The properties of quantum materials are commonly tuned using experimental variables such as pressure, magnetic field and doping. Here we explore a different approach using irreversible, plastic ...deformation of single crystals. We show that compressive plastic deformation induces low-dimensional superconductivity well above the superconducting transition temperature (T
) of undeformed SrTiO
, with evidence of possible superconducting correlations at temperatures two orders of magnitude above the bulk T
. The enhanced superconductivity is correlated with the appearance of self-organized dislocation structures, as revealed by diffuse neutron and X-ray scattering. We also observe deformation-induced signatures of quantum-critical ferroelectric fluctuations and inhomogeneous ferroelectric order using Raman scattering. Our results suggest that strain surrounding the self-organized dislocation structures induces local ferroelectricity and quantum-critical dynamics that strongly influence T
, consistent with a theory of superconductivity enhanced by soft polar fluctuations. Our results demonstrate the potential of plastic deformation and dislocation engineering for the manipulation of electronic properties of quantum materials.
A pivotal challenge posed by unconventional superconductors is to unravel how superconductivity emerges upon cooling from the generally complex normal state. Here, we use nonlinear magnetic response, ...a probe that is uniquely sensitive to the superconducting precursor, to uncover remarkable universal behaviour in three distinct classes of oxide superconductors: strontium titanate, strontium ruthenate, and the cuprate high-T
materials. We find unusual exponential temperature dependence of the diamagnetic response above the transition temperature T
, with a characteristic temperature scale that strongly varies with T
. We correlate this scale with the sensitivity of T
to local stress and show that it is influenced by intentionally-induced structural disorder. The universal behaviour is therefore caused by intrinsic, self-organized structural inhomogeneity, inherent to the oxides' perovskite-based structure. The prevalence of such inhomogeneity has far-reaching implications for the interpretation of electronic properties of perovskite-related oxides in general.
Despite 35 years of investigation, much remains to be understood regarding charge transport in semiconducting polymers, including the ultimate limits on their conductivity. Recently developed ion gel ...gating techniques provide a unique opportunity to study such issues at very high charge carrier density. Here we have probed the benchmark polymer semiconductor poly(3-hexylthiophene) at electrochemically induced three-dimensional hole densities approaching 10(21) cm(-3) (up to 0.2 holes per monomer). Analysis of the hopping conduction reveals a remarkable phenomenon where wavefunction delocalization and Coulomb gap collapse are disrupted by doping-induced disorder, suppressing the insulator-metal transition, even at these extreme charge densities. Nevertheless, at the highest dopings, we observe, for the first time in a polymer transistor, a clear Hall effect with the expected field, temperature and gate voltage dependencies. The data indicate that at such mobilities (~0.8 cm(2)V(-1) s(-1)), despite the extensive disorder, these polymers lie close to a regime of truly diffusive band-like transport.
Psychiatric assistance dogs for military veterans with posttraumatic stress disorder (PTSD) currently make up over 19% of assistance dog partnerships globally. We conducted a systematic review of the ...literature relating to these partnerships, with specific aims to (1) summarize their characteristics, (2) evaluate the quality of existing evidence, and (3) summarize outcomes. A total of 432 records were independently screened (Cohen's kappa = 0.90). Of these, 41 articles (29 peer-reviewed publications and 12 unpublished dissertations) met inclusion criteria. Data extraction was conducted to address the research aims, including a meta-analysis (quantitative outcomes) and meta-synthesis (qualitative outcomes). All peer-reviewed publications on the topic of psychiatric assistance dogs for veterans with PTSD were published within the last five years. The majority of included articles were quantitative (53%), 41% were qualitative, and 6% employed mixed methods. Mean methodological rigor scores were 80% for peer reviewed articles and 71% for dissertations, where higher scores represent more rigorous methodology. Quantitative articles reported significant improvements in the domains of PTSD severity, mental health, and social health. Impacts on physical health and global quality of life appear inconclusive. Meta-analysis (9 articles) revealed that partnership with an assistance dog had a clinically meaningful, significant, and large effect on PTSD severity scores (g = -1.129; p<0.0001). Qualitative meta-synthesis identified two third order constructs: (1) Impact on the individual: mental & physical health and (2) Impact beyond the individual: building relationships & connection. This synthesis of increasingly prevalent research on assistance dogs for veterans with PTSD provides support for the impact of this complementary and integrative health intervention on PTSD symptom severity, and signs of meaningful improvements in adjacent domains including mental and social health. Gaps between quantitative and qualitative findings, along with the need to report greater demographic detail, highlight key opportunities for future research.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The opioid receptors (OR) regulate food intake. Still, despite extensive pre-clinical research, the overall effects and individual contribution of the mu (MOR), kappa (KOR), and delta (DOR) OR ...subtypes to feeding behaviors and food intake remain unclear. To address this, we conducted a pre-registered systematic search and meta-analysis of rodent dose-response studies to evaluate the impact of central and peripheral administration of non-selective and selective OR ligands on intake, motivation, and choice of food. All studies had a high bias risk. Still, the meta-analysis confirmed the overall orexigenic and anorexigenic effects of OR agonists and antagonists, respectively. Our results support a larger orexigenic role for central MOR agonists among OR subtypes and that peripheral OR antagonists reduce motivation for and intake of preferred foods. In binary food choice studies, peripheral OR agonists selectively increase the intake of fat-preferred foods; in contrast, they did not increase the intake of sweet carbohydrate-preferred foods. Overall, these data support that OR regulation of intake, motivation, and choice is influenced by food macronutrient composition.
