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At least 199 records · Page 11Linked to original sources
PubMed2005

Incidence and progression of myopia in Singaporean school children.

PURPOSE: To determine the incidence and progression rates of myopia in young Singaporean children. METHODS: A prospective cohort study, the Singapore Cohort Study of the Risk Factors for Myopia (SCORM), was conducted in two schools in Singapore (1999-2002). Children aged 7 to 9 years (n=981) were followed up over a 3-year period. Cycloplegic autorefraction and biometry parameter measures were performed annually, according to the same protocol. RESULTS: The 3-year cumulative incidence rates were 47.7% (95% confidence interval [CI]: 42.2-53.3), 38.4% (95% CI: 31.4-45.4), and 32.4% (95% CI: 21.8-43.1) for 7-, 8-, and 9-year-old children, respectively. The 3-year cumulative incidence rates were higher in Chinese (49.5% vs. 27.2%) and in 7-year-old compared with 9-year-old children at baseline (47.7% vs. 32.4%), though the latter relationship was of borderline significance after adjustment for race, gender, amount of reading (books/week), and parental myopia (P=0.057). Premyopic children with greater axial lengths, vitreous chamber depths, and thinner lenses were more prone to the development of myopia, after controlling for age, gender, race, reading, and parental myopia. The 3-year mean cumulative myopia progression rates were -2.40 D (95% CI: -2.57 to -2.22) in 7-year-old myopic children, -1.97 (95% CI: -2.16 to -1.78) in 8-year-olds, and -1.71 (95% CI: -1.98 to -1.44) in 9-year-olds. CONCLUSIONS: Both the incidence and progression rates of myopia are high in Singaporean children.

Age Distribution↗
PubMed2006

Depth of interaction resolution measurements for a high resolution PET detector using position sensitive avalanche photodiodes.

We explore dual-ended read out of LSO arrays with two position sensitive avalanche photodiodes (PSAPDs) as a high resolution, high efficiency depth-encoding detector for PET applications. Flood histograms, energy resolution and depth of interaction (DOI) resolution were measured for unpolished LSO arrays with individual crystal sizes of 1.0, 1.3 and 1.5 mm, and for a polished LSO array with 1.3 mm pixels. The thickness of the crystal arrays was 20 mm. Good flood histograms were obtained for all four arrays, and crystals in all four arrays can be clearly resolved. Although the amplitude of each PSAPD signal decreases as the interaction depth moves further from the PSAPD, the sum of the two PSAPD signals is essentially constant with irradiation depth for all four arrays. The energy resolutions were similar for all four arrays, ranging from 14.7% to 15.4%. A DOI resolution of 3-4 mm (including the width of the irradiation band which is approximately 2 mm) was obtained for all the unpolished arrays. The best DOI resolution was achieved with the unpolished 1 mm array (average 3.5 mm). The DOI resolution for the 1.3 mm and 1.5 mm unpolished arrays was 3.7 and 4.0 mm respectively. For the polished array, the DOI resolution was only 16.5 mm. Summing the DOI profiles across all crystals for the 1 mm array only degraded the DOI resolution from 3.5 mm to 3.9 mm, indicating that it may not be necessary to calibrate the DOI response separately for each crystal within an array. The DOI response of individual crystals in the array confirms this finding. These results provide a detailed characterization of the DOI response of these PSAPD-based PET detectors which will be important in the design and calibration of a PET scanner making use of this detector approach.

Equipment Design↗
PubMed1996

Facial soft-tissue thicknesses in the adult male Zulu.

