Time-asymmetric fluctuations in the atmosphere: daily mean temperatures and total-column ozone

Fluctuations breaking time-reversal symmetry are common attributes of dissipative systems operating far from equilibrium. Recent developments in non-equilibrium statistical physics represent a significant step towards an understanding of how time-reversible microscopic laws can yield to inherent irreversibility on meso- or macroscopic scales. Most of the theoretical conclusions consider quantities (e.g. entropy production) that are difficult to obtain with an appropriate accuracy in real systems. Probably less-complicated measures, such as the simple step-number ratio used in this work, can also help to characterize time-asymmetric fluctuations. In the first part, we give a short summary of recent results on asymmetric daily mean temperature changes. The second part discusses total-column ozone fluctuations, where statistically significant asymmetries are also detected. A detailed correlation analysis of ozone signals and high-altitude temperature records supports the strong coupling between tropospheric dynamics and stratospheric processes on synoptic time scales.     

Effective path length in attenuated total reflection spectroscopy

Attenuated total reflection (ATR) spectroscopy is now the most popular sampling technique for the measurement of infrared spectra of condensed phase samples. Most practitioners of ATR spectroscopy use the equation for depth of penetration, d(p), to estimate the path length of the evanescent wave through the sample. However, the effective path length, d(e), of the evanescent wave in an ATR measurement, i.e., the equivalent path length in a transmission measurement that would lead to an absorption band of the same intensity, is a more accurate metric than d(p). In measurements designed to obtain the absorptivity of bands in the spectrum of a strongly absorbing viscous liquid, we have shown that the refractive index used in the expressions for d(e) must be modified to take into account the effect of anomalous dispersion before accurate effective path lengths and band absorptivities can be measured.     

Anisotropy of the mean free path length in stationary gas flows

Using the concept of the anisotropy of the mean free path length we study the transition from continuous to rarefied flow for spherical and cylindrical gas sources for rigid and Maxwellian molecules.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 18, No. 4, pp. 671–677, April, 1970.     

Optical path difference in a plane-parallel uniaxial plate

The flux of energy given by the Poynting vector Se and the kt-wave vector normal to the geometrical wavefront for the extraordinary ray propagating through uniaxial crystals can be evaluated by using the theory developed by Avenda?o-Alejo et al. [J. Opt. Soc. Am. A 19, 1668 (2002)] and Avenda?o-Alejo and Stavroudis [J. Opt. Soc. Am. A 19, 1674 (2002)]. We give here the equations necessary to evaluate the general dispersion angle Se x kt. Additionally we define two new dispersion angles, Se x A and kt x A, where A is the crystal axis vector. With these new dispersion angles we evaluate the optical path length traversed by the extraordinary ray in a plane-parallel uniaxial plate when the crystal axis lies in the plane of incidence.     

Optical seeing-mechanism of formation of thin turbulent laminae in the atmosphere

Data from balloon soundings taken at sites in the Canary Islands, France, and Chile are used to show that hydrodynamic instability, perhaps engendered by the propagation of buoyancy (gravity) or other waves, leads to the formation of thin, turbulent laminae, or "seeing layers." These seeing layers occur almost invariably in pairs and exhibit large values for the temperature-structure coefficient C(T)(2) because they form where the gradient of temperature is particularly steep. The refractive-index-structure coefficient is correspondingly large, and so these layers adversely affect the quality of optical propagation. The mechanism proposed here is already known to create clear air turbulence in the stratosphere, and we show how it is consistent with the formation of thin turbulent seeing layers in the troposphere and the stratosphere at night, when the atmosphere is generally stably stratified.     

Temperature-concentration dependence of the correlation length of concentration fluctuations in liquid binary systems

An analysis is made of the correlation length of the concentration fluctuations in liquid binary systems over a wide range of temperature and composition. A quantitative relationship is obtained between the correlation length, the concentration, and the temperature. It is shown that the correlation length is determined by regions of different thermodynamic stability of a homogeneous solution, bounded by binodal and spinodal curves. Pis’ma Zh. Tekh. Fiz. 23, 84–88 (February 12, 1997)     

A modular path length corrector for recirculating linacs

We present a novel modular magnetic system that can introduce a large and continuously variable path length difference without simultaneous variation of the longitudinal dispersion. This is achieved by using a combination of an electrically adjustable magnetic chicane and a mechanically adjustable focusing chicane. We describe how such a system may be made either isochronous or with a given longitudinal dispersion, and show that the nonlinear terms in such a system are relatively small.     

Optical remote sensing of surface roughness through the turbulent atmosphere

Using a CO(2), cw, coherent lidar, we have measured the surface roughness of diffuse targets through 1000 m of turbulent atmosphere. The technique measures the phase fluctuations of the speckle field at the receiver and relates the measured phase variance to the surface roughness. Measurements were made with aluminum targets that had been sandblasted with 8-, 16-, and 30-grit material and also with a flame-sprayed aluminum target. It was found that a linear relationship exists between the standard deviation (SD) of the unwrapped phase fluctuations and the SD of the target surface-height fluctuations. Good results were obtained with modest transmitter power and small receiver optics in just a few seconds of averaging time.     

Optical transmission filters for observation of lightning phenomena in the Earth atmosphere

Very narrowband transmission filters, as parts of an instrument for the study of lightning phenomena, are described. Their performance must be maintained at an incidence angle of ±5.5° and this condition poses some limitations on the minimum bandwidth of the order of a few nanometers. The fabrication of such coatings on large area substrates is quite challenging because of the required thickness accuracy. Moreover, their performance should be not influenced by the environmental conditions in space.     

Exploring network structures via blockmodeling of the shortest path length matrix

Among the various methods of network analyses, blockmodeling is one of the key approaches to analyzing network structures. It can be applied not only to position analysis of the individual nodes, but also to cohesive subgroup discovery of the whole network. In this paper, we explore network structures via blockmodeling of the shortest path length matrix. First of all, we dichotomize the shortest path length matrix with different thresholds to generate reachability matrices within different steps. Then, through blockmodeling of the reachability matrix within n steps, we can analyze the network based on the cohesive subgroup, n-clique. Furthermore, through blockmodeling of the maximum reachability matrix, we can fit the network properly into the bowtie structure.     

Propagation of a general multi-Gaussian beam in turbulent atmosphere in a slant path

The propagation of a multi-Gaussian beam in turbulent atmosphere in a slant path is studied. The analytical expression for the average intensity of a general multi-Gaussian beam is derived. As special cases the average intensities of a two- and a four-Gaussian beam are investigated and numerically calculated. The investigation reveals that at lower altitude and with large sigma the intensity distribution at the receiver plane can have a shape (multiple peaks) similar to that at the source plane. But with increase in altitude or decrease in sigma, the multiple peaks gradually disappear and evolve into the profile of a fundamental Gaussian beam. From the comparisons between the different propagations we can see that the beam spreading due to wavelength and initial waist width in a slant path is much slower than that in a horizontal path.     

Assessment of near-infrared path length in fibrous phantom and muscle tissue

The first derivative of the pseudo-absorption spectrum of a water-loaded cotton wool (water-CW) phantom, which mimics muscle tissues, was used to determine the light path length in the near-infrared (NIR) region. The light path length increased as the density of the turbid medium decreased. It is independent of both water content in the range of 75-85% (by weight) and the diffuse reflecting reference used to determine the pseudo-absorbance. The path length determination procedure was verified by measurements of diffuse reflectance in chicken breast tissue for which the path length of 1.8 mm (differential path length factor, DPF = 2.1) was found to be similar to the path length of NIR light of 1.5-2.2 mm (DPF = 1.8-2.6) in a water-CW phantom of density similar to chicken breast. We conclude that the NIR light path length can serve as a characteristic of muscle tissue density.     

Temperature effects on the optical path length of infrared liquid transmission cells

Infrared (IR) spectroscopy is widely used for studies of temperature-dependent properties of liquids and solutions, such as thermal denaturation of proteins and other molecules of biological interest. The variation of the spectroscopic signals with temperature can be affected by the changes in the optical path length due to the thermal expansion of the components of the sample cell. In this report we investigate the temperature dependence of the optical path length for a liquid IR sample cell of a design typical for aqueous solution experiments. The path lengths were measured from the interference fringes, both in dry cells and with cells partially filled with water. We found that the optical path length variations are significant, on the order of several percent within the temperature range used (0-87 °C). Several commercially available spacers (Teflon, mylar, and lead) and gaskets (Teflon, lead, silicone rubber, Viton, and neoprene) were tested to find materials with either the smallest or most reproducible effect. Teflon, due to its phase transition (known as the "knee point") near room temperature, leads to abrupt changes in path length when used as either spacer or gasket component. On the other hand, Teflon is preferred for its inertness, while several of the other tested materials, most notably lead, are not practically usable due to adhesion to the cell windows upon heating and contact with the aqueous sample. The combination that yielded the most reproducible results, with minimal complications due to adhesion, was Teflon spacer with neoprene gaskets. The implications of the optical path length changes for the temperature-dependent IR experiments and their possible corrections are discussed.     

Optical quality micromachining of glass with focused laser-produced metal plasma etching in the atmosphere

Recent results are reported about the optical quality surface finish obtained on glass substrates with focused laser beam produced metal plasma etching in the atmosphere. The bombardment of high-speed, high-temperature electrons from an underdense plasma on the surface of glass substrates appears to play a dominant role in this process. The effective laser fluence window for this high-quality glass machining on common microscope slides is relatively narrow. With a Corning microslide 2947, and by use of carbon steel as the plasma source, we obtained parameters between 3.5 and 4.5 J/cm2. Above the upper limit, laser-induced optical breakdown occurs in the glass material and leads to the formation of microcracks. Below the lower limit, the process was found to be ineffective. In these experiments highly defined, clean, sharp-edged, 50 x 50 micropit arrays of 15.0-microm diameter with a depth of 3.2 microm and a center-to-center separation of 18.0 microm were fabricated on Corning microslide 2947 glass substrates.     

The unique features of wave flow with a change in the length of the film path

The maximum, wave amplitudes are analyzed for a change in the spray density and in the length of the film path for a liquid flowing under the action of gravity on the outside surface of a vertical tube.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 16, No. 1, pp. 140–144, January, 1969.     

Measurement and data-processing approach for estimating the spatial statistics of turbulence-induced index of refraction fluctuations in the upper atmosphere

We present a method of data reduction and analysis that has been developed for a novel experiment to measure the spatial statistics of atmospheric turbulence in the tropopause. We took measurements of temperature at 15 points on a hexagonal grid for altitudes from 12,000 to 18,000 m while suspended from a balloon performing a controlled descent. From the temperature data we estimate the index of refraction and study the spatial statistics of the turbulence-induced index of refraction fluctuations. We present and evaluate the performance of a processing approach to estimate the parameters of isotropic models for the spatial power spectrum of the turbulence. In addition to examining the parameters of the von Kármán spectrum, we have allowed the so-called power law to be a parameter in the estimation algorithm. A maximum-likelihood-based approach is used to estimate the turbulence parameters from the measurements. Simulation results presented here show that, in the presence of the anticipated levels of measurement noise, this approach allows turbulence parameters to be estimated with good accuracy, with the exception of the inner scale.     

双Wollaston棱镜的光程差及其色散

深入研究了的光程差与棱镜楔角以及空间变量-入射角三者的关系,并进行了计算机模拟.发现了对方解石构成的双Wollaston棱镜,光程差有较大的变化范围,光程差和入射角的关系有较好的线性的条件是:棱镜楔角在22°附近,入射角在-50°到10°范围内变化.然后对光程差的色散特性进行了分析和计算机模拟,结果表明,双Wollaston棱镜的光程差明显依赖于光波长,根据拟合结果它们的关系可以用三阶多项式来表述.本结果为偏振型空间调制干涉光谱仪的设计和应用提供了理论依据.