bluuebunny/crossref_metadata_2025 huggingface dataset:
Microgrid tie‐line power fluctuation mitigation with virtual energy storage
Authors: Sun Yushu , Tang Xisheng , Sun Xiaozhe , Jia Dongqiang , Zhang Guowei
Published: October 2018

There is a large amount of controllable loads in the microgrid. They can be described as virtual energy storage to participate in microgrid tie‐line power fluctuation mitigation. Firstly, in order to meet the grid‐connected requirement, the wavelet packet decomposition algorithm is used to smooth the tie‐line power fluctuation. Furthermore, in order to prevent overcharge and overdischarge of battery or virtual energy storage, the power allocation between two types of energy storage is implemented equally based on the concept of energy. In addition, the fuzzy control strategy is applied to revise virtual energy storage power based on its SOC (i.e. state‐of‐charge), so that virtual energy storage can operate within a reasonable work range. Finally, an example is given to verify the effectiveness of the control strategy.
Comparison of the characteristics of three kinds of HVDC systems with ABB, SIMENS, and Cigre Benchmark
Authors: Jian Zou , Hua Huang , Yong Cui , Minjie Jin , Danzhen Gu , Mingrui Dong , Jian Zeng
Published: October 2018

This study presents the comparison among three control systems: Cigre Benchmark model, ABB model, and SIMENS model based on PSCAD. Firstly, the control systems which refer to Cigre Benchmark control model, ABB control model, and SIMENS control model are introduced, respectively. Analysis and comparison are done on these control systems about their design theories, control logic, and functional models, and the advantages and disadvantages of each control system are concluded. Secondly, simulations in both normal and fault conditions are done in order to verify the conclusions. On the one hand, the steady‐state response characteristics of these three high‐voltage direct current (HVDC) models are obtained and compared by setting different voltage of the receiving terminal AC bus. On the other hand, the transient response characteristics of these three HVDC models under different operating conditions are obtained, such as symmetrical and asymmetrical short‐circuit fault, line switching on or off etc. The research results will provide experiences and references for the future optimisation of the HVDC control system.
Analysis on SSR frequency components by studying two‐dimensional modulation of synchronous generator's flux linkage
Authors: Li Juan , Yuan Xiaoming , Zhang Meiqing , Liu Zhihao
Published: October 2018

As China's AC transmission system with series capacitor and HVDC transmission technology are widely used in long‐distance and large‐scale power transmission network, sub‐synchronous resonance (SSR) problem becomes more prominent. This paper studied induction generator effect (IGE) and torsional interaction (TI) of synchronous generator by focusing on amplitude and frequency modulation of synchronous generator's flux linkage. IGE involves only electric system dynamics, which will only cause amplitude modulation of flux linkage, resulting in one or two frequency component added in stator current of non‐salient pole synchronous generator (NPSG) or salient pole synchronous generator (SPSG) respectively. TI involves both electric and mechanical system dynamics, which will cause both amplitude and frequency modulation of flux linkage, resulting in multiple sub and super‐synchronous frequency components added in stator current by means of Bessel function. This result will provide a new reference to understand the SSR phenomena containing multiple frequency components in practical power system. The IEEE first benchmark model is used to demonstrate the accuracy of the analysis results.
Single‐phase grouding fault analysis and control scheme of transformerless flexible multistate switch
Authors: Xu Feng , Lu Yi , Xuan Xiaohua , Yu Haihong , Qiu Peng , Jiang Daozhuo
Published: October 2018

The compact design is suitable for the urban areas with intensive loads. The flexible multistate switch (FMS) can effectively reduce the footprint by removing transformers, which is the development trend of the flexible AC distribution equipment. In PSCAD/EMTDC, a simulation model containing two supply areas embedded in a transformerless FMS is built. Through the single‐phase grounding fault simulation under the arc suppression coil grounding, the characteristics of zero‐sequence component of FMS are analysed. By means of circuit analysis and sequence component decomposition, the intrinsic mechanism of AC/DC voltage fluctuation in the non‐fault supply area caused by the zero‐sequence component at the fault area is analysed, and the simulation result is explained. Based on the feeder transformation, a new protection and control scheme is proposed to overcome the problem of the zero‐sequence ride through among different supply areas.
Application of emergency control of central air conditioning in safe and stable operation of large power grid
Authors: Liu Meng , Guo Qiwei , Zhang Guohui , Su Jianjun
Published: October 2018

Air conditioning is a load with thermal inertia, and short time control will not cause an obvious negative impact on user power consumption. Compared with the traditional mini‐split‐type air conditioner, it has the advantages of flexible control method, strong controllability, large power of the monomer, and so on. This paper studies the application potential of emergency control of central air conditioning in safe and stable operation of large power grid. Firstly, the working principle of central air conditioner and the model of central air conditioning are introduced. On this basis, the emergency control strategy of central air conditioning is put forward. Furthermore, the control strategy of central air conditioning response control signal of safety and stability control or frequency deviation signal is put forward. Finally, a practical engineering case is given to illustrate the feasibility of the proposed strategy and its application in a large power grid.
Coordinated control of independent DC micro‐grid based on fuzzy‐PI algorithm
Authors: Cheng Zhi Ping , Xu Ya Li , Zhang Han Nian , Gao Jin Feng
Published: October 2018

