Permanent Network Research Articles

Teleseismic evidence for structural heterogeneity in East Japan forearc from seafloor S-net data

We measure and analyze 4381 P-wave and 4307 S-wave arrival times of 48 teleseismic events recorded at 150 stations of a permanent seafloor seismic network (S-net) installed in the outer-rise and forearc region off East Japan. The obtained relative travel-time residuals amounting to ~3 s at the S-net stations are generally negative on the incoming Pacific and Philippine Sea plates and positive on the continental Okhotsk plate, which reflect high and low seismic velocities, respectively. This pattern is generally consistent with previous results on the seismic velocity structure of the crust and upper mantle beneath the East Japan forearc and the outer-rise area. Large early arrivals (~2.0 s) appear in the southern part of the S-net for the teleseismic events in the southwestern direction, which are mainly due to southwestward steepening of the subducting Pacific slab beneath Kanto. In the study region, the Pacific slab is the most significant anomaly with a thickness of ~90 km and a seismic velocity of 5–6 % higher than that of the surrounding mantle. Early arrivals (~1.5 s) also appear at the S-net stations off South Hokkaido, which are caused by northwestward steepening of the Pacific slab beneath the Tohoku-Hokkaido junction area. These results shed new light on the structural heterogeneity and subduction dynamics of the East Japan arc.

Analysis of the Impact of High Temporal Resolution Tropospheric Parameters on GNSS Station Coordinate and Troposphere Estimation

Abstract Troposphere modeling accuracy can seriously influence the performances of precise Global Navigation Satellite System (GNSS) positioning. The temporal interpolation accuracies of troposphere parameters become important with the improvement in troposphere modeling, especially during the periods of severe weather changes. In this study, a one-month experiment was conducted for 10 EUREF Permanent GNSS Network (EPN) stations to analyze the temporal interpolation errors of numerical weather model (NWM) derived troposphere parameters and their influences on GNSS station coordinate and troposphere estimation. The root mean square (RMS) of the differences between the 1- and 6-hourly European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis v5 (ERA5)-derived troposphere parameters are 0.72/11.52 mm for the zenith hydrostatic/wet delay (ZHD/ZWD), while are 7.09/91.84 mm for the slant hydrostatic/wet delay (SHD/SWD) at a 3^° elevation angle. The corresponding influences on the estimated up component and ZWD are 1.28 and 0.79 mm, respectively, in the daily static Precise Point Positioning (PPP) ambiguity resolution (AR) solutions. However, the accuracy improvements are insignificant in the daily static solutions, mainly due to the drop of temporal interpolation errors with increasing elevation angles and the influences of other unmodeled systematic errors. In the 4-hourly static solutions, the accuracies of the up component improve 0.51 mm (5.9% in relative) and 0.29 mm (3.5% in relative) during the severe and stable period, respectively. The impacts cannot be ignored in some GNSS subdaily applications, for example, monitoring non-tidal ocean loading effect, bedrock and monument thermal elastic effect, etc.

A Growth-Survival Trade-Off Along an Elevation Gradient Is Altered by Earthquake Disturbance in a Monodominant Southern Beech Forest.

Tree growth-survival relationships link two demographic processes that individually dictate the composition, structure and functioning of forest ecosystems. While these relationships vary intra-specifically, it remains unclear how this reflects environmental variation and disturbance. We examined the influence of a 700-m elevation gradient and an Mw = 6.7 earthquake on intra-specific variability in growth-survival relationships. We expected that survival models that incorporated recent growth would be better supported than those only using other factors known to influence tree survival. We used a permanent plot network that representatively sampled a monodominant Nothofagus forest in New Zealand's Southern Alps in 1974 and that was remeasured seven times through to 2009. The relationships were assessed using pre-earthquake growth and survival, pre-earthquake growth and post-earthquake survival (0-5 years post-earthquake), and post-earthquake growth and survival (5+ years post-earthquake). Survival was related to growth of 4504 trees on 216 plots using Bayesian modelling. We hypothesised there would be a positive, logistic relationship between growth and survival. Pre-earthquake, we found a positive, logarithmic growth-survival relationship at all elevations. At higher elevations, trees grew more slowly but had higher survival than trees at lower elevations, supporting our hypothesised demographic trade-off with elevation. The earthquake altered growth-survival relationships from those found pre-earthquake and 0-5 years post-earthquake survival held little relationship with growth. A strong, logarithmic growth-survival relationship developed 5+ years post-earthquake because of enhanced survival of fast-growing trees yet low survival of slow-growing trees. Synthesis. Our findings demonstrate a trend in growth-survival relationships along an elevation gradient. If we assume a gradual climate warming is the equivalent of a forest stand shifting to a lower elevation, then data from our pre-earthquake period suggest that tree growth-survival relationships at any elevation could adjust to faster growth and lower survival. We also show how these novel growth-survival relationships could be altered by periodic disturbance.

