306 research outputs found
The Pricing of Asian Options in Uncertain Volatility Model
This paper studies the pricing of Asian options when the volatility of the underlying
asset is uncertain. We use the nonlinear Feynman-Kac formula in the G-expectation theory
to get the two-dimensional nonlinear PDEs. For the arithmetic average fixed strike Asian
options, the nonlinear PDEs can be transferred to linear PDEs. For the arithmetic average
floating strike Asian options, we use a dimension reduction technique to transfer the two-dimensional
nonlinear PDEs to one-dimensional nonlinear PDEs. Then we introduce the
applicable numerical computation methods for these two classes of PDEs and analyze the
performance of the numerical algorithms
The impacts of precipitation increase and nitrogen addition on soil respiration in a semiarid temperate steppe
Soil respiration, Rs, is strongly controlled by water availability in semiarid grasslands. However, how Rs is affected by precipitation change (either as rainfall or as snowfall) especially under increasing nitrogen (N) deposition has been uncertain. A manipulative experiment to investigate the responses of growing season Rs to changes in spring snowfall or summer rainfall with or without N addition was conducted in the semiarid temperate steppe of China during three hydrologically contrasting years. Our results showed that both spring snow addition and summer water addition significantly increased Rs by increasing soil moisture. The effect of spring snow addition only occurred in years with both relatively lower natural snowfall and later snowmelt time. Summer water addition showed a much stronger effect on Rs by increasing plant root growth and microbial activities, but the magnitude also largely depended on the possible legacy effect of previous year precipitation. Our results indicated that precipitation increase in the form of snowfall had weaker effects than that in the form of rainfall as the former only accounted for less than 30% of total precipitation. Compared with other ecosystem processes, Rs was less responsible for increase in N deposition as it did not increase root productivity and microbial activities in the soils. Our results provided field data constraints for modeling the ecosystem carbon balance under the future global change scenarios in semiarid grasslands
Water and nitrogen availability co-control ecosystem CO2 exchange in a semiarid temperate steppe
Both water and nitrogen (N) availability have significant effects on ecosystem CO2 exchange (ECE), which includes net ecosystem productivity (NEP), ecosystem respiration (ER) and gross ecosystem photosynthesis (GEP). How water and N availability influence ECE in arid and semiarid grasslands is still uncertain. A manipulative experiment with additions of rainfall, snow and N was conducted to test their effects on ECE in a semiarid temperate steppe of northern China for three consecutive years with contrasting natural precipitation. ECE increased with annual precipitation but approached peak values at different precipitation amount. Water addition, especially summer water addition, had significantly positive effects on ECE in years when the natural precipitation was normal or below normal, but showed trivial effect on GEP when the natural precipitation was above normal as effects on ER and NEP offset one another. Nitrogen addition exerted non-significant or negative effects on ECE when precipitation was low but switched to a positive effect when precipitation was high, indicating N effect triggered by water availability. Our results indicate that both water and N availability control ECE and the effects of future precipitation changes and increasing N deposition will depend on how they can change collaboratively in this semiarid steppe ecosystem
Semiconductor saturable absorber mirror passively Q-switched 2.97 Îźm fluoride fiber laser
A diode-cladding-pumped mid-infrared passively Q-switched Ho 3+-doped fluoride fiber laser using a reverse designed broad band semiconductor saturable mirror (SESAM) was demonstrated. Nonlinear reflectivity of the SESAM was measured using an in-house Yb3+-doped mode-locked fiber laser at 1062 nm. Stable pulse train was produced at a slope efficient of 12.1% with respect to the launched pump power. Maximum pulse energy of 6.65 ÎźJ with a pulse width of 1.68 Îźs and signal to noise ratio (SNR) of ~50 dB was achieved at a repetition rate of 47.6 kHz and center wavelength of 2.971 Îźm. To the best of our knowledge, this is the first 3 Îźm region SESAM based Q-switched fiber laser with the highest average power and pulse energy, as well as the longest wavelength from mid-infrared passively Q-switched fluoride fiber lasers
