Periodical growth rings in cephalopod statoliths

In this paper a direct age determination method for squid is introduced. Periodical growth rings in statoliths of the squid Gonatus fabricii (Lichtenstein, 1818) are described. By comparison with the previously determined growth rate of juvenile specimens and a bimodal monthly size distribution, growth rings, called first-order bands, are for the first time shown to be daily whereas bands of second and third order are fortnightly and monthly, respectively. The relationship between the pen length and both statolith length and the number of growth rings are shown. Presence of organic material in statoliths and its significance for banding are demonstrated. Periodical growth rings are also shown in statoliths of Rossia glaucopis (Lovén, 1845) and Alloteuthis subulata (Lamarck, 1798)

Bias and temperature dependence of the 0.7 conductance anomaly in Quantum Point Contacts

The 0.7 (2e^2/h) conductance anomaly is studied in strongly confined, etched GaAs/GaAlAs quantum point contacts, by measuring the differential conductance as a function of source-drain and gate bias as well as a function of temperature. We investigate in detail how, for a given gate voltage, the differential conductance depends on the finite bias voltage and find a so-called self-gating effect, which we correct for. The 0.7 anomaly at zero bias is found to evolve smoothly into a conductance plateau at 0.85 (2e^2/h) at finite bias. Varying the gate voltage the transition between the 1.0 and the 0.85 (2e^2/h) plateaus occurs for definite bias voltages, which defines a gate voltage dependent energy difference $\Delta$. This energy difference is compared with the activation temperature T_a extracted from the experimentally observed activated behavior of the 0.7 anomaly at low bias. We find \Delta = k_B T_a which lends support to the idea that the conductance anomaly is due to transmission through two conduction channels, of which the one with its subband edge \Delta below the chemical potential becomes thermally depopulated as the temperature is increased.Comment: 9 pages (RevTex) with 9 figures (some in low resolution

Associations between patterns of human intestinal schistosomiasis and snail and mammal species richness in Uganda:can we detect a decoy effect?

In recent years, ecological research has suggested several mechanisms by which biodiversity might affect the risk of acquiring infectious diseases (i.e., the decoy, dilution or amplification effects), but the topic remains controversial. While many experimental studies suggest a negative relationship between biodiversity and disease, this relationship is inherently complex, and might be negative, positive or neutral depending on the geographical scale and ecological context. Here, applying a macroecological approach, we look for associations between diversity and disease by comparing the distribution of human schistosomiasis and biogeographical patterns of freshwater snail and mammal species richness in Uganda. We found that the association between estimated snail richness and human infection was best described by a negative correlation in non-spatial bi- and multivariate logistic mixed effect models. However, this association lost significance after the inclusion of a spatial component in a full geostatistical model, highlighting the importance of accounting for spatial correlation to obtain more precise parameter estimates. Furthermore, we found no significant relationships between mammal richness and schistosomiasis risk. We discuss the limitations of the data and methods used to test the decoy hypothesis for schistosomiasis, and highlight key future research directions that can facilitate more powerful tests of the decoy effect in snail-borne infections, at geographical scales that are relevant for public health and conservation.<br /