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Sort order. Mar 29, Maripat-luna rated it it was amazing. I highly recommend this book to persons who are not afraid to question or challenge the status quo of traditional patriarchal teachings and archetypes, to anyone who searches for the Divine who seems so far away. I recommend this novel for wome A Finely Woven Tapestry of Women, Story, Mysticism and a Glimpse of The Feminine Divine Divine In this book Christin Lore Weber weaves a golden thread between past and present, far and near, sacred and profane, in her distinctive voice of beautiful prose.

I recommend this novel for women of courage searching for a glimpse of the God in whose image we are made. Most of all I recommend this book to those who are brave enough to ask difficult questions of themselves, even at the risk of being called heretic. Well, I wrote the book, so my thoughts about it are biased.

All I can say is that the writing of it which took years initiated in me a transformation of soul.

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Jill Beerman rated it really liked it Sep 03, Kathleen rated it it was amazing Dec 19, Tasha marked it as to-read Jul 08, Christine marked it as to-read May 21, There are no discussion topics on this book yet. About Christin Lore Weber. Christin Lore Weber. Books by Christin Lore Weber. The reasons for these discrepancies have been sought in different visual conditions but could not be clarified to date.

This was in fact not surprising, because it has been known since the time of Helmholtz that there is no single visual criterion that can define the 3D orientation of the eyes providing optimal retinal correspondences in near vision Helmholtz ; Hepp ; Van Rijn and Van den Berg At the level of single targets, however, it is possible to define the optimal orientation of the eyes for single binocular vision.

From a visuomotor standpoint, it is Donders' and Listing's laws that guarantee the existence of retinal correspondences in far vision by laying down the relations between azimuth, elevation, and torsion of each eye. Although the same kinematic principles do allow for binocular vision of near targets in the horizontal plane of regard, they fail for targets off the horizontal plane. In these circumstances the optimal binocular kinematics turns out to be more complex because of the emergence of 2D disparities in the binocular field of fixations.

A key difference of the presently proposed kinematics and the more simple Helmholtz kinematics is that in a binocular setting, the Donders-Listing kinematics entail torsional rather than horizontal-vertical disparities for targets off the horizontal plane of regard. Such torsional disparities arise even under the condition of symmetric ocular vergence, which is in line with the experimentally well-established observations of disjunctive torsion of the eyes in near vision Fig.

Comparison of 2-dimensional disparities of single targets created by the Helmholtz kinematic model and the Donders-Listing model. Note zero disparity of projected targets in the horizontal plane of regard. B : Donders-Listing model with the same angular parameters as in A. Target images fall to either side of the respective Helmholtz circle, depending on the eye-to-target distance, except for targets in the horizontal plane of regard with zero disparity. Note the symmetric torsional disparities for symmetric vergence.

After torsional fusion, target images align with the respective Helmholtz circles open circles.

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Normed planar projection map of right and left retina: right center of rotation at horizontal meridian 0, left center of rotation at horizontal meridian 1; iso-eccentricity circles relative to right center are shown in black and those relative to left center in gray. A crucial property of torsional disparities is that they can be locally eliminated by modulating ocular torsion without affecting the intrinsic geometry of the retinal projection images.

The torsion required for binocular fusion of the disjunctive Listing positions in the binocular visual field is prima facie a simple function of the estimated binocular target position and the associated Listing positions of each eye. However, the azimuth and elevation of these positions relative to each eye are linked to each other via the eye-to-target distances and the anatomically fixed interocular distance.

As illustrated by the concept of normed target space Figs. Generally, the two eyes must torque by different amounts depending on the respective eye-to-target distance.

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More specifically, the torsion required for fusion depends exponentially on target distance. At constant vergence it depends linearly on elevation in the intermediate- and large-distance range Fig. A striking observation was the steadily increasing torsion of the eyes during refixation saccades, which abruptly stopped and returned to smaller values at the time of target acquisition Fig.

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This behavior was observed consistently in all three animals. It was recently found that ocular torsion may enhance or oppose stereoscopic vision, suggesting that the search zones for detecting corresponding features on the retinas are retina-fixed Schreiber et al. Disparity-selective neurons in the visual cortex V1, on the other hand, have been shown to encode a larger range of horizontal than vertical disparities Barlow et al. On the oculomotor side, we found that horizontal and vertical disparities in peripheral viewing are in fact taken as torsional disparities driving torsional adjustments of the eyes Figs.

Taking these findings together suggests that torsional disparity represents a crucial stimulus in stereoscopic vision. If so, it is plausible that the brain actively modulates ocular torsion in search for corresponding features during refixation saccades: In fact, ocular torsion sweeps the epipolar lines relative to either eye across the frontal projection of the retinae with the result that the two retinal projection images can be correlated with each other without affecting their intrinsic geometry.

Thereby, the predominantly horizontally organized disparity zones acquire a vertical dimension. In this view, the observed active modulation of ocular torsion might represent an important mechanism that helps search for corresponding retinal features localizing a small target in near space. Although we have studied refixation saccades in a restricted field of view, the principals of ocular kinematics outlined in this report may also shed some new light on the debate about the role of vertical disparity detection in stereoscopic depth perception Read et al.

Donders' law states that the ocular orientation of each eye during fixation of a target does not depend on the location of the previously fixated target whatever path the eye may take in the configuration space of rotations Donders In far vision, this fundamental law in oculomotor control holds in the monocular as well as in the binocular visual fixation space because of the normally strong yoking of saccades.

