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1.
J Environ Manage ; 319: 115529, 2022 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-35816966

RESUMO

Increasing concerns related to the negative environmental impacts of food waste havemotivated the development of new solutions to complete the waste cycle of organic residues. One particular "waste" product, the solid digestate from anaerobic digestion, has been identified for further bioprocessing. Black soldier fly (BSF, Hermetia illucens) larvae are known for their great potential in the processing of organic waste. In this study, this potential was investigated to further process the digestate waste stream. Digestate is considered a low potential source of nutrients for larvae due to the presence of different fiber fractions. However, the lignocellulosic matter in this residue could be enzymatically hydrolyzed to release residual carbohydrates. For this study, digestate from a full-scale anaerobic digestion plant in Quebec (Canada) which processes a range of feedstocks (fruits, vegetables, garden wastes, sludge derived from dairy processing and wastewater treatment) was sourced. Digestate was treated with Accelerase® DUET enzyme complex to hydrolyze lignocellulosic matter and compared to a standard diet. For each treatment, 600 four-day old larvae were fed daily with 160 g (70% relative humidity) of diets for 6 days and harvested 3 days later. Although their growth and total biomass were significantly lower than the standard diet, larvae fed on hydrolyzed digestate were almost two times larger than the larvae fed on crude digestate. Furthermore, the content of organic matter, lipids and minerals in the diets and frass were analyzed. Finally, the feasibility of applying BSF treatment for digestate valorization is discussed. According to this study, enzyme-treated digestate does not allow efficient larval growth compared to the standard diet. The development of a more effective method of pretreatment is required for BSF larvae to become an eco-friendly solution for digestate valorization.


Assuntos
Dípteros , Eliminação de Resíduos , Animais , Biocombustíveis , Alimentos , Larva
2.
Chemosphere ; 301: 134672, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35472617

RESUMO

Although Glyphosate-based herbicides are often marketed as environmentally friendly and easily biodegradable, its bioavailability and risks to wildlife raise significant concerns. Among non-target organisms, earthworms which live in close contact with the soil can be directly exposed to pesticides and harmed. We investigated soil contamination and the exposure of earthworms to glyphosate, its metabolite AMPA, and glufosinate in an arable landscape in France, both in treated (i.e. temporary grasslands and cereal fields under conventional farming), and nontreated habitats (i.e. hedgerows, permanent grasslands and cereal fields under organic farming) (n = 120 sampling sites in total). Glyphosate, AMPA and glufosinate were detected in 88%, 58% and 35% of the soil samples, and in 74%, 38% and 12% of the earthworm samples, respectively. For both glyphosate and AMPA, concentrations in soils were at least 10 times lower than predicted environmental concentrations. However, the maximum glyphosate soil concentration measured (i.e., 0.598 mg kg-1) was only 2 to 3 times lower than the concentrations revealed to affect earthworms (survival and avoidance) in the literature. These compounds were found both in conventional and organic farming fields, thus supporting a recent study, and for the first time they were detected in hedgerows and grasslands. However, glyphosate and AMPA were more frequently detected in soils from cereal fields and hedgerows than in grasslands, and median concentrations measured in soils from cereal fields were significantly higher than in the two other habitats. Bioaccumulation of glyphosate and AMPA in earthworms was higher than expected according to the properties of the molecules. Our findings raised issues about the high occurrence of glyphosate and AMPA in soils from cropped and more natural areas in arable landscapes. They also highlight the potential for transfer of these molecules in terrestrial food webs as earthworms are prey for numerous animals.


Assuntos
Herbicidas , Oligoquetos , Poluentes do Solo , Aminobutiratos , Animais , Glicina/análogos & derivados , Herbicidas/análise , Herbicidas/toxicidade , Solo , Poluentes do Solo/análise , Ácido alfa-Amino-3-hidroxi-5-metil-4-isoxazol Propiônico , Glifosato
3.
Sci Total Environ ; 734: 139108, 2020 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-32460067

