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The derivation of the scattering force and the gradient force on a spherical particle due to an electromagnetic wave often invokes the Clausius-Mossotti factor, based on an ad hoc physical model. In this article, we derive the expressions including the Clausius-Mossotti factor directly from the fundamental equations of classical electromagnetism. Starting from an analytic expression for the force on a spherical particle in a vacuum using the Maxwell stress tensor, as well as the Mie solution for the response of dielectric particles to an electromagnetic plane wave, we derive the scattering and gradient forces. In both cases, the Clausius-Mossotti factor arises rigorously from the derivation without any physical argumentation. The limits agree with expressions in the literature.

We consider the problem of sorting, by size, spherical particles of order 100 nm radius. The scheme we analyze consists of a heterogeneous stream of spherical particles flowing at an oblique angle across an optical Gaussian mode standing wave. Sorting is achieved by the combined spatial and size dependencies of the optical force. Particles of all sizes enter the flow at a point, but exit at different locations depending on size. Exiting particles may be detected optically or separated for further processing. The scheme has the advantages of accommodating a high throughput, producing a continuous stream of continuously dispersed particles, and exhibiting excellent size resolution. We performed detailed Monte Carlo simulations of particle trajectories through the optical field under the influence of convective air flow. We also developed a method for deriving effective velocities and diffusion constants from the Fokker-Planck equation that can generate equivalent results much more quickly. With an optical wavelength of 1064 nm, polystyrene particles with radii in the neighborhood of 275 nm, for which the optical force vanishes, may be sorted with a resolution below 1 nm.

The vapors in equilibrium with condensates of DyI3, DyI3/InI, TmI3, and TmI3/TlI were observed over the temperature range from 900 K to 1400 K using x-ray induced fluorescence. The total densities of each element (Dy, Tm, In, Tl, and I) in the vapor, summed over all atomic and molecular species, were determined. Dramatic enhancements in the total vapor densities of Dy and Tm were observed in the vapors over DyI3/InI and TmI3/TlI as compared to the vapors over pure DyI3 and pure TmI3, respectively. An enhancement factor exceeding 10 was observed for Dy at T ≈ 1020 K, decreasing to 0 at T ≈ 1250 K. An enhancement factor exceeding 20 was observed for Tm at T ≈ 1040 K, decreasing to 0 at T ≈ 1300 K. Such enhancements are expected from the formation of the vapor-phase hetero-complexes DyInI4 and TmTlI4. Numerical simulations of the thermo-chemical equilibrium suggest the importance of additional complexes in liquid phases. A description of the measurement technique is given. Improvements in the absolute calibration lead to an approximately 40% correction to previously reported preliminary results [J. J. Curry et al., Chem. Phys. Lett. 507, 52 (2011); Appl. Phys. Lett. 100, 083505 (2012)].

We describe the use of phosphor image plates for recording spectra in the vacuum ultraviolet (VUV) and for determining accurate relative and absolute intensities. We investigated the spatial uniformity, noise, linearity of the response to VUV light, fading characteristics, saturation characteristics, reproducibility of the image when scanned multiple times, and long-term stability and lifetime of the plates. We find that the plates have a linear intensity response with a dynamic range of more than 4 orders of magnitude. We also show that they have potential as an absolute detector for VUV radiation.

The potential of an x-ray magnifier prepared from a pair of asymmetrically cut crystals is studied to explore high energy x-ray imaging capabilities at high intensity laser facilities. OMEGA-EP and NIF when irradiating mid and high Z targets can be a source of high-energy x-rays whose production mechanisms and use as backlighters are a subject of active research. This paper studies the properties and potential of existing asymmetric cut crystal pairs from the National Institute of Standards and Technology (NIST) built in a new enclosure for imaging x-ray sources. The technique of the x-ray magnifier has been described previously. This new approach is aimed to find a design that could be used at laser facilities by magnifying the x-ray source into a screen far away from the target chamber center, with fixed magnification defined by the crystals' lattice spacing and the asymmetry angles. The magnified image is monochromatic and the imaging wavelength is set by crystal asymmetry and incidence angles. First laboratory results are presented and discussed.

In 1999, the American Osteopathic Association approved plans for "substantive change" to the medical curriculum at Lake Erie College of Osteopathic Medicine (LECOM) in Erie, Pa. In addition to the school's traditional, lecture-based curriculum, LECOM sought to create alternative--but distinct--learning pathways: independent study (described elsewhere) and problem-based learning (PBL). After selecting a long-standing, successful PBL program to guide our efforts and after a 1-year period of planning, developing, piloting, and refining the program, we introduced PBL in the 2000-2001 academic year. This learning pathway consists of carefully constructed cases that allow for progressive disclosure across group-tutorial sessions, from patient presentation to diagnosis and management. With more than 5 years of data on student performance and evaluations, LECOM can investigate the merits of its three basic science learning pathways. The description of LECOM's longitudinal database will allow program evaluators to assess and compare each of the three basic science learning pathways.

