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result(s) for
"Velavan, A."
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The Impact of Formation of Oxide Layer on the Piston Crown Using Micro - Arc Oxidation on the Characteristics of the Spark Ignition Engine
by
Vikneswaran, M.
,
Velavan, A.
,
Saravanan, C.G.
in
Base metal
,
Carbon monoxide
,
Ceramic coatings
2019
In the present study, experiments were conducted to compare the effect of oxide layer formation on the piston crown coated using Micro-Arc Oxidation (MAO) with uncoated piston on the combustion and emission characteristics of the port injected Spark Ignition engine fueled by gasoline. The micro-arc oxidation (MAO) coating technique is the modern process to form a ceramic oxide layer on the reactive metal substrate (base metal) by electrochemical and electro-thermal oxidation in an alkaline electrolytic solution. Using MAO technique, an oxide layer of thickness 72 μm was formed on the piston crown. This oxide layer acts as a thermal barrier to reduce the in-cylinder heat rejection and increase the durability of the piston by withstanding high temperature and pressure produced during combustion. Combustion flames have been captured using the AVL combustion analyzer to analyze the development and propagation of flames within the engine cylinder. From the flame images, it was observed that propagation of flame was faster in MAO coated piston compared to uncoated piston. This is because of higher local temperature inside the combustion chamber that was resulted due to low thermal conductivity of MAO layer. It was also found that carbon monoxide (CO) and hydrocarbon (HC) emissions were reduced as a result of efficient fuel combustion, while NOx emissions increased because of increased combustion temperatures for MAO coated pistons. Keywords: Electro-thermal oxidation, Flame propagation, Micro-arc oxidation, Piston crown, Thermal barrie
Journal Article
Community Dynamics and Engagement Strategies in Establishing Demographic Development and Environmental Surveillance Systems: A Multi-Site Report from India
by
Kumar, Tivendra
,
Velavan, A.
,
Palo, Subrata Kumar
in
Community health services
,
Data collection
,
Demographic aspects
2023
Background: Six diverse Demographic Development and Environmental Surveillance System (DDESS) sites were established in urban slum, urban resettlement, peri-urban, rural, and tribal areas located in Northern, North-East, Eastern, and Southern regions of India from June 2020 to March 2022. Understanding the community dynamics and engaging people in the community is critically important in the process of establishing DDESS. We ascertained the barriers, challenges, and facilitators during the establishment of multiple DDESS sites across India. Methods: This was a cross-sectional descriptive mixed-methods study. Results: Multiple barriers and challenges encountered were reported in the process of community engagement (CE), such as geographical inaccessibility, language barriers, adverse weather, non-responsiveness due to perceived lack of individual benefit or financial gain, fear of contracting COVID-19, COVID-19 vaccine hesitancy, etc. Facilitators in the CE process were pre-existing links with the community, constitution of community advisory boards, community need assessment, concomitant delivery of outreach health services, and skill-building facilities. Conclusion: Most community barriers in the development of DDESS sites in resource-limited settings can be overcome through a multipronged approach, including effective community engagement by focusing on demonstrating trust at the local level, enlisting community mobilization and support, utilizing pre-existing community linkages, initiating community diagnosis, and meeting perceived community health needs.
Journal Article
Neural parameter calibration for dengue outbreak forecasting
by
Velavan, Thirumalaisamy P.
,
Nguyen, Khuong Trung Dang
,
Tran, Khanh Duc
in
Accuracy
,
Animals
,
Asia, Southeastern - epidemiology
2026
Dengue fever poses a growing public health challenge in tropical and subtropical regions, with transmission driven by complex interactions among viral and host. Computational models, often expressed as ordinary differential equations (ODEs), are widely used to understand complex systems such as dengue fever transmission dynamics. However, traditional parameter estimation methods such as Markov chain Monte Carlo (MCMC) often require complex setups and are computationally expensive. In this study, we choose a compartmental model extended to human and mosquito populations, estimate its parameters using neural parameter calibration (NPC), and validate the approach using datasets collected from South America and Southeast Asia. The extended compartment model (ECM) is expressed using seven ODEs, describing dengue transmission dynamics between humans and mosquitoes. NPC involves using a neural network to learn the posterior distribution of parameters and initial conditions of the model in consideration. We analyzed six surveillance datasets on cumulative dengue cases, comprising data from three cities (Bello, Iquitos, and San Juan) and three Southeast Asian countries (Vietnam, the Philippines, and Cambodia). NPC achieved significantly faster run times than MCMC: 408 seconds on average versus 2616.01 seconds for city-level analyses and 368 seconds on average versus 2998.83 seconds for country-level analyses. Meanwhile, it delivers comparable accuracy: mean squared error (MSE) 0.00678 versus 0.01638 for the city datasets; and 0.00605 versus 0.01897 for the country datasets. The experimental results demonstrate that combining ECM with NPC enables accurate dengue outbreak forecasts at substantially lower computational cost, offering a practical tool that supports timely response, especially in low-resource environments such as Southeast Asia.
