bluuebunny/crossref_metadata_2025 huggingface dataset:
Moderne Zeiten: Heute wissen, was morgen gebraucht wird
Authors: Thalmayr Maria
Published: February 2019

Zukunftsforscher erwarten durch die voranschreitende Digitalisierung und insbesondere durch den verstärkten Einsatz Künstlicher Intelligenz (KI) einen ähnlich umwälzenden Fortschritt wie durch die Erfindung der Elektrizität. Diese technische Revolution zu antizipieren und Handlungsempfehlungen abzuleiten, ist augenblicklich eine der dringendsten Aufgaben des ÖVKT.
Innovationspreis der Wissenschaftlichen Gesellschaft für krankenhaustechnik: Instrument der Nachwuchsförderung für das Krankenhaus
Authors: Hohenberg Gregor
Published: February 2019

Preise für den wissenschaftlichen Nachwuchs sind mehr als eine Ehrenbekundung für die einzelnen Preisträger. Vielmehr sind sie ein Indikator für die aktuellen Entwicklungen im Fach und ein Spiegel dafür, wie der wissenschaftliche Nachwuchs die Branche wahrnimmt. Die WGKT wird 2019 zum fünften Mal den Innovationspreis ausschreiben.
Oxidative Coupling of N-Methoxyamides and Related Compounds toward Aromatic Hydrocarbons by Designer μ-Oxo Hypervalent Iodine Catalyst
Authors: Dohi Toshifumi , Sasa Hirotaka , Dochi Mio , Yasui Chihiro , Kita Yasuyuki
Published: February 2019

Oxidative coupling strategies that can directly convert the C–H group for chemical transformations are, in theory, ideal synthetic methods to reduce the number of synthetic steps and byproduct generation. Hypervalent iodine reagents have now become one of the most promising tools in developing oxidative couplings due to their unique reactivities that are replacing metal oxidants. As part of our continuous development of oxidative coupling reactions, we describe in this report highly efficient μ-oxo hypervalent iodine catalysts for the direct oxidative coupling of N-methoxyamides and related compounds with aromatic hydrocarbons. The excellent TONs, up to over 100 times, with a best catalyst loading of 0.5 mol% were determined for the oxidative C–H/N–H coupling method, which can provide the most straightforward route to obtaining these unique arylamide compounds.
Palladium(II)-Catalyzed C(sp3)–H Activation of N,O-Ketals towards a Method for the β-Functionalization of Ketones
Authors: Ho Danny , Calleja Jonas , Gaunt Matthew
Published: February 2019

A method for the formal β-functionalization of aliphatic ketones via a palladium-catalyzed sp3 C–H activation pathway is reported. An N,O-ketal directs an aliphatic C–H carbonylation to form γ-lactams which upon hydrolysis generate γ-keto carboxylic acids. This C–C bond-forming reaction is tolerant of a range of functional groups, enabling the synthesis of a range of synthetically important building blocks. Furthermore, the concepts underlying this transformation have also enabled the development of a related C–H alkenylation process to highly functionalised heterocycles.
Asymmetric Kulinkovich Hydroxycyclopropanation of Alkenes Mediated by Titanium(IV) TADDOLate Complexes
Authors: Iskryk Marharyta , Barysevich Maryia , Ošeka Maksim , Adamson Jasper , Kananovich Dzmitry
Published: February 2019

Asymmetric Kulinkovich cyclopropanation of carboxylic ­esters with prochiral alkenes is reported. The process is mediated by ­titanium(IV) (4R,5R)-TADDOLate complexes and affords correspondingly (Z)- or (E)-cyclopropanols with up to 84–87% ee in the event of intra- or intermolecular olefin ligand exchange in intermediate titanacyclopropane [titanium(II)-alkene] species. Configuration of the olefin double bond is preserved in the cyclopropane products, pointing out on ­total retention of configuration at Ti–C bond in the cyclopropane forming step. The results have been interpreted in the framework of ate complex mechanism, suggesting formation of pentacoordinated titanium ate species as a prerequisite of high enantiocontrol.
A Concise Approach for Producing Optically Pure Carboxylic Acid Segments for the Synthesis of Bicyclic Depsipeptide Histone Deacetylase Inhibitors
Authors: Katoh Tadashi , Narita Koichi , Sayar Noel , Saijo Ken , Ishioka Chikashi
Published: February 2019

Optically pure carboxylic acid segments, which are common key intermediates for the synthesis of naturally occurring bicyclic depsipeptide histone deacetylase inhibitors, have been produced efficiently. The method features the chromatographic separation of two diastereomers, which were formed by direct amide condensation of racemic (3RS,4E)-3-hydroxy-7-mercaptohept-4-enoic acid (rac-Hmh) with chiral amino acids. This approach offers a reliable and practical method for producing optically pure carboxylic acid segments, which can facilitate easier access to important anticancer agents derived from them.
Efficiency and Selectivity Aspects in the C–H Functionalization of Aliphatic Oxygen Heterocycles by Photocatalytic Hydrogen Atom Transfer
Authors: Raviola Carlotta , Ravelli Davide
Published: February 2019

