Efficient Optimization for Rank-based Loss Functions

The accuracy of information retrieval systems is often measured using complex loss functions such as the average precision (AP) or the normalized discounted cumulative gain (NDCG). Given a set of positive and negative samples, the parameters of a retrieval system can be estimated by minimizing these loss functions. However, the non-differentiability and non-decomposability of these loss functions does not allow for simple gradient based optimization algorithms. This issue is generally circumvented by either optimizing a structured hinge-loss upper bound to the loss function or by using asymptotic methods like the direct-loss minimization framework. Yet, the high computational complexity of loss-augmented inference, which is necessary for both the frameworks, prohibits its use in large training data sets. To alleviate this deficiency, we present a novel quicksort flavored algorithm for a large class of non-decomposable loss functions. We provide a complete characterization of the loss functions that are amenable to our algorithm, and show that it includes both AP and NDCG based loss functions. Furthermore, we prove that no comparison based algorithm can improve upon the computational complexity of our approach asymptotically. We demonstrate the effectiveness of our approach in the context of optimizing the structured hinge loss upper bound of AP and NDCG loss for learning models for a variety of vision tasks. We show that our approach provides significantly better results than simpler decomposable loss functions, while requiring a comparable training time.Comment: 15 pages, 2 figure

Intermittency analysis of high-lift airfoil with slat cove fillers

Experimental measurements were carried out to assess the aeroacoustic characteristics of 30P30N airfoil fitted with two different types of slat cove fillers at the aeroacoustic facility at the University of Bristol. The results are presented for the angle of attack α = 18◦ at a free-stream velocity of U∞ = 30 m/s which corresponds to a chord-based Reynolds number of Rec = 7 × 10◦ . Simultaneous measurements of the unsteady surface pressure were made at several locations in the vicinity of slat cove and at the far-field location to gain a deeper understanding of the slat noise generation mechanism. The results are analyzed using a higher-order statistical approach to determine the nature of the broadband hump seen at low-frequency for the 30P30N high-lift airfoil observed in recent studies and also to further understand the tone generation mechanism within the slat cavity. A series of cross-correlation and coherence of the unsteady pressure measurements are carried out to identify and isolate the low-frequency hump. Wavelet analysis is performed to investigate the nature of the slat-wing resonant intermittent events in both time and frequency domains. The far-field noise measurement results showed that significant noise reduction can be achieved by the use of slat cove fillers. A series of far-field and near-field correlation are also presented to show the propagated noise from the slat.5s

Transportation of lymph node biopsy specimens in selective Kirchner’s liquid medium for culture of tubercle bacilli

Lymph node biopsy specimens, obtained from 297 paediatric and adult patients with tuberculous lymphadenitis at Madurai, were transported in selective Kirchner’s liquid medium (KL-T) to the Tuberculosis Research Centre, Madras and processed for culture. Mycobucterium tuberculosis was isolated from 201 (68%) specimens. Of the 192 specimens received within 4 days of resection, 134 (69.8%) yielded M. tuberculosis on culture and of the 105 specimens received after 5 days, 67 (63.8%) were culture positive; the difference was not statistically significant. By incubating KL-T alone further, after removing the gland for processing, it was found that mere contact with the excised node during transportation was enough to retrieve 77 (38.3%) of the total of 201 positive isolates obtained, the delay did not affect the culture positivity rate. Thus, lymph node specimens for culture of tubercle bacilli can be stored in the refrigerator for up to 15 days and transported in KL-T at ambient temperature for 18-20 h without any loss in culture positivity

Has My Algorithm Succeeded? An Evaluator for Human Pose Estimators

Abstract. Most current vision algorithms deliver their output ‘as is’, without indicating whether it is correct or not. In this paper we propose evaluator algorithms that predict if a vision algorithm has succeeded. We illustrate this idea for the case of Human Pose Estimation (HPE). We describe the stages required to learn and test an evaluator, including the use of an annotated ground truth dataset for training and testing the evaluator (and we provide a new dataset for the HPE case), and the development of auxiliary features that have not been used by the (HPE) algorithm, but can be learnt by the evaluator to predict if the output is correct or not. Then an evaluator is built for each of four recently developed HPE algorithms using their publicly available implementations: Eichner and Ferrari [5], Sapp et al. [16], Andriluka et al. [2] and Yang and Ramanan [22]. We demonstrate that in each case the evaluator is able to predict if the algorithm has correctly estimated the pose or not.

