Functional evolution of the feeding system in rodents

The masticatory musculature of rodents has evolved to enable both gnawing at the incisors and chewing at the molars. In particular, the masseter muscle is highly specialised, having extended anteriorly to originate from the rostrum. All living rodents have achieved this masseteric expansion in one of three ways, known as the sciuromorph, hystricomorph and myomorph conditions. Here, we used finite element analysis (FEA) to investigate the biomechanical implications of these three morphologies, in a squirrel, guinea pig and rat. In particular, we wished to determine whether each of the three morphologies is better adapted for either gnawing or chewing. Results show that squirrels are more efficient at muscle-bite force transmission during incisor gnawing than guinea pigs, and that guinea pigs are more efficient at molar chewing than squirrels. This matches the known diet of nuts and seeds that squirrels gnaw, and of grasses that guinea pigs grind down with their molars. Surprisingly, results also indicate that rats are more efficient as well as more versatile feeders than both the squirrel and guinea pig. There seems to be no compromise in biting efficiency to accommodate the wider range of foodstuffs and the more general feeding behaviour adopted by rats. Our results show that the morphology of the skull and masticatory muscles have allowed squirrels to specialise as gnawers and guinea pigs as chewers, but that rats are high-performance generalists, which helps explain their overwhelming success as a group

Young Stars with SALT

We present a spectroscopic and kinematic analysis of 79 nearby M dwarfs in 77 systems. All are low-proper-motion southern hemisphere objects and were identified in a nearby star survey with a demonstrated sensitivity to young stars. Using low-resolution optical spectroscopy from the Red Side Spectrograph (RSS) on the South African Large Telescope (SALT), we have determined radial velocities, H-alpha, Lithium 6708\AA, and Potassium 7699\AA~equivalent widths linked to age and activity, and spectral types for all our targets. Combined with astrometric information from literature sources, we identify 44 young stars. Eighteen are previously known members of moving groups within 100 parsecs of the Sun. Twelve are new members, including one member of the TW Hydra moving group, one member of the 32 Orionis moving group, nine members of Tucana-Horologium, one member of Argus, and two new members of AB Doradus. We also find fourteen young star systems that are not members of any known groups. The remaining 33 star systems do not appear to be young. This appears to be evidence of a new population of nearby young stars not related to the known nearby young moving groups.Comment: 23 pages, 11 figures, 6 tables. Accepted to Ap

Google Maps as a Transformational Learning Tool in the Study Abroad Experience

This article examines the role that spatial orientation and location can play on a study abroad program. Jessica Stephenson and M. Todd Harper paired a Google Maps project with autoethnography in order to help students understand their own experience of space abroad as well as how they themselves shaped that space. Students were asked to create a personalized Google Map of the sites that they visited in Rome, Orvieto, Florence, and Montepulciano, Italy. Students then added facts about the sites as well as their own photos and personal experience. They were then asked to use their personalized Google Maps as a heuristic for longer autoethnographic papers relating to the themes of pilgrimage and journey. In so doing, students realized that space is alive, constantly changing and evolving

Immunostaining for Homer reveals the majority of excitatory synapses in laminae I-III of the mouse spinal dorsal horn

The spinal dorsal horn processes somatosensory information before conveying it to the brain. The neuronal organization of the dorsal horn is still poorly understood, although recent studies have defined several distinct populations among the interneurons, which account for most of its constituent neurons. All primary afferents, and the great majority of neurons in laminae I–III are glutamatergic, and a major factor limiting our understanding of the synaptic circuitry has been the difficulty in identifying glutamatergic synapses with light microscopy. Although there are numerous potential targets for antibodies, these are difficult to visualize with immunocytochemistry, because of protein cross-linking following tissue fixation. Although this can be overcome by antigen retrieval methods, these lead to difficulty in detecting other antigens. The aim of this study was to test whether the postsynaptic protein Homer can be used to reveal glutamatergic synapses in the dorsal horn. Immunostaining for Homer gave punctate labeling when viewed by confocal microscopy, and this was restricted to synapses at the ultrastructural level. We found that Homer puncta were colocalized with the AMPA receptor GluR2 subunit, but not with the inhibitory synapse-associated protein gephyrin. We also examined several populations of glutamatergic axons and found that the great majority of boutons were in contact with at least one Homer punctum. These results suggest that Homer antibodies can be used to reveal the great majority of glutamatergic synapses without antigen retrieval. This will be of considerable value in tracing synaptic circuits, and also in investigating plasticity of glutamatergic synapses in pain states

