Evidence for Adiabatic Magnetization of cold Dy_N Clusters

Magnetic properties of Dy_N clusters in a molecular beam generated with a liquid helium cooled nozzle are investigated by Stern-Gerlach experiments. The cluster magnetizations \mu_z are measured as a function of magnetic field (B = 0 - 1.6T) and cluster size (16 < N < 56). The most important observation is the saturation of the magnetization \mu_z(B) at large field strengths. The magnetization approaches saturation following the power law |\mu_z-\mu_0| proportional to 1/\sqrt{B}, where \mu_0 denotes the magnetic moment. This gives evidence for adiabatic magnetization.Comment: 4 pages, 3 figure

Tool-Use Training in a Species of Rodent: The Emergence of an Optimal Motor Strategy and Functional Understanding

Tool use is defined as the manipulation of an inanimate object to change the position or form of a separate object. The expansion of cognitive niches and tool-use capabilities probably stimulated each other in hominid evolution. To understand the causes of cognitive expansion in humans, we need to know the behavioral and neural basis of tool use. Although a wide range of animals exhibit tool use in nature, most studies have focused on primates and birds on behavioral or psychological levels and did not directly address questions of which neural modifications contributed to the emergence of tool use. To investigate such questions, an animal model suitable for cellular and molecular manipulations is needed.) to use a rake-like tool with their forelimbs to retrieve otherwise out-of-reach rewards. Eventually, they mastered effective use of the tool, moving it in an elegant trajectory. After the degus were well trained, probe tests that examined whether they showed functional understanding of the tool were performed. Degus did not hesitate to use tools of different size, colors, and shapes, but were reluctant to use the tool with a raised nonfunctional blade. Thus, degus understood the functional and physical properties of the tool after extensive training.Our findings suggest that tool use is not a specific faculty resulting from higher intelligence, but is a specific combination of more general cognitive faculties. Studying the brains and behaviors of trained rodents can provide insights into how higher cognitive functions might be broken down into more general faculties, and also what cellular and molecular mechanisms are involved in the emergence of such cognitive functions

Trauma exposure and factors associated with ICD-11 PTSD and complex PTSD in adolescence: a cross-cultural study in Japan and Lithuania

Aims: Cross-cultural studies of posttraumatic stress disorder (PTSD) and complex PTSD (CPTSD) based on ICD-11 diagnostic criteria are scarce, especially in adolescence. The study aimed to evaluate the trauma exposure, prevalence and factors associated with PTSD and CPTSD in general populations of adolescents in Lithuania and Japan. Methods: The study sample comprised 1746 adolescents from Lithuania (n = 832) and Japan (n = 914), 49.8% female. The mean age of study participants was 15.52 (S.D. = 1.64), ranging from 12 to 18 years. ICD-11 posttraumatic disorders were assessed using the International Trauma Questionnaire – Child and Adolescent version (ITQ-CA). Results: More than half of the adolescents in a total sample (61.5%) reported exposure to at least one traumatic event in their lifetime, 80.0% in Lithuania and 44.6% in Japan, with a higher prevalence of interpersonal trauma in Lithuania and more natural disaster exposure in Japan. The prevalence of PTSD was 5.2% (95% CI 3.8–6.9%) and 2.3% (95% CI 1.4–3.5%), CPTSD 12.3% (95% CI 10.1–14.7%) and 4.1% (95% CI 2.9–5.5%) in Lithuanian and Japanese samples, respectively. Cumulative trauma exposure, female gender, loneliness and financial difficulties in family predicted both PTSD and CPTSD in the total sample. Loneliness discriminated CPTSD v. PTSD in both Lithuanian and Japanese samples. Conclusions: This cross-cultural study is among the first which reported different patterns of trauma exposure in Asian Japanese and Lithuanian adolescents in Europe. Despite differences in trauma exposure and PTSD/CPTSD prevalence, we found similar predictors in both studies, particularly the importance of cumulative trauma exposure for PTSD/CPTSD, and social interpersonal factors for the risk of CPTSD. The study supports the universality of traumatic stress reactions to adverse life experiences in adolescence across cultures and regions and highlights different levels of traumatisation of adolescents in various countries

Tool-use learning by common marmosets (Callithrix jacchus)

