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Journal articles on the topic 'Sentinel'

Author: Grafiati

Published: 4 June 2021

Last updated: 7 July 2024

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1

Keeling, Matt J., Samik Datta, Daniel N. Franklin, Ivor Flatman, Andy Wattam, Mike Brown, and Giles E. Budge. "Efficient use of sentinel sites: detection of invasive honeybee pests and diseases in the UK." Journal of The Royal Society Interface 14, no. 129 (April 2017): 20160908. http://dx.doi.org/10.1098/rsif.2016.0908.

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Sentinel sites, where problems can be identified early or investigated in detail, form an important part of planning for exotic disease outbreaks in humans, livestock and plants. Key questions are: how many sentinels are required, where should they be positioned and how effective are they at rapidly identifying new invasions? The sentinel apiary system for invasive honeybee pests and diseases illustrates the costs and benefits of such approaches. Here, we address these issues with two mathematical modelling approaches. The first approach is generic and uses probabilistic arguments to calculate the average number of affected sites when an outbreak is first detected, providing rapid and general insights that we have applied to a range of infectious diseases. The second approach uses a computationally intensive, stochastic, spatial model to simulate multiple outbreaks and to determine appropriate sentinel locations for UK apiaries. Both models quantify the anticipated increase in success of sentinel sites as their number increases and as non-sentinel sites become worse at detection; however, unexpectedly sentinels perform relatively better for faster growing outbreaks. Additionally, the spatial model allows us to quantify the substantial role that carefully positioned sentinels can play in the rapid detection of exotic invasions.

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2

Ridley, A. R., N. J. Raihani, and M. B. V. Bell. "Experimental evidence that sentinel behaviour is affected by risk." Biology Letters 6, no. 4 (February 24, 2010): 445–48. http://dx.doi.org/10.1098/rsbl.2010.0023.

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Sentinels are a conspicuous feature of some cooperative societies and are often assumed to provide benefits in terms of increased predator detection. Similar to other cooperative behaviours, variation in investment in sentinel behaviour should reflect variation in the benefits of such behaviour. However, evidence for this is inconclusive: to date experiments have manipulated the cost of sentinel behaviour, and considerations of changes in the benefits of sentinel activity on investment patterns are lacking. Here, we experimentally manipulated the benefits of sentinel behaviour in the cooperatively breeding pied babbler ( Turdoides bicolor ) to assess whether this had any impact on sentinel activity. We simulated the presence of an unseen predator using playbacks of heterospecific alarm calls, and the presence of an actual predator using a model snake. In both cases, the increase in perceived predation risk caused an increase in sentinel activity, demonstrating that investment in sentinel activity increases when the benefits are greater.

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Ostreiher, Roni, and Aviad Heifetz. "The sentinel behaviour of Arabian babbler floaters." Royal Society Open Science 4, no. 2 (February 2017): 160738. http://dx.doi.org/10.1098/rsos.160738.

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The sentinel behaviour of 38 Arabian babbler adult floaters, who lived alone within a territory belonging to a foreign group, was studied and compared with their own sentinel behaviour in the past, when they were group members. All floaters acted as sentinels and uttered ‘alarm calls’. This suggests that sentinel activity is due at least, in part, to selfish motives. Floaters sentinelled less than they did as group members, with the decrease in sentinel activity sharper for ex-dominants than for ex-subordinates. One possible explanation for these differences is that sentinel activity is aimed not only at detecting predators, but also at detecting foreign conspecifics. Within a group, the latter incentive is stronger for breeding dominants than for subordinates, whereas all floaters alike may be trying to detect the owners of the territory in which they were roaming but also to avoid being detected by them. Other possible explanations are that floaters have less time and energy for sentinel activity because they are weaker or because foraging is more difficult in a foreign territory. This may be especially so for dominants who used to enjoy privileged access to food in their group. No significant difference was found in the rate of sentinels' ‘alarm calls’ between floaters and group members, suggesting that their main purpose is predator–prey communication, of which warning groupmates may be a side benefit.

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4

RAGUSA-NETTO, J. "Sentinels in Saltator atricollis (Passeriformes: Emberizidae)." Revista Brasileira de Biologia 61, no. 2 (May 2001): 317–22. http://dx.doi.org/10.1590/s0034-71082001000200015.

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I studied the existence of sentinels in Saltator atricollis in a 'campo-cerrado' (Brazilian savanna) during the breeding seasons of 1994-95 and 1995-96. Groups of this species consisted of two to seven birds (N = 25). Sentinels were present (mean ± sd) 62% ± 9% of the time, and most sentinel bouts lasted from less than one to six minutes (although in some occasions for more than 30 min.). Overlap of two or more sentinels occurred on average only 3.2% of the time with birds on guard. Sentinels commonly gave contact calls in the beginning and/or at the end of a sentinel bout. The group size had no effect on time with sentinels. However the encounter rate between raptors and groups significantly influenced the time guarded. The results of this study suggests that the ability of sentinels to detect predators may play a central role as an anti-predator device.

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5

Racloz, V., C. Griot, and K. D. C. Stärk. "Sentinel surveillance systems with special focus on vector-borne diseases." Animal Health Research Reviews 7, no. 1-2 (June 2006): 71–79. http://dx.doi.org/10.1017/s1466252307001120.

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In the past few decades, vector-borne diseases have been spreading into countries previously free of these agents. It is necessary for a surveillance method to be tailored to the biology of these agents in order to detect their incursion. Using a sentinel herd system, it is possible to target high-risk areas where occurrence is most probably due to vector presence. Since the 1970s, diseases such as Akabane, vesicular stomatitis and Bluetongue disease have successfully been monitored using cattle herds as sentinels in many countries such as Saudi Arabia, Australia, China, Indonesia, Sultanate of Oman and most recently in countries in Western Europe. This paper reviews the strengths and weaknesses of sentinel herd surveillance systems in general. In order to determine their efficacy, the following criteria were found to be essential: the choice of sentinel locations, sentinel animal, seasonality of sampling and diagnostic testing methods. We conclude that due to its ability to focus on a specific disease, sentinel herd systems have been successful in the early detection of the spread of a targeted agent. This review is used as a basis for recommendations for the development of future sentinel herd systems.

