Vertical-external-cavity surface-emitting lasers and quantum dot lasers

The use of cavity to manipulate photon emission of quantum dots (QDs) has been opening unprecedented opportunities for realizing quantum functional nanophotonic devices and also quantum information devices. In particular, in the field of semiconductor lasers, QDs were introduced as a superior alternative to quantum wells to suppress the temperature dependence of the threshold current in vertical-external-cavity surface-emitting lasers (VECSELs). In this work, a review of properties and development of semiconductor VECSEL devices and QD laser devices is given. Based on the features of VECSEL devices, the main emphasis is put on the recent development of technological approach on semiconductor QD VECSELs. Then, from the viewpoint of both single QD nanolaser and cavity quantum electrodynamics (QED), a single-QD-cavity system resulting from the strong coupling of QD cavity is presented. A difference of this review from the other existing works on semiconductor VECSEL devices is that we will cover both the fundamental aspects and technological approaches of QD VECSEL devices. And lastly, the presented review here has provided a deep insight into useful guideline for the development of QD VECSEL technology and future quantum functional nanophotonic devices and monolithic photonic integrated circuits (MPhICs).Comment: 21 pages, 4 figures. arXiv admin note: text overlap with arXiv:0904.369

A Bimodal Science Measurements for Earth Remote Sensing on a 3U CubeSat Platform

Solar energetic events, which include solar flares and solar mass ejections affect the Earth\u27s atmosphere. While solar energetic events have been observed to influence the chemistry of the mesospheric ozone, a comprehensive collection of quantitative data detailing the frequency, energy, and intensity of these interactions with the mesosphere have, to our knowledge, not before been collected. High-energy charged particles from solar energetic events can ionize molecules found within the mesosphere, accelerating the formation rate of reactive hydrogen atoms and nitrogen oxides. This results in reactions that catalyze the conversion of ozone back into diatomic oxygen. The Variability in Atmosphere – Solar Energetic Event study (VIA-SEEs) mission intends to utilize a 3U-CubeSat in Low Earth Orbit (LEO) to establish a singular data set for the purpose of understanding the correlation between flux in solar energetic events and variability in total reactive nitrogen oxides (NOy) and ozone (O3) concentrations in the mesosphere. This mission intends to produce a unique data set using a bimodal measurement scheme involving two instruments – one Variability in Atmosphere (VIA) commercial-off-the-shelf spectrophotometer for measuring NOy and O3 concentrations, and one in-house designed and fabricated solid-state radiation detector for observing the energy and flux of solar energetic electrons and protons

Effect of the structure of Ni nanoparticles on the electrocatalytic activity of Ni@Pd/C for formic acid oxidation

Ni@Pd/C catalysts were synthesized, using Ni/C with different crystalline structures prepared with various ligands. A series of characterizations were performed by transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy. The results indicated the electrocatalysts with amorphous/crystalline (denoted as Nia and Nic) Ni structures decorated with Pd. The formic acid electrocatalytic oxidation results showed that the peak current of Nia@Pd/C was about 1.2 times higher than that of Nic@Pd/C. The good electrochemical performance and stability of Pd-modified amorphous Ni substrate reveals that the core structure plays an important role in the electrocatalytic activity and the change of the structure can improve the activity and stability of electrocatalysts.Web of Scienc

The October 2012 magnitude (Mw) 7.8 earthquake offshore Haida Gwaii, Canada

Alison L. Bird et al. report on the Mw 7.8 earthquake offshore Haida Gwaii, Canada, from 2012 for the Summary of the Bulletin of the International Seismological Centre

Knowledge development approaches and breakthrough innovations in technology-based new firms

Compared to large established firms, technology-based new firms (TBNF) seem well placed to produce breakthrough innovations although questions remain as to their adeptness at subsequent exploitation. Building on the innovation and strategy literatures, the study identifies two different knowledge development approaches or modes (business models) in TBNFs – internal versus external - and examines their relation to breakthrough innovation and subsequent progression of the product to market. The internal mode assembles knowledge inside the firm to generate its innovations, whereas the external mode relies heavily on alliances to develop and assemble knowledge among firms embedded in a creative network. The study uses a unique panel dataset of 69 UK new biotechnology firms over an 11-year period to explore this issue empirically. The findings show that the external knowledge development mode is associated with more breakthrough innovations and a faster movement of innovations to market. The externally focused mode is not impeded by its relative lack of internal knowledge; it uses partners to access, assemble and develop a wide scope of knowledge in a flexible manner. In addition, partners provide deep domain expertise to undertake the requisite deep-dives. In contrast, the internal mode has the huge challenge of assembling knowledge resources internally and suffers from a quicker onset of path dependence that impedes the generation of breakthroughs. This study provides a choice of business models (internal or external) that is associated with different breakthrough and speed to market performance outcomes. Going forward, policy makers and managers seeking breakthrough innovations and speedy progression of the innovations to market should consider the potential resource efficiency of the external mode and the vital role played by collaborations – small firm versus large firm and private versus public entities

CYP17 5'-UTR MspA1 polymorphism and the risk of premenopausal breast cancer in a German population-based case–control study

INTRODUCTION: Studies on the association between the cytochrome P450c17α gene (CYP17) 5'-untranslated region MspA1 genetic polymorphism and breast cancer risk have yielded inconsistent results. Higher levels of estrogen have been reported among young nulliparous women with the A2 allele. Therefore we assessed the impact of CYP17 genotypes on the risk of premenopausal breast cancer, with emphasis on parity. METHODS: We used data from a population-based case–control study of women aged below 51 years conducted from 1992 to 1995 in Germany. Analyses were restricted to clearly premenopausal women with complete information on CYP17 and encompassed 527 case subjects and 904 controls, 99.5% of whom were of European descent. The MspA1 polymorphism was analyzed using PCR-RFLP (PCR–restriction fragment length polymorphism) assay. RESULTS: The frequencies of the variant allele among the cases and controls were 43% and 41%, respectively. Overall, CYP17 A1/A2 and A2/A2 genotypes compared with the A1/A1 genotype were not associated with breast cancer, with adjusted odds ratios (ORs) of 1.04 and 1.23, respectively. Among nulliparous women, however, breast cancer risk was elevated for the A1/A2 (OR = 1.31; 95% confidence interval (CI) 0.74 to 2.32) and the A2/A2 genotype (OR = 2.12; 95% CI 1.04 to 4.32) compared with the A1/A1 genotype, with a trend towards increasing risk associated with number of A2 alleles (P = 0.04). Otherwise, the CYP17 polymorphism was found neither to be an effect modifier of breast cancer risks nor to be associated with stage of disease. CONCLUSION: Our results do not indicate a major influence of CYP17 MspA1 polymorphism on the risk of premenopausal breast cancer, but suggest that it may have an impact on breast cancer risk among nulliparous women. The finding, however, needs to be confirmed in further studies

Age-related accrual of methylomic variability is linked to fundamental ageing mechanisms

Background: Epigenetic change is a hallmark of ageing but its link to ageing mechanisms in humans remains poorly understood. While DNA methylation at many CpG sites closely tracks chronological age, DNA methylation changes relevant to biological age are expected to gradually dissociate from chronological age, mirroring the increased heterogeneity in health status at older ages. Results: Here, we report on the large-scale identification of 6366 age-related variably methylated positions (aVMPs) identified in 3295 whole blood DNA methylation profiles, 2044 of which have a matching RNA-seq gene expression profile. aVMPs are enriched at polycomb repressed regions and, accordingly, methylation at those positions is associated with the expression of genes encoding components of polycomb repressive complex 2 (PRC2) in trans. Further analysis revealed trans-associations for 1816 aVMPs with an additional 854 genes. These trans-associated aVMPs are characterized by either an age-related

Blood lipids influence DNA methylation in circulating cells

Background: Cells can be primed by external stimuli to obtain a long-term epigenetic memory. We hypothesize that long-term exposure to elevated blood lipids can prime circulating immune cells through changes in DNA methylation, a process that may contribute to the development of atherosclerosis. To interrogate the causal relationship between triglyceride, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol levels and genome-wide DNA methylation while excluding confounding and pleiotropy, we perform a stepwise Mendelian randomization analysis in whole blood of 3296 individuals. Results: This analysis shows that differential methylation is the consequence of inter-individual variation in blood lipid levels and not vice versa. Specifically, we observe an effect of triglycerides on DNA methylation at three CpGs, of LDL cholesterol at one CpG, and of HDL cholesterol at two CpGs using multivariable Mendelian randomization. Using RNA-seq data available for a large subset of individuals (N = 2044), DNA methylation of these six CpGs is associated with the expression of CPT1A and SREBF1 (for triglycerides), DHCR24 (for LDL cholesterol) and

An integrative genomics approach identifies Hypoxia Inducible Factor-1 (HIF-1)-target genes that form the core response to hypoxia

The transcription factor Hypoxia-inducible factor 1 (HIF-1) plays a central role in the transcriptional response to oxygen flux. To gain insight into the molecular pathways regulated by HIF-1, it is essential to identify the downstream-target genes. We report here a strategy to identify HIF-1-target genes based on an integrative genomic approach combining computational strategies and experimental validation. To identify HIF-1-target genes microarrays data sets were used to rank genes based on their differential response to hypoxia. The proximal promoters of these genes were then analyzed for the presence of conserved HIF-1-binding sites. Genes were scored and ranked based on their response to hypoxia and their HIF-binding site score. Using this strategy we recovered 41% of the previously confirmed HIF-1-target genes that responded to hypoxia in the microarrays and provide a catalogue of predicted HIF-1 targets. We present experimental validation for ANKRD37 as a novel HIF-1-target gene. Together these analyses demonstrate the potential to recover novel HIF-1-target genes and the discovery of mammalian-regulatory elements operative in the context of microarray data sets