Small-scale Events Research Articles

Evaluation of Appropriate Material Models in LS-DYNA for MM-ALE Finite Element Simulations of Small-Scale Explosive Airblast Tests on Clay Soils

This study conducted finite element simulations of a small scale, explosive airblast on clay soil in LS-DYNA using multi-material arbitrary Lagrangian–Eulerian methods. An explosive mass of 100.9 g with a 7.6 cm blast height was simulated in this study under two-dimensional conditions. The study compared four different material models to evaluate their ability to simulate explosively-induced airblast loads on cohesive soils. Material models included the Soil and Foam pressure dependent strength model, the Pseudo Tensor pressure dependent strength model, the FHWA Drucker–Prager model and the Two-Invariant Geologic Cap model. Crater dimensions were measured from the simulations and compared to the results of airblast experiments performed in another study. Three material models ran to completion with the exception of the Geologic Cap model, which terminated early in the calculation due to plasticity algorithm errors caused by the large strain increments. While the remaining three models somewhat over-predicted crater depth, the diameter dimensions and crater volumes from the Soil and Foam and particularly the Pseudo Tensor model compared very well to the experimental data. The crater shape from the FHWA model did not match particularly well with experimental results and was larger than the experimental crater. A simplified, pressure dependent strength model such as Soil and Foam model or the Pseudo Tensor model is therefore recommended for modeling small-scale airblast events on cohesive soils. The Pseudo Tensor model compared particularly well to experimental results and predicted crater dimensions very well. Additional studies with the Geologic Cap model implementing smoothed particle hydrodynamics are recommended which may resolve the errors associated with large strain increments.

The world’s toughest mountain race

PurposeThe Climbathon is an annual mountain running championship that takes place in Kinabalu Park, Sabah, Malaysian Borneo. Participants race to the peak (4,095.2 metres) and back, a distance of 21 kilometres of rainforest and mountain terrain, with a steep vertical gain of 2,300 metres. The purpose of this paper is to evaluate the first 25 years of the Climbathon and to identify the key success factors behind the staging of this small-scale international sports event in Southeast Asia.Design/methodology/approachThe research design for this study is interpretive, utilises a qualitative case study approach incorporating analysis of documents, oral history interviews, and personal observations gained through attendance and volunteering at the event which produced six insights, suggested as key success factors for the Climbathon. This study was guided by one key research question, to understand what has ensured the continuity of this small-scale international sports event known as the Climbathon.FindingsFindings suggest the Climbathon has endured the test of time due to an innovative use of the summit trail, adherence to international sporting regulations, a pro sports tourism public policy led by the tourism ministry, membership to international sports organisations, corporate sponsorship, and a special sense of place towards Mount Kinabalu and the Climbathon for the event organisers, volunteers and officials.Research limitations/implicationsThis case study presents knowledge about the Climbathon but findings are not generalisable. Any application of the success factors would have to be as guidelines adapted for a specific sport event. The use of oral history as part of a case study is subjective and open to interpretation. Future work could incorporate interviews with participants, spectators, volunteers and the local sub-committees to gain alternative perspectives.Originality/valueThis study makes an original contribution to the events and tourism field by presenting a case study on the success factors of the Mount Kinabalu International Climbathon. The study suggests a three pillar model of “Place-Plan-People” which may be used as a guiding philosophy for event development and delivery of small-scale international sports tourism events in Asia and elsewhere. The inclusion of oral history as part of a case study research design is novel and useful when knowledge is not available in any published form.

Why do People Attend Sport Events at Mature Tourist Destinations? An Analysis of Visitors’ Motivation to Attend the Windsurf World Cup on Sylt

Abstract Introduction. Sport events have become a popular tool for the marketing of tourist destinations. In this regard, it has to be kept in mind that the effects events can generate for destinations largely depend on the motivation of the attendees. Building on this insight, the aim of this paper is to compare the motivational structures of two types of visitors (primary purpose event visitors and casual visitors) to the German island of Sylt during a Windsurf World Cup. This event-destination combination was chosen because it represents the tendency for popular tourist resorts to use small-scale sport events in their marketing efforts. Material and methods. The research was conducted using an a priori segmentation of event attendees as casual visitors and primary purpose event visitors that is based on a well-established theoretical background. Results. The results revealed that both visitor groups were mainly motivated by cheering for the surfers and indulging in vicarious achievement. Furthermore, both showed some interest in learning more about the destination. Interestingly, many other motives that had been identified in (sport) tourism research did not seem to be very relevant for the respondents. Conclusion. Event marketers should heavily emphasise the opportunity to watch and closely relate to the surfers. Thus, including internationally popular athletes - if they are also popular in Germany - as well as local heroes in the event seems to be reasonable.

