89 research outputs found
Nonlinearity-induced optical torque
Optically-induced mechanical torque leading to the rotation of small objects
requires the presence of absorption or breaking cylindrical symmetry of a
scatterer. A spherical non-absorbing particle cannot rotate due to the
conservation of the angular momentum of light upon scattering. Here, we suggest
a novel physical mechanism for the angular momentum transfer to non-absorbing
particles via nonlinear light scattering. The breaking of symmetry occurs at
the microscopic level manifested in nonlinear negative optical torque due to
the excitation of resonant states at the harmonic frequency with higher
projection of angular momentum. The proposed physical mechanism can be verified
with resonant dielectric nanostructures, and we suggest some specific
realizations.Comment: 7 pages, 4 figure
PYRIDOXINE EFFECT ON NERVE CONDUCTION AND CELL DEATH IN EMBRYONIC CHICK
The role that sensory feedback plays in the proper assembly of the sensorimotor system during early stages of development is not fully understood. Fortunately, vitamin B6 (pyridoxine) has been shown to elicit detrimental effects that are specific to only large diameter sensory neurons in adult humans, dogs, cats (Pearson et al. 2003), rats (Helgren et al. 1997), guinea pigs (Xu et al. 1989), and developing chicken embryos when administered at high dosages (Sharp & Bekoff 2001; Fedorovich & Sharp 2010). The specificity of vitamin B6 was examined in this study as a potential tool for eliminating a specific type of sensory neuron during the development of the sensorimotor system. I used electrophysiological stimulation of the proximal end of N. Ischiadicus while recording from either the distal end of N. Ischiadicus or the short branch of Ramus medialis in eleven and thirteen day old (E11 and E13, respectively) chicken embryo to test the hypothesis that pyridoxine lesion impairs signal propagation in the large diameter sensory axons. Additionally, I used a histological technique to test if pyridoxine specifically eliminated the affected neurons via an apoptotic pathway. Recordings from the short branch of Ramus medialis were first characterized to determine the optimal parameters for nerve stimulations. We found that a one millisecond stimulus duration with a twenty seconds inter-stimulus interval and a current intensity smaller then 300 µA was sufficient to examine the changes in the compound action potential (CAP) after the lesion. Subsequent to pyridoxine overdose on E7 and E8, examination of CAPs recorded from the N. Ischiadicus has shown a significant decrease in the amplitude of trough one when data were normalized to peak one in E11 embryos. In contrast, there was a significant decrease in the amplitude of trough one and a decreasing trend in the amplitude of peak one when the data were normalized to peak two in the E13 embryos. These findings suggest that pyridoxine overdose at E7 and E8 impairs the propagation of action potentials in large diameter axons in the developing embryo by at least E11. In addition, further examination of CAPs has shown a significant increase in peak one velocity and the peak one onset velocity (t-test, p\u3c0.05) when comparing between E11 and E13 control groups. Since myelination greatly contributes to the velocity of potential propagation in the axon, these data suggest that myelination is continuing during this time period of development and likely contributes to the changes seen when examining the effects of pyridoxine in E11 and E13 embryos. Histological examination of the third lumbosacral dorsal root ganglion in nine day old chicken embryo using TUNEL revealed a significant decrease in the number of apoptotic cells between control and treated groups, suggesting that pyridoxine has either eliminated type Ia sensory neurons, including those normally undergoing programmed cell death at E9, by 48 hours of the initial treatment or that pyridoxine has delayed the normal process of programmed cell death to a later stage of development
Relationship between heterozygosity and quantitative traits: intralocus interactions and multiple-locus averaging
Inferences in Leuciscinae (Pisces, Cyprinidae) Phylogeny and Taxonomy Based on Cytochrome B Sequence Distances and on Enzyme Loci Diversity
Relationship between heterozygosity and quantitative traits: intralocus interactions and multiple-locus averaging
Electroconductivity of Crust and Upper Mantle
Available from VNTIC / VNTIC - Scientific & Technical Information Centre of RussiaSIGLERURussian Federatio
Allozyme heterozygosity and morphological homeostasis in pink salmon, Oncorhynchus gorbuscha (Walbaum): evidences from family analysis
Analysis of association between allozyme variability and fitness characteristics in the fry of pink salmon (Oncorhynchus gorbuscha) in mass crosses
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