Rock, Paper, Scissors: Durable Ephemera and Networks of Stone in Quanzhou’s Zhenguo Pagoda

The Indian Ocean region is a continuum of social, economic, and cultural engagements. It is also a remarkably elastic matrix of human relations that has profoundly influenced and been influenced by global engagements. These interregional engagements raise questions of how to frame global circularities within Indian Ocean pasts. How have imbrications with other world regions affected the networks and boundaries of the Indian Ocean region? And how have Indian Ocean societies affected the wider world? To answer these questions this article traces Indian Ocean histories within global contexts between the sixteenth and early twentieth centuries. It offers a stereoscopic history of Indian Ocean Africa that appreciates Indian Ocean linkages alongside the region's global entanglements, which in turn demonstrates how Africa's Indian Ocean rim has affected and been affected by wider global relationships. The article suggests that imbrications of regional and extraregional networks do not negate the Indian Ocean's coherence or the central importance of regional linkages. Rather, it argues that such imbrications prompt alternative ways of perceiving Indian Ocean worlds: namely, as layered matrices shaped by the dual articulation of Indian Ocean rim societies.

aDetailedstudies of the low to intermediate seismicity in two coastal regions of Norway have been used in a comparison between earthquake locations from local high-precision networks on the one side and locations using a sparse regional array network on the other side. To this end, a reference set of 32 low-magnitude earthquakes have been located using two local temporary networks in northern and western Norway, with estimated epicenter accuracies better than 5 and 10 km, respectively. Comparisons are made between the local network solutions and the NORSAR Generalized Beamforming (GBF) system, which provides automatic phase association and location estimates using the Fennoscandian regional array network. The median automatic GBF location error is of the order of 20-30 km when four or more arrays detect the event, increasing to about 80-100 km when only two arrays are available, and the automatic GBF bulletin is essentially complete down to magnitude ML= 2.0. Most of the mislocation vectors of the NORSAR GBF solutions are oriented perpendicular to the Norwegian coast, and with a tendency to pull the location in a southeasternly direction. The GBF performance is clearly better, both in terms of accuracy and completeness, than the performance of the automatic bulletin of the Prototype International Data Center (PIDC) which uses data from essentially the same network. The analyst reviewed NORSAR and PIDC bulletins show, not unexpectedly, an improvement in location accuracy compared to the automatic solutions and appear to be of similar quality for the few common events, with an average mislocation of about 20 km. The NORSAR reviewed bulletin is more complete at low magnitudes compared to PIDC, and there appears to be a potential for significant improvements in the PIDC processing of small seismic events in this region.

aDetailedstudies of the low to intermediate seismicity in two coastal regions of Norway have been used in a comparison between earthquake locations from local high-precision networks on the one side and locations using a sparse regional array network on the other side. To this end, a reference set of 32 low-magnitude earthquakes have been located using two local temporary networks in northern and western Norway, with estimated epicenter accuracies better than 5 and 10 km, respectively. Comparisons are made between the local network solutions and the NORSAR Generalized Beamforming (GBF) system, which provides automatic phase association and location estimates using the Fennoscandian regional array network. The median automatic GBF location error is of the order of 20-30 km when four or more arrays detect the event, increasing to about 80-100 km when only two arrays are available, and the automatic GBF bulletin is essentially complete down to magnitude ML= 2.0. Most of the mislocation vectors of the NORSAR GBF solutions are oriented perpendicular to the Norwegian coast, and with a tendency to pull the location in a southeasternly direction. The GBF performance is clearly better, both in terms of accuracy and completeness, than the performance of the automatic bulletin of the Prototype International Data Center (PIDC) which uses data from essentially the same network. The analyst reviewed NORSAR and PIDC bulletins show, not unexpectedly, an improvement in location accuracy compared to the automatic solutions and appear to be of similar quality for the few common events, with an average mislocation of about 20 km. The NORSAR reviewed bulletin is more complete at low magnitudes compared to PIDC, and there appears to be a potential for significant improvements in the PIDC processing of small seismic events in this region.

