bluuebunny/crossref_metadata_2025 huggingface dataset:
The Human Plasmin-Derived Light (B) Chain·Streptokinase Complex: A Second-Generation Thrombolytic Agent
Authors: Robbins K C , Summaria L , Wohl R C , Bell W R
Published: July 2018

Specific assay methods for the human plasmin-derived light (B) chain · streptokinase (B·SK) complex, in terms of both streptokinase (SK) and urokinase (UK) International Units, are described. The kinetic properties of various SK activator complexes with plasminogen, Val 442-plasmin, and the plasmin-derived light (B) chain were compared to SK in terms of their catalytic efficiencies and Lineweaver-Burk plots. Similar kinetic data, and Lineweaver-Burk plots, are described for both highly purified high-molecular weight UK and low-molecular weight UK, including different clinical UK preparations. The B·SK complex has the highest catalytic efficiency of all the activator species studied. The Lineweaver-Burk plots of each of the various activator species are “fingerprints” of the enzymatic character of the activator. The B-SK complex is more like UK than SK, as an activator, in activating non-human plasminogen species. The biological halflife of the B·SK complex, in a dog model, was determined to be about 4 hr which is longer than the biological half-life(s) of SK in the same animal model, namely 0.6 hr (47%) and 2.8 hr (53%). This new second-generation activator complex may prove to be a useful thrombolytic agent in the treatment of thromboembolic diseases.
Intra-Coronary Thrombolysis with Streptokinase or Lys-Plasminogen/Urokinase in Acute Myocardial Infarction: Effects on Recanalization and Blood Fibrinolysis
Authors: de Prost D , Guerot C , Laffay N , Horellou M H , Samama M
Published: July 2018

Forty-two patients with total occlusion of a coronary vessel were treated with intracoronary fibrinolytic agents. Four therapeutic protocols were compared: group I received streptokinase (SK) as a continuous infusion; group II and III received SK as a bolus at different doses and group IV received lysplasminogen (Pg) plus urokinase (UK); maximal doses were 350,000 IU of SK and 250,000 IU of UK plus 75 μK of Pg. Thrombolysis was assessed by coronary angiography. Coagulation studies were performed prior to, 15 min and 6 hr after the end of the thrombolytic treatment. Recanalization was achieved in 27 of the 31 SK-treated patients (87%) and in 7 of the 11 Pg-UK- treated patients (63.6%). The recanalization frequency was the same in the three SK-treated groups, even though when SK was administered as a bolus, the dose was significantly less than when administered on a continuous infusion. Although systemic fibrinolysis occurred in all 4 groups of patients, this effect was less pronounced in the UK-treated patients than in the three SK- treated groups. This study also shows that recanalization can be achieved with a dose of SK lower than the anti-SK antibody level. Haemorrhagic side effects were minimal in all patients studied. Severe defibrination is usually considered a risk of haemorrhage. These preliminary results suggest that bolus injection of SK or the use of UK plus lys-Pg can reduce the level of defibrination and thus the haemorrhagic risk.
Haemostatic Variables and the Outcome of Myocardial Infarction
Authors: Haines A P , Howarth D , North W R S , Goldenberg Eva , Stirling Yvonne , Meade T W , Raftery E B , Millar Craig M W
Published: July 2018

In a study of 272 patients with myocardial infarction (MI) the 68 who died within 1 year had significantly higher levels of factor VIIIR:Ag, factor VIII:C, fibrinogen, α1 antitrypsin and α2 macroglobulin than those who survived. The mean white cell count (WCC) and peak creatine kinase (CK) were also significantly higher in those who died compared with the survivors. There was considerable intercorrelation between many of the haemostatic variables, WCC and CK as well as between many of the clinical predictors of outcome and the laboratory variables. The differences in haemostatic variables between those who died and those who survived may merely reflect the size of the infarct; alternatively, the haemostatic system may influence prognosis following an MI.
Effect of Cyclic AMP and Cyclic GMP on Thromboplastin (Factor III) Synthesis in Human Monocytes In Vitro
Authors: Lyberg Torstein
Published: July 2018

Human monocytes in vitro respond to various agents (immune complexes, lectins, endotoxin, the divalent ionophore A 23187, 12-0-tetradecanoyl-phorbol 13-acetate [TPA], purified protein derivative [PPD] of Bacille Calmette-Guerin) with an increased synthesis of the protein component of thromboplastin. The effect of cyclic AMP and cyclic GMP on this response has been studied. Dibutyryl-cyclic AMP, prostaglandin E1 and the phosphodiesterase inhibitors 3-butyl-1-methyl-xanthine (MIX) and rac -4-(3-butoxy-4-methoxybenzyl)-2-imidazolidinone (Ro 201724), separately and in combination have a pronounced inhibitory effect on the response to immune complexes and PPD, and a moderate effect on the response to endotoxin and lectins. The effect on TPA response and on the response to A 23187 was slight. Dibutyryl-cyclic GMP (1 mM) gave a slight inhibition of the TPA arid IC response, but had essentially no effect on the response to other inducers. The intracellular cAMP level increased when monocytes were incubated with IC, TPA or A 23187 followed by a decrease to basal levels within 1-2 hr, whereas lectin (PHA) and PPD did not induce such changes. The cAMP response to endotoxin varied. Stimulation with IC induced an increase in monocyte cGMP levels, whereas the other stimulants did not cause such changes.
Protein C Deficiency in Two Austrian Families
Authors: Pabinger-Fasching I , Bertina R M , Lechner K , Niessner H , Korninger Ch
Published: July 2018

