The application of prolate spheroidal wave functions to the detection and estimation of bandlimited signals

Prolate spheroidal wave functions for solution of Fredholm equation for bandlimited signal detectio

Band limited image restoration by linear mean-square estimation

Linear estimator optimum for data on finite interval for restoration of image

Ionospheric scintillation studies

The diffracted field of a monochromatic plane wave was characterized by two complex correlation functions. For a Gaussian complex field, these quantities suffice to completely define the statistics of the field. Thus, one can in principle calculate the statistics of any measurable quantity in terms of the model parameters. The best data fits were achieved for intensity statistics derived under the Gaussian statistics hypothesis. The signal structure that achieved the best fit was nearly invariant with scintillation level and irregularity source (ionosphere or solar wind). It was characterized by the fact that more than 80% of the scattered signal power is in phase quadrature with the undeviated or coherent signal component. Thus, the Gaussian-statistics hypothesis is both convenient and accurate for channel modeling work

Factorization of spectra by discrete Fourier transforms

Discrete Fourier transform factorization of arbitrary spectral density function

Incoherent Scatter Radar Observations of Westward Electric Fields and Plasma Densities in the Auroral Ionosphere, 1

This paper reports the results of incoherent scatter radar observations of high-altitude ion drifts and other plasma parameters made February 24, 1972, at Chatanika, Alaska (L = 5.7), during a period of magnetic disturbance. For this experiment, conducted between 0909 to 1303 UT (2309 to 0303 AST), the radar line of sight was held fixed in the magnetic meridian plane so that the observed north-south ion drifts could be interpreted in terms of a westward electric field that ranged in magnitude from −10 to +35 mV m−1. The results confirm many effects found previously through other experimental techniques. Southward ion drifts predominated during the 4-hour observation period. Several times the westward electric field inside large regions of enhanced electron density was substantially smaller than the field outside these regions. In addition, on several occasions these walls or bands of ionization were found to drift southward at about the same speed as the E⊥ × B drift in the surrounding plasma. The plasma inside the enhanced region, however, did not share the drift motion but remained relatively stationary with respect to the radar. The present observations of F 2 layer densities and temperatures indicate an unusual increase in electron density just before the onset of a large substorm. Finally, measurements of the height and peak density of the auroral E layer show significant variations in the intensity and average energy of the electron flux. These variations appear to be related to auroral breakup and a transition to steady precipitation of moderately soft electrons

Incoherent-Scatter Radar Observations of Westward Electric Fields, 2

In this paper we describe the results of a series of geomagnetic meridian plane radar incoherent scatter plasma transport measurements. From such data the eastward (zonal) component of the electric field can be deduced. The results show that the electric field has an eastward component whenever the discrete auroras are northward of the region of the measurement. The zonal field component turns westward as the discrete auroras move equatorward of the region of the measurement. Thus there is an eastward electric field boundary near the equatorward limit of the discrete aurora, which is the poleward boundary of the diffuse aurora during undisturbed periods. During a particularly disturbed period we also observed three pronounced substorm-related enhancements of the westward-directed zonal field. For midnight and morning sector substorms the enhancements preceded the substorm onset times by 20-30 min. We show from meridian chain all-sky camera data that all three enhancements coincided with equatorward expansions of the auroral oval

Oxidative DNA damage bypass in Arabidopsis thaliana requires DNA polymerase λ and proliferating cell nuclear antigen 2

The oxidized base 7,8-oxoguanine (8-oxo-G) is the most common DNA lesion generated by reactive oxygen species. This lesion is highly mutagenic due to the frequent misincorporation of A opposite 8-oxo-G during DNA replication. In mammalian cells, the DNA polymerase (pol) family X enzyme DNA pol l catalyzes the correct incorporation of C opposite 8-oxo-G, together with the auxiliary factor proliferating cell nuclear antigen (PCNA). Here, we show that Arabidopsis thaliana DNA pol l, the only member of the X family in plants, is as efficient in performing error-free translesion synthesis past 8-oxo-G as its mammalian homolog. Arabidopsis, in contrast with animal cells, possesses two genes for PCNA. Using in vitro and in vivo approaches, we observed that PCNA2, but not PCNA1, physically interacts with DNA pol l, enhancing its fidelity and efficiency in translesion synthesis. The levels of DNA pol l in transgenic plantlets characterized by overexpression or silencing of Arabidopsis POLL correlate with the ability of cell extracts to perform error-free translesion synthesis. The important role of DNA pol l is corroborated by the observation that the promoter of POLL is activated by UV and that both overexpressing and silenced plants show altered growth phenotypes

Gastric Mucosa Mucous Layer Thickness in Liver Cirrhosis with Portal Hypertensive Gastropathy Compare to Functional Dyspepsia

Background: This study aimed to investigate gastric mucosa mucous layer thickness in portal hypertensive gastropathy (PHG) compare to normal mucosa in functional dyspepsia and its correlation with several variables such as child class, severity of esophageal varices and gastropathy. Methods: Biopsy specimens were taken from the antrum and corpus from both group of patients with PHG and functional dyspepsia. The specimen was given cryometric for frozen section. Tissue were sliced by sagital section 11 µm, placed in object glass, fixed and stained to evaluate mucous thickness and giemsa stained to observe Helicobacter pylori. Measurement of mucous thickness was done upward muscularis mucosa started from upper epithelial layer from foveale tip until outer mucous layer on 15 points which were marked randomly and calculate the mean value by micrometer (µm). Results: Mean value of antral mucous thickness in PHG was 13.30 ± 6.5 µm, while in the functional dyspepsia it was 25.59 ± 5.66 µm. Statistical analysis for both kinds of mucous thickness was p<0.001. Mean corpus mucous thickness in PHG was 10.6 ± 6.81 µm, while mucous thickness in dyspepsia was 32.54 ± 6.51 µm. Statistical analysis revealed p<0.001. This result showed significant difference of mucous thickness of antrum and corpus statistically between PHG and dyspepsia as control group. Conclusion: The study had proven the presence of decreased gastric mucosa mucous layer thickness in corpus and antrum in PHG. Thus, therapeutic approach to increase mucous thickness must be considered in patients with PHG

Photoluminescence studies of a perceived white light emission from a monolithic InGaN/GaN quantum well structure

In this work we demonstrate by photoluminescence studies white light emission from a monolithic InGaN/GaN single quantum well structure grown by metal organic chemical vapour deposition. As-grown and thermally annealed samples at high temperature (1000 °C, 1100 °C and 1200 °C) and high pressure (1.1 GPa) were analysed by spectroscopic techniques, and the annealing effect on the photoluminescence is deeply explored. Under laser excitation of 3.8 eV at room temperature, the as-grown structure exhibits two main emission bands: a yellow band peaked at 2.14 eV and a blue band peaked at 2.8 eV resulting in white light perception. Interestingly, the stability of the white light is preserved after annealing at the lowest temperature (1000 °C), but suppressed for higher temperatures due to a deterioration of the blue quantum well emission. Moreover, the control of the yellow/blue bands intensity ratio, responsible for the white colour coordinate temperatures, could be achieved after annealing at 1000 °C. The room temperature white emission is studied as a function of incident power density, and the correlated colour temperature values are found to be in the warm white range: 3260–4000 K

Doppler spectra of airborne sound backscattered by the free surface of a shallow turbulent water flow

Measurements of the Doppler spectra of airborne ultrasound backscattered by the rough dynamic surface of a shallow turbulent flow are presented in this paper. The interpretation of the observed acoustic signal behavior is provided by means of a Monte Carlo simulation based on the Kirchhoff approximation and on a linear random-phase model of the water surface elevation. Results suggest that the main scattering mechanism is from capillary waves with small amplitude. Waves that travel at the same velocity of the flow, as well as dispersive waves that travel at a range of velocities, are detected, studied and used in the acoustic Doppler analysis. The dispersive surface waves are not observed when the flow velocity is slow compared to their characteristic velocity. Relatively wide peaks in the experimental spectra also suggest the existence of nonlinear modulations of the short capillary waves, or their propagation in a wide range of directions. The variability of the Doppler spectra with the conditions of the flow can affect the accuracy of the flow velocity estimations based on backscattering Doppler. A set of different methods to estimate this velocity accurately and remotely at different ranges of flow conditions is suggested