bluuebunny/crossref_metadata_2025 huggingface dataset:
Highly porous micro-roughened structures developed on aluminum surface using the jet of rotating arc discharges at atmospheric pressure
Authors: Asadollahi Siavash , Farzaneh Masoud , Stafford Luc
Published: February 2018

Aluminum 6061 samples were exposed to the jet of an atmospheric pressure rotating arc discharge operated in either nitrogen or air. After multiple passes of treatment with an air-based plasma jet at very short source-to-substrate distances, scanning electron microscopy combined with x-ray photoelectron spectroscopy revealed a highly porous micro-roughened alumina-based structure on the surface of aluminum. Based on optical emission spectroscopy and high-speed optical imaging of the jet interacting with aluminum samples, it was found that the process is mainly driven by the energy transfer from the plasma source to the surface through transient plasma-transferred arcs. The occurrence of multiple arc discharges over very short time scales can induce rapid phase transformations of aluminum with characteristics similar to the ones usually observed during laser ablation of materials with femto- to nanosecond laser pulses or during the formation of cathode spots on the surface of metals.
Bounds on the discrete spectrum of lattice Schrödinger operators
Authors: Bach V. , de Siqueira Pedra W. , Lakaev S. N.
Published: February 2018

We discuss the validity of the Weyl asymptotics—in the sense of two-sided bounds—for the size of the discrete spectrum of (discrete) Schrödinger operators on the d-dimensional, d ≥ 1, cubic lattice Zd at large couplings. We show that the Weyl asymptotics can be violated in any spatial dimension d ≥ 1—even if the semi-classical number of bound states is finite. Furthermore, we prove for all dimensions d ≥ 1 that, for potentials well behaved at infinity and fulfilling suitable decay conditions, the Weyl asymptotics always hold. These decay conditions are mild in the case d ≥ 3 while stronger for d = 1, 2. It is well known that the semi-classical number of bound states is—up to a constant—always an upper bound on the size of the discrete spectrum of Schrödinger operators if d ≥ 3. We show here how to construct general upper bounds on the number of bound states of Schrödinger operators on Zd from semi-classical quantities in all space dimensions d ≥ 1 and independently of the positivity-improving property of the free Hamiltonian.
The electromagnetic properties of plasma produced by hypervelocity impact
Authors: Zhang Qingming , Gong Liangfei , Ma Yuefen , Long Renrong , Gong Zizheng
Published: February 2018

The change of electron density in moving plasma in this paper is empirically determined according to multiple ground-based experimental results and the assumption of the Maxwell distribution. Moreover, the equation of the magnetic field intensity, dominated by the current due to the collective electron movement during the expansion, is presented on the basis of the Biot-Savart law, and its relationship with time and space is subsequently depicted. In addition, hypervelocity impact experiments on a 2AL12 target have been carried out using a two-stage light gas gun to accelerate a 2AL12 projectile of 6.4 mm to 6.2 km/s. Spiral coils are designed to measure the intensity of the electromagnetic field induced by this impact. The experimental results show that the magnetic field strength is an alternate pulse maintaining nearly 1 ms and its maximum is close to 15 μT, which is strong enough to interfere with the communication circuit and chip in spacecrafts. Lastly, numerical simulation of the magnetic field intensity using this experimental parameter reveals that the intensity in our estimation from our theory tends to be well consistent with the experimental data in the first peak of the pulse signal.
Electrostatically actuated thermal switch device for caloric film
Authors: Almanza Morgan , Depreux Lucas , Parrain Fabien , LoBue Martino
Published: February 2018

An innovative thermal switch device using a thin metallic film electrostatically actuated by an electrode mainly conceived for caloric cooling is studied. Our study focuses on the characterization of the thermal conductance at the interface for the “on” and “off” states. Our setup uses the current passing through the metallization of the film as a heater, while the temperature is deduced from the measurement of its electrical resistivity. Using a thermal diffusion model and our measurements, we deduce the on and off state thermal conductances, and we achieve an on/off conductance ratio of 103. Lastly, we use a simple finite-time thermodynamic model to estimate the efficiency at maximum power, and we would obtain by integrating a standard electrocaloric film in our thermal switch. The result is a micro-refrigerator working at 85% of Carnot efficiency with a power density of 228 W g−1 which is far more than what it has been currently demonstrated.
Controlling the formation and stability of ultra-thin nickel silicides - An alloying strategy for preventing agglomeration
Authors: Geenen F. A. , van Stiphout K. , Nanakoudis A. , Bals S. , Vantomme A. , Jordan-Sweet J. , Lavoie C. , Detavernier C.
Published: February 2018

