Direct current hopping conductance in one-dimensional diagonal disordered systems

Based on a tight-binding disordered model describing a single electron band, we establish a direct current （de） electronic hopping transport conductance model of one-dimensional diagonal disordered systems, and also derive a dc conductance formula. By calculating the dc conductivity, the relationships between electric field and conductivity and between temperature and conductivity are analysed, and the role played by the degree of disorder in electronic transport is studied. The results indicate the conductivity of systems decreasing with the increase of the degree of disorder, characteristics of negative differential dependence of resistance on temperature at, low temperatures in diagonal disordered systems, and the conductivity of systems decreasing with the increase of electric field, featuring the non-Ohm＇s law conductivity.

Abnormal electric transport property and magnetoresistance stability of La-Sr-K-Mn-O system

The perovskite samples La1-x（Sr1-yKy）xMnO3 （y = 0.0, 0.2, 04, 0.6, 0.8） were prepared by the solid-state reaction method with comparatively low sintering tem- perature and with comparatively short sintering time, and the electric transport property and temperature stability of MR of this system were studied. The p-T curves show the abnormal phenomenon that with the increase of K doping amount, resistivity increases, and the insulator-metal transition temperature decreases, which is because the influence of the occupation disorder degree of A-site ions σ2 on the electric transport property of perovskite manga- nites is larger than that of the radius of A-site ions （rA）. In the temperature range below 225 K, MR increases contin- uously with the decrease of temperature, which is the characteristic of low-field magnetoresistance; in the com- paratively wide temperature range near 250 K, the MR- T curves of all the samples are comparatively fiat, and the value of MR almost does not change with temperature, which shows the temperature stability of magnetoresis- tance, and can be explained by the competition between the low-field magnetoresistance induced by spin-dependent tunneling of surface phase and the intrinsic magnetoresis- tance of grain phase. The magnetoresistance value of the sample with y = 0.8 keeps at （7.92 ±0.36） % in the very wide temperature range of 225-275 K, and this is a goodreference for the preparation of this kind of sample with practical application value in the future.

Connectivity differences between adult male and female patients with attention deficit hyperactivity disorder according to resting-state functional MRI

Attention deficit hyperactivity disorder（ADHD） is a pervasive psychiatric disorder that affects both children and adults. Adult male and female patients with ADHD are differentially affected, but few studies have explored the differences. The purpose of this study was to quantify differences between adult male and female patients with ADHD based on neuroimaging and connectivity analysis. Resting-state functional magnetic resonance imaging scans were obtained and preprocessed in 82 patients. Group-wise differences between male and female patients were quantified using degree centrality for different brain regions. The medial-, middle-, and inferior-frontal gyrus, superior parietal lobule, precuneus, supramarginal gyrus, superior- and middle-temporal gyrus, middle occipital gyrus, and cuneus were identified as regions with significant group-wise differences. The identified regions were correlated with clinical scores reflecting depression and anxiety and significant correlations were found. Adult ADHD patients exhibit different levels of depression and anxiety depending on sex, and our study provides insight into how changes in brain circuitry might differentially impact male and female ADHD patients.