Planar Rayleigh scattering results in helium-air mixing experiments in a Mach-6 wind tunnel

Planar Rayleigh scattering measurements with an argon—fluoride excimer laser are performed to investigate helium mixing into air at supersonic speeds. The capability of the Rayleigh scattering technique for flow visualization of a turbulent environment is demonstrated in a large-scale, Mach-6 facility. The detection limit obtained with the present setup indicates that planar, quantitative measurements of density can be made over a large cross-sectional area (5 cm × 10 cm) of the flow field in the absence of clusters

Formation of the high-affinity agonist state of the α1-adrenergic receptor at cold temperatures does not require a G-protein

AbstractTwo methods were employed to uncouple hepatic α1-adrenergic receptors from their associated G-protein (termed Gp) in order to determine wether locking of the α1-receptor in a high-affinity agonist state at cold temperatures (2°C) represents formation of a ternary complex. Uncoupling is defined as the inability to observe the GppNHp-sensitive, high-affinity agonist state of the receptor in [3H]prazosin competition binding studies performed at 25°C. The first method for achieving uncoupling involved brief alkalinization and resulted in greater 95% loss of several G-proteins. The second method involved proteolytic cleavage of either part or all of the α1-receptor coupling domain from the binding domain. Following either treatment, receptors were converted to the high-affinity agonist state at 2°C. Thus, while formation of the high-affinity state of the receptor at higher temperatures may require Gp, formation of this state at 2°C does not require Gp or even the entire α1-adregenic receptor

Lattice Green Function (at 0) for the 4d Hypercubic Lattice

The generating function for recurrent Polya walks on the four dimensional hypercubic lattice is expressed as a Kampe-de-Feriet function. Various properties of the associated walks are enumerated.Comment: latex, 5 pages, Res. Report 1

Uniqueness of the mass in the radiating regime

The usual approaches to the definition of energy give an ambiguous result for the energy of fields in the radiating regime. We show that for a massless scalar field in Minkowski space-time the definition may be rendered unambiguous by adding the requirement that the energy cannot increase in retarded time. We present a similar theorem for the gravitational field, proved elsewhere, which establishes that the Trautman-Bondi energy is the unique (up to a multiplicative factor) functional, within a natural class, which is monotonic in time for all solutions of the vacuum Einstein equations admitting a smooth ``piece'' of conformal null infinity Scri.Comment: 8 pages, revte

Application of a Fast Isoprene Sensor (FIS) for measuring isoprene production from marine samples

Research into isoprene production from marine sources traditionally relies on gas chromatography techniques which are labor intensive, provide a slow sample turnover, and require significant method training. An alternative method is the use of a Fast Isoprene Sensor (FIS), a chemiluminescence‐based approach that provides real time isoprene analysis, but is relatively simple to run and also portable. Until now, the FIS has been used in terrestrial but not aquatic isoprene studies. Due to the added difficulties with marine compared with terrestrial sampling, particularly potential interference from dimethyl sulfide (DMS), we have developed a new protocol that allows accurate and reliable data to be obtained from FIS analysis. The detection limit of our modified system to standard gas was 0.02 nM (0.5 ppbv), while minimum isoprene production detected by the FIS was 0.59 nmol h−1 (for Thalassiosira weissflogii). We also compared our FIS‐based approach with GC analysis of isoprene emission from marine samples of micro‐ and macro‐algae, and demonstrated a strong similarity (r2 = 0.910, slope = 1.003). The ability to use FIS analysis with marine samples will significantly broaden the scope of isoprene research in marine environments, permitting remote field work, and allow previously unanswered questions to be addressed.</jats:p

(p,q)-Deformations and (p,q)-Vector Coherent States of the Jaynes-Cummings Model in the Rotating Wave Approximation

