The Design of a Piezoelectric Heart Assist Device

A piezoelectric heart assist device was designed, and preliminary tests were performed in vitro and in vivo. The device has the advantages of simple construction, low power consumption (approximately one watt), electrical rather than pneumatic drive, and noiseless operation. The device consists of piezoelectric bender elements forming two cantilevers. A unique feature of the device is that two tungsten alloy masses, 0.44 kg each, were added to the free ends of the cantilevers to reduce the resonant frequency to 2.5 Hz. The driving voltage was a 320 V peak-to-peak square wave synchronized with a paced heartbeat.     

Investigations of axisymmetric deformation of geometrically nonlinear,rotationally orthotropic,circular plates

Some results of qualitative investigations and of numerical solutions to the problem of axisymmetrical deformations of circular, geometrically non-linear, rotationally orthotropic plates are presented. The qualitative studies reveal certain general characteristics of behavior and proofs are obtained only on the basis of form, in analogy to the qualitative theory of differential equations. For numerical solutions we employ the shooting method in combination with the ‘deformation map’, which is similar to Poincaré's phase plane.     

Slow rotation in the bimetric theory of gravitation

The equations describing the moment of inertia and the dragging of inertial frames of slowly rotating neutron stars are derived according to Rosen's bimetric theory of gravitation. Numerical calculations of the properties of neutron stars according to the bimetric theory and general relativity were made using several equations of state. The general trend found is that in the bimetric theory neutron stars with a given mass induce a smaller dragging of inertial frames than in general relativity. The moment of inertia of low-mass stars also is smaller in the bimetric theory. For high-mass stars, however, the moment of inertia is found to be larger in the bimetric theory.In partial fulfillment of the requirements for the D.Sc. degree.     

Potato kugel

LetP be a solid, homogeneous, compact, connected “potato” in space which attracts each point outside it (according to Newton’s law) as if all its mass were concentrated at a single point. Answering a question of Lee Rubel, we show thatP is a ball. The same conclusion is also obtained under substantially weakened hypotheses.     

The preparation of some cyclic phosphonates and their use in olefin synthesis

The preparation and the use in olefin synthesis of two 5-membered cyclic phosphonates, 2-carbethoxy-methyl 4,5-dimethyle-2-oxo-1,3,2-dioxaphospholane (4b) and 2-cyanomethyl-4,5-dimethyl-2-oxo-1,3,2-diox-aphospholane (4c) and the 6-membered phosphonates, 2-carbalkoxymethyl-5,5-dimethyl-2-oxo-1,3,2-diox-aphosphorinanes (5a and 5b) and 2-cyanomethyl-5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorinane (5c) are described. Reactions of 4b with aromatic and aliphatic aldehydes lead to preferential formation of cis-olefins. Reactions of the other cyclic phosphonates with aldehydes lead to various mixtures of cis and trans olefins.     

Heat evolution of micelle formation, dependence of enthalpy, and heat capacity on the surfactant chain length and head group

Micelle formation by many surfactants is endothermic at low temperatures but exothermic at high temperatures. In this respect, dissociation of micelles (demicellization) is similar to dissolving hydrocarbons in water. However, a remarkable difference between the two processes is that dissolving hydrocarbons is isocaloric at about 25 degrees C, almost independently of the hydrocarbon chain length, whereas the temperature (T*) at which demicellization of different surfactants is athermal varies over a relatively large range. We have investigated the temperature dependence of the heat of demicellization of three alkylglucosides with hydrocarbon chains of 7, 8, and 9 carbon atoms. At about 25 degrees C, the heat of demicellization of the three studied alkylglucosides varied within a relatively small range (DeltaH=-7.8+/-0.4 kJ/mol). The temperature dependence of DeltaH(demic) indicates that within the studied temperature range the heat capacity of demicellization (DeltaC(P,demic)) is about constant. The value of DeltaC(P,demic) exhibited an apparently linear dependence on the surfactant's chain length (DeltaC(P,demic)/n(CH(2))=47+/-7 kJ/mol K). Our interpretation of these results is that (i) the transfer of the head groups from micelles to water is exothermic and (ii) the temperature dependence of the heat associated with water-hydrocarbon interactions is only slightly affected by the head group. This implies that the deviation of the value of T* from 25 degrees C results from the contribution of the polar head to the overall heat of demicellization. Calorimetric studies of other series of amphiphiles will have to be conducted to test whether the latter conclusion is general.     

A minimal area problem in conformal mapping

LetS denote the usual class of functionsf holomorphic and univalent in the unit diskU such thatf(0)=f′(0)−1=0. The main result of the paper is that area (f(U) ≥27π/7)(2-α)⁻² for allf∈S such that |f″(0)|=2α, 1/2<α<2. This solves a long-standing extremal problem for the class of functions considered.     

Transition from zero-dimensional to one-dimensional behavior in InAs and CdSe nanorods

Tunneling and optical spectroscopy performed on InAs nanorods 7–25 nm long, reveal a clear dependence of the band gap on length. This (zero-dimension like) behavior is different from that of CdSe rods, where the band gap is nearly independent of length, a signature of quasi-one-dimensionality. The transition between these two regimes is governed by the ratio between the Bohr radius and the nanorods length. The gaps measured by tunneling spectroscopy are larger than the optical gaps by a factor that depends on the tunneling configuration. This is attributed to a combination of the Coulomb interaction and the voltage division between the two tunnel junctions in the STM experiment. However, the tunneling gaps were found to reduce in dense aggregates of rods.     

Average acoustic pulse dispersion length in condensed matter channels

This paper is concerned with ‘a probing pulse’ propagating in an inhomogeneous condensed state medium. The pulse expands as it travels. This expansion may be correlated to a material-characteristic dimension – such as the size of a grain or of a free path between scattering sites or of a domain – which is a random variable with a mean denoted as g_s . Moreover, we may ascribe to the propagation a loss constant which is proportional to g_s . The process derives from the fact that, for a relatively large number of scattering sites, it is possible to model the propagation media in terms of a repetitive electrical network. The model supports a Gaussian (bell shape) impulse response and defines g_s . Both theoretical and experimental (ultrasonic) results are provided. The experimental method is relatively fast to perform and the results are highly reproducible.     

Light‐Triggered Release of Trapped Charges in Molecular Assemblies

We demonstrate the mediation of charge transport and release in thin films and devices by shifting the redox properties of layers of metal complexes by light. The nanoscale surface arrangement of both photo‐ and electrochemically‐active components is essential for the function of the thin films. Layers of well‐defined ruthenium complexes on indium‐tin‐oxide electrodes provide electron‐transport channels that allow the electrochemical addressing of layers of isostructural cobalt complexes. These cobalt complexes are electrochemically inactive when assembled directly on transparent metal‐oxide electrodes. The interlayer of ruthenium complexes on such electrodes allows irreversible oxidation of the cobalt complexes. However, shifting the redox properties of the ruthenium complexes by excitation with light opens up an electron‐transport channel to reduce the cobalt complexes; hence releasing the trapped positive charges.