Deep Sites Research Articles

Use of floating acylphosphine oxide-based photoinitiators to reduce surface oxygen inhibition of UV-LED photopolymerization

a series of acylphosphine oxide-based self-floating photoinitiators (PIs) of (TPO-F/Si/C12/C22) for improving the surface oxygen inhibition resistance are synthesized by following the modification of the traditional PI of ethyl phenyl(2,4,6-trimethylbenzoyl)phosphinate (TPO-L). The four self-floating PIs bear low surface free energy units of fluorine, polysiloxane, C12 and C22 long chain aliphatic alkane, respectively. The self-floating ability are assessed by UV absorption spectra and further confirmed by the X-ray photoelectron spectroscopy (XPS) and the water contact angle tests. The self-floating ability of the PIs can enable the UV-LED photopolymerization of the acrylic monomers to conquer the surface oxygen inhibition by increasing the local PI concentration, which is evidenced by ATR-IR, confocal Raman microscopy (CRM) and Photo-DSC. The self-floating ability enriches the PIs in the upper layers to consume the surface oxygen as well as to enable the fast cure of the resin surface to stop the further penetration of the oxygen into deeper sites.

Evaluation of Long-Term Impacts of CO2 Leakage on Groundwater Quality Using Hydrochemical Data from a Natural Analogue Site in South Korea

Three hydrochemical types of CO2-rich water (i.e., Na-HCO3, Ca-Na-HCO3 and Ca-HCO3) occur together in the silicate bedrock (granite and gneiss) of Gangwon Province in South Korea. As a natural analogue of geological carbon storage (GCS), this can provide implications for the environmental impacts of the leakage of CO2 from deep GCS sites. By using hydrochemical and isotopic datasets that were collected for previous and current studies, this study aimed to carefully scrutinize the hydrochemical differences in the three water types with an emphasis on providing a better understanding of the impacts of long-term CO2 leakage on groundwater quality (especially the enrichments of minor and trace metals). As a result, the Na-HCO3 type CO2-rich water contained higher Li, Rb and Cs than the Ca-HCO3 type, whereas Fe, Mn and Sr were higher in the Ca-HCO3 type than in the Na-HCO3 type despite the similar geological setting, which indicate that the hydrochemical differences were caused during different geochemical evolutionary processes. The δ18O and δD values and tritium concentrations indicated that the Na-HCO3 type was circulated through a deep and long pathway for a relatively long residence time in the subsurface, while the Ca-HCO3 type was strongly influenced by mixing with recently recharged water. These results were supported by the results of principal component analysis (PCA), whose second component showed that the Na-HCO3 type had a significant relation with alkali metals such as Li, Rb and Cs as well as Na and K and also had a strong relationship with Al, F and U, indicating an extensive water-rock interaction, while the Ca-HCO3 type was highly correlated with Ca, Mg, Sr, Fe and Mn, indicating mixing and reverse cation exchange during its ascent with hydrogeochemical evolution. In particular, the concentrations of Fe, Mn, U and Al in the CO2-rich water, the result of long-term water-rock interaction and cation exchange that was enhanced by CO2 leakage into silicate bedrock, exceeded drinking water standards. The study results show that the leakage of CO2 gas and CO2-rich fluid into aquifers and the subsequent hydrogeochemical processes can degrade groundwater quality by mobilizing trace elements in rocks and consequently may pose a health risk.

The periodontopathic bacteria in placenta, saliva and subgingival plaque of threatened preterm labor and preterm low birth weight cases: a longitudinal study in Japanese pregnant women.

