Long wavelength quantum-dot lasers selectively populated using tunnel injection

Using measured amplified spontaneous emission data, we have derived and analysed the carrier distribution of a five-layer tunnelling injection quantum-dot structure at temperatures of 300 K and 350 K. The results are consistent with the direct injection of electrons from the injector well into a subset of lower energy dot states. The carrier distribution spectra contain features which suggest that dots of a particular size within the ensemble are preferentially populated leading to a reduced spectral broadening of the emission.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58108/2/sst7_5_018.pd

Wireless transfer of power by a 35-GHz metamaterial split-ring resonator rectenna

Wireless transfer of power via high frequency microwave radiation using a miniature split ring resonator rectenna is reported. RF power is converted into DC power by integrating a rectification circuit with the split ring resonator. The near-field behavior of the rectenna is investigated with microwave radiation in the frequency range between 20-40 GHz with a maximum power level of 17 dBm. The observed resonance peaks match those predicted by simulation. Polarization studies show the expected maximum in signal when the electric field is polarized along the edge of the split ring resonator with the gap and minimum for perpendicular orientation. The efficiency of the rectenna is on the order of 1% for a frequency of 37.2 GHz. By using a cascading array of 9 split ring resonators the output power was increased by a factor of 20

Decoy activity through microRNAs : the therapeutic implications

Introduction: microRNAs (miRNAs), small noncoding RNAs, are deregulated in several diseases including cancer. miRNAs regulate gene expression at a posttranscriptional level by binding to 5´UTR, coding regions or 3´UTR of messenger RNAs (mRNA), inhibiting mRNA translation or causing mRNA degradation. The same miRNA can have multiple mRNA targets, and the same mRNA can be regulated by various miRNAs. Areas covered: Recently, seminal contributions by several groups have implicated miRNAs as components of an RNA--RNA language that involves crosstalk between competing endogenous RNAs through a decoy mechanism. We review the studies that described miRNAs as players in a biological decoy activity. miRNAs can either be trapped by competing endogenous RNAs or interact with proteins that have binding sites for mRNAs. Expert opinion: The miRNA decoy functions have implications for the design of therapeutic approaches in human diseases, including specific ways to overcome resistance to drug therapy and future miRNA-based clinical trials design.M.I.A. is supported by a PhD fellowship (SFRH/BD/47031/2008) from Fundacão para a Ciência e Tecnologia, Portugal. Dr. Calin is The Alan M. Gewirtz Leukemia & Lymphoma Society Scholar. He is also supported as a Fellow at The University of Texas MD Anderson Research Trust, as a University of Texas System Regents Research Scholar, and by the CLL Global Research Foundation. Work in Dr. Calin’s laboratory is supported in part by an NIH/NCI grant (CA135444), a Department of Defense Breast Cancer Idea Award, Developmental Research Awards in Breast Cancer, Ovarian Cancer, Brain Cancer, Prostate Cancer, Multiple Myeloma, and Leukemia SPOREs, the Laura and John Arnold Foundation, the RGK Foundation and the Estate of C. G. Johnson, Jr. The authors disclose no conflicts of interests and no funding was received in preparation of this manuscript

Freeze casting of porous monolithic composites for hydrogen storage

Hydrogen storage by adsorption offers operational benefits over energy intensive compression techniques. Incorporating physisorption materials in compression stores could improve hydrogen capacities, reducing the volume or pressure needed for storage vessels. However, such materials are often presented as fine powders and development efforts to date have predominantly focused on improving hydrogen uptake alone. Without due attention to industry-relevant attributes, such as handling, processability, and mechanical properties it is unlikely that these materials will find commercial application. In the paper, the desirable mechanical properties of hydrogen-adsorbent PIM-1 are exploited to yield a series of composite monoliths doped with a high surface area activated carbon, intended to act as pressure vessel inserts. Freeze casting techniques were successfully adapted for use with chloroform, facilitating the production of coherent and controlled three-dimensional geometries. This included the use of an innovative elastomeric mould made by additive manufacture to allow facile adoption, with the ability to vary multiple forming factors in the future. The composite monolith formed exhibited a stiffness of 0.26 GPa, a compressive strength of 6.7 MPa, and an increased BET surface area of 847 m2 g−1 compared to PIM-1 powders, signifying the first steps towards producing hydrogen adsorbents in truly useful monolithic forms

Statistical analysis of the velocity field in a mechanical precessing jet flow

An experimental investigation of a precessing jet issuing from a mechanically rotating nozzle directed at an angle of α=45° relative to the axis of rotation is reported. Both conventional and conditional statistics of the velocity field of the jet were measured using a combined hot-wire and cold-wire (to identify any reverse flow) probe. Three distinct values (≈0.005, 0.01, and 0.02) of the precession Strouhal number Stp (≡ rotation frequency × nozzle diameter / jet exit bulk velocity) were used to assess the effect of varying Stp. The measurements reveal that the Strouhal number in general has significant influence on the entire mixing field generated by a precessing jet. The occurrence of precession at all the Strouhal numbers of investigation produces a central recirculation zone at x ≤ 7d, where x is a distance measured from the rotating nozzle exit. A critical Strouhal number, i.e., Stp,cr ≈0.008 for the present case, is identified: at Stp ≥ Stp,cr the core jet converges to the axis of rotation while at Stp ≥ Stp,cr it does not. The characteristics of the turbulent flow in the near and intermediate regions are quite different and depend upon the magnitude of Stp. The near-field region, x/d ≤ 10-15, is dominated by a regime of global precession of the entire jet. As a result, the large-scale entrainment of the ambient fluid is substantially enhanced while the fine-scale turbulent mixing is suppressed. Under the supercritical regime (i.e., Stp ≥ Stp,cr), the jet in the far field resembles some features of the nonprecessing counterpart. Nevertheless, significant differences still retain in the statistical properties. © 2005 American Institute of Physics.J. Mi and G. J. Natha

Sequential Reassortments Underlie Diverse Influenza H7N9 Genotypes in China

Initial genetic characterizations have suggested that the influenza A (H7N9) viruses responsible for the current outbreak in China are novel reassortants. However, little is known about the pathways of their evolution and, in particular, the generation of diverse viral genotypes. Here we report an in-depth evolutionary analysis of whole-genome sequence data of 45 H7N9 and 42 H9N2 viruses isolated from humans, poultry, and wild birds during recent influenza surveillance efforts in China. Our analysis shows that the H7N9 viruses were generated by at least two steps of sequential reassortments involving distinct H9N2 donor viruses in different hosts. The first reassortment likely occurred in wild birds and the second in domestic birds in east China in early 2012. Our study identifies the pathways for the generation of diverse H7N9 genotypes in China and highlights the importance of monitoring multiple sources for effective surveillance of potential influenza outbreaks.National Natural Science Foundation (China) (31125016)National Natural Science Foundation (China) (31371338)National Center for Biotechnology Information (U.S.) (Major National Earmark Project for Infectious Diseases, 2013ZX10004611-002)National Basic Research Program of China (973 Program)National Basic Research Program of China (973 Program, grant, 2009CB918503)National Science and Technology Major Projects (2012ZX10004214001002)Jiangsu Sheng (China) (Priority Academic Program Development of Jiangsu Higher Education Institutions)National Natural Science Foundation (China) (31100950)MIT International Science and Technology Initiative