We give a short proof of the Torelli theorem for $ALH^*$ gravitational instantons using the authors’ previous construction of mirror special Lagrangian fibrations in del Pezzo surfaces and rational elliptic surfaces together with recent work of Sun-Zhang. In particular, this includes an identification of 10 diffeomorphism types of $ALH^*_b$ gravitational instantons.

Background: Nursing home (NH) residents and staff were at high risk for COVID-19 early in the pandemic; several studies estimated seroprevalence of infection in NH staff to be 3-fold higher among CNAs and nurses compared to other staff. Risk mitigation added in Fall 2020 included systematic testing of residents and staff (and furlough if positive) to reduce transmission risk. We estimated risks for SARS-CoV-2 infection among NH staff during the first winter surge before widespread vaccination. Methods: Between February and May 2021, voluntary serologic testing was performed on NH staff who were seronegative for SARS-CoV-2 in late Fall 2020 (during a previous serology study at 14 Georgia NHs). An exposure assessment at the second time point covered prior 3 months of job activities, community exposures, and self-reported COVID-19 vaccination, including very recent vaccination (≤4 weeks). Risk factors for seroconversion were estimated by job type using multivariable logistic regression, accounting for interval community-incidence and interval change in resident infections per bed. Results: Among 203 eligible staff, 72 (35.5%) had evidence of interval seroconversion (Fig. 1). Among 80 unvaccinated staff, interval infection was significantly higher among CNAs and nurses (aOR, 4.9; 95% CI, 1.4–20.7) than other staff, after adjusting for race and interval community incidence and facility infections. This risk persisted but was attenuated when utilizing the full study cohort including those with very recent vaccination (aOR, 1.8; 95% CI, 0.9–3.7). Conclusions: Midway through the first year of the pandemic, NH staff with close or common resident contact continued to be at increased risk for infection despite enhanced infection prevention efforts. Mitigation strategies, prior to vaccination, did not eliminate occupational risk for infection. Vaccine utilization is critical to eliminate occupational risk among frontline healthcare providers.

Funding: None

Disclosures: None

The observation that 64% of English adults are overweight or obese despite a rising prevalence in weight-loss attempts suggests our understanding of energy balance is fundamentally flawed. Weight-loss is induced through a negative energy balance; however, we typically view weight change as a static function, in that energy intake and energy expenditure are independent variables, resulting in a fixed rate of weight-loss assuming a constant energy deficit. Such static modelling provides the basis for the clinical assumption that a 14644 kJ (3500 kcal) deficit translates to a 1 lb weight-loss. However, this ‘3500 kcal (14644 kJ) rule’ is consistently shown to significantly overestimate weight-loss. Static modelling disregards obligatory changes in energy expenditure associated with the loss of metabolically active tissue, i.e. skeletal muscle. Additionally, it disregards the presence of adaptive thermogenesis, the underfeeding-associated fall in resting energy expenditure beyond that caused by loss of fat-free mass. This metabolic manipulation of energy expenditure is observed from the onset of energy restriction to maintain weight at a genetically pre-determined set point. As a result, the observed magnitude of weight-loss is disproportionally less, followed by earlier weight plateau, despite strict compliance to a dietary intervention. By simulating dynamic changes in energy expenditure associated with underfeeding, mathematical modelling may provide a more accurate method of weight-loss prediction. However, accuracy at an individual level is limited due to difficulty estimating energy requirements, physical activity and dietary intake in free-living individuals. In the present paper, we aim to outline the contribution of dynamic changes in energy expenditure to weight-loss resistance and weight plateau.

