3,100 research outputs found
Thermo-mechanical analysis of dental silicone polymers
Soft lining materials are used to replace the inner surface of a conventional complete denture, especially for weak elderly patients, with delicate health who cannot tolerate the hard acrylic denture base. Most of these patients have fragile supporting mucosa, excessive residual ridge resorption, particularly on the mandibular arch. The application of a soft liner to the mandibular denture allows absorbing impact forces during mastication and relieving oral mucosa. Actually, the silicone rubbers constitute the main family of commercialised soft lining materials. This study was conducted to understand the relationships between the mechanical properties and the physical structure of polysiloxanes. For this purpose, a series of polysiloxanes of various chemical compositions have been investigated. The evolution of their physical structure as a function of temperature has been followed by differential scanning calorimetry (DSC). In order to facilitate comparisons, the mechanical modulus has been analysed upon the same heating rate using dynamic mechanical analysis (DMA). Polysiloxanes actually commercialised as soft denture liners are three-dimensional networks: the flexibility of chains allows a crystalline organisation in an amorphous phase leading to the low value of the shear modulus. The dynamic mechanical analysis shows that they are used in the rubbery state. So, polysiloxanes have steady mechanical properties during physiological utilisation
Radial Velocities as an Exoplanet Discovery Method
The precise radial velocity technique is a cornerstone of exoplanetary
astronomy. Astronomers measure Doppler shifts in the star's spectral features,
which track the line-of/sight gravitational accelerations of a star caused by
the planets orbiting it. The method has its roots in binary star astronomy, and
exoplanet detection represents the low-companion-mass limit of that
application. This limit requires control of several effects of much greater
magnitude than the signal sought: the motion of the telescope must be
subtracted, the instrument must be calibrated, and spurious Doppler shifts
"jitter" must be mitigated or corrected. Two primary forms of instrumental
calibration are the stable spectrograph and absorption cell methods, the former
being the path taken for the next generation of spectrographs. Spurious,
apparent Doppler shifts due to non-center-of-mass motion (jitter) can be the
result of stellar magnetic activity or photospheric motions and granulation.
Several avoidance, mitigation, and correction strategies exist, including
careful analysis of line shapes and radial velocity wavelength dependence.Comment: Invited review chapter. 13pp. v2 includes corrections to Eqs 3-6,
updated references, and minor edit
Epidemiology of Robin sequence in the UK and Ireland: an active surveillance study
Background:
Birth prevalence of Robin sequence (RS) is commonly reported as 1 case per 8000–14 000 live births. These estimates are based on single-source case ascertainment and may miss infants who did not require hospital admission or those without overt upper airway obstruction at birth.
Objectives:
To identify the true birth prevalence of RS with cleft palate in the UK and Ireland from a population-based birth cohort with high case ascertainment.
Methods:
Active surveillance of RS with cleft palate was carried out in the UK/Ireland using dual sources of case ascertainment: British Paediatric Surveillance Unit (BPSU) reporting card and nationally commissioned cleft services. Clinical data were collected from notifying clinicians at two time points.
Results:
173 live-born infants met the surveillance case definition, giving a birth prevalence of 1 case per 5250 live births (19.1 per 100 000 (95% CI 16.2 to 21.9)), and 1:2690 in Scotland. 47% had non-isolated RS, with Stickler syndrome the most common genetic diagnosis (12% RS cases). Birth prevalence derived from the combined data sources was significantly higher than from BPSU surveillance alone.
