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1.
Behav Processes ; 184: 104338, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33513433

RESUMO

Two of the main hypotheses put forth to explain the function of immature social play are the Social Skill Hypothesis and the Motor Training Hypothesis focussing on whether play can improve social competence to develop cooperative social networks or physical abilities to outcompete others, respectively. Here, we tested these hypotheses on a monkey species, the wild gelada (Theropithecus gelada) from the Kundi plateau, Ethiopia. This species is organized in bands divided in One-Male Units (OMUs), united only via social play. Immatures form 'play units' in which individuals from the same and different OMUs interact. We analysed the potential differences between inter- and intra-OMU play to verify which of the two hypotheses (Social Skill or Motor Training Hypothesis) best explains the function of play in geladas. We analysed 527 video-recorded social play sessions and found mixed support for both hypotheses. In agreement with the Social Skill Hypothesis, we found that play in geladas shows scarce social canalization being similarly distributed across age, sex and group membership. In line with the Motor Training Hypothesis, we detected higher levels of competition (shorter and more unbalanced sessions) in inter-OMU compared to intra-OMU play. Hence, in geladas play can be a tool for both the development of social relationships and the improvement of the physical skills necessary to cope with either future mates or competitors. In conclusion, neither hypothesis can be discarded and both hypotheses concur in explaining why immature geladas peculiarly form 'play units' embracing both ingroup and outgroup members.


Assuntos
Theropithecus , Adaptação Psicológica , Animais , Etiópia , Processos Grupais , Comportamento Social
2.
Int Wound J ; 17(4): 987-991, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32285613

RESUMO

Peripheral arterial disease (PAD) and its most severe form, critical limb ischaemia (CLI), are very common clinical conditions related to atherosclerosis and represent the major causes of morbidity, mortality, disability, and reduced quality of life (QoL), especially for the onset of ischaemic chronic leg ulcers (ICLUs) and the subsequent need of amputation in affected patients. Early identification of patients at risk of developing ICLUs may represent the best form of prevention and appropriate management. In this study, we used a Prediction System for Chronic Leg Ulcers (PredyCLU) based on fuzzy logic applied to patients with PAD. The patient population consisted of 80 patients with PAD, of which 40 patients (30 males [75%] and 10 females [25%]; mean age 66.18 years; median age 67.50 years) had ICLUs and represented the case group. Forty patients (100%) (27 males [67.50%] and 13 females [32.50%]; mean age 66.43 years; median age 66.50 years) did not have ICLUs and represented the control group. In patients of the case group, the higher was the risk calculated with the PredyCLU the more severe were the clinical manifestations recorded. In this study, the PredyCLU algorithm was retrospectively applied on a multicentre population of 80 patients with PAD. The PredyCLU algorithm provided a reliable risk score for the risk of ICLUs in patients with PAD.

3.
J Chem Phys ; 152(7): 074203, 2020 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-32087640

RESUMO

Valence-to-core x-ray emission spectroscopy (VtC XES) combines the sample flexibility and element specificity of hard x-rays with the chemical environment sensitivity of valence spectroscopy. We extend this technique to study geometric and electronic structural changes induced by photoexcitation in the femtosecond time domain via laser-pump, x-ray probe experiments using an x-ray free electron laser. The results of time-resolved VtC XES on a series of ferrous complexes [Fe(CN)2n(2, 2'-bipyridine)3-n]-2n+2, n = 1, 2, 3, are presented. Comparisons of spectra obtained from ground state density functional theory calculations reveal signatures of excited state bond length and oxidation state changes. An oxidation state change associated with a metal-to-ligand charge transfer state with a lifetime of less than 100 fs is observed, as well as bond length changes associated with metal-centered excited states with lifetimes of 13 ps and 250 ps.

4.
Angew Chem Int Ed Engl ; 59(10): 4043-4050, 2020 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-31919948

RESUMO

Ni,N-doped carbon catalysts have shown promising catalytic performance for CO2 electroreduction (CO2 R) to CO; this activity has often been attributed to the presence of nitrogen-coordinated, single Ni atom active sites. However, experimentally confirming Ni-N bonding and correlating CO2 reduction (CO2 R) activity to these species has remained a fundamental challenge. We synthesized polyacrylonitrile-derived Ni,N-doped carbon electrocatalysts (Ni-PACN) with a range of pyrolysis temperatures and Ni loadings and correlated their electrochemical activity with extensive physiochemical characterization to rigorously address the origin of activity in these materials. We found that the CO2 R to CO partial current density increased with increased Ni content before plateauing at 2 wt % which suggests a dispersed Ni active site. These dispersed active sites were investigated by hard and soft X-ray spectroscopy, which revealed that pyrrolic nitrogen ligands selectively bind Ni atoms in a distorted square-planar geometry that strongly resembles the active sites of molecular metal-porphyrin catalysts.

