107,910 research outputs found
Co-teaching Biology 1100 with Dr. Jason Gee
No full textFor my Senior Honors Project, I participated in co-teaching an Introductory Biology, or Biology 1100, class alongside department faculty member Dr. Jason Gee. My overall goals for this project were to better master the concepts of basic biological principles as set forth by the course material, as well as, to become experienced in the art of projecting what knowledge I had learned in the field of biology from myself to the students who attended introductory biology. I did so by creating an original PowerPoint lecture presentation that I would present to the students, as well as, created an Active Learning Exercise that corresponded to the lecture presentation and required that students actively apply the knowledge they had just learned. This paper reflects on the co-teaching experience as a whole and summarizes the main points that I learned to improve upon my experiences
The dynamics of O-2 adsorption on Pt(533): Step mediated molecular chemisorption and dissociation
No full textThe dissociative adsorption of oxygen on the stepped Pt(533) surface has been investigated using supersonic molecular beams by measuring the initial dissociative sticking probability S-0 as a function of incident kinetic energy E-i, angle Phi, surface temperature T-S, and S as a function of coverage Theta. By comparison with dynamical data available on the Pt(111) surface we have been able to establish that step sites dominate the dissociative adsorption process. S-0(E-i) for oxygen on Pt(533) at T-S=200 in the energy range 52 meV-1.4 eV shows a similar functional dependence to results on Pt(111), however, the magnitude of S-0 on Pt(533) is significantly greater at all energies. The measurement of S-0(Phi), scattering in a plane perpendicular to the step direction at E-i=1.18 eV at T-S=350 K, reveals a strong and asymmetric angular dependence which contains contributions associated with activated adsorption and dissociation of the chemisorbed precursor on the (111) terraces, and a second contribution associated with activated dissociation through a similar channel at the step sites. The latter exhibits a maximum in S-0(Phi) at 35 degrees, near the angle corresponding to the normal of the (100) step plane. S-0(T-S) at E-i=1.18 eV and Phi =0 degrees reveals a much smaller temperature dependence in the range 150 >T-S(K)> 800 on Pt(533) than on Pt(111). At E-i=1.18 eV and Phi =0 degrees ca. 15%-25% of dissociation takes place through molecules impinging directly at step sites. The remaining fraction dissociate through activated adsorption of the chemisorbed species on the (111) terrace and subsequent partition between desorption, and dissociation at step sites. Dissociation of the chemisorbed precursor on the (111) terrace appears highly activated, a result which is consistent with theory. The rapid decrease in S-0(E-i) observed below 0.15 eV on Pt(533), observed also on Pt(111), is consistent with a trapping mechanism where the need to dissipate energy limits the probability of adsorption, and subsequent dissociation, of the physisorbed precursor. Kinetic modelling of this partition on Pt(533), between the conversion of the physisorbed precursor to the chemisorbed species, and desorption yields DeltaE=120 meV and v(d)/v(pc)=80. We conclude that the effective barrier to conversion of the physisorbed to chemisorbed species on Pt(533) is effectively zero. We conclude that defects will tend to dominate this conversion process on the close packed surface. In addition to this channel, at E-i=0.05 meV ca. 50% of molecules dissociate through the same channel operating at higher energy on Pt(533)
The R Package geepack for Generalized Estimating Equations
No full textThis paper describes the core features of the R package geepack, which implements the generalized estimating equations (GEE) approach for fitting marginal generalized linear models to clustered data. Clustered data arise in many applications such as longitudinal data and repeated measures. The GEE approach focuses on models for the mean of the correlated observations within clusters without fully specifying the joint distribution of the observations. It has been widely used in statistical practice. This paper illustrates the application of the GEE approach with geepack through an example of clustered binary data.
T. G. Mac Gee. The Southeast Asian City, 1967
No full textKayser Bernard. T. G. Mac Gee. The Southeast Asian City, 1967. In: Revue géographique des Pyrénées et du Sud-Ouest, tome 40, fascicule 2, 1969. pp. 219-220
Letter, [Author unclear] to Paulina T. Merritt
No full textHandwritten letter to Paulina Merritt from an unknown author, October 1, 1876.
