bluuebunny/crossref_metadata_2025 huggingface dataset:
Neutralization of a Low Molecular Weight Heparin (LHN-1) and Conventional Heparin by Protamine Sulfate in Rats
Authors: Diness V , Østergaard P B
Published: July 2018

The neutralization of a low molecular weight heparin (LHN-1) and conventional heparin (CH) by protamine sulfate has been studied in vitro and in vivo. In vitro, the APTT activity of CH was completely neutralized in parallel with the anti-Xa activity. The APTT activity of LHN-1 was almost completely neutralized in a way similar to the APTT activity of CH, whereas the anti-Xa activity of LHN-1 was only partially neutralized.

In vivo, CH 3 mg/kg and LHN-1 7.2 mg/kg was given intravenously in rats. The APTT and anti-Xa activities, after neutralization by protamine sulfate in vivo, were similar to the results in vitro. In CH treated rats no haemorrhagic effect in the rat tail bleeding test and no antithrombotic effect in the rat stasis model was found at a protamine sulfate to heparin ratio of about 1, which neutralized APTT and anti-Xa activities. In LHN-1 treated rats the haemorrhagic effect was neutralized when APTT was close to normal whereas higher doses of protamine sulfate were required for neutralization of the antithrombotic effect. This probably reflects the fact that in most experimental models higher doses of heparin are needed to induce bleeding than to prevent thrombus formation. Our results demonstrate that even if complete neutralization of APTT and anti-Xa activities were not seen in LHN-1 treated rats, the in vivo effects of LHN-1 could be neutralized as efficiently as those of conventional heparin. The large fall in blood pressure caused by high doses of protamine sulfate alone was prevented by the prior injection of LHN-1.
Further Characterization of Wheat Germ Agglutinin Interaction with Human Platelets: Exposure of Fibrinogen Receptors
Authors: Lebret Marilyne , Rendu Francine
Published: July 2018

It was previously shown that (i) Wheat germ agglutinin, (WGA)-induced platelet activation occurred when only 17% of the lectin binding sites were occupied on the platelet surface and (ii) WGA caused the release of a platelet constituent which in turn participates in the observed effect. We now further define the platelet activation induced by WGA: the lectin induces a binding of fibrinogen to specific surface receptors. 125I-fibrinogen binding increases with the WGA concentration from 5 to 15 ug/ ml. Binding occurs without addition of exogenous calcium; its analysis demonstrated 54000 sites with a Ka = 0.8 × 106 M-1, Addition of 1 mM Ca2+ enhances the 125I-fibrinogen binding and reveals a second class of sites with higher affinity (9200 sites, Ka = 0.17 x 108 M-1). This 125I-fibrinogen binding is totally abolished by EDTA, ATP and arginine, and inhibited by 75% by CP/CPK; cyclooxygenase inhibitors and PGE1 also reduce the fibrinogen binding. Thus the WGA-induced fibrinogen binding is (1) release-dependent and (2) responsible for the aggregation process but not for the agglutinating effect of the lectin.
ADP-Induced Platelet Release Reaction in Acute Stroke
Authors: Mulley G P , Heptinstall S , Taylor P M , Mitchell J R A
Published: July 2018

The extent of the ADP-induced platelet release reaction has been determined in 107 patients admitted to hospital with acute stroke. In 43 of the patients a precise diagnosis was obtained and in those with proven thromboembolic stroke the mean extent of the release reaction was significantly higher than for those with either primary haemorrhagic stroke or those with subarachnoid haemorrhage. Enhanced platelet reactivity was also found in the patients in whom a precise diagnosis could not be obtained, most of whom probably had cerebral infarction. Comparison of the results obtained for patients with stroke with those obtained for individuals who had not experienced a stroke showed that thromboembolic stroke is associated with platelet hyperactivity while haemorrhagic stroke is associated with platelet hypoactivity. The part that abnormalities of platelet behaviour, whether causal or consequential, might play in occlusive stroke and intra-cranial haemorrhage is discussed and the need for large scale prospective studies is emphasised.
Contribution of Adrenaline to the Fibrinolytic Activity Evoked by E. Coli Endotoxin in the Rat
Authors: Fracasso J F , Rothschild A M
Published: July 2018

Intravenous injection of E. coli endotoxin (ETX), of adrenaline (AD) or of carbamylcholine (CBCH), caused fibrinolytic activity (FA), directly detectable on plasminogen-rich fibrin plates, to appear in the plasma of the rat. Adrenodemedul- lation abolished responses to ETX or CBCH, but enhanced those to AD. Rats given ETX exhibited marked hypotension, followed by a compensatory phase of normotension abolished by adrenodemedullation and significantly attenuated by phenoxy- benzamine, an a-adrenergic blocking agent which however failed to block FA caused by either ETX or AD. Aspirin, but not indomethacin, inhibited FA evoked by ETX, AD or CBCH. These results suggest that FA evoked by ETX in the rat is caused by AD released from the adrenal gland and does involve the fatty acid cyclooxygenase system.
Decreased Antithrombin III Activity in Diabetes May Be Due to Non-Enzymatic Glycosylation – A Preliminary Report
Authors: Ceriello A , Russo P Dello , Zuccotti C , Florio A , Nazzaro S , Pietrantuono C , Rosato G B
Published: July 2018

Antithrombin III activity was moderately but significantly decreased in insulin dependent diabetics (p <0.005), while no difference has been found between the diabetic (n = 25) and control groups (n = 22) in antithrombin III plasma concentration.

