Substrate orientation and alloy composition effects in n-type SiGe quantum cascade structures

We show using a theoretical self-consistent effective mass/rate equation approach that n-type SiGe-based quantum cascade lasers are potentially made viable by either using the (111) orientation or a Ge-rich substrate

Multiscale modeling of magnetic materials: Temperature dependence of the exchange stiffness

For finite-temperature micromagnetic simulations the knowledge of the temperature dependence of the exchange stiffness plays a central role. We use two approaches for the calculation of the thermodynamic exchange parameter from spin models: (i) based on the domain-wall energy and (ii) based on the spin-wave dispersion. The corresponding analytical and numerical approaches are introduced and compared. A general theory for the temperature dependence and scaling of the exchange stiffness is developed using the classical spectral density method. The low-temperature exchange stiffness A is found to scale with magnetization as m(1.66) for systems on a simple cubic lattice and as m(1.76) for an FePt Hamiltonian parametrized through ab initio calculations. The additional reduction in the scaling exponent, as compared to the mean-field theory (A similar to m(2)), comes from the nonlinear spin-wave effects

On the coherence/incoherence of electron transport in semiconductor heterostructure optoelectronic devices

This paper compares and contrasts different theoretical approaches based on incoherent electron scattering transport with experimental measurements of optoelectronic devices formed from semiconductor heterostructures. The Monte Carlo method which makes no a priori assumptions about the carrier distribution in momentum or phase space is compared with less computationally demanding energy-balance rate equation models which assume thermalised carrier distributions. It is shown that the two approaches produce qualitatively similar results for hole transport in p-type Si1-xGex/Si superlattices designed for terahertz emission. The good agreement of the predictions of rate equation calculations with experimental measurements of mid- and far-infrared quantum cascade lasers, quantum well infrared photodetectors and quantum dot infrared photodetectors substantiate the assumption of incoherent scattering dominating the transport in these quantum well based devices. However, the paper goes on to consider the possibility of coherent transport through the density matrix method and suggests an experiment that could allow coherent and incoherent transport to be distinguished from each other

Characterization of hepcidin response to holotransferrin in novel recombinant TfR1 HepG2 cells

Hepcidin is the key regulator of systemic iron homeostasis. The iron-sensing mechanisms and the role of intracellular iron in modulating hepatic hepcidin secretion are unclear. Therefore, we created a novel cell line, recombinant-TfR1 HepG2,expressing iron-response-element-independent TFRC mRNA to promote cellular iron overload and examined the effect of excess holotransferrin (5 g/L) on cell-surface TfR1, iron content, hepcidin secretion and mRNA expressions of TFRC, HAMP, SLC40A1,HFE and TFR2. Results showed that the recombinant cells exceeded levels of cell surface TfR1 in wild-type cells under basal (2.8-fold; p<0.03) and holotransferrin supplemented conditions for 24 h and 48 h (4.4- and 7.5-fold, respectively; p<0.01). Also, these cells showed higher intracellular iron content than wild-type cells under basal (3-fold; p<0.03) and holotransferrin-supplemented conditions (6.6-fold at 4 h; p<0.01). However, hepcidin secretion was not higher than wild-type cells. Moreover, holotransferrin treatment to recombinant cells did not elevate HAMP responses compared to untreated or wild-type cells. In conclusion, increased intracellular iron content in recombinant cells did not increase hepcidin responses compared to wild-type cells, resembling hemochromatosis. Furthermore, TFR2 expression altered within 4 h of treatment, while HFE expression altered later at 24 h and 48 h, suggesting that TFR2 may function prior to HFE in HAMP regulation

Combating pancreatic cancer with PI3K pathway inhibitors in the era of personalised medicine

Pancreatic ductal adenocarcinoma (PDAC) is among the most deadly solid tumours. This is due to a generally late-stage diagnosis of a primarily treatment-refractory disease. Several large-scale sequencing and mass spectrometry approaches have identified key drivers of this disease and in doing so highlighted the vast heterogeneity of lower frequency mutations that make clinical trials of targeted agents in unselected patients increasingly futile. There is a clear need for improved biomarkers to guide effective targeted therapies, with biomarker-driven clinical trials for personalised medicine becoming increasingly common in several cancers. Interestingly, many of the aberrant signalling pathways in PDAC rely on downstream signal transduction through the mitogen-activated protein kinase and phosphoinositide 3-kinase (PI3K) pathways, which has led to the development of several approaches to target these key regulators, primarily as combination therapies. The following review discusses the trend of PDAC therapy towards molecular subtyping for biomarker-driven personalised therapies, highlighting the key pathways under investigation and their relationship to the PI3K pathway

Algorithm for numerical integration of the rigid-body equations of motion

A new algorithm for numerical integration of the rigid-body equations of motion is proposed. The algorithm uses the leapfrog scheme and the quantities involved are angular velocities and orientational variables which can be expressed in terms of either principal axes or quaternions. Due to specific features of the algorithm, orthonormality and unit norms of the orientational variables are integrals of motion, despite an approximate character of the produced trajectories. It is shown that the method presented appears to be the most efficient among all known algorithms of such a kind.Comment: 4 pages, 1 figur

A new species of the lenticel fungal genus Claviradulomyces (Ostropales) from the Brazilian Atlantic forest tree Xylopia sericea (Annonaceae)

Claviradulomyces xylopiae sp. nov. is introduced for a fungus occurring in association with abnormal (enlarged, spongy) lenticels of Xylopia sericea (Annonaceae), a common tree of the Atlantic forest and Cerrado ecosystems in Brazil. This is the second species described in the genus and, although it is morphologically distinct from the type species, C. dabeicola from West Africa, it possesses the same characteristics. Apothecial ascomata have periphysoids and paraphyses that are inflated apically (clavate), and ornamented with denticles (raduliform). Furthermore, similar to the type species, it also has long-cylindric or acerose, aseptate ascospores and conidia. An additional asexual morph was produced in culture and is described. Molecular studies of C. dabeicola and the new species confirmed a placement in Ostropales, although a relationship to Odontotremataceae was not supported. Both species were consistently in association with abnormal lenticular development on their woody hosts. It remains to be ascertained, however, if these are the causal agents of the bark disorders, or, simply, opportunistic colonisers. The finding of the second species in the genus Claviradulomyces on a plant from a distantly related family to that of the host of C. dabeicola (Erythroxylaceae) for the genus on a different continent suggests that fungi in this genus may be common on lenticels of other woody plants, and could even have a pantropical distribution. It is possible that fungi in the genus have remained unreported until now because lenticels have remained neglected as a habitat surveyed by mycologists

Homogenization of weakly coupled systems of Hamilton--Jacobi equations with fast switching rates

We consider homogenization for weakly coupled systems of Hamilton--Jacobi equations with fast switching rates. The fast switching rate terms force the solutions converge to the same limit, which is a solution of the effective equation. We discover the appearance of the initial layers, which appear naturally when we consider the systems with different initial data and analyze them rigorously. In particular, we obtain matched asymptotic solutions of the systems and rate of convergence. We also investigate properties of the effective Hamiltonian of weakly coupled systems and show some examples which do not appear in the context of single equations.Comment: final version, to appear in Arch. Ration. Mech. Ana

The need for biokineticists in the South African public health care system

Background: Noncommunicable diseases (NCDs) are increasingly prevalent within South Africa. Physical inactivity is a significant, independent and modifiable risk factor increasing the prevalence of NCDs.Discussion: The integration of physical activity programmes into the primary health care system through multidisciplinary platforms is thus advocated for and envisioned to be more cost-effective than current practices. However, currently within the primary health care setting of South Africa, there is an absence of health care professionals adequately equipped to develop and implement physical activity programmes. Biokineticists, whose scope of practice is to improve physical functioning and health through exercise as a modality, are ideally suited to developing and implementing physical activity programmes in the public sector. Yet despite their evident demand, the role of the biokineticist is not incorporated into the national public health care system.Conclusion: This short report calls firstly, for the inclusion of biokinetics into the public health care sector, and secondly, for the funding of multidisciplinary community health programmes supporting education, healthy eating and physical activity levels.Keywords: noncommunicable disease, physical activity, community health programme, primary health car

An assessment of Evans' unified field theory I

Evans developed a classical unified field theory of gravitation and electromagnetism on the background of a spacetime obeying a Riemann-Cartan geometry. This geometry can be characterized by an orthonormal coframe theta and a (metric compatible) Lorentz connection Gamma. These two potentials yield the field strengths torsion T and curvature R. Evans tried to infuse electromagnetic properties into this geometrical framework by putting the coframe theta to be proportional to four extended electromagnetic potentials A; these are assumed to encompass the conventional Maxwellian potential in a suitable limit. The viable Einstein-Cartan(-Sciama-Kibble) theory of gravity was adopted by Evans to describe the gravitational sector of his theory. Including also the results of an accompanying paper by Obukhov and the author, we show that Evans' ansatz for electromagnetism is untenable beyond repair both from a geometrical as well as from a physical point of view. As a consequence, his unified theory is obsolete.Comment: 39 pages of latex, modified because of referee report, mistakes and typos removed, partly reformulated, taken care of M.W.Evans' rebutta