This study determined the quantity of periodontopathic bacteria in saliva, subgingival plaque, and placenta on the threatened preterm labor (TPL) and preterm low birth weight (PLBW) subjects in order to identify specific periodontal pathogens with high association to adverse pregnancy outcomes. We used real-time PCR with TaqMan probe and ELISA to detect the amount of Aggregatibacter actinomycetemcomitans, Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, Fusobacterium nucleatum, and Prevotella intermedia in subgingival plaque, saliva, and placenta tissue, in addition to serum IgG titers against these bacteria in 28 patients with TPL and 36 healthy pregnant women. Thirteen of 64 births delivered PLBW infants. All 6 periodontopathic bacteria were detected in the placenta samples. The amount of F. nucleatum and detection frequency of T. denticola in placental samples was significantly higher in the TPL group than in the healthy group. Meanwhile, the age, anti-P. gingival IgG in serum, amount of P. gingivalis and T. forsythia in plaque samples, detection frequency of P. intermedia in saliva, and percentage of pocket probing depth ≥ 5mm were higher in TPL-PLBW births than those in TPL-Healthy delivery (HD) group and/or in H-HD group. Ordinal logistic regression analysis revealed that the presence of F. nucleatum in placental tissues was significantly associated with TPL, while the maternal age was significantly associated with PLBW in TPL. Our findings suggested all 6 bacteria may access the placenta. The increased presence of F. nucleatum in placenta might be related to TPL, while advanced maternal age might be associated with PLBW in TPL. Periodontal therapy should be applied to reduce the deep periodontal pocket sites and the colonization of periodontal pathogens in high-risk population.

Sex ratio of Stygiopontius senokuchiae (Dirivultidae, Copepoda), an endemic copepod species at deep hydrothermal vent sites, is biased to males

Stygiopontius copepods (Dirivultidae, Siphonostomatoida, Crustacea) are among the most successful meiobenthic organisms at deep-sea hydrothermal vents. Most of their ecology is not yet known, including the spatiotemporal differences in their sex ratios and their controlling factors. We investigated spatial variation in the sex ratio of adult Stygiopontius senokuchiae and its association with environmental parameters, including food quality at hydrothermal vent chimney structures in the calderas of three neighboring sea knolls (Bayonnaise Knoll, Myojin Knoll, and Myojin-sho Caldera) in the western North Pacific Ocean. Their sex ratio was significantly biased to males from 1:1, which was different from some of the other Stygiopontius species. The ratios did not show a significant correlation with the density of total adults. While previous studies have shown that the abundance of S. senokuchiae is positively associated with δ13C values of detritus on active chimneys, multivariate analyses in this study did not detect any significant association between their sex ratio and any investigated parameters including δ13C. These findings suggest that neither population density nor chemoautotrophic food availability drives the sexual difference in the spatial distribution around vents among the adults of the species.

Broad morphological and reproductive variability of the endangered macroalga Lychnothamnus barbatus in the depth gradient

Factors that strongly affect morphological features and reproductive effort of charophytes (Charophyta, Characeae) are the depth of occurrence and light availability. Eutrophication of waters and global warming change the level and transparency of waters. As a response to light limitation, an elongation of the charophyte thallus and a decrease in the number of mature oogonia with increasing depth have been reported. The object of this study was the globally endangered charophyte Lychnothamnus barbatus, the only living representative of the genus and a sensitive bioindicator of low trophic conditions. We hypothesised that: (1) the morphological variability and (2) the number of mature oogonia decrease with increasing depth. The study was carried out in Lake Kuźnickie, a mesotrophic lake in Western Poland, hosting a stable and abundant population of L. barbatus. At shallow sites (0.5 – 4.0 m), L. barbatus revealed high variability in weight and branching of the thallus. The individuals were less elongated and produced less mature oogonia than those from deep sites (5.0 - 6.5 m). The latter were more homogeneous and characterised by significantly elongated thalli and high fertility. The first hypothesis was confirmed, while the second was falsified. We suggest that L. barbatus forms two phenotypes, one less variable and better adapted to deep waters and the other more variable and better adapted to shallow, more changeable environments. This rare macroalga may optimise resource allocation depending on environmental conditions and its phenotypic plasticity may be a key adaptation to global changes.

