Optimal Shift Research Articles

Novel Mach–Zehnder Interferometer Waveguide Design as a Light Delivery System for Heat-Assisted Magnetic Recording

We propose a light delivery system to the near-field transducer (NFT) of a heat-assisted magnetic recording (HAMR) head using a Mach–Zehnder interferometer (MZI) waveguide arrangement with a transverse electric (TE) mode coupled to the planar waveguide from a single mode fiber. The proposed design offers great flexibility in the coupling of light to the NFT in order to match the desired radiation pattern of the antenna and thus to optimize the energy transfer. Furthermore, it allows excitation of particular surface plasmon (SP) resonances of the transducer (quadrupole or higher) by controlling the coupling angle and the phase of the two beams of light. The optimum phase shift between the TE waveguide modes incident on the NFT can be achieved either statically by making one of the MZI arms longer/shorter compared with the other one, or dynamically by changing the mode effective index of the MZI waveguide arm through electro-optic or thermo-optic modulation. In addition, the proposed MZI waveguide arrangement enables easier coupling from a laser with coupling losses from laser to MZI waveguide being below 3 dB and the design enables an arrangement of the NFT placed either on the top of the waveguide at the termination side of the MZI or between the rib and the ridge at the maximum of the electric field of the waveguide, which maximizes the SP resonance enhancement of the NFT. Another advantage is that the magnetic-write pole, in our design, can be easily integrated on the same chip, preferably above the center of the MZI, between the two arms of the interferometer and away from the propagating mode, thus avoiding blocking of the light path.

Covalent linkage of alkalothermophilic catalase onto functionalized cellulose

Catalase from a thermophilic bacterium belonging to the genus Geobacillus was purified and covalently immobilized onto a functionalized polymer via a spacer with an objective to improve its kinetic and biochemical properties. This is the first report on the purification and immobilization of catalase from the genus Geobacillus. The tetrameric catalase of about 221 kDa was successfully purified using a multistep purification strategy. A shift in pH and temperature optima from 8.0 to 9.0 and 55 °C to 60 °C, respectively was recorded after covalent binding of catalase onto the functionalized matrix. The kinetic constants i.e. Km, Vmax, Kcat and Kcat/Km were found to be 1.2 mM, 4.43 × 106 IU, 6.3 × 105 s−1 and 5.25 × 108 s−1 M−1 for free, and 1.8 mM, 4.01 × 106 IU, 5.9 × 105 s−1 and 3.20 × 108 s−1 M−1 for immobilized catalase, respectively. The ease of binding of alkalothermophilic catalase from a novel isolated bacterium G. extremocatsoochus sp. nov., MTCC 5873 onto a low cost activated cellulose support demonstrated enhanced pH and thermal stability as compared to its free counterpart. This immobilized catalase preparation with improved characteristics has good potential for diverse applications. The present findings provide valuable information on how to tailor enzymes and supported polymer matrices to improve the performance of a biocatalyst.

熱・放射線同時照射した難燃EPRケーブル絶縁体の劣化加速倍率に関する検討

Flame-retardant ethylene-propylene-diene rubbers were subjected to acceleration aging with simultaneous heat and radiation in the air to evaluate the acceleration factor. Mechanical properties under various dose rates, temperatures, and degradation time (0-1050 Gy/h, 80-120°C, 0-42481 hours) were measured to find the optimal shift factor to minimize the data scattering. The estimated shift factor was applied to the oxygen induction time which may correspond to remaining amount of antioxidants. Obtained aging characteristics were found to suggest that the degradation proceeds after consumption of antioxidants. The present study also revealed that the optimum shift parameter of the degradation process may also be applied to aging characteristics obtained under low oxygen pressure conditions.

