A Mean-Field Theory for Coarsening Faceted Surfaces

A mean-field theory is developed for the scale-invariant length distributions observed during the coarsening of one-dimensional faceted surfaces. This theory closely follows the Lifshitz-Slyozov-Wagner theory of Ostwald ripening in two-phase systems [1-3], but the mechanism of coarsening in faceted surfaces requires the addition of convolution terms recalling the work of Smoluchowski [4] and Schumann [5] on coalescence. The model is solved by the exponential distribution, but agreement with experiment is limited by the assumption that neighboring facet lengths are uncorrelated. However, the method concisely describes the essential processes operating in the scaling state, illuminates a clear path for future refinement, and offers a framework for the investigation of faceted surfaces evolving under arbitrary dynamics. [1] I. Lifshitz, V. Slezov, Soviet Physics JETP 38 (1959) 331-339. [2] I. Lifshitz, V. Slyozov, J. Phys. Chem. Solids 19 (1961) 35-50. [3] C. Wagner, Elektrochemie 65 (1961) 581-591. [4] M. von Smoluchowski, Physikalische Zeitschrift 17 (1916) 557-571. [5] T. Schumann, J. Roy. Met. Soc. 66 (1940) 195-207

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

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

Rhizobium leguminosarum bv. trifolii produces Lipo-chitin oligosaccharides with nodE-dependent highly unsaturated fatty acyl moieties. An electrospray ionization and collision-induced dissociation tandem mass spectrometric study

Microbial Biotechnolog

Host specificity of Rhizobium leguminosarum is determined by the hydrophobicity of highly unsaturated fatty acyl moieties of the nodulation factors

The nodE genes of Rhizobium leguminosarum bvs, trifolii and viciae strains are the major determinants of the host range of nodulation, Using mass spectrometry we have analyzed the structures of the major and minor lipooligosaccharides produced by two R, leguminosarum strains that differ only in the origin of the nod genes, The strain containing the nod genes of R. l. by. viciae produces lipo-chitin oligosaccharide (LCO) molecules that contain the common cis-vaccenyl (C18:1) or a highly unsaturated acyl (C18:4) group that is determined by nodE (Spaink et al, Nature 354:125-130, 1991), Here we show that, in addition, minor quantities of analogous molecules that contain different common fatty acyl groups such as stearyl (C18:0), palmityl (C16:0), and palmitoyl (C16:1) groups are produced, The set of LCOs produced by the strain containing the R. l. by. trifolii nod genes is similar, but major differences are found in the length and unsaturation of the fatty acyl groups of various LCOs. The R. l, by. trifolii strain does not produce LCO molecules that contain the C18:4 fatty acyl group. Instead, a complex mixture of other unsaturated fatty acyl groups containing either two, three, or four double bonds is produced, These novel fatty acyl groups are more hydrophobic than the C18:4 fatty acyl group found in by. viciae, as judged by highperformance liquid chromatography retention times, probably as a result of the longer carbon chain length, the lack of a cis double bond, or both, Another difference is that the relative amount of highly unsaturated fatty acid-containing LCOs produced by R. l. by. trifolii is much smaller An isogenic R. l. by. trifolii strain containing a Tn5 insertion in the nodE gene only produces LCOs containing the common fatty acyl groups and not the highly unsaturated types, The results indicate that the difference in the host range of the R. l. bvs, viciae and trifolii is determined by the overall hydrophobicity of the highly unsaturated fatty acyl moieties of LCOs rather than by a specific structural feature.Microbial Biotechnolog

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

Long-term wastewater monitoring of SARS-CoV-2 viral loads and variants at the major international passenger hub Amsterdam Schiphol Airport: A valuable addition to COVID-19 surveillance

Wastewater-based epidemiological surveillance at municipal wastewater treatment plants has proven to play an important role in COVID-19 surveillance. Considering international passenger hubs contribute extensively to global transmission of viruses, wastewater surveillance at this type of location may be of added value as well. The aim of this study is to explore the potential of long-term wastewater surveillance at a large passenger hub as an additional tool for public health surveillance during different stages of a pandemic. Here, we present an analysis of SARS-CoV-2 viral loads in airport wastewater by reverse-transcription quantitative polymerase chain reaction (RT-qPCR) from the beginning of the COVID-19 pandemic in Feb 2020, and an analysis of SARS-CoV-2 variants by whole-genome next-generation sequencing from Sep 2020, both until Sep 2022, in the Netherlands. Results are contextualized using (inter)national measures and data sources such as passenger numbers, clinical surveillance data and national wastewater surveillance data. Our findings show that wastewater surveillance was possible throughout the study period, irrespective of measures, as viral loads were detected and quantified in 98.6 % (273/277) of samples. Emergence of SARS-CoV-2 variants, identified in 91.0 % (161/177) of sequenced samples, coincided with increases in viral loads. Furthermore, trends in viral load and variant detection in airport wastewater closely followed, and in some cases preceded, trends in national daily average viral load in wastewater and variants detected in clinical surveillance. Wastewater-based epidemiology at a large international airport is a valuable addition to classical COVID-19 surveillance and the developed expertise can be applied in pandemic preparedness plans for other (emerging) pathogens in the future