bluuebunny/crossref_metadata_2025 huggingface dataset:
Toward Wearable EEG-based Alertness Detection System Using SVM with Optimal Minimum Channels
Authors: Yang Mihong , Li Huiyan , Sun Xiaozhou , Yang Li , Duan Hailong , Che Yanqiu , Han Chunxiao
Published: October 2018

Alertness is the state of attention by high sensory awareness. A lack of alertness is one of the main reasons of serious accidents. Traffic accidents caused by driver’s drowsy driving have a high fatality rate. This paper presents an EEG-based alertness detection system. In order to ensure the convenience and long-term wearing comfort of EEG recordings, the wearable electrode cap will be the principal choice in the future, and the selection of channels will be limited. We first built a 3-D simulated driving platform using Unity3D. Then, we perform an experiment with driving drift task. EEG signals are recorded form frontal and occipital regions. We select data segments using the driving reaction time, classify the state of alertness with a support vector machine (SVM), and select the optimal combination of channels with minimum number of channels. Our results demonstrate that alertness can be classified efficiently with one channel (PO6) at accuracy of 93.52%, with two channels (FP1+PO6) at 95.85% and with three channels (FP1+PO6+PO5 and FP1+PO6+POZ) at 96.11%.
Research on Operation Analysis and Evaluation Method of Ergonomics for Virtual Assembly
Authors: Gou Guobin , Zhang Xu , Yan Yuehui
Published: October 2018

With the rapid development of digital technology and virtual reality technology, virtual reality technology has been paid more and more attention by more and more people. To investigate the application of virtual assembly simulation and improve ergonomics, the study on the interactive assembly operation has been performed. A Comprehensive Evaluation Method for ergonomics based on simulation of virtual assembly operations is proposed, aiming at avoid inadequate working postures, effectively improve assembly quality and shorten the production cycle. In this paper, the virtual assembly technology is introduced to the assembly process of an industrial manipulator. Details of the virtual assembly simulation process of an industrial manipulator design and its implementation are presented. This proposed method provides great support to the design of assembly process and brings about good change in the ergonomics of machine and system visualization. The analysis of this instance plays a guiding role in the optimization of human factors engineering.
Chronische Kopfschmerzen bei Kindern und Jugendlichen
Authors: Blankenburg Markus , Schroth Michael , Braun Sarah
Published: October 2018

Primäre Kopfschmerzerkrankungen wie Spannungskopfschmerzen und Migräne beginnen in der Kindheit und werden mit der Einschulung und Pubertät häufiger. Bei Spannungskopf-schmerzen spielt die zentrale Schmerzsensibilisierung und Aktivierung zentraler nozizeptiver Neurone eine wichtige Rolle. Die Migräne ist eine primäre Erkrankung des Gehirns mit Auffälligkeiten schmerzmodulierender Systeme und der kortikalen Reizverarbeitung. Bei beiden Kopfschmerzformen spielen bio-psycho-soziale Faktoren eine entscheidende Rolle. Sekundäre Kopfschmerzen durch eine entzündliche oder strukturelle hirnorganische Ursache sind selten. Die Diagnose erfolgt anhand der Anamnese und der körperlichen Untersuchung sowie apparativer Untersuchungen bei Auffälligkeiten. Bei Spannungskopfschmerzen steht die multimodale Schmerztherapie im Vordergrund, bei Migräne die medikamentöse Therapie der Attacken und bei sekundären Kopfschmerzen die Behandlung der Grunderkrankung. Behandlungsziele sind die Minderung der Schmerzwahrnehmung, Förderung von Kontroll- und Selbstwirksamkeitserfahrungen, die Steigerung der körperlichen Leistungsfähigkeit sowie die Wiederaufnahme normaler Alltagsstrukturen und sozialer Kontakte als Voraussetzung für eine zunehmende Schmerzminderung.
Continuous Passive Motion Does Improve Range of Motion, Pain and Swelling After ACL Reconstruction: A Systematic Review and Meta-Analysis
Authors: Jaspers Theo , Taeymans Jan , Hirschmüller Anja , Baur Heiner , Hilfiker Roger , Rogan Slavko
Published: October 2018

Background This systematic review and meta-analysis evaluates the results of empirical studies on the effects of CPM on rehabilitation after ACL reconstruction. The research question was: what are the effects of CPM on ROM, swelling and pain after ACL reconstruction?

Patients/Material and Methods We searched in MEDLINE, Embase, CINAHL, Cochrane and PEDro up to January 2018. Standardized mean differences (SMD) were expressed as Hedgesʼ g, in order to correct for overestimation of the true effect in small study samples. The 95% confidence intervals (95% CI) were calculated for both the individual studies and the overall weighted estimate. Outcomes were range of motion, pain and swelling.

Results Eight studies comprising 442 participants were included in the meta-analysis. Beneficial effects of CPM could be identified for the need for pain medication (Hedgesʼ g = 0.93; 95% CI = 0.41 to 1.45 during the first 24 hours after surgery), the number of PCA button pushes by the patient during the first 24 hours after surgery (MD = 31.20; 95% CI = 11.35 to 51.05), on regaining knee flexion on the third to the seventh postoperative day (MD = 11.6°; 95% CI = 1.96 to 21.33) as well as in the third to the sixth postoperative week (Hedgesʼ g = 0.93; 95% CI = 0.41 to 1.44) and on swelling of the knee in the fourth to sixth postoperative week (Hedgesʼ g = 0.77; 95% CI = 0.35 to 1.18).

