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1.
Phys Rev Lett ; 131(20): 201802, 2023 Nov 17.
Artigo em Inglês | MEDLINE | ID: mdl-38039466

RESUMO

We search for energetic electron recoil signals induced by boosted dark matter (BDM) from the galactic center using the COSINE-100 array of NaI(Tl) crystal detectors at the Yangyang Underground Laboratory. The signal would be an excess of events with energies above 4 MeV over the well-understood background. Because no excess of events are observed in a 97.7 kg·yr exposure, we set limits on BDM interactions under a variety of hypotheses. Notably, we explored the dark photon parameter space, leading to competitive limits compared to direct dark photon search experiments, particularly for dark photon masses below 4 MeV and considering the invisible decay mode. Furthermore, by comparing our results with a previous BDM search conducted by the Super-Kamionkande experiment, we found that the COSINE-100 detector has advantages in searching for low-mass dark matter. This analysis demonstrates the potential of the COSINE-100 detector to search for MeV electron recoil signals produced by the dark sector particle interactions.

2.
Front Cardiovasc Med ; 10: 1258890, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38155993

RESUMO

Introduction: Sudden cardiac arrest is a major cause of morbidity and mortality worldwide and remains a major public health problem for which better non-invasive prediction tools are needed. Primary preventive therapies, such as implantable cardioverter defibrillators, are not personalized and not predictive. Most of these devices do not deliver life-saving therapy during their lifetime. The individual relationship between fatal arrhythmias and cardiac function abnormalities in predicting cardiac death risk has rarely been explored. Methods: We retrospectively analyzed the measurements at rest for 191 patients with acute chest pain (ACP) magnetocardiographically. Our recently introduced analyses are able to detect inhomogeneities of the depolarization and repolarization. Moreover, electrically silent phenomena-intracellular ionic currents as well as vortex currents-can be measured and quantified. All included ACP patients were recruited in 2009 at Yonsei University Hospital and were followed up until 2022. Results: During half of the follow-up period (6.5 years), 11 patients died. Out of all the included nine clinical, eight magnetocardiographical, and nine newly introduced magnetoionographical parameters we tested in this study, three parameters revealed themselves to be outstanding at predicting death: heart rate-corrected QT (QTc) prolongation, depression of repolarization current IKr + IKs, and serum creatinine (all significant in Cox regression, p < 0.05). They clearly predicted cardiac death over the 6.5 years duration (sensitivity 90.9%, specificity 85.6%, negative predictive accuracy 99.4%). Cardiac death risk was more than ninefold higher in patients with low repolarization reserve and QTc prolongation in comparison with the remaining patients with ACP (p < 0.001). The non-parametric Kaplan-Meier statistics estimated significantly lower survival functions from their lifetime data (p < 0.001). Discussion: To the best of our knowledge, these are the first data linking magnetocardiographical and magnetoionographical parameters and subsequent significant fatal events in people, suggesting structural and functional components to clinical life-threatening ventricular arrhythmogenesis. The findings support investigation of new prevention strategies and herald those new non-invasive techniques as complementary risk stratification tools.

