Feasibility study of full-reactor gas core demonstration test

Separate studies of nuclear criticality, flow patterns, and thermodynamics for the gas core reactor concept have all given positive indications of its feasibility. However, before serious design for a full scale gas core application can be made, feasibility must be shown for operation with full interaction of the nuclear, thermal, and hydraulic effects. A minimum sized, and hence minimum expense, test arrangement is considered for a full gas core configuration. It is shown that the hydrogen coolant scattering effects dominate the nuclear considerations at elevated temperatures. A cavity diameter of somewhat larger than 4 ft (122 cm) will be needed if temperatures high enough to vaporize uranium are to be achieved

Modeling the Impact of Operator Trust on Performance in Multiple Robot Control,

We developed a system dynamics model to simulate the impact of operator trust on performance in multiple robot control. Analysis of a simulated urban search and rescue experiment showed that operators decided to manually control the robots when they lost trust in the autonomous planner that was directing the robots. Operators who rarely used manual control performed the worst. However, the operators who most frequently used manual control reported higher workload and did not perform any better than operators with moderate manual control usage. Based on these findings, we implemented a model where trust and performance form a feedback loop, in which operators perceive the performance of the system, calibrate their trust, and adjust their control of the robots. A second feedback loop incorporates the impact of trust on cognitive workload and system performance. The model was able to replicate the quantitative performance of three groups of operators within 2.3%. This model could help us gain a greater understanding of how operators build and lose trust in automation and the impact of those changes in trust on performance and workload, which is crucial to the development of future systems involving humanautomation collaboration.This research is sponsored by the Office of Naval Research and the Air Force Office of Scientific Research

The Coordination Chemistry of “[BP_3]NiX” Platforms: Targeting Low-Valent Nickel Sources as Promising Candidates to L_3Ni=E and L_3Ni≡E Linkages

A series of divalent, monovalent, and zerovalent nickel complexes supported by the electron-releasing, monoanionic tris(phosphino)borate ligands [PhBP_3] and [PhBP^(iPr)_3] ([PhBP_3] = [PhB(CH_2PPh_2)_3]-, [PhBP^(iPr)_3] = [PhB(CH_2PiPr_2)_3]-) have been synthesized to explore fundamental aspects of their coordination chemistry. The pseudotetrahedral, divalent halide complexes [PhBP_3]NiCl (1), [PhBP_3]NiI (2), and [PhBP^(iPr)_3]NiCl (3) were prepared by the metalation of [PhBP_3]Tl or [PhBP^(iPr)_3]Tl with (Ph_3P)_2NiCl_2, NiI_2, and (DME)NiCl_2 (DME = 1,2-dimethoxyethane), respectively. Complex 1 is a versatile precursor to a series of complexes accessible via substitution reactions including [PhBP_3]Ni(N_3) (4), [PhBP_3]Ni(OSiPh_3) (5), [PhBP_3]Ni(O-p-tBu-Ph) (6), and [PhBP_3]Ni(S-p-tBu-Ph) (7). Complexes 2−5 and 7 have been characterized by X-ray diffraction (XRD) and are pseudotetrahedral monomers in the solid state. Complex 1 reacts readily with oxygen to form the four-electron-oxidation product, {[PhB(CH_2P(O)Ph_2)_2(CH_2PPh_2)]NiCl} (8A or 8B), which features a solid-state structure that is dependent on its method of crystallization. Chemical reduction of 1 using Na/Hg or other potential 1-electron reductants generates a product that arises from partial ligand degradation, [PhBP_3]Ni(η^2-CH_2PPh_2) (9). The more sterically hindered chloride 3 reacts with Li(dbabh) (Hdbabh = 2,3:5,6-dibenzo-7-azabicyclo[2.2.1]hepta-2,5-diene) to provide the three-coordinate complex [κ^2-PhBP^(iPr)_3]Ni(dbabh) (11), also characterized by XRD. Chemical reduction of complex 1 in the presence of L-type donors produces the tetrahedral Ni(I) complexes [PhBP_3]Ni(PPh_3) (12) and [PhBP3]Ni(CNtBu) (13). Reduction of 3 following the addition of PMe_3 or tert-butyl isocyanide affords the Ni(I) complexes [PhBP^(iPr)_3]Ni(PMe_3) (14) and [PhBP^(iPr)_3]Ni(CN^tBu) (15), respectively. The reactivity of these [PhBP_3]Ni^IL and [PhBP^(iPr)_3]NiI^L complexes with respect to oxidative group transfer reactions from organic azides and diazoalkanes is discussed. The zerovalent nitrosyl complex [PhBP_3]Ni(NO) (16) is prepared by the reaction of 1 with excess NO or by treating 12 with stoichiometric NO. The anionic Ni(0) complexes [[κ^2-PhBP_3]Ni(CO)_2][^nBu_4N] (17) and [[κ^2-PhBP^(iPr)_3]Ni(CO)_2][ASN] (18) (ASN = 5-azoniaspiro[4.4]nonane) have been prepared by reacting [PhBP_3]Tl or [PhBP^(iPr)_3]Tl with (Ph_3P)_2Ni(CO)_2 in the presence of R_4NBr. The photolysis of 17 appears to generate a new species consistent with a zerovalent monocarbonyl complex which we tentatively assign as {[PhBP_3]Ni(CO)}{^nBu_4N}, although complete characterization of this complex has been difficult. Finally, theoretical DFT calculations are presented for the hypothetical low spin complexes [PhBP_3]Ni(N^tBu), [PhBP^(iPr)_3]Ni(N^tBu), [PhBP^(iPr)_3]Ni(NMe), and [PhBP^(iPr)_3]Ni(N) to consider what role electronic structure factors might play with respect to the relative stability of these species

