Interplay of Aharonov-Bohm and Berry phases in gate-defined graphene quantum dots

We study the influence of a magnetic flux tube on the possibility to electrostatically confine electrons in a graphene quantum dot. Without magnetic flux tube, the graphene pseudospin is responsible for a quantization of the total angular momentum to half-integer values. On the other hand, with a flux tube containing half a flux quantum, the Aharonov-Bohm phase and Berry phase precisely cancel, and we find a state at zero angular momentum that cannot be confined electrostatically. In this case, true bound states only exist in regular geometries for which states without zero-angular-momentum component exist, while non-integrable geometries lack confinement. We support these arguments with a calculation of the two-terminal conductance of a gate-defined graphene quantum dot, which shows resonances for a disc-shaped geometry and for a stadium-shaped geometry without flux tube, but no resonances for a stadium-shaped quantum dot with a $\pi$-flux tube.Comment: 7 pages, 5 figure

Microbial Cell Factories / \u201cDirect cloning in Lactobacillus plantarum: Electroporation with non-methylated plasmid DNA enhances transformation efficiency and makes shuttle vectors obsolete\u201d

Background: Lactic acid bacteria (LAB) play an important role in agricultural as well as industrial biotechnology. Development of improved LAB strains using e.g. library approaches is often limited by low transformation efficiencies wherefore one reason could be differences in the DNA methylation patterns between the Escherichia coli intermediate host for plasmid amplification and the final LAB host. In the present study, we examined the influence of DNA methylation on transformation efficiency in LAB and developed a direct cloning approach for Lactobacillus plantarum CD033. Therefore, we propagated plasmid pCD256 in E. coli strains with different dam/dcm-methylation properties. The obtained plasmid DNA was purified and transformed into three different L. plantarum strains and a selection of other LAB species. Results: Best transformation efficiencies were obtained using the strain L. plantarum CD033 and non-methylated plasmid DNA. Thereby we achieved transformation efficiencies of ~ 109 colony forming units/\u3bcg DNA in L. plantarum CD033 which is in the range of transformation efficiencies reached with E. coli. Based on these results, we directly transformed recombinant expression vectors received from PCR/ligation reactions into L. plantarum CD033, omitting plasmid amplification in E. coli. Also this approach was successful and yielded a sufficient number of recombinant clones. Conclusions: Transformation efficiency of L. plantarum CD033 was drastically increased when non-methylated plasmid DNA was used, providing the possibility to generate expression libraries in this organism. A direct cloning approach, whereby ligated PCR-products where successfully transformed directly into L. plantarum CD033, obviates the construction of shuttle vectors containing E. coli-specific sequences, as e.g. a ColEI origin of replication, and makes amplification of these vectors in E. coli obsolete. Thus, plasmid constructs become much smaller and occasional structural instability or mutagenesis during E. coli propagation is excluded. The results of our study provide new genetic tools for L. plantarum which will allow fast, forward and systems based genetic engineering of this species

Implications of atmospheric conditions for analysis of surface temperature variability derived from landscape-scale thermography

Thermal infrared (TIR) cameras perfectly bridge the gap between (i) on-site measurements of land surface temperature (LST) providing high temporal resolution at the cost of low spatial coverage and (ii) remotely sensed data from satellites that provide high spatial coverage at relatively low spatio-temporal resolution. While LST data from satellite (LSTsat) and airborne platforms are routinely corrected for atmospheric effects, such corrections are barely applied for LST from ground-based TIR imagery (using TIR cameras; LSTcam). We show the consequences of neglecting atmospheric effects on LSTcamof different vegetated surfaces at landscape scale. We compare LST measured from different platforms, focusing on the comparison of LST data from on-site radiometry (LSTosr) and LSTcamusing a commercially available TIR camera in the region of Bozen/Bolzano (Italy). Given a digital elevation model and measured vertical air temperature profiles, we developed a multiple linear regression model to correct LSTcamdata for atmospheric influences. We could show the distinct effect of atmospheric conditions and related radiative processes along the measurement path on LSTcam, proving the necessity to correct LSTcamdata on landscape scale, despite their relatively low measurement distances compared to remotely sensed data. Corrected LSTcamdata revealed the dampening effect of the atmosphere, especially at high temperature differences between the atmosphere and the vegetated surface. Not correcting for these effects leads to erroneous LST estimates, in particular to an underestimation of the heterogeneity in LST, both in time and space. In the most pronounced case, we found a temperature range extension of almost 10 K

