Dust particles from comets and asteroids collected at the Earth's orbit: Parent-daughter relationships

The relative contributions of comets and asteroids to the reservoir of dust in the interplanetary medium is not well known. There are direct observations of dust released from comets and there is evidence to associate the IRAS dust bands with possible collisions of Asteroids in the main belt. It is believed that one may combine lab analysis of the physics and chemistry of captured particles with orbital data in order to identify comet and asteroid parent bodies. It is possible to use the collected orbits of the dust to connect with its source in two ways. One is to consider the long time orbit evolution of the dust under Poynting-Robertson drag. The other is to look at the prompt orbit change of dust from comets onto trajectories that intersect the earth's orbit. In order to characterize the orbits of dust particles evolved over a long period of time, a study of its orbital evolution was undertaken. Various parameters associated with these dust orbits as they cross the Earth's orbit were considered in order to see if one may discriminate between particles evolved from comets and asteroids. The method was to calculate by a numerical procedure the orbits of dust particles after they left their parent bodies. It appears that as the particles pass the Earth's orbit, asteroidal grains and cometary grains can be differentiated on the basis of their measured orbital eccentricities even after much planetary perturbation. Broad parent daughter associations can be made on this basis from measurement of their trajectories intercepted in earth orbit

Meteoroid capture cell construction

A thin membrane covering the open side of a meteoroid capture cell causes an impacting meteoroid to disintegrate as it penetrates the membrane. The capture cell then contains and holds the meteoroid particles for later analysis

VARIABLE INTEREST RATES AND THE FINANCIAL PERFORMANCE OF DAIRY FARM BUSINESSES

Resource /Energy Economics and Policy,

Chemopreventive Effects of Pterostilbene in Metastatic Prostate Cancer Cells

Recent studies find that pterostilbene (PTS) exhibits more favorable drug properties and similar chemopreventive effects to its structural analogue resveratrol (RSV). However, few studies describe the activity of PTS in prostate cancer (PCa). Here, we conducted cell count experiments to assess the effects of PTS on metastatic PCa cell viability and to compare the potency of PTS to RSV in this respect. We also performed experiments to assess the effects of PTS on the androgen receptor (AR) and AR-mediated events. We used qPCR to measure the mRNA levels of the androgenresponsive gene (ARG), prostate-specific antigen (PSA), and Western blots to assess the expression and subcellular localization of the AR protein in LNCaP cells. We found that PTS inhibited cell viability more potently than RSV in androgen-dependent LNCaP and androgen-independent PC-3 cells. These inhibitory effects were time and dosedependent and suggest that PTS may provide chemopreventive effects at multiple stages of disease. PTS also inhibited androgen-induced PSA mRNA levels in LNCaP cells. However, this inhibitory effect could not be fully attributed to changes in the androgeninduced expression or nuclear translocation of AR protein. Therefore, further investigation is required to elucidate PTS’s effects on AR-mediated events and to assess the clinical applicability of PTS in PCa

Improving Phonemic Awareness in ESL Pronunciation Using Shadowing During Tutorials: Implications for ESL Teachers

Although there are numerous reasons to improve pronunciation instruction, the teaching of phonologic structures in English has become less popular among k-12 classrooms. This study proposes that the use of a relatively new technique may positively improve ESL students\u27 pronunciation of American Standard English. This technique is known as shadowing. The data obtained was analyzed and evaluated in terms of phonological structures. The motivation to do this particular study came from previous research concerning word boundaries and phonological structures of consonants, in addition to my previous experience as an ESL tutor and instructor at SCSU. Students were making too many phonemic errors. This study will provide evidence for specific effects on phonemic awareness and also in regards to fluency and accuracy. To accomplish this, a shadowing methodology was used. The participants performed three types of audio-recorded speech samples both before and after their weekly tutorial sessions. Each would serve as a pre-test/post-test. First, spontaneous speech samples were used. Second, rehearsed speech samples were used. Third, read aloud activities were conducted to produce recorded speech samples. The recordings of speech samples were provided by four native speakers of English, two Caucasian males and two Caucasian females. This generated the authentic speech samples necessary for data analysis. The activities stemmed from a modified activity from the St. Cloud State ESL Department\u27s Tutorial packet. The samples were assessed by native speakers of English (speech sample raters) who listened to samples and scored each one based on a speech rubric provided by the researcher. The results of the data collected (scores from raters) were calculated and presented in the form of paired TTests. Common problems associated with pronunciation and whether the use of shadowing leads to an increased level of phonemic awareness were the target objectives for the elicited data. The students were divided into two groups. Student Group, A used a written transcript while making the shadowing attempts and Student Group B did not. The results indicated that most of the comparisons did not yield statistically significant results (gender and language yielded no significance). However, even though two of the mean scores for groups A and B ( comparing pre and post-test) yielded a difference, none of them were statistically significant as neither were equal or greater than the Alpha value of 0.05