Policy, Performativity and Partnership: an Ethical Leadership Perspective

This article identifies the need to think differently about educational partnerships in a changing and turbulent post compulsory policy environment in England. The policy and institutional contexts in which universities and colleges currently operate seem to be fuelling performativity at the expense of educational values. There appears to be a sharp interruption in the steady increase in educational partnerships as a vehicle for increasing and widening participation in higher education. We are witnessing a marked change in university / college relationships that appears to be a consequence of government calling a halt to increased participation in higher education, creating an increasingly competitive market for a more limited pool of student places. The implication that educational policy at the national level determines a particular pattern or mode of leadership decision making throughout an institution should however be resisted. Policy developments that challenge the moral precepts of education should not be allowed to determine how a leader acts, rather they should prompt actions that are truly educational, rooted in morality, and atached to identifiable educational values. Educational leaders have agency to resist restricted discourses in favour of ethical and principled change strategies that are a precondition for sustainable transformative partnerships in post compulsory education. University leaders in particular are called upon to use their considerable influence to resist narrow policy or managerial instrumentalism or performativity and embrace alternatives that are both educationally worthwhile and can enhance institutional resilience

Establishing and Prioritising Research Questions for the Treatment of Alopecia Areata: The Alopecia Areata Priority Setting Partnership

BACKGROUND: Alopecia areata is a common hair loss disorder that results in patchy to complete hair loss. Many uncertainties exist around the most effective treatments for this condition. OBJECTIVES: To identify uncertainties in alopecia areata management and treatment that are important to both service users (people with hair loss, carers and relatives) and healthcare professionals. METHODS: An alopecia areata priority setting partnership was established between patients, their carers and relatives, and healthcare professionals to identify the most important uncertainties in alopecia areata. The methodology of the James Lind Alliance was followed to ensure a balanced, inclusive and transparent process. RESULTS: In total 2747 treatment uncertainties were submitted by 912 participants, of which 1012 uncertainties relating to alopecia areata (and variants) were analyzed. Questions were combined into "indicative uncertainties" following a structured format. A series of ranking exercises further reduced this list to a top 25 that were taken to a final prioritization workshop where the top 10 priorities were agreed. CONCLUSIONS: We present the top 10 research priorities for alopecia areata to guide researchers and funding bodies to support studies important to both patients and clinicians. This article is protected by copyright. All rights reserved

