Variable Phases Research Articles

Initial concentration-time profile of gentamicin determines efficacy against Enterobacter cloacae ATCC 13047.

In vitro studies were designed to investigate the influence of peak drug concentration (Cmax), the area under the concentration-time curve (AUC), and, consequently, the trough concentration on the bactericidal effects of gentamicin against Enterobacter cloacae (MIC, 0.5 mg/liter) by simulating bolus versus infusion administration and bolus dosing with altered drug clearance. Bacteria in the lag phase were exposed to gentamicin concentration-time profiles modelling either bolus or infusion dosing (AUC constant, Cmax changing) with 30-min postdose peak concentrations (Cpeak30) of 4, 6, 8, and 10 mg/liter or bolus dosing with normal and double drug clearance (Cmax constant, AUC changing) corresponding to normal clearance profiles with Cpeak30 of 6 and 8 mg/liter. Exposure to gentamicin caused early bactericidal effects apparent by 2 h, followed by variable bacteriostatic and recovery phases. Exposure to bolus profiles resulted in greater bactericidal activity than the corresponding infusion profile up to a Cpeak30 of 8 mg/liter. At a Cpeak30 of 10 mg/liter, there were no differences in bactericidal effect. Double clearance profiles had a reduced bactericidal effect at 6 mg/liter compared to the corresponding normal clearance profile, but no differences in bactericidal effect were observed for 8-mg/liter double and normal clearance profiles. These results suggest that the initial exposure (i.e., 0 to 30 min) is a more important determinant for bacterial killing than the AUC or trough concentration for this bacterium. Subject to confirmation of these findings with other gram-negative bacteria, to optimize aminoglycoside efficacy the initial exposure (Cmax) should be maximized by giving higher doses or bolus administration at intervals which may not produce detectable trough concentrations. Clinical trials with a broad range of patients, especially those with higher clearance, would confirm these in vitro observations and define optimal dosing recommendations.

Standing light fields for cold atoms with intrinsically stable and variable time phases

We present a novel method to realise a standing light field with a stable configuration in two or three dimensions. A single standing wave formed by two counterpropagating beams is folded and brought into intersection with itself. The values of the relative timephases are stable, a priori known, and can be altered arbitrarily by means of retardation plates. The polarisation configurations of three orthogonal standing waves include the standard magnetooptical trap and a novel three-dimensional pure polarisation lattice which we have investigated in a first spectroscopic measurement, providing strong evidence for atomic localisation in both cases.

Développement d'instabilités thermiques dans un écoulement horizontal en convection mixte: le point de vue de Lagrange

As part of the study of mixed convection in flow in a horizontal cylindrical duct uniformly heated at the wall, we show a thermal instability phenomenon. This manifests itself through large amplitude temporal fluctuations of the wall temperature which leads to an intermittent thermal behaviour of the system. Temperature fluctuations are characterized by variable stationary phases which succeed them. This paper provides, at first, a brief description of the experimental loop; then some numerical results corresponding to the stable state, and some experimental results related to the thermal instabilities are reported. Finally we propose a description of the properties of the phenomenon using a non-linear map. This map is defined by a characteristic function related to the thermohydrodynamic state of the flow. This approach based on a Lagrangian model allows us essentially to show the non-linear aspect of the system.

