Persistence of plastic debris and its colonization by bacterial communities after two decades on the abyssal seafloor

The fate of plastic debris entering the oceans is largely unconstrained. Currently, intensified research is devoted to the abiotic and microbial degradation of plastic floating near the ocean surface for an extended period of time. In contrast, the impacts of environmental conditions in the deep sea on polymer properties and rigidity are virtually unknown. Here, we present unique results of plastic items identified to have been introduced into deep-sea sediments at a water depth of 4150 m in the eastern equatorial Pacific Ocean more than two decades ago. The results, including optical, spectroscopic, physical and microbial analyses, clearly demonstrate that the bulk polymer materials show no apparent sign of physical or chemical degradation. Solely the polymer surface layers showed reduced hydrophobicity, presumably caused by microbial colonization. The bacterial community present on the plastic items differed significantly (p < 0.1%) from those of the adjacent natural environment by a dominant presence of groups requiring steep redox gradients (Mesorhizobium, Sulfurimonas) and a remarkable decrease in diversity. The establishment of chemical gradients across the polymer surfaces presumably caused these conditions. Our findings suggest that plastic is stable over extended times under deep-sea conditions and that prolonged deposition of polymer items at the seafloor may induce local oxygen depletion at the sediment-water interface

Numerical model of the spatio-temporal dynamics in a water strider group

The water strider group demonstrates a very complex dynamics consisting of competition for the food items, territoriality and aggression to the conspecific individuals, escaping from the predators, etc. The situation is even more complex due to the presence of different instars, which in most water strider species live in the same habitat and occupy the same niche. The presented swarm model of water striders demonstrates the realistic population dynamics. For the swarm formation in the model, attraction and repulsion forces were used. Animal motion in the model takes into account inertia and kinetic energy dissipation effects. The model includes three different rates related to the growth of individuals: food appearance rate, food assimilation rate, and stored energy loss rate. The results of our modeling show that the size distribution of individuals seems to be an adequate measure for population status, and it has a characteristic shape for different model parameter combinations. Distribution of the distances between nearest neighbors is other important measure of the population density and its dynamics. Parameters of the model can be tuned in such a way, that the shape of both distributions in a steady phase coincides with that shape observed in a natural population, which helps to understand the factors leading to particular momentary distribution of both parameters (size and distance) in the population. From this point of view, the model can predict how both distributions can further develop from certain state depending on particular combination of factors

Multi-Technique Investigation of a Biomimetic Insect Tarsal Adhesive Fluid

There is substantial motivation to develop novel adhesives which take advantage of the superior adhesive strength and adaptability of many natural animal adhesives; however, the tools typically used to study these mechanisms are incapable of determining the precise interactions of molecules at an adhesive interface. In this study, a surface specific, order sensitive vibrational spectroscopy called sum frequency generation (SFG) is, for the first time, combined with multiple bulk characterization techniques to examine a novel, simple biomimetic adhesive fluid inspired by tarsal fluid of insects. Insects perform complex adhesive demands, including sticking, climbing vertically and running upside-down with little difficulty. Thus, we hypothesize that both bulk and surface specific properties of the fluid contribute to the success of this wet adhesive mechanism. SFG spectra of biomimetic emulsion exhibited similar hydrocarbon organization on hydrophobic and hydrophilic substrates to natural beetle fluid previously studied with the same method. Bulk characterization techniques indicated that the emulsion had a shear-thinning profile with the ability to enhance traction forces during climbing and low surface tension ideal for surface wetting on the majority of natural surfaces. Multi-technique comparisons between emulsion and pure squalane revealed that a hydrocarbon only based fluid could not replicate the traction promoting properties of the emulsion. We conclude that the insect tarsal fluid adhesive mechanism relies upon contributions from both surface-specific properties optimizing traction force and bulk properties promoting rapid surface wetting and maintaining pull-off force for fast detachment

Extensive collection of femtoliter pad secretion droplets in beetle Leptinotarsa decemlineata allows nanoliter microrheology

Pads of beetles are covered with long, deformable setae, each ending in a micrometric terminal plate coated with secretory fluid. It was recently shown that the layer of the pad secretion covering the terminal plates is responsible for the generation of strong attractive forces. However, less is known about the fluid itself because it is produced in extremely small quantity. We here present a first experimental investigation of the rheological properties of the pad secretion in the Colorado potato beetle {\it Leptinotarsa decemlineata}. Because the secretion is produced in an extremely small amount at the level of the terminal plate, we first develop a procedure based on capillary effects to collect the secretion. We then manage to incorporate micrometric beads, initially in the form of a dry powder, and record their thermal motion to determine the mechanical properties of the surrounding medium. We achieve such a quantitative measurement within the collected volume, much smaller than the $1 {\rm \mu}$l sample volume usually required for this technique. Surprisingly, the beetle secretion was found to behave as a purely viscous liquid, of high viscosity. This suggests that no specific complex fluid behaviour is needed during beetle locomotion. We build a scenario for the contact formation between the spatula at the setal tip and a substrate, during the insect walk. We show that the attachment dynamics of the insect pad computed from the high measured viscosity is in good agreement with observed insect pace. We finally discuss the consequences of the secretion viscosity on the insect adhesion

