bluuebunny/crossref_metadata_2025 huggingface dataset:
Dust-driven viscous ring-instability in protoplanetary disks
Authors: Dullemond C. P. , Penzlin A. B. T.
Published: November 2017

Protoplanetary disks often appear as multiple concentric rings in dust continuum emission maps and scattered light images. These features are often associated with possible young planets in these disks. Many non-planetary explanations have also been suggested, including snow lines, dead zones and secular gravitational instabilities in the dust. In this paper we suggest another potential origin. The presence of copious amounts of dust tends to strongly reduce the conductivity of the gas, thereby inhibiting the magneto-rotational instability, and thus reducing the turbulence in the disk. From viscous disk theory it is known that a disk tends to increase its surface density in regions where the viscosity (i.e. turbulence) is low. Local maxima in the gas pressure tend to attract dust through radial drift, increasing the dust content even more. We have investigated mathematically if this could potentially lead to a feedback loop in which a perturbation in the dust surface density could perturb the gas surface density, leading to increased dust drift and thus amplification of the dust perturbation and, as a consequence, the gas perturbation. We find that this is indeed possible, even for moderately small dust grain sizes, which drift less efficiently, but which are more likely to affect the gas ionization degree. We speculate that this instability could be triggered by the small dust population initially, and when the local pressure maxima are strong enough, the larger dust grains get trapped and lead to the familiar ring-like shapes. We also discuss the many uncertainties and limitations of this model.
Thermal fracturing on comets
Authors: Attree N. , Groussin O. , Jorda L. , Rodionov S. , Auger A.-T. , Thomas N. , Brouet Y. , Poch O. , Kührt E. , Knapmeyer M. , Preusker F. , Scholten F. , Knollenberg J. , Hviid S. , Hartogh P.
Published: November 2017

We simulate the stresses induced by temperature changes in a putative hard layer near the surface of comet 67P/Churyumov-Gerasimenko with a thermo-viscoelastic model. Such a layer could be formed by the recondensation or sintering of water ice (and dust grains), as suggested by laboratory experiments and computer simulations, and would explain the high compressive strength encountered by experiments on board the Philae lander. Changes in temperature from seasonal insolation variation penetrate into the comet’s surface to depths controlled by the thermal inertia, causing the material to expand and contract. Modelling this with a Maxwellian viscoelastic response on a spherical nucleus, we show that a hard, icy layer with similar properties to Martian permafrost will experience high stresses: up to tens of MPa, which exceed its material strength (a few MPa), down to depths of centimetres to a metre. The stress distribution with latitude is confirmed qualitatively when taking into account the comet’s complex shape but neglecting thermal inertia. Stress is found to be comparable to the material strength everywhere for sufficient thermal inertia (≳50 J m−2 K−1 s−1∕2) and ice content (≳45% at the equator). In this case, stresses penetrate to a typical depth of ~0.25 m, consistent with the detection of metre-scale thermal contraction crack polygons all over the comet. Thermal fracturing may be an important erosion process on cometary surfaces which breaks down material and weakens cliffs.
Size-dependent modification of asteroid family Yarkovsky V-shapes
Authors: Bolin B. T. , Morbidelli A. , Walsh K. J.
Published: November 2017

Context.The thermal properties of the surfaces of asteroids determine the magnitude of the drift rate cause by the Yarkovsky force. In the general case of Main Belt asteroids, the Yarkovsky force is indirectly proportional to the thermal inertia, Γ.

Aims.Following the proposed relationship between Γ and asteroid diameterD, we find that asteroids’ Yarkovsky drift rates might have a more complex size dependence than previous thought, leading to a curved familyV-shape boundary in semi-major axis, a, vs. 1/Dspace. This implies that asteroids are drifting faster at larger sizes than previously considered decreasing on average the known ages of asteroid families.

Methods.The V-Shape curvature is determined for >25 families located throughout the Main Belt to quantify the Yarkovsky size-dependent drift rate.

Results.We find that there is no correlation between family age andV-shape curvature. In addition, theV-shape curvature decreases for asteroid families with larger heliocentric distances suggesting that the relationship between Γ andDis weaker in the outer MB possibly due to homogenous surface roughness among family members.
2-Phenyl-2,3-dihydrobenzo[d]thiazole: A Mild, Efficient, and Highly Active in situ Generated Chemoselective Reducing Agent for the One-Pot Synthesis of 5-Monoalkylbarbiturates in Water
Authors: Deka Dibakar , Kalita Subarna
Published: November 2017

A metal- and catalyst-free reductive alkylation protocol for the one-pot synthesis of 5-monoalkylbarbiturates from barbituric acids and aldehydes using the in situ generated chemoselective reducing agent 2-phenyl-2,3-dihydrobenzo[d]thiazole from 2-aminothiophenol and benzaldehyde is described. The notable advantages of the protocol are operational simplicity, mild reaction conditions, high yield, short reaction time, and simple workup and purification process which make it highly attractive.
Pseudohypoaldosteronism Type 1—An Exercise in Clinical Deduction and Critical Management
Authors: Girish Meenakshi , Pazare Pradeep , Jaiswal Archana , Banait Yash , Kumar Richa
Published: November 2017