The C–H to C–C conversion in aliphatic oxygen heterocycles (dioxolanes, 1,3-dioxane, or cyclic carbonates) by photocatalytic hydrogen atom transfer and subsequent trapping of the resulting radical with phenyl vinyl sulfone was investigated. The performance of three different photocatalysts, namely tetrabutylammonium decatungstate and the aromatic ketones thioxanthone and 9-fluorenone, was compared. The UV-light-absorbing decatungstate anion is more efficient and permits the use of a smaller excess of hydrogen donor than the aromatic ketones, although the ketones could be excited by visible light. Further intramolecular selectivity studies revealed that aromatic ketones afforded a higher proportion of functionalization at the acetalic versus the ethereal positions than did the decatungstate anion.
Tandem Schiff-Base Formation/Heterocyclization: An Approach to the Synthesis of Fused Pyrazolo–Pyrimidine/Isoxazolo-Pyrimidine Hybrids
Authors: Behera Manoranjan , Sambaiah M. , Mallesham Poosa , Shiva Kumar K. , Bobde Yamini , Hota Prasanta , Yennam Satyanarayana , Ghosh Balaram
Published: February 2019

A new synthesis of pyrazolo[4,3-d]pyrimidines and isoxazolo[4,5-d]pyrimidines is described. Key steps in the synthesis involve Stille coupling of 4,6-dichloro-2-phenyl-pyrimidine with tributyl(1-ethoxyvinyl)stannane and tandem Schiff-base formation/heterocyclization of 2,6-di-aryl-5-fluoro-4-acetylpyrimidine with hydrazines or ­hydroxylamine to give pyrazolo[4,3-d]pyrimidines and isoxazolo[4,5-d]pyrimidines, respectively. The position of the fluoro group in the ­pyrimidine ring is important for the success of heterocylization reaction.
1,2-Dihydrochromeno[2,3-c]pyrrol-3-one Derivatives: Synthesis and HPLC-ECD Analysis
Authors: Tóth László , Kiss-Szikszai Attila , Vasvári Gábor , Fenyvesi Ferenc , Vecsernyés Miklós , Mátyus Péter , Antus Sándor , Mándi Attila , Kurtán Tibor
Published: February 2019

Ethyl-3-formyl-6-methoxy-(2H)-chromene-2-carboxylate was transformed to N-substituted 1,2-dihydrochromeno[2,3-c]pyrrol-3-ones in a domino reductive amination–lactamization reaction. Isomerization of the double bond and the inherently labile stereogenic center was studied, and HPLC-ECD analysis of a chiral 1,2-dihydrochromeno[2,3-c]pyrrol-3(3aH)-one derivative aided by TDDFT-ECD calculation allowed configurational assignment of the separated enantiomers. Antiproliferative activity of the products was demonstrated on the CaCo-2 human epithelial colorectal adenocarcinoma cell line.
Treatment Strategies for the Claudicant
Authors: Pereira Keith
Published: February 2019

Peripheral arterial disease (PAD) is a prevalent, morbid, and mortal disease. Claudication represents an early, yet common manifestation of PAD. A clinical history and physical examination combined with an ankle-brachial index can help make a diagnosis of claudication. Due to the polyvascular nature of the underlying atherosclerosis, PAD is often associated with heart disease and stroke. Although health implications of PAD derive from both its limb and cardiovascular manifestations, claudication is life-threatening, less limb-threatening. Medical modification of cardiovascular risk factors and exercise are the cornerstone in the treatment of claudication. Revascularization in claudication is focused at improvement in claudication symptoms and functional status, rather than aggressive attempts at limb salvage. The aim of this article is to summarize the strategies in the treatment of claudication, to serve as a concise and informative reference for physicians who are managing these patients. A framework of the decision-making process in the management of patients with claudication is shown, which can be applied in clinical practice.
Noninvasive Arterial Testing: What and When to Use
Authors: Mittleider Derek
Published: February 2019

Peripheral arterial disease (PAD) represents a growing public health issue that continues to be underdiagnosed. In its most severe form, critical limb ischemia, it contributes to expanding morbidity with minor and major limb amputations. PAD is strongly associated with increased mortality, as it is known to be concomitant with coronary and cerebrovascular disease. Diagnosis of PAD relies on noninvasive arterial testing, a class of tests that can provide physiologic or morphologic information. Physiologic tests such as ankle-brachial index, toe-brachial index, pulse volume recordings, and arterial duplex evaluation are the mainstay of gateway evaluation and surveillance. Morphologic exams such as computer tomographic angiography and magnetic resonance angiography are appropriate for preprocedural anatomic evaluation in patients with established vascular disease. This review focuses on physiologic exams.
Pharmacology of Peripheral Arterial Disease in the Angio Suite: What Every Interventionalist Should Know
Authors: Watts Micah
Published: February 2019

Safe and effective treatment of peripheral arterial disease (PAD) and critical limb ischemia can be routinely performed in the angiography suite. A systematic understanding of the medications commonly used during these procedures is essential. This review discusses the traditional roles of the medications used in PAD procedures, the existing evidence basis for those roles, potential alternatives, and evolving techniques. Developing a familiarity with these medications can help improve outcomes and safety for the patients being treated.
The Chronic Care Model and Chronic Condition Self-Management: An Introduction for Audiologists
Authors: Hickson Louise , Keidser Gitte , Meyer Carly , Convery Elizabeth
Published: February 2019

