Universal equation of state for wave turbulence in a quantum gas.

Boyle's 1662 observation that the volume of a gas is, at constant temperature, inversely proportional to pressure, offered a prototypical example of how an equation of state (EoS) can succinctly capture key properties of a many-particle system. Such relationships are now cornerstones of equilibrium thermodynamics1. Extending thermodynamic concepts to far-from-equilibrium systems is of great interest in various contexts, including glasses2,3, active matter4-7 and turbulence8-11, but is in general an open problem. Here, using a homogeneous ultracold atomic Bose gas12, we experimentally construct an EoS for a turbulent cascade of matter waves13,14. Under continuous forcing at a large length scale and dissipation at a small one, the gas exhibits a non-thermal, but stationary, state, which is characterized by a power-law momentum distribution15 sustained by a scale-invariant momentum-space energy flux16. We establish the amplitude of the momentum distribution and the underlying energy flux as equilibrium-like state variables, related by an EoS that does not depend on the details of the energy injection or dissipation, or on the history of the system. Moreover, we show that the equations of state for a wide range of interaction strengths and gas densities can be empirically scaled onto each other. This results in a universal dimensionless EoS that sets benchmarks for the theory and should also be relevant for other turbulent systems.

Phylogeographic reconstruction of the emergence and spread of Powassan virus in the northeastern United States.

Powassan virus is an emerging tick-borne virus of concern for public health, but very little is known about its transmission patterns and ecology. Here, we expanded the genomic dataset by sequencing 279 Powassan viruses isolated from Ixodes scapularis ticks from the northeastern United States. Our phylogeographic reconstructions revealed that Powassan virus lineage II was likely introduced or emerged from a relict population in the Northeast between 1940 and 1975. Sequences strongly clustered by sampling location, suggesting a highly focal geographical distribution. Our analyses further indicated that Powassan virus lineage II emerged in the northeastern United States mostly following a south-to-north pattern, with a weighted lineage dispersal velocity of ~3 km/y. Since the emergence in the Northeast, we found an overall increase in the effective population size of Powassan virus lineage II, but with growth stagnating during recent years. The cascading effect of population expansion of white-tailed deer and I. scapularis populations likely facilitated the emergence of Powassan virus in the northeastern United States.

Universal prethermal dynamics of Bose gases quenched to unitarity.

Understanding strongly correlated phases of matter, such as the quark-gluon plasma and neutron stars, and in particular the dynamics of such systems, for example, following a Hamiltonian quench (a sudden change in some Hamiltonian parameter, such as the strength of interparticle interactions) is a fundamental challenge in modern physics. Ultracold atomic gases are excellent quantum simulators for these problems, owing to their tunable interparticle interactions and experimentally resolvable intrinsic timescales. In particular, they provide access to the unitary regime, in which the interactions are as strong as allowed by quantum mechanics. This regime has been extensively studied in Fermi gases1,2. The less-explored unitary Bose gases3-11 offer possibilities12 such as universal physics controlled solely by the gas density13,14 and new forms of superfluidity15-17. Here, through momentum- and time-resolved studies, we explore degenerate and thermal homogeneous Bose gases quenched to unitarity. In degenerate samples, we observe universal post-quench dynamics in agreement with the emergence of a prethermal state18-24 with a universal non-zero condensed fraction22,24. In thermal gases, the dynamic and thermodynamic properties generally depend on the gas density and the temperature, but we find that they can still be expressed in terms of universal dimensionless functions. Surprisingly, we find that the total quench-induced correlation energy is independent of the gas temperature. These measurements provide quantitative benchmarks and challenges for the theory of unitary Bose gases.

Disturbing the Spatial Organization of Biofilm Communities Affects Expression of agr-Regulated Virulence Factors in Staphylococcus aureus.

