Outcomes after trans-tibial amputation: The relationship between quiet stance ability, strength of the hip abductor muscles and gait

Background and Purpose Previous research regarding the symmetry of trans-tibial amputees has examined weight distribution and various gait parameters between prosthetic and sound limbs. However, to date, no known research has determined if asymmetry is present in the strength of the hip abductor muscles or if correlations exist between these categories of symmetry. The purpose of the present study was, therefore, to document asymmetry present in stance, strength and gait measures, and to determine the relationship between these variables. Method Twenty-three elderly, unilateral trans-tibial amputees stood on two adjacent forceplates whilst the weight distribution and standard deviation (SD) of the anterior-posterior and the medio-lateral centre of pressure excursion (COPE) under each limb was recorded during four 40 s trials: quiet stance (QS), with eyes open and eyes closed; and even stance (ES), with eyes open and eyes closed. Gait measures (velocity, cadence, step and stride lengths, stance:swing ratio and period of double support) over 10 m of fast, yet safe walking and measures of the strength of hip abductor muscles were also obtained by use of a stride analyser and a dynamometer, respectively. Results No significant differences were found between QS and ES measures. However, significantly more weight was taken on the sound limb than on the amputated limb. Notably, more anterior-posterior movement occurred under the sound limb than the amputated limb, with this becoming more apparent with the eyes closed. Movement in the medio-lateral direction was found to be the same between sides. No differences in muscle strength or gait measures between limbs were demonstrated. However. strong hip abductor muscles were correlated with increased weight-bearing on the amputated limb, improved gait parameters and reduced medio-lateral COPE under the amputated limb. Conclusions This research confirms the asymmetrical nature of amputee stance and demonstrates symmetry of strength and gait measures between limbs. The correlations between hip abductor muscle strength, weight distribution and gait measures illustrates the importance of pre- and postoperative training of these muscles. Copyright © 2002 Whurr Publishers Ltd.

A uniform white-noise model for fixed-point roundoff errors in digital systems

Fixed-point roundoff noise in digital implementation of linear systems arises due to overflow, quantization of coefficients and input signals, and arithmetical errors. In uniform white-noise models, the last two types of roundoff errors are regarded as uniformly distributed independent random vectors on cubes of suitable size. For input signal quantization errors, the heuristic model is justified by a quantization theorem, which cannot be directly applied to arithmetical errors due to the complicated input-dependence of errors. The complete uniform white-noise model is shown to be valid in the sense of weak convergence of probabilistic measures as the lattice step tends to zero if the matrices of realization of the system in the state space satisfy certain nonresonance conditions and the finite-dimensional distributions of the input signal are absolutely continuous.

Independent and conjugate eye movements during optokinesis in teleost fish

In response to movements involving a large part of the visual field, the eyes of vertebrates typically show an optokinetic nystagmus, a response in which both eyes are tightly yoked. Using a comparative approach, this study sets out to establish whether fish with independent spontaneous eye movements show independent optokinetic nystagmus in each eye. Two fish with independent spontaneous eye movements, the pipefish Corythoichthyes intestinalis and the sandlance Limnichthyes fasciatus were compared with the butterflyfish Chaetodon rainfordi, which exhibits tightly yoked eye movements. In the butterflyfish a single whole-field stimulus elicits conjugate optokinesis, whereas the sandlance and pipefish show asynchronous optokinetic movements. In a split drum experiment, when both eyes were stimulated in opposite directions with different speeds, both the sandlance and the pipefish compensated independently with each eye. The optokinetic response in the butterflyfish showed some disconjugacy but was generally confused. When one eye was occluded, the seeing eye was capable of driving the occluded eye in both the butterflyfish and the pipefish but not in the sandlance. Monocular occlusion therefore unmasks a link between the two eyes in the pipefish, which is overridden when both eyes receive visual input. The sandlance never showed any correlation between the eyes during optokinesis in all stimulus conditions. This suggests that there are different levels of linkage between the two eyes in the oculomotor system of teleosts, depending on the visual input.

Morphological shifts in island-dwelling birds: The roles of generalist foraging and niche expansion

Passerine birds living on islands are usually larger than their mainland counterparts, in terms of both body size and bill size. One explanation for this island rule is that shifts in morphology are an adaptation to facilitate ecological niche expansion. In insular passerines, for instance, increased bill size may facilitate generalist foraging because it allows access to a broader range of feeding niches. Here we use morphologically and ecologically divergent races of white-eyes (Zosteropidae) to test three predictions of this explanation: (1) island populations show a wider feeding niche than mainland populations; (2) island-dwelling populations are made up of individual generalists; and (3) within insular populations there is a positive association between size and degree of foraging generalism. Our results provide only partial support for the traditional explanation. In agreement with the core prediction, island populations of white-eye do consistently display a wider feeding niche than comparative mainland populations. However, observations of individually marked birds reveal that island-dwelling individuals are actually more specialized than expected by chance. Additionally, neither large body size nor large bill size are associated with generalist foraging behavior per se. These latter results remained consistent whether we base our tests on natural foraging behavior or on observations at an experimental tree, and whether we use data from single or multiple cohorts. Taken together, our results suggest that generalist foraging and niche expansion are not the full explanation for morphological shifts in island-dwelling white-eyes. Hence, we review briefly five alternative explanations for morphological divergence in insular populations: environmental determination of morphology, reduced predation pressure, physiological optimization, limited dispersal, and intraspecific dominance.

Changes in postural stability in women aged 20 to 80 years

Background. A study of postural stability was undertaken to identify the relationship between vision and support surface across age decades. Understanding when reliance on vision for postural stability emerges and the support conditions contributing to this instability may provide the evidence required to introduce falls-prevention strategies in younger age decades. Methods. We measured postural stability in 453 women aged 20 to 80 years using the Balance Master force-plate system while the women performed the modified Clinical Test for the Sensory Interaction and Balance (firm and foam surfaces, eyes open and closed) and the Single-Limb Stance Test (eyes open and closed). Results. Women in their 60s and 70s were more unstable than younger women in bilateral stance on a firm surface with the eyes closed. This instability was evident from the 50s when a foam surface was introduced and from the 40s when single-limb stance was tested with eyes closed. A further decline in stability was demonstrated for each subsequent decade when the eyes were closed in single-limb stance. Conclusions. Age, visual condition, and support surface were significant variables influencing postural stability in women. Reliance on vision for postural stability was evident for women from the 40s when single-limb stance was tested, from the 50s when bilateral stance on foam was tested, and from the 60s when a firm surface was used. The cause(s) of this decline in stability requires further investigation, and screening for postural instability between the ages of 40 and 60 is advocated.

Mean anisotropy of homogeneous Gaussian random fields and anisotropic norms of linear translation-invariant operators on multidimensional integer lattices

Sensitivity of output of a linear operator to its input can be quantified in various ways. In Control Theory, the input is usually interpreted as disturbance and the output is to be minimized in some sense. In stochastic worst-case design settings, the disturbance is considered random with imprecisely known probability distribution. The prior set of probability measures can be chosen so as to quantify how far the disturbance deviates from the white-noise hypothesis of Linear Quadratic Gaussian control. Such deviation can be measured by the minimal Kullback-Leibler informational divergence from the Gaussian distributions with zero mean and scalar covariance matrices. The resulting anisotropy functional is defined for finite power random vectors. Originally, anisotropy was introduced for directionally generic random vectors as the relative entropy of the normalized vector with respect to the uniform distribution on the unit sphere. The associated a-anisotropic norm of a matrix is then its maximum root mean square or average energy gain with respect to finite power or directionally generic inputs whose anisotropy is bounded above by a≥0. We give a systematic comparison of the anisotropy functionals and the associated norms. These are considered for unboundedly growing fragments of homogeneous Gaussian random fields on multidimensional integer lattice to yield mean anisotropy. Correspondingly, the anisotropic norms of finite matrices are extended to bounded linear translation invariant operators over such fields.

Visual Biology of Hawaiian Coral Reef Fishes. I. Ocular Transmission and Visual Pigments

The visual biology of Hawaiian reef fishes was explored by examining their eyes for spectral sensitivity of their visual pigments and for transmission of light through the ocular media to the retina. The spectral absorption curves for the visual pigments of 38 species of Hawaiian fish were recorded using microspectrophotometry. The peak absorption wavelength (lambda(max)) of the rods varied from 477-502 nm and the lambda(max) of individual species conformed closely to values for the same species previously reported using a whole retina extraction procedure. The visual pigments of single cone photoreceptors were categorized, dependent on their lambda(max)-values, as ultraviolet (347-376 nm), violet (398-431 nm) or blue (439-498 nm) sensitive cones. Eight species possessed ultraviolet-sensitive cones and 14 species violet-sensitive cones. Thus, 47% of the species examined displayed photosensitivity to the short-wavelength region of the spectrum. Both identical and nonidentical paired and double cones were found with blue sensitivity or green absorption peaks (> 500 nm). Spectrophotometry of the lens, cornea, and humors for 195 species from 49 families found that the spectral composition of the light transmitted to the retina was most often limited by the lens (73% of species examined). Except for two unusual species with humor-limited eyes, Acanthocybium solandri (Scombridae) and the priacanthid fish, Heteropriacanthus cruentatus, the remainder had corneal-limited eyes. The wavelength at which 50% of the light was blocked (T50) was classified according to a system modified from Douglas and McGuigan (1989) as Type I, T50 < = 355 nm, (32 species); Type IIa, 355 < T50 < = 380 nm (30 species); Type IIb, 380 < T50 405 nm (84 species). Possession of UV-transmitting ocular media follows both taxonomic and functional lines and, if the ecology of the species is considered, is correlated with the short-wavelength visual pigments found in the species. Three types of short-wavelength vision in fishes are hypothesized: UV-sensitive, UV-specialized, and violet-specialized. UV-sensitive eyes lack UV blockers (Type I and IIa) and can sense UV light with the secondary absorption peak or beta peak of their longer wavelength visual pigments but do not possess specialized UV receptor cells and, therefore, probably lack UV hue discrimination. UV-specialized eyes allow transmission of UV light to the retina (Type I and IIa) and also possess UV-sensitive cone receptors with peak absorption between 300 and 400 nm. Given the appropriate perceptual mechanisms, these species could possess true UV-color vision and hue discrimination. Violet-specialized eyes extend into Type IIb eyes and possess violet-sensitive cone cells. UV-sensitive eyes are found throughout the fishes from at least two species of sharks to modern bony fishes. Eyes with specialized short-wavelength sensitivity are common in tropical reef fishes and must be taken into consideration when performing research involving the visual perception systems of these fishes. Because most glass and plastics are UV-opaque, great care must be taken to ensure that aquarium dividers, specimen holding containers, etc., are UV-transparent or at least to report the types of materials in use.

Colet??nea planejamento e or??amento governamental: volume 2: pref??cio

Estabelece o objetivo da publica????o de se tornar material did??tico para a forma????o de servidores da Administra????o P??blica brasileira

Colet??nea planejamento e or??amento governamental: volume 2: a aus??ncia de uma teoria or??ament??ria

A respeito do aspecto mais significativo da or??amenta????o p??blica, ou seja, a aloca????o de gastos para diferentes prop??sitos de forma a se atingir o melhor retorno, a literatura or??ament??ria norte-americana ?? bastante ??rida. Esfor??ados estudiosos do campo or??ament??rio t??m-se ocupado principalmente com a organiza????o e o procedimento para a prepara????o do or??amento, as formas como as solicita????es de fundos s??osubmetidas, o formato da pe??a or??ament??ria em si e quest??es similares1.N??o se pode negar que esses aspectos merecem a considera????o a eles dispensada, quando se lembra da inacredit??vel resist??ncia ?? ado????o dos mais rudimentares quesitos b??sicos do or??amento e se observa sua condi????o insatisfat??ria ainda hoje em algumas jurisdi????es. No entanto, a dedica????o de energia para o estabelecimento da mec??nica do or??amento desviou a aten????o do problema essencial do or??amento (no lado do gasto), a saber: em que se deve basear a decis??o de se alocar x d??lares para a atividade a em vez de ser para a atividade b

Colet??nea planejamento e or??amento governamental: volume 2: conflitos e solu????es no or??amento federal

Esta obra trata da pol??tica e dos processos de elabora????o do or??amento federal e das pol??ticas que surgem da??. N??o h?? discuss??o completa sobre or??amento sem levar em considera????o esses tr??s aspectos. Muitas atividades governamentais combinam processo e pol??tica, por??m o or??amento ?? diferente, porque determinadas tarefas b??sicas precisam ser conclu??das a cada ano. Independentemente de qu??o dif??ceis sejam as escolhas e qu??o incerto seja o cen??rio futuro, o presidente precisa apresentar uma proposta e o Congresso precisa autorizar as dota????es. Se o presidente ou o Congresso decidirem que n??o ?? o momento de fazer mudan??as na pol??tica tribut??ria ou de abordar determinada proposta legislativa, qualquer um dos dois pode postergar as a????es at?? que se chegue a um acordo. Por??m, n??o podem esquivar-se da sua responsabilidade de decidir sobre o or??amento. Caso contr??rio, programas federais e organismos param, por aus??ncia de financiamento, e assim, tamb??m, o trabalho do governo. Ainda assim, mesmo quando ocorrem paralisa????es ??? mais recentemente em 1995-1996 ???, no final das contas, chega-se a um acordo entre o presidente e o Congresso

Colet??nea planejamento e or??amento governamental: volume 2: do or??amento por programas para o or??amento de desempenho: o desafio para economias de mercado emergentes

Primeiramente, este documento revisa a evolu????o do antigo modelo de or??amento de desempenho, introduzido nos Estados Unidos h?? mais de meio s??culo, para o novo modelo de or??amento de desempenho. Este, que cont??m muitos dos elementos do antigo modelo, est?? sendo cada vez mais aplicado em economias avan??adas, incluindo a dos Estados Unidos. Usando a classifica????o de modelos de or??amento derivada deste estudo, pode-se considerar que muitas das economias de mercado emergentes introduziram algum tipo de or??amento por programas, embora se saiba que o termo ?? utilizado de v??rias maneiras. Contudo, essas economias ainda precisam avan??ar para o or??amento por produtos e, subseq??entemente, incorporar as reformas necess??rias para o novo or??amento de desempenho. Neste documento, ser?? discutido que, pelo fato de n??o realizarem esse avan??o, as economias de mercado emergentes n??o conseguiram utilizar plenamente seus or??amentos por programas para melhorar a gest??o de seus or??amentos. Reconhece-se que dar esse passo n??o ?? f??cil e exige que quatro principais elementos sejam introduzidos e/ou fortalecidos para assegurar o sucesso de tal investida. Esses elementos devem ser considerados como a base da estrat??gia para a introdu????o do novo modelo de or??amento de desempenho.

Colet??nea planejamento e or??amento governamental: volume 2: temas e quest??es sobre a gest??o da despesa p??blica

O artigo est?? dividido em tr??s partes. Na primeira parte, as caracter??sticas do novo pacote de reformas de gest??o de despesa p??blica s??o visualizadas em termos da situa????o futura ??? ano 2020. Na segunda, s??o discutidos os acontecimentos passados que contribu??ram para a evolu????o do novo pacote. Na terceira, as inova????es do or??amento cumulativo ou da gest??o da despesa s??o discutidas em termos de sua adequa????o para satisfazer as expectativas atuais, bem como a utilidade do pacote no contexto de rubricas cambiantes de despesa p??blica.