Unveiling the cause of hybrid morphology radio sources (HyMoRS)

19 pages, 4 figures, 6 tables. Accepted for publication in MNRASHybrid morphology radio sources (HyMoRS) are a rare group of radio galaxies in which differing Fanaroff & Riley morphologies (FR I/II) are observed for each of the two lobes. While they potentially provide insights into the formation of lobe structure, particle acceleration, and the FR dichotomy, previous work on HyMoRS has mainly been limited to low-resolution studies, searches for new candidates, and milliarcsecond-scale VLBI observations of the core region. In this paper, we use new multi-array configuration Very Large Array (VLA) observations between 1 and 8 GHz to determine the morphology of HyMoRS on arcsecond scales and perform the first well-resolved spectral study of these unusual sources. We find that while the apparent FR I lobe is centre-brightened, this is the result of a compact acceleration region resembling a hotspot with a spectrum more consistent with an FR II ("strong-flavour") jet. We find that the spectra of the apparent FR I lobes are not similar to their classical counterparts and are likely the result of line-of-sight mixing of plasma across a range of spectral ages. We consider possible mechanisms that could lead to the formation of HyMoRS under such conditions, including environment asymmetry and restarted sources, concluding through the use of simple modelling that HyMoRS are the result of orientation effects on intrinsically FR II sources with lobes non-parallel to the inner jet.Peer reviewedFinal Accepted Versio

Observed increases in North Atlantic tropical cyclone peak intensification rates

Quickly intensifying tropical cyclones (TCs) are exceptionally hazardous for Atlantic coastlines. An analysis of observed maximum changes in wind speed for Atlantic TCs from 1971 to 2020 indicates that TC intensification rates have already changed as anthropogenic greenhouse gas emissions have warmed the planet and oceans. Mean maximum TC intensification rates are up to 28.7% greater in a modern era (2001–2020) compared to a historical era (1971–1990). In the modern era, it is about as likely for TCs to intensify by at least 50 kts in 24 h, and more likely for TCs to intensify by at least 20 kts within 24 h than it was for TCs to intensify by these amounts in 36 h in the historical era. Finally, the number of TCs that intensify from a Category 1 hurricane (or weaker) into a major hurricane within 36 h has more than doubled in the modern era relative to the historical era. Significance tests suggest that it would have been statistically impossible to observe the number of TCs that intensified in this way during the modern era if rates of intensification had not changed from the historical era. © 2023, Springer Nature Limited

Risk-Informed Interference Assessment for Shared Spectrum Bands: A Wi-Fi/LTE Coexistence Case Study

Interference evaluation is crucial when deciding whether and how wireless technologies should operate. In this paper we demonstrate the benefit of risk-informed interference assessment to aid spectrum regulators in making decisions, and to readily convey engineering insight. Our contributions are: we apply, for the first time, risk assessment to a problem of inter-technology spectrum sharing, i.e. Wi-Fi/LTE in the 5 GHz unlicensed band, and we demonstrate that this method comprehensively quantifies the interference impact. We perform simulations with our newly publicly-available tool and we consider throughput degradation and fairness metrics to assess the risk for different network densities, numbers of channels, and deployment scenarios. Our results show that no regulatory intervention is needed to ensure harmonious technical Wi-Fi/LTE coexistence: for the typically large number of channels available in the 5 GHz band, the risk for Wi-Fi from LTE is negligible, rendering policy and engineering concerns largely moot. As an engineering insight, Wi-Fi coexists better with itself in dense, but better with LTE, in sparse deployments. Also, both main LTE-in-unlicensed variants coexist well with Wi-Fi in general. For LTE intra-technology inter-operator coexistence, both variants typically coexist well in the 5 GHz band, but for dense deployments, implementing listen-before-talk causes less interference

