Carbon Nanotubes in Helically Modulated Potentials

We calculate effects of an applied helically symmetric potential on the low energy electronic spectrum of a carbon nanotube in the continuum approximation. The spectrum depends on the strength of this potential and on a dimensionless geometrical parameter, P, which is the ratio of the circumference of the nanotube to the pitch of the helix. We find that the minimum band gap of a semiconducting nanotube is reduced by an arbitrarily weak helical potential, and for a given field strength there is an optimal P which produces the biggest change in the band gap. For metallic nanotubes the Fermi velocity is reduced by this potential and for strong fields two small gaps appear at the Fermi surface in addition to the gapless Dirac point. A simple model is developed to estimate the magnitude of the field strength and its effect on DNA-CNT complexes in an aqueous solution. We find that under typical experimental conditions the predicted effects of a helical potential are likely to be small and we discuss several methods for increasing the size of these effects.Comment: 12 pages, 10 figures. Accepted for publication in Physical Review B. Image quality reduced to comply with arxiv size limitation

Continuum Theory for Piezoelectricity in Nanotubes and Nanowires

We develop and solve a continuum theory for the piezoelectric response of one dimensional nanotubes and nanowires, and apply the theory to study electromechanical effects in BN nanotubes. We find that the polarization of a nanotube depends on its aspect ratio, and a dimensionless constant specifying the ratio of the strengths of the elastic and electrostatic interactions. The solutions of the model as these two parameters are varied are discussed. The theory is applied to estimate the electric potential induced along the length of a BN nanotube in response to a uniaxial stress.Comment: 4 pages in RevTex4, 2 epsf figure

Can conventional forces really explain the anomalous acceleration of Pioneer 10/11 ?

A conventional explanation of the correlation between the Pioneer 10/11 anomalous acceleration and spin-rate change is given. First, the rotational Doppler shift analysis is improved. Finally, a relation between the radio beam reaction force and the spin-rate change is established. Computations are found in good agreement with observational data. The relevance of our result to the main Pioneer 10/11 anomalous acceleration is emphasized. Our analysis leads us to conclude that the latter may not be merely artificial.Comment: 9 pages, no figur

Seeds Buffering for Information Spreading Processes

Seeding strategies for influence maximization in social networks have been studied for more than a decade. They have mainly relied on the activation of all resources (seeds) simultaneously in the beginning; yet, it has been shown that sequential seeding strategies are commonly better. This research focuses on studying sequential seeding with buffering, which is an extension to basic sequential seeding concept. The proposed method avoids choosing nodes that will be activated through the natural diffusion process, which is leading to better use of the budget for activating seed nodes in the social influence process. This approach was compared with sequential seeding without buffering and single stage seeding. The results on both real and artificial social networks confirm that the buffer-based consecutive seeding is a good trade-off between the final coverage and the time to reach it. It performs significantly better than its rivals for a fixed budget. The gain is obtained by dynamic rankings and the ability to detect network areas with nodes that are not yet activated and have high potential of activating their neighbours.Comment: Jankowski, J., Br\'odka, P., Michalski, R., & Kazienko, P. (2017, September). Seeds Buffering for Information Spreading Processes. In International Conference on Social Informatics (pp. 628-641). Springe

Strategic distribution of seeds to support diffusion in complex networks

© 2018 Jankowski et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Usually, the launch of the diffusion process is triggered by a few early adopters–i.e., seeds of diffusion. Many studies have assumed that all seeds are activated once to initiate the diffusion process in social networks and therefore are focused on finding optimal ways of choosing these nodes according to a limited budget. Despite the advances in identifying influencing spreaders, the strategy of activating all seeds at the beginning might not be sufficient in accelerating and maximising the coverage of diffusion. Also, it does not capture real scenarios in which marketing campaigns continuously monitor and support the diffusion process by seeding more nodes. More recent studies investigate the possibility of activating additional seeds as the diffusion process goes forward. In this work, we further examine this approach and search for optimal ways of distributing seeds during the diffusion process according to a pre-allocated seeding budget. Theoretically, we show that a universally best solution does not exist, and we prove that finding an optimal distribution of supporting seeds over time for a particular network is an NP-hard problem. Numerically, we evaluate several seeding strategies on different networks regarding maximising the coverage and minimising the spreading time. We find that each network topology has a best strategy given some spreading parameters. Our findings can be crucial in identifying the best strategies for budget allocation in different scenarios such as marketing or political campaigns