The electrical contact of the source and drain regions in state-of-the-art CMOS transistors is nowadays facilitated through NiSi, which is often alloyed with Pt in order to avoid morphological agglomeration of the silicide film. However, the solid-state reaction between as-deposited Ni and the Si substrate exhibits a peculiar change for as-deposited Ni films thinner than a critical thickness of tc = 5 nm. Whereas thicker films form polycrystalline NiSi upon annealing above 450 °C, thinner films form epitaxial NiSi2 films that exhibit a high resistance toward agglomeration. For industrial applications, it is therefore of utmost importance to assess the critical thickness with high certainty and find novel methodologies to either increase or decrease its value, depending on the aimed silicide formation. This paper investigates Ni films between 0 and 15 nm initial thickness by use of “thickness gradients,” which provide semi-continuous information on silicide formation and stability as a function of as-deposited layer thickness. The alloying of these Ni layers with 10% Al, Co, Ge, Pd, or Pt renders a significant change in the phase sequence as a function of thickness and dependent on the alloying element. The addition of these ternary impurities therefore changes the critical thickness tc. The results are discussed in the framework of classical nucleation theory.
Bifurcation of avoided crossing at an exceptional point in the dispersion of sound and light in locally resonant media
Authors: Maznev A. A.
Published: February 2018

The avoided crossing behavior in the interaction of propagating sound or light waves with resonant inclusions is analyzed using a simple model of an acoustic medium containing damped mass-spring oscillators, which is shown to be equivalent to the Lorentz oscillator model in the elementary dispersion theory in optics. Two classes of experimental situations dictating the choice in the analysis of the dispersion relation are identified. If the wavevector is regarded as the independent variable and frequency as a complex function of the wavevector, then the avoided crossing bifurcates at an exceptional point at a certain value of the parameter γβ−1/2, where γ and β characterize the oscillator damping and interaction strength, respectively. This behavior is not observed if the wavevector is regarded as a complex function of frequency.
Cumulant expansions for measuring water exchange using diffusion MRI
Authors: Ning Lipeng , Nilsson Markus , Lasič Samo , Westin Carl-Fredrik , Rathi Yogesh
Published: February 2018

The rate of water exchange across cell membranes is a parameter of biological interest and can be measured by diffusion magnetic resonance imaging (dMRI). In this work, we investigate a stochastic model for the diffusion-and-exchange of water molecules. This model provides a general solution for the temporal evolution of dMRI signal using any type of gradient waveform, thereby generalizing the signal expressions for the Kärger model. Moreover, we also derive a general nth order cumulant expansion of the dMRI signal accounting for water exchange, which has not been explored in earlier studies. Based on this analytical expression, we compute the cumulant expansion for dMRI signals for the special case of single diffusion encoding (SDE) and double diffusion encoding (DDE) sequences. Our results provide a theoretical guideline on optimizing experimental parameters for SDE and DDE sequences, respectively. Moreover, we show that DDE signals are more sensitive to water exchange at short-time scale but provide less attenuation at long-time scale than SDE signals. Our theoretical analysis is also validated using Monte Carlo simulations on synthetic structures.
Tunable hole injection of solution-processed polymeric carbon nitride towards efficient organic light-emitting diode
Authors: Zhang Xiaowen , Zheng Qinghong , Tang Zhenyu , Li Wanshu , Zhang Yan , Xu Kai , Xue Xiaogang , Xu Jiwen , Wang Hua , Wei Bin
Published: February 2018

Polymeric carbon nitride (CNxHy) has been facilely synthesized from dicyandiamide and functions as a solution-processed hole injection layer in organic light-emitting diodes (OLEDs). The measurements using X-ray diffraction, atomic force microscopy, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, and impedance spectroscopy elucidate that CNxHy exhibits superior film morphology and extra electric properties such as tailored work function and tunable hole injection. The luminous efficiency of CNxHy-based OLED is found to improve by 76.6% in comparison to the counterpart using favorite solution-processed poly(ethylene dioxythiophene):poly(styrene sulfonate) as the hole injection layer. Our results also pave a way for broadening carbon nitride applications in organic electronics using the solution process.
Oscillatory mode transition for supersonic open cavity flows
Authors: Kumar Mayank , Vaidyanathan Aravind
Published: February 2018

The transition in the primary oscillatory mode in an open cavity has been experimentally investigated and the associated characteristics in a Mach 1.71 flow has been analyzed. The length-to-depth (L/D) ratios of the rectangular cavities are varied from 1.67 to 3.33. Unsteady pressure measurement and flow visualization are employed to understand the transitional flow physics. Flow visualization revealed the change in oscillation pattern from longitudinal mode to transverse mode and is also characterized by the presence of two bow shocks at the trailing edge instead of one. The transition is found to occur between L/D 1.67 and 2, marked by a change in the feedback mechanism, resulting in a shift from the vortex circulation driven transverse feedback mode to the oscillating shear layer driven longitudinal feedback mode. Cavities oscillating in the transition mode exhibit multiple tones of comparable strength. Correlation analysis indicated the shift in the feedback mechanism. Wavelet analysis revealed the temporal behaviour of tones during transition. Tone switching is observed in deeper cavities and is attributed to the occurrence of two bow shocks as evident from the temporo-spectral characteristics of transition that affects the shear layer modal shape.
Force fields for monovalent and divalent metal cations in TIP3P water based on thermodynamic and kinetic properties
Authors: Mamatkulov Shavkat , Schwierz Nadine
Published: February 2018

Metal cations are essential in many vital processes. In order to capture the role of different cations in all-atom molecular dynamics simulations of biological processes, an accurate parametrization is crucial. Here, we develop force field parameters for the metal cations Li+, Na+, K+, Cs+, Mg2+, Ca2+, Sr2+, and Ba2+ in combination with the TIP3P water model that is frequently used in biomolecular simulations. In progressing toward improved force fields, the approach presented here is an extension of previous efforts and allows us to simultaneously reproduce thermodynamic and kinetic properties of aqueous solutions. We systematically derive the parameters of the 12-6 Lennard-Jones potential which accurately reproduces the experimental solvation free energy, the activity derivative, and the characteristics of water exchange from the first hydration shell of the metal cations. In order to reproduce all experimental properties, a modification of the Lorentz-Berthelot combination rule is required for Mg2+. Using a balanced set of solution properties, the optimized force field parameters aim to capture the fine differences between distinct metal cations including specific ion binding affinities and the kinetics of cation binding to biologically important anionic groups.
High-resolution photoelectron spectroscopy of TiO3H2−: Probing the TiO2− + H2O dissociative adduct
Authors: DeVine Jessalyn A. , Abou Taka Ali , Babin Mark C. , Weichman Marissa L. , Hratchian Hrant P. , Neumark Daniel M.
Published: February 2018

Slow electron velocity-map imaging spectroscopy of cryogenically cooled TiO3H2− anions is used to probe the simplest titania/water reaction, TiO20/− + H2O. The resultant spectra show vibrationally resolved structure assigned to detachment from the cis-dihydroxide TiO(OH)2− geometry based on density functional theory calculations, demonstrating that for the reaction of the anionic TiO2− monomer with a single water molecule, the dissociative adduct (where the water is split) is energetically preferred over a molecularly adsorbed geometry. This work represents a significant improvement in resolution over previous measurements, yielding an electron affinity of 1.2529(4) eV as well as several vibrational frequencies for neutral TiO(OH)2. The energy resolution of the current results combined with photoelectron angular distributions reveals Herzberg-Teller coupling-induced transitions to Franck-Condon forbidden vibrational levels of the neutral ground state. A comparison to the previously measured spectrum of bare TiO2− indicates that reaction with water stabilizes neutral TiO2 more than the anion, providing insight into the fundamental chemical interactions between titania and water.
Origin of the size-dependence of the equilibrium van der Waals binding between nanostructures
Authors: Tao Jianmin , Perdew John P. , Tang Hong , Shahi Chandra
Published: February 2018

Nanostructures can be bound together at equilibrium by the van der Waals (vdW) effect, a small but ubiquitous many-body attraction that presents challenges to density functional theory. How does the binding energy depend upon the size or number of atoms in one of a pair of identical nanostructures? To answer this question, we treat each nanostructure as a whole object, not as a collection of atoms. Our calculations start from an accurate static dipole polarizability for each considered nanostructure, and an accurate equilibrium center-to-center distance for the pair (the latter from experiment or from the vdW-DF-cx functional). We consider the competition in each term −C2k/d2k (k = 3, 4, 5) of the long-range vdW series for the interaction energy, between the size dependence of the vdW coefficient C2k and that of the 2kth power of the center-to-center distance d. The damping of these vdW terms can be negligible, but in any case, it does not affect the size dependence for a given term in the absence of non-vdW binding. To our surprise, the vdW energy can be size-independent for quasi-spherical nanoclusters bound to one another by vdW interaction, even with strong nonadditivity of the vdW coefficient, as demonstrated for fullerenes. We also show that, for low-dimensional systems, the vdW interaction yields the strongest size-dependence, in stark contrast to that of fullerenes. We illustrate this with parallel planar polycyclic aromatic hydrocarbons. The size dependences of other morphologies or bonding types lie between, as shown by sodium clusters.
Computing energy levels of CH4, CHD3, CH3D, and CH3F with a direct product basis and coordinates based on the methyl subsystem
Authors: Zhao Zhiqiang , Chen Jun , Zhang Zhaojun , Zhang Dong H. , Wang Xiao-Gang , Carrington Tucker , Gatti Fabien
Published: February 2018

Quantum mechanical calculations of ro-vibrational energies of CH4, CHD3, CH3D, and CH3F were made with two different numerical approaches. Both use polyspherical coordinates. The computed energy levels agree, confirming the accuracy of the methods. In the first approach, for all the molecules, the coordinates are defined using three Radau vectors for the CH3 subsystem and a Jacobi vector between the remaining atom and the centre of mass of CH3. Euler angles specifying the orientation of a frame attached to CH3 with respect to a frame attached to the Jacobi vector are used as vibrational coordinates. A direct product potential-optimized discrete variable vibrational basis is used to build a Hamiltonian matrix. Ro-vibrational energies are computed using a re-started Arnoldi eigensolver. In the second approach, the coordinates are the spherical coordinates associated with four Radau vectors or three Radau vectors and a Jacobi vector, and the frame is an Eckart frame. Vibrational basis functions are products of contracted stretch and bend functions, and eigenvalues are computed with the Lanczos algorithm. For CH4, CHD3, and CH3D, we report the first J > 0 energy levels computed on the Wang-Carrington potential energy surface [X.-G. Wang and T. Carrington, J. Chem. Phys. 141(15), 154106 (2014)]. For CH3F, the potential energy surface of Zhao et al. [J. Chem. Phys. 144, 204302 (2016)] was used. All the results are in good agreement with experimental data.
Modelling the egg components and internal cycle length of laying hens
Authors: Bendezu H. C. P. , Sakomura N. K. , Malheiros E. B. , Gous R. M. , Ferreira N. T. , Fernandes J. B. K.
Published: February 2018