Conclusions:
Birth prevalence of RS in the UK/Ireland derived from active surveillance is higher than reported by epidemiological studies from several other countries, and from UK-based anomaly registries, but consistent with published retrospective data from Scotland. Dual case ascertainment sources enabled identification of cases with mild or late-onset airway obstruction that were managed without hospital admission. Studies of aetiology and equivalent well-designed epidemiological studies from other populations are needed to investigate the identified geographical variability in birth prevalence
Undifferentiated HepaRG cells show reduced sensitivity to the toxic effects of M8OI through a combination of CYP3A7-mediated oxidation and a reduced reliance on mitochondrial function
\ua9 2024 The AuthorsThe methylimidazolium ionic liquid M8OI (1-octyl-3-methylimidazolium chloride, also known as [C8mim]Cl) has been detected in the environment and may represent a hazard trigger for the autoimmune liver disease primary biliary cholangitis, based in part on studies using a rat liver progenitor cell. The effect of M8OI on an equivalent human liver progenitor (undifferentiated HepaRG cells; u-HepaRG) was therefore examined. u-HepaRG cells were less sensitive (>20-fold) to the toxic effects of M8OI. The relative insensitivity of u-HepaRG cells to M8OI was in part, associated with a detoxification by monooxygenation via CYP3A7 followed by further oxidation to a carboxylic acid. Expression of CYP3A7 - in contrast to the related adult hepatic CYP3A4 and CYP3A5 forms - was confirmed in u-HepaRG cells. However, blocking M8OI metabolism with ketoconazole only partly sensitized u-HepaRG cells. Despite similar proliferation rates, u-HepaRG cells consumed around 75% less oxygen than B-13 cells, reflective of reduced dependence on mitochondrial activity (Crabtree effect). Replacing glucose with galactose, resulted in an increase in u-HepaRG cell sensitivity to M8OI, near similar to that seen in B-13 cells. u-HepaRG cells therefore show reduced sensitivity to the toxic effects of M8OI through a combination of metabolic detoxification and their reduced reliance on mitochondrial function
Evaluation of Xpert® MTB/RIF and ustar easyNAT™ TB IAD for diagnosis of tuberculous lymphadenitis of children in Tanzania : a prospective descriptive study
Fine needle aspiration biopsy has become a standard approach for diagnosis of peripheral tuberculous lymphadenitis. The aim of this study was to compare the performance of Xpert MTB/RIF and Ustar EasyNAT TB IAD nucleic acid amplification assays, against acid-fast bacilli microscopy, cytology and mycobacterial culture for the diagnosis of TB lymphadenitis in children from a TB-endemic setting in Tanzania.; Children of 8Â weeks to 16Â years of age, suspected of having TB lymphadenitis, were recruited at a district hospital in Tanzania. Fine needle aspirates of lymph nodes were analysed using acid-fast bacilli microscopy, liquid TB culture, cytology, Xpert MTB/RIF and EasyNAT. Latent class analysis and comparison against a composite reference standard comprising "culture and/or cytology" was done, to assess the performance of Xpert MTB/RIF and EasyNAT for the diagnosis of TB lymphadenitis.; Seventy-nine children were recruited; 4 were excluded from analysis. Against a composite reference standard of culture and/or cytology, Xpert MTB/RIF and EasyNAT had a sensitivity and specificity of 58Â % and 93Â %; and 19Â % and 100Â % respectively. Relative to latent class definitions, cytology had a sensitivity of 100Â % and specificity of 94.7Â %.; Combining clinical assessment, cytology and Xpert MTB/RIF may allow for a rapid and accurate diagnosis of childhood TB lymphadenitis. Larger diagnostic evaluation studies are recommended to validate these findings and on Xpert MTB/RIF to assess its use as a solitary initial test for TB lymphadenitis in children
Understanding a Pacific Islander Young Adult Perspective on Access to Higher Education
The Pacific Islander (PI) community suffers disproportionately from illnesses and diseases, including diabetes, heart disease and cancer. While there are tremendous health needs within the PI community, there are few health care providers from the community that exist to help address these particular needs. Many efforts have focused on health care workforce diversity to reduce and eliminate health disparities, but few have examined the issues faced in the health care work force pipeline. Understanding educational attainment among PI young adults is pivotal in speaking to a diverse health care workforce where health disparities among Pacific Islanders (PIs) may be addressed. This paper provides an in-depth, qualitative assessment of the various environmental, structural, socio-economic, and social challenges that prevent PIs from attaining higher education; it also discusses the various needs of PI young adults as they relate to psychosocial support, retention and recruitment, and health career knowledge and access. This paper represents a local, Southern California, assessment of PI young adults regarding educational access barriers. We examine how these barriers impact efforts to address health disparities and look at opportunities for health and health-related professionals to reduce and care for the high burden of illnesses and diseases in PI communities
Internal construct validity of the Warwick-Edinburgh Mental Well-being Scale (WEMWBS): a Rasch analysis using data from the Scottish Health Education Population Survey
Background: The Warwick-Edinburgh Mental Well-Being Scale (WEMWBS) was developed to meet demand for instruments
to measure mental well-being. It comprises 14 positively phrased Likert-style items and fulfils classic criteria for scale development. We report here the internal construct validity of WEMWBS from the perspective of the Rasch measurement model.
