bluuebunny/crossref_metadata_2025 huggingface dataset:
Two-Dimensional Electron Gas Transport Properties in AlGaN/(In)GaN/AlGaN Double-Heterostructure Field Effect Transistors
Authors: Maeda Narihiko , Saitoh Tadashi , Tsubaki Kotaro , Nishida Toshio , Kobayashi Naoki
Published: April 2019

Two-dimensional electron gas transport properties have been investigated in nitride double-heterostructures. A striking effect has been observed that the two-dimensional electron gas mobility has been drastically enhanced in the AlGaN/GaN/AlGaN double-heterostructure, compared with that in the conventional AlGaN/GaN single-heterostructure. The observed mobility enhancement has been shown to be mainly due to the enhanced polarization-induced electron confinement in the double-heterostructure, and additionally due to the improvement of the interface roughness in the structure. Device operation of an AlGaN/GaN/AlGaN double-heterostructure field effect transistor has been demonstrated: a maximum transconductance of 180 mS/mm has been obtained for a 0.4 μm-gate-length device. In the double-heterostructure using InGaN channel, the increased capacity for the two-dimensional electron gas has been observed. The AlGaN/(In)GaN/AlGaN double-heterostructures are effective for improving the electron transport properties.
Homo-epitaxial growth on misoriented GaN substrates by MOCVD
Authors: Zauner A.R.A. , Schermer J.J. , van Enckevort W.J.P. , Kirilyuk V. , Weyher J.L. , Grzegory I. , Hageman P.R. , Larsen P.K.
Published: April 2019

The N-side of GaN single crystals with off-angle orientations of 0°, 2°, and 4° towards the [100] direction was used as a substrate for homo-epitaxial MOCVD growth. The highest misorientation resulted in a reduction of the density of grown hillocks by almost two orders of magnitude as compared with homo-epitaxial films grown on the exact (000) surface. The features still found on the 4° misoriented sample after growth can be explained by a model involving the interaction of steps, introduced by the misorientation and the hexagonal hillocks during the growth process.
High-Quality AlGaN/GaN Grown on Sapphire by Gas-Source Molecular Beam Epitaxy using a Thin Low-Temperature AlN Layer
Authors: Jurkovic M. J. , Li L.K. , Turk B. , Wang W. I. , Syed S. , Simonian D. , Stormer H. L.
Published: April 2019

Growth of high-quality AlGaN/GaN heterostructures on sapphire by ammonia gas-source molecular beam epitaxy is reported. Incorporation of a thin AlN layer grown at low temperature within the GaN buffer is shown to result in enhanced electrical and structural characteristics for subsequently grown heterostructures. AlGaN/GaN structures exhibiting reduced background doping and enhanced Hall mobilities (2100, 10310 and 12200 cm2/Vs with carrier sheet densities of 6.1 × 1012 cm−2, 6.0 × 1012 cm−2, and 5.8 × 1012 cm−2 at 300 K, 77 K, and 0.3 K, respectively) correlate with dislocation filtering in the thin AlN layer. Magnetotransport measurements at 0.3 K reveal well-resolved Shubnikov-de Haas oscillations starting at 3 T.
High Quality AlN and GaN Grown on Si(111) by Gas Source Molecular Beam Epitaxy with Ammonia
Authors: Nikishin Sergey A. , Faleev Nikolai N. , Antipov Vladimir G. , Francoeur Sebastien , Peralta Luis Grave de , Seryogin George A. , Holtz Mark , Prokofyeva Tat’yana I. , Chu S. N. G. , Zubrilov Andrei S. , Elyukhin Vyacheslav A. , Nikitina Irina P. , Nikolaev Andrei , Melnik Yuriy , Dmitriev Vladimir , Temkin Henryk
Published: April 2019

We describe the growth of high quality AlN and GaN on Si(111) by gas source molecular beam epitaxy (GSMBE) with ammonia (NH3). The initial nucleation (at 1130−1190K) of an AlN monolayer with full substrate coverage resulted in a very rapid transition to two-dimensional (2D) growth mode of AlN. The rapid transition to the 2D growth mode of AlN is essential for the subsequent growth of high quality GaN, and complete elimination of cracking in thick ( > 2 μm) GaN layers. We show, using Raman scattering (RS) and photoluminescence (PL) measurements, that the tensile stress in the GaN is due to thermal expansion mismatch, is below the ultimate strength of breaking of GaN, and produces a sizable shift in the bandgap. We show that the GSMBE AlN and GaN layers grown on Si can be used as a substrate for subsequent deposition of thick AlN and GaN layers by hydride vapor phase epitaxy (HVPE).
MBE Growth of Nitride-Arsenide Materials for long Wavelength Opto-electronics
Authors: Spruytte Sylvia G. , Coldren Christopher W. , Marshall Ann F. , Larson Michael C. , Harris James S.
Published: April 2019

Nitride-Arsenide materials were grown by molecular beam epitaxy (MBE) using a radio frequency (rf) nitrogen plasma. The plasma conditions that maximize the amount of atomic nitrogen versus molecular nitrogen were determined using the emission spectrum of the plasma. Under constant plasma source conditions and varying group III flux, the nitrogen concentration in the film is inversely proportional to the group III flux (i. e. the nitrogen sticking coefficient is unity). The relationship between nitrogen concentration in the film and lattice parameter of the film is not linear for nitrogen concentrations above 2.9 mole % GaN, indicating that some nitrogen is incorporated on other locations than the group V lattice sites. For films with these higher nitrogen concentrations, XPS indicates that the nitrogen exists in two configurations: a Gallium-Nitrogen bond and another type of nitrogen complex in which nitrogen is less strongly bonded to Gallium atoms. Annealing removes this nitrogen complex and allows some of the nitrogen to diffuse out of the film. Annealing also improves the crystal quality of GaAsN quantum wells.
Mg Segregation, Difficulties of P-Doping in GaN
Authors: Liliental-Weber Z. , Benamara M. , Swider W. , Washburn J. , Grzegory I. , Porowski S. , Dupuis R.D. , Eiting C.J.
Published: April 2019

