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"Randall, G"
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Formation of matter-wave soliton trains by modulational instability
Nonlinear systems can exhibit a rich set of dynamics that are inherently sensitive to their initial conditions. One such example ismodulational instability, which is believed to be one of the most prevalent instabilities in nature. By exploiting a shallow zero-crossing of a Feshbach resonance, we characterize modulational instability and its role in the formation of matter-wave soliton trains from a Bose-Einstein condensate. We examine the universal scaling laws exhibited by the system and, through real-time imaging, address a long-standing question of whether the solitons in trains are created with effectively repulsive nearest-neighbor interactions or rather evolve into such a structure.
Journal Article
Variation of stress levels, burnout, and resilience throughout the academic year in first-year medical students
Medical student wellness is of great concern in the health care field. A growing number of studies point to increases in suicide, depression, anxiety, mood disorders, and burnout related to physician lifestyles. Mental health issues commencing in medical school have been suggested to have a significant impact on future physician lifestyle and burnout. Tracking the mental health of medical students at the University of Toledo College of Medicine and Life Sciences (UTCOMLS) with standardized indices will help elucidate triggers of poor mental health. Anonymous surveys were developed and distributed to preclinical medical students at five strategic time points throughout the 2018 2019 academic year. Surveys collected basic demographic information as well as inventories measuring perceived stress, burnout, resilience, and mindfulness. 172 M1s (83 males and 89 females) were included in the study and average response rate for the first 4 (out of 5) surveys averaged 74.8%. M1 males and females had on average increased personal burnout over time with females consistently scoring higher. Both males and females had an increase in stress from August to each subsequent month (p<0.05). Females reported a higher level of perceived stress than males in the beginning and middle of the academic year (p<0.05). Both males and females report a gradual decrease in resiliency throughout the academic year. These surveys demonstrated over half of males and females in medical school reported higher perceived stress scores than their gender-matched peers in the general United States population. Our study strengthens documented trends in resiliency, perceived stress, and burnout amongst medical students. More study in designing targeted approaches to ameliorate these findings in the medical student population is warranted.
Journal Article
Thermal disruption of a Luttinger liquid
The Tomonaga–Luttinger liquid (TLL) theory describes the low-energy excitations of strongly correlated one-dimensional (1D) fermions. In the past years, a number of studies have provided a detailed understanding of this universality class. More recently, theoretical investigations that go beyond the standard low-temperature, linear-response TLL regime have been developed. While these provide a basis for understanding the dynamics of the spin-incoherent Luttinger liquid, there are few experimental investigations in this regime. Here we report the observation of a thermally induced, spin-incoherent Luttinger liquid in a
6
Li atomic Fermi gas confined to 1D. We use Bragg spectroscopy to measure the suppression of spin-charge separation and the decay of correlations as the temperature is increased. Our results probe the crossover between the coherent and incoherent regimes of the Luttinger liquid and elucidate the roles of the charge and the spin degrees of freedom in this regime.
Low-energy excitations of strongly correlated systems are described by the Tomonaga–Luttinger liquid theory. Here the authors employ Bragg spectroscopy to demonstrate a spin-incoherent Luttinger liquid in
6
Li atoms using charge and spin excitations.
Journal Article
The transformative impact of rent-seeking theory on the study of public choice
Prior to the introduction of rent seeking into public choice, the research program was focused primarily on collective decision-making. The incorporation of rent-seeking into public choice shifted the emphasis of the research program toward analyzing causes of government failure. Although Gordon Tullock’s 1967 article clearly lays out the concept of rent-seeking, the transformation of the public choice research program by the theory of rent-seeking did not occur until after the publication of Anne Krueger’s 1974 article on the rent-seeking society. This paper explains why Krueger’s presentation of the paper at the Public Choice Center at Virginia Tech was instrumental in this transformative shift in the public choice research program.