One of the most critical and common features of tool use is that the tool essentially functions as a part of the body. This feature is likely rooted in biological features that are shared by tool users. To establish an ideal primate model to explore the neurobiological mechanisms supporting tool-use behaviours, we trained common marmosets, a small New World monkey species that is not usually associated with tool use, to use a rake-shaped tool to retrieve food. Five naive common marmosets were systematically trained to manipulate the tool using a 4-stage, step-by-step protocol. The relative positions of the tool and the food were manipulated, so that the marmosets were required to (1) pull the tool vertically, (2) move the tool horizontally, (3) make an arc to retrieve a food item located behind the tool and (4) retrieve the food item. We found considerable individual differences in tool-use technique; for example, one animal consistently used a unilateral hand movement for all of the steps, whereas the others (n = 4) used both hands to move the tool depending on the location of the food item. After extensive training, all of the marmosets could manipulate the rake-shaped tool, which is reported in this species for the first time. The common marmoset is thus a model primate for such studies. This study sets the stage for future research to examine the biological mechanisms underlying the cognitive ability of tool use at the molecular and genetic levels

Characteristic tunnel-type conductivity and magnetoresistance in a CoO-coated monodispersive Co cluster assembly

We have studied electrical conductivity, sigma, and magnetoresistance in a CoO-coated monodispersive Co cluster assembly fabricated by a plasma-gas-aggregation-type cluster beam deposition technique. The temperature dependence of sigma is described in the form of log sigma vs 1/T for 7<T <80 K. The magnetoresistance ratio (rho(0)=rho(3T))/rho(0) increases sharply with decreasing temperature below 25 K: from 3.5% at 25 K to 20.5% at 4.2 K. This marked increase (by a factor of 6) is much larger than those observed for conventional metal-insulator granular systems. These results are ascribed to the Coulomb blockade effect in the monodispersed cluster assemblies. (C) 1999 American Institute of Physics. [S0003-6951(99)01901-4]

Magnetic properties of monodispersed Co/CoO clusters

Monodispersed Co/CoO cluster assemblies with the mean cluster sizes of 6 and 13 nm have been prepared by a plasma-gas condensation type cluster beam deposition apparatus. We measured the effects of the oxygen gas flow rate during deposition, temperature, and cluster size on the coercivity and hysteresis loop shift induced by field cooling. The large exchange bias field (10.2 kOe) and coercivity (5 kOe) were observed at 5 K for the monodispersed Co/CoO cluster assembly with d=6 nm. The correlations between unidirectional anisotropy and uniaxial anisotropy, training effect and magnetic relaxation can be interpreted by the hypothesis of a spin disorder in the interfacial layer between the antiferromagnetic CoO shell and the ferromagnetic Co core

Preparation and magnetic properties of oxide-coated monodispersive Co cluster assembly

Oxide-coated monodispersive Co duster assemblies with the mean cluster size of 6 and 13 nm have been prepared by a plasma-gas-condensation type cluster beam deposition apparatus. The magnetic properties of the samples prepared without and with introducing oxygen gas into the deposition chamber are compared. The exchange anisotropy induced by interfacial exchange coupling between the ferromagnetic Co core and the antiferromagnetic cobalt oxide shell has been studied by measuring the hysteresis loop shift of the field-cooled samples and the low field thermomagnetic curve

Dynamic Social Adaptation of Motion-Related Neurons in Primate Parietal Cortex

Social brain function, which allows us to adapt our behavior to social context, is poorly understood at the single-cell level due largely to technical limitations. But the questions involved are vital: How do neurons recognize and modulate their activity in response to social context? To probe the mechanisms involved, we developed a novel recording technique, called multi-dimensional recording, and applied it simultaneously in the left parietal cortices of two monkeys while they shared a common social space. When the monkeys sat near each other but did not interact, each monkey's parietal activity showed robust response preference to action by his own right arm and almost no response to action by the other's arm. But the preference was broken if social conflict emerged between the monkeys—specifically, if both were able to reach for the same food item placed on the table between them. Under these circumstances, parietal neurons started to show complex combinatorial responses to motion of self and other. Parietal cortex adapted its response properties in the social context by discarding and recruiting different neural populations. Our results suggest that parietal neurons can recognize social events in the environment linked with current social context and form part of a larger social brain network

Structure and Magnetic Properties of the MnBi Low Temperature Phase

High purity MnBi low temperature phase has been prepared and analyzed using magnetic measurements and neutron diffraction. The low-temperature phase of the MnBi alloy has a coercivity μ0iHc of 2.0 T at 400 K, and exhibits a positive temperature coefficient from 0 to at least 400 K. The neutron data refinement indicated that the Mn atom changes its spin direction from c axis above room temperature to nearly perpendicular to the c axis at 50 K. A canted magnetic structure has been observed below 200 K. The anisotropy field increases with increasing temperature which gives rise to a high coercivity at the higher temperatures. The anisotropic bonded magnets have maximum energy products (BH)max of 7.7 and 4.6 MGOe at room temperature and 400 K, respectively