Gyrotropic Zener tunneling and nonlinear IV curves in the zero-energy Landau level of graphene in a strong magnetic field

We have investigated tunneling current through a suspended graphene Corbino disk in high magnetic fields at the Dirac point, i.e. at filling factor $\nu$ = 0. At the onset of the dielectric breakdown the current through the disk grows exponentially before ohmic behaviour, but in a manner distinct from thermal activation. We find that Zener tunneling between Landau sublevels dominates, facilitated by tilting of the source-drain bias potential. According to our analytic modelling, the Zener tunneling is strongly affected by the gyrotropic force (Lorentz force) due to the high magnetic fieldComment: 7 pages, 4 figure

Utilization of drones in vertical profile measurements of the atmosphere

Numerical weather predicition and climate models require accurate and continuous measurements of the atmosphere. Radiosoundings conducted daily all over the world provide the backbone for these measurements thanks to their accuracy and high spatial resolution. However they are expensive and thus are limited to only a few profile measurements per day. Especially within boundary layer this is not enough and to fill this gap a new type of drone-based measurement system has been developed. The recent emergence of drones has brought new opportunities in atmospheric research and in this study their utilization in meteorological profiling is investigated. The measurement system consists of an octocopter with a Vaisala RD41 dropsonde attached underneath for temperature and humidity measurements. This drone is accompanied by a custom-build ground station that allows autonomous operation. With the drone measurements up to 450m were possible. To investigate the capabilities of drone-borne setups for vertical profiling, the temperature and humidity measurements were compared between ascending and descending legs of the flight as well as collocated radiosonde measurements. Statistical analysis on the differences between the measured profiles was conducted and individual case studies were performed for better understanding of the effects caused by the drone and the different atmospheric conditions. The results indicate a warm bias in the drone measurements when compared against radiosonde measurements, and this bias is higher during the ascend leg. Ascend leg shows a bias of 0.4 !C when compared against the radiosonde measurements and the descend leg shows a bias of 0.2 !C. The ascend leg shows a bias of 0.3 !C when compared against the descend leg. The relative humidity measurements with the drone show a dry bias when compared against radiosonde measurements. The ascending leg has a bias of −1.9% and the descending leg −0.3 %. The difference between ascend and descend legs is −1.4 %. Thus the descending leg agrees better with the radiosonde measurements, but also the ascending leg generally agrees with the radiosonde measurements within half a degree in temperature and two percentage relative humidity

Problems in dynamic input validation

Tiedon eheys ja virheettömyys ovat tärkeitä seikkoja lähes jokaisessa tietojärjestelmässä. Erityisesti näiden seikkojen tärkeys korostuu tuotannonohjausjärjestelmissä ja muissa liiketoiminnalle kriittisissä ohjelmistoissa, joissa talletettua tietoa käytetään esim. asiakastietojen hallintaan, toiminnan seurantaan tai laskutukseen. Tietojen eheys voidaan varmistaa tarkistamalla tieto palvelimella ennen sen tallentamista tietokantaan. Usein kuitenkin on vaatimuksena, että virheiden pitää näkyä jo tietoa muokattaessa, jolloin käyttäjä voi reagoida virheisiin heti (dynaaminen tarkistus). Jos tarkistettavat tiedot ja niihin liittyvät liiketoimintasäännöt ovat lisäksi monimutkaisia, päädytään herkästi hankaluuksiin esimerkiksi suorituskyvyn ja tarkistuskoodin kahdentumisen suhteen. Diplomityössä toteutetaan yleiskäyttöinen ja dynaaminen syötteentarkistusjärjestelmä osana laajempaa web-pohjaista järjestelmää. Järjestelmän dynaamiseen syötteentarkistukseen liittyviin haasteisiin vastataan ja niihin esitetään ratkaisu. Työssä käydään läpi toteutukselle asetettuja reunaehtoja, käydään seikkaperäisesti läpi vaatimukset täyttävä syötteentarkistimen toteutus sekä arvioidaan ratkaisun onnistumista esimerkiksi yleiskäyttöisyyden, ylläpidettävyyden ja suorituskyvyn suhteen. Työssä sivutaan nopeasti myös tietojen siirtoa uutta järjestelmää edeltäneestä sovelluksesta ja näiden tietojen tarkistamista uuden järjestelmän liiketoimintasäännöillä, jolloin voidaan käyttää samaa tarkistuslogiikkaa sekä uuteen että vanhaan tietoon. Työssä esiteltyä ratkaisua voidaan pitää onnistuneena kohdejärjestelmän tarpeisiin, kunhan suorituskykyyn liittyviin ongelmiin kiinnitetään tulevaisuudessa huomiota. Suorituskykyongelmat eivät kuitenkaan suoraan johdu suoraan syötteentarkistusjärjestelmän arkkitehtuurista, eivätkä ne tavanomaisissa tilanteissa ole kovin vakavia. Samanlaista teknistä ratkaisua voidaankin hyvin käyttää hyödyksi myös muunlaisissa web-järjestelmissä