Conclusion This meta-analysis suggests that CPM has beneficial effects on pain reduction during the first two postoperative days, on knee flexion during the first to the sixth postoperative weeks and on swelling between the fourth and the sixth postoperative weeks. However, the risk-of-bias scores do not allow a high level of evidence.
Classical Massage and Acupuncture in Chronic Back Pain – Non-Inferiority Randomised Trial
Authors: Klassen Erika , Wiebelitz Karl-Ruediger , Beer André-Michael
Published: October 2018

Background Currently, there is a need for scientific evidence on the efficacy of classical massage therapy for chronic, unspecific back pain, especially for the improvement in functional impairment and long-term pain reduction. According to the National Health Care Guidelines, classical massage for nonspecific low back pain may only be prescribed in combination with exercise therapy and a share of the remuneration. Acupuncture, on the other hand, is recognised in the guidelines as an independent treatment for chronic back pain and is remunerated by health insurance companies. This raises the question of whether classical massage therapy is not inferior compared to acupuncture, based on the therapy of the GERAC study. The Clinic of Naturopathy in Blankenstein, Hattingen uses classical massage therapy subjectively successfully in patients with back pain. To objectify the success of the treatment, a randomised controlled, non-inferiority study was conducted.

Methods The efficacy of classical massage (KMT, n = 66) was compared with acupuncture therapy (AKU, n = 66) in patients with chronic back pain. The primary endpoint was the non-inferiority of classical massage compared with the acupuncture treatment in respect of the impairment in everyday life, with the help of the Hannover function questionnaire (HFAQ) and the reduction in pain (“Von Korff”-Questionnaire) at the follow-up after one month.

Results In the per-protocol analysis during the period between enrollment in the study and follow-up, the responder rate of the KMT was 56.5% and thus tended to be inferior to the responder rate of the AKU with 62.5% (Δ = − 6%; KIΔ: − 23.5 to + 11.4%).

Conclusions The results show that classical massage therapy is not significantly inferior to acupuncture therapy in the period from admission to follow-up. Thus, the non-inferiority of the KMT to the AKU cannot be proven in the context of the defined irrelevance area.
Utilization of 1H-Indole-3-carboxaldehyde as a Precursor for the Synthesis of Bioactive Indole Alkaloids
Authors: Kirsch Gilbert , El-Sawy Eslam , Abdelwahab Ahmed
Published: October 2018

Indole alkaloids constitute a large class of natural products and their diverse and complex structures have been attributed to potent biological activities such as anticancer, anti-inflammatory, antimicrobial, antimalarial, antiplasmodial and protein kinase inhibition. The isolation of bioactive compounds from natural sources is difficult, costly and an extremely time-consuming process, therefore synthetic pathways are more convenient than natural separation to deliver such compounds in considerable amounts. In this respect, this review provides comprehensive information on the structures and the synthesis of bioactive indole alkaloids utilizing 1H-indole-3-carboxaldehyde and its derivatives as starting compounds.

1 Overview

2 Phytoalexins

2.1 Brassinin, Cyclobrassinin and Brassitin

2.2 1-Methoxybrassinin, 1-Methoxyspirobrassinol and 1-Methoxyspirobrassinin

2.3 4-Methoxybrassinin and 4-Methoxycyclobrassinin

2.4 Cyclobrassinone

2.5 Brassilexin

2.6 (S)-(–)-Spirobrassinin

2.7 Camalexin

3 Bis(indole) Alkaloids: Rhopaladines A–D

4 Coscinamides A and B

5 α-Cyclopiazonic Acid

6 Dipodazine

7 Isocryptolepine

8 Apparicine

9 Carbazole Alkaloids: Mukonine and Clausine E

10 Indolmycin

11 Conclusion
Advances in Catalytic Aerobic Oxidations by Activation of Dioxygen-Monooxygenase Enzymes and Biomimetics
Authors: Zografos Alexandros , Petsi Marina
Published: October 2018

Monooxygenases are not only some of the most versatile machineries in our lives, but also some of the most explored enzymes in modern organic synthesis. They provide knowledge and inspiration on how the most abandoned oxidant, dioxygen, can be activated and utilized to deliver selective oxidations. This review presents an outline in the mechanisms that Nature uses to succeed in these processes and recent indicative examples on how chemists use this knowledge to develop selective oxidation protocols based on dioxygen as the terminal oxidant.

1 Introduction

2 Monooxygenases

2.1 Metal-Based Monooxygenases

2.1.1 Cytochromes

2.1.2 Copper-Dependent Monooxygenases

2.1.3 Heme-Independent Iron Monooxygenases

2.1.4 Pterin-Dependent Monooxygenases

2.2 Metal-Free Monooxygenases

2.2.1 Flavin-Dependent Monooxygenases

2.2.2 Systems without Cofactors

3 Biomimetic Aerobic Oxidations

3.1 Aerobic Oxidations Based on Metal Catalysts

3.1.1 Epoxidations and Allylic Oxidations

3.1.2 Oxidations of Unactivated Carbon Atoms and Benzylic Oxidations

3.1.3 Oxidations of Aryl Groups

3.1.4 Heteroatom Oxidations

3.2 Aerobic Oxidations Based on Organocatalysts

3.2.1 Baeyer–Villiger Oxidations

3.2.2 Oxidations of Aryl Groups

3.2.3 Heteroatom Oxidations

4 Conclusion
Multicomponent Reactions in the Synthesis of γ-Lactams
Authors: Vicario Javier , Palacios Francisco , Martinez de Marigorta Edorta , de los Santos Jesús , Ochoa de Retana Ana
Published: October 2018

This review summarizes the synthesis of γ-lactam ring using multicomponent reactions.

