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Summary: DC‐DC converters play a vital role in the integration of renewable energy sources. Modular multilevel converter (MMC) has emerged as a highly promising option for high‐voltage high‐power applications, for DC‐AC and DC‐DC conversion, thanks to its distinctive characteristics. An inherent limitation of using traditional MMC in DC‐DC conversion is the occurrence of arm energy drift, leading to imbalanced voltages across capacitors of submodules (SMs). Many approaches have been presented in the literature to address the energy drift issue during DC‐DC conversion process. In this paper, a novel bidirectional hybrid modular multilevel DC‐DC converter with balanced arm energy has been proposed. The proposed converter consists of one high‐voltage valve and two legs. Each leg is equipped with half‐bridge submodules (HB‐SMs) in the upper arm and full‐bridge submodules (FB‐SMs) in the lower arm. The proposed architecture enables the parallel connection between series‐connected capacitors of the upper arm and series‐connected capacitors of the lower arm during the equalization period. The parallel connectivity enables the energy transfer between the upper and lower arms in the same leg, hence preventing energy drift issues. A detailed illustration of converter operational concept, mathematical analysis, design, and efficiency estimation are presented. The presented simulation and experimental results show the bidirectional power flow ability and the promising behavior of the proposed converter during normal operating conditions with balanced arm energy. Finally, a comparison between the proposed converter and other existing topologies has been made to show the superiority of the proposed converter over the other alternatives. The proposed converter has a lower count of insulated gate bipolar transistors (IGBTs) and eliminates the usage of isolating transformers when compared to the energy equalization modules approach. In addition, unlike the other alternatives, the proposed converter has a DC fault blocking capability. [ABSTRACT FROM AUTHOR]

Detailed experimental characterization of a laser‐clad metal matrix composite (MMC) consisting of hard tungsten carbide particles embedded in a comparatively soft nickel‐based matrix is provided. Special focus of the investigations is placed on the relationship between the microstructure of the as‐deposited reinforcing particles and their hardness. Therefore, thermally induced dissolution of carbides caused by laser metal deposition (LMD) processing is studied. The as‐received powder blend mainly consists of fused spherical particles of ditungsten carbides (W2C, W2C1−x) and monotungsten carbides (WC, WC1−x). Dissolution of large particles at the matrix/particle interfaces and fragmentation or even complete dissolution of small particles due to the high process temperature of LMD is observed. Primary W2C/W2C1−x phases are partially dissoluted, and layers of secondary WC/NixWyC phases are formed at the matrix/particle interfaces. As these surface layers are less hard than the as‐received particles, the local hardness gradually decreases from the inner region of the particles across the surface layer toward the matrix, which is supposed to improve bonding of the particles inside the matrix. The hardness depends on the grain size and on the crystal structure of the carbides. Even when the crystal structures are identical, particles consisting of fine grains have considerably higher hardness than particles consisting of coarse grains. [ABSTRACT FROM AUTHOR]

The joint influence of the stratospheric quasi‐biennial oscillation (QBO) and the El Niño Southern Oscillation (ENSO) on the polar vortex, subtropical westerly jets (STJs), and wave patterns during boreal winter is investigated in 40 years (1979–2018) of monthly mean ERA‐Interim reanalyses. The method of Wallace et al. (1993), https://doi.org/10.1175/15200469(1993)050<1751:ROTESQ>2.0.CO;2 is used to conduct a QBO phase angle sweep. QBO westerly (W) and easterly (E) composites are then segregated by the phase of ENSO. Two pathways are described by which the QBO mean meridional circulation (MMC) influences the northern winter hemisphere. The "stratospheric pathway" modulates stratospheric planetary wave absorption via the Holton‐Tan mechanism. The "tropospheric pathway" modulates the tropical and subtropical upper troposphere and lower stratosphere. QBO MMC anomalies exhibit a checkerboard pattern in temperature and arched structures in zonal wind which extend into midlatitudes, and are stronger on the winter side. During QBO W, the polar vortex and STJs are enhanced. QBO signals in the polar vortex are amplified during La Niña. During El Niño and QBO W, the strongest STJs occur, and a warm pole/wave two pattern is found. During El Niño and QBO E, a trough is found over Eurasia and a ridge over the North Atlantic, in a wave one pattern. El Niño diminishes QBO anomalies in the tropical stratosphere and reduces the poleward extent and amplitude of the QBO MMC, thereby influencing the stratospheric pathway. Effects on the boreal winter hemisphere are attributed to the combined influence of the QBO and ENSO via both pathways. Plain Language Summary: Seasonal forecasts in the Northern Hemisphere winter can be improved by a better understanding of the influence of two phenomena seated in the tropics: the stratospheric quasi‐biennial oscillation (QBO), with periodicity ∼2–3 years, and the El Niño Southern Oscillation (ENSO), with periodicity ∼3–7 years. This paper shows how the QBO and ENSO jointly influence the polar night vortex and tropospheric jet stream. During periods of QBO westerly winds, the polar vortex is stronger and more symmetric, and the tropospheric jet stream is stronger, while during QBO easterlies the vortex and jet stream are weaker. This QBO signal is enhanced during La Niña and is nearly absent during El Niño. Key Points: Two pathways are described by which the quasi‐biennial oscillation (QBO) mean meridional circulation (MMC) influences the northern winter hemisphereThe asymmetric extension of QBO MMC cells into the winter hemisphere is modulated by El Niño Southern OscillationDuring El Niño, the polar vortex anomaly exhibits a wave two pattern for QBO westerly and wave one pattern for QBO easterly [ABSTRACT FROM AUTHOR]