The morphometric method of forensic facial reconstruction rests heavily on the use of facial soft tissue depth measurements. In reconstructing the Negroid face, much use has been made of the tables of soft tissue thickness of American Negroid cadavers. However, the genetic complexities of American blacks are well known. In addition it is felt that measurements made on the living are of more value than those made on the dead. In view of this it was decided to set up a table of norms for facial soft tissue depths of the living Zulu, an African Negroid who has remained relatively free from genetic admixture with other populations. The tightly controlled sample consisted of 55 healthy male Zulus, aged 20 to 35. Tissue depths at established landmarks were measured from lateral and oblique cephalometric radiographs. These were then combined with ultrasonic readings at other landmarks on the subject's face to yield a comprehensive set of tissue depth data. This paper presents a set of average facial soft tissue depth measurements from the Zulu face that results in the development of a new profile. It also provides a method for linking two systems of measurement.

Adult↗
PubMed1986

High-frequency ultrasound measurement of patch test reactions.

53 patients who produced 34 positive patch test reactions (+/- 15, +10, ++4, +++5) had their reactions read by a high-frequency pulsed ultrasonic (A-scan) dermal depth detector with a resolution of 0.05 mm. The positive reactions were compared with both random and regional controls. The machine could not differentiate between + or +/- reactions from the control readings. However, for 75% of ++ cases and 80% of +++ cases, a significant change was confirmed by the detector. It is concluded that the high-frequency ultrasound method is of little use in confirming or quantifying of positive patch test results.

Adolescent↗
PubMed2003

Evaluation of two water-equivalent phantom materials for output calibration of photon and electron beams.

Two commercially available water-equivalent solid phantom materials were evaluated for output calibration in both photon (6-15 MV) and electron (6-20 MeV) beams. The solid water 457 and virtual water materials have the same chemical composition but differ in manufacturing process and density. A Farmer-type ionization chamber was used for measuring the output of the photon beams at 5- and 10-cm depth and electron beams at maximum buildup depth in the solid phantoms and in natural water. The water-equivalency correction factor for the solid materials is defined as the ratio of the chamber reading in natural water to that in the solid at the same linear depth. For photon beams, the correction factor was found to be independent of depth and was 0.987 and 0.993 for 6- and 15-MV beams, respectively, for solid water. For virtual water, the corresponding correction factors were 0.993 and 0.998 for 6- and 15-MV beams, respectively. For electron beams, the correction factors ranged from 1.013 to 1.007 for energies of 6 to 20 MeV for both solid materials. This indicated that the water-equivalency of these materials is within +/- 1.3%, making them suitable substitutes for natural water in both photon and electron beam output measurements over a wide energy range. These correction factors are slightly larger than the manufacturers' advertised values (+/- 1.0% for solid water and +/- 0.5% for virtual water). We suggest that these corrections are large enough in most cases and should be applied in the calculation of beam outputs.

Electrons↗
PubMed2002

Success with academic English: reflections of deaf college students.

The study identified social, educational, and demographic characteristics of deaf postsecondary students who demonstrated strong reading and writing skills. Questionnaire information, information from institutional databases, and in-depth personal interviews were used to identify factors and characteristics that positively influenced the attainment of strong academic literacy skills. Among the areas investigated were school experiences, reading and writing experiences, study habits and attitudes, communication preferences, personality traits, and home and family background. Results of the study generally support previous work conducted with talented hearing youth. Several primary themes emerged from the study: heavy parental involvement in early education and educational decisions, differing modes of communication but extensive family communication, early exposure to and intensive experiences with reading and writing, an enjoyment of reading, a relatively limited social life, high parental and secondary school expectations, the importance of television, and positive self-image.

Achievement↗
PubMed2005

Selecting patients for flexible sigmoidoscopy. Determinants of incomplete depth of insertion.