Development and Application of Blast Casting Technique in Large-Scale Surface Mines: A Case Study of Heidaigou Surface Coal Mine in China

Blast casting is a high-efficiency technique applied in surface mines for overburden removal and results in stripping cost savings. According to ballistic theory and center-of-mass frame basic movement principles, key factors influencing blast casting effect were analyzed, which include bench height and mining panel width, inclined angle of blast holes, explosive unit consumption (EUC), delay-time interval, presplitting, and blast hole pattern parameters. An intelligent design software was developed for obtaining better breaking and casting effect, and the error rates predicted with actual result can be controlled with 10%. Blast casting technique was successfully applied in Heidaigou Surface Coal Mine (HSCM) with more than 34% of material casted into the inner dump. A ramp ditch was set within the middle inner dump for coal transportation. The procedure of stripping and excavating was implemented separately and alternately in the two sections around the middle ramp ditch. An unconstrained-nonlinear model was deduced for optimizing the shift distance of the middle ramp. The calculation results show that optimum shift distance of HSCM is 480 m, and the middle ditch should be shifted after 6 blast casting mining panels being stripped.

Synthesis of galacto-oligosaccharides from lactose using immobilized cells of Kluyveromyces marxianus NCIM 3551

Sodium alginate immobilized cells of Kluyveromyces marxianus NCIM 3551 cells were used for synthesis of galacto-oligosaccharides (GOS) using lactose as a substrate through transgalactosylation approach. The immobilized cells retained 84.4% of the original β-galactosidase activity displayed by free cells. An increase in thermo-stability and a slight shift in pH optimum was observed for β-galactosidase in immobilized cells. Maximum GOS concentration of 72.0g/L and specific GOS productivity 60.0g/L/U was obtained using free cells as opposed to 42.6g/L and productivity of 35.6g/L/U for immobilized cells. A repeated batch reaction was carried out using free and immobilized cells for 10 cycles, of 3h each, using 20% lactose (w/v) with a nearly similar productivity of 24.0g/L/h and 21.3g/L/h respectively. Based on the stability of the immobilized cells, continuous synthesis of GOS was carried out for 10 days in packed bed bioreactor using immobilized cells at a loading of 28.8 units/reactor volume. A yield of 64.0g/L of GOS and a productivity of 21.3g/L/h was achieved at an optimized flow rate of 1.0mL/min. The system here demonstrated the feasibility of using whole cells for production of GOS in a packed bed reactor.

Clinical evaluation of a model-updated image-guidance approach to brain shift compensation: experience in 16 cases.

Brain shift during neurosurgical procedures must be corrected for in order to reestablish accurate alignment for successful image-guided tumor resection. Sparse-data-driven biomechanical models that predict physiological brain shift by accounting for typical deformation-inducing events such as cerebrospinal fluid drainage, hyperosmotic drugs, swelling, retraction, resection, and tumor cavity collapse are an inexpensive solution. This study evaluated the robustness and accuracy of a biomechanical model-based brain shift correction system to assist with tumor resection surgery in 16 clinical cases. Preoperative computation involved the generation of a patient-specific finite element model of the brain and creation of an atlas of brain deformation solutions calculated using a distribution of boundary and deformation-inducing forcing conditions (e.g., sag, tissue contraction, and tissue swelling). The optimum brain shift solution was determined using an inverse problem approach which linearly combines solutions from the atlas to match the cortical surface deformation data collected intraoperatively. The computed deformations were then used to update the preoperative images for all 16 patients. The mean brain shift measured ranged on average from 2.5 to 21.3 mm, and the biomechanical model-based correction system managed to account for the bulk of the brain shift, producing a mean corrected error ranging on average from 0.7 to 4.0 mm. Biomechanical models are an inexpensive means to assist intervention via correction for brain deformations that can compromise surgical navigation systems. To our knowledge, this study represents the most comprehensive clinical evaluation of a deformation correction pipeline for image-guided neurosurgery.

Temperature-dependent responses of the photosynthetic and chlorophyll fluorescence attributes of apple (Malus domestica) leaves during a sustained high temperature event

