Exterior and Symmetric Powers of Modules for Cyclic 2-Groups

We prove a recursive formula for the exterior and symmetric powers of modules for a cyclic 2-group. This makes computation straightforward. Previously, a complete description was only known for cyclic groups of prime order

On the characters of the Sylow p-subgroups of untwisted Chevalley groups Y_n(p^a)

Let $UY_n(q)$ be a Sylow p-subgroup of an untwisted Chevalley group $Y_n(q)$ of rank n defined over $\mathbb{F}_q$ where q is a power of a prime p. We partition the set $Irr(UY_n(q))$ of irreducible characters of $UY_n(q)$ into families indexed by antichains of positive roots of the root system of type $Y_n$. We focus our attention on the families of characters of $UY_n(q)$ which are indexed by antichains of length 1. Then for each positive root $\alpha$ we establish a one to one correspondence between the minimal degree members of the family indexed by $\alpha$ and the linear characters of a certain subquotient $\overline{T}_\alpha$ of $UY_n(q)$. For $Y_n = A_n$ our single root character construction recovers amongst other things the elementary supercharacters of these groups. Most importantly though this paper lays the groundwork for our classification of the elements of $Irr(UE_i(q))$, $6 \le i \le 8$ and $Irr(UF_4(q))$

The effect of road noise on sound pressure levels and preferred listening levels using personal listening devices

Using a PLD in an automobile introduces unique threats such as volume levels set at higher levels to reduce the masking effects of road noise that enters the automobile. Passengers enjoying prolonged PLD exposure may be at an increased risk of noise exposure or fluctuating sound pressure levels resulting in hearing loss. Historically, hazardous noise has been primarily associated with industrial/occupational activities; however, harmful noise from recreational activities is also prevalent. The Center for Disease Control (2015) lists turning down PLD volume as one of their top three methods for reducing the possibility of NIHL in children. Excessive listening level and prolonged duration of use put listeners at risk for increased thresholds and other repercussions of hearing damage. The combined effect of simulated road noise and PLD volume was measured in a simulated ear canal. The principal investigator collected all sound levels using KEMAR; no human participants. A pre-selected movie scene was delivered to KEMAR at normal listening levels through earbuds and headphones separately, while in the presence of road noise. The movie scene and road noise were increased in 5 dB steps and recorded. The results showed earbuds are better designed for eliminating the masking effects of road noise, yet headphones are better designed for limiting the maximum SPLs. Frequent volume changes as high as 41 dB were reported in this study

On the decomposition numbers of the Ree groups F42(q2) in non-defining characteristic

AbstractWe compute the ℓ-modular decomposition matrices of the simple Ree groups F42(q2), where q2=22n+1 and n>0, for all primes ℓ>3 up to some entries in the unipotent and one entry in the non-unipotent characters. We determine the smallest degree of a nontrivial irreducible ℓ-modular representation of F42(q2) for all primes ℓ>3 and also obtain results on the 3-modular decomposition matrices of F42(q2)

Investigations on the localized surface plasmon resonances of nickel sulfide nanostructures

