287 research outputs found
Comparative study of Clâ, Clâ/Oâ, and Clâ/Nâ inductively coupled plasma processes for etching of high-aspect-ratio photonic-crystal holes in InP
An extensive investigation has been performed on inductively coupled plasmaetching of InP. An important motivation for this work is the fabrication of high-aspect-ratio holes for photonic crystals. The essential chemistry is based on Clâ with the addition of Nâ or Oâ for sidewall passivation. The influence of different process parameters such as gas flows, temperature,pressure, ion energy, and inductively coupled plasma power on the hole geometry is presented. It is concluded that photonic crystals can be etched with Clâ only; however, temperature and pressure control is critical. Adding passivation gases largely broadens the window in the parameter space for hole etching. Most importantly, etching of narrow holes can be carried out at higher temperatures where the etching is mass limited and spontaneous etching of InP by Clâ occurs.Part of this research is supported by NanoNed, a technology program of the Dutch
Ministry of Economic Affairs
Polarization tomography of metallic nanohole arrays
We report polarization tomography experiments on metallic nanohole arrays
with square and hexagonal symmetry. As a main result, we find that a fully
polarized input beam is partly depolarized after transmission through a
nanohole array. This loss of polarization coherence is found to be anisotropic,
i.e. it depends on the polarization state of the input beam. The depolarization
is ascribed to a combination of two factors: i) the nonlocal response of the
array due to surface plasmon propagation, ii) the non-plane wave nature of a
practical input beam.Comment: 4 pages, 3 figures, 1 table, submitted to PR
Localization of the 17q breakpoint of a constitutional 1;17 translocation in a patient with neuroblastoma within a 25-kb segment located between the ACCN1 and TLK2 genes and near the distal breakpoints of two microdeletions in neurofibromatosis type I patients.
We have constructed a 1.4-Mb P1 artificial chromosome/bacterial artificial chromosome (PAC/BAC) contig spanning the 17q breakpoint of a constitutional translocation t(1;17)(p36.2;q11.2) in a patient with neuroblastoma. Three 17q breakpoint-overlapping cosmids were identified and sequenced. No coding sequences were found in the immediate proximity of the 17q breakpoint. The PAC/BAC contig covers the region between the proximally located ACCN1 gene and the distally located TLK2 gene and SCYA chemokine gene cluster. The observation that the 17q breakpoint region could not be detected in any of the screened yeast artificial chromosome libraries and the localization of the 17q breakpoint in the vicinity of the distal breakpoints of two microdeletions in patients with neurofibromatosis type 1 suggest that this chromosomal region is genetically unstable and prone to rearrangement
InP-based two-dimensional photonic crystals filled with polymers
Polymer filling of the air holes of Indium Phosphide based two-dimensional
photonic crystals is reported. After infiltration of the holes with a liquid
monomer and solidification of the infill in situ by thermal polymerization,
complete filling is proven using scanning electron microscopy. Optical
transmission measurements of a filled photonic crystal structure exhibit a
redshift of the air band, confirming the complete filling.Comment: To be published in Appl. Phys. Let
Dynamic ordering and frustration of confined vortex rows studied by mode-locking experiments
The flow properties of confined vortex matter driven through disordered
mesoscopic channels are investigated by mode locking (ML) experiments. The
observed ML effects allow to trace the evolution of both the structure and the
number of confined rows and their match to the channel width as function of
magnetic field. From a detailed analysis of the ML behavior for the case of
3-rows we obtain ({\it i}) the pinning frequency , ({\it ii}) the onset
frequency for ML ( ordering velocity) and ({\it iii}) the
fraction of coherently moving 3-row regions in the channel. The
field dependence of these quantities shows that, at matching, where is
maximum, the pinning strength is small and the ordering velocity is low, while
at mismatch, where is small, both the pinning force and the ordering
velocity are enhanced. Further, we find that , consistent
with the dynamic ordering theory of Koshelev and Vinokur. The microscopic
nature of the flow and the ordering phenomena will also be discussed.Comment: 10 pages, 7 figure, submitted to PRB. Discussion has been improved
and a figure has been adde
Kiyang-yang, a West-African Postwar Idiom of Distress
In 1984, a healing cult for young barren women in southern Guinea Bissau developed into a movement, Kiyang-yang, that shook society to its foundations and had national repercussions. âIdiom of distressâ is used here as a heuristic tool to understand how Kiyang-yang was able to link war and post-war-related traumatic stress and suffering on both individual and group levels. An individual experience born from a traumatic origin may be generalized into an idiom that diverse sectors of society could embrace for a range of related reasons. We argue that, for an idiom to be understood and appropriated by others, there has to be resonance at the level of symbolic language and shared experiences as well as at the level of the culturally mediated contingent emotions it communicates. We also argue that through its symbolic references to structural causes of suffering, an idiom of distress entails a danger for those in power. It can continue to exist only if its etiology is not exposed or the social suffering it articulates is not eliminated. We finally argue that idioms of distress are not to be understood as discrete diagnostic categories or as monodimensional expressions of âtraumaâ that can be addressed
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