Hand corer versus van Veen grab in harbour sediments: Efficiency estimation in the study of macrobenthic communities

Se compararon los resultados obtenidos con una draga van Veen de 0,05 m 2 de superficie operativa con los de un core manual de sección rectangular (10 x 17 x 35 cm) en muestreos de macrofauna de sedimentos del puerto de Ceuta. El número de especies obtenido por ambos procedimientos de muestreo fue similar. Sin embargo, las densidades de las especies numéricamente impor- tantes fueron significativamente superiores en las muestras extraídas con core, sobre todo en el caso de los poliquetos, lo que se tradujo en un descenso en los valores de diversidad y equitatividad. Al considerar los valores medios de las tres estaciones estudiadas, las densidades del molusco Paphia aurea y de los poliquetos Cirratulus cirratus , Exogone verugera y Platynereis dumerilii fueron significativamente superiores en las muestras tomadas con core manual. Los crustáceos tienen una clara preferencia por los estratos superficiales de la columna de sedimento, mientras que algunos moluscos y muchos poliquetos son capaces de penetrar alcanzando niveles más profundos. De ahí que sus abundancias queden subestimadas con la draga van Veen, que extrae un semici- lindro de sedimento en lugar de un prisma y tiene un grado de profundización dependiente del tipo de sedimento.A comparison of benthic macrofauna from sediments of the harbour of Ceuta collected with a van Veen grab (0.05 m 2 ) and a hand corer (10 x 17 x 35 cm) was conducted. The number of species collected with the two devices was similar. However, densities of numerically important species were higher with the hand core, especially for the polychaetes, resulting in a decrease of diversity and evenness indexes. Considering the mean values for the three stations selected, densities of the mollusc Paphia aurea and the polychaetes Cirratulus cirratus , Exogone verugera and Platynereis dumerilii were significantly higher with the core. The crustaceans show preference for superficial levels in the sediment column whereas some molluscs and many polychaetes are able to reach deeper levels. Therefore, densities of molluscs and polychaetes are underestimated with the van Veen grab, which takes out a semicylinder of sediment instead of a prism, and the degree of penetration into the sediment depends on the type of substrate

Price Inflation and Exchange Rate Pass-Through in Chile

A price equation based on a model of imperfect competition was estimated using quarterly data for Chile from 1986:1 to 2001:1. The estimation includes the first difference of the dependent variable following the literature on the estimation of linear quadratic adjustment cost (LQAC) models, when the target and some of the driving variables follow I(2) processes. The equation is used to generate out-of-sample inflation forecast, of a narrower-than the-CPI price index. We can conclude from the estimation results: i) exchange-rate pass-through depends positively on economic activity (output gap) explaining why pass-through has been so low in recent years in Chile. In other words, a negative output gap has compensated the inflationary impact of exchange-rate depreciation; ii) productivity reduces unit labor costs and inflation; iii) wages and foreign prices are positively related to inflation; iv) Finally, expected inflation acceleration is significant, confirming that expectations matter determining inflation.

Polychaete assemblages and sediment pollution in a harbour with two opposing entrances

The harbour at Ceuta is one of the most important harbours in the Strait of Gibraltar. The sediments are moderately polluted with organic matter and heavy metals but the harbour has two opposing entrances and a connecting channel which increases water renewal and dissolved oxygen across the harbour. For these special conditions, the value of the soft bottom polychaete community as a bioindicator, and possible advantages of the presence of two harbour entrances on biotic assemblages, were studied. Twenty-one stations were selected, and 27 variables were measured in the sediment of each station. The polychaete species richness and Shannon diversity values were similar inside and outside the harbour. Nevertheless, the Pielou evenness index was significantly higher in the external stations due to high densities of some species of polychaetes such as Pseudomalacoceros tridentata and Capitella capitata inside the harbour. The multivariate approach based on polychaete species composition was much more sensitive than univariate analyses at discriminating between internal and external stations. The pollution gradient and granulometric parameters were the main factors affecting polychaete distribution. Polychaete species richness and diversity in sediments inside Ceuta harbour were higher than in conventional harbours due to the positive effects of increased water renewal. These results should be taken into consideration in design, construction and remodelling of future harbours.Ministerio de Educación, Cultura y Deporte de España. FPU AP98/2861706

