Levitation of non-magnetizable droplet inside ferrofluid

The central theme of this work is that a stable levitation of a denser non-magnetizable liquid droplet, against gravity, inside a relatively lighter ferrofluid -- a system barely considered in ferrohydrodynamics -- is possible, and exhibits unique interfacial features; the stability of the levitation trajectory, however, is subject to an appropriate magnetic field modulation. We explore the shapes and the temporal dynamics of a plane non-magnetizable droplet levitating inside ferrofluid against gravity due to a spatially complex, but systematically generated, magnetic field in two dimensions. The effect of the viscosity ratio, the stability of the levitation path and the possibility of existence of multiple-stable equilibrium states is investigated. We find, for certain conditions on the viscosity ratio, that there can be developments of cusps and singularities at the droplet surface; this phenomenon we also observe experimentally and compared with the simulations. Our simulations closely replicate the singular projection on the surface of the levitating droplet. Finally, we present an dynamical model for the vertical trajectory of the droplet. This model reveals a condition for the onset of levitation and the relation for the equilibrium levitation height. The linearization of the model around the steady state captures that the nature of the equilibrium point goes under a transition from being a spiral to a node depending upon the control parameters, which essentially means that the temporal route to the equilibrium can be either monotonic or undulating. The analytical model for the droplet trajectory is in close agreement with the detailed simulations. (See draft for full abstract).Comment: This article has been published in a revised form in Journal of Fluid Mechanics http://dx.doi.org/10.1017/jfm.2018.733. Copyright: copyright holde

Positive Feedback Regulation Results in Spatial Clustering and Fast Spreading of Active Signaling Molecules on a Cell Membrane

Positive feedback regulation is ubiquitous in cell signaling networks, often leading to binary outcomes in response to graded stimuli. However, the role of such feedbacks in clustering, and in spatial spreading of activated molecules, has come to be appreciated only recently. We focus on the latter, using a simple model developed in the context of Ras activation with competing negative and positive feedback mechanisms. We find that positive feedback, in the presence of slow diffusion, results in clustering of activated molecules on the plasma membrane, and rapid spatial spreading as the front of the cluster propagates with a constant velocity (dependent on the feedback strength). The advancing fronts of the clusters of the activated species are rough, with scaling consistent with the Kardar-Parisi-Zhang (KPZ) equation in one dimension. Our minimal model is general enough to describe signal transduction in a wide variety of biological networks where activity in the membrane-proximal region is subject to feedback regulation.Comment: 37 pages, 8 figures. Journal of Chemical Physics (in press

Numerical analysis of film boiling around horizontal cylindrical surfaces

Papers presented to the 11th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 20-23 July 2015.Stability of vapor film over a horizontal heater drags attention due to its wide spread applications in nuclear reactors, metal processing, manufacturing and chemical refineries. Existence of vapor film around the heater can cause advantages as well as disadvantages for various applications in industry and daily life. Hence understanding the film formation and its subsequent release in the form of bubble are dealt carefully by researchers in heat transfer community. Critical vapor thickness and average heat flux are the essential parameters which govern the release of vapor mass in the form of isolated bubbles from the surface. Experimental evidences have been reported in order to find out film dynamics for some specific fluids. However understanding it from the fundamental physics is still due and becomes a major challenge for heat transfer community. In this paper, numerical analysis of the film boiling heat transfer on a horizontal cylinder is presented to determine the effect of superheating on the heat transfer coefficient and film thickness in a pool. Findings from the present study will develop knowhow about the film formation and its role in enhancing the boiling heat transfer coefficient.am201

Elektroencefalografske, elektrokardigrafske i spirometrijske promjene u koza uzrokovane propofolom

