An Artificial Gut/Absorption Simulator: Understanding the Impact of Absorption on In Vitro Dissolution, Speciation, and Precipitation of Amorphous Solid Dispersions.

Upon dissolution, amorphous solid dispersions (ASDs) of poorly water-soluble compounds can generate supersaturated solutions consisting of bound and free drug species that are in dynamic equilibrium with each other. Only free drug is available for absorption. Drug species bound to bile micelles, polymer excipients, and amorphous and crystalline precipitate can reduce the drug solute's activity to permeate, but they can also serve as reservoirs to replenish free drug in solution lost to absorption. However, with multiple processes of dissolution, absorption, and speciation occurring simultaneously, it may become challenging to understand which processes lead to an increase or decrease in drug solution concentration. Closed, nonsink dissolution testing methods used routinely, in the absence of drug removal, allow only for static equilibrium to exist and obscure the impact of each drug species on absorption. An artificial gut simulator (AGS) introduced recently consists of a hollow fiber-based absorption module and allows mass transfer of the drug from the dissolution media at a physiological rate after tuning the operating parameters. In the present work, ASDs of varying drug loadings were prepared with a BCS-II model compound, ketoconazole (KTZ), and hypromellose acetate succinate (HPMCAS) polymer. Simultaneous dissolution and absorption testing of the ASDs was conducted with the AGS, and simple analytical techniques were utilized to elucidate the impact of bound drug species on absorption. In all cases, a lower amount of crystalline precipitate was formed in the presence of absorption relative to the nonsink dissolution "control". However, formation of HPMCAS-bound drug species and crystalline precipitate significantly reduced KTZ absorption. Moreover, at high drug loading, inclusion of an absorption module was shown to enhance ASD dissolution. The rank ordering of the ASDs with respect to dissolution was significantly different when nonsink dissolution versus AGS was used, and this discrepancy could be mechanistically elucidated by understanding drug dissolution and speciation in the presence of absorption.

Photochemical C(sp3)-H Activation for Diversity-Oriented Synthesis of 3-Functionalized Oxindoles.

Heteroatom-adjacent C(sp3) radical cyclization of N-arylacrylamides provides a straightforward pathway to synthesize valuable 3-functionalized oxindoles. Traditional cyclization reactions normally require harsh conditions or transition-metal catalysts. Here, we developed a metal-free, diversity-oriented synthesis of 3-functionalized oxindoles via photochemically induced selective cleavage of C(sp3)-H bonds. A variety of 3-substituted oxindoles with functionalities such as ethers, polyhalogens, benzyl, and formyl groups can be obtained by a rational design. This strategy is characterized by its simple operation and mild conditions, aligning well with the developmental requirements for sustainable chemistry. The gram-scale continuous-flow synthesis and efficient construction of bioactive molecules highlight its practical utility.

A Refined Thin-Film Model for Drug Dissolution Considering Radial Diffusion - Simulating Powder Dissolution.

PURPOSE: We aim to present a refined thin-film model describing the drug particle dissolution considering radial diffusion in spherical boundary layer, and to demonstrate the ability of the model to describe the dissolution behavior of bulk drug powders. METHODS: The dissolution model introduced in this study was refined from a radial diffusion-based model previously published by our laboratory (So et al. in Pharm Res. 39:907-17, 2022). The refined model was created to simulate the dissolution of bulk powders, and to account for the evolution of particle size and diffusion layer thickness during dissolution. In vitro dissolution testing, using fractionated hydrochlorothiazide powders, was employed to assess the performance of the model. RESULTS: Overall, there was a good agreement between the experimental dissolution data and the predicted dissolution profiles using the proposed model across all size fractions of hydrochlorothiazide. The model over-predicted the dissolution rate when the particles became smaller. Notably, the classic Nernst-Brunner formalism led to an under-estimation of the dissolution rate. Additionally, calculation based on the equivalent particle size derived from the specific surface area substantially over-predicted the dissolution rate. CONCLUSION: The study demonstrated the potential of the radial diffusion-based model to describe dissolution of drug powders. In contrast, the classic Nernst-Brunner equation could under-estimate drug dissolution rate, largely due to the underlying assumption of translational diffusion. Moreover, the study indicated that not all surfaces on a drug particle contribute to dissolution. Therefore, relying on the experimentally-determined specific surface area for predicting drug dissolution is not advisable.

