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At least 613 records · Page 34Linked to original sources
PubMed2006

Planar gold nanoparticle clusters as microscale mirrors.

Dispersible microscale mirror particles were synthesized by linkage of citrate-coated gold nanoparticles and 3-aminopropylsilyl-modified Ca2Nb3O10 perovskite nanoplates. The mirror particles reflect 14-19% of light in the 500-800 nm wavelength interval with retention of polarization. Due to their directional reflection properties, laser-irradiated micromirror dispersions in solvents exhibit Brownian motion-driven multicolor blinking behavior.

Journal Article↗
PubMed2000

Double-helical cyclic peptides: design, synthesis, and crystal structure of figure-eight mirror-image conformers of adamantane-constrained cystine-containing cyclic peptide cyclo (Adm-Cyst)(3).

A large number of macrocycles containing alternating repeats of cystine diOMe(-NH-CH(CO(2)Me)-CH(2)-S-)(2) and either a conformationally rigid aromatic/alicyclic moiety or a flexible polymethylene unit (X) in the cyclic backbone with ring size varying from 13- to 78-membered have been examined by spectral ((1)H NMR, FT-IR, CD) and X-ray crystallography studies for unusual conformational preferences. While (1)H NMR measurements indicated a turnlike conformation for all macrocycles, stabilized by intramolecular NH.CO hydrogen bonding, as also supported by FT-IR spectra in chloroform, convincing proof for beta-turn structures was provided by circular dichroism studies. Single-crystal X-ray studies on 39-membered cyclo (Adm-L-Cyst)(3) revealed a double-helical fold (figure-eight motif) for the macrocycle. Only a right-handed double helix was seen in the macrocycle constructed from L-cystine. The mirror-image macrocycle made up of D-cystine units exhibited a double helix with exactly the opposite screw sense, as expected. The enantiomeric figure-eights were stabilized by two intramolecular NH. CO hydrogen bonds and exhibited identical (1) H NMR and FT-IR spectra. The CD spectra of both isomers had a mirror-image relationship. The present results have clearly brought out the importance of cystine residues in inducing turn conformation that may be an important deciding factor for the adoption of topologically important structures by macrocycles containing multiple S-S linkages.

Crystallography, X-Ray↗
PubMed2004

Mirror-image carbohydrates: synthesis of the unnatural enantiomer of a blood group trisaccharide.

Methyl D-glucoside and d-glucose pentaacetate are transformed, respectively, into methyl alpha-O-glucuronide 3 and hydroxymethyl beta-C-glucuronide 9, which undergo decarboxylative elimination efficiently to produce 4-deoxypentenoside 4 and L-glucal 10. These unsaturated pyranosides provide an expeditious entry into mirror-image oligosaccharides, as demonstrated in the synthesis of the unnatural enantiomer of the H-type II blood group determinant trisaccharide (D-Fuc-(alpha1-->2)-L-Gal-(beta1-->4)-L-GlcNAc-beta-OMe). This work illustrates that D-glucose, a common starting material in the synthesis of naturally occurring carbohydrates, can also be used to prepare their mirror-image analogues.

ABO Blood-Group System↗
PubMed1999

Dipole source analysis in persistent mirror movements.

To elucidate the pathomechanism underlying persistent mirror movements (MM), we modelled the origin of electric brain activity associated with these movements. Movement-related cortical potentials (MRCP) in a group of subjects affected by persistent mirror movements were compared with those of a control group. The data of the normal subjects were best explained with two bilaterally active electric sources in the sensorimotor cortices with a clear preponderance of the hemisphere contralateral to the movement. In contrast, the MM subjects presented a fairly symmetric source activity in both hemispheres during unilateral intended movements. In the control group, the source representing the activity of the motor cortex ipsilateral to the moving finger reduced activity before the beginning of the movement; this was interpreted as an inhibition of the ipsilateral motor cortex during unilateral movement. In the MM group, however, this inhibition was not seen. Furthermore, while normal subjects demonstrated no relevant activity of an additional source placed near midline motor structures (supplementary motor area; SMA), subjects with MM showed considerable activity of this dipole source. These findings suggest that subjects with persistent MM have abnormal bilateral activation of the primary motor areas, probably together with an additional activation of mesial motor structures. This assumption fits well with the observation of an incomplete decussation of the pyramidal tract. The bilateral activation is then explained as a compensatory strategy in order to achieve sufficient force in the innervated target muscles.

