The circadian timing system regulates many aspects of metabolic physiology, including the postprandial response to meals(1). Experimental inversion of circadian and behavioural rhythms by 12 hours adversely effects markers of metabolic health(2). We investigated effects of a more modest 5hour delay in behavioural cycles.

Fourteen participants completed an 8-day in-patient laboratory protocol, with controlled sleepwake opportunities, light-dark cycles, and diet. The 5-hour delay in behavioural cycles was induced by delaying sleep opportunity. We measured: melatonin to confirm central circadian phase; fasting markers and postprandial metabolism; energy expenditure; subjective sleepiness; and appetite, throughout the waking period.

After the phase delay, there was slower gastric emptying at breakfast, lower fasting plasma glucose, higher postprandial plasma glucose and triglycerides, and lower thermic effect of feeding. Any changes were abolished or attenuated within 48-72 hours. Further, we show no difference in 16 h waking energy expenditure.

These data extend our previous findings, which showed no time-of-day effect on energy expenditure in healthy adults.

OBJECTIVES/GOALS: Fluid boluses are administered to hypotensive, critically ill children but may not reverse hypotension, leading to delay of vasoactive infusion, end-organ damage, and mortality. We hypothesize that a machine learning-based model will predict which children will have sustained response to fluid bolus. METHODS/STUDY POPULATION: We will conduct a single-center retrospective observational cohort study of hypotensive critically ill children who received intravenous isotonic fluid of at least 10 ml/kg within 72 hours of pediatric intensive care unit admission between 2013 and 2023. We will extract physiologic variables from stored bedside monitors data and clinical variables from the EHR. Fluid responsive (FR) will be defined as a MAP increase by 310%. We will construct elastic net, random forest, and a long short-term memory models to predict FR. We will compare complicated course (multiple organ dysfunction on day 7 or death by day 28) between: 1) FRs and non-FRs, 2) predicted FRs and non-FRs, 3), FRs and non-FRs stratified by race/ethnicity, and 4) FRs and non-FRs stratified by sex as a biologic variable. RESULTS/ANTICIPATED RESULTS: We anticipate approximately 800 critically ill children will receive 2,000 intravenous isotonic fluid boluses, with a 60% rate of FR. We anticipate being able to complete all three models. We hypothesize that the model with the best performance will be the long short-term memory model and the easiest to interpret will be the tree-based random forest model. We hypothesize non-FRs will have a higher complicated course than FRs and that predicted non-FRs will have a higher rate of complicated course than FRs. Based on previous adult studies, we hypothesize that there will be a higher rate of complicated course in patients of black race and/or Hispanic ethnicity when compared to non-Hispanic white patients. We also hypothesize that there will be no difference in complicated course when comparing sex as a biologic variable. DISCUSSION/SIGNIFICANCE: We have a critical need for easily-deployed, real-time prediction of fluid response to personalize and improve resuscitation for children in shock. We anticipate the clinical application of such a model will decrease time with hypotension for critically ill children, leading to decreased morbidity and mortality.

Several studies have shown that finishing bulls kept in housing systems with fully slatted concrete floors are impaired in their lying behaviour and locomotion due to the hardness and slipperiness of the ground. The aim of this study was to investigate the effects of floor quality (straw-bedded lying area, rubber-coated slats, concrete slats) on the lying behaviour of finishing bulls. The floor type did not influence the total lying duration, but the number of lying bouts and the number of short standing periods decreased with increasing hardness of the floor in the lying area. In addition, bulls showed more interrupted lying-down and standing-up movements on concrete and rubber-coated slats than on straw bedding. On the other hand, atypical lying-down and standing-up instances, slipping and falling were reduced on rubber-coated slats and on straw bedding compared to concrete slats. Displacements of lying animals were observed more often on rubber-coated slats than on concrete slats or straw bedding. In conclusion, rubber-coated slats improve traction on the ground but are not able to provide as soft a lying area as straw bedding. Rubber coating can thus serve to improve welfare for finishing bulls kept on concrete slats but cannot be considered equivalent to straw bedding.

Translocation and rehabilitation programmes are critical tools for wildlife conservation. These methods achieve greater impact when integrated in a combined strategy for enhancing population or ecosystem restoration. During 2002–2016 we reared 37 orphaned southern sea otter Enhydra lutris nereis pups, using captive sea otters as surrogate mothers, then released them into a degraded coastal estuary. As a keystone species, observed increases in the local sea otter population unsurprisingly brought many ecosystem benefits. The role that surrogate-reared otters played in this success story, however, remained uncertain. To resolve this, we developed an individual-based model of the local population using surveyed individual fates (survival and reproduction) of surrogate-reared and wild-captured otters, and modelled estimates of immigration. Estimates derived from a decade of population monitoring indicated that surrogate-reared and wild sea otters had similar reproductive and survival rates. This was true for males and females, across all ages (1–13 years) and locations evaluated. The model simulations indicated that reconstructed counts of the wild population are best explained by surrogate-reared otters combined with low levels of unassisted immigration. In addition, the model shows that 55% of observed population growth over this period is attributable to surrogate-reared otters and their wild progeny. Together, our results indicate that the integration of surrogacy methods and reintroduction of juvenile sea otters helped establish a biologically successful population and restore a once-impaired ecosystem.