A quantitative study of neurochemically-defined populations of inhibitory interneurons in the superficial dorsal horn of the mouse spinal cord

Around a quarter of neurons in laminae I-II of the dorsal horn are inhibitory interneurons. These play an important role in modulating somatosensory information, including that perceived as pain or itch. Previous studies in rat identified four largely non-overlapping neurochemical populations among these cells, defined by expression of galanin, neuropeptide Y (NPY), neuronal nitric oxide synthase (nNOS) or parvalbumin. The galanin cells were subsequently shown to coexpress dynorphin. Several recent studies have used genetically-modified mice to investigate the function of different interneuron populations, and it is therefore important to determine whether the same pattern applies in mouse, and to estimate the relative sizes of these populations. We show that the neurochemical organisation of inhibitory interneurons in mouse superficial dorsal horn is similar to that in the rat, although a larger proportion of these neurons (33%) express NPY. Between them, these four populations account for ∼75% of inhibitory cells in laminae I-II. Since ∼25% of inhibitory interneurons in this region belong to a novel calretinin-expressing type, our results suggest that virtually all inhibitory interneurons in superficial dorsal horn can be assigned to one of these five neurochemical populations. Although our main focus was inhibitory neurons, we also identified a population of excitatory dynorphin-expressing cells in laminae I-II that are largely restricted to the medial part of the mid-lumbar dorsal horn, corresponding to glabrous skin territory. These findings are important for interpretation of studies using molecular-genetic techniques to manipulate the functions of interneuron populations to investigate their roles in somatosensory processing

Language effects on bargaining

Language is critical to coordination in groups. Though, how language affects coordination in groups is not well understood. We prime distributive and integrative language in a bargaining experiment to better understand the links between group outcomes and communication. We accomplish this by priming interests or positions language in randomized groups. We find that priming positions as opposed to interests language leads to agreements where controllers, subjects with unilateral authority over the group outcome, receive a larger share of the benefits but where the total benefits to the group are unaffected. In contrast to common justifications for the use of integrative language in bargaining, our experimental approach revealed no significant differences between priming interests and positions language in regards to increasing joint outcomes for the groups. Across treatments, we find subjects that use gain frames and make reference to visuals aids during bargaining experience larger gains for the group, while loss frames and pro-self language experience larger gains for the individual through side payments. This finding suggests a bargainer’s dilemma: whether to employ language that claims a larger share of group’s assets or employ language to increase joint gains

Leveraging the Interdependencies Between Barrier Islands and Backbarrier Saltmarshes to Enhance Resilience to Sea-Level Rise

Barrier islands and their backbarrier saltmarshes have a reciprocal relationship: aeolian and storm processes transport sediment from the beaches and dunes to create and build marshes along the landward fringe of the island. In turn, these marshes exert a stabilizing influence on the barrier by widening the barrier system and forming a platform onto which the island migrates, consequently slowing landward barrier migration and inhibiting storm breaching. Here, we present a novel framework for applying these natural interdependencies to managing coastal systems and enhancing barrier-island resilience. Further, we detail application of these principles through a case study of the design of a marsh creation project that showcases the interdisciplinary engagement of scientists, engineers, stakeholders, and policymakers. Specifically, we describe: (1) the ecologic, sedimentologic, stratigraphic, and morphologic data obtained from the southern 4 km of Cedar Island (Virginia, United States) and nearby backbarrier tidal channels, tidal flats, and flood-tidal deltas, and (2) the use of those data to develop an engineering and design plan for the construction of a high (46 ha) and low (42 ha) fringing marsh platform located behind the island, proximal to a former ephemeral inlet. Additionally, we chronicle the process used to narrow five initial alternative designs to the optimal final plan. This process involved balancing best-available existing science and models, considering design and financial constraints, identifying stakeholder preferences, and maximizing restoration benefits of habitat provision and shoreline protection. Construction of this marsh would: (1) provide additional habitat and ecosystem benefits, (2) slow the rapid migration (up to 15 m/yr at present) of the barrier island, and (3) hinder island breaching. Ultimately, this project – presently at the final design and permitting stage – may enhance the storm and sea-level rise resilience of the island, backbarrier marshes and lagoons, and the mainland town community; and provide an example of a novel science-based approach to coastal resilience that could be applied to other global barrier settings