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6

Zaias, Julia, Catia Farrington, Robert S. Livingston, and Linda W. Waterman. "Seroconversion of 1-year-old Mice to Murine Norovirus." Journal of the American Association for Laboratory Animal Science 58, no. 2 (March 1, 2019): 197–200. http://dx.doi.org/10.30802/aalas-jaalas-18-000054.

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Rodent sentinel screening for adventitious pathogens is an integral part of many biomedical research institutes and universities that use rodents in research. Typical screening programs involving live sentinel animals typically purchase young SPF sentinel animals that are sampled and replaced quarterly. Previous reports suggest that mice as old as 6 mo are effective sentinels for various agents. In efforts to reduce the number of animals used in our sentinel program, we wanted to investigate the possibility of keeping sentinel animals inhouse for 12 mo at a time. We exposed mice (age, 40 to 48 wk) to murine norovirus (MNV) to test whether they could reliably produce detectable levels of antibodies (similar to younger mice) to this adventitious pathogen. Mice first exposed to MNV at 40 to 48 wk of age seroconverted to MNV after both direct inoculation (through gavage) and indirect exposure (from soiled-bedding transfer) at the same or greater frequency than mice first exposed at 8 to 12 wk of age. These findings indicate that, at least for MNV, sentinel residence time can be extended from 3 to 12 mo without compromising the reliability of seroconversion, thus ultimately reducing sentinel animal numbers. This practice, combined with nonanimal testing modalities (for example, exhaust duct sampling), can increase the sensitivity and specificity of rodent surveillance programs and minimize the use of live animals.

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7

Tarpanelli, Angelica, Alessandro C. Mondini, and Stefania Camici. "Effectiveness of Sentinel-1 and Sentinel-2 for flood detection assessment in Europe." Natural Hazards and Earth System Sciences 22, no. 8 (August 2, 2022): 2473–89. http://dx.doi.org/10.5194/nhess-22-2473-2022.

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Abstract. Inundation is one of the major natural hazards in Europe. The evaluation of the flood hazard and risk is not straightforward mainly due to the monitoring system that is poor or not uniformly distributed in the territory. The ESA Earth Observation Program, including a series of satellites, Sentinels, for the operative observation of the natural phenomenon, e.g. the inundations, can potentially reduce the gap. Sentinel-1 (SAR: synthetic aperture radar) and Sentinel-2 (optical) have been demonstrated to be suitable for mapping flooded areas, but despite the medium–high spatial and temporal resolution of the sensors, the mapping of inundated territories is often partial or missing. The objective of this study is to evaluate through a synthetic study the effectiveness of Sentinel-1 and Sentinel-2 in the systematic assessment of floods in Europe, where the flood events have durations ranging from some hours to a few days. To reach the target, we analysed 10 years of river discharge data over almost 2000 sites in Europe, and we extracted flood events over some established thresholds as proxies of riverine inundations. Based on the revisit time of the satellite constellations and cloud coverage, we derived the percentage of potential inundation events that Sentinel-1 and Sentinel-2 could be able to observe. Results show that assuming the configuration of a constellation of two satellites for each mission and considering the ascending and descending orbit, on average 58 % of flood events are potentially observable by Sentinel-1 and only 28 % by Sentinel-2 due to the cloud coverage.

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Lepitzki, Dwayne A. W., Marilyn E. Scott, and J. Daniel McLaughlin. "Assessing cercarial transmission of Cyathocotyle bushiensis and Sphaeridiotrema pseudoglobulus by use of sentinel snails." Canadian Journal of Zoology 72, no. 5 (May 1, 1994): 885–91. http://dx.doi.org/10.1139/z94-120.

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Sentinel snails (Bithynia tentaculata) were used to assess spatial and temporal variation in cercarial transmission of Cyathocotyle bushiensis and Sphaeridiotrema pseudoglobulus at two field locations in southern Quebec and southeastern Ontario from mid-August to the end of October, 1989. Sentinels acquired infections with both digeneans; however, low levels of metacercariae of C. bushiensis precluded any conclusions regarding transmission of this parasite from being reached. In contrast, extensive spatial heterogeneity existed in the S. pseudoglobulus – snail system. Sentinel snails within 10 m of each other were apparently exposed to vastly different levels of naturally occurring cercariae. All size classes of sentinels were apparently equally susceptible to cercarial infections but no consistent temporal differences in infection levels were found.

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9

Wang, S., B. Yang, Y. Zhou, F. Wang, R. Zhang, and Q. Zhao. "SNOW COVER MAPPING AND ICE AVALANCHE MONITORING FROM THE SATELLITE DATA OF THE SENTINELS." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-3 (April 30, 2018): 1765–72. http://dx.doi.org/10.5194/isprs-archives-xlii-3-1765-2018.

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In order to monitor ice avalanches efficiently under disaster emergency conditions, a snow cover mapping method based on the satellite data of the Sentinels is proposed, in which the coherence and backscattering coefficient image of Synthetic Aperture Radar (SAR) data (Sentinel-1) is combined with the atmospheric correction result of multispectral data (Sentinel-2). The coherence image of the Sentinel-1 data could be segmented by a certain threshold to map snow cover, with the water bodies extracted from the backscattering coefficient image and removed from the coherence segment result. A snow confidence map from Sentinel-2 was used to map the snow cover, in which the confidence values of the snow cover were relatively high. The method can make full use of the acquired SAR image and multispectral image under emergency conditions, and the application potential of Sentinel data in the field of snow cover mapping is exploited. The monitoring frequency can be ensured because the areas obscured by thick clouds are remedied in the monitoring results. The Kappa coefficient of the monitoring results is 0.946, and the data processing time is less than 2&thinsp;h, which meet the requirements of disaster emergency monitoring.