The effects of Propofol-induced electroencephalographic, electrocardiographic and spirometric changes were studied at a lower dose rate (0.4 mg/kg body mass, intravenously) and at higher dose rate (0.5 mg/kg body mass, intravenously) in four apparently healthy goats 10 to 14 months old, weighing 9 to 12 kg. Electroencephalographic results showed that anesthesia was induced with a change of distorted β wave patterns to α waves within one minute. The α wave patterns continued for 5 to 6 minutes at the lower dose (0.4 mg/kg body mass) while they persisted for 12 to 13 minutes at the higher dose (0.5 mg/kg body mass). At the lower dose, recovery was predictable after 5 minutes on reversal of the EEG pattern from α to β waves, whereas at the higher dose α wave patterns continued for 15 minutes. The occurrence of the righting reflfl ex was noticed after the disappearance of α waves. The heart rate increased with both the dose rates within the fifi rst 5 minutes and decreased after 10 and 15 minutes of induction. Inverted T waves were found in two goats at the lower dose while at the higher dose it was found to be inverted in three of the four goats. One of the goats inducted with the higher dose showed tachycardia, with ectopic beats from the 5th to 7th minute post induction. On average, apnea was noticed for the fifi rst 30 seconds at the lower dose and for 42 seconds at the higher dose. One of the animals receiving the higher dose showed apnea for 314 seconds. This goat was given artififi cial respiration after 106 seconds and then again after 296 seconds to resuscitate it. The animal showed severe respiratory distress with abdominal respiration during the fifi rst few seconds. The tidal volume did not return to normal until 15 minutes after induction. This indicates that Propofol has a respiratory depressant activity in goats and positive pressure ventilation must be provided. It does not induce analgesia and should be accompanied by analgesics .Istraživane su elektroencefalografske, elektrokardiografske i spirometrijske promjene uzrokovane propofolom u četiri zdrave koze u dobi od 10 do 14 mjeseci, mase od 9 do 12 kg. Propofol im je bio primijenjen intravenski u malim (0,4 mg/kg tjelesne mase) i većim (0,5 mg/kg tjelesne mase) dozama. Rezultati elektroencefalografi je pokazali su da se pri izazvanoj anesteziji obrazac β vala promijenio u α valove u tijeku jedne minute. Obrasci α vala nastavili su se tijekom 5 do 6 minuta kod primjene male doze (0,4 mg/kg tjelesne mase) dok su kod primjene veće doze (0,5 mg/kg tjelesne mase) trajali 12 do 13 minuta. Kod primjene manje doze oporavak se mogao očekivati nakon pet minuta s povratkom EEG obrasca s α na β val, dok je kod većih doza α val trajao do 15 minuta. Pojava refleksa dizanja bila je zapažena nakon nestanka α valova. Učestalost srčanih otkucaja povećala se kod primjene obiju doza tijekom prvih pet minuta, a smanjila se nakon 10 i 15 minuta. Negativan T val bio je ustanovljen u dvije koze kod primjene manje doze, dok je kod primjene veće doze on bio ustanovljen u tri koze. Jedna koza koja je dobila veću dozu pokazivala je tahikardiju s ektopičnim otkucajima od pete do sedme minute nakon indukcije. Apneja se prosječno javljala tijekom prvih 30 sekundi kod primjene manje doze, a tijekom 42 sekunde kod primjene veće doze. U jedne koze apneja je pri primjeni veće doze bila zabilježena tijekom 314 sekundi. Toj je kozi za buđenje dano umjetno disanje nakon 106 sekundi te ponovljeno nakon 296 sekundi. Životinje su pokazivale težak dišni poremećaj s trbušnim disanjem u tijeku prvih nekoliko sekundi. Vrijednosti su se vratile na normalu nakon 15 minuta. Rezultati pokazuju da propofol smanjuje dišnu aktivnost u koza te je nužno primijeniti ventilaciju s pozitivnim tlakom. On ne dovodi do gubitka osjeta boli te treba primijeniti analgetike

Eleketroencefalografski pokazatelji za vrijeme anestezije propofolom i ksilazin-ketaminom u koza

