Microcalcification evaluation in computer assisted diagnosis for digital mammography

In order to develop applications for z;isual interpretation of medical images, the early detection and evaluation of microcalcifications in digital mammograms is verg important since their presence is oftenassociated with a high incidence of breast cancers. Accurate classification into benign and malignant groups would help improve diagnostic sensitivity as well as reduce the number of unnecessa y biopsies. The challenge here is the selection of the useful features to distinguish benign from malignant micro calcifications. Our purpose in this work is to analyse a microcalcification evaluation method based on a set of shapebased features extracted from the digitised mammography. The segmentation of the microcalcificationsis performed using a fixed-tolerance region growing method to extract boundaries of calcifications with manually selected seed pixels. Taking into account that shapes and sizes of clustered microcalcificationshave been associated with a high risk of carcinoma based on digerent subjective measures, such as whether or not the calcifications are irregular, linear, vermiform, branched, rounded or ring like, our efforts were addressed to obtain a feature set related to the shape. The identification of the pammeters concerning the malignant character of the microcalcifications was performed on a set of 146 mammograms with their real diagnosis known in advance from biopsies. This allowed identifying the following shape-based parameters as the relevant ones: Number of clusters, Number of holes, Area, Feret elongation, Roughness, and Elongation. Further experiments on a set of 70 new mammogmms showed that the performance of the classification scheme is close to the mean performance of three expert radiologists, which allows to consider the proposed method for assisting the diagnosis and encourages to continue the investigation in the senseof adding new features not only related to the shape

Imprecise measurements in quantum mechanics

In this thesis the structure and properties of imprecise quantum measurements are investigated. The starting point for this investigation is the representation of a quantum observable as a normalized positive operator measure. A general framework to describe measurement inaccuracy is presented. Requirements for accurate measurements are discussed, and the relation of inaccuracy to some optimality criteria is studied. A characterization of covariant observables is given in the case when they are imprecise versions of a sharp observable. Also the properties of such observables are studied. The case of position and momentum observables is studied. All position and momentum observables are characterized, and the joint positionmomentum measurements are discussed.

Técnicas para análise de desempenho de computadores

A series of open source benchmarks for computer performance analysis of personal computers with a focus on computational chemistry calculations is presented. The results returned by these tests are discussed and used to correlate with the actual performance of a set of computers available for research on two computing intensive fields of chemistry, quantum chemical and molecular simulation calculations.

Magnetic and transport properties of InGaAs quantum wells with Mn

In the present work structural, magnetic and transport properties of InGaAs quantum wells (QW) prepared by MBE with an remote Mn layer are investigated. By means of high-resolution X-ray diffractometry the structure of the samples is analyzed. It is shown that Mn ions penetrate into the QW. Influence of the thickness of GaAs spacer and annealing at 286 ºС on the properties of the system is shown. It is shown that annealing of the samples led to Mn activation and narrowing of the Mn layer. Substantial role of 2D holes in ferromagnetic ordering in Mn layer is shown. Evidence for that is observation of maximum at 25 – 55 K on the resistivity temperature dependence. Position of maximum, which is used for quantitative assessment of the Curie temperature, correlates with calculations of the Curie temperature for structures with indirect interaction via 2D holes’ channel. Dependence of the Curie temperature on the spacer thickness shows, that creation of applicable spintronic devices needs high-precision equipment to manufacture extra fine structures. The magnetotransport measurements show that charge carrier mobility is very low. This leads to deficiency of the anomalous Hall effect. At the same time, magnetic field dependences of the magnetization at different temperatures demonstrate that systems are ferromagnetically ordered. These facts, most probably, give evidence of presence of the ferromagnetic MnAs clusters.

Quantum-to-classical crossover in full counting statistics

The reduction of quantum scattering leads to the suppression of shot noise. In this Letter, we analyze the crossover from the quantum transport regime with universal shot noise to the classical regime where noise vanishes. By making use of the stochastic path integral approach, we find the statistics of transport and the transmission properties of a chaotic cavity as a function of a system parameter controlling the crossover. We identify three different scenarios of the crossover.

