Simulating Discrete and Rhythmic Multi-joint Human Arm Movements by Optimization of Nonlinear Performance Indices

An optimization approach applied to mechanical linkage models is used to simulate human arm movements. Predicted arm trajectories are the result of minimizing a nonlinear performance index that depends on kinematic or dynamic variables of the movement. A robust optimization algorithm is presented that computes trajectories which satisfy the necessary conditions with high accuracy. It is especially adapted to the analysis of discrete and rhythmic movements. The optimization problem is solved by parameterizing each generalized coordinate (e.g., joint angular displacement) in terms of Jacobi polynomials and Fourier series, depending on whether discrete or rhythmic movements are considered, combined with a multiple shooting algorithm. The parameterization of coordinates has two advantages. First, it provides an initial guess for the multiple shooting algorithm which solves the optimization problem with high accuracy. Second, it leads to a low dimensional representation of discrete and rhythmic movements in terms of expansion coefficients. The selection of a suitable feature space is an important prerequisite for comparison, recognition and classification of movements. In addition, the separate computational analysis of discrete and rhythmic movements is motivated by their distinct neurophysiological realizations in the cortex. By investigating different performance indices subject to different boundary conditions, the approach can be used to examine possible strategies that humans adopt in selecting specific arm motions for the performance of different tasks in a plane and in three-dimensional space

A Virally Encoded Chaperone Specialized for Folding of the Major Capsid Protein of African Swine Fever Virus

It is generally believed that cellular chaperones facilitate the folding of virus capsid proteins, or that capsid proteins fold spontaneously. Here we show that p73, the major capsid protein of African swine fever virus (ASFV) failed to fold and aggregated when expressed alone in cells. This demonstrated that cellular chaperones were unable to aid the folding of p73 and suggested that ASFV may encode a chaperone. An 80-kDa protein encoded by ASFV, termed the capsid-associated protein (CAP) 80, bound to the newly synthesized capsid protein in infected cells. The 80-kDa protein was released following conformational maturation of p73 and dissociated before capsid assembly. Coexpression of the 80-kDa protein with p73 prevented aggregation and allowed the capsid protein to fold with kinetics identical to those seen in infected cells. CAP80 is, therefore, a virally encoded chaperone that facilitates capsid protein folding by masking domains exposed by the newly synthesized capsid protein, which are susceptible to aggregation, but cannot be accommodated by host chaperones. It is likely that these domains are ultimately buried when newly synthesized capsid proteins are added to the growing capsid shell

Reticular drusen associated with geographic atrophy in age-related macular degeneration

PURPOSE: To characterize reticular drusen (RDR) in patients with geographic atrophy (GA) secondary to age-related macular degeneration (AMD) in a prospective, multicenter, natural history study. METHODS: Confocal scanning laser ophthalmoscopy (cSLO) three-field fundus autofluorescence (FAF; exc., 488; em., 500-700 nm), near-infrared reflectance (IR; 820 nm), and blue reflectance (BR; 488 nm) images as well as red-free (RF) and color fundus (CF) camera photographs were recorded in 458 GA patients. The digital images were evaluated by two independent readers with subsequent senior reader arbitration for prevalence and topographic distribution of RDR using a modified Early Treatment Diabetic Retinopathy Study grid. RESULTS: RDR were detected with at least one cSLO modality in 286 of 458 (62%) patients in either eye (bilateral 207 [45%]) and were visible in fundus camera photographs in 66 of 371 (18%) patients (bilateral 48 [13%]). Prevalence of RDR by cSLO imaging was associated with increasing age (P = 0.007) and female sex (P = 0.007), but not with GA total lesion area (P = 0.38). Cohen kappa statistics showed good interobserver agreement for FAF (0.81) and IR (0.82) imaging modes, and moderate agreement was found for BR (0.48), RF (0.48), and CF (0.40). On three-field FAF images RDR were present most frequently superior to the fovea (99%). CONCLUSIONS: RDR represent a common phenotypic hallmark in GA eyes. RDR are readily identified using cSLO imaging technology. These observations may explain the high prevalence determined herein, in contrast to previous reports based on fundus photographs. Incorporation of these novel imaging modalities in future natural history studies may facilitate efforts aimed at defining the role and predictive value of RDR in the progression of AMD. (ClinicalTrials.gov number, NCT00599846.