Forest vintages and carbon sequestration

In the current paper we examine the role of forest carbon sequestration benefits in optimal forest management. When carbon benefits are considered not only the forested area is relevant, but also the flow of carbon between land and the atmosphere through the carbon cycle. To account for all these impacts a multi-vintage forest setting is used, following Salo and Tahvonen (2004). The model is extended to three different carbon accounting methods to measure the benefits form carbon sequestration: carbon flow regime, tonne-year crediting and average storage. In the case of the carbon flow regime, the impact on the optimal management and allocation of land will depend upon the amount of carbon released when the forest is harvested. Under the other two accounting systems optimal steady state forest area will be increased, and in cases where optimal management imply cyclical harvesting, considering carbon benefits will always increase cycles dimension.

The Hyperbolic Forest Owner

This paper examines the implications of quasi-hyperbolic inter-temporal preferences to the Faustman model. The use of decreasing discount rates leads to dynamically inconsistent behavior. To solve this problem a two-stages optimization decision model is developed. The resulting actual cutting time will be anticipated compared to the Faustman optimal cutting time. If, alternatively, the equivalent constant rate of discount is the empirically observed discount rate, then the optimal cutting time is the same, but the present value of profits for the hyperbolic forest owner is always higher than the one resulting from the equivalent constant discount rate. All these results apply to both the single and the multiple rotation problems.Hyperbolic discounting; time preference; dynamic inconsistency; Faustman model; optimal rotation

Effect of liquid-phase surface tension on hydrodynamics of a three-phase airlift reactor with an enlarged degassing zone

The effect of the addition of ethanol (10 g/l) to the liquid-phase on gas and solids holdup, circulation and mixing times and interstitial liquid velocity in a threephase airlift reactor was investigated. The airlift reactor (60 l) is of the concentric draught-tube type with an enlarged degassing zone. Ca-alginate beads were used as solid-phase and airflow rate (from 1.9 to 90.2 l/min) and solids loading (0-30% (v/v)) were manipulated. Riser and downcomer gas holdup were found to increase with the addition of ethanol, leading to a decrease on the relative solids holdup. The presence of ethanol seems to have no influence on the circulation time. On the other hand, mixing time variation depends on the solids loading and airflow rate. Riser and downcomer interstitial liquid velocity are lower for ethanol solution than for water.Junta Nacional de Investigação Científica e Tecnológica (JNICT) - PRAXIS/2/2.1/ BIO/1061/95 , grant GGP XXI/BD/2937/96

Hydrodynamic studies in an airlift reactor with an enlarged degassing zone

The hydrodynamic behaviour of a 60 l threephase airlift bioreactor, of the concentric draught tube type, with an enlarged degassing zone has been studied. Ca-alginate beads were used as the solid phase. Airflow rate (from 1.9 to 90.2 l/min), solids loading (0% to 40% (v/v)) and solids density (1016 and 1038 kg/m³) were manipulated and their influence on solids and gas holdup, circulation and mixing times and in the interstitial liquid velocity was determined. Riser and downcomer solids holdup was found to decrease with the increase of airflow rate and to increase with solids loading and density. On the contrary, gas holdup in the riser and in the downcomer increased with airflow rate and decreased with solids loading and density. By increasing airflow rate, a decrease in circulation time was observed while the effects of solids loading and density were negligible. Mixing time decreased with airflow rate, increased with solids density, in the studied range, and presented a maximum for solids loading of approximately 20% (v/v).Junta Nacional de Investigação Científica e Tecnológica (JNICT) Instituto de Biotecnologia e Química Fina (IBQF) - GGP XXI/BD/2937/9

Oxygen mass transfer in a high solids loading three-phase internal-loop airlift reactor

Determinations of volumetric mass transfer coefficient were conducted in a three-phase internal-loop airlift reactor with an enlarged degassing zone. The effect of parameters such as the airflow rate (riser superficial gas velocities between 0.01 and 0.5 m/s), solids loading (up to 30%, v/v), solids density (1023 and 1048 kg/m3) and the liquid-phase properties on kLa was studied. It was observed that the increase of the airflow rate and the introduction of ethanol enhanced the volumetric mass transfer coefficient in the system. On the contrary, the progressive introduction of solids and a small increase on solids density were responsible for the diminishing of the mass transfer rate. Correlations for the volumetric mass transfer coefficient with the riser superficial gas velocity and solids loading were determined for the two solids density and the two liquid-phases. A good agreement between experimental data and the calculated values was obtained.Instituto de Biotecnologia e Química Fina. Fundação para a Ciência e a Tecnologia -PRAXIS/2/2.1/BIO/1061/95, GGPXXI/BD/2937/96. EC - INCO-COPERNICUS - no. ERB IC15-CT98-0904

