102 research outputs found
Noise removal at the rod synapse of mammalian retina
No full textMammalian rods respond to single photons with a hyperpolarization of about 1 mV which is accompanied by continuous noise. Since the mammalian rod bipolar cell collects signals from 20–100 rods, the noise from the converging rods would overwhelm the single-photon signal from one rod at scotopic intensities (starlight) if the bipolar cell summed signals linearly (Baylor et al., 1984). However, it is known that at scotopic intensities the retina preserves single-photon responses (Barlow et al., 1971; Mastronarde, 1983). To explore noise summation in the rod bipolar pathway, we simulated an array of rods synaptically connected to a rod bipolar cell using a compartmental model. The performance of the circuit was evaluated with a discriminator measuring errors in photon detection as false positives and false negatives, which were compared to physiologically and psychophysically measured error rates. When only one rod was connected to the rod bipolar, a Poisson rate of 80 vesicles0s was necessary for reliable transmission of the single-photon signal. When 25 rods converged through a linear synapse the noise caused an unacceptably high false positive rate, even when either dark continuous noise or synaptic noise where completely removed. We propose that a threshold nonlinearity is provided by the mGluR6 receptor in the rod bipolar dendrite (Shiells & Falk, 1994) to yield a synapse with a noise removing mechanism. With the threshold nonlinearity the synapse removed most of the noise. These results suggest that a threshold provided by the mGluR6 receptor in the rod bipolar cell is necessary for proper functioning of the retina at scotopic intensities and that the metabotropic domains in the rod bipolar are distinct. Such a nonlinear threshold could also reduce synaptic noise for cortical circuits in which sparse signals converge. <br/
Will novel protein foods beat meat? : consumer acceptance of meat substitutes - a multidisciplinary research approach
No full textMeat production places a heavy burden on the environment and therefore options are sought to reduce meat consumption. One option is to let new meat substitutes take the place of meat on the plate. This can only succeed when these products are acceptable to consumers. The thesis investigated which factors are involved in consumer acceptance of meat substitutes to reduce the consumption of meat. Looking back in time, it becomes apparent that in development and acceptance of food substitutes, like margarine and sugar substitutes, different factors played a role. Technology advances and governmental policy measures could create favourable preconditions but the degree of replacement ultimately depended on consumer acceptance. This required a product quality comparable to the original products and a fit with consumer needs. The process of substitution generally takes many years, both from consumer acceptance and from product development point of view. First of all, consumers need to have a reason to choose for meat substitutes instead of meat. Therefore, drivers and barriers to use meat substitutes were identified by two surveys. Opposed to the ethical motives of heavy-users of meat substitutes (mainly vegetarians), non-users and light/medium-users were primarily focussed on the sensory and familiarity aspects of foods. These aspects were not at all recognized in meat substitutes by these consumers. Meat was judged more positively overall, which explains the choice for meat. In addition, food neophobia (the tendency to avoid new foods) was a large barrier for initial trial and a meat-like meat substitute was preferred to begin with. Secondly, the identification of a product as an alternative to meat is important. A categorization study showed that consumer perceptions are largely influenced by a deep-rooted taxonomic classification of meat (e.g. beef, pork). In order to be considered as an alternative to meat, a certain degree of similarity is needed. Meat substitutes were grouped together with processed meats (like sausages) due to a similar appearance and similar application in meals, but not with unprocessed meats. New concepts that were radically different from meat in appearance were not at all recognized as alternatives. In the third place, meat substitutes need to result in a comparable product experience as meat, such as satiety feelings after eating. The protein content is an important factor in satiety. A product inventory indicated that the majority of meat substitutes has a lower protein content than meat. In a consumption study it was shown that meat substitutes high in protein were able to induce stronger feelings of satiety, even more than the meat reference products. However, meat substitutes with a low protein content were less satiating. Finally, it should be possible to eat meat substitutes regularly without getting bored. A repeated consumption test was performed with two meat substitutes and a meat reference. It was found that initially the meat reference was liked most but after 20 exposures the difference in liking disappeared. Both boredom and increased liking of products were observed. Strikingly, there were more persons with an increased liking for the meat substitute dissimilar to meat (tofu). This is in line with the mere exposure effect implicating that unfamiliar products are liked better over time. In conclusion, meat is obviously anchored in our culinary culture and it will take time to change this. The use of substitutes introduces specific challenges due to a direct comparison and competition with meat. Meat substitutes need to offer additional benefits, which is not yet the case for the majority of consumers. At present, it seems too early for radically new protein products, since a certain level of similarity to meat is essential. Improvement of the sensory appeal of meat substitutes needs to be continued and it is worthwhile to explore other options further, like combined plant/ meat protein products. Meat production places a heavy burden on the environment and therefore options are sought to reduce meat consumption. One option