Silicon optomechanics

Optomechanics might provide the key to realize various signal processing functions on a chip. In this proceeding we focus on silicon Nano-Optomechanical Systems (NOMS) and provide an overview of several types of optomechanical devices

An empirical economic model to reveal behaviour characteristics driving the evolution of agriculture in Belgium

Effective design of agricultural policies requires an understanding of the drivers behind the evolution of the agricultural sector. This project builds an evolutionary economic model of the Belgian agricultural sector, as a testing ground for new policies. This agent-based model simulates the dairy, cow and pig sector. The model is calibrated to historical data of production and farm diversity during the period 2003 - 2013. Profit maximising agents cannot replicate the historical trends. When assuming heterogeneous behaviours, the actual evolution can be reproduced much more closely. The calibration reveals key behaviour variables. The evolution in the agricultural sector can only be explained when accounting for a resistance to change at farm level or at market level. However, this approach cannot determine the exact location of this resistance. The resistance to change can result from personal convictions of the farmer or from market rigidities and learning effects

Single-component organic solar cells—Perspective on the importance of chemical precision in conjugated block copolymers

Organic photovoltaics (OPV) present a promising thin-film solar cell technology with particular benefits in terms of weight, aesthetics, transparency, and cost. However, despite being studied intensively since the mid 90's, OPV has not entered the mass consumer market yet. Although the efficiency gap with other thin-film photovoltaics has largely been overcome, active layer stability and performance reproducibility issues have not been fully resolved. State-of-the-art OPV devices employ a physical mixture of electron donor and acceptor molecules in a bulk heterojunction active layer. These blends are prone to morphological changes, leading to performance losses over time. On the other hand, in “single-component” organic solar cells, the donor and acceptor constituents are chemically connected within a single material, preventing demixing and thereby enhancing device stability. Novel single-component materials affording reasonably high solar cell efficiencies and improved lifetimes have recently emerged. In particular, the combination of donor and acceptor structures in conjugated block copolymers (CBCs) presents an exciting approach. Nevertheless, the current CBCs are poorly defined from a structural point of view, while synthetic protocols remain unoptimized. More controlled synthesis followed by proper structural analysis of CBCs is, however, essential to develop rational structure-property-device relations and to drive the field forward. In this perspective, we provide a short overview of the state-of-the-art in single-component organic solar cells prepared from CBCs, reflect on their troublesome characterization and the importance of chemical precision in these structures, give some recommendations, and discuss the potential impact of these aspects on the field

How HRM affects corporate financial performance: Evidence from Belgian SMEs.

In this paper, we provide a summary of several results from a study of HRM in small and medium-sized enterprises in Belgium. The central issue is whether the investment in HRM practices for smaller organizations is 'profitable'. This study differs in three ways from existing research. (1) It deals with the results from a survey of organizations with between 10 and 100 employees from various sectors. (2) In composing an index for 'HRM intensity', we started with a different interpretation of HRM practices, which also fits in more closely with the Belgian institutional context. (3) The operationalization of performance is based on a number of financial indicators which also help determine the 'state of health' of a company. Using the results of the survey, we examined the link between the score for HRM intensity, some performance outcomes and the financial performance of the organization using structural equation modeling. The results show that intensive HRM also offers added value for smaller organizations. Firstly, HRM intensification has a highly positive effect on productivity and, through productivity, reduces personnel costs/added value. This effect is sufficiently strong to compensate for the increased costs associated with intensive HRM. On top of this 'compensation effect', HRM intensity also has major effects on the profitability of the company.

How HRM affects corporate financial performance. Evidence from Belgian SMEs. Paper.

Employment; Expected; Managers; Studies; Management; Performance;

A general framework for quantifying the effects of land-use history on ecosystem dynamics

Land-use legacies are important for explaining present-day ecological patterns and processes. However, an overarching approach to quantify land-use history effects on ecosystem properties is lacking, mainly due to the scarcity of high-quality, complete and detailed data on past land use. We propose a general framework for quantifying the effects of land-use history on ecosystem properties, which is applicable (i) to different ecological processes in various ecosystem types and across trophic levels; and (ii) when historical data are incomplete or of variable quality. The conceptual foundation of our framework is that past land use affects current (and future) ecosystem properties through altering the past values of resources and conditions that are the driving variables of ecosystem responses. We describe and illustrate how Markov chains can be applied to derive past time series of driving variables, and how these time series can be used to improve our understanding of present-day ecosystem properties. We present our framework in a stepwise manner, elucidating its general nature. We illustrate its application through a case study on the importance of past light levels for the contemporary understorey composition of temperate deciduous forest. We found that the understorey shows legacies of past forest management: high past light availability lead to a low proportion of typical forest species in the understorey. Our framework can be a useful tool for quantifying the effect of past land use on ecological patterns and processes and enhancing our understanding of ecosystem dynamics by including legacy effects which have often been ignored