Image-guided core needle biopsy in the diagnosis of malignant lymphoma: comparison with surgical excision biopsy

PurposeThis study aimed to compare the efficacy and safety of image-guided core needle biopsy (CNB) with those of surgical excision biopsy (SEB) for the diagnosis of lymphoma, and to clarify the indication of CNB in clinical practice. MethodThis retrospective study included 263 image-guided CNB cases and 108 SEB cases that were performed at our institution between January 2014 and December 2018. The rate of patients with performance status of grade 1–4 was higher in the CNB group than in the SEB group (43.7% vs. 24.1%, P < 0.01). Waiting time to biopsy and diagnosis was shorter for CNB group than for SEB group (4 days vs. 7 days, 13 days vs. 15 days, P < 0.01). The rate of biopsy at the deep sites was higher in the CNB group than in the SEB group (53.2% vs. 8.3%, P < 0.01). Successful biopsy and complication rates were compared between the 2 groups. ResultsThere were no significant differences between the CNB and SEB groups in successful biopsy rates (89.0% vs. 93.5%, P = 0.25). The grade 3 complication rate was significantly lower for CNB group than for SEB group (0% vs. 4.6%, P < 0.01), although there was no significant difference in overall complication rates (4.9% vs. 6.5%, respectively, P = 0.61). ConclusionsCNB showed high diagnostic yield comparable to SEB for suspected lymphoma. CNB was especially recommended to the cases with low-PS, lesions in the deep sites, and requiring early pathological diagnosis.

Progress in the oxidative dehydrogenation of light alkanes to light olefins on metal-free catalysts

Light alkenes are the key building blocks in chemical industry. Dehydrogenation of light alkanes to light olefins offers an important route for the value-added utilization of alkanes and the diversification in olefin supplies. Featured with the free coking and no thermodynamic restriction, oxidative dehydrogenation of alkanes to olefins has attracted much attention. The early reported metal oxide catalysts usually have good activities, but tend to deeply oxidize olefins to CO2, leading to poor yield of olefin products. Later on, metal-free catalysts start to catch the eye. As a new estabilished catalytic system, metal-free boron-based catalysts show distinctive reaction characteristics of the high selectivity of olefins and the inhibition of deep oxidation reactions, as compared to metal-based catalysts. Hexagonal boron nitride ( h -BN) was first proved to be a highly active catalyst in the oxidative dehydrogenation reaction. Afterwards, some borides (e.g., SiB6, CB4) and supported boron catalysts have also been reported. The boron-based catalysts exhibit high activities and selevtivities to olefins with negligible formations of CO2, which provides a new sight in the selective cleavage of C–H bonds. In the combination of spectroscopic and kinetic analysis, the BO x species on the catalyst surface was determined as the active sites. The unique catalysis of boron-based catalysts updates the traditional perception on the alkane activation and has becoming a new hotspot worldwide. Besides, other metal-free catalysts, nanostructured carbon-based materials including carbon nanotubes, carbon nanofibers and nano-diamonds have also been shown a great potential in the dehydrogenation of light alkanes. The carbonyl/quinone groups are verified to be the active sites for dehydrogenation of light alkanes; the carboxyl, carboxylic anhydride and lactone groups could act as deep oxidative sites and cause the reduction of olefin selectivity. Moreover, doping of heteroatoms (B, P and N) into carbon matrix is effective for the improvement of olefin selectivity. This review timely highlights the recent developments of metal-free catalysts in the oxidative dehydrogenation of light alkanes, particulary focusing on the newly established boron-based catalytic system. At the end, we propose the perspective research directions of the dehydrogenation of light alkanes.

Hatchery technology restores the spawning ground of phytophilic fish in the urban river of Yangtze Estuary, China

Due to the concrete slope protection projects conducted around urban rivers in many megalopolises, increased attention has been paid to fish biodiversity losses accompanying urban development. Hatchery technology is a promising method for restoring fisheries where spawning substrates are degraded and/or lacking. In the current study, a Phragmites australis stereo artificial floating wetland (SAFW) was constructed in an urban river (Tuanwang River, Shanghai), and palm sheets were laid under the SAFW frame to imitate the spawning grounds for phytophilous fish. Fish species with five spawning types were distinguished from nineteen fish species in the study area. After viscid eggs were found to be attached to the palm sheets, the eggs were distinguished by the subunit of the mitochondrial cytochrome C oxidase I gene. All of the eggs belonged to six fish species: Culter ilishaeformis, Cyprinus carpio, Cyprinus auratus, Cultrichthys erythropterus, Rhodeus sinensis, and Hemiculter leucisculus. Cyprinus auratus and Cyprinus carpio accounted for the vast majority, and the number of these species was significantly greater than that of the other species. Dissolved oxygen and light intensity at the water surface were significantly higher than those at the deep water sites (p < 0.05), and all viscid eggs were inclined to be distributed at water depths of -0.5 and − 1.5 m. The results of redundancy analysis (RDA) showed that both water depth and dissolved oxygen were the main environmental variables in all spawning periods. The current study suggested that the relatively inexpensive P. australis SAFW was a useful hatchery technology for creating spawning grounds for phytophilous fish in urban rivers.

