Dislocation random walk under cyclic deformation.

Dislocation motion under cyclic loading is of great interest from theoretical and practical viewpoints. In this paper, we develop a random walk model for the purpose of evaluating the diffusion coefficient of dislocation under cyclic loading condition. The dislocation behavior was modeled as a series of binomial stochastic processes (one-dimensional random walk), where dislocations are randomly driven by the external load. The probability distribution of dislocation motion and the diffusion coefficient per cycle were analytically derived from the random-walk description as a function of the loading condition and the microscopic material properties. The derived equation was validated by comparing the predicted diffusion coefficient with the molecular dynamics simulation result copper under cyclic deformation. As a result, we confirmed fairly good agreement between the random walk model and the molecular dynamics simulation results.

Inductive Determination of Rate-Reaction Equation Parameters for Dislocation Structure Formation Using Artificial Neural Network.

The reaction-diffusion equation approach, which solves differential equations of the development of density distributions of mobile and immobile dislocations under mutual interactions, is a method widely used to model the dislocation structure formation. A challenge in the approach is the difficulty in the determination of appropriate parameters in the governing equations because deductive (bottom-up) determination for such a phenomenological model is problematic. To circumvent this problem, we propose an inductive approach utilizing the machine-learning method to search a parameter set that produces simulation results consistent with experiments. Using a thin film model, we performed numerical simulations based on the reaction-diffusion equations for various sets of input parameters to obtain dislocation patterns. The resulting patterns are represented by the following two parameters; the number of dislocation walls (p2), and the average width of the walls (p3). Then, we constructed an artificial neural network (ANN) model to map between the input parameters and the output dislocation patterns. The constructed ANN model was found to be able to predict dislocation patterns; i.e., average errors in p2 and p3 for test data having 10% deviation from the training data were within 7% of the average magnitude of p2 and p3. The proposed scheme enables us to find appropriate constitutive laws that lead to reasonable simulation results, once realistic observations of the phenomenon in question are provided. This approach provides a new scheme to bridge models for different length scales in the hierarchical multiscale simulation framework.

Dogs show left facial lateralization upon reunion with their owners.

Domestic dogs demonstrate behavioral laterality in response to emotional stimuli; those responses include tail wagging and head turning. The dog is the species with the closest relationship to humans; dogs can express strong social emotions (e.g., attachment and separation anxiety) to specific persons, such as their owners. In this study, we examined whether dogs demonstrate more facial laterality when reunited with their owners than when they encounter an unfamiliar person in an unfamiliar situation. We also examined whether the observed laterality was specific to positive social stimuli (i.e., the owner) or a general response to nonsocial positive stimuli (i.e., toys). The dogs' facial expressions were recorded by a high-speed video camera during the presentation of emotional stimuli and the acceleration rates of parts of their faces were analyzed. The results showed that the left eyebrow moved more when the owner was present than at baseline. No bias in terms of eyebrow movement was observed when the dogs saw attractive toys. These results suggest that dogs show facial laterality in response to emotional stimuli. This laterality was specific to social stimuli, probably reflecting the dog's attachment to the owner.

Anti-aquaporin-4 antibody-positive optic neuritis treated with double-filtration plasmapheresis.

PURPOSE: The anti-aquaporin-4 (AQP4) antibody was recently reported to be associated with neuromyelitis optica (NMO). Optic nerve involvements in many NMO cases are bilateral and the prognosis is poor. However, it has been suggested that plasma exchange is effective for those patients when steroid pulse therapy is ineffective. Herein, we report successful treatment of a patient with NMO using double-filtration plasmapheresis (DFPP). CASE: A 22-year-old woman consulted a neurologist for neck pain in March 2008. High-intensity lesions were shown in the cervical spinal cord by T2-weighted magnetic resonance imaging. On July 15, the patient was referred to our department for a headache and pain and blurred vision in the left eye. The best-corrected visual acuity was 20/50 and 20/500 in the right and left eyes, respectively, with visual field defects observed in both. After 3 courses of steroid pulse therapy, anti-AQP4 antibodies were positive. In November, the patient again noticed visual acuity loss in the left eye and was treated by additional steroid pulse therapy, which was not effective. Next, she underwent plasma exchange therapy, though it was stopped due to hypotension and dyspnea. The next day, the patient underwent DFPP treatment and visual function gradually recovered. CONCLUSION: It is important to consider NMO when steroid pulse therapy is not effective. We successfully and safely treated NMO in a young adult patient using DFPP.

Severe optic neuropathy caused by dichloromethane inhalation.

PURPOSE: In this paper, we report a case of severe optic neuropathy caused by dichloromethane inhalation. CASE: A 65-year-old man fell unconsciousness while cleaning a dichloromethane tank containing a small amount of dichloromethane (purity greater than 99%) and was transported to the emergency department of our hospital, after which he was treated with hyperbaric oxygen therapy. After 1 month, narrowing of the visual field in both eyes was noted and the patient was referred to our department for additional examinations. Visual acuity was 0.3 in both eyes, which demonstrated normal reactions to light, while the critical flicker frequency (CFF) values were 30 and 25 Hz in the right and left eye, respectively. There were no abnormal findings shown in slit-lamp and fundus examinations, except for a mild cataract. Concentric contractions of the visual field by 10 degrees in both eyes were shown by a Goldmann perimetry examination, while an electroretinogram (ERG) and visual evoked cortical potential (VECP) examination exhibited nearly normal results. We diagnosed the condition as optic neuropathy caused by organic solvent poisoning, based on the decreased visual acuity, decreased CFF values, and visual-field narrowing. Although the patient was treated with vitamin B(12), visual disturbance, optic nerve atrophy, and results of VECP examinations worsened in both eyes, whereas ERG examination results were normal. CONCLUSIONS: Based on our findings, we considered that the central nervous system, including the optic nerve, was more severely damaged than the retina due to the normal findings in the ocular fundus and ERG examinations. Since dichloromethane produces carbon monoxide when catabolized in the liver, carbon monoxide toxicity together with the direct toxic effect of dichloromethane were considered to contribute to optic neuropathy in this case. The outcome for the present patient was poor.

[Vitrectomy for proliferative diabetic retinopathy].

PURPOSE: We reviewed the outcome of vitrectomy for proliferative diabetic retinopathy (DR) and evaluated factors affecting the final visual outcome. METHODS: We performed primary vitreous surgery for proliferative DR in 148 eyes of 118 cases in three years from July 1999 to August 2002. All cases were followed for at least 3 months. We excluded vitreous surgery for diabetic maculopathy. Ages ranged from 24 to 80 (mean 57) years. Average postoperative follow-up period was 15 months. We evaluated the stage of DR by the new Fukuda classification. RESULT: Preoperative classification consisted of BIV (54 eyes, 36%), BV (94 eyes, 64%), and BV + VI (36 eyes). Final visual acuity was improved by 2 lines or more in 102 eyes (69%), remained unchanged in 28 eyes (19%), and decreased by two lines or more in 18 eyes (12%). There was a statistical correlation between preoperative visual acuity and final visual acuity. Earlier stages of DR had better visual outcome. Compared to the surgical outcome in the 1990s, the percentage of worsened eyes decreased. CONCLUSION: Vitrectomy for proliferative DR may be beneficial if performed in the earlier stages of DR or if the patient has better visual acuity before vitrectomy.