Journal Article
Unfractionated heparin versus bivalirudin in primary percutaneous coronary intervention (HEAT-PPCI): an open-label, single centre, randomised controlled trial
2014
Bivalirudin, with selective use of glycoprotein (GP) IIb/IIIa inhibitor agents, is an accepted standard of care in primary percutaneous coronary intervention (PPCI). We aimed to compare antithrombotic therapy with bivalirudin or unfractionated heparin during this procedure.
In our open-label, randomised controlled trial, we enrolled consecutive adults scheduled for angiography in the context of a PPCI presentation at Liverpool Heart and Chest Hospital (Liverpool, UK) with a strategy of delayed consent. Before angiography, we randomly allocated patients (1:1; stratified by age [<75 years vs ≥75 years] and presence of cardiogenic shock [yes vs no]) to heparin (70 U/kg) or bivalirudin (bolus 0·75 mg/kg; infusion 1·75 mg/kg per h). Patients were followed up for 28 days. The primary efficacy outcome was a composite of all-cause mortality, cerebrovascular accident, reinfarction, or unplanned target lesion revascularisation. The primary safety outcome was incidence of major bleeding (type 3–5 as per Bleeding Academic Research Consortium definitions). This study is registered with ClinicalTrials.gov, number NCT01519518.
Between Feb 7, 2012, and Nov 20, 2013, 1829 of 1917 patients undergoing emergency angiography at our centre (representing 97% of trial-naive presentations) were randomly allocated treatment, with 1812 included in the final analyses. 751 (83%) of 905 patients in the bivalirudin group and 740 (82%) of 907 patients in the heparin group had a percutaneous coronary intervention. The rate of GP IIb/IIIa inhibitor use was much the same between groups (122 patients [13%] in the bivalirudin group and 140 patients [15%] in the heparin group). The primary efficacy outcome occurred in 79 (8·7%) of 905 patients in the bivalirudin group and 52 (5·7%) of 907 patients in the heparin group (absolute risk difference 3·0%; relative risk [RR] 1·52, 95% CI 1·09–2·13, p=0·01). The primary safety outcome occurred in 32 (3·5%) of 905 patients in the bivalirudin group and 28 (3·1%) of 907 patients in the heparin group (0·4%; 1·15, 0·70–1·89, p=0·59).
Compared with bivalirudin, heparin reduces the incidence of major adverse ischaemic events in the setting of PPCI, with no increase in bleeding complications. Systematic use of heparin rather than bivalirudin would reduce drug costs substantially.
Liverpool Heart and Chest Hospital, UK National Institute of Health Research, The Medicines Company, AstraZeneca, The Bentley Drivers Club (UK).
Journal Article
Occult Hepatitis B Virus Infection in Nigerian Blood Donors and Hepatitis B Virus Transmission Risks
by
Oluyinka, Opaleye O.
,
Velavan, Thirumalaisamy P.
,
Tong, Hoang Van
in
Adult
,
Antibodies
,
Antigens
2015
Occult hepatitis B virus infection (OBI) characterized by the absence of detectable HBsAg remains a potential threat in blood safety. We investigated the actual prevalence, viral factors and genotype of OBI infections in Nigerian blood donors.
Serum collected from two blood banks were reconfirmed as HBsAg seronegative by ELISA. Forty HBsAg positive samples were employed as controls. HBV-DNA was amplified from all donors and viral loads were determined using quantitative real-time PCR. Antibodies to the HBV core, surface and HBe antigen (anti-HBc,anti-HBs,HBeAg) were measured. The PreS/S and PreC/C regions of the HBV genome were sequenced.
