BoostNet: Bootstrapping detection of socialbots, and a case study from Guatemala

We present a method to reconstruct networks of socialbots given minimal input. Then we use Kernel Density Estimates of Botometer scores from 47,000 social networking accounts to find clusters of automated accounts, discovering over 5,000 socialbots. This statistical and data driven approach allows for inference of thresholds for socialbot detection, as illustrated in a case study we present from Guatemala.Comment: 7 pages, 4 figure

Transition to farming more likely for small, conservative groups with property rights, but increased productivity is not essential

Theories for the origins of agriculture are still debated, with a range of different explanations offered. Computational models can be used to test these theories and explore new hypotheses; Bowles and Choi [Bowles S, Choi J-K (2013) Proc Natl Acad Sci USA 110(22):8830–8835] have developed one such model. Their model shows the coevolution of farming and farming-friendly property rights, and by including climate variability, replicates the timings for the emergence of these events seen in the archaeological record. Because the processes modeled occurred a long time ago, it can be difficult to justify exact parameter values; hence, we propose a fitting to idealized outcomes (FIO) method to explore the model’s parameter space in more detail. We have replicated the model of Bowles and Choi, and used the FIO method to identify complexities and interactions of the model previously unidentified. Our results indicate that the key parameters for the emergence of farming are group structuring, group size, conservatism, and farming-friendly property rights (lending further support to Bowles and Choi’s original proposal). We also find that although advantageous, it is not essential that farming productivity be greater than foraging productivity for farming to emerge. In addition, we highlight how model behaviors can be missed when gauging parameter sensitivity via a fix-all-but-one variation approach

Northern Ireland's Property Market Crisis: Insights from Minsky’s Financial Instability Hypothesis

The financial crisis of 2007 has shown that standard mainstream macroeconomic models underpinned by general equilibrium theory fail to anticipate, explain and provide guidance on how to respond to such events (Stiglitz, 2011). Evidence in the Northern Ireland context has further suggested that applying these models to property markets may be inappropriate given the underlying statistical properties of these time series (Gallagher et al., 2015). These issues combined suggest that there may be merit in examining cases of financial crises through alternative theoretical frameworks and in adopting a more pluralist approach. With this in mind, this paper investigates whether Minsky’s (1975, 1986, 1992) Financial Instability Hypothesis can assist in understanding the recent property market crisis in Northern Ireland, which was severe by both national and international standards. Using qualitative evidence to analyse the behaviours of borrowers represented by property developers and lenders represented by banks over the course of the business cycle, this paper assesses the relevance of Minsky’s arguments. The findings show that Minsky’s Financial Instability Hypothesis explains the incidents observed in NI’s property market in recent years

Evolutionary Models for the Origins of Agriculture

The transition from hunting and gathering to farming at the end of the Pleistocene was one of the most important events in human history, having major impacts on human demography, evolution, health, culture, technology, and social stratification. The reasons why some societies switched to farming are still debated, with climate stabilisation and population pressure as popular hypotheses. However, since these processes occurred so long ago, investigating the transition can be difficult without the use of mathematical models. In this thesis I investigate the effect of various factors, including population size, conservatism, property rights, environmental conditions, climate variability, and mobility, on the transition to farming using evolutionary models. I do this by implementing an intensive parameter sensitivity analysis method on an existing game theoretical model (Bowles and Choi, 2013) for the origins of agriculture, and also develop and explore my own agent-based models of social and environmental interactions. Using the Bowles and Choi model, I find that the key parameters for the emergence of farming are group structuring, group size, conservatism, and farming-friendly property rights. The analysis of this model also shows that although advantageous, it is not essential for the emergence of farming for farming productivity to be greater than foraging productivity. In the development of my own model, I first consider mobility changes in a forager population, and find that low depletion and high growth rates can lead to reduced mobility, low fitness, and high population density. When I add subsistence behaviours to the model I find that three behaviours can evolve in response to different environmental conditions; mobile foraging, sedentary foraging, and sedentary farming. I also find a relationship between reduced mobility, the emergence of farming, decreased fitness and high population densities. Additionally, my model predicts that population pressure was caused by, but not causal of, the switch to farming. Importantly, these results concur with the observed archaeological data and ethnographic record, and highlight the value of using modelling to validate and/or challenge observed data

Potential use of oxygen as a metabolic biosensor in combination with T2*-weighted MRI to define the ischemic penumbra