Preparation and epitope analysis of monoclonal antibodies against African swine fever virus DP96R protein.

BACKGROUND: Many proteins of African swine fever virus (ASFV, such as p72, p54, p30, CD2v, K205R) have been successfully expressed and characterized. However, there are few reports on the DP96R protein of ASFV, which is the virulence protein of ASFV and plays an important role in the process of host infection and invasion of ASFV. RESULTS: Firstly, the prokaryotic expression vector of DP96R gene was constructed, the prokaryotic system was used to induce the expression of DP96R protein, and monoclonal antibody was prepared by immunizing mice. Four monoclonal cells of DP96R protein were obtained by three ELISA screening and two sub-cloning; the titer of ascites antibody was up to 1:500,000, and the monoclonal antibody could specifically recognize DP96R protein. Finally, the subtypes of the four strains of monoclonal antibodies were identified and the minimum epitopes recognized by them were determined. CONCLUSION: Monoclonal antibody against ASFV DP96R protein was successfully prepared and identified, which lays a foundation for further exploration of the structure and function of DP96R protein and ASFV diagnostic technology.

Immobilization of Perylenetetracarboxylic Dianhydride on Al2O3 for Efficiently Photocatalytic Sulfide Oxidation.

Perylenetetracarboxylic dianhydride (PTCDA) derivatives have received significant attention as molecule photocatalysts. However, the poor recyclability of molecule-type photocatalysts hinders their widespread applications. Herein, immobilization of PTCDA on Al2O3 was achieved by simply physical mixing, which not only dramatically improved their recyclability, but also surprisingly improved the reactivity. A mechanism study suggested that the photo-exited state (PTCDA*) of PTCDA could promote the oxidation of thioanisole to generate PTCDA•-, which sequentially reduces oxygen to furnish superoxide radicals to achieve the catalytic cycle. Herein, the immobilization support Al2O3 was able to facilitate the strong adsorption of thioanisole, thereby boosting the photocatalytic activity. This work provides a new insight that the immobilization of organic molecular photocatalysts on those supports with proper adsorption sites could furnish highly efficient, stable, and recyclable molecular-based heterogeneous photocatalysts.

Development of an Amorphous Solid Dispersion Formulation for Mitigating Mechanical Instability of Crystalline Form and Improving Bioavailability for Early Phase Clinical Studies.

In this work, an amorphous solid dispersion (ASD) formulation was systematically developed to simultaneously enhance bioavailability and mitigate the mechanical instability risk of the selected crystalline form of a development drug candidate, GDC-0334. The amorphous solubility advantage calculation was applied to understand the solubility enhancement potential by an amorphous formulation for GDC-0334, which showed 2.7 times theoretical amorphous solubility advantage. This agreed reasonably well with the experimental solubility ratio between amorphous GDC-0334 and its crystalline counterpart (∼2 times) in buffers of a wide pH range. Guided by the amorphous solubility advantage, ASD screening was then carried out, focusing on supersaturation maintenance and dissolution performance. It was found that although the type of polymer carrier did not impact ASD performance, the addition of 5% (w/w) sodium dodecyl sulfate (SDS) significantly improved the GDC-0334 ASD dissolution rate. After ASD composition screening, stability studies were conducted on selected ASD powders and their hypothetical tablet formulations. Excellent stability of the selected ASD prototypes with or without tablet excipients was observed. Subsequently, ASD tablets were prepared, followed by in vitro and in vivo evaluations. Similar to the effect of facilitating the dissolution of ASD powders, the added SDS improved the disintegration and dissolution of ASD tablets. Finally, a dog pharmacokinetic study confirmed 1.8 to 2.5-fold enhancement of exposure by the developed ASD tablet over the GDC-0334 crystalline form, consistent with the amorphous solubility advantage of GDC-0334. A workflow of developing an ASD formulation for actual pharmaceutical application was proposed according to the practice of this work, which could provide potential guidance for ASD formulation development in general for other new chemical entities.

