bluuebunny/crossref_metadata_2025 huggingface dataset:
Enhanced ferromagnetism in BiFeO3 powders by rapid combustion of graphite powders
Authors: Xu Qingyu , Hu Cheng , Wang Ji , Du Jun
Published: December 2016

The magnetoelectric applications of BiFeO3 are strongly limited by the very weak ferromagnetism, due to the cycloidal modulated antiferromagnetic structure. In this paper, a rapid combustion method was adopted to prepare BiFeO3 powders. The amorphous BiFeO3 precursors prepared by sol-gel method were mixed with graphite powders and calcined at 350 °C for 5 minutes. BiFeO3 powders were crystallized well with grain size of 30 nm due to the local high temperature during the rapid combustion of graphite powders in short time, and the high crystallinity was confirmed by the Raman spectra. Clear room temperature ferromagnetism has been observed, with significantly large coercivity of 0.19 kOe and magnetization of 0.48 emu/g at 10 kOe, which is much larger than that of BiFeO3 powders sintered at 600 °C (negligible small coercivity and 0.092 emu/g at 10 kOe). The enhancement of ferromagnetism has been attributed to the suppression of the cancellation of canted spins due to the much smaller crystallite size than the cycloidal modulation period.
Study on the electron emission process of the pseudospark during the hollow cathode phase under nanosecond pulsed voltage
Authors: Zhang J. , Li X. , Liu Y. , Zhao J. , Zhang Q.
Published: December 2016

Pseudospark discharge, discovered in 1979, has remarkable parameters that may make it useful in various applications. This paper explores the influence of the cathode aperture on the breakdown characteristics of pseudospark discharge. In addition, the discharge process in both the main gap and the cathode aperture has been researched by a high-speed framing camera. Results revealed that the influence of the structure of the hollow cathode on the breakdown voltage characteristics lies in the structure of the cathode aperture. Besides, the delay of the electron emission process has been calculated based on the explosive electron emission model. In the end, a possible reason for the great discharge current and high increase rate of the discharge current has been discussed.
Communication: Many-body stabilization of non-covalent interactions: Structure, stability, and mechanics of Ag3Co(CN)6 framework
Authors: Liu Xiaofei , Hermann Jan , Tkatchenko Alexandre
Published: December 2016

Stimuli-responsive metal-organic frameworks (MOFs) and other framework materials exhibit a broad variety of useful properties, which mainly stem from an interplay of strong covalent bonds within the organic linkers with presumably weak van der Waals (vdW) interactions which determine the overall packing of the framework constituents. Using Ag3Co(CN)6 as a fundamental test case—a system with a colossal positive and negative thermal expansion [A. L. Goodwin et al., Science 319, 794 (2008)]—we demonstrate that its structure, stability, dielectric, vibrational, and mechanical properties are critically influenced by many-body electronic correlation contributions to non-covalent vdW interactions. The Ag3Co(CN)6 framework is a remarkable molecular crystal, being visibly stabilized, rather than destabilized, by many-body vdW correlations. A detailed comparison with H3Co(CN)6 highlights the crucial role of strongly polarized metallophilic interactions in dictating the exceptional properties of denser MOFs. Beyond MOFs, our findings indicate that many-body electronic correlations can substantially stabilize polarizable materials, providing a novel mechanism for tuning the properties of nanomaterials with intricate structural motifs.
Simulation of the photodetachment spectrum of HHfO− using coupled-cluster calculations
Authors: Mok Daniel K. W. , Dyke John M. , Lee Edmond P. F.
Published: December 2016

The photodetachment spectrum of HHfO− was simulated using restricted-spin coupled-cluster single-double plus perturbative triple {RCCSD(T)} calculations performed on the ground electronic states of HHfO and HHfO−, employing basis sets of up to quintuple-zeta quality. The computed RCCSD(T) electron affinity of 1.67 ± 0.02 eV at the complete basis set limit, including Hf 5s25p6 core correlation and zero-point energy corrections, agrees well with the experimental value of 1.70 ± 0.05 eV from a recent photodetachment study [X. Li et al., J. Chem. Phys. 136, 154306 (2012)]. For the simulation, Franck-Condon factors were computed which included allowances for anharmonicity and Duschinsky rotation. Comparisons between simulated and experimental spectra confirm the assignments of the molecular carrier and electronic states involved but suggest that the experimental vibrational structure has suffered from poor signal-to-noise ratio. An alternative assignment of the vibrational structure to that suggested in the experimental work is presented.
Structural characterization of niobium oxide thin films grown on SrTiO3 (111) and (La,Sr)(Al,Ta)O3 (111) substrates
Authors: Dhamdhere Ajit R. , Hadamek Tobias , Posadas Agham B. , Demkov Alexander A. , Smith David J.
Published: December 2016

Niobium oxide thin films have been grown by molecular beam epitaxy on SrTiO3 (STO) (111) and (La0.18Sr0.82)(Al0.59Ta0.41)O3 (LSAT) (111) substrates. Transmission electron microscopy (TEM) confirmed the formation of high quality films with coherent interfaces. Films grown with higher oxygen pressure on STO (111) resulted in a (110)-oriented NbO2 phase with a distorted rutile structure, which can be described as body-centered tetragonal. The a lattice parameter of NbO2 was determined to be ∼13.8 Å in good agreement with neutron diffraction results published in the literature. Films grown on LSAT (111) at lower oxygen pressure produced the NbO phase with a defective rock salt cubic structure. The NbO lattice parameter was determined to be a ≈ 4.26 Å. The film phase/structure identification from TEM was in good agreement with in situ x-ray photoelectron spectroscopy measurements that confirmed the dioxide and monoxide phases, respectively. The atomic structure of the NbO2/STO and NbO/LSAT interfaces was determined based on comparisons between high-resolution electron micrographs and image simulations.
Effect of ambient on electrical transport properties of ultra-thin Au nanowires
Authors: Amin Kazi Rafsanjani , Kundu Subhajit , Biswas Sangram , Roy Ahin , Singh Abhishek Kumar , Ravishankar N. , Bid Aveek
Published: December 2016