Hearing health care is biomedically focused, device-centered, and clinician-led. There is emerging evidence that these characteristics—all of which are hallmarks of a health care system designed to address acute, rather than chronic, conditions—may contribute to low rates of help-seeking and hearing rehabilitation uptake among adults with hearing loss. In this review, we introduce audiologists to the Chronic Care Model, an organizational framework that describes best-practice clinical care for chronic conditions, and suggest that it may be a viable model for hearing health care to adopt. We further introduce the concept of chronic condition self-management, a key component of chronic care that refers to the knowledge and skills patients use to manage the effects of a chronic condition on all aspects of daily life. Drawing on the chronic condition evidence base, we demonstrate a link between the provision of effective self-management support and improved clinical outcomes and discuss validated methods with which clinicians can support the acquisition and application of self-management skills in their patients. We examine the extent to which elements of chronic condition self-management have been integrated into clinical practice in audiology and suggest directions for further research in this area.
Calcified Prolactinoma of the Pituitary Gland: Illustrative Case Reports Highlighting Medical versus Surgical Intervention
Authors: Tavakol Sherwin , Hasan Asma , Wedemeyer Michelle A. , Bakhsheshian Joshua , Liu Chia-Shang J. , Shiroishi Mark S. , Mathew Anna , Carmichael John D. , Zada Gabriel
Published: February 2019

The presence of calcification is uncommon in pituitary adenomas, and often lends support to other diagnoses including craniopharyngioma. The majority of calcified pituitary adenomas are prolactin-secreting tumors. We report two patients with calcified macroprolactinomas, one that was treated medically with a biochemical response and partial tumor response, and one that was treated successfully via an endoscopic endonasal transsphenoidal approach. Suspected calcified prolactinomas can be initially managed medically as per standard treatment for typical prolactinomas; however, the presence of diffuse calcification may hinder tumor shrinkage. Tumors that are refractory to medical treatment can be safely managed with surgery.
Endometriosis and Recurrent Pregnancy Loss as New Risk Factors for Venous Thromboembolism during Pregnancy and Post-Partum: The JECS Birth Cohort
Authors: Sugiura-Ogasawara Mayumi , Ebara Takeshi , Matsuki Taro , Yamada Yasuyuki , Omori Toyonori , Matsumoto Yosuke , Kato Sayaka , Kano Hirohisa , Kurihara Takahiro , Saitoh Shinji , Kamijima Michihiro ,   and the Japan Environment & Children's Study (JECS) Group
Published: February 2019

Background Since venous thromboembolism (VTE) is one of the causes of maternal mortality, several guidelines recommend prophylaxis using low molecular weight heparin for women in high-risk groups. The number of large population-based studies examining predictors for VTE has been limited, and there has been no study based on a Japanese population.

Objective Our objective was to examine VTE risk factor during the pregnancy and post-partum period.

Materials and Methods A nationwide birth cohort study known as the ‘Japan Environment and Children's Study (JECS)’ was conducted by the Ministry of the Environment. The subjects consisted of 103,070 pregnancies recruited by the JECS between January 2011 and March 2014. Pregnant women completed the questionnaires during the first and second/third trimester. Their medical records were transcribed by physicians or research coordinators at registration, just after delivery and at 1 month after delivery.

Results The frequency of VTE was 7.5 per 10,000 pregnancies (77 of 103,070) during the pregnancy and post-partum period. After the adjustment of multiple covariates for each factor, endometriosis and recurrent pregnancy loss (RPL) were identified as novel independent risk factors for VTE. Adjusted odds ratios were as follows: 2.70 (95% confidence interval, 1.21–6.00) for endometriosis and 6.13 (2.48–15.16) for RPL. Threatened abortion, threatened pre-term birth, pre-term birth and caesarean section were ascertained to be risk factors for VTE.

Conclusion Careful attention should be given to novel predictors, such as endometriosis and a history of RPL, to prevent VTE during the pregnancy and post-partum period.
Sciatic Neuropathy in a Dog Secondary to a Bursitis
Authors: Gomes César , Anderson Angus , Stewart Jennifer
Published: February 2019

A 4-year-old Dogue de Bordeaux developed acute onset sciatic neuropathy 9 weeks following stifle surgery of the contralateral pelvic limb. Pelvic radiography showed mild bilateral hip dysplasia. Magnetic resonance imaging of the pelvis and lumbosacral spine showed a fluid-filled structure caudal to the hip joint of the affected limb that was causing compression of the sciatic nerve. The lesion was surgically excised and bursitis was confirmed on histological examination. This is the first report of sciatic neuropathy secondary to bursitis in the dog.
Immediate and Sustained Effect of Neonatal Teaching in a Perinatal Setting in Urban Laos
Authors: Hoehn Thomas , Genet Petra , Balan Percy , Schramm Dirk , Verde Pablo Emilio , Phengsavanh Alongkone
Published: February 2019

Objective This study aimed to quantify knowledge on neonatal topics among obstetricians and pediatricians participating in a perinatal teaching program aimed at reducing neonatal mortality in Laos.

Study Design Obstetricians and pediatricians from Vientiane and the surrounding areas participated in a 1-week teaching program in obstetric and neonatal topics and responded to pre- and posttests questionnaires to quantify their knowledge.

