The tear (lacrimal) meniscus height in human eyes: a useful clinical measure or an unusable variable sign?

PURPOSE: To review notes and reports in the literature on assessments of human tear meniscus height (TMH) with the view to defining what the current state of knowledge is, and allow comparisons with data obtained on elderly individuals. METHODS: TMH data was obtained from 97 elderly individuals without significant eye disease. Photo-slit-lamp views, perpendicular to the lower marginal tear strip, were used to obtain close-up images by videography over approximately 30s. Repeated measures at the same location separated by a few seconds (time-dependent TMH measures, tTMH), or repeated measures along the length of the middle portion of the lower eyelid (position-dependent TMH measures, pTMH) were made. The results were compared to those from published reports of TMH. RESULTS: For elderly individuals, tTMH averaged 0.185+/-0.088 mm, while pTMH averaged 0.189+/-0.093 mm. The distribution of TMH measures however included a number of data sets with a much higher average, and which could be separated from the main group of data using cluster analyses approach (> 0.23 mm, P < 0.001). Literature-reported values for TMH, assessed by a perpendicular view, average 0.215 mm (range of average values from 0.163 to 0.350 mm), whereas those made from a tangential view average 0.343 mm (range 0.215-0.460 mm). CONCLUSIONS: The average TMH value of close to 0.2mm in the elderly, as compared to the small number of individuals with rather greater TMH values of up to 0.7 mm, might therefore be considered as indicative of their having normal tear volume, with a few individuals having reflex tearing. Based on the data and literature values, a lower cut-off limit for normal would be /=0.25 mm would indicate reflex tearing and/or sub-optimal tear drainage. An alternative interpretation is that elderly individuals have a subnormal tear film volume, with just a few individuals having adequate tear volume. Further work is clearly needed to resolve this issue.     

Damage evolution in compacted graphite iron during thermomechanical fatigue testing

Thermomechanical fatigue properties of a compacted graphite iron in an out of phase configuration are investigated for different maximum temperatures and mechanical strain ranges. Furthermore, the stress–strain hysteresis loops are analysed, and, in particular, the unloading modulus, i.e. the elastic modulus measured during specimen unloading, is obtained from each cycle. This material parameter has earlier been explicitly related to the amount of microcracking in cast irons. The results show that the unloading modulus linearly declines with the numbers of cycles in all tests performed. In addition, the rate of change of the unloading modulus is closely related to the number of cycles to failure. Accordingly, it is concluded that microcracks are independently propagated by fatigue until a point of rapid crack linking resulting in ultimate failure. This is supported by microstructural analyses consisting of optical microscope images taken at different stages throughout the life of a specimen.     

Turbulent Operation of the Visco Seal

A theoretical analysis of the turbulent operation of the visco seal is presented. The resulting turbulent sealing equation correlated well with test data. It is shown, that good sealing capability can be obtained over a wide range of geometrical variables. It was also found that for shaft diameters over 1 inch, curvature effects are small; and that within the accuracy of the test data, the sealing capability is independent of thread location, shaft or sleeve. Power loss for seals of length to diameter ratio greater than one can be conservatively estimated by treating the seal as a smooth shaft rotating in a close clearance sleeve and neglecting the grooves.     

Effects of polymerization catalyst technology on the melt processing stability of polyethylenes. part 2. single stabilizer performance

