Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 54
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Bull Exp Biol Med ; 176(4): 481-485, 2024 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-38492104

RESUMO

We performed complex analysis of the association of polymorphic variants rs7903146 of the TCF7L2 gene and rs1801282 of the PPARG gene with metabolic parameters, insulin resistance, and ß-cell function in a group of patients with early signs of carbohydrate metabolism disturbances in a sample of Tyumen citizens. The study group consisted of 64 people (39 women, 25 men) aged 40-70 years. The distribution of frequencies of alleles and genotypes of the polymorphic markers rs7903146 and rs1801282 was analyzed and associations of carriage of major homozygous polymorphisms with various phenotypic traits were identified. Genotyping for polymorphic variants of TCF7L2 and PPARG genes was performed using allele-specific PCR with primers provided by Synthol company. Carriers of homozygotes for allele C of the polymorphic marker rs7903146 significantly differed from other respondents by a higher level of C-peptide, as well as by the presence of associations with waist circumference, elevated level of glycated hemoglobin, and arterial hypertension. Carriers of homozygotes for the allele C of the rs1801282 polymorphism of the PPARG gene differed from the group of carriers of homozygotes for the allele G and the group of heterozygote carriers by higher levels of triglycerides, as well as the presence of associations with waist circumference and the level of glycated hemoglobin.


Assuntos
Diabetes Mellitus Tipo 2 , PPAR gama , Proteína 2 Semelhante ao Fator 7 de Transcrição , Feminino , Humanos , Masculino , Metabolismo dos Carboidratos , Diabetes Mellitus Tipo 2/genética , Genótipo , Hemoglobinas Glicadas/genética , Polimorfismo Genético/genética , Polimorfismo de Nucleotídeo Único/genética , PPAR gama/genética , Proteína 2 Semelhante ao Fator 7 de Transcrição/genética
2.
Nat Mater ; 22(7): 867-872, 2023 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-37349399

RESUMO

The emergence of a topological transition of the polaritonic dispersion in twisted bilayers of anisotropic van der Waals materials at a given twist angle-the photonic magic angle-results in the diffractionless propagation of polaritons with deep-subwavelength resolution. This type of propagation, generally referred to as canalization, holds promise for the control of light at the nanoscale. However, the existence of a single photonic magic angle hinders such control since the canalization direction in twisted bilayers is unique and fixed for each incident frequency. Here we overcome this limitation by demonstrating multiple spectrally robust photonic magic angles in reconfigurable twisted α-phase molybdenum trioxide (α-MoO3) trilayers. We show that canalization of polaritons can be programmed at will along any desired in-plane direction in a single device with broad spectral ranges. These findings open the door for nanophotonics applications where on-demand control is crucial, such as thermal management, nanoimaging or entanglement of quantum emitters.


Assuntos
Fótons , Anisotropia
3.
Mater Horiz ; 10(7): 2427-2435, 2023 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-37139604

RESUMO

A global trend towards miniaturization and multiwavelength performance of nanophotonic devices drives research on novel phenomena, such as bound states in the continuum and Mietronics, as well as surveys for high-refractive index and strongly anisotropic materials and metasurfaces. Hexagonal boron nitride (hBN) is one of the promising materials for future nanophotonics owing to its inherent anisotropy and prospects of high-quality monocrystal growth with an atomically flat surface. Here, we present highly accurate optical constants of hBN in the broad wavelength range of 250-1700 nm combining imaging ellipsometry measurements, scanning near-field optical microscopy and first-principles quantum mechanical computations. hBN's high refractive index, up to 2.75 in the ultraviolet (UV) and visible range, broadband birefringence of ∼0.7, and negligible optical losses make it an outstanding material for UV and visible range photonics. Based on our measurement results, we propose and design novel optical elements: handedness-preserving mirrors and subwavelength waveguides with dimensions of 40 nm operating in the visible and UV ranges, respectively. Remarkably, our results offer a unique opportunity to bridge the size gap between photonics and electronics.

