Bottom Time Research Articles

3D Printed Stent from Graphene-Polyethylene Glycol Diacrylate Using Digital Light Processing Technique

Abstract This paper presents the development of the photocurable resin material based on the graphene reinforced polyethylene glycol diacrylate (gPEGDA) for vascular stent fabrication using a commercial 3D printer. 3D printing with digital light processing (DLP) technique is an attractive alternative for low-cost fast fabrication with high accuracy. Four photocurable resin compositions were prepared by mixing PEGDA and varied composition of graphene and the photoinitiator according to the design of experiment of 22 full factorial design. The diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (TPO) photoinitiator was adopted to meet the required 405 nm UV-light source wavelength of the 3D printer for stent fabrication. Material characterization of the UV-absorbance and viscosity tests were conducted and optimized to obtain resin printability. Mechanical characteristics tests were conducted to obtain the best resin composition for stent application. For this purpose, the tensile tests were conducted according to the ASTM D638 standard using the type-V specimen size. The test specimens were 3D printed with varied UV exposure time 20 and 30 seconds. Finally, the stents were successfully fabricated using a commercial 3D printer DLP with the bottom parameter time setting of 60 seconds, and the UV exposure time of 30 seconds. The resin material was applicable for 3D printing of the stent. The result has shown that 3D printer with DLP technique is suitable for stent fabrication with excellent surface quality. Moreover, the innovative bioresorbable stent materials and fabrication approach could open up new possibilities in the development of medical devices, particularly in the treatment of vascular diseases.

Breath-hold capacities and circadian dive rhythmicity shape optimal foraging strategies in a polar marine mammal, the Weddell seal (Leptonychotes weddellii)

Air-breathing vertebrates must balance their response to diel shifts in prey accessibility with physiological thresholds and the need to surface after each dive. Weddell seal (Leptonychotes weddellii) dive behaviors were tracked across the year under rapidly-changing light regimes in the Ross Sea, Antarctica ( ~ 75-77°S). This provides a ‘natural experiment’ with free-living seals experiencing 24-hrs of light (Polar Day), light/dark cycling, and continuous darkness (Polar Night). The Weddell seal’s temporal niche switches from nocturnal diving in the summer to diurnality for the remainder of the year. Rhythmicity in dive efforts (depth, duration, post-dive surface recuperation, bottom time, and exceeding physiologic thresholds) is stronger and more closely circadian during times of the year with light/dark cycling compared with Polar Day or Night. With light/dark cycling, animals also make the most extreme dives (those that far exceed the calculated aerobic dive limit, cADL) significantly earlier than solar noon. Offsetting the longest dives that require longer surface recuperation times from mid-day allows animals to maximize total dive time under high-light conditions conducive for visual hunting. We identify an optimal foraging strategy to exploit a diel preyscape in a highly-seasonal environment, while balancing tradeoffs imposed by physiological thresholds in a diving mammal.

Association between current of injury and intraoperative R wave amplitude fluctuation immediately after active fixation pacing lead implantation

