Fast Cycle Research Articles

Effect of fasting and re-feeding cycles on growth, glucose level, glycogen level, and digestive enzyme activity of Nile tilapia juveniles (Oreochromis niloticus) for cost-effective aquaculture

Effect of fasting and re-feeding cycles on growth, glucose level, glycogen level, and digestive enzyme activity of Nile tilapia juveniles (Oreochromis niloticus) for cost-effective aquaculture

Effects of Ion Valence States and Radii on the Performance of Solid-State PEDOT:PSS Electrochromic Devices.

Ion transport is a critical factor influencing the performance of electrochromic devices (ECDs). In this work, the effects of the valence state and ionic radius of six cations, Li+, Na+, K+, Mg2+, Zn2+, and Al3+, on the performance of poly(3,4-ethylenedioxythiophene)-polystyrene sulfonic acid (PEDOT:PSS)-based ECDs are investigated. Both ion migration and diffusion are discussed as processes that were analyzed, with results indicating that the primary contributor to the response of ECDs is ion migration. The response time decreases with increasing ionic valence and ionic radius, with the valence state having the predominant effect on response speed. Multivalent ions, due to strong electric field forces, migrate more rapidly and intercalate fewer ions at equivalent reaction charges, thereby facilitating a faster response. ECDs with larger-radius ions, which exhibit slower diffusion rates, also achieve faster response speeds. Among the tested ECDs with various electrolytes, the Al3+-based ECD demonstrates the fastest colored/bleached response time of 0.36/0.4 s. In addition, ions with larger radii introduce greater steric hindrance and structural damage during insertion and extraction, leading to ion retention issues and reduced cycling stability. After 500 cycles (2025 s) under a square wave voltage of ±1.5 V, the peak current of ECDs with Li+ (0.60 Å) electrolyte decreased by only 5.07/5.66%, whereas for K+ (1.33 Å) electrolyte, the decrease was 11.55/12.37%. ECDs utilizing small-radius, higher-valence ions, such as Al3+, achieved both fast response and high cycling stability, with peak current reductions of only 6.98/5.01%. Additionally, the charge storage dynamics were examined by analyzing the contributions from surface-controlled and diffusion-controlled charges, further confirming that ion migration dominates in ECDs. The high contribution of surface-controlled charges (80%) supports the fast response of ECDs and contributes to the high coloration efficiency (592.6 cm2/C for Al3+-based devices).

TMIC-52. DECODING METABOLIC INTERACTIONS IN GLIOBLASTOMA TUMOR MICROENVIRONMENT THROUGH COMPREHENSIVE SPATIAL TRANSCRIPTOMIC AND PROTEOMIC ANALYSIS

Abstract INTRODUCTION Within the GBM microenvironment, distinct micro-niches arise from independent cancer cell lineages with unique metabolic needs, characterized as Fast Cycling Cells (FCCs) and Slow Cycling Cells (SCCs). FCCs preferentially utilize aerobic glycolysis for energy, whereas treatment-resistant SCCs depend on lipid metabolism. Our study decodes the molecular and spatial heterogeneity within the GBM microenvironment, focusing on the dichotomy of immune infiltrates and the metabolic interactions between SCCs and the immune compartment in human GBM patients. METHODS We performed spatial transcriptomics and proteomics combined with geospatially resolved single-cell neighborhood analysis of IHC-stained GBM tissues using CellProfiler and the SNAQ algorithm that we developed to investigate the specific immune microenvironment of SCCs and FCCs. Holotomography and fluorescence-based time-lapse imaging coupled with flow cytometry were used to study lipid transfer between immune cells and GBM cells. Finally, the effects of pharmacological and genetic targeting of lipid transfer were investigated both in vitro and in vivo. RESULTS Our study establishes a connection between spatial metabolic heterogeneity and immune diversity, highlighting how specific tumor cell lineages correlate with characteristic immune micro-niches. In particular, SCCs exploit the metabolic properties of recruited immunosuppressive myeloid-derived cells, which metabolically support tumor cells by facilitating lipid transport and supporting SCC metabolism. Our results show that inhibiting lipid transfer affect SCCs, remodels the immune microenvironment, delays tumor growth and improves disease outcome. Our study also demonstrates a correlation between predicted sensitivity to lipid-modifying drugs, such as statins, and the SCC phenotype. This correlation could enable stratification and selection of patients most likely to benefit from such treatments. CONCLUSIONS This study establishes critical connections between the TME, cellular metabolism, anti-tumor immunity, and treatment vulnerabilities. Our research provides novel insights into how metabolic exchanges contribute to tumor progression and suggests that targeting metabolic interactions could be an effective therapeutic strategy for GBM.

