3,088 research outputs found
The Design and Fabrication of Platform Device for Dna Amplification
Thermalcycler were extensively used machine for amplify DNA sample. One of
the major problems in the working time was that it spent most of time for
cooling and heating. In order to improve the efficient, this study presented a
novel method for amplify DNA sample. For this concept, the DNA sample in the
silicon chamber which was pushed by a beam through three temperature regions
around a center and then the DNA segments could be amplified rapidly after 30
cycles. The polymerase chain reaction platform was composed of thin-film
heaters, copper plates, DC powers, and temperature controllers. The
photolithography and bulk etching technologies were utilized to construct the
thin-film heater and DNA reaction chambers. Finally, 1 pound gL 100bp DNA
segment of E. coli K12 was amplified successfully within 36 minutes on this PCR
platform.Comment: Submitted on behalf of TIMA Editions
(http://irevues.inist.fr/tima-editions
Detectability of dirty dust grains in brown dwarf atmospheres
Dust clouds influence the atmospheric structure of brown dwarfs, and they
affect the heat transfer and change the gas-phase chemistry. However, the
physics of their formation and evolution is not well understood. In this
letter, we predict dust signatures and propose a potential observational test
of the physics of dust formation in brown dwarf atmosphere based on the
spectral features of the different solid components predicted by dust formation
theory. A momentum method for the formation of dirty dust grains (nucleation,
growth, evaporation, drift) is used in application to a static brown dwarf
atmosphere structure to compute the dust grain properties, in particular the
heterogeneous grain composition and the grain size. Effective medium and Mie
theory are used to compute the extinction of these spherical grains. Dust
formation results in grains whose composition differs from that of grains
formed at equilibrium. Our kinetic model predicts that solid amorphous SiO2[s]
(silica) is one of the most abundant solid component followed by amorphous
MgSiO4[s] and MgSiO3[s], while SiO2[s] is absent in equilibrium models
because it is a metastable solid. Solid amorphous SiO2[s] possesses a strong
broad absorption feature centered at 8.7mum, while amorphous
Mg2SiO4[s]/MgSiO3[s] absorb at 9.7mum beside other absorption features at
longer wavelength. Those features at lambda < 15mum are detectable in
absorption if grains are small (radius < 0.2mum) in the upper atmosphere as
suggested by our model. We suggest that the detection of a feature at 8.7mum in
deep infrared spectra could provide evidence for non-equilibrium dust formation
that yields grains composed of metastable solids in brown dwarf atmospheres.
This feature will shift towards 10mum and broaden if silicates (e.g. fosterite)
are much more abundant.Comment: A&A Letter, accepte
Parker Instability in a Self-Gravitating Magnetized Gas Disk: I. Linear Stability Analysis
To be a formation mechanism of such large-scale structures as giant molecular
clouds (GMCs) and HI superclouds, the classical Parker instability driven by
external gravity has to overcome three major obstacles: The convective motion
accompanying the instability generates thin sheets than large condensations.
The degree of density enhancement achieved by the instability is too low to
make dense interstellar clouds. The time and the length scales of the
instability are significantly longer and larger than the estimated formation
time and the observed mean separation of the GMCs, respectively. This paper
examines whether a replacement of the driving agent from the external to the
self gravity might remove these obstacles by activating the gravitational
instability in the Galactic ISM disk. The self gravity can suppress the
convective motions, and a cooperative action of the Jeans and the Parker
instabilities can remove all the obstacles confronting the classical version of
the Parker instability. The mass and mean separation of the structures
resulting from the odd-parity undular mode solution are shown to agree better
with the HI superclouds than with the GMCs. We briefly discuss how inclusions
of the external gravity and cosmic rays would modify behaviors of the
odd-parity undular mode solution.Comment: 53 pages, 21 figure
Self-consistent modelling of the dust component in protoplanetary and circumplanetary disks: the case of PDS 70
Direct observations of young stellar objects are important to test
established theories of planet formation. PDS 70 is one of the few cases where
robust evidence favours the presence of two planetary mass companions inside
the gap of the transition disk. Those planets are believed to be going through
the last stages of accretion from the protoplanetary disk, a process likely
mediated by a circumplanetary disk (CPD). We aim to develop a three dimensional
radiative transfer model for the dust component of the PDS 70 system which
reproduces the system's global features observed at two different wavelengths:
855 with ALMA and 1.25 with VLT/SPHERE.