We describe a novel magnetic resonance imaging technique for detecting metabolism indirectly through changes in oxyhemoglobin:deoxyhemoglobin ratios and T2* signal change during ‘oxygen challenge’ (OC, 5 mins 100% O2). During OC, T2* increase reflects O2 binding to deoxyhemoglobin, which is formed when metabolizing tissues take up oxygen. Here OC has been applied to identify tissue metabolism within the ischemic brain. Permanent middle cerebral artery occlusion was induced in rats. In series 1 scanning (n=5), diffusion-weighted imaging (DWI) was performed, followed by echo-planar T2* acquired during OC and perfusion-weighted imaging (PWI, arterial spin labeling). Oxygen challenge induced a T2* signal increase of 1.8%, 3.7%, and 0.24% in the contralateral cortex, ipsilateral cortex within the PWI/DWI mismatch zone, and ischemic core, respectively. T2* and apparent diffusion coefficient (ADC) map coregistration revealed that the T2* signal increase extended into the ADC lesion (3.4%). In series 2 (n=5), FLASH T2* and ADC maps coregistered with histology revealed a T2* signal increase of 4.9% in the histologically defined border zone (55% normal neuronal morphology, located within the ADC lesion boundary) compared with a 0.7% increase in the cortical ischemic core (92% neuronal ischemic cell change, core ADC lesion). Oxygen challenge has potential clinical utility and, by distinguishing metabolically active and inactive tissues within hypoperfused regions, could provide a more precise assessment of penumbra

Vigorous star formation hidden by dust in a galaxy at z=1.4z=1.4

Near-infrared surveys have revealed a substantial population of enigmatic faint galaxies with extremely red optical-to-near-infrared colours and with a sky surface density comparable to that of faint quasars. There are two scenarios for these extreme colours: (i) these distant galaxies have formed virtually all their stars at very high redshifts and, due to the absence of recently formed stars, the colours are extremely red and (ii) these distant galaxies contain large amounts of dust, severely reddening the rest-frame UV--optical spectrum. HR10 ($z = 1.44$) is considered the archetype of the extremely red galaxies. Here we report the detection of the continuum emission from HR10 at 850$\mu$m and at 1250$\mu$m, demonstrating that HR10 is a very dusty galaxy undergoing a major episode of star formation. Our result provides a clear example of a high-redshift galaxy where the star formation rate inferred from the ultraviolet luminosity would be underestimated by a factor up to 1000, and shows that great caution should be used to infer the global star formation history of the Universe from optical observations only.Comment: 12 pages, 1 figure, Nature, in press (30 April 1998

Patient expectations of fair complaint handling in hospitals: empirical data

BACKGROUND: A common finding in several studies is patients' dissatisfaction with complaint handling in health care. The reasons why are for the greater part unknown. The key to an answer may be found in a better understanding of patients' expectations. We investigated patients' expectations of complaint handling in hospitals. METHODS: Subjects were patients who had lodged a complaint at the complaint committees of 74 hospitals in the Netherlands. A total of 424 patients (response 75%) completed a written questionnaire at the start of the complaint procedures. Derived from justice theory, we asked what they expected from fair procedures, fair communication and fair outcome of complaint handling. RESULTS: The predominant reason for complainants to lodge a complaint was to prevent the incident from happening again. Complainants expected fair procedures from the complaint committee, in particular an impartial position. This was most important to 87% of the complainants. They also expected to be treated respectfully. Furthermore, they expected the hospital and the professional involved to respond to their complaint. A change in hospital performances was the most wanted outcome of complaint handling, according to 79% of the complainants. They also expected disclosure from the professionals. Professionals should admit a mistake when it had occurred. More complainants (65%) considered it most important to get an explanation than an apology (41%). Only 32% of complainants expected the professional to make an effort to restore the doctor-patient relationship. A minority of complainants (7%) wanted financial compensation. CONCLUSION: Nearly all complainants want to prevent the incident from happening again, not out of pure altruism, but in order to restore their sense of justice. We conclude that complaint handling that does not allow for change is unlikely to meet patients' expectations. Secondly, complaint handling should not be left exclusively to complaint committees, the responses of hospital and professionals are indispensable

