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At least 1,099 records · Page 61Linked to original sources
PubMed1997

Determination of the foveal cone spacing by ocular speckle interferometry: limiting factors and acuity predictions.

We have developed a high-resolution imaging technique, based on speckle interferometry, for the objective determination of the cone spacing in the living human fovea. The spatial resolution attained with this technique is theoretically diffraction limited by the pupil size. However, the highest frequency that we measure varies greatly among subjects, especially for fully dilated pupils. We have conducted several experiments (determination of the cutoff frequency of ocular speckle interferometry, the double-pass modulation transfer function, and the Stiles-Crawford effect) that indicate that, as expected, the resolution is not limited by the incoherent modulation transfer function. We found, though, a high correlation between the cutoff frequency and the width of the eye's Stiles-Crawford function. This implies that the resolution depends on the structural properties of the cone mosaic itself. In addition, we have compared the Nyquist frequency of the cone mosaic, determined objectively by our technique, with the grating visual acuity measured in the same eyes at the same foveal eccentricities. For our subjects, visual resolution nearly matches the Nyquist frequency within the fovea, except at the foveal center, where the optical transfer function of the eye attenuates the contrast of frequencies close to the Nyquist limit to a value below threshold.

Cell Count↗
PubMed1999

Gardening work and heavy metals in urban environment.

Urban soil may be a source of occupational exposure to various pollutants in gardening and land cultivation. This paper presents data of a one-year follow-up of lead, cadmium, nickel, chromium, and vanadium in the environment of the city of Bologna. Samples of soil and leaves were collected at three locations; gardens from the inner-city high-traffic area, parks in moderate-traffic area, and parks in suburban, low-traffic area. The top and deeper layers of soil and leaves were mainly polluted by lead at all locations, which corresponded to the traffic density. Personal samplers recorded greater concentrations of airborne metals than did the area samplers but the values kept below the threshold limit established by the American Conference of Governmental Industrial Hygienists for the working environment. Due to cumulative nature and interactive effects of toxic metals with other toxic and essential elements, long-term exposure to metals in the urban environment may be a health risk for occupationally exposed gardeners.

Cadmium↗
PubMed2001

Case work guidelines and interpretation of short tandem repeat complex mixture analysis.

Interpretation guidelines for short tandem repeat casework analysis are difficult to construct. As soon as a set of guidelines are developed, a new case evolves that does not fit the painstakingly written document. The casework analysts gather and amend the guidelines again, and again. This article seeks to demonstrate that general guidelines can be set and written such that it can be used for any detection format. Guidelines published by the Scientific Working Group for DNA Analysis Methods, a working group of DNA forensic experts in the United States, are used to set the format for the written protocol on interpretations. The rule "the interpretation of results in casework is a matter of professional judgment and expertise. Not every situation can or should be covered by a preset rule" is stressed. Development of minimum and maximum threshold values, heterozygote ratios, stochastic limits, and determination of major and minor components based on validation studies is discussed. The paper travels through setting criteria to evaluate internal lane standards and amplification controls. It continues with establishing ranges for interpretation and defining true alleles versus anomalies. Examples of a variety of profiles are given and the potential interpretation, using signal intensities and genetics. In addition, report writing strategies and wording routinely used by the Pennsylvania State Police DNA Laboratory System are given.

Alleles↗
PubMedDate not supplied

[Particulate matter (PM10) air pollution, daily mortality, and hospital admissions: recent findings].

The first studies conducted to evaluate a possible association between air pollution and mortality date back to the serious events that occurred in the Mosa Valley, Belgium (1930), in the small city of Donora ("killer fog" incident of 1948) and in London (1952). The latter episode led to the introduction of air pollution control policies. Following the introduction of air pollution control measures in economically advanced cities in the 60s and 70s, the concentration levels of pollutants reached were believed, for many years, to be risk free. However, despite improvements in air quality achieved by many industrialized countries the negative effects of air pollution remain today an important public health problem. Among all air pollutants, particulate matter is the type of air pollution that causes the most numerous and serious effects on human health, because of the broad range of diverse toxic substances it contains,. For this reason, when assessing human health risk, PM10 may be considered to be a reliable indicator of the impact of global air pollution. Various epidemiologic studies conducted in the last 10 years, such as the Air Pollution and Health-European Approach (APHEA) project, the National Morbidity, Mortality and Air Pollution (NMMAPS) Study and Italian Meta-analysis of Studies on the short-term effects of Air pollution (MISA), have shown that current ambient concentrations of PM10 may lead to increased mortality and morbidity. Various studies have reported mean increases in mortality below 1% for 10 ?g/mc increases of ambient PM10. Studies have also underscored the role of particulate matter in aggravating cardiorespiratory diseases and consequently increasing hospital admissions. Air quality standards have been recently revised by legislation. The EU has issued a directive that sets limiting values and, where appropriate, threshold values, for the different air pollutants.

Air Pollution↗
PubMed1986

[Computerized tomography studies in the assessment of radiogenic pneumopathy in an animal experiment].

An animal experimental study was conducted in 56 piglets exposed to radiation to establish new assessment criteria on radiogenic pneumopathy by employing computed tomography for diagnosis. The accurately measurable density changes in the lung parenchyma exposed to radiation appear invariably as soon as a dose-dependent threshold value is exceeded. Tolerance limits can be determined for 60Co and neutron irradiation in different fractions and single doses, the enhancement of lung density being correlated with the irradiation dose. It is not possible to establish a volume-dependent decrease in the tolerance dose. Likewise, there is no radiation-promoted co-reaction of adjacent pulmonary tissue not subjected to irradiation exposure. These results apply to the experimental animals used in the study.

Animals↗
PubMed1997

The effect of threshold amounts for reporting malpractice payments to the National Practitioner Data Bank: analysis using the closed claims data base of the Office of the Assistant Secretary of Defense (Health Affairs).

The study determines the extent to which payment thresholds for reporting malpractice claims to the National Practitioner Data Bank identifies substandard health care delivery in the Department of Defense. Relevant data were available on 2,291 of 2,576 medical malpractice claims reported to the closed medical malpractice case data base of the Office of the Assistant Secretary of Defense (Health Affairs). Amount paid was analyzed as a diagnostic test using standard of care assessment from each military Surgeon General office as the criterion. Using different paid threshold amounts per claim as a positive test, the sensitivity of identifying substandard care declined from 0.69 for all paid cases to 0.41 for claims over $40,000. Specificity increased from 0.75 for all paid claims to 0.89 for claims over $40,000. Positive and negative predictive values and likelihood ratio were similar at all thresholds. Malpractice case payment was of limited value for identifying substandard medical practice. All paid claims missed about 30% of substandard care, and reported about 25% of acceptable medical practice.

Government Agencies↗
PubMed2003

Replica-free evaluation of the neuronal population information with mixed continuous and discrete stimuli: from the linear to the asymptotic regime.

Recent studies have explored theoretically the ability of populations of neurons to carry information about a set of stimuli, both in the case of purely discrete or purely continuous stimuli, and in the case of multidimensional continuous angular and discrete correlates, in the presence of additional quenched disorder in the distribution. An analytical expression for the mutual information has been obtained in the limit of large noise by means of the replica trick. Here, we show that the same results can actually be obtained in most cases without the use of replicas, by means of a much simpler expansion of the logarithm. Fitting the theoretical model to real neuronal data, we show that the introduction of correlations in the quenched disorder improves the fit, suggesting a possible role of signal correlations-actually detected in real data-in a redundant code. We show that even in the more difficult analysis of the asymptotic regime, an explicit expression for the mutual information can be obtained without resorting to the replica trick despite the presence of quenched disorder, both with a Gaussian and with a more realistic thresholded-Gaussian model. When the stimuli are mixed continuous and discrete, we find that with both models the information seem to grow logarithmically to infinity with the number of neurons and with the inverse of the noise, even though the exact general dependence cannot be derived explicitly for the thresholded-Gaussian model. In the large noise limit, lower values of information were obtained with the thresholded-Gaussian model, for a fixed value of the noise and of the population size. On the contrary, in the asymptotic regime, with very low values of the noise, a lower information value is obtained with the Gaussian model.

