Cyclic Variation Research Articles

Effects of intake conditions on a dual-fuel spark-assisted compression ignition engine with polyoxymethylene dimethyl ether and methanol as fuels

Dual-fuel spark-assisted compression ignition (DF-SACI) is an advanced engine combustion mode. The use of polyoxymethylene dimethyl ether (PODE) and methanol as fuel can reduce the carbon emissions of the DF-SACI engine. To improve the combustion continuity and minimize the knocking and emissions of DF-SACI engines, the effects of intake heating and boosting were investigated. The results showed that the combination of intake heating and delayed spark ignition promoted fuel diffusion and prevented multi-peak heat release. Intake boosting promoted the transformation of compression ignition into flame propagation ignition. Intake heating and boosting allowed engine combustion optimization. The brake thermal efficiency was 41.4 % and 44 % when the brake mean effective pressure was 0.6 and 0.8 MPa, respectively, and the maximum pressure rise rate, coefficient of cyclic variation in the indicated mean effective pressure, and emissions were within reasonable ranges. A high intake air temperature combined with delayed spark ignition reduced the enrichment of PODE, thereby reducing the self-ignition probability of the fuel mixture, which can reduce knocking. When intake boosting was applied, the adoption of an excess air coefficient (λ) of 1.8 eliminated knocking under most conditions. Intake heating improved fuel reactivity and increased the ratio of compression ignition, to allow for the simultaneous reduction of hydrocarbon (HC) and NOx emissions. The effects of intake boosting on NOx and HC emissions were related to the energy ratio of PODE. As the energy ratio of PODE is between 47 % and 68 %, the appropriate increase in λ reduced both HC and NOx emissions. The results are conducive to the development of low-carbon engines and can provide a new direction for engine research.

Detecting Geothermal Anomalies Using Multi-Temporal Thermal Infrared Remote Sensing Data in the Damxung–Yangbajain Basin, Qinghai–Tibet Plateau

Geothermal energy is an eco-friendly, renewable source of underground thermal energy that exists in the interior of the earth. By tapping into these formations, fluids can be channeled to heat the rock formations above, resulting in a significantly higher land surface temperature (LST). However, LST readings are influenced by various factors such as sun radiation, cyclical variations, and precipitation, which can mask the temperature anomalies caused by geothermal heat. To address these issues and highlight the LST anomalies caused by geothermal heat, this paper proposes a methodology to efficiently and quickly calculate the multi-temporal LST leveraging of the Google Earth Engine (GEE) in the Damxung–Yangbajain basin, Qinghai–Tibet Plateau. This method incorporates terrain correction, altitude correction, and multi-temporal series comparison to extract thermal anomaly signals. The existing geothermal manifestations are used as a benchmark to further refine the methodology. The results indicate that the annual mean winter LST is a sensitive indicator of geothermal anomaly signals. The annual mean winter LST between 2015 and 2020 varied from −14.7 °C to 26.7 °C, with an average of 8.6 °C in the study area. After altitude correction and water body removal, the annual mean winter LST varied from −22.1 °C to 23.3 °C, with an average of 6.2 °C. When combining the distribution of faults with the results of the annual mean winter LST, this study delineated the geothermal potential areas that are located predominantly around the fault zone at the southern foot of the Nyainqentanglha Mountains. Geothermal potential areas exhibited a higher LST, ranging from 12.6 °C to 23.3 °C. These potential areas extend to the northeast, and the thermal anomaly range reaches as high as 19.6%. The geothermal potential area makes up 8.2% of the entire study area. The results demonstrate that the approach successfully identified parts of known geothermal fields and indicates sweet spots for future research. This study highlights that utilizing the multi-temporal winter LST is an efficient and cost-effective method for prospecting geothermal resources in plateau environments.

Cyclic Analysis of In-Cylinder Vortex Interactions Based on Data-Driven Detection and Characterization Framework

Abstract The complex vortex flow interactions are critical to affect the fuel–air mixing and combustion stability in direct-injection engine. However, due to the strong cyclic variations inside engine, the multiscale swirl flow characteristics with cyclic details are difficult to be sufficiently revealed. Therefore, a vortex detection and characterization framework, including physical and data-driven methods, is implemented to elucidate the cyclic vortex interaction process. In this study, a high-speed time-resolved particle image velocimetry is applied to record the spatiotemporal flow behavior under three different swirl ratio conditions. First, the presence of vortex motion is detected at each crank angle for each engine cycle. Results show that the vortex interaction processes under different swirl ratio conditions exhibit distinctive characteristics. The presence of multiple vortices and their interactions are found to trigger dramatic changes and variations in swirl flow behavior. Then, the individual-cycle analysis of the vortex interaction effects on flow characteristics is conducted. The vortex characteristics including vortex location, strength, and size are examined with cyclic detail using data-driven unsupervised clustering. Results indicate that the vortex merging is the main source inducing the vortex characteristics variations. Furthermore, the occurrence and duration of the vortex merging process are found to be closely related to the intake swirl ratio and valve lift profile. Increased swirl ratio and valve lift cause vortex to merge earlier and reduce the merging duration. This finding provides a potential idea to alleviate the cyclic variation issue by controlling the vortex merging process.

Evaluation of dibutyl maleate/diesel blends on combustion, performance and emissions in a DI diesel engine

Ignition characteristics of diesel are weak due to higher viscosity and density especially at cold start conditions. So, it is seen that the usage of dibutyl maleate having high content of oxygen as an additive to improve the bad properties of pure diesel is essential and sensible. In this research, a single cylinder DI diesel engine was operated at four different engine loads including 4.12, 9.61, 15.10 and 20.60 Nm to observe and see the influences of dibutyl maleate on performance and combustion characteristics such as heat release rate, in-cylinder pressure, ignition delay etc. and thermal efficiency. It was found that in-cylinder pressure decreased with the addition of dibutyl maleate whereas remarkable increase was observed on pressure rise rate and ringing intensity with fuel blends. ID (Ignition delay) period increased with dibutyl maleate addition into diesel due to lower cetane number while combustion duration shortened with fuel blends compared to diesel. Besides, indicated thermal efficiency decreased about 20.18% and 24.25% with D90DBM10 and D90DBM20 respectively according to neat diesel at 15.10 Nm. Specific fuel consumption increased 5.08% and 8.13% with D90DBM10 and D90DBM20 respectively compared that neat diesel. It was also seen that cyclic variations increased in case of usage dibutyl maleate addition. Test results also demonstrated that HC (Hydrocarbon) and soot reduced while CO (carbon monoxide), CO2 (carbon dioxide) and NOx (nitrogen oxides) raised with the usage of dibutyl maleate compared to neat diesel.

Investigation of deformation coordination between optical fibre and borehole sand backfill

Land subsidence has threatened the safety of municipal infrastructures and even that of inhabitants. As one of the deformation monitoring methods, distributed optical fibre sensing (DOFS) technology has been developed for the investigation of land subsidence. The deformation coordination between the optical fibre and soil (DCf-s) under different conditions is critical for land subsidence monitoring with DOFS. In this paper, a medium-sized triaxial apparatus was modified for testing the DCf-s. Consolidated drained triaxial tests were conducted to investigate the effect of sand types on the DCf-s. By linearly fitting the deformation of the sensing cable with that of the triaxial specimen, the other factors that affect the DCf-s, such as the confining pressure, dry or wet state of the soil and cyclic variation of the loads, can be discussed. The experiments reveal that better DCf-s comes with a larger particle size, poor gradation of sand and larger confining pressure. The DCf-s of wet sand is better than that of dry sand. The DCf-s coefficient tends to be stable with an increase of loading cycles. The DCf-s obtained and its dependence on influencing factors can be used to modify the measured cable strain in practical land subsidence monitoring with DOFS.

Probability life calculation model of beam element application and study in welded structures reliability analysis

Statistical size and geometrical size are the main factors affecting the service life of mechanical structure calculation. To explore the reliability of the lifespan of beam structures, a probability lifespan numerical calculation method based on Vector Form Intrinsic Finite Element Method (VFIFEM) was proposed, and the method was verified through full lifespan experiments on I-beam welded structures. First, a fatigue fracture model that considers the coupling of residual stress (RS) and cyclic load variations was established. Based on this fatigue fracture model, a probability lifespan calculation model for beam elements was defined by proposing a cross-sectional shape correction coefficient and a position correction coefficient. The proposed probability lifespan model for beam elements was used to calculate the I-beam welded structure, and the calculated results were compared with the full lifespan experiment results, which were close in statistical results, with all experimental results falling within the [10%, 90%] interval except for one experiment. This method effectively couples the influence of statistical size and geometric size on probability lifespan, providing a new approach for the structure probability lifespan calculation in the future.

