Fitness Bands Research Articles

Measurements of Starspot Parameters on Active Stars using Molecular Bands in Echelle Spectra

We present results from a study of starspot areas (fS) and temperatures (TS), primarily on active, single-lined spectroscopic binaries, determined using molecular absorption bands. Expanding upon our previous studies, we have analyzed multiorder echelle spectra of eight systems to simultaneously measure several different molecular bands and chromospheric emission lines. We determined starspot parameters by fitting the molecular bands of interest, using spectra of inactive G and K stars as proxies for the nonspotted photosphere of the active stars, and using spectra of M stars as proxies for the spots. At least two bands with different Teff sensitivities are required. We found that fitting bands other than the TiO 7055 and 8860 A features does not greatly extend the temperature range or sensitivity of our technique. The 8860 A band is particularly important because of its sharply different temperature sensitivity. We did not find any substantial departures from fS or TS that we have measured previously based on single-order spectra. We refined our derived spot parameters using contemporaneous photometry where available. We found that using M giants as spot proxies for subgiant active stars often underestimates fS needed to fit the photometry; this is presumably due to the increase in strength of the TiO bands with decreasing gravity. We also investigated correlations between fS and chromospheric emission, and we developed a simple method to measure nonspot temperature (TQ) solely from our echelle spectra.

Improved fits of the effective masses at Γ in the spin-orbit, second-nearest-neighborsp3s*model: Results from analytic expressions

We derive and study exact analytic expressions for the effective masses of the conduction--and all three hole--bands at \ensuremath{\Gamma} in the spin-orbit, second-nearest-neighbor ${\mathrm{sp}}^{3}{s}^{*}$ model. Using these expressions we determine parameters for six common III-V materials (GaAs, AlAs, GaSb, AlSb, InAs, and InP), tailored for [001]-oriented heterostructure calculations. Beyond their use in fitting band structures, the effective-mass formulas show that the second-nearest-neighbor ${\mathrm{sp}}^{3}{s}^{*}$ model is not without limitations. We show that there is an upper bound on the reproducible electron--light-hole effective-mass mismatch, so that even this model may not be sufficient for certain materials.

Generalized Slater-Koster method for fitting band structures

A tight-binding procedure is presented for fitting electronic band structures of crystals. It is based on a fully automated method of determining all possible independent matrix elements for arbitrary crystal structures. A fit, using this method, for the band structure of hexagonal close-packed Tc is more than an order of magnitude better than previous fits.

Simulation program suitable for hot carrier studies: An efficient multiband Monte Carlo model using both full and analytic band structure description for silicon

An efficient Monte Carlo model using both the full electronic band structure calculated from the empirical pseudopotential method and fitted, anisotropic, analytic bands is described. With the simulation program suitable for hot carrier studies, electron dynamics (i.e., scattering processes) are treated using the pseudopotential bands, where the accuracy of the band structure is most critical, while the electron kinetics (i.e., electron free flight between scattering and postscattering momentum selection) is treated using the fitted, analytic bands in order to greatly enhance the computational efficiency of the simulator. The analytic, multiband, multivalley model has 65 ellipsoidal, nonparabolic valleys and fits both the density of states and the electron E(k) dispersion relations of the pseudopotential band. The scattering ‘‘matrix elements’’ effect is also explored and an efficient model for this was developed and implemented for the first time in the framework of an analytic band. With this model, it is possible to include band-structure effects with greatly enhanced physical accuracy and central processing unit times comparable to other fitted band models. Excellent agreement is obtained between results using this new model and those from experiments and computationally more demanding simulators.

Raman structural characterization of clear human lens lipid membranes.

