bluuebunny/crossref_metadata_2025 huggingface dataset:
Algorithmic Approach for Intraoperative Salvage of Venous Congestion in DIEP Flaps
Authors: Bartlett Erica , Zavlin Dmitry , Menn Zachery , Spiegel Aldona
Published: February 2018

Background Flap congestion is a frequently described intraoperative complication during autologous breast reconstruction with abdominal perforator flaps, which, if not addressed, can lead to detrimental results such as flap failure. Here, we describe our institution's algorithm of intraoperative salvage of congested flaps and present their outcomes.

Patients and Methods All patient charts from 2002 to 2016 of a single plastic surgeon were reviewed for patients who underwent deep inferior epigastric perforator flap breast reconstruction resulting in 602 patients and 831 flaps. Of those, 38 women (6.3%) with 40 congested flaps (4.8%) were included in this study. Based on the algorithm guiding the selection of additional venous anastomosis, the patients' surgical details, outcomes, as well as their demographic characteristics are evaluated.

Results Average age and body mass index of our cohort were 47.0 ± 8.0 years and 26.1 ± 3.9, respectively. Ten patients (26.3%) were current or former smokers while 20 (52.6%) required external radiation. Thirty-two congested flaps (80.0%) were predominantly salvaged with a superficial inferior epigastric vein (SIEV)-to-deep inferior epigastric vein (comitante) anastomosis. An SIEV-to-internal mammary vein comitante anastomosis was the second favorite option (5 flaps, 12.5%). Five patients suffered minor complications within a mean follow-up of 18.8 ± 12.3 months without flap failure, bleeding, or infection.

Conclusions Venous flap congestion is an uncommon intraoperative intricacy during free tissue transfer for autologous breast reconstruction. Our proposed algorithm primarily recommends adding an additional venous anastomosis between the superficial and deep drainage system and results and favorable outcomes without major complications.
Gastrointestinal Hemorrhage: A Review of Treatment Modalities and Emerging Therapies
Authors: Strong Andrew , El-Hayek Kevin , Landreneau Joshua
Published: February 2018

Gastrointestinal bleeding (GIB) may present as an acute or chronic condition. Acute GIB can carry significant risk of mortality. After stabilization and resuscitation, localization and control of active hemorrhage are paramount. Several modalities are available for localization. An increasing number of tools are available to interventional radiologists, endoscopists, and surgeons to intervene to achieve hemostasis. Here reviewed are an array of endoscopic, transarterial, and surgical methods to diagnose and treat GIB, with a focus on new and emerging technologies.
Illness Severity Predicts Death and Brain Injury in Asphyxiated Newborns Treated with Hypothermia
Authors: Wang Hui , Beltempo Marc , Rampakakis Emmanouil , Sanon Priscille-Nice , Barbosa Vargas Stephanie , Maluorni Julie , Saint-Martin Christine , Wintermark Pia
Published: February 2018

Objective To determine if illness severity during the first days of life predicts adverse outcome in asphyxiated newborns treated with hypothermia.

Study Design We conducted a retrospective cohort study of asphyxiated newborns treated with hypothermia. Illness severity was calculated daily during the first 4 days of life using the Score for Neonatal Acute Physiology II (SNAP-II score). Adverse outcome (death and/or brain injury) was recorded. Differences in SNAP-II scores between the newborns with and without adverse outcome were assessed.

Result 214 newborns were treated with hypothermia. The average SNAP-II score over the first 4 days of life was significantly worse in newborns developing adverse outcome. The average SNAP-II score was an excellent predictor of death (area under the curve [AUC]: 0.93; p < 0.001) and a fair predictor of adverse outcome (AUC: 0.73; p < 0.001). The average SNAP-II score remained a significant predictor of adverse outcome (odds ratio [95% confidence interval]: 1.08 [1.04–1.12]; p < 0.001), after adjusting for baseline characteristics, degree of initial asphyxial event, and initial severity of encephalopathy.

Conclusion In asphyxiated newborns treated with hypothermia, not only the initial asphyxial event but also the illness severity during the first days of life was a significant predictor of death or brain injury.
Von der Abschlussarbeit zur Publikation – Erfolgreich publizieren
Authors: Baschung-Pfister Pierrette
Published: February 2018

Wer studiert, krönt sein Studium mit einer Abschlussarbeit zu einem spezifischen Thema. Damit von den Erkenntnissen nicht nur Betreuer und Gutachter erfahren, kann der Studierende die Ergebnisse in einem Journal publizieren. Dafür muss eine wissenschaftliche Arbeit bestimmte Kriterien erfüllen.
Macular Edema in Childhood Uveitis
Authors: Garweg Justus
Published: February 2018

Background Pediatric uveitis is associated with a high incidence of severe and frequently permanent visual loss. This article summarizes the current understanding of the disease and the therapeutic options that are available to improve treatment outcomes.

Methods A Medline search spanning the last 10 years was undertaken using the key terms “pediatric uveitis” or “childhood uveitis” and “macular edema”. Articles which appertained to case reports or small case series were excluded from consideration, whereas those in which the opinions of experts were expressed, as well as reviews, were not. The information contained in these latter two forms of publication was particularly valuable, owing to the scarcity of prospective clinical data appertaining to the treatment of pediatric uveitis-associated macular edema.

Results Ten years ago, 34% of children who presented with uveitis manifested secondary complications at the time of diagnosis. During the ensuing 3 years of treatment, this rose to 86%. Heightening awareness of the disease with earlier referrals to expert centers, as well as the advent of therapeutic strategies involving anti-TNF agents and intravitreal corticosteroids, have led to a decrease in the incidence of legal blindness in the affected eyes from 18 – 69% to below 8% during a five-year course of treatment.