5.
Phys Chem Chem Phys ; 22(5): 2660-2666, 2020 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-31441480

RESUMO

Femtosecond-resolved Extended X-ray Absorption Fine Structure (EXAFS) measurements of solvated transition metal complexes are successfully implemented at the X-ray Free Electron Laser LCLS. Benchmark experiments on [Fe(terpy)2]2+ in solution show a signal-to-noise ratio on the order of 500, comparable to typical 100 ps-resolution synchrotron measurements. In the few femtoseconds after photoexcitation, we observe the EXAFS fingerprints of a short-lived (∼100 fs) intermediate as well as those of a vibrationally hot long-lived (∼ns) excited state.

6.
Rev Sci Instrum ; 90(11): 113101, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31779391

RESUMO

We present results obtained with a new soft X-ray spectrometer based on transition-edge sensors (TESs) composed of Mo/Cu bilayers coupled to bismuth absorbers. This spectrometer simultaneously provides excellent energy resolution, high detection efficiency, and broadband spectral coverage. The new spectrometer is optimized for incident X-ray energies below 2 keV. Each pixel serves as both a highly sensitive calorimeter and an X-ray absorber with near unity quantum efficiency. We have commissioned this 240-pixel TES spectrometer at the Stanford Synchrotron Radiation Lightsource beamline 10-1 (BL 10-1) and used it to probe the local electronic structure of sample materials with unprecedented sensitivity in the soft X-ray regime. As mounted, the TES spectrometer has a maximum detection solid angle of 2 × 10-3 sr. The energy resolution of all pixels combined is 1.5 eV full width at half maximum at 500 eV. We describe the performance of the TES spectrometer in terms of its energy resolution and count-rate capability and demonstrate its utility as a high throughput detector for synchrotron-based X-ray spectroscopy. Results from initial X-ray emission spectroscopy and resonant inelastic X-ray scattering experiments obtained with the spectrometer are presented.

7.
ACS Appl Mater Interfaces ; 11(30): 26863-26871, 2019 Jul 31.
Artigo em Inglês | MEDLINE | ID: mdl-31310093

RESUMO

With promising activity and stability for the oxygen reduction reaction (ORR), transition metal nitrides are an interesting class of non-platinum group catalysts for polymer electrolyte membrane fuel cells. Here, we report an active thin-film nickel nitride catalyst synthesized through a reactive sputtering method. In rotating disk electrode testing in a 0.1 M HClO4 electrolyte, the crystalline nickel nitride film achieved high activity and selectivity to four-electron ORR. It also exhibited good stability during 10 and 40 h chronoamperometry measurements in acid and alkaline electrolyte, respectively. A combined experiment-theory approach, with detailed ex situ materials characterization and density functional theory calculations, provides insight into the structure of the catalyst and its surface during catalysis. Design strategies for activity and stability improvement through alloying and nanostructuring are discussed.

8.
Nutrients ; 11(7)2019 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-31323779

RESUMO

This study aimed to investigate the influence of a single dose of either beetroot juice (BR) or sodium nitrate (NIT) on performance in a 10 km handcycling time trial (TT) in able-bodied individuals and paracyclists. In total, 14 able-bodied individuals [mean ± SD; age: 28 ± 7 years, height: 183 ± 5 cm, body mass (BM): 82 ± 9 kg, peak oxygen consumption (VO2peak): 33.9 ± 4.2 mL/min/kg] and eight paracyclists (age: 40 ± 11 years, height: 176 ± 9cm, BM: 65 ± 9 kg, VO2peak: 38.6 ± 10.5 mL/min/kg) participated in the study. All participants had to perform three TT on different days, receiving either 6 mmol nitrate as BR or NIT or water as a placebo. Time-to-complete the TT, power output (PO), as well as oxygen uptake (VO2) were measured. No significant differences in time-to-complete the TT were found between the three interventions in able-bodied individuals (p = 0.80) or in paracyclists (p = 0.61). Furthermore, VO2 was not significantly changed after the ingestion of BR or NIT in either group (p < 0.05). The PO to VO2 ratio was significantly higher in some kilometers of the TT in able-bodied individuals (p < 0.05). The ingestion of BR or NIT did not increase handcycling performance in able-bodied individuals or in paracyclists.