Cyclic Mean Stress Variation Effect on Pipe Ratcheting

Cyclic Mean Stress Variation Effect on Pipe Ratcheting

Blade strain analysis from field measurements on a vertical axis wind turbine

In this paper, the 10 kW WindQuest Vertical Axis Wind Turbine (VAWT) has been instrumented by strain gauges during its trials in the Ifremer in situ test site of Brest to study the effects of the structural dynamic response of the blades under operating conditions. Static and dynamic effects have been investigated as a function of the rotational speed when the rotor operates under stable wind conditions. The analysis segregates the influence of the gravitational, inertial, and aerodynamic loading components on the flapwise bending stress of the blades. The study of the cyclic variations on the blade strain at different Tip-Speed Ratios leads to the identification of the dynamic stall effect on the unsteady loads, while the spectral analysis describes the system eigenfrequencies excited by the interaction of the wind and the structure's motion. The results provide useful data to validate numerical models for VAWT blades with similar design and evaluate the structural fatigue.

An Experimental Comparison of Cyclic Variations in Diesel–Natural Gas and POMDME–Natural Gas Dual Fuel Combustion

Abstract Cyclic variations in internal combustion engines are caused by various factors, including combustion mixture stratification, in-cylinder flows, local fluctuations in air-fuel ratio, etc. Cyclic variations have a profound impact on engine performance and emissions. In this study, cyclic variations in dual fuel combustion are analyzed, comparing diesel–natural gas (NG) and polyoxymethylene dimethyl ether (POMDME)-NG dual fuel combustion. Cyclic variability was initially quantified using the coefficient of variation of gross indicated mean effective pressure (IMEPg) computed from experimental cylinder pressure data. The cases analyzed in this study had a coefficient of variation (COV) of IMEPg greater than or around 5%, which was the lower limit of onset of instability for this engine. Experiments were performed at two fixed start of injection (SOI) of high-cetane fuel: 310 CAD and 350 CAD. For all experiments, a constant load of 5 bar IMEPg was maintained, and the intake boost pressure and rail pressure were fixed at 1.5 bar and 500 bar, respectively. For each case, 1000 cycles of cylinder pressure data were recorded, filtered, and processed using an in-house heat release analysis code for each cycle. A comparison between individual cycles and the “ensemble averaged cycle” was made for both diesel–NG and POMDME–NG combustion. For the early SOI of 310 CAD, the peak cylinder pressure fluctuations of individual cycle were found to be ± 15 bar for both fuel combinations, compared to the ensemble averaged cycle, and < 1/10th of the cycles had an IMEPg lower than 0.05 bar of the ensemble averaged cycle. However, the peak pressure fluctuations were found to be lower for POMDME–NG (±3 bar) than diesel–NG dual fuel combustion at 350 CAD SOI, indicating lower cyclic variations. The higher reactivity of POMDME helped reduce fluctuations in combustion phasing at the retarded SOI. The presence of cycles of deterioration and cycles of recovery were also observed with diesel–NG combustion for 310 CAD SOI, and the scatter in the IMEPg return map was similar for both fuel combinations. The IMEPg return map for POMDME–NG combustion was less scattered at the 350 CAD SOI.

NY Bootes: An Active Deep and Low-mass-ratio Contact Binary with a Cool Companion in a Hierarchical Triple System

The first detailed photometric and spectroscopic study of G-type short-period binary NY Boo is presented. The radial velocity curve was obtained by the cross-correlation function (CCF) method based on LAMOST and SDSS spectra, which derived its mass ratio as q = 0.139(1/7.2). The CCF profiles of the SDSS spectra clearly show the existence of a cool third component, which is supported by the results of the orbital period investigation. The period study based on the O-C analysis indicates that besides a long-term decrease, the orbital period has a periodic oscillation due to the light-travel time effect caused by a third body. When the third light contribution is consistent with the CCF results, the orbit of the third body and the inner pair are non-coplanar with m 3 = 0.31 M ⊙. Combining with the TESS light curves, it is found that the target is a deep and low-mass-ratio contact binary (DLMRCB) with a fill-out factor of f = 73%. The notable asymmetry in light curves was detected and explained by the spot model very well. The spectroscopic profiles, the cyclic variation in the O-C diagram, and the radial velocity curve and light-curve solutions all suggest that NY Boo is a hierarchical triple system with a cool tertiary component orbiting around an active DLMRCB. With the orbital period shrinking, the binary may eventually merge. The period of NY Boo decreases faster than other shrinking DLMRCB, together with active inner pair and non-coplanar tertiary component, making NY Boo an important target for studying the late evolution of binaries.