RESUMO

Organic micropollutants (OMPs) such as polycyclic aromatic hydrocarbons, nonylphenols and pharmaceutical products are ubiquitous in organic wastes generated by most human activities. Those wastes are mainly recycled by land spreading, most often after treatments, such as liming, dewatering, composting or anaerobic digestion. It has been shown essentially at lab scales that biological treatments have an effect on the removal of some OMPs. However, less is known on the role of each step of industrial treatment lines combining physico-chemical and biological treatments on the OMP fate and removal. The present study focuses on the impact of waste treatment on the fate of 53 OMPs along 10 industrial treatment lines treating urban, agricultural wastes or mixtures. The combination of studying a diversity of organic wastes and of OMPs with different characteristics (solubility, ionic charges, hydrophobicity etc.), sampling in situ industrial sites, quantifying native OMP concentrations and looking at each step of complete treatment lines allows for a global and representative view of the OMP fate in the French organic waste treatment sector. Less studied wastes, i.e. territorial mixtures, revealed intermediate OMP contents and compositions, between urban and agricultural wastes. Dewatering and liming, usually dismissed, had a noticeable effect on concentrations. Anaerobic digestion and composting had significant effects on the removal of all pollutant families. Combination of processes enhanced most OMP dissipation. Here we showed for the first time that the process type rather than the waste origin affects dissipation of organic micropollutants. Such data could be used to build and validate dynamic models for the fate of OMPs on solid waste treatment plants.


Assuntos
Resíduos Sólidos , Anaerobiose , Compostagem , Humanos , Esgotos , Eliminação de Resíduos Líquidos
4.
Science ; 367(6485)2020 03 27.
Artigo em Inglês | MEDLINE | ID: mdl-32217702

RESUMO

Marine food-reliant subsistence systems such as those in the African Middle Stone Age (MSA) were not thought to exist in Europe until the much later Mesolithic. Whether this apparent lag reflects taphonomic biases or behavioral distinctions between archaic and modern humans remains much debated. Figueira Brava cave, in the Arrábida range (Portugal), provides an exceptionally well preserved record of Neandertal coastal resource exploitation on a comparable scale to the MSA and dated to ~86 to 106 thousand years ago. The breadth of the subsistence base-pine nuts, marine invertebrates, fish, marine birds and mammals, tortoises, waterfowl, and hoofed game-exceeds that of regional early Holocene sites. Fisher-hunter-gatherer economies are not the preserve of anatomically modern people; by the Last Interglacial, they were in place across the Old World in the appropriate settings.


Assuntos
Dieta , Homem de Neandertal , Exoesqueleto , Animais , Arqueologia , Oceano Atlântico , Aves , Cavernas , Peixes , Mamíferos , Nozes , Pinus , Portugal , Alimentos Marinhos , Tartarugas
5.
Phys Chem Chem Phys ; 19(44): 30139-30146, 2017 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-29104979

RESUMO

We explored polarization mechanisms at the interface between a dielectric material (an electrolyte) and an insulating liquid, during electrowetting actuation. Native surface charge density due to hydrophobic coating has been measured as an offset voltage for which the contact angle is at its minimum. Surface charge densities as low as 0.023 mC m-2 have been measured using this method, demonstrating that electrowetting can be used as a probe to measure native surface charge density. This effect strongly differs depending on the kind of polarization and is at the origin of major discrepancies between alternative and direct polarization during electrowetting actuation. A new model describing electrowetting actuation is also proposed, leading to a more predictive description as well as useful recommendations on materials to obtain a stable actuation under DC polarization.

6.
Environ Sci Pollut Res Int ; 24(4): 3985-3996, 2017 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-27915427

RESUMO

Volatilization may represent a major dissipation pathway for pesticides applied to soils or crops, and these losses may be modified by soil surface conditions or in the presence of plant residues. This paper investigates the effect of surface conditions on volatilization through experimental results. The two experiments consisted of volatilization flux measurements for 3 days after an application of S-metolachlor together with benoxacor: one with two wind tunnels to compare the effect of the presence of crop residues on the soil on volatilization losses and another one at the field scale from bare soil without crop residues. Volatilization fluxes were large immediately after application (between 77 and 223 ng m-2 s-1 for S-metolachlor depending on experimental conditions), decreasing down to a few nanograms per square meter per second on the last day. Volatilization fluxes followed a diurnal cycle driven by environmental conditions. The losses found for both compounds were in accordance with their physicochemical properties. The crop residue on the soil surface modified soil surface conditions-primarily the soil water content essentially, the degradation of S-metolachlor, and the dynamics of volatilization loss.


