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PubMed2006

SPASM: a 3D-ASM for segmentation of sparse and arbitrarily oriented cardiac MRI data.

A new technique (SPASM) based on a 3D-ASM is presented for automatic segmentation of cardiac MRI image data sets consisting of multiple planes with arbitrary orientations, and with large undersampled regions. Model landmark positions are updated in a two-stage iterative process. First, landmark positions close to intersections with images are updated. Second, the update information is propagated to the regions without image information, such that new locations for the whole set of the model landmarks are obtained. Feature point detection is performed by a fuzzy inference system, based on fuzzy C-means clustering. Model parameters were optimized on a computer cluster and the computational load distributed by grid computing. SPASM was applied to image data sets with an increasing sparsity (from 2 to 11 slices) comprising images with different orientations and stemming from different MRI acquisition protocols. Segmentation outcomes and calculated volumes were compared to manual segmentation on a dense short-axis data configuration in a 3D manner. For all data configurations, (sub-)pixel accuracy was achieved. Performance differences between data configurations were significantly different (p<0.05) for SA data sets with less than 6 slices, but not clinically relevant (volume differences<4 ml). Comparison to results from other 3D model-based methods showed that SPASM performs comparable to or better than these other methods, but SPASM uses considerably less image data. Sensitivity to initial model placement proved to be limited within a range of position perturbations of approximately 20 mm in all directions.

Algorithms↗
PubMed1997

Poststroke depression: an examination of the literature.

OBJECTIVE: To examine literature on poststroke depression (PSD). DATA SOURCES: More than 200 articles related to stroke and depression were selected from a computer-based search spanning 1985 to 1995. STUDY SELECTION: All relevant articles on PSD. Articles in foreign languages, case studies, anecdotal reports, book chapters, and reviews were excluded. DATA EXTRACTION: Summary findings were independently reviewed by the authors. DATA SYNTHESIS: PSD remains a frequent sequela of stroke; its prevalence remains uncertain because of continued methodologic problems in defining subject groupings and in utilizing psychiatrically normed assessment tools with neurologically impaired individuals, and because of the poor specificity/sensitivity of neuroendocrine markers in determining a diagnosis. The etiology of PSD appears to be complex and not fully understood. Although there has been much research on PSD, this review highlights the sparsity of available literature on its treatment. CONCLUSION: The review points out the further need for more carefully designed studies of PSD that examine both assessment and treatment.

Antidepressive Agents↗
PubMed1998

Color vision in two observers with highly biased LWS/MWS cone ratios.

Two sisters, heterozygous carriers for congenital X-linked protanopia, were diagnosed as normal trichromats by the Rayleigh match on the anomaloscope. The heterozygous state was established by molecular analysis of their visual pigment genes. The normal color match establishes that the spectral sensitivities of their long-wavelength-sensitive (LWS) and middle-wavelength-sensitive (MWS) cone visual photopigments are within normal variability. Their FM 100-hue test error scores were low, demonstrating superior chromatic discrimination. Heterochromatic flicker photometric (HEP) spectral sensitivities were like those of protanopes. The estimated LWS/MWS cone ratios from the HFP data were 0.09/1 and 0.03/1, compared with ratios in the range of 0.6/1 to 10/1 for typical normal trichromats. Measurements of chromatic grating acuity on chromatically selective backgrounds were performed to study the cone mosaic. The data were consistent with a sparsity of LWS cones. Both protan carriers showed normal spectral sensitivities for all three cone types under cone isolating chromatic adaptation and normal three-peaked curves for increment thresholds on a white pedestal. Hue estimation, run on one carrier was normal. The equilibrium yellow locus was measured in the other carrier and was in the range of normal trichromats. The data indicate that normal color vision can occur even when the LWS/MWS cone ratio is quite abnormal.

Adaptation, Ocular↗
PubMed1984

Inner ear anomalies in Waardenburg's syndrome associated with Hirschsprung's disease.