Impedance characteristics of the floating capacitor in the submodule (SM) of a modular multilevel converter (MMC) change due to its chemical and aging characteristics. This can result in a rise of voltage ripple across SM capacitors, uneven power distribution among the SMs and could also interrupt the operation with prolonged use of degraded capacitors. Existing balancing approaches are presented for the MMC with equal SM capacitance and ignored the effect of capacitor degradation as well as parameter mismatch. Hence, a closed‐loop control scheme that incorporates the effect of capacitor degradation is much necessitated. This study aims to overcome this gap by proposing a new power balancing control algorithm for SM capacitors, which effectively controls and evenly distributes the power among SMs. The efficacy of the proposed strategy is substantiated through PLECS simulations and OPAL‐RT/OP4510 controller‐based experiments on a single‐phase MMC laboratory prototype. [ABSTRACT FROM AUTHOR]

Power oscillation damping (POD) is one of the ancillary services expected from high‐voltage direct current (HVDC) converters. When providing POD to the ac side, converters draw power from the dc side, which can cause distortion to the dc voltage especially in the case of limited dc capacitance. In meshed/multi‐terminal HVDC grids, where dc voltage regulation is distributed using a dc voltage droop control strategy, the distortion due to the POD controller action is propagated to other connected ac grids because of the droop action. This propagation can be reduced by using the inherent energy storage capability of the modular multilevel converter (MMC), which is a common converter topology for HVDC. Different methods to utilise the energy stored in the MMC for the purpose of POD have been proposed in the literature. This study presents a detailed analysis and experimental validation of one of these methods, referred to as virtual capacitance support, which increases the effective dc grid capacitance by using the stored energy of multiple MMCs connected in the same grid. The experiments, which were carried out using power hardware in the loop setup, demonstrated the effectiveness of the method. [ABSTRACT FROM AUTHOR]

Objectives: To describe a new first-trimester sonographic sign, the 'crash sign', associated with fetal open spina bifida, and to evaluate its clinical usefulness in the first-trimester diagnosis of spina bifida.Methods: This was a retrospective review of patients referred to three fetal medicine centers in the first trimester (11 + 0 to 13 + 6 weeks) with suspected spina bifida. Spina bifida was confirmed by direct visualization of the spinal defect on ultrasound by two experts and, when possible, by fetal postmortem examination. Ultrasound images were reviewed for the presence of the crash sign, which is the posterior displacement of the mesencephalon and deformation against the occipital bone in the axial view. The first-trimester ultrasound images of a mixed group of 10 cases and 40 control fetuses without spina bifida were assessed for the presence of the crash sign by two assessors blinded to the diagnosis.Results: The crash sign was present in 48 out of 53 confirmed cases of spina bifida. Of these, 27 had isolated spina bifida and 21 had an associated anomaly. Of the five cases without the crash sign, one had isolated spina bifida and four had an associated anomaly. The crash sign was not reported in any of the control fetuses.Conclusions: We have described a new first-trimester sonographic marker for the diagnosis of spina bifida. Our results suggest that the crash sign may be a useful tool in the first-trimester detection of spina bifida. Prospective evaluation of the crash sign would be beneficial, ideally in a routine clinical screening ultrasound setting. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