Comparative Evaluation of Particle Size Reduction, Salt Formation, and Amorphous Formulation on the Biopharmaceutical Performance of a Weak Base Drug Candidate.

Various approaches have been developed to enhance the solubility or dissolution rate for the delivery of poorly water-soluble molecules. In this work, guided by an in silico solubility sensitivity analysis for oral absorption, a comparative assessment of the biopharmaceutical performance of a jet-milled free base, a tosylate salt, and a 50:50 (w/w) amorphous solid dispersion (ASD) with hydroxypropyl methylcellulose acetate succinate (HPMCAS) of a weak base drug candidate, GDC-3280, was conducted. Successful particle size reduction without amorphization or form change was confirmed for the jet-milled free base. The potential of solubility enhancement and desupersaturation risk were identified for tosylate salt and ASD formulation by measurements of tosylate salt solubility product constant (Ksp) and amorphous solubility of GDC-3280. In vitro dissolution testing demonstrated dissolution rate improvement for the jet-milled free base when compared with the unmilled free base and confirmed solubility enhancement followed by desupersaturation for GDC-3280 tosylate salt and ASD formulation. A crystallization inhibitor, hydroxypropyl methylcellulose (HPMC), was found to slow down the desupersaturation of tosylate salt solution, providing general insights for the development of pharmaceutical salts with disproportionation risks. Finally, a pharmacokinetic study in dogs showed that the in vivo exposure increased by 1.7- to 2-fold for the tosylate salt and ASD formulation compared with the jet-milled free base, consistent with the in silico solubility sensitivity analysis for the fraction of drug absorbed. Overall, this work provides insights into the evaluation of multiple formulation approaches for enhancing the biopharmaceutical performance of poorly water-soluble drugs.

Prevalence and the age of onset patterns of stroke in Jiangsu Province, China.

OBJECTIVES: Little was known regarding the current age of onset patterns of stroke. This study aimed to examine the prevalence of stroke and explore the age of onset patterns of stroke in Jiangsu Province, China. MATERIALS AND METHODS: Participants were recruited from April 2012 to April 2013 in Jiangsu Province, China. Survival analysis models were used to evaluate the hazards of stroke by a single year of age. Kaplan-Meier analysis and the log-rank test were used to explore the disparities of the age of onset patterns of stroke. RESULTS: This population-based study was conducted among 39,887 participants aged ≥ 18 years in Jiangsu Province, China. Of the 740 (1.9%) events of stroke, 13.2% suffered from hemorrhagic stroke (HS) and 86.8% suffered from ischemic stroke (IS). The prevalence of HS and IS were 0.3% and 1.7%, respectively. The estimated mean age of onset of stroke was 71.98 (95% CI: 71.97-71.99) years by the survival model. Up to age of 45 years, the estimated hazards of stroke onset were at a relatively low level. From the age of 45 years, the increases in hazards accelerated and peaked at age 75 years. Urban, smoking, and drinking males had a higher risk of stroke than their counterparts (P < 0.05). However, no such difference was found among females. CONCLUSIONS: The findings emphasize the importance of implementing stroke prevention interventions in Jiangsu Province, China, especially for urban, smoking, and drinking males. It is of great significance to strengthen comprehensive management of health-related behaviors, including smoking cessation and moderate consumption of alcohol to have sustained beneficial effects on stroke risk. Chenlu He and Qian Chen contributed equally to this work.

Exploring fear of cancer recurrence and related factors among breast cancer patients: A cross-sectional study.

