Homology and symmetry breaking in Rayleigh-Benard convection: Experiments and simulations

Algebraic topology (homology) is used to analyze the weakly turbulent state of spiral defect chaos in both laboratory experiments and numerical simulations of Rayleigh-Benard convection.The analysis reveals topological asymmetries that arise when non-Boussinesq effects are present.Comment: 21 pages with 6 figure

TÜKETİCİLERİN PERAKENDECİ TERCİHLERİNDE ETKİLİ OLAN DAVRANIŞSAL FAKTÖRLER VE SÜPERMARKET UYGULAMASI

ABSTRACT In this study, face to face surveys have been conducted with a group of 325 consumers who shop from supermarkets, in order to determine the degree of importance of behavioral factors that play a role on consumers' retail preferences and to find out about the degree of relationship between these factors and demographic and socioeconomic characteristics of consumers. The above mentioned sample size has been determined in the % 1 importance level of Trabzon city population. While questions regarding consumer profile have been tested with Frequency Distribution; analyses involving comparions have been done using Kendall's Tau Correlation. In addition Factor Analysis and a connected Reliability Analysis have been done.Bu çalışmada, tüketicilerin perakendeci tercihlerinde rol oynayan davranışsal faktörlerin önem dereceleri ortaya konulup; bu faktörlerin tüketicilerin demografik ve sosyo-ekonomik özelikleriyle ilişkilerinin ne yönlü olduğunu saptamak amacıyla; süpermarketlerden bizzat alışveriş yapan 325 kişilik bir müşteri grubuna yüzyüze anket yöntemi uygulanmıştır. Anılan örnek büyüklüğü, Trabzon il nüfusu göz önüne alınarak % 1 önem derecesi çerçevesinde belirlenmiştir. Tüketicilerin profilini belirleyen sorular, Frekans Dağılımı ile test edilirken; karşılaştırmalı analizlerde, Kendall's Tau Korelasyon Analizi uygulanmıştır. Faktör Analizi ve buna bağlı olarak Güvenilirlik Analizi de geçekleştirilmiştir

Low cost, ultra-high throuhput particle counting using inertial microfluidics

In this work, an ultra-high throughput microfluidic particle counting system is demonstrated. For the particle counting, a low cost custom-design optical hardware is developed. The microfluidic chip utilizes the inertial microfluidics to focus the particles in a certain location which significantly enhanced the optical signal utilized for the quantification of the number concentration. The effect of the particle focusing on the counting performance is demonstrated. The proposed system has a potential to be portable and has a capability to process 10 ml of sample within couple minutes

Solidification of Metallic Alloys: Does the Structure of the Liquid Matter?

In 1952, Frank (Proc R Soc Lond Ser-Math Phys Sci 215:43-46, 1952) already postulated that Icosahedral Short Range Order (ISRO) of atoms in the liquid could possibly explain the large nucleation undercoolings measured in metallic alloys by Turnbull and Fisher (J Chem Phys 17:71-73, 1949). About thirty years later, this conjecture was proven to be key for the understanding of Quasicrystals (QC) formation (Shechtman et al. in Phys Rev Lett 53:20, 1951-3, 1984). More recently, it has been found that a few tens to thousand ppm of solute elements in Al-base and Au-base alloys can influence the nucleation and growth of the primary fcc phase via mechanisms involving ISRO and QC formation. ISRO has also been found to limit the mobility, and thus diffusion, of atoms in the liquid. This can lead to out-of-equilibrium conditions, e.g., the formation of metastable phases or supersaturated solid solution, at reduced velocity compared to alloys where ISRO is not predominantly present. Finally, there are several experimental evidences that ISRO is also responsible for twinned dendrites formation in Al alloys. The present contribution summarizes these recent findings and points out the implications that these might have in the field of solidification and additive manufacturing

Flagellar waveform dynamics of freely swimming algal cells

We present quantitative measurements of time-dependent flagellar waveforms for freely swimming biflagellated algal cells, for both synchronous and asynchronous beating. We use the waveforms in conjunction with resistive force theory as well as a singularity method to predict a cell's time-dependent velocity for comparison with experiments. While net propulsion is thought to arise from asymmetry between the power and recovery strokes, we show that hydrodynamic interactions between the flagella and cell body on the return stroke make an important contribution to enhance net forward motion.Process and EnergyMechanical, Maritime and Materials Engineerin

Enhancement of biomixing by swimming algal cells in two-dimensional films

Fluid mixing in active suspensions of microorganisms is important to ecological phenomena and presents a fascinating stochastic process. We investigate the mixing produced by swimming unicellular algal cells (Chlamydomonas) in quasi-two-dimensional liquid films by simultaneously tracking the motion of the cells and that of microscopic passive tracer particles advected by the fluid. The reduced spatial dimension of the system leads to long-range flows and a surprisingly strong dependence of tracer transport on the concentration of swimmers, which is explored over a wide range. The mean square displacements are well described by a stochastic Langevin model, which is used to parameterize the mixing. The effective diffusion coefficient D grows rapidly with the swimmer concentration PHI as D ∼ PHI 3/2, as a result of the increasing frequency of tracer-swimmer interactions and the long-range hydrodynamic disturbances created by the swimmers. Conditional sampling of the tracer data based on the instantaneous swimmer position shows that the rapid growth of the diffusivity enhancement with concentration must be due to particle interactions with multiple swimmers simultaneously. Finally, the anomalous probability distributions of tracer displacements become Gaussian at high concentration, but manifest strong power-law tails at low concentration, while the tracer displacements always grow diffusively in time.National Science Foundation (U.S.) (Grant No. NSF DMR-0803153