Snell's Law for a vortex dipole in a Bose-Einstein condensate

A quantum vortex dipole, comprised of a closely bound pair of vortices of equal strength with opposite circulation, is a spatially localized travelling excitation of a planar superfluid that carries linear momentum, suggesting a possible analogy with ray optics. We investigate numerically and analytically the motion of a quantum vortex dipole incident upon a step-change in the background superfluid density of an otherwise uniform two-dimensional Bose-Einstein condensate. Due to the conservation of fluid momentum and energy, the incident and refracted angles of the dipole satisfy a relation analogous to Snell's law, when crossing the interface between regions of different density. The predictions of the analogue Snell's law relation are confirmed for a wide range of incident angles by systematic numerical simulations of the Gross-Piteavskii equation. Near the critical angle for total internal reflection, we identify a regime of anomalous Snell's law behaviour where the finite size of the dipole causes transient capture by the interface. Remarkably, despite the extra complexity of the surface interaction, the incoming and outgoing dipole paths obey Snell's law.Comment: 16 pages, 7 figures, Scipost forma

Storage stability of whole and nibbed, conventional and high oleic peanuts (<i>Arachis hypogeae </i>L.)

Peanuts are increasingly being used as nibbed ingredients in cereal bars, confectionery and breakfast cereals. However, studies on their oxidative stability in this format are limited. Storage trials to determine the stability to oxidation were carried out on whole and nibbed kernels of conventional (CP) and high oleic (HOP) peanuts, with respect to temperature and modified atmosphere packaging. HOP exhibited the highest oxidative stability, with a lag phase in whole kernels of 12–15 weeks before significant oxidation occurred. HOP also showed higher levels of intrinsic antioxidants, a trolox equivalent antioxidant capacity (TEAC) of 70 mMol equivalence and radical scavenging percentage (RSP) of 99.8 % at the beginning of storage trials, whereas CP showed values of 40 mMol and 81.2 %, respectively. The intrinsic antioxidants at the beginning of these storage trials were shown to affect the peroxide value (PV), where RSP and TEAC decreased, and PV increased. Therefore, in peanuts the processing format (nibbed or whole) had the highest influence on susceptibility of lipid oxidation, highest to lowest importance: processing format &gt; temperature &gt; atmospheric conditions

Assessing the effects of the first 2 years of industry-led badger culling in England on the incidence of bovine tuberculosis in cattle in 2013–2015

Culling badgers to control the transmission of bovine tuberculosis (TB) between this wildlife reservoir and cattle has been widely debated. Industry-led culling began in Somerset and Gloucestershire between August and November 2013 to reduce local badger populations. Industry-led culling is not designed to be a randomised and controlled trial of the impact of culling on cattle incidence. Nevertheless, it is important to monitor the effects of the culling and, taking the study limitations into account, perform a cautious evaluation of the impacts. A standardised method for selecting areas matched to culling areas in factors found to affect cattle TB risk has been developed to evaluate the impact of badger culling on cattle TB incidence. The association between cattle TB incidence and badger culling in the first two years has been assessed. Descriptive analyses without controlling for confounding showed no association between culling and TB incidence for Somerset, or for either of the buffer areas for the first two years since culling began. A weak association was observed in Gloucestershire for Year 1 only. Multivariable analysis adjusting for confounding factors showed that reductions in TB incidence were associated with culling in the first two years in both the Somerset and Gloucestershire intervention areas when compared to areas with no culling (IRR: 0.79, 95%CI: 0.72-0.87, p<0.001 and IRR: 0.42, 95%CI: 0.34-0.51, p<0.001 respectively). An increase in incidence was associated with culling in the 2 km buffer surrounding the Somerset intervention area (IRR: 1.38, 95%CI: 1.09-1.75, p=0.008), but not in Gloucestershire (IRR: 0.91, 95%CI: 0.77-1.07, p=0.243). As only two intervention areas with two years’ of data are available for analysis, and the biological cause-effect relationship behind the statistical associations is difficult to determine, it would be unwise to use these findings to develop generalisable inferences about the effectiveness of the policy at present

GROVITH PERFORMANCE OF LARGE DIAMETER RATIAN (Calamus) PLANTED UNDER PINE PLANTATIONS AT SINHARAJA BUFFERZONE

Rattans can be considered as the most important non-timber forest product. Due to heavyexploitation from the wild, the resource is declining at an alarming rate. The present studyexamined the growth performance in terms of plant height, total lengths of stems,diameter, clump formation and number of live leaves and average growth rates of threelarge diameter rattan species, namely Calamus zeylanicus Becc., Calamus thwaitesiiBecc., and Calamus ovoideus Thw. ex Trim, planted under pine plantations in the bufferzone of Sinharaja, Sri Lanka. Four sites of rattan plantations in ages, 8, 9, 10 and 12 yearswere selected with each site consisting of five plots. Lengths of stems were estimated andstern diameter was measured without the sheath. Number of live leaves and stems in aclump were counted in each plant. Number of pine trees of each site was counted and soilanalysis was carried out to depict the site 9ualit'l.The highest stem lengths were recorded in the oldest site and the highest mean heightrecorded afer 12 years was 20 m. Results showed that the height increases with the ageand the average growth rate decreases. The highest avera~e growth rate, 1.87 m per yearwas recorded in the 8 year old plantation and the lowest, 1.75 m was recorded in the 12year old plantation Average number of stems in a plant varies from 1 to 4 stems per plantin all four sites. Average diameter of stems i:l all sites was in the range of 1.8 to 2.1 ern,irrespective of the age of the plantation. The average number of leaves declined with theage of the plantation. In conclusion it is possible to say that although the stem lengthincreases With the age of the plantation, the average growth rate decreases. Average stemdiameter and number of stems in a plant have not shown' any relationship with the age.