The study on the stability of DC bus voltage is one of the key issues for researching independent DC microgrid. This paper has studied the independent DC microgrid with photovoltaic and energy‐storage systems. The variable step incremental conductance method was taken to realise maximum power point tracking (MPPT). The self‐adaptive Fuzzy‐PI controller was designed to optimise the traditional double closed‐loop control strategy. The energy management system was built to achieve coordinated control of the independent DC microgrid. The simulation results show that the improved strategy can get better robustness and system performance comparing with the traditional PI method.
Influence of the wind turbine blade model on echo's Doppler characteristics
Authors: Tang Bo , Hao Bin , Huang Li , Yang Jiawei
Published: October 2018

Wind turbines have serious electromagnetic interference to nearby radar stations. Accurately obtaining the Doppler characteristics of wind turbine's radar echo is the key technology and precondition to solve this problem. Based on the point scattering model of the wind turbines, the expression of the echo of the wind turbine blade scattering point model which is located at any point in the space is given, and the Doppler characteristic of the wind turbine blade echo is analysed by combining the existing integral model, which proves that the existing integral model is a special case of the scattering point model. Based on the radar resolution and Rayleigh resolution criteria, the scattering point spacing of the wind turbine blade is given. The simulation model is established according to the actual size of the wind turbines. After the analysis and comparison of the scattering point model and the integral wind turbine blade model, the simulation results of the wind turbine radar Doppler results are consistent with the theoretical analysis, which is of great significance to obtain the Doppler characteristics of the wind turbine blades.
Analysis of resonant characteristics of Yunnan power grid under different operating modes of AC/DC hybrid systems
Authors: Helin Liu , Jun Wen , Shiyou Yu , Jiaqi Li
Published: October 2018

Resonance or harmonic amplification occurs when the frequency of the harmonics generated by the converter station is near the inherent resonance frequency of the substation. Considering there are six DC projects in the Yunnan power grid, analysing the resonant characteristics of the grid is imperative for safety reasons. This study establishes a simulation platform of the Yunnan power grid based on the Power System Analysis Software Package and formulates the modelling principles and simulation steps. In order to successfully analyse the resonant characteristics of a substation under normal operation mode and put forward any necessary suggestions, the impedance frequency of all 500 kV substations in the power grid are scanned. This is followed by studying, the influence of different operation modes of Yunnan power grid and different operation modes of DC system of Luxi converter station on the resonant characteristics of Yunnan substation. Based on these results, effective measures for resonance suppression are proposed.
Harmonic analysis of AC‐bus voltage in converter station based on time–frequency transformation
Authors: Dandan Zhao , Hua Huang , Junhua Liu , Wenbin Zhao , Heng Jin , Jiamin Zhang , Huawei Huang
Published: October 2018

The disturbance of the AC system has become one of the main causes of commutation failure in the high voltage direct current (HVDC) transmission system. Here, the time–frequency transformation method is used to analyse the AC‐bus voltage disturbance from the perspective of the harmonic content of the AC power network. The time–frequency transformation for AC‐bus voltage disturbance is difficult due to its characteristics of time variability and time fixity. With comparative analysis of various transformation methods, the method of combining the wavelet packet transform with the short‐time Fourier transform can meet the requirement of time–frequency analysis of the AC voltage disturbance very well, and this method was used to analyse the fault recording data of Fengjing Convert Station when commutation failure occurred in recent years. The result shows that the AC‐bus voltage mainly contained third and fifth harmonics, and there was a certain amount of even harmonics, and the low‐order harmonics would be more in the case of a remote fault. In addition, there were more harmonics in the voltage when faults occurred in the 500 kV system, while there were more low‐order harmonics when faults occurred in the other voltage class systems.
Characteristics of commutation failure based on fault recording
Authors: Zheng Han , Jingkai Zhu , Jian Zou , Jia Chen , Hua Huang , Heng Jin , Dan‐dan Zhao
Published: October 2018

Commutation failure of the high‐voltage direct current (HVDC) transmission system is common fault in a converter station. The fault recording in one converter station when commutation failure caused by the disturbance of the AC system was collected, and the turn‐off angle of valves, zero‐crossing offset, and landing amplitude of bus voltage were calculated and statistically analysed. The results suggested that, in the case of commutation failure, the turn‐off angle of the 82% of cases was <8°, and there were a few cases whose turn‐off angle was very nearly the same as that in normal operation. The number of cases whose zero‐crossing offset was <10° accounted for 95% of the total, and the zero‐crossing offset of the AC bus line voltage generally presented a positive correlation with the reverse cut‐off time of the valves. The landing amplitude of the AC bus voltage before the time point for commutation failure analysis fall within 10% for >90% cases, and the average was ∼4.6%. The number of cases, whose zero sequence voltage peaks was <50 kV, accounted for 97% of the total. The results will provide basic data for analysing the main influencing factors of commutation failure and setting up countermeasures for the HVDC system.
Online dynamic voltage stability assessment method of AC/DC power systems
Authors: Wang Yongbo , Li Kuan , Zhang Guohui , Su Jianjun , Xie Jiping , Li Jialu
Published: October 2018

