Interplay of charge, spin and lattice degrees of freedom on the spectral properties of the one-dimensional Hubbard-Holstein model

We calculate the spectral function of the one dimensional Hubbard-Holstein model using the time dependent Density Matrix Renormalization Group (tDMRG), focusing on the regime of large local Coulomb repulsion, and away from electronic half-filling. We argue that, from weak to intermediate electron-phonon coupling, phonons interact only with the electronic charge, and not with the spin degrees of freedom. For strong electron-phonon interaction, spinon and holon bands are not discernible anymore and the system is well described by a spinless polaronic liquid. In this regime, we observe multiple peaks in the spectrum with an energy separation corresponding to the energy of the lattice vibrations (i.e., phonons). We support the numerical results by introducing a well controlled analytical approach based on Ogata-Shiba's factorized wave-function, showing that the spectrum can be understood as a convolution of three contributions, originating from charge, spin, and lattice sectors. We recognize and interpret these signatures in the spectral properties and discuss the experimental implications.Comment: 8 pages, 7 figure

Etiology, risk factors, mortality and morbidity of status epilepticus in children: A retrospective cross-sectional study in Tehran, Iran

Background: Risk factors identification associated with status epilepticus is valuable in order to prevent morbidity and mortality in children. This study aimed to consider the etiology, risk factors, morbidity and mortality in children with status epilepticus. Methods: This retrospective cross-sectional study was performed on 119 patients aged from one month old to 15 years old. Patients� data were recorded, including basic demographic, etiology and clinical information. The different risk factors correlated to morbidity and mortality were evaluated in this study. Results: The most common etiologies were acute symptomatic and febrile status epilepticus by 32.8 and 22.7, respectively. Abnormal brain imaging results were reported far more frequently in patients with a history of neurodevelopmental delay and previous status epilepticus (p<0.001). The overall morbidity and mortality rates were 18.9 and 10.9, respectively; while these rates in patients with delayed development (45.16 and 18.42, respectively) were significantly higher than patients with normal development (8 and 7.4, respectively). The morbidity rates in patients with previous seizures and previous status epilepticus were remarkably higher than those without previous history of seizure (26.41 vs 11.32; p=0.047) and without previous status epilepticus (36.36 versus 14.28; p=0.018). The length of hospital stay in patients with mortality was considerably longer than patients without mortality (12.30 ± 16.1 days vs 7.29 ± 6.24 days; p=0.033). The mortality rate in patients with normal Lumbar Puncture result was notably lower than those with abnormal LP result (2.9 vs 50). The morbidity rate in patients with abnormal brain imaging results (p<0.001) was significantly greater than those in patients with normal results. The mortality rate was relatively higher in patients with abnormal imaging results compared to those normal results. Etiology was an important predictor of mortality and morbidity rates; acute symptomatic (32.8), febrile status epilepticus (22.7) and remote symptomatic (16.8) etiologies were the most common underlying causes of S.E. While in children less than 3 years old, the acute symptomatic etiology and febrile status epilepticus etiologies were estimated as the most common, in most patients older than 3 years old the most common etiology of status epilepticus was unknown. Congenital brain defects etiology had the highest mortality (36.36) and morbidity (42.85) rate. The lowest morbidity (3.84) and mortality (0) rates were for patients with febrile status epilepticus etiology. Conclusion: Age, developmental delay, history of previous status epilepticus, the length of hospital stay, abnormal brain imaging results and the underlying etiology of status epilepticus were associated with increased morbidity and mortality among children with status epilepticus. © 2020 Vafaee-Shahi et al

Etiology, risk factors, mortality and morbidity of status epilepticus in children: A retrospective cross-sectional study in Tehran, Iran

