Category Archives: Research News

At the 48th convocation of USJ, the first-ever PhD graduate from the Department, Dr. Manjula Perera was conferred. Her primary supervisor was Dr. Ravindra Lokupitiya of the Department of Statistics, USJ. Her PhD thesis title was “Estimation of global scale carbon fluxes using Maximum Likelihood ensemble filter“. She was co-supervised by the following academics:

• Prof. A. Scott Denning, Professor, Department of Atmospheric Science, Colorado State
  University, Fort Collins, CO 80523-1371 USA.
• Prof. E. Y. K. Lokupitiya, Professor in Environmental Science, Department of Zoology
  and Environment Sciences, University of Colombo, Colombo, Sri Lanka.
• Dr. Prabir Kumar Patra, Principal Scientist, Research Institute for Global Change,
  JAMSTEC, 3173-25 Showa-machi, Kanazawa-ku, Yokohama, 236-0001, Japan.
• Prof. R. G. N. Meegama, Professor in Computer Science, Department of Computer
  Science, Faculty of Applied Sciences, University of Sri Jayewardenepura, Gangodawila,
  Nugegoda, Sri Lanka.

Dr. Perera would like to thank the following institutes for the grants she received for her PhD studies.

• National Research Council, Sri Lanka (NRC-036)
• Asia-Pacific Network for Global Change Research (APN); grant#ARCP2011-11NMY-
  Patra/Canadell).

Her thesis abstract is as follows:

More advanced data assimilation methods based on statistical and mathematical knowledge are needed to cater to the increased amount of CO₂ measurements collected in various platforms. In addition to existing flasks, continuous and aircraft data, CO₂ measurements obtained by passenger aircrafts and satellites increase the observation network and provide more constraints on surface carbon flux estimation. This thesis mainly focuses on estimating the surface carbon sources and sinks using CONTRAIL aircraft observations, in addition to the existing in-situ measurements using the ensemble based data assimilation method called Maximum Likelihood Ensemble Filter (MLEF) coupled with Parameterized Chemistry Transport model (PCTM). A pseudodata experiment was carried out by adding CONTRAIL measurements to the observation vector using MLEF coupled with PCTM model, which was driven by GEOS-4 (Goddard Earth Observation System, version 4) weather data for the model validation. Next, MLEF code was developed to conduct the real data experiment to identify the capability on estimating surface carbon fluxes for the period 2009-2011. PCTM model was driven by Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA2) weather data. Solving separate multiplicative biases added for photosynthesis, respiration, and air-sea gas exchange fluxes the estimated fluxes were obtained. Hourly land fluxes, Gross Primary Production (GPP) and respiration obtained from Simple Biosphere-version 3 (SiB3) model, Takahashi ocean fluxes and Brenkert fossil fuel emissions were used.

Pseudodata experiment results showed a considerable uncertainty reduction for Asian region and more than 50% reduction for North American and European regions. According to the results of the real data experiment, North America showed about 60-80% uncertainty reduction while the Asian and European regions showed moderate results with 50-60% uncertainty reduction. Most other land and oceanic regions showed less than 30% uncertainty reduction. The results were mainly compared with the results of well-known CarbonTracker (CT2017) which is a CO₂ measurement and modeling system developed by NOAA (National Oceanic and Atmospheric Administration). The spatial distribution of estimated mean annual fluxes over North America, Australia and Tropical Asia showed good agreement with the CarbonTracker results when aggregated into large regions. The biases were poorly constrained in the regions where the CO₂ observations are not sufficiently dense such as South America and Africa. Long-term averaged fluxes were compared with several other inversion studies and showed similar results for the Boreal North America, Temperate North America and Australia. The results reveal the capability of MLEF method to assimilate large CO₂ observation vectors with high performance parallel computing environment with less cost and less time.  The impact of satellite observations with MLEF needs to be investigated further and this study forms the basis of the future work in this area.

Keywords: Data assimilation, Maximum Likelihood Ensemble Filter, CONTRAIL aircraft observations, Carbon sources and sinks, CO₂ modeling

Dr. Chathuri Jayasinghe of Department of Statistics, USJ recently collaborated with a team from Lanka Hospital Blood Cancer Centre (LHBCC) to conduct multiple studies with the aim of investigating the applicability of treatment protocols from developed countries to treat and care for Sri Lankan blood cancer patients. The studies evaluated the treatment and care outcome for local patients with adult acute Myeloid Leukaemia, Hodgkin Lymphoma, Plasma Cell Myeloma and were shown to be comparable to high-income countries (1, 2, 5, 6). At present locally, there is excessive mortality for blood cancers that are potentially curable in the west (1). Further, there is a scarcity of Sri Lankan data particularly for these cancers and scant research in the literature.

Dr. Jayasinghe contributed to the conception, design, acquisition, analysis of data and publishing of these multiple researches conducted by the team led by Dr. Saman Hewamana of LHBCC. Results of these studies which were mainly derived using survival analysis techniques with expertise of Dr. Jayasinghe suggests that mortality can be reduced and the burden on the health care system can be minimized if diagnosed and treated in an appropriate setting. Apart from treating blood cancers, LHBCC has also trained the first-ever group of haemato-oncology trainees from government hospitals. This holds promise for blood cancer care in Sri Lanka and will give trust and belief to patients and medical staff alike about the achievable targets.

Another recent research study published by the group has shown blood cancer care can be continued safely during the Covid-19 pandemic if proper strategies are implemented and that this would help to prevent late stage presentation and adverse outcomes (3).  In another study, the management  and  mortality  of  neutropenic  episodes  among  Haemato-Oncology  patients were investigated and the manuscript that was written based on its findings is currently under review (4).

