17 Result(s)

Article

Vertebral Dimensions: Influence of X-Ray Technique and Patient Size on Measurements

In this study a new reference value, ``corrected vertebral dimension,'' is presented for vertebral height measurements. Of 68 females (age 18–88 years; mean 44.2 years) and 40 males (age 16–81 years; mean 55 ...

J. W. van Bodegom, J. W. Kuiper, R. R. van Rijn… in Calcified Tissue International (1998)

Article

Influence of surrounding soft tissue and bone of the pelvis on quantitative CT measurements of the femoral neck

J. W. Kuiper, C. van Kuijk, H. Slis, J L Grashuis… in Osteoporosis International (1996)

Article

Skin thickness does not reflect bone mineral density in postmenopausal women

Skin and bone both contain primarily type I collagen in connective tissue matrices and are assumed to be related due to this common organic constituent. The purpose of this study was to investigate whether ski...

A. J. Smeets MD, J. W. Kuiper, C. van Kuijk, B. Berning… in Osteoporosis International (1994)

Article

The effect of air velocity on the wingstroke frequency of the blowflyCalliphora erythrocephala

The effect of air velocity and pressure on the wingstroke frequency ofCalliphora erythrocephala, flying in a windtunnel, was studied. The results can be understood by considering the flight mechanism as a mechani...

H. Otzen, J. W. Kuiper in Journal of comparative physiology (1983)

Article

On the correlation model: Performance of a movement detecting neural element in the fly visual system

The applicability of the basic principles of the correlation model to the description of the activity of a movement detecting neuron in the third optic ganglion of the fly's visual system has been investigated...

W. H. Zaagman, H. A. K. Mastebroek, J. W. Kuiper in Biological Cybernetics (1978)

Article

Receptive field characteristics of a directionally selective movement detector in the visual system of the blowfly

Action potentials evoked by stepwise-moving visual stimuli have been recorded extracellularly from the horizontally selective movement detectors in the lobula complex of the blowflyCalliphora erythrocephala (M.).

W. H. Zaagman, H. A. K. Mastebroek, T. Buyse… in Journal of comparative physiology (1977)

Article

Retinal lattice, visual field and binocularities in flies

The arrangements of ommatidia are charted and the visual fields of the compound eyes are plotted for both male and female of the dipteran speciesMusca domestica L.,Calliphora erythrocephala M.,Stomoxys calcitrans

D. G. M. Beersma, D. G. Stavenga, J. W. Kuiper in Journal of comparative physiology (1977)

Article

Insect pupil mechanisms

The pupil mechanism of Hymenoptera (suborder Apocrita) has been studied by simultaneous recordings of transmission and reflection from the compound eye of virtually intact animals. It is confirmed that the lig...

D. G. Stavenga, J. W. Kuiper in Journal of comparative physiology (1977)

Article

Insect pupil mechanisms

The hypothesis that the glow observable in dark adapted butterfly eyes is extinguished upon light adaptation by the action of migrating retinula cell pigment granules (Stavenga, 1975a) has been investigated. E...

D. G. Stavenga, J. A. J. Numan, J. Tinbergen… in Journal of comparative physiology (1977)

Article

Organization of visual axes in the compound eye of the flyMusca domestica L. and behavioural consequences

The previously derived optical demands for the neural superposition eye are experimentally tested in the compound eye ofMusca domestica L. The optical requirements are fulfilled except in the marginal regions.

D. G. M. Beersma, D. G. Stavenga, J. W. Kuiper in Journal of comparative physiology (1975)

Article

Photopigment conversions expressed in receptor potential and membrane resistance of blowfly visual sense cells

IN spite of the fact that intracellular recordings from photoreceptor cells have been possible for many years and knowledge regarding the photochemistry of these cells has been steadily increasing, it is still...

H. MUIJSER, J. T. LEUTSCHER-HAZELHOFF, D. G. STAVENGA, J. W. KUIPER in Nature (1975)

Article

Photopigment conversions expressed in pupil mechanism of blowfly visual sense cells

VISUAL sense cells of flies are depolarised at illumination^1–3. This event triggers the pupil mechanism: pigment granules dispersed throughout the cytoplasm migrate towards the rhabdomere, that is, the light-guid...

D. G. STAVENGA, J. H. FLOKSTRA, J. W. KUIPER in Nature (1975)

Chapter and Conference Paper

Rhodopsin Processes and the Function of the Pupil Mechanism in Flies

In the photoreceptor cells of the compound eye of the fly pigment granules migrate under the influence of a change in light intensity (1). The light flux in the cell’s rhabdomere, which contains the visual pig...

D. G. Stavenga, A. Zantema, J. W. Kuiper in Biochemistry and Physiology of Visual Pigments (1973)

Article

High-precision Repetitive Firing in the Insect Optic Lobe and a Hypothesis for its Function in Object Location

WE have encountered, in the optic lobe of the insect Calliphora erythrocephala, a layer of elements firing spontaneously at a very constant rate of about 50 spikes per sec. The observed waveform depends on the po...

J. W. KUIPER, J. T. LEUTSCHER-HAZELHOFF in Nature (1965)

Article

Non-linear Microphonic Response of Labyrinth Organs to Stimuli consisting of Two Pure Tones

IN a study of the microphonio effect of the lateral line of fishes¹, we found a remarkable response to a stimulus consisting of two pure sine waves acting at the same time on the sense organ. These effects are de...

HL. DE VRIES, J. W. KUIPER, D. R. UBBENS in Nature (1955)