SEEDLING SURVIVAL AND GROWTH OF NINE LATE-SUCCESSESIONAL SPECIES ACROSS A TOPOGRAPHIC GRADIENT IN SINHARAJA RAIN FOREST

Growth performance of seedlings belong to nine late-successesional canopy treespecies was studied at three different topographic positions (ridgetop, midslopeand valley) in the Sinharaja rain forest, southwest Sri Lanka. Seedlings wereplanted in plots located in valleys, midslops and ridgetops. In each site fourcanopy openings and four adjacent understoreys were selected to plant seedlingsof nine late-successional canopy tree species. Seedling growth and mortality weremonitored for three years.Results demonstrated that a clear difference in survival and growth amongspecies. These differences appeared to be related to the availability of soilmoisture and groundstorey radiation regimes of the forest. SIlOrea distichaexhibits high growth rate than others in each topographic position in each site.Seedlings of Mesua ferrea and Shorea megistophylla exhibit a higher survivalthan other species in canopy openings and understorey conditions of alltopographic positions. Growth performance and survival of their species will bemonitored for several years to study the nich specialization of the latesuccessionalcanopy tree seedlings

COMPETITION AMONG LATE·SUCCESSIONAL TREE SPECIES ACROSS DIFFERENT TOPOGRAPHIC POSITIONS OF A SRI LANKAN RAIN FOREST.

The plant height growth, canopy expansion and foliar nutrients allocations provide theevidence to understand competitive role by canopy species in part of light and soilmoisture gradient. Experiments were designed to investigate competitive outcomes ofnine late-succesional tree seedlings in different light and soil moisture regimes. Treespecies were planted in the canopy gap and forest understory in different topographicpositions; valley, midslope and ridgetop. At the end of every year height, root collardiameter, leaf number and mortality were recorded. Results showed that Shoreatrapezifolia and Syzygium rubicundum can be regarded as the most light demandingspecies with competitive superiors as judged from its height increment, leaf and branchesincrements with crown structure, root collar diameter and leaf nutrients allocatingpattern. At other extremes are Mesua ferrea and Shorea worthingtonii, most which arethe most, shade tolerant and with lower competitive ability in this group. Patterns incompetitive hierarchy among late successional canopy species strongly support sitespecialisation and establishment of regeneratio

EFFECT OF LIGHT AND SOIL NUTRIENT ON SEEDLING MORPHOLOGY OF Syzygium SPECIES OF A LOWLAND RAIN FOREST IN SRI LANKA

Knowledge or how light and soil nutrient availability affect seedling morphology inrelation to seedling growth is critical for understanding the regeneration establishment ofseedlings beneath rain forest canopies. This study measured changes in seedlingmorphology or four related tree species in the family Myrtaccae in relation to differingcombinations of light and soil nutrients. Species selected were canopy and sub canopytrees or rain forest in southwest Sri Lanka.Shelters were constructed in the full open that created light treatments representing a rangeof photosynthetic Photon Flux Densities (PFD) and red: r:u' red ratios found in the rainforest. Within each shelter seedlings were Icrtiliscd with phosphorous. potassium andmagnesium nutrients. Newly germinated seedlings of each of four species (S. firntum, S.makul , S. opcrculatum, S'. rubicuudumv were grown for one and half years after which theywere dug up and measured for. shoot length. root length. root collar diameter. leaf number.leaf area. and dry masses of roots. stems and leaves.Shoot length and leaf area auaincd maxima in shelters simulruing large forest openings(400nh. Root length. root collar diameter and dry masses gain were highest in full suntreatment. Compared with nutrient treatments phosphorus promoted greatestmorphological measurements for all species. The results suggest that these species exhibitgreater morphological responsiveness to increase in irradiancc and to addition ofphosphorous Icrtiliscr.