Microseismicity is well known to be observable at nearly any location on the earth. Historical trends of felt earthquakes do not do sufficiently characterize the frequency and distribution of microseismic events. Regional earthquake networks are typically not designed to detect and locate microseismic events, which can have negative magnitudes. Only three earthquakes were recorded in Sumner County since 1977 by regional seismic networks operating in Kansas. A local network was recently deployed over a producing oil field in Sumner County, Kansas, to monitor microseismic activity. From July to September, 2014, fifteen seismometers were deployed in a 1.2 km2 area. In two months of recording, 125 microseismic events were detected within 15 km of the network ranging in magnitude from -0.6 to 2.4, none of which were reported by the regional network operators. The observed microseismic activity is most likely both natural and anthropogenic related to reservoir activity. Caution is called for when interpreting the source and cyclicity of microseismic events detected by localized temporary networks with minimal to no background data. Without having an understanding of the localized seismic activity the source and recursion of present activity cannot be assumed. Even with a regional network in place, it is critical to establish baseline microseismicity through many cycles and periods of subsurface activity.

Manual delineation on all breathing phases of lung cancer 4D CT image datasets can be challenging, exhaustive, and prone to subjective errors because of both the large number of images in the datasets and variations in the spatial location of tumors secondary to respiratory motion. The purpose of this work is to present a new deep learning-based framework for fast and accurate segmentation of lung tumors on 4D CT image sets. The proposed DL framework leverages motion region convolutional neural network (R-CNN). Through integration of global and local motion estimation network architectures, the network can learn both major and minor changes caused by tumor motion. Our network design first extracts tumor motion information by feeding 4D CT images with consecutive phases into an integrated backbone network architecture, locating volume-of-interest (VOIs) via a regional proposal network and removing irrelevant information via a regional convolutional neural network. Extracted motion information is then advanced into the subsequent global and local motion head network architecture to predict corresponding deformation vector fields (DVFs) and further adjust tumor VOIs. Binary masks of tumors are then segmented within adjusted VOIs via a mask head. A self-attention strategy is incorporated in the mask head network to remove any noisy features that might impact segmentation performance. We performed two sets of experiments. In the first experiment, a five-fold cross-validation on 20 4D CT datasets, each consisting of 10 breathing phases (i.e., 200 3D image volumes in total). The network performance was also evaluated on an additional unseen 200 3D images volumes from 20 hold-out 4D CT datasets. In the second experiment, we trained another model with 40 patients' 4D CT datasets from experiment 1 and evaluated on additional unseen nine patients' 4D CT datasets. The Dice similarity coefficient (DSC), center of mass distance (CMD), 95th percentile Hausdorff distance (HD95 ), mean surface distance (MSD), and volume difference (VD) between the manual and segmented tumor contour were computed to evaluate tumor detection and segmentation accuracy. The performance of our method was quantitatively evaluated against four different methods (VoxelMorph, U-Net, network without global and local networks, and network without attention gate strategy) across all evaluation metrics through a paired t-test. The proposed fully automated DL method yielded good overall agreement with the ground truth for contoured tumor volume and segmentation accuracy. Our model yielded significantly better values of evaluation metrics (p<0.05) than all four competing methods in both experiments. On hold-out datasets of experiment 1 and 2, our method yielded DSC of 0.86 and 0.90 compared to 0.82 and 0.87, 0.75 and 0.83, 081 and 0.89, and 0.81 and 0.89 yielded by VoxelMorph, U-Net, network without global and local networks, and networks without attention gate strategy. Tumor VD between ground truth and our method was the smallest with the value of 0.50 compared to 0.99, 1.01, 0.92, and 0.93 for between ground truth and VoxelMorph, U-Net, network without global and local networks, and networks without attention gate strategy, respectively. Our proposed DL framework of tumor segmentation on lung cancer 4D CT datasets demonstrates a significant promise for fully automated delineation. The promising results of this work provide impetus for its integration into the 4D CT treatment planning workflow to improve the accuracy and efficiency of lung radiotherapy.

Regional and local seismic networks have become ubiquitous throughout the world to study local seismotectonics, to provide immediate hypocentral and magnitude information following felt or damaging earthquakes, to create ShakeMaps of the ground shaking due to earthquakes, and to form the sensing backbone of incipient early warning systems of earthquake shaking. They also provide data for earthquake forecasting research, nuclear test monitoring, and analyses of nonearthquake events such as explosions, intense storms, mine collapses, etc . Some seismic networks are aimed at detecting and recording seismic events down to the lowest possible magnitude, while others are strong-motion networks that aim to properly record the strongest possible ground shaking that can take place. Significant resources are invested annually in regional and local seismic monitoring, and such networks have become a permanent fixture in many areas of the world. Is it important to record and process seismograms of all earthquakes down to magnitude 3? Magnitude 2? Magnitude 1? Magnitude 0 or below? My purpose in writing this opinion piece is not to question the intrinsic need for regional and local networks. On the other hand, I do feel it is important that there should be a full and informed public discussion about the importance of the small earthquakes that we record. Is it important to record and process seismograms of all earthquakes down to magnitude 3? Magnitude 2? Magnitude 1? Magnitude 0 or below? Informed discussions on these issues sometimes take place when a decision must be made about a particular site, such as whether to put a high-level radioactive waste repository at Yucca Mountain in Nevada. But for the most part, regional and local seismic networks, once they have been initiated, tend to grow based on a “more is better” philosophy as funding is available. I believe that the existence and …

The Global Positioning System (GPS) has emerged over the last 10 years as the premier space geodetic technique for geologic observation with the benefits of both accuracy and economy. GPS data from more than 260 stations were processed utilizing GIPSY-OASIS software, and all available RINEX files for these stations beginning on January 1, 1993. The uniform processing strategy, combined with a rigorous independent error estimate of site velocities and the broad geographical distribution of these sites resulted in a global high-precision surface velocity data set. This data set has been used to: (1) compare the effects of different GPS antenna and monument types on data noise; (2) examine in detail the rigidity of the North America plate; (3) constrain the rate of deformation in the northern Gulf of Mexico; (4) define a model for Recent (Holocene) time global plate motions. The weighted root mean square scatter about the best fit line through the daily position estimates are used to assess the effects of different antenna and monument types on North America. The data set is sensitive to glacial isostatic adjustment as indicated by the decrease in chinu 2 from 1.3 to 1.0 by excluding those sites on rigid North America within a radius of 1,800 km of Hudson Bay. The resulting 64 site solution for the angular velocity of North America give a mean rate residual of 1 mm/yr. GULFNET, a regional GPS network created in 1997 in the northern Gulf Coast to measure strain across this active "passive margin" is described. Preliminary results suggest that deformation is occurring as predicted by the regional paradigm for deformation, i.e. Gulfward motion along normal faults. A new model for Recent global plate velocities (REVEL) describes the relative velocities of 14 plates. For several plate pairs, statistically significant differences are observed between the geodetically and geologically determined velocities reflecting changes in plate velocity through time. Some of the rate differences reflect gradual slowing associated with convergent plate boundaries, and may reflect increased resistance to subduction or convergence associated with decreased slab pull and/or crustal thickening.

Understanding Local Networks and Their Links to Competitiveness: Global competitiveness and local networks - a review of the literature, Peter Brown and Rod B. McNaughton Clusters, industrial districts and competitiveness, Frank McDonald and Giovanna Vertova Networks and proximity - theory and evidence from the car and telecommunications industries, Anastassios Gentzoglanis Region knowledge and competitiveness, Sean B. O'Hagan and Milford B. Green. Innovation in Local Networks: Spatially binding linkages in manufacturing product chains, Edward J. Feser and Stuart H. Sweeney Skills networks and local dynamics, Patrick Burlat and Sophie Peillon Birthing biotech - agglomerations in San Diego and Atlanta, Susan Walcott Innovation networks in reconversion regions - the case of Styria, Franz Todtling, Michaela Trippl and Hubert Bratl. The Constraints of Local Networks: Limits of local networks - use of local and external knowledge in technological adaptation in the Seto Ceramics industry, Hiro Izushi Lean and its limits - the Toyota production system in Chukyo and Northern Kyushu, Japan, David W. Edgington Local and global networks in the economics of SMEs - is proximity the only thing that matters?, Mario A. Maggioni and Alberto Bramanti The spatial configuration of inter-firm networks in producer service agglomerations, Neil Coe and Alan Townsend. Contexts of Network Strategies: Rural entrepreneurs - using personal networks as a business strategy, Mae Deans Developing and co-ordinating regional networks for international competitiveness - the case of Queensland agribusiness exports, Sheelagh Matear, Brett Tucker, Andrew McCarroll and Les Brown Integration in the multinational corporation - the problem of subsidiary embeddedness, Ulf Andersson and Mats Forsgren.

Geographically positioned between inland eastern and central Africa and the Indian Ocean, the Swahili coast has fascinated scholars for centuries if not millennia. One of the earliest texts addressing this region is the frequently cited Periplus of the Erythraean Sea, a mid-first century ce text detailing trade and navigational information for the Red Sea and Indian Ocean. Western scholars have struggled with how to categorize coastal east Africa, at times claiming it as part of a broader Middle Eastern cultural sphere, and at others labelling it as specifically African. Stephanie Wynne-Jones and Adria LaViolette's The Swahili World adds to and complicates these discourses by presenting fifty-six studies by sixty-one authors on various topics related to the study of coastal eastern Africa. This edited volume works across a broad time period, ranging from the first century ce to the present day. Through these collected studies Wynne-Jones and LaViolette bring together varied discourses in order to highlight the complex historical and historiographic processes that come to bear on Swahili coast studies.Wynne-Jones and LaViolette divided their volume into three broadly defined sections roughly organized according to theme and chronology: environment, background, and Swahili historiography; the Swahili age; and the early modern and modern Swahili coast. Within these sections, various subsections highlight the environment, scholarship on the Swahili world, the formation of the Swahili coast, urbanism, daily life, trade, architecture, and colonialism. This project brings together researchers working in a variety of fields from institutions across the globe. As both Wynne-Jones and LaViolette are archaeologists, these studies are more heavily weighted towards archaeological work, including contributions by Thomas Biginagwa, Paul Sinclair, Jeffrey Fleisher, Felix Chami, and Dashu Qin, among many others. However, it also includes studies by historians, art historians, anthropologists, independent scholars, museum professionals, and environmental scientists. These are individuals working in the United States, Kenya, Tanzania, the United Kingdom, China, Sweden, Germany, France, Norway, Australia, Canada, South Africa, Italy, Spain, and Madagascar. Such a diverse assemblage represents a truly novel undertaking in Swahili coast studies, bringing together disciplines that often draw from each other, but may not be in direct communication as they are here.Within these sections a number of themes regularly surface throughout the edited volume, namely, the complex nature of Swahili coast historiography, the diversity and plurality of notions of the Swahili coast, urbanism and stone architecture, trade and connectivity, and the colonial legacy. The continued emergence of these themes encourages readers to reconsider the nature of area studies boundaries, cultural property, historiographic privilege, and eastern Africa's place in a global world order.Questions of historiography arise early on, with Wynne-Jones and LaViolette's introductory chapter raising the question of how the term “Swahili” is applied, when, and to what effect. They argueDespite this, Swahili, proto-Swahili, and pre-Swahili are all used regularly throughout the volume, regardless of time frame, and the hunt for an “originary moment” for the formation of the Swahili coast plagues several studies. In “Decoding the Genetic Ancestry of the Swahili,” Ryan L. Raaum and his coauthors use DNA sampling to definitively argue for a largely African ancestry to Swahili coast urbanism and cultural development with “a trickle of non-African males into Swahili communities over a long period of time” (p. 98). In contrast, Paul Sinclair argues against “searching for the original spark that resulted in the florescence of Swahili architectural, economic, trading and literary achievements” and instead emphasizes the “likelihood of a multi-centered developmental trajectory of urban complexity in the region,” which means “acknowledging the abilities of agropastoralist and farming communities along the coast in creating conditions to attract and actively participate in trade and exchange, with all of its ensuing consequences” (p. 190).Rather than developing a definable framework for who the Swahili are and when and where they originate, what emerges throughout these chapters is a truly diverse sense of Swahili geographies and cultures. As Abungu et al. note, the Swahili coast has been classically defined as the “area between the southern Somalia coast and northern Mozambique … dotted with stone-built settlements of domestic houses, mosques, tombs, wells and well-planned narrow streets running north-south and east-west” (p. 642). However, various authors throughout this volume add to and contest this narrow definition. For instance, Anneli Ekblom and Paul Sinclair include Chibuene in south-central Mozambique as part of this diverse coastal trading culture. Similarly, Henry T. Wright states that “The Comorian Archipelago is an intimate part of” the Swahili world (p. 266), and Chantal Radimilahy shows the interconnections between Mahilaka in northern Madagascar and coastal Kenya and Tanzania.Within this expanding geography, internal differentiations and divisions have also become increasingly important. City-states participated in maritime trade to varying degrees at different points in time. For instance, Zanzibar saw unprecedented levels of maritime trade between 1100 and 1400 ce and again when the Omani Būsa’īdī Sultan Sa’īd named Zanzibar as his capital in the nineteenth century. In contrast, Pawlowicz notes thatIt was not until the sixteenth century that these communities adopted a more Indian Ocean-centric outlook, a time that saw economic decline for many other major cities in this region, such as Kilwa and Zanzibar. Within these cities, we also see varying degrees of class and gender distinction. Wynne-Jones highlights how women likely played a more active public role in the early modern period (p. 295). And several articles note that the distinction between upper and lower classes was less structured prior to the nineteenth century. Stone and earthen architecture were often built side-by-side, Bissell noting that “Swahili structures could be expanded and solidified over time” to effectively become stone (p. 593).This purported distinction between stone and earthen architecture is at the center of Swahili coast studies, where stone is seen as a necessary quality of urban formation. However, several authors in this volume reference the ongoing relationships and continuities between cities, towns, and villages, as well as the continuities and coexistence of stone and earthen architecture. There was never a simple divide between wealthy, urban patricians with stone homes and poor, rural farmers with