Animals↗
PubMed1981

Predictive value and threshold detectability of lung tumors.

The visibility limit of soft tissue nodules in the lungs is 3 mm on a chest radiography, yet lung cancers are rarely detected until the tumors are 8-10 mm in size. This paper presents data on the size distribution of nodular lung cancers and noncancerous nodular noise on chest radiographs. These data are analyzed in decision-making terms and show that when the size is 8-10 mm, observers can separate true cancers from noise that mimics cancer, with a probability of being correct, or a predictive value, of 90% or more.

Decision Making↗
PubMedDate not supplied

[Proposed microbiological indexes for the assessment of air quality in buildings].

An assessment of biological risk in the workplace requires the measurement of microorganisms present in the air. Although it is currently difficult to establish a dose-response relationship on the basis of existing epidemiological data, the number and types of microorganisms present offer a useful index when evaluating the quality of the air. Using the results obtained from a study of 226 different offices located in buildings equipped with forced ventilation we propose an assessment of contamination levels based on a Global Index of Microbial Contamination/m3 (GIMC/m3). This index is calculated as the sum of the values of the total microbial count determined for mesophilic bacteria, psychrophilic bacteria and fungi in all sampled areas. GIMC/m3 fluctuates between a minimum value of 23 and a maximum value of 18.069: the mean value varies depending on the ventilation system mode setting, with a value of 145 when operating in the heating mode, 265 in the air-conditioning mode and 258 under simple forced ventilation. 95.5% of the offices under study had a GIMC/m3 value of below 1000: this value is proposed as a threshold limit above which a more extensive assessment of contamination levels based on the measurement of further microbiological indexes should be carried out. To this aim we propose an Index of Mesophilic bacterial Contamination (IMC), obtained by calculating the ratio between the CFU/m3 value measured for mesophilic and psychrophilic bacteria in the same sampling point. The measurement of the Amplification Index (AI) completes the evaluation and this is determined by calculating the ratio between the GICM/m3 values measured inside the building and those measured outside. When considering these observations as a whole we are able to classify the various work areas under study into groups and categories according to the observed values of the proposed microbial contamination indexes.

Air Microbiology↗
PubMed2005

Aesthetic thresholds and blackening of stone buildings.

This work investigates public perception of the blackening of light coloured stone historic buildings in some European countries. It used on-site questionnaires to explore the perceived lightness of the façades in terms of opinions that the building is dirty or needs cleaning. There was a clear relation between opinions about the dirtiness of a building and views that it should be cleaned. Visitors to buildings found the assignment of colour or a grey scale value to buildings relatively easy despite the fact that they are typically made up of many shades. There was a strong relationship between the perceived lightness of a building and the opinion that it was dirty. This relationship was used to establish potential levels of blackening that may be publicly acceptable and propose some aesthetic thresholds. Such thresholds suggest approaches to setting limit values for elemental carbon in the air, such that significant buildings do not become unacceptably discoloured. Developments of this kind contribute to the regulation of non health aspects of air pollution and aid decision making in the management of significant buildings.

Air Pollution↗
PubMed1991

Comparative evaluation of three ambulatory plethysmographic devices as regards accuracy and handling in daily practice.

