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1.
J Am Chem Soc ; 146(14): 9564-9574, 2024 Apr 10.
Artigo em Inglês | MEDLINE | ID: mdl-38557024

RESUMO

The serotonergic transmitter system plays fundamental roles in the nervous system in neurotransmission, synaptic plasticity, pathological processes, and therapeutic effects of antidepressants and psychedelics, as well as in the gastrointestinal and circulatory systems. We introduce a novel small molecule fluorescent agent, termed SERTlight, that specifically labels serotonergic neuronal cell bodies, dendrites, and axonal projections as a serotonin transporter (SERT) fluorescent substrate. SERTlight was developed by an iterative molecular design process, based on an aminoethyl-quinolone system, to integrate structural elements that impart SERT substrate activity, sufficient fluorescent brightness, and a broad absence of pharmacological activity, including at serotonin (5-hydroxytryptamine, 5HT) receptors, other G protein-coupled receptors (GPCRs), ion channels, and monoamine transporters. The high labeling selectivity is not achieved by high affinity binding to SERT itself but rather by a sufficient rate of SERT-mediated transport of SERTlight, resulting in accumulation of these molecules in 5HT neurons and yielding a robust and selective optical signal in the mammalian brain. SERTlight provides a stable signal, as it is not released via exocytosis nor by reverse SERT transport induced by 5HT releasers such as MDMA. SERTlight is optically, pharmacologically, and operationally orthogonal to a wide range of genetically encoded sensors, enabling multiplexed imaging. SERTlight enables labeling of distal 5HT axonal projections and simultaneous imaging of the release of endogenous 5HT using the GRAB5HT sensor, providing a new versatile molecular tool for the study of the serotonergic system.


Assuntos
Corantes Fluorescentes , Serotonina , Animais , Serotonina/metabolismo , Corantes Fluorescentes/metabolismo , Neurônios/metabolismo , Proteínas da Membrana Plasmática de Transporte de Serotonina/metabolismo , Encéfalo/metabolismo , Mamíferos/metabolismo
2.
Medicina (Kaunas) ; 58(12)2022 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-36557034

RESUMO

Background and Objectives: Kawasaki Disease (KD) incidence has been on the rise globally throughout the years, particularly in the Asia Pacific region. KD can be diagnosed based on several clinical criteria. Due to its systemic inflammatory nature, multi-organ involvement has been observed, making the diagnosis of KD more challenging. Notably, several studies have reported KD patients presenting with hepatobiliary abnormalities. Nonetheless, comprehensive data regarding the hepatobiliary manifestations of KD are limited in Malaysia, justifying a more in-depth study of the disease in this country. Thus, in this article, we aim to discuss KD patients in Malaysia with hepatobiliary manifestations. Materials and Methods: A total of six KD patients with hepatobiliary findings who presented at Hospital Canselor Tuanku Muhriz (HCTM) from 2004 to 2021 were selected and included. Variables including the initial presenting signs and symptoms, clinical progress, laboratory investigations such as liver function test (LFT), and ultrasound findings of hepatobiliary system were reviewed and analyzed. Results: Out of these six KD patients, there were two patients complicated with hepatitis and one patient with gallbladder hydrops. Different clinical features including jaundice (n = 3) and hepatomegaly (n = 4) were also observed. All patients received both aspirin and intravenous immunoglobulin (IVIG) as their first-line treatment and all of them responded well to IVIG. The majority of them (n = 5) had a complete recovery and did not have any cardiovascular and hepatobiliary sequelae. Conclusions: Despite KD mostly being diagnosed with the classical clinical criteria, patients with atypical presentations should always alert physicians of KD as one of the possible differential diagnoses. This study discovered that hepatobiliary manifestations in KD patients were not uncommon. More awareness on the epidemiology, diagnosis, and management of KD patients with hepatobiliary manifestations are required to allow for the initiation of prompt treatment, thus preventing further complications.


