Spontaneous and piezoelectric polarization effects on the outputcharacteristics of AlGaN/GaN heterojunction modulation doped FETs

We report on the calculation of electrical characteristics of AlGaN/GaN heterojunction field effect transistors (HFETs). The model is based on the self-consistent solution of the Schrodinger and Poisson equations coupled to a quasi-2D model for the current flow. Both single and double heterojunction devices are analyzed for [0001] or [000-1] growth directions. The onset of a parasitic p-channel for particular growth directions and alloy concentrations is also shown     

Full band approach to tunneling in MOS structures

Using atomistic quantum mechanical tight-binding (TB) methods that include the full band structure, we study electron tunneling through three-dimensional models of n/sup +/-Si/SiO/sub 2//p-Si capacitors with thicknesses between 0.7 and 4.4 nm. We find that the microscopic oxide structure influences transmission coefficients and tunnel currents significantly. The best agreement with experimental current-thickness and current-voltage data is obtained for a model derived from the /spl beta/-cristobalite polytype of SiO/sub 2/ that has a fairly small conduction band mass of 0.34 m/sub 0/. Standard approximate effective mass-based methods reproduce the TB results only if an energy and oxide thickness dependence of the mass parameter is introduced.     

Insights into Intra-Tumoral Heterogeneity: Transcriptional Profiling of Chemoresistant MPM Cell Subpopulations Reveals Involvement of NFkB and DNA Repair Pathways and Contributes a Prognostic Signature

Chemoresistance is a hallmark of malignant pleural mesothelioma (MPM) management and the expression of ALDH1A3 is responsible for the survival and activity of MPM chemoresistant cell subpopulations (ALDH^bright cells). We enriched mesothelioma ALDH^bright cells to near homogeneity by FACS sorting and an Aldefluor assay and performed unbiased Affymetrix gene expression profiling. Viability and ELISA assays were used to rule out significant apoptosis in the sorted cell subpopulations and to assess target engagement by butein. Statistical analysis of the results, pathway enrichment and promoter enrichment were employed for the generation of the data. Q-RTPCR was used to validate a subset of the identified, modulated mRNAs In this work, we started from the observation that the mRNA levels of the ALDH1A3 isoform could prognostically stratify MPM patients. Thus, we purified MPM ALDH^bright cells from NCI-H2595 cells and interrogated their gene expression (GES) profile. We analyzed the GES of the purified cells at both a steady state and upon treatment with butein (a multifunctional tetrahydroxy-chalcone), which abates the ALDH^bright cell number, thereby exerting chemo-sensitizing effects in vitro and in vivo. We identified 924 genes modulated in a statistically significant manner as a function of ALDH status and of the response to the inhibitor. Pathway and promoter enrichment identified the molecular determinant of high ALDH status and how butein treatment altered the molecular portrait of those chemoresistant cell subpopulations. Further, we unraveled an eighteen-gene signature with high prognostic significance for MPM patients, and showed that most of the identified prognostic contributors escaped the analysis of unfractionated samples. This work proves that digging into the unexplored field of intra-tumor heterogeneity (ITH) by working at the cell subpopulation level may provide findings of prognostic relevance, in addition to mechanistic insights into tumor resistance to therapy.     

Coupling atomistic and continuous media models for electronic device simulation

In this article we highlight the necessity of atomistic based, fully quantum mechanical simulation approaches for modern electronic devices and their coupling with classical models. We review different ways of such couplings and provide application examples.     

Exploring molecular motors and switches at the single-molecule level

Single-molecule techniques have propelled an impressive number of biophysical studies during the last decade. From relatively simple video-microscopy techniques, to sophisticated manipulation and detection apparata, single-molecule techniques are capable of tracking the movements and the reaction trajectories of single enzymatic units. By observing microspheres attached to biomolecules it is possible to follow the motion of molecular motors, or to detect conformational "switching" induced by regulatory proteins. Micromanipulation tools like optical tweezers have been widely applied to understand the mechanisms of linear molecular motors, and have allowed the measurement of the elementary steps and the forces produced by several motor proteins, including myosin, kinesin, and dynein. New experimental assays based on magnetic or optical "wrenches," which are able to apply and detect torques on rotary motors and biopolymers, are opening new possibilities in this field. Here, established and emerging magneto-optical manipulation and video-tracking techniques are reviewed, in the perspective of single molecular motors and regulatory proteins studies.     

Full-band tunneling in high-κ dielectric MOS structures

High-κ oxides such as ZrO₂ and HfO₂ have attracted great interest, due to their physical properties, suitable to replacement of SiO₂ as gate dielectric materials. In this work, we investigate the tunneling properties of ZrO₂ and HfO₂ high-κ oxides, by applying quantum mechanical methods that include the full-band structure of Si and oxide materials. Semiempirical sp³s*d tight-binding parameters have been determined to reproduce ab initio band dispersions. Transmission coefficients and tunneling current have been calculated for Si/ZrO₂/Si and Si/HfO₂/Si MOS structures, showing a very low gate leakage current in comparison to SiO₂-based structures with equivalent oxide thickness.     

Concurrent multiscale simulation of electronic devices

In this paper we present a multiscale framework for the simulation of electronic devices allowing the coupling of continuum and atomistic models in a transparent way. We introduce the basic features of the TiberCAD simulation software which is based on the multiscale simulation concept, and we show a simulation example to illustrate the basic aspects of a multiscale simulation.     

Liquid Crystalline Networks toward Regenerative Medicine and Tissue Repair

The communication reports the use of liquid crystalline networks (LCNs) for engineering tissue cultures with human cells. Their ability as cell scaffolds for different cell lines is demonstrated. Preliminary assessments of the material biocompatibility are performed on human dermal fibroblasts and murine muscle cells (C2C12), demonstrating that coatings or other treatments are not needed to use the acrylate‐based materials as support. Moreover, it is found that adherent C2C12 cells undergo differentiation, forming multinucleated myotubes, which show the typical elongated shape, and contain bundles of stress fibers. Once biocompatibility is demonstrated, the same LCN films are used as a substrate for culturing human induced pluripotent stem cell‐derived cardiomyocites (hiPSC‐CMs) proving that LCNs are capable to develop adult‐like dimensions and a more mature cell function in a short period of culture in respect to standard supports. The demonstrated biocompatibility together with the extraordinary features of LCNs opens to preparation of complex cell scaffolds, both patterned and stimulated, for dynamic cell culturing. The ability of these materials to improve cell maturation and differentiation will be developed toward engineered heart and skeletal muscular tissues exploring regenerative medicine toward bioartificial muscles for injured sites replacement.     

Optimal reconfiguration policy to react to product changes

The increasing frequency of product and process modifications may significantly undermine the profitability of those production systems that are designed only on the basis of the current product requirements and eventually on the expectations of future variations of the market volumes. Indeed, the product typically evolves during its life cycle, by changing its technological characteristics and therefore its requirements on the production system. As a consequence, the production system may be forced to run in an inefficient and costly manner because it is no longer consistent with the modified product. This paper describes the reconfiguration problem of production systems and proposes the optimal reconfiguration policy to react to product changes, on uniformly distributed market demand and uniformly distributed technological requirements. A numerical case based on a real problem supports the applicability of the proposed reconfiguration policy.