the magnesium end-member of ferropericlase, at conditions ranging from 1.6 to 8.3 GPa and 875–1,270 K. We analyse the flow laws and microstructures of the recovered samples using electron microscopy and compare our observations with predictions from the literature. We identify a first mechanism for samples deformed at 1,270 K, attributed to a regime controlled by grain boundary sliding accommodated by diffusion, and characterized by a small grain size, an absence of texture, and no intracrystalline deformation. At 1,070 K and below, the deformation regime is controlled by dislocations. The samples show a more homogeneous grain size distribution, significant texture, and intracrystalline strains. In this regime, deformation is controlled by the ⟨110⟩{110} slip system and a combined ⟨110⟩{110} and ⟨110⟩{100} slip, depending on pressure and temperature. Based on these results, we propose an updated deformation map for polycrystalline MgO at mantle conditions. The implications for ferropericlase and seismic observations in the Earth’s lower mantle are discussed.

International audience; The morphogenesis of most carbonaceous microstructures that resemble microfossils in Archean (4–2.5 Ga old) rocks remains debated. The associated carbonaceous matter may even—in some cases—derive from abiotic organic molecules. Mineral growths associated with organic matter migration may mimic microbial cells, some anatomical features, and known microfossils—in particular those with simple spheroid shapes. Here, spheroid microstructures from a chert of the ca. 3.4 Ga Strelley Pool Formation (SPF) of the Pilbara Craton (Western Australia) were imaged and analyzed with a combination of high-resolution in situ techniques. This provides new insights into carbonaceous matter distributions and their relationships with the crystallographic textures of associated quartz. Thus, we describe five new types of spheroids and discuss their morphogenesis. In at least three types of microstructures, wall coalescence argues for migration of carbonaceous matter onto abiotic siliceous spherulites or diffusion in poorly crystalline silica. The nanoparticulate walls of these coalescent structures often cut across multiple quartz crystals, consistent with migration in/on silica prior to quartz recrystallization. Sub-continuous walls lying at quartz boundaries occur in some coalescent vesicles. This weakens the “continuous carbonaceous wall” criterion proposed to support cellular inferences. In contrast, some clustered spheroids display wrinkled sub-continuous double walls, and a large sphere shows a thick sub-continuous wall with pustules and depressions. These features appear consistent with post-mortem cell alteration, although abiotic morphogenesis remains difficult to rule out. We compared these siliceous and carbonaceous microstructures to coalescent pyritic spheroids from the same sample, which likely formed as “colloidal” structures in hydrothermal context. The pyrites display a smaller size and only limited carbonaceous coatings, arguing that they could not have acted as precursors to siliceous spheroids. This study revealed new textural features arguing for abiotic morphogenesis of some Archean spheroids. The absence of these features in distinct types of spheroids leaves open the microfossil hypothesis in the same rock. Distinction of such characteristics could help addressing further the origin of other candidate microfossils. This study calls for similar investigations of metamorphosed microfossiliferous rocks and of the products of in vitro growth of cell-mimicking structures in presence of organics and silica.

Organic microfossils preserved in three dimensions in transparent mineral matrices such as cherts/quartzites, phosphates, or carbonates are best studied in petrographic thin sections. Moreover, microscale mass spectrometry techniques commonly require flat, polished surfaces to minimize analytical bias. However, contamination by epoxy resin in traditional petrographic sections is problematic for the geochemical study of the kerogen in these microfossils and more generally for the in situ analysis of fossil organic matter. Here, we show that epoxy contamination has a molecular signature that is difficult to distinguish from kerogen with time-of-flight secondary ion mass spectrometry (ToF-SIMS). This contamination appears pervasive in organic microstructures embedded in micro- to nano-crystalline carbonate. To solve this problem, a new semi-thin section preparation protocol without resin medium was developed for micro- to nanoscale in situ investigation of insoluble organic matter. We show that these sections are suited for microscopic observation of Proterozoic microfossils in cherts. ToF-SIMS reveals that these sections are free of pollution after final removal of a