A model that can estimate the changes that occur to the composition of egg components over time is an important tool for the nutritionists, since it can provide information about the nutrients required by a laying hen to achieve her potential egg output. In this context, the present study was aimed to model the potential egg production of laying hens during the egg-production period. One hundred and twenty Hy-Line W36 and ISA-Brown layers were used from 18 to 60 weeks of age, with each bird being an experimental unit. The birds were housed in individual cages during the experimental period. Egg production (%), egg weight (g) and the weight of egg components were recorded for each bird. The data were used to calculate the parameters of equations for predicting the weights of yolk, albumen and shell, and for predicting internal cycle length. The predicted results were evaluated by regressing residual (observed minus predicted) values of the predicted values centred of their average value. The equations for predicting mean yolk weight with age are for Hy-Line W36 (y1) and ISA-Brown (y2) respectively. Albumen and shell weights for Hy-Line W36 were described by the equations 15.07 × (yolk weight)0.37 and 0.70 × (yolk + albumen weight)0.50 respectively, and for ISA-Brown, 21.99 × (yolk weight)0.24 and 1.60 × (yolk + albumen weight)0.34 respectively. The average internal cycle length over time for Hy-Line W36 (ICL1) is described by the model 22.95 + 5.24 × (0.962t) + 0.02 × t and for ISA-Brown by 24.01 + 10.29 × (0.94t) + 0.004 × t, where t is the age at first egg (days). The assessment of the results indicated that the equations for predicting egg weight were more accurate for Hy-Line W36 but less precise for both strains, whereas the equation models for predicting the internal cycle lengths were more accurate and precise for ISA-Browns. The models could predict the potential weight of egg components and the rate of laying associated with the internal cycle lengths, and, on the basis of this information, it is possible to improve the nutrient requirement estimated.
Angiogenic patterning by STEEL, an endothelial-enriched long noncoding RNA
Authors: Man H. S. Jeffrey , Sukumar Aravin N. , Lam Gabrielle C. , Turgeon Paul J. , Yan Matthew S. , Ku Kyung Ha , Dubinsky Michelle K. , Ho J. J. David , Wang Jenny Jing , Das Sunit , Mitchell Nora , Oettgen Peter , Sefton Michael V. , Marsden Philip A.
Published: February 2018

Significance

Endothelial cells (ECs) form the inner cellular lining of blood vessels and are necessary in the establishment and maintenance of the closed cardiovascular system, especially the physiology of regulated blood flow to and from tissues. Recently, long noncoding RNAs (lncRNAs) have been described to have roles in gene regulation for a variety of processes, including stem cell functions and differentiation of stem cells into tissues. This work identifies lncRNAs that are enriched in ECs and further characterizes the lncRNA, spliced-transcript endothelial-enriched lncRNA (STEEL). STEEL promotes the formation of intact blood vessels by ECs in vivo. Moreover, STEEL regulates transcription of a key mediator of local blood flow, endothelial nitric oxide synthase (eNOS), and a key sensor of hemodynamic forces, Kruppel-like factor 2 (KLF2).
Molecular basis for diversification of yeast prion strain conformation
Authors: Ohhashi Yumiko , Yamaguchi Yoshiki , Kurahashi Hiroshi , Kamatari Yuji O. , Sugiyama Shinju , Uluca Boran , Piechatzek Timo , Komi Yusuke , Shida Toshinobu , Müller Henrik , Hanashima Shinya , Heise Henrike , Kuwata Kazuo , Tanaka Motomasa
Published: February 2018

Significance

On the basis of the amino acid sequence, a polypeptide folds into a unique structure. In contrast, aggregation-prone proteins often misfold into distinct aggregate conformations. Interestingly, each distinct aggregate conformation can dictate different phenotypic consequences, such as cellular toxicity. However, the underlying mechanism of the origin of such structural diversity of protein aggregates has been a critical open question. Using the intrinsically disordered domain of yeast prion protein Sup35, we revealed the structural diversification of prion aggregate is triggered by thermodynamic fluctuations within the monomeric protein prior to aggregation. Our findings not only provide a clue to explain previously puzzling observations in prion biology but also have important implications for therapeutic approaches for human diseases in which protein aggregation is involved.
Adult-born neurons boost odor–reward association
Authors: Grelat Anne , Benoit Laura , Wagner Sébastien , Moigneu Carine , Lledo Pierre-Marie , Alonso Mariana
Published: February 2018

Significance

Odor–reward association during appetitive learning is a fundamental process that requires multiple forms of plasticity. In the adult olfactory bulb, the continual production of newborn interneurons contributes to the functional plasticity of the system, placing the newcomers in a key position to participate in olfactory associative learning. Here, we demonstrate that adult-born neurons, but not preexisting ones, contain information about learned positive value. Moreover, specific heightening of this signal improves associative learning and odor value update and is enough in some cases to trigger behavior even without odor stimulus. Collectively, our findings show an important role of this adult-born interneuron population in odor–reward association and unveil the relevance of odor value encoding at early stages of sensory processing.
Trophic redundancy reduces vulnerability to extinction cascades
Authors: Sanders Dirk , Thébault Elisa , Kehoe Rachel , Frank van Veen F. J.
Published: February 2018

