bluuebunny/crossref_metadata_2025 huggingface dataset:
Sediment Trapping and Carbon Sequestration in Floodplains of the Lower Atchafalaya Basin, LA: Allochthonous Versus Autochthonous Carbon Sources
Authors: Hupp Cliff R. , Kroes Daniel E. , Noe Gregory B. , Schenk Edward R. , Day Richard H.
Published: February 2019

Recent studies suggest that about 2 Pg of organic C is stored on floodplains worldwide. The present study indicates the Atchafalaya River, fifth largest river in the United States in terms of discharge, traps 30 mm/year of sediment on average within its floodplain, which is the highest average nonepisodic rate of fluvial deposition on the U.S. Coastal Plain. We installed sediment sampling stations at 23 sites, normally in transect, in the Atchafalaya Basin; these sites represent the range of hydrogeomorphic conditions on the floodplain based on hydrologic connectivity with the river main stem. The rate of sedimentation translates into about 12.5 Tg/year and includes 694 Mg/year of organic C. Highest sedimentation rates are associated with areas of high connectivity to channels and prograding deltaic processes. The δ13C content suggests that 35% of deposited C is derived from river‐suspended sediment compared to litterfall in the basin. Thus, much of the organic C sequestered is allochthonous material. However, isolated interior sites with limited connectivity to the channel may generate and sequester large amounts of autochthonous C. The substantial trapping of both autochthonous and allochthonous C (392 Mg/year) make this freshwater‐forested floodplain critical in storage of material before reaching the coastal delta and estuary. This C deposition rate (340 g C·m−2·yr−1) exceeds all other rates reported in recent Blue Carbon and Tidal Freshwater Forested Wetland studies. Atchafalaya C sequestration occurs in/near areas with tidal influence and like other coastal systems is an important site for trapping mineral and organic sediment and in global C cycling.
The Potential Hidden Age of Dissolved Organic Carbon Exported by Peatland Streams
Authors: Dean Joshua F. , Garnett Mark H. , Spyrakos Evangelos , Billett Michael F.
Published: February 2019

Radiocarbon (14C) is a key tracer for detecting the mobilization of previously stored terrestrial organic carbon (C) into aquatic systems. Old C (>1,000 years BP) may be “masked” by postbomb C (fixed from the atmosphere post‐1950 CE), potentially rendering bulk aquatic dissolved organic C (DOC) 14C measurements insensitive to old C. We collected DOC with a modern 14C signature from a temperate Scottish peatland stream and decomposed it to produce CO2 under simulated natural conditions over 140 days. We measured the 14C of both DOC and CO2 at seven time points and found that while DOC remained close to modern in age, the resultant CO2 progressively increased in age up to 2,356 ± 767 years BP. The results of this experiment demonstrate that the bulk DO14C pool can hide the presence of old C within peatland stream DOC export, demonstrating that bulk DO14C measurements can be an insensitive indicator of peatland disturbance. Our experiment also demonstrates that this old C component is biologically and photochemically available for conversion to the greenhouse gas CO2, and as such, bulk DO14C measurements do not reflect the 14C signature of the labile organic C pool exported by inland water systems more broadly. Moreover, our experiment suggests that old C may be an important component of CO2 emissions to the atmosphere from peatland aquatic systems, with implications for tracing and modeling interactions between the hydrological and terrestrial C cycles.
Pyrogenic carbon erosion after the Rim Fire, Yosemite National Park: The Role of Burn Severity and Slope
Authors: Abney Rebecca B. , Kuhn Timothy J. , Chow Alex , Hockaday William , Fogel Marilyn L. , Berhe Asmeret Asefaw
Published: February 2019

Pyrogenic carbon (PyC) is an incomplete combustion by‐product with longer soil residence times compared with nonpyrogenic components of the soil carbon (C) pool and can be preferentially eroded in fire‐affected landscapes. To investigate geomorphic and fire‐related controls on PyC erosion, sediment fences were established in three combinations of slope (high 13.9–37.3%; moderate 0–6.7%) and burn severity (high; moderate) plots within the perimeter of the Rim Fire in 2013, Yosemite National Park, California, USA. After each major precipitation event following the fire, we determined transport rates of total sediment, fine and coarse sediment fractions, and C and nitrogen (N). We measured stable isotope (δ13C and δ15N) compositions and 13C‐nuclear magnetic resonance spectra of soils and eroded sediments. The highest total and fine (<2 mm) sediment transport in high severity burned areas correlated with initial discharge peaks from an adjacent stream, while moderate burn severity sites had considerably more of the >2 mm fraction transported than high burn severity sites. The δ13C and δ15N values and 13C‐nuclear magnetic resonance analyses indicated that sediment eroded from moderate severity burn areas included fresh organic matter that was not as significantly affected by the fire, whereas sediments from high severity burn areas were preferentially enriched in PyC. Our results indicate that along a single hillslope after the Rim Fire, burn severity acted as a primary control on PyC transport postfire, with slope angle likely playing a secondary role. The preferential erosion of PyC has major implications for the long‐term persistence of PyC within the soil system.
Global Demonstration of Local Liebig's Law Behavior for Tree‐Ring Reconstructions of Climate
Authors: Stine A. R.
Published: February 2019

