Average Beta Research Articles

Visible-infrared self-amplified spontaneous emission amplifier free electron laser undulator

The visible-infrared self-amplified spontaneous emission amplifier (VISA) free electron laser (FEL) is an experimental device designed to show self-amplified spontaneous emission (SASE) to saturation in the near infrared to visible light energy range. It generates a resonant wavelength output from 800\char21{}600 nm, so that silicon detectors may be used to characterize the optical properties of the FEL radiation. VISA is designed to show how SASE FEL theory corresponds with experiment in this wavelength range, using an electron beam with emittance close to that planned for the future Linear Coherent Light Source at SLAC. VISA comprises a 4 m pure permanent magnet undulator with four 99 cm segments, each of 55 periods, 18 mm long. The undulator has distributed focusing built into it, to reduce the average beta function of the 70\char21{}85 MeV electron beam to about 30 cm. There are four FODO cells per segment. The permanent magnet focusing lattice consists of blocks mounted on either side of the electron beam, in the undulator gap. The most important undulator error parameter for a free electron laser is the trajectory walk-off, or lack of overlap of the photon and electron beams. Using pulsed wire magnet measurements and magnet shimming, we were able to control trajectory walk-off to less than $\ifmmode\pm\else\textpm\fi{}50\ensuremath{\mu}\mathrm{m}$ per field gain length.

Overview of LHD experiments

During the first two years of the LHD experiment the following resultshave been achieved: (i) higher Te (Te(0) = 4.4 keV at ⟨ne⟩ = 5.3 × 1018 m-3and Pabs = 1.8 MW); (ii) higher confinement (τE = 0.3 s, Te(0) = 1.1 keV at ⟨ne⟩ = 6.5 × 1019 m-3and Pabs = 2.0 MW); (iii) higher stored energy, Wpdia = 880 kJ at B = 2.75 T. High performance plasmas have been realized in the inward shifted magneticaxis configuration (R = 3.6 m) where helical symmetry is recovered and the particle orbitproperties are improved by a trade-off of MHD stability properties due to the appearance of amagnetic hill. Energy confinement was systematically higher than that predicted by theInternational Stellarator Scaling 95 by up to a factor of 1.6 and was comparable with theELMy H mode confinement capability in tokamaks. This confinement improvement is attributed to configuration control (inward shift of the magnetic axis) and to the formation of a high edgetemperature. The average beta value achieved reached 2.4% at B = 1.3 T, the highest betavalue ever obtained in a helical device, and so far no degradation of confinement by MHDphenomena has been observed. The inward shifted configuration has also led to successful ICRFminority ion heating. ICRF powers up to 1.3 MW were reliably injected into the plasma withoutsignificant impurity contamination, and a plasma with a stored energy of 200 kJ was sustainedfor 5 s by ICRF alone. As another important result, long pulse discharges of more than 1 min were successfully achieved separately with an NBI heating of 0.5 MW and with an ICRFheating of 0.85 MW.

Goals and status of Heliotron J

A new helical-axis heliotron device, Heliotron J, is now being constructedat the Institute of Advanced Energy of Kyoto University with the goal ofdemonstrating its improved helical confinement property in the helical-axisheliotron line. The design feature of Heliotron J is, as compared with that ofHeliotron E, the reduced neoclassical transport (near the tokamak levelaccording to the DKES code) and the enhanced average beta limit (4% for theMercier criterion) with small bootstrap current, which carries the potentialfor developing the currentless `quasi-isodynamic' optimization. The deviceparameters are as follows: the major plasma radius of 1.2 m, the averageplasma minor radius of 0.1-0.2 m, the magnetic field strength on the magneticaxis of 1.5 T, the vacuum rotational transform of 0.2-0.8 with a low magneticshear, and the magnetic well depth of 1.5% at the plasma edge, with heatingsystems such as ECH(0.5 MW), NBI(1.5 MW), and ICRF(2.5 MW). The feasibility ofthe helical-axis heliotron concept and its ability to explore high-qualityconfinement surfaces with a divertor will be fully tested in Heliotron J. Thefirst plasma was planned to be produced in the autumn of 1999.