3.
Artigo em Inglês | MEDLINE | ID: mdl-37260034

RESUMO

BACKGROUND: Respiratory microbiome studies have fostered our understanding of various phenotypes and endotypes of heterogeneous asthma. However, the relationship between the respiratory microbiome and clinical phenotypes in children with asthma remains unclear. We aimed to identify microbiome-driven clusters reflecting the clinical features of asthma and their dominant microbiotas in children with asthma. METHODS: Induced sputum was collected from children with asthma, and microbiome profiles were generated via sequencing of the V3-V4 region of the 16S rRNA gene. Cluster analysis was performed using the partitioning around medoid clustering method. The dominant microbiota in each cluster was determined using the Linear Discriminant Effect Size analysis. Each cluster was analyzed for association among the dominant microbiota, clinical phenotype, and inflammatory cytokine. RESULTS: Eighty-three children diagnosed with asthma were evaluated. Among four clusters reflecting the clinical characteristics of asthma, cluster 1, dominated by Haemophilus and Neisseria, demonstrated lower post-bronchodilator (BD) forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) than that in the other clusters and more mixed granulocytic asthma. Neisseria negatively correlated with pre-BD and post-BD FEV1/FVC. Haemophilus and Neisseria positively correlated with programmed death-ligand (PD-L)1. CONCLUSION: To our knowledge, this study is the first to analyze the relationship between an unbiased microbiome-driven cluster and clinical phenotype in children with asthma. The cluster dominated by Haemophilus and Neisseria showed fixed airflow obstruction and mixed granulocytic asthma, which correlated with PD-L1 levels. Thus, microbiome-driven unbiased clustering can help identify new asthma phenotypes related to endotypes in childhood asthma.

4.
Opt Express ; 29(4): 5658-5664, 2021 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-33726100

RESUMO

We demonstrate a 4,294,967,296-quadrature amplitude modulation (QAM) based Y-00 quantum stream cipher system carrying a 160-Gb/s 16-QAM signal transmitted over 320-km SSMF. The ultra-dense QAM cipher template is realized by an integrated two-segment silicon photonics I/Q modulator.

5.
Epidemiol Psychiatr Sci ; 29: e176, 2020 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-33077022

RESUMO

AIMS: To investigate the association between parity and the risk of incident dementia in women. METHODS: We pooled baseline and follow-up data for community-dwelling women aged 60 or older from six population-based, prospective cohort studies from four European and two Asian countries. We investigated the association between parity and incident dementia using Cox proportional hazards regression models adjusted for age, educational level, hypertension, diabetes mellitus and cohort, with additional analysis by dementia subtype (Alzheimer dementia (AD) and non-Alzheimer dementia (NAD)). RESULTS: Of 9756 women dementia-free at baseline, 7010 completed one or more follow-up assessments. The mean follow-up duration was 5.4 ± 3.1 years and dementia developed in 550 participants. The number of parities was associated with the risk of incident dementia (hazard ratio (HR) = 1.07, 95% confidence interval (CI) = 1.02-1.13). Grand multiparity (five or more parities) increased the risk of dementia by 30% compared to 1-4 parities (HR = 1.30, 95% CI = 1.02-1.67). The risk of NAD increased by 12% for every parity (HR = 1.12, 95% CI = 1.02-1.23) and by 60% for grand multiparity (HR = 1.60, 95% CI = 1.00-2.55), but the risk of AD was not significantly associated with parity. CONCLUSIONS: Grand multiparity is a significant risk factor for dementia in women. This may have particularly important implications for women in low and middle-income countries where the fertility rate and prevalence of grand multiparity are high.


Assuntos
Doença de Alzheimer/epidemiologia , Demência/epidemiologia , Paridade/fisiologia , Idoso , Idoso de 80 Anos ou mais , China/epidemiologia , Estudos de Coortes , Europa (Continente)/epidemiologia , Feminino , Psiquiatria Geriátrica , Humanos , Incidência , Vida Independente , Pessoa de Meia-Idade , Gravidez , Modelos de Riscos Proporcionais , República da Coreia/epidemiologia , Fatores de Risco , Fatores Socioeconômicos
7.
Clin Radiol ; 75(2): 157.e9-157.e19, 2020 02.
Artigo em Inglês | MEDLINE | ID: mdl-31711637

