A Variational Principle for Thermodynamical Waves

When the dissipative processes are dominant in the system, the assumption of local equilibrium holds good and the space time evolution of irreversible system can be described by the variational principle of GYARMATI. However when imposed changes in the state variables are fast, the system can not be in a state of local equilibrium and to define the nonequilibrium state of the system it is necessary to extend the formalism of classical irreversible thermodynamics. The wave approach of Onsagerian thermodynamics is one such pursuit and is a direct generalization of the original Onsager-Machlup proposition. An important consequence of this theory is that it leads to transport equations with finite propagation velocities, which are referred to as thermodynamical waves. In this note we endeavour to write the appropriate form of GYARMATI'S variational principle for thermodynamical waves.     

Effect of structural misalignments on the temperature variation of basal plane electrical conductivity of graphite

The amount and extent of structural misaligments in natural graphite crystals have been determined, and the temperature variation of the basal plane electrical conductivity (σ_⊥) of naturally occurring graphite has also been studied from 300 to 90 K. The conductivity (σ_⊥) has been found to obey a law σ_⊥α($\text{1}\text{T}$) down to a certain temperature θ (θ varying from sample to sample), below which the variation deviates from linearity towards lower values of σ_⊥. This behaviour, which was earlier thought to be a characteristic of graphite and whose origin could not be traced, has been shown to be an effect of the structural misalignments usually present in natural samples of graphite.     

Entanglement of a photon and a collective atomic excitation

We describe a new experimental approach to probabilistic atom-photon (signal) entanglement. Two qubit states are encoded as orthogonal collective spin excitations of an unpolarized atomic ensemble. After a programmable delay, the atomic excitation is converted into a photon (idler). Polarization states of both the signal and the idler are recorded and are found to be in violation of the Bell inequality. Atomic coherence times exceeding several microseconds are achieved by switching off all the trapping fields--including the quadrupole magnetic field of the magneto-optical trap--and zeroing out the residual ambient magnetic field.     

Correcting movement errors in frequency-sweeping interferometry

Absolute distance measurements can be performed with an interferometric method that uses only a single tunable laser. This method has one major drawback, because a small target movement of the order of one wavelength during a measurement will be interpreted as a movement of one synthetic wavelength. This effect is usually mitigated by adding a second (nonscanning) laser. We show that absolute distance measurements can be performed with only one laser if the movements encountered are smooth, on the time scale of one measurement. In this case the movement errors can be compensated with a simple algorithm that combines several subsequent measurements. First experimental results show good agreement with theory.     

Analysis and characterization of photo-plethysmographic signal

Qualitative assessment of the overall clinical status of the subject and characterization of complex cardiovascular dynamics from digital blood volume pulsations measured noninvasively using a photo-plethysmographic device is addressed. A novel concept is employed to detect the dominant nonsinusoidal periodicity embedded in the data series and to extract the associated periodic component. The detection and the extraction of periodic component is performed with moving window to accommodate the variations of the physiological oscillations. The covariance matrix formed by the gradually varying pattern is used as a simple measure of qualitative assessment. Further, the characterization of the underlying system in the light of nonlinear dynamical analysis is also presented. The stable subjects are shown to behave as a low-dimensional system whereas the diseased subjects exhibit comparatively high dimensional activity.     

Highly Birefringent Microstructure Fiber with Zero Dispersion Wavelength at 0.64 Micrometer

Abstract

In this article, we have designed a microstructure fiber, which consists of elliptical air holes at the core region. We have investigated its optical properties using finite difference time domain method. The fundamental mode of the proposed microstructure fiber can induce very high birefringence. It has been realized that the value of birefringence is mainly decided by the shape of the air holes present in the first and second rings. The zero dispersion wavelengths of both fast and slow axes have been shifted to 0.64 micrometer. The proposed birefringent microstructure fiber may be useful in optical communication and sensors.     

Ion dynamics in NaBF<Subscript>4</Subscript> salt-complexed PVC–PEO blend polymer electrolytes: correlation between average ion hopping length and network structure

Electrical transport properties of a series of NaBF₄ salt-doped PVC–polyethylene oxide blend polymer electrolytes are studied using impedance spectroscopy. X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry are implemented to characterize the structural properties of the electrolytes. The characterization data clearly indicate that the interaction between the dopant salt and the polymer host substantially influences the overall crystallinity of the electrolytes. Experimental frequency-dependent complex conductivity and loss tangent data are analyzed using a physical model to extract separately the mobile ion concentration and ion mobility of the charge carriers and the type of their thermal activation. The average hopping length of free ions, which essentially controls the macroscopic ion transport within the electrolytes, is found to be strongly correlated to the network structure of the electrolytes. Both the dc conductivity and free ion mobility are observed to be strongly coupled with the segmental dynamics of blend polymer host over the entire range of ion content studied.     

A total synthesis of the methyl glycoside of ganglioside GM(1)

The total synthesis of the methyl glycoside of GM(1) (1b) has been accomplished. The key step in the synthesis involves the sulfonamidoglycosidation reaction, which is used to create a beta-linkage leading to a GalNAc residue joined to the C4 hydroxyl group of a galactose unit of a C3 sialylated lactosyl moiety. The "proximal hydroxyl" directing effect, which has been postulated before, manifests in this context as well leading to the preponderant formation of the beta-glycoside. Together with asialo GM(1) and other substructures, the GM(1) methyl glycoside has been submitted for biological assays as potential ligands for bacterial and viral infection sites.