1 Introduction

2 Pyrrolidin-2-ones

3 Pyrrolin-2-ones (Dihydro-2H-pyrrol-2-ones)

4 Final Remarks
Ethical Issues in Vascular Neurology
Authors: Wheeler Natalie , Murali Sadhana , Sattin Justin
Published: October 2018

There are ethical aspects to each of the three phases of cerebrovascular disease: hyperacute management, acute prognostication and management of early complications, and long-term recovery and reintegration with the community. This article addresses ethical concerns pertinent to each phase. First, we discuss ethical issues regarding consent for thrombolysis and endovascular treatment for acute ischemic stroke, including a review of considerations regarding the provision of acute stroke treatment advice over the telephone. Next, we discuss capacity for consent and prognostication after ischemic stroke and intracranial hemorrhage, with a focus on the problems of the self-fulfilling prophecy. Finally, we discuss residual disability and patients' return to driving. Consideration of these ethical dimensions of cerebrovascular disease will assist neurologists in caring for patients and families suffering from this complex condition.
Progressive Devascularization: A Novel Surgical Approach for Placenta Previa
Authors: Saad Antonio , Kirsch Nathan , Saade George , Hankins Gary
Published: October 2018

Background The gold standard for antenatal diagnosis of placenta previa is the transvaginal ultrasonography. In placenta previa cases, separation of placental and uterine tissues is challenging even for the most experienced surgeons. Life-threatening obstetrical complications from cesarean deliveries with placenta previa include peripartum hemorrhage, coagulopathy, blood transfusion, peripartum hysterectomy, and multiple organ failure.

Cases We detailed the 3 cases of placenta previa that underwent bilateral uterine artery ligation; if hemostasis was not achieved, horizontal mattress sutures were placed in the lower uterine segment. All patients were discharged with minimal morbidity.

Conclusion For patients with placenta previa and low risk for placenta creta, counseling should include the risk for maternal morbidity and criteria for pursuing peripartum hysterectomy. Our devascularization, a stepwise surgical approach, shows promising outcomes in placenta previa cases.

Précis We propose a novel surgical approach, using a progressive devascularization surgical technique, for management of women with placenta previa, undergoing cesarean delivery.
Retrosigmoid Craniectomy for Vestibular Schwannoma with Hearing Preservation
Authors: Tolisano Anthony M. , Patel Ankur R. , Barnett Samuel L. , Isaacson Brandon
Published: October 2018

Objectives To describe a retrosigmoid craniectomy, hearing-preservation approach for resection of vestibular schwannoma.

Design/Setting/Participants A video of a single patient undergoing the above approach at a tertiary care skull base surgery program.

Results This video demonstrates a retrosigmoid craniectomy approach for resection of an enlarging intracanalicular vestibular schwannoma in a patient with normal hearing. The video highlights the pertinent surgical anatomy and outlines in a step-by-step fashion the surgical steps. The patient obtained a gross total resection with preservation of hearing.

Conclusion A retrosigmoid craniectomy approach for vestibular schwannoma offers a potentially hearing preservation approach for selected tumors.

The link to the video can be found at: https://youtu.be/VM663XztRZw.
Data-driven computation of molecular reaction coordinates
Authors: Bittracher Andreas , Banisch Ralf , Schütte Christof
Published: October 2018

The identification of meaningful reaction coordinates plays a key role in the study of complex molecular systems whose essential dynamics are characterized by rare or slow transition events. In a recent publication, precise defining characteristics of such reaction coordinates were identified and linked to the existence of a so-called transition manifold. This theory gives rise to a novel numerical method for the pointwise computation of reaction coordinates that relies on short parallel MD simulations only, but yields accurate approximation of the long time behavior of the system under consideration. This article presents an extension of the method towards practical applicability in computational chemistry. It links the newly defined reaction coordinates to concepts from transition path theory and Markov state model building. The main result is an alternative computational scheme that allows for a global computation of reaction coordinates based on commonly available types of simulation data, such as single long molecular trajectories or the push-forward of arbitrary canonically distributed point clouds. It is based on a Galerkin approximation of the transition manifold reaction coordinates that can be tuned to individual requirements by the choice of the Galerkin ansatz functions. Moreover, we propose a ready-to-implement variant of the new scheme, which computes data-fitted, mesh-free ansatz functions directly from the available simulation data. The efficacy of the new method is demonstrated on a small protein system.
Multipoint vertical-Thomson scattering diagnostic on HL-2A tokamak
Authors: Huang Y. , Wang Y. Q. , Hou Z. P. , Ren L. L. , Liu C. H. , Feng Z. , Luo C. W.
Published: October 2018

