Imbalanced Conditions Research Articles

Evidence for contrasting roles of dimethylsulfoniopropionate production in Emiliania huxleyi and Thalassiosira oceanica.

Summary Dimethylsulfoniopropionate (DMSP) is a globally abundant marine metabolite and a significant source of organic carbon and sulfur for marine microbial ecosystems with the potential to influence climate regulation. However, the physiological function of DMSP has remained enigmatic for >30 yr. Recent insight suggests that there are different physiological roles for DMSP based on the cellular DMSP concentrations in producers.Differential production of DMSP was tested with multiple physiological experiments that altered nitrate availability, salinity and temperature to create stressed growth and target different metabolic conditions in Emiliania huxleyi, a high DMSP producer and Thalassiosira oceanica, a low DMSP producer. Emiliania huxleyi intracellular DMSP did not respond to metabolically imbalanced conditions, while Thalassiosira oceanica intracellular DMSP was significantly correlated to stressed growth rate across all conditions tested and exhibited a plastic response on a timescale of hours in nonsteady‐state.The previous assumption that proposed DMSP mechanism(s) can be universally applied to all producers is shown to be unlikely. Rather, two distinct ecological roles for DMSP likely exist that differ by producer type, where: (1) the primary role of DMSP in high producers is a constitutive compatible solute; and (2) DMSP production in low producers is a finely tuned stress response.

Single-particle properties of a strongly interacting Bose-Fermi mixture with mass and population imbalance

We theoretically investigate strong-coupling properties of a Bose-Fermi mixture. In the mass- and population-balanced case, two of the authors have shown that a strong hetero-pairing interaction in this mixture brings about coupling phenomena between Fermi atomic excitations and Bose atomic and composite molecular excitations, that appear as an anomalous multiple peak structure in the single-particle spectral weight (SW). [D. Kharga, {\it et. al.}, J. Phys. Soc. Jpn. {\bf 86}, 084301 (2017)]. In this paper, extending this previous work, we show that, although these many-body phenomena are sensitive to mass and population imbalances between the Bose and Fermi components, SW still exhibits the multiple peak structure in a moderately mass-imbalanced $^{87}$Rb-$^{40}$K and $^{23}$Na-$^{40}$K mixtures. We also point out that the photoemission spectrum is a useful quantity to observe this spectral anomaly. Since a real trapped Bose-Fermi mixture is usually accompanied by mass and (local) population imbalance, our results would contribute to the study of a strongly interacting Bose-Fermi mixture, under realistic imbalanced conditions.

Synthetic minority oversampling for function approximation problems

Imbalanced data sets are a common occurrence in important machine learning problems. Research in improving learning under imbalanced conditions has largely focused on classification problems (ie, problems with a categorical dependent variable). However, imbalanced data also occur in function approximation, and far less attention has been paid to this case. We present a novel stratification approach for imbalanced function approximation problems. Our solution extends the SMOTE oversampling preprocessing technique to continuous-valued dependent variables by identifying regions of the feature space with a low density of examples and high variance in the dependent variable. Synthetic examples are then generated between nearest neighbors in these regions. In an empirical validation, our approach reduces the normalized mean-squared prediction error in 18 out of 21 benchmark data sets, and compares favorably with state-of-the-art approaches.

Step-Growth Polymerization Method for Ultrahigh Molecular Weight Polymers.

The preparation of polymers with an ultrahigh molecular weight (>106 g/mol; UHMW) is always a challenge for homogeneous step-growth polymerization. Herein, a unique homogeneous step-growth polymerization method was developed to prepare various UHMW polymers. In this approach, a double-strain-promoted azide-alkyne click reaction (DSPAAC) with a reactive intermediate was used as the polymerization reaction, and sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DIBOD) and bis-azide compounds with 2,6-diisopropylphenyl azide terminals were used as the monomer pairs. The DSPAAC reaction, with a reactive intermediate, facilitated this polymerization method to efficiently prepare UHMW polymers under convenient, stoichiometrically imbalanced conditions using a slight excess of DIBOD to bis-azide monomer. In addition, the click nature of the DSPAAC reaction facilitated this polymerization method to synthesize UHMW polymers under ambient conditions, requiring no catalysts. The resultant UHMW polymers presented strong fluorescence peaking at 423 nm, good thermal property with the glass transition temperature up to 270 °C, and good mechanical property with Young's modulus above 1 GPa.

Three-Phase Lines to Single-Phase Coil Planar Contactless Power Transformer

This paper proposes a three-phase lines to single-phase coil planar contactless power transformer. The transformer has the primary consisting of three-phase line cables arrayed in parallel on a plane and the secondary of single-phase coil. The proposed transformer is studied for application to automatic guided vehicles (AGVs). Uniform power transfer that is independent of the position of the AGVs is an important issue for this transformer, because of the sparse arrangement of the primary lines. To ensure that the transformer achieves uniform power transfer, the structure and dimensions of the primary are studied using numerical analysis. Additionally, an equivalent model of the proposed transformer, which is applicable to the imbalanced conditions, is presented. The equivalent model proves analytically that balanced three-phase voltage and balanced three-phase current conditions, which can be created using appropriate circuit configurations, enable uniform power transfer. The results of experiments in which the prototype of the transformer is applied to the target AGV confirm that under balanced-current conditions, which can be generated using a three-phase LCL circuit, the proposed transformer can transfer sufficient uniform power to drive the AGV.

