Rough Ones Research Articles

Ants’ Ability in Solving Simple Problems

Aiming to know the extent of the ants’ cognitive abilities, we set Myrmica ruginodis workers in four problematic situations. We discovered that these ants could walk round a barrier, by foraging and navigating as usual, using known visual cues. They could walk preferentially on smooth substrates instead of rough ones, but did not memorize their choice. This behavior may be due to the easier deposit of pheromones on a smooth substrate. The ants could establish a single way when having only two narrow paths for going in and out of their nest. This was the consequence of the ants’ traffic and of the distinct pheromonal deposits while going in and out of the nest. The oldest ants needing sugar water could push a door for getting such water. They did so by having the audacity to go on walking, whatever the presence of a door. Such a door is not a tool sensu stricto. Future studies will examine if ants can lean new techniques, can use tools and/or can learn using tools.

Shear-driven segregation of dry granular materials with different friction coefficients.

We report the first experimental demonstration of bulk segregation in a shear-driven dry granular mixture, where the particles only differ in their surface friction coefficients. We found that the smoother particles tend to sink to the bottom of the shear zone, while rough particles migrate to the top of the sample. This phenomenon is similar to the well known kinetic sieving in particle mixtures with size heterogeneity. In the present case the smooth particles have a higher probability to penetrate into voids created by the shearing than the rough ones. Discrete element simulations were carried out and reproduced the experimentally observed segregation patterns. Moreover, simulations performed in the absence of gravity revealed that rough particles tend to remain in the shear zone, while the smooth particles are being expelled from it. We propose a mechanism in which the smooth particles are driven towards regions of lower shear rate.

External Pressure Coefficients on the Atypical High-Rise Building – Computing Simulation and Measurements in Wind Tunnel

This paper deals with determination of the external pressure coefficients on the new planned high-rise building with atypical cross-section. The building will be built in the center of Bratislava (Slovakia). The real area surrounding of the designed building was also considered. The main aim of this research was to find out the accuracy of the results obtained by computing simulation. Two types of surfaces of the model were taken into account – smooth and rough ones. The real structure had the surface roughened by using a façade with windows and columns between them. As the reference values of external pressure coefficients were considered the results obtained from the experimental measurements carried out in the wind tunnel laboratory. Short description of the designed structure and its surroundings, wind tunnel laboratory, experimental measurements, scale model of the structure, and computing simulation with considered input parameters are mentioned here. The Computational Fluid Dynamics (CFD) simulation was performed using 3D Reynolds-averaged Navier-Stokes CFD with the SST k-ω turbulence model. At the end of the paper, obtained results are discussed and some recommendations for planning engineers are presented.

Visualization of Sweat Fingerprints on Various Surfaces Using a Conjugated Polyelectrolyte.

A conformation-variable conjugated polyelectrolyte responding to oppositely charged biomolecules was examined as an imaging agent for the detection of latent fingerprints (LFPs). Sulfonated poly(diphenylacetylene) (SPDPA) produces high-resolution fluorescence (FL) LFP images by simple wetting of the target objects with the polymer solution without any additional treatment. SPDPA readily interacts with LFP sweat components (especially amino acids) via electrostatic interactions, leading to significantly enhanced FL images in a "turn-on" mode. The FL emission enhancement was examined in a model reaction between SPDPA and an amino acid standard. Visualization with SPDPA is effective on various surfaces, including both rough (paper) and smooth (glass and plastic) ones. Moreover, SPDPA readily interacts with extremely thin sweat LFPs, especially on smooth glass surfaces.

Characterization of composites based on biodegradable poly(vinyl alcohol) and nanostructured fly ash with an emphasis on polymer–filler interaction

A thermal power station fly ash (FA) was mechanochemically activated by high-energy ball milling that yielded nanostructured FA. This nanostructured FA was incorporated into biodegradable poly(vinyl alcohol) (PVA) matrix by solution mixing and ultrasonication. Transmission electron micrographs revealed that the smooth spherical particles of FA were changed into irregular and rough ones; in addition, the particle size of FA was reduced to a few hundred nanometers, and its specific surface area value increased after the high-energy milling process. All these factors, in turn, led to a thermodynamically favorable interaction between the mechanochemically activated FA and PVA as evidenced by Fourier transform infrared spectroscopy. The incorporation of a very small amount of the nanostructured FA led to an increase in crystallinity of the polymer matrix. The glass transition temperature of the PVA matrix increased by about 18°C when 5 wt% of the nanostructured FA was used as the reinforcement.