Ion-scale secondary flux ropes generated by magnetopause reconnection as resolved by MMS.

New Magnetospheric Multiscale (MMS) observations of small‐scale (~7 ion inertial length radius) flux transfer events (FTEs) at the dayside magnetopause are reported. The 10 km MMS tetrahedron size enables their structure and properties to be calculated using a variety of multispacecraft techniques, allowing them to be identified as flux ropes, whose flux content is small (~22 kWb). The current density, calculated using plasma and magnetic field measurements independently, is found to be filamentary. Intercomparison of the plasma moments with electric and magnetic field measurements reveals structured non‐frozen‐in ion behavior. The data are further compared with a particle‐in‐cell simulation. It is concluded that these small‐scale flux ropes, which are not seen to be growing, represent a distinct class of FTE which is generated on the magnetopause by secondary reconnection.

Attracting athletes to small-scale sports events using motivational decision-making factors

This study proposes and tests a model related to small-scale sport events using a conceptual model and a survey of athletes who participate in sporting events analyzed using structural equation modeling and fuzzy-set qualitative comparative analysis (fsQCA). The fsQCA results yield three models implying that small-scale event participants require a combination of attributes to consider or eventually participate. The SEM findings reveal that involvement, travel motives, and decision factors significantly affect motivational factors, and motivational factors significantly affect decision factors. A combination of positive motivation factors, positive involvement, and negative travel motives can significantly influence decision factors.

Small-Scale Crisis Events Impact on Price Discovery and Volatiliy Transmission Across Financial Markets: Evidence from Terror Attacks, Assassinations, North-Korean Saber-Rattling, and Natural Disasters

We examine the impact of 51 terrorist attacks, three wars, an assassination, and other national security-related shocks on stock markets located in nations proximate to the crises and on American Depository Receipts (ADRs) of firms headquartered in those same nations. ADRs are securities that trade on American markets that entitle investors to the cash flows (denominated in dollars) of foreign firms. We find that small-scale terrorist attacks that receive little media attention do not affect ADR returns. Large scale terrorist attacks, the assassination of Benazir Bhutto, highly provocative actions by North Korea, and small-scale wars affect ADR returns while natural disasters do not. The negative effect on ADRs is short lived. We also examine the volatility structures of two ADR indexes (Korea and India) and their underlying home market indexes. We find that there is bi-directional information flow between the ADR markets and the home market indexes. We find evidence that various shocks affect the volatility structures of these indexes, both ADR and home market indexes.

Elite Active Sport Tourists: Economic Impacts And Perceptions of Destination Image

Active sport tourism has been defined as travel away from the home environment to actively participate in sport. However there is a dearth of research focusing on active sport tourists. Furthermore, researchers also identified a significant gap existed in the sport tourism literature regarding elite athletes. Although research focusing on hallmark sport events has been abundant, several researchers have identified a lack of research on small-scale sport events. Thus, the purpose of this research was to provide an analysis of elite active sport tourists' expenditures and the resultant direct economic impact of these expenditures, as well as their perceptions of the host destination in a small-scale international sport event: East Asian Games. A total of 140 elite athletes from eight different countries and regions in East Asia participated in this study.