Impact of temperature on the performance of compost-based landfill biocovers

Methane (CH4) emissions from landfills are a major contributor to global greenhouse gas emissions. Compost-based biocovers offer a viable approach to reduce CH4 emissions from landfills; however, the effectiveness in climates with varying temperatures is not well understood. The methane removal performances of two compost-based biocover materials (food and yard waste compost) were examined under different temperature conditions using laboratory column experiments. A reactive transport model was used to simulate the experimental results to develop a better quantitative understanding of the effect of temperature on overall methane removal efficiency. As expected, experimental results indicated that the oxidation rate was influenced by temperature, as it was reduced when the temperature decreased from 22 °C to 8 °C. However, some oxidation was observed at a lower temperature, which was confirmed by CO2 concentrations above the initial level and the observed temperatures above the exposure temperature along the height of biocover column. Furthermore, results showed that when the compost-based materials were subjected to 8 °C and then increased to 22 °C, methane oxidation within the material recovered quickly and returned to similar oxidation rates as observed before the temperature was reduced, suggesting that compost-based biocovers may not be affected by cyclic temperature variations when used in colder climates. Methane oxidation capacity was limited by the maximum oxidation rate, the biocover porosity, and the gas saturation profile that affects residence time and overall methane oxidation in the columns. The model results show that the CH4 oxidation rate was reduced by one order of magnitude when the temperature decreased from 22 °C to 8 °C. Therefore, the calculated Q10 values were 4.19 and 5.18 for the food and yard waste compost, respectively. Overall, compost-based landfill biocovers, such as food and yard waste compost, are capable of mitigate CH4 emissions from old and small landfills under different temperature conditions.

An interpretable machine learning model to predict off-pump coronary artery bypass grafting-associated acute kidney injury.

Off-pump coronary artery bypass grafting-associated acute kidney injury (OPCAB-AKI) is related to 30-day perioperative mortality. Existing mathematical models cannot be applied to help clinicians make early diagnosis and intervention decisions. This study used an interpretable machine learning method to establish and screen an optimized OPCAB-AKI prediction model. Clinical data of 1110 patients who underwent OPCAB in the Department of Cardiac Surgery of General Hospital of Northern Theater Command (Shenyang, China) from January 2018 to December 2020 were collected retrospectively. Four machine learning models were used, including logistic regression (LR), decision tree (DT), random forest (RF), and eXtreme Gradient Boosting (XGBoost). The SHapley Additive exPlanation (SHAP) tool was used for explanatory analysis of the black-box model. The mean absolute value of the characteristic SHAP parameter was defined and sorted. The correlation between the characteristic parameters and OPCAB-AKI was determined based on the SHAP value. A quantitative analysis of a single characteristic and an interaction analysis of multiple characteristics were carried out for the main risk factors. The RF prediction model had the best performance, with an area under the curve (AUC) of 0.90, a precision rate of 0.80, an accuracy rate of 0.83, a recall rate of 0.74, and an F1 score of 0.78 for positive samples. The interpretation analysis of the SHAP model results showed that intraoperative urine volume contributed to the greatest extent to the RF model, and other parameters included intraoperative sufentanil dosage, intraoperative dexmedetomidine dosage, cyclic variation coefficient during the induction period, intraoperative hypotension duration, age, preoperative baseline serum creatinine, body mass index (BMI), and Acute Physiology, Age and Chronic Health Evaluation (APACHE) II score. The model constructed by the RF ensemble learning algorithm predicted OPCAB-AKI, and indicators such as intraoperative urine volume were closely related to OPCAB-AKI.