Foraminiferal community response to seasonal anoxia in Lake Grevelingen (the Netherlands)

Abstract. Over the last decades, hypoxia in marine coastal environments has become more and more widespread, prolonged and intense. Hypoxic events have large consequences for the functioning of benthic ecosystems. In severe cases, they may lead to complete anoxia and the presence of toxic sulfides in the sediment and bottom-water, thereby strongly affecting biological compartments of benthic marine ecosystems. Within these ecosystems, benthic foraminifera show a high diversity of ecological responses, with a wide range of adaptive life strategies. Some species are particularly resistant to hypoxia–anoxia, and consequently it is interesting to study the whole foraminiferal community as well as species-specific responses to such events. Here we investigated the temporal dynamics of living benthic foraminiferal communities (recognised by CellTracker™ Green) at two sites in the saltwater Lake Grevelingen in the Netherlands. These sites are subject to seasonal anoxia with different durations and are characterised by the presence of free sulfide (H2S) in the uppermost part of the sediment. Our results indicate that foraminiferal communities are impacted by the presence of H2S in their habitat, with a stronger response in the case of longer exposure times. At the deepest site (34 m), in summer 2012, 1 to 2 months of anoxia and free H2S in the surface sediment resulted in an almost complete disappearance of the foraminiferal community. Conversely, at the shallower site (23 m), where the duration of anoxia and free H2S was shorter (1 month or less), a dense foraminiferal community was found throughout the year except for a short period after the stressful event. Interestingly, at both sites, the foraminiferal community showed a delayed response to the onset of anoxia and free H2S, suggesting that the combination of anoxia and free H2S does not lead to increased mortality, but rather to strongly decreased reproduction rates. At the deepest site, where highly stressful conditions prevailed for 1 to 2 months, the recovery time of the community takes about half a year. In Lake Grevelingen, Elphidium selseyense and Elphidium magellanicum are much less affected by anoxia and free H2S than Ammonia sp. T6. We hypothesise that this is not due to a higher tolerance for H2S, but rather related to the seasonal availability of food sources, which could have been less suitable for Ammonia sp. T6 than for the elphidiids.

Spatial Epidemiology of the Stony-Coral-Tissue-Loss Disease in Florida

The stony-coral-tissue-loss disease has recently caused widespread loss of coral along the Florida reef tract. Yet little is known about where, when, and why this coral disease outbreak occurred. In the absence of a definitive pathogen, it is essential to characterize the ecology of the disease and document the spatio-temporal dynamics of the outbreak. Here, we investigate the epizootiology of the stony-coral-tissue-loss disease at multiple spatial and temporal scales along the Florida reef tract from May 2014 to December 2017. We used spatial interpolation to characterize the disease hotspots, Ripley’s K analysis to examine contagion, a spatio-temporal model to assess rates of spread, and a Bayesian model to examine ecological and environmental covariates that may have influenced the occurrence and severity of the outbreak. Our results show that the disease affected reefs at the scale of hundreds of kilometers, with significant clusters of up to 140 km. The epizootic clearly followed a contagion model, suggesting that the disease was highly contagious. The rate of spread of the epizootic was linear and moved slightly faster to the north (~ 100 m d-1) than to the south (~ 92 m d-1). The difference in rate of spread between the north and south direction may indicate currents facilitated transmission. The analyzed dataset showed that the epizootic affected at least 19 coral species and that deep and diverse sites were at greater risk of the disease than shallow and low diversity sites.

