4,873 research outputs found
A projective two-weight code related to the simple group of Conway
No full textA binary projective two-weight code related to the sporadic simple group of Conway is constructed as a faithful and absolutely irreducible submodule of the permutation module induced by the primitive action of on the cosets of . The dual code of this code is a uniformly packed code. The geometric significance of the codewords of the code can be traced to the vectors in the Leech lattice, thus revealing that the stabilizer of any non-zero weight codeword in the code is a maximal subgroup of . Similarly, the stabilizer of the codewords of minimum weight in the dual code is a maximal subgroup of . As by-product, a new strongly regular graph on 16777216 vertices and valency 98280 is constructed using the codewords of the code.11 page
The 2D/3D dynamics of wall-bounded low-Rm magnetohydrodynamic (MHD) turbulence
No full textWith this experimental study, we give evidence that the dynamics of low-Rm MHD turbulence depends on the diffusion length l_z, which corresponds to the distance over which the Lorentz force is able to diffuse momentum before it is balanced by inertia
Inspiratory muscle dysfunction after prolonged periods of mechanical ventilation; two case studies
No full textBackground and purposeMechanical ventilation necessitates periods of bed rest and relative immobility that, combined with other factors, lead to skeletal muscle atrophy. As the respiratory muscles are skeletal muscles, they are theoretically prone to disuse atrophy. Sustained maximal inspiratory pressure (SMIP) measures are a new form of assessment of inspiratory muscle function that may reflect inspiratory work capacity. The aim of this study was to establish whether inspiratory or peripheral muscle function is abnormal after a period of prolonged mechanical ventilation, and whether any changes in function occur during a prolonged weaning programme.MethodsTwo adult patients who had required mechanical ventilation on a general intensive care unit for more than 14 days consented to take part in the study. Baseline SMIP, standard maximal inspiratory pressure (MIP) and handgrip strength measures were performed when weaning began. Repeated SMIP, MIP and grip measures were taken twice a week during the weaning programme until each patient was able to breathe without support for 48 hours.FindingsBaseline SMIP and handgrip measures were found to be abnormally low in both subjects. SMIP measures increased over a series of measurement sessions, in parallel with increases in measures of handgrip and diminishing levels of respiratory support. Standard MIP measures started from a level that would generally indicate ability to breathe without support and showed little change over time.ConclusionsIf SMIP is accepted as a reliable measure of inspiratory muscle function, then these findings support the hypothesis that periods of mechanical ventilation have a detrimental effect on respiratory muscle function. These findings also suggest that SMIP is responsive to changing inspiratory muscle function, but as they are from uncontrolled studies, no firm conclusions can be drawn
In silico modeling of asthma
No full textThe incidence of asthma is increasing throughout the world, especially among children, to the extent that it has become a medical issue of serious global concern. Appropriately, numerous pharmacologic drugs and clinical protocols for the treatment and prophylaxis of the disease have been reported. From a scientific perspective, a review of the literature suggests that the targeted delivery of an aerosol would, in a real sense, enhance the efficacy of an inhaled medicine. Therefore, in accordance with published data we have developed a mathematical description of disease-induced effects of disease on airway morphology. A morphological algorithm defining the heterogeneity of asthma has been integrated with a computer code that formulates the behavior and fate of inhaled drugs. In this work, predicted drug particle deposition patterns have been compared with SPECT images from experiments with healthy human subjects (controls) and asthmatic patients. The asthma drug delivery model simulations agree with observations from human testing. The results indicate that in silico modeling provides a technical foundation for addressing effects of disease on the administration of aerosolized drugs, and suggest that modeling should be used in a complementary manner with future inhalation therapy protocols
Digluconate and Isopropyl Alcohol Biocide Formulation
No full textEffective surface disinfection is a fundamental infection control strategy within healthcare. This study assessed the antimicrobial efficacy of novel biocide formulations comprising 5% and 2% eucalyptus oil (EO) combined with 2% chlorhexidine digluconate (CHG) and 70% isopropyl alcohol (IPA) contained within a wipe. The efficacy of this novel antimicrobial formulation to remove and eliminate methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli and Candida albicans from steel surfaces was investigated. Adpression studies of pre-contaminated wipes were also utilised to assess their potential to induce cross-contamination between hard surfaces. Furthermore, the bactericidal nature of the EO-formulation was established in addition to time-kill. The EO-containing formulations demonstrated bactericidal antimicrobial efficacy against all microorganisms and did not induce surface cross-contamination. There was no significant difference (p < 0.05) between the 5% and 2% EO formulations in their ability to remove microorganisms from steel surfaces, however both significantly (p < 0.05) removed more than the control formulations. Microbial biofilms were eliminated within 10 min (p < 0.05) when exposed to the EO formulations. Our novel EO-formulation demonstrated rapid antimicrobial efficacy for potential disinfection and elimination of microbial biofilms from hard surfaces and may therefore be a useful adjunct to current infection control strategies currently employed within healthcare facilities