305. Ocena wyników leczenia i czynników prognostycznych chorych na raka piersi we wczesnym stopniu zaawansowania po oszczędzających operacjach i napromienianiu

CelAnaliza niepowodzeń po leczeniu i zbadanie czynników prognostycznych ryzyka nawrotu i zgonu chorych na raka piersi leczonych metodą oszczędzającą.Materiał i metodaW Centrum Onkologii w Warszawie w latach 1995–1998 leczono 184 chorych na raka piersi w stopniach I-II metodą oszczędzającą. Mediana obserwacji – 66 miesięcy. U 53% chorych (98/184) zastosowano chemio i/lub hormonoterapię. Do analizy proporcjonalnego ryzyka Cox’a włączono następujące czynniki: wiek, stan hormonalny chorych, rodzinne występowanie raka piersi, lokalizacja raka, postać przedkliniczna versus kliniczna, pT, pN, typ i złośliwość histopatologiczna raka, obecność CDIS w raku inwazyjnym, ocena mikroskopowa marginesów i receptorów ER i PGR. Prawdopodobieństwo przeżycia obliczano metodą Kaplana-Meiera.WynikiU 9% chorych (18/197) rozpoznano nawrót raka piersi: u 5% wznowę, u 4% przerzuty. Wznowy w piersi wystąpiły w ciągu 3 i 5 lat od operacji odpowiednio u: 40% (4/10) i u 80% (8/10) chorych. Prawdopodobieństwo 5-letniego wyleczenia miejscowego, przeżycia bezobjawowego i całkowitego dla 184 chorych wyniosły odpowiednio: 95%, 91% i 97%. W analizie wieloczynnikowej jedynym istotnym statystycznie (p<0.05) czynnikiem mającym związek z ryzykiem wystąpienia nawrotu okazała się: postać kliniczna raka. Chore z kliniczną postacią raka miały 6-cio krotnie wyższe ryzyko nawrotu niż chore z rozpoznaniem przedklinicznej postaci raka. Na ryzyko zgonu z powodu raka piersi istotny statystycznie wpływ miała jedynie wielkość guza. Chore z rozpoznaniem T2 miały 9 krotnie wyższe ryzyko zgonu niż chore z T1.WniosekNajlepsze rokowanie mają chore z przedkliniczną postacią raka piersi z guzem nie większym niż 2 cm. Uzyskane wyniki uzasadniają kontynuowanie dotychczas stosowanego leczenia w Centrum Onkologii

Design and analysis of a cantilever biosensor based on a boron nitride nanotube

In this paper, we introduce a single-walled boron nitride nanotube (SWBNNT)-based cantilever biosensor, and investigate its bending deformation. The BNNT-based cantilever is modelled by accounting that the surface of the cantilever beam is coated with the antibody molecule. We have considered two main approaches for the mechanical deformation of the BNNT beam. The first one is differential surface stress produced by the binding of biomolecules onto its surface, and the second one is the charge released from the biomolecular interaction. In addition, other parameters including length of beam, variation of beam&rsquo;s location and chiralities of the BNNT have been taken into consideration to design the cantilever biosensor. The computed results are in good agreement with the well known electrostatic equations that govern the deformation of the cantilever.<br /

McLaughlin Crater as a Candidate Landing Site for Humans on Mars

McLaughlin Crater is an ancient (Noachian) Martian impact crater located at 337.6 East, 21.9 North, just south of the dichotomy boundary. This site should be considered for future landed exploration because: a) it is located at the boundary of three types of scientifically important terrain that will yield key results about the geological evolution and habitability of Mars; b) it contains surfaces where radiometric dating can be related to age dates estimated from crater counting, c) it contains volatile-rich rocks that will not only yield interesting results regarding ancient atmospheric chemistry, but will also be high quality, accessible targets for in-situ resource utilization (ISRU), and d) the site within the crater provides a flat, low-risk and low-elevation landing zone, which will facilitate landing large payloads on Mars