The objective of this study was to follow changes in the temperature-dependent responses of photosynthesis and photosystem II performance in leaves of field-grown trees of Malus domestica (Borkh.) cv. ‘Red Gala’ before and after exposure to a long-term heat event occurring late in the growing season. Light-saturated photosynthesis was optimal at 25 °C before the heat event. The high temperatures caused a reduction in rates at low temperatures (15–20 °C) but increased rates at high temperatures (30–40 °C) and a shift in optimum to 30 °C. Rates at all temperatures increased after the heat event and the optimum shifted to 33 °C, indicative of some acclimation to the high temperatures occurring. Photosystem II attributes were all highly temperature-dependent. The operating quantum efficiency of PSII during the heat event declined, but mostly at high temperatures, partly because of decreased photochemical quenching but also from increased non-photochemical quenching. However, a further reduction in PSII operating efficiency occurred after the heat event subsided. Non-photochemical quenching had subsided, whereas photochemical quenching had increased in the post-heat event period and consistent with a greater fraction of open PSII reaction centres. What remained uncertain was why these effects on PSII performance appeared to have no effect on the process of light-saturated photosynthesis. However, the results provide an enhanced understanding of the impacts of sustained high temperatures on the photosynthetic process and its underlying reactions, notably photochemistry.

Performances of a CHP Stirling system fuelled with glycerol

The simultaneous productions of mechanical work and low-grade heat by a Stirling engine cogeneration powered by crude glycerol are studied analytically. The study focuses on searching the appropriate values of engine physical parameters to minimize the specific fuel consumption to optimize the work production regardless of the low-grade heat production. The modeling considers the equation of combustion, finite heat transfer between the sources and the working gas, non-perfect regenerator, non-isothermal transformations and non-sinusoidal volume variations during the crankshaft rotation. The optimum operating temperature of the engine hot source and the optimum piston-displacer angular phase shift are determined for alpha, beta and gamma Stirling engines according to the engines swept volume ratio. Results show that the optimum configuration changes considerably with the value of the coefficient of heat transfer. The minimum specific glycerol consumption is 1024 ggly./kWh and is obtained with alpha type engine. Best performance for beta type is quasi-similar but in this last case, the indicated work production is higher than for alpha engine.

A single amino acid substitution within catalytically non-active N-terminal domain of catechol 2,3-dioxygenase (C23O) increases enzyme activity towards 4-chlorocatechol

In this work we have shown for the first time the effect of Met65Thr substitution on the activity of catechol 2,3-dioxygenase (C23O) from Planococcus sp. strain S5. Even though the 3D model does not reveal the influence of an amino acid substitution on the enzyme active site structure, the Thr65 variant differed in lower pH optimum and lower Km from the wild type enzyme. Activity measurements with various catechols as the substrates showed almost 1.5-times higher activity of the mutant protein in comparison to the wild type enzyme against 4-methylcatechol and its remarkably high activity towards 4-chlorocatechol. From the computational studies it follows that the difference in activity of the wild type and mutant form of C23O towards 4-chlorocatechol is most likely linked to the shift of the pH optimum caused by the presence of the two additional H-bonds between Ser307 and Thr65 which anchor the C-terminal fragment of the protein. This work reveals the role of the N-terminal domain, which is considered to be catalytically inactive, in modulation of the C23O activity and the obtained results may facilitate the engineering of C23Os for bioremediation of environments contaminated with chloroaromatic compounds.

Study of torque matching of revolving vane compressor and expander

An investigation was carried out to find the most optimum configuration, particularly the torque matching characteristics, of an integrated Revolving Vane compressor- expander. To carry out the study, a mathematical model of the integrated compressor-expander was developed. An open cycle air refrigeration system was adopted. The controlled parameter was the angle shift between the compressor and the expander. The observed parameters were the peak torque requirement and the bearing load. The results show that when properly matched, the peak torque can be reduced by more than 65% while the bearing loads can be reduced by up to 25%, depending on operating conditions. Unfortunately, the optimum angle shifts for peak torque do not always coincide with those for bearing load. When the pressure and inertial components of the torques are comparable or when the inertial component is dominant, the optimum angle shifts for peak torque and bearing load are around 180° and 330°, respectively. When the pressure component is dominant, the optimum angle shift for peak torque is equal to the angle difference between the pressure peak torques of the compressor and the expander while for bearing load is around 150°.

