Brain mass estimation by head circumference and body mass methods in neonatal glycaemic modelling and control

Introduction

Hyperglycaemia is a common complication of stress and prematurity in extremely low-birth-weight infants. Model-based insulin therapy protocols have the ability to safely improve glycaemic control for this group. Estimating non-insulin-mediated brain glucose uptake by the central nervous system in these models is typically done using population-based body weight models, which may not be ideal.

Method

A head circumference-based model that separately treats small-for-gestational-age (SGA) and appropriate-for-gestational-age (AGA) infants is compared to a body weight model in a retrospective analysis of 48 patients with a median birth weight of 750 g and median gestational age of 25 weeks. Estimated brain mass, model-based insulin sensitivity (S_I) profiles, and projected glycaemic control outcomes are investigated. SGA infants (5) are also analyzed as a separate cohort.

Results

Across the entire cohort, estimated brain mass deviated by a median 10% between models, with a per-patient median difference in S_I of 3.5%. For the SGA group, brain mass deviation was 42%, and per-patient S_I deviation 13.7%. In virtual trials, 87–93% of recommended insulin rates were equal or slightly reduced (Δ < 0.16 mU/h) under the head circumference method, while glycaemic control outcomes showed little change.

Conclusion

The results suggest that body weight methods are not as accurate as head circumference methods. Head circumference-based estimates may offer improved modelling accuracy and a small reduction in insulin administration, particularly for SGA infants.     

4-(α-吡啶甲酰基)-PMP的合成与谱学特性研究

合成了新吡唑啉酮类试剂1-苯基-3-甲基-4-(α-吡啶甲酰基)-吡唑啉-5-酮(简称4-(α-吡啶甲酰基)-PMP,下同)。在表征分子结构的同时,对其红外、紫外吸收光谱,核磁共振氢谱、碳谱,质谱等谱学特性和质谱裂解规律进行了分析与研究。     

Method for characterization of triacylglycerols and fat-soluble vitamins in edible oils and fats by supercritical fluid chromatography

This study demonstrates the usefulness of capillary supercritical fluid chromatography (SFC) for the characterization of triacylglycerols of edible oils and fats. Triacylglycerols were separated according to the acyl carbon number and the degree of unsaturation on a 25% cyanopropyl/25% phenyl/50% methylpolysiloxane stationary phase. Valuable information concerning the triacylglycerol composition of berry oils was obtained, despite the overlapping of certain triacylglycerol peaks. Simultaneous analysis of fat-soluble vitamins and triacylglycerols is not practical by capillary SFC with flame-ionization detection because of the low concentration of naturally-occurring fat-soluble vitamins in edible oils. Therefore, higher loading of the sample, which led to overloading of triacylglycerols, was required to get reasonable peaks for fat-soluble vitamins. The method was applied to the characterization of triacylglycerols and tocopherols in sea buckthorn pulp and seed oil, and cloudberry seed oil without any sample purification prior to SFC. In addition, the stationary phase proved useful for separating the more complex mixtures of triacylglycerols found in milk fat and in fish oil.     

模拟三相流化床中颗粒尺寸对单气泡传质系数的影响

本文在模拟三相流化床中,测量了单气泡的传质系数,实验结果表明颗粒直径对气-液传质系数影响显著。颗粒直径较大时,传质系数有明显提高。     

Matrix‐assisted laser desorption/ionization mass spectrometry of synthetic polymers. VI. Analysis of phenol–urea–formaldehyde cocondensates

Phenolic resoles can be regarded as copolymers of phenol and formaldehyde that are distributed in the chain length and the number of methylol groups per molecule. While other spectroscopic methods like FTIR and NMR only give average structures, MALDI–TOF mass spectrometry is able to resolve the oligomer distribution of phenolic resoles. Using 2,5‐dihydroxybenzoic acid or 2,4,6‐trihydroxyacetophenone as matrices, MALDI–TOF spectra are obtained where each oligomer peak can be assigned to a particular chemical structure. Thus, the degree of polymerization and the number of reactive methylol groups can be determined. For urea‐modified resoles, in addition to phenol–formaldehyde and urea–formaldehyde structures, for the first time, phenol–urea–formaldehyde cocondensate structures can be identified directly. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 2540–2548, 2003     

Separation of kinetics and mass-transfer in a batch alkoxylation reaction

The quantitative aspects of the role of interfacial mass-transfer and reaction kinetics in ethoxylation of lauryl alcohol were examined in a batch recirculation reactor. The liquid droplets falling through a gas column were obtained by utilizing a recirculation loop and a set of spray nozzles. The CO₂/NaOH reaction was employed to characterize the interfacial area. The alkoxylation reaction was studied at temperatures between 124°C and 171°C, at catalyst levels between 0.09 and 0.50 weight percent and at ethylene oxide partial pressures between 68 kPa and 204 kPa. A model was developed which permits the prediction of reactor performance at various operating conditions. The mass-transfer during free fall dominates the interfacial mass-transfer and the contributions during the drop formation and coalescence stages are small. The rate of ethylene oxide (EO) addition to lauryl alcohol was constant during the batch run, indicating similar activity for the unreacted lauryl alcohol and the lauryl alcohol ethoxylated to varying extents. The rate of ethoxylation is first-order in both catalyst and ethylene oxide concentrations. The liquid-phase reaction kinetics and interfacial mass-transfer occur in series, with kinetics dominating the overall ethoxylation rate. As expected, an increasing role of mass transfer is observed at higher temperatures, and/or higher catalyst concentrations where the kinetic rate becomes significantly high. The intrinsic activation energy for the ethoxylation of lauryl alcohol is 55.2 kJ/mole.     

Study of Hydrodynamics,Mixing and Gas‐Liquid Mass Transfer in a Split‐Rectangular Airlift Reactor

Global hydrodynamic characteristics, liquid mixing and gas‐liquid mass transfer for a 63 L split‐rectangular airlift reactor were studied. Correlations for gas holdup and overall liquid circulation velocity were derived for the air‐water system as a function of the specific power input; these were compared to data and correlations for reactor volumes between 4.7 L and 4600 L. A partial recirculation of small bubbles in the riser was observed when U_gr > 0.03 m/s, which was attributed to the use of a single‐orifice nozzle as the gas phase distributor. The dimensionless mixing time and the overall axial dispersion coefficient were nearly constant for the range of gas flow rates studied. However, values of K_L/d_B were greater than those reported in previous studies and this is caused by the partial recirculation of the gas phase in the riser. While scale effects remain slight, the use of a gas distributor favouring this partial recirculation seems adequate for mass transfer in split‐rectangular airlift reactors.     

Separation of Triacylglycerol Species from Interesterified Oils by High-Performance Liquid Chromatography

Using a 1,3-regioselective lipase as a catalyst, soybean oil and olive oil were interesterified with the short-chain triacylglycerol tributyrin (1,2,3-tributyrylglycerol) to produce mixtures of structured triacylglycerols (SL-TAG). The SL-TAG were purified by column chromatography and analyzed by both normal-phase (silica column; NP_SIL) and reversed-phase [octadecyl silane (ODS) column] high-performance liquid chromatography (HPLC). Individual SL-TAG molecular species were detected by evaporative light-scattering detection, and characterized by mass spectrometry. NP_SIL HPLC successfully separated the newly synthesized SL-TAG into two groups of TAG: one composed of one butyryl group and two long-chain fatty acyl groups (from soybean or olive oil); the second was composed of two butyryl groups and one long-chain fatty acyl group. The SL-TAG species were further analyzed by reversed-phase HPLC which gave a more detailed separation of the TAG species present in the two SL-TAG.     

Study of mass transfer in a vertically moving particle bed electrode

A study was made of the influence of process parameters on the mass-transfer coefficient in a flow-through cell with a cascade of rotating drums partially filled with conductive particles (called the vertically moving particle bed). Copper deposition from an acidic sodium sulphate solution was used as the model reaction. To evaluate the experimental data a macrohomogeneous mathematical model of potential and current density distribution inside the cell was developed. The electrolyte flow distribution between the empty space above the particle bed and through the bed was evaluated. On the basis of these results the following correlation is proposed: