Frictional Effects in Biomimetic Scales Engagement

Scales engagement can contribute significantly to nonlinear bending behavior of elastic substrates with rigid biomimetic scales. In this letter, we investigate the role of friction in modulating the nonlinearity that arises due to self-contact of scales through an analytical investigation. We model the friction as dry Coulomb type friction between rigid links and the substrate is taken to be linear elastic. Our results reveal that frictional effects give rise to two possible locking mechanisms, namely static friction lock and kinetic friction lock. These locks arise due to a combination of interfacial behavior and geometry. In addition to these extremes, the frictional behavior is found to increase stiffness of the structure. This dual nature of friction which influences both system operation and its terminal limit results in the maximum relative frictional work to lie at intermediate friction coefficients and not at the extremes of frictional limits.Comment: 4 pages, 4 figure

Wrinkling reveals a new isometry of pressurized elastic shells

We consider the point indentation of a pressurized, spherical elastic shell. Previously it was shown that such shells wrinkle once the indentation reaches a threshold value. Here, we study the behaviour of this system beyond the onset of instability. We show that rather than simply approaching the classical `mirror-buckled' shape, the wrinkled shell approaches a new, universal shape that reflects a nontrivial type of isometry. For a given indentation depth, this ``asymptotic isometry", which is only made possible by wrinkling, is reached in the doubly asymptotic limit of weak pressure and vanishing shell thickness.Comment: 6 pages main text plus 14 pages of supplementary informatio

Evolution of star clusters on eccentric orbits: semi-analytical approach

We study the dynamical evolution of star clusters on eccentric orbits using a semi-analytical approach. In particular we adapt and extend the equations of EMACSS code, introduced by Gieles et al. (2014), to work with eccentric orbits. We follow the evolution of star clusters in terms of mass, half-mass radius, core radius, Jacobi radius and the total energy over their dissolution time. Moreover, we compare the results of our semi-analytical models against $N$-body computations of clusters with various initial half-mass radius, number of stars and orbital eccentricity to cover both tidally filling and under-filling systems. The evolution profiles of clusters obtained by our semi-analytical approach closely follow those of $N$-body simulations in different evolutionary phases of star clusters, from pre-collapse to post-collapse. Given that the average runtime of our semi-analytical models is significantly less than that of $N$-body models, our approach makes it feasible to study the evolution of large samples of globular clusters on eccentric orbits.Comment: 11 pages, 4 figures, 1 table. Accepted for publication in MNRA

Prediction of damaged zone in longwall working panels

In longwall mining, the instability of roadways can affect the mine safety, production rate and consequently the economic condition of mine. Therefore their stability analysis is one the most important technical problems in underground mining. The stability analysis and the design of support systems have to be investigated from two points of view; 1) the pressure and displacements of damaged zone around gate roadways due to the construction process and stress redistribution and 2) the working loading due to coal seam extraction and overburden caving that extends the damaged zone size. The aim of this research is the calculation of working effect on the damaged zone around gate roadway considering geomechincal properties of medium and the geometric characteristic of the roads and working. Therefore, a method has been obtained to calculate the total damaged zone area and working influence coefficient using geometric concepts and mathematical relations, then a design algorithm has been suggested based on the obtained method