In this letter we present systematic studies of the dynamics of surface adsorption of various chemicals on ultra-thin single crystalline gold nanowires (AuNW) through sensitive resistance fluctuation spectroscopy measurements coupled with ab initio simulations. We show that, contrary to expectations, the adsorption of common chemicals like methanol and acetone has a profound impact on the electrical transport properties of the AuNW. Our measurements and subsequent calculations establish conclusively that in AuNW, semiconductor-like sensitivity to the ambient arises because of changes induced in its local density of states by the surface adsorbed molecules. The extreme sensitivity of the resistance fluctuations of the AuNW to ambient suggests their possible use as solid-state sensors.
Enhanced infrared detectors using resonant structures combined with thin type-II superlattice absorbers
Authors: Goldflam M. D. , Kadlec E. A. , Olson B. V. , Klem J. F. , Hawkins S. D. , Parameswaran S. , Coon W. T. , Keeler G. A. , Fortune T. R. , Tauke-Pedretti A. , Wendt J. R. , Shaner E. A. , Davids P. S. , Kim J. K. , Peters D. W.
Published: December 2016

We examined the spectral responsivity of a 1.77 μm thick type-II superlattice based long-wave infrared detector in combination with metallic nanoantennas. Coupling between the Fabry-Pérot cavity formed by the semiconductor layer and the resonant nanoantennas on its surface enables spectral selectivity, while also increasing peak quantum efficiency to over 50%. Electromagnetic simulations reveal that this high responsivity is a direct result of field-enhancement in the absorber layer, enabling significant absorption in spite of the absorber's subwavelength thickness. Notably, thinning of the absorbing material could ultimately yield lower photodetector noise through a reduction in dark current while improving photocarrier collection efficiency. The temperature- and incident-angle-independent spectral response observed in these devices allows for operation over a wide range of temperatures and optical systems. This detector paradigm demonstrates potential benefits to device performance with applications throughout the infrared.
Enhancement of photocurrent in GaInNAs solar cells using Ag/Cu double-layer back reflector
Authors: Aho Timo , Aho Arto , Tukiainen Antti , Polojärvi Ville , Salminen Turkka , Raappana Marianna , Guina Mircea
Published: December 2016

The effect of a Ag/Cu-based double-layer back reflector on current generation in GaInNAs single-junction solar cell is reported. Compared to Ti/Au reflector, the use of Ag/Cu led to a 28% enhancement of short-circuit current density, attaining a value of ∼14 mA/cm2 at AM1.5D (1000 W/m2) under a GaAs filter. The enhanced current generation is in line with requirements for current-matching in GaInP/GaAs/GaInNAs triple-junction solar cells. The Ag/Cu reflectors also had a low contact resistivity of the order of 10−6 Ω·cm2 and none of the samples exhibited notable peeling of metals in the adhesion tests. Moreover, no discernible diffusion of the metals into the semiconductor was observed after thermal annealing at 200 °C.
Cu-metalated carbyne acting as a promising molecular wire
Authors: Tu Xingchen , Wang Hao , Shen Ziyong , Wang Yongfeng , Sanvito Stefano , Hou Shimin
Published: December 2016

The atomic structure and electronic transport properties of Cu-metalated carbyne are investigated by using the non-equilibrium Green’s function formalism combined with density functional theory. Our calculations show that the incorporation of Cu atom in carbyne improves its robustness against Peierls distortion, thus to make Cu-metalated carbyne behave as a one-dimensional metal. When a finite Cu-metalated carbyne chain is connected to two (111)-oriented platinum electrodes, nearly linear current-voltage characteristics are obtained for both the atop and adatom binding sites. This is due to the efficient electronic coupling between the Cu-metalated carbyne chain and the Pt electrodes, demonstrating the promising applications of Cu-metalated carbyne chains as molecular wires in future electronic devices.
From tunneling to contact in a magnetic atom: The non-equilibrium Kondo effect
Authors: Choi Deung-Jang , Abufager Paula , Limot Laurent , Lorente Nicolás
Published: December 2016

A low-temperature scanning tunneling microscope was employed to study the differential conductance in an atomic junction formed by an adsorbed Co atom on a Cu(100) surface and a copper-covered tip. A zero-bias anomaly (ZBA) reveals spin scattering off the Co atom, which is assigned to a Kondo effect. The ZBA exhibits a characteristic asymmetric lineshape when electrons tunnel between tip and sample, while upon the tip-Co contact it symmetrizes and broadens. Through density functional theory calculations and the non-equilibrium non-crossing approximation, we show that the lineshape broadening is mainly a consequence of the additional coupling to the tip, while non-equilibrium effects only modify the large-bias tails of the ZBA.
Electric-field-induced antiferromagnetic resonance in antiferromagnetic insulators with spin-orbit coupling
Authors: Sekine Akihiko , Chiba Takahiro
Published: December 2016

