Nanoscale ear drum: Graphene based nanoscale sensors

The difficulty in determining the mass of a sample increases as its size diminishes. At the nanoscale, there are no direct methods for resolving the mass of single molecules or nanoparticles and so more sophisticated approaches based on electromechanical phenomena are required. More importantly, one demands that such nanoelectromechanical techniques could provide not only information about the mass of the target molecules but also about their geometrical properties. In this sense, we report a theoretical study that illustrates in detail how graphene membranes can operate as nanoelectromechanical mass-sensor devices. Wide graphene sheets were exposed to different types and amounts of molecules and molecular dynamic simulations were employed to treat these doping processes statistically. We demonstrate that the mass variation effect and information about the graphene-molecule interactions can be inferred through dynamical response functions. Our results confirm the potential use of graphene as mass detector devices with remarkable precision in estimating variations in mass at molecular scale and other physical properties of the dopants

Rotational symmetry and degeneracy: a cotangent-perturbed rigid rotator of unperturbed level multiplicity

We predict level degeneracy of the rotational type in diatomic molecules described by means of a cotangent-hindered rigid rotator. The problem is shown to be exactly solvable in terms of non-classical Romanovski polynomials. The energies of such a system are linear combinations of t(t+1) and 1/[t(t+1)+1/4] terms with the non-negative integer principal quantum number t=n+|/bar{m}| being the sum of the degree n of the polynomials and the absolute value, |/bar{m}|, of the square root of the separation constant between the polar and azimuthal motions. The latter obeys, with respect to t, the same branching rule, |/bar{m}|=0,1,..., t, as does the magnetic quantum number with respect to the angular momentum, l, and, in this fashion, the t quantum number presents itself indistinguishable from l. In effect, the spectrum of the hindered rotator has the same (2t+1)-fold level multiplicity as the unperturbed one. For small t values, the wave functions and excitation energies of the perturbed rotator differ from the ordinary spherical harmonics, and the l(l+1) law, respectively, while approaching them asymptotically with increasing t. In this fashion the breaking of the rotational symmetry at the level of the representation functions is opaqued by the level degeneracy. The model provides a tool for the description of rotational bands with anomalously large gaps between the ground state and its first excitation.Comment: 10 pages, 6 figures; Molecular Physics 201

Self Selection Does Not Increase Other-Regarding Preferences among Adult Laboratory Subjects, but Student Subjects May Be More Self-Regarding than Adults

We use a sequential prisoner's dilemma game to measure the other-regarding behavior in samples from three related populations in the upper Midwest of the United States: 100 college students, 94 non-student adults from the community surrounding the college and 1,069 adult trainee truckers in a residential training program. Both of the first two groups were recruited according to procedures commonly used in experimental economics (i.e., via e-mail and bulletin-board advertisements) and therefore subjects self-selected into the experiment. Because the structure of their training program reduced the opportunity cost of participating dramatically, 91% of the solicited trainees participated in the third group, so there was little scope for self-selection in this sample. We find no differences in the elicited other-regarding preferences between the self-selected adults and the adult trainees, suggesting that selection into this type of experiment is unlikely to bias inferences with respect to non-student adult subjects. We also test (and reject) the more specific hypothesis that approval-seeking subjects are the ones most likely to select into experiments. At the same time, we find a large difference between the self-selected students and the self-selected adults from the surrounding community: the students appear considerably less pro-social. Regression results controlling for demographic factors confirm these basic findings.methodology, selection bias, laboratory experiment, field experiment, other-regarding behavior, social preferences, truckload, trucker

Seyfert's Sextet: where is the gas?

Seyfert's Sextet (a.k.a HCG 79) is one of the most compact and isolated galaxy groups in the local Universe. It shows a prominent diffuse light component that accounts for ~50% of the total observed light. This likely indicates that the group is in an advanced evolutionary phase, which would predict a significant hot gaseous component. Previous X-ray observations had suggested a low luminosity for this system, but with large uncertainties and poor resolution. We present the results from a deep (70 ks), high resolution Chandra observation of Seyfert's Sextet, requested with the aim of separating the X-ray emission associated with the individual galaxies from that of a more extended inter-galactic component. We discuss the spatial and spectral characteristics of this group we derive with those of a few similar systems also studied in the X-ray band. The high resolution X-ray image indicates that the majority of the detected emission does not arise in the compact group but is concentrated towards the NW and corresponds to what appears to be a background galaxy cluster. The emission from the group alone has a total luminosity of ~1x10^40 erg/s in the (0.5-5) keV band. Most of the luminosity can be attributed to the individual sources in the galaxies, and only ~2x10^39 erg/s is due to a gaseous component. However, we find that this component is also mostly associated with the individual galaxies of the Sextet, leaving little or no residual in a truly IGM component. The extremely low luminosity of the diffuse emission in Seyfert's Sextet might be related to its small total mass.Comment: 8 pages, 7 figures. Accepted on A&