Assuntos
Beta vulgaris/química , Sucos de Frutas e Vegetais , Nitratos/administração & dosagem , Adulto , Pressão Sanguínea , Suplementos Nutricionais , Frequência Cardíaca , Humanos , Masculino , Pessoa de Meia-Idade , Oxigênio/metabolismo , Raízes de Plantas/química , Traumatismos da Medula Espinal
9.
J Synchrotron Radiat ; 26(Pt 3): 629-634, 2019 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-31074425

RESUMO

An X-ray emission spectrometer that can detect the sulfur Kα emission lines with large throughput and a high energy resolution is presented. The instrument is based on a large d-spacing perfect Bragg analyzer that diffracts the sulfur Kα emission at close to backscattering angles. This facilitates the application of efficient concepts routinely employed in hard X-ray spectrometers towards the tender X-ray regime. The instrument described in this work is based on an energy-dispersive von Hamos geometry that is well suited for photon-in photon-out spectroscopy at X-ray free-electron laser and synchrotron sources. Comparison of its performance with previously used instrumentation is presented through measurements using sulfur-containing species performed at the LCLS. It is shown that the overall signal intensity is increased by a factor of ∼15. Implementation of this approach in the design of a tender X-ray spectroscopy endstation for LCLS-II is also discussed.

10.
Angew Chem Int Ed Engl ; 57(46): 15045-15050, 2018 Nov 12.
Artigo em Inglês | MEDLINE | ID: mdl-30134041

RESUMO

Methanol is a major fuel and chemical feedstock currently produced from syngas, a CO/CO2 /H2 mixture. Herein we identify formate binding strength as a key parameter limiting the activity and stability of known catalysts for methanol synthesis in the presence of CO2 . We present a molybdenum phosphide catalyst for CO and CO2 reduction to methanol, which through a weaker interaction with formate, can improve the activity and stability of methanol synthesis catalysts in a wide range of CO/CO2 /H2 feeds.

11.
Chemistry ; 23(59): 14760-14768, 2017 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-28749554

RESUMO

We report high-energy-resolution X-ray absorption spectroscopy detection of ethylene and CO ligands adsorbed on catalytically active iridium centers isolated on zeolite HY and on MgO supports. The data are supported by density functional theory and FEFF X-ray absorption near-edge modelling, together with infrared (IR) spectra. The results demonstrate that high-energy-resolution X-ray absorption spectra near the iridium LIII (2p3/2 ) edge provide clearly ascribable, distinctive signatures of the ethylene and CO ligands and illustrate effects of supports and other ligands. This X-ray absorption technique is markedly more sensitive than conventional IR spectroscopy for characterizing surface intermediates, and it is applicable to samples having low metal loadings and in reactive atmospheres and is expected to have an increasing role in catalysis research by facilitating the determination of mechanisms of solid-catalyzed reactions through identification of reaction intermediates in working catalysts.

12.
Exp Neurol ; 293: 62-73, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28359740

RESUMO

Vasoactive intestinal peptide (VIP) is one of the neuropeptides showing the strongest up-regulation in the nociceptive pathway after peripheral nerve injury and has been proposed to support neuropathic pain. Nevertheless, the story may be more complicated considering the known suppressive effects of the peptide on the immune reactivity of microglial cells, which have been heavily implicated in the onset and maintenance of pain after nerve injury. We here used mice deficient in VIP and the model of spared nerve injury, characterized by persistent tactile hypersensitivity. While tactile hypersensitivity developed similarly to wild type mice for the ipsilateral hindpaw, only transgenic mice showed a mirror-image tactile hypersensitivity in the contralateral hindpaw. This exacerbated neuropathic pain phenotype appeared to be mediated through a local mechanism acting at the level of the lumbar spinal cord as a distant nerve lesion in the front limb did not lead to hindpaw hypersensitivity in VIP-deficient mice. Innocuous tactile hindpaw stimulation was found to increase a neuronal activation marker in the bilateral superficial laminae of the lumbar dorsal horn of VIP-deficient, but not wild type mice, after SNI. A deeper study into the immune responsiveness to the nerve lesion also proved that VIP-deficient mice had a stronger early pro-inflammatory cytokine response and a more pronounced microglial reactivity compared to wild type controls. The latter was also observed at four weeks after spared nerve injury, a time at which bilateral tactile hypersensitivity persisted in VIP-deficient mice. These data suggest an action of VIP in neuropathic states that is more complicated than previously assumed. Future research is now needed for a deeper understanding of the relative contribution of receptors and fiber populations involved in the VIP-neuropathic pain link.