We study theoretically spin dynamics in three-dimensional antiferromagnetic insulators with spin-orbit coupling. We focus on the antiferromagnetic insulators whose low-energy effective model possesses a topological term called the θ term. By solving the Landau-Lifshitz-Gilbert equation in the presence of the θ term, we show that the antiferromagnetic resonance can be realized by ac electric fields along with static magnetic fields. The antiferromagnetic resonance can be detected via the spin pumping from the Néel field and net magnetization. We calculate both contributions to the pumped spin current, and find that the magnitude of the ac electric field to cause the resonance state is very small (∼ 1 V/m). This indicates that spin currents can be generated efficiently. The mechanism of the antiferromagnetic resonance in this study is understood as the inverse process of the dynamical chiral magnetic effect.
Chemistry, growth kinetics, and epitaxial stabilization of Sn2+ in Sn-doped SrTiO3 using (CH3)6Sn2 tin precursor
Authors: Wang Tianqi , Pitike Krishna Chaitanya , Yuan Yakun , Nakhmanson Serge M. , Gopalan Venkatraman , Jalan Bharat
Published: December 2016

PbTiO3-based ferroelectrics have impressive electroactive properties, originating from the Pb2+ 6s2 electron lone-pair, which cause large elastic distortion and electric polarization due to cooperative pseudo Jahn-Teller effect. Recently, tin-based perovskite oxide (SnTiO3) containing Sn2+ and a chemistry similar to that of the 6s2 lone-pair has been identified as a thermally stable, environmentally friendly substitute for PbTiO3-based ferroelectrics. However experimental attempts to stabilize Sn2+ on the A-site of perovskite ATiO3 have so far failed. In this work, we report on the growth of atomically smooth, epitaxial, and coherent Sn-alloyed SrTiO3 films on SrTiO3 (001) substrates using a hybrid molecular beam epitaxy approach. With increasing Sn concentration, the out-of-plane lattice parameter first increases in accordance with the Vegard’s law and then decreases for Sn(Sr+Ti+Sn) at. % ratio > 0.1 due to the incorporation of Sn2+ at the A-site. Using a combination of high-resolution X-ray photoelectron spectroscopy and density functional calculations, we show that while majority of Sn is on the B-site, there is a quantitatively unknown fraction of Sn being consistent with the A-site occupancy making SrTiO3 polar. A relaxor-like ferroelectric local distortion with monoclinic symmetry, induced by A-site Sn2+, was observed in Sn-doped SrTiO3 with Sn(Sr+Ti+Sn) at. % ratio = 0.1 using optical second harmonic generation measurements. The role of growth kinetics on the stability of Sn2+ in SrTiO3 is discussed.
Magnetic ground state of Dy3+ in DyNiAl4
Authors: Hutchison Wayne D. , Stewart Glen A. , Cadogan J. M. , Princep Andrew , Stewart Ross , Ryan D. H.
Published: December 2016

Previously, the bulk magnetisation of polycrystalline DyNiAl4 was found to reach barely half its expected saturation value with a 9 T applied field. New inelastic neutron scattering and 161Dy-Mössbauer spectroscopy results suggest that the crystal field splitting for Dy3+ in DyNiAl4 is dominated by B20 with a low temperature local Dy3+ moment close to its full free-ion value of ± 10 μB. Considering that the magnetization for related single crystal specimens (e.g. for TbNiAl4) typically grows more rapidly with the applied field directed along the easy axis, the slower response for DyNiAl4 powder must be due to a strong magneto-crystalline anisotropy hindering the moment realignment.
Spin transport in antiferromagnetic NiO and magnetoresistance in Y3Fe5O12/NiO/Pt structures
Authors: Hung Yu-Ming , Hahn Christian , Chang Houchen , Wu Mingzhong , Ohldag Hendrik , Kent Andrew D.
Published: December 2016

We have studied spin transport and magnetoresistance in yttrium iron garnet (YIG)/NiO/Pt trilayers with varied NiO thickness. To characterize the spin transport through NiO we excite ferromagnetic resonance in YIG with a microwave frequency magnetic field and detect the voltage associated with the inverse spin-Hall effect (ISHE) in the Pt layer. The ISHE signal is found to decay exponentially with the NiO thickness with a characteristic decay length of 3.9 nm. This is contrasted with the magnetoresistance in these same structures. The symmetry of the magnetoresistive response is consistent with spin-Hall magnetoresistance (SMR). However, in contrast to the ISHE response, as the NiO thickness increases the SMR signal goes towards zero abruptly at a NiO thickness of ≃ 4 nm, highlighting the different length scales associated with the spin-transport in NiO and SMR in such trilayers.
Molecular beam epitaxy of Cd3As2 on a III-V substrate
Authors: Schumann Timo , Goyal Manik , Kim Honggyu , Stemmer Susanne
Published: December 2016

