ONLINE LEARNING WITH BANDITS FOR COVERAGE

With the rapid growth in velocity and volume, streaming data compels decision support systems to predict a small number of unique data points in due time that can represent a massive amount of correlated data without much loss of precision. In this work, we formulate this problem as the {\it online set coverage problem} and propose its solution for recommendation systems and the patrol assignment problem. We propose a novel online reinforcement learning algorithm inspired by the Multi-Armed Bandit problem to solve the online recommendation system problem. We introduce a graph-based mechanism to improve the user coverage by recommended items and show that the mechanism can facilitate the coordination between bandits and therefore, reduce the overall complexity. Our graph-based bandit algorithm can select a much smaller set of items to cover a vast variety of users’ choices for recommendation systems. We present our experimental results in a partially observable real-world environment. We also study the patrol assignment as an online set coverage problem, which presents an additional level of difficulty. Along with covering the susceptible routes by learning the diversity of attacks, unlike in recommendation systems, our technique needs to make choices against actively engaging adversarial opponents. We assume that attacks over those routes are posed by intelligent entities, capable of reacting with their best responses. Therefore, to model such attacks, we used the Stackelberg Security Game. We augment our graph-based bandit defenders with adaptive adjustment of reward coming from this game to perplex the attackers and gradually succeed over them by maximizing the confrontation. We found that our graph bandits can outperform other Multi-Arm bandit algorithms when a simulated annealing-based scheduling is incorporated to adjust the balance between exploration and exploitation

A Graph-based Bandit Algorithm for Maximum User Coverage in Online Recommendation Systems

We study a type of recommendation systems problem, in which the system must be able to cover as many users’ tastes as possible while users’ tastes change over time. This problem can be viewed as a variation of the maximum coverage problem, where the number of sets and elements within any sets can change dynamically. When the number of distinctive elements is large, an exhaustive search for even a fixed number of elements is known to be computationally expensive. Many known algorithms tend to have exponential growth in complexity. We propose a novel graph based UCB1 algorithm that effectively minimizes the number of elements to consider, thereby reducing the search space greatly. The algorithm utilizes a new rewarding scheme to choose items that satisfy more user types as it construct a relational graph between items to choose. Experiments show that the new algorithm performs better than existing techniques such as Ranked Bandits [17] and Independent Bandits [12] in terms of satisfying diverse types of users while minimizing computational complexity

Long-Term Hydraulic Adjustment of Three Tropical Moist Forest Tree Species to Changing Climate

Xylem hydraulic adjustment to global climatic changes was reported from temperate, boreal, and Mediterranean tree species. Yet, the long-term hydraulic adjustment in tropical tree species has not been studied so far. Here we developed the first standard chronologies of three hydraulic trait variables for three South Asian moist forest tree species to analyze their long-term hydraulic responses to changing climate. Based on wood anatomical measurements, we calculated Hagen–Poiseuille hydraulically weighted vessel diameter (DH), potential specific hydraulic conductivity (KS), and vulnerability index (VX) and developed standard chronologies of these variables for Chukrasia tabularis, Toona ciliata, and Lagerstroemia speciosa which are different in their xylem structure, wood density, shade tolerance, growth rates, and habitat preferences. Bootstrap correlation analysis revealed that vapor pressure deficit (VPD) strongly positively influenced the xylem water transport capacity in C. tabularis, whereas T. ciliata was affected by both temperature and precipitation. The hydraulic conductivity of L. speciosa was mainly affected by temperature. Different adjustment strategies were observed among the species, probably due to the differences in life history strategies and xylem properties. No positive relationship of conductivity and radial growth was found, but a trade-off between hydraulic safety and efficiency was observed in all studied species

