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PubMed2005

Breakdown of the mirror image symmetry in the optical absorption/emission spectra of oligo(para-phenylene)s.

The absorption and emission spectra of most luminescent, pi-conjugated, organic molecules are the mirror image of each other. In some cases, however, this symmetry is severely broken. In the present work, the asymmetry between the absorption and fluorescence spectra in molecular systems consisting of para-linked phenyl rings is studied. The vibronic structure of the emission and absorption bands is calculated from ab initio quantum chemical methods and a subsequent, rigorous Franck-Condon treatment. Good agreement with experiment is achieved. A clear relation can be established between the strongly anharmonic double-well potential for the phenylene ring librations around the long molecular axis and the observed deviation from the mirror image symmetry. Consequences for related compounds and temperature dependent optical measurements are also discussed.

Journal Article↗
PubMed1986

Tactile recognition of laterally inverted mirror images by children: intermanual transfer and rotation of the palm.

Intermanual tactile recognition of laterally inverted mirror shapes was studied, with special reference to the role of the thumb. Children were allowed to feel the shapes either with the whole hand, with only four fingers (excluding the thumb), or with only the index finger. Intramanual recognition was also studied after rotation of the hand from the palm down/up to the palm up/down orientation. The thumb was found not to be important for intermanual mirror reversals, and only of limited importance for intramanual reversals. There was no evidence that coding with reference to the hand is of importance for either inter or intramamual reversals. The explanations for the two kinds of reversals are quite different.

Age Factors↗
PubMed2005

Interaction of vision and movement via a mirror.

I have noticed a striking effect that vision can have on movement: when a person makes circular motions with both hands, clockwise with the left hand, counterclockwise with the right hand, while watching the reflection of one hand in a parasagitally placed mirror, if one arm makes a vertical excursion, the other arm tends to make the same vertical excursion, but not typically if the excursing arm is viewed in plain vision. This observation may help in understanding how visual feedback via a mirror may be beneficial for rehabilitation of some patients with movement deficits secondary to certain neurologic conditions, and illustrates that the traditional division of neural processes into sensory input and motor output is somewhat arbitrary.

Feedback, Psychological↗
PubMed2004

Effect of hydrogen-switchable mirrors on the Casimir force.

We present systematic measurements of the Casimir force between a gold-coated plate and a sphere coated with a hydrogen-switchable mirror. Hydrogen-switchable mirrors are shiny metals that can become transparent upon hydrogenation. Despite such a dramatic change of the optical properties of the sphere, we did not observe any significant decrease of the Casimir force after filling the experimental apparatus with hydrogen. This counterintuitive result can be explained by the Lifshitz theory that describes the Casimir attraction between metallic and dielectric materials.

Gold↗
PubMed2005

Mirror-symmetry breaking in the Soai reaction: a kinetic understanding.

Kinetic modeling using nonlinear differential equations is proposed to analyze the spontaneous generation of enantiomeric excess in the autocatalytic addition of diisopropylzinc to prochiral pyrimidine carbaldehydes (Soai reaction). Our approach reproduces experimentally observed giant chiral amplification from an initial enantiomeric excess of <10(-6)% to >60%, high sensitivity and positive response to the presence of minute amounts of chiral initiator at concentrations <10(-14) M, and spontaneous absolute asymmetric synthesis from achiral starting conditions. From our numerical simulations using kinetic schemes derived from the Frank model, including stereospecific autocatalysis and mutual inhibition, we have shown that it is possible to reproduce the mirror-symmetry-breaking behavior of the Soai reaction under batch conditions leading to a bimodal enantiomeric product distribution. Mirror-symmetry breaking was found to be resistant to a loss of stereoselectivity up to 30%. While the mutual inhibition between enantiomers seems to originate from the presence of dimerization equilibria, the exact nature of the autocatalytic stereoselective process still remains to be revealed. From the kinetic viewpoint, simple autocatalysis involving monomers as the catalytic species is consistent with all reported experimental effects of the Soai reaction.

Journal Article↗
PubMed1996

Mirror symmetry breaking at the molecular level.

Reasoning from two basic principles of molecular physics, P invariance of electromagnetic interaction and the second law of thermodynamics, one would conclude that mirror symmetry retained in the world of chiral molecules. This inference is fully consistent with what is observed in inorganic nature. However, in the bioorganic world, the reverse is true. Mirror symmetry there is definitely broken. Is it possible to account for this phenomenon without going beyond conventional concepts of the kinetics of enantioselective processes? This study is an attempt to survey all existing hypotheses containing this phenomenon.

DNA↗
PubMed2005

Training with a mirror in rehabilitation of the hand.

