The Hausdorff dimension of random walks and the correlation length critical exponent in Euclidean field theory

We study the random walk representation of the two-point function in statistical mechanics models near the critical point. Using standard scaling arguments we show that the critical exponent $\nu$ describing the vanishing of the physical mass at the critical point is equal to $\nu_\theta/ d_w$. $d_w$ is the Hausdorff dimension of the walk. $\nu_\theta$ is the exponent describing the vanishing of the energy per unit length of the walk at the critical point. For the case of O(N) models, we show that $\nu_\theta=\varphi$, where $\varphi$ is the crossover exponent known in the context of field theory. This implies that the Hausdorff dimension of the walk is $\varphi/\nu$ for O(N) models.Comment: 11 pages (plain TeX

Development of a multicomponent-multisize liberation model

Journal ArticleThis paper is concerned with the development of a kinetic model for mineral liberation by grinding. Existing population balance size reduction models are extended to include two minerals with an arbitrary number of locked particle fractions. The validity of this approach to liberation modelling is demonstrated for the ball mill grinding of a copper ore in batch laboratory and continuous pilot plant mills

Microscopic Model for High-spin vs. Low-spin ground state in [Ni2M(CN)8][Ni_2{M(CN)_8]} (M=MoV,WV,NbIVM=Mo^V, W^V, Nb^{IV}) magnetic clusters

Conventional superexchange rules predict ferromagnetic exchange interaction between Ni(II) and M (M=Mo(V), W(V), Nb(IV)). Recent experiments show that in some systems this superexchange is antiferromagnetic. To understand this feature, in this paper we develop a microscopic model for Ni(II)-M systems and solve it exactly using a valence bond approach. We identify the direct exchange coupling, the splitting of the magnetic orbitals and the inter-orbital electron repulsions, on the M site as the parameters which control the ground state spin of various clusters of the Ni(II)-M system. We present quantum phase diagrams which delineate the high-spin and low-spin ground states in the parameter space. We fit the spin gap to a spin Hamiltonian and extract the effective exchange constant within the experimentally observed range, for reasonable parameter values. We also find a region in the parameter space where an intermediate spin state is the ground state. These results indicate that the spin spectrum of the microscopic model cannot be reproduced by a simple Heisenberg exchange Hamiltonian.Comment: 8 pages including 7 figure

Occurrence of a bisexual strain of the Brine shrimp Artemia

The importance of the brine shrimp, Artemia in larviculture was recognised for the first time when Scale (1933, Trans. Am. Fish. Soc.. 63 : 129-130) described the value of the nauplii of Artemia as an ideal food for fish fry. Later several investigators found that the freshly hatched nauplii of the brine shrimp are the most suitable and also very convenient food for the early larval stages of various species of fishes and crustaceans

Two dimensional lattice Gross--Neveu model with domain-wall fermions

We investigate the two dimensional lattice Gross--Neveu model in large flavor number limit using the domain-wall fermion formulation, as a toy model of lattice QCD. We study nonperturbative behaviorn of the restoration of chiral symmetry of the domain-wall fermions as the extent of the extra dimension $(N_s)$ is increased to infinity. We find the the parity broken phase (Aoki phase) for finite $N_s$, and study the phase diagram, which is related to the mechanism of the chiral restoration in $N_s\to\infty$ limit. The continuum limit is taken and $O(a)$ scaling violation of observables vanishes in $N_s\to\infty$ limit. We also examine the systematic dependencies of observables to the parameters.Comment: 36 pages (26 figures), Latex (epsf style-file needed

Towards T.R.I.C.K. 2.0 – A tool for the evaluation of the vehicle performance through the use of an advanced sensors system

In the last years, the tire technological development has played a fundamental role in motorsport and in automotive industry. The tire contact patch forces have a great influence on the vehicle behavior, so their correct estimation is a crucial task to understand how to improve the car performance. In order to identify the tire interaction characteristic, it is also necessary to use a procedure that allows the correct evaluation of the slip angles in the different operating conditions. This paper presents an evolution of the T.R.I.C.K. tool developed by the UniNa vehicle dynamics research group. In the first version of this tool an 8 degree of freedom vehicle model has been implemented and, starting from the experimental data acquired, the T.R.I.C.K. calculates the interaction forces and the tire slips using the equilibrium equations. Using more car parameters and further data obtained from track sessions and dedicated tests, in the presented release of the tool, new formulations have been developed for a more accurate calculation of the tire-road forces. The effectiveness of the treatments is assessed using experimental data and the simulator outputs. The new formulations introduced in this paper allows, depending on the availability of additional vehicle data and acquisition sensors, to estimate the interaction forces with different and more accurate methodologies than the equilibrium equations, while retaining very reduced simulation times. In this way it is possible to carry out a more precise study of vehicle dynamics with the possibility of investigating and significantly improving performance

Effects of heat energy on morphology and properties of selective inhibition sintered high density polyethylene

This study provides an account of comprehensive experimentation and mechanical characterisation of high density polyethylene (HDPE) parts that are fabricated through an additive manufacturing process called selective inhibition sintering (SIS). In this study, test specimens are fabricated by selective fusing of HDPE particles through controlled heating. Morphological studies and mechanical property evaluation of these specimens are carried out to assess the impact of energy on sintering of HDPE particles and structural integrity. Results indicate that, heat energy up to a threshold level of 28.48 J/mm2 results in superior fusion of the HDPE particles, and further increase causes degradation of the structure. Surface roughness, tensile and flexural properties of SIS parts are compared with those of injection moulded parts for assessing their suitability to engineering applications

Prvo izvješće o jakoj crijevnoj kapilariozi uzrokovanoj oblićem Baruscapillaria obsignata u farmski uzgojenih biserki (Numida meleagris).