We compared a computed strain gauge plethysmograph (SGP1) with a Gutmann strain gauge plethysmograph (SGP2) and a photoplethysmograph (PPG) in 24 normal and 12 radiologically proven postphlebitic limbs with respect to assessment of the calf pump function, discrimination between normal and pathologic values, and handling. Recovery time (RT50), refilling volume (RV) and the Index (RT50xRV) were measured at the ankle and the calf in each limb after 20 dorsiflexions of the feet in the sitting position. The PPG device could only measure RT50. There was a strong positive correlation in RT50, RV and Index values between SGP1 and SGP2 at the ankle and at the calf (p less than 0.001), but none in RT50 ankle and calf values between PPG and SGP1 (p = 0.1) and PPG and SGP2 (p = 0.1). The comparison between normal and postphlebitic limbs revealed significant differences for all three values RT50, RV and Index only for SGP1 ankle measurements (p less than 0.02, p less than 0.01, respectively). Ankle RT50 values were significantly longer than calf RT50 values for both strain gauge devices (p less than 0.01), where PPG results were not influenced by the site of measurement. The average number of tests required to obtain a valid curve in each limb at the ankle and calf was lowest for SGP1 measurements. Vein calf pump function is easily and accurately assessed by SGP1 ankle measurements. However a threshold limit between normal and pathologic values can not be defined either for RT50 or for RV values in the individual case, and the creation of an Index adds little to solve this problem.

Adult↗
PubMed2006

Upper susceptibility threshold limits with confidence intervals: a method to identify normal and abnormal population values for laboratory toxicological parameters, based on acetylcholinesterase activities in sea lice.

The interpretation and importance of comparing field values of susceptibility to pesticides with a laboratory reference strain that might bear little resemblance to the actual situation in the field are problematic and a continuing subject of debate. In this paper a procedure for defining a 'normal sensitive' population from a field study of 383 individuals to provide a basis for analysing and interpreting in vitro results is described and examined. Instead of using only the 95th percentile, the upper and lower confidence limits for the 95th percentile were also compared to select the best estimation of the limit for the normal material. A field population constrained by the upper confidence limit for the 95th percentile provides appropriate descriptions of the normal material in this study. This approach should prove useful in studies of pesticide resistance in field populations.

Acetylcholinesterase↗
PubMedDate not supplied

Biological monitoring of occupational exposure to isoflurane by measurement of isoflurane exhaled breath.

The relationship between isoflurane environmental concentrations in operating rooms and the corresponding isoflurane concentration in the exhaled air of the operating personnel at the end of the exposure has been investigated. Isoflurane was retained in an adsorbent cartridge and after thermal desorption the concentration was estimated by gas chromatography. Significant correlation between environmental and exhaled air isoflurane concentrations allowed the establishment of a biological exposure index and biological exposure limits corresponding to proposed atmospheric threshold values.

Air↗
PubMed1991

Global tracking of the ocular fundus pattern imaged by scanning laser ophthalmoscopy.

This paper presents an algorithm for the automatic global tracking of ocular fundus landmarks in video image sequences generated by scanning laser ophthalmoscopy (SLO). The tracking algorithm is based on the computation of the discrete unnormalized cross-correlation of an interactively preselected small template and respective images in time sequences of fundus patterns. The correlation is executed with binary images derived from an automatical threshold limitation of the grey-value images. Due to the [+1/-1] representation of the binary images the unnormalized correlation functions directly relate to the Hamming distance of the template and the objects in the images. Experiments show that even templates with features distorted by noise are accurately recognized at any position. The accuracy of position detection is better than 0.4%. Possible hardware implementations of the algorithm which would reduce computation time are briefly mentioned.

Algorithms↗
PubMed2006

Role of murF in cell wall biosynthesis: isolation and characterization of a murF conditional mutant of Staphylococcus aureus.

The Staphylococcus aureus murF gene was placed under the control of a promoter inducible by IPTG (isopropyl-beta-d-thiogalactopyranoside). It was demonstrated that murF is an essential gene; it is cotranscribed with ddlA and growth rate, level of beta-lactam antibiotic resistance, and rates of transcription of the mecA and pbpB genes paralleled the rates of transcription of murF. At suboptimal concentrations of the inducer, a UDP-linked muramyl tripeptide accumulated in the cytoplasm in parallel with the decline in the amounts of the normal pentapeptide cell wall precursor. The abnormal tripeptide component incorporated into the cell wall as a monomeric muropeptide, accompanied by a decrease in the oligomerization degree of the peptidoglycan. However, incorporation of the tripeptide into the cell wall was limited to a relatively low threshold value. Further reduction of the amounts of pentapeptide cell wall precursor caused a gradual decrease in the cellular amounts of peptidoglycan, the production of a thinner peripheral cell wall, aberrant septae, and an overall increase in the diameter of the cells. The observations suggest that the role of murF exceeds its primary function in peptidoglycan biosynthesis and may also be involved in the control of cell division.