Staphylococcus aureus uses quorum sensing and nutrient availability to control the expression of agr-regulated virulence factors. Quorum sensing is mediated by autoinducing peptide (AIP), which at a high concentration reduces expression of surface attachment proteins (coa, fnbpA) and increases expression of exotoxins (lukS) and proteases (splA). Nutrient availability can be sensed through the saeS/saeR system. Low nutrients increase expression of saeR, which augments expression of coa and fnbpA, distinct from the activity of AIP. The formation of spatial structure, such as biofilms, can alter quorum sensing and nutrient acquisition. In natural environments, biofilms encounter forces that may alter their spatial structure. These forces may impact quorum sensing and/or nutrient acquisition and thus affect the expression of agr-regulated virulence factors. However, this has not been studied. We show that periodically disturbing biofilms composed of S. aureus using a physical force affected the expression of agr-regulated virulence factors. In nutrient-poor environments, disturbance increased the expression of coa, fnbpA, lukS, and splA. Disturbance in a nutrient-rich environment at low or high disturbance amplitudes moderately reduced expression of coa and fnbpA but increased expression of lukS and splA. Interestingly, at an intermediate amplitude, the overall expression of agr-regulated virulence factors was the lowest; expression of lukS and splA remained unchanged relative to an undisturbed biofilm, while expression of coa and fnbpA significantly decreased. We hypothesize that these changes are a result of disturbance-driven changes in access to AIP and nutrients. Our results may allow the identification of environments where virulence is enhanced, or reduced, owing to a disturbance. IMPORTANCE Bacteria, such as Staphylococcus aureus, integrate signals from the environment to regulate genes encoding virulence factors. These signals include those produced by quorum-sensing systems and nutrient availability. We show that disturbing the spatial organization of S. aureus populations can lead to changes in the expression of virulence factors, likely by altering the ways in which S. aureus detects these signals. Our work may allow us to identify environments that increase or reduce the expression of virulence factors in S. aureus.

Frequency and Geographic Distribution of Borrelia miyamotoi, Borrelia burgdorferi, and Babesia microti Infections in New England Residents.

BACKGROUND: Borrelia miyamotoi is a relapsing fever spirochete that relatively recently has been reported to infect humans. It causes an acute undifferentiated febrile illness that can include meningoencephalitis and relapsing fever. Like Borrelia burgdorferi, it is transmitted by Ixodes scapularis ticks in the northeastern United States and by Ixodes pacificus ticks in the western United States. Despite reports of clinical cases from North America, Europe, and Asia, the prevalence, geographic range, and pattern of expansion of human B. miyamotoi infection are uncertain. To better understand these characteristics of B. miyamotoi in relation to other tickborne infections, we carried out a cross-sectional seroprevalence study across New England that surveyed B. miyamotoi, B. burgdorferi, and Babesia microti infections. METHODS: We measured specific antibodies against B. miyamotoi, B. burgdorferi, and B. microti among individuals living in 5 New England states in 2018. RESULTS: Analysis of 1153 serum samples collected at 11 catchment sites showed that the average seroprevalence for B. miyamotoi was 2.8% (range, 0.6%-5.2%), which was less than that of B. burgdorferi (11.0%; range, 6.8%-15.6%) and B. microti (10.0%; range, 6.5%-13.6%). Antibody screening within county residence in New England showed varying levels of seroprevalence for these pathogens but did not reveal a vectoral geographical pattern of distribution. CONCLUSIONS: Human infections caused by B. miyamotoi, B. burgdorferi, and B. microti are widespread with varying prevalence throughout New England.

Jamestown Canyon Virus in Collected Mosquitoes, Maine, United States, 2017-2019.

Jamestown Canyon virus (JCV) is a mosquito-borne arbovirus that circulates in North America. We detected JCV in 4 pools of mosquitoes collected from midcoastal Maine, USA, during 2017-2019. Phylogenetic analysis of a JCV sequence obtained from Aedes cantator mosquitoes clustered within clade A, which also circulates in Connecticut, USA.

Effect of institution volume on mortality and outcomes in osteoporotic hip fracture care.

Hospitals that treat more patients with osteoporotic hip fractures do not generally have better care outcomes than those that treat fewer hip fracture patients. Institutions that do look after more such patients tend, however, to more consistently perform relevant health assessments. INTRODUCTION: An inveterate link has been found between institution case volume and a wide range of clinical outcomes; for a host of medical and surgical conditions. Hip fracture patients, notwithstanding the significance of this injury, have largely been overlooked with regard to this important evaluation. METHODS: We used the UK National Hip Fracture database to determine the effect of institution hip fracture case volume on hip fracture healthcare outcomes in 2019. Using logistic regression for each healthcare outcome, we compared the best performing 50 units with the poorest performing 50 institutions to determine if the unit volume was associated with performance in each particular outcome. RESULTS: There were 175 institutions with included 67,673 patients involved. The number of hip fractures between units ranged from 86 to 952. Larger units tendered to perform health assessments more consistently and mobilise patients more expeditiously post-operatively. However, patients treated at large institutions did not have any shorter lengths of stay. With regard to most other outcomes there was no association between the unit number of cases and performance; notably mortality, compliance with best practice tariff, time to surgery, the proportion of eligible patients undergoing total hip arthroplasty, length of stay delirium risk and pressure sore risk. CONCLUSIONS: There is no relationship between unit volume and the majority of health care outcomes. It would seem that larger institutions tend to perform better at parameters that are dependent upon personnel numbers. However, where the outcome is contingent, even partially, on physical infrastructure capacity, there was no difference between larger and smaller units.

