Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 84
Filtrar
Mais filtros

Base de dados
País/Região como assunto
Tipo de documento
Intervalo de ano de publicação
1.
Strahlenther Onkol ; 200(4): 335-345, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-37646818

RESUMO

PURPOSE: This study aimed to assess clinical, treatment, and prognostic features in patients with brain metastases (BM) from solid tumors achieving long-term survival (LTS). Further, the accuracy of diagnosis-specific Graded Prognostic Assessment scores (ds-GPA) to predict LTS was evaluated. METHODS: Patients admitted for radiotherapy of BM between 2010 and 2020 at a large tertiary cancer center with survival of at least 3 years from diagnosis of BM were included. Patient, tumor, treatment characteristics and ds-GPA were compiled retrospectively. RESULTS: From a total of 1248 patients with BM, 61 (4.9%) survived ≥ 3 years. In 40 patients, detailed patient charts were available. Among LTS patients, median survival time from diagnosis of BM was 51.5 months. Most frequent primary tumors were lung cancer (45%), melanoma (20%), and breast cancer (17.5%). At the time of diagnosis of BM, 11/40 patients (27.5%) had oligometastatic disease. Estimated mean survival time based on ds-GPA was 19.7 months (in 8 cases estimated survival < 12 months). Resection followed by focal or whole-brain radiotherapy (WBRT) was often applied (60%), followed by primary stereotactic radiotherapy (SRT) (20%) or WBRT (20%). 80% of patients received systemic treatment, appearing particularly active in specifically altered non-small lung cancer (NSCLC), melanoma, and HER2-positive breast cancer. Karnofsky performance score (KPS) and the presence of oligometastatic disease at BM diagnosis were persisting prognostic factors in LTS patients. CONCLUSION: In this monocentric setting reflecting daily pattern of care, LTS with BM is heterogeneous and difficult to predict. Effective local treatment and modern systemic therapies often appear crucial for LTS. The impact of concomitant diseases and frailty is not clear.


Assuntos
Neoplasias Encefálicas , Neoplasias da Mama , Neoplasias Pulmonares , Melanoma , Radiocirurgia , Humanos , Feminino , Estudos Retrospectivos , Neoplasias Pulmonares/patologia , Prognóstico , Neoplasias Encefálicas/secundário , Radiocirurgia/efeitos adversos , Neoplasias da Mama/patologia
2.
Phys Rev Lett ; 121(13): 137403, 2018 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-30312105

RESUMO

Using ultrafast ≃2.5 fs and ≃25 fs self-amplified spontaneous emission pulses of increasing intensity and a novel experimental scheme, we report the concurrent increase of stimulated emission in the forward direction and loss of out-of-beam diffraction contrast for a Co/Pd multilayer sample. The experimental results are quantitatively accounted for by a statistical description of the pulses in conjunction with the optical Bloch equations. The dependence of the stimulated sample response on the incident intensity, coherence time, and energy jitter of the employed pulses reveals the importance of increased control of x-ray free electron laser radiation.

3.
Phys Rev Lett ; 118(2): 024801, 2017 Jan 13.
Artigo em Inglês | MEDLINE | ID: mdl-28128585

RESUMO

The interference pattern of a circular photon source has long been used to define the optical diffraction limit. Here we show the breakdown of conventional x-ray diffraction theory for the fundamental case of a "source," consisting of a back-illuminated thin film in a circular aperture. When the conventional spontaneous x-ray scattering by atoms in the film is replaced at high incident intensity by stimulated resonant scattering, the film becomes the source of cloned photon twins and the diffraction pattern becomes self-focussed beyond the diffraction limit. The case of cloned x-ray biphotons is compared to and distinguished from the much studied case of entangled optical biphotons.

4.
Phys Rev Lett ; 116(1): 019902, 2016 Jan 08.
Artigo em Inglês | MEDLINE | ID: mdl-26799050

RESUMO

This corrects the article DOI: 10.1103/PhysRevLett.115.107402.

