240 research outputs found

    A charge dependent long-ranged force drives tailored assembly of matter in solution

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    The interaction between charged objects in solution is generally expected to recapitulate two central principles of electromagnetics: (i) like-charged objects repel, and (ii) they do so regardless of the sign of their electrical charge. Here we demonstrate experimentally that the solvent plays a hitherto unforeseen but crucial role in interparticle interactions, and importantly, that interactions in the fluid phase can break charge-reversal symmetry. We show that in aqueous solution, negatively charged particles can attract at long range while positively charged particles repel. In solvents that exhibit an inversion of the net molecular dipole at an interface, such as alcohols, we find that the converse can be true: positively charged particles may attract whereas negatives repel. The observations hold across a wide variety of surface chemistries: from inorganic silica and polymeric particles to polyelectrolyte- and polypeptide-coated surfaces in aqueous solution. A theory of interparticle interactions that invokes solvation at an interface explains the observations. Our study establishes a specific and unanticipated mechanism by which the molecular solvent may give rise to a strong and long-ranged force in solution, with immediate ramifications for a variety of particulate and molecular processes including tailored self-assembly, gelation and crystallization, as well as biomolecular condensation, coacervation and phase segregation. These findings also shed light on the solvent-induced interfacial electrical potential - an elusive quantity in electrochemistry and interface science implicated in many natural and technological processes, such as atmospheric chemical reactions, electrochemical energy storage and conversion, and the conduction of ions across cell membranes.Comment: 20 pages, 6 figure

    HI Narrow Self-Absorption in Dark Clouds: Correlations with Molecular Gas and Implications for Cloud Evolution and Star Formation

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    We present the results of a comparative study of HI narrow self-absorption (HINSA), OH, 13CO, and C18O in five dark clouds. The HINSA follows the distribution of the emission of the carbon monoxide isotopologues, and has a characteristic size close to that of 13CO. This confirms that the HINSA is produced by cold HI which is well mixed with molecular gas in well-shielded regions. The ratio of the atomic hydrogen density to total proton density for these sources is 5 to 27 x 10^{-4}. Using cloud temperatures and the density of HI, we set an upper limit to the cosmic ray ionization rate of 10^{-16} s^{-1}. Comparison of observed and modeled fractional HI abundances indicates ages for these clouds to be 10^{6.5} to 10^{7} yr. The low values of the HI density we have determined make it certain that the time scale for evolution from an atomic to an almost entirely molecular phase, must be a minimum of several million years. This clearly sets a lower limit to the overall time scale for star formation and the lifetime of molecular clouds

    Sarcopenia Is an Independent Risk Factor for Proximal Junctional Disease Following Adult Spinal Deformity Surgery

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    Study Design: Retrospective cohort study. Objectives: Sarcopenia is a risk factor for medical complications following spine surgery. However, the role of sarcopenia as a risk factor for proximal junctional disease (PJD) remains undefined. This study evaluates whether sarcopenia is an independent predictor of proximal junctional kyphosis (PJK) and proximal junctional failure (PJF) following adult spinal deformity (ASD) surgery. Methods: ASD patients who underwent thoracic spine to pelvis fusion with 2-year clinical and radiographic follow-up were reviewed for development of PJK and PJD. Average psoas cross-sectional area on preoperative axial computed tomography or magnetic resonance imaging at L4 was recorded. Previously described PJD risk factors were assessed for each patient, and multivariate linear regression was performed to identify independent risk factors for PJK and PJF. Disease-specific thresholds were calculated for sarcopenia based on psoas cross-sectional area. Results: Of 32 patients, PJK and PJF occurred in 20 (62.5%) and 12 (37.5%), respectively. Multivariate analysis demonstrated psoas cross-sectional area to be the most powerful independent predictor of PJK (P = .02) and PJF (P = .009). Setting ASD disease–specific psoas cross-sectional area thresholds of <12 cm2 in men and <8 cm2 in women resulted in a PJF rate of 69.2% for patients below these thresholds, relative to 15.8% for those above the thresholds. Conclusions: Sarcopenia is an independent, modifiable predictor of PJK and PJF, and is easily assessed on standard preoperative computed tomography or magnetic resonance imaging. Surgeons should include sarcopenia in preoperative risk assessment and consider added measures to avoid PJF in sarcopenic patients

