Comment on "Nonreciprocal light propagation in a silicon photonic circuit"

We show that the structure demonstrated by Feng et al. (Reports, 5 August 2011, p. 729) cannot enable optical isolation because it possesses a symmetric scattering matrix. Moreover, one cannot construct an optical isolator by incorporating this structure into any system as long as the system is linear and time-independent and is described by materials with a scalar dielectric function.     

A case study of capture-recapture methodology using scrapie surveillance data in Great Britain

We applied capture–recapture methodology (CRC) to data from three surveillance sources (statutory notification, abattoir survey (AS) and fallen stock (FS) survey) to estimate the number of holdings infected with scrapie in Great Britain and to assess the sensitivity of the surveillance network. Between January 1, 2002 and March 31, 2003, 144 holdings were identified by the three sources. Using CRC modelling techniques, we estimated a minimum lower bound for the total number of holdings infected as 642. A biologically plausible positive dependence between the statutory reporting and the fallen stock survey was found statistically significant. The sensitivity of the three sources combined was very low. The integration of the three overlapping sources provided a better understanding of the interactions within the surveillance network. However, the scarcity of the data and reduced overlapping among sources only allowed for very cautious inferences to be drawn about the true proportion of scrapie affected holdings in the national population. Future surveys and surveillance activities should be planned such that the resulting data can be used more effectively as part of CRC modelling approaches.     

Twin pregnancies following transfer of single embryos in three mares: A case report

Spontaneous development of identical or monozygotic twins is a rare event in the horse. Monozygotic twins develop after division of a single embryo. This report documents three cases in which twin embryos developed following surgical transfer of a single morula stage embryo into the uterus of a synchronized recipient mare.     

A mathematical model linking tree sap flow dynamics to daily stem diameter fluctuations and radial stem growth

To date, models for simulating sap flow dynamics in individual trees with a direct link to stem diameter variation include only the diameter fluctuation driven by a change in stem water storage. This paper reports results obtained with a comprehensive flow and storage model using whole-tree leaf transpiration as the only input variable. The model includes radial stem growth based on Lockhart's equation for irreversible cell expansion. It was demonstrated that including growth is essential to obtaining good simulation results. To model sap flow dynamics, capacitance of storage tissues was assumed either constant (i.e., electrical analogue approach) or variable and dependent on the water content of the respective storage tissue (i.e., hydraulic system approach). These approaches resulted in different shapes for the desorption curve used to calculate the capacitance of storage tissues. Comparison of these methods allowed detection of specific differences in model simulation of sap flow at the stem base (F(stem)) and stem diameter variation (D). Sensitivity analysis was performed to select a limited subset of identifiable parameters driving most of the variability in model predictions of F(stem) and D Both the electrical analogue and the hydraulic system approach for the flow and storage model were successfully calibrated and validated for the case of a young beech tree (Fagus sylvatica L.). Use of an objective model selection criterion revealed that the flow and storage model based on the electrical analogue approach yielded better predictions.     

<Emphasis Type="Italic">Amaranthus leaf mottle virus</Emphasis>: 3′-end RNA sequence proves classification as distinct virus and reveals affinities within the genus <Emphasis Type="Italic">Potyvirus</Emphasis>

Amaranthus leaf mottle virus (AmLMV) was classified as a member of the genus Potyvirus on the basis of its particle morphology, serology, and biological properties (Casetta et al., 1986). Based on these properties, an Amaranthus viridis-infecting virus isolated in Spain, causing mottle and leaf blistering as well as reduced growth has been identified as AmLMV. The 3′ terminal genomic region of this and a reference isolate from Italy has been sequenced and reveals a 95% nucleotide identity between the two isolates. The sequenced part comprises the coat protein with 281 amino acids and 315 nucleotides of the 3′ untranslated region (UTR) preceding a polyadenylated tail. Pairwise comparisons and phylogenetic analysis of the nucleotide and deduced amino acid sequences of the CP and 3′ UTR of the cloned cDNAs with those of other potyviruses shows that AmLMV is a distinct potyvirus closely related to Potato virus Y.     

Conduciveness of different soilless growing media to <Emphasis Type="Italic">Pythium</Emphasis> root and crown rot of cucumber under near-commercial conditions

Substrates made from rockwool, coir dust, pumice and perlite were compared for conduciveness to Pythium root and crown rot in cucumber under near-commercial conditions. Rockwool slabs of 7 cm height were more conducive to the Pythium disease than coir dust slabs, pumice or perlite under these conditions. Temperature, oxygen concentration and water content were determined in the substrates to explain differences in conduciveness between the inorganic substrates rockwool, pumice and perlite by differences in the physical conditions. Temperature and oxygen concentration could not explain the differences but the higher disease level on rockwool was associated with a much higher water content of this substrate as compared to coir dust, pumice and perlite. Increasing the height of the substrate from 7 to 14 cm greatly decreased the percentage of diseased plants due to the Pythium disease on rockwool but had no effect on the level of disease on perlite when the substrate had been infested 4 cm below the planting hole. This difference in response in substrate height between rockwool and perlite could be explained by a much larger decrease in water content with substrate height in the rockwool than in the perlite substrate. Temperature in the substrates were above 30 °C for more than 6 h on sunny days in June and reached maximum values of 35 °C or more. These temperatures are highly favourable for the pathogen P. aphanidermatum but will have adverse effects on most biocontrol strains.     