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10

Pla, Magda, Gerard Bota, Andrea Duane, Jaume Balagué, Antoni Curcó, Ricard Gutiérrez, and Lluís Brotons. "Calibrating Sentinel-2 Imagery with Multispectral UAV Derived Information to Quantify Damages in Mediterranean Rice Crops Caused by Western Swamphen (Porphyrio porphyrio)." Drones 3, no. 2 (May 21, 2019): 45. http://dx.doi.org/10.3390/drones3020045.

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Making agricultural production compatible with the conservation of biological diversity is a priority in areas in which human–wildlife conflicts arise. The threatened Western Swamphen (Porphyrio porphyrio) feeds on rice, inducing crop damage and leading to decreases in rice production. Due to the Swamphen protection status, economic compensation policies have been put in place to compensate farmers for these damages, thus requiring an accurate, quantitative, and cost-effective evaluation of rice crop losses over large territories. We used information captured from a UAV (Unmanned Aerial Vehicle) equipped with a multispectral Parrot SEQUOIA camera as ground-truth information to calibrate Sentinel-2 imagery to quantify damages in the region of Ebro Delta, western Mediterranean. UAV vegetation index NDVI (Normalized Difference Vegetation Index) allowed estimation of damages in rice crops at 10 cm pixel resolution by discriminating no-green vegetation pixels. Once co-registered with Sentinel grid, we predicted the UAV damage proportion at a 10 m resolution as a function of Sentinel-2 NDVI, and then we extrapolated the fitted model to the whole Sentinel-2 Ebro Delta image. Finally, the damage predicted with Sentinel-2 data was quantified at the agricultural plot level and validated with field information compiled on the ground by Rangers Service. We found that Sentinel2-NDVI data explained up to 57% of damage reported with UAV. The final validation with Rangers Service data pointed out some limitations in our procedure that leads the way to improving future development. Sentinel2 imagery calibrated with UAV information proved to be a viable and cost-efficient alternative to quantify damages in rice crops at large scales.

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11

Schirdewahn, Frederik, Hartmut H. K. Lentz, Vittoria Colizza, Andreas Koher, Philipp Hövel, and Beatriz Vidondo. "Early warning of infectious disease outbreaks on cattle-transport networks." PLOS ONE 16, no. 1 (January 6, 2021): e0244999. http://dx.doi.org/10.1371/journal.pone.0244999.

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Surveillance of infectious diseases in livestock is traditionally carried out at the farms, which are the typical units of epidemiological investigations and interventions. In Central and Western Europe, high-quality, long-term time series of animal transports have become available and this opens the possibility to new approaches like sentinel surveillance. By comparing a sentinel surveillance scheme based on markets to one based on farms, the primary aim of this paper is to identify the smallest set of sentinel holdings that would reliably and timely detect emergent disease outbreaks in Swiss cattle. Using a data-driven approach, we simulate the spread of infectious diseases according to the reported or available daily cattle transport data in Switzerland over a four year period. Investigating the efficiency of surveillance at either market or farm level, we find that the most efficient early warning surveillance system [the smallest set of sentinels that timely and reliably detect outbreaks (small outbreaks at detection, short detection delays)] would be based on the former, rather than the latter. We show that a detection probability of 86% can be achieved by monitoring all 137 markets in the network. Additional 250 farm sentinels—selected according to their risk—need to be placed under surveillance so that the probability of first hitting one of these farm sentinels is at least as high as the probability of first hitting a market. Combining all markets and 1000 farms with highest risk of infection, these two levels together will lead to a detection probability of 99%. We conclude that the design of animal surveillance systems greatly benefits from the use of the existing abundant and detailed animal transport data especially in the case of highly dynamic cattle transport networks. Sentinel surveillance approaches can be tailored to complement existing farm risk-based and syndromic surveillance approaches.

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12

Howe, Alexander A., Sean A. Parks, Brian J. Harvey, Saba J. Saberi, James A. Lutz, and Larissa L. Yocom. "Comparing Sentinel-2 and Landsat 8 for Burn Severity Mapping in Western North America." Remote Sensing 14, no. 20 (October 20, 2022): 5249. http://dx.doi.org/10.3390/rs14205249.

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Accurate assessment of burn severity is a critical need for an improved understanding of fire behavior and ecology and effective post-fire management. Although NASA Landsat satellites have a long history of use for remotely sensed mapping of burn severity, the recently launched (2015 and 2017) European Space Agency Sentinel-2 satellite constellation offers increased temporal and spatial resolution with global coverage, combined with free data access. Evaluations of burn severity derived from Landsat and Sentinel generally show comparable results, but these studies only assessed a small number of fires with limited field data. We used 912 ground calibration plots from 26 fires that burned between 2016 and 2019 in western North America to compare Sentinel- and Landsat-derived burn severity estimates with the field-based composite burn index. We mapped burn severity using two methods; the well-established paired scene approach, in which a single pre- and post-fire scene are selected for each fire, and also a mean image compositing approach that automatically integrates multiple scenes using the cloud-based remote sensing platform Google Earth Engine. We found that Sentinel generally performed as well or better than Landsat for four spectral indices of burn severity, particularly when using atmospherically corrected Sentinel imagery. Additionally, we tested the effects of mapping burn severity at Sentinel’s finer spatial resolution (10 m) on estimates of the spatial complexity of stand-replacing fire, resulting in a 5% average reduction per-fire in area mapped as high-severity patch interiors (24,273 ha total) compared to mapping at the resolution of Landsat (30 m). These findings suggest Sentinel may improve ecological discrimination of fine-scale fire effects, but also warrant caution when comparing estimates of burn severity spatial patterns derived at different resolutions. Overall, these results indicate that burn severity mapping will benefit substantially from the integration of Sentinel imagery through increased imagery availability, and that Sentinel’s higher spatial resolution improves opportunities for examining finer-scale fire effects across ecosystems.

