Leucine supplementation mimics the effects of caloric restriction on yeast chronological lifespan

Gorospe Choco Michael,Jemiseye Olumide Temitayo,이성근 대한독성 유전단백체 학회 2022 Molecular & cellular toxicology Vol.18 No.1

Backgrounds Leucine prototrophic yeast exhibits extended longevity and related phenotypes similar to yeast grown under calorie restriction (CR) condition. The extended longevity of leucine prototrophic yeast is thought to be a function of abundant cellular leucine level. Objective To verify the similar effects of leucine-induced and CR-induced chronological life span (CLS), leucine prototrophic and auxotrophic yeast cells were grown in the presence or absence of exogenous leucine supplementation and CR condition, and their lifespan and various phenotypes were examined. Results Leucine supplementation induced CLS extension, increased cellular Cox2p levels, and decreased cell death. These phenotypes were similar to those of the cells grown under CR. Interestingly, simultaneous treatment with exogenous leucine supplementation and CR led to a synergistic effect. CLS and cellular Cox2p levels increased further by simultaneous treatment compared to the observations in cells treated with either leucine supplementation or CR. Similarly, the rate of cell death of simultaneously treated cells was signifi cantly lower than that of cells undergoing only one treatment. Conclusion Leucine-induced CLS extension and a decreased in the rate of cell death observed in this study verified the function of leucine in cell death prevention and CLS extension in yeast. Interestingly, leucine-induced changes were similar to CR-induced changes. The results in this study suggest that leucine can function as a CR mimetic.

Delamination behaviour of GdBCO coated conductor tapes under transverse tension

Gorospe, A.,Nisay, A.,Dizon, J.R.,Shin, H.S. North-Holland 2013 Physica. C, Superconductivity Vol.494 No.-

The electromechanical property behaviour of 2G coated conductor (CC) tapes fabricated by multi-layer deposition process both in the in-plane and transverse direction should be understood. The CC tapes are used in the fabrication of epoxy resin-impregnated coils. In such case, the Lorentz force due to the high magnetic field applied as well as the thermal stress due to the difference in coefficient of thermal expansion (CTE) among constituent layers during cooling to cryogenic temperature will induce transversely applied load to the surface of CC tapes in coils. Hence, the CC tape should have a good mechanical property in the transverse direction in order to maintain its superior performance under magnetic field. In this study, a test frame which gives precisely aligned transverse load was devised. Using the fixture, the delamination behaviours including the delamination strength of the GdBCO CC tapes under transverse tensile loading were investigated. Large variation on the delamination strength of the CC tapes was recorded and might have resulted from the slit edge effect and the inhomogeneity of the CC tapes. The I<SUB>c</SUB> degradation behaviour under transverse load was related to the location where delamination occurred in the sample.

Investigation on the electromechanical properties of RCE-DR GdBCO CC tapes under transversely applied load

Gorospe, Alking B.,Shin, Hyung-Seop The Korea Institute of Applied Superconductivity a 2014 한국초전도저온공학회논문지 Vol.16 No.4

REBCO coated conductor (CC) tapes with superior mechanical and electromechanical properties are preferable in applications such as superconducting coils and magnets. The CC tapes should withstand factors that can affect their performance during fabrication and operation of its applications. In coil applications, CC tapes experience different mechanical constraints such as tensile or compressive stresses. Recently, the critical current ($I_c$) degradation of CC tapes used in coil applications due to delamination were already reported. Thermal cycling, coefficient of thermal expansion mismatch among constituent layers, screening current, etc. can induce excessive transverse tensile stresses that might lead to the degradation of $I_c$ in the CC tapes. Also, CC tapes might be subjected to very high magnetic fields that induce strong Lorentz force which possibly affects its performance in coil applications. Hence, investigation on the delamination mechanism of the CC tapes is very important in coiling, cooling, operation and design of prospect applications. In this study, the electromechanical properties of REBCO CC tapes fabricated by reactive co-evaporation by deposition and reaction (RCE-DR) under transversely applied loading were investigated. Delamination strength of the CC tape was determined using the anvil test. The $I_c$ degraded earlier under transverse tensile stress as compared to that under compressive one.