Liebig's law of the minimum posits that at any given time the growth factor that is least abundant, relative to physiological requirements, controls plant growth. Dendrochronological reconstructions of temperature and precipitation invoke Liebig's law to justify using tree growth as a proxy for climate and when choosing which trees to sample, but historically reconstruction techniques have not accounted for the influence of Liebig's law on differential growth between sampled trees within a given site. Such an influence implies that site‐wide limitations associated with regional climate variability would be most strongly expressed in tree rings experiencing high relative growth in a given year. We demonstrate that local Liebig's law stresses are globally identifiable across ring width and density data sets produced by over 300 different researchers. Furthermore, the local signature of Liebig's law is found at both temperature‐ and moisture‐limited sites. Chronologies based on trees undergoing the highest relative growth in a given year more accurately record climate variability than the mean chronology, especially at sites where more trees were sampled. These results suggest the potential for better reconstructing historical climate variability through pairing intensive tree‐ring sampling with a quantitative focus on those trees experiencing the highest relative growth.
The Future of Scientific Drilling in the North Pacific and Arctic
Authors: Worthington Lindsay , St. John Kristen , Coakley Bernard
Published: February 2019

International Ocean Discovery Program Workshop; Mount Hood, Oregon, 25–27 September 2018
Lessons from President George H. W. Bush for the Present Political Environment
Authors: Davidson Eric
Published: February 2019

The “White House effect” can compel support for science and protect the environment—or damage both.
How Will Melting Glaciers Affect Streamflow?
Authors: Stanley Sarah
Published: February 2019

High-resolution modeling of summertime streamflow in the Pacific Northwest reveals the effects of glacial retreat on streamflow will vary by elevation.
Science Agencies Play Catch-Up After the Shutdown
Authors: Showstack Randy
Published: February 2019

The National Science Foundation assesses the impact of the shutdown and prepares for another possible lapse in funding.
Optimized seeded Bridgman growth and temperature dependent THz optical properties of LiInS2 crystals
Authors: Qiao Jie , Liang Qijun , Wang Shanpeng , Xiong Xixi , Tao Xutang , Dekorsy Thomas
Published: February 2019

High quality and large size nonlinear optical LiInS2 (LIS) crystals were successfully grown by the optimized seeded Bridgman method.
Lone pair effects on ternary infrared nonlinear optical materials
Authors: Yin Ruonan , Hu Cong , Lei Bing-Hua , Pan Shilie , Yang Zhihua
Published: February 2019

By incorporating structural factors to compensate for the effects of crystal structure alignment, a quantitative method to estimate the lone pair activity is proposed which indicates that a larger R factor is beneficial to achieve a larger SHG response.
Regulating effect of heterojunctions on electrocatalytic oxidation of methanol for Pt/WO3-NaTaO3 catalysts
Authors: Bi Xi , Bai Ping , Lv Juanjuan , Yang Ting , Chai Zhanli , Wang Xiaojing , Wang Cheng
Published: February 2019

Pt/WO3-NaTaO3 composite catalysts for different W/Ta molar ratios were obtained via a facile hydrothermal method.
Use of γ-valerolactone and glycerol derivatives as bio-based renewable solvents for membrane preparation
Authors: Rasool M. A. , Vankelecom I. F. J.
Published: February 2019

Current solvents used in membrane preparation are often toxic, environmentally unfriendly and prepared from non-sustainable resources.
TbIII/3d–TbIII clusters derived from a 1,4,7-triazacyclononane-based hexadentate ligand with field-induced slow magnetic relaxation and oxygen-sensitive luminescence
Authors: Wen He-Rui , Zhang Jia-Li , Liang Fu-Yong , Yang Kai , Liu Sui-Jun , Liao Jin-Sheng , Liu Cai-Ming
Published: February 2019

A family of new TbIII/3d–TbIII cluster complexes based on N,N′,N′′-tris(3,5-dimethyl-2-hydroxybenzyl)-1,4,7-triazacyclononane have been synthesized and they exhibit interesting magnetic and luminescent properties.
SO2F2 mediated dehydrative cross-coupling of alcohols with electron-deficient olefins in DMSO using a Pd-catalyst: one-pot transformation of alcohols into 1,3-dienes
Authors: Lekkala Revathi , Lekkala Ravindar , Moku Balakrishna , Qin Hua-Li
Published: February 2019

A Pd-catalyzed, SO2F2 mediated dehydrative cross-coupling of alcohols with electron-deficient olefins for the construction of 1,3-dienes was developed.
Towards red-light o-carborane derivatives with both aggregation induced emission and thermally activated delayed fluorescence combining quantum chemistry calculation with molecular dynamics simulation
Authors: Duan Ying-Chen , Gao Ying , Geng Yun , Wu Yong , Shan Guo-Gang , Zhao Liang , Zhang Min , Su Zhong-Min
Published: February 2019

We investigated a series of o-carborane derivatives and designed new red-light derivatives by combining DFT with MD simulation. The reason of their TADF was explored and the AIE property was analyzed in water, crystal and film surroundings.
Zinc ion coordination significantly improved the transfection efficiency of low molecular weight polyethylenimine
Authors: Fang Huapan , Lin Lin , Chen Jie , Wu Jiayan , Tian Huayu , Chen Xuesi
Published: February 2019

