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At least 487 records · Page 27Linked to original sources
PubMedDate not supplied

Mirror image myopic anisometropia in two pairs of monozygotic twins.

Two sets of monozygotic twins with mirror image myopic anisometropia are reported. The first set were two boys aged 1 year 8 months. There was a right eye myopic anisometropia in one twin, and a left eye myopic anisometropia in the other. The differences in refractive power between both eyes were 11.6 and 7.6 dpt, respectively (spherical equivalent). The second set were two 6-year-old boys. The right eye had myopic anisometropia in one twin, while the left eye was affected in the other. The differences in refractive power between both eyes were 6.5 and 3.7 dpt, respectively (spherical equivalent). Exotropia was recognized in 3 cases. Previously only two sets of monozygotic twins with mirror image myopic anisometropia have been reported. Monozygotic twins with mirror image myopic anisometropia are extremely rare.

Anisometropia↗
PubMedDate not supplied

Exclusive lower extremity mirror movements and diastematomyelia.

Mirror movements usually seen in the Klippel-Feil syndrome are most commonly appreciated in the upper extremities. Lower extremity involvement is seen rarely and when observed, is found in conjunction with upper extremity mirror movements. We report what we believe to be the first case of mirror movements found exclusively in the lower extremities in a female patient presenting with tethered cord syndrome. Our hopes are that this report will help elucidate mechanisms involved with these anomalous movements, as currently there is no commonly accepted etiology.

Adolescent↗
PubMed2006

Maternal mirror syndrome after in utero aortic valve dilation. A case report.

Fetal hydrops of various etiologies can be associated with maternal mirror syndrome. The exact pathophysiology of this rare disorder remains unclear, yet it can result in significant maternal and fetal morbidity. The recent advances in prenatal diagnosis and therapeutic interventions have focused on altering the course of pathologies associated with an expected poor prognosis. Severe fetal aortic valve stenosis with its potential for hypoplastic left heart fit this category. We report a case of maternal mirror syndrome in a parturient following intrauterine therapy for severe fetal aortic stenosis and hydrops. Despite a technically successful intervention, the mother required emergency cesarean section. We review the few reports of mirror syndrome as well as the current approaches to fetal aortic stenosis. This case reinforces the need for in depth risk analysis prior to fetal interventions. It also emphasizes the advantage of earlier detection and therapy with fetal aortic stenosis since fetal hydrops carries a somber prognosis.

Adult↗
PubMed2005

Mirror neurons responding to observation of actions made with tools in monkey ventral premotor cortex.

In the present study, we describe a new type of visuomotor neurons, named tool-responding mirror neurons, which are found in the lateral sector of monkey ventral premotor area F5. Tool-responding mirror neurons discharge when the monkey observes actions performed by an experimenter with a tool (a stick or a pair of pliers). This response is stronger than that obtained when the monkey observes a similar action made with a biological effector (the hand or the mouth). These neurons respond also when the monkey executes actions with both the hand and the mouth. The visual and the motor responses of each neuron are congruent in that they share the same general goal, that is, taking possession of an object and modifying its state. It is hypothesized that after a relatively long visual exposure to tool actions, a visual association between the hand and the tool is created, so that the tool becomes as a kind of prolongation of the hand. We propose that tool-responding mirror neurons enable the observing monkey to extend action-understanding capacity to actions that do not strictly correspond to its motor representations. Our findings support the notion that the motor cortex plays a crucial role in understanding action goals.

Action Potentials↗
PubMed2005

Symmetry cues for matching mirrored objects.

The study explores cues for matching pairs of objects. These objects were arranged into mirror-symmetrical displays and the task was to judge whether a pre-specified 180 degree rotation around the X, Y or Z axis carries one object into the mirror object. For some rotations, the object's mirror symmetry (M) and, for other rotations, the object's point-symmetry (P) could serve as a cue. The matching results suggest that M is a better cue than P, say M > P. Various attempts are made to explain this effect. The most promising one focuses on simplest structural object representations as these capture M and not P. It is furthermore plausible that M captured by reference frames at high hierarchical representation levels, say M1, serves as a better cue than M captured at low levels, say M2. The prediction M1 > M2 > P merely applies to the open surface objects in the experiment. For the closed solid objects in the experiment the expectation is M1 = M2 = P. Both predictions roughly agree with the accuracy and reaction-time data. The results suggest the perceptual relevance of representation cues and, aditionally, that cues stemming from reference frames at higher hierarchical representation levels are more effective than those from lower levels.

Cues↗
PubMed1989

Teaching indirect mirror laryngoscopy.

Indirect mirror laryngoscopy is difficult to learn. An anatomic model of the oropharynx and larynx is described here. This model is used to familiarize medical students with the component skills of mirror laryngoscopy. The students progress to competency at mirror laryngoscopy on patients more quickly after initial use of this model.

Laryngoscopy↗
PubMed1986

Electromyographic studies of congenital mirror movements.