Visitor expenditure within a mountain bike event portfolio: Determinants, outcomes, and variations

ABSTRACTGradually community and scholarly support for large-scale sport events is declining as sustainability and efficiency are becoming primary concerns. Thus, a drive for the creation of small-scale event portfolios that comply with a community’s resources and infrastructure is developing. In the current study, a portfolio of four small-scale mountain bike events located in the Northwest United States were investigated to better understand their impact on the local economy. An online survey was conducted after each event that assessed visitor spending, travel behavior, and participant demographics resulting in a total sample of N = 614. Through general linear modeling, chi-square testing, and multiple regression each of the four events were compared with each other and determinants of visitor expenditure were tested. The results demonstrated the four events significantly differed in regards to total expenditure, daily expenditure, daily expenditure per person, trip duration, amount of travel party event participants, travel distance, age, income, and lodging type/location. Overall expenditure and daily expenditure per person were found to be significantly determined by participant travel distance, travel party size, trip duration, and income. Managerial implications derived from these results for destinations and event organizers are discussed.

Bringing the banjo back to life: The field of Dutch independent folk music as participatory culture

In this paper we investigate factors underlying the production of independent folk music (indie folk) in the Netherlands. By studying the creation, distribution and reception of indie folk music through in-depth interviewing, we argue that the social production of indie folk music is affected by a shift towards ‘participatory culture’ brought about by the rise of the Internet and Web 2.0. We note how Web 2.0 helps musicians to educate themselves and to develop careers in music. Secondly, from the perspective of both musicians and gatekeepers, participatory culture links their preferences for participatory aesthetics, decreasing boundaries between creators, distributors and users. Within the idiom of folk music, they distinguish themselves from the mainstream, creating more sincere performances. Thirdly, from the perspective of the audience, fans actively contribute by organizing small-scale events, enabling the audience to establish (trans)local scenes, reframing music as a social experience.

Sequence Stratigraphic Analysis of the Youngest Nonmarine Sequence In the Cretaceous Ferron Notom Delta, South Central Utah, U.S.A.

Abstract This study evaluates the nature and internal complexity of high-frequency fluvial aggradational cycles and linked paleosols that were previously not recognized in nonmarine sequences of the Turonian Ferron Notom Delta in Central Utah. Detailed facies analysis of the ∼ 33-meter-thick youngest nonmarine sequence (Sequence 1) reveals 11 depositional facies that build 33 fluvial aggradational cycles, 9 fluvial aggradation cycles sets, and 3 sequences, in what was previously classified as a single 100 ka, 4th- or 5th-order sequence. Fluvial aggradation cycles in the succession are either simple floodplain bedsets or single channel stories that are bounded by paleosols or erosional surfaces. They represent depositional events that likely do not span more than 2 ka. Depositional periods are followed by short hiati (10 to < 400 a) characterized by subaerial exposure, and soil development, possibly reflecting floodplain abandonment or short-term river avulsions. Fluvial aggradational cycle sets show systematic stacking of fluvial aggradational cycles, and are analogous to parasequence sets. They are represented by either compound floodplain bedsets or multi-story channel sandstones, bounded by relatively mature paleosols or erosionally top-truncated. They represent multiple small-scale depositional events that span not more than 14 ka followed by relatively long (100 a to < 1 ka) hiati, characterized by subaerial exposure and soil development, which suggest a relationship to longer-term floodplain abandonment, due to either longer-term avulsion or fluvial entrenchment during base-level falls. Fluvial aggradational cycle sets are often capped by coals and carbonaceous strata. Marine trace fossils and dinocysts above coal beds suggest marine transgression due to compactional subsidence or sea-level rise. The scale of cyclicity of the fluvial aggradation cycle sets (14 ka) is similar to underlying marine parasequences (10 to 15 ka) and suggests that nonmarine and marine cycles have a similar control. Fluvial sequences are aggregates of fluvial aggradational cycle sets that are bounded by unconformities or their correlative conformities that represent longer periods (1 to 5 ka) of subaerial exposure and pedogenic development. Cyclicity on the sequence scale in this succession is attributed to high-frequency Milankovitch-scale (∼ 20 ka, 40 ka) rises and falls in sea level.