First and Second Sound in a Compressible 3D Bose Fluid.

The two-fluid model is fundamental for the description of superfluidity. In the nearly incompressible liquid regime, it successfully describes first and second sound, corresponding, respectively, to density and entropy waves, in both liquid helium and unitary Fermi gases. Here, we study the two sounds in the opposite regime of a highly compressible fluid, using an ultracold ^{39}K Bose gas in a three-dimensional box trap. We excite the longest-wavelength mode of our homogeneous gas, and observe two distinct resonant oscillations below the critical temperature, of which only one persists above it. In a microscopic mode-structure analysis, we find agreement with the hydrodynamic theory, where first and second sound involve density oscillations dominated by, respectively, thermal and condensed atoms. Varying the interaction strength, we explore the crossover from hydrodynamic to collisionless behavior in a normal gas.

Emergence of a turbulent cascade in a quantum gas.

A central concept in the modern understanding of turbulence is the existence of cascades of excitations from large to small length scales, or vice versa. This concept was introduced in 1941 by Kolmogorov and Obukhov, and such cascades have since been observed in various systems, including interplanetary plasmas, supernovae, ocean waves and financial markets. Despite much progress, a quantitative understanding of turbulence remains a challenge, owing to the interplay between many length scales that makes theoretical simulations of realistic experimental conditions difficult. Here we observe the emergence of a turbulent cascade in a weakly interacting homogeneous Bose gas-a quantum fluid that can be theoretically described on all relevant length scales. We prepare a Bose-Einstein condensate in an optical box, drive it out of equilibrium with an oscillating force that pumps energy into the system at the largest length scale, study its nonlinear response to the periodic drive, and observe a gradual development of a cascade characterized by an isotropic power-law distribution in momentum space. We numerically model our experiments using the Gross-Pitaevskii equation and find excellent agreement with the measurements. Our experiments establish the uniform Bose gas as a promising new medium for investigating many aspects of turbulence, including the interplay between vortex and wave turbulence, and the relative importance of quantum and classical effects.

Measuring laser beams with a neural network.

A deep neural network (NN) is used to simultaneously detect laser beams in images and measure their center coordinates, radii, and angular orientations. A dataset of images containing simulated laser beams and a dataset of images with experimental laser beams-generated using a spatial light modulator-are used to train and evaluate the NN. After training on the simulated dataset the NN achieves beam parameter root mean square errors (RMSEs) of less than 3.4% on the experimental dataset. Subsequent training on the experimental dataset causes the RMSEs to fall below 1.1%. The NN method can be used as a stand-alone measurement of the beam parameters or can compliment other beam profiling methods by providing an accurate region-of-interest.

Injections and infections: understanding syringe service program utilization in a rural state.

BACKGROUND: Increasing rates of injection drug use (IDU) associated-infections suggest significant syringe service program (SSP) underutilization. Our study objective was to assess practices of safe injection techniques and to determine predictors of SSP utilization in a rural state. PATIENTS AND METHODS: This was a fifteen-month cross-sectional study of participants hospitalized with IDU-associated infections in Maine. Data were collected through Audio Computer-Assisted Self-Interview survey and medical record review. Descriptive analyses were performed to characterize demographics, health characteristics, and injection practices. The primary outcome was SSP utilization, and the main independent variable was self-reported distance to SSP. Logistic regression analyses were performed to identify factors associated SSP utilization, controlling for gender, homelessness, history of overdose, having a primary care physician and distance to SSP. RESULTS: Of the 101 study participants, 65 participants (64%) reported past 3 month SSP utilization, though only 33% used SSPs frequently. Many participants (57%) lived more than 10 miles from an SSP. Participants who lived less than 10 miles of an SSP were more likely to use an SSP (adjusted odds ratio 5.4; 95% CI 1.9-15.7). CONCLUSIONS: Our study highlights unsafe injection practices and lack of frequent SSP utilization among people admitted with IDU-associated infections in a rural state. Especially given increasing stimulant use, these results also highlight the need for SSP access. Particularly in rural areas where patients may live more than 10 miles from an SSP, expansion of harm reduction services, including mobile units, should be a priority.