Abstract Background Active fixation lead stability and pacing threshold adequacy are predictable from assessment of current of injury (COI) prevalence. However, time courses of R wave amplitude value immediately after implantation varies despite of COI prevalence. Objective This study aims to clarify whether intraoperative R wave amplitude fluctuation is associated with COI, and the adequacy assessment is possible. Methods Consecutive recipients of active fixation lead implanted to right ventricular (RV) septum from April to November 2023 were enrolled. R wave amplitude values automatically measured by programmer were continuously recorded from immediately after implantation to generator connection. The final R wave amplitude value greater than 4 mV was determined as implantation success. The successful implantation time courses of R wave amplitude value classified into following three types (Figure 1): (1) the Dipper type; R wave amplitude transiently decreases to the bottom value and then increases, (2) the Riser type; R wave amplitude shows a upward trend (no decline) for the first 5 minutes after active fixation, and (3) the other type. The primary outcome was prevalence of favorable amplitude increase defined as the final R wave amplitude value exceeding that of immediately after the active fixation. Results Among 106 of RV lead implantations in 78 consecutive pacemaker recipients, 73 successful implantation records were evaluated (5 missing data and 28 unsuccess implantations). According to the continuous R wave amplitude records, 51 and 19 successful implantation time courses could be classified into the Dipper and Riser types, respectively. In the Dipper type, the median screw-in to bottom time (SBT) was 5 (interquartile range: 5–12) minutes, and then R wave amplitude improved to mean of 1.7 ± 0.6 times higher than the bottom value. The electrogram (EGM) immediately after active fixation showed R wave < COI pattern, and gradually changed to R wave > COI pattern by the withdrawal of COI over time. Among them, 26 implantations showed favorable amplitude increases and significantly shorter SBT than the remaining implantations (6 ± 4 minutes vs. 10 ± 5 minutes, P=0.03). The ROC analysis showed the predictive cut-off value of SBT for favorable amplitude increase was 6 minutes (AUC:0.73, sensitivity:0.81, specificity:0.60). In the Riser type, acceptable R wave amplitude and R wave > COI pattern EGM were consistently recorded, and finally obtained the favorable amplitude increase in all implantations. Conclusion More than 95% of R wave amplitude fluctuation patterns immediately after successful lead implantation could be classified as the Dipper or Riser types. The mechanism might be associated with a competition among R wave amplitude and COI magnitude, and the prediction of favorable R wave amplitude increase might be possible by the EGM patterns obtained immediately after active lead fixation and the subsequent 5–6 minutes of observation.Success implantation time coursesClinical implication

Background predation risk induces anxiety-like behaviour and predator neophobia in zebrafish

Prey face a major challenge in balancing predator avoidance with other essential activities. In environments with high risk, prey may exhibit neophobia (fear of novelty) due to the increased likelihood of novel stimuli being dangerous. The zebrafish, Danio rerio, is an established model organism for many scientific studies. Although spatial and object neophobia in zebrafish have received previous attention, little is known about the role of background risk in inducing neophobia in zebrafish. Here, we present two experiments using zebrafish to explore whether background predation risk can induce anxiety-like behaviour in a novel environment and neophobic responses when exposed to a novel odour. Over five days, we repeatedly exposed zebrafish to either high background risk in the form of chemical alarm cues (i.e., injured conspecific cues that indicate a predator attack) or a low-risk water control stimulus. In Experiment 1, when tested in a novel tank, zebrafish exposed to high predation risk displayed anxiety-like responses (reduced activity and increased bottom time spent) compared to their low-risk counterparts. Moreover, high-risk individuals showed reduced intra-session habituation to the novel tank compared to low-risk individuals. In Experiment 2, high-risk individuals exhibited fear responses toward a novel odour, unlike low-risk individuals. These results reveal that short-term repeated exposures to high risk can induce anxiety-like behaviour and predator odour neophobia in zebrafish.

A novel method of computation for anchorage length based on the propagation characteristics of anchor excitation stress wave

ABSTRACT Detecting the anchoring length is an integral part of the quality inspection of the bolt anchoring, which is crucial to the safety of the roadway support. This paper studies the influence of the anchoring length on the propagation characteristics of the exciting stress wave of the bolt. The research finds that the change in the anchoring length affects the attenuation rate and frequency distribution of the stress wave signal amplitude. Under the same test conditions, the anchoring length negatively correlates with the consolidation wave velocity. The VMD analysis and processing method decomposes the original detection signal once or the characteristic mode function twice. The bottom reflection time is obtained from the bottom reflection signal identified according to the decomposed mode function. Based on the propagation characteristics of the exciting stress wave in the anchor rod, a method of calculating the anchoring length using the bottom reflection time is proposed. Experimental verification of anchoring models for different anchoring lengths is carried out. The calculated results are consistent with the actual anchoring length; the longer the length, the smaller the relative error. The error rate meets the accuracy requirements of on-site engineering tests and guarantees safe production.

