The History of Galaxy Formation in Groups: An Observational Perspective

We present a pedagogical review on the formation and evolution of galaxies in groups, utilizing observational information from the Local Group to galaxies at z~6. The majority of galaxies in the nearby universe are found in groups, and galaxies at all redshifts up to z~6 tend to cluster on the scale of nearby groups (~1 Mpc). This suggests that the group environment may play a role in the formation of most galaxies. The Local Group, and other nearby groups, display a diversity in star formation and morphological properties that puts limits on how, and when, galaxies in groups formed. Effects that depend on an intragroup medium, such as ram-pressure and strangulation, are likely not major mechanisms driving group galaxy evolution. Simple dynamical friction arguments however show that galaxy mergers should be common, and a dominant process for driving evolution. While mergers between L_* galaxies are observed to be rare at z < 1, they are much more common at earlier times. This is due to the increased density of the universe, and to the fact that high mass galaxies are highly clustered on the scale of groups. We furthermore discus why the local number density environment of galaxies strongly correlates with galaxy properties, and why the group environment may be the preferred method for establishing the relationship between properties of galaxies and their local density.Comment: Invited review, 16 pages, to be published in ESO Astrophysics Symposia: "Groups of Galaxies in the Nearby Universe", eds. I. Saviane, V. Ivanov, J. Borissov

Preventie van preferente stroming in de zandgrond van een golfbaan

Veel zandbovengronden met een grasvegetatie hebben waterafstotende eigenschappen. Deze hydrofobe eigenschappen komen naar voren als het vochtgehalte van de grond beneden een kritieke grens daalt. Na het bereiken van deze grens zal de infiltratiesnelheid van neerslag en beregeningswater sterk afnemen. De indringing van het water gaat dan ongelijkmatig en er ontstaan preferente stroombanen in de grond. Op golfbaan "De Pan" in Bosch en Duin onderzochten we de effecten van het toedienen van een surfactant op de bevochtiging en de variatie van het vochtgehalte van de toplaag in een fairwa

Modulation masking produced by second-order modulators

Recent studies suggest that an auditory nonlinearity converts second-order sinusoidal amplitude modulation (SAM) (i.e., modulation of SAM depth) into a first-order SAM component, which contributes to the perception of second-order SAM. However, conversion may also occur in other ways such as cochlear filtering. The present experiments explored the source of the first-order SAM component by investigating the ability to detect a 5-Hz, first-order SAM probe in the presence of a second-order SAM masker beating at the probe frequency. Detection performance was measured as a function of masker-carrier modulation frequency, phase relationship between the probe and masker modulator, and probe modulation depth. In experiment 1, the carrier was a 5-kHz sinusoid presented either alone or within a notched-noise masker in order to restrict off-frequency listening. In experiment 2, the carrier was a white noise. The data obtained in both carrier conditions are consistent with the existence of a modulation distortion component. However, the phase yielding poorest detection performance varied across experimental conditions between 0° and 180°, confirming that, in addition to nonlinear mechanisms, cochlear filtering and off-frequency listening play a role in second-order SAM perception. The estimated magnitude of the modulation distortion component ranges from 5%-12%

Pitch discrimination and phase sensitivity in young and elderly subjects and its relationship to frequency selectivity

Frequency difference limens for pure tones (DLFs) and for complex tones (DLCs) were measured for four groups of subjects: young normal hearing, young hearing impaired, elderly with near-normal hearing, and elderly hearing impaired. The auditory filters of the subjects had been measured in earlier experiments using the notched-noise method, for center frequencies (fc) of 100, 200, 400, and 800 Hz. The DLFs for both impaired groups were higher than for the young normal group at all fc's (50-4000 Hz). The DLFs at a given fc were generally only weakly correlated with the sharpness of the auditory filter at that fc, and some subjects with broad filters had near-normal DLFs at low frequencies. Some subjects in the elderly normal group had very large DLFs at low frequencies in spite of near-normal auditory filters. These results suggest a partial dissociation of frequency selectivity and frequency discrimination of pure tones. The DLCs for the two impaired groups were higher than those for the young normal group at all fundamental frequencies (fo) tested (50, 100, 200, and 400 Hz); the DLCs for the elderly normal group were intermediate. At fo = 50 Hz, DLCs for a complex tone containing only low harmonics (1-5) were markedly higher than for complex tones containing higher harmonics, for all subject groups, suggesting that pitch was conveyed largely by the higher, unresolved harmonics. For the elderly impaired group, and some subjects in the elderly normal group, DLCs were larger for a complex tone with lower harmonics (1-12) than for tones without lower harmonics (4-12 and 6-12) for fo's up to 200 Hz. Some elderly normal subjects had markedly larger-than-normal DLCs in spite of near-normal auditory filters. The DLCs tended to be larger for complexes with components added in alternating sine/cosine phase than for complexes with components added in cosine phase. Phase effects were significant for all groups, but were small for the young normal group. The results are not consistent with place-based models of the pitch perception of complex tones; rather, they suggest that pitch is at least partly determined by temporal mechanisms

Improved Lattice Gauge Field Hamiltonian

Lepage's improvement scheme is a recent major progress in lattice $QCD$, allowing to obtain continuum physics on very coarse lattices. Here we discuss improvement in the Hamiltonian formulation, and we derive an improved Hamiltonian from a lattice Lagrangian free of $O(a^2)$ errors. We do this by the transfer matrix method, but we also show that the alternative via Legendre transformation gives identical results. We consider classical improvement, tadpole improvement and also the structure of L{\"u}scher-Weisz improvement. The resulting color-electric energy is an infinite series, which is expected to be rapidly convergent. For the purpose of practical calculations, we construct a simpler improved Hamiltonian, which includes only nearest-neighbor interactions.Comment: 30 pages, LaTe

Telehealth tinnitus therapy during the COVID-19 outbreak in the UK : uptake and related factors

OBJECTIVE : The Audiology Department at the Royal Surrey County Hospital usually offers face-to-face audiologist-delivered cognitive behavioural therapy (CBT) for tinnitus rehabilitation. During COVID-19 lockdown, patients were offered telehealth CBT via video using a web-based platform. This study evaluated the proportion of patients who took up the offer of telehealth sessions and factors related to this. DESIGN : Retrospective service evaluation. STUDY SAMPLE : 113 consecutive patients whose care was interrupted by the lockdown. RESULTS : 80% of patients accepted telehealth. The main reasons for declining were not having access to a suitable device and the belief that telehealth appointments would not be useful. Compared to having no hearing loss in the better ear, having a mild or moderate hearing loss increased the chance of declining telehealth by factors of 3.5 (p = 0.04) and 14.9 (p = 0.038), respectively. High tinnitus annoyance as measured via the visual analogue scale increased the chance of declining telehealth appointments by a factor of 1.4 (p = 0.019). CONCLUSIONS : Although CBT via telehealth was acceptable to most patients, alternatives may be necessary for the 20% who declined. These tended to have worse hearing in their better ear and more annoying tinnitus.https://www.tandfonline.com/loi/iija20hj2022Speech-Language Pathology and Audiolog