Parametric instability of an integrated micromechanical oscillator by means of active optomechanical feedback

Mass sensing and time keeping applications require high frequency integrated micromechanical oscillators. To overcome the increasing mechanical stiffness of these structures sensitive optical vibration detection and efficient actuation is required. Therefore we have implemented an active feedback system, where the feedback signal is provided by the optical gradient force that is present between nanophotonic waveguides on a silicon-on-insulator chip. We found that access to the parametric instability regime can be easily controlled by tuning the wavelength. (C) 2011 Optical Society of Americ

Effect of challenge of pigs previously immunised with inactivated vaccines containing homologous and heterologous Mycoplasma hyopneumoniae strains

<p>Abstract</p> <p>Background</p> <p><it>Mycoplasma hyopneumoniae </it>is the primary cause of enzootic pneumonia in pigs. Although vaccination is an important control tool, the results observed under field conditions are variable. This may be due to antigenic differences between the strains circulating in pig herds and the vaccine strain. This study compared the protective efficacy of four bacterins against challenge infection with a highly virulent field strain of <it>M. hyopneumoniae</it>.</p> <p>Seventy eight, one-week old piglets were randomly assigned to five treatment groups (A, B, C, D, E), 14 piglets each, and a negative control group (F) consisting of 8 piglets. All pigs were injected at 1 (D7) and 4 weeks of age (D28), with 2 ml of either a placebo or a bacterin based on selected <it>M. hyopneumoniae </it>strains, namely A (F7.2C), B (F20.1L), C (B2V1W20 1A-F), D (J strain), E (placebo; positive control), F (placebo; negative control). At D56, all pigs except those of group F were challenged intratracheally with 7 ml culture medium containing 10⁷CCU/ml of <it>M. hyopneumoniae </it>strain F7.2C. All pigs were euthanized and necropsied at D84. The severity of coughing and pneumonia lesions were the main parameters. Immunofluorescence (IF) testing, nested PCR testing of bronchoalveolar lavage (BAL) fluid and serology for <it>M. hyopneumoniae </it>were also performed.</p> <p>Results</p> <p>The different bacterins only slightly improved clinical symptoms (average 0.38 in vaccinated groups vs. 0.45 in group E) and histopathological lung lesions (average 3.20 in vaccinated groups vs. 3.45 in group E), but did not improve macroscopic lung lesions (score 4.30 vs. 4.03 in group E). None of the vaccines was significantly and/or consistently better or worse than the other ones. All bacterins evoked a serological response in the vaccinated animals. All pigs, except those from group F, were positive with nPCR in BAL fluid at D84.</p> <p>Conclusion</p> <p>The bacterins did not induce a clear overall protection against challenge infection, and there were no significant differences in protective efficacy between bacterins containing homologous and heterologous <it>M. hyopneumoniae </it>strains. Further research is necessary to better characterize the antigens involved in protection and to elucidate the protective immunity responses following <it>M. hyopneumoniae </it>vaccination and/or infection.</p

Individualistic responses of forest herb traits to environmental change

Intraspecific trait variation (ITV; i.e. variability in mean and/or distribution of plant attribute values within species) can occur in response to multiple drivers. Environmental change and land-use legacies could directly alter trait values within species but could also affect them indirectly through changes in vegetation cover. Increasing variability in environmental conditions could lead to more ITV, but responses might differ among species. Disentangling these drivers on ITV is necessary to accurately predict plant community responses to global change. We planted herb communities into forest soils with and without a recent history of agriculture. Soils were collected across temperate European regions, while the 15 selected herb species had different colonizing abilities and affinities to forest habitat. These mesocosms (384) were exposed to two-level full-factorial treatments of warming, nitrogen addition and illumination. We measured plant height and specific leaf area (SLA). For the majority of species, mean plant height increased as vegetation cover increased in response to light addition, warming and agricultural legacy. The coefficient of variation (CV) for height was larger in fast-colonizing species. Mean SLA for vernal species increased with warming, while light addition generally decreased mean SLA for shade-tolerant species. Interactions between treatments were not important predictors. Environmental change treatments influenced ITV, either via increasing vegetation cover or by affecting trait values directly. Species' ITV was individualistic, i.e. species responded to different single resource and condition manipulations that benefited their growth in the short term. These individual responses could be important for altered community organization after a prolonged period