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Glasbergen, Brad, Michael Abebe, Khuzaima Daudjee, and Amit Levi. "Sentinel." Proceedings of the VLDB Endowment 13, no. 12 (August 2020): 2720–33. http://dx.doi.org/10.14778/3407790.3407856.

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&NA;. "SENTINEL." Clinical Nuclear Medicine 24, no. 10 (October 1999): 827. http://dx.doi.org/10.1097/00003072-199910000-00044.

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Heuser, Richard R. "SENTINEL." Journal of the American College of Cardiology 69, no. 21 (May 2017): 2679. http://dx.doi.org/10.1016/j.jacc.2017.02.069.

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16

Chakravarthy, S. "Sentinel." ACM SIGMOD Record 26, no. 2 (June 1997): 572–75. http://dx.doi.org/10.1145/253262.253409.

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Hershenow, Nick. "Sentinel." Missouri Review 20, no. 2 (1997): 9–19. http://dx.doi.org/10.1353/mis.1997.0040.

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Pan, Mary. "Sentinel." Fourth Genre 26, no. 1 (February 1, 2024): 125–33. http://dx.doi.org/10.14321/fourthgenre.26.1.0125.

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Indarto, Indarto, Marga Mandala, Fery Febrian Arifin, and Farid Lukman Hakim. "APLIKASI CITRA SENTINEL-2 UNTUK PEMETAAN TUTUPAN DAN PERUNTUKAN LAHAN PADA TINGKAT DESA." JURNAL GEOGRAFI 12, no. 02 (August 1, 2020): 189. http://dx.doi.org/10.24114/jg.v12i02.16970.

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Sentine-2 menjanjikan citra yang gratis, pada ketelitian spasial sedang dan ketelitian spektral tinggi. Data citra ini mungkin dapat digunakan sebagai dasar pemetaan tutupan lahan (land cover) dan pruntukan lahan (land use) sampai dengan level Desa. Artikel ini bertujuan untuk membandingkan dan mengevaluasi peta tematik yang dihasilkan dari: (1) Klasifikasi dari citra Sentinel-2A, (b) digitasi manual dari Google Earth Image, (c) dan peta RBI (Rupa Bumi Indonesia). Citra Sentinel-2A, citra google earth dan peta RBI digital digunakan sebagai input utama. Pengolahan citra Sentinel-2A mencakup: atmosferic correction, image composite, klasifikasi terbimbing, koleksi training area, dan uji-akurasi. Selanjutnya, ke tiga jenis peta tematik yang dihasilkan digunakan untuk membandingkan luasan per jenis tutupan lahan yang dipetakan dan interpretasi perubahan peruntukan lahan yang terjadi. Selanjutnya, wilayah empat desa digunakan sebagai sampel pengukuran. Penelitian menghasilkan peta tematik tutupan dan peruntukan lahan pada level Desa. Perbandingan peta tematik menunjukkan bahwa citra Sentinel mampu untuk menangkap fitur tutupan lahan yang utama (yaitu: Lahan-sub-optimal kering, lahan irigasi, lahan non-irigasi, area terbangun, hutan-perkebunan, dan badan air) pada level desa. Lebih lanjut peta yang dihasilkan dari citra Sentinel dapat digunakan untuk memperbaharui, perencanaan dan evaluasi kegiatan pembangunan di Desa. Kata Kunci: Sentinel-2A, Pemetaan, Tutupan Lahan, peruntukan lahan, desa.Sentinel-2 provide a free of cost imagery in medium spatial and high spectral resolutions. These data promise a rapid, low-cost and easy to apply imagery for the end-user. These free data may produce a rationale thematic land cover and land use (LCLU) map at the village level. This paper aims to compare and to evaluate the thematics maps created by (a) Sentinel-2, (b) digitalisation from Google Earth and (c) RBI (Rupa Bumi Indonesia) Digital Map. Sentinel-2 image, google earth image, and RBI digital map used as the primary input. The treatment of sentinel 2A imagery consists of atmospheric correction, image composite, supervised classification, collecting training areas, and accuracy assessment. The three types of maps use to compare area extent mapped for each type of land cover (LC), and the interpretation of land-use change occurred. Four villages used as samples of measurement. The research produces thematic LCLU maps at the village level. Comparison of maps shows that Sentinel capable of capturing major LC (i.e., Dry-marginal land, non-irrigated area, irrigated area, pavement areas, forest - plantation, and water body) at the village level. Moreover, Sentinel-2A produce more detail of land cover type. Finally, the maps derived from Sentinel data provide data for up-dating, planning and evaluation of village development.Keywords : Sentinel-2A, mapping, land cover, land use, village.

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Matter, H. C. "Pertussis surveillance in Switzerland, 1992 to 1997 – a large epidemic in 1994. What next?" Eurosurveillance 4, no. 12 (December 1, 1999): 130–33. http://dx.doi.org/10.2807/esm.04.12.00051-en.

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Cases of whooping cough have been recorded by the Swiss Sentinel Surveillance Network ‘Sentinella’ (SSSN) since June 1991 to monitor pertussis trends in Switzerland and to assess the current vaccination strategy. The Sentinella network consists of a sampl

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Miller, Manuel, and Markus Brielmeier. "Environmental samples make soiled bedding sentinels dispensable for hygienic monitoring of IVC-reared mouse colonies." Laboratory Animals 52, no. 3 (November 16, 2017): 233–39. http://dx.doi.org/10.1177/0023677217739329.