Root Hair Adhesion in Posidonia oceanica (L.) Delile Seedlings: A Numerical Modelling Approach

Animals and plants use adhesion to move, to anchor to a substrate, or to disperse seeds and fruits. Some plants developed a root pad as a common strategy to adhere to consolidated substrates. In the marine environment, the seagrass Posidonia oceanica attaches fi rmly to consolidated substrates via adhesive root hairs, forming a pad structure. We used novel morphological and ultrastructural data to develop a numerical model to study the dynamics of root hair adhesion during contact formation on rough consolidated substrates for this species. Morphological analysis, conducted using Scanning Electron Microscope, highlighted the role of root hair branching in pad formation. Transmission Electron Microscope microscopy allowed us to identify a glue-like substance at the pad/ substrate interface. The numerical model highlighted the role played by the cell wall ’ s elasticity in pad formation and its importance in guaranteeing a fi rm adhesion. Furthermore, the effectiveness of these mechanisms was assessed at different simulated roughness levels. Increasing knowledge on the adhesion mechanism of seagrass to consolidated substrates could be pivotal in developing advanced seedling-based restoration protocols. The fi ndings of this study could contribute to restoration activities planned to contrast seagrass regression. Transplanting initiatives using seedlings can now better address the search for suitable and low-impact ways to fi x germinated plants to the substrate

Власні хвилі в неоднорідному за перерізом відкритому циліндричному діелектричному хвилеводі

By the point matching method, taking into account only the even electric longitudinal field components, is considered the eigenvalue problem – constant propagation in inhomogeneous dielectric waveguide. The following model is accepted: a dielectric waveguide of round cross-section with single circular heterogeneity. A result of numerical studies of the dependence of the propagation constant for different types of waves, depending on the parameters and the location of the in homogeneity, are introduced. The results of the study can be extended to the study of waveguides with a cross section of different shapes and/or contain multiple heterogeneous domains with different parametersМетодом точечного согласования, с учетом только четных продольных составляющих электрического поля, решается задача на собственные значения – постоянные распространения волн в неоднородном волновод круглого поперечного сечения с одной неоднородностью круглой формы. Приведены результаты численных исследований зависимости постоянной распространения для разных типов волн в зависимости от параметров и месторасположения неоднородности. Результаты данной работы можно расширить для исследования волноводов, имеющих сечение другой формы и/или содержащих несколько неоднородных областей с разными параметрами.Методом точкового узгодження, з врахуванням лише парних поздовжніх складових електричного поля, розв’язується задача на власні значення – сталі поширення хвиль в неоднорідному діелектричному хвилеводі. Розглядається наступна модель: діелектричний хвилевід кругового поперечного перетину з однією неоднорідністю кругової форми. Наведені результати чисельних досліджень залежності сталої поширення для різних типів хвиль в залежності від параметрів та місцеположення неоднорідності. Результати даної роботи можуть бути поширені для дослідження хвилеводів, які мають перетин іншої форми та/або містятьдекілька неоднорідних областей з різними параметрам