earthen ones. Cities depended on neighboring towns and villages for trade goods and sustenance, and individuals often moved within and between these spaces quite freely.Various authors demonstrate throughout this volume how mobility and exchange are visible in the transfer of raw goods, finished products, people, and ideas across Africa and the Indian Ocean. Ceramics represent one of the largest assemblages in the archaeological record, and they demonstrate a broad exchange of technologies and designs from southern Somalia to Mozambique to the Comoros. A type of low-fired ceramic with incised geometric decoration known as Triangular-Incised Ware (TIW) or Early Tana Tradition (ETT) ceramics was popular across these sites, indicating a high degree of communication relating to production and design practices. More broadly, Morales and Prendergast point out that the local and global uses of cowries show the incredible importance of Swahili coast sites in regional and transregional trade networks (p. 345). Indeed, mobility and exchange were such a regular fixture of coastal life that it can be difficult to assign meaningful geographic or cultural labels to objects and ideas. Erik Gilbert discusses this in his chapter on dhow trading vessels, in which he notes that the distinction between an “eastern African” or “South Arabian” ship is rarely clear cut. Indeed, the dhow's “owner might be from one place, its captain from another, its crew from yet another, and the ship itself might be constructed someplace that neither owner, captain, nor crew called home” (p. 383). Clearly, traditional area studies boundaries fall short in addressing the complex ways in which residents of east Africa associated with their environments.At the heart of each of these themes, the impact of colonial policy making can be readily felt. The desire to define “the Swahili” emerged from colonial processes of classification, ordering the world into neat categories of “African” or “Arab,” categories which residents of the Swahili coast casually and purposefully resisted. Claiming a Swahili identity in the late nineteenth and early twentieth centuries implied an urban, civilized identity. However, Daren Ray notes that by the second quarter of the twentieth century, many who had previously claimed a Swahili identity had subsequently adopted the label “Shirazi” because Swahili had acquired an implied inferior status (p. 70). The legacy of these labels is particularly well addressed in Lydia Wilson Marshall and Herman Kiriama's “The Legacy of Slavery on the Swahili Coast.” In this chapter, the authors explore the ties between ethnic labels, land ownership, and political rights in nineteenth and twentieth century eastern Africa. Their study shows how the oft-cited abolition date of 1897 obscures the ongoing legacies of forced labor, land dispossession, and political and social alienation faced by those with slave descent throughout east Africa.In many instances, these chapters do not necessarily present newly documented research, but rather a synthesis of the various projects undertaken on particular cities or topics related to Swahili coast studies. Exceptions to this include LaViolette's chapter on “Craft and Industry” or William Cunningham Bissell's interrogation of “The Modern Life of Swahili Stonetowns.” Additionally, the fact that many of these chapters provide synthesis of and commentary on established research should not detract from their value. Indeed, the amassing of these studies into a single, coherent volume represents an enormous undertaking on the part of Wynne-Jones and LaViolette and should mark The Swahili World as the standard text for newcomers to the field, as well as established scholars.Considering the diverse and complex views approached throughout Wynne-Jones and LaViolette's volume, The Swahili World will appeal to a range of audiences. However, it will hold special interest for students and scholars of the Arabian Peninsula, Indian Ocean, and East Africa. At times the language assumes a specialist's knowledge. For instance, Wright's chapters on the Comoros repeatedly use the terms “Dembeni phase” and “Hanyundu phase” without defining them. And the confusion caused by the changing uses of Swahili, pre-Swahili, and proto-Swahili by different authors could have been alleviated with disclaimers in the introduction or with authors each defining the terms used for themselves. Indeed, Radimilahy's assertion that Mahilaka was originally a Swahili town begs the question of why such a descriptive marker is significant, particularly for the time period she is discussing (roughly 900–1500 ce). Why should Radimilahy want to claim the term “Swahili” for northern Madagascar?Additionally, for those consulting it as a coherent volume rather than as individual studies, a stronger framing in the introduction and conclusion could have added more depth to the text as a whole. Unsurprisingly, given the diverse topics and scholars represented, a number of the studies reflect conflicting and contradictory viewpoints. For instance, Tom Fitton's assertion that “Zanzibar's history can be seen as a microcosm of the wider Swahili coast,” (p. 239) is at odds with the plural histories presented elsewhere in the volume. Jeffrey Fleisher's investigation of “Town and Village” underscores the very different urban trajectories of Mtwapa, Pemba, Kilwa, Lamu, Songo Mnara, Mikindani, and the Comoros, trajectories seemingly at odds with the claim that Zanzibar is a microcosm of the history of coastal eastern Africa. Fitton's understanding of Zanzibar is not unpopular within the field of Swahili coast studies, where stonetowns such as Kilwa, Zanzibar, Mombasa, and Lamu are seen as paradigmatic icons of Swahili history and culture. For many, however, such views obscure the fact that cities, towns, and villages were temporally, geographically, and economically contingent spaces with different access to and engagement in maritime and terrestrial trade. Highlighting these conflicting historiographic trends might have allowed for a more productive tension between chapters.Ultimately, The Swahili World presents a fascinating overview of the complex and, at times, contradictory nature of Swahili coast studies. The various articles, written by a diverse set of authors, provide thoughtful and nuanced investigations, which effectively link together the fields of archaeology, anthropology, art history, and environmental science, among others. The range of approaches and material covered should make The Swahili World a standard text for scholars of eastern Africa and the Indian Ocean alike. Through their work, Wynne-Jones and LaViolette have brought together a truly thought-provoking volume that will continue to prompt new conversations about Africa's role in medieval and early modern globalization.