Assuntos
Síndrome de Linfonodos Mucocutâneos , Humanos , Lactente , Síndrome de Linfonodos Mucocutâneos/complicações , Síndrome de Linfonodos Mucocutâneos/diagnóstico , Síndrome de Linfonodos Mucocutâneos/epidemiologia , Imunoglobulinas Intravenosas/uso terapêutico , Aspirina/uso terapêutico , Diagnóstico Diferencial , Malásia , Estudos Retrospectivos
3.
J Drugs Dermatol ; 20(3): 307-310, 2021 03 01.
Artigo em Inglês | MEDLINE | ID: mdl-33683079

RESUMO

Acne vulgaris is a common skin disease that manifests clinically as comedones, papules, nodules, and cysts. In this single center, open-label pilot study (ISRCTN13992386), we aimed to evaluate the effectiveness of UP256 cream, a newly patented topical product containing 0.5% bakuchiol, on facial acne and acne-related post-inflammatory hyperpigmentation (PIH). A series of 13 subjects enriched for Fitzpatrick skin types III–VI with mild or moderate acne received treatment with UP256 twice daily for 12 weeks. Efficacy assessments included changes in inflammatory and non-inflammatory lesions as well as a reduction in Evaluator Global Severity Score (EGSS) assessments of acne severity and PIH. Safety, adverse events, and cutaneous tolerability were evaluated throughout the study. UP256 significantly reduced the number of inflammatory lesions and improved existing PIH. UP256 was also cosmetically acceptable and well tolerated by all study subjects. Overall, our results demonstrate that monotherapy with UP256 improves mild to moderate acne and may be particularly well suited for individuals with skin of color. J Drugs Dermatol. 2021;20(3):307-310. doi:10.36849/JDD.5655.


Assuntos
Acne Vulgar/tratamento farmacológico , Fenóis/administração & dosagem , Creme para a Pele/administração & dosagem , Acne Vulgar/diagnóstico , Adolescente , Adulto , Criança , Face , Feminino , Humanos , Masculino , Fenóis/efeitos adversos , Projetos Piloto , Índice de Gravidade de Doença , Creme para a Pele/efeitos adversos , Resultado do Tratamento , Adulto Jovem
4.
Inorg Chem ; 58(17): 11730-11737, 2019 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-31415155

RESUMO

We report crystal growth, AC and DC magnetic susceptibilities [χ(T, H)], magnetization [M(T, H)], and heat capacity [CP(T, H)] measurement results of GdSbTe single crystal. GdSbTe is isostructural to the confirmed nonmagnetic nodal-line semimetal ZrSiS of noncentrosymmetric tetragonal crystal structure in space group P4/nmm (No. 129), but it shows additional long-range antiferromagnetic spin ordering for the Gd spins of S = 7/2 below TN. Both χ(T, H) and CP(T, H) measurements confirm the existence of a long-range antiferromagnetic (AFM) spin ordering of Gd spins below TN ∼ 12 K, and an additional spin reorientation/recovery (sr) behavior is identified from the change of on-site spin anisotropy between Tsr1 ∼ 7 and Tsr2 ∼ 4 K. The anisotropic magnetic susceptibilities of χ(T, H) below TN clearly demonstrate that the AFM long-range spin ordering of GdSbTe has an easy axis parallel to the ab-plane direction. The field- and orientation-dependent magnetization of M(T, H) at 2 K shows two plateaus to indicate the spin-flop transition for H||ab near ∼2.1 T and a metamagnetic state near ∼5.9 T having ∼1/3 of the fully polarized magnetization by the applied field. The heat capacity measurement results yield Sommerfeld coefficient of γ ∼ 7.6(4) mJ/mol K2 and θD ∼ 195(2) K being less than half of that for the nonmagnetic ZrSiS. A three-dimensional (3D) AFM spin structure is supported by the ab initio calculations for Gd having magnetic moment of 7.1 µB and the calculated AFM band structure indicates that GdSbTe is a semimetal with bare density of states (0.36 states/eV fu) at the Fermi level, which is 10 times smaller than the measured one to suggest strong spin-fluctuation.

5.
Phys Rev Lett ; 118(13): 135901, 2017 Mar 31.
Artigo em Inglês | MEDLINE | ID: mdl-28409955

RESUMO

Low-dimensional materials could display anomalous thermal conduction that the thermal conductivity (κ) diverges with increasing lengths, in ways inconceivable in any bulk materials. However, previous theoretical or experimental investigations were plagued with many finite-size effects, rendering the results either indirect or inconclusive. Indeed, investigations on the anomalous thermal conduction must demand the sample length to be sufficiently long so that the phenomena could emerge from unwanted finite-size effects. Here we report experimental observations that the κ's of single-wall carbon nanotubes continuously increase with their lengths over 1 mm, reaching at least 8640 W/mK at room temperature. Remarkably, the anomalous thermal conduction persists even with the presence of defects, isotopic disorders, impurities, and surface absorbates. Thus, we demonstrate that the anomalous thermal conduction in real materials can persist over much longer distances than previously thought. The finding would open new regimes for wave engineering of heat as well as manipulating phonons at macroscopic scales.