Assuntos
Acetamidas/análise , Produtos Agrícolas/química , Oxazinas/análise , Resíduos de Praguicidas/análise , Solo/química , Volatilização
7.
Sci Total Environ ; 576: 671-682, 2017 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-27810754

RESUMO

An increasing number of studies pointed out the ubiquitous presence of medical residues in surface and ground water as well as in soil compartments. Not only antibiotics can be found in the environment but also their transformation products about which little information is generally available. The development of bacterial resistance to antibiotics is particularly worrying as it can lead to sanitary and health problems. Studies about the dissemination of antibiotics and associated resistances in the Bolivian Altiplano are scarce. We provide baseline information on the occurrence of Sulfamethoxazole (SMX) and Trimethoprim (TMP) antibiotics as well as on the most common human SMX transformation products (TP) and on the occurrence of sulfonamide resistance genes. The studied water and soil compartments presented high levels of antibiotic pollution. This situation was shown to be mainly linked with uncontrolled discharges of treated and untreated wastewaters, resulting on the presence of antibiotics in the Titicaca Lake. SMX TPs were detected in surface waters and on soil sampled next to the wastewater treatment plant (WWTP). SMX resistance genes sulI and sulII were widely detected in the basin hydrological network, even in areas unpolluted with antibiotics. Mechanisms of co-selection of antibiotic- and metal- resistance may be involved in the prevalence of ARG's in pristine areas with no anthropogenic activity and free of antibiotic pollution.


Assuntos
Antibacterianos/análise , Genes Bacterianos , Lagos/química , Poluentes Químicos da Água/análise , Bolívia , Farmacorresistência Bacteriana/genética , Sulfametoxazol/análise , Trimetoprima/análise , Águas Residuárias
8.
Gene Ther ; 23(8-9): 664-72, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-27111151

RESUMO

Anti-tumor cellular immunotherapies that implement a suicide gene system can limit potential undesirable effects. In a haplo-identical bone marrow transplant clinical trial, over 90% of iCaspase-9-expressing cells were eradicated after AP1903 exposure, and signs of graft-versus-host disease disappeared. Nevertheless, low numbers of genetically modified T cells survived this treatment. We studied genetically modified cell lines (GMCL) that carried a dual iCaspase-9/ΔCD19 DNA construct (ΔCD19=truncated CD19). With AP1903 exposure, a low percentage of cells (1.47±0.67%; n=5 replications) persisted in vitro. Repeated exposures to increasing AP1903 doses generated low (GMCLLR) and high AP1903-responders (GMCLHR), which expressed different levels of surface ΔCD19 and intracellular iCaspase-9. Compared with GMCLHR, GMCLLR exhibited higher methylation of 5'-long-terminal repeat (LTR) promoters, both in the number of sequences with at least one methylated CpG (16 vs 51.5%, respectively) and in the number of CpG islands (1.2 vs 8.9%, respectively). Four days of 5-azacytidine exposure reduced methylation and increased ΔCD19 and iCaspase-9 expression. Interestingly, LTR demethylation restored GMCLLR sensitivity to AP1903 by 24.3-fold (1.8 vs 43.8%) without affecting GMCLHR. We showed that 5'-LTR-methylation inhibited transgene expression and caused AP1903 hypo-responsiveness. Treating with a hypomethylating agent restored AP1903 sensitivity. This approach can be applied in further clinical trials to improve iCaspase-9 response if low response is detected.


Assuntos
Azacitidina/farmacologia , Caspase 9/genética , Metilação de DNA/efeitos dos fármacos , Genes Transgênicos Suicidas/genética , Terapia Genética/métodos , Doença Enxerto-Hospedeiro/terapia , Antígenos CD19/genética , Transplante de Medula Óssea/efeitos adversos , Transplante de Medula Óssea/métodos , Caspase 9/metabolismo , Doença Enxerto-Hospedeiro/etiologia , Humanos , Células Jurkat , Compostos Orgânicos/farmacologia , Transplante Homólogo/métodos
9.
J Phys Condens Matter ; 28(17): 176003, 2016 May 05.
Artigo em Inglês | MEDLINE | ID: mdl-27028697

RESUMO

A nuclear magnetic resonance study of the sulfate ion reorientations in ß-LiNaSO4 has been carried out. The influence of the SO4 reorientational jumps on the quadrupolar interactions of (7)Li nuclei was investigated by a jump reorientational model, which has not previously been applied to sulfates. The activation energy required for the SO4 reorientations was found to be 0.19 eV. It was also revealed that the SO4 reorientational disorder should be associated with a small anomaly of a heat capacity at around 600 K, which was previously observed experimentally.

