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1.
Hong Kong Med J ; 30(4): 291-299, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-39147587

RESUMO

INTRODUCTION: Type 2 diabetes mellitus (T2DM) is becoming increasingly common among children and adolescents worldwide, including those in Hong Kong. This study analysed the characteristics and prevalence of microvascular complications among paediatric T2DM patients in Hong Kong at diagnosis and 2 years after diagnosis. METHODS: All patients aged <18 years who had been diagnosed with DM at public hospitals in Hong Kong were recruited into the Hong Kong Childhood Diabetes Registry. Data collected at diagnosis and 2 years after diagnosis were retrospectively retrieved from the Registry for patients diagnosed from 2014 to 2018. RESULTS: Median haemoglobin A1c (HbA1c) levels were 7.5% (n=203) at diagnosis and 6.5% (n=135) 2 years after diagnosis; 59.3% of patients achieved optimal glycaemic control (HbA1c level <7%) at 2 years. A higher HbA1c level at diagnosis was associated with worse glycaemic control at 2 years (correlation coefficient=0.39; P<0.001). The presence of dyslipidaemia (adjusted odds ratio [aOR]=3.19; P=0.033) and fatty liver (aOR=2.50; P=0.021) at 2 years were associated with suboptimal glycaemic control. Diabetic neuropathy and retinopathy were rare in our cohort, but 18.6% of patients developed microalbuminuria (MA) within 2 years after diagnosis. Patients with MA had a higher HbA1c level at 2 years (median: 7.2% vs 6.4%; P=0.037). Hypertension was a risk factor for MA at 2 years, independent of glycaemic control (aOR=4.61; P=0.008). CONCLUSION: These results highlight the importance of early diagnosis and holistic management (including co-morbidity management) for paediatric T2DM patients.


Assuntos
Diabetes Mellitus Tipo 2 , Hemoglobinas Glicadas , Controle Glicêmico , Sistema de Registros , Humanos , Hong Kong/epidemiologia , Diabetes Mellitus Tipo 2/complicações , Masculino , Feminino , Criança , Adolescente , Hemoglobinas Glicadas/análise , Estudos Retrospectivos , Angiopatias Diabéticas/epidemiologia , Angiopatias Diabéticas/diagnóstico , Prevalência , Glicemia/análise , Fatores de Risco , Pré-Escolar
2.
Philos Trans A Math Phys Eng Sci ; 377(2155): 20190013, 2019 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-31424345

RESUMO

This paper focuses on the Gap Rock lighthouse, a legendary maritime infrastructure built 130 years ago in the Chinese territory and an early example of joint venture among the Qing Dynasty, the British Empire and the Hong Kong Colonial Government over a course of two decades. Based on 4 years of cross-territorial archival and field research as well as in-depth interviews with descendants of two key stakeholders, the origin of this lasting legacy on the sea is traced, followed by a detailed account of its challenging processes of planning, design and construction, and of the considerable damage to the compound by a severe typhoon in 1893. A qualitative analysis of the key contributing factors of the damage was conducted by taking into consideration the Island's unique topography and the historical records of territorial weather reports. A re-construction of the typhoon impact on the Lighthouse is presented to explain the possible mistakes in its siting and design that eventually caused the severe damage. This serves as a reminder of the significance of a thorough geographical investigation for any infrastructure for all construction professionals in the face of climatic change. This article is part of the theme issue 'Environmental loading of heritage structures'.