Methods: The model was applied to data collected from 779 respondents in Wave 12 (Autumn 2006) of the Scottish Health
Education Population Survey. Respondents were aged 16–74 (average 41.9) yrs.
Results: Initial fit to model expectations was poor. The items 'I've been feeling good about myself', 'I've been interested in new things' and 'I've been feeling cheerful' all showed significant misfit to model expectations, and were deleted. This led to a marginal improvement in fit to the model. After further analysis, more items were deleted and a strict unidimensional seven item scale (the Short Warwick Edinburgh Mental Well-Being Scale (SWEMWBS)) was resolved. Many items deleted because of misfit with
model expectations showed considerable bias for gender. Two retained items also demonstrated bias for gender but, at the
scale level, cancelled out. One further retained item 'I've been feeling optimistic about the future' showed bias for age. The correlation between the 14 item and 7 item versions was 0.954. Given fit to the Rasch model, and strict unidimensionality, SWEMWBS provides an interval scale estimate of mental well-being.
Conclusion: A short 7 item version of WEMWBS was found to satisfy the strict unidimensionality expectations of the Rasch model, and be largely free of bias. This scale, SWEMWBS, provides a raw score-interval scale transformation for use in parametric procedures. In terms of face validity, SWEMWBS presents a more restricted view of mental well-being than the 14 item WEMWBS, with most items representing aspects of psychological and eudemonic well-being, and few covering hedonic well-being or affect. However, robust measurement properties combined with brevity make SWEMWBS preferable to WEMWBS at present for monitoring mental well-being in populations. Where face validity is an issue there remain arguments for continuing to collect data on the full 14 item WEMWBS
Understanding the dynamics of Toll-like Receptor 5 response to flagellin and its regulation by estradiol
© 2017 The Author(s). Toll-like receptors (TLRs) are major players of the innate immune system. Once activated, they trigger a signalling cascade that leads to NF-ΰ B translocation from the cytoplasm to the nucleus. Single cell analysis shows that NF-ΰ B signalling dynamics are a critical determinant of transcriptional regulation. Moreover, the outcome of innate immune response is also affected by the cross-talk between TLRs and estrogen signalling. Here, we characterized the dynamics of TLR5 signalling, responsible for the recognition of flagellated bacteria, and those changes induced by estradiol in its signalling at the single cell level. TLR5 activation in MCF7 cells induced a single and sustained NF-k B translocation into the nucleus that resulted in high NF-k B transcription activity. The overall magnitude of NF-k B transcription activity was not influenced by the duration of the stimulus. No significant changes are observed in the dynamics of NF-k B translocation to the nucleus when MCF7 cells are incubated with estradiol. However, estradiol significantly decreased NF-k B transcriptional activity while increasing TLR5-mediated AP-1 transcription. The effect of estradiol on transcriptional activity was dependent on the estrogen receptor activated. This fine tuning seems to occur mainly in the nucleus at the transcription level rather than affecting the translocation of the NF-k B transcription factor
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