Delamination Characteristics in Wide REBCO Coated Conductor Tapes Under Transverse Loading

Gorospe, Alking,Dedicatoria, Marlon J.,Hyung-Seop Shin Institute of Electrical and Electronics Engineers 2015 IEEE transactions on applied superconductivity Vol.25 No.3

<P>Superior characteristics and great potential of coated conductor (CC) tapes are some of the promises in pursuit of energy efficient application in electrical field. However, in electric device applications, the coefficient of thermal expansion (CTE) mismatch of each constituent layer, screening current, excessive radial tensile stresses during operation, and other coil fabrication related reasons might cause delamination damage in CC tapes. It was reported that the delamination among its constituent layers resulted to the degradation of its electromechanical properties on coil application. Therefore, the investigation on its delamination behavior is necessary for device application design. In this study, using the anvil test method, the delamination behaviors in 12-mm-wide Cu stabilized and brass laminated GdBa<SUB>2</SUB>Cu<SUB>3</SUB>Oy CC tapes with stainless steel substrate were investigated. The mechanical delamination strength of the CC tapes for differently assembled upper anvil and CC tape configurations about widthwise direction was investigated by using a 4 mm × 8 mm size upper anvil. Mechanical delamination strength of the CC tape was not enhanced by the addition of brass laminate and showed no significant difference depending on the superconducting side or the substrate side. Furthermore, both CC tapes exhibited similar delamination mechanisms and sites but showed different fracture morphologies.</P>

Delamination behaviors of GdBCO CC tapes under different transverse loading conditions

Gorospe, Alking B.,Bautista, Zhierwinjay M.,Shin, Hyung-Seop The Korea Institute of Applied Superconductivity a 2015 한국초전도저온공학회논문지 Vol.17 No.3

In superconducting coil applications particularly in wet wound coils, coated conductor (CC) tapes are subjected to different type of stresses. These include hoop stress acting along the length of the CC tape and the Lorentz force acting perpendicular to the CC tape's surface. Since the latter is commonly associated with delamination problem of multi-layered CC tapes, more understanding and attention on the delamination phenomena induced in the case of coil applications are needed. Difference on the coefficient of thermal expansion (CTE) of each constituent layer of the CC tape, the bobbin, and the impregnating materials is the main causes of delamination in CC tapes when subjected to thermal cycling. The CC tape might also experience cyclic loading due to the energizing scheme (on - off) during operation. In the design of degradation-free superconducting coils, therefore, characterization of the delamination behaviors including mechanism and strength in REBCO CC tapes becomes critical. In this study, transverse tensile tests were conducted under different loading conditions using different size of upper anvils on the GdBCO CC tapes. The mechanical and electromechanical delamination strength behaviors of the CC tapes under transverse tensile loading were examined and a two-parameter Weibull distribution analysis was conducted in statistical aspects. As a result, the CC tape showed similar range of mechanical delamination strength regardless of cross-head speed adopted. On the other hand, cyclic loading might have affected the CC tape in both upper anvil sizes adopted.

Delamination behaviour in differently copper laminated REBCO coated conductor tapes under transverse loading

Gorospe, A.,Nisay, A.,Shin, H.S. North-Holland 2014 Physica. C, Superconductivity Vol.504 No.-

Laminated HTS coated conductor (CC) tapes having a unique multi-layer structure made them vulnerable when exposed to transverse loading. Electromechanical transport properties of these CC tapes can be affected by excessive transverse stresses. Due to the coefficient of thermal expansion (CTE) mismatch and incompatibility among constituent materials used in coil applications, delamination among layers occurs and causes critical current, I<SUB>c</SUB> degradation in the CC tapes. In this study, the delamination behaviors in copper (Cu) solder-laminated CC tapes by soldering and surround Cu-stabilized ones by electroplating under transverse tension loading were investigated. Similarly to the surround Cu-stabilized CC tapes in our previous reports, the Cu solder-laminated CC tapes also showed an abrupt and gradual I<SUB>c</SUB> degradation behavior. However, the Cu solder-laminated CC tapes showed different delamination morphologies as compared to the surround Cu-stabilized CC tapes; the superconducting side and the substrate side of the Cu solder laminated CC tapes were totally separated by delamination. On the other hand, the brass laminate did not show any significant effect on the delamination strength when it is added upon the surround Cu-stabilized CC tapes.