Adolescent↗
PubMed1991

Forgetting and the mirror effect in recognition memory: concentering of underlying distributions.

The mirror effect is a strong regularity in recognition memory: If there are two conditions, A and B, with A giving higher recognition accuracy, then old items in A are recognized as old better than old items in B, and also new items in A are recognized as new better than new items in B. The mirror effect is explained by attention/likelihood theory, which also makes several new, counterintuitive predictions. One is that any variable, such as forgetting, that affects recognition changes the responses to new as well as old stimuli. In terms of underlying distributions, forgetting produces concentering, the bilateral movement of distributions, both new (noise) and old (signal), toward a midpoint. Data from two forced-choice experiments are reported that support the prediction of concentering and other predictions drawn from the theory. It is argued that current theories of memory, which are strength theories, cannot handle these regularities.

Attention↗
PubMed1997

Intact mirror-tracing and impaired rotary-pursuit skill learning in patients with Huntington's disease: evidence for dissociable memory systems in skill learning.

Skill learning in early-stage Huntington's disease (HD) patients was compared with that of normal controls on 2 perceptual-motor tasks, rotary pursuit and mirror tracing. HD patients demonstrated a dissociation between impaired rotary-pursuit and intact mirror-tracing skill learning. These results suggest that different forms of perceptual-motor skill learning are mediated by separable neural circuits. A striatal memory system may be essential for sequence or open-loop skill learning but not for skills that involve the closed-loop learning of novel visual-response mappings. It is hypothesized that working memory deficits in HD resulting from frontostriatal damage may account broadly for intact and impaired long-term learning and memory in HD patients.

Adult↗
PubMed2007

The mirror effect and mixture signal detection theory.

The mirror effect for word frequency refers to the finding that low-frequency words have higher hit rates and lower false alarm rates than high-frequency words. This result is typically interpreted in terms of conventional signal detection theory (SDT), in which case it indicates that the order of the underlying old item distributions mirrors the order of the new item distributions. However, when viewed in terms of a mixture version of SDT, the order of hits and false alarms does not necessarily imply the same order in the underlying distributions because of possible effects of mixing. A reversal in underlying distributions did not appear for fits of mixture SDT models to data from 4 experiments.

Attention↗
PubMed1996

Age differences in the ability of chimpanzees to distinguish mirror-images of self from video images of others.

To evaluate Heyes's (1994) claim that chimpanzees are incapable of using mirrored information to obtain otherwise unavailable information about the self, we exposed two different age groups of chimpanzees (3-year-olds and 7- to 10-year-olds) to mirrors and video images of conspecifics. Their reactions to these stimuli were videotaped and were later scored for behavioral indices of self-recognition by a trained observer who was blind to the purpose and conditions of the study. Some types of behavior (contingent facial and body movements) were clearly influenced by the type of stimulus that the chimpanzees were viewing but not by age; however, other behaviors (self-exploration) were affected by age in conjunction with the type of stimulus the animals were viewing. The results suggest that, unlike self-exploratory behavior, contingent facial and body movements may not, by themselves, be reliable indicators of self-recognition.

Aging↗
PubMed1988

Chemical probing of homopurine-homopyrimidine mirror repeats in supercoiled DNA.

We have recently shown that under superhelical stress and/or acid pH the homopurine-homopyrimidine tracts conforming to the mirror symmetry (H palindromes) form a novel DNA structure, the H form. According to our model, the H form includes (1) a triplex formed by half of the purine strand and by the homopyrimidine hairpin and (2) the unstructured other half of the purine strand. We used four specially designed sequences to demonstrate that, in accordance with our model, the mirror symmetry is essential for facile formation of the H form detected by two-dimensional gel electrophoresis. Here we report that, under conditions favouring the H-form extrusion, guanines of the 3' half of the purine strand are protected against alkylation by dimethylsulphate, whereas adenines of the 5' half of the purine strand react with diethyl pyrocarbonate. These data indicate that the 3' half of the homopurine strand is within the triplex whereas the 5' half is unstructured, in full agreement with our model.

DNA, Superhelical↗
PubMed2000

The homeobox gene mirror links EGF signalling to embryonic dorso-ventral axis formation through notch activation.