Drivers of summer oxygen depletion in the central North Sea

Abstract. In stratified shelf seas, oxygen depletion beneath the thermocline is a result of a greater rate of biological oxygen demand than the rate of supply of oxygenated water. Suitably equipped gliders are uniquely placed to observe both the supply through the thermocline and the consumption of oxygen in the bottom layers. A Seaglider was deployed in the shallow (≈ 100 m) stratified North Sea in a region of known low oxygen during August 2011 to investigate the processes regulating supply and consumption of dissolved oxygen below the pycnocline. The first deployment of such a device in this area, it provided extremely high-resolution observations, 316 profiles (every 16 min, vertical resolution of 1 m) of conductivity, temperature, and depth (CTD), dissolved oxygen concentrations, backscatter, and fluorescence during a 3-day deployment.The high temporal resolution observations revealed occasional small-scale events (&lt; 200 m or 6 h) that supply oxygenated water to the bottom layer at a rate of 2 ± 1 µmol dm−3 day−1. Benthic and pelagic oxygen sinks, quantified through glider observations and past studies, indicate more gradual background consumption rates of 2.5 ± 1 µmol dm−3 day−1. This budget revealed that the balance of oxygen supply and demand is in agreement with previous studies of the North Sea. However, the glider data show a net oxygen consumption rate of 2.8 ± 0.3 µmol dm−3 day−1, indicating a localized or short-lived (&lt; 200 m or 6 h) increase in oxygen consumption rates. This high rate of oxygen consumption is indicative of an unidentified oxygen sink. We propose that this elevated oxygen consumption is linked to localized depocentres and rapid remineralization of resuspended organic matter.The glider proved to be an excellent tool for monitoring shelf sea processes despite challenges to glider flight posed by high tidal velocities, shallow bathymetry, and very strong density gradients. The direct observation of these processes allows more up to date rates to be used in the development of ecosystem models.

Energy cascade in internal-wave attractors

One of the pivotal questions in the dynamics of the oceans is related to the cascade of mechanical energy in the abyss and its contribution to mixing. Here, we propose internal-wave attractors in the large-amplitude regime as a unique self-consistent experimental and numerical setup that models a cascade of triadic interactions transferring energy from large-scale monochromatic input to multi-scale internal-wave motion. We also provide signatures of a discrete wave turbulence framework for internal waves. Finally, we show how, beyond this regime, we have a clear transition to a regime of small-scale high-vorticity events which induce mixing.

First simultaneous SST/CRISP and IRIS observations of a small-scale quiet Sun vortex

Ubiquitous small-scale vortices have recently been found in the lower atmosphere of the quiet Sun in state-of-the-art solar observations and in numerical simulations. We investigate the characteristics and temporal evolution of a granular-scale vortex and its associated upflows through the photosphere and chromosphere of a quiet Sun internetwork region. We analyzed high spatial and temporal resolution ground- and spaced-based observations of a quiet Sun region. The observations consist of high-cadence time series of wideband and narrowband images of both H-alpha 6563 A and Ca II 8542 A lines obtained with the CRisp Imaging SpectroPolarimeter (CRISP) instrument at the Swedish 1-m Solar Telescope (SST), as well as ultraviolet imaging and spectral data simultaneously obtained by the Interface Region Imaging Spectrograph (IRIS). A small-scale vortex is observed for the first time simultaneously in H-alpha, Ca II 8542 A, and Mg II k lines. During the evolution of the vortex, H-alpha narrowband images at -0.77 A and Ca II 8542 A narrowband images at -0.5 A, and their corresponding Doppler Signal maps, clearly show consecutive high-speed upflow events in the vortex region. These high-speed upflows with a size of 0.5-1 Mm appear in the shape of spiral arms and exhibit two distinctive apparent motions in the plane of sky for a few minutes: (1) a swirling motion with an average speed of 13 km/s and (2) an expanding motion at a rate of 4-6 km/s. Furthermore, the spectral analysis of Mg II k and Mg II subordinate lines in the vortex region indicates an upward velocity of up to about 8 km/s along with a higher temperature compared to the nearby quiet Sun chromosphere. The consecutive small-scale vortex events can heat the upper chromosphere by driving continuous high-speed upflows through the lower atmosphere.

