The readout of negatively charged nitrogen-vacancy centre electron spins is essential for applications in quantum computation, metrology and sensing. Conventional readout protocols are based on the ...detection of photons emitted from nitrogen-vacancy centres, a process limited by the efficiency of photon collection. We report on an alternative principle for detecting the magnetic resonance of nitrogen-vacancy centres, allowing the direct photoelectric readout of nitrogen-vacancy centres spin state in an all-diamond device. The photocurrent detection of magnetic resonance scheme is based on the detection of charge carriers promoted to the conduction band of diamond by two-photon ionization of nitrogen-vacancy centres. The optical and photoelectric detection of magnetic resonance are compared, by performing both types of measurements simultaneously. The minima detected in the measured photocurrent at resonant microwave frequencies are attributed to the spin-dependent ionization dynamics of nitrogen-vacancy, originating from spin-selective non-radiative transitions to the metastable singlet state.
Efficient delivery of stabilized nucleic acids (NAs) into cells and release of the NA payload are crucial points in the transfection process. Here we report on the fabrication of a nanoscopic ...cellular delivery carrier that is additionally combined with a label-free intracellular sensor device, based on biocompatible fluorescent nanodiamond particles. The sensing function is engineered into nanodiamonds by using nitrogen-vacancy color centers, providing stable non-blinking luminescence. The device is used for monitoring NA transfection and the payload release in cells. The unpacking of NAs from a poly(ethyleneimine)-terminated nanodiamond surface is monitored using the color shift of nitrogen-vacancy centers in the diamond, which serve as a nanoscopic electric charge sensor. The proposed device innovates the strategies for NA imaging and delivery, by providing detection of the intracellular release of non-labeled NAs without affecting cellular processing of the NAs. Our system highlights the potential of nanodiamonds to act not merely as labels but also as non-toxic and non-photobleachable fluorescent biosensors reporting complex molecular events.
Nanodiamond or nanocrystalline diamond is a broad term used to describe a plethora of materials. It is generally accepted that nanocrystalline diamond (NCD) consists of facets less than 100 nm in ...size, whereas a second term “ultrananocrystalline diamond” (UNCD) has been coined to describe material with grain sizes less than 10 nm. These differences in morphology originate in the growth process. Conventional hydrogen rich gas phases produce facetted diamond with grain size proportional to film thickness and low sp
2 content. If these films are thin the grains can be less than 100 nm and hence NCD. By starving the plasma of hydrogen, the reduction in etching of sp
2 can lead to re-nucleation. At the extreme this results in very small grain sizes of around 3–5 nm, UNCD.
The electronic properties of these two materials are vastly different. NCD is basically very thin microcrystalline diamond and thus can be doped with boron. It is intrinsically transparent, with absorption increasing with doping level. UNCD is highly absorbing due to its higher sp
2 content, and exhibits a reduced bandgap due to disorder. By adding nitrogen to the gas phase, the density of states within the bandgap increases and ultimately metallic conductivity can be achieved. This conductivity is n-type but not doping.
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4.
An Abaqus plugin for fatigue predictions Nesladek, M; Spaniel, M
Advances in engineering software (1992),
January 2017, 2017-01-00, 20170101, Volume:
103
Journal Article
Peer reviewed
•The program provides a large number of prediction methods for material damage.•Plain fatigue, creep and thermo-mechanical fatigue are covered.•The solution can be obtained directly from the local ...Abaqus/CAE session.•The solver engine can employ multiple CPU cores.
This paper presents the features and functions of a software tool called Fatigue Prediction Utility for Abaqus/CAE (FPU). It is designed as a plugin for the Abaqus commercial FE code allowing for fatigue predictions based on the results of Abaqus FE analyses. It also contains an interface for data transfer between Abaqus and PragTic, a standalone fatigue post-processor. The program contains a simple and intuitive graphical interface, which makes preparation of a fatigue analysis straightforward. The FPU fatigue solver may be executed on multiple CPU cores independently from Abaqus/CAE, which allows large-scale problems to be solved on server machines in reasonable time. An overview of the functionality of the plugin, available prediction models and the concept of data exchange between Abaqus and PragTic is given. Illustrative examples are given, where appropriate, in order to introduce features of the tool. Possible ways of adapting the code for interconnection with an FE solver other than Abaqus are discussed.
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This paper describes the way in which a specialized validation set intended for quick validation of new multiaxial fatigue strength estimation models in the high‐cycle fatigue regime was prepared. ...The rules established for accepting various data sets into the complete FatLim database are briefly described. This final FatLim database contained 282 data items at the moment this paper was written. The paper describes how FatLim has been reduced to a smaller validation set, marked as AMSD25. The criteria used for accepting the data items for this small‐scale test set are based on evaluating the mean and the standard deviation of the fatigue index errors obtained for each data item on the basis of 18 different prediction criteria. The items that got into the AMSD25 validation set are described, and potential issues are noted. The comparison between the original FatLim validation set and the shortened AMSD25 data set is presented. It shows that the in‐phase load cases without any mean stress effect are generally well mastered by most criteria, and they can be excluded as insignificant from any such analysis. However, the mean stress effect is generally poorly incorporated. Future multiaxial fatigue strength criteria should focus on load cases including mean stresses.