Background: Risk factors identification associated with status epilepticus is valuable in order to prevent morbidity and mortality in children. This study aimed to consider the etiology, risk factors, morbidity and mortality in children with status epilepticus. Methods: This retrospective cross-sectional study was performed on 119 patients aged from one month old to 15 years old. Patients� data were recorded, including basic demographic, etiology and clinical information. The different risk factors correlated to morbidity and mortality were evaluated in this study. Results: The most common etiologies were acute symptomatic and febrile status epilepticus by 32.8 and 22.7, respectively. Abnormal brain imaging results were reported far more frequently in patients with a history of neurodevelopmental delay and previous status epilepticus (p<0.001). The overall morbidity and mortality rates were 18.9 and 10.9, respectively; while these rates in patients with delayed development (45.16 and 18.42, respectively) were significantly higher than patients with normal development (8 and 7.4, respectively). The morbidity rates in patients with previous seizures and previous status epilepticus were remarkably higher than those without previous history of seizure (26.41 vs 11.32; p=0.047) and without previous status epilepticus (36.36 versus 14.28; p=0.018). The length of hospital stay in patients with mortality was considerably longer than patients without mortality (12.30 ± 16.1 days vs 7.29 ± 6.24 days; p=0.033). The mortality rate in patients with normal Lumbar Puncture result was notably lower than those with abnormal LP result (2.9 vs 50). The morbidity rate in patients with abnormal brain imaging results (p<0.001) was significantly greater than those in patients with normal results. The mortality rate was relatively higher in patients with abnormal imaging results compared to those normal results. Etiology was an important predictor of mortality and morbidity rates; acute symptomatic (32.8), febrile status epilepticus (22.7) and remote symptomatic (16.8) etiologies were the most common underlying causes of S.E. While in children less than 3 years old, the acute symptomatic etiology and febrile status epilepticus etiologies were estimated as the most common, in most patients older than 3 years old the most common etiology of status epilepticus was unknown. Congenital brain defects etiology had the highest mortality (36.36) and morbidity (42.85) rate. The lowest morbidity (3.84) and mortality (0) rates were for patients with febrile status epilepticus etiology. Conclusion: Age, developmental delay, history of previous status epilepticus, the length of hospital stay, abnormal brain imaging results and the underlying etiology of status epilepticus were associated with increased morbidity and mortality among children with status epilepticus. © 2020 Vafaee-Shahi et al

DIFFUSION LAYER GROWTH MECHANISM IN ASPN METHOD USING AN IRON CAGE FOR ST52 STEEL

- The mechanism of diffusion layer growth in plasma nitrided coatings applied on a St52 steel using an active screen is investigated. The nitriding was performed at 450,500 and 550 ◦C temperature nitriding times of 5, 10 and 15 h, in a gas mixture containing 20 vol. % H2: 80 vol. % N2 and DC-pulsed plasma nitriding unit. The surface, cross section and the thickness of diffusion of specimens was studied in terms of optical and scanning electron microscopy. According to the measurements of diffusion layer thickness, values of Q and D0 for nitrogen diffusion in substrate were calculated as 50585 (j/mol) and 4.11&times;10-10 (m2/s)respectively. The variations of depth of hardness during nitriding period was determine

Oxalate-assisted solvothermal synthesis of octahedral LiMn1.5Ni0.5O4 particles for lithium-ion batteries

Submicron octahedral LiMn1.5Ni0.5O4 particles were easily prepared by solvothermal synthesis method. The effects of synthesis conditions including precursors' concentration (0.09 and 0.18 M), calcination temperature (700 and 800 °C), and calcination time (2 and 8 h) were studied by modern characterization techniques. The octahedral LiMn1.5Ni0.5O4 particles with disordered spinel structure (space group of Fd3¯m) were obtained by calcination at 800 °C for 2 h. With the increase of precursors’ concentration and prolonging the calcination time, the particle size increased from 220 to 845 nm and the particle size distribution became wider. Furthermore, the corners and edges of the octahedral particles were chamfered by appearing the (100) family planes at longer calcination times. The truncated LiMn1.5Ni0.5O4 particles showed a high discharge specific capacity of 133 mAh g−1 at current rate of 0.1C and a high capacity retention of 99.3% following 50 cycles

ON THE REACTIONS IN ILMENITE, ALUMINUM AND GRAPHITE SYSTEM

Al2O3/TiC composites are used as cutting tools for machining gray cast iron and steels. The addition of iron improves the toughness of Al2O3/TiC composites. Ilmenite, aluminum and graphite can be used to produce in-situ Al2O3/TiC&ndash;Fe composites. However, the formation mechanism and reaction sequences of this system are not clear enough. Therefore, the present research is designed to determine the reactions mechanism of the first step of reactions that may be occurred between raw materials. In this research, pure ilmenite was synthesized to eliminate the effects of impurities available in the natural ilmenite in the system. The milled and pressed samples, prepared from the synthesized ilmenite, aluminum and graphite mixture with a molar ratio of 1:2:1, were heat treated at 720&deg;C for 48h. In addition, two samples one containing ilmenite and aluminum with a molar ratio of 1:2 and ilmenite and graphite with a molar ratio of 1:1 were heat treated at 720&deg;C for 48h. The final products were analyzed with XRD. It was found that at 720&deg;C, aluminum reacts with FeTiO3, forming Fe, TiO2 and Al2O3. Since the aluminum content used in the mixture was more than the stoichiometry for reaction of ilmenite and aluminum, some unreacted aluminum remains. Therefore, the residual aluminum reacts with the reduced Fe to form Fe2Al5

THE FORMATION OF TiAl3 DURING HEAT TREATMENT IN EXPLOSIVELY WELDED Ti-Al MULTILAYERS

Metallic-intermetallic laminate (MIL) composites are promising materials for structural applications especially in the aerospace industry. One of the interesting laminate composites is the Ti-TiAl 3 multilayer. In this work, commercially pure sheets of aluminum and titanium with almost equal thickness of around 0.5 mm were explosively joined. The achieved multilayers were annealed at 630 ℃in different times so that an intermetallic layer was formed at the Ti/Al interface. The resulting microstructure was studied by optical and scanning electron microscopy and Energy Dispersive Spectroscopy (EDS). TiAl3 was the only intermetallic phase that was observed in all annealing times. The kinetics of the formation of TiAl 3 was investigated and compared to previous research studies performed on Ti-Al multilayers which were fabricated using methods other than explosive welding

Effect of Aluminium Injection into the Crystalizator on Type, Composition and Activity of Inclusions in Low Carbon Steel

This study was intended to investigate the effect of injection of aluminium into the crystallizator on type, composition and activity of inclusions in low carbon steel grade USD7. The steel is made in Zob-e-Ahan Isfahan factory and its porosities and inclusions results in the problem of rupturing during rolling process. To improve the quality of this steel, 2.4 mm diameter pure aluminum wires were injected in to the crystallizator at the rate of 2, 4, 6 or 8 m/min in certain periods and then sampling was done. The results indicated that much of the added aluminum changed to aluminum oxide slag, and the remaining part altered the chemical composition of the inclusions. Increased aluminum caused an increase in the activity of alumina and reduction in the activity of other oxides in the slag and existing inclusions in the melt. By increasing Al2O3 activity from 0.313 to 0.649, the Al2O3 formation and oxygen exclusion probability increased in the system. Scanning electron microscopy showed that without aluminium injection, most of inclusions were FeO-MnO type placed around existing porosities in the ingot. The optimum rate of aluminum injection was found to be 4 m/min

Investigation of heat pipe heat exchanger effectiveness and energy saving in air conditioning systems using silver nanofluid

The present study attempts to use the methanol–silver nanofluid filled heat pipe heat exchanger and compares the effectiveness as well as the energy saving with pure methanol. A heat pipe heat exchanger has been tested in a test rig under steady-state conditions. The lengths of both the evaporator and the condenser sections of the heat exchanger were 700 mm, and its central adiabatic section had a length of 160 mm. The heat exchanger had 36 plate finned copper thermosyphons arranged in three rows. The inlet air temperature across the evaporator section was varied in the range of 33–43 °C while the inlet air temperature to the condenser section was nearly constant to be 13 °C. First, pure methanol was used as the working fluid with a fill ratio of 50 % of the evaporator section length, and then dilute dispersion of silver nanoparticles in methanol was employed as the working fluid. The nanofluid used in the present study is 20 nm diameter silver nanoparticles. The experiments were performed to compare the heat pipe heat exchanger effectiveness and energy saving, using nanofluid and pure methanol. The inlet air relative humidity across the evaporator section was varied between 35 and 80 %. The sensible effectiveness of the heat pipe heat exchanger obtained from experiments varied about 5–22 % for pure methanol and 9–32 % for methanol–silver nanofluid. Based on these experimental results, using methanol–silver nanofluid leads to energy saving around 8.8–31.5 % for cooling and 18–100 % for reheating the supply air stream in an air conditioning system