Laser lithography for dental alloy treatment - biological response

Event Abstract Back to Event Laser lithography for dental alloy treatment - biological response Maksym Pogorielov1, Oleg Mishchenko2, 3 and Nataliia Zaitseva1 1 Sumy State University, Ukraine 2 TM “Zircon-Prior”, Ukraine 3 Zhaporizhzhia State Medical University, Ukraine Background: Metals and ceramics have been widely used in dental surgery over the last 40 years. Dental implants applied as an alternative treatment method for the prosthodontic restoration of partially or fully edentulous patients. However, there are many reports about implant failures observed in 6% to 11% of cases[1]. A major factor that determines the success of dental implantation is osseointegration, which is the stable anchorage of an implant in living bone achieved by direct bone-to-implant contacts. High-quality osseointegration stand for an accelerated healing process, high stability, and durability of the dental implant. The main factors that can change osteointegration are alloy’s biomechanics and surface characteristics. The surface properties of implants are essential to the response of cells at biomaterial interface, affecting the growth and quality of newly formed bone tissue. In vitro studies have shown that osteoblastic cells attach, spread and proliferate more rapidly on smooth surfaces than on rough ones. However, osteoblasts present higher rate of differentiation and matrix mineralization and higher production of growth factors in the presence of rough substrates[2]. There are different methods to create nanostructured surfaces with high relevance for industry. Lithography techniques, such as electro-beam lithography, focused ion beam lithography and photolithography have been commonly used, but they are complicated, present high cost, and are time consuming. An alternative for the fabrication of nanostructures is the use of femtosecond laser, this is one of the most promising methods to modify the physical properties of materials[3]. The aim of our research was to evaluate tissue response in subcutaneous implantation of different alloys with laser lithography surface treatment. Materials and Methods: In our experiment we used standard Ti and Zr alloy. The surface of materials was treated by laser lithography technique (LLT) to make grooves in nanoscale size (from 45 to 150 nm). Untreated alloy we used as a control group. Materials were implanted subcutaneous to 24 Wistar rats (6 for each alloy). After 10 days materials removed and studied by SEM. Results: LLT allows create rough surface on both Ti and Zr alloy with size from 45 to 150 nm. Using such technique we can generate faster and cheaper nanostructures in a single-step process. But standard LLT made more regular grooves on Ti alloy compare the Zr, and should be modified for different metals (fig. 1) In 10 days after implantation non-treated, both Ti and Zr, alloys covered by thin connective tissue capsule and easy removed. Their surface has no cell attachment and only a few collagen fibers. Well-developed connective tissue growth around LLT-treated alloy in 10 days of experiment. After the alloy removed we can observe fibroblast and leucocytes attachment to the material surface. The fibroblasts have elongated processes that join cells with LLT-modified surface. Cell density does not depend on alloy type. Fibroblasts secret collagen fibers that random covers alloy surface (fig. 1). Figure 1. SEM of Ti and Zr alloy before and after 10 days of subcutaneous implantation. Conclusion: We have used the laser lithography technique to modify different metal alloy to made nanoscale rough surface. It leaded to optimization of connective tissue cell attachment and collagen secretion that could be used for medical implant improvement. The cell reaction did not depend on alloy type.

Effects of etching parameters on ZnO nanotubes evolved from hydrothermally synthesized ZnO nanorods

This paper reports fabrication and characterization of ZnO nanotubes on Au cylindrical spirals. Highly oriented single-crystalline ZnO nanorods were hydrothermally synthesized on Au cylindrical spirals and were etched in NaOH solution to form nanotubes. Effects of etching parameters on the lengths, wall thicknesses and morphologies of the ZnO nanotubes were studied with the etching period, etching temperature and NaOH concentration regulated respectively. It turns out that the etching parameters affect significantly the morphologies of the ZnO nanotubes but negligibly the lengths and wall thicknesses. The surfaces of the ZnO nanotube-coated Au cylindrical spirals tend to be Gaussian rough ones as the etching parameters become larger. Adjusting the etching temperature readily gives rise to perfect ZnO nanotubes. The results are beneficial for large-scale preparation of ZnO nanotubes with controllable sizes and morphologies in nanodevices.