Raman spectroscopy was used for the first time to characterize the structure of lipid membranes prepared from the nuclear and cortical regions of 48 and 69 year old clear human lenses. The interface region carbonyl band appears as a doublet at 1742 and 1728 cm-1. The lower frequency band is characteristic of a hydrogen bonded carbonyl group, perhaps to bilayer water. From the intensity of the curve fit bands, we calculate that 43% of the carbonyl groups are hydrogen bonded. Our data show that the hydrocarbon chains of the nuclear lipids are 1.4 times more saturated than those of the cortical lipids. The molar ratio of phospholipid CH2/= C-H groups was calculated to be 13 and 18 for cortical and nuclear lipids, respectively. Hydrocarbon chain disorder was estimated to be 72 and 58% (+/- 8% disorder) for the cortical and the nuclear lipids, respectively. Raman spectroscopy is sensitive to structural differences in various regions of the lipid bilayer and could be an effective tool to explore lipid and protein interactions in terms of lens region, age and opacity.

On the use of nonparametric regression for model checking

SUMMARY The use of nonparametric regression is explored to check the fit of a parametric regression model. The principal aim is to check the validity of the regression curve rather than necessarily to detect outliers. A pseudo likelihood ratio test is developed to provide a global assessment of fit and simulation bands are used to indicate the nature of departures from the model. The types of data considered include discrete response variables, where standard diagnostic techniques are often not appropriate, and first-order autoregressive series. Several numerical examples are given. Nonparametric regression can be used in an informal graphical way to assess the relationship between a response and an explanatory variable. In this paper we aim to develop more formal methods of assessing the assumptions of a parametric model, in particular when regression diagnostics of the type developed for normal linear models are not readily available. The principal aim is to check the validity of the systematic part of the model by comparing a nonparametric estimate of the regression curve with a parametric one. Such a comparison may also identify outliers, although the distinction between outliers and model inadequacy is not always easy. Two techniques are used to assess the fit of a parametric model. In ? 2, confidence bands are constructed around the fitted regression curve by simulation. A comparison of these with the nonparametric curve gives an indication of the nature of any departures from the model. In ? 3, a pseudo likelihood ratio test is developed. This provides a quantitative global assessment of fit. In applying these ideas, special emphasis is given to discrete data, and notably logistic regression, because of the difficulty in applying standard residual-based model checking techniques to this type of response variable. A Poisson regression example is discussed in ? 4. However, the underlying ideas have wider applications. Autoregressive time series of order 1 are discussed in ? 6. Sections 5 and 7 discuss general issues. We first discuss the context of binary regression with a single covariate and the difficulties caused by the discreteness of the response variable. The observed data are assumed to be of the form (xi, yi, ni), where xi is a covariate value, and yi has a binomial

Absolute absorption cross sections at high resolution in the A2Πi – X2Πi band system of ClO

Chlorine monoxide (ClO) has been produced at temperatures near 315 K in a fast-flow system at total pressures (of argon diluent) in the range 1.0–2.0 mm Hg. The transmittance of ultraviolet radiation has been determined with a spectral resolution of 0.0054 nm for all 35ClO ν′–0 A2Π3/2 – X2Π3/2 sub-bands in the range 3 ≤ ν′ ≤ 12 (305.9–274.9 nm). The ClO column density obtained with 8 or 12 traversals of the radiation along an 80 cm cell was in the range 1.0–2.0 × 1017 cm−2.The experimental transmittance profiles for each sub-band have been reproduced closely by synthetic spectrum calculations. The parameters required as input to the programs were optimized by nonlinear least-squares techniques. The fitted (Lorentzian) linewidths are on average more than double those previously reported from visual estimates of linewidths on photographic plates. The fitted band strengths lead to a well-defined electronic transition moment variation for the A – X system of ClO, which is in excellent agreement with an earlier determination by Mandelman and Nicholls from spectra at lower resolution (0.22 nm) with unresolved rotational structure.

Perspectives in the theory of nuclear collective motion

This report discusses three different subjects. The first is the development of a generalized version of the VMI (variable moment of inertia) model which ties it to the original form of IBM (interacting boson model) and provides a possibility of fitting vibrational spectra with generalized vibrational formulas. The second is a suggestion for fitting band crossing calculations of the phenomenological type more completely than has hitherto been done into the framework of the VMI method. The third, which we consider the most important and far reaching, is the description of a complete mathematical method for the microscopic derivation of the IBM from a conventional shell model Hamiltonian. In addition to elements already foreseen by previous authors, we propose a solution for the most important problem outstanding not only within the framework of the IBM, but also in all previous work on boson expansion. We refer to the problem of actually selecting, in a general fashion, the most collective excitations. We introduce a criterion that the subspace constructed from these excitations should possess an average energy which is lower than the rest of the shell model space and explain how this criterion can be implemented in practice.

An analytic method for calculating stress induced changes in Fermi surfaces

A method is described which drives analytic expressions for stress induced changes in Fermi surfaces. The authors differentiate a small folded down secular equation in a region of k space close to the symmetry point k0. The fractional change in cross sectional area for the K point in the hcp Brillouin zone is found to be delta lnA/ delta sigma =B delta (EF-Ek)/ delta sigma -C delta V/ delta lnq, where B and C are coefficients whose values depend on the parameters EF, EK, V and S-V and S being pseudopotential and spin-orbit coupling matrices, respectively. These parameters may be extracted from any well fitted band structure calculation, and together with the elastic constants may be used to evaluate delta lnA/ delta sigma . Comparison of theory with experiment is made for the zinc third band electron needles, and for the cigars in beryllium and magnesium. The agreement is in general satisfactory and, more importantly, leads to an understanding of the results.

Expanded use of auxiliary personnel in orthodontic practice

A survey of all Massachusetts orthodontists was conducted to determine the tasks presently delegated to auxiliaries and the procedures to be delegated to trained personnel in the future. Responses were received from 111 of 198 orthodontists. More than 85 per cent of the respondents presently involved auxiliaries in patient education, dental and lateral head radiography, minor emergency adjustments, and removal of cement. Placement and removal of arch wires, checking of loose bands, tracing of lateral head radiographs, taking of impressions, and removal of separators, were delegated by 55 to 80 per cent of the orthodontists questioned. Fewer than half of the respondents allowed auxiliaries to tie elastic thread, insert separators, fit, cement, and remove bands, fit retainers or headgears, or construct arch wires. If properly trained auxiliaries become available, and if their involvement is legal and covered by malpractice insurance, more than 60 per cent of the orthodontists plan to delegate all procedures mentioned except fitting, cementing, and removal of bands, fitting of retainers, and construction of arch wires. Those favoring expansion of auxiliary duties had been in practice less than 10 years, in cities over 50,000, treating more than twenty patients per day, in offices with three or more chairs, and presently employing two or more dental assistants. Male auxiliaries would be acceptable to 50 per cent of the orthodontists polled. The major reservations of opponents to expanded auxiliary duties involved (1) potential impaired quality of service, (2) hazard to patient-orthodontist relationship, and (3) nonacceptance by patient and/or parent. Those who favored expansion of auxiliary duties were concerned with the difficulty in training, high salary level, and insufficient patient load to warrant their employment.

On the fitting of electronic energy bands to symmetrized plane waves

The possibility of fitting electronic energy bands throughout the Brillouin zone to sets of symmetrized plane waves is investigated in some detail. EPM computed energy bands serve to illustrate the various methods and their shortcomings.

Resolution of Ambiguity in Derivation of Pseudopotentials from Phase Shifts

In fitting electronic band structures of solids by means of scattering phase shifts, the level of the muffin-tin potential can be chosen at will relative to the Fermi level. Different choices correspond to distinct ways of expressing the total valence-electron density as a sum of atomic contributions.

GENETIC STRUCTURE OF POPULATIONS. III. NATURAL SELECTION AND CONCEALED GENETIC VARIABILITY IN A NATURAL POPULATION OF DROSOPHILA MELANOGASTER

Natural selection is a composite of forces acting on the gene pool of a population. Mather (1953) has pointed out two components of selection which are, in a sense, opposed to one another. These are selection for stability or immediate fitness and selection for the maintenance of variability or flexibility by which trend changes can be brought about. In naturally outbreeding populations selection for the maintenance of stability should be directed toward the maintenance of developmental homeostasis. It is this type of stabilizing selection which has been emphasized by Schmalhausen (1949), Waddington (1957), Lerner (1958), and others. But the natural environment is not constant. Short-term fluctuations and longterm time trends occur, exerting a directional selection pressure on the gene pool (Mather, loc. cit.). How, then, and within the limits of effective population size, may both stabilizing and directional selection take place in the natural environment with no reduction in population fitness and how may such changes be detected? Mean viability of the random heterozygotes is directly associated with population fitness (Band and Ives, 1963a; Dobzhansky and Spassky, 1963; Dobzhansky, 1964). It is dependent on the underlying genotypic constitution of the population and should be subject to the effects of natural selection at the genotypic level. Mean viability remains relatively constant when the same random array of random heterozygotes is tested in different laboratory temperatures (Spassky et al., 1960; Band and Ives, 1963a) and similar when random heterozygotes from different populations are tested in the same laboratory environment (Dobzhansky and Spassky, 1963). In turn, mean viability is determined by the contribution of various heterozygous classes to this fitness component (Wallace, 1962; Band and Ives, 1963a; Dobzhansky and Spassky, 1963). Experiments of Wallace (1955) and Breese and Mather (1960) also indicate that viability is not the maximum attainable. Consequently mean viability of the random heterozygotes becomes a better measure of the effectiveness of natural selection to maintain population fitness under changing environmental conditions than conventional metric traits. Variance components of viability for the random heterozygotes are also determined from the relative contributions of different heterozygous classes (Band and Ives, 1963a). If mean viability among the random heterozygotes remains relatively constant, then the maintenance of population fitness for viability may be the outcome of the joint effects of directional selection at the genotypic level and selection for the maintenance of developmental homeostasis, leading to the retention of genetic diversity in the population. Experiments on heterozygotes in different fluctuating environments (Band, 1963c) suggest that this may be the case and that directional selection pressure exerted by the environment may be minimized or impeded by selection for the maintenance of developmental homeostasis among the random heterozygotes. The retention of a coadapted gene pool may thus arise as an interaction between these two components of selection. By choice of appropriate statistical techniques, it should be possible to determine if one or both components of 1 The major portion of this investigation was done in the Department of Zoology, University of British Columbia. The research was supported by grants from the National Science Foundation and National Research Council of Canada.

Banded-cast metal crowns

This paper describes a practical and rapid technical procedure for constructing a clinically satisfactory complete metal veneer banded-cast type of crown. The technic deviates from the procedure more commonly utilized in that it eliminates the custom makeup of a fitted band from flat plate gold stock requiring the sweat­ ing or soldering so frequently disliked by many dentists. This banded-cast type of crown must not be confused with the other types which use rolled stock gold plate such as the swaged, or the swagedcast or soldered combination methods.

AN ABDOMINO-INGUINAL SUPPORTER. FOR USE AFTER HERNIOTOMY.

patient should not be allowed to get up until three weeks have elapsed after the operation and then only if the wound is sound. The question of a supporting bandage or a truss will then have to be considered.—Treves, Manual of Operative Surgery, 1892, Vol. 2, page 530. A spring truss should not be worn after the operation as its pressure tends to cause premature absorption of the lymph, but the abdominal wall requiresa certain amount of support for some months. In infants this may be managed with a skein of Berlin wool as already described; but for children and adults the form of appliance known as Harrison's truss answers best. It consists of a well fitting pelvic band and two short thigh pieces made of linen; like a pair of very short drawers fitting tightly and fastened with lacers; a perineal band prevents its ascending, and may in