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Control of Movement and Posture
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Learning a motor skill is not by itself very useful if the learned skill cannot be stored and retrieved later. Where and how memories are stored and how they are retrieved remains conjectural. It is generally assumed that memories are stored in synapses. Macromolecules have also been implicated in memory storage and retrieval. In his classical experiments conducted early in the twentieth century, the American neuropsychologist Karl Lashley showed that rats retained the memory of a learned motor task even after 98% of the cortical areas related to the task were removed, irrespective of which areas were spared. This suggested a distributed nature of memory, as in a hologram, which is a two-dimensional recording on a photographic medium of an interference pattern produced by a laser beam, part of which is applied directly to the medium and the other part is reflected from a three-dimensional object. When a laser beam of the same frequency is applied to the medium, a hologram appears as a three-dimensional image of the object. Holograms of different objects can be stored on the same medium using laser beams of different frequencies. An important aspect of holography is that any small part of the hologram can be used to reproduce the image of the whole object, which means that the information on the object is stored in a distributed manner. What neuronal mechanisms can give rise to distributed memory also remains conjectural.
Coded Aperture Tomography
Published in Bhagwat D. Ahluwalia, Tomographic Methods in Nuclear Medicine: Physical Principles, Instruments, and Clinical Applications, 2020
U. Raff, R. E. Hendrick, W. R. Hendee
Simple applications of Fresnel zone plates to nuclear medicine have been reported by several authors.8, 28-33 The source of radiation (i.e., the patient) is placed in front of the zone plate and the encoded information is captured on transparency film. Images representing planes through the source distribution are reconstructed by transmitting coherent light through the transparency. Images are reconstructed in three dimensions, as in standard holography. This analog tomographic approach offers two major advantages: (1) the photon collection efficiency is a factor of approximately 100 greater than the efficiency of usual collimators and (2) the spatial resolution is improved beyond that obtained with conventional devices.
Roughness (Measured by Profilometry: Mechanical, Optical, and Laser)
Published in Enzo Berardesca, Peter Elsner, Klaus-P. Wilhelm, Howard I. Maibach, Bioengineering of the Skin: Methods and Instrumentation, 2020
The principle of holographic measurement is based on the separation of laser light into two parts (Figure 6). The wave U0 is sent to the measuring object after it is stretched at the optic LP1 The reference wave Ur spreads directly through the optic LP2 to the plane of projection P. The result of the superposition of both waves is a hologram in the plane of projection due to the coherence of the laser light. Similar to the phenomenon described earlier, this hologram is also an interference picture, containing information on the distribution of amplitude and phase of the reflected wave. Illuminating the hologram out of an appropriate illumination angle, the beam of illumination is diffracted by the interference pattern. The vertical resolution of this method is dependent on the wavelength of the light used. Actually, used instruments have a resolution of <10 nm based on ranges of nearly 1 mm. This is adequate to measure the human skin surface. Nevertheless, at the moment a successful application is not known.
A simple geometric method for 3D morphology reconstruction of a cell based on two orthogonal phase images
Published in Computer Assisted Surgery, 2019
Yawei Wang, Hao Han, Lei Wang, Jingrong Liao, Bing Xie, Ying Ji, Yuanyuan Xu
Tomography phase microscopy (TPM) [7–12] is an new and developing technological tool that quantitatively produces the distribution of RI and three-dimensional structure of phase object. TPM usually has two realization way such as rotating sample and multi-beam projection, images obtained can be applied to reconstruct the three-dimensional structure on the basis of parallelism method. For instance, Choi proposed one TPM technique based on alien Mach–Zehnder interference principle [7]. In this method, a tilting galvanometer-mounted mirror is used to change the angle of the laser beam to obtain the phase information at multiple angles. Finally, with an improved reconstruction algorithm to these phases, the RI tomograms of an HT29 cell were obtained. In Ref. [10], an advance TPM approach was proposed, which combines an external off-axis interferometer and a holographic optical tweezers. In this method, the interferometric projection set an angular range of 180° with 5° steps can be collected by using rotation of the cells. Then, with the classical filtered back-projection algorithm to these projection data, the 3D refractive index of a yeast cell in suspension was reconstructed.
Military and industrial performance: the critical role of noise controls
Published in International Journal of Audiology, 2019
Kurt. D. Yankaskas, Jeffrey M. Komrower
The measurements made during flight operations utilised extensive arrays of microphones and accelerometers distributed under the flight deck, with a concentration of under-aircraft launch areas. This was about 20% of the 4.5 acres of the flight deck for high resolution and propagation paths. Recently, 3D acoustic holography was utilised, a measurement technology from the automotive industry. A spherical microphone/camera array maps sound energy from space surfaces which are superimposed on a 360-degree picture of the space being measured. This allows visualisation of the acoustic hot spots and the positive identification of the primary paths through which acoustic energy enters that space. It also helps to determine how acoustic treatments can be selectively applied to surfaces, which results in a weight/cost savings and a fine tuning of the CAD acoustic model. An acoustic array measurement from an aircraft launch sequence is shown in Figure 3.
Janusian, anomic, agent, and steward: How employees perceive the identity of healthcare organizations
Published in International Journal of Healthcare Management, 2018
Francisco Guilherme Nunes, Luis Manuel Martins
Multiple identities describe the existence of diversified views of the organization that can be more or less in conflict, or place more or less contradictory demands on members. A common approach to describe these possibilities implies distinguishing ideographic and holographic organizations.21 In an ideographic organization, different groups hold diverse conceptualizations of an organization's identity. This would be the case of a hospital's identity being described in fundamentally different ways by doctors, nurses, and managers. In a holographic organization, multiple identities are held by all organizational members, who look at the same organization as having two or more defining core features, and the possible tension coming from this duality is espoused to some extent by all members. HCOs are good examples of holographic organizations because more and more of them have to deal with the seemingly irresolvable conflict between seeking to reduce costs and being financially viable while maintaining an increasingly demanding level of quality care for patients. But more importantly, if one organization fails to accomplish just one of these demands, the survival of the entire organization will be at risk.22 Thus, to somehow conciliate the multiple identities of HCO becomes a central management concern.