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Accurate knowledge of the health status of experimental animals is pivotal to high scientific and ethical standards in biomedical research. Individually ventilated cages (IVCs) are becoming the predominant system for housing laboratory mice, as they prevent cage-to-cage infections. However, this feature constitutes a major drawback for hygienic monitoring of mouse colonies, as traditional screening programs build on reliable transmission of infectious agents from experimental animals to sentinel mice commonly tested as representatives for the mouse colonies. In recent years, the laboratory animal community has realized that sentinels are ineffectual for screening mouse colonies in IVC systems because infections are often not transmitted to sentinels and therefore remain undetected. Furthermore, sentinel monitoring results in high numbers of used animals. In contrast, environmental monitoring provides a more reliable approach to identify and exclude pathogens in rodent colonies. In recent studies we provided evidence that polymerase chain reaction analysis of exhaust air particles is superior to soiled bedding sentinels for different agents. In this study, we show that testing pooled environmental samples generates more meaningful information compared to soiled bedding sentinels during routine hygienic monitoring in different barriers.

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Chen, Yueqing, Sijia Qiao, Guangxin Zhang, Y. Jun Xu, Liwen Chen, and Lili Wu. "Investigating the potential use of Sentinel-1 data for monitoring wetland water level changes in China’s Momoge National Nature Reserve." PeerJ 8 (February 17, 2020): e8616. http://dx.doi.org/10.7717/peerj.8616.

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Background Interferometric Synthetic Aperture Radar (InSAR) has become a promising technique for monitoring wetland water levels. However, its capability in monitoring wetland water level changes with Sentine-1 data has not yet been thoroughly investigated. Methods In this study, we produced a multitemporal Sentinel-1 C-band VV-polarized SAR backscatter images and generated a total of 28 interferometric coherence maps for marsh wetlands of China’s Momoge National Nature Reserve to investigate the interferometric coherence level of Sentinel-1 C-VV data as a function of perpendicular and temporal baseline, water depth, and SAR backscattering intensity. We also selected six interferogram pairs acquired within 24 days for quantitative analysis of the accuracy of water level changes monitored by Sentinel-1 InSAR. The accuracy of water level changes determined through the Sentinel-1 InSAR technique was calibrated by the values of six field water level loggers. Results Our study showed that (1) the coherence was mainly dependent on the temporal baseline and was little affected by the perpendicular baseline for Sentinel-1 C-VV data in marsh wetlands; (2) in the early stage of a growing season, a clear negative correlation was found between Sentinel-1 coherence and water depth; (3) there was an almost linear negative correlation between Sentinel-1 C-VV coherence and backscatter for the marsh wetlands; (4) once the coherence exceeds a threshold of 0.3, the stage during the growing season, rather than the coherence, appeared to be the primary factor determining the quality of the interferogram for the marsh wetlands, even though the quality of the interferogram largely depends on the coherence; (5) the results of water level changes from InSAR processing show no agreement with in-situ measurements during most growth stages. Based on the findings, we can conclude that although the interferometric coherence of the Sentinel-1 C-VV data is high enough, the data is generally unsuitable for monitoring water level changes in marsh wetlands of China’s Momoge National Nature Reserve.

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RAGUSA-NETTO, J. "Raptors and "campo-cerrado" bird mixed flock led by Cypsnagra Hirundinacea (Emberizidae:Thraupinae)." Revista Brasileira de Biologia 60, no. 3 (August 2000): 461–67. http://dx.doi.org/10.1590/s0034-71082000000300011.

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Bird mixed flocks including Cypsnagra hirundinacea and Neothraupis fasciata as species with sentinels were studied in "campo-cerrado" in order to investigate the possible relationship between alertness and the mixed flock leadership. This study was conducted from March to September 1996 and mixed flocks were observed on average for 2:30h. The time with sentinels were recorded for C. hirundinacea and N. fasciata. The sentinels of Cypsnagra hirundinacea performed most of the vigilance (time with sentinel was on average 42 ± 17%, 41 ± 17% of which by C. hirundinacea, whereas only 1.2 % by N. fasciata) and gave all the alarm calls recorded (54% of the encounters with raptors stimulated alarm calls). A relationship was verified between time with sentinel and the rate of encounters with raptor (ANOVA, F = 3.0, P < 0.05). The results of this study are an evidence for the anti-predatory function of mixed flocks, in campo-cerrado, and the alertness as a major feature of a leader species, since C. hirundinacea always led those flocks.

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Rodrigues, Ana Paula, Rita Carvalho Fonseca, and Carlos Matias-Dias. "Rede Médicos-Sentinela como Instrumento de Vigilância em Saúde [Pública]." Acta Médica Portuguesa 29, no. 1 (January 29, 2016): 5. http://dx.doi.org/10.20344/amp5938.

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<p>Current strategies of European health advocate the strengthening of the role of public health, requiring from decision-makers the ability to defend and enhance the health of individuals and populations in all policies. In the pursuit of this objective, public health should be evidence-based and so public health surveillance, seen as an important tool of public health since the nineteenth century, plays a central role in public health practice through the production and dissemination of the health information necessary for health planning and for evaluation of public health actions. Within the practice of public health estimations of disease frequency are important for outbreak control, health assessment, health needs assessment and estimation of health gains, but unfortunately these estimations are not always available for the entire population. In those cases and for diseases with high prevalence sentinel surveillance based in sentinel networks have some advantages for specific groups, namely needed of scarce resources and obtainment of quick results.<br />The central role of family doctors in chronic disease management, their knowledge on individuals and families and their responsibilities in the management of a clear defined patients list are characteristics that make general practice an appropriate context to develop a sentinel network. In fact, in Portugal there is a general practitioner sentinel network named Rede Médicos-Sentinela working since 1989 which estimated, for the last 25 years, incidence rates of several chronic diseases, some of them targeted on national priority health programs. Thus, we consider that Rede Médicos-Sentinela can be integrated in a national surveillance system for chronic diseases in Portugal.</p>

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Rodrigues, Ana Paula, Rita Carvalho Fonseca, and Carlos Matias-Dias. "Rede Médicos-Sentinela como Instrumento de Vigilância em Saúde [Pública]." Acta Médica Portuguesa 29, no. 1 (January 29, 2016): 5. http://dx.doi.org/10.20344/amp.5938.