Results Although questions were predominantly related to neonatal topics, obstetricians performed significantly better than pediatricians during the pretest. Both groups increased their knowledge significantly as quantified by the results of the posttest.

Conclusion The teaching program was effective in improving knowledge on perinatal mortality related topics of the participants. These results may be related to the fact that most of the obstetricians had participated in a structured teaching program previously, whereas the pediatricians did not. We thus speculate that there is a sustained effect of even a 1-week teaching program in neonatology even several years after the initial teaching.
Putting speculation and new materialisms in dialogue
Authors: Moffat Luke
Published: February 2019

Over the past decade, numerous disciplines have taken on speculation as a method for research, a tool for thought, or a topic of study. In so doing, sociology, politics, design, geography and other disciplines have all helped to readdress the nature and potential of speculation, as a way of thinking, but also as a way to bridge the gap between theory and practice, something that often plagues philosophy. Despite the variety of perspectives in this range of disciplines, they often draw upon a common philosophical canon. This paper explores current discussions of speculation in the context of speculative philosophy, as well as work in new materialisms from Karen Barad, and Jane Bennett, to address some potential exchanges between new materialisms and speculation. The paper concludes with a brief description of a symposium held in 2018 that explored these themes across disciplines. It advocates further exchanges between speculative and new materialist approaches, as one way of figuring the place of matter in theory.
(Anti-)symmetrizing wave functions
Authors: Krishnan Chethan , Kumar K. V. Pavan , Subramanian P. N. Bala
Published: February 2019

The construction of fully (anti-)symmetric states with many particles, when the single particle state carries multiple quantum numbers, is a problem that seems to have not been systematically addressed in the literature. A quintessential example is the construction of ground state baryon wave functions where the color singlet condition reduces the problem to just two (flavor and spin) quantum numbers. In this paper, we address the general problem by noting that it can be re-interpreted as an eigenvalue equation and provide a formalism that applies to the generic number of particles and the generic number of quantum numbers. As an immediate result, we find a complete solution to the two quantum number case, from which the baryon wave function problem with an arbitrary number of flavors follows. As a more elaborate illustration that reveals complications not visible in the two quantum number case, we present the complete class of states possible for a system of five fermionic particles with three quantum numbers each. Our formalism makes systematic use of properties of the symmetric group and Young tableaux. Even though our motivations to consider this question have their roots in Sachdev-Ye-Kitaev-like tensor models and holography, the problem and its solution should have broader applications.
Instantaneous measurement of high-power millimeter-wave beam for 28 GHz gyrotron
Authors: Matsukura Maho , Shimamura Kohei , Suzuki Masatoshi , Mizojiri  , Yokota Shigeru , Minami Ryutaro , Kariya Tsuyoshi , Imai Tsuyoshi
Published: February 2019

An instantaneous measurement system of high-power millimeter-wave was proposed and demonstrated with a 28 GHz gyrotron at the Plasma Research Center, University of Tsukuba. The high-power detector consists of an attenuator and a linear polarized microstrip antenna with an F-class load rectifier, which is a commonly used system for radio-frequency wireless power transmission. The detector obtained the power distribution of the gyrotron output beam which showed good agreement with the infrared camera image. The rectenna array detector received 45 W RF input power with a 0.4 ms response time. The results revealed that the proposed narrow band detector is useful as an imaging sensor and power meter for high-power millimeter-wave beam output with a wide wavelength range.
AlGaN polarization-doped field effect transistor with compositionally graded channel from Al0.6Ga0.4N to AlN
Authors: Armstrong Andrew M. , Klein Brianna A. , Baca Albert G. , Allerman Andrew A. , Douglas Erica A. , Colon Albert , Abate Vincent M. , Fortune Torben R.
Published: February 2019

Polarization-doped field effect transistors (PolFETs) were realized with an unintentionally doped AlxGa1-xN channel layer graded over Al compositions 0.60 ≤ x ≤ 1.0 with a maximum current density of 188 mA/mm (+10 V gate-to-source bias) and an on-resistance of 85 mΩ mm. The average mobility in the PolFET channel was estimated to be 320 cm2/V s, which exceeds that of previous AlGaN metal-semiconductor field effect transistors (MESFETs) and heterojunction field effect transistors (HFETs) of similar Al composition. The breakdown voltage was greater than 620 V, indicating an average critical electric field of >210 V/μm, which is substantially better than ∼100 V/μm that is typically achieved in GaN HFETs. These findings demonstrate that Al-rich PolFETs are attractive alternatives to MESFETs and HFETs for achieving simultaneously high channel electron density and mobility in high voltage switches.
The spectral background problem of portable fiber Raman instruments and a solution for the on-site detection of extremely weak signals
Authors: Li Haibo , Gu Yuejiao , Li Gan , Li Changmao , Lv Junbo , Zheng Shaotao , Hu Yin , Tang Tao
Published: February 2019