Moreover, antithrombin III activity was inversely correlated with glycosylated plasma proteins (r = -0.57; p <0.01).

These data show that in diabetes there is a depressed biological activity of antithrombin III and suggest that this reflects nonenzymatic
glycosylation of antithrombin III protein.
Shortening of Platelet Survival by Induced Hypercholesterolaemia In Rabbits and Its Prolongation by Anagrelide
Authors: Barrett P A , Butler K D
Published: July 2018

Induction of atherosclerosis in rabbits by feeding a cholesterol enriched diet reduced the platelet half-life in male rabbits from 37.0 ± 4.1 hr to 30.1 ± 3.9 hr (mean ± S.D. p ≤0.01). Platelets from these animals exhibited increased sensitivity to arachidonic acid but decreased sensitivity to ADP. No significant change was found in aggregation to collagen or thrombin, or in the production of thomboxane B2 induced by collagen.

The reduced platelet survival was dependent upon the recipient animal and not the platelet donor. Platelets from cholesterol- fed animals survived normally in normal animals, whereas platelets from normal animals in cholesterol-fed animals had a reduced platelet survival even compared to platelets from cholesterol-fed animals. This might suggest that some functional change had occurred in the cholesterol platelet in response to its altered environment.

Anagrelide (1 mg/kg/day) normalised shortened platelet survival in both male and female rabbits fed the high cholesterol diet.
The Use of Evacuated Tubes for Blood Collection in Oral Anticoagulant Control
Authors: van den Besselaar A M H P , van Halem-Visser L P , Loeliger E A
Published: July 2018

The prothrombin time (PT) test is used to monitor oral anticoagulant therapy. Contact activation of patient blood samples in vitro may shorten the PT and thus lead to underestimation of the degree of anticoagulation. Commercial evacuated tubes for blood collection have been reported to induce shortening of the PT. The Thrombotest modification of the PT determination was used to investigate the properties of different brands of evacuated siliconized tubes. Two recently manufactured batches of such tubes did not induce appreciable shortening of the PT and can therefore be recommended for use in monitoring oral anticoagulant treatment.
The Novel Effect of a New Prostacyclin Analogue ZK36374 on the Aggregation of Human Platelets in Whole Blood
Authors: Saniabadi A R , Lowe G D O , Belch J J F , Forbes C D , Prentice C R M , Barbenel J C
Published: July 2018

Platelet aggregation was studied at 37° C in citrated whole human blood, using the Ultra Flo 100 Whole Blood Platelet Counter. Aggregation was measured as a fall in the number of single platelets following addition of an aggregating agent. At peak aggregation, the fall in the number of platelets induced by ADP (10 μM), collagen (1 μg/ml) or thrombin (0.2 U/ml) was about 90%. When blood was incubated with the prostacyclin- analogue ZK36374, the aggregation responses to ADP, collagen and thrombin were reduced with IC50’S = 0.5, 1.5 and 3 nM respectively and the corresponding IC100’S were: 1, 3 and 12 nM. When ZK36374 was added at peak aggregation, the number of single platelets increased significantly due to disaggregation of preformed platelet aggregates. It is concluded that the present technique represents a rapid, sensitive and more physiological approach for investigating the effects of pharmacological agents on platelet aggregation.
Investigation Including VIIIR: AG Multimeric Analysis of a Large Kindred with Type IIA von Willebrand’s Disease Showing a Dominant Inheritance and Similar Gene Expression in Four Generations
Authors: Hill F G H , Enayat M S , George A J
Published: July 2018

Forty-two members of a family have been studied with bleeding times, platelet aggregation, platelet retention in glass beads, measurement of factor VIII associated activity, 2-dimensional electrophoresis and multimeric analysis of factor VIII related antigen (VIIIR:AG). Eleven individuals with type IIA disease and one with asymptomatic and another with symptomatic type I disease have been studied. The degree of absence of high and intermediate multimers and the abnormal triplet configuration in the two remaining multimers was consistent in all affected family members. Multimeric analysis provides a unique and precise way of studying qualitative defects of VIIIR:AG and thereby the evaluation of gene expression in family studies.
Mepacrine Blockade of Arachidonate-lnduced Washed Platelet Aggregation: Relationship to Mepacrine Inhibition of Platelet Cyclooxygenase
Authors: Raz Amiram
Published: July 2018

Mepacrine, in addition to its established antilipolytic activity, was also found to inhibit the conversion of 14C-arachidonic acid to 14C-thromboxane B2 in human washed platelets. In the concentration range of 3.33-33 μM, mepacrine exerted a dose dependent inhibition of arachidonate conversion to thromboxane B2 in parallel to inhibition of arachidonate-induced platelet aggregation. Mepacrine inhibition of thromboxane formation was not accompanied by a concomitant increase in other cyclooxygenase products. Furthermore, mepacrine did not affect platelet transformation of added prostaglandin H2 to thromboxane A2 and other products. These results indicate that mepacrine inhibits the cyclooxygenase enzyme and not thromboxane synthase. In washed platelets, mepacrine inhibition of arachidonic acid conversion to thromboxane A2 appears to be a major factor in the overall inhibitory effect of the compound on the combined process of arachidonate release from cellular phospholipids and its conversion to proaggregatory products.
Fibrinolytic Activity and the Effects of Beta-Pyridylcarbinol (Ronicol) in Patients with Arteriosclerosis Obliterans
Authors: Grodzińska L , Basista M , Kȩdzior A , Korbut R , Kostka-Trąbka E , Gryglewski R
Published: July 2018

