Clamping, COKAM, KADS, and OMOS : the construction and operationalization of a KADS conceptual model

For a simplified version of the clamping tool selection problem in mechanical engineering, the knowledge acquisition tool COKAM is applied to obtain an informal knowledge base and explanation structures from technical documents and previously solved cases. The output of COKAM is used to construct a three layered KADS conceptual model, which is then transformed into an operational model in the language OMOS. The OMOS formalization allows to verify the informal KADS conceptual model and to check the completeness of the domain knowledge. The results of this analysis are utilized in the next knowledge elicitation session with COKAM

Modelling of density dependent groundwater flow in the south-western Belgian coastal plain

The study area is situated at the landward border of the Belgian western coastal plain at the right bank of the river Ijzer. The phreatic aquifer is of quaternary age. Until about the 12th century, the hydrology of the area was influenced by the North Sea. The area was criss-crossed by tidal channels and gullies and the aquifer was mainly filled with salt water. From about 1100 AD, the area was gradually reclaimed, halting the influence of the sea. The channels silted up. Fresh water started to infiltrate replacing the salt water. This leads to the actual distribution of fresh and salt water. Fresh water lenses are found below the creek ridges, the former tidal channels where the aquifer consists mainly of sandy sediments. In the adjacent area the phreatic aquifer consists of less permeable sediments (clay, silt and peat) and is still mainly filled with salt water. In these areas where the water table is slightly lower than in the creek ridges, only a thin lens of fresh water occurs above the salt water. A preliminary field survey was performed to compliment the existing data. In these field survey a number of drillings were executed and observation wells were installed. The variation of the salt content with depth was inferred from electrical conductivities measured with the focused electromagnetic induction method. A pumping test was performed to derive the hydraulic conductivity of the channel sediments. All these data were integrated in a 3D density dependent model, using the MOCDENS3D code to simulate the evolution of the water quality distribution from 1100 AD until a few centuries in the future. The simulations demonstrate that the fresh water lenses under the channels are formed in about 400 years. These fresh water lenses can only be considered as a limited water resource in this area. The influence of this drainage on the groundwater flow and water quality distribution is illustrated by the model. The mean drainage level is below mean sea level. In the creek ridges there is an important upward flow of fresh water under the drainage canals. In the adjacent areas with low permeable sediments the drainage and flow is very small. The salt water in these sediments is trapped since the land reclamation in the 12th century and will stay there for many centuries

Internal Cholinergic Regulation of Learning and Recall in a Model of Olfactory Processing

In the olfactory system, cholinergic modulation has been associated with contrast modulation and changes in receptive fields in the olfactory bulb, as well the learning of odor associations in olfactory cortex. Computational modeling and behavioral studies suggest that cholinergic modulation could improve sensory processing and learning while preventing pro-active interference when task demands are high. However, how sensory inputs and/or learning regulate incoming modulation has not yet been elucidated. We here use a computational model of the olfactory bulb, piriform cortex (PC) and horizontal limb of the diagonal band of Broca (HDB) to explore how olfactory learning could regulate cholinergic inputs to the system in a closed feedback loop. In our model, the novelty of an odor is reflected in firing rates and sparseness of cortical neurons in response to that odor and these firing rates can directly regulate learning in the system by modifying cholinergic inputs to the system. In the model, cholinergic neurons reduce their firing in response to familiar odors—reducing plasticity in the PC, but increase their firing in response to novel odor—increasing PC plasticity. Recordings from HDB neurons in awake behaving rats reflect predictions from the model by showing that a subset of neurons decrease their firing as an odor becomes familiar

Data-driven honeybee antennal lobe model suggests how stimulus-onset asynchrony can aid odour segregation

Insects have a remarkable ability to identify and track odour sources in multi-odour backgrounds. Recent behavioural experiments show that this ability relies on detecting millisecond stimulus asynchronies between odourants that originate from different sources. Honeybees, Apis mellifera , are able to distinguish mixtures where both odourants arrive at the same time (synchronous mixtures) from those where odourant onsets are staggered (asynchronous mixtures) down to an onset delay of only 6 ms. In this paper we explore this surprising ability in a model of the insects' primary olfactory brain area, the antennal lobe. We hypothesize that a winner-take-all inhibitory network of local neurons in the antennal lobe has a symmetry-breaking effect, such that the response pattern in projection neurons to an asynchronous mixture is different from the response pattern to the corresponding synchronous mixture for an extended period of time beyond the initial odourant onset where the two mixture conditions actually differ. The prolonged difference between response patterns to synchronous and asynchronous mixtures could facilitate odour segregation in downstream circuits of the olfactory pathway. We present a detailed data-driven model of the bee antennal lobe that reproduces a large data set of experimentally observed physiological odour responses, successfully implements the hypothesised symmetry-breaking mechanism and so demonstrates that this mechanism is consistent with our current knowledge of the olfactory circuits in the bee brain