4.
NPJ 2D Mater Appl ; 7(1): 31, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38665481

RESUMO

Optical nanoresonators are key building blocks in various nanotechnological applications (e.g., spectroscopy) due to their ability to effectively confine light at the nanoscale. Recently, nanoresonators based on phonon polaritons (PhPs)-light coupled to lattice vibrations-in polar crystals (e.g., SiC, or h-BN) have attracted much attention due to their strong field confinement, high quality factors, and their potential to enhance the photonic density of states at mid-infrared (mid-IR) frequencies, where numerous molecular vibrations reside. Here, we introduce a new class of mid-IR nanoresonators that not only exhibit the extraordinary properties previously reported, but also incorporate a new degree of freedom: twist tuning, i.e., the possibility of controlling their spectral response by simply rotating the constituent material. To achieve this result, we place a pristine slab of the van der Waals (vdW) α-MoO3 crystal, which supports in-plane hyperbolic PhPs, on an array of metallic ribbons. This sample design based on electromagnetic engineering, not only allows the definition of α-MoO3 nanoresonators with low losses (quality factors, Q, up to 200), but also enables a broad spectral tuning of the polaritonic resonances (up to 32 cm-1, i.e., up to ~6 times their full width at half maximum, FWHM ~5 cm-1) by a simple in-plane rotation of the same slab (from 0 to 45°). These results open the door to the development of tunable and low-loss IR nanotechnologies, fundamental requirements for their implementation in molecular sensing, emission or photodetection applications.

5.
Nat Commun ; 12(1): 4325, 2021 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-34267201

RESUMO

Refraction between isotropic media is characterized by light bending towards the normal to the boundary when passing from a low- to a high-refractive-index medium. However, refraction between anisotropic media is a more exotic phenomenon which remains barely investigated, particularly at the nanoscale. Here, we visualize and comprehensively study the general case of refraction of electromagnetic waves between two strongly anisotropic (hyperbolic) media, and we do it with the use of nanoscale-confined polaritons in a natural medium: α-MoO3. The refracted polaritons exhibit non-intuitive directions of propagation as they traverse planar nanoprisms, enabling to unveil an exotic optical effect: bending-free refraction. Furthermore, we develop an in-plane refractive hyperlens, yielding foci as small as λp/6, being λp the polariton wavelength (λ0/50 compared to the wavelength of free-space light). Our results set the grounds for planar nano-optics in strongly anisotropic media, with potential for effective control of the flow of energy at the nanoscale.

6.
Sci Adv ; 7(14)2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33811076

RESUMO

Polaritons with directional in-plane propagation and ultralow losses in van der Waals (vdW) crystals promise unprecedented manipulation of light at the nanoscale. However, these polaritons present a crucial limitation: their directional propagation is intrinsically determined by the crystal structure of the host material, imposing forbidden directions of propagation. Here, we demonstrate that directional polaritons (in-plane hyperbolic phonon polaritons) in a vdW crystal (α-phase molybdenum trioxide) can be directed along forbidden directions by inducing an optical topological transition, which emerges when the slab is placed on a substrate with a given negative permittivity (4H-silicon carbide). By visualizing the transition in real space, we observe exotic polaritonic states between mutually orthogonal hyperbolic regimes, which unveil the topological origin of the transition: a gap opening in the dispersion. This work provides insights into optical topological transitions in vdW crystals, which introduce a route to direct light at the nanoscale.

7.
Nat Commun ; 12(1): 854, 2021 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-33558559

RESUMO

Large optical anisotropy observed in a broad spectral range is of paramount importance for efficient light manipulation in countless devices. Although a giant anisotropy has been recently observed in the mid-infrared wavelength range, for visible and near-infrared spectral intervals, the problem remains acute with the highest reported birefringence values of 0.8 in BaTiS3 and h-BN crystals. This issue inspired an intensive search for giant optical anisotropy among natural and artificial materials. Here, we demonstrate that layered transition metal dichalcogenides (TMDCs) provide an answer to this quest owing to their fundamental differences between intralayer strong covalent bonding and weak interlayer van der Waals interaction. To do this, we made correlative far- and near-field characterizations validated by first-principle calculations that reveal a huge birefringence of 1.5 in the infrared and 3 in the visible light for MoS2. Our findings demonstrate that this remarkable anisotropy allows for tackling the diffraction limit enabling an avenue for on-chip next-generation photonics.

8.
J Labelled Comp Radiopharm ; 61(7): 533-539, 2018 06 15.
Artigo em Inglês | MEDLINE | ID: mdl-29493011

RESUMO

SCH 430765 and SCH 500496 are potent and selective antagonists of the NPY5 receptor. NPY5 receptor antagonists have the potential for the treatment of obesity. [35 S]SCH 500946 was prepared for a competition binding assay which led to the identification of SCH 430765. Three distinct isotopically labelled forms of SCH 430765 were synthesized. [3 H]SCH 430765 was prepared for a preliminary absorption, distribution, metabolism and excretion data evaluation of the compound and [14 C]SCH 430765 for more definitive absorption, distribution, metabolism and excretion data work. In addition, [13 C2 ,2 H4 ]SCH 430765 was prepared as an internal standard for a LC-MS bioanalytical method. The paper discusses the synthesis of 3 isotopically labelled forms of SCH 430765 and [35 S]SCH 500946.


