An investigation into approximate solutions for deterministic and stochastic multi-dimensional sequencing

A description is given of an investigation in detail into the validity of the overlap integral method for describing planar optical waveguide junctions. A comparison between the results of this method and that of a rigorous mode-matching approach is taken

Abstract and Generic Rigidity in the Plane

AbstractWe consider the concept of abstract two-dimensional rigidity and provide necessary and sufficient conditions for a matroid to be an abstract rigidity matroid of a complete graph. This characterization is a natural extension of the characterization of graphic matroids due to Graver or Sachs. We also give an example of an abstract rigidity matroid which is not infinitesimal

Wiretapping a hidden network

We consider the problem of maximizing the probability of hitting a strategically chosen hidden virtual network by placing a wiretap on a single link of a communication network. This can be seen as a two-player win-lose (zero-sum) game that we call the wiretap game. The value of this game is the greatest probability that the wiretapper can secure for hitting the virtual network. The value is shown to equal the reciprocal of the strength of the underlying graph. We efficiently compute a unique partition of the edges of the graph, called the prime-partition, and find the set of pure strategies of the hider that are best responses against every maxmin strategy of the wiretapper. Using these special pure strategies of the hider, which we call omni-connected-spanning-subgraphs, we define a partial order on the elements of the prime-partition. From the partial order, we obtain a linear number of simple two-variable inequalities that define the maxmin-polytope, and a characterization of its extreme points. Our definition of the partial order allows us to find all equilibrium strategies of the wiretapper that minimize the number of pure best responses of the hider. Among these strategies, we efficiently compute the unique strategy that maximizes the least punishment that the hider incurs for playing a pure strategy that is not a best response. Finally, we show that this unique strategy is the nucleolus of the recently studied simple cooperative spanning connectivity game

Transistor-Based Studies of Heavy Dop-ing Effects in n-GaAs

The n2ieDp product (where n2ie is the np product and Dp is the minority hole mobility) in heavily doped n‐GaAs has been measured by electrical characterization of p‐n‐p GaAs homojunction transistors with base dopings ranging from approximately 1×1017 to 9×1018 cm−3. The measured n2ieDp product decreases as the doping density increases. These results suggest that nie is roughly constant with doping density, in sharp contrast to the large increase observed for p‐type GaAs. This work shows that when designing GaAs bipolar devices, it is important to consider the large difference in effective band gap between n+ and p+ regions

Characterization of photon recycling in thin crystalline GaAs light emitting diodes

Gallium arsenide light emitting diodes (LEDs) were fabricated using molecular beam epitaxial films on GaAs substrates and removed by epitaxial lift-off (ELO). Lifted off devices were then mounted on a Si wafer using a Pd/Au/Cr contact layer, which also served as a back surface reflector. Devices were characterized by electrical and optical measurements, and the results for devices on the GaAs substrate were compared to those for EL0 devices. EL0 LEDs coated with a ZnS/MgF2 antireflection coating exhibited an optical output that was up to six times that of LEDs on GaAs substrates. At the same time, the measured current-voltage characteristics of the EL0 devices displayed a lower IZ = 1 current component. EL0 LEDs with efficiencies up to 12.5% were realized. We attribute these results to photon recycIing enhanced by the back-surface reflector in the EL0 LEDs. The luminescence versus current and current versus voltage characteristics of the LEDs were analyzed to obtain the nonradiative minority carrier lifetimes and the photon recycling factors. The results demonstrate that the measured characteristics are well described by photon recycling theory. EL0 LEDs may prove useful for characterizing recombination processes in LEDs, and thin-crystalline structures could provide substantial efficiency enhancements for LEDs and solar cells

Microgravity’s Effect on the Virulence of Bacteriophage qB on Escherichia coli as a Possible Indicator of the Down-Regulation of Host Factor Hfq

Faculty Research Day 2018: Student Spaceflight Experiments Program FinalistFaculty Research Day 2018: Undergraduate Student Poster 2nd PlaceThe virulence of viruses is a topic of interest for the wellbeing of human health during space travel. Little research has been conducted on differing virulence between bacteriophages in space and on earth. However, prior research suggests evidence that a difference may exist. Hfq is an RNA binding global regulator protein present in E. coli which has been shown to be required for Coliphage qB to infect E. coli.  In a squid-vibrio experiment conducted under simulated microgravity, the hfq protein production was seen to be down-regulated in Vibrio fischeri. Our experiment aims to imitate results found by Grant under a real microgravity situation in Escherichia coli, given that Hfq is highly conserved in bacteria. The experiment will compare the virulence of Coliphage qB on E. coli in space to the virulence on land. The resulting difference in rates of Coliphage qB infection of E. coli may hint at unknown molecular mechanisms that bacteria and/or viruses employ under the effects of microgravity, and may provide evidence to suggest that hfq is also down-regulated in E. coli in microgravity. The implications of the results found by this experiment will be a step into determining the virulence of viruses and other infectious organisms during spaceflight and may lead to effective preventative measures to safeguard the health of humans in space