Consistent sets of estimates for regressions with correlated or uncorrelated measurement errors in arbitrary subsets of all variables

Statistical Methods

Injection locking of an electro-optomechanical device

The techniques of cavity optomechanics have enabled significant achievements in precision sensing, including the detection of gravitational waves and the cooling of mechanical systems to their quantum ground state. Recently, the inherent non-linearity in the optomechanical interaction has been harnessed to explore synchronization effects, including the spontaneous locking of an oscillator to a reference injection signal delivered via the optical field. Here, we present the first demonstration of a radiation-pressure driven optomechanical system locking to an inertial drive, with actuation provided by an integrated electrical interface. We use the injection signal to suppress drift in the optomechanical oscillation frequency, strongly reducing phase noise by over 55 dBc/Hz at 2 Hz offset. We further employ the injection tone to tune the oscillation frequency by more than 2 million times its narrowed linewidth. In addition, we uncover previously unreported synchronization dynamics, enabled by the independence of the inertial drive from the optical drive field. Finally, we show that our approach may enable control of the optomechanical gain competition between different mechanical modes of a single resonator. The electrical interface allows enhanced scalability for future applications involving arrays of injection-locked precision sensors.Comment: Main text: 10 pages, 7 figures. Supplementary Information: 5 pages, 4 figure

30 years of hay meadow succession without fertilization: how does it affect soil and avifauna groups?

In the present study we investigated the effects of hay meadow succession in the brook valley system of the Drentse A Nature Reserve, in the NE of the Netherlands. In particular, we compared the plant and soil fauna composition in five grasslands that differed in the stage of vegetation succession in two well-studied chronosequences, dry and wet respectively. The sampled meadows include a control site (still fertilized meadow), a 5, 15, 25 and 32 years stage of vegetation succession after the cessation of fertilizer application. At all sites, vegetation and earthworm composition was studied in replicate subplots of 4 m2 respectively 0.04 m² each. Moreover, the breeding birds have been monitored in the area over the last 28 years by mapping territories overlapping the meadows of the chronosequences. Concerning the plants we found that diversity was increasing with time of succession. In the wet meadow series the plant species richness increased from ca. 13 species per site (40 m2) to a maximum of ca. 49 species per site in the latest successional stage. In the drier parts the increase in species was less and reached an over all maximum of 27 species in the intermediate (15 years old) stage of the succession in 40 m2, but still increased to a mean of 15 species at the scale of 4 m2 plots in the oldest stage. The diversity and abundance of earthworms dropped significantly over time of succession. The species all belonged to 4 genera with Allolobophora being the most abundant. Soil pH dropped significantly during the succession even below 3.8 in the dry series. This largely explains the unfavourable conditions for the earthworms to survive in the oldest stages of the dry succession. The earthworm biomass dropped in nearly all sites below 25 g/m2 during the summer period, indicating unfavourable conditions for a suit of grassland breeding waders.The abundance of breeding birds in general was low due to the rather small area covered in this study. Anyhow we could find obvious changes in the breeding bird community. In particular waders such as Lapwing (Vanellus vanellus) and Black-tailed Godwit (Limosa limosa) disappeared completely from the area and were followed up by Curlew (Numenius arquata) and Snipe (Gallinago gallinago) being currently also rare in the area. Probably due to changes in grassland vegetation (increase of amongst others Cirsium palustre) and insect abundance the Stonechat (Saxicola torquata) has entered the area as a breeding bird. The same happens to a set of bird species typical for developing carr woodlands such as Lesser Spotted Woodpecker (Dendrocopos minor) and Golden Oriole (Oriolus oriolus).Die vorliegende Studie thematisiert am Beispiel der Fließgewässerniederung der Drentse A, einem großflächigen Schutzgebiet im Nordosten der Niederlande, die Folgen einer langjährigen Heuwiesennutzung ohne Düngung. Im Einzelnen wurde von uns die Zusammensetzung der Vegetation und Bodenfauna auf fünf Grünlandflächen untersucht, die sich in der Dauer der Ausmagerung unterschieden. Getrennt betrachtet wurden dabei die bachnahen, moorigen Niederungsbereichen und die angrenzenden sandigen Geestbereiche. Die ausgewählten Grünlandflächen waren zum Zeitpunkt der Aufnahmen seit 5, 15, 25, und 32 Jahren gemäht aber nicht mehr gedüngt worden. Eine weitere, nach wie vor konventionell bewirtschaftete Wiesenfläche (incl. Düngung) diente als Kontrolle. Auf allen Flächen wurde die Vegetation und Regenwurmfauna in 10 Plots mit einer Größe von jeweils 4 m² bzw. 0.04 m² untersucht. Darüber hinaus wurden über 28 Jahre hinweg die Brutvögel des Gebietes mittels Revierkartierung erfasst. Die Pflanzenartendiversität hat sich mit Dauer der Ausmagerung signifikant erhöht. Sie stieg in den bachnahen Bereichen von 13 Arten in der Kontrollfläche (40 m²) auf 49 Arten in der am längsten ausgemagerten Grünlandfläche an. In den trockenen Geestbereichen war der Anstieg deutlich schwächer. Bezogen auf die Gesamtfläche von 40 m² wurden die meisten Arten hier in der 15 Jahre lang ausgemagerten Grünlandfläche gefunden, während bei Betrachtung der 4 m² großen Aufnahmepunkte die höchste Artenzahl ebenfalls in der ältesten Untersuchungsfläche lag. Die Diversität und Abundanz der Regenwürmer nahm mit Dauer der Ausmagerung ab. Die festgestellten Arten gehörten zu 4 Gattungen, wobei die Gattung Allolobophora am individuenreichsten vertreten war. Mit Dauer der Ausmagerung sank besonders im trockenen bachfernen Geestbereich der Boden-pH-Wert auf unter 3,8 ab. Die damit einhergehenden pessimalen Lebensbedingungen erklären hinreichend die geringe Diversität und Dichte von Regenwürmern in diesen Bereichen. An fast allen Standorten sank die Biomasse der Regenwürmer zum Sommer hin auf Werte unter 25 g/m², so dass für viele Limikolen zu dieser Zeit pessimale Ernährungsbedingungen bestehen. Die Zahl der Brutvogelarten war aufgrund des recht kleinen Untersuchungsgebietes insgesamt gering. Dennoch konnten auffallende Veränderungen in der Brutvogelgemeinschaft beobachtet werden. Während Limikolen wie Kiebitz (Vanellus vanellus) und Uferschnepfe (Limosa limosa) vollständig aus dem Gebiet verschwanden, wanderten der Große Brachvogel und die Bekassine ein. Allerdings sind auch sie aktuell nur noch selten im Gebiet vertreten. Dafür hat sich inzwischen das Schwarzkehlchen (Saxicola torquata) als Brutvogel eingestellt – möglicherweise eine Folge der sich ändernden Grünlandvegetation (hier: Zunahme von Pflanzenarten, die als Ansitzwarten fungieren können wie etwa Cirsium palustre) in Kombination mit einem verbesserten Nahrungsangebot an Makroinvertebraten. Eingewandert sind zwischenzeitlich auch eine Reihe weiterer Vogelarten, wie Pirol (Oriolus oriolus) und Kleinspecht (Dendrocopos minor), die charakteristisch für sich entwickelnde Bruchwälder sind. Letztere haben sich, meist kleinflächig, auf ehemaligen Feuchtgrünlandstandorten entwickelt