3.
BMC Health Serv Res ; 17(1): 757, 2017 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-29162086

RESUMO

BACKGROUND: eHealth has potential for supporting interdisciplinary care in contemporary traumatic brain injury (TBI) rehabilitation practice, yet little is known about whether this potential is being realised, or what needs to be done to further support its implementation. The purpose of this study was to explore health professionals' experiences of, and attitudes towards eHealth technologies to support interdisciplinary practice within rehabilitation for people after TBI. METHODS: A qualitative study using narrative analysis was conducted. One individual interview and three focus groups were conducted with health professionals (n = 17) working in TBI rehabilitation in public and private healthcare settings across regional and metropolitan New South Wales, Australia. RESULTS: Narrative analysis revealed that participants held largely favourable views about eHealth and its potential to support interdisciplinary practice in TBI rehabilitation. However, participants encountered various issues related to (a) the design of, and access to electronic medical records, (b) technology, (c) eHealth implementation, and (d) information and communication technology processes that disconnected them from the work they needed to accomplish. In response, health professionals attempted to make the most of unsatisfactory eHealth systems and processes, but were still mostly unsuccessful in optimising the quality, efficiency, and client-centredness of their work. CONCLUSIONS: Attention to sources of disconnection experienced by health professionals, specifically design of, and access to electronic health records, eHealth resourcing, and policies and procedures related to eHealth and interdisciplinary practice are required if the potential of eHealth for supporting interdisciplinary practice is to be realised.


Assuntos
Atitude do Pessoal de Saúde , Lesões Encefálicas Traumáticas/reabilitação , Pessoal de Saúde , Telemedicina , Adulto , Atenção à Saúde , Registros Eletrônicos de Saúde , Grupos Focais , Humanos , Entrevistas como Assunto , Pessoa de Meia-Idade , New South Wales , Equipe de Assistência ao Paciente , Pesquisa Qualitativa , Telemedicina/métodos
4.
Allergy ; 70(6): 689-96, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25773990

RESUMO

RATIONALE: Nasal allergen provocations may be useful in investigating the pathophysiology of allergic rhinitis and effects of treatments. OBJECTIVE: To use grass pollen nasal allergen challenge (NAC) to investigate the effects of allergen immunotherapy in a cross-sectional study. METHODS: We studied nasal and cutaneous responses in untreated subjects with seasonal grass-pollen allergic rhinitis (n = 14) compared with immunotherapy-treated allergics (n = 14), plus a nonatopic control group (n = 14). Volunteers underwent a standardized NAC with 2000 biological units of timothy grass allergen (equivalent to 1.3 µg major allergen, Phl p5). Nasal fluid was collected and analysed by ImmunoCAP and multiplex assays. Clinical response was assessed by symptom scores and peak nasal inspiratory flow (PNIF). Cutaneous response was measured by intradermal allergen injection. Retrospective seasonal symptom questionnaires were also completed. RESULTS: Immunotherapy-treated patients had lower symptom scores (P = 0.04) and higher PNIF (P = 0.02) after challenge than untreated allergics. They had reduced early (P = 0.0007) and late (P < 0.0001) skin responses, and lower retrospective seasonal symptom scores (P < 0.0001). Compared to untreated allergics, immunotherapy-treated patients had reduced nasal fluid concentrations of IL-4, IL-9 and eotaxin (all P < 0.05, 8 h level and/or area under the curve comparison), and trends for reduced IL-13 (P = 0.07, area under the curve) and early-phase tryptase levels (P = 0.06). CONCLUSIONS: Nasal allergen challenge is sensitive in the detection of clinical and biological effects of allergen immunotherapy and may be a useful surrogate marker of treatment efficacy in future studies.


Assuntos
Citocinas/imunologia , Mucosa Nasal/imunologia , Phleum/imunologia , Extratos Vegetais/uso terapêutico , Pólen/imunologia , Rinite Alérgica Sazonal/tratamento farmacológico , Rinite Alérgica/tratamento farmacológico , Administração Intranasal , Adulto , Secreções Corporais/imunologia , Estudos de Casos e Controles , Estudos Transversais , Dessensibilização Imunológica , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Mucosa Nasal/metabolismo , Rinite Alérgica/imunologia , Rinite Alérgica Sazonal/imunologia , Imunoterapia Sublingual , Resultado do Tratamento , Adulto Jovem
5.
Nat Genet ; 18(1): 76-80, 1998 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-9425906

