\emph{Ab initio} theory of N2V\text{N}_{2}\text{V} defect as quantum memory in diamond

$\text{N}_{2}\text{V}$ defect in diamond is characterized by means of \emph{ab initio} methods relying on density functional theory calculated parameters of a Hubbard model Hamiltonian. It is shown that this approach appropriately describes the energy levels of correlated excited states induced by this defect. By determining its critical magneto-optical parameters, we propose to realize a long-living quantum memory by $\text{N}_{2}\text{V}$ defect in diamond.Comment: 4 figures and 5 table

A Harris-type van der Waals density functional scheme

Large biomolecular systems, whose function may involve thousands of atoms, cannot easily be addressed with parameter-free density functional theory (DFT) calculations. Until recently a central problem was that such systems possess an inherent sparseness, that is, they are formed from components that are mutually separated by low-electron-density regions where dispersive forces contribute significantly to the cohesion and behavior. The introduction of, for example, the van der Waals density functional (vdW-DF) method [PRL 92, 246401 (2004)] has addressed part of this sparse-matter system challenge. However, while a vdW-DF study is often as computationally efficient as a study performed in the generalized gradient approximation, the scope of large-sparse-matter DFT is still limited by computer time and memory. It is costly to self-consistently determine the electron wavefunctions and hence the kinetic-energy repulsion. In this paper we propose and evaluate an adaption of the Harris scheme [PRB 31, 1770 (1985)]. This is done to speed up non-selfconsistent vdW-DF studies of molecular-system interaction energies. Also, the Harris-type analysis establishes a formal link between dispersion-interaction effects on the effective potential for electron dynamics and the impact of including selfconsistency in vdW-DF calculations [PRB 76, 125112 (2007)].Comment: 15 page

Vanadium pentoxide (V2O5): a van der Waals density functional study

The past few years has brought renewed focus on the physics behind the class of materials characterized by long-range interactions and wide regions of low electron density, sparse matter. There is now much work on developing the appropriate algorithms and codes able to correctly describe this class of materials within a parameter-free quantum physical description. In particular, van der Waals (vdW) forces play a major role in building up material cohesion in sparse matter. This work presents an application to the vanadium pentoxide (V2O5) bulk structure of two versions of the vdW-DF method, a first-principles procedure for the inclusion of vdW interactions in the context of density functional theory (DFT). In addition to showing improvement compared to traditional semilocal calculations of DFT, we discuss the choice of various exchange functionals and point out issues that may arise when treating systems with large amounts of vacuum.Comment: 5 pages, 4 figures, 1 tabl

Strongly inhomogeneous distribution of spectral properties of silicon-vacancy color centers in nanodiamonds

The silicon-vacancy (SiV) color center in diamond is a solid-state single photon emitter and spin quantum bit suited as a component in quantum devices. Here, we show that the SiV center in nanodiamond exhibits a strongly inhomogeneous distribution with regard to the center wavelengths and linewidths of the zero-phonon-line (ZPL) emission at room temperature. We find that the SiV centers separate in two clusters: one group exhibits ZPLs with center wavelengths within a narrow range of approximatly 730 nm to 742 nm and broad linewidths between 5 nm and 17 nm, whereas the second group comprises a very broad distribution of center wavelengths between 715 nm and 835 nm, but narrow linewidths from below 1 nm up to 4 nm. Supported by ab initio Kohn-Sham density functional theory calculations we show that the ZPL shifts of the first group are consistently explained by strain in the diamond lattice. Further, we suggest, that the second group showing the strongly inhomogeneous distribution of center wavelengths might be comprised of modified SiV centers. Whereas single photon emission is demonstrated for SiV centers of both clusters, we show that emitters from different clusters show different spectroscopic features such as variations of the phonon sideband spectra and different blinking dynamics

A construção da imagem técnica no jogo da publicidade

Este artigo busca apontar as contribuições de Vilém Flusser para os estudos da publicidade. Para isso recorre à noção de imagem técnica para propor uma reflexão sobre o processo de concepção das imagens publicitárias, bem como aos conceitos de aparelho, programação e jogo para pensarmos a dinâmica deste processo e o contexto em que essas imagens são produzidas. A partir da perspectiva que Flusser oferece sobre o trabalho na era pós-industrial, é necessário pensar o publicitário alinhado à uma nova categoria: os “jogadores”; e como, por meio do conceito de jogo, é possível considerar novas conjecturas do trabalho criativo no ambiente publicitário

Sob nova direção? A publicidade na era da programação e o publicitário deslocado // Under new management? The advertising in the programming era and the advertiser outsider

Este artigo propõe uma discussão sobre o ato de protesto simbólico dos funcionários da agência Leo Burnett de Chicago em que os funcionários cobriram o nome do seu fundador na fachada do prédio da agência com uma folha de papel onde lia-se “Marcel”. O protesto ocorreu após a proibição da participação da agência em premiações e festivais do setor, em favorecimento dos investimentos destinados à implantação da plataforma de inteligência artificial Marcel. Ao analisar a atitude dos publicitários da agência sob o viés da teoria crítica, é possível observar que as agências já vêm passando por um processo de automatização desde a década de 1970 e que essa medida apenas consolida um cenário que favorece a cultura da eficácia e o enfraquecimento da criatividade nos processos, cenário este que grande parte dos publicitários endossou até o presente momento. A própria agência Leo Burnett destaca-se nesse cenário com a sistematização da sua plataforma de trabalho através dos métodos de avaliação intitulado de GPC

Desorption of n-alkanes from graphene: a van der Waals density functional study

A recent study of temperature programmed desorption (TPD) measurements of small n-alkanes (CNH2N+2) from C(0001) deposited on Pt(111) shows a linear relationship of the desorption energy with increasing n-alkane chain length. We here present a van der Waals density functional study of the desorption barrier energy of the ten smallest n-alkanes (N = 1 to 10) from graphene. We find linear scaling with N, including a nonzero intercept with the energy axis, i.e., an offset at the extrapolation to N = 0. This calculated offset is quantitatively similar to the results of the TPD measurements. From further calculations of the polyethylene polymer we offer a suggestion for the origin of the offset.Comment: 3 pictures, 1 tabl

Cytoreductive Surgery and Hyperthermic Intrathoracic Chemotherapy by Video-Assisted Surgery for Pleural Malignancies: Technical Aspects and Safety Profile

Background: Pleural malignancies are challenging conditions in terms of possibility of cure. Recent growing interest towards Hyperthermic Intrathoracic Chemotherapy (HITHOC) after Cytoreductive Surgery (CRS) has been referred. Minimally invasive approach (VATS) may be suggest in this context but evidence is still lacking. Methods: A preliminary experience in seven patients submitted to cytoreductive surgery and HITHOC is described, with a focus on technical aspects related to VATS approach, operating median time and postoperative complication. Results: A triportal VATS approach has been employed in all cases. Median time of surgery including pleural perfusion was 200 min (range 165 to 370). Mean blood loss was 217 cc (range 100 and 600). Thirty days mortality was nothing. Conclusion: VATS cytoreductive surgery and HITHOC is a safe procedure and could be proposed in the setting of a multimodality strategy employing adjuvant radio-chemotherapy in referral centers