Alpha and beta dose gradients in tooth enamel

New results describing gradients in effective alpha and beta doses within a layer of tooth enamel in planar geometry are presented. The alpha (track) dose to an enamel layer is calculated using an algorithm similar to that of Aitken (Aitken, M.J., 1987. Alpha dose to a thin layer. Ancient TL 5, 1–3.). The code for ROSY version 1.4 ( Brennan, B.J., Rink, W.J., Rule, E.M., Schwarcz, H.P., Prestwich, W.V., 1999. The ROSY ESR dating software. Ancient TL, in press. ) incorporates this algorithm. The approach allows for variation of the alpha track dose near the edges of the enamel, and we describe the gradient of the alpha track dose within 40 μm of each edge of the enamel for natural sources. In ESR or luminescence dating of naturally thin layers, for which stripping of the surface layer containing the alpha dose gradients may not be feasible, age estimates may change by as much as 5–10% when the detailed alpha dose calculation is included. Modern Monte Carlo-based results for the variation of beta dose for depths up to 2 mm are compared with ROSY results. For external irradiation by different sources, the attenuation of the ROSY dose estimate with depth is usually less rapid than that of the Monte Carlo-based estimate. The ROSY estimate of average beta dose to a layer in this case is between 5 and 18% higher than the Monte Carlo estimate.

Glycosaminoglycan conformation: do aqueous molecular dynamics simulations agree with x-ray fiber diffraction?

Glycosaminoglycan-protein interactions are biologically important and require an appreciation of glycan molecular shape in solution, which is presently unavailable. In previous studies we found strong similarity between aqueous molecular dynamics (MD) simulations and published x-ray diffraction refinements of hyaluronan. We have applied a similar approach here to chondroitin and dermatan, attempting to clarify some of the issues raised by the x-ray diffraction literature relating to chondroitin and dermatan sulfate. We predict that chondroitin has the same beta(1-->4) linkage conformation as hyaluronan, and that their average beta(1-->3) conformations differ. This is explained by changes in hydrogen-bonding across this linkage, resulting from its axial hydroxyl, causing a different sampling of left-handed helices in chondroitin (2.5- to 3.5-fold) as compared with hyaluronan (3.0- to 4.0-fold). Few right-handed helices, which lack intramolecular hydrogen-bonds, were sampled during our MD simulations. Thus, we propose that the 8-fold helix observed in chondroitin-6-sulfate, represented in the literature as an 8(3) helix (right-handed), though it has never been refined, is more likely to be 8(5) (left-handed) helix. Molecular dynamics simulations implied that (4)C(1) and (2)S(O), but not (1)C(4), forms of iduronate could be used in refinements of dermatan x-ray fiber diffraction patterns. Current models of 8-fold dermatan sulfate chains containing (4)C(1) iduronate refine to right-handed helices, which possess no intramolecular hydrogen-bonds. However, MD simulations predict that models containing (2)S(O) iduronate could provide better (8(5) helix) starting structures for refinement. Thus, the 8-fold dermatan sulfate refinement (8(3) helix) could be in error.

Influence of companion animals on the physical and psychological health of older people: an analysis of a one-year longitudinal study.

To examine whether companion animals or attachment to a companion animal was associated with changes in physical and psychological health in older people and whether the relationships between physical and psychological health and human social networks were modified by the presence or absence of a companion animal. A 1-year longitudinal study with standardized telephone interview data collected at baseline and repeated at 1-year Wellington County, Ontario, Canada An age- and sex stratified random sample (baseline n = 1054; follow-up n = 995) of noninstitutionalized adults aged 65 and older (mean age = 73, SD +/- 6.3) Social Network Activity was measured using a family and non-family social support scale, participation in an organized social group, involvement in the affairs of the social group, the practice of confiding in others, feelings of loneliness, and the perceived presence of support in a crisis situation. Chronic conditions were measured as the current number of selected health problems. Pet ownership was assessed by the report of owning a dog or a cat and the Lexington Attachment to Pets Scale score. Physical health was assessed as the ability to perform Activities of Daily Living (ADLs). Psychological health was measured as a summed score comprising the level of satisfaction regarding one's health, family and friend relationships, job, finances, life in general, overall happiness, and perceived mental health. Sociodemographic variables assessed include subject age, sex, marital status, living arrangements, education, household income, and major life events. Pet owners were younger, currently married or living with someone, and more physically active than non-pet owners. The ADL level of respondents who did not currently own pets deteriorated more on average (beta = -.270, P = .040) than that of respondents who currently owned pets after adjusting for other variables during the 1-year period. No statistically significant direct association was observed between pet ownership and change in psychological well-being (P > .100). However, pet ownership significantly modified the relationship between social support and the change in psychological well-being (P = .001) over a 1-year period. The results demonstrate the benefits of pet ownership in maintaining or slightly enhancing ADL levels of older people. However, a more complex relationship was observed between pet ownership and an older person's well-being.

