Rigorous Multicomponent Reactive Separations Modelling : Complete Consideration of Reaction-Diffusion Phenomena

This paper gives the first step of the development of a rigorous multicomponent reactive separation model. Such a model is highly essential to further the optimization of acid gases removal plants (CO2 capture, gas treating, etc.) in terms of size and energy consumption, since chemical solvents are conventionally used.Firstly, two main modelling approaches are presented: the equilibrium-based and the rate-based approaches. Secondly, an extended rate-based model with rigorous modelling methodology for diffusion-reaction phenomena is proposed. The film theory and the generalized Maxwell-Stefan equations are used in order to characterize multicomponent interactions. The complete chain of chemical reactions is taken into account. The reactions can be kinetically controlled or at chemical equilibrium, and they are considered for both liquid film and liquid bulk. Thirdly, the method of numerical resolution is described. Coupling the generalized Maxwell-Stefan equations with chemical equilibrium equations leads to a highly non-linear Differential-Algebraic Equations system known as DAE index 3. The set of equations is discretized with finite-differences as its integration by Gear method is complex. The resulting algebraic system is resolved by the Newton- Raphson method. Finally, the present model and the associated methods of numerical resolution are validated for the example of esterification of methanol. This archetype non-electrolytic system permits an interesting analysis of reaction impact on mass transfer, especially near the phase interface. The numerical resolution of the model by Newton-Raphson method gives good results in terms of calculation time and convergence. The simulations show that the impact of reactions at chemical equilibrium and that of kinetically controlled reactions with high kinetics on mass transfer is relatively similar. Moreover, the Fick’s law is less adapted for multicomponent mixtures where some abnormalities such as counter-diffusion take place

Bi-layer splitting in overdoped high TcT_{c} cuprates

Recent angle-resolved photoemission data for overdoped Bi2212 are explained. Of the peak-dip-hump structure, the peak corresponds the $\vec q =0$ component of a hole condensate which appears at $T_c$. The fluctuating part of this same condensate produces the hump. The bilayer splitting is large enough to produce a bonding hole and an electron antibonding quasiparticle Fermi surface. Smaller bilayer splittings observed in some experiments reflect the interaction of the peak structure with quasiparticle states near, but not at, the Fermi surface.Comment: 4 pages with 2 figures - published versio

An epidemiological study of common drugs in the health supply chain

PurposeThe study aims to provide insights into the availability of common drugs with respect to disease load, regarding three common childhood diseases, acute respiratory infection (ARI), diarrhoea and malaria. The study flags an important issue regarding the level of expertise of the present system to address humanitarian logistics in case of emergency.Design/methodology/approachA mixed‐method approach using both qualitative and quantitative study techniques was used to collect data. Hospital level data were collected from randomly selected primary health centers and community health centers. a cohort of three community health centers and nine primary health centers were selected for the study. The data collected were both on disease load and availability of drugs during the study period (2009‐2012), using a retrospective cohort. Expert interviews were conducted of practising medical practitioners on classification of drugs into Vital, Essential and Desirable categories.FindingsResults show that the month of September represents the highest morbidity (case loads of all three diseases taken together). Acute respiratory infection is most prevalent among the three diseases, with total case loads of 1,539 cases during the month of September (during 2009‐2012). However the Vital and Essential drugs availability for acute respiratory infection was found to be 7 per cent, 57 per cent for malaria and 98 per cent for diarrhoea. Drug supply was not only inadequate but also uneven and erratic, having weak correlation with the pattern of disease morbidity.Research limitations/implicationsCases who attended the government‐owned health centres were only considered for the study and it did not consider those who were attended by private practitioners. The study did highlight the capability of the system to manage ongoing health supplies and the extent of vulnerability it can pose in case of any humanitarian crisis but the latter remains outside the scope of the present study.Originality/valueThe study adds to the existing body of literature by demonstrating the gap that exists in availability of drugs against requirement, for common childhood illness. The study provides health policy makers with a useful guide to establish drugs requirement based on disease load, which holds policy implications across other low and middle income countries as well.</jats:sec

Nodal positivity between &lt;12 and &gt;12 lymph nodes harvested in colorectal cancer undergoing SLNM compared with conventional surgery

4048 Background: Sentinel Lymph Node Mapping (SLNM) upstages significantly more patients (pts) than conventional surgery (Conv Sx) in Colon Cancer (CCa). According to current guidelines, the examination of 12 or more LNs are required to ensure accurate staging. Our study compares the rates of nodal positivity between differing numbers of total Lymph Nodes (LNs) harvested to see if the nodal positivity of &lt;12 LN harvested by SLNM is equivalent to &gt;12 LN obtained by Conv Sx. Methods: Of 951 pts with CCa, 545 pts underwent SLNM and standard oncological resection; 406 pts received Conv Sx without SLNM. The total number of LNs harvested for each pt as well as number of pts with metastatic LNs were recorded. Pts were grouped according to 2–11 LNs, 12–25 LNs and &gt;25 LNs. Results: Of 951 pts, 81 pts in SLNM group and 6 in Conv Sx group were excluded due to benign disease. Average (avg) total nodes harvested in 2–11 node group for SLNM and Conv Sx was 7.9 vs 6.8 nodes respectively. Overall nodal positivity for SLNM pts and Conv Sx pts in the 2–11 node groups was 48% vs. 33% (p=.02). In the 12–25 node group, avg total number of LNs harvested was 17.23 and 16.32 respectively. In the 12–25 node group, 53% of pts in the SLNM arm had +ve nodes vs 44% (p=0.17) in the Conv Sx group. In pts with &gt;25 nodes harvested avg nodal positivity was 33.78% vs 32.38% for SLNM and Conv Sx. Overall nodal positivity was 55% for SLNM vs 37% for Conv Sx group. When SLNM pts with 2–11 LN harvested were compared to Conv Sx pts with 12–25 LN harvested, nodal positivity was 48% vs 44% (p=0.55). Conclusions: Increased survival has been shown when &gt;12 nodes are harvested in CCa. On avg SLNM identified a higher number of total nodes than conventional surgery. In addition, SLNM pts had higher nodal positivity with &lt;12 LNs harvested compared to the nodal positivity of &gt;12 nodes harvested in the Conv Sx group. A higher number of LN harvested coupled with a greater nodal positivity with less LNs make SLNM a more accurate way to stage CCa. [Table: see text] No significant financial relationships to disclose. </jats:p