    Sources of Cosmic Dust in the Earth's Atmosphere

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    There are four known sources of dust in the inner solar system: Jupiter Family comets, Asteroids, Halley Type comets, and Oort Cloud comets. Here we combine the mass, velocity and radiant distributions of these cosmic dust populations from an astronomical model with a chemical ablation model to estimate the injection rates of Na and Fe into the Earth's upper atmosphere, as well as the flux of cosmic spherules to the surface. Comparing these parameters to lidar observations of the vertical Na and Fe fluxes above 87.5 km, and the measured cosmic spherule accretion rate at South Pole, shows that Jupiter Family Comets contribute (80 ± 17) % of the total input mass (43 ± 14 t d¯¹), in good accord with COBE and Planck observations of the Zodiacal Cloud

    Latinos and Latinas in Communal Settings: A Grounded Theory of Recovery

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    Semi-structured interviews were conducted with 12 Latino/a residents of a mutual help residential recovery program (Oxford House) in order to elicit their experiences of the program’s therapeutic elements. A model of recovery emerged from the analysis including several themes supported by existing literature: personal motivation and readiness to change, mutual help, sober environment, social support, and accountability. Consistent with a broad conceptualization of recovery, outcomes included abstinence, new life skills, and increased self-esteem/sense of purpose. Most participants were the only Latino/a in their Houses; however, cultural differences did not emerge as salient issues. The study’s findings highlight potential therapeutic aspects of mutual-help communal recovery programs and suggest that English-speaking, bicultural Latinos/as have positive experiences and may benefit from participating in these programs

    Four-dimensional electrical resistivity imaging for monitoring pumping-induced saltwater intrusion in a coastal aquifer

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    Conventional views of saltwater intrusion (SWI), where a basal saline wedge extends inland below fresh groundwater, can be complicated by the influence of saltwater cells in the upper part of aquifers in areas affected by tidal cycles. Distinguishing the contribution of each saltwater source may prove fundamental for well design and resource management. Application of time-lapse electrical resistivity imaging (ERI) during a 32-h pumping test in a pristine unconfined coastal sand aquifer, affected by strong tidal ranges (>2 m), aimed to evaluate the potential of the method to characterize the source of induced SWI in four dimensions (three dimensions and time). Water level monitoring during the test revealed that at the end of pumping, the upper 2 m of the aquifer had dewatered in the vicinity of the well field, reversing hydraulic gradients between the aquifer and the sea. This induced SI, with mixing models of well head water quality suggesting that saline water contributions to total discharge rose from 4 % to 8 %. ERI results reflected dewatering through an increase in resistivity in the upper 2-6 m of the aquifer, while a decline in resistivity, relative to background conditions, occurred immediately below this, reflecting the migration of saline water through the upper layers of the aquifer to the pumping well. By contrast no change in resistivity occurred at depth, indicating no significant change in contribution from the basal saline water to discharge. Test findings suggest that future water resource development at the site should focus on close monitoring of shallow pumping, or pumping from deeper parts of the aquifer, while more generally demonstrating the value of time-lapse geophysical methods in informing coastal water resource management

