Natural multiparticle entanglement in a Fermi gas

We investigate multipartite entanglement in a noninteracting fermion gas, as a function of fermion separation, starting from the many particle fermion density matrix. We prove that all multiparticle entanglement can be built only out of two-fermion entanglement. Although from the Pauli exclusion principle we would always expect entanglement to decrease with fermion distance, we surprisingly find the opposite effect for certain fermion configurations. The von Neumann entropy is found to be proportional to the volume for a large number of particles even when they are arbitrarily close to each other. We will illustrate our results using different configurations of two, three, and four fermions at zero temperature although all our results can be applied to any temperature and any number of particles.     

Theoretical Investigation of the Excited States of 2‐Nitrobenzyl and 4,5‐Methylendioxy‐2‐nitrobenzyl Caging Groups†

The photochemistry of caged compounds of the o‐nitrobenzyl type has been investigated thoroughly in the past. However, even recently new side reactions have been discovered. Earlier, we reported [Bley, F., K. Schaper, and H. Görner (2008), Photochem. Photobiol. 84 162–171] that we found long‐lived triplet states which do not lead to product formation for the bathochromic absorbing compounds with 4,5‐methylendioxy‐2‐nitrobenzyl caging group. Here, we report on theoretical studies which explain the special behavior of these compounds. These studies reveal that the bathochromic shift of absorption for these compounds compared with o ‐nitrobenzyl compounds themselves is not due to a shift in energy of the involved states, but due to a substantial change of oscillator strength of the respective transitions. The lack of reactivity of the triplet state of 4,5‐methylendioxy‐2‐nitrobenzyl compounds can be attributed to state switching. In the triplet manifold the lowest state is a nonreactive charge transfer state, while the lowest state in the singlet manifold is a reactive local excitation in the nitro‐group. From these results we conclude that it will be most likely not possible to create derivatives of caged compounds based on the o ‐nitrobenzyl caging group which have absorption which is shifted even more strongly to longer wavelengths.     

Optimizing cross-reactivity with evolutionary search for sensors

We report a straightforward evolutionary procedure to build an optimal sensor array from a pool of DNA sequences oriented toward three-way junctions. The individual sensors were mined from this pool under separate selection pressures to interact with four steroids, while allowing cross-reactivity, in a manner designed to achieve perfect classification of individual steroids. The resulting sensor array had three sensors and displayed discriminatory capacity between steroid classes over full ranges of concentrations. We propose that similar protocols can be used whenever we have two or more classes of samples, with individual classes being defined through gross differences in ratios of dominant families of responsive components.     

Inclusion complexes of amlodipine besylate and cyclodextrins

In this paper the procedure for the preparation of inclusion complexes of amlodipine besylate with β-cyclodextrin (β-CD) and 2-hydrohypropyl-β-cyclodextrin (HPβ-CD) and their structural characterization was described. Molecular inclusion complexes of amlodipine besylate are prepared by the coprecipitation method and characterised by the application of spectroscopic methods FTIR, ¹H-NMR and XRD. The photosensitivity of amlodipine besylate in the inclusion complexes was also determined with respect to uncomplexed agent. DSC curves indicate the loss of the clear peak due to melting of amlodipine besylate at about 200°C, while on XR diffractograms certain reflections are lost belonging to amlodipine besylate in complexes. This indicates its inclusion in the vacancies of the host. The inclusion of amlodipine besylate with cyclodextrins increases the stability, i.e. decreases the photosensitivity of amlodipine besylate.      

The protection of Nifedipin from photodegradation due to complex formation with β-cyclodextrin

The inclusion complex β-cyclodextrin:nifedipin was prepared in solid state by coprecipitation with 1:1 mol ratio. The structure of the obtained complex and nifedipin was characterized by use of X-ray diffraction (XR), infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and differential scanning calorimetry (DSC) methods. The photodegradation of nifedipin and the β-cyclodextrin:nifedipin inclusion complex in solid state was monitored under natural daylight by infrared spectroscopy, whereby the free nifedipin degraded four to five times faster than the complexed nifedipin. The photodegradation products of both free and complexed nifedipin, formed during irradiation at 350 nm (with corresponding energy flux of 18 W m⁻²) were monitored by liquid chromatography during various time intervals. The speed of formation of nitroso- and nitro-phenyl derivatives by nifedipin irradiation was significantly higher than those of complexed nifedipin irradiation, which indicates its increased photostability in the inclusion complex. The effect on this property is significant because it contributes both to the improvement of the therapeutic effect of nifedipin and to the safer application thereof.