Logistics-related customer complaints in the South African retail industry

Abstract: Intense competition in the South African fast-moving customer goods (FMCG) retailing industry often results in price wars that encourage customer switching behaviour. Time and place utility provided by distribution, equates to customer service and forms part of the competitive strategy of retailers. Solving last-mile logistical problems in-store could be a valuable strategy in differentiation and building customer loyalty. The purpose of this study was to explore the nature of logistics-related customer complaints concerning South African mass grocery retailers (MGR) as lodged on customer complaints website Hellopeter.com, pertaining to the three largest MGR groups for the period of one year ending August 2016..

Free spectral range electrical tuning of a high quality on-chip microcavity

Reconfigurable photonic circuits have applications ranging from next-generation computer architectures to quantum networks, coherent radar and optical metamaterials. However, complete reconfigurability is only currently practical on millimetre-scale device footprints. Here, we overcome this barrier by developing an on-chip high quality microcavity with resonances that can be electrically tuned across a full free spectral range (FSR). FSR tuning allows resonance with any source or emitter, or between any number of networked microcavities. We achieve it by integrating nanoelectronic actuation with strong optomechanical interactions that create a highly strain-dependent effective refractive index. This allows low voltages and sub-nanowatt power consumption. We demonstrate a basic reconfigurable photonic network, bringing the microcavity into resonance with an arbitrary mode of a microtoroidal optical cavity across a telecommunications fibre link. Our results have applications beyond photonic circuits, including widely tuneable integrated lasers, reconfigurable optical filters for telecommunications and astronomy, and on-chip sensor networks.Comment: Main text: 7 pages, 3 figures. Supplementary information: 7 pages, 9 figure

Implicit threat vigilance among violent offenders diagnosed with antisocial personality disorder:The impact of ostracism and control threat

The present study investigated the role of control as a moderator in reaction to ostracism among male violent offenders diagnosed with ASPD (N = 33) compared to a control sample consisting of males from the normal population without a known history of violence, or diagnosis of ASPD, matched for age and educational level (N = 35). Participants played an altered version of the Cyberball game in which they could control the course of the game or not. The authors predicted and found that having control prior to ostracism would mitigate the effect of ostracism on implicit threat vigilance among violent offenders diagnosed with ASPD, but not among normal individuals. The results suggest that control needs are crucial in the typology of ASPD

Radiation pressure-tunable photoluminescence and upconversion lasing on a chip

The ability to tune the wavelength of light emission on a silicon chip is important for scalable photonic networks, distributed photonic sensor networks and next generation computer architectures. Here we demonstrate light emission in a chip-scale optomechanical device, with wide tunablity provided by radiation pressure. To achieve this, we develop an optically active double-disk optomechanical system through implantation of erbium ions. We observe radiation pressure tuning of photoluminescence in the telecommunications band with a wavelength range of 520 pm, green upconversion lasing with a threshold of $340\pm 70 \; \mu$W, and optomechanical self-pulsing caused by the interplay of radiation pressure and thermal effects. These results provide a path towards widely-tunable micron-scale lasers for photonic networks.Comment: Main text 6 pages, 5 figures; Appendix 3 pages, 3 figure

A Bayesian analysis for censored Rayleigh model using a generalised hypergeometric prior

Based on a type II censored sample, Bayesian estimation for the scale parameter of the Rayleigh model is carried out under the assumption of the squared error loss function. A generalised hypergeometric distribution with its versatile shape of tails is introduced as a prior, and beta special cases are examined. A simulation study is carried out to investigate the sensitivity of four special cases of this beta prior family in terms of bias, frequentist coverage and mean square error and to determine their effect on robustness. Prediction bounds are derived for the lifetime of unused components using this beta prior family. A data set is used to illustrate and support some of the findings