5.
Phys Rev Lett ; 117(2): 027401, 2016 Jul 08.
Artigo em Inglês | MEDLINE | ID: mdl-27447522

RESUMO

X-ray diffractive imaging with laterally coherent x-ray free-electron laser (XFEL) pulses is increasingly utilized to obtain ultrafast snapshots of matter. Here we report the amazing disappearance of single-shot charge and magnetic diffraction patterns recorded with resonantly tuned, narrow bandwidth XFEL pulses. Our experimental results reveal the exquisite sensitivity of single-shot charge and magnetic diffraction patterns of a magnetic film to the onset of field-induced stimulated elastic x-ray forward scattering. The loss in diffraction contrast, measured over 3 orders of magnitude in intensity, is in remarkable quantitative agreement with a recent theory that is extended to include diffraction.

6.
Phys Rev Lett ; 115(10): 107402, 2015 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-26382702

RESUMO

X-ray absorption by matter has long been described by the famous Beer-Lambert law. Here, we show how this fundamental law needs to be modified for high-intensity coherent x-ray pulses, now available at x-ray free electron lasers, due to the onset of stimulated elastic forward scattering. We present an analytical expression for the modified polarization-dependent Beer-Lambert law for the case of resonant core-to-valence electronic transitions and incident transform limited x-ray pulses. Upon transmission through a solid, the resonant absorption and dichroic contrasts are found to vanish with increasing x-ray intensity, with the stimulation threshold lowered by orders of magnitude through a resonant superradiantlike effect. Our results have broad implications for the study of matter with x-ray lasers.


Assuntos
Modelos Teóricos , Difração de Raios X , Dicroísmo Circular/métodos , Cobalto/química , Elasticidade , Ferro/química , Magnetismo/métodos , Níquel/química
7.
Phys Rev Lett ; 115(9): 096601, 2015 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-26371670

RESUMO

We have used a MHz lock-in x-ray spectromicroscopy technique to directly detect changes in magnetic moment of Cu due to spin injection from an adjacent Co layer. The elemental and chemical specificity of x rays allows us to distinguish two spin current induced effects. We detect the creation of transient magnetic moments of 3×10^{-5}µ_{B} on Cu atoms within the bulk of the 28 nm thick Cu film due to spin accumulation. The moment value is compared to predictions by Mott's two current model. We also observe that the hybridization induced existing magnetic moments at the Cu interface atoms are transiently increased by about 10% or 4×10^{-3}µ_{B} per atom. This reveals the dominance of spin-torque alignment over Joule heat induced disorder of the interfacial Cu moments during current flow.

8.
Nat Mater ; 12(4): 293-8, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23503010

RESUMO

Ultrafast laser techniques have revealed extraordinary spin dynamics in magnetic materials that equilibrium descriptions of magnetism cannot explain. Particularly important for future applications is understanding non-equilibrium spin dynamics following laser excitation on the nanoscale, yet the limited spatial resolution of optical laser techniques has impeded such nanoscale studies. Here we present ultrafast diffraction experiments with an X-ray laser that probes the nanoscale spin dynamics following optical laser excitation in the ferrimagnetic alloy GdFeCo, which exhibits macroscopic all-optical switching. Our study reveals that GdFeCo displays nanoscale chemical and magnetic inhomogeneities that affect the spin dynamics. In particular, we observe Gd spin reversal in Gd-rich nanoregions within the first picosecond driven by the non-local transfer of angular momentum from larger adjacent Fe-rich nanoregions. These results suggest that a magnetic material's microstructure can be engineered to control transient laser-excited spins, potentially allowing faster (~ 1 ps) spin reversal than in present technologies.

