To Grow or Defend? Effects of Competition and Herbivory on Common Milkweed, Asclepias syriaca

To gain a better understanding of the drivers of escalation in defenses in common milkweed, Asclepias syriaca, we tested two hypotheses: (1) increased plant density results in competition which lowers plant defenses to herbivory and (2) Natural and simulated herbivory should induce the same defensive responses in milkweed as long as the simulated herbivory is done in the same relative amount and to the same plant tissue as natural herbivory. Our study consisted of common milkweed grown at low and high densities, which were then subjected to natural herbivory by monarch caterpillars or simulated herbivory done by ripping of foliar tissue. Plant size and defenses were sampled three times within a 72 hour timeframe. Our density treatments showed that competition has significant effects on all measures of size. As expected, plants in the low-density treatments were consistently larger than those in the high-density treatment. For example, leaf area in the low-density was 44.47± 2.84 cm2 versus the high-density which was 27.81± 2.57 cm2 (P = 0.003). Height and basal stem diameter showed similar results. Plants in the high-density treatment had higher cardenolide concentrations than those in the low-density treatment after 24 and 48 hours, but this pattern reversed at 72 hours (P = 0.04). We also found that simulated herbivory induced significantly higher cardenolide concentrations than natural herbivory across both density treatments after 72 hours: Simulated = 7.20 ± 0.31, Caterpillar = 6.44 ± 0.31 μg mg-1 (P = 0.04)

Spatial Coherence of a Polariton Condensate

We perform Young's double-slit experiment to study the spatial coherence properties of a two-dimensional dynamic condensate of semiconductor microcavity polaritons. The coherence length of the system is measured as a function of the pump rate, which confirms a spontaneous buildup of macroscopic coherence in the condensed phase. An independent measurement reveals that the position and momentum uncertainty product of the condensate is close to the Heisenberg limit. An experimental realization of such a minimum uncertainty wave packet of the polariton condensate opens a door to coherent matter-wave phenomena such as Josephson oscillation, superfluidity, and solitons in solid state condensate systems

Double-layer shocks in a magnetized quantum plasma

The formation of small but finite amplitude electrostatic shocks in the propagation of quantum ion-acoustic waves (QIAWs) obliquely to an external magnetic field is reported in a quantum electron-positron-ion (e-p-i) plasma. Such shocks are seen to have double-layer (DL) structures composed of the compressive and accompanying rarefactive slow-wave fronts. Existence of such DL shocks depends critically on the quantum coupling parameter $H$ associated with the Bohm potential and the positron to electron density ratio $\delta$. The profiles may, however, steepen initially and reach a steady state with a number of solitary waves in front of the shocks. Such novel DL shocks could be a good candidate for particle acceleration in intense laser-solid density plasma interaction experiments as well as in compact astrophysical objects, e.g., magnetized white dwarfs.Comment: 4 pages, 1 figure (to appear in Physical Review E

Peningkatan Hasil Belajar Siswa pada Pembelajaran Kpk dan Fpb di Sdn 04 Delta Pawan Ketapang

. This study about learning and FPB and KPK on Elementary School 04 Delta Pawan Ketapang. The purpose of this study to determine the increase in student learning outcomes in mathematics learning by registering in fourth grade Elementary School District 04 Delta Pawan Ketapang. Methods This study uses descriptive method. This research is a form of classroom action research. Techniques of data collection using direct observation and measurement, while the means of collecting data using observation sheets and achievement test. The results show the ability of teachers to plan learning in the first cycle of the score 2 to score 3 in cycle 2. The ability of teachers to implement the learning in the first cycle of an average score of 2.64 to 3.97 in cycle 2. Increased student learning outcomes, in cycle 1 the average value of 65.59 into 86.06 in cycle 2. Students who achieve a passing grade on cycle 1 of 7 people (41.12 %), in cycle 2 as many as 14 people (82.35 %) , with an increase of 41.28 %

Quantum effects in linear and non-linear transport of T-shaped ballistic junction

We report low-temperature transport measurements of three-terminal T-shaped device patterned from GaAs/AlGaAs heterostructure. We demonstrate the mode branching and bend resistance effects predicted by numerical modeling for linear conductance data. We show also that the backscattering at the junction area depends on the wave function parity. We find evidence that in a non-linear transport regime the voltage of floating electrode always increases as a function of push-pull polarization. Such anomalous effect occurs for the symmetric device, provided the applied voltage is less than the Fermi energy in equilibrium

The impact of the spacecraft system SÄNGER on the composition of the middle atmosphere

A two-dimensional chemical model and physical considerations are used to estimate the impact of the spacecraft system SÄNGER on stratospheric and mesospheric ozone in relation to other spacecraft and other anthropogenic perturbations. Perturbations of middle atmospheric NOy H2O and H2 concentrations, and their impact on the radiative balance of the atmosphere, including contrail formation, are discussed. It is found, that in case of about 24 launches per year the perturbations due to SÄGER are about negligible on a global scale. However, if a SÄGER version would be used for a hypersonic fleet of commercial aircraft a serious ozone depletion is predicted. © 1992 by Wax Planck Society