There are two proven dietary approaches to shift type 2 diabetes (T2D) into remission: low-energy diets (LEDs) and low-carbohydrate diets (LCDs). These approaches differ in their rationale and application yet both involve carbohydrate restriction, either as an explicit goal or as a consequence of reducing overall energy intake. The aims of this systematic review were to identify, characterise and compare existing clinical trials that utilised ‘low-carbohydrate’ interventions with differing energy intakes. Electronic databases CENTRAL, CINAHL, Embase, MEDLINE and Scopus were searched to identify controlled clinical trials in adults with T2D involving low-carbohydrate intake (defined as <130 g carbohydrate/d) and reporting weight and glycaemic outcomes. The initial database search yielded 809 results, of which fifteen studies met the inclusion criteria. Nine out of fifteen studies utilised LCDs with moderate or unrestricted energy intake. Six trials utilised LEDs (<1200 kcal/d), with all except one incorporating meal replacements as part of a commercial weight loss programme. Interventions using both restricted and unrestricted (ad libitum) energy intakes produced clinically significant weight loss and reduction in glycated haemoglobin (HbA1c) at study endpoints. Trials that restricted energy intake were not superior to those that allowed ad libitum low-carbohydrate feeding at 12 and 24 months. An association was observed across studies between average weight loss and reduction in HbA1c at 6, 12 and 24 months, indicating that sustained weight loss is key to T2D remission. Further research is needed to specifically ascertain the weight-independent effects of carbohydrate restriction on glycaemic control in T2D.

Among 353 healthcare personnel in a longitudinal cohort in 4 hospitals in Atlanta, Georgia (May–June 2020), 23 (6.5%) had severe acute respiratory coronavirus virus 2 (SARS-CoV-2) antibodies. Spending >50% of a typical shift at the bedside (OR, 3.4; 95% CI, 1.2–10.5) and black race (OR, 8.4; 95% CI, 2.7–27.4) were associated with SARS-CoV-2 seropositivity.

The intermittent energy restriction (IER) approach to weight loss involves short periods of substantial (>70 %) energy restriction (ER) interspersed with normal eating. Studies to date comparing IER to continuous energy restriction (CER) have predominantly measured fasting indices of cardiometabolic risk. This study aimed to compare the effects of IER and CER on postprandial glucose and lipid metabolism following matched weight loss. In all, twenty-seven (thirteen male) overweight/obese participants (46 (sem 3) years, 30·1 (sem 1·0) kg/m2) who were randomised to either an IER intervention (2638 kJ for 2 d/week with an overall ER of 22 (sem 0·3) %, n 15) or a CER intervention (2510 kJ below requirements with overall ER of 23 (sem 0·8) %) completed the study. Postprandial responses to a test meal (over 360 min) and changes in anthropometry (fat mass, fat-free mass, circumferences) were assessed at baseline and upon attainment of 5 % weight loss, following a 7-d period of weight stabilisation. The study found no statistically significant difference in the time to attain a 5 % weight loss between groups (median 59 d (interquartile range (IQR) 41–80) and 73 d (IQR 48–128), respectively, P=0·246), or in body composition (P≥0·437). For postprandial measures, neither diet significantly altered glycaemia (P=0·266), whereas insulinaemia was reduced comparatively (P=0·903). The reduction in C-peptide tended (P=0·057) to be greater following IER (309 128 (sem23 268) to 247781 (sem20 709) pmol×360 min/l) v. CER (297 204 (sem25 112) to 301 655 (sem32 714) pmol×360 min/l). The relative reduction in TAG responses was greater (P=0·045) following IER (106 (sem30) to 68 (sem 15) mmol×360 min/l) compared with CER (117 (sem 43) to 130 (sem 31) mmol×360 min/l). In conclusion, these preliminary findings highlight underlying differences between IER and CER, including a superiority of IER in reducing postprandial lipaemia, which now warrant targeted mechanistic evaluation within larger study cohorts.