is to let new meat substitutes take the place of meat on the plate. This can only succeed when these products are acceptable to consumers. The thesis investigated which factors are involved in consumer acceptance of meat substitutes to reduce the consumption of meat. Looking back in time, it becomes apparent that in development and acceptance of food substitutes, like margarine and sugar substitutes, different factors played a role. Technology advances and governmental policy measures could create favourable preconditions but the degree of replacement ultimately depended on consumer acceptance. This required a product quality comparable to the original products and a fit with consumer needs. The process of substitution generally takes many years, both from consumer acceptance and from product development point of view. First of all, consumers need to have a reason to choose for meat substitutes instead of meat. Therefore, drivers and barriers to use meat substitutes were identified by two surveys. Opposed to the ethical motives of heavy-users of meat substitutes (mainly vegetarians), non-users and light/medium-users were primarily focussed on the sensory and familiarity aspects of foods. These aspects were not at all recognized in meat substitutes by these consumers. Meat was judged more positively overall, which explains the choice for meat. In addition, food neophobia (the tendency to avoid new foods) was a large barrier for initial trial and a meat-like meat substitute was preferred to begin with. Secondly, the identification of a product as an alternative to meat is important. A categorization study showed that consumer perceptions are largely influenced by a deep-rooted taxonomic classification of meat (e.g. beef, pork). In order to be considered as an alternative to meat, a certain degree of similarity is needed. Meat substitutes were grouped together with processed meats (like sausages) due to a similar appearance and similar application in meals, but not with unprocessed meats. New concepts that were radically different from meat in appearance were not at all recognized as alternatives. In the third place, meat substitutes need to result in a comparable product experience as meat, such as satiety feelings after eating. The protein content is an important factor in satiety. A product inventory indicated that the majority of meat substitutes has a lower protein content than meat. In a consumption study it was shown that meat substitutes high in protein were able to induce stronger feelings of satiety, even more than the meat reference products. However, meat substitutes with a low protein content were less satiating. Finally, it should be possible to eat meat substitutes regularly without getting bored. A repeated consumption test was performed with two meat substitutes and a meat reference. It was found that initially the meat reference was liked most but after 20 exposures the difference in liking disappeared. Both boredom and increased liking of products were observed. Strikingly, there were more persons with an increased liking for the meat substitute dissimilar to meat (tofu). This is in line with the mere exposure effect implicating that unfamiliar products are liked better over time. In conclusion, meat is obviously anchored in our culinary culture and it will take time to change this. The use of substitutes introduces specific challenges due to a direct comparison and competition with meat. Meat substitutes need to offer additional benefits, which is not yet the case for the majority of consumers. At present, it seems too early for radically new protein products, since a certain level of similarity to meat is essential. Improvement of the sensory appeal of meat substitutes needs to be continued and it is worthwhile to explore other options further, like combined plant/ meat protein products. <br/
Past Unemployment Experience and Health Status
No full textThis paper explores the relationship between individual past unemployment experience and alternative measures of individual health state after controlling for a number of current characteristics and current socio-economic status. Three alternative indicators of past unemployment status are used namely; the number and the duration of past unemployment spells. The study finds a cumulative effect of prolonged past unemployment experience on current individual health status. It also finds that those who are wealthier are also healthier. Finally the different institutional and cultural frameworks prevailing across different E.U countries appear to affect the health - past unemployment experience relationship.European Commission, Fifth Framework Programme “Quality of Life and
Management of Living Resources” (contract number: QLRT-2001-02292)
The health hazards of unemployment and poor education: the socioeconomic determinants of health duration in the European Union
No full textThe effect of socioeconomic status on the likelihood that an individual enters a period of poor health is examined using an Accelerated Failure Time methodology. This study employs data from the European Community Household Panel for the years 1994-2002 across 13 European countries, using the Physical and Mental Health Problems, Illnesses and Disabilities measure of physical health. Some socioeconomic status indicators do impact on the length of time an individual remains in good health – these being unemployment, which has a negative effect, and education, which has a positive effect – but others, such as income, have far less of an impact. Age and gender effects are also found.European Commission, Fifth Framework
Programme “Quality of Life and Management of Living Resources” (contract number:
QLRT-2001-02292)
Impact of ejecta morphology and composition on the electromagnetic signatures of neutron star mergers
No full textContains fulltext :
195454.pdf (Publisher’s version ) (Open Access
Two-step numerical procedure for complex permittivity retrieval of dielectric materials from reflection measurements
No full textA two-step measurement procedure has been proposed for measurement of complex permittivity of dielectric materials using one-port reflection measurements.