A real scale application of a novel set of spatial and similarity features for detection and classification of natural seismic sources from distributed acoustic sensing data

SUMMARY Distributed acoustic sensing (DAS) turns a fibre optic into a very dense network of equally distributed seismic sensors. We focused on the high-density sampling of the seismic wavefield, expressed in strain rates, measured by DAS. Classical approaches used to identify seismic signals rely on the recorded features at one station, but it is difficult to include spatial information in case of dense seismic station networks. This work aims at introducing new spatial and similarity features for seismic event classification suitable to analyse DAS observations. We propose a processing chain based on the XGBoost algorithm and the use of specifically designed spatiotemporal and similarity features for the event classification, and Markov random field for the spatial clustering. The methodology is designated to be applied on a continuous stream of DAS observations. We tested our processing chain to detect earthquakes and quarry blasts recorded in the region by permanent seismic networks and included in the RENASS catalogue. These events are part of a strain-rate seismic survey carried out during a 3 weeks campaign of DAS measurements along à 91 km fibre optic cable deployed in the central Pyrenees mountains (France). Despite the high anthropogenic activities along the fibre optic path, the proposed method succeeded in detecting earthquakes of magnitude >0.4 and quarry blasts of magnitude >1.0 while limiting the number of false alarms. This performance is particularly noteworthy for low-magnitude events, where detection is accomplished despite a lower signal-to-noise ratio compared to traditional seismometers. The methodology opens the door to real time detection and classification of seismic events measured with long-distance fibre optic systems.

Construction of urban tomographic synthetic aperture radar double-tier permanent scatterer network combined with region-growing algorithm

Construction of urban tomographic synthetic aperture radar double-tier permanent scatterer network combined with region-growing algorithm

Crustal imaging and characterization of active faults with a large-N nodal deployment - Application to the Chaînons Béarnais region (western Pyrenees foothills, France)

Understanding the driving forces and nature of intraplate seismicity remains a major unsolved problem in seismology. In the western Pyrénées, seismicity is concentrated in a narrow region that follows the boundary between the Axial Zone and the North Pyrenean Zone. Despite the presence of a permanent network in the region, the geometry of active faults, and their relationship with crustal structures, remain elusive, owing to significant earthquake location uncertainties. Here, we exploit data recorded by a large-N nodal array deployed in the Chaînons Béarnais region during four weeks of 2022 in order to image crustal structures and characterize active faults. We automatically detected and picked P and S waves with PhaseNet, resulting in a catalog of over 500 events, half of which are located beneath the temporary deployment. Tomographic images obtained from the inversion of P and S arrival times provide detailed insight into the geometry of folds and thrusts in the sedimentary cover, as well as the presence of a main fault in the basement which dips northward with an angle of 65° (Chaînons Béarnais normal fault). Seismicity relocation within the 3D model obtained by tomography shows that earthquakes are concentrated along this main active fault, extending from the top of the basement to a depth of approximately 16 km. These results demonstrate that passive imaging approaches can offer cost-effective alternatives to traditional controlled source imaging for seismotectonic studies and natural resource exploration in regions with active seismicity.