BACKGROUND: Flexible sigmoidoscopy (FS) is an effective method to prevent and reduce mortality from colorectal carcinoma (CRC). Incomplete depth of insertion (IDI) during FS may result in missed polyps and carcinomas. To determine whether it is possible to predict IDI, the authors analyzed factors that affected the depth of insertion in FS. METHODS: For the current study, FS results were recorded prospectively over a 5-year period. A questionnaire was administered to the patient by the investigator prior to FS to collect data, including age, gender, weight, comorbid illnesses, history of prior abdominal and pelvic surgeries, family history of colon carcinoma or polyps, and prior FS or colonoscopies. The depth of insertion of the flexible sigmoidoscope from the anal verge, which was defined as the reading on the outside of the instrument at its maximal insertion, was measured in centimeters. IDI was defined as a depth of insertion < 50 cm. Classification and regression tree analysis was used to develop a model that included variables predictive of IDI. RESULTS: The best classification tree included gender, age < 69 years (in women), and a history of hysterectomy. Men had a < 5% risk of an IDI and women age < 69 years without a hysterectomy fared as well (6.6%). Older women and younger women who underwent hysterectomy had higher rates of IDI (29.2% and 22.3%, respectively.) CONCLUSIONS: The authors developed a model based on age, gender, and hysterectomy status that, after further validation, may be useful for predicting which patients likely will have an incomplete examination. In those patients who have a high probability of IDI, the choice can be made to offer colonoscopy or perform FS under sedation, with analgesia, or with the help of distraction techniques.

Age Distribution↗
PubMed1998

[Correlations between factors and intraocular pressure following photorefractive keratectomy].

OBJECTIVE: To evaluate the factors related to intraocular pressure (IOP) after excimer laser photorefractive keratectomy (PRK). METHODS: 86 cases 150 eyes of myopia followed over six months after PRK were studied with noncontact tonometer (NCT). RESULT: After PRK, a decrease in the IOP was observed. Post-operatively, the IOP reading at 1st month was the highest. The reduction of IOP may be related to the decrease in corneal thickness and corneal curvature (r = 0.361, P < 0.01; r = 0.188, P < 0.05). Regression equation for IOP drop (kPa) = - 0.059 - 0.038X(1) + 0.009X(2)[X(1) = ablation depth (microm), X(2) = decrease in corneal curvature (D)]. CONCLUSION: IOP readings after PRK are influenced by corneal thickness, corneal curvature and eye drug times.

Adult↗
PubMedDate not supplied

Ultrasound biomicroscopy of tangential keratotomy incision depth after penetrating keratoplasty.

PURPOSE: To assess the accuracy and reproducibility of using ultrasound biomicroscopy to measure corneal refractive incisions in vivo. SETTINGS: Department of Ophthalmology, University of Vienna, Austria. METHODS: Ultrasound biomicroscopy was performed in five eyes of five patients who had previous tangential keratotomy for high postkeratoplasty astigmatism. Depth of the incision scar was documented, and the measurements were compared with those obtained preoperatively by ultrasound pachymetry readings of the corneal thickness and with the settings of the diamond knife blade. RESULTS: The measured depths reached 84.7% +/- 12.9 (SD) of corneal thickness compared with the intended 89.1 +/- 6.7% depth of incision. The relation between knife setting and achieved depth was 95.3 +/- 15.9%. CONCLUSION: Ultrasound biomicroscopy provided high-quality images of the incision scars, accurately measuring actual incision depth in vivo. It may become a clinically useful tool for the refractive surgeon as it contributes to the predictability and accuracy of keratorefractive procedures.

Astigmatism↗
PubMed1995

Clinical effectiveness of fluoride-releasing elastomers. II. Enamel microhardness levels.

The purpose of this study was to examine the effect of fluoride-releasing elastomers on enamel microhardness levels. Sixteen teeth from four patients scheduled to have premolars extracted as part of their orthodontic treatment were examined in this study. Orthodontic brackets were bonded to the buccal surface of the test teeth with a nonfluoridated adhesive. Two of the patients had fluoride-releasing elastomers placed on the right upper and lower brackets and conventional elastomers placed on the left side. This sequence was reversed for the remaining two patients. After 1 calendar month, the experimental teeth were extracted, sectioned, and embedded in acrylic. Microhardness tests were performed 50 to 75 microns cervical to the bracket. Indentations were taken at the surface and continued in 20 microns increments to a depth of 200 microns. Results showed the enamel was significantly harder (p < 0.05) in the fluoride group at the 20 microns depth compared with the control group. No other microhardness readings showed a statistically significant difference.