The effects of a range of thermal and light stabilizers on the melt stability (investigated via multiple pass extrusion) and color stability of three different polyethylenes (PEs) were examined. The PEs varied in terms of the catalyst system used to synthesize the polymers and included an HDPE produced by using a chromium‐based Phillips catalyst and two LLDPEs produced via chromium‐based metallocene and titanium‐based Ziegler‐Natta catalysts. The additive types included a range of phenolics of different functionality, phosphites, hindered piperidines, an hydroxylamine, and Vitamin E. The results obtained for the three PEs confirmed that primary antioxidants (AOs) such as highly hindered and less, hindered phenols or hydroxylamines promoted good melt stability but in some cases tended toward yellowing. The secondary AOs such as the phosphites or thioethers behaved in the opposite way; color suppression was good, but melt stabilization was poor. It was also shown that for different types of phenols (all with similar molar activity), reducing steric hindrance to the phenolic OH enhanced the tendency to form chromophoric groups and hence color led to better efficiency than high hindrance. Those phenol with higher molar activity (mol OH/kg AO) showed the best processing performance. J. VINYL ADDIT. TECHNOL., 2012. © 2012 Society of Plastics Engineers     

Molecular and phylogenetic approaches for assessing sources of Cryptosporidium contamination in water

The high sequence diversity and heterogeneity observed within species or genotypes of Cryptosporidium requires phylogenetic approaches for the identification of novel sequences obtained from the environment. A long-term study on Cryptosporidium in the agriculturally-intensive South Nation River watershed in Ontario, Canada was undertaken, in which 60 sequence types were detected. Of these sequence types 33 were considered novel with no identical matches in GenBank. Detailed phylogenetic analysis identified that most sequences belonged to 17 previously described species: Cryptosporidium andersoni, Cryptosporidium baileyi, Cryptosporidium hominis, Cryptosporidium parvum, Cryptosporidium ubiquitum, Cryptosporidium meleagridis, muskrat I, muskrat II, deer mouse II, fox, vole, skunk, shrew, W12, W18, W19 and W25 genotypes. In addition, two new genotypes were identified, W27 and W28. C. andersoni and the muskrat II genotype were most frequently detected in the water samples. Species associated with livestock made up 39% of the total molecular detections, while wildlife associated species and genotypes accounted for 55% of the Cryptosporidium identified. The human pathogenic species C. hominis and C. parvum had an overall prevalence of 1.6% in the environment, indicating a small risk to humans from the Cryptosporidium present in the watershed. Phylogenetic analysis and knowledge of host-parasite relationships are fundamental in using Cryptosporidium as a source-tracking or human health risk assessment tool.     

Evaluation of the Performance of Annular Denuder Samplers

Two annular denuder samplers were evaluated for the determination of atmospheric nitric acid, SO 2 , and fine particulate sulfate and nitrate. One, the University Research Glassware (URG) sampler, used an elutriator-impactor to remove coarse particles prior to sampling the aerosol through the denuder sections for the removal of acid gases. The second, the Rupprecht and Patashnick (R&P) ChemSpec, removes the acid gases in diffusion denuder sections and then removes coarse particles prior to the collection of fine particles. Possible sampling artifacts examined included the removal of HNO 3 (g) by the inlet of the URG sampler before the collection of this gas-phase species by the diffusion denuder, resulting in the underestimation of HNO 3 (g) and the deposition of some coarse particles in the R&P denuders prior to the removal of these larger particles, and the collection of fine particles on a filter, resulting in the overestimation of HNO 3 (g) and SO 2 (g). Samples were collected in Riverside, CA, Bakersfield, CA, and Provo, UT. Both sampling artifacts were found to be present. However, the effect on the determination of HNO 3 (g) by the URG sampler and on the determination of particulate-phase sulfate and nitrate by the R&P ChemSpec were both small, on the order of a few tenths of a microgram per cubic meter.     

Scanning Electron Microscopy and Energy Dispersive X-Ray Microanalysis of Perna canaliculus Mussel Larvae Adhesive Secretion

The morphology and nature of the adhesive secretion from Perna canaliculus mussel larvae settled on glass and on Teflon® was observed by scanning electron microscopy techniques. The settled larvae were imaged by field emission scanning electron microscopy and the adhesive footprints left on the substrate after the organisms' removal by cryo-scanning electron microscopy. Environmental scanning electron microscopy images on glass and Teflon substrates showed the adhesive in its natural hydrated condition. Moreover, micrographs under increasing humidity conditions showed swelling behaviour of the larval adhesive which revealed its hygroscopic nature. The mussel larvae adhesive spreading behaviour on glass compared with Teflon showed that it is hydrophilic. Additionally, energy dispersive X-ray microanalysis provided information of the elemental composition of the larval adhesive, revealing the presence of sulfur, phosphorus, and calcium. Calcium may be present due to its favourable interactions with polyanionic moieties leading to formation of a gel-like adhesive secretion.     

