Setting the hook for specific single walled carbon nanotubes (SWCNT)

The electronic properties of SWCNTs depend strongly on well-defined characteristics such as their diameter, n,m-indices and chirality.[1–4] Traditional purification methods do not allow to selectively obtain samples of SWCNTs with precisely defined characteristics and high purity. The separation and purification of SWCNTs is an ongoing challenge as the selectivity towards traditional means of purification remains low at best. Here, we propose a new strategy to achieve a controlled and selective debundling and separation of SWCNTs depending on their size and chirality. The focus of this thesis is the design and synthesis of a molecular hook for specific SWCNTs. Conceptually, the hook consists of a chiral building block with a concave π-system, which can be accessed using stereospecific Diels-Alder reactions as key steps. Polymerization with interlinking building blocks then leads to chiral ribbons, which are envisaged to selectively coat a specific SWCNT and disperse it. The driving force for the coating process is mainly the interaction of the SWCNT with the concave π-moiety while the size exclusion is defined by the resulting secondary structure of the polymer, the polymer backbone and the interlinking molecules. Variation of the interlinking building blocks allows altering of the properties of the polymer at a late stage in the synthesis and ultimately defines the dispersion capability of the polymer. Each of the three successfully synthesized copolymers contains an enantiomerically pure ethenoanthracene derivative as the concave π-moiety. As a reliable release of the coated SWCNT is highly desirable, we further present a diamine monomer unit designed for Schiff base linked copolymerization that will allow for acid-labile depolymerization resulting in uncoating of the dispersed SWCNTs. Each of the polymer was characterized and the dispersion capability assessed subsequently

The connection between noise and quantum correlations in a double quantum dot

We investigate the current and noise characteristics of a double quantum dot system. The strong correlations induced by the Coulomb interaction create entangled two-electron states and lead to signatures in the transport properties. We show that the interaction parameter phi, which measures the admixture of the double-occupancy contribution to the singlet state and thus the degree of entanglement, can be directly accessed through the Fano factor of super-Poissonian shot noise.Comment: 5 pages, major revision, to be published in Phys. Rev.

Multiparticle entanglement under the influence of decoherence

We present a method to determine the decay of multiparticle quantum correlations as quantified by the geometric measure of entanglement under the influence of decoherence. With this, we compare the robustness of entanglement in GHZ-, cluster-, W- and Dicke states of four qubits and show that the Dicke state is most robust. Finally, we determine the geometric measure analytically for decaying GHZ and cluster states of an arbitrary number of qubits.Comment: 5 pages, 3 figures, v2: final version, to appear as a Rapid Communication in PR

Carcinoid daganatok

The authors review the most important clinical aspects of carcinoid tumors. Carcinoid tumors originating in neuroendocrine cells are rare, usually slowly-growing neoplasms, however, they may present as aggressive and rapidly progressing tumors. Epidemiologic data indicates that their prevalence is gradually increasing, which may be explained, at least in part, by the development and wider use of advanced diagnostic methods. A considerable proportion of patients with neuroendocrine tumors are symptom-free, whereas others may have carcinoid syndrome or symptoms of other endocrine syndromes. Early diagnosis may be established by the measurement of biochemical markers (serum chromogranin A, urinary 5-hydroxyindoleacetic acid) and advanced localization methods. A considerable number of patients are diagnosed at the late stages of the disease; in these cases surgical cure is not possible but surgical and/or interventional radiologic procedures which reduce tumoral mass should be still considered. The most effective drugs for symptomatic treatment of carcinoid tumors are somatostatin analogues; in addition to their beneficial effect on clinical symptoms they may stabilize tumor growth for many years and, less frequently, may produce tumor regression. The use of chemotherapeutic agents is considered in patients with aggressive, rapidly growing and advanced tumors; initial findings with temozolomide and thalidomide in clinical trials raise the possibility that these chemotherapeutic agents may prove to be new therapeutic options. Radioisotope-labeled peptide receptor therapy with 131 I-MIBG, 90 Y-DOTA-TOC or 177 Lu-DOTA-TOC may offer a highly effective option for patients with progressive and advanced stage of neuroendocrine tumors. Initial observations obtained in clinical trials with some tyrosine kinase inhibitors, antibodies against tyrosine kinases, and with inhibitors of mammalian target of rapamycin (mTOR) support the possibility that at least some of these new agents may have a role in future treatment options in patients with advanced neuroendocrine tumors