A zinc ion coordination-contained polycationic gene delivery system.
Metal organic framework derived Nb2O5@C nanoparticles grown on reduced graphene oxide for high-energy lithium ion capacitors
Authors: Jiao Xinyan , Hao Qingli , Xia Xifeng , Wu Zongdeng , Lei Wu
Published: February 2019

For the first time, M-Nb2O5@C/rGO composites are fabricated by annealing the precursor of GO supported Nb-metal organic frameworks.
First-principles study of VPO4O as a cathode material for rechargeable Mg batteries
Authors: Wu Jiandong , Gao Guohua , Wu Guangming , Liu Limeng , Ma Jinfu , Chen Yuhong
Published: February 2019

The electrochemical properties of VPO4O as a cathode for Mg batteries were studied by performing first principles calculations.
Cooperation between an alcoholic proton and boryl species in the catalytic gem-hydrodiborylation of carboxylic esters to access 1,1-diborylalkanes
Authors: He Zeyu , Zhu Qing , Hu Xiyu , Wang Lu , Xia Chungu , Liu Chao
Published: February 2019

Cooperation between an alcoholic proton and boryl species in the selective gem-hydrodiborylation of carboxylic esters is described.
A bioinspired approach for construction of the [7-5-6-5] all-carbon tetracyclic core of logeracemin A
Authors: Gao Lingzhi , Cheng Bin , Yue Huijie , Cao Suyan , Wang Jiang-Li , Xu Liang
Published: February 2019

An efficient successive Michael/double aldol/dehydration reaction approach for the spiro-linked DEFF′ tetracyclic core ring systems of logeracemin A was developed.
Oblique fed ring antenna mounted in car headlight for automotive applications
Authors: Borah P. , Bezboruah T.
Published: February 2019

An oblique fed ring antenna designed and fabricated for its use in automotive applications is presented. The ring antenna is mounted on a car headlight at a certain height around the bulb with the help of a nylon supporting post. The reflector of the car headlight polished with conducting paint is made to act as the reflector for the ring antenna. Return loss performances are measured and compared for different heights of the ring antenna as well as for different parts associated with the headlight. Free space radiation pattern measurement of the ring antenna is carried out to have an insight of the effect of the light reflector for both the vertical and horizontal polarisations.
Target tracking based on improved square root cubature particle filter via underwater wireless sensor networks
Authors: Feng Hailin , Cai Zhiwei
Published: February 2019

Target tracking in underwater wireless sensor networks (UWSNs) has two fundamental issues that tracking accuracy and energy consumption. Although the application of particle filter in target tracking is considered in recent years, degeneracy phenomenon and particle impoverishment always restrict its capacity and application. This paper proposes an improved square root cubature particle filter (ISRCPF) to improve tracking accuracy. The authors employ self‐adaptive artificial fish swarm algorithm (AFSA) to optimise the particles, which makes the particles move towards to high likelihood region and maintains the diversity of the particles. Moreover, a sensor selection scheme is provided, which reduces energy consumption of the network by exactly waking up four sensor nodes at each time, while preserving tracking accuracy. Additionally, the authors propose a novel fusion method called similarity fusion method (SFM) to fuse local estimates together and then obtain a better result for distributed fusion architecture (DFA). The simulation results demonstrate that the proposed methods have superior performance.
Performance evaluation of communication technologies and network structure for smart grid applications
Authors: Bian Desong , Kuzlu Murat , Pipattanasomporn Manisa , Rahman Saifur , Shi Di
Published: February 2019

The design of an effective and reliable communication network supporting smart grid applications requires the selection of appropriate communication technologies and protocols. The objective of this study is to study and quantify the capabilities of an advanced metring infrastructure (AMI) to support the simultaneous operation of major smart grid functions. These include smart metring, price‐induced controls, distribution automation, demand response, and electric vehicle charging/discharging applications in terms of throughput and latency. OPNET is used to simulate the performance of selected communication technologies and protocols. Research findings indicate that smart grid applications can operate simultaneously by piggybacking on an existing AMI infrastructure and still achieve their latency requirements.
Research on visible light indoor positioning technique using two light sources andspecular reflection cancellation
Authors: Zhang Wenqiang , Feng Lifang , Che Ping
Published: February 2019

Here, a high accuracy camera‐based visible light indoor positioning system (IPS) has been investigated. A novel two LEDs‐based positioning algorithm is proposed aiming at solving the problems of positioning ambiguity with a good trade‐off between high accuracy and computational complexity. The simulation results show that the positioning errors of the proposed 2‐LED positioning algorithm achieves 2 cm when the resolution of the image sensor (IS) exceeds 2500 pixels/line. A specular reflection cancellation scheme is presented to further reduce the positioning errors when specular reflection interference occurs. The simulation results show that the positioning errors can be reduced to 2.71 cm after using the specular reflection cancellation.
Alleviation of LED nonlinearity impact in visible light communication using companding and predistortion
Authors: Lu Huimin , Jin Jianli , Wang Jianping
Published: February 2019