Significance

Initial species loss can lead to follow-on extinctions because of the interconnectedness of species in ecosystems. The loss of biodiversity through human impact can change the structure of ecological communities, which, models predict, can affect the likelihood of secondary extinctions. Uniquely, we provide an empirical demonstration of this with a plant-insect food web experiment by focusing on a particular secondary extinction mechanism. This mechanistic approach leads to specific, empirically testable hypotheses that can inform the development of predictive models on the consequences of changes in ecological community structure.
Socioeconomic and Geographical Disparities in Prescription and Illicit Opioid-Related Overdose Deaths in Orange County, California, from 2010–2014
Authors: Marshall John R. , Gassner Stephen F. , Anderson Craig L. , Cooper Richelle J. , Lotfipour Shahram , Chakravarthy Bharath
Published: February 2018

Background: Reports indicate a geographic effect of socioeconomic inequalities on the occurrence of opioid-related fatal overdoses. This study aims to (1) estimate the rates of opioid-related overdoses, (2) estimate the association of benzodiazepine co-ingestion with opioid-related deaths, (3) estimate associations between socioeconomic indicators and opioid-related deaths, and (4) map the distribution of fatal overdoses, in Orange County (OC), California. Methods: An ecologic study was conducted of all opioid- related deaths (1205 total) from 2010 to 2014 obtained from the OC Coroner Division database (1065 OC residents, 55 nonresidents, 85 OC homeless) (analyzed 2016–2017). Rates of opioid overdose, benzodiazepine co-ingestion prevalence, and associations with socioeconomic status (SES; education, poverty, median income) using ZIP code analysis in the residential and homeless communities were calculated. Results: Of 1205 deaths, 904 involved prescription-type opioids, 223 involved heroin, 39 involved both, and 39 not stated; 973 were classified unintentional overdoses, 180 suicides, and 52 undetermined; 49% of cases involved benzodiazepines. Prescription-type opioid and heroin death rates for residents were 5.4/ 100,000 person-years (95% confidence interval [CI]: 5.0–5.8) and 1.2/100,000 person-years (95% CI: 1.0–1.4), respectively. Males, age group 45–54, and Caucasian race had the highest rate (13.6/100,000) of opioid mortality. The highest death rates were seen in homeless adults, at 136/100,000 person-years for prescription-type opioids (95% CI: 99.0–185.5) and 156/100,000 person-years for heroin (95% CI: 116.8–209.5). Conclusions: The burden of prescription-type opioid–related deaths in OC affects all demographics and levels of SES; there is a disproportionately high rate of opioid-related deaths in the OC homeless population.
Stac proteins associate with the critical domain for excitation–contraction coupling in the II–III loop of CaV1.1
Authors: Polster Alexander , Nelson Benjamin R. , Papadopoulos Symeon , Olson Eric N. , Beam Kurt G.
Published: February 2018

In skeletal muscle, residues 720–764/5 within the CaV1.1 II–III loop form a critical domain that plays an essential role in transmitting the excitation–contraction (EC) coupling Ca2+ release signal to the type 1 ryanodine receptor (RyR1) in the sarcoplasmic reticulum. However, the identities of proteins that interact with the loop and its critical domain and the mechanism by which the II–III loop regulates RyR1 gating remain unknown. Recent work has shown that EC coupling in skeletal muscle of fish and mice depends on the presence of Stac3, an adaptor protein that is highly expressed only in skeletal muscle. Here, by using colocalization as an indicator of molecular interactions, we show that Stac3, as well as Stac1 and Stac2 (predominantly neuronal Stac isoforms), interact with the II–III loop of CaV1.1. Further, we find that these Stac proteins promote the functional expression of CaV1.1 in tsA201 cells and support EC coupling in Stac3-null myotubes and that Stac3 is the most effective. Coexpression in tsA201 cells reveals that Stac3 interacts only with II–III loop constructs containing the majority of the CaV1.1 critical domain residues. By coexpressing Stac3 in dysgenic (CaV1.1-null) myotubes together with CaV1 constructs whose chimeric II–III loops had previously been tested for functionality, we reveal that the ability of Stac3 to interact with them parallels the ability of these constructs to mediate skeletal type EC coupling. Based on coexpression in tsA201 cells, the interaction of Stac3 with the II–III loop critical domain does not require the presence of the PKC C1 domain in Stac3, but it does require the first of the two SH3 domains. Collectively, our results indicate that activation of RyR1 Ca2+ release by CaV1.1 depends on Stac3 being bound to critical domain residues in the II–III loop.
The discovery of the ability of rod photoreceptors to signal single photons
Authors: Pugh Edward N.
Published: February 2018

Vertebrate rod photoreceptors evolved the astonishing ability to respond reliably to single photons. In parallel, the proximate neurons of the visual system evolved the ability to reliably encode information from a few single-photon responses (SPRs) as arising from the presence of an object of interest in the visual environment. These amazing capabilities were first inferred from measurements of human visual threshold by Hecht et al. (1942), whose paper has since been cited over 1,000 times. Subsequent research, in part inspired by Hecht et al.’s discovery, has directly measured rod SPRs, characterized the molecular mechanism responsible for their generation, and uncovered much about the specializations in the retina that enable the reliable transmission of SPRs in the teeth of intrinsic neuronal noise.
Improving the characterization of calcium channel gating pore currents with Stac3
Authors: Chahine Mohamed
Published: February 2018

