Ordering of Diblock Copolymer Materials on Patterned Substrates: a Single Chain in Mean Field Simulation Study

Summary: The directed assembly of diblock copolymers on patterned substrates is a way to create nanoscopically structured materials. We study the structure and kinetics of diblock copolymers on patterned substrates by simulating a large ensemble of independent chains in an external field. This external field depends on the density created by the ensemble of molecules and it is frequently updated as to mimic the instantaneous interactions of a molecule with its neighbors. This approximate, particle-based field theoretical method allows (i) to incorporate arbitrary chain architecture (ii) to include fluctuations and (iii) the explicit propagation of the chain conformations in time permits us to study the kinetics of structure formation. The factors that control the accuracy of the method are quantitatively discussed and the reconstruction of the soft morphology at substrate patterns that deviate from the periodic morphology of the diblock in the bulk are illustrated.     

A correlation image velocimetry-based study of high-pressure fuel spray tip evolution

A correlation image velocimetry (CIV) technique has been developed to study the evolution of the leading edge, or tip, of isothermal high-pressure fuel sprays. Adaptations of the analysis permit determination of both the average spray tip motion and the spatial distribution of velocity along the spray edge. From these measurements, three distinct regions of the tip’s evolution have been observed and scaling relations developed. Further investigation has revealed significant uniformity in the radial evolution of the spray tip, despite the apparent similarity to turbulent jet flow. Examination of pdfs of the average tip velocity reveals among the many repeatable injection events a significant amount of variability and that this variability extends to regions near the nozzle, implying that among the sources of shot-to-shot viability is the atomisation process itself.     

String tension in the three-dimensional Abelian Higgs model

We measure the expectation values of the Wilson loops for the radially active Abelian Higgs Model in three dimensions with Higgs chargeq=1 andq=2. We observe a drastic fall-off of the area term as we pass to the Higgs phase, as well as a peak of the perimetric term at the phase transition. Implications of our results for other Higgs models are also discussed.     

Self-dual supergravity from N = 2 strings

A new heterotic N = 2 string with manifest target space supersymmetry is constructed by combining a conventional N = 2 string in the right-moving sector and a Green-Schwarz-Berkovits type string in the left-moving sector. The corresponding sigma mode] is then obtained by turning on background fields for the massless excitations. We compute the beta functions and we partially check the OPE's of the superconformal algebra perturbatively in t', all in superspace. The resulting field equations describe N = 1 self-dual supergravity.     

Controlled Chemical Derivatisation of Carbon Nanotubes with Imaging,Targeting, and Therapeutic Capabilities

In drug delivery, carbon nanotubes (CNTs) hold a great potential as carriers because of their ability to easily cross biological barriers and be internalised into cells. Their high aspect ratio allows multi‐functionalisation and their development as a multimodal platform for targeted therapy. In this article, we report the controlled covalent derivatisation of triple‐functionalised CNTs with the anticancer drug gemcitabine, folic acid as a targeting ligand and fluorescein as a probe. The anticancer activity of gemcitabine was maintained after covalent grafting onto the CNTs. The functionalised nanotubes were internalised into both folate‐positive and negative cells, suggesting the passive diffusion of CNTs. Overall, our approach is versatile and offers a precise chemical control of the sidewall functionalisation of CNTs and the possibility to manoeuvre the types of functionalities required on the nanotubes for a multimodal therapeutic strategy.     

Robust and sensitive high-performance liquid chromatographic-UV detection technique for the determination of tigecycline in rabbit plasma

An isocratic HPLC method with detection at 248 nm was developed and fully validated for the determination of tigecycline in rabbit plasma. Minocycline was used as an internal standard. A Hypersil BDS RP-C18 column (250 x 4.6 mm, 5 microm particle size) was used with the mobile phase phosphate buffer (pH 7.10, 0.070 M)-acetonitrile (76 + 24, v/v) at a flow rate of 1.0 mL/min. The elution time of tigecycline and minocycline was approximately 8.1 and 9.9 min, respectively. Calibration curves of tigecycline were linear in the concentration range of 0.021-3.15 microg/mL in plasma. The LOD and LOQ in plasma were estimated as 7 and 21 ng/mL, respectively. The intraday and interday precision values of the method were in the range of 5.0-7.1 and 5.6-9.1%, while the corresponding accuracy values were in the ranges of 92.8-111.1 and 97.6-102.3%, respectively. At the LOQ, the intraday precision was 18.7%, while intraday and interday accuracy values were 97.3 and 98.0%, respectively. Robustness of the proposed method was studied using a Plackett-Burman experimental design. A pharmacokinetic profile is presented for confirmation of the applicability of the method to pharmacokinetic studies.     

Combined effect of temperature and organic modifier concentration on the retention under single mode gradient conditions in reversed-phase HPLC

The combined effect of temperature, T, and organic modifier concentration, phi, on the retention under gradient conditions in RPLC is studied by considering, both theoretically and experimentally gradients, of phi at constant T and gradients of T at constant phi. Two approaches are examined: in the first approach the prediction of the elution time of a sample solute is based on the isocratic/isothermal properties of this solute. The second approach is based on a direct fitting procedure of a proper retention model to 2-D isocratic/T-gradient or isothermal/phi-gradient retention data. These approaches were tested using alkylbenzes in eluting systems modified by ACN. We found that both approaches can give excellent predictions under certain prerequisites. However, the first approach exhibits the notable advantage that it can be used effectively to predict retention times under any kind of phi-gradients at constant T or T-gradients at constant phi. The second approach has the advantage that it is relatively simple but its applicability is very restricted since its predictions are satisfactory only if the gradients are of the same kind with those used in the fitting procedure and the conditions lie within those used for fitting.     

Anamorsin is a [2Fe-2S] cluster-containing substrate of the Mia40-dependent mitochondrial protein trapping machinery

Human anamorsin was implicated in cytosolic iron-sulfur (Fe/S) protein biogenesis. Here, the structural and metal-binding properties of anamorsin and its interaction with Mia40, a well-known oxidoreductase involved in protein trapping in the mitochondrial intermembrane space (IMS), were characterized. We show that (1), anamorsin contains two structurally independent domains connected by an unfolded linker; (2), the C-terminal domain binds a [2Fe-2S] cluster through a previously unknown cysteine binding motif in Fe/S proteins; (3), Mia40 specifically introduces two disulfide bonds in a twin CX(2)C motif of the C-terminal domain; (4), anamorsin and Mia40 interact through an intermolecular disulfide-bonded intermediate; and (5), anamorsin is imported into mitochondria. Hence, anamorsin is the first identified Fe/S protein imported into the IMS, raising the possibility that it plays a role in cytosolic Fe/S cluster biogenesis also once trapped in the IMS.     

Criticality features in ULF magnetic fields prior to the 2011 Tohoku earthquake

The criticality of ULF (Ultra-low-frequency) magnetic variations is investigated for the 2011 March 11 Tohoku earthquake (EQ) by natural time analysis. For this attempt, some ULF parameters were considered: (1) F_h (horizontal magnetic field), (2) F_z (vertical magnetic field), and (3) D_h (inverse of horizontal magnetic field). The first two parameters refer to the ULF radiation, while the last parameter refers to another ULF effect of ionospheric signature. Nighttime (L.T. = 3 am ± 2 hours) data at Kakioka (KAK) were used, and the power of each quantity at a particular frequency band of 0.03–0.05 Hz was averaged for nighttime hours. The analysis results indicate that F_h fulfilled all criticality conditions on March 3–5, 2011, and that the additional parameter, D_h reached also a criticality on March 6 or 7. In conclusion, criticality has reached in the pre-EQ fracture region a few days to one week before the main shock of the Tohoku EQ.