In the procedure, as a first step, a graphical method is applied to analyze on the complex reflection-coefficient plane the general pattern of dielectric behavior of the sample. Then, as a second step, optimization algorithms are utilized for retrieving electrical properties of samples. The procedure requires measurement of complex reflectionscattering parameters of at least two samples with different lengths. It has been validated by X-band measurements of three polyvinyl chloride samples with lengths 5, 10, and 20mm.Hasar, UC.; Barroso, JJ.; Kaya, Y.; Ertugrul, M.; Bute, M.; Catalá Civera, JM. (2014). Two-step numerical procedure for complex permittivity retrieval of dielectric materials from reflection measurements. Applied Physics A. 116(4):1701-1710. doi:10.1007/s00339-014-8303-9S170117101164U. Kaatze, Metrologia 47, S91 (2010)J.M. Catalá-Civera, F. Peñaranda-Foix, D. Sánchez-Hernández, E. de los Reyes, Microwave. Opt. Technol. Lett. 25, 191 (2000)A.E. Engin, IEEE Trans. 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Origin and pathogenesis of nodular lymphocyte–predominant Hodgkin lymphoma as revealed by global gene expression analysis
No full textThe pathogenesis of nodular lymphocyte–predominant Hodgkin lymphoma (NLPHL) and its relationship to other lymphomas are largely unknown. This is partly because of the technical challenge of analyzing its rare neoplastic lymphocytic and histiocytic (L&H) cells, which are dispersed in an abundant nonneoplastic cellular microenvironment. We performed a genome-wide expression study of microdissected L&H lymphoma cells in comparison to normal and other malignant B cells that indicated a relationship of L&H cells to and/or that they originate from germinal center B cells at the transition to memory B cells. L&H cells show a surprisingly high similarity to the tumor cells of T cell–rich B cell lymphoma and classical Hodgkin lymphoma, a partial loss of their B cell phenotype, and deregulation of many apoptosis regulators and putative oncogenes. Importantly, L&H cells are characterized by constitutive nuclear factor {kappa}B activity and aberrant extracellular signal-regulated kinase signaling. Thus, these findings shed new light on the nature of L&H cells, reveal several novel pathogenetic mechanisms in NLPHL, and may help in differential diagnosis and lead to novel therapeutic strategies
First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole
No full textContains fulltext :
202543.pdf (Publisher’s version ) (Open Access
First M87 Event Horizon Telescope Results. V. Physical Origin of the Asymmetric Ring
No full textContains fulltext :
202544.pdf (Publisher’s version ) (Open Access
3C 279 Event Horizon Telescope imaging
No full textWe release a data set to accompany the "First 3C279 Event Horizon Telescope Results" paper (Kim et al. 2020). The data set is derived from the Science Release 1 (SR1) of the Event Horizon Telescope (EHT)'s April 2017 observation campaign (EHTC et al. 2019ApJ...875L...3E). This data set contains 3C279 data for both low and high bands for all observed days (April 5th, 6th, 10th, 11th, 2017). Data from the 2017 observations were processed through three independent reduction pipelines (Blackburn et al., 2019ApJ...882...23B, Janssen et al., 2019A&A...626A..75J, EHTC et al. 2019ApJ...875L...3E). This release includes the fringe fitted, a-priori calibrated, and network calibrated data from the EHT-HOPS pipeline, which is the primary data set for the First 3C279 EHT results. Independent flux calibration is performed based on estimated station sensitivities during the campaign (Issaoun et al., 2017, EHT Memo 2017-CE-02, Janssen et al. 2019A&A...626A..75J,). A description of the data properties, their validation, and estimated systematic errors is given in EHTC et al. (2019ApJ...875L...3E) with additional details in Wielgus et al. (2019, https://eventhorizontelescope.org/for-astronomers/memos). The data are time averaged to 10 seconds and frequency averaged over all 32 intermediate frequencies (IFs). All polarization information is explicitly removed. To make the resulting 'uvfits' files compatible with popular very-long-baseline interferometry (VLBI) software packages, the circularly polarized cross-hand visibilities 'RL' and 'LR' are set to zero along with their errors, while parallel-hands 'RR' and 'LL' are both set to an estimated Stokes I value. Measurement errors for 'RR' and 'LL' are each set to sqrt(2) times the statistical errors for Stokes I. All uvfits files are located in the "uvfits/" subdirectory. Easy- to-read csv and txt files are derived from the uvfits files and provided in "csv" and "txt", respectively. Scripts that generate these files from the original SR1 data are also included. Finally, the run.sh script in the top directory will convert uvfits files into csv and txt files. The three tgz files are gzipped tarballs that contains uvfits, txt, and csv files, respectively. They are included in this repository for convenience
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