Clementine Observations of the Zodiacal Light and the Dust Content of the Inner Solar System

Using the Moon to occult the Sun, the Clementine spacecraft used its navigation cameras to map the inner zodiacal light at optical wavelengths over elongations of 3-30 degrees from the Sun. This surface brightness map is then used to infer the spatial distribution of interplanetary dust over heliocentric distances of about 10 solar radii to the orbit of Venus. We also apply a simple model that attributes the zodiacal light as being due to three dust populations having distinct inclination distributions, namely, dust from asteroids and Jupiter-family comets (JFCs), dust from Halley-type comets, and an isotropic cloud of dust from Oort Cloud comets. The best-fitting scenario indicates that asteroids + JFCs are the source of about 45% of the optical dust cross-section seen in the ecliptic at 1 AU, but that at least 89% of the dust cross-section enclosed by a 1 AU radius sphere is of a cometary origin. When these results are extrapolated out to the asteroid belt, we find an upper limit on the mass of the light-reflecting asteroidal dust that is equivalent to a 12 km asteroid, and a similar extrapolation of the isotropic dust cloud out to Oort Cloud distances yields a mass equivalent to a 30 km comet, although the latter mass is uncertain by orders of magnitude.Comment: To be published in Icaru

Dust evolution from comets and asteroids: Their velocities at Earth orbit intersection

In this study on the evolution of dust particles from comets and asteroids, the effects of accurate many-body planetary motion on the gravitational perturbations of the dust grains are computed. In a computer simulation, dust grains of radius 10, 30, and 100 micron were released at perihelion passage from each of 36 different celestial bodies: 16 main asteroids, 15 short period comets with perihelion greater than 1 AU, and 5 short period comets with perihelion less than 1 AU. It is found that when dust grains evolve to intersection with the earth's orbit, they nearly always retain orbital characteristics indicative of their origins. Grains from main belt asteroids differ significantly in orbital characteristics, especially orbital eccentricity, from grains that evolve from comets

Orbital evolution of dust from comet Schwassmann-Wachmann 1: A case of one-to-one resonance trapping

In a recent study we have modeled the orbital evolution of dust particles released from comets and asteroids in the solar system. The source bodies were either asteroids inside Jupiter's orbit or comets from the Jupiter family of comets. However there are other dust producing parent bodies in the solar system of interest, one of these is comet P/Schwassman-Wachmann 1. Since comet Schwassman-Wachmann 1, which has an orbit outside of Jupiter's orbit, is an active dust producer and has low eccentricity, dust particle evolution from it is of interest. We report on a particular 2 micron radius particle that captured into a 1 to 1 mean motion resonance orbit with Saturn

Lunar horizon glow and the Clementine mission

The Clementine spacecraft is to be launched into Earth orbit in late January for subsequent insertion into lunar orbit in late February, 1994. There, its primary mission is to produce -- over a period of about two months -- a new photographic map of the entire surface of the Moon; this will be done, in a variety of wavelengths and spatial resolutions, in a manner greatly superior to that previously accomplished for the whole Moon. It will then go on to fly by and photograph the asteroid Geographos. A secondary goal that has been accepted for this mission is to take a series of photographs designed to capture images of, and determine the brightness and extent of, the Lunar Horizon Glow (LHG). One form of LHG is caused by the solar stimulation of emission from Na and K atoms in the lunar exosphere. The scale height of this exosphere is of the order of 100 km. There are also brighter LHG components, with much smaller scale heights, that appear to be caused by scattered off of an exospheric lunar dust cloud

Bounds on the entanglability of thermal states in liquid-state nuclear magnetic resonance

The role of mixed state entanglement in liquid-state nuclear magnetic resonance (NMR) quantum computation is not yet well-understood. In particular, despite the success of quantum information processing with NMR, recent work has shown that quantum states used in most of those experiments were not entangled. This is because these states, derived by unitary transforms from the thermal equilibrium state, were too close to the maximally mixed state. We are thus motivated to determine whether a given NMR state is entanglable - that is, does there exist a unitary transform that entangles the state? The boundary between entanglable and nonentanglable thermal states is a function of the spin system size $N$ and its temperature $T$. We provide new bounds on the location of this boundary using analytical and numerical methods; our tightest bound scales as $N \sim T$, giving a lower bound requiring at least $N \sim 22,000$ proton spins to realize an entanglable thermal state at typical laboratory NMR magnetic fields. These bounds are tighter than known bounds on the entanglability of effective pure states.Comment: REVTeX4, 15 pages, 4 figures (one large figure: 414 K