Twenty Years of Thermal Infrared Observations (2004–2024) at Campi Flegrei Caldera (Italy) by the Permanent Surveillance Ground Network of INGV-Osservatorio Vesuviano

Thermal infrared (TIR) time series images acquired by ground, proximal TIR stations provide valuable data to study evolution of surface temperature fields of diffuse degassing volcanic areas. This paper presents data processing results related to TIR images acquired since 2004 by six ground stations in the permanent thermal infrared surveillance network at Campi Flegrei (TIRNet) set up by INGV-Osservatorio Vesuviano. These results are reported as surface temperature and heat flux time series. The processing methodologies, also discussed in this paper, allow for presentation of the raw TIR image data in a more comprehensible form, suitable for comparisons with other geophysical parameters. A preliminary comparison between different trends in the surface temperature and heat flux values recorded by the TIRNet stations provides evidence of peculiar changes corresponding to periods of intense seismicity at the Campi Flegrei caldera. During periods characterized by modest seismicity, no remarkable evidence of common temperature variations was recorded by the different TIRNet stations. Conversely, almost all the TIRNet stations exhibited common temperature variations, even on a small scale, during periods of significant seismic activity. The comparison between the seismicity and the variations in the surface temperature and heat flux trends suggests an increase in efficiency of heat transfer between the magmatic system and the surface when an increase in seismic activity was registered. This evidence recommends a deeper, multidisciplinary study of this correlation to improve understanding of the volcanic processes affecting the Campi Flegrei caldera.

Epoxy-based multifunctional re-bondable polymer with self-healing, shape memory and superb bonding properties

Thermoset epoxy resin-based materials are widely used, but their permanent cross-linked network limits their processability and reusability, which can lead to environmental burdens. In this work, by exploiting the weak reactivity of aniline to design appropriate reaction ratios, we achieved a linear link between the epoxy resin and the curing agent. This linear link, along with the crosslinking points provided by the flexibly branched polyurethanes, avoids the inherent brittleness associated with the highly crosslinked network of conventional epoxy resins. As a result, the adhesive exhibits extraordinary improvements in extensibility and toughness. The lap shear strength, tensile strength and elongation at break reach 11.9 MPa, 14.4 MPa and 607 %, respectively. The fracture toughness is as high as 109.6 kJ/m2, far beyond the existing epoxy adhesives. The synergistic effect of disulfide bonds and hydrogen bonds confers the adhesive with self-healing and repeatable bonding characteristics. The multi-level hydrogen bonding and appropriate phase separation structure are key to optimizing toughness, resulting in excellent comprehensive performance. The introduction of polyurethane not only improves toughness but also enhances the interfacial bonding force between the adhesive and the substrate, broadening the scope of applications. The prepared high-performance polymers provide new insights into reusable epoxy adhesives.

Barrack-Building, Mapping, and Settlement in Eighteenth-Century Ireland

The history of residential army barracks in Ireland has in recent years become a focus for more concerted study. 1 While a number of works focused upon individual barracks have been published over the years since the 1970s, 2 the first substantive consideration as to why a permanent country-wide network of barracks was built in Ireland in the late 1690s and early eighteenth century was first published in 2012. This work assessed why these barracks were built, how they were paid for, and ultimately what purposes they served. 3 Since then, additional work has been undertaken with regard to a more comprehensive identification and inventorying of over 360 such barracks built between 1690 and 1922. 4 However, while some consideration has been given to the impact of the building of a country-wide network of barracks upon cartographic practice, 5 there has been little to no assessment of the impact that such residential army barracks had upon patterns of settlement. It is the aim of this article to assess these interlinked elements of barrack-building, mapping, and settlement patterns in relation to each other in an eighteenth-century context, with a particular focus upon barracks built in County Armagh. 6

Crustal 3‐D S‐Wave Velocity and Azimuthal Anisotropy in the Sanjiang Lateral Collision Zone in the SE Margin of the Tibetan Plateau