Devonian climate, sea level and evolutionary events: an introduction

The face of Planet Earth has changed significantly through geological time. Dynamic processes active today, such as plate tectonics and climate change, have shaped the Earth’s surface and impacted biodiversity patterns from the beginning. Organisms, on the other hand, have the capacity to significantly alter Earth’s hydrological and geochemical cycles, its atmosphere and climate, sediments, and even hard rocks deep down under the surface. Abiotic– biotic interactions characterize Earth’s system history and, together with biotic competition and food webs, were the main trigger of evolutionary change, innovations and biodiversity fluctuations. Within the Palaeozoic, the Devonian was an especially interesting time interval as it was characterized by the ‘mid-Paleozoic predator revolution’ (Signor & Brett 1984; Brett 2003) and the related ‘nekton revolution’ (Klug et al. 2010), characterized by the blooms of free-swimming cephalopods, including the oldest ammonoids, and fish groups (e.g. toothed sharks and giant placoderms), the rise of more advanced vertebrates, including the oldest tetrapods (e.g. Blieck et al. 2007, 2010; Niedzwiedzki et al. 2010), the most extensive reef complexes of the Phanerozoic (e.g. Kiessling 2008), and the ‘greening of land’ by the diversification and spread of land plants, including the oldest forests (e.g. Stein et al. 2012; Giesen & Berry 2013), which resulted in new soil types and changing weathering. These major evolutionary trends did not unfold in a long interval of environmental stability, but in times of numerous and repeated, geologically brief, global events that punctuated prolonged periods, up to several million years in duration, of relative stability, termed ecological-evolutionary subunits (EE subunits: Boucot 1990; Brett & Baird 1995; Brett et al. 2009). The bounding events, even those of lesser intensity, produced major re-structuring in local to global ecosystems and are seen as critical drivers of long-term evolutionary patterns (Brett 2012). These linked abiotic and biotic events and extinctions of different magnitude have been summarized by House (1983, 1985, 2002), Walliser (1984, 1996) and, more recently, by Becker et al. (2012). The Devonian event succession is summarized in Figure 1. Two first-order mass extinctions at the Frasnian–Famennian boundary (Kellwasser Crisis) and at the end of the Devonian (Hangenberg Crisis), characterized by the loss of major fossil groups (classes and orders) and complete ecosystems (e.g. metazoan reefs, early forests), have to be viewed in the context of a complex global event sequence. There are important similarities between discrete pulses/phases of the major biotic crises and individual smaller-scale events. In our understanding, second-order global events are characterized by sudden extinctions in many groups and ecosystems, including the complete disappearance of several widespread and diverse organism groups (orders and families). Examples are the basal Emsian atopus Event, where the planktonic graptolites finally died out, the Taghanic Crisis, Frasnes events and Lower Kellwasser Event. Third-order global events show globally elevated extinction rates, often at lower taxonomic level (genera and species), but within many clades and in several ecosystems. Examples are the Silurian–Devonian boundary Klonk Event, and the Daleje, Chotěc, Kacak, Condroz and Annulata events. Fourth-order global extinctions refer to the sudden disappearance of relatively fewer but widespread groups, which implies a global, not regional, trigger. This category may include the Lochkovian–Pragian boundary

Geological and Sedimentological Evidence of a Large Tsunami Occurring ~1100 Year BP from a Small Coastal Lake along the Bay of La Paz in Baja California Sur, Mexico

The importance of small-scale seismic events in enclosed water bodies, which can result in large tsunami waves capable of affecting comprehensive damage over small, geographically-confined areas are generally overlooked, although recognizing the occurrence of such events is a necessary element in adequately assessing the risk of natural hazards at specific locations. Here we present evidence for a probable large localized tsunami that occurred within the Bay of La Paz, Baja California Sur, ~1100 year before present (BP), which resulted in the creation of a shelly ridge at an elevation of ~2 m above mean high water (MHW). This ridge consists of a continuous wedge of poorly mixed marine sands and shells ~50 cm in depth deposited along the entire seaward edge of the lake. The marine shells collected from terrestrial environments around the lake include species from a variety of environments, including offshore species with minimum preferred depths of &gt;13 m. The evidence suggests that this material was likely deposited by a tsunami with a runup of 2–3.6 m above MHW, probably associated with the slumping of an island along the tectonically active eastern edge of the bay.