9.
Phys Rev Lett ; 108(23): 237202, 2012 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-23003984

RESUMO

The nature of the ferromagnetic, charge, orbital, and antiferromagnetic order in La0.35Pr0.275Ca0.375MnO3 on the nano- and microscale was investigated by photoemission electron microscopy (PEEM) and resonant elastic soft x-ray scattering (RSXS). The structure of the ferromagnetic domains around the Curie temperature T(C) indicates that they nucleate under a high degree of lattice strain, which is brought about by the charge, orbital, and antiferromagnetic order. The combined temperature-dependent PEEM and RSXS measurements suggest that the lattice distortions associated with charge and orbital order are glassy in nature and that phase separation is driven by the interplay between it and the more itinerant charge carriers associated with ferromagnetic metallic order, even well below T(C).

10.
Phys Rev Lett ; 106(16): 167202, 2011 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-21599407

RESUMO

We present the first space- and time-resolved images of the spin-torque-induced steady-state oscillation of a magnetic vortex in a spin-valve nanostructure. We find that the vortex structure in a nanopillar is considerably more complicated than the 2D idealized structure often-assumed, which has important implications for the driving efficiency. The sense of the vortex gyration is uniquely determined by the vortex core polarity, confirming that the spin-torque acts as a source of negative damping even in such a strongly nonuniform magnetic system. The orbit radius is ∼10 nm, in agreement with micromagnetic simulations.

11.
J Hosp Infect ; 111: 132-139, 2021 May.
Artigo em Inglês | MEDLINE | ID: mdl-33582200

RESUMO

BACKGROUND: Vancomycin-resistant enterococci (VRE) may cause nosocomial outbreaks. This article describes all VRE carriers that were identified in 2018 at Elisabeth-Tweesteden Hospital, Tilburg, The Netherlands. AIM: To investigate the genetic relatedness of VRE isolates and the possibility of a common environmental reservoir using environmental sampling and whole-genome sequencing (WGS). METHODS: Infection control measures consisted of contact isolation, contact surveys, point prevalence screening, environmental sampling, cleaning and disinfection. VRE isolates were sequenced using a MiSeq sequencer (Illumina, San Diego, CA, USA), and assembled using SPAdes v.3.10.1. A minimal spanning tree and a neighbour joining tree based on allelic diversity of core-genome multi-locus sequence typing and accessory genes were created using Ridom SeqSphere+ software (Ridom GmbH, Münster, Germany). FINDINGS: Over a 1-year period, 19 VRE carriers were identified; of these, 17 were part of two outbreaks. Before environmental cleaning and disinfection, 55 (14%) environmental samples were VRE-positive. Fifty-one isolates (23 patient samples and 28 environmental samples) were available for WGS analysis. Forty-four isolates were assigned to ST117-vanB, five were assigned to ST17-vanB, and two were assigned to ST80-vanB. Isolates from Outbreak 1 (N=22) and Outbreak 2 (N=22) belonged to ST117-vanB; however, WGS showed a different cluster type with 257 allelic differences. CONCLUSION: WGS of two outbreak strains provided discriminatory information regarding genetic relatedness, and rejected the hypothesis of a common environmental reservoir. A high degree of environmental contamination was associated with higher VRE transmission. Quantification of environmental contamination may reflect the potential for VRE transmission and could therefore support the infection control measures.


Assuntos
Infecção Hospitalar , Enterococcus faecium , Infecções por Bactérias Gram-Positivas , Enterococos Resistentes à Vancomicina , Infecção Hospitalar/epidemiologia , Surtos de Doenças , Enterococcus faecium/genética , Infecções por Bactérias Gram-Positivas/epidemiologia , Hospitais de Ensino , Humanos , Tipagem de Sequências Multilocus , Países Baixos , Vancomicina , Enterococos Resistentes à Vancomicina/genética
12.
J Clin Virol ; 141: 104909, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34271540

