392 research outputs found
Auto-oscillation threshold, narrow spectral lines, and line jitter in spin-torque oscillators based on MgO magnetic tunnel junctions
We demonstrate spin torque induced auto-oscillation in MgO-based magnetic
tunnel junctions. At the generation threshold, we observe a strong line
narrowing down to 6 MHz at 300K and a dramatic increase in oscillator power,
yielding spectrally pure oscillations free of flicker noise. Setting the
synthetic antiferromagnet into autooscillation requires the same current
polarity as the one needed to switch the free layer magnetization. The induced
auto-oscillations are observed even at zero applied field, which is believed to
be the acoustic mode of the synthetic antiferromagnet. While the phase
coherence of the auto-oscillation is of the order of microseconds, the power
autocorrelation time is of the order of milliseconds and can be strongly
influenced by the free layer dynamics
Auto-oscillation threshold and line narrowing in MgO-based spin-torque oscillators
We present an experimental study of the power spectrum of current-driven
magnetization oscillations in MgO tunnel junctions under low bias. We find the
existence of narrow spectral lines, down to 8 MHz in width at a frequency of
10.7 GHz, for small applied fields with clear evidence of an auto-oscillation
threshold. Micromagnetics simulations indicate that the excited mode
corresponds to an edge mode of the synthetic antiferromagnet
Transverse component of the magnetic field in the solar photosphere observed by Sunrise
We present the first observations of the transverse component of photospheric
magnetic field acquired by the imaging magnetograph Sunrise/IMaX. Using an
automated detection method, we obtain statistical properties of 4536 features
with significant linear polarization signal. Their rate of occurrence is 1-2
orders of magnitude larger than values reported by previous studies. We show
that these features have no characteristic size or lifetime. They appear
preferentially at granule boundaries with most of them being caught in downflow
lanes at some point in their evolution. Only a small percentage are entirely
and constantly embedded in upflows (16%) or downflows (8%).Comment: Accepted for the Sunrise Special Issue of ApJ
A Preference for Contralateral Stimuli in Human Object- and Face-Selective Cortex
Visual input from the left and right visual fields is processed predominantly in the contralateral hemisphere. Here we investigated whether this preference for contralateral over ipsilateral stimuli is also found in high-level visual areas that are important for the recognition of objects and faces. Human subjects were scanned with functional magnetic resonance imaging (fMRI) while they viewed and attended faces, objects, scenes, and scrambled images in the left or right visual field. With our stimulation protocol, primary visual cortex responded only to contralateral stimuli. The contralateral preference was smaller in object- and face-selective regions, and it was smallest in the fusiform gyrus. Nevertheless, each region showed a significant preference for contralateral stimuli. These results indicate that sensitivity to stimulus position is present even in high-level ventral visual cortex
Long-term acquired everolimus resistance in pancreatic neuroendocrine tumours can be overcome with novel PI3K-AKT-mTOR inhibitors
Background:The mTOR-inhibitor everolimus improves progression-free survival in advanced pancreatic neuroendocrine tumours (PNETs). However, adaptive resistance to mTOR inhibition is described.Methods:QGP-1 and BON-1, two human PNET cell lines, were cultured with increasing concentrations of everolimus up to 22 weeks to reach a dose of 1 μM everolimus, respectively, 1000-fold and 250-fold initial IC 50. Using total DNA content as a measure of cell number, growth inhibitory dose-response curves of everolimus were determined at the end of resistance induction and over time after everolimus withdrawal. Response to ATP-competitive mTOR inhibitors OSI-027 and AZD2014, and PI3K-mTOR inhibitor NVP-BEZ235 was studied. Gene expression of 10 PI3K-Akt-mTOR pathway-related genes was evaluated using quantitative real-time PCR (RT-qPCR).Results:Long-term everolimus-treated BON-1/R and QGP-1/R showed a significant reduction in everolimus sensitivity. During a drug holiday, gradual return of everolimus sensitivity in BON-1/R and QGP-1/R led to complete reversal of resistance after 10-12 weeks. Treatment with AZD2014, OSI-027 and NVP-BEZ235 had an inhibitory effect on cell proliferation in both sensitive and resistant cell lines. Gene expression in BON-1/R revealed downregulation of MTOR, RICTOR, RAPTOR, AKT and HIF1A, whereas 4EBP1 was upregulated. In QGP-1/R, a downregulation of HIF1A and an upregulation of ERK2 were observed.Conclusions:Long-term everolimus resistance was induced in two human PNET cell lines. Novel PI3K-AKT-mTOR pathway-targeting drugs can overcome everolimus resistance. Differential gene expression profiles suggest different mechanisms of everolimus resistance in BON-1 and QGP-1
Een 18de-eeuwse wraksite op de Buiten Ratel-zandbank (Belgische territoriale wateren): 1. Multidisciplinair onderzoek van het vondstenmateriaal
In 1996 werd op de Buiten Ratel-zandbank, op 9 mijl van de kust, ter hoogte van Koksijde, een houten scheepswrak gelokaliseerd. Het werd onderzocht door een groep sportduikers, met de naam NATA. Jarenlange verkenning van de wraksite leverde talrijke vondsten op. In 2003 zochten de duikers steun bij het toenmalige IAP (Instituut voor het Archeologisch Patrimonium), nu Vlaams Instituut voor het Onroerend Erfgoed (VIOE), om het onderzoek en de conservatie op wetenschappelijke basis verder te zetten. Het VIOE ontfermde zich over het onderzoek van de tot nu toe geborgen materiële resten van de wraksite.