10.
Public Health Action ; 6(4): 210-211, 2016 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-28123954

RESUMO

Leadership positions in global health are greatly skewed toward men; the imbalance is more pronounced in low- and middle-income countries (LMICs). The under-representation of women in leadership is a threat to gender equality, and also impacts the improvement of women's health outcomes globally. In this perspectives piece, we assert that the promotion and retention of women in global health leadership has a ripple effect that can achieve improvement in global health outcomes. We present pragmatic, actionable solutions to promote and retain female global health leaders in this field.


Les positions de dirigeant dans la santé du monde sont largement orientées vers les hommes et ce déséquilibre est encore plus prononcé dans les pays à revenu faible et moyen. La sous-représentation des femmes en termes de dirigeant menace l'égalité des genres et a également un impact sur l'amélioration de l'état de santé des femmes dans le monde. Dans cette perspective, nous affirmons que la promotion et la rétention des femmes au sein du leadership de la santé dans le monde a un effet d'entraînement qui peut aboutir à une amélioration de l'état de santé dans le monde. Nous présentons des solutions pragmatiques et réalisables pour promouvoir et retenir des leaders féminins en matière de santé dans le monde.


Los puestos directivos en materia de salud mundial se asignan de manera desproporcionada a los hombres; este desequilibrio es aun más notorio en los países de ingresos bajos y medianos. La subrepresentación de las mujeres en los cargos de responsabilidad pone en peligro la equidad entre los hombres y las mujeres y tiene además repercusiones en los resultados de salud de las mujeres en el mundo. En el presente artículo de opinión, se sostiene que promover a las mujeres a las funciones directivas relacionadas con la salud mundial y facilitar su permanencia en ellas genera una reacción en cadena que puede dar lugar a mejores resultados de salud a escala mundial. Se proponen soluciones viables y prácticas encaminadas a estimular la presencia de las mujeres en los cargos de responsabilidad en materia de salud mundial y a respaldar su permanencia en esta actividad.

11.
B-ENT ; Suppl 26(1): 155-171, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-29461740

RESUMO

Acute external ear lesions: clinical aspects, assessment and management. We reviewed the literature concerning the assessment and the management of the external ear traumas, which is not very rich. Nevertheless, we outlined the practical attitudes in the four major conditions met: the auricular haematoma, the auricular perichondritis, the auricular laceration and auricular bums. All these pathologies must be promptly treated because there is a risk of perichondritis, which can destroy the cartilage and will result in a severely deformed ear. Auricular haematomas must be drained as soon as possible, lacerations with exposed cartilage must be stitched urgently, and burnt ears should be washed, coated with alginates (Flaminal@) and covered with a loose dressing. Antibioprophyl- axy should always be prescribed after a complete microbiological sampling.


Assuntos
Alginatos/uso terapêutico , Antibacterianos/uso terapêutico , Bandagens , Queimaduras/terapia , Pavilhão Auricular/lesões , Glucose Oxidase/uso terapêutico , Hematoma/terapia , Lacerações/terapia , Lactoperoxidase/uso terapêutico , Polietilenoglicóis/uso terapêutico , Irrigação Terapêutica , Combinação de Medicamentos , Orelha Externa/lesões , Humanos , Técnicas de Sutura
12.
Solid State Nucl Magn Reson ; 71: 80-6, 2015 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-26279074

RESUMO

An expression for the dipolar correlation function characterizing the fluctuations of the Hamiltonian under uncorrelated diffusion of two cationic sub-lattices in a solid has been obtained. A corresponding formula, which can be used for fitting the two-step temperature dependencies of the NMR line width, has been deduced. We also considered the case of a distribution of correlation times and deduced a corresponding analytical fitting function. Elaborated expressions have been applied to the NMR line width analysis of LiNaSO4 in the temperature range 295-788 K.