RESUMO

Human chromosomes terminate in a series of T2AG3 repeats, which, together with associated proteins, are essential for chromosome stability. In somatic cells, these sequences are known to be gradually lost through successive cells divisions; however, information about changes on specific chromosomes is not available. Individual telomeres could mediate important biological effects as was shown in yeast, in which loss of a single telomere results in cell-cycle arrest and chromosome loss. We now demonstrate by quantitative fluorescence in situ hybridization (Q-FISH; ref. 7) that the number of T2AG3 repeats on specific chromosome arms is very similar in different tissues from the same donor and varies only to some extent between donors. In all sixteen individuals studied, telomeres on chromosome 17p were shorter than the median telomere length--a finding confirmed by analysis of terminal restriction fragments from sorted chromosomes. These observations provide evidence of chromosome-specific factors regulating the number of T2AG3 repeats in individual telomeres and raise the possibility that the relatively short telomeres on chromosome 17p contribute to the frequent loss of 17p alleles in human cancers.


Assuntos
Cromossomos Humanos Par 17 , Telômero , Adulto , Células da Medula Óssea , Carbocianinas , Células Cultivadas , Fibroblastos/citologia , Corantes Fluorescentes , Humanos , Processamento de Imagem Assistida por Computador , Hibridização in Situ Fluorescente , Indóis , Metáfase , Sequências Repetitivas de Ácido Nucleico
6.
Nanomaterials (Basel) ; 13(10)2023 May 18.
Artigo em Inglês | MEDLINE | ID: mdl-37242087

RESUMO

Mn4N thin film is one of the potential magnetic mediums for spintronic devices due to its ferrimagnetism with low magnetization, large perpendicular magnetic anisotropy (PMA), thermal stability, and large domain wall velocity. Recent experiments confirmed the existence of tunable magnetic skyrmions in MgO/Mn4N/CuxPt1-x(x = 0, 0.5, 0.9, 0.95), and density functional theory (DFT) calculation provided a large theoretical value of the interfacial Dzyaloshinskii-Moriya interaction (iDMI) of Mn4N/Pt, which is consistent with the predicted chemical trend of the DMI in transition metal/Pt films. So far, the measured DMI has not been reported in Mn4N, which is needed in order to support the predicted large DMI value. This paper reports the average DMI of MgO/Mn4N(17 nm)/CuxPt1-x(3 nm) extracted from the anomalous Hall effect with various tilted angles, which is based on magnetic droplet theory with DMI effects. The DMI decreases from 0.267 mJ/m2 to 0.011 mJ/m2 with non-linear tendencies as Cu concentration in the CuxPt1-x capping layer increases from 0 to 1, demonstrating the control of the DMI through the CuxPt1-x capping layer. Furthermore, a solid solution model is developed based on an X-ray photoelectron spectroscopy (XPS) compositional depth profile to analyze the possible effects on the DMI from the mixing layers at the surface of Mn4N. After taking into account the mixing layers, the large DMI in Mn4N film with Pt capping is consistent with the predicted DMI.

7.
J Nutr Health Aging ; 27(2): 166-171, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36806871

RESUMO

OBJECTIVES: Malnutrition, particularly protein insufficiency, is common in institutionalised older adults and increases morbidity, mortality, and costs. We aimed to determine whether 12 months supplementation using high-protein foods (milk, cheese, yoghurt) prevents malnutrition in older adults. DESIGN: Cluster randomised control study. SETTING: Sixty Australian aged care facilities. PARTICIPANTS: Older adults living in aged care homes (n=654, mean age 86.7±7.2 years, 72% females). Intervention Facilities randomly allocated to a high-protein (n=30 intervention) or regular (n=30 controls) menu. MEASUREMENTS: Nutritional status assessed using the Mini Nutrition Assessment (MNA) tool and fasting morning blood samples (n=302) assayed for haemoglobin (Hb) and albumin. Food intake was monitored 3-monthly using visual plate waste assessment. Measurements at baseline and month 12 were analysed using random effects model accounting for clustering (facility), repeated measure and confounders. RESULTS: Addition of 11g of protein as 1.5 servings of high-protein foods daily preserved nutritional status that deteriorated in controls [MNA screen (-0.68, 95%CI: -1.03, -0.32, p<0.001) and total (-0.90, 95%CI: -1.45, -0.35, p=0.001) scores], resulting in group differences in MNA screen (0.62, 95%CI: 0.17, 1.06, p=0.007) and total (0.81, 95%CI: 0.11, 1.51, p=0.023) scores and group difference in Hb (3.60g/L, 95%CI: 0.18, 7.03, p=0.039), the net result of preservation with intervention (0.19g/L, 95%CI: -2.04, 2.42, p=0.896) and a decline in controls (-3.41g/L, 95%CI: -6.01, -0.82, p=0.010). No group differences were observed for serum albumin. CONCLUSION: Consumption of high-protein foods is a pragmatic approach to maintaining nutritional status in older adults in aged-care.