Competition-based model of pheromone component ratio detection in the moth

For some moth species, especially those closely interrelated and sympatric, recognizing a specific pheromone component concentration ratio is essential for males to successfully locate conspecific females. We propose and determine the properties of a minimalist competition-based feed-forward neuronal model capable of detecting a certain ratio of pheromone components independently of overall concentration. This model represents an elementary recognition unit for the ratio of binary mixtures which we propose is entirely contained in the macroglomerular complex (MGC) of the male moth. A set of such units, along with projection neurons (PNs), can provide the input to higher brain centres. We found that (1) accuracy is mainly achieved by maintaining a certain ratio of connection strengths between olfactory receptor neurons (ORN) and local neurons (LN), much less by properties of the interconnections between the competing LNs proper. An exception to this rule is that it is beneficial if connections between generalist LNs (i.e. excited by either pheromone component) and specialist LNs (i.e. excited by one component only) have the same strength as the reciprocal specialist to generalist connections. (2) successful ratio recognition is achieved using latency-to-first-spike in the LN populations which, in contrast to expectations with a population rate code, leads to a broadening of responses for higher overall concentrations consistent with experimental observations. (3) when longer durations of the competition between LNs were observed it did not lead to higher recognition accuracy

Identifying metabolites by integrating metabolome databases with mass spectrometry cheminformatics.

Novel metabolites distinct from canonical pathways can be identified through the integration of three cheminformatics tools: BinVestigate, which queries the BinBase gas chromatography-mass spectrometry (GC-MS) metabolome database to match unknowns with biological metadata across over 110,000 samples; MS-DIAL 2.0, a software tool for chromatographic deconvolution of high-resolution GC-MS or liquid chromatography-mass spectrometry (LC-MS); and MS-FINDER 2.0, a structure-elucidation program that uses a combination of 14 metabolome databases in addition to an enzyme promiscuity library. We showcase our workflow by annotating N-methyl-uridine monophosphate (UMP), lysomonogalactosyl-monopalmitin, N-methylalanine, and two propofol derivatives

One-way trip: Influenza virus' adaptation to gallinaceous poultry may limit its pandemic potential

We hypothesise that some influenza virus adaptations to poultry may explain why the barrier for human-to-human transmission is not easily overcome once the virus has crossed from wild birds to chickens. Since the cluster of human infections with H5N1 influenza in Hong Kong in 1997, chickens have been recognized as the major source of avian influenza virus infection in humans. Although often severe, these infections have been limited in their subsequent human-to-human transmission, and the feared H5N1 pandemic has not yet occurred. Here we examine virus adaptations selected for during replication in chickens and other gallinaceous poultry. These include altered receptor binding and increased pH of fusion of the haemagglutinin as well as stalk deletions of the neuraminidase protein. This knowledge could aid the delivery of vaccines and increase our ability to prioritize research efforts on those viruses from the diverse array of avian influenza viruses that have greatest human pandemic potential

Phenomenology of Light Particles on Earth and in the Sky

In dieser Arbeit werden drei Aspekte der Phänomenologie leichter Teilchen in Erweiterungen des Standardmodells diskutiert. Zuerst werden neuartige Grenzen an die Wechselwirkungen neuer leichter Teilchen mit Fermionen des Standardmodells aus der Molekülspektroskopie abgeleitet, was starke Schranken an die Kopplungen neuer Skalar-, Vektor- und Axialvektorteilchen mit keV-Massen setzt. Anschließend werden mehrere Neutrino-Observablen mit Hilfe einer einfachen und gut motivierten Klasse von Flavor-Modellen vorhergesagt, wodurch ein schmaler bevorzugter Bereich für die absolute Neutrino-Massenskala resultiert, der mit zukünftigen Experimenten erforscht werden kann. Schließlich werden neue Grenzen an flavor-verletzende Kopplungen von Axionen an leichte Quarks aus der Beobachtung der Supernova SN1987A bestimmt, die den Energieverlust durch leichte Teilchen, die in $\Lambda$-Hyperon-Zerfällen und -Bremsstrahlung produziert werden, beschränkt

Zoonotic and pandemic influenza A viruses: lessons from H5N1 and H2N2

Influenza A viruses can be directly transmitted from animals to humans (zoonotic viruses), cause worldwide outbreaks (pandemic viruses) or infect people annually (seasonal viruses). Influenza A viruses that are transmitted efficiently from one person to another have in common that they can spread via the air. We have studied zoonotic H5N1 and pandemic H2N2 influenza viruses with respect to their evolution over time, their potential to transmit via the air, and the virus properties that are required to be efficiently transmitted via the air. From 1997 onwards, H5N1 influenza viruses have occasionally infected humans resulting in severe illness and several deaths. To investigate if this new zoonotic virus had the capacity to spread via the air, we adapted this virus to ferrets, an animal model often used to study airborne transmission of influenza A viruses. We have shown that as little as five mutations in the genetic material of the virus, changing three virus properties, are sufficient for the virus to transmit via the air. Since influenza A viruses evolve constantly, our immune system cannot protect us from infections with new influenza viruses that might emerge in the future. H2N2 influenza virus has caused a pandemic in 1957 and caused seasonal outbreaks in humans until 1968. We have shown that the pandemic potential of H2H2 influenza viruses circulating in birds is low. Furthermore, we have investigated the genetic diversity of H2N2 influenza viruses over time and have determined the mutations that had an effect on recognition by the immune system