In order to suppress the nonlinearity impact of light‐emitting diodes (LEDs) on the performance of visible light communication (VLC), the combined method including companding and predistortion was proposed in this work. The modified companding and predistortion based on the LED characteristic analysis were used corresponding to the output current ‐input voltage (I‐V) and light output‐injected current (L‐I) nonlinearity, respectively. Using the combined method, the performances of the DC‐biased optical orthogonal frequency division multiplexing (DCO‐OFDM) VLC system were analysed. It is demonstrated that the non‐linear distortion of OFDM transmitted signal is alleviated, thus the received signal quality is increased. As a result, the bit error rate (BER) performance of VLC system is improved obviously by using the combined method of companding and predistortion. Furthermore, the applicability of this combined method is also verified by analysing the nonlinearity suppression of the VLC system using different LED. The results reveal that both the impact from LED's I‐V and L‐I nonlinearity can be alleviated using the proposed method combining from companding and predistortion for DCO‐OFDM VLC system.
Controllability and observability of networked singular systems
Authors: Zhu Zhen‐Hua , Guan Zhi‐Hong , Li Tao , Chen Jie , Jiang Xiao‐Wei
Published: February 2019

The controllability and observability of networked systems are studied, where the network topology is directed and the nodes are time‐invariant singular linear systems. Under the regularity assumption, a specific condition for the R‐controllability of the network with single‐input single‐output node‐systems is first established. Furthermore, necessary and sufficient conditions are derived for the R‐controllability and C‐controllability of the network with multi‐input multi‐output node systems. It is shown that the controllability of the overall system is an integrated result of the network topology, the subsystem dynamics, the external inputs, and the inner interactions. Additionally, corresponding observability criteria for such systems are also obtained, which indicate that the observability of the whole system depends only on the parameters of its subsystem. Finally, several examples are given to illustrate the proposed results.
Finite‐time consensus protocol for stochastic multi‐agent systems
Authors: Chen Xiurong , Li Juan , Wu Ziku , Yu Jiashang
Published: February 2019

To solve the problem that the frame of finite‐time consensus in probability has not been proposed, this note discusses the finite‐time consensus in probability for stochastic multi‐agent systems. The main contributions exist in (i) a framework for constructing effectively distributed protocols is presented to improve the convergence rate of protocol, which can ensure the finite‐time consensus in probability for stochastic multi‐agent systems under undirected connected communication topology; (ii) the relationship is discussed between the convergence time and the influence factors including the protocol parameters, the algebraic connectivity, and the initial state. Finally, some simulations are performed to verify the effectiveness of the theoretical results.
Input‐to‐state stability of contractive EMPC of non‐linear systems with bounded disturbances
Authors: Defeng He , Tianxiang Qiu , Liangye Lu
Published: February 2019

In this work, the authors consider the robust control problem of model predictive control (MPC) for economic criterion optimisation of constrained uncertain non‐linear systems with unknown but bounded additive disturbances. The authors propose a robust economic MPC (EMPC) scheme with guaranteed input‐to‐state stability (ISS) to solve the robust control problem. By imposing a modified Lyapunov‐based contractive constraint, the optimal control problem of the EMPC is formulated based on the nominal state prediction of the uncertain system. Then some sufficient conditions of Lipschitz continuity and terminal elements are derived to guarantee recursive feasibility and ISS of the EMPC with respect to the disturbance by the arguments of robust invariant sets and ISS. Two examples consisting of a chemical reaction process and a vehicle system are used to demonstrate the effectiveness of the proposed scheme.
On model‐based detectors for linear time‐invariant stochastic systems under sensor attacks
Authors: Murguia Carlos , Ruths Justin
Published: February 2019

A vector‐valued model‐based cumulative sum (CUSUM) procedure is proposed for identifying faulty/falsified sensor measurements. First, given the system dynamics, the authors derive tools for tuning the CUSUM procedure in the fault/attack‐free case to fulfil the desired detection performance (in terms of false alarm rate). They use the widely‐used chi‐squared fault/attack detection procedure as a benchmark to compare the performance of the CUSUM. In particular, they characterise the state degradation that a class of attacks can induce the system while enforcing that the detectors (CUSUM and chi‐squared) do not raise alarms. In doing so, they find the upper bound of state degradation that is possible by an undetected attacker. They quantify the advantage of using a dynamic detector (CUSUM), which leverages the history of the state, over a static detector (chi‐squared), which uses a single measurement at a time. Simulations of a chemical reactor with a heat exchanger are presented to illustrate the performance of their tools.
Distributed multi‐vehicle task assignment in a time‐invariant drift field with obstacles
Authors: Bai Xiaoshan , Yan Weisheng , Cao Ming , Xue Dong
Published: February 2019

This study investigates the task assignment problem where a fleet of dispersed vehicles needs to visit multiple target locations in a time‐invariant drift field with obstacles while trying to minimise the vehicles' total travel time. The vehicles have different capabilities, and each kind of vehicles can visit a certain type of the target locations; each target location might require to be visited more than once by different kinds of vehicles. The task assignment problem has been proven to be NP‐hard. A path planning algorithm is first designed to minimise the time for a vehicle to travel between two given locations through the drift field while avoiding any obstacle. The path planning algorithm provides the travel cost matrix for the target assignment, and generates routes once the target locations are assigned to the vehicles. Then, a distributed algorithm is proposed to assign the target locations to the vehicles using only local communication. The algorithm guarantees that all the visiting demands of every target will be satisfied within a total travel time that is at worst twice of the optimal when the travel cost matrix is symmetric. Numerical simulations show that the algorithm can lead to solutions close to the optimal.
Data‐based predictive control for networked non‐linear multi‐agent systems consensus tracking via cloud computing
Authors: Tan Haoran , Huang Zhiwu , Wu Min
Published: February 2019