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There is a continuous search for solid state spin qubits operating at room temperature with excitation in the infrared communication bandwidth. Recently, we have introduced the photoelectric ...detection of magnetic resonance (PDMR) to read the electron spin state of nitrogen-vacancy (NV) centers in diamond, a technique which is promising for applications in quantum information technology. By measuring the photoionization spectra on a diamond crystal, we found two ionization thresholds of unknown origin. On the same sample we also observed absorption and photoluminescence signatures that were identified in the literature as Ni-associated defects. We performed ab initio calculations of the photoionization cross section of the nickel split-vacancy complex (NiV) and N-related defects in their relevant charge states and fitted the concentration of these defects to the measured photocurrent spectrum, which led to a surprising match between experimental and calculated spectra. This study enabled us to identify the two unknown ionization thresholds with the two acceptor levels of NiV. Because the excitation of NiV is in the infrared, the photocurrent detected from the paramagnetic NiV color centers is a promising way towards the design of electrically readout qubits.
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Abstract
To achieve the expected level of sensitivity of third-generation gravitational-wave (GW) observatories, more accurate and sensitive instruments than those of the second generation must be ...used to reduce all sources of noises. Amongst them, one of the most relevant is seismic noise, which will require the development of a better isolation system, especially at low frequencies (below 10 Hz), the operation of large cryogenic silicon mirrors, and the improvement of optical wavelength readouts. In this framework, this article presents the activities of the E-TEST (Einstein Telescope Euregio Meuse-Rhine Site & Technology) to develop and test new key technologies for the next generation of GW observatories. A compact isolator system for a large silicon mirror (100 kg) at low frequency (
<
10 Hz) is proposed. The design of the isolator allows the overall height of the isolation system to be significantly compact and also suppresses seismic noise at low frequencies. To minimize the effect of thermal noise, the isolation system is provided with a 100 kg silicon mirror which is suspended in a vacuum chamber at cryogenic temperature (25–40 K). To achieve this temperature without inducing vibrations to the mirror, a radiation-based cooling strategy is employed. In addition, cryogenic sensors and electronics are being developed as part of the E-TEST to detect vibrational motion in the penultimate cryogenic stage. Since the commonly used silicon material is not transparent below the wavelengths typically used in the 1
µ
m range for GW detectors, new optical components and lasers must be developed in the range above 1500 nm to reduce absorption and scattering losses. Therefore, solid-state and fiber lasers with a wavelength of 2090 nm, matching high-efficiency photodiodes, and low-noise crystalline coatings are being developed. Accordingly, the key technologies provided by E-TEST serve crucially to reduce the limitations of the current generation of GW observatories and to determine the technical design for the next generation.
► We carried out fretting fatigue tests of creep-resistant chromium steel. ► A set of multiaxial fatigue criteria was verified. ► Stress fields in the test specimens computed by FEA were analysed by ...the criteria. ► The digital image correlation method can be used for the friction calibration. ► The criteria cannot handle various pressure load correctly.
Current knowledge about the fretting phenomenon and multiaxial fatigue criteria is briefly reviewed. Experimental equipment for fretting fatigue testing at the Czech Technical University (CTU) in Prague is introduced, and the results of experiments are presented. The digital image correlation (DIC) method was employed to calibrate the friction coefficient in a numerical model. This detailed model of the fretting-fatigue experimental setup was then used for computing the stress field histories of periodically loaded specimens. This data was used as input for the multiaxial fatigue criteria, and the prediction quality of the criteria was verified. The prediction model assessment results are presented. The results indicate that the criteria are not capable of handling the different damage mechanisms, which vary with the pressure load of the contact interface. A certain correction reflecting the contact kinematic behaviour therefore needs to be introduced into their mathematical formulation. The DIC method performed well in capturing local displacements in the vicinity of the stick–slip interface, and it provided necessary data for calibrating the friction coefficient.
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We propose and experimentally demonstrate a method to strongly increase the sensitivity of spin measure-ments on nitrogen vacancy (NV) centers in diamond, which can be readily implemented in existing ...quantum sensing experiments. While charge state transitions of this defect are generally considered a parasitic effect to be avoided, we show here that these can be used to significantly increase the NV centers spin contrast, a key quantity for high-sensitivity magnetometry and high-fidelity state readout. The protocol consists of a two-step procedure, in which the charge state of the defect is first purified by a strong laser pulse, followed by weak illumination to obtain high spin polarization. We observe a relative improvement of the readout contrast by 17% and infer a reduction of the initialization error of more than 50%. The contrast enhancement is accompanied by a beneficial increase of the readout signal. For long sequence durations, typically encountered in high-resolution magnetometry, a measurement speedup by a factor of &gt;1.5 is extracted, and we find that the technique is beneficial for sequences of any duration. Additionally, our findings give detailed insight into the charge and spin polarization dynamics of the NV center and provide actionable insights for direct optical, spin-to-charge, and electrical readout of solid-state spin centers.
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