Congenital inner ear anomalies are reported in temporal bones of a 22-month-old boy with Waardenburg's syndrome and Hirschsprung's disease. Although no changes in the central auditory pathway were identified, peripheral lesions of the cochlear and vestibular membranous labyrinth were observed. Bilateral atrophy of the organ of Corti and stria, and a sparsity of spiral ganglion cells were observed in the cochlea. Degeneration of the vestibular end organs, including a loss of Scarpa's ganglion cells, was also seen. This is the first report of temporal bone histopathology associated with Waardenburg's syndrome and Hirschsprung's disease. The pathoembryology of these inner ear anomalies associated with aganglionosis of the colon supports the hypothesis that Waardenburg's syndrome and Hirschsprung's disease are hereditary defects of neural crest cells.

Abnormalities, Multiple↗
PubMed1986

Keratoma hereditaria mutilans: report of a case with successful surgical treatment.

A case of constriction band at the fingers arising from keratosis palmoplantaris is reported. Excision of the band and closure of wound by Z-plasties resulted in complete relief of clinical symptoms and vascular insufficiencies. Histologic examination revealed the variability of this skin lesion even in the same patient. The sparsity of keratohyaline matrix in the horn cells in the skin may contribute to the constriction ring formation.

Biopsy↗
PubMed1998

The application of volume deformation to three-dimensional facial reconstruction: a comparison with previous techniques.

Facial reconstruction has been widely criticised for its subjective nature and is thus often viewed as a last resort. Recent computer-aided reconstructions, which claim to be objective, may be subject to similar errors. To date, both manual reconstructions and computer-aided techniques have been limited to using the same tissue depth data reference tables. We propose that it is not solely the accuracy of the soft tissue depth data, but the sparsity of landmarks, which contributes to a lack of understanding of how soft tissue changes between the landmarks. The authors feel that a new approach to facial reconstruction using a computer graphics technique known as volume deformation addresses some of the problems encountered in the past. A review of previous methods is provided with discussion of the strengths and limitations of these techniques. In addition, areas are highlighted where the new deformation-based approach may offer possible solutions.

Computer Graphics↗
PubMed2002

Projective ART for clustering data sets in high dimensional spaces.

A new neural network architecture (PART) and the resulting algorithm are proposed to find projected clusters for data sets in high dimensional spaces. The architecture is based on the well known ART developed by Carpenter and Grossberg, and a major modification (selective output signaling) is provided in order to deal with the inherent sparsity in the full space of the data points from many data-mining applications. This selective output signaling mechanism allows the signal generated in a node in the input layer to be transmitted to a node in the clustering layer only when the signal is similar to the top-down weight between the two nodes and, hence, PART focuses on dimensions where information can be found. Illustrative examples are provided, simulations on high dimensional synthetic data and comparisons with Fuzzy ART module and PROCLUS are also reported.

Algorithms↗
PubMedDate not supplied

On structure-exploiting trust-region regularized nonlinear least squares algorithms for neural-network learning.

This paper briefly introduces our numerical linear algebra approaches for solving structured nonlinear least squares problems arising from 'multiple-output' neural-network (NN) models. Our algorithms feature trust-region regularization, and exploit sparsity of either the 'block-angular' residual Jacobian matrix or the 'block-arrow' Gauss-Newton Hessian (or Fisher information matrix in statistical sense) depending on problem scale so as to render a large class of NN-learning algorithms 'efficient' in both memory and operation costs. Using a relatively large real-world nonlinear regression application, we shall explain algorithmic strengths and weaknesses, analyzing simulation results obtained by both direct and iterative trust-region algorithms with two distinct NN models: 'multilayer perceptrons' (MLP) and 'complementary mixtures of MLP-experts' (or neuro-fuzzy modular networks).

Algorithms↗
PubMed1998

Continuing education programme - Victorian Institute of Forensic Medicine.

