Findings from an in-depth annual tree-ring radiocarbon intercomparison

The radiocarbon (¹⁴C) calibration curve so far contains annually resolved data only for a short period of time. With accelerator mass spectrometry (AMS) matching the precision of decay counting, it is now possible to efficiently produce large datasets of annual resolution for calibration purposes using small amounts of wood. The radiocarbon intercomparison on single-year tree-ring samples presented here is the first to investigate specifically possible offsets between AMS laboratories at high precision. The results show that AMS laboratories are capable of measuring samples of Holocene age with an accuracy and precision that is comparable or even goes beyond what is possible with decay counting, even though they require a thousand times less wood. It also shows that not all AMS laboratories always produce results that are consistent with their stated uncertainties. The long-term benefits of studies of this kind are more accurate radiocarbon measurements with, in the future, better quantified uncertainties

A Measurement of the Proton Structure Function F ⁣2(x,Q2)F_{\!2}(x,Q^2)

A measurement of the proton structure function $F_{\!2}(x,Q^2)$ is reported for momentum transfer squared $Q^2$ between 4.5 $GeV^2$ and 1600 $GeV^2$ and for Bjorken $x$ between $1.8\cdot10^{-4}$ and 0.13 using data collected by the HERA experiment H1 in 1993. It is observed that $F_{\!2}$ increases significantly with decreasing $x$, confirming our previous measurement made with one tenth of the data available in this analysis. The $Q^2$ dependence is approximately logarithmic over the full kinematic range covered. The subsample of deep inelastic events with a large pseudo-rapidity gap in the hadronic energy flow close to the proton remnant is used to measure the "diffractive" contribution to $F_{\!2}$.Comment: 32 pages, ps, appended as compressed, uuencoded fil

Efficient method for transport simulations in quantum cascade lasers

An efficient method for simulating quantum transport in quantum cascade lasers is presented. The calculations are performed within a simple approximation inspired by Büttiker probes and based on a finite model for semiconductor superlattices. The formalism of non-equilibrium Green’s functions is applied to determine the selected transport parameters in a typical structure of a terahertz laser. Results were compared with those obtained for a infinite model as well as other methods described in literature

Discussão teórica sobre o conceito de perdas do Sistema Toyota de Produção: inserindo a lógica do ganho da Teoria das Restrições Theoretical discussion of the concept of wastes in the Toyota Production System: introducing the throughput logic of the Theory of Constraints

Este estudo apresenta uma reflexão teórica a respeito dos possíveis impactos nos indicadores da Teoria das Restrições (TOC) provocados pelas Sete Perdas abordadas no Sistema Toyota de Produção (STP) e por um tipo de perda não relatada neste contexto. Trata-se da 'Perda por má definição do mix de produtos' influenciada pelo uso de métodos inadequados para formular o mix de produtos. Desta forma é construído um neologismo conceitual identificado como as 'Pergas' para demostrar as perdas de Ganho global (TOC), derivadas desta prática. A necessidade de combater as perdas nos processos deve-se a não agregação de valor ao produto, bem como a geração de custos, motivando, em algumas situações, o compromentimento à competitividade da organização. Em sentido similar, o combate às Pergas proporciona um incremento nos índices monitorados pelos indicadores Globais da TOC por meio da constiuição de um mix de produtos que contribua com a meta da empresa. Um referencial estrutural é desenvolvido relacionando as Sete Perdas abordadas no STP e os indicadores da TOC, o qual fornecerá subsídios para fundamentar as relações impactantes e possibilitará a proposição de ações de melhoria tendo por objetivo minimizar os impactos apresentados.<br>This study presents a theoretical reflection about the possible impacts on of the Theory of Constraints (TOC) indicators caused by the Seven Wastes in the Toyota Production System (TPS) and a type of waste which is not included in that context. It refers to the 'waste due to unsatisfactory definition of product mix' influenced by the use of inappropriate methods to formulate the product mix. Therefore, a conceptual neologism is introduced, identified as the "Pergas" to demonstrate the overall gain waste derived from this practice. The need to reduce process waste is due to the fact that no value is added to the product and the cost increase putting at risk, in some situations, the organizational competitiveness. Similarly, the fight against "Pergas" leads to an increase in the indexes monitored by the Global indicators of TOC, through the creation of a mix of products that contributes to the company's goal. A structural framework was developed relating the seven Wastes addressed in the TPS and TOC indicators, which will provide subsidies to support the relations that cause impacts and will enable the proposal of improvement actions focusing on reducing the impacts presented