An Effective Route to Control the Magnetic-Phase Transition and Magnetocaloric Effect of La_0.7Ca_0.3MnO₃ Nanoparticles

Phan, T. L.,Thanh, T. D.,Ho, T. A.,Manh, T. V.,Tran, Q. T.,Lampen, P.,Phan, M. H.,Yu, S. C. IEEE 2014 IEEE transactions on magnetics Vol.50 No.11

<P>This paper points out that the magnetic-phase transition and magnetocaloric effect of La<SUB>0.7</SUB>Ca<SUB>0.3</SUB>MnO<SUB>3</SUB> (LCMO) can be easily controlled by using the mechanical milling method. Changing the milling time from 5 to 30 min, we have obtained LCMO nanoparticles (NPs) with average crystallite sizes (d, determined by the Williamson-Hall method) ranging from 100 to 45 nm. The magnetic studies (based on a superconducting quantum interference device) and simple analyses (based on Banerjee's criteria) prove the magnetic-phase transformation from the first-order to the second-order, which takes place at a threshold value of d located in the range 60-70 nm. Compared with the as-prepared LCMO sample (a first-order magnetic phase transition), though the d decrease reduces the values of the T<SUB>C</SUB>, magnetization, magnetic-entropy change, and refrigerant capacity, but the width of the magnetic phase transition is increased remarkably. This widens the working range of LCMO NPs in magnetic refrigeration applications. We believe that the presence of surface-related effects, lattice strain, and distortions leads to Mn<SUP>3+</SUP>-Mn<SUP>4+</SUP> ferromagnetic interactions in LCMO NPs weaker than that in the as-prepared sample.</P>

Influence of Cr Doping on the Critical Behavior of Amorphous Alloy Ribbons Fe_{78–<i>x</i>}Cr_<i>x</i>Si₄Nb₅B₁₂Cu₁

Phan, T. L.,Thanh, P. Q.,Chau, N.,Huu, C. X.,Ngo, D.-T,Ho, T. A.,Thanh, T. D.,Yu, S. C. IEEE 2014 IEEE transactions on magnetics Vol.50 No.11

<P>Though many previous works focused on studying Cr-doped Fe-Si-Nb-B-Cu amorphous alloys, magnetic-interaction mechanisms in these materials have not been carefully investigated yet. Dealing with these issues, we have prepared the amorphous alloy ribbons Fe<SUB>78-x</SUB>Cr<SUB>x</SUB>Si<SUB>4</SUB>Nb<SUB>5</SUB>B<SUB>12</SUB>Cu<SUB>1</SUB> with x= 1, 3, and 6, and then studied their magnetic and critical properties. Magnetization versus temperature and magnetic-field measurements, MHT, performed on a vibrating sample magnetometer reveal that the Cr-content increase in Fe<SUB>78-x</SUB>Cr<SUB>x</SUB>Si<SUB>4</SUB>Nb<SUB>5</SUB>B<SUB>12</SUB>Cu<SUB>1</SUB> reduces the T<SUB>C</SUB> from 430 K for x= 1 to about 322 K (for x= 6). This indicates the decline of ferromagnetic (FM) exchange interactions between Fe atoms when there is the presence of Cr atoms. We have also analyzed the M(H) data at the temperatures in the vicinity of the T<SUB>C</SUB> using the modified Arrott plot method and the scaling hypothesis, and determined the values of the critical exponents β = 0.367-0.376 and γ = 1.315-1.338. These values are close to those expected for the 3-D Heisenberg model with β = 0.365 and γ = 1.336, proving the existence of short-range FM order in the amorphous alloy ribbons.</P>

OPTIMIZATION RESEARCH FOR A HIGH PRESSURE COMMON RAIL DIESEL ENGINE BASED ON SIMULATION

Y. LIU,Y.-T. ZHANG,T. QIU,X. DING,Q. XIONG 한국자동차공학회 2010 International journal of automotive technology Vol.11 No.5

ABSTRACT−A TP (Temperature Phase) model is presented to carry out optimization calculation for a high-pressure common rail diesel engine. Temperature is the most important parameter in the TP model. For the lower branch (when temperature T < 850 K) of the S-shaped curve (auto-ignition phase), a 6-step ad-hoc model with adjusted rate constants of nheptane is used, referred to steady state assumption. Steady state assumption is based on the observation that, due to very fast chemical processes in combustion problems, many chemical species and reactions are in a quasi-steady state or partial equilibrium. When a species is assumed to be in the steady state, the corresponding differential equation can be replaced by an algebraic relation, which reduces the computational costs. For the middle branch (850 K ≤ T < 1100 K) of the S-shaped curve, a 4-step model is used to calculate the unstable phase. For the upper branch (T≥1100 K) of the S-shaped curve, onestep model is used because the one-step model has widely been used in descriptions of flame stability where it essentially serves as a model that produces a thin flame with strong temperature sensitivity. When zone temperature T<1500 K, only the soot precursors –PAHs (Polycyclic aromatic hydrocarbons) is created and there is no soot emission. When zone temperature T≥1500 K, PAHs and soot source terms (particle inception, surface growth, oxidation, coagulation) are calculated. The TP model is then applied in multidimensional simulations to carry out optimizing, which reduces experiment cost. The results of cylinder pressures, the corresponding heat release rates, NOx and soot with variation of injection time at constant rail pressure, variation of EGR-rate at constant rail pressure and variation of rail pressure at constant EGR-rate between simulation and experimental data are analyzed. The results indicate that the TP model can carry out optimization and CFD (computational fluid dynamics) and can be a tool to calculate for a high-pressure common rail diesel engine.

Gambogic acid induces apoptotic cell death in T98G glioma cells

Thida, M.,Kim, D.W.,Tran, T.T.T.,Pham, M.Q.,Lee, H.,Kim, I.,Lee, J.W. Pergamon Press 2016 Bioorganic & medicinal chemistry letters Vol.26 No.3

Gambogic acid (GA), a natural product with a xanthone structure, has a broad range of anti-proliferative effects on cancer cell lines. We evaluated GA for its cytotoxic effects on T98G glioblastoma cells. GA exhibited potent anti-proliferative activity and induced apoptosis in T98G glioblastoma cells in a dose-dependent manner. Incubation of cells with GA revealed apoptotic features including increased Bax and AIF expression, cytochrome c release, and cleavage of caspase-3, -8, -9, and PARP, while Bcl-2 expression was downregulated. Furthermore, GA induced reactive oxygen species (ROS) generation in T98G cells. Our results indicate that GA increases Bax- and AIF-associated apoptotic signaling in glioblastoma cells.

Molecular mechanisms of subtype-specific inhibition of neuronal T-type calcium channels by ascorbate.

Nelson, Michael T,Joksovic, Pavle M,Su, Peihan,Kang, Ho-Won,Van Deusen, Amy,Baumgart, Joel P,David, Laurence S,Snutch, Terrance P,Barrett, Paula Q,Lee, Jung-Ha,Zorumski, Charles F,Perez-Reyes, Edward Society for Neuroscience 2007 The Journal of neuroscience Vol.27 No.46

<P>T-type Ca2+ channels (T-channels) are involved in the control of neuronal excitability and their gating can be modulated by a variety of redox agents. Ascorbate is an endogenous redox agent that can function as both an anti- and pro-oxidant. Here, we show that ascorbate selectively inhibits native Ca(v)3.2 T-channels in peripheral and central neurons, as well as recombinant Ca(v)3.2 channels heterologously expressed in human embryonic kidney 293 cells, by initiating the metal-catalyzed oxidation of a specific, metal-binding histidine residue in domain 1 of the channel. Our biophysical experiments indicate that ascorbate reduces the availability of Ca(v)3.2 channels over a wide range of membrane potentials, and inhibits Ca(v)3.2-dependent low-threshold-Ca2+ spikes as well as burst-firing in reticular thalamic neurons at physiologically relevant concentrations. This study represents the first mechanistic demonstration of ion channel modulation by ascorbate, and suggests that ascorbate may function as an endogenous modulator of neuronal excitability.</P>

Robust Magnetic Order of Ce 4f-electrons Coexisting with Superconductivity in CeFeAsO1−xFx

T. Shang,L. Jiao,J. Dai,H. Q. Yuan,F. F. Balakirev,W. Z. Hu,N. L. Wang 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12

The electrical resistance of CeFeAsO1−xFx (x = 0.06 and 0.08) has been measured in magneticfields up to 40 T. At zero field, the sample with x = 0.06 shows a structural phase transition aroundTS 100 K, followed by a spin-density-wave (SDW) transition around TSDW 30 K. For x =0.08, the structural phase transition is suppressed down to TS 60 K without a clear anomalyassociated with the Fe-SDW transition, and superconductivity shows up at TC 25 K. At lowertemperatures, both samples show a clear resistive peak around TN 4 K, which is associated withthe antiferromagnetic (AFM) transition of Ce 4f-electrons. Strikingly, zero resistance is recoveredupon a further lowering of the temperature to below TN for x = 0.08. Moreover, we found thatthe AFM transition of Ce 4f-electrons at 4 K hardly change when a magnetic field of up to 40 Twas applied. This was true even in the case of x = 0.08, for which the superconductivity had beenpartially suppressed at such a large field.

Effects of Previous Electrochemical and Chemical Corrosions on Surface Layer Softening During Electrochemical Cold Drawing of Q235 Bar

T. J. Chen,B. Q. Yang 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.12

Influences of previous electrochemical corrosion and chemical corrosion in H2SO4aqueous solution on surface layer softeningduring electrochemical cold drawing (ECD) of Q235 steel bar were investigated. Results indicate that these two corrosionsall further soften the steel during the subsequent ECD and make the ECD to easier conduct, and the effect from the formercorrosion is larger than that from the latter one. Two modes of corrosion can slightly soften or plasticize the bar surfacelayer due to the increased vacancy clusters, but the contribution of this softening or plasticizing itself to the further softeningduring ECD is very limited, and the further softening should be mainly attributed to the relaxation of dislocations throughabsorbing the vacancy clusters and the resulted weakening of work hardening. The current applied during the electrochemicalcorrosion can promote more vacancy clusters to form in a deeper region beneath the bar surface, and thus the relaxingdegree for the dislocations and the influence region are larger than those from the chemical corrosion respectively, resultingin the greater softening.

Generating Short-Pulse Laser by Using a Quenched Distributed Feedback Dye Laser

D. Q. Hoa,V. Duong,P. Long,T. H. Nhung,T. Imasaka 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.6

The quenching effect of a distributed feedback dye laser is detail studied. In detail a simulation model of combined dye lasers relying on the rate equation system with both lasers having a common lasing medium is demonstrated. The calculation using this model for a dye material shows that single picosecond pulses are attained for a quenched distributed feedback laser (Q/DFDL) over a large lasing range of dye materials. The simulation results using pyrromethene 567 dye provided single pulses of 49 ps with high narrowband as could possibily be approached.

Coronary Atherosclerosis T₁-Weighed Characterization With Integrated Anatomical Reference

Xie, Y.,Kim, Y.J.,Pang, J.,Kim, J.S.,Yang, Q.,Wei, J.,Nguyen, C.T.,Deng, Z.,Choi, B.W.,Fan, Z.,Bairey Merz, C.N.,Shah, P.K.,Berman, D.S.,Chang, H.J.,Li, D. Elsevier Science B.V. Amsterdam 2017 JACC CARDIOVASCULAR IMAGING Vol.10 No.6

Objectives: The aim of this work is the development of coronary atherosclerosis T<SUB>1</SUB>-weighted characterization with integrated anatomical reference (CATCH) technique and the validation by comparison with high-risk plaque features (HRPF) observed on intracoronary optical coherence tomography (OCT) and invasive coronary angiography. Background: T<SUB>1</SUB>-weighted cardiac magnetic resonance with or without contrast media has been used for characterizing coronary atherosclerosis showing promising prognostic value. Several limitations include: 1) coverage is limited to proximal coronary segments; 2) spatial resolution is low and often anisotropic; and 3) a separate magnetic resonance angiography acquisition is needed to localize lesions. Methods: CATCH acquired dark-blood T<SUB>1</SUB>-weighted images and bright-blood anatomical reference images in an interleaved fashion. Retrospective motion correction with 100% respiratory gating efficiency was achieved. Reference control subjects (n = 13) completed both pre- and post-contrast scans. Stable angina patients (n = 30) completed pre-contrast scans, among whom 26 eligible patients also completed post-contrast scans. After cardiac magnetic resonance, eligible patients (n = 22) underwent invasive coronary angiography and OCT for the interrogation of coronary atherosclerosis. OCT images were assessed and scored for HRPF (lipid-richness, macrophages, cholesterol crystals, and microvessels) by 2 experienced analysts blinded to magnetic resonance results. Results: Per-subject analysis showed none of the 13 reference control subjects had coronary hyperintensive plaques (CHIP) in either pre-contrast or post-contrast CATCH. Five patients had CHIP on pre-contrast CATCH and 5 patients had CHIP on post-contrast CATCH. Patients with CHIP had greater lipid abnormality than those without. Per-segment analysis showed elevated pre- and post-contrast plaque to myocardium signal ratio in the lesions with HRPF versus those without. Positive correlation was observed between plaque to myocardium signal ratio and OCT HRPF scoring. CHIP on pre-contrast CATCH were associated with significantly higher stenosis level than non-CHIP on invasive coronary angiography. Conclusions: CATCH provided accelerated whole heart coronary plaque characterization with simultaneously acquired anatomical reference. CHIP detected by CATCH showed positive association with high-risk plaque features on invasive imaging studies.

Comparative Palm Oil Trade Performance in Indonesia, Malaysia, and the Philippines

Maria Noriza Q,Herrera,Renen Szilardo C,de Guzman,Dinah Pura T,Depositario,Loida E,Mojica,Jeanette Angelin B,Madamba The International Academy of Global Business and T 2019 The International Academy of Global Business and T Vol.15 No.2

Purpose – As one of the most traded commodities in the world with tremendous economic significance, palm oil is an inexpensive source of oil. This paper examined and compared the palm oil trade performance of the Philippines relative to its top palm oil producing neighbors, Indonesia and Malaysia, by analyzing importexport volume trends of the said food commodity, consumption and production trends, self-sufficiency, import dependence, and shifting patterns of comparative advantage. Design/Methodology/Approach – Secondary data covering the period from 1964 through 2018 were collected from various sources, and descriptive analysis coupled with trend analysis were employed with respect to import and export, production, and consumption performance. Other trade indicators were computed, to wit: balance of trade, self-sufficiency ratio, import dependency ratio, and normalized trade balance. Implications were drawn after the comparative analysis among the three countries was done. Findings – An increase in the volume of the palm oil supply in the Philippines is evident, and this is attributed to increasing importation. Relative to Malaysia and Indonesia, the Philippines lags behind in international trade. While Philippine palm oil industry growth has been stagnant in terms of international trade by virtue of its net importer status, Malaysia and Indonesia have overtaken the country significantly, having attained selfsufficiency in the commodity with trade surpluses, and the gap is expected to widen in the coming years. It is interesting to note that the Philippines, Malaysia, and Indonesia had identical production volumes and growth rates until the last decade of the 21st century. A steadily growing industry, palm oil is foreseen to continue being a vital industry, not only to top producing countries such as Malaysia and Indonesia but also in the Philippines, which is trying to improve its palm oil trade performance by expanding production. Research Implications – The study findings imply expansion and income opportunities not only for local oil palm producers, processors, and traders in the Philippines but also for foreign market entrants.