Twenty-one patients with arteriosclerosis obliterans of lower extremities were treated with beta-pyridylcarbinol (Ronicol) for five weeks. The long-term therapy with beta-pyridylcarbinol did not influence platelet aggregability. Activation of the fibrinolytic system was observed. This fibrinolytic effect of Ronicol was abolished in patients treated with aspirin. In most cases a slight clinical improvement was seen, manifested by elongation of pain-free walking distance and increased blood flow in affected limbs. It is concluded that the therapeutic effect of Ronicol in humans may be partly mediated by the release of endogenous prostacyclin.
Non-Thrombogenicity of Clean Glass Revealed by Native Whole Blood Assay in Bead Columns
Authors: Bergeron J A , DiNovo J M , Razzano A F , Dodds W J
Published: July 2018

The previously described native whole blood assay for materials in solution or suspension has been adapted to materials in a bead column configuration. These experiments showed that the glass itself accounts for little or none of the high blood-reactivity observed with conventional glass bead columns. Columns composed solely of soft glass that was “cleaned” by heat treatment (500-595° C 18 hr, electric oven) were benign toward flowing native whole blood for all variables measured (platelet count and platelet-free plasma [C14]-serotonin content, platelet factor 3 and factor XII activities, and recalcification time) with the standard contact protocol. In addition, the effluent successfully maintained perfusion of the isolated kidney, a measure of the ability of platelets to support vascular integrity. Prolonged (30 min) normothermic contact with titrated whole blood increased the subsequent reactivity of initially clean glass toward whole blood albeit to a level much less than that of conventional glass bead columns.
Regulation of Thromboplastin Synthesis in Mouse Placental Cells In Vitro
Authors: Dalaker Knut , Prydz Hans
Published: July 2018

Mouse placental cells are probably constitutive producers of the thromboplastin apoprotein in vitro. The effect of cyclic AMP- elevating compounds on their expression of thromboplastin activity has been studied. Dibutyryl cyclic AMP, the phosphodiesterase inhibitor Ro 20-1724 and the adenyl cyclase stimulator forskolin all decrease the synthesis of thromboplastin. Prostaglandin E2 and the phosphodiesterase inhibitor butyl-methyl-xanthine have a biphasic dose dependent effect. A stimulation was observed at low concentrations, whereas higher doses decreased the synthesis of thromboplastin. Adrenaline had no effect. Combination of two compounds, each at maximally inhibiting concentration gave no significant additive inhibitory effect, showing that they probably act via the same pathway.
Homeopathic Treatment of Insomnia and Symptom Clusters Related to Cerebral Chemotoxicity in Oncology
Authors: Marechaud Natalia , Deana Nicolas , Wendling Julie , Bagot Jean-Lionel
Published: July 2018

Background During chemotherapy, the correlation between insomnia and fatigue, anxiety, pain, depressed mood, and cognitive disorders makes these subjective complaints a ‘symptom cluster’ with common biological mechanisms. The theory of cerebral inflammation following the production of pro-inflammatory cytokines (high level of interleukin 1-β [IL1-β], IL6 and tumour necrosis factor-alpha) is currently the most generally accepted. Understanding these mechanisms should allow us to propose a chemoprotective homeopathic treatment of the nervous system.

Methods By retaining the inflammatory aetiology, we combined the rubrics ‘Inflammation of the brain’, ‘Inflammation of the meninges’, ‘Inflammation of the nerves’ with the symptom cluster: insomnia, fatigue, depressive state and memory disorders.

Results After repertorisation, we propose the following homeopathic protocol: Belladonna 15c, Phosphorus 15c, Cerebral cortex 4c and Nerves 4c, two pills of each medicine to be sucked together before breakfast, lunch and dinner, on each day of chemotherapy and for the following 2 days.

Conclusion This selected protocol, derived from a physiopathological knowledge of the symptoms, seems to be well suited to the prevention and treatment of post-chemotherapeutic cerebral inflammation. It is essential to start the homeopathic treatment before the chemotherapy session to anticipate the emergence of the ‘chemo-brain’ side effects. This proposed prevention protocol must be confirmed and quantified by randomised studies.
Cardiomyopathy Associated with Zinc Deficiency after Bariatric Surgery
Authors: Yahalom Malka , Koren Ofir , Rozner Ehud , Turgeman Yoav
Published: July 2018

Noncompliance with vitamin and mineral supplement protocol after bariatric surgery may lead to true-elements deficiency. Among them, zinc and selenium deficiencies were closely related to cardiac complications, such as myocardial fibrosis, heart failure, and arrhythmias.

We describe a 30-year-old female, 6 weeks after delivery and 5 years after bariatric surgery, who was admitted to the cardiology department because of dyspnea and clinical evidence of heart failure, as well as an echocardiogram that demonstrated reduced systolic left ventricular function. Standard antifailure regimen shows mild benefit. Zinc supplements added to treatment lead to significant clinical and echocardiographic improvement.
Availability of Resources for After-Hours Surgical Management of Eye Injuries
Authors: Chen Tina , Colby Kathryn , Rodriguez Sarah , Slidell Mark , Kandel Jessica , Shah Hassan
Published: July 2018

Background Approximately 2.4 million eye injuries per year occur in the United States. Because of the complexity of these injuries, many of these cases present to academic institutions. Ophthalmology residency programs have a wide range of resources available for eye injuries requiring after-hours surgical intervention.

Purpose The purpose of this study was to determine availability of resources for after-hours eye surgery and their effect on clinician satisfaction.

Methods Association of University Professors of Ophthalmology (AUPO) program directors were surveyed to assess the availability of eye-trained operating room (OR) nurses, functional operating microscopes, and suitable surgical supplies. The primary outcome measure was the availability of resources for after-hours eye surgery. Secondary outcome measures included the impact of resources on clinician satisfaction.

Results Fifty-seven program directors completed the survey. Most programs operated at level 1 trauma centers (95%), had access to a functional microscope (95%), and had frequent adequate surgical supplies (88%). On the other hand, only 28 (49%) programs reported consistent access to OR nurses with ophthalmologic training. Clinician satisfaction scores were three times higher for programs with frequent access to trained surgical OR staff than for programs without (p < 0.001).

Conclusion Approximately half of programs report consistent access to ophthalmologic-trained OR staff after hours. In contrast, most programs report access to a functional microscope and surgical supplies. The results of this survey suggest that directing resources toward improving access to after-hours staffing with specialty OR staff may improve clinician satisfaction.
“Contrecoup” Paravalvular Leak Closure
Authors: Agbor-Etang Brian B. , Rao Ravi M. , Mukherjee Ashis , Sethi Prabhdeep S. , Pai Ramdas G.
Published: July 2018

Paravalvular aortic regurgitation affects some patients after surgically implanted prosthesis. The number of patients affected is likely to increase with increased utilization of nonsurgical valve replacement techniques. These patients are at increased risk of persistent clinical symptoms often requiring repair. Clinical and procedural outcomes are of importance when performing these procedures and managing these patients. We describe a case where two different leaks around an aortic prosthesis improved with closure of one defect.
Atomic-pair theorem for universal matrix representatives of molecules and atomic clusters in non-relativistic Born-Oppenheimer approximation
Authors: Langhoff P. W. , Mills J. D. , Boatz J. A.
Published: July 2018

The mathematical underpinnings of a universal atomic-pair based approach to ab initio calculations of the electronic wave functions and energies of molecules and other atomic clusters are reported in non-relativistic Born-Oppenheimer approximation. The general approach utilizes the closure of an orthonormal (Eisenschitz-London) outer product of atomic spectral eigenstates to support totally antisymmetric aggregate eigenstates in the absence of explicit term-by-term atomic-product basis antisymmetry. Meaningful definitions of atomic-pair interaction operators and of their corresponding universal matrix representatives on the atomic product basis are obtained in this way for calculations on physical and chemical aggregates. Symmetric-group-based permutation-symmetry methods for partitioning of aggregate Hamlitonian matrices, performed to date by unitary transformations to remove unphysical “non-Pauli” states after aggregate Hamiltonian matrix construction, are supplemented here with a new two-step procedure. The new approach, which combines explicit antisymmetrization of atomic pair matrices with unitary transformation of aggregate Hamiltonian matrices, is described here in complete mathematical detail. Conditions are established from the new development under which enforcement of pairwise-atomic antisymmetry alone can be sufficient for calculations of electronic energies, providing an efficient approach for practical applications, as well as long-absent theoretical support for related semi-empirical and ad hoc methods widely employed in computational molecular physics and quantum chemistry. An exact expression is obtained for total electronic energies from the solution of the Schrödinger equation in the universal form of sums over pairwise-atomic interaction energies uniquely defined within a molecule in the absence of subjective additional conditions. Wigner rotation matrices are employed to orient pairs of interacting atoms within an aggregate in the implementation of the approach, requiring calculations of the universal pair interaction matrices as functions of radial separations only. Such information can be obtained once and for all from molecular diatomic calculations and retained for subsequent use, avoiding repeated evaluations of the electronic integrals commonly required in conventional variational determinations of accurate potential energy surfaces. Diagonalizations of large Hamiltonian matrices are avoided in favor of optical potential, Krylov-Lanczos, and previously described Stieltjes-Techebycheff methods in determination of aggregate Schrödinger eigenspectra.
The dimensionless dissipation rate and the Kolmogorov (1941) hypothesis of local stationarity in freely decaying isotropic turbulence
Authors: McComb W. D. , Fairhurst R. B.
Published: July 2018