Assuntos
Desnutrição , Estado Nutricional , Idoso , Feminino , Humanos , Idoso de 80 Anos ou mais , Masculino , Austrália , Desnutrição/prevenção & controle , Avaliação Nutricional , Instituição de Longa Permanência para Idosos
8.
Nanomaterials (Basel) ; 13(21)2023 Oct 27.
Artigo em Inglês | MEDLINE | ID: mdl-37947693

RESUMO

The ability to manipulate spins in magnetic materials is essential in designing spintronics devices. One method for magnetic switching is through strain. In VO2 on TiO2 thin films, while VO2 remains rutile across the metal-insulator transition, the in-plane lattice area expands going from a low-temperature insulating phase to a high-temperature conducting phase. In a VO2/TbFeCo bilayer, the expansion of the VO2 lattice area exerts tension on the amorphous TbFeCo layer. Through the strain effect, magnetic properties, including the magnetic anisotropy and magnetization, of TbFeCo can be changed. In this work, the changes in magnetic properties of TbFeCo on VO2/TiO2(011) are demonstrated using anomalous Hall effect measurements. Across the metal-insulator transition, TbFeCo loses perpendicular magnetic anisotropy, and the magnetization in TbFeCo turns from out-of-plane to in-plane. Using atomistic simulations, we confirm these tunable magnetic properties originating from the metal-insulator transition of VO2. This study provides the groundwork for controlling magnetic properties through a phase transition.

9.
Nano Lett ; 11(2): 556-60, 2011 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-21186782

RESUMO

Half-Heuslers would be important thermoelectric materials due to their high temperature stability and abundance if their dimensionless thermoelectric figure of merit (ZT) could be made high enough. The highest peak ZT of a p-type half-Heusler has been so far reported about 0.5 due to the high thermal conductivity. Through a nanocomposite approach using ball milling and hot pressing, we have achieved a peak ZT of 0.8 at 700 °C, which is about 60% higher than the best reported 0.5 and might be good enough for consideration for waste heat recovery in car exhaust systems. The improvement comes from a simultaneous increase in Seebeck coefficient and a significant decrease in thermal conductivity due to nanostructures. The samples were made by first forming alloyed ingots using arc melting and then creating nanopowders by ball milling the ingots and finally obtaining dense bulk by hot pressing. Further improvement in ZT is expected when average grain sizes are made smaller than 100 nm.


Assuntos
Nanoestruturas/química , Nanoestruturas/ultraestrutura , Nanotecnologia/métodos , Semicondutores , Cristalização/métodos , Condutividade Elétrica , Substâncias Macromoleculares/química , Teste de Materiais , Conformação Molecular , Tamanho da Partícula , Propriedades de Superfície , Condutividade Térmica
10.
Sci Rep ; 12(1): 19945, 2022 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-36402797

RESUMO

In spintronics, it is important to be able to manipulate magnetization rapidly and reliably. Several methods can control magnetization, such as by applying current pulses or magnetic fields. An applied current can reverse magnetization with nanosecond speed through the spin torque effect. For faster switching, subpicosecond switching with femtoseconds laser pulse has been achieved in amorphous rare-earth transition-metal ferrimagnets. In this study, we employed atomistic simulations to investigate ultrafast switching in a synthetic antiferromagnet with bilayer amorphous FeGd ferrimagnets. Using a two-temperature model, we demonstrated ultrafast switching in this synthetic antiferromagnet without external magnetic fields. Furthermore, we showed that if we initially stabilize a skyrmion in this heterostructure, the ultrafast laser can switch the skyrmion state using the same mechanism. Furthermore, this bilayer design allows the control of each ferrimagnetic layer individually and opens the possibility for a magnetic tunnel junction.