Measurement properties of quality-of-life measurement instruments for infants, children and adolescents with eczema: a systematic review

Background: Quality of life (QoL) is one of the core outcome domains identified by the Harmonising Outcome Measures for Eczema (HOME) initiative to be assessed in every eczema trial. There is uncertainty about the most appropriate QoL instrument to measure this domain in infants, children and adolescents. Objectives: To systematically evaluate the measurement properties of existing measurement instruments developed and/or validated for the measurement of QoL in infants, children and adolescents with eczema. Methods: A systematic literature search in PubMed and EMBASE, complemented by a thorough hand search of reference lists, retrieved studies on measurement properties of eczema QoL instruments for infants, children and adolescents. For all eligible studies, we judged the adequacy of the measurement properties and the methodological study quality with the COnsensus-based Standards for the selection of health Measurement INstruments (COSMIN) checklist. Results from different studies were summarized in a best evidence synthesis and formed the basis to assign four degrees of recommendation. Results: 17 articles, 3 of which were found by hand search, were included. These 17 articles reported on 24 instruments. No instrument can be recommended for use in all eczema trials because none fulfilled all required adequacy criteria. With adequate internal consistency, reliability and hypothesis testing, the US version of the Childhood Atopic Dermatitis Impact Scale (CADIS), a proxy-reported instrument, has the potential to be recommended depending on the results of further validation studies. All other instruments, including all self-reported ones, lacked significant validation data. Conclusions: Currently, no QoL instrument for infants, children and adolescents with eczema can be highly recommended. Future validation research should primarily focus on the CADIS, but also attempt to broaden the evidence base for the validity of self-reported instruments

Evaluation of novel inducible promoter/repressor systems for recombinant protein expression in Lactobacillus plantarum

Background: Engineering lactic acid bacteria (LAB) is of growing importance for food and feed industry as well as for in vivo vaccination or the production of recombinant proteins in food grade organisms. Often, expression of a transgene is only desired at a certain time point or period, e.g. to minimize the metabolic burden for the host cell or to control the expression time span. For this purpose, inducible expression systems are preferred, though cost and availability of the inducing agent must be feasible. We selected the plasmid free strain Lactobacillus plantarum 3NSH for testing and characterization of novel inducible promoters/repressor systems. Their feasibility in recombinant protein production was evaluated. Expression of the reporter protein mCherry was monitored with the BioLector® micro-fermentation system. Results: Reporter gene mCherry expression was compared under the control of different promoter/repressor systems: PlacA (an endogenous promoter/repressor system derived from L. plantarum 3NSH), PxylA (a promoter/repressor system derived from Bacillus megaterium DSMZ 319) and PlacSynth (synthetic promoter and codon-optimized repressor gene based on the Escherichia coli lac operon). We observed that PlacA was inducible solely by lactose, but not by non-metabolizable allolactose analoga. PxylA was inducible by xylose, yet showed basal expression under non-induced conditions. Growth on galactose (as compared to exponential growth phase on glucose) reduced basal mCherry expression at non-induced conditions. PlacSynth was inducible with TMG (methyl -D-thiogalactopyranoside) and IPTG (isopropyl -D-1-thiogalactopyranoside), but also showed basal expression without inducer. The promoter PlacSynth was used for establishment of a dual plasmid expression system, based on T7 RNA polymerase driven expression in L. plantarum. Comparative Western blot supported BioLector® micro-fermentation measurements. Conclusively, overall expression levels were moderate (compared to a constitutive promoter). Conclusions: We evaluated different inducible promoters, as well as an orthologous expression system, for controlled gene expression in L. plantarum. Furthermore, here we provide proof of concept for a T7 RNA polymerase based expression system for L. plantarum. Thereby we expanded the molecular toolbox for an industrial relevant and generally regarded as safe (GRAS) strain.(VLID)101641

Fabrication and Mechanical Characterisation of Titanium Lattices with Graded Porosity

Electron Beam Melting (EBM) is an Additive Manufacturing technique which can be used to fabricate complex structures from alloys such as Ti6Al4V, for example for orthopaedic applications. Here we describe the use of EBM for the fabrication of a novel Ti6Al4V structure of a regular diamond lattice incorporating graded porosity, achieved via changes in the strut cross section thickness. Scanning Electron Microscopy and micro computed tomography analysis confirmed that generally EBM reproduced the CAD design of the lattice well, although at smaller strut sizes the fabricated lattice produced thicker struts than the model. Mechanical characterisation of the lattice in uniaxial compression showed that its behaviour under compression along the direction of gradation can be predicted to good accuracy with a simple rule of mixtures approach, knowing the properties and the behaviour of its constituent layers

Microbial Cell Factories / Enhancement of solubility in Escherichia coli and purification of an aminotransferase from Sphingopyxis sp. MTA144 for deamination of hydrolyzed fumonisin B1

Background: Fumonisin B1 is a cancerogenic mycotoxin produced by Fusarium verticillioides and other fungi. Sphingopyxis sp. MTA144 can degrade fumonisin B1, and a key enzyme in the catabolic pathway is an aminotransferase which removes the C2-amino group from hydrolyzed fumonisin B1. In order to study this aminotransferase with respect to a possible future application in enzymatic fumonisin detoxification, we attempted expression of the corresponding fumI gene in E. coli and purification of the enzyme. Since the aminotransferase initially accumulated in inclusion bodies, we compared the effects of induction level, host strain, expression temperature, solubility enhancers and a fusion partner on enzyme solubility and activity. Results: When expressed from a T7 promoter at 30\ub0C, the aminotransferase accumulated invariably in inclusion bodies in DE3 lysogens of the E. coli strains BL21, HMS174, Rosetta 2, Origami 2, or Rosetta-gami. Omission of the isopropyl-beta-D-thiogalactopyranoside (IPTG) used for induction caused a reduction of expression level, but no enhancement of solubility. Likewise, protein production but not solubility correlated with the IPTG concentration in E. coli Tuner(DE3). Addition of the solubility enhancers betaine and sorbitol or the co-enzyme pyridoxal phosphate showed no effect. Maltose-binding protein, used as an N-terminal fusion partner, promoted solubility at 30\ub0C or less, but not at 37\ub0C. Low enzyme activity and subsequent aggregation in the course of purification and cleavage indicated that the soluble fusion protein contained incorrectly folded aminotransferase. Expression in E. coli ArcticExpress(DE3), which co-expresses two cold-adapted chaperonins, at 11\ub0C finally resulted in production of appreciable amounts of active enzyme. Since His tag-mediated affinity purification from this strain was hindered by co-elution of chaperonin, two steps of chromatography with optimized imidazole concentration in the binding buffer were performed to obtain 1.45 mg of apparently homogeneous aminotransferase per liter of expression culture. Conclusions: We found that only reduction of temperature, but not reduction of expression level or fusion to maltose-binding protein helped to produce correctly folded, active aminotransferase FumI in E. coli. Our results may provide a starting point for soluble expression of related aminotransferases or other aggregation-prone proteins in E. coli

The Inchon Landing: A Case Study in Amphibious Planning

The landing at Inchon in September 1950 is one of the most dramatic such transitions from defense to attack in the annals of war

The Inchon Landing: A Case Study in Amphibious Planning

The landing at Inchon in September 1950 is one of the most dramatic such transitions from defense to attack in the annals of war