280 research outputs found
Sharing a common origin between the rotational and linear doppler effects
The well-known linear Doppler effect arises from the linear motion between source and observer, while the less well-known rotational Doppler effect arises from the rotational motion. Here, we present both theories and experiments illustrating the relationship between the rotational and linear Doppler effects. A spiral phaseplate is used to generate a light beam carrying orbital angular momentum and the frequency shift is measured arising from its rotational and/or linear motion. By considering either the motion-induced time-evolving phase or the momentum and energy conservation in light-matter interactions, we derive the rotational Doppler shift, linear Doppler shift, and overall Doppler shift associated with rotational and linear motions. We demonstrate the relationship between rotational and linear Doppler shifts, either of which can be derived from the other effect, thereby illustrating their shared origin. Moreover, the close relationship between rotational and linear Doppler effects is also deduced for a more general moving rough surface
Observable frequency shifts via spin-rotation coupling
The phase perturbation arising from spin-rotation coupling is developed as a
natural extension of the celebrated Sagnac effect. Experimental evidence in
support of this phase shift, however, has yet to be realized due to the
exceptional sensitivity required. We draw attention to the relevance of a
series of experiments establishing that circularly polarized light, upon
passing through a rotating half-wave plate, is changed in frequency by twice
the rotation rate. These experiments may be interpreted as demonstrating the
role of spin-rotation coupling in inducing this frequency shift, thus providing
direct empirical verification of the coupling of the photon helicity to
rotation. A neutron interferometry experiment is proposed which would be
sensitive to an analogous frequency shift for fermions. In this arrangement,
polarized neutrons enter an interferometer containing two spin flippers, one of
which is rotating while the other is held stationary. An observable beating in
the transmitted neutron beam intensity is predicted.Comment: LaTeX, 15 pages with 4 PostScript figures, submitted to Phys. Lett.
A phenomenological theory of nonphotochemical laser induced nucleation
Our analysis of the experimental data related to nonphotochemical laser
induced nucleation in solutions leads to the inevitable conclusion that the
phase transformation is initiated by particles that are metallic in nature.
This conclusion appears paradoxical because the final products are dielectric
crystals. We show that the experimental results are well accounted for by the
theory of electric field induced nucleation of metallic particles that are
elongated in the direction of the field. However, new physical and chemical
insights are required to understand the structure of the metallic precursor
particles and the kinetics of subsequent dielectric crystallization.Comment: 5 pages 4 figure
Optical angular momentum in a rotating frame
It is well established that light carrying orbital angular momentum (OAM) can be used to induce a mechanical torque causing an object to spin. We consider the complementary scenario: will an observer spinning relative to the beam axis measure a change in OAM as a result of their rotational velocity? Remarkably, although a linear Doppler shift changes the linear momentum of a photon, the angular Doppler shift induces no change in the angular momentum. Further, we examine the rotational Doppler shift in frequency imparted to the incident light due to the relative motion of the beam with respect to the observer and consider what must happen to the measured wavelength if the speed of light c is to remain constant. We show specifically that the OAM of the incident beam is not affected by the rotating observer and that the measured wavelength is shifted by a factor equal and opposite to that of the frequency shift induced by the rotational Doppler effect
Rotational Doppler shift of the phase-conjugated photon
The rotational Doppler shift of a photon with orbital angular momentum is shown to be an even multiple of the angular frequency
of the reference frame rotation when photon is reflected from the
phase-conjugating mirror. We consider the one-arm phase-conjugating
interferometer which contains Dove prisms or other angular momentum
altering elements rotating in opposite directions. When such interferometer is
placed in the rotating vehicle the
rotational Doppler shift appears and rotation of the helical interference
pattern with angular frequency occurs. The
accumulation of angular Doppler shift via successive passage through the
image-inverting prisms is due to the phase conjugation, for conventional
parabolic retroreflector the accumulation is absent. The features of such a
vortex phase conjugating interferometry at the single photon level are
discussed.Comment: 6 pages, 3 figures, submitted to referred journa
Control over phase separation and nucleation using a laser-tweezing potential