AbstractThe eastward extrusion of the Tibetan Plateau materials has caused intricate tectonic deformations and frequent seismic activities in the Sanjiang lateral collision zone (SLCZ). To reveal crust structures and deformation mechanisms, we investigate high‐resolution structural features of crustal depth (≤40 km). A 3‐D S‐wave velocity and azimuthal anisotropy model is constructed by the direct tomography method with Rayleigh phase velocity at periods of 2–40 s from multiple temporary seismic arrays and regional permanent network. In the middle‐to‐lower crust, an obvious low‐velocity zone is confined by the large‐scale fault systems of Jinhe‐Qinghe fault and Chenhai fault (CHF) to the northeast and east, Lancangjiang fault (LCJF) and Red River fault (RRF) to the west, with strong N‐S‐oriented anisotropy, which evident differs from the ENE‐WSW‐oriented weak anisotropy in the high‐velocity zone on the northeastern side. We consider that the weak material may be obstructed by large faults and the high‐velocity zone, resulting in complex crustal deformation and tectonic boundary. The crustal low‐velocity materials beneath the Tengchong volcano (TCV) are probably separated with those from the Tibetan Plateau. The low‐velocity beneath the Chuxiong basin (CXB) may be combinations of partial melts and fluid derived from shear deformation and deep material upwelling. The segmented anisotropy at the NW end of the RRF suggests complex deformation by crustal flow, emphasizing the important influence of faults on anisotropic pattern. The complex anisotropy in the fault intersection of the Lijiang‐Xiaojinhe fault and RRF also highlights the important role of these faults in shaping crustal deformation.

Anisotropic structure at shallow depths across the Japan Trench

Anisotropic structures within the crust are frequently perceived to originate from stress-induced cracks, which have been mainly estimated on land through different wave speeds of orthogonally polarized S waves propagating in the anisotropic media. However, such estimations of crustal anisotropic structures in ocean areas, particularly for subduction zones around trenches, have not been investigated in detail due to the lack of long-term ocean bottom observations. In this study, we used ocean bottom seismometers of a permanent network deployed across the Japan Trench and the southern part of the Kuril Trench and applied the shear-wave splitting analysis to P-to-s converted waves extracted by receiver function analyses using teleseismic events. We estimated the anisotropic structures in marine sediments and oceanic crust for the incoming Pacific Plate and marine sediments for the overriding North American Plate. The obtained fast polarization directions for the incoming plate are mainly oriented to be parallel to the trench axis for the marine sediment and oceanic crust, which are formed by normal faults and cracks due to the upward plate bending in the outer-rise region, whereas results for marine sediments at the northern part of the Japan Trench are obliquely aligned to the trench axis. The oblique direction is consistent with the magnetic lineations of the incoming plate, indicating that ancient faults within the plate, which were formed in the shallow part of the crust during the creation of the oceanic plate at the ridge, are reactivated by the plate flexure. For the overriding plate, the fast polarization directions in the northern and southern parts of the study area are nearly normal to the trench axis. The central part shows two distinct features: the fast polarization directions parallel to the trench axis and small degrees of anisotropy. These patterns may reflect crack alignments associated with the lateral variation in postseismic crustal deformation after the 2011 Tohoku-Oki earthquake. Our results suggest substantial lateral variations in the stress field at the tip of the overriding plate along the strike direction.Graphical

GNSS Real-Time ZTD/PWV Retrieval Based on PPP with Broadcast Ephemerides

GNSS precise point positioning (PPP) plays an important role in retrieving atmospheric water vapor values and performing numerical weather prediction. However, traditional PPP relies on real-time orbits and clocks, which require continuous internet or satellite communication. Improved broadcast ephemerides of GNSSs offer new opportunities for PPP with broadcast ephemerides (BE-PPP) instead of using precise ephemeride products. Therefore, we investigated the feasibility of utilizing BE-PPP for retrieving zenith tropospheric delay (ZTD) and precipitable water vapor (PWV) data. We processed the GPS/Galileo observations from 80 IGS stations during a 30-day experiment to retrieve ZTD values using both real-time PPP (RT-PPP) and BE-PPP solutions. Then, we processed observations from 20 EUREF Permanent GNSS Network (EPN) stations to retrieve PWV data. The IGS final tropospheric products were used to validate the ZTD, and radiosonde (RDS) and ERA5 data were used to validate the PWV. The results show that the real-time ZTD from BE-PPP agrees well with that from RT-PPP: the standard deviation (STD) of the ZTD is 1.07 cm when using BE-PPP and 0.6 cm when using RT-PPP. Furthermore, the STD of the PWV is 1.69 mm when using BE-PPP, and 0.96 mm when using RT-PPP, compared to the ERA5-PWV. Compared to the RDS-PWV, the STD is 3.09 mm when using BE-PPP and 1.39 mm when using RT-PPP. In conclusion, the real-time ZTD/PWV products obtained using the BE-PPP solution are consistent with those of RT-PPP and meet the requirements of NWP, so this method can be used as an effective complement to RT-PPP to expand its application potential.

Microseismicity detection and spatial-temporal migration in the Xinfengjiang reservoir, Guangdong, China

There have been many earthquakes in the Xinfengjiang Reservoir (XFJR) in the past 60 years since the M6.1 earthquake that occurred in 1961. In the XFJR, seismicity has migrated from southeast to northwest; however, the mechanisms for this migration have not yet been fully investigated. In this study, we used six years of data from both permanent and temporary seismic networks in the XFJR to detect >23,500 earthquake events using the EQTransformer. The minimum magnitude of completeness of the earthquake catalog decreased to −0.1, and the spatial distribution of the microearthquakes showed clear high-angle faults in the area, which included a new fault within the reservoir. The focal mechanism inversion results showed that earthquakes in the northwestern cluster changed from strike-slip to dip-slip faults with time whereas those in the southeastern cluster remained a mixture of strike-slip and dip-slip faults. Further analysis showed that spatiotemporal variation in the northwestern reservoir was due to earthquake migration along different faults. Overall, we concluded that earthquake in the whole XFJR area were affected by water infiltration along fault zone; Coulomb stress transfer may also contribute to the migration of earthquakes from southeast to northwest direction.

Topological Rearrangement-Induced Mesoscale Phase Redistribution to Enhance the Fatigue Resistance of Polymer Blends.

Maintaining a high modulus to simultaneously withstand deformation and increase fatigue resistance to restrict crack propagation in a material presents a significant challenge. In this work, a straightforward strategy was developed to address this issue in polymers. A dynamic network was incorporated into a permanent one prior to the formation of the latter, and two incompatible polymer networks were created to prevent common phase separation. The mechanical and fatigue resistance properties were substantially enhanced by the exact modulation of the soft and hard phase distribution by precise control over the densities of dynamic and permanent networks as well as the number of reprocessing steps. The experimental results demonstrated a nearly 9-fold increase in the fatigue life of polyurethane compared with traditional design methods and a 2.5 times increase in modulus. This strategy shows potential for the design of fatigue-resistant thermosetting and thermoplastic materials. The results offer new insight into the development of durable, high-performance materials that are reprocessable and compatible.

Energy-Magnitude Station Corrections across the Conterminous United States

Abstract The determination of source parameters requires corrections for propagation and site effects. The source parameter of interest for this study is the radiated seismic energy, which we use in turn to compile a global energy magnitude Me catalog. The energy estimated for P waves recorded at distances between 20° and 98° is corrected for propagation effects using the numerical Green’s function for the AK135Q model, in which the correction is performed in the spectral domain over the frequency range 0.012–1 Hz. To quantify the impact of site effects on Me, we perform a mixed-effects regression to isolate repeated station effects from event and propagation contributions to the overall magnitude variability. We find that the standard deviation of the interstation residuals is 0.19, whereas the standard deviation of the path-to-path residuals is 0.24. To discuss the spatial variability of the station-specific magnitude residuals, we analyze the results obtained for permanent and temporary networks installed in the conterminous United States. The high density of stations considered (4502 stations from 97 networks) allows us to compare a map of the station corrections with the physiographic classification of the United States. We find a good agreement, with positive magnitude corrections for stations installed in the Atlantic Plain and in the Interior Plains divisions; negative corrections characterize installations in the Rocky Mountains system, in the Interior Highlands, in the ranges of the Pacific Mountains division and in the Appalachian Highlands. Moreover, the alternation of positive and negative magnitude corrections corresponds well with the province and section subdivisions.