A 3800 yr paleoseismic record (Lake Hazar sediments, eastern Turkey): Implications for the East Anatolian Fault seismic cycle

The East Anatolian Fault (EAF) in Turkey is a major active left-lateral strike-slip fault that was seismically active during the 19th century but mostly quiet during the 20th century. Geodetic data suggests that the fault is creeping along its central part. Here we focus on its seismic history as recorded in the sediments of Lake Hazar in the central part of the EAF. Sediment cores were studied using X-ray imagery, magnetic susceptibility, grain-size, loss-on-ignition and X-ray fluorescence measurements. Recurring thin, coarse-grained sediment units identified as turbidites in all cores were deposited synchronously at two deep study sites. The turbidite ages are inferred combining radiocarbon and radionuclide (137Cs and 210Pb) dating in an Oxcal model. A mean recurrence interval of ∼190 yrs is obtained over 3800 yrs. Ages of the recent turbidites correspond to historical earthquakes reported to have occurred along the EAF Zone or to paleoruptures documented in trenches just northeast of Lake Hazar. The turbidites are inferred to be earthquake-triggered. Our record demonstrates that Lake Hazar has been repeatedly subjected to significant seismic shaking over the past 3800 yrs. The seismic sources are variable: ∼65% of all turbidites are associated with an EAF source. The seismic cycle of central EAF is thus only partly impacted by creep.

Combined chronological and mineral magnetic approaches to reveal age variations and stratigraphic heterogeneity in the Yangtze River subaqueous delta

Delta deposits show large spatial heterogeneity in terms of depositional rate and age, which is critical to the study of delta erosion in response to the declining fluvial sediment load observed at many river mouths in the world. In this study, we show that the magnetic susceptibility (χ) can be an indicator to reveal age variations and stratigraphic heterogeneity in the Yangtze River subaqueous delta. Ages of three short sediment cores (<2 m) collected at 20–32 m water depth from the Yangtze River subaqueous delta were determined using 210Pb, 137Cs, and optically stimulated luminescence (OSL) dating. In addition, depth variation of χ, which is influenced by post-depositional diagenesis and hence age, was used to roughly infer sediment ages among the cores in a simple way. The profiles of 210Pb, 137Cs, and OSL dating results indicate the spatial variability of ages, ranging from the last 100 years to >1700 years. The cores at shallow water depths are younger than those from deeper sites. Modern deposits (i.e., <100 years old) occur primarily at water depths shallower than ca. 30 m. The core in the northern part of the subaqueous delta shows much older ages than the core at the southern site with similar water depth, which is caused by their longer distance relative to the mouth of active sediment discharge distributary. Profile of χ confirms such spatial variation of ages in terms of depth distribution pattern and χ value. Older sediments (>800 a) show lower and uniform χ values due to the reductive dissolution of ferrimagnetic minerals, while younger sediments (<350 a) show higher χ values in the top layer but they decline with increasing depth. Considering the quick way of magnetic measurement, stratigraphic correlation based on χ can be used first to screen for cores before they are subjected to more detailed dating. This study shows that the methodological approach of combining sediment dating with magnetic measurement has great potential in revealing heterogeneous deltaic deposits.

Coke Size Degradation and Its Reactivity Across the Tuyere Regions in a Large-Scale Blast Furnace of Hyundai Steel

It has been well recognized that coke samples can be effectively taken out of working blast furnaces using a drilling machine at the tuyere level. The core represents samples with different temperature profiles at various tuyere regions of a large blast furnace. The average coke size at the tuyere level is known to be about 50 pct smaller than the charged cokes. Using fixed bed reactor and XRD techniques, the cokes sampled were studied for CO2 reactivity and crystallinity, respectively. The apparent reaction rate of coke rapidly increases in the raceway zone, followed by a decrease as the samples are taken at deeper sites in the furnace where the Fe2O3 and CaO contents are high in the bosh and raceway zones in the high temperature regions. In this study, samples extracted at the tuyere level of a large blast furnace were examined to characterize the coke size degradation and the effect of coke graphitization on the reactivity and fines generation at various locations around the tuyere level.

