Magnetoresistance and negative differential resistance in Ni/Graphene/Ni vertical heterostructures driven by finite bias voltage: A first-principles study

Using the nonequilibrium Green function formalism combined with density functional theory, we study finite-bias quantum transport in Ni/Gr_n/Ni vertical heterostructures where $n$ graphene layers are sandwiched between two semi-infinite Ni(111) electrodes. We find that recently predicted "pessimistic" magnetoresistance of 100% for $n \ge 5$ junctions at zero bias voltage $V_b \rightarrow 0$, persists up to $V_b \simeq 0.4$ V, which makes such devices promising for spin-torque-based device applications. In addition, for parallel orientations of the Ni magnetizations, the $n=5$ junction exhibits a pronounced negative differential resistance as the bias voltage is increased from $V_b=0$ V to $V_b \simeq 0.5$ V. We confirm that both of these nonequilibrium effects hold for different types of bonding of Gr on the Ni(111) surface while maintaining Bernal stacking between individual Gr layers.Comment: 6 pages, 5 figures, PDFLaTeX; Figure labels correcte

Effector mechanisms of anti-CD20 monoclonal antibodies in B cell malignancies.

Activation of the complement system by tumor cells was long believed to only benefit the host. Overexpression of complement inhibitors by many tumor cell types and results obtained in several experimental animal models were all in agreement with this hypothesis. However, recent reports imply that the situation is more complex than initially believed and that under certain circumstances tumor cells may use complement to their own advantage, e.g. by recruitment of suppressor T cells or promoting local angiogenesis. Such a dual role of complement may also be apparent when considering the effect of therapeutic monoclonal antibodies (mAb) used to successfully treat B cell malignancies, such as CD20 mAbs. Some argue that besides direct tumor cell killing by mAbs, two main immune effector mechanisms, complement dependent cytotoxicity (CDC) and antibody dependent cellular cytotoxicity (ADCC), may be competing with each other. Experiments aiming at answering the question whether complement is our friend or foe in mAb therapy ended up with seemingly contradictory conclusions. Herein, we revisit the existing knowledge on this pivotal issue based on rituximab and other anti-CD20 mAb as a model of therapeutic agents

Atomic-scale model for the contact resistance of the nickel-graphene interface

We perform first-principles calculations of electron transport across a nickel-graphene interface. Four different geometries are considered, where the contact area, graphene and nickel surface orientations and the passivation of the terminating graphene edge are varied. We find covalent bond formation between the graphene layer and the nickel surface, in agreement with other theoretical studies. We calculate the energy-dependent electron transmission for the four systems and find that the systems have very similar edge contact resistance, independent of the contact area between nickel and graphene, and in excellent agreement with recent experimental data. A simple model where graphene is bonded with a metal surface shows that the results are generic for covalently bonded graphene, and the minimum attainable edge contact resistance is twice the ideal edge quantum contact resistance of graphene.Comment: 12 pages, 6 figure

Taloudelliset eturyhmät politiikan sisäpiirissä : tutkimus liike-elämän poliittisesta vaikuttamisesta kolmikantaisessa Suomessa 1968—2011

