The modulator is a key component in optical communications. Several graphene-based amplitude modulators have been reported based on electro-absorption. However, graphene phase modulators (GPMs) are ...necessary for functions such as applying complex modulation formats or making switches or phased arrays. Here, we present a 10 Gb s–1 GPM integrated in a Mach–Zehnder interferometer configuration. This is a compact device based on a graphene-insulator–silicon capacitor, with a phase-shifter length of 300 μm and extinction ratio of 35 dB. The GPM has a modulation efficiency of 0.28 V cm at 1,550 nm. It has 5 GHz electro-optical bandwidth and operates at 10 Gb s–1 with 2 V peak-to-peak driving voltage in a push–pull configuration for binary transmission of a non-return-to-zero data stream over 50 km of single-mode fibre. This device is the key building block for graphene-based integrated photonics, enabling compact and energy-efficient hybrid graphene–silicon modulators for telecom, datacom and other applications.
From the wide spectrum of potential applications of graphene, ranging from transistors and chemical sensors to nanoelectromechanical devices and composites, the field of photonics and optoelectronics ...is believed to be one of the most promising. Indeed, graphene's suitability for high-speed photodetection was demonstrated in an optical communication link operating at 10 Gbit s(-1). However, the low responsivity of graphene-based photodetectors compared with traditional III-V-based ones is a potential drawback. Here we show that, by combining graphene with plasmonic nanostructures, the efficiency of graphene-based photodetectors can be increased by up to 20 times, because of efficient field concentration in the area of a p-n junction. Additionally, wavelength and polarization selectivity can be achieved by employing nanostructures of different geometries.
Objective:
The objective was to provide guidelines to clinicians for the evaluation, treatment, and prevention of vitamin D deficiency with an emphasis on the care of patients who are at risk for ...deficiency.
Participants:
The Task Force was composed of a Chair, six additional experts, and a methodologist. The Task Force received no corporate funding or remuneration.
Consensus Process:
Consensus was guided by systematic reviews of evidence and discussions during several conference calls and e-mail communications. The draft prepared by the Task Force was reviewed successively by The Endocrine Society's Clinical Guidelines Subcommittee, Clinical Affairs Core Committee, and cosponsoring associations, and it was posted on The Endocrine Society web site for member review. At each stage of review, the Task Force received written comments and incorporated needed changes.
Conclusions:
Considering that vitamin D deficiency is very common in all age groups and that few foods contain vitamin D, the Task Force recommended supplementation at suggested daily intake and tolerable upper limit levels, depending on age and clinical circumstances. The Task Force also suggested the measurement of serum 25-hydroxyvitamin D level by a reliable assay as the initial diagnostic test in patients at risk for deficiency. Treatment with either vitamin D2 or vitamin D3 was recommended for deficient patients. At the present time, there is not sufficient evidence to recommend screening individuals who are not at risk for deficiency or to prescribe vitamin D to attain the noncalcemic benefit for cardiovascular protection.
Ultrashort-pulse lasers with spectral tuning capability have widespread applications in fields such as spectroscopy, biomedical research and telecommunications. Mode-locked fibre lasers are ...convenient and powerful sources of ultrashort pulses, and the inclusion of a broadband saturable absorber as a passive optical switch inside the laser cavity may offer tuneability over a range of wavelengths. Semiconductor saturable absorber mirrors are widely used in fibre lasers, but their operating range is typically limited to a few tens of nanometres, and their fabrication can be challenging in the 1.3-1.5 microm wavelength region used for optical communications. Single-walled carbon nanotubes are excellent saturable absorbers because of their subpicosecond recovery time, low saturation intensity, polarization insensitivity, and mechanical and environmental robustness. Here, we engineer a nanotube-polycarbonate film with a wide bandwidth (>300 nm) around 1.55 microm, and then use it to demonstrate a 2.4 ps Er(3+)-doped fibre laser that is tuneable from 1,518 to 1,558 nm. In principle, different diameters and chiralities of nanotubes could be combined to enable compact, mode-locked fibre lasers that are tuneable over a much broader range of wavelengths than other systems.
Over the last 3 years new definitions of sarcopenia by the Sarcopenia Definition and Outcome Consortium (2020, SDOC), European Working Group on Sarcopenia in Older People (2019, EWGSOP2) and Asian ...Working Group on Sarcopenia (2019, AWGS2) have been proposed. The objective of this scoping review was to explore predictive validity of these current sarcopenia definitions for clinical outcomes. We followed the PRISMA checklist for scoping reviews. Based on a systematic search performed by two independent reviewers of databases (Pubmed and Embase) articles comparing predictive validity of two or more sarcopenia definitions on prospective clinical outcomes published since January 2019 (the year these definitions were introduced) were included. Data were extracted and results collated by clinical outcomes and by sarcopenia definitions, respectively. Of 4493 articles screened, 11 studies (mean age of participants 77.6 (SD 5.7) years and 50.0% female) comprising 82 validity tests were included. Overall, validity tests on the following categories of clinical outcomes were performed: fracture (n = 40, assessed in one study), mortality (n = 18), function (n = 11), institutionalization (n = 7), falls (n = 4), and hospitalization (n = 2). Thereby, EWGSOP2 was investigated in 15 validity tests (18.3%) on all categories of clinical outcomes, whereas SDOC was investigated in four validity tests (4.9%) in one study on fractures in men only, and none of the validity tests investigated predictive validity by the AWGS2. However, we were not able to pool the data using a meta‐analytic approach due to important methodological heterogeneity between the studies. We identified various definitions of clinical outcomes that were used to test predictive validity of sarcopenia definitions suggesting that an agreement on an operational definition of a clinical outcome is key to advance in the field of sarcopenia. Moreover, data on predictive validity using the sarcopenia definitions by the SDOC and AWGS2 are still scarce and lacking, respectively. In a next step, prospective studies including both women and men are needed to compare predictive validity of current sarcopenia definitions on defined key clinical outcomes.