RESUMO

AIM: To compare the diagnostic performance of prostate magnetic resonance imaging (MRI) with an endorectal coil (ERC) to performance without an ERC using either body-array (BAC) or pelvic phased-array coil (PAC) in staging T3 prostate cancer. MATERIALS AND METHODS: An electronic search of the PUBMED and EMBASE databases was performed until 10 October 2018 to identify studies performing a head-to-head comparison of prostate MRI using a 1.5 or 3 T magnet with an ERC and with a BAC/PAC for staging T3 prostate cancer. Pooled sensitivity and specificity of all studies were plotted in a hierarchical summary receiver operating characteristic plot. The diagnostic performance of the two techniques in staging T3 disease was evaluated using bivariate random-effects meta-analysis. RESULTS: Eight studies comparing head-to-head prostate MRI with an ERC and with a BAC/PAC were identified of which six studies compared the diagnostic performance. The pooled sensitivity and specificity of MRI with an ERC for detecting T3a, T3b and T3a+b was 53% and 95%; 52% and 92%; 72% and 65% respectively. For MRI with a BAC/PAC these were 34%, and 95%; 45% and 94%; 70% and 66%. There was no statistical difference between an ERC and a BAC/PAC in terms of sensitivity (p=0.41) and specificity (p=0.63) for T3a. The area under the receiver operating characteristic (AUROC) curve for T3a, T3b and T3a+b was 0.830, 0.901, 0.741 for an ERC and 0.790, 0.645, 0.711 for BAC, respectively. CONCLUSION: There is no significant difference in the diagnostic performance of MRI of prostate with an ERC and with a BAC/PAC in staging T3 prostate cancer.


Assuntos
Imageamento por Ressonância Magnética , Neoplasias da Próstata/diagnóstico , Adulto , Idoso , Humanos , Imageamento por Ressonância Magnética/instrumentação , Imageamento por Ressonância Magnética/métodos , Masculino , Pessoa de Meia-Idade , Imageamento por Ressonância Magnética Multiparamétrica/instrumentação , Imageamento por Ressonância Magnética Multiparamétrica/métodos , Estadiamento de Neoplasias/métodos , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/patologia , Reto , Sensibilidade e Especificidade
8.
Phys Rev Lett ; 123(5): 056802, 2019 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-31491285

RESUMO

We demonstrate an unusual manifestation of coherent scattering for electron waves in mesoscopic quantum point contacts, in which fast electron dynamics allows the phonon system to serve as a quasistatic source of disorder. The low-temperature conductance of these devices exhibits a giant (≫2e^{2}/h) zero bias anomaly (ZBA), the features of which are reproduced in a nonequilibrium model for coherent scattering from the "frozen" phonon disorder. According to this model, the ZBA is understood to result from the in situ electrical manipulation of the phonon disorder, a mechanism that could open up a pathway to the on-demand control of coherent scattering in the solid state.

9.
Phys Rev Lett ; 123(3): 031302, 2019 Jul 19.
Artigo em Inglês | MEDLINE | ID: mdl-31386435

RESUMO

We present new constraints on the dark matter-induced annual modulation signal using 1.7 years of COSINE-100 data with a total exposure of 97.7 kg yr. The COSINE-100 experiment, consisting of 106 kg of NaI(Tl) target material, is designed to carry out a model-independent test of DAMA/LIBRA's claim of WIMP discovery by searching for the same annual modulation signal using the same NaI(Tl) target. The crystal data show a 2.7 cpd/kg/keV background rate on average in the 2-6 keV energy region of interest. Using a χ-squared minimization method we observe best fit values for modulation amplitude and phase of 0.0092±0.0067 cpd/kg/keV and 127.2±45.9 d, respectively.

10.
Phys Rev Lett ; 122(13): 131802, 2019 Apr 05.
Artigo em Inglês | MEDLINE | ID: mdl-31012610

RESUMO

A search for inelastic boosted dark matter (IBDM) using the COSINE-100 detector with 59.5 days of data is presented. This relativistic dark matter is theorized to interact with the target material through inelastic scattering with electrons, creating a heavier state that subsequently produces standard model particles, such as an electron-positron pair. In this study, we search for this electron-positron pair in coincidence with the initially scattered electron as a signature for an IBDM interaction. No excess over the predicted background event rate is observed. Therefore, we present limits on IBDM interactions under various hypotheses, one of which allows us to explore an area of the dark photon parameter space that has not yet been covered by other experiments. This is the first experimental search for IBDM using a terrestrial detector.

