Adversarial Attacks on Time Series

Time series classification models have been garnering significant importance in the research community. However, not much research has been done on generating adversarial samples for these models. These adversarial samples can become a security concern. In this paper, we propose utilizing an adversarial transformation network (ATN) on a distilled model to attack various time series classification models. The proposed attack on the classification model utilizes a distilled model as a surrogate that mimics the behavior of the attacked classical time series classification models. Our proposed methodology is applied onto 1-Nearest Neighbor Dynamic Time Warping (1-NN ) DTW, a Fully Connected Network and a Fully Convolutional Network (FCN), all of which are trained on 42 University of California Riverside (UCR) datasets. In this paper, we show both models were susceptible to attacks on all 42 datasets. To the best of our knowledge, such an attack on time series classification models has never been done before. Finally, we recommend future researchers that develop time series classification models to incorporating adversarial data samples into their training data sets to improve resilience on adversarial samples and to consider model robustness as an evaluative metric.Comment: 13 pages, 7 figures, 6 table

Timage -- A Robust Time Series Classification Pipeline

Time series are series of values ordered by time. This kind of data can be found in many real world settings. Classifying time series is a difficult task and an active area of research. This paper investigates the use of transfer learning in Deep Neural Networks and a 2D representation of time series known as Recurrence Plots. In order to utilize the research done in the area of image classification, where Deep Neural Networks have achieved very good results, we use a Residual Neural Networks architecture known as ResNet. As preprocessing of time series is a major part of every time series classification pipeline, the method proposed simplifies this step and requires only few parameters. For the first time we propose a method for multi time series classification: Training a single network to classify all datasets in the archive with one network. We are among the first to evaluate the method on the latest 2018 release of the UCR archive, a well established time series classification benchmarking dataset.Comment: ICANN19, 28th International Conference on Artificial Neural Network

Low Viral Load Does Not Exclude Significant Liver Damage in Patients with Chronic HBV Infection in Bangladesh

Background: In general, it is assumed that patients with chronic hepatitis B virus (HBV) infection with high viral load exhibit increased liver damages. Accordingly, the treatment guidelines emphasize on reducing viral load in chronic HBV carriers. The ethical and scientific basis of these observations was mainly accumulated from investigations from developed countries of the world. More than 80% chronic HBV carriers live in the developing nations of the world, but little is known about relationship between HBV viral load and extent of liver damages in these countries. In this study, we addressed this issue to provide insights about this. Methods: In this retrospective study we reviewed the records of 210 chronic hepatitis B (CHB) patients from our pool of 561 Bangladeshi CHB patients. All of these 210 patients had low HBV DNA (<105 copies/ml by PCR). Of them 16 were HBeAg +ve and rest 194 HBeAg -ve. They have also been tested for other serologic markers of HBV (i.e. HBsAg, anti-HBe), HCV (i.e. anti-HCV) and serum alaninetransaminase (ALT) level. All patients also underwent per-cutaneous liver biopsy. Results: 37.5% (6/16) HBeAg +ve patients with low HBV DNA had significant hepatic necro-inflammation (HAI-NI ≥7), whereas this figure was 31.44% (61/194) in case of HBeAg -ve patients. On the other hand significant hepatic fibrosis (HAI-F ≥3) was observed in 31.25% (5/16) and 14.4% (28/194) in HBeAg +ve and -ve patients respectively. Conclusion: This study shows that a correlation could not be established between viral load and liver damage in patients with CHB in Bangladesh. A significant percentage of patients with low HBV DNA may have marked hepatic necro-inflammation and fibrosis, more so in case of HBeAg +ve CHB. Further study may be needed to find out the influence of other factors on liver damages in CHB patients in developing nations like Bangladesh, where about 8 million chronic HBV carriers are living. Most of these patients have not been characterized and treatment modalities have not been defined for them. Our study may suggest the research direction for management of these cases. Key Words: Low HBV DNA; Chronic hepatitis B; Hepatic necro-inflammation; Hepatic fibrosis.DOI: 10.3329/bsmmuj.v1i1.3693 BSMMU J 2008; 1(1): 19-2

Abdominal cystic echinococcosis in Bangladesh: a hospital-based study

Introduction: Cystic echinococcosis (CE) is reported from nearly all geographic areas of Bangladesh, but little information is available on its epidemiologic and clinical features. The aim of this study was to describe the clinical manifestations of hepatic and abdominal CE cases presenting to tertiary referral hospitals in Dhaka, Bangladesh. Methodology: A retrospective study was conducted via chart reviews of hepatic and abdominal CE patients under care at tertiary referral hospitals in Dhaka, Bangladesh, between 2002 and 2011. Age, sex, education level, occupation, urban versus rural residence, drinking water source, history of dog ownership, cyst type and location, and clinical manifestations were recorded for all patients. Results: Of the 130 patients enrolled, 92 (70.8%) were female and 38 (29.2%) were male. The majority of patients were from rural (76.2%) rather than urban (23.8%) areas. All cases were from the northern part of the country, with no cases reported from the south or southeast. Most patients were between 21 and 40 years of age. A total of 119 patients (91.5%) had cysts only in the liver, with the remaining 8.5% having cysts in both the liver and lungs or in the abdominal cavity. Seventy-six (58.5%) of the hepatic cysts were stage CE1, indicating recent infection. Conclusions: Active transmission of Echinococcus granulosus appears to be occurring in Bangladesh, as indicated by the high number of CE1 hepatic cysts seen at tertiary care hospitals. Community ultrasound screening studies are warranted to better define the distribution of cases and risk factors for parasite transmission

Accurate Time Series Classification Using Deep Learning and Partial Observations

Over the past decade, there has been a significant increase in interest in classifying time series data. Typically, there are two objectives of classifying time series data, efficiency (speed) and effectiveness (accuracy). In this dissertation, we propose a framework to detect optimal partial observations to classify time series data. Further, we propose a few deep learning architectures to improve the classification accuracy of univariate and multivariate time series data. Finally, we present an architecture that successfully generates adversarial samples on a couple of time series classification models. These adversaries possess a security concern and would require further research to defend against

Autoimmune hepatitis showing spontaneous remission and acute exacerbation

ABSTRACTAutoimmune hepatitis (AIH) represents a chronic liver disease with a progressive nature. Cortocosteroid therapy is routinely used to control this pathological condition. Herein, we describe a case of AIH with spontaneous remission and exacerbation. A previously healthy young Japanese woman presented with features of acute hepatitis. The patient was not acutely infected with hepatotrophic viruses and the possibility of drug-induced AIH was also excluded. A diagnosis of AIH was made from subjective symptoms and laboratory data, which showed increased levels of liver enzymes, total bilirubin, IgG and positive titers of antinuclear antibody. Finally, liver biopsy revealed an expansion of portal tracts and infiltration of mononuclear cells, including plasma cells. This patient experienced a total of three episodes of acute exacerbation of AIH during the past 5 years, two of which subsided spontaneously. An immunosuppressive drug was used to control the last episode of acute exacerbation of AIH, which was very similar to acute hepatitis. The immunosuppressive drug was withdrawn 7 months after the last epoisode of acute exacerbation of AIH and the patient is now passing an uneventful course. There are cases of spontaneous remission and acute exacerbation of AIH, although the underlying mechanism of this pathological process is yet to be determined. Liver biopsy is needed to diagnose these cases. Periodic follow up of these patients is required for proper management