We present very detailed images of the photosphere of an AGB star obtained with the PIONIER instrument, installed at the Very Large Telescope Interferometer (VLTI). The images show a well defined stellar disc populated by a few convective patterns. Thanks to the high precision of the observations we are able to derive the contrast and granulation horizontal scale of the convective pattern for the first time in a direct way. Such quantities are then compared with scaling relations between granule size, effective temperature, and surface gravity that are predicted by simulations of stellar surface convection.

Rib bone biopsy samples are often used to estimate changes in skeletal mineral reserves in cattle but differences in sampling procedures and the bone measurements reported often make interpretation and comparisons among experiments difficult. ‘Full-core’ rib bone biopsy samples, which included the external cortical bone, internal cortical bone and trabecular bone (CBext, CBint and Trab, respectively), were obtained from cattle known to be in phosphorus (P) adequate (Padeq) or severely P-deficient (Pdefic) status. Experiments 1 and 2 examined growing steers and Experiment 3 mature breeder cows. The thickness of cortical bone, specific gravity (SG), and the amount and concentration of ash and P per unit fresh bone volume, differed among CBext, CBint and Trab bone. P concentration (mg/cc) was closely correlated with both SG and ash concentrations (pooled data, r=0.99). Thickness of external cortical bone (CBText) was correlated with full-core P concentration (FC-Pconc) (pooled data, r=0.87). However, an index, the amount of P in CBext per unit surface area of CBext (PSACB; mg P/mm2), was more closely correlated with the FC-Pconc (pooled data, FC-Pconc=37.0+146×PSACB; n=42, r=0.94, RSD=7.7). Results for measured or estimated FC-Pconc in 10 published studies with cattle in various physiological states and expected to be Padeq or in various degrees of Pdefic status were collated and the ranges of FC-Pconc indicative of P adequacy and P deficiency for various classes of cattle were evaluated. FC-Pconc was generally in the range 130 to 170 and 100 to 120 mg/cc fresh bone in Padeq mature cows and young growing cattle, respectively. In conclusion, the FC-Pconc could be estimated accurately from biopsy samples of CBext. This allows comparisons between studies where full-core or only CBext biopsy samples of rib bone have been obtained to estimate changes in the skeletal P status of cattle and facilitates evaluation of the P status of cattle.

Coinfection with human immunodeficiency virus (HIV) and viral hepatitis is associated with high morbidity and mortality in the absence of clinical management, making identification of these cases crucial. We examined characteristics of HIV and viral hepatitis coinfections by using surveillance data from 15 US states and two cities. Each jurisdiction used an automated deterministic matching method to link surveillance data for persons with reported acute and chronic hepatitis B virus (HBV) or hepatitis C virus (HCV) infections, to persons reported with HIV infection. Of the 504 398 persons living with diagnosed HIV infection at the end of 2014, 2.0% were coinfected with HBV and 6.7% were coinfected with HCV. Of the 269 884 persons ever reported with HBV, 5.2% were reported with HIV. Of the 1 093 050 persons ever reported with HCV, 4.3% were reported with HIV. A greater proportion of persons coinfected with HIV and HBV were males and blacks/African Americans, compared with those with HIV monoinfection. Persons who inject drugs represented a greater proportion of those coinfected with HIV and HCV, compared with those with HIV monoinfection. Matching HIV and viral hepatitis surveillance data highlights epidemiological characteristics of persons coinfected and can be used to routinely monitor health status and guide state and national public health interventions.

The calving interval (CI) can potentially impact the economic results of dairy farms. This study highlighted the most profitable CI and innovated by describing this optimum as a function of the feeding system of the farm. On-farm data were used to represent real farm conditions. A total of 1832 accounts of farms recorded from 2007 to 2014 provided economic, technical and feeding information per herd and per year. A multiple correspondence analysis created four feeding groups: extensive, low intensive, intensive and very intensive herds. The gross margin and some of its components were corrected to account for the effect of factors external to the farm, such as the market, biological status, etc. Then the corrected gross margin (cGMc) and its components were modelled by CI parameters in each feeding system by use of GLM. The relationship between cGMc and the proportion of cows with CI<380 days in each feeding group showed that keeping most of the cows in the herd with CI near to 1 year was not profitable for most farms (for the very intensive farms there was no effect of the proportion). Moreover, a low proportion of cows (0% to 20%) with a near-to-1-year CI was not profitable for the extensive and low intensive farms. Extending the proportion of cows with CI beyond 459 days until 635 days (i.e. data limitation) caused no significant economic loss for the extensive and low intensive farms, but was not profitable for the intensive and very intensive farms. Variations of the milk and feeding components explained mainly these significant differences of gross margin. A link between the feeding system and persistency, perceptible in the milk production and CI shown by the herd, could explain the different relationships observed between the extent of CI and the economic results in the feeding groups. This herd-level study tended to show different economic optima of CI as a function of the feeding system. A cow-level study would specify these tendencies to give CI objectives to dairy breeders as a function of their farm characteristics.