Friction Between Steel and Snow in Dependence of the Steel Roughness

The purpose of this study was to analyze the effect of the surface structure on the friction between steel and snow. On a linear tribometer positioned inside a cold laboratory, four steel skis with different running surfaces were tested over a wide range of velocity, snow temperature and normal force. The surface roughness was measured with a focus variation microscope. The friction tests showed that the surface roughness had a major effect on friction between steel and snow, with higher friction for smooth surfaces than for rough ones. The effect was particularly strong for temperatures close to the melting point, where the friction strongly increased for smooth surfaces. The degree of dependence was affected by the gliding speed, leading to two different kinds of velocity-dependent friction curves. Increased adhesion and wet friction due to an increase in contact area were interpreted as cause for the higher friction of smooth surfaces.

Mycobacterium abscessus: An environmental mycobacteria being a human pathogen

BackgroundMycobacterium abscessus is an opportunistic organism common in the environment. This species rarely cause infections in immunocompetent individuals. Certain patient groups, however, can get severe infections, e.g., in skin, soft tissues or lungs, as well as disseminated infections. During the last years, this organism has emerged as a major pathogen in patients with cystic fibroses. M. abscessus exhibits two different colony types: one with smooth and shining morphology, the other with rough and dry morphology. The smooth strains are considered wild-types, which become rough due to mutation. These features make the M. abscessus variants particularly interesting for scientific studies, since the results of such analyses can be a basis for creating theories also concerning other mycobacteria. AimThe aim of this study is to analyze potential differences between smooth and rough strains of M. abscessus concerning human host response. MethodsM. abscessus strains isolated at the Mycobacterial Laboratory in Gothenburg, Sweden were analyzed morphologically. The ability of monocytes to internalize the two colony variants of M. abscessus was studied, as well as the cytokine response. ResultsThe analyses showed that isolates from the wound mainly exhibit smooth colony formation, while those from airways generally are of the rough phenotype. Human monocytes easily internalized the smooth varieties of M. abscessus, whereas the rough ones rarely were internalized. Differences between the two types, concerning the capacity to induce cytokines, were also revealed. Discussion and conclusionsThe wound isolates of M. abscessus were mainly smooth, while the lung isolates were rough. The rough variants that lack certain surface glycolipids are likely to be more hydrophobic and aerosol transmissible than the smooth strains, which might explain why the rough ones are more often associated with infections in the airways than are the smooth ones. Studies on other mycobacteria have also shown a link between hydrophobicity and aerosol transmission.These studies showed that human monocytes easily internalize smooth M. abscessus cells, but rarely the rough ones. This capacity of the rough cells to avoid internalization is in all probability also due to absence or reduction of certain surface glycolipids. The lack of these surface lipids makes the rough bacteria stick to each other forming so-called cords, which are aggregates of many cells and thus difficult to internalize. The absence of glycolipids exposing other surface structures of the bacteria cell may also contribute to prevent internalization. Even if intracellular survival is regarded as the most important virulence factor of mycobacteria, it is nevertheless likely that the capacity to avoid internalization can contribute to pathogenesis at several mycobacterioses. It is possible that this phenomenon is important at tuberculosis, since Mycobacterium tuberculosis cells form rough colonies.

Bounds on the mean residual lifetime of progressive type II right censored order statistics

In this paper, we present some sharp upper bounds on the deviations of the mean residual lifetime of progressive type II right censored order statistics from the mean residual lifetime, m(t)=E(X t )=E(X−t|X>t), for arbitrary t>0. We also describe the distributional forms for which the bounds are attained. The obtained bounds are numerically evaluated and compared with other classical rough ones. AMS subject classifications 62G30, 62E15

Dry friction of microstructured polymer surfaces inspired by snake skin.

The microstructure investigated in this study was inspired by the anisotropic microornamentation of scales from the ventral body side of the California King Snake (Lampropeltis getula californiae). Frictional properties of snake-inspired microstructured polymer surface (SIMPS) made of epoxy resin were characterised in contact with a smooth glass ball by a microtribometer in two perpendicular directions. The SIMPS exhibited a considerable frictional anisotropy: Frictional coefficients measured along the microstructure were about 33% lower than those measured in the opposite direction. Frictional coefficients were compared to those obtained on other types of surface microstructure: (i) smooth ones, (ii) rough ones, and (iii) ones with periodic groove-like microstructures of different dimensions. The results demonstrate the existence of a common pattern of interaction between two general effects that influence friction: (1) molecular interaction depending on real contact area and (2) the mechanical interlocking of both contacting surfaces. The strongest reduction of the frictional coefficient, compared to the smooth reference surface, was observed at a medium range of surface structure dimensions suggesting a trade-off between these two effects.