Capillarid worms are known to cause severe infection of the gastrointestinal tract and mortality, especially in Galliformes. In the present study, guinea fowl carcasses received from an organized poultry farm were investigated for the cause of death. The clinical history reported included reduced feed intake, diarrhea, lethargy and weakness in the flock. On necropsy examination, excess catarrhal exudate in the duodenal lumen (catarrhal enteritis), diphtheritic membrane formation, petichiae or ecchymotic haemorrhages on the mucosa of the duodenum were consistent findings. Mucosal scrapings and worms collected from dead birds examined microscopically revealed the presence of numerous thin adult worms, larvae, and barrel-shaped eggs with prominent bipolar plugs consistent with the morphology of Capillaria spp. Histopathologically, duodenal epithelial desquamation, mucosal thickening, blunting and clubbing of villi, goblet cell hyperactivity, and prominent thickening of the tunica muscularis were observed. Severe intestinal capillariosis resulted in reduced appetite, poor nutrient absorption, unthriftiness, diarrhea, and finally the death of the birds. This paper highlights the importance of regular screening and deworming in farmed guinea fowls. This appears to be the first report with regard to the intestinal form of capillariosis caused by Baruscapillaria obsignata in farmed helmeted guinea fowls.Poznato je da su oblići porodice Capillaridae uzročnici jakih invazija probavnog sustava i uginuća ptica, osobito reda Galliformes. Istraživanje se temelji na rezultatima postmortalnih pretraga biserki uginulih na farmi. Iz povijesti bolesti bilo je vidljivo da su ptice slabije uzimale hranu, imale su proljev, bile potištene i slabe. Razudbom uginulih ptica dokazan je obilni kataralni eksudat u lumenu dvanaesnika (kataralni enteritis), tvorba difteričnih membrana te petehijalna ili ekhimotična krvarenja na sluznici dvanaesnika. Mikroskopiranjem strugotina sluznice uginulih ptica uočeni su mnogi tanki oblići te jaja bačvasta oblika s izraženim bipolarnim čepovima što se podudaralo s izgledom jaja oblića roda Capillaria. Patohistološkom pretragom ustanovljena je deskvamacija epitela dvanaesnika, zadebljanje sluznice, zadebljanje crijevnih resica, hiperaktivnost vrčastih stanica te izraženo zadebljanje mišićnog sloja. Jaka kapilarioza imala je za posljedicu smanjeni tek, slabu apsorpciju hranjivih tvari, slab prirast, proljev i uginuće ptica. U radu se naglašava važnost redovitog pretraživanja i dehelmintizacije farmski uzgajanih biserki. Ovo je prvi nalaz objektivno dokazane crijevne kapilarioze uzrokovane oblićem Baruscapillaria obsignata u farmski uzgojenih biserki

Correlated responses to selection for faster development and early reproduction in Drosophila: the evolution of larval traits

Studies on selection for faster development in Drosophila have typically focused on the trade-offs among development time, adult weight, and adult life span. Relatively less attention has been paid to the evolution of preadult life stages and behaviors in response to such selection. We have earlier reported that four laboratory populations of D. melanogaster selected for faster development and early reproduction, relative to control populations, showed considerably reduced preadult development time and survivorship, dry weight at eclosion, and larval growth rates. Here we study the larval phase of these populations in greater detail. We show here that the reduction in development time after about 50 generations of selection is due to reduced duration of the first and third larval instars and the pupal stage, whereas the duration of the second larval instar has not changed. About 90% of the preadult mortality in the selected populations is due to larval mortality. The third instar larvae, pupae, and freshly eclosed adults of the selected populations weigh significantly less than controls, and this difference appears during the third larval instar. Thereafter, percentage weight loss during the pupal stage does not differ between selected and control populations. The minimum amount of time a larva must feed to subsequently complete development is lower in the selected populations, which also exhibit a syndrome of reduced energy expenditure through reduction in larval feeding rate, larval digging and foraging activity, and pupation height. Comparison of these results with those observed earlier in populations selected for adaptation to larval crowding and faster development under a different protocol from ours reveal differences in the evolved traits that suggest that the responses to selection for faster development are greatly affected by the larval density at which selection acts and on details of the selection pressures acting on the timing of reproduction

A hybrid approach of anfis—artificial bee colony algorithm for intelligent modeling and optimization of plasma arc cutting on monel™ 400 alloy

This paper focusses on a hybrid approach based on genetic algorithm (GA) and an adaptive neuro fuzzy inference system (ANFIS) for modeling the correlation between plasma arc cutting (PAC) parameters and the response characteristics of machined Monel 400 alloy sheets. PAC experiments are performed based on box-behnken design methodology by considering cutting speed, gas pressure, arc current, and stand-off distance as input parameters, and surface roughness (Ra), kerf width (kw), and micro hardness (mh) as response characteristics. GA is efficaciously utilized as the training algorithm to optimize the ANFIS parameters. The training, testing errors, and statistical validation parameter results indicated that the ANFIS learned by GA outperforms in the forecasting of PAC responses compared with the results of multiple linear regression models. Besides that, to obtain the optimal combination PAC parameters, multi-response optimization was performed using a trained ANFIS network coupled with an artificial bee colony algorithm (ABC). The superlative responses, such as Ra of 1.5387 µm, kw of 1.2034 mm, and mh of 176.08, are used to forecast the optimum cutting conditions, such as a cutting speed of 2330.39 mm/min, gas pressure of 3.84 bar, arc current of 45 A, and stand-off distance of 2.01 mm, respectively. Furthermore, the ABC predicted results are validated by conducting confirmatory experiments, and it was found that the error between the predicted and the actual results are lower than 6.38%, indicating the adoptability of the proposed ABC in optimizing real-world complex machining processes