Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 6 de 6
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Elife ; 122023 Jul 07.
Artigo em Inglês | MEDLINE | ID: mdl-37417736

RESUMO

When we comprehend language from speech, the phase of the neural response aligns with particular features of the speech input, resulting in a phenomenon referred to as neural tracking. In recent years, a large body of work has demonstrated the tracking of the acoustic envelope and abstract linguistic units at the phoneme and word levels, and beyond. However, the degree to which speech tracking is driven by acoustic edges of the signal, or by internally-generated linguistic units, or by the interplay of both, remains contentious. In this study, we used naturalistic story-listening to investigate (1) whether phoneme-level features are tracked over and above acoustic edges, (2) whether word entropy, which can reflect sentence- and discourse-level constraints, impacted the encoding of acoustic and phoneme-level features, and (3) whether the tracking of acoustic edges was enhanced or suppressed during comprehension of a first language (Dutch) compared to a statistically familiar but uncomprehended language (French). We first show that encoding models with phoneme-level linguistic features, in addition to acoustic features, uncovered an increased neural tracking response; this signal was further amplified in a comprehended language, putatively reflecting the transformation of acoustic features into internally generated phoneme-level representations. Phonemes were tracked more strongly in a comprehended language, suggesting that language comprehension functions as a neural filter over acoustic edges of the speech signal as it transforms sensory signals into abstract linguistic units. We then show that word entropy enhances neural tracking of both acoustic and phonemic features when sentence- and discourse-context are less constraining. When language was not comprehended, acoustic features, but not phonemic ones, were more strongly modulated, but in contrast, when a native language is comprehended, phoneme features are more strongly modulated. Taken together, our findings highlight the flexible modulation of acoustic, and phonemic features by sentence and discourse-level constraint in language comprehension, and document the neural transformation from speech perception to language comprehension, consistent with an account of language processing as a neural filter from sensory to abstract representations.


Assuntos
Compreensão , Linguística , Compreensão/fisiologia , Idioma , Fala/fisiologia , Acústica , Estimulação Acústica/métodos
2.
Food Chem ; 141(2): 1187-91, 2013 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-23790902

RESUMO

A new chiral micellar electrokinetic chromatography-laser induced fluorescence (MEKC-LIF) method was developed using sodium dodecylbenzene sulphonate (SDBS) as surfactant for the determination of chiral amino acids in pomegranate juices. The use of SDBS as the micellar medium enhanced the fluorescence intensities of amino acids derivatised with fluorescein isothiocyanate (FITC). The amino acid profile of pomegranate juices was compared to apple amino acids and l-Asn was proposed as a marker for the adulteration of pomegranate juices with apple juices.


Assuntos
Aminoácidos/análise , Bebidas/análise , Cromatografia Capilar Eletrocinética Micelar/métodos , Contaminação de Alimentos/análise , Lythraceae/química , Malus/química , Cromatografia Capilar Eletrocinética Micelar/instrumentação
3.
Int J Biol Macromol ; 50(4): 1165-8, 2012 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-22269346

RESUMO

Sodium alginate/sodium montmorillonite hybrid films were prepared by casting from the suspension of sodium alginate and different clay samples. Clay samples had been modified with a cationic surfactant, a cationic polymer, and a small polar molecule, respectively. Benzethonium chloride, polyethyleneimine and urea were used as clay modifiers. The composite films begin to disintegrate at a higher temperature and with less weight loss than the pure alginate films. This suggests an enhancement of the film thermal stability due to the modification of the alginate with clay samples.