13.
Transfus Clin Biol ; 22(3): 132-40, 2015 Aug.
Artigo em Francês | MEDLINE | ID: mdl-26068883

RESUMO

Scientific advances in the last decade have demonstrated the critical role of host immune system in the elimination and suppression of cancer cells. Better knowledge of signaling pathways has enabled the development of new cancer immunotherapy. The discovery of negative feedback mechanisms following the lymphocyte activation has promoted the development of new antibodies targeting molecule inhibitors such as PD1, PDL1 or CTLA-4. Dramatic results were obtained with melanoma. Checkpoint inhibitors (pembrolizumab and ipilimumab) have many advantages in terms of rate of objective response and overall survival. Recent studies in translational research aimed to understand and analyze mechanisms of action of anti-PD1/anti-PDL1. Expression of PDL1 in the tumor is associated with a significantly greater objective response rate (immunohistochemistry). Nevertheless, limits with tumor immunohistochemical analysis encourage new biomarkers research. Other immunotherapy approaches, such as cell and gene therapies using engineered T cells call for further advancements to broaden their applicability. However, these therapies are very expensive and their manufacturing process very restrictive, which could lately limit their use in case of inefficiency of checkpoint inhibitors or when lymphocytic infiltration in tumor is absent. In this case, the objective would be to engineer ex vivo the patient's immune system by restoring the ability of T cells to identify and suppress tumor cells. Currently, two gene-reprogramming tools are under development: chimeric antigen receptor and TCR modified T cells.


Assuntos
Doenças Hematológicas/terapia , Imunoterapia/métodos , Neoplasias/terapia , Terapias em Estudo , Complexo CD3/genética , Complexo CD3/imunologia , Técnicas de Reprogramação Celular/tendências , Ensaios Clínicos como Assunto , Terapia Genética/tendências , Doenças Hematológicas/imunologia , Humanos , Cadeias Pesadas de Imunoglobulinas/genética , Cadeias Pesadas de Imunoglobulinas/imunologia , Cadeias Leves de Imunoglobulina/genética , Cadeias Leves de Imunoglobulina/imunologia , Região Variável de Imunoglobulina/genética , Região Variável de Imunoglobulina/imunologia , Imunoterapia/tendências , Imunoterapia Adotiva , Terapia de Alvo Molecular/tendências , Neoplasias/imunologia , Receptores de Antígenos de Linfócitos T/uso terapêutico , Receptores de Antígenos de Linfócitos T alfa-beta/genética , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/imunologia , Proteínas Recombinantes de Fusão/uso terapêutico , Anticorpos de Cadeia Única/imunologia , Anticorpos de Cadeia Única/uso terapêutico , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/transplante , Transgenes , Pesquisa Translacional Biomédica/tendências
14.
Gene Ther ; 22(2): 172-80, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25394253

RESUMO

Hepatitis C virus (HCV)-induced, end-stage liver disease is a major indication for liver transplantation, but systematic graft reinfection accelerates liver disease recurrence. Transplantation recipients may be ineligible for direct-acting antivirals, owing to toxicity, resistance or advanced liver disease. Adoptive immunotherapy with liver graft-derived, ex vivo-activated lymphocytes was previously shown to prevent HCV-induced graft reinfections. Alternatively, the applicability and therapeutic efficacy of adoptive immunotherapy may be enhanced by 'ready for use' suicide gene-modified lymphocytes from healthy blood donors; moreover, conditional, prodrug-induced cell suicide may prevent potential side effects. Here, we demonstrate that allogeneic suicide gene-modified lymphocytes (SGMLs) could potently, dose- and time-dependently, inhibit viral replication. The effect occurs at effector:target cell ratios that exhibits no concomitant cytotoxicity toward virus-infected target cells. The effect, mediated mostly by CD56+ lymphocytes, is interleukin-2-dependent, IFN-γ-mediated and, importantly, resistant to calcineurin inhibitors. Thus, post-transplant immunosuppression may not interfere with this adoptive cell immunotherapy approach. Furthermore, these cells are indeed amenable to conditional cell suicide; in particular, the inducible caspase 9 suicide gene is superior to the herpes simplex virus thymidine kinase suicide gene. Our data provide in vitro proof-of-concept that allogeneic, third-party, SGMLs may prevent HCV-induced liver graft reinfection.


Assuntos
Hepacivirus/imunologia , Hepatite C/prevenção & controle , Linfócitos/fisiologia , Caspase 9/genética , Linhagem Celular Tumoral , Terapia Genética , Humanos , Imunoterapia Adotiva , Transplante Homólogo , Replicação Viral
15.
Mar Genomics ; 18PB: 141-144, 2014 12.
Artigo em Inglês | MEDLINE | ID: mdl-25468063

