Quantum field theory predicts a nonlinear response of the vacuum to strong electromagnetic fields of macroscopic extent. This fundamental tenet has remained experimentally challenging and is yet to be tested in the laboratory. A particularly distinct signature of the resulting optical activity of the quantum vacuum is vacuum birefringence. This offers an excellent opportunity for a precision test of nonlinear quantum electrodynamics in an uncharted parameter regime. Recently, the operation of the high-intensity Relativistic Laser at the X-ray Free Electron Laser provided by the Helmholtz International Beamline for Extreme Fields has been inaugurated at the High Energy Density scientific instrument of the European X-ray Free Electron Laser. We make the case that this worldwide unique combination of an X-ray free-electron laser and an ultra-intense near-infrared laser together with recent advances in high-precision X-ray polarimetry, refinements of prospective discovery scenarios and progress in their accurate theoretical modelling have set the stage for performing an actual discovery experiment of quantum vacuum nonlinearity.

As mid-southern U.S. rice producers continue to adopt furrow-irrigated rice (FIR) production practices, supplementary management efforts will be vital in combating Palmer amaranth due to the extended germination period provided by the lack of a continual flood. Previous research has revealed the ability of cover crops to suppress Palmer amaranth emergence in corn, cotton, and soybean production systems; however, research on cover crop weed control efficacy in rice production is scarce. Therefore, trials were initiated in Arkansas in 2022 and 2023 to evaluate the effect of cover crops across five site years on rice emergence, groundcover, grain yield, and total Palmer amaranth emergence. The cover crops evaluated were cereal rye, winter wheat, Austrian winterpea, and hairy vetch. Cover crop biomass accumulation varied by site year, ranging from 430 to 3,440 kg ha-1, with cereal rye generally being the most consistent producer of high-quantity biomass across site years. Rice growth and development were generally unaffected by cover crop establishment; however, all cover crops reduced rice emergence by up to 30% in one site year. Rice groundcover was reduced by 13% from cereal rye in one site year two weeks before heading but cover crops did not impact rough rice grain yield in any of the site years. Palmer amaranth emergence was reduced by 19 and 35% with cereal rye relative to the absence of a cover crop when rice was planted in April in Marianna and May in Fayetteville, respectively. In most trials, Palmer amaranth emergence was not reduced by a cereal cover crop. In most instances, legume cover crops resulted in less Palmer amaranth emergence than without a cover crop. Based on these results, legume cover crops appear to provide some suppression of Palmer amaranth emergence in FIR while having a minimal effect on rice establishment and yield.

Furrow-irrigated rice (Oryza sativa L.) hectares are increasing in the Midsouth. The lack of sustained flooding creates a favorable environment for weed emergence and persistence, which makes Palmer amaranth (Amaranthus palmeri S. Watson) difficult to control throughout the growing season. The negative yield impacts associated with season-long A. palmeri interference in corn, cotton, and soybean have been evaluated. However, there is limited knowledge of the weed’s ability to influence rice grain yield. Research was initiated in 2022 and 2023 to determine the effect of A. palmeri time of emergence relative to rice on weed seed production and grain yield. Cotyledon stage A. palmeri plants were marked every seven days, beginning one week before rice emergence through four weeks after rice emergence. Amaranthus palmeri seed production decreased exponentially as emergence timing was delayed relative to rice, and seed production increased by 447 seed plant-1 for every one-gram increase in weed biomass. Without rice competition and from the earliest emergence timing, A.palmeri produced 540,000 seeds plant-1. Amaranthus palmeri that emerged one week before the crop had the greatest spatial influence on rice, with grain yield loss of 5% and 50% at a distance of 1.4 m and 0.40 m from the weed, respectively. As A. palmeri emergence was delayed, the area of influence decreased. However, A. palmeri plants emerging 3.5 weeks after rice emergence still negatively affected grain yield and produce sufficient seed to replenish the soil seedbank, potentially impacting long-term crop management decisions. These results show that the time of A. palmeri emergence is a crucial factor influencing rice grain yield and weed seed production, which can be used to determine the consequences of escapes in rice.

