Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 51
Filtrar
Mais filtros

Base de dados
País/Região como assunto
Tipo de documento
Intervalo de ano de publicação
1.
RSC Adv ; 10(13): 7918-7926, 2020 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-35492179

RESUMO

CaMn1-x Nb x O3 (x = 0, 0.5, 0.6, 0.7 and 0.10) thin films have been grown by a two-step sputtering/annealing method. First, rock-salt-structured (Ca,Mn1-x ,Nb x )O thin films were deposited on 11̄00 sapphire using reactive RF magnetron co-sputtering from elemental targets of Ca, Mn and Nb. The CaMn1-x Nb x O3 films were then obtained by thermally induced phase transformation from rock-salt-structured (Ca,Mn1-x Nb x )O to orthorhombic during post-deposition annealing at 700 °C for 3 h in oxygen flow. The X-ray diffraction patterns of pure CaMnO3 showed mixed orientation, while Nb-containing films were epitaxially grown in [101] out of-plane-direction. Scanning transmission electron microscopy showed a Ruddlesden-Popper (R-P) secondary phase in the films, which results in reduction of the electrical and thermal conductivity of CaMn1-x Nb x O3. The electrical resistivity and Seebeck coefficient of the pure CaMnO3 film were measured to 2.7 Ω cm and -270 µV K-1 at room temperature, respectively. The electrical resistivity and Seebeck coefficient were reduced by alloying with Nb and was measured to 0.09 Ω cm and -145 µV K-1 for x = 0.05. Yielding a power factor of 21.5 µW K-2 m-1 near room temperature, nearly eight times higher than for pure CaMnO3 (2.8 µW K-2 m-1). The power factors for alloyed samples are low compared to other studies on phase-pure material. This is due to high electrical resistivity originating from the secondary R-P phase. The thermal conductivity of the CaMn1-x Nb x O3 films is low for all samples and is the lowest for x = 0.07 and 0.10, determined to 1.6 W m-1 K-1. The low thermal conductivity is attributed to grain boundary scattering and the secondary R-P phase.

2.
J Mater Sci ; 54(2): 1434-1442, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30930478

RESUMO

Cr2N is commonly found as a minority phase or inclusion in stainless steel, CrN-based hard coatings, etc. However, studies on phase-pure material for characterization of fundamental properties are limited. Here, Cr2N thin films were deposited by reactive magnetron sputtering onto (0001) sapphire substrates. X-ray diffraction and pole figure texture analysis show Cr2N (0001) epitaxial growth. Scanning electron microscopy imaging shows a smooth surface, while transmission electron microscopy and X-ray reflectivity show a uniform and dense film with a density of 6.6 g cm-3, which is comparable to theoretical bulk values. Annealing the films in air at 400 °C for 96 h shows little signs of oxidation. Nano-indentation shows an elastic-plastic behavior with H = 18.9 GPa and E r = 265 GPa. The moderate thermal conductivity is 12 W m-1 K-1, and the electrical resistivity is 70 µΩ cm. This combination of properties means that Cr2N may be of interest in applications such as protective coatings, diffusion barriers, capping layers and contact materials.

3.
Nanoscale Adv ; 1(9): 3680-3685, 2019 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-36133532

RESUMO

MXenes are a rapidly growing family of 2D materials that exhibit a highly versatile structure and composition, allowing for significant tuning of the materials properties. These properties are, however, ultimately limited by the surface terminations, which are typically a mixture of species, including F and O that are inherent to the MXene processing. Other and robust terminations are lacking. Here, we apply high-resolution scanning transmission electron microscopy (STEM), corresponding image simulations and first-principles calculations to investigate the surface terminations on MXenes synthesized from MAX phases through Lewis acidic melts. The results show that atomic Cl terminates the synthesized MXenes, with mere residual presence of other termination species. Furthermore, in situ STEM-electron energy loss spectroscopy (EELS) heating experiments show that the Cl terminations are stable up to 750 °C. Thus, we present an attractive new termination that widely expands the MXenes' functionalization space and enables new applications.

4.
Eur Geriatr Med ; 10(2): 275-283, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-34652762

RESUMO

Falls are a major public health concern in the older population, and certain medication classes are a significant risk factor for falls. However, knowledge is lacking among both physicians and older people, including caregivers, concerning the role of medication as a risk factor. In the present statement, the European Geriatric Medicine Society (EuGMS) Task and Finish group on fall-risk-increasing drugs (FRIDs), in collaboration with the EuGMS Special Interest group on Pharmacology and the European Union of Medical Specialists (UEMS) Geriatric Medicine Section, outlines its position regarding knowledge dissemination on medication-related falls in older people across Europe. The EuGMS Task and Finish group is developing educational materials to facilitate knowledge dissemination for healthcare professionals and older people. In addition, steps in primary prevention through judicious prescribing, deprescribing of FRIDs (withdrawal and dose reduction), and gaps in current research are outlined in this position paper.