Recent studies in vertebrates and Drosophila melanogaster have revealed that Fringe-mediated activation of the Notch pathway has a role in patterning cell layers during organogenesis. In these processes, a homeobox-containing transcription factor is responsible for spatially regulating fringe (fng) expression and thus directing activation of the Notch pathway along the fng expression border. Here we show that this may be a general mechanism for patterning epithelial cell layers. At three stages in Drosophila oogenesis, mirror (mirr) and fng have complementary expression patterns in the follicle-cell epithelial layer, and at all three stages loss of mirr enlarges, and ectopic expression of mirr restricts, fng expression, with consequences for follicle-cell patterning. These morphological changes are similar to those caused by Notch mutations. Ectopic expression of mirr in the posterior follicle cells induces a stripe of rhomboid (rho) expression and represses pipe (pip), a gene with a role in the establishment of the dorsal-ventral axis, at a distance. Ectopic Notch activation has a similar long-range effect on pip. Our results suggest that Mirror and Notch induce secretion of diffusible morphogens and we have identified TGF-beta (encoded by dpp) as such a molecule in germarium. We also found that mirr expression in dorsal follicle cells is induced by the EGF-receptor (EGFR) pathway and that mirr then represses pip expression in all but the ventral follicle cells, connecting EGFR activation in the dorsal follicle cells to repression of pip in the dorsal and lateral follicle cells. Our results suggest that the differentiation of ventral follicle cells is not a direct consequence of germline signalling, but depends on long-range signals from dorsal follicle cells, and provide a link between early and late events in Drosophila embryonic dorsal-ventral axis formation.

Animals↗
PubMed2003

Impact of weight loss and regain on quality of life: mirror image or differential effect?

OBJECTIVE: To compare the impact of weight regain and weight loss on health-related quality of life. RESEARCH METHODS AND PROCEDURES: Subjects were 122 (106 women, 16 men) overweight and obese participants in a weight reduction program (phentermine-fenfluramine and dietary counseling) who had initially lost at least 5% of their total body weight and then regained at least 5% of their weight during the follow-up period. Follow-up periods ranged from 10 to 41 months (mean, 28 months). Participants completed the Impact of Weight on Quality of Life-Lite, an obesity-specific health-related quality of life (HRQOL) measure, at 3-month intervals. RESULTS: Mean BMI at baseline was 40.9 +/- 6.6 kg/m(2) (range, 29.2 to 63.7 kg/m(2)). Average weight loss from entry was 18.8 +/- 6.7% (range, 6.0% to 43.7%), and average regain was 10.1 +/-4.4% of baseline weight (range, 5.0% to 30.6%). The effects of weight regain on HRQOL mirrored the effects of weight loss-rates of HRQOL change were similar in magnitude but different in direction for comparable weight loss and regain. Those with more severe initial impairments in HRQOL experienced greater improvements in HRQOL during weight loss as well as greater deterioration during weight regain than those with less severe impairments. DISCUSSION: Weight loss and regain produced mirror image changes in HRQOL. The initial severity of HRQOL impairment had a greater impact on the magnitude of HRQOL change than the direction of weight change. Findings underscore the importance of maintaining weight loss for the purposes of retaining obesity-specific HRQOL benefits.

Adult↗
PubMed1996

Epitope analysis of the Goodpasture antigen using a resonant mirror biosensor.

We have used a new technique for studying molecular interactions-a resonant mirror biosensor-to identify B cell epitopes within the Goodpasture antigen, which has recently been identified as the non-collagenous domain of the alpha 3-chain of type IV collagen (alpha 3(IV)NC1). Recombinant antigen (r-alpha 3) was immobilized onto the sensing surface of a sample cuvette, and the binding of patients' autoantibodies or a MoAb to the Goodpasture antigen was followed in real time. All patients' sera bound r-alpha 3 in this system, while control sera did not bind. A MoAb inhibited the binding of all patients' autoantibodies to r-alpha 3, from 27% to 90% (mean inhibition 60%), and patients' sera cross-inhibited the binding of each other to the antigen. Binding was inhibited by pre-incubation of autoantibody with both native sheep alpha 3(IV)NC1 and purified human alpha 3(IV)NC1 monomers. Inhibition experiments using soluble overlapping peptides from human alpha 3(IV)NC1 identified putative B cell epitopes. These results suggest that there is a major immunodominant epitope on the Goodpasture antigen, and that there is very limited heterogeneity in the autoantibody response in Goodpasture's disease. The resonant mirror biosensor can be successfully used to monitor antibody-antigen binding using polyclonal sera, and to map epitopes on autoantigens.