RESUMO

BACKGROUND: The current reference standard to diagnose a SARS-CoV-2 infection is real-time reverse transcriptase polymerase chain reaction (RT-PCR). This test poses substantial challenges for large-scale community testing, especially with respect to the long turnaround times. SARS-CoV-2 antigen tests are an alternative, but typically use a lateral flow assay format rendering them less suitable for analysis of large numbers of samples. METHODS: We conducted an evaluation of the Diasorin SARS-CoV-2 antigen detection assay (DAA) compared to real-time RT-PCR (Abbott). The study was performed on 248 (74 qRT-PCR positive, 174 qRT-PCR negative) clinical combined oro-nasopharyngeal samples of individuals with COVID-19-like symptoms obtained at a Municipal Health Service test centre. In addition, we evaluated the analytical performance of DAA with a 10-fold dilution series of SARS-CoV-2 containing culture supernatant and compared it with the lateral flow assay SARS-CoV-2 Roche/SD Biosensor Rapid Antigen test (RRA). RESULTS: The DAA had an overall specificity of 100% (95%CI 97.9%-100%) and sensitivity of 73% (95%CI 61.3%-82.7%) for the clinical samples. Sensitivity was 86% (CI95% 74.6%-93.3%) for samples with Ct-value below 30. Both the DAA and RRA detected SARS-CoV-2 up to a dilution containing 5.2 × 102 fifty-percent-tissue-culture-infective-dose (TCID50)/ml. DISCUSSION: The DAA performed adequately for clinical samples with a Ct-value below 30. Test performance may be further optimised by lowering the relative light unit (RLU) threshold for positivity assuming the in this study used pre-analytical protocol . The test has potential for use as a diagnostic assay for symptomatic community-dwelling individuals early after disease onset in the context of disease control.


Assuntos
COVID-19 , SARS-CoV-2 , Humanos , Nasofaringe , Sensibilidade e Especificidade
13.
Nature ; 432(7019): 885-8, 2004 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-15602557

RESUMO

Our knowledge of the structure of matter is largely based on X-ray diffraction studies of periodic structures and the successful transformation (inversion) of the diffraction patterns into real-space atomic maps. But the determination of non-periodic nanoscale structures by X-rays is much more difficult. Inversion of the measured diffuse X-ray intensity patterns suffers from the intrinsic loss of phase information, and direct imaging methods are limited in resolution by the available X-ray optics. Here we demonstrate a versatile technique for imaging nanostructures, based on the use of resonantly tuned soft X-rays for scattering contrast and the direct Fourier inversion of a holographically formed interference pattern. Our implementation places the sample behind a lithographically manufactured mask with a micrometre-sized sample aperture and a nanometre-sized hole that defines a reference beam. As an example, we have used the resonant X-ray magnetic circular dichroism effect to image the random magnetic domain structure in a Co/Pt multilayer film with a spatial resolution of 50 nm. Our technique, which is a form of Fourier transform holography, is transferable to a wide variety of specimens, appears scalable to diffraction-limited resolution, and is well suited for ultrafast single-shot imaging with coherent X-ray free-electron laser sources.

14.
Nature ; 428(6985): 831-3, 2004 Apr 22.
Artigo em Inglês | MEDLINE | ID: mdl-15103370

RESUMO

In magnetic memory devices, logical bits are recorded by selectively setting the magnetization vector of individual magnetic domains either 'up' or 'down'. In such devices, the fastest and most efficient recording method involves precessional switching: when a magnetic field B(p) is applied as a write pulse over a period tau, the magnetization vector precesses about the field until B(p)tau reaches the threshold value at which switching occurs. Increasing the amplitude of the write pulse B(p) might therefore substantially shorten the required switching time tau and allow for faster magnetic recording. Here we use very short pulses of a very high magnetic field to show that under these extreme conditions, precessional switching in magnetic media supporting high bit densities no longer takes place at well-defined field strengths; instead, switching occurs randomly within a wide range of magnetic fields. We attribute this behaviour to a momentary collapse of the ferromagnetic order of the spins under the load of the short and high-field pulse, thus establishing an ultimate limit to the speed of deterministic switching and magnetic recording.

15.
Nature ; 405(6788): 767-9, 2000 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-10866191

RESUMO

The arrangement of spins at interfaces in a layered magnetic material often has an important effect on the properties of the material. One example of this is the directional coupling between the spins in an antiferromagnet and those in an adjacent ferromagnet, an effect first discovered in 1956 and referred to as exchange bias. Because of its technological importance for the development of advanced devices such as magnetic read heads and magnetic memory cells, this phenomenon has received much attention. Despite extensive studies, however, exchange bias is still poorly understood, largely due to the lack of techniques capable of providing detailed information about the arrangement of magnetic moments near interfaces. Here we present polarization-dependent X-ray magnetic dichroism spectro-microscopy that reveals the micromagnetic structure on both sides of a ferromagnetic-antiferromagnetic interface. Images of thin ferromagnetic Co films grown on antiferromagnetic LaFeO3 show a direct link between the arrangement of spins in each material. Remanent hysteresis loops, recorded for individual ferromagnetic domains, show a local exchange bias. Our results imply that the alignment of the ferromagnetic spins is determined, domain by domain, by the spin directions in the underlying antiferromagnetic layer.

16.
Science ; 292(5525): 2299-302, 2001 Jun 22.
Artigo em Inglês | MEDLINE | ID: mdl-11423654

RESUMO

We used near-edge x-ray absorption fine structure (NEXAFS) spectroscopy to link the orientational bond order at three carbonaceous surfaces-rubbed polyimide, ion beam-irradiated polyimide, and ion beam-irradiated diamondlike carbon films-with the direction of liquid crystal (LC) alignment on these surfaces. We show that, in general, LC alignment can be created on any carbonaceous substrate by inducing orientational order at its surface. Our results form the scientific basis for LC alignment layers consisting of amorphous carbon films in which orientational order near the surface is induced by a directional low-energy ion beam.

17.
Nat Commun ; 10(1): 1756, 2019 04 15.
Artigo em Inglês | MEDLINE | ID: mdl-30988403

RESUMO

Sub-picosecond magnetisation manipulation via femtosecond optical pumping has attracted wide attention ever since its original discovery in 1996. However, the spatial evolution of the magnetisation is not yet well understood, in part due to the difficulty in experimentally probing such rapid dynamics. Here, we find evidence of a universal rapid magnetic order recovery in ferrimagnets with perpendicular magnetic anisotropy via nonlinear magnon processes. We identify magnon localisation and coalescence processes, whereby localised magnetic textures nucleate and subsequently interact and grow in accordance with a power law formalism. A hydrodynamic representation of the numerical simulations indicates that the appearance of noncollinear magnetisation via optical pumping establishes exchange-mediated spin currents with an equivalent 100% spin polarised charge current density of 107 A cm-2. Such large spin currents precipitate rapid recovery of magnetic order after optical pumping. The magnon processes discussed here provide new insights for the stabilization of desired meta-stable states.

18.
Protein Eng Des Sel ; 21(4): 241-6, 2008 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-18252750

RESUMO

Alzheimer's disease (AD) is a progressive neurodegenerative disorder. The 'amyloid cascade hypothesis' assigns the amyloid-beta-peptide (Abeta) a central role in the pathogenesis of AD. Although it is not yet established, whether the resulting Abeta aggregates are the causative agent or just a result of the disease progression, polymerization of Abeta has been identified as a major feature during AD pathogenesis. Inhibition of the Abeta polymer formation, thus, has emerged as a potential therapeutic approach. In this context, we identified peptides consisting of d-enantiomeric amino acid peptides (d-peptides) that bind to Abeta. D-peptides are known to be more protease resistant and less immunogenic than the respective L-enantiomers. Previously, we have shown that a 12mer D-peptide specifically binds to Abeta amyloid plaques in brain tissue sections from former AD patients. In vitro obtained binding affinities to synthetic Abeta revealed a K(d) value in the submicromolar range. The aim of the present study was to investigate the influence of this d-peptide to Abeta polymerization and toxicity. Using cell toxicity assays, thioflavin fluorescence, fluorescence correlation spectroscopy and electron microscopy, we found a significant effect of the d-peptide on both. Presence of D-peptides (dpep) reduces the average size of Abeta aggregates, but increases their number. In addition, Abeta cytotoxicity on PC12 cells is reduced in the presence of dpep.


