Nernst and Seebeck effect in a graphene nanoribbon

The thermoelectric power, including the Nernst and Seebeck effects, in graphene nanoribbon is studied. By using the non-equilibrium Green function combining with the tight-binding Hamiltonian, the Nernst and Seebeck coefficients are obtained. Due to the electron-hole symmetry, the Nernst coefficient is an even function of the Fermi energy while the Seebeck coefficient is an odd function regardless of the magnetic field. In the presence of a strong magnetic field, the Nernst and Seebeck coefficients are almost independent of the chirality and width of the nanoribbon, and they show peaks when the Fermi energy crosses the Landau levels. The height of $n$-th (excluding $n=0$) peak is $[\ln2/|n|]$ for the Nernst effect and is $\ln2/n$ for the Seebeck effect. For the zeroth peak, it is abnormal with height $[2\ln2]$ for the Nernst effect and the peak disappears for the Seebeck effect. When the magnetic field is turned off, however, the Nernst effect is absent and only Seebeck effect exists. In this case, the Seebeck coefficient strongly depends on the chirality of the nanoribbon. The peaks are equidistant for the nanoribbons with zigzag edge but are irregularly distributed for the armchair edge. In particular, for the insulating armchair ribbon, the Seebeck coefficient can be very large near the Dirac point. When the magnetic field varies from zero to large values, the differences among the Seebeck coefficients for different chiral ribbons gradually vanish and the nonzero value of Nernst coefficient appears first near the Dirac point then gradually extents to the whole energy region.Comment: 8 pages, 7 figure

The Effect of Human Activity Both Disturbances and Mowing on Golden Rod Abundance in Danby Grasslands YorkU

<p>This lab was conducted by sampling a specific plant species called Golden Rod in order to explore the effect of disturbance and previously mowed areas to plant abundance. Mowed area closer to disturbances would have less abundance compared to unmowed area further away from the disturbance. This took place in York University at a grassland area near the Danby Wood Lot. The data was collected for two days, October 14th and 21th, 2015 from 3:00pm – 5:00pm. On Wednesday October 14th, the weather was slightly sunny 13 °C slightly breezy. The sampling area had slightly dry grass but the plants were alive. On Wednesday October 21st, the weather was clear, sunny (14 °C) and there was no breeze. The sampling area was very dry in the moved but not in the unmowed area; a lot of plants were dying off in that area specifically common milkweed and Common Plantain. The golden rod plants were found in a clumped distribution and were still alive during both days. There were no animals or bugs that were spotted in the sampling area. There were two disturbances in the sampling area on either sides of the grassland; Severn Road and Keele Street. Distance 1 refers to the egde of the grassland from Keele Street till a replicate and distance 2 refers to the edge of the grassland from Severn Road till a replicate.</p> <p>The collaborators for this lab were A. Amin, L. Trans, J. Quach and S. Alvi. The collaborators were split into two groups; one collecting samples in the mowed area (L. Trans, J. Quach and S. Alvi.) and the other collected data for the mowed sampling area (A. Amin and I. Darman). The sampling method used in this study was belt transect sampling using two 30m belt transects, 1m by 1m quadrats and the Plant quick-identification guide (provided on the course website). The sampling area stretched 100m vertically from the edge of the side walk on Severn Road to the grassland. Five 100m transects, were measured each 10 meters horizontally apart along the sidewalk (1 Transects in the mowed area, 1 for unmowed and 3 for a mixture of both). Each belt transect had a 1m by 1m quadrat placed every 5m anywhere about maximum 3m from each side of the belt transect tape starting from 0m and ending at 100m (21 replicates per transect). The 30m transect was used to measure out 100m by first collecting data for the first 6 replicates (30m), then measuring another 30m from the last point which adds another 6 replicates (60m) and the same is done for the next 6 (90m), 2 replicates (100m) and one more replicate at the end of the transect. This sums the sampling size to be 105 replicates and the abundance of golden rods was recorded in each of them. Measurements were done by I. Darman for the mowed area and L. Trans, J. Quach and S. Alvi. for the unmowed area. The abundance of the plant were visually counted and recorded in a notebook by A. Amin in the mowed area and by L. Trans, J. Quach and S. Alvi. in the unmowed area. The plant identification guide was used to identify the Golden Rods. About half of the data was collected during the first days (50 replicates) and the other half was left for the last day (50 replicates).</p

Plant Sampling Techniques and Data - Heath Aster - Lab 2 Dataset 2

<p>Equipment: 2 Transect</p> <p>This lab was conducted by sampling a specific plant species called (White) Heath Aster using a transect on York University at a grassland area near the Danby Woodlot which took place on September 23, 2015 from 3:00pm – 5:00pm. The weather was breezy with temperatures around 23°C and the sky was slightly cloudy. The area in the grassland was concentrated with Heath Aster plant.</p> <p>The collaborators for this lab was A. Amin and J. Quach. J. Quach recorded the data on notebook and held the transect in position while both I. Darman and A. Amin identified the plant, counted the number of leaves and flowers, and took measurements using transects. 20 individual plants were recorded along the transect. After that, the height of each plant was recorded from the ground position using the second transect till the highest flat point. The number of flowers and leaves per plant was estimated by first counting the leaves or flowers on a small portion of the plant, counting the number of portions on each plant and multiplied both number (portions x leaves or flowers in one portion).</p> <p>The level of crowdedness was rated from a scale of 0-3 within a distance of 50 cm. 0 meaning an open area, 1 meaning some plant nearby, 2 meaning quite a few plant and 3 meaning very crowded.</p

Field Sample Training With Insects - Pan Trap - Lab 3 Dataset 2

<p>Equipment: 17 Pans, Soapy water, Sieve</p> <p>This lab was conducted by sampling grassland and wood lot areas on York University near the Danby Woodlot which took place on September 30, 2015 from 3:00pm – 5:00pm. The weather was breezy with temperatures around 17°C and the sky was slightly cloudy. The area in the grassland was slightly crowded with common milkweed and Red Clover plants. The wood lot habitat had a few Maple Trees and samplings.</p> <p>In the grassland, 9 pans were placed on the ground and in the wood lot 8 pans were placed on the ground. The collaborators for this lab were A. Amin and J. Quach. J. Quach placed the pans on the ground while A. Amin poured about 100 - 200ml off soapy water into each pan. The pans were arranged vertically, with alternating colours (blue, white and yellow) each 1 meter apart. There were no inclines or major obstacles in the grassland or the wood lot. At times it would be difficult to align the pans vertically without disturbing the environment so the solution was to place it at an angle but still keep the distance between each pan 1 meter. After an hour, I. Darman collected the pans while J. Quach took pictures of each pan and A. Amin cleared the pans using a sieve. I. Darman identified and recorded the insect type and abundance. The type of insect and abundance was recorded for each pan separately.</p> <p>For this experiment, it was initially designed to have equal number of pans for each habitat. However one pan was missing and there were more white plates placed in the woodlot.</p