Modelling surface waves in anisotropic structures II: Examples

Surface waves in several anisotropic geological settings are studied by numerical simulation. Asymptotic point-source synthetic seismograms are obtained using formulas from a companion paper, the group velocities and mode-excitation factors being evaluated via variational integrals. Some alternative waveform approximations and ray-path effects are explored and the possible significances of peculiarities of anisotropy, such as wavefront folding, are at least partially assessed. Model one is a 5-layer oceanic environment with ±5.6% aligned vertical-crack S-wave anisotropy in the upper crust. The 2–3 s waveforms often have highest group velocities at 45° to the cracks and there are very strong transverse components from a vertical source. Maslov and ray/WKBJ waveforms agree well, even though for some modes and frequencies azimuthal group-velocity variations imply the latter is suspect. The Maslov-integral end-point signals mean that it too requires care and the so-called quasi-WKBJ approximation is a viable alternative. Periods approaching 1 s and/or high crack densities lead to very complicated group-velocity geometry indeed. The second model has ±2% upper-mantle mineral-alignment anisotropy, with its isotropic component constrained to agree with model ak135. The 20–30 s waveforms from a transversely-isotropic source force have fundamental ‘Rayleigh’ and ‘Love’ packets showing clear azimuthal phase anomalies but surprisingly standard polarizations and amplitudes. Only higher modes show such variable amplitudes and phases that they might be identified as likely due to anisotropy. Around 10-s period the higher-mode family has an interesting banded group-velocity structure and as the period is lowered further, two modes separate out and the band tightens in what may be a characteristic feature. Two candidate models of mantle-plume anisotropy show distinct azimuthal dependencies of mode velocities. Point-source surface-wave rays tracked in one plume model display shadows and focusing and show how initially folded wavefronts can unfold in the lateral variations. The upper-mantle models are numerically taxing. R/T coefficients and mode slownesses can be found using double-precision arithmetic, but depth profiles and variational-integrals sometimes require greater accuracy. We find that while displacements near the stack top and bottom may be obtained quite easily, as frequency increases it becomes increasingly difficult to compute those at mid-depth. We find no reason to believe that the Kennett invariant-embedding scheme has lesser accuracy than others.

Synchronization of circadian rhythms of house sparrows by oral melatonin: effects of changing period.

House sparrows (Passer domesticus) whose circadian rhythms of locomotor activity and feeding had been abolished by pinealectomy were held in constant dim light and periodically exposed to melatonin in the drinking water. By alternating 8 h of melatonin water with variable phases of tap water, rhythms with periods (T) ranging from 21 to 27 h were produced. When melatonin was administered in rhythms with periods of 23, 24, and 25 h, feeding and locomotion behavior of most birds were rhythmic and synchronized with the exogenous melatonin rhythm. The rest phase coincided approximately with the phase of melatonin availability. Under melatonin cycles < 23 h and > 25 h, fewer birds had synchronized rhythms. Nonsynchronized birds were either arrhythmic or they expressed free-running rhythms. Under melatonin rhythms with periods between 23 and 26 h, the phase-angle difference between defined phases of the behavioral rhythms and the melatonin rhythm became more positive with increasing T. These data are consistent with the hypothesis (a) that periodic exogenous melatonin can substitute, at least to a certain degree, for the endogenous plasma melatonin rhythm normally resulting from the periodic melatonin secretion by the pineal gland, and (b) that this melatonin rhythm acts on another oscillator, possibly the SCN, as part of the overall circadian pacemaking system.

Late Triassic to Middle Jurassic stratigraphy, palaeogeography and tectonics west of the British Isles

Abstract The Upper Triassic to Middle Jurassic stratigraphy of the Atlantic margin basins west of the British Isles (including Celtic Sea, Porcupine, Slyne, Erris, Hebrides, and west of Shetland) is summarized in terms of six major genetic sequences, defined as packages of conformable strata separated by surfaces of abrupt major facies change. They indicate common tectonic histories and are interpreted as representing episodes of evolution comprising extensional phases with laterally variable sequences (1A Late Triassic to Early Sinemurian; 2A latest Toarcian to Late Bajocian), thermal and loading sag phases (1B mid-Sinemurian to earliest Toarcian; 2B Late Bajocian to Bathonian) and stabilization phases with sequences of reduced thicknesses and hiatuses (1C Toarcian; 2C Late Bathonian to Callovian). The basins west of Shetlands, north of the Wyville-Thomson Ridge, have a different history, especially in the Early Jurassic. Similarly, basins south of an extension of the Clare Lineament (south of Celtic Sea and Porcupine Basins) differ in having limited Middle Jurassic subsidence. These transverse elements divide the Atlantic basin system into local subsystems, each of which has a different tectonic history.

Nonstoichiometry in oxides

Nonstoichiometry phenomena have been extensively studied in oxide systems. It is proposed that some models developed for oxides could be usefully extended for understanding nonstoichiometry in other systems. Many aspects of nonstoichiometry are closely connected with order-disorder phenomena. The broad field of nonstoichiometric compounds extends from variable composition phases with randomly distributed point defects (entropy controlled systems) to sets of discrete intermediate sompounds, each corresponding with a fully ordered state resulting from assimilation or annihilation of defects (enthalpy controlled systems). Between these two extreme cases, one finds intermediate situations such as clusters with a short range order, shear structures with possibly swinging shear planes, coherent intergrowths and infinitly adaptive structures in which any composition, even irrational, corresponds with an unique ordered structure.

An Insight into Early Reproductive Processes through thein VivoModel of Ovum Donation

To gain insight into early reproductive processes we have prospectively designed ovum donation protocols to elucidate several phenomena relating to embryo implantation and pregnancy sustenance. Artificial endometrial cycles with variable follicular phases were induced in 60 recipients by sequential estrogen and progesterone. A total of 964 oocytes were retrieved throughout 43 ovum donation attempts, for an average of 22.4 (range, 16-41) eggs/retrieval. The overall delivery rate per egg retrieval (donors and recipients combined) was 72.1% (31 of 43). The shortest estrogen stimulation (short follicular phase) resulting in ongoing pregnancies was 5 days in duration, while the longest (long follicular phase) was 35 days in duration before progesterone initiation. Utilization of variable length follicular phases, artificially extended the stage of endometrial receptivity to over 4 weeks. To assess the window of implantation, same age embryos were transferred onto endometrium of different maturational stages. Pregnancies were documented with embryo transfers between luteal day 1 (day 15) to luteal day 6 (day 20), extending the window of implantation in the human to at least 6 consecutive days. To evaluate the relative contribution of oocyte quality and endometrial receptivity to pregnancy outcome, common source ova were transferred onto endometrium with variable hormonal exposure. Despite the drastically different follicular phase estradiol levels and periods of exposure, similar delivery rates were attained in donor cycles (29.4%) and recipient cycles during short follicular phases (29.6%). Slightly higher delivery rates (39.4%) were observed with long follicular phases. The comparable pregnancy rates in donors and recipients are attributed to the common source oocytes regardless of endometrial stimulation.

Mid-Archaean evolution of the Eastern Indian Craton: geochemical and isotopic evidence from the Bonai pluton

The Archaean Eastern Indian Craton consists of several granitoid batholiths intruding greenstone-like sequences. The Bonai pluton, one such body in the central sector of the craton, consists of a dominant porphyritic and a subordinate equigranular variety ranging in composition from trondhjemite to granite. Xenoliths of massive trondhjemite, migmatite and quartzite occur in both phases. The granitoid xenoliths represent remnants of a sialic crust and are the oldest recognizable element in the Bonai pluton. These are high-Al 2O 3 trondhjemites with a highly fractionated rare earth element (REE) pattern. A Pb-Pb isochron age of 3369 ± 57 Ma has been obtained from a few spatially related xenoliths. The porphyritic and equigranular granitoids show similar petrographic characteristics and most of the samples show a calc-alkaline trondhjemitic association. A few granite samples, however, belong to a normal calc-alkaline association. The trondhjemitic samples are of the low-Al 2O 3 type with fractionated light REE (LREE), flat heavy REE (HREE) and a marked negative Eu anomaly. Granites of the calc-alkaline association have an identical REE pattern. Pb isotopic data for all samples together yield a Pb-Pb isochron age of 3163 ± 126 Ma. The REE characteristics of the two trondhjemite suites can be generated by partial melting of a mafic source with variable residual phases at different depths. On the other hand, the normal calc-alkaline granite may be generated by partial melting of trondhjemite similar in composition to that represented by the 3369-Ma xenoliths. Isotopic ages and the chemical nature of the Bonai pluton are similar to those identified in the adjacent Singhbhum Granite Complex. It is suggested that the entire Eastern Indian Craton has a common mid-Archaean history. The earliest sialic crust formed at ∼ 3400 Ma, and was followed by trondhjemitic addition at ∼ 3300 Ma. During this phase, restricted reworking of the older sialic crust produced calc-alkaline granites.

Numerical simulations of the seasonal response of the thermosphere to propagating tides

The UCL three-dimensional coupled ionosphere — thermosphere model has been modified by the addition of a forcing function for the (2,2), (2,3) and (2,4) semi-diurnal tidal modes near to the lower boundary (80 km). The effects of introducing this forcing are examined at high latitudes and the results are compared with recent EISCAT lower thermosphere wind data from May and July, 1987. The addition of lower boundary forcing with a suitable choice of amplitude and phase is shown to improve the fit of the model to observed data at high latitudes. However, quite variable lower boundary tidal forcing amplitudes and phases are required to match data from different observing periods. This indicates that tides of the lower thermosphere do not uniformly respond to classical Hough functions.

Investigation of backscattering effects on the correlation properties of a He–Ne ring laser

By making provisions for retroreflecting the two emerging counterrotating waves back into the laser cavity with variable amplitudes and phases, we have investigated backscattering effects in a He–Ne ring laser. In particular, we have measured the intensity flucuations and the intensity cross correlation between the two counterpropagating modes as the pump parameter and the phase of the backscattering are varied. We confirm the prediction based on third-order laser theory that equal-time moments depend on backscattering only through the combination R1 + R2*, where R1 and R2 are complex backscattering coefficients. Good agreement between experiment and third-order laser theory is obtained so long as the normalized pump parameter is below approximately 100.

Interactive effects of stress and photoperiod history on gonadal condition in male Syrian hamsters.

A study of the effects of melatonin injections given to male Syrian hamsters (Mesocricetus auratus) late in the light phase in a 14L:10D photoperiod included control, oil-injected hamsters that had been transferred from a 16L:8D photoperiod. Many oil-injected hamsters underwent gonadal regression under these conditions. A literature review indicated that endocrine effects of 'control' injections are fairly common but that they might depend on previous photoperiodic history. A second study found that hamsters born and raised in 16L:8D had larger testes at 150 days of age than those raised in 14L:10D. Transfer from 16L:8D to 14L:10D caused some unhandled hamsters to show gonadal regression while transfer to 14L:10D combined with daily oil injections caused most hamsters to undergo gonadal regression. Injections in animals maintained in 14L:10D throughout the study did not cause gonadal regression. These results indicate that stress effects can confound interpretation of drug treatments that require daily injections. They also demonstrate that the endocrine system of male Syrian hamsters distinguishes two photoperiods that are longer than the critical daylength (12.5 h). The effects of shortening daylengths may be potentiated by environmental stressors; together these may trigger gonadal regression at variable annual phases in anticipation of the critical daylength.

The high incidence of mismated feet in the population.

All Americans, and most likely all individuals in all societies, have mismated feet; that is, the two feet of probably no individual are exactly alike in size, shape, or proportions. This conclusion was based on the findings of a demographic foot-measurement survey embracing 6800 adults (4000 females, 2800 males), conducted in 1981-1982 by the Prescription Footwear Association. The findings may explain why the ideal or expectation of "perfect" shoe fit is virtually impossible, although they do not suggest that adequate or satisfactory shoe fit is not attainable in most instances involving so-called "normal" feet. They also indicate that a mild degree of "breaking in" is required with most new footwear, although never necessitating any distress. This article presents the methodology of the survey and foot measurements, along with the found data and their significance regarding the traditional processes of search of "proper" shoe fit and the obvious need for higher levels of professional shoe-fitting skills and service. The article also analyzes and discusses some little known or seldom considered complexities of shoe fit and the foot-shoe relationship that surfaces from this study, for example, the role of shoe design, shoe-sizing systems, consumer shoe-buying attitudes, and shoe materials, the four variable phases of shoe fit (static, weightbearing, functional, and thermal), and the availability of shoe sizes in stores.

An in vitro study of lymphocyte migration in the presence of premalignant and malignant oral lesions

The application of a continuous-time Markov chain theory to characterize and quantitate lymphocyte migratory paths in the presence of premalignant and malignant oral lesions, has been presented. Early and premalignant lesions induce either a positive (towards the lesion), random or negative migration (away from the lesion) response in host lymphocytes. The lack of consistency most likely reflects the varying stages in host-tumor cell interaction during the early and variable phases in the tumor's natural history. Invasive cancers invariably induce a negative migration response in host lymphocytes. A possible mechanism and the implication of such a response on the efficacy of host-tumor interaction are discussed.