Assuntos
Piperidinas/síntese química , Piperidinas/farmacologia , Receptores de Neuropeptídeo Y/antagonistas & inibidores , Isótopos de Carbono , Radioisótopos de Carbono , Técnicas de Química Sintética , Marcação por Isótopo , Piperidinas/química , Radioquímica , Radioisótopos de Enxofre , Trítio
9.
J Labelled Comp Radiopharm ; 60(4): 194-199, 2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28129428

RESUMO

MK 3814 is a potent and selective antagonist of the A2a receptor. A2a receptor antagonists have the potential for the treatment of Parkinson disease. Three distinct isotopically labelled forms of MK 3814 were synthesized. [3 H]MK 3814 was prepared for a preliminary absorption, distribution, metabolism, and excretion data (ADME) evaluation of the compound and [14 C]MK 3814 for more definitive ADME work, including an absorption, metabolism, and excretion study in man. In addition, [2 H4 ]MK 3814 was prepared as an internal standard for a liquid chromatography mass spectrometry bioanalytical method. This paper discusses the synthesis of 3 isotopically labelled forms of MK 3814.


Assuntos
Radioisótopos de Carbono/química , Deutério/química , Pirimidinas/química , Pirimidinas/síntese química , Triazóis/química , Triazóis/síntese química , Trítio/química , Técnicas de Química Sintética , Marcação por Isótopo
10.
J Labelled Comp Radiopharm ; 59(5): 190-6, 2016 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-26991320

RESUMO

Vicriviroc or SCH 417690 is a potent and selective antagonist of the CCR5 receptor. CCR5 receptor antagonists have the potential for the treatment of HIV infections. Four distinct isotopically labelled forms of SCH 417690 were synthesized. Low specific activity [(3) H]SCH 417690 was prepared for a preliminary absorption, distribution, metabolism and excretion evaluation of the compound and [(14) C]SCH 417690 for more definitive absorption, distribution, metabolism and excretion work, including an absorption, metabolism and excretion study in man. In addition, high specific activity [(3) H]SCH 417690 was prepared for CCR5 receptor binding work and [(2) H4 ]SCH 417690 was prepared as an internal standard for a liquid chromatography-mass spectrometry bioanalytical method. The paper discusses the synthesis of four isotopically labelled forms of SCH 417690.


Assuntos
Radioisótopos de Carbono/química , Piperazinas/química , Piperazinas/síntese química , Pirimidinas/química , Pirimidinas/síntese química , Trítio/química , Técnicas de Química Sintética , Marcação por Isótopo
11.
J Labelled Comp Radiopharm ; 58(2): 36-41, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25689968

RESUMO

The synthesis of [(3)H]SCH 466036, [Me-(3)H3]SCH 466036, [(13)C,(2)H3,(15)N]SCH 466036 and [(14)C]SCH 466036 is described. [(3)H]SCH 466036 was prepared in two steps via Raney Ni-catalysed exchange with tritiated water. [Me-(3)H3]SCH 466036 was prepared in a single step from [(3)H]methyl iodide in 45% yield. [(13)C,(2)H3,(15)N]SCH 466036 was prepared in two steps from [(15)N]hydroxylamine and [(13)C,(2)H3]methyl iodide with an overall yield of 16%. [(14)C]SCH 466036 was prepared in seven steps from [(14)C]potassium cyanide in an overall yield of 13%.


Assuntos
Aminopiridinas/síntese química , Antagonistas dos Receptores Histamínicos H3/síntese química , Piperidinas/síntese química , Compostos Radiofarmacêuticos/síntese química , Aminopiridinas/farmacologia , Radioisótopos de Carbono/química , Deutério/química , Isótopos de Nitrogênio/química , Piperidinas/farmacologia , Trítio/química
12.
Lik Sprava ; (7): 96-100, 2013.
Artigo em Russo | MEDLINE | ID: mdl-25509922

RESUMO

Installed significantly more pronounced positive effect on clinical manifestations and laboratory indicators of liver in patients with chronic alcoholic hepatitis who received within 4 weeks of basal therapy in conjunction with Gepatomax Forte in comparison with a group of patients with chronic alcoholic hepatitis who received during the same time only basic therapy. Side adverse effects in the group of patients receiving Gepatomax Forte were not registered.