This study investigates the consensus tracking problem for a class of networked non‐linear multi‐agent systems (NNMASs) using cloud computing. To achieve the stability and output consensus of the NNMAS and to actively compensate for two‐channel network delays, a data‐based cloud predictive control scheme is proposed. The design of the proposed novel control scheme, which only depends on the historical input and output data of the agents without using the explicit or implicit information of its structure, is detailed. Sufficient conditions are derived to guarantee the stability and output consensus of the closed‐loop NNMAS. Both numerical simulations and cloud‐based practical experiments are conducted to demonstrate the effectiveness of the proposed scheme. The outcome promotes the engineering application of cloud computing in multi‐agent systems.
Asymptotical stability contouring control of dual‐arm robot with holonomic constraints: modified distributed control framework
Authors: Dong Yunlong , Nuchkrua Thanana , Shen Tan
Published: February 2019

The authors analyse the contour error dynamics in contouring control of dual‐arm robotic manipulators with holonomic constraints. With the modified dynamics of robot, the dynamics of dual‐arm robot with holonomic constraints is symetrically transformed into dynamics error problem by considering the equivalent error method. It becomes the control problem of stabilisation such that it is suitable for robust control approach to improve control performance in terms of contouring control, i.e. contour accuracy with high speed. The proposed method can deal with both analytic and non‐analytic functions of desired path in task space. The experimental results reveal that the proposed method yields excellent performance in comparison to conventional distributed control. As a result, the proposed method can lead to the development of a modified distributed control for high degree of freedom robot manipulators.
Coherent H∞ control for linear quantum passive systems with model uncertainties
Authors: Lu Xiujuan , Kuang Sen
Published: February 2019

The coherent robust control problem for a class of linear quantum passive systems with model uncertainties is considered in this study, where both the plant and the controller are described by quantum stochastic differential equations (QSDEs). In the framework of language, the model uncertainties are translated into the uncertainties in the Hamiltonian, the coupling operators, and the scattering matrices. Based on the quantum bounded real lemma, the robust controller design of the original uncertain plant is transformed into the controller design of a new scaled system without model uncertainties. Further, the latter is transformed into the solving problem of a couple of Riccati equations and therefore the numerical solutions of the coefficient matrices of QSDEs associated with the controller dynamics are obtained. Finally, numerical simulations on an optical system coupled to three optical channels are performed to verify the effectiveness of the method proposed in this study.
Optimal load ratio control for dual‐receiver dynamic wireless power transfer maintaining stable output voltage
Authors: Liu Yeran , Mai Ruikun , Liu Dengwei , Zhou Kunzhuo , He Zhengyou , Li Weihua
Published: February 2019

Dynamic wireless power transfer (DWPT) system can provide a power supply for electric vehicles (EVs) in motion which can increase the available charging time, lessen the anxiety of driving range, and reduce the batteries in EVs. Aimed at optimising the system efficiency while regulating the output voltage, an optimal load ratio control strategy is proposed to optimise the power distribution of the dual‐receiver DWPT system, and to reduce the losses of the system as the receivers move along the transmitter track. The control strategy is implemented in the receiver side without the mutual inductance detection and the communication with the transmitter side. With the proposed method, the efficiency of the DWPT system can be optimised while the output voltage of the system can be regulated simultaneously. An experimental prototype is set up to validate the proposed method. The system efficiency with proposed method reaches 90.8–91.9% during various conditions in the experiments. The maximum efficiency improvement is 2.5% compared with the efficiency of the single receiver method, and it increases to 2.6% compared to that of the current balancing method.
Order‐statistic‐based sub‐band detector for range distributed target
Authors: Jiang Qi , Chen Zhuming , Jing Maoqiang , Wang Jinkai
Published: February 2019

Current range distributed target detectors use idealised primary data, which incorporates all the scattering centres of target without additional noise‐only range cells beyond the target's boundaries. In practical applications, primary data are extracted by preliminaries (sliding window method, for example), which may cause the loss of target energy and the degradation of detectors' performance. To overcome the problem, this paper resorts to the principles of frequency agility and devises an order‐statistic‐based sub‐band detector (OS‐SD) without preliminaries to extract primary data. OS‐SD assumes no a priori knowledge about the structure of the distributed target. Its design guarantees the bounded constant alarm false rate (bounded CFAR) property. The performance assessment conducted by Monte Carlo simulations confirms the effectiveness and robustness of the proposed detector.
Deep X-ray view of the Class I YSO Elias 29 with XMM-Newton and NuSTAR
Authors: Pillitteri I. , Sciortino S. , Reale F. , Micela G. , Argiroffi C. , Flaccomio E. , Stelzer B.
Published: February 2019