Chahine highlights new work that exploits the increased expression of human CaV1.1 at the plasma membrane after coexpression with Stac3.
On the extension of isometries between the unit spheres of a C*-algebra and 𝐵(𝐻)
Authors: Fernández-Polo Francisco , Peralta Antonio
Published: February 2018

Given two complex Hilbert spacesHHandKK, letS(B(H))S(B(H))andS(B(K))S(B(K))denote the unit spheres of the C∗^*-algebrasB(H)B(H)andB(K)B(K)of all bounded linear operators onHHandKK, respectively. We prove that every surjective isometryf:S(B(K))→S(B(H))f: S(B(K)) \to S(B(H))admits an extension to a surjective complex linear or conjugate linear isometryT:B(K)→B(H)T: B(K)\to B(H). This provides a positive answer to Tingley’s problem in the setting ofB(H)B(H)spaces.
Some remarks on topological 𝐾-theory of dg categories
Authors: Antieau Benjamin , Heller Jeremiah
Published: February 2018

Using techniques from motivic homotopy theory, we prove a conjecture of Anthony Blanc about semi-topological

K
K

-theory of dg categories with finite coefficients. Along the way, we show that the connective semi-topological

K
K

-theories defined by Friedlander-Walker and by Blanc agree for quasi-projective complex varieties and we study étale descent of topological

K
K

-theory of dg categories.
Commonly used trafficking blocks disrupt ARF1 activation and the localization and function of specific Golgi proteins
Authors: Gilbert Catherine E. , Sztul Elizabeth , Machamer Carolyn E.
Published: February 2018

ADP-ribosylation factor (ARF) proteins are key regulators of the secretory pathway. ARF1, through interacting with its effectors, regulates protein trafficking by facilitating numerous events at the Golgi. One unique ARF1 effector is golgin-160, which promotes the trafficking of only a specific subset of cargo proteins through the Golgi. While studying this role of golgin-160, we discovered that commonly used cold temperature blocks utilized to synchronize cargo trafficking (20 and 16°C) caused golgin-160 dispersal from Golgi membranes. Here, we show that the loss of golgin-160 localization correlates with a decrease in the levels of activated ARF1, and that golgin-160 dispersal can be prevented by expression of a GTP-locked ARF1 mutant. Overexpression of the ARF1 activator Golgi brefeldin A–resistant guanine nucleotide exchange factor 1 (GBF1) did not prevent golgin-160 dispersal, suggesting that GBF1 may be nonfunctional at lower temperatures. We further discovered that several other Golgi resident proteins had altered localization at lower temperatures, including proteins recruited by ARF-like GTPase 1 (ARL1), a small GTPase that also became dispersed in the cold. Although cold temperature blocks are useful for synchronizing cargo trafficking through the Golgi, our data indicate that caution must be taken when interpreting results from these assays.
Effectiveness, Longevity, and Complications of Facelift by Barbed Suture Insertion
Authors: Bertossi Dario , Botti Giovanni , Gualdi Alessandro , Fundarò Piero , Nocini Riccardo , Pirayesh Ali , van der Lei Berend
Published: February 2018

Background

Minimally invasive facelift techniques involving barbed suture insertion have become popular among patients who wish to correct facial tissue ptosis.

Objectives

The authors sought to determine the effectiveness, longevity, complications, and postoperative sequelae associated with facelift by means of barbed polydioxanone (PDO) threads.

Methods

A total of 160 consecutive patients who underwent facelift with barbed threads were evaluated retrospectively. For malar augmentation and correction of nasolabial grooves, 2 or 3 PDO threads (23 gauge) were placed per side; for treatment of mandibular lines, 2 to 4 PDO threads (21 gauge) were inserted per side.

Results

Immediately after suture placement and for 1 month postoperatively, patients experienced improvement in facial tissue ptosis. This aesthetic result declined noticeably by 6 months and was absent by 1 year. The overall complication rate in the early postoperative period was 34% (55 of 160 patients). Eighteen patients (11.2%) had superficial displacement of the barbed sutures, 15 (9.4%) experienced transient erythema, 10 (6.2%) had infection, 10 (6.2%) experienced skin dimpling, and 2 (1.2%) had temporary facial stiffness.

Conclusions

Placement of barbed threads yields instantaneous improvement in facial ptosis that is no longer apparent by 1 year. Given this transient benefit and the complication rate of 34%, we recommend limiting this procedure to patients with contraindications for more invasive facial surgery.

Level of Evidence: 4
A Randomized Controlled Trial of a Text Messaging Intervention to Promote Virologic Suppression and Retention in Care in an Urban Safety-Net Human Immunodeficiency Virus Clinic: The Connect4Care Trial
Authors: Christopoulos Katerina A , Riley Elise D , Carrico Adam W , Tulsky Jacqueline , Moskowitz Judith T , Dilworth Samantha , Coffin Lara S , Wilson Leslie , Johnson-Peretz Jason , Hilton Joan F
Published: February 2018

Background

Text messaging is a promising strategy to support human immunodeficiency virus (HIV) care engagement, but little is known about its efficacy in urban safety-net HIV clinics.