Transmission electron microscopy has been used to study defects formed in Mg-doped GaN crystals. Three types of crystals have been studied: bulk crystals grown by a high pressure and high temperature process with Mg added to the Ga solution and two types of crystals grown by metal-organic chemical vapor deposition (MOCVD) where Mg was either delta-doped or continuously doped. Spontaneous ordering was observed in bulk crystals. The ordering consists of Mg rich planar defects on basal planes separated by 10.4 nm and occurs only for growth in the N to Ga polar direction (000 N polarity). These planar defects exhibit the characteristics of stacking faults with a shift vector of a 1/3 [1 00] +c/2 but some other features identify these defects as inversion domains. Different type of defects were formed on the opposite site of the crystal (Ga to N polar direction), where the growth rate is also an order of magnitude faster compared to the growth with N-polarity. These defects are three-dimensional: pyramidal and rectangular, empty inside with Mg segregation on internal surfaces. The same types of defects seen for the two growth polarities in the bulk crystals were also observed in the MOCVD grown GaN samples with Mg delta doping, but were not observed in the crystals where Mg was added continuously.
Characteristics of Ti/Pt/Au Ohmic Contacts on p-type GaN/AlxGa1−xN Superlattices
Authors: Zhou L. , Khan F. , Ping A.T. , Osinsk A. , Adesida I.
Published: April 2019

Ti/Pt/Au metallization on p-type GaN/AlxGa1−xN (x=0.10 and 0.20) superlattices (SL) were investigated as ohmic contacts. Current-voltage and specific contact resistance measurements indicate enhanced p-type doping in the superlattice structures compared to that in GaN. Ti/Pt/Au is shown to be an effective ohmic metallization scheme on p-type GaN/AlxGa1−xN superlattices. A specific contact resistance of Rc = 4.6×10−4 ω-cm2 is achieved for unalloyed Ti/Pt/Au on GaN/Al0.2Ga0.8N SL. This is reduced to 1.3×10−4 ω-cm2 after annealing for 5 minutes at 300 °C.
High Quality Non-Alloyed Pt Ohmic Contacts to P-Type GaN Using Two-Step Surface Treatment
Authors: Jang Ja-Soon , Park Seong-Ju , Seong Tae-Yeon
Published: April 2019

Two-step surface-treatment is introduced to obtain low resistance Pt contacts to p-type GaN. The first step is performed after the mesa etching process using buffered oxide etch (BOE) and ammonium sulfide [(NH4)2Sx]. This is followed by the second step using BOE. The Pt contact, which was treated sequentially using ultrasonically boiled BOE (10 min) and boiled (NH4)2Sx (10 min), produces a specific contact resistance of 3.0 (±3.8)×10−5 Ωcm2. However, the contact, that was simply BOE-treated, yields 3.1 (±1.1)×10−2 Ωcm2. This indicates that the two-step surface treatment is promising technique for obtaining high quality ohmic contacts to p-GaN. Investigation of the electronic transport mechanisms using current-voltage-temperature (I-V-T) data indicates that thermionic field emission is dominant in the surface-treated Pt contacts.
Electron Beam Pumping in Nitride Vertical Cavities with GaN/ Al0.25 Ga0.75 N Bragg Reflectors
Authors: Klausing H. , Aderhold J. , Fedler F. , Mistele D. , Stemmer J. , Semchinova O. , Graul J. , Dänhardt J. , Panzer S.
Published: April 2019

Electron beam pumped surface emitting lasers are of great interest for a variety of applications, such as Laser Cathode Ray Tubes (LCRT) in projection display technology or high power UV light sources for photolithography.

Two distributed Bragg reflector (DBR) samples were grown by plasma assisted molecular beam epitaxy (PAMBE). The active regions of the samples are a GaN:Si bulk layer and a multihetero (MH) structure, respectively.

Also, a separately grown single DBR stack was studied to find optical transmission and reflection properties which were compared to transfer matrix simulations.
The Formation of in-rich Regions at The Perphery of The Inverted Hexahonal Pits of InGaN thin-films Grown by Metalorganic Vapor Phase Epitaxy
Authors: Li P. , Chua S. J. , Hao M. , Wang W. , Zhang X. , Sugahara T. , Sakai S.
Published: April 2019

InGaN thin films were grown by low-pressure metalorganic-vapor-phase-epitaxy (MOVPE) and characterized by cathodoluminescence (CL) and scanning electron microscopy (SEM). SEM images showed that InGaN samples have inverted hexagonal pits which are formed by the In segregation on the (1011) surfaces. Room temperature CL at the wavelengths corresponding to the GaN band edge, the In-poor and In-rich regions showed that the In–rich regions formed at the periphery of the hexagonal pits.
Optical Properties of AlGaN Quantum Well Structures
Authors: Hirayama Hideki , Enomoto Yasushi , Kinoshita Atsuhiro , Hirata Akira , Aoyagi Yoshinobu
Published: April 2019

We demonstrate 230-250 nm efficient ultraviolet (UV) photoluminescence (PL) from AlN(AlGaN)/AlGaN multi-quantum-wells (MQWs) fabricated by metal-organic vapor-phase-epitaxy (MOVPE). Firstly, we show the PL properties of high Al content AlGaN bulk (Al content: 85-95%) emitting from near band-edge. We systematically investigated the PL properties of AlGaN-MQWs consisting of wide bandgap AlGaN (Al content: 53-100%) barrier. We obtained efficient PL emission of 234 and 245 nm from AlN/Al0.18Ga0.82N and Al0.8Ga0.2N/Al0.18Ga0.82N MQWs, respectively, at 77 K. The optimum value of well thickness was approximately 1.5 nm. The emission from the AlGaN MQWs were several tens of times stronger than that of bulk AlGaN. We found that the most efficient PL is obtained at around 240 nm from AlGaN MQWs with Al0.8Ga0.2N barriers. Also, we found that the PL from AlGaN MQW is as efficient as that of InGaN QWs at 77 K.
Phonons and Free Carriers in a Strained Hexagonal GaN-AlN Superlattice Measured by Infrared Ellipsometry and Raman Spectroscopy
Authors: Schubert M. , Kasic A. , Tiwald T.E. , Woollam J.A. , Härle V. , Scholz F.
Published: April 2019