    Cosmic dust fluxes in the atmospheres of Earth, Mars and Venus

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    The ablation of cosmic dust injects a range of metals into planetary upper atmospheres. In addition, dust particles which survive atmospheric entry can be an important source of organic material at a planetary surface. In this study the contribution of metals and organics from three cosmic dust sources – Jupiter-Family comets (JFCs), the Asteroid belt (AST), and Halley-Type comets (HTCs) – to the atmospheres of Earth, Mars and Venus is estimated by combining a Chemical Ablation Model (CABMOD) with a Zodiacal Cloud Model (ZoDy). ZoDy provides the mass, velocity, and radiant distributions for JFC, AST, and HTC particles. JFCs are shown to be the main mass contributor in all three atmospheres (68% for Venus, 70% Earth, and 52% for Mars), providing a total input mass for Venus, Earth and Mars of 31 ± 18 t d⁻¹, 28 ± 16 t d⁻¹ and 2 ± 1 t d⁻¹, respectively. The mass contribution of AST particles increases with heliocentric distance (6% for Venus, 9% for Earth, and 14% for Mars). A novel multiphase treatment in CABMOD, tested experimentally in a Meteoric Ablation Simulator, is implemented to quantify atmospheric ablation from both the silicate melt and Fe-Ni metal domains. The ratio of Fe:Ni ablation fluxes at Earth, Mars and Venus are predicted to be close to their CI chondritic ratio of 18, in agreement with mass spectrometric measurements of Fe+:Ni+ = 20.0–₈.₀+¹³·⁰ in the terrestrial ionosphere. In contrast, lidar measurements of the neutral atoms at Earth indicate Fe:Ni = 38 ± 11, and observations by the Neutral Gas and Ion Mass Spectrometer on the MAVEN spacecraft at Mars indicate Fe+:Ni+ = 43–₁₀+¹³. Given the slower average entry velocity of cosmic dust particles at Mars, the accretion rate of unmelted particles in Mars represents 60% of the total input mass, of which a significant fraction of the total unmelted mass (22%) does not reach an organic pyrolysis temperature (~900 K), leading to a flux of intact carbon of 14 kg d⁻¹. This is significantly smaller than previous estimates

    Adult-perpetrated Animal Abuse: A Systematic Literature Review

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    Adults perpetrate the majority of animal abuse incidents yet clinicians are left with very little evidence base to advance/enhance their practice. The purpose of this systematic review is to synthesize and evaluate the current literature on adult-perpetrated animal abuse and to identify the etiological factors related to this type of offending. Twenty-three studies met the specific inclusion criteria but most importantly, they examined the characteristics of adult perpetrators of animal abuse. The findings from this review were demarcated by sample type: (1) participants were the perpetrators of the animal abuse or held offence-supportive attitudes; and (2) participants were victims of intimate partner violence reporting incidents of animal abuse perpetrated by their partner. From the perpetrator perspective, there were key developmental (i.e., maladaptive parenting strategies), behavioral (such as varied offending behaviors), and psychological (e.g., callousness, empathy deficits) factors highlighted in the literature. Finally, in the context of intimate partner violence, findings indicated that perpetrators abuse animals to control, coerce, intimidate and/or manipulate their victims (this effect is moderated by the victims’ emotional attachment to their pet). This review inherently underlines treatment targets that could achieve greater clinical gains, but we also conclude that more empirical and theoretical work is needed in order to set an agenda that prioritizes future research and effective practice. Keywords: animal abuse, animal cruelty, adult perpetrators, offending behavior, intimate partner violenc

    Adult-perpetrated Animal Abuse: A Systematic Literature Review

    Get PDF
    Adults perpetrate the majority of animal abuse incidents yet clinicians are left with very little evidence base to advance/enhance their practice. The purpose of this systematic review is to synthesize and evaluate the current literature on adult-perpetrated animal abuse and to identify the etiological factors related to this type of offending. Twenty-three studies met the specific inclusion criteria but most importantly, they examined the characteristics of adult perpetrators of animal abuse. The findings from this review were demarcated by sample type: (1) participants were the perpetrators of the animal abuse or held offence-supportive attitudes; and (2) participants were victims of intimate partner violence reporting incidents of animal abuse perpetrated by their partner. From the perpetrator perspective, there were key developmental (i.e., maladaptive parenting strategies), behavioral (such as varied offending behaviors), and psychological (e.g., callousness, empathy deficits) factors highlighted in the literature. Finally, in the context of intimate partner violence, findings indicated that perpetrators abuse animals to control, coerce, intimidate and/or manipulate their victims (this effect is moderated by the victims’ emotional attachment to their pet). This review inherently underlines treatment targets that could achieve greater clinical gains, but we also conclude that more empirical and theoretical work is needed in order to set an agenda that prioritizes future research and effective practice. Keywords: animal abuse, animal cruelty, adult perpetrators, offending behavior, intimate partner violenc
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