Integrating testing with reliability

The activities of software testing and reliability are integrated for the purpose of demonstrating how the two activities interact in achieving testing efficiency and the reliability resulting from these tests. Integrating means modeling the execution of a variety of tests on a directed graph representation of an example program. A complexity metric is used to construct the nodes, edges, and paths of the example program. Models are developed to represent the efficiency and achieved reliability of black box and white box tests. Evaluations are made of path, independent path, node, program construct, and random tests to ascertain which, if any, is superior with respect to efficiency and reliability. Overall, path testing has the edge in test efficiency. The results depend on the nature of the directed graph in relation to the type of test. Although there is no dominant method, in most cases the tests that provide detailed coverage are better. For example, path testing discovers more faults than independent path testing. Predictions are made of the reliability and fault correction that results from implementing various test strategies. It is believed that these methods can be used by researchers and practitioners to evaluate the efficiency and reliability of other programs. Copyright © 2008 John Wiley & Sons, Ltd.     

Alternatives for examining daughter performance of progeny-test bulls between official evaluations

In August 2007, the USDA changed from calculating official genetic evaluations quarterly to triannually in conjunction with the schedule change for international evaluations. To offset part of the delay in providing genetic information because of the reduced frequency of official evaluations, industry cooperators requested that interim evaluations be initiated for progeny-test (PT) bulls based on first-lactation records from PT daughters and their contemporaries that calved recently in cooperator herds. Alternatives for interim evaluations were studied to determine which would characterize genetic merit of PT bulls most accurately. Four alternative Holstein data sources were examined based on maximum data interval (most recent 12 or 18 mo of first calvings) and minimum number of PT daughters in herd (≥1 or ≥ 5). The highest correlation between August 2006 interim and official evaluations for milk yield was 0.980 for interim evaluations based on the most recent 18 mo of first calvings from cooperator herds with ≥1 PT daughter. That high correlation confirmed that interim evaluations based on limited data could provide genetic estimates of value between official evaluations. With the support of the Council on Dairy Cattle Breeding, the USDA initiated 3 interim evaluations each year with release limited to PT bulls with ≥10 daughters and an increase in reliability since the most recent official evaluation.     

Investigation of country bias in international genetic evaluations using full-brother information

International Bull Evaluation Service evaluations from May 2005 were examined for country bias by comparing Holstein full-brother families. Countries with ≥25 bulls in multicountry full-brother families were included. The model fit evaluations of US estimated breeding values (EBV) by absorbing full-brother family and producing solutions for country of brothers. For yield and somatic cell score, 24,611 and 22,802 bulls, respectively, were included in the analysis. The study was repeated fitting evaluations on the scales of 9 countries other than the United States. On all countries’ scales, bulls from Australia, Germany, Great Britain, and Japan had greater EBV for milk yield than did their full brothers from the United States; Italian bulls had lower EBV. Bulls from Australia, Great Britain, and South Africa had an advantage in EBV for fat yield. For EBV for protein yield, bulls from Germany, Great Britain, Japan, and South Africa had an advantage, whereas bulls from the Netherlands were disadvantaged. For somatic cell score, US bulls were advantaged compared with bulls from South Africa. Significance and rankings of apparent biases were similar across country scales of the international evaluations. Causes of those differences are unknown; differences in incorporation of parental data in national and International Bull Evaluation Service evaluations are a possibility.