Pseudohypoaldosteronism type 1 (PHA1) is a life-threatening disorder for two reasons, first because it causes severe hyperkalemia and second because the rarity of the disorder means that diagnosis is often delayed due to the lack of clinician familiarity with this condition. In this case report, we have described how even to an unsuspecting mind and eye, a systematic approach can lead to reversal of the severe hyperkalemia and arrive at the diagnosis of PHA1 as a cause of hyperkalemia. Long-term management can be successful only with dedicated care, and the prognosis is unfortunately worsened by the lack of availability of sodium-K resin in many countries, including India.
Survival from Septic Shock Secondary to Disseminated Group A Streptococcal Infection after Central Extracorporeal Membrane Oxygenation
Authors: Asfari A. , Ahmed M. , Edwards L. , Irby K. , Agarwal A. , Pasala S. , Prodhan P. , Frazier B. , Sanders R.
Published: November 2017

Objective The objective of this study was to describe a case of severe life-threatening acute respiratory distress syndrome (ARDS) and septic shock in a child who responded to a prolonged extracorporeal membrane oxygenation (ECMO) support course utilizing different cannulation techniques depending on the physiological derangement until he recovered.

Design This is a case report.

Setting This study was done at the medical–surgical pediatric intensive care unit in an academic freestanding children's hospital.

Patient A previously healthy 4-year-old boy was presented with respiratory distress and fever. He was diagnosed with respiratory syncytial viral upper respiratory tract infection and group A β-hemolytic Streptococcus septic shock.

Interventions The patient was referred to peripheral ECMO for hemodynamic, ventilatory, and oxygenation support; conversion to central ECMO to augment blood flow; and transition to extracorporeal carbon dioxide removal before successful wean off extracorporeal support.

Measurements and Main Results Patient experienced severe pediatric ARDS and septic shock that were refractory to maximal medical therapy. Patient was able to be decannulated after 75 days of extracorporeal support. He was weaned completely off of mechanical ventilation and oxygen after 6 months. The only neurological deficit he exhibited was poor fine motor skills of his hands for which he continued to receive physical therapy.

Conclusion Central ECMO may benefit children with pediatric ARDS and septic shock who require higher flows than what can be provided from peripheral ECMO. Extracorporeal membrane carbon dioxide removal may be an effective option in children who do not respond to mechanical ventilation alone.
Predictors of PDA Treatment in Preterm Neonates Who Had Received Prophylactic Indomethacin
Authors: ElSayed Yasser , Ojah Cecil , Alvaro Ruben , Shah Prakesh , Dunn Michael , Louis Deepak ,   for the Canadian Neonatal Network Investigators
Published: November 2017

Objective To identify clinical factors those predict the need for patent ductus arteriosus (PDA) treatment in preterm neonates who had received prophylactic indomethacin.

Patients and Methods Preterm neonates with <28 weeks' gestational age admitted to level III neonatal intensive care units (NICUs) in Canada between 2010 and 2015 and who had received prophylactic indomethacin were included. Primary outcome was surgical ligation of PDA, while secondary outcomes were any PDA treatment and common neonatal morbidities.

Results Of the 7,024 eligible neonates, 843 (12%) neonates had received prophylactic indomethacin. Of them, 84 neonates (10%) required surgical ligation while 367 neonates (44%) received medical or surgical treatment for PDA. Logistic regression analyses identified gestational age (odds ratio [OR]: 0.71, 95% confidence interval [CI]: 0.58–0.87) and outborn status (OR: 2.07, 95% CI: 1.09–3.93) as predictors for surgical ligation. Maternal hypertension (OR: 0.57, 95% CI: 0.37–0.89), rupture of membranes (ROM) ≥24 hours (OR: 0.68, 95% CI: 0.48–0.96), and surfactant treatment (OR: 1.70, 95% CI: 1.09–2.66) were predictors for medical or surgical treatment of PDA.

Conclusion In extremely preterm neonates who had received prophylactic indomethacin, gestational age and outborn status were predictors for surgical ligation of PDA, while maternal hypertension, ROM ≥24 hours, and surfactant treatment were associated with the medical or surgical treatment of PDA.
Prevalence and Progression Rate of Diabetic Retinopathy in Type 2 Diabetes Patients in Correlation with the Duration of Diabetes
Authors: Voigt Margarete , Schmidt Sebastian , Lehmann Thomas , Köhler Benjamin , Kloos Christof , Voigt Ulrich , Meller Daniel , Wolf Gunter , Müller Ulrich , Müller Nicolle
Published: November 2017

Aims We examined prevalence and progression of retinopathy in dependence on diabetes duration in order to estimate the probability of progression.

Patients/Methods In a retrospective cohort-analysis from an academic outpatient department of endocrinology and metabolic diseases we analyzed 17461 consultations of 4513 patients with DM2 from 1987 to 2014. 50.3% of the patients (n=2272) had at least one documented result of funduscopy.

Results 25.8% of the patients had retinopathy (20.2% non-proliferative, 4.7% proliferative, 0.7% were not classified, 0.1% blindness). The prevalence of retinopathy in dependence on diabetes duration was 1.1% at diagnosis, 6.6% after 0<5 years, 12% after 5<10 years, 24% after 10<15 years, 39.9% after 15<20 years, 52.7% after 20<25 years, 58.7% after 25<30 years and 63% after ≥30 years. In a subset of 586 (25.7%) patients with retinal photography of 3 consecutive years 7.0% showed deterioration after one and 12.2% after two years; 2.6% improved after one and 2.8% after two years. 201 (34.3%) of this group had<10 years diabetes and lower deterioration (4.5% worsened after one and 9.5% after two years). Their retinopathy mainly transformed from no retinopathy to non-proliferative. Four patients (2.0%) developed proliferative retinopathy.

