A fuzzy clustering algorithm enhancing local model interpretability

In this work, simple modifications on the cost index of particular local-model fuzzy clustering algorithms are proposed in order to improve the readability of the resulting models. The final goal is simultaneously providing local linear models (reasonably close to the plant’s Jacobian) and clustering in the input space so that desirable characteristics (regarding final model accuracy, and convexity and smoothness of the cluster membership functions) are improved with respect to other proposals in literature. Some examples illustrate the proposed approach.     

Selective employment of chemokine receptors as human immunodeficiency virus type 1 coreceptors determined by individual amino acids within the envelope V3 loop

The chemokine receptor CCR5 acts as an essential cofactor for cell entry by macrophage-tropic human immunodeficiency virus type 1 (HIV-1) strains, whereas CXCR4 acts as an essential cofactor for T-cell-line-adapted strains. We demonstrated that the specific amino acids in the V3 loop of the HIV-1 envelope protein that determine cellular tropism also regulate chemokine coreceptor preference for cell entry by the virus. Further, a strong correlation was found between HIV-1 strains classified as syncytium inducing in standard assays and those using CXCR4 as a coreceptor. These data support the hypothesis that progressive adaptation to additional coreceptors is a key molecular basis for HIV-1 phenotypic evolution in vivo.     

Comparison of two methods of surfactant administration and the effect on dosing-associated hypoxemia

OBJECTIVE: The purpose of our study was to test the hypothesis that surfactant dosing through a proximal sideport adapter on an endotracheal tube leads to more dosing-associated hypoxemia compared with a method of dosing that uses a double-lumen endotracheal tube. STUDY DESIGN: Using adequate sample size to compare significant changes in O2 saturation (power > 0.8, alpha < 0.05) we enrolled 36 infants with respiratory distress syndrome in this randomized trial. A 10% change in O2 saturation was considered clinically significant. Nineteen infants received 38 doses of surfactant through the sideport adapter. Seventeen infants received 31 doses of surfactant through the nonventilation lumen of a double-lumen endotracheal tube. Two main outcome measures were assessed: time-averaged O2 saturation values 30 minutes after dosing and the largest absolute fall in O2 saturation for each patient. RESULTS AND CONCLUSIONS: Time-averaged O2 saturation measures were higher in the proximal sideport group (p = 0.02), but the magnitude of difference was probably not clinically significant. No significant difference was detected between groups when we compared largest absolute drop in O2 saturation. Secondary analyses found no effect of birth weight or dose number (second vs third dose) on either outcome measure.     

Predicting bleaching results with computer imaging

Vital bleaching can be a relatively unpredictable treatment. Photographs of previous cases and cosmetic imaging, although useful, may lead to unrealistic expectations on the part of the patient. The high-tech mystique of computer imaging and viewing one's own teeth has a significant impact on the dental patient. Whether imaged by the dentist or an auxiliary, patients must be aware of alternatives that may exist both before and during treatment. Cosmetic imaging should be used as an adjunct to, not as the prime motivator for, treatment planning in bleaching cases. Excellent communication between the practitioner and patient is the most important factor in assuring positive bleaching results and patient satisfaction.     

A CONSTITUTIVE MODEL FOR ELASTIC-PLASTIC DEFORMATION UNDER CYCLIC MULTIAXIAL STRAINING

Abstract— The yield criterion is interpreted as defining the metric of the stress space. Hydrostatic stresses correspond to null geodesies. The plastic strain increment represents a normal projection of the increment undergone by a certain scalar function (hardening function) which depends only on the distance between stress points. This establishes a flow rule formally equivalent to the Prandtl-Reuss equations. Consideration of un-loading processes leads to the analysis of equivalent paths and to the definition of a generalized length or separation which provides a new representation of kinematic hardening.     

Apoptosis in heart transplantation

Apoptosis, or programmed cell death, is a mechanism of cell death that plays a major role during development, homeostasis, and in many disease states. The interaction of the cell membrance protein, Fas, with its ligand, Fas ligand, induces apoptosis in Fas-bearing cells. Several factors induce apoptosis in mammalian cardiomyocytes, including reperfusion injury, hypoxia, mechanical stretch, myocardial infarction, rapid ventricular pacing, and hypertensive heart failure. Although studies in the transplanted hearts of rodents and humans have shown the presence of Fas, Fas ligand, and apoptosis in the myocardium, there is controversy regarding which cells in the myocardium are actually undergoing apoptosis after heart transplantation. It is even less clear what type of relationship, if any, apoptosis has to allograft rejection or post-transplant graft coronary vasculopathy. This review summarizes the current knowledge regarding apoptosis in the transplanted heart and discusses some of the controversies surrounding this new and rapidly expanding area of investigation.     

Perceptual learning of spatial localization: specificity for orientation, position, and context

Discrimination of simple visual attributes can improve significantly with practice. We have trained human observers to perform peripherally presented tasks involving the localization of short line segments and examined the specificity of the learning for the visual location, orientation, and geometric arrangement of the trained stimulus. Several weeks of training resulted in dramatic threshold reductions. The learning was specific for the orientation and location of the trained stimulus, indicating the involvement of the earliest cortical stages in the visual pathway where the orientation and location of stimuli are mapped with highest resolution. Furthermore, improvement was also specific for both the configuration of the trained stimulus and the attribute of the stimulus that was under scrutiny during training. This degree of specificity suggests that the learning cannot be achieved by cortical recruitment alone, as proposed in current models, but is likely to involve a refinement of lateral interactions within the cortex and possibly a gating of lower level changes by attentional mechanisms.     

