Collaborative Learning of Stochastic Bandits over a Social Network

We consider a collaborative online learning paradigm, wherein a group of agents connected through a social network are engaged in playing a stochastic multi-armed bandit game. Each time an agent takes an action, the corresponding reward is instantaneously observed by the agent, as well as its neighbours in the social network. We perform a regret analysis of various policies in this collaborative learning setting. A key finding of this paper is that natural extensions of widely-studied single agent learning policies to the network setting need not perform well in terms of regret. In particular, we identify a class of non-altruistic and individually consistent policies, and argue by deriving regret lower bounds that they are liable to suffer a large regret in the networked setting. We also show that the learning performance can be substantially improved if the agents exploit the structure of the network, and develop a simple learning algorithm based on dominating sets of the network. Specifically, we first consider a star network, which is a common motif in hierarchical social networks, and show analytically that the hub agent can be used as an information sink to expedite learning and improve the overall regret. We also derive networkwide regret bounds for the algorithm applied to general networks. We conduct numerical experiments on a variety of networks to corroborate our analytical results.Comment: 14 Pages, 6 Figure

Epidemic Spreading with External Agents

We study epidemic spreading processes in large networks, when the spread is assisted by a small number of external agents: infection sources with bounded spreading power, but whose movement is unrestricted vis-\`a-vis the underlying network topology. For networks which are `spatially constrained', we show that the spread of infection can be significantly speeded up even by a few such external agents infecting randomly. Moreover, for general networks, we derive upper-bounds on the order of the spreading time achieved by certain simple (random/greedy) external-spreading policies. Conversely, for certain common classes of networks such as line graphs, grids and random geometric graphs, we also derive lower bounds on the order of the spreading time over all (potentially network-state aware and adversarial) external-spreading policies; these adversarial lower bounds match (up to logarithmic factors) the spreading time achieved by an external agent with a random spreading policy. This demonstrates that random, state-oblivious infection-spreading by an external agent is in fact order-wise optimal for spreading in such spatially constrained networks

A retrospective study to assess prevalence of gestational diabetes mellitus among those who delivered in Saveetha Medical College and Hospital

Background: Gestational diabetes mellitus (GDM) defined as any degree of carbohydrate intolerance with onset or first recognition during pregnancy contributes to about 90% of diabetes complicating pregnancy. GDM imposes risks for both mother and fetus, some of which continues throughout the life of mother and child. The objective of the present study was to determine the prevalence of gestational diabetes mellitus and the associated risk factors among those who delivered in Saveetha medical college and hospital.Methods: A retrospective study was conducted by analysing the medical records of the patients who were admitted in the Department of Obstetrics and Gynaecology over a period of 1 year at Saveetha medical college and hospital, Chennai, Tamil Nadu, India. The diagnosis of GDM was made mainly by 75gm one step oral glucose tolerance test (OGTT). The guideline endorses 2-hours 75-gm OGTT, irrespective of last meal timings with a cut off value of ≥140 mg/dl. All data was analysed by simple descriptive statistics and percentage method.Results: In the present study, the total number of deliveries for 1 year from April 2018 - March 2019 were 511 and among those the total number of antenatal mothers with GDM who delivered were 46. Therefore the prevalence of GDM was calculated to be 9% or 90 per thousand deliveries. In the present study, 37 (65.1%) pregnant women of GDM group were seen in the age group of above 25 years, 27 (58.59%) were multiparous, 25(54.25%) pregnant females with GDM were found to have overweight and obese out of 46 cases.Conclusions: Our current study concludes the Prevalence of GDM in Saveetha Medical College Hospital is 9% between April 2018-March 2019. We have identified the following risk factors for developing GDM: multiparity≥2; previous history of diabetes mellitus; age ≥ 25; BMI ≥25; and family history of diabetes

Stress Redistribution Near a Crack in Maraging Steel using Composite Patch

The presence of a crack significantly reduces the load bearing capacity of a structure made of fracture prone material. The conventional process of repairing a defect is gouging and filling the gouged location by rewelding. It is not only time consuming but also constrained by the number of repairs that can be done as material properties degrade with each round of rewelding. In an attempt to overcome the limitation of the conventional repair process, repairing a defect using composite patch is proposed. The study is carried out on Maraging steel (M250) and the defect considered is a crack. Stress intensity factor (SIF), being an important parameter in fracture-based design, it is evaluated in Abaqus. Extended finite element method is used to model the crack. SIF is used to predict the failure load of a surface cracked tension specimen and the same is compared with the values reported in literature. Composite patch is modelled using woven ply properties. A separate layer of adhesive is also modelled to predict the properties adhesive properties. Failure analysis of each component namely, the Maraging steel plate, the composite patch and the adhesive is carried.  It was observed that the addition of a composite patch completely nullifies the presence of a crack. The patch with thickness 1mm and woven ply properties is having minimal damage initiation and likely to survive. The adhesive properties required is also obtained from the finite element analysis.  Thus, it was observed that a composite patch with woven ply properties and thickness 1mm is able to completely nullify the effect of a crack when bonded with a suitable adhesive as predicted by the analysis