11.
East Asian Arch Psychiatry ; 31(4): 87-96, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34987119

RESUMO

OBJECTIVES: To investigate the association between alcohol use and depression among university students in Hong Kong, their stress-coping methods, and their knowledge and perception of the effects of alcohol on health. METHODS: 345 full-time undergraduate students from The University of Hong Kong were invited to complete a questionnaire to assess their alcohol consumption (Alcohol Use Disorders Identification Test, CAGE questionnaire), depressive symptoms (Patient Health Questionnaire-9), and stress-coping methods (Coping Orientation to Problems Experienced Inventory), as well as knowledge and perception of alcohol consumption on health. Multiple linear regression was used to determine significant variables associated with depressive symptoms. Multinominal logistic regression was used to determine the effect of such variables on depressive symptom caseness and AUDIT drinking risk groups. RESULTS: 43.2% of respondents were moderate- to high-risk drinkers, but only 23.2% were self-reported as moderate- to high-level drinkers. 57.9% of respondents had mild to severe depressive symptoms. Probable depression was more likely to occur in female students, those with higher general stress, those who do not use social support for stress-coping, and those who smoke. High-risk drinkers were more likely to occur in older students, smokers, those with higher household income, and those with higher general stress levels. Students with higher levels of depressive symptoms and higher risk of alcohol consumption were more likely to use avoidance for stress-coping. 89.5% of students considered alcohol consumption moderately to very harmful to health, but students demonstrated only moderate knowledge levels of alcohol consumption on health. CONCLUSION: Alcohol consumption and depressive symptoms are prevalent among university students in Hong Kong. The use of avoidance for stress-coping is common in those with higher levels of depressive symptoms and higher-risk drinkers. Students tend to avoid seeking help for depressive symptoms and potentially take up drinking as a coping strategy. Context-specific approaches should be used when providing counselling services for student wellbeing in university settings. Further education of university students on knowledge and perception of alcohol consumption on health should be provided.


Assuntos
Alcoolismo , Universidades , Adaptação Psicológica , Idoso , Consumo de Bebidas Alcoólicas/epidemiologia , Alcoolismo/epidemiologia , Depressão/epidemiologia , Feminino , Humanos , Percepção , Estudantes , Inquéritos e Questionários
12.
BMJ ; 375: n2364, 2021 10 20.
Artigo em Inglês | MEDLINE | ID: mdl-34670754

RESUMO

OBJECTIVE: To assess the antifracture efficacy and safety of a nutritional intervention in institutionalised older adults replete in vitamin D but with mean intakes of 600 mg/day calcium and <1 g/kg body weight protein/day. DESIGN: Two year cluster randomised controlled trial. SETTING: 60 accredited residential aged care facilities in Australia housing predominantly ambulant residents. PARTICIPANTS: 7195 permanent residents (4920 (68%) female; mean age 86.0 (SD 8.2) years). INTERVENTION: Facilities were stratified by location and organisation, with 30 facilities randomised to provide residents with additional milk, yoghurt, and cheese that contained 562 (166) mg/day calcium and 12 (6) g/day protein achieving a total intake of 1142 (353) mg calcium/day and 69 (15) g/day protein (1.1 g/kg body weight). The 30 control facilities maintained their usual menus, with residents consuming 700 (247) mg/day calcium and 58 (14) g/day protein (0.9 g/kg body weight). MAIN OUTCOME MEASURES: Group differences in incidence of fractures, falls, and all cause mortality. RESULTS: Data from 27 intervention facilities and 29 control facilities were analysed. A total of 324 fractures (135 hip fractures), 4302 falls, and 1974 deaths were observed. The intervention was associated with risk reductions of 33% for all fractures (121 v 203; hazard ratio 0.67, 95% confidence interval 0.48 to 0.93; P=0.02), 46% for hip fractures (42 v 93; 0.54, 0.35 to 0.83; P=0.005), and 11% for falls (1879 v 2423; 0.89, 0.78 to 0.98; P=0.04). The risk reduction for hip fractures and falls achieved significance at five months (P=0.02) and three months (P=0.004), respectively. Mortality was unchanged (900 v 1074; hazard ratio 1.01, 0.43 to 3.08). CONCLUSIONS: Improving calcium and protein intakes by using dairy foods is a readily accessible intervention that reduces the risk of falls and fractures commonly occurring in aged care residents. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry ACTRN12613000228785.