Arabidopsis cytosolic alpha‐glycan phosphorylase, PHS2, is important during carbohydrate imbalanced conditions

Arabidopsis thaliana has two isoforms of alpha-glycan phosphorylase (EC 2.4.1.1), one residing in the plastid and the other in the cytosol. The cytosolic phosphorylase, PHS2, acts on soluble heteroglycans that constitute a part of the carbohydrate pool in a plant. This study aimed to define a physiological role for PHS2. Under standard growth conditions phs2 knock-out mutants do not show any clear growth phenotype, and we hypothesised that during low-light conditions where carbohydrate imbalance is perturbed, this enzyme is important. Soil-grown phs2 mutant plants developed leaf lesions when placed in very low light. Analysis of soluble heteroglycan (SHG) levels showed that the amount of glucose residues in SHG was higher in the phs2 mutant compared to wild-type plants. Furthermore, a standard senescence assay from soil-grown phs2 mutant plants showed that leaves senesced significantly faster in darkness than the wild-type leaves. We also found decreased hypocotyl extension in in vitro-grown phs2 mutant seedlings when grown for long time in darkness at 6°C. We conclude that PHS2 activity is important in the adult stage during low-light conditions and senescence, as well as during prolonged seedling development when carbohydrate levels are unbalanced.

QEEG Index for Early Detection of Imbalanced Conditions During Aerobatics

QEEG Index for Early Detection of Imbalanced Conditions During Aerobatics

Charge recombination in disordered neat polymer films under imbalanced excitation conditions studied using the recombination time of flight technique

It has recently been suggested that the charge recombination rate in amorphous polymers could be affected by the energy distribution of electrons and holes as well as that of the resulting excitons. To test this hypothesis, we developed a new method for measuring charge recombination under highly imbalanced conditions. We find that if the electron density is higher than that of the holes, increasing the electron density further results in reduction of the recombination coefficient. We attribute this to the very different energy distribution between low and high carrier densities, which is not accounted for in the Langevin recombination model.

Transcriptomic response of the toxic prymnesiophyte Prymnesium parvum (N. Carter) to phosphorus and nitrogen starvation

The ichthyotoxic and mixotrophic prymnesiophyte Prymnesium parvum is known to produce dense virtually monospecific blooms in marine coastal, brackish, and inshore waters. Fish-killing Pyrmnesium blooms are often associated with macronutrient imbalanced conditions based upon shifts in ambient nitrogen (N):phosphorus (P) ratios. We therefore investigated nutrient-dependent cellular acclimation mechanisms of this microalga based upon construction of a normalized expressed sequence tag (EST) library. We then profiled the transcriptome of P. parvum under nutrient-replete conditions as well as under nitrogen (N) and phosphorus (P) limitation via microarray analyses. Twenty-three genes putatively involved in acclimation to low nutrient levels were identified, among them three phosphate transporters, which were highly upregulated under P-starvation. In contrast, the expression of genes involved in transport and acquisition of ammonium or nitrate/nitrite was unaltered in N-starved cells. We propose that genes upregulated under P- or N-starvation lend themselves as potential tools to monitor nutrient limitation effects at the cellular level and indirectly the potential for initiation and maintenance of toxic blooms of P. parvum.

Single-Switch Cell Voltage Equalizer Using Multistacked Buck-Boost Converters Operating in Discontinuous Conduction Mode for Series-Connected Energy Storage Cells

The cell voltage imbalance of series-connected energy storage cells, such as supercapacitors (SCs) and lithium-ion cells, causes premature deterioration and a decrease in the available energies of the cells. Various equalization techniques have been developed for diminishing such imbalances. However, since the number of switches, sensors, and/or multiwinding transformers present in conventional equalizers is directly proportional to the number of series connections of the cells, the circuit complexity and cost of the equalizers are prone to increase with the number of series connections. In this paper, single-switch cell voltage equalizers using multistacked buck-boost converters, such as the single-ended primary inductor converter (SEPIC), Zeta, and Ćuk converters, are proposed. These equalizers consist of passive components and a single switch, significantly reducing the complexity of the circuit when compared with that of conventional equalizers. In addition, when the proposed equalizers operate in discontinuous conduction mode, feedback control is not required to limit currents flowing through cells and circuit components. The proposed equalizers are compared with conventional topologies in terms of the number of active and passive components required. Operating analyses were conducted under both cell-voltage-balanced and -imbalanced conditions. Experimental equalization tests were performed for four series-connected SCs using the SEPIC-based single-switch equalizer. The energies of the series-connected SCs were preferentially redistributed by the equalizer to the cell(s) having the lowest voltage, resulting in the elimination of the cell voltage imbalance and subsequent uniformity of the cell voltages.