Epitaxial, strain-engineered Dirac semimetal heterostructures promise tuning of the unique properties of these materials. In this study, we investigate the growth of thin films of the recently discovered Dirac semimetal Cd3As2 by molecular beam epitaxy. We show that epitaxial Cd3As2 layers can be grown at low temperatures (110 °C–220 °C), in situ, on (111) GaSb buffer layers deposited on (111) GaAs substrates. The orientation relationship is described by (112)Cd3As2 || (111) GaSb and [11¯0]Cd3As2 || [1¯01]GaSb. The films are shown to grow in the low-temperature, vacancy ordered, tetragonal Dirac semimetal phase. They exhibit high room temperature mobilities of up to 19300 cm2/Vs, despite a three-dimensional surface morphology indicative of island growth and the presence of twin variants. The results indicate that epitaxial growth on more closely lattice matched buffer layers, such as InGaSb or InAlSb, which allow for imposing different degrees of epitaxial coherency strains, should be possible.
Synthesis and characterization of yttrium iron garnet (YIG) nanoparticles - Microwave material
Authors: Sharma Vinay , Saha Jitendra , Patnaik Satyabrata , Kuanr Bijoy K.
Published: December 2016

Magnetic Yttrium Iron Garnet (YIG) nanoparticles (NPs) were prepared by sol–gel (SG) and solid-state (SS) reaction methods to elucidate the nanoscale size on the magnetic behavior of NPs. It is found that YIG prepared by these two methods are different in many ways. The average NP sizes prepared by SG and SS methods were calculated by Scherrer formula from XRD data. SEM images show the change in grain size for both types of NPs. The sintering temperature required to form pure garnet phase is 750°C for SG and 1000°C for SS NPs. The saturation magnetizations (Ms) were 1070 Oe for SG and 1125 Oe for SS NPs, respectively. The coercivity (Hc) of SS NPs are twice larger than SG NPs. This is due to the larger crystal sizes of the SS NPs, hence more crystal boundaries. Dynamic properties were studied by ferromagnetic resonance (FMR) technique in field-sweep and frequency-sweep mode at different fixed frequencies and at different fixed magnetic fields, respectively. Resonance field (Hr) observed to increase linearly with frequency both for SS and SG NPs. The stop-band bandwidth (frequency linewidth) is narrower for SG NPs in comparison to SS NPs. Microwave absorption property make this material as a strong candidate for microwave device applications.
New p- and n-type ferromagnetic semiconductors: Cr-doped BaZn2As2
Authors: Gu Bo , Maekawa Sadamichi
Published: December 2016

We find new ferromagnetic semiconductors, Cr-doped BaZn2As2, by employing a combined method of the density functional theory and the quantum Monte Carlo simulation. Due to a narrow band gap of 0.2 eV in host BaZn2As2 and the different hybridization of 3d orbitals of Cr impurity, the impurity bound states have been induced both below the top of valence band and above the bottom of conduction band. The long-range ferromagnetic coupling between Cr impurities is obtained with both p- and n-type carriers.
Observation of toroidal Alfvén eigenmodes during minor disruptions in ohmic plasmas
Authors: Liu Yangqing , Tan Yi , Gao Zhe , Xu Yuhong , Hu Youjun , Chai Song , Jiang Yanzheng , Ke Rui , Zhong Heng , Wang Wenhao
Published: December 2016

Toroidal Alfvén eigenmodes (TAEs) excited in purely ohmically heated plasmas without any auxiliary heating have been identified for the first time in the SUNIST spherical tokamak. The TAE modes are observed during minor disruptions and have a frequency range of 150–500 kHz. The mode structure analysis indicates the existence of both m/n = −3/−1 and −4/−1 harmonics, propagating in the electron diamagnetic direction in the laboratory frame of reference. These TAEs appear simultaneously with the generation of runaway electrons in the current quench phase, accompanying with the density sweeping during the minor disruption. Possible driving mechanisms and potential applications of these TAEs are discussed.
Communication: Interaction of BrO radical with the surface of water
Authors: Zhu Chongqin , Gao Yurui , Zhong Jie , Huang Yingying , Francisco Joseph S. , Zeng Xiao Cheng
Published: December 2016

Solvation of a BrO radical in a slab of water is investigated using adaptive buffered force quantum mechanics/molecular mechanics (QM/MM) dynamics simulations. The simulation results show that the BrO radical exhibits preference towards the water surface with respect to the interior region of the water slab, despite BrO’s high affinity to water. Another important finding is the weakening of (BrO)Br⋯O(water) interaction at the water surface due to competitive interactions between (BrO)Br⋯O(water) and (water)H⋯O(water). As such, the BrO-water slab interaction is dominated by (BrO)O⋯H(water) interaction, contrary to that in the gas phase, suggesting that the reactive site for the BrO radical at the air/water surface is more likely the Br site. The conclusion from this study can offer deeper insight into the reactivity of the BrO radical at the air/water interface, with regard to atmospheric implications.
Statistical exchange-coupling errors and the practicality of scalable silicon donor qubits
Authors: Song Yang , Das Sarma S.
Published: December 2016

Recent experimental efforts have led to considerable interest in donor-based localized electron spins in Si as viable qubits for a scalable silicon quantum computer. With the use of isotopically purified 28Si and the realization of extremely long spin coherence time in single-donor electrons, the recent experimental focus is on two-coupled donors with the eventual goal of a scaled-up quantum circuit. Motivated by this development, we simulate the statistical distribution of the exchange coupling J between a pair of donors under realistic donor placement straggles, and quantify the errors relative to the intended J value. With J values in a broad range of donor-pair separation (5<|R|<60 nm), we work out various cases systematically, for a target donor separation R0 along the [001], [110] and [111] Si crystallographic directions, with |R0|=10,20 or 30 nm and standard deviation σR=1,2,5 or 10 nm. Our extensive theoretical results demonstrate the great challenge for a prescribed J gate even with just a donor pair, a first step for any scalable Si-donor-based quantum computer.
Thermal conductivity of ferrimagnet GdBaMn2O5.0 single crystals
Authors: Wu J. C. , Zhao J. Y. , Xu H. S. , Liu X. G. , Taskin A. A. , Ando Yoichi , Zhao X. , Sun X. F.
Published: December 2016