6.
Soft Matter ; 13(18): 3314-3327, 2017 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-28418057

RESUMO

High resolution surface textures, when rationally designed, provide an attractive surface engineering approach to enhance surface functionalities. Designing smart surfaces by coupling surface texture with shape memory polymers has garnered attention in achieving tunable mechanical properties. We investigate the structure-mechanical property relationships for programmable, shape-memorizing submicron-scale pillar arrays subjected to flat-punch compression. The geometrically-dependent deformation of structured surfaces with two different aspect ratios (250 nm-pillars 1 : 1 and 550 nm-pillars 2.4 : 1) were investigated, and their moduli were found to be lower than that of non-patterned surface. From finite element analysis, the pillar deformation is correlated to a mechanistic transition from a discrete, unidirectional compression of 250 nm-pillars to lateral constraints caused by interpillar contact in 550 nm-pillars. This lateral pillar-pillar contact in the 550 nm-pillars resulted in an increased and maximum strain-dependent modulus but lower elastic recovery and energy dissipation as compared with the 250 nm-pillars. Furthermore, the compressive responses of temporarily shaped pillars (programmed by stretching) were compared with the permanently shaped pillars. The extent of lateral constraints controlled by pillar shape and spacing in 550 nm-pillars was responsible for the modulus differences between the original and stretched patterns, whereas the modulus of 250 nm-pillars remained as a constant value with different levels of stretching. This study provides mechanistic insights into how the mechanical behavior can be modulated by designing the aspect ratio of shape memory pillar arrays and by programming the surface geometry, thus revealing the potential of developing ingenious designs of responsive surfaces sensitive to mechanical deformation.

7.
Opt Express ; 24(15): 16479-86, 2016 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-27464101

RESUMO

We employ a self-assembly method to fabricate dielectric microsphere arrays that can be transferred to any desired positions. The arrays not only enable far-field, broad-band, high-speed, large-area, and wide-angle field of views but also achieve superresolution reaching λ/6.4. We also find that many proposed theories are insufficient to explain the imaging properties; including the achieved superresolution, effects of immersion, and unusual size-dependent magnification. The half-immersed microspheres certainly do not behave like any ordinary solid immersion lenses and new mechanisms must be incorporated to explain their unusual imaging properties.

8.
Inorg Chem ; 54(9): 4303-9, 2015 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-25864534

RESUMO

By both experimental measurements and theoretical calculations, we investigated the magnetic and electronic properties of Li2Cu(WO4)2 as a tungstate-bridged quasi-one-dimensional (1D) copper spin-(1/2) chain system. Interestingly, magnetic susceptibility χ(T) and specific heat measurements show that the system undergoes a three-dimensional antiferromagnetic (AF)-like ordering at TN ≈ 3.7 K, below a broad χ(T) maximum at ∼8.9 K indicating a low-dimensional short-range AF spin correlation. Bonner-Fisher model fitting of χ(T) leads to an AF intrachain exchange constant of J/kB = 15.8 ± 0.1 K, and mean-field theory estimation gives an interchain coupling constant of J⊥/kB = 1.6 K, which supports the quasi-1D nature of this spin system. Theoretical evaluation of exchange coupling constants within the generalized gradient approximation (GGA) plus on-site Coulomb interaction (U) shows that the dominant AF exchange interaction is of ∼13.9 K along the a-axis with weak interchain coupling, in agreement with the experimental result of a quasi-1D spin-(1/2) chain system. The GGA+U calculations also predict that Li2Cu(WO4)2 is a charge transfer-type AF semiconductor with a direct band gap of 1.5 eV.