Protein C antigen was determined by Laurell rocket immunelectrophoresis in 225 patients with a history of venous thrombosis. Among these patients two females with protein C deficiency were detected. Additional studies in the families of the protein C deficient patients revealed further 7 family members with protein C deficiency. In 8 not anticoagulated patients with protein C deficiency the protein C ranged from 36 to 62% (median: 45%). In one patient on oral anticoagulant treatment protein C antigen concentration was < 10%, FII and F X were 65 and 50%, respectively. The pattern of inheritance was consistent with autosomal dominant inheritance. 5 of the 9 protein C deficient patients had severe thrombotic tendency characterized by recurrent deep venous thrombosis (n = 4), pulmonary embolism (n = 1), probable mesenteric vein thrombosis (n = 1) and superficial thrombophlebitis (n = 2). All protein C deficient patients without thrombosis were less than 17 years old.
Cell-Free Synthesis of Factor VIII Related Protein
Authors: Chan Vivian , Chan T K
Published: July 2018

Polyadenylated ribonucleic acid (RNA) was isolated from confluent human endothelial cells in culture and translated in a cell-free rabbit reticulocyte lysate protein-synthesizing system. Using specific immunopredpitation, the translation product was found to contain 1.58% VIH related protein (VIIIR), which has a molecular weight of 0.26 × 106, similar to the subunit of VIIIR present in normal plasma. This indicated that VIIIR messenger RNA is responsible for the synthesis of subunits only and intracellular post-translational events are required for the assembly of tetramer and multimers.
Platelet Function, Size and Yield in Whole Blood and in Platelet-Rich Plasma Prepared Using Differing Centrifugation Force and Time in Domestic and Food-Producing Animals
Authors: Clemmons R M , Bliss E L , Dorsey-Lee M R , Seachord C L , Meyers K M
Published: July 2018

The effects of centrifugation force and time upon platelets function, mean platelet volume and platelet yield were compared with whole blood platelet counts and size in citrated blood samples from the bovine, canine, caprine, equine, feline, ovine and porcine species. The results were similar, for a given species, irregardless of sample volume. Bovine, caprine, feline and ovine platelet yields and mean platelet volumes were maximal when platelet-rich plasma was prepared using longer centrifugation times and lower gravitational forces. Canine, equine and porcine platelet yields and mean platelet volumes were maximal when platelet-rich plasma was prepared using shorter centrifugation times and higher gravitational forces. Platelet aggregation to adenosine diphosphate or arachidonic add was not effected by the method of platelet-rich plasma preparation in bovine, caprine, feline, ovine or pordne platelets. Equine platelet aggregation was maximal when platelet-rich plasma was prepared using longer centrifugation times and lower gravitational forces. Canine platelet aggregation, particularly arachidonic add-induced aggregation, was maximal when platelet-rich plasma was prepared using short centrifugation times and higher gravitational forces. It appeared that the effects of centrifugation parameters upon platelet yield depended upon the relative difference between platelet and red blood cell volumes.
Monocrotaline Pyrrole-Induced Pulmonary Hypertension in Fawn-Hooded Rats with Platelet Storage Pool Deficiency: 5-Hydroxytryptamine Uptake by Isolated, Perfused Lungs
Authors: Hilliker Katherine S , Bell Thomas G , Roth Robert A
Published: July 2018

Platelets are believed to be involved in the development of monocrotaline pyrrole (MCTP)-induced pulmonary hypertension. To help identify the role of the platelet, the cardiopulmonary toxicity of MCTP was examined in fawn-hooded (FH) rats, a strain with a platelet function defect. Both Sprague-Dawley (SD) and FH rats developed right ventricular hypertrophy and increased lung weights and exhibited decreased biogenic amine removal by isolated, perfused lung preparations after MCTP treatment. The responses of the FH rats were not significantly different from those of the SD rats, suggesting that platelet uptake and release of 5-hydroxytryptamine (5HT) are not the platelet functions involved in MCTP-induced pulmonary hypertension. The FH rats had an interesting strain-related difference from SD rats; isolated lungs from FH rats removed and metabolized a greater proportion of perfused 5HT than the SD rats.
Dipyridamole Inhibits Platelet Aggregation in Whole Blood
Authors: Gresele P , Zoja C , Deckmyn H , Arnout J , Vermylen J , Verstraete M
Published: July 2018

Dipyridamole possesses antithrombotic properties in the animal and in man but it does not inhibit platelet aggregation in plasma. We evaluated the effect of dipyridamole ex vivo and in vitro on platelet aggregation induced by collagen and adenosine- 5’-diphosphate (ADP) in human whole blood with an impedance aggregometer. Two hundred mg dipyridamole induced a significant inhibition of both ADP- and collagen-induced aggregation in human blood samples taken 2 hr after oral drug intake. Administration of the drug for four days, 400 mg/day, further increased the antiplatelet effect. A significant negative correlation was found between collagen-induced platelet aggregation in whole blood and dipyridamole levels in plasma (p <0.001). A statistically significant inhibition of both collagen (p <0.0025) and ADP-induced (p <0.005) platelet aggregation was also obtained by incubating whole blood in vitro for 2 min at 37° C with dipyridamole (3.9 μM). No such effects were seen in platelet-rich plasma, even after enrichment with leukocytes. Low-dose adenosine enhanced in vitro inhibition in whole blood.

Our results demonstrate that dipyridamole impedes platelet aggregation in whole blood by an interaction with red blood cells, probably involving adenosine.
Differences Between Heterozygous Dominant and Recessive von Willebrand’s Disease Type I Expressed by Bleeding Symptoms and Combinations of Factor VIII Variables
Authors: Wahlberg T B , Blombäck M , Ruggeri Z M
Published: July 2018

Three families with von Willebrand’s disease (vWd) type I were investigated. A reliable identification of healthy and diseased individuals was achieved by number of bleeding symptoms, assays of bleeding time, FVIII:C (one stage and two stage), VIIIR: Ag (EIA) and ristocetin cofactor. The diagnoses - vWd or non-vWd were confirmed by laboratory indices based on predictive values of positive and negative tests, also including VIIIR: Ag (IRMA and RIA). The last mentioned two variables did not contribute to significantly better identification of vWd versus health. The best single test variable for this purpose was ristocetin cofactor. One vWd family had significantly higher levels of ristocetin cofactor and shorter bleeding time than the other two vWd families and is probably the typical example of a family transmitting classical severe vWd.
Effects of Superoxide Dismutase and Catalase on Disseminated Intravascular Coagulation In Rats
Authors: Yoshikawa T , Murakami M , Yoshida N , Seto O , Kondo M
Published: July 2018

The effects of superoxide dismutase (SOD) and catalase on endotoxin-induced experimental disseminated intravascular coagulation (DIC) were studied in rats. Experimental DIC was induced by a 4 hr sustained infusion of endotoxin at a dose of 100 mg/kg. The rats were subcutaneously injected with SOD at 0.5, 5.0 or 50.0 mg/kg, or catalase at 0.01, 0.1 or 1.0 mg/kg, followed by the continuously infusion of 100 mg/kg/4hr of endotoxin. A preventive effect against DIC was noted in all the parameters, such as fibrinogen and fibrin degradation products, fibrinogen level, prothrombin time, partial thromboplastin time, platelet count and the number of renal glomeruli with fibrin thrombi, in the rats treated with 50.0 mg/kg of SOD or 1.0 mg/kg of catalase. When 50.0 mg/kg of SOD or 1.0 mg/kg of catalse was injected subcutaneously at 1, 2 or 3 hr after the initiation of the endotoxin-infusion, the protective effect against DIC was noted in all the parameters.
Fate of Thrombin and Thrombin-Antithrombin-III Complex Adsorbed to a Heparinized Biomaterial: Analysis of the Enzyme-Inhibitor Complexes Displaced by Plasma
Authors: Hatton Mark W C , Rollason Gordon , Sefton Michael V
Published: July 2018

Heparin covalently-linked to polyvinyl alcohol (PVA) is a biomaterial which is of potential value as a non-thrombogenic coating. 125I-labelled thrombin adsorbed to heparin-PVA beads was not dislodged by phosphate-buffered saline, pH 7.4, although radioactivity was progressively displaced from the adsorbent by fibrinogen-free human plasma. Analysis by gel filtration and affinity chromatography showed that the released radioactivity was distributed between (thrombin-antithrombin-III) complex (approx. 70%) and, probably, (thrombin-α-2-macroglobulin) complex (approx. 30%). Less efficient thrombin displacement was obtained by either bovine serum albumin (5% w/v) or antithrombin-III-free human plasma: in the latter case, the dislodged enzyme was presumably associated with α-2-macroglobulin. Purified α-2-macroglobulin did not displace thrombin from heparin-PVA. The quantity of thrombin displaced by an α- 2-macroglobulin-free plasma fraction compared well with fibrinogen-free plasma: The eluted enzyme was largely associated with antithrombin-III. Purified antithrombin-III did not displace thrombin from heparin-PVA despite causing >70% inactivation of the bound enzyme. Subsequent treatment with fibrinogen-free plasma dislodged (thrombin-antithrombin-III) at a similar rate to that of bound thrombin. We conclude that plasma contains a component(s) which displaces (thrombin-antithrombin-III) complex from immobilised heparin: presumably this leaves the heparin sites free for further use in enzyme inactivation.
Evidence that Platelet α-Granules Are a Major Determinant of Platelet Density: Studies in Storage Pool Deficiency
Authors: Vicic William J , Weiss Harvey J
Published: July 2018

Density-related subpopulations of platelets were obtained by centrifuging platelets obtained from venous blood on a discontinuous gradient of arabinogalactan (Stractan). Four subpopulations were obtained in fractions of the gradient with densities ≤1.058, 1.065, 1.070, and 1.092 g/ml. The percentage of the total platelet population recovered in these various fractions in 5 patients with congenital storage pool deficiency who are deficient only in dense granules (δ-SPD) was similar to that observed in 8 normal subjects. In contrast, a shift in the density distribution towards a higher percentage of less dense platelets was observed in 3 patients (aδ-SPD) who are deficient in both a and dense granules. The results of these studies strongly suggest that agranules are a major determinant of platelet density.
Immunoradiometric Assays for Human Coagulation Factor VII Using Polyclonal Antibodies Against the Ca(II)-Dependent and Ca(II)-Independent Conformation
Authors: Bom V J J , van Tilburg N H , Es C Krommenhoek-van , Bertina R M
Published: July 2018