The effects of Reynolds number ($R_{\unicode[STIX]{x1D706}}$) and Stokes number ($St$) on particle-pair relative velocity (RV) are investigated systematically using a recently developed planar four-frame particle tracking technique in a novel homogeneous and isotropic turbulence chamber. We compare the measured results with direct numerical simulation (DNS), verifying whether the conclusions of the DNS for simplified conditions and limited $R_{\unicode[STIX]{x1D706}}$ are still valid in reality. Two experiments are performed: varying $R_{\unicode[STIX]{x1D706}}$ between 246 and 357 at six $St$ values, and varying $St$ between 0.02 and 4.63 at five $R_{\unicode[STIX]{x1D706}}$ values. The measured mean inward particle-pair RV $\langle w_{r}^{-}\rangle$ as a function of separation distance $r$ is compared with the DNS under closely matched conditions. At all experimental conditions, an excellent agreement is achieved, except when the particle separation distance $r\lesssim 10\unicode[STIX]{x1D702}$ ($\unicode[STIX]{x1D702}$ is the Kolmogorov length scale), where the experimental $\langle w_{r}^{-}\rangle$ is consistently higher, possibly due to particle polydispersity and finite laser thickness in the experiments (Dou et al., arXiv:1712.07506, 2017). At any fixed $St,\langle w_{r}^{-}\rangle$ is essentially independent of $R_{\unicode[STIX]{x1D706}}$, echoing the DNS finding of Ireland et al. (J. Fluid Mech., vol. 796, 2016, pp. 617–658). At any fixed $R_{\unicode[STIX]{x1D706}}$, $\langle w_{r}^{-}\rangle$ increases with $St$ at small $r$, showing dominance of the path-history effect in the dissipation range when $St\gtrsim O(1)$, but decreases with $St$ at large $r$, indicating dominance of inertial filtering. We further compare the $\langle w_{r}^{-}\rangle$ and RV variance $\langle w_{r}^{2}\rangle$ from experiments with DNS and theoretical predictions by Pan & Padoan (J. Fluid Mech., vol. 661, 2010, pp. 73–107). For $St\lesssim 1$, experimental $\langle w_{r}^{-}\rangle$ and $\langle w_{r}^{2}\rangle$ match these values well at $r\gtrsim 10\unicode[STIX]{x1D702}$, but they are higher than both DNS and theory at $r\lesssim 10\unicode[STIX]{x1D702}$. For $St\gtrsim 1$, $\langle w_{r}^{-}\rangle$ from all three match well, except for $r\lesssim 10\unicode[STIX]{x1D702}$, for which experimental values are higher, while $\langle w_{r}^{2}\rangle$ from experiment and DNS are much higher than theoretical predictions. We discuss potential causes of these discrepancies. What this study shows is the first experimental validation of $R_{\unicode[STIX]{x1D706}}$ and $St$ effect on inertial particle-pair $\langle w_{r}^{-}\rangle$ in homogeneous and isotropic turbulence.

Monolithic integrated thin film tandem solar cells consisting of a high bandgap perovskite top cell and a low bandgap thin film bottom cell are expected to reach higher power conversion efficiencies (PCEs) with lower manufacturing cost and environmental impacts than the market-dominant crystalline silicon photovoltaics. There have been several demonstrations of 4-terminal and 2-terminal perovskite tandem devices with CuInGaSe2 (CIGS) or CuInSe2 (CIS) and, similar to the other tandem structures, the optimization of this device relies on optimal choice for the perovskite bandgap and thickness. Therefore, further advancement will be enabled by tuning the perovskite absorber to maximize the photocurrent limited by the current match condition. Here, we systematically study the optical absorption and transmission of perovskite thin films with varying absorber band gap. Based on these results, we model the photocurrent generations in both perovskite and CIS subcells and estimate the performances of projected tandem devices by considering the ideally functioning perovskite and CIS device. Our results show that for perovskite layers with 500 nm thickness the optimal bandgap is around 1.6 eV. With these configurations, PCEs above 20% could be achieved by monolithically integrated perovskite/CIS tandem solar cells. Also by modelling the absorption at every layer we calculate the quantum efficiency at each subcell in addition to tracking optical losses.

Photoluminescence (PL) spectroscopy has been used to study the defect levels in thin film copper indium diselenide (CuInSe2, CIS) which we are developing as the absorber layer for the bottom cell of a monolithically grown perovskite/CuInSe2 tandem solar cell. Temperature and laser power dependent PL measurements of thin film CIS for two different Cu/In ratios (0.66 and 0.80) have been performed. The CIS film with Cu/In = 0.80 shows a prominent donor-to-acceptor peak (DAP) involving a shallow acceptor of binding energy ∼22 meV, with phonon replica at ∼32 meV spacing. In contrast, PL measurement of CIS film for Cu/In = 0.66 taken at 20 K exhibited an asymmetric and broad PL spectrum with peaks at 0.845 eV and 0.787 eV. Laser intensity dependent PL revealed that the observed peaks 0.845 eV and 0.787 eV shift towards higher energy (aka j-shift) at ∼11.7 meV/decade and ∼ 8 meV/decade with increase in laser intensity respectively. The asymmetric and broad spectrum together with large j-shift suggests that the observed peaks at 0.845 eV and 0.787 eV were related to band-to-tail (BT) and band-to-impurity (BI) transition, respectively. Such a band-tail-related transition originates from the potential fluctuation of defect states at low temperature. The appearance of band related transition in CIS film with Cu/In = 0.66 is the indicator of the presence of large number of charged defect states.