The Pulmonary Metastasectomy in Colorectal Cancer cohort study: Analysis of case selection, risk factors and survival in a prospective observational study of 512 patients

AIM: We wanted to examine survival in patients with resected colorectal cancer (CRC) whose lung metastases are or are not resected. METHODS: Teams participating in the study of Pulmonary Metastasectomy in Colorectal Cancer (PulMiCC) identified potential candidates for lung metastasectomy and invited their consent to join Stage 1. Baseline data related to CRC and fitness for surgery were collected. Eligible patients were invited to consent for randomization in the PulMiCC randomized controlled trial (Stage 2). Sites were provided with case report forms for non-randomized patients to record adverse events and death at any time. They were all reviewed at 1 year. Baseline and survival data were analysed for the full cohort. RESULTS: Twenty-five clinical sites recruited 512 patients from October 2010 to January 2017. Data collection closed in October 2020. Before analysis, 28 patients with non-CRC lung lesions were excluded and three had withdrawn consent leaving 481. The date of death was known for 292 patients, 136 were alive in 2020 and 53 at earlier time points. Baseline factors and 5-year survival were analysed in three strata: 128 non-randomized patients did not have metastasectomy; 263 had elective metastasectomy; 90 were from the randomized trial. The proportions of solitary metastases for electively operated and non-operated patients were 69% and 35%. Their respective 5-year survivals were 47% and 22%. CONCLUSION: Survival without metastasectomy was greater than widely presumed. Difference in survival appeared to be largely related to selection. No inference can be drawn about the effect of metastasectomy on survival in this observational study

Pulmonary Metastasectomy in Colorectal Cancer burden of care study: analysis of local treatments for lung metastases and systemic chemotherapy in 220 patients in the PulMiCC cohort

AIM: To examine the burden of further treatments in patients with colorectal cancer (CRC) following a decision about lung metastasectomy. METHODS: Five teams participating in the study of Pulmonary Metastasectomy in Colorectal Cancer (PulMiCC) provided details on subsequent local treatments for lung metastases including the use of chemotherapy. For patients in three groups (no metastasectomy, one metastasectomy or multiple local interventions), baseline factors and selection criteria for additional treatments were examined. RESULTS: The five teams recruited 220 patients between October 2010 and January 2017. No lung metastasectomy was performed in 51 patients, 114 had one, and 55 patients had multiple local interventions. Selection for initial metastasectomy was associated with non-elevated CEA, fewer metastases, and no prior liver metastasectomy. These patients also had better ECOG scores and lung function at baseline. Four sites provided information on chemotherapy in 139 patients: 79 (57%) had 1-5 courses of chemotherapy, to a total of 179 courses. The patterns of survival after one or multiple metastasectomy interventions showed evidence of guarantee-time bias contributing to an impression of benefit over no metastasectomy. After repeated metastasectomy, a significantly higher risk of death was observed with no apparent reduction in chemotherapy usage. CONCLUSION: Repeated metastasectomy is associated with higher risk of death without reducing use of chemotherapy. Continued monitoring without surgery might reassure patients with indolent disease or allow response assessment during systemic treatment. Overall, the carefully collected information from the PulMICC study provides no indication of an important survival benefit from metastasectomy

Reports of the AAAI 2019 spring symposium series

Applications of machine learning combined with AI algorithms have propelled unprecedented economic disruptions across diverse fields in industry, military, medicine, finance, and others. With the forecast for even larger impacts, the present economic impact of machine learning is estimated in the trillions of dollars. But as autonomous machines become ubiquitous, recent problems have surfaced. Early on, and again in 2018, Judea Pearl warned AI scientists they must "build machines that make sense of what goes on in their environment," a warning still unheeded that may impede future development. For example, self-driving vehicles often rely on sparse data; self-driving cars have already been involved in fatalities, including a pedestrian; and yet machine learning is unable to explain the contexts within which it operates