31P NMR studies of unsonicated aqueous dispersions of neutral and acidic phospholipids. Effects of phase transitions, p2H and divalent cations on the motion in the phosphate region of the polar headgroup

1. The 129 MHz (non-proton decoupled) and 36.4 MHz (proton decoupled) 31P NMR spectra arising from unsonicated aqueous dispersions of well defined species of phospholipid have been investigated. The phospholipids employed (and the parameters varied) include phosphatidylcholine (temperature), phosphatidylethanolamine (temperature), phosphatidic acid (temperature and p2H) and phosphatidylglycerol (temperature, p2H and Ca2+ (or Mg2+)) concentration. 2. At p2H = 7 the 31 P MNR spectra arising from saturated species of phosphatidylcholine, phosphatidylethanolamine and phosphatidylglycerol become progressively broader as the temperature is reduced below the phase transition, demonstrating reduced motion in the phosphate region of the polar headgroup. 3. In the liquid crystalline state at p2H = 7 the molecular dipolar order parameters obtained for saturated species of phosphatidylcholine, phosphatidylethanolamine and phosphatidylglycerol and very similar, and are independent of the acyl chain length for species derived from lauric and myristic acid. Thus the motion in the methylene-phosphate-methylene region is similar for these different liquid crystaline phospholipid species. 4. The 31 P NMR spectra of aqueous dispersions of 14:0/14:0 phosphatidic acid display anomalous temperature and p2H dependences. The effective chemical shift anistropy (delta v CSA EFF) at 5 degrees C varies from 71 ppm at p2H = 8.5 to 38 ppm at p2H = 2.5. Further, the motion in the phosphate region is relatively insensitive to the gel or liquid crystalline nature of the hydrocarbon chains. 5. The addition of 40 mol% Ca2+ (or Mg2+) to saturated species of phosphatidylglycerol causes an increase of approx. 20 degrees C in the hydrocarbon phase transition temperature as indicated by 31 P NMR. Equimolar concentrations of Ca2+ increase the transition temperature by approx. 70 degrees C, and no 31P NMR signal could be observed for the very condensed precipitate formed below this temperature. In the liquid crystalline state the motion in the phosphate region of the polar headgroup is not significantly affected by the presence of Ca+ or Mg2+. 6. The 31P NMR spectra obtained from 18 : 1c/18 : 1c phosphatidylethanolamine are consistent with a phase transition from a lamellar to an hexagonal (HII) phase in the region 10-15 degrees C. 7. The observed narrowing of the 31 P NMR spectra of aqueous dispersions of phospholipids as the temperature is raised toward the hydrocarbon transition temperature is discussed in terms of the "pretransition" observed in calorimetric studies.     

Mixed mode fracture toughness of GFRP composites

Glass fibre reinforced polymer (GFRP) composites are used in a wide range of applications as a structural material. They have high specific mechanical properties but are prone to delamination as a result of manufacturing defects and impact/shock loading. The ability of the structure to continue to carry load after damage and the subsequent propensity of the damage to propagate are important considerations for the design of damage tolerant composite structures. In order to accurately predict the stability of damage under load, relevant mechanical properties of the material must be accurately determined. In particular, mixed mode fracture toughness data is required in order to study the damage criticality in such structures. This paper describes an experimental study to determine Mixed Mode fracture toughness for thick glass/vinylester specimens. The test methodology used for the experiments and its difficulties will be discussed. Mixed mode fracture toughness results are presented, as are Mode I and Mode II fracture toughness results obtained via Double Cantilever Beam (DCB) and End Notch Flexure (ENF) tests, respectively.     

A method for using legacy data for metamodel-based design of large-scale systems

Despite a steady increase in computing power, the complexity of engineering analyses seems to advance at the same rate. Traditional parametric design analysis is inadequate for the analysis of large-scale engineering systems because of its computational inefficiency; therefore, a departure from the traditional parametric design approach is required. In addition, the existence of legacy data for complex, large-scale systems is commonplace. Approximation techniques may be applied to build computationally inexpensive surrogate models for large-scale systems to replace expensive-to-run computer analysis codes or to develop a model for a set of nonuniform legacy data. Response-surface models are frequently utilized to construct surrogate approximations; however, they may be inefficient for systems having with a large number of design variables. Kriging, an alternative method for creating surrogate models, is applied in this work to construct approximations of legacy data for a large-scale system. Comparisons between response surfaces and kriging are made using the legacy data from the High Speed Civil Transport (HSCT) approximation challenge. Since the analysis points already exist, a modified design-of-experiments technique is needed to select the appropriate sample points. In this paper, a method to handle this problem is presented, and the results are compared against previous work.     

Mixed-integer linear programming models for batch sterilization of packaged-foods plants

Batch sterilization with individual retorts is a common mode of operation in many food-canning plants. Although high-speed processing with continuous rotary or hydrostatic retort systems is used in very large canning factories, such systems are not economically feasible in the majority of small- to medium-sized canneries. In such canneries, sterilization is carried out in a battery of retorts as a batch process. Although the unloading and reloading operations for each retort are labor intensive, a well-designed and managed plant can operate with surprising efficiency if it has the optimum number of retorts and scheduling of retort operation. The objective of this research was to present two mathematical models for sterilization scheduling in food-canning plants. The first model developed is for the case where given amount of different canned food products with specific quality requirements would be sterilized within a minimum plant operation time in an autoclave of given capacity. The second model addresses the problem of maximizing the amount of sterilized products in an autoclave of given capacity for given plant operation time. The developed models were based on mixed-integer linear programming and incorporated the possibility of simultaneous sterilization. Simultaneous sterilization applies mainly to small canneries with few retorts. In these situations, retorts often operate with only partial loads because of the small lot sizes, and they are severely under-utilized. In order to demonstrate the feasibility of the mixed-integer linear programming (MILP) models, several examples involving the sterilization of different products were included in this research. The methodology proposed in this study is of special relevance for small- and medium-sized food-canning plants that normally work with many different products at the same time.     

Techniques for monitoring protein misfolding and aggregation in vitro and in living cells

Protein misfolding and aggregation have been considered important in understanding many neurodegenerative diseases and recombinant biopharmaceutical production. Various traditional and modern techniques have been utilized to monitor protein aggregation in vitro and in living cells. Fibril formation, morphology and secondary structure content of amyloidogenic proteins in vitro have been monitored by molecular probes, TEM/AFM, and CD/FTIR analyses, respectively. Protein aggregation in living cells has been qualitatively or quantitatively monitored by numerous molecular folding reporters based on either fluorescent protein or enzyme. Aggregation of a target protein is directly correlated to the changes in fluorescence or enzyme activity of the folding reporter fused to the target protein, which allows non-invasive monitoring aggregation of the target protein in living cells. Advances in the techniques used to monitor protein aggregation in vitro and in living cells have greatly facilitated the understanding of the molecular mechanism of amyloidogenic protein aggregation associated with neurodegenerative diseases, optimizing culture conditions to reduce aggregation of biopharmaceuticals expressed in living cells, and screening of small molecule libraries in the search for protein aggregation inhibitors.     

Mealtime Behaviors and Food Consumption of Perceived Picky and Nonpicky Eaters through Home Use Test

Picky eating has been investigated through numerous surveys and food recalls, but few studies have applied in‐home meal evaluations as a method to investigate behaviors and food preferences of children perceived by their parent to be a picky eater (PE) or nonpicky eater (NPE). A 2‐wk in‐home meal study was completed to investigate differences in PE and NPE mealtime behaviors and food selections using real‐time parental observations. Parents (n = 170) and their 2‐ to 4‐y‐old children (83 PE and 87 NPE) evaluated 5 standardized meals in‐home. Parents recorded their child's and their own hedonic liking of the products and completed an assessment of their child's behavior and consumption at each meal. Significant differences were found between perceived PE and NPE children for all 16 behaviors assessed. On average, perceived NPE were assessed to consume a higher percentage of the meal served and to have higher acceptance scores for most of the foods evaluated. Some foods, though, like breaded chicken and plain pasta, were liked equally by PE and NPE. Several significant differences in hedonic liking were revealed when PE children were compared to their parents. Yet, few differences in liking occurred between NPE children and their parents or between the 2 parental groups. Because study participants evaluated meals real‐time rather than memory recall, the differences and similarities found between perceived PE and NPE may be considered direct experiential evidence with reduced subjective bias as created when subjects recall past experiences. Thus, findings from this study can provide the foundation to establish an objective definition and classification of PE and NPE.     

Drop printing of pharmaceuticals: Effect of molecular weight on PEG coated‐naproxen/PEG 3350 solid dispersions

Solid dispersions have been used to enhance the bioavailability of poorly water‐soluble active pharmaceutical ingredients (APIs). However, the solid‐state phase, compositional uniformity, and scale‐up problems are issues that need to be addressed. To allow for highly controllable products, the drop printing (DP) technique can provide precise dosages and predictable compositional uniformity of APIs in two‐/three‐dimensional structures. DP was used to prepare naproxen (NAP)/polyethylene glycol 3350 (PEG 3350) solid dispersions with PEG coatings of different molecular weights (MWs). A comparison of moisture‐accelerated crystallization inhibition by different PEG coatings was assessed. Scanning electron microscopy, second harmonic generation microscopy, and differential scanning calorimetry analysis were performed to characterize the morphology and quantify the apparent crystallinity of NAP within the solid dispersions. Thermogravimetric analysis was employed to measure the water content within each sample. The results suggest that the moisture‐accelerated crystallization inhibition capability of the PEG coatings increased with increasing MW of the PEG coating. Besides, to demonstrate the flexibility of DP technology on manufacturing formulation, multilayer tablets with different PEG serving as barrier layers were also constructed, and their dissolution behavior was examined. By applying DP and appropriate materials, it is possible to design various carrier devices used to control the release dynamics of the API. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4502–4508, 2015