Conclusions/Interpretations Within the first 10 years of diabetes duration, the prevalence of retinopathy is low and the progression infrequent. Most patients have a non-proliferative form which can be reversible and rarely requires interventions. Patients with DM2 without retinopathy and good glycaemic control do not run into additional risk from expanding funduscopy intervals to biennial.
Zugang zur stationären Rehabilitation bei Methamphetaminabhängigkeit – Barrieren und Optimierungspotenziale aus Expertenperspektive
Authors: Hoffmann Laura , Schumann Nadine , Richter Matthias
Published: November 2017

Ziel Die Studie exploriert, welche zentralen Barrieren den Zugang zur stationären Rehabilitation bei Methamphetaminabhängigkeit aus Expertensicht beeinträchtigen und wie diese behoben werden können.

Methodik In 39 semi-strukturierten Einzelinterviews wurden Erfahrungen und Perspektiven von Experten unterschiedlicher Versorgungsbereiche analysiert. Anschließend wurden die Ergebnisse der Einzelinterviews in 2 professionsübergreifenden Fokusgruppen diskutiert. Die Datenanalyse erfolgte mithilfe des interpretativen Auswertungsverfahrens nach Meuser & Nagel.

Ergebnisse Der Zugang zur stationären Rehabilitation für Methamphetaminabhängige wird insbesondere durch strukturelle Barrieren beeinträchtigt. Dazu gehören z. B. eine erschwerte Zuweisung zur Reha über Hausärzte, ein zu selten bedientes Nahtlosigkeitsverfahren, Kapazitätsprobleme der Rehakliniken sowie ein intransparentes Verfahren der Klinikauswahl durch den Träger.

Schlussfolgerung Der Zugang zur stationären Reha für Methamphetaminabhängige ist durch unterschiedliche Barrieren beeinträchtigt. Es gilt künftig v. a. Hausärzte für mehr Offenheit gegenüber Drogenkonsumenten und deren Besonderheiten zu sensibilisieren, einen nahtlosen Übergang von der Entgiftungs- zur Rehabilitationsbehandlung zu gewährleisten sowie differenzierte, bedarfsgerechte Reha-Angebote für die Betroffenen bereitzustellen.
Constricted microfluidic devices to study the effects of transient high shear exposure on platelets
Authors: Alsmadi Nesreen Z. , Shapiro Sarah J. , Lewis Christopher S. , Sheth Vinit M. , Snyder Trevor A. , Schmidtke David W.
Published: November 2017

Due to the critical roles that platelets play in thrombosis during many biological and pathological events, altered platelet function may be a key contributor to altered hemostasis, leading to both thrombotic and hemorrhagic complications. Platelet adhesion at arterial shear rates occurs through binding to von Willebrand Factor via the glycoprotein (GP) GPIb receptor. GPIb binding can induce platelet activation distinguishable by P-selectin (CD62P) surface expression and αIIbβ3 activation, resulting in platelet aggregation and formation of the primary hemostatic plug to stop bleeding. Previous studies have used cone and plate viscometers to examine pathologic blood flow conditions, applied shear rates that are relatively low, and examined exposure times that are orders of magnitude longer compared to conditions present in ventricular assist devices, mechanical heart valves, or pathologic states such as stenotic arteries. Here, we evaluate the effect of short exposure to high shear on granule release and receptor shedding utilizing a constricted microfluidic device in conjunction with flow cytometry and enzyme-linked immunosorbent assay. In this study, platelets were first perfused through microfluidic channels capable of producing shear rates of 80 000–100 000 s−1 for exposure times of 0–73 ms. We investigated platelet activation by measuring the expression level of CD62P (soluble and surface expressed), platelet factor 4 (PF4), and beta-thromboglobulin (βTG). In addition, we measured potential platelet receptor shedding of GPVI and GPIb using flow cytometry. The results showed that a single pass to high shear with short exposure times (milliseconds) had no effect on the levels of CD62P, GPVI and GPIb, or on the release of alpha granule content (PF4, βTG, and sP-selectin).
1 μs broadband frequency sweeping reflectometry for plasma density and fluctuation profile measurements
Authors: Clairet F. , Bottereau C. , Medvedeva A. , Molina D. , Conway G. D. , Silva A. , Stroth U. ,   ASDEX Upgrade Team,   Tore Supra Team,   EUROfusion MST1 Team
Published: November 2017

Frequency swept reflectometry has reached the symbolic value of 1 μs sweeping time; this performance has been made possible, thanks to an improved control of the ramp voltage driving the frequency source. In parallel, the memory depth of the acquisition system has been upgraded and can provide up to 200 000 signals during a plasma discharge. Additional improvements regarding the trigger delay determination of the acquisition and the voltage ramp linearity required by this ultra-fast technique have been set. While this diagnostic is traditionally dedicated to the plasma electron density profile measurement, such a fast sweeping rate can provide the study of fast plasma events and turbulence with unprecedented time and radial resolution from the edge to the core. Experimental results obtained on ASDEX Upgrade plasmas are presented to demonstrate the performances of the diagnostic.
Apparent and microscopic dynamic contact angles in confined flows
Authors: Omori Takeshi , Kajishima Takeo
Published: November 2017