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<p>Current strategies of European health advocate the strengthening of the role of public health, requiring from decision-makers the ability to defend and enhance the health of individuals and populations in all policies. In the pursuit of this objective, public health should be evidence-based and so public health surveillance, seen as an important tool of public health since the nineteenth century, plays a central role in public health practice through the production and dissemination of the health information necessary for health planning and for evaluation of public health actions. Within the practice of public health estimations of disease frequency are important for outbreak control, health assessment, health needs assessment and estimation of health gains, but unfortunately these estimations are not always available for the entire population. In those cases and for diseases with high prevalence sentinel surveillance based in sentinel networks have some advantages for specific groups, namely needed of scarce resources and obtainment of quick results.<br />The central role of family doctors in chronic disease management, their knowledge on individuals and families and their responsibilities in the management of a clear defined patients list are characteristics that make general practice an appropriate context to develop a sentinel network. In fact, in Portugal there is a general practitioner sentinel network named Rede Médicos-Sentinela working since 1989 which estimated, for the last 25 years, incidence rates of several chronic diseases, some of them targeted on national priority health programs. Thus, we consider that Rede Médicos-Sentinela can be integrated in a national surveillance system for chronic diseases in Portugal.</p>

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Rabiei, Saman, Ehsan Jalilvand, and Massoud Tajrishy. "A Method to Estimate Surface Soil Moisture and Map the Irrigated Cropland Area Using Sentinel-1 and Sentinel-2 Data." Sustainability 13, no. 20 (October 14, 2021): 11355. http://dx.doi.org/10.3390/su132011355.

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Considering variations in surface soil moisture (SSM) is essential in improving crop yield and irrigation scheduling. Today, most remotely sensed soil moisture products have difficulties in resolving irrigation signals at the plot scale. This study aims to use Sentinel-1 radar backscatter and Sentinel-2 multispectral imagery to estimate SSM at high spatial (10 m) and temporal resolution (at least 5 days) over an agricultural domain. Three supervised machine learning algorithms, multilayer perceptron (MLP), a convolutional neural network (CNN), and linear regression models, were trained to estimate changes in SSM based on the variation in surface reflectance and backscatter over five different crops. Results showed that CNN is the best algorithm as it understands spatial relations and better represents two-dimensional images. Estimated values for SSM were in agreement with in-situ measurements regardless of the crop type, with RMSE=0.0292 (cm3/cm3) and R2=0.92 for the Sentinel-2 derived SSM and RMSE=0.0317 (cm3/cm3) and R2=0.84 for the Sentinel-1 soil moisture data. Moreover, a time series of estimated SSM based on Sentinel-1 (SSM-S1), Sentinel-2 (SSM-S2), and SSM derived from SMAP-Sentinel1 was compared. The developed SSM data showed a significantly higher mean SSM state over irrigated agriculture relative to the rainfed cropland area during the irrigation season. The multiple comparisons (fisher LSD) were tested and found that these two groups are different (pvalue=0.035 in 95% confidence interval). Therefore, by employing the maximum likelihood classification on the SSM data, we managed to map the irrigated agriculture. The overall accuracy of this unsupervised classification is 77%, with a kappa coefficient of 65%.

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Cai, Jiannan, Qiancai Jiang, Yafei Shi, and Jiabin Wang. "Leaf area index retrieval of urban vegetation based on sentinel-2 data in Zhongshan, South China." Bangladesh Journal of Botany 49, no. 4 (December 31, 2020): 1103–9. http://dx.doi.org/10.3329/bjb.v49i4.52559.

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Leaf area index (LAI) is an important indicator of vegetation growth and health monitoring. The free access of Sentinel-2 optical satellite data from European Space Agency (ESA) since June 2015 made it possible to determine dynamic monitoring of LAI in a large area and a short re-entry period, owing to its high spatial resolution (up to 10 m) and unique band combination. These features of Sentinel-2 may bring great application potential in urban forestry management and ecological environment monitoring. In case of Zhongshan city in Guangdong Province, based on Sentinels Application Platform (SNAP) software and two scenes of Sentinel-2 data, LAI of the whole city, as well as specific areas, were retrieved and analyzed. The retrieval result was consistent with the ecological spatial pattern and the vegetation protection status in Zhongshan city, also highly consistent with the field LAI measurement in the forest in a reservoir. The result indicates that this method has good applicability and accuracy in urban LAI inversion.

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Costi, Juliana, Phelype Haron Oleinik, Caroline Barbosa Monteiro, Wiliam Correa Marques, and Jorge Arigony-Neto. "An Automated Structure for Acquiring and Processing Sentinel-1 Data and its Applicability for Coastal Studies." Defect and Diffusion Forum 372 (March 2017): 122–31. http://dx.doi.org/10.4028/www.scientific.net/ddf.372.122.

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The present work develops an automated structure to search, download and pre process Synthetic Aperture RADAR imagery acquired by the Sentinel-1 mission. A Python script defines the area and time of interest, performs the search for relevant products and download them using the Application Program Interfaces Hub of the Sentinels Scientific Data Hub. The preprocessing steps are performed using the Graph Processing Tool, which allows for a batch-mode execution of the Sentinel-1 Toolbox operators. Both steps are combined in a Bash program that performs the entire chain daily, without the need of users interaction. We demonstrate applicabilities of the processed data for coastal studies of the Rio Grande do Sul state. The structure is built aiming to 1) increase the usage of the open-access Sentinel-1 SAR data by reducing the processing time and 2) further develop automated detection systems for targets such as oil spills, ships and flooded areas.