Tutkimus esittää tulkinnan suomalaisen liike-elämän poliittisesta edunvalvonnasta ja vaikuttamisesta tulopolitiikan syntymisen jälkeen. Tutkimus asettaa suomalaisen yhteiskunnan läpinäkyvyyden ja korruptiivisuuden aikaisempaa kriittisempään valoon. Liike-elämällä on oletettua suurempi rooli suomalaisessa poliittisessa päätöksenteossa. EU- ja EMU-ratkaisuissa liike-elämän vaikutus oli ratkaiseva. Tutkimuksen perusteella korporatiivisen järjestelmän fundamentit ovat työmarkkinajärjestöjen jäsenmaksuperintäsopimus, ansiosidonnainen työeläkejärjestelmä ja työehtojen yleissitovuus. Niiden varaan rakentui vakaa taloudellinen kasvu 1970-luvulta alkaen ja kolmikantainen sopimusjärjestelmä. Työnantajat saivat työeläkejärjestelmässä pankkien rinnalle niukan rahan maailmassa työeläkkeiden takaisinlainausjärjestelmän, joka oli tärkeä yritysrahoituksen vaihtoehto pankkien dominanssille. Jäsenmaksuperintäsopimuksella työnantajat keräsivät verovaroin tuetut jäsenmaksut henkilöstöltä, jolloin uudessa kehitysvaiheessa olevat ammattiliitot kasvoivat työnantajien kannalta neuvotteluhakuisiksi. Työehtojen yleissitovuus oli yllätys sekä työnantajille että työntekijöille: sen sääti vastoin STK:n ja SAK:n tahtoa viimeinen vasemmistoenemmistöinen eduskunta 1970. Hallitus tukee korporaatioiden neuvotteluasemaa, antaa veroetuja sekä kuuntelee ja toteuttaa sovittuja sosiaalipoliittisia ehdotuksia. EU- ja EMUratkaisuissa eturyhmien rooli vahvistui, kun ratkaisun myötä finanssi- ja työmarkkinapolitiikasta tuli tärkeimmät talouspolitiikan sisäiset ohjausvälineet. Tutkimuksessa uutta vaihetta kutsutaan EU-korporatismiksi. Työmarkkinajärjestelmä Suomessa kytkee aktiiviset kansalaiset suuriin poliittisiin ratkaisuihin ja siihen perustuu korporatiivisen systeemin vahva legitimiteetti. Tutkimustulosten valossa korporaatiot hallitsevat Suomessa sisäpiirin poliittista vaikuttamista eli suoria suhteita päätöksentekijöihin. Mutta korporaatioilla on myös epäsuorassa vaikuttamisessa johtava rooli. Korporatismiin Suomessa liittyy ajattelutapa, että sisäpiirin poliittiset suhteet eli työmarkkinasuhteet ovat osa päätöksentekojärjestelmää, eivät lobbausta. Suomalainen käsitys lobbaamisesta on perustunut ajatukseen, että lobbaus olisi vain toimintaa, jolla pyritään korporaatioiden ulkopuolelta vaikuttamaan poliittiseen päätöksentekoon. Tutkimustulosten valossa lobbarit jaetaan kuuteen luokkaan, joita ovat toimeksiantajat, luotetut, palkkasuhteiset, sopimussuhteiset, asiantuntijat ja vapaaehtoiset. Luokittelu on osittain hierarkkinen, missä toimeksiantajatedustavat kaverikapitalismia – sisäpiiriä, jolla on yritysten, järjestöjen ja valtiovallan sisäpiiritietoa enemmän kuin lainsäätäjillä. Koska politiikasta Suomesta puuttuvat sisäpiirisäännöt, kaverikapitalismilla on suuri vaikutus myös poliittiseen päätöksentekoon. Esimerkiksi kaverikapitalismi on integroinut palkansaajajärjestöt osaksi korporatiivista omistajapolitiikkaa. Politiikan tutkimus on laiminlyönyt talouden ja yritysten roolia. Tämä tutkimus tekee eron sisäpiirin ja ulkopiirin vaikuttamisen välillä. Sisäpiirin lobbaajat hallitsevat asymmetristä tietoa ja vaikuttavat sen avulla – sekä taloudessa että politiikassa. Tutkimuksessa päädytään tulkintaan, että Nokiasta tuli 1990-luvun EU-korporatismin kauden vaikuttaja. Tämän rinnalla alkoi kehitys, jossa liike-elämän huippujärjestöjen sisällä yritysten keskinäinen kilpailu kiristyi eri omistajaryhmien välillä. Suomalaisen korporatismin juuret ovat Tammikuun kihlauksessa 1940, mikä yhdisti hajanaisen kansakunnan. Sodan jälkeen se ilmeni yhteistyölinjana, jota myöhemmin kutsuttiin suomettumiseksi. Sen vaihtoehto oli kommunistinen Suomi, jonka yhteistyökapitalismi torjui menestyksellisesti. Kovilla otteilla tarkoitetaan erityisesti sisäpiiritiedolla operoimista, jolloin lainsäätäjällä ei ole aitoja poliittisia vaihtoehtoja – vain sisäpiirin