Optical and Electrical Properties of InAs/GaAs Quantum-dot Solar Cells

Ryan P. Smith,한임식,김종수,노삼규,임재영 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.6

We investigated the optical and the electrical properties of InAs quantum-dot solar cells (QDSCs)with various InAs deposition thicknesses () via photoluminescence (PL), spectral response (SR),and current density-voltage (J-V) measurements. We fabricated three QDSCs with thicknesses of2.0, 2.5, and 3.0 monolayers (MLs). Our measurements revealed the effects of the QD size onthe spectral response, the conversion efficiency (η) and the device parameters. The QDSCs had amaximum η of 17% for = 2.0 ML under AM1.5G conditions. The change of device parameters invarious QDSCs could be explained by the effects of the balance between enhanced carrier productionfrom the QD layers and carrier trapping/re-capturing by strain-induced defect/QD states.

Cytokine profiles in intensive care unit delirium

Ryan J. Smith,Christian Lachner,Vijay P. Singh,Shubham Trivedi,Biswajit Khatua,Rodrigo Cartin-Ceba 대한중환자의학회 2022 Acute and Critical Care Vol.37 No.3

Background: Neuroinflammation causing disruption of the blood-brain barrier and immune cell extravasation into the brain parenchyma may cause delirium; however, knowledge of the exact pathophysiologic mechanism remains incomplete. The purpose of our study was to determine whether cytokine profiles differ depending on whether delirium occurs in the setting of sepsis, coronavirus disease 2019 (COVID-19), or recent surgery.Methods: This prospective observational cohort study involved 119 critically ill patients admitted to a multidisciplinary intensive care unit (ICU) during 2019 and 2020. Delirium was identified using the validated confusion assessment method for the ICU. Multiple delirium risk factors were collected daily including clinical characteristics, hospital course, lab values, vital signs, surgical exposure, drug exposure, and COVID-19 characteristics. Serums samples were collected within 12 hours of ICU admission and cytokine levels were measured.Results: The following proinflammatory cytokines were elevated in our delirium population: tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-18, C-C motif ligand (CCL) 2, CCL3, C-X-C motif chemokine ligand (CXCL)1, CXCL10, IL-8, IL-1 receptor antagonist, and IL-10. Analysis of relative cytokine levels in those patients that developed delirium in the setting of sepsis, COVID-19, and recent surgery showed elevations of CCL2, CXCL10, and TNF-α in both the sepsis and COVID-19 group in comparison to the postsurgical population. In the postsurgical group, granulocyte colony-stimulating factor was elevated and CXCL10 was decreased relative to the opposing groups.Conclusions: We identify several cytokines and precipitating factors known to be associated with delirium. However, our study suggests that the cytokine profile associated with delirium is variable and contingent upon delirium precipitating factors.

Temperature Dependence of the Optical Properties of High-density GaAs Quantum Dots

Ryan P. Smith,김종수,이상준,노삼규,김진수,임재영,송진동 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.9

We investigate the effect of the quantum dot (QD) density on the thermal escape and the retrapping processes of carriers for unstrained GaAs/AlGaAs QDs through temperature-dependent photoluminescence measurements. We fabricated high-density GaAs QDs (8.4 ?10¹⁰/cm², dot-dot distance ∼34 nm) on an Al_0.3Ga_0.7As/GaAs (111)A surface by using droplet epitaxy. The average lateral size and height of the GaAs QDs are 24 and 6 nm, respectively. Temperature-dependent photoluminescence (PL) studies show that high-density GaAs QDs undergo a sigmoidal-shape energy shift. The sigmoidal dependence of the PL peak energy can be explained by thermal escaping of carriers followed by re-trapping by QDs. Our analysis indicates that the re-trapping probability of thermally-escaped carriers increases with decreasing dot-to-dot distance (corresponding to an increase in the QD density).