X-ray emission is a characteristic feature of young stellar objects (YSOs) and the result of the interplay between rotation, magnetism, and accretion. For this reason high energy phenomena are key elements to understand the process of star formation, the evolution of their circumstellar disks, and eventually the formation of planets. We investigated the X-ray characteristics of the Class I YSO Elias 29 with joint XMM-Newton and NuSTAR observations of total duration 300 ks and 450 ks, respectively. These are the first observations of a very young (<1 Myr) stellar object in a band encompassing simultaneously both soft and hard X-rays (0.3 − 10 keV in XMM-Newton and ≈3 − 80 keV in NuSTAR). The quiescent spectrum is well described by one thermal component at ∼4.2 keV absorbed by NH ∼ 5.5  ×  1022 cm−2. In addition to the hot Fe complex at 6.7 keV, we observed fluorescent emission from Fe at ∼6.4 keV, confirming the previous findings. The line at 6.4 keV is detected during quiescent and flaring states and its flux is variable. The equivalent width is found varying in the range ≈0.15 − 0.5 keV. These values make unrealistic a simple model with a centrally illuminated disk and suggest a role of the cavity containing Elias 29 and possible reverberation processes that could occur in it. We observed two flares that have durations of 20 ks and 50 ks, respectively, and we observed the first flare with both XMM-Newton and NuSTAR. For this flare, we used its peak temperature and timing as diagnostics to infer a loop size of about 1 − 2 R⊙ in length, which is about 20%–30% of the stellar radius. This implies a relatively compact structure. We systematically observed an increase in NH of a factor five during the flares. This behavior has been observed during flares previously detected in Elias 29 with XMM-Newton and ASCA. The phenomenon suggests that the flaring regions could be buried under the accretion streams and at high stellar latitudes because the X-rays from flares pass through gas denser than the gas along the line of sight of the quiescent corona. In a different scenario, a contribution from scattered soft photons to the primary coronal emission could mimic a shallower NH in the quiescent spectrum. In the spectrum of the full NuSTAR exposure, we detect hard X-ray emission in the band ≈20 − 80 keV which is in excess with respect to the thermal emission and that is significant at a level of ≥2σ. We speculate that the hard X-ray emission could be due to a population of energetic electrons accelerated by the magnetic field along the accretion streams. These particles, along with X-ray photons with E >  7.11 keV, could be responsible for pumping up the Fe fluorescence when hitting cold Fe in the circumstellar disk.
STiC: A multiatom non-LTE PRD inversion code for full-Stokes solar observations
Authors: de la Cruz Rodríguez J. , Leenaarts J. , Danilovic S. , Uitenbroek H.
Published: February 2019

The inference of the underlying state of the plasma in the solar chromosphere remains extremely challenging because of the nonlocal character of the observed radiation and plasma conditions in this layer. Inversion methods allow us to derive a model atmosphere that can reproduce the observed spectra by undertaking several physical assumptions. The most advanced approaches involve a depth-stratified model atmosphere described by temperature, line-of-sight velocity, turbulent velocity, the three components of the magntic field vector, and gas and electron pressure. The parameters of the radiative transfer equation are computed from a solid ground of physical principles. In order to apply these techniques to spectral lines that sample the chromosphere, nonlocal thermodynamical equilibrium effects must be included in the calculations. We developed a new inversion code STiC (STockholm inversion Code) to study spectral lines that sample the upper chromosphere. The code is based on the RH forward synthesis code, which we modified to make the inversions faster and more stable. For the first time, STiC facilitates the processing of lines from multiple atoms in non-LTE, also including partial redistribution effects (PRD) in angle and frequency of scattered photons. Furthermore, we include a regularization strategy that allows for model atmospheres with a complex depth stratification, without introducing artifacts in the reconstructed physical parameters, which are usually manifested in the form of oscillatory behavior. This approach takes steps toward a node-less inversion, in which the value of the physical parameters at each grid point can be considered a free parameter. In this paper we discuss the implementation of the aforementioned techniques, the description of the model atmosphere, and the optimizations that we applied to the code. We carry out some numerical experiments to show the performance of the code and the regularization techniques that we implemented. We made STiC publicly available to the community.
High-resolution confirmation of an extended helium atmosphere around WASP-107b
Authors: Allart R. , Bourrier V. , Lovis C. , Ehrenreich D. , Aceituno J. , Guijarro A. , Pepe F. , Sing D. K. , Spake J. J. , Wyttenbach A.
Published: February 2019

Context. Probing the evaporation of exoplanet atmospheres is key to understanding the formation and evolution of exoplanetary systems. The main tracer of evaporation in the UV is the Lyman-α transition, which can reveal extended exospheres of neutral hydrogen. Recently, the near-infrared (NIR) metastable helium triplet (10 833 Å) revealed extended thermospheres in several exoplanets. This opens a new window into evaporation.

Aims. We aim at spectrally resolving the first helium absorption signature detected in the warm Saturn WASP-107b with the Wide Filed Camera 3 on board the Hubble Space Telescope (HST/WFC3).

Methods. We obtained one transit of WASP-107b with CARMENES installed on the 3.5 m telescope at the Calar Alto observatory.

Results. We detect an excess helium absorption signature of 5.54 ± 0.27% (20σ) in the planet rest frame during the transit. The detection is in agreement with the previous detection achieved with HST/WFC3. The signature shows an excess absorption in the blue part of the lines, suggesting that He I atoms are escaping from the atmosphere of WASP-107b. We interpret the time-series absorption spectra using the 3D EVE code. Our observations can be explained by combining an extended thermosphere that fills half of the Roche lobe and a large exospheric tail sustained by an escape rate of metastable helium of about 106 g s−1. In this scenario, however, the upper atmosphere needs to be subjected to a reduced photoionisation and radiation pressure from the star for the model to match the observations.