Amino Acid Sequence↗
PubMed2000

Studies of a magnetically focused electrostatic mirror. I. Experimental test of the first order properties

When a uniform magnetic field is superimposed on a uniform electrostatic field, the combination can act as a magnetically focused mirror. This mirror is predicted to have aberrations of opposite sign to those of a magnetic lens and may therefore be useful as a corrector. We have built an electron optical system to test these ideas. The results are presented in two papers. This first paper describes the general design and the results of the measurements of the first order properties. The second paper (Tsai, F., J. Microsc. 197 (2000) 118-135) will describe the measurements of the aberration properties.

Journal Article↗
PubMed2002

Adaptive correction of depth-induced aberrations in multiphoton scanning microscopy using a deformable mirror.

We demonstrate adaptive aberration correction for depth-induced spherical aberration in a multiphoton scanning microscope with a micromachined deformable mirror. Correction was made using a genetic learning algorithm with two-photon fluorescence intensity feedback to determine the desired shape for an adaptive mirror. For a 40x/0.6 NA long working distance objective, the axial scanning range was increased from 150 mm to 600 mm.

Microscopy, Confocal↗
PubMed2003

Probing highly confined optical fields in the focal region of a high NA parabolic mirror with subwavelength spatial resolution.

Parabolic mirrors with a high numerical aperture can be conveniently used to produce highly confined optical fields in the focal region. Furthermore, these fields can have interesting polarization behaviour due to the high numerical aperture. In particular, if the mirror is illuminated with a size matched radially polarized or azimuthally polarized doughnut mode, the electric field has in the focal region almost exclusively a longitudinal or a transverse polarization component. Such field distributions are interesting for applications in confocal or near-field optical microscopy. Here we present experimental results where we have probed some of these field distributions by raster scanning a fine gold tip in nanometer steps through the focal region and detecting the scattered light intensity. The measured intensity patterns are compared with corresponding vector-field calculations.

Journal Article↗
PubMed2003

A strict response criterion yields a mirror effect in the novelty paradigm.

According to the novelty/encoding hypothesis (NEH; Tulving & Kroll, 1995), efficacy of encoding information into long-term memory depends on the movelty of the information. Recognition accuracy is higher for novel than for previously familiarized material. This novelty effect is not a mirror effect: the superiority of novel over familiar items is not found in the hit rates but only in the false-alarm rates. The main result in the present replication study was that novel hit rates were higher than familiar ones when the most confident responses were examined separately, and thus a mirror effect could be demonstrated for these data, for both the low- and the high-frequency words. Similarly, the word-frequency effect on hits was stronger when a stricter response criterion was applied. It was concluded that the novelty effect and the word-frequency effect are more similar to one another than has hitherto been thought.

Adult↗
PubMed1987

[Origin of mirror writing in children].

In left-handedness it is not the right hemisphere which usually dominates, as previously assumed but rather the left, as recent studies show. The development of right- and left-handedness is considered here in the light of the findings of Eccles, who substantiated the hypothesis of a relationship between the brain and a consciousness which is to be seen as basically independent of this organ. Right- and left-handedness are engendered by the interplay between consciousness and certain liasion areas in the brain. When the subject's will dictates a movement, consciousness exercises a strong influence on the impulse pattern of the modules. In genetically conditioned left-handedness it is not primarily motoric, but rather neuronal factors which are responsible for the reversal in the direction of writing and mirror-image script. Left-handed children who produce mirror-handwriting can be retrained to write normally by exercises and by assimilating conscious experience.

Aged↗
PubMed1998

Mirror movements associated with cervical meningocele: case report.

A patient with mirror movements associated with cervical meningocele has been presented in this report. The MRI showed normal cerebrum and cervical meningocele, and an anomaly at the posterior to the cervical spinal cord-medulla junction. Unilateral transcranial magnetic stimulation evoked bilateral responses at similar latencies on the thenar muscles which are quite different from those observed in normal subjects. This case adds another etiological cause to the mirror movements.

Adult↗