The fundamental principles of low-pressure discharges containing a minority of barium (5-20 mtorr) in a rare gas at pressure 1-20 torr have been investigated, using a numerical model of the positive column, with a view to assessing the potential of these discharges as a light source. The principle resonance line of neutral barium is from the 6p(1)P1 state and has a wavelength of 553 nm, which is close to the center of the photopic eye response curve. This green line can be augmented by radiation from barium ions to produce a "white" light. Published cross-section measurements suggest that the 6p(1)P1 state is heavily quenched by collisions with rare-gas atoms, reducing the radiation efficiency. The measured quenching cross section is much smaller for neon than other rare gases. Spectral line broadening by these same collisions, on the other hand, enhances the escape of radiation from the discharge through the line wings. The present paper reports the results of detailed calculations of the influence of rare-gas quenching and line broadening on discharge parameters (power balance, electric field, electron temperature, and density) as a function of discharge current, rare-gas, and barium vapor pressure.

The ovariectomized rat bearing estrogen-containing silastic capsules underwent a primary FSH rise at 1700 hrs on all days studied. A more prolonged secondary FSH rise also occurs beginning at 2100 hrs. The primary FSH rise was attenuated or blocked by injection of charcoal-extracted porcine follicular fluid (pFF) or an extract of pFF (pFFX) limited to substances having molecular weights between 10,000 and 30,000 d. Application of pFFX directly to the dorsal anterior hypothalamic area (dAHA) by means of chronically implanted cannulas resulted in attenuation of the primary FSH rise. Similar application to medial preoptic area (mPOA) was without effect. These findings suggest that an active FSH suppressing agent, presumably ovarian inhibin, may be acting at least in part at the level of the central nervous system.

A new technique has been developed for the generation and shaping of KrF laser pulses on a picosecond time scale using a fast electro-optic modulator. Subnanosecond electrical pulses with an amplitude much greater than the half-wave voltage are applied to the Pockels cell, which generates a train of short ultraviolet pulses. The first pulse in this train is then isolated and shortened to 30 psec by the combined effect of propagation through a saturated amplifier and optical breakdown in xenon.

The North American opossum is born 12 days after conception and is therefore available for experimental manipulation in an immature state. We have used the opossum to study the growth of cortical axons into the brainstem and spinal cord and have obtained evidence that such growth occurs in an orderly fashion. Cortical axons reach the ventral mesencephalon 12 days after birth and some of them have grown into the caudal medulla where they decussate by 23 days. At the latter stage immature cortical axons also distribute to the midbrain tegmentum, the basilar pons, the inferior olive and the hilum of the nucleus cuneatus. Cortical axons first enter the spinal cord about 30 days after birth where they are present in the white matter before growing into the dorsal horn. The forelimb placing reaction does not develop until well after cortical axons have reached cervical levels. Axons from the cerebral cortex grow into the spinal cord before there is evidence for cortical innervation of either the red nucleus or the bulbar reticular formation and well before pyramidal cells of the neocortex are mature. The relatively late development of corticospinal and corticobulbar systems contrasts markedly with the early growth of bulbospinal axons.

Pentobarbitone-blocked pro-oestrous rats were subjected to either limited mating (maximum of 30 mounts), all-night cohabitation with males or stimulation of the vagina and cervix with a glass rod (2 or 5 min) to determine which type of stimulus was most effective in inducing ovulation. All-night cohabitation was the most successful procedure and resulted in 100% ovulation in those rats which mated. Treatment with either phenoxybenzamine, propranolol or pimozide did not interfere with this copulation-induced ovulation whereas methysergide treatment completely blocked copulation-induced ovulation. Administration of atropine resulted in a loss of mating behaviour and these animals therefore did not ovulate. Further experiments provided evidence that administration of atropine also blocked ovulation in response to vaginal stimulation with a glass rod. Pretreatment with methysergide or atropine had no effect upon the percentage of pentobarbitone-blocked, pro-oestrous rats ovulating in response to administration of LH releasing hormone (LHRH). However, those rats given atropine shed significantly fewer ova per rat following LHRH or LH infusion when compared with controls. These results suggest that the synaptic mechanisms responsible for mediating copulation-induced ovulation are different from those mediating steroid-induced ovulation, and that ovarian cholinergic receptors may play a role in ovulation.