AIMS: Fear of cancer recurrence (FCR) is a multifaceted concept influenced by individual characteristics, social support, psychological factors. This study aims to identify distinct FCR profiles among breast cancer patients and explore the associated variables with these patterns. DESIGN: A cross-sectional study was conducted from April 2022 to March 2023. METHODS: A convenience sample of 339 patients completed a questionnaire that assessed general and disease-related data, including the Fear of Progression Questionnaire-Short Form, Social Support Rating Scale, Medical Coping Modes Questionnaire. Statistical analysis involved latent profile analysis (LPA) and multinomial logistic regression. RESULTS: Three latent patterns of FCR were found: the low fear (28.9%), the moderate fear (51.3%), and the high fear (18.0%). The study identified the social support, family monthly income, employment status, utilization of confrontation coping mode and avoidance coping mode, as factors that impacted the FCR. CONCLUSIONS: Social support, family monthly income, employment status, and medical coping modes have been found to impact the FCR among newly diagnosed breast cancer patients. Healthcare professionals should focus on addressing FCR at diagnosis and implement effective interventions, such as promoting social support and encouraging adaptive coping, to alleviate this concern. IMPACT: Urgently addressing the FCR in Chinese breast cancer patients is imperative due to its profound influence on their holistic health. Through advanced LPA, we categorized the FCR progression, highlighting risks. These findings have implications for healthcare strategies, offering new insights to manage the FCR and improve patient well-being. Our study adds a fresh perspective to the factors underlying the FCR in breast cancer patients, contributing to the broader comprehension and management of this complex survivorship issue. PATIENT OR PUBLIC CONTRIBUTION: No patient or public contribution.

Investigating relationships between landscape patterns and surface runoff from a spatial distribution and intensity perspective.

Rapid urbanization changes landscape patterns and results in frequent urban waterlogging issues, which affect citizens' daily lives and cause economic loss. Understanding the spatial patterns and impact factors associated with urban waterlogging under different rainfall intensities has significant implications for mitigating this hazard. In this study, the runoff depth calculated according to the Storm Water Management Model (SWMM) simulation results was used to investigate the spatial characteristics of urban waterlogging. Multiple scenario-based designs, a correlation analysis, and a stepwise regression model were employed to detect the relationship between surface runoff depth and landscape patterns under different rainfall intensities. The results show that when the rainfall intensity reached 12.5 mm/12 h, the conversion rate of rainfall to runoff increased significantly, indicating an increased waterlogging risk. Areas with impervious surface proportions of 25-50% and 75-100% were shown to require more attention due to the strong sensitivity of the surface runoff depth to an increase in the impervious surface. It is most cost-effective to maintain the original high-density vegetation or increase the vegetation density from 0-25% to 25-50% for urban green space. Additionally, the landscape configuration also affects the surface runoff depth. The fragmented, scattered, or regular shape of impervious surface patches can reduce surface runoff effectively; larger and less fragmented green space was also shown to have a surface runoff controlling. The adjusted R2 values were greater than 0.6 for all stepwise regression models, indicating that the landscape variables selected in the study can effectively predict the surface runoff depth. These models also showed that the landscape composition had a more profound contribution than the landscape configuration on runoff depth. These findings provide meaningful insights and perspectives for urban waterlogging hazard mitigation, quantitative landscape planning, and risk management. The method proposed by this study provides a referable framework for future studies on urban waterlogging and its response to the landscape in the context of global climate change.

Assessing the Interrelationship of Microstructure, Properties, Drug Release Performance, and Preparation Process for Amorphous Solid Dispersions Via Noninvasive Imaging Analytics and Material Characterization.