The conventional capacitor voltage balancing strategy of the modular multi‐level converter (MMC) requires real‐time sorting in each control cycle, which brings huge computational load to the controller. Therefore, a fast capacitor voltage balancing method for MMC is proposed. Based on the conventional strategy, this method combines the operating rules of the sub‐module (SM), considering the voltages of SMs and historical information on charging and discharging of the capacitor. It selects the appropriate insert object and insertion process according to the relationship between the number of the switched‐on and switched‐off SMs in the last control cycle, and quickly forms the ordered sequence of SMs in the control cycle. The simulation results show that the proposed strategy can achieve voltage balancing with low computational complexity, significantly improve the system simulation speed, and effectively reduce the controller resources occupied by the balancing strategy. [ABSTRACT FROM AUTHOR]

In view of the short-circuit fault characteristics, the protection technique of the dc lines limits the development of the modular multi-level converter (MMC)-based HVDC grid in a large extent. This study derives the calculation formulas of the transient voltages of internal and external faults and proposes a single-end protection scheme based on the transition period (TP) from the abrupt changing point to the first extreme point of the fault voltage. Due to the current-limiting reactors, the TP of the internal fault is much shorter than that of the external fault, which is used to discriminate internal fault from external fault. A four-terminal symmetrical bipolar HVDC grid based on MMC is modelled using PSCAD/EMTDC, and simulation results demonstrate the validity of the new proposed dc transmission line protection method. [ABSTRACT FROM AUTHOR]

Modular multilevel converter (MMC) has a very good application prospect in the flexible high-voltage direct current (HVDC) transmission, but higher self-loss will affect the efficiency and restrict the development. Here, the MMC in voltage source converter-based HVDC as the research object, the control and modulation algorithms are designed on the basis of analysing its working principle. The capacitor voltage imbalance problem is existed in the converter because that the capacitor of each module is independent. The factors of switching actions in balancing control technology based on the sorting method of sub-module capacitor voltages are analysed in detail. Then, an optimised balancing control algorithm by setting two balancing control thresholds is proposed to reduce the average switching frequency. Finally, a two ends HVDC transmission system was built in MATLAB/SIMULINK to verify the optimisation. The simulation research results show that the optimised balancing control can ensure sub-module capacitor voltage is in balanced and does not increase the AC output voltage harmonic content, and obviously reduce the average switching frequency of switching devices, and with the increase of number of level, the more obvious optimisation effect. [ABSTRACT FROM AUTHOR]

This study presents a survey on the existing fault diagnosis methods (FDMs) of the switch devices for the rapidly developing modular multilevel converters (MMCs). Three categories, namely mechanism‐based, signal processing‐based and artificial intelligence‐based FDMs, are evaluated and summarised depending on the operating principles. Mechanism‐based FDMs detect the faults by comparing the inner characteristics of MMC or their derived parameters with the expected values. Signal processing‐based FDMs detect the faults via comparing the processed output voltage or current with their expected values. Artificial intelligence‐based FDMs detect the faults in the way of employing a trained intelligent classifier. Methods belonging to each category are introduced in detail via comparing a lot of criteria of the FDMs. Then, a figure‐of‐merit is defined to evaluate various FDMs. Finally, the summary is given and the developing tendency is recommended for future work. [ABSTRACT FROM AUTHOR]

Summary: RecQ helicases are important caretakers of genome stability and occur in varying copy numbers in different eukaryotes. Subsets of RecQ paralogs are involved in DNA crosslink (CL) repair. The orthologs of AtRECQ2, AtRECQ3 and AtHRQ1, HsWRN, DmRECQ5 and ScHRQ1 participate in CL repair in their respective organisms, and we aimed to define the function of these helicases for plants. We obtained Arabidopsis mutants of the three RecQ helicases and determined their sensitivity against CL agents in single‐ and double‐mutant analyses. Only Athrq1, but not Atrecq2 and Atrecq3, mutants proved to be sensitive to intra‐ and interstrand crosslinking agents. AtHRQ1 is specifically involved in the repair of replicative damage induced by CL agents. It shares pathways with the Fanconi anemia‐related endonuclease FAN1 but not with the endonuclease MUS81. Most surprisingly, AtHRQ1 is epistatic to the ATPase RAD5A for intra‐ as well as interstrand CL repair. We conclude that, as in fungi, AtHRQ1 has a conserved function in DNA excision repair. Additionally, HRQ1 not only shares pathways with the Fanconi anemia repair factors, but in contrast to fungi also seems to act in a common pathway with postreplicative DNA repair. [ABSTRACT FROM AUTHOR]