With the increasing requirement of the courts for forensic experts to engage in ongoing education, a continuing education programme (CEP) was developed in the field of clinical forensic medicine at the Victorian Institute of Forensic Medicine in 1996. This programme has been described and was initially established to provide a means of education for the contracted forensic medical officers who provide forensic services to the police via the Institute throughout the State of Victoria. Owing to the sparsity of the population and the considerable distances between forensic practitioners, the CEP was designed to cater for individuals who are working alone: in effect, a distance education programme. Forensic pathologists expressed interest in the programme and it was subsequently modified to include forensic pathology cases. Currently, the programme caters for both clinicians and pathologists, and takes the form of four to five cases with related questions which are circulated several times per year. The cases include a mixture of both challenging and ordinary procedural types that may present to practitioners working in either clinical forensic medicine or forensic pathology, or both. The areas covered include: * injury interpretation * procedural matters in relation to adult and child sexual and physical assault * pharmacology/toxicology interpretation of findings * medico-legal issues (e.g. confidentiality, consent, etc.) * issues relating to alcohol and drugs * traffic medicine * clinical and legal aspects of sudden natural death * suspicious deaths * suicide * interpretation of findings at autopsy * fitness for interview * fitness to plead * psychiatric issues * general clinical medical issues. The presentation of each case includes relevant and appropriate details/findings and may include photographs. A series of questions follow which are answered in either short answer or multiple-choice format. The answers are returned and are correlated by a review panel of forensic physicians and pathologists, and a commentary with the response outcomes is distributed to all those involved. This also includes pertinent references. The cases presented here and in subsequent issues are selected from this programme.

Journal Article↗
PubMed2005

Harmonic theory of thermal two-photon absorption in benzene.

A correlation function formalism is applied to compute the two-photon absorption spectrum of benzene. Using harmonic Hamiltonians for the ground and excited electronic states, we find that the theory agrees qualitatively with the experimentally observed sparsity of the thermal two-photon absorption spectrum as compared with the single-photon absorption spectrum. An expression for the average vibrational energy in the excited state is derived. We find that cooling of the nascent vibrational energy in the electronically excited state is not as extensive in the two-photon absorption process as compared to the single-photon case.

Journal Article↗
PubMed2000

Behavioral treatment of PTSD in a perpetrator of manslaughter: a single case study.

Studies of posttraumatic stress disorder (PTSD) have predominantly focused on victims of trauma. Some studies have examined the after-effects of a person's own violent actions in combat or police situations. However, there is a sparsity of literature examining the development of PTSD in convicted perpetrators of violent crime, and there is no literature concerning the treatment of PTSD in such perpetrators. This single-case study presents the outcome of behavioral treatment in one case in which the patient had PTSD consequential to being a perpetrator of manslaughter. The theoretical implications of this case are briefly discussed.

Female↗
PubMed1999

Adhesion of oral Candida species to human buccal epithelial cells following brief exposure to nystatin.

Opportunistic oral infections caused by Candida albicans and non-albicans Candida species are particularly common in compromised patients. Nystatin, which belongs to the polyene group of antimycotics, is frequently used as a topical agent in the treatment of oro-pharyngeal candidosis. It is recognized that due to the delivery mode of nystatin (i.e. topical, intermittent), as well as the cleansing effect of saliva within the oral environment, the yeasts undergo a relatively brief exposure to this drug during treatment. Nevertheless, there is a sparsity of data on the effect of such brief exposure to nystatin on the pathogenic attributes of Candida such as their adherence to host surfaces. The adhesion of microbes to host mucosal surfaces is a major determinant of successful colonization and infection. Thus the main aim of our investigation was to compare the in vitro adhesion of 30 oral isolates of Candida belonging to six different species (comprising Candida albicans, Candida tropicalis, Candida glabrata, Candida guilliermondii, Candida krusei and Candida parapsilosis) to human buccal epithelial cells, following their brief exposure (1 h) to minimum inhibitory concentration of nystatin, and subsequent removal of the drug. The adhesion of these isolates to buccal epithelial cells was assessed by a previously described adhesion assay. Compared with the controls, there was a significant reduction in buccal epithelial cell adhesion of all six Candida species after drug exposure (54%-68%). However the adhesion of C. albicans isolates was the least affected by nystatin exposure, which was significantly different from that of the non-albicans species. These findings imply that sub-therapeutic levels of nystatin, which are likely to persist in the oral cavity during dosing intervals, may also be beneficial, as they inhibit candidal colonization. The significant difference in nystatin-induced suppression of adhesion between C. albicans and the non-albicans species investigated is a further testimonial for the pre-eminent virulence of the former species.