The pilot injected fuel masses generally are in the 1–4mg range for automotive diesel engines and are affected by significant dispersion, which represents an issue for injection control systems. A ...new methodology has been developed for real-time evaluation of the fuel injected in small injections in diesel engines.
The measurement requires the installation of a single pressure transducer on a pipe connecting the injector to the rail. A simple algorithm, which is based on the mass conservation and momentum balance equations, written with respect to a reference frame that is integral with the pressure wave front, has been elaborated to convert the experimental pressure time history into an instantaneous flow rate. The results on the flow-rate through the pipe that connects the injector to the rail are compared with the corresponding numerical outcomes from a 1D model of the fuel injection system.
The estimated fuel quantities that enter the injector have been verified to be well correlated with the measured volumes of the fuel injected in small injections. The relation that has been found could be implemented in the engine electronic control unit and employed together with the pressure transducer installed at the inlet of the injector for a more accurate real-time control of both the injected mass and the system high-pressure.
•Direct and indirect acting injectors are tested considering multiple injections.•The injection fusion threshold is higher for ballistic injectors than for stroke-end limited injectors.•The internal ...dynamics of the injector is analyzed for closely-coupled double injections.•Different regimes are identified and classified in the short dwell time range.•Innovative rate shaping injection schedules are defined for solenoid injectors.
The multiple injection performance of Common Rail injectors has been analyzed at a hydraulic test rig as the dwell time was varied. The dependence of the injected volume on the dwell time has been investigated for direct acting piezoelectric and hydraulically-controlled (or indirect-acting) servo injectors. The injected fuel volumes in the long dwell-time range have been shown to be affected by the pressure waves that travel along the high pressure circuit for hydraulically-controlled servo injectors. On the other hand, the influence of pressure-wave-induced disturbances on multiple injection performance has been shown to be negligible for direct acting piezoelectric injectors.
An analysis of closely-coupled injections has been conducted on a solenoid injector. When the dwell time is progressively reduced below a critical value, an increase in the fuel quantity that is injected in the second shot is observed. Injection fusion phenomena occur as the dwell time is diminished below a certain threshold and a maximum in the fuel volume, which is injected during the joint injections, is eventually detected for a very short electric dwell time value close to 100μs. The cycle-to-cycle dispersion around this dwell time value results to be reduced significantly.
A previously developed 1D model of the fuel injection system has been applied to analyze the injector transients. Detailed knowledge of the injection dynamics in the short dwell time region is of fundamental importance to optimize the implementation of both discontinuous and continuous rate shaping strategies. At present, there is a great deal of interest in these advanced schedules, since they can allow a minimization of soot emissions, fuel consumption and combustion noise to be achieved in diesel engines equipped with indirect-acting injectors.
During the last glacial period, large millennial-scale temperature oscillations-the 'Dansgaard/Oeschger' cycles-were the primary climate signal in Northern Hemisphere climate archives from the high ...latitudes to the tropics. But whether the influence of these abrupt climate changes extended to the tropical and subtropical Southern Hemisphere, where changes in insolation are thought to be the main direct forcing of climate, has remained unclear. Here we present a high-resolution oxygen isotope record of a U/Th-dated stalagmite from subtropical southern Brazil, covering the past 116,200 years. The oxygen isotope signature varies with shifts in the source region and amount of rainfall in the area, and hence records changes in atmospheric circulation and convective intensity over South America. We find that these variations in rainfall source and amount are primarily driven by summer solar radiation, which is controlled by the Earth's precessional cycle. The Dansgaard/Oeschger cycles can be detected in our record and therefore we confirm that they also affect the tropical hydrological cycle, but that in southern subtropical Brazil, millennial-scale climate changes are not as dominant as they are in the Northern Hemisphere.
Graphene integrated photonics provides several advantages over conventional Si photonics. Single layer graphene (SLG) enables fast, broadband, and energy-efficient electro-optic modulators, optical ...switches and photodetectors (GPDs), and is compatible with any optical waveguide. The last major barrier to SLG-based optical receivers lies in the current GPDs' low responsivity when compared to conventional PDs. Here we overcome this by integrating a photo-thermoelectric GPD with a Si microring resonator. Under critical coupling, we achieve >90% light absorption in a ~6 μm SLG channel along a Si waveguide. Cavity-enhanced light-matter interactions cause carriers in SLG to reach ~400 K for an input power ~0.6 mW, resulting in a voltage responsivity ~90 V/W, with a receiver sensitivity enabling our GPDs to operate at a 10
bit-error rate, on par with mature semiconductor technology, but with a natural generation of a voltage, rather than a current, thus removing the need for transimpedance amplification, with a reduction of energy-per-bit, cost, and foot-print.
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