Delayed-Action Preparations↗
PubMed1994

Issues in chemical dependency treatment and aftercare for people with learning differences.

Without major adaptations, current substance abuse treatment models may not be productive for people with learning differences. The study described in this article examined ways to create accessibility to generic chemical dependency treatment for people with learning differences. A key informant survey of chemical dependency workers and developmental disabilities workers was conducted to determine the needs of chemical dependency treatment programs, staff, and people with learning differences in making treatment accessible. Training and information needs were identified, and responses were compared between the two groups of providers. Chemical dependency treatment staff need more information and training on differing learning and socialization skills, differences in reading comprehension, and personal prejudices or stereotypes. In-depth screening is also required to determine the appropriateness of integrated or specialized services or some combination of both.

Adult↗
PubMed2006

Illness trajectories in Mexican children with juvenile idiopathic arthritis and their parents.

BACKGROUND: We hypothesize that the qualitative approach of socio-cultural aspects in children with juvenile idiopathic arthritis (JIA) and their parents would improve the understanding of their illness. OBJECTIVE: To explain the phenomenon of experiencing JIA within a specific cultural context. METHODS: The theoretical position of this research was based on the substantive theories of suffering, explanatory models and illness experience. Its design was that of qualitative field, and its analysis followed the interpretative grounded theory methodology. Data were collected by in-depth interviews and notes; tape recordings were transcribed verbatim, read and imported into the ATLAS/ti 4.2 software. Data conceptualization, categorization and interpretation were based on the constant comparison method. RESULTS: A total of 16 adults and six children from 10 families were interviewed. 'Pilgrimage' (metaphorically referred by some of the parents) was a major code in the study that reflected the religious reference to the trajectory of pain, faith and hope. For children, pilgrimage was conformed by immediate concepts; for parents, by historical and immediate experiences influenced by JIA subtype. Pilgrimage was consistent with the model of the illness trajectory theory, which conceptually relates to the idea that the course of chronic diseases is variable and modifiable throughout time. CONCLUSION: The qualitative approach of JIA provides wide and deep information on the perception that children and parents have about the disease. The illness trajectory theory corresponds to pilgrimage, the theoretical model for JIA in this study.

Adolescent↗
PubMed1992

A thermoluminescent dosimetry intercomparison in operational power station fields.

A dosimetry intercomparison was held among the five agencies in Canada that are recognized by the Atomic Energy Control Board as competent to perform external dosimetry. Exposures of thermoluminescent dosimeter badges were made under operational conditions to radiation fields in Candu nuclear generating stations. Details of the method are described including the large, block-type phantoms (with a rotating front face so that all badges were equally exposed) and a small device to measure the depth-dose distribution. Thirty-six exposures (or "runs") were made, exposing 522 badges for periods of 1 h-2 d. Normalization between the runs was based on the absorbed dose at 1,000 mg cm-2 for each run, as measured by the depth-dose device. Using this method, the average relative readings for the five participants ranged from 1.01-1.40 (dimensionless).

Canada↗
PubMedDate not supplied

Magnetic resonance sounding applied to aquifer characterization.

Magnetic resonance sounding (MRS) is distinguished from other geophysical tools used for ground water investigation by the fact that it measures a magnetic resonance signal generated directly from subsurface water molecules. An alternating current pulse energizes a wire loop on the ground surface and the MRS signal is generated; subsurface water is indicated, with a high degree of reliability, by nonzero amplitude readings. Measurements with varied pulse magnitudes then reveal the depth and thickness of water saturated layers. The hydraulic conductivity of aquifers can also be estimated using boreholes for calibration. MRS can be used for both predicting the yield of water supply wells and for interpolation between boreholes, thereby reducing the number of holes required for hydrogeological modeling. An example of the practical application of MRS combined with two-dimensional electrical imaging, in the Kerbernez and Kerien catchments area of France, demonstrates the efficiency of the technique.