GdBaMn2O5.0 is a double-perovskite ferrimagnet consisting of pyramidal manganese layers. In this work, we study the in-plane and the c-axis thermal conductivities of GdBaMn2O5.0 single crystals at low temperatures down to 0.3 K and in high magnetic fields up to 14 T. The κc(T) curve shows a broad hump below the Néel temperature (TN = 144 K), which indicates the magnon heat transport along the c axis. Whereas, the κa(T) shows a kink at TN, caused by a magnon-phonon scattering effect. This anisotropic behavior is caused by the anisotropy of spin interactions along different directions. At very low temperatures, magnetic-field-induced changes of κa and κc, which is likely due to phonon scattering by free Gd3+ spins, is rather weak. This indicates that the spin coupling between Gd3+ and Mn2+/Mn3+ is rather strong at low temperatures.
Directional heat transport through thermal reflection meta-device
Authors: Hu Run , Zhou Shuling , Shu Weicheng , Xie Bin , Ma Yupu , Luo Xiaobing
Published: December 2016

Directional heat transfer may be hard to realize due to the fact that heat transfer is diffusive. In this paper, we try to take one step forward based on the transformation thermodynamics. A special structure and meta-device is proposed to “reflect” the heat flow directionally–just like the mirror to the light beam, in which the heat flow just one-time changes the direction rather than gradually changing the directions in isotropic materials. The benefits of such thermal reflection meta-device are discussed by comparing the corresponding thermal resistance with the same structures of isotropic materials. The proposed meta-device is verified to possess the low thermal resistance and high heat transfer ability with least energy loss, and can be made by nature-existing isotropic materials with specific structures.
Suspension medium's impact on the EPD of nano-YSZ on Fecralloy
Authors: Khanali O. , Rajabi M. , Baghshahi S. , Ariaee S.
Published: December 2016

Electrophoretic deposition (EPD) was employed to coat yttria-stabilised zirconia (YSZ) on Fecralloy. Various non-aqueous solvents were utilised to achieve smooth crack-free YSZ coatings. The EPD parameters, including solvent type, sedimentation height, zeta potential, particle size, pH and deposition weight, were studied. The micro-structural evolution and mechanical properties of the coatings were studied by the field emission scanning electron microscopy and micro-hardness, respectively. It was found that coatings obtained from 0.4 g L−1 I2 acetyl–acetone were uniform, smooth and crack free. Also they had narrow particle size distributions and higher zeta potential in the suspension. The experimental results revealed that suspension stability was a requirement for obtaining high-quality coatings and deposition yield for stable suspensions was higher; however, particle coagulation resulted in coatings with low green density and poor sinter ability. A transition in deposition mechanism from linear to parabolic was observed during EPD where deposition rate was decreased by time.

GRAPHICAL ABSTRACT
Ultra-Short-Course Antibiotics for Patients With Suspected Ventilator-Associated Pneumonia but Minimal and Stable Ventilator Settings
Authors: Klompas Michael , Li Lingling , Menchaca John T. , Gruber Susan ,   for the Centers for Disease Control and Prevention Epicenters Program
Published: December 2016

Background.

Many patients started on antibiotics for possible ventilator-associated pneumonia (VAP) do not have pneumonia. Patients with minimal and stable ventilator settings may be suitable candidates for early antibiotic discontinuation. We compared outcomes among patients with suspected VAP but minimal and stable ventilator settings treated with 1–3 days vs >3 days of antibiotics.

Methods.

We identified consecutive adult patients started on antibiotics for possible VAP with daily minimum positive end-expiratory pressure of ≤5 cm H2O and fraction of inspired oxygen ≤40% for at least 3 days within a large tertiary care hospital between 2006 and 2014. We compared time to extubation alive vs ventilator death and time to hospital discharge alive vs hospital death using competing risks models among patients prescribed 1–3 days vs >3 days of antibiotics. All models were adjusted for patient demographics, comorbidities, severity of illness, clinical signs of infection, and pathogens.

Results.

There were 1290 eligible patients, 259 treated for 1–3 days and 1031 treated for >3 days. The 2 groups had similar demographics, comorbidities, and clinical signs. There were no significant differences between groups in time to extubation alive (hazard ratio [HR], 1.16 for short- vs long-course treatment; 95% confidence interval [CI], .98–1.36), ventilator death (HR, 0.82 [95% CI, .55–1.22]), time to hospital discharge alive (HR, 1.07 [95% CI, .91–1.26]), or hospital death (HR, 0.99 [95% CI, .75–1.31]).

Conclusions.

