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First-person object-interaction tasks in high-fidelity, 3D, simulated environments such as the AI2Thor virtual home-environment pose significant sample-efficiency challenges for reinforcement learning (RL) agents learning from sparse task rewards. To alleviate these challenges, prior work has provided extensive supervision via a combination of reward-shaping, ground-truth object-information, and expert demonstrations. In this work, we show that one can learn object-interaction tasks from scratch without supervision by learning an attentive object-model as an auxiliary task during task learning with an object-centric relational RL agent. Our key insight is that learning an object-model that incorporates object-attention into forward prediction provides a dense learning signal for unsupervised representation learning of both objects and their relationships. This, in turn, enables faster policy learning for an object-centric relational RL agent. We demonstrate our agent by introducing a set of challenging object-interaction tasks in the AI2Thor environment where learning with our attentive object-model is key to strong performance. Specifically, we compare our agent and relational RL agents with alternative auxiliary tasks to a relational RL agent equipped with ground-truth object-information, and show that learning with our object-model best closes the performance gap in terms of both learning speed and maximum success rate. Additionally, we find that incorporating object-attention into an object-model's forward predictions is key to learning representations which capture object-category and object-state., Accepted to IJCAI 2021

ObjectivesTo establish the proportion of mild traumatic brain injury (mTBI) diagnosis among people presenting to an emergency department (ED), to determine the accuracy of recorded ED diagnoses. We also aimed to describe challenges in mTBI case identification and its acute hospital management.Design and settingA retrospective chart review of all ED attendances to a major trauma hospital, over a 9-month period (June 2015–February 2016).ParticipantsAdults aged 18–65 years consecutively presenting to an ED.Primary outcome measuresProportion of mTBI diagnosis among ED attendances (ie, confirmed mTBI based on the WHO criteria or indeterminate mTBI based on secondary criteria), and proportion of accurately recorded mTBI diagnosis by ED clinicians (ie, ‘mTBI’, ‘concussion’).ResultsOf 30 479 ED attendances, 351 (1.15%) confirmed mTBI diagnosis and 180 (0.6%) indeterminate diagnosis were identified. Only 81 (23.1%) individuals with a confirmed mTBI had a ‘mTBI diagnosis’ clearly recorded in the medical notes. Of the allocated discharge diagnosis codes to the two identified cohorts, 89.8% were not indicative of mTBI. Intracranial injuries were found in 31 (8.5%) confirmed cases. Glasgow Coma Scale scores were consistently assessed in the ED but identified only 117 (33.3%) confirmed mTBI cases. Post-traumatic amnesia (PTA) testing was able to confirm acute cognitive impairment in 113 (62.1%) of those who were tested (182, 51.3%).ConclusionsmTBI is a common, but an under-recognised cause for ED attendance. Despite challenges, the use of an operational definition such as the WHO diagnostic criteria can improve accuracy in mTBI identification. Acute management may be enhanced by rapid assessment of PTA.

A unique property of size-resolved metal nanocluster particles is their "superatom"-like electronic shell structure. The shell levels are highly degenerate, and it has been predicted that this can enable exceptionally strong superconducting-type electron pair correlations in certain clusters composed of just tens to hundreds of atoms. Here we report on the observation of a possible spectroscopic signature of such an effect. A bulge-like feature appears in the photoionization yield curve of a free cold aluminum cluster and shows a rapid rise as the temperature approaches approximately 100 K. This is an unusual effect, not previously reported for clusters. Its characteristics are consistent with an increase in the effective density of states accompanying a pairing transition, which suggests a high-temperature superconducting state with Tc>~100 K. Our results highlight the promise of metal nanoclusters as high-Tc building blocks for materials and networks.

Cryogenic molecular beam experiments show that the ferroelectric dipole moments of small niobium clusters with an even number of valence electrons n are typically greater than those with odd n. This is verified in alloy clusters NbNXM where X=Al, Au, O, Mn, Fe, and Co; N≤100;M≤3. Like in superconducting alloys, Mn doping quenches the effect while Al and Au enhance it, suggesting a relation between cluster ferroelectricity and bulk superconductivity. A correlated ground state is proposed where the even-odd effect is caused by the depolarizing effect of a single unpaired electron.

