The center of mass and center of charge of the electron

9th Biennial Conference on Classical and Quantum Relativistic Dynamics of Particles and Fields (IARD)

Avaliação da percepção da dor no tratamento ortodôntico: ensaio clínico randomizado

O objetivo deste trabalho foi avaliar através de questionários de escalas visuais analógicas a percepção da dor após a inserção do primeiro arco ortodôntico, comparando-se o efeito analgésico de ibuprofeno, acetaminofeno, placebo e goma de mascar. Este trabalho também partiu da hipótese de que ibuprofeno, acetaminofeno e gomas de mascar seriam mais eficazes que placebo no controle da dor de origem ortodôntica e que gomas de mascar poderiam ser uma alternativa ao uso de ibuprofeno e acetaminofeno no manejo da dor dentária de origem ortodôntica. Neste estudo, tomaram parte 41 pacientes da Clínica de Ortodontia da Faculdade de Odontologia da Universidade do Estado do Rio de Janeiro. Os pacientes foram aleatoriamente distribuídos em cinco diferentes grupos: placebo, acetaminofeno 500 miligramas, ibuprofeno 400 miligramas, goma de mascar e controle. Todos os indivíduos tiveram bráquetes com slots .022" colados em seus dentes e molares bandados em uma das arcadas. Os grupos placebo, ibuprofeno e acetaminofeno foram orientados a tomar 01 cápsula do respectivo composto logo após a inserção do arco inicial de liga de níquel-titânio de dimensão .014 e, se a dor persistisse, a cada 6 horas por uma semana.O grupo goma de mascar foi orientado a mascar um tablete de goma por 5 minutos imediatamente após a inserção do arco inicial de liga de níquel-titânio de dimensão .014 e a cada 6 horas por 5 minutos durante uma semana, caso a dor persistisse. O grupo controle recebeu nenhum método de controle da dor. Os indivíduos foram orientados a marcar nas escalas visuais analógicas nas primeiras 24 horas, às 09:00, 13:00, 17:00, 21:00 a percepção de dor espontânea e durante a mastigação. Do terceiro até o vigésimo primeiro dia as marcações foram feitas somente em dois tempos às 09:00 e 21:00. Através da análise estatística descritiva, concluiu-se que o placebo foi mais eficiente que ibuprofeno, acetaminofeno e goma de mascar no controle da dor ortodôntica, tanto em dor espontânea quanto em dor durante a mastigação. O grupo goma de mascar foi tão eficiente quanto o acetaminofeno no controle da dor espontânea 24 horas após a inserção do arco inicial. Para alívio da dor durante a mastigação, a goma de mascar pode ser uma alternativa à atuação medicamentosa no controle da dor ortodôntica.

Citotécnico: análise do processo de trabalho em laboratórios de citopatologia e anatomopatologia no Estado do Rio de Janeiro.