The interaction of relativistically intense lasers with opaque targets represents a highly non-linear, multi-dimensional parameter space. This limits the utility of sequential 1D scanning of experimental parameters for the optimization of secondary radiation, although to-date this has been the accepted methodology due to low data acquisition rates. High repetition-rate (HRR) lasers augmented by machine learning present a valuable opportunity for efficient source optimization. Here, an automated, HRR-compatible system produced high-fidelity parameter scans, revealing the influence of laser intensity on target pre-heating and proton generation. A closed-loop Bayesian optimization of maximum proton energy, through control of the laser wavefront and target position, produced proton beams with equivalent maximum energy to manually optimized laser pulses but using only 60% of the laser energy. This demonstration of automated optimization of laser-driven proton beams is a crucial step towards deeper physical insight and the construction of future radiation sources.

We present the development and characterization of a high-stability, multi-material, multi-thickness tape-drive target for laser-driven acceleration at repetition rates of up to 100 Hz. The tape surface position was measured to be stable on the sub-micrometre scale, compatible with the high-numerical aperture focusing geometries required to achieve relativistic intensity interactions with the pulse energy available in current multi-Hz and near-future higher repetition-rate lasers ($>$kHz). Long-term drift was characterized at 100 Hz demonstrating suitability for operation over extended periods. The target was continuously operated at up to 5 Hz in a recent experiment for 70,000 shots without intervention by the experimental team, with the exception of tape replacement, producing the largest data-set of relativistically intense laser–solid foil measurements to date. This tape drive provides robust targetry for the generation and study of high-repetition-rate ion beams using next-generation high-power laser systems, also enabling wider applications of laser-driven proton sources.

Humpback whales (Megaptera novaeangliae) exhibit maternally driven fidelity to feeding grounds, and yet occasionally occupy new areas. Humpback whale sightings and mortalities in the New York Bight apex (NYBA) have been increasing over the last decade, providing an opportunity to study this phenomenon in an urban habitat. Whales in this area overlap with human activities, including busy shipping traffic leading into the Port of New York and New Jersey. The site fidelity, population composition and demographics of individual whales were analysed to better inform management in this high-risk area. Whale watching and other opportunistic data collections were used to identify 101 individual humpback whales in the NYBA from spring through autumn, 2012–2018. Although mean occurrence was low (2.5 days), mean occupancy was 37.6 days, and 31.3% of whales returned from one year to the next. Individuals compared with other regional and ocean-basin-wide photo-identification catalogues (N = 52) were primarily resighted at other sites along the US East Coast, including the Gulf of Maine feeding ground. Sightings of mother-calf pairs were rare in the NYBA, suggesting that maternally directed fidelity may not be responsible for the presence of young whales in this area. Other factors including shifts in prey species distribution or changes in population structure more broadly should be investigated.

ABSTRACT IMPACT: Current practice guidelines offer a variety of treatment options for sternal reconstruction but complications and infections remain a serious surgical problem. This work seeks to provide a comprehensive picture of the com-morbidities and reconstructive methods that lead to success and improve patient outcomes. OBJECTIVES/GOALS: Patients that undergo cardiac surgery via the median sternotomy approach are at risk of wound complications that require repair. We seek to evaluate how outcomes of sternal reconstruction are influenced by patient comorbidities, flap usage and internal mammary artery grafts and methods of sternal closure. METHODS/STUDY POPULATION: We identified patients between 2005 and 2020 who underwent sternotomy followed by debridement and flap coverage at our institution. Comorbidities, method of reconstruction, demographic data, surgical history, and other factors pertaining to mortality and morbidity were collected. The data will then be analyzed to identify population characteristics using logistic regression variables to determine univariate and adjusted multivariable measures of association with mortality. We present the pre-liminary data analyzed using chi-square and one-way anova in R. RESULTS/ANTICIPATED RESULTS: In this study we present a preliminary characterization of one institution’s sternal reconstruction patient outcomes with a variety of reconstruction methods including pectoralis advancement flaps, omental flaps and latissumus dorsi flaps. Notable preoperative comorbidities include 50% of patients > age 60, 18% with diabetes mellitus, 18 % with diagnosed hypertension, 18% with COPD, and 9% with a smoking history DISCUSSION/SIGNIFICANCE OF FINDINGS: In an evolving cardiothoracic landscape, clinical characteristics of patients being treated for sternal reconstructive surgery present a moving target. Understanding current risk factors, preoperative management and timing for aggressive surgical treatment offers an opportunity to update treatment protocol and maximize successful outcomes.

