An Assessment Of A Practical Experience Requirement For Undergraduate Business Majors

Approximately five years ago, the University of Mary Hardin-Baylor added a unique, practical work experience requirement to the customary graduation requirements for an undergraduate business degree.  This paper examines the perceived value of this requirement from the perspective of the students (now alumni) who have been subject to the requirement and the full-time faculty who advise undergraduates. 90% of the responding alumni believe that this practical requirement is a good idea, has been valuable to them and should be enhanced and continued

Body temperatures of modern and extinct vertebrates from ^(13)C-^(18)O bond abundances in bioapatite

The stable isotope compositions of biologically precipitated apatite in bone, teeth, and scales are widely used to obtain information on the diet, behavior, and physiology of extinct organisms and to reconstruct past climate. Here we report the application of a new type of geochemical measurement to bioapatite, a “clumped-isotope” paleothermometer, based on the thermodynamically driven preference for ^(13)C and ^(18)O to bond with each other within carbonate ions in the bioapatite crystal lattice. This effect is dependent on temperature but, unlike conventional stable isotope paleothermometers, is independent from the isotopic composition of water from which the mineral formed. We show that the abundance of ^(13)C-^(18)O bonds in the carbonate component of tooth bioapatite from modern specimens decreases with increasing body temperature of the animal, following a relationship between isotope “clumping” and temperature that is statistically indistinguishable from inorganic calcite. This result is in agreement with a theoretical model of isotopic ordering in carbonate ion groups in apatite and calcite. This thermometer constrains body temperatures of bioapatite-producing organisms with an accuracy of 1–2 °C. Analyses of fossilized tooth enamel of both Pleistocene and Miocene age yielded temperatures within error of those derived from similar modern taxa. Clumped-isotope analysis of bioapatite represents a new approach in the study of the thermophysiology of extinct species, allowing the first direct measurement of their body temperatures. It will also open new avenues in the study of paleoclimate, as the measurement of clumped isotopes in phosphorites and fossils has the potential to reconstruct environmental temperatures

Constraints on the formation and diagenesis of phosphorites using carbonate clumped isotopes

The isotopic composition of apatites from sedimentary phosphorite deposits has been used previously to reconstruct ancient conditions on the surface of the earth. However, questions remain as to whether these minerals retain their original isotopic composition or are modified during burial and lithification. To better understand how apatites in phosphorites form and are diagenetically modified, we present new isotopic measurements of δ^(18)O values and clumped-isotope-based (Δ_(47)) temperatures of carbonate groups in apatites from phosphorites from the past 265 million years. We compare these measurements to previously measured δ^(18)O values of phosphate groups from the same apatites. These results indicate that the isotopic composition of many of the apatites do not record environmental conditions during formation but instead diagenetic conditions. To understand these results, we construct a model that describes the consequences of diagenetic modification of phosphorites as functions of the environmental conditions (i.e., temperature and δ^(18)O values of the fluids) during initial precipitation and subsequent diagenesis. This model captures the basic features of the dataset and indicates that clumped-isotope-based temperatures provide additional quantitative constraints on both the formational environment of the apatites and subsequent diagenetic modification. Importantly, the combination of the model with the data indicates that the δ^(18)O values and clumped-isotope temperatures recorded by phosphorites do not record either formation or diagenetic temperatures, but rather represent an integrated history that includes both the formation and diagenetic modification of the apatites

Mantle heterogeneity during the formation of the North Atlantic Igneous Province: Constraints from trace element and Sr-Nd-Os-O isotope systematics of Baffin Island picrites

