Search results for "POTENT"

Earth resistance measurements in urban contexts: Problems and possible solutions

2017

Both EN 50522 and IEEE Std. 81 propose the Fall of Potential Method (FPM) to carry out the measurement of the resistance to earth of an Earthing System (ES). However, in urban areas, the recommended distances between the ES and auxiliary electrodes are not easy to respect, due to the presence of buildings and tarmac. Moreover, unknown buried metallic parts, as well as the interconnection among the ESs made by the Distributor System Operator, could modify the earth potential profile of the area, affecting the measurement results. In this paper, the issues that could affect the measurement result if FPM is used in an urban context are presented. A parametric analysis, carried out with Comsol …

Sapropeļa kūdras, sapropeļa kokskaidu siltumizolācijas plāksnes un to īpašības

2014

Siltumizolācijas materiāli, kuros par pildvielu tiktu izmantoti vietējie biomasas produkti, bet par saistvielu kalpotu dabiskas izcelsmes saistvielas, piemēram, sapropelis, uzskatāmi par inovatīviem un to pielietošana sekmētu ekoloģiskās būvniecības nozares attīstību. Šādu risinājumu izstrāde ir aktuāla, jo Latvijā ir ievērojami sapropeļa resursi, kuru izmantošanu kavē to nepietiekama izpēte un ekoloģiskās būvniecības nozares intensīva attīstība. Pētījuma mērķis ir iegūt sapropeļa-koksnes, kūdras-koksnes siltumizolācijas plāksnes, noteikt optimālās plātnes sastāva attiecības un raksturot iegūto plātņu īpašības. Veikto pētījumu rezultātā tika noteiktas siltumizolācijas materiālu paraugu mehā…

Marine food web perspective to fisheries‐induced evolution

2021

Abstract Fisheries exploitation can cause genetic changes in heritable traits of targeted stocks. The direction of selective pressure forced by harvest acts typically in reverse to natural selection and selects for explicit life histories, usually for younger and smaller spawners with deprived spawning potential. While the consequences that such selection might have on the population dynamics of a single species are well emphasized, we are just beginning to perceive the variety and severity of its propagating effects within the entire marine food webs and ecosystems. Here, we highlight the potential pathways in which fisheries‐induced evolution, driven by size‐selective fishing, might reson…

Discrete cortical representations and their stability in the presence of synaptic turnover

2015

Population imaging in mouse auditory cortex revealed clustering of neural responses to brief complex sounds: the activity of a local population typically falls close to one out of a small number of observed states [1]. These clusters appear to group sets of auditory stimuli into a discrete set of activity patterns and could thereby form the basis for representations of sound categories. However, to be useful for the brain, such representations should be robust against fluctuations in the underlying circuitry, which are significant even in the absences of any explicit learning paradigm [2]. Here we introduce a novel firing rate based circuit model of mouse auditory cortex to study the emerge…

Conformational equilibrium of chorismate. A QM/MM theoretical study combining statistical simulations and geometry optimisations in gas phase and in …

2003

We report a theoretical study on the conformational equilibrium of chorismate that precedes its rearrangement to prephenate, an important enzyme-catalyzed reaction. In first place we show that the usual classification of chorismate conformers based on the relative position of the hydroxyl and ether bridge, pseudo-diaxial and pseudo-diequatorial, is not the only relevant factor from the point of view of the a posteriori rearrangement. Here we also analyse another complementary geometrical classification based on the interatomic distance between the carbon atoms to be bounded. Using the umbrella sampling approach and this distance as distinguished internal reaction coordinate, the gas phase A…

Adenine and 2-aminopurine: Paradigms of modern theoretical photochemistry

2006

Distinct photophysical behavior of nucleobase adenine and its constitutional isomer, 2-aminopurine, has been studied by using quantum chemical methods, in particular an accurate ab initio multiconfigurational second-order perturbation theory. After light irradiation, the efficient, ultrafast energy dissipation observed for nonfluorescent 9H-adenine is explained here by the nonradiative internal conversion process taking place along a barrierless reaction path from the initially populated 1 (ππ* L a ) excited state toward a low-lying conical intersection (CI) connected with the ground state. In contrast, the strong fluorescence recorded for 2-aminopurine at 4.0 eV with large decay lifetime …

2015

Primary neuronal cultures share many typical features with the in vivo situation, including similarities in distinct electrical activity patterns and synaptic network interactions. Here, we use multi-electrode array (MEA) recordings from spontaneously active cultures of wildtype and GAD67-GFP transgenic mice to evaluate which spike parameters differ between GABAergic interneurons and principal, putatively glutamatergic neurons. To analyze this question we combine MEA recordings with optical imaging in sparse cortical cultures to assign individual spikes to visually-identified single neurons. In our culture system, excitatory and inhibitory neurons are present at a similar ratio as described…

A theoretical study of the intramolecular charge transfer in 4-(dimethylamino)benzethyne

2014

We have investigated the non-adiabatic relaxation processes occurring in the singlet manifold of 4-(dimethylamino)benzethyne (DMABE){,} a molecule isoelectronic with 4-(dimethylamino)benzonitrile (DMABN) but lacking its characteristic dual fluorescence{,} using multireference perturbation theory methods. The results obtained point out to the existence of a two-fold decay mechanism in which the population of the initially accessed La state bifurcates towards a locally excited (LE) and a [small pi][sigma]* state. Further relaxation to an emitting intramolecular charge transfer (ICT) state is impeded due to the presence of pronounced energy barriers along their associated potential energy surf…

Chapter 21 Immunohistochemical evidence for a co-transmitter role of opioid peptides in primary sensory neurons

1988

Publisher Summary The purpose of this chapter is to answer several open questions regarding opioid peptides by using a highly sensitive light microscopic (LM) immunohistochemical approach. The chapter mentions the immunohistochemical evidence for a co-transmitter role of opioid peptides in primary sensory neurons. It introduces the concept that there is a functionally important tandem constellation of transmitters in a specific nociceptive population of primary sensory afferents consisting of (1) an inhibitory transmitter family, the opioid peptides, and (2) an excitatory transmitter family, the tachykinins. Small-diameter primary sensory neurons not only transmit nociceptive messages to ce…

150 years of rowing faster: what are the sources of more and more speed?

2015

Rowing has a 150 yr+ competitive history. Examining results from historic races like Oxford-Cambridge (established 1829) and the world championships (established 1893) reveals a linear increase in boat speed by 2-3% per decade. Boat velocity increases if propulsive power is increased and/or power losses are reduced. Over time, the propulsive power capacity of elite rowers has increased. Part of this increase is a result of recruiting athletes from a population that has become taller (1-3 cm per decade) and heavier. Modern world class rowers are typically 190-200 cm tall and weigh 90-100 kg. However, physical capacity does not scale directly with body dimensions but conforms instead to biolo…