11.
Transplant Proc ; 50(10): 3673-3680, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30577254

RESUMO

BACKGROUND: Multidetector computerized tomography (MDCT) is considered to be a fast noninvasive diagnostic technique for the evaluation of postoperative complications in patients with liver transplantation (LT). However, its role has not been fully established in the diagnosis for detecting complications after liver transplantation. The aim of this work was to evaluate the diagnostic performance of MDCT for detecting abdominal complications in the early and late periods after LT. METHODS: We retrospectively enrolled 75 patients who had undergone LT from March 2006 to January 2010, followed by MDCT from March 2006 to November 2017. Patients were divided into 2 groups according to the timing after LT: within the first 3 months (early period) or ≥3 months after LT (late period). We evaluated vascular, biliary, and other complications on MDCT. Angiography, endoscopic retrograde cholangiography, and percutaneous transhepatic cholangiography were used as reference standards. RESULTS: We initially found 77 complications in 45 patients (60.0%) with the use of MDCT. After comparison with the reference standards, 83 complications were diagnosed in 49 patients (65.3%). Forty-seven complications (34 vascular, 10 biliary, 3 other complications) were diagnosed in 33 patients (44.0%) during the early period, and 36 complications (6 vascular, 20 biliary, 10 other complications) were detected in 27 patients (36.0%) in the late period. The sensitivity, specificity, and diagnostic accuracy of MDCT for diagnosing overall complications were, respectively, 93.6%, 90.2%, and 92.0% in the early period (for vascular complications: 97.1%, 92.6%, and 94.3%,; for biliary complications: 80.0%, 100%, and 97.7%) and 77.8%, 98.1%, and 89.8% in the late period (for vascular complications: 83.3%, 100%, and 98.9%; for biliary complications: 65.0%, 98.6%, and 90.9%). CONCLUSIONS: Although MDCT in the late period should be interpreted with caution in patients with suspected biliary complication, MDCT is a reliable diagnostic technique for the identification of early and late abdominal complications after LT.


Assuntos
Transplante de Fígado/efeitos adversos , Tomografia Computadorizada Multidetectores/métodos , Complicações Pós-Operatórias/diagnóstico por imagem , Adulto , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Complicações Pós-Operatórias/etiologia , Estudos Retrospectivos , Sensibilidade e Especificidade
12.
Allergy ; 73(8): 1686-1699, 2018 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-29420850

RESUMO

BACKGROUND: Chitotriosidase (chitinase 1, Chit1), a major true chitinase in humans, is induced in childhood asthma and has been implicated in the pathogenesis of a variety of inflammatory and tissue remodeling responses. However, the role and the mechanisms that underlie these contributions to the diseases have not been defined. We hypothesized that Chit1 plays a significant role in the pathogenesis of allergic asthma. METHODS: Wild-type and Chit1-deficient mice and cells in culture were used to define the roles of Chit1 in models of allergic adaptive Th2 inflammation. In addition, the levels of sputum Chit1 were evaluated in pediatric asthma patients and compared to control. RESULTS: The levels of sputum Chit1 were significantly increased in the patients with childhood asthma. Mice with Chit1 null mutation demonstrated enhanced allergic Th2 inflammatory and cytokine and IgE responses to OVA or house dust mite allergen sensitization and challenge. However, the expression levels of TGF-ß1 were significantly decreased with a diminished number of Foxp3+ regulatory T cells (Treg) in the lungs of Chit1-/- mice compared to WT controls. In vitro, the absence of Chit1 significantly reduced TGF-ß-stimulated conversion of CD4+ CD25- naïve T cells to CD4+ Foxp3+ Treg cells, suggesting Chit1 is required for optimal effect of TGF-ß1 in Treg cell differentiation. CONCLUSION: Chit1 plays a protective role in the pathogenesis of allergic inflammation and asthmatic airway responses via regulation of TGF-ß expression and Foxp3+ Treg cells.