9.
Small ; 10(19): 3986-96, 2014 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-24947558

RESUMO

First-line cancer chemotherapy necessitates high parenteral dosage and repeated dosing of a combination of drugs over a prolonged period. Current commercially available chemotherapeutic agents, such as Doxil and Taxol, are only capable of delivering single drug in a bolus dose. The aim of this study is to develop dual-drug-loaded, multilayered microparticles and to investigate their antitumor efficacy compared with single-drug-loaded particles. Results show hydrophilic doxorubicin HCl (DOX) and hydrophobic paclitaxel (PTX) localized in the poly(dl-lactic-co-glycolic acid, 50:50) (PLGA) shell and in the poly(l-lactic acid) (PLLA) core, respectively. The introduction of poly[(1,6-bis-carboxyphenoxy) hexane] (PCPH) into PLGA/PLLA microparticles causes PTX to be localized in the PLLA and PCPH mid-layers, whereas DOX is found in both the PLGA shell and core. PLGA/PLLA/PCPH microparticles with denser shells allow better control of DOX release. A delayed release of PTX is observed with the addition of PCPH. Three-dimensional MCF-7 spheroid studies demonstrate that controlled co-delivery of DOX and PTX from multilayered microparticles produces a greater reduction in spheroid growth rate compared with single-drug-loaded particles. This study provides mechanistic insights into how distinctive structure of multilayered microparticles can be designed to modulate the release profiles of anticancer drugs, and how co-delivery can potentially provide better antitumor response.


Assuntos
Microesferas , Polímeros/química , Esferoides Celulares/química , Antineoplásicos/química , Doxorrubicina/química , Sistemas de Liberação de Medicamentos , Humanos , Interações Hidrofóbicas e Hidrofílicas , Ácido Láctico/química , Células MCF-7 , Microscopia Confocal , Microscopia Eletrônica de Varredura , Polianidridos/química , Poliésteres , Ácido Poliglicólico/química , Copolímero de Ácido Poliláctico e Ácido Poliglicólico , Análise Espectral Raman
10.
Opt Express ; 22 Suppl 4: A1128-36, 2014 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-24978075

RESUMO

Large and periodic anti-ring arrays are fabricated by using a monolayer of polymer/nanosphere hybrid technique and applied as back reflectors in substrate-type hydrogenated amorphous silicon (a-Si:H) thin-film solar cells. The structure of each anti-ring comprises a nanodome centered inside a nanohole. The excitation of Bloch wave surface plasmon polaritons is observed in the Ag-coated anti-ring arrays. The nanodomes of the anti-ring arrays turn out to enhance large-angle light scattering and increase the effective optical path in the solar cell. The resulting efficiency of an ultrathin a-Si:H (thickness: 150 nm) solar cell is enhanced by 39% compared to that with a flat back reflector and by 13% compared to that with a nanohole back reflector.

11.
Phys Rev Lett ; 113(13): 137201, 2014 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-25302915

RESUMO

We investigate the quantum anomalous Hall effect (QAHE) and related chiral transport in the millimeter-size (Cr(0.12)Bi(0.26)Sb(0.62))2Te3 films. With high sample quality and robust magnetism at low temperatures, the quantized Hall conductance of e²/h is found to persist even when the film thickness is beyond the two-dimensional (2D) hybridization limit. Meanwhile, the Chern insulator-featured chiral edge conduction is manifested by the nonlocal transport measurements. In contrast to the 2D hybridized thin film, an additional weakly field-dependent longitudinal resistance is observed in the ten-quintuple-layer film, suggesting the influence of the film thickness on the dissipative edge channel in the QAHE regime. The extension of the QAHE into the three-dimensional thickness region addresses the universality of this quantum transport phenomenon and motivates the exploration of new QAHE phases with tunable Chern numbers. In addition, the observation of scale-invariant dissipationless chiral propagation on a macroscopic scale makes a major stride towards ideal low-power interconnect applications.

