Liquid Crystal Orientation and Shape Optimization for the Active Response of Liquid Crystal Elastomers.

Liquid crystal elastomers (LCEs) are responsive materials that can undergo large reversible deformations upon exposure to external stimuli, such as electrical and thermal fields. Controlling the alignment of their liquid crystals mesogens to achieve desired shape changes unlocks a new design paradigm that is unavailable when using traditional materials. While experimental measurements can provide valuable insights into their behavior, computational analysis is essential to exploit their full potential. Accurate simulation is not, however, the end goal; rather, it is the means to achieve their optimal design. Such design optimization problems are best solved with algorithms that require gradients, i.e., sensitivities, of the cost and constraint functions with respect to the design parameters, to efficiently traverse the design space. In this work, a nonlinear LCE model and adjoint sensitivity analysis are implemented in a scalable and flexible finite element-based open source framework and integrated into a gradient-based design optimization tool. To display the versatility of the computational framework, LCE design problems that optimize both the material, i.e., liquid crystal orientation, and structural shape to reach a target actuated shapes or maximize energy absorption are solved. Multiple parameterizations, customized to address fabrication limitations, are investigated in both 2D and 3D. The case studies are followed by a discussion on the simulation and design optimization hurdles, as well as potential avenues for improving the robustness of similar computational frameworks for applications of interest.

Topology optimization of 3D photonic crystals with complete bandgaps.

The design of photonic crystals with complete bandgaps has recently received considerable research focus for numerous reasons. This work leverages well-known nonlinear programming techniques to alleviate the non-smoothness caused by degenerate eigenvalues such that topology optimization problems can be solved with the open-source IPOPT software. A fully-vectorial plane wave expansion technique is used with an iterative eigensolver to efficiently predict dispersion properties of candidate structures. Nonlinear programming is employed to solve the inverse problem of designing three-dimensional periodic structures that exhibit complete two-dimensional (2D) and three-dimensional (3D) photonic bandgaps. Mesh refinement is performed to alleviate the large computational burden of designing and analyzing photonic crystals, and a periodic density filter is implemented to impose a minimum feature size for manufacturability considerations.

HPLC Plasma Assay of a Novel Anti-MRSA Compound, Kaempferol-3-O-Alpha-L-(2",3"-di-p-coumaroyl)rhamnoside, from Sycamore Leaves.

Methicillin-resistant Staphylococcus aureus (MRSA) is a serious pathogen that is resistant to current antibiotic therapy. Thus, there is an urgent need for novel antimicrobial agents that can effectively combat these new strains of drug-resistant "superbugs". Recently, fractionation of an extract from Platanus occidentalis (American sycamore) leaves produced an active kaempferol molecule, 3-O-alpha-L-(2",3"-di-p-coumaroyl)rhamnoside (KCR), in four isomeric forms; all four isomers exhibit potent anti-MRSA activity. In order to further the preclinical development of KCR as a new antibiotic class, we developed and validated a simple analytical method for assaying KCR plasma concentration. Because KCR will be developed as a new drug, although comprising four stereoisomers, the analytical method was devised to assay the total amount of all four isomers. In the present work, both a plasma processing procedure and an HPLC method have been developed and validated. Mouse plasma containing KCR was first treated with ethanol and then centrifuged. The supernatant was dried, suspended in ethanol, centrifuged, and the supernatant was injected into an HPLC system comprising a Waters C18, a mobile phase composing methanol, acetonitrile, and trifluoroacetic acid and monitored at 313 nm. The method was validated by parameters including a good linear correlation, a limit of quantification of 0.27 microg/mL, and high accuracy. In summary, this method allows a rapid analysis of KCR in the plasma samples for pharmacokinetics studies.

Using a simple HPLC approach to identify the enzymatic products of UTL-5g, a small molecule TNF-α inhibitor, from porcine esterase and from rabbit esterase.

UTL-5g is a novel small-molecule chemoprotector that lowers hepatotoxicity, nephrotoxicity, and myelotoxicity induced by cisplatin through TNF-α inhibition among other factors. As a prelude to investigating the metabolites of UTL-5g, we set out to identify the enzymatic products of UTL-5g under the treatment of both porcine liver esterase (PLE) and rabbit liver esterase (RLE). First, a number of mixtures made by UTL-5g and PLE were incubated at 25°C. At predetermined time points, individual samples were quenched by acetonitrile, vortexed, and centrifuged. The supernatants were then analyzed by reversed-phase HPLC (using a C18 column). The retention times and UV/vis spectra of individual peaks were compared to those of UTL-5g and its two postulated enzymatic products; thus the enzymatic products of UTL-5g were tentatively identified. Secondly, a different HPLC method (providing different retentions times) was used to cross-check and to confirm the identities of the two enzymatic products. Based on the observations, it was concluded that under the treatment of PLE, the major enzymatic products of UTL-5g were 5-methyliosxazole-3-carboxylic acid (ISOX) and 2,4-dichloroaniline (DCA). Treatment of UTL-5g by RLE also provided the same enzymatic products of UTL-5g from esterase. These results indicate that the peptide bond in UTL-5g was cleaved by PLE/RLE. Michaelis-Menten kinetics showed that the Km values of UTL-5g were 2.07mM with PLE and 0.37mM with RLE indicating that UTL-5g had a higher affinity with RLE. In summary, by a simple HPLC approach, we have concluded that the peptide bond in UTL-5g was cleaved by esterase from either porcine liver or rabbit liver in vitro and afforded DCA (at a mole ratio of 1:1) and ISOX. However, further studies are needed in order to determine whether UTL-5g is metabolized by microsomal enzymes to produce ISOX and DCA.

A novel method for detection of phosphorylation in single cells by surface enhanced Raman scattering (SERS) using composite organic-inorganic nanoparticles (COINs).

BACKGROUND: Detection of single cell epitopes has been a mainstay of immunophenotyping for over three decades, primarily using fluorescence techniques for quantitation. Fluorescence has broad overlapping spectra, limiting multiplexing abilities. METHODOLOGY/PRINCIPAL FINDINGS: To expand upon current detection systems, we developed a novel method for multi-color immuno-detection in single cells using "Composite Organic-Inorganic Nanoparticles" (COINs) Raman nanoparticles. COINs are Surface-Enhanced Raman Scattering (SERS) nanoparticles, with unique Raman spectra. To measure Raman spectra in single cells, we constructed an automated, compact, low noise and sensitive Raman microscopy device (Integrated Raman BioAnalyzer). Using this technology, we detected proteins expressed on the surface in single cells that distinguish T-cells among human blood cells. Finally, we measured intracellular phosphorylation of Stat1 (Y701) and Stat6 (Y641), with results comparable to flow cytometry. CONCLUSIONS/SIGNIFICANCE: Thus, we have demonstrated the practicality of applying COIN nanoparticles for measuring intracellular phosphorylation, offering new possibilities to expand on the current fluorescent technology used for immunoassays in single cells.

Simplified method of hepatic fibrosis quantification: design of a new morphometric analysis application.

INTRODUCTION: Semiquantitative evaluation of liver specimens is considered the standard method for measuring fibrosis; however, these systems lack the precision of a quantitative technique. METHODS: We developed an image analysis application (FibroXact) that automates and simplifies color segmentation. Trichrome slides were scanned and the program was used to evaluate each pixel based upon hue, lightness, and saturation values. Percent fibrosis was automatically calculated after thresholding. RESULTS: Linear regression demonstrated a strong relationship between the FibroXact result and the semiquantitative result (P<0.001). CONCLUSION: We have developed an image analysis application to quantify liver fibrosis. Correlation between our results and a standard semiquantitative system was demonstrated.

Clostridium difficile among hospitalized patients receiving antibiotics: a case-control study.

OBJECTIVES: Clostridium difficile is the most common cause of infectious nosocomial diarrhea and can be found in up to 30% of asymptomatic hospitalized patients. Our primary aim was to compare the clinical characteristics of hospitalized patients who received antibiotics and developed C. difficile-associated diarrhea (CDAD) with those of hospitalized patients who received antibiotics and did not develop the disease. DESIGN: Case-control study comprising inpatients at a single institution. PATIENTS: Case-patients were defined as patients who had diarrhea and tested positive for C. difficile. Control-patients (matched 4:1 to case-patients) were defined as patients who received antibiotics for at least 5 days and did not develop CDAD. RESULTS: On univariate analysis, nine variables were associated with CDAD. Only three of the variables, need for intensive care, length of stay, and macrolide antibiotic use, were found to be significant (P < .05) on logistic regression analysis. The odds ratios for status as a CDAD case were 3.68 (CI95, 1.44 to 9.40) for stay in the intensive care unit and 1.03 (CI95, 1.02 to 1.05) for each day of hospital stay. Receipt of macrolide antibiotics reduced risk significantly; the odds ratio was 0.23 (CI95, 0.19 to 0.87). CONCLUSIONS: We identified need for intensive care and length of stay as important risk factors for the development of CDAD. We also identified macrolide antibiotic use as protective against its development. Patients receiving intensive care may represent a population to study for targeted prophylaxis.

Endoscopic pyloric injection of botulinum toxin A for the treatment of refractory gastroparesis.

BACKGROUND: Botulinum toxin A injected into the pyloric sphincter has been reported in small case series to treat gastroparesis. This study reviews the use of this treatment in a large number of patients with gastroparesis. METHODS: Patients who underwent pyloric botulinum injection for treatment of gastroparesis were identified. Response was defined as improvement or resolution of the patient's major symptom and/or two minor symptoms for 4 weeks. RESULTS: Of 115 patients treated, 63 patients met the study criteria. There were 53 women, 10 men, mean age 42 years. Most patients (56%) had idiopathic gastroparesis. Twenty-seven of 63 (43%) patients experienced a symptomatic response to treatment. By stepwise logistic regression, male gender was associated with response to treatment (OR 3.27: 95% CI[1.31, 8.13], p = 0.01). Vomiting as a major symptom was associated with a lack of response (OR 0.16: 95% CI[0.04, 0.67], p = 0.01). Despite the association of male gender with response, the mean duration of response for those patients responding, with a minimum of 3 months' follow-up was 4.9 months (+/-2.7 months) for women and 3.5 months (+/-0.71 months) for men (p = 0.59). The corresponding medians and interquartile ranges (IQR) were 5 (IQR 3-6) for females and 3.5 (IQR 3-4) for males. CONCLUSIONS: Of the patients, 43% had a response to botulinum toxin treatment that lasted a mean of approximately 5 months. Male gender was associated with a response to this therapy; however, durability of response was unrelated to gender. Vomiting as a major symptom predicted no response.