Assuntos
Asma/metabolismo , Fatores de Transcrição Forkhead/biossíntese , Hexosaminidases/análise , Hexosaminidases/metabolismo , Hipersensibilidade/metabolismo , Linfócitos T Reguladores/metabolismo , Fator de Crescimento Transformador beta1/metabolismo , Análise de Variância , Animais , Distribuição de Qui-Quadrado , Criança , Modelos Animais de Doenças , Feminino , Humanos , Interleucina-10/metabolismo , Mutação com Perda de Função , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Camundongos Transgênicos , Escarro/enzimologia , Células Th2/metabolismo
13.
Clin Exp Immunol ; 192(2): 151-164, 2018 05.
Artigo em Inglês | MEDLINE | ID: mdl-29363753

RESUMO

Food allergy is a major public health problem. Studies have shown that long-term interactions between activated leucocyte cell adhesion molecule (ALCAM/CD166) on the surface of antigen-presenting cells, and CD6, a co-stimulatory molecule, influence immune responses. However, there are currently no studies on the functions of ALCAM in food allergy. Therefore, we aimed to identify the functions of ALCAM in ovalbumin (OVA)-induced food allergy using ALCAM-deficient mice. Wild-type (WT) and ALCAM-deficient (ALCAM-/- ) mice were sensitized intraperitoneally and with orally fed OVA. The mice were killed, and parameters related to food allergy and T helper type 2 (Th2) immune responses were analysed. ALCAM serum levels increased and mRNA expression decreased in OVA-challenged WT mice. Serum immunoglobulin (Ig)E levels, Th2 cytokine mRNA and histological injuries were higher in OVA-challenged WT mice than in control mice, and these were attenuated in ALCAM-/- mice. T cell proliferation of total cells, CD3+ CD4+ T cells and activated T cells in immune tissues were diminished in OVA-challenged ALCAM-/- mice. Proliferation of co-cultured T cells and dendritic cells (DCs) was decreased by the anti-CD6 antibody. In addition, WT mice sensitized by adoptive transfer of OVA-pulsed ALCAM-/- BM-derived DCs showed reduced immune responses. Lastly, serum ALCAM levels were higher in children with food allergy than in control subjects. In this study, serum levels of ALCAM were elevated in food allergy-induced WT mice and children with food allergy. Moreover, immune responses and T cell activation were attenuated in OVA-challenged ALCAM-/- mice. These results indicate that ALCAM regulates food allergy by affecting T cell activation.


Assuntos
Molécula de Adesão de Leucócito Ativado/genética , Hipersensibilidade Alimentar/imunologia , Regulação da Expressão Gênica/imunologia , Células Th2/imunologia , Molécula de Adesão de Leucócito Ativado/sangue , Transferência Adotiva , Animais , Antígenos CD/genética , Antígenos CD/imunologia , Antígenos de Diferenciação de Linfócitos T/genética , Antígenos de Diferenciação de Linfócitos T/imunologia , Proliferação de Células , Criança , Pré-Escolar , Técnicas de Cocultura , Citocinas/genética , Citocinas/imunologia , Células Dendríticas/imunologia , Modelos Animais de Doenças , Feminino , Humanos , Imunoglobulina E/sangue , Ativação Linfocitária , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Knockout , Ovalbumina
14.
Eur Phys J C Part Fields ; 78(6): 490, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30956554

RESUMO

The COSINE-100 dark matter search experiment is an array of NaI(Tl) crystal detectors located in the Yangyang Underground Laboratory (Y2L). To understand measured backgrounds in the NaI(Tl) crystals we have performed Monte Carlo simulations using the Geant4 toolkit and developed background models for each crystal that consider contributions from both internal and external sources, including cosmogenic nuclides. The background models are based on comparisons of measurement data with Monte Carlo simulations that are guided by a campaign of material assays and are used to evaluate backgrounds and identify their sources. The average background level for the six crystals (70 kg total mass) that are studied is 3.5 counts/day/keV/kg in the (2-6) keV energy interval. The dominant contributors in this energy region are found to be 210 Pb and 3 H.

15.
Opt Express ; 26(24): 31607-31616, 2018 Nov 26.
Artigo em Inglês | MEDLINE | ID: mdl-30650744

RESUMO

We investigated the electromagnetically induced transparency (EIT)-like effects in planar metamaterials (MMs) at microwave (GHz) frequencies. The specific MMs that were used in this study consist of cut-wire resonator/ring resonator, which achieved the dual EIT-like effects in a single-layer through the bright- and quasi-dark-mode coupling and the lattice mode coupling. In addition, by varying the distance between the two resonators, the quad-band EIT spectral response in the microwave region was obtained, and the group refractive index at the EIT-like resonance of proposed design reached up to 4,000. This study provides the design approach to the multispectral EIT-like effects and might suggest potential applications in a variety of fields, for example, low-loss slow-light device, multiple switching sensor, and other sensing devices.

16.
Clin Radiol ; 73(2): 158-167, 2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-28958581

RESUMO

AIM: To evaluate the yield of staging bone scintigraphy in patients with treatment-naive prostate cancer. MATERIALS AND METHODS: A computerised search of the MEDLINE and EMBASE databases was performed to find relevant original literature. Studies that investigated the positivity of a staging bone scintigraphy according to prostate-specific antigen (PSA) levels and/or Gleason score in patients with treatment-naive prostate cancer were eligible for inclusion. Meta-analytic pooling was performed using the inverse variance method for calculating weights. RESULTS: Fifty-four eligible studies, which included a total sample size of 20,421 patients, were included. The pooled proportions of the positive bone scintigraphy in patients with PSA ≤10, 10 20 were 3.5% (95% confidence interval [CI]: 2.4-5%), 6.9% (95% CI: 4.5-10.3%), and 41.8% (95% CI: 36.3-47.6%). The pooled proportions of the positive bone scintigraphy examinations in patients with Gleason score ≤6, 7, and ≥8 were 4.1% (95% CI: 2-8%), 10% (95% CI: 6.1-15.8%), and 28.7% (95% CI: 21.8-36.8%). Meta-regression analysis revealed that the Gleason score was a significant factor affecting study heterogeneity in patients with PSA ≤10 (p = 0.04). Pooled proportions of positive bone scintigraphy examinations showed 3.4% in patients with a PSA of ≤10 and 3.3% in patients with 10

Assuntos
Neoplasias Ósseas/diagnóstico por imagem , Neoplasias Ósseas/secundário , Neoplasias da Próstata/patologia , Humanos , Masculino , Próstata/diagnóstico por imagem , Cintilografia/métodos
17.
Scand J Surg ; 107(3): 244-251, 2018 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-29284364

RESUMO

BACKGROUND: Sarcopenia, reduced skeletal muscle mass, is associated with frailty, injuries, and mortality. The purpose of this study was to evaluate the impact of computed tomography-determined sarcopenia on surgical complications and outcomes after resection of non-small cell lung cancer. METHODS: For a total 272 non-small cell lung cancer patients that underwent surgery between 2011 and 2016, cross-sectional area of muscle at the third lumbar vertebra (L3) was retrospectively measured using preoperative chest computed tomography images. Sarcopenia was defined as an L3 muscle index of <55 cm2/m2 for men and of <39 cm2/m2 for women. Clinical characteristics, postoperative complications, disease-free survival, and overall survival of patients with or without sarcopenia were compared. RESULTS: A total of 60.3% ( n = 164) were male, and mean patient age was 62.9 ± 9.6 years. The prevalence of sarcopenia was 22.4% for all study subjects, 32.9% for men, and 6.5% for women. No significant difference was observed between patients with or without sarcopenia in terms of intensive care unit or hospital stay ( p = 0.502 and p = 0.378, respectively), and the presence of sarcopenia was not associated with postoperative complications. Furthermore, no significant difference was observed between the 3-year disease-free survival rate (74.3% vs 66.7%, p = 0.639) or 3-year overall survival rate (83.9% vs 87.7%, p = 0.563) of patients with or without sarcopenia. CONCLUSION: Sarcopenia as determined by preoperative computed tomography does not appear to have a negative impact on surgical outcome or overall survival for resected non-small cell lung cancer patients.


