64-Pixel Mo80Si20 superconducting nanowire single-photon imager with a saturated internal quantum efficiency at 1.5 µm.

A superconducting nanowire single-photon imager (SNSPI) uses a time-multiplexing method to reduce the readout complexity. However, due to the serial connection, the nanowire should be uniform so that a common bias can set all segments of the nanowire to their maximum detection efficiency, which becomes more challenging as the scalability (i.e., the length of the nanowire) increases. Here, we have developed a 64-pixel SNSPI based on amorphous Mo80Si20 film, which yielded a uniform nanowire and slow transmission line. Adjacent detectors were separated by delay lines, giving an imaging field of 270 µm × 240 µm. Benefiting from the high kinetic inductance of Mo80Si20 films, the delay line gave a phase velocity as low as 4.6 µm/ps. The positions of all pixels can be read out with a negligible electrical cross talk of 0.02% by using cryogenic amplifiers. The timing jitter was 100.8 ps. Saturated internal quantum efficiency was observed at a wavelength of 1550 nm. These results demonstrate that amorphous film is a promising material for achieving SNSPIs with large scalability and high efficiency.

[The Association between the Level of Plasma D-dimer and Disease Severity and Prognosis of Mycoplasma pneumoniae Pneumonia in Children].

OBJECTIVE: To explore the association between the levels of plasma D-dimer and the disease severity and prognosis of Mycoplasma pneumoniae pneumonia (MPP) in children. METHODS: We retrospectively analyzed the clinical data of pediatric MPP patients who were admitted in our hospital between January 1, 2016 and December 31, 2018. According to the peak value of D-dimer, patients were divided into the normal group (D-dimer<0.55 mg/L) and the elevated group (D-dimer≥0.55 mg/L). Information regarding the demographics, clinical manifestations, auxiliary examinations and treatments of patients in the two groups was compared. RESULTS: Of the 231 MPP patients included in the study, 70 were in the normal group and 161 were in the elevated group. The age of patients in the D-dimer elevated group was significantly higher than that of the normal group ( P<0.01). Compared with the normal group, the elevated group had longer lengths of fever, hospital stay and antibiotic therapy, and more severe radiographic manifestations (all P<0.01). In addition, the incidence of extrapulmonary complications, refractory MPP and severe MPP in the elevated group were significantly higher than those in the normal group ( P<0.01). As for the laboratory data, we found that neutrophils, C-reactive protein, lactate dehydrogenase, interleukin-6, interleukin-10 and interferon-γ were significantly higher in the elevated group than those in the normal group ( P<0.05). After treatments, all patients showed improvement and were discharged, but the proportions of patients requiring glucocorticoids, bronchoscopy, thoracentesis were significantly higher in the elevated group than those in the normal group ( P<0.05). Follow-up findings showed that the absorption rate of lung lesions 4 weeks after admission was significantly higher, the time needed for lung lesions absorption was significantly shorter, and the incidence of pulmonary sequelae was significantly lower in the normal group than those in the elevated group (all P<0.05). Correlation analysis showed that D-dimer level was positively correlated with the severity of pneumonia ( r=0.272, P=0.000) and the incidence of pulmonary sequelae ( r=0.235, P=0.000). CONCLUSION: Pediatric patients of MPP who had elevated plasma D-dimer had clinical manifestations that were more severe, required longer duration of treatment and longer recovery time for lung lesions, and were more likely to have pulmonary sequelae.

A Superconducting Binary Encoder with Multigate Nanowire Cryotrons.

Many classic and quantum devices need to operate at cryogenic temperatures, demanding advanced cryogenic digital electronics for processing the input and output signals on a chip to extend their scalability and performance. Here, we report a superconducting binary encoder with ultralow power dissipation and ultracompact size. We introduce a multigate superconducting nanowire cryotron (nTron) that functions as an 8-input OR gate within a footprint of approximately 0.5 µm2. Four cryotrons compose a 4-bit encoder that has a bias margin of 18.9%, an operation speed greater than 250 MHz, an average switching jitter of 75 ps, and a power dissipation of less than 1 µW. We apply this encoder to read out a superconducting-nanowire single-photon detector array whose pixel location is digitized into a 4-bit binary address. The small size of the nanowire combined with the low power dissipation makes nTrons promising for future monolithic integration.

Local Magnetoelectric Effect in La-Doped BiFeO3 Multiferroic Thin Films Revealed by Magnetic-Field-Assisted Scanning Probe Microscopy.

Multiferroic La-doped BiFeO3 thin films have been prepared by a sol-gel plus spin-coating process, and the local magnetoelectric coupling effect has been investigated by the magnetic-field-assisted scanning probe microscopy connected with a ferroelectric analyzer. The local ferroelectric polarization response to external magnetic fields is observed and a so-called optimized magnetic field of ~40 Oe is obtained, at which the ferroelectric polarization reaches the maximum. Moreover, we carry out the magnetic-field-dependent surface conductivity measurements and illustrate the origin of local magnetoresistance in the La-doped BiFeO3 thin films, which is closely related to the local ferroelectric polarization response to external magnetic fields. This work not only provides a useful technique to characterize the local magnetoelectric coupling for a wide range of multiferroic materials but also is significant for deeply understanding the local multiferroic behaviors in the BiFeO3-based systems.

Polarization-dependent interfacial coupling modulation of ferroelectric photovoltaic effect in PZT-ZnO heterostructures.

Recently, ferroelectric perovskite oxides have drawn much attention due to potential applications in the field of solar energy conversion. However, the power conversion efficiency of ferroelectric photovoltaic effect currently reported is far below the expectable value. One of the crucial problems lies in the two back-to-back Schottky barriers, which are formed at the ferroelectric-electrode interfaces and blocking most of photo-generated carriers to reach the outside circuit. Herein, we develop a new approach to enhance the ferroelectric photovoltaic effect by introducing the polarization-dependent interfacial coupling effect. Through inserting a semiconductor ZnO layer with spontaneous polarization into the ferroelectric ITO/PZT/Au film, a p-n junction with strong polarization-dependent interfacial coupling effect is formed. The power conversion efficiency of the heterostructure is improved by nearly two orders of magnitude and the polarization modulation ratio is increased about four times. It is demonstrated that the polarization-dependent interfacial coupling effect can give rise to a great change in band structure of the heterostructure, not only producing an aligned internal electric field but also tuning both depletion layer width and potential barrier height at PZT-ZnO interface. This work provides an efficient way in developing highly efficient ferroelectric-based solar cells and novel optoelectronic memory devices.