Interferometric control of spin-polarized electron populations at a metal surface observed by multiphoton photoemission

In an interferometric pump-probe experiment, we demonstrate the phase tuning of the spin polarization of photoelectrons emitted in a three-photon process from Cu(001). A phase shift of pi between delayed ultrafast circularly polarized light pulses can switch the spin polarization from +/-20% to -/+40%. In the delay regime of overlapping pulses, we show the dominating role of optical interference effects in determining the spin polarization. For longer delays, we detect the influence of the coherent material response, manifested in both the final state electron population as well as the final state spin polarization.     

Hydrogen Transport and Evolution in Ni-MH Batteries by Neutron Imaging

Efficiency losses due to side reactions are one of the main challenges in battery development. Despite providing valuable insights, the results of standard analysis on the individual components cannot be simply extrapolated to the full operating system. Therefore, non-destructive, and high resolution approaches that allow the investigation of the full system are desired. Herein, we combined neutron radiography and tomography with electrical monitoring of the state of charge of commercial Ni-mischmetal hydride batteries, to track the exchange and transport of hydrogen under operating conditions. This non-destructive approach allowed both the quantification of the hydrogen distribution in the electrodes in 4D, and the distinction between the electrochemically exchanged hydrogen and the hydrogen gas pressure generated by side reactions, as a function of the applied potential and current. One of the most counter-intuitive observation is that the generation of hydrogen gas during discharge depends on the charging state of the battery. The results presented provide critical new insights in the mechanisms governing the electrochemical processes during Nimischmetal hydride battery operation, and also pave the way for the extrapolation of this approach to the investigation of state-of-the-art Li-ions batteries.     

Quantum mechanics on a space-time lattice using path integrals in a minkowski metric

A simple model of many-body quantum mechanics governed by completely local interactions in ordinary three-dimensional space is presented. The equations of motion, involving no Euclideanization of time, are elementary extensions of those describing random walks on a square lattice, and are far simpler than those obtained through standard path-integral theory. A quantity is defined in terms of populations of particles on the lattice, whose expectation value is proportional to the square of the multiparticle wave functions associated with the system; for sufficiently microscopic measurement scales, this generalized density may take on negative values, thereby circumventing the constraints imposed by Bell's inequality.     

In vitro antibiofilm activity of the freshwater bryozoan Hyalinella punctata: a case study of Pseudomonas aeruginosa PAO1

The antibiofilm and possible antiquorum sensing effects against the strain Pseudomonas aeruginosa PAO1 of five crude extracts of the freshwater bryozoan Hyalinella punctata (Hancock, 1850) were evaluated in vitro for the first time. H. punctata ethyl acetate extract (HpEtAc) exhibited the highest antibiofilm activity reducing the biofilm formation of P. aeruginosa PAO1 in the range of 80.63–88.13%. While all tested extracts reduced the twitching motility of the aforementioned bacterial strain, HpEtAc showed to be the most effective. Finally, at a concentration of 0.5 MIC, the same extract mostly inhibited the production of pyocyanin by P. aeruginosa PAO1 (71.53%). In comparison both with the positive controls used (streptomycin and ampicillin, 67.13 and 69.77%, respectively), HpEtAc was found to inhibit pyocyanin in a higher extent. An extensive chemical characterisation of this particular extract may result in isolation and identification of novel lead compounds targeting P. aeruginosa, an opportunistic human pathogen.     

Light-triggered polymerase chain reaction

Photochemical control of the polymerase chain reaction has been achieved through the incorporation of light-triggered nucleotides into DNA.     

Brillouin zone spectroscopy of nonlinear photonic lattices

We present a novel, real-time, experimental technique for linear and nonlinear Brillouin zone spectroscopy of photonic lattices. The method relies on excitation with random-phase waves and far-field visualization of the spatial spectrum of the light exiting the lattice. Our technique facilitates mapping the borders of the extended Brillouin zones and the areas of normal and anomalous dispersion within each zone. For photonic lattices with defects (e.g., photonic crystal fibers), our technique enables far-field visualization of the defect mode overlaid on the extended Brillouin zone structure of the lattice. The technique is general and can be used for photonic crystal fibers as well as for periodic structures in areas beyond optics.     

The Universal Arrow of Time

Statistical physics cannot explain why a thermodynamic arrow of time exists, unless one postulates very special and unnatural initial conditions. Yet, we argue that statistical physics can explain why the thermodynamic arrow of time is universal, i.e., why the arrow points in the same direction everywhere. Namely, if two subsystems have opposite arrow-directions at a particular time, the interaction between them makes the configuration statistically unstable and causes a decay towards a system with a universal direction of the arrow of time. We present general qualitative arguments for that claim and support them by a detailed analysis of a toy model based on the baker’s map.     

Preparation of cellulosic fibers with biological activity by immobilization of trypsin on periodate oxidized viscose fibers

In this study, a biologically active fibrous material was designed by immobilizing trypsin on viscose fibers. The viscose yarn was first oxidized with sodium periodate to produce aldehyde groups and then employed as a support for subsequent immobilization of trypsin through bovine serum albumin. The oxidation by sodium periodate caused changes in the chemical and physical properties of the modified yarn samples, which were evaluated by determining the aldehyde group content, fineness and tensile strength of yarn. The viscose fibers oxidized under the most severe conditions (0.4 % NaIO₄, 360 min) exhibited the maximum amount of introduced aldehyde groups (1.284 mmol/g), but also the highest decrease in tensile strength. The trypsin activity was assayed with N-α-benzoyl-DL-arginine p-nitroanilide hydrochloride, whereas the amount of bound trypsin was determined by Bradford method. Trypsin immobilized on oxidized viscose yarn retained 97.3 and 83.8 % of the initial activity over 60 days of storage at 4 and 25 °C, respectively, and remained firmly attached to the carrier. The potential application of obtained bioactive fibers is in the treatment of wounds.     

Development of a novel RP‐HPLC method for the efficient separation of aripiprazole and its nine impurities

The development of an RP‐HPLC method for the separation of aripiprazole and its nine impurities was performed with the use of partial least squares regression, response surface plot methodology, and chromatographic response function. The HPLC retention times and computed molecular parameters of the aripiprazole and its nine impurities were further used for the quantitative structure–retention relationship (QSRR) study. The QSRR model, R²: 0.899, Q²: 0.832, root mean square error of estimation: 4.761, root mean square error of prediction: 6.614, was developed. Very good agreement between the predicted and observed retention times (t_R) for three additional aripiprazole impurities (TC1–TC3) indicated the high prediction potential of the QSRR model for t_R evaluation of other aripiprazole impurities and metabolites. The developed HPLC method is the first reported method for the efficient separation of aripiprazole and its nine impurities, which could be used for the analysis of an additional three aripiprazole impurities (TC1–TC3).