Treatment with a mirror gives an illusion of function in a missing or non-functioning hand. The method is based on the concept that the central representation of phantoms and body image can change rapidly, and has been described in the treatment of phantom pain and stroke. We show in three pilot cases new applications for the use of the mirror in rehabilitation after hand surgery.

Activities of Daily Living↗
PubMed2003

Amyotrophic lateral sclerosis (ALS) and mirror movements in a patient with polymicrogyria.

We report on a case of polymicrogyria with benign childhood epilepsy and amyotrophic lateral sclerosis (ALS). While performing dexterity tasks with either hand, strong unsustained mirror movements of the unintended hand were observed. The patient was seen over a period of three years and, as often seen in ALS, there was a moderate progress of the motor neuron disease affecting the upper and lower motor neuron in an asymmetrical manner. In addition, more rapidly progressive bulbar symptoms could be observed by the clinical and neurophysiological examination. MRI revealed polymicrogyria of the right frontal lobe with irregular bumpy inner and outer surface and abnormally thick and smooth cortex, dysplastic insular cortex and asymmetrically widened Sylvial fissure. No signs of atrophy, especially of the motorcortex and corticospinal tract were observed. The corpus callosum was completely developed and of normal size. We hypothesize an enrolment of the dysplastic right frontal lobe pathophysiology of the observed mirror movements.

Amyotrophic Lateral Sclerosis↗
PubMed1977

Daughter 3T3 cells. Are they mirror images of each other?

Using a new technique to visualize the tracks of moving 3T3 cells and combining it with the visualization of actin-containing microfilament bundles by indirect immunofluorescence (Lazarides, E. and K. Weber. 1974, Proc. Natl. Acad. Sci. U.S.A. 71:2268-2272), I present experiments which suggest that: (a) 30-40% of the pairs of daughter 3T3 mouse fibroblasts in noncloned cultures have mirror symmetrical actin-bundle patterns. (b) The angle between separating daughter cells is approx. 90 degrees or 180 degrees and seems related to the directions of certain actin-containing bundles. (c) Approximately 40% of separately moving daughter cells which did not collide with any other cell in the culture performed directional changes in a mirror symmetrical way. Both daughter cells entered the next mitosis at approximately the same time. I suggest that the actin-bundle pattern, the angle of separation, major directional changes during interphase, and the time of the next mitosis are predetermined by the parental cell.

Actins↗
PubMed2000

A comparison of modified Howland circuits as current generators with current mirror type circuits.

Multi-frequency electrical impedance tomography (EIT) systems require stable voltage controlled current generators that will work over a wide frequency range and with a large variation in load impedance. In this paper we compare the performance of two commonly used designs: the first is a modified Howland circuit whilst the second is based on a current mirror. The output current and the output impedance of both circuits were determined through PSPICE simulation and through measurement. Both circuits were stable over the frequency ranges 1 kHz to 1 MHz. The maximum variation of output current with frequency for the modified Howland circuit was 2.0% and for the circuit based on a current mirror 1.6%. The output impedance for both circuits was greater than 100 kohms for frequencies up to 100 kHz. However, neither circuit achieved this output impedance at 1 MHz. Comparing the results from the two circuits suggests that there is little to choose between them in terms of a practical implementation.

Biomedical Engineering↗
PubMed2001

Mirrored-self misidentification: two cases of focal onset dementia.

We present two patients in whom the mirror sign, the inability to recognize one's own reflected image, was a stable and persisting symptom signalling the onset of a progressive dementing illness. Extensive neuropsychological testing was conducted with both patients, with particular emphasis on face processing and the understanding of reflected space. Both patients were also investigated with structural imaging techniques (computed tomography and magnetic resonance imaging). Although the neuroimaging results were not strongly lateralizing for either patient, neuropsychological testing revealed striking right hemisphere dysfunction with relatively intact left hemisphere cognitive function in both patients. Of particular interest was the patients' dissociation on tests of face processing; one patient, FE, had significant face processing deficits while the other patient, TH, had relatively intact face processing. Further testing with TH revealed striking deficits in his ability to interpret reflected space. The results of the face processing tests are discussed in the context of current models of normal face processing, with particular emphasis on the affective component in face recognition. We propose that a combination of cognitive deficits underlie the mirror sign delusion, including perceptual, affective and reasoning impairments, and also discuss the contributions of cortical and subcortical lesions in these two patients and in delusions in general.

Aged↗
PubMed1989

The mirror's use in suicide.

Eleven suicides in which the victim took his or her life while looking into a mirror are presented. The psychoanalytic implications of this extreme form of narcissism are discussed. Investigators should have a high index of suspicion of suicide in cases where a dead body is positioned in front of or near a mirror.

