Probing confined phonon modes by transport through a nanowire double quantum dot

Strong radial confinement in semiconductor nanowires leads to modified electronic and phononic energy spectra. We analyze the current response to the interplay between quantum confinement effects of the electron and phonon systems in a gate-defined double quantum dot in a semiconductor nanowire. We show that current spectroscopy of inelastic transitions between the two quantum dots can be used as an experimental probe of the confined phonon environment. The resulting discrete peak structure in the measurements is explained by theoretical modeling of the confined phonon mode spectrum, where the piezoelectric coupling is of crucial importance.Comment: 4 pages, 4 figures; final versio

Imaging a 1-electron InAs quantum dot in an InAs/InP nanowire

Nanowire heterostructures define high-quality few-electron quantum dots for nanoelectronics, spintronics and quantum information processing. We use a cooled scanning probe microscope (SPM) to image and control an InAs quantum dot in an InAs/InP nanowire, using the tip as a movable gate. Images of dot conductance vs. tip position at T = 4.2 K show concentric rings as electrons are added, starting with the first electron. The SPM can locate a dot along a nanowire and individually tune its charge, abilities that will be very useful for the control of coupled nanowire dots

Application of phage display and plasmid display to broaden the specificity of human Fbs1 for capture of N-glycosylated peptides

The objective of this study was to develop a method for selective and comprehensive enrichment of N-linked glycopeptides to facilitate biomarker discovery. The natural function of human Fbs1 is to bind misfolded N-linked glycoproteins by recognition of the common pentasaccharide core motif (Man3GlcNAc2) of the N-glycan. We show that Fbs1 is able to bind diverse types of N-linked glycomolecules, however, wild-type Fbs1 preferentially binds high mannose containing glycans. To reduce the bias during N-glycomolecule enrichment experiments, we isolated Fbs1 variants with altered specificity through mutagenesis and plasmid display selection. Five cycles of E. coli propagation and in vitro panning against immobilized fetuin resulted in a pool of variants with improved binding for complex N-glycopeptides. The most valuable Fbs1 variant enabled substantially unbiased N-glycopeptide enrichment from a level of 3.5% to 66% when applied to IgG-depleted serum. Importantly, plasmid display is a rapid method for altering substrate binding specificity that is an attractive alternative to phage display. M13 phage display of Fbs1 was also accomplished by non-standard methodology. Since Fbs1 folding is impaired by disulfide bond formation in the E.coli periplasm, a mutant E.coli host was critical for proper display on the surface of M13 phage. Furthermore, display of functional Fbs1 could only be achieved by expressing the pIII-Fbs1 fusion protein with an SRP-dependent signal peptide. Significance: The Fbs1 study revealed that plasmid display is a powerful alternative to phage display. In particular, plasmid display is appropriate for non-secretory proteins. The plasmid display selection process is very rapid as 5 cycles may be performed in 5 days. Our efforts to display Fbs1 by M13 phage display were met by complication. In response, we developed a method capable of functional display of non-secretory protein on the surface of M13 phage. Reference: Chen M and Samuelson JC “A DsbA-deficient Periplasm Enables Functional Display of a Protein with Redox-Sensitive Folding on M13 Phage” Biochemistry (2016) 55(23):3175-9

AN EXAMINATION OF AN EARLY INTERVENTION READING PROGRAM FOCUSING ON THE PROGRESS MONITORING OF LITERACY SKILLS AND THE READING SELF-CONCEPTS OF STRUGGLING READERS

The purpose of this study was to examine progress monitoring, reading self-concept, and the literacy skills of first and second grade struggling readers. Progress monitoring is an instructional process used by teachers to assess students’ academic performance on a regular basis, typically weekly or monthly. When based on the skill level of the student, the targeted remediation, and the goals of the intervention, progress monitoring may be used with various reading interventions. The use of progress monitoring is central to good decision-making in a Response to Intervention model. Academic self-concept has become an integral part of education. Connections have been made regarding academic achievement and academic self-concept. Self-concept specifically of reading is vital in the primary years when the main focus of education is learning to read. This study utilized a quasi-experimental research methodology as well as a correlational design. The sample size of 40 participants consisted of approximately 19 students in the experimental group and 21 students in the comparison group. All students in the experimental group participated in a reading support program with a Language Arts Consultant (LAC). The LAC’s participated in training utilizing progress monitoring and incorporating biweekly follow-up, specific to each individual student’s daily interventions. Students met in groups of three, for 30 minutes, four to five times per week. All struggling readers in the comparison groups were seen in small groups for 30 minutes, four to five times a week. They were instructed by an Early Literacy Tutor (ELT) who had not been trained in and did not utilize progress monitoring. A two-group multivariate analysis of variance (MANOVA) was conducted utilizing core reading words, core writing words, phonemes, and spelling, as the four dependent variables measuring literacy skills. These are four of the nine scores yielded from the Dominie Reading and Writing Assessment Portfolio (DeFord, 2004). The independent variable of reading support group consisted of two levels, progress monitoring and no progress monitoring. Results indicated no significant differences in group means of core reading words, core writing words, phonemes, and spelling. A standard multiple regression procedure was conducted consisting of progress monitoring and reading self-concept as the predictor variables, and literacy skills, as measured by core reading words, as the criterion variable. The Reading Self-Concept Scale (Chapman & Tunmer, 1995a) was utilized to measure struggling readers reading self-concept. Results indicated no significance in progress monitoring and reading self-concept as predictors of students’ literacy skills