Modular multilevel converters (MMCs) play a critical role in the future energy Internet pattern. Therefore, proper models for the simulation of complex systems with multiple MMCs are required. This study proposes a simplified equivalent model (SEM) based on the implicit trapezoidal method and Thevenin equivalent. The model can accurately simulate arm voltages of the MMC and is thus capable of simulating system‐level transients after faults and disturbances, circulating currents and subsynchronous oscillation components. Subsequently, a hybrid model combining SEM and a detailed equivalent model (DEM) is built to improve the overall simulation speed in scenarios where submodule‐level transients are mixed with system‐level ones. Finally, this study notes that the major difference between DEM and SEM results only from the voltage‐balancing cycle. An experiential formula is given to regulate SEM when the voltage‐balancing cycle is large, where the difference may become obvious/insufferable. [ABSTRACT FROM AUTHOR]

In the grid‐connected modular multilevel converter (MMC) system, AC grid faults not only cause current imbalance and distortion which may lead MMC shutdown but also bring imbalance issues to the circulating currents and the module capacitor voltages. In this paper, a flexible protected control method employed in the dual d–q coordinates is presented. A weighting factor is introduced in the AC current controller to flexibly adjust the positive‐ and negative‐sequence components. The mathematical models of the converter based on the Kirchhoff law and the energy balance equations are investigated. Considering the system requirements such as the allowed maximum AC current and the allowed maximum capacitor voltage ripple in phase unit, the design principle of the flexible controller is proposed. Finally, the simulation results from MATLAB/Simulink as well as experimental results from a scaled‐down MMC prototype are presented to verify the theoretical analysis. © 2018 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [ABSTRACT FROM AUTHOR]

This study proposes a stationary coordinate system‐based virtual‐multilevel model predictive control strategy with error feedback for the control of the modular multilevel converter (MMC). In order to reduce the number of considered states for the ac‐side current control, a cost function is established according to the mathematical model of the MMC in the two‐phase stationary coordinate system. The selection of the output voltage levels is optimised with the introduction of the virtual‐multilevel algorithm. By using real‐time submodule (SM) capacitor voltages in current prediction, the circulating current control is combined with the SM capacitor voltage sorting to improve the control accuracy of the circulating current. This study also proposes an error feedback correction method to eliminate the steady‐state error in current control and avoid parameter sensitivity of the control performance. The simulation results and experimental results from a down‐scaled MMC prototype are provided to verify the validity and efficiency of the proposed method. [ABSTRACT FROM AUTHOR]

In the electromagnetic transient (EMT) simulation programs, the candidate integration methods backward Euler (BE) method and Trapezoidal rule (TR) are normally used to discretise the submodule capacitors in modular multilevel converter (MMCs). This study proposes linear time complexity sorting algorithms for nearest level control‐based BE and TR MMC models to further accelerate the EMT simulation of the equivalent MMC‐HVdc models. First, the capacitor voltage increments in the charging and discharging processes are investigated from an EMT point of view. Second, for both BE and TR methods, although the actual capacitor voltage increments are not identical at each time step, the voltage ranking of the capacitors from the same inserted/bypassed category at each control period are proved to be unchanged. Taking this advantage, when preparing the entire ranked voltage table for the next control period, the sorting can be significantly simplified since one only needs to compare the capacitor voltages from capacitor categories of ascending orders. Third, when implementing the sorting algorithms, at most (N –1) comparisons for BE model and (2N –3) comparisons for TR model are required, showing that the proposed sorting algorithms have linear time complexities. Finally, all the proposed approaches are validated by EMT simulations on MATLAB/Simulink. [ABSTRACT FROM AUTHOR]

Traditional low voltage high power wind energy conversion system (WECS) requires heavy cables and large step‐up grid interfacing transformers. In recent years, power rating of offshore wind turbines already exceeds 10 MW, and medium voltage (MV) converters have become strongly demanded. Modular multilevel converter (MMC) is suitable for MV high power applications. However, there are two technical difficulties for MMC when applied in MV permanent magnet synchronous generator (PMSG) WECS. The first one is the large sub module (SM) voltage fluctuation caused by low frequency and high amplitude PMSG phase current. The other one is the low voltage ride through (LVRT) problem. Overall control strategy based on carrier‐phase‐shifted ‐sinusoidal pulse width modulation technique of the MMC WECS is proposed. For the first difficulty mentioned, a second‐order circulating current injection method based on closed‐loop control is proposed. For the LVRT problem, a distributed braking chopper solution is provided. The effectiveness of the injection method and the distributed braking chopper solution are validated by simulation of a 5 MW/3.3 kV MMC WECS. Influences of the current injection amplitude on SM voltages and arm currents are discussed and a trade‐off method is given to optimise system design, which is also verified by simulation. [ABSTRACT FROM AUTHOR]