Direct processing of PbZr0.53Ti0.47O3 films on glass and polymeric substrates
This work was supported by the U.S. National Science Foundation under grant No. CMMI-1537262, Science Foundation Ireland (SFI) under the US-Ireland R&D Partnership Programme Grant Number SFI/14/US/I3113, the China Scholarship Council, and the Department of Education and Learning NI through grant USI-082.This work reports on direct crystallization of PbZr0.53Ti0.47O3 (PZT) thin films on glass and polymeric substrates, using pulsed thermal processing (PTP). Specifically, xenon flash lamps deliver pulses of high intensity, short duration, broadband light to the surface of a chemical solution deposited thin film, resulting in the crystallization of the film. Structural analysis by X-ray diffraction (XRD) and transmission electron microscopy show the existence of perovskite structure in nano-sized grains (â¤5âŻnm). Local functional analysis by band excitation piezoelectric spectroscopy and electrostatic force microscopy confirm the presence of a ferroelectric phase and retention of voltage-written polarization for multiple days. Based on structural and functional analyses, strategies are discussed for optimization of pulse voltage and duration for the realization of crystalline ferroelectric thin films. For âź200âŻnm-thick PZT films on glass substrates, 500âŻÎźs-long pulses were required for crystallization, starting with 100 pulses at 350âŻV, 10 or 25 pulses at 400âŻV and in general lower number of pulses at higher voltages (resulting in higher radiant energy). Overall power densities of >6.4âŻkW/cm2 were needed for appearance of peaks corresponding to the perovskite phase in the XRD. Films on glass processed at 350â400âŻV had a higher degree of 111-oriented perovskite grains. Higher applied radiant energy (through increased pulse voltage or count) resulted in more random and/or partially 001-oriented films. For âź1âŻÎźm-thick PZT films on polymeric substrates, 10 to 25 250âŻÎźs-long pulses at voltages ranging between 200 to 250âŻV, corresponding to power densities of âź2.8âŻkW/cm2, were optimal for maximized perovskite phase crystallization, while avoiding substrate damage.PostprintPeer reviewe
Maximizing information : a machine learning approach for analysis of complex nanoscale electromechanical behavior in defect-rich PZT films
F.Z. and B.J.R. gratefully acknowledge support from the China Scholarship Council and Science Foundation Ireland (US-Ireland R&D Partnership Programme (SFI/14/US/I3113) and Career Development Award (SFI/17/CDA/4637) with support from the Sustainable Energy Authority of Ireland). A.N. gratefully acknowledges support from the Engineering and Physics Sciences Research Council (EPSRC) through grants EP/R023751/1 and EP/L017008/1. A.K. gratefully acknowledges support from Department of Education and Learning NI through grant USI-082 and Engineering and Physical Sciences Research Council via grant EP/S037179/1. K.W., Y.Y., and N.B.G. gratefully acknowledge support from the US National Science Foundation through grant CMMI-1537262 and DMR-1255379. K.W. and N.B.G. also acknowledge support through DMR-2026976. This publication has emanated from research supported in part by a grant from Science Foundation Ireland under Grant numbers SFI/14/US/I3113 and SFI/17/CDA/4637.Scanning Probe Microscopy (SPM) based techniques probe material properties over microscale regions with nanoscale resolution, ultimately resulting in investigation of mesoscale functionalities. Among SPM techniques, piezoresponse force microscopy (PFM) is a highly effective tool in exploring polarization switching in ferroelectric materials. However, its signal is also sensitive to sample-dependent electrostatic and chemo-electromechanical changes. Literature reports have often concentrated on the evaluation of the Off-field piezoresponse, compared to On-field piezoresponse, based on the latter's increased sensitivity to non-ferroelectric contributions. Using machine learning approaches incorporating both Off- and On-field piezoresponse response as well as Off-field resonance frequency to maximize information, switching piezoresponse in a defect-rich Pb(Zr,Ti)O3 thin film is investigated. As expected, one major contributor to the piezoresponse is mostly ferroelectric, coupled with electrostatic phenomena during On-field measurements. A second component is electrostatic in nature, while a third component is likely due to a superposition of multiple non-ferroelectric processes. The proposed approach will enable deeper understanding of switching phenomena in weakly ferroelectric samples and materials with large chemo-electromechanical response.Publisher PDFPeer reviewe