Assuntos
Acidentes por Quedas/prevenção & controle , Cálcio da Dieta/uso terapêutico , Proteínas Alimentares/uso terapêutico , Fraturas do Quadril/prevenção & controle , Osteoporose/dietoterapia , Fraturas por Osteoporose/prevenção & controle , Idoso , Idoso de 80 Anos ou mais , Austrália/epidemiologia , Método Duplo-Cego , Feminino , Seguimentos , Fraturas do Quadril/epidemiologia , Fraturas do Quadril/etiologia , Instituição de Longa Permanência para Idosos , Humanos , Incidência , Estimativa de Kaplan-Meier , Masculino , Osteoporose/complicações , Fraturas por Osteoporose/epidemiologia , Fraturas por Osteoporose/etiologia , Modelos de Riscos Proporcionais , Estudos Prospectivos , Comportamento de Redução do Risco , Resultado do Tratamento
13.
J Exp Med ; 193(2): 169-80, 2001 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-11148221

RESUMO

Immune responses induced during the early stages of chronic viral infections are thought to influence disease outcome. Using HIV as a model, we examined virus-specific cytotoxic T lymphocytes (CTLs), T helper cells, and viral genetic diversity in relation to duration of infection and subsequent response to antiviral therapy. Individuals with acute HIV-1 infection treated before seroconversion had weaker CTL responses directed at fewer epitopes than persons who were treated after seroconversion. However, treatment-induced control of viremia was associated with the development of strong T helper cell responses in both groups. After 1 yr of antiviral treatment initiated in acute or early infection, all epitope-specific CTL responses persisted despite undetectable viral loads. The breadth and magnitude of CTL responses remained significantly less in treated acute infection than in treated chronic infection, but viral diversity was also significantly less with immediate therapy. We conclude that early treatment of acute HIV infection leads to a more narrowly directed CTL response, stronger T helper cell responses, and a less diverse virus population. Given the need for T helper cells to maintain effective CTL responses and the ability of virus diversification to accommodate immune escape, we hypothesize that early therapy of primary infection may be beneficial despite induction of less robust CTL responses. These data also provide rationale for therapeutic immunization aimed at broadening CTL responses in treated primary HIV infection.


Assuntos
Infecções por HIV/imunologia , Infecções por HIV/virologia , HIV-1/genética , Imunidade Celular , Doença Aguda , Sequência de Aminoácidos , Terapia Antirretroviral de Alta Atividade , Sequência de Bases , Estudos de Coortes , Primers do DNA/genética , Epitopos/genética , Feminino , Variação Genética , Infecções por HIV/tratamento farmacológico , Soropositividade para HIV/imunologia , Soropositividade para HIV/virologia , Humanos , Estudos Longitudinais , Masculino , Dados de Sequência Molecular , RNA Viral/sangue , RNA Viral/genética , Linfócitos T Citotóxicos/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Fatores de Tempo
14.
Sci Rep ; 10(1): 1844, 2020 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-31996762

RESUMO

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

15.
Sci Rep ; 10(1): 7447, 2020 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-32366864

RESUMO

Skyrmions can be stabilized in magnetic systems with broken inversion symmetry and chiral interactions, such as Dzyaloshinskii-Moriya interactions (DMI). Further, compensation of magnetic moments in ferrimagnetic materials can significantly reduce magnetic dipolar interactions, which tend to favor large skyrmions. Tuning DMI is essential to control skyrmion properties, with symmetry breaking at interfaces offering the greatest flexibility. However, in contrast to the ferromagnet case, few studies have investigated interfacial DMI in ferrimagnets. Here we present a systematic study of DMI in ferrimagnetic CoGd films by Brillouin light scattering. We demonstrate the ability to control DMI by the CoGd cap layer composition, the stack symmetry and the ferrimagnetic layer thickness. The DMI thickness dependence confirms its interfacial nature. In addition, magnetic force microscopy reveals the ability to tune DMI in a range that stabilizes sub-100 nm skyrmions at room temperature in zero field. Our work opens new paths for controlling interfacial DMI in ferrimagnets to nucleate and manipulate skyrmions.

