Localised labyrinthine patterns in ecosystems

Self-organisation is a ubiquitous phenomenon in ecosystems. These systems can experience transitions from a uniform cover towards the formation of vegetation patterns as a result of symmetry-breaking instability. They can be either periodic or localised in space. Localised vegetation patterns consist of more or less circular spots or patches that can be either isolated or randomly distributed in space. We report on a striking patterning phenomenon consisting of localised vegetation labyrinths. This intriguing pattern is visible in satellite photographs taken in many territories of Africa and Australia. They consist of labyrinths which is spatially irregular pattern surrounded by either a homogeneous cover or a bare soil. The phenomenon is not specific to particular plants or soils. They are observed on strictly homogenous environmental conditions on flat landscapes, but they are also visible on hills. The spatial size of localized labyrinth ranges typically from a few hundred meters to ten kilometres. A simple modelling approach based on the interplay between short-range and long-range interactions governing plant communities or on the water dynamics explains the observations reported here.

Effects of Corrosion to the Performance of Steel Reinforcement Embedded in Concrete under Different Aggressive Environments

The corrosion of reinforcement steel bars in concrete has been established as the major factor causing widespread degradation of concrete structures. Corrosion of reinforcement in concrete leads to reduction of good bonding between steel and concrete, decrease of steel cross-sectional area, cracking and loss of serviceability. This paper investigates the behavior and Performance of reinforcement bar embedded in concrete structure under a variety of aggressive environments. The study used 16 mm diameter reinforcement bars embedded in concrete with a uniform cover of 50 mm in 200 mm x 200 mm x 750 mm concrete beam, the curing period of concrete is 28 days. After completion of 28 days’ moisture curing period, the beam was loaded in flexure causing cracking of the concrete, thereby exposing the steel reinforcements. The cracked reinforced concrete beams were then immersed in different aggressive solutions of H2So4 (Sulfuric Acid), HCl (hydrochloric acid), HNO3 (hydrogen trioxonitrate), NaOH (sodium hydroxide) and NaCl (Sodium Chloride) for a duration of six months. At the end of this curing period, the embedded steel reinforcement was removed and cleaned off the attached concrete, and then tested for change in strength, diameter, and weight loss. The results obtained shows that corrosion affect steel reinforcement in concrete under HCl, H2SO4 and HNO3 with 15%,13% and 11% very high rate change in strength respectively. Also, the NaCl and HCl, were recorded with 15% and 11% very high rate effects on reduction/addition in diameter of steel reinforcement respectively. And finally, the HCl, and H2SO4 were recorded with 24.1% having the same and very high rate effects on reduction in weight (weight loss).

Uniform cover inequalities for the volume of coordinate sections and projections of convex bodies

The classical Loomis–Whitney inequality and the uniform cover inequality of Bollobás and Thomason provide upper bounds for the volume of a compact set in terms of its lower dimensional coordinate projections. We provide further extensions of these inequalities in the setting of convex bodies. We also establish the corresponding dual inequalities for coordinate sections; these uniform cover inequalities for sections may be viewed as extensions of Meyer’s dual Loomis–Whitney inequality.

Application of New Methods of Environment Analysis and Assessment in Landscape Audits – Case Studies of Urban Areas Like Czestochowa, Poland

Following the 2000 European Landscape Convention, a new act strengthening landscape protection instruments has been in force since 2015. It sets forth legal aspects of landscape shaping (Dziennik Ustaw 2015, poz. 774) and introduces landscape audits at the province level. A landscape audit consists in identification and characterization of selected landscapes, assessment of their value, selection of so-called priority landscapes and identification of threats for preservation of their value. An audit complies with GIS standards. Analyses use source materials, i.e. digital maps of physical-geographical mesoregions, current topographic maps of digital resources of cartographic databases, latest orthophotomaps and DTMs, maps of potential vegetation, geobotanic regionalization, historic-cultural regionalization and natural landscape types, documentation of historical and cultural values and related complementary resources. A special new methodology (Solon et al. 2014), developed for auditing, was tested in 2015 in an urban area (Myga-Piatek et al. 2015). Landscapes are characterized by determining their analytic (natural and cultural) and synthetic features, with particular focus on the stage of delimitation and identification of landscape units in urban areas. Czestochowa was selected as a case study due to its large natural (karst landscapes of the Czestochowa Upland, numerous forests, nature reserves) and cultural (Saint Mary’s Sanctuary, unique urban architecture) potential. Czestochowa is also a city of former iron ore and mineral resources exploitation, still active industry, dynamic urban sprawl within former farming areas, and dynamically growing tourism. Landscape delimitation and identification distinguished 75 landscape units basing on uniform landscape background (uniform cover and use of the land). Landscape assessment used a new assessment method for anthropogenic transformation of landscape – the indicator describing the correlation between the mean shape index (MSI) and the Shannon diversity index (SHDI) (Pukowiec-Kurda, Sobala 2016). Particular threats and planning suggestions, useful in development of urban areas, were presented for selected priority landscapes.

