The Landé factors of electrons and holes in lead halide perovskites: universal dependence on the band gap

The Landé or g-factors of charge carriers are decisive for the spin-dependent phenomena in solids and provide also information about the underlying electronic band structure. We present a comprehensive set of experimental data for values and anisotropies of the electron and hole Landé factors in hybrid organic-inorganic (MAPbI₃, MAPb(Br_0.5Cl_0.5)₃, MAPb(Br_0.05Cl_0.95)₃, FAPbBr₃, FA_0.9Cs_0.1PbI_2.8Br_0.2, MA=methylammonium and FA=formamidinium) and all-inorganic (CsPbBr₃) lead halide perovskites, determined by pump-probe Kerr rotation and spin-flip Raman scattering in magnetic fields up to 10 T at cryogenic temperatures. Further, we use first-principles density functional theory (DFT) calculations in combination with tight-binding and k ⋅ p approaches to calculate microscopically the Landé factors. The results demonstrate their universal dependence on the band gap energy across the different perovskite material classes, which can be summarized in a universal semi-phenomenological expression, in good agreement with experiment.

The Landé factors govern all the spin-related basic phenomena and are the key parameters which guide spintronics applications. Here, Kirstein et al. demonstrate a universal dependence of the Landé factors on the bandgap energy of several perovskite materials.

COMPREHENSIVE BACTERIOLOGICAL STUDY OF THE VAGINAL DISCHARGE DURING BACTERIAL VAGINOSIS

Along with sexually transmitted infections opportunistic pathogens and normal microbiota are becoming increasingly clinically important. Opportunistic pathogens can lead to purulent-inflammatory process of the genitals The aim of the current work was to detect qualitative and quantitative composition of vagina contents in non-specific bacterial vaginosis. Vaginal microbiota of 298 women aged from 16 to 64 years old was analyzed. Examination was provided by polymerase chain reaction. In normocenosis with domination of enterobacteria the prevalence index of conditionally-pathogenic microflora wasn't more than 3 lg GE/sample. With absence of mycoplasmas the quantity of conditionally-pathogenic microorganisms wasn't more than 104,5. At same time in patients with dysbiosis of I and II levels index of conditionally-pathogenic microflora was from 3 to 1 and less than 1 lg GE/sample accordingly; there was diagnosed a significant decrease of the total bacterial mass. Simultaneously, decreasing of Lactobacillus quantity (more expressed in dysbiosis-II) meanwhile appearance of mycoplasmas and utmost constant quantity of Candida was revealed. A comprehensive determination of a wide range of opportunistic pathogens on the background of normal flora in the vaginal discharge of women of different ages had been studied.

Evidence of Large Polarons in Photoemission Band Mapping of the Perovskite Semiconductor CsPbBr_{3}

Lead-halide perovskite (LHP) semiconductors are emergent optoelectronic materials with outstanding transport properties which are not yet fully understood. We find signatures of large polaron formation in the electronic structure of the inorganic LHP CsPbBr_{3} by means of angle-resolved photoelectron spectroscopy. The experimental valence band dispersion shows a hole effective mass of 0.26±0.02 m_{e}, 50% heavier than the bare mass m_{0}=0.17 m_{e} predicted by density functional theory. Calculations of the electron-phonon coupling indicate that phonon dressing of the carriers mainly occurs via distortions of the Pb-Br bond with a Fröhlich coupling parameter α=1.81. A good agreement with our experimental data is obtained within the Feynman polaron model, validating a viable theoretical method to predict the carrier effective mass of LHPs ab initio.

[Skull injury in childhood: comparison of ultrasonography with conventional X-rays and computerized tomography]

PURPOSE

The purpose of our study was to compare the value of ultrasound, conventional x-ray diagnosis and CT in detecting skull fractures and intracranial haemorrhage in children suffering from a head injury.

MATERIAL AND METHODS

We examined 210 children who had a head injury. In all cases the calvarium was investigated by ultrasound using a 7.0 MHz linear transducer. In children with an open fontanel (n = 190) the cerebrum was screened additionally by ultrasound following a standard protocol. The sonographic findings were correlated to the x-ray examination (n = 21) and CT (n = 13).

RESULTS

Ultrasound enabled diagnosis of linear calvarial fractures (n = 29), depressed fractures (n = 6) and intracranial haemorrhage (n = 8). X-Ray and CT examination confirmed the diagnosis of linear calvarial fractures in 16 cases, of depressed fractures in 6 cases. CT confirmed the sonographic diagnosis of intracranial haemorrhage in 8 cases.

CONCLUSION

Ultrasound as a primary method can replace the conventional x-ray in detecting calvarial fracture and posttraumatic sequelae. Additional CT examination depends on the sonographic and neurological status.

The value of sonography in the detection of osteomyelitis

PURPOSE

A retrospective study was carried out in order to determine the role of sonography in establishing the diagnosis in extremity osteomyelitis.

MATERIALS AND METHODS

The imaging documents of 24 infants and children aged from 2 weeks to 13 years with osteomyelitis (acute 21, chronic 3) were reviewed. Sonograms and conventional radiographs were available in all patients. Additional skeletal scintigraphy had been performed in 13 patients and MRI in only 3. Special emphasis was put on the different ultrasound findings and their onset in the course of disease.

RESULTS

Intra-articular fluid collections (in 15 cases) and/or subperiosteal abscess formation (in 12) were the most frequent early sonographic findings, and preceded any radiographic changes by several days in 11 of these cases. Together with positive clinical signs of inflammation, they were usually sufficient to establish the correct diagnosis. In selected cases, fluid or abscess puncture for immediate microscopic and later bacteriological studies was carried out under sonographic control. In addition, sonography was also able to detect superficial cortical erosion and even an intramedullary focus in a very young patient.

CONCLUSION

Ultrasonography is a very helpful tool for establishing the correct diagnosis in osteomyelitis and reducing the frequency of additional imaging studies.