Phonon and free-carrier effects in a strained hexagonal (α) {GaN}l-{AlN}msuperlattice (SL) heterostructure (l = 8 nm, m = 3 nm) are studied by infrared spectroscopic ellipsometry (IRSE) and micro (µ)-Raman scattering. Growth of the heterostructures was performed by metal-organic vapor phase epitaxy (MOVPE) on (0001) sapphire. An unstrained 1 µm-thick α-GaN layer was deposited prior to the SL. SL phonon modes are identified combining results from both IRSE and µ-Raman techniques. The shift of the GaN-sublayer phonon modes is used to estimate an average compressive SL stress of σxx ∼ - 4.3 GPa. The IRSE data reveal a free-carrier concentration of ne ∼ 5×1018 cm−3 within the undoped SL GaN-sublayers. According to the vertical carrier confinement, the free-carrier mobility is anisotropic, and the lateral mobility (µ⊥ ∼ 400 cm2/Vs, polarization E⊥c-axis) exceeds the vertical mobility (µ|| ∼ 24 cm2/Vs, E||c) by one order of magnitude.
Spectroscopic Ellipsometry Analysis of InGaN/GaN and AlGaN/GaN Heterostructures Using a Parametric Dielectric Function Model
Authors: Wagner J. , Ramakrishnan A. , Obloh H. , Kunzer M. , Köhler K. , Johs B.
Published: April 2019

Spectroscopic ellipsometry (SE) has been used for the characterization of AlGaN/GaN and InGaN/GaN heterostructures. The resulting pseudodielectric function spectra were analyzed using a multilayer approach, describing the dielectric functions of the individual layers by a parametric oscillator model. From this analysis, the dielectric function spectra of GaN, AlxGa1−xN (x≤0.16), and In0.13Ga0.87N were deduced. Further, the dependence of the AlxGa1−xN band gap energy on the Al mole fraction was derived and compared with photoluminescence data recorded on the same material. The SE band gap data are compatible with a bowing parameter close to 1 eV for the composition dependence of the AlxGa1−xN gap energy. Finally, the parametric dielectric functions have been used to model the pseudodielectric function spectrum of a complete GaN/AlGaN/InGaN LED structure.
Photoluminescence Enhancement and Morphological Properties of Carbon Codoped GaN:Er
Authors: Overberg M.E , Abernathy C.R. , Pearton S. J. , Wilson R. G. , Zavada J. M.
Published: April 2019

The surface morphology and the room temperature 1.54 µm photoluminescence (PL) intensity from GaN:Er grown by gas source molecular beam epitaxy have been investigated as a function of C concentration as introduced by CBr4. Similar to previous results with increasing Er level, increasing the C concentration initially improved the surface smoothness as measured by atomic force microscopy (AFM) and scanning electron microscopy (SEM), with RMS roughness improving by a factor of seven over undoped GaN. The PL also improved dramatically. However, the highest amounts of C investigated produced a decrease in the PL as well as a roughening of the film surface. These effects indicate that the GaN:Er had reached its C solubility limit, producing an increased amount of defect induced nonradiative recombination.
Comparison of the Optical Properties of Er3+ Doped Gallium Nitride Prepared by Metalorganic Molecular Beam Epitaxy (Mombe) and Solid Source Molecular Beam Epitaxy (SSMBE)
Authors: Hömmerich U. , Seo J. T. , MacKenzie J. D. , Abernathy C. R. , Birkhahn R. , Steckl A. J. , Zavada J. M.
Published: April 2019

We report on the luminescence properties of Er doped GaN grown prepared by metalorganic molecular beam epitaxy (MOMBE) and solid-source molecular beam epitaxy (SSMBE) on Si substrates. Both types of samples emitted characteristic 1.54 µm PL resulting from the intra-4f Er3+ transition 4I13/2→4I15/2. Under below-gap excitation the samples exhibited very similar 1.54 µm PL intensities. On the contrary, under above-gap excitation GaN: Er (SSMBE) showed ∼80 times more intense 1.54 µm PL than GaN: Er (MOMBE). In addition, GaN: Er (SSMBE) also emitted intense green luminescence at 537 nm and 558 nm, which was not observed from GaN: Er (MOMBE). The average lifetime of the green PL was determined to be 10.8 µs at 15 K and 5.5 µs at room temperature. A preliminary lifetime analysis suggests that the decrease in lifetime is mainly due to the strong thermalization between the 2H11/2 and 4S3/2 excited states. Nonradiative decay processes are expected to only weakly affect the green luminescence.
Processing And Device Performance Of GaN Power Rectifiers
Authors: Zhang A.P. , Dang G.T. , Cao X.A. , Cho H. , Ren F. , Han J. , Chyi J.-I. , Lee C.-M. , Nee T.-E. , Chuo C.-C. , Chi G.-C. , Chu S.N.G. , Wilson R.G. , Pearton S.J.
Published: April 2019

Mesa and planar geometry GaN Schottky rectifiers were fabricated on 3-12µm thick epitaxial layers. In planar diodes utilizing resistive GaN, a reverse breakdown voltage of 3.1 kV was achieved in structures containing p-guard rings and employing extension of the Schottky contact edge over an oxide layer. In devices without edge termination, the reverse breakdown voltage was 2.3 kV. Mesa diodes fabricated on conducting GaN had breakdown voltages in the range 200-400 V, with on-state resistances as low as 6m Ω·cm−2.
The microstructure and electrical properties of directly deposited TiN ohmic contacts to Gallium Nitride.
Authors: Ruterana P. , Nouet G. , Kehagias Th. , Komninou Ph. , Karakostas Th. , di Forte Poisson M.A. , Huet F.
Published: April 2019