Conclusion Early diagnosis and strict control of inflammatory activity have led to a dramatic reduction in the incidence of vision-threatening secondary complications. In the majority of cases, it has also been possible to resolve cystoid macular edema, which, if insufficiently controlled by systemic therapy, usually responds well to intravitreal dexamethasone implants.
Effektivität und Sicherheit eines modifizierten Tipdesigns bei der torsionalen Phakoemulsifikation
Authors: Schmidt Sabine , Hubich Sophie , Vetter Jan , Wirbelauer Christopher
Published: February 2018

Hintergrund Die torsionale Phakoemulsifikation hat durch eine veränderte Bewegung des Phakotips eine effektivere Kernfragmentierung zur Folge. In dieser klinischen Untersuchung sollten die Auswirkungen einer modifizierten Spitze des Phakoemulsifikationshandgriffs und einer aktiven Flüssigkeitssteuerung auf die Effektivität der Phakoemulsifikation sowie die Sicherheit des Hornhautendothels überprüft werden.

Material und Methoden Es wurde eine prospektiv randomisierte 2 : 1-Studie durchgeführt, bei der 40 Patienten mit dem Mini-flared Kelman Tipp und dem Infiniti®-System (Gruppe 1) und 20 Patienten mit dem Intrepid® Balanced Tipp und dem Centurion®-System (Gruppe 2) operiert wurden. Die Studie wurde von der Qualitätskommission der Augenklinik Marzahn genehmigt. Wir analysierten die kumulative Energie sowie das Hornhautendothel mit der Endothelmikroskopie (CEM 530, Nidek) prä- und postoperativ in beiden Gruppen.

Ergebnisse Die Gruppen unterschieden sich präoperativ nicht hinsichtlich Visus, Alter, Geschlecht, Bulbuslänge, Hornhautendothelzahl und Kernhärte (LOCS3). Alle Operationen verliefen komplikationslos. Die kumulative Energie war in Gruppe 1 (Mini-flared Kelman Tipp, Infiniti-System) um 38% signifikant höher als in Gruppe 2 (Balanced Tipp, Centurion-System; p < 0,05). Der Hornhautendothelzellverlust betrug 8% in Gruppe 1 und 10,3% in Gruppe 2 (p > 0,05). Die Größe der Zellen (Polymegatismus) nahm in beiden Gruppen postoperativ signifikant zu, in Gruppe 1 um + 37 µm (p < 0,05) und in Gruppe 2 um + 54 µm (p < 0,05). Es bestand jedoch kein Unterschied zwischen den Gruppen (p > 0,05). Die Anzahl der hexagonalen Zellen (Pleomorphismus) und die Hornhautdicke (Pachymetrie) unterschied sich weder prä- noch postoperativ zwischen beiden Gruppen (p > 0,05).

Schlussfolgerung Im Vergleich zur torsionalen Phakoemulsifikation mit dem Mini-flared Kelman Tipp und standardisiertem Flüssigkeitsdruck ist die torsionale Phakoemulsifikation mit einem modifizierten Tipdesign und aktiver Flüssigkeitssteuerung um 38% effektiver hinsichtlich der kumulativen Energie. Der Verlust der Hornhautendothelzellen unterscheidet sich bei der Operation zwischen den beiden Systemen nicht. Die Zellgröße (Polymegatismus) nahm in beiden Gruppen signifikant zu, die Anzahl der hexagonalen Zellen (Pleomorphismus) und die Hornhautdicke bleiben bei der Operation mit beiden Systemen gleich, sodass das Verfahren in Bezug auf das Hornhautendothel in etwa gleichermaßen sicher ist.
Mut zur Bewegung – ein Fallbeispiel
Authors: de Ruijter Renée
Published: February 2018

Frau Meier
1
hat zunehmend Angst vor Bewegung, da dann ihre
Schmerzen unerträglich werden. Aber auch nachts findet sie keine Ruhe. Die an sich unternehmenslustige
Patientin zieht sich immer mehr aus ihrem sozialen Umfeld zurück. Eine sorgfältige Anamnese und Untersuchung
führen die Therapeutin Renée de Ruijter auf den richtigen Behandlungspfad. Eine verbesserte eigene Kontrolle
der Patientin über ihre Beschwerden entpuppt sich dabei als Schlüssel zu mehr Lebensqualität.
Der Effekt von Manueller Therapie auf Kokzygodynie
Authors: Harlacher Anne , Möller Dirk , von Piekartz Harry
Published: February 2018

Für die Schmerzentstehung von Kokzygodynie können sowohl lokale als auch entfernte Strukturen verantwortlich
sein. Deshalb gilt es, die Quellen der Symptome für jeden Einzelfall zu identifizieren und durch Clinical
Reasoning zu untermauern. Da keine Korrelation zwischen den Symptomen und dem Grad der Steißbeinkrümmung
besteht, lässt sich ein Behandlungserfolg nicht mit der Korrektur der Steißbeinstellung erklären. Der
Therapieverlauf muss durch andere Parameter kontrolliert werden, wie z. B. Schmerzreduktion und Verbesserung
der funktionalen Beeinträchtigungen. Da die Kokzygodynie eng mit psychosozialen Prozessen in Verbindung zu
stehen scheint, ist bei Kindern und chronischen Schmerzgeschehen besondere Aufmerksamkeit geboten.