La specie imprevista (presentazione)
No full textPresentazione dell'edizione italiana de "La specie imprevista" (2013) di Henry Gee, senior editor di Nature per Life Sciences
Mesozoic plants and dinosaur herbivory
No full textFor most of their existence, herbivorous dinosaurs fed on a gymnospermdominated flora. Starting from a simple reptilian herbivory, ornithischian dinosaurs evolved complex chewing dentitions and mechanisms, while sauropodomorph dinosaurs retained the primitive condition of not chewing. Some advanced theropod dinosaurs evolved a bird-type herbivory with a toothless beak and a gastric mill. Dinosaur digestive tract remains, coprolites, and other trace fossils offer little evidence for dinosaur food preferences. Ferns, seed ferns, ginkgoes, and the Cheirolepidiaceae were previously viewed as the food plants favored by dinosaurs. However, animal nutrition science, comparative herbivore physiology, and digestive tract anatomy of modern herbivores suggest otherwise. In fermentation experiments, energy release is much greater in horsetails and most conifers, especially Araucaria, than in many ferns, cycads, and podocarp conifers. Sauropods as bulk feeders must have relied on plants that provided much biomass and regenerated foliage quickly, namely, conifers and ginkgoes. This argues against most ferns and cycads, which offer little biomass and energy
The role of steps in the dynamics of hydrogen dissociation on Pt(533)
No full textThe dissociative adsorption of H-2 and D-2 on Pt(533) (Pt{4(111)x(100)}) has been investigated using temperature programmed desorption and supersonic molecular beams. Associative desorption of D-2 from (100) step sites is observed at lowest exposures in TPD (assigned beta(3)) at 375 K. Saturation of this peak at Theta(H)=0.14 corresponds to the filling of half of the available four-fold sites at the (100) step edge. At higher coverages, additional desorption takes place from the (111) terraces in a broad peak below 300 K similar to that observed (assigned beta(1) and beta(2)) for the Pt(111) surface. The incident kinetic energy (E-i), surface temperature (T-s), coverage (Theta(D)), and incident angle (Phi) dependence of the dissociative sticking probability (S) was also measured. The initial dissociative sticking probability (S-0) first decreases with increasing kinetic energy over the range 0 < E-i(meV)< 150 (low energy component), and subsequently increases (high energy component). Comparison with D-2 dissociation on Pt(111), where (S-0) increases linearly with E-i, leads to the conclusion that it is the step sites that are responsible for the low energy component to dissociation on Pt(533). The high energy component is a result of a direct dissociation channel on (111) terraces of the Pt(533) surface. The probability of dissociation through the direct channel on the (111) terraces is found to be independent of T-s. The probability of dissociation through the low energy component associated with the (100) steps, over most of the range of E-i where it contributes, is also shown to be independent of T-s. Only at the very lowest value (6.6 meV) of E-i investigated does S-0 exhibit a (negative) temperature dependence. A (0.8-Theta(D))(2) dependence (where 0.8 is the measured saturation coverage) of S with Theta(D) is observed at E-i=180 meV where the direct channel dominates. However, the dependence of S on Theta(D) exhibits characteristics similar to those expected for precursor mediated dissociation at E-i=16 meV and E-i=6.6 meV where the low energy channel dominates. The angular dependence S-0(Phi) scattering in a plane perpendicular to the step direction is asymmetric about the Pt(533) surface normal at both E-i=6.6 meV and E-i=180 meV. At 180 meV S-0(Phi) can be understood by considering direct dissociation at the (111) terrace and (100) step plane. At 6.6 meV, S-0 tends to scale with total energy. The observed characteristics of the low energy channel is discussed in the light of models [specifically the role steps and defects, precursors (accommodated and dynamical), and steering] suggested to account for the low energy component for H-2/D-2 dissociation and exchange on metal surfaces presenting low activation barriers. At lowest energies (E-i=6.6 meV) dissociation through a conventional accommodated precursor takes place. In addition, more significant proportion of sticking in the range 0 < E-i(meV)< 150 takes place through an indirect channel involving an unaccommodated precursor dissociating at step sites, and is unlikely to be accounted for through a steering mechanism
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