Characterization of a Quantum Light Source Based on Spontaneous Parametric Down-Conversion

We have built a quantum light source capable of producing different types of quantum states. The quantum light source is based on entangled state preparation in the process of spontaneous parametric down-conversion. The single-photon detection rate of eight-hundred thousand per second demonstrates that we have created a bright state-of-the-art quantum light source. As a part of the characterization we measured two-photon quantum interference in a Hong-Ou-Mandel interferometer.Comment: 33 page

Yields of oxidized volatile organic compounds during the OH radical initiated oxidation of isoprene, methyl vinyl ketone, and methacrolein under high-NO_x conditions

We present first-generation and total production yields of glyoxal, methylglyoxal, glycolaldehyde, and hydroxyacetone from the oxidation of isoprene, methyl vinyl ketone (MVK), and methacrolein (MACR) with OH under high NO_x conditions. Several of these first-generation yields are not included in commonly used chemical mechanisms, such as the Leeds Master Chemical Mechanism (MCM) v. 3.2. The first-generation yield of glyoxal from isoprene was determined to be 2.1 (±0.6)%. Inclusion of first-generation production of glyoxal, glycolaldehyde and hydroxyacetone from isoprene greatly improves performance of an MCM based model during the initial part of the experiments. In order to further improve performance of the MCM based model, higher generation glyoxal production was reduced by lowering the first-generation yield of glyoxal from C5 hydroxycarbonyls. The results suggest that glyoxal production from reaction of OH with isoprene under high NO_x conditions can be approximated by inclusion of a first-generation production term together with secondary production only via glycolaldehyde. Analogously, methylglyoxal production can be approximated by a first-generation production term from isoprene, and secondary production via MVK, MACR and hydroxyacetone. The first-generation yields reported here correspond to less than 5% of the total oxidized yield from isoprene and thus only have a small effect on the fate of isoprene. However, due to the abundance of isoprene, the combination of first-generation yields and reduced higher generation production of glyoxal from C5 hydroxycarbonyls is important for models that include the production of the small organic molecules from isoprene

Controlling cyanobacterial harmful blooms in freshwater ecosystems

Cyanobacteria's long evolutionary history has enabled them to adapt to geochemical and climatic changes, and more recent human and climatic modifications of aquatic ecosystems, including nutrient over-enrichment, hydrologic modifications, and global warming. Harmful (toxic, hypoxia-generating, food web altering) cyanobacterial bloom (CyanoHAB) genera are controlled by the synergistic effects of nutrient (nitrogen and phosphorus) supplies, light, temperature, water residence/flushing times, and biotic interactions. Accordingly, mitigation strategies are focused on manipulating these dynamic factors. Strategies based on physical, chemical (algaecide) and biological manipulations can be effective in reducing CyanoHABs. However, these strategies should invariably be accompanied by nutrient (both nitrogen and phosphorus in most cases) input reductions to ensure long-term success and sustainability. While the applicability and feasibility of various controls and management approaches is focused on freshwater ecosystems, they will also be applicable to estuarine and coastal ecosystems. In order to ensure long-term control of CyanoHABs, these strategies should be adaptive to climatic variability and change, because nutrient-CyanoHAB thresholds will likely be altered in a climatically more-extreme world

Observation of nonlinear bands in near-field scanning optical microscopy of a photonic-crystal waveguide

We have measured the photonic bandstructure of GaAs photonic-crystal waveguides with high energy and momentum resolution using near-field scanning optical microscopy. Intriguingly, we observe additional bands that are not predicted by eigenmode solvers, as was recently demonstrated by Huisman et al. [Phys. Rev. B 86, 155154 (2012)]. We study the presence of these additional bands by performing measurements of these bands while varying the incident light power, revealing a non-linear power dependence. Here, we demonstrate experimentally and theoretically that the observed additional bands are caused by a waveguide-specific near- field tip effect not previously reported, which can significantly phase-modulate the detected field.Comment: 6 pages, 5 figure

Evidence for multiple structural genes for the γ chain of human fetal hemoglobin

A sequence with a specific residue at each position was proposed for the γ chain of human fetal hemoglobin by Schroeder et al. (1) after a study in which hemoglobin from a number of individual infants was used. We have now examined in part the fetal hemoglobin components of 17 additional infants and have observed that position 136 of the γ chain may be occupied not only by a glycyl residue, as previously reported, but also by an alanyl residue

Controlling the quality factor of a tuning-fork resonance between 9 K and 300 K for scanning-probe microscopy

We study the dynamic response of a mechanical quartz tuning fork in the temperature range from 9 K to 300 K. Since the quality factor Q of the resonance strongly depends on temperature, we implement a procedure to control the quality factor of the resonance. We show that we are able to dynamically change the quality factor and keep it constant over the whole temperature range. This procedure is suitable for applications in scanning probe microscopy.Comment: 5 pages, 6 figure

Collineation group as a subgroup of the symmetric group

Let $\Psi$ be the projectivization (i.e., the set of one-dimensional vector subspaces) of a vector space of dimension $\ge 3$ over a field. Let $H$ be a closed (in the pointwise convergence topology) subgroup of the permutation group $\mathfrak{S}_{\Psi}$ of the set $\Psi$. Suppose that $H$ contains the projective group and an arbitrary self-bijection of $\Psi$ transforming a triple of collinear points to a non-collinear triple. It is well-known from \cite{KantorMcDonough} that if $\Psi$ is finite then $H$ contains the alternating subgroup $\mathfrak{A}_{\Psi}$ of $\mathfrak{S}_{\Psi}$. We show in Theorem \ref{density} below that $H=\mathfrak{S}_{\Psi}$, if $\Psi$ is infinite.Comment: 9 page

Current wishes to die; characteristics of middle-aged and older Dutch adults who are ready to give up on life:a cross-sectional study

BACKGROUND: Literature shows that middle-aged and older adults sometimes experience a wish to die. Reasons for these wishes may be complex and involve multiple factors. One important question is to what extent people with a wish to die have medically classifiable conditions. AIM: (1) Estimate the prevalence of a current wish to die among middle-aged and older adults in The Netherlands; (2) explore which factors within domains of vulnerability (physical, cognitive, social and psychological) are associated with a current wish to die; (3) assess how many middle-aged and older adults with a current wish to die do not have a medically classifiable condition and/or an accumulation of age-related health problems. METHODS: Data of 2015/16 from the Longitudinal Aging Study Amsterdam were used for this cross-sectional study (1563 Dutch middle-aged and older adults aged between 57 and 99 years), obtained through structured medical interviews and self-reported questionnaires. Three experienced physicians assessed whether the participants with a current wish to die could be classified as having a medically classifiable condition and/or an accumulation of age-related health problems. RESULTS: N = 62 participants (4.0%) had a current wish to die. Having a current wish to die was associated with multiple characteristics across four domains of vulnerability, among which: self-perceived health, problems with memory, self-perceived quality of life and meaningfulness of life. Fifty-four participants with a current wish to die were assessed with having a medically classifiable condition, of which one was also assessed with having an accumulation of age-related health problems. Six people were assessed to have neither, and for two people it was unclear. CONCLUSION: A small minority of middle-aged and older adults in the Netherlands have a current wish to die. Most of them can be classified with a medical condition and one person with an accumulation of age-related health problems. Furthermore, the findings show that having a current wish to die is multi-faceted. There is still a need for more knowledge, such as insight in to what extent suffering stemming from the medical classifiable disease contributes to the development of the wish to die