There is a long-standing debate in the literature of stratified flows over topography concerning the correct dimensionless number to refer to as a Froude number. Common definitions using external quantities of the flow include $U/(ND)$ , $U/(Nh_{0})$ , and $Uk/N$ , where $U$ and $N$ are, respectively, scales for the background velocity and buoyancy frequency, $D$ is the depth, and $h_{0}$ and $k^{-1}$ are, respectively, height and width scales of the topography. It is also possible to define an internal Froude number $Fr_{\unicode[STIX]{x1D6FF}}=u_{0}/\sqrt{g^{\prime }\unicode[STIX]{x1D6FF}}$ , where $u_{0}$ , $g^{\prime }$ , and $\unicode[STIX]{x1D6FF}$ are, respectively, the characteristic velocity, reduced gravity, and vertical length scale of the perturbation above the topography. For the case of hydrostatic lee waves in a deep ocean, both $U/(ND)$ and $Uk/N$ are insignificantly small, rendering the dimensionless number $Nh_{0}/U$ the only relevant dynamical parameter. However, although it appears to be an inverse Froude number, such an interpretation is incorrect. By non-dimensionalizing the stratified Euler equations describing the flow of an infinitely deep fluid over topography, we show that $Nh_{0}/U$ is in fact the square of the internal Froude number because it can identically be written in terms of the inner variables, $Fr_{\unicode[STIX]{x1D6FF}}^{2}=Nh_{0}/U=u_{0}^{2}/(g^{\prime }\unicode[STIX]{x1D6FF})$ . Our scaling also identifies $Nh_{0}/U$ as the ratio of the vertical velocity scale within the lee wave to the group velocity of the lee wave, which we term the vertical Froude number, $Fr_{vert}=Nh_{0}/U=w_{0}/c_{g}$ . To encapsulate such behaviour, we suggest referring to $Nh_{0}/U$ as the lee-wave Froude number, $Fr_{lee}$ .

Nioghalvfjerdsfjorden glacier is a >60 km long and 20 km wide floating outlet glacier located at 79°30’ N, 22° W, draining a large area of the northeast Greenland ice sheet. Climate, mass-balance and dynamics studies were carried out on the glacier in three field seasons in 1996, 1997 and 1998. As part of this work, tidal-movement observations were carried out by simultaneous differential global positioning system (GPS) measurements at several locations distributed on the glacier surface. The GPS observations were performed continuously over several tidal cycles. At the same time, tiltmeter measurements were carried out in the grounding zones along the glacier margins and upstream, where the glacier leaves the main ice sheet A tide gauge installed in the sea immediately in front of the glacier front recorded the tide in the open sea during the field seasons. The observations show that the main part of the glacier tongue responds as a freely floating plate to the phase and amplitude of the local tide in the sea. However, kilometre-wide flexure zones exist along the marginal and upstream grounding lines. Attempts to model the observed tidal deflection and tilt patterns in the flexure zone by elastic-beam theory are unsuccessful, in contrast to previous findings by other investigators. The strongest disagreement between our measurements and results derived from elastic-beam theory is a significant variation of the phase of the tidal records with distance from the grounding line (most clearly displayed by the tilt records). We suggest that the viscous properties of glacier ice must be taken into account, and consequently that a viscoelastic-beam model must be used to adequately describe tidal bending of floating glaciers.

In theoretical treatments of tidal bending of floating glaciers, the glacier is usually modelled as an elastic beam with uniform thickness, resting on an elastic foundation. With a few exceptions, values of the elastic (Young’s) modulus E of ice derived from tidal deflection records of floating glaciers are in the range 0.9–3 GPa. It has therefore been suggested that the elastic-beam model with a single value of E ≈ 1GPa adequately describes tidal bending of glaciers. In contrast, laboratory experiments with ice give E = 9.3 GPa, i.e. 3–10 times higher than the glacier-derived values. This suggests that ice creep may have a significant influence on tidal bending of glaciers. Moreover, detailed tidal-deflection and tilt data from Nioghalvfjerdsfjorden glacier, northeast Greenland, cannot be explained by elastic-beam theory. We present a theory of tidal bending of glaciers based on linear viscoelastic-beam theory. A four-element, linear viscoelastic model for glacier ice with a reasonable choice of model parameters can explain the observed tidal flexure data. Implications of the viscoelastic response of glaciers to tidal forcing are discussed briefly.