Construct and face validity of SINERGIA laparoscopic virtual reality simulator

Purpose Laparoscopic techniques have nowadays become a gold standard in many surgical procedures, but they imply a more difficult learning skills process. Simulators have a fundamental role in the formative stage of new surgeons. This paper presents the construct and face validity of SINERGIA laparoscopic virtual reality simulator in order to decide whether it can be considered as an assessment tool. Methods Twenty people participated in this study, 14 were novices and 6 were experts. Five tasks of SINERGIA were included in the study: coordination, navigation, navigation and touch, precise grasping and coordinate traction. For each one of these tasks, a certain number of metrics are automatically recorded. All subjects accomplished each task only once and filled in two questionnaires. A statistical analysis was made and results from both groups were compared with the Mann–Whitney U-test, considering significant differences when P ≤ 0.05. Internal consistency of the system has been analyzed with the Cronbach’s alpha test. Results Novices and experts positively rated SINERGIA characteristics. At least one of the evaluated metrics of each exercise presented significant differences between both groups. Nevertheless, all metrics under study gave a better punctuation to the executions accomplished by experts (lower time, higher efficiency, fewer errors. . .) than to those made by novices. Conclusion SINERGIA laparoscopic virtual reality simulator is able to discriminate subjects according to their level of experience in laparoscopic surgery; therefore, it can be used within a training program as an assessment too

Prospective study evaluating the relative sensitivity of 18F-NaF PET/CT for detecting skeletal metastases from renal cell carcinoma in comparison to multidetector CT and 99mTc-MDP bone scintigraphy, using an adaptive trial design.

BACKGROUND: The detection of occult bone metastases is a key factor in determining the management of patients with renal cell carcinoma (RCC), especially when curative surgery is considered. This prospective study assessed the sensitivity of (18)F-labelled sodium fluoride in conjunction with positron emission tomography/computed tomography ((18)F-NaF PET/CT) for detecting RCC bone metastases, compared with conventional imaging by bone scintigraphy or CT. PATIENTS AND METHODS: An adaptive two-stage trial design was utilized, which was stopped after the first stage due to statistical efficacy. Ten patients with stage IV RCC and bone metastases were imaged with (18)F-NaF PET/CT and (99m)Tc-labelled methylene diphosphonate ((99m)Tc-MDP) bone scintigraphy including pelvic single photon emission computed tomography (SPECT). Images were reported independently by experienced radiologists and nuclear medicine physicians using a 5-point scoring system. RESULTS: Seventy-seven lesions were diagnosed as malignant: 100% were identified by (18)F-NaF PET/CT, 46% by CT and 29% by bone scintigraphy/SPECT. Standard-of-care imaging with CT and bone scintigraphy identified 65% of the metastases reported by (18)F-NaF PET/CT. On an individual patient basis, (18)F-NaF PET/CT detected more RCC metastases than (99m)Tc-MDP bone scintigraphy/SPECT or CT alone (P = 0.007). The metabolic volumes, mean and maximum standardized uptake values (SUV mean and SUV max) of the malignant lesions were significantly greater than those of the benign lesions (P < 0.001). CONCLUSIONS: (18)F-NaF PET/CT is significantly more sensitive at detecting RCC skeletal metastases than conventional bone scintigraphy or CT. The detection of occult bone metastases could greatly alter patient management, particularly in the context when standard-of-care imaging is negative for skeletal metastases.This work was supported by Cancer Research UK [grant number C19212/A16628]. The authors also received research support from the National Institute of Health Research Cambridge Biomedical Research Centre, Engineering and Physical Sciences Research Council Imaging Centre in Cambridge and Manchester, and the Cambridge Experimental Cancer Medicine Centre. The research has also been partly funded by a generous donation from the family and friends of a patient.This is the final version of the article. It first appeared from Oxford University Press via http://dx.doi.org/10.1093/annonc/mdv28

Removing rician bias in diffusional kurtosis of the prostate using real-data reconstruction.

Purpose To compare prostate diffusional kurtosis imaging (DKI) metrics generated using phase-corrected real data with those generated using magnitude data with and without noise compensation (NC).Methods Diffusion-weighted images were acquired at 3T in 16 prostate cancer patients, measuring 6 b-values (0-1500 s/mm2 ), each acquired with 6 signal averages along 3 diffusion directions, with noise-only images acquired to allow NC. In addition to conventional magnitude averaging, phase-corrected real data were averaged in an attempt to reduce rician noise-bias, with a range of phase-correction low-pass filter (LPF) sizes (8-128 pixels) tested. Each method was also tested using simulations. Pixelwise maps of apparent diffusion (D) and apparent kurtosis (K) were calculated for magnitude data with and without NC and phase-corrected real data. Average values were compared in tumor, normal transition zone (NTZ), and normal peripheral zone (NPZ).Results Simulations indicated LPF size can strongly affect K metrics, where 64-pixel LPFs produced accurate metrics. Relative to metrics estimated from magnitude data without NC, median NC K were lower (P < 0.0001) by 6/11/8% in tumor/NPZ/NTZ, 64-LPF real-data K were lower (P < 0.0001) by 4/10/7%, respectively.Conclusion Compared with magnitude data with NC, phase-corrected real data can produce similar K, although the choice of phase-correction LPF should be chosen carefully