582 research outputs found
Efficient storage of urodynamic signals by computer: application of FAN adaptive sampling
Digital storage of urodynamic signals such as detrusor pressure and flowrate at a sufficiently high sampling rate (10 samples per second) to allow subsequent analysis requires considerable computer memory. A procedure for compressing these data by deleting redundant samples (the fan method of adaptive sampling) was tested. The method allows a flexible adaptation to specific hardware and a compromise between storage requirements and accuracy. In this study the number of samples required for adequate reconstruction of the detrusor pressure signal could be varied from 80% to 4% of the original number of samples by varying the average difference between reconstructed and original signal from 0.01 to 2 cm H2O. Fast components of the measurements (for example cough peaks) which were lost if a lower sampling rate or averaging was used to obtain equally low storage requirements were unaffected by this compression technique
Renormalization group maps for Ising models in lattice gas variables
Real space renormalization group maps, e.g., the majority rule
transformation, map Ising type models to Ising type models on a coarser
lattice. We show that each coefficient of the renormalized Hamiltonian in the
lattice gas variables depends on only a finite number of values of the
renormalized Hamiltonian. We introduce a method which computes the values of
the renormalized Hamiltonian with high accuracy and so computes the
coefficients in the lattice gas variables with high accuracy. For the critical
nearest neighbor Ising model on the square lattice with the majority rule
transformation, we compute over 1,000 different coefficients in the lattice gas
variable representation of the renormalized Hamiltonian and study the decay of
these coefficients. We find that they decay exponentially in some sense but
with a slow decay rate. We also show that the coefficients in the spin
variables are sensitive to the truncation method used to compute them.Comment: 22 pages, 9 color postscript figures; minor revisions in version
An Evaluation of Contractility Parameters Determined from Isometric Contractions and Micturition Studies
In a group of 110 patients of mixed pathology 218 micturitions were investigated. Using an on-line computer, two contractility parameters were calculated: the parameter U/l, which is derived from the isometric pressure rise in the detrusor before micturition actually started, and the parameter wmax, which is derived from flow and pressure during micturition. It was found that neither of the parameters conforms to the definition of an ideal contractility parameter. Both parameters are subject to the influence of the urethral resistance or the degree of neurogenic stimulation of the bladder, and both measure to some degree the actual performance of the detrusor during a given micturition instead of its myogenic properties. Nevertheless, by dividing patients into groups according to these two measured values, it was shown that clinically relevant types of detrusor behaviour can be distinguished
Clinical comparison of bladder contractility parameters calculated from isometric contractions and pressure-flow studies
Parameters describing the contractility of the urinary bladder can be calculated from both isometric contractions and pressure-flow studies. The first method has the advantage of making very little demand either on the patient or on the urodynamicist, and the disadvantage of yielding a parameter that is not clearly related to muscle physiology. The second method demands more from both patient and experimenter but yields straightforward parameters. For a group of 86 patients with mixed pathologic findings, a correlation between the two types of parameters was demonstrated, showing that both methods test, at least partly, the same mechanism
Urinary bladder function and its control in healthy females
Recordings in eight healthy female volunteers of bladder (detrusor) pressure and flow rate, obtained during bladder filling and during voiding, both through the urethra and through a catheter, demonstrate that a model of bladder function in which the detrusor muscle is considered as completely passive during filling and fully activated during voiding is inadequate. Assessment of the detrusor contraction strength by a new method (described in APPENDIX A) shows that in ideal normal voidings the contraction strength rises to values of 11-24 W/m2 and is sustained or rises slightly until the bladder is empty. During unstable detrusor contractions, which even in these healthy women are observed during bladder filling and also during inhibited voidings through the urethra, the contraction is weaker. During voidings through a catheter the detrusor contraction is weak, variable, and fades away before the bladder is empty. An elementary feedback analysis demonstrates that the effect of the micturition reflex governing detrusor behavior differs according to whether or not voiding is taking place. The reflex does not lead to a simple on-off mechanism but to a more complex behavior that is consistent with the observations and that appears to be important for the understanding of pathological obstructed micturition. </jats:p
Fish recolonization in temperate Australian rockpools: a quantitative experimental approach
Understanding recolonization processes of intertidal fish
assemblages is integral for predicting the consequences of significant natural or anthropogenic impacts on the intertidal zone. Recolonization of experimentally defaunated intertidal rockpools by fishes at Bass Point, New
South Wales (NSW), Australia, was assessed quantitatively by using one long-term and two short-term studies.
Rockpools of similar size and position at four sites within the intertidal zone were repeatedly defaunated of their
fish fauna after one week, one month, and three months during two shortterm studies in spring and autumn (5 months each), and every six months for the long-term study (12 months). Fish assemblages were highly resilient to experimental perturbations—recolonizing to initial fish assemblage structure within 1−3 months. This recolonization was primarily due to subadults (30−40 mm TL) and adults
(>40 mm TL) moving in from adjacent rockpools and presumably to abundant species competing for access to
vacant habitat. The main recolonizers were those species found in highest numbers in initial samples, such as
Bathygobius cocosensis, Enneapterygius rufopileus, and Girella elevata. Defaunation did not affect the size
composition of fishes, except during autumn and winter when juveniles (<30 mm TL) recruited to rockpools. It appears that Bass Point rockpool fish assemblages are largely controlled by postrecruitment density-dependent
mechanisms that indicate that recolonization may be driven by deterministic mechanisms
Investigation Between the S377G3 GATA-4 Polymorphism and Migraine
Migraine is a common and painful neurological disorder, with genetic and environmental components. Several conditions have been shown to be comorbid with migraine, notably a cardiac malformation affecting the interatrial septum and leading to patent foramen ovale (PFO). Mutations in the development regulatory gene GATA-4, located on human chromosome 8p23.1-p22, have been found to be responsible for some cases of congenital heart defects including PFO. To determine whether the GATA-4 gene is involved in migraine, the present study performed an association analysis of a common GATA-4 variant that results in a change of amino acid (S377G), in a large case/control population (275 unrelated Caucasian migraineurs versus 275 control individuals). The results showed that there was no significant association for this polymorphism between migraine and controls (χ² = 0.84, P = 0.66). Thus it appears that the GATA-4 (S377G) mutation does not play a significant role in common migraine susceptibility
Standardization of terminology of lower urinary tract function: pressure-flow studies of voiding, urethral resistance, and urethral obstruction
The 1988 version of the collated reports on standardisation of terminology, which appeared in Neurourology and Urodynamics, vol. 7, pp. 403–427, contains material relevant to pressure flow studies in many different sections. This report is a revision and expansion of Sections 4.2 and 4.3 and parts of Sections 6.2 and 7 of the 1988 report. It contains a recommendation for a provisional standard method for defining obstruction on the basis of pressure-flow data.
2. Evaluation of Micturition
2.1. Pressure-Flow Studies
At present, the best method of analysing voiding function quantitatively is the pressure-flow study of micturition, with simultaneous recording of abdominal, intravesical and detrusor
pressures and flow rate (Fig. A.1.6.1).
Direct inspection of the raw pressure and flow data before, during and at the end of micturition is essential, because it allows artefacts and untrustworthy data to be recognised and eliminated. More detailed analyses of pressure-flow relationships, described below, are advisable to aid diagnosis and to quantify data for research studies.
The flow pattern in a pressure-flow study should be representative of free flow studies in the same patient. It is important to eliminate artefacts and unrepresentative studies before applying more detailed analyses.
Pressure-flow studies contain information about the behaviour of the urethra and the behaviour of the detrusor.This report has been produced at the request of the International Continence Society. It was
approved at the twenty-fifth annual meeting of the society in Sydney, Australia
GLSM's for partial flag manifolds
In this paper we outline some aspects of nonabelian gauged linear sigma
models. First, we review how partial flag manifolds (generalizing
Grassmannians) are described physically by nonabelian gauged linear sigma
models, paying attention to realizations of tangent bundles and other aspects
pertinent to (0,2) models. Second, we review constructions of Calabi-Yau
complete intersections within such flag manifolds, and properties of the gauged
linear sigma models. We discuss a number of examples of nonabelian GLSM's in
which the Kahler phases are not birational, and in which at least one phase is
realized in some fashion other than as a complete intersection, extending
previous work of Hori-Tong. We also review an example of an abelian GLSM
exhibiting the same phenomenon. We tentatively identify the mathematical
relationship between such non-birational phases, as examples of Kuznetsov's
homological projective duality. Finally, we discuss linear sigma model moduli
spaces in these gauged linear sigma models. We argue that the moduli spaces
being realized physically by these GLSM's are precisely Quot and hyperquot
schemes, as one would expect mathematically.Comment: 57 pp, LaTeX; v3: refs added, material on weighted Grassmannians
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