New Constraints on Isospin-Violating Dark Matter

We derive bounds on the dark matter annihilation cross-section for low-mass (5-20 GeV) dark matter annihilating primarily to up or down quarks, using the Fermi-LAT bound on gamma-rays from Milky Way satellites. For models in which dark matter-Standard Model interactions are mediated by particular contact operators, we show that these bounds can be directly translated into bounds on the dark matter-proton scattering cross-section. For isospin-violating dark matter, these constraints are tight enough to begin to constrain the parameter-space consistent with experimental signals of low-mass dark matter. We discuss possible models that can evade these bounds.Comment: 6 pages, 2 figures, LaTeX, some clarifications and minor errors corrected, citations adde

The Cretaceous-Paleogene boundary deposit in the Gulf of Mexico : oceanic basin response to the Chicxulub impact and geomechanics of reservoir-scale sand injectites, Panoche Hills, California

Hydrocarbon exploration in the last decade has yielded sufficient data to evaluate the Gulf of Mexico basin response to the Chicxulub asteroid impact. Given its passive marine setting and proximity to the impact structure on the Yucatán Peninsula, the Gulf is the premier locale in which to study the near-field geologic effect of a massive bolide impact. We mapped a thick (dm- to hm-scale) deposit of carbonate debris at the Cretaceous-Paleogene boundary that is ubiquitous in the Gulf and readily identifiable on borehole and seismic data. We interpret deposits seen in seismic and borehole data in the distal deepwater Gulf to be predominately muddy debrites with minor turbidites based on cores in the southeastern Gulf. Mapping of the deposit in the northern Gulf of Mexico reveals that the impact redistributed roughly 1.05 x 10⁵ km³ of sediment therein, and over 1.98 x 10⁵ km³ Gulf-wide. Deposit distribution suggests that the majority of sediment derived from coastal and shallow-water environments throughout the Gulf via seismic and megatsunamic processes initiated by the impact. The Texas shelf and northern margin of the Florida Platform were primary sources of sediment, while the central and southern Florida Platform underwent more localized platform collapse. Crustal structure of the ancestral Gulf influenced post-impact deposition both directly and indirectly through its control on salt distribution in the Louann salt basin. Nevertheless, impact-generated deposition overwhelmed virtually all topography and depositional systems at the start of the Cenozoic, blanketing the Gulf with carbonate debris within days. The Panoche Giant Injection Complex (PGIC) in central California is a complete injectite system. We measured hundreds of injectites over ~600 m of stratigraphic thickness in two locales in order to determine geomechanical controls on injection. We document an injectite architecture in the PGIC that we interpret to reflect a reversal in paleostress state from reverse to strike-slip or normal with proximity to the paleoseafloor. We demonstrate that injectite aperture and bulk strain decrease with distance from the injection source. We model this behavior with three hydraulic fracture geometries and conclude that injectites formed via radially propagating hydraulic fractures. We document a northeast-southwest paleo-orientation preference of subvertical injectites, which reflects the control of Farallon plate subduction on stress state at the PGIC. We estimate that the PGIC was complete and active for ~1 Ma and punctuated by ~20–150 ky-long periods of quiescence based on thickness and spacing of extrudites in the PGIC.Geological Science

Isospin-Violating Dark Matter Benchmarks for Snowmass 2013

Isospin-violating dark matter (IVDM) generalizes the standard spin-independent scattering parameter space by introducing one additional parameter, the neutron-to-proton coupling ratio f_n/f_p. In IVDM the implications of direct detection experiments can be altered significantly. We review the motivations for considering IVDM and present benchmark models that illustrate some of the qualitatively different possibilities. IVDM strongly motivates the use of a variety of target nuclei in direct detection experiments.Comment: LaTeX, 5 pages, 4 figures. v2: minor figure revision

Isospin-Violating Dark Matter

Searches for dark matter scattering off nuclei are typically compared assuming that the dark matter's spin-independent couplings are identical for protons and neutrons. This assumption is neither innocuous nor well motivated. We consider isospin-violating dark matter (IVDM) with one extra parameter, the ratio of neutron to proton couplings, and include the isotope distribution for each detector. For a single choice of the coupling ratio, the DAMA and CoGeNT signals are consistent with each other and with current XENON constraints, and they unambiguously predict near future signals at XENON and CRESST. We provide a quark-level realization of IVDM as WIMPless dark matter that is consistent with all collider and low-energy bounds.Comment: 5 pages; v2: added references and fixed figures for Mac users; v3: published version; v4: fixed erroneous Ar values in table

Xenophobic dark matter

We consider models of xenophobic dark matter, in which isospin-violating dark matter–nucleon interactions significantly degrade the response of xenon direct detection experiments. For models of near-maximal xenophobia, with neutron-to-proton coupling ratio f_n/f_p ≈ -0.64, and dark matter mass near 8 GeV, the regions of interest for CoGeNT and CDMS-Si and the region of interest identified by Collar and Fields in CDMS-Ge data can be brought into agreement. This model may be tested in future direct, indirect, and collider searches. Interestingly, because the natural isotope abundance of xenon implies that xenophobia has its limits, we find that this xenophobic model may be probed in the near future by xenon experiments. Near-future data from the LHC and Fermi-LAT may also provide interesting alternative probes of xenophobic dark matter

Flip the Prison: Using a Holistic, Interdisciplinary Approach to Transform Closed Prisons and Adjudicated Youth