Microconical silicon structures influence NGF‐induced PC12 cell morphology

Micro-and nanofabrication techniques provide the opportunity to develop new types of cell culture platform, where the effect of various topographical cues on cellular functions such as proliferation and differentiation can be studied. In this study, PC12 cells were cultured on patterned silicon (Si) surfaces comprising arrays of microcones (MCs) exhibiting different geometrical characteristics and surface chemistries. It was illustrated that, in the absence of nerve growth factor (NGF), PC12 cells increased proliferation on all types of patterned surface, as compared to flat Si surfaces. However, in the presence of NGF, PC12 cells showed different responses, depending on the plating surface. Unlike low and intermediate rough MC surfaces, highly rough ones exhibiting large distances between MCs did not support PC12 cell differentiation, independently of the MCs' chemical coatings. These results suggest that the geometrical characteristics of MCs alone can influence specific cellular functions. Tailoring of the physical properties of arrays of Si MCs in order to identify which combinations of MC topologies and spatially defined chemistries are capable of driving specific cellular responses is envisaged.

Cencerradas y matracas en Navarra durante el Antiguo Régimen: funciones y objetivos

During the Old Regime rough musics ones acted in the majority of the occasions like control mechanisms and repression of the collective behaviors. In them their causes were worth of a series of instruments to heighten their activities, being tried this way to legitimize their actions. The present article has as an aim to study these events rendering a special attention to its functions and objectives. Nevertheless, the main task will consist of deepening in the cases seen in the kingdom of Navarre, organizing them in two groups: 1. weedings; 2. immoral behaviors; 3. government actions. All this with the intention to understand of a satisfactory way these practices of communitarian justice.

Radiostereometric analysis of early implant migration – a valuable tool to ensure proper introduction of new implants

Radiostereometric analysis of early implant migration – a valuable tool to ensure proper introduction of new implants

High-fidelity reversible data hiding scheme based on pixel-value-ordering and prediction-error expansion

This paper presents a high-fidelity reversible data hiding scheme for digital images based on a new prediction strategy called pixel-value-ordering (PVO) and the well-known prediction-error expansion (PEE) technique. Specifically, a host image is first divided into non-overlapped equal-sized blocks. Then the maximum and minimum values of each block are predicted by other pixels of the block according to their pixel value orders. With such a PVO-based predictor, data embedding is implemented via PEE. The incorporation of PVO into PEE has an advantage in reducing the number of shifted pixels, and thus it can alleviate the degradation in image quality. Consequently, the proposed method can embed adequate data into a host image with rather limited distortion. The PSNR of a marked image versus its original one is guaranteed to be above 51.14dB. In addition, a solution is provided to further improve the embedding performance by priorly using the flat blocks to embed data while leaving the rough ones unchanged. We demonstrate the proposed method outperforms some advanced prior arts with abundant experimental results.

Directed transport of confined Brownian particles with torque

We investigate the influence of an additional torque on the motion of Brownian particles confined in a channel geometry with varying width. The particles are driven by random fluctuations modeled by an Ornstein-Uhlenbeck process with given correlation time τ_{c}. The latter causes persistent motion and is implemented as (i) thermal noise in equilibrium and (ii) noisy propulsion in nonequilibrium. In the nonthermal process a directed transport emerges; its properties are studied in detail with respect to the correlation time, the torque, and the channel geometry. Eventually, the transport mechanism is traced back to a persistent sliding of particles along the even boundaries in contrast to scattered motion at uneven or rough ones.