LTE in Unlicensed Bands is neither Friend nor Foe to Wi-Fi

Proponents of deploying LTE in the 5 GHz band for providing additional cellular network capacity have claimed that LTE would be a better neighbour to Wi-Fi in the unlicensed band, than Wi-Fi is to itself. On the other side of the debate, the Wi-Fi community has objected that LTE would be highly detrimental to Wi-Fi network performance. However, there is a lack of transparent and systematic engineering evidence supporting the contradicting claims of the two camps, which is essential for ascertaining whether regulatory intervention is in fact required to protect the Wi-Fi incumbent from the new LTE entrant. To this end, we present a comprehensive coexistence study of Wi-Fi and LTE-in-unlicensed, surveying a large parameter space of coexistence mechanisms and a range of representative network densities and deployment scenarios. Our results show that, typically, harmonious coexistence between Wi-Fi and LTE is ensured by the large number of 5 GHz channels. For the worst-case scenario of forced co-channel operation, LTE is sometimes a better neighbour to Wi-Fi - when effective node density is low - but sometimes worse - when density is high. We find that distributed interference coordination is only necessary to prevent a "tragedy of the commons" in regimes where interference is very likely. We also show that in practice it does not make a difference to the incumbent what kind of coexistence mechanism is added to LTE-in-unlicensed, as long as one is in place. We therefore conclude that LTE is neither friend nor foe to Wi-Fi in the unlicensed bands in general. We submit that the systematic engineering analysis exemplified by our case study is a best-practice approach for supporting evidence-based rulemaking by the regulator.Comment: accepted for publication in IEEE Acces

Neutral hydrogen gas, past and future star-formation in galaxies in and around the 'Sausage' merging galaxy cluster

CIZA J2242.8+5301 ($z = 0.188$, nicknamed 'Sausage') is an extremely massive ($M_{200}\sim 2.0 \times 10^{15}M_\odot$ ), merging cluster with shock waves towards its outskirts, which was found to host numerous emission-line galaxies. We performed extremely deep Westerbork Synthesis Radio Telescope HI observations of the 'Sausage' cluster to investigate the effect of the merger and the shocks on the gas reservoirs fuelling present and future star formation (SF) in cluster members. By using spectral stacking, we find that the emission-line galaxies in the 'Sausage' cluster have, on average, as much HI gas as field galaxies (when accounting for the fact cluster galaxies are more massive than the field galaxies), contrary to previous studies. Since the cluster galaxies are more massive than the field spirals, they may have been able to retain their gas during the cluster merger. The large HI reservoirs are expected to be consumed within $\sim0.75-1.0$ Gyr by the vigorous SF and AGN activity and/or driven out by the out-flows we observe. We find that the star-formation rate in a large fraction of H$\alpha$ emission-line cluster galaxies correlates well with the radio broad band emission, tracing supernova remnant emission. This suggests that the cluster galaxies, all located in post-shock regions, may have been undergoing sustained SFR for at least 100 Myr. This fully supports the interpretation proposed by Stroe et al. (2015) and Sobral et al. (2015) that gas-rich cluster galaxies have been triggered to form stars by the passage of the shock.Comment: Accepted to MNRAS, 14 pages, 9 figures, 7 table

Varying genesis and landfall locations for North Atlantic tropical cyclones in a warmer climate

Tropical cyclones (TCs) are one of the most dangerous hazards that threaten U.S. coastlines. They can be particularly damaging when they occur in densely populated areas, such as the U.S. Northeast. Here, we investigate seasonal-scale variations in TC genesis and subsequent first landfall locations of \u3e 37,000 synthetic TCs that impact the U.S. Northeast from the pre-industrial era (prior to 1800) through a very high emissions future (RCP8.5; 2080–2100). TC genesis in the Main Development Region decreases across all parts of the season from the pre-industrial to the future, with the greatest decreases in the proportion of genesis (up to 80.49%) occurring in the early and late seasons. Conversely, TC genesis in a region near the U.S. southeast coast increases across all parts of the season from the pre-industrial to the future, with the greatest increases in the proportion of genesis (up to 286.45%) also occurring in the early and late seasons. Impacts of changing TC genesis locations are highlighted by variations in where TCs make their first landfall over the same time periods, with an increase in landfalls along the mid-Atlantic seaboard from Delaware to North Carolina during all parts of the season from the pre-industrial to the future. © 2023, The Author(s)