Machine learning-inspired study of dynamical parameters of single vapor bubble under nucleate flow boiling regime

Heat transfer performance of nucleate boiling is interlinked with the departure dynamics of vapor bubbles, which also serves as the basis for heat transfer partitioning schemes and bubble growth models. Given the fast transients and multiple bubble ebullition cycles, boiling experiments lead to voluminous data that are to be analysed for determining the bubble dynamic parameters, and subsequently, the boiling heat transfer rates. Conventional approach of manual handling of such temporal and spatially-resolved experimental data is inherently time-consuming and error-prone. In the backdrop of these limitations, importance of machine learning algorithms gets highlighted in making the entire process automated and accurate as they minimize the need of any human intervention. The present work explores the potential of machine learning techniques towards quantifying the bubble departure characteristics and heat transfer partitioning during nucleate flow boiling. Water-based experiments have been conducted in a vertical channel under varying subcooling levels (ΔTsub = 2, 5, and 8 K) and flow rates (Re = 2400, and 3600). Mask R-CNN machine learning (ML) model is employed to evaluate the temporal variations of dynamical parameters of vapor bubbles and departure characteristics. The bubble departure characteristics as well as the corresponding evaporative and convective heat transfer rates, as retrieved through ML-generated masks, showed a strong dependence on the level of bulk fluid subcooling and flow rates. Heat transfer partitioning analysis revealed a competing interplay between the evaporative and condensation components of overall boiling heat transfer rates. These findings demonstrate the potential of ML techniques towards optimizing the thermal performance of boiling phenomena that have significant implications in a range of critical engineering applications.

Optimizing Palmer amaranth (Amaranthus palmeri) genetic testing of seeds using real-time (quantitative) PCR

Abstract The Amaranthus genus contains numerous agronomic weedy species that are widely distributed across the United States. The seeds of many Amaranthus species are morphologically indistinguishable. The Minnesota Department of Agriculture declared Palmer amaranth (Amaranthus palmeri S. Watson) a prohibited noxious weed seed in 2016. Any Amaranthus spp. seeds that are identified as contaminants during routine seed testing require genetic testing to determine whether A. palmeri is present. This research aimed to validate and optimize the molecular detection of A. palmeri in seed. We refined the DNA extraction from pools of Amaranthus spp. seeds ranging in size from 1 to 100 seeds to improve sample testing throughput. Real-time polymerase chain reaction (qPCR) using primers developed by Murphy and colleagues correctly identified the presence of A. palmeri genetics in 84 samples containing 0, 1, 2, 25, or 50 A. palmeri seeds in samples containing up to 100 seeds. The method specificity was examined using 17 Amaranthus species and 4 hybrids of unknown genetics. The Murphy regular qPCR cycle amplified Watson’s amaranth (Amaranthus watsonii Standl.), spleen amaranth (Amaranthus dubius Mart. ex Thell.), and spiny amaranth (Amaranthus spinosus L.), which would result in false-positive calls; however, the fast cycle only identified A. watsonii as a potential false positive. Examination of the Murphy primer binding site revealed an identical sequence for A. palmeri and A. watsonii. Additional markers were evaluated and optimized for use in qPCR to eliminate the risk of a false positive. The additional markers did eliminate the amplification of A. dubius and A. spinosus but did not eliminate the amplification for A. watsonii. Currently, A. watsonii is not known to be distributed outside of its limited native range and is not expected to be encountered in samples.

Mediterranean Aquaponics: Fasting and Refeeding in a Polyculture Aquaponic System

The use of Mediterranean euryhaline fish and halophytes in aquaponics presents a sustainable and alternative approach to food production. The present study investigates the effect of compensatory growth on sea bass (Dicentrarchus labrax) and Baltic prawn (Palaemon adspersus) co-cultivated with the halophytic glasswort (Salicornia europaea). Three autonomous systems were established, each containing forty-five sea bass, nine Baltic prawns, and eight glasswort plants, with different feeding regimes for each treatment: (i) daily feeding (treatment A), (ii) three days of feeding per week followed by four days of fasting (treatment B), and (iii) feeding for seven days followed by seven days of fasting (treatment C). The growth performance of the fish was significantly higher in treatment B. Conversely, the feed conversion ratio (FCR) was notably higher in treatment A. As for the prawns, their final body weight and length were similar across all treatments. The glasswort plants also demonstrated significantly improved growth in treatment B. These results indicate that the incorporation of feeding and fasting cycles can be an effective feed management strategy for polyculture aquaponic systems. Additionally, food deprivation had a positive impact on the growth performance of both glasswort and prawns.

Understanding ultrafast rechargeable Al/graphite battery by visualizing phase separation

Al/graphite batteries (ABs) using ionic liquid electrolytes exhibit exceptionally fast charging and cycling stability. However, the mechanisms underlying their high rate capabilities remains elusive. In this study, in situ optical microscopy is employed to investigate the intercalation dynamics of single-flake graphite in ABs. Observations reveal that surface reaction limitations, rather than AlCl4− mass transfer, primarily govern performance in the graphite cathode. During charging under varying current densities, the ABs display distinct phase separation behaviour with an intercalation wave morphology, indicating that surface reactions restrict the intercalation process. This finding explains the ultrafast recharge capability of ABs, where active sites in graphite become nearly fully intercalated with AlCl4− at high current densities. Additionally, slight rate performance loss occurs due to increasing ohmic and charge transfer polarisation (ηohm and ηct) at higher current densities. To address this limitation, we propose increasing the cut-off voltage as a straightforward and effective method to mitigate these polarization effects. This study offers valuable insights into the electrochemical behaviour of rechargeable secondary ion batteries by visualising their phase separation.

Revealing interfacial degradation of Bi2Te3-based micro thermoelectric device under current shocks

Micro thermoelectric devices (micro-TEDs) offer great potential for IoT and electronic thermal management. However, they face challenges with reliability under high current densities. This study elucidates the failure mechanisms of Bi2Te3-based micro-TEDs subjected to current shocks. Experimental results indicate that at a high current density of 1800 A/cm2, the internal resistance of micro-TEDs increased by 12.9 % to 2.034 Ω. This led to a 52.0 % decrease in maximum output power at a 20 K temperature difference, dropping to 1.53 mW. Additionally, as the frequency of ON/OFF current applied to micro-TED increases, the resistance growth rate jumped from 0.764 mΩ/h for slow power cycling to 2.328 mΩ/h for fast power cycling. This indicates that higher cycling frequencies exacerbate the degradation of the device. In-situ TEM analysis revealed that current-induced elemental diffusion and electrical stress release led to the formation of NiTe2 nanoparticles and intergranular fractures within the Bi2Te3 materials. These results indicate that interfacial degradation and subsequent grain delamination are primary causes to micro-TED failure under current shocks. These findings underscore the significance of considering electrical stress in micro-TED design to enhance reliability and performance for high-power applications.

Validation and user experience of a dry electrode based Health Patch for heart rate and respiration rate monitoring

Successful implementation of remote monitoring of vital signs outside of the hospital setting hinges on addressing three crucial unmet needs: longer-term wear, skin comfort and signal quality. Earlier, we developed a Health Patch research platform that uses self-adhesive dry electrodes to measure vital digital biomarkers. Here, we report on the analytical validation for heart rate, heart rate variability and respiration rate. Study design included n = 25 adult participants with data acquisition during a 30-minute exercise protocol involving rest, squats, slow, and fast cycling. The Shimmer3 ECG Unit and Cosmed K5, were reference devices. Data analysis showed good agreement in heart rate and marginal agreement in respiratory rate, with lower agreement towards higher respiratory rates. The Lin’s concordance coefficient was 0.98 for heart rate and 0.56 for respiratory rate. Heart rate variability (RMSSD) had a coefficient of 0.85. Participants generally expressed a positive experience with the technology, with some minor irritation from the medical adhesive. The results highlighted potential of this technology for short-to-medium term clinical use for cardiorespiratory health, due to its reliability, accuracy, and compact design. Such technology could become instrumental for remote monitoring providing healthcare professionals with continuous data, remote assessment and enhancing patient outcomes in cardiorespiratory health management.

Personality in motion: How intuition and sensing personality traits relate to lower limb rebound performance.