5.
Drugs Aging ; 36(4): 299-307, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30741371

RESUMO

Falls are a major public health concern in the older population, and certain medication classes are a significant risk factor for falls. However, knowledge is lacking among both physicians and older people, including caregivers, concerning the role of medication as a risk factor. In the present statement, the European Geriatric Medicine Society (EuGMS) Task and Finish group on fall-risk-increasing drugs (FRIDs), in collaboration with the EuGMS Special Interest group on Pharmacology and the European Union of Medical Specialists (UEMS) Geriatric Medicine Section, outlines its position regarding knowledge dissemination on medication-related falls in older people across Europe. The EuGMS Task and Finish group is developing educational materials to facilitate knowledge dissemination for healthcare professionals and older people. In addition, steps in primary prevention through judicious prescribing, deprescribing of FRIDs (withdrawal and dose reduction), and gaps in current research are outlined in this position paper.


Assuntos
Acidentes por Quedas/prevenção & controle , Analgésicos Opioides/efeitos adversos , Anticonvulsivantes/efeitos adversos , Geriatria/métodos , Psicotrópicos/efeitos adversos , Inibidores de Simportadores de Cloreto de Sódio e Potássio/efeitos adversos , Acidentes por Quedas/estatística & dados numéricos , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Europa (Continente) , União Europeia , Geriatria/normas , Humanos , Polimedicação , Fatores de Risco
6.
J Nanosci Nanotechnol ; 8(1): 393-9, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18468089

RESUMO

The growth of Diluted Magnetic Semiconducting (DMS) Zn(1-x)Mn(x)S (0 < or = x < 0.6) nanowires (NWs) using a three-zone furnace and two solid sources is reported. The approach is generally applicable to many binary and ternary NW systems that grow by the Vapor-Liquid-Solid growth mechanism. Mn concentration was controlled by the temperature of the Mn source. The Zn/Mn ratio was found to determine the crystalline structure, i.e., wurtzite or zinc blende. High-resolution transmission electron microscopy measurements revealed highly crystalline single phase NWs. The vibrational properties of the DMS NWs with different Zn/Mn ratios were studied by correlating their Raman scattering spectra with the composition measured by Energy Dispersive X-Ray Spectroscopy (EDS). We find that the transverse optical (TO) phonon band disappears at the lowest Mn concentrations, while the longitudinal optical (LO) phonon band position was found insensitive to x. Three additional Raman bands were observed between the ZnS q = 0 TO and LO phonons when Mn atoms were present in the NWs. These bands are similar to those reported previously for bulk Zn(1-x)Mn(x)S and their origin is still controversial.

7.
J Nanosci Nanotechnol ; 8(1): 1-26, 2008 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-18468051

RESUMO

This paper provides a review of the state-of-the-art electronic-structure calculations of semiconductor nanowires. Results obtained using empirical k.p, empirical tight-binding, semi-empirical pseudopotential, and with ab initio methods are compared. For conciseness, we will restrict our detailed discussions to free-standing plain and modulated nanowires. Connections to relevant experimental data, particularly band gaps and polarization anisotropy, will be made since these results depend crucially on the electronic properties. For completeness, a brief review on the synthesis of nanowires is included.

8.
J Mater Sci ; 53(6): 4294-4305, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-31997832

RESUMO

Scandium nitride has recently gained interest as a prospective compound for thermoelectric applications due to its high Seebeck coefficient. However, ScN also has a relatively high thermal conductivity, which limits its thermoelectric efficiency and figure of merit (zT). These properties motivate a search for other semiconductor materials that share the electronic structure features of ScN, but which have a lower thermal conductivity. Thus, the focus of our study is to predict the existence and stability of such materials among inherently layered equivalent ternaries that incorporate heavier atoms for enhanced phonon scattering and to calculate their thermoelectric properties. Using density functional theory calculations, the phase stability of TiMgN2, ZrMgN2 and HfMgN2 compounds has been calculated. From the computationally predicted phase diagrams for these materials, we conclude that all three compounds are stable in these stoichiometries. The stable compounds may have one of two competing crystal structures: a monoclinic structure (LiUN2 prototype) or a trigonal superstructure (NaCrS2 prototype; R 3 ¯ mH). The band structure for the two competing structures for each ternary is also calculated and predicts semiconducting behavior for all three compounds in the NaCrS2 crystal structure with an indirect band gap and semiconducting behavior for ZrMgN2 and HfMgN2 in the monoclinic crystal structure with a direct band gap. Seebeck coefficient and power factors are also predicted, showing that all three compounds in both the NaCrS2 and the LiUN2 structures have large Seebeck coefficients. The predicted stability of these compounds suggests that they can be synthesized by, e.g., physical vapor deposition.

