23 research outputs found
Spin in quantum field theory
No full textI introduce spin in field theory by emphasizing the close connection between quantum field theory and quantum mechanics. First, I show that the spinstatistics connection can be derived in quantum mechanics without relativity or field theory. Then, I discuss path integrals for spin without using spinors. Finally, I show how spin can be quantized in a path-integral approach, without introducing anticommuting variables
LC-MS-based detection of silkworm pupae in feed with and without prior immunoaffinity enrichment
No full textDue to their advantageous nutrient composition and high feed conversion efficiency, insects may be an alternative protein source for human and animal nutrition. Recently authorised for feeding purposes in the European Union, silkworm pupae are vastly and cheaply available by-products from sericulture that have been successfully replacing fish meal in aquaculture feed. In order to enable silkworm detection by official control, we firstly identified potential, easily detectable peptide targets from dried silkworm pupae subjected to a standard mass spectrometry (MS)-based bottom-up proteomic workflow. Secondly, a targeted method with an optional immunoaffinity enrichment (IAE) step was developed. Method validation provided a highly reproducible limit of detection of 0.05% (w/w) silkworm pupae in various feeds (aquaculture, poultry, pig) that proved independent from the experimenter and whether IAE was included in sample preparation or not. Furthermore, the method’s specificity and robustness were assessed. © 2023 Wageningen Academic Publishers
A novel antibody-based enrichment and mass spectrometry approach for the detection of species-specific blood peptides in feed matrices
No full textBlood is an important animal by-product and an attractive source for animal feed production. However, the outspread of bovine spongiform encephalopathy led to strict regulations on the usage of animal by-products in animal feed. Although, the ban on certain processed animal proteins has been partially abolished in recent years, it is still challenging to distinguish legal from illegal protein additives in complex feed products using analytical methods. To overcome these gaps, this study aimed to develop a tissue-specific and sensitive immuno-based enrichment and mass spectrometry-based detection method to identify haemoglobin peptides of ruminant or porcine origin when mixed in a background of vegetal feed, fish meal, aquaculture feed, blood compounds, or milk powder. Here we report the first analytical method able to species-specifically detect adulterations of as little as 0.05%–1% (w/w) ruminant blood meal in various matrices on a quadrupole-time of flight instrument
Four-wave-mixing response of spin-orbit split-off excitons in InP: Isolation of many-body effects through interference
No full textExperimenting with open innovation in science (ois) practices: a novel approach to co-developing research proposals
No full textCo-producing scientific research with those who are affected by it is an emerging phenomenon in contemporary science. This article summarizes and reflects on both the process and outcome of a novel experiment to co-develop scientific research proposals in the field of Open Innovation in Science (OIS), wherein scholars engaged in the study of open and collaborative practices collaborated with the “users” of their research, i.e., scientists who apply such practices in their own research. The resulting co-developed research proposals focus on scientific collaboration, open data, and knowledge sharing and are available as an appendix to this article.Keywords: Open Innovation in Science (OIS); co-production of scientific research; co-development of research proposal
The Social Capital of Venture Capitalists and Its Impact on the Funding of Start-Up Firms
No full textHow does the social capital of venture capitalists (VCs) affect the funding of start-ups? Extant entrepreneurship literature conceptualizes a substitute effect between the social and financial capital that new firms attain from their investors. On the contrary, by building on the rich social capital literature, we hypothesize a positive effect of VCs’ social capital, derived from past syndication, on the amount of money that start-ups receive. Specifically, we argue that both structural aspects of VCs’ social network, such as the number of connections and the spanning of structural holes, and relational aspects, such as the diversity of network partners’ attributes, provide VCs with superior access to information about current investment objects and opportunities to leverage them in the future, increasing their willingness to invest in these firms. Our empirical results, derived from a novel dataset containing more than 5,000 funding rounds in the Internet and IT sector, strongly confirm our hypotheses. Both structural and relational attributes of VCs’ syndication networks have a significant influence on the funds received by start-up firms, highlighting the importance of a social capital perspective on new venture funding. We discuss the implications of our findings for theories of venture capital and entrepreneurship, showing that the role and effect of VCs’ social capital on start-up firms is much more complex than previously argued in the literature.social networks;social capital;start-ups;venture capital;structural holes
Mass Spectrometry-Based Immunoassay for the Quantification of Banned Ruminant Processed Animal Proteins in Vegetal Feeds
No full textThe
ban of processed animal proteins (PAPs) in feed for farmed
animals introduced in 2001 was one of the main EU measures to control
the bovine spongiform encephalopathy (BSE) crisis. Currently, microscopy
and polymerase chain reaction (PCR) are the official methods for the
detection of illegal PAPs in feed. However, the progressive release
of the feed ban, recently with the legalization of nonruminant PAPs
for the use in aquaculture, requires the development of alternative
methods to determine the species origin and the source (legal or not).
Additionally, discussions about the need for quantitative tests came
up, particularly if the zero-tolerance-concept is replaced by introducing
PAP thresholds. To address this issue, we developed and partially
validated a multiplex mass spectrometry-based immunoassay to quantify
ruminant specific peptides in vegetal cattle feed. The workflow comprises
a new sample preparation procedure based on a tryptic digestion of
PAPs in suspension, a subsequent immunoaffinity enrichment of the
released peptides, and a LC-MS/MS-based analysis for peptide quantification
using isotope labeled standard peptides. For the very first time,
a mass spectrometry-based method is capable of detecting and quantifying
illegal PAPs in animal feed over a concentration range of 4 orders
of magnitude with a detection limit in the range of 0.1% to 1% (w/w)
Application of Mass Spectrometry-Based Immunoassays for the Species- and Tissue-Specific Quantification of Banned Processed Animal Proteins in Feeds
No full textProcessed
Animal Proteins (PAPs) are considered as a sustainable
protein source to improve the nutritional profile of feed for livestock
and aquaculture. However, the use of these proteins is strongly regulated
since the bovine spongiform encephalopathy (BSE) crisis. The reintroduction
of nonruminant PAPs for use in aquaculture in 2013 has driven the
need for alternative analytical methods to determine the species origin
as well as the tissue source (legal or not). The current official
methods, light microscopy and polymerase chain reaction, do not fulfill
these requirements. Furthermore, future methods need to be quantitative,
because the pending zero-tolerance-concept is planned to be replaced
by accurate thresholds. Here, we developed a 7-plex mass spectrometry-based
immunoassay that is capable of quantifying 0.1% (w/w) ruminant PAP
in feed in a tissue- and species-specific way. The workflow comprises
a 2 h tryptic digestion of PAPs in suspension, an immunoaffinity enrichment of peptides, and LC–MS/MS-based
quantification. In combination with a previously published assay for
species identification, we were able to confirm the species and tissue
origin of six ring trial samples obtained in former PCR
and microscopy proficiency tests. The sensitive, quantitative, species-
and tissue-specific character of the developed assays meets the requirements
for new methods for PAP detection and can be used in future feed authentication
studies