Performance assessment of longitudinal flow through rod bundle arrangements using entropy generation minimization approach

Longitudinal flow through central subchannel structures in an array of fuel rods in a nuclear reactor plays an important role in removing the heat generated inside the fuel rods. In this paper, an entropy generation analysis has been carried out for assessment of the performance of an infinite triangular as well as a square subchannel for single-phase forced turbulent flow. The performance is evaluated with the objective function being the overall entropy generation in a central subchannel. Various constraints such as dimensionless flow area subtended by the array of rods, pitch to diameter ratio for the configuration of rod bundles and volumetric heat generation to power density ratio of the subchannel imposed by power restrictions have been considered. The parameters include the dimensionless wall heat flux, duty parameter, length to diameter ratio for fuel rods, Reynolds number etc. It has been observed that for a pitch to diameter ratio constraint the square subchannel generates lesser amount of entropy and thus more acceptable compared to triangular structure. For the same constraint the optimum Reynolds number shifts towards higher value compared to triangular one. For dimensionless flow area constraint, on the other hand, the analysis reveals completely reverse phenomenon.

Selection towards different adaptive optima drove the early diversification of locomotor phenotypes in the radiation of Neotropical geophagine cichlids

BackgroundSimpson envisaged a conceptual model of adaptive radiation in which lineages diversify into “adaptive zones” within a macroevolutionary adaptive landscape. However, only a handful of studies have empirically investigated this adaptive landscape and its consequences for our interpretation of the underlying mechanisms of phenotypic evolution. In fish radiations the evolution of locomotor phenotypes may represent an important dimension of ecomorphological diversification given the implications of locomotion for feeding and habitat use. Neotropical geophagine cichlids represent a newly identified adaptive radiation and provide a useful system for studying patterns of locomotor diversification and the implications of selective constraints on phenotypic divergence in general.ResultsWe use multivariate ordination, models of phenotypic evolution and posterior predictive approaches to investigate the macroevolutionary adaptive landscape and test for evidence of early divergence of locomotor phenotypes in Geophagini. The evolution of locomotor phenotypes was characterized by selection towards at least two distinct adaptive peaks and the early divergence of modern morphological disparity. One adaptive peak included the benthic and epibenthic invertivores and was characterized by fishes with deep, laterally compressed bodies that optimize precise, slow-swimming manoeuvres. The second adaptive peak resulted from a shift in adaptive optima in the species-rich ram-feeding/rheophilic Crenicichla-Teleocichla clade and was characterized by species with streamlined bodies that optimize fast starts and rapid manoeuvres. Evolutionary models and posterior predictive approaches favoured an early shift to a new adaptive peak over decreasing rates of evolution as the underlying process driving the early divergence of locomotor phenotypes.ConclusionsThe influence of multiple adaptive peaks on the divergence of locomotor phenotypes in Geophagini is compatible with the expectations of an ecologically driven adaptive radiation. This study confirms that the diversification of locomotor phenotypes represents an important dimension of phenotypic evolution in the geophagine adaptive radiation. It also suggests that the commonly observed early burst of phenotypic evolution during adaptive radiations may be better explained by the concentration of shifts to new adaptive peaks deep in the phylogeny rather than overall decreasing rates of evolution.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-015-0348-7) contains supplementary material, which is available to authorized users.

Harvest control rules for mixed-stock fisheries coping with autocorrelated recruitment variation, conservation of weak stocks, and economic well-being

Dynamic programming is used to construct harvest control rules that account for persistent changes in productivity, exploitation rate constraints that prevent extinction of nontarget weak stocks, and an economic objective that recognizes moderate income to be more important to fishermen than maximization of total profit. Persistent productivity changes imply downward adjustment in spawning abundance targets during periods of low productivity, while conservation constraints simply imply upper limits on exploitation rate at high stock sizes. When the economic objective is to maximize the logarithm of net income (diminishing marginal utility or welfare from higher incomes), the optimum control rule shifts from a fixed escapement form to a curve where exploitation rate increases smoothly from zero at the minimum stock size that can be fished profitably to the upper limit set by a conservation constraint. This policy is not the fixed-exploitation rate form that has been historically suggested as a way of stabilizing harvests without major loss in profits. Application of harvest control rules constructed using dynamic programming in a mixed-stock salmon fishery in fact results in total profits close to those obtainable with fixed escapement policies but without the frequent low catches or closures implied by fixed escapement policies.

