Bloch oscillations at room temperature in graphene/h-BN electrostatic superlattices.

In this manuscript, we report the fabrication and the measurements of Bloch oscillations at room temperature in electrostatic graphene/h-BN superlattices. The electrostatic superlattice consists of an array of tilted metallic electrodes deposited over graphene monolayer/h-BN monolayer grown on 2 inch wafers of doped Si/SiO2. We show the formation of minibands at room temperature, negative differential resistance and the evidence of Bloch oscillations. The experimental results are sustained by numerical modelling of these 2D superlattices. The experimental results are sustained by numerical modelling of these 2D superlattices. At room temperature, we have measured a period of Bloch oscillations of 55 meV which corresponds to a frequency of 13 THz.

Wafer-scale graphene-ferroelectric HfO2/Ge-HfO2/HfO2 transistors acting as three-terminal memristors.

In this paper we report a set of experiments at the wafer level regarding field-effect transistors with a graphene monolayer channel transferred on the ferroelectric HfO2/Ge-HfO2/HfO2 three-layer structure. This kind of transistor has a switching ratio of 103 between on and off states due to the bandgap in graphene induced by the ferroelectric structure. Both top and back gates effectively control the carriers' charge flow in graphene. The transistor acts as a three-terminal memristor, termed a memtransistor, with applications in neuromorphic computation.

Effectiveness, safety, and acceptability of first-trimester medical termination of pregnancy performed by non-doctor providers: a systematic review.

BACKGROUND: Previous systematic reviews have concluded that medical termination of pregnancy (TOP) performed by non-doctor providers may be as effective and safe as when provided by doctors. Medical treatment of incomplete miscarriage by non-doctor providers and the treated women's acceptance of non-doctor providers of TOP has not previously been reviewed. OBJECTIVES: To review the effectiveness, safety, and acceptability of first-trimester medical TOP, including medical treatment for incomplete miscarriage, by trained non-doctor providers. SEARCH STRATEGY AND SELECTION CRITERIA: A search strategy using appropriate medical subject headings was developed. Electronic databases (PubMed, Popline, Cochrane, CINAHL, Embase, and ClinicalTrials.gov) were searched from inception through April 2016. Randomised controlled trials and comparative observational studies were included. DATA COLLECTION AND ANALYSIS: Meta-analyses were performed for included randomised controlled trials regarding the outcomes of effectiveness and acceptability to women. Certainty of evidence was established using the GRADE approach assessing study limitations, consistency of effect, imprecision, indirectness and publication bias. MAIN RESULTS: Six papers were included. Medical TOP and medical treatment of incomplete miscarriage is probably equally effective when performed by non-doctor providers as when performed by doctors (RR 1.00; 95% CI 0.99-1.01). Women's acceptance, reported as overall satisfaction with the allocated provider, is probably equally high between groups (RR 1.00; 95% CI 1.00-1.01). CONCLUSION: Medical TOP and medical treatment of incomplete miscarriage provided by trained non-doctor providers is probably equally as effective and acceptable to women as when provided by doctors. TWEETABLE ABSTRACT: Medical termination of pregnancy performed by doctors and non-doctors can be equally effective and acceptable.

Overview of abortion cases with severe maternal outcomes in the WHO Multicountry Survey on Maternal and Newborn Health: a descriptive analysis.