The use of intravenous anaesthesia for short term surgical procedures in animal husbandry practices is increasing. However, information on the quality of an anaesthetic regime in goats has remained inadequate. Therefore, electroencephalographic studies were conducted on twelve apparently healthy adult female Barbari crossbred goats, aged 2 to 4 years, to assess the anaesthetic quality of a propofol and xylazine-ketamine combination. Quantitative analysis of EEG parameters [Total power, Median Frequency, Spectral Edge Frequency 90 (SEF-90) and Relative Power (RP) of different frequency bands delta (δ), theta (θ), alpha (α) and beta (β)] were assessed pre-experimentally (control), and at one, five, 10, 30 min, one hr, and two hr after intravenous propofol (4 mg/kg) and xylazine (0.05 mg/kg)-ketamine (4 mg/kg) administration. After propofol and xylazine-ketamine administration total power, RP-δ and θ increased significantly (P<0.05) while SEF 90, MF, RP-α and RP-β decreased. Most of the EEG changes were adequately depicted in vertex and parietal channels. Spectral analysis of EEG tracings suggested that propofol produced minimum anaesthetic stress and is a safer and better choice for short term anaesthesia in goats.U stočarskoj praksi se za kratkotrajne kirurške zahvate sve više primjenjuje intravenska anestezija. Nedostaju međutim podaci na temelju kojih bi se ustanovila kvaliteta anestezijskog protokola u koza. Kako bi se procijenila kvaliteta kombinacije anestetika propofola i ksilazin-ketamina, provedena je analiza elektoencefalografskih pokazatelja u 12 zdravih odraslih koza. Koze su bili križanci barbari pasmine u dobi od 2 do 4 godine. Kvantitativna analiza EEG pokazatelja (total power, median frequency, SEF-90, relative power delta-δ, theta-θ, alfa-α i beta-β frekvencijskih pojaseva) procijenjeni su prije pokusa (kontrolna skupina), te 1, 5, 10, 30 minuta, jedan sat i dva sata nakon intravenske primjene propofola (4 mg/kg) i ksilazin (0,05 mg/kg)-ketamina (4 mg/kg). Nakon primjene propofola i ksilazin-ketamina total power, te relative power-δ i relative power-θ znakovito su porasli (P < 0,05), dok su se SEF 90, median frequency, relative power-α i relative power-β snizili. Većina EEG promjena odgovarajuće je prikazana u verteksu i parijetalnim kanalima. Spektralna analiza EEG-a upućuje na to da propofol u anestezijskom protokolu uzrokuje minimalan stres te je, u usporedbi sa ksilazin-ketaminom, za kratkotrajnu anesteziju koza sigurniji i bolji izbor

Inter-Landau-level Andreev Reflection at the Dirac Point in a Graphene Quantum Hall State Coupled to a NbSe2 Superconductor

Superconductivity and quantum Hall effect are distinct states of matter occurring in apparently incompatible physical conditions. Recent theoretical developments suggest that the coupling of quantum Hall effect with a superconductor can provide a fertile ground for realizing exotic topological excitations such as non-abelian Majorana fermions or Fibonacci particles. As a step toward that goal, we report observation of Andreev reflection at the junction of a quantum Hall edge state in a single layer graphene and a quasi-two dimensional niobium diselenide (NbSe2) superconductor. Our principal finding is the observation of an anomalous finite-temperature conductance peak located precisely at the Dirac point, providing a definitive evidence for inter-Landau level Andreev reflection in a quantum Hall system. Our observations are well supported by detailed numerical simulations, which offer additional insight into the role of the edge states in Andreev physics. This study paves the way for investigating analogous Andreev reflection in a fractional quantum Hall system coupled to a superconductor to realize exotic quasiparticles.Comment: published verio

Evidence of a compensated semimetal with electronic correlations at the CNP of twisted double bilayer graphene