Adult↗
PubMed2003

Supraspinal contribution to development of both tonic nociception and referred mirror hyperalgesia: a comparative study between formalin test and bee venom test in the rat.

BACKGROUND: The roles of descending facilitatory pathway from the rostral medial medulla (RMM) in development of persistent spontaneous nociception and hyperalgesia were evaluated in the bee venom (BV) test and the formalin test. METHODS: Bilateral lesions of the RMM with ibotenic acid, a soma-selective neurotoxin, were performed to study their effects on the spontaneous pain-related behaviors and hyperalgesia, which were determined by counting the number of flinching reflex per 5 min (1 h) and by measuring paw withdrawal thermal latency (PWTL) and mechanical threshold (PWMT) to radiant heat and von-Frey filaments to both hind paws in conscious rats, respectively. RESULTS: 1) Bilateral lesions of the RMM produced a similarly significant inhibition of persistent spontaneous flinching reflexes in the BV test and the formalin test; however, the inhibitory effect occurred in the late 50 min (11-60 min), but not the first 10 min (0-10 min) following intraplantar injection of either BV or formalin. 2) Bilateral lesions of the RMM prevented the development of the BV-induced referred mirror heat hyperalgesia occurred in the noninjected paw, but had no effect on the primary heat and mechanical hyperalgesia occurred in the injected paw. CONCLUSIONS: The present results provide a new line of behavioral evidence that tonic activation of descending facilitatory pathway contributes to the establishment of 1) the BV and formalin-induced persistent spontaneous nociception; and 2) the BV-induced referred mirror heat hyperalgesia and the central sensitization, but not the primary heat and mechanical hyperalgesia.

Animals↗
PubMed1993

Leonardo Da Vinci's right-to-left "mirrored" writing revisited.

Leonardo Da Vinci's anatomical drawings continue to attract the attention of the medical community. One of the intriguing aspects of these drawings is Da Vinci's use of right-to-left mirrored writing. Many hypotheses have been proposed to explain his mirrored writing. This article presents a new explanation that takes into consideration the drawing material used and Da Vinci's known innovative ability. A collection of his anatomical drawings is currently on display in Boston at the Museum of Fine Arts.

Anatomy↗
PubMed2003

Connecting mirror neurons and forward models.

Two recent developments in motor neuroscience are promising the extension of theoretical concepts from motor control towards cognitive processes, including human social interactions and understanding the intentions of others. The first of these is the discovery of what are now called mirror neurons, which code for both observed and executed actions. The second is the concept of internal models, and in particular recent proposals that forward and inverse models operate in paired modules. These two ideas will be briefly introduced, and a recent suggestion linking between the two processes of mirroring and modelling will be described which may underlie our abilities for imitating actions, for cooperation between two actors, and possibly for communication via gesture and language.

Models, Neurological↗
PubMed1983

Two fatal bicyclist injuries from extended rear view mirrors.

Rear view mirrors mounted on the sides of vans and small trucks may extend beyond the sides of the vehicles and pose a hazard to other road users. Case reports of two bicyclists fatally injured by extended rear view mirrors of small trucks are presented.

Accidents, Traffic↗
PubMed1998

Bilateral (mirror-image) aneurysms at the origin of the posteroinferior cerebellar artery: case report.

OBJECTIVE AND IMPORTANCE: This case demonstrates mirror-image aneurysms at the origin of the posteroinferior cerebellar arteries. To the best of our knowledge, this location has not been previously described. Identification of this entity is important for surgical planning. CLINICAL PRESENTATION: The patient presented with a history of a sentinel headache 1 week before his Grade I subarachnoid hemorrhage occurred. Before operative intervention, the patient developed acute deterioration of his mental status from hydrocephalus. After appropriate treatment for the hydrocephalus, he maintained a stable neurological course throughout evaluation and therapy. INTERVENTION: The patient underwent bilateral clipping of his aneurysms in a prone position without consequence. CONCLUSION: This case demonstrates a highly unusual mirror-image aneurysm of the proximal posteroinferior cerebellar arteries. Although multiple aneurysms are commonplace, to the best of our knowledge, this is the first reported case of bilateral posteroinferior cerebellar artery aneurysms at their origin. Also, the surgical approach is unique and allows bilateral clipping at the same operative setting.

Cerebellar Diseases↗
PubMed2000

Mirror foot.

Mirror image polydactyly is a rare congenital abnormality that may occur in isolation, or in association with multiple congenital anomalies. A case of unilateral mirror foot with an ipsilateral short, broad tibia is described. The clinical, radiologic, and operative findings are presented, and current theories of embryo-pathogenesis are reviewed.

Female↗