OBJECTIVE: To summarise individual and institutional characteristics of abortion-related severe maternal outcomes reported at health facilities. DESIGN: Secondary analysis of data from the WHO Multicountry Survey on Maternal and Newborn Health. SETTING: 85 health facilities in 23 countries. SAMPLE: 322 women with abortion-related severe maternal outcomes. METHODS: Frequency distributions and comparisons of differences in characteristics between cases of maternal near miss and death using Fisher's exact tests of association. MAIN OUTCOME MEASURES: Individual and institutional characteristics and frequencies of potentially life-threatening conditions, and interventions provided to women with severe maternal outcomes, maternal near miss, and maternal death. RESULTS: Most women with abortion-related severe maternal outcomes (SMOs) were 20-34 years old (65.2%), married or cohabitating (92.3%), parous (84.2%), and presented with abortions resulting from pregnancies at less than 14 weeks of gestation (67.1%). The women who died were younger, more frequently without a partner, and had abortions at ≥14 weeks of gestation, compared with women with maternal near miss (MNM). Curettage was the most common mode of uterine evacuation. The provision of blood products and therapeutic antibiotics were the most common other interventions recorded for all women with abortion-related SMOs; those who died more frequently had antibiotics, laparotomy, and hysterectomy, compared with women with MNM. Although haemorrhage was the most common cause of abortion-related SMO, infection (alone and in combination with haemorrhage) was the most common cause of death. CONCLUSION: This analysis affirms a number of previously observed characteristics of women with abortion-related severe morbidity and mortality, despite the fact that facility-based data on abortion-related SMO suffers a number of limitations.

Graphene-like metal-on-silicon field-effect transistor.

This paper presents a field-effect transistor with a channel consisting of a two-dimensional electron gas located at the interface between an ultrathin metallic film of Ni and a p-type Si(111) substrate. The gate length is L = 2 µm, its width is W = 180 µm, and the source-drain separation is 188 µm, the role of the gate dielectric being played by the surface states of the ultrathin metal layer. We have demonstrated that the two-dimensional electron gas channel is modulated by the gate voltage. The dependence of the drain current on the drain voltage has no saturation region, similar to a field-effect transistor based on graphene. The drain current is 2 mA at a drain voltage of 3 V and a gate voltage of 1.07 V, while the transconductance is 0.6 mS for a drain voltage of 6 V and a gate voltage of 1 V. However, the transport in this transistor is not ambipolar, as in graphene, but unipolar.

Ultrabroadband photodetection based on graphene ink.

We report photodetection in a very large spectral bandwidth, which encompasses ultraviolet, visible and near infrared, using graphene inks or graphene inks functionalized with either gold or silver nanoparticles, or gold nanoparticles further encapsulated with bovine serum albumin deposited on interdigitated electrodes fabricated on a silicon dioxide/silicon substrate. In contrast to gold-functionalized graphene inks, which have responsivities better than 1 mA W(-1) at a 0.1 V bias over the huge bandwidth extending from 215 to 2500 nm, Ag-functionalized inks show at least a four-fold increased responsivity, with a record value of 13.7 mA W(-1) in near infrared.

Real-time detection of deoxyribonucleic acid bases via their negative differential conductance signature.

In this Brief Report, we present a method for the real-time detection of the bases of the deoxyribonucleic acid using their signatures in negative differential conductance measurements. The present methods of electronic detection of deoxyribonucleic acid bases are based on a statistical analysis because the electrical currents of the four bases are weak and do not differ significantly from one base to another. In contrast, we analyze a device that combines the accumulated knowledge in nanopore and scanning tunneling detection and which is able to provide very distinctive electronic signatures for the four bases.

Writing simple RF electronic devices on paper with carbon nanotube ink.

This paper shows that we can print on paper simple high-frequency electronic devices such as resistances, capacitances or inductances, with values that can be changed in a controllable manner by an applied dc voltage. This tunability is achieved with the help of an ink containing functionalized carbon nanotubes and water. After the water is evaporated from the paper, the nanotubes remain steadily imprinted on paper, showing a semiconducting behavior and tunable electrical properties.

GaN membrane metal-semiconductor-metal ultraviolet photodetector.

GaN is a wide-bandgap semiconductor with still unexplored capabilities for ultraviolet detection. To exploit GaN properties better for ultraviolet detection, a metal-semiconductor-metal-type photodetector structure was designed and manufactured on a 2.2 microm thin GaN membrane fabricated by micromachining techniques. As a result, a very low dark current (30 pA at 3 V) and a maximum responsivity of 14 mA/W at a wavelength of 370 nm were obtained.

Reconfigurable electro-optical waveguide for optical processing.