Of the 429 blood donors, 72(17%) were confirmed as OBI by DNA detection in different reference labs and excluded the concern of possible contamination. Of the 72 OBI samples, 48(67%) were positive for anti-HBc, 25(35%) positive for anti-HBs, and 2(3%) positive for HBeAg. Of the 72 OBI samples, 31(43%) were seropositive for either anti-HBc, anti-HBs or HBeAg, 21 (30%) positive for both anti-HBc and anti-HBs,one positive for both anti-HBc and HBeAg. None of the OBI samples were positive for all three serological markers. The viral load was <50copies/ml in the OBI samples and genotype E was predominant. The L217R polymorphism in the reverse transcriptase domain of the HBV polymerase gene was observed significantly higher in OBI compared with HBsAg positive individuals (P<0.0001).
High incidence of OBI is relevant in high endemic areas worldwide and is a general burden in blood safety. This study signifies the high prevalence of OBI and proposes blood donor samples in Nigeria should be pre-tested for OBI by nucleic acid testing (NAT) and/or anti-HBc prior to transfusion to minimize the HBV infection risk.
Journal Article
Double fuzzy clustering-driven context neural network for intrusion detection in cloud computing
2025
Cyber security must be implemented when using cloud computing to identify and protect malevolent intrusions and strengthen the organizations capacity against cyberattacks. Detecting network intrusions with zero false alarms is a challenge. A number of intrusion detection systems (IDS) for cloud computing (CC) environments have put forward recently. The existing IDS exhibit significant false positive rates, poor classification accuracy, and over-fitting. Therefore, a Double Fuzzy Clustering-Driven Context Neural Network for Intrusion Detection in Cloud Computing (DFCCNN-BWOA-IDC) is proposed in this paper. Initially, the input data is gleaned from DARPA dataset. The input data is pre-processed utilizing Sequential pre-processing through orthogonalization (SPORT) method to replace the missing values and remove the duplicate values. After that, the pre-processing data is fed to the recursive feature elimination (REF) approach for selecting optimal features. Then the selected features are supplied to the DFCCNN to categorize the data as Normal or Anomaly. Finally, the Beluga Whale Optimization algorithm (BWOA) is proposed to enhance the weight parameters of DFCCNN classifier, which precisely detects the attacks. The proposed DFCCNN-BWOA-IDC approach is activated in MATLAB. The DFCCNN-BWOA-IDC method reaches better accuracy of 98.89% which is 15.98%, 13.59% and 19.53% higher than the existing approaches, like intrusion detection in CC with the help of hybrid deep learning approach (DKNN-CRDO-IDC), intrusion detection scheme under hybrid teacher learning optimization facilitates deep RNN in web and cloud computing (TL-DRNN-IDC), Intrusion detection scheme utilizing deep learning and Capuchin Search Algorithm for cloud and IoT (CNN-CapSA-IDC) respectively.
Journal Article
COVID-19 in Africa: between hope and reality
by
Ntoumi, Francine
,
Velavan, Thirumalaisamy P
in
Africa South of the Sahara - epidemiology
,
Clinical trials
,
Congo - epidemiology
2021
Preparation, however, is becoming increasingly difficult in many African countries, especially in central African countries, such as Republic of the Congo and others, where the effects of the Ebola virus disease epidemic on the economy and health structures are still being felt. Given the fragile health systems in most sub-Saharan African countries, new and re-emerging infectious disease outbreaks can paralyse health systems and existing structures. Both authors contributed equally and are members of the Pan-African Network for Rapid Research, Response and Preparedness for Infectious Diseases Epidemics, which is funded through the European and Developing Countries Clinical Trials Partnership (grant number RIA2016E-1609).
Journal Article
Implications of SiC/Al2O3 Reinforced Al-Mg-Zn Alloy Hybrid Nano Composites Using Vacuum Sintering Method
by
Velavan, K.
,
Anbuchezhiyan, G.
,
Senthilkumar, N.
in
Alloy powders
,
Alloys
,
Aluminum base alloys
2021
The present study investigates aluminium alloy powder (Al7075) of mesh size 60 μm and the reinforcement SiC of varying its weight percentage (2 wt%, 4 wt%, 6 wt%) and keeping constant Al
2
O
3
(2 wt%) of particle size <50 nm has been used to synthesis aluminium alloy hybrid nanocomposites. The compaction pressure (350 MPa) and the sintering temperature (750 °C) are used to develop such hybrid composites. The microstructure and mechanical behaviour of progressed composites have been characterized as per ASTM standards. The aluminium alloy hybrid composites sintered effectively and the strengthening particles are consistently disseminated in the matrix alloy without indication of the cluster along with the fine grains of intra dendrite grain boundaries that are precipitated throughout grains of an aluminum matrix. In comparison with base alloy, the hardness (14%) and compressive strength (24%) of synthesized composites have been increased invariably. ASTM B117 salt spray experiment has been performed to study the corrosion properties of incorporated composites. It has been inferred that corrosion-resistant is improved due to the presence of interface AlC
2
, Al
2
SiC between the intermixtures. This act as a barrier for disruption and it minimizes the effect of oxidation of developed aluminium hybrid composites.
Journal Article
Incidence of Occult Hepatitis B Infection (OBI) and hepatitis B genotype characterization among blood donors in Cameroon
by
Mbencho, Macqueen Ngum
,
Velavan, Thirumalaisamy P.
,
Achidi, Eric A.
in
Adolescent
,
Adult
,
Amino acid substitution
2024
Occult hepatitis B infection (OBI) is characterized by the presence of hepatitis B virus (HBV) DNA at low levels in serum (<200 IU/mL) with a negative hepatitis B surface antigen (HBsAg) test. OBI remains a major challenge to blood safety, particularly in HBV-endemic regions like Cameroon, where HBV detection relies solely on HBsAg testing. This cross-sectional study aimed to investigate the actual incidence and genotype characteristics of OBI in Cameroonian blood donors.
Between March and June 2023, samples were collected from 288 HBsAg-negative blood donors aged 18 to 55 years and analysed for antibodies against the HBV core (anti-HBc) and surface antigens (anti-HBs). Following DNA extraction from the serum samples, qualitative nested PCR and quantitative real-time PCR were used to detect HBV viral DNA and viral load respectively. For positive samples, sequencing of a fragment of the S gene was performed to identify the circulating HBV genotypes.
The findings revealed that 58% (n = 167/288) of blood donors tested positive for anti-HBc, 29% (n = 83/288) tested positive for anti-HBs, and 26% (n = 75/288) being positive for both anti-HBc and anti-HBs. Occult hepatitis was confirmed in 4.5% of the blood donors, all of whom belonged to either HBV genotypes A or E, which are predominant in Cameroon. The amino acid substitution sA184V associated with HBsAg detection failure in genotype E was observed in 70% of OBI sequences, and the HBsAg immune escape variants (sT131N and sS143L) implicated in OBI were also observed. The mutation rtN139K in the reverse transcriptase (RT) domain of the overlapping HBV polymerase (P) gene was present in 17% of OBI-positive sequences of genotype E, likely contributing to masking HBsAg secretion.
The results suggest a considerable risk of transfusion-transmitted HBV in this region. Therefore, to ensure blood safety, nucleic acid testing (NAT) is recommended, as relying solely on HBsAg assays is insufficient to eliminate this risk.
Journal Article
Characterization of dengue patients in Vietnam: Clinical, virological, and IL-10 profiles during 2021– 2022 outbreaks
2025
The pathogenesis of dengue is attributed to a complex interaction between the dengue virus (DENV) and the host immune system. The aim of this study is to investigate the clinical, virological, and Interleukin-10 (IL-10) profiles of dengue patients in Vietnam from two consecutive outbreaks in 2021 and 2022.
A total of n=306 dengue patients were examined, who were clinically stratified according to dengue without warning signs (DF; n=178), dengue with warning signs (DWS; n=115) and severe dengue (SD; n=13). Patients were screened for dengue, Zika and chikungunya viruses. DENV were subjected to serotype specific real-time RT-PCR. Interleukin-10 (IL-10) levels were measured by ELISA, and IL-10 promoter variants (-1082G/A; -819C/T; -592C/A) were genotyped by direct Sanger sequencing to determine a possible association with susceptibility to dengue and disease severity.
No chikungunya or Zika viruses were detected. Patients were infected by one of the three different DENV serotypes (DENV-1, -2, -4). Plasma IL-10 levels were significantly elevated in patients (DF vs. DWS, p=0.004; DF vs. SD, p=0.001; DWS vs. SD, p=0.015). While the IL-10 allele -819C contributed to an increased risk of dengue (OR = 1.5, 95% CI = 1.1-2.0, p=0.04), genotype -1082GA showed a protective role against the disease (OR = 0.45, 95% CI = 0.27-0.72, p=0.009), and allele -1082G showed a protective role against DWS (OR = 0.44, 95% CI = 0.22-0.81, p=0.049). Also, the IL-10 GTA (-1082G/-819T/-592A) haplotype was observed to confer protection (OR = 0.31, 95% CI = 0.14-0.67, p< 0.003).
While DENV-1 and DENV-2 were the predominant serotypes in circulation, plasma IL-10 levels and IL-10 promoter variants were also significantly associated with dengue and its severity.
Journal Article