Assuntos
Hepatite Alcoólica/tratamento farmacológico , Lecitinas/uso terapêutico , Silimarina/uso terapêutico , Ácido Tióctico/uso terapêutico , Adulto , Combinação de Medicamentos , Feminino , Hepatite Alcoólica/diagnóstico , Humanos , Lecitinas/administração & dosagem , Testes de Função Hepática , Masculino , Pessoa de Meia-Idade , Silimarina/administração & dosagem , Ácido Tióctico/administração & dosagem , Resultado do Tratamento
13.
J Cell Mol Med ; 8(2): 241-8, 2004.
Artigo em Inglês | MEDLINE | ID: mdl-15256072

RESUMO

To study effects of short-term cerebral ischemia, hippocampal slice cultures were subjected to oxygen and glucose deprivation (OGD) followed by a period of normoxic reoxygenation. Propidium iodide staining, and MTT/formazan-assay were used to evaluate cell viability and metabolic activity. CA1 pyramidal cells were analyzed at the light- and electron microscopic levels. Cell damage was found to be insignificant during the first hour after 10 min OGD but profound following 4 h, showing delayed neuronal cell damage caused by short-term OGD. Our model can be used to characterize the mechanisms of cell damage caused by mild cerebral ischemia. These data might apply to further development of neuroprotective tools for the treatment of brain diseases.


Assuntos
Glucose/farmacologia , Hipocampo/efeitos dos fármacos , Hipocampo/patologia , Oxigênio/farmacologia , Animais , Sobrevivência Celular/efeitos dos fármacos , Glucose/deficiência , Hipocampo/enzimologia , Hipocampo/metabolismo , L-Lactato Desidrogenase/metabolismo , Microscopia Eletrônica de Transmissão , Ratos , Ratos Wistar , Fatores de Tempo , Técnicas de Cultura de Tecidos
14.
Fiziol Zh (1994) ; 50(2): 94-100, 2004.
Artigo em Ucraniano | MEDLINE | ID: mdl-15174211

RESUMO

We studied morphofunctional changes in organotypic hippocampal slice cultures (OHSC) subjected to oxygen-glucose deprivation (OGD) for 10, 30, and 60 min followed by normoxic reoxygenation for 1, 4, and 24 h. Cell viability was estimated using trypan blue (TB) staining, lactate dehydrogenase (LDH) assay, and MTT/formazan assay. Structural changes in CA1 area of OHSC were analyzed by light and electron microscopy. No significant signs of destruction were found in the cultures 1 h following 10 min OGD; moreover, clear increase in cell metabolic activity was determined by MTT/formazan assay. Ultrastructural analysis of CA1 stratum radiatum revealed an increase in the number of glial processes and the number of perforated and multiple synapses as compared to the control, where simple synapses were relatively more numerous. 4 h following 10 min OGD, manifestations of cell damage in the cultures appeared and become profound at 24 h after OGD. We suppose that mild (10 min) OGD leads to plastic changes in neurons and delayed cell damage. 30 and 60 min OGD resulted in more early and pronounced cell damage as compared to 10 min OGD. To conclude, clear dependence of cell damage on the duration of deprivation as well as reoxygenation was observed. The model of ischemic damage in the slice cultures appears convenient to be used to analyze properties and mechanisms of neural cell response to OGD and to test neuroprotective tools.


Assuntos
Glucose/metabolismo , Hipocampo/patologia , Oxigênio/metabolismo , Animais , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/fisiologia , Meios de Cultura , Glucose/farmacologia , Hipocampo/metabolismo , Hipocampo/ultraestrutura , Microscopia Confocal , Microscopia Eletrônica , Neurônios/metabolismo , Neurônios/ultraestrutura , Técnicas de Cultura de Órgãos , Oxigênio/farmacologia , Ratos , Fatores de Tempo
16.
Med Tekh ; (5): 35-7, 2003.
Artigo em Russo | MEDLINE | ID: mdl-14603849

RESUMO

An experience of using, at the State Sanitary and Epidemiologic Supervision (SSES), the Control X-ray Dosimeter (DRK-1) to calculate the dose-square product in the radiation-and-hygienic evaluation of medical X-ray units of different types is described in the paper. The qualitative evaluation monitoring applicable to X-ray equipment is based on the finding and subsequent analysis of graphic dose-square relationships, i.e. anode voltage(measured manually or by X-ray exposure meter), exposition time, anode current, and current-time product. Real graphs for both normally functioning and for malfunctioning units are depicted. The unit radiation output is described.