Assuntos
Músculos do Dorso/diagnóstico por imagem , Carcinoma Pulmonar de Células não Pequenas/cirurgia , Neoplasias Pulmonares/cirurgia , Pneumonectomia/efeitos adversos , Sarcopenia/diagnóstico por imagem , Idoso , Carcinoma Pulmonar de Células não Pequenas/complicações , Feminino , Humanos , Neoplasias Pulmonares/complicações , Masculino , Pessoa de Meia-Idade , Cuidados Pré-Operatórios , Prognóstico , Sarcopenia/complicações , Tomografia Computadorizada por Raios X , Resultado do Tratamento
18.
Phys Rev Lett ; 119(7): 077205, 2017 Aug 18.
Artigo em Inglês | MEDLINE | ID: mdl-28949689

RESUMO

Magneto-optical Kerr effect (MOKE) microscopy measurements of magnetic bubble domains demonstrate that Ar^{+} irradiation around 100 eV can tune the Dzyaloshinskii-Moriya interaction (DMI) in Pt/Co/Pt trilayers. Varying the irradiation energy and dose changes the DMI sign and magnitude separately from the magnetic anisotropy, allowing tuning of the DMI while holding the coercive field constant. This simultaneous control emphasizes the different physical origins of these effects. To accurately measure the DMI, we propose and apply a physical model for a poorly understood peak in domain wall velocity at zero in-plane field. The ability to tune the DMI with the spatial resolution of the Ar^{+} irradiation enables new fundamental investigations and technological applications of chiral nanomagnetics.

19.
Phys Rev B ; 95(10)2017 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-28758157

RESUMO

We theoretically analyze contributions from the Kondo effect to the spin polarization and spin diffusion length in all-metal nonlocal spin valves. Interdiffusion of ferromagnetic atoms into the normal metal layer creates a region in which Kondo physics plays a significant role, giving discrepancies between experiment and existing theory. We start from a simple model and construct a modified spin drift-diffusion equation which clearly demonstrates how the Kondo physics not only suppresses the electrical conductivity but even more strongly reduces the spin diffusion length. We also present an explicit expression for the suppression of spin polarization due to Kondo physics in an illustrative regime. We compare this theory to previous experimental data to extract an estimate of the Elliot-Yafet probability for Kondo spin flip scattering of 0.7 ± 0.4, in good agreement with the value of 2/3 derived in the original theory of Kondo.

20.
Science ; 357(6346): 71-75, 2017 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-28684521

RESUMO

The interactions that lead to the emergence of superconductivity in iron-based materials remain a subject of debate. It has been suggested that electron-electron correlations enhance electron-phonon coupling in iron selenide (FeSe) and related pnictides, but direct experimental verification has been lacking. Here we show that the electron-phonon coupling strength in FeSe can be quantified by combining two time-domain experiments into a "coherent lock-in" measurement in the terahertz regime. X-ray diffraction tracks the light-induced femtosecond coherent lattice motion at a single phonon frequency, and photoemission monitors the subsequent coherent changes in the electronic band structure. Comparison with theory reveals a strong enhancement of the coupling strength in FeSe owing to correlation effects. Given that the electron-phonon coupling affects superconductivity exponentially, this enhancement highlights the importance of the cooperative interplay between electron-electron and electron-phonon interactions.

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