•How opioid receptors regulate feeding behavior and intake remains unclear.•The macronutrient content of foods might influence the effects of opioid receptors on intake.•Central mu-selective agonists might selectively increase intake of fat-enriched foods.•Opioid receptor ligands appear to reduce motivation for food.•Opioid receptor agonists selectively increase intake of preferred fat, but not of sweet carbohydrate foods.
Strontium titanate (SrTiO3) is a foundational material in the emerging field of complex oxide electronics. Although its bulk electronic and optical properties are rich and have been studied for ...decades, SrTiO3 has recently become a renewed focus of materials research catalysed in part by the discovery of superconductivity and magnetism at interfaces between SrTiO3 and other non-magnetic oxides. Here we illustrate a new aspect to the phenomenology of magnetism in SrTiO3 by reporting the observation of an optically induced and persistent magnetization in slightly oxygen-deficient bulk SrTiO3-δ crystals using magnetic circular dichroism (MCD) spectroscopy and SQUID magnetometry. This zero-field magnetization appears below ~18 K, persists for hours below 10 K, and is tunable by means of the polarization and wavelength of sub-bandgap (400-500 nm) light. These effects occur only in crystals containing oxygen vacancies, revealing a detailed interplay between magnetism, lattice defects, and light in an archetypal complex oxide material.
We report the observation of the Hall effect at hole densities up to 6×10¹³ cm⁻² (0.3 holes/molecule) on the surface of electrolyte-gated rubrene crystals. The perplexing peak in the conductance as ...a function of gate voltage is confirmed to result from a maximum in mobility, which reaches 4 cm² V⁻¹ s⁻¹ at 2.5×10¹³ cm⁻². Measurements to liquid helium temperatures reveal that this peak is markedly asymmetric, with bandlike and hopping-type transport occurring on the low density side, while unconventional, likely electrostatic-disorder-affected transport dominates the high density side. Most significantly, near the mobility peak the temperature coefficient of the resistance remains positive to as low as 120 K, the low temperature resistance becomes weakly temperature dependent, and the conductance reaches within a factor of 2 of e²/h, revealing conduction unprecedentedly close to a two-dimensional metallic state.
There has been a tremendous recent surge of interest in copper zinc tin sulfide (Cu2ZnSnS4, CZTS) as a photovoltaic material, because its optical and electronic properties are well-suited for solar ...cells, and its elemental constituents are abundant in the earth’s crust. Here we have studied the formation mechanisms of CZTS films, and the factors that control the cation stoichiometry during ex situ sulfidation of precursor Cu–Zn–Sn alloy films in a closed isothermal system. We find that the Cu/Sn ratio in CZTS is self-regulating and approaches 2, regardless of the initial composition of the precursor films, provided that adequate Sn is available in the sulfidation system. If precursor films are initially tin rich, excess Sn evaporates in the form of SnS. If precursor films are initially Sn-deficient, the inclusion of solid Sn in the sulfidation ampule readily generates SnS vapor, which mitigates the films’ Sn deficiency to return the Cu/Sn ratio to 2. When sulfidized for sufficiently long times at sufficiently high temperatures (e.g., 600 °C, 8 h), films with similar Cu/Zn ratios exhibit similar phase compositions, such that if Cu/Zn >2, a Cu2SnS3 impurity phase is present in addition to CZTS, and if Cu/Zn < 2, a ZnS impurity phase occurs. To achieve phase-pure, void-free films, Sn-deficient precursor films with Cu/Zn in the desired range (typically close to, but slightly less than 2) can be sulfidized with excess Sn in a closed system, or a system that maintains a SnS vapor pressure over the film. Time-dependent sulfidation experiments were performed to elucidate the mechanism of this Sn self-regulation. During the formation of CZTS, almost all of the Sn is found to leave the film as SnS, later reincorporation of the Sn occurring through reactions between SnS vapor and CuS to form Cu2SnS3. The ZnS and Cu2SnS3 phases within the films then interdiffuse to form CZTS. Because Cu/Sn is 2 in both Cu2SnS3 and CZTS, the Cu/Sn ratio tends to 2 when sufficient Sn is included in the system to consume all Cu. This strategy is useful for avoiding Cu–S minority phases, provided the films are sulfidized to the point of equilibrium phase composition.
Detailed experiments designed to optimize and understand the solvent vapor annealing of cylinder-forming poly(styrene)-block-poly(lactide) thin films for nanolithographic applications are reported. ...By combining climate-controlled solvent vapor annealing (including in situ probes of solvent concentration) with comparative small-angle X-ray scattering studies of solvent-swollen bulk polymers of identical composition, it is concluded that a narrow window of optimal solvent concentration occurs just on the ordered side of the order–disorder transition. In this window, the lateral correlation length of the hexagonally close-packed ordering, the defect density, and the cylinder orientation are simultaneously optimized, resulting in single-crystal-like ordering over 10 μm scales. The influences of polymer synthesis method, composition, molar mass, solvent vapor pressure, evaporation rate, and film thickness have all been assessed, confirming the generality of this behavior. Analogies to thermal annealing of elemental solids, in combination with an understanding of the effects of process parameters on annealing conditions, enable qualitative understanding of many of the key results and underscore the likely generality of the main conclusions. Pattern transfer via a Damascene-type approach verified the applicability for high-fidelity nanolithography, yielding large-area metal nanodot arrays with center-to-center spacing of 38 nm (diameter 19 nm). Finally, the predictive power of our findings was demonstrated by using small-angle X-ray scattering to predict optimal solvent annealing conditions for poly(styrene)-block-poly(lactide) films of low molar mass (18 kg mol–1). High-quality templates with cylinder center-to-center spacing of only 18 nm (diameter of 10 nm) were obtained. These comprehensive results have clear and important implications for optimization of pattern transfer templates and significantly advance the understanding of self-assembly in block copolymer thin films.
PDF