Quantum suppression of shot noise in field emitters

We have analyzed the shot noise of electron emission under strong applied electric fields within the Landauer-Bttiker scheme. In contrast to the previous studies of vacuum-tube emitters, we show that in new generation electron emitters, scaled down to the nanometer dimensions, shot noise much smaller than the Schottky noise is observable. Carbon nanotube field emitters are among possible candidates to observe the effect of shot-noise suppression caused by quantum partitioning.

O ensino de química quântica e o computador na perspectiva de projetos

This paper aims to discuss and reflect about the use of computers in the teaching of Quantum Chemistry. A course on Computational Quantum Chemistry concentrating on Medicinal Chemistry projects was developed for undergraduate and graduate students. The results showed that students got more motivated and involved when there is an articulation between theory and practice. This work presents an alternative way to teach Theoretical Chemistry using projects.

Probing quantum gravity using photons from a flare of the active galactic nucleus Markarian 501 observed by the MAGIC telescope

We analyze the timing of photons observed by the MAGIC telescope during a flare of the active galactic nucleus Mkn 501 for a possible correlation with energy, as suggested by some models of quantum gravity (QG), which predict a vacuum refractive index similar or equal to 1 + (E/M-QGn)(n), n = 1, 2. Parametrizing the delay between gamma-rays of different energies as Delta t = +/-tau E-1 or Delta t = +/-tau E-q(2), we find tau(1) = (0.030 +/- 0.012) s/GeV at the 2.5-sigma level, and tau(q) = (3.71 +/- 2.57) x 10(-6) s/GeV2, respectively. We use these results to establish lower limits M-QG1 > 0.21 X 10(18) GeV and M-QG2 > 0.26 x 10(11) GeV at the 95% C.L. Monte Carlo studies confirm the MAGIC sensitivity to propagation effects at these levels. Thermal plasma effects in the source are negligible, but we cannot exclude the importance of some other source effect.

Computer-aided discovery of biological activity spectra for anti-aging and anti-cancer olive oil oleuropeins

Aging is associated with common conditions, including cancer, diabetes, cardiovascular disease, and Alzheimer"s disease. The type of multi‐targeted pharmacological approach necessary to address a complex multifaceted disease such as aging might take advantage of pleiotropic natural polyphenols affecting a wide variety of biological processes. We have recently postulated that the secoiridoids oleuropein aglycone (OA) and decarboxymethyl oleuropein aglycone (DOA), two complex polyphenols present in health‐promoting extra virgin olive oil (EVOO), might constitute a new family of plant‐produced gerosuppressant agents. This paper describes an analysis of the biological activity spectra (BAS) of OA and DOA using PASS (Prediction of Activity Spectra for Substances) software. PASS can predict thousands of biological activities, as the BAS of a compound is an intrinsic property that is largely dependent on the compound"s structure and reflects pharmacological effects, physiological and biochemical mechanisms of action, and specific toxicities. Using Pharmaexpert, a tool that analyzes the PASS‐predicted BAS of substances based on thousands of"mechanism‐ effect" and"effect‐mechanism" relationships, we illuminate hypothesis‐generating pharmacological effects, mechanisms of action, and targets that might underlie the anti‐aging/anti‐cancer activities of the gerosuppressant EVOO oleuropeins.

Quantum magnetic deflagration in Mn12 acetate

We report controlled ignition of magnetization reversal avalanches by surface acoustic waves in a single crystal of Mn12 acetate. Our data show that the speed of the avalanche exhibits maxima on the magnetic field at the tunneling resonances of Mn12. Combined with the evidence of magnetic deflagration in Mn12 acetate [Y. Suzuki et al., Phys. Rev. Lett. 95, 147201 (2005)], this suggests a novel physical phenomenon: deflagration assisted by quantum tunneling.

Brain-Computer Interfaces, Virtual Reality, and Videogames

Major challenges must be tackled for brain-computer interfaces to mature into an established communications medium for VR applications, which will range from basic neuroscience studies to developing optimal peripherals and mental gamepads and more efficient brain-signal processing techniques.