Flip the Prison: Is a collective Impact Model for transforming closed prisons into farms and educational centers utilizing mental health therapy, youth focused, sustainable agricultural entrepreneurship and service learning to stabilize adjudicated youth in the community. Of interest to educators, mental health clinicians, veterans, community leaders, clergy and entrepreneurs

Solution pans and linear sand bedforms on the bare-rock limestone shelf of the Campeche Bank, Yucatán Peninsula, Mexico

A high-resolution, near-surface geophysical survey was conducted in 2013 on the Campeche Bank, a carbonate platform offshore of Yucatán, Mexico, to provide a hazard assessment for future scientific drilling into the Chicxulub impact crater. It also provided an opportunity to obtain detailed information on the seafloor morphology and shallow stratigraphy of this understudied region. The seafloor exhibited two morphologies: (1) small-scale (<2 m) bare-rock karstic features, and (2) thin (<1 m) linear sand accumulations overlying the bedrock. Solution pans, circular to oblong depressions featured flat bottoms and steep sides, were the dominant karstic features; they are known to form subaerially by the pooling of rainwater and dissolution of carbonate. Observed pans were 10–50 cm deep and generally 1–8 m wide, but occasionally reach 15 m, significantly larger than any solution pan observed on land (maximum 6 m). These features likely grew over the course of many 10's of thousands of years in an arid environment while subaerially exposed during lowered sea levels. Surface sands are organized into linear bedforms oriented NE-SW, 10's to 100's meters wide, and kilometers long. These features are identified as sand ribbons (longitudinal bedforms), and contained asymmetric secondary transverse bedforms that indicate NE-directed flow. This orientation is incompatible with the prevalent westward current direction; we hypothesize that these features are storm-generated

An online learning algorithm for adapting leg stiffness and stride angle for efficient quadruped robot trotting

Animals adjust their leg stiffness and stride angle in response to changing ground conditions and gait parameters, resulting in improved stability and reduced energy consumption. This paper presents an online learning algorithm that attempts to mimic such animal behavior by maximizing energy efficiency on the fly or equivalently, minimizing the cost of transport of legged robots by adaptively changing the leg stiffness and stride angle while the robot is traversing on grounds with unknown characteristics. The algorithm employs an approximate stochastic gradient method to change the parameters in real-time, and has the following advantages: (1) the algorithm is computationally efficient and suitable for real-time operation; (2) it does not require training; (3) it is model-free, implying that precise modeling of the robot is not required for good performance; and (4) the algorithm is generally applicable and can be easily incorporated into a variety of legged robots with adaptable parameters and gaits beyond those implemented in this paper. Results of exhaustive performance assessment through numerical simulations and experiments on an under-actuated quadruped robot with compliant legs are included in the paper. The robot platform used a pneumatic piston in each leg as a variable, passive compliant element. Performance evaluation using simulations and experiments indicated that the algorithm was capable of converging to near-optimal values of the cost of transport for given operating conditions, terrain properties, and gait characteristics with no prior knowledge of the terrain and gait conditions. The simplicity of the algorithm and its demonstrably improved performance make the approach of this paper an excellent candidate for adaptively controlling tunable parameters of compliant, legged robots

Defining Ecological Drought for the Twenty-First Century

THE RISING RISK OF DROUGHT. Droughts of the twenty-first century are characterized by hotter temperatures, longer duration, and greater spatial extent, and are increasingly exacerbated by human demands for water. This situation increases the vulnerability of ecosystems to drought, including a rise in drought-driven tree mortality globally (Allen et al. 2015) and anticipated ecosystem transformations from one state to another—for example, forest to a shrubland (Jiang et al. 2013). When a drought drives changes within ecosystems, there can be a ripple effect through human communities that depend on those ecosystems for critical goods and services (Millar and Stephenson 2015). For example, the “Millennium Drought” (2002–10) in Australia caused unanticipated losses to key services provided by hydrological ecosystems in the Murray–Darling basin—including air quality regulation, waste treatment, erosion prevention, and recreation. The costs of these losses exceeded AUD $800 million, as resources were spent to replace these services and adapt to new drought-impacted ecosystems (Banerjee et al. 2013). Despite the high costs to both nature and people, current drought research, management, and policy perspectives often fail to evaluate how drought affects ecosystems and the “natural capital” they provide to human communities. Integrating these human and natural dimensions of drought is an essential step toward addressing the rising risk of drought in the twenty-first century

Mutations in SLC39A14 disrupt manganese homeostasis and cause childhood-onset parkinsonism-dystonia.

Although manganese is an essential trace metal, little is known about its transport and homeostatic regulation. Here we have identified a cohort of patients with a novel autosomal recessive manganese transporter defect caused by mutations in SLC39A14. Excessive accumulation of manganese in these patients results in rapidly progressive childhood-onset parkinsonism-dystonia with distinctive brain magnetic resonance imaging appearances and neurodegenerative features on post-mortem examination. We show that mutations in SLC39A14 impair manganese transport in vitro and lead to manganese dyshomeostasis and altered locomotor activity in zebrafish with CRISPR-induced slc39a14 null mutations. Chelation with disodium calcium edetate lowers blood manganese levels in patients and can lead to striking clinical improvement. Our results demonstrate that SLC39A14 functions as a pivotal manganese transporter in vertebrates.Action Medical ResearchThis is the final version of the article. It first appeared from Nature Publishing Group via http://dx.doi.org/10.1038/ncomms1160