Essential oils active components emerged as captivating antimicrobials to control biofilms developed on food contact surfaces. Free and nanoencapsulated carvacrol (CAR) and thymol (THY) were assessed as antimicrobials against Salmonella Enteritidis biofilms adhered to stainless steel. The developed spherical nanocapsules using the spray-drying technique showed an average size ranged between 159.25 and 234.76 nm and zeta potential values ranged between 23.60 and 24.66 mV. The minimal inhibitory concentrations (MIC) of free THY and CAR were both 1.25 mg L-1. Nanoencapsulation reduced MIC values to 0.62 mg L-1 (THY) and 0.31 mg L-1 (CAR). Furthermore, the exposure to free and nanoencapsulated CAR and THY induced a destabilization of bacterial membranes with obvisous morphological deformations and a pronounced leakage of potassium ions and green fluorescent proteins. Eradication of S. Enteritidis biofilms developed on stainless steel was achieved following a 15 min treatment with nanoencapsulated CAR and THY at 2 MIC. Free antimicrobial exposures induced up to 4.27 log CFU cm(-2) reductions. Additionally, the ecotoxicity tests against Daphnia magna crustaceans reported a non-toxicity of both free and nanoencapsulated CAR and THY after 48 h exposure. Thereby, both CAR and THY antimicrobials proved to be promising natural surface disinfectants that require further exploration and incorporation in food industries.

Biofilms are involved in serious problems in medical and food sectors due to their contribution to numerous severe chronic infections and foodborne diseases. The high resistance of biofilms to antimicrobial agents makes their removal as a big challenge. In this study, spray-drying was used to develop microcapsules containing carvacrol, a natural antimicrobial agent, to enhance its activity against P. aeruginosa and E. faecalis biofilms. The physicochemical properties and microscopic morphology of the realized capsules and cells were characterized. The minimum inhibitory concentration of encapsulated carvacrol (E-CARV) (1.25 mg mL-1) was 4-times lower than that of free carvacrol (F-CARV) (5 mg mL-1) against P. aeruginosa, while it remained the same against E. faecalis (0.625 mg mL-1). E-CARV was able to reduce biofilm below the detection limit for P. aeruginosa and by 5.5 log CFU ml-1 for E. faecalis after 15 min of treatment. Results also showed that F-CARV and E-CARV destabilize the bacterial cell membrane leading to cell death. These results indicate that carvacrol exhibited a strong antimicrobial effect against both bacterial biofilms. In addition, spray-drying could be used as an effective tool to enhance the antibiofilm activity of carvacrol, while reducing the concentrations required for disinfection of abiotic surfaces.

International audience; Aims: In this study, benzalkonium chloride (BAC) microcapsules were developed for surface disinfection purpose and were evaluated against Listeria monocytogenes and Escherichia coli biofilms.Methods and Results: Microcapsules were prepared with two different strategies: uncomplexed BAC‐microcapsules (UBM), containing BAC and maltodextrins and complexed BAC‐microcapsules (CBM) containing BAC complexed by pectin and maltodextrins. The minimum inhibitory concentrations (MICs) of free and microencapsulated BAC was investigated against two food pathogens: L. monocytogenes and E. coli. The antibiofilm activities of UBM and CBM against L. monocytogenes and E. coli biofilms formed on stainless steel at 37°C were evaluated and compared to BAC used under its free form. MICs of encapsulated BAC were up to 4‐fold lower than those of free BAC. The UBM and CBM showed higher antibiofilm effect when compared to the free BAC.Conclusions: Overall, results demonstrated that microencapsulation enhanced the antibacterial activity of BAC against L. monocytogenes and E. coli biofilms.Significance and Impact of the Study: The application of such BAC microcapsule‐based delivery systems can improve surface disinfection procedures and reduce the required BAC concentrations and the related cytotoxicity of this antimicrobial compound.

