How to embed three-dimensional flexible electrodes in microfluidic devices for cell culture applications

This communication describes a simple, rapid and cost effective method of embedding a conductive and flexible material within microfluidic devices as a means to realize uniform electric fields within cellular microenvironments. Fluidic channels and electrodes are fabricated by traditional soft-lithography in conjunction with chemical etching of PDMS. Devices can be deformable (thus allowing for a combination of electro-mechanical stimulation), they are made from inexpensive materials and easily assembled by hand; this method is thus accessible to a wide range of laboratories and budgets.     

Composing dinatural transformations: Towards a calculus of substitution

Dinatural transformations, which generalise the ubiquitous natural transformations to the case where the domain and codomain functors are of mixed variance, fail to compose in general; this has been known since they were discovered by Dubuc and Street in 1970. Many ad hoc solutions to this remarkable shortcoming have been found, but a general theory of compositionality was missing until Petri?, in 2003, introduced the concept of g-dinatural transformations, that is, dinatural transformations together with an appropriate graph: he showed how acyclicity of the composite graph of two arbitrary dinatural transformations is a sufficient and essentially necessary condition for the composite transformation to be in turn dinatural. Here we propose an alternative, semantic rather than syntactic, proof of Petri?'s theorem, which the authors independently rediscovered with no knowledge of its prior existence; we then use it to define a generalised functor category, whose objects are functors of mixed variance in many variables, and whose morphisms are transformations that happen to be dinatural only in some of their variables.We also define a notion of horizontal composition for dinatural transformations, extending the well-known version for natural transformations, and prove it is associative and unitary. Horizontal composition embodies substitution of functors into transformations and vice-versa, and is intuitively reflected from the string-diagram point of view by substitution of graphs into graphs.This work represents the first, fundamental steps towards a substitution calculus for dinatural transformations as sought originally by Kelly, with the intention then to apply it to describe coherence problems abstractly. There are still fundamental difficulties that are yet to be overcome in order to achieve such a calculus, and these will be the subject of future work; however, our contribution places us well in track on the path traced by Kelly towards a calculus of substitution for dinatural transformations.     

Laboratory simulation of inertial and frictional effects on barotropic rotating flows over and past obstacles: Comparison with simple numerical and analytical models

Summary This paper presents the results of laboratory experiments designed to simulate some basic process of large-scale flows interacting with obstacles, also in order to better understand details of subsynoptic disturbances that are created in the lee of large topographic features. For this event, the experimental facilities of the Istituto di Cosmogeofisica of Consiglio Nazionale delle Ricerche (CNR) were exploited, consisting in a hydraulic channel mounted on a rotating platform, along whose longitudinal axis a hemispherical obstacle was towed at various speeds. Because of the conversion of potential vorticity, the experimental results showed, as expected, the existence of a region of anticyclonic circulation, located above the obstacle; however, also an asymmetric pattern of positive vorticity located downwind of the obstacle did appear, which cannot be interpreted in terms of simple quasi-geostrophic inviscid dynamics. This behaviour is not surprising, if one considers that the real flow near the obstacle could hardly ever match the conditions of inviscid quasi-geostrophy (Ro≪1,E∼0), but was similar to that characterising the zone close to the surface of the obstacle, where inertial and viscous effects are not negligible. Finally, in order to investigate the importance of these effects on the interaction processes, simple numerical and analytical models were applied, by which the consistency of some laboratory simulations, chosen among the most significant ones, could be compared.     

FIR spectroscopy of ethyl bromide and trioxane: New laser transitions and assignments

Eight new optically pumped far infrared laser transitions from ethyl bromide and 22 from trioxane are presented. For each new line we give the wavelength, the polarization relative to that of the pump laser and the absorption offset relative to the CO₂ center frequency. The assignment of the rotovibrational states for the pump and the emission transitions of ethyl bromide are calculated. We also partly assigned the rotational levels of trioxane.     

Erratum to: “Weak corrections to gluon-induced top–antitop hadro-production” [Phys. Lett. B 639 (2006) 513]

This is an Erratum to a Letter of ours [S. Moretti, M.R. Nolten, D.A. Ross, Phys. Lett. B 639 (2006) 513]. After its publication, we have discovered a mistake in a numerical program that affects the results presented therein. We provide here the corrected version.     