An abundance of empirical correlations between a dynamic contact angle and a capillary number representing a translational velocity of a contact line have been provided for the last decades. The experimentally obtained dynamic contact angles are inevitably apparent contact angles but often undistinguished from microscopic contact angles formed right on the wall. As Bonn et al. [“Wetting and spreading,” Rev. Mod. Phys. 81, 739–805 (2009)] pointed out, however, most of the experimental studies simply report values of angles recorded at some length scale which is quantitatively unknown. It is therefore hard to evaluate or judge the physical validity and the generality of the empirical correlations. The present study is an attempt to clear this clutter regarding the dynamic contact angle by measuring both the apparent and the microscopic dynamic contact angles from the identical data sets in a well-controlled manner, by means of numerical simulation. The numerical method was constructed so that it reproduced the fine details of the flow with a moving contact line predicted by molecular dynamics simulations [T. Qian, X. Wang, and P. Sheng, “Molecular hydrodynamics of the moving contact line in two-phase immiscible flows,” Commun. Comput. Phys. 1, 1–52 (2006)]. We show that the microscopic contact angle as a function of the capillary number has the same form as Blake’s molecular-kinetic model [T. Blake and J. Haynes, “Kinetics of liquid/liquid displacement,” J. Colloid Interface Sci. 30, 421–423 (1969)], regardless of the way the flow is driven, the channel width, the mechanical properties of the receding fluid, and the value of the equilibrium contact angle under the conditions where the Reynolds and capillary numbers are small. We have also found that the apparent contact angle obtained by the arc-fitting of the interface behaves surprisingly universally as claimed in experimental studies in the literature [e.g., X. Li et al., “An experimental study on dynamic pore wettability,” Chem. Eng. Sci. 104, 988–997 (2013)], although the angle deviates significantly from the microscopic contact angle. It leads to a practically important point that it suffices to measure arc-fitted contact angles to make formulae to predict flow rates in capillary tubes.
An in situ simultaneous measurement system combining photoelasticity and caustics methods for blast-induced dynamic fracture
Authors: Qiu Peng , Yue Zhongwen , Zhang Shichun , Li Zhanfei
Published: November 2017

Photoelasticity and caustics methods are extensively used in the history of dynamic fracture mechanics. However, there is little work for the combination of them in the same experiment associated with high loading rate in extreme conditions. In the present work, it is the first time to build a simultaneous measurement system which can use photoelasticity and caustics methods at the same instant for in situ optical investigations of blast-induced dynamic fracture. To illustrate the capability of this system, an explosion experiment using a 2D epoxy plate is conducted, yielding consistent results between two methods. This novel system provides rich experimental data including local-field information for the crack tip and full-field information for blasting waves.
Sub-500 fs electronically nonadiabatic chemical dynamics of energetic molecules from the S1 excited state: Ab initio multiple spawning study
Authors: Ghosh Jayanta , Gajapathy Harshad , Konar Arindam , Narasimhaiah Gowrav M. , Bhattacharya Atanu
Published: November 2017

Energetic materials store a large amount of chemical energy. Different ignition processes, including laser ignition and shock or compression wave, initiate the energy release process by first promoting energetic molecules to the electronically excited states. This is why a full understanding of initial steps of the chemical dynamics of energetic molecules from the excited electronic states is highly desirable. In general, conical intersection (CI), which is the crossing point of multidimensional electronic potential energy surfaces, is well established as a controlling factor in the initial steps of chemical dynamics of energetic molecules following their electronic excitations. In this article, we have presented different aspects of the ultrafast unimolecular relaxation dynamics of energetic molecules through CIs. For this task, we have employed ab initio multiple spawning (AIMS) simulation using the complete active space self-consistent field (CASSCF) electronic wavefunction and frozen Gaussian-based nuclear wavefunction. The AIMS simulation results collectively reveal that the ultrafast relaxation step of the best energetic molecules (which are known to exhibit very good detonation properties) is completed in less than 500 fs. Many, however, exhibit sub-50 fs dynamics. For example, nitro-containing molecules (including C–NO2, N–NO2, and O–NO2 active moieties) relax back to the ground state in approximately 40 fs through similar (S1/S0)CI conical intersections. The N3-based energetic molecule undergoes the N2 elimination process in 40 fs through the (S1/S0)CI conical intersection. Nitramine-Fe complexes exhibit sub-50 fs Fe–O and N–O bond dissociation through the respective (S1/S0)CI conical intersection. On the other hand, tetrazine-N-oxides, which are known to exhibit better detonation properties than tetrazines, undergo internal conversion in a 400-fs time scale, while the relaxation time of tetrazine is very long (about 100 ns). Many other characteristics of sub-500 fs nonadiabatic decay of energetic molecules are discussed. In the end, many unresolved issues associated with the ultrafast nonadiabatic chemical dynamics of energetic molecules are presented.
Combining extrapolation with ghost interaction correction in range-separated ensemble density functional theory for excited states
Authors: Alam Md. Mehboob , Deur Killian , Knecht Stefan , Fromager Emmanuel
Published: November 2017