Very short antibiotic courses (1–3 days) were associated with outcomes similar to longer courses (>3 days) in patients with suspected VAP but minimal and stable ventilator settings. Assessing serial ventilator settings may help clinicians identify candidates for early antibiotic discontinuation.
Improvised antibiotic loaded hip spacers in the presence of acetabular wall defects
Authors: Kumar Narinder
Published: December 2016

It is quite challenging to use antibiotic-loaded hip spacers in the first stage of a two-stage revision hip arthroplasty in patients with infected hip arthroplasty with medial acetabular wall or proximal femoral defect. We describe a technique of an improvised hip spacer using a monopolar hip prosthesis, which is easily reproducible and provides a stable, mobile hip without any significant risk of intrapelvic migration of the spacer or compromise in the amount of antibiotics required. In addition, a long, custom-made monopolar hip prosthesis can also be successfully used as a hip spacer in patients with proximal femoral as well as medial acetabular wall bone defects.
Strategy and outcome statements in academic and nonacademic orthopaedic surgery institutions
Authors: Job Alan , Glezos Christopher D. , Sharan Alok
Published: December 2016

Background:

As the United States healthcare system transitions to a value-based system, it is becoming increasingly important for health care providers and institutions to maintain a strategy that allows them to remain competitive and meet patient demands. The purpose of this study was to compare the number of academic orthopaedic surgery institutions to nonacademic orthopaedic surgery institutions that publish their strategy statements online. As delivering superior patient outcomes is critical for a successful strategy in a value-based system, the study also aims to compare the rates of published outcome scores on the websites of the two groups. It was hypothesized that nonacademic institutions would have greater rates of strategic statements and outcome scores that are published online compared to academic institutions.

Methods:

The websites of all 149 academic orthopaedic institutions in the United Stated and the top 21 U.S. News ranked nonacademic orthopaedic surgery institutions were evaluated for predetermined categories of strategy and outcome scores.

Results:

It was found that 95% of nonacademic institutions had strategic statements compared to only 38% of academic institutions. Similarly 30% of nonacademic institutions presented a patient outcome score on their website compared to only 14.3% of academic institutions.

Conclusions:

It is clear that nonacademic orthopaedic institutions are competing with strategies focused on components of value-based care and positive patient outcomes in order to attract the patient population.
Plain radiographic evaluation of the patellofemoral joint: technique and image interpretation
Authors: Saper Michael G. , Fine Landon , Shneider David A.
Published: December 2016

Patellofemoral problems are among the most common knee problems in orthopaedics and yet are the most poorly understood and poorly treated. There is no well-defined or standardized classification pertaining to this pathologic process. Diagnostic imaging is a critical component of the evaluation and treatment decision process. A variety of radiographic measurements have been described as indicators of structural disease, but comprehensive information recommending radiographic interpretation of patellofemoral dysfunction is lacking. This paper summarizes our recommendations regarding the most important aspects of radiographic technique and image interpretation to adequately evaluate the patellofemoral joint in patients with anterior knee pain or instability.
Healing of Atypical Subtrochanteric Femur Fractures After Cephalomedullary Nailing: Which Factors Predict Union?
Authors: Cho Jae-Woo , Oh Chang-Wug , Leung Frankie , Park Ki-Chul , Wong Merng Koon , Kwek Ernest , Kim Han-Ju , Oh Jong-Keon
Published: December 2016

Objectives:

The purpose of this study was to determine the healing rate and time to union of atypical subtrochanteric fractures treated with cephalomedullary nailing.

Design:

Retrospective review, descriptive, and analytic study.

Setting:

Six level 1 trauma centers.

Patients/Participants:

The study included 42 patients with 48 displaced, atypical, bisphosphonate-associated subtrochanteric femur fractures who underwent surgical intervention.

Intervention:

Cephalomedullary femur nailing.

Main Outcome Measurement:

The main outcome measures were radiologic healing and time to union.

Results:

The primary healing rate after cephalomedullary nailing of bisphosphonate-associated subtrochanteric femur fractures was 68.7% (33/48 patients). Mean time to union was 10.7 months. Malalignment was determined using the differences in neck–shaft angle (the difference between the normal side and the surgically repaired side) and sagittal angulation. These all proved to be significantly correlated with failure and delayed healing time. The cutoff points for neck–shaft angle, difference in neck–shaft angle, and sagittal angulation were 125.6, 4.4, and 5.5 degrees, respectively (receiver operating characteristic curve analysis).

Conclusions:

The healing rate of atypical subtrochanteric femur fractures treated with cephalomedullary nailing is lower than that previously reported for atypical femur fractures. The quality of fracture reduction proved to be the most important factor in bony union and time to union.

Level of Evidence:

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.
Serum Mast Cell Tryptase as a Marker of Posttraumatic Joint Contracture in a Rabbit Model
Authors: Kopka Michaela , Monument Michael J. , Befus A. Dean , Zhang Mei , Hart David A. , Salo Paul T. , Schneider Prism S. , Fan Cun-Yi , Liang Xiangdang , Garven Alexandra , Hildebrand Kevin A.
Published: December 2016

Objectives:

Mast cells have been identified as key mediators of posttraumatic joint contracture, and stabilizing medications (ketotifen) have been shown to decrease contracture severity. Serum mast cell tryptase (SMCT) levels are used clinically to monitor mast cell–mediated conditions. The goals of this study were to determine if SMCT levels are elevated in the setting of joint contracture, if they can be decreased in association with ketotifen therapy, and if they correlate with contracture severity.

Methods:

This study used a previously developed rabbit model in which 39 animals were divided into 4 groups: operatively created joint contracture (ORC, n = 13), operatively created contracture treated with ketotifen at 2 doses (KF0.5, n = 9; KF1.0, n = 9), and healthy rabbits (NC, n = 8). Range of motion measures were performed at 8 weeks after the surgery. Serum samples were collected on postoperative days 1, 3, 5, 7, 21, 35, and 49. SMCT levels were measured using a rabbit-specific enzyme-linked immunosorbent assay.