IntroductionPrevious literature confirms that a mild traumatic brain injury (mTBI) may result in long-term emotional impacts and, in vulnerable subgroups, cognitive deficits. The accurate diagnosis of mTBI and its written documentation is an important first step towards providing appropriate and timely clinical care. Surveillance studies involving emergency department (ED) and hospital-based data need to be prioritised as these provide incident mTBI estimates. This project will advance existing research findings by estimating the occurrence of mTBI among those attending an ED and quantifying the accuracy of mTBI diagnoses recorded by ED staff through a comprehensive audit of ED records.Methods and analysisRetrospective chart reviews (between June 2015 and June 2016) of electronic clinical records from an ED in Sydney (New South Wales, Australia) will be conducted. The study population will include persons aged 18–65 years who attended the ED with any clinical features potentially indicative of mTBI. The WHO operational criteria for the clinical identification of mTBI cases is the presence of: (1) a Glasgow Coma Scale (GCS) of 13–15 after 30 min postinjury or on presentation to hospital; (2) one or more of the following: post-traumatic amnesia (PTA) of less than 24 hours’ duration, confusion or disorientation, a witnessed loss of consciousness for ≤30 min and/or a positive CT brain scan. We estimate that 30 000 ED attendances will be screened and that a sample size of 500 cases with mTBI will be identified during this 1-year period, which will provide reliable estimates of mTBI occurrence in the ED setting.Ethics and disseminationThe study was approved by the Northern Sydney Local Health District Ethics Committee. The committee deemed this study as low risk in terms of ethical issues. The written papers from this study will be submitted for publication in quality peer-reviewed medical and health journals. Study findings will be disseminated via presentations at national/international conferences and peer-reviewed journals.

Cryogenic cluster beam experiments have provided crucial insights into the evolution of the metallic state from the atom to the bulk. Surprisingly, one of the most fundamental metallic properties, the ability of a metal to efficiently screen electric fields, is still poorly understood in small clusters. Theory has predicted that many small Na clusters are unable to screen charge inhomogeneities and thus have permanent dipole moments. High precision electric deflection experiments on cryogenically cooled Na$_N$ ($N, 4 pages, 3 figures

Stern–Gerlach deflection measurements have been performed on rare earth clusters TbN, HoN, and TmN (N≤40) at cryogenic temperatures (T≤77 K). TbN and HoN share a common size dependence in their magnetic moments. They both exhibit common “magic number” sizes which show reduced net magnetic moments, similar to previous observations for Gd and Dy clusters. TmN have smaller magnetic moments that do not differ significantly between cluster sizes. The reduced net magnetic moments are evidence that the atomic moments are canceled by a canted or antiferromagnetic alignment. Electric deflection experiments reveal that TmN have electric dipole moments and show an enhanced response to an electric field compared to TbN and HoN.

The magnetic moments and electric dipoles of Tb and Pr clusters are investigated using the Stern–Gerlach deflection technique. The addition of a single oxygen atom induces an increase in the electric dipole of TbN clusters, however the magnetic moment is largely not affected. In Pr neither the magnetic moment nor the electric dipole is affected. This raises questions as to the role of conduction electrons in the exchange interaction of rare earth clusters, and puts into doubt the validity of the Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange mechanism in small systems.

Electric deflections of niobium clusters in molecular beams show that they have permanent electric dipole moments at cryogenic temperatures but not higher temperatures, indicating that they are ferroelectric. Detailed analysis shows that the deflections cannot be explained in terms of a rotating classical dipole, as claimed by Anderson et al. The shapes of the deflected beam profiles and their field and temperature dependences indicates that the clusters can exist in two states, one with a dipole and the other without. Cluster with dipoles occupy lower energy states. Excitations from the lower states to the higher states can be induced by low fluence laser excitation. This causes the dipole to vanish., 25 pages, 7 figures

The production of silver cluster cations Ag(n)(2+) (for several selected sizes in the range n = 39-119) and Ag(n)(3+) (for n = 58, 61, 67) by electron impact ionization of neutral precursors has been studied. The scaling of appearance energies with cluster radius follows the metallic droplet model but, curiously, with a slope which is estimated to be quite different from the literature values for single ionization, Ag(n)(+), as well as for the appearance of smaller Ag(n)(2+) ions. It is also found that as the electron energy increases, the yield of high-charge cations grows faster than that of singly-charged Ag(n)(+). This behavior is consistent with the power-law dependence of post-threshold ionization. The mechanisms involved in multiple ionization phenomena in clusters of noble metals are not yet fully understood and call for further experimental and theoretical examination.