Human coagulation factor VII is a trace plasma protein belonging to the vitamin K-dependent factors. Two specific and sensitive immunoradiometric assays for factor VII were developed using immunopurified rabbit antibodies against the Ca(II)-independent and Ca(II)-dependent conformation of factor VII. Both assays were insensitive to the activation state of factor VII. The distribution of factor VII antigen was studied in 40 healthy individuals and the antigen level in normal plasma was calculated to be 0.52-0.62 μg/ml. The two assays were used in a comparative study of factor VII procoagulant activity and factor VII antigen in patients treated with oral anticoagulants.
Maternal and Fetal Death on Weekends
Authors: Moaddab Amirhossein , Dildy Gary , Belfort Michael , Sangi-Haghpeykar Haleh , Davidson Christina , Clark Steven
Published: July 2018

Background Higher mortality rates have been reported in patients admitted to the hospital on weekends. This study aimed to compare maternal mortality ratio (MMR), fetal mortality ratio, and other maternal and neonatal outcomes by day of death or delivery in the United States.

Methods Our database consisted of a population-level analysis of live births and maternal and fetal deaths between 2004 and 2014 in the United States from the Centers for Disease Control and Prevention's National Center for Health Statistics. We also examined the relationship between these deaths and various documented maternal and fetal clinical conditions.

Results A total of 2,061 maternal deaths occurred on weekends and 5,510 deaths on weekdays. During the same period of time, 65,063 and 210,851 cases of fetal demise were delivered on weekends and on weekdays, respectively. Maternal mortality was significantly higher on weekends than weekdays (22.9 vs. 15.3/100,000 live births, p < 0.001) as was fetal mortality (7.21 vs. 5.85/100,000, p < 0.001), despite a lower frequency of serious comorbidities among women delivering on weekends.

Conclusion Our data demonstrate a significant increase in the U.S. MMR and stillbirth delivery on weekends. Relative representation of antepartum, intrapartum, and postpartum deaths cannot be ascertained from these data.
Outcomes after Neonatal Seizures in Infants Less Than 29 Weeks' Gestation: A Population-Based Cohort Study
Authors: Iwami Hiroko , Isayama Tetsuya , Lodha Abhay , Canning Rody , Abou Mehrem Ayman , Lee Shoo , Synnes Anne , Shah Prakesh ,   for the Canadian Neonatal Network and Canadian Neonatal Follow-Up Network Investigators
Published: July 2018

Objective The aim of this study was to evaluate the association between neonatal seizure and neurodevelopmental impairment (NDI) at 18 to 24 months in extremely preterm neonates. The association between anticonvulsants use and NDI was also assessed.

Study Design In this retrospective cohort study of infants born at <29 weeks' gestation from the Canadian Neonatal Network and Canadian Neonatal Follow-Up Network databases, we compared mortality and neurodevelopmental outcomes in infants who had neonatal seizures with those without seizures after adjusting for confounders.

Results Of the 2,762 eligible neonates, 133 (4.8%) had seizures. Infants who had seizures were of lower gestation (25.2 vs. 26.2 weeks) and birth weight (819 vs. 920 g) and had higher rates of adverse outcomes. Neonatal seizure was associated with higher odds of composite outcome of death or significant NDI (74 vs. 27%; adjusted odds ratio [OR]: 3.4; 95% confidence interval [CI]: 2.2–5.4). Death or significant NDI was higher in infants with seizures treated with anticonvulsants than those without treatment (89 vs. 70%); however, when adjusted for confounders, it was not significantly different (adjusted OR: 3.5; 95% CI: 0.83–14.6).

Conclusion Neonatal seizures were independently associated with higher odds of death or significant NDI at 18 to 24 months of age. Relationship of anticonvulsant and neurodevelopmental outcomes needs further studies.
Innovative Solution for Grasping Forceps Support Suction to Facilitate Uniportal Video-Assisted Thoracoscopic Surgery
Authors: Zhang Xugang , Yang Lei , Wang Jianrui , Wei Bo
Published: July 2018

Uniportal video-assisted thoracoscopic surgery has been limited to the use of very few instruments, which but at least include energy device, grasping forceps, and suction. The last two instruments must be temporarily replaced by each other in response to situation. This step prolongs operative duration and potentially impairs the surgical efficiency. We describe a novel instrument design of grasping forceps support suction. Its continuous suction can clear the smoke and blood simultaneously to keep the operative field dry and clean, minimize the requirement to exchange surgical devices, and allow for optimized surgical workflow.
Ground states of quantum electrodynamics with cutoffs
Authors: Takaesu Toshimitsu
Published: July 2018

In this paper, we investigate a system of quantum electrodynamics with cutoffs. The total Hamiltonian is a self-adjoint operator on a boson-fermion Fock space. It is shown that under spatially localized conditions and momentum regularity conditions, the total Hamiltonian has a ground state for all values of coupling constants. In particular, its multiplicity is finite.
Causality, dynamical systems and the arrow of time
Authors: Paluš Milan , Krakovská Anna , Jakubík Jozef , Chvosteková Martina
Published: July 2018