Creencias populares y enseñanza de la Biología

The existence of some popular beliefs has been referred to by several studies. A few of these popular beliefs, which seem to be also widespread in Portugal, are related to biological contents. Therefore, it can be expected that many students hold some of these beliefs when they come to the biology classes. Based on this suspicion, the authors decided to investigate: - The degree of adhesion shown by students with different biology backgrounds, to some popular beliefs. - The importance given by some biology textbooks to the popular beliefs

Forest Vintages and Carbon Sequestration

In the current paper we examine the role of forest carbon sequestration benefits in optimal forest management. When carbon benefits are considered not only the forested area is relevant, but also the flow of carbon between land and the atmosphere through the carbon cycle. To account for all these impacts a multi-vintage forest setting is used, following Salo and Tahvonen (2004). The model is extended to three different carbon accounting methods to measure the benefits form carbon sequestration: carbon flow regime, tonne-year crediting and average storage. In the case of the carbon flow regime, the impact on the optimal management and allocation of land will depend upon the amount of carbon released when the forest is harvested. Under the other two accounting systems optimal steady state forest area will be increased, and in cases where optimal management imply cyclical harvesting, considering carbon benefits will always increase cycles dimension.N/

Continuous versus Discrete Time Forest Management Models with Carbon Sequestration Benefits

Forest literature uses both continous and discrete time models to study forest management problems, and when carbon sequestration benefits are considered, the results obtained in both approaches are not always equivalent. This issue is relevant from a policy point of view if credits are to be allocated to forest owners within the implementation of the Kyoto Protocol. This note explores the impact of different carbon sequestration accounting methods on both settings. It studies the specific conditions for optimal rotation period and the value of a marginal unit of bare land on a one stand model and compare them with the long run optimal stationary steady state of a forest vintage model.N/

The Hyperbolic Forest Owner

This paper examines the implications of quasi-hyperbolic inter-temporal preferences to the Faustman model. The use of decreasing discount rates leads to dynamically inconsistent behavior. To solve this problem a two-stages optimization decision model is developed. The resulting actual cutting time will be anticipated compared to the Faustman optimal cutting time. If, alternatively, the equivalent constant rate of discount is the empirically observed discount rate, then the optimal cutting time is the same, but the present value of profits for the hyperbolic forest owner is always higher than the one resulting from the equivalent constant discount rate. All these results apply to both the single and the multiple rotation problems.N/

Gold@mesoporous silica nanocarriers for the effective delivery of antibiotics and by-passing of β-lactam resistance

POCI-01-0145-FEDER-007265 PD/BD/142865/2018 CEECIND/00648/2017 UIDB/04077/2020 Sem PDF conforme despacho.Current antibiotics effectiveness relies on higher doses and administration frequency, which are responsible for the growth of antimicrobial resistance (AMR). AMR is one of the major threatening issues of the century with last-line antibiotics already failing. To overcome such problems associated with bacterial infections, nanoparticles combined with antibiotics emerged as a promising strategy. In this work, nanocarriers comprising of gold–silica core–shell mesoporous nanoparticles (Au@MNs) and silica mesoporous nanoparticles (MNs) were synthesized, loaded with amoxicillin (Amox) and ofloxacin and investigated regarding its antibacterial activity towards S. aureus, methicillin-resistant S. aureus (MRSA), E. coli and P. aeruginosa. Both nanocarriers showed a beneficial role in the effective delivery of amoxicillin against MRSA and the well-known β-lactam resistant P. aeruginosa. Reductions of 10-fold (Amox@MNs) and 20-fold (Amox@Au@MNs) in the amount of antibiotic to treat P. aeruginosa; and a reduction of 20-fold (Amox@MNs) towards MRSA allied to a full reversion of resistance, strongly supports the promising potential of these nanocarriers to tackle antibiotics resistance.publishersversionpublishe