The functional reanimation of paralyzed limbs.

The functional reanimation of paralyzed limbs has been a longstanding goal of neural prosthetic research, but clinically successful applications have been elusive. Natural voluntary limb movement requires four major elements: actuators (i.e., motor units), sensors (i.e., somatosensory afferents), commands (i.e., cerebral cortical activity), and control (i.e., integration of the previous three elements at various levels of the neuraxis). Prosthetic equivalents of each of these elements are, as yet, primitive and often cumbersome to deploy, but new technologies promise substantial improvements for all. This article focuses on one such technology, bionic neuon (BION) modular microimplants, and its relationship to alternative and complementary technologies. The challenge remains to select and integrate them into systems that can be tailored efficiently to the widely disparate needs of patients with various patterns of weakness and paralysis.     

Policies to reduce energy use and carbon emissions in the UK

The UK differs from may other industrialized nations in that its carbon dioxide (CO₂) emissions from energy use have declined in recent years despite relatively rapid economic growth. In all sectors but transport, substantial reductions have already occurred in the level of carbon emissions per unit of GDP output. At the same time, a number of official and unofficial studies have pointed out that the UK has one of the largest remaining potentials amongst comparable industrialized countries for achieving further CO₂ reductions through the implementation of cost-effective energy efficiency and fuel switching measures. This paper discusses past and present patterns of energy use and carbons emissions in the UK. The analysis then examines historical trends in UK energy policy and presents policy options for further reducing the UK's energy-use and carbon emissions in the future.     

Mass-Balance Model of Pulmonary Oxygen Transport

A dynamic lumped-parameter model for pulmonary gas transport has been developed to characterize the lung and predict the effect of various parameter changes. The gas side of the lung is modeled as a series and parallel arrangement of five perfectly mixed, variable-volume compartments that correspond roughly to airway and alveolar regions. The blood side of the lung is modeled as a series of perfectly mixed, constant-volume compartments that represent the pulmonary capillary bed. From nonsteady mass balances, equations are derived which yield the time course of concentration for each compartment. Model simulations indicate that the oxygen-hemoglobin reaction does not reach equilibrium in the pulmonary capillaries, an assumption commonly made in analyses of pulmonary oxygen transport. Simulations also show the extent to which breathing amplitude and rate can affect the oxygen level in the blood leaving the lung. A comparison of simulations for a normal state and chronic obstructive lung disease (COLD) with identical input conditions demonstrates that the oxygen level in the blood leaving the lung is much lower in COLD. Also, the simulations are compared with experimental findings.     

Determination of diffusion coefficients of water in cellulose acetate membranes

The determination of the diffusion coefficient for water in various porosity cellulose acetate membranes by a gravimetric method, using a humidified carrier gas, is described. It was found to be impossible to obtain meaningful results for very porous membranes, although dense membranes gave limiting values of diffusion coefficient at high carrier gas velocities. This phenomenon is explained in terms of the dissipation of the heat of sorption by the forced convection provided by the carrier gas. The variation of diffusion coefficient with concentration of water in dense cellulose acetate is explained in terms of clustering of water molecules in the polymer at high concentration.     

Free and esterified sterols of cotton buds and anthers

Capillary gas liquid chromatography analyses were conducted on free and esterified sterol fractions of cotton (Gossypium hirsutum cv. Stoneville 213) floral buds and anthers. The free sterols of both cotton buds and anthers consist mainly of the common plant sterols sitosterol, stigmasterol and 24ζ-methylcholest-5-en-3β-ol. The composition of esterified sterols of cotton buds and anthers were similar, and consisted of pollinastanol, 31-norcycloartanol, cycloartenol, 31-norcycloartenol, 24-dehydropolinastanol and sitosterol. Desmosterol was also present in both the free and esterified sterols of anthers. The identities of the sterols were confirmed by gas chromatography-mass spectrometry analyses. Esterified sterols accounted for 46.7 and 88.7% of total sterols of cotton bud and anthers, respectively. The ratio of esterified sterol to free sterol per gram of tissue is about 8∶1 in anthers. The Δ⁵-sterols of the esterified sterols of cotton buds and anthers account for only 17 and 9.2% of the total sterols, respectively.     

Control policies for an industrial acetylene hydrogenation reactor

This paper addresses the problem of finding optimal operational policies for an acetylene reactor for day to day operation. A lumped parameter model based on four main reactions is developed and used to examine the effects of the reactor manipulated variables on key reaction parameters. An optimal and a sub-optimal operational policy which minimize the ethylene loss over time are formulated and the solution techniques are presented. The results indicate that the reactor model is in good agreement with industrial plant data. The performance of the optimal control policy is very similar to the performance of the sub-optimal control policy. However, the sub-optimal formulation, while retaining the dominant features of the optimal response, reduces the computational requirements. Finally, some issues concerning the real-time implementation of an advanced acetylene reactor control scheme are presented. These include the estimation of the optimum regeneration cycle, a recursive model update algorithm, the process optimizer and their overall coordination. A preliminary analysis of the benefits associated with the advanced control scheme suggests a considerable reduction in the yearly ethylene loss.     

Hand and foot purpura ("glove and sock" syndrome) caused by parvovirus B19 infection

After a period of general nonspecific symptoms (weakness; nocturnal sweating) for a few days a 29-year-old man suddenly developed a purpura-like rash on both hands and feet ("glove and sock") with mild itching and oedema. A blood count demonstrated leukopenia (2100/microliters) with neutropenia (1100/microliters), thrombocytopenia (81,000/microliters) and reticulocytopenia (1/1000), while haemoglobin content was normal. The bone-marrow showed almost complete reduction of erythropoiesis with the presence of giant proerythroblasts. Granulopoiesis and megakaryopoiesis were unremarkable. Positive tests for IgM and IgG antibodies against parvovirus B19 established the diagnosis of infection with this organism. The rash, blood picture and bone-marrow changes all regressed spontaneously, without any treatment, within a week. The petechial or purpuric "glove and sock" syndrome may be a special form of parvovirus B19 infection.