An expression for the dimensionless dissipation rate was derived from the Kármán-Howarth equation by an asymptotic expansion of the second- and third-order structure functions in powers of the inverse Reynolds number. The implications of the time-derivative term for the assumption of local stationarity (or local equilibrium) which underpins the derivation of the Kolmogorov “4/5” law for the third-order structure function were studied. It was concluded that neglect of the time-derivative cannot be justified by reason of restriction to certain scales (the inertial range) nor to large Reynolds numbers. In principle, therefore, the hypothesis cannot be correct, although it may be a good approximation. It follows, at least in principle, that the quantitative aspects of the hypothesis of local stationarity could be tested by a comparison of the asymptotic dimensionless dissipation rate for free decay with that for the stationary case. But in practice this is complicated by the absence of an agreed evolution time te for making the measurements during the decay. However, we can assess the quantitative error involved in using the hypothesis by comparing the exact asymptotic value of the dimensionless dissipation in free decay calculated on the assumption of local stationarity to the experimentally determined value (e.g., by means of direct numerical simulation), as this relationship holds for all measuring times. Should the assumption of local stationarity lead to significant error, then the “4/5” law needs to be corrected. Despite this, scale invariance in wavenumber space appears to hold in the formal limit of infinite Reynolds numbers, which implies that the “−5/3” energy spectrum does not require correction in this limit.
Parametrization of reflectometry fluctuation frequency spectra for systematic study of fusion plasma turbulence
Authors: Sun Y. , Sabot R. , Hornung G. , Heuraux S. , Hacquin S. , Verdoolaege G.
Published: July 2018

We describe a way to parameterize power spectra extracted from fixed-frequency reflectometry data, with a view to systematic studies of turbulence properties in tokamak plasmas. Analysis of typical frequency spectra obtained from a new database suggests decomposition in a set of four key components: the direct current component, low-frequency fluctuations, broadband (BB) turbulence, and the noise level. For the decomposition in the identified components, different kinds of functions are tested and their fitting performance is analyzed to determine the optimal spectrum parametrization. In particular, for the BB turbulence, three models are compared qualitatively based on a number of representative spectrum test cases, notably the generalized Gaussian, the Voigt, and the Taylor model. In addition, quantitative performance testing is accomplished using the weighted residual sum of squares and the Bayesian information criterion in a large database including 350 000 spectra obtained in Tore Supra. Next, parametrization by the Taylor model is applied to Ohmically heated plasmas, and a BB energy basin is systematically observed in the core plasma region, which shrinks with decreasing radial position of the q = 1 surface. This basin might be explained by a drop of the density fluctuation level inside the q = 1 surface.
On the propagation of regularity and decay of solutions to the Benjamin equation
Authors: Guo Boling , Qin Guoquan
Published: July 2018

In this paper, we investigate some special regularities and decay properties of solutions to the initial value problem of the Benjamin equation. The main result shows that for initial datum u0∈Hs(R) with s > 3/4, if the restriction of u0 belongs to Hl((x0, ∞)) for some l∈Z+ and x0∈R, then the restriction of the corresponding solution u(·, t) belongs to Hl((α, ∞)) for any α∈R and any t ∈ (0, T). Consequently, this type of regularity travels with infinite speed to its left as time evolves.
A study on blowup solutions to the focusing L2-supercritical nonlinear fractional Schrödinger equation
Authors: Dinh Van Duong
Published: July 2018

We study the dynamical properties of blowup solutions to the focusing L2-supercritical nonlinear fractional Schrödinger equation i∂tu − (−Δ)su = −|u|αu on [0,+∞)×Rd, where d≥2,d2d−1≤s<1, 4sd<α<4sd−2s, and the initial data u(0)=u0∈Ḣsc∩Ḣs is radial with the critical Sobolev exponent sc. To this end, we establish a compactness lemma related to the equation by means of the profile decomposition for bounded sequences in Ḣsc∩Ḣs. As a result, we obtain the Ḣsc-concentration of blowup solutions with bounded Ḣsc-norm and the limiting profile of blowup solutions with critical Ḣsc-norm.
Effects of temperature and redshift on the refractive index of semiconductors
Authors: Geng Peiji , Li Weiguo , Zhang Xuyao , Deng Yong , Kou Haibo , Chen Liming , Wu Xiaozhi
Published: July 2018

A theoretical model is developed to study the effect of temperature on the refractive index of semiconductors. The model can be used to predict the refractive index at temperatures ranging from near absolute zero to high temperatures. The theoretical results at wavelengths far from the band-edge region agree well with the available experimental results. In the near-band-edge region, the redshift is found to have an obvious effect on the refractive index at elevated temperatures, and a method is provided for considering this effect. Further verification of the model considering the redshift is included and is consistent with the available experimental results. This theoretical method for prediction of temperature-dependent refractive indices of semiconductors may be helpful in the design of the optical devices.
Multi-kilowatt-class heaters for large hollow cathodes
Authors: Wordingham Christopher J. , Taunay Pierre-Yves C. R. , Choueiri Edgar Y.
Published: July 2018

Heater materials and geometry are analyzed to address the requirements of large lanthanum hexaboride hollow cathodes. Larger hollow cathodes are capable of increased discharge currents but require higher heater powers to ignite. Existing cathode heaters suffer from material interactions and increased failure rates at high temperatures and are currently not viable for high-power operation; graphite heaters can provide order-of-magnitude increases in heater power and operational life simultaneously. Two models, a simplified circuit model and a finite-element model, were developed to predict the heater operating temperature and resistance. The operational life of the heater was estimated using a vacuum sublimation model. A graphite heater was fabricated and tested using a large-diameter lanthanum hexaboride hollow cathode to demonstrate feasibility as a high-power heater material. The prototype has repeatedly achieved cathode ignition and was tested at up to 4.5 kW of heater power. Heater voltage and current were measured prior to ignition and used to calculate the heater resistance. The measured resistance is within 8% of the predicted value for the circuit model and within 2.5% of the finite-element prediction. At cathode ignition temperatures, the vacuum sublimation model predicts an order-of-magnitude increase in operational life as compared to existing cathode heaters; for a peak surface operating temperature of 1500 °C, the vacuum sublimation model predicts a 1%-loss life of approximately 400 kh.
Linear scanning tunneling spectroscopy over a large energy range in black phosphorus
Authors: Guo Hongli , Cui Xingxia , Zhou Weiqing , Han Ding , Lin Chungwei , Cao Limin , Feng Min
Published: July 2018