Analytics on Fireworks Algorithm Solving Problems with Shifts in the Decision Space and Objective Space

Fireworks algorithms for solving problems with the optima shift in decision space and/or objective space are analyzed in this paper. The standard benchmark problems have several weaknesses in the research of swarm intelligence algorithms for solving single objective problems. The optimum is in the center of search range, and is the same at each dimension of the search space. The optimum shift in decision space and/or objective space could increase the difficulty of problem solving. A mapping strategy, modular arithmetic mapping, is utilized in the original fireworks algorithm to handle solutions out of search range. The solutions are implicitly guided to the center of search range for problems with symmetrical search range via this strategy. The optimization performance of fireworks algorithm on shift functions may be affected by this strategy. Four kinds of mapping strategies, which include mapping by modular arithmetic, mapping to the boundary, mapping to stochastic region, and mapping to limited stochastic region, are compared on problems with different dimensions and different optimum shift range. From experimental results, the fireworks algorithms with mapping to the boundary, or mapping to limited stochastic region obtain good performance on problems with the optimum shift. This is probably because the search tendency is kept in these two strategies. The definition of population diversity measurement is also proposed in this paper, from observation on population diversity changes, the useful information of fireworks algorithm solving different kinds of problems could be obtained.

Identification and regulation of the catalytic promiscuity of (-)-γ-lactamase from Microbacterium hydrocarbonoxydans.

Mhg, a previously reported (-)-γ-lactamase from Microbacterium hydrocarbonoxydans, was identified to have perhydrolase activity by combining structure similarity search with activity assays. Kinetic studies illustrated that perhydrolysis was the native activity owing to lower K m and higher k cat/K m values. Experimental evidence showed that both hydrolysis and perhydrolysis reactions took place at the same active center. Engineering of the putative substrate-binding pocket revealed that Leu233 site played a vital role in the aspects of selective catalysis, soluble protein expression level and optimum temperature shift, etc. The mutants L233A, L233P, and L233T retained (-)-γ-lactamase activity but lost perhydrolase activity, while L233M only kept perhydrolase activity. Substitutions of Leu233 could dramatically influence the state of expressed protein. Computational analysis explicitly explained the relationships between mutations and γ-lactamase activity changes. Our investigations demonstrated that it was an efficient method to identify the enzyme catalytic promiscuity by combining 3D structure alignment with activity validations, and engineering of substrate-binding pocket could serve as a promising way to regulate activities of promiscuous enzymes.

Inverse diffusion and partially premixed flames with elliptical/swirling- and cross-flows

The combustion performance of inverse diffusion and partially premixed flames was optimized by employing concentric elliptical ports with variable relative angular orientation, co-swirling, and cross-flow opposing jets of different inclination angles. The flexible and favorably active control of combustion was pronounced by changing the nozzle relative angular orientation. The optimum angular shift was found to be 20° where the flame length was shortened by 39% from the case of 0° and the NOx levels were reduced to about 0.51 g/kg of fuel for the inverse partially premixed flames. At such optimum angular shift, the minimum CO and NOx emissions respectively decreased to 17.1 and 1.52 g/kg of fuel for the inverse diffusion flames. The elliptical jets increased the size of the swirling flow recirculation zone by about 28%. Increasing the inner aspect ratio consistently increased the combustion efficiency, where the CO emissions reach minimum values of 12.3 and 6.22 g/kg of fuel respectively for the inverse diffusion and partially premixed flames. The correspondingly minimum NOx emissions were thus 0.89 and 0.51 g/kg of fuel at a cross-flow momentum flux ratio of 2.0. Splitting the opposing cross-flow air jets by increasing their inclination angle above 0° duplicated the stagnation zone vortical impact to enrich the average turbulent energy at the major axis tips. The inclination angle of 15° was the optimum at no swirl while increasing the outer swirl angle shifted the optimum inclination angle to 25°. The inner/outer co-swirl of 45°/60° thus provided a minimum CO emission of 11.1 g/kg of fuel for the inverse diffusion flame and 2.65 g/kg of fuel for the inverse partially premixed flame.