Quasiaxially symmetric stellarators with three field periods

Compact hybrid configurations with two field periods have been studied recently as candidates for a proof of principle experiment at the Princeton Plasma Physics Laboratory. This project has led us to the discovery of a family of quasiaxially symmetric stellarators with three field periods that have significant advantages, although their aspect ratios are a little larger. They have reversed shear and perform better in a local analysis of ballooning modes. Nonlinear equilibrium and stability calculations predict that the average beta limit will be at least as high as 4% if the bootstrap current turns out to be as big as that expected in comparable tokamaks. The concept relies on a combination of helical fields and bootstrap current to achieve adequate rotational transform at low aspect ratio.

The Time-Series Behavior of IPO Betas

We examine individual IPO betas and provide further evidence that the documented decline in IPO betas results primarily from a seasoning or information effect and not from the delisting of high beta securities. We employ stochastic coefficient regression analysis which permits the estimation of individual IPO betas at all points in time, and therefore avoids disadvantages associated with grouped cross-sectional beta estimates and average individual time-series beta estimates. We find that IPO firms with the lowest betas are more likely to delist, and that individual IPO betas, on average, decline over time which provides support for the information hypothesis.

Nature, properties, and origin of low‐frequency waves from an oblique shock to the inner magnetosheath

We analyze the high time‐resolution profiles of the electron density and of the magnetic field and the plasma parameters recorded by ISEE 1 and 2 during a crossing of the Earth's magnetosheath at 1430 LT. Compressive and Alfvén ion cyclotron modes (AIC modes) are identified by comparing the measured magnetic polarization and electron parallel compressibility with the results of calculations in an unstable kinetic linear model. A criterion to discuss the accuracy of the wave vector direction of mirror modes is established; an efficient method to disentangle mirror and AIC modes is presented and applied. From the bow shock to the inner sheath we identify successively (1) compressive modes and AIC modes in the oblique shock, (2) a pure AIC mode region of circularly and elliptically polarized waves in a layer 0.3 RE thick adjacent to the undershoot, (3) a mixed region 2 RE thick where both mirror modes and AIC modes are observed, (4) a pure mirror mode region. The nature of the dominant mode appears to be controlled by the depth in the magnetosheath, more than by the local values of βp and the proton temperature anisotropy Tp⊥/Tp‖. In the outer sheath the unusual identification of a pure Alfvénic region for a large average proton beta βp = 13 and a moderate proton temperature anisotropy could be explained by a relatively low density of α particles. The mirror modes are three‐dimensional structures with their major axis along the magnetic field and with their minor axis nearly perpendicular to the magnetopause surface. We estimate the dimensions of ordered structures observed in the middle of the magnetosheath for a βp around 7 ± 1 and Tp⊥/Tp‖ around 1.5; the minor axis of regular mirror modes is typically between 1300 and 1900 km long; the intermediate dimension is larger than either 2200 or 2700 km, while the major axis is larger than either 2700 or 3400 km. For the first time the measured parallel compressibility of the pure mirror modes is shown to be in relatively good agreement with the linear model predictions for 4 < βp < 11. The absence of AIC modes in the inner sheath suggests that these modes cannot grow or propagate in regions where mirror modes are well developed and that AIC wave energy is not transferred across a large‐amplitude mirror mode region.

SMALL FIRM AND VALUE EFFECTS IN THE CANADIAN STOCK MARKET

AbstractWe examine the relation among average returns, market beta, firm size, and book‐to‐market value for Canadian stocks during 1975–92. We document a negative relation between average return and the market capitalization of firms, but find no relation between average return and market beta. While the small firm effect is significant during a period of reduced capital gains tax, it is noticeably lower than during the period leading up to the change. We find that average returns are positively related to book‐to‐market value especially during the period of lower capital gains tax.

Book-to-market, firm size, and the turn-of-the-year effect: Evidence from Pacific-Basin emerging markets

This paper investigates the relationship between expected stock returns and market beta, book-to-market equity, and size in five Pacific-Basin emerging markets: Hong Kong, Korea, Malaysia, Taiwan, and Thailand. In all the markets examined, the relationship between average stock return and market beta is weak. On the other hand, the book-to-market equity can explain the cross-sectional variation of expected stock returns in Hong Kong, Korea, and Malaysia, while the size effect is significant in all markets except Taiwan. Interestingly, the degree of the relation between average return and book-to-market equity coincides with the magnitude of the average book-to-market ratio in a country. We also find that large firms in Hong Kong and small firms in Korea have experienced higher returns in January. We argue that the different pattern of the `turn-of-the-year' effect between Hong Kong and Korea may be attributed to a different composition of investors. The majority of investors in Hong Kong are foreign institutional investors, while investors in Korea are mainly individuals.

On the possible excitation of electromagnetic ion cyclotron waves in solar ejecta

We study the possibility of exciting electromagnetic ion cyclotron waves (EICWs) in solar ejecta (CMEs) by a kinetic instability driven by ion temperature anisotropies. Our approach is to vary key parameters about assumed baseline values. Since Tp,‖ > Tp,⊥ in most solar ejecta, the polarization of the unstable waves is right‐handed. If the average proton beta is low (βp ≤ 0.3), the activity is negligible for moderate temperature ratios, Tp,‖/Tp,⊥. Increasing βp increases both the frequency range and the instability growth rate. Increasing the temperature anisotropy brings about qualitatively similar effects as increasing βp, with comparable growth rates. Increasing the relative alpha‐to‐proton density ratio η has two effects: the active frequency range is shifted toward lower frequencies and the growth rate increases. Between η = 0 and η = 0.15, the maximum growth rate increases by a factor of ∼20, highlighting the importance of the alphas for generating this instability. A case that may represent some magnetic clouds with exceptional parameters, βp = 0.2, Tp,‖/Tp,⊥ = 10, and η = 0.08 − 0.15, is considered. The maximum growth rate is found to be twice the reference CME case, while the active frequency range is 3 times wider. We conclude that EICWs should be present in some ejecta and possibly also in those magnetic clouds with relatively weak magnetic field, high He++ content, and large Tp,‖/Tp,⊥ ratios, and whose βp is high, for example, through interaction with a succeeding fast stream. We also suggest that substantial changes with respect to normal conditions should occur in the power spectrum of EICWs in the terrestrial plasma depletion layer when a CME, or a magnetic cloud, with negative anisotropy passes Earth.

Beta, size and returns: a study on the French Stock Exchange

The aim of this paper is to test the relationship between average returns and beta of French stocks over the last six years (1990–1995). Numerous and contradictory studies recently published in the American literature have cast doubts as to whether beta plays a role at all when it comes to explaining average returns on the American Stock Exchange (e.g. Fama and French, 1992; Pettengill et al., 1995). As the results obtained seem to depend upon the methodology used, we propose to implement some of the methodological advances advocated in these recent papers to test for the usefulness of beta as a determinant of returns on the French Stock Exchange. This subject has not been dealt with in recent literature.