Using several methods for detection of causality in time series, we show in a numerical study that coupled chaotic dynamical systems violate the first principle of Granger causality that the cause precedes the effect. While such a violation can be observed in formal applications of time series analysis methods, it cannot occur in nature, due to the relation between entropy production and temporal irreversibility. The obtained knowledge, however, can help to understand the type of causal relations observed in experimental data, namely, it can help to distinguish linear transfer of time-delayed signals from nonlinear interactions. We illustrate these findings in causality detected in experimental time series from the climate system and mammalian cardio-respiratory interactions.
Anatomy of leadership in collective behaviour
Authors: Garland Joshua , Berdahl Andrew M. , Sun Jie , Bollt Erik M.
Published: July 2018

Understanding the mechanics behind the coordinated movement of mobile animal groups (collective motion) provides key insights into their biology and ecology, while also yielding algorithms for bio-inspired technologies and autonomous systems. It is becoming increasingly clear that many mobile animal groups are composed of heterogeneous individuals with differential levels and types of influence over group behaviors. The ability to infer this differential influence, or leadership, is critical to understanding group functioning in these collective animal systems. Due to the broad interpretation of leadership, many different measures and mathematical tools are used to describe and infer “leadership,” e.g., position, causality, influence, and information flow. But a key question remains: which, if any, of these concepts actually describes leadership? We argue that instead of asserting a single definition or notion of leadership, the complex interaction rules and dynamics typical of a group imply that leadership itself is not merely a binary classification (leader or follower), but rather, a complex combination of many different components. In this paper, we develop an anatomy of leadership, identify several principal components, and provide a general mathematical framework for discussing leadership. With the intricacies of this taxonomy in mind, we present a set of leadership-oriented toy models that should be used as a proving ground for leadership inference methods going forward. We believe this multifaceted approach to leadership will enable a broader understanding of leadership and its inference from data in mobile animal groups and beyond.
Lévy noise induced transition and enhanced stability in a gene regulatory network
Authors: Wu Fengyan , Chen Xiaoli , Zheng Yayun , Duan Jinqiao , Kurths Jürgen , Li Xiaofan
Published: July 2018

We investigate a quantitative bistable two-dimensional model (MeKS network) of gene expression dynamics describing the competence development in the Bacillus subtilis under the influence of Lévy as well as Brownian motions. To analyze the transitions between the vegetative and the competence regions therein, two dimensionless deterministic quantities, the mean first exit time (MFET) and the first escape probability, are determined from a microscopic perspective, as well as their averaged versions from a macroscopic perspective. The relative contribution factor λ, the ratio of non-Gaussian and Gaussian noise strengths, is adopted to identify an optimum choice in these transitions. Additionally, we use a recent geometric concept, the stochastic basin of attraction (SBA), to exhibit a pictorial comprehension about the influence of the Lévy motion on the basin stability of the competence state. Our main results indicate that (i) the transitions between the vegetative and the competence regions can be induced by the noise intensities, the relative contribution factor λ and the Lévy motion index α; (ii) a higher noise intensity and a larger α with smaller jump magnitude make the MFET shorter, and the MFET as a function of λ exhibits one maximum value, which is a signature of the noise-enhanced stability phenomenon for the vegetative state; (iii) a larger α makes the transition from the vegetative to the adjacent competence region to occur at the highest probability. The Lévy motion index α0≈0.5 (a larger jump magnitude with a lower frequency) is an ideal choice to implement the transition to the non-adjacent competence region; (iv) there is an expansion in SBA when α decreases.
Glassy dynamics in mutant huntingtin proteins
Authors: Kang Hongsuk , Luan Binquan , Zhou Ruhong
Published: July 2018

Causative to the neurodegenerative Huntington’s disease (HD), a mutational huntingtin (HTT) protein consists of an unusual expansion on the poly-glutamine (polyQ) region in the first exon (exon-1) domain. Despite its significance on HD progression, the structural role of the exon-1 with the polyQ region is still elusive. As HTT is an intrinsically disordered protein (IDP), a large ensemble of various conformations (instead of a mostly single native conformation) is required to characterize its structural properties and to infer biological functions, which is challenging even for the most state-of-the-art experimental techniques. For this reason, molecular dynamics (MD) simulations with enhanced sampling techniques are ideal to compliment experiment on collecting such a large ensemble of thermodynamically accessible structures. Here, we performed large-scale temperature replica-exchange MD (T-REMD) simulations on the exon-1 with an illustration on the necessity of using T-REMD instead of unbiased regular MD. By comparing T-REMD data and unbiased MD data, we discovered that (1) the dynamics of polyQ regions are extremely sluggish and glassy at the room temperature and the relaxation of the system cannot be achieved within a reasonable amount of time without utilizing an enhanced sampling method and (2) an ensemble of protein structures containing the surprising cis-peptide bonds in the proline-rich domain can be obtained at much elevated temperatures. Our results may provide valuable insights for future studies on the HTT as well as other IDPs using the T-REMD method.
Ultra-low percolation threshold in epoxy resin–onion-like carbon composites
Authors: Palaimiene E. , Macutkevic J. , Banys J. , Selskis A. , Fierro V. , Celzard A. , Schaefer S. , Shenderova O.
Published: July 2018