Major internal nuclear matrix proteins are common to different human cell types

Cancer invasion and metastasis are associated with matrix degradation. We describe a novel in vivo model of invasion by squamous epithelial neoplastic cells derived from transgenic mice grown on acellular human dermis. Human dermis was subjected to multiple freeze-thaw cycles to render it acellular, maintaining the basement membrane of the former dermal-epidermal junction. Cells representing discrete stages of a multistep transgenic mouse model of epidermal carcinogenesis (neonatal transgenic keratinocytes, moderately/poorly differentiated squamous cell carcinoma, and lymph node metastasis) were seeded onto the basement membrane surface, grown in culture for 4 days, grafted in a subpannicular pocket of athymic mice, and harvested after 3 weeks. Histological analysis demonstrated that neonatal transgenic keratinocytes did not degrade the basement membrane or invade the underlying dermis. In contrast, malignant cells derived from both a moderately differentiated squamous carcinoma and a lymph node metastasis were highly invasive. Immunohistochemical analysis revealed collagenase only in nests of invading malignant cells in contact with the dermal matrix, but not in the tumor mass remaining above the basement membrane, suggesting that this proteinase may be required for stromal invasion. This novel model recapitulates the events seen in malignant invasion: transgenic keratinocytes are unable to penetrate the dermis while cells from a moderately differentiated carcinoma and from lymph node metastasis consistently invade.     

Is incarceration during pregnancy associated with infant birthweight?

To address the hypothesis that tumor necrosis factor (TNF)-alpha has a role in obesity-associated insulin resistance or the regulation of in vivo lipid metabolism, mice with targeted disruption of the TNF-alpha gene were generated and studied. The absence of TNF-alpha protein in TNF-null (-/-) mice was confirmed. Lean or obese (gold-thioglucose [GTG]-injected) homozygous (-/-) mice were compared with lean or obese age- and sex-matched wild-type (+/+) mice derived from the same line at 13, 19, and 28 weeks of age. The following parameters were significantly affected in lean -/- versus +/+ mice: Body weight was not affected until week 28 (decreased by 14%); epididymal fat pad weight also decreased (25%) at this time, as did percentage body fat (16%), while percentage body protein was increased 13%. Fed plasma insulin levels decreased 47% (28 weeks), triglyceride levels decreased (all three ages; maximum 35% at 19 weeks), and fed plasma leptin decreased 33% (28 weeks). Fasting glucose was slightly (10%) reduced, but the glucose response to an oral glucose tolerance test (OGTT) was not affected. There was a trend (NS) toward increased total adipose tissue lipoprotein lipase in -/- versus +/+ mice. GTG-treatment resulted in obese -/- and +/+ mice with equal mean body weights (42 and 58% increased weight versus lean mice). The following parameters were significantly different in obese -/- mice: fasting plasma glucose decreased 13% (28 weeks), fed plasma insulin decreased 67% (28 weeks), and insulin response to OGTT was decreased by 50%. For both groups of obese mice, glucose levels during the OGTT were substantially increased compared with those in lean mice; however, mean stimulated glucose levels were 20% lower in obese -/- versus +/+ mice. We conclude 1) that TNF-alpha functions to regulate plasma triglycerides and body adiposity and 2) that although TNF-alpha contributes to reduced insulin sensitivity in older or obese mice, the absence of TNF-alpha is not sufficient to substantially protect against insulin resistance in the GTG hyperphagic model of rodent obesity.     

Worksite characteristics and changes in worksite tobacco-control initiatives. Results from the COMMIT study

Few studies have prospectively examined the characteristics associated with worksite adoption of tobacco-control initiatives. Data were collected as part of the Community Intervention Trial (COMMIT) for Smoking Cessation, which conducted interventions in 11 communities. This smoking cessation intervention was based on community organization principles and delivered through multiple community channels, including worksites, health care providers, the media, and cessation resources. This article reports results from telephone interviews of intervention community worksites having 50 or more employees, conducted at baseline and the end of the intervention period. Among worksites that responded to both baseline and final surveys, 83% had not adopted a smoke-free policy at baseline, and 61% did not offer any cessation aid or quitting resources at baseline. By the final survey, 34% of those with no smoking ban at baseline had become smoke-free, and 36% of those offering no cessation assistance at baseline were offering cessation resources at the follow-up. The prevalence of policy adoption was higher among worksites employing more female employees and offering other health-promotion activities; manufacturing businesses were significantly less likely than businesses other than service and wholesale/retail businesses to adopt policies. Adoption of cessation programs was significantly more likely among worksites employing 100 to 249 workers, compared with those employing 50 to 99 workers; those predominantly employing men; those offering other types of health-promotion activities; and those with a higher rate of turnover. These results provide important information about the characteristics of worksites likely to engage in tobacco-control efforts. Health educators and others may choose to target those worksites most ready for adoption of tobacco control policies and programs, as indicated by these findings.