Overview of the ARIES-RS reversed-shear tokamak power plant study

The ARIES-RS tokamak is a conceptual, D–T-burning 1000 MWe power plant. As with earlier ARIES design studies, the final design of ARIES-RS was obtained in a self-consistent manner using the best available physics and engineering models. Detailed analyses of individual systems together with system interfaces and interactions were incorporated into the ARIES systems code in order to assure self-consistency and to optimize towards the lowest cost system. The ARIES-RS design operates with a reversed-shear plasma and employs a moderate aspect ratio ( A=4.0). The plasma current is relatively low ( I p=11.32 MA) and bootstrap current fraction is high ( f BC=0.88). Consequently, the auxiliary power required for RF current drive is relatively low (∼80 MW). At the same time, the average toroidal beta is high ( β=5%), providing power densities near practical engineering limits (the peak neutron wall loading is 5.7 MW m −2). The toroidal-field (TF) coil system is designed with relatively `conventional' materials (Nb 3Sn and NbTi conductor with 316SS structures), and is operated at a design limit of ∼16 T at the coil in order to optimize the design point. The ARIES-RS design uses a self-cooled lithium blanket with vanadium alloy as the structural material. The V-alloy has low activation, low afterheat, high temperature capability and can handle high heat flux. A self-cooled liquid lithium blanket is simple, and with the development of an insulating coating, has low operating pressure. Also, this blanket gives excellent neutronics performance. Detailed analysis has been performed to minimize the cost and maximize the performance of the blanket and shield. One of the distinctive features of this design is the integration of the first wall, blanket, parts of the shield, divertor and stability shells into an integral unit within each sector. The maintenance scheme consists of horizontal removal of entire sectors. Prior to the initiation of the ARIES-RS study, a set of top-level requirements and goals for fusion demonstration and commercial power plants was evolved in collaboration with representatives from US electric utilities and from industry. The degree to which ARIES-RS reached these requirements and goals and the necessary trade-offs are described and the high-leverage areas and key R&D items are presented.

Radioactivity in zircon and building tiles.

Zircon (ZrSiO4) is commonly used in the manufacture of glazed tiles. In this study we found high concentrations of the radionuclides 226Ra, 232Th, 40K in zircon sand. The average radium equivalent (A(Ra) + 1.26 A(Th) + 0.086 A(k)) in zircon sand is 17,500 Bq kg(-1), which is 106 times as much as that in ordinary building materials. The external radiation (gamma + beta) dose rates in air at 5 cm from the surface of piles of zircon sand sacks range from 1.1 to 4.9 x 10(-2) mGy h(-1) with an average of 2.1 x 10(-2) mGy h(-1). Although no elevated gamma-ray radiation or radon exhalation rate was detected in rooms decorated with glazed tiles, which is characteristic of combined alpha, beta and gamma emitting thin materials, the average gamma-ray radiation dose rate at the surface of the tile stacks in shops is 1.5 times as much as the indoor background level. The average area density of total beta emitting radionuclides in glazed floor tiles and glazed wall tiles is 0.30 Bq cm(-2) and 0.28 Bq cm(-2), respectively. It was estimated that the average beta dose rates in tissue at a depth 7 mg cm(-2) with a distance 20-100 cm from the floor tiles were 3.2 to 0.9 x 10(-7) Gy h(-1). The study indicates that the beta-rays from glazed tiles might be one of the main factors leading to an increase in ionizing radiation received by the general public. Workers in glazed tile manufacturing factories and in tile shops or stores may be exposed to elevated levels of both beta-rays and gamma-rays from zircon sand or glazed tile stacks. No elevated radiation from unglazed tiles was detected.

Beta doses in tooth enamel by “one-group” theory and the ROSY ESR dating software

A new method of calculating beta doses for one-dimensional geometries, based on “one-group” theory, is presented. In typical situations it is found that this approach leads to average beta doses which are significantly lower (by up to 50%) than those from Grün's DATA software. For various natural sources, our beta dose rate estimates are slightly greater than expected from calculations based on Monte Carlo data, while the DATA results agree well with the experimental results of Aitken et al. (1985) for the uranium and thorium decay chains. Further experimental evidence is desirable to resolve this issue. We compare age estimates calculated using new ESR dating software called ROSY, which incorporates this approach, with those from DATA. Because of the difference in beta dose estimates, ROSY ages are generally older than the corresponding DATA ages, there being little difference in gamma and alpha dose estimates. We do however observe significant discrepancies in cosmic dose estimates. Examination of results for El Castillo Cave, Spain, by Rink et al. (1996) suggests that the ROSY age estimates are the more accurate.

