A numerical model of multimode fiber PON frequency response

Frequency response of passive optical network (PON) based on multimode fibers is investigated. The network comprises fibers, connectors and splitters/couplers. It is shown that due to mode filtering at splitters, the frequency response is different for different network nodes in otherwise symmetrical network.     

Noise map validation by continuous noise monitoring

This paper presents a comparison of two noise assessments in the Gdansk agglomeration in Poland. One is based on the noise map produced by computational method for the city in 2007, the second one is based on real data from continuous measurements acquired by a noise monitoring network operating in the city since 2008. Differences are shown and analyzed. Additionally, seasonal and weekday influence on noise indicators (L_DEN, L_D, L_E and L_N) is analyzed and discussed in this paper.     

Determination of T1-spin-lattice relaxation time in a two-level system by continuous wave multiquantum electron paramagnetic resonance spectroscopy in a presence of tetrachromatic microwave irradiation

Applicability of continuous wave multiquantum EPR methods to study relaxation times at X-band is examined. Multiquantum transitions excited in a two-level system by tetrachromatic irradiation are used for these studies. The Bloch equation model is applied to simulate lineshapes of the three quantum transitions as a function of frequency difference between exciting fields. The dependence of multiquantum transition signals on relaxation times and microwave amplitude is shown. On this basis a method of deducing relaxation times from these signals is formulated. The case of a homogeneously and inhomogeneously broadened resonance line is considered. Two experimental methods are used to verify the proposed hypothesis: the X-band continuous wave multiquantum EPR with four frequencies microwave field and saturation recovery EPR. The values of T₁ obtained from CW MQ EPR and SR EPR are compared.     

LocalH-theorem for a kinetic variational theory

A localH-theorem is derived for a recently proposed extension of Enskog kinetic theory to a dense model fluid composed of particles with interactions extending beyond a hard core.On leave from: Katedra Fizyki, Uniwersytetu Szczecinskiego, 70-451 Szczecin, Poland.     

Escape Through a Small Opening: Receptor Trafficking in a Synaptic Membrane

We model the motion of a receptor on the membrane surface of a synapse as free Brownian motion in a planar domain with intermittent trappings in and escapes out of corrals with narrow openings. We compute the mean confinement time of the Brownian particle in the asymptotic limit of a narrow opening and calculate the probability to exit through a given small opening, when the boundary contains more than one. Using this approach, it is possible to describe the Brownian motion of a random particle in an environment containing domains with small openings by a coarse grained diffusion process. We use the results to estimate the confinement time as a function of the parameters and also the time it takes for a diffusing receptor to be anchored at its final destination on the postsynaptic membrane, after it is inserted in the membrane. This approach provides a framework for the theoretical study of receptor trafficking on membranes. This process underlies synaptic plasticity, which relates to learning and memory. In particular, it is believed that the memory state in the brain is stored primarily in the pattern of synaptic weight values, which are controlled by neuronal activity. At a molecular level, the synaptic weight is determined by the number and properties of protein channels (receptors) on the synapse. The synaptic receptors are trafficked in and out of synapses by a diffusion process. Following their synthesis in the endoplasmic reticulum, receptors are trafficked to their postsynaptic sites on dendrites and axons. In this model the receptors are first inserted into the extrasynaptic plasma membrane and then random walk in and out of corrals through narrow openings on their way to their final destination.     

pH‐controlled reaction divergence of decarboxylation versus fragmentation in reactions of dihydroxyfumarate with glyoxylate and formaldehyde: parallels to biological pathways

The reactions of dihydroxyfumarate with glyoxylate and formaldehyde exhibit a unique pH‐controlled mechanistic divergence leading to different product suites by two distinct pathways. The divergent reactions proceed via a central intermediate (2,3‐dihydroxy‐oxalosuccinate, 3 , in the reaction with glyoxylate and 2‐hydroxy‐2‐hydroxymethyl‐3‐oxosuccinate, 14 , in the reaction with formaldehyde). At pH 7–8, products ( 7 , 8 , and 15 ) exclusively from a decarboxylation of the intermediate are observed, while at pH 13–14, products ( 9 , 10 , and 16 ) solely derived from a hydroxide‐promoted fragmentation of the intermediate are formed. The decarboxylative and fragmentation pathways are mutually exclusive and do not appear to coexist under the range of pH (7–14) conditions investigated. Herein, we employ a combination of quantitative ¹³C NMR measurements and density functional theory calculations to provide a rationale for this pH‐driven reaction divergence. These rationalizations also hold true for the reactions of dihydroxyfumarate produced in situ by the catalytic cyanide‐mediated dimerization of glyoxylate. In addition, the non‐enzymatic decarboxylation and fragmentation transformations of these central intermediates ( 3 and 14 ) appear to have intriguing parallels to the enzymatic reactions of oxalosuccinate and formation of glyceric acid derivatives in extant metabolism – the high and low pH mimicking the precise control exerted by the enzymes over reaction pathways. Copyright © 2016 John Wiley & Sons, Ltd.     

Investigation studies involving sound absorbing parameters of roadside screen panels subjected to aging in simulated conditions

The paper presents the results of investigation studies involving the impact of atmospheric factors on sound-absorbing parameters of roadside acoustic screen panels. The research studies comprised the aging test consisting of 1000 cycles in simulated conditions, sound absorption measurements and surface morphology tests, using the SEM scanning method. The simulation of aging consisted of 100 or 150 cycles at a time. Then, the panels were investigated in the reverberation chamber to define their sound-absorbing properties. The process was repeated until 1000 cycles were completed. Basing on the carried out tests, a statistical linear model was worked out which was used to estimate the value of a single number sound absorption coefficient after successive aging cycles. The optimality of the model was demonstrated by means of a statistical test confirming normal distribution of random residuals. For the research studies, we employed an innovative structural design of panels for which aging characteristics were obtained. Basing on the obtained results and on the statistical analysis, the prospects to maintain acoustic properties of the panels during their service life was estimated.