The modular multilevel converter (MMC) will be used in power systems more and more widely. The main circuit parameter design of the MMC impacts the initial investment and the operating performance of the system. In this study the parameter design problem of several important elements in the main circuit of the MMC, such as the link transformer, the arm reactor, the sub‐module (SM) capacitor and the SM power electronic devices are analysed. Based on the fundamental equivalent circuit of the MMC, the design method for the rated valve side no‐load voltage of the link transformer is proposed; and the variation range of the rated valve side no‐load voltage is determined as (1.00–1.05)/2 times of the DC side voltage. By introducing the concept of the equivalent capacity discharging time constant H, the nearly constant relationship between the fluctuation ratio of the SM capacitor voltage and the H‐value for different projects is discovered, which means the H‐value is independent of particular projects. In this study, the corresponding parameters of several practical projects are analysed and the recommended H‐value is given as 40 ms. The voltage and current stress of the SM power electronic devices is investigated for the four extreme operating conditions by the analytical formulae of the MMC; and it is discovered that the current stress of the SM power electronic devices changes greatly with the operating condition. By introducing the concepts of the phase unit series resonance frequency and the circulating current resonance frequency, the principle for designing the parameter of the arm inductor is established. Through analysing the corresponding parameters of several real projects, the recommended value of the phase unit series resonance frequency is given as the rated frequency of the connected AC system. [ABSTRACT FROM AUTHOR]

The modular multilevel converter (MMC) is one of the best potential candidates for high‐voltage direct current (HVDC). Various kinds of faults may occur in an MMC‐HVDC system. The system should be restarted by deblocking the converter after a temporary fault is cleared or a fault is isolated, thus recovering the power transmission as soon as possible. This study analyses the recovery process after the converter is deblocked. The analysis shows that the capacitor voltages of the three upper arms or the three lower arms can be rebalanced quickly, and the power transmission and the DC voltage can be recovered with the original main controller. However, the speed of rebalancing the capacitor voltages of the upper arm and the lower arm depends on the arm resistance, the modulation index and so on, and is probably slow. To improve the damping characteristic of the MMC, a dedicated supplementary controller is proposed based on the concept of 'virtual arm resistance'. Time‐domain simulation studies based on PSCAD/EMTDC are performed to verify the analysis and the proposed controller. [ABSTRACT FROM AUTHOR]

The design of control circuit for a solar fed cascaded multilevel inverter to reduce the number of semiconductor switches is presented in this study. The design includes 'binary', 'trinary' and 'modified multilevel connection' (MMC)‐based topologies suitable for varying input sources from solar photovoltaic's (PV). In binary mode, 2Ns+1−1 output voltage levels are obtained where Ns is the number of individual inverters. This is achieved by digital logic functions which includes counters, flip‐flops and logic gates. In trinary mode, 3Ns levels are achieved by corresponding look‐up table. MMC intends design in both control and power circuits to provide corresponding output voltage levels by appropriate switching sequences. Hence to obtain a 15‐level inverter, the conventional method requires 28 switches and in binary mode 12 switches are needed. In trinary mode with the same 12 switches, 27 levels can be obtained whereas in MMC only 7 switches are employed to achieve 15 levels. The advantage of these three designs is in the reduction of total harmonic distortion by increasing the levels. Simulations are carried out in MATLAB/Simulink and comparisons were made. All the three topologies are experimentally investigated for a 3 kWp solar PV plant and power quality indices were measured. [ABSTRACT FROM AUTHOR]

Composite material Ferro-Titanit® is produced powder-metallurgical by Deutsche Edelstahlwerke GmbH (DEW) and is commonly used for wear and corrosion resistant component parts. Materials properties can be attributed to the microstructure which consists of a corrosion resistant metallic matrix and a huge amount of approx. 50 vol.% of hard Ti-monocarbides. Although Ferro-Titanit® possesses a high amount of hard particles, the material can be machined by turning and drilling in solution annealed condition. Due to the alloying content (Mo, Cr, TiC) of Ferro-Titanit®, there is a high motivation to recover those elements by a recycling process of the chips, thus expensive and limited resources can be saved. On idea of a recycling process can be found in the redensification of those chips by electro discharge sintering (EDS). In this work, chips of the material Ferro-Titanit® were densified by EDS technique and the resulting microstructure was investigated by optical and scanning electron microscopy. Furthermore, microstructure and hardness of the EDS densified specimens was discussed with regard to the microstructure of conventionally sintered Ferro-Titanit®-samples in laboratory conditions. [ABSTRACT FROM AUTHOR]

