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The Biomechanics of Keratorefractive Surgery
Corneal biomechanics is the study of the mechanical properties and responses of the cornea. The cornea’s remarkable transparency and strength allow it to contain the intraocular pressure, serve as a protective layer and act as the major refracting surface of the eye. The shape of the cornea, and hence its refractive properties, is directly determined by its ultrastructural and biomechanical properties. In keratorefractive surgery the aim is to alter the cornea’s refractive power by changing its shape. In the early days of laser vision correction it was assumed that the postoperative change in corneal shape was determined directly by the pattern of tissue ablation.1 Now it is clear that this is an oversimplification because biomechanical and wound healing changes also influence final corneal shape.2 This is illustrated by the hyperopic shift that typically occurs following phototherapeutic keratectomy, a procedure that a simple shape subtraction theory would predict to be refractively neutral. Like all technical subjects biomechanics has its own language and this complicates understanding for the non-specialist. The purpose of this article is not to review biomechanical theory in general or even to describe all that is known about corneal biomechanics but rather to provide the reader with an understanding of the most clinically relevant concepts and principles so enabling an appreciation of how this important subject can impact on clinical practice
AM symbiotic traits can be selected using conventional breeding methods in durum wheat
Non-Peer ReviewedThe management of the arbuscular mycorrhizal (AM) symbiosis, could improve plant’s
efficiency of fertilizer use. The development and function of an AM symbiosis is largely
controlled by the genotype of the host plant. Thus, it may be possible to improve crop nutrient use
efficiency by the selection of genotypes with improve symbiotic effectiveness. Variability in
the AM symbiotic development of durum wheat genotypes must be present in breeder plant
material for a breeding program to be effective. We tested in the greenhouse under two levels of
fertility, the hypothesis that durum wheat genotypes representative of five mapping populations
vary in their ability to form the AM symbiosis. We found variations in the influence of the
commercial AM fungus Glomus intraradices on root colonization, nutrition, and yield of durum
wheat. This variation indicates that it is possible to select durum genotypes for improved
symbiosis formation using conventional breeding methods
Tweeting the Meeting: An In-Depth Analysis of Twitter Activity at Kidney Week 2011
In recent years, the American Society of Nephrology (ASN) has increased its efforts to use its annual conference to inform and educate the public about kidney disease. Social media, including Twitter, has been one method used by the Society to accomplish this goal. Twitter is a popular microblogging service that serves as a potent tool for disseminating information. It allows for short messages (140 characters) to be composed by any author and distributes those messages globally and quickly. The dissemination of information is necessary if Twitter is to be considered a tool that can increase public awareness of kidney disease. We hypothesized that content, citation, and sentiment analyses of tweets generated from Kidney Week 2011 would reveal a large number of educational tweets that were disseminated to the public. An ideal tweet for accomplishing this goal would include three key features: 1) informative content, 2) internal citations, and 3) positive sentiment score. Informative content was found in 29% of messages, greater than that found in a similarly sized medical conference (2011 ADA Conference, 16%). Informative tweets were more likely to be internally, rather than externally, cited (38% versus 22%, p<0.0001), thereby amplifying the original information to an even larger audience. Informative tweets had more negative sentiment scores than uninformative tweets (means −0.162 versus 0.199 respectively, p<0.0001), therefore amplifying a tweet whose content had a negative tone. Our investigation highlights significant areas of promise and improvement in using Twitter to disseminate medical information in nephrology from a scientific conference. This goal is pertinent to many nephrology-focused conferences that wish to increase public awareness of kidney disease
Novel Quantitative Real-Time LCR for the Sensitive Detection of SNP Frequencies in Pooled DNA: Method Development, Evaluation and Application
BACKGROUND: Single nucleotide polymorphisms (SNP) have proven to be powerful genetic markers for genetic applications in medicine, life science and agriculture. A variety of methods exist for SNP detection but few can quantify SNP frequencies when the mutated DNA molecules correspond to a small fraction of the wild-type DNA. Furthermore, there is no generally accepted gold standard for SNP quantification, and, in general, currently applied methods give inconsistent results in selected cohorts. In the present study we sought to develop a novel method for accurate detection and quantification of SNP in DNA pooled samples. METHODS: The development and evaluation of a novel Ligase Chain Reaction (LCR) protocol that uses a DNA-specific fluorescent dye to allow quantitative real-time analysis is described. Different reaction components and thermocycling parameters affecting the efficiency and specificity of LCR were examined. Several protocols, including gap-LCR modifications, were evaluated using plasmid standard and genomic DNA pools. A protocol of choice was identified and applied for the quantification of a polymorphism at codon 136 of the ovine PRNP gene that is associated with susceptibility to a transmissible spongiform encephalopathy in sheep. CONCLUSIONS: The real-time LCR protocol developed in the present study showed high sensitivity, accuracy, reproducibility and a wide dynamic range of SNP quantification in different DNA pools. The limits of detection and quantification of SNP frequencies were 0.085% and 0.35%, respectively. SIGNIFICANCE: The proposed real-time LCR protocol is applicable when sensitive detection and accurate quantification of low copy number mutations in DNA pools is needed. Examples include oncogenes and tumour suppressor genes, infectious diseases, pathogenic bacteria, fungal species, viral mutants, drug resistance resulting from point mutations, and genetically modified organisms in food
Screening of antigenemia and isolation of Cryptococcus neoformans and C. gattii from cloaca and crop of birds in the state of Paraná, Brazil
The effects of aging of scientists on their publication and citation patterns
The average age at which U.S. researchers get their first grant from NIH has
increased from 34.3 in 1970, to 41.7 in 2004. These data raise the crucial
question of the effects of aging on the scientific creativity and productivity
of researchers. Those who worry about the aging of scientists usually believe
that the younger they are the more creative and productive they will be. Using
a large population of 13,680 university professors in Quebec, we show that,
while scientific productivity rises sharply between 28 and 40, it increases at
a slower pace between 41 and 50 and stabilizes afterward until retirement for
the most active researchers. The average scientific impact per paper decreases
linearly until 50-55 years old, but the average number of papers in highly
cited journals and among highly cited papers rises continuously until
retirement. Our results clearly show for the first time the natural history of
the scientific productivity of scientists over their entire career and bring to
light the fact that researchers over 55 still contribute significantly to the
scientific community by producing high impact papers.Comment: 12 pages, 4 figure
Theoretical investigation of noncollinear phase-matched parametric four-photon amplification of ultrashort light pulses in isotropic media
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