Zn-Zn porphyrin dimer-sensitized solar cells: toward 3-D light harvesting.

Zn-Zn porphyrin dimers have been incorporated into thin dye-sensitized solar cells (DSSCs) to boost their light harvesting efficiency. The photoexcited dimers show efficient and fast electron injection into TiO(2) indicating that both photoexcited chromophores contribute to current generation. The improved light harvesting ability coupled to enhanced DSSC performance demonstrates the potential of 3-D light harvesting arrays as next generation light harvesters for artificial solar energy conversion systems.

Tuning the optical properties of ZnTPP using carbonyl ring fusion.

Zinc meso-tetraphenylporphyrin (ZnTPP) was modified in such a way to allow the effect of an asymmetric structural distortion on its optical properties to be investigated. This involved the fusion of a phenyl group to an adjacent pyrrole ring via a carbonyl bridge. With the aid of Density Functional Theory (DFT) and time-dependent DFT (TD-DFT) calculations it was found that the asymmetric distortion away from planarity induced by the carbonyl fusion resulted in a loss of degeneracy in the two lowest unoccupied molecular orbitals (LUMOs).

Effects of film coating thickness and drug layer uniformity on in vitro drug release from sustained-release coated pellets: a case study using terahertz pulsed imaging.

Film coating thickness and terahertz electric field peak strength (TEFPS) were determined using terahertz pulsed imaging (TPI) and employed for the analysis of sustained-release coated pellets (theophylline layered sugar cores coated with Kollicoat SR:Kollicoat IR polymer blends). The effects of coating thickness, drug layer uniformity and optional curing were investigated using eight batches of pellets. Ten pellets from each batch were imaged with TPI to analyse the coating morphology (depicted in TEFPS) and thickness prior to release measurements.

Analysis of solid-state transformations of pharmaceutical compounds using vibrational spectroscopy.

Objectives: Solid-state transformations may occur during any stage of pharmaceutical processing and upon storage of a solid dosage form. Early detection and quantification of these transformations during the manufacture of solid dosage forms is important since the physical form of an active pharmaceutical ingredient can significantly influence its processing behaviour, including powder flow and compressibility, and biopharmaceutical properties such as solubility, dissolution rate and bioavailability.

Key Findings: Vibrational spectroscopic techniques such as infrared, near-infrared, Raman and, most recently, terahertz pulsed spectroscopy have become popular for solid-state analysis since they are fast and non-destructive and allow solid-state changes to be probed at the molecular level.

Investigating the relationship between drug distribution in solid lipid matrices and dissolution behaviour using Raman spectroscopy and mapping.

In this study, in situ and mapping Raman spectroscopic measurements were used to investigate the physical structure of solid lipid extrudates and relate the structure to dissolution behaviour. Theophylline anhydrate was extruded with tripalmitin, with and without the water-soluble polymer, polyethylene glycol 10000. Raman mapping of the extrudate cores revealed that drug particles of diverse size were dispersed in a continuous lipid phase with or without polyethylene glycol.

Investigating dissolution performance critical areas on coated tablets: a case study using terahertz pulsed imaging.

During the process development of coated tablets, knowledge on the formation and the location of film coating 'weak spots' is a key factor to the success of the process and the resulting product batch. It is understood that the performance of the product batch may be greatly limited, and often compromised, by weak spots on the tablet film coat. This study uses circular, biconvex tablets to investigate the ability of terahertz pulsed imaging (TPI) to identify the affected areas on the tablet film coat that are critical for dissolution performance.

Electronic studies on oligothienylenevinylenes: understanding the nature of their ground and excited electronic states.

The electronic and molecular structures of a family of oligothienylenevinylenes for organic solar cells are studied by means of UV/Vis, fluorescence and Raman spectroscopy, aided by quantum chemical calculations. By using different anchoring groups, the alteration of the electronic properties upon inserting electron-withdrawing groups into different positions on the oligothienylenevinylene backbone is determined. In addition, a thorough study of the photophysical properties is carried out to understand their potential use in optoelectronic devices.

Increases in muscle activity produced by vibration of the thigh muscles during locomotion in chronic human spinal cord injury.

The purpose of this study was to determine whether the muscle vibration applied to the quadriceps has potential for augmenting muscle activity during gait in spinal cord injured (SCI) individuals. The effects of muscle vibration on muscle activity during robotic-assisted walking were measured in 11 subjects with spinal cord injury (SCI) that could tolerate weight-supported walking, along with five neurologically intact individuals. Electromyographic (EMG) recordings were made from the tibialis anterior (TA), medial gastrocnemius (MG), rectus femoris (RF), vastus lateralis (VL), and medial hamstrings (MH) during gait.

Correlating thermodynamic and kinetic parameters with amorphous stability.

Poor physical stability is one of the single most important factors limiting the widespread use of the amorphous state in pharmaceutics. The purpose of this study is to move away from the case study approach by investigating thermodynamic and kinetic parameters as potential predictors of physical stability of amorphous drugs for a larger sample set (12 drugs). The relaxation time, fragility index and configurational thermodynamic properties (enthalpy, entropy and Gibbs free energy) were calculated and correlated to the actual stability behaviour, obtained for 12 drugs.

Monitoring the film coating unit operation and predicting drug dissolution using terahertz pulsed imaging.

Understanding the coating unit operation is imperative to improve product quality and reduce output risks for coated solid dosage forms. Three batches of sustained-release tablets coated with the same process parameters (pan speed, spray rate, etc.) were subjected to terahertz pulsed imaging (TPI) analysis followed by dissolution testing.

Trinuclear copper(I) complex containing 3,4,9,10,15,16-hexamethyl-1,6,7,12,13,18-hexaazatrinaphthylene: a structural, spectroscopic, and computational study.

The compound [(Cu(PPh(3))(2))(3)(HATNMe(6))](BF(4))(3) has been synthesized and characterized by X-ray crystallography, resonance Raman spectroscopy, and density functional theory (DFT) calculations. The X-ray structure of solvated [(Cu(PPh(3))(2))(3)(HATNMe(6))](BF(4))(3) [rhombohedral, R3, a = b = 21.6404(4) A, c = 53.

Linker conjugation effects in rhenium(I) bifunctional hole-transport/emitter molecules.

Spectroscopic, electrochemical and density functional theory (DFT) methods have been employed to investigate a group of [Re(CO)(3)(HT)(phen)](+) complexes (phen = 1,10-phenanthroline), and in particular the level of electronic communication between various hole-transporting (HT) ligands and the rhenium centre. Here, the HT ligand consists of a coordinating pyridine connected to dimethylaniline group through a single-, double- or triple-bond-connecting system. Electronic absorption, resonance Raman, and steady-state emission spectroscopy combined with lifetime studies and DFT calculations suggest that multiple dpi(Re)-->pi*(phen) metal-to-ligand charge transfers (MLCTs) exist for each complex, two of which significantly absorb at about 340 and 385 nm, and one that emits at approximately 540 nm.

Ankle load modulates hip kinetics and EMG during human locomotion.

The purpose of this research was to examine the role of isolated ankle-foot load in regulating locomotor patterns in humans with and without spinal cord injury (SCI). We used a powered ankle-foot orthosis to unilaterally load the ankle and foot during robotically assisted airstepping. The load perturbation consisted of an applied dorsiflexion torque designed to stimulate physiological load sensors originating from the ankle plantar flexor muscles and pressure receptors on the sole of the foot.

Metabolic and mechanical energy costs of reducing vertical center of mass movement during gait.

Objectives: To test the hypothesis that reducing vertical center of mass (COM) displacement will lower the metabolic cost of human walking. To examine changes in joint work associated with increasing and decreasing vertical COM movement during gait.

Design: Randomized repeated measures.

Vibrational spectroscopy and quantum chemical studies of 1,6,7,12,13,18-hexaazatrinaphthylene and related compounds.

The spectral properties of 1,6,7,12,13,18-hexaazatrinaphthylene (HATN) and a number of related compounds are modeled using density functional theory, B3LYP. The calculations predict the frequencies with mean absolute deviation of 6 cm(-1) and there is little improvement on going to basis sets larger than 6-31 G(d). The substituent effects on the observed spectra are modeled effectively in both frequency shifts and relative intensities.

Solid form screening--a review.

Solid form screening, the activity of generating and analysing different solid forms of an active pharmaceutical ingredient (API), has become an essential part of drug development. The multi-step screening process needs to be designed, performed and evaluated carefully, since the decisions made based on the screening may have consequences on the whole lifecycle of a pharmaceutical product. The selection of the form for development is made after solid form screening.

Terahertz pulsed imaging as an analytical tool for sustained-release tablet film coating.

The ability of terahertz pulsed imaging (TPI) to be employed as an analytical tool for monitoring a film coating unit operation and to assess the success of a subsequent process scale-up was explored in this study. As part of a process scale-up development, a total of 190 sustained-release tablets were sampled at 10% increments of the amount of polymer applied, from a lab-scale and a pilot-scale coating run. These tablets were subjected to TPI analysis, followed by dissolution testing.

Understanding the solid-state forms of fenofibrate--a spectroscopic and computational study.

The aim of this study was to investigate the structure of different solid-state forms of fenofibrate, a drug that lacks strong intermolecular interactions such as hydrogen bonding. In addition to a structural analysis of crystalline and amorphous fenofibrate using infrared and Raman spectroscopy combined with density functional theory calculations [B3LYP 6-31G(d)], solid-state changes that occur upon recrystallization of amorphous fenofibrate were monitored and described using in situ Raman spectroscopy. A comparison of the calculated vibrational spectra of a fenofibrate monomer and two dimer structures with the experimental vibrational spectra of crystalline and amorphous fenofibrate revealed conformational differences in the orientation of the two benzyl rings in the fenofibrate molecule and structural differences between the different solid-state forms in aliphatic parts of the drug molecule.

Perspectives in the use of spectroscopy to characterise pharmaceutical solids.

Knowledge of the solid-state properties is one of the key issues in understanding the performance of drugs. Recent developments in spectroscopic techniques have made them popular tools for solid phase analysis; they are fast, accurate and suitable for real-time measurements during processing, and further, they can be used to obtain structural understanding of solid forms, for example, by the use of multivariate analysis and computational chemistry. In this article emerging topics related to spectroscopic analysis of pharmaceutical solids are reviewed.

Synthesis and complexation of multiarmed cycloveratrylene-type ligands: observation of the "boat" and "distorted-cup" conformations of a cyclotetraveratrylene derivative.

Investigations of a previously reported ligand, hexakis(2-pyridylmethyl)cyclotricatechylene (1), and a new tetrameric bridging ligand, octakis(2-pyridylmethyl)cyclotetracatechylene (2), the latter constructed on a larger cyclotetraveratrylene (CTTV) scaffold, are described. Variable-temperature NMR studies support a "sofa" conformation for 2, akin to studies on the parent compound. The coordination chemistry of 2 and its smaller trimeric homologue have also been investigated with silver(I), copper(II) and palladium(II) salts.

Recent pharmaceutical applications of Raman and terahertz spectroscopies.

This review outlines recent applications of Raman and terahertz spectroscopies within the field of pharmaceutical research. Of the two approaches, Raman is better established and more accessible, and is responsible for the majority of reviewed studies. Both techniques feature limitations, however, which are discussed in the context of methods used to circumvent apparent restrictions.

Applications of terahertz pulsed imaging to sustained-release tablet film coating quality assessment and dissolution performance.

The potential of terahertz pulsed imaging (TPI) to predict the dissolution performance in sustained-release tablets was investigated in this study. Batches of coated tablets with similar weight gain during the coating process at the lab and pilot scales were subjected to non-destructive imaging by TPI and subsequently analysed by dissolution testing. The results from the dissolution tests revealed significant differences in the product performance between the lab and pilot scales (Student t-test, P<0.

Locomotor adaptation to a powered ankle-foot orthosis depends on control method.

Background: We studied human locomotor adaptation to powered ankle-foot orthoses with the intent of identifying differences between two different orthosis control methods. The first orthosis control method used a footswitch to provide bang-bang control (a kinematic control) and the second orthosis control method used a proportional myoelectric signal from the soleus (a physiological control). Both controllers activated an artificial pneumatic muscle providing plantar flexion torque.