244 research outputs found
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
Evaluation of effectiveness of instruction and study habits in two consecutive clinical semesters of the medical curriculum munich (MeCuM) reveals the need for more time for self study and higher frequency of assessment
<p>Abstract</p> <p>Background</p> <p>Seven years after implementing a new curriculum an evaluation was performed to explore possibilities for improvements.</p> <p>Purposes: To analyze students' study habits in relation to exam frequency and to evaluate effectiveness of instruction.</p> <p>Methods</p> <p>Time spent on self study (TSS) and the quantity of instruction (QI) was assessed during the internal medicine and the surgical semester. Students and faculty members were asked about study habits and their evaluation of the current curriculum.</p> <p>Results</p> <p>The TSS/QI ratio as a measure of effectiveness of instruction ranges mainly below 1.0 and rises only prior to exams. Students and teachers prefer to have multiple smaller exams over the course of the semester. Furthermore, students wish to have more time for self-guided study.</p> <p>Conclusions</p> <p>The TSS/QI ratio is predominantly below the aspired value of 1.0. Furthermore, the TSS/QI ratio is positively related to test frequency. We therefore propose a reduction of compulsory lessons and an increase in test frequency.</p
Characterization of rhizobium tropici CIAT899 nodulation factors: the role of nodH and nodPQ genes in their sulfation
We have purified and characterized the nodulation factors produced by Rhizobium tropici CIAT899. This strain produces a large variety of nodulation factors, these being a mixture of sulfated or nonsulfated penta- or tetra-chitooligosaccharides to which any of six different fatty acyl moieties may be attached to nitrogen of the nanreducing terminal residue, In this mixture we have also found methylated or nonmethylated lipo-chitin oligosaccharides. Here we describe a novel lipo-chitin-oligosaccharide consisting of a linear backbone of 4 N-acetylglucosamine residues and one mannose that is the reducing-terminal residue and bearing a C18:1 fatty acyl moiety on the nonreducing terminal residue. In addition, we have identified, cloned, and sequenced R. tropici nodH and nodPQ genes, generated mutations in the nodH and nodQ genes, and tested the mutant strains far nodulation in Phaseolus and Leucaena plants, Our results indicate that the sulfate group present in wildtype Nod factors plays a major role in nodulation of Leucaena plants by strain CIAT899 of R. tropici.Microbial Biotechnolog
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
International patent families: from application strategies to statistical indicators
This paper provides an in-depth analysis of the characteristics of international patent families, including their domestic component. We exploit a relatively under-studied feature of patent families, namely the number of patents covering the same invention within a given jurisdiction. Using this information, we highlight common patterns in the structure of international patent families, which reflect both the patenting strategies of innovators and the peculiarities of the different patent systems. While the literature has extensively used family size, i.e. the number of countries in which a given invention is protected, as a measure of patent value, our results suggest that the number of patent filings in the priority country within a patent family as well as the timespan between the first and last fillings within a family are other insightful indicators of the value of patented innovations
Lateral Distribution of Muons in IceCube Cosmic Ray Events
In cosmic ray air showers, the muon lateral separation from the center of the
shower is a measure of the transverse momentum that the muon parent acquired in
the cosmic ray interaction. IceCube has observed cosmic ray interactions that
produce muons laterally separated by up to 400 m from the shower core, a factor
of 6 larger distance than previous measurements. These muons originate in high
pT (> 2 GeV/c) interactions from the incident cosmic ray, or high-energy
secondary interactions. The separation distribution shows a transition to a
power law at large values, indicating the presence of a hard pT component that
can be described by perturbative quantum chromodynamics. However, the rates and
the zenith angle distributions of these events are not well reproduced with the
cosmic ray models tested here, even those that include charm interactions. This
discrepancy may be explained by a larger fraction of kaons and charmed
particles than is currently incorporated in the simulations
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