Direct Measurement of the Spin-Orbit Interaction in a Two-Electron InAs Nanowire Quantum Dot

We demonstrate control of the electron number down to the last electron in tunable few-electron quantum dots defined in catalytically grown InAs nanowires. Using low temperature transport spectroscopy in the Coulomb blockade regime we propose a simple method to directly determine the magnitude of the spin-orbit interaction in a two-electron artificial atom with strong spin-orbit coupling. Due to a large effective g-factor |g*|=8+/-1 the transition from singlet S to triplet T+ groundstate with increasing magnetic field is dominated by the Zeeman energy rather than by orbital effects. We find that the spin-orbit coupling mixes the T+ and S states and thus induces an avoided crossing with magnitude $\Delta_{SO}$=0.25+/-0.05 meV. This allows us to calculate the spin-orbit length $\lambda_{SO}\approx$127 nm in such systems using a simple model.Comment: 21 pages, 7 figures, including supplementary note

Fuel Injector: Air swirl characterization aerothermal modeling, phase 2, volume 2

A well integrated experimental/analytical investigation was conducted to provide benchmark quality data relevant to prefilming type airblast fuel nozzle and its interaction with combustor dome air swirler. The experimental investigation included a systematic study of both single-phase flows that involved single and twin co-axial jets with and without swirl. A two-component Phase Doppler Particle Analyzer (PDPA) equipment was used to document the interaction of single and co-axial air jets with glass beads that simulate nonevaporating spray and simultaneously avoid the complexities associated with fuel atomization processes and attendant issues about the specification of relevant boundary conditions. The interaction of jets with methanol spray produced by practical airblast nozzle was also documented in the spatial domain of practical interest. Model assessment activities included the use of three turbulence models (k-epsilon, algebraic second moment (ASM) and differential second moment (DSM)) for the carrier phase, deterministic or stochastic Lagrangian treatment of the dispersed phase, and advanced numerical schemes. Although qualitatively good comparison with data was obtained for most of the cases investigated, the model deficiencies in regard to modeled dissipation rate transport equation, single length scale, pressure-strain correlation, and other critical closure issues need to be resolved before one can achieve the degree of accuracy required to analytically design combustion systems

Common Learning with Intertemporal Dependence

Consider two agents who learn the value of an unknown parameter by observing a sequence of private signals. Will the agents commonly learn the value of the parameter, i.e., will the true value of the parameter become approximate common-knowledge? If the signals are independent and identically distributed across time (but not necessarily across agents), the answer is yes (Cripps, Ely, Mailath, and Samuelson, 2008). This paper explores the implications of allowing the signals to be dependent over time. We present a counterexample showing that even extremely simple time dependence can preclude common learning, and present sufficient conditions for common learning.Common learning, common belief, private signals, private beliefs

Common Learning

Consider two agents who learn the value of an unknown parameter by observing a sequence of private signals. The signals are independent and identically distributed across time but not necessarily across agents. We show that that when each agent's signal space is finite, the agents will commonly learn its value, i.e., that the true value of the parameter will become approximate common-knowledge. In contrast, if the agents' observations come from a countably infinite signal space, then this contraction mapping property fails. We show by example that common learning can fail in this case.Common learning, Common belief, Private signals, Private beliefs

Common Learning

Consider two agents who learn the value of an unknown parameter by observing a sequence of private signals. The signals are independent and identically distributed across time but not necessarily across agents. We show that that when each agent's signal space is finite, the agents will commonly learn its value, i.e., that the true value of the parameter will become approximate common-knowledge. In contrast, if the agents' observations come from a countably infinite signal space, then this contraction mapping property fails. We show by example that common learning can fail in this case.Common learning, common belief, private signals, private beliefs