Assuntos
Peptídeos beta-Amiloides/antagonistas & inibidores , Peptídeos beta-Amiloides/metabolismo , Citotoxinas/antagonistas & inibidores , Peptídeos/química , Peptídeos/farmacologia , Peptídeos beta-Amiloides/toxicidade , Animais , Benzotiazóis , Morte Celular/efeitos dos fármacos , Citotoxinas/metabolismo , Citotoxinas/toxicidade , Microscopia Eletrônica , Células PC12 , Peptídeos/metabolismo , Polímeros/metabolismo , Ligação Proteica , Estrutura Secundária de Proteína/efeitos dos fármacos , Ratos , Espectrometria de Fluorescência , Especificidade por Substrato , Tiazóis/metabolismo
19.
Physiol Res ; 57 Suppl 3: S1-10, 2008.
Artigo em Inglês | MEDLINE | ID: mdl-18481919

RESUMO

Agonist-induced subcellular redistribution of G-protein coupled receptors (GPCR) and of trimeric guanine-nucleotide binding regulatory proteins (G-proteins) represent mechanisms of desensitization of hormone response, which have been studied in our laboratory since 1989. This review brings a short summary of these results and also presents information about related literature data covering at least small part of research carried out in this area. We have also mentioned sodium plus potassium dependent adenosine triphosphatase (Na, K-ATPase) and 3H-ouabain binding as useful reference standard of plasma membrane purity in the brain.


Assuntos
Encéfalo/metabolismo , Proteínas de Ligação ao GTP/metabolismo , Proteínas Heterotriméricas de Ligação ao GTP/metabolismo , Hormônios/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Animais , Membrana Celular/enzimologia , Membrana Celular/metabolismo , Cricetinae , Regulação para Baixo , Proteínas de Ligação ao GTP/química , Proteínas Heterotriméricas de Ligação ao GTP/química , Multimerização Proteica , Ratos , Transdução de Sinais/fisiologia , ATPase Trocadora de Sódio-Potássio/metabolismo , Frações Subcelulares/metabolismo
20.
Nat Commun ; 9(1): 1035, 2018 03 07.
Artigo em Inglês | MEDLINE | ID: mdl-29515124

RESUMO

"The technical support from SLAC Accelerator Directorate, Technology Innovation Directorate, LCLS laser division and Test Facility Division is gratefully acknowledged. We thank S.P. Weathersby, R.K. Jobe, D. McCormick, A. Mitra, S. Carron and J. Corbett for their invaluable help and technical assistance. Research at SLAC was supported through the SIMES Institute which like the LCLS and SSRL user facilities is funded by the Office of Basic Energy Sciences of the U.S. Department of Energy under Contract No. DE-AC02-76SF00515. The UED work was performed at SLAC MeV-UED, which is supported in part by the DOE BES SUF Division Accelerator & Detector R&D program, the LCLS Facility, and SLAC under contract Nos. DE-AC02-05-CH11231 and DE-AC02-76SF00515. Use of the Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515."and"Work at BNL was supported by DOE BES Materials Science and Engineering Division under Contract No: DE-AC02-98CH10886. J.C. would like to acknowledge the support from National Science Foundation Grant No. 1207252. E.E.F. would like to acknowledge support from the U.S. Department of Energy (DOE), Office of Basic Energy Sciences (BES) under Award No. DE-SC0003678."This has been corrected in both the PDF and HTML versions of the Article.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA