Low Alpha Values Research Articles

Performance of Relaying System with NOMA over Symmetric a-Stable Noise Channels

Objectives: This paper investigates the performance of a candidate 5G transmission system technique that is Non-Orthogonal Multiple Access (NOMA) over α-stable channels. This type of channel gets more attention in the research community because of its ability to model new IoT scenarios. However, there is a research gap in applying this type of channel to different wireless communications scenarios. In this work, we envision a scenario where users employ NOMA communications in the presence of an obstacle. As our mathematical analysis and simulation results show, there is a significant difference in performance when considering α-stable channels. Methods: To characterize the performance of the proposed noise channel, performance metrics such as outage probability and achievable rate are discussed. More particularly, we derive expressions for both outage probability and achievable rate for three NOMA users, considering the near user as a relay. In this paper, we consider additive symmetric α-stable noise channels with alpha α ∈ (1, 2). We present expressions for achievable rate and outage probability for each user (near, middle, and far) and investigate its behavior for different values of alpha (α). Findings: Based on the simulation results, it is shown that the high achievable rate observed for low alpha values while reduced as alpha is increased. Also, due to the influence of alpha, the outage probability is highly affected by α for small rate thresholds (Ro). In an envisioned scenario of three users with only one user forwarding the transmission to the other two, our results show that the near and middle users’ outage probability decreases as alpha α increases. Novelty: Despite this extensive study of the NOMA on individual channels, transmission under α-stable channel is not considered to the best of the authors’ knowledge. Keywords: NOMA, relaying, Cooperative Non-Orthogonal Multiple Access, Symmetric α-Stable Noise Channels, Achievable rate

Machine Learning to Discern Interactive Clusters of Risk Factors for Late Recurrence of Metastatic Breast Cancer.

Simple SummaryBreast cancer is the most frequently diagnosed cancer and second leading cause of cancer-related death among women worldwide. After initial tumor resection, breast cancer may recur locally and/or in distant organs within several months to years or even decades. Multiple methods exist to prognosticate disease progression in the early months and years after diagnosis. However, further efforts are needed to identify risk factors that relate to recurrence beyond the initial 5-year window. In this study, we applied machine learning to retrieve single and interactive clinical and pathological risk factors of 5-, 10- and 15-year metastases.Background: Risk of metastatic recurrence of breast cancer after initial diagnosis and treatment depends on the presence of a number of risk factors. Although most univariate risk factors have been identified using classical methods, machine-learning methods are also being used to tease out non-obvious contributors to a patient’s individual risk of developing late distant metastasis. Bayesian-network algorithms can identify not only risk factors but also interactions among these risks, which consequently may increase the risk of developing metastatic breast cancer. We proposed to apply a previously developed machine-learning method to discern risk factors of 5-, 10- and 15-year metastases. Methods: We applied a previously validated algorithm named the Markov Blanket and Interactive Risk Factor Learner (MBIL) to the electronic health record (EHR)-based Lynn Sage Database (LSDB) from the Lynn Sage Comprehensive Breast Center at Northwestern Memorial Hospital. This algorithm provided an output of both single and interactive risk factors of 5-, 10-, and 15-year metastases from the LSDB. We individually examined and interpreted the clinical relevance of these interactions based on years to metastasis and reliance on interactivity between risk factors. Results: We found that, with lower alpha values (low interactivity score), the prevalence of variables with an independent influence on long-term metastasis was higher (i.e., HER2, TNEG). As the value of alpha increased to 480, stronger interactions were needed to define clusters of factors that increased the risk of metastasis (i.e., ER, smoking, race, alcohol usage). Conclusion: MBIL identified single and interacting risk factors of metastatic breast cancer, many of which were supported by clinical evidence. These results strongly recommend the development of further large data studies with different databases to validate the degree to which some of these variables impact metastatic breast cancer in the long term.

Impact of a massive dust storm on the gross alpha, gross beta, 40K, 137Cs, 210Pb, 7Be activities measured in atmospheric aerosols collected in Tenerife, Canary Islands

Abstract From February 22 to 24, 2020, an intense dust storm affected the Spanish archipelago of the Canary Islands. Here we assess the radiological impact on the Canary Islands population of several natural and artificial radionuclides (40K, 137Cs, 210Pb, 7Be), and other radiological parameters (gross alpha and gross beta activity concentrations) measured in atmospheric aerosols before, during and after the dust storm. Total Suspended Matter highly correlated with PM10 (Pearson's correlation coefficient, ro = 0.98), showed increments ranging from 849% to 1778% against the background average levels, reaching levels of >3000 μg m−3. 40K and 137Cs radionuclides showed activity values over the minimum detection activity from January to March 2020, coupled with dust intrusion episodes during the study. This finding supports the use of these radionuclides as radiotracers for African low altitude dust intrusions occurring particularly during winter months over the Canary Islands. A high correlation between gross beta and 210Pb activities suggests that the latter is the main source for gross beta emitters in aerosol samples collected in the study region. 210Pb and 7Be showed a moderate positive correlation and did not show any significant change during the storm, suggesting a similar dynamics of alpha and beta emitters in the low atmosphere. A Principal Component Analysis of these observations showed two components representing a Saharan component (based on 40K, 137Cs, gross alpha, and PM10) and a heterogeneous component representing North Atlantic and Europe air masses (based on 7Be, 210Pb, and gross beta). In addition, a K-means cluster analysis helped to disentangle the origin of air masses arriving at the archipelago. Three different clusters were identified: a continental cluster (based on gross beta, 210Pb, and 7Be activity concentrations); an oceanic cluster (with low values of PM10 air concentrations, gross beta, gross alpha, and 210Pb, and 7Be and 40K activity concentrations), reflecting the Atlantic air contributions with lower radionuclide activity and microparticulate matter; and a dust intrusion cluster (with high PM10 values and 137Cs, 40K and gross alpha activity concentrations) representing dust intrusion episodes observed in Tenerife Island. These studies allow the detection and monitoring of radioactive elements, estimating the potential radiological risk to the population associated with mineral dust intrusions.

Sleep Network Deterioration as a Function of Dim-Light-At-Night Exposure Duration in a Mouse Model.

Artificial light, despite its widespread and valuable use, has been associated with deterioration of health and well-being, including altered circadian timing and sleep disturbances, particularly in nocturnal exposure. Recent findings from our lab reveal significant sleep and sleep electroencephalogram (EEG) changes owing to three months exposure to dim-light-at-night (DLAN). Aiming to further explore the detrimental effects of DLAN exposure, in the present study, we continuously recorded sleep EEG and the electromyogram for baseline 24-h and following 6-h sleep deprivation in a varied DLAN duration scheme. C57BL/6J mice were exposed to a 12:12 h light:DLAN cycle (75lux:5lux) vs. a 12:12 h light:dark cycle (75lux:0lux) for one day, one week, and one month. Our results show that sleep was already affected by a mere day of DLAN exposure with additional complications emerging with increasing DLAN exposure duration, such as the gradual delay of the daily 24-h vigilance state rhythms. We conducted detrended fluctuation analysis (DFA) on the locomotor activity data following 1-month and 3-month DLAN exposure, and a significantly less healthy rest-activity pattern, based on the decreased alpha values, was found in both conditions compared to the control light-dark. Taking into account the behavioral, sleep and the sleep EEG parameters, our data suggest that DLAN exposure, even in the shortest duration, induces deleterious effects; nevertheless, potential compensatory mechanisms render the organism partly adjustable and able to cope. We think that, for this reason, our data do not always depict linear divergence among groups, as compared with control conditions. Chronic DLAN exposure impacts the sleep regulatory system, but also brain integrity, diminishing its adaptability and reactivity, especially apparent in the sleep EEG alterations and particular low alpha values following DFA.

Microscopic adaptation of BaHfO3 and Y2O3 artificial pinning centers for strong and isotropic pinning landscape in YBa2Cu3O7–x thin films

A study of 3 vol% Y2O3 + 2–6 vol% BaHfO3 double-doped YBa2Cu3O7–x (BHO DD) epitaxial thin films was carried out to explore the morphology adaption of c-axis aligned one-dimensional BHO artificial pinning centers (1D APCs) to secondary Y2O3 nanoparticles (3D APCs). BHO 1D APCs have been predicted to have the least rigidity in an elastic strain energy model in APC/YBa2Cu3O7–x nanocomposite films. Consequently, they could be best ‘tuned’ away from the c-axis alignment by local strains generated by the Y2O3 3D APCs. This provides an opportunity to generate mixed-morphology APCs, especially at high BHO concentrations. Motivated by this, we have carried out a systematic study of the transport critical current density Jc(H, T, θ) on the BHO DD samples in magnetic fields (H) up to 90 kOe at different H orientations from H//c-axis (θ = 0), to θ = 45°, and to H//ab-plane (θ = 90°). Enhanced pinning at all three orientations was observed as illustrated in the comparable low alpha (α) values in the range of 0.13–0.25 at 65 K, which is consistent with the mixed 1D (in c-axis) + 2D (in ab-plane) + 3D APCs observed in transmission electron microscopy (TEM). Upon increasing BHO concentration from 2 to 4 vol%, a monotonic increase of the accommodation field H* at θ = 0°, 45° and 90° was observed, indicative of the APC concentration increase of the mixed morphologies. At 6 vol% BHO, the H* continues the increase to 85 kOe at H//c-axis (θ = 0), and >90 kOe H//ab-plane (θ = 90°), while it decreases from 80 to 85 kOe at 2–4 vol% to 60 kOe at 6 vol% at θ = 45°, which is consistent with the TEM observation of the connection of 3D APCs, appeared at lower BHO concentration into 2D ones in ab-plane at the higher BHO concentrations. These results shed light on the quantitative adaptation of APCs of mixed morphologies with increasing BHO doping in the BHO DD thin films and are important for controlling the APC pinning landscape towards minimal angular dependence.

Spectral analysis highlight developmental EEG changes in preterm infants without overt brain damage

Early markers of neurological outcome in the absence of overt brain damage are scarce in extreme prematurity. The aim of this study was to compare spectral EEG values of infants born near term with those of infants born at extremely low gestational age (ELGA) but having attained near term age. We aimed also to evaluate whether spectral EEG features were related with neurological outcome. The ELGA group consisted of 12 neonates born between 23+2 and 27+6 weeks; the control group consisted of nine infants born 34–35+2 weeks, tested within the first week of life. All neonates underwent multichannel EEG recordings at 35 weeks post-conception. None of the subjects had apparent neurological abnormalities or risk factors at the time of recording. EEG data were transformed into the frequency domain and divided into delta (0.5–4Hz), theta (5–7Hz), alpha (8–13Hz), beta (14–20Hz) frequency bands; relative EEG power values were calculated. ELGA group was compared with the control group using a mixed analysis of variance. Outcome was evaluated at one year of age by Griffiths’ scales. A principal effect of frequency and an interaction effect of frequency * group was found. The total relative power of the delta band was significantly higher in ELGA than in control group, whereas in the remaining frequency bands total relative power was lower in ELGA than in control group. Higher values of delta and lower values of alpha and beta spectral power correlated with poor outcome. We provide preliminary results suggesting that, as early as 35 weeks post conception, infants born extremely preterm fail to develop the age specific pattern of EEG spectral activity, in the absence of neurological neonatal risk.

Co2C nanoprisms with strong facet effect for Fischer-Tropsch to olefins reaction

Lower olefins refer to ethylene, propylene and butylene, which are vital building block in the chemical industry. They are fundamental chemicals of the greatest consumption among the organic chemicals all over the world. Large amount of chemical products, such as packing materials, cosmetics, synthetic rubber, coatings are the derivatives of lower olefins. In traditional petrochemical industry, lower olefins are mainly derived from oil-based feedstocks. With the rapid depletion of the limited petroleum, there is an urgent need for processes that can produce lower olefins from alternative feedstocks. The syngas, which is a promising alternative feedstock as it can be obtained from reforming of natural gas, gasification of coal or biomass, can be transformed into lower olefins through indirect or direct reaction. The indirect process mainly refers to the methanol to olefins (MTO) technology [1]. The direct conversion of syngas to lower olefins is one of the most challenging subjects in the field of C1 chemistry. It is considered as an attractive alternative non-petroleum-based production route due to its process simplicity and low energy consumption [2]. Bifunctional catalysis used composite catalysts, such as OX-ZEO and Fischer-Tropsch to olefins (FTO) reaction are twomain routes for the direct conversion of syngas to lower olefins [3]. Recent work by Bao et al. [4] and Wang et al. [5] reported that oxides-molecular sieve coupling catalysts exhibited very high selectivity toward lower olefins at relative high temperature of ca. 400°C, but this method is not yet in commercial use. As the reaction process for FTO is very similar to that for typical FT synthesis, FT catalysts can be used for production of lower olefins after suitable catalyst modification. De Jong et al. [6] reported that Fe-based catalysts promoted by S andNa and using α-alumina or carbon nanofiber as weakly interactive supports exhibited excellent performance for selective formation of lower olefins (61 C%). They also found the particle size of iron carbide plays a crucial role for direct production of lower olefins via syngas, and they suggested lower olefins are produced at promoted terrace sites [7]. However, these reactions normally need temperatures from 300°C to 350°C, which would cause carbon deposition on the catalyst surface and catalyst sintering, deactivating the catalyst and shortening its lifetime [2]. The primary aims of FTO are to maximize lower olefins selectivity while reduce methane production with high stability. The maximum selectivity toward C2−C4 olefins is achieved with an alpha value of about 0.5 according to the ordinary Anderson–Schulz–Flory (ASF) model [8,9]. One of the most efficient ways of shifting product selectivity to low alpha values is by increasing reaction temperature. However, a decrease on the chain growth probability results in an increase of methane selectivity as indicated by the ASF product distribution. In addition, the produced olefins were prone to be further hydrogenated to paraffins especially at high temperature and resulted in decreased selectivity to lower olefins. Moreover, the particle sintering and coke formation at high temperature would lead to serious deactivation [10]. Due to the above limitation, there was no catalyst suitable for the industrial application of the direct conversion of syngas into lower olefins via the Fischer-Tropsch synthesis. Based on the general analysis, most of the reported FTO catalysts are still a kind of FT catalyst with low alpha value. The product distribution still obeys the ordinary ASF model. Obviously, with the goal of high selectivity to lower olefin, lowmethane selectivity and high stability simultaneously, it is necessary to develop new FTO catalyst which deviates from ASF distribution at mild reaction conditions.

Electro-cortical measures during visual and kinesthetic imagery performance following visual- and auditory-guided instructions

Electroencephalography (EEG) measures can provide extensive and detailed knowledge of how the brain works during imagery. Prior to imagery performance, individuals may acquire information on how to imagine the movement through either visual or auditory instructions. The purpose of this study was to determine differences in cerebral cortical activation during kinesthetic and visual imagery performance while following visual- and audio-guided imagery instructions. EEG recordings were collected from 28 participants and guided imagery instructions were given in two versions: audio and visual. The results revealed that lower alpha values (8–10 Hz) were greater when participants were performing kinesthetic imagery following auditory instructions as opposed to following visual instructions. Furthermore, lower alpha values were greater at the right hemisphere than the left hemisphere and greater at the right temporal site than the left temporal site. In the upper alpha band (11–13 Hz), results showed that values were greater at the temporal site in the right hemisphere than the temporal site in the left hemisphere. In addition, upper alpha values were greater at the right hemisphere than the left hemisphere and greater at the right temporal site than the left temporal site. The findings of this study suggest that electro-cortical measures can detect differences of the processes involved during guided imagery performance while following either audio or video instructions. In the applied setting, practitioners can implement neurofeedback techniques to assess the specific mental effort required by individuals following guided instructions to perform imagery.

LOW VIRIAL PARAMETERS IN MOLECULAR CLOUDS: IMPLICATIONS FOR HIGH-MASS STAR FORMATION AND MAGNETIC FIELDS

Whether or not molecular clouds and embedded cloud fragments are stable against collapse is of utmost importance for the study of the star formation process. Only "supercritical" cloud fragments are able to collapse and form stars. The virial parameter, alpha=M_vir/M, which compares the virial to the actual mass, provides one way to gauge stability against collapse. Supercritical cloud fragments are characterized by alpha<2, as indicated by a comprehensive stability analysis considering perturbations in pressure and density gradients. Past research has suggested that virial parameters alpha>2 prevail in clouds. This would suggest that collapse towards star formation is a gradual and relatively slow process, and that magnetic fields are not needed to explain the observed cloud structure. Here, we review a range of very recent observational studies that derive virial parameters <<2 and compile a catalogue of 1325 virial parameter estimates. Low values of alpha are in particular observed for regions of high mass star formation (HMSF). These observations may argue for a more rapid and violent evolution during collapse. This would enable "competitive accretion" in HMSF, constrain some models of "monolithic collapse", and might explain the absence of high--mass starless cores. Alternatively, the data could point at the presence of significant magnetic fields ~1 mG at high gas densities. We examine to what extent the derived observational properties might be biased by observational or theoretical uncertainties. For a wide range of reasonable parameters, our conclusions appear to be robust with respect to such biases.

The Effect of Colour and Transparency on the Perception of Overlaid Grids

Overlaid reference elements need to be sufficiently visible to effectively relate to the underlying information, but not so obtrusive that they clutter the presentation. We seek to create guidelines for presenting such structures through experimental studies to define boundary conditions for visual intrusiveness. We base our work on the practice of designers, who use transparency to integrate overlaid grids with their underlying imagery. Previous work discovered a useful range of alpha values for black or white grids overlayed on scatterplot images rendered in shades of gray over gray backgrounds of different lightness values. This work compares black grids to blue and red ones on different image types of scatterplots and maps. We expected that the coloured grids over grayscale images would be more visually salient than black ones, resulting in lower alpha values. Instead, we found that there was no significant difference between the boundaries set for red and black grids, but that the boundaries for blue grids were set consistently higher (more opaque). As in our previous study, alpha values are affected by image density rather than image type, and are consistently lower than many default settings. These results have implications for the design of subtle reference structures.

Spinning up black holes with super-critical accretion flows

We study the process of spinning up black holes by accretion from slim disks in a wide range of accretion rates. We show that for super-Eddington accretion rates and low values of the viscosity parameter alpha (\lesssim 0.01) the limiting value of the dimensionless spin parameter a_* can reach values higher than a_*=0.9978 inferred by Thorne (1974) in his seminal study. For \mdot=10\mdot_{Edd} and alpha=0.01 spin equilibrium is reached at a_*=0.9994. We show that the equilibrium spin value depends strongly on the assumed value of alpha. We also prove that for high accretion rates the impact of captured radiation on spin evolution is negligible.

The Women's Health Questionnaire (WHQ): A psychometric evaluation of the 36‐item Norwegian version

The Women's Health Questionnaire (WHQ) was designed specifically to study possible changes that occur during menopause. The purpose of this study was to perform a psychometric evaluation of the Norwegian version of the WHQ by examining the factor structure and construct validity of the instrument. Data used for the evaluation were collected at baseline of the ACUFLASH study, a randomized, controlled clinical trial that evaluated the effect of acupuncture treatment on menopausal symptoms. Altogether, 267 women with a very high frequency of hot flushes were included in the study. Some deficiencies in the WHQ questionnaire were observed when applied to this sample, including an unclear factor structure, low alpha values for some dimensions, and a strong floor effect in the vasomotor symptoms dimension. The total scale score appears reliable, but care should be taken when interpreting some of the subscales.

Phase Behavior and Microstructure of Microemulsions Containing the Hydrophobic Ionic Liquid 1-Butyl-3-methylimidazolium Hexafluorophosphate

The phase behavior and microstructure of the ternary system water/1-butyl-3-methylimidazolium hexafluorophosphate (bmimPF(6))/Triton X-100 was studied as a function of temperature and ionic liquid (IL) mass fraction alpha. In the present study, a hydrophobic IL instead of commonly used organic solvents such as n-alkanes is used. The fish-shaped region is distorted at low and high values of alpha, whereas it is symmetric at intermediate alpha. With increasing alpha, the extension of the three-phase region decreases regarding the surfactant concentration range, whereas it increases regarding the temperature range. For comparison the phase behavior of two ternary water/bmimPF(6)/alkyl oligoethyleneoxide (C(i)E(j)) systems has been investigated. Our results are compared with those obtained for water/n-alkane/C(i)E(j) and IL/n-alkane/C(i)E(j) systems, respectively.