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Ghosh, Debashis B., Nikolaus Michalopoulos, Caspar Wickham, Timothy Davidson, and Mohammed R. Keshtgar. "Sentinella: Portable gamma camera versus conventional scintigram for intraoperative sentinel lymph node detection in breast cancer." Journal of Clinical Oncology 30, no. 27_suppl (September 20, 2012): 22. http://dx.doi.org/10.1200/jco.2012.30.27_suppl.22.

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22 Background: Sentinel lymph node biopsy (SLNB) is a standard practice for staging the axilla in breast cancer. Access to nuclear medicine department and sentinel node imaging remain an issue in number of hospitals in the UK and rest of the world. Preoperative scintigrams are performed to confirm uptake of radioactivity and localisation of nodes in centres where facilities are available. Sentinella is a portable imaging camera used intraoperatively to produce real time visual localisation of SLNs. Sentinella was tested in a controlled laboratory environment at our centre followed by the first use of this device in breast cancer patients from UK. Methods: Sensitivity and spatial resolution of Sentinella was compared with conventional gamma camera (CGC).Intraoperative Sentinella Scans were performed in 130 patients and their yield compared with Lymphoscintigrams from CGC. Further Sentinella scans were performed after the axilla was deemed clear by silent activity of hand held gamma probe. Results: Sentinella resolution is comparable with the CGC for objects close to the camera. Sentinella detects high radioactivity (500 kBq) faster than CGC (1 vs 2.5min). In cases of low radioactivity (10kBq) Sentinella was equally accurate and faster than CGC, when placed nearer to skin.Intra-operative Sentinella scans detected an average of 2 sentinel nodes compared to 1.4 nodes by CGC scans. Sentinella demonstrated a serial decay in activity with removal of every hot node and its LED guidance helped in detecting residual nodes. Sentinella picked up extra nodes in 5/130 cases after the axilla was found silent using hand held gamma probe. In 2/130 cases extra nodes found using Sentinella had presence of cancer that led to a complete axillary clearance. Conclusions: This data confirms the excellent sensitivity and specificity of the machine in localisation of radioactive nodes. This new imaging technique increases our pick up of SLNs intraoperatively that are missed due to inadequate visualisation and provide a superior detection compared to static scintigram imaging. This portable gamma camera can replace the use of conventional lymphoscintigrams saving camera time and cost.

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Mohammadi, Ayub, Sadra Karimzadeh, Shazad Jamal Jalal, Khalil Valizadeh Kamran, Himan Shahabi, Saeid Homayouni, and Nadhir Al-Ansari. "A Multi-Sensor Comparative Analysis on the Suitability of Generated DEM from Sentinel-1 SAR Interferometry Using Statistical and Hydrological Models." Sensors 20, no. 24 (December 16, 2020): 7214. http://dx.doi.org/10.3390/s20247214.

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Digital elevation model (DEM) plays a vital role in hydrological modelling and environmental studies. Many essential layers can be extracted from this land surface information, including slope, aspect, rivers, and curvature. Therefore, DEM quality and accuracy will affect the extracted features and the whole process of modeling. Despite freely available DEMs from various sources, many researchers generate this information for their areas from various observations. Sentinal-1 synthetic aperture radar (SAR) images are among the best Earth observations for DEM generation thanks to their availabilities, high-resolution, and C-band sensitivity to surface structure. This paper presents a comparative study, from a hydrological point of view, on the quality and reliability of the DEMs generated from Sentinel-1 data and DEMs from other sources such as AIRSAR, ALOS-PALSAR, TanDEM-X, and SRTM. To this end, pair of Sentinel-1 data were acquired and processed using the SAR interferometry technique to produce a DEM for two different study areas of a part of the Cameron Highlands, Pahang, Malaysia, a part of Sanandaj, Iran. Based on the estimated linear regression and standard errors, generating DEM from Sentinel-1 did not yield promising results. The river streams for all DEMs were extracted using geospatial analysis tool in a geographic information system (GIS) environment. The results indicated that because of the higher spatial resolution (compared to SRTM and TanDEM-X), more stream orders were delineated from AIRSAR and Sentinel-1 DEMs. Due to the shorter perpendicular baseline, the phase decorrelation in the created DEM resulted in a lot of noise. At the same time, results from ground control points (GCPs) showed that the created DEM from Sentinel-1 is not promising. Therefore, other DEMs’ performance, such as 90-meters’ TanDEM-X and 30-meters’ SRTM, are better than Sentinel-1 DEM (with a better spatial resolution).

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Fierke, M. K., M. C. Whitmore, C. Foelker, J. D. Vandenberg, and J. Carlson. "Delimitation and management of emerald ash borer (Coleoptera: Buprestidae): case study at an outlier infestation in southwestern New York State, United States of America." Canadian Entomologist 145, no. 5 (August 2, 2013): 577–87. http://dx.doi.org/10.4039/tce.2013.39.

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AbstractWe present a case study in which we developed an adaptive delimitation technique and implemented and evaluated management of emerald ash borer (EAB), Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), in the first infestation discovered in New York State, United States of America. Delimitation was accomplished using 106 girdled “sentinel” trees and management included girdling 18 clusters of trees as population “sinks” to attract EAB and concentrate larvae for removal. Weekly monitoring of traps hung in sentinel trees facilitated early detection of EAB on 12 trees and allowed deployment of additional sentinels and sinks. Sentinel trees were felled and debarked; 12 were positive for EAB larvae and the spatial extent of infestation estimated at ∼48 km2. Sinks nearest the infestation core had the highest numbers of larvae. Larval densities were significantly greater in girdled trees than in proximate ungirdled trees suggesting removal of girdled trees prior to the following year's emergence would lower local EAB densities. Sinks deployed in response to an EAB on a sentinel tree purple prism trap more than 0.6 km from the centre of the known infestation were negative for EAB indicating these would not be effective for managing an infestation of similar size and in similar habitats. This case study provides valuable information to land managers to facilitate delimitation and management of newly discovered EAB infestations.

