The Last Stages of Terrestrial Planet Formation: Dynamical Friction and the Late Veneer

The final stage of terrestrial planet formation consists of the cleanup of residual planetesimals after the giant impact phase. Dynamically, a residual planetesimal population is needed to damp the high eccentricities of the terrestrial planets after the giant impact stage. Geochemically, highly siderophile element (HSE) abundance patterns inferred for the terrestrial planets and the Moon suggest that a total of about 0.01 M_Earth of chondritic material was delivered as `late veneer' by planetesimals to the terrestrial planets after the end of giant impacts. Here we combine these two independent lines of evidence for a leftover population of planetesimals and show that: 1) A residual planetesimal population containing 0.01 M_Earth is able to damp the eccentricities of the terrestrial planets after giant impacts to their observed values. 2) At the same time, this planetesimal population can account for the observed relative amounts of late veneer added to the Earth, Moon and Mars provided that the majority of the late veneer was delivered by small planetesimals with radii <10m. These small planetesimal sizes are required to ensure efficient damping of the planetesimal's velocity dispersion by mutual collisions, which in turn ensures that the planets' accretion cross sections are significantly enhanced by gravitational focusing above their geometric values. Specifically we find, in the limit that the relative velocity between the terrestrial planets and the planetesimals is significantly less than the terrestrial planets' escape velocities, that gravitational focusing yields an accretion ratio Earth/Mars~17, which agrees well with the accretion ratio inferred from HSEs of 12-23. For the Earth-Moon system, we find an accretion ratio of ~200, which is consistent with estimates of 150-700 derived from HSE abundances that include the lunar crust as well as mantle component. (Abridged)Comment: accepted for publication in ApJ, 9 pages, 4 figures; minor corrections, additional references adde

The needs of young carers and the role of the school nurse

Young carers provide a significant contribution to society in their caring role, which is in line with the UK Government’s Big Society agenda. In contrast with their contribution to society, young carers have huge associated costs related to poor outcomes and the numbers that end up not in employment, education or training (NEET). Missing school due to caring responsibilities is likely to have an effect on future education and job prospects. Understanding the impact of the caring role on the school experience of young carers will enable school nurses to provide appropriate support for young carers, improving their school experience and subsequent outcomes

Making a Difference: Creating New Gateways to Mental Health and Wellness

Participants were invited to voluntarily participate in one of three focus groups which were held in the Near East Side community. The focus groups were facilitated by a person who has cultural awareness and competence in the African American community and a psychiatric/mental health clinical nurse specialist. Participants completed an informed consent form and a demographic questionnaire. During the group, the co-facilitators asked a series of questions. The responses were audiotape recorded. However, the participants' names were not connected to their voices or to their demographic questionnaire. In addition, all participants were told that what was said in the focus group was private and were encouraged not to talk about what is said in the group outside of the group. Each focus group lasted one hour. Light refreshments were available. Participants who needed help with transportation were provided a COTA bus ticket. At the end of the group, each participant received a $30 gift card for participating in the group. The co-facilitators provided written information to participants about stress and community resources for participants who desired more information. Participants who attended the focus group may have experienced some feelings when they spoke about stress or traumatic life events or when they heard others speak. These feelings may have included sadness, anger or other emotions. No one was forced to speak; participants may have elected to not answer a question or to be silent during the group if they wished. The co-facilitators were available to participants at the end of the focus group to provide information or referrals if the participant desired more information or services to cope with stress.AUTHOR AFFILIATION: Elizabeth Fitzgerald, Associate Professor of Clinical Nursing, College of Nursing, [email protected] (Corresponding Author); Morgan Ciehanski, BSN Honors Student, The Ohio State University; Caroline Buck, BSN Honors Student, The Ohio State University; Barbara Warren, Professor of Clinical Nursing, The Ohio State University.This poster will display the results of a qualitative research study on stress to help identify the resources, services and sources of support that members of the Near East Side community prefer and desire. In all, 28 African-American adults participated in focus groups. Audiotaped recordings of the focus groups were transcribed, and themes emerged from the data. The themes of toxic stress and communal discipline will be discussed. The importance of collaboration between academic institutions and community partners through a steadfast presence in the community will be highlighted