Characteristic Irreversible Critical Strain Limit of GdBCO-Coated Conductor Tapes Under Various Temperature and Magnetic Field Conditions

Gorospe, Alking,Bautista, Zhierwinjay,Hyung-Seop Shin,Oguro, Hidetoshi,Awaji, Satoshi IEEE 2017 IEEE transactions on applied superconductivity Vol.27 No.4

<P>Superior mechanical and electromechanical properties of the coated conductor (CC) tapes made them a viable option for coil and magnet applications. In this study, investigation on the characteristics of I<SUB>c</SUB> under different B, T, and ε conditions were conducted. Tensile load was applied using the Katagiri type test rig under different high magnetic field and low-temperature conditions wherein irreversible strain, ε<SUB>irr</SUB> was determined. The I<SUB>c</SUB> behavior with magnetic field of both reactive co-evaporation by deposition and reaction (RCE-DR) and metal organic chemical vapor deposition (MOCVD) processed CC tapes at different T and B were obtained. The critical irreversible strain limit ε<SUB>irr</SUB> of Cu-stabilized REBCO CC tape increased with decreasing temperature from 65 K down to 20 K. This behavior was resulted from the increased yield strength of the CC tape due to thermal hardening effect.</P>

Critical current degradation behaviour of GdBCO CC tapes in pure torsion and combined tension-torsion modes

Gorospe, Alking,Bautista, Zhierwinjay,Shin, Hyung-Seop IOP 2016 Superconductor science & technology Vol.29 No.10

<P>Coated conductor (CC) tapes utilized in high-current-density superconducting cables are commonly subjected to different loading modes, primarily torsion and tension especially in the case of twisted stacked-tape cable. Torsion load can occur due to twisting along the length or when winding the CC tapes around a former, while tension load can occur due to pre-tension when coiled and as a hoop stress when the coil is energized. In this study, electromechanical properties of single CC tapes under torsion load were investigated using a new test apparatus. The results could provide basic information for cable designers to fully characterize stacked cables. Copper-electroplated and brass-laminated CC tapes fabricated with different deposition techniques were subjected to pure torsion and combined tension-torsion loading. The critical current, <I>I</I> <SUB>c</SUB> degradation behaviours of CC tapes under torsional deformation were examined. Also, the effect of further external lamination on the <I>I</I> <SUB>c</SUB> degradation behaviour of the CC tapes under such loading conditions was investigated. In the case of the combined tension-torsion test, short samples were subjected to twist pitches of 200 mm and 100 mm. Critical parameters including reversible axial stress and strain in such twist pitch conditions were also investigated.</P>

Influence of Edge Geometry on the Delamination Strength of REBCO CC Tapes Using Anvil Test Method

Gorospe, Alking,Dedicatoria, Marlon James,Hyung-Seop Shin Institute of Electrical and Electronics Engineers 2016 IEEE transactions on applied superconductivity Vol.26 No.4

<P>In wet-wound epoxy impregnated coils, the whole coated conductor (CC) tape structure experiences radial/ transverse tensile stress due to large Lorentz force, which might induce delamination damage and in turn affects its transport performance during operation. The characterization of the delamination strength of CC tapes is therefore necessary for such practical applications. The anvil testing method was done to characterize the mechanical properties of REBCO CC tapes considering the possible transverse tensile stress condition in CC tape windings in coil applications. The delamination strength of three different CC tape samples slit from a 12-mm-wide one was determined using two different sized upper Cu anvils. It was observed that the slitting process has resulted to different CC tape edge geometries such as burrs and filleted corners of the substrate layer. As a result, significantly lower mechanical delamination strength was exhibited by the CC tapes when their whole width was covered by the upper anvil. Using the wide upper anvil, the edge geometry such as burrs and thick stabilizing layer played an important role on the delamination damage of the CC tape. Using a statistical method, the intrinsic strength of the CC tapes was distinguished from those that were affected by poor soldering, misalignment, and other external factors during the tests. Delamination sites mainly occurred within the REBCO film and on the buffer/REBCO interface. Finally, delamination schematics were drawn based on the delaminated CC tape's morphology.</P>

LETTER TO THE EDITOR : Parvimonas micra chest wall abscess following transthoracic lung needle biopsy

( Luis Gorospe ),( Isabel Bermudez Coronel Prats ),( Carol F Gomez Barbosa ),( Maria E Olmedo Garcia ),( Angel Ruedas Lopez ),( Vicente Gomez Del Olmo ) 대한내과학회 2014 The Korean Journal of Internal Medicine Vol.29 No.6