THE PREVALENCE OF CUTANEOUS LEISHMANIASIS IN EAST OF AHVAZ COUNTY, SOUTH-WESTERN IRAN

Objectives: Cutaneous Leishmaniasis (CL) is a zoonotic parasitological disease. This disease cause always important health challenges for the human communities. It is common in many parts of the globe. This research was designed to determine the epidemiology of CL in East of Ahvaz County during 2003- 2013. Methods: This was a descriptive cross-sectional study. The disease was diagnosed based on clinical examination and microscopic observation of the parasite in the ulcer site. The patient's Information such as age, gender, number and sites of ulcer (s) on the body, month and residence area were recorded. Data analysis was performed using SPSS software. Results: Totally, 2287 cases were detected during 2003 – 2013. About 53.4% patients were male and 46.4% female. The highest frequency infected age groups were observed in 10-19 years old (n=550 ,24%). Nearly 37 % of the patients had one and 38.1% had three ulcers. The most common location of ulcers were on hands (n=1022, 44.7%) and then on feet (n=501, 21.9%). Totally 1877 of the patients were infected in rural areas. Based on the appearance of the lesion it was found that 410 cases (17.9%) were of the dry type and 1877 cases (82.1%) were wet type. Concluaions: Such high prevalence and incidence rates are alarming and require control and prevention measures. Further epidemiological studies of CL are suggested. Key words: Epidemiology, Cutaneous Leishmaniasis, Iran

Real-time reversible tunable elasticity in cellular solids via electromagnetic actuation

The ability for reversible, real-time control of elastic moduli in solids can find significant application in advanced mechanical components, protective structures, and biomedical devices. Here, we propose a novel concept for controlling the linear and nonlinear elastic properties of cellular structures via electromagnetically triggered mechanisms in the cellular solid. Three structural systems with orthotropic material properties were proposed and studied numerically, experimentally, and analytically. Using the proposed concept, the elastic modulus can be controlled over two to four orders of magnitude. The Poisson ratio of the isotropic structure can be varied from 0 to 0.5 continuously. The adjustments over nonlinear elastic (i.e., buckling) behavior of the structure are achieved by activation of supplementary cell walls in the lattice through electromagnetic actuation. Magnetic actuation will hamper the first symmetrical buckling pattern of the structure and force the structure to buckle according to a higher buckling pattern with smaller sinusoidal wavelength in the cell walls. The uniaxial buckling strength of the structure was tuned over two orders of magnitude

Morphohistological characteristic of digestive tract of an endemic cichlid fish, Iranocichla hormuzensis Coad, 1982 (Teleostei: Cichlidae)

Objective of the current study was to investigate morphohistology of digestive tract of Iranocichla hormuzensis, one of two native cichlid fishes in Iran. The species present omnivorous feeding habits and restricted in shallow, high temperatures and high salinity water in Mehran River and its drainages. This species has a terminal mouth with several rows of serrated incisive teeth, which covered the upper and lower lips. Esophagus is a short tubular between pharynx and stomach, stomach is relatively small and sac-shape, and intestine is long. Gastric wall, through the digestive tube, consists of four layers of mucosa, submucosa, muscularis, and serosa with some characters specialized for each organ, such as a well-developed mucosa layer and numerous goblet cell in the ventral section of stomach. Morphohistology of digestive tract of I. hormuzensis supports its generalist diet

Comparison of patient-centered and family-centered teaching methods (based on empowerment model) on the laboratory variables of patients with type II diabetes

Background and aims: Considering the important role of the family in patients with diabetes in management and good control of the disease, the present study was conducted to compare the efficacy of patient-centered and family-centered teaching methods (based on empowerment model) on the laboratory variables of patients with type II diabetes. Methods: This was a quasi-experimental study and applied. 147 patients with type 2 diabetes refrred to diabetic center of shahroud were divided into three groups: control (A), patient-centered intervention (B), and family-centered intervention (C) through simple random allocation. Before the intervention and three months after that, nonfasting and fasting blood glucose, cholesterol, triglycerides, and low and high-density lipoprotein was carried out from patients as laboratory indexes. The intervention was carried out in the form of patient-centered in group B and family-centered in group C and routine education was conducted in the control group. Data was analysed using SPSS software and Chi-square and ANOVA tests. Results: There was no significant difference in the demographic variables and laboratory variables among the three groups before the intervention (P>0.050). A significant difference was found between all of these variables after the intervention FBS: (P=0.012), BS: (P=0.002), triglicerid: (P=0.015), cholesterol: (P=0.013), LDL: (P=0.010), HDL: (P=0.022). A significant difference was reported between all of the laboratory variables in the intervetion groups in comparision with the control group (P<0.050). While no significant difference was seen in the level of these variables between the B and C groups, the reduction of the level of these variables was more in the family-centered intervention group in comparison with patient-centered group. Conclusion: Due to the significant differences in the results of traditional method empowerment approaches, using this model to enhance the clinical indicators recommended. Also, taking into consideration the important role of the family in the management and control of diabetes, will be facilitated the achievement of optimal control and desirable