Will Smarter Marketing End Social Discrimination? A Critical Review

Purpose - There are two claims made by the web marketing/advertising industry. 1) By collecting, managing, and mining data, companies serve consumer’s best interests and 2) by adopting sophisticated analytics web marketers avoid discriminations that disserve individuals. Although we share an interest in ending social discrimination, we are more circumspect about pronounced individualism and technological fixes. Despite its appeal, or perhaps because of it, we should not accept the claim at face value. In this paper we argue that social discrimination may not disappear under smarter marketing; more overt forms may wane only to be replaced by more subtle forms. Design/methodology/approach - We compare the two most important techniques of smarter marketing- predictive analytics and Facebook\u27s social graph- with current discriminatory practices of weblining and e-scoring. While noting advances against overt discrimination we describe how smarter marketing allows for covert forms. Findings - Innovative strategies to record and mine users’ tastes and social connectivity for marketing purposes open the way for covert social discrimination. Originality/value - We provide a critical assessment of two claims made by the web marketing/advertising industry: 1) By monitoring consumer web activity and collecting, managing, and mining data, companies serve consumer’s best interests and 2) by adopting sophisticated analytics web marketers avoid discriminations that disserve individuals

Evolving Tropical Cyclone Tracks in the North Atlantic in a Warming Climate

Tropical cyclone (TC) track characteristics in a changing climate remain uncertain. Here, we investigate the genesis, tracks, and termination of \u3e35,000 synthetic TCs traveling within 250 km of New York City (NYC) from the pre‐industrial era (850–1800 CE) to the modern era (1970–2005 CE) to the future (2080–2100 CE). Under a very high‐emissions scenario (RCP8.5), TCs are more likely to form closer to the United States (U.S.) southeast coast (\u3e15% increase), terminate in the northeastern Atlantic (\u3e6% increase), and move most slowly along the U.S. Atlantic coast (\u3e15% increase) from the pre‐industrial to future. Under our modeled scenarios, TCs are more likely to travel within 100 km of Boston, MA, USA (p = 0.01) and Norfolk, VA, USA (p = 0.05) than within 100 km of NYC in the future. We identify reductions in the time between genesis and the time when TCs come within 100 km of NYC, Boston, or Norfolk, as well as increased duration of TC impacts from individual storms at all three cities in the future

Social Networking and the Perception of Privacy within the Millennial Generation

Has technology caused a generational divide between current college age users (Millennial Generation) who have no problems posting intimate details of their personal life on the Web and more traditional older users who seem to value privacy? This paper presents the results of a survey of 251 university students and follow-up focus groups on the topic of the perceptions of social networking and privacy. We will use Facebook as an example of social networking, and review attitudes about privacy and control over personal information among traditional and non-traditional college age users and light and heavy users of social networking sites

The rise and fall of star-formation in z∼0.2\bf z\sim0.2 merging galaxy clusters

CIZA J2242.8+5301 (`Sausage') and 1RXS J0603.3+4213 (`Toothbrush') are two low-redshift ($z\sim0.2$), massive ($\sim2\times10^{15}M_\odot$), post-core passage merging clusters, which host shock waves traced by diffuse radio emission. To study their star-formation properties, we uniformly survey the `Sausage' and `Toothbrush' clusters in broad and narrow band filters and select a sample of $201$ and $463$ line emitters, down to a rest-frame equivalent width ($13${\AA}). We robustly separate between H$\alpha$ and higher redshift emitters using a combination of optical multi-band (B, g, V, r, i, z) and spectroscopic data. We build H$\alpha$ luminosity functions for the entire cluster region, near the shock fronts, and away from the shock fronts and find striking differences between the two clusters. In the dynamically younger, $1$ Gyr old `Sausage' cluster we find numerous ($59$) H$\alpha$ emitters above a star-formation rate (SFR) of $0.17$ M_{\sun} yr$^{-1}$ surprisingly located in close proximity to the shock fronts, embedded in very hot intra-cluster medium plasma. The SFR density for the cluster population is at least at the level of typical galaxies at $z\sim2$. Down to the same star-formation rate, the possibly dynamically more evolved `Toothbrush' cluster has only $9$ H$\alpha$ galaxies. The cluster H$\alpha$ galaxies fall on the SFR-stellar mass relation $z\sim0.2$ for the field. However, the `Sausage' cluster has an H$\alpha$ emitter density $>20$ times that of blank fields. If the shock passes through gas-rich cluster galaxies, the compressed gas could collapse into dense clouds and excite star-formation for a few $100$ Myr. This process ultimately leads to a rapid consumption of the molecular gas, accelerating the transformation of gas-rich field spirals into cluster S0s or ellipticals.Comment: Accepted for publication in MNRAS after minor referee report. 21 pages, 15 figures, 5 table