antama vaihtoehto. Suomen korkea ammatillinen järjestäytymisaste tukee järjestelmän legitimiteettiä – yli 65 prosenttia työvoimasta on sitoutunut siihen. Tulopolitiikan edunvalvojista on syntynyt erivapauksia nauttiva sisäpiiri. Eduskunta ja valtioneuvosto ovat tulleet aika ajoin entistä riippuvaisemmiksi korporaatioista. Vaikka eurooppalaisessa vertailussa Suomi on ollut vähän korruptoitunut maa, uusien kriteerien valossa Suomen korporatiivista järjestelmää voidaan kutsua rakenteellisesti korruptiiviseksi. Suomesta puuttuvat politiikan sisäpiirisäännöt. Suomeen tarvitaan lobbareiden itsesäätelyn lisäksi lakiin perustuvaa säätelyä, jotta eduskunnan asema vahvistuisi. Korporaatioiden rooli työeläkeyhtiöiden hallinnoissa vahvistui osana rahaliittopäätöstä. Kun muissa pohjoismaissa korporatismin ote hellitti, Suomessa se vahvistui. Liike-elämän ajattelutavassa tapahtui muutos 2006, kun teknologiateollisuuden työnantajat eivät enää antaneet Etelärannan EK:lle mandaattia solmia keskitettyjä tulosopimuksia. Tutkimuksessa osoitetaan, että Suomessa käytetään lobbaukseen rahaa yli 120 € per capita, kun ammattiliittojen jäsenmaksut työttömyysturvalla vähennettynä lasketaan mukaan. Tutkimus osoittaa, että julkisen valinnan teoria toimii selittäjänä suomalaisessa korporatismissa ja että vapaamatkustajan ongelma kärjistyy. Anastasiadiksen teoria politiikan sisäpiiristä toimii suomalaisen sisäpiiri-ilmiön selittäjänä. Poliittinen passiivisuus äänestysaktiivisuudella mitattuna on voimistunut tutkimusjaksolla, kun nukkuvien puolueen kannatus on kasvanut 18 prosentista 38 prosenttiin.Economic Interest Groups as Political Insiders. A Research on the Lobbying of Finnish business community in the Tripartite system between 1968–2011. The study provides an interpretation of the influence of political interest groups in the Finnish business community (later the Business) and its lobbying after the national income policy agreement. The research puts the transparency and corruption of Finnish society in a more critical light. The Business has a greater role than earlier assumed in Finnish political decision-making. In the EU and EMU solutions, the impact of the Business was crucial. Based on the research, the membership fee collection agreement, the earnings-related pension scheme and the universality of working conditions form the foundations of the corporate system. These and a tripartite contract system were the basis of stable economic growth since the 1970’s. Within the earnings-related pension scheme employers were able to – when there was a shortage of money – reborrow from paid employment pensions, which became a new and important corporate financing alternative to the banks’ dominance. With the new agreement employers, instead of communists who were active in the unions, collected tax deductible fees from workers to labor unions. As a result of this trade unions became more willing to negotiate. The law on universality of working conditions was a surprise for both employers and employees: it was in violation of the will of corporations in the last socialist majority parliament in 1970. In 2001 corporations supported universality. The government supports corporate bargaining positions, gives tax benefits, as well as listens to and delivers agreed social policy proposals. In the EU and EMU solutions the roles of these interest groups strengthened. Financial and labor market policies became the most important internal policy instruments to regulate economic policy. In the study, this new phase is called EU corporatism. The labor market system in Finland connects active citizens to major political solutions. It has given a strong legitimacy to corporatism in Finland. In the light of the results of the study corporations are the insiders in the political process and they have regular direct relations with