We reveal the unique electronic characteristics of the conduction band (CB) of black phosphorus (BP) by combining low-temperature scanning tunneling microscopy/spectroscopy (STM/STS), density functional theory calculations, analytic fitting, and model simulations. We discover that the differential conductance spectrum, which represents the local density of states (LDOS) of BP, exhibits a linear character over a large energy range in the unoccupied electronic state region. Combining theoretical calculations, we demonstrate that the linear character right above the conduction band minimum originates from a specific combination of the anisotropic band dispersions of BP's CB. In particular, the wave function of BP's CB possesses a pronounced density between BP layers and extends into the vacuum significantly, which is in sharp contrast to those of adjacent bands. This makes the CB dominate STS signals even when the energy is sufficiently high to involve other bands, and maintains the linearity of the STS spectrum over a wide energy range. The fact that the CB provides linear DOS and possesses pronounced wave function density in BP interlayers provides new insights for engineering the electronic structures and properties of BP and BP based materials.
Formation of dipolarization fronts after current sheet thinning
Authors: Xu Y. , Fu H. S. , Norgren C. , Hwang K.-J. , Liu C. M.
Published: July 2018

Dipolarization front (DF)—a sharp boundary separating hot tenuous plasmas from cold dense plasmas—is a key structure responsible for particle acceleration and energy transport in the magnetotail. How such a structure is formed has been unclear so far. Two possible mechanisms suggested in previous studies are magnetic reconnection and spontaneous formation. Both of them require current sheet thinning as a prerequisite. However, observational evidence of the DF formation associated with current sheet thinning has not been reported. In this study, we present such an observation, showing the DF formation after current sheet thinning. We estimate the half thickness of the current sheet to be ∼1000 km and the rate of current sheet thinning as ∼38 km/s. We find that the DF is likely formed at XGSM ≈ −20 RE. During the current sheet thinning, the plasma becomes cold and dense; during DF formation, many magnetic islands are produced. Although current sheet thinning and DF formation have been individually analyzed in the previous studies, this study, for the first time, links the two transient processes in the magnetotail.
Distributions and integration in superspace
Authors: Guzmán Adán Alí , Sommen Franciscus
Published: July 2018

Distributions in superspace constitute a very useful tool for establishing an integration theory. In particular, distributions have been used to obtain a suitable extension of the Cauchy formula to superspace and to define integration over the superball and the supersphere through the Heaviside and Dirac distributions, respectively. In this paper, we extend the distributional approach to integration over more general domains and surfaces in superspace. The notions of domain and surface in superspace are defined by smooth bosonic phase functions g. This allows us to define domain integrals and oriented (as well as non-oriented) surface integrals in terms of the Heaviside and Dirac distributions of the superfunction g. It will be shown that the presented definition for the integrals does not depend on the choice of the phase function g defining the corresponding domain or surface. In addition, some examples of integration over a super-paraboloid and a super-hyperboloid will be presented. Finally, a new distributional Cauchy-Pompeiu formula will be obtained, which generalizes and unifies the previously known approaches.
Particle separation in surface acoustic wave microfluidic devices using reprogrammable, pseudo-standing waves
Authors: Simon Gergely , Pailhas Yan , Andrade Marco A. B. , Reboud Julien , Marques-Hueso Jose , Desmulliez Marc P. Y. , Cooper Jonathan M. , Riehle Mathis O. , Bernassau Anne L.
Published: July 2018

We report size and density/compressibility-based particle sorting using on-off quasi-standing waves based on the frequency difference between two ultrasonic transducers. The 13.3 MHz fundamental operating frequency of the surface acoustic wave microfluidic device allows the manipulation of particles on the micrometer scale. Experiments, validated by computational fluid dynamics, were carried out to demonstrate size-based sorting of 5–14.5 μm diameter polystyrene (PS) particles and density/compressibility-based sorting of 10 μm PS, iron-oxide, and poly(methyl methacrylate) particles, with densities ranging from 1.05 to 1.5 g/cm3. The method shows a sorting efficiency of >90% and a purity of >80% for particle separation of 10 μm and 14.5 μm, demonstrating better performance than similar sorting methods recently published (72%–83% efficiency). The sorting technique demonstrates high selectivity separation of particles, with the smallest particle ratio being 1.33, compared to 2.5 in previous work. Density/compressibility-based sorting of polystyrene and iron-oxide particles showed an efficiency of 97 ± 4% and a purity of 91 ± 5%. By varying the sign of the acoustic excitation signal, continuous batch acoustic sorting of target particles to a desired outlet was demonstrated with good sorting stability against variations of the inflow rates.
A low-steering piezo-driven mirror
Authors: Magnan E. , Maslek J. , Bracamontes C. , Restelli A. , Boulier T. , Porto J. V.
Published: July 2018

