Size-dependent exchange bias in single phase Mn_3O_4 nanoparticles

Glassy magnetic behavior and exchange bias phenomena are observed in single phase Mn3O4 nanoparticles.Dynamics scaling analysis of the ac susceptibility and the Henkel plot indicate that the observed glassy behavior at low temperature can be understood by taking into account the intrinsic behavior of the individual particles consisting of a ferrimagnetic（FIM） core and a spin-glass surface layer.Field-cooled magnetization hysteresis loops display both horizontal and vertical shifts.Dependence of the exchange bias field（HE） on the cooling field shows an almost undamped feature up to 70 kOe,indicating the stable exchange bias state in Mn3O4.HE increases as the particle size decreases due to the higher surface/volume ratio.The occurrence of the exchange bias can be attributed to the pinning effect of the frozen spin-glass surface layer upon the FIM core.

Electro-acupuncture Treatment for Internet Addiction: Evidence of Normalization of Impulse Control Disorder in Adolescents

Objective： To observe the impacts of electro-acupuncture（EA） and psychological intervention（PI） on impulsive behavior among internet addiction（IA） adolescents. Methods： Thirty-two IA adolescents were allocated to either EA（16 cases） or PI（16 cases） group by a randomized digital table. Subjects in the EA group received EA treatment and subjects in the PI group received cognition and behavior therapy. All adolescents underwent 45-d intervention. Sixteen healthy volunteers were recruited into a control group. Barratt Impulsiveness Scale（BIS-11） scores, Young＇s Internet Addiction Test（IAT） as well as the ratio of brain N-acetyl aspartate（NAA） to creatine（NAA/Cr） and choline（Cho） to creatine（Cho/Cr） were recorded by magnetic resonance spectroscopy before and after intervention respectively. Results： The IAT scores and BIS-11 total scores in both EA and PI group were remarkably decreased after treatment（P〈0.05）, while EA group showed more significant decrease in certain BIS-11 sub-factors（P〈0.05）. Both NAA/Cr and Cho/Cr were significantly improved in EA group after treatment（P〈0.05）; however, there were no significant changes of NAA/Cr or Cho/Cr in PI group after treatment（P〉0.05）. Conclusions： Both EA and PI had significantly positive effect on IA adolescents, especially in the aspects of psychological experiences and behavioral expressions, EA might have an advantage over PI in terms of impulsivity control and brain neuron protection. The mechanism underlying this advantage might be related to the increased NAA and Cho levels in prefrontal and anterior cingulate cortices.