Controlling Hybrid Polyhydroxyurethane Adhesive and Rheological Properties by Partial Carbonation of Biobased Epoxy Monomer.

Controlling hybrid material properties by simple monomer design offers an elegant pathway to prepare thermoset adhesives with tunable properties. Herein, biobased hybrid polyhydroxyurethane/polyepoxy is prepared starting from partially carbonated cashew nut shell epoxy derivatives (NC514) and m-xylene diamine (MXDA). The curing reactions, that is, epoxy-amine and cyclic carbonate aminolysis, monitored by ATR-IR spectroscopy at 50°C are found to be concomitant yielding highly homogeneous materials. Hybrid networks are extensively characterized by swelling tests, TGA, DMA, DSC, tensile tests, rheology, and lap-shear-test on aluminum substrates. The introduction of hydroxyurethane moieties within the epoxy-amine networks enhanced the adhesion properties (up to 20% compare to neat epoxy resins) by combining hydrogen bonding capability and vitrimeric properties (thermoset able to flow). Rheological characterizations and reprocessing tests demonstrated that hybrid adhesives with up to 47 mol% of cyclic carbonate groups are capable of covalent exchange (internally catalyzed by tertiary amine) while keeping similar thermomechanical properties and enhanced adhesion strength compare to the permanent epoxy network.

Mantle deformation in the highly oblique indo-burma subduction system inferred from shear wave splitting measurements

We utilized shear wave splitting analysis of teleseismic SKS, SKKS, and PKS phases to infer upper mantle deformational fabrics across a substantial area of Southeast Asia, where splitting measurements were previously limited. We used newly available permanent and temporary broadband seismic networks deployed across the Indo-Burma subduction zone and the eastern Indochina peninsula. The resulting 492 well-constrained splitting and 654 null measurements from 185 stations reveal clear large-scale patterns in the mantle deformational fabrics in response to the highly oblique active subduction and a large transform plate boundary. We identified two distinct domains of mantle deformation fabrics in the western Burma microplate and the eastern Indochina peninsula. In the former, trench parallel N-S fast polarization directions with an average lag time (δt) of 1.9 s are observed beneath the Indo-Burman Ranges. We suggest the observed splitting is partly due to anisotropy in the sub-slab region and relates to shear induced by the north moving Indian plate. The lithospheric fabric within the Indo-Burman Ranges and underlying subducting slab fabric contribute to produce the observed average δt of 1.9 s. The δt value decreases to an average of 1.0 s towards the back-arc until we reach the dextral Sagaing fault. In the second domain, starting approximately 100 km east of the Sagaing fault, we observe a consistent E-W fast direction with an average δt of 1.10 s in the eastern Shan-Thai and Indochina blocks. We interpret the E-W fabric as due to the deformation associated with the westward spreading of the Hainan mantle plume, possibly driven by overriding plate motion. Low velocities in the shallow mantle and late Cenozoic intraplate volcanism in this region support the plume-driven asthenospheric flow model in the Indochina peninsula. The sudden transition of the fast polarization direction from N-S to E-W along the eastern edge of the Burma microplate indicates the Sagaing fault acts as a mantle flow boundary between the subduction dominated trench parallel flow to the west and plume induced asthenospheric flow to the east. We also observed no net splitting beneath the Bengal basin which is most likely due to the presence of frozen vertical fabric resulting from the Kerguelen plume activity during Early Cretaceous.