Some progress has been made to develop the multipoint Thomson scattering (TS) diagnostic for the HL-2A tokamak physics experiments. Hardware of silicon avalanche photodiode detector electronics is improved, which provides two output signal channels. In one channel, only the rapid TS signal is the output after deducting the influence of the background slow-varying plasma light. In the other, both the rapid TS signal and the plasma background signal are the output. In the latest HL-2A experiment campaign, the newly developed electronics are tested and TS signals can be obtained from each of the two channels, where the signal is digitized by 12-bit transient recorder sampled at 1 GS/s. Laser beam alignment is fulfilled by using motorized stages to control the laser beam passing through ∼10 mm-wide narrow throats of the lower and upper closed divertors with small movements and then the stray laser light is reduced. New modules of fast digitizers with more than 100 channels are installed and will be used to record TS pulse signals. On the basis of these achievements, about 15-point measurements of plasma electron temperature and density by Thomson scattering diagnostic will come into operation in the upcoming HL-2A experiment campaign.
Dual-laser wavelength Thomson scattering at Wendelstein 7-X
Authors: Pasch E. , Beurskens M. N. A. , Bozhenkov S. A. , Fuchert G. , Wolf R. C. ,   W7-X Team
Published: October 2018

This paper presents the approach of the dual-laser wavelength Thomson scattering (TS) system for the Wendelstein 7-X stellarator. The dual-laser wavelength TS method is based on two lasers with different wavelengths being fired quasi-simultaneously. This method has two advantages compared to a single laser wavelength TS system. First, the dual laser availability allows an in situ spectral calibration, and second, higher electron temperatures can be measured without any change in the spectral filter setup of the polychromators. The W7-X dual-laser wavelength TS concept is based on high power lasers: a set of standard Nd:YAG lasers with λ = 1064 nm wavelength and a Nd:YAG laser with λ = 1319 nm wavelength newly developed for this application. This laser uses a different transition line with 34% efficiency compared to the main 1064 nm Nd:YAG line. Simulations of the expected performance of the new dual-laser wavelength system show that electron temperatures up to Te = 15 keV can be measured compared to the original design parameter up to Te = 10 keV. The in situ spectral calibration can be performed using a range of temperatures from 1 keV to 10 keV using TS measurements of the 1064 nm versus 1319 nm TS simultaneously.
Characterization of a two-channel, high resolution hard x-ray microscope using Fresnel zone plates for laser-plasma interaction experiments
Authors: Do A. , Briat M. , Chaleil A. , Rubbelynck C. , Lebugle M. , David C. , Troussel P.
Published: October 2018

New X-ray imaging techniques are currently being developed at the “Commissariat à l’énergie atomique et aux énergies alternatives” in the context of Inertial Confinement Fusion. Fresnel zone plates (FZPs) are being considered as they can perform high-resolution and high-flux imaging in the X-ray domain. Here we present the characterization of a bi-lens FZPs resolution used in an imager prototype, designed for the LULI2000 laser facility. Characterization was performed on a synchrotron radiation facility and on a femtosecond laser facility. The resolution of the two FZP channels was measured to be between 2.4 μm and 5.2 μm and the expected total resolution for the diagnostic was to be 3.3 μm.
Spin-wave coupled spin torque oscillators for artificial neural network
Authors: Arai Hiroko , Imamura Hiroshi
Published: October 2018

The spin-wave coupled spin-torque-oscillator is studied for a processing unit of an artificial neural network by numerically solving the Landau-Lifshitz-Gilbert equation incorporating the Slonczewski spin-torque term. The spin-wave coupling is controlled by tuning the Heisenberg and Dzyaloshinskii-Moriya interactions and also by externally applying the oscillating magnetic field. The activation function of the processing unit is varied by the spin-wave coupling. The artificial neural network computation is also demonstrated by performing the recognition of the handwritten digits in the MNIST database. By using the sigmoid-like activation function, the learning is conducted by the algorithm used for the conventional feedforward neural network. The obtained recognition accuracy is 0.853.
A multi-scale simulation of hot spot initiation of detonation utilizing experimental measurements
Authors: Kim Yoocheon , Lee Younghun , Yoh Jack J.
Published: October 2018

Empirical and phenomenological hydrodynamic reactive flow models, such as the ignition-and-growth and Johnson–Tang–Forest models, have been effective in predicting the shock initiation and detonation characteristics of various energetic substances. These models utilize the compression and pressure properties of the reacting mixture to quantify its reaction rate. However, it has long been known that the shock initiation of detonation is controlled by local reaction sites called ‘hot spots’. In this study, a hot-spot model based on the temperature-dependent Arrhenius reaction rate is developed. The complex reaction process of the target explosive is addressed by conducting differential scanning calorimetry experiments whereas the reaction rate is determined using the Friedman isoconversional method. The hot spot is approximated by the region of high pressure accumulation due to multiple shock reverberations within the polymer binder, which is surrounded by the bulk explosive. The mesoscale smoothed particle hydrodynamic simulation is adopted to identify the peak temperatures within the hot spots. These peak temperatures obtained from the mesoscale level are then used to initialize the random sites of heat release prior to conducting the full-scale hydrodynamic simulation of the shock-to-detonation transition (SDT). To validate the simulation, the distance to detonation is compared with the reported experimental value to validate the initiation process of the proposed model and an 18-mm-radius rate stick is experimentally tested to confirm the reproducibility of the detonation properties. The comparison shows that the detonation properties and the initiation process of the explosive are well characterized, while no-go conditions are observed if no mesoscale hot-spot model is included in the hydrodynamic simulation. Therefore, the SDT process can be well described by the present model based on multi-scale hot-spot initiation.
Tutorial: Concepts for closely mimicking biological learning with memristive devices: Principles to emulate cellular forms of learning
Authors: Ziegler M. , Wenger Ch. , Chicca E. , Kohlstedt H.
Published: October 2018