This paper deals with dielectric/electrical properties of composite films based on onion-like carbon (OLC) as filler in an epoxy resin matrix. The measurements were carried out in a very broad range of frequencies (20 Hz–34 GHz), and the results show that the percolation threshold in these composites is related to the size of the OLC aggregates, the biggest aggregates leading to the lowest threshold (0.7 vol. %). The observed critical exponent reasonably agrees with the theoretical value. Composites comprising 10.89 vol. % of 250 nm-big OLC aggregates exhibit dielectric permittivity as high as 60 000 and electrical conductivity as high as 0.05 S/m at 20 Hz.
Interaction of human serum albumin with dendritic polyglycerol sulfate: Rationalizing the thermodynamics of binding
Authors: Ran Qidi , Xu Xiao , Dey Pradip , Yu Shun , Lu Yan , Dzubiella Joachim , Haag Rainer , Ballauff Matthias
Published: July 2018

We study the thermodynamics of the interaction between human serum albumin (HSA) and dendritic polyglycerol sulfate (dPGS) of different sizes (generations) by isothermal titration calorimetry (ITC) and computer simulations. The analysis by ITC revealed the formation of a 1:1 complex for the dPGS-G2 of second generation. The secondary structure of HSA remained unchanged in the presence of dPGS-G2, as shown by circular dichroism. For higher generations, several HSA are bound to one polymer (dPGS-G4: 2; dPGS-G5.5: 4). The Gibbs free energy ΔGb was determined at different temperatures and salt concentrations. The binding constant Kb exhibited a logarithmic dependence on the salt concentration thus indicating a marked contribution of counterion-release entropy to ΔGb. The number of released counterions (∼4) was found to be independent of temperature. In addition, the temperature dependence of ΔGb was small, whereas the enthalpy ΔHITC was found to vary strongly with temperature. The corresponding heat capacity change ΔCp,ITC for different generations was of similar values [8 kJ/(mol K)]. The nonlinear van’t Hoff analysis of ΔGb revealed a significant heat capacity change ΔCp,vH of similar magnitude [6 kJ/(mol K)] accompanied by a strong enthalpy-entropy compensation. ΔGb obtained by molecular dynamics simulation with implicit water and explicit ions coincided with experimental results. The agreement indicates that the enthalpy-entropy compensation assigned to hydration effects is practically total and the binding affinity is fully governed by electrostatic interactions.
Electrical behavior of Pb0.95La0.05Zr0.54Ti0.46O3 thin film based capacitors: Influence of space charge region
Authors: Kotru S. , Batra V. , Harshan V. N.
Published: July 2018

We investigated the influence of space charge region (SCR) on the electrical properties of Pb0.95La0.05Zr0.54Ti0.46O3 (PLZT) thin film based capacitor structures. The metal/PLZT/Pt capacitors were prepared by using metal electrodes (Pt, Au, Al) of varying work function as top electrodes, and Pt as a bottom electrode. The SCR formed at the top interface between the PLZT film and the metal differs from each other in three capacitor structures. The results obtained from the hysteresis, dielectric, and leakage current measurements were analyzed to understand the variation in the electrical properties of the capacitors arising from the different SCRs formed at the interfaces. Among the three, the Pt/PLZT/Pt capacitor showed highest polarization and permittivity, and lowest FCC and coercive field. The Al/PLZT/Pt capacitor showed lowest polarization and permittivity, but higher coercive field and FCC. The leakage current increased with a decrease in work function of the top electrode. The Schottky conduction mechanism was found to be dominant in all the three capacitors. Both the photovoltaic parameters (short circuit photocurrent denisty and open circuit photovoltage) increased with the increase in work function of the top electrodes. These studies suggest the existence of wider SCR and higher space charge field at the top interface in the case of capacitor designed with an Al (or Au) top electrode as compared to the capacitor designed with a Pt top electrode.
Stability analysis of a periodic system of relativistic current filaments
Authors: Vanthieghem A. , Lemoine M. , Gremillet L.
Published: July 2018

The nonlinear evolution of current filaments generated by the Weibel-type filamentation instability is a topic of prime interest in space and laboratory plasma physics. In this paper, we investigate the stability of a stationary periodic chain of nonlinear current filaments in counterstreaming pair plasmas. We make use of a relativistic four-fluid model and apply the Floquet theory to compute the two-dimensional unstable eigenmodes of the spatially periodic system. We examine three different cases, characterized by various levels of nonlinearity and asymmetry between the plasma streams: a weakly nonlinear symmetric system, prone to purely transverse merging modes; a strongly nonlinear symmetric system, dominated by coherent drift-kink modes whose transverse periodicity is equal to, or an integer fraction of the unperturbed filaments; a moderately nonlinear asymmetric system, subject to a mix of kink and bunching-type perturbations. The growth rates and profiles of the numerically computed eigenmodes agree with particle-in-cell simulation results. In addition, we derive an analytic criterion for the transition between dominant filament-merging and drift-kink instabilities in symmetric two-beam systems.
Charge fluctuation effects on the shape of flexible polyampholytes with applications to intrinsically disordered proteins
Authors: Samanta Himadri S. , Chakraborty Debayan , Thirumalai D.
Published: July 2018