The extrapolation technique of Savin [J. Chem. Phys. 140, 18A509 (2014)], which was initially applied to range-separated ground-state-density-functional Hamiltonians, is adapted in this work to ghost-interaction-corrected (GIC) range-separated ensemble density-functional theory (eDFT) for excited states. While standard extrapolations rely on energies that decay as μ−2 in the large range-separation-parameter μ limit, we show analytically that (approximate) range-separated GIC ensemble energies converge more rapidly (as μ−3) towards their pure wavefunction theory values (μ → +∞ limit), thus requiring a different extrapolation correction. The purpose of such a correction is to further improve on the convergence and, consequently, to obtain more accurate excitation energies for a finite (and, in practice, relatively small) μ value. As a proof of concept, we apply the extrapolation method to He and small molecular systems (viz., H2, HeH+, and LiH), thus considering different types of excitations such as Rydberg, charge transfer, and double excitations. Potential energy profiles of the first three and four singlet Σ+ excitation energies in HeH+ and H2, respectively, are studied with a particular focus on avoided crossings for the latter. Finally, the extraction of individual state energies from the ensemble energy is discussed in the context of range-separated eDFT, as a perspective.
Pressure effects on interfacial surface contacts and performance of organic solar cells
Authors: Agyei-Tuffour B. , Doumon N. Y. , Rwenyagila E. R. , Asare J. , Oyewole O. K. , Shen Z. , Petoukhoff C. E. , Zebaze Kana M. G. , Ocarroll D. M. , Soboyejo W. O.
Published: November 2017

This paper explores the effects of pressure on the interfacial surface contacts and the performance of organic solar cells. A combination of experimental techniques and analytical/computational models is used to study the evolving surface contacts profiles that occur when compliant, semi-rigid and rigid particles are interlocked between adjacent layers in model solar cell structures. The effects of layer surface roughness and interlocked (trapped) particles are also considered along with the effects of surface energy, adhesion energy, and pressure. The results show that increased interfacial contact lengths and decreased void lengths are associated with the application of increased pressure. Increased pressure also results in significant improvements in power conversion efficiency. These improvements in power conversion efficiency are associated with the closure up of micro- and nano-voids due to the application of pressure to layers produced via spin coating and thermal evaporation. The results suggest that pressure-induced contacts can be used to enhance the performance of organic solar cells.
Bandwidth enhancement scheme demonstration on direct modulation active-MMI laser diode using multiple photon photon resonance
Authors: Hong B. , Kitano T. , Mori T. , Jiang H. , Hamamoto K.
Published: November 2017

By introducing properly designed multiple photo photon resonances (PPRs) on an active-Multimode Interferometer Laser Diode, the confirmed direct modulation bandwidth was enhanced from less than 5 GHz to at least 34 GHz. Multiple oscillating cavities that have slightly different free space ranges (FSRs) are integrated within a single device. The overlap between such FSRs contributes to multiple wavelength differences that are directly related to the PPR frequencies. Evaluated PPR frequencies from experimental data match with designed frequencies. The potential of the 100 GHz level bandwidth of the device has been proved.
Noise activated bistable sensor based on chaotic system with output defined by temporal coding and firing rate
Authors: Korneta Wojciech , Gomes Iacyel
Published: November 2017

Traditional bistable sensors use external bias signal to drive its response between states and their detection strategy is based on the output power spectral density or the residence time difference (RTD) in two sensor states. Recently, the noise activated nonlinear dynamic sensors driven only by noise based on RTD technique have been proposed. Here, we present experimental results of dc voltage measurements by noise-driven bistable sensor based on electronic Chua's circuit operating in a chaotic regime where two single scroll attractors coexist. The output of the sensor is quantified by the proportion of the time the sensor stays in one state to the total observation time and by the spike-count rate with spikes defined by crossings between attractors. The relationship between the stimuli and particular observable for different noise intensities is obtained, the usefulness of each coding scheme is discussed, and the optimal noise intensity for detection is indicated. It is shown that the obtained relationship is the same for any observation time when population coding is used. The optimal time window for both detection and the number of units in population coding is found. Our results may be useful for analyses and understanding of the neural activity and in designing bistable storage elements at length scales where thermal fluctuations drastically increase and the effect of noise must be taken into consideration.
Raman spectroscopy study of damage induced in cerium dioxide by swift heavy ion irradiations
Authors: Costantini Jean-Marc , Miro Sandrine , Gutierrez Gaëlle , Yasuda Kazuhiro , Takaki Seiya , Ishikawa Norito , Toulemonde Marcel
Published: November 2017