Results:

Levels of SMCT were highest in the operatively created joint contracture group and were significantly greater compared with both ketotifen groups (P < 0.001). Levels were highest at postoperative day 1 with a trend to decrease over time. A positive correlation between SMCT levels and contracture severity was observed in all operative groups (P < 0.05).

Conclusions:

Levels of SMCT are elevated in the setting of joint contracture, decreased in association with ketotifen therapy, and positively correlated with contracture severity. This is the first study to establish a relationship between SMCT and joint injury. Measurement of SMCT may be valuable in identifying those at risk of posttraumatic joint contracture.
Health Literacy in Orthopaedic Trauma Patients
Authors: Cosic Filip , Kimmel Lara , Edwards Elton
Published: December 2016

Objective:

This study aimed to determine the level of health literacy in a postoperative orthopaedic trauma population and to evaluate the efficacy of a simple predischarge discussion strategy, targeted at improving health literacy.

Design:

A pre–post intervention study was conducted from April 2014 to January 2015.

Setting:

Academic Level 1 trauma center.

Participants:

One hundred ninety consecutive orthopaedic trauma patients with operatively managed lower limb fractures were recruited. All eligible participants agreed to participate.

Intervention:

The first ninety-nine patients received usual care (UC). The following 91 patients received a structured predischarge discussion, including x-rays, written and verbal information, from the orthopaedic staff (DG). Patients were then randomized into health literacy evaluation before first outpatient review or after first outpatient review.

Main Outcome Measures:

The primary outcome measure was a questionnaire determining health literacy.

Results:

Ninety-six (97%) of the UC patients and 87 (96%) of the discussion patients (DG) completed the interview. UC preoutpatient (n = 46) demonstrated a mean score of 4.67 of a maximum 8. UC postoutpatient (n = 50) demonstrated a mean score of 5.42. DG preoutpatient (n = 47) demonstrated a mean score of 6.70. DG postoutpatient (n = 40) demonstrated a mean score of 7.08.

Conclusions:

Australian orthopaedic trauma patients demonstrate poor health literacy, with this not showing improvement after their first outpatient follow-up visit. The use of a time efficient, structured predischarge discussion improved patient health literacy.

Level of Evidence:

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.
Classification of Cruciate Ligament Dysplasia and the Severity of Congenital Fibular Deficiency
Authors: Walker Janet L. , Milbrandt Todd A. , Iwinski Henry J. , Talwalkar Vishwas R.
Published: December 2016

Background:

Dysplasia of the cruciate ligaments has been found in many patients with congenital fibular deficiency. A recent classification system has shown that radiographic tibial spine changes can predict the hypoplasia and aplasia of the cruciate ligaments. We used this radiographic classification to determine the frequency of these abnormalities and how they correlate with the severity of fibular deficiency and lateral femoral condylar hypoplasia.

Methods:

Using a hospital database search for fibular deficiency, 99 patients ≥6 years with unilateral fibular deficiency were identified. Existing radiographs of both knees were available for 75 patients and reviewed for the tibial spine changes and Achterman and Kalamchi classification of the fibular deficiency. Measurements of femoral condyle heights in 74 of 75 patients were recorded before any surgery to the distal femoral physis to assess lateral femoral condylar hypoplasia.

Results:

Twenty-two patients had hypoplasia of the lateral tibial spine+normal medial spine, 29 had absence of the lateral tibial spine+hypoplastic medial spine, and 11 had absence of both tibial spines. Five tibial spines were normal and 8 were unclassifiable. The severity of the tibial spine dysplasia, particularly absence of the lateral tibial spine, correlated with the severity of the fibular deficiency. (P<0.0001) The mean lateral femoral condylar hypoplasia, measured by involved: uninvolved lateral condyle heights, was 0.85±0.11. Those with some preservation of the lateral tibial spine had less lateral femoral condylar hypoplasia (P=0.0009). This lateral femoral condylar hypoplasia was positively associated with the severity of the fibular absence (P=0.039) and foot ray deficiency (P=0.036).

Conclusions:

The severity of cruciate ligament dysplasia in fibular deficiency is directly correlated with the severity of fibular absence, lateral femoral condylar hypoplasia, and the absence of foot rays. This suggests that the embryological factors involved have a complex interplay for all of these clinical findings.

Level of Evidence:

Level III.
Chance Fractures in the Pediatric Population Are Often Misdiagnosed
Authors: Andras Lindsay M. , Skaggs Kira F. , Badkoobehi Haleh , Choi Paul D. , Skaggs David L.
Published: December 2016

Background:

Flexion injuries of the spine range from mild compression fractures to severe flexion-distraction injuries, that is, Chance fractures. Chance fractures are often unstable and Arkader and colleagues demonstrated improved outcomes when Chance fractures are treated operatively compared with those managed nonoperatively.

Methods:

A retrospective review was conducted of all patients treated over a 5-year period (2008 to 2013) for a flexion injury, either a Chance or a compression fracture, of the thoracolumbar spine at our tertiary pediatric level I trauma center. Patients were excluded if they had prior spine surgery or had a pathologic fracture.

Results:

Of the 26 patients who met the inclusion criteria, 27% (7/26 patients) had a Chance fracture and 73% (19/26) had compression fracture(s). The mean age of the 7 patients with Chance fractures was 14.6 years (range, 13 to 16 y). In total, 71% (5/7) of the patients with Chance fractures were initially misdiagnosed: (3 as compression fractures, 1 as a burst fracture, 1 as muscular pain) and 80% (4/5) of these misdiagnoses were made by a neurosurgeon or orthopaedic surgeon. Average delay to correct diagnosis was 95 days (range, 2 to 311 d), with 57% (4/7) of the patients having ≥1 month delay. These 4 patients with a Chance fracture and ≥1 month delay in correct diagnosis presented to our clinic electively with chronic back pain. None of the patients with Chance fractures had a neurological injury. Six patients with posterior ligamentous disruption were treated with surgical instrumentation and fusion. All Chance fractures occurred between the levels of T12 and L3.