Using metal oxide gas sensors to estimate the emission rates and locations of methane leaks in an industrial site: assessment with controlled methane releases

Abstract. Fugitive methane (CH4) emissions occur in the whole chain of oil and gas production, including from extraction, transportation, storage, and distribution. Such emissions are usually detected and quantified by conducting surveys as close as possible to the source location. However, these surveys are labour-intensive, are costly, and fail to not provide continuous emissions monitoring. The deployment of permanent sensor networks in the vicinity of industrial CH4 emitting facilities would overcome the limitations of surveys by providing accurate emission estimates, thanks to continuous sampling of emission plumes. Yet high-precision instruments are too costly to deploy in such networks. Low-cost sensors using a metal oxide semiconductor (MOS) are presented as a cheap alternative for such deployments due to their compact dimensions and to their sensitivity to CH4. In this study, we demonstrate the ability of two types of MOS sensors (TGS 2611-C00 and TGS 2611-E00) manufactured by Figaro® to reconstruct a CH4 signal, as measured by a high-precision reference gas analyser, during a 7 d controlled release campaign conducted by TotalEnergies® in autumn 2019 near Pau, France. We propose a baseline voltage correction linked to atmospheric CH4 background variations per instrument based on an iterative comparison of neighbouring observations, i.e. data points. Two CH4 mole fraction reconstruction models were compared: multilayer perceptron (MLP) and second-degree polynomial. Emission estimates were then computed using an inversion approach based on the adjoint of a Gaussian dispersion model. Despite obtaining emission estimates comparable with those obtained using high-precision instruments (average emission rate error of 25 % and average location error of 9.5 m), the application of these emission estimates is limited to adequate environmental conditions. Emission estimates are also influenced by model errors in the inversion process.

Preparation and Characterization of Novel Poly(thiourethane)-Poly(isocyanurate) Covalent Adaptable Networks: Effect of the Catalysts.

Poly(thiourethane)-based covalent adaptable networks are synthesized by reacting a trimer of hexamethylene diisocyanate (Desmodur N3300) containing isocyanurate groups in its structure with 1,6-hexanedithiol. The catalysts evaluated for this process include dibutyltin dilaurate (DBTDL), lanthanum triflate (La(OTf)3), and a thermal precursor of 1,8-diazabicyclo[5.4.0]undec-7-ene (BGDBU). The use of DBTDL results in the initiation of curing upon mixing, while the other two catalysts exhibit a latency period in the reactive mixture, with curing starting at about 90°C. Notably, the use of the lanthanum salt produces an additional minor exothermic reaction at 80°C. This phenomenon corresponds to the trimerization of isocyanates rending isocyanurates, leaving a portion of unreacted thiols. Materials prepared with BGDBU or La(OTf)3 present shorter relaxation times than those prepared with DBTDL. Nevertheless, the materials containing the lanthanum salt do not reach complete relaxation, likely due to the reinforcement of the permanent network through increased isocyanurate content. The formation of isocyanurates produces a stoichiometric imbalance, leaving unreacted thiols. This transforms the exchange process into a dual mechanism involving a dissociative process of thiourethanes to isocyanate and thiol, along with an interchange through thiol attacking the thiourethane group. The materials exhibit good recyclability and self-healing characteristics.

Dynamics of Policy Network in the Development of Rainbow Village in Semarang City

This article aims to analyze the problems of the Rainbow Village in Semarang City. The success of the Rainbow Village at the beginning of its development contrasts with the current conditions that are empty of visitors, damaged paint conditions, and many wild plants growing along the road between people's houses. The problem analysis will focus on studying policy networks in implementing Kampung Pelangi. The existence of policy networks in implementation and policy-making is interesting to examine because the process involves a political process that is not only controlled by the state but involves various actors and diverse interests. Through qualitative methods and the theoretical framework of Waarden and Rhodes' policy networks, this paper wants to answer how the dynamics of policy networks run and the types of policy networks that develop. As a result of the study, the Rainbow Village policy network tends to be unstable and only runs when this program goes viral in the early days of implementation. The network built involves three important policy stakeholders, namely civil society, the private sector, and the government. The interaction between actors in policy networks tends to be unbalanced so there are inequalities in the distribution of resources and authority. This causes pokdarwis as the leading actor of the network to have difficulty maintaining the network's existence. The type of policy network is an issue network, where the network is temporary when program issues arise and network actors are not bound in a permanent network.