The damage induced in cerium dioxide by swift heavy ion irradiation was studied by micro-Raman spectroscopy. For this purpose, polycrystalline sintered pellets were irradiated by 100-MeV Kr, 200-MeV Xe, 10-MeV, and 36-MeV W ions in a wide range of fluence and stopping power (up to ∼28 MeV μm−1). No amorphization of ceria was found whatsoever, as shown by the presence of the peak of Raman-active T2g mode (centered at 467 cm−1) of the cubic fluorite structure for all irradiation conditions. However, a clear decrease of the T2g mode peak intensity was observed as a function of ion fluence to an asymptotic relative value of about 45%. Similar decays were also observed for satellite peaks and second-order peaks. Track radii deduced from the decay kinetics for the 36-MeV W ion data are in good agreement with previous determinations by X-ray diffraction and reproduced by the inelastic thermal spike model for low ion velocities. However, interaction between the nuclear and electronic stopping powers is needed to describe the decay kinetics of 10-MeV W ion data by the thermal spike process. Moreover, the asymmetrical broadening of the main T2g peak after irradiation was analyzed with different theoretical models.
Methods to locate saddle points in complex landscapes
Authors: Bonfanti Silvia , Kob Walter
Published: November 2017

We present a class of simple algorithms that allows us to find the reaction path in systems with a complex potential energy landscape. The approach does not need any knowledge on the product state and does not require the calculation of any second derivatives. The underlying idea is to use two nearby points in the configuration space to locate the path of the slowest ascent. By introducing a weak noise term, the algorithm is able to find even low-lying saddle points that are not directly reachable by means of the slowest ascent path. Since the algorithm only makes use of the value of the potential and its gradient, the computational effort to find saddle points is linear in the number of degrees of freedom if the potential is short-ranged. We test the performance of the algorithm for three potential energy landscapes. For the Müller-Brown surface, we find that the algorithm always finds the correct saddle point. For the modified Müller-Brown surface, which has a saddle point that is not reachable by means of the slowest ascent path, the algorithm is still able to find this saddle point with high probability. For the case of a three-dimensional Lennard-Jones cluster, the algorithm is able to find the lowest energy barrier with high probability, showing that the method is also efficient in landscapes with many dimensions.
Noncommutative Riemannian geometry from quantum spacetime generated by twisted Poincaré group
Authors: Aguillón Cesar A. , Much Albert , Rosenbaum Marcos , Vergara J. David
Published: November 2017

We investigate a quantum geometric space in the context of what could be considered an emerging effective theory from quantum gravity. Specifically we consider a two-parameter class of twisted Poincaré algebras, from which Lie-algebraic noncommutativities of the translations are derived as well as associative star-products, deformed Riemannian geometries, Lie-algebraic twisted Minkowski spaces, and quantum effects that arise as noncommutativities. Starting from a universal differential algebra of forms based on the above-mentioned Lie-algebraic noncommutativities of the translations, we construct the noncommutative differential forms and inner and outer derivations, which are the noncommutative equivalents of the vector fields in the case of commutative differential geometry. Having established the essentials of this formalism, we construct a bimodule, which is required to be central under the action of the inner derivations in order to have well-defined contractions and from where the algebraic dependence of its coefficients is derived. This again then defines the noncommutative equivalent of the geometrical line-element in commutative differential geometry. We stress, however, that even though the components of the twisted metric are by construction symmetric in their algebra valuation, it is not so for their inverse, and thus to construct it, we made use of Gel’fand’s theory of quasi-determinants, which is conceptually straightforward but computationally quite complicated beyond an algebra of 3 generators. The consequences of the noncommutativity of the Lie-algebra twisted geometry are further discussed.
Factors that affect general practice as a choice of medical speciality: implications for policy development
Authors: Vohra Amit , Ladyshewsky Richard , Trumble Stephen
Published: November 2017

Objective This article critically appraises the range of personal, professional and social factors that affect the choice of speciality across medical students, prevocational doctors, general practice registrars and general practitioners. Methods This qualitative study applied constructs from the fields of decision theory and career theory to better understand the complex nature of choosing a speciality. In all, 47 in-depth interviews were conducted with participants at different stages of their career cycle. The data was codified and analysed using NVivo to identify key factors that influenced speciality choice. Results The research identified 77 individual findings influencing general practice as a choice of medical speciality. These were distilled into a matrix to show that factors such as money, prestige and peer interaction did not have a compelling effect, whereas clinical and academic role models, flexibility, work–life balance, scope of practice, connection with patients, training environment and practical opportunities did. Conclusion The findings indicate that the decision in relation to the choice of medical speciality is a complex cognitive process that is undertaken within a personal, social and professional context particular to each individual. What is known about the topic? Current literature aims to quantify changes in attitudes towards choice of speciality or the effect of particular variables in isolation while ignoring the complexity of this decision process and how the numerous variables compare with each other. What does this paper add? The present study is the first intergenerational research on this topic in the Australian context and the paper dismisses the role of prestige and remuneration as key drivers of choice in picking general practice as a speciality, noting that money is merely a ‘hygiene factor’. What are the implications for policy makers? A policy framework outlining 10 key principles is presented to assist policy makers seeking to affect workforce outcomes by applying policy levers to influence doctors’ choice of speciality.
Comparative ecotoxicity study of glycerol-biobased solvents
Authors: Perales Eduardo , García Cristina Belén , Lomba Laura , García José Ignacio , Pires Elísabet , Sancho Mari Carmen , Navarro Enrique , Giner Beatriz
Published: November 2017

