bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of titanium plate fixation on bone healing
Authors: Abdullah Norain Binti , Nakai Masaaki , Kawamura Yuki , Yamamoto Ei , Niinomi Mitsuo
Published: October 2020

Bone formation which is a process before bone remodeling in fracture healing process, was investigated in this study by fixing metallic plate after an artificially created defect in a rabbit femur. Although a complete bone remodeling takes about 6 weeks, present study was conducted by observing the condition of the bone within 3 weeks of healing period. An artificial defect was made in a rabbit femur and Ti-6Al-4V ELI (Ti-64) fixation plate was fixed with two screws on both ends while a defect without fixation was set as the control. After 3 weeks, the femur bone was harvested and evaluated with scanning electron microscopy, Vickers hardness test, and X-ray diffraction analysis. Ti-64 fixation showed rapid bone formation but external callus remaining on the defect area and its surrounding bone area. This bone callus may be replaced with healed bone with the passage of time. On the other hand, control showed incomplete bone formation and bone callus formed in the area without the defect, including further regions from the defect area. This may be affected by irregular load transmission and instability around the bone defect area. We conclude that, Ti-64 fixation shows better bone formation and bone hardness than the control.
Oxygen/nitrogen-assisted embrittlement of titanium alloys exposed at elevated temperature
Authors: Texier D. , Sirvin Q. , Velay V. , Salem M. , Monceau D. , Mazères B. , Andrieu E. , Roumiguier R. , Dod B.
Published: October 2020

Due to high solubility of oxygen and nitrogen in titanium alloys, the influence of the diffusion zone on the macroscopic tensile properties of pre-oxidized annealed Ti-6Al-4V tensile specimens was examined at room temperature. Thin microtensile specimens were prepared with different thicknesses ranging from 100 µm to 500 µm and then exposed at 750°C for durations between 5 and 200h. A dedicated gripping technique was developed in the present study to investigate the brittleness of such pre-oxidized and ultrathin specimens at room temperature. Tensile testing was paired with digital image correlation techniques to assess both macroscopic deformation and full-field strain maps. High temperature pre-oxidation treatments significantly decreased the ductility of the specimen and the tensile strength of the materials (yield strength and ultimate tensile strength). Fractographic examinations revealed typical brittle fracture features in the oxygen/nitrogen-affected diffusion zone in the periphery of the cross-section while the fracture remained ductile in the core of the specimen for most of the specimens. Some specimens fully failed in a brittle manner for “(pre-ox. duration)1/2/thickness” configurations with ratio equal or higher than 0.45 h1/2.µm-1.
Thermodynamic Investigation of Titanium Hydride Formation from Reduction of Titanium (Ⅳ) Chloride with Magnesium Hydride in Presence of Hydrogen Atmosphere
Authors: Ardani Mohammad Rezaei , Noor Ahmad Fauzi Mohd , Sheikh Abdul Hamid Sheikh Abdul Rezan , Rahman Mohamed Abdul , Lee Hooi Ling , Ibrahim Ismail
Published: October 2020

Thermodynamic assessment and experimental investigation for formation of titanium hydride (TiH2) from reduction of titanium tetrachloride (TiCl4) with magnesium hydride (MgH2) were carried out under hydrogen atmosphere. In this method, TiH2 production at low temperature was investigated, which can be used for further dehydrogenation process in titanium powder metallurgy. The effects of temperature, time, amount of titanium trifluoride (TiF3) as catalyst, and ball milling time of MgH2 on reduction process were evaluated. The range of each parameters were set to 250-350°C for temperature, 2-4 hr for reaction time, 4-10 wt% for TiF3, and 1-2 hr for ball milling time. The phase transformations after reduction process were studied by X-ray diffraction (XRD) and energy-dispersive X-ray (EDX) analyziz. The morphology of powders was analyzed by scanning electron microscope (SEM). The results showed that titanium trichloride (TiCl3) was formed as major product in experiments for the above conditions. However, with increasing the reaction time above 10hr, characterization study of the final products confirmed the formation of TiH2 as major product. Our findings indicated that producing of TiH2 from reduction of TiCl4 with MgH2 at low temperature was feasible and could lead to low cost synthesis method for TiH2 for titanium powder production.
Laser based manufacturing of titanium aluminides
Authors: Rittinghaus Silja-Katharina , Molina Ramirez Veronica Rocio , Vogelpoth Andreas , Hecht Ulrike , Schmelzer Janett
Published: October 2020

Lightweight titanium aluminides (TiAl, ρ = 3.9 – 4.1 g/cm3) gain in importance as high temperature structural material. The known properties like high strength and creep resistance combined with high corrosion and wear are of continuous interest for turbomachinery applications like low pressure turbine blades. Additive manufacturing (AM) provides the possibility for near-net-shape production of functional complex parts and can contribute to reduce consumption and costs of material, tooling and finishing. The typical high brittleness and oxygen affinity of TiAl cause special requirements for processing this material with AM. In this work, recent progress in Additive Manufacturing of the TiAl alloys of the nominal compositions Ti-43.5Al-4Nb-1Mo-0.1B (at.-percent, TNM™-B1), Ti-48Al-2Cr-2Nb (at.-percent, GE4822) and Ti-45Al-2Nb-2Mn-0.8B (at.-percent, 4522XDTM) is presented. Microstructures resulting from both Laser Powder Bed Fusion (LPBF) and Direct Laser Deposition (DED) are compared with respect to the characteristics of the manufacturing processes. Hardness measurements according to Vickers are performed, and pressure strength tests are performed on selected samples. The crack-free additive manufacturing of complex geometries made of TiAl is demonstrated as well as an approach for manufacturing hybrid parts combining DED and LPBF.
Industrial applications of modelling tools to simulate the PAMCHR casting and VAR process for Ti64
Authors: Doridot Emiliane , Hans Stéphane , Jardy Alain , Bellot Jean-Pierre
Published: October 2020

The PAMCHR (Plasma Arc Melting Cold Hearth Refining) process followed by a VAR (Vacuum Arc Remelting) melting is used to recycle Ti64 scrap for aeronautical applications. The produced ingot quality is linked to the quality of charging materials and to numerous operating parameters. Ecotitanium (a company created by UKAD, a joint-venture between Aubert & Duval and UKTMP, ADEME and Crédit Agricole Centre France) launched a program with the Institut Jean Lamour dedicated to the development of specific modelling tools in order to get a better understanding of operating parameters effect on the final ingot quality. A model of the PAMCHR casting was developed and used to describe the heat transfer, liquid metal flow and alloying elements behavior during mixing in the liquid pool followed by segregation during solidification. The effect of PAMCHR electrode composition on the final VAR ingot composition is also studied using the SOLAR VAR model. Model validation by comparison with industrial ingots is presented with some examples of operating parameters sensitivity study.
Titanium alloy design and casting process development using an Integrated Computational Materials Engineering (ICME) approach
Authors: Liang Zhi , Miao Jiashi , Sachdev Anil K. , Williams James C. , Luo Alan A.
Published: October 2020

The application of titanium components is generally limited by their high raw material and manufacturing costs. In this paper, a lower cost cast titanium alloy based on the Ti-Al-Fe system has been designed using an ICME approach. The new alloy Ti-6Al-5Fe-0.05B-0.05C (all wt.%) significantly reduces raw material cost and demonstrates improved castability compared with the baseline Ti-6Al-4V alloy. The fine primary and secondary α phase microstructure in the new alloy, due to Fe partitioning, provides exceptionally high strength (1023 MPa yield strength and 1136 MPa ultimate tensile strength) and reasonable ductility (3.7% elongation) for structural applications. On the manufacturing front, the high cost multi-step investment casting process currently used can now be replaced with a low-cost permanent mold casting process using steel molds and a novel ceramic coating. An experimental casting setup, including an induction skull melting (ISM) system, a gravity tilt-pour system and a ceramic-coated H13 steel mold, has been used to produce near-net-shape permanent metallic mold castings with the new titanium alloy developed. Using this setup, and aided by casting process simulation, a prototype automotive connecting rod was cast successfully. The ZrO2 ceramic coating applied to the H13 steel mold was proven effective in minimizing the metal-mold reactions.
Transformations, Recrystallization, Microtexture and Plasticity in Titanium Alloys
Authors: Balachandran Shanoob , Tripathi Abhishek , Banerjee Arunima , Chinara Manaswini , Teja Ravi , Suresha S.J. , Choudhuri Deep , Banerjee Rajarshi , Banerjee Dipankar
Published: October 2020

The objective of this contribution is to summarise the range of α crystallography and distribution that arises from the β to α transformation and the hot working of α/β alloys and their recrystallisation and relate these features to the slip character of these alloys. α morphology and distribution have been mapped as a function of β stabilizer content and aging temperature. A dominant transgranular grouping of α variants with a common close packed direction characterizes transformation patterns across the entire range of β stabilizer content. Recrystallization during thermomechanical processing in the α/β regime has been studied with the help of fine scale, orientation image mapping techniques. Two distinct recrystallization processes have been identified. The first is associated with the well-known α globularisation process. An alternative recrystallization process has also been described in which newly recrystallized α and β grains form with the Burgers orientation relationship with each other. This process has been called epitaxial recrystallization. The role of transformation and recrystallisation texture on the plasticity of titanium alloys is assessed through quantitative EBSD /TEM based analysis of slip systems in the α phase and slip transfer between the α and β phases.
Significantly fast spinodal decomposition and inhomogeneous nanoscale martensitic transformation in Ti–Nb–O alloys
Authors: ISHIGURO Yuya , TSUKADA Yuhki , KOYAMA Toshiyuki
Published: October 2020

The β phase spinodal decomposition during continuous cooling in Ti‒Nb‒O alloys is investigated by the phase-field method. Addition of only a few at.%O to Ti‒23Nb (at.%) alloy remarkably increases the driving force of the β phase spinodal decomposition. During isothermal heat treatment at 1000 K and 1100 K in Ti‒23Nb‒3O (at.%) alloy, the β phase separates into β1 phase denoted as (Ti)1(O, Va)3 and β2 phase denoted as (Ti, Nb)1(Va)3, resulting in the formation of nanoscale concentration modulation. The phase decomposition progresses in 0.3‒20 ms. In Ti‒23Nb‒XO alloys (X = 1.0, 1.2, 2.0), the spinodal decomposition occurs during continuous cooling with the rate of 500 K s‒1, indicating that the spinodal decomposition occurs during water quenching in the alloys. It is assumed that there is a threshold value of oxygen composition for inducing the spinodal decomposition because it does not occur during continuous cooling in Ti‒23Nb‒0.6O (at.%) alloy. The concentration modulation introduced by the β phase decomposition has significant effect on the β→α” martensitic transformation. Hence, it seems that for controlling microstructure and mechanical properties of Ti‒Nb‒O alloys, careful control of heat treatment temperature and cooling rate condition is required.
Effects of Mo segregation on Charpy absorbed energy in Ti-12Mo alloys
Authors: Emura Satoshi , Ji Xin , Min Xiaohua , Tsuchiya Koichi
Published: October 2020

Beta phase stabilizing elements such as Mo have strong tendency to segregate. We have introduced swirly type segregation of Mo in Ti-12Mo (mass %) alloy through groove bar rolling. After solution treatment and low temperature aging, hard omega phase was precipitated heterogeneously, which improved the room temperature tensile elongation values without sacrificing tensile strength. In this study, the effect of Mo segregation and heterogeneous distribution of omega phase on Charpy absorbed energy was investigated in Ti-12Mo alloy. Samples with two types of segregation were prepared; namely, swirly segregation in bar rolled sample and layered segregation in plate rolled sample. For comparison, we have also prepared Ti-12Mo bar samples with lesser Mo segregation, through high temperature thermomechanical treatment. Charpy impact tests were carried out at room temperature, 373 K and 473 K, respectively, using the samples after aging to introduce isothermal omega-phase. The samples with the segregation exhibited higher Charpy absorbed energy, especially at higher temperature of 473 K, while the sample with the swirly segregation showed higher Charpy absorbed energy than that with the layered segregation. The sample with lesser Mo segregation exhibited brittle intergranular fracture surface after Charpy testing. On the contrary, samples with Mo segregation exhibited ductile transgranular fracture surfaces.
In-situ EBSD characterization of deformation behavior of primary alpha phase in Ti-6Al-4V
Authors: Li Wansong , Yamasaki Shigeto , Mitsuhara Masatoshi , Nakashima Hideharu
Published: October 2020

Uniaxial tension experiments and electron back-scatter diffraction were performed on a bimodal Ti-6Al-4V alloy to study the deformation behavior of primary hcp-Ti (αp). It was found that the obtained tensile strength and elongation of the studied Ti-6Al-4V from the in-situ tensile test are higher than of which derived from the regular tensile test. The strain could be accommodated by the activation of slip systems and by grain rotations during the deformation. The prismatic slip is the primary slip mode of αp. According to kernel average misorientation analysis, we found that the dislocations mainly distributed near grain boundaries and subgrain boundaries, and partially located around slip lines. Calculated rotation angles and average rotation rates show that the rotation heterogeneity occurred among grains and subgrains.
Thermal Stability and Recrystallization of Titanium Grade 4 with Ultrafine-Grained Structure
Authors: Dyakonov Grigory , Mironov Sergey , Yakovleva Tatyana , Semenova Irina
Published: October 2020

The paper examined annealing behavior of ultrafine-grained Ti Grade 4. The ultrafine-grained microstructure was produced by equal-channel angular pressing (ECAP) technique by using a Conform scheme and was characterized by a mean grain size of d=0.3 μm and non-equilibrium grain boundaries. The ultrafine-grained structure was found to be stable up to 400°C. The excellent thermal stability was attributed to a strain-ageing, i.e., the enhanced diffusion of interstitial solutes resulting in a formation of solute atmospheres at/near grain boundaries and dislocations. At 450–500°C, a rapid growth of strain-free grains was observed to occur. This process eliminated severely-deformed microstructure and gave rise to abrupt material softening. A further increase of the annealing temperature above 600°С resulted in precipitation of lenticular dispersoids as well as iron-rich globular β-particles. This surprising phenomenon promoted a subtle hardening effect.
TRIP Titanium Alloy Design
Authors: Meng Fan , Yan Jia-Yi , Olson Gregory B
Published: October 2020

Building on successful development experience of transformation induced plasticity (TRIP) steels, an analogous concept was taken to design high performance titanium alloys. This article describes a computational design framework of novel near-α TRIP titanium alloys with both high yield strength and fracture toughness for naval structural applications using a systems design approach integrating processing/structure/properties/performance relations. Predictive models including a transformation stability model based on Olson-Cohen heterogeneous martensite nucleation theory for titanium alloys was proposed. Integration of the models with CALPHAD software and databases enables parametric design optimization to meet design objectives. The developed models were calibrated with experimental measurements.
Development of α - β type titanium alloy Ti-4.5Al-2.5Cr-1.2Fe-0.1C-0.3Cu-0.3Ni having good forgeability and machinability
Authors: KONNO Takashi , TAMURA Keitaro , ITSUMI Yoshio , YOKOCHI Kohei , AKAZAWA Koichi , OYAMA Hideto , CHODA Takashi
Published: October 2020

Development of a titanium alloy having excellent hot forgeability and machinability while having the same properties as Ti-64 alloy is effective in reducing the total cost of titanium parts. To develop a new alpha-beta type titanium alloy which has good hot forgeability, machinability and tensile properties equivalent to those of Ti-64 alloy at room temperature, Ti-4.5Al-2.5Cr-1.2Fe-0.1C-nCu-nNi (n=0 to 2) were prepared and evaluated.

The new alloy showed tensile properties equivalent to that of Ti-64 alloy at room temperature. On the other hand, the hot deformation stress of new alloy was about 30% lower than that of Ti-64 alloy, and the excellent deformability was confirmed. The addition of Cu and Ni to Ti-4.5Al-2.5Cr-1.2Fe-0.1C alloy suppressed the amount of wear of tool and improved the machinability. Tool life of new alloy machining is extended by about 1.5 times compared to that of Ti-64 alloy. Addition of Cu and Ni is considered to reduce the reactivity between tool and workpiece and improve machinability.
Plastic deformation of beta-Ti-Mo alloys with isothermal omega phase
Authors: Tsuchiya Koichi , Emura Satoshi , Ji Xin , Gutierrez Ivan , Hara Toru
Published: October 2020

Aging of metastable beta-Ti alloys leads to the precipitation of omega phase, resulting in a significant loss in ductility (omega brittleness). This presentation reports the results of 3D observations of isothermal omega phase by an orthogonal FIB/SEM system. It was revealed that the shape of omega phase particles varies with the particle size. By serial sectioning, it was possible to obtain a 3D image for the volume of several micrometer cube containing numerous omega particles. The volume fraction of omega phase was qualitatively determined. The value was much lower than the previous investigation by X-ray diffraction by Hickman in 1969. The SEM and TEM revealed the formation of shear bands in the cold rolled samples, where the shearing of omega phase and transformation into beta phase while maintaining the depletion of Mo was found. After the HPT deformation, white etching layers are formed near the median plane of the disc, where the omega phase particles were absent and exhibit significantly lower hardness values. These findings may help to clarify the cause of brittleness in beta Ti alloys with isothermal omega phase.
Mechanisms of oxide dependent tribological behavior in Ti / Steel sliding and influence of nanostructured surfaces
Authors: Maurel Pierre , Weiss Laurent , Bocher Philippe , Fleury Eric , Grosdidier Thierry
Published: October 2020

The tribological behavior of pure titanium having coarse-grained or nanostructured surfaces has been investigated against a steel ball moved with an alternative motion. The nanostructures were obtained by Surface Mechanical Attrition Treatment (SMAT) both at room and at cryogenic temperatures. An unexpected wear behavior was revealed: the hard steel ball was abraded for all cases even if it was several times harder compared to the Ti surface. This was due to the formation of a third body consisting of hard Ti oxides. Interestingly, important variations of the coefficient of friction were also revealed during the rubbing process. These variations could be separated into three successive stages, each with its specific wear mechanisms. The wear regimes were related to changes in the third body layer formed between the Ti and steel surfaces. SMAT changed the formation kinetics of the third body. The temperature at which the SMAT was conducted also introduced different third body formation kinetics. Important variations in the wear resistance were consequently observed between each surface condition.
MICROSTRUCTURAL EVOLUTIONS AND MECHANICAL PROPERTIES DURING LONG-TERM AGEING OF TITANIUM ALLOY Ti-17
Authors: Maury Nicolas , Dehmas Moukrane , Archambeau-Mirguet Claude , Delfosse Jérôme , Aeby-Gautier Elisabeth
Published: October 2020

Microstructural evolutions and resulting mechanical properties have been investigated in the near-β Ti-17 alloy following long- term ageing heat-treatment up to 6000 h at 450 °C. The initial microstructure was bimodal lamellar, consisting of two populations of α grains (αlam-primary and αsecondary) in a β phase matrix. Two microstructures were obtained either via controlled heat- treatments from the β phase field - in order to generate significant differences in the grain fraction, size, density and spatial distribution - or sampled from a part submitted to an industrial processing route. High energy XRD reveals that whatever the initial microstructure, the amount of α phase increases significantly after 1000 h long-term ageing. Complementary SEM and image analysis characterizations enable to deduce that this evolution is the consequence of αsecondary growth and/or coarsening. Also, TEM observations and EDX analysis show that the Mo and Cr contents of the β phase increase and that α2 nano-precipitates form within the αlam-primary grains. Considering the mechanical properties, long-term ageing leads to an increase in the yield and ultimate tensile strength, as well as a decrease in the elongation at failure, at an extent which depends on the ageing time.
Dynamic recrystallization behavior of the Ta-containing TiAl alloy in isothermal deformation
Authors: Luo Y.Y. , Mao X.N. , Yang H.Y. , Yin Y.F. , Zhao Z.Z. , Guo D.Z.
Published: October 2020

The dynamic recrystallization behavior of as-cast Ti-46.5Al-3Ta-2Cr-0.2W alloy during isothermal compression process with nominal deformation of 50% and strain rates from 0.01s to 1s was investigated by electron microscopy. The results showed that the deformation mechanism of this alloy can be concluded as grain boundary sliding and mechanical twins, which induce the final dynamic recrystallization. The phase boundary bulging was found to be the major nucleation mechanism responsible for the lamellar globularization and the formation of recrystallized γ grains inside the lamellar colony under the high strain rate. The recrystallized γ grains induced by the twinning is the main mechanism for refining α2 lamellar microstructures under low strain rate.
Elastic constants of Ti-15Mo single crystals and their evolution with thermal treatment
Authors: Janovskaa M. , Nejezchlebova J. , Sedlak P. , Grabec T. , Stoklasova P. , Smilauerova J. , Janecek M. , Kratky S. , Seiner H.
Published: October 2020

Elastic constants of single crystals of metastable β-phase of the Ti-15Mo alloy were studied by ultrasonic methods with the aim to observe the dependence of these constants on formation of isothermal ω particles. Two ultrasonic methods were applied: resonant ultrasound spectroscopy for monitoring the temperature evolution of the elastic constants, and transient grating spectroscopy for identification of the local material symmetry at a fixed temperature. Samples with different heat treatments (isothermal ageing at 300 °C and ageing under the same temperature with uniaxial [111] loading) were studied. The results prove that the isothermal omega particles always exactly follow the original cubic symmetry of the β matrix, and that the evolutions of the elastic constants of the β-ω multi-phase crystals can be reliably approximated using Hill’s homogenizing procedure, assuming cubic elastic constants of the β-phase and isotropic elastic constants representing the ω particles.
Effect of microstructure on Ti3Al precipitation during ageing of Ti-6Al-4V alloy
Authors: Callegari B. , Marçola J. V. , Aristizabal K. , Soldera F. A. , Mücklich F. , Pinto H. C.
Published: October 2020

The aim of the present work is to explore the age-hardening potential of Ti-6Al-4V (Ti-64) alloy with variation of the starting microstructure, with attention to the precipitation of nano-sized Ti3Al phase, as influenced by microstructural features. The alloy was either solution-treated or deformed by compression at temperatures above and below its β-transus to produce microstructures comprising martensitic, lamellar and globular α morphologies, as well as the existence or absence of β phase, and subsequently submitted to ageing treatments at 400°C/8h using in situ x-ray diffraction. Precipitated fractions of Ti3Al were obtained via Rietveld refinement and aged microstructures were characterized by micro-hardness measurements. Results show that α2 precipitation is favored by a globular morphology of α and hindered by a martensitic α morphology, and suggest that the presence of β phase also has as influence on precipitation.
Direct Evidence for Dynamic Phase Transformation during High Temperature Deformation in Ti-64
Authors: Daniel Christopher S. , Nguyen Chi-Toan , Atkinson Michael D. , da Fonseca João Quinta
Published: October 2020

The microstructure of Ti-64 strongly affects the forming and in-service behaviour of aerospace components. The development of microstructure, including crystallographic texture, during thermomechanical processing involves changes caused by deformation, annealing and phase transformation. Recently, it has been reported that deformation and transformation occur concurrently, in a dynamic α → β transformation process, driven by the net flow softening it produces. Here, we present the results of an in-situ synchrotron diffraction experiment that aimed to detect and measure the extent of dynamic phase transformation during hot deformation and its contribution to the crystallographic texture of the alloy. Forged Ti-64 samples were deformed in uniaxial tension at 950°C and a strain rate of about 0.02 s-1, using an electro-thermal mechanical tester (ETMT) mounted on the I12: JEEP beamline at Diamond Light Source. By using a high energy 89 keV synchrotron X-ray beam and a fast acquisition rate (10 Hz) we were able to measure, during deformation, the internal elastic lattice strains in the two phases, the crystallographic texture of both phases and the α → β phase fraction. The results show, for the first time, direct evidence of dynamic transformation during isothermal hot deformation.
Selection of the optimal air liquefaction cycle for liquid air energy storage
Authors: Shmeleva Elizaveta A. , Arkharov Ivan A.
Published: October 2020

The report analyzes and selects the liquefaction cycle for Liquid Air Energy Storage. The specific liquefaction coefficient and the coefficient of thermodynamic perfection were calculated for the following cycles: the Linde-Hampson cycle, the Claude cycle, the Heylandt Cycle, the Collins cycle, and the cycle with two expanders. The criterion for optimizing cycles is the maximum value of the liquefaction coefficient. The Claude cycle was chosen as the optimal cycle for use in the Liquid Air Energy Storage. Its exergy efficiency was calculated.
Optimization of a compressed gaseous CO2 energy recovery dry ice pelletizer
Authors: Smorodin Anatoliy I. , Gimadeev Artur I.
Published: October 2020

The disadvantages of the existing dry ice electromechanical pelletizers have been revealed. A schematic flow diagram of the new dry ice energy recovery pelletizer and a carbon dioxide TS diagram with the processes of the new pelletizer have been presented. The functions of the diameter of the piston expander of the new dry ice pelletizer and dry ice pressing pressure depending on the pressure of compressed gaseous CO2 have been derived. The optimal diameters of a piston expander for the dry ice pelletizer have been determined.
Applications with semipermeable membranes for humidity recovery in HVAC systems
Authors: Krause Ralph , Rosenbaum Hannes , Herzog Ralf
Published: October 2020

Both the sensible heat recovery and the combined heat and humidity recovery are state of the art. Of particular importance is the humidity recovery in winter season. The transfer of water vapor from the humidity-laden exhaust air to the very dry fresh air is very important for a good room air quality.

However, all systems established on the market require that supply and exhaust air streams crosses within the device. Practical enthalpy recovery systems for plant concepts with local separation of supply and exhaust air are not available on the market until now.

In order to close this gap, the ILK Dresden works on a R&D project. The objective is the development of a textile heat exchanger, which - integrated into circulatory composite systems - can transmit not only sensible heat but also humidity between spatially separated air streams. The functional principle is based on a liquid sorption process via semipermeable membranes.

The current state of the development will be presented. Furthermore an outlook is given how it is intended to proceed in the project in further steps.
Analysis of losses in the mixing section of the central air conditioner using the entropy-statistical method
Authors: Zdobnov M.I. , Lavrov N.A. , Shishov V.V.
Published: October 2020

The article presents an entropy-statistical analysis of losses in the mixing section of a central air conditioner. The temperature and humidity of the outdoor and recirculating air were measured. The methodology for determining losses using the entropy-statistical method is presented in the work. The calculation of losses in the mixing section of the central air conditioner due to the mixing of air flows depending on the flow rate of the supply and recirculation air as well as due to hydraulic losses. A comparative analysis of the results is carried out and the distribution diagrams of the component losses are presented. Proposed conclusions regarding the way to reduce losses.
Der Schockraum als Nahtstelle zwischen Präklinik und Klinik
Authors: Bogner-Flatz Viktoria , Hinzmann Dominik , Kanz Karl-Georg , Bernhard Michael
Published: October 2020

Die ständige Vorhaltung und Verfügbarkeit eines Schockraums zur Versorgung von kritisch kranken und schwer verletzten Patienten ist eine wesentliche und für die transsektorale Notfallversorgung wichtige klinische Ressource. In diesem Artikel sollen die derzeitigen Entwicklungen der Schockraumbereitstellung in Deutschland aufgezeigt werden.
Primärprävention des Schlaganfalls
Authors: Gerloff Christian , Diener Hans-Christoph
Published: October 2020

Der Schlaganfall ist eine der Hauptursachen für bleibende Behinderungen. Daher hat die Primärprävention eines ersten Schlaganfalls eine hohe Priorität. Die Primärprävention des ischämischen Schlaganfalls umfasst die Änderung des Lebensstils und der Ernährung, die Behandlung von Risikofaktoren wie Bluthochdruck, Diabetes mellitus und Lipidstörungen, die Thrombozytenaggregationshemmung bei Patienten mit hohem Gefäßrisiko und die Antikoagulation bei Vorhofflimmern (AF). Zu den wichtigsten präventiven Strategien in der Primärprävention von Hirnblutungen gehören die Behandlung von Bluthochdruck, die Reduzierung des Alkoholkonsums und der Verschluss des linken Vorhofohrs bei Patienten mit Vorhofflimmern und dauerhafte Kontraindikationen für eine orale Antikoagulation.
Risk Stratification for the Intensive Care Unit Following Pancreaticoduodenectomy
Authors: Deichmann Steffen , Ballies Uwe , Petrova Ekaterina , Bolm Louisa , Honselmann Kim , Frohneberg Laura , Keck Tobias , Wellner Ulrich Friedrich , Bausch Dirk
Published: October 2020

Introduction In view of the limited capacities in intensive care units and the increasing economic burden, identification of risk factors could allow better and more efficient
planning. Therefore, the aim of this study was to assess independent risk factors for the duration of intensive care unit stay after pancreatoduodenectomy (PD).

Methods 147 patients who underwent pancreatoduodenectomy in the time period from 2013 to 2015 were identified from a prospective database and a retrospective analysis was performed.
The primary endpoint was length of time spent in the ICU. A retrograde analysis was performed using univariate and multivariate regression analysis. All pre-, intra- and postoperative
parameters were considered in the analysis.

Results The median time spent in the intensive care unit (ICU) is one day. The univariate analysis demonstrated increased pack years, cerebrovascular events, anticoagulation,
elevated creatinine and CA 19-9 as preoperative risk factors. In multivariate analysis, antihypertensive medication (AHT; OR 2.46; 95% CI 1.57 – 3.87; p = 0.05), operation time (OR 1.01; 95%
CI 1.00 – 1.01; p = 0.03), extended LAD (OR 5.46; 95% CI 2.77 – 10.75; p = 0.01) and severe PPH (OR 4.01; 95% CI 2.07 – 7.76; p = 0.04) are significant risk factors for longer ICU stay.

Discussion Patients with cardiovascular risk factors and elevated preoperative creatinine level are at greater risk for a prolonged ICU stay. Risk and benefit of an extended LAD
should be weighed during the operation. Median duration on ICU/IMC after PD is one day or less for patients without risk factors. Whether routine monitoring in the ICU/IMC after PD is
necessary must be clarified in further studies.
Therapie der intrazerebralen und subarachnoidalen Blutung
Authors: Huttner Hagen B. , Gerner Stefan T. , Sprügel Maximilian I.
Published: October 2020

In den letzten Jahren gab es deutliche Fortschritte in der Akutbehandlung von Patienten mit intrazerebraler Blutung (ICB) und Subarachnoidalblutung (SAB). Allerdings sind die Letalität weiterhin hoch und das funktionelle Outcome der Überlebenden oft stark eingeschränkt. Während bei der ICB aufgrund des Parenchymdefekts häufig motorische Einschränkungen im Vordergrund stehen, leiden SAB-Patienten auch an alltagsrelevanten Folgeschäden wie Kopfschmerzen, Depressionen und kognitiven Einschränkungen. Bei der Behandlung der ICB stehen die Vermeidung einer frühen Blutungsprogression durch Blutdruckmanagement und Hämostase im Vordergrund sowie die Erprobung neuerer minimal-invasiver Techniken zur Blutungsausräumung. Weiterhin eine Herausforderung stellt das Management des Perifokalödems, des Hirndrucks, des Ventrikeleinbruchs und Hydrozephalus sowie die langfristige antithrombotische Therapie dar. Bei der SAB steht die zügige Aneurysmaausschaltung und Hydrozephalusbehandlung im Fokus der Akuttherapie. Neue Aspekte haben sich auch bei der Vermeidung und Behandlung von Vasospamen und sekundären zerebralen Ischämien ergeben. Weitere Forschungsfelder sind das optimale Drainagemanagement, mittels Ventrikel- und Lumbaldrainagen, sowie die intraventrikuläre Fibrinolyse. Die vorliegende Übersichtsarbeit geht auf diese relevanten Themenkomplexe in der Akut- und Langzeittherapie von ICB- und SAB-Patienten ein und gibt einen Überblick zu der aktuellen Datenlage und Kontroversen in diesen Behandlungsfeldern.
Insulinpumpe, kontinuierliche und kapilläre Glukosemessung bei Kindern, Jugendlichen und Erwachsenen mit Diabetes mellitus: Daten des DPV-Registers zwischen 1995 und 2019
Authors: Schöttler Hanna , Auzanneau Marie , Best Frank , Braune Katarina , Freff Markus , Heidtmann Bettina , Jung Ralf , Karges Beate , Klee Daniela , Müller Antonia , Schierloh Ulrike , Vogel Christian , Holl Reinhard W.
Published: October 2020

Ziel dieser Beobachtungsstudie ist die Beschreibung der aktuellen Nutzung von Diabetestechnologien bei Patienten/-innen mit Diabetes mellitus.

Methode Auswertung von Daten des DPV-Registers zur Nutzung der Insulinpumpentherapie (CSII), kontinuierlicher Glukosemessung (CGM) und der Selbstmessung der Blutglukose (SMBG) aus 497 teilnehmenden Zentren in Deutschland, Österreich, Luxemburg und der Schweiz zwischen 1995 und 2019. Die Daten wurden bei Patienten/-innen mit Diabetes Typ 1 (Alter ≥ 0,5 Jahre) für 5 Altersgruppen ausgewertet. Zusätzlich wurden aktuelle (zwischen 2017 und 2019) Geschlechtsunterschiede in der Verwendung von Diabetestechnologie bei Typ-1-Patienten/-innen untersucht, ebenso wie die Nutzung von Insulinpumpen und CGM für Patienten/-innen mit Insulintherapie bei Typ-2-DM, bei zystischer Fibrose (CFRD), bei anderen Pankreaserkrankungen, neonatalem Diabetes und Maturity Onset Diabetes of the Young (MODY).

Ergebnisse Es zeigte sich bei Patienten/-innen mit Diabetes Typ 1 ein Anstieg der CSII-Nutzung von 1995 bis 2019 von 1 % auf 55 % (2019: < 6 Jahre: 89 %; 6–< 12 Jahre: 67 %; 12–< 18 Jahre: 52 %; 18–< 25 Jahre: 48 %; ≥ 25 Jahre: 34 %). Die CGM-Nutzung erhöhte sich ab 2016 bis 2019 von 9 % auf 56 % (2019: 67 %; 68 %; 61 %; 47 %; 19 % der jeweiligen Altersgruppe). Die SMBG nahmen von 1995 bis 2015 insbesondere in den jüngeren Altersgruppen zu, gefolgt von einem Rückgang seit dem Jahr 2016 (Alle Patienten: 1995: 3,3/Tag; 2016: 5,4/Tag; 2019: 3,8/Tag). Weibliche Patienten mit Typ-1-Diabetes führten häufiger eine CSII und mehr SMBG als männliche Patienten durch (56 %/48 %, jeweils p-Wert: < 0,0001), während sich bei der CGM-Nutzung keine signifikanten Unterschiede zeigten.

Zwischen 2017 und 2019 erfolgte eine Nutzung von Insulinpumpen und CGM bei neonatalem Diabetes (CSII 87 %; CGM 38 %), bei MODY (CSII 14 %; CGM 28 %) und bei CFRD (CSII 18 %; CGM 22 %). CGM und CSII wurden dagegen nur selten von Menschen mit Insulintherapie und Diabetes Typ 2 (CSII < 1 %; CGM 1 %) und bei anderen Pankreaserkrankungen (CSII 3 %; CGM 4 %) genutzt.

Schlussfolgerung Moderne Diabetestechnologien werden derzeit insbesondere von pädiatrischen Patienten/-innen mit Diabetes Typ 1, aber auch von Menschen mit neonatalem Diabetes breit genutzt, von Patienten/-innen mit MODY und CFRD sowie Erwachsenen mit Diabetes Typ 1 in etwas geringerem Maße mit ansteigendem Trend. Dagegen sind diese Technologien in der Therapie des Typ-2-Diabetes und bei anderen Pankreaserkrankungen zurzeit nur wenig verbreitet.
Helical Carbenium Ion-Based Organic Photoredox Catalyst: A Versatile and Sustainable Option in Red-Light-Induced Reactions
Authors: Gianetti Thomas , Mei Liangyong
Published: October 2020

The development of a sustainable catalytic system for red-light-induced photocatalysis is presented. The catalytic system consists of a helical carbenium ion-based organic photoredox catalyst (PC) that is capable of using low-energy red light (λmax = 640 nm) for both photooxidations and photoreductions. Its successful applications in the aerobic oxidative hydroxylation of arylboronic acids and in the oxidation of benzylic C(sp3)–H bonds (reductive quenching), as well as in dual transition-metal/organocatalyzed C–H arylations and intermolecular atom-transfer radical additions (oxidative quenching) provide further support for its role as a versatile and efficient organic PC.

1 Introduction

2 Red-Light-Induced Photocatalysis

3 Properties of N,N′-Dipropyl-1,13-dimethoxyquinacridinium Tetrafluoroborate

4 Two Proposed Representative Catalytic Cycles of [
n
Pr-DMQA+][BF4
–]

5 Applications of [
n
Pr-DMQA+][BF4
–] in Red-Light-Induced Photocatalysis

6 Conclusion
Synthesis of Fused Pyrimido[1,6-a]indolones via Rhodium(III)-Catalyzed Cascade Annulations
Authors: Raji Reddy Chada , Bodasu Srinivas , Mallesh Kathe , Prapurna Y. Lakshmi
Published: October 2020

A novel method for the synthesis of fused pyrimido[1,6-a]-indolone derivatives by annulation of 2-alkynylaryl aldehydes/2-alkynyl­arylidene ketones with N-(pivaloyloxy)-1H-indole-1-carboxamide catalyzed by rhodium has been accomplished. The reaction proceeds through C–H activation based annulation with alkyne moiety followed by addition of nitrogen on to aldehyde/activated alkene to give the products in moderate to good yields. Highly fluorescent dipyrrinone analogues could be synthesized from the derived products.
Inter- and Intramolecular [2+2+2] Cycloaddition of Alkyne Triple Bonds to the Carbonyl Function of Aldehydes and Ketones Enabled by η5-Cyclopentadienylcobalt(L)(L′)
Authors: Vollhardt K. Peter C. , Colovray-Gotteland Véronique , Harvey Daniel F. , Johnson Barry M. , Ung Christopher S.
Published: October 2020

1,7-Octadiyne underwent [2+2+2] cycloaddition to acetone in the presence of η5-cyclopentadienylcobalt(L)(L′) complexes to give (η5-cyclopentadienyl)[(1,4,4a,8a-η4)-5,6,7,8-tetrahydro-3,3-dimethyl-3H-2-benzopyran]cobalt, in which the two triple bonds and the carbonyl moiety have combined to engender a 2H-pyran ring complexed to CpCo. The scope of this reaction was explored, including cocyclizations of ynals and ynones with bis(trimethylsilyl)acetylene, as well as all-intramolecular reorganizations of α,ω-diynals and -diynones. Two major trajectories were observed in the case of aldehydes, the (often minor) [2+2+2] pathway and a competing trail featuring a formal 1,5-hydride shift that results in CpCo–dienones. The latter is obviated for ketone substrates. Preliminary chemistry of selected complexes uncovered unprecedented reactions, such as acid-catalyzed ring openings and additions of amines, the latter providing access to novel carbon frames.
Utilization of Borane-Catalyzed Hydrosilylation as a Dearomatizing Tool: Six-Membered Cyclic Amidine Synthesis from Isoquinolines and Pyridines
Authors: Cao Vinh Do , Jo Dong Geun , Joung Seewon , Kim Huiae , Kim Changeun , Yun Seula
Published: October 2020

In this study, a convenient strategy to synthesize six-membered­ cyclic amidines from isoquinolines and pyridines has been developed. Borane-catalyzed hydrosilylation of each N-heteroarene was utilized as a dearomatizing tool. Substrate scope is broad with respect to both isoquinolines and pyridines, with various reaction pathways depending on the substitution pattern of the N-heteroarenes. The reaction mechanism and reactivity of each class of N-heteroarenes has been discussed. The resulting six-membered (Z)-sulfonyl amidine products are rarely reported and are mostly unprecedented. The scalability of this method and versatility of the cyclic amidine products are also presented.
Association between DNA Damage and Serum Levels of Copper, Zinc, and Selenium in Full-Term Neonates with Late-Onset Sepsis
Authors: Wahby Aliaa Ahmed , Elwassif Maha , Magdy Mai , Hamid Tamer A. Abdel , Ibrahim Alshaymaa A.
Published: October 2020

Objective The alteration in certain trace elements is usually associated with impaired immune function and higher oxidative stress. Therefore, these elements are suggested to play an important role in the pathogenesis of neonatal sepsis. We aimed to evaluate copper (Cu), zinc (Zn), and selenium (Se) serum levels in full-term neonates with late-onset sepsis (LOS) and correlate these levels with DNA damage and other risk factors of sepsis.

Methods The study included a group of 100 neonates diagnosed with sepsis serving as the case group and another one of 60 neonates serving as the control group. DNA damage was assessed using the comet assay method and trace elements were measured using inductively coupled plasma mass spectrometry.

Results Compared with controls, the percentage of DNA damage was significantly elevated in patients with sepsis, while serum levels of Cu, Zn, and Se were markedly decreased (p = 0.001). A strong negative correlation was revealed between Se and DNA damage (r = −0.6, p = 0.001). However, no correlations were found between Cu or Zn and DNA damage. Univariate logistic regression analysis revealed that DNA damage as well as Cu, Zn, and Se serum levels can be considered as relevant risk factors for neonatal sepsis (p = 0.008, 0.004, 0.004, and 0.003, respectively). Receiver-operating characteristic curve analysis showed that the strongest indicator for neonatal sepsis was Se (area under the curve [AUC] = 0.94, confidence interval [CI] = 0.9–0.98, p = 0.001), followed by Cu (AUC = 0.9, CI = 0.85–0.96, p = 0.001), and then Zn (AUC = 0.87, CI = 0.8–0.93, p = 0.001).

Conclusion The percentage of DNA damage may help in the assessment of neonatal sepsis severity. Altered levels of Cu, Zn, and Se may play significant role in the pathogenesis of neonatal sepsis. Se serum level is strongly correlated with percentage of DNA damage. Therefore, Se can predict the severity of LOS.
Observation of split defect-bound excitons in twisted WSe2/WSe2 homostructure
Authors: Zeng Cheng , Zhong Jiahong , Wang Yun-Peng , Yu Juan , Cao Lingkai , Zhao Ziliang , Ding Junnan , Cong Chunxiao , Yue Xiaofei , Liu Zongwen , Liu Yanping
Published: October 2020

The excitonic effects in two-dimensional transition metal dichalcogenides and their heterostructures have been extensively investigated. Significantly, the moiré excitons, induced by a moiré superlattice in a twisted heterostructure, have triggered tremendous attention, demonstrating the practicability of artificial excitonic crystals. Besides, recent works have shown that the excitonic states in homostructures also exhibit novel properties worthy of further development. Here, we present a tear-and-stack technique for fabricating a regular or a twisted homostructure. Such a strategy was utilized to reassemble a monolayer WSe2 into a twisted homostructure, and various excitons from this structure have been identified in the photoluminescence spectra. Interestingly, the unusual equidistant splitting was first observed in the defect-bound excitons. It is believed that this phenomenon is attributed to the various defect states and the local stacking patterns. This interpretation is supported by theoretical calculations, which show the dependence of the energy band structure on different defect states and local stacking patterns. These unconventional defect-bound excitons are key building blocks in the research of homostructures that highlight the feasibility of artificially manipulating local excitons for practical applications.
Sensitivity and dimensionality of atomic environment representations used for machine learning interatomic potentials
Authors: Onat Berk , Ortner Christoph , Kermode James R.
Published: October 2020

Faithfully representing chemical environments is essential for describing materials and molecules with machine learning approaches. Here, we present a systematic classification of these representations and then investigate (i) the sensitivity to perturbations and (ii) the effective dimensionality of a variety of atomic environment representations and over a range of material datasets. Representations investigated include atom centered symmetry functions, Chebyshev Polynomial Symmetry Functions (CHSF), smooth overlap of atomic positions, many-body tensor representation, and atomic cluster expansion. In area (i), we show that none of the atomic environment representations are linearly stable under tangential perturbations and that for CHSF, there are instabilities for particular choices of perturbation, which we show can be removed with a slight redefinition of the representation. In area (ii), we find that most representations can be compressed significantly without loss of precision and, further, that selecting optimal subsets of a representation method improves the accuracy of regression models built for a given dataset.