Eine gängige Behandlungsoption bei Kokzygodynie stellt die muskuloskeletale Therapie dar, über deren
Wirksamkeit allerdings wenig bekannt ist. Aus diesem Grund ging dieser systematische Literaturreview der
Forschungsfrage nach, ob sich Kokzygodynie mit muskuloskeletaler Therapie effektiv behandeln lässt. Obwohl die
Validität der ausgewählten Studien eher gering ausfiel, waren ihre Ergebnisse durchweg positiv. Insgesamt
erwies sich muskuloskeletale Therapie bei Kokzygodynie als effektive Behandlungsform.
Botulinum Toxin for the Treatment of Cyclic Strabismus in Children: Three Case Reports
Authors: Wipf Monika , Bok-Beaube Corinne , Palmowski-Wolfe Anja
Published: February 2018

Cyclic strabismus is a rare disease of unknown origin. If untreated, it leads to manifest strabismus with the risk of amblyopia in children. Treatment is generally surgical. Here we report on three children in whom cyclic esotropia was successfully treated with one bimedial injection of 5 IU Botox®. All patients remained orthotropic with good stereo functions at the last follow-ups at 16, 11, and 8 months. Botulinum toxin offered a minimally invasive treatment option in these patients.
Das SIG als Schmerzquelle identifizieren – SIGnalwirkung
Authors: Vielitz Arne
Published: February 2018

Tests, die das Sakroiliakalgelenk untersuchen, gibt es viele. Doch keiner ist alleine aussagekräftig genug, um das Gelenk zuverlässig als Schmerzquelle zu identifizieren. Daher empfehlen Experten, verschiedene Schmerzprovokationstests für das SIG zu kombinieren. manuelletherapie-Herausgeber Arne Vielitz stellt sie vor.
Umgang mit depressiven Patienten – Wie abgestorben
Authors: Maxeiner Sandra , Rühle Hedda
Published: February 2018

„Ich kann das nicht. Das bringt doch alles nichts.“ Sätze wie diese sind für Physiotherapeuten, die depressive Patienten behandeln, keine Seltenheit. Wer unter einer Depression leidet, ist oft in einem Teufelskreis aus Antriebslosigkeit, Inaktivität und mangelndem Selbstwertgefühl gefangen. Dr. Sandra Maxeiner und Hedda Rühle beschreiben, wie Physiotherapeuten den richtigen Zugang zu diesen Patienten finden.
Coercivity enhancement of FePd thin films prepared by the post-annealing of off-stoichiometric magnetron-sputtered multilayers
Authors: Nguyen Duc-Chau , Chu Chia-Chin , Lee Chih-Hao , Lai Wei-Chiao , Chang Chia-Seng
Published: February 2018

Attainment of perpendicular coercivity higher than 900 Oe and accurate calculation of the degree of long-range order in an FePd alloy thin film is essential in the realization of the perpendicular magnetic recording media. Here, we prepared the off-stoichiometric FePd films through the multilayer growth of [Fe(2 nm)/Pd(2 nm)] × 30 deposited on MgO(001) substrates by magnetron sputtering. The effects of post-annealing these films at 700 °C for 1 and 10 h on their surface morphologies, and crystallographic and magnetic characteristics were investigated. The results show that, with increasing annealing time, the FePd thin films are predominantly (001)-oriented with a progressive increase of the grain size and surface roughness, as well as the improved crystallinity and reduced micro-strain. Accordingly, the perpendicular coercivity is significantly increased to the value of 1.5 kOe, and Pd loses its 4d electrons upon alloying. Furthermore, analysis of X-ray absorption data elucidates some structural details of the Fe scattering phase in addition to the dominant tetragonal FePd phase. We also present a way of determining the long-range order parameter for the FePd alloy thin film, using the combined information of the tetragonality ratio extracted from extended x-ray absorption fine-structure spectroscopy and the stoichiometric deviation of the thin film.
Path integrals with higher order actions: Application to realistic chemical systems
Authors: Lindoy Lachlan P. , Huang Gavin S. , Jordan Meredith J. T.
Published: February 2018

Quantum thermodynamic parameters can be determined using path integral Monte Carlo (PIMC) simulations. These simulations, however, become computationally demanding as the quantum nature of the system increases, although their efficiency can be improved by using higher order approximations to the thermal density matrix, specifically the action. Here we compare the standard, primitive approximation to the action (PA) and three higher order approximations, the Takahashi-Imada action (TIA), the Suzuki-Chin action (SCA) and the Chin action (CA). The resulting PIMC methods are applied to two realistic potential energy surfaces, for H2O and HCN–HNC, both of which are spectroscopically accurate and contain three-body interactions. We further numerically optimise, for each potential, the SCA parameter and the two free parameters in the CA, obtaining more significant improvements in efficiency than seen previously in the literature. For both H2O and HCN–HNC, accounting for all required potential and force evaluations, the optimised CA formalism is approximately twice as efficient as the TIA formalism and approximately an order of magnitude more efficient than the PA. The optimised SCA formalism shows similar efficiency gains to the CA for HCN–HNC but has similar efficiency to the TIA for H2O at low temperature. In H2O and HCN–HNC systems, the optimal value of the a1 CA parameter is approximately 13, corresponding to an equal weighting of all force terms in the thermal density matrix, and similar to previous studies, the optimal α parameter in the SCA was ∼0.31. Importantly, poor choice of parameter significantly degrades the performance of the SCA and CA methods. In particular, for the CA, setting a1 = 0 is not efficient: the reduction in convergence efficiency is not offset by the lower number of force evaluations. We also find that the harmonic approximation to the CA parameters, whilst providing a fourth order approximation to the action, is not optimal for these realistic potentials: numerical optimisation leads to better approximate cancellation of the fifth order terms, with deviation between the harmonic and numerically optimised parameters more marked in the more quantum H2O system. This suggests that numerically optimising the CA or SCA parameters, which can be done at high temperature, will be important in fully realising the efficiency gains of these formalisms for realistic potentials.
Magnetic moment and magnetic anisotropy of Ge3Mn5 thinfilms on Ge(111) substrate: A density functional study
Authors: Yuan H. K. , Cui H. , Liu B. , Tian C. L. , Wang J. Z. , Kuang A. L. , Chen H.
Published: February 2018