PURPOSE: The purpose of this work is to evaluate the interrelationship of microstructure, properties, and dissolution performance for amorphous solid dispersions (ASDs) prepared using different methods. METHODS: ASD of GDC-0810 (50% w/w) with HPMC-AS was prepared using methods of spray drying and co-precipitation via resonant acoustic mixing. Microstructure, particulate and bulk powder properties, and dissolution performance were characterized for GDC-0810 ASDs. In addition to application of typical physical characterization tools, we have applied X-Ray Microscopy (XRM) to assess the contribution of microstructure to the characteristics of ASDs and obtain additional quantification and understanding of the drug product intermediates and tablets. RESULTS: Both methods of spray drying and co-precipitation produced single-phase ASDs. Distinct differences in microstructure, particle size distribution, specific surface area, bulk and tapped density, were observed between GDC-0810 spray dried dispersion (SDD) and co-precipitated amorphous dispersion (cPAD) materials. The cPAD powders prepared by the resonant acoustic mixing process demonstrated superior compactibility compared to the SDD, while the compressibility of the ASDs were comparable. Both SDD powder and tablets showed higher in vitro dissolution than those of cPAD powders. XRM calculated total solid external surface area (SA) normalized by calculated total solid volume (SV) shows a strong correlation with micro dissolution data. CONCLUSION: Strong interrelationship of microstructure, physical properties, and dissolution performance was observed for GDC-0810 ASDs. XRM image-based analysis is a powerful tool to assess the contribution of microstructure to the characteristics of ASDs and provide mechanistic understanding of the interrelationship.

Comparing desorption properties of pollutants on bentonite particles and in compacted bentonite.

Desorption is one of the main factors causing groundwater and soil pollution. Therefore, the study of clay desorption characteristics is important for the prediction of groundwater and soil pollution. In previous studies, batch tests and column tests were used to study the desorption characteristics of pollutants on clay. However, the desorption parameters obtained via the two test methods were often quite different. To investigate differences in the desorption characteristics of different pollutants on clay particles and in compacted clay, batch and column desorption tests were conducted using cadmium chloride, fulvic acid, and sodium phosphate as the adsorbates and bentonite as the adsorbent. It was found that the unit particle surface area desorption distribution coefficients of pollutants on bentonite particles were approximately equal to the unit pore surface area distribution coefficients of pollutants in compacted bentonite. This indicates that the desorbed amount per unit of surface area is basically consistent, regardless of whether they are sorbed on particles or in compacted bentonite. A simple formula for determining the desorption retardation factor of pollutants in compacted bentonite is presented. The results of this study provide a reference for the prediction and evaluation of groundwater and soil pollution.

Tetra-benzothiadiazole-based [12]Cycloparaphenylene with Bright Emission and Its Supramolecular Assembly.

The radial conjugated π-system of cycloparaphenylenes (CPPs) makes them intriguing fluorophores and unique supramolecular hosts. However, the bright photoluminescence (PL) of CPPs was limited to the blue light and the supramolecular assembly behavior of large CPPs was rarely investigated. Here we present the synthesis of tetra-benzothiadiazole-based [12]cycloparaphenylene (TB[12]CPP), which exhibits a lime to orange PL with an excellent quantum yield up to 82 % in solution. The PL quantum yield of TB[12]CPP can be further improved to 98 % in polymer matrix. Benefiting from its enlarged size, TB[12]CPP can accommodate a fullerene derivative or concave-convex complexes of fullerene and buckybowl through the combined π-π and C-H⋅⋅⋅π interactions. The latter demonstrates the first case of a ternary supramolecule of CPPs.

Life history is a key factor explaining functional trait diversity among subtropical grasses, and its influence differs between C3 and C4 species.

Life history and photosynthetic type both affect the economics of leaf physiological function. Annual plants have lower tissue densities and resource-use efficiencies than perennials, while C4 photosynthesis, facilitated in grasses by specific changes in leaf anatomy, improves photosynthetic efficiency and water-use efficiency, especially in hot climates. This study aimed to determine whether C4 photosynthesis affects differences in functional traits between annual and perennial species. We measured 26 traits and characterised niche descriptors for 42 grasses from subtropical China. Differences in the majority of traits were explained by life history. The ranges of annual species (particularly C4 annuals) extended to regions with greater temperature seasonality and lower precipitation, and annuals had less-negative turgor-loss points, higher specific leaf areas, and lower water-use efficiencies, stomatal conductances, and leaf areas per stem area than perennials. Photosynthetic type largely affected leaf physiology as expected, but interacted with life history in determining specific traits. Leaf hydraulic conductance was intermediate in perennials, highest in C4-annuals, and lowest in C3-annuals. Densities of stomata and stem vessels were similar across C3-perennials and C4 species, but stomatal densities were lower and stem vessel densities higher in C3-annuals. Phylogenetic principal component analysis confirmed that in this subtropical environment life history is the predominant axis separating species, and annuals and perennials were more different within C3 than C4 grasses. The interplay between life history and photosynthetic type may be an overlooked factor in shaping the physiological ecology of grasses.

Evaluation of Accuracy of Amorphous Solubility Advantage Calculation by Comparison with Experimental Solubility Measurement in Buffer and Biorelevant Media.

The accuracy of amorphous solubility advantage calculation was evaluated by experimental solubility measurement. Ten structurally diverse compounds were studied to test the generlity of the theoretical calculation. Three reported methods of calculating Gibbs free energy difference between amorphous and crystalline solids were evaluated. Experimental solubility advantage was measured by direct dissolution of amorphous solid in buffer. When necessary, hydroxypropyl methylcellulose acetate succinate (HPMCAS) was predissolved in buffer to inhibit desupersaturation. By direct dissolution, the effect of different preparation methods on amorphous solubility was also studied. Finally, solubility measurement was performed in fasted state simulated intestinal fluid (FaSSIF) to assess the effect of bile salt on the concentration-based amorphous solubility advantage. The results showed that the assumption of constant heat capacity differences between crystal and supercooled liquid or amorphous solid is sufficient for accurate theoretical calculation, which is attributed to the fact that the heat capacity of crystal is nearly parallel to that of supercooled liquid or amorphous solid. Different preparation methods do not have significant impact on amorphous solubility advantage. Experimental measurement agrees with the theoretical calculation within a factor of 0.7 to 1.8. The concentration-based amorphous solubility advantage in FaSSIF agrees well with theoretical calculation. This work demonstrates that theoretical calculation of amorphous solubility advantage is robust and can be applied in early drug development for assessing the utility of the amorphous phase.

Effect of Microenvironmental pH Modulation on the Dissolution Rate and Oral Absorption of the Salt of a Weak Acid - Case Study of GDC-0810.

PURPOSE: The purpose of this work is to investigate the effect of microenvironmental pH modulation on the in vitro dissolution rate and oral absorption of GDC-0810, an oral anti-cancer drug, in human. METHODS: The pH-solubility profile of GDC-0810 free acid and pHmax of its N-Methyl-D-glucamine (NMG) salt were determined. Precipitation studies were conducted for GDC-0810 NMG salt at different pH values. GDC-0810 200-mg dose NMG salt tablet formulations containing different levels of sodium bicarbonate as the pH modifier were tested for dissolution under the dual pH-dilution scheme. Three tablet formulations were evaluated in human as a part of a relative bioavailability study. A 200-mg dose of GDC-0810 was administered QD with low fat food. RESULTS: Intrinsic solubility of GDC-0810 free acid was found to be extremely low. The pHmax of the NMG salt suggested a strong tendency for form conversion to the free acid under GI conditions. In vitro dissolution profiles showed that the dissolution rate and extent of GDC-0810 increased with increasing the level of sodium bicarbonate in the formulation. The human PK data showed a similar trend for the geometric mean of Cmax and AUC0-t for formulations containing 5%, 10%, and 15% sodium bicarbonate, but the difference is not statistically significant. CONCLUSION: Incorporation of a basic pH modifier, sodium bicarbonate, in GDC-0810 NMG salt tablet formulations enhanced in vitro dissolution rate of GDC-0810 via microenvironmental pH modulation. The human PK data showed no statistically significant difference in drug exposure from tablets containing 5%, 10%, and 15% sodium bicarbonate.

Correction to: Application of a Novel 'Make and Test in Parallel' Strategy to Investigate the Effect of Formulation on the Pharmacokinetics of GDC-0810 in Healthy Subjects.

The Publisher regrets the typesetting mistake of retaining incorrect text in the Figure 1 caption. The correct text for the caption is "Molecular Structure of GDC-0810 NMG Salt". The original article has been corrected.

Application of a Novel 'Make and Test in Parallel' Strategy to Investigate the Effect of Formulation on the Pharmacokinetics of GDC-0810 in Healthy Subjects.

PURPOSE: GDC-0810, administered orally, was used in Phase I and II clinical studies to treat estrogen receptor positive breast cancers. It contains N-methyl-D-glucamine (NMG) salt of GDC-0810 with 10% sodium lauryl sulfate (SLS) as a surfactant and 15% sodium bicarbonate (NaHCO3) as an alkalizing agent to aid dissolution. To improve the processability of the formulation and reduce potential mucosal irritation in future Phase III clinical studies, the salt form and the amount of excipient required further optimization. To achieve this, we employed a novel "Make and Test in Parallel" strategy that facilitated selecting formulation in a rapid timeframe. METHODS: RapidFACT®, a streamlined, data-driven drug product optimization platform was used to bridge Phase I/II and Phase III formulations of GDC-0810. Five prototype formulations, varying in either the form of active pharmaceutical ingredient and/or the levels of the excipients SLS and NaHCO3 were assessed. Uniquely, the specific compositions of formulations manufactured and dosed were selected in real-time from emerging clinical data. RESULTS: The study successfully identified a Phase III formulation with a reduced SLS content, which when administered following a low-fat meal, gave comparable pharmacokinetic exposure to the Phase I/II formulation administered under the same conditions. CONCLUSIONS: Our novel 'Make and Test in Parallel' approach enabled optimization of GDC-0810 formulation in a time- and cost-efficient fashion.

Full-color reflectance-tunable filter based on liquid crystal cladded guided-mode resonant grating.

This work proposes a tunable reflective guided-mode resonant (GMR) filter that incorporates a 90° twisted nematic liquid crystal (TNLC). The GMR grating acts as an optical resonator that reflects strongly at the resonance wavelength and as an alignment layer for LC. The 90° TNLC functions as an achromic polarization rotator that alters the polarization of incident light. The resonance wavelength and reflectance of such a filter can be controlled by setting the angle of incidence and driving the 90° TNLC, respectively. The designed filter exhibits a very large spectral shift in resonance wavelength from 710 to 430 nm, which covers the entire visible spectrum. The transmittance can be tuned to within 10 V at various resonance wavelengths. The hybrid GMR - LC filter is compact, has a simple design, and is easy to fabricated. It can therefore be used in practical applications.

Synthesis and crystal structures of gold nanowires with Gemini surfactants as directing agents.

The preparation of crystalline gold nanowires (NWs) by using gemini surfactants as directing agents through a three-step seed-mediated method is reported. Unlike the nanorods with relatively low aspect ratios (typically below 20) obtained by using cetyltrimethylammonium bromide as a directing agent, the NWs obtained in this investigation can reach up to 4.4 µm, and the largest aspect ratio is calculated to be 210. For this, each of seven different gemini surfactants are utilized as directing agents, and the length and/or aspect ratio of the NWs can be tuned by varying the hydrocarbon chain lengths of the gemini surfactants. Both single and twinned crystalline structures are elucidated by selected-area electron diffraction and high-resolution transmission electron microscopy studies. The use of gemini surfactants not only advances the synthesis of gold nanostructures, but improves the understanding of the growth mechanism for seed-mediated growth.