Remarkable stability of an instability-prone lentiviral vector plasmid in Escherichia coli Stbl3

Large-scale production of plasmid DNA to prepare therapeutic gene vectors or DNA-based vaccines requires a suitable bacterial host, which can stably maintain the plasmid DNA during industrial cultivation. Plasmid loss during bacterial cell divisions and structural changes in the plasmid DNA can dramatically reduce the yield of the desired recombinant plasmid DNA. While generating an HIV-based gene vector containing a bicistronic expression cassette 5′-Olig2cDNA-IRES-dsRed2-3′, we encountered plasmid DNA instability, which occurred in homologous recombination deficient recA1 Escherichia coli strain Stbl2 specifically during large-scale bacterial cultivation. Unexpectedly, the new recombinant plasmid was structurally changed or completely lost in 0.5 L liquid cultures but not in the preceding 5 mL cultures. Neither the employment of an array of alternative recA1 E. coli plasmid hosts, nor the lowering of the culture incubation temperature prevented the instability. However, after the introduction of this instability-prone plasmid into the recA13E. coli strain Stbl3, the transformed bacteria grew without being overrun by plasmid-free cells, reduction in the plasmid DNA yield or structural changes in plasmid DNA. Thus, E. coli strain Stbl3 conferred structural and maintenance stability to the otherwise instability-prone lentivirus-based recombinant plasmid, suggesting that this strain can be used for the faithful maintenance of similar stability-compromised plasmids in large-scale bacterial cultivations. In contrast to Stbl2, which is derived wholly from the wild type isolate E. coli K12, E. coli Stbl3 is a hybrid strain of mixed E. coli K12 and E. coli B parentage. Therefore, we speculate that genetic determinants for the benevolent properties of E. coli Stbl3 for safe plasmid propagation originate from its E. coli B ancestor

What are the experiences of adults returning to work following recovery from Guillain-Barré syndrome? An interpretative phenomenological analysis

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2009 Informa UK Ltd.Purpose. Guillain-Barré syndrome (GBS) is a transient inflammatory disorder affecting peripheral nerves, characterised by weakness and numbness in limbs, upper body and face. Residual problems affect a large minority, and complicate return to work. This qualitative study explored the experiences of people who returned to work following their diagnosis of GBS and recovery, to gain insight into factors that facilitated or inhibited this process. Method. Five people participated in in-depth interviews. Individual and common experiences were explored through interpretative phenomenological analysis. Findings. Three recurring themes are presented: the perceived value of work; losing and recovering a familiar identity at work; and dilemmas around using support and adaptations at work. Certain individual issues also emerged but are beyond the scope of this article. Participants tended to measure their recovery in terms of returning to work yet continued to experience certain physical and psychosocial difficulties at work related to GBS, which required active coping strategies. Limited public awareness of GBS was perceived as a hindrance when returning to work. Conclusion. This study provides a rich account of the experiences that people encounter returning to work following GBS. Rehabilitation specialists may offer more effective preparation for this process, drawing upon the issues identified

Quantum interference in deformed carbon nanotube waveguides

Quantum interference (QI) in two types of deformed carbon nanotubes (CNTs), i.e., axially stretched and AFM tip-deformed CNTs, has been investigated by the pi-electron only and four-orbital tight-binding (TB) method. It is found that the rapid conductance oscillation (RCO) period is very sensitive to the applied strains, and decreases in an inverse proportion to the deformation degree, which could be used as a powerful experimental tool to detect precisely the deformation degree of the deformed CNTs. Also, the sigma-pi coupling effect is found to be negligible under axially stretched strain, while it works on the transport properties of the tip-deformed CNTs.Comment: 14 pages and 5 figure

A distinct sortase SrtB anchors and processes a streptococcal adhesin AbpA with a novel structural property.

Surface display of proteins by sortases in Gram-positive bacteria is crucial for bacterial fitness and virulence. We found a unique gene locus encoding an amylase-binding adhesin AbpA and a sortase B in oral streptococci. AbpA possesses a new distinct C-terminal cell wall sorting signal. We demonstrated that this C-terminal motif is required for anchoring AbpA to cell wall. In vitro and in vivo studies revealed that SrtB has dual functions, anchoring AbpA to the cell wall and processing AbpA into a ladder profile. Solution structure of AbpA determined by NMR reveals a novel structure comprising a small globular α/β domain and an extended coiled-coil heliacal domain. Structural and biochemical studies identified key residues that are crucial for amylase binding. Taken together, our studies document a unique sortase/adhesion substrate system in streptococci adapted to the oral environment rich in salivary amylase

Thermalized Displaced Squeezed Thermal States

In the coordinate representation of thermofield dynamics, we investigate the thermalized displaced squeezed thermal state which involves two temperatures successively. We give the wavefunction and the matrix element of the density operator at any time, and accordingly calculate some quantities related to the position, momentum and particle number operator, special cases of which are consistent with the results in the literature. The two temperatures have diffenent correlations with the squeeze and coherence components. Moreover, different from the properties of the position and momentum, the average value and variance of the particle number operator as well as the second-order correlation function are time-independent.Comment: 7 pages, no figures, Revtex fil

Improve the performance of transfer learning without fine-tuning using dissimilarity-based multi-view learning for breast cancer histology images

Breast cancer is one of the most common types of cancer and leading cancer-related death causes for women. In the context of ICIAR 2018 Grand Challenge on Breast Cancer Histology Images, we compare one handcrafted feature extractor and five transfer learning feature extractors based on deep learning. We find out that the deep learning networks pretrained on ImageNet have better performance than the popular handcrafted features used for breast cancer histology images. The best feature extractor achieves an average accuracy of 79.30%. To improve the classification performance, a random forest dissimilarity based integration method is used to combine different feature groups together. When the five deep learning feature groups are combined, the average accuracy is improved to 82.90% (best accuracy 85.00%). When handcrafted features are combined with the five deep learning feature groups, the average accuracy is improved to 87.10% (best accuracy 93.00%)

Algebraic treatment of PT\mathcal{PT}-symmetric coupled oscillators

The purpose of this paper is the discussion of a pair of coupled linear oscillators that has recently been proposed as a model of a system of two optical resonators. By means of an algebraic approach we show that the frequencies of the classical and quantum-mechanical interpretations of the optical phenomenon are exactly the same. Consequently, if the classical frequencies are real, then the quantum-mechanical eigenvalues are also real

Void Growth in BCC Metals Simulated with Molecular Dynamics using the Finnis-Sinclair Potential

The process of fracture in ductile metals involves the nucleation, growth, and linking of voids. This process takes place both at the low rates involved in typical engineering applications and at the high rates associated with dynamic fracture processes such as spallation. Here we study the growth of a void in a single crystal at high rates using molecular dynamics (MD) based on Finnis-Sinclair interatomic potentials for the body-centred cubic (bcc) metals V, Nb, Mo, Ta, and W. The use of the Finnis-Sinclair potential enables the study of plasticity associated with void growth at the atomic level at room temperature and strain rates from 10^9/s down to 10^6/s and systems as large as 128 million atoms. The atomistic systems are observed to undergo a transition from twinning at the higher end of this range to dislocation flow at the lower end. We analyze the simulations for the specific mechanisms of plasticity associated with void growth as dislocation loops are punched out to accommodate the growing void. We also analyse the process of nucleation and growth of voids in simulations of nanocrystalline Ta expanding at different strain rates. We comment on differences in the plasticity associated with void growth in the bcc metals compared to earlier studies in face-centred cubic (fcc) metals.Comment: 24 pages, 12 figure

Integro-differential diffusion equation for continuous time random walk

In this paper we present an integro-differential diffusion equation for continuous time random walk that is valid for a generic waiting time probability density function. Using this equation we also study diffusion behaviors for a couple of specific waiting time probability density functions such as exponential, and a combination of power law and generalized Mittag-Leffler function. We show that for the case of the exponential waiting time probability density function a normal diffusion is generated and the probability density function is Gaussian distribution. In the case of the combination of a power-law and generalized Mittag-Leffler waiting probability density function we obtain the subdiffusive behavior for all the time regions from small to large times, and probability density function is non-Gaussian distribution.Comment: 12 page