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At least 973 records · Page 54Linked to original sources
PubMed1991

Auditory localization under conditions of unilateral fitting of different hearing aid systems.

The spatial localization function of hearing-impaired listeners, usually fitted bilaterally with BTE, ITE or ITC devices, was tested under conditions of unilateral fitting of each of their own hearing aids, and unilateral fitting of stock versions of each of the other types. For the BTE wearers average localization accuracy and individual variability were not greatly changed when wearing only their left ear device, compared with bilateral aided performance. In ITE wearers, unilateral fitting in either ear led to somewhat poorer performance than bilateral. In the ITC wearers unilateral fitting produced inconsistent outcomes. Both BTE and ITE wearers fared poorly when fitted unilaterally with stock forms of devices 'foreign' to them, whereas ITC wearers did not show such a contrasting outcome. A group of non-impaired listeners showed severe disruption of localization under unilateral BTE and ITC hearing aid conditions, and to a lesser extent with ITEs. Results for the hearing-impaired listeners are interpreted in terms of adaptation to different usage patterns, with BTE wearers suggested as having adapted to their own systems unilaterally as well as bilaterally.

Auditory Threshold↗
PubMed2003

A system to assess fitness of dairy cows responding to exercise training.

Objectives were to develop a system to administer exercise training to dairy cows, to measure potential physiological indicators of fitness, and to assess physical fitness. Nonlactating, nonpregnant multiparous Holstein cows (n = 19) were in one of three exercise training treatments: no exercise; 1-h exercise; or 2-h exercise by walking 3 km/h every other day for 60 d in a mechanical walker. Treadmill tests on d 15, 30, 45, and 60 consisted of walking (5 km/h) with 1.6% increases in slope at 3-min intervals until heart rates reached 180 beats per minute (experimentally specified maximum) or until cows refused to walk. Fitness indices analyzed in tests as single datum points at maximal heart rates were length of time of test, heart rate, and plasma L-lactate concentration at end of the test, and change in heart rate and lactate concentration during the test. Exercised (1 or 2 h) cows had longer times to end of tests than nonexercised cows. Maximal and change in heart rates or plasma lactate during tests did not indicate improved physical fitness. However, when all data were evaluated as repeated measures of day and minute of tests, reductions of heart rates and plasma lactate concentrations were greatest on d 60 between exercised and nonexercised cows indicating improved fitness. Acid-base measurements were not found useful in this study. Changes of heart rates and plasma lactate concentrations over time (repeated measures) of treadmill tests quantified the physical fitness of dairy cows and can be used to compare potential responses to different exercise training treatments in this system.

Acid-Base Equilibrium↗
PubMed1982

Attaining and measuring physical fitness in dairy cattle.

Research with dairy cows was to determine whether dairy cows in confinement are in poor physical condition, if programmed exercise improves physical fitness, and which physiological measures are most useful indicators of physical fitness. If maintenance of physiologic homeostasis when an animal is under a work load is a valid criterion of physical fitness, dairy cows in confinement are in poor physical condition, and physical fitness can be improved by programmed exercise. Walking cows at 4 km/h for a distance of 8 km daily for 5 days per wk for 8 wk prepartum improved their physical fitness. Useful hemic indicators of improved fitness were less increase in erythrocyte numbers and hemoglobin concentration and less decrease in oxygen tension, carbon dioxide, carbonic acid contents, and base excess than in poorly conditioned cattle under work load. Venous blood was satisfactory for these measurements. Also valued were heart and respiratory rates, except these rates being sensitive to extraneous disturbances may be less reliable.

Animals↗
PubMed2001

Cerebellar fits in children with Chiari I malformation.

OBJECT: The authors describe a series of children with Chiari I malformation who presented with fulminating symptoms of "cerebellar fits" characterized by drop attacks with or without deterioration of consciousness, opisthotonic posturing, and varying degrees of respiratory compromise. METHODS: A retrospective analysis was undertaken of the medical records of 47 consecutive patients undergoing surgery for symptomatic Chiari I malformations at Rainbow Babies and Children's Hospital. Thirteen (28%) of the 47 patients presented with complaints consistent with cerebellar fits. Before the correct diagnosis was made, nine (69%) of the 13 children had previously undergone evaluation with electroencephalography and/or electrocardicography and Holter monitoring because of suspected cortical epilepsy or cardiogenic syncope. In each of the 13 children magnetic resonance imaging demonstrated pegged cerebellar tonsils herniated below the foramen magnum. A deep indentation or blanched discoloration of the cerebellar tonsils was noted in five (38%) of these 13 patients at the time of surgery. Of patients with symptomatic Chiari I malformations, the mean degree of tonsillar herniation was significantly less for those in whom cerebellar fits occurred than those in whom they were absent (8.8 mm and 13.9 mm, respectively; p = 0.007). In only one of the patients with cerebellar fits was a syrinx present, and this was a small focal lower thoracic collection. Spells resolved after surgery in all patients who presented with cerebellar fits. CONCLUSIONS: Cerebellar fits may mimic other disorders such as cardiogenic syncope and epileptic seizures. The correct diagnosis may be delayed or the conditions may be misdiagnosed by those who fail to consider Chiari I malformation as a cause of drop attacks, abnormal extensor posturing, and apneic spells in children. The response to decompressive surgery in these patients is gratifying.

Adolescent↗
PubMedDate not supplied

Evaluation of the precision of fit between the Procera custom abutment and various implant systems.

PURPOSE: It has been suggested that the CAD/CAM Procera custom abutment may be universally applied with multiple implant systems. An acceptable fit between the internal hexagon of an abutment and the external hexagon of various implant systems, along with true interchangeability of the Procera abutment screw, would support this concept. This study determined the precision of fit of the CAD/CAM-produced Procera abutment onto the external hexagon and bearing surfaces of implants from 6 implant manufacturers and the interchangeability of the Procera abutment screw with these systems. MATERIALS AND METHODS: This investigation consisted of 3 parts: (1) direct measurement of the internal hexagon and bearing surface of each Procera abutment and the external hexagon and the bearing surface of 6 implants from 6 different systems, (2) radiographic examination of 30 Procera abutment-implant junctions following tightening to 32 Ncm to determine the precision of fit between the bearing surfaces and the top of the external hexagon of the implant with the superior surface of the internal hexagon of the abutment, and (3) examination of 3 abutment screws and 3 implants from the various manufacturers for interchangeability based on American National Standards. RESULTS: The mean flat-to-flat external hexagons of the implants measured between 2.67 and 2.69 mm. The Procera abutment's flat-to-flat internal hexagon measured 2.73 mm. The height of the various implant systems' external hexagon ranged from 0.69 to 0.81 mm. The height of the Procera abutment blanks was 0.90 mm. Radiographic examination demonstrated that not all of the manufacturers' screws fit appropriately within the internal screw bore of the Procera abutment. The internal bore of all implant systems studied had a metric thread designation of M2 x 0.4 - 6H. The metric thread designation of all abutment screws examined was M2 x 0.4 - 6g. The greatest variations in the dimensions of the abutment screws measured were seen in the diameter of the screw head, which ranged from 2.12 to 2.69 mm. DISCUSSION: The Procera abutment's internal hexagon fit the external hexagon of all implant systems evaluated. The Procera abutment screw fit the internal screw bore of the implant systems tested. CONCLUSION: The Procera abutment with its screw can be universally applied to the implant systems studied. This fact, plus the CAD/CAM feature of this system, would thus provide a dynamic approach to satisfying the design and spatial needs of implant placements observed clinically.

Computer-Aided Design↗
PubMedDate not supplied

Improving the fit of implant-supported superstructures using the spark erosion technique.

PURPOSE: The purpose of this study was to determine whether the passive fit of the implant-retained single-cast framework could be improved by spark erosion treatment. MATERIALS AND METHODS: An initial cast was produced in a transparent resin material. Five Branemark System implants were arranged in the interforaminal region, and abutments were placed on them with a torque of 20 Ncm. An impression was made using a standard impression technique described by Branemark. A corresponding master cast suitable for the spark erosion post-framework fabrication was produced. From this master cast, 12 frameworks were produced in a conventional single-cast procedure. Six of these were made of a high-gold alloy (Stabilor G); the other 6 were made of pure titanium (Biotan). These frameworks were then refined using the SAE Secotec Spark Erosion System. To measure the accuracy of the framework fit, the frameworks were measured before and after the spark erosion treatment using 2 different measurement methods-scanning electron microscopy to measure the gap widths (Sheffield test) and photoelastic stress analysis. RESULTS: The results of both measurement techniques correlated and demonstrated significant improvement in the accuracy of fit or in the passive fit for all 12 frameworks after spark erosion treatment. This improvement was statistically significant for the titanium frameworks. DISCUSSION: Dental practitioners and technicians should strive to achieve a precise passive fit of frameworks and superstructures to minimize additional stress at the interfaces of the prosthesis, abutment, and implant. CONCLUSION: The clinical use of the spark erosion technique to refine framework fit is recommended. (More than 50 references.)

Birefringence↗
PubMedDate not supplied

An innovative method for evaluation of the 3-D internal fit of CAD/CAM crowns fabricated after direct optical versus indirect laser scan digitizing.

PURPOSE: A procedure for 3-D analysis of the internal fit of fixed restorations has been developed. This study tested this method for investigating the fit of all-ceramic crowns. MATERIALS AND METHODS: Twelve data sets of a prepared maxillary canine were acquired by direct digitizing of the metal master die (CEREC 3 camera) and by digitizing gypsum dies after conventional impression taking (CEREC 3 scan), respectively. Using these data sets, 24 all-ceramic single crowns each were machined out of two glass-ceramics. The method is based on duplicated gypsum dies of the metal master, which were made for each crown. The space between the duplicate die and the internal surface of the respective crown was filled with a low-viscosity addition silicone. These silicone films (replicas) and their corresponding dies were digitized in the same measuring position. The internal fit was calculated and quantitatively and qualitatively analyzed. RESULTS: The mean and maximum positive deviations were 348 microm and 986 microm (camera), respectively, and 294 microm and 830 microm (scan), respectively, for Vitablocs Mk II and 332 microm and 920 microm (camera), respectively, and 307 microm and 852 microm (scan), respectively, for ProCAD. For both systems, the deviations were highest at the edges. CEREC scan yielded significantly better internal fit accuracy compared to the CEREC camera. CONCLUSION: Evaluation of the internal 3-D fit using the innovative method proved to be suitable. Indirect data acquisition using impression taking showed improved internal fit compared with the direct procedure. However, the differences between the data-acquisition techniques are small compared to their absolute values.

Calcium Sulfate↗
PubMed2005

[Effect of camera control devices of Cerec 2 on the fit of CAD/CAM all-ceramic copyings of posterior tooth].

OBJECTIVE: To investigate the effect of camera control devices of Cerec 2 on the fit of CAD/CAM all-ceramic copyings of posterior tooth. METHODS: 24 all-ceramic copyings were made by Cerec 2 with camera control devices and that without camera control devices. Copyings were embed and sectioned, then SEM and image analyzer was used to measure the space between the copyings and dies at the marginal opening, the axial wall, and the occlusal adaptation at the measurement locations. RESULTS: The marginal fit at buccal space of copyings with camera control devices group was smaller than that without camera control devices group (P < 0.05). The internal fit of of copyings had statistically significant difference at mesio-axial, disto-axial, bucco-axial, bucco-occlusal, linguo-occlusal and disto-occlusal space between camera control device group and without camera control devices group (P < 0.05). There was no statistical difference on the marginal fit and internal fit of copyings between Vita MK II and porous alumina oxide (P < 0.05). CONCLUSION: The Cerec 2 with camera control devices reduced effectively the inaccuracy of inner space of copyings which contributed from the technical errors of the operator, and provided well-proportioned space for adhesive. Both the fit of copyings made of Vita MK II and porous alumina oxide satisfied the clinical demand.

Aluminum Oxide↗
PubMed2005

Multigenerational versus single generation studies to estimate herbicide resistance fitness cost in Arabidopsis thaliana.

The evolution of resistance in response to pesticide selection is expected to be delayed if fitness costs are associated with resistance genes. The estimate of fitness costs usually involves comparing major growth traits of resistant versus susceptible individuals in the absence of pesticide. Ideally, a measure of changes in resistance allele frequency over several generations would allow the best estimate of the overall fitness cost of a resistance gene. In greenhouse conditions, we monitored the dynamics of the evolution of the frequencies of six herbicide-resistant mutations (acetolactate synthase, cellulose synthase, and auxin-induced target genes) in the model species Arabidopsis thaliana in a multigenerational study covering five to seven nonoverlapping generations. The microevolutionary dynamics in experimental populations indicated a mean fitness cost of 38%, 73%, and 94% for the ixr1-2, axr1-3, and axr2-1 resistances, respectively; no fitness cost for the csr1-1, and ixr2-1 resistances; and a transient advantage for the aux1-7 resistance. The result for the csr1-1 resistance contrasts with a cost of 37% based on total seed number in a previous study, demonstrating that single generation studies could have limitation for detecting cost. A positive frequency dependence for the fitness cost was also detected for the ixr1-2 resistance. The results are discussed in relation to the maintenance of polymorphism at resistance loci.

2,4-Dichlorophenoxyacetic Acid↗
PubMed2006

[Preload and ventricular lusitropism; logistic and monoexponential function fittings].

A logistic function has been found to fit the isovolumic left ventricular (LV) relaxation pressure curve and the isometric relaxation force curve of the papillary muscle much more precisely than the conventional monoexponential function. Therefore, the logistic time constant (tauL) has been proposed as a better index of the rate of cardiac relaxation or lusitropism than the conventional monoexponential time constant (tauE). Many investigators have reported that tauE changes with preloading. We analysed and compared the effect of LV volume (LVV) loading on both logistic and monoexponential fittings and their time constants of the isovolumic LV relaxation pressure curve in the excised, cross-circulated canine hearts. We found that the logistic fitting was superior to the monoexponential fitting at any LVV. LVV loading did not affect tauL at all but affected tauE slightly. The logistic fitting more reliably characterises the lusitropism than the monoexponential fitting, and tauL, serving as a more reliable ventricular lusitropism index, is independent of changes in LVV loading or the Frank-Starling effect.

Anesthesia↗
PubMed2006

Effects of competition on the fitness of wild and crop-wild hybrid sunflower from a diversity of wild populations and crop lines.

Gene flow between crop fields and wild populations often results in hybrids with reduced fitness compared to their wild counterparts due to characteristics imparted by the crop genome. But the specifics of the evolutionary outcome of crop-wild gene flow may depend on context, varying due to local environmental conditions and genetic variation within and among wild populations and among crop lines. To evaluate context-dependence of fitness of F1 hybrids, sunflower crop lines were crossed with nine wild populations from across the northern United States. These crop-wild hybrids and their wild counterparts were grown under agricultural conditions in the field with and without wheat competition. Hybrids were far less fecund than wild plants, yet more likely to survive to reproduce. There was considerable variability among wild populations for fecundity and the specific crop line used to generate the crop-wild hybrid significantly affected fecundity. The fitness deficit suffered by crop-wild hybrids varied by population, as did the rankings of the crop-wild hybrids from three different crop lines. Wheat competition decreased fecundity and survival considerably and hampered seed production of wild plants more than that of hybrids. Genotype x environment interactions indicated that the response of fitness to competition differed by population. Consequently, the fitness of hybrids relative to wild plants varied considerably among wild populations and was not consistent across environments. Notably, relative fitness of hybrids was greater under competitive conditions. This research is the first study of its kind to demonstrate that the consequences of crop-wild gene flow are context dependent and contingent on the genetics of the specific wild populations and the local biotic and abiotic conditions.

Biodiversity↗
PubMed2006

[Accurate curve fitting and revising of infrared data based on NUBSC].

Accurate curve fitting of infrared spectrum data is important for building standard spectrum, and is the basic requirement for qualitative and quantitative spectral analysis. In the present paper, B-Spline was used to accurately fit the infrared spectrum data. Based on the max norm distances of B-Spline curve fitting arithmetic, this method not only resolved the curve fitting problem of infrared data, but also provided a convenient way to orient peak values of spectrum. The authors introduced the B-Spline, realized curve fitting of quadratic non-uniform B-Spline curves (for short: NUBSC), and described the precision control of curve fitting of infrared spectrum data.

English Abstract↗
PubMed1990

Person-environment fit as a predictor of hospital pharmacist job performance.

The relationship between person-environment fit and job performance of hospital pharmacists was examined. Person-environment fit is the extent to which personal needs are supplied in the work environment. Pharmacists (n = 86) from 10 hospitals completed a survey that assessed their need for certain attributes in the work environment and their perception of the extent to which those attributes were supplied. Statements from the Jackson Personality Research Form A were used to assess need for achievement, autonomy, cognitive structure, endurance, order, and social recognition. Statements from the same form were used to assess the degree to which respondents perceived that the hospital pharmacy environment supplied the six attributes. Person-environment fit was calculated by subtracting the environmental supply score from the personal need score. Job performance was rated by supervisors. The respondents' highest need was for achievement and lowest need was for autonomy. The supply of five of the attributes was rated similarly; the supply of autonomy was perceived to be significantly lower. Scores for person-environment fit showed that the need for endurance was most closely matched by the work environment and the need for autonomy was most poorly matched. Overall job performance was not predicted by the person-environment fit score for any of the attributes. The supply of autonomy predicted 17% of the variance in performance scores. Job performance was significantly associated with the environmental supply of autonomy but not with person-environment fit.

Employee Performance Appraisal↗
PubMed1995

Micromotion of cementless hemispherical acetabular components. Does press-fit need adjunctive screw fixation?

Adult human cadaver pelves were tested to determine micromotion at the prosthesis-bone interface in cementless hemispherical acetabular components during simulated single-limb stance. The micromotion of non-press-fit components with screw fixation in response to cyclic loads to a maximum of 1500N was compressive (interface closing) at the superior iliac rim and distractive (interface opening) at the inferior ischial rim; that of press-fit components was compressive all around the acetabular rim regardless of screw fixation. Adding screws to the component decreased the micromotion at the site of the screw, but sometimes increased it at the opposite side. Two dome screws with the press-fit component decreased the micromotion at the superior iliac rim but at the inferior ischial rim there was either no change or increased movement. A press-fit cup shows less micromotion than a non-press-fit cup with screw fixation. The addition of screws to a press-fit cup does not necessarily increase the initial stability.

Adult↗
PubMed1998

Using item mean squares to evaluate fit to the Rasch model.

Throughout the mid to late 1970's considerable research was conducted on the properties of Rasch fit mean squares. This work culminated in a variety of transformations to convert the mean squares into approximate t-statistics. This work was primarily motivated by the influence sample size has on the magnitude of the mean squares and the desire to have a single critical value that can generally be applied to most cases. In the late 1980's and the early 1990's the trend seems to have reversed, with numerous researchers using the untransformed fit mean squares as a means of testing fit to the Rasch measurement models. The principal motivation is cited as the influence sample size has on the sensitivity of the t-converted mean squares. The purpose of this paper is to present the historical development of these fit indices and the various transformations and to examine the impact of sample size on both the fit mean squares and the t-transformations of those mean squares. Because the sample size problem has little influence on the person mean square problem, due to the relatively short length (100 items or less), this paper focuses on the item fit mean squares, where it is common to find the statistics used with sample sizes ranging from 30 to 10,000.

Computer Simulation↗
PubMed1998

The mutation rate and the distribution of mutational effects of viability and fitness in Drosophila melanogaster.

The empirical distributions of the average viability and fitness of mutation accumulation lines of Drosophila melanogaster were analyzed using minimum distance estimation. Data come from two different experimental designs where mutations were allowed to accumulate: 1) in copies of chromosome II protected from natural selection and recombination (viability: Mukai et al., 1972; Ohnishi, 1977; fitness: Houle et al., 1992), 2) in inbred lines derived from the same isogenic stock (viability: Fernández & López-Fanjul, 1996; fitness: this paper). Information from all data sets converged, indicating that the mutational rates were small, about 1% for viability and 3% for fitness. For both traits, the rate of mutational decline appears to be smaller than suggested by previous studies (about one-fifth of the latter), the average mutational effect was neither severe nor very slight, ranging from -0.1 to -0.3, and the distribution of mutant effects was, at most, slightly leptokurtic. Therefore, the mutational load in natural populations is one to two orders of magnitude smaller than previously thought (as based upon analyses conditional to estimates of the mutational decline of viability or fitness that appear to be biased upward). Over 95% of the mutational variance of each trait was contributed by non-slightly deleterious mutations (absolute homozygous effect larger than 0.03 or 0.1, depending on the data set considered) occurring at a rate not higher than 0.025 per haploid genome and generation. Our data suggest that most deleterious mutations affecting fitness act mainly through a single component-trait.

Animals↗
PubMed2024

Estimation of SARS-CoV-2 fitness gains from genomic surveillance data without prior lineage classification.

The emergence of SARS-CoV-2 variants with increased fitness has had a strong impact on the epidemiology of COVID-19, with the higher effective reproduction number of the viral variants leading to new epidemic waves. Tracking such variants and their genetic signatures, using data collected through genomic surveillance, is therefore crucial for forecasting likely surges in incidence. Current methods of estimating fitness advantages of variants rely on tracking the changing proportion of a particular lineage over time, but describing successful lineages in a rapidly evolving viral population is a difficult task. We propose a method of estimating fitness gains directly from nucleotide information generated by genomic surveillance, without a priori assigning isolates to lineages from phylogenies, based solely on the abundance of single nucleotide polymorphisms (SNPs). The method is based on mapping changes in the genetic population structure over time. Changes in the abundance of SNPs associated with periods of increasing fitness allow for the unbiased discovery of new variants, thereby obviating a deliberate lineage assignment and phylogenetic inference. We conclude that the method provides a fast and reliable way to estimate fitness advantages of variants without the need for a priori assigning isolates to lineages.

COVID-19↗
PubMed2026

Epistasis and the changing fitness landscapes of SARS-CoV-2.

Since its emergence in late 2019, millions of SARS-CoV-2 genomes have been generated as part of global efforts to monitor the evolution and spread of the virus. This unprecedented volume of data provides a unique opportunity to study viral evolution at unparalleled resolution. In particular, individual genomic sites can be observed to have mutated independently thousands of times. These mutation counts have been used to estimate site-specific mutation rates and fitness effects for most mutations across the viral genome. Here, we use these data to investigate how the landscape of mutational fitness costs has changed over the course of the pandemic. SARS-CoV-2 evolution over the past 6 years has been characterized by the emergence of distinct variants separated by long branches corresponding to evolutionary saltations involving up to 50 mutations. We compare inferred fitness landscapes of the Spike protein across these variants and find that shifts in the estimated effects of non-synonymous mutations are linked to genetic differences between them. Sites with altered fitness costs are enriched near positions where the genetic backgrounds differ. To explain the observed changes, we introduce a model with pairwise epistatic interactions between mutations and residues that differ between variants. This model is able to explain about half of the variance in the shifts of fitness effects and suggests that each mismatch between variants substantially alters mutation effects at typically 1 to 3 additional positions.

SARS-CoV-2↗