Search results for "PION"

2021

Studies on the function of PRDM9 in model systems and its evolution during vertebrate divergence shed light on the basic molecular mechanisms of hybrid sterility and its evolutionary consequences. However, information regarding PRDM9-homolog, PRDM7, whose origin is placed in the primate evolutionary tree, as well as information about the fast-evolving DNA-binding zinc finger array of strepsirrhine PRDM9 are scarce. Thus, we aimed to narrow down the date of the duplication event leading to the emergence of PRDM7 during primate evolution by comparing the phylogenetic tree reconstructions of representative primate samples of PRDM orthologs and paralogs. To confirm our PRDM7 paralogization patt…

Silver-Catalyzed C-C Bond Formation between Methane and Ethyl Diazoacetate in Supercritical CO2

2011

Even in the context of hydrocarbons’ general resistance to selective functionalization, methane’s volatility and strong bonds pose a particular challenge. We report here that silver complexes bearing perfluorinated indazolylborate ligands catalyze the reaction of methane (CH4) with ethyl diazoacetate (N2CHCO2Et) to yield ethyl propionate (CH3CH2CO2Et). The use of supercritical carbon dioxide (scCO2) as the solvent is key to the reaction’s success. Although the catalyst is only sparingly soluble in CH4/CO2 mixtures, optimized conditions presently result in a 19% yield of ethyl propionate (based on starting quantity of the diazoester) at 40°C over 14 hours.

Reduced presynaptic efficiency of excitatory synaptic transmission impairs LTP in the visual cortex of BDNF-heterozygous mice

2006

The neurotrophin brain-derived neurotrophic factor (BDNF) plays an important role in neuronal survival, axonal and dendritic growth and synapse formation. BDNF has also been reported to mediate visual cortex plasticity. Here we studied the cellular mechanisms of BDNF-mediated changes in synaptic plasticity, excitatory synaptic transmission and long-term potentiation (LTP) in the visual cortex of heterozygous BDNF-knockout mice (BDNF(+/-)). Patch-clamp recordings in slices showed an approximately 50% reduction in the frequency of miniature excitatory postsynaptic currents (mEPSCs) compared to wild-type animals, in the absence of changes in mEPSC amplitudes. A presynaptic impairment of excita…

Dendritic Ih selectively blocks temporal summation of unsynchronized distal inputs in CA1 pyramidal neurons.

2004

The active dendritic conductances shape the input-output properties of many principal neurons in different brain regions, and the various ways in which they regulate neuronal excitability need to be investigated to better understand their functional consequences. Using a realistic model of a hippocampal CA1 pyramidal neuron, we show a major role for the hyperpolarization-activated current, I-h, in regulating the spike probability of a neuron when independent synaptic inputs are activated with different degrees of synchronization and at different distances from the soma. The results allowed us to make the experimentally testable prediction that the I-h in these neurons is needed to reduce ne…

Metallic core nano-devices as drug delivery systems

2014

Graduate of Riga Polytechnic Institute, Engineer and Athlete Mārtiņš Stabiņš

2020

The aim of the article is to reveal the performance of Mārtiņš Stabiņš, a graduate of the Faculty of Automation and Computer Technology (1972; FACT) of Riga Polytechnic Institute (RPI), in the profession of engineer and high achievements in sports, becoming a Latvian champion in athletics several times, to reveal his daily life during his study years in the 1960s–1970s. Despite the fact that M. Stabiņš’ sports achievements have already described, this article summarizes his successes as well as reveals hitherto little-known and unpublished documents about his family, daily life, developments and interests. This is the first major research on the life of an engineer and athlete during seven …

«Per non dar moto alle fabriche»: l'ingegnere regio Scipione Basta e la costruzione della cappella Roano nel duomo di Monreale

2015

«PER NON DAR MOTO ALLE FABBRICHE»: THE ROYAL ENGINEER SCIPIONE BASTA AND THE CONSTRUCTION OF THE ROANO CHAPEL IN THE CATHEDRAL OF MONREALE. In December 1686 the Royal Engineer Scipione Basta, a personality still largely to be investigated but which seems to portend a specific expertise in techno-constructive issues and in particular in structural reinforcement, was appointed by the Viceroyal Government to draw up a technical report concerning some delicate constructive aspects of the project of the architect fra Giovanni da Monreale for the chapel commissioned by the archbishop Roano for the cathedral. Due to the particular configuration of the building to be constructed –a domed octagonal …

Nuclear medium modification of the structure function

2011

Abstract We study the nuclear effects in the electromagnetic structure function F 2 ( x , Q 2 ) in the deep inelastic lepton–nucleus scattering process by taking into account Fermi motion, binding, pion and rho meson cloud contributions. Calculations have been done in a local density approximation using relativistic nuclear spectral functions which include nucleon correlations. The ratios R F 2 A ( x , Q 2 ) = 2 F 2 A ( x , Q 2 ) A F 2 D ( x , Q 2 ) are obtained and compared with recent JLab results for light nuclei with special attention to the slope of the x distributions. This magnitude shows a non-trivial A dependence and it is insensitive to possible normalization uncertainties. The re…

Triton calculations with the new Nijmegen potentials

1993

Triton properties are calculated using new nucleon-nucleon potentials, which were fit to the world nucleon-nucleon data. All potentials are charge dependent and explicitly incorporate the mass difference between the charged and neutral pions. Three of these models have a nearly optimal chi**2 per degree of freedom and can therefore be considered as alternative partial wave analyses, which in quality can almost compete with the Nijmegen partial-wave analysis. The triton binding energy obtained with three local models (Nijm II, Reid93, AV18) can be summarized as 7.62 +_ 0.01 MeV, which is nearly 900 keV lower than experiment. The non-local model Nijm I binds by 7.72 MeV.

Chiral restoration from pionic atoms?

2002

We evaluate widths and shifts of pionic atoms using a theoretical microscopical potential in which the pion decay constant $f_\pi$ is changed by an in--medium density dependent one ($f_\pi(\rho)$), predicted by different partial Chiral restoration calculations. We show that the results obtained for shifts and widths are worse than if this modification were not implemented. On the other hand, we argue that in microscopic many body approaches for the pion selfenergy, based on effective Lagrangians, the mechanisms responsible for the change of $f_\pi$ in the medium should be automatically incorporated. Therefore, the replacement of $f_\pi$ by $f_\pi(\rho)$ in the many body derivation of the mi…