High sensitivity and low spectral background of the Raman instruments are essential for the analysis of weak Raman-active samples. The design of the present portable fiber Raman probes leads to an interferential background that limits the application of the portable Raman technique in many situations. In this work, the spectral backgrounds of commercial probes with different optical configurations were analyzed, and the results indicated the backgrounds arose from the objective lenses and the dichroic filters. A universal solution was proposed, and a flat and clean background was achieved by utilizing the longpass optical configuration and an off-axis parabolic mirror. Combined with a high-throughput spectrometer with a research-grade CCD, this portable Raman equipment was successfully applied to identify the corrosion products on the surface of uranium (with extremely weak Raman signals). The developed portable Raman instrument with high sensitivity and low background is anticipated to be very useful for the on-site Raman detection of weak signals.
Electronic nose using a bio-inspired neural network modeled on mammalian olfactory system for Chinese liquor classification
Authors: Liu Ying-Jie , Zeng Ming , Meng Qing-Hao
Published: February 2019

The simplification of data processing is the frontier domain for electronic nose (e-nose) applications, whereas there are a lot of manual operations in a traditional processing procedure. To solve this problem, we propose a novel data processing method using the bio-inspired neural network modeled on the mammalian olfactory system. Through a neural coding scheme with multiple squared cosine receptive fields, continuous sensor data are simplified as the spike pattern in virtual receptor units. The biologically plausible olfactory bulb, which mimics the structure and function of main olfactory pathways, is designed to refine the olfactory information embedded in the encoded spikes. As a simplified presentation of cortical function, the bionic olfactory cortex is established to further analyze olfactory bulb’s outputs and perform classification. The proposed method can automatically learn features without tedious steps such as denoising, feature extraction and reduction, which significantly simplifies the processing procedure for e-noses. To validate algorithm performance, comparison studies were performed for seven kinds of Chinese liquors using the proposed method and traditional data processing methods. The experimental results show that squared cosine receptive fields and the olfactory bulb model are crucial for improving classification performance, and the proposed method has higher classification rates than traditional methods when the sensor quantity and type are changed.
Robust quantum anomalous Hall effect with electrically tunable band gap in Ta-decorated silicene
Authors: Qian Jiahui , Zhang Jiayong , Wu Qixing , Lin Zhenghao
Published: February 2019

Electronic structures and topological properties of silicene adsorbed with 5d transition metal atom Ta (silicene-Ta) are investigated by using the first-principles calculations. The Ta atom prefers to adsorb at the hollow site of silicene. We demonstrate that the quantum anomalous Hall (QAH) effect can be realized in the studied silicene-Ta system, whose Fermi level is found to be located exactly inside the spin-orbit coupling induced nontrivial bulk band gap. In addition, the heterostructure of silicene-Ta/BN is built and explored. By applying an external vertical electric field, the realized topologically nontrivial bulk band gap can be enlarged effectively. Our calculations show that the achieved QAH effect is robust against the Ta adatom adsorption coverage (∼1%–6%) and disorder, making the experimental observation highly flexible. Our findings will greatly promote the experimental realization and practical application of the QAH effect in silicene-based systems.
Microfluidic-based observation of local bacterial density under antimicrobial concentration gradient for rapid antibiotic susceptibility testing
Authors: Kim Seunggyu , Lee Seokhun , Kim Ju-Kang , Chung Hyun Jung , Jeon Jessie S.
Published: February 2019

The need for accurate and efficient antibiotic susceptibility testing (AST) has been emphasized with respect to the emerging antimicrobial resistance of pathogenic bacteria which has increased over the recent decades. In this study, we introduce a microfluidic system that enables rapid formation of the antibiotic concentration gradient with convenient bacterial growth measurement based on color scales. Furthermore, we expanded the developed system to analyze combinatory effects of antibiotics and measured the collective antibiotic susceptibility of bacteria compared to single microfluidic AST methods. By injecting a continuous flow precisely into the channel, the system enabled the concentration gradient to be established between two parallel channels of different antibiotic concentrations within 30 min, before bacteria enter the exponential growth phase. Moreover, the local bacterial growth levels under antibiotic gradient were quantitatively determined by calculating the position-specific grayscale values from the microscopic images and were compared with the conventional optical density measurement method. We tested five antibiotic types on our platform for the pathogenic Gram-negative bacteria strain Pseudomonas aeruginosa, and we were able to determine the minimum inhibitory concentration (MIC) at which 90% to 95% of bacterial growth was inhibited. Finally, we demonstrated the efficacy of our system by showing that most of the antibiotic MICs determined in our platform show good agreement with the MIC range suggested by the Clinical and Laboratory Standards Institutes.
Dual role of surfactant-producing reaction in immiscible viscous fingering evolution
Authors: Tsuzuki Reiko , Ban Takahiko , Fujimura Masanari , Nagatsu Yuichiro
Published: February 2019