International audience; Silver nanowires (AgNW) are new nanomaterials designed to be incorporated into transparent conductive films in electronics, microelectrodes, heated surfaces and others. Although in these films, the AgNW are generally protected by a coating material, a risk for release of silver at all stages of the nanoproduct life cycle does exist due to corrodibility of the metal. Since ionic and nanoparticulate Ag represent a toxicological risk for a large number of living cells, there is a need for quantifying the potential Ag release from these product components. We developed an electrochemical method to evaluate possible corrosion activity of silver in AgNW transparent conductive films (TCFs) and concomitant Ag + release. A polysiloxane polymer was used as protective coating of AgNW TCFs. A consistent correlation is observed between the degree of corrosion and the coatings' characteristics , in particular the thicknesses. A major advantage of the new approach, compared to classical aging studies, is the short experimentation time: 20 min are sufficient for a diagnostic result. The method is an accelerated corrosion and release test. It is environmentally sound methodology with use of very low electric power and with no harmful reagents. A particularly attractive application could be in the field of environmental risk assessment of metals from portable electronics and biosensors.

The FC Formation of the Francevillian of Gabon displays the oldest Gunflint-type assemblage of microfossils that is hosted in shallow-water stromatolites. The FC Formation was deposited between 2.14 and 2.08 billion years ago (Ga), after the Great Oxygenation Event (∼2.4–2.3 Ga) and near the end of the Lomagundi event (∼2.3–2.06 Ga). Although they have been used as a benchmark for the search for older microfossils, the nature of Gunflint-type microfossils has remained elusive due to their simple shapes, their small sizes, and their alteration. Here, we report the first nanoscale study of Francevillian Gunflint-type microfossils. We used a combination of Raman spectroscopy, palynology, in situ focused ion beam sectioning, and analytical electron microscopy. In spite of the relatively high thermal maturity of organic matter (inferred peak burial temperature ∼296 ± 30 °C), spherical cell walls ( Huroniospora ) and filamentous sheaths ( Gunflintia minuta : ≤3 µm in diameter, and broader filaments) are preserved. Organic matter in/on cell walls and sheaths, is associated with nanocrystalline quartz, whereas coarser quartz crystals fill and surround the microfossils. This pattern, likely inherited from recrystallization of texturally heterogenous opal generations, could have allowed the observed preservation of organic structures and limited migrations of organic matter. Moreover, we demonstrate the preservation of thick-sheathed broad (>3 µm) filaments for the first time in a stromatolitic Gunflint-type assemblage; such thick sheaths are common in cyanobacteria, but not in other filamentous bacteria. We distinguished two types of star-shaped organic microstructures ( Eoastrion ) but found no diagnostic evidence for/against a microfossil nature at the nanoscale. Furthermore, we show that titanium is commonly associated with organic structures of microfossils, likely as a result of diagenetic mineralization. In contrast, iron-rich nanocrystals associated with microfossils occur in quartz, not in organic matter, and could possibly represent recrystallized biominerals.

We report a new assemblage of carbonaceous microfossils intimately associated with siderite and Fe-silicates, from a black chert nodule included in iron formation of the ca. 2.45–2.21 Ga Turee Creek Group, Western Australia. This chert comprises microbial fabrics dominated by filaments preserved in matrix of nano- to micrometric quartz. Filaments occur in clumps and in a cobweb-like fabric interspersed with coarse crystalline, void filling quartz granules. We studied this chert with optical microscopy combined with Scanning Transmission Electron Microscope observations of Focused Ion Beam sections of microfossils. This distinguished three types of well-preserved fossil interpreted as polysaccharide sheaths that usually do not preserve chains of cells (trichomes): Type 1 comprises narrow filaments with thin continuous kerogen sheaths, Type 2 comprises narrow filaments with thick granular sheaths, and Type 3 comprises broad filaments with thin sheaths. Type 4 filaments are poorly preserved as granular kerogen. Organic ultrastructures of Type 2–4 microfossils are variably replaced by siderite crystals, associated with minor Fe-silicates. Iron isotope analyses on bulk powder and reactive iron fraction show indistinguishable and highly positive δ 56 Fe values (+1.45‰ relative to the reference IRMM-014), indicating that the bulk of siderite derives from reduction of Fe(III)-oxides. This provides indirect evidence that the microbial community was originally associated with Fe(III)-oxides. Siderite and Fe-silicates are found with Type 2–4 but not Type 1 filaments, suggesting that only the former were encrusted by Fe(III)-oxides, which may have been reduced in situ . Siderite and Fe-silicates could result from oxidation of organic matter in filaments coupled with microbial and/or thermal reduction of Fe(III)-bio(?)minerals. The increasing abundance of siderite correlated with decreasing organic matter preservation in filaments supports that this reaction occurred to variable extents, in situ on each microfossil. Type 2–4 microfossils may thus represent iron-oxidizing bacteria. These microbial mats display strong similarities with those associated with immediately overlying carbonate rocks of the Turee Creek Group, where filaments were interpreted as sulfur-oxidizing bacteria. Some filamentous bacteria can oxidize both iron and sulfur. Such metabolic versatility could have enabled benthic microbial mats to thrive in the drastically changing chemical conditions of the Great Oxidation Event.