Production of multipartite entanglement for electron spins in quantum dots

We propose how to generate genuine multipartite entanglement of electron spin qubits in a chain of quantum dots using the naturally available single-qubit rotations and two-qubit Heisenberg exchange interaction in the system. We show that the minimum number of required operations to generate entangled states of the GHZ-, cluster and W-type scales linearly with the number of qubits and estimate the fidelities of the generated entangled cluster states. As the required single and two-qubit operations have recently been realized, our proposed scheme opens the way for experimental investigation of multipartite entanglement with electron spin qubits.Comment: 8 pages, 2 Figure

A Facebook hatása a hírfogyasztásra: közönségépítés helyett közösségépítés

A közösségi oldalak elterjedése, különösen a ma már több mint 700 millió regisztrált felhasználót jegyző Facebook jelentős hatással van a médiafogyasztási, azon belül a hírfogyasztási szokásokra. Az internetezők ma már nemcsak a portálokra látogatva értesülhetnek a legfrissebb hírekről, hanem egy közösségi oldal felületén is megtehetik ugyanezt, ahol személyes ismerőseik osztják meg az általuk érdekesnek tartott híreket. Nem más történik tehát, hogy a professzionális szerkesztés mellett megjelent a social filtering, vagyis a közösségi szűrő jelensége is. A cikk azt vizsgálja, hogy a közösségi média, ezen belül is a Facebook milyen hatással van a médiafogyasztási szokásokra, a hírportáloknak milyen szempontokat kell figyelembe venniük, amikor a közösségi stratégiájukat kialakítják. Állításainkat empirikusan is igazoljuk, az atlatszo.hu oldal látogatottsági adatait vizsgálva bemutatjuk, hogy egy újonnan indult oknyomozó portál miként tud közösséget és ezen keresztül közönséget építeni a Facebook segítségével

Magyarország gravitációs lineamenstérképe = Gravity lineament map of Hungary

Az Eötvös Loránd Geofizikai Intézetben felépített Országos Gravitációs Adatbázis, amely több mint 380000 mérési pontot tartalmaz, országos fedettséget biztosít. Első lépésben elkészítettük az 500000-es Bouguer-anomália térképet, amit kisebb módszertani ismertetővel publikáltunk a Geophysical Transactions (2006. Vol. 45, No. 2) számában. Ezután a gravitációs anomáliák sűrűség-, mélység- és méret-függését vizsgálatuk. Az eredmények azt mutatták, hogy a gravitációs anomáliatér spektrális jellege független a sűrűségkontraszttól, a test méretétől és azt elsődlegesen a hatók mélysége határozza meg. Szűrési és képfeldolgozási munkák eredményeként több transzformált térkép is készült, amelyek lineamens kijelölésre alkalmasak voltak. Az utolsó fázisában elvégzett feldolgozásaink során a lineamenseket automatikus (horizontális gradiens módszer, Euler 3D módszer) és a félautomatikus (automatikus + manuális) eljárásokkal jelöltük ki. A feldolgozások során meghatároztuk a legfontosabb gravitációs lineamenseket és a lineamens rendszer bekerült az ELGI országos geofizikai alaptérképei közé. Az eredményeinket számos előadáson bemutattuk, a legérdekesebb lineamenseket a Magyar Geofizika (2006. 47. évfolyam, 2. szám) cikkében publikáltuk. Meggyőződésünk, hogy az eredményeink számos más kutatási témának szolgáltatnak földtanilag hasznos információt és az OTKA keretén belül végzett módszertani kutatásaink újabb kutatási célokat generáltak. | The National Hungarian Gravity Database developed by Eötvös Loránd Geophysical Institute consists of more than 380000 measured data, which cover the whole country. In the first stage we have constructed the Bouguer anomaly map of Hungary (scale 1:500000) and later published it with a small methodological guide in Geophysical Transactions (2006. Vol. 45, No. 2). After that we have studied the dependence of the anomalies from density contrast, depth and the size of the causative bodies. The results showed that spectral behavior depends only on the depth of the causative body, and is independent of density contrast and size of the body. Using different filtering and image processing methods on gravity map, we have created a lot of different maps to detect the gravity lineaments. In the last stage of the work gravity lineaments were designed using automatic (horizontal gradient method, Euler 3D method) and semiautomatic (automatic + manual) methods of line detection. The main gravity lineaments were determined and the system of lineaments was archived and put into the country size geophysical base maps of ELGI. Our results were presented on many conferences and the most interesting line structures were published in Hungarian Geophysics (2006. Vol. 47, No.2.). We think that our results gave important geological information for many other research themes and showed a lot of new interesting scientific purposes