Photo-effects on the viscosity of titania nanoparticle suspensions in conducting and insulating medium

York R. Smith,David Heermance,Ryan N. Smith 한국유변학회 2016 Korea-Australia rheology journal Vol.28 No.1

The effect of illumination on the viscosity of titania suspensions in silicone oil (insulating medium) and an aqueous buffer (conducting medium) was investigated. Commercially available P25 anatase titania was suspended at a volume fraction of 0.5%. A 12.3% increase in viscosity was observed when silicone oil suspension was used as the medium, while a 2.47% decrease in viscosity was observed for the aqueous buffer suspension after exposure to UV-vis irradiation. The capability of the suspension medium to scavenge photoinduced charges results in the observed photorheological effects. The results presented here demonstrate a new method for influencing the rheological properties of nanoparticle suspensions.

THE EFFECT OF HOST GALAXIES ON TYPE Ia SUPERNOVAE IN THE SDSS-II SUPERNOVA SURVEY

Lampeitl, Hubert,Smith, Mathew,Nichol, Robert C.,Bassett, Bruce,Cinabro, David,Dilday, Benjamin,Foley, Ryan J.,Frieman, Joshua A.,Garnavich, Peter M.,Goobar, Ariel,Im, Myungshin,Jha, Saurabh W.,Marrin IOP Publishing 2010 The Astrophysical journal Vol.722 No.1

Contribution of prostaglandin E2 signal pathway to anti-Plasmodium immunity in Anopheles gambiae

Hyeogsun Kwon,Ryan C. Smith 한국응용곤충학회 2019 한국응용곤충학회 학술대회논문집 Vol.2019 No.10

Evaluation of the Junction’s Electric Field and the Ideality Factor of GaAs p-n junction Solar Cells by Using Photoreflectance Spectroscopy

손창원,한임식,Ryan P. Smith,김종수,노삼규,최현광,임재영 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.7

We investigated the optical and the electrical properties of GaAs solar cells (SCs) by usingphotoreflectance (PR) spectroscopy and current-voltage (J-V) measurements. The electric fields(Fj) in p-n junctions were evaluated through an analysis of the Franz-Keldysh oscillations (FKOs)of the PR spectra. From the excitation light intensity (Iex) dependence of the PR, we found thatthe photovoltaic effect resulted in a reduction of the Fj . The Fj was gradually reduced by up to37% from the dark built-in electric field when the Iex was increased (Iex = 2.3 181 mW/cm2). We evaluated the ideality factor (n) of the SC via PR spectroscopy, and the results matched theresults of the J-V measurements well. From these results, we demonstrate that the Fj and the n ofthe SCs can be evaluated by using PR spectroscopy.

Pro-Inflammatory Enzymes, Cyclooxygenase 1, Cyclooxygenase 2, and 5-Lipooxygenase, Inhibited by Stabilized Rice Bran Extracts

Bill Roschek Jr.,Ryan C. Fink,Dan Li,Matthew McMichael,Christine M. Tower,Robert D. Smith,Randall S. Alberte 한국식품영양과학회 2009 Journal of medicinal food Vol.12 No.3

Rice bran, the outer bran and germ of the kernel and a by-product of rice milling, is rich in phytonutrients but has been underutilized because of lipid content instability. New methods for the processing of rice bran have yielded a stabilized form that is increasingly used in foods and dietary supplements. Recent studies have documented a role for stabilized rice bran (SRB) in treating diabetes and arthritis, although little is known of the bioactive compounds that impart these health benefits. Here we characterize the chemical composition of three extracts of SRB and identify the functional bioactives contributing to the inhibitory properties against three key pro-inflammatory enzymes (cyclooxygenase [COX] 1, COX2, and 5-lipoxygenase [5-LOX]) that control the inflammatory cascade involved in impaired joint health, pain, and arthritis. One extract (SRB-AI) demonstrated significant COX1 and COX2 inhibitory activities with 50% inhibitory concentration (IC50) values for COX1 and COX2 of 305 and 29μg/mL, respectively, but no 5-LOX inhibition. The second extract (SRB-AII) inhibited COX1, COX2, and 5-LOX with IC50 values of 310, 19, and 396μg/mL, respectively. The third extract (SRB-AIII), a blend of SRB-AI and SRB-AIII, inhibited COX1, COX2, and 5-LOX with respective IC50 values of 48, 11, and 197μg/mL. Analysis of the extracts by direct analysis in real time time of flight-mass spectrometry revealed that SRB-AI, SRB-AII, and SRB-AIII contain over 620, 770, and 810 compounds, respectively. Of these, 17 were identified as key bioactives for COX and/or LOX inhibition. These SRB extracts have applications for functional foods and dietary supplements for control of inflammation and joint health.