Research on Small-Cap Value Rotation Investment Strategy Based on "Size Effect" - Evidence from the Chinese Stock Market

Abstract This paper investigates the small-cap value rotation investment strategy. This paper analyzes the rationality and applicability of small-market rotation strategy from two aspects: theoretical analysis and practical test. This paper first sorts out and expounds the theoretical basis of small-cap rotation investment strategy. Subsequently, the details of the strategy are introduced in additional with some notice that the investor should pay attention to. Besides, its returns and applicability are examined, which is based on the real data from Chinese stock market. The results indicate that the small-cap value rotation investment strategy remains viable in today's Chinese stock market, but its applicability exhibits certain cyclical variations. Therefore, when adopting such an investment strategy, careful consideration of its specific applicability is necessary. JEL classification numbers: G11, G14, G24. Keywords: Size Effect, Small-Cap, Investment Strategy.

Development of Electrochromic Devices, Based on Polymeric Gel, for Energy Saving Applications.

In this work, the implementation of an electrochromic device (10 cm × 10 cm in size) for energy saving applications has been presented. As electrochromic system has been used with an electrochromic solution (ECsol) made by ethyl viologen diperchlorate [EV(ClO4)2], 1,1'-diethyl ferrocene (DEFc) and propylene carbonate (PC), as solvent. The final system has been obtained by mixing the ECsol, described above, with a polymeric system made by Bisphenol-A glycerolate (1 glycerol/phenol) diacrylate (BPA) and 2,2-Dimethoxy-2-phenylacetophenone (Irgacure 651) in a weight percentage equal to 60:40% w/w, respectively. Lithography has been used to make a spacer pattern with a thickness of about 15-20 µm between the two substrates. Micro-Raman spectroscopy confirmed the presence of the EV•+ as justified by the blue color of the electrochromic device in the ON state. Electrochemical and optical properties of the electrochromic device have been studied. The device shows reversible electrochromic behavior as confirmed by cyclic color variation due to the reduction and oxidation process of the EV2+/EV•+ couple. The electrochromic device shows a variation of the % transmittance in the visible region at 400 nm of 59.6% in the OFF state and 0.48% at 3.0 V. At 606 nm the transmittance in the bleached state is 84.58% in the OFF state and then decreases to 1.01% when it is fully colored at 3.0 V. In the NIR region at 890 nm, the device shows a transmittance of 74.3% in the OFF state and 23.7% at 3.0 V while at 1165 nm the values of the transmittance changed from 83.21% in the OFF state to 1.58% in the ON state at 3.0 V. The electrochromic device shows high values of CCR% and exhibits excellent values of CE in both visible and near-infrared regions when switched between OFF/ON states. In the NIR region at 890 nm, electrochromic devices can be used for the energy-saving of buildings with a promising CE of 120.9 cm2/C and 420.1 cm2/C at 1165 nm.

Characterisation of Variants of Cyclic di-GMP Turnover Proteins Associated with Semi-Constitutive rdar Morphotype Expression in Commensal and Uropathogenic Escherichia coli Strains.

Expression of rdar (red, dry, and rough) colony morphology-based biofilm formation in Escherichia coli is highly variable. To investigate the molecular mechanisms of semi-constitutive rdar morphotype formation, we compared their cyclic di-GMP turnover protein content and variability to the highly regulated, temperature-dependent morphotype of the historical and modern ST10 isolates E. coli MG1655 and Fec10, respectively. Subsequently, we assessed the effects of cyclic di-GMP turnover protein variants of the EAL phosphodiesterases YcgG and YjcC and the horizontally transferred diguanylate cyclase DgcX on biofilm formation and motility. The two YcgG variants with truncations of the N-terminal CSS signaling domain were oppositely effective in targeting downregulation of rdar biofilm formation compared to the full-length reference protein. Expression of the C-terminal truncated variants YjcCFec67 and YjcCTob1 showed highly diminished apparent phosphodiesterase activity compared to the reference YjcCMG1655. For YjcCFec101, substitution of the C-terminus led to an apparently inactive enzyme. Overexpression of the diguanylate cyclase DgcX contributed to upregulation of cellulose biosynthesis but not to elevated expression of the major biofilm regulator csgD in the "classical" rdar-expressing commensal strain E. coli Fec10. Thus, the c-di-GMP regulating network is highly complex with protein variants displaying substantially different apparent enzymatic activities.