9.
Chem Commun (Camb) ; 53(69): 9554-9557, 2017 Aug 24.
Artigo em Inglês | MEDLINE | ID: mdl-28804799

RESUMO

Incorporation of layers of noble metals in non-van der Waals layered materials may be used to form novel layered compounds. Recently, we demonstrated a high-temperature-induced exchange process of Au with Si in the layered phase Ti3SiC2, resulting in the formation of Ti3AuC2 and Ti3Au2C2. Here, we generalize this technique showing that Au/Ti2AlC and Au/Ti3AlC2 undergo an exchange reaction at 650 °C to form Ti2Au2C and Ti3Au2C2 and determine their structures by electron microscopy, X-ray diffraction, and ab initio calculations. These results imply that noble-metal-containing layered phases should be possible to synthesize in many systems. The metal to be introduced should be inert to the transition-metal carbide layers, and exhibit negative heat of mixing with the initial A element in a liquid phase or two-phase liquid/solid region at the annealing temperature.

10.
J Nutr Health Aging ; 21(1): 92-104, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-27999855

RESUMO

The Strategic Implementation Plan of the European Innovation Partnership on Active and Healthy Ageing (EIP on AHA) proposed six Action Groups. After almost three years of activity, many achievements have been obtained through commitments or collaborative work of the Action Groups. However, they have often worked in silos and, consequently, synergies between Action Groups have been proposed to strengthen the triple win of the EIP on AHA. The paper presents the methodology and current status of the Task Force on EIP on AHA synergies. Synergies are in line with the Action Groups' new Renovated Action Plan (2016-2018) to ensure that their future objectives are coherent and fully connected. The outcomes and impact of synergies are using the Monitoring and Assessment Framework for the EIP on AHA (MAFEIP). Eight proposals for synergies have been approved by the Task Force: Five cross-cutting synergies which can be used for all current and future synergies as they consider overarching domains (appropriate polypharmacy, citizen empowerment, teaching and coaching on AHA, deployment of synergies to EU regions, Responsible Research and Innovation), and three cross-cutting synergies focussing on current Action Group activities (falls, frailty, integrated care and chronic respiratory diseases).


Assuntos
Envelhecimento , Comportamentos Relacionados com a Saúde , População Branca , Acidentes por Quedas/prevenção & controle , Idoso , Idoso de 80 Anos ou mais , Doença Crônica , Comportamento Cooperativo , Europa (Continente) , Idoso Fragilizado , Humanos , Múltiplas Afecções Crônicas , Inovação Organizacional , Polimedicação , Inquéritos e Questionários
11.
J Phys Chem B ; 109(49): 23358-65, 2005 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-16375307

RESUMO

We present results of a systematic high-resolution transmission electron microscopy study of the thermal evolution of bundled single-walled carbon nanotubes (SWNTs) subjected to approximately 4-h high-temperature heat treatment (HTT) in a vacuum at successively higher temperatures up to 2200 degrees C. We have examined purified SWNT material derived from the HiPCO and ARC processes. These samples were found to thermally evolve along very different pathways that we propose depend on three factors: (1) initial diameter distribution, (2) concomitant tightness of the packing of the tubes in a bundle, and (3) the bundle size. Graphitic nanoribbons (GNR) were found to be the dominant high-temperature filament in ARC material after HTT = 2000 degrees C; they were not observed in any heat-treated HiPCO material. The first two major steps in the thermal evolution of HiPCO and ARC material agree with the literature, i.e., coalescence followed by the formation of multiwall carbon nanotubes (MWNTs). However, ARC material evolves to bundled MWNTs, while HiPCO evolves to isolated MWNTs. In ARC material, we find that the MWNTs collapse into multishell GNRs. The thermal evolution of these carbon systems is discussed in terms of the diameter distribution, nanotube coalescence pathways, C-C bond rearrangement, diffusion of carbon and subsequent island formation, as well as the nanotube collapse driven by van der Waals forces.

12.
Chem Commun (Camb) ; 51(30): 6560-3, 2015 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-25768789

RESUMO

We report the discovery of a new hexagonal Mo2Ga2C phase, wherein two Ga layers ­ instead of one ­ are stacked in a simple hexagonal arrangement in between Mo2C layers. It is reasonable to assume this compound is the first of a larger family.