decision-makers. But corporations have also a leading role in indirect influence. The corporate idea – the political thinking in Finland – means that the political relations of corporations, i.e. the labor market system, are part of the decision-making system rather than lobbying. The Finnish concept of lobbying has been based on the idea that only influencing political decision-making by parties other than corporations is lobbying. Over 65% of the workforce belong to unions. The results of the research divide lobbyists into six categories, such as principals (or clients), trusted persons, employees, contract workers, experts and volunteers. The classification is partially hierarchical, where the clients represent crony capitalism – an inner circle with more insider information on companies, organizations and the government than legislators have. As politics in Finland lacks insider rules, crony capitalism also has a strong influence on political decision-making. For example, crony capitalism has incorporated labor unions into corporate ownership policy. This is executed within the framework of the earnings-related pension scheme. Political research has neglected the role of the economy and businesses. This study makes a difference between the inner circle and the influence of the outer circle. Insiders’ lobbyists control asymmetric information and exercise influence with it - both in business and politics. The study concludes that Nokia became the influential factor of the 1990’s EU corporatism. Alongside this, a trend began in which, among the top business associations, competition of power and regulation became intensified between different ownership groups. The roots of Finnish corporatism are in the Betrothal of January 1940, which united the divided nation. After the war, it emerged as a co-operation policy, which was later referred to as finlandization. The alternative was a communist Finland, which was successfully defeated by income policy cooperation. Hard-handedness means operating with insider information where the legislator does not have genuine political options - just an option given by the insiders. Income policy interest groups have become a privileged group of insiders. The Finnish parliament and Government have become more and more dependent on corporations from time to time. Although compared with the rest of Europe corruption in Finland has been negligible, in the light of the new criteria the Finnish corporate system can be called structurally corrupted. Finland lacks insider rules in politics. In addition to the self-regulation of the lobbyists, Finland requires legislation-based regulation in order to strengthen the position of the Parliament. It requires an agreement on how to define who is a lobbyist. The role of corporations strengthened in the corporate governance system of pension insurance companies as a part of the monetary union decision. When in the other Nordic countries the grip of corporatism loosened, in Finland it strengthened. A change in the politics of the business elite occurred in 2006, when employers in the technology industry no longer issued a mandate to the Confederation of Finnish Industries EK (Elinkeinoelämän keskusliitto, EK) to negotiate centralized labour agreements. The study shows that in Finland €120 per capita is spent on lobbying when labor union membership fees minus unemployment insurance costs are included. The research shows that the theory of public choice is a defining factor in Finnish corporatism and that the problem of the free rider is becoming topical in the political arena. Anastasiadis’s idea of political insiderism is a factor in explaining the Finnish insider phenomenon. Political passivity, measured by voting in elections, intensified during the research period, when the support of ”the sleeping voters’ party” grew from 18% to 38%

