Desalination by forward osmosis: Identifying performance limiting parameters through module-scale modeling

In this study, we analyze the effects of membrane properties, namely water permeability, solute permeability, and structural parameter, on the overall performance of an FO membrane module to extract water from simulated seawater (0.6 M NaCl). By considering the thermodynamic limit of operation, we demonstrate that the maximum achievable water recovery is practically independent of membrane properties, and higher maximum water recovery is achievable with counter-current compared to co-current mode. Analysis of the module-scale model indicates that reducing the support layer structural parameter offers substantial reductions in the membrane area required to achieve a specified water recovery. For example, a 25% reduction of the structural parameter of a state-of-the-art thin-film composite (TFC) membrane (from 400 to 300 μm) yields a sizable 20% reduction in membrane area. In contrast, quintupling the water permeability coefficient (from 2.0 to 10.0 L m−2 h−1 bar−1) of a modern TFC membrane generates only a modest 10% saving in membrane area. In addition, because of the permeability-selectivity trade-off that governs current polymeric membranes, doubling the water permeability coefficient would cause crippling ~7-fold increases in forward and reverse solute permeation. This quantitative study models the potential performance of a module-scale FO desalination process and firmly highlights the need to prioritize the reduction of support layer mass transport resistances over water permeability increases in membrane development

Functional jerks, tics, and paroxysmal movement disorders

Functional jerks are among the most common functional movement disorders. The diagnosis of functional jerks is mainly based on neurologic examination revealing specific positive clinical signs. Differentiation from other jerky movements, such as tics, organic myoclonus, and primary paroxysmal dyskinesias, can be difficult. In support of a functional jerk are: acute onset in adulthood, precipitation by a physical event, variable, complex, and inconsistent phenomenology, suggestibility, distractibility, entrainment and a Bereitschaftspotential preceding the movement. Although functional jerks and tics share many similarities, characteristics differentiating tics from functional jerks are: urge preceding the tic, childhood onset, rostrocaudal development of the symptoms, a positive family history of tics, attention-deficit hyperactivity disorder or obsessive-compulsive symptoms, and response to dopamine antagonist medication. To differentiate functional jerks from organic myoclonus, localization of the movements can give direction. Further features in support of organic myoclonus include: insidious onset, simple and consistent phenomenology, and response to benzodiazepines or antiepileptic medication. Primary paroxysmal dyskinesias and functional jerks share a paroxysmal nature. Leading in the differentiation between the two are: a positive family history, in combination with video recordings revealing a consistent symptom pattern in primary paroxysmal dyskinesias. In this chapter functional jerks and their differential diagnoses will be discussed in terms of epidemiology, symptom characteristics, disease course, psychopathology, and supportive neurophysiologic tests

Functional jerks, tics, and paroxysmal movement disorders

Functional jerks are among the most common functional movement disorders. The diagnosis of functional jerks is mainly based on neurologic examination revealing specific positive clinical signs. Differentiation from other jerky movements, such as tics, organic myoclonus, and primary paroxysmal dyskinesias, can be difficult. In support of a functional jerk are: acute onset in adulthood, precipitation by a physical event, variable, complex, and inconsistent phenomenology, suggestibility, distractibility, entrainment and a Bereitschaftspotential preceding the movement. Although functional jerks and tics share many similarities, characteristics differentiating tics from functional jerks are: urge preceding the tic, childhood onset, rostrocaudal development of the symptoms, a positive family history of tics, attention-deficit hyperactivity disorder or obsessive-compulsive symptoms, and response to dopamine antagonist medication. To differentiate functional jerks from organic myoclonus, localization of the movements can give direction. Further features in support of organic myoclonus include: insidious onset, simple and consistent phenomenology, and response to benzodiazepines or antiepileptic medication. Primary paroxysmal dyskinesias and functional jerks share a paroxysmal nature. Leading in the differentiation between the two are: a positive family history, in combination with video recordings revealing a consistent symptom pattern in primary paroxysmal dyskinesias. In this chapter functional jerks and their differential diagnoses will be discussed in terms of epidemiology, symptom characteristics, disease course, psychopathology, and supportive neurophysiologic tests

Functional jerks, tics, and paroxysmal movement disorders

Functional jerks are among the most common functional movement disorders. The diagnosis of functional jerks is mainly based on neurologic examination revealing specific positive clinical signs. Differentiation from other jerky movements, such as tics, organic myoclonus, and primary paroxysmal dyskinesias, can be difficult. In support of a functional jerk are: acute onset in adulthood, precipitation by a physical event, variable, complex, and inconsistent phenomenology, suggestibility, distractibility, entrainment and a Bereitschaftspotential preceding the movement. Although functional jerks and tics share many similarities, characteristics differentiating tics from functional jerks are: urge preceding the tic, childhood onset, rostrocaudal development of the symptoms, a positive family history of tics, attention-deficit hyperactivity disorder or obsessive-compulsive symptoms, and response to dopamine antagonist medication. To differentiate functional jerks from organic myoclonus, localization of the movements can give direction. Further features in support of organic myoclonus include: insidious onset, simple and consistent phenomenology, and response to benzodiazepines or antiepileptic medication. Primary paroxysmal dyskinesias and functional jerks share a paroxysmal nature. Leading in the differentiation between the two are: a positive family history, in combination with video recordings revealing a consistent symptom pattern in primary paroxysmal dyskinesias. In this chapter functional jerks and their differential diagnoses will be discussed in terms of epidemiology, symptom characteristics, disease course, psychopathology, and supportive neurophysiologic tests