Age of the Lower Vindhyan sediments, Central India

The basic issue raised by the two simultaneous and sensational reports in 1998 of body fossil evidence (worm tracks and small shelly fauna, respectively) of multicellular life in the Lower Vindhyan sediments, is the true age of the latter. Is the true age Mid-Proterozoic as believed so far, on limited geochronological data and assumed by Seilacher et al.? Or is it only Early Cambrian, as was argued by Azmi and supported by a single preliminary Ar-Ar age of 617 Ma measured soon after the reports? Although both the fossil evidences are now equivocal, the basic issue remains. We report consistent Rb-Sr ages for glauconies from the Lower Vindhyan sediments (Semri Group) near Chitrakut, which constrain the onset of the earliest Vindhyan sedimentation to not later than 1600 Ma. Considering other available chronological constraints, the Vindhyan basin is likely to preserve a rare, very long and least disturbed record of Pre-cambrian sedimentation

Towards Protecting Critical National Assets and Preparedness for Response to Hazardous Chemical, Biological and Radiological Attacks

Hazardous chemical, biological and radiological (CBR) materials are catching attention of unscrupulous actors for creating terror and havoc. Threat perception for use of such materials by terrorists and non-state actors for malicious purposes, is not imaginative but real and imminent in today’s context. World has witnessed a number of such incidences in the recent years, e.g., Mustard gas attack against Kurdish forces in Iraq; ricin laced letters sent to US President and others senators; use of Nerve gas agents in Syria; capturing of Uranium from University of al- Mousal, Iraq by IS, etc. National assets like critical buildings where main legislative, historical building, Hospitals are some of the likely targets for CBR attacks attract quick coverage by media. Authorities related with managing and safeguarding mechanisms of the facilities to prevent such events happening also to enhance their capabilities as well as effective response. Essential CBR security should include measures to rapidly detect and effectively deter the CBR incidences their deleterious consequences. In this review, protection of the critical facilities from CBR attacks and capacity in terms of infrastructure, specialised training and mutual aid have been discussed

Effect of a behaviour-change intervention on handwashing with soap in India (SuperAmma): a cluster-randomised trial.

BACKGROUND: Diarrhoea and respiratory infections are the two biggest causes of child death globally. Handwashing with soap could substantially reduce diarrhoea and respiratory infections, but prevalence of adequate handwashing is low. We tested whether a scalable village-level intervention based on emotional drivers of behaviour, rather than knowledge, could improve handwashing behaviour in rural India. METHODS: The study was done in Chittoor district in southern Andhra Pradesh, India, between May 24, 2011, and Sept 10, 2012. Eligible villages had a population of 700-2000 people, a state-run primary school for children aged 8-13 years, and a preschool for children younger than 5 years. 14 villages (clusters) were selected, stratified by population size (1200), and randomly assigned in a 1:1 ratio to intervention or control (no intervention). Clusters were enrolled by the study manager. Random allocation was done by the study statistician using a random number generator. The intervention included community and school-based events incorporating an animated film, skits, and public pledging ceremonies. Outcomes were measured by direct observation in 20-25 households per village at baseline and at three follow-up visits (6 weeks, 6 months, and 12 months after the intervention). Observers had no connection with the intervention and observers and participant households were told that the study was about domestic water use to reduce the risk of bias. No other masking was possible. The primary outcome was the proportion of handwashing with soap at key events (after defecation, after cleaning a child's bottom, before food preparation, and before eating) at all follow-up visits. The control villages received a shortened version of the intervention before the final follow-up round. Outcome data are presented as village-level means. FINDINGS: Handwashing with soap at key events was rare at baseline in both the intervention and control groups (1% [SD 1] vs 2% [1]). At 6 weeks' follow-up, handwashing with soap at key events was more common in the intervention group than in the control group (19% [SD 21] vs 4% [2]; difference 15%, p=0·005). At the 6-month follow-up visit, the proportion handwashing with soap was 37% (SD 7) in the intervention group versus 6% (3) in the control group (difference 31%; p=0·02). At the 12-month follow-up visit, after the control villages had received the shortened intervention, the proportion handwashing with soap was 29% (SD 9) in the intervention group and 29% (13) in the control group. INTERPRETATION: This study shows that substantial increases in handwashing with soap can be achieved using a scalable intervention based on emotional drivers. FUNDING: Wellcome Trust, SHARE

A rare diagnosis with a common presentation: a case report on uterine sarcoma

Uterine sarcomas are rare soft tissue tumors which constitute 3% to 7% of overall uterine malignancies. Endometrial stromal sarcoma (ESS) is a rare type of uterine sarcoma arising from the mesodermal component of the body of the uterus. It constitutes around 0.2% of all the uterine tumors. It primarily occurs in perimenopausal women. One third of cases are seen in postmenopausal women. The presentation is not very different from an abnormal uterine bleeding, abdominal pain or a mass effect. Here we discuss an interesting case of 70 years female with a very common presentation of utero-vaginal prolapse but turned out to be a very rare postoperative diagnosis of uterine sarcoma