We present a piezo-driven translatable mirror with excellent pointing stability, capable of driving at frequencies up to tens of kilohertz. Our system uses a tripod of piezo actuators with independently controllable drive voltages, where the ratios of the individual drive voltages are tuned to minimize residual tilting. Attached to a standard ∅ = 12.7 mm mirror, the system has a resonance-free mechanical bandwidth up to 51 kHz, with displacements up to 2 μm at 8 kHz. The maximum static steering error is 5.5 μrad/μm displaced, and the dynamic steering error is lower than 0.6 μrad μm−1. This simple design should be useful for a large set of optical applications where tilt-free displacements are required, and we demonstrate its application in an ensemble of cold atoms trapped in periodically driven optical lattices.
Chirality at two-dimensional surfaces: A perspective from small molecule alcohol assembly on Au(111)
Authors: Liriano Melissa L. , Larson Amanda M. , Gattinoni Chiara , Carrasco Javier , Baber Ashleigh E. , Lewis Emily A. , Murphy Colin J. , Lawton Timothy J. , Marcinkowski Matthew D. , Therrien Andrew J. , Michaelides Angelos , Sykes E. Charles H.
Published: July 2018

The delicate balance between hydrogen bonding and van der Waals interactions determines the stability, structure, and chirality of many molecular and supramolecular aggregates weakly adsorbed on solid surfaces. Yet the inherent complexity of these systems makes their experimental study at the molecular level very challenging. In this quest, small alcohols adsorbed on metal surfaces have become a useful model system to gain fundamental insight into the interplay of such molecule-surface and molecule-molecule interactions. Here, through a combination of scanning tunneling microscopy and density functional theory, we compare and contrast the adsorption and self-assembly of a range of small alcohols from methanol to butanol on Au(111). We find that longer chained alcohols prefer to form zigzag chains held together by extended hydrogen bonded networks between adjacent molecules. When alcohols bind to a metal surface datively via one of the two lone electron pairs of the oxygen atom, they become chiral. Therefore, the chain structures are formed by a hydrogen-bonded network between adjacent molecules with alternating adsorbed chirality. These chain structures accommodate longer alkyl tails through larger unit cells, while the position of the hydroxyl group within the alcohol molecule can produce denser unit cells that maximize intermolecular interactions. Interestingly, when intrinsic chirality is introduced into the molecule as in the case of 2-butanol, the assembly changes completely and square packing structures with chiral pockets are observed. This is rationalized by the fact that the intrinsic chirality of the molecule directs the chirality of the adsorbed hydroxyl group meaning that heterochiral chain structures cannot form. Overall this study provides a general framework for understanding the effect of simple alcohol molecular adstructures on hydrogen bonded aggregates and paves the way for rationalizing 2D chiral supramolecular assembly.
Grand canonical diffusion-influenced reactions: A stochastic theory with applications to multiscale reaction-diffusion simulations
Authors: del Razo Mauricio J. , Qian Hong , Noé Frank
Published: July 2018

Smoluchowski-type models for diffusion-influenced reactions (A + B → C) can be formulated within two frameworks: the probabilistic-based approach for a pair A, B of reacting particles and the concentration-based approach for systems in contact with a bath that generates a concentration gradient of B particles that interact with A. Although these two approaches are mathematically similar, it is not straightforward to establish a precise mathematical relationship between them. Determining this relationship is essential to derive particle-based numerical methods that are quantitatively consistent with bulk concentration dynamics. In this work, we determine the relationship between the two approaches by introducing the grand canonical Smoluchowski master equation (GC-SME), which consists of a continuous-time Markov chain that models an arbitrary number of B particles, each one of them following Smoluchowski’s probabilistic dynamics. We show that the GC-SME recovers the concentration-based approach by taking either the hydrodynamic or the large copy number limit. In addition, we show that the GC-SME provides a clear statistical mechanical interpretation of the concentration-based approach and yields an emergent chemical potential for nonequilibrium spatially inhomogeneous reaction processes. We further exploit the GC-SME robust framework to accurately derive multiscale/hybrid numerical methods that couple particle-based reaction-diffusion simulations with bulk concentration descriptions, as described in detail through two computational implementations.
Dynamic/static displacement sensor based on magnetoelectric composites
Authors: Yang Yikun , Yang Bintang , Niu Muqing
Published: July 2018

This study presents a dynamic/static displacement sensor based on both end fixed Terfenol-D/PZT (lead zirconate titanate) magnetoelectric composites. Owing to the fixed boundary condition, the magnetostriction of Terfenol-D under the magnetic field is limited and the stress acts on PZT through mechanical coupling, and finally, an induced voltage is generated due to the piezoelectric effect in PZT. The magnetic field applied on the magnetoelectric composites varies with the displacement of the permanent magnet which represents the displacement to be measured. In that case, the determination of displacement can be transformed into determining the variation of the magnetic field. The experimental results manifest that the frequency of magnetoelectric voltage is the same as the frequency of displacement. The dynamic displacement sensitivity of this sensor increases with the increase in the input frequency in the low frequency range and the decrease in the length of the air gap. The sensitivity is 6.549 mV/μm with a 0.75 mm air gap for dynamic displacement at 10 Hz and 0.84 μV/μm with a 2.5 mm air gap and an external magnetic field at 1 kHz for static displacement. It can be concluded that the displacement measuring mechanism based on the magnetoelectric effect is a promising robust and accurate method.
Analysis of equilibrium and turbulent fluxes across the separatrix in a gyrokinetic simulation
Authors: Keramidas Charidakos I. , Myra J. R. , Parker S. , Ku S. , Churchill R. M. , Hager R. , Chang C. S.
Published: July 2018