Soft X-ray spectro-tomography provides three-dimensional (3D) chemical mapping based on natural X-ray absorption properties. Since radiation damage is intrinsic to X-ray absorption, it is important to find ways to maximize signal within a given dose. For tomography, using the smallest number of tilt series images that gives a faithful reconstruction is one such method. Compressed sensing (CS) methods have relatively recently been applied to tomographic reconstruction algorithms, providing faithful 3D reconstructions with a much smaller number of projection images than when conventional reconstruction methods are used. Here, CS is applied in the context of scanning transmission X-ray microscopy tomography. Reconstructions by weighted back-projection, the simultaneous iterative reconstruction technique, and CS are compared. The effects of varying tilt angle increment and angular range for the tomographic reconstructions are examined. Optimization of the regularization parameter in the CS reconstruction is explored and discussed. The comparisons show that CS can provide improved reconstruction fidelity relative to weighted back-projection and simultaneous iterative reconstruction techniques, with increasingly pronounced advantages as the angular sampling is reduced. In particular, missing wedge artifacts are significantly reduced and there is enhanced recovery of sharp edges. Examples of using CS for low-dose scanning transmission X-ray microscopy spectroscopic tomography are presented.

Two intermittent fasting variants, intermittent energy restriction (IER) and time-restricted feeding (TRF), have received considerable interest as strategies for weight-management and/or improving metabolic health. With these strategies, the pattern of energy restriction and/or timing of food intake are altered so that individuals undergo frequently repeated periods of fasting. This review provides a commentary on the rodent and human literature, specifically focusing on the effects of IER and TRF on glucose and lipid metabolism. For IER, there is a growing evidence demonstrating its benefits on glucose and lipid homeostasis in the short-to-medium term; however, more long-term safety studies are required. Whilst the metabolic benefits of TRF appear quite profound in rodents, findings from the few human studies have been mixed. There is some suggestion that the metabolic changes elicited by these approaches can occur in the absence of energy restriction, and in the context of IER, may be distinct from those observed following similar weight-loss achieved via modest continuous energy restriction. Mechanistically, the frequently repeated prolonged fasting intervals may favour preferential reduction of ectopic fat, beneficially modulate aspects of adipose tissue physiology/morphology, and may also impinge on circadian clock regulation. However, mechanistic evidence is largely limited to findings from rodent studies, thus necessitating focused human studies, which also incorporate more dynamic assessments of glucose and lipid metabolism. Ultimately, much remains to be learned about intermittent fasting (in its various forms); however, the findings to date serve to highlight promising avenues for future research.

The intermittent energy restriction (IER) approach to weight loss involves short periods of substantial (75–100 %) energy restriction (ER) interspersed with normal eating. This study aimed to characterise the early metabolic response to these varying degrees of ER, which occurs acutely and prior to weight loss. Ten (three female) healthy, overweight/obese participants (36 (SEM 5) years; 29·0 (sem 1·1) kg/m2) took part in this acute three-way cross-over study. Participants completed three 1-d dietary interventions in a randomised order with a 1-week washout period: isoenergetic intake, partial 75 % ER and total 100 % ER. Fasting and postprandial (6-h) metabolic responses to a liquid test meal were assessed the following morning via serial blood sampling and indirect calorimetry. Food intake was also recorded for two subsequent days of ad libitum intake. Relative to the isoenergetic control, postprandial glucose responses were increased following total ER (+142 %; P=0·015) and to a lesser extent after partial ER (+76 %; P=0·051). There was also a delay in the glucose time to peak after total ER only (P=0·024). Both total and partial ER interventions produced comparable reductions in postprandial TAG responses (−75 and −59 %, respectively; both P<0·05) and 3-d energy intake deficits of approximately 30 % (both P=0·015). Resting and meal-induced thermogenesis were not significantly affected by either ER intervention. In conclusion, our data demonstrate the ability of substantial ER to acutely alter postprandial glucose–lipid metabolism (with partial ER producing the more favourable overall response), as well as incomplete energy-intake compensation amongst overweight/obese participants. Further investigations are required to establish how metabolism adapts over time to the repeated perturbations experienced during IER, as well as the implications for long-term health.