Random polyampholytes (PAs) contain positively and negatively charged monomers that are distributed randomly along the polymer chain. The interaction between charges is assumed to be given by the Debye-Huckel potential. We show that the size of the PA is determined by an interplay between electrostatic interactions, giving rise to the polyelectrolyte effect due to net charge per monomer (σ) and an effective attractive PA interaction due to charge fluctuations, δσ. The interplay between these terms gives rise to non-monotonic dependence of the radius of gyration, Rg, on the inverse Debye length, κ, when PA effects are important (δσσ>1). In the opposite limit, Rg decreases monotonically with increasing κ. Simulations of PA chains, using a charged bead-spring model, further corroborate our theoretical predictions. The simulations unambiguously show that conformational heterogeneity manifests itself among sequences that have identical PA parameters. A clear implication is that the phases of PA sequences, and by inference intrinsically disordered proteins (IDPs), cannot be determined using only the bare PA parameters (σ and δσ). The theory is used to calculate the changes in Rg on N, the number of residues for a set of IDPs. For a certain class of IDPs, with N between 24 and 441, the size grows as Rg ∼ N0.6, which agrees with data from small angle X-ray scattering experiments.
Gold nanoparticle distribution in polyelectrolyte brushes loaded at different pH conditions
Authors: Boyaciyan Dikran , Braun Larissa , Löhmann Oliver , Silvi Luca , Schneck Emanuel , von Klitzing Regine
Published: July 2018

Composites made of polymer brushes with inclusions of gold nanoparticles (AuNPs) combine the responsive nature of polymer brushes with the optical properties of the AuNPs, which offers the possibility to be used as colorimetric sensors. To this end, it is crucial to know how AuNPs are distributed inside the brush. Here, this distribution was elucidated by neutron reflectometry with contrast variation and a self-consistent reflectivity analysis based on the analytical parameterization of the volume fraction profiles of all chemical components. In contrast to former studies, this analysis allows the determination of the spatial distribution of components separately from each other: polyelectrolyte, AuNP, and water. Cationic poly-[2-(Methacryloyloxy) ethyl] trimethylammonium chloride (PMETAC) brushes were loaded with 5 nm AuNPs, which were coated with a pH-sensitive capping. The pH was varied during the incubation of the brush in the AuNP suspension. At a lower pH, AuNPs form aggregates in suspension and are attached to the brush periphery. They adsorb into the brush but do not fully penetrate it due to their bulkiness. At a higher pH, AuNP suspensions are electrostatically stabilized and the AuNPs penetrate the brush entirely. However, the AuNP distribution over the brush is not homogeneous but decreases gradually toward the substrate. Penetration of the AuNPs leads to a more extended conformation of the brush. According to the results of the detailed analysis of all components, an increase in water content could be excluded as a reason for brush swelling but replacement of water by the AuNP was observed.
Extended exchange interactions stabilize long-period magnetic structures in Cr1∕3NbS2
Authors: Aczel A. A. , DeBeer-Schmitt L. M. , Williams T. J. , McGuire M. A. , Ghimire N. J. , Li L. , Mandrus D.
Published: July 2018

The topologically protected, chiral soliton lattice is a unique state of matter offering intriguing functionality, and it may serve as a robust platform for storing and transporting information in future spintronic devices. While the monoaxial chiral magnet Cr1∕3NbS2 is known to host this exotic state in an applied magnetic field, its detailed microscopic origin has remained a matter of debate. Here, we work towards addressing this open question by measuring the spin wave spectrum of Cr1∕3NbS2 over the entire Brillouin zone with inelastic neutron scattering. The well-defined spin wave modes allow us to determine the values of several microscopic interactions for this system. The experimental data are well-explained by a Heisenberg Hamiltonian with exchange constants up to the third nearest neighbor and an easy plane magnetocrystalline anisotropy term. Our work shows that both the second and third nearest neighbor exchange interactions contribute to the formation of the helimagnetic and chiral soliton lattice states in this robust three-dimensional magnet.
Evolution of foamed aluminum melt at high rate tension: A mechanical model based on atomistic simulations
Authors: Mayer Polina N. , Mayer Alexander E.
Published: July 2018

Dynamics of foamed metal melt relates to the following problems: cavitations in melt at negative pressure; ablation and nanostructuring of the surface layer of materials under the action of powerful sub picosecond laser pulses; additive manufacturing; and production of solid foamed metals. We propose a mechanical model of the foamed melt evolution at the stage of bubble enlargement—after the completion of their nucleation and before the breaking of the inter-bubble walls. The foamed melt is considered as a system of strongly connected bubbles; their size variations are driven by surface forces. The interconnected system of equations for the second time derivatives of the bubble radii is derived by using the Lagrange formalism. The model is verified by comparison with the molecular dynamic (MD) simulation data for aluminum melt at high-rate uniform tension. An algorithm for searching of individual pores is developed and used to analyze the MD data. The size distribution of pores in the melt at the considered stage of enlargement is found to be close to the normal distribution on a finite interval. Evolution of the foamed melt structure is completely determined by the surface tension. The surface tension makes the largest bubbles growing and all the smaller bubbles collapsing, which leads to rapid reduction of the total number of bubbles. The foamed melt maintains negative pressure determined only by the size distribution of bubbles and the surface tension coefficient.
High-throughput culture and embedment of spheroid array using droplet contact-based spheroid transfer
Authors: Kim Hwisoo , Cho Chang Hyun , Park Je-Kyun
Published: July 2018