Adsorption of Methylene Blue using Bottom Ash: Experimental Design, Isotherm Analysis, and Optimum Conditions

<p><span lang="EN-US" style="font-size:12.0pt"><span style="line-height:107%"><span style="font-family:"Times New Roman",serif"><span style="color:black">This study investigated the removal of methylene blue (MB) via adsorption using waste bottom ash.  The bottom ash, sourced from a waste storage site in the Çorlu district of Tekirdağ province, Thrace Region, was utilized as the adsorbent. The research examined the impact of several variables on MB removal, including bottom ash dosage, pH, contact time, and agitation speed. It was found that all parameters had a single-variable effect, while pH exhibited a quadratic effect on MB removal in a model-based analysis. The optimization of the model for maximum MB removal identified the optimal conditions as 0.978 g bottom ash dosage, pH 3, 15 minutes of adsorption time, and 50 rpm agitation speed. Under these conditions, the model predicted an MB removal efficiency of 71%, which was experimentally confirmed to be 72.5%. The adsorption process was found to fit with the Freundlich isotherm, indicating a multilayer adsorption mechanism on the heterogeneous surface of the adsorbent. This research not only highlights the feasibility of using bottom ash from coal combustion as an economical adsorbent for dye-contaminated wastewater but also underscores its potential to inform and inspire future studies on waste recycling and wastewater treatment. </span></span></span></span></p>

Hydraulic modeling study and control algorithm design of double-layer pipe dual-gradient drilling

Deepwater drilling has the problem of narrow safe density window, and double-layer pipe dual-gradient drilling is one of the effective ways to solve the narrow safe density window. Due to the different structure and process principle with MPD, there is an urgent need to establish the hydraulic model and control algorithm of double-layer pipe dual-gradient drilling in order to realize the normal regulation of bottom hole pressure during drilling. Based on the hydraulic theory of managed pressure drilling and considering the influence of the three-channel structure of double-layer pipe and the downhole hydraulic lift pump in double-layer pipe dual-gradient drilling, a hydraulic model of double-layer pipe dual-gradient drilling has been established and verified in land well tests. Based on the double-layer pipe dual-gradient drilling hydraulic model, a control algorithm based on pressure regulation and flow rate regulation is established considering the principle of double-layer pipe dual-gradient drilling process. The simulation results show that the control algorithm based on flow rate regulation can greatly reduce the bottom hole pressure regulation time by controlling the size of the flow rate of the return fluid. When the bottom hole pressure is increased from 25 MPa to 26 MPa, the regulation time is 11min, which basically meets the requirements of field operation. The hydraulic model and control algorithm of double-layer pipe dual-gradient drilling are favorable to the bottom hole pressure regulation during drilling and reduce the response time.

Arctic puzzle: Pioneering a northern shrimp (Pandalus borealis) habitat model in Disko Bay, West Greenland

Recent advancements in spatial modelling leverage remote sensing data and statistical species-environment relationships to forecast the distribution of a specific species. Our study focuses on Disko Bay in West Greenland, recognized as a significant marine biodiversity hotspot in the region. We conducted comprehensive analyses using multiple datasets spanning from 2010 to 2019, incorporating shrimp and fish surveys, commercial shrimp fishery catches, high-resolution (25 × 25 m) multibeam bathymetry and backscatter data along with a medium-resolution (200 × 200 m) bathymetric model, measured and modelled oceanographic data, and satellite chlorophyll data. Through multivariate regression analysis, we tested the significance of various physical factors (seafloor depth, sediment class, bottom water temperature, bottom water salinity, bottom current velocity, space, and time), biological factors (chlorophyll a, Greenland halibut (Reinhardtius hippoglossoides)), and anthropogenic impact (shrimp fishery; standardized catch per unit effort) on the density of northern shrimp in the area. Our results indicate a significant association between northern shrimp density, seafloor depth, and sediment class, explaining 36 % of the variation in shrimp density. Subsequently, we developed a high-resolution (optimized) spatial linear mixed–effect model to map the distribution of northern shrimp across Disko Bay, representing the first model of its kind developed for an Arctic area. The optimal habitat for northern shrimp is characterized by medium-deep waters (approximately 150–350 m), turbulent conditions, and mixed sediments, predominantly located in the northern and southern regions of Disko Bay. Notably, the northern region hosts a relatively diverse benthic community, with northern shrimp and sponges as the primary contributors of epibenthic biomass. This novel high-resolution model significantly enhances our understanding of the physical drivers and detailed spatial patterns influencing the distribution of northern shrimp in the Arctic.

