The word problem distinguishes counter languages

Counter automata are more powerful versions of finite-state automata where addition and subtraction operations are permitted on a set of n integer registers, called counters. We show that the word problem of $\Z^n$ is accepted by a nondeterministic $m$-counter automaton if and only if $m \geq n$.Comment: 8 page

Cone types and geodesic languages for lamplighter groups and Thompson's group F

We study languages of geodesics in lamplighter groups and Thompson's group F. We show that the lamplighter groups $L_n$ have infinitely many cone types, have no regular geodesic languages, and have 1-counter, context-free and counter geodesic languages with respect to certain generating sets. We show that the full language of geodesics with respect to one generating set for the lamplighter group is not counter but is context-free, while with respect to another generating set the full language of geodesics is counter and context-free. In Thompson's group F with respect to the standard finite generating set, we show there are infinitely many cone types and no regular language of geodesics with respect to the standard finite generating set. We show that the existence of families of "seesaw" elements with respect to a given generating set in a finitely generated infinite group precludes a regular language of geodesics and guarantees infinitely many cone types with respect to that generating set.Comment: 30 pages, 13 figure

Random subgroups of Thompson's group FF

We consider random subgroups of Thompson's group $F$ with respect to two natural stratifications of the set of all $k$ generator subgroups. We find that the isomorphism classes of subgroups which occur with positive density are not the same for the two stratifications. We give the first known examples of {\em persistent} subgroups, whose isomorphism classes occur with positive density within the set of $k$-generator subgroups, for all sufficiently large $k$. Additionally, Thompson's group provides the first example of a group without a generic isomorphism class of subgroup. Elements of $F$ are represented uniquely by reduced pairs of finite rooted binary trees. We compute the asymptotic growth rate and a generating function for the number of reduced pairs of trees, which we show is D-finite and not algebraic. We then use the asymptotic growth to prove our density results.Comment: 37 pages, 11 figure

A Study of Queer Affect and Relation in Curatorial Practice and Writing

This thesis develops a recent impulse in feminist and queer curatorial theory to propose affect, relation and emotion as important dynamics within the development of curatorial studies and, more specifically, curatorial writing within times of crisis. Initially situated within a time where the so-called ‘crisis of care’1 has dominated curatorial thinking, witnessed across both art, political and social institutions, this research became quickly entwined with the realities of its unfolding during the now-ongoing Covid-19 pandemic. This research proposes that affect and relation might trouble the assumed neutral or institutional nature of the figure of the ‘curator’ specifically through reflexive curatorial writing. Key concepts from queer theory including distance and proximity2 are important anchors within the thesis’ engagement with writing as a reflexive method, particularly as it pertained to the isolation of Covid. The first chapter defines key terms as well as expands on the idea of the curatorial within an institutional sense as being insufficient for an expansive sense of relation. The second chapter instead situates bodies and proximity as central figures of importance within the research. The final chapters look specifically to curatorial writing as a site where affect’s circulation might bring us closer towards transformative ways of understanding pleasure, love and trust within the curatorial. Drawing from previous curatorial practice and projects, writing in this thesis becomes a central site of curatorial affect, with a capacity to develop both analytical and synthetical engagements with curatorial knowledge and queer theory, as well as to transform being-affected into affective action. This contribution both offers alternatives to and challenges more conventional curatorial writing, and more widely, heteronormative forms of knowledge production. 1 Noor Alé,, “Curatorial (Mis)care in an Age of Ongoing Crises,” Banff Centre for Arts and Creativity, 2021. Available Online: https://www.banffcentre.ca/bici/curatorial-miscare-age-ongoing-crises (last accessed 27.06.22). 2 Sara Ahmed, Queer Phenomenology, First Edition (Durham, NC: Duke University Press Books, 2006)

Consensus and experience trump leadership, suppressing individual personality during social foraging

