Diffusion and Home Range Parameters from Rodent Population Measurements in Panama

Simple random walk considerations are used to interpret rodent population data collected in Hantavirus-related investigations in Panama regarding the short-tailed cane mouse, \emph{Zygodontomys brevicauda}. The diffusion constant of mice is evaluated to be of the order of (and larger than) 200 meters squared per day. The investigation also shows that the rodent mean square displacement saturates in time, indicating the existence of a spatial scale which could, in principle, be the home range of the rodents. This home range is concluded to be of the order of 70 meters. Theoretical analysis is provided for interpreting animal movement data in terms of an interplay of the home ranges, the diffusion constant, and the size of the grid used to monitor the movement. The study gives impetus to a substantial modification of existing theory of the spread of the Hantavirus epidemic which has been based on simple diffusive motion of the rodents, and additionally emphasizes the importance for developing more accurate techniques for the measurement of rodent movement.Comment: 18 pages, 5 figure

Bacterial secretion and the role of diffusive and subdiffusive first passage processes

Open Access ArticleBy funneling protein effectors through needle complexes located on the cellular membrane, bacteria are able to infect host cells during type III secretion events. The spatio-temporal mechanisms through which these events occur are however not fully understood, due in part to the inherent challenges in tracking single molecules moving within an intracellular medium. As a result, theoretical predictions of secretion times are still lacking. Here we provide a model that quantifies, depending on the transport characteristics within bacterial cytoplasm, the amount of time for a protein effector to reach either of the available needle complexes. Using parameters from Shigella flexneri we are able to test the role that translocators might have to activate the needle complexes and offer semi-quantitative explanations of recent experimental observations.Engineering and Physical Sciences Research Council (EPSRC)Medical Research Council (MRC

Influence of a Sulphur Dioxide Active Storage System on the Quality of Ribes rubrum L. Berries

The aim of this study was to evaluate the post-harvest changes in the quality of red currants ( Ribes rubrum L.) cv. ‘Rovada’ after 60 days of storage under modified atmosphere packaging (MAP) conditions. The storage unit was a pallet, and two treatments were performed. The CO 2 -MAP treatment was used as a control, while the SO 2 -MAP treatment was CO 2 -MAP plus SO 2 . The initial gas composition was 15.0 kPa O 2 and 10.0 kPa CO 2 inside all MAPs, while SO 2 -generating active sheets were added to pellets in SO 2 -MAP treatment. Weight loss, total soluble solid content, titratable acidity, total phenolic and anthocyanin contents, antioxidant activity, microbial count, and visual and sensorial appearance were monitored after 30 and 60 days. The results showed that berries stored with SO 2 maintained the quality parameters for up to 60 days. Exposure to SO 2 was effective in controlling yeast evolution, reducing the population both at 30 and 60 days at one and two orders of magnitude, respectively. Red currants stored under SO 2 MAP obtained better visual quality score compared to CO 2 MAP-treated berries throughout storage. Active emitters of SO 2 , such as those proposed in this study, can be promising solutions to improve the post-harvest storage of red currants and the berries marketability

Influence of harvest method on the quality and storage of highbush blueberry

Blueberry quality is one of the most important elements that needs to be evaluated when automatisation processes, such as harvest automation, occur along the supply chain. The aim of this work was to evaluate the suitability of two blueberry cultivars, of new introduction for the area of study, to the mechanical harvest. Particularly the influence of harvest method was evaluated on the quality of cv. Cargo® and Top Shelf® for a short storage time (max. 28 days) in normal atmosphere assuming so an immediate sale of blueberries. Samples mechanically harvested were compared in terms of qualitative performance with samples manually picked throught two activity carried on two years. In the activity 1 a preliminary laboratory test simulation of mechanical harvest was carried on to evaluate the attitude of both cultivars to the automatisation process and the berries were evaluated immediately after the harvest time. The activity 2 was aimed to evaluate the quality of berries mechanically harvested in field and after the storage process at 2 ± 1 °C and 90% RH in a cold room for 28 days under normal atmospheric conditions (NA). The higher percentage of shrivelled berries for the simulation of mechanical harvest samples (SEH) (activity 1) and berries harvested with the Easy Harvester machine® (EH samples) (activity 2) in the post-harvest period was probably due to the low % of pruin on berries skin content at the harvest time (0 days). All samples although achieved a quality assessment equivalent to still marketable berries after 28 days of storage. TSSC were significantly higher in the EH group for both years. TSSC and TA were higher in Cargo® than in Top Shelf®. In general the automatisation of the harvesting process did not significantly affect blueberry quality after storage

Diffusion and Home Range Parameters for Rodents: Peromyscus maniculatus in New Mexico

We analyze data from a long term field project in New Mexico, consisting of repeated sessions of mark-recaptures of Peromyscus maniculatus (Rodentia: Muridae), the host and reservoir of Sin Nombre Virus (Bunyaviridae: Hantavirus). The displacements of the recaptured animals provide a means to study their movement from a statistical point of view. We extract two parameters from the data with the help of a simple model: the diffusion constant of the rodents, and the size of their home range. The short time behavior shows the motion to be approximately diffusive and the diffusion constant to be 470+/-50m^2/day. The long time behavior provides an estimation of the diameter of the rodent home ranges, with an average value of 100+/-25m. As in previous investigations directed at Zygodontomys brevicauda observations in Panama, we use a box model for home range estimation. We also use a harmonic model in the present investigation to study the sensitivity of the conclusions to the model used and find that both models lead to similar estimates.Comment: The published paper in Ecol. Complexity has an old version of Figure 6. Here we have put the correct version of Figure