Irreversibility line and flux pinning properties in iron-based high-T_c superconductor SmFeAsO_0.85

Ahmad, D.,Park, I.,Kim, G.C.,Lee, J.H.,Ren, Z.A.,Kim, Y.C. North-Holland 2009 Physica. C, Superconductivity Vol.469 No.15

The irreversibility line and flux pinning properties of high-T<SUB>c</SUB> superconductor SmFeAsO<SUB>0.85</SUB> were studied using DC magnetization data. Polycrystalline SmFeAsO<SUB>0.85</SUB> was prepared in a high pressure synthesis apparatus under the pressure of 6GPa. The results of DC susceptibility showed the superconducting transition at about 55K. A critical current density J<SUB>c</SUB>(B) was calculated using Bean's critical state model. At low temperatures (=<20K), J<SUB>c</SUB>(B) showed a relatively high value with weak dependence on an applied magnetic field. At higher temperatures, a stronger dependence of the magnetic field was observed, which resulted from decrease in a critical current density probably due to the flux creep effect. The irreversibility line (IL) agreed well with the flux creep theory of Matsushita et al. A comparison of normalized pinning force density with the theoretical models showed that the irreversible behavior in SmFeAsO<SUB>0.85</SUB> is dominated mainly by normal point pinning (δT<SUB>c</SUB>) and surface pinning mechanisms.

Arterial Steal to the Penumbra Area in Patients with Acute MCA Occlusion: A Quantitative Angiographic Analysis

René van den Berg,Jenna J. Wildeman,Olvert A. Berkhemer,Rogier V. Immink,Henk A. Marquering,Charles B.L.M. Majoie,Dagmar Verbaan,Ed T. van Bavel 대한신경중재치료의학회 2020 Neurointervention Vol.15 No.3

Purpose: In acute middle cerebral artery (MCA) occlusion, collateral vessels provide retrograde supply to the occluded territory. We hypothesized that such collateral flow reduces perfusion of the non-occluded donor region (steal effect).Materials and Methods: Patients with an MCA occlusion with opacification of both ipsi- and contralateral anterior cerebral arteries (ACA) on angiography prior to endovascular treatment were selected. Arteriovenous transit time (AVTT) for both ACA territories was compared for different grades of collateral supply to the MCA territory. In addition, the influence of diabetes and hypertension was analyzed. After successful revascularization, AVTT was re-assessed to determine reversibility.Results: Forty-one patients were analyzed. An AVTT of 8.6 seconds (standard deviation [SD] 2.4 seconds) was seen in the ACA territory of the affected hemisphere in comparison to 6.6 seconds (SD 2.1 seconds) for the contralateral side (P<0.001). A more prolonged (but not significant) AVTT was seen in cases with a higher collateral grade. No difference in AVTT was seen in patients with diabetes or hypertension. After successful MCA revascularization, AVTT delay was 7.4 seconds (SD 2.1 seconds).Conclusion: A cerebral steal effect occurs in patients with an acute MCA occlusion, probably related to augmented flow to the penumbra area.

Perinatal Immunization With Vaccine-Grade Listeria monocytogenes Provides Protection Against Murine Th2 Airway Inflammation

Sheka Yagub Aloyouni,Charis-Patricia Segeritz,Ashley M. Sherrid,Matthew J. Gold,Daniela I. M. Loeffler,Marie-Renée Blanchet,Bing Cai,Jeremy Hirota,Kelly M. McNagny,Tobias R. Kollmann 대한천식알레르기학회 2014 Allergy, Asthma & Immunology Research Vol.6 No.4

Purpose: Asthma is a chronic respiratory disorder that leads to inflammation and narrowing of the airways. Its global prevalence has attained epidemiclevels and treatment options that reach beyond temporary relief of symptoms are urgently needed. Since the processes leading to clinicallysymptomatic asthma start early in life, we set out to systematically evaluate a neonatal immunotherapeutic based on Listeria monocytogenes (Lm)for the control of allergic sensitization. Methods: We modified Lm to express the model allergen, ovalbumin (OVA), and tested the ability of neonatalimmunization with this strain to control allergic sensitization in a mouse model of OVA-induced asthma. Mice were immunized as newborns withlive or heat killed LmOVA or live Lm, followed 6 weeks later by allergic sensitization with OVA. In order to determine whether the TH1-polarizing effectof this vaccine vector inadvertently may exacerbate development of certain TH1-driven allergic diseases, mice immunized as newborns were assessedin a model of adult hypersensitivity pneumonitis (HP). Results: Both LmOVA and Lm-control vaccines were highly effective in providinglong-lasting protection from airway inflammation after only one immunization given perinatally. Serum antibody levels and lung cytokine productionsuggest that this prophylactic strategy is associated with an allergen specific TH1-dominated response. Specifically, LmOVA vaccinated mice displayedsignificantly elevated OVA-specific serum IgG2a, but no difference in anti-OVA IgE antibodies and only slightly decreased anti-OVA IgG1 antibodies. Importantly, Lm-based neonatal vaccination did not exacerbate Th1/Th17 driven HP, arguing against broad spectrum immune skewing. Conclusions:Our findings highlight the promise of early life Lm-based immunomodulatory interventions as a prophylactic strategy for allergic asthma.