When the stoichiometric TiN was deposited directly on GaN, we obtained columnar TiN grains of 5-20 nm section which cross the whole film thickness and are rotated mostly around the [111] axis. The conventional epitaxial relationship is obtained and no amorphous patches are observed at the interface. The deposition of TiN on Si doped GaN layers lead to the formation of an ohmic contact, whereas we obtain a rectifying contact on p type layers.
Highly Chemical Reactive Ion Etching of Gallium Nitride
Authors: Karouta F. , Jacobs B. , Moerman I. , Jacobs K. , Weyher J.L. , Porowski S. , Crane R. , Hageman P.R.
Published: April 2019

A highly chemical reactive ion etching process has been developed for MOVPE-grown GaN on sapphire. The key element for the enhancement of the chemical property during etching is the use of a fluorine containing gas in a chlorine based chemistry. In the perspective of using GaN substrates for homo-epitaxy of high quality GaN/AlGaN structures we have used the above described RIE process to smoothen Ga-polar GaN substrates. The RMS value, measured by AFM, went from 20 Å (after mechanical polishing) down to 4 Å after 6 minutes of RIE. Etching N-polar GaN resulted in a higher etch rate than Ga-polar materials (165 vs. 110 nm/min) but the resulting surface was quite rough and suffers from instability problems. Heat treatment and HCl dip showed a partial recovery of Schottky characteristics after RIE.
Improved Low Resistance Contacts of Ni/Au and Pd/Au to p-Type GaN Using a Cryogenic Treatment
Authors: Park Mi-Ran , Anderson Wayne A. , Park Seong-Ju
Published: April 2019

A low resistance Ohmic contact to p-type GaN is essential for reliable operation of electronic and optoelectronic devices. Such contacts have been made using Ni/Au and Pd / Au contacts to p-type Mg-doped GaN (1.41×1017 cm−3) grown by metalorganic chemical vapor deposition ( MOCVD ) on ( 0001 ) sapphire substrates. Thermal evaporation was used for the deposition of those metals followed by annealing at temperatures of 400 ∼ 700 °C in an oxygen and nitrogen mixed gas ambient, then subsequently cooled in liquid nitrogen which reduced the specific contact resistance from the range of 9.46∼2.80×10−2 Ωcm2 to 9.84∼2.65×10−4 Ωcm2 for Ni/Au and from the range of 8.35∼5.01×10−4 Ωcm2 to 3.34∼1.80×10−4 Ωcm2 for Pd/Au. The electrical characteristics for the contacts were examined by the current versus voltage curves and the specific contact resistance was determined by use of the circular transmission line method (c-TLM). The effects of the cryogenic process on improving Ohmic behavior (I-V linearity) and reducing the specific contact resistance will be discussed from a microstructural analysis which reveals the metallurgy of Ohmic contact formation.
Focused Ion Beam Etching of Nanometer-Size GaN/AlGaN Device Structures and their Optical Characterization by Micro-Photoluminescence/Raman Mapping
Authors: Kuball M. , Benyoucef M. , Morrissey F.H. , Foxon C.T.
Published: April 2019

We report on the nano-fabrication of GaN/AlGaN device structures using focused ion beam (FIB) etching, illustrated on a GaN/AlGaN heterostructure field effect transistor (HFET). Pillars as small as 20nm to 300nm in diameter were fabricated from the GaN/AlGaN HFET. Micro-photoluminescence and UV micro-Raman maps were recorded from the FIB-etched pattern to assess its material quality. Photoluminescence was detected from 300nm-size GaN/AlGaN HFET pillars, i.e., from the AlGaN as well as the GaN layers in the device structure, despite the induced etch damage. Properties of the GaN and the AlGaN layers in the FIB-etched areas were mapped using UV Micro-Raman spectroscopy. Damage introduced by FIB-etching was assessed. The fabricated nanometer-size GaN/AlGaN structures were found to be of good quality. The results demonstrate the potential of FIB-etching for the nano-fabrication of III-V nitride devices.
Emission at 247 nm from GaN quantum wells grown by MOCVD
Authors: Someya Takao , Hoshino Katsuyuki , Harris Janet C. , Tachibana Koichi , Kako Satoshi , Arakawa Yasuhiko
Published: April 2019

Photoluminescence (PL) spectra were measured at room temperature for GaN quantum wells (QWs) with Al0.8Ga0.2N barriers, which were grown by atmospheric-pressure metal organic chemical vapor deposition (MOCVD). The thickness of the GaN QW layers was systematically varied from one monolayer to four monolayers. We clearly observed a PL peak at a wavelength as short as 247 nm (5.03 eV) from one monolayer-thick QWs. The effective confinement energy is as large as 1.63 eV.
Identification of As, Ge and Se Photoluminescence in GaN Using Radioactive Isotopes
Authors: Stötzler A. , Weissenborn R. , Deicher M. , Collaboration ISOLDE
Published: April 2019

We report on experiments which unequivocal identify the chemical nature of optical transitions related to As (2.58 eV), Ge (3.398 eV) and Se (1.49 eV) found in the photoluminescence (PL) spectra of GaN. For this purpose epitaxial GaN layers were doped by ion implantation (60 keV, 3×1012 cm−2) with the radioactive isotopes 71As and 72Se. The isotope 71As (half-life 64.28 h) decays first into 71Ge (11.43 d), which finally transmutes into stable 71Ga. The isotope 72Se decays via 72As (26 h) into stable 72Ge. These chemical transmutations were monitored with photoluminescence spectroscopy (PL). The half-lives resulting from exponential fits on our PL data are in excellent agreement with the half-lives of the isotopes. Our experiments clearly show that in each case the luminescence center involves exactly one As, Ge or Se atom. In addition to this, the results imply that no optically active GaN antisite exists.
Predicting Bankruptcy at Polish Companies: A Comparison of Selected Machine Learning and Deep Learning Algorithms
Authors: Wyrobek Joanna
Published: April 2019