Magnetism and magnetic anisotropy energy (MAE) of the Ge3Mn5 bulk, free-standing surface, and Ge3Mn5(001)|Ge(111) thinfilms and superlattice have been systemically investigated by using the relativistic first-principles electronic structure calculations. For Ge3Mn5 adlayers on Ge(111) substrates within Mn1 termination, the direction of magnetization undergoes a transition from in-plane at 1 monolayer (ML) thickness (MAE = −0.50 meV/ML) to out-of-plane beginning at 3 ML thickness (nearly invariant MAE = 0.16 meV/ML). The surficial/interfacial MAE is extracted to be 1.23/−0.54 meV for Mn1-termination; the corresponding value is 0.19/1.03 meV for Mn2/Ge-termination; the interior MAE is averaged to be 0.09 meV per ML. For various Ge3Mn5 systems, the in-plane lattice expansion and/or interlayer distance contraction would enhance the out-of-plane MAE. Our theoretical magnetic moments and MAEs fit well with the experimental measurements. Finally, the origination of MAE is elucidated under the framework of second-order perturbation with the electronic structure analyses.
Low-energy electron collisions with proline and pyrrolidine: A comparative study
Authors: Barbosa Alessandra Souza , Freitas Thiago Corrêa , Bettega M. H. F.
Published: February 2018

We present a comparative study on the calculated cross sections obtained for the elastic collisions of low-energy electrons with the amino acid proline (C5H9NO2) and its building block pyrrolidine (C4H9N). We employed the Schwinger multichannel method implemented with pseudopotentials to compute integral, differential, and momentum transfer cross sections in the static-exchange plus polarization approximation, for energies up to 15 eV. We report three shape resonances for proline at around 1.7 eV, 6.8 eV, and 10 eV and two shape resonances for pyrrolidine centered at 7 eV and 10.2 eV. The present resonance energies are compared with available experimental data on vertical attachment energies and dissociative electron attachment, where a good agreement is found. From the comparison of the present results with available calculated cross sections for the simplest carboxylic acid, formic acid (HCOOH), and from electronic structure calculations, we found that the first resonance of proline, at 1.7 eV, is due the presence of the carboxylic group, whereas the other two structures, at 6.8 eV and 10 eV, clearly arise from the pyrrolidine ring. A comparison between the differential cross sections for proline and pyrrolidine at some selected energies of the incident electron is also reported in this paper.
Global potential energy surface of ground state singlet spin O4
Authors: Mankodi Tapan K. , Bhandarkar Upendra V. , Puranik Bhalchandra P.
Published: February 2018

A new global potential energy for the singlet spin state O4 system is reported using CASPT2/aug-cc-pVTZ ab initio calculations. The geometries for the six-dimensional surface are constructed using a novel point generation scheme that employs randomly generated configurations based on the beta distribution. The advantage of this scheme is apparent in the reduction of the number of required geometries for a reasonably accurate potential energy surface (PES) and the consequent decrease in the overall computational effort. The reported surface matches well with the recently published singlet surface by Paukku et al. [J. Chem. Phys. 147, 034301 (2017)]. In addition to the O4 PES, the ground state N4 PES is also constructed using the point generation scheme and compared with the existing PES [Y. Paukku et al., J. Chem. Phys. 139, 044309 (2013)]. The singlet surface is constructed with the aim of studying high energy O2–O2 collisions and predicting collision induced dissociation cross section to be used in simulating non-equilibrium aerothermodynamic flows.
Thermodynamic properties of confined square-well fluids with multiple associating sites
Authors: Trejos Víctor M. , Quintana-H Jacqueline
Published: February 2018

In this work, a molecular simulation study of confined hard-spheres particles with square-well (SW) attractive interactions with two and four associating SW sites based on the first-order perturbation form of Wertheim’s theory is presented. An extended version of the Gibbs ensemble technique for inhomogeneous fluids [A. Z. Panagiotopoulos, Mol. Phys. 62, 701 (1987)] is used to predict the adsorption density profiles for associating fluids confined between opposite parallel walls. The fluid is confined in four kinds of walls: hard-wall, SW wall, Lennard-Jones (LJ) 12-6 wall potential, and LJ 10-4 wall potential. We analyze the behavior of the confined system for several supercritical temperatures as a function of variation of molecular parameters: potential range λ, bulk densities ρb*, pore width H, cutoff range interaction rc*, and range of the potential and depth of the particle-wall (λw, εw*). Additionally, we include predictions for liquid-vapor coexistence of bulk associative particles and how their critical properties are modified by the presence of associative sites in the molecule. The molecular simulation data presented in this work are of prime importance to the development of theoretical approaches for inhomogeneous fluids as classical density functional theory. The simulation results presented here are resourceful for predicting adsorption isotherms of real associating fluids such as water.
Study of iridium silicide monolayers using density functional theory
Authors: Popis Minh D. , Popis Sylvester V. , Oncel Nuri , Hoffmann Mark R. , Çakır Deniz
Published: February 2018