Whether individual behavior in social settings correlates with behavior when individuals are alone is a fundamental question in collective behavior. However, evidence for whether behavior correlates across asocial and social settings is mixed, and no study has linked observed trends with underlying mechanisms. Consistent differences between individuals in boldness, which describes willingness to accept reward over risk, are likely to be under strong selection pressure. By testing three-spined sticklebacks (Gasterosteus aculeatus) in a risky foraging task alone and repeatedly in shoals, we demonstrate that the expression of boldness in groups is context-specific. Whereas personality is repeatable in a low-risk behavior (leaving a refuge), the collectively made consensus decision to then cross the arena outweighs leadership by bolder individuals, explaining the suppression of personality in this context. However, despite this social coordination, bolder individuals were still more likely to feed. Habituation and satiation over repeated trials degrade the effect of personality on leaving the refuge and also whether crossing the arena is a collective decision. The suppression of personality in groups suggests that individual risk-taking tendency may rarely represent actual risk in social settings, with implications for the evolution and ecology of personality variation

The word problem distinguishes counter languages

Counter automata are more powerful versions of finite state automata where addition and subtraction operations are permitted on a set of n integer registers, called counters. We show that the word problem of Zn is accepted by a nondeterministic m-counter automaton if and only if m >= n

Quantifying test–retest reliability of repeated objective attentional measures in Lewy body dementia

Objective cognitive impairment is a feature of Lewy body dementia (LBD), and computerised attentional tasks are commonly used as outcome measures in interventional trials. However, the reliability of these measures, in the absence of interventions, are unknown. This study examined the reliability of these attentional measures at short-term and longer-term follow-up stages. LBD patients (n = 36) completed computerised attentional tasks (Simple and Choice Reaction Time, and Digit Vigilance (SRT, CRT, DV)) at short-term (Day 0 – Day 5) and longer-term (4 and 12 weeks) follow-up. Intra-class correlations (ICCs) were calculated to assess test-retest reliability. At short-term, the reciprocal SRT, CRT and DV mean reaction time to correct answers, the reciprocal DV coefficient of variation, and reciprocal power of attention (PoA) all showed excellent levels of reliability (all ICCs > 0.90). The reciprocal PoA showed the highest level of reliability (ICC = 0.978). At longer-term follow-up, only the reciprocal PoA had excellent levels of reliability (ICC = 0.927). Reciprocal SRT, CRT and DV reaction time to correct answers, and the CRT coefficient of variation values, showed good levels of test-retest reliability (ICCs ≥ 0.85). Contrary to expectations, most attentional measures demonstrated high levels of test-retest reliability at both short-term and longer-term follow-up time points. The reciprocal PoA composite measure demonstrated excellent levels of test-retest reliability, both in the short-term and long-term. This indicates that objective attentional tasks are suitable outcome measures in LBD studies and that the composite PoA measure may offer the highest levels of reliability

The influence of hippocampal atrophy on the cognitive phenotype of dementia with Lewy bodies.