Spheroids are one of the most representative models of 3D cell culture, which can be easily formed using conventional hanging drop method. However, medium change and spheroid transferring process are the bottlenecks that reduce the throughput of the entire process in the hanging drop culture. In addition, the embedment of spheroid into hydrogel still depends on the individual pipetting process. To overcome these issues, we present poly(dimethylsiloxane) (PDMS)-based simple devices which can exploit droplet contact-based spheroid transfer using a drop array chip (DAC) having an array of well structures and peripheral rims. When the upper spheroid-containing drops were in contact with the lower liquid drops, the air–liquid interface disappeared at the merged surface and the spheroids settled down due to gravitational force. This method was applied to repetitive medium change and live/dead staining of spheroids cultured with the hanging drop method. To simultaneously embed the spheroids into the corresponding collagen hydrogel drops, a PDMS-based pillar array chip (PAC) was contacted in advance with the spheroid-containing DAC. The contacted PAC then contained the spheroids trapped in small drops of liquid reduced in volume to around 0.5 μl. Consequently, the spheroids were embedded into the collagen drops at once by contacting the spheroid-containing PAC with the collagen-loaded DAC. The embedded spheroids using the DAC–PAC contacting method showed a reliable invasion behavior compared to the embedded spheroids using conventional manual pipetting.
Ultraviolet optical excitation of near infrared emission of Yb-doped crystalline aluminum oxynitride thin films
Authors: Giba Alaa E. , Pigeat P. , Bruyere S. , Rinnert H. , Mücklich F. , Gago R. , Horwat D.
Published: July 2018

Yb3+ ions hold promises for high power emission in the near infrared (NIR). Yet, relevant matrices, comprising mediators to excite Yb3+, have to be found and the optical mechanisms have to be studied in detail. The purpose of this study is to report on the optical excitation and emission mechanisms of NIR photoluminescence (PL) of Yb-doped crystalline aluminum oxynitride thin films prepared at room temperature using reactive magnetron sputtering. Crystal structure and chemical composition are analyzed by transmission electron microscope and Rutherford backscattering spectrometry, respectively. Photoluminescence spectroscopies are used to investigate the excitation and emission mechanisms. NIR emission at 985 nm is obtained under indirect optical excitation using the 325 nm line of a He-Cd laser, the excitation mechanism is explored by photoluminescence excitation measurement (PLE), and the fine structure of the emitted energy levels is investigated by performing PL measurements at low temperature (LTPL). PLE shows that the host defects play the role of mediators to transfer the excitation energy to Yb ions. This offers different possibilities for the development of multiple excitation channels for Yb3+. Stark splitting of the energy levels of the 2F5/2 and 2F7/2 transitions is evidenced using LTPL in the 78 to 295 K range. Electronic transitions are ascribed to experimental emission lines based on good agreement with theoretical values. Moreover, the activation energies for PL thermal quenching are determined and correspond to the energy difference between highest energy quenched lines and thermally activated “hotlines.”
Chaos in Kuramoto oscillator networks
Authors: Bick Christian , Panaggio Mark J. , Martens Erik A.
Published: July 2018

Kuramoto oscillators are widely used to explain collective phenomena in networks of coupled oscillatory units. We show that simple networks of two populations with a generic coupling scheme, where both coupling strengths and phase lags between and within populations are distinct, can exhibit chaotic dynamics as conjectured by Ott and Antonsen [Chaos 18, 037113 (2008)]. These chaotic mean-field dynamics arise universally across network size, from the continuum limit of infinitely many oscillators down to very small networks with just two oscillators per population. Hence, complicated dynamics are expected even in the simplest description of oscillator networks.
Communication: Heavy-Rydberg states of HD and the electron affinity of the deuterium atom
Authors: Beyer Maximilian , Merkt Frédéric
Published: July 2018

The electron affinity of the deuterium atom has been determined to be 6086.81(27) cm−1 from a measurement of the difference between the D+ + H− and H+ + D− ion-pair dissociation energies and a thermochemical cycle involving the electron affinity of H and the ionization energies of H and D. Heavy-Rydberg states and the ion-pair dissociation thresholds of HD were accessed with good efficiency using a three-photon excitation sequence through the B Σu+1 (v = 22, N = 1) and H¯ Σg+1 (v = 9, N = 0) intermediate levels and the threshold positions were determined using the method of threshold-ion-pair-production spectroscopy.
New Products
Authors: Mandelis Andreas
Published: July 2018

In order to supplement manufacturers’ information, this Department will welcome the submission by our readers of brief communications reporting measurements on the physical properties of materials which supersede earlier data or suggest new research applications.
Simple devices enhance the embedment of spheroids into hydrogel array
Authors: Agner Mary Alexandra
Published: July 2018

Chips with well and pillar structures allow for bypassing the bottlenecks of the hanging drop method when culturing and embedding spheroids.
Surface-enhanced Raman spectroscopy in modern chemical analysis: advances and prospects
Authors: Eremina Olga E. , Semenova Anna A. , Sergeeva Elena A. , Brazhe Nadezhda A. , Maksimov Georgy V. , Shekhovtsova Tatyana N. , Goodilin Evgene A. , Veselova Irina A.
Published: July 2018

The review concerns the state of the art, the advances in and prospects for application of surface-enhanced Raman spectroscopy (SERS) in chemical analysis. Key advantages (nondestructive origin, high sensitivity and selectivity, easiness of sample preparation) and drawbacks (a relatively small number of analytes, insufficient metrological characteristics of certain objects) of the method are pointed out. Particular attention is paid to the development of novel chemical approaches and to the design of versatile optical sensors to significantly enhance the analytical potential of the method and to extend the range of analytes. Examples are given of the application of SERS in key branches of science and technology that require both qualitative and quantitative chemical analysis of complex objects,viz., environmental monitoring, fuel and energy area, medical diagnosis, biology and biochemistry.

The bibliography includes 502 references.