Exceptionally high heat flux needed to sustain the Northeast Greenland Ice Stream

Abstract. The Northeast Greenland Ice Stream (NEGIS) currently drains more than 10 % of the Greenland Ice Sheet area and has recently undergone significant dynamic changes. It is therefore critical to accurately represent this feature when assessing the future contribution of Greenland to sea level rise. At present, NEGIS is reproduced in ice sheet models by inferring basal conditions using observed surface velocities. This approach helps estimate conditions at the base of the ice sheet but cannot be used to estimate the evolution of basal drag in time, so it is not a good representation of the evolution of the ice sheet in future climate warming scenarios. NEGIS is suggested to be initiated by a geothermal heat flux anomaly close to the ice divide, left behind by the movement of Greenland over the Icelandic plume. However, the heat flux underneath the ice sheet is largely unknown, except for a few direct measurements from deep ice core drill sites. Using the Ice Sheet System Model (ISSM), with ice dynamics coupled to a subglacial hydrology model, we investigate the possibility of initiating NEGIS by inserting heat flux anomalies with various locations and intensities. In our model experiment, a minimum heat flux value of 970 mW m−2 located close to the East Greenland Ice-core Project (EGRIP) is required locally to reproduce the observed NEGIS velocities, giving basal melt rates consistent with previous estimates. The value cannot be attributed to geothermal heat flux alone and we suggest hydrothermal circulation as a potential explanation for the high local heat flux. By including high heat flux and the effect of water on sliding, we successfully reproduce the main characteristics of NEGIS in an ice sheet model without using data assimilation.

Behavioural maintenance of highly localised jellyfish (Copula sivickisi, class Cubozoa) populations

The medusae of cubozoan jellyfishes have sophisticated behaviours and are strong swimmers. Therefore, they have the potential to influence their distribution and connectivity among populations. We used ecological and behavioural data in combination with local oceanography to estimate the potential of medusae in the cubozoan Copula sivickisi to disperse from local populations at scales of hundreds of meters to kilometres. The distribution of C. sivickisi was mapped on a fringing reef at Magnetic Island, Queensland, Australia, with underwater jellyfish camera units (JCams). The availability of reef habitat, dominated by Sargassum sp. algae and coral, had a significant effect on the abundance of medusae. Medusae were 11–7 times more abundant at shallow (≤ 4.1 m) and mid-depth (4.2–7 m) sites with high to moderate habitat availability, compared to deep sites (≥ 7.1 m) where habitat availability was low. Further, medusae were absent at sites far from suitable habitat, both alongshore and in deeper waters. Medusae displayed preferential habitat selection. They were found low in the water column near reefs in depth stratified plankton tows and they preferentially attached to Sargassum in a habitat choice experiment. The swimming speeds of C. sivickisi medusae were determined experimentally and were equivalent to or faster than most of the current speeds measured where the populations occured. The results suggested that medusae can attach to habitat and swim against currents to maintain positions on reefs, thereby restricting dispersal. Incipient speciation is highly likely within the species’ cosmopolitan distribution.

Variation in the Occurrence of fimA Genotypes of Porphyromonas gingivalis in Periodontal Health and Disease.

Porphyromonas gingivalis is regarded as a “keystone pathogen” in periodontitis. The fimbria assists in the initial attachment, biofilm organization, and bacterial adhesion leading to the invasion and colonization of host epithelial cells. The present study aimed to investigate the occurrence of fimA genotypes in patients with chronic periodontitis and healthy individuals in the Indian population, and to study their association with the number of P. gingivalis cells obtained in subgingival plaque samples of these subjects. The study comprised 95 samples from the chronic periodontitis (CP) group and 35 samples from the healthy (H) group, which were detected positive for P. gingivalis in our previous study. Fimbrial genotyping was done by PCR and PCR-restriction fragment length polymorphism (RFLP). The fimA type II was more prevalent in the CP group (55.89%), followed by type IV (30.52%), whereas in the H group, type I was the most prevalent fimbria (51.42%). The quantity of P. gingivalis cells increased with the presence of fimA types II and III. Our results suggest a strong relationship between fimA types II and IV and periodontitis, and between type I and the healthy condition. The colonization of organisms was increased with the occurrence of type II in deep periodontal sites, which could play an important role in the progression of the disease.