OBJECTIVE: The level of hippocampal atrophy in dementia with Lewy bodies (DLB) is typically less than that observed in Alzheimer's disease (AD). However, it is not known how the cognitive phenotype of DLB is influenced by hippocampal atrophy or the atrophy of adjacent medial temporal lobe structures. METHODS: Dementia with Lewy bodies (n = 65), AD (n = 76) and control (n = 63) participants underwent 3T magnetic resonance imaging and cognitive Cambridge Cognitive Examination and Mini-Mental State Examination (CAMCOG and MMSE) assessments. Hippocampal volume, and parahippocampal, entorhinal and temporal pole cortical thickness, was compared between groups. Regression models were used to investigate whether hippocampal volume and cortical thickness associated with global cognition and cognitive subdomains. RESULTS: Dementia with Lewy bodies, AD and control participants showed significantly different hippocampal, parahippocampal and entorhinal cortical thinning, where atrophy was greatest in AD and intermediate in DLB. Temporal pole thickness was reduced in DLB and AD compared with control participants. In DLB, but not AD, hippocampal volume associated with total CAMCOG, CAMCOG memory and MMSE scores. In DLB, parahippocampal, entorhinal and temporal pole thickness associated with total CAMCOG and CAMCOG memory scores, parahippocampal thickness associated with MMSE scores, and entorhinal thickness associated with CAMCOG executive function scores. CONCLUSIONS: In this large sample, these results are in agreement with other studies indicating that hippocampal atrophy is less severe in DLB than AD. Hippocampal atrophy and medial temporal lobe cortical thickness were associated with the severity of cognitive symptoms, suggesting that atrophy in these structures, as a potential proxy of AD pathology, may partly mediate specific DLB cognitive symptoms. © 2017 The Authors. International Journal of Geriatric Psychiatry Published by John Wiley & Sons Ltd.This research was supported by the following: Wellcome Trust Starter Grants scheme for Clinical Lecturers (BH090112 to J-P.T.); Wellcome Intermediate Clinical Fellowship (BH083281 to J-P. T.); the Sir Jules Thorn Charitable Trust (05/JTA) and by the National Institute of Health Research (NIHR) Newcastle Biomedical Research Unit based at Newcastle upon Tyne Hospitals NHS Foundation Trust and Newcastle University

A cryogenic rotation stage with a large clear aperture for the half-wave plates in the Spider instrument

We describe the cryogenic half-wave plate rotation mechanisms built for and used in Spider, a polarization-sensitive balloon-borne telescope array that observed the Cosmic Microwave Background at 95 GHz and 150 GHz during a stratospheric balloon flight from Antarctica in January 2015. The mechanisms operate at liquid helium temperature in flight. A three-point contact design keeps the mechanical bearings relatively small but allows for a large (305 mm) diameter clear aperture. A worm gear driven by a cryogenic stepper motor allows for precise positioning and prevents undesired rotation when the motors are depowered. A custom-built optical encoder system monitors the bearing angle to an absolute accuracy of +/- 0.1 degrees. The system performed well in Spider during its successful 16 day flight.Comment: 11 pages, 7 figures, Published in Review of Scientific Instruments. v2 includes reviewer changes and longer literature revie

Transcranial direct current stimulation in the treatment of visual hallucinations in Charles Bonnet syndrome: A randomized placebo-controlled crossover trial.

Objective To investigate the potential therapeutic benefits and tolerability of inhibitory transcranial direct current stimulation (tDCS) on the remediation of visual hallucinations in Charles Bonnet Syndrome (CBS). Design Randomized, double-masked(blind), placebo-controlled crossover trial. Participants Sixteen individuals diagnosed with CBS secondary to visual impairment caused by eye disease experiencing recurrent visual hallucinations. Intervention All participants received four consecutive days of active and placebo cathodal stimulation (current density: 0.29mA/cm2) to the visual cortex (Oz) over two defined treatment weeks, separated by a four-week wash-out period. Main Outcome Measures Ratings of visual hallucination frequency and duration following active and placebo stimulation, accounting for treatment order, using a 2x2 repeated measures model. Secondary outcomes included impact ratings of visual hallucinations and electrophysiological measures. Results When compared to placebo treatment, active inhibitory stimulation of visual cortex resulted in a significant reduction in the frequency of visual hallucinations measured by the North East Visual Hallucinations Interview, with a moderate-to-large effect size. Impact measures of visual hallucinations improved in both placebo and active conditions suggesting support and education for CBS may have therapeutic benefits. Participants who demonstrated greater occipital excitability on electroencephalography assessment at the start of treatment were more likely to report a positive treatment response. Stimulation was found to be tolerable in all participants with no significant adverse effects reported, including no deterioration in pre-existing visual impairment. Conclusions Findings indicate that inhibitory tDCS of visual cortex may reduce the frequency of visual hallucinations in people with CBS, particularly individuals who demonstrate greater occipital excitability prior to stimulation. tDCS may offer a feasible, novel intervention option for CBS with no significant side effects, warranting larger scale clinical trials to further characterize its efficacy