NOVI MODEL ZA PREDVIĐANJE NAPREDOVANJA TUNELSKOGA BUŠAĆEG STROJA U TVRDIM STIJENAMA

The prediction of the advance rate of a Tunnel Boring Machine (TBM) in hard rock conditions is one of the most important concerns for estimating the time and costs of a tunnel project. In this paper, in the first step, a model based on Rock Engineering Systems (RES) is proposed to predict geotechnical risks (representing media characteristics) in rock TBM tunnelling. Fifteen main parameters that influence the geotechnical hazards were used in the modelling. In establishing an interaction matrix and also a parameter rating, the views of five experts were taken into account. The Vulnerability Index (VI) (geotechnical risk levels) for 2058 datasets out of 2168 sets of data from 53 geological zones in 11 km of the Zagros long tunnel was obtained. In the second step, based on the machine operating parameters such as torque, cutter head rotation per minute, cutter normal force and media characteristics (represented by VIs), which were used as input parameters and advance rate was used as an output parameter, while using 2058 datasets, linear and non-linear multiple regression analyses were carried out. 110 datasets (out of 2168 datasets), which were not used in the modelling, were applied to evaluate the performance of regression models and other models in literature and the results were compared. The obtained results showed that the new linear model proposed with R2=0.83 and RMSE=0.12 has a better performance than the other models.Predviđanje brzine napredovanja tunelskoga bušaćeg stroja u tvrdim stijenama jedna je od najvažnijih stvari kod procjene vremena i troškova izradbe tunela. Prikazana je priprema stijenskoga inženjerskog sustava, modela kojim se predviđa geotehnički rizik (ovisan o svojstvima stijena) kod izradbe tunela bušaćim strojevima. Uporabljeno je 15 varijabli koje utječu na spomenuti rizik. Na temelju 5 ekspertnih mišljenja postavljena je interakcijska matrica i rangiranje varijabli. Indeks ranjivosti, kao izvedenica geotehničkoga rizika, izračunan je za 2058 (od ukupno 2168) skupova podataka, uzorkovanih u 55 geoloških zona kroz 11 km dugačak tunel Zagros. U sljedećemu koraku proučeni su operativni parametri strojeva poput okretnoga momenta, rotacije glave sjekača po minuti, sile na glavi te svojstava stijena (prikazanih indeksom ranjivosti). Oni su bili ulazne varijable, a iznos napredovanja izlazna. Na temelju 2058 podataka izračunane su linearne i nelinearne višestruke regresije. Dodatnih 110 podataka (nisu korišteni za modeliranje) uporabljeni su za provjeru regresijskih (i drugih) modela. Rezultati su pokazali kako novi linearni model, s vrijednostima R2 = 0,83 i RMSE = 0,12, ima bolja svojstva nego drugi razmatrani modeli

Karyosystematics of Kol tooth-carp, Aphanius darabensis (Teleostei: Cyprinodontidae)

The karyological and cytological characteristics of an endemic cyprinodont fish of Iran, Aphanius darabensis Esmaeili, Teimori, Gholami & Reichenbacher, 2014 have been investigated for the first time by examining metaphase chromosomes spreads obtained from gill epithelial and kidney cells. The diploid chromosome number of A. darabensis is 48. The karyotype consisted of five submetacentric and 19 subtelocentric pairs of chromosomes (5sm+19st). The fundamental number (FN) is 58. Sex chromosomes were cytologically indistinguishable in this tooth-carp. According to this study and previous karyological reports from other cyprinodont species, it can be suggested that the diploid number (2n=48) is common amongst cyprinodont fishes. These results can be used as basic informations in population studies and management and conservation programs