Ultra-thin corrugated metamaterial film as large-area transmission dynode

Large-area transmission dynodes were fabricated by depositing an ultra-thin continuous film on a silicon wafer with a 3-dimensional pattern. After removing the silicon, a corrugated membrane with enhanced mechanical properties was formed. Mechanical materials, such as this corrugated membrane, are engineered to improve its strength and robustness, which allows it to span a larger surface in comparison to flat membranes while the film thickness remains constant. The ultra-thin film consists of three layers (Al$_2$O$_3$ /TiN/Al$_2$O$_3$) and is deposited by atomic layer deposition (ALD). The encapsulated TiN layer provides in-plane conductivity, which is needed to sustain secondary electron emission. Two types of corrugated membranes were fabricated: a hexagonal honeycomb and an octagonal pattern. The latter was designed to match the square pitch of a CMOS pixel chip. The transmission secondary electron yield was determined with a collector-based method using a scanning electron microscope. The highest transmission electron yield was measured on a membrane with an octagonal pattern. A yield of 2.15 was achieved for 3.15 keV incident electrons for an Al$_2$O$_3$ /TiN/Al$_2$O$_3$ tri-layer film with layer thicknesses of 10/5/15 nm. The variation in yield across the surface of the corrugated membrane was determined by constructing a yield map. The active surface for transmission secondary electron emission is near 100%, i.e. a primary electron generates transmission secondary electrons regardless of the point of impact on the corrugated membrane

Presynaptic actions of 4-Aminopyridine and γ-aminobutyric acid on rat sympathetic ganglia in vitro

Responses to bath-applications of 4-aminopyridine (4-AP) and -aminobutyric acid (GABA) were recorded intracellularly from neurones in the rat isolated superior cervical ganglion. 4-aminopyridine (0.1–1.0 mmol/l) usually induced spontaneous action potentials and excitatory postsynaptic potentials (EPSPs), which were blocked by hexamethonium. Membrane potential was unchanged; spike duration was slightly increased. Vagus nerve B-and C-fibre potentials were prolonged. In 4-AP solution (0.1–0.3 mmol/l), GABA (0.1 mmol/l), 3-aminopropanesulphonic acid or muscimol evoked bursts of spikes and EPSPs in addition to a neuronal depolarization. These bursts, which were not elicited by glycine, glutamate, taurine or (±)-baclofen, were completely antagonised by hexamethonium, tetrodotoxin or bicuculline methochloride. It is concluded that: (a) 4-AP has a potent presynaptic action on sympathetic ganglia; (b) presynaptic actions of GABA can be recorded postsynaptically in the presence of 4-AP; and (c) the presynaptic GABA-receptors revealed in this condition are similar to those on the postsynaptic membrane

Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

Baade-Wesselink distances and the effect of metallicity in classical cepheids

The aim of this paper is to investigate the metallicity dependence of the $PL$-relation in $V$ and $K$ based on a sample of 68 Galactic Cepheids with individual Baade-Wesselink distances (some of the stars also have an HST-based parallax) and individually determined metallicities from high-resolution spectroscopy. Literature values of the $V$-band, $K$-band and radial velocity data have been collected for a sample of 68 classical cepheids that have their metallicity determined in the literature from high-resolution spectroscopy. Based on a $(V-K)$ surface-brightness relation and a projection factor derived in a previous paper, distances have been derived from a Baade-Wesselink analysis. $PL$- and $PLZ$-relations in $V$ and $K$ are derived. The effect of the adopted dependence of the projection factor on period is investigated. The change from a constant $p$-factor to one recently suggested in the literature with a mild dependence on $\log P$ results in a less steep slope by 0.1 unit, which is about the 1-sigma error bar in the slope itself. The observed slope in the $PL$-relation in $V$ in the LMC agrees with both hypotheses. In $K$ the difference between the Galactic and LMC slope is larger and would favour a mild period dependence of the $p$-factor. The dependence on metallicity in $V$ and $K$ is found to be marginal, and independent of the choice of $p$-factor on period. This result is severely limited by the small range in metallicity covered by the Galactic Cepheids.Comment: A&A accepte

Verbonden door wederkerigheid

Het vervullen van sociale behoeften beschermt ouderen tegen eenzaamheid en isolatie en draagt bij aan hun welbevinden. Relaties met anderen zijn een middel om in sociale behoeften te voorzien. Deze relaties kunnen intiem en meer perifeer zijn, beide zijn gerelateerd aan welbevinden en kwaliteit van leven. Wederkerigheid in een relatie, maar ook het iets (terug) doen in een buurt of maatschappij kan er voor zorgen dat er verbondenheid ontstaat en dat men zich onafhankelijk en betekenisvol voelt. In dit artikel gaan we in op het belang van wederkerigheid, onafhankelijkheid, verbondenheid en op het betekenisvol oud worden