Crop rotation sequencing to minimize yield losses of summer-irrigated lowland rice in Myanmar caused by the rice root-knot nematode Meloidogyne graminicola

Abstract

The effect of different rice-based crop rotation sequences on the population densities of Meloidogyne graminicola and on the yield of rice was evaluated in a microplot experiment under lowland rice field conditions. Ten treatments of cropping sequences were grown in four successive growing seasons: continuous growing of the susceptible rice cultivar Thihtatyin (rice-rice-rice-rice), four treatments of 1- season crop rotation sequences (rice-rice-chickpea-rice, rice-rice-black gram-rice, rice-rice-soybean-rice, rice-rice-cowpea-rice), and five treatments of 2-season crop rotation sequences (groundnut-rice-chickpea-rice, green gram-rice-black gram-rice, cowpea-rice-soybean-rice, sesame-rice-cowpea-rice, sunflower-rice-sesame-rice). Population densities of M. graminicola recovered from the rice plants and the nematode multiplication factors (Mf) in the soil in the continuous rice cropping sequence (rice-rice-rice-rice) was the highest among the ten cropping sequences. Lowest nematode Mf in the soil was observed in the 2-season crop rotation sequence sunflower-rice-sesame-rice and the highest was observed in the 1-season crop rotation sequence rice-rice-cowpea-rice among the nine crop rotation sequences. Highest rice yield was obtained in the 2-season crop rotation sequences green gram-rice-black gram-rice, sesame-rice-cowpea-rice and sunflower-rice-sesame-rice, which were about 2 times higher compared with the 1-season crop rotation sequences and about 3 times higher compared with the continuous rice cropping sequence.     

Factors affecting the field performance of an attracticide against the codling moth Cydia pomonella

Factors affecting the efficacy of an attracticide strategy for the control of the codling moth Cydia pomonella L (Lepidoptera: Tortricidae) were investigated using laboratory and field experiments. The sex-pheromone-based insect-control strategy utilises 100-microliters droplets of a sticky, paste-like formulation containing 1 mg g-1 (E,E)-8,10-dodecadien-1-ol (codlemone) as an attractant for male moths and 40 mg g-1 cyfluthrin, a contact insecticide, applied to branches in the upper parts of the tree crown. The longevity of the treatment under field conditions was assessed in the laboratory by biological testing of variously aged samples of the attracticide formulation which had been applied to the bark of apple trees growing in commercial orchards. Electroantennogram responses of male moth antennae were used to compare codlemone release from the attracticide after different lengths of environmental exposure. Changes in insecticidal efficacy of the same samples were assessed with reference to the speed of knockdown (KT50) and the mortalities after 48 h among populations of male moths confined in cages containing samples of fresh and field-aged formulations. Gradual declines in both the amount of pheromone released and insecticidal activity were observed over the 10-week period of the experiments. Various factors associated with the behaviour of codling moths in the field which might influence the attracticide strategy were also investigated. Although the vertical position of attracticide sources within apple trees had a strong influence on their attractiveness, their horizontal position had none. Results of field trials showed that efficacy of the attracticide depends on the population density of the pest. Under the conditions of the current study a density of three or more sources per tree (= 4500 sources per ha) was required to attain satisfactory levels of codling moth control.     

Untersuchungen zum Auftreten von Druckstellen an Äpfeln nach der Auslagerung

Zusammenfassung Es wurde untersucht, welche Faktoren die Empfindlichkeit von ?pfeln für Druckstellen unmittelbar nach der CA/ULO-Lagerung (CA = Controlled Atmosphere, ULO = Ultra Low Oxygen) beeinflussen. Früchte der Sorten ‘Golden Delicious’ und ‘Jonagold’ wurden nach der CA/ULO-Lagerung für fünf Tage bei vier verschiedenen Nachlagerungsbedingungen (kühl in und ohne Folienbeutel, warm in und ohne Folienbeutel) aufbewahrt. Direkt nach der Auslagerung, ein Tag und fünf Tage sp?ter wurden die ?pfel mittels zwei Apparaturen unterschiedlichen Belastungen ausgesetzt, um Druckstellen zu erzeugen. Weitere gemessene Parameter waren die Fruchtfleischfestigkeit, der Gelbwert, der Gewichtsverlust, der Zellbruchpunkt und die Schalenbruchfestigkeit. Das Ausma? der Druckstellen nahm mit steigender Belastung der Früchte zu. Die warm gelagerten Früchte zeigten mit zunehmender Zeit der Nachlagerung eine geringere Druckstellenempfindlichkeit. Die kühl gelagerten Früchte der Sorte ‘Golden Delicious’ zeigten eine Zunahme der Druckstellenempfindlichkeit im Verlauf der Nachlagerung, die der Sorte ‘Jonagold’ eine Abnahme oder keine Ver?nderung. Ein Zusammenhang zwischen der Druckstellenempfindlichkeit und der Fruchtfleischfestigkeit, dem Zellbruchpunkt oder der Schalenbruchfestigkeit wurde nicht festgestellt.