We use this model to investigate the physical properties of the planetary
companion PDS 70 c and its potential circumplanetary disk. We select initial
values for the physical properties of the planet and CPD through appropriate
assumptions about the nature and evolutionary stage of the object. We modify
iteratively the properties of the protoplanetary disk until the predictions
retrieved from the model are consistent with both data sets. We provide a model
that jointly explains the global features of the PDS 70 system seen in
submillimeter and polarised-scattered light. Our model suggests that spatial
segregation of dust grains is present in the protoplanetary disk. The
submillimeter modelling of the PDS 70 c source favours the presence of an
optically thick CPD and places an upper limit to its dust mass of 0.7
. Furthermore, analysis of the thermal structure of the CPD
demonstrates that the planet luminosity is the dominant heating mechanism of
dust grains inside 0.6 au from the planet while heating by stellar photons
dominates at larger planetocentric distances.Comment: accepted for publication in A&
Eta Car through the eyes of interferometers
The core of the nebula surrounding Eta Carinae has recently been observed
with VLT/NACO, VLTI/VINCI, VLTI/MIDI and VLTI/AMBER in order to spatially and
spectrally constrain the warm dusty environment and the central object.
Narrow-band images at 3.74 and 4.05 micron reveal the structured
butterfly-shaped dusty environment close to the central star with an
unprecedented spatial resolution of about 60 mas. VINCI has resolved the
present-day stellar wind of Eta Carinae on a scale of several stellar radii
owing to the spatial resolution of the order of 5 mas (11 AU). The VINCI
observations show that the object is elongated with a de-projected axis ratio
of approximately 1.5. Moreover the major axis is aligned with that of the large
bipolar nebula that was ejected in the 19th century. Fringes have also been
obtained in the Mid-IR with MIDI using baselines of 75m. A peak of correlated
flux of 100 Jy is detected 0.3" south-east from the photocenter of the nebula
at 8.7 micron is detected. This correlated flux is partly attributed to the
central object but it is worth noting that at these wavelengths, virtually all
the 0.5" x 0.5" central area can generate detectable fringes witnessing the
large clumping of the dusty ejecta. These observations provide an upper limit
for the SED of the central source from 3.8 to 13.5 micron and constrain some
parameters of the stellar wind which can be compared to Hillier's model.
Lastly, we present the great potential of the AMBER instrument to study the
numerous near-IR emissive lines from the star and its close vicinity. In
particular, we discuss its ability to detect and follow the faint companion.Comment: 12 pages, published in proceedings of the ESO-EII Workshop "The power
of optical / IR interferometry
Factors associated with failed treatment : an analysis of 121,744 women embarking on their first IVF cycles
Peer reviewedPublisher PD
Size- and density-controlled deposition of Ag nanoparticle films by a novel low-temperature spray chemical vapour deposition method—research into mechanism, particle growth and optical simulation
Ag nanoparticles have attracted interest for plasmonic absorption enhancement of solar cells. For this purpose, well-defined particle sizes and densities as well as very low deposition temperatures are required. Thus, we report here a new spray chemical vapour deposition method for producing Ag NP films with independent size and density control at substrate temperatures even below 100 °C, which is much lower than for many other techniques. This method can be used on different substrates to deposit Ag NP films. It is a reproducible, low-cost process which uses trimethylphosphine (hexafluoroacetylacetonato) silver as a precursor in alcoholic solution. By systematic variation of deposition parameters and classic experiments, mechanisms of particle growth and of deposition processes as well as the low decomposition temperature of the precursor could be explained. Using the 3D finite element method, absorption spectra of selected samples were simulated, which fitted well with the measured results. Hence, further applications of such Ag NP films for generating plasmonic near field can be predicted by the simulation
Behavioural Susceptibility Theory: Professor Jane Wardle and the Role of Appetite in Genetic Risk of Obesity
Purpose of Review: There is considerable variability in human body weight, despite the ubiquity of the 'obesogenic' environment. Human body weight has a strong genetic basis and it has been hypothesised that genetic susceptibility to the environment explains variation in human body weight, with differences in appetite being implicated as the mediating mechanism; so-called 'behavioural susceptibility theory' (BST), first described by Professor Jane Wardle. This review summarises the evidence for the role of appetite as a mediator of genetic risk of obesity. Recent Findings: Variation in appetitive traits is observable from infancy, drives early weight gain and is highly heritable in infancy and childhood. Obesity-related common genetic variants identified through genome-wide association studies show associations with appetitive traits, and appetite mediates part of the observed association between genetic risk and adiposity. Summary: Obesity results from an interaction between genetic susceptibility to overeating and exposure to an 'obesogenic' food environment
Striation mechanism and triggered striation in dielectric microdischarge plasma
The striation mechanism of dielectric microdischarges, as in many plasma devices, is extensively explored by collisional kinetic and fluid simulations. Striation in a typical dielectric microdischarge device predominantly occurs near the anode region and is basically governed by the ionization-dominated ??-processes, wherein surface and space charges collectively dictate the phenomenon in a complex manner. A novel type of striation has been investigated by us near the cathode region, which is dominated by ??-processes and is driven by the secondary-electron emission mechanism.close101
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