Multiobjective Optimization of Stereolithography for Dental Bridge Based on a Simple Shape Model Using Taguchi and Response Surface Methods

Stereolithography (SLA) has become an essential photocuring 3D printing process for producing parts of complex shapes from photosensitive resin exposed to UV light. The selection of the best printing parameters for good accuracy and surface quality can be further complicated by the geometric complexity of the models. This work introduces multiobjective optimization of SLA printing of 3D dental bridges based on simple CAD objects. The effect of the best combination of a low-cost resin 3D printer’s machine parameter settings, namely normal exposure time, bottom exposure time and bottom layers for less dimensional deviation and surface roughness, was studied. A multiobjective optimization method was utilized, combining the Taguchi method with response surface methodology and the desirability function technique. The predicted optimal values for the cube’s dimensional deviation and surface roughness were 0.0517 mm and 2.8079 µm, respectively. The experiments’ validation of the findings confirmed the results, which were determined to be 0.0560 and 0.064667 mm and 2.770 and 2.6431 µm for the dimensional deviation and surface roughness for the cube and bridge, respectively. The percentages of prediction errors between the predicted optimum results and the printed response were 7.68% and 1.36% for dimensional deviation and surface roughness, respectively. This study demonstrates that the robust method used produced a dental bridge with good accuracy and a smooth surface.

Fluoxetine rescues the depressive-like behaviour induced by reserpine and the altered emotional behaviour induced by nicotine withdrawal in zebrafish: Involvement of tyrosine hydroxylase.

Nicotine cessation leads to anxiety and depression. The suitability of the zebrafish model of anhedonia using reserpine and fluoxetine was evaluated. Fluoxetine was also used to reduce nicotine withdrawal-induced anhedonic state. Zebrafish were exposed to reserpine (40 mg/l) and then to fluoxetine (0.1 mg/l) for 1 week. Anhedonia was evaluated in the Novel Tank Diving and Compartment Preference tests. Another group was exposed to nicotine (1 mg/l/2 weeks) and then exposed to fluoxetine. Anxiety and anhedonia were evaluated 2-60 days after. Tyrosine hydroxylase (TH) immunoreactivity and microglial morphology (labelled by 4C4 monoclonal antibody) in the parvocellular pretectal nucleus (PPN), dorsal part, and of calcitonin gene-related peptide (CGRP) in the hypothalamus were also analysed. Less time in the top and increased latency to the top in reserpine compared to a drug-free group was found. Fluoxetine rescued reserpine-induced the reduced time in the top. Seven and 30 days after nicotine withdrawal more time in the bottom and similar time in the Compartment Preference test, rescued by fluoxetine, were shown. In the PPN, 30-day withdrawal induced an increase in TH immunoreactivity, but fluoxetine induced a further significant increase. No changes in PPN microglia morphology and hypothalamic CGRP were detected. Our findings validate the suitability of the zebrafish model of anhedonia using the reserpine-induced depression-like behaviour and the predictivity using fluoxetine. Fluoxetine rescued nicotine withdrawal-induced anhedonic state, opening the possibility to screen new drugs to alleviate anxiety and depression in smokers during abstinence.