Задача мікрохвильової візуалізації для двовимірної екранованої структури

Introduction. Microwave imaging is noninvasive method for determination objects internal structure (complex dielectric permittivity) by means of electromagnetic fields. Algorithm for solving microwave imaging problem of two-dimensional shielded objects is described. Methods. The direct problem is solved by finite element method, inverse problem by iterative Newton-Gauss method using Tikhonov regularization. Sensitivity matrix is calculated with numerically efficient method based on the reciprocity principle. Results. Solution of the inverse problem without noise makes it possible to determine the value of the dielectric constant of each element of the object up to a third mark. In the case of incorporation of noise, results of the inverse problem solution are unsatisfactory, since the algorithm converges only with significant signal/noise ratio. Conclusions. Further work should be directed to improve algorithm for solving the inverse problem, especially on the algorithm of calculating the sensitivity matrix.Приведен алгоритм решения задачи микроволновой визуализации для двумерной экранированной структуры. Прямая задача решается методом конечных элементов, обратная задача - итерационным методом Ньютона - Гаусса с использованием регуляризации по Тихонову. Матрица чувствительности вычисляется с помощью численно эффективного метода на основе принципа взаимности. Получены неудовлетворительные результаты решения обратной задачи, поскольку алгоритм сходиться только при значительном отношении сигнал/шум. Поэтому, дальнейшую работу необходимо направить на доработку алгоритма решения обратной задачи.Наведено алгоритм розв’язку задачі мікрохвильової візуалізації для двовимірної екранованої структури. Пряма задача розв’язується методом скінчених елементів, зворотна задача – ітераційним методом Ньютона-Гауса з використанням регуляризації за Тихоновим. Матриця чутливості обчислюється за допомогою чисельно ефективного методу на основі принципу взаємності. Отримані незадовільні результати розв’язку зворотної задачі, оскільки алгоритм збігається лише при значному відношенні сигнал/шум. Тому, подальшу роботу необхідно зосередити на вдосконаленні алгоритму розв’язку зворотної задачі

Задача на власні значення відкритого неоднорідного діелектричного хвилеводу

Introduction. Algorithm for solving eigenvalue problem of open inhomogeneous dielectric waveguide is presented. Open waveguide divided into two regions. Inner inhomogeneous region is discretized using node–edge finite elements. Fields in outer unbounded homogeneous region expanded into cylindrical harmonics. The final nonlinear eigenvalue problem is solved using inverse iteration procedure. Results. Calculated surface waves of circular inhomogeneous object. Literature overview on the excitation of open waveguide is presented. Conclusions. Above algorithm allow to determine the discrete spectrum of waves in open inhomogeneous waveguideПриведен алгоритм решения задачи на собственные значения поперечно неоднородного диэлектрического волновода. Используется метод конечных элементов совместно с разложением поля по цилиндрическим гармоникам во внешней неограниченной области. Получены результаты расчета для поверхностных волн. Приведен обзор работ по возбуждению открытых волноводов, из которого следует необходимость учета полного спектра волн при расчете диэлектрических структур методом разложения полей по собственным функциям.Наведено алгоритм для розрахунку власних хвиль та власних значень поперечно неоднорідного діелектричного хвилеводу, який поєднує метод кінцевих елементів та розклад поля по циліндричним гармонікам у зовнішній необмеженій області. Отримані результати розрахунку для поверхневих хвиль. Наведено огляд літератури зі збудження відкритих хвилеводів, з якого слідує необхідність врахування повного спектра хвиль при розрахунку діелектричних структур методом розкладу полів по власним функціям

METHODS OF THE PATTERN FORMATION IN NUMERICAL MODELING OF BIOLOGICAL PROBLEMS

Evolution of different systems can be described in terms of their relaxation to the minimums of some effective potential relief. This observation leads us to face us with a question how to generate corresponding potential patterns which describe adequately various physical and biological systems. In this review, we present a number of different ways of generating such potentials demanded by the problems of different kinds. For example, we reproduce such a generation in the framework of a simple theory of phase transitions, automatic blocking of the growing phase nucleation and universal large scale structure. Being frozen at late stages of their evolution they form majority of meta-stable structures which we observe in real world. Counting on above-mentioned universality of naturally-generated fractal structures and their further utilization in numerical simulations of biological problems, we reproduce also formal algorithms of generation of such structures based on random deposition technique and Fourier-transform approaches

Developing your own graduate employees: Employer perspectives on the value of a degree apprenticeship

The purpose of this paper is to offer an employer perspective on the value of degree apprenticeships (DAs) less than a year after the first apprentices commenced their studies for a bachelor's degree in September 2015. Design/methodology/approach - This case focusses on one of the first DAs in the UK. It draws on evidence from interviews with HR professionals responsible for the DA in two contrasting companies, an international PLC and a smaller, fast growing enterprise. Findings - Both employers consider that the DA meets recruitment needs in ways that other options do not. They particularly value the ability of apprentices to make an immediate contribution in the workplace. For the smaller employer the university support structures are a significant advantage. Only the larger employer formally input into the curriculum prior to validation but both feel they can tailor content to suit their needs. Both see investing in the DA as excellent value for money. Practical implications - The value of strong relationships, trust and ongoing dialogue between partners emerges as a key component in fulfilling the need of employers. Originality/value - The DA model recasts employers as the purchasers of higher education and affords them a key role in developing provision tailored to their needs. Implications of this new model for employers, universities and learners are potentially profound and hard to predict. This case study is based on part of the early stage of a three-year research programme. It provides a unique, early insight into two employers' rationales for engaging with the DA programme and their initial experiences