An experimental study on immiscible viscous fingering (VF) with chemical reaction is described, whereby a surfactant produced in a radial Hele-Shaw cell results in a decrease in interfacial tension. The surfactant is formed at the interface between alkaline solution (sodium hydroxide) and a long-chain fatty acid (linoleic acid). This topic is closely related to alkaline flooding, which is an enhanced oil recovery method. The reaction was found to have two opposing effects on VF depending on the flow rate, namely, narrowing and widening of the fingers. Moreover, the influences of the reaction on VF evolution can be categorized into five different types based on the effects appearing in VF evolution and the fingering width and area at the maximum observation region. Possible mechanisms for each type are proposed, and an argument based on scaling of the VF properties using dimensionless numbers gives support to the proposed mechanisms. This dual role of the reaction in immiscible VF evolution may contribute to establishing optimal conditions for alkaline flooding. Moreover, the finding that one chemical reaction has two opposing effects on flow is of value from the standpoint of fundamental studies of reacting flow dynamics.
Magnetohydrodynamical equilibria with current singularities and continuous rotational transform
Authors: Zhou Yao , Huang Yi-Min , Reiman A. H. , Qin Hong , Bhattacharjee A.
Published: February 2019

We revisit the Hahm–Kulsrud–Taylor (HKT) problem, a classic prototype problem for studying resonant magnetic perturbations and 3D magnetohydrodynamical equilibria. We employ the boundary-layer techniques developed by Rosenbluth, Dagazian, and Rutherford (RDR) for the internal m = 1 kink instability, while addressing the subtle difference in the matching procedure for the HKT problem. Pedagogically, the essence of RDR's approach becomes more transparent in the reduced slab geometry of the HKT problem. We then compare the boundary-layer solution, which yields a current singularity at the resonant surface, to the numerical solution obtained using a flux-preserving Grad–Shafranov solver. The remarkable agreement between the solutions demonstrates the validity and universality of RDR's approach. In addition, we show that RDR's approach consistently preserves the rotational transform, which hence stays continuous, contrary to a recent claim that RDR's solution contains a discontinuity in the rotational transform.
Ab initio based investigation of thermal transport in superlattices using the Boltzmann equation: Assessing the role of phonon coherence
Authors: Ye Erika , Minnich Austin J.
Published: February 2019

The role of the coherent interference of phonons on thermal transport in artificial materials such as superlattices is of intense interest. Recent experimental studies report a non-monotonic trend in thermal conductivity with interface density which is attributed to band-folding of thermal phonons. Various models have been proposed to interpret these measurements, but most make simplifying assumptions that make definitively attributing the trends to the coherent transport difficult. Here, we investigate thermal transport in superlattices in the incoherent limit using the Boltzmann equation with intrinsic phonon dispersions and lifetimes calculated from first-principles. We find that the Boltzmann equation is unable to predict the non-monotonic behavior of thermal conductivity versus superlattice period, supporting the interpretation of phonon interference in recent experiments.
Vacuum ultraviolet excited state dynamics of small amides
Authors: Larsen Martin A. B. , Sølling Theis I. , Forbes Ruaridh , Boguslavskiy Andrey E. , Makhija Varun , Veyrinas Kévin , Lausten Rune , Stolow Albert , Zawadzki Magdalena M. , Saalbach Lisa , Kotsina Nikoleta , Paterson Martin J. , Townsend Dave
Published: February 2019

Time-resolved photoelectron spectroscopy in combination with ab initio quantum chemistry calculations was used to study ultrafast excited state dynamics in formamide (FOR), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMA) following 160 nm excitation. The particular focus was on internal conversion processes within the excited state Rydberg manifold and on how this behavior in amides compared with previous observations in small amines. All three amides exhibited extremely rapid (<100 fs) evolution from the Franck–Condon region. We argue that this is then followed by dissociation. Our calculations indicate subtle differences in how the excited state dynamics are mediated in DMA/DMF as compared to FOR. We suggest that future studies employing longer pump laser wavelengths will be useful for discerning these differences.
Electromagnetic effect on geodesic acoustic mode with adiabatic electrons
Authors: Huang Wenlong , Ren Haijun , Xu X. Q.
Published: February 2019

The geodesic acoustic mode (GAM) is analytically investigated by taking into account the finite-orbit-width (FOW) resonance effect to the second order and the finite β effect. The general dispersion relation is derived from the gyro-kinetic equations in the presence of nonzero δA∥, the parallel component of the perturbed magnetic vector potential. Transparent and concise expressions for the GAM frequency and Landau damping rate in the presence of the second order FOW effect and finite β effect are first presented. It is clearly shown that the m = ±2 harmonics dominant δA∥ and the kinetic expression of δA∥ have the same form as the fluid one. For the real frequency, the electromagnetic effect introduces a term on the order of q2β, which is comparable to the second order electrostatic terms, namely, the terms introduced by the second order FOW resonance effect. While for the collisionless damping rate, δA∥ does not directly introduce β–dependent terms, but affects the damping rate via modifying the real frequency. Besides, our analytical result shows good agreement with the numerical examinations.
Phase detection of spin waves in yttrium iron garnet and metal induced nonreciprocity
Authors: Trossman Jonathan , Lim Jinho , Bang Wonbae , Ketterson John B. , Tsai C. C.
Published: February 2019

We report experiments which characterize spin wave propagation in a thin (111) yttrium iron garnet film for arbitrary angles between the in-plane magnetic field and the mode wavevectors. By measuring the magnetic field evolution of the phase of the wave traveling across the film, we deduce the frequency dependence of the wavevector, the dispersion relation, from which the mode velocity follows. Additionally, we observe multiple nodes in the regime of the propagating Damon-Eshbach mode; these arise from avoided crossings associated with the higher, exchange split, standing wave modes along the film normal, the positions of which correlate with the direct absorption measurements of their positions. This information allows a determination of the exchange parameter. Using this technique, we examine the nonreciprocity in spin wave propagation that results from an adjacent metal layer.
Metal phthalocyanines interaction with Co mediated by a moiré graphene superlattice
Authors: Avvisati Giulia , Gargiani Pierluigi , Mondelli Pierluigi , Presel Francesco , Bignardi Luca , Baraldi Alessandro , Betti Maria Grazia
Published: February 2019