Extraction of Asymptomatic Tooth With And Without Antibiotic Therapy

Background: Extraction of asymptomatic tooth constitutes a large proportion of maxillofacial surgery procedure and antibiotics are indiscriminately prescribed before and after tooth extraction in Bangladesh. Objectives: This cross sectional study was designed to evaluate the efficacy of postoperative antibiotic therapy in reducing postoperative morbidity in two groups following extraction of asymptomatic tooth. Methods: A total of 112 patients, 54 Female and 58 Male, aged 16 to 35 years comprised the study materials. Diagnosis was made by accurate history, clinical examination and radiographs. Clinical examination was done to assess the presence or absence of local infection, pain, swelling and mucosal coverage whereas Orthopantomogram (OPG) and Intraoral Periapical (IOPA) radiographs were taken to assess the angulations, position and bony coverage. Tooth extraction was performed with buccal guttering technique after adequate elevation and reflection of full thickness mucoperiosteal flap. The Control Group was given Cap. Amoxicillin 500mg, orally daily for 5 days postoperatively. The Study Group was not given antibiotics. Pain, swelling and trismus were evaluated preoperatively and on 2nd, 7th and 14th postoperative day. Data was processed and analyzed using SPSS version 16.0 for windows and was compiled and test of significance was done using Chi square (x²) test and unpairedt test. Results: Statistical analysis of the data indicated that pain and swelling was significantly reduced and significant maximum mouth opening was achieved, when preoperative and postoperative results were compared, in both the groups P > 0.05, statistically not significant. Conclusion: There were no significant differences among the groups in the incidence of postoperative morbidity (pain, swelling and trismus).DOI: http://dx.doi.org/10.3329/bsmmuj.v5i1.10996 BSMMU J 2012; 5(1):24-2

Bone Grafts in Jaw Cysts- Hydroxyapatite & Allogenic Bone A Comparative Study

Background: Auto bone is the gold standard in bone grafting. However, the morbidity and additional surgical time associated with its collection, as well as the limited supply, have stimulated the search for substitutes. Allograft is more limited than autograft because it yields more variable clinical results. Composite synthetic grafts offer an alternative because Hydroxyapatite is chemically identical to the inorganic matrix of living bones and it can be processed synthetically. The intent was to evaluate these two graft materials for clinical use and to provide an insight on the different grafting strategies to enhance bone formation. Objective: To find out the bone healing process and the prognostic value for the patient using hydroxyapatite alloplastic material and allogenic bone graft. Method: Total 28 patients were included in the study after the clinical and radiological evaluation where 14 cases were treated with allogenic-bone graft and rest 14 cases were treated with hydroxyapatite alloplastic material after enucleation of the cystic lesion in random manner. The integration of hydroxyapatite and allogenic bone was assessed with postoperative lesion diameter, trabecular pattern, histopathological and scintigraphic examination of the successful graft cases. Statistical analysis was carried out by ‘unpaired T test' and ‘Chi square' test. Result: The radiological, histopathological and scintigraphical outcome of the patients treated with hydroxyaptite granule bone graft were clinically and statistically superior in comparison with those who were treated with allogenic bone graft. Conclusion: This safe and osteoconductive hydroxyapatite appears suitable for filling bone defects and bone cavities, showing less resorption and a rapid osseous integration. Key words: Hydroxyapatite; allogenic bone; scintigraphy; radiology; histopathology.DOI: 10.3329/bsmmuj.v2i1.3707 BSMMU J 2009; 2(1): 25-3

Correction of Anterior Open Bite and Facial Profile by Orthognathic Surgery A Case Report

This case report describes the treatment of a severe anterior open bite, Class III malocclusion with a history of digitsucking. An 18 years-old male presented with a significant anteroposterior and vertical discrepancy of face. The patient’sface was concave with procumbent lips. He had an anterior open bite of 11 mm, a reverse overjet of 8 mm, and atransverse maxillary deficiency on right side. The orthognathic surgery was elected as an option of treatment to correctthe anterior open bite with improvement of facial profile.Keywords: Anterior open bite; Transverse maxillary deficiency; Vertical excess; Orthognathic surgery.DOI: 10.3329/bsmmuj.v3i1.5512BSMMU J 2010; 3(1): 31-3

Stressors perceived by the clinical undergraduate medical students towards the end of course