Characterizing Antarctic air-breathing predator dive patterns on a common prey base from stationary echosounders

Diving patterns of air-breathing predators were monitored from three moored subsurface upward-looking echosounders. Complete and partial dive profiles were visible on active acoustic records as echoes that started and/or returned to the surface. Dive metrics: maximum dive depths, durations, and wiggle count were measured and angles, distances, and velocities, were calculated at each site. Dive shapes ‘U’, ‘V’ and ‘W’ were derived using the number of wiggles and the percentage of dive bottom time. Dive profiles were classified into four types with type 1 dives being short in total duration and distance, low velocities, small angles, shallow, and linked to ‘U’ and ‘W’ shapes. Type 2 dives were short in distance, had low velocities, shallow depths, and were linked to ‘V’ dives. Dive types 3 and 4 had higher velocities, larger angles, longer total durations, and were deeper than types 1 and 2. Observed dive types could correspond to travelling, exploring, and foraging predator behaviors. Significant predator-prey overlaps occurred with predator dive profile counts correlated with krill aggregation thickness, density, and depth. This study demonstrates the utility of using stationary active acoustics to identify predator dive profiles with a simultaneous characterization of the potential prey field.

High‐resolution diving data collected from foraging area reveal that leatherback turtles dive faster to forage longer

AbstractDespite multiple studies examining the diving behavior of leatherback sea turtles (Dermochelys coriacea) at coarse resolution over broad distances, there is still a paucity of high‐resolution diving data collected in areas where foraging has been confirmed. Short‐term (~1–3 h) deployments of suction cup tags with time–depth recorders (TDRs) on 10 free‐swimming leatherback turtles in a foraging area off Nova Scotia, Canada during August and September (2007–2014), captured a total of 161 dives. High‐resolution (1–5 s sampling rate) dive profile data indicated variability in diving behavior between and within individuals. On average, turtles spent 55.7% of their time diving and 44.3% at the surface. Turtles generally performed short (mean duration = 250.4 s [SD = 47.9 s]) and shallow dives (mean depth = 24.3 m [SD = 5.8 m]). We recorded a mean dive descent rate of 0.32 m/s, which is faster than values recorded for leatherbacks in tropical waters. This may reflect differences in environment, behavioral mode (e.g., foraging vs. inter‐nesting), and body condition. Linear mixed‐effects models suggest a significant positive correlation between descent rate and mean depth, maximum depth, and integrated vertical bottom movement (IVBM). Turtles with faster descent rates dove deeper and increased their predicted foraging behavior (IVBM, or the sum of absolute differences in depth changes while at the bottom portion of their dives). Models additionally showed that dive time, bottom time, and IVBM were all positively correlated to the post‐dive surfacing. This suggests that turtles required more time at the surface to recover and/or handle prey following longer dives characterized by increased vertical movement at the bottom portion of the dive. Dives were complex; the application of standard dive type/shape analysis may be over‐simplified and inappropriate for leatherbacks foraging in these habitats. These results portray a novel and detailed look at the foraging dynamics of a diving marine reptile.

Behavioral Study of 3- and 5-Halocytisine Derivatives in Zebrafish Using the Novel Tank Diving Test (NTT)

Anxiety is a serious mental disorder, and recent statistics have determined that 35.12% of the global population had an anxiety disorder during the COVID-19 pandemic. A mechanism associated with anxiolytic effects is related to nicotinic acetylcholine receptor (nAChR) agonists, principally acting on the α4β2 nAChR subtype. nAChRs are present in different animal models, including murine and teleosteos ones. Zebrafish has become an ideal animal model due to its high human genetic similarities (70%), giving it high versatility in different areas of study, among them in behavioral studies related to anxiety. The novel tank diving test (NTT) is one of the many paradigms used for studies on new drugs related to their anxiolytic effect. In this work, an adult zebrafish was used to determine the behavioral effects of 3- and 5-halocytisine derivatives, using the NTT at different doses. Our results show that substitution at position 3 by chlorine or bromine decreases the time spent by the fish at the bottom compared to the control. However, the 3-chloro derivative at higher doses increases the bottom dwelling time. In contrast, substitution at the 5 position increases bottom dwelling at all concentrations showing no anxiolytic effects in this model. Unexpected results were observed with the 5-chlorocytisine derivative, which at a concentration of 10 mg/L produced a significant decrease in bottom dwelling and showed high times of freezing. In conclusion, the 3-chloro and 3-bromo derivatives show an anxiolytic effect, the 3-chlorocytisine derivative being more potent than the 3-bromo derivative, with the lowest time at the bottom of the tank at 1mg/L. On the other hand, chlorine, and bromine at position 5 produce an opposite effect.