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Girsang, Dhea Vonisa, I. Made Yuliara, and Ni Nyoman Ratini. "ESTIMATION OF PB AND TOTAL SUSPENDED SOLID (TSS) CONCENTRATION BASED ON REMOTE SENSING DATA." Indonesian Physical Review 6, no. 1 (December 20, 2022): 42–50. http://dx.doi.org/10.29303/ipr.v6i1.165.

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Research has been carried out on the comparison of the concentration of Pb and Total Suspended Solid (TSS) of laboratory test results with Sentinel-2A satellite image data recorded on August 25, 2021 at the Suwung estuary dam, Denpasar city. The method used to compare the 2 measurement results is through testing by paired sample correlation and the graph. The result from the measurement show that the TSS value between Sentine-2A and laboratory has a fairly close value but the Pb value between Sentinel-2A and the laboratory have a much differences. The differences of the value between Sentinel-2A images and laboratory data can be caused by differences in the image recording time and field data collection time. This can result in changes or dynamics of water conditions that result in changes in the value and distribution Pb and then the radiometric influence of differences in Pb values on images and laboratory data can be caused by radiometric influences or interference with wave propagation in the air.

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Paget, W. J., H. Zimmermann, and H. Vorkauf. "A national measles epidemic in Switzerland in 1997 : consequences for the elimination of measles by the year 2007." Eurosurveillance 5, no. 2 (February 1, 2000): 17–20. http://dx.doi.org/10.2807/esm.05.02.00025-en.

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Clinical cases of measles have been reported to the Swiss Sentinel Surveillance Network (Sentinella) since June 1986 and measles infections have been monitored by the national laboratory notification system since January 1988. These two surveillance syste

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34

Bader-LeNormand, Kathleen. "Swamp Sentinel." English Journal 86, no. 4 (April 1997): 51. http://dx.doi.org/10.2307/821000.

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Farrell, L. "The sentinel." BMJ 343, no. 16 1 (November 16, 2011): d7328. http://dx.doi.org/10.1136/bmj.d7328.

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36

KOBS, ANN. "Sentinel Event." Nursing Management (Springhouse) 29, no. 2 (February 1998): 10???13. http://dx.doi.org/10.1097/00006247-199802000-00001.

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Mahlke, Scott A., William Y. Chen, Roger A. Bringmann, Richard E. Hank, Wen-Mei W. Hwu, B. Ramakrishna Rau, and Michael S. Schlansker. "Sentinel scheduling." ACM Transactions on Computer Systems 11, no. 4 (November 1993): 376–408. http://dx.doi.org/10.1145/161541.159765.

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SoRelle, Ruth. "Sentinel EDs." Emergency Medicine News 25, no. 10 (October 2003): 8. http://dx.doi.org/10.1097/00132981-200310000-00010.

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Manuel, J. "Sentinel school." Environmental Health Perspectives 104, no. 9 (September 1996): 934–36. http://dx.doi.org/10.1289/ehp.96104934.

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Kowalczyk, Dominik. "Wolfram: Sentinel." Leonardo Music Journal 12 (December 2002): 83–84. http://dx.doi.org/10.1162/lmj.2002.12.83b.

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Petska, Hillary W., and Lynn K. Sheets. "Sentinel Injuries." Pediatric Clinics of North America 61, no. 5 (October 2014): 923–35. http://dx.doi.org/10.1016/j.pcl.2014.06.007.

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&NA;. "SENTINEL NODE." Clinical Nuclear Medicine 24, no. 12 (December 1999): 1006. http://dx.doi.org/10.1097/00003072-199912000-00049.

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&NA;. "SENTINEL NODE." Clinical Nuclear Medicine 25, no. 1 (January 2000): 83. http://dx.doi.org/10.1097/00003072-200001000-00045.

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Uren, R. F., J. F. Thompson, and R. Howman-Giles. "Sentinel Nodes." Clinical Nuclear Medicine 25, no. 3 (March 2000): 234. http://dx.doi.org/10.1097/00003072-200003000-00025.

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Leong, Stanely P. L. "Sentinel Nodes." Clinical Nuclear Medicine 25, no. 3 (March 2000): 234. http://dx.doi.org/10.1097/00003072-200003000-00026.

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Boxen, I., D. McCready, and J. R. Ballinger. "Sentinel Nodes." Clinical Nuclear Medicine 25, no. 3 (March 2000): 234. http://dx.doi.org/10.1097/00003072-200003000-00027.

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Evans, Randolph W., Esma Dilli, and David W. Dodick. "Sentinel Headache." Headache: The Journal of Head and Face Pain 49, no. 4 (April 2009): 599–603. http://dx.doi.org/10.1111/j.1526-4610.2009.01381.x.

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de Falco, F. A. "Sentinel headache." Neurological Sciences 25, S3 (October 2004): s215—s217. http://dx.doi.org/10.1007/s10072-004-0289-1.

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Kovács, A. F., P. Acker, U. Berner, and J. H. Risse. "Sentinel-Lymphknotenexstirpation." HNO 49, no. 8 (August 1, 2001): 646–53. http://dx.doi.org/10.1007/s001060170063.

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Pynn, Manning. "Orlando Sentinel." Newspaper Research Journal 24, no. 1 (January 2003): 188–89. http://dx.doi.org/10.1177/073953290302400121.

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