Fabrication of Polyimide-Modified UHMWPE Composites and Enhancement Effect on Tribological Properties

Polyimide-modified ultrahigh molecular weight polyethylene (UHMWPE) composites were fabricated by hot-press molding process. Mesoscopic morphologies of polyimide/UHMWPE blending systems show high compatibility between the phases of polyimide and UHMWPE when the weight ratio of polyimide is no more than 50?wt%. Investigation of the tribological properties with a reciprocating ball-on-flat contact tribometer shows that the polyimide filler has important effects on the friction and wear behavior of UHMWPE composites. Compared to pure UHMWPE, the composite with 50?wt% polyimide improved tribological properties best and exhibited 43.1% reduction in friction coefficient and 66.7% reduction in wear volume loss.     

Conformation Analysis of GalNAc‐Appended Sugar Amino Acid Foldamers as Glycopeptide Mimics

Sugar amino acid (SAA)‐based foldamers with well‐defined secondary structures were appended with N‐acetylgalactosamine (GalNAc) sugars to access sequence‐defined, multidentate glycoconjugates with full control over number, spacing and position. Conformation analysis of these glycopeptides by extensive NMR spectroscopic studies revealed that the appended GalNAc units had a profound influence on the native conformational behaviour of the SAA foldamers. Whereas the 2,5‐cis glycoconjugate showed a helical structure in water, comprising of two consecutive 16‐membered hydrogen bonds, its 2,5‐trans congener displayed an unprecedented 16/10‐mixed turn structure not seen before in any glycopeptide foldamer.     

Scale-up of pump-mix mixers using CFD

Effect of scale on the drop size distribution in a pump-mix mixer has been studied. A network of zones model was developed to predict the drop size distribution at different locations in the mixer. Computational fluid dynamics model was used to obtain the flow patterns in the mixer and to identify zones based on the flow patterns. Population balance equation was solved for all the zones of the mixer. The model was validated with the experimental data over a wide range of parameters as well experimental data from the published literature. The model was further extended for scale-up studies. Two different scale-up criteria were studied. It was observed that equal power consumption per unit mass and geometrical similarity is a better scale-up criterion as compared with equal tip speed criterion for pump-mix mixers.     

Comparing error estimation measures for polynomial and kriging approximation of noise-free functions

Error estimation measures are useful for assessing uncertainty in surrogate predictions. We use a suite of test problems to appraise several error estimation measures for polynomial response surfaces and kriging. In addition, we study the performance of cross-validation error measures that can be used with any surrogate. We use 1,000 experimental designs to obtain the variability of error estimates with respect to the experimental designs for each problem. We find that the (actual) errors for polynomial response surfaces are less sensitive to the choice of experimental designs than the kriging errors. This is attributed to the variability in the maximum likelihood estimates of the kriging parameters. We find that no single error measure outperforms other measures on all the problems. Computationally expensive integrated local error measures (standard error for polynomials and mean square error for kriging) estimate the actual root mean square error very well. The distribution-free cross-validation error characterized the actual errors reasonably well. While the estimated root mean square error for polynomial response surface is a good estimate of the actual errors, the process variance for kriging is not. We explore a few methods of simultaneously using multiple error measures and demonstrate that the geometric means of several combinations of error measures improve the assessment of the actual errors over individual error measures.     

Pharmacokinetics and safety of tobramycin after once-daily administration in patients with cystic fibrosis

STUDY OBJECTIVE: Tobramycin is commonly used to treat respiratory tract infections in patients with cystic fibrosis. We designed a study to determine the pharmacokinetics and safety of once-daily dosing of tobramycin in this population. DESIGN: Multiple blood samples were collected from each patient, and serum concentrations of tobramycin were determined by a fluorescence polarization immunoassay. Blood urea nitrogen and serum creatinine levels were measured every 2 to 3 days, and audiometric evaluations were performed at the start and end of therapy. MEASUREMENTS AND RESULTS: Eighteen patients (mean age, 24.6 years) received tobramycin at doses of 7 to 15 mg/kg/d as a single-dose infusion over 20 min. The maximum serum concentration of tobramycin ranged from 40.1 to 64.6 mg/L. A mean dose of 11.9+/-1.9 mg/kg was needed to obtain a theoretical mean peak serum concentration of 42.4+/-4.5 mg/L. The mean total body clearance, apparent volume of distribution, and elimination half-life was 1.7+/-0.4 mL/min/kg, 0.27+/-0.06 L/kg, and 1.8+/-0.3 h, respectively. The period of time that the serum concentration exceeded eight times the theoretical minimum inhibitory concentration of 1 mg/L ranged from 2.1 to 4.4 h, which was nearly five times longer compared with the use of divided daily doses in the same patients during previous hospitalizations. No nephrotoxicity, ototoxicity, or adverse effects occurred in any patient. CONCLUSION: Based on our data, tobramycin may be used safely in once-daily doses to treat exacerbations of respiratory tract infections in patients with cystic fibrosis.     

Ensemble of surrogates

The custom in surrogate-based modeling of complex engineering problems is to fit one or more surrogate models and select the one surrogate model that performs best. In this paper, we extend the utility of an ensemble of surrogates to (1) identify regions of possible high errors at locations where predictions of surrogates widely differ, and (2) provide a more robust approximation approach. We explore the possibility of using the best surrogate or a weighted average surrogate model instead of individual surrogate models. The weights associated with each surrogate model are determined based on the errors in surrogates. We demonstrate the advantages of an ensemble of surrogates using analytical problems and one engineering problem. We show that for a single problem the choice of test surrogate can depend on the design of experiments.     

Stability of enalapril maleate in three extemporaneously prepared oral liquids

The stability of enalapril 1 mg/mL (as the maleate) in deionized water, citrate buffer solution, and a sweetened suspending agent at two temperatures was studied. Twenty enalapril 10-mg tablets were crushed to a powder. Deionized water, citrate buffer solution, or sweetened vehicle was added to produce three 200-mL batches of each liquid; the expected final concentration of enalapril in each was 1 mg/mL. Each formulation was stored in 10 60-mL bottles, 5 of which were stored at 4 degrees C and 5 at 25 degrees C. Samples were collected on days 0, 7, 14, 28, 42, 56, 70, and 91 for visual inspection and analysis by high-performance liquid chromatography; pH was measured at each sampling time as well. The mean concentration of enalapril in the three liquids at 4 degrees C was > 94% of the initial concentration throughout the 91-day study period. At 25 degrees C, the mean concentration of enalapril was > 90% for 56 days and > 92% for 91 days in both citrate buffer solution and sweetened vehicle. The pH of the liquid prepared with deionized water and stored at 25 degrees C decreased by 2.0 pH units. Enalapril 1 mg/mL (as the maleate) in three extemporaneously compounded oral liquids was stable for 91 days at 4 and 25 degrees C with the exception of enalapril in deionized water, which was stable for only 56 days at 25 degrees C.     

Eosin-G and ethyl eosin dye sensitized CdS nanowires towards dye sensitized solar cells applications

One dimensional (1-D) CdS nanowires have been grown through a low temperature chemical route and have been sensitized with eosin-G and ethyl eosin dyes to broaden the absorption spectrum of CdS and to enhance the photoelectrochemical (PEC) performance under illumination. The used method is advantageous due to its simplicity, low cost, scalability, and controllability. Interestingly, eosin-G and ethyl eosin dyes yield nearly four- and six-fold increase in device efficiency compared to bare CdS when tested in dye-sensitized solar cell assembly. Structural, surface morphological, optical, and surface wettability studies have been formulated for CdS, whereas identification of materials along with PEC investigations were conducted through current density–voltage (J-V), external quantum efficiency (EQE), characteristics under the illumination of 94.6 mW/cm² (AM 1.5G), and electrochemical impedance spectroscopy (EIS).