Computation of design parameters and visualization of Goertler vortices

A method for analyzing an airfoil regarding Goertler type instability was presented. A model for the visualizatin of Goertler vortices was designed and fabricated. A smoke generating apparatus was made to be used in the experiment. Experiments were conducted to photograph the vortices, however, the smoke generated was not enough to bring out the vortices

Observation of coherent population trapping in a V-type two-electron system

We observe coherent population trapping (CPT) in a two-electron atom---$^{174}$Yb---using the $\rm {^1S_0,F=0} \rightarrow {^3P_1,F'=1}$ transition. CPT is not possible for such a transition according to one-electron theory because the magnetic sublevels form a V-type system, but in a two-electron atom like Yb, the interaction of the electrons transforms the level structure into a $\Lambda$-type system, which allows the formation of a dark state and hence the observation of CPT. Since the two levels involved are degenerate, we use a magnetic field to lift the degeneracy. The single fluorescence dip then splits into five dips---the central unshifted one corresponds to coherent population oscillation, while the outer four are due to CPT. The linewidth of the CPT resonance is about 300 kHz and is limited by the natural linewidth of the excited state, which is to be expected because the excited state is involved in the formation of the dark state.Comment: 5 pages, 5 figures, 2 table

Observation of the nuclear magnetic octupole moment of 173^{173}Yb from precise measurements of hyperfine structure in the 3P2{^3P}_2 state

We measure hyperfine structure in the metastable ${^3P}_2$ state of $^{173}$Yb and extract the nuclear magnetic octupole moment. We populate the state using dipole-allowed transitions through the ${^3P}_1$ and ${^3S}_1$ states. We measure frequencies of hyperfine transitions of the ${^3P}_2 \rightarrow {^3S}_1$ line at 770 nm using a Rb-stabilized ring cavity resonator with a precision of 200 kHz. Second-order corrections due to perturbations from the nearby ${^3P}_1$ and ${^1P}_1$ states are below 30 kHz. We obtain the hyperfine coefficients as: $A=-742.11(2)$ MHz, $B=1339.2(2)$ MHz, which represent two orders-of-magnitude improvement in precision, and $C=0.54(2)$ MHz. From atomic structure calculations, we obtain the nuclear moments: quadrupole $Q=2.46(12)$ b and octupole $\Omega=-34.4(21)$ b\,$\times \mu_N$.Comment: 5 pages, 1 figur

A Conceptual Model of the Incubation of New Technology-Based Ventures: a Social Capital Perspective

Technology incubators are newer organizational forms that are created to support and accelerate the development and success of affiliated ventures, particularly new technology-based ventures. Current literature regarding incubators has suggested that an understanding of the incubation process is important when seeking to understand how affiliated ventures develop and grow. However, very little is known about the incubation process, particularly the incubation of technology-based ventures. Prior literature suggests that technology-based ventures develop in terms of both business and technological development and that the incubation process varies along these dimensions. Thus, understanding the incubation of technology–based ventures must consider the differing but simultaneous dynamics of business and technological development. Drawing from the social capital, entrepreneurship, incubation, and organizational learning literature, a conceptual model of the incubation of new technology-based ventures within technology incubators is presented.incubators; new technology-based ventures; entrepreneurship; innovation.

Innovation and Productivity in U.S. Industry

macroeconomics, U.S. industry, productivity, manufacturing, textiles, chemicals

Information theoretical study of cross-talk mediated signal transduction in MAPK pathways

Biochemical networks related to similar functional pathways are often correlated due to cross-talk among the homologous proteins in the different networks. Using a stochastic framework, we address the functional significance of the cross-talk between two pathways. Our theoretical analysis on generic MAPK pathways reveals cross-talk is responsible for developing coordinated fluctuations between the pathways. The extent of correlation evaluated in terms of the information theoretic measure provides directionality to net information propagation. Stochastic time series and scattered plot suggest that the cross-talk generates synchronization within a cell as well as in a cellular population. Depending on the number of input and output, we identify signal integration and signal bifurcation motif that arise due to inter-pathway connectivity in the composite network. Analysis using partial information decomposition quantifies the net synergy in the information propagation through these branched pathways.Comment: Revised version, 17 pages, 5 figure

Optical frequency metrology with a Rb-stabilized ring-cavity resonator -- Study of cavity-dispersion errors

We have developed a technique to measure the absolute frequencies of optical transitions by using an evacuated Rb-stabilized ring-cavity resonator as a transfer cavity. We study possible wavelength-dependent errors due to dispersion at the cavity mirrors by measuring the frequency of the same transition in the $D_2$ line of Cs at three cavity lengths. We find no discernable change in values within our error of 30 kHz. Our values are consistent with measurements using the frequency-comb technique and have similar accuracy.Comment: 3 pages, 2 figure

Role of relaxation time scale in noisy signal transduction

Intracellular fluctuations, mainly triggered by gene expression, are an inevitable phenomenon observed in living cells. It influences generation of phenotypic diversity in genetically identical cells. Such variation of cellular components is beneficial in some contexts but detrimental in others. To quantify the fluctuations in a gene product, we undertake an analytical scheme for studying few naturally abundant linear as well as branched chain network motifs. We solve the Langevin equations associated with each motif under the purview of linear noise approximation and quantify Fano factor and mutual information. Both quantifiable expressions exclusively depend on the relaxation time (decay rate constant) and steady state population of the network components. We investigate the effect of relaxation time constraints on Fano factor and mutual information to indentify a time scale domain where a network can recognize the fluctuations associated with the input signal more reliably. We also show how input population affects both quantities. We extend our calculation to long chain linear motif and show that with increasing chain length, the Fano factor value increases but the mutual information processing capability decreases. In this type of motif, the intermediate components are shown to act as a noise filter that tune up input fluctuations and maintain optimum fluctuations in the output. For branched chain motifs, both quantities vary within a large scale due to their network architecture and facilitate survival of living system in diverse environmental conditions.Comment: 14 pages, 6 figure

Atomic fountain of laser-cooled Yb atoms for precision measurements

We demonstrate launching of laser-cooled Yb atoms in a cold atomic fountain. Atoms in a collimated thermal beam are first cooled and captured in a magneto-optic trap (MOT) operating on the strongly-allowed ${^1S}_0 \rightarrow {^1P}_1$ transition at 399~nm (blue line). They are then transferred to a MOT on the weakly-allowed ${^1S}_0 \rightarrow {^3P}_1$ transition at 556~nm (green line). Cold atoms from the green MOT are launched against gravity at a velocity of around 2.5~m/s using a pair of green beams. We trap more than $10^7$ atoms in the blue MOT and transfer up to 70\% into the green MOT. The temperature for the odd isotope, $^{171}$Yb, is $\sim$1~mK in the blue MOT, and reduces by a factor of 40 in the green MOT.Comment: 6 pages, 7 figure