Violence begetting violence: An examination of extremist content on deep Web social networks

Several incidents of mass violence in 2019 were preceded by manifestoes posted to deep Web social media sites by their perpetrators. These sites, most notably 4chan and 8chan, are buried in the deep Web, away from the neutralizing effects of broad public discourse. Many of the posts to these sites reference earlier extremist incidents, and indeed the incidents themselves mimic aspects of previous attacks. Building on previous research, this paper examines these deep Web social media sites. Through an analysis of traffic and posts, we confirm that these sites often act as a self-reinforcing community of users encouraging each other to violence, and we map a statistically significant rise in &amp;rdquo;post volume&amp;rdquo; on these sites immediately following terrorist attacks.

Photocurrent Response in Ambipolar Transistors Based on Single Laterally Stacked Crystals: The Role of Charge Trapping and Release

Organic semiconductors are currently implemented in photoresponsive devices due to their versatility. The aim of this study was to investigate the photoresponsive properties of an ambipolar field-effect transistor with only one laterally stacked C8-BTBT/PTCDI-C5 semiconductor crystal wire prepared using solution processing and mechanical cutting. The photoresponsive characteristics of the device were investigated under different irradiance levels, and the photogating effect was found to be the major contributor to the photocurrent. From the dynamic response of the device under light pulses, it was found that the trapping and release processes are dependent on the irradiance. A mathematical description of the dynamic response was proposed based on the trapping and release of photogenerated holes at deep and shallow trap sites with two discrete energy levels. Although the trapped charge density and trapping rates in the shallow traps exhibited expected trends under different irradiances, the charges in the deep traps exhibited anomalous irradiance dependence. On the basis of the findings, a description for the trapping behavior in the laterally stacked C8-BTBT/PTCDI-C5 system was proposed, and the usefulness of the simple kinetic model of trapping and release was analyzed.

Deep trap sites suppressing space charge injection in polycyclic aromatic compounds doped XLPE composite

In this study, the space charge characteristics in the polycyclic aromatic compounds doped cross-linked polyethylene (XLPE) composite were analysed by integration current (Q(t)) method and quantum chemical calculation. Experimentally, the space charge behaviours of XLPE composites modified by the three selected polycyclic aromatic compounds during polarisation and depolarisation process at 25 and 80°C were measured by Q(t) method, respectively. The energy levels and 3D potential distributions of the three polycyclic aromatic compounds were calculated by density functional theory. The experimental and calculation results indicate that the polycyclic aromatic compound C with deep carrier traps and stronger polarity exhibits outstanding ability to reduce space charge injection than the others at both 25 and 80°C. Generally, 4,4′-bis (dimethyl amino) benyil has great potential as the organic additive for DC cable insulation from the view of space charge suppression.

Spatio-Temporal Assessment of Quarry Sites in Mpape, Abuja, Nigeria

The study mapped and analyzed spatiotemporal variability of quarry sites in Mpape District, Bwari Area Council of Abuja. The study used high-resolution IKONOS satellite image, ASTERDEM and Hi-Target Differential GNSS receivers. The result showed that nine quarry sites exist in Mpape with three abandoned and six are active while three are located in the center of Mpape with one active and two abandoned. The depth analysis revealed that the deepest site is 25 m at Julius Berger quarry site and the lowest depth was 6 m at Dantata quarry site. The study also reveals that the rocky surfaces has the highest elevation and are located in the upper and lower region of Mpape. The quarry sites and settlement are located on a high elevation ground. Importantly, the study revealed that the derelict ponds were formed because of rigorous quarry activities, since there are no tributaries connecting each of the derelict ponds. The buffer analysis carried out at 100 and 150 m distances revealed that settlements are already engulfing the three quarry sites located at the core center of Mpape. Also, Chinese quarry site has been encroached, while the other six do not have settlement contiguous to them at 100 and 150 m buffer distances.