Classes of (p,q)-deformations of the Jaynes-Cummings model in the rotating wave approximation are considered. Diagonalization of the Hamiltonian is performed exactly, leading to useful spectral decompositions of a series of relevant operators. The latter include ladder operators acting between adjacent energy eigenstates within two separate infinite discrete towers, except for a singleton state. These ladder operators allow for the construction of (p,q)-deformed vector coherent states. Using (p,q)-arithmetics, explicit and exact solutions to the associated moment problem are displayed, providing new classes of coherent states for such models. Finally, in the limit of decoupled spin sectors, our analysis translates into (p,q)-deformations of the supersymmetric harmonic oscillator, such that the two supersymmetric sectors get intertwined through the action of the ladder operators as well as in the associated coherent states.Comment: 1+25 pages, no figure

Normal Ordering for Deformed Boson Operators and Operator-valued Deformed Stirling Numbers

The normal ordering formulae for powers of the boson number operator $\hat{n}$ are extended to deformed bosons. It is found that for the `M-type' deformed bosons, which satisfy $a a^{\dagger} - q a^{\dagger} a = 1$, the extension involves a set of deformed Stirling numbers which replace the Stirling numbers occurring in the conventional case. On the other hand, the deformed Stirling numbers which have to be introduced in the case of the `P-type' deformed bosons, which satisfy $a a^{\dagger} - q a^{\dagger} a = q^{-\hat{n}}$, are found to depend on the operator $\hat{n}$. This distinction between the two types of deformed bosons is in harmony with earlier observations made in the context of a study of the extended Campbell-Baker-Hausdorff formula.Comment: 14 pages, Latex fil

Boost-rotation symmetric type D radiative metrics in Bondi coordinates

The asymptotic properties of the solutions to the Einstein-Maxwell equations with boost-rotation symmetry and Petrov type D are studied. We find series solutions to the pertinent set of equations which are suitable for a late time descriptions in coordinates which are well adapted for the description of the radiative properties of spacetimes (Bondi coordinates). By calculating the total charge, Bondi and NUT mass and the Newman-Penrose constants of the spacetimes we provide a physical interpretation of the free parameters of the solutions. Additional relevant aspects on the asymptotics and radiative properties of the spacetimes considered, such as the possible polarization states of the gravitational and electromagnetic field, are discussed through the way

On the Two q-Analogue Logarithmic Functions

There is a simple, multi-sheet Riemann surface associated with e_q(z)'s inverse function ln_q(w) for 0< q < 1. A principal sheet for ln_q(w) can be defined. However, the topology of the Riemann surface for ln_q(w) changes each time "q" increases above the collision point of a pair of the turning points of e_q(x). There is also a power series representation for ln_q(1+w). An infinite-product representation for e_q(z) is used to obtain the ordinary natural logarithm ln{e_q(z)} and the values of sum rules for the zeros "z_i" of e_q(z). For |z|<|z_1|, e_q(z)=exp{b(z)} where b(z) is a simple, explicit power series in terms of values of these sum rules. The values of the sum rules for the q-trigonometric functions, sin_q(z) and cos_q(z), are q-deformations of the usual Bernoulli numbers.Comment: This is the final version to appear in J.Phys.A: Math. & General. Some explict formulas added, and to update the reference

Energy of Isolated Systems at Retarded Times as the Null Limit of Quasilocal Energy

We define the energy of a perfectly isolated system at a given retarded time as the suitable null limit of the quasilocal energy $E$. The result coincides with the Bondi-Sachs mass. Our $E$ is the lapse-unity shift-zero boundary value of the gravitational Hamiltonian appropriate for the partial system $\Sigma$ contained within a finite topologically spherical boundary $B = \partial \Sigma$. Moreover, we show that with an arbitrary lapse and zero shift the same null limit of the Hamiltonian defines a physically meaningful element in the space dual to supertranslations. This result is specialized to yield an expression for the full Bondi-Sachs four-momentum in terms of Hamiltonian values.Comment: REVTEX, 16 pages, 1 figur