The assembling of metal phthalocyanines on the rippled moiré superlattice of graphene/Ir(111) intercalated with one Co layer is driven by the site-dependent polarization field induced by the incommensurate graphene-Co interface. We have performed an X-ray absorption and photoemission study to unveil the role of the metallic centers and of the organic ligands in the molecule-Co interaction process mediated by graphene. Notably, we consider different electronic molecular orbitals, i.e. phthalocyanines with Cu and Mn metallic ions. The spectroscopic response suggests almost unaltered CuPc molecular states upon adsorption, and the rippled graphene carpet decouples completely the electronic interaction between the molecules and the Co layer, while a slight hybridization is present for MnPcs. MnPc molecules, trapped in the valleys of the moiré graphene superlattice, slightly intermix, through the orbitals protruding out of the molecular plane, with the underlying Co, while the organic ligands are almost unaltered. Graphene acts as an interlayer and mediates the interaction between metal phthalocyanines and the metallic substrate, preventing a strong chemical intermixing and enabling the assembly of almost unaltered molecules, preserving their electronic/magnetic state.
Perspective: Towards single shot time-resolved microscopy using short wavelength table-top light sources
Authors: Helk T. , Zürch M. , Spielmann C.
Published: February 2019

Time-resolved imaging allows revealing the interaction mechanisms in the microcosm of both inorganic and biological objects. While X-ray microscopy has proven its advantages for resolving objects beyond what can be achieved using optical microscopes, dynamic studies using full-field imaging at the nanometer scale are still in their infancy. In this perspective, we present the current state of the art techniques for full-field imaging in the extreme-ultraviolet- and soft X-ray-regime which are suitable for single exposure applications as they are paramount for studying dynamics in nanoscale systems. We evaluate the performance of currently available table-top sources, with special emphasis on applications, photon flux, and coherence. Examples for applications of single shot imaging in physics, biology, and industrial applications are discussed.
Warped phase coherence: An empirical synchronization measure combining phase and amplitude information
Authors: Minati Ludovico , Yoshimura Natsue , Frasca Mattia , Drożdż Stanisław , Koike Yasuharu
Published: February 2019

The entrainment between weakly coupled nonlinear oscillators, as well as between complex signals such as those representing physiological activity, is frequently assessed in terms of whether a stable relationship is detectable between the instantaneous phases extracted from the measured or simulated time-series via the analytic signal. Here, we demonstrate that adding a possibly complex constant value to this normally null-mean signal has a non-trivial warping effect. Among other consequences, this introduces a level of sensitivity to the amplitude fluctuations and average relative phase. By means of simulations of Rössler systems and experiments on single-transistor oscillator networks, it is shown that the resulting coherence measure may have an empirical value in improving the inference of the structural couplings from the dynamics. When tentatively applied to the electroencephalogram recorded while performing imaginary and real movements, this straightforward modification of the phase locking value substantially improved the classification accuracy. Hence, its possible practical relevance in brain-computer and brain-machine interfaces deserves consideration.
Multifunctional reflection in acoustic metagratings with simplified design
Authors: Fu Yangyang , Cao Yanyan , Xu Yadong
Published: February 2019

In this work, we propose and demonstrate a simple acoustic metagrating with binary phase modulation that can be employed to achieve multifunctional reflection with high efficiency, including three-channel retroreflection, quasi-retroreflection, and specular reflection. Although only two sub-elements are designed for the acoustic metagratings, the efficiency of multifunctional reflection is well preserved. By changing the desired retroreflection angle, the incident range of quasi-retroreflection and specular reflection can be effectively tuned. Our work provides an alternative way for planar acoustic devices with versatility and enables the development of acoustic metasurfaces with a simplified design.
On the chaotic pole of attraction for Hindmarsh-Rose neuron dynamics with external current input
Authors: Doungmo Goufo Emile Franck , Tabi Conrad Bertrand
Published: February 2019

Since the neurologists Hindmarsh and Rose improved the Hodgkin-Huxley model to provide a better understanding on the diversity of neural response, features like pole of attraction unfolding complex bifurcation for the membrane potential was still a mystery. This work explores the possible existence of chaotic poles of attraction in the dynamics of Hindmarsh-Rose neurons with an external current input. Combining with fractional differentiation, the model is generalized with the introduction of an additional parameter, the non-integer order of the derivative σ, and solved numerically thanks to the Haar Wavelets. Numerical simulations of the membrane potential dynamics show that in the standard case where the control parameter σ=1, the nerve cell’s behavior seems irregular with a pole of attraction generating a limit cycle. This irregularity accentuates as σ decreases (σ=0.9 and σ=0.85) with the pole of attraction becoming chaotic.
Numerical study on the jet formation of simple-geometry heavy gas inhomogeneities
Authors: Fan E. , Guan Ben , Wen Chih-Yung , Shen Hua
Published: February 2019