Trata-se de um estudo sobre o processo de trabalho dos citotécnicos que atuam em laboratórios de Anatomopatologia e Citopatologia no Estado do Rio de Janeiro, cujo objetivo geral é: analisar a percepção dos citotécnicos sobre as competências necessárias à execução de sua atividade laboral; e específicos: (1) descrever a atividade laboral do citotécnico; (2) identificar o modo de produção da atividade por meio das inter-relações de trabalho; (3) conhecer e compreender as implicações do trabalho do citotécnico nas ações de controle do câncer. A investigação foi de abordagem qualitativa, de natureza descritiva e social, realizada em três laboratórios de Anatomopatologia e Citopatologia no Estado do Rio de Janeiro, com a participação de 33 citotécnicos. Os dados foram obtidos pela técnica de entrevista semiestruturada, aplicação de questionário, e grupo focal, no período de janeiro a agosto de 2014, e analisados com base na Análise de Conteúdo de Bardin, tendo como unidade de registro o tema. Os resultados revelaram: dos 33 citotécnicos, 73% são do sexo feminino; 34% estão distribuídos em igual percentual para as faixas etárias entre 41 a 50 anos e 51 a 60 anos. Com relação à variável do grau de escolaridade, 43% possuem especialização e 24% concluíram o curso superior. Em relação ao cargo exercido, 73% atuam como citotécnicos e 70% são funcionários públicos. O trabalho do citotécnico tem especificidade única desse trabalhador de nível técnico, que é a realização da primeira análise do exame citopatológico, com ações articuladas e complementares de natureza técnica, de gestão, e educativas vinculadas à equipe, com ênfase nos princípios de prevenção e promoção da saúde. Por meio da escala de avaliação do contexto de trabalho, foram avaliadas as condições físicas, materiais e organizacionais do processo de trabalho. O quesito clareza, na definição das tarefas, foi o maior valorado com 4,7% de média, seguido das relações socioprofissionais com média de 4,0%. Os resultados da análise de conteúdo revelaram: na trajetória da atividade laboral, emergiram quatro categorias associadas à motivação e ao ingresso na ocupação por pessoas de referência na formação, acesso ao mercado de trabalho, busca pelo aperfeiçoamento profissional e aprendizagem prática no trabalho; no conceito de modo de produção, emergiram cinco categorias: responsabilidade de salvar vidas, crítica em relação ao próprio trabalho com qualidade, características físicas, atividades distintas do citotécnico e do histotécnico, visão do trabalho com otimismo; nas condições de trabalho, emergiram quatro categorias: trabalho em equipe e responsabilidade individual, ambiguidade em relação à autonomia, precarização do trabalho, esperança no reconhecimento da profissão. O trabalho do citotécnico é uma ocupação fracamente regulamentada, que se caracteriza por ausência de perfil profissional específico compatível com o escopo de prática real observada no trabalho levando a condições de trabalho precário. O reconhecimento ocorre entre os próprios trabalhadores que se valorizam por serem responsáveis pela promoção da saúde tornando seu trabalho socialmente útil.

Átomos hidrogenoides em espaços com dimensionalidade D6=3: os casos não relativístico e relativístico

A possibilidade da existência de átomos de hidrogênio estáveis em dimensões superiores a três é abordada. O problema da dimensionalidade é visto como um problema de Física, no qual relacionam-se algumas leis físicas com a dimensão espacial. A base da análise deste trabalho faz uso das equações de Schrödinger (não relativística) e de Dirac (relativística). Nos dois casos, utiliza-se a generalização tanto do setor cinemático bem como o setor de interação coulombiana para variar o parâmetro topológico dimensão. Para o caso não relativístico, os auto-valores de energia e as auto-funções são obtidas através do método numérico de Numerov. Embora existam soluções em espaços com dimensões superiores, os resultados obtidos no presente trabalho indicam que a natureza deve, de alguma maneira, se manifestar em um espaço tridimensional.

Broadband ultrafast pulse generation with double wall carbon nanotubes

Materials with nonlinear optical properties are much sought after for ultrafast photonic applications. Mode-locked lasers can generate ultrafast pulses using saturable absorbers[1]. Currently, the dominant technology is based on semiconductor saturable absorber mirrors (SESAMs). However, narrow tuning range (tens of nm), complex fabrication and packaging limit their applications[2]. Single wall nanotubes (SWNTs) and graphene offer simpler and cost-effective solutions[1]. Broadband operation can be achieved in SWNTs using a distribution of tube diameters[1,3], or by using graphene[4-8], due to the gapless linear dispersion of Dirac electrons[8,9]. © 2011 IEEE.

Non-linear photoluminescence from graphene

Graphene is in the focus of research due to its unique electronic and optical properties. Intrinsic graphene is a zero gap semiconductor with a linear dispersion relation for E-k leading to zero-effective-mass electrons and holes described by Fermi-Dirac theory. Since pristine graphene has no bandgap no photoluminescence would be expected. However, recently several groups showed non-linear photoluminescence from pristine graphene putting forward different physical models explaining this remarkable effect [1-3]. © 2011 IEEE.

Wideband tunable, high-power, graphene mode-locked ultrafast lasers

Ultrafast passively mode-locked lasers with spectral tuning capability and high output power have widespread applications in biomedical research, spectroscopy and telecommunications [1,2]. Currently, the dominant technology is based on semiconductor saturable absorber mirrors (SESAMs) [2,3]. However, these typically have a narrow tuning range, and require complex fabrication and packaging [2,3]. A simple, cost-effective alternative is to use Single Wall Carbon Nanotubes (SWNTs) [4,10] and Graphene [10,14]. Wide-band operation is possible using SWNTs with a wide diameter distribution [5,10]. However, SWNTs not in resonance are not used and may contribute to unwanted insertion losses [10]. The linear dispersion of the Dirac electrons in graphene offers an ideal solution for wideband ultrafast pulse generation [10,15]. © 2011 IEEE.