Scanning Electrochemical Microscopy. 59. Effect of Defects and Structure on Electron Transfer through Self-Assembled Monolayers

Electron transfer (ET) rate kinetics through n-alkanethiol self-assembled monolayers (SAMs) of alkanethiols of different chain lengths [Me(CH2)nSH; n=8, 10, 11, 15] on Au and Hg surfaces and ferrocene (Fc)-terminated SAMs (poly-norbornylogous and HS(CH2)12CONHCH2Fc) on Au were studied using cyclic voltammetry and scanning electrochemical microscopy (SECM). The SECM results allow determination of the ET kinetics of solution-phase Ru(NH3)63+/2+ through the alkanethiol SAMs on Au and Hg. A model using the potential dependence of the measured rate constants is proposed to compensate for the pinhole contribution. Extrapolated values of koML for Ru(NH3)63+/2+ using the model follow the expected exponential decay (beta is 0.9) for different chain lengths. For a Fc-terminated poly-norbornyl SAM, the standard rate constant of direct tunneling (ko is 189+/-31 s(-1)) is in the same order as the ko value of HS(CH2)12CONHCH2Fc. In blocking and Fc SAMs, the rates of ET are demonstrated to follow Butler-Volmer kinetics with transfer coefficients alpha of 0.5. Lower values of alpha are treated as a result of the pinhole contribution. The normalized rates of ET are 3 orders of magnitude higher for Fc-terminated than for blocking monolayers. Scanning electron microscopy imaging of Pd nanoparticles electrochemically deposited in pinholes of blocking SAMs was used to confirm the presence of pinholes.

Impact of Porous Electrode Properties on the Electrochemical Transfer Coefficient

The rate of an activation-controlled electrochemical reaction is determined by two key parameters, the exchange current density, io, and the transfer coefficient, alpha, which is inversely related to the Tafel slope. Assuming that the symmetry factor, beta, is 0.5, the minimum alpha value should be 0.5 for all standard reaction mechanisms, with alpha values larger than this indicating a better electrocatalytic mechanism. The primary goal of this paper is to better understand why alpha values of < 0.5 are often observed experimentally, with specific examples given for the oxygen reduction reaction. These low alpha values cannot be explained by adsorption behavior, but they can result when reactions occur within a porous electrode structure. Consistent with past literature related to Tafel slope predictions, we show that long and narrow pores, a low ionic or electronic conductivity of the electrode layer, and a high io value can cause alpha to be < 0.5, most typically 0.25. However, alpha values between 0.25 and 0.5 are also encountered in practice. We show here that such alpha values can be obtained for reactions occurring at porous films that have nonuniform properties. We also show that the overpotential range over which alpha changes from 0.5 to 0.25 can be quite broad, especially at high temperatures, and thus can be misinterpreted as a true Tafel region with a transfer coefficient between 0.25 and 0.5.

Enthalpy Changes upon Dilution and Ionization of Poly(l-glutamic acid) in Aqueous Solutions

The enthalpy changes accompanying the dilution and ionization of poly(L-glutamic acid) in water have been measured at 25 degrees C for two degrees of polymerization (DP = 115 and DP = 480) at various degrees of ionization, alpha, for a concentration range from about 0.2 to 0.002 monomol/L. The heat of dilution displays an unusual dependence on the degree of ionization, which is in sharp contrast to the behavior of other weak carboxylic polyelectrolytes, such as poly(acrylic acid). The exothermic heat effects observed at low values of alpha become endothermic for the region where the helix-coil transition is most pronounced, and for high degrees of ionization, they are exothermic again. Evidently, an endothermic heat effect, produced by an additional conformational transition in the dilution process, is superimposed on the exothermic enthalpy of dilution, and it overweighs the latter in the region of alpha where the conformational transition is prevailing. The calorimetric titration curve, which gives the dependence of the heat of ionization, deltaH(i), on alpha, has a maximum and is typical for poly(carboxylic acids) which undergo pH-induced conformational transition, such as poly(methacrylic acid). The values of deltaH(i) obtained at two polymer concentrations indicate that the enthalpy of ionization depends on the polypeptide concentration.

Uptake of Organic Gas Phase Species by 1-Methylnaphthalene

Organic compounds are a significant component of tropospheric aerosols. In the present study, 1-methylnaphthalene was selected as a surrogate for aromatic hydrocarbons (PAHs) found in tropospheric aerosols. Mass accommodation coefficients (alpha) on 1-methylnaphthalene were determined as a function of temperature (267 K to 298 K) for gas-phase m-xylene, ethylbenzene, butylbenzene, alpha-pinene, gamma-terpinene, p-cymene, and 2-methyl-2-hexanol. The gas uptake studies were performed with droplets maintained under liquid-vapor equilibrium conditions using a droplet train flow reactor. The mass accommodation coefficients for all of the molecules studied in these experiments exhibit negative temperature dependence. The upper and lower values of alpha at 267 and 298 K respectively are as follows: for m-xylene 0.44 +/- 0.05 and 0.26 +/- 0.03; for ethylbenzene 0.37 +/- 0.03 and 0.22 +/- 0.04; for butylbenzene 0.47 +/- 0.06 and 0.31 +/- 0.04; for alpha-pinene 0.47 +/- 0.07 and 0.10 +/- 0.05; for gamma-terpinene 0.37 +/- 0.04 and 0.12 +/- 0.06; for p-cymene 0.74 +/- 0.05 and 0.36 +/- 0.07; for 2-methyl-2-hexanol 0.44 +/- 0.06 and 0.29 +/- 0.06. The uptake measurements also yielded values for the product HD(l)(1/2) for most of the molecules studied (H = Henry's law constant, D(l) = liquid-phase diffusion coefficient). Using calculated values of D(l), the Henry's law constants (H) for these molecules were obtained as a function of temperature. The H values at 298 K in units 10(3) M atm(-1) are as follows: for m-xylene (0.48 +/- 0.05); for ethylbenzene (0.50 +/- 0.08); for butylbenzene (3.99 +/- 0.93); for alpha-pinene (0.53 +/- 0.07); for p-cymene (0.23 +/- 0.07); for 2-methyl-2-hexanol (1.85 +/- 0.29).

Design procedure for carbon removal in contact stabilization activated sludge process

The contact stabilization activated sludge process (CSASP) has been adopted and applied in full scale plants treating domestic sewage. Acquiring smaller volume thereby reducing costs and achieving the same treatment efficiency as the conventional activated sludge plants are the main advantages of the CSASP. This activated sludge modification is especially ideal for small to mid-scale plants where influent wastewater contains a high fraction of particulate COD. The simulation results reveal that the same amount of mass sludge can be retained in the system with almost 30% volume reduction compared to conventional activated sludge plants. It is also found that the CSASP treatment efficiency increases when the particulate COD fraction of an influent domestic wastewater increases. The most important process component in the design of CSASP is the sludge distribution factor (alpha) which directly affects the effluent characterization. Having most of the biomass in the stabilization reactor (meaning low alpha values) decreases the nominal hydraulic retention time (thetaHN) of the system. However the sludge distribution factor must be high enough to ensure an acceptable effluent quality.

Convective instability of magnetic fluids.

A theoretical investigation of the convective instability problem in the thin horizontal layer of a magnetic fluid heated from below is carried out. The effects of the relaxation time tau and the vortex (rotational) viscosity xi are considered and discussed. The Chebyshev pseudospectral method is employed to solve the eigenvalue problems and numerical calculations are carried out for a number of magnetic fluids and in full range of the magnetic field. A variety of results under gravity-free conditions are also presented and the critical temperature gradient are determined for a variety of situations. It is shown that the consideration of (xi,tau), in the stability analysis, is most effective in the thin layer of the fluid and at low values of Langevin parameter alpha(L).

The Effect of Tetrazole and Its Amino Derivatives on the Kinetics of Peroxidase Oxidation of Chromogenic Substrates

The peroxidase-catalyzed oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS), o-phenylenediamine (PDA), and 3,3',5,5'-tetramethylbenzidine (TMB) was found to be activated by tetrazole and 5-aminotetrazole (AT) and weakly inhibited by 1,5-diaminotetrazole. The activating action of tetrazole and AT on the PDA and TMB oxidation was clearly discompetitive and that on ABTS was non-competitive. The coefficients (degrees) of activation alpha were determined for three substrates and two activators; they depended on the substrate type and the buffer nature and increased along with the pH growth from 6.4 to 7.2. For AT and tetrazole, the maximal alpha values were 4140 and 800 M(-1), respectively, upon the PDA oxidation and 3570 and 540 M(-1), respectively, upon the TMB oxidation. Lower alpha values (145 and 58 M(-1) for tetrazole and AT, respectively) were characteristic of the peroxidase oxidation of ABTS. The activation of peroxidase oxidation of the substrates by tetrazole and AT at pH > or = 5.4 was explained by the nucleophilic nature of the activators interacting with the amino acid residues in the peroxidase active site according to the mechanism of acid-base catalysis. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 3; see also http://www.maik.ru.