On the nature of optically active centres in selfactivated luminophors of the CaWO 4 type

The evidence in favour of the assumption that impurities of V group elements creates defects of the MeO′ 4 type (centres of luminescence), MeȮ 3 and V Ȯ, or WO 3 (capture centres) which are responsible for recombination afterglow different from the steady-state luminescence spectral distribution ( Me = As, Sb, Nb, Ta; V 0 - oxygen vacancy) are presented. These same impurities, and phosphorous, lead to quenching of luminescence observed as afterglow with excitation quanta greater than 6.3 eV. This corresponds to the valued of the energy gap. Experimental data together with results of thermodynamic analysis lead to the conclusion that the luminescence of CaWO 4 and of other undoped oxygen containing compounds of transition elements luminophors is caused by direct self-activation connected with ability of these elements to convert spontaneously into a lower valency state and to form variable phases (non-stoichiometric compounds). It is proposed that in case of CaWO 4 centres of luminescence are formed by W 5+.

THE ROTATING CURRENT DIPOLE METHOD ‐ A FIELD TEST*

AbstractThe outputs and neutral of a three phase generator are converted to six amplitude variable phases in a 3.5 kW 400 Hz transmitter. These outputs are applied to six groundimplanted electrodes, producing a horizontally rotating current dipole in the subsurface.An investigation of the radiation pattern in the vertical magnetic field indicates, in symmetry and closure control, considerable advantages in this form of galvanic energization. These include optimization of inductive anomalies and the ability to interpret phase observations on a spatial basis in depth sounding and orebody location.

Phase equilibria in BaF 2(Y, Ln)F 3 systems

Data are presented on phase equilibria at 877 ± 10°C in the systems BaF 2(Y,Ln)F 3, where Ln = SmLu. All the systems show cubic solid solutions based on BaF 2 and variable composition phases ▪ of structure derived from the CaF 2 type (rhombohedral distortion). Syngony and unit cell dimensions have been determined on monocrystals; crystallographic parameters of ten trigonal phases have been adduced. The existence of solid solutions of BaF 2 in high-temperature α-LnF 3(LaF 3 type) at the given isothermal section indicates stabilization of the LaF 3 structure type by heterovalent isomorphous replacement. In the systems BaF 2(Y,Ln)F 3 with Ln = DyYb, monoclinic compounds BaR 2F 8 are formed. X-ray parameters, derived from single crystal and polycrystalline specimens, of six monoclinic BaR 2F 8 compounds are presented. In the BaF 2LuF 3 system we have isolated and studied for the first time a compound of the approximate composition BaLu 2F 8 which crystallizes in rhombic syngony and has a marked range of homogeneity.

Optimum Reception of Coded Multiple Frequency Keying in Presence of Random Variable Phases

Wide-band multiple frequency-shift keying is perturbed by random phases in the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M \geq 2</tex> frequency slots. We consider a coded digital system, where the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">M</tex> phases can be treated as mutually dependent random variables. If their joint distribution is known, the optimum (maximum-likelihood) receiver is shown to be in general very complicated. We show that there are a few phase distributions and signal-to-noise-ratio extremes for which the optimum receiver and its performance can be simply described. If the joint phase distribution is not known, we give an appropriate minimax receiver with a guaranteed performance. This performance is evaluted for orthogonal coding, white Gaussian noise, and nonfading signals. It is valid for all joint phase distributions.

Variable selectivity stationary phases for gas chromatography

Variable selectivity stationary phases for gas chromatography

C. Abnormal rituals in stress situations the rigidification of behaviour

Behaviour sequences commonly consist of highly variable appetitive phases leading to rather fixed consummatory acts. Action-pattern rigidity is typical of the terminal moments of a reaction chain. This basic fact is all too often obscured by the artificial conditions of behaviour studies. Observations on laboratory or captive animals tend to conceal the degree of variability of the earlier phases of each sequence. The simplicity and sterility of the unnatural environment offered to the animal causes differential damage to its motoric performance, attacking the early stages more and the later stages less. A caged animal will feed, drink, nest and copulate, but it cannot set off on lengthy quests for food, water, nest material or a mate. Notorious laboratory devices such as the Skinner-box have served to eliminate totally any possibility for motoric variability. The emphasis in laboratory studies of this kind has been steadfastly concentrated on the variability in the relationship between simple stimuli and an artificially rigidified response. Although the study of this (SR) relationship is an important aspect of animal psychology, it is extremely misleading to overstress its importance as has been done so often in the past. To equate it with the whole topic of animal behaviour is like claiming that the gaming rooms of Las Vegas reflect the whole of human endeavour.