Non-ideal Experimental Conditions Research Articles

Effects of some nonideal experimental conditions on a micromaser-based preparation of bimodal number states

The practical feasibility of a conditional experimental scheme for generating bimodal number states, taking into account from the beginning some important technological limits of the current experimental setup, is analyzed. The influence of the unavoidable occurrence of a nonideal performance in a realistic apparatus on the interaction mechanism chosen for guiding the cavity field towards the desired bimodal Fock state is pointed out.

Influence of decorrelation on Heisenberg-limited interferometry with quantum correlated photons

The feasibility of a Heisenberg-limited phase measurement using a Mach-Zehnder interferometer fed with twin photon correlated light is investigated theoretically. To take advantage of the Heisenberg limit, $1/N$, for the phase sensitivity, one wants the number of correlated photons, $N$, to be high. This favors the use of parametric oscillation rather than the weaker but better correlated source given by parametric down-conversion. In real systems, decorrelation arising from photon absorption, mode mismatch, and nonideal detectors must be considered. In this paper we address the problem of detection when correlated photons are used as the input. We study the influence of photon statistics and of imperfect quantum correlation of the input light, and show that it is still possible to break the classical $1/\sqrt{N}$ phase sensitivity limit in nonideal experimental conditions. All the results are valid in the general case of quantum correlated bosons.

Digital image holography

Digital image holography (DIH) is an interferometric method that allows one to superpose the states of the device investigated at different times. The interference fringes produced are similar to those obtained by real-time holography and are interpretable in the same way. High-contrast interference fringes are reliably obtained even under nonideal experimental conditions. In DIH a CCD camera captures the superposition of a phase-variant object beam and a temporally constant reference beam. The phase difference between these two beams is calculated. The way this is done differs from digital speckle pattern interferometry and other related methods. The temporal phase shift of the object beam is calculated from the phase difference between object and reference beam at two different times. The resulting interference intensity depends on the phase shift of the object beam.

Thermal activation analysis of dislocations in obstacle fields

The strength of metals as a function of temperature is still not very well understood, even in the case where thermal overcoming of obstacles by dislocations is believed not to be superimposed by other temperature dependent effects, like solute atom diffusion. Our simulation calculations offer a means to close some of the gaps in understanding, as they exclude both superimposed effects of any kind as well as errors due to non-ideal experimental conditions. In this contribution our results concerning the activation enthalpy and -volume for obstacles of atomic size are presented. The simulations reveal that for equivalent conditions an obstacle field can well be compared to an equidistant obstacle arrangement to be overcome. Another simplification of the activation model can be done by replacing this obstacle row by a continuous obstacle wall without affecting the activation parameters. From this it has to be concluded that the activation volume does not always depend on the obstacle spacing due to first principles. A length L is introduced which for a concrete obstacle spacing determines the number of obstacles to be overcome simultaneously for thermal activation. Calculations on obstacle fields show that for solute atom concentrations between 0.1% and 20%, this length L rather than the obstacle spacing controls thermal activation.

An extension to the dynamic plane source technique for measuring thermal conductivity, thermal diffusivity, and specific heat of dielectric solids

The recently developed dynamic plane source (DPS) technique for simultaneous determination of the thermal properties of fast thermally conducting materials with thermal conductivities between 200 and 2 W/mK has now been extended for studying relatively slow conducting materials with thermal conductivities equal or below 2 W/mK. The method is self-checking since the thermal conductivity, thermal diffusivity specific heat, and effusivity of the material are obtained independently from each other. The theory of the technique and the experimental arrangement are given in detail. The data evaluation procedure is simple and makes it possible to reveal the distortions due to the nonideal experimental conditions. The extension to the DPS technique has been implemented at room temperature to study the samples of cordierite-based ceramic Cecorite 130P (thermal conductivity equal to 1.48 W/mK), rubber (0.403 W/mK), and polycarbonate (0.245 W/mK). The accuracy of the method is within ±5%.

7] Nonstationary noise analysis and application to patch clamp recordings

Publisher Summary This chapter discusses studies of nonstationary fluctuations of sodium currents in bovine adrenal chromaffin cells for estimating the temperature and pressure dependence of the conductance of voltage-activated sodium channels as an application of the analysis method. The procedure presented allows a rapid analysis of noise records obtained under nonideal experimental conditions based on objective selection criteria. Although single-channel analysis surpasses noise analysis in many instances, there are still regimes, where it cannot be successfully applied for various reasons. In this regard, nonstationary noise analysis retain its value for electrophysiological research in particular, as ever fainter electrical signals are being investigated in biological membranes. To demonstrate the methods, the temperature and pressure dependence of the sodium channel conductance are measured, and in both respects, the sodium channel shows features similar to other ion channels. Both findings are in accord with the physical picture of a rather free ion diffusion through the channel pore which, unlike the channel gating mechanism, does not involve protein rearrangements associated with measurable activation volumes.

Analysis of errors associated with passive ventilation measurement techniques

In small building where ventilation is the primary mechanism for removing indoor air pollutants, interest in converting the resulting energy load on the heating or cooling system of the building is significant. The desire of making field measurements of this time-varying quantity has led to the development of many approaches. The simplest one is called the passive ventilation measurement technique which typically measures the average concentration of a constantly emitted tracer gas from which the average ventilation rate can be estimated. This study relied on mathematical models combined with typical wheather data to calculate how an ideal passive ventilation measurement would perform; simulations were then conducted based on two house types in four seasons and six climates. It was found that the passive technique significantly underpredicted the average ventilation and that the use of multiple tracers accomplished marginal improvement. Inadequate mixing was found to be a major impediment to the interpretation of the results and could completely invalidate the measurement. Not covered in this report are the additional errors associated with measurement uncertainty, instrumentation limitations and non-ideal experimental conditions.

Quantitation of carbon types using DEPT/QUAT NMR pulse sequences: application to fossil-fuel-derived oils

A practical procedure is described whereby the fraction of carbon types ( TCH/sub n/, n = 0-3) in fossil-fuel-derived oils under ideal and nonideal experimental conditions can be quantitatively determined by using the pulse sequences DEPT (distortionless enhancement by polarization transfer) and QUAT (quarternary-only carbon spectra). Because these two techniques differ in the mechanism for signal enhancement, the NMR data are not directly related and, thus, a methodology was developed to relate the NMR data from the two techniques. The procedure was tested by using a pure compounds, o-ethyltoluene, and a model hydrocarbon mixture containing 10 components of known concentration. It is shown that a previously described method in the literature used to compensate for the missetting or field inhomogeneity of the H pulse and to provide qualitatively good edited spectra can also be used to obtain quantitative carbon-type analysis. The methodology described is shown to be useful not only for pure compounds and simple mixtures but also for the analysis of complex mixtures such as fossil-fuel-derived products. The DEPT/QUAT technique is preferred over most quantitative spin-echo experiments because the time necessary for data acquisition and reduction is much less.

Broadband excitation of quadrupolar order by modified jeener-broekaert sequences

Modified Jeener-Broekaert experiments are proposed for use in NMR spectroscopy of spins S = 1 nuclei in anisotropic phase. The new pulse sequences provide efficient creation of quadrupolar order over a wide range of values of the quadrupolar splitting. Experiments and computer simulations show that the new sequences can be used even under non-ideal experimental conditions.

Detection of O and N atoms by two-photon laser-induced fluorescence

The sensitive detection of ground-state atomic species under nonideal experimental conditions, such as those found in combustion reseach or plasmas, has been a problem for many years. Single-photon detection techniques such as resonance fluorescence are not applicable, since the medium is generally opaque at VUV wavelengths. We describe a new general detection scheme for atomic species based on two-photon excitation using wavelengths that will be transmitted and its application to the detection of oxygen1 and nitrogen atoms.