Sr-Nd-Os-O isotope and major and trace element data from ~62 Ma picrites from Baffin Island constrain the composition of mantle sources sampled at the inception of North Atlantic Igneous Province (NAIP) magmatism. We recognize two compositional types. Depleted (N-type) lavas have low 87Sr/86Sri (0.702990–0.703060) and 187Os/188Osi (0.1220–0.1247) and high 143Nd/144Ndi (0.512989–0.512999) and are depleted in incompatible elements relative to primitive mantle. Enriched (E-type) lavas have higher 87Sr/86Sri (0.703306–0.703851) and 187Os/188Osi (0.1261–0.1303), lower 143Nd/144Ndi (0.512825–0.512906), and incompatible element concentrations similar to, or more enriched than, primitive mantle. There is also a subtle difference in oxygen isotope composition; E-type lavas are marginally lower in δ18Oolivine value (5.16–4.84‰) than N-type lavas (5.15–5.22‰). Chemical and isotopic variations between E- and N-type lavas are inconsistent with assimilation of crust and/or subcontinental lithospheric mantle and appear to instead reflect mixing between melts derived from two distinct mantle sources. Strontium-Nd-O isotope compositions and incompatible trace element abundances of N-type lavas suggest these are largely derived from the depleted upper mantle. The 187Os/188Osi ratios of N-type lavas can also be explained by such a model but require that the depleted upper mantle had γOs of approximately −5 to −7 at 62 Ma. This range overlaps the lowest γOs values measured in abyssal peridotites. Baffin Island lava compositions are also permissive of a model involving recharging of depleted upper mantle with 3He-rich material from the lower mantle (Stuart et al., Nature, 424, 57–59, 2003), with the proviso that recharge had no recognizable effect on the lithophile trace element and Sr-Nd-Os-O isotope composition. The origin of the enriched mantle component sampled by Baffin Island lavas is less clear but may be metasomatized and high-temperature-altered recycled oceanic lithosphere transported within the proto Iceland plume. Differences between Baffin Island lavas and modern Icelandic basalts suggest that a range of enriched and depleted mantle sources have been tapped since the inception of magmatism in the province. Similarities between Baffin Island lavas erupted and those of similar age from East and West Greenland also suggest that the enriched component in Baffin Island lavas may have been sampled by lavas erupted over a wide geographic range

Measurement of intact methane isotopologues, including ^(13)CH_3D

Methane (CH_4) is both a significant greenhouse gas and resource. Its present and past cycling can be studied through measurements of concentration and/or bulk isotopic ratios (^(13)C/^(12)C, D/H, and ^(14)C/^(12)C). Currently, isotope ratios are measured by mass spectrometric analysis of H_2 and CO_2 produced from CH_4, or by spectroscopy of CH_4. However, the interpretation of bulk isotopic variations of CH_4 are often equivocal, necessitating additional tracers

An fMRI Study of Responses to Sexual Stimuli as a Function of Gender and Sensation Seeking: A Preliminary Analysis

Although sexual cues produce stronger neural activation in men than in women, mechanisms underlying this differential response are unclear. We examined the relationship of sensation seeking and the brain’s response to sexual stimuli across gender in 27 subjects (14 men, M = 25.2 years, SD = 3.6, 85.2% Caucasian) who underwent functional magnetic resonance imaging (fMRI) while viewing sexual and nonsexual images. Whole-brain corrected significant clusters of regional activation were extracted and associated with gender, sensation seeking, and sexual behaviors. Men responded more to sexual than nonsexual images in the anterior cingulate/medial prefrontal cortex (ACC/mPFC), anterior insula/lateral orbitofrontal cortex, bilateral amygdala, and occipital regions. Sensation seeking related positively to ACC/mPFC (r = 0.65, p = 0.01) and left amygdala (r = 0.66, p = 0.01) response in men alone, with both of these correlations being significantly larger in men than in women (ps < 0.03). The relationship between brain responses and self-reported high-risk and low-risk sexual behaviors showed interesting, albeit nonsignificant, gender-specific trends. These findings suggest the relationship between sexual responsivity, sensation seeking, and sexual behavior is gender specific. This study indicates a need to identify the gender-specific mechanisms that underlie sexual responsivity and behaviors. In addition, it demonstrates that the nature of stimuli used to induce positive mood in imaging and other studies should be carefully considered