Have you ever seen a phonon?

At Lund University we have designed a computer exercise devoted to phonons. The idea is that by combining numerical and graphical tools to visualise the temporal and spatial variations of the lattice vibrations, the students will obtain a more intuitive feeling for the relationship between the formulas and the physical reality that they attempt to describe. As an additional bonus, the numerical model can be extended beyond the traditional textbook treatment. Impurities have important consequences for the low-temperature electrical conductivity of metals, but even the simplest models, such as a single impurity in an infinite linear chain, cannot be solved analytically. This system can however easily be considered with our computer model.Here we will summarize the experience gained during the development and teaching of this computer exercise, touching on topics such as computational details and how the computer work can be integrated with the lectures. In addition, the numerical model used and the results derived from it will also be presented, with emphasis on the pedagogical aspect

On the variation in crack-opening stresses at different locations in a three-dimensional body

Crack propagation and closure behavior of thin, and thick middle crack tension specimens under constant amplitude loading were investigated using a three dimensional elastic plastic finite element analysis of fatigue crack propagation and closure. In the thin specimens the crack front closed first on the exterior (free) surface and closed last in the interior during the unloading portion of cyclic loading; a load reduced displacement technique was used to determine crack opening stresses at specified locations in the plate from the displacements calculated after the seven cycle. All the locations were on the plate external surface and were located near the crack tip, behind the crack tip, at the centerline of the crack. With this technique, the opening stresses at the specified points were found to be 0.52, 0.42, and 0.39 times the maximum applied stress

Killing of CLL and NHL cells by rituximab and ofatumumab under limited availability of complement.

Rituximab and ofatumumab are anti-CD20 antibodies applicable to treatment for non-Hodgkin's lymphoma and chronic lymphocytic leukemia (CLL). Effectiveness of both immunotherapeutics may depend on exhaustible complement system. To model the efficacy of complement usage by ofatumumab and rituximab under limited complement availability, we compared complement-dependent cytotoxicity exerted by these antibodies at low (5 and 10 %) and physiological (50 %) serum concentration in twelve CD20-positive cell lines and six freshly isolated CLL cells. Simultaneously, we assessed the expression of CD20 and membrane-bound complement inhibitors. Ratios of CD20 to CD59 and/or CD55 distinguished highly sensitive cells lysed equally efficient by both antibodies from the moderately sensitive cells, which were killed more efficiently by ofatumumab

ATK-ForceField: A New Generation Molecular Dynamics Software Package

ATK-ForceField is a software package for atomistic simulations using classical interatomic potentials. It is implemented as a part of the Atomistix ToolKit (ATK), which is a Python programming environment that makes it easy to create and analyze both standard and highly customized simulations. This paper will focus on the atomic interaction potentials, molecular dynamics, and geometry optimization features of the software, however, many more advanced modeling features are available. The implementation details of these algorithms and their computational performance will be shown. We present three illustrative examples of the types of calculations that are possible with ATK-ForceField: modeling thermal transport properties in a silicon germanium crystal, vapor deposition of selenium molecules on a selenium surface, and a simulation of creep in a copper polycrystal.Comment: 28 pages, 9 figure

General atomistic approach for modeling metal-semiconductor interfaces using density functional theory and nonequilibrium Green's function

Metal-semiconductor contacts are a pillar of modern semiconductor technology. Historically, their microscopic understanding has been hampered by the inability of traditional analytical and numerical methods to fully capture the complex physics governing their operating principles. Here we introduce an atomistic approach based on density functional theory and non-equilibrium Green's function, which includes all the relevant ingredients required to model realistic metal-semiconductor interfaces and allows for a direct comparison between theory and experiments via I-V bias curves simulations. We apply this method to characterize an Ag/Si interface relevant for photovoltaic applications and study the rectifying-to-Ohmic transition as function of the semiconductor doping.We also demonstrate that the standard "Activation Energy" method for the analysis of I-V bias data might be inaccurate for non-ideal interfaces as it neglects electron tunneling, and that finite-size atomistic models have problems in describing these interfaces in the presence of doping, due to a poor representation of space-charge effects. Conversely, the present method deals effectively with both issues, thus representing a valid alternative to conventional procedures for the accurate characterization of metal-semiconductor interfaces

Semi-Empirical Model for Nano-Scale Device Simulations

We present a new semi-empirical model for calculating electron transport in atomic-scale devices. The model is an extension of the Extended H\"uckel method with a self-consistent Hartree potential. This potential models the effect of an external bias and corresponding charge re-arrangements in the device. It is also possible to include the effect of external gate potentials and continuum dielectric regions in the device. The model is used to study the electron transport through an organic molecule between gold surfaces, and it is demonstrated that the results are in closer agreement with experiments than ab initio approaches provide. In another example, we study the transition from tunneling to thermionic emission in a transistor structure based on graphene nanoribbons.Comment: 8 pages, 8 figures. Submitted to PR