Reaction times identify a Pavlovian component in a two-choice discrimination

Six pigeons discriminated on discrete trials between two colors. In Experiment 1, two luminous spots were both either blue or green and the reinforced responses were "peck left" for blue and "peck right" for green. In Experiment 2, the hue of a center spot controlled subsequent choice pecks to left or right. In both experiments response bias was manipulated in two ways. During stimulus frequency ("SF") sessions correct responses brought food on 40% of trials; in "imbalanced" blocks of sessions one hue appeared on 80% of trials and the other on 20%. During reinforcement probability ("RNF") sessions the hues appeared equally often, but in imbalanced blocks the hues signaled different reinforcement probabilities, either 64% or 16%. In "balanced" control blocks the hues appeared equally often and were both reinforced at 40%. The experiments gave similar results. When bias was computed from choice percentages the imbalanced conditions yielded substantial response bias, and the amount of bias was about the same under RNF and SF treatments. However, reaction times (RTs) gave a different outcome. RNF imbalance slowed responses directed at the less reinforced stimulus, but SF imbalance had little RT effect (Experiment 1) or no effect (Experiment 2). These results suggest that choice was controlled by an instrumental stimulus-response-reinforcement association, whereas RTs were controlled by a Pavlovian stimulus-reinforcement association.

Pd(0)-catalyzed polycondensation of methyl propargyl carbonate and bisphenols under stoichiometrically imbalanced conditions

We found that a novel Pd(0)-catalyzed polycondensation of methyl propargyl carbonate (1) and bisphenol analogs 4 such as 4,4′-dihydroxydiphenyl ether (4b) proceeded successfully and gave polyethers 5 having exomethylene groups. The polycondensation was affected by the kind of bisphenol analogs used. The molar ratio of 1 and 4 also affected the polymerization behavior. Polyethers 5 with higher molecular weights were obtained by polymerization with 0.5 equiv of 4 toward 1. The use of 1 equiv of 4 gave poor results. When 4,4′-dihydroxybenzophenone (4d) was employed as a nucleophile, benzenesulfonamide (13) was needed as an additive for obtaining the corresponding polyether with higher molecular weight. The Pd(0)-catalyzed condensation of 1 and p-hydroxyacetophenone was conducted as a model reaction. The desired compound and three by-products were produced. Two of the by-products were formed by reaction of 1 and methanol liberated from 1. The other one appeared to be formed via hydrogenolysis. The formation of the by-products suggested that some terminal reactions took place in the polycondensation of 1 and 4. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2250–2261, 2008

Characterization of IIP2 and DC-offsets in transconductance mixers

Envelope distortion in transconductance mixers is analyzed in this paper. The analysis consists of a simplified theoretical study, simulation results, and measurements about several implemented mixers. The studied mixers are active single-balanced and double-balanced structures. A theoretical mismatch analysis is carried out instead of a complex mixer nonlinearity analysis; this gives an intuitive sense of even-order nonlinearity in balanced mixers, and provides information about the fundamental restrictions of second-order input intercept point (IIP2) and the relations of different imbalances to actual performance. The analysis uses a number of simplifying assumptions, but without losing generality. The IIP2 is sensitive to any mismatch in a differential circuit topology. It will be shown that an excellent IIP2 can be achieved in slightly imbalanced conditions by a controllable mismatch device.

Performance analysis of packet switches with input and output buffers

Abstract We develop an analytical model of a nonblocking packet switch with input and output queues that is able to transfer up to L packets per slot to a given switch output. It is modeled as a finite input and output queueing system with 1 L ⩽ N , where switch size N is finite. We investigate the effect of parameters L , N , traffic load P and input/output buffer size on the packet loss performance. We solve the model by using the matrix method that is better suited for numerical computation to handle a realistic range of several parameters considered. In addition, we analyze an input and output queueing system with adaptive input control for the nonblocking packet switch. With numerical results of this study, we show that the input and output queueing switch having a minimal value of L (e.g., L = 2) can easily be realized, keeping the packet loss performance at an acceptable level. We also show that with the adaptive control scheme one can prevent the performance degradation of the switch with L = 2 under imbalanced traffic conditions, and can minimize the size of buffers required at output ports so that it is approximately the same as that at input ports.

MODIFIED CURRENT INJECTION TECHNIQUE

Abstract An alternate method of determining the harmonic currents of a six pulse AC-DC converter is described. This method uses the harmonic voltages to predict the firing angles and the resulting injected harmonic currents. The model avoids the complexities of power flow solutions methods and offers more accuracy than the usual current injection techniques. Also, the model is able to operate under balanced or imbalanced conditions. Its accuracy is shown with time domain solutions.

Magnetic Shunt for Three Phase Reactors

For three phase shunt reactors to function effectively in EHV power systems the behavior of the circuit reluctance must be known under all operating conditions. Difficulties have occurred in effectively designing electromagnetic circuits with multiple air gaps in shunt reactors. This paper describes design techniques for magnetic shunts which can be applied to three phase shunt reactors resulting in size and weight reduction. Performance characteristics of shunt reactors under imbalanced system conditions are presented and magnetic shunt performance for a 345 kV, 100 MVAR three phase shunt reactor is given.