Insolvency prediction is one of the crucial abilities in corporate finance and financial management. It is critical in accounts receivable management, capital budgeting decisions, financial analysis, capital structure management, going concern assessment and co-operation with other companies. The purpose of this paper is to compare the efficiency of selected deep learning and machine learning algorithms trained on a representative sample of Polish companies for the period 2008–2017. In particular, the paper tested the following popular machine learning algorithms: discriminant analysis (DA), logit (L), support vector machines (SVM), random forest (RF), gradient boosting decision trees (GB), neural network with one hidden layer (NN), convolutional neural network (CNN), and naïve Bayes (NB). The research hypotheses evaluated in the paper state that if one has access to a large sample of companies, the most accurate algorithm (first choice) in bankruptcy prediction will be gradient boosting decision trees (H1), random forest (H2) and neural networks (H3) (deep learning) algorithms. The initial hypotheses were formulated based on the practitioners’ opinions regarding the usefulness of various machine learning and artificial intelligence algorithms in bankruptcy prediction. As the results of the research suggest, both deep learning and machine learning algorithms proved to have very comparable efficiency. The new factor introduced in the paper was that the training of the models was carried out on a representative sample of companies (for years 2008–2013) and also the testing phase used a significant number of bankrupt and active companies (validation included a completely different set of companies than those used in the training phase: data were taken from a different time period, 2014–2017, and companies in both sets were also completely different).
Koncepcja zarządzania zasobami i usługami informatycznymi w sądach powszechnych
Authors: Grabowski Mariusz
Published: April 2019

The paper describes good practice in IT resource and service management, developed during the implementation of a pilot study of good governance of judiciary units in the project “PWP Education in the time and cost management of judicial proceedings – case management” of the Human Capital Programme. The paper presents a detailed description of good practice objectives and the effects of their implementation.
Developing the competency of ‘collaborative clinical practice’
Authors: Iqbal Maha Pervaz , Velan Gary , O'Sullivan Anthony J , Olupeliyawa Asela M. , Balasooriya Chinthaka
Published: April 2019

This article was migrated. The article was not marked as recommended. With the increasing complexity of healthcare delivery and patient case mix, and the aging population, health professionals are expected to function more often and more effectively as members of multidisciplinary teams. Competency based medical education (CBME) advocates that the professional development of doctors should be fostered from the start of medical school through to medical practice and with continuing professional development. Strategies for developing teamwork among health professionals and students range from minimal, implicit to explicit (Earnest et al., 2017). Considering this continuum of medical education and the spectrum of educational strategies, we propose a framework for the programmatic approach which can be used in developing competence in 'collaborative clinical practice'.
A demonstration of the use of a unified service model for urban infrastructure networks
Authors: Kielhauser Clemens , Adey Bryan T
Published: April 2019

Planning interventions on urban infrastructure networks requires the consideration of costs of interventions and interruptions to the service provided by the infrastructure. It also requires taking into consideration how these costs and interruptions change due to the proximity of close networks. For example, it is less expensive to replace a gas pipe if the road is open, and, if a pipe is being replaced, there is a probability that the adjacent water pipe will be hit, resulting in a loss of service. Determining the optimal intervention programme for a single network is challenging as one has to consider all the objects within the network. Determining the optimal intervention programmes for multiple networks is even more challenging, particularly because the number of possible intervention programmes explodes. In this paper, the application of a unified model of the service provided by urban infrastructure networks to be used in the search for optimal intervention programmes on multiple networks simultaneously is presented. By using a single equation for all networks, the model enables an increase in the speed of calculation compared to traditional models, as a single equation can be used. The reductions in accuracy from more traditional models are discussed.
Free-radical graft copolymerisation of fluorine nanocellulose surfactants
Authors: Guo Xiaopeng , Wang Haihua , Li Deqiang
Published: April 2019

Nanocellulose surfactants (CSFs) were prepared by grafting sodium allyl sulfonate (C3H5NaO3S) and trifluoroethyl methacrylate (C6H7F3O2) into nanocellulose through free-radical graft copolymerisation. The copolymerisation was carried out by one-step and two-step approaches to preparing CSF-1 and CSF-2 surfactants, respectively. The structure and properties of CSF-1 and CSF-2 were characterised by infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and surface/interfacial tension measurement. Compared with CSF-1, which was prepared with the one-step approach, a higher fluorine (F) content and a lower crystallinity degree were detected for CSF-2, which was prepared with the two-step approach. The surface tension, critical micelle concentration and oil/water interfacial tension values of the CSFs were 32·5 mN/m, 0·36 g/l and 4·8 × 10−2 mN/m, respectively, for CSF-1 and 27·4 mN/m, 0·33 g/l, 1·9 × 10−2 mN/m, respectively, for CSF-2. The lower surface and interfacial tensions confirmed that CSF-2 was endowed with superior surface activity and oil-displacement efficiency. Additionally, CSF-2 displayed enhanced emulsification power in comparison with CSF-1.
Information in Yield Spread Trades
Authors: Park Yang-Ho
Published: April 2019

Using positions data on bond futures, I document that speculators' spread trades contain private information about future economic activities and asset prices. Strong steepening trades are associated with negative payroll surprises in subsequent months and can predict asset markets' reaction to future payroll releases, suggesting that speculators hold superior information about future payrolls. Steepening trades can also predict the rise of stock prices within a few hours before subsequent FOMC announcements, implying that the pre-FOMC stock drift is driven by informed speculation. Overall, evidence highlights spread traders' superior information and its important role in explaining announcement returns and pre-announcement drifts.
Relationships among forest vegetation, plant diversity and some environmental factors in Türkmen Mountain (Eskişehir-Kütahya, Turkey)
Authors: ARSLAN Münevver , GÜLSOY Serkan , KARATAŞ Rıza , KORAY Ertan Şeref , KAPTANOĞLU Aliye Sepken , MERT Ahmet , KAVGACI Ali , ÖZKAN Kürşad
Published: April 2019