Modular multilevel converter (MMC) is troubled by the inherent second harmonic of single‐phase ac power. By adding feedforward to the modulation signal, low‐frequency harmonic voltages are significantly reduced thus overcoming an important weakness of MMC. Capacitors of sub‐modules do not have to be over‐sized. If desired for protection, transformers can be wye‐connected with grounded neutral. The reduction method is based on harmonic function analysis. In addition to deriving algebraic formulae of harmonic voltage components of 'open loop' control, this study makes original contributions by deriving formulae which include feedforward control. Analytical insights from the formulae have shown the way to design feedforward methods to reduce low‐frequency harmonics. Validation is by simulations using SIMULINK/MATLAB. [ABSTRACT FROM AUTHOR]

In this study two-dimensional finite element model of Al/SiC metal matrix composites (MMC) are investigated by the use of ABAQUS/Explicit software. Chip formations and machining forces during machining of MMC have been studied and compared to experimental data. It was found that the resulted chips in simulation and the generated chips in experiments both have saw-tooth in appearance. On the other hand, the obtained cutting forces diagrams from simulation and experimental conditions have considerable fluctuating with passing cutting time. This is due to the interaction between tool and SiC particles during chip formation. [ABSTRACT FROM AUTHOR]

The HRDC (helicase and RNase D C-terminal) domain at the C-terminal of WRNp (Werner protein) (1150-1229 amino acids) and BLMp (Bloom protein) (1212-1292 amino acids) recognize laser microirradiation-induced DNA dsbs (double-strand breaks). However, their role in the recognition of DNA damage other than dsbs has not been reported. In this work, we show that HRDC domain of both the proteins can be recruited to the DNA damage induced by MMS (methyl methanesulfonate) and MMC (methyl mitomycin C). GFP (green fluorescent protein)-tagged HRDC domain produces distinct foci-like respective wild-types after DNA damage induced by the said agents and co-localize with α-H2AX. However, in time course experiment, we observed that the foci of HRDC domain exist after 24 h of removal of the damaging agents, while the foci of full-length protein disappear completely. This indicates that the repair events are not completed by the presence of protein corresponding to only the HRDC domain. Consequently, cells overexpressing the HRDC domain fail to survive after DNA damage, as determined by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2 H-tetrazolium bromide] assay. Moreover, 24 h after removal of damaging agents, the extent of DNA damage is greater in cells overexpressing HRDC domain compared with corresponding wild-types, as observed by comet assay. Thus, our observations suggest that HRDC domain of both WRN and BLM can also recognize different types of DNA damages, but for the successful repair they fail to respond to subsequent repair events. [ABSTRACT FROM AUTHOR]

Background Knowledge about human cyclic fasting motility (MMC) and the postprandial response is mostly based on manometric findings in the upper small intestine. Hardly any data exist on human ileal motility, as the acquisition of data has been limited by methodological concerns. The aim was to study human jejunal and ileal motility in an optimized manometric setting. Methods Solid-state 24-h-manometry was performed in the jejunum and ileum of healthy individuals, applying a strict protocol for fasting, resting, and the consumption of a standardized meal. Both visual qualitative and validated computerized quantitative contraction and propagation analysis were performed. Key Results MMC occurs in similar frequency in the jejunum and ileum, but it was significantly shorter in the jejunum at night. By many characteristics, ileal motility was less intense and propagative than jejunal: less migrating clustered contractions, and slower propagation velocity and shorter distance in phases II and III, and postprandially - possibly slowing and enhancing nutrient absorption. Prolonged propagated contractions in some individuals were identified as a unique ileal propulsive pattern. Postprandially, an abrupt conversion to a digestive motility pattern occurs simultaneously independent of the region. Conclusions & Inferences We found similar basic phenomena of fasting and postprandial motility in the jejunum and ileum of healthy humans. However, different calibration of propagative and contractile activity and special motor events in the ileum may account for a different physiological role in digestion. Future studies of small-bowel motility in healthy and diseased subjects focusing on segmental differences of proximal and distal intestine may be rewarded. [ABSTRACT FROM AUTHOR]

The material composite was fabricated by the unidirectional solidification method in the eutectic composition alloy. Performing unidirectional solidification of Ni-Al-Mo alloy in eutectic composition produces γ phase -Ni and γ′ phase-Ni3Al as a matrix, and the phase-Mo growth into fibrous and lamellar-like structure. The aim of this research was to study the characteristics of Ni-Al-Mo after various heat treatment conditions. The specimens were solution-treated at temperatures of 1180°C and 1280°C, followed by water quenching. In addition, aging treatments were carried out at various temperatures (from 700°C to 1000°C) and at different time durations. The microstructure, mechanical properties and characteristics of non-treated, solution-treated and aging specimens were investigated. It was found that the mechanical properties of unidirectional solidified Ni-Al-Mo can be improved by solution treatment whilst the strength through performing an aging treatment. The optimized conditions were at 1280°C and 4 hours for water quenching (solution treatment), followed by an aging process at 800°C and 4 hours. These treatments led to an increase of mechanical properties due to uniformly precipitations of finely dispersed γ′ phase-Ni3Al throughout the specimens. [ABSTRACT FROM AUTHOR]

Aim: The aim of this study was to evaluate the quality of the performance of everyday activities in children with spina bifida. Methods: Fifty children with spina bifida (of 65 children in a geographic cohort), aged 6 to14 years, were evaluated with Assessment of Motor and Process Skills. Results: Compared with age-normative values, 60% of the children with spina bifida were found to have motor ability measures below 2 SD and 48% process ability measures below 2 SD. Most of the children with spina bifida had difficulties performing well-known everyday activities in an effortless, efficient and independent way, relating to both motor and process skills. The motor skills hardest to accomplish involved motor planning and the process skills hardest to accomplish were adaptation of performance and initiations of new steps, thus actually getting the task done. Conclusion: To reach autonomy in life, children with spina bifida may need particular guidance to learn not only how to do things but also how to get things done. [ABSTRACT FROM AUTHOR]

Abstract: To understand physiological roles of tissue mast cells, we established a culture system where bone marrow-derived immature mast cells differentiate into the connective tissue-type mast cell (CTMC)-like cells through modifying the previous co-culture system with Swiss 3T3 fibroblasts. Our system was found to reproducibly mimic the differentiation of CTMCs on the basis of several criteria, such as granule maturation and sensitivity to cationic secretagogues. The gene expression profile obtained by the microarray analyses was found to reflect many aspects of the differentiation. Our system is thus helpful to gain deeper insights into terminal differentiation of CTMCs. [Copyright &y& Elsevier]

Abstract The effects of enteric nerve stimuli were investigated on spontaneously occurring colonic migrating motor complexes (CMMCs) in isolated mouse colon. Changes in circular smooth muscle tension were recorded simultaneously from the proximal, mid and distal regions of an in vitro preparation of whole mouse colon at 36 ± 1 °C. The CMMCs were recorded from all preparations with a mean interval between contractions ranging from 135.2 ± 9.3 to 163.3 ± 22.4 s. The CMMCs migrated spontaneously from the proximal to distal colon and were abolished by tetrodotoxin (1 μ mol L-1 ). In approximately half of all trials (57 of 103, n = 31), trains of stimuli (20 Hz, 2–5 s, 1 ms, 40–70 V) delivered to the mid or distal regions of colon, during the intervals between CMMCs, elicited a premature CMMC. However, similar trains of stimuli delivered to the proximal colon were without similar effects (33 trials, n = 13). It is suggested that in isolated whole mouse colon, CMMCs can be evoked prematurely by trains of electrical stimuli applied to the enteric nerves. The observation that nerve stimuli failed to evoke a premature CMMC from the proximal colon suggests that selective activation of functional ascending pathways may be required to initiate a premature CMMC. [ABSTRACT FROM AUTHOR]

Quantitative analysis of myoelectric activity (EMG), to investigate small intestinal motility in rats, is normally based on manual classification into sequences of phase I, phase II and phase III. This classification is partly subjective. We aimed to develop a more objective method for the analysis of the migrating myoelectric complex (MMC). From the EMG, a derived signal is calculated as a measure of activity. Depending on the level of this derived signal, the EMG is classified into `quiescent phase', `irregular phase' or `activity front'. The threshold levels for these phases are automatically calculated from the EMG data. A proposal for subdivision into MMCs is automatically generated. To calculate MMC length, the user must manually reject nonpropagated activity fronts. While developing the method, more than 19 derived signals were tested. These included variants of spike frequency, signal power and spike-burst length. The spike frequency signal was chosen because it gave minimal deviation from manual classification. Using the new automated method, recordings from the jejunum of 15 healthy rats were analysed (6 h each). The calculated phase lengths were consistent with the results of manual analysis. The presented method allows objective analysis of the interdigestive EMG signals of the small intestine. [ABSTRACT FROM AUTHOR]