A Simple, Reliable, and Inexpensive Intraoperative External Expansion System for Enhanced Autologous Structural Fat Grafting

Carlo M. Oranges,Mathias Tremp,Barbara Ling,Reto Wettstein,René D. Largo,Dirk J. Schaefer 대한성형외과학회 2016 Archives of Plastic Surgery Vol.43 No.5

External volume expansion of the recipient site by suction has been proposed as a way of improving fat graft survival. The objective of this study was to present an innovative and simple intraoperative external expansion system to enhance small-volume autologous fat grafting (40–80 mL) and to discuss its background and its mechanism of action. In this system, expansion is performed using a complete vacuum delivery system known as the Kiwi VAC- 6000M with a PalmPump (Clinical Innovations). The recipient site is rapidly expanded intraoperatively 10 times for 30 seconds each with a negative pressure of up to 550 mm Hg before autologous fat injection. During this repetitive stimulation, the tissues become grossly expanded, developing macroscopic swelling that regresses slowly over the course of hours following the cessation of the stimulus. The system sets various mechanisms in motion, including scar release, mechanical stimulation, edema, ischemia, and inflammation, which provide an environment conducive for cell proliferation and angiogenesis. In order to maintain the graft construct in its expansive state, all patients are encouraged postoperatively to use the Kiwi three times daily for one minute per session over the course of three days. The handling of this system is simple for both the patients and the surgeon. Satisfactory clinical outcomes have been achieved without significant complications.

Whole ceramic-like microreactors from inorganic polymers for high temperature or/and high pressure chemical syntheses

Ren, W.,Perumal, J.,Wang, J.,Wang, H.,Sharma, S.,Kim, D. P. Royal Society of Chemistry 2014 Lab on a chip Vol.14 No.4

Two types of whole ceramic-like microreactors were fabricated from inorganic polymers, polysilsesquioxane (POSS) and polyvinylsilazane (PVSZ), that were embedded with either perfluoroalkoxy (PFA) tube or polystyrene (PS) film templates, and subsequently the templates were removed by physical removal (PFA tube) or thermal decomposition (PS). A POSS derived ceramic-like microreactor with a 10 cm long serpentine channel was obtained by an additional 'selective blocking of microchannel' step and subsequent annealing at 300 degrees C for 1 h, while a PVSZ derived ceramic-like microreactor with a 14 cm long channel was yielded by a co-firing process of the PVSZ-PS composite at 500 degrees C for 2 h that led to complete decomposition of the film template leaving a microchannel behind. The obtained whole ceramic-like microfluidic devices revealed excellent chemical and thermal stabilities in various solvents, and they were able to demonstrate unique chemical performance at high temperature or/and high pressure conditions such as Michaelis-Arbuzov rearrangement at 150-170 degrees C, Wolff-Kishner reduction at 200 degrees C, synthesis of super-paramagnetic Fe3O4 nanoparticles at 320 degrees C and isomerisation of allyloxybenzene to 2-allylphenol (250 degrees C and 400 psi). These economic ceramic-like microreactors fabricated by a facile non-lithographic method displayed excellent utility under challenging conditions that is superior to any plastic microreactors and comparable to glass and metal microreactors with high cost.