The reactive power absorption of conventional line commutated converter–high‐voltage direct current transmission systems challenges on the voltage stability of AC/DC power systems. Many online dynamic voltage stability assessment approaches have been put forward to AC power systems, but the impact of DC transmissions is seldom taken into account for AC/DC power systems. In this study, an online dynamic voltage stability assessment method of AC/DC power systems is proposed. The proposed method models the converter as an equivalent AC voltage source in series with the internal impedance by utilising the control mode model of DC transmission systems and the measured data of the converter bus. The equivalent AC voltage source can identify the dynamic of DC transmissions. Then the AC/DC power system can be modelled by the equivalent AC power system. Based on the nodal equivalent method, the proposed method establishes a voltage stability index of the equivalent AC power systems for the dynamic voltage stability assessment of AC/DC power systems. The simulation demonstrated the effectiveness of the proposed method.
Commutation failure caused by AC filter switching In HVDC system
Authors: Liu Meng , Zheng Lei , Shi Fangfang , Li Kuan
Published: October 2018

Switching AC filter may cause harmonic impact, which may lead to commutation failure of HVDC system. Here, the commutation failure mechanism of HVDC system caused by AC filter switching is studied. The circuit and mathematical model of the transient process simulation of filter switching are established, and the time‐domain solution of the overvoltage of each filter including voltage reduction and distortion is given. The commutation failure mechanism of HVDC system is analysed based on the commutation failure analysis method of harmonic voltage and time area. The simulation results verify the effectiveness of the mechanism analysis of commutation failure caused by AC filter switching in HVDC system.
Frequency deviation peak calculation of sending‐end network in large asynchronous interconnected power grid
Authors: Sheng Wei , Xu Zheng , Guo Xiangyang
Published: October 2018

The asynchronous connection by high‐voltage direct current (HVDC) links optimises the power angle stability of the large area power grid. However on the side of the sending‐end, the loss of DC links causes high frequency, of which the frequency deviation peak is an important index in the study of the power grid frequency stability. In this study, the method to calculate the peak value of frequency deviation based on the change rate of the frequency deviation is obtained by analysing a single‐machine system. Then, the application of method is extended to the actual power system to study HVDC additional control and generator tripping. Finally, the single‐machine power grid and Yunnan Power Grid are simulated, respectively, to verify the accuracy and the feasibility of the method. The simulation results show that the method is accurate and applicable to the actual power grid, which has practical value of engineering.
Review of the DC voltage coordinated control strategies for multi‐terminal VSC‐MVDC distribution network
Authors: Simiyu Patrobers , Xin Ai , Bitew Girmaw T. , Shahzad Muhammad , Kunyu Wang , Tuan Luu K.
Published: October 2018

The multi‐terminal voltage sourced converter medium‐voltage DC (VSC‐MVDC) distribution network has high prospects for future development, hence the proposed alternative for the AC distribution in commercial and industrial applications. However, a number of obstacles stand on its way in realising its immense potential in the modern power system. This study presents a review and focuses on the complexity of controlling DC voltage/power flow in the multi‐terminal DC (MTDC) grids and the possible DC voltage coordinated control approaches aimed at identifying the suitable control strategies for the proposed MVDC distribution grids. Several centralised and distributed DC voltage control strategies for MTDC have been considered. In conclusion, the droop‐based control strategies have been identified as reliable, flexible, and expandable with high dynamic performance and minimal communication needs in MTDC grids. These strategies are suitable and adaptable for stable and secure operation of the proposed multi‐terminal MVDC distribution network. The study recommends a comparative study of the key DC voltage coordination control features of the droop‐based control strategies using the multi‐terminal VSC‐MVDC distribution network dynamic model for future studies.
Engineering practice of large‐scale millisecond accurate load control system of large power grid
Authors: Haoming Hu , Qian Zhou , Ningyu Zhang , Peng Wei , Zhanfei Cui
Published: October 2018

Under the background of large‐scale development and utilization of clean energy, there are serious security and stability risks and load balance problems in power grids with high penetration of clean energy and high portion of external power supply. Therefore, Jiangsu Electric Power Company has started the construction of the millisecond accurate load control system (MALCS). In this article, the theoretical basis of the MALCS is introduced from several aspects: the interruptible load, steady state, and transient state control technique of large‐scale load. On this basis, the authors put forward the overall architecture, transmission channel structure, and control strategy of the MALCS. Subsequently, this article introduces the first‐phase and the second‐phase projects of MALCS construction in Jiangsu power grid, and the actual load‐shedding test of Jiangsu MALCS. The results of the actual test show that the overall motion time of the Jiangsu MALCS meets the design requirements, and the MALCS can offer an effective frequency support to Jiangsu and East China Power Grid in case of severe failures. Finally, this article summarises the experience of MALCS construction, introduces the expansion plan of MALCS, and forecasts the future development direction and application of the system.
Modelling and analysis of the UHVDC transmission receiving system considering 300 Mvar novel synchronous condenser
Authors: Ma Yiming , Ruan Ling , Xiao Yang , Zhou Libing , Wang Jin , Tao Qian
Published: October 2018

This study presents an analytical modelling method of the ultra‐high voltage direct current (UHVDC) receiving system including converter station, AC power grid, novel synchronous condenser, and wind turbine. A detailed model of UHVDC receiving converter station, considering the novel synchronous condenser system, is proposed. A simplified model of wind farm is established to consider the influence of renewable generation plant near to converter station. Based on the proposed model, the characteristics of novel synchronous condenser is studied in different dynamic condition of power grid, like AC voltage drop and DC bipolar blocking. A numerical simulation model by Simulink® is applied to validate the presented analytical model.
Analysis of the influence of dynamic components of AC/DC system on transient voltage stability based on energy function method
Authors: Zhang Wenqian , Du Zhaobin , Huang Changshu , Xia Chengjun , Zhang Yao
Published: October 2018