Exploiting mTOR cellular signalling to promote retinal ganglion cell survival and axon regeneration after traumatic optic neuropathy

Retinal ganglion cell (RGC) apoptosis and failure of optic nerve (ON) axon regeneration contribute to profound visual loss after traumatic optic neuropathy (TON), for which clinically effective treatments are lacking. Experimental manipulations of cellular signalling have identified phosphoinositide-3-kinase (PI3K) and its downstream mediators mTOR and GSK3$\beta$ as important regulators of neuronal survival and axon regeneration in an animal model of TON, using targeted siRNA to knock-down key negative regulators of cellular signalling, and to investigate underlying mechanisms using retinal cultures. Intravitreal treatment with siRNA targeting RTP801, a stress-induced inhibitor of mTOR, promoted RGC survival and axon elongation after ON crush (ONC), and potentiated reactive gliosis. In vitro, siRTP801- induced neuroprotection was direct, but required GFAP$^+$ activated retinal glia to stimulate neurite elongation. siRTP801 also potentiated levels of glial-derived Trk-dependent neurotrophic factors. Knock-down of the axon growth cone/apoptosis regulator GSK3$\beta$ was also neuroprotective, promoted modest axon elongation after ONC, and increased neurite sprouting in vitro. GSK3$\beta$ suppression counteracted neurite growth-inhibition induced by CNS myelin-derived Nogo. Combined treatment with siRTP801/siGSK3$\beta$ augmented axon regeneration after ONC. These findings support a clinically translatable siRNA approach targeting PI3K/mTOR signalling as the basis for development of novel neuroprotective/axogenic therapies

Pacification and Gender in Colonial Africa: Evidence from the Ethnographic Atlas

We combine the date-of-observation found in Murdock’s Ethnographic Atlas and a newly-constructed dataset on the date-of-colonization at the ethnic-group level to study the effects of the duration of colonial rule on a variety of political, economic, and social characteristics of ethnic groups in Africa. We find that the duration of colonial rule caused a dramatic shift in gender roles in Africa by increasing the relative status of men in lineage and inheritance systems but also reducing polygyny as a marriage system. A causal role for the duration of colonial rule is confirmed by a difference-in-difference analysis that uses never-colonized ethnic groups as a control group and by an analysis of changes in kinship terminology that tests for within-group changes in descent and inheritance rules. We are able to rule out missionary influence and Islam as mechanisms for these effects

Publix Supermarkets, Inc.

All traditional brick-and-mortar retailers are struggling with how best to deal with threats from online retailers. However, the supermarket industry is also dealing with pressure from new foreign entrants like Aldi and Lidl. Perhaps nowhere is this more evident than in the southeastern United States, where Publix operates. Publix is an employee-owned supermarket chain with excellent service, high margins and strong growth in sales and profits. The company has also had some success with Internet offerings. However, is the company’s business model going to sustain it in this increasingly competitive industry, or are changes needed? This case focuses on the entrance of Publix into the Richmond Virginia market

Si microwire-array solar cells

Si microwire-array solar cells with Air Mass 1.5 Global conversion efficiencies of up to 7.9% have been fabricated using an active volume of Si equivalent to a 4 μm thick Si wafer. These solar cells exhibited open-circuit voltages of 500 mV, short-circuit current densities (J_(sc)) of up to 24 mA cm^(-2), and fill factors >65% and employed Al_2O_3 dielectric particles that scattered light incident in the space between the wires, a Ag back reflector that prevented the escape of incident illumination from the back surface of the solar cell, and an a-SiN_x:H passivation/anti-reflection layer. Wire-array solar cells without some or all of these design features were also fabricated to demonstrate the importance of the light-trapping elements in achieving a high J_(sc). Scanning photocurrent microscopy images of the microwire-array solar cells revealed that the higher J_(sc) of the most advanced cell design resulted from an increased absorption of light incident in the space between the wires. Spectral response measurements further revealed that solar cells with light-trapping elements exhibited improved red and infrared response, as compared to solar cells without light-trapping elements