Are the MCVL tax data useful? Ideas for mining

This article analyzes the tax data from the Spanish “Continuous Sample of Working life”, which contains an overview for each fiscal year of all income tax withholdings and prepayments on earned income, economic activities and income assignments of salaried workers, pensioners and recipients of unemployment benefits. To that end, we present the characteristics of these data; we provide a detailed statistical description for the years 2004-2009, linked to information from personal files and those of contributors to the Spanish social security system; and we highlight the opportunities for analysis of some issues related to the labour market and income distribution.tax data, MCVl, income, labour market, panel dat

The influence of previous labour market experiences on subsequent job tenure

The aim of this paper is to analyse the influence of individual’s previous labour market experiences on the duration of subsequent job matches in the Spanish labour market. The study draws on a sample of workers extracted from a Spanish administrative dataset. We find evidence on the existence of a scarring effect: the longer the time spent in non-employment since previous job separation, the shorter the duration of subsequent re-employment relationships. Other result is that workers whose previous job match terminated due to the ending of a temporary contract are very likely to come back to employment under another temporary job and have a higher probability of job termination. The exhaustion of unemployment benefits also seems to exert a scarring effect on job duration.job tenure, job separations, non-employment, employment.

PWM Control of a Buck Converter with an Amorphous Core Coil

Pulse-width modulation is widely used to control electronic converters. One of the most topologies used for high DC voltage/low DC voltage conversion is the Buck converter. It is obtained as a second order system with a LC filter between the switching subsystem and the load. The use of a coil with an amorphous magnetic material core instead of air core lets design converters with smaller size. If high switching frequencies are used for obtaining high quality voltage output, the value of the auto inductance L is reduced throughout the time. Then, robust controllers are needed if the accuracy of the converter response must not be affected by auto inductance and load variations. This paper presents a robust controller for a Buck converter based on a state space feedback control system combined with an additional virtual space variable which minimizes the effects of the inductance and load variations when a not-toohigh switching frequency is applied. The system exhibits a null steady-state average error response for the entire range of parameter variations. Simulation results are presented

Políticas de Estabilización en Chile Durante los Noventa

This paper provides econometric evidence on the effectiveness of targeting inflation in order to reduce the rate of inflation in Chile in the 1991-97 period. This paper shows that the inflation target altered the inflationary dynamic, by following through with out–of-sample forecasts with VAR models. Second, this paper estimates the Central Bank’s feedback rule by using a semi-structural VAR, which shows that an unexpected and temporary real interest shock can reduce the inflationary gap. However, this paper argues that the strategy of using unexpected and temporary shocks to explain the decline in inflation is misleading. The paper supports this with consideration to the fact that the inflation target was an announced, decreasing, and permanent policy. Third, by using an unrestricted VAR, this paper performs dynamic solutions that assume an exogenous and known path for the inflation target. The results indicate that the decreasing inflation target gradually led inflation to the single-digit range without a drop in output. However, the real appreciation observed during this period and connected with a capital inflow shock was also an important element to explain the decline in the rate of inflation.

Development of an electrochemical maltose biosensor

In this work, electrochemical maltose biosensors based on mutants of the maltose binding protein (MBP) are developed. A ruthenium II complex (Ru II ), which is covalently attached to MBP, serves as an electrochemical reporter of MBP conformational changes. Biosensors were made through direct attachment of Ru II complex modified MBP to gold electrode surfaces. The responses of some individual mutants were evaluated using square wave voltammetry. A maltose-dependent change in Faradic current and capacitance was observed. It is therefore demonstrated that biosensors using generically this family of bacterial periplasmic binding proteins (bPBP) can be made lending themselves to facile biorecognition element preparation and low cost electrochemical transduction

Using the Own Flexibility of a Climbing Robot as a Double Force Sensor

Force sensors are used when interaction tasks are carried out by robots in general, and by climbing robots in particular. If the mechanics and electronics systems are contained inside the own robot, the robot becomes portable without external control. Commercial force sensors cannot be used due to limited space and weight. By selecting the links material with appropriate stiffness and placing strain gauges on the structure, the own robot flexibility can be used such as force sensor. Thus, forces applied on the robot tip can be measured without additional external devices. Only gauges and small internal electronic converters are necessary. This paper illustrates the proposed algorithm to achieve these measurements. Additionally, experimental results are presented

Torque control of switched reluctance motors

This paper presents the performance of an instantaneous torque control method. The simulation and experimental results illustrate the capability of Switched Reluctance Motors (SRM) being used in the motor drive industry. Based on experimental data, the advantages of this control method and its disadvantages in practical implementation were studied. The model used in the simulation is the linear magnetic model which has the 12/8 structure, the same structure as the experimental switched reluctance motor