Digestão anaeróbia de resíduos sólidos

A digestão anaeróbia de resíduos sólidos é um processo biológico de reciclagem através do qual a matéria orgânica é convertida em metano e dióxido de carbono na ausência de oxigénio. Nos últimos 25 anos, assistiu‐se a avanços no desenvolvimento desta tecnologia aplicada a resíduos sólidos urbanos, apesar de esta tecnologia já se encontrar implementada na Europa, onde se pode contabilizar mais de 50 unidades, que tratam cerca de 1 milhão de toneladas de resíduos/ano, situando‐se a maior parte das instalações na Alemanha. No entanto, em países como Portugal não existe ainda nenhuma estação de tratamento deste tipo. Estes dados indicam que se deve fazer um esforço e investir em investigação para se observar um aumento da implementação desta tecnologia na Europa. O resíduo proveniente das cozinhas é tipicamente um resíduo orgânico biodegradável, que é essencialmente constituído por proteína, celulose, amido e gordura. Numa primeira etapa deste projecto de investigação avaliou‐se qual a influência de cada um dos referidos componentes no processo de digestão anaeróbia, assim como a influência do teor de sólidos presente e ainda qual a importância da razão resíduo/inóculo. Foram realizados ensaios em descontínuo com um resíduo sintético e outro real, com diferentes concentrações de sólidos (entre 1.8 e 24%) e diferentes razões de resíduo/inóculo (entre 0.2 e 30 gSV/gSV). Comparou‐se a taxa de metanização e a produção cumulativa de metano para diferentes misturas de proteína, celulose, amido e gordura. Estas experiências indicaram que a quantidade de gordura limita a biodegradabilidade do resíduo, bem como a taxa de metano produzida. A razão resíduo/inóculo é um parâmetro crítico especialmente para um teor de sólidos superior a 5% pois a taxa de produção de metano aumenta com a diminuição da razão resíduo/inóculo de 1.35 gSV/gSV para 0.2 gSV/gSV. A comparação do resíduo real com o resíduo sintético demonstrou que, embora a taxa de produção de metano seja idêntica, a biometanização é superior para o resíduo real

Neel order in the two-dimensional S=1/2 Heisenberg Model

The existence of Neel order in the S=1/2 Heisenberg model on the square lattice at T=0 is shown using inequalities set up by Kennedy, Lieb and Shastry in combination with high precision Quantum Monte Carlo data.Comment: 4 pages, 1 figur

BP Reduction, Kidney Function Decline, and Cardiovascular Events in Patients without CKD.

BACKGROUND AND OBJECTIVES: In the Systolic Blood Pressure Intervention Trial (SPRINT), intensive systolic BP treatment (target <120 mm Hg) was associated with fewer cardiovascular events and higher incidence of kidney function decline compared with standard treatment (target <140 mm Hg). We evaluated the association between mean arterial pressure reduction, kidney function decline, and cardiovascular events in patients without CKD. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We categorized patients in the intensive treatment group of the SPRINT according to mean arterial pressure reduction throughout follow-up: <20, 20 to <40, and ≥40 mm Hg. We defined the primary outcome as kidney function decline (≥30% reduction in eGFR to <60 ml/min per 1.73 m2 on two consecutive determinations at 3-month intervals), and we defined the secondary outcome as cardiovascular events. In a propensity score analysis, patients in each mean arterial pressure reduction category from the intensive treatment group were matched with patients from the standard treatment group to calculate the number needed to treat regarding cardiovascular events and the number needed to harm regarding kidney function decline. RESULTS: In the intensive treatment group, 1138 (34%) patients attained mean arterial pressure reduction <20 mm Hg, 1857 (56%) attained 20 to <40 mm Hg, and 309 (9%) attained ≥40 mm Hg. Adjusted hazard ratios for kidney function decline were 2.10 (95% confidence interval, 1.22 to 3.59) for mean arterial pressure reduction between 20 and 40 mm Hg and 6.22 (95% confidence interval, 2.75 to 14.08) for mean arterial pressure reduction ≥40 mm Hg. In propensity score analysis, mean arterial pressure reduction <20 mm Hg presented a number needed to treat of 44 and a number needed to harm of 65, reduction between 20 and <40 mm Hg presented a number needed to treat of 42 and a number needed to harm of 35, and reduction ≥40 mm Hg presented a number needed to treat of 95 and a number needed to harm of 16. CONCLUSIONS: In the intensive treatment group of SPRINT, larger declines in mean arterial pressure were associated with higher incidence of kidney function decline. Intensive treatment seemed to be less favorable when a larger reduction in mean arterial pressure was needed to attain the BP target.info:eu-repo/semantics/publishedVersio

Optimized generation of spatial qudits by using a pure phase spatial light modulator

We present a method for preparing arbitrary pure states of spatial qudits, namely, D-dimensional (D > 2) quantum systems carrying information in the transverse momentum and position of single photons. For this purpose, a set of D slits with complex transmission are displayed on a spatial light modulator (SLM). In a recent work we have shown a method that requires a single phase-only SLM to control independently the complex coefficients which define the quantum state of dimension D. The amplitude information was codified by introducing phase gratings inside each slit and the phase value of the complex transmission was added to the phase gratings. After a spatial filtering process we obtained in the image plane the desired qudit state. Although this method has proven to be a good alternative to compact the previously reported architectures, it presents some features that could be improved. In this paper we present an alternative scheme to codify the required phase values that minimizes the effects of temporal phase fluctuations associated to the SLM where the codification is carried on. In this scheme the amplitudes are set by appropriate phase gratings addressed at the SLM while the relative phases are obtained by a lateral displacement of these phase gratings. We show that this method improves the quality of the prepared state and provides very high fidelities of preparation for any state. An additional advantage of this scheme is that a complete 2\pi modulation is obtained by shifting the grating by one period, and hence the encoding is not limited by the phase modulation range achieved by the SLM. Numerical simulations, that take into account the phase fluctuations, show high fidelities for thousands of qubit states covering the whole Bloch sphere surface. Similar analysis are performed for qudits with D = 3 and D = 7.Comment: 12 pages, 7 figure