With the interconnection of large power networks, transient voltage stability of AC/DC power systems has been paid more attention in recent years. To investigate main influence of generating facility, high‐voltage direct current (HVDC) and motor load for transient voltage stability, from the perspective of the generalised branch potential energy, the new indexes, and analysis method is proposed here. First, an energy function for AC/DC system is constructed with major dynamic components, namely classical HVDC control systems and motors in third‐order model. Accordingly, the influence effects of the above major dynamic elements are investigated based on indexes from the corresponding generalised branch potential energy. With the rule of change in transient potential energy distribution in the network and information in stability margins, an evaluating procedure is established. Here, the judgment of transient voltage stability employs a heuristic energy function method. Finally, simulation tests on three‐machine system with a HVDC transmission line are conducted in PSAT package, and the obtained results demonstrate the feasibility and effectiveness of the proposed method.
Field measurement and verification of the UHF calibration platform based on the GTEM cell
Authors: Yi‐fan Wang , Jin‐long Gong , Jian‐ling Jiang , Zhi‐guo Tang , Fei Wang
Published: October 2018

The measurable electric field of the partial discharge ultra‐high‐frequency (PD UHF) detection system calibrated by a gigahertz transverse electromagnetic cell (GTEM) has been used as a key indicator to evaluate the performance of the detection system and regarded as the electric power standard. In this study, the sweep frequency and pulse signal were injected to the GTEM cell, and then the waveform and amplitude of the calibrated field strength were calculated by using the transfer function and voltage response of the monopole antennas. In the case of sweep frequency, comparing the measured result of the Narda field strength metre and the calculated result of monopole antennas, the error was found to be <8%, which verifies the correctness of the calibration of the monopole antennas to the steady‐state electric field in the GTEM. In the case of pulse injection, comparing the simulation result of computer simulation technology and the calculated result of monopole antennas, the error of the peak of the field strength was found to be 1.7%, which verifies the correctness of the calibration of the monopole antennas to the pulse electric field in the GTEM.
Paramount importance of using distributed extra‐low direct current voltage in the built environment
Authors: Kinn Moshe C.
Published: October 2018

If solar panels and wind turbines can generate direct current (dc) voltage, and all electrical and electronic loads can operate directly off dc voltage, why is the distribution network within the built environment an alternating current (ac) system? In a world where carbon footprint is in focus, why are systems dc–ac–dc and not dc–dc–dc? Historically, voltage drop and therefore the need for larger gauge wiring were seen as technical and economic barriers to extra‐low dc voltage systems. However, prices and power needs have lowered, it is now technically and economically feasible to use dc systems for the built environment. Such systems can provide energy independence and energy security. Examples of niche usage of solar photovoltaics that are providing electricity in the developing world are used to show that distributed dc voltage can have direct positive impacts on many of the UNs, sustainability development goals. Given the advantages of distributed dc electricity systems over centralised ac systems, it is concluded that policy makers and NGOs have to take on board dc as a sustainable solution to help the billions of people that either are not connected to electricity or use fossil fuels that are adversely effecting there health.
Documentation of multiple species of marine fish trapped in Atlantic salmon sea-cages in Norway
Authors: Fjelldal Per Gunnar , Solberg Monica F. , Glover Kevin A. , Folkedal Ole , Nilsson Jonatan , Finn Roderick Nigel , Hansen Tom Johnny
Published: October 2018

The production of salmonids in sea-cages has been developed for monoculture of the target species. However, we show here for the first time, that wild fish may enter sea-cages used for farming of Atlantic salmon (Salmo salar L.) in Norway, out-grow the mesh size, and thereafter become permanently trapped. Within seven different sea-cages located in western Norway, eight different species of wild fish were identified; European eel (Anguilla anguilla), sea trout (Salmo trutta L.), cod (Gadus morhua), haddock (Melanogrammus aeglefinus), saithe (Pollachius virens), pollack (Pollachius pollachius), hake (Merluccius merluccius) and whiting (Merlangius merlangus). In the two most extreme cases, a 5 × 5 × 7 m cage with 311 farmed salmon (903 g) also contained 542 whiting (79 g), 77 haddock (43 g), and 5 cod (26 g), and a 12 × 12 × 15 m cage with 1695 farmed salmon (559 g) also contained 1196 haddock (35 g), 1115 whiting (31 g), 46 cod (23 g), 23 saithe (48 g), 15 pollock (22 g), 5 sea trout (54 g), and 2 hake (29 g). The present study thus demonstrates that aquaculture cages designed for monoculture may attract and effectively ‘trap’ wild fish. We did not investigate the frequency of this occurrence, and the ecological significance of these observations remains unclear. However, with the ever-increasing number of sea-cages used for global aquaculture, this is clearly a topic for further research.
Optimal Sizing of Hybrid Energy Storage System Taking into Account Economic Factors and Power Allocation
Authors: Pang Ming , Shi Yikai , Wang Wendong , Pang Shun
Published: October 2018

The sizing of hybrid energy storage system (HESS) for smoothing wind power fluctuations was studied in this paper. The goal of the proposed method is to find the optimal sizing of the battery and supercapacitor, and its meet the constraints of the power ramp rate constraint and the economic cost. Therefore, a power allocation strategy which based on the operating period of battery and the cutoff frequency of battery absorption power was proposed. The sizing optimization model, which considered the cost structure of HESS, the ESS characteristics and cycle life in different operating modes, is established by using minimum daily cost as objective function. The results of numerical example shows that the cycle life of ESS can be effectively extended with reasonable operating period of battery and the cutoff frequency of battery absorption power, the cost of HESS can be reduced.
Optimization of Process Parameters for Robotic Fibre Placement
Authors: Zhao Pan , Shi Yaoyao , Kang Chao , Yu Tao , Deng Bo , Zhang Hongji , Chen Zhen
Published: October 2018