Reversal of a distal intestinal loop is a surgical therapy intended to cure rapid intestinal transit in short bowel syndrome. To be active, a reversed loop must present a retrograde propagation of electromyographic patterns and must not be so long as to cause total obstruction. The aim of the current study was to propose methods to calculate the minimal length of the intestinal reversed loop taking into consideration the two previous conditions. Intestinal electromyograms were recorded in 65 rats at short-term (4 days after surgery) and ten rats at long-term (50 days after surgery). Control rats demonstrated that the preprandial regular spiking activity (RSA) of the migrating myoelectrical complex (MMC) extended simultaneously a definite part of the intestine which corresponds to the minimal length to reverse. A similar result can be obtained from a trigonometric representation. Whatever the method, the minimal lengths allowing the recording of RSA decreased along the rat intestine from 6 cm (proximal jejunum) to 4 cm (distal ileum). The experiments demonstrated that shorter loops did not present the preprandial RSA. In conclusion, the minimal reversed length depends on intestinal electromyographic parameters and, thereby, on the intestinal level. [ABSTRACT FROM AUTHOR]

We have investigated the effect of 5-hydroxytryptamine (5-HT) and different 5-HT-receptor antagonists and atropine on the migrating myoelectric complex in the rat small intestine. Infusion of 5-HT dose-dependently shortened the interval between phase III of the migrating myoelectric complex (MMC). In untreated animals the interval in upper jejunum was 19.1 (16.0–22.1) min. At doses of 10 and 20 nmol kg–1 min–1, the interval decreased to 15.2 (12.0–18.4) and 10.2 (9.4–11.0) min, respectively. The 5-HT3-receptor antagonist ondansetron (0.5 mg kg–1) alone increased the MMC interval from 20.8 (15.1–26.5) to 33.9 (19.4–48.4) min. Neither methiothepin (0.5 mg kg–1) nor ketanserin (0.5 mg kg–1), selective for 5-HT15-HT2-and 5-HT2-receptors, respectively, changed the MMC interval. The 5-HT4-receptor antagonist GR 113808 (0.5 mg kg–1) disrupted the MMC and induced irregular spiking activity. Ondansetron and atropine antagonized the 5-HT-induced shortening of the MMC interval. Neither methiothepin nor ketanserin affected the response to 5-HT. GR 113808 did not block the response to 5-HT in half of the animals; however, in the remaining ones MMC was disrupted and irregular spiking induced. In conclusion, these results show that 5-HT dose-dependently stimulates the cycling of the MMC in the small intestine via 5-HT3-receptors and a cholinergic final pathway. Our findings encourage further studies on the role of the 5-HT3-receptor in the control of gastrointestinal motility. [ABSTRACT FROM AUTHOR]

The micromechanical fracture behaviour of C/Mg–Al composites of varying interface reactivity was investigated by scanning electron microscope bending tests. Structure and chemistry of fibre/matrix interlayers were studied down to the atomic scale by imaging and spectroscopical transmission electron microscope techniques (high-resolution electron microscopy, energy dispersive X-ray spectroscopy, parallel-recording electron energy loss spectroscopy and energy-filtered transmission electron microscopy). The chemical reactions at the fibre/matrix interfaces of the C/Mg–Al composites were found to form plate-shaped carbidic precipitates, mainly Al2MgC2, which strongly influence the composite's mechanical properties by changing the fibre/matrix bonding strength. [ABSTRACT FROM AUTHOR]

Forming processes such as rolling or forging require detailed knowledge of the flow of the stress and deformation behavior at hot working conditions. Therefore, the deformation behavior of 16‐7‐6 CrMnNi TRIP steel with 30 vol% MgPSZ composite is studied by hot‐compression tests at a strain rate of 1 s−1. And highly particle reinforced TRIP‐Matrix‐Composite in a temperature range between 700 and 1200 °C show obvious changes in the flow curve behavior. At 700 °C, a step like shape with plateaus is clearly pronounced. With increasing temperature, this effect is not observed but the flow curves are shifted to lower stresses. Furthermore, dynamic recrystallization is observed above 800 °C deformation temperature. To identify the deformation mechanisms as well as the failure mechanisms, the microstructure evolution is studied at 700 °C for different strain values. The microstructure is investigated using light‐optical and secondary electron microscopy (SEM). Local damage by particle fracture and void formation around particles is evident during deformation. Remarkably, the ceramic particles reorient with increasing strain to form a certain banding and therefore a structural anisotropy. [ABSTRACT FROM AUTHOR]