Assuntos
Alginatos/química , Silicatos de Alumínio/química , Materiais Biocompatíveis/química , Benzetônio/química , Argila , Ácido Glucurônico/química , Ácidos Hexurônicos/química , Interações Hidrofóbicas e Hidrofílicas , Polietilenoimina/química , Análise Espectral , Tensoativos/química , Ureia/química , Difração de Raios X
4.
J Agric Food Chem ; 58(17): 9764-9, 2010 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-20715772

RESUMO

Chemical and biochemical properties of standard, hybrid, and grafted melons cultivated under the same agricultural conditions in adjacent fields in the Cumra region of Turkey were investigated and compared based on pH, Brix, antioxidant activity, total phenolics, ascorbic acid, individual phenolics, sugar, and organic acid values. Seventeen different phenolic constituents were quantified by reverse phase high-performance liquid chromatography (RP-HPLC). The highest phenolic acid variability and content were detected in the standard melon. Sugar and organic acid compositions of melon cultivars were tested by capillary electrophoresis, and significant differences in types and contents of individual sugars and organic acids were determined among the cultivars. Standard Cinikiz Cumra melons had the highest ascorbic acid, total phenolics, and total sugar contents. The fructose/glucose ratio increased three times in grafted melon as compared with standard melon. While sugar alcohol mannitol existed in the standard and hybrid cultivars, this constituent disappeared in the grafted types. Citric acid found in the standard cultivar was not detected in the hybrid and grafted types. Consequently, it was concluded that the nutritional value of melons changed by the application of hybridization, grafting, or standard (open pollinated) production methods. The standard melon was found to have the highest score in terms of taste, because of its highest sweetness and sourness. It was also found preferable because of its high antioxidant activity, total phenolic and ascorbic acid contents.


Assuntos
Cucurbitaceae/metabolismo , Antioxidantes/metabolismo , Ácido Ascórbico/metabolismo , Carboidratos/análise , Cromatografia Líquida de Alta Pressão , Cucurbitaceae/classificação , Eletroforese Capilar , Concentração de Íons de Hidrogênio , Fenóis/metabolismo
5.
Electrophoresis ; 31(13): 2174-9, 2010 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-20533326

RESUMO

A non-ionic micellar electrokinetic chromatography method coupled to laser-induced fluorescence detection was developed for the quantitative determination of biogenic amines. Complete resolution of six biogenic amines - FITC derivatives - was achieved in less than 10 min, employing 10 mM Brij 35 in 75 mM borate buffer and at pH 9.7 as the running electrolyte. Relative fluorescence intensities of biogenic amines enhanched considerably and separation time decreased considerably when Brij 35 was substituted for SDS in the same buffer. The detection limits of the method for biogenic amines were found between 0.416 and 1.26 nM. The precisions for the corrected peak areas were calculated as between 1.63 and 3.24 %RSD. The applicability of the method was demonstrated by analyzing biogenic amines in the processed, brined, and dry-salted fish samples. The method is simple and rapid, and widely applicable for the determination of biogenic amines in food samples.


Assuntos
Aminas Biogênicas/análise , Cromatografia Capilar Eletrocinética Micelar/métodos , Peixes , Análise de Alimentos/métodos , Conservação de Alimentos , Cloreto de Sódio/química , Animais , Modelos Lineares , Reprodutibilidade dos Testes , Sais/química , Sensibilidade e Especificidade , Espectrometria de Fluorescência
6.
Anal Chim Acta ; 617(1-2): 196-9, 2008 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-18486658

RESUMO

In the present study, field amplified sample stacking (FASS) techniques in the nonaqueous capillary electrophoresis method (NACE) were introduced for the on-line concentration of the acrylamide to improve acrylamide detection at 210 nm by diode-array detection. Acetonitrile (ACN) as a nonaqueous solvent permits acrylamide to be protonated through the change of its acid-base chemistry, allowing capillary electrophoretic separation of this compound. Choosing 30 mmol L(-1) HClO(4), 20 mmol L(-1) NaClO(4), 218 mmol L(-1) CH(3)COOH in ACN as the separation electrolyte and employing sample stacking methods, the LOD value of acrylamide was decreased to 2.6 ng mL(-1) with electrokinetic injection and 4.4 ng mL(-1) with hydrodynamic injection. Optimized stacking conditions were applied to the determination of acrylamide in several foodstuffs. The method is simple, rapid, inexpensive, and widely applicable for the determination of acrylamide in food samples.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...