Variability in stratification and flushing times of the Gautami–Godavari estuary, India

In order to examine the influence of forcing (river flow and tides) and anthropogenic activities (dredging and dam regulation) on stratification, a study was conducted over a period of 19 months (June 2008–December 2009) in the Gautami–Godavari estuary (G–GE) during spring and neap tide periods covering entire spectrum of discharge over a distance of 36 km from the mouth. The bathymetry of the estuary was recently changed due to dredging of ∼20 km of the estuary from the mouth for transportation of barges. This significantly changed the mean depth and salinity of the estuary from its earlier state. The variations in the distribution of salinity in the Godavari estuary are driven by river discharge during wet period (June–November) and tides during dry period (December–May). The weak stratification was observed during high discharge (July–August) and no discharge (January–June) periods associated with dominant fresh water and marine water respectively. The strong stratification was developed associated with decrease in discharge during moderate discharge period (October–December). Relatively stronger stratification was noticed during neap than spring tides. The 15 psu isohaline was observed to have migrated ∼2–3 km more towards upper estuary during spring than neap tide suggesting more salt enters during former than latter period. Total salt content was inversely correlated with river discharge and higher salt of about 400×106 m3 psu was observed during spring than neap tide. Flushing times varied between less than a day and more than a month during peak and no discharge periods respectively with lower times during spring than neap tide. The flushing times are controlled by river discharge during high discharge period, tides during dry period and both (river discharge and tides) under moderate discharge period. This study suggests that modification of discharge, either natural due to weak monsoon or artificial such as dam constructions and re-routing the river flow, may have significant impact on the stratification and biogeochemistry of the Godavari estuary

Распространенность инфекции HPV/p16+ среди пациентов с орофарингеальной плоскоклеточной карциномой в центре высокоспециализированной медицинской помощи в Южной Индии

Introduction. Oropharyngeal squamous cell carcinomas are often found to be associated with human papilloma virus (HPV) infection. The prevalence of HPV infection among oropharyngeal squamous cell carcinomas patients in India is comparatively lower to that of the same worldwide. Aim. To find out the prevalence of HPV infection among oropharyngeal squamous cell carcinomas patients who presented in our hospital.Settings and design. Retrospective cross-sectional study.Materials and methods. Tissue block of 60 patients with biopsy-proven oropharyngeal squamous cell carcinomas were subjected to immunohistochemistry for evaluating p16 expression. The p16 expression pattern was correlated with the demographic details. Data was entered in Microsoft Excel and Statistical Analysis was done with the help of SPSS version 22 (IBM Corp. Released, 2013. IBM SPSS Statistics for Windows, Version 22.0. Armonk, NY: IBM Corp.).Results. Prevalence of HPV infection in our study was found to be 11.7 %. 85.8 % of all p16-positive patients had moderate-well differentiated disease. 6 out of 7 p16-positive patients had higher T stage (T3–4). All the patients who were p16+ were found to have a higher Nodal stage (N2–3). 100 % of all p16+ patients were found to have stage IV disease.Conclusion. Prevalence of HPV infection was found to be similar to that of previous studies conducted in India. These patients also presented with advanced nodal disease at presentation and thereby, an advanced overall stage.Введение. Орофарингеальная плоскоклеточная карцинома часто связана с заражением вирусом папилломы человека (ВпЧ). Распространенность инфекции ВпЧ среди пациентов с данной патологией в Индии сравнительно ниже, чем в других странах.Цель исследования – определить распространенность инфекции ВпЧ среди пациентов с орофарингеальной плоскоклеточной карциномой, получавших лечение в нашей больнице.Дизайн исследования. Ретроспективное одномоментное исследование.Материалы и методы. Образцы тканей 60 пациентов с подтвержденным биопсией диагнозом «орофарингеальная плоскоклеточная карцинома» были исследованы иммуногистохимически на экспрессию p16. Было проведено сравнение профиля экспрессии p16 с демографическими данными. полученные результаты оценены с помощью программы Microsoft Excel. Статистический анализ выполнен с использованием программного обеспечения SPSS version 22 (IBM Corp. Released, 2013. IBM SPSS Statistics для Windows, версия 22.0, Армонк, Нью-Йорк: IBM Corp.).Результаты. Частота встречаемости ВпЧ в нашем исследовании составила 11,7 %. Среднеи высокодифференцированное заболевание наблюдалось у 85,8 % пациентов с положительной экспрессией p16. Шесть из 7 больных с такой экспрессией p16 имели более высокую T-стадию (T3–4), а все больные с таким показателем – высокую N-стадию (N2–3). У всех пациентов с положительной экспрессией p16 наблюдалось заболевание стадии IV.Заключение. Распространенность инфекции ВпЧ была близкой к значениям, полученным в других исследованиях в Индии. Для пациентов с этой инфекцией также были характерны вовлеченность лимфатических узлов (N-стадия) в патологический процесс и более высокая общая стадия заболевания