3,275 research outputs found
High-efficiency cell concepts on low-cost silicon sheets
The limitations on sheet growth material in terms of the defect structure and minority carrier lifetime are discussed. The effect of various defects on performance are estimated. Given these limitations designs for a sheet growth cell that will make the best of the material characteristics are proposed. Achievement of optimum synergy between base material quality and device processing variables is proposed. A strong coupling exists between material quality and the variables during crystal growth, and device processing variables. Two objectives are outlined: (1) optimization of the coupling for maximum performance at minimal cost; and (2) decoupling of materials from processing by improvement in base material quality to make it less sensitive to processing variables
Significance of thermal fluctuations and hydrodynamic interactions in receptor-ligand mediated adhesive dynamics of a spherical particle in wall bound shear flow
The dynamics of adhesion of a spherical micro-particle to a ligand-coated
wall, in shear flow, is studied using a Langevin equation that accounts for
thermal fluctuations, hydrodynamic interactions and adhesive interactions.
Contrary to the conventional assumption that thermal fluctuations play a
negligible role at high Pclet numbers, we find that for particles
with low surface densities of receptors, rotational diffusion caused by
fluctuations about the flow and gradient directions aids in bond formation,
leading to significantly greater adhesion on average, compared to simulations
where thermal fluctuations are completely ignored. The role of wall
hydrodynamic interactions on the steady state motion of a particle, when the
particle is close to the wall, has also been explored. At high Pclet
numbers, the shear induced force that arises due to the stresslet part of the
Stokes dipole, plays a dominant role, reducing the particle velocity
significantly, and affecting the states of motion of the particle. The coupling
between the translational and rotational degrees of freedom of the particle,
brought about by the presence of hydrodynamic interactions, is found to have no
influence on the binding dynamics. On the other hand, the drag coefficient,
which depends on the distance of the particle from the wall, plays a crucial
role at low rates of bond formation. A significant difference in the effect of
both the shear force and the position dependent drag force, on the states of
motion of the particle, is observed when the Plet number is small.Comment: The manuscript has been accepted as an article in Physical Review E
Journa
On dysregulated inflammation and airway host defense
Acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), and cystic fibrosis (CF) are characterized by dysregulated inflammation of the airways. The increased influx of immune cells and the accumulation of cytokines lead to cell death, tissue destruction and impaired pulmonary function. Intracellular proteins like histones and granule proteins of neutrophils, DNA fibers act as Danger-Associated Molecular Patterns (DAMPs), further promoting tissue damage. As a result, the lungs of such patients are at an increased risk of infection due to impaired host defense functions. During inflammation, there is an increased expression of osteopontin (OPN), a highly anionic phosphoglycoprotein, in the airways and it is involved in cell recruitment, tissue remodeling, and repair. In this thesis we show that OPN can interact with many cationic proteins and peptides present in the extracellular milieu of the inflamed airways. In the first paper included in this thesis we show that OPN bound to extracellular histones have protective function against DAMPs-induced inflammation. In the second paper, we show that OPN binds to several common innate antibiotics and abrogate their antimicrobial activities. Taken together, these data suggest that OPN can modulate the host immune functions, thereby increasing the susceptibility of the patients with airway inflammatory diseases to acquire infections.Use of anti-inflammatory drugs like roflumilast is a common treatment strategy in COPD to ameliorate severe exacerbations. In the third paper we highlight the adverse effects of roflumilast, in a murine acute airway infection model. The findings suggest that use of this drug can impair host defense functions of immune cells, thereby increasing the susceptibility of COPD patients to bacterial pathogens. DNase I is used to clear the airways of CF patients from highly viscous, high molecular weight eDNA rich sputum. In the fourth paper of this thesis, we elucidated the molecular aspects of the fragmented DNA that are important to exhibit antimicrobial properties against the common CF lung pathogen, i.e. P. aeruginosa. The findings highlight a novel aspect of host defense that could be employed treating bacteria resistant against conventional antibiotics
Photovoltaic research needs industry perspective
An industries perspective of photovoltaic research needs is presented. Objectives and features of industry needs are discussed for the materials, devices, processes, and reliability research categories
On associating Fast Radio Bursts with afterglows
A radio source that faded over six days, with a redshift of
host, has been identified by Keane et al. (2016) as the transient afterglow to
a fast radio burst (FRB 150418). We report follow-up radio and optical
observations of the afterglow candidate and find a source that is consistent
with an active galactic nucleus. If the afterglow candidate is nonetheless a
prototypical FRB afterglow, existing slow-transient surveys limit the fraction
of FRBs that produce afterglows to 0.25 for afterglows with fractional
variation, , and 0.07 for , at 95%
confidence. In anticipation of a barrage of bursts expected from future FRB
surveys, we provide a simple framework for statistical association of FRBs with
afterglows. Our framework properly accounts for statistical uncertainties, and
ensures consistency with limits set by slow-transient surveys.Comment: Accepted version (ApJL
Gossip Codes for Fingerprinting: Construction, Erasure Analysis and Pirate Tracing
This work presents two new construction techniques for q-ary Gossip codes
from tdesigns and Traceability schemes. These Gossip codes achieve the shortest
code length specified in terms of code parameters and can withstand erasures in
digital fingerprinting applications. This work presents the construction of
embedded Gossip codes for extending an existing Gossip code into a bigger code.
It discusses the construction of concatenated codes and realisation of erasure
model through concatenated codes.Comment: 28 page
Faraday conversion and magneto-ionic variations in Fast Radio Bursts
The extreme, time-variable Faraday rotation observed in the repeating fast
radio burst (FRB) 121102 and its associated persistent synchrotron source
demonstrates that some FRBs originate in dense, dynamic and possibly
relativistic magneto-ionic environments. Here we show that besides rotation of
the linear-polarisation vector (Faraday rotation), such media can generally
convert linear to circular polarisation (Faraday conversion). We use
non-detection of Faraday conversion, and the temporal variation in Faraday
rotation and dispersion in bursts from FRB\,121102 to constrain models where
the progenitor inflates a relativistic nebula (persistent source) confined by a
cold dense medium (e.g. supernova ejecta). We find that the persistent
synchrotron source, if composed of an electron-proton plasma, must be an
admixture of relativistic and non-relativistic (Lorentz factor )
electrons. Furthermore we independently constrain the magnetic field in the
cold confining medium, which provides the Faraday rotation, to be between
and mG. This value is close to the equipartition magnetic field of the
confined persistent source implying a self-consistent and over-constrained
model that can explain the observations.Comment: Submitted to MNRAS; An error in arguments of sec 2.2 of the previous
version has been correcte
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