A Review of the Stereo lithography 3D Printing Process and the Effect of Parameters on Quality

Stereo lithography (SLA) three-dimensional (3D) printing process is a type of additive manufacturing techniques that uses digital models from computer-aided design to automatically produce customized 3D objects. Around 30 years, it has been widely utilized in the manufacturing, design, engineering, industrial sectors and its applications in dentistry for manufacturing prosthodontics are very important. The stereo lithography technology is highly regarded because it can produce items with excellent precision especially when selecting the best process parameters. This review article offers a useful and scientific summary of SLA three-dimensional printing technology and its brief history. The specific type of 3D printers which is SLA type based on light curing resin and material overview is also presented. Moreover, the survey was conducted to gain substantial knowledge of the various advantages and disadvantages of SLA 3D printing. According to this study, a summary has been specified on the accuracy of SLA 3D printers and various factors that affected its accuracy and dimension measurement namely layer thickness, normal exposure time, bottom or top exposure time, post processing and room temperature. The majority of works in the literatures conducted till date are on improving the physical part attributes like dimensional accuracy and surface roughness but the improving of the mechanical properties have received less attention and need more focusing in the future works.

Development of 3D DLP Printed Sustained Release Ibuprofen Tablets and Their Pharmacokinetic Evaluation in Rats.

The objective of the present study was to develop digital light processing (DLP) 3D printed sustained release ibuprofen (IBU) tablets using 3D DLP printers for evaluation in in vitro release and in vivo pharmacokinetic studies with their in vitro-in vivo correlation. The resin formulation and printing parameters were optimized using quality by design (QbD) approach, and IBU tablets were printed using DLP printers which works at 385 and 405nm wavelengths. Our results demonstrated that formulation consisting of polyethylene glycol diacrylate (PEGDA) 700, water, IBU, and riboflavin printed at 40-s bottom layer exposure time and 30-s exposure time produced tablets using both 385 and 405nm wavelengths. In vitro dissolution studies showed > 70% drug release at the end of 24h when printed at 405nm wavelength with no significant difference between tablets printed at 385nm. In vivo pharmacokinetic evaluation of the optimized 3D printed tablets printed at 405nm at oral dose of 30mg/kg in rats showed sustained release of IBU with significantly (p < 0.05) higher Cmax of 30.12 ± 2.45µg/mL and AUC(0-24h) of 318.97 ± 16.98 (µg/mL × h) compared to marketed IBU tablet (control). In vivo-in vitro correlation studies showed 80% of drug was absorbed in vivo within 3h from the pulverized 3D printed tablet, whereas intact 3D tablet showed sustained release of IBU with > 75% IBU release in 24h in vitro. Overall, IBU tablets fabricated using DLP printing demonstrated sustained release and enhanced systemic absorption with no significant difference in their release profile at different wavelengths.

Combined effects of climatic change and hydrological conditions on thermal regimes in a deep channel-type reservoir