Pulmonary clearance rate of two chemically different forms of inhaled pertechnetate
No full textAttempts to image the pulmonary deposition site of radiolabeled aerosols delivered by dry powder inhalers (DPIs) and pressurized metered-dose inhalers (pMDIs) using single photon emission computed tomography (SPECT) have been limited by the rapid pulmonary clearance of radiolabel. To determine whether aqueous solubility of the radiolabel is a significant factor, the pulmonary clearance rates of two chemically different forms of Tc-99m were calculated. A dry powder formulation of terbutaline sulphate was radiolabeled for inhalation by Turbuhaler (AstraZeneca) using the water-soluble salt sodium pertechnetate and the water-insoluble salt tetraphenylarsonium pertechnetate. A pilot study was conducted during which two control subjects each inhaled the two radiolabeled aerosols on separate days. Intrasubject clearance rates for the two species were very similar. It was therefore concluded that water insolubility of the pertechnetate salt alone was not enough to extend the lung residency time of the radiolabel
Posture changes the deposition pattern of an inhaled aerosol
No full textRationale: A complete understanding of the mechanisms underlying the regional deposition of an inhaled aerosol is not as yet available. The role of particle size and respiratory manoeuvre are appreciated but the impact that posture may have is not. This study aimed to evaluate the effect of changes in posture on regional deposition of an inhaled aerosol.Methods: Randomised, cross-over trial with three limbs. Ten, healthy male (22-38 yr) subjects were enrolled. Each individual inhaled a nebulised suspension of radiolabelled human serum albumin (HSA) on three separate occasions in three different positions (sitting, lying and right side lying). The aerosol was delivered in a controlled manner using a closed nebuliser circuit incorporating a pneumotachograph. Gamma scintigraphy was used to assess the regional deposition of the radio-aerosol.Results: A comparison of the activity between the right and left lung demonstrated marked changes in deposition. With the subject in right side lying there was a marked increase in the deposition in the dependant (i.e. right) lung. This was significant (p=0.001).Conclusion: Changes in body posture result in changes in the deposition pattern of an inhaled aerosol. This may have clinical implications
Triangular Constellations in Flows
No full textParticles advected on the surface of a fluid can exhibit fractal clustering. The local structure of a fractal set is described by its dimension , which is the exponent of a power-law relating the mass in a ball to its radius : . It is desirable to characterise the {\em shapes} of constellations of points sampling a fractal measure, as well as their masses. The simplest example is the distribution of shapes of triangles formed by triplets of points, which we investigate for fractals generated by chaotic dynamical systems. The most significant parameter describing the triangle shape is the ratio of its area to the radius of gyration squared. We show that the probability density of has a phase transition: is independent of and approximately uniform below a critical flow compressibility , which we estimate. For the distribution appears to be described by two power laws: when , and when
Evaluation of the accuracy and precision of lung aerosol deposition measurements from single-photon emission computed tomography using simulation
No full textSingle-photon emission computed tomography (SPECT) imaging is being increasingly used to assess inhaled aerosol deposition. This study uses simulation to evaluate the errors involved in such measurements and to compare them with those from conventional planar imaging. SPECT images of known theoretical distributions of radioaerosol in the lung have been simulated using lung models derived from magnetic resonance studies in human subjects. Total lung activity was evaluated from the simulated images. A spherical transform of the lung distributions was performed, and the absolute penetration index (PI) and a relative value expressed as a fraction of that in a simulated ventilation image were calculated. All parameters were compared with the true value used in the simulation, and the errors were assessed. An iterative method was used to correct for the partial volume effect, and its effectiveness in improving errors was evaluated. The errors were compared with those of planar imaging. The precision of measurements was significantly better for SPECT than planar imaging (2.8 vs 6.3% for total lung activity, 6 vs 20% for PI, and 3 vs 6% for relative PI). The method of correcting for the influence of the partial volume effect significantly improved the accuracy of PI evaluation without affecting precision. SPECT is capable of accurate and precise measurements of aerosol distribution in the lung, which are improved compared with those measured by conventional planar imaging. A technique for correcting the SPECT data for the influence of the partial volume effect has been described. Simulation is demonstrated as a valuable method of technique evaluation and comparison
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