Elucidating Kinetic, Adsorption and Partitioning Phenomena from a Single Well Tracer Method: Laboratory and Bench Scale Studies

This study is aimed at giving some insights on kinetics, adsorption and partitioning of ethyl acetate during a single well tracer test. Synthetic formation water, an specific crude oil and a silicate-dolomite rock were used during experiments performed in laboratory and bench scale systems. Independent sets of experiments were designed to calculate the partition coefficient of ethyl acetate between the formation water and the oil, to develop a kinetic model for the hydrolysis of ethyl acetate, and to derive isotherm and kinetic models for the adsorption of ethyl acetate on the rock. These tracer experiments were evaluated at a concentration range (100–300 mmol.L−1) similar to that supposed to be used in the single well tracer method. All parameters determined from these experiments were validated describing observations from stirred batch and column systems, in which kinetic, adsorption and partitioning phenomena occurred at the same time. Pseudo-heterogeneous models, accounting for three phases namely the formation water, the rock and the oil, were applied to elucidate the interaction of the different mechanisms involved in these set-ups. Main results are summarized as follows: (i) partition coefficients (KEA) were apparent varying from ca. 5–8 because of thermodynamic constraints; (ii) kinetic models for the hydrolysis of ethyl acetate were developed under acid and basic conditions since at neutral ones there were negligible conversions; (iii) the combined Langmuir-Freundlich isotherm and the Langmuir kinetics were the most suitable models describing equilibrium and adsorption rate observations, respectively; (iv) the studied rock adsorbed significant amounts of ethyl acetate, leading to a maximum adsorption capacity (qEAm) of ca. 7.0 mmol.g−1 at studied operating conditions; (v) the adsorption kinetic model rather than the simplified isotherm model seems necessary to describe this phenomenon from the single well test evaluating ethyl acetate as the tracer; and (vi) partition, hydrolysis and adsorption parameters evaluated from independent experiments allowed us to describe observations from both stirred batch and column systems. These results disclose the importance of accounting for partition, hydrolysis and adsorption mechanisms in a single well method using ethyl acetate as the tracer.

Clinical Profile and Biochemical Abnormalities of Neonatal Seizure at NICU of a Tertiary Care Hospital

Seizures are most common neurological emergency in the neonatal period and present as a diagnostic and therapeutic challenge to clinicians worldwide. This prospective observational study was conducted in the Neonatal Intensive Care Unit of Mymensingh Medical College Hospital from January 2015 to March 2015. Total 318 patients were enrolled in the study who presented with convulsion. Most of the patients were term (72.95%) and birth weight was normal (77.3%). Around 75% patients were delivered at home. Most common causes of convulsion were Perinatal Asphyxia (78%) followed by Septicemia, Hypoglycemia and Meningitis in order of frequency. Commonest type of seizure was subtle seizure (45.5%). Most of the patients recovered completely (73%) and 8.4% patients died due to complications.

Hydrodesulfurization of Dibenzothiophene in a Micro Trickle Bed Catalytic Reactor under Operating Conditions from Reactive Distillation

The hydrodesulfurization (HDS) of dibenzothiophene (DBT) is investigated over a commercial NiMoP/γ-Al2O3 catalyst in a micro trickled bed reactor (Micro-TBR) at operating conditions of a reactive distillation (RD) column. An analysis with and without reaction is carried out to have a first understanding on the complex interaction between kinetics and transport phenomena. A set of well-accepted criteria is evaluated to elucidate the presence of heat and mass transport limitations. Residence time distribution (RTD) experiments are performed to evaluate axial dispersion through the estimation of axial dispersion coefficient (Daxial,L) from a convection-dispersion model. Experiments with reaction are carried out using hydrogen and DBT as feedstock at reaction temperatures from 533 to 599 K, pressures from 1.5 to 2.5 MPa and inlet molar flow of DBT from 4 to 12×10–8 mol.s–1. A pseudo heterogeneous model accounting for mass transport limitations is used to describe experiments under reaction conditions. The main findings can be summarized as follows: most of RD operating conditions lead to the presence of interfacial mass transport limitations at both interfaces L-S and G-L; convection-dispersion model is able to describe satisfactorily RTD observations, suggesting that axial dispersion phenomena are negligible; conversion of DBT ranges from ca. 22 to 90% having a selectivity to by-product molecules from 30 to 80%, respectively; and the pseudo heterogeneous reaction model describes observations adequately obtaining activation energies ranging from 49 to 62 kJ mol–1 at pressures from 1.5 to 2.5 MPa, respectively. Estimated activation energies are comparatively lower than the activation energies reported in literature for the conventional HDS process, i.e. 40–160 kJ.mol–1, thereby suggesting an apparent catalytic energy savings by using RD technology.

A multicenter prospective hospital-based surveillance to estimate the burden of rotavirus gastroenteritis in children less than five years of age in India

BACKGROUND

Rotavirus is the leading cause of severe, dehydrating diarrhea in children aged <5 years globally, with an estimated 25 million outpatient visits and 2 million hospitalizations attributable to rotavirus infections each year. The aim of this hospital-based surveillance was to summarize the local epidemiological and virological features of rotavirus and to estimate the disease burden in the population under surveillance in India.

METHODS

During the 16 months surveillance period from April 2011 through July 2012, a total of 4711 children under the age of 5 years were admitted with acute diarrhea at 12 medical centers attached to medical schools throughout India. Stool samples were randomly collected from 2051 (43.5%) subjects and were analyzed for rotavirus positivity using commercial enzyme immunoassay kit (Premier Rotaclone Qualitative Elisa) at the respective study centers. Rotavirus positive samples were genotyped for VP7 and VP4 by reverse-transcription polymerase chain reaction (RT-PCR) at a central laboratory.

RESULTS

During the study period, maximum number of rotavirus related hospitalizations were reported from December 2011 through February 2012. Out of the 2051 stool samples tested for rotavirus, overall 541 (26.4%) samples were positive for rotavirus VP6 antigen in stool. The highest positivity was observed in the month of December, 2011 (52.5%) and lowest in the month of May, 2011 (10.3%). We found that majority of the rotavirus positive cases (69.7%) were in children <24 months of age. The most common genotypes reported were G1 (38%), G2 (18%), G9 (18%), G12 (9%) and mixed strains (17%).

CONCLUSIONS

The results of this study confirm the significant burden of acute rotavirus gastroenteritis as a cause of hospitalizations in under five children in India.

Analysis of the CSF model for simulated loss of coolant accident conditions

An experimental facility called Containment Studies Facility (CSF) has been constructed at the Bhabha Atomic Research Centre (BARC) for the purpose of research and development in the area of nuclear reactor containment thermal hydraulics. The facility consists of reinforced concrete containment structural model (CM) and a Primary Heat Transport Model (PHTM) vessel. The containment model of CSF is divided into high enthalpy V1 volume (dry well) and low enthalpy V2 volume (wet well). The PHTM and associated pump and piping system is designed for simulating the Loss of Coolant Accident (LOCA) conditions within the containment model. Experiments were carried out in CSF for 30 bar and 50 bar blowdown conditions. Pressure, temperature and other transient parameters were recorded. The experimental results were compared with outputs of modeling carried out using RELAP code and in-house containment thermal hydraulic code CONTRAN.