Hydraulic simulation of negatively buoyant plumes

Summary The results of a hydraulic simulation of denser-than-air plumes in a neutral atmosphere are presented and discussed. The behaviour of these amission is of particular practical interest in connection with problems of geothermal drilling. The experimental data, concerning the height and the horizontal distance from the source of the maximum plume rise, as well as the distance where the plume touches ground, were compared with simple analytical formulae available in the literature. It was found that plume rise is described with sufficient accuracy by Meroney's model; for touchdown distance an empirical formula, obtained fitting the data from the present experiment, is proposed. It was seen, moreover, that in the examined range of variability of the emission parameters the best value to be adopted for the entrainment coefficient is β=0.4.

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Riassunto Si presentano e discutono i risultati di uno studio in vasca idraulica del comportamento in atmosfera neutra di getti piú densi dell'aria, di particolare interesse in relazione a problemi di perforazione di pozzi geotermici. I dati sperimentali, riguardanti il massimo sovrainnalzamento dei pennacchi, la distanza orizzontale dalla ciminiera a cui tale massimo viene raggiunto, nonché la distanza alla quale il pennacchio ricade al suolo, sono stati confrontati con semplici formule analitiche reperibili in letteratura. Si è trovato che il ?plume rise? è descritto con sufficiente accuratezza dal modello di Meroney, mentre per la distanza di ricaduta si propone una formula empirica ottenuta per interpolazione dei dati di questo esperimento. Si è visto inoltre che nell'intervallo qui esaminato di variabilità dei parametri di emissione il valore piú opportuno da assegnare al coefficiente di ?entrainment? à β=0.4.

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Theoretical and experimental power spectra of neutron monitor time series in 1978

Summary A comprehensive model for the spectral analysis of neutron monitor data is presented. The contributions to the power spectrum include scintillations in the interplanetary magnetic field caused by cosmic-ray diffusion along and perpendicularly to the field and Forbush-decrease effects. The effects of the Earth's rotation and of nonlinear interactions between particles and fields are taken into account. The model is then compared with the 1978 data of the ?polar? station of Alert and the ?quasi-equatorial? station of Deep River and the agreement is very satisfactory.

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Riassunto Si presenta un modello generale per l'analisi spettrale dei dati da monitori di neutroni. I contributi allo spettro di potenza includono le scintillazioni nel campo magnetico interplanetario dovute alla diffusione dei raggi cosmici lungo il campo e perpendicolarmente ad esso e gli effetti delle diminuzioni Forbush. Si considerano anche gli effetti della rotazione della Terra e delle interazioni non lineari fra particelle e campi. Il modello è quindi confrontato con i dati 1978 della stazione ?polare? di Alert e di quella ?quasi equatoriale? di Deep River e l'accordo risulta molto soddisfacente.

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Резюме Предлагается общая модель для спектрального анализа данных с нейтронных мониторов. Вклады в степенной спектр включают сцинтилляции в межпланетном магнитном поле, обусловленние диффузией космуческих лучей вдоль и перпендикулярно полю и эффектами ?уменьшений? форбуша. Учитываются эффекты вращения Земли и нелинейных взаимодействий между частицами и полями. Затем предложенная модель сравнивается с данными, полученными в 1978 г. на ?полярной? станции Алерт и на ?квазиэкваториальной? станции Дип Ривер. Получено удовлетворительное согласие.

     

Electron microscopic study of dendritic growths on the anode during prebreakdown conditions in an organic residual gas

Anodic growths on tungsten electrodes as a result of an applied electrostatic field with an atmosphere of benzonitrile (from about 5 × 10^?4 to 10^?5 torr) are studied as a function of many parameters. In order to observe the growth phenomena at high resolution in situ, the experiments were performed in an electron microscope. The growth rate of the dendrites is found to be irregular; an expression for dependence on the electric field is proposed to explain the evolution of needle length versus time t: The mechanism of branching is also discussed.     

IR-FIR Transferred lamb-dip spectroscopy in optically pumped molecular lasers

Pump saturation effects are reported for CH₃ and CH₃F optically pumped molecular lasers. The Lamb-dip of the pumping transition is observed directly in the optoacoustic absorption signal and as a transferred Lamb-dip in the emission of various FIR laser lines (CH₃F 496 μm, CH₃OH 119, 70.5 and 96.5 μm) . The offset of the absorbing transitions and their Stark effect are directly investigated. Results are also reported for the unassigned CH₃OH 164 μm line.