Brain Computer Interface for Virtual Reality Control

A brain-computer interface (BCI) is a new communication channel between the human brain and a computer. Applications of BCI systems comprise the restoration of movements, communication and environmental control. In this study experiments were made that used the BCI system to control or to navigate in virtual environments (VE) just by thoughts. BCI experiments for navigation in VR were conducted so far with synchronous BCI and asynchronous BCI systems. The synchronous BCI analyzes the EEG patterns in a predefined time window and has 2 to 3 degrees of freedom.

Uma perspectiva computacional sobre catálise enzimática

Enzymes are extremely efficient catalysts. Here, part of the mechanisms proposed to explain this catalytic power will be compared to quantitative experimental results and computer simulations. Influence of the enzymatic environment over species along the reaction coordinate will be analysed. Concepts of transition state stabilisation and reactant destabilisation will be confronted. Divided site model and near-attack conformation hypotheses will also be discussed. Molecular interactions such as covalent catalysis, general acid-base catalysis, electrostatics, entropic effects, steric hindrance, quantum and dynamical effects will also be analysed as sources of catalysis. Reaction mechanisms, in particular that catalysed by protein tyrosine phosphatases, illustrate the concepts.

Quantum dynamics of the parabolic model

Kvanttimekaniikan teoriassa suljettuja, ympäristöstään eristettyjä systeemejä koskevat tulokset ovat hyvin tunnettuja. Eräs tärkeä erityispiirre tällaisille systeemeille on, että niiden aikakehitys on unitaarista. Oletus siitä, että systeemi on suljettu, on osaltaan tietysti vain yksinkertaistus. Käytännössä kaikki kvanttimekaaniset systeemit vuorovaikuttavat ympäristönsä kanssa ja tästä johtuen niiden dynamiikka monimutkaistuu oleellisesti. Kuitenkin tietyissä tapauksissa systeemin aikakehitys voidaan ratkaista, ainakin approksimatiivisesti. Tärkeimpinä esimerkkeinä on ympäristön joko nopea tai erittäin hidas muutos kvanttisysteemin ominaiseen aikaskaalaan verrattuna. Näistä erityisesti jälkimmäinen on käyttökelpoinen oletus monissa fysikaalisissa tilanteissa. Tällöin voidaan suorittaa niin sanottu adiabaattinen approksimaatio. Sen mukaan systeemi, joka on aikakehityksen generoivan Hamiltonin operaattorin ominaistilassa, pysyy vastaavassa ominaistilassa ympäristön muuttuessa äärettömän hitaasti, mikäli systeemin eri energiatasot eivät leikkaa toisiaan. Todellisissa tilanteissa muutos ei tietenkään voi olla äärettömän hidasta ja myös energiatasojen leikkaukset ovat mahdollisia, jolloin tapahtuu transitio eri ominaistilojen välillä. Energiatasojen leikkauksilla on oleellisia vaikutuksia erittäin monissa fysikaalisissa prosesseissa ja niitä kuvaamaan on luotu monia malleja kvanttimekaniikan alkuajoista lähtien aina tähän päivään saakka. Nykyinen teknologinen kehitys on avannut uudenlaisen mahdollisuuden ilmiön kokeelliseen varmentamiseen ja hyödyntämiseen. Tämän vuoksi kyseisten mallien dynamiikan ja erityisesti energiatasojen useiden peräkkäisten leikkausten aiheuttamien koherenssi-ilmiöiden selvittäminen on tärkeää. Tässä työssä käsitellään kvanttimekaanisia kaksitasosysteemejä, joissa esiintyy energiatasojen leikkauksia sekä niiden pitkän aikavälin dynamiikkaa. Tutkielmassa perehdytään tarkemmin kahteen tiettyyn malliin. Näistä ensimmäinen, Landau-Zener -malli, on tunnetuin ja sovelluksissa käytetyin malli. Kuitenkin erityisen mielenkiinnon kohteena on niin kutsuttu parabolinen malli, jolle johdetaan eri approksimaatioita käyttäen asymptoottiset transitiotodennäköisyydet eri tilojen välille. Näitä verrataan numeerisiin tuloksiin.