Cell Wall↗
PubMed1993

[How badly does the "normal-hearing" young man of 1992 hear in the high frequency range?].

In the course of a clinical study we examined young men believed to have normal hearing. Volunteers with a positive history for noise deafness were excluded from further study. Normal hearing was verified by pure-tone audiometry if the hearing loss did not exceed 15 dB for each test tone between 250 Hz and 8000 Hz. As this limit is far below normative threshold values (DIN ISO 7029) we expected to find a large number of otological normal subjects. Using pure-tone audiometry, ABR and noise exposure, we found that 65% of the young male volunteers (mean age 25 years) did not meet the criteria for audiologic normality. The pure-tone thresholds for these subjects were comparable to the expected levels of their fathers' generation.

Adult↗
PubMed1995

Accuracy of breath-by-breath analysis of flow-volume loop in identifying sleep-induced flow-limited breathing cycles in sleep apnoea-hypopnoea syndrome.

1. Inspiratory flow limitation is involved in the pathophysiology of sleep-related breathing disorders. Since the definition of flow-limited cycle is based on a dissociation between flow and respiratory efforts, identification of inspiratory flow limitation requires upper airway or intrathoracic pressure measurements. We examined the accuracy of the analysis of the flow-volume loop of a tidal breath in identifying inspiratory flow limitation during sleep in ten patients with a sleep apnoea-hypopnoea syndrome. 2. Measurements were taken during continuous positive airway pressure trials. After data acquisition, the presence of inspiratory flow limitation was identified by the presence of an inspiratory plateau or decrease in inspiratory flow independently of the increase in inspiratory efforts. The flow-volume loop was reconstructed for each breathing cycle by plotting the instantaneous flow and the tidal volume. The instantaneous inspiratory and expiratory flows were measured at 50% of the respective portion of the tidal volume, and a breath-by-breath analysis of the mid-tidal volume-flow ratio (inspiratory/expiratory ratio) was obtained. The analysis of the flow-volume loop was compared with standard inspiratory flow limitation criteria using different values of the inspiratory/expiratory ratio threshold, below which breathing cycles were classified as flow-limited. With a lower limit of the normal inspiratory/expiratory ratio threshold of 0.97, the sensitivity and specificity of the method were both 76%. In each subject, the proportion of breathing cycles identified as flow-progressively decreased with an increasing positive pressure level.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed2005

Fluoride intake and fractional urinary fluoride excretion of Colombian preschool children.

AIMS: The purpose of this study was to assess the total fluoride intake and the fractional urinary fluoride excretion (FUFE) relative to the customary daily fluoride (F) ingestion in preschool children between 48-59 months of age. DESIGN: Total fluoride ingestion, from dietary and toothpaste samples was determined in 120 young children, dwellers of four Colombian cities. A "duplicate plate" technique was used. In Colombia, table salt is fluoridated to a concentration of between 180-220 mg F/kg. Individual (n=96) FUFE values were calculated as the ratio between the total amount of F excreted in the urine and the total amount of F ingested, over a 24-hour period. RESULTS: The average daily F-intake was 0.098 mg F/kg/day; 95% C.I. = 0.085-0.111 mg F/kg/day. The proportion of fluoride ingestion from toothpaste to the total fluoride intake was higher than 66% in all cities. The average FUFE values of subjects from each of the four Colombian cities under study did not differ significantly (ANOVA; p >0.91). The average 24-hour FUFE value for preschool children was 0.33; 95% C.I. = 0.29-0.37. CONCLUSIONS: The results obtained suggest that preschool children residing in Colombian urban areas are ingesting amounts of fluoride above the upper limit of the proposed safe threshold. FUFE values are similar to those reported in previous studies where daily F-doses were equal or higher than 0.064 mg F/kg.

Beverages↗