Electric Conductivity↗
PubMed2006

Automated SNP detection from a large collection of white spruce expressed sequences: contributing factors and approaches for the categorization of SNPs.

BACKGROUND: High-throughput genotyping technologies represent a highly efficient way to accelerate genetic mapping and enable association studies. As a first step toward this goal, we aimed to develop a resource of candidate Single Nucleotide Polymorphisms (SNP) in white spruce (Picea glauca [Moench] Voss), a softwood tree of major economic importance. RESULTS: A white spruce SNP resource encompassing 12,264 SNPs was constructed from a set of 6,459 contigs derived from Expressed Sequence Tags (EST) and by using the bayesian-based statistical software PolyBayes. Several parameters influencing the SNP prediction were analysed including the a priori expected polymorphism, the probability score (PSNP), and the contig depth and length. SNP detection in 3' and 5' reads from the same clones revealed a level of inconsistency between overlapping sequences as low as 1%. A subset of 245 predicted SNPs were verified through the independent resequencing of genomic DNA of a genotype also used to prepare cDNA libraries. The validation rate reached a maximum of 85% for SNPs predicted with either PSNP > or = 0.95 or > or = 0.99. A total of 9,310 SNPs were detected by using PSNP > or = 0.95 as a criterion. The SNPs were distributed among 3,590 contigs encompassing an array of broad functional categories, with an overall frequency of 1 SNP per 700 nucleotide sites. Experimental and statistical approaches were used to evaluate the proportion of paralogous SNPs, with estimates in the range of 8 to 12%. The 3,789 coding SNPs identified through coding region annotation and ORF prediction, were distributed into 39% nonsynonymous and 61% synonymous substitutions. Overall, there were 0.9 SNP per 1,000 nonsynonymous sites and 5.2 SNPs per 1,000 synonymous sites, for a genome-wide nonsynonymous to synonymous substitution rate ratio (Ka/Ks) of 0.17. CONCLUSION: We integrated the SNP data in the ForestTreeDB database along with functional annotations to provide a tool facilitating the choice of candidate genes for mapping purposes or association studies.

Algorithms↗
PubMed1987

Periodontally diseased vs. normal roots as evaluated by scanning electron microscopy and electron probe analysis.

A scanning electron microscope and electron probe study was carried out to compare root structure from deep within periodontal pockets with roots exhibiting no periodontal disease. To eliminate the possibility of extraneous ion introduction or deletion, no attempt was made to subject the roots to fixation, embedding, or dehydration prior to sectioning and viewing in the electron microscope. Mineral content and concentration were determined with an electron probe on two specimens per tooth. On one specimen, only the external cemental surface was analyzed. On an adjacent cross section, readings were taken from the surface and at incremental depths into the root. A nonparametric statistical analysis compared diseased with nondiseased roots. The following conclusions can be drawn from the study: (1) Consistent and repeatable qualitative electron probe analyses can be performed on human teeth with minimal specimen preparation. This gives a more accurate assessment, since the integrity of the crystalline structure is not disrupted. (2) Minerals consistently found were P, Ca, Cu, Zn, Mg and Na. They were in similar concentrations throughout the area analyzed. (3) Mg and Cu showed higher values in the nondiseased teeth. (4) There were no differences in concentrations for Ca, P, Zn, and Na between roots exposed to a periodontal pocket and nondiseased roots.

Copper↗
PubMed1999

Outcomes data made easy.

Dx Index is a quick and easy method for quantifying patients' oral health. A number scale from 1 to 10 provides an easy-to-understand assessment of the dental health status of either an individual or a large group. During routine oral examinations, areas such as decayed teeth, pocket depth, inflammation and oral hygiene are numbered by level. Reading the lowest number on a chart pertaining to these categories gives a rapid overall score of dental health.

DMF Index↗