The main topic of this thesis was the examination of the optical properties of nanoparticles consisting of metallic nickel sulfide phases. For this, new syntheses to obtain various colloidal dispersions of Ni3S2, Ni3S4, and α-NiS nanostructures as well as core-shell particles with gold cores were developed. These materials all exhibit prominent absorbance features in the visible part of the electromagnetic spectrum which were confirmed to be caused by localized surface plasmon resonances (LSPRs). Since the field of plasmonic materials active in this spectral region is otherwise confined to noble metal nanoparticles, the novel nickel sulfide particles were evaluated with regard to their molar extinction coefficient. An analysis of the results compared to commonly used gold nanocrystals showed that Ni3S2 nanostructures could achieve very similar values while the necessary precursors for their synthesis are much less expensive than the respective noble metal precursors. Furthermore, hollow nickel sulfide nanoparticles were synthesized to be able to profit from the advantages of hollow nanostructures in regards to applications as nanosensors. This was achieved via the nanoscale Kirkendall effect starting from nickel nanoparticles. The obtained hollow nickel sulfide nanoparticles showed a much sharper LSPR absorbance band making them a more promising material for sensorics. Additionally, α-NiS and Au-α-NiS nanoparticles were investigated regarding their metal-insulator type phase transition and its influence on their LSPR. It could be shown, that the optical density of the colloidal dispersions can be tuned by varying the temperature, resulting in a temperature-switchable plasmonic material.Das Hauptthema dieser Arbeit war die Untersuchung der optischen Eigenschaften von Nanopartikeln bestehend aus metallischen Nickelsulfid-Phasen. Dazu wurden neue Synthesen entwickelt, um kolloidale Dispersionen von Ni3S2-, Ni3S4- und α-NiS-Nanostrukturen sowie Kern-Schale-Partikel mit Goldkernen zu erhalten. Diese Materialien zeigen auffällige Extinktionsbanden im sichtbaren Teil des elektromagnetischen Spektrums, die lokalisierten Oberflächenplasmonenresonanzen (LOPRs) zugeordnet werden konnten. Da das Feld der in diesem Spektralbereich aktiven plasmonischen Materialien auf Edelmetall-Nanopartikel beschränkt ist, wurden die neuartigen Nickelsulfid-Partikel hinsichtlich ihres molaren Extinktionskoeffizienten untersucht. Ein Vergleich der Ergebnisse mit denen der häufig verwendeten Goldnanokristalle zeigte, dass Ni3S2-Nanostrukturen sehr ähnliche Werte erreichen können, während die für ihre Synthese notwendigen Vorstufen deutlich günstiger sind als die der Edelmetalle. Darüber hinaus wurden hohle Nickelsulfid-Nanopartikel synthetisiert, um die Vorteile hohler Nanostrukturen im Hinblick auf Anwendungen als Nanosensoren nutzen zu können. Dies wurde über den nanoskaligen Kirkendall-Effekt ausgehend von Nickel-Nanopartikeln erreicht. Die erhaltenen hohlen Nickelsulfid-Nanopartikel zeigten eine deutlich schärfere LOPR-Extinktionsbande, was sie zu einem vielversprechenderen Material für die Sensorik macht. Darüber hinaus wurden α-NiS- und Au-α-NiS-Nanopartikel hinsichtlich ihres Metall-Isolator Übergangs und dessen Einfluss auf ihre LOPR untersucht. Es konnte gezeigt werden, dass die optische Dichte der kolloidalen Dispersionen durch Variation der Temperatur eingestellt werden kann, was sie zu einem temperaturschaltbaren plasmonischen Material macht

Entwicklung einer bildanalytischen Methode zur Abschätzung des Leguminosenanteils in Futterbaugemengen

A pot experiment in a greenhouse was conducted to follow the question how to esti-mate dominance of legumes in legume/grass swards by image analysis. Pure swards and binary legume/grass mixtures of red clover, white clover, lucerne and perennial ryegrass were sown in two week intervals and harvested together 35, 49 or 63 days after sowing to have different old swards. Digital photos of all variants were taken one day before harvesting. Sward composition was detected by fractionating biomass in grass, legumes and unsown species as reference. Eight images of the oldest swards were selected for determining an optimal image analysis procedure with Optimas®. This image analysis procedure was used for all variants of all ages. The estimated dominances of legumes were compared to the references. Using image analysis for estimating the dominance of legumes we could detect first good results. Red and white clover both pure and mixtures show a closer relationship with the reference than lucerne and grass. Legumes identification in pure grass swards with image analysis can be caused by weeds with rounded leaves (Stel-laria media) and visible ground. The dominance of lucerne determined by image analysis was lower then the measured dry matter yield (%). The younger the swards the more inexactly are the calculations because the visible ground increases. Next intended steps are verifying a relationship for swards of different ages and checking further procedures of image analysis

Untersuchungen zur Ökologie des Monteverde im westlichen Anaga-Gebirge auf Teneriffa, Kanarische Inseln

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