Recently, magic-angle twisted bilayer graphene (MATBLG) has shown the emergence of various interaction-driven novel quantum phases at the commensurate fillings of the moir'e superlattice, while the charge neutrality point (CNP) remains mostly a vanilla insulator. Here, we show an emerging phase of nearly compensated semimetallicity at the CNP of twisted double bilayer graphene (TDBLG), a close cousin of MATBLG, with signatures of electronic correlation. Using electrical and thermal transport, we find almost two orders of magnitude enhancement of the thermopower in magnetic fields much smaller than the extreme quantum limit, accompanied by a large magnetoresistance($\sim 2500\%$) at CNP. This provides indisputable experimental evidence that TDBLG near CNP is a compensated semimetal. Moreover, at low temperatures, we observe an unusual sublinear temperature dependence of resistance. A recent theory predicts the formation of an excitonic metal near CNP, where small electron and hole pockets coexist. We understand the sublinear temperature dependence in terms of critical fluctuations in this theory

Assessment of genetic diversity among 16 promising cultivars of ginger using cytological and molecular markers

Ginger (Zingiber officinale Roscoe) is an economically important plant, valued all over the world. The existing variation among 16 promising cultivars as observed through differential rhizome yield (181.9 to 477.3 g) was proved to have a genetic basis using different genetic markers such as karyotype, 4C nuclear DNA content and random amplified polymorphic DNA (RAPD). The karyotypic analysis revealed a differential distribution of A, B, C, D and E type of chromosomes among different cultivars as represented by different karyotype formulas. A significant variation of 4C DNA content was recorded in ginger at an intraspecific level with values ranging from 17.1 to 24.3 pg. RAPD analysis revealed a differential polymorphism of DNA showing a number of polymorphic bands ranging from 26 to 70 among 16 cultivars. The RAPD primers OPC02, OPA02, OPD20 and OPN06 showing strong resolving power were able to distinguish all 16 cultivars. The extent of genetic diversity among these cultivars was computed through parameters of gene diversity, sum of allele numbers per locus and Shannon&apos;s information indices. Cluster analysis, Nei&apos;s genetic similarity and genetic distances, distribution of cultivars into special distance classes and principal coordinate analysis and the analysis of molecular variance suggested a conspicuous genetic diversity among different cultivars studied. The genetic variation thus detected among promising cultivars of ginger has significance for ginger improvement programs. Key words: Ginger, Karyotype, RAPD Introduction Zingiber officinale is rich in secondary metabolites such as oleoresin. It possesses an unique combination of properties like anti-inflammatory, aphrodisiac, antioxidant and antibacterial activity S. Nayak et al. · Genetic Diversity among Ginger Cultivars In the past decade, DNA polymorphism has become the marker of choice for the identification and characterization of plants. It is a relatively reliable, generally applicable method to obtain large samples of markers from any species of plant. However, each marker system samples a different fraction of the genomes and therefore has a different resolving power, range of applicability and probability of homology. The random amplified polymorphic DNA (RAPD) technique has been widely used in cultivar identification programs The objectives of this study were to (1) fingerprint ginger cultivars for identification and (2) detect the genetic diversity and relatedness of 16 cultivars sampled from different geographical regions using karyotypic analysis, 4C DNA content and RAPD analysis. In this study, many analytical procedures such as a n-j method, bootstrapping, spatial genetic structure analysis (SGS), and analysis of molecular variance (AMOVA) have been widely used to derive genetic distances among cultivars and to assess