India's foreign exchange earners

India's export earnings from fishery products have touched an all-time record of Rs. 33.07 crores in 1969. The most important items which have contributed to this are processed prawn products, frozen lobster tails and frozen frog legs. Even though frogs are not of marine origin, they are processed and exported along with marine products so that for all practical purposes they are reckoned as seafood. Naturally, it is sure to be of absorbing interest to the processors and technological research workers as well as to the general public to know how many varieties/species of these occur in our country and also the localities where they are available. The following is an exhaustive list of the different species of prawns, lobsters and frogs that are found in our country, together with vernacular names wherever available, parts of India where they occur and the largest size (length) to which they grow. The figures in brackets on the left side show the progressive total. The different genera have been arranged in the order of their commercial importance and not according to any scientific principles.

The shear mode of multilayer graphene

The quest for materials capable of realizing the next generation of electronic and photonic devices continues to fuel research on the electronic, optical and vibrational properties of graphene. Few-layer graphene (FLG) flakes with less than ten layers each show a distinctive band structure. Thus, there is an increasing interest in the physics and applications of FLGs. Raman spectroscopy is one of the most useful and versatile tools to probe graphene samples. Here, we uncover the interlayer shear mode of FLGs, ranging from bilayer graphene (BLG) to bulk graphite, and suggest that the corresponding Raman peak measures the interlayer coupling. This peak scales from ∼43cm -1 in bulk graphite to ∼31cm -1 in BLG. Its low energy makes it sensitive to near-Dirac point quasiparticles. Similar shear modes are expected in all layered materials, providing a direct probe of interlayer interactions. © 2012 Macmillan Publishers Limited. All rights reserved.

Positive Correlations in Tunneling through coupled Quantum Dots

Due to the Fermi-Dirac statistics of electrons the temporal correlations of tunneling events in a double barrier setup are typically negative. Here, we investigate the shot noise behavior of a system of two capacitively coupled quantum dot states by means of a Master equation model. In an asymmetric setup positive correlations in the tunneling current can arise due to the bunching of tunneling events. The underlying mechanism will be discussed in detail in terms of the current-current correlation function and the frequency-dependent Fano factor.

Extreme sensitivity of graphene photoconductivity to environmental gases.

Graphene is a single layer of covalently bonded carbon atoms, which was discovered only 8 years ago and yet has already attracted intense research and commercial interest. Initial research focused on its remarkable electronic properties, such as the observation of massless Dirac fermions and the half-integer quantum Hall effect. Now graphene is finding application in touch-screen displays, as channels in high-frequency transistors and in graphene-based integrated circuits. The potential for using the unique properties of graphene in terahertz-frequency electronics is particularly exciting; however, initial experiments probing the terahertz-frequency response of graphene are only just emerging. Here we show that the photoconductivity of graphene at terahertz frequencies is dramatically altered by the adsorption of atmospheric gases, such as nitrogen and oxygen. Furthermore, we observe the signature of terahertz stimulated emission from gas-adsorbed graphene. Our findings highlight the importance of environmental conditions on the design and fabrication of high-speed, graphene-based devices.

Ultrafast collinear scattering and carrier multiplication in graphene.

Graphene is emerging as a viable alternative to conventional optoelectronic, plasmonic and nanophotonic materials. The interaction of light with charge carriers creates an out-of-equilibrium distribution, which relaxes on an ultrafast timescale to a hot Fermi-Dirac distribution, that subsequently cools emitting phonons. Although the slower relaxation mechanisms have been extensively investigated, the initial stages still pose a challenge. Experimentally, they defy the resolution of most pump-probe setups, due to the extremely fast sub-100 fs carrier dynamics. Theoretically, massless Dirac fermions represent a novel many-body problem, fundamentally different from Schrödinger fermions. Here we combine pump-probe spectroscopy with a microscopic theory to investigate electron-electron interactions during the early stages of relaxation. We identify the mechanisms controlling the ultrafast dynamics, in particular the role of collinear scattering. This gives rise to Auger processes, including charge multiplication, which is key in photovoltage generation and photodetectors.