Environmental contextThe search for alternative solvents to prevent environmental damage is one of the main interests in ‘green’ sciences. Five of these new substances from biodiesel production were evaluated to assess their negative environmental effects. The results obtained showed that three of these chemicals may be harmless for short exposure in aquatic biomodels. Although more tests are required, this family of compounds promises to be safe and useful for industrial purposes.
AbstractGlycerol-biobased ethers have a high potential as solvents owing to their chemical inertness and diversity, which allows modulation of their properties, such as polarity, hydrophobicity or viscosity, depending on the specific needs in each case. Despite their renewable source, the environmental compatibility of these solvents needs to be checked. The acute ecotoxicity of five glycerol-derived solvents (3-ethoxy-1,2-propanediol, 1,3-diethoxy-2-propanol, 3-butoxy-1,2-propanediol , 1,3-dibutoxy-2-propanol and 1,2,3-tributoxypropane ) was evaluated in a systematic study using several bioindicators covering the trophic chain (the crustacean Daphnia magna, the fish Danio rerio and the green alga Chlamydomonas reinhardtii). These results were compared with the previously studied bioindicator Vibrio fischeri. According to the hypothesis of the present work, the toxicity of these solvents increased as a function of their lipophilicity, which is related to the increase in the number and length of the alkyl chains in the basic structure; accordingly, the least toxic compound for all the aquatic organisms was 3-ethoxy-1,2-propanediol and the most toxic solvent was 1,2,3-tributoxypropane, except in the case of D. rerio and V. fischeri, with 1,3-dibutoxy-2-propanol the most toxic chemical. Potential damage caused by eventual emissions, was evaluated using the Environmental Health and Safety Approach, a methodology used for detecting risks related to the environment and the human health. Using available physicochemical and toxicity data, each chemical compound receives a score for the categories health, safety and environment. The best candidates considered as least dangerous for a short exposure time according to the studied biomodels are 3-ethoxy-1,2-propanediol, 3-butoxy-1,2-propanediol and 1,3-diethoxy-2-propanol.
Role of the antioxidant system in the regulation of the chlorophyll biosynthesis pathway in the vascular plant Cucumis sativus
Authors: Dhepe Aarti , Joshi Komal
Published: November 2017

In this study, the role of the antioxidant system has been examined in the regulation of the chlorophyll biosynthesis pathway in the vascular plant Cucumis sativus L. To generate reactive oxygen species (ROS), etiolated (E) and green (G) cucumber cotyledons were treated with methyl viologen (MV) or were exposed to high light (HL, 400–500 µE m–2 s–1). ROS generation was confirmed by measuring proline and H2O2 concentrations. With the effects of the MV- and HL-induced oxidative stress, it was observed that the chlorophyll biosynthesis pathway was severely affected in the HL-treated etiolated cotyledons (E-HL), MV-treated etiolated cotyledons (E-MV) and in MV-treated green cotyledons (G-MV) at 5-amino levulinic acid (ALA) as well as at protoporphyrin IX and Mg-protoporphyrin IX monomethyl ester levels. The antioxidant assays conducted showed that the ascorbate peroxidase (APX) activity had decreased in the E-HL, E-MV and G-MV cotyledons along with the levels of ascorbate and lutein. A decrease in the NADPH-dependent thioredoxin reductase (NTRC) was also observed in the MV-treated cotyledons with a significant impairment of the catalase activity in the E-HL cotyledons. Conversely, in the HL-treated green i.e. G-HL cotyledons, where the accumulation of H2O2 and the inhibition of chlorophyll biosynthesis were not observed, an increase in the levels of APX, NTRC, peroxiredoxin, ascorbate, glutathione and lutein was noted. Thus, the results obtained suggested that the antioxidant system could influence the flow of the chlorophyll biosynthesis pathway through maintaining the levels of H2O2.
Unraveling the structure and chemical mechanisms of highly oxygenated intermediates in oxidation of organic compounds
Authors: Wang Zhandong , Popolan-Vaida Denisia M. , Chen Bingjie , Moshammer Kai , Mohamed Samah Y. , Wang Heng , Sioud Salim , Raji Misjudeen A. , Kohse-Höinghaus Katharina , Hansen Nils , Dagaut Philippe , Leone Stephen R. , Sarathy S. Mani
Published: November 2017

Significance

Highly oxygenated molecules are involved in autooxidation reactions leading to the formation of secondary organic aerosols (SOAs); they are also critical intermediates in autooxidation processes for liquid hydrogen degradation and the ignition of fuels in advanced combustion systems. However, these reactions are still poorly understood. In this study, we unveil a generalized reaction mechanism involving the autooxidation of peroxy radicals with at least three stages of sequential O2addition. We elucidate important underlying kinetics and structural characteristics of autooxidation processes used for developing new technologies including those aimed at reducing climatically active SOAs and pollutants from fuel combustion. We show that advances can be made by bridging experimental and theoretical methods used by atmospheric and combustion scientists.
Spin susceptibility of charge-ordered YBa
2
Cu
3
O

y

across the upper critical field
Authors: Zhou Rui , Hirata Michihiro , Wu Tao , Vinograd Igor , Mayaffre Hadrien , Krämer Steffen , Reyes Arneil P. , Kuhns Philip L. , Liang Ruixing , Hardy W. N. , Bonn D. A. , Julien Marc-Henri
Published: November 2017