Dr. Chathuri Jayasinghe research interests include survival analysis methods and applications, nonparametric and parametric estimation methods, medical statistics and software reliability growth models. Her fundamental research work related to these areas has been published in journals such as IEEE Transactions on Reliability, the Journal of Statistical Planning and Inference, the Communications in Statistics (Theory and Methods).

Related references:

1. Saman Hewamana, Lakmali Kandabadage, Thurairajah Skandarajah, Natasha Pieris, Eranga Perera, Mahesh Harischandra, Ananda Wijewickrama, Chandana Wickramarathna, Gnani Somasundaram, Vadivelu Srinivasan, Surjit Somiah, Priyankara Jayawardena, Mehendra Perera, Dehan Gunasekera, Chathuri Jayasinghe, Godvin Constantine, Sanjeewa Munasinghe, Chandu De Silva, Bandula Wijesiriwardena, Jayantha Balawardena. Applicability of Western protocols in resource-limited setting: Real-world data of long-term outcome of intensive treatment of adult acute myeloid leukaemia in Sri Lanka. eJHaem. 2021; 2: 555– 561. https://doi.org/10.1002/jha2.191
2. Saman Hewamana, Lakmali Kandabadage, Thurairajah Skandarajah, Natasha Peiris, Sobitha Abeyaratne, Gehan Arseculeratne, Eranga Perera, Mahesh Harischandra, Ananda Wijewickrama, Gnani Somasundaram, Vadivelu Srinivasan, Surjit Somiah, Priyankara Jayawardena, Rohini Wadanamby, Geethani Galagoda, Chathuri Jayasinghe, Chandu De Silva, Sanjeewa Munasinghe, Bandula Wijesiriwardena, Jayantha Balawardena. Applicability of protocols from high-income countries in a resource limited setting; real world data of histopathology, clinical features and long-term outcome of Hodgkin Lymphoma in Sri Lanka, The Lancet EClinicalMedicine, Volume 38, 2021, 100998, ISSN 2589-5370, https://doi.org/10.1016/j.eclinm.2021.100998.
3. Saman Hewamana, Thurairajah Skandarajah, Chathuri Jayasinghe, Samadhi Deshapriya, Dhananjani Senarathna, Dilip Gayashan, Natasha Peiris, Eranga Perera, Mahesh Harischandra, Surjit Somiah, Nihal Munasinghe, Sangeetha Hewawasam, Gehan Arseculeratne, Rohini Wadanamby, Geethani Galagoda, Jayantha Balawardena. Blood cancer care in a resource limited setting during the Covid-19 outbreak; a single center experience from Sri Lanka. PLOS ONE, 16(9), e0256941 (2021). https://doi.org/10.1371/journal.pone.0256941
4. Saman Hewamana, Thurairajah Skandarajah, Chathuri Jayasinghe, Samadhi Deshapriya, Dhananjani Senarathna, Gehan Arseculeratne, Mahesh Harischandra, Gnani Somasundaram, Vadivelu Srinivasan, Surjit Somiah, Nihal Munasinghe, Sangeetha Hewawasam, Lalith Ekanayake, Rohini Wadanamby, Geethani Galagoda, Thet Thet Lin, Jayantha Balawardena. Adapting Supportive Care Guidelines from High-income Countries; Real World Data on Approach to Neutropenic Sepsis in Haemato-Oncology Patients in Sri Lanka, 15 July 2021, PREPRINT (Version 1) available at Research Square [https://doi.org/10.21203/rs.3.rs-626896/v1]
5. Saman Hewamana, Prasanna Gunasena, Chathuri Jayasinghe, Mahesh Harischandra, Thurairajah Skandarajah, Sobitha Abeyaratne, Lalith Ekanayake, Gnani Somasundaram, Surjit Somiah, Vadivelu Srinivasan, Gehan Arseculeratne, Neomal Perera, Jayaindra Fernando, Nihal Munasinghe, Ashfaq Mowlana, Samadhi Deshapriya, Supun Mawathakubura, Chandana Wickramarathna, Ananda Wijewickrama, Priyankara Jayawardena, Eranga Perera, Natasha Peiris, Sarath Paranawithana, Chithranga Perera, Sanjeewa Munasinghe, Chandu De Silva, Rohini Wadanamby, Geethani Galagoda, Thet Thet Lin, Bandula Wijesiriwardena, Jayantha Balawardena; Survival estimates of patients with plasma cell myeloma after first line therapy in a resource limited setting using protocols from high-income countries. October 2021, Submitted.
6. Saman Hewamana, Prasanna Gunasena, Chathuri Jayasinghe, Mahesh Harischandra, Thurairajah Skandarajah, Sobitha Abeyaratne, Lalith Ekanayake, Gnani Somasundaram, Surjit Somiah, Vadivelu Srinivasan, Gehan Arseculeratne, Neomal Perera, Jayaindra Fernando, Mazhar Faiz, Nihal Munasinghe, Ashfaq Mowlana, Samadhi Deshapriya, Supun Mawathakubura, Chandana Wickramarathna, Ananda Wijewickrama, Priyankara Jayawardena, Eranga Perera, Natasha Peiris, Sarath Paranawithane, Chitranganie Perera, Chitranga Kariyawasam, Sanjeewa Munasinghe, Chandu De Silva, Rohini Wadanamby, Geethani Galagoda, Thet Thet Lin, Bandula Wijesiriwardena, Jayantha Balawardena; Feasibility of transplantation for plasma cell disorders in resource constrained setting; real-world data on safety, survival and cost of treatment from the first blood cancer centre in Sri Lanka.  In preparation.