RESUMO

Reducing dietary phosphorus (P) is a common approach to reduce effluent P outputs. The potential resulting P-deficiency is known to negatively impact fish bone condition and might result in vertebral deformities. To date, no large-scale study involving deep sequencing of the bone transcriptome has been conducted in salmonids and vertebral molecular changes remain poorly described. This study aims to provide the first comprehensive vertebral transcriptome for rainbow trout (Oncorhynchus mykiss) to allow functional and quantitative expression studies. Fish weighing 60.8±1.6g, were fed for 27weeks using two practical diets having 0.29% (deficient) and 0.45% (sufficient) available phosphorus (P), respectively. Deep sequencing was conducted using HiSeq2000 Illumina 100 paired-end technology from pooled P-deficient and P-sufficient fish and individuals displaying vertebral deformities. Over 140 million trimmed paired-end reads were assembled de novo with Trinity and resulted in 679,869 transcripts with a mean length of 542.5bp. From these sequences, 340,747 matched with referenced ESTs from rainbow trout. Furthermore, 141,909 and 117,564 sequences were functionally annotated against Nr and Uniprot databases, respectively. Interestingly, we observed putative homologue sequences for most of the key components involved in bone formation and turnover in mammals.

16.
Nurs Stand ; 28(24): 63, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24517698

RESUMO

Male or female, people seeking medical attention in the UK are entitled to receive the same level of nursing care. But what about care for transgender and transexual people?


Assuntos
Transexualidade , Feminino , Pessoal de Saúde , Humanos , Masculino
17.
Ultrasonics ; 54(7): 1851-60, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24388406

RESUMO

The TOFD (Time of Flight Diffraction) technique is a classical ultrasonic inspection method used in ultrasonic non-destructive evaluation (NDE). This inspection technique is based on an arrangement of two probes of opposite beam directions and allows a precise positioning and a quantitative evaluation of the size of cracks contained in the inspected material thanks to their edges diffraction echoes. Among the typical phenomena arising for such an arrangement, head waves, which propagate along the specimen surface and are chronologically the first waves reaching the receiver, are notably observed. Head wave propagation on planar surfaces in TOFD configurations is well known. However, realistic inspection configurations often involve components with irregular surfaces, like steel excavated specimens. Surface irregularity is responsible for numerous effects on the scattering of bulk waves, causing the melting of surface and bulk mechanisms in the head wave propagation. In order to extend the classical ray approach on these complex cases, a generic algorithm of ray tracing between interface points (GIRT) has been designed. With respect to time of flight minimization (i.e. the Generalized Fermat's Principle), ray paths can be computed by GIRT for different natures of waves scattered by the complex surfaces or by flaws. The head wave fronts computed by GIRT are notably in good agreement with FEM simulated results. This algorithm, based on pure kinematic analysis of waves propagation, represents a first step in the future development of a complete ray theory for head waves simulation on irregular interfaces.

18.
Ultrasonics ; 54(7): 1880-90, 2014 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-24199956

RESUMO

Topological imaging is a recent method. So far, it has been applied to bulk waves, and high resolution has been demonstrated for imaging scatterers even with a single ultrasonic insonification of the inspected medium. This method consists of (i) emitting waves and measuring the response of the medium; (ii) solving two propagation problems: the direct problem, where the experimental source is simulated, and the adjoint problem, where the source is the time-reversed difference between the measured wave field and that obtained from the direct problem; (iii) computing the image by simply multiplying both wave fields together in the frequency domain, and integrating over the frequency. The speed of the method depends only on the cost of the field computations that are performed in the defect-free medium. The present work deals with the application of topological imaging to plate guided waves. Combining modal theory and Fourier analysis, the computations are performed in a very short time. In the investigated cases, two-dimensional in-plane imaging is based on propagation of the single S0 Lamb mode. Despite very high dispersion of that mode, scatterers are accurately located and the spatial resolution is equal to about one wavelength.

20.
Solid State Nucl Magn Reson ; 40(2): 72-7, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21741223

RESUMO

(77)Se (I=1/2) solid-state NMR is a very sensitive probe of the local structure of selenide glasses, which themselves are promising for optical applications. In this work, we show that although (77)Se has a low natural abundance (7.58%) and a wide spectral range, the sensitivity can be dramatically increased using Carr-Purcell-Meiboom-Gill (CPMG) trains of rotor-synchronized π pulses during the detection of (77)Se magnetization but may be affected by chemical shift anisotropy when the Magic Angle Spinning rate is not fast enough and by offset effects. The indirect dimension of the T(2)(CPMG)-resolved spectrum shows a strong influence of the J-couplings between naturally occurring (77)Se pairs. The resulting spectra show that the structural model known as "chains crossing model" is not entirely suitable to describe the glassy network of the Se-rich compositions.

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