The fundamental indication of the departure of quantum mechanics from the classical world is the so-called quantum coherence. Typically, we define it as the characteristic of systems which are in a ...superposition of states yielding interference patterns in certain kinds of experiments. In addition to its captivating philosophical implications, quantum coherence turned out to be a valuable tool in different areas, ranging from quantum information to biology, where it was used to describe several fundamental processes. Here, we go one step further to study how classical uncertainties in a mixture of similar states reduce quantum coherence in quantum scattering theory. To this end, we deal with different examples, all of them with roots in the widely studied Feynman's two-slit thought experiment. We finally propose an operational and intuitive definition of the concept of coherence length whose implications largely transcend the simplicity of the corresponding mathematical development, as it is demonstrated when applied to the analysis of some recent atomic and molecular processes.
Coxiella burnetii is an intracellular pathogenic bacterium and etiological agent of Q fever in humans. Recently, the bacterium has been set free from the strictly intracellular condition by ...successful cultivation in acidified citrate cysteine medium. Here, we report a bacterial cell counting method that allows rapid quantification of the absolute or relative number of live cells of C. burnetii in a high throughput manner. The method utilizes TaqMan-based quantitative polymerase chain reaction (qPCR) targeting a single dotA gene for determination of genome equivalent (GE) presented either as DNA or complementary DNA (cDNA) synthesized via reverse transcription. The assay was shown to be specific, sensitive and efficiently reproducible. The quantification was linear over a range of 30 to 3x108 copies. Since there is only one copy of the dotA gene per Coxiella chromosome, the calculated dotA copy numbers can be compared to the number of bacterial cells. Finally, we demonstrated the potential of the method to assess effects of antibiotic on cell viability and to determine the antibiotic-tolerant fraction within a cell population. Keywords: Coxiella burnetii; Q fever; real-time polymerase chain reaction; copy number; antibiotic; axenic media; dotA gene.
Two series of Ni and Co catalysts supported onto La-Al2O3 were prepared and the CO2 hydrogenation reactions investigated. The catalytic performance was evaluated in terms of the evolution with the ...reaction temperature of the CO2 conversion and product (CH4 and CO) yields, as well as specific activities (TOF) and apparent activation energies. CH4 was the favored product over both metals while the TOF for CH4 formation was about three times higher for Ni than Co at 240–265 °C. Metallic particle size effects were found, with the TOF for CH4 formation decreasing over both Ni and Co as the mean metallic size decreased. In contrast, the TOF for CO formation tended to increase at a decreasing particle size for the catalysts with the smallest Ni particle sizes. The apparent activation energies for Ni and Co were very similar and significantly decreased to values of 73–79 kJ/mol when the metallic dispersion increased. The catalysts were prepared using the all-in-one method, resulting in (poly)vinyl alcohol (PVA) being a key additive that allowed us to enhance the dispersion of Ni and Co to give very effective catalysts. This comparative study joins the few existing ones in the literature in which catalysts based on these metals operated under strictly the same reaction conditions.
We study the time evolution of an incoherent mixture of quantum states and demonstrate, in very simple terms, a quantum mechanical equivalent of van Cittert-Zernike theorem, which can be easily ...explained to Quantum Physics students with a basic knowledge of the density matrix theory. Finally, we exemplify this result by applying it to the quantitative analysis of the coherence of a beam of particles in atomic collisions.
Since the publication of the primate brain volumetric dataset of Stephan and colleagues in the early 1980s, no major new comparative datasets covering multiple brain regions and a large number of ...primate species have become available. However, technological and other advances in the last two decades, particularly magnetic resonance imaging (MRI) and the creation of institutions devoted to the collection and preservation of rare brain specimens, provide opportunities to rectify this situation. Here, we present a new dataset including brain region volumetric measurements of 39 species, including 20 species not previously available in the literature, with measurements of 16 brain areas. These volumes were extracted from MRI of 46 brains of 38 species from the Netherlands Institute of Neuroscience Primate Brain Bank, scanned at high resolution with a 9.4-T scanner, plus a further 7 donated MRI of 4 primate species. Partial measurements were made on an additional 8 brains of 5 species. We make the dataset and MRI scans available online in the hope that they will be of value to researchers conducting comparative studies of primate evolution.
Templated synthesis of proteins containing non-natural amino acids (nnAAs) promises to expand the chemical space available to biological therapeutics and materials, but existing technologies are ...still limiting. Addressing these limitations requires a deeper understanding of the mechanism of protein synthesis and how it is perturbed by nnAAs. Here we examine the impact of nnAAs on the formation and ribosome utilization of the central elongation substrate: the ternary complex of native, aminoacylated tRNA, thermally unstable elongation factor, and GTP. By performing ensemble and single-molecule fluorescence resonance energy transfer measurements, we reveal that both the (R)- and (S)-β2 isomers of phenylalanine (Phe) disrupt ternary complex formation to levels below in vitro detection limits, while (R)- and (S)-β3-Phe reduce ternary complex stability by 1 order of magnitude. Consistent with these findings, (R)- and (S)-β2-Phe-charged tRNAs were not utilized by the ribosome, while (R)- and (S)-β3-Phe stereoisomers were utilized inefficiently. (R)-β3-Phe but not (S)-β3-Phe also exhibited order of magnitude defects in the rate of translocation after mRNA decoding. We conclude from these findings that non-natural amino acids can negatively impact the translation mechanism on multiple fronts and that the bottlenecks for improvement must include the consideration of the efficiency and stability of ternary complex formation.
Synopsis We study the appearance of quantum vortices in the ionization of atoms by positron impact. We avoid the standard restrictions on the final-state variables, in order to study vortices as ...submanifolds of codimension 2 in the multidimensional space of definition of the T-matrix element. In particular we demonstrate that three isolated vortices previously observed under a collinear geometry, actually correspond to a two-dimensional cut on a single vortex line.
Ethylene Propylene Diene rubber (EPDM), is present in many applications. However, its crosslinked structure makes difficult its recycling. The use of devulcanized EPDM, (dEPDM) as a component of ...elastomeric composites, is a real possibility to reuse EPDM scraps. In this study, three matrices (natural rubber (NR), styrene butadiene rubber (SBR) and EPDM rubber) have been tested including devulcanized EPDM as a recycled component. The EPDM previously was devulcanized using a thermomechanical process followed by microwave irradiation. The resulting devulcanized EPDM was blended with the matrixes and then the new compound was vulcanized again. The samples showed a general increase of their mechanical properties and their thermal stability specially marked for NR and SBR. Compositions including about 40 phr dEPDM within the EPDM matrix exhibited a difference in their general behavior that it was manifested by a general decrease in properties compared with lower amounts of dEPDM. In order to further understand this behavior, the samples were analyzed in terms of cross-link density, swelling degree, and scanning electron microscopy. The study of the microstructure of the samples indicated that microagglomerates of dEPDM are formed inside the samples. In case of NR or SBR the agglomerates were very linked to the matrix through the covalent bonds established in the crosslinking process. In the case of the EPDM matrix, the agglomerates presented less interfacial cross-links. The cross-linking takes place preferentially within the dEPDM microdomains and this results in a relative decrease in mechanical properties and thermal stability when compared to NR and SBR.
•The focus is on whether dEPDM samples with NR, EPDM and SBR matrices have good properties and how much dEPDM can support.•The three compounds tested showed a general increase of their mechanical and thermal properties for NR and SBR than EPDM.•The microstructure indicate that agglomerates of EPDMd was formed inside the samples. The linkage is higher in NR than EPDM.
Rationale
Topiramate is an anticonvulsant drug which has been evaluated as a therapeutic option for the treatment of cocaine addiction during the last decade.
Objectives
The purpose of this study was ...to evaluate the effects of topiramate on the reinforcing actions of cocaine. To this aim, the topiramate-mediated regulation of acquisition and extinction phases of the cocaine conditioned place preference (CPP) was assessed in young-adult mice using three experimental designs.
Methods
Topiramate (50 mg/kg, p.o.) was given as follows: (1) during cocaine (1 and 25 mg/kg, i.p.) conditioning sessions (4 days) and cocaine (25 mg/kg) post-conditioning session; (2) 2 weeks before and during cocaine conditioning (25 mg/kg); and (3) during extinction of CPP induced by cocaine (25 mg/kg). In the first experimental design, changes in tyrosine hydroxylase (TH) and dopamine transporter (DAT) gene expressions were measured in the ventral tegmental area (VTA).
Results
Topiramate significantly increased cocaine-induced CPP and delayed or failed to produce extinction after the first cocaine reinstatement extinction in the first and second experiments. Furthermore, treatment with topiramate after place conditioning blocked the extinction of cocaine-induced CPP. TH and DAT gene expression in the VTA was significantly lower both with topiramate alone and in combination with cocaine compared with animals receiving only cocaine.
Conclusions
These findings suggest that topiramate increases the rewarding properties of cocaine, at least in part, by regulating dopaminergic signaling in the mesolimbic circuit. Consequently, the results of this study do not support the use of topiramate for the treatment of problems related to cocaine dependence.
Highlights
• Topiramate increases the rewarding properties of cocaine in CPP
• Topiramate alters dopaminergic signaling in the mesolimbic circuit
• Topiramate delays the extinction of cocaine-induced CPP
• TH and DAT gene expression in the VTA decreases with topiramate and/or with cocaine
• Results show that it should limit the use of topiramate in cocaine-dependent subjects
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