Dusty Plasma Correlation Function Experiment

Dust particles immersed within a plasma environment, such as those in protostellar clouds, planetary rings or cometary environments, will acquire an electric charge. If the ratio of the inter-particle potential energy to the average kinetic energy is high enough the particles will form either a "liquid" structure with short-range ordering or a crystalline structure with long range ordering. Many experiments have been conducted over the past several years on such colloidal plasmas to discover the nature of the crystals formed, but more work is needed to fully understand these complex colloidal systems. Most previous experiments have employed monodisperse spheres to form Coulomb crystals. However, in nature (as well as in most plasma processing environments) the distribution of particle sizes is more randomized and disperse. This paper reports experiments which were carried out in a GEC rf reference cell modified for use as a dusty plasma system, using varying sizes of particles to determine the manner in which the correlation function depends upon the overall dust grain size distribution. (The correlation function determines the overall crystalline structure of the lattice.) Two dimensional plasma crystals were formed of assorted glass spheres with specific size distributions in an argon plasma. Using various optical techniques, the pair correlation function was determined and compared to those calculated numerically.Comment: 6 pages, Presented at COSPAR '0

Temperature mapping and thermal lensing in large-mode, high-power laser diodes

The authors use high-resolution charge-coupled device based thermoreflectance to derive two dimensional facet temperature maps of a λ = 1.55 μmλ=1.55μm InGaAsP/InPInGaAsP∕InP watt-class laser that has a large (>5×5 μm2)(>5×5μm2) fundamental optical mode. Recognizing that temperature rise in the laser will lead to refractive index increase, they use the measured temperature profiles as an input to a finite-element mode solver, predicting bias-dependent spatial mode behavior that agrees well with experimental observations. These results demonstrate the general usefulness of high-resolution thermal imaging for studying spatial mode dynamics in photonic devices.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87806/2/201110_1.pd

AlloRep: A Repository of Sequence, Structural and Mutagenesis Data for the LacI/GalR Transcription Regulators

Protein families evolve functional variation by accumulating point mutations at functionally important amino acid positions. Homologs in the LacI/GalR family of transcription regulators have evolved to bind diverse DNA sequences and allosteric regulatory molecules. In addition to playing key roles in bacterial metabolism, these proteins have been widely used as a model family for benchmarking structural and functional prediction algorithms. We have collected manually curated sequence alignments for >ﾠ3000 sequences, in vivo phenotypic and biochemical data for >ﾠ5750 LacI/GalR mutational variants, and noncovalent residue contact networks for 65 LacI/GalR homolog structures. Using this rich data resource, we compared the noncovalent residue contact networks of the LacI/GalR subfamilies to design and experimentally validate an allosteric mutant of a synthetic LacI/GalR repressor for use in biotechnology. The AlloRep database (freely available at www.AlloRep.org) is a key resource for future evolutionary studies of LacI/GalR homologs and for benchmarking computational predictions of functional change

Coarse-grained model of entropic allostery

Many signaling functions in molecular biology require proteins to bind to substrates such as DNA in response to environmental signals such as the simultaneous binding to a small molecule. Examples are repressor proteins which may transmit information via a conformational change in response to the ligand binding. An alternative entropic mechanism of "allostery" suggests that the inducer ligand changes the intramolecular vibrational entropy, not just the mean static structure. We present a quantitative, coarse-grained model of entropic allostery, which suggests design rules for internal cohesive potentials in proteins employing this effect. It also addresses the issue of how the signal information to bind or unbind is transmitted through the protein. The model may be applicable to a wide range of repressors and also to signaling in trans-membrane proteins

Cryo-EM structure of lysenin pore elucidates membrane insertion by an aerolysin family protein

Lysenin from the coelomic fluid of the earthworm Eisenia fetida belongs to the aerolysin family of small β-pore-forming toxins (β-PFTs), some members of which are pathogenic to humans and animals. Despite efforts, a high-resolution structure of a channel for this family of proteins has been elusive and therefore the mechanism of activation and membrane insertion remains unclear. Here we determine the pore structure of lysenin by single particle cryo-EM, to 3.1 Å resolution. The nonameric assembly reveals a long β-barrel channel spanning the length of the complex that, unexpectedly, includes the two pre-insertion strands flanking the hypothetical membrane-insertion loop. Examination of other members of the aerolysin family reveals high structural preservation in this region, indicating that the membrane-insertion pathway in this family is conserved. For some toxins, proteolytic activation and pro-peptide removal will facilitate unfolding of the pre-insertion strands, allowing them to form the β-barrel of the channel

Turnaround Time and Efficiency of Pediatric Outpatient Brain Magnetic Resonance Imaging: a Multi-institutional Cross-Sectional Study

BACKGROUND: Aside from single-center reports, few data exist across pediatric institutions that examine overall MRI turnaround time (TAT) and the determinants of variability. OBJECTIVE: to determine average duration and determinants of a brain MRI examination at academic pediatric institutions and compare the duration to those used in practice expense relative value units (RVUs). MATERIALS AND METHODS: This multi-institutional cross-sectional investigation comprised four academic pediatric hospitals. We included children ages 0 to \u3c 18 years who underwent an outpatient MRI of the brain without contrast agent in 2019. Our outcome of interest was the overall MRI TAT derived by time stamps. We estimated determinants of overall TAT using an adjusted log-transformed multivariable linear regression model with robust standard errors. RESULTS: The average overall TAT significantly varied among the four hospitals. A sedated brain MRI ranged from 158 min to 224 min, a non-sedated MRI from 70 min to 112 min, and a limited MRI from 44 min to 70 min. The most significant predictor of a longer overall TAT was having a sedated MRI (coefficient = 0.71, 95% confidence interval [CI]: 0.66-0.75; P \u3c 0.001). The median MRI scan time for a non-sedated exam was 38 min and for a sedated exam, 37 min, approximately double the duration used by the Relative Value Scale (RVS) Update Committee (RUC). CONCLUSION: We found considerable differences in the overall TAT across four pediatric academic institutions. Overall, the significant predictors of turnaround times were hospital site and MRI pathway (non-sedated versus sedated versus limited MRI)

Hemoglobin A1c improvements and better diabetes-specific quality of life among participants completing diabetes self-management programs: A nested cohort study

BACKGROUND: Numerous primary care innovations emphasize patient-centered processes of care. Within the context of these innovations, greater understanding is needed of the relationship between improvements in clinical endpoints and patient-centered outcomes. To address this gap, we evaluated the association between glycosylated hemoglobin (HbA(1c)) and diabetes-specific quality of life among patients completing diabetes self-management programs. METHODS: We conducted a retrospective cohort study nested within a randomized comparative effectiveness trial of diabetes self-management interventions in 75 diabetic patients. Multiple linear regression models were developed to examine the relationship between change in HbA(1c) from baseline to one-year follow-up and Diabetes-39 (a diabetes-specific quality of life measure) at one year. RESULTS: HbA(1c) levels improved for the overall cohort from baseline to one-year follow-up (t (74) = 3.09, p = .0029). One-year follow up HbA(1c) was correlated with worse overall quality of life (r = 0.33, p = 0.004). Improvements in HbA(1c) from baseline to one-year follow-up were associated with greater D-39 diabetes control (β = 0.23, p = .04) and D-39 sexual functioning (β = 0.25, p = .03) quality of life subscales. CONCLUSIONS: Improvements in HbA(1c) among participants completing a diabetes self-management program were associated with better diabetes-specific quality of life. Innovations in primary care that engage patients in self-management and improve clinical biomarkers, such as HbA(1c), may also be associated with better quality of life, a key outcome from the patient perspective

Integrated photonic structures for photon-mediated entanglement of trapped ions

Trapped atomic ions are natural candidates for quantum information processing and have the potential to realize or improve quantum computing, sensing, and networking. These applications often require the collection of individual photons emitted from ions into guided optical modes, in some cases for the production of entanglement between separated ions. Proof-of-principle demonstrations of such photon collection from trapped ions have been performed using high-numerical-aperture lenses and single-mode fibers, but integrated photonic elements in ion-trap structures offer advantages in scalability and manufacturabilty over traditional optics. In this paper we analyze structures monolithically fabricated with an ion trap for collecting single photons from ions, coupling them into integrated waveguides, and manipulating them via interference. We discuss practical considerations for realizing photon-mediated entanglement between trapped ions using these waveguide-based devices.Comment: 17 pages, 6 figures, 2 table

Submicron thermal imaging of high power slab coupled optical waveguide laser (SCOWL

ABSTRACT Nonradiative power dissipation within and near the active region of a high power single mode slab coupled optical waveguide laser is directly measured by CCD-based thermoreflectance, including its variation with device bias. By examining the high spatial resolution temperature profile at the optical output facets, we quantify heat spreading from the source in the active region both downward to the substrate and upward to the metal top contact