Compared with labour-intensive and time-consuming processing of conventional fabrication methods, the robotic fiber placement process greatly improves the flexibility of the fiber placement process and allows for the construction of more complex structures. Based on the study of the placement process, the intimate contact process and healing process were analysed theoretically. The key process parameters for affecting the quality of the composite component were put forward:hot gas torch temperature, compaction force and laying velocity. In order to analyse the fabrication process for laying the cylindrical parts with 0-degree tow direction, the model of the process parameters coupling affected the interlaminar bond strength was established, according to the design of the response surface method. The reliability and validity of the model were verified by the analysis of variance. The optimal process parameters of fiber placement were obtained. The results show that the model is effective and the optimum peeling force of the laying products is 24.1 N under the optimum process parameters.
Modeling Cantilever Branch Structure of Aero-Engine Power Turbine and Analyzing Its Influence
Authors: Xia Yebao , Ren Xingmin , Yang Yongfeng
Published: October 2018

In the power turbine component of an aero-engine, there exists a unique cantilever branch structure, on which turbine disks are mounted. Due to the cantilever's characteristics, this structure exhibits a vibration of large amplitude; thus its characteristics need to be studied in detail.In this paper, the motion equations combining the structure and the shaft were deduced; then its vibration mode was given, and the criticl speed was computed; finally the unbalance response of an integrated rotor system was simulated.The calculation results are compared with the simulation results without considering the branch structure.Some key parameters' influences are studied thoroughly, e.g., the branch shaft's length, the flange's offset and the installation orientation. As the results show, the branch structure has a large influence on the vibration mode and critical speed of the rotor system, thus it should not be simplified and ignored in modelling; After adjusting the branch structure's parameters, the characteristics of a vibration mode do not change, and the effects of branch structural parameters on critical speed are closely related to the corresponding vibration mode; the bending stiffness and the critical speed of the rotor system both decreased with increasing branch shaft's length; if reducing the flange's offset and fabricating the branch structure reversely, a sharp increase in the unbalance response of the turbine disc will occur. In conclusion, the dynamical characteristics of the integrated rotor system can be optimized through reasonably designing the branch structure.
Research of Image Retrieval Method Based on Improved Feature
Authors: Qiao Honghai , Deng Zhenghong , Xue Jing , Song Qun
Published: October 2018

In the process of image retrieval, the traditional single feature can't reflect the distribution and details of image color and content, which have some adverse influence on the performance of image retrieval. This paper presents an image retrieval method based on improved color and texture feature. According to the mean of the HSV color model region, algorithm obtains the mean eigenvectors of the color feature by using the improved correlation weight model. The image decomposition transformation is obtained through the Haar wavelet. In the low-frequency component of the image decomposition, the low-frequency texture feature vector is obtained according to the low-frequency feature structure model. The similarity of image is calculated by the Canberra distance. Experimental results show that:the methods of retrieval are tested in Corel-1000 and Corel-5000 standard gallery, which accuracy rate and retrieval rate have been improved accordingly.
Mayfly (Ephemeroptera) assemblages of a Pannonian lowland mountain, with first records of the parasite Symbiocladius rhithrogenae (Zavrel, 1924) (Diptera: Chironomidae)
Authors: Vilenica Marina , Ergović Viktorija , Mihaljević Zlatko
Published: October 2018

Despite increasing numbers of studies on aquatic insects in South-East European streams, there are still gaps in the knowledge about their distribution and assemblage composition in many regions. As one of the most abundant and sensitive aquatic insects, mayflies are widely used as bioindicator taxa. With the main goal of improving the knowledge of South-East European mayflies, a study was conducted of 15 streams along a Pannonian lowland mountain, in spring and summer 2017. A total of 18 mayfly taxa were recorded, where Ephemera danica Müller, 1764 and Baetis rhodani (Pictet, 1843) were the most widespread. All sites were characterized with the domination of rhithral elements, with similar shares of grazers/scrapers and detritivores. Nevertheless, sites at lower altitudes generally had a higher share of potamal and littoral elements, and a higher share of detritivores than at higher altitudes. NMDS analysis separated sites mainly based on sampling period. Although Heptageniidae nymphs were recorded in all streams, the parasitic chironomid Symbiocladius rhithrogenae (Zavrel, 1924) was recorded attached to three nymphs of Rhithrogena group semicolorata, each in a different stream. These records represent the first report of this species for Croatia. The current study contributes significantly to our knowledge of mayfly assemblages and species distribution in South-East Europe. Moreover, with a newly recorded species, this study indicates that the knowledge of the Croatian chironomid fauna is still growing.
Fragmentation de Marangoni : les gouttes qui s’éclatent
Authors: Keiser Ludovic , Bense Hadrien , Sturtz Cyril , Colinet Pierre , Roman Benoît , Bico José , Reyssat Étienne
Published: October 2018

Une goutte d'eau déposée à la surface d'un bain d'huile de tournesol forme une lentille liquide flottante. Une goutte d'alcool, au contraire, s'étale à la surface de l'huile. Un mélange d'eau et d'alcool produit un spectaculaire phénomène d'étalement et de fragmentation spontanée.

Si la goutte contient suffisamment d'alcool, elle donne naissance en quelques secondes à une myriade de gouttelettes dont la taille dépend fortement de la composition initiale. La combinaison de l'hydrodynamique, du mouillage et de l'évaporation est à l'origine de cette instabilité originale.
Langzeitergebnisse des seroserös eingebetteten und getaperten Ileums als efferentes Segment verschiedener Harnableitungsreservoire („Fulda-Nippel“)
Authors: Stein Johannes , Müller Stefan C. , Hauser Stefan , Fechner Guido
Published: October 2018

Hintergrund Die Arbeitsgruppe um Kälble stellte 2008 das „Serosa lined and tapered ileum“ („Fulda-Nippel“) als neuen Kontinenzmechanismus des modifizierten MAINZ-Pouch-I vor. In Anlehnung an das Prinzip von Abol-Enein wird ein getapertes Ileumsegment in einen seroserösen Tunnel aus einem zweiten „U“-förmigen Ileumsegment eingebettet. Bei dieser Technik werden Kontinenzmechanismus und Augmentation miteinander kombiniert. Sie kann in allen Pouchformen und auch als kontinente Vesikostomie genutzt werden.

Patienten und Methoden In der urologischen Klinik des Universitätsklinikums Bonn wurde diese Technik seit 2008 in bisher 21 Fällen bei unterschiedlichen Indikationen verwendet. In der ersten Analyse von 2011 konnte der Nippel bereits durch geringe Frühkomplikationsraten überzeugen. Ziel dieser Studie ist die Re-Evaluation der Technik insbesondere im Hinblick auf Stenose- und Inkontinenzraten im Langzeitverlauf.

Ergebnisse Bei einer mittleren Nachbeobachtungszeit von 37 Monaten traten Stomastenosen in 33 % der Fälle auf. Eine Inkontinenz des Nippels wurde bei 21 % (n = 4) der Patienten beobachtet. Bei zwei der Patienten war die Ursache der Inkontinenz das komplette Ausgleiten des Nippels aus der seroserösen Einbettung.

Schlussfolgerung In der Langzeitanalyse zeigen sich ähnliche Stenose- und Inkontinenzraten im Vergleich zu den zwei etabliertesten Techniken, dem Appendixnippel und dem Ileuminvaginationsnippel. Trotz Limitation aufgrund der kleinen Fallzahl ist der Fulda-Nippel zumindest als eine adäquate „Zweitlinientechnik“ bei Versagen der initialen Methode anzusehen. Als Vesikostomie bietet der Fulda-Nippel den Vorteil, Augmentation und Kontinenzmechanismus elegant miteinander zu vereinen und sollte hier auch als Primärtechnik Verwendung finden.
Ist die Verordnung von vergrößernden Sehhilfen anhand der Krankenakte möglich oder bedarf es einer Beratung in einer Sehbehindertenambulanz?
Authors: Engesser Diana , Engesser Raphael , Stifter Julia , Atzrodt Lisa , Böhringer Daniel , Reinhard Thomas
Published: October 2018

Hintergrund Viele Sehbehinderte und Blinde können mit vergrößernden Sehhilfen wieder Lesefähigkeit erreichen. Diese Hilfsmittel werden an der Klinik für Augenheilkunde in Freiburg in der Sehbehindertenambulanz im Rahmen einer zeitaufwendigen Sprechstunde erprobt und verordnet. Es stellt sich deshalb die Frage, ob die Auswahl und Verordnung der Sehhilfen auch automatisiert nach Aktenlage möglich ist.

Methoden Mittels Datenbankrecherche wurden zwischen 2001 und 2016 folgende Parameter aus den Arztbriefen der Sehbehindertenambulanz extrahiert: Diagnose, bestkorrigierte Sehschärfe, Vergrößerungsbedarf, verordnete Sehhilfe und Versorgungswunsch. Die Sehhilfenverordnungen (optische Lupen, elektronische Lupen und Bildschirmlesegeräte) wurden mittels statistischer Modelle vorhergesagt und mit den tatsächlichen Verordnungen verglichen.

Ergebnisse Die Datenbankrecherche erbrachte insgesamt 1203 Patienten. 64% waren weiblich, das mediane Lebensalter betrug 80 Jahre. Verordnet wurden 29% Bildschirmlesegeräte, 11% elektronische Lupen, 34% optische Lupen und 26% sonstige Hilfsmittel bzw. kein Hilfsmittel. Die Übereinstimmung zwischen statistisch vorhergesagter und tatsächlicher Sehhilfenverordnung betrug insgesamt nur 73%. Dabei erwies sich der Vergrößerungsbedarf als statistisch signifikantester Faktor.