Methods

We conducted a randomized controlled trial of a supportive and motivational text messaging intervention, Connect4Care (C4C), among viremic patients who had a history of poor retention or were new to the clinic. Participants were randomized (stratified by new or established HIV diagnosis status) to receive either of the following for 12 months: (1) thrice-weekly intervention messages, plus texted primary care appointment reminders and a monthly text message requesting confirmation of study participation or (2) texted reminders and monthly messages alone. Viral load was assessed at 6 and 12 months. The primary outcome was virologic suppression (<200 copies/mL) at 12 months, estimated via repeated-measures log-binomial regression, adjusted for new-diagnosis status. The secondary outcome was retention in clinic care.

Results

Between August 2013 and November 2015, a total of 230 participants were randomized. Virologic suppression at 12 months was similar in intervention and control participants (48.8% vs 45.8%, respectively), yielding a rate ratio of 1.07 (95% confidence interval, .82–1.39). Suppression was higher in those with newly diagnosed infection (78.3% vs 45.3%). There were no intervention effects on the secondary outcome. Exploratory analyses suggested that patients with more responses to study text messages had better outcomes, regardless of arm.

Conclusions

The C4C text messaging intervention did not significantly increase virologic suppression or retention in care. Response to text messages may be a useful way for providers to gauge risk for poor HIV outcomes.

Clinical Trials Registration

NCT01917994.
‘Nonnatus dictus quod caeso defunctae matris utero prodiit’. Postmortem Caesarean Section in the Late Middle Ages and Early Modern Period
Authors: Foscati Alessandra
Published: February 2018

Historians call sectio in mortua the act of opening the abdomen of a woman who has died during pregnancy or in childbirth in order to extract a baby. According to recent studies, the sectio is considered to be a routine practice carried out by male surgeons from the end of the Middle Ages, particularly in Italy, where the evidence of the sectio being performed by a midwife is scanty. But was it really such a popular operation at the time, and can the figure of the midwife be seen as secondary? It is also known that the operation was qualified through aspects which went beyond the surgical sphere, such as religion, myth, and especially law. How did these fields interact? This article highlights the complexity of sectio through the interpretation of different sources spanning from the late Middle Ages to the Early Modern period.
How Mentor Identity Evolves: Findings From a 10-Year Follow-up Study of a National Professional Development Program
Authors: Balmer Dorene F. , Darden Alix , Chandran Latha , D’Alessandro Donna , Gusic Maryellen E.
Published: February 2018

Purpose

Despite academic medicine’s endorsement of professional development and mentoring, little is known about what junior faculty learn about mentoring in implicit curricula of professional development programs, and how their mentor identity evolves in this context. The authors explored what faculty–participants in the Educational Scholars Program implicitly learned about mentoring and how the implicit curriculum affected mentor identity transformation.

Method

Semistructured interviews with 19 of 36 former faculty–participants were conducted in 2016. Consistent with constructivist grounded theory, data collection and analysis overlapped. The authors created initial codes informed by Ibarra’s model for identity transformation, iteratively revised codes based on incoming data patterns, and created visual representations of relationships amongst codes to gain a holistic, shared understanding of the data.

Results

In the implicit curriculum, faculty–participants learned the importance of having multiple mentors, the value of peer mentors, and the incremental process of becoming a mentor. The authors used Ibarra’s model to understand how the implicit curriculum worked to transform mentor identity: Faculty–participants reported observing mentors, experimenting with different ways to mentor and to be a mentor, and evaluating themselves as mentors.

Conclusions

The Educational Scholars Program’s implicit curriculum facilitated faculty–participants taking on mentor identity via opportunities it afforded to watch mentors, experiment with mentoring, and evaluate self as mentor, key ingredients for identity construction. Leaders of professional development programs can develop faculty as mentors by capitalizing on what faculty–participants learn in the implicit curriculum and deliberately structuring postgraduation mentoring opportunities.
Gamification in Action: Theoretical and Practical Considerations for Medical Educators
Authors: Rutledge Chrystal , Walsh Catharine M. , Swinger Nathan , Auerbach Marc , Castro Danny , Dewan Maya , Khattab Mona , Rake Alyssa , Harwayne-Gidansky Ilana , Raymond Tia T. , Maa Tensing , Chang Todd P.
Published: February 2018

Gamification involves the application of game design elements to traditionally nongame contexts. It is increasingly being used as an adjunct to traditional teaching strategies in medical education to engage the millennial learner and enhance adult learning. The extant literature has focused on determining whether the implementation of gamification results in better learning outcomes, leading to a dearth of research examining its theoretical underpinnings within the medical education context. The authors define gamification, explore how gamification works within the medical education context using self-determination theory as an explanatory mechanism for enhanced engagement and motivation, and discuss common roadblocks and challenges to implementing gamification.