12.
J Drugs Dermatol ; 11(7): 834-6, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22777225

RESUMO

INTRODUCTION: Ultraviolet B (UVB, 290 nm to 320 nm) has been reported to modulate the cytokine-mediated inflammatory process in various inflammatory skin conditions, including production of TNF-α, IL-1α, IL-6, IL-8, and IL-10. We constructed an in vitro model system involving co-culture of different cell types to study the effect of UVB on the inflammatory process using nitric oxide (NO) and tumor necrosis factor (TNF)-α as markers of inflammation. OBJECTIVE: This study was conducted to quantitatively assess the products secreted by human epithelial keratinocytes in the presence and absence of macrophages/monocytes. METHODS: Cells were exposed to UVB radiation (50 mJ to 200 mJ per cm2) or treated with bacterial lipopolysaccharide (LPS) as stimulator of inflammatory response. Nitric oxide (NO) was measured by modified Griess assay and TNF-α was measured by quantitative ELISA. For the co-culture system, SC monocytes were seeded in a 24-well Transwell tissue culture plate whereas irradiated keratinocytes were seeded in the individual baskets subsequently placed on top of the monocyte cultures, and samples of culture supernatants were collected at 1 to 6 days. RESULTS: When primary human epidermal keratinocytes (NHEK) were irradiated with UVB, a dose-dependent stimulation of TNF-α production was observed (33% to 200% increase). TNF-α production was not changed significantly in SC monocytes/NHEK co-culture. In contrast, when macrophages were irradiated with UVB, significant inhibition of NO production (40% suppression, P<0.001) was seen. CONCLUSION: This improved model of cutaneous inflammation could use multiple cells to study their interactions and to offer convenience, reproducibility, and a closer approximation of in vivo conditions.


Assuntos
Acne Vulgar/terapia , Inflamação/terapia , Modelos Biológicos , Terapia Ultravioleta/métodos , Acne Vulgar/patologia , Animais , Técnicas de Cocultura , Ensaio de Imunoadsorção Enzimática , Células Epiteliais/metabolismo , Células Epiteliais/efeitos da radiação , Humanos , Inflamação/patologia , Interleucinas/metabolismo , Interleucinas/efeitos da radiação , Queratinócitos/metabolismo , Queratinócitos/efeitos da radiação , Lipopolissacarídeos/toxicidade , Camundongos , Camundongos Endogâmicos BALB C , Óxido Nítrico/metabolismo , Óxido Nítrico/efeitos da radiação , Fagócitos/metabolismo , Fagócitos/efeitos da radiação , Fator de Necrose Tumoral alfa/metabolismo , Fator de Necrose Tumoral alfa/efeitos da radiação , Raios Ultravioleta
13.
J Mater Sci Mater Med ; 23(1): 81-8, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-22127404

RESUMO

This work reports how novel multi-layered (from double-layered to quadruple-layered) microparticles comprising immiscible polymers can be fabricated through a simple, economical, reliable and versatile one-step solvent evaporation method. These multi-layered microparticles would be excellent candidates to overcome problems inherent in single-layered microparticles for drug delivery. Particle morphologies, layer configurations, and drug distribution were determined by scanning electron microscopy and Raman mapping. Key process parameters achieving the formation of the multi-layered structure were identified. Encapsulation of multiple drugs and layer localization of these drugs within these multi-layered microparticles have also shown to be possible, which were driven by drug-polymer affinity. This one-step fabrication technique can therefore be used for tailoring particle designs, thus facilitating the development of multiparticulate drug delivery devices.


Assuntos
Microesferas , Polímeros/química , Cromatografia Líquida de Alta Pressão , Desenho de Fármacos , Microscopia Eletrônica de Varredura , Análise Espectral Raman
14.
Adv Sci (Weinh) ; 9(23): e2105720, 2022 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-35713280

RESUMO

Optical response of crystalline solids is to a large extent driven by excitations that promote electrons among individual bands. This allows one to apply optical and magneto-optical methods to determine experimentally the energy band gap -a fundamental property crucial to our understanding of any solid-with a great precision. Here it is shown that such conventional methods, applied with great success to many materials in the past, do not work in topological Dirac semimetals with a dispersive nodal line. There, the optically deduced band gap depends on how the magnetic field is oriented with respect to the crystal axes. Such highly unusual behavior is explained in terms of band-gap renormalization driven by Lorentz boosts which results from the Lorentz-covariant form of the Dirac Hamiltonian relevant for the nodal line at low energies.

