844 research outputs found
Recommended from our members
Nanotailoring Stereolithography Resins for Unique Applications using Carbon Nanotubes
Nanostructured materials and exploiting their properties in stereolithography (SL) may open
new markets for unique rapidly manufactured functional devices. Controlled amounts of multiwalled carbon nanotubes (MWCNTs) were successfully dispersed in SL epoxy-based resins and
complex three-dimensional (3D) parts were successfully fabricated by means of a multi-material
SL setup. The effect of the nanosized filler was evaluated using mechanical testing. Small
dispersions of MWCNTs resulted in significant effects on the physical properties of the
polymerized resin. A MWCNT concentration of .05 wt% (w/v) in DSM Somos® WaterShed™
11120 resin increased the ultimate tensile stress and fracture stress an average of 17% and 37%,
respectively. Electron microscopy was used to examine the morphology of the nanocomposite
and results showed affinity between the MWCNTs and SL resin and identified buckled
nanotubes that illustrated strong interfacial bonding. These improved physical properties may
provide opportunities for using nanocomposite SL resins in end-use applications. Varying types
and concentrations of nanomaterials can be used to tailor existing SL resins for particular
applications.Mechanical Engineerin
Trapping and observing single atoms in the dark
A single atom strongly coupled to a cavity mode is stored by
three-dimensional confinement in blue-detuned cavity modes of different
longitudinal and transverse order. The vanishing light intensity at the trap
center reduces the light shift of all atomic energy levels. This is exploited
to detect a single atom by means of a dispersive measurement with 95%
confidence in 0.010 ms, limited by the photon-detection efficiency. As the atom
switches resonant cavity transmission into cavity reflection, the atom can be
detected while scattering about one photon
Momentum diffusion for coupled atom-cavity oscillators
It is shown that the momentum diffusion of free-space laser cooling has a
natural correspondence in optical cavities when the internal state of the atom
is treated as a harmonic oscillator. We derive a general expression for the
momentum diffusion which is valid for most configurations of interest: The atom
or the cavity or both can be probed by lasers, with or without the presence of
traps inducing local atomic frequency shifts. It is shown that, albeit the
(possibly strong) coupling between atom and cavity, it is sufficient for
deriving the momentum diffusion to consider that the atom couples to a mean
cavity field, which gives a first contribution, and that the cavity mode
couples to a mean atomic dipole, giving a second contribution. Both
contributions have an intuitive form and present a clear symmetry. The total
diffusion is the sum of these two contributions plus the diffusion originating
from the fluctuations of the forces due to the coupling to the vacuum modes
other than the cavity mode (the so called spontaneous emission term). Examples
are given that help to evaluate the heating rates induced by an optical cavity
for experiments operating at low atomic saturation. We also point out
intriguing situations where the atom is heated although it cannot scatter
light.Comment: More information adde
Influence of drying process variables on fresh and osmotically pre-treated mushrooms.
The aim of this work was to study the drying of fresh and osmotically dehydrated mushrooms and evaluate their qualities. The osmotic treatment was carried out at 20 °C with a 10% w.w?1 salt solution, 80 rpm agitation and 60 min immersion time. The mushrooms were dried in a vertical bed dryer with forced air-flow. An experimental design was applied to evaluate the influence of the temperature and air velocity on the drying constant, obtained according to an exponential model and on the colour difference between the dried and fresh samples. Using Response Surface Methodology, a condition was chosen to obtain the largest drying constants and smallest colour differences. The optimum conditions for the drying process were 70 °C and 2.0 m/s, and 80 °C and 2.5 m/s for fresh and osmotically dehydrated mushrooms, respectively. The dried mushrooms aresented â-glucan content values of 6.14 ± 0.55 and 6.77 ± 0.47 g.100 g?1 d.b under the optimised drying conditions. Osmotically dehydrated samples showed a slower re-hydration rate and smaller water activity than samples without pre-treatment
Light force fluctuations in a strongly coupled atom-cavity system
Between mirrors, the density of electromagnetic modes differs from the one in free space. This changes the radiation properties of an atom as well as the light forces acting on an atom. It has profound consequences in the strong-coupling regime of cavity quantum electrodynamics. For a single atom trapped inside the cavity, we investigate the atom-cavity system by scanning the frequency of a probe laser for various atom-cavity detunings. The avoided crossing between atom and cavity resonance is visible in the transmission of the cavity. It is also visible in the loss rate of the atom from the intracavity dipole trap. On the normal-mode resonances, the dominant contribution to the loss rate originates from dipole-force fluctuations which are dramatically enhanced in the cavity. This conclusion is supported by Monte-Carlo simulations
Vacuum-stimulated cooling of single atoms in three dimensions
Taming quantum dynamical processes is the key to novel applications of
quantum physics, e.g. in quantum information science. The control of
light-matter interactions at the single-atom and single-photon level can be
achieved in cavity quantum electrodynamics, in particular in the regime of
strong coupling where atom and cavity form a single entity. In the optical
domain, this requires permanent trapping and cooling of an atom in a
micro-cavity. We have now realized three-dimensional cavity cooling and
trapping for an orthogonal arrangement of cooling laser, trap laser and cavity
vacuum. This leads to average single-atom trapping times exceeding 15 seconds,
unprecedented for a strongly coupled atom under permanent observation.Comment: 4 pages, 4 figure
Influence of osmotic dehydration and high temperature short time processes on dried sweet potato (Ipomoea batatas Lam.).
The puffing operation is carried out at as intermediate stage in the drying process. When reconstituted, the dehydrated puffed productpresents a more pleasing appearance than the material that has not been puffed. The high temperature and short time process (HTST) was employed to obtain puffed sweet potato slices from both in natura and osmotically pretreated with sucrose and salt solutions samples. Processing time was the most significant variable affecting moisture content, water activity and rehydration. All the empirical models obtained using response surface methodology were considered predictive. The best conditions for the HTST sweet potato slices were obtained using a temperature of 160 C and time of 22 min for samples with no osmotic treatment and a temperature of 150 C and time of 10 min for samples submitted to the osmotic treatment. Scanning electronic microscopy confirmed the formation of pores within the tissue, and surface sealing during the HTST process as the samples puffed up (volume increase). The shortest convective drying time corresponded to the sample treated only by the HTST process. 2007 Elsevier Ltd. All rights reserved
Preliminary fabrication and characterization of electron beam melted Ti–6Al–4V customized dental implant
The current study was aimed to fabricate customized root form dental implant using
additive manufacturing technique for the replacement of missing teeth. The root form dental
implant was designed using GeomagicTM and MagicsTM, the designed implant was directly manufactured
by layering technique using ARCAM A2TM electron beam melting system by employing medical
grade Ti–6Al–4V alloy powder. Furthermore, the fabricated implant was characterized in terms
of certain clinically important parameters such as surface microstructure, surface topography,
chemical purity and internal porosity. Results confirmed that, fabrication of customized dental implants using additive rapid manufacturing technology offers an attractive method to produce
extremely pure form of customized titanium dental implants, the rough and porous surface texture
obtained is expected to provide better initial implant stabilization and superior osseointegration
Effect of osmotic dehydration on the drying kinetics and quality of cashew apple,
The effect of different osmotic pretreatments on cashew apple drying kinetics and product quality were investigated
- …