The global Hangenberg Crisis (Devonian–Carboniferous transition): review of a first-order mass extinction

Abstract The global Hangenberg Crisis near the Devonian–Carboniferous boundary (DCB) represents a mass extinction that is of the same scale as the so-called ‘Big Five’ first-order Phanerozoic events. It played an important role in the evolution of many faunal groups and destroyed complete ecosystems but affected marine and terrestrial environments at slightly different times within a short time span of c. 100–300 kyr. The lower crisis interval in the uppermost Famennian started as a prelude with a minor eustatic sea-level fall, followed rather abruptly by pantropically widespread black shale deposition (Hangenberg Black Shale and equivalents). This transgressive and hypoxic/anoxic phase coincided with a global carbonate crisis and perturbation of the global carbon cycle as evidenced by a distinctive positive carbon isotope excursion, probably as a consequence of climate/salinity-driven oceanic overturns and outer-shelf eutrophication. It is the main extinction level for marine biota, especially for ammonoids, trilobites, conodonts, stromatoporoids, corals, some sharks, and deeper-water ostracodes, but probably also for placoderms, chitinozoans and early tetrapods. Extinction rates were lower for brachiopods, neritic ostracodes, bryozoans and echinoderms. Extinction patterns were similar in widely separate basins of the western and eastern Prototethys, while a contemporaneous marine macrofauna record from high latitudes is missing altogether. The middle crisis interval is characterized by a gradual but major eustatic sea-level fall, probably in the scale of more than 100 m, that caused the progradation of shallow-water siliciclastics (Hangenberg Sandstone and equivalents) and produced widespread unconformities due to reworking and non-deposition. The glacio-eustatic origin of this global regression is proven by miospore correlation with widespread diamictites of South America and South and North Africa, and by the evidence for significant tropical mountain glaciers in eastern North America. This isolated and short-lived plunge from global greenhouse into icehouse conditions may follow the significant drawdown of atmospheric CO 2 levels due to the prior massive burial of organic carbon during the global deposition of black shales. Increased carbon recycling by intensified terrestrial erosion in combination with the arrested burial of carbonates may have led to a gradual rise of CO 2 levels, re-warming, and a parallel increase in the influx of land-derived nutrients. The upper crisis interval in the uppermost Famennian is characterized by initial post-glacial transgression and a second global carbon isotope spike, as well as by opportunistic faunal blooms and the early re-radiation of several fossil groups. Minor reworking events and unconformities give evidence for continuing smaller-scale oscillations of sea-level and palaeoclimate. These may explain the terrestrial floral change near the Famennian–Tournaisian boundary and contemporaneous, evolutionarily highly significant extinctions of survivors of the main crisis. Still poorly understood small-scale events wiped out the last clymeniid ammonoids, phacopid trilobites, placoderms and some widespread brachiopod and foraminiferan groups. The post-crisis interval in the lower Tournaisian is marked by continuing eustatic rise (e.g. flooding of the Old Red Continent), and significant radiations in a renewed greenhouse time. But the recovery had not yet reached the pre-crisis level when it was suddenly interrupted by the global, second-order Lower Alum Shale Event at the base of the middle Tournaisian.

Paleoenvironmental evidence for first human colonization of the eastern Caribbean

Identifying and dating first human colonization of new places is challenging, especially when group sizes were small and material traces of their occupations were ephemeral. Generating reliable reconstructions of human colonization patterns from intact archaeological sites may be difficult to impossible given post-depositional taphonomic processes and in cases of island and coastal locations the inundation of landscapes resulting from post-Pleistocene sea-level rise. Paleoenvironmental reconstruction is proving to be a more reliable method of identifying small-scale human colonization events than archaeological data alone. We demonstrate the method through a sediment-coring project across the Lesser Antilles and southern Caribbean. Paleoenvironmental data were collected informing on the timing of multiple island-colonization events and land-use histories spanning the full range of human occupations in the Caribbean, from the initial forays into the islands through the arrival and eventual domination of the landscapes and indigenous people by Europeans. In some areas, our data complement archaeological, paleoecological, and historical findings from the Lesser Antilles and in others amplify understanding of colonization history. Here, we highlight data relating to the timing and process of initial colonization in the eastern Caribbean. In particular, paleoenvironmental data from Trinidad, Grenada, Martinique, and Marie-Galante (Guadeloupe) provide a basis for revisiting initial colonization models of the Caribbean. We conclude that archaeological programs addressing human occupations dating to the early to mid-Holocene, especially in dynamic coastal settings, should systematically incorporate paleoenvironmental investigations.

