Mineralogy of Pegmatites

Guidebook for fifty-second annual meeting of the New England Intercollegiate Geological Conference field trips in West-Central Maine, October 8-9, 1960: Trip

Positive effect of predators on prey growth rate through induced modifications of prey behaviour

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72834/1/j.1461-0248.2002.00287.x.pd

How Dependent Are Species‐Pair Interaction Strengths On Other Species In The Food Web?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117139/1/ecy200485102754.pd

Lethal And Nonlethal Predator Effects On An Herbivore Guild Mediated By System Productivity

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117135/1/ecy2006872347.pd

A Review Of Trait‐Mediated Indirect Interactions In Ecological Communities

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/117099/1/ecy20038451083.pd

Compression of tetrahedrally bonded SiO2 liquid and silicate liquid‐crystal density inversion

We have investigated the response to pressure of liquid SiO2 by performing a quantitatively realistic Monte Carlo simulation. The model liquid was restricted to at most four‐fold Si‐O coordination by the effective imposition of an infinite potential barrier to a fifth bond. We thus obtained an unambiguous comparison of the compression mechanisms of solid and liquid tetrahedral networks. In spite of this restriction, the density of the simulated liquid exceeds that of the corresponding models of quartz, coesite and cristobalite at high pressure. The efficient compression of the liquid results from a continuous restructuring of the network that leaves the mean Si‐Si distance virtually unchanged and does not require an increase in the coordination number. The restructuring is effected by local breaking and reconnecting of bonds, a mechanism that is not available to a perfect crystal

Formation of corrensite, chlorite and chlorite-mica stacks by replacement of detrital biotite in low-grade pelitic rocks

Transmission and scanning electron microscopy were utilized to investigate the nature and mechanisms of alteration of abundant detrital biotite of volcanic origin and progressive modification of phyllosilicate aggregates in a prograde sequence of pelitic rocks (illite crystallinity index = 0.19–0.58dΛ2θ) from the GaspÉ Peninsula in Quebec. Detrital biotite has been diagenetically altered to form corrensite and chlorite through two mechanisms; (1) layer-by-layer replacement gave rise to interstratification of packets of layers and complex mixed layering via several kinds of layer transitions between biotite and chlorite, corrensite or smectite; (2) dissolution-transport-precipitation resulted in the formation of relatively coarse-grained aggregates of randomly orientated, corrensite-rich flakes and fine-grained corrensite intergrown with chlorite and illite in the matrix. The data show that stacks consisting of alternating packets of trioctahedral and dioctahedral phyllosilicates originated during early diagenesis when lenticular fissures in strained altering biotite were filled by dioctahedral clays. Subsequent prograde evolution of dioctahedral clays occurred through deformation, dissolution and crystallization, and overgrowth. Illite evolved to muscovite, with K in part provided through biotite alteration, and corrensite/chlorite to homogeneous chlorite. The alteration of detrital biotite is closely related to the formation of titanite and magnetite in diagenetic rocks, and pyrite, calcite and anatase or rutile in the higher grade rocks. The observations demonstrate that detrital biotite of volcanic origin may be the principal precursor of chlorite in chlorite-rich metapelites originating in marginal basins. The mineral parageneses suggest that the transitions from corrensite to chlorite and illite to muscovite may be a function of local chemistry and time.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75643/1/j.1525-1314.1994.tb00065.x.pd

Mechanisms Of Nonlethal Predator Effect On Cohort Size Variation: Ecological And Evolutionary Implications

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/116938/1/ecy20078861536.pd

Application of Small Molecule Receptors to the Analysis of Post-translational Modifications Using Fluorescent Indicator Displacement Assays.

This dissertation focuses on the application of small molecule receptors to a fluorescent assay for the study of histone post-translational modifications, both in real-time enzyme reactions and endpoint characterization of analytes. In the first section, dynamic combinatorial chemistry was used to generate a series of A2X receptors that varied the functionality of the X monomer. This allowed us to systematically study the contribution of pocket depth and electrostatic interactions on binding methylated lysine. We discovered that changing the location of a carboxylate increased affinity to K(Me)2, presumably through a salt bridge, while an additional carboxylate increased affinity across the entire lysine series. Additionally, formation of a deeper binding pocket saw a selectivity increase for K(Me)3 over the lower methylation states. The remaining sections describe the application of the Waters lab suite of receptors to fluorescence indicator displacement assays (IDAs). In these assays, fluorescence signal is directly proportional to the competitive binding of a histone analyte. We applied a sensor system using the receptor A2N and the fluorophore Lucigenin (LCG) to study the enzymatic dimethylation of histone H3 lysine 9 by the methyltransferase G9a. Optimization of the enzymatic buffer system established an effective methyltransferase reaction to short histone 3 peptide substrates. Applying these conditions to the fluorescent assay we are able to monitor enzymatic activity, allowing future experiments to test enzyme response to neighboring modifications in the ‘histone code’. This assay was also applied to the preliminary examination of the arginine methyltransferases, demonstrating the general applicability of the assay to the full range of enzymatic methylation reactions. With the large number of receptors previously established, we sought to develop a general discriminatory assay capable of recognizing histone modifications beyond the designed scope of the sensor. By combining the fluorescent IDA signal for four different receptors, A2B, A2D, A2N, and A2G, we were able to accurately classify thirteen different histone peptides in a single output. Each peptide had multiple modifications, including arginine methylation and lysine methylation, as well as lysine methylation and threonine phosphorylation. The classification assay was able to distinguish both the degree of modification as well as the site of the specific modifications, all based on the slight perturbations neighboring residues make on binding affinity. This assay was also preliminarily applied to the sensing of complex enzymatic reactions by performing a mock kinase experiment, in which we were able to classify distinct ‘time-point’ of enzymatic phosphorylation on two separate substrates. The final section focuses on the expansion of the target class of analytes for the combinatorial sensor array. While the previous study focused on modification-neighboring methylation events, here we describe the classification of the neutral modifications of arginine and lysine, reactions that abolish positive charge and weaken the affinity of the analytes to the receptor. Notably we are able to identify peptides based not just on how many charges are lost, but which specific residues are neutralized and where in the sequence the modification takes place. This opens the door to a large number of enzymatic reactions and histone analytes for which traditional methods of study are insufficient.Doctor of Philosoph

SEM/STEM observations of magnetite in carbonates of eastern North America: Evidence for chemical remagnettzation during the Alleghenian Orogeny

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95085/1/grl5458.pd