13.
Metabolism ; 38(9): 869-73, 1989 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-2528051

RESUMO

Sex steroid treatment is associated with side effects. The number of deaths and morbidity cases in 425 transsexual patients treated with cross-gender hormones were evaluated retrospectively and compared with the expected number in a similar reference group of the population. The number of deaths in male-to-female transsexuals was five times the number expected, due to increased numbers of suicide and death of unknown cause. Combined treatment with estrogen and cyproterone acetate in 303 male-to-female transsexuals was associated with a 45-fold increase of thromboembolic events, hyperprolactinemia (400-fold), depressive mood changes (15-fold), and transient elevation of liver enzymes. Androgen treatment in 122 female-to-male transsexuals was associated with weight increase greater than 10% (17.2%) and acne (12.3%). In both groups persistent liver enzyme abnormalities could be attributed to other causes than sex steroids (hepatitis B and alcohol abuse). Much of the morbidity was minor and reversible with appropriate treatment or temporary discontinuation of hormone treatment. Thus, the dilemma of prescribing cross gender hormones in view of the needs of these patients is not resolved. Explanation of possible side effects and careful clinical judgment remain the cornerstone of the clinical decision to prescribe cross-gender hormones. Furthermore, follow up of this relatively young population to disclose long-term side effects and to elucidate the association of sex steroids with coronary heart disease, as well as efforts to reduce the risk of thromboembolic events, are required.


Assuntos
Hormônios Esteroides Gonadais/efeitos adversos , Transexualidade/tratamento farmacológico , Adolescente , Adulto , Idoso , Ciproterona/efeitos adversos , Ciproterona/análogos & derivados , Acetato de Ciproterona , Estrogênios/efeitos adversos , Feminino , Hormônios Esteroides Gonadais/uso terapêutico , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores Sexuais , Testosterona/efeitos adversos , Testosterona/análogos & derivados , Transexualidade/mortalidade
14.
J Nanosci Nanotechnol ; 3(4): 335-9, 2003 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-14598449

RESUMO

Gallium phosphide nanowires with a most probable diameter of approximately 20.0 nm and more than 10 microns in length have been synthesized by pulsed laser vaporization of a heated GaP/5% Au target. The morphology and microstructure of GaP nanowires have been investigated by scanning electron microscopy and transmission electron microscopy. Twins have been observed along the crystalline nanowires, which have a growth direction of [111]. Raman scattering shows a 4 cm-1 downshift of the longitudinal optical phonon peak in the nanowire with respect to the bulk; the transverse optical phonon frequency and line width are, however, the same as in the bulk. The quantum confinement model first proposed by Richter et al. cannot explain the observed behavior of the Raman modes.


Assuntos
Cristalografia/métodos , Gálio/química , Nanotecnologia/instrumentação , Nanotecnologia/métodos , Nanotubos/química , Nanotubos/ultraestrutura , Fosfinas/química , Análise Espectral Raman/métodos , Condutividade Elétrica , Instalação Elétrica , Conformação Molecular , Fosfinas/síntese química , Semicondutores
15.
J Nanosci Nanotechnol ; 3(1-2): 139-43, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-12908242

RESUMO

We report the pressure dependence for the radial (omega R) and tangential (omega T) band frequencies in debundled single-walled carbon nanotubes (SWNTs) derived from laser-synthesized SWNT bundles. As previously described, a chemical procedure was used to prepare debundled SWNTs from as-prepared, large SWNT bundles. The normalized pressure coefficient for omega R in the debundled sample was compared with the corresponding value in the bundled sample to quantify the strength of van der Waals interactions between tubes in these nanotube materials. Furthermore, the pressure dependences for the radial (omega R) and tangential (omega T) band frequencies in debundled tubes were also compared with corresponding dependences predicted for isolated SWNTs, obtained with generalized tight binding molecular dynamic (GTBMD) simulations described in our previous work. The results presented here collectively suggest that the van der Waals interaction is still strong in the debundled sample studied here, which contained predominantly small bundles of SWNTs rather than isolated tubes.