Assessment of mutation probabilities of KRAS G12 missense mutants and their long-timescale dynamics by atomistic molecular simulations and Markov state modeling

A mutated KRAS protein is frequently observed in human cancers. Traditionally, the oncogenic properties of KRAS missense mutants at position 12 (G12X) have been considered as equal. Here, by assessing the probabilities of occurrence of all KRAS G12X mutations and KRAS dynamics we show that this assumption does not hold true. Instead, our findings revealed an outstanding mutational bias. We conducted a thorough mutational analysis of KRAS G12X mutations and assessed to what extent the observed mutation frequencies follow a random distribution. Unique tissue-specific frequencies are displayed with specific mutations, especially with G12R, which cannot be explained by random probabilities. To clarify the underlying causes for the nonrandom probabilities, we conducted extensive atomistic molecular dynamics simulations (170 its) to study the differences of G12X mutations on a molecular level. The simulations revealed an allosteric hydrophobic signaling network in KRAS, and that protein dynamics is altered among the G12X mutants and as such differs from the wild-type and is mutation-specific. The shift in long-timescale conformational dynamics was confirmed with Markov state modeling. A G12X mutation was found to modify KRAS dynamics in an allosteric way, which is especially manifested in the switch regions that are responsible for the effector protein binding. The findings provide a basis to understand better the oncogenic properties of KRAS G12X mutants and the consequences of the observed nonrandom frequencies of specific G12X mutations.Peer reviewe

Docking-Based 3D-QSAR Studies for 1,3,4-oxadiazol-2-one Derivatives as FAAH Inhibitors

This work aimed to construct 3D-QSAR CoMFA and CoMSIA models for a series of 31 FAAH inhibitors, containing the 1,3,4-oxadiazol-2-one moiety. The obtained models were characterized by good statistical parameters: CoMFA Q2 = 0.61, R2 = 0.98; CoMSIA Q2 = 0.64, R2 = 0.93. The CoMFA model field contributions were 54.1% and 45.9% for steric and electrostatic fields, respectively. In the CoMSIA model, electrostatic, steric, hydrogen bond donor, and hydrogen acceptor properties were equal to 34.6%, 23.9%, 23.4%, and 18.0%, respectively. These models were validated by applying the leave-one-out technique, the seven-element test set (CoMFA r2test-set = 0.91; CoMSIA r2test-set = 0.91), a progressive scrambling test, and external validation criteria developed by Golbraikh and Tropsha (CoMFA r20 = 0.98, k = 0.95; CoMSIA r20 = 0.98, k = 0.89). As the statistical significance of the obtained model was confirmed, the results of the CoMFA and CoMSIA field calculation were mapped onto the enzyme binding site. It gave us the opportunity to discuss the structure–activity relationship based on the ligand–enzyme interactions. In particular, examination of the electrostatic properties of the established CoMFA model revealed fields that correspond to the regions where electropositive substituents are not desired, e.g., in the neighborhood of the 1,3,4-oxadiazol-2-one moiety. This highlights the importance of heterocycle, a highly electronegative moiety in this area of each ligand. Examination of hydrogen bond donor and acceptor properties contour maps revealed several spots where the implementation of another hydrogen-bond-donating moiety will positively impact molecules’ binding affinity, e.g., in the neighborhood of the 1,3,4-oxadiazol-2-one ring. On the other hand, there is a large isopleth that refers to the favorable H-bond properties close to the terminal phenoxy group of a ligand, which means that, generally speaking, H-bond acceptors are desired in this area

Coupling between electrons and optical phonons in suspended bilayer graphene

Using electrical transport experiments and shot noise thermometry, we investigate electron-phonon heat transfer rate in a suspended bilayer graphene. Contrary to monolayer graphene with heat flow via three-body supercollision scattering, we find that regular electron–optical-phonon scattering in bilayer graphene provides the dominant scattering process at electron energies ≳0.15 eV. We determine the strength of these intrinsic heat flow processes of bilayer graphene and find good agreement with theoretical estimates when both zone edge and zone center optical phonons are taken into account.Peer reviewe

Lonkkamurtumien leikkausmenetelmien komplikaatiot alkoholin väärinkäyttäjillä

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