Het eerste hoofdstuk van het artikel geeft een overzicht van de observaties van de wraksite via duikonderzoek en via gespecialiseerde technieken vanop een onderzoeksschip. In hoofdstuk 2 worden de objecten beschreven, hun betekenis aan boord van het schip besproken, evenals hun datering en herkomst. Hoofdstuk 3 brengt alle informatie samen en geeft aan wat er in de toekomst nog aan onderzoek kan gebeuren
Role of Traveling Executives at MNC
Objectives To investigate whether serum 25-hydroxy vitamin D (25(OH)D) is associated with physical performance in men and women. Design Cross-sectional. Setting Emergency departments (EDs) of five hospitals. Participants Older adults who visited an ED because of a fall (N = 616). Measurements Physical performance was assessed using the Timed Up and Go Test, the Five Time Sit to Stand Test, handgrip strength, and the tandem stand test. Multivariate linear regression was used to assess the association between physical performance and log-transformed 25(OH)D concentration adjusted for potential confounders. Results In men, higher serum 25(OH)D concentration was significantly associated with better handgrip strength (regression coefficient (B) = 3.86, 95% confidence interval (CI) = 2.04-5.69), faster TUG time (B = -2.82, 95% CI = -4.91 to -0.73), and faster FTSS time (B = -3.39, 95% CI = -5.67 to -1.11). In women, higher serum 25(OH)D concentration was significantly associated with faster TUG time (B = -2.68, 95% CI = -4.87 to -0.49). Conclusion A positive association was found between serum 25(OH)D level and physical performance in men and women. Intervention studies are needed of vitamin D-deficient older men and women to further investigate the effect of vitamin D supplementation in this group. © 2013, The American Geriatrics Society
Routine versus on demand removal of the syndesmotic screw; a protocol for an international randomised controlled trial (RODEO-trial)
Background: Syndesmotic injuries are common and their incidence is rising. In case of surgical fixation of the syndesmosis a metal syndesmotic screw is used most often. It is however unclear whether this screw needs to be removed routinely after the syndesmosis has healed. Traditionally the screw is removed after six to 12 weeks as it is thought to hamper ankle functional and to be a source of pain. Some studies however suggest this is only the case in a minority of patients. We therefore aim to investigate the effect of retaining the syndesmotic screw on functional outcome. Design: This is a pragmatic international multicentre randomised controlled trial in patients with an acute syndesmotic injury for which a metallic syndesmotic screw was placed. Patients will be randomised to either routine removal of the syndesmotic screw or removal on demand. Primary outcome is functional recovery at 12 months measured with the Olerud-Molander Score. Secondary outcomes are quality of life, pain and costs. In total 194 patients will be needed to demonstrate non-inferiority between the two interventions at 80% power and a significance level of 0.025 including 15% loss to follow-up. Discussion: If removal on demand of the syndesmotic screw is non-inferior to routine removal in terms of functional outcome, this will offer a strong argument to adopt this as standard practice of care. This means that patients will not have to undergo a secondary procedure, leading to less complications and subsequent lower costs.Peer reviewe
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