The aim of this
study is to determine the vascular plant diversity of forest vegetation in Türkmendağ
and to reveal vegetation-environmental relationships. The sampling was done using the Braun-Blanquet method in 95 grids. Two
subplots were sampled in each grid.  Plant
groups were determined by hierarchical classification clustering analysis. The
relations between plant groups and environmental variables were examined by
non-parametric test statistics. Alpha, beta and gamma (α, β, γ) values, which
are the species diversity indices of plant groups and sample areas were
calculated. The interrelationships among the diversity components (α, βw and
γ) of the sample areas, and the site factors were analysed by regression tree
method. The best regression tree model was built by tree layer, shrub layer,
slope, RI, limestone and altitude respectively. According to statistical
analysis, the same variables played dominant roles for the distribution of
plant groups. When we evaluate all three plant species diversity components
together, plant groups endowed with the highest species diversity are Group 1,
Group 2, Group 4 and Group 8.
European Union – USA: transatlantic agreement free trade and investment: past and present
Authors: Martynov Andrei , Khan Yevgen
Published: April 2019

The paper deals with relationship between European Union and USA in the context of Transatlantic Trade and Investment Partnership. These are the need for the positive dynamic of world economic. The paper analyzes the criticism of this process. The debate itself takes place in the continuum Transatlantic Partnership. The USA president Barack Obama hope managed to define features of Transatlantic Trade and Investment Partnership between USA and EU. The author distinguishes social, geo-political and many factors of the analyzed phenomenon of this project.
Creation of NATO and his role in the British–American relationship
Authors: Klynina Tetyana
Published: April 2019

Creation of NATO in the article is characterized. End of World War II gave a powerful impetus to the development of US foreign policy activities, relegating thus isolationism by the wayside. It became clear that in order to prevent a repetition of aggression in the world is necessary to create a collective security system. Close British–American cooperation during war escalated into a comprehensive Atlantic partnership, whose power was based in ideological, economic, political and military factors. Creation of the North Atlantic Treaty Organization finally secured registration of the US military and political cooperation and the UK in the form of cooperation within NATO.
ANDRESEN, Sophia de Mello Breyner. Coral e outros poemas. Org. Eucanaã Ferraz. 1. ed. São Paulo: Companhia das Letras, 2018.
Authors: Soares Sofia Glória De Almeida
Published: April 2019

ANDRESEN, Sophia de Mello Breyner. Coral e outros poemas. Org. Eucanaã Ferraz. 1. ed. São Paulo: Companhia das Letras, 2018.
Sophia de Mello Breyner Andresen e sua mitologia pessoal
Authors: Guimarães Maria da Conceição Oliveira
Published: April 2019

Resumo: O propósito deste artigo é demonstrar que existe na poesia sophiana uma mitologia pessoal suportada por um olhar arguto e verticalizado sobre as coisas reais vistas e por uma palavra de compromisso ético. A pesquisa sobre esses dois pontos, olhar e palavra, foi conduzida pelos depoimentos de amigos e familiares e pelos seus próprios textos que demonstram o seu olhar particularizado sobre o mundo que a rodeia. Constata-se, ao final, que o olhar arguto e a palavra sacralizada por uma ética são os pilares de sua mitologia pessoal.Palavras-chave: Sophia de Mello Breyner Andresen; poesia portuguesa contemporânea; Grécia; mito.Abstract: The purpose of this article is to demonstrate that in Sophia Andresen’s poetry there is a personal mythology supported by a sharp and deep look about the real things and by a poetic word of ethical commitment. The research on these two points, the look and the poetical word, was conducted by the testimonies of friends and family and her own texts have demonstrated her particularized view of the world. In the end, it is observed that the sharp look and the sacralized word by an ethic are the pillars of her personal mythology.Keywords: Sophia de Mello Breyner Andresen; Portuguese contemporary poetry; Greece; myth.
Ser dividido: concepções modernas na poesia de Sophia de Mello Breyner Andresen
Authors: Canilha Samla Borges
Published: April 2019

Resumo: Entre os grandes poetas que os portugueses legaram ao mundo, está Sophia de Mello Breyner Andresen. Com uma obra notável, tanto pela extensão quanto pela qualidade, a poeta destaca-se como um objeto ainda a se tratar na academia, de forma que o tempo apenas serve à sua consagração. É buscando reforçar o refinamento característico de sua obra que, neste artigo, demonstro como, a partir da leitura de Coral, a poesia de Andresen pode ser pensada a partir da concepção de lírica moderna proposta por Hugo Friedrich. Para tanto, a leitura do texto literário foi realizada considerando-se a discussão sobre os conceitos de lírica e de lírica moderna, em específico, atentado-se a textos além do de Friedrich. Disso, pude observar como a poesia de Andresen serve de expressão da divisão provocada no homem pelo mundo moderno. Essa divisão, porém, pode ser salva pela transfiguração, através da linguagem, da realidade em poesia. Palavras-chave: Sophia de Mello Breyner Andresen; lírica moderna; modernidade.Abstract: Among the great poets that the Portuguese introduced to the world is Sophia de Mello Breyner Andersen. With a notable work, in both extension and quality, the poet stand out as an object yet to be treated by the academia, as the time seems to increase the validation of her work. It’s in the path of the characteristic refinement of her work that this article seeks to demonstrate, from the reading of Coral, that Andersen’s poetry can be studied in the light of Hugo Friedrich concepts of modern lyric. For this task, the reading of the literary text was done taking into consideration the discussion of lyric, in general, and modern lyric, in particular, paying close attention to the works beyond Friedrich. This reading lead to the conclusion that Andersen’s poetry works as a mean of expression of the division that the modern world induces in the human being. This division, however, can be saved by transfiguration, through language, of the reality into poetry.Keywords: Sophia de Mello Breyner Andresen; modern lyric; modernity.
Babaların Okul Öncesi Dönemdeki Çocuklarıyla İlişkisinin Bazı Değişkenlere Göre İncelenmesi
Authors: UZUN Halil , BARAN Gülen
Published: April 2019