Assuntos
Hiperalgesia/etiologia , Hiperalgesia/genética , Inflamação Neurogênica/etiologia , Inflamação Neurogênica/genética , Traumatismos dos Nervos Periféricos/complicações , Peptídeo Intestinal Vasoativo/deficiência , Animais , Proteínas de Ligação ao Cálcio/metabolismo , Citocinas/metabolismo , Modelos Animais de Doenças , Feminino , Lateralidade Funcional/genética , Regulação da Expressão Gênica/genética , Proteína Glial Fibrilar Ácida/metabolismo , Hiperalgesia/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteínas dos Microfilamentos/metabolismo , Neuralgia/etiologia , Inflamação Neurogênica/metabolismo , Medição da Dor , Proteínas Proto-Oncogênicas c-fos/metabolismo , Fatores de Tempo , Peptídeo Intestinal Vasoativo/genética
13.
J Am Chem Soc ; 138(39): 12935-12947, 2016 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-27574817

RESUMO

Extensive chlorination of γ-Al2O3 results in the formation of highly Lewis acidic surface domains depleted in surface hydroxyl groups. Adsorption of methyltrioxorhenium (MTO) onto these chlorinated domains serves to activate it as a low temperature, heterogeneous olefin metathesis catalyst and confers both high activity and high stability. Characterization of the catalyst reveals that the immobilized MTO undergoes partial ligand exchange with the surface, whereby some Re sites acquire a chloride ligand from the modified alumina while donating an oxo ligand to the support. More specifically, Re LIII-edge EXAFS and DFT calculations support facile ligand exchange between MTO and Cl-Al2O3 to generate [CH3ReO2Cl+] fragments that interact with a bridging oxygen of the support via a Lewis acid-base interaction. According to IR and solid-state NMR, the methyl group remains intact, and does not evolve spontaneously to a stable methylene tautomer. Nevertheless, the chloride-promoted metathesis catalyst is far more active and productive than MTO/γ-Al2O3, easily achieving a TON of 100 000 for propene metathesis in a flow reactor at 10 °C (compared to TON < 5000 for the nonchlorinated catalyst). Increased activity is a consequence of both a larger fraction of active sites and a higher intrinsic activity for the new sites. Increased stability is tentatively attributed to a stronger interaction between MTO and chlorinated surface regions, as well as extensive depletion of the Brønsted acidic surface hydroxyl population. The reformulated catalyst represents a major advance for Re-based metathesis catalysts, whose widespread use has thus far been severely hampered by their instability.

14.
Int Wound J ; 13(6): 1349-1353, 2016 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-26542425

RESUMO

Chronic leg ulcers (CLUs) are a common occurrence in the western population and are associated with a negative impact on the quality of life of patients. They also cause a substantial burden on the health budget. The pathogenesis of leg ulceration is quite heterogeneous, and chronic venous ulceration (CVU) is the most common manifestation representing the main complication of chronic venous disease (CVD). Prevention strategies and early identification of the risk represent the best form of management. Fuzzy logic is a flexible mathematical system that has proved to be a powerful tool for decision-making systems and pattern classification systems in medicine. In this study, we have elaborated a computerised prediction system for chronic leg ulcers (PredyCLU) based on fuzzy logic, which was retrospectively applied on a multicentre population of 77 patients with CVD. This evaluation system produced reliable risk score patterns and served effectively as a stratification risk tool in patients with CVD who were at the risk of developing CVUs.


Assuntos
Lógica Fuzzy , Úlcera da Perna/epidemiologia , Flebite/epidemiologia , Idoso , Idoso de 80 Anos ou mais , Estudos de Casos e Controles , Doença Crônica , Feminino , Humanos , Incidência , Itália/epidemiologia , Úlcera da Perna/diagnóstico , Úlcera da Perna/terapia , Masculino , Flebite/diagnóstico , Valor Preditivo dos Testes , Estudos Retrospectivos , Medição de Risco , Índice de Gravidade de Doença , Úlcera Varicosa/diagnóstico , Úlcera Varicosa/epidemiologia , Cicatrização/fisiologia
15.
Sci Rep ; 5: 10666, 2015 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-26053681

RESUMO

Dorsal root avulsion results in permanent impairment of sensory functions due to disconnection between the peripheral and central nervous system. Improved strategies are therefore needed to reconnect injured sensory neurons with their spinal cord targets in order to achieve functional repair after brachial and lumbosacral plexus avulsion injuries. Here, we show that sensory functions can be restored in the adult mouse if avulsed sensory fibers are bridged with the spinal cord by human neural progenitor (hNP) transplants. Responses to peripheral mechanical sensory stimulation were significantly improved in transplanted animals. Transganglionic tracing showed host sensory axons only in the spinal cord dorsal horn of treated animals. Immunohistochemical analysis confirmed that sensory fibers had grown through the bridge and showed robust survival and differentiation of the transplants. Section of the repaired dorsal roots distal to the transplant completely abolished the behavioral improvement. This demonstrates that hNP transplants promote recovery of sensorimotor functions after dorsal root avulsion, and that these effects are mediated by spinal ingrowth of host sensory axons. These results provide a rationale for the development of novel stem cell-based strategies for functionally useful bridging of the peripheral and central nervous system.


Assuntos
Axônios/fisiologia , Células-Tronco Embrionárias Humanas/fisiologia , Regeneração Nervosa/fisiologia , Células Receptoras Sensoriais/fisiologia , Traumatismos da Medula Espinal/fisiopatologia , Raízes Nervosas Espinhais/fisiologia , Células-Tronco/fisiologia , Animais , Gânglios Espinais/fisiologia , Humanos , Masculino , Camundongos , Medula Espinal/fisiologia
16.
Neurosci Res ; 95: 78-82, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25697394

RESUMO

Spinal glial reactivity has been strongly implicated in pain that follows peripheral nerve injury. Among the many therapeutic agents that have been tested for anti-allodynia through immune modulation is the atypical methylxanthine propentofylline. While propentofylline shows a potent anti-allodynia effect after nerve transection injury, we here demonstrate that, when propentofylline is used intrathecally at the effective immune-modulatory dose, allodynia after rat nerve crush injury is completely preserved. Microglial/macrophage Iba-1 and astrocytic GFAP expression, increased in the dorsal horn of nerve crushed animals, was, however, effectively attenuated by propentofylline. Effective modulation of spinal glial reactivity is, thus, no assurance for anti-allodynia.


Assuntos
Hiperalgesia/metabolismo , Hiperalgesia/psicologia , Neuroglia/efeitos dos fármacos , Neuroglia/metabolismo , Corno Dorsal da Medula Espinal/metabolismo , Xantinas/administração & dosagem , Animais , Proteínas de Ligação ao Cálcio/metabolismo , Feminino , Proteína Glial Fibrilar Ácida/metabolismo , Hiperalgesia/tratamento farmacológico , Injeções Espinhais , Proteínas dos Microfilamentos/metabolismo , Compressão Nervosa , Neuralgia/tratamento farmacológico , Neuralgia/metabolismo , Limiar da Dor/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Recuperação de Função Fisiológica/efeitos dos fármacos , Nervo Isquiático/lesões , Corno Dorsal da Medula Espinal/efeitos dos fármacos
17.
Exp Neurol ; 263: 91-101, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25311268