Nonequilibrium dynamics of photoexcited electrons in graphene: Collinear scattering, Auger processes, and the impact of screening

We present a combined analytical and numerical study of the early stages (sub-100-fs) of the nonequilibrium dynamics of photoexcited electrons in graphene. We employ the semiclassical Boltzmann equation with a collision integral that includes contributions from electron-electron (e-e) and electron-optical phonon interactions. Taking advantage of circular symmetry and employing the massless Dirac fermion (MDF) Hamiltonian, we are able to perform an essentially analytical study of the e-e contribution to the collision integral. This allows us to take particular care of subtle collinear scattering processes - processes in which incoming and outgoing momenta of the scattering particles lie on the same line - including carrier multiplication (CM) and Auger recombination (AR). These processes have a vanishing phase space for two-dimensional MDF bare bands. However, we argue that electron-lifetime effects, seen in experiments based on angle-resolved photoemission spectroscopy, provide a natural pathway to regularize this pathology, yielding a finite contribution due to CM and AR to the Coulomb collision integral. Finally, we discuss in detail the role of physics beyond the Fermi golden rule by including screening in the matrix element of the Coulomb interaction at the level of the random phase approximation (RPA), focusing in particular on the consequences of various approximations including static RPA screening, which maximizes the impact of CM and AR processes, and dynamical RPA screening, which completely suppresses them. © 2013 American Physical Society.

Static analysis of Euler-Bernoulli beams with multiple unilateral cracks under combined axial and transverse loads

The paper deals with the static analysis of pre-damaged Euler-Bernoulli beams with any number of unilateral cracks and subjected to tensile or compression forces combined with arbitrary transverse loads. The mathematical representation of cracks with a bilateral behaviour (i.e. always open) via Dirac delta functions is extended by introducing a convenient switching variable, which allows each crack to be open or closed depending on the sign of the axial strain at the crack centre. The proposed model leads to analytical solutions, which depend on four integration constants (to be computed by enforcing the boundary conditions) along with the Boolean switching variables associated with the cracks (whose role is to turn on and off the additional flexibility due to the presence of the cracks). An efficient computational procedure is also presented and numerically validated. For this purpose, the proposed approach is applied to two pre-damaged beams, with different damage and loading conditions, and the results so obtained are compared against those given by a standard finite element code (in which the correct opening of the cracks is pre-assigned), always showing a perfect agreement. © 2013 Elsevier Ltd. All rights reserved.

Graphene modelocked VECSELs

In the past decade, passively modelocked optically pumped vertical external cavity surface emitting lasers (OPVECSELs), sometimes referred to as semiconductor disk lasers (OP-SDLs), impressively demonstrated the potential for generating femtosecond pulses at multi-Watt average output powers with gigahertz repetition rates. Passive modelocking with a semiconductor saturable absorber mirror (SESAM) is well established and offers many advantages such as a flexible design of the parameters and low non-saturable losses. Recently, graphene has emerged as an attractive wavelength-independent alternative saturable absorber for passive modelocking in various lasers such as fiber or solid-state bulk lasers because of its unique optical properties. Here, we present and discuss the modelocked VECSELs using graphene saturable absorbers. The broadband absorption due to the linear dispersion of the Dirac electrons in graphene makes this absorber interesting for wavelength tunable ultrafast VECSELs. Such widely tunable modelocked sources are in particularly interesting for bio-medical imaging applications. We present a straightforward approach to design the optical properties of single layer graphene saturable absorber mirrors (GSAMs) suitable for passive modelocking of VECSELs. We demonstrate sub-500 fs pulses from a GSAM modelocked VECSEL. The potential for broadband wavelength tuning is confirmed by covering 46 nm in modelocked operation using three different VECSEL chips and up to 21 nm tuning in pulsed operation is achieved with one single gain chip. A linear and nonlinear optical characterization of different GSAMs with different absorption properties is discussed and can be compared to SESAMs. © 2014 SPIE.