For the owners of printing presses in early twentieth century China, the decision to adopt mechanized printing was made because it was profitable to produce a large quantity of products in a shorter time. This chapter discusses the regional and local networks that introduced mechanized print technology into China. By emphasizing regional and local factors, a unique system of Chinese print capitalism that combined what was globally available with what was domestically rooted. The chapter examines the impact of the national school system on the readership market, and focuses on the Journal of National Essence to illustrate how the school system gave some young scholars an opportunity to claim a leading role in national debates. It also briefs about how national crises, especially the perceived loss of Chinese territorial sovereignty, became a marketing ploy for journals. Keywords: Chinese print capitalism; Journal of National Essence ; local networks; regional networks; territorial sovereignty

It is quite easy to estimate the variance-covariance (VCV) matrix for single session surveys or local networks, but difficult where these local networks are combined together to form a regional network. Our main aim is to develop an appropriate VCV model to combine all the different types of networks, either global, regional or local. By careful estimation and combination of the individual VCVs of the local networks, we can form a unique VCV for local, regional and global networks. Different techniques are used to derive appropriate models for the variancecovariance components of the Global Positioning System (GPS) networks. The VCV models were estimated using homogeneous and heterogeneous data. The variance-covariance components are empirically derived using (a) the covariance of the observations of homogeneous data, (b) a combination of the covariance of the observationsP −1 and the covariance of the signal componentsC ss (for either homogeneous and/or heterogeneous data), (c) only the variances are used to determine the variancecovariance, their covariances being zeros. We compare the solutions of the VCV developed for homogeneous and/or heterogeneous data with other developed VCVs. It was observed that the derived VCV model for the combined homogeneous and/or heterogeneous data of case (b) gives the best estimates in all cases.