We studied two patients with congenital mirror movements. In one, the movements were associated with impaired sensation and a cervicodorsal meningocele. In the other, no abnormality of the nervous system was found. In an EMG study, the normal temporal characteristics, response latency, duration, and amount of EMG on the normal and mirror sides suggest that similar motor commands are responsible for both voluntary and mirror movements.

Adolescent↗
PubMed2000

Reorganization of the motor cortex in a patient with congenital hemiparesis and mirror movements.

Abnormal branching of corticospinal fibers from the unaffected motor cortex is responsible for mirror movements in patients with congenital hemiparesis, but it is unknown which mechanisms enable these patients to lateralize motor activity. Using multiunit electromyographic analysis and transcranial magnetic stimulation, the authors provide evidence for nonbranched crossed and uncrossed corticospinal projections and intracortical inhibition of the mirror hand. They propose that this remarkable reorganization of the unaffected motor cortex helps these patients to reduce mirror movements.

Adult↗
PubMed2006

Capicua regulates follicle cell fate in the Drosophila ovary through repression of mirror.

The dorsoventral axis of the Drosophila egg is established by dorsally localized activation of the epidermal growth factor receptor (Egfr) in the ovarian follicular epithelium. Subsequent positive- and negative-feedback regulation generates two dorsolateral follicle cell primordia that will produce the eggshell appendages. A dorsal midline domain of low Egfr activity between the appendage primordia defines their dorsal boundary, but little is known about the mechanisms that establish their ventral limit. We demonstrate that the transcriptional repressor Capicua is required cell autonomously in ventral and lateral follicle cells to repress dorsal fates, and functions in this process through the repression of mirror. Interestingly, ectopic expression of mirror in the absence of capicua is observed only in the anterior half of the epithelium. We propose that Capicua regulates the pattern of follicle cell fates along the dorsoventral axis by blocking the induction of appendage determinants, such as mirror, by anterior positional cues.

Animals↗
PubMed2003

Retrospective case study of carbon dioxide laser stapedotomy with lens-based and mirror-based micromanipulators.

Most clinical studies on carbon dioxide (CO2) (lambda = 10.6 mm) laser stapedotomy have been carried out with the laser guided by a conventional lens-based micromanipulator, with the attendant risks of correct aiming (HeNe) and surgical (CO2) beam misalignment. Hence, engineering advances have attempted to improve laser targeting as well as the spot size focus. The development of the mirror-based micromanipulator was a response to this need but no data concerning its use in stapes surgery is available. We performed a retrospective case-series review of patients treated for otosclerosis between 1992 and 2000. Primary laser stapedotomy was performed in 218 consecutive patients. In the first 78 procedures, the aiming beam (HeNe, lambda = 632 nm) and surgical beam (CO2) were guided with a conventional lens-based micromanipulator whereas in the subsequent 140 procedures, they were guided by using a mirror-based micromanipulator. Hearing was tested at six and 12 months. The mean (SD) airbone gap was 5 dB (4.5) and 4.5 dB (3.9). The mean closure was 15 dB (9.9) and 14.4 dB (9.4). The mean change in the high-tone bone-conduction level was 5.5 dB (7.3) and 7.8 dB (7.5). Overheating of the facial canal produced transient facial paralysis in one case and was due to misalignment of the beams with the lens-based micromanipulator. Use of the mirror-based micromanipulator obviated the need to verify alignment. The light-weight and superior optical yield of this system made it possible to reduce the number of impacts on the footplate by the integral restitution of the energy source. This study demonstrated that the CO2 laser is an effective method for performing stapedotomy. In addition, microtrauma to the labyrinth is reduced by its ability to perform calibrated footplate fenestration without mechanical or vibrational injury to the inner ear. The optical reflection micromanipulator simplified beam alignment and enhanced surgical comfort.

Adolescent↗
PubMed2003

Experimental anxiety and antiepileptics: the effects of valproate and vigabatrin in the mirrored chamber test.

The potential anxiolytic-like effects of valproate (VPA; 200, 300 and 400 mg/kg i.p.) and vigabatrin (GVG; 150, 300 and 450 mg/kg i.p.) were evaluated in an experimental model of anxiety in mice. The mirrored chamber test was the model selected. In this study, anxiogenic-like behavior was induced by pretreatment with m-chlorophenylpiperazine hydrochloride (m-CPP; 1 mg/kg i.p.). For comparative purposes, the effects of an established reference anxiolytic, lorazepam (LOR; 0.025, 0.05 and 0.10 mg/kg i.p.) were also evaluated. Results showed that 2 weeks of repeated treatment with 200, 300 and 400 mg/kg of VPA or, to a lesser extent, 300 and 450 mg/kg i.p. of GVG, antagonized the anxiogenic effects of m-CPP. VPA induced behavioral changes very similar to those produced by lorazepam, i.e., a decrease in the latency time to enter the mirrored chamber and an increase in the time spent in the mirrored chamber. The anxiolytic-like potency of GVG was lower than that of VPA in this test. In conclusion, these data provide additional evidence for the anxiolytic-like effects of VPA and substantiate its role in the treatment of anxiety disorders and in the withdrawal state of ethanol or sedative-hypnotics.