Control over the nucleation of new phases is highly desirable but elusive. Even though there is a long history of crystallization engineering by varying physicochemical parameters, controlling which polymorph crystallizes or whether a molecule crystallizes or forms an amorphous precipitate is still a poorly understood practice. Although there are now numerous examples of control using laser-induced nucleation, the absence of physical understanding is preventing progress. Here we show that the proximity of a liquid–liquid critical point or the corresponding binodal line can be used by a laser-tweezing potential to induce concentration gradients. A simple theoretical model shows that the stored electromagnetic energy of the laser beam produces a free-energy potential that forces phase separation or triggers the nucleation of a new phase. Experiments in a liquid mixture using a low-power laser diode confirm the effect. Phase separation and nucleation using a laser-tweezing potential explains the physics behind non-photochemical laser-induced nucleation and suggests new ways of manipulating matter
Sulfhydryl compounds and antioxidants inhibit cytotoxicity to outer hair cells of a gentamicin metabolite in vitro
Aminoglycoside antibiotics such as gentamicin have long been known to destroy cochlear and vestibular hair cells in vivo. In the cochlea outer hair cells are preferentially affected. In contrast, gentamicin will not damage outer hair cells in vitro unless it has been enzymatically converted to a cytotoxic metabolite. Several potential inhibitors of this enzymatic reaction were tested in an in vitro assay against outer hair cells isolated from the guinea pig cochlea. Viability of hair cells (viable cells as per cent of total number of cells observed) averaged about 70% under control conditions. Addition of metabolized gentamicin significantly reduced viability to less than 50% in one hour. Sulfhydryl compounds (glutathione, dithioerythritol) and antioxidants (vitamin C, phenylene diamine, trolox) prevented the cytotoxic actions of the gentamicin metabolite. Inhibitors of aminc oxidases and compounds reportedly protective against renal and acute lethal toxicity of aminoglycosides (poly--aspartate and pyridoxal phosphate, respectively) were ineffective as protectants. The results reinforce the hypothesis that gentamicin is enzymatically converted to a cytotoxin and imply the participation of sulfhydryl-sensitive groups or free radicals in this reaction. Alternatively or additionally, sulfhydryl compounds or antioxidants may participate in detoxification reactions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31500/1/0000422.pd
Attenuation of gentamicin ototoxicity by glutathione in the guinea pig in vivo
The effect of glutathione co-therapy on the expression of gentamicin ototoxicity was tested in pigmented guinea pigs. The first group of animals was injected with gentamicin (100 mg/kg body weight/day) for two weeks followed by 10 weeks of rest. A second group received glutathione by gastric gavage immediately prior to each gentamicin injection. Two groups of controls were treated either with saline injections or glutathione gavage alone. Auditory brainstem responses, taken at 2-week intervals, revealed a progressive gentamicin-induced hearing loss reaching a 30 to 40 dB threshold shift at 2 kHz, approximately 60 dB at 8 kHz and 80 dB at 18 kHz. Glutathione co-therapy slowed the progression of hearing loss and significantly attenuated the final threshold shifts by 20 to 40 dB. Morphological evaluation confirmed hair cell loss after gentamicin treatment and protection by glutathione. Drug serum levels were assayed at 2 and 7 days of treatment. There were no differences between the gentamicin (mean = 183 [mu]g/ml; range, 90 to 300) and the gentamicin/glutathione group (mean = 164 [mu]g/ml; range, 80 to 320). Antimicrobial activity of gentamicin was tested against Staphylococcus aureus and Pseudomonas aeruginosa. A 30-fold molar excess of glutathione did not influence the efficacy of gentamicin. These studies suggest that glutathione protects against ototoxicity by interfering with the cytotoxic mechanism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31501/1/0000423.pd
Phase Behavior of a Block Copolymer/Salt Mixture through the Order-to-Disorder Transition
Mixtures of block copolymers and lithium salts are promising candidates for lithium battery electrolytes. Structural changes that occur during the order-to-disorder transition (ODT) in a diblock copolymer/salt mixture were characterized by small-angle X-ray scattering (SAXS). In salt-free block copolymers, the ODT is sharp, and the domain size of the ordered phase decreases with increasing temperature. In contrast, the ODT of the diblock copolymer/salt mixture examined here occurs gradually over an 11 °C temperature window, and the domain size of the ordered phase is a nonmonotonic function of temperature. We present an approach to estimate the fraction of the ordered phase in the 11 °C window where ordered and disordered phases coexist. The domain spacing of the ordered phase increases with increasing temperature in the coexistence window. Both findings are consistent with the selective partitioning of salt into the ordered domains, as predicted by Nakamura et al. ( ACS Macro Lett. 2013, 2, 478−481)
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