Response or reaction of the mind to the pressure of life is stress. Medical students of Bangladesh are in stress to meet the demands of the curriculum. This study was conducted on the regularly passed final year students of a medical college to find out the nature of stresses perceived by them. The response was collected on a validated structured set of questionnaire, 3 weeks prior to the University level summative examination and 63 students (33 male and 30 female) participated in the study. Stress was expressed in five levels and scored as 0 to 4. Academic related factors were identified as maximum stress provoking (2.5 ± 1.3) than group activity (1.6 ± 1.4), drive (1.4 ± 1.5), teaching-learning (2.3 ± 1.3), personnel (1.8 ± 1.6) or social (1.9 ± 1.5) related factors. Of that group of stress, ‘falling behind reading schedule’ and ‘large amount of content to be learned’ were revealed as heavy stressors. Examination was identified as a severe stressor in 42.4% male, but was marked less (16.7%) in the female. ‘Too much restriction in the campus’ was observed as heavy stressors among the factors other than the academic related stressors. Students may be motivated to develop a coping strategy for academic and teaching-learning related stress

Study of Frozen Section Biopsy as Intraoperative Procedure for Oral Squamous Cell Carcinoma in BSMMU

Background: Frozen section biopsy technique often helps a rapid diagnosis of a mass during surgery which in turn may helps a surgeon to know the status of the margins of his resection before closing. Objective: The study was done to achieve tumour free surgical margin after resection of oral squamous cell carcinoma (OSCC). The study also examined to determine positive margins and its relation to tumour size, grade and stage of oral squamous cell carcinoma. Method: This cross sectional study was done in 29 patients of oral sqamous cell carcinoma. Result: One hundred eleven margins of frozen section (FS) biopsy were taken from 29 patients (mean 3.8) for comparing with the permanent sections of the same tissue sample. Among them, one false positive and three false negative were found and an accuracy rate was 96.4%. Out of one hundred eleven margins, 32 (28.8%) were positive and 79 (71.2%) were negative. In case of T3 and T4 tumour, the number of the positive margins was greater (respectively 27.8% and 50%). In stage III and stage IV cases, the number of positive margins was greater (29.1 and 30% respectively). Regarding histopathology grading, grade III was the highest (33.3%). Conclusion: The intra-operative frozen section biopsy plays an important role to achieve tumour free surgical margin in the resection of oral squamous cell carcinoma. In this study, it was also observed that the number of positive margins increased in relation to increased tumour size and tumour stage (cTNM). Key Words: Oral squamous cell carcinoma; Frozen section biopsy; Radiotherapy; Chemotherapy.DOI: 10.3329/bsmmuj.v2i1.3704 BSMMU J 2009; 2(1): 8-1

Mandibular Deformity Correction by Distraction Osteogenesis

Distraction osteogenesis (DO) is a biological process of new bone formation. It could be used as an alternative treatment method for the correction of mandibular hypoplastic deformity. Modern distraction osteogenesis evolved primarily from the work of Gavriel llizarov. DO has been first applied to craniofacial region since McCarthy et al. In this case report, the patient was 17 years old male with bird face deformity due to hypoplasia of mandible resulted from bilateral TMJ ankylosis due to the fracture of both condyle at the age of 4 years. Patient’s intraincisal opening was absent 1 year back. He underwent condylectomy in both sides to release the ankylosis and to increase intraincisal opening. His mandibular length was markedly short. To increase his mandibular antero-posterior length, mandibular body distraction was done in Oral and Maxillofacial Surgery department, BSMMU. Through this procedure length of the body of mandibule was increased by 10 mm, occlusion was edge to edge and his lower facial appearance increased markedly. Mandibular body distraction osteogenesis was considerably effective when performed in a hypoplastic mandible to facilitate post-operative functional and esthetic restoration. Long term follow-up is necessary to evaluate relapse and complications. DOI: 10.3329/bsmmuj.v3i2.7061BSMMU J 2010; 3(2): 103-10