Photoreflectance을 이용한 InAs/GaAs 양자점 국소전기장 분포에 관한 연구

한임식,조현준,이상조,손창원,Ryan P. Smith,하재두,박동욱,배인호,김종수,이상준,노삼규 한국물리학회 2012 새물리 Vol.62 No.2

Using photoreflectance spectroscopy(PR), we investigated the optical properties of InAs/GaAs quantum dots (QDs) grown by using molecular beam epitaxy. In the PR spectra of the InAs QD sample, we observed the Franz-Keldysh oscillation (FKO) and determined the localized electric field distribution of the InAs QD sample from the period of the FKO by using the fast Fourier transform (FFT) method. Two components of the FKO frequency due to the heavy-hole and the light-hole transitions existed at a given localized electric field. We suggest that the localized electric fields are strongly correlated to the quantum dot strain field distribution on the GaAs interface. 본 연구에서는 분자선박막성장 장치로 제작된 InAs/GaAs 양자점의 광학적특성을 photoreflectance spectroscopy(PR)를 이용하여 연구하였다. InAs 양자점이 삽입된 시료의 PR 신호에서 시료내부의 전기장에 의한Franz-Keldysh oscillation(FKO)이 관측되었다. 관측된 FKO 신호로부터fast Fourier 변환 (FFT)을 이용하여 InAs 양자점에 의해 형성된국소화된 전기장을 측정하였다. 주어진 전기장에 의해 나타나는 FKO의주파수는 전자-무거운 정공 (e-hh)과 전자-가벼운 정공 (e-lh)간의전이에 의해 두 가지 성분으로 나타난다. 연구결과로부터 InAs 양자점과GaAs 계면에서 양자점에 의한 응력 분포에 의해 국소화된 전기장이형성됨을 제안하였다.

3D printing of multiple container models and their trajectory tests in calm water

Li, Yi,Yu, Hanqi,Smith, Damon,Khonsari, M.M.,Thiel, Ryan,Morrissey, George,Yu, Xiaochuan Techno-Press 2022 Ocean systems engineering Vol.12 No.2

More and more shipping containers are falling into the sea due to bad weather. Containers lost at sea negatively affect the shipping line, the trader and the consumer, and the environment. The question of locating and recovering dropped containers is a challenging engineering problem. Model-testing of small-scaled container models is proposed as an efficient way to investigate their falling trajectories to salvage them. In this study, we first build a standard 20-ft container model in SOLIDWORKS. Then, a three-dimensional (3D) geometric model in the STL (Standard Tessellation Language) format is exported to a Stratasys F170 Fused Deposition Modeling (FDM) printer. In total, six models were made of acrylonitrile styrene acrylate (ASA) and printed for the purpose of testing. They represent three different loading conditions with different densities and center of gravity (COG). Two samples for each condition were tested. The physical models were dropped into the towing tank of University of New Orleans (UNO). From the experimental tests, it is found that the impact of the initial position after sinking can cause a certain initial rolling velocity, which may have a great impact on the lateral displacement, and subsequently affect the final landing position. This series of model tests not only provide experimental data for the study of the trajectory of box-shape objects but also provide a valuable reference for maritime salvage operations and for the pipeline layout design.