RESUMO

Vasoactive intestinal peptide (VIP) has potent immune modulatory actions that may influence the course of neurodegenerative disorders associated with chronic inflammation. Here, we show the therapeutic benefits of a modified peptide agonist stearyl-norleucine-VIP (SNV) in a transgenic rat model of amyotrophic lateral sclerosis (mutated superoxide dismutase 1, hSOD1(G93A)). When administered by systemic every-other-day intraperitoneal injections during a period of 80 days before disease, SNV delayed the onset of motor dysfunction by no less than three weeks, while survival was extended by nearly two months. SNV-treated rats showed reduced astro- and microgliosis in the lumbar ventral spinal cord and a significant degree of motor neuron preservation. Throughout the treatment, SNV promoted the expression of the anti-inflammatory cytokine interleukin-10 as well as neurotrophic factors commonly considered as beneficial in amyotrophic lateral sclerosis management (glial derived neuroptrophic factor, insulin like growth factor, brain derived neurotrophic factor). The peptide nearly totally suppressed the expression of tumor necrosis factor-α and repressed the production of the pro-inflammatory mediators interleukin-1ß, nitric oxide and of the transcription factor nuclear factor kappa B. Inhibition of tumor necrosis factor-α likely accounted for the observed down-regulation of nuclear factor kappa B that modulates the transcription of genes specifically involved in amyotrophic lateral sclerosis (sod1 and the glutamate transporter slc1a2). In line with this, levels of human superoxide dismutase 1 mRNA and protein were decreased by SNV treatment, while the expression and activity of the glutamate transporter-1 was promoted. Considering the large diversity of influences of this peptide on both clinical features of the disease and associated biochemical markers, we propose that SNV or related peptides may constitute promising candidates for amyotrophic lateral sclerosis treatment.


Assuntos
Esclerose Amiotrófica Lateral/patologia , Anti-Inflamatórios/farmacologia , Medula Espinal/efeitos dos fármacos , Superóxido Dismutase/efeitos dos fármacos , Peptídeo Intestinal Vasoativo/farmacologia , Esclerose Amiotrófica Lateral/metabolismo , Animais , Western Blotting , Modelos Animais de Doenças , Humanos , Imuno-Histoquímica , Fármacos Neuroprotetores/farmacologia , Ratos , Ratos Sprague-Dawley , Ratos Transgênicos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Medula Espinal/metabolismo , Medula Espinal/patologia , Superóxido Dismutase/biossíntese , Superóxido Dismutase/genética , Superóxido Dismutase-1
18.
Sensors (Basel) ; 13(8): 11007-31, 2013 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-23966193

RESUMO

In some application fields, such as underwater archaeology or marine biology, there is the need to collect three-dimensional, close-range data from objects that cannot be removed from their site. In particular, 3D imaging techniques are widely employed for close-range acquisitions in underwater environment. In this work we have compared in water two 3D imaging techniques based on active and passive approaches, respectively, and whole-field acquisition. The comparison is performed under poor visibility conditions, produced in the laboratory by suspending different quantities of clay in a water tank. For a fair comparison, a stereo configuration has been adopted for both the techniques, using the same setup, working distance, calibration, and objects. At the moment, the proposed setup is not suitable for real world applications, but it allowed us to conduct a preliminary analysis on the performances of the two techniques and to understand their capability to acquire 3D points in presence of turbidity. The performances have been evaluated in terms of accuracy and density of the acquired 3D points. Our results can be used as a reference for further comparisons in the analysis of other 3D techniques and algorithms.


Assuntos
Algoritmos , Artefatos , Interpretação de Imagem Assistida por Computador/métodos , Imageamento Tridimensional/métodos , Radar , Imersão , Água
19.
Phys Chem Chem Phys ; 15(32): 13354-62, 2013 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-23873523

RESUMO

Niobium-containing silica materials obtained by deposition via liquid-phase grafting or dry impregnation of niobocene(iv) dichloride are active and selective catalysts in the epoxidation of alkenes in the presence of aqueous hydrogen peroxide. The generation of the catalytically-active Nb species was followed step-by-step, and investigated using a combined DR-UV-Vis, NIR, Raman, XRD, XANES and EXAFS analyses. At the end of the grafting procedure, the nature of the surface active species can be described as an oxo-Nb(v) site, tripodally grafted onto the silica surface in close proximity to other Nb(v) centres. The liquid-phase methodology provides a better dispersion of the metal sites onto the siliceous support than the dry-impregnation approach. The niobium-silica catalysts were then tested in the epoxidation of cyclohexene and 1-methylcyclohexene, as model substrates.


Assuntos
Cicloparafinas/química , Ciclopentanos/química , Compostos de Epóxi/síntese química , Nióbio/química , Compostos Organometálicos/química , Dióxido de Silício/química , Catálise , Domínio Catalítico , Compostos de Epóxi/química
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