Schlussfolgerungen Die Zuverlässigkeit einer automatisierten Verordnung von vergrößernden Sehhilfen nach Aktenlage ist für den klinischen Alltag nicht ausreichend. Deshalb ist eine individuelle und persönliche Beratung mit ausführlicher Erprobung von vergrößernden Sehhilfen in der Sprechstunde wichtig. Hinzu kommt, dass dort neben der reinen Hilfsmittelverordnung regelhaft auch eine psychosoziale Beratung erfolgt.
Indikationen für den Einsatz von Endoanchors: State of the Art
Authors: Oikonomou Kyriakos , Kasprzak Piotr , Schierling Wilma , Kopp Reinhard , Pfister Karin
Published: October 2018

Komplikationen während der Nachsorge, wie das Versagen der Abdichtung und Migration mit Endoleckage, sind die Achillesferse der endovaskulären abdominellen (EVAR) sowie thorakalen (TEVAR) Aneurysmareparatur. Anatomische Merkmale im Bereich der proximalen und distalen Landungszone einschließlich Thrombus, Verkalkung, Kinking und Halsdilatation können die Nachhaltigkeit einer endovaskulären Reparatur beeinträchtigen. Endoanchors wurden entwickelt, um die Sicherheit einer handgenähten Aortenanastomose nachzuahmen. Dieser Bericht gibt einen Überblick über die aktuelle Literatur zur Verwendung von Endoanchors bei EVAR und TEVAR. Zu den Indikationen für die Anwendung gehören die primäre Implantation zur Sicherung der proximalen oder distalen Landungszone im Falle einer „hostile“-Anatomie oder einer intraoperativen Typ-I-Endoleckage/suboptimalen Apposition an die Aortenwand sowie die sekundäre Anwendung zur Behandlung von Typ-I-Endoleckagen und Stentprothesenmigration häufig in Kombination mit einer proximalen oder distalen Verlängerung der Stentprothese. Abschließend werden die perioperativen Ergebnisse der ersten 100 Patienten analysiert, die mit TEVAR/EVAR und Endoanchors primär oder sekundär bei Re-Interventionen in unserer Abteilung behandelt wurden. In dem Zeitraum von März 2011 bis November 2015 wurden 100 Patienten (85 Männer; 15 Frauen) mit einem Durchschnittsalter von 70 ± 9,7 Jahren behandelt. 82 Anwendungen erfolgten in der abdominellen und 18 in der thorakalen Aorta. Die Implantation wurde während des primären EVAR-/TEVAR-Eingriffes in 80 Fällen durchgeführt (Gruppe A), 20 Patienten wurden sekundär behandelt (Gruppe B). Der technische Erfolg der Implantation betrug 100%. Der klinische Erfolg betrug 98%. Keine Endoanchors wurden verloren. Die perioperative Mortalität betrug 4%, die Morbidität 7%. Im Rahmen der 30-Tages-Kontrolle zeigten sich bei 8/96 überlebenden Patienten Endoleckagen. Bei 7/8 Patienten handelte es sich um Typ-II-Endoleckagen, lediglich ein Patient mit sekundärer, proximaler Verlängerung einer thorakalen Stentprothese zeigte eine persistierende Typ-I-Endoleckage.
Increased Oral Bioavailability of Piperine from an Optimized Piper nigrum Nanosuspension
Authors: Zafar Fatiqa , Jahan Nazish , Bhatti Haq ,   Khalil-Ur-Rahman
Published: October 2018

The aim of the present study was to enhance the pharmaceutical potential and oral bioavailability of piperine, which is the bioactive constituent of Piper nigrum, using the nanosuspension approach. Nanoprecipitation, which is a simple and reproducible process, was used for nanosuspension formulation. To prepare a pharmaceutical-grade nanosuspension with the required particle size, important formulation parameters (amount of plant extract, concentration of stabilizer, and antisolvent-to-solvent ratio) were optimized using the central composite design of response surface methodology. The optimized nanosuspension was characterized using scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, and in vitro dissolution testing as well as by measuring the zeta potential. In vivo pharmacokinetic studies were conducted to determine the bioavailability of the prepared nanosuspension. Results of the optimization study indicated that 0.13% plant extract, 0.25% stabilizer, and an antisolvent-to-solvent ratio of 10.0 were the best parameters to obtain a homogeneous nanosuspension with the required particle size. The optimized nanosuspension demonstrated a mean particle size, polydispersity index, and zeta potential of 172.5 nm, 0.241, and − 16.6 mV, respectively. The results of the characterization studies illustrated that the nanosuspension was in the nanometer size range and had good surface morphology. The optimized nanosuspension showed a better dissolution rate and a 3.65-fold higher oral bioavailability for the P. nigrum nanosuspension than its coarse suspension. The present outcomes clearly demonstrated that to obtain an effective therapeutic potential, nanoformulation of medicinal plants is a better alternative than conventional dosage forms.
A Straightforward Synthesis to Novel 1,10-Phenanthrolines with Fused Thiophene Structure
Authors: Bauer Matthias , Tünnermann Maike , Rehsies Pia , Flörke Ulrich
Published: October 2018

We report here a straightforward synthesis for a series of new structures with fused 1,10-phenanthroline-thiophene connection. They are synthesized with a modified Hinsberg thiophene procedure, followed by successive modification to yield several 5,7-disubstituted thieno[3,4-f][1,10]phenanthrolines, most notable thiophene-substituted compounds that could be potentially of use for organic electronics ­applications. For some selected examples, crystal structures were ­obtained, showing a nearly coplanar arrangement around the fused connection, also beneficial for an effective electron transfer in organic electronics or solar cells.
A Cascade Suzuki–Miyaura/Diels–Alder Protocol: Exploring the Bifunctional Utility of Vinyl Bpin
Authors: Cain David , McLaughlin Calum , Molloy John , Carpenter-Warren Cameron , Anderson Niall , Watson Allan
Published: October 2018