In situ rare-earth element (REE) compositions have been measured in early vertebrate microremains from the Lower Devonian basin of Andrée Land (Svalbard), with the aim of obtaining information about their early depositional environment and potential reworking. Vertebrate microremains with different histology were used for the analyses, sourced from two different localities of marginal marine to freshwater sediments from geographically distant parts of the Grey Hœk Formation (Skamdalen and Tavlefjellet members). We selected thelodont and undescribed ?chondrichthyan scales, which allowed us to define potential taxonomic, histological, and taphonomic variables of the REE uptake. Results showed REE concentrations to be relatively uniform within the scales of each taxon, but apparent discrepancies were visible between the studied localities and separate taxa. The compilation of REE abundance patterns as well as REE ratios have revealed that thelodont and ?chondrichthyan originating from the same locality must have had different burial and early diagenetic histories. The shapes of the REE profiles, together with the presence and absence of the Eu and Ce anomalies, equally suggested different depositional and diagenetic environments for these two sympatric taxa resulting from either stratigraphical or long-distance reworking. The REE concentrations appear to have visible differences between separate dental tissues, particularly between enameloid and dentine of thelodonts, emphasizing the importance of in situ measurements in microfossil biomineral geochemistry.

Rare earth element (REE) compositions of Nostolepis sp. scales, spines, plates and tesserae from Ohesaare bone beds were measured by in situ microsampling using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The obtained REE concentrations, normalized to Post-Archean Australian Shale concentrations, were evaluated using basic geochemical calculations and quantifications. The REE compositions were nearly identical across all the morphotypes and histologies of Nostolepis microremains, showing flat REE patterns with slight depletion in heavy REEs. There was no visible enrichment in middle REEs, indicating good geochemical preservation of bioapatite and absence of any pronounced fractionated REE incorporation during later stages of diagenesis. The shale-normalized (La/Yb)SN and (La/Sm)SN REE ratio compilations indicated adsorption as the dominating REE uptake mechanism across all datapoints. The absence of well-defined Ce anomaly suggested oxic palaeoseawater conditions, which agrees with the existing interpretations of the Ohesaare sequence as high-energy shoal and regressive open ocean sedimentary environments.

Rare earth elements (REEs) have been analysed from fossil vertebrate microremains (thelodont scales) from the Vesiku Bone Bed, Saaremaa, Estonia, using in situ microsampling by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Well-preserved scales of three species of the genus Thelodus (T. carinatus, T. laevis and Thelodus sp.) show very uniform REE patterns with slightly lower overall REE concentrations in enameloid than in dentine, with enrichment in middle REEs, depletion in heavy REEs and pronounced negative europium anomaly, but no cerium anomaly. The results of this study suggest a similar diagenetic history and possibly contemporaneous habitats for all three Thelodus species, as well as possible suboxic to anoxic conditions of the bottom and pore waters during the formation of the Vesiku Bone Bed.