Embodied cognition asserts a symbiotic relationship between cognitive processes and the physical body, raising an intriguing question: could personality traits be intertwined with the biomechanical performance of the lower limb? This study aimed to explore this connection by examining how personality traits, assessed using the Myers-Briggs Type Indicator (MBTI), relate to lower limb rebound power (RP) measured through the five-repetition rebound jump test. Eighty participants completed two sessions: a biomechanical analysis of hopping using an Optojump® system to measure contact time, flight time, and RP, and a personality traits assessment categorizing traits across four MBTI axes: extraversion-introversion (favorite world); sensing-intuition (information processing preference); thinking-feeling (decision making); and judging-perceiving (structure). Participant characteristics did not significantly differ across MBTI axes (p≥0.07), minimizing potential confounding factors. Notably, individuals classified as intuitive showed significantly longer flight times (p = 0.02) and larger RP (p = 0.007) compared to sensing individuals, suggesting a greater reliance on the fast stretch-shortening cycle and showcasing superior use of their lower limb structures as springs. This suggests potential implications for sports performance, with intuition individuals possibly excelling in plyometric sports. However, no significant associations were found between biomechanical performance and the other three MBTI axes (p≥0.12), challenging the initial hypothesis. This research provides initial insights into the nuanced relationship between personality traits and movement patterns, indicating the potential for tailored physical interventions to enhance adherence and optimize responses in training programs.

Cyclicity of slow–fast cycles with one self-intersection point and two nilpotent contact points*

Cyclicity of slow–fast cycles with one self-intersection point and two nilpotent contact points*

Conducting LixPOy Interface Generated From Insulating Residual Lithium Compounds on LiNi0.8Mn0.1Co0.1O2 Surface Improves Cycle Life and Assists in Fast Cycling.

LiNi0.8Mn0.1Co0.1O2 (NMC811) is the most promising cathode material for future Li-ion batteries (LIBs). However, the bulk and surface structural instabilities retard its commercial success. Surface chemical instability toward exposure to moisture (H2O and CO2) leads to the formation of residual lithium compounds (RLCs: Li2CO3, LiOH) on the surface. The alkaline RLCs form a resistive layer on the surface of NMC811 by undergoing parasitic side reactions with electrolytes. Herein, an "Adverse-to-Beneficial" approach is proposed to eliminate RLCs by chemically transforming them into a LixPOy (Li3PO4 and LiPO3) interface. The interface protects the NMC811 surface from moisture attack and unwanted side reactions with electrolytes. It enhances the cycle life by retaining 70% of the initial capacity after 300 cycles at a 0.5C rate and 60% after 500 cycles, even at a 5C rate in a voltage window of 3.0-4.3V versus Li+/Li. The coexistence of two Li-conducting phases lowers the voltage polarization of the kinetically sluggish H1 → M phase transition to unlock fast cycling, reduces cationic disorder, improves coulombic efficiency, enhances ion diffusion kinetics, and minimizes particle crack formation after long-term cycling. Hence, the LixPOy interface yields multifaceted benefits in the storage, processing, and electrochemistry of NMC811.

An efficient beam sweeping scheme with backup paging occasions in NR-Unlicensed Spectrum

With the increasing demand of user applications and the shortage of cellular spectrum, New Radio (NR) access to Unlicensed Spectrum (NR-U) is getting significant attention. Listen Before Talk (LBT) procedure is used to sense unlicensed channel availability prior to transmission. The transmissions are subjected to LBT procedure failure, which brings extra delay as they are postponed to the next available transmission opportunity. This excess delay also affects time-critical procedures, such as paging. The directional communication in NR requires beamforming, which further complicates paging procedure as additional paging message transmissions are needed to cover all the beams. In this work, we propose an NR-U paging mechanism (called FF_BP) consisting of Full and Fast Paging Cycles with Backup Paging Occasions (POs). Full Paging uses a normal NR-U paging cycle and broadcasts a paging message on all the beams. On the other hand, Fast Paging, which targets delay-sensitive mobile users, uses a shorter paging cycle and broadcasts a paging message on selected beams only. The Backup POs deal with LBT procedure failure impairments while paging broadcast on selective beams reduces paging resource usage. We analyze FF_BP using a discrete-time semi-Markov chain model and validate the model by extensive simulations. The simulation results show that FF_BP outperforms several baseline mechanisms in terms of average paging delay