Bioelectrochemical conversion of CO2 to value added product formate using engineered Methylobacterium extorquens

The conversion of carbon dioxide to formate is a fundamental step for building C1 chemical platforms. Methylobacterium extorquens AM1 was reported to show remarkable activity converting carbon dioxide into formate. Formate dehydrogenase 1 from M. extorquens AM1 (MeFDH1) was verified as the key responsible enzyme for the conversion of carbon dioxide to formate in this study. Using a 2% methanol concentration for induction, microbial harboring the recombinant MeFDH1 expressing plasmid produced the highest concentration of formate (26.6 mM within 21 hours) in electrochemical reactor. 60 ??M of sodium tungstate in the culture medium was optimal for the expression of recombinant MeFDH1 and production of formate (25.7 mM within 21 hours). The recombinant MeFDH1 expressing cells showed maximum formate productivity of 2.53 mM/g-wet cell/hr, which was 2.5 times greater than that of wild type. Thus, M. extorquens AM1 was successfully engineered by expressing MeFDH1 as recombinant enzyme to elevate the production of formate from CO2 after elucidating key responsible enzyme for the conversion of CO2 to formate

Overshoot mechanism in transient excitation of THz and Gunn oscillations in wide-bandgap semiconductors

A detailed study of high-field transient and direct-current (DC) transport in GaN-based Gunn diode oscillators is carried out using the commercial simulator Sentaurus Device. Applicability of drift-diffusion (DD) and hydrodynamic (HD) models to high-speed, highfrequency devices is discussed in depth, and the results of the simulations from these models are compared. It is shown, for a highly homogeneous device based on a short (2 μm) supercritically doped (1017 cm-3) GaN specimen, that the DD model is unable to correctly take into account some essential physical effects which determine the operation mode of the device. At the same time, the HD model is ideally suited to solve such problems due to its ability to incorporate non-local effects. We show that the velocity overshoot near the device contacts and space charge injection and extraction play a crucial role in defining the operation mode of highly homogeneous short diodes in both the transient regime and the voltagecontrolled oscillation regime. The transient conduction current responses are fundamentally different in the DD and HD models. The DD current simply repeats the velocity-field (v-F) characteristics, and the sample remains in a completely homogeneous state. In the HD model, the transient current pulse with a full width at half maximum of approximately 0.2 ps is increased about twofold due to the carrier injection (extraction) into (from) the active region and the velocity overshoot. The electron gas is characterized by highly inhomogeneous distributions of the carrier density, the electric field and the electron temperature. The simulation of the DC steady states of the diodes also shows very different results for the two models. The HD model shows the trapped stable anodic domain in the device, while the DD model completely retains all features of the v-F characteristics in a homogeneous gas. Simulation of the voltage-controlled oscillator shows that it operates in the accumulation layer mode generating microwave signals at 0.3 to 0.7 THz. In spite of the fact that the known criterion of a Gunn domain mode n0L > (n0L)0 was satisfied, no Gunn domains were observed. The explanation of this phenomenon is given. © 2012 Momox et al

Teaching the history of geography:Current challenges and future directions

Drawing upon the personal reflections of geographical educators in Brazil, Canada, the UK, and the US, this Forum provides a state-of-the-discipline review of teaching in the history of geography; identifies the practical and pedagogical challenges associated with that teaching; and offers suggestions and provocations as to future innovation. The Forum shows how teaching in the history of geography is valued – as a tool of identity making, as a device for cohort building and professionalization, and as a means of interrogating the disciplinary present – but also how it is challenged by neoliberal educational policies, competing priorities in curriculum design, and sub-disciplinary divisions

Effect of cellular and extracellular pathology assessed by T1 mapping on regional contractile function in hypertrophic cardiomyopathy

Background Regional contractile dysfunction is a frequent finding in hypertrophic cardiomyopathy (HCM). We aimed to investigate the contribution of different tissue characteristics in HCM to regional contractile dysfunction. Methods We prospectively recruited 50 patients with HCM who underwent cardiovascular magnetic resonance (CMR) studies at 3.0 T including cine imaging, T1 mapping and late gadolinium enhancement (LGE) imaging. For each segment of the American Heart Association model segment thickness, native T1, extracellular volume (ECV), presence of LGE and regional strain (by feature tracking and tissue tagging) were assessed. The relationship of segmental function, hypertrophy and tissue characteristics were determined using a mixed effects model, with random intercept for each patient. Results Individually segment thickness, native T1, ECV and the presence of LGE all had significant associations with regional strain. The first multivariable model (segment thickness, LGE and ECV) demonstrated that all strain parameters were associated with segment thickness (P < 0.001 for all) but not ECV. LGE (Beta 2.603, P = 0.024) had a significant association with circumferential strain measured by tissue tagging. In a second multivariable model (segment thickness, LGE and native T1) all strain parameters were associated with both segment thickness (P < 0.001 for all) and native T1 (P < 0.001 for all) but not LGE. Conclusion Impairment of contractile function in HCM is predominantly associated with the degree of hypertrophy and native T1 but not markers of extracellular fibrosis (ECV or LGE). These findings suggest that impairment of contractility in HCM is mediated by mechanisms other than extracellular expansion that include cellular changes in structure and function. The cellular mechanisms leading to increased native T1 and its prognostic significance remain to be established

Cyclic Nucleotide Phosphodiesterases and Compartmentation in Normal and Diseased Heart

International audienceCyclic nucleotide phosphodiesterases (PDEs) degrade the second messengers cAMP and cGMP, thereby regulating multiple aspects of cardiac function. This highly diverse class of enzymes encoded by 21 genes encompasses 11 families which are not only responsible for the termination of cyclic nucleotide signalling, but are also involved in the generation of dynamic microdomains of cAMP and cGMP controlling specific cell functions in response to various neurohormonal stimuli. In myocardium, the PDE3 and PDE4 families are predominant to degrade cAMP and thereby regulate cardiac excitation-contraction coupling. PDE3 inhibitors are positive inotropes and vasodilators in human, but their use is limited to acute heart failure and intermittent claudication. PDE5 is particularly important to degrade cGMP in vascular smooth muscle, and PDE5 inhibitors are used to treat erectile dysfunction and pulmonary hypertension. However, these drugs do not seem efficient in heart failure with preserved ejection fraction. There is experimental evidence that these PDEs as well as other PDE families including PDE1, PDE2 and PDE9 may play important roles in cardiac diseases such as hypertrophy and heart failure. After a brief presentation of the cyclic nucleotide pathways in cardiac cells and the major characteristics of the PDE superfamily, this chapter will present their role in cyclic nucleotide compartmentation and the current use of PDE inhibitors in cardiac diseases together with the recent research progresses that could lead to a better exploitation of the therapeutic potential of these enzymes in the future

Stability, Entrapment and Variant Formation of Salmonella Genomic Island 1

<div><h3>Background</h3><p>The <em>Salmonella</em> genomic island 1 (SGI1) is a 42.4 kb integrative mobilizable element containing several antibiotic resistance determinants embedded in a complex integron segment In104. The numerous SGI1 variants identified so far, differ mainly in this segment and the explanations of their emergence were mostly based on comparative structure analyses. Here we provide experimental studies on the stability, entrapment and variant formation of this peculiar gene cluster originally found in <em>S</em>. Typhimurium.</p> <h3>Methodology/Principal Findings</h3><p>Segregation and conjugation tests and various molecular techniques were used to detect the emerging SGI1 variants in <em>Salmonella</em> populations of 17 <em>Salmonella enterica</em> serovar Typhimurium DT104 isolates from Hungary. The SGI1s in these isolates proved to be fully competent in excision, conjugal transfer by the IncA/C helper plasmid R55, and integration into the <em>E. coli</em> chromosome. A trap vector has been constructed and successfully applied to capture the island on a plasmid. Monitoring of segregation of SGI1 indicated high stability of the island. SGI1-free segregants did not accumulate during long-term propagation, but several SGI1 variants could be obtained. Most of them appeared to be identical to SGI1-B and SGI1-C, but two new variants caused by deletions via a short-homology-dependent recombination process have also been detected. We have also noticed that the presence of the conjugation helper plasmid increased the formation of these deletion variants considerably.</p> <h3>Conclusions/Significance</h3><p>Despite that excision of SGI1 from the chromosome was proven in SGI1⁺<em>Salmonella</em> populations, its complete loss could not be observed. On the other hand, we demonstrated that several variants, among them two newly identified ones, arose with detectable frequencies in these populations in a short timescale and their formation was promoted by the helper plasmid. This reflects that IncA/C helper plasmids are not only involved in the horizontal spreading of SGI1, but may also contribute to its evolution.</p> </div

Observation of associated near-side and away-side long-range correlations in √sNN=5.02 TeV proton-lead collisions with the ATLAS detector

Two-particle correlations in relative azimuthal angle (Δϕ) and pseudorapidity (Δη) are measured in √sNN=5.02  TeV p+Pb collisions using the ATLAS detector at the LHC. The measurements are performed using approximately 1  μb-1 of data as a function of transverse momentum (pT) and the transverse energy (ΣETPb) summed over 3.1<η<4.9 in the direction of the Pb beam. The correlation function, constructed from charged particles, exhibits a long-range (2<|Δη|<5) “near-side” (Δϕ∼0) correlation that grows rapidly with increasing ΣETPb. A long-range “away-side” (Δϕ∼π) correlation, obtained by subtracting the expected contributions from recoiling dijets and other sources estimated using events with small ΣETPb, is found to match the near-side correlation in magnitude, shape (in Δη and Δϕ) and ΣETPb dependence. The resultant Δϕ correlation is approximately symmetric about π/2, and is consistent with a dominant cos⁡2Δϕ modulation for all ΣETPb ranges and particle pT