Impacts of climate extremes on gross primary production under global warming

The impacts of historical droughts and heat-waves on ecosystems are often considered indicative of future global warming impacts, under the assumption that water stress sets in above a fixed high temperature threshold. Historical and future (RCP8.5) Earth system model (ESM) climate projections were analyzed in this study to illustrate changes in the temperatures for onset of water stress under global warming. The ESMs examined here predict sharp declines in gross primary production (GPP) at warm temperature extremes in historical climates, similar to the observed correlations between GPP and temperature during historical heat-waves and droughts. However, soil moisture increases at the warm end of the temperature range, and the temperature at which soil moisture declines with temperature shifts to a higher temperature. The temperature for onset of water stress thus increases under global warming and is associated with a shift in the temperature for maximum GPP to warmer temperatures. Despite the shift in this local temperature optimum, the impacts of warm extremes on GPP are approximately invariant when extremes are defined relative to the optimal temperature within each climate period. The GPP sensitivity to these relative temperature extremes therefore remains similar between future and present climates, suggesting that the heat- and drought-induced GPP reductions seen recently can be expected to be similar in the future, and may be underestimates of future impacts given model projections of increased frequency and persistence of heat-waves and droughts. The local temperature optimum can be understood as the temperature at which the combination of water stress and light limitations is minimized, and this concept gives insights into how GPP responds to climate extremes in both historical and future climate periods. Both cold (temperature and light-limited) and warm (water-limited) relative temperature extremes become more persistent in future climate projections, and the time taken to return to locally optimal climates for GPP following climate extremes increases by more than 25% over many land regions.

DEVELOPMENT OF A FOUR-SPEED AUTOMATIC TRANSMISSION WITH OVERDRIVE

A new four–speed automatic transmission with overdrive has been developed and put into production for the purpose of improvement of fuel economy and the reduction of engine noise. The transmission has the following characteristics: gear train arrangement with overdrive unit; lower overdrive gear ratio; shift feel controls for clutch–to–clutch shifting; optimum shift points on fuel economy, driveability and exhaust emissions; lockout system of overdrive gear. For optimum gear ratios, shift points, and smooth shift feel controls, computer simulations were used to provide design direction. This paper describes the design features and the confirmation testings of the transmission, and also refers to effects on fuel economy and noise reduction of the transmission in the vehicle.

Adaptive fixation in two-locus models of stabilizing selection and genetic drift.

The relationship between quantitative genetics and population genetics has been studied for nearly a century, almost since the existence of these two disciplines. Here we ask to what extent quantitative genetic models in which selection is assumed to operate on a polygenic trait predict adaptive fixations that may lead to footprints in the genome (selective sweeps). We study two-locus models of stabilizing selection (with and without genetic drift) by simulations and analytically. For symmetric viability selection we find that ∼16% of the trajectories may lead to fixation if the initial allele frequencies are sampled from the neutral site-frequency spectrum and the effect sizes are uniformly distributed. However, if the population is preadapted when it undergoes an environmental change (i.e., sits in one of the equilibria of the model), the fixation probability decreases dramatically. In other two-locus models with general viabilities or an optimum shift, the proportion of adaptive fixations may increase to >24%. Similarly, genetic drift leads to a higher probability of fixation. The predictions of alternative quantitative genetics models, initial conditions, and effect-size distributions are also discussed.

Six-Phase Fractional-Slot-per-Pole-per-Phase Permanent-Magnet Machines With Low Space Harmonics for Electric Vehicle Application

This paper discusses the development of new winding configuration for six-phase permanent-magnet (PM) machines with 18 slots and 8 poles, which eliminates and/or reduces undesirable space harmonics in the stator magnetomotive force. The proposed configuration improves power/torque density and efficiency with a reduction in eddy-current losses in the rotor permanent magnets and copper losses in end windings. To improve drive train availability for applications in electric vehicles (EVs), this paper proposes the design of a six-phase PM machine as two independent three-phase windings. A number of possible phase shifts between two sets of three-phase windings due to their slot-pole combination and winding configuration are investigated, and the optimum phase shift is selected by analyzing the harmonic distributions and their effect on machine performance, including the rotor eddy-current losses. The machine design is optimized for a given set of specifications for EVs, under electrical, thermal and volumetric constraints, and demonstrated by the experimental measurements on a prototype machine.