Conclusions:

The majority of pediatric Chance fractures in this series were initially misdiagnosed (71%; 5/7) or mistreated (14%; 1/7) by neurosurgeons or orthopaedic surgeons. Mean time to the correct diagnosis was 3 months for the Chance fractures in this series.

Level of Evidence:

Level IV.
Systemic treatment for thymic malignancies
Authors: Girard Nicolas , Merveilleux du Vignaux Claire
Published: December 2016

Purpose of review

The management of thymic epithelial tumors is a paradigm of multidisciplinary collaboration. Chemotherapy may be administered as part of curative-intent sequential strategy integrating subsequent surgery or radiotherapy, or as an exclusive treatment if local treatment is not achievable. Recurrences of thymic epithelial tumors should be managed according to the same strategy as newly diagnosed tumors.

Recent findings

More options have become available for advanced, refractory, and recurrent thymic epithelial tumors, which include cytotoxic agents such as carboplatin–paclitaxel, pemetrexed, and oral etoposide. Angiogenesis targeting is a standard in advanced lines of treatment, after results of a phase II trial with sunitinib were reported. Ongoing studies are assessing the opportunity of targeting the immune-response checkpoint programmed death-1/programmed death ligand-1, with preliminary promising results whereas safety, with a higher risk of auto-immunity, may represent a concern.

Overall, a dramatic improvement in our knowledge of the management of thymic tumors has occurred in the past few years, resulting in the development of databases, translational research programmes, and clinical trials. Although access to innovative strategies represents a major challenge, as the rarity of the tumor precludes specific approval of drugs to be obtained, patient-centered initiatives, such as the establishment of dedicated networks, are warranted.
Usability Evaluation and Implementation of a Health Information Technology Dashboard of Evidence-Based Quality Indicators
Authors: Schall Mark Christopher , Cullen Laura , Pennathur Priyadarshini , Chen Howard , Burrell Keith , Matthews Grace
Published: December 2016

Health information technology dashboards that integrate evidence-based quality indicators can efficiently and accurately display patient risk information to promote early intervention and improve overall quality of patient care. We describe the process of developing, evaluating, and implementing a dashboard designed to promote quality care through display of evidence-based quality indicators within an electronic health record. Clinician feedback was sought throughout the process. Usability evaluations were provided by three nurse pairs and one physician from medical-surgical areas. Task completion times, error rates, and ratings of system usability were collected to compare the use of quality indicators displayed on the dashboard to the indicators displayed in a conventional electronic health record across eight experimental scenarios. Participants rated the dashboard as “highly usable” following System Usability Scale (mean, 87.5 [SD, 9.6]) and Poststudy System Usability Questionnaire (mean, 1.7 [SD, 0.5]) criteria. Use of the dashboard led to reduced task completion times and error rates in comparison to the conventional electronic health record for quality indicator–related tasks. Clinician responses to the dashboard display capabilities were positive, and a multifaceted implementation plan has been used. Results suggest application of the dashboard in the care environment may lead to improved patient care.
Differentiating Intralymphatic Histiocytosis, Intravascular Histiocytosis, and Subtypes of Reactive Angioendotheliomatosis: Review of Clinical and Histologic Features of All Cases Reported to Date
Authors: Mazloom Sean E. , Stallings Alicia , Kyei Angela
Published: December 2016

Reactive angioendotheliomatosis (REA) is a rare benign angioproliferative condition of the skin, which has been noted to occur in patients with a variety of underlying systemic diseases. Histopathologically, this condition is characterized by vascular proliferation, and endothelial cell hyperplasia within the lumina and around dermal vessels, without significant cellular atypia. Since the first case of RAE was reported in 1958, multiple histologic patterns of benign cutaneous vascular proliferations with similar clinical presentations to RAE have been described in the literature and have been proposed as subtypes of the originally described condition. Among these entities are diffuse dermal angiomatosis (DDA), acroangiodermatitis, glomeruloid angioendotheliomatosis, and angiomatosis associated with cryoproteins. It has also been proposed that another entity, characterized by the benign proliferation of histiocytes within the lumina of cutaneous vessels, is a subtype of RAE. Histiocytosis within dermal vessels, in conjunction with skin pathology, was first reported in 1994. Based on the appearance of involved vessels, it was initially believed that the histiocytic proliferations were within the lumina of capillaries. Hence, the term intravascular histiocytosis was introduced to describe this histologic finding. However, subsequent introduction of an immunohistochemical (IHC) marker specific for lymphatic vessels demonstrated that most cases of cutaneous histiocyte proliferation are intralymphatic, rather than truly intravascular. However, there have also been reports of IHC-confirmed cases of true intravascular (intracapillary) histiocytosis. In this study, clinical and histologic data from all of the cases of RAE and IHC-confirmed cases of intravascular histiocytosis and intralymphatic histiocytosis reported in the literature to date are examined. Through comparison of the frequency with which key clinical and histologic features present in cases of each group, the authors provide improved clarity of the similarities and differences between these 3 entities.