Although previous gamification research has largely focused on determining whether implementation of gamification in medical education leads to better learning outcomes, the authors recommend that future research should explore how and under what conditions gamification is likely to be effective. Selective, purposeful gamification that aligns with learning goals has the potential to increase learner motivation and engagement and, ultimately, learning. In line with self-determination theory, game design elements can be used to enhance learners’ feelings of relatedness, autonomy, and competence to foster learners’ intrinsic motivation. Poorly applied game design elements, however, may undermine these basic psychological needs by the overjustification effect or through negative effects of competition. Educators must, therefore, clearly understand the benefits and pitfalls of gamification in curricular design, take a thoughtful approach when integrating game design elements, and consider the types of learners and overarching learning objectives.
Radiation-Induced Painful Neurogenic Hypertrophy Treated With Botulinum Toxin A
Authors: Filippakis Alexandra , Ho Doreen T. , Small Juan E. , Small Kirstin M. , Ensrud Erik R.
Published: February 2018

Painful neurogenic hypertrophy is a rare complication of radiation therapy. We report a 27-year-old woman with a history of adenoid cystic carcinoma of the submandibular gland presented with painful twitching of her left shoulder. Electrodiagnostic studies were consistent with a diagnosis of radiation-induced spinal accessory nerve hyperactivity. The patient failed conventional medical therapy. She was treated with an injection of botulinum toxin A, and within 1 month experienced significant relief of symptoms. We thus conclude that Botulinum toxin is a therapeutic option for the pain associated with radiation-induced peripheral nerve hyperactivity.
COL6A and LAMA2 Mutation Congenital Muscular Dystrophy: A Clinical and Electrophysiological Study
Authors: Verma Sumit , Goyal Parul , Guglani Lokesh , Peinhardt Charlotte , Pelzek Diane , Barkhaus Paul E.
Published: February 2018

Objectives:

COL6A and LAMA2 are subtypes of congenital muscular dystrophy.

Methods:

Retrospective chart review of clinical findings, spirometry, muscle histology, muscle ultrasound, neuroimaging, and Electromyography (EMG)/Nerve Conduction Study data in genetically confirmed COL6A and LAMA2 subjects.

Results:

We identified 8 COL6A and 6 LAMA2 subjects: the female-to-male ratio was 1.3:1 and the mean age was 11.9 ± 3.6 years. Gross motor delays since birth, proximal muscle weakness, and contractures were noted in both groups. Joint hyperlaxity and skin changes (follicular hyperkeratosis and muscle biopsy scar thinning) were unique to COL6A. Severe scoliosis, macrocephaly, and nonambulatory status were common in LAMA2. Increasing age was associated with poor respiratory function in COL6A. There was central “cloud appearance” on rectus femoris muscle ultrasound in COL6A and white matter T2 hyperintensity on brain magnetic resonance imaging in LAMA2. LAMA2 also showed demyelinating polyneuropathy. Neurogenic changes on EMG and muscle histology were noted in 37% and 33% of COL6A cases, respectively.

Conclusions:

COL6A has unique skin changes, central cloud appearance on muscle ultrasound. LAMA2 has demyelinating polyneuropathy and white matter changes on brain imaging. The presence of neurogenic changes on EMG and muscle histology in COL6A suggests motor axonal neuropathy. Genetic testing remains the gold standard in confirming COL6A congenital muscular dystrophy.
Amiodarone Rifampicin Drug–Drug Interaction Management With Therapeutic Drug Monitoring
Authors: Oude Munnink Thijs H. , Demmer Anna , Slenter Roel H. J. , Movig Kris L. L.
Published: February 2018

The authors present a case of a 69-year-old man with arrhythmogenic right ventricular cardiomyopathy controlled with amiodarone and an infected orthopedic prosthesis requiring treatment with rifampicin. This combination involves a pharmacokinetic drug–drug interaction leading to subtherapeutic drug concentrations of amiodarone and its active metabolite. The long half-life of amiodarone and its active metabolite in combination with the late onset and offset of cytochrome P4503A (CYP3A4) induction by rifampicin makes this a challenging drug–drug interaction to cope with in clinical practice. Before, during, and after rifampicin treatment, the serum concentrations of amiodarone and its active metabolite were measured and the amiodarone dose was adjusted accordingly. The amiodarone dose required to maintain effective concentrations was 450% of the initial dose. The drug–drug interaction between amiodarone and rifampicin is relevant, both clinically and pharmacokinetically, and can be managed by dose adjustments of amiodarone based on serum concentrations.
A CASE OF INTRARETINAL PERIPAPILLARY NEOVASCULARIZATION IN ABCA4-RELATED RETINOPATHY
Authors: Essilfie Juliet O. , Huynh An , Gorin Michael B. , Sadda SriniVas R.
Published: February 2018

Purpose:

To report a case of ABCA4-related retinopathy and potential complications.

Methods:

The authors describe a case report of intraretinal neovascularization in a patient with ABCA4-related retinopathy and describe the multimodal retinal imaging findings.

Results:

A 49-year-old woman presents with cystoid macular edema and diffuse intraretinal and perivascular hyperpigmentation in both eyes. Genetic testing confirmed ABCA4-related retinopathy. Fluorescein angiography revealed peripapillary intraretinal neovascularization in the absence of any other identifiable retinal pathology.

Conclusion:

To the authors' knowledge, this is the first reported case of intraretinal neovascularization–associated ABCA4-related retinopathy. Ancillary testing of ABCA4-related retinopathy with fluorescein angiography or optical coherence tomography angiography may be helpful in identifying this rare complication.