Generalized quasi-uniformity in terms of covers

Recently g-quasi uniformity has been introduced, and in the literature there al-ready is the notion of strong quasi-uniform cover for quasi-uniform spaces. Here inthis paper we generalize the notion of strong quasi-uniform cover to study g-quasiuniformity in terms of it. As applications, we also formulate some g-topologicalconcepts via this new type of cover.

The metrisability of precompact sets

A uniform space is trans-separable if every uniform cover has a countable subcover. We show that a uniform space is trans-separable if it contains a suitable family of precompact sets. Applying this result to locally convex spaces, we are able to deduce that the precompact subsets of a wide class of spaces are metrisable. The proof of our main Theorem is based on a cardinality argument, and is reminiscent of the classical Bolzano-Weierstrass Theorem.

Clearcutting Central New York Northern Hardwood Stands

Clearcutting proved effective for regenerating central New York stands that were dominated by sugar maple along with American beech, black cherry, white ash, red maple, and basswood. Findings from five stands for periods of 7-13 years following clearcutting show densities equivalent to 2,400 to 9,400 saplings of commercial species per acre on 64-100% of the milacres sampled. In each stand, a minimum of 81% of the 6.6 ft radius sample plots were stocked with at least one sapling of a commercial species, suggesting that site occupancy will be fairly complete and uniform as these stands mature. All sites contained abundant regeneration of commercial species immediately after logging, ranging from 15,000 to 57,000 seedlings per acre, but as many as 90% of these were less than 1 ft tall. The species composition generally reflected the original forest with abundant sugar maple and American beech. However, large amounts of black cherry and white ash also appeared on some sites. Many bramble seedlings germinated during the first growing season after logging and developed into a dense uniform cover by the third year. However, the brambles declined as crown closure occurred in the new stands, and disappeared before the tenth year. Clearcutting should successfully regenerate stands of New York northern hardwoods having conditions similar to those of this study. North. J. Appl. For. 6:75-78, June 1989.

The Development of a Helicopter Spraying Machine

Experiments were carried out to study the possibilities of using ground or crop interference with the spray laden slip-stream of a helicopter flying slowly in the ground cushion to obtain a high dynamic catch of spray droplets. Experiments were carried out in 1945 and 1946 with a Sikorski type Y.R.4.B. helicopter and experimental spraying gear designed for the purpose.The forward portion of the slip-stream annulus was explored by means of spraybars placed in three different positions. The position in the sector between angles of 15° and 45° with the direction of forward flying was found to give the best all-round cover and was the position in which the spray deposit was less influenced by alterations in the control-surfaces of the helicopter.To obtain a fairly wide swathe of approximately 70 ft., the equivalent of two rotor diameters, the forward speed of 6–8 m.p.h. was found to be optimal, and it was observed that not only was good cover of the upper surfaces of the leaves obtained but the spray-laden slip-stream also gave a good cover of the vertical surfaces of the plants outside the rotary periphery and, in certain boom positions, descended and in rebounding produced a cover of the lower surfaces.In order to obtain maximum dynamic catch and a good cover of the lower surfaces of leaves, spray-bars must not be more than 6 ft. above ground.Helicopter spraying is wind dependent and in wind velocities above 12 m.p.h. uniform cover of spray deposit does not appear to be feasible.The performance of the flattened out slip-stream and rebound depends on the type of crop, and as this affects the dynamic catch to a considerable degree, this phenomenon will be the subject of a special investigation.The forward portion of the slip-stream was found to give a more even spray deposit than the aft portion because in the latter case vortices are caused by the rotor blades which affect the spray deposit.In view of its limitations as regards speed and dependence on wind velocity, economic application of spray chemicals by helicopter at a degree of efficiency and workmanship equal to that of ground machines is only possible with a heavy load-carrying helicopter. A specification for such a machine has been issued to the manufacturers of rotory wing aircraft.It is hoped that this report will be followed by a report on the performance data of the new spraying apparatus designed for the Sikorski S.51 which is based on the results of these investigations.