the structure of genetic data in a reduced dimensional space. Materials and Methods Plant materials Sixteen promising cultivars of ginger (Zingiber officinale) were included in the present study which were collected from the turmeric germplasm collection of the Orissa University of Agriculture and Techology (OUAT), Bhubaneswar, Orissa, India. These cultivars were initially collected from different parts of India Karyotype analysis Young and healthy root-tips of different cultivars of ginger were pre-treated in a (0.02 m) hydroxyquinoline mixture (1:1) for 3.5 h at 14 ∞C followed by overnight fixation in propionic ethanol. Chromosome staining was made in 2% lacto propionic orcin after cold hydrolysis in 5 n HCl for 7 min. Root-tips were squashed in 45% propionic acid. Ten well scattered metaphase plates were selected for karyotype analysis of each species. The chromosome morphology was determined following the method of 4C DNA content For Feulgen cytophotometric estimation of 4C DNA, ten fixed root-tips from each cultivar (2n = 22 chromosomes) were hydrolysed in 1 n HCl for 12 min at 60 ∞C, washed in distilled water and stained in Schiff&apos;s reagent for 2 h at 14 ∞C; each root-tip squash was prepared in 75% acetic acid. Ten scorings were made from each slide and the 4C DNA content was estimated from metaphase chromosomes using a NIKON Optiphot microscope with a microspectrophotometer following the method of Sharma and Sharma (1980) with monochromatic light at 550 nm. In situ DNA values were obtained on the basis of optical density measurements which were converted to picograms (pg) using Vant Hoff&apos;s 4C nuclear DNA value (67.1 pg) for Allium cepa as standard Isolation of DNA Total plant DNA was isolated from fresh and young leaves. The leaves were harvested freshly and washed thoroughly with cold autoclaved distilled water and then blotted to dry. About 2 g leaf was excised from the upper tip portion of the buds. DNA extraction was done on the day of collection. The genomic DNA was isolated following the protocol of Doyle and Doyle (1990) with a little modification. Insoluble poly(vinylpyrrolidone) was added to the leaf tissue prior to grinding. The crude DNA was purified with RNase A (@ 60 µg ml Ð1 of DNA solution) followed by washing with S. Nayak et al. · Genetic Diversity among Ginger Cultivars 487 purified chloroform/isoamylalcohol (24:1). To test the quality and quantity of the purified DNA, the samples were electrophoresed in a 0.8% agarose gel along with a known amount of uncut lambda DNA (Bangalore Genei Pvt. Ltd, Bangalore, India) as standard. The sample DNA was diluted as 25 ng µl Ð1 for RAPD-PCR analysis. RAPD amplification Twenty random decamer primers (Operon Tech., USA) from A, C, D and N series (OPA02, 03, 04, 08, 16; OPAF14; OPC02, 05; OPD03, 07, 08, 18, 20; and OPN02, 03, 04, 06, 07, 10, 12) were used for RAPD analysis. RAPD assays were performed in a final volume of 25 µl containing 10 mm Tris-HCl [tris(hydroxymethyl)aminomethane], pH 9.0, 1.5 mm MgCl 2 , 50 mm KCl and 0.01% gelatin, 200 µm of each dNTPs, 0.4 µm primer, 25 ng template DNA and 0.5 unit of Taq DNA polymerase (Bangalore Genei, Bangalore, India). The RAPD analysis was performed as per the methodology described by The amplification products were electrophoresed in 1.5% agarose gel containing ethidium bromide (@ 0.5 µg ml Ð1 ) in TAE buffer (40 mm Tris base, 20 mm sodium acetate, 20 mm EDTA, glacial acetic acid to pH 7.2) for 3 h at 60 V. A total of 2.5 µl loading buffer (1.0 X TAE, 50% glycerol, 0.25% bromophenol blue and 0.25% xylene cyanol) was added to each reaction before electrophoresis. After electrophoresis, the gels were observed under an UV-transilluminator, documented in Gel-Doc 2000 (Bio-Rad) and photographed. Resolving power According to Prevost and Wilkinson (1999) the resolving power (Rp) of a primer is: Rp = Σ IB, where IB (band informativeness) takes the value of: 1-[2 ¥ (0.5 Ð p)], p being the proportion of the 16 genotypes (ginger cultivars analyzed) containing the band. Data collection and analysi