Cascade reactions are an important strategy in reaction ­design, allowing streamlining of chemical synthesis. Here we report a cascade Suzuki–Miyaura/Diels–Alder reaction, employing vinyl Bpin as a bifunctional reagent in two distinct roles: as an organoboron nucleo­phile for cross-coupling and as a Diels–Alder dienophile. Merging these two reactions enables a rapid and operationally simple synthesis of functionalized carbocycles in good yield. The effect of the organoboron subtype on Diels–Alder regioselectivity was investigated and postsynthetic modifications were carried out on a model substrate. The potential for a complementary Heck/Diels–Alder process was also assessed.
Laboratory D-dimer measurement: Improved agreement between methods through calibration
Authors: Woods Timothy , Kitchen Dianne , Kitchen Steve , Walker Isobel , Jennings Ian
Published: October 2018

Accurate and precise measurement of plasma D-dimer levels is important in the diagnosis and management of venous thromboembolism. Considerable variability in D-dimer results obtained using different methods has, however, been reported in multicentre studies. This study explored in two separate multicentre exercises the degree of precision amongst laboratory D-dimer measurements, and the degree by which inter-method agreement could be improved using a calibration curve model. The first exercise demonstrated generally good within-centre precision, with 82% of the centres reporting results for two identical but differently coded samples within 10% of each other. However, six centres reported results which would have excluded deep vein thrombosis (DVT) for one sample but failed to exclude DVT for the other, identical sample. In the second exercise, overall between-method precision of D-dimer results for two samples was shown to improve markedly when a calibration model was applied, using the consensus median values obtained by all participants for three “calibration plasmas” to recalculate D-dimer values. For centres reporting results in fibrinogen equivalent units (FEUs),between-centre coefficients of variation (CVs) fell from 25.9% to 11.6% and 22.4% to 7.7%, respectively, for the two samples. For centres reporting in ng/ml, CVs fell from 45.3–21.6% and 40.8–11.6%,respectively. In conclusion, improved harmonisation of D-dimer results by different methods may be achieved by a calibration model and common calibrant plasmas.
Radioiodtherapie beim differenzierten Schilddrüsenkarzinom
Authors: Eschner Wolfgang , Grünwald Frank , Lassmann Michael , Verburg Frederik , Luster Markus , Dietlein Markus
Published: October 2018

Die Verfahrensanweisung zur Radioiodtherapie beim differenzierten Schilddrüsenkarzinom (Version 4) wurde von einer repräsentativen Expertengruppe im informellen Konsens verabschiedet und entspricht damit einer Leitlinie der ersten Stufe (S1) nach den Kriterien der Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften (AWMF). Die Verfahrensanweisung ergänzt die S2-Leitlinie zur operativen Behandlung maligner Schilddrüsenerkrankungen um die nuklearmedizinischen Aspekte. Bezüglich der Indikationsstellung zur ablativen Radioiodtherapie beim kleinen papillären Schilddrüsenkarzinom und beim minimal invasiven follikulären Schilddrüsenkarzinom ohne Angioinvasion, bezüglich der empirischen Bemessung der 131I-Therapieaktivität sowie bezüglich der exogenen versus endogenen TSH-Stimulation bei der ablativen Radio-iodtherapie werden Handlungskorridore beschrieben. Der Text enthält die Auswertungen aus der National Cancer Database und der SEER-Database (jeweils USA), wonach die ablative Radioiodtherapie bereits in einer Niedrig-Risiko Konstellation die Überlebensrate verbessert. Der statistische Nachweis eines solchen Nutzens setzt ein nationales Krebsregister mit Langzeitdaten voraus.
The World Veterinary Orthopaedic Congress: “Synergy in Action”
Authors: Ehrhart Nicole , Kowaleski Mike , Van Ryssen Bernadette , Pozzi Antonio
Published: October 2018

Syn-er-gy (noun) –

the interaction of two elements that when combined produce a total effect that is greater than the sum of the individual elements; the working together of two things to produce a result greater than the sum of their individual effects.*
Systemic treatment of advanced differentiated and medullary thyroid cancer
Authors: Fassnacht M. , Mueller S. P. , Kreissl M. C.
Published: October 2018

In den vergangenen Jahren wurden drei neue Substanzen für die molekular gezielte Therapie des fortgeschrittenen und progredienten Schilddrüsenkarzinoms zugelassen: Vandetanib und Cabozantinib für das medulläre Schilddrüsenkarzinom sowie Sorafenib für das Radioiod-refraktäre differenzierte Schilddrüsenkarzinom. Die Selektion der Patienten durch ein interdisziplinäres Team sowie die Aufklärung der Patienten spielt eine wesentliche Rolle, wenn diese Behandlung in Betracht gezogen bzw. begonnen wird. Nur Patienten mit hoher Tumorlast und/oder symptomatischer bzw. progredienter Erkrankung, die lokalen Therapien nicht zugänglich ist, sollten behandelt werden. Um eine gute Lebensqualität zu erhalten, ist das Management der unerwünschten Arzneimittelwirkungen von größter Bedeutung. Aufgrund der Wirkweise der Tyrosinkinasehemmer ist der Verlauf der Tumormarker Calcitonin und Thyreoglobulin nur bedingt zur Beurteilung des Therapieansprechens und zum Follow-up geeignet, deshalb kommt der morphologischen und metabolischen Bildgebung besondere Bedeutung zu. Ein umschriebener oder geringer Progress sollte nicht unbedingt die Beendigung der Behandlung oder eine Therapieumstellung nach sich ziehen. In der nahen Zukunft werden weitere Substanzen verfügbar sein.