Dynamics at the crystal-melt interface in a supercooled chalcogenide liquid near the glass transition.

Direct quantitative measurements of nanoscale dynamical processes associated with structural relaxation and crystallization near the glass transition are a major experimental challenge. These type of processes have been primarily treated as macroscopic phenomena within the framework of phenomenological models and bulk experiments. Here, we report x-ray photon correlation spectroscopy measurements of dynamics at the crystal-melt interface during the radiation induced formation of Se nano-crystallites in pure Se and in binary AsSe4 glass-forming liquids near their glass transition temperature. We observe a heterogeneous dynamical behaviour where the intensity correlation functions g2(q, t) exhibits either a compressed or a stretched exponential decay, depending on the size of the Se nano-crystallites. The corresponding relaxation timescale for the AsSe4 liquid increases as the temperature is raised, which can be attributed to changes in the chemical composition of the melt at the crystal-melt interface with the growth of the Se nano-crystallites

Properties of bio-oil and bio-char produced by sugar cane bagasse pyrolysis in a stainless steel tubular reactor

In this study, compositional analysis of the products obtained by thermal degradation of sugar cane bagasse at various pyrolysis temperatures (300, 350, 400, 450, 500, 550, 600, 650, 700, 750 and 800 °C) and heating rate (5, 10, 20 and 50 °C/min) was studied. Sugar cane bagasse was pyrolyzed in a stainless steel tubular reactor. The aim of this work was to experimentally investigate how the temperature and heating rate affects liquid and char product yields via pyrolysis and to determine optimal condition to have a better yield of these products. Liquid product (bio-oil) obtained under the most suitable conditions were characterized by elemental analysis, FT-IR, C-NMR and HNMR. In addition, column chromatography was employed to determine the aliphatic fraction (Hexane Eluate); gas chromatography and FT-IR were achieved on aliphatic fractions. For char product (bio-char), the elemental chemical composition and yield of the char were determined. The results of our work showed that the amount of liquid product (bio-oil) from pyrolysis of sugar cane bagasse increases with increasing the final temperature and decreases with increasing the heating rate. The highest yield of liquid product is obtained from the samples at 550 °C and at the heating rate of 5°C/min, the maximal average yield achieved almost 32.80 wt%. The yield of char generally decreases with increasing the temperature, the char yield passes from 39.7 wt% to 21 wt% at the heating rate of 5°C/min and from 32 wt% to 17.2 wt% at the heating rate of 50 °C/min at the same range of temperature (300–800 °C). The analysis of bio-oil showed the presence of an aliphatic character and that it is possible to obtain liquid products similar to petroleum from sugar cane bagasse waste. The solid products (bio-char) obtained in the presence of nitrogen (N2) contain a very important percentage of carbon and high higher heating values (HHV)

Domain fluctuations in a ferroelectric low-strain BaTiO3 thin film

A ferroelectric BaTiO3 thin film grown on a NdScO3 substrate was studied using x-ray photon correlation spectroscopy (XPCS) to characterize thermal fluctuations near the a/b to a/c domain structure transformation present in this low-strain material, which is absent in the bulk. XPCS studies provide a direct comparison of the role of domain fluctuations in first- and second-order phase transformations. The a/b to a/c domain transformation is accompanied by a decrease in fluctuation timescales, and an increase in intensity and correlation length. Surprisingly, domain fluctuations are observed up to 25 degrees C above the transformation, concomitant with the growth of a/c domains and coexistence of both domain types. After a small window of stability, as the Curie temperature is approached, a/c domain fluctuations are observed, albeit slower, potentially due to the structural transformation associated with the ferroelectric to paraelectric transformation. The observed time evolution and reconfiguration of domain patterns highlight the role played by phase coexistence and elastic boundary conditions in altering fluctuation timescales in ferroelectric thin films

Evidence of extreme domain wall speeds under ultrafast optical excitation

Time-resolved ultrafast EUV magnetic scattering was used to test a recent prediction of >10 km/s domain wall speeds by optically exciting a magnetic sample with a nanoscale labyrinthine domain pattern. Ultrafast distortion of the diffraction pattern was observed at markedly different timescales compared to the magnetization quenching. The diffraction pattern distortion shows a threshold-dependence with laser fluence, not seen for magnetization quenching, consistent with a picture of domain wall motion with pinning sites. Supported by simulations, we show that a speed of $\approx$ 66 km/s for highly curved domain walls can explain the experimental data. While our data agree with the prediction of extreme, non-equilibrium wall speeds locally, it differs from the details of the theory, suggesting that additional mechanisms are required to fully understand these effects.Comment: 5 pages, 4 figures; Supplemental Material: 8 pages, 9 figure

Symmetry-dependent ultrafast manipulation of nanoscale magnetic domains

Femtosecond optical pumping of magnetic materials has been used to achieve ultrafast switching and recently to nucleate symmetry-broken magnetic states. However, when the magnetic order parameter already presents a broken-symmetry state, such as a domain pattern, the dynamics are poorly understood and consensus remains elusive. Here, we resolve the controversies in the literature by studying the ultrafast response of magnetic domain patterns with varying degrees of translation symmetry with ultrafast x-ray resonant scattering. A data analysis technique is introduced to disentangle the isotropic and anisotropic components of the x-ray scattering. We find that the scattered intensity exhibits a radial shift restricted to the isotropic component, indicating that the far-from-equilibrium magnetization dynamics are intrinsically related to the spatial features of the domain pattern. Our results suggest alternative pathways for the spatiotemporal manipulation of magnetism via far-from-equilibrium dynamics and by carefully tuning the ground-state magnetic textures

Extreme Domain Wall Speeds under Ultrafast Optical Excitation

Time-resolved ultrafast EUV magnetic scattering was used to test a recent prediction of > 10 km=s domain wall speeds by optically exciting a magnetic sample with a nanoscale labyrinthine domain pattern. Ultrafast distortion of the diffraction pattern was observed at markedly different timescales compared to the magnetization quenching. The diffraction pattern distortion shows a threshold dependence with laser fluence, not seen for magnetization quenching, consistent with a picture of domain wall motion with pinning sites. Supported by simulations, we show that a speed of ≈66 km=s for highly curved domain walls can explain the experimental data. While our data agree with the prediction of extreme, nonequilibrium wall speeds locally, it differs from the details of the theory, suggesting that additional mechanisms are required to fully understand these effects

Magnetic behavior of multi-principal element alloys and ultrafast domain dynamics in CoFe/Ni ferromagnetic multilayers

Permanent magnets composed primarily of rare earth elements are critical components in electric vehicle motors. With the recent surge in electric vehicle sales, demand for rare earth elements has dramatically increased, elevating costs. Thus, there is strong interest in identifying rare-earth-free alternatives for permanent magnet applications. The multi- principal element alloy (MPEA) family has emerged as a promising candidate. MPEAs contain three or more principal constituent elements, some of which may be magnetic such as Fe, Co, Cr, Mn, and Ni. In this thesis, I will first discuss our investigation of the magnetic properties of FeCoCrMnSi-based MPEAs. Multiple magnetic phase transitions were observed via zero-field-cooled/field-cooled magnetization measurements, indicating a rich magnetic phase diagram. Spectroscopic measurements revealed ferromagnetic ordering of Fe, Co and Cr, while Mn exhibited no long-range magnetization. Our results illustrate the rich and complex magnetic properties of MPEAs.In addition to permanent magnet applications, controlling mesoscopic magnetic textures may enable next-generation energy-efficient magnetic memory and data storage. The second portion of my talk will focus on ultrafast manipulation of magnetic textures. Domain wall motion in ferromagnets driven by magnetic fields, electrical currents, or spin waves is typically quite slow, below 100 m/s. Furthermore, the Walker breakdown phenomenon limits domain wall velocities at higher driving fields or currents as precession of spins approaches the ferromagnetic resonance frequency. However, far-from-equilibrium dynamics induced through ultrafast optical excitation may allow overcoming these limitations and accessing nonequilibrium material behavior. In fact, recent theoretical work predicted superdiffusive spin current-driven domain wall velocities up to 14 km/s in optically pumped ferromagnets. We experimentally tested this prediction in a magnetically textured CoFe/Ni multilayer film using time-resolved extreme ultraviolet magnetic scattering with 50 fs resolution. For the highest optical pump fluences, we observed domain wall velocities up to 66 km/s, approaching the theoretical limit set by magnon group velocity. These findings demonstrate that far-from-equilibrium optical excitation can dramatically accelerate mesoscale magnetic textures. Our studies open the possibility of manipulating the ground state to achieve far-from-equilibrium effects at mesoscopic length scales. The implications of such nonequilibrium spin kinetics likely extend to understanding and harnessing ultrafast phenomena in quantum materials

Cyclosporine in dermatology results of a pilot study

Introduction: Cyclosporine (CsA) is a calcineurin inhibitor immunosuppressive. Although highly effective, CsA is not used widely in India because of high cost and fear of serious adverse effects. Paucity of studies on use of CsA in dermatological conditions in India, led to the conduct of this pilot study. Aim: The aim of this study were to determine the efficacy and safety of CsA in various dermatological conditions. Materials and Methods: A total 10 patients of age 8 to 55 years, 4 of lichen planus, 3 of psoriasis (including 1 of psoriatic erythroderma) and 3 of atopic dermatitis were selected for this study. All patients were exhibited 3 to 5 mg/kg/day of oral CsA for a maximum period of 12 weeks. Results: CsA produced an extremely rapid, almost ‘magical’ response; the side effects were minimal and did not warrant withdrawal of the drug. We found a rapid response in psoriasis, the patient of psoriatic erythroderma showed onset of action in 72 hours while the 2 patients of plaque psoriasis showed 75 % reduction in PASI score in 2–3 weeks. All patients of lichen planus showed rapid onset of action in form of decreased/ no fresh lesions in 3 to 4 days. Patients of atopic dermatitis showed 50% reduction in the six areas six sign atopic dermatitis score at end of 4 weeks. The response in atopics was relatively slower requiring higher doses and relapses were encountered on dose reduction. Relapses were seen in all ten cases on discontinuing treatment. In severe cases with frequent history of relapses, relatively safer and cheaper immunosuppressives like methotrexate or azathioprine may be added while tapering the dose of CsA. Careful patient selection and monitoring are required to produce optimum results