Significance

The upper critical field

H

c
2

is a fundamental, and technologically important, property that measures the ability of a superconductor to withstand magnetic fields. Recently, there has been a controversy regarding the values
H

c
2

in high-
T

c

copper oxides, particularly in YBa
2
Cu
3
O

y

when a charge density wave (CDW) is present. Here, taking advantage of nuclear magnetic resonance, a local probe that can measure the intrinsic spin susceptibility

χ
spin

of the superconducting planes, we observe an essentially linear increase in

χ
spin

up to a point in the range of 20–40 T, followed by a constant value. This saturation point is in accord with previous measurements of
H

c
2

. Our data suggest that the CDW drastically reduces

H

c
2

in YBa
2
Cu
3
O

y

.
Patterns of coevolving amino acids unveil structural and dynamical domains
Authors: Granata Daniele , Ponzoni Luca , Micheletti Cristian , Carnevale Vincenzo
Published: November 2017

Significance

Patterns of pairwise correlations in sequence alignments can be used to reconstruct the network of residue-residue contacts and thus the three-dimensional structure of proteins. Less explored, and yet extremely intriguing, is the functional relevance of such coevolving networks: Do they encode for the collective motions occurring in proteins at thermal equilibrium? Here, by combining coevolutionary coupling analysis with a state-of-the-art dimensionality reduction approach, we show that the network of pairwise evolutionary couplings can be analyzed to reveal communities of amino acids, which we term “evolutionary domains,” that are in striking agreement with the quasi-rigid protein domains obtained from elastic network models and molecular dynamics simulations.
Relationship of tropospheric stability to climate sensitivity and Earth’s observed radiation budget
Authors: Ceppi Paulo , Gregory Jonathan M.
Published: November 2017

Significance

In current climate models, the anticipated amount of warming under greenhouse gas forcing, quantified by the “effective climate sensitivity,” increases as time passes. Consequently, effective climate sensitivity values inferred from the historical record may underestimate the future warming. However, the mechanisms of this increase in effective climate sensitivity are not understood, limiting our confidence in climate model projections of future climate change. Here, we present observational and modeling evidence that the magnitude of effective climate sensitivity partly depends on the evolution of the vertical profile of atmospheric warming. In climate models, as the Earth warms overall, the warming becomes increasingly muted aloft, and this alters the strength of feedbacks controlling the radiative response to greenhouse gas forcing.
Robust zero resistance in a superconducting high-entropy alloy at pressures up to 190 GPa
Authors: Guo Jing , Wang Honghong , von Rohr Fabian , Wang Zhe , Cai Shu , Zhou Yazhou , Yang Ke , Li Aiguo , Jiang Sheng , Wu Qi , Cava Robert J. , Sun Liling
Published: November 2017

Significance

High-entropy alloys (HEAs) are made from multiple transition-metal elements in equimolar or near-equimolar ratios. The elements in HEAs arrange themselves randomly on the crystallographic positions of a simple lattice. In addition to their excellent mechanical properties, one HEA has been reported to display superconductivity. In this work, we report that the Ta–Nb–Hf–Zr–Ti high-entropy alloy superconductor exhibits extraordinarily robust zero-resistance superconductivity under pressure up to 190.6 GPa. This is an observation of the zero-resistance state of a superconductor all the way from 1-bar pressure to the pressure of the earth’s outer core without structure phase transition, making the superconducting HEA a promising candidate for new application under extreme condition.
Vasopressin excites interneurons to suppress hippocampal network activity across a broad span of brain maturity at birth
Authors: Spoljaric Albert , Seja Patricia , Spoljaric Inkeri , Virtanen Mari A. , Lindfors Jenna , Uvarov Pavel , Summanen Milla , Crow Ailey K. , Hsueh Brian , Puskarjov Martin , Ruusuvuori Eva , Voipio Juha , Deisseroth Karl , Kaila Kai
Published: November 2017

Significance

The transition from placental to lung-based oxygen supply at mammalian birth involves an obligatory period of asphyxia, which is further aggravated by complications during delivery. This oxygen deprivation is a major threat to the fetal brain, and, under such conditions, hormonal and cardiovascular mechanisms are activated to enhance brain perfusion. Our work now demonstrates an intrinsic mechanism in the fetal brain whereby vasopressin activates hippocampal interneurons, leading to desynchronization and suppression of neuronal network activity in species (rat and guinea pig) that are born at widely different stages of brain maturation. Silencing of synchronous neuronal activity by vasopressin is expected to decrease neuronal energy demand and prevent maladaptive synaptic plasticity, thus acting as a pan-mammalian neuroprotective mechanism during birth.
High-resolution mapping ofcis-regulatory variation in budding yeast
Authors: Kita Ryosuke , Venkataram Sandeep , Zhou Yiqi , Fraser Hunter B.
Published: November 2017

Significance

Genetic variants affecting gene-expression levels are a major source of phenotypic variation. Using 85 diverse isolates ofSaccharomyces cerevisiae, we mapped genetic variants that affect gene expression with 50-fold higher resolution than previously possible. By doing so, we were able to pinpoint likely causal variants and investigate their molecular mechanisms. We found that these genetic variants are generally under negative selection, but also that clinical yeast isolates have undergone positive selection for up-regulation of genes involved in biofilm suppression. Altogether, our results demonstrate the power of high-resolution mapping of genetic variants that affect gene expression, particularly in understanding the molecular mechanisms of regulatory variation and the natural selection acting on this variation.