A highly versatile electro-optically induced waveguide is proposed, and some of its applications are discussed. The In(1-s)Ga(s)As(t)P(1-t)-based device can reconfigure an arbitrary refractive-index profile with high speed by using an array of stripe electrodes deposited along the device. This device can act as a variable fractional Fourier transformer or as a beam shaper. Some nonguiding applications based on a specific refractive-index patterning that is normal to the light-propagation direction, such as phase modulation and beam steering, can also be implemented with this device.

Tomographic amplitude and phase recovery of vertical-cavity surface-emitting lasers by use of the ambiguity function.

The amplitude and the phase of a multimode vertical-cavity surface-emitting laser (VCSEL) are recovered by a simple tomographic procedure based on the ambiguity function. The results are of considerable importance for any field of optics in which VCSELs are employed.

Characterization of wave fronts of light beams by use of tunneling cantilevers.

We show that by use of an array of micromechanical tunneling cantilevers we can determine the amplitude and phase profile of an incident light beam. When there is no phase jump the phase profile can be determined by the measurement of two sets of the tunneling currents that correspond to a steplike applied bias, which induces a Franz-Keldysh effect in the cantilevers. The case of phase jump is also discussed.

Optical realization of the ambiguity function of real two-dimensional light sources.

We propose a setup that can generate the sectional ambiguity function of a two-dimensional real light source. The setup is easy to implement; the theoretical analysis and experimental results are given.

Single device for laser source measurements from the ultraviolet to the far infrared.

We propose a new device, based on an array of micromechanical cantilevers, that measures both the wavelength and the optical power of a laser source with constant efficiency over a large spectral interval from the ultraviolet to the far infrared. To measure the wavelength, the thickness of the cantilevers must vary linearly along the array. The characteristics of this device are calculated, and an example is given for the design of an array of Si cantilevers that cover the 0.33-11-microm spectral range.

Variant fractional Fourier transformer for optical pulses.

We demonstrate that it is possible to perform a fractional Fourier transform of an incident pulse with a continuously variable degree of fractionality, using a dispersive and nonlinear Kerr medium. This medium acts as a linear waveguide for the optical pulse if its intensity is small and if the refractive index is nonlinearly time-dependently modified by a simultaneously launched bright soliton. For optical pulses the dispersive and nonlinear medium is perfectly equivalent to a graded-index refractive medium for optical beams.

Implementation of the spatial and the temporal cross-ambiguity function for waveguide fields and optical pulses.

On the basis of space-time duality, we propose experimental setups to implement the cross-ambiguity function optically in space and time in one and two dimensions. In space the cross-ambiguity is shown to be related to the coupling efficiency between butt-joined optical waveguides. In time it is related to the spectrogram or the frequency-resolved optical gating techniques for the characterization of optical pulses.

Experimental demonstration of a continuously variant fractional fourier transformer.

We demonstrate that an off-axis illuminated hemispherical-rod microlens acts as a fractional Fourier transformer with a continuously varying degree of fractionality. A complete theoretical treatment of the device as well as experimental results are presented.

Phase-space measurements of micro-optical objects.

The phase-space measurement of micro-optical objects with submillimeter dimensions is reported for the first time to our knowledge. The experimental data were compared with simulated results from interferometric measurements and were found to be in good agreement.

Optical actuation of micromechanical tunneling structures with applications in spectrum analysis and optical computing.

An efficient method for optically actuating a micromechanical cantilever is presented for the first time to our knowledge. Measurable responses can be obtained for moderate light sources if electron tunneling occurs between the cantilever tip and a metallic contact below it. The small deflection of the cantilever that is due to light pressure is sufficient then to produce large tunneling current variations. On the basis of this effect several applications such as a miniaturized spectrum analyzer and one-step optical computing units for addition, integration, or differentiation of one-dimensional or two-dimensional optical signals are presented.

Hemispherical-rod microlens as a variant fractional Fourier transformer.

It is shown that a hemispherical-rod microlens can act as a fractional Fourier transform device with a continuously varying degree of fractionality. It is believed to be the first proposed device to perform such a task; its most immediate applications include optical tomography.