Journal Article
Water soluble phosphate fertilizers for crops grown in calcareous soils - an outdated paradigm for recycled phosphorus fertilizers
Background and aims The current paradigm for phosphorus (P) fertilizers applied to calcareous soil is that almost entirely water soluble P fertilizers are efficient and sparingly soluble P fertilizers are not efficient P sources for crops. We hypothesize that this paradigm does not apply to recycled P fertilizers and that other P pools can explain the plant use of recycled P fertilizers on calcareous soil. Methods We applied 33P isotopic dilution method to evaluate recycled P fertilizers based on plant P uptake from fertilizer relative to plant uptake from a water soluble P reference fertilizer. The predictability of fertilizer effectiveness based on sequentially extracted P forms and X-ray diffraction pattern of recycled fertilizers derived from sewage sludge, human urine and organic waste was evaluated. Results The plant experiments showed that tested recycled P fertilizers including compost were more effective than rock phosphate. The water insoluble P contained in urine based products was almost as effective as a fully water soluble P fertilizer. The tested recycled P fertilizers are characterized by complex P compounds differing in solubility which were so far not considered in the water and citric acid extraction methods. The fraction of resin- and NaHCO3 extractable fertilizer P explained effectiveness of P fertilizer applied to the calcareous and to an acidic soil. Conclusion We concluded that water solubility is not required when P forms in recycled products are comparable to reactions products of rock phosphate based fertilizers in soil. Alternatives to fully water soluble P fertilizers are available to supply P to crops grown on calcareous soil efficiently.
Journal Article
Universality in Three- and Four-Body Bound States of Ultracold Atoms
Under certain circumstances, three or more interacting particles may form bound states. Although the general few-body problem is not analytically solvable, the so-called Efimov trimers appear for a system of three particles with resonant two-body interactions. The binding energies of these trimers are predicted to be universally connected to each other, independent of the microscopic details of the interaction. By exploiting a Feshbach resonance to widely tune the interactions between trapped ultracold lithium atoms, we find evidence for two universally connected Efimov trimers and their associated four-body bound states. A total of 11 precisely determined three- and four-body features are found in the inelastic-loss spectrum. Their relative locations on either side of the resonance agree well with universal theory, whereas a systematic deviation from universality is found when comparing features across the resonance.
Journal Article
In vivo genome editing using a high-efficiency TALEN system
Although zebrafish is an important animal model for basic vertebrate biology and human disease modelling, rapid targeted genome modification has not been possible in this species; here a technique based on improved artificial transcription activator-like effector nucleases (TALENs) allows precise sequence modifications at pre-determined genomic locations.
Rewriting the zebrafish genome
Although well established as a model for studying basic vertebrate biology and human disease, the zebrafish has been lacking in one important respect: rapid targeted genome modification has not been possible in this species. Now, Stephen C. Ekker and colleagues report an approach that brings targeted genome editing and functional genomic applications to the zebrafish. The technique is based on improvements in artificial transcription activator-like effector nucleases (TALENs). Using this system, the authors precisely modify sequences at predefined genomic locations — for example, adding a custom-designed EcoRV site, which is successfully transmitted through the germline.
The zebrafish (
Danio rerio
) is increasingly being used to study basic vertebrate biology and human disease with a rich array of
in vivo
genetic and molecular tools. However, the inability to readily modify the genome in a targeted fashion has been a bottleneck in the field. Here we show that improvements in artificial transcription activator-like effector nucleases (TALENs) provide a powerful new approach for targeted zebrafish genome editing and functional genomic applications
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. Using the GoldyTALEN modified scaffold and zebrafish delivery system, we show that this enhanced TALEN toolkit has a high efficiency in inducing locus-specific DNA breaks in somatic and germline tissues. At some loci, this efficacy approaches 100%, including biallelic conversion in somatic tissues that mimics phenotypes seen using morpholino-based targeted gene knockdowns
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. With this updated TALEN system, we successfully used single-stranded DNA oligonucleotides to precisely modify sequences at predefined locations in the zebrafish genome through homology-directed repair, including the introduction of a custom-designed
EcoRV
site and a modified
loxP
(
mloxP
) sequence into somatic tissue
in vivo
. We further show successful germline transmission of both
EcoRV
and
mloxP
engineered chromosomes. This combined approach offers the potential to model genetic variation as well as to generate targeted conditional alleles.
Journal Article
Conscious choice and economic progress
Economic progress is the result of entrepreneurship that introduces new and improved products into markets, and uncovers more efficient production processes. Entrepreneurial activity takes place in an uncertain environment, and is the result of the conscious choices of entrepreneurs. Economic progress cannot occur without the conscious choices of individuals, both as entrepreneurs and as consumers. This paper compares the concept of conscious choice with the frequently-used concept of rational choice. The study of consciousness has been multidisciplinary, mostly within philosophy, biology, and psychology. Economics has had little to offer to the study of consciousness, and has taken little from that interdisciplinary area of inquiry. This paper offers economists an introduction to the study of conscious choice, and shows why conscious choice is essential to the creation of economic progress.
Journal Article
