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The first measurement of lepton-jet momentum imbalance and azimuthal correlation in lepton-proton scattering at high momentum transfer is presented. These data, taken with the H1 detector at HERA, are corrected for detector effects using an unbinned machine learning algorithm (multifold), which considers eight observables simultaneously in this first application. The unfolded cross sections are compared with calculations performed within the context of collinear or transverse-momentum-dependent factorization in quantum chromodynamics as well as Monte Carlo event generators.
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The strong coupling constant α s is determined from inclusive jet and dijet cross sections in neutral-current deep-inelastic ep scattering (DIS) measured at HERA by the H1 collaboration using next-to-next-to-leading order (NNLO) QCD predictions. The dependence of the NNLO predictions and of the resulting value of α s ( m Z ) at the Z-boson mass m Z are studied as a function of the choice of the renormalisation and factorisation scales. Using inclusive jet and dijet data together, the strong coupling constant is determined to be α s ( m Z ) = 0.1157 ( 20 ) exp ( 29 ) th . Complementary, α s ( m Z ) is determined together with parton distribution functions of the proton (PDFs) from jet and inclusive DIS data measured by the H1 experiment. The value α s ( m Z ) = 0.1142 ( 28 ) tot obtained is consistent with the determination from jet data alone. The impact of the jet data on the PDFs is studied. The running of the strong coupling is tested at different values of the renormalisation scale and the results are found to be in agreement with expectations.
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During the investigation of the degradation products of 2,4,6-trinitrotoluene (TNT) using ion mobility spectrometry (IMS), 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4-dichlorophenol (DCP) were found to have IMS responses which overlapped those of the TNT degradation products. It was observed that the Cl(-) reactant ion chemistry, often used for explosives analysis, was not always successful in resolving peak overlap of analytes and interferents. It is shown here that resolution of the analytes and interferences can sometimes be achieved using only air for the formation of reactant ions, at other times through the use of Br(-) as an alternative to Cl(-) for producing reactant ions, and also through the promotion of adduct stability by lowering the IMS temperature.
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The efficiency of chloride reactant ion formation, when chlorinated hydrocarbon reagent chemicals were added to the ionization region of an ion mobility spectrometer, corresponded to the electron attachment rate constant of the chemical. The chemicals investigated here included chloromethane, dichlormethane, trichloromethane, tetrachloromethane and chlorobenzene, with tetrachloromethane producing the greatest amount of chloride reactant ions for the amount of chemical added. Reagent chemicals with smaller electron attachment rate constants required the addition of more chemical to reach functional reactant ion levels. The excess neutral reagent molecules clustered to the chloride reactant ions and reduced the effectiveness of abstracting a proton from 2,4,6-trinitrotoluene (TNT). The effect of clustering was different for each chemical. Tetrachloromethane, which had the least exothermic clustering reaction, had the most effective production of the (TNT-H)(-) product ion per mole of reagent chemical. Bromide and iodide ions were also investigated as potential reactant ions. Bromide was found to effectively produce the proton abstracted (TNT-H)(-) ion. Iodide, however, was not a strong enough base to form (TNT-H)(-) from TNT. There was no apparent transfer of an electron to TNT by chloride, bromide or iodide.
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BACKGROUND: The primary purpose of public policy requiring vision testing for driver license renewal is to identify individuals with functional vision impairments and, when necessary, to restrict their driving. This is based on the presumption that poor vision is causally related to poor driving and traffic crashes. METHODS: The AOA Environmental and Occupational Vision Committee performed a synthesis of relevant empirical literature on policy-based research and developed potential options for enhancing traffic safety. RESULTS: Presently, some states require vision testing for driver's license renewal and some do not. Regional and nationwide studies report that vision-related license renewal policies are associated with enhanced traffic safety. However, contemporary vision screening tests may be of limited value in identifying individuals with functional vision impairments. CONCLUSION: The most cost-effective and valid method for identifying, treating and counseling visually impaired drivers is to require a comprehensive eye examination as a condition for driver license renewal for those with a high prevalence or high probability of vision impairment.
Assuntos
Exame para Habilitação de Motoristas , Condução de Veículo , Política de Saúde , Optometria/normas , Testes Visuais/normas , Visão Ocular/fisiologia , Acidentes de Trânsito/prevenção & controle , Envelhecimento/fisiologia , Guias como Assunto , Humanos , Estados Unidos , Transtornos da Visão/diagnósticoRESUMO
BACKGROUND: This study was performed to investigate the relationship between vision reaction time (VRT) and batting, fielding, and pitching skill in baseball. METHODS: A vision screening of 213 professional baseball players in the Southern Baseball League was performed, and the visual reaction times of these players were determined. Official Southern Baseball League statistics were consulted to obtain the players' batting average, fielding average, and earned run average. RESULTS: The mean visual reaction time for all players was 239 msec. There was no significant association between mean VRT and age or race. The mean VRT for dominant eyes was not significantly different from the mean VRT for nondominant eyes. For the 92 players who batted at least 100 times, an association was found between mean VRT and batting average (p = 0.017). For the 168 fielders in the league playing at least 20 games, no statistically significant association was found between mean VRT and fielding average. Similarly, no association was found between mean VRT and earned run average for the B8 pitchers who had participated in more than 20 games. CONCLUSIONS: An association was found between visual reaction time and batting skill in baseball. No association was found between visual reaction time and fielding or pitching skill.
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Beisebol , Destreza Motora/fisiologia , Tempo de Reação/fisiologia , Visão Ocular/fisiologia , Humanos , Testes Visuais/métodos , Acuidade VisualRESUMO
BACKGROUND: The relationship between eye dominance and batting skill in baseball has been investigated, but conflicting results have been obtained. In addition, little attention has been given to the relationship, if any, between eye dominance and fielding and pitching skill. METHODS: A vision screening of 215 professional baseball players in the Southern Baseball League was performed and the eye dominance of these players was determined by a sighting test. Handedness for batting, fielding, and pitching was determined by history. RESULTS: The screening revealed that 66 percent of players were right-eye dominant and that, of 92 players who met the criteria established to qualify for the league batting championship, 60 percent had matched dominance of eye and hand. When official league batting averages were obtained for these 92 players, it was found that there was no statistically significant difference between batters with matched dominance (.278 mean batting average). For the 149 fielders in the league, no statistically significant differences based on eye dominance were found for fielding average (.893 matched dominance, .864 crossed dominance); for the 89 pitchers, a similar result was obtained. Pitchers were also evaluated with respect to eye dominance and earned run average, but no significant difference was found (3.91 matched dominance, 4.03 crossed dominance). CONCLUSIONS: Results indicate that there is no association between eye dominance, and hitting, fielding, or pitching skill in baseball.
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Beisebol , Lateralidade Funcional , Mãos/fisiologia , Fenômenos Fisiológicos Oculares , HumanosRESUMO
Fourth year optometry students screened 745 preschoolers using a slightly altered Modified Clinical Technique (MCT) under the supervision of a faculty doctor. Children who failed the MCT were randomly selected and then matched by age, sex, and ethnic origin to children who had passed the screening battery. The 61 screening failures and 45 matched controls were later given full eye examinations with cycloplegia by University of Alabama at Birmingham faculty doctors who were unaware of the screening results. The positive predictive value (PPV) (0.52) and negative predictive value (NPV) (0.78) of the MCT were calculated directly from the 2 x 2 contingency table crossing screening results and a standard diagnosis. Sensitivity [0.50, k(1,0) = 0.29], specificity [0.79, k(0,0) = 0.30], efficiency [0.70, k(0.5,0) = 0.29] of the MCT, and the prevalence (0.30) of children failing the standard diagnosis were estimated using statistics appropriate to the prospective sampling design. The reproducibility of the diagnosis, estimated by analyzing multiple, independent diagnosis of each study child by seven doctors was moderate (kappa D 0.58). Statistics summarizing the agreement between the MCT and the diagnosis by the individual study doctor are similar to those obtained with comparison to the standard diagnosis. The characteristics of the MCT may be generalized only to similar populations that are screened by clinicians with similar experience, using the same tests.
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Pré-Escolar , Optometria/educação , Estudantes de Ciências da Saúde , Transtornos da Visão/diagnóstico , Seleção Visual/métodos , Criança , Análise Fatorial , Reações Falso-Positivas , Feminino , Humanos , Masculino , Valor Preditivo dos Testes , Prevalência , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
The purpose of this study was to evaluate the effects of the residual astigmatism of contact lens wearers on the visual comfort of these individuals when using a video display terminal (VDT). We hypothesized that small amounts of uncorrected residual astigmatism of the type that is normally left uncorrected produce visual discomfort in the use of these devices even though visual acuity is relatively unaffected. Twelve subjects (ages 18 to 36 years) with corrected visual acuities of at least 20/25 (in each eye at distance with their contact lens correction) participated. All subjects were soft contact lens wearers who reported comfortable, well-adapted lens wear for a minimum of 1 year prior to the study. All subjects had between 0.50 and 1.00 D of residual astigmatism in each eye (mean = 0.68D). Our double-masked cross-over experiment included two 25-minute periods during which the subject read from a VDT. In a trial frame over their contact lens correction, the subjects were randomly assigned to wear either a test lens pair or a control lens pair (+0.12 DS) during the first period and the alternative pair during the second period. The test lens pair corrected all residual astigmatism (the over refraction). The control lens pair was considered a placebo. A questionnaire was used to obtain ratings of visual discomfort. Our analysis of the data indicated greater reported visual comfort for the test lens pair (Wilcoxon signed-rank test, p less than 0.01). These results suggest careful consideration be given to the correction of residual astigmatism of contact lens wearers who are VDT users.
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Astigmatismo/fisiopatologia , Terminais de Computador , Lentes de Contato Hidrofílicas , Adolescente , Adulto , Feminino , Humanos , Masculino , Distribuição Aleatória , Inquéritos e Questionários , Visão Ocular/fisiologia , Acuidade VisualRESUMO
The purpose of this study was to evaluate the effects of small amounts of uncorrected astigmatism on the visual comfort of video display terminal (VDT) users. We hypothesized that these small errors produce visual discomfort in the use of these devices even though visual acuity is relatively unaffected. Eight subjects (ages 23-35 years) with corrected visual acuities of 20/20 participated. Our double-masked cross-over experiment included two 25-minute periods during which the subject read from a VDT. The subjects were randomly assigned to wear either the test lens pair (+0.50 D x 090) or a control lens pair (+0.12 DS) over their best correction during the first period and the alternative pair during the second period. A questionnaire was used to obtain ratings of visual discomfort. Our analysis of the data indicated greater reported eyestrain for the test lens pair (Wilcoxon signed-rank test, p = 0.01). These results suggest careful consideration be given to the correction of small amounts of astigmatic errors for VDT users.
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Astigmatismo/complicações , Terminais de Computador , Transtornos da Visão/etiologia , Adulto , Método Duplo-Cego , Feminino , Humanos , Masculino , Inquéritos e Questionários , Acuidade VisualRESUMO
Three models of alpha-track detector (ATD) Rn monitors were exposed in Environmental Protection Agency (EPA) Rn chambers to obtain estimates of precision and bias for the National Residential Radon Survey (NRRS). Exposures in this study ranged from 37 to 740 Bq y m-3 (1 to 20 pCi y L-1), plus blanks. These exposures correspond to the range expected in most U.S. residences. All detectors were purchased through a Rn mitigation firm to assure that the vendors did not give special attention to the ATDs used in this study. Ten ATDs of each model were studied at 12 exposures. The mean and standard deviation of the reported values for each model were calculated and compared with the continuously monitored chamber concentrations to determine the bias and precision at each exposure. Results of this analysis were discussed with the vendors, who took corrective actions. Changes in track counting procedures and calibrations improved detector performance. Readings of one detector were adjusted based on a regression of the monitored values on the reported values.
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Monitoramento de Radiação/instrumentação , Radônio/análise , Partículas alfa , Estudos de Avaliação como AssuntoRESUMO
Preferential looking using square waves is commonly used to measure visual acuity of infants. Since sine-wave gratings have the advantage of presenting only a single spatial frequency, we completed a study to develop and validate a set of acuity cards using sine waves. The subjects were 83 children (mean age = 41.5 months, range = 3 to 69 months). The sine-wave cards were compared with Teller cards. Identical visual acuity was determined in 83% of the cases. Wilcoxon non-parametric analysis provided no evidence to reject the null hypothesis of equal visual acuities between the two methods. We conclude that sine-wave cards may be used to measure the preferential looking acuity of children.
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Testes Visuais/métodos , Acuidade Visual , Criança , Pré-Escolar , Estudos de Avaliação como Assunto , Feminino , Humanos , Lactente , Masculino , Reprodutibilidade dos Testes , Seleção Visual/métodos , Testes Visuais/instrumentaçãoRESUMO
An intermittent darkening of the visual field (ganzfeld "blankout") is perceived during bowl perimetry. Since this may be a form of rivalry, we hypothesized that occluding the nontested eye with a translucent occluder may eliminate the phenomenon. Ten normal subjects underwent visual field testing with both a translucent and an opaque occluder. Eight of the 10 reported darkening to occur with the opaque patch, while none reported it with the translucent occluder. The darkening occurred with a mean latency of 10.9 seconds, occupied 34.4% of the time, and on average occurred 3.25 times per minute. With the translucent occluder, retest threshold variability was 18.8% less and sensitivity was increased by 0.7 dB. The elimination of this darkening using translucent occluders in bowl perimetry will allow reduced variability and increased sensitivity and comfort.
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Iluminação , Curativos Oclusivos , Testes de Campo Visual/métodos , Adulto , Escuridão , Desenho de Equipamento , Humanos , Sensibilidade e Especificidade , Testes de Campo Visual/instrumentação , Campos VisuaisRESUMO
The purpose of this study was to investigate dry storage of rigid gas-permeable contact lenses as an alternative to wet storage. This study evaluated the constancy of lens base curve between the two storage methods for lens materials that spanned the spectrum of oxygen permeability values. The differences found in lens base curve between wet and dry storage for any lens material evaluated did not reach a level considered to be clinically significant, although differences in average base curve constancy did exist among the lens materials. Base curve change did not increase with increasing lens material oxygen permeability value (Dk).
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Lentes de Contato , Óptica e Fotônica , Dessecação , Oxigênio , Permeabilidade , Distribuição AleatóriaRESUMO
The correspondence status of 68 constant, early-age onset strabismics was evaluated with three common clinical tests to determine the prevalence of anomalous retinal correspondence (ARC) and which clinical features of the strabismus were most highly associated with the ARC. Ninety-six per cent, 71%, and 51% of the patients manifested ARC with the striated lens test, the synoptophore, and the afterimage test, respectively. The clinical features of the strabismus that were correlated, although weakly, with the diagnosis of ARC were: (1) the magnitude of the deviation at near for the striated lens test; (2) the age of the patient at the time of testing and the laterality of the deviation on the synoptophore; and (3) the age of the patient at the time of testing, the change in the deviation from distance to near, and the spherical equivalent refractive error for the afterimage test. A low correlation also existed between the age of the patient and the depth of ARC (superficial or deep-rooted). We conclude that the clinical features of strabismus cannot be utilized effectively to predict the status of retinal correspondence.
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Estrabismo/complicações , Transtornos da Visão/diagnóstico , Adolescente , Fatores Etários , Pré-Escolar , Esotropia/complicações , Exotropia/complicações , Feminino , Humanos , Masculino , Fatores Sexuais , Testes VisuaisRESUMO
The purpose of this study was to assess a new criterion for binocular comfort analogous to the classical Sheard's criterion. Instead of equating the fusional demand with the monocular phoria as is done when Sheard's criterion is applied, the new criterion uses a calculated binocular fusional demand. The binocular demand was derived using a clinical measurement of the convergence accommodation per convergence (CA/C) ratio. Sheard's criterion was also evaluated. Other commonly used indicators of binocularity (heterophoria, vergences, accommodative amplitude, facility and response, fixation disparity, and the associated phoria) were measured. One hundred subjects (52 males, 48 females; mean age 26 years) were classified as either symptomatic or asymptomatic by an interviewing clinician. The examining clinician was intentionally masked as to the classification of the subjects. We hypothesized that the new criterion would best discriminate between the two groups of patients inasmuch as it is based on currently accepted dual-interaction models of accommodation and vergence. Our analysis confirmed that the CA/C ratio corresponded closely to those published previously (mean = 0.06 D/delta). Significant differences (p less than 0.05) were determined between the symptomatic and asymptomatic groups for gender, near phoria through a +2.00 D add, accommodative amplitude, positive vergences at near, and both the classical Sheard's and the new criterion. The new criterion was the best discriminator between the groups, identifying 72% correctly, an improvement of 6% over the classical Sheard's. However, various stepwise discriminant analysis procedures consistently failed to demonstrate that the calculated binocular fusional demand or the new criterion was superior to the near phoria or the classical Sheard's value. These results suggest potential clinical utility for new procedures based on recently described models of accommodation and vergence, but further development appears necessary.
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Convergência Ocular , Movimentos Oculares , Visão Binocular , Acomodação Ocular , Adolescente , Adulto , Feminino , Humanos , Masculino , Inquéritos e Questionários , Disparidade VisualRESUMO
Although the effects of using video display terminals (VDTs) have been examined from a number of perspectives, there has been relatively little study of the effect of small uncorrected refractive errors in the production of visual discomfort. The purpose of this study was to examine the level of six commonly assessed symptoms in a sample of 32 VDT operators via a questionnaire and to determine whether these were related to their habitual small refractive errors. The subjects reported substantial prevalence (55-81%) of each of the symptoms except double vision (16%). After a complete vision examination, the VDT operators were classified as relative myopes, hyperopes, astigmats or emmetropes. The criterion was a minimum of 0.50 D in the most ameotropic eye. Using this criterion, analysis showed that small refractive errors were significantly related to the reported level of symptoms of VDT operators. These results suggest the utility of proper refractive correction for the comfortable use of a VDT and the value of further research into this putative causal relationship.
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Sistemas Computacionais , Erros de Refração/complicações , Adolescente , Adulto , Feminino , Cefaleia/etiologia , Humanos , Masculino , Doenças Profissionais/etiologia , Erros de Refração/fisiopatologia , Inquéritos e Questionários , Transtornos da Visão/etiologiaRESUMO
Accommodative spasm (AS) is rarely reported in the literature. We studied 17 patients with accommodative spasm. Most patients were clinically emmetropic. Ten patients also manifested a spasm of the near reflex (SNR). The probable etiology of the accommodative disorder for most patients was psychogenic as revealed by case histories and visual field analysis. Treatment consisted primarily of plus reading lenses and, in some instances, orthoptic training. Some patients also underwent psychological counseling. Follow-up ranged from 2 months to 30 months. Although visual symptoms improved for most patients, only four patients had complete resolution of the spasm.
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Acomodação Ocular , Erros de Refração/fisiopatologia , Transtornos da Visão/fisiopatologia , Adolescente , Adulto , Criança , Feminino , Humanos , Hiperopia/fisiopatologia , Masculino , Erros de Refração/psicologia , Erros de Refração/terapia , Estudos Retrospectivos , Espasmo , Transtornos da Visão/psicologia , Transtornos da Visão/terapia , Acuidade VisualRESUMO
Convergence insufficiency (CI) is a well-known syndrome of binocular visual dysfunction. In a review of 58 papers, considerable variation was noted in the criteria used to define the condition. Symptoms and decreased positive fusional vergences (both at the nearpoint) were the only criteria named in more than one-half of the studies. An extended nearpoint of convergence (NPC) and increased exophoria at near were criteria in about one-third of the papers. Examination of data in the reviewed papers shows that although considerable variability was noted, the distance exodeviation, distance negative vergences, visual acuity, refraction, and stereopsis were about the same as population norms. Positive vergences, negative vergence at near, and NPC were somewhat less than population norms. Vergences relative to Sheard's criterion, the near exophoria, accommodative amplitude, and the AC/A ratio were consistently below those derived from population norms. This considerable variation may largely be a result of different criteria used for diagnosis, subpopulations within the data, and other confounding factors.
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Convergência Ocular , Movimentos Oculares , Transtornos da Visão/fisiopatologia , Acomodação Ocular , Exotropia/complicações , Exotropia/fisiopatologia , Humanos , Valores de Referência , Transtornos da Visão/complicações , Transtornos da Visão/diagnósticoRESUMO
The purpose of this study was to assess the effects of horizontal and vertical vergence training on fusional vergences and the fixation disparity (FD) curve. Thirty-four subjects were divided into three groups. One-third served as controls and the other two-thirds underwent 5 h of supervised horizontal and vertical vergence training, respectively. Before and after the 4 week training period, vergences and FD curves were measured by a single individual who was intentionally uninformed of each subject's group. We hypothesized that the subjects in the horizontal training group would have increased vergence amplitudes and flatter FD slopes. Our analysis revealed that the positive vergences increased significantly for those in the horizontal group. No evidence was found to suggest changes in any variables related to the FD curve. Because type II errors were likely to be unacceptably large, further work is necessary to determine the relation between fusional vergence training and variables derived from the FD curve.