Transcriptomic fingerprinting of Pseudomonas putida under alternative physiological regimes

Pseudomonas putida KT2440 is a metabolically versatile soil bacterium useful both as a model biodegradative organism and as a host of catalytic activities of biotechnological interest. In this report, we present the high-resolution transcriptome of P. putida cultured on different carbon sources as revealed by deep sequencing of the corresponding RNA pools. Examination of the data from growth on substrates that are processed through distinct pathways (glucose, fructose, succinate and glycerol) revealed that > 20% of the P. putida genome is differentially expressed depending on the ensuing physiological regime. Changes affected not only metabolic genes but also a suite of global regulators e.g. the rpoS sigma subunit of RNAP, various cold-shock proteins and the three HU histone-like proteins. Specifically, the genes encoding HU subunit variants hupA, hupB and hupN drastically altered their expression levels (and thus their ability to form heterodimeric combinations) under the diverse growth conditions. Furthermore, we found that two small RNAs, crcZ and crcY, known to inhibit the Crc protein that mediates catabolite repression in P. putida, were both down-regulated by glucose. The raw transcriptomic data generated in this work is made available to the community through the Gene Expression Omnibus database.This work was supported by the BIO and FEDER CONSOLIDER-INGENIO programs of the Spanish Ministry of Economy and Competitiveness, the MICROME, ST-FLOW and ARISYS Contracts of the EU, the ERANET Program and funding from the Autonomous Community of Madrid (PROMPT).Peer reviewe

Wave function mapping conditions in Open Quantum Dots structures

We discuss the minimal conditions for wave function spectroscopy, in which resonant tunneling is the measurement tool. Two systems are addressed: resonant tunneling diodes, as a toy model, and open quantum dots. The toy model is used to analyze the crucial tunning between the necessary resolution in current-voltage characteristics and the breakdown of the wave functions probing potentials into a level splitting characteristic of double quantum wells. The present results establish a parameter region where the wavefunction spectroscopy by resonant tunneling could be achieved. In the case of open quantum dots, a breakdown of the mapping condition is related to a change into a double quantum dot structure induced by the local probing potential. The analogy between the toy model and open quantum dots show that a precise control over shape and extention of the potential probes is irrelevant for wave function mapping. Moreover, the present system is a realization of a tunable Fano system in the wave function mapping regime.Comment: 6 pages, 6 figure

Static correction of Maude programs with assertions

[Otros] In this paper, we present a novel transformation method for Maude programs featuring both automatic program diagnosis and correction. The input of our method is a reference specification of the program behavior that is given in the form of assertions together with an overly general program whose execution might violate the assertions. Our correction technique translates into a refined program in which every computation is also a computation in that satisfies the assertions of . The technique is first formalized for topmost rewrite theories, and then we generalize it to larger classes of rewrite theories that support nested structured configurations. Our technique copes with infinite space states and does not require the knowledge of any failing run. We report experiments that assess the effectiveness of assertion-driven correction.This work has been partially supported by the EU (FEDER) and the Spanish Ministerio de Economia y Competitividad under grant TIN2015-69175-C4-1-R, and by Generalitat Valenciana PROMETEOII/2015/013 and PROMETEO/2019/098Alpuente Frasnedo, M.; Ballis, D.; Sapiña-Sanchis, J. (2019). Static correction of Maude programs with assertions. Journal of Systems and Software. 153:64-85. https://doi.org/10.1016/j.jss.2019.03.061S648515

Carbon nanotube, graphene, nanowire, and molecule-based electron and spin transport phenomena using the non-equilibrium Green function method at the level of first principles theory

Based on density functional theory (DFT), we have developed algorithms and a program code to investigate the electron transport characteristics for a variety of nanometer scaled devices in the presence of an external bias voltage. We employed basis sets comprised of linear combinations of numerical type atomic orbitals and k-point sampling for the realistic modeling of the bulk electrode. The scheme coupled with the matrix version of the non-equilibrium Green function method enables determination of the transmission coefficients at a given energy and voltage in a self-consistent manner, as well as the corresponding current-voltage (I-V) characteristics. This scheme has advantages because it is applicable to large systems, easily transportable to different types of quantum chemistry packages, and extendable to describe time-dependent phenomena or inelastic scatterings. It has been applied to diverse types of practical electronic devices such as carbon nanotubes, graphene nano-ribbons, metallic nanowires, and molecular electronic devices. The quantum conductance phenomena for systems involving quantum point contacts and I-V curves are described for the dithiol-benzene molecule in contact with two Au electrodes using the k-point sampling method.Comment: 20 pages, 14 figures. submitte