Efficient organic solar cells enabled by simple non-fused electron donors with low synthetic complexity
Abstract Fusedâring electron donors boost the efficiency of organic solar cells (OSCs), but they suffer from high cost and low yield for their large synthetic complexity (SC > 30%). Herein, the authors develop a series of simple nonâfusedâring electron donors, PF1 and PF2, which alternately consist of furanâ3âcarboxylate and 2,2â˛âbithiophene. Note that PF1 and PF2 present very small SC of 9.7% for their inexpensive raw materials, facile synthesis, and high synthetic yield. Compared to their allâthiopheneâbackbone counterpart PTâE, two new polymers feature larger conjugated plane, resulting in higher hole mobility for them, especially a value up to â10 â4 cm 2 V â1 ¡s for PF2 with longer alkyl side chain. Meanwhile, PF1 and PF2 exhibit larger dielectric constant and deeper electronic energy level versus PTâE. Benefiting from the better physicochemical properties, the efficiencies of PF1â and PF2âbased devices are improved by â16.7% and â71.3% relative to that PTâEâbased devices, respectively. Furthermore, the optimized PF2âbased devices with introducing PC 71 BM as the third component deliver a higher efficiency of 12.40%. The work not only indicates that furanâ3âcarboxylate is a simple yet efficient building block for constructing nonâfusedâring polymers but also provides a promising electron donor PF2 for the lowâcost production of OSCs.A simple structure nonâfusedâring electron donor PF2 alternately consisting of furanâ3âcarboxylate and 2,2â˛âbithiophene presents very small synthetic complexity of 9.7% as well as low material cost of â19.0 $ g â1 . More importantly, PF2 delivers a high efficiency of 12.4% coupled with strong operational stability. imag
HSPA12A Unstabilizes CD147 to Inhibit Lactate Export and Migration in Human Renal Cell Carcinoma
This is an open access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/). See http://ivyspring.com/terms for full terms and conditions. Background: Metastasis accounts for 90% of cancer-associated mortality in patients with renal cell carcinoma (RCC). However, the clinical management of RCC metastasis is challenging. Lactate export is known to play an important role in cancer cell migration. This study investigated the role of heat shock protein A12A (HSPA12A) in RCC migration. Methods: HSPA12A expression was examined in 82 pairs of matched RCC tumors and corresponding normal kidney tissues from patients by immunoblotting and immunofluorescence analyses. The proliferation of RCC cells was analyzed using MTT and EdU incorporation assays. The migration of RCC cells was evaluated by wound healing and Transwell migration assays. Extracellular acidification was examined using Seahorse technology. Protein stability was determined following treatment with protein synthesis inhibitor cycloheximide and proteasome inhibitor MG132. Mass spectrometry, immunoprecipitation, and immunoblotting were employed to examine protein-protein interactions. Results: RCC tumors from patients showed downregulation of HSPA12A, which was associated with advanced tumor node metastasis stage. Intriguingly, overexpression of HSPA12A in RCC cells inhibited migration, whereas HSPA12A knockdown had the opposite effect. Lactate export, glycolysis rate, and CD147 protein abundance were also inhibited by HSPA12A overexpression but promoted by HSPA12A knockdown. An interaction of HSPA12A with HRD1 ubiquitin E3 ligase was detected in RCC cells. Further studies demonstrated that CD147 ubiquitination and proteasomal degradation were promoted by HSPA12A overexpression whereas inhibited by HSPA12A knockdown. Notably, the HSPA12A overexpression-induced inhibition of lactate export and migration were abolished by CD147 overexpression. Conclusion: Human RCC shows downregulation of HSPA12A. Overexpression of HSPA12A in RCC cells unstabilizes CD147 through increasing its ubiquitin-proteasome degradation, thereby inhibits lactate export and glycolysis, and ultimately suppresses RCC cell migration. Our results demonstrate that overexpression of HSPA12A might represent a viable strategy for managing RCC metastasis
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