TheF-ΘDiagram and Average Beta Values in an RFP Equilibrium

The F -Θ diagram and average beta values of a finite-pressure plasma in a toroid are considered by the use of the equilibrium configuration of a reversed field pinch (RFP) reported recently. Here F is the field reversal ratio, Θ is the pinch parameter, and beta values mean the ratio of the plasma pressure to the magnetic pressure. The equilibrium is a generalization of the force-free field model. The F , Θ and beta values averaged over the plasma cross section are derived. The F and average beta values obtained here are graphically shown as a function of Θ. It is found that the results agree with experimental findings.

Organochlorine residues in rural drinking water sources of northern and north Eastern India

Abstract Organochlorine pesticide residues concentrations in water samples collected from rural areas of northern and north eastern districts of India were studied. In the study, pesticide residues were detected in both the surface and ground water although the concentrations detected were below the WHO prescribed limit. Alpha HCH, total HCH and aldrin were detected in all the samples. The total DDT was detected in 90.9% ground water and 82% surface water samples. The average beta HCH and pp’ DDT concentrations were found to be higher as compared to their other metabolites. Ground water had alpha HCH, beta HCH, gamma HCH, op'DDT, pp”; DDT, pp'DDE pp’ DDD, endosulfan and aldrin higher by 4.6% , 14.06%, 2.4%, 24.2%, 15.6%, 101.02%, 174%, 57.85% and 24.73% as compared to surface water. The correlation between pesticide residues and nitrate concentration was non significant and could be due to their low concentration.

Function of the upstream hypersensitive sites of the chicken beta-globin gene cluster in mice.

We have shown previously that the chicken beta A-globin gene, with its 3' enhancer, is expressed in a copy number-dependent manner in transgenic mice. The expression level was low but increased approximately 6-fold upon inclusion of 11 kb of upstream DNA containing four DNase I hypersensitive sites. To study the effect of the individual upstream hypersensitive sites on transgene expression, we produced lines of mice in which the individual upstream sites were linked to the beta A gene and enhancer. RNA levels were measured in blood from adult animals. With each of these four constructs, the level of transgene RNA per DNA copy varied over a > 20-fold range. These data suggest that addition of a hypersensitive site to the beta A-globin/enhancer region abrogates its position independent expression. The average beta A-globin expression per copy in the lines carrying an upstream site was comparable with that in lines without an upstream site. Thus, no single upstream hypersensitive site accounts for the higher level of beta A-globin expression seen in mice containing the complete upstream region. We had shown previously that control of the chicken beta-globin cluster is distributed between at least two regions, the beta A/epsilon enhancer and the upstream region. Our current results suggest that the control mediated by the upstream DNA is itself distributed and is not due to a single hypersensitive site.

The Association Between the Level of International Diversification and Risk

AbstractThis study analyzes the association between the degree of international involvement (DOI) and risk. Both systematic risk (measured by the market model beta) and total risk (measured by variance of return) are analyzed. Betas of fully diversified foreign stock portfolios are shown to be lower than betas of domestic portfolios. Therefore, if the beta of a foreign investment by a U.S. firm is equal to the average beta of an investment in the foreign market, then overall firm beta will decrease as DOI increases (hypothesis). While total risk might be decreased due to the diversification provided by increasing DOI, currency, political, and other risks could cause total risk to increase. Briefly, the results of this study suggest that (1) systematic risk is negatively related to DOI even after controlling for other factors known to be associated with systematic risk, (2) intertemporal changes in systematic risk are negatively related to intertemporal changes in DOI, and (3) in contrast to the results of previous research, DOI is not negatively related to total risk and, in fact, intertemporal changes in total firm risk are marginally positively related to intertemporal changes in DOI.Our results suggest that increasing DOI decreases systematic risk but increases total risk. Year to year changes in both beta and variance of return appear to be related to year to year changes in DOI. While currency, political, and other risks of international operations increase total risk, these risks apparently can be diversified away resulting in a beta that behaves as a blending of its previous level and the beta of a fully diversified investment in the foreign market.