IRISSi iv LINE PROFILES: AN INDICATION FOR THE PLASMOID INSTABILITY DURING SMALL-SCALE MAGNETIC RECONNECTION ON THE SUN

Our understanding of the process of fast reconnection has undergone a dramatic change in the last 10 years driven, in part, by the availability of high-resolution numerical simulations that have consistently demonstrated the break-up of current sheets into magnetic islands, with reconnection rates that become independent of Lundquist number, challenging the belief that fast magnetic reconnection in flares proceeds via the Petschek mechanism that invokes pairs of slow-mode shocks connected to a compact diffusion region. The reconnection sites are too small to be resolved with images but these reconnection mechanisms, Petschek and the plasmoid instability, have reconnection sites with very different density and velocity structures and so can be distinguished by high-resolution line-profiles observations. Using IRIS spectroscopic observations we obtain a survey of typical line profiles produced by small-scale events thought to be reconnection sites on the Sun. Slit-jaw images are used to investigate the plasma heating and re-configuration at the sites. A sample of 15 events from two active regions is presented. The line profiles are complex with bright cores and broad wings extending to over 300 km/s. The profiles can be reproduced with the multiple magnetic islands and acceleration sites that characterise the plasmoid instability but not by bi-directional jets that characterise the Petschek mechanism. This result suggests that if these small-scale events are reconnection sites, then fast reconnection proceeds via the plasmoid instability, rather than the Petschek mechanism during small-scale reconnection on the Sun.

Diversification of four human HOX gene clusters by step-wise evolution rather than ancient whole-genome duplications.

HOX genes encode transcriptional factors that play a pivotal role in specifying regional identity in nearly every bilateral animal. The birth of HOX gene cluster and its subsequent evolution, either in regulation or function, underlie the evolution of many bilaterian features and hence to the evolutionary radiation of this group. Despite of this importance, evolution of HOX cluster in vertebrates remains largely obscure because the phylogenetic history of these genes is poorly resolved. This has led to the controversy about whether four HOX clusters in human originated through two rounds (2R) of whole-genome duplications or instead evolved by small-scale events early in vertebrate evolution. Recently, the large-scale phylogenetic analysis of triplicate and quadruplicate paralogous regions residing on human HOX-bearing chromosomes provided an unprecedented insight into events that shaped vertebrate genome early in their history. Based on these data and comparative genomic analysis of fruit fly, red floor beetle, and human, this study infers the genic content of minimal HOX locus in the Urbilaterian and reconstructs its duplication history. It appears that four HOX clusters of humans are not remnants of polyploidy events in vertebrate ancestry. Rather, current evidence suggests that one-to-four transition in HOX cluster number occurred by three-step sequential process involving regional duplication events. Therefore, it is concluded that the evolutionary origin of vertebrate novelties, including the complexity of their body, is the consequence of small-scale genetic changes at widely different times over their history.

3D magnetic field configuration of small-scale reconnection events in the solar plasma atmosphere

The outer solar atmosphere, i.e., the corona and the chromosphere, is replete with small energy-release events, which are accompanied by transient brightening and jet-like ejections. These events are considered to be magnetic reconnection events in the solar plasma, and their dynamics have been studied using recent advanced observations from the Hinode spacecraft and other observatories in space and on the ground. These events occur at different locations in the solar atmosphere and vary in their morphology and amount of the released energy. The magnetic field configurations of these reconnection events are inferred based on observations of magnetic fields at the photospheric level. Observations suggest that these magnetic configurations can be classified into two groups. In the first group, two anti-parallel magnetic fields reconnect to each other, yielding a 2D emerging flux configuration. In the second group, helical or twisted magnetic flux tubes are parallel or at a relative angle to each other. Reconnection can occur only between anti-parallel components of the magnetic flux tubes and may be referred to as component reconnection. The latter configuration type may be more important for the larger class of small-scale reconnection events. The two types of magnetic configurations can be compared to counter-helicity and co-helicity configurations, respectively, in laboratory plasma collision experiments.