In near visual space, the question arises how Donders' law might be realized, because now the ocular motion required for fixation of a binocular target is a compounded rotation in three rather than just two rotation planes. What does the third rotational degree of motion freedom determine when the eye saccades between binocular targets in near visual space?

The answer lies in the particular geometry of disjunctive eye positions on the vertical direction circles in relation to the neighboring binocular positions on the associated Helmholtz circle. For fusion of the dichoptic target images, these positions must share the same frontoparallel depth plane, which guarantees that there is one and only one path in the configuration space of rotations that connects those disjunctive positions with the binocular position in question. Because the two possible points of intersection of the respective vertical direction circle and the respective frontoparallel plane are in symmetric position relative to the horizontal plane of regard Fig.

For saccades between the monocular and binocular field or outside the binocular field of fixations, this singular connectivity obviously does not exist, because the Helmholtz circle of binocular positions is not a direction circle for eye movements. Saccade thus may start from or land on a Listing position in near vision that cannot be fused for physical reasons, in which case Donders' law just holds for each eye separately.

In contrast to far vision, the binocular extension of Donders' law requires an extra effort of the brain to fuse the images of the two eyes to establish stereoscopic vision. The Donders-Listing kinematics of the eyes implies that vertical rotations typically occur in planes that are tilted about the vertical axis toward the Helmholtz plane of binocular positions in the visual field.

The kinematics of far-near re-fixation saccades

Viewed in frontal projection, the tangential lines to Listing positions on the vertical direction circles thus increasingly incline toward the Helmholtz circle with increasing eccentricity of visual lines Fig. Since ocular torsion can only locally eliminate these disparities, the fusion of the disparate monocular target images in near vision is bound to interfere with the perception of the visual field in specific ways. One well-studied example is the perception of verticality, which has been shown to deviate from the physical vertical in near vision as might be expected from the distribution of torsional disparities along the Helmholtz circle in symmetric vergence Fig.

The possible influence of torsional disparity gradients across the binocular visual field on perception remains to be investigated for a review on binocular vision, see Howard and Rogers No conflicts of interest, financial or otherwise, are declared by the authors.

An analogous compounded rotation was used for the left eye see Figs. The Donders-Listing kinematics used in this study consisted of a rotation in the horizontal plane of regard, exerted by a rotation operator R AO , followed by a rotation in the vertical direction plane, exerted by a rotation operator denoted R BA. Note that R BAO does not generate torsion.

The Donders-Listing model combines the Donders-Listing kinematics with rotations of the eye in a common frontoparallel plane, which fuse the disparate target images of the right and left eye. Note that the tilt is zero for zero elevation because the torsion required for binocular vision vanishes as the elevation approaches zero. Only one of these positions is close to the target. Present address of H. Journal home Ahead of Print Issues.

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    Volume Issue 8. Submit Subscribe. This Journal. Quick Search in Journals Search this journal. Journal Menu. Control of Movement. Bernhard J. Hess, Neurology Dept. This is the final version - click for previous version. Export citation Add to favorites Get permissions Track citations. Abstract We have analyzed the three-dimensional spatiotemporal characteristics of saccadic refixations between far and near targets in three behaviorally trained rhesus monkeys. Download figure Download PowerPoint.

    Model comparison and R 2. Am Stat 48 : —, The neural mechanism of binocular depth discrimination. J Physiol : —, An unexpected specialization for horizontal disparity in primary visual cortex. Nature : —, Seeing in three dimensions: the neurophysiology of stereopsis. Trends Cogn Sci 4 : 80—90, Beitrag zur Lehre von den Bewegungen des menschlichen Auges. Google Scholar Enright JT.

    Ocular translation and cyclotorsion due to changes in fixation distance. Vision Res 20 : —, Considerations on Listing's law and the primary position by means of a matrix description of eye position control. Biol Cybern 60 : —, Handbuch der Phyiologischen Optik. Hamburg, Germany: Voss, Google Scholar Hepp K. Oculomotor control: Listing's law and all that. Curr Opin Neurobiol 4 : —, Theoretical explanations of Listing's law and their implication for binocular vision. Vision Res 35 : —, Listing's law: visual, motor or visuomotor?

    Amsterdam: Hartwood Academic, Google Scholar Hess BJ. Dual-search coil for measuring 3-dimensional eye movements in experimental animals. Vision Res 30 : —, Three-dimensional visuo-motor control of saccades. Learn more. Evidence in radar, reflectance, and visible imagery indicates that surface and subsurface water ice is present inside permanently shadowed regions in the north polar region of Mercury.

    The origin of this ice and the time at which it was delivered to the planet are both unknown. Finding the smallest, most easily eroded ice deposits on Mercury can help answer these questions. We consider two possible delivery methods for these deposits: a gradual, slow accumulation by micrometeorites or solar wind implantation and an episodic deposition, either primordial or by a recent comet impact.

    Craters near the north pole of Mercury, one of the warmest planets in the solar system, cast persistent shadows that are so cold they can trap water ice for billions of years. Although many observations show that ice is present inside these polar cold traps, its age and the way it was delivered to the planet are not well known. Due to the relative shallowness of these micro cold traps , an episodic deposition, such as a comet impact, is a more probable delivery mechanism than an ongoing slow accumulation by micrometeorites.

    Using previously estimated surface erosion rates, we find that the age of this ice is most likely lower than million years. Volume , Issue 8. If you do not receive an email within 10 minutes, your email address may not be registered, and you may need to create a new Wiley Online Library account. If the address matches an existing account you will receive an email with instructions to retrieve your username.

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