The basic building blocks of every neural network are neurons and their inter-cellular connections, called synapses. In nature, synapses play a crucial role in learning and memory, since they are plastic, which means that they change their state depending on the neural activity of the respectively coupled neurons. In neuromorphic systems, the functionality of neurons and synapses is emulated in hardware systems by employing very-large-scale integration technology. In this context, it seems rather natural to use non-volatile memory technology to mimic synaptic functionality. In particular, memristive devices are promising candidates for neuromorphic computing, since they allow one to emulate synaptic functionalities in a detailed way with a significantly reduced power usage and a high packing density. This tutorial aims to provide insight on current investigations in the field to address the following fundamental questions: How can functionalities of synapses be emulated with memristive devices? What are the basic requirements to realize artificial inorganic neurons and synapses? Which material systems and device structures can be used for this purpose? And how can cellular synaptic functionality be used in networks for neuromorphic computing? Even if those questions are part of current research and not yet answered in detail, our aim is to present concepts that address those questions. Furthermore, this tutorial focuses on spiking neural models, which enables mimicking biological computing as realistically as possible.
Invited Review Article: Multi-tip scanning tunneling microscopy: Experimental techniques and data analysis
Authors: Voigtländer Bert , Cherepanov Vasily , Korte Stefan , Leis Arthur , Cuma David , Just Sven , Lüpke Felix
Published: October 2018

In scanning tunneling microscopy, we witness in recent years a paradigm shift from “just imaging” to detailed spectroscopic measurements at the nanoscale and multi-tip scanning tunneling microscope (STM) is a technique following this trend. It is capable of performing nanoscale charge transport measurements like a “multimeter at the nanoscale.” Distance-dependent four-point measurements, the acquisition of nanoscale potential maps at current carrying nanostructures and surfaces, as well as the acquisition of I − V curves of nanoelectronic devices are examples of the capabilities of the multi-tip STM technique. In this review, we focus on two aspects: How to perform the multi-tip STM measurements and how to analyze the acquired data in order to gain insight into nanoscale charge transport processes for a variety of samples. We further discuss specifics of the electronics for multi-tip STM and the properties of tips for multi-tip STM, and present methods for a tip approach to nanostructures on insulating substrates. We introduce methods on how to extract the conductivity/resistivity for mixed 2D/3D systems from four-point measurements, how to measure the conductivity of 2D sheets, and how to introduce scanning tunneling potentiometry measurements with a multi-tip setup. For the example of multi-tip measurements at freestanding vapor liquid solid grown nanowires, we discuss contact resistances as well as the influence of the presence of the probing tips on the four point measurements.
A single electron transistor charge sensor in strong rf fields
Authors: Lewis R. M. , Harris C. T. , Shaner E. A.
Published: October 2018

We measure the charge sensitivity, Se, of a single electron transistor (SET) in the presence of strong (Vrf ∼ e/Cg) spurious radio frequency (rf) signals at frequencies up to 50 MHz, where Cg is the gate capacitance. Although Se appears to degrade when exposed to Vrf, we find that broadening of conduction peaks is largely due to the measurement technique and show that Se is maintained even with strong Vrf present. We show cancellation of a known Vrf signal at 1 MHz, demonstrating that a stable bias point in the presence of rf signals is possible.
Enhanced multiferroic properties of lead-free (1-x)GaFeO3-(x)Co0.5Zn0.5Fe2O4 composites
Authors: Ghani Awais , Yang Sen , Rajput S. S. , Ahmed S. , Murtaza Adil , Zhou Chao , Zhang Yin , Song Xiaoping , Ren Xiaobing
Published: October 2018

Multiferroic composites of (1-x)GaFeO3-(x)Co0.5Zn0.5Fe2O4 with x = 0.0, 0.1, 0.2, and 1 were prepared using a conventional solid state reaction method. The X-ray diffraction patterns confirmed that the composites consisted of cubic spinel Co0.5Zn0.5Fe2O4 and orthorhombic GaFeO3 phases. The coexistence of both magnetic and ferroelectric orderings at ambient temperature was confirmed by measuring M-H and P-E loops. The inclusion of Co0.5Zn0.5Fe2O4 enhanced magnetization and dielectric constant, as well as improved the ferroelectric properties of GaFeO3. The leakage current (9.33 × 10−8 A/cm2) of composite (x = 0.20) is found to be much lower as compared to pure GaFeO3. The value of saturation magnetization increased to 30.6 emu/g at 300 K. This large enhancement of magnetization, as well as the presence of ferroelectricity, is promising for enabling future magnetoelectric applications.
Feed-forward comb-assisted coherence transfer to a widely tunable DFB diode laser
Authors: Gotti Riccardo , Sala Tommaso , Prevedelli Marco , Kassi Samir , Marangoni Marco , Romanini Daniele
Published: October 2018