The Swahili in East Africa exported precious commodities like gold, ivory, and rock crystal. Nowadays, these ‘commercial items’ are mostly invisible to the archaeologists because they are ‘by nature’ gross materials for export. Fortunately, the use of historical and ethnographic sources, combined with recent archaeological researches, allow us to trace the history of this trade, from the ʿAbbāsid to the late Fatimid period. Far from the well-known gold trade, the study of ivory and rock crystal allows us to present local and regional commercial networks and the trade in the Indian Ocean during the early medieval period.

Iceberg harmonic tremor (IHT) emanating from tabular icebergs in the Southern Ocean and along calving margins of the Antarctic Ice Sheet is a complex, evolving signal at frequencies above approximately 0.5 Hz. IHT has been observed as T phases on islands in the equatorial Pacific, as hydroacoustic signals in the Indian Ocean, and by local and regional Antarctic seismic networks. To identify the IHT source mechanism and to understand its relevance to iceberg calving, evolution, and breakup, we deployed seismometers on a giant (25 by 50 km) tabular iceberg called C16 in the Ross Sea, Antarctica, during a uniquely accessible period (austral summer, 2003–2004) when it was aground against the northern shore of Ross Island. During the deployment period, C16 was in sporadic contact with another giant tabular iceberg, B15A, that was moving under the influence of local ocean currents. This study reveals that the C16‐associated IHT was a manifestation of extended episodes of discrete, repeating stick‐slip icequakes (typically thousands of individual subevents per hour) produced when the cliff‐like edges of the tabular icebergs underwent glancing, strike‐slip collisions. The IHT signal that we observed is thus not a phenomenon associated with iceberg elastic or fluid resonance modes, but is instead the consequence of long sequences of very regularly spaced and similar pulses of seismic radiation from these constituent stick‐slip subevents. IHT represents a newly identified glaciogenic source of seismicity that can be used to improve our understanding of iceberg dynamics and possibly of ice shelf disintegration processes.

Actor networks are relevant to provide vocational education and training. Many studies have focused on such networks without a clear regional focus. Suggesting a conceptual approach of regional actor networks based on contributions of business education and economic geography, this study analyses the regional actor network in the tourism sector in Cancún (Mexico). Methodologically, the study follows an exploratory qualitative approach. The results illustrate that there are two dominant axes within the regional network, which comprise on the one hand hotels cooperating with applied universities, and on the other hand hotels cooperating with vocational schools. This local actor network has impacts on the practical relevance that vocational education and training provides to the learners, and generates a particular, and rather vulnerable, way of regional development.

Research Article| July 01, 1995 Council of the National Seismic System (CNSS) Background and Update Walter Arabasz; Walter Arabasz Department of Geology and Geophysics University of Utah Salt Lake City, UT84112 arabasz@seis.utah.edu (W. A.) Search for other works by this author on: GSW Google Scholar Steve Malone Steve Malone Geophysics Program AK 50 University of Washington Seattle, WA 98105 steve@geophys.washington.edu (S. M.) Search for other works by this author on: GSW Google Scholar Seismological Research Letters (1995) 66 (4): 29–30. https://doi.org/10.1785/gssrl.66.4.29 Article history first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Walter Arabasz, Steve Malone; Council of the National Seismic System (CNSS) Background and Update. Seismological Research Letters 1995;; 66 (4): 29–30. doi: https://doi.org/10.1785/gssrl.66.4.29 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietySeismological Research Letters Search Advanced Search This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.