The thermal regime in large reservoirs plays a significant role in the water quality and ecosystem succession; however, little is known about the impacts of regional climate changes and hydrological conditions on a sizeable stratified reservoir with strong inflow conditions, i.e., the Xiangjiaba Reservoir. Using measured data from 2014 to 2018, the monthly and seasonal variations of the water temperature, thermal stability, and their influencing factors were addressed by using empirical models. The results showed substantial variability and seasonality in the reservoir water temperature, which correlated highly with the air temperature, inflow water temperature, and discharge. Correspondingly, there was a seasonal varying thermal stratification in the reservoir's yearly cycle, with its duration being up to 4 ~ 5months, the maximum surface-bottom water temperature difference being up to 7 ~ 10°C. There were significant positive correlations between Schmidt's stability index of the thermal structure and inflow-reservoir temperature difference and the surface-bottom temperature differences, while negative correlations with large discharge. Moreover, the inflow tends to influence thermal stability by retaining hypolimnion cold water, with its maximum bottom hysteresis residence time being up to ~ 4months. Research findings indicated that climate warming in the recent 30years (1988 ~ 2017) would cause a 0.213°C/decade and 0.153kJ/m2/decade increase in reservoir surface water temperature and Schmidt's stability index, respectively. Among these variations, the inflow temperature increase caused by climate change accounted for the largest proportion, i.e., 0.16°C/decade and 0.115kJ/m2/decade. Therefore, climate warming significantly affected the thermal regimes in this large reservoir, and the inflow water temperature increase due to warm air was the main factor altering the reservoir's thermal structure. Findings from the present study provide a fresh perspective on how to best optimize the deep channel-type reservoirs' water quality in the face of anticipated climate change.

Internal solitary waves enhancing turbulent mixing in the bottom boundary layer of continental slope

The importance of internal solitary waves (ISWs) to the energy and material transport in the upper ocean has been confirmed, but how ISWs affect turbulent mixing in the bottom boundary layer is lack of direct field observation. To reveal the characteristics of ISWs and the turbulent mixing they cause in the bottom boundary layer, a 36-h fine-scale observation of ISWs and their influence on turbulent mixing was conducted at the South China Sea slope (water depth: 659 m). During the observation, a group of ISWs passed by with horizontal and vertical velocities of 0.2 and 0.04 m/s at 0.1 m above bottom (mab) respectively, resulting in strong velocity shear exceeding 0.5 m/s per meter. When the ISWs passed through the slope, although they did not deform and break near the seabed, they increased the bottom shear stress, turbulent kinetic energy production rate and turbulent kinetic energy dissipation rate ( ε ) at 0.6 mab several times. The ISWs induced ε reached O (10 −6 ) W/kg, which was one order of magnitude higher than the previously observed ε in the upper ocean of the South China Sea slope. At the same observation site, the internal tides induced ε in the bottom boundary layer was O (10 −5 ) W/kg, which indicated that the internal tides played a more important role than the ISWs in enhancing bottom turbulent mixing. • Direct observation reveals strong internal solitary waves near seabed of slope. • Solitary waves cause strong velocity (0.2 m/s) near seabed at depth of 659 m. • Internal solitary waves increase bottom layer turbulent mixing several times.

The Effect of Bottom Ash Ball-Milling Time on Properties of Controlled Low-Strength Material Using Multi-Component Coal-Based Solid Wastes

As the conventional disposal method for industrial by-products and wastes, landfills can cause environmental pollution and huge economic costs. However, some secondary materials can be effectively used to develop novel underground filling materials. Controlled low-strength material (CLSM) is a highly flowable, controllable, and low-strength filling material. The rational use of coal industry by-products to prepare CLSM is significant in reducing environmental pollution and value-added disposal of solid waste. In this work, five different by-products of the coal industry (bottom ash (BA), fly ash, desulfurized gypsum, gasification slag, and coal gangue) and cement were used as mixtures to prepare multi-component coal industry solid waste-based CLSM. The microstructure and phase composition of the obtained samples were analyzed by scanning electron microscopy and X-ray diffraction. In addition, the particle size/fineness of samples was also measured. The changes in fresh and hardened properties of CLSM were studied using BA after ball milling for 20 min (BAI group) and 45 min (BAII group) that replaced fly ash with four mass ratios (10 wt%, 30 wt%, 50 wt%, and 70 wt%). The results showed that the CLSM mixtures satisfied the limits and requirements of the American Concrete Institute Committee 229 for CLSM. Improving the mass ratio of BA to fly ash and the ball-milling time of the BA significantly reduced the flowability and the bleeding of the CLSM; the flowability was still in the high flowability category, the lowest bleeding BAI70 (i.e., the content of BA in the BAI group was 70 wt%) and BAII70 (i.e., the content of BA in the BAII group was 70 wt%) decreased by 48% and 64%, respectively. Furthermore, the 3 d compressive strengths of BAI70 and BAII70 were increased by 48% and 93%, respectively, compared with the group without BA, which was significantly favorable, whereas the 28 d compressive strength did not change significantly. Moreover, the removability modulus of CLSM was calculated, which was greater than 1, indicating that CLSM was suitable for structural backfilling that requires a certain strength. This study provides a basis for the large-scale utilization of coal industry solid waste in the construction industry and underground coal mine filling.