The transfer of phase coherence from an ultrastable master laser to a distributed feedback diode laser, using an optical comb as a transfer oscillator, is obtained via a new scheme allowing continuous scanning across the whole tuning range of the slave laser together with absolute frequency determination. This is accomplished without phase lock loops, through a robust high-bandwidth feed-forward control acting directly on the slave laser output radiation. The correction is obtained by means of a dual-parallel Mach–Zehnder interferometer used as an optical single-sideband modulator. Coherence transfer across a master–slave frequency gap of 14 THz yields an ∼10 kHz linewidth providing high injection efficiency of an optical cavity with finesse 250 000. This allows demonstrating a cavity ring-down absorption spectrum of low-pressure ambient air over a 300 GHz spectral window.
Terahertz wide-angle metamaterial absorber fabricated by printed circuit board technique
Authors: Qi Limei , Liu Chang
Published: October 2018

A wide-angle terahertz metamaterial absorber is designed, fabricated, and measured. The resonant structure on the top layer of the absorber consists of two metal crosses with different sizes. The wider and higher absorption is achieved when compared with the structures that only consist of a large or small cross under different incident angles. Physical mechanisms of the absorption are clarified by their electric field distributions. The influence of the permittivity and the loss tangent of the dielectric on the absorptions are also investigated. The terahertz band sample was developed based on a double-faced copper dielectric plate using the conventional printed circuit board (PCB) technique. This saves time and allows for low cost and large-area fabrication as an alternative to the expensive conventional lithography method. The reflection spectra of the sample at oblique incidence are directly obtained using a vector network analyzer in conjunction with a quasi-optical test bench, which is used instead of the most common Fourier Transform Infrared spectrometry or Terahertz (THz) time-domain spectroscopy method in the terahertz band. The measured results are in good agreement with those of the simulation. The proposed terahertz metamaterial absorber will be crucial in the implementation of future terahertz sensors, THz communication systems, and other emerging THz technologies.
Analysis of the optical parameters of amorphous ternary oxides Sn1−xZnxO and Sn1−xNixO processed by combinatorial ion-beam sputter deposition
Authors: Becker M. , Michel F. , Polity A. , Klar P. J.
Published: October 2018

We employed combinatorial ion-beam sputter deposition (IBSD) at low substrate temperatures of 100 °C to generate thin films of the amorphous ternary oxides Sn1−xZnxO (a-TZO) and Sn1−xNixO (a-TNO) with continuous compositional gradients over a distance of several centimeters in the film plane. The spatial compositional profiles were assessed by X-ray photoelectron spectroscopy measurements and indicate that amalgamation of the binary source materials spans the entire compositional range of both amorphous ternary alloys. Combinatorial IBSD thus offers an interesting alternative to conventional growth techniques employed in combinatorial growth. Furthermore, correlating the information on lateral composition with lateral measurements of the optical bandgap and of the refractive index dispersion shows that the bandgap as a function of x is almost linear for both alloys in the entire composition range and the compositional dependence of the refractive index can be well described by the effective-medium approach of Bruggeman. The optical results indicate that a-TZO (xZn>0.7) and a-TNO (xNi>0.3), both of which are formed of abundant chemical elements, may act as substitute materials for resource-critical indium tin oxide at least in some applications.
Length dependence of viscoelasticity of entangled-DNA solution with and without external stress
Authors: Tanoguchi Masaya , Murayama Yoshihiro
Published: October 2018

We observed the diffusive motion of a micron-sized bead in an entangled-DNA solution to investigate the effect of the viscoelasticity on the bead motion. In the absence of external stress (passive microrheology), subdiffusion appears in the timescale of 0.1–10 s, and the normal diffusion recovers in longer timescales. We evaluated the apparent viscosity and elasticity, which yields a simple relaxation time for the viscoelastic medium. We found that the absence of DNA-length dependence for the time-dependent diffusion is explained by the simple relaxation of the viscoelastic media rather than the reptation dynamics, including the disentanglement. On the other hand, in the presence of a small external stress in active microrheology, the bead motion showed clear length dependence owing to the viscoelasticity. These results suggest that the viscoelasticity of the entangled DNA is highly sensitive to the external stress, even in the linear response regime.
Characterization of thin film evaporation in micropillar wicks using micro-Raman spectroscopy
Authors: Zhang Lenan , Zhu Yangying , Lu Zhengmao , Zhao Lin , Bagnall Kevin R. , Rao Sameer R. , Wang Evelyn N.
Published: October 2018

Thin film evaporation on microstructured surfaces is a promising strategy for high heat flux thermal management. To enhance fundamental understanding and optimize the overall heat transfer performance across a few microns thick liquid film, however, requires detailed thermal characterizations. Existing characterization techniques using infrared thermometry or contact-mode temperature sensors such as thermocouples and resistance temperature detectors cannot accurately measure the temperature of the thin liquid film near the three-phase contact line due to the restriction of low spatial resolution or temperature sensitivity. In this work, we developed a non-contact, in situ temperature measurement approach using a custom micro-Raman spectroscopy platform which has a spatial resolution of 1.5 μm and temperature sensitivity within 0.5 °C. We utilized this method to characterize thin film evaporation from fabricated silicon micropillar arrays. We showed that we can accurately measure the local thin film temperature and map the overall temperature distribution on the structured surfaces at different heat fluxes. We investigated the effects of micropillar array geometries and showed that the temperature rise of the liquid was reduced with the decreasing micropillar pitch due to the increased fraction of the thin film area. This work offers a promising method with micro-Raman to quantify phase change heat transfer on microstructured surfaces. This characterization technique can significantly aid mechanistic understanding and wick structure optimization for various phase-change based thermal management devices.
Perspective: Identification of collective variables and metastable states of protein dynamics
Authors: Sittel Florian , Stock Gerhard
Published: October 2018