Predictability of Evolutionary Trajectories in Fitness Landscapes

Experimental studies on enzyme evolution show that only a small fraction of all possible mutation trajectories are accessible to evolution. However, these experiments deal with individual enzymes and explore a tiny part of the fitness landscape. We report an exhaustive analysis of fitness landscapes constructed with an off-lattice model of protein folding where fitness is equated with robustness to misfolding. This model mimics the essential features of the interactions between amino acids, is consistent with the key paradigms of protein folding and reproduces the universal distribution of evolutionary rates among orthologous proteins. We introduce mean path divergence as a quantitative measure of the degree to which the starting and ending points determine the path of evolution in fitness landscapes. Global measures of landscape roughness are good predictors of path divergence in all studied landscapes: the mean path divergence is greater in smooth landscapes than in rough ones. The model-derived and experimental landscapes are significantly smoother than random landscapes and resemble additive landscapes perturbed with moderate amounts of noise; thus, these landscapes are substantially robust to mutation. The model landscapes show a deficit of suboptimal peaks even compared with noisy additive landscapes with similar overall roughness. We suggest that smoothness and the substantial deficit of peaks in the fitness landscapes of protein evolution are fundamental consequences of the physics of protein folding.

In vitro evaluation of the PEtU-PDMS material immunocompatibility: the influence of surface topography and PDMS content

The aim of the present work is to evaluate the in vitro immunocompatibility of an elastomeric material with feasible applications in the cardiovascular field. In particular, since it is well known that surface chemistry and topography play a key role in the foreign body response, their influence on human monocytes was evaluated. The material, constituted by a poly(ether)urethane (PEtU) and a polydimethylsiloxane (PDMS), was synthesized to manufacture films and small-diameter vascular grafts with three different surface topographical features, smooth, rough and porous, and siloxane rates, 10, 30 and 40. Human THP-1 monocytes have been cultured for 72 h on the films and human blood has been circulating for 2 h into the grafts to assess leukocyte adhesion and cytokine releases. Materials extracts were utilized to evaluate monocyte apoptosis. Smooth films showed lower cell adhesion degrees than rough and porous ones. All the PEtU-PDMS (poly(ether)urethane-polydimethylsiloxane) films and vascular grafts induced a narrow inflammatory response, as demonstrated by slight cytokine secretion levels, in particular samples with the highest PDMS contents (30 and 40%) induced the lowest IL-1b secretion. Moreover, an absence of monocyte apoptosis advises that the negligible release values have not to be ascribed to material toxicity. In the end, surface topography showed to affect only monocyte adhesion while siloxane content the cytokine release. Therefore, the possibility to modify the above tested parameters during material synthesis and manufacture could allow to bound the inflammatory potency of the PEtU-PDMS devices and render them excellent candidates for cardiovascular reconstruction.

Design of dental implants, influence on the osteogenesis and fixation

The fixation and the bone ingrowth at the interface of porous cylindrical implants (total porosity of 37% and average pores diameter of 480 microm) were compared in vivo to rough cylindrical implants (R (a) = 5.3 microm), both of commercially pure titanium, made by powder metallurgy. The implants were inserted into the tibias of 20 rabbits and the animals were sacrificed 4 and 8 weeks after surgery. The percentage of bone-implant contact observed in porous implant was significantly larger than in the rough ones for all of sacrifice periods, respectively, 57% vs. 46% after 4 weeks, and 59% vs. 50% after 8 weeks. The mechanical tests showed a significant increase in the shear strength of the porous implants for the two analyzed periods, 4 and 8 weeks (14 and 20 MPa), when compared with rough ones (4 and 13 MPa). These results suggest that porous implants improve the contact at the implant-bone interface and increase the fixation to the bone, improving the osseointegration. Thus, the porous implant might be an alternative to dental implant in less favorable conditions, and appear to be better fixed to bone, offering promising alternatives.

Importance of plant physical cues in host acceptance for oviposition by Busseola fusca

AbstractPlant and surrogate stems exhibiting specific combinations of physical cues were used to determine which plant‐related stimuli influence the oviposition of Busseola fusca (Fuller) (Lepidoptera: Noctuidae). The number of eggs and egg batches laid per female increased with an increase in diameter of both natural and artificial stems. Direct observations of the oviposition behaviour (walking, antennating, and sweeping with the ovipositor) indicated that the female moths preferred oviposition supports with a large diameter and non‐pubescent or smooth surfaces over pubescent or rough ones. Pubescence and rough surfaces significantly affected the behavioural steps leading to oviposition by interfering with the ovipositor sweep process necessary to find a suitable oviposition site. Furthermore, more eggs and egg batches were laid on soft than rigid supports. The rigidity of the support affected the proper insertion of the ovipositor for egg deposition. Our results underline the importance of physical stimuli in B. fusca's choice of an oviposition site, which may facilitate the identification of potential host plants or preferred oviposition sites on a plant for this species.