Forecast combination-based forecast reconciliation: Insights and extensions

In this paper, we build upon a recently proposed forecast combination-based approach to the reconciliation of a simple hierarchy (Hollyman R., Petropoulos F., Tipping M.E., Understanding forecast reconciliation, European Journal of Operational Research, 2021, 294, 149–160) and extend it in some new directions. In particular, we provide insights into the nature and mathematical derivation of the level-l conditional coherent (LlCC) point forecast reconciliation procedure for an elementary two-level hierarchy. We show that: (i) the LlCC procedure is the result of a linearly constrained minimization of a quadratic loss function, with an exogenous constraint given by the base forecast of the top level series of the hierarchy, which is not revised; and (ii) endogenous constraints may also be considered in the same framework, thereby resulting in level conditional reconciled forecasts where both the top and the bottom level time series forecasts are coherently revised. In addition, we show that the LlCC procedure (i.e., with exogenous constraints but the result also holds in the endogenous case) does not guarantee the non-negativity of the reconciled forecasts, which can be an issue in cases when non-negativity is a natural attribute of the variables that need to be forecast (e.g., sales and tourism flows). Finally, we consider two forecasting experiments to evaluate the performance of various cross-sectional forecast combination-based point forecast reconciliation procedures (vis-à-vis the state-of-the-art procedures) in a fair setting. In this framework, due to the crucial role played by the (possibly different) models used to compute the base forecasts, we re-interpret the combined conditional coherent reconciliation procedure (CCCH) of Hollyman et al. (2021) as a forecast pooling approach, and show that accuracy improvements may be obtained by adopting a simple forecast averaging strategy.

Downscaling Satellite-Based Estimates of Ocean Bottom Pressure for Tracking Deep Ocean Mass Transport

Gravimetry measurements from the GRACE and GRACE-Follow-On satellites provide observations of ocean bottom pressure (OBP), which can be differenced between basin boundaries to infer mass transport variability at a given level in the deep ocean. However, GRACE data products are limited in spatial resolution, and conflate signals from many depth levels along steep continental slopes. To improve estimates of OBP variability near steep bathymetry, ocean bottom pressure observations from a JPL GRACE mascon product are downscaled using an objective analysis procedure, with OBP covariance information from an ocean model with horizontal grid spacing of ∼18 km. In addition, a depth-based adjustment was applied to enhance correlations at similar depths. Downscaled GRACE OBP shows realistic representations of sharp OBP gradients across bathymetry contours and strong currents, albeit with biases in the shallow ocean. In validations at intraannual (3–12 month) timescales, correlations of downscaled GRACE data (with depth adjustment) and in situ bottom pressure recorder time series were improved in ∼79% of sites, compared to correlations that did not involve downscaled GRACE. Correlations tend to be higher at sites where the amplitude of the OBP signal is larger, while locations where surface eddy kinetic energy is high (e.g., Gulf Stream extension) are more likely to have no improvement from the downscaling procedure. The downscaling procedure also increases the amplitude (standard deviation) of OBP variability compared to the non-downscaled GRACE at most sites, resulting in standard deviations that are closer to in situ values. A comparison of hydrography-based transport from RAPID with estimates based on downscaled GRACE data suggests substantial improvement from the downscaling at intraannual timescales, though this improvement does not extend to longer interannual timescales. Possible efforts to improve the downscaling technique through process studies and analysis of alongtrack GRACE/GRACE-FO observations are discussed.