Nucleosynthesis signatures of neutrino-driven winds from proto-neutron stars: a perspective from chemical evolution models

We test the hypothesis that the observed first-peak (Sr, Y, Zr) and second-peak (Ba) s-process elemental abundances in low-metallicity Milky Way stars, and the abundances of the elements Mo and Ru, can be explained by a pervasive r-process contribution originating in neutrino-driven winds from highly-magnetic and rapidly rotating proto-neutron stars (proto-NSs). We construct chemical evolution models that incorporate recent calculations of proto-NS yields in addition to contributions from AGB stars, Type Ia supernovae, and two alternative sets of yields for massive star winds and core-collapse supernovae. For non-rotating massive star yields from either set, models without proto-NS winds underpredict the observed s-process peak abundances by $0.3$-$1\,\text{dex}$ at low metallicity, and they severely underpredict Mo and Ru at all metallicities. Models incorporating wind yields from proto-NSs with spin periods $P \sim 2$-$5\,\text{ms}$ fit the observed trends for all these elements well. Alternatively, models omitting proto-NS winds but adopting yields of rapidly rotating massive stars, with $v_{\rm rot}$ between $150$ and $300\,\text{km}\,\text{s}^{-1}$, can explain the observed abundance levels reasonably well for $\text{[Fe/H]}<-2$. These models overpredict [Sr/Fe] and [Mo/Fe] at higher metallicities, but with a tuned dependence of $v_{\rm rot}$ on stellar metallicity they might achieve an acceptable fit at all [Fe/H]. If many proto-NSs are born with strong magnetic fields and short spin periods, then their neutrino-driven winds provide a natural source for Sr, Y, Zr, Mo, Ru, and Ba in low-metallicity stellar populations. Conversely, spherical winds from unmagnetized proto-NSs overproduce the observed Sr, Y, and Zr abundances by a large factor.Comment: Accepted for publication in MNRA

Duration of symptoms resulting from lumbar disc herniation: effect on treatment outcomes: analysis of the Spine Patient Outcomes Research Trial (SPORT).

BACKGROUND: The purpose of the present study was to determine if the duration of symptoms affects outcomes following the treatment of intervertebral lumbar disc herniation. METHODS: An as-treated analysis was performed on patients enrolled in the Spine Patient Outcomes Research Trial (SPORT) for the treatment of intervertebral lumbar disc herniation. Randomized and observational cohorts were combined. A comparison was made between patients who had had symptoms for six months or less (n = 927) and those who had had symptoms for more than six months (n = 265). Primary and secondary outcomes were measured at baseline and at regular follow-up intervals up to four years. The treatment effect for each outcome measure was determined at each follow-up period for the duration of symptoms for both groups. RESULTS: At all follow-up intervals, the primary outcome measures were significantly worse in patients who had had symptoms for more than six months prior to treatment, regardless of whether the treatment was operative or nonoperative. When the values at the time of the four-year follow-up were compared with the baseline values, patients in the operative treatment group who had had symptoms for six months or less had a greater increase in the bodily pain domain of the Short Form-36 (SF-36) (mean change, 48.3 compared with 41.9; p \u3c 0.001), a greater increase in the physical function domain of the SF-36 (mean change, 47.7 compared with 41.2; p \u3c 0.001), and a greater decrease in the Oswestry Disability Index score (mean change, -41.1 compared with -34.6; p \u3c 0.001) as compared with those who had had symptoms for more than six months (with higher scores indicating less severe symptoms on the SF-36 and indicating more severe symptoms on the Oswestry Disability Index). When the values at the time of the four-year follow-up were compared with the baseline values, patients in the nonoperative treatment group who had had symptoms for six months or less had a greater increase in the bodily pain domain of the SF-36 (mean change, 31.8 compared with 21.4; p \u3c 0.001), a greater increase in the physical function domain of the SF-36 (mean change, 29.5 compared with 22.6; p = 0.015), and a greater decrease in the Oswestry Disability Index score (mean change, -24.9 compared with -18.5; p = 0.006) as compared with those who had had symptoms for more than six months. Differences in treatment effect between the two groups related to the duration of symptoms were not significant. CONCLUSIONS: Increased symptom duration due to lumbar disc herniation is related to worse outcomes following both operative and nonoperative treatment. The relative increased benefit of surgery compared with nonoperative treatment was not dependent on the duration of the symptoms