SEEDLING GROWTH PERFORMANCE OF FOUR Syzygium species IN THE SIMULATED LIGHT AND SOIL NUTRIENT ENVIRONMENTS OF A RAIN FOREST IN SRI LANKA

Seedlings of four species of Syzygium (S. firmum, S. makul, S. operculatum, S.rubicundutn) were investigated for differences in growth and survival after one and halfyears growth in a nursery experiment. All four species co-exist in the moist evergreen rainforest of South western Sri Lanka. S. firmum is a canopy tree on valleys to midslopes. S.rubicundum is considered a canopy tree of late-successional forest on hill mid slops. BothS. makul and S. operculatum arc sub canopy trees of late-successional forest alongstreamways of lower slopes and valleys.Seedlings of each species were grown within replicated light and soil nutrient treatmentsfound in the groundstorey forest environments. The light treatments exposed seedlings toi) full sun; ii) sunlight like that at the center of a 200 m2 forest opening. iii) sunlight likethat at the center of a 400 m2 canopy opening; iv) 50% shade of sunlight with qualitysimilar to the outside edge of a 400 m2 canopy opening on the shaded side; v) 20% ofsunlight with a quality similar to the inside edge of a 400 m2 canopy opening on theshaded side and vi) I% of sunlight with a quality and amount similar to the forestunderstorey. Within each light treatment seedlings were grown with additions ofphosphorus, potassium, magnesium, al\ three combined and a control with no additionalnutrients. At the end of one and half years seedlings were measured for net photosynthesis,height increment, leaf number and survival.Seedling survival for all species was low in the forest understorey treatment. Both survivaland seedling height were greatest in shelters simulating forest openings. Leaf productionwas highest in full sun and inside edge light treatments and all species had their greatestnet photosynthesis in the inside edge treatment. For nutrient treatments phosphoruspromoted greatest seedling growth in all species

EFFECT OF SHADING ON SURViVAL AND GROWTH OF Mesua (CLUSIACEAE) AND Shorea (DIPTEOCARPACEAE) SEEDLINGS ACROSSTOPOGRAPHIC GRADIENT IN SINHARAJA RAIN FOREST, SOUTHWEST SRI lANKA

The effect of shading on survival and growth of two species of Mesua (Clusiaceae) andfour species of Shorea (Dipteocarpaceaeh planted seedlings were investigated at differenttopographic positions in Sinharaja rain forest All occur together as canopy dominant treesIII Sinharaja rain forest Twelve-understory sites were selected, four each on differenttopographic posilions valley, midslope and ridgetop. Measurements of height, number ofleaves, root collar diameter and the mortality were recorded over a five-year period.Hemispherical canopy photographs were taken to calculate Indirect Site Factor (ISF),Direct Site Factor (DSF), and the Leaf Area Index (LAI). Analysis of photographsdemonstrated that LAI decreased from valley to ridge top while DSF and ISF increasedfrom the valley to ridge top. After five years thirty-four (34 %) seedlings died in the ridgelop and the lowest mortality was recorded in the midslope. Seedlings of Mesua ferrea L.had the highest survival than other species in all understory conditions and the lowestsurvival rate recorded for Shorea trapezifolia (Thw.) Ashton. Results showed cleardifferences in survival and growth among species. These differences appeared related (0availability of soil moisture and understory radiation regimes

THE VARIATION IN LEAr STRUCTURE O~ SEEDLINGS IN THE FAMILIES DIPTEROCARPACEAE, CLUSIACEAE, AND MYRTACEAE UNDER DIFFERENT LIGHT ENVIRONMENTS

Light has been characicriscd as the most important environmental factor that affect the leafstructure of tree seedlings in tropical rain forest in South and Southeast Asia. Many studieshave been carried out on leaf structure of early-successional and late-successional specic-,and also among the species within the same successional status. These studies have helpedin creating a clear understanding of ecological distribution in relation to each species. Thepresent study examined the leaf structure or six canopy tree species that are considered to berelatively shade tolerant in lowland rain forests in Sri Lanka.Seedlings of Dipteracarpus tevlcnticns, D. hispidus (Diptcrocarpaceae), Mesua f{'ITNI. M.nagassarium (Clusiaccac). Sy:rgillillfirnllll'/1 and S. rubicundum (Myrtaccac) were grown indifferent controlled environmental shelters that simulated a range of light environmentsfound in the ground storey of the rain forest. Two treatments exposed seedlings to differentduration of full sunlight. These simulated the groundstorey Photosynthetic Photon FluxDensity (PFD) that were comparable to the centres of about 200 m2 and 400 m2 canopyopenings. Three other shelters exposed seedlings to uniform diffuse light conditions thatsimulated amounts and qualities of radiation similar to that of the forest undcrstorey (PFD50. R:FR ratio 0.46: PPO 350. R:FR ratio 0.97; PFO XOO,R:FR ratio 1.05). A control lighttreatment proved full sun light quality (PPFD 200n, R:FR ratio 1.27) for the seedlinggrowth.The attributes measured were thickness of leaf blade. upper and lower epidermis. palisademesophyll and number of layers, and stomatal frequency. Results show that S\'~\'gil/lllspecies have highest in leaf blade, palisade cell thickness and stomatal frequency followedin order by MC.I'I.w&gt;Dipterocarpus. This suggests that S\'~ygillill species are more lighttolerant but less in drought tolerance. The thickest upper and lower epidermis inDipterocarpus reveal that they are more efficient in water use. Svzygiun: and Dipteroiarpusexhibit rows in palisidac mcsophyll when exposed to full sun. These findings elucidatesome of the relationships between leaf anatomy and the species ecology across the foresttopography.