Entanglement dynamics of coupled qubits and a semi-decoherence free subspace

We study the entanglement dynamics and relaxation properties of a system of two interacting qubits in the cases of (I) two independent bosonic baths and (II) one common bath. We find that in the case (II) the existence of a decoherence-free subspace (DFS) makes entanglement dynamics very rich. We show that when the system is initially in a state with a component in the DFS the relaxation time is surprisingly long, showing the existence of semi-decoherence free subspaces.     

Ultrafast transverse thermoelectric response in c‐axis inclined epitaxial La0.5Sr0.5CoO3 thin films

Ultrafast transverse thermoelectric voltage response has been observed in c‐axis inclined epitaxial La_0.5Sr_0.5CoO₃thin films. Voltage signals with the rise time of 7 ns have been detected under the irradiation of pulse laser with duration of 28 ns. A concept, named response rate ratio, has been proposed to evaluate the intrinsic response rate, and this ratio in La_0.5Sr_0.5CoO₃is smaller than that in other reported materials. The low resistivity is thought to be responsible for the ultrafast response, as low resistivity induces small optical penetration depth, and response time has a monotonous increasing relationship with this depth.

     

Endomorphisms of graphs II. Various unretractive graphs

In this part of the article we investigate graphs for which different endomorphism monoids coincide. We consider endomorphisms, strong endomorphisms and automorphisms. Coincidences are investigated for joins of graphs and some lexicographic products. In an additional section the graphs with the respective properties are listed up to 8 vertices in two cases and up to 5 vertices in the remaining case.     

Reply to the ‘Comment on “Uncommon structural and bonding properties in Ag16B4O10” by A. Lobato,Miguel Á. Salvadó, and J. Manuel Recio,Chem. Sci., 2021, 12, DOI: 10.1039/D1SC02152D

Where are the excess electrons in Ag₁₆B₄O₁₀?

Ag₁₆B₄O₁₀ features an exotic scheme of chemical bonding and extends the growing family of subvalent silver oxides. These findings constitute a new general and intrinsic facet of the chemistry of silver, which has not been fully understood, yet, and definitely deserves to be analysed from different perspectives. Against this background, we distinctly appreciate the efforts made by A. Lobato, Miguel Á. Salvadó, and J. Manuel Recio (LSR) in studying these phenomena at the example of the title compound.¹ While the computational results presented in the Comment article well comply with those published in our original paper,² the interpretations follow different routes. Whereas LSR focus on the analogy of pattern of the Electron Localization Function (ELF) in position space in the title compound with those found in elemental silver, we interpreted the electronic structure of Ag₁₆B₄O₁₀, both in position and reciprocal space, also considering the interactions between cationic and anionic partial structures.     

Speciation of antimony(III) and antimony(V) in cell extracts by anion chromatography/inductively coupled plasma mass spectrometry

An analytical method for the separation and quantification of Sb(III) and Sb(V) using anion chromatography with ICP-MS is presented. The optimum conditions for the separation of the antimony species were established with 15 mmol/L nitric acid at pH 6 as eluent system on a PRP-X100 column. The retention times for antimony(V) and antimony(III) were 85 s and 300 s with detection limits of 0.06 microg/L and 0.29 microg/L, respectively. The proposed method was applied to cell extracts of Leishmania donovani, which were incubated with antimony(III) and antimony(V). Some metabolism seemed to occur within the cells.     

Speciation of antimony(III) and antimony(V) in cell extracts by anion chromatography/ inductively coupled plasma mass spectrometry

An analytical method for the separation and quantification of Sb(III) and Sb(V) using anion chromatography with ICP-MS is presented. The optimum conditions for the separation of the antimony species were established with 15 mmol/L nitric acid at pH 6 as eluent system on a PRP-X100 column. The retention times for antimony(V) and antimony(III) were 85 s and 300 s with detection limits of 0.06 μg/L and 0.29 μg/L, respectively. The proposed method was applied to cell extracts of Leishmania donovani, which were incubated with antimony(III) and antimony(V). Some metabolism seemed to occur within the cells.     

Trans-cis isomerization is responsible for the red-shifted fluorescence in variants of the red fluorescent protein eqFP611

An important class of red fluorescent proteins (RFPs) feature a 2-iminomethyl-5-(4-hydroxybenzylidene)imidazolinone chromophore. Among these proteins, eqFP611 has the chromophore in a coplanar trans orientation, whereas the cis isomer is preferred by other RFPs such as DsRed and its variants. In the photoactivatable protein asFP595, the chromophore can even be switched from the nonfluorescent trans to the fluorescent cis state by light. By using X-ray crystallography, we have determined the structure of dimeric eqFP611 at high resolution (up to 1.1 A). In the far-red emitting eqFP611 variant d2RFP630, which carries an additional Asn143Ser mutation, the chromophore resides predominantly (approximately 80%) in the cis isomeric state, and in RFP639, which has Asn143Ser and Ser158Cys mutations, the chromophore is found completely in the cis form. The pronounced red shift of excitation and emission maxima of RFP639 can thus unambiguously be assigned to trans-cis isomerization of the chromophore. Among RFPs, eqFP611 is thus unique because its chromophore is highly fluorescent in both the cis and trans isomeric forms.     

Reactivity of 2,2′‐Bis(2N‐(1,1′,3,3′‐tetramethyl‐guanidino))diphenylene‐amine with CuI and [Cu(MeCN)4][PF6]: Benzimidazole Formation vs. Cu Oxidation

The reaction of 2,2′‐Bis(2N‐(1,1′,3,3′‐tetramethyl‐guanidino))diphenylene‐amine (TMG₂PA) ( 1 ) with CuI in MeCN results in the formation of [Cu^II(TMG₂PA^amid)I] ( 2 ) indicatingthat Cu^I is the target of an oxidative attack of the N‐H proton of the ligand which itself is converted to molecular hydrogen. In contrast, if [Cu(MeCN)₄][PF₆] is used as the Cu^I source, [Cu^I₂(TMGbenz)₂][PF₆]₂ ( 3 ) is obtained instead. The use of the non‐coordinating counterion [PF₆]^– apparently prevents Cu^I from oxidation but induces itself a cyclisation reaction within the ligand which results in the formation of a benzimidazole‐guanidine ligand.     

Multidentate surface ligand exchange for the immobilization of CdSe/ZnS quantum dots and surface quantum dot-oligonucleotide conjugates

A method for synthesizing multidentate thiol ligands on fused silica surfaces (e.g., optical fibers) was developed for the immobilization of CdSe/ZnS quantum dots (QDs) capped with hydrophilic or hydrophobic ligands. This work was motivated by the poor stability of QDs immobilized via monodentate thiol ligands and the need for stable immobilization strategies in the development of sensor technologies based on QDs. Multi-dentate immobilization was able to withstand washing protocols, and surface ligand exchange occurred via self-assembly through the zinc-metal affinity interaction. Atomic force and scanning electron microscopy images suggested that the QDs were immobilized at high density, approximately 2-4 x 10 (13) cm (-2). It was possible to immobilize one, two, or three colors of QD. Upon immobilization, 1-2 nm bathochromic shifts in the PL spectra were observed. This was attributed to both ligand exchange and the change in local environment. The change in environment was accompanied by a decrease in PL lifetime. Self-assembly of immobilized QD-oligonucleotide and QD-avidin conjugates was also demonstrated. These conjugates were able to hybridize with complementary oligonucleotide and bind biotin, respectively. This versatile immobilization chemistry is an important step in the development of surface-based QD nanosensors. Such technology requires QDs to be immobilized such that they remain accessible to target molecules in solution.     

Microwave-assisted synthesis of 3,6-di(pyridin-2-yl)pyridazines: unexpected ketone and aldehyde cycloadditions

3,6-Di(pyridin-2-yl)pyridazines are an interesting class of compounds because of their metal-coordinating ability resulting in the self-assembly into [2x2] gridlike metal complexes with copper(I) or silver(I) ions. These and other substituted pyridazines can be prepared by the inverse-electron-demand Diels-Alder reactions between acetylenes and 1,2,4,5-tetrazines. In this contribution, the effect of (superheated) microwave conditions on these generally slow cycloadditions is described. The cycloaddition of acetylenes to 3,6-di(pyridin-2-yl)-1,2,4,5-tetrazine could be accelerated from several days reflux in toluene or N,N-dimethylformamide to several hours in dichloromethane at 150 degrees C. In addition, the unexpected cycloaddition of the enol tautomers of various ketones and aldehydes to 3,6-di(pyridin-2-yl)-1,2,4,5-tetrazine is described in detail providing an alternative route for the synthesis of (substituted) pyridazines.