Assuntos
Radiografia/instrumentação , Radiometria/instrumentação , Tecnologia Radiológica/instrumentação , Equipamentos para Diagnóstico , Desenho de Equipamento , Controle de Qualidade , Doses de Radiação
17.
Fiziol Zh (1994) ; 49(1): 38-45, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-12675022

RESUMO

Myelin sheaths, wrapping axons, perform the following important functions: support, protection, feeding and isolation. Injury of myelin compact structure leads to an impairment and severe illness of the nerve system. Exact mechanisms underlying the myelination process and myelin sheaths damage have not established yet. Therefore search for substances, which provide regulatory and protective effects on the normal myelination as well as stimulating action on the remyelination after myelin damage, is of special interest. Recently it was shown that extract from mushroom Hericium erinaceus had activating action on the nerve tissue. So the aim of the present work was to study an influence of an extract from H. erinaceus on the cerebellar cells and the process of myelination in vitro. Obtained data revealed the normal growth of the nerve and glial cells with extract at cultivating. No pathologic or toxic action of the extract has been found. The cell ultrastructure was intact and similar to that observed in vivo. The process of myelination in the presence of the extract began earlier as compared to controls and was characterised by a higher rate. Thus, extract of H. erinaceus promoted normal development of cultivated cerebellar cells and demonstrated a regulatory effect on the process of myelin genesis process in vitro.


Assuntos
Basidiomycota/química , Bainha de Mielina/ultraestrutura , Fármacos Neuroprotetores/farmacologia , Animais , Adesão Celular/efeitos dos fármacos , Divisão Celular/efeitos dos fármacos , Células Cultivadas , Cerebelo/efeitos dos fármacos , Cerebelo/ultraestrutura , Microscopia Eletrônica , Bainha de Mielina/efeitos dos fármacos , Fármacos Neuroprotetores/isolamento & purificação , Ratos , Ratos Wistar
18.
Arch Clin Neuropsychol ; 16(6): 587-604, 2001 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-14590156

RESUMO

Neuropsychological deficits in children diagnosed with attention deficit/hyperactivity disorder (ADHD) have been well documented utilizing various neuropsychological tests. Only recently has research begun to examine if similar deficits are present in adults with ADHD. A neuropsychological testing battery was constructed that assessed verbal learning and memory, psychomotor speed, and sustained attention--all demonstrated to be deficient in individuals with ADHD. Fifty-six self-referred nonmedicated adults with a DSM-IV diagnosis of ADHD and 38 normal comparison adults participated. ADHD adults demonstrated verbal and nonverbal memory deficits and decreased psychomotor speed compared to normal controls. Differences between ADHD and normal adults were not documented on traditional measures of executive functioning. A pattern of results emerged whereby ADHD adults' performance, particularly with regard to psychomotor speed, became more impaired as task complexity increased. This study's results largely corroborate similar neuropsychological testing results in ADHD children and recent ADHD adult findings, and support a frontal lobe dysfunction hypothesis of ADHD.

19.
Med Tekh ; (3): 15-7, 1998.
Artigo em Russo | MEDLINE | ID: mdl-9720011

RESUMO

The effective dose obtained by a patient on X-ray diagnostic studies may be determined by the Russian and foreign devices that measure the product of the absorbed dose by the radiation area while using the transition factors presented. They are calculated by the published data on the surface and effective doses per exposure unit, which are obtained on the phantoms by thermoluminescence dosimetry by taking into account the area of radiation, anode voltage, and projection, which characterize the standard conditions for performing basic X-ray diagnostic studies of adults and children (5 age groups). In the anode voltage range 40-120 kV, the factors are 10(-4) to 2.10.cm2) with errors of about +/- 32%.


Assuntos
Radiografia/estatística & dados numéricos , Adulto , Criança , Humanos , Doses de Radiação , Radiometria/instrumentação , Radiometria/estatística & dados numéricos
20.
Med Tekh ; (3): 39-42, 1998.
Artigo em Russo | MEDLINE | ID: mdl-9720019

RESUMO

Basic Russian documents providing radiation safety for a patient during X-ray studies are dealt with. They identify 3 groups of individuals exposed to radiation with relevant annual control levels of an effective dose, necessitates to keep a radiation dose log, and enlists of individual protective means, etc. During different X-ray diagnostic studies, the patient's effective dose may be estimated by the table from the guidelines or from the readings. The characteristics of Russian apparatuses (ID-01 is under production, DRIM-1 has undergone technical and clinical tests) and foreign (PTW-Diamentor E, M1, M2, M3 and VacuDAP 2001) apparatuses which measure the exposure dose are product.


Assuntos
Proteção Radiológica/instrumentação , Radiografia/instrumentação , Humanos , Doses de Radiação , Radiometria/instrumentação , Federação Russa
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...