Animals↗
PubMed2002

Chromium-scandium multilayer mirrors for the nitrogen K(alpha) line in the water window region.

Chromium-scandium (Cr-Sc) is a promising material combination for multilayer mirrors in the water window region. A possible x-ray source for laboratory use in this wavelength range is the nitrogen K(alpha) line at 3.16 nm. High reflectivities at this wavelength can be achieved with Cr-Sc multilayer mirrors if the interfaces between adjacent layers are smooth. The growth parameters of the magnetron sputtering process for these materials have been optimized. It is shown that the reflectivity of such mirrors can be considerably improved by the application of a proper bias voltage during film growth. The high quality of the multilayer films is demonstrated with copper K(alpha) x-ray reflection and transmission electron microscopy. The reflective properties of the multilayers close to the nitrogen K(alpha) line were measured with synchrotron radiation for different angles of incidence. Reflectivities between R = 5.9% for near-normal incidence (theta = 1.5 degrees) and R = 29.6% for theta = 59.9 degrees were measured.

Chromium↗
PubMed2002

Wind-induced deformations in a segmented mirror.

A Zernike expansion of wind-induced deformations in a segmented mirror is described. The wind model is a frozen turbulent field with a Kolmogorov spectrum for scales smaller than the outer scale and a flat spectrum for scales larger than the outer scale. The approach allows a mode-by-mode comparison of the wave-front error contributions from atmospheric phase distortions, wind-induced deformations, and the mirror control system noise. This is used to design a controller that minimizes the mirror surface errors by application of corrections based on edge sensor measurements and wave-front measurements on a guide star.

Journal Article↗
PubMed2002

Polynomial-based optical true-time delay devices with microelectromechanical mirror arrays.

We previously reported optical true-time delay devices, based on the White cell, to support phased-array radars. In particular, we demonstrated a quadratic device, in which the number of delays obtainable was proportional to the square of the number of times the light beam bounced in the cell. Here we consider the possibilities when a microelectromechanical (MEM) tip/tilt mirror array with multiple stable states is used. We present and compare designs for quadratic, quartic, and octic cells using MEM mirror arrays with two, three, and five micro-mirror tilt angles. An octic cell with a three-state MEM can produce 6,339 different delays in just 17 bounces.

Journal Article↗
PubMed2002

Optimization of chirped mirrors.

We demonstrate that a highly efficient global optimization of chirped mirrors can be performed with the memetic algorithm. The inherently high sensitivity of chirped-mirror characteristics to manufacturing errors can be reduced significantly by means of the stochastic quasi-gradient algorithm. The applicability of these algorithms is not limited to chirped mirrors.

Journal Article↗
PubMed2002

Organic microcavity light-emitting diodes with metal mirrors: dependence of the emission wavelength on the viewing angle.

Organic microcavity light-emitting diodes typically exhibit a blueshift of the emitting wavelength with increasing viewing angle. We have modeled the shift of the resonance wavelength for several metal mirrors. Eight metals (Al, Ag, Cr, Ti, Au, Ni, Pt, and Cu) have been considered top or bottom mirrors, depending on their work functions. The model fully take into account the dependence of thephase change that occurs on reflection on angle and wavelength for both s and p polarization, as well as on dispersion in the organic layers. Different contribution to the emission wavelength shift are discussed. The influence of the thickness of the bottom mirror and of the choice and thickness of the organic materials inside the cavity has been investigated. Based on the results obtained, guidelines for a choice of materials to reduce blueshift are given.

Journal Article↗
PubMed2003

Thermal forming of glass microsheets for x-ray telescope mirror segments.

We describe a technology to mass-produce ultrathin mirror substrates for x-ray telescopes of near Wolter-I geometry. Thermal glass forming is a low-cost method to produce high-throughput, spaceborne x-ray mirrors for the 0.1-200-keV energy band. These substrates can provide the collecting area envisioned for future x-ray observatories. The glass microsheets are shaped into mirror segments at high temperature by use of a guiding mandrel, without polishing. We determine the physical properties and mechanisms that elucidate the formation process and that are crucial to improve surface quality. We develop a viscodynamic model for the glass strain as the forming proceeds to find the conditions for repeatability. Thermal forming preserves the x-ray reflectance and scattering properties of the raw glass. The imaging resolution is driven by a large wavelength figure. We discuss the sources of figure errors, and we calculate the relaxation time of surface ripples.

Journal Article↗
PubMed2003

Houghton anastigmatic telescope containing aspheric mirrors that allows corrector position as a free parameter.

A family of catadioptric telescopes is investigated, characterzied with two-element, full-aperture afocal corrector lenses and aspherical, focusing, primary mirrors or primary-secondary mirror combination. Third-order aberration and design equation are provided for anastigmatic systems in which corrector position must be a free parameter, forcing the consideration of aspherics on the mirrored surfaces.

Journal Article↗