5,793 research outputs found
Corrosion Behavior of Parylene-Metal-Parylene Thin Films in Saline
In this paper, we study the corrosion behavior of parylene-metal-parylene thin films using accelerated-lifetime soak tests. The samples under test are thin film resistors with a 200 nm layer of Au sandwiched by parylene-C on both sides, fabricated with parylene-metal skin technology. The samples are tested in hot saline both passively and actively, and different failure modes are observed using optical and electron-beam metrologies. Bubbles and delamination are first seen in the samples after 2 days of soaking under passive conditions, and followed by metal corrosion. While under active conditions, either bubbles or parylene breakdowns are observed depending on the thickness of parylene packaging. These results contribute to a better understanding of the failure mechanisms of parylene packaging in body fluids
Weak and Strong coupling regimes in plasmonic-QED
We present a quantum theory for the interaction of a two level emitter with
surface plasmon polaritons confined in single-mode waveguide resonators. Based
on the Green's function approach, we develop the conditions for the weak and
strong coupling regimes by taking into account the sources of dissipation and
decoherence: radiative and non-radiative decays, internal loss processes in the
emitter, as well as propagation and leakage losses of the plasmons in the
resonator. The theory is supported by numerical calculations for several
quantum emitters, GaAs and CdSe quantum dots and NV centers together with
different types of resonators constructed of hybrid, cylindrical or wedge
waveguides. We further study the role of temperature and resonator length.
Assuming realistic leakage rates, we find the existence of an optimal length at
which strong coupling is possible. Our calculations show that the strong
coupling regime in plasmonic resonators is accessible within current technology
when working at very low temperatures (<4K). In the weak coupling regime our
theory accounts for recent experimental results. By further optimization we
find highly enhanced spontaneous emission with Purcell factors over 1000 at
room temperature for NV-centers. We finally discuss more applications for
quantum nonlinear optics and plasmon-plasmon interactions.Comment: published as Phys. Rev. B 87, 115419 (2013
Triggered Star Formation by Massive Stars
We present our diagnosis of the role that massive stars play in the formation
of low- and intermediate-mass stars in OB associations (the Lambda Ori region,
Ori OB1, and Lac OB1 associations). We find that the classical T Tauri stars
and Herbig Ae/Be stars tend to line up between luminous O stars and
bright-rimmed or comet-shaped clouds; the closer to a cloud the progressively
younger they are. Our positional and chronological study lends support to the
validity of the radiation-driven implosion mechanism, where the Lyman continuum
photons from a luminous O star create expanding ionization fronts to evaporate
and compress nearby clouds into bright-rimmed or comet-shaped clouds. Implosive
pressure then causes dense clumps to collapse, prompting the formation of
low-mass stars on the cloud surface (i.e., the bright rim) and
intermediate-mass stars somewhat deeper in the cloud. These stars are a
signpost of current star formation; no young stars are seen leading the
ionization fronts further into the cloud. Young stars in bright-rimmed or
comet-shaped clouds are likely to have been formed by triggering, which would
result in an age spread of several megayears between the member stars or star
groups formed in the sequence.Comment: 2007, ApJ, 657, 88
Enhanced dispersion interaction in confined geometry
The dispersion interaction between two point-like particles confined in a
dielectric slab between two plates of another dielectric medium is studied
within a continuum (Lifshitz) theory. The retarded (Casimir-Polder) interaction
at large inter-particle distances is found to be strongly enhanced as the
mismatch between the dielectric permittivities of the two media is increased.
The large-distance interaction is multiplied due to confinement by a factor of
at zero temperature, and by
at finite temperature, \gamma=\ein(0)/\eout(0)
being the ratio between the static dielectric permittivities of the inner and
outer media. This confinement-induced amplification of the dispersion
interaction can reach several orders of magnitude.Comment: 4 page
Relativistic Generalization of the Gamow Factor for Fermion Pair Production or Annihilation
In the production or annihilation of a pair of fermions, the initial-state or
final-state interactions often lead to significant effects on the reaction
cross sections. For Coulomb-type interactions, the Gamow factor has been
traditionally used to take into account these effects. However the Gamow factor
needs to be modified when the magnitude of the coupling constant or the
relative velocity of two particles increases. We obtain the relativistic
generalization of the Gamow factor in terms of the overlap of the Feynman
amplitude with the relativistic wave function of two fermions with an
attractive Coulomb-type interaction. An explicit form of the corrective factor
is presented for the spin-singlet S-wave state. While the corrective factor
approaches the Gamow factor in the non-relativistic limit, we found that the
Gamow factor significantly over-estimates the effects when the coupling
constant or the velocity is large.Comment: 16 pages, 4 figures in LaTe
Peripheral Inflammation, \u3cem\u3eApolipoprotein E4\u3c/em\u3e, and Amyloid-β Interact to Induce Cognitive and Cerebrovascular Dysfunction
Cerebrovascular dysfunction is rapidly reemerging as a major process of Alzheimer’s disease (AD). It is, therefore, crucial to delineate the roles of AD risk factors in cerebrovascular dysfunction. While apolipoprotein E4 (APOE4), Amyloid-β (Aβ), and peripheral inflammation independently induce cerebrovascular damage, their collective effects remain to be elucidated. The goal of this study was to determine the interactive effect of APOE4, Aβ, and chronic repeated peripheral inflammation on cerebrovascular and cognitive dysfunction in vivo. EFAD mice are a well-characterized mouse model that express human APOE3 (E3FAD) or APOE4 (E4FAD) and overproduce human Aβ42 via expression of 5 Familial Alzheimer’s disease (5xFAD) mutations. Here, we utilized EFAD carriers [5xFAD+/−/APOE+/+ (EFAD+)] and noncarriers [5xFAD−/−/APOE+/+ (EFAD−)] to compare the effects of peripheral inflammation in the presence or absence of human Aβ overproduction. Low-level, chronic repeated peripheral inflammation was induced in EFAD mice via systemic administration of lipopolysaccharide (LPS; 0.5 mg/kg/wk i.p.) from 4 to 6 months of age. In E4FAD+ mice, peripheral inflammation caused cognitive deficits and lowered post-synaptic protein levels. Importantly, cerebrovascular deficits were observed in LPS-challenged E4FAD+ mice, including cerebrovascular leakiness, lower vessel coverage, and cerebral amyloid angiopathy-like Aβ deposition. Thus, APOE4, Aβ, and peripheral inflammation interact to induce cerebrovascular damage and cognitive deficits
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