In this study, we investigated physical and electronic properties of possible two-dimensional structures formed by Si (silicon) and Ir (iridium). To this end, different plausible structures were modeled by using density functional theory and the cohesive energies calculated for the geometry of optimized structures, with the lowest equilibrium lattice constants. Among several candidate structures, we identified three mechanically (via elastic constants and Young's modulus), dynamically (via phonon calculations), and thermodynamically stable iridium silicide monolayer structures. The lowest energy structure has a chemical formula of Ir2Si4 (called r-IrSi2), with a rectangular lattice (Pmmn space group). Its cohesive energy was calculated to be −0.248 eV (per IrSi2 unit) with respect to bulk Ir and bulk Si. The band structure indicates that the Ir2Si4 monolayer exhibits metallic properties. Other stable structures have hexagonal (P-3m1) and tetragonal (P4/nmm) cell structures with 0.12 and 0.20 eV/f.u. higher cohesive energies, respectively. Our calculations showed that Ir-Si monolayers are reactive. Although O2 molecules exothermically dissociate on the surface of the free-standing iridium silicide monolayers with large binding energies, H2O molecules bind to the monolayers with a rather weak interaction.
Intrinsic electronic defects and multiple-atom processes in the oxidic semiconductor Ga2O3
Authors: Schmeißer Dieter , Henkel Karsten
Published: February 2018

We report on the electronic structure of gallium oxide (Ga2O3) single crystals as studied by resonant photoelectron spectroscopy (resPES). We identify intrinsic electronic defects that are formed by mixed-atomic valence states. We differentiate three coexisting defect states that differ in their electronic correlation energy and their spatial localization lengths. Their relative abundance is described by a fractional ionicity with covalent and ionic bonding contributions. For Ga2O3, our analyses of the resPES data enable us to derive two main aspects: first, experimental access is given to determine the ionicity based on the original concepts of Pauling and Phillips. Second, we report on multi-atomic energy loss processes in the Ga2p core level and X-ray absorption data. The two experimental findings can be explained consistently in the same context of mixed-atomic valence states and intrinsic electronic defects.
Double negatively charged carbon vacancy at the h- and k-sites in 4H-SiC: Combined Laplace-DLTS and DFT study
Authors: Capan Ivana , Brodar Tomislav , Pastuović Željko , Siegele Rainer , Ohshima Takeshi , Sato Shin-ichiro , Makino Takahiro , Snoj Luka , Radulović Vladimir , Coutinho José , Torres Vitor J. B. , Demmouche Kamel
Published: February 2018

We present results from combined Laplace-Deep Level Transient Spectroscopy (Laplace-DLTS) and density functional theory studies of the carbon vacancy (VC) in n-type 4H-SiC. Using Laplace-DLTS, we were able to distinguish two previously unresolved sub-lattice-inequivalent emissions, causing the broad Z1/2 peak at 290 K that is commonly observed by conventional DLTS in n-type 4H-SiC. This peak has two components with activation energies for electron emission of 0.58 eV and 0.65 eV. We compared these results with the acceptor levels of VC obtained by means of hybrid density functional supercell calculations. The calculations support the assignment of the Z1/2 signal to a superposition of emission peaks from double negatively charged VC defects. Taking into account the measured and calculated energy levels, the calculated relative stability of VC in hexagonal (h) and cubic (k) lattice sites, as well as the observed relative amplitude of the Laplace-DLTS peaks, we assign Z1 and Z2 to VC(h) and VC(k), respectively. We also present the preliminary results of DLTS and Laplace-DLTS measurements on deep level defects (ET1 and ET2) introduced by fast neutron irradiation and He ion implantation in 4H-SiC. The origin of ET1 and ET2 is still unclear.
Local viscosity distribution in bifurcating microfluidic blood flows
Authors: Kaliviotis E. , Sherwood J. M. , Balabani S.
Published: February 2018

The red blood cell (RBC) aggregation phenomenon is majorly responsible for the non-Newtonian nature of blood, influencing the blood flow characteristics in the microvasculature. Of considerable interest is the behaviour of the fluid at the bifurcating regions. In vitro experiments, using microchannels, have shown that RBC aggregation, at certain flow conditions, affects the bluntness and skewness of the velocity profile, the local RBC concentration, and the cell-depleted layer at the channel walls. In addition, the developed RBC aggregates appear unevenly distributed in the outlets of these channels depending on their spatial distribution in the feeding branch, and on the flow conditions in the outlet branches. In the present work, constitutive equations of blood viscosity, from earlier work of the authors, are applied to flows in a T-type bifurcating microchannel to examine the local viscosity characteristics. Viscosity maps are derived for various flow distributions in the outlet branches of the channel, and the location of maximum viscosity magnitude is obtained. The viscosity does not appear significantly elevated in the branches of lower flow rate as would be expected on the basis of the low shear therein, and the maximum magnitude appears in the vicinity of the junction, and towards the side of the outlet branch with the higher flow rate. The study demonstrates that in the branches of lower flow rate, the local viscosity is also low, helping us to explain why the effects of physiological red blood cell aggregation have no adverse effects in terms of in vivo vascular resistance.
Semiconducting SWNTs sorted by polymer wrapping: How pure are they?
Authors: Derenskyi Vladimir , Gomulya Widianta , Gao Jia , Bisri Satria Zulkarnaen , Pasini Mariacecilia , Loo Yueh-Lin , Loi Maria Antonietta
Published: February 2018