16.
Science ; 241(4873): 1640-2, 1988 Sep 23.
Artigo em Inglês | MEDLINE | ID: mdl-17820894

RESUMO

The synthesis and properties of a class of metallic glasses containing up to 90 atomic percent aluminum are reported. The unusual formability of the glasses and their structural features are pointed out. Mechanical properties including tensile fracture strength and Young's modulus are reported along with crystallization temperatures. The unusually high strengths of the aluminum glasses can be of significant importance in obtaining high-strength low-density materials.

17.
Science ; 261(5122): 737-9, 1993 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-17757209

RESUMO

Bulk icosahedral-quasicrystalline aluminum-palladium-rhenium alloys of high structural quality and thermal stability are found to exhibit low-temperature electrical resistivities that are four orders of magnitude larger than those found in disordered metals and metallic glasses. Experiments suggest that these quasiperiodic alloys, which have a semimetallic electron density, are insulators at low temperature. The findings are discussed in light of theories on electron localization and band-gap formation in ordered metallic systems.

18.
Science ; 243(4887): 66-9, 1989 Jan 06.
Artigo em Inglês | MEDLINE | ID: mdl-17780424

RESUMO

Evidence suggests that superconducting, orthorhombic YBa(2)Cu(3)O(6+x)+ (x greater, similar 0.5) is always produced by oxidation of the oxygen-deficient, tetragonal form (x less, similar 0.5) of this phase (commonly referred to as 123). A synthetic route whereby solution-derived, carbon-free precursors are decomposed at 650 degrees to 700 degrees C in inert atmosphere to yield tetragonal 123 is now available. Appropriate precursors include hydrated oxides derived from the hydrolysis of organometallic solutions and aqueous solution-derived hyponitrites. Subsequent oxidation of the tetragonal phase at 400 degrees C results in submicrometer particles of orthorhombic 123. Superconductivity (T(c) onset approximately 87 K) has been confirmed in these materials by both Meissner effect and specific-heat measurements.

19.
Science ; 240(4851): 495-7, 1988 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-17784070

RESUMO

New phases of the type La2-xAx(l+)CUO4-y have been prepared where A(l+) is sodium or potassium. The sodium phases are superconducting for x values from 0.2 to 0.5 at temperatures up to about 40 K. In addition, there are unusual magnetic properties below about 10 K that may be indicative of spin glass behavior. Phases of the type La2-xKxCuO4-y could only be prepared with x values up to about 0.1, and these phases are not superconducting above 4.2 K.

20.
Sci Rep ; 9(1): 15501, 2019 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-31664046

RESUMO

High entropy alloys (HEA) are a new type of high-performance structural material. Their vast degrees of compositional freedom provide for extensive opportunities to design alloys with tailored properties. However, compositional complexities present challenges for alloy design. Current approaches have shown limited reliability in accounting for the compositional regions of single solid solution and composite phases. For the first time, a phenomenological method analysing binary phase diagrams to predict HEA phases is presented. The hypothesis is that the HEA structural stability is encoded within the phase diagrams. Accordingly, we introduce several phase-diagram inspired parameters and employ machine learning (ML) to classify 600+ reported HEAs based on these parameters. Compared to other large database statistical prediction models, this model gives more detailed and accurate phase predictions. Both the overall HEA prediction and specifically single-phase HEA prediction rate are above 80%. To validate our method, we demonstrated its capability in predicting HEA solid solution phases with or without intermetallics in 42 randomly selected complex compositions, with a success rate of 81%. The presented search approach with high predictive capability can be exploited to interact with and complement other computation-intense methods such as CALPHAD in providing an accelerated and precise HEA design.

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