Antifungal Agents↗
PubMed2002

Imperfect optics may be the eye's defence against chromatic blur.

The optics of the eye cause different wavelengths of light to be differentially focused at the retina. This phenomenon is due to longitudinal chromatic aberration, a wavelength-dependent change in refractive power. Retinal image quality may consequently vary for the different classes of cone photoreceptors, cells tuned to absorb bands of different wavelengths. For instance, it has been assumed that when the eye is focused for mid-spectral wavelengths near the peak sensitivities of long- (L) and middle- (M) wavelength-sensitive cones, short-wavelength (bluish) light is so blurred that it cannot contribute to and may even impair spatial vision. These optical effects have been proposed to explain the function of the macular pigment, which selectively absorbs short-wavelength light, and the sparsity of short-wavelength-sensitive (S) cones. However, such explanations have ignored the effect of monochromatic wave aberrations present in real eyes. Here we show that, when these effects are taken into account, short wavelengths are not as blurred as previously thought, that the potential image quality for S cones is comparable to that for L and M cones, and that macular pigment has no significant function in improving the retinal image.

Adult↗
PubMed1977

Ultrastructural and metabolic determinants of resistance to azo-dye susceptibility to nitrosamine carcinogenesis of the guinea-pig.

During diethylnitrosamine (DEN) administration, a distinctive difference was observed between rats and guinea-pigs in the sequence of ultrastructural changes in the hepatic endoplasmic reticulum (ER). In DEN-induced hepatic tumour cells in the guinea-pig there was extensive proliferation of the rough ER, while the smooth ER was quite sparse; in the premalignant liver the opposite was noted. This is in contrast to the rat, in which administration of either DEN or 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) brings about, in both premalignant and malignant hepatic tissue, proliferation of the smooth ER and sparsity of the rough ER. Yet, as in the rat, the number of ribosomes on the outer surface of the guinea-pig liver rough ER is greatly reduced and this is paralleled by a 49% decrease of the RNA/protein ratio as early as 4 weeks of nitrosamine administration. The decrease of RNA/protein ratio and ultrastructurally observed loss of ribosomes from the ER, following nitrosamine administration, correlate with a decrease of photometric response of microsomal suspensions to the sulphydryl probe, p-chloromercuribenzoate. While azo-dye-reductase activity is higher in untreated rats than in untreated guinea-pigs, feeding 3'-Me-DAB for 6 weeks brings about a 76% decrease in the rat, but no significant decrease in the guinea-pig, which is refractory to azo-dye carcinogenesis. Thus, the ability of the liver to inactivate the dye is greatly decreased in the rat, but not in the guinea-pig, as administration progresses toward the threshold dose for tumorigenesis. On the other hand, constitutive levels of nitrosamine dealkylase are identical in the 2 species and remain essentially unchanged following administration of DEN for 10 weeks. Inasmuch as nitrosamine dealkylation represents activating metabolism, this provides a rationale for the comparable susceptibility of the rat and guinea-pig to DEN carcinogenesis. Of the 2 enzymes in the 2 species, it is only azo-dye reductase in the guinea-pig which appears to be unregulated by glucose repression, since starvation brings about no change in this activity. Starvation-induced increase of azo-dye reductase in the rat is not influenced by administration of 3'-Me-DAB and only slightly by DEN. The starvation-induced increase of nitrosamine dealkylation is abolished, however, in both species by administration of DEN but only slightly decreased by 3'-Me-DAB.

