The Formation of Distal Impact Ejecta

Here we present two models for the dynamics of ejection and formation of distal impact ejecta. The first model focuses on the most highly shocked material that forms a massive expanding vapor plume or fireball. In this model molten droplets or spherules condense from the vapor. We model the expanding vapor plume using a one dimensional Lagrangian hydrocode. The condensation of droplets is treated by directly coupling the equations for homogeneous nucleation and growth with our hydrocode. The second model is focused on less energetic material ejected as part of the excavation flow. Using the iSALE hydrocode, we determine the details of the excavation flow and formation of the ejecta curtain. Using this information and some simple analytical approximations we produce a model for the formation of melt droplet spherules, melt fragments, and accretionary impact lapilli, within this flow. Using our model for spherules produced in the vapor plume, we create a method to estimate the size of an impactor and impact velocity required to create a spherule layer. The impactor size depends on the thickness of the layer and the impact velocity depends on the size of the spherules within the layer. Using observations of known spherule layers and the derived dependence on impactor size, we show that the impactor flux on Earth was significantly higher ~2-3.5 Gyr ago than it is today. Our model for the less energetic material ejected as part of the ejecta curtain predicts how ejecta particle sizes depend on impactor size and ejection velocity. In the future, this model can also be used to estimate the scale of an impact required to make observed distal impact ejecta layers

\u3cem\u3eAPOE\u3c/em\u3e and Alzheimer’s Disease: Neuroimaging of Metabolic and Cerebrovascular Dysfunction

Apolipoprotein E4 (ApoE4) is the strongest genetic risk factor for late onset Alzheimer’s Disease (AD), and is associated with impairments in cerebral metabolism and cerebrovascular function. A substantial body of literature now points to E4 as a driver of multiple impairments seen in AD, including blunted brain insulin signaling, mismanagement of brain cholesterol and fatty acids, reductions in blood brain barrier (BBB) integrity, and decreased cerebral glucose uptake. Various neuroimaging techniques, in particular positron emission topography (PET) and magnetic resonance imaging (MRI), have been instrumental in characterizing these metabolic and vascular deficits associated with this important AD risk factor. In the current mini-review article, we summarize the known effects of APOE on cerebral metabolism and cerebrovascular function, with a special emphasis on recent findings via neuroimaging approaches

Force of Beauty or Object of Desire? The Priming Effects of Makeup Video Advertisements on Self-Objectification in College Women

Women are too often valued for their beauty and have shifted their focus from character to body improvement (Brumberg, 1998). Objectification theory (Frederickson & Roberts, 1997) posits that sexual objectification socializes females to evaluate themselves based on looks. Self-objectification is the attempt to control this external perception by monitoring one’s physical appearance. Women are more likely to think “How do I look?” than “What am I capable of?” The priming effects of positive and negative body-focused makeup advertisements on college-aged women’s level of self-objectification were examined in two separate studies. In study one, 87 participants viewing positive vs. negative advertisements reported more traits and abilities; this was especially true for high self-objectifiers. Participants viewing positive advertisements reported more positive emotions, suggesting the salutary role that positive messaging may play. Results were replicated in study two, with 172 participants who viewed positive vs. negative advertisements reporting significantly fewer body shape statements, more trait and abilities, as well as more physical competence statements. In addition, individuals who viewed advertisements with non-objectifying content responded with a significantly greater number of positively valenced statements and significantly fewer negative statements about themselves in comparison to women who viewed objectifying advertisements. These results suggest that marketers should eschew advertising that sexually objectifies women and promotes unattainable beauty goals. Future research should evaluate cumulative and long-term effects of advertisement and examine whether exposure that leads to lower levels of objectification also minimizes negative consequences associated with objectifying media influences (e.g., body shame, depression, eating disorder)

Effects of increasing soybean hulls in finishing diets with wet or modified distillers grains plus solubles on performance and carcass characteristics of beef steers

Two experiments evaluated feeding soybean hulls (SBH) in finishing diets that contain distillers grains plus solubles on performance and carcass characteristics. Dietary concentrations of SBH were 0, 12.5, 25, and 37.5% of diet DM. In Exp. 1, 167 crossbred yearling steers (395 ± 22 kg of BW) were fed for 117 d in a randomized block design in which pelleted SBH replaced dry-rolled corn. All diets contained 25% modified distillers grains plus solubles, 15% corn silage, and 5% liquid supplement. As SBH concentration increased, DMI decreased linearly (P = 0.04). Gain and G:F decreased linearly (P \u3c 0.01) in response to increasing concentrations of SBH, which decreased relative energy value from 91 to 79% of corn. Hot carcass weight linearly decreased (P \u3c 0.01) by 24 kg as SBH increased. In Exp. 2, a randomized block design used 160 backgrounded steer calves (363 ± 16 kg of BW) in a 138-d finishing study with 0, 12.5, 25, or 37.5% SBH in the meal form. Basal ingredients consisted of a 1:1 ratio of high-moisture corn and dry-rolled corn, 40% wet distillers grains plus solubles, 8% sorghum silage, and 4% dry meal supplement. There was a tendency (P = 0.12) for a quadratic increase in ADG and G:F as dietary SBH increased, with numerically greatest ADG and G:F with 12.5% SBH. Feeding 12.5 to 25% SBH with 40% wet distillers grains plus solubles (Exp. 2) had little effect on performance but decreased ADG and G:F in diets with 25% modified distillers grains plus solubles (Exp. 1)

Conversion between Triplet Pair States Is Controlled by Molecular Coupling in Pentadithiophene Thin Films

In singlet fission (SF) the initially formed correlated triplet pair state, 1(TT), may evolve toward independent triplet excitons or higher spin states of the (TT) species. The latter result is often considered undesirable from a light harvesting perspective but may be attractive for quantum information sciences (QIS) applications, as the final exciton pair can be spin-entangled and magnetically active with relatively long room temperature decoherence times. In this study we use ultrafast transient absorption (TA) and time-resolved electron paramagnetic resonance (TR-EPR) spectroscopy to monitor SF and triplet pair evolution in a series of alkyl silyl-functionalized pentadithiophene (PDT) thin films designed with systematically varying pairwise and long-range molecular interactions between PDT chromophores. The lifetime of the (TT) species varies from 40 ns to 1.5 μs, the latter of which is associated with extremely weak intermolecular coupling, sharp optical spectroscopic features, and complex TR-EPR spectra that are composed of a mixture of triplet and quintet-like features. On the other hand, more tightly coupled films produce broader transient optical spectra but simpler TR-EPR spectra consistent with significant population in 5(TT)0. These distinctions are rationalized through the role of exciton diffusion and predictions of TT state mixing with low exchange coupling J versus pure spin substate population with larger J. The connection between population evolution using electronic and spin spectroscopies enables assignments that provide a more detailed picture of triplet pair evolution than previously presented and provides critical guidance for designing molecular QIS systems based on light-induced spin coherence