Assuntos
Cristalização/métodos , Teste de Materiais/métodos , Nanotubos de Carbono/química , Nanotubos de Carbono/classificação , Análise Espectral Raman/métodos , Catálise , Metais/química , Conformação Molecular , Nanotecnologia/métodos , Nanotubos de Carbono/isolamento & purificação , Pressão , Semicondutores , Propriedades de Superfície
16.
J Nanosci Nanotechnol ; 2(6): 621-6, 2002 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-12908425

RESUMO

Here we report Raman scattering studies of ropes of Single-walled carbon nanotubes (SWNTs) grown by a high CO pressure process. Five samples from five different batches were studied as a function of excitation wavelength. Three of these samples exhibited Raman spectra similar to that found for SWNTs made by pulsed laser vaporization of arc-discharge methods. The other two samples were found by Raman scattering to contain a significant fraction of tubes with diameter < 1.0 nm. These samples exhibited unusual spectra that, however, can be well understood within the existing models for the electronic and phononic states in SWNTs. Spectra recorded with 1064 nm for the sample having a significant fraction of smaller diameter tubes shows strong modes present between 500 and 1200 cm-1. We suggest these modes arise due to the enhancement of Raman cross-section for small diameter tubes.


Assuntos
Monóxido de Carbono/química , Cristalização/métodos , Nanotecnologia/métodos , Nanotubos de Carbono/química , Análise Espectral Raman/métodos , Simulação por Computador , Gases/química , Modelos Moleculares , Conformação Molecular , Nanotubos de Carbono/classificação , Pressão
17.
IEEE Trans Neural Netw ; 3(5): 815-8, 1992.
Artigo em Inglês | MEDLINE | ID: mdl-18276481

RESUMO

A foundational development of propositional fuzzy logic programs is presented. Fuzzy logic programs are structured knowledge bases including uncertainties in rules and facts. The precise specifications of uncertainties have a great influence on the performance of the knowledge base. It is shown how fuzzy logic programs can be transformed to neural networks, where adaptations of uncertainties in the knowledge base increase the reliability of the program and are carried out automatically.

18.
Comput Methods Programs Biomed ; 61(3): 209-19, 2000 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-10710183

RESUMO

The objective was to build a computer-based decision support system (DSS), which could apply the formal rules embedded in guidelines regarding pharmacological treatment of hypertension. The aim was also to test VISUAL BASIC as a development tool for DSS's in health care. From the Swedish guidelines for treatment of hypertension, the most widely accepted and scientifically best proved treatment strategies were chosen and implemented as rules. A DSS that is capable of applying the evidence-based rules extracted from guidelines regarding drug treatment of hypertension, to any patient's medical profile, was constructed. The output consists of a recommendation regarding preferred generic drug class and also a written report, reflecting decision steps provided by the rule-base and inference engine. We also provide methods for formalising an implementable language of guidelines. A mainstream programming language like VISUAL BASIC can be an alternative when building complicated decision support systems. A logic formal notation can facilitate communication between the expert and the programmer. The program is a stand-alone product independent of computerized medical records and thereby easy to install and maintain.


Assuntos
Anti-Hipertensivos/uso terapêutico , Sistemas de Apoio a Decisões Clínicas , Hipertensão/tratamento farmacológico , Anti-Hipertensivos/economia , Qualidade de Produtos para o Consumidor , Guias como Assunto , Humanos
19.
Int J Obstet Anesth ; 4(2): 89-92, 1995 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15636984

RESUMO

Forty patients had epidural catheters placed for analgesia in active labour. For caesarean section patients in the epidural (EA) group (n = 20) had epidural anaesthesia with 0.5% bupivacaine supplemented if necessary with 2% lidocaine with adrenaline. Patients in the general anaesthesia (GA) group (n = 20) had standardized general anaesthesia for surgery. In both groups 4 mg of morphine in 8 ml of 0.25% bupivacaine was given epidurally after delivery of the baby. During the first 3 h of the postoperative period, as long as the epidural block was effective, patients in the EA group experienced significantly less pain. At 6, 12 and 24 h pain estimations were equal in both groups. Patients in the EA group consumed significantly less pain medication during the first 24 h after surgery (P = 0.0002). Itching was less frequent in the GA group (P = 0.011). It is concluded that epidural administration of 4 mg of morphine produces more effective postoperative pain relief when emergency caesarean section is conducted under epidural than when it is conducted under general anaesthesia.

20.
Artigo em Inglês | MEDLINE | ID: mdl-7569742

RESUMO

Non-linear models, such as given by neural networks and fuzzy logic, have established a good reputation for medical data analysis as computational and logical counterparts to statistical methods. Whereas multilayer perceptrons perform well with large data sets, a combination of neural learning together with fuzzy logical network interpretations provides a network reduction well suited for smaller data sets. The aim of this paper is to present an approach to neural fuzzy systems data analysis and knowledge acquisition in laboratory information systems. We also describe a software system, DiagaiD, which provides an analysis and development workbench involving laboratory data.


Assuntos
Sistemas de Informação em Laboratório Clínico , Sistemas Computacionais , Interpretação Estatística de Dados , Lógica Fuzzy , Redes Neurais de Computação , Dinâmica não Linear , Software
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA