ON TWO-POINT RESOLUTION OF IMAGING SYSTEMS

In this paper a new criterion is proposed for optical two-point resolution, applicable to coherent, incoherent, and partially coherent imaging. Unlike classical resolution criteria, such as Rayleigh's, the new criterion takes account of the presence of errors in the observed intensity distributions. Based on a parameter estimation approach, it shows how the resolvability of the imaged point sources depends on these errors. Additionally, a test for the resolvability of the point sources from a given set of observations is presented. Moreover, a procedure is proposed for the computation of the errors having minimum energy among all errors undermining the resolution. The results presented include, as a special case, earlier results on two-point resolution of strictly incoherent imaging systems

The effect of canopy position on growth and mortality in mixed sapling communities during self-thinning

This research investigates how species in the sapling phase differ in growth and survival depending on light availability (as estimated by canopy position) by means of tree-ring analysis and modelling mortality. We harvested 120 live and 158 dead saplings in self-thinning communities consisting of Silver birch (Betula pendula Roth.), Scots pine (Pinus sylvestris L.), Japanese larch (Larix kaempferi Carr.) and Douglas fir (Pseudotsuga menziesii Mirb. Franco) in the Netherlands. Results are evaluated within the framework of a trade-off between high-light growth and low-growth survival. Radial growth, measured at ground level, generally declined over time. In addition, a decreasing light availability further reduced growth in all species except Douglas fir. Trees died when radial growth was reduced to about 0.5 mm year¿1. Mortality in all species except Scots pine was significantly related to recent growth, but mortality curves were not different. The light-demanding Silver birch and Japanese larch differed from the shade-tolerant Douglas fir in both high-light growth and low-growth mortality, in line with a growth-survival trade-off. The light-demanding Scots pine did not fit this pattern as it was unable to transfer high radial growth into height gain, leaving it in suppressed canopy positions. This indicates the importance of height growth in the growth-survival trade-off. Differences in mortality probabilities affect the potential for coexistence, however, in all species also fast-growing individuals died suggesting additional factors causing mortality during self-thinning, other than direct competition for ligh

The reconstructed residual error: a novel segmentation evaluation measure for reconstructed images in tomography

In this paper, we present the reconstructed residual error, which evaluates the quality of a given segmentation of a reconstructed image in tomography. This novel evaluation method, which is independent of the methods that were used to reconstruct and segment the image, is applicable to segmentations that are based on the density of the scanned object. It provides a spatial map of the errors in the segmented image, based on the projection data. The reconstructed residual error is a reconstruction of the difference between the recorded data and the forward projection of that segmented image. The properties and applications of the algorithm are v

The costs and benefits of estimating T-1 of tissue alongside cerebral blood flow and arterial transit time in pseudo-continuous arterial spin labeling

Multi-post-labeling-delay pseudo-continuous arterial spin labeling (multi-PLD PCASL) allows for absolute quantification of the cerebral blood flow (CBF) as well as the arterial transit time (ATT). Estimating these perfusion parameters from multi-PLD PCASL data is a non-linear inverse problem, which is commonly tackled by fitting the single-compartment model (SCM) for PCASL, with CBF and ATT as free parameters. The longitudinal relaxation time of tissue T-1t is an important parameter in this model, as it governs the decay of the perfusion signal entirely upon entry in the imaging voxel. Conventionally, T-1t is fixed to a population average. This approach can cause CBF quantification errors, as T-1t can vary significantly inter- and intra-subject. This study compares the impact on CBF quantification, in terms of accuracy and precision, of either fixing T-1t, the conventional approach, or estimating it alongside CBF and ATT. It is shown that the conventional approach can cause a significant bias in CBF. Indeed, simulation experiments reveal that if T-1t is fixed to a value that is 10% off its true value, this may already result in a bias of 15% in CBF. On the other hand, as is shown by both simulation and real data experiments, estimating T-1t along with CBF and ATT results in a loss of CBF precision of the same order, even if the experiment design is optimized for the latter estimation problem. Simulation experiments suggest that an optimal balance between accuracy and precision of CBF estimation from multi-PLD PCASL data can be expected when using the two-parameter estimator with a fixed T-1t value between population averages of T-1t and the longitudinal relaxation time of blood T-1b

Экспериментальный анализ фонетических изменений в английской речи датско-английских билингвов

Одним из ключевых показателей, присущих двуязычному речевому поведению молодых датчан, является специфическая маркированность их английского произношения, что обращает на себя внимание уже с первых минут общения с ними. Эта маркированность произношения проявляется как следствие фонологической интерференции, которая возникает под влиянием артикуляции, интонации, ритмики, ударения первого (датского) языка на соответствующие параметры произношения второго (английского) языка.Одним з ключових показників, властивих двомовній мовній поведінці молодих данців, є специфічна маркированість їх англійської вимови, що звертає на себе увагу вже з перших хвилин спілкування з ними. Ця маркированість вимови виявляється як наслідок фонологічної інтерференції, яка виникає під впливом артикуляції, інтонації, ритміки, наголосу першої (данської) мови на відповідні параметри вимови другої (англійської) мови

Релігійний чинник у процесі вдосконалення Конституції України

Multiple states of woody cover under similar climate conditions are found in both conceptual models and observations. Due to the limitation of the observed woody cover data set, it is unclear whether the observed bimodality is caused by the presence of multiple stable states or is due to dynamic growth processes of vegetation. In this study, we combine a woody cover data set with an above ground biomass data set to investigate the simultaneous occurrences of savanna and forest states under different precipitation forcing. To interpret the results we use a recently developed vegetation dynamics model (the Balanced Optimality Structure Vegetation Model), in which the effect of fires is included. Our results show that bimodality also exists in above ground biomass and retrieved vegetation structure. In addition, the observed savanna distribution can be understood as derived from a stable state and a slightly drifting (transient) state, the latter having the potential to shift to the forest state. Finally, the results indicate that vegetation structure (horizontal vs. vertical leaf extent) is a crucial component for the existence of bimodality

Occupational therapy for community dwelling elderly people: a systematic review

OBJECTIVE: Occupational therapy might play an important role in maintaining independent living for community dwelling elderly people. The aim of this systematic review is to determine whether occupational therapy improves outcome for people who are >/=60 years and are living independently. METHODS: An extensive search in MEDLINE, CINAHL, EMBASE, AMED and SCISEARCH until July 2002 was performed. Studies with controlled and uncontrolled designs were included. Six intervention categories were distinguished and individually analysed using a best-evidence synthesis, based on the type of design, the methodological quality, type of outcome measures and statistical significance of findings. RESULTS: 17 studies were included, ten of which were randomised clinical trials. Six randomised clinical trials had a high methodological quality. Strong evidence is present for the efficacy of advising on assistive devices as part of a home hazards assessment on functional ability. There is some evidence for the efficacy of training of skills combined with a home hazard assessment in decreasing the incidence of falls in elderly people at high risk of falling. Some evidence is available for the efficacy of comprehensive occupational therapy on functional ability, social participation and quality of life. Insufficient evidence is present for the efficacy of counselling the primary caregiver of dementia patients about maintaining the patient's functional abilities. CONCLUSION: This review shows that occupational therapy interventions for community dwelling elderly people results in positive outcomes. Future research in the efficacy of occupational therapy in elderly patient groups such as people with dementia is recommended. Furthermore, research into tailoring interventions to the needs of elderly patients is recommended. (aut.ref.