It is proposed in this dissertation a traffic optimization model based on neuro-fuzzy inference systems (ANFIS) to be applied in real-time optimization, targeting the architecture of the traffic control system deployed in the city of Curitiba, considering its properties and restrictions. The model presented herein has a similar approach to the best known dynamic traffic optimization system, SCOOT, implementing hill-climbing optimization on a performance index defined as a weighted sum of the links' measures of effectiveness. However, the nature of the traffic flow sampling in Curitiba, by not distinguishing the flow tuning rates, implies the simulation model should be closer to those implemented by offline traffic simulation tools. Transyt, which is one of the most popular offline traffic simulators, was used in order to generate training data and as a reference to validate the results. Real-time optimization based on the mathematical model of Transyt cannot be applied to systems with a large number of intersections in the current state of technology, due to the high computational costs of the algorithms, unless by imposing restrictions on the search space. ANFIS was used in order to capture the knowledge of the simulator, which means to approximate Transyt's outputs. ANFIS was chosen due to its precision and low execution time. Its estimations made it possible the real-time execution of optimization algorithms for a very large number of intersections. Regarding the optimization processes, well-known methods such as EQUISAT and hill-climbing were used. A hybrid optimization method was also validated using a genetic algorithm to provide an initial state for the hill-climbing method. Neste trabalho propõe-se um método de otimização de tráfego baseado em sistemas de inferência neuro-fuzzy (ANFIS). Esse método deve ser aplicável a um contexto de otimização em tempo real e orientado à arquitetura do sistema de controle de tráfego da cidade de Curitiba, considerando suas características e restrições. O modelo proposto apresenta similaridades com o principal sistema de otimização dinâmica de tráfego existente, denominado SCOOT, empregando o método hill-climbing sobre um índice de desempenho calculado pela ponderação das estimativas de eficiência dos links. Entretanto, a amostragem de dados de fluxo no sistema de Curitiba, por não fornecer medida das conversões em tempo real, determina que o modelo de simulação seja mais aproximado ao utilizado por ferramentas offline de otimização. Empregou-se o Transyt, uma das mais populares ferramentas de simulação e otimização offline, na geração de dados de treinamento ao ANFIS e como referência para validação dos resultados. O alto custo computacional do modelo matemático implementado no Transyt impede sua aplicação na otimização em tempo real de um grande número de cruzamentos sem que se imponha restrições no espaço de busca. Utilizou-se o ANFIS para extrair o conhecimento do simulador, ou seja, aproximar seus resultados. Optou-se pelo ANFIS por apresentar boa precisão e baixo custo computacional e assim sua utilização viabilizou a execução de algoritmos de otimização para um grande número de cruzamentos. Com relação aos processos de otimização, utilizou-se métodos consagrados como o EQUISAT e o hill-climbing, mas também foi avaliado o uso de um algoritmo genético para geração de um estado inicial ao hill-climbing, em um otimizador híbrido.

Resumo O presente artigo promove uma análise comparativa dos modelos de federalismo norte-americano e brasileiro, traçando-se como critério de avaliação seus respectivos níveis de centralização política e considerando o problema central adotado pela pesquisa, que consiste na aproximação do modelo federativo brasileiro de um regime unitário. A confrontação parte de uma seleção dos três precedentes recentes mais paradigmáticos da Suprema Corte norte-americana em matéria de federalismo, trazendo as controvérsias enfrentadas por esses julgadores ao contexto normativo brasileiro. Sustenta-se a hipótese de que a quantidade de critérios alternativos de federalização e a forma com que estes são afirmados em sede jurisdicional são determinantes no entendimento dos níveis de centralização alcançados em cada modelo. O objetivo do presente trabalho não é somente afirmar que o federalismo formal encontrado no Brasil é mais centralizado, mas indicar como o modelo jurisdicional observado nos Estados Unidos consegue preservar um regime coerente e de ampla autonomia dos estados pela marcante atuação da Suprema Corte. Abstract This paper promotes a comparative analysis of American and Brazilian models of federalism assuming their levels of political centralization as main criterion. The central problem faced herein is the Brazilian approach of Unitarian regime. The confrontation starts from the selection of the three most paradigmatic precedents of the recent U.S. Supreme Court’s concerns over federalism and continues bringing its practical controversies to the Brazilian normative context. The hypothesis holds that the amount of alternative criteria of federalization, and the way they are upheld on judicial review, are crucial to understand the levels of political centralization achieved in each model. The aim of this work is rather indicate how jurisdictional federalism found in United States can preserve a consistent model, with States robustly autonomous, than only argue the more centralized character of Brazilian formal federalism.