The jet formation of gas inhomogeneities under the impact of a planar shock wave is an interesting phenomenon that is closely related to shock convergence. In this study, a series of heavy gas inhomogeneities with very simple geometries (square, rectangle, circle, and triangle) are numerically reproduced to trace the source of the jet formation. Special attention is given to the wave patterns that lead to the formation of specific jet forms. The shock-accelerated multicomponent flow is simulated by solving inviscid compressible Euler equations. An up-wind characteristic space-time conservation element and solution element scheme is adopted, and a five-equation model is used to treat the gas interface. The jet types that emerge in the experimental images are explained based on the numerical results, and a typical shock pattern that ensures the jet formation is uncovered. It is found that, physically, the jet is initiated by the impact of the internal Mach stem, and the jet growth is nourished by the high speed gas flow induced by this Mach stem. The width of the jet is determined by the height of the internal Mach stem. Geometrically, a focal wedge enveloped by slip lines emerges in the gas inhomogeneity, in which the gas is accelerated. It is found that the existence of the focal wedge and the coordinates of the wedge tip can be used as qualitative criteria to illustrate the mechanism of the jet formation. These criteria provide a more intuitive basis for understanding the direction, scale, and process of jet formation.
Integrated high electron mobility transistors in GaAs/AlGaAs heterostructures for amplification at sub-Kelvin temperatures
Authors: Tracy L. A. , Reno J. L. , Fallahi S. , Manfra M. J.
Published: February 2019

We demonstrate the use of custom high electron mobility transistors (HEMTs) fabricated in GaAs/AlGaAs heterostructures to amplify current from quantum dot devices. The amplifier circuit is located adjacent to the quantum dot device, at sub-Kelvin temperatures, in order to reduce the impact of cable capacitance and environmental noise. Using this circuit, we show a current gain of 380 for 0.56 μW of power dissipation, with a bandwidth of 2.7 MHz and current noise referred to the input of 24 fA/Hz1/2 for frequencies of 0.1–1 MHz. The power consumption required for similar gain is reduced by more than a factor of 20 compared to a previous demonstration using a commercial off-the-shelf HEMT. We also demonstrate integration of a HEMT amplifier circuit on-chip with a quantum dot device, which has the potential to reduce parasitics and should allow for more complex circuits with reduced footprints.
Wake dynamics of low-Reynolds-number flow around a two-dimensional airfoil
Authors: Deng Jian , Sun Liping , Shao Xueming
Published: February 2019

We perform two-dimensional simulations of unsteady flow separation around a NACA0015 airfoil. We consider five different angles of attack, 10°, 12.5°, 15°, 17.5°, and 20°, with the Reynolds number varying from 100 to 1300. The central aim is to study the wake dynamics under the low-Reynolds-number condition, when the flow is most likely experiencing transitions between different states. For the low angles of attack of α = 10° and α = 12.5°, we find different branches on the Strouhal-Reynolds number relationship curves. Specifically, for α = 10°, we identify four distinct branches, marked with L1 to L4, in which the second discontinuity between L3 and L4 is proved to be hysteretic, characterized by the wake deflection. The branches L1 and L2 differ from the other two in the near-body flow topology, with the “trailing-edge vortex” mode for the first two, while the “separation vortex” mode for the last two. For the high angles of attack, α = 15°, 17.5°, and 20°, we cannot find marked discontinuity on the Strouhal-Reynolds number relationship curve. We further demonstrate that the flow transits to a chaotic state by a sequence of successive period-doubling bifurcations at α = 20°. Our results suggest that the operation of micro unmanned air vehicles in very low Reynolds numbers should be treated with caution because the flow is very sensitive to the Reynolds number, as well as the angle of attack.
Capturing complexities with composite operator and differential operators with non-singular kernel
Authors: Atangana Abdon , Mekkaoui Toufik
Published: February 2019

The composite operator has been used in functional analysis with a clear application in real life. Nevertheless, a pure mathematical concept becomes very useful if one can apply it to solve real world problems. Modeling chaotic phenomena, for example, has been a concern of many researchers, and several methods have been suggested to capture some of them. The concept of fractional differentiation has also been used to capture more natural phenomena. Now, in elementary school, when composing two functions, we obtain a new function with different properties. We now ask when we compose two equations, could we a get new dynamics? Could we capture new natural problems? In this work, we make use of the composite operator to create a new kind of chaotic attractors built from two different attractors. In the linear case, we obtain integro-differential equations (classical and fractional) in the Caputo-Fabrizio case. We suggested a new numerical scheme to solve these new equations using finite difference, Simpson, and Lagrange polynomial approximations. Without loss of generality, we solve some examples with exact solutions and compare them with our proposed numerical scheme. The results of the comparison leave no doubt to believe that the proposed method is highly accurate as the error is of the order of 10−4.
Vacuum ultraviolet light provides clues for ultrafast amide dynamics
Authors: Liebendorfer Adam
Published: February 2019

Femtosecond pulses of vacuum ultraviolet light allow researchers to investigate amide excited state dynamics, including mixed Rydberg/valence states and how amide functionality may influence resistance to UV damage in larger molecular systems.