Short-channel field-effect transistors (FETs) prepared from semiconducting single-walled carbon nanotube (s-SWNT) dispersions sorted with poly(2,5-dimethylidynenitrilo-3,4-didodecylthienylene) are demonstrated. Electrical analysis of the FETs shows no evidence of metallic tubes out of a total number of 646 SWNTs tested, implying an estimated purity of our semiconducting SWNT solution higher than 99.85%. These findings confirm the effectiveness of the polymer-wrapping technique in selecting semiconducting SWNTs, as well as the potential of sorted nanotubes for the fabrication of short channel FETs comprising from 1 to up to 15 nanotubes without inter-nanotube junctions.
Relative permittivity in the electrical double layer from nonlinear optics
Authors: Boamah Mavis D. , Ohno Paul E. , Geiger Franz M. , Eisenthal Kenneth B.
Published: February 2018

Second harmonic generation (SHG) spectroscopy has been applied to probe the fused silica/water interface at pH 7 and the uncharged 11¯02 sapphire/water interface at pH 5.2 in contact with aqueous solutions of NaCl, NaBr, NaI, KCl, RbCl, and CsCl as low as several 10 μM. For ionic strengths up to about 0.1 mM, the SHG responses were observed to increase, reversibly for all salts surveyed, when compared to the condition of zero salt added. Further increases in the salt concentration led to monotonic decreases in the SHG response. The SHG increases followed by decreases are found to be consistent with recent reports of phase interference and phase matching in nonlinear optics. By varying the relative permittivity employed in common mean field theories used to describe electrical double layers and by comparing our results to available literature data, we find that models recapitulating the experimental observations are the ones in which (1) the relative permittivity of the diffuse layer is that of bulk water, with other possible values as low as 30, (2) the surface charge density varies with salt concentration, and (3) the charge in the Stern layer or its thickness varies with salt concentration. We also note that the experimental data exhibit sensitivity depending on whether the salt concentration is increased from low to high values or decreased from high to low values, which, however, is not borne out in the fits, at least within the current uncertainties associated with the model point estimates.
Nanostructure of propylammonium nitrate in the presence of poly(ethylene oxide) and halide salts
Authors: Stefanovic Ryan , Webber Grant B. , Page Alister J.
Published: February 2018

Nanoscale structure of protic ionic liquids is critical to their utility as molecular electrochemical solvents since it determines the capacity to dissolve salts and polymers such as poly(ethylene oxide) (PEO). Here we use quantum chemical molecular dynamics simulations to investigate the impact of dissolved halide anions on the nanostructure of an archetypal nanostructured protic ionic liquid, propylammonium nitrate (PAN), and how this impacts the solvation of a model PEO polymer. At the molecular level, PAN is nanostructured, consisting of charged/polar and uncharged/nonpolar domains. The charged domain consists of the cation/anion charge groups, and is formed by their electrostatic interaction. This domain solvophobically excludes the propyl chains on the cation, which form a distinct, self-assembled nonpolar domain within the liquid. Our simulations demonstrate that the addition of Cl− and Br− anions to PAN disrupts the structure within the PAN charged domain due to competition between nitrate and halide anions for the ammonium charge centre. This disruption increases with halide concentration (up to 10 mol. %). However, at these concentrations, halide addition has little effect on the structure of the PAN nonpolar domain. Addition of PEO to pure PAN also disrupts the structure within the charged domain of the liquid due to hydrogen bonding between the charge groups and the terminal PEO hydroxyl groups. There is little other association between the PEO structure and the surrounding ionic liquid solvent, with strong PEO self-interaction yielding a compact, coiled polymer morphology. Halide addition results in greater association between the ionic liquid charge centres and the ethylene oxide components of the PEO structure, resulting in reduced conformational flexibility, compared to that observed in pure PAN. Similarly, PEO self-interactions increase in the presence of Cl− and Br− anions, compared to PAN, indicating that the addition of halide salts to PAN decreases its utility as a molecular solvent for polymers such as PEO.
Polymer solar cells: P3HT:PCBM and beyond
Authors: Berger P. R. , Kim M.
Published: February 2018

For the last two decades, polymer solar cells (PSCs) have been a cynosure of the photovoltaic community, as evidenced by the growing number of patent applications and scientific publications. Efforts to achieve high power conversion efficiency in PSC, propelled by advances in device architecture, material combination, and nanomorphology control, evolved into poly(3-hexylthiophene-2,5-diyl) (P3HT):phenyl-C61-Butyric-Acid-Methyl Ester (PCBM) bulk heterojunction PSCs, which had been the best seller in PSC research for a decade. Subsequently, PSC research was redirected towards the synthesis of low bandgap materials and optimization of tandem cells, which led to a power conversion efficiency of ∼13%. Even though this efficiency may not be sufficient enough to compete with that of inorganic solar cells, unique properties of PSCs, such as mass roll-to-roll production capability, as well as flexibility and lightness, suggest their niche market opportunities. In this review, an overview of developments in PSCs is presented during the last three decades encompassing pre- and post-P3HT:PCBM era. Emphasis is given on evolution in device architecture, coupled with material selection for pre-P3HT:PCBM era, and synthesis of low-bandgap materials, coupled with a tandem structure for post-P3HT:PCBM era. Last but not least, efforts toward the longer operational lifetime of PSCs by encapsulation are reviewed.
The critical particle size for enhancing thermal conductivity in metal nanoparticle-polymer composites
Authors: Lu Zexi , Wang Yan , Ruan Xiulin
Published: February 2018

Polymers used as thermal interface materials are often filled with high-thermal conductivity particles to enhance the thermal performance. Here, we have combined molecular dynamics and the two-temperature model in 1D to investigate the impact of the metal filler size on the overall thermal conductivity. A critical particle size has been identified above which thermal conductivity enhancement can be achieved, caused by the interplay between high particle thermal conductivity and the added electron-phonon and phonon-phonon thermal boundary resistance brought by the particle fillers. Calculations on the SAM/Au/SAM (self-assembly-monolayer) system show a critical thickness Lc of around 10.8 nm. Based on the results, we define an effective thermal conductivity and propose a new thermal circuit analysis approach for the sandwiched metal layer that can intuitively explain simulation and experimental data. The results show that when the metal layer thickness decreases to be much smaller than the electron-phonon cooling length (or as the “thin limit”), the effective thermal conductivity is just the phonon portion, and electrons do not participate in thermal transport. As the thickness increases to the “thick limit,” the effective thermal conductivity recovers the metal bulk value. Several factors that could affect Lc are discussed, and it is discovered that the thermal conductivity, thermal boundary resistance, and the electron-phonon coupling factor are all important in controlling Lc.
Effects of hydrostatic pressure on spin-lattice coupling in two-dimensional ferromagnetic Cr2Ge2Te6
Authors: Sun Y. , Xiao R. C. , Lin G. T. , Zhang R. R. , Ling L. S. , Ma Z. W. , Luo X. , Lu W. J. , Sun Y. P. , Sheng Z. G.
Published: February 2018

Spin-lattice coupling plays an important role in both formation and understanding of the magnetism in two-dimensional magnetic semiconductors (2DMS). In this paper, the steady pressure effects on the lattice structure, Raman resonances, and magnetization of a 2DMS Cr2Ge2Te6 have been studied by both experiments and first principles calculations. It is found that the bond length of Cr-Cr decreases, the angle of Cr-Te-Cr diverges from 90°, and the Raman modes Eg3 and Ag1 show an increase with the application of external pressure. Consequently, the magnetic phase transition temperature TC decreases from 66.6 K to 60.6 K (∼9%) as the pressure increases from 0 to 1 GPa. These pressure effects not only confirm the existence of strong spin-lattice coupling but also reveal the detailed information about the lattice deformation effect on the magnetic properties in such 2DMS, which would be a benefit for the further understanding and manipulation of the magnetism in 2D materials.
Adsorption of squaraine molecules to Au(111) and Ag(001) surfaces
Authors: Luft Maike , Groß Boris , Schulz Matthias , Lützen Arne , Schiek Manuela , Nilius Niklas
Published: February 2018

The adsorption of anilino squaraines, an important chromophore for the use in organic solar cells, to Ag(001) and Au(111) has been studied with scanning tunneling microscopy. Self-assembly into square building blocks with eight molecules per unit cell is revealed on the Ag surface, while no ordering effects occur on gold. The squaraine-silver interaction is mediated by the carbonyl and hydroxyl oxygens located in the center of the molecule. The intermolecular coupling, on the other hand, is governed by hydrogen bonds formed between the terminal isobutyl groups and oxygen species of adjacent molecules. The latter gets maximized by rotating the molecules by a few degrees against a perfect square alignment. A similar molecular pattern does not form on Au(111) due to symmetry mismatch. Moreover, the high electronegativity of gold reduces the directing effect of oxygen-metal bonds that trigger the ordering process on silver. As a consequence, only frustrated three-fold symmetric units that do not expand into an ordered molecular network are present on the gold surface.
Modeling of surface roughness effects on Stokes flow in circular pipes
Authors: Song Siyuan , Yang Xiaohu , Xin Fengxian , Lu Tian Jian
Published: February 2018

Fluid flow and pressure drop across a channel are significantly influenced by surface roughness on a channel wall. The present study investigates the effects of periodically structured surface roughness upon flow field and pressure drop in a circular pipe at low Reynolds numbers. The periodic roughness considered exhibits sinusoidal, triangular, and rectangular morphologies, with the relative roughness (i.e., ratio of the amplitude of surface roughness to hydraulic diameter of the pipe) no more than 0.2. Based upon a revised perturbation theory, a theoretical model is developed to quantify the effect of roughness on fully developed Stokes flow in the pipe. The ratio of static flow resistivity and the ratio of the Darcy friction factor between rough and smooth pipes are expressed in four-order approximate formulations, which are validated against numerical simulation results. The relative roughness and the wave number are identified as the two key parameters affecting the static flow resistivity and the Darcy friction factor.
Fast neutron irradiation tests of flash memories used in space environment at the ISIS spallation neutron source
Authors: Andreani C. , Senesi R. , Paccagnella A. , Bagatin M. , Gerardin S. , Cazzaniga C. , Frost C. D. , Picozza P. , Gorini G. , Mancini R. , Sarno M.
Published: February 2018

This paper presents a neutron accelerated study of soft errors in advanced electronic devices used in space missions, i.e. Flash memories performed at the ChipIr and VESUVIO beam lines at the ISIS spallation neutron source. The two neutron beam lines are set up to mimic the space environment spectra and allow neutron irradiation tests on Flash memories in the neutron energy range above 10 MeV and up to 800 MeV. The ISIS neutron energy spectrum is similar to the one occurring in the atmospheric as well as in space and planetary environments, with intensity enhancements varying in the range 108- 10 9 and 106- 10 7 respectively. Such conditions are suitable for the characterization of the atmospheric, space and planetary neutron radiation environments, and are directly applicable for accelerated tests of electronic components as demonstrated here in benchmark measurements performed on flash memories.
In-flight neutron spectra as an ICF diagnostic for implosion asymmetries
Authors: Cerjan C. , Sayre D. B. , Sepke S. M.
Published: February 2018

The yield and spectral shape of the neutrons produced during in-flight reactions provide stringent constraints upon the symmetry of the fully compressed fuel conditions in Inertial Confinement Fusion implosions. Neutron production from a specific deuterium gas-filled implosion is simulated in detail and compared with the experimental neutron spectra along two lines-of-sight. An approximate reactivity formulation is applied to obtain further insight into the underlying fuel configuration. This analysis suggests that the differences observed in the observed spectra correspond to angularly dependent triton velocity distributions created by an asymmetric plasma configuration.
Plasmonic-enhanced targeted nanohealing of metallic nanostructures
Authors: Yang Hangbo , Lu Jinsheng , Ghosh Pintu , Chen Ziyao , Wang Wei , Ye Hui , Yu Qian , Qiu Min , Li Qiang
Published: February 2018

Healing defects of metallic structures is an essential procedure for manufacturing and maintaining integrated devices. Current nanocomposite-assisted microhealing methodologies are inadequate for nanoscopic applications because of their concomitant contamination and limited operation accuracy. In this paper, we propose an optically controllable targeted nanohealing technique by utilizing the plasmonic-enhanced photothermal effect. The healing of nanogaps between two silver nanowires (NWs) is achieved by increasing the incident laser power in steps. Partial connection of NWs can be readily obtained using this technique, while near-perfect connection of NWs with the same crystal orientations is obtained only when the lattices on the two opposing facets are matched after recrystallization. This non-contaminating nanohealing technique not only provides deeper insight into the heat/mass transfer assisted by plasmonic photothermal conversion in the nanoscale but also suggests avenues for recovering mechanical, electronic, and photonic properties of defected metallic nanodevices.
Robust method for long-term energy and pointing stabilization of high energy, high average power solid state lasers
Authors: Boge Robert , Horáček Jakub , Mazůrek Petr , Naylon Jack A. , Green Jonathan T. , Hubka Zbyněk , Šobr Václav , Novák Jakub , Batysta František , Antipenkov Roman , Bakule Pavel , Rus Bedřich
Published: February 2018

A robust and simple method is presented for ensuring constant energy and pointing of a high average power solid state laser on a target. In addition to providing long-term stability, this scheme also eliminates any drifts in energy or pointing resulting from the initial warm-up after a cold start. This is achieved using two separate feedback loops: one loop stabilizes the pointing of the beam external to the amplifier cavity and the other locks the cavity mode to have optimum overlap with the pump spot on the active medium. The key idea of the cavity mode stabilization is to monitor the overlap of the cavity mode and the gain medium with a camera and control it with an actively controlled, intra-cavity mirror. While this method is demonstrated on a thin-disk regenerative amplifier, it can also be applied to a wide variety of solid state laser amplifiers.
Enhanced output-performance of piezoelectric poly(vinylidene fluoride trifluoroethylene) fibers-based nanogenerator with interdigital electrodes and well-ordered cylindrical cavities
Authors: Gui Jinzheng , Zhu Yezi , Zhang Lingling , Shu Xi , Liu Wei , Guo Shishang , Zhao Xingzhong
Published: February 2018

A piezoelectric nanogenerator based on poly(vinylidene fluoride trifluoroethylene) [P(VDF-TrFE)] nanofibers with an Au interdigital electrode (IDT)/P(VDF-TrFE) nanofiber film/well-ordered cylindrical cavity structure was prepared by combining Au IDTs with a rotary collector to obtain highly aligned P(VDF-TrFE) nanofiber arrays. The Au IDTs work not only as parallel electrodes to collect P(VDF-TrFE) nanofibers during electrospinning but also as charge-collecting electrodes in the nanogenerator. The well-ordered cylindrical cavities improve output performance by enhancing the deformation of P(VDF-TrFE) nanofiber films when subjected to external force. The nanogenerator performs well; as an example of application, we demonstrate energy harvesting from human walking, with a peak output voltage of 5 V and a peak short-circuit current of 1.2 μA. Such a device could have practical applications in wearable, self-powered devices.
Communication: The electronic entropy of charged defect formation and its impact on thermochemical redox cycles
Authors: Lany Stephan
Published: February 2018

The ideal material for solar thermochemical water splitting, which has yet to be discovered, must satisfy stringent conditions for the free energy of reduction, including, in particular, a sufficiently large positive contribution from the solid-state entropy. By inverting the commonly used relationship between defect formation energy and defect concentration, it is shown here that charged defect formation causes a large electronic entropy contribution manifesting itself as the temperature dependence of the Fermi level. This result is a general feature of charged defect formation and motivates new materials design principles for solar thermochemical hydrogen production.
Nanocrystalline SiC film thermistors for cryogenic applications
Authors: Mitin V. F. , Kholevchuk V. V. , Semenov A. V. , Kozlovskii A. A. , Boltovets N. S. , Krivutsa V. A. , Slepova A. S. , Novitskii S. V.
Published: February 2018

We developed a heat-sensitive material based on nanocrystalline SiC films obtained by direct deposition of carbon and silicon ions onto sapphire substrates. These SiC films can be used for resistance thermometers operating in the 2 K–300 K temperature range. Having high heat sensitivity, they are relatively low sensitive to the magnetic field. The designs of the sensors are presented together with a discussion of their thermometric characteristics and sensitivity to magnetic fields.