Designing interactive demonstrations of optics phenomena

The United Nations and Unesco have declared 2015 to be the international year of light. The Optics department of the faculty of Applied Physics from the TU Delft has decided to contribute to this effort by designing optics experiments to be displayed at the Science Center Delft. The goal of this project was to manage first year students that helped design and explain these experiments. Another part was to design an experiment involving lithography. The students were split into three groups, each with a different subject, polarization, cloaking and light emitting diodes. The management part of the subject went well; ten experiments were designed and the principle behind them were explained on posters. I have learned that communication is very important in teamwork and that the group members need to be motivated in order get the proper results.OpticsImaging Science & TechnologyApplied Science

To meet, to matter, and to have fun: The development, implementation, and evaluation of an intervention to fulfil the social needs of older people

Interventions for older people are often not evaluated and, if evaluated, are not proven successful. Based on a systematic literature review and two qualitative studies about the social needs of older people, an intervention has been developed, implemented, and evaluated. Important social needs that emerged from these studies are connectedness, meaningfulness, and independence. Samsam, the developed intervention, aims to fulfil these needs. Samsam is a place where older (native Dutch speaking) people teach the Dutch language to expats, refugees, and immigrants. Two group interviews and one interview with a total of seven older participants were held to find out what the experiences are with this intervention to fulfil the social needs of older people. After analysis, three themes emerged: (1) The general experience of Samsam, (2) connectedness, and (3) meaningfulness and status. Results indicate that the volunteers are content with the conditions of the intervention, although it is sometimes hard work. The older participants indicated that helping other people and contributing to society is important for them. The intervention also has a strong social and fun element which contributes to their feeling of connectedness. The intervention fulfils various social needs, such as connectedness, meaningfulness, and status. When participating in Samsam, participants feel connected to each other, to the students, and to society. The older participants want to have meaningful lives and use their skills and talents. Samsam offers possibilities for them to do so. We further found that participants have some common characteristics such as an openness to others and to other cultures. An openness towards others and to society helps older people to connect. Most interventions focus on stimulating contact between older people, primarily on their need for affection. We conclude that meaningfulness and status are important social needs. Successful interventions for older people should focus more on fulfilling these needs—for example, by engaging in purposeful activities. It becomes easier to connect when a person feels useful

When your world gets smaller: How older people try to meet their social needs, including the role of social technology

Social needs are important basic human needs. When social needs are not fulfilled, it can lead to mental and physical health problems. In an ageing society, meeting the social needs of older adults is important to sustain their wellbeing and quality of life. Social technology is used by younger people attempting to fulfil social needs. The aim of this study is to understand the social needs of older people and the role of social technology in fulfilling these needs. Using this information we will uncover opportunities for (technological) interventions. We conducted a qualitative explorative field study by interviewing 19 community-dwelling older adults. The participants were selected by professional care-givers with the help of a list of criteria for people at risk of social isolation or loneliness. Semi-structured interviews were held, using a topic list covering the following topics: social networks, social support, connectedness, neighbourhood, activities and hobbies, as well as use of and experiences with social technology. After thematic analysis, inductive codes were attached to quotations relevant to the research question. The results were described in four sections: (a) social needs and relationships; (b) the influence of life history and personality; (c) possibilities and barriers to meet social needs; and (d) use of and attitude towards social technology. The results indicate that the group of participants is heterogeneous and that their social needs and the way they try to meet these are diverse. The Social Production Functions Theory of Successful Aging (SPF-SA) was found to be a useful basis for interpreting and presenting the data. Social needs such as connectedness, autonomy, affection, behavioural confirmation and status are important for the wellbeing of older people. Although the need for affection is most easy to fulfil for older people, it looks like satisfaction of the need for behavioural confirmation and status are in some cases preferred, especially by the male participants. Resources such as relationships, activities, personal circumstances and social technology can help meet social needs. Where there is a lack of (physical) resources such as health problems, reduced mobility, death of network members, fear of rejection and gossip, and poor financial circumstances, meeting social needs can be more difficult for some older people. Social technology now plays a modest role in the lives of older people and in fulfilling their social needs. Because of its potential and its role in the lives of younger people, social technology can be seen as a promising resource in the satisfaction of social needs. However, since it is yet unknown how and to what extent the use of social network technologies, such as Facebook, can be beneficial for older people, more research in this area is needed. Based on our findings, we conclude that the world of older individuals is getting smaller. The loss of resources, e.g. the loss of one's health and mobility, may make it more difficult for an older person to connect with the world outside, which may result in a smaller social network. We therefore suggest that interventions to support older adults to meet their social needs may focus on two aspects: supporting and improving the world close by and bringing the world outside a little bit closer