Microstructural characteristics evolution of asphalt mastics under cyclic environmental temperature variations

Environmental temperature-effect is the primary factor responsible for asphalt pavement failure. Asphalt pavement exposed to the atmosphere is constantly subjected to the thermal cycles induced by environmental temperature fluctuations, and the resulting thermal cracks significantly reduce the durability of asphalt pavement. Nevertheless, the influence of cyclic temperature variations on the performance degradation of asphalt binder materials is often overlooked. To address this, accelerated thermal cycling test was conducted on two asphalt mastics to simulate repeated environmental temperature variations. Dynamic shear rheological test (DSR) and atomic force microscopy test (AFM) were performed to characterize the evolution of the macroscopic rheological properties and microstructural characteristics under five cyclic temperature ranges. Pearson correlation analysis was utilized to explore the correlation between macro and micro properties. Following thermal cycling, it was observed that the two asphalt mastics experienced a decline in their viscous properties and became more elastic, resulting in a decrease in their stress relaxation capacity and asphalt-aggregate interaction on a macroscopic level. The microstructure transitioned from a multiphase to a homogeneous structure, while the expansion of the valley structure indicated the accumulation of microscopic defects. The larger the temperature variations and the higher the cyclic temperatures are, the more severe the deterioration in the viscoelasticity and microstructures of asphalt mastics is; the degradation of the micromechanical characteristics directly affects the macroscopic rheological properties. The bee structure ratio, the adhesion, and relaxation properties are sensitive to cyclic temperature variations and recommended to characterize the thermal cycling resistance. In comparison to 90# asphalt mastic, the SBS modified asphalt mastic exhibits great resistance to thermal deterioration. This study deepens the understanding of the causes of asphalt pavement performance deterioration in regions with frequent environmental temperature fluctuations.

Evaluation of hydrogen injection and oxygen enrichment strategies in an ammonia-hydrogen dual-fuel engine under high compression ratio

Ammonia with low reactivity still faces some challenges as the main fuel for engines. Hydrogen and oxygen, as two combustion improvers, are expected to solve ammonia’s reluctance to combust. To date, the application of oxygen enrichment strategies in ammonia-hydrogen dual-fuel engines is very rare, which motivates this study. The main objective of this investigation is to explore optimal hydrogen injection strategies and evaluate the effectiveness of oxygen enrichment strategies for the engine. Optimizing hydrogen injection parameters can vary the ammonia-hydrogen premixing degree, thus improving the flame kernel formation and flame propagation velocity. This is supported by the shortened CA0-90, lowered cyclic variation, and elevated thermal efficiency and power. Oxygen-enriched strategies enhance the heat release process and mitigate the negative effects of ammonia on the ignition process, which reduces cyclic variation and prominently increases power. However, the elevated oxygen concentration may increase the adiabatic flame temperature of the mixture and thus heat transfer loss, which decreases brake thermal efficiency. Moreover, a hypothesis that an ammonia-hydrogen engine may be employed in a hybrid power system in the future is proposed. The results of this work can be used as raw data for developing a hybrid power system.

Orbital Period Variations in HT Cas: Evidence for Additional Angular Momentum Loss and a High-eccentricity Giant Planet

We present a timing study of the short-period eclipsing cataclysmic variable (CV) HT Cas. Based on new eclipse times derived from our photometric monitoring and archival optical data, combined with historical timings, spanning ∼42 yr, we detect a secular decrease in the orbital period at a rate of and a cyclic period wiggle with an amplitude of 79.3 s and a period of 30.28 yr. We find that neither gravitational radiation nor magnetic braking can explain the observed decrease rate, suggesting the presence of additional angular momentum loss (AML). The empirical consequential AML (eCAML) model developed by Schreiber et al. can well match the observed orbital decay in HT Cas, and the physical mechanism for eCAML is most likely attributable to the frictional AML following nova eruptions. As for the cyclic variation, the best explanation is the influence of an unseen companion in orbit around the binary. The derived orbital parameters reveal that the hypothetical third body could be a giant planet with mass of M 3 ≃ 14M Jup that is moving on a highly eccentric orbit (e = 0.82). Taken together the results of the present study suggest that HT Cas is a unique triple system containing a high-eccentricity giant planet and it has the potential to become an ideal laboratory in which to test models of CV evolution.

Sedimentology of the Jura Molasse: Miocene tidal clastics and freshwater carbonates from the Tramelan-2 Borehole, NW Switzerland

The Tramelan-2 borehole (Canton Bern, Switzerland) continuously cored a 275.60 m sequence of Palaeogene to Neogene sediments, providing a rare opportunity for sedimentological analysis of the Jura Molasse. Lithostratigraphy, sedimentary facies and heavy minerals allow correlation with the classical Swiss Molasse. Evidence for clastic input from Alpine and non-Alpine sources is consistent with deposition at the northern feather edge of the Molasse Basin. Grey sandstones at the base of the succession are tentatively interpreted as fluvial facies of the Lower Freshwater Molasse (USM). These are overlain by erosively-based conglomerates, interpreted as winnowed storm lags of locally-derived clasts and distantly-sourced Alpine material at the transgressive base of the Upper Marine Molasse (OMM). Above this, a range of plane-laminated and cross-bedded bioclastic sandstones are interpreted as the deposits of a meso- or macrotidal flat or estuarine complex. Facies evolution in the upper OMM records a series of stacked regressive cycles within an overall upward trend of reducing current energy, reflecting a transition from offshore to nearshore shallow marine environments. The unconformably overlying Upper Freshwater Molasse (OSM) passes upwards from micaceous siltstones and marls into a series of freshwater carbonates, dominated by lacustrine limestones which are arranged in repeated regressive cycles, each capped by organic-rich horizons. The middle part of the carbonate interval comprises palustrine limestones with pedogenetic fabrics recording periodic subaerial exposure. Stable isotope signatures from the palustrine facies reflect subaerial pedogenetic overprint, while the lacustrine carbonates record cyclical variations in δ13C which may reflect increases in organic material during progressive lake fill and/or an increased influence of aquifer waters during flooding events. The Jura Molasse onlapped a Mesozoic carbonate pediment hosting a regional karst system which remained active at least until the Burdigalian transgression on footwall highs bounding the Delémont Basin, and locally into the Langhian near Tramelan. This configuration controlled subsequent deposition of OSM carbonates which onlapped erosional and potentially early tectonic relief, and were deposited in groundwater-fed seasonal lacustrine/palustrine environments, where the karstic aquifer controls on seasonal hydrology appear to have been comparable to Caribbean freshwater carbonate wetland systems today.

Initiation and accumulation of loading induced changes to native collagen content and microstructural damage in the cartilaginous endplate

BACKGROUND CONTEXTInjury to the cartilaginous endplate (CEP) is linked to clinically relevant low back disorders, including intervertebral disc degeneration and pain reporting. Despite this link to clinical disorders, the CEP injury pathways and the modulating effect of mechanical loading parameters on the pace of damage accumulation remains poorly understood. PURPOSEThis study examined the effect of cyclic loading on the initiation and accumulation of changes to native collagen content (type I, type II) and microstructural damage in the central region of cadaveric porcine CEPs. STUDY DESIGNIn vitro longitudinal study. METHODSOne hundred fourteen porcine cervical spinal units were included (N=6 per group). The study contained a control group (no cyclic loading) and 18 experimental groups that differed by loading duration (1,000, 3,000, 5,000 cycles), joint posture (flexed, neutral), and cyclic peak compression variation (10%, 20%, 40%). Multicolor immunofluorescence staining was used to quantify loading induced changes to type I (ie, subchondral bone) and type II (ie, endplate) native collagen content (fluorescence area, fluorescence intensity) and microstructural damage (pore area [transverse plane], void area along the CEP-bone border [sagittal plane]). RESULTSSignificant main effects of loading duration and posture were observed for fluorescence area and fluorescence intensity of type I and II collagen. In the transverse plane, type II fluorescence area significantly decreased following 1,000 cycles (-12%), but a significant change in fluorescence intensity was not observed until 3,000 cycles (-17%). Type II fluorescence area (-14%) and intensity (-10%) were both significantly less in flexed postures compared to neutral. Similar trends were observed for type I collagen in the sagittal plane sections. Generally, significant changes to fluorescence area were accompanied by the development of microstructural voids along the endplate-subchondral bone border. CONCLUSIONSThese findings demonstrate that microstructural damage beneath the endplate surface occurs before significant changes to the density of native type I and II collagen fibers. Although flexed postures were associated with greater and accelerated changes to native collagen content, the injury initiation mechanism appears similar to neutral. CLINICAL SIGNIFICANCENeutral joint postures can delay the initiation and pace of microdamage accumulation in the CEP during low-to-moderate demand lifting tasks. Furthermore, the management of peak compression exposures appeared relevant only when a neutral posture was maintained. Therefore, clinical low back injury prevention and load management efforts should consider low back posture in parallel with applied joint forces.