Conclusions. We confirm the presence of helium in the atmosphere of WASP-107b at high confidence. The helium feature is detected from space and from the ground. The ground-based high-resolution signal brings detailed information about the spatial and dynamical structure of the upper atmosphere, and simulations suggest that the He I signature of WASP-107b probes both its thermosphere and exosphere, establishing this signature as a robust probe of exoplanetary upper atmospheres. Surveys with NIR high-resolution spectrographs (e.g. CARMENES, the Spectromètre infrarouge (SPIRou), or the Near-Infrared Planet Searcher (NIRPS)) will deliver a statistical understanding of exoplanet thermospheres and exospheres through the helium triplet.
Analyse und Management von postoperativen Schmerzen nach
Sialendoskopie
Authors: Nachtsheim Lisa , Pick Carina , Klußmann Jens Peter , Löser Johannes , Lüers Jan-Christoffer
Published: February 2019

Hintergrund Die Sialendoskopie ist ein minimal-invasives Verfahren zur
Diagnostik und Therapie von Erkrankungen des Speicheldrüsengangsystems. Sie kann
in ITN und in LA durchgeführt werden. Vor diesem Hintergrund ist die
postoperative Schmerzsituation interessant, über deren Ausmaß aktuell jedoch
wenig bekannt ist. Daher wurden in dieser Studie die postoperativen Schmerzen
nach Sialendoskopie in LA und ihr Schmerzmanagement in einer quantitativen
Untersuchung erfasst und analysiert.

Material und Methoden Es wurden 103 Patienten in die retrospektive Studie
eingeschlossen, bei denen im Zeitraum von 2013 bis 2015 eine Sialendoskopie der
Glandula parotis oder der Glandula submanibularis in Lokalanästhesie
durchgeführt wurde. Analysiert wurden die postoperativen Schmerzen in Ruhe und
bei Belastung am Operationstag, sowie am ersten und zweiten postoperativen Tag.
Die Schmerzen wurden anhand einer numerischen Rating Skala (NRS 0–10) erfasst,
welche im Rahmen des QUIPS-Projektes (Qualitätsverbesserung in der
postoperativen Schmerztherapie) verwendet wird.

Ergebnisse Am Operationstag betrug der Schmerz in Ruhe 0,9 ± 1,9 und bei
Belastung 0,7 ± 1,4. Am ersten postoperativen Tag wurden Schmerzen von 1,2 ± 1,8
in Ruhe und 0,9 ± 1,9 bei Belastung festgestellt. Am zweiten postoperativen Tag
zeigte sich eine Reduktion der Schmerzen auf 0,75 ± 1,6 in Ruhe und 0,73 ± 1,5
bei Belastung. Insgesamt wurden Metamizol (Novalgin®) und Ibuprofen
als häufigste postoperative Analgetika eingesetzt. Am Operationstag erhielten
37,9 % der Patienten Schmerzmittel, am ersten postoperativen Tag 26,2 % der
Patienten und am zweiten postoperativen Tag 12,6 % der Patienten.

Schlussfolgerung Sialendoskopien der Glandula submandibularis und parotis
sind mit moderaten postoperativen Schmerzen verbunden, welche sich gut mit
Nicht-Opioiden behandeln lassen.
Microsurgical Experience with Pedicle-Sparing Transfacet Approach for Thoracic Disk Herniation
Authors: Çelik Suat , Samancı Yavuz , Özkaya Ferdi , Peker Olgün
Published: February 2019

Purpose Thoracic disk herniation (TDH) is relatively uncommon. The surgical approach differs from lumbar or cervical disk herniations because serious complications are associated with the posterior approach in TDH. Various different approaches have been tried for the surgical removal of TDH, but most of them are cumbersome surgeries such as thoracotomy or thoracoscopic or anterior approaches with or without instrumentation. The requirement for a simplified, familiar, and less morbid surgery has motivated some new approaches. A pedicle-sparing transfacet approach (PSTA) was first described in 1995, but to date no sufficient clinical series has been presented in the literature to report on its feasibility and applicability along with complication and morbidity rates. Our objective was to assess the feasibility of the PSTA under microscopic visualization in a cumulative clinical series.

Methods Twenty-eight consecutive patients with no response to medical/physical treatment with and without motor weakness of their lower extremities underwent the surgery for TDH via the PSTA under microscopic visualization by a senior neurosurgeon. Preoperative and postoperative low extremity muscle strength, sensation, reflex status, and visual analog scores (VAS), Nurick grades, and complications were recorded. Postoperative MRI within 24 hours was performed. The median follow-up period was 33 months.

Results The patients consisted of 16 men and 12 women. The disk levels ranged from T8 to T12–L1. All but one patient received one-level surgery. One patient was operated on two levels. A total of 21 patients had paracentral disk herniations; the other 7 had central disk herniations. Postoperative MRI showed satisfactory removal of disk herniation in all but one patient. There was no infection, wrong level surgery, or incidental durotomy. Median VAS levels significantly improved after the operation from 7.4 to 2.3. The Nuric grades decreased from 2.7 to 1.6 after surgery.