15.
Phys Rev Lett ; 107(18): 186602, 2011 Oct 28.
Artigo em Inglês | MEDLINE | ID: mdl-22107659

RESUMO

The thermoelectric power of a material, typically governed by its band structure and carrier density, can be varied by chemical doping that is often restricted by solubility of the dopant. Materials showing large thermoelectric power are useful for many industrial applications, such as the heat-to-electricity conversion and the thermoelectric cooling device. Here we show a full electric-field tuning of thermoelectric power in a dual-gated bilayer graphene device resulting from the opening of a band gap by applying a perpendicular electric field on bilayer graphene. We uncover a large enhancement in thermoelectric power at a low temperature, which may open up a new possibility in low temperature thermoelectric application using graphene-based device.

16.
J Adv Res ; 28: 269-275, 2021 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-33364062

RESUMO

INTRODUCTION: Space travel nowadays relies on physical ejection of propellants, which is challenged by reachable distance of a vehicle in desirable time. In contrast, electromagnetic propulsion was proposed to be a potential solution without need of carrying bulky mass of propellants, by using force interaction of local magnetic dipoles with the external natural magnetic field. Further development of this technique, however, has been daunted by extremely small magnetic induction that can be obtained. OBJECTIVES: To generate a significant thrust by a system with a reasonable scale, we propose an alternative concept of design, based on the variation of local magnetic dipole moments that has not been considered. METHODS: A magnetic dipole is created by wrapping a solenoid around an iron core. It is varied spatially by changing the cross-sectional area of the solenoid, hence giving a gradient of magnetic dipole moment. The interaction force is measured by an in-house force sensor based on a cantilever, which has a high sensitivity of one micro-Newton. In addition, numerical simulation is used to calculate the magnetic field and created force via the Maxwell stress tensor. RESULTS: As shown by experimental measurements and numerical simulations, a substantially larger magnitude of force is obtained on the solenoid with varying cross-sectional area, indicating a much stronger interaction with the geomagnetic field. Furthermore, to enhance electric current with negligible dissipation, a superconducting solenoid can be adopted at low temperature in space. With readily attainable conditions of operation, we demonstrate generation of a thrust comparable to that of present electric propulsion thrusters which are deemed as the most promising techniques for long-term space travel. CONCLUSIONS: By incorporating supplementary means, we provide a breakthrough solution for constructing an efficient thruster with minimal energy consumption and nearly null propellant load for near-Earth transportation and deep-space exploration.

17.
ACS Chem Neurosci ; 12(24): 4546-4553, 2021 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-34817175

RESUMO

Myriad neuropsychiatric disorders are due to dopamine dysfunction. However, understanding these disorders is limited by our ability to measure dopamine storage and release. Fluorescent false neurotransmitters (FFNs), small-molecule dyes that co-transit through the synaptic vesicle cycle, have allowed us to image dopamine in cell culture and acute brain slice, but in vivo microscopy is constrained by the biopenetrance of light. Here, we adapt FFNs into magnetic resonance false neurotransmitters (MFNs). The design principles guiding MFNs are (1) the molecule is a valid false neurotransmitter and (2) it has a 19F-substituent near a pH-sensing functional group, which (3) has pKa close to 6 so that the probe within vesicles is protonated. We demonstrate that MFN103 meets these criteria. While a magnetic resonance spectroscopy (MRS) signal was too low for measurement in vivo with the current technology, in principle, MFNs can quantify neurotransmitters within and without synaptic vesicles, which may underlie noninvasive in vivo analysis of dopamine neurotransmission.


Assuntos
Dopamina , Vesículas Sinápticas , Corantes Fluorescentes , Espectroscopia de Ressonância Magnética , Neurotransmissores , Transmissão Sináptica
18.
Sci Rep ; 11(1): 16070, 2021 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-34373527