Yirminci yüzyılda, birçok araştırmacı, anne-baba
tutum ve davranışlarının çocuk gelişiminde etkili olduğunu belirtmiştir.
Bununla birlikte, annelerle ilgili birçok araştırmaya ek olarak, son yıllarda
birçok araştırma, çocuk gelişimine etkili olduğu düşünülen babalara
odaklanmıştır. Bu doğrultuda, bu araştırmada okul öncesi dönem çocukları ve
babaları arasındaki ilişki düzeyinin bazı değişkenlere göre belirlenmesi
amaçlanmıştır. Bu çalışmada betimsel tarama modeli kullanılmıştır. Araştırmaya,
anaokulunda çocuğu olan ve Kilis ilinde yaşayan 158 baba katılmıştır. Veri
toplama aracı olarak Çocuk Ebeveyn İlişki Ölçeği Baba Formu (Uzun ve Baran,
2015) kullanılmıştır. Verilerin analizinde Kruskall Wallis ve Mann Whitney U
testlerinden yararlanılmıştır. İstatistiksel analiz sonucunda, babaların yaşı,
çocuğun yaşı, evlilik süresi, çocuğun doğum sırası ve babanın eğitim durumu
açısından gruplar arasında anlamlı farklılıklar olduğu görülmüştür. Mevcut
çalışmanın bulgularına dayanarak, babanın eğitim durumundaki artışın baba ile
çocuk arasındaki ilişkiyi olumlu yönde etkilediği tespit edilmiştir. Bununla
birlikte, genç babaların çocuklarıyla ilişki düzeyinin, yaşlı babalardan daha
olumlu olduğu bulunmuştur. Ayrıca bulgular, uzun evlilik süresinin baba çocuk
arasındaki ilişkiyi olumsuz etkilediğini göstermiştir.
Surgical profile and management of carpal tunnel syndrome among sample of Iraqi patients attending a teaching hospital
Authors: Al-Imari Amir Naif Kadum , Bakkour Amine Mohammed , Surriah Mohammed Hillu , Saaid Ayaad Makki
Published: April 2019

Background: Carpal tunnel syndrome (CTS) is a common condition that causes pain, numbness, and weakness in the hands and wrist. CTS affecting female more than male, and diagnosed by EMG and NCS. The aim of this study was to describe the profile and surgical management among sample of Iraqi patients.Methods: Sixty-two patients collected from the neuro-surgical departments of the specialized surgical hospital from June 2015 till June 2018, all patients studied thoroughly regarding age, sex, associated diseases, clinical features, EMG studies, surgery and out come and follow up for at least one year.Results: There was around 2:1 female: male, with age predominant between 40-60 years. All the patients had pain (aching) and most of them numbness, and tingling and only 1/3 had atrophy of muscle of the hand all diagnosed by EMG and NCS, treated surgically results were good compared with other studies regarding complications and final outcome.Conclusions: Surgery for CTS is safe and successful surgery under meticulus procedure and appropriate choice of patients.
Predictive value of the risk factors for amputation of lower extremity in patients with diabetic foot in Al-Karama teaching hospital
Authors: Surriah Mohammed Hillu , Al-Imari Amir Naif Kadum , Bakkour Amine Mohammed , Al-Asadi Riad Rahman Jallod
Published: April 2019

Background: Diabetic foot disease is a foot that exhibits any pathology that results directly from diabetic mellitus or any long-term chronic complication of diabetes mellitus. The aim of the study was to determine the risk factors and indications for amputations among diabetics.Methods: this clinical prospective study includes 120 diabetic foot patients admitted to AL- Karama teaching hospital from 1st January 2015 to 1st January 2019. All patients assessed for age, gender, duration of diabetes, hyperglycemia at admission and control of diabetes, history of smoking, hypertension, assess dominant foot and examination of diabetic foot lesion and classify it according to Meggit-Wagner grading status, indications for amputation and outcome.Results: The male to female ratio was 2:1. Most frequent age group of patients treated by amputation was between 50-80 years. Among patients treated with amputation (68.33%) of patients had diabetes mellitus for 11-20 years. From patients admitted with diabetic foot (53.33%) were smokers. Regarding hypertension (93.33%) of all patients were hypertensive. It was noted that (65%) of patients lesion occur in dominant foot Regarding Wagner's grading system (36.66%) of patients were grade 4 followed by grade 1 (21.66%). regarding mode of treatment (53.33%) of patients treated by amputation and other treated conservatively. Only 3 patients from 60 died while other discharged well after complete treatment.Conclusions: Increasing in age, long duration of diabetes mellitus, poor control of diabetes, smoking and occurrence of lesion in dominant foot all considered as a significant risk factors for increase liability amputation.
The use of prosthetic mesh in adult inguinal hernia repair
Authors: Majeed Laith Qauis , Surriah Mohammed Hillu , Bakkour Amine Mohammed , Saaid Ayaad Makki
Published: April 2019

Background: An abdominal wall hernia is a protrusion of a viscus or part of a viscus through an abnormal opening in the wall of the abdominal cavity. Different approaches have been described in regards to management and repair of hernia. The present study aims at showing the rate of frequency to use the prosthetic mesh versus classical repair in adult inguinal hernia.Methods: A retrospective study lasted from October 2014 to July 2018 in Al-Karama Teaching Hospital. The study Samples consist of 315 patients with inguinal hernia, the age group (20-70) years old they were diagnosed according to clinical examination. There are 76 patients operated on using mesh technique (tension free).Results: All patients in our series were male, with age group (20-70) years. However, the inguinal hernia more frequent with increase age. In age groups; (40-49) was 25 patients (32.89%). The indirect inguinal hernias are most common in the young 65% whereas direct hernias are most common in the old. In our series sixty-one (80.26%) patients with indirect inguinal hernias, eleven (11.82%) patients with direct hernias and six (5.263%) patients with pantaloon type.Conclusions: The frequent uses of mesh in inguinal hernioplasty increasing with age. Tension –free hernioplasty is technically simple surgical operation, which can be used to repair any groin hernia. The use of mesh patch with or without plug is technically easier to work than the classical methods and far simple to secure to surrounding tissues.
Efeitos mutagênicos e citotóxicos do óleo essencial de Lantana camara usando Teste do Micronúcleo em medula óssea de camundongos
Authors: Figueira Aline Carneiro Gomes , De Sousa Maria Alice Montes , Sampaio Lucas Rodrigues , De Jesus Hiago Vieira , Maia Ana Paula Vilela Machado , Lemes Susy Ricardo , Manso João Antonio Xavier , De Campos Calebe Bertolino Marins , Rodrigues Lucas Henrique Nascimento Silva , Fortes Jakeline Soares , Duarte Sabrina Sara Moreira , De Sousa Daniel Ferreira , Da Silva Cláudio Carlos , Reis Paulo Roberto De Melo
Published: April 2019

Este estudo objetivou avaliar as atividades mutagênicas e antimutagênicas, citotóxicas e anticitotóxicas do óleo essencial de Lantana camara através do teste do micronúcleo em medula óssea de camundongos. Foram utilizados 40 camundongos divididos em 8 grupos de 5 animais cada. Para a avaliação da mutagenicidade os camundongos receberam doses intraperitoneais de 300 mg/kg, 600 mg/kg e 1200 mg/kg do óleo essencial de Lantana camara. Para a avaliação da antimutagenicidade e anticitotoxicidade os animais receberam as mesmas doses do óleo essencial concomitantemente com doxorrubicina 2 mg/kg (controle positivo). O óleo de soja foi usado como controle negativo. A avaliação das atividades mutagênicas e antimutagênicas foi feita através da determinação da frequência de eritrócitos policromáticos micronucleados (EPCMN), enquanto que a avaliação das atividades citotóxicas e anticitotóxica ocorreu pela razão de eritrócitos policromáticos (ENC)/eritrócitos normocromáticos (ENC). Os resultados mostraram que na avaliação das atividades mutagênicas e citotóxicas, apenas as doses de 600 mg/kg e 1200 mg/kg apresentaram diferenças significativas em relação ao controle negativo. Nenhuma das três doses do óleo essencial administradas juntamente com doxorrubicina apresentou diferença significativa quando comparadas ao controle positivo. Concluiu-se que o óleo essencial de Lantana camara apresentou atividades mutagênicas e citotóxicas apenas nas doses de 600 mg/kg e 1200 mg/kg, porém nenhuma das doses testadas apresentou atividades antimutagênicas e anticitotóxicas.
СИНТЕЗ НИТРИДА НИОБИЯ В УСЛОВИЯХ ТЕПЛОВОГО ВЗРЫВА СМЕСЕЙ НАНОПОРОШКА АЛЮМИНИЯ С ПЕНТАОКСИДОМ НИОБИЯ
Authors: (Alexandra O. Chudinova) Чудинова Александра Олеговна , (Alexander P. Ilyin) Ильин Александр Петрович , (Lyudmila O. Root) Роот Людмила Олеговна , (Andrey V. Mostovshchikov) Мостовщиков Андрей Владимирович , (Ekaterina A. Bespalova) Беспалова Екатерина Александровна , (Atulya Manuraj) Атулиа Манурадж
Published: April 2019

Актуальность. Получение тугоплавких нитридов в воздухе в условиях теплового взрыва смесей нанопорошка алюминия с оксидами металлов представляет практический интерес для материаловедения и для теории реакционной способности воздуха при высоких температурах. Такой синтез является наименее энергозатратным и не требует сложного оборудования. Для протекания синтеза необходим только нагрев исходной шихты, затем процесс протекает самoпроизвольнo. Синтез нитридсодержащих продуктов в воздухе с использованием атмосферного азота при нормальных условиях представляет интерес для получения новых видов керамики, добавок в обрабатывающий инструмент, для дисперсного упрочнения полимерных и композиционных материалов. Цель исследования: экспериментально определить состав продуктов сгорания смесей нанопорошка алюминия с пентаоксидом ниобия в воздухе. Объект: порошок, содержащий нитрид ниобия, полученный при сжигании смеси нанопорошка алюминия с пентаоксидом ниобия в воздухе. Методы: рентгенофазовый анализ (дифрактометр Дифрей-401), дифференциальный термический анализ (термоанализатор SDT Q600, фирма Instrument). На основании результатов дифференциального термического анализа были рассчитаны четыре параметра активности смeсей: температура начала окисления (tн.о, °C), степень окисленности (α, %), максимальная скорость окисления (vmax, мг/мин), удельный тепловой эффект (ΔН, Дж/г). Рентгенофазовый анализ использовали для изучения фазового состава продуктов окисления. Результаты. Процесс горения смесей нанопорошка алюминия с пентаоксидом ниобия в воздухе протекал в две стадии с формированием нитрида ниобия Nb2N. Согласно рентгенофазовому анализу, выход нитрида ниобия в продукте сгорания смеси НП Al:Nb2O5=3:1 в мольном соотношении (при массе смесей НП Al:Nb2O5=2,64:1,36) достигал максимума и составлял 47 отн. %. Расчет изобарно-изотермического потенциала показал, что нитрид ниобия должен окисляться кислородом воздуха. Причиной стабилизации кристаллической фазы Nb2N является дезактивация кислорода воздуха излучением горящего нанопорошка алюминия.