The isotope dependence of plasma transport will have a significant impact on the performance of future D-T experiments in JET and ITER and eventually on the fusion gain and economics of future reactors. In preparation for future D-T operation on JET, dedicated experiments and comprehensive transport analyses were performed in H, D and H-D mixed plasmas. The analysis of the data has demonstrated an unexpectedly strong and favourable dependence of the global confinement of energy, momentum and particles in ELMy H-mode plasmas on the atomic mass of the main ion species, the energy confinement time scaling as ${\tau _E}\sim {A^{0.5}}$ (Maggi et al., Plasma Phys. Control. Fusion, vol. 60, 2018, 014045; JET Team, Nucl. Fusion, vol. 39, 1999, pp. 1227–1244), i.e. opposite to the expectations based only on local gyro-Bohm (GB) scaling, ${\tau _E}\sim {A^{ - 0.5}}$, and stronger than in the commonly used H-mode scaling for the energy confinement (Saibene et al., Nucl. Fusion, vol. 39, 1999, 1133; ITER Physics Basis, Nucl. Fusion, vol. 39, 1999, 2175). The scaling of momentum transport and particle confinement with isotope mass is very similar to that of energy transport. Nonlinear local GENE gyrokinetic analysis shows that the observed anti-GB heat flux is accounted for if collisions, E × B shear and plasma dilution with low-Z impurities (9Be) are included in the analysis (E and B are, respectively the electric and magnetic fields). For L-mode plasmas a weaker positive isotope scaling ${\tau _E}\sim {A^{0.14}}$ has been found in JET (Maggi et al., Plasma Phys. Control. Fusion, vol. 60, 2018, 014045), similar to ITER97-L scaling (Kaye et al., Nucl. Fusion, vol. 37, 1997, 1303). Flux-driven quasi-linear gyrofluid calculations using JETTO-TGLF in L-mode show that local GB scaling is not followed when stiff transport (as is generally the case for ion temperature gradient modes) is combined with an imposed boundary condition taken from the experiment, in this case predicting no isotope dependence. A dimensionless identity plasma pair in hydrogen and deuterium L-mode plasmas has demonstrated scale invariance, confirming that core transport physics is governed, as expected, by the 4 dimensionless parameters ρ*, ν*, β, q (normalised ion Larmor radius, collisionality, plasma pressure and safety factor) consistently with global quasi-linear gyrokinetic TGLF calculations (Maggi et al., Nucl. Fusion, vol. 59, 2019, 076028). We compare findings in JET with those in different devices and discuss the possible reasons for the different isotope scalings reported from different devices. The diversity of observations suggests that the differences may result not only from differences affecting the core, e.g. heating schemes, but are to a large part due to differences in device-specific edge and wall conditions, pointing to the importance of better understanding and controlling pedestal and edge processes.

The thickness of glaciers in High-Mountain Asia (HMA) is critical in determining when the ice reserve will be lost as these glaciers thin but is remarkably poorly known because very few measurements have been made. Through a series of ground-based and airborne field tests, we have adapted a low-frequency ice-penetrating radar developed originally for Antarctic over-snow surveys, for deployment as a helicopter-borne system to increase the number of measurements. The manoeuvrability provided by helicopters and the ability of our system to detect glacier beds through thick, dirty, temperate ice makes it well suited to increase greatly the sample of measurements available for calibrating ice thickness models on the regional and global scale. The Bedmap Himalayas radar-survey system can reduce the uncertainty in present-day ice volumes and therefore in projections of when HMA's river catchments will lose this hydrological buffer against drought.