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Thomson scattering of a probe wave by the Langmuir fluctuations inside a plasma layer with a parabolic density profile is considered. The collisional damping of plasma fluctuations is taken into account. The plasma line part of the scattered spectrum is calculated depending on the layer thickness, electron collision frequency, and the form of the distribution functions for the electrons and ions. Simple analytic expressions for the plasma line shape and characteristic spectrum width are found. It is shown that this plasma line is asymmetric, and the asymmetry depends on the layer type (maximum or minimum). Some important plasma parameters, such as the electron collision frequency and the sign of the electron density deviation inside the layer can be obtained from the plasma line spectrum calculated in this paper. Key words: Thomson scattering, Langmuir fluctuations, plasma line. Nous examinons la diffusion Thomson d'une onde de sonde (probe wave) par les fluctuations de Langmuir a l'interieur d'une couche de plasma avec un profil de densite parabolique. Nous tenons compte de l'amortissement collisionnel des fluctuations du plasma. La partie raie du plasma dans le spectre diffuse est calculee en fonction de l'epaisseur de la couche, de la frequence des collisions electroniques et de la forme des fonctions de distribution pour les electrons et les ions. Nous obtenons une expression analytique simple pour la forme de raie du plasma et la largeur du spectre caracteristique. Nous montrons que cette raie du plasma est asymetrique et que l'asymetrie depend du type de couche (minimum ou maximum). D'importants parametres du plasma, comme la frequence de collision electronique et le signe de la deviation de densite electronique a l'interieur de la couche, peuvent etre obtenus des spectres de raie du plasma calcules ici. [Traduit par la Redaction] Mots-cles : diffusion de Thomson, fluctuations de Langmuir, raie du plasma, diagnostique du plasma, collisions electroniques., 1. Introduction Thomson (incoherent) scattering of electromagnetic waves is a powerful tool used to observe plasma fluctuations of various types [1-4]. By analysis of the Doppler shifted backscatter spectrum, valuable [...]

Author(s): Jeremy B. Clark [1]; Florent Lecocq [1]; Raymond W. Simmonds [1]; Jos Aumentado [1]; John D. Teufel (corresponding author) [1] Quantum fluctuations of the electromagnetic vacuum produce measurable physical [...]

Structural fluctuations of a protein are essential for the function of native proteins and for protein folding. To understand how the main chain in the native state of a protein fluctuates on different time scales, we examined the rotational correlation functions (RCFs), C(t), of the backbone N-H bonds and of the dihedral angles [gamma] built on four consecutive [C.sup.[alpha]] atoms. Using molecular dynamics simulations of a model [alpha]/[beta] protein (VA3) in its native state, we demonstrate that these RCFs decay as stretched exponentials, In [C(t)][approximately equal to][D.sub.[alpha]][t.sup.[alpha]] with a constant [D.sub.[alpha]] and an exponent [alpha] (0 anomalous diffusion | model-free approach | power law | free-energy landscape doi/ 10.1073/pnas.1013674107

Thermodynamic fluctuation theory originated with Einstein, who inverted the relation S=[k.sub.B] ln [OMEGA] to express the number of states in terms of entropy: [OMEGA]=exp(S/[k.sub.B]). The theory's Gaussian approximation is discussed in most statistical mechanics texts. I review work showing how to go beyond the Gaussian approximation by adding covariance, conservation, and consistency. This generalization leads to a fundamentally new object: The thermodynamic Riemannian curvature scalar R, a thermodynamic invariant. I argue that [absolute value of R] is related to the correlation length and suggest that the sign of R corresponds to whether the interparticle interactions are effectively attractive or repulsive. [c] 2010 American Association of Physics Teachers. [DOI: 10.1119/1.3459936]

In this article, we report the use of a fiber-optic Mach-Zehnder interferometer as a high-precision temperature sensor, and we investigate the effects of small temperature fluctuations on the reliability of the device as a surface biosensor. We found that typical temperature fluctuations generally cause sensor responses large enough that they must be compensated for before reliable surface chemistry measurements can be undertaken. These findings are particularly relevant in light of the recent surge of interest in fiber-optic based biosensors of various designs. [c] 2010 Optical Society of America OCIS codes: 060.2370, 060.2430, 120.3180, 170.1580.

Laser vibrometry (LV) is originally a laser-based, line-of-sight measurement technique dedicated to the analysis of surface vibrations. It was lately adapted at TU Graz for monitoring the stability of an air-methane flame (Giuliani, et al., 2006, ASME Turbo Expo, ASME Paper No. GT2006-90413). This paper reports on the mapping of density fluctuations measured with LV in a premixed air-methane flame (free jet; swirl stabilized) with a forced flow modulation (quarter-wave resonator; amplification with a siren). In order to correlate the density fluctuations with the jet aerodynamics and turbulent flame shape, stereoscopic particle image velocimetry and high-speed schlieren visualizations were used. This paper addresses issues regarding the estimate of density fluctuations, the transform from line-of-sight to local measurement with tomographic methods, and the potential of the method for detailed description of thermoacoustic couplings. One emphasized application of LV is its ability to perform precise and low-cost benchmark stability tests on a combustor during the design phase (time-resolved measurement, high frequency and phase resolution on the 5 Hz-20 kHz range with the present equipment and settings, near-constant spectral sensitivity over a large bandwidth, and no seeding required; measurement possible over the whole combustion volume). [DOI: 10.1115/1.3159373]

The next generation nuclear power/advanced gas reactor (NGNP/AGR) fuel development and qualification program included the design, installation, and testing of a 6-in. diameter nuclear fuel particle coater to demonstrate quality tri-structural isotropic (TRISO) fuel production on a small industrial scale. Scale-up from the laboratory-scale coater faced challenges associated with an increase in the kernel charge mass, kernel diameter, and a redesign of the gas distributor to achieve adequate fluidization throughout the deposition of the four TRISO coating layers. TRISO coatings are applied at very high temperatures in atmospheres of dense particulate clouds, corrosive gases, and hydrogen concentrations over 45% by volume. The severe environment, stringent product and process requirements, and the fragility of partially-formed coatings limit the insertion of probes or instruments into the coater vessel during operation. Pressure instrumentation were installed on the gas inlet line and exhaust line of the 6-in. coater to monitor the bed differential pressure and internal pressure fluctuations emanating from the fuel bed as a result of bed and gas 'bubble' movements. These instruments are external to the particle bed and provide a glimpse into the dynamics of fuel particle bed during the coating process and data that could be used to help ascertain the adequacy of fluidization and, potentially, the dominant fluidization regimes. Pressure fluctuation and differential pressure data are not presently useful as process control instruments, but data suggest a link between the pressure signal structure and some measurable product attributes that could be exploited to get an early estimate of the attribute values. [DOI: 10.1115/1.3126772] Keywords: pressure fluctuations, Hurst exponent, spouted bed, particle properties

The hydrodynamic pressure field is important for the design and safety of steeply sloping stepped spillways, which are typically designed for considerably lower maximum specific discharges than smooth spillways. The hydraulic performance of stepped spillways at high velocities may compromise its use due to major concern with safety against cavitation damage. Hydraulic model investigations were conducted in different large-size stepped chutes to characterize the nonaerated flow region which is potentially prone to cavitation damage and the pressure field acting on the step faces. The clear water depths and energy dissipation in the developing flow region are described in terms of integral measures of the turbulent boundary layer. Expressions for the location of and the flow depth at the inception point of air entrainment are derived. Pressure distributions on the horizontal and vertical faces of the step along the spillway are presented. Measurements indicated a different behavior of the pressure field in the aerated and nonaerated flow region. The mean and fluctuating pressure coefficients along the spillway are approximated by a regression function. The vertical face near the outer step edge close to the inception point of air entrainment is identified as a critical region for predicting cavitation inception in flow over stepped spillways. From the analysis of the pressure fluctuations in that region a maximum velocity of 15 m/s is proposed as a criterion to avoid extreme negative pressures in typical prototype steeply sloping stepped spillways, eventually leading to the occurrence of cavitation in the nonaerated flow. DOI: 10.1061/(ASCE)HY. 1943-7900.0000118 CE Database subject headings: Spillway; Dams; Air entrainment; Cavitation; Hydrodynamic pressure.

The Casimir effect, a key observable realization of vacuum fluctuations, is usually taught in graduate courses on quantum field theory. The growing importance of Casimir forces in microelectromechanical systems motivates this subject as a topic for graduate many-body physics courses. To this end, we revisit the Casimir effect using methods common in condensed matter physics. We recover previously derived results and explore the implications of the analogies implicit in this treatment. [DOI: 10.1119/1.3194050]

When a relativistic perturbation is given to the horizon of a Schwarzschild black hole, a new supersurface near the horizon will be obtained. Using the gravitational anomaly method proposed by Robinson and Wilczek, Hawking radiation from this new supersurface is calculated. It is found that the first law of thermodynamics can also be constructed successfully on this supersurface. The expressions of the characteristic position and temperature are very similar to the previous results for the event horizon of a Vaidya black hole. Comparing with the Vaidya black hole, we conclude that Hawking radiation and the thermodynamics of a Vaidya black hole should be indeed constructed at the apparent horizon instead of the event horizon. PACS Nos: 04.70.Dy, 04.70.Bw, 97.60.Lf Lorsqu'une perturbation relativiste agit sur l'horizon d'un trou noir de Schwarzschild, nous obtenons une nouvelle supersurface pres de l'horizon. Utilisant la methode d'anomalie gravitationnelle de Robinson et Wilczek, nous calculons la radiation de Hawking emanant de cette nouvelle supersurface. Nous observons que la premiere loi de la thermodynamique se construit avec succes sur cette supersurface. Les expressions pour la position caracteristique et la temperature sont tres semblables aux resultats existants pour l'horizon des evenements d'un trou noir de Vaidya. Comparant avec le trou noir de Vaidya, nous concluons que la radiation de Hawking et la thermodynamique d'un trou noir de Vaidya devraient etre construits a l'horizon apparent, plutot qu'a l'horizon des evenements. [Traduit par la Redaction], 1. Introduction Hawking's significant discovery [1, 2] that black holes evaporate ushered in a new era in black-hole physics. Based on Hawking radiation, the thermodynamical relation has been successfully constructed [...]

Competing populations in shared spaces with nonrenewable resources do not necessarily wage a battle for dominance at the cost of extinction of the less-fit strain if there are fitness advantages to the presence of the other strain. We report on the use of nanofabricated habitat landscapes to study the population dynamics of competing wild type and a growth advantage in stationary phase (GASP) mutant strains of Escherichia coil in a sealed and heterogeneous nutrient environment. Although GASP mutants are competitors with wild-type bacteria, we find that the 2 strains cooperate to maximize fitness (long-term total productivity) via spatial segregation: despite their very close genomic kinship, wild-type populations associate with wild-type populations and GASP populations with GASP populations. Thus, wild-type and GASP strains avoid each other locally, yet fitness is enhanced for both strains globally. This computation of fitness enhancement emerges from the local interaction among cells but maximizes global densities. At present we do not understand how fluctuations in both spatial and temporal dimensions lead to the emergent computation and how multilevel aggregates produce this collective adaptation. biophysics | competition | ecology | microbiology

Four measurement principles based on the theory of fluctuation in the regular transmittance through a dispersion of large cylindrical particles are presented. The principles concern the measurement of particle concentration, particle length classes, particle length, and particle width. In previous publications, the measurement principles were briefly presented. A more complete description, experimental demonstrations, and a number of considerations needed to understand the region of validity of the different principles, as well as their uncertainty, are presented. A recently published simulation model [Appl. Opt. 47, 993 (2008)] is used. The basic ideas of the measurement principles within their respective regions of validity are supported. OCIS codes: 290.7050, 120.7000.

We studied the EEG background activity of Alzheimer's disease (AD) patients with detrended fluctuation analysis (DFA). DFA provides an estimation of the scaling information and long-range correlations in time series. We recorded the EEG in 11 AD patients and 11 age-matched controls. Our results showed two scaling regions in all subjects' channels (for limited time scales from 0.01 to 0.04 s and from 0.08 to 0.43 s, respectively), with a clear bend when their corresponding slopes ([[alpha].sub.1] and [[alpha].sub.2]) were different. No significant differences between groups were found with [[alpha].sub.1]. However, [[alpha].sub.2] values were significantly lower in control subjects at electrodes T5, T6, and O1 (p < 0.01, Student's t-test). These findings suggest that the scaling behavior of the EEG is sensitive to AD. Although [[alpha].sub.2] values allowed us to separate AD patients and controls, accuracies were lower than with spectral analysis. However, a forward stepwise linear discriminant analysis with a leave-one-out cross-validation procedure showed that the combined use of DFA and spectral analysis could improve the diagnostic accuracy of each individual technique. Thus, although spectral analysis outperforms DFA, the combined use of both techniques may increase the insight into brain dysfunction in AD. Index Terms--Alzheimer's disease (AD), detrended fluctuation analysis (DFA), EEG, scaling behavior.

The fluctuations of funnel solutions of intersecting D1 and D3 branes are quite explicitly discussed by treating different modes and different directions of the fluctuation at the presence of world [...]

Fluctuations in the abundance of molecules in the living cell may affect its growth and well being. For regulatory molecules (e.g., signaling proteins or transcription factors), fluctuations in their expression can affect the levels of downstream targets in a network. Here, we develop an analytic framework to investigate the phenomenon of noise correlation in molecular networks. Specifically, we focus on the metabolic network, which is highly inter-linked, and noise properties may constrain its structure and function. Motivated by the analogy between the dynamics of a linear metabolic pathway and that of the exactly soluble linear queuing network or, alternatively, a mass transfer system, we derive a plethora of results concerning fluctuations in the abundance of intermediate metabolites in various common motifs of the metabolic network. For all but one case examined, we find the steadystate fluctuation in different nodes of the pathways to be effectively uncorrelated. Consequently, fluctuations in enzyme levels only affect local properties and do not propagate elsewhere into metabolic networks, and intermediate metabolites can be freely shared by different reactions. Our approach may be applicable to study metabolic networks with more complex topologies or protein signaling networks that are governed by similar biochemical reactions. Possible implications for bioinformatic analysis of metabolomic data are discussed. noise correlation | biochemical networks | nonequilibrium steady-state

The main subject of this work is an experimental investigation of the existence of a local-time effect on the laboratory scale, i.e. longitudinal distances between locations of measurements from one [...]

A rapid increase of the fluctuation of ionization yield in Xe + 3%[sup.3]He gas mixture irradiated with thermal neutrons is observed at density above 0.18 [+ or -] 0.01 g/[cm.sup.3] (8.3 x [10.sup.20] [cm.sup.-3]). The significance and possible explanation of this experimental observation is discussed. Index Terms--High-pressure xenon, [sup.3]He, density, ionization yield, fluctuations, clusters.

We describe an experimental breadboard developed for the investigation of nonequilibrimn fluctuations induced by macroscopic temperature and concentration gradients under microgravity conditions. Under these conditions the amplitude of the fluctuations diverges strongly for long wavelengths. The setup was developed at the University of Milan and at the University of California at Santa Barbara within the gradient-driven fluctuations experiment (GRADFLEX) project of the European Space Agency, in collaboration with the National Aeronautics and Space Administration. The apparatus uses a quantitative shadowgraph technique for characterization of the static power spectrum of the fluctuations S(q) and the measurement of their dynamics. We present preliminary experimental results for S(q) obtained in the presence of gravity for gradient-driven fluctuations for two cases, those induced in a liquid mixture with a concentration gradient produced by the Sorer effect and those induced in a single-component fluid by a temperature gradient. OCIS codes: 120.5820, 070.2580, 110.6760, 040.2840, 100.2000.

We develop heuristic derivations of two alternative principles of least action. A particle moving in one dimension can reverse direction at will if energy conservation is the only criterion. Such arbitrary changes in the direction of motion are eliminated by demanding that the Maupertuis--Euler abbreviated action, equal to the area under the momentum versus position curve in phase space, has the smallest possible value consistent with conservation of energy. Minimizing the abbreviated action predicts particle trajectories in two and three dimensions and leads to the more powerful Hamilton principle of least action, which not only generates conservation of energy, but also predicts motion even when the potential energy changes with time. Introducing action early in the physics program requires modernizing the current obscure and confusing terminology of variational mechanics. [DOI: 10.1119/1.1848516]

The model by Prigogine and Nicolis suggesting how microscopic fluctuations can instigate major changes in macroscopic configurations stands as a landmark contribution, helping to incite the current explosion of interest [...]

The fictive temperature (T(sub f) ) and fluorine concentration dependence of structure fluctuation in SiO2 glass were investigated by small-angle x-ray scattering measurement, in this study. It was found that density fluctuation solely contributes to the T(sub f) dependence of structure fluctuation.

Fluctuations in the natural environment introduce variability into the biological systems that exist within them. In this paper, we develop a model for the influence of random fluctuations in the environment on a simple epidemiological system. The model describes the infection of a dynamic host population by an environmentally sensitive pathogen and is based on the infection of sugar beet plants by the endoparasitic slime-mold vector Polymyxa betae. The infection process is switched on only when the temperature is above a critical value. We discuss some of the problems inherent in modeling such a system and analyze the resulting model by using asymptotic techniques to generate closed-form solutions for the mean and variance of the net amount of new inoculum produced within a season. In this way, the variance of temperature profile can be linked with that of the inoculum produced in a season and hence the risk of disease. We also examine the connection between the model developed in this paper and discrete Markov-chain models for weather.

Experiments are performed to study the effect of cavity geometry and Mach number on the characteristics of compressible rectangular cavity flows. The study indicates that the corresponding length-to-depth ratio for the open- and transitional-type cavities increases with higher freestream Mach number. The depth-to-incoming boundary-layer thickness ratio is another important parameter to define the type of the cavity flow. The upstream influence region is minimized with the presence of a cavity, and larger downstream influence region is observed for the transitional-closed- and closed-type cavities. The distributions of surface pressure fluctuations show similar trend as those of static pressure distributions. The amplitude of surface pressure fluctuations increases toward the rear face for an open-type cavity, whereas a minor peak near the middle of the cavity floor is observed for a closed-type cavity. A transitional-type cavity induces more intense surface pressure fluctuations at the cavity floor. Higher levels of pressure fluctuations near the rear face are observed at higher Mach numbers for the transitional-and open-type cavities.

Byline: Milan M. Airkovic (1) Keywords: arrow of time; anthropic principle; entropy; philosophy of cosmology Abstract: A modern assessment of the classical Boltzmann-Schuetz argument for large-scale entropy fluctuations as the origin of our observable cosmological domain is given.The emphasis is put on the central implication of this picture which flatly contradicts the weak anthropic principle as an epistemological statement about the universe. Therefore, to associate this picture with the anthropic principle as it is usually done is unwarranted. In particular, Feynman's criticism of theanthropic principle based on the entropy-fluctuation picture is a product of this semantic confusion. Author Affiliation: (1) Astronomical Observatory of Belgrade, Volgina 7, 11160, Belgrade, Serbia, Yugoslavia Article History: Registration Date: 12/10/2004

An experimental investigation was conducted to study the transonic flow past convex corners. The mean surface pressure indicated strong--viscous interactions, and the interaction region increased with the freestream Mach number and the convex-corner angle. Unsteadiness of the interaction was characterized by an intermittent region and a local peak pressure fluctuation. The peak pressure fluctuations and the tentative boundary between the attached and separated flows could be scaled with the convex-corner angle and a second-order freestream Mach number ([M.sup.2.sub.[infinity]][eta]).

Capillary flow experiments are described with fluorescent molecules, bacteria, and microspheres using fluorescence correlation spectroscopy as an analytical tool. The flow velocity in the microcapillary is determined by fitting autocorrelation traces with a model containing parameters related to diffusion and flow. The flow profile of pressure-driven flow inside a microcapillary is determined by using the fluorescence fluctuations of a small dye molecule. It was found that bacteria and microspheres are retarded in their flow by optical forces produced by the laser beam.

A simple new approach is described and demonstrated for measuring the number of independent emitters along with the fluorescence intensity, lifetime, and emission wavelength for trajectories and images of single molecules and multichromophoric systems using a single PC plug-in card for time-correlated single-photon counting. The number of independent emitters present in the detection volume can be determined using the interphoton times in a manner similar to classical antibunching experiments. In contrast to traditional coincidence analysis based on pulsed laser excitation and direct measurement of coincident photon pairs using a time-to-amplitude converter, the interphoton distances are retrieved afterward by recording the absolute arrival time of each photon with nanosecond time resolution on two spectrally separated detectors. Intensity changes that result from fluctuations of a photophysical parameter can be distinguished from fluctuations due to changes in the number of emitters (e.g., photobleaching) in single chromophore and multi-chromophore intensity trajectories. This is the first report to demonstrate imaging with contrast based on the number of independently emitting species within the detection volume.

A laser-diode-pumped intracavity frequency-doubled Nd:YAP/KTP laser is presented. Over 110 mw of TE[M.sub.00] single-frequency output power at 540-nm wavelength was obtained. The output green laser was employed to pump a semimonolithic nondegenerate optical parametric oscillator to produce intensity quantum correlated twin beams at 1080 nm, and the maximum quantum noise squeezing of 74% (5.9dB) on the intensity difference fluctuation between the twin beams is observed. The threshold was reduced and the stability was increased significantly when compared with similar lamp-pumped systems. OCIS codes: 140.3580, 140.3560, 140.3480, 270.6570.

The distribution function in a classical gas at equilibrium is determined by correlations among local momenta fluctuations. External observers may be able to determine distribution when special conditions pertain to Brownian particles.

The importance of the inlet conditions of the dispersed-phase fluctuating velocity on the analysis associated with the stochastic Lagrangian method, which is commonly used in the simulation of two-phase turbulent flows, is demonstrated through two well-defined problems. One is under the inlet condition of the carrier-phase turbulent kinetic energy [k.sub.g] larger than the dispersed-phase turbulent kinetic energy [k.sub.p]. The other is associated with [k.sub.g] < [k.sub.p]. A solution procedure accounting for the inlet conditions of the fluctuating dispersed-phase velocities in the stochastic Lagrangian calculation is developed. It is also concluded that the unsteady drag coefficient has to be considered in the model formulation when the condition of the Stokes number larger than O([10.sup.1]) is encountered in the examined two-phase turbulent flowfield.

Research is presented concerning the reduction which can be achieved in the fluctuation of signal intensity through the conservation of the total energy of the signal and pump in an optical wave mixing system.

The thermodynamic approach that treats fluctuations as larger-scale manifestations of atoms, is discussed.

This resource letter provides an introductory guide to the literature on the Casimir force. Journal articles and books are cited for the following topics: introductory articles and books, calculations, dynamical Casimir effect, mechanical analogs, applications, and experiments.

Research was conducted to examine the fluctuation induced conductivity (FIC) of two high critical temperature superconductors (HTSC) namely Bi2Sr2Ca1O(sub 8+infinity) and Y(sub 1-x)Ca(sub x)Ba2Cu3O(sub y). An evaluation of the FIC was carried out as well as a comparison with the theoretically derived values from the proposed model. Results show that both the HTSC materials studied have similar behavior concerning the crossover which is revealed with the different extents of the fluctuations regions.

Research was conducted to examine the sound wave spread in narrow Josephson junctions using the model of a Brownian particle moving within a potential well in a fluctuating temperature field. The emphasis was on the physical basis of the sound wave amplification by Josephson junction with introduction of relaxation time of the coherent phase as the output of a self-consistent solution of the Fokker-Planck equation.

The behavior of a charged two-level fluctuator in an Al-AlO(sub x)-Al single-electron transistor (SET) in the normal state was studied over a temperature range from 85 mK to 3 K. The experimental data were compared to a model that assumes the fluctuator is located in one of the tunnel junctions and undergoes inelastic scattering with phonons and transport electrons. The behavior in the superconducting state is predicted using the parameters from the normal state data.

The correlation functions of the fluctuations of vibrational frequencies of azide ions and carbon monoxide in proteins are determined directly from stimulated photon echoes generated with femtosecond infrared pulses. The asymmetric stretching vibration of azide bound to carbonic anhydrase II exhibits a pronounced evolution of its vibrational frequency distribution on the time scale of a few picoseconds, which is attributed to modifications of the ligand structure through interactions with the nearby Thr-199. When azide is bound in hemoglobin, a more complex evolution of the protein structure is required to interchange the different ligand configurations, as evidenced by the much slower relaxation of the frequency distribution in this case. The time evolution of the distribution of frequencies of carbon monoxide bound in hemoglobin occurs on the [approximately equal to]10-ps time scale and is very nonexponential. The correlation functions of the frequency fluctuations determine the evolution of the protein structure local to the probe and the extent to which the probe can navigate those parts of the energy landscape where the structural configurations are able to modify the local potential energy function of the probe.

Research was conducted to carry out a three-dimensional atomistic simulation study of random dopant induced threshold voltage lowering and fluctuations in sub-0.1 micron metal oxide semiconductor field effect transistors on a large statistical scale. The effective channel length was determined as the distance between the metallurgical pn junctions of the source and the drain at the Si/SiO2 interface. Results indicated that threshold voltage lowering and fluctuations were directly proportional with increases in the doping level.

The permeable reattachment surface was shown to induce the peak rms wall-pressure to fluctuate downstream. The upstream convection of disturbances produced at the reattachment which was inhibited by the permeable surface seemed to contribute to the fluctuation. The replacement of the permeable reattachment surface region also weakened the instantaneous mirror image of the reattaching structure which altered pressure disturbances via pressure-strain terms.

Using known properties of the exact wave function, a number of one-parameter variational wave functions for the ground states of atomic two-electron systems have been constructed. The best energies found compare favorably with those obtained in other work.

D'Alembert's variational principle and Noether's theorem to the existence of conservation laws were used to derive conservation laws for dynamic systems with variable mass, which is exclusively nonconservative in the general instance. The terms that describe the mass variation expand Noether's identity in such instances. A conservation law exists if Noether's identity is satisfied.

Four kinds of routinely employed variational functionals were used to formulate the inequality principles of the kineto-static contact problem of two elastic bodies in the common relative motion. This incremental frictional contact problem involved Hu-Washizu and Hellinger-Reissner functionals. The functional of Hu-Washizu can be used to obtain the associated principles based on the Reissner potential energy and complementary energy functionals.

An analysis of Brownian motion based upon a 'Langevin equation' form of Newton's second law provides a physically motivated introduction to the theory of continuous Markov processes, which in turn illuminates the subtle mathematical underpinnings of the Langevin equation. But the Langevin approach to Brownian motion requires one to assume that the collisional forces of the bath molecules on the Brownian particle artfully resolve themselves into a 'dissipative drag' component and a 'zero-mean fluctuating' component. A physically more plausible approach is provided by a simple discrete-state jump Markov process that models in a highly idealized way the immediate effects of individual molecular collisions on the velocity of the Brownian particle. The predictions of this jump Markov process model in the continuum limit are found to precisely duplicate the predictions of the Langevin equation, thereby validating the critical two-force assumption of the Langevin approach.

Temporal fluctuations have recently been discovered in the dark current of proton-displacement-damaged CCDs. These fluctuations take the form of random telegraph signals with well defined amplitudes and time constants (for the high and low dark current states). Temperature and annealing behavior have been studied, as has the dependence on proton fluence. A bistable defect mechanism is proposed.

Experimental results for the noise of photon-correlation and photon-structure functions are presented. The noise dependences on the mean count rate and on the sampling time are investigated by means of a specifically built linear fluctuation analyzer, and the results are compared with theoretical predictions. The predicted mean count rate dependence and sampling time dependence of the noise are confirmed by the experimental analysis. Some discrepancies between analytical expressions and experimental results are observed in the crossover predictions. The results show that the structure function has better noise performance for relatively high mean count rates and for long sampling times, which strongly suggests a wider use of this statistical estimator in measurements requiring good accuracy, as in the case of uniform sampling.

Seasonally varying spectral and cross-spectral calculations are carried out on multiyear time series of vertically and zonally averaged daily zonal wind fields to describe the seasonal cycle of the 40-50-day oscillation of atmospheric angular momentum. Intraseasonal variability (including 40-50-day fluctuations) of global momentum is largest in late boreal winter and smallest in boreal autumn; however, the 40-50-day spectral peak is most pronounced in boreal summer when lower-frequency intraseasonal variance is depressed. The 40-50-day spectral peak in global momentum is much less pronounced and apparently is restricted to a narrower frequency band, than corresponding peaks in zonal wind spectra from individual tropical rawinsonde stations. Contributions to global momentum fluctuations from three near-equal-area latitude bands (tropics, Northern Hemisphere, and Southern Hemisphere) are compared, confirming that intraseasonal momentum fluctuations are tropical in origin. The variance of extratropical momentum at this time scale is about an order of magnitude less than the tropical momentum variability. Coherent tropical-extratropical interactions are found principally in boreal winter, with the highest coherence between the tropics and Northern Hemisphere. The corresponding phase difference between tropical and Northern Hemisphere momentum is suggestive of poleward propagation of momentum out of the tropics.