RESUMO

The growth of SrRuO[Formula: see text] (SRO) thin film with high-crystallinity and low residual resistivity (RR) is essential to explore its intrinsic properties. Here, utilizing the adsorption-controlled growth technique, the growth condition of initial SrO layer on TiO[Formula: see text]-terminated SrTiO[Formula: see text] (STO) (001) substrate was found to be crucial for achieving a low RR in the resulting SRO film grown afterward. The optimized initial SrO layer shows a c(2 [Formula: see text] 2) superstructure that was characterized by electron diffraction, and a series of SRO films with different thicknesses (ts) were then grown. The resulting SRO films exhibit excellent crystallinity with orthorhombic-phase down to [Formula: see text] 4.3 nm, which was confirmed by high resolution X-ray measurements. From X-ray azimuthal scan across SRO orthorhombic (02 ± 1) reflections, we uncover four structural domains with a dominant domain of orthorhombic SRO [001] along cubic STO [010] direction. The dominant domain population depends on t, STO miscut angle ([Formula: see text]), and miscut direction ([Formula: see text]), giving a volume fraction of about 92 [Formula: see text] for [Formula: see text] 26.6 nm and [Formula: see text] (0.14[Formula: see text], 5[Formula: see text]). On the other hand, metallic and ferromagnetic properties were well preserved down to t [Formula: see text] 1.2 nm. Residual resistivity ratio (RRR = [Formula: see text]/[Formula: see text]) reduces from 77.1 for t [Formula: see text] 28.5 nm to 2.5 for t [Formula: see text] 1.2 nm, while [Formula: see text] increases from 2.5 [Formula: see text]cm for t [Formula: see text] 28.5 nm to 131.0 [Formula: see text]cm for t [Formula: see text] 1.2 nm. The ferromagnetic onset temperature ([Formula: see text]) of around 151 K remains nearly unchanged down to t [Formula: see text] 9.0 nm and decreases to 90 K for t [Formula: see text] 1.2 nm. Our finding thus provides a practical guideline to achieve high crystallinity and low RR in ultra-thin SRO films by simply adjusting the growth of initial SrO layer.

19.
Anal Chem ; 82(4): 1277-82, 2010 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-20017529

RESUMO

Raman mapping measurements were performed on the cross section of the ternary-phase biodegradable double-walled microsphere (DWMS) of poly(D,L-lactide-co-glycolide) (50:50) (PLGA), poly(L-lactide) (PLLA), and poly(epsilon-caprolactone) (PCL), which was fabricated by a one-step solvent evaporation method. The collected Raman spectra were subjected to a band-target entropy minimization (BTEM) algorithm in order to reconstruct the pure component spectra of the species observed in this sample. Seven pure component spectral estimates were recovered, and their spatial distributions within DWMS were determined. The first three spectral estimates were identified as PLLA, PLGA 50:50, and PCL, which were the main components in DWMS. The last four spectral estimates were identified as semicrystalline polyglycolic acid (PGA), dichloromethane (DCM), copper-phthalocyanine blue, and calcite, which were the minor components in DWMS. PGA was the decomposition product of PLGA. DCM was the solvent used in DWMS fabrication. Copper-phthalocyanine blue and calcite were the unexpected contaminants. The current result showed that combined Raman microscopy and BTEM analysis can provide a sensitive characterization tool to DWMS, as it can give more specific information on the chemical species present as well as the spatial distributions. This novel analytical method for microsphere characterization can serve as a complementary tool to other more established analytical techniques, such as scanning electron microscopy and optical microscopy.


Assuntos
Microscopia , Microesferas , Análise Espectral Raman , Biopolímeros/química , Entropia , Microscopia Eletrônica de Varredura , Solventes/química
20.
Small ; 6(9): 1003-11, 2010 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-20358528

RESUMO

Particulate systems have tremendous potential to achieve controlled release and targeted delivery of drugs. However, conventional single-layered particles have several inherent limitations, including initial burst release, the inability to provide zero-order release, and a lack of time-delayed or pulsatile release of therapeutic agents. Multilayered particles have the potential to overcome these disadvantages. Herein, it is shown how triple-layered polymeric microparticles can be fabricated through a simple, economical, reliable, and versatile one-step solvent evaporation technique. Particle morphologies and layer configurations are determined by scanning electron microscopy, polymer dissolution tests, and Raman mapping. Key fabrication parameters that affect the formation of triple-layered polymeric microparticles comprising poly(DL-lactide-co-glycolide) (50:50), poly(L-lactide), and poly(ethylene-co-vinyl acetate) (40 wt% vinyl acetate) are discussed, along with their formation mechanisms. Layer thickness and the configurations of these microparticles are altered by changing the polymer mass ratios. Finally, it is shown that drugs can be localized in specific layers of the microparticles. This fabrication process can therefore be used to tailor microparticle designs, thus allowing such "designer" particulate drug-delivery systems to function across a wide range of applications.


Assuntos
Cápsulas/síntese química , Preparações de Ação Retardada/síntese química , Polímeros/química , Cristalização/métodos , Composição de Medicamentos/métodos , Teste de Materiais
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