Surge in Anaplasmosis Cases in Maine, USA, 2013-2017.

Incidence of human granulocytic anaplasmosis is rising in Maine, USA. This increase may be explained in part by adoption of tick panels as a frequent diagnostic test in persons with febrile illness and in part by range expansion of Ixodes scapularis ticks and zoonotic amplification of Anaplasma phagocytophilum.

Seroprevalence of Borrelia burgdorferi, B. miyamotoi, and Powassan Virus in Residents Bitten by Ixodes Ticks, Maine, USA.

We conducted a serosurvey of 230 persons in Maine, USA, who had been bitten by Ixodes scapularis or I. cookei ticks. We documented seropositivity for Borrelia burgdorferi (13.9%) and B. miyamotoi (2.6%), as well as a single equivocal result (0.4%) for Powassan encephalitis virus.

The public and private benefit of an impure public good determines the sensitivity of bacteria to population collapse in a snowdrift game.

When cooperation is critical for survival, cheating can lead to population collapse. One mechanism of cooperation that permits the coexistence of cooperators and cheaters is an impure public good, whose public benefits are shared, but with a private benefit retained by the cooperator. It has yet to be determined how the contributions of the public and private benefit affect population survival. Using simulations and experiments with ß-lactamase-expressing bacteria, we found that for a given amount of public and private benefit, the population was most sensitive to collapse when initiated from an intermediate fraction of cooperators due to the near-concurrent collapse of the cooperator and cheater populations. We found that increasing the ratio of public to private benefit increased sensitivity to collapse. A low ratio allowed cooperators to survive on their private benefit after the public benefit could not rescue the cheaters. A high ratio allowed the cheaters to survive to high concentrations of ampicillin due to the high public benefit. However, small increases in ampicillin caused a rapid decline in the entire population as the private benefit was insufficient to allow self-rescue of the cooperators. Our findings have implications in the persistence of populations that rely on cooperation for survival.

Timing between successive introduction events determines establishment success in bacteria with an Allee effect.

Propagule pressure is a leading determinant of population establishment. Yet, an experimental understanding of how propagule size and number (two principal parts of propagule pressure) determine establishment success remains incomplete. Theoretical studies suggest that the timing between introduction events, a component of propagule number, can influence establishment success. However, this dynamic has rarely been explored experimentally. Using Escherichia coli engineered with an Allee effect, we investigated how the timing of two introduction events influences establishment. For populations introduced below the Allee threshold, establishment occurred if the time between two introduction events was sufficiently short, with the length of time between events further reduced by reducing growth rate. Interestingly, we observed that as the density of bacteria introduced in one introduction event increased, the time between introduction events that allowed for establishment increased. Using a mathematical model, we provide support that the mechanism behind these trends is the ability of the first population to modify the environment, which can pave the way for establishment of the second population. Our results provide experimental evidence that the temporal distribution of introduction events regulates establishment, furthering our understanding of propagule pressure and may have implications in invasion biology and infectious disease.

Can Three-Body Recombination Purify a Quantum Gas?

Three-body recombination in quantum gases is traditionally associated with heating, but it was recently found that it can also cool the gas. We show that in a partially condensed three-dimensional homogeneous Bose gas three-body loss could even purify the sample, that is, reduce the entropy per particle and increase the condensed fraction η. We predict that the evolution of η under continuous three-body loss can, depending on small changes in the initial conditions, exhibit two qualitatively different behaviors-if it is initially above a certain critical value, η increases further, whereas clouds with lower initial η evolve towards a thermal gas. These dynamical effects should be observable under realistic experimental conditions.

Correction for Fletcher et al., "Vaccine Potential of the Neisseria meningitidis 2086 Lipoprotein".

[This corrects the article DOI: 10.1128/IAI.72.4.2088-2100.2004.].

Fatal Deer Tick Virus Infection in Maine.

Deer tick virus (DTV), a genetic variant (lineage II) of Powassan virus, is a rare cause of encephalitis in North America. We report a fatal case of DTV encephalitis following a documented bite from an Ixodes scapularis tick and the erythema migrans rash associated with Lyme disease.