First-principles study of the crystal structures and physical properties of H₁₈-BN and Rh6-BN

Ren, X.Y.,Zhao, C.X.,Niu, C.Y.,Wang, J.Q.,Jia, Y.,Cho, J.H. North-Holland 2016 Physics letters. Section A. Vol.380 No.46

<P>As the analog of carbon allotropes, new three-dimensional (3D) boron nitride (BN) allotropes have attracted much attention of researchers due to their great importance in fundamental sciences and wide practical applications. Here, based on first-principles density-functional theory calculations, we predict two new stable BN allotropes: One is H-18-BN with the P (6) over bar m2 (D-3h(1)) symmetry containing eighteen atoms in the hexagonal unit cell and the other is Rh6-BN with the R (3) over barm (C-3v(5)) symmetry containing six atoms in the rhombohedral primitive unit cell. The dynamic stabilities of the two structures are examined through the phonon spectrum analysis as well as molecular dynamics simulations, whereas the mechanical properties are analyzed by elastic constants, bulk modulus and shear modulus. From the analysis of the enthalpy evolution with respect to pressure, we find that h-BN can be transformed into either H-18-BN or RH6-BN structure under a higher pressure of similar to 15 GPa. We also find that both the H-18-BN and Rh6-BN allotropes are brittle materials with indirect band gaps of 2.31 and 4.48 eV, respectively. The simulated XRD spectra provide detailed structural information of H-18-BN and Rh6-BN for future experimental examinations. Our findings not only greatly enrich the existing structural family of 3D-BN materials but also stimulate further experiments. (C) 2016 Elsevier B.V. All rights reserved.</P>

A penny-shaped interfacial crack between piezoelectric layer and elastic half-space

J.H. Ren,Y.S. Li,W. Wang 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.1

An interfacial penny-shaped crack between piezoelectric layer and elastic half-space subjected to mechanical and electric loads is investigated. Using Hankel transform technique, the mixed boundary value problem is reduced to a system of singular integral equations. The integral equations are further reduced to a system of algebraic equations with the aid of Jacobi polynomials. The stress intensity factor and energy release rate are determined. Numerical results reveal the effects of electric loadings and material parameters of composite on crack propagation and growth. The results seem useful for design of the piezoelectric composite structures and devices of high performance.

A penny-shaped interfacial crack between piezoelectric layer and elastic half-space

Ren, J.H.,Li, Y.S.,Wang, W. Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.1

An interfacial penny-shaped crack between piezoelectric layer and elastic half-space subjected to mechanical and electric loads is investigated. Using Hankel transform technique, the mixed boundary value problem is reduced to a system of singular integral equations. The integral equations are further reduced to a system of algebraic equations with the aid of Jacobi polynomials. The stress intensity factor and energy release rate are determined. Numerical results reveal the effects of electric loadings and material parameters of composite on crack propagation and growth. The results seem useful for design of the piezoelectric composite structures and devices of high performance.

Fluorescent bioimaging of pH: from design to applications

Hou, J. T.,Ren, W.,Li, K.,Seo, J.,Sharma, A.,Yu, X. Q.,Kim, J. Royal Society of Chemistry, etc 2017 Chemical Society reviews Vol.46 No.8

<P>Protons play crucial roles in many physiological and pathological processes, such as receptor-mediated signal transduction, ion transport, endocytosis, homeostasis, cell proliferation, and apoptosis. The urgent demand for pH imaging and measurement in biological systems has incited the development of fluorescent pH probes. Numerous fluorescent probes have been reported, but many lack the abilities needed for biological applications. Hence, the development of new pH probes with better biocompatibility, sensitivity, and site-specificity is still indispensable. This review highlights the recent trends in the development of fluorescent materials as essential tools for tracing pH variations in the biological processes of diverse living systems.</P>

Facile synthesis of porous TiO₂ nanospheres and their photocatalytic properties

Huang, J.,Ren, H.,Liu, X.,Li, X.,Shim, J.J. Academic Press 2015 Superlattices and microstructures Vol.81 No.-

Uniform and monodisperse porous TiO<SUB>2</SUB> nanospheres were synthesized by a hydrothermal method. Techniques of X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller (BET) nitrogen adsorption-desorption, UV-vis absorption spectroscopy, and transmission electron microscopy were used to characterize the structure and morphology of the products. The BET surface area of the porous TiO<SUB>2</SUB> nanospheres was calculated to be 26.1cm<SUP>2</SUP>g<SUP>-1</SUP>. In addition, the obtained porous TiO<SUB>2</SUB> nanospheres were used as catalyst to photodegrade methylene blue, Rhodamine B, methyl orange, p-nitrophenol, and eosin B. Compared to commercial TiO<SUB>2</SUB> powder, the as-prepared porous TiO<SUB>2</SUB> nanospheres exhibited higher catalytic activities due to their large surface areas and porous nanostructures. The photocatalytic reaction rate constant of the porous TiO<SUB>2</SUB> nanospheres in photocatalytic decomposition of methylene blue and Rhodamine B under simulated solar light were calculated as 0.0545min<SUP>-1</SUP> and 0.0579min<SUP>-1</SUP>, respectively. Moreover, the catalyst was demonstrated to have good stability and reusability.