The SOL width is a parameter of paramount importance in modern tokamaks as it controls the power density deposited at the divertor plates, critical for plasma-facing material survivability. An understanding of the parameters controlling it has consequently long been sought [Connor et al. Nucl. Fusion 39(2), 169 (1999)]. Prior to Chang et al. [Nucl. Fusion 57(11), 116023 (2017)], studies of the tokamak edge have been mostly confined to reduced fluid models and simplified geometries, leaving out important pieces of physics. Here, we analyze the results of a DIII-D simulation performed with the full-f gyrokinetic code XGC1 which includes both turbulence and neoclassical effects in realistic divertor geometry. More specifically, we calculate the particle and heat E × B fluxes along the separatrix, discriminating between equilibrium and turbulent contributions. We find that the density SOL width is impacted almost exclusively by the turbulent electron flux. In this simulation, the level of edge turbulence is regulated by a mechanism that we are only beginning to understand: ∇B-drifts and ion X-point losses at the top and bottom of the machine, along with ion banana orbits at the low field side, result in a complex poloidal potential structure at the separatrix which is the cause of the E × B drift pattern that we observe. Turbulence is being suppressed by the shear flows that this potential generates. At the same time, turbulence, along with increased edge collisionality and electron inertia, can influence the shape of the potential structure by making the electrons non-adiabatic. Moreover, being the only means through which the electrons can lose confinement, it needs to be in a balance with the original direct ion orbit losses to maintain charge neutrality.
Two-dimensional multiferroic semiconductors with coexisting ferroelectricity and ferromagnetism
Authors: Qi Jingshan , Wang Hua , Chen Xiaofang , Qian Xiaofeng
Published: July 2018

Low-dimensional multiferroicity, though highly scarce in nature, has attracted great attention due to both fundamental and technological interests. Using first-principles density functional theory, we show that ferromagnetism and ferroelectricity can coexist in monolayer transition metal phosphorus chalcogenides (TMPCs)-CuMP2X6 (M = Cr, V; X = S, Se). These van der Waals layered materials represent a class of 2D multiferroic semiconductors that simultaneously possess ferroelectric and ferromagnetic orders. In these monolayer materials, Cu atoms spontaneously move away from the center atomic plane, giving rise to nontrivial electric dipole moment along the plane normal. In addition, their ferromagnetism originates from indirect exchange interaction between Cr/V atoms, and their out-of-plane ferroelectricity suggests the possibility of controlling electric polarization by external vertical electric field. Monolayer semiconducting TMPCs thus provide a solid-state 2D materials platform for realizing 2D nanoscale switches and memory devices patterned with top and bottom electrodes.
Steady-state space-charge-limited current analysis of mobility with negative electric field dependence
Authors: Bhattarai Gyanendra , Caruso Anthony N. , Paquette Michelle M.
Published: July 2018

We revisit the theory of steady-state space-charge-limited current (SS-SCLC) enhanced by Frenkel emission originally addressed by Murgatroyd using analytical rather than numerical integration to obtain an exact solution. For the first time, the analysis is also extended to the case of mobility exhibiting negative field dependence, generally observed in disordered materials at lower electric field. For the case of positive electric field dependence, we confirm that Murgatroyd's original solution is close to the exact solution for low and moderately high electric fields. At a very high field, the exact solution is consistent with the analytical solution given by Barbe. For the case of negative electric field dependence, the fit expression retains the same functional form as Murgatroyd's solution, however with a different exponential factor of −0.801. The development of SS-SCLC theory for the case of negative field dependence is an important step in the generalization of this analysis technique to the investigation of complex materials such as disordered organic semiconductors.
On the structure of the drifton phase space and its relation to the Rayleigh–Kuo criterion of the zonal-flow stability
Authors: Zhu Hongxuan , Zhou Yao , Dodin I. Y.
Published: July 2018

The phase space of driftons (drift-wave quanta) is studied within the generalized Hasegawa–Mima collisionless-plasma model in the presence of zonal flows. This phase space is made intricate by the corrections to the drifton ray equations that were recently proposed by Parker [J. Plasma Phys. 82, 595820602 (2016)] and Ruiz et al. [Phys. Plasmas 23, 122304 (2016)]. Contrary to the traditional geometrical-optics (GO) model of the drifton dynamics, it is found that driftons can not only be trapped or passing but also accumulate spatially while experiencing indefinite growth of their momenta. In particular, it is found that the Rayleigh–Kuo threshold known from geophysics corresponds to the regime when such “runaway” trajectories are the only ones possible. On one hand, this analysis helps to visualize the development of the zonostrophic instability, particularly its nonlinear stage, which is studied here both analytically and through wave-kinetic simulations. On the other hand, the GO theory predicts that zonal flows above the Rayleigh–Kuo threshold can only grow; hence, the deterioration of intense zonal flows cannot be captured within a GO model. In particular, this means that the so-called tertiary instability of intense zonal flows cannot be adequately described within the quasilinear wave kinetic equation, contrary to some previous studies.