Conclusions The microsurgical PSTA is a safe and feasible technique with a significantly shorter surgeon's learning curve. The approach offers a wide surgical window; moreover, it can by increased by tilting the surgical table allowing satisfactory decompression of TDH. After PSTA, segmental instrumentation is not required.
Placement of External Ventricular Drain: Comparison of Two Methods
Authors: Schwarm Frank , Stein Marco , Uhl Eberhard , Reinges Marcus , Bender Michael
Published: February 2019

Background Insertion of a frontal external ventricular drain (EVD) is a common emergency procedure in neurosurgery. Malpositioning of the EVD and/or triggering a new intracerebral or intraventricular hemorrhage (nICVH) are typical complications. The standard procedure (SP) uses a tape measure to identify the Kocher's point for placement of a frontal burr hole. A faster alternative to determine the correct position is the freehand technique (FHT). This study compared both techniques with regard to the correct positioning of the EVD tip and the induction catheter-induced nICVH.

Methods We performed a retrospective analysis of patients who required an EVD for acute or chronic hydrocephalus between January 2013 and March 2014. The study consisted of two groups. In the first group, EVDs were placed with the FHT. In the second group the SP was used. Postoperative computed tomography scans were analyzed regarding correct positioning of the ventricular catheter, malpositioning of the tip of the EVD using a 4-point-scale, and evidence for catheter-induced nICVH.

Results A total of 95 patients could be included. The FHT was performed in 43 cases and the SP in 52 cases. No significant differences between the two groups were found regarding the correct position of the EVD tip (p = 0.38) and nICVH (p = 0.12). There was no significant difference in malpositioning of the EVD tip between the groups (p = 0.34).

Conclusion Our results show no significant differences between the two methods with regard to correct position, malpositioning, and nICVH. Thus we conclude that the FHT is a fast, safe, and effective alternative to the SP.
Endoscopic Transnasal Resection of Suprasellar Teratoma
Authors: Ajlan Abdulrazag M. , Albakr Abdulrahman , Alsaleh Saad , Alkhalidi Hisham
Published: February 2019

Background Intracranial teratomas are rare tumors that usually present during the second decade of life. Among intracranial teratomas, suprasellar germ cell tumors in particular are extremely rare. We present the case of an 18-year-old girl who underwent a successful endoscopic transnasal resection of a suprasellar teratoma with a mixed germ cell component.

Case Description An 18-year-old girl presented with progressive visual disturbance, headache, weight loss, and fatigue for 2 weeks. She had decreased vision in her right eye and double vision when looking to the right side. On examination, she had right-side complete abducens nerve palsy and partial oculomotor nerve palsy bilaterally. Brain imaging revealed a large suprasellar lesion consistent with a germ cell tumor. The patient underwent a transnasal endoscopic resection of the lesion. Pathology showed a mixed germ cell tumor (80% mature cystic teratoma, 18% yolk sac tumor, and 2% germinoma). The mature teratomatous elements identified included skin with sebaceous material, hair, cartilage, acini, colonic mucosa, muscle, nerve bundles, and adipose tissue. Postoperative magnetic resonance imaging (MRI) showed residual tumor in the left cavernous sinus and anterior clinoid process superiorly. At a 1-year follow-up, the double vision had resolved, and her vision showed progressive improvement. The patient was maintained on treatment for diabetes insipidus, hypothyroidism, and adrenal insufficiency. Her last MRI showed no signs of tumor progression.

Conclusions The present case demonstrates a safe endoscopic transnasal surgical resection of a rare suprasellar tumor, mixed teratoma, with intra-axial extension. The endoscopic transnasal approach can be considered a valid option for a suprasellar lesion.
Transsphenoidal Removal of Retroclival Chondroma with Pituitary Transposition Manifesting as Repeated Subarachnoid Hemorrhage: A Case Report
Authors: Ogawa Yoshikazu , Niizuma Kuniyasu , Tominaga Teiji
Published: February 2019

Background Intracranial chondromas are extremely rare and represent only 0.2% of all intracranial primary neoplasms. The histologic appearance lacks nuclear atypism and mitoses, and it usually shows low growth potential, although these benign features do not necessarily imply a good prognosis.

Case Description A 44-year-old man was referred to our institution with a subarachnoid hemorrhage (SAH). He had a history of SAH 5 years previously that was diagnosed as unknown etiology at another hospital. Head magnetic resonance imaging showed a large tumor located in the prepontine cistern and extending up to the interpeduncular cistern, and the tumor was irregularly enhanced with contrast medium. Retrospective analysis of the original computed tomography of 5 years earlier identified a small contrast enhancing defect behind the dorsum sellae. Tumor removal was planned to prevent repeated SAH and control the apparently growing tumor. An extended transsphenoidal approach was performed. The pituitary gland was dissected from the bottom of the sellar floor and transposed forward to the prechiasmatic cistern with preservation of the pituitary stalk and its blood supply, and subtotal removal of the tumor was achieved. Postoperative diabetes insipidus disappeared within a few days, and the patient was discharged without neurologic or endocrinologic deficits. Histologic examination established the diagnosis as chondroma without a sarcomatous component. Follow-up examination 3 months after surgery showed a re-enlargement of the residual tumor, and gamma knife surgery was performed.

Conclusions Intracranial chondroma sometimes manifests as intracranial hemorrhage and grows comparatively rapidly in a short period despite the benign histologic features. A long and careful follow-up period is essential.