The statistical analysis of molecular dynamics simulations requires dimensionality reduction techniques, which yield a low-dimensional set of collective variables (CVs) {xi} = x that in some sense describe the essential dynamics of the system. Considering the distribution P(x) of the CVs, the primal goal of a statistical analysis is to detect the characteristic features of P(x), in particular, its maxima and their connection paths. This is because these features characterize the low-energy regions and the energy barriers of the corresponding free energy landscape ΔG(x) = −kBT ln P(x), and therefore amount to the metastable states and transition regions of the system. In this perspective, we outline a systematic strategy to identify CVs and metastable states, which subsequently can be employed to construct a Langevin or a Markov state model of the dynamics. In particular, we account for the still limited sampling typically achieved by molecular dynamics simulations, which in practice seriously limits the applicability of theories (e.g., assuming ergodicity) and black-box software tools (e.g., using redundant input coordinates). We show that it is essential to use internal (rather than Cartesian) input coordinates, employ dimensionality reduction methods that avoid rescaling errors (such as principal component analysis), and perform density based (rather than k-means-type) clustering. Finally, we briefly discuss a machine learning approach to dimensionality reduction, which highlights the essential internal coordinates of a system and may reveal hidden reaction mechanisms.
Black phosphorus with a unique rectangular shape and its anisotropic properties
Authors: Hsiao Yao , Chang Po-Yen , Fan Kai-Lin , Hsu Ning-Chun , Lee Si-Chen
Published: October 2018

Black Phosphorus (BP) is a 2D material with high hole mobility. However, due to its fast degradation property under ambient air, fast crystal orientation determination is required for the fabrication of BP transistor along the crystal orientation with the highest mobility. In this paper, a method for producing BP flakes with a special rectangular shape was developed. This shape provides important information about the crystal orientation of BP. By using polarized Raman measurements, it was demonstrated that the Raman peak ratios of two specific lattice vibration modes would change from 2 to 1 when the polarized laser light is parallel to armchair (AC) and zigzag (ZZ) orientations of BP. In addition, by using the rectangular BP, the mobility in the AC direction was measured to be larger than that in the ZZ direction by a factor of 2. The BP transistor with hexagonal boron nitride (h-BN) encapsulation on both top and bottom sides were also fabricated to avoid the degradation and improve the device performance.
Impact of γ-ray irradiation on graphene nano-disc non-volatile memory
Authors: Xi K. , Bi J. S. , Hu Y. , Li B. , Liu J. , Xu Y. N. , Liu M.
Published: October 2018

The effects of irradiation on graphene nano-disc (GND) non-volatile memory devices were investigated by 60Co γ-rays. The electrical characteristics of the devices were measured before and after γ-irradiation with doses ranging from 50 to 1000 krad (Si). The electrical properties of the devices in the pristine and erased states were nearly unchanged in response to ionizing doses up to 1 Mrad (Si). However, the electrical properties of the devices in the programmed states were significantly degraded with increasing dose levels. The degradation was mainly the result of photoemission, positive charge traps in the surrounding oxides, and holes injected into the GND trapping layer. This study improves the understanding of radiation effects on graphene-based nano-electronic devices.
Camera array-based digital image correlation for high-resolution strain measurement
Authors: Shao Xinxing , Chen Zhenning , Dai Xiangjun , He Xiaoyuan
Published: October 2018

Digital image correlation (DIC) is a well-known technique for non-contact, non-destructive, full-field deformation measurement in experimental solid mechanics. Although DIC has been widely used in science and engineering, the resolution of strain measurement with DIC is limited by imaging resolution and is much lower than that obtained with a strain gauge. To achieve a breakthrough in strain measurement using DIC, a camera array-based DIC method is proposed herein for high-resolution strain measurement. Twenty-five industrial cameras were assembled into a plane array, with each camera capturing a part of the specimen. A novel calibration-based image stitching method is proposed and was applied to these images and their corresponding displacement fields. The strain field was then calculated based on the stitched displacement fields. The use of the camera array greatly improved the measurement spatial resolution of DIC and made high-resolution strain measurement possible. Both static error analysis and four point-bending experiments were performed to demonstrate the feasibility and effectiveness of the proposed method, and a full-field strain resolution of 10 με was achieved.
Single crystal diamond micro-disk resonators by focused ion beam milling
Authors: Graziosi Teodoro , Mi Sichen , Kiss Marcell , Quack Niels
Published: October 2018

We report on single crystal diamond micro-disk resonators fabricated in bulk chemical vapor deposition diamond plates (3 mm × 3 mm × 0.15 mm) using a combination of deep reactive ion etching and Focused Ion Beam (FIB) milling. The resulting structures are micro-disks of few μm in diameter and less than 1 µm thick, supported by a square or diamond section pillar resulting from the multi-directional milling. Thin aluminum and chromium layers are used to ground the substrate, limit the ion implantation, and prevent edge rounding and roughening. FIB damage is then removed by a combination of hydrofluoric acid etching, oxygen plasma cleaning, and annealing at 500 °C for 4 h in air. We experimentally characterize the optical behavior of the devices by probing the transmission of a tapered fiber evanescently coupled to the micro-disk, revealing multiple resonances with a quality factor up to 5700 in the S- and C-band.
Role of band alignment at the transparent front contact/emitter interface in the performance of wide bandgap thin film solar cells
Authors: Liyanage Geethika K. , Phillips Adam B. , Heben Michael J.
Published: October 2018

Recent numerical modeling and experimental work have shown that appropriate conduction band alignment at the emitter/absorber interface is critically important for high efficiency CdTe solar cells. To date, however, the properties of the transparent conducting oxide (TCO)/emitter interface have not been thoroughly investigated. Here, we use numerical modeling to determine the role of the conduction band alignment at the TCO/emitter interface. Our findings are increasingly important to device performance as efforts are made to widen the bandgap of the absorber. We also investigate the relative importance of the barrier caused by poor front contact versus the barrier at the back contact. It is well known that a barrier at the back contact can reduce the open circuit voltage of the device and produce rollover in the current density-voltage but is not well appreciated that a barrier at the front of the device can play a completely analogous role. We also show that for optimum device performance at any absorber bandgap, the conduction band of the TCO must be no more than 0.3 eV below the conduction band of the emitter.
Local structure of stoichiometric and oxygen-deficient A2Ti6O13 (A = Li, Na, and K) studied by X-ray absorption spectroscopy and first-principles calculations
Authors: Kanchanawarin Jarin , Limphirat Wanwisa , Promchana Pratya , Sooknoi Tawan , Maluangnont Tosapol , Simalaotao Kodchakorn , Boonchun Adisak , Reunchan Pakpoom , Limpijumnong Sukit , T-Thienprasert Jiraroj
Published: October 2018

Oxygen vacancy defects (VO) in Ti-based oxides play important roles in catalytic processes despite limited knowledge regarding their formation and characterization. Here, we demonstrate the use of X-ray absorption spectroscopy (XAS) measurements to compare the relative proportion of VO defects in as-grown alkali hexatitanate A2Ti6O13 (A = Li, Na, K). Both X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) regions were studied. The similarity of measured XANES spectra of Ti K-edge in all samples indicates the presence of (Ti4+)O6 units in good agreement with reported X-ray diffraction results. The small influence of cations A at the tunnel was observed and can be well reproduced in the simulated spectra. In addition, we present a semi-quantitative approach to intuitively determine the content of VO defects in oxygen-deficient K2Ti6O13-x by in situ time-resolved XAS measurements under reducing conditions (10%H2/Ar, 50-650 °C). The in situ XANES measurements indicate that the oxidation state of bulk Ti remains the same as the as-grown sample, i.e., 4+, at elevated temperatures. By in situ EXAFS measurements, the relative number of VO defects is highest at a reduction temperature of ∼550 °C and slightly decreases after that. To confirm the formation of VO defects, first-principles calculations were independently carried out using a 126-atom K2Ti6O13 supercell with VO at various positions. Based on calculated EXAFS, the removal of the oxygen atom nearest to the tunnel, which is the lowest energy structure, provides a good match to the experimental spectra.
Micropatterning of organic electronic materials using a facile aqueous photolithographic process
Authors: Ðerek Vedran , Jakešová Marie , Berggren Magnus , Simon Daniel T. , Głowacki Eric Daniel
Published: October 2018

Patterning organic semiconductors via traditional solution-based microfabrication techniques is precluded by undesired interactions between processing solvents and the organic material. Herein we show how to avoid these problems easily and introduce a simple lift-off method to pattern organic semiconductors. Positive tone resist is deposited on the substrate, followed by conventional exposure and development. After deposition of the organic semiconductor layer, the remaining photoresist is subjected to a flood exposure, rendering it developable. Lift-off is then performed using the same aqueous developer as before. We find that the aqueous developers do not compromise the integrity of the organic layer or alter its electronic performance. We utilize this technique to pattern four different organic electronic materials: epindolidione (EPI), a luminescent semiconductor, p-n photovoltaic bilayers of metal-free phthalocyanine and N,N’-dimethyltetracarboxylic diimide, and finally the archetypical conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT). The result of our efforts is a facile method making use of well-established techniques that can be added to the toolbox of research and industrial scientists developing organic electronics technology.
Using radiation pressure to develop a radio-frequency power measurement technique traceable to the redefined SI
Authors: Holloway Christopher L. , Simons Matthew T. , Kautz Marcus D. , Haddab Abdulaziz H. , Novotny David , Lehman John H. , Williams Paul A. , Shaw Gordon A.
Published: October 2018

We discuss a power-measurement technique traceable to the International System of Units (SI) based on radiation pressure (or radiation force) inherent in an electromagnetic wave. A measurement of radiation pressure offers the possibility for a power measurement traceable to the kilogram and to Planck's constant through the redefined SI. Towards this goal, we performed measurements of the radiation pressure in a radio-frequency (RF) electromagnetic field at three frequencies (26.5 GHz, 32.5 GHz, and 40.0 GHz) and power levels ranging from 2 W to 25 W using a commercially available mass scale. We show comparisons between the RF power obtained with this technique and those obtained with a conventional power meter. The results in this paper represent the first step towards the realization of a more direct link to RF power within the newly redefined SI.