Animals↗
PubMed2001

Cystoid macular oedema in uveitis: an unsolved problem.

Most papers on the subject of CMO associated with uveitis are retrospective, combine patients with different disease aetiologies, at different stages of evolution, and often describe patients who were previous treatment failures with other therapies besides the one under consideration. There are almost no prospective randomised double-masked controlled studies. This is perhaps in part due to the relative sparsity of uveitis patients seen by many uveitis centres. At the moment, treatment is largely empirical, based in large part on the studies, and others, quoted above. The need to regularly repeat courses of therapy, loss of efficacy of certain form of therapy after repeated use, and cumulative side-effects, all need to be taken into consideration when interpreting results and deciding upon the best approach to be adopted. The risks to the patient's well-being increase with the addition of systemic medication, and long-term steroid use can cause hypertension, induce or exacerbate diabetes, cause premature osteoporosis, cushingoid features, peptic ulceration and aseptic necrosis of the femoral head. Immunosuppressive drugs can be nephrotoxic, hepatotoxic, cause hypertension, gastric disturbances and excessive hair growth. The assessment of macular changes, both structurally and functionally, is the key aspect in understanding visual loss in CMO and also in predicting potential visualrecovery. The combined use of the various tools mentioned here, such as SLO, OCT and electrodiagnostic tests, may give us some of the necessary answers in this process. However, all these tests will need to be validated. A prospective analysis of CMO in cases of uveitis, especially if coupled with therapeutic intervention, will give us the opportunity to achieve this objective.

Humans↗
PubMed2002

Strategically designed sample composition for fastest screening of polychlorinated biphenyl congeners in water samples.

A new strategy for preparing composite samples of special interest and applicability in environmental screening studies is presented. The use of supersaturated experimental design matrices to conduct the sample composition of water sample specimens in screening studies is demonstrated. In contrast to well known conventional sample composition, this strategic approach provides analytical objects allowing the accurate prediction of analyte concentration levels in the original individual sample specimens while fixing the number of experiments to be carried out down to the very number of sample specimens. This will be of special importance when dealing with analytes that require complicated, labour intensive and expensive analytical processes. To reach this goal, two main conditions must be fulfilled. The first one is the sparsity effect (Pareto principle) which holds for the specimens in the sampling campaign. This means that the number of really anomalous or contaminated specimens, as compared to the total number of specimens to be analysed, is low. In environmental screening studies, frequently this situation can be reasonably assumed. The second condition is to have an effective manner to develop and solve the experimental designs required to build-up the composite samples. The challenging problem of screening PCBs in water samples has been tackled to show the usefulness of this strategic approach by combining chemometrically assisted sample composition and rapid analysis using solid-phase microextraction of the composite samples.

Environmental Monitoring↗
PubMed2006

A fast correlated electronic structure method for computing interaction energies of large van der Waals complexes applied to the fullerene-porphyrin dimer.

A new implementation of the scaled opposite spin Møller-Plesset (SOS-MP2) method is briefly described, which exploits the locality and sparsity of expansion coefficients and as a result has computational costs that increase approximately quadratically with molecular size. The performance of SOS-MP2 for describing stacked pi-complexes is carefully investigated using the benzene, ethylene, uracil, and naphthalene dimers as model systems. It is demonstrated that counterpoise-corrected SOS-MP2 results, extrapolated towards the complete basis set (CBS) limit using a two-point extrapolation scheme, can yield association energies that are reasonably close to the best available numbers, when the single scale factor is chosen as 1.55 for extrapolating results at the cc-pVDZ and cc-pVTZ levels. This methodology yields an interaction energy for the fullerene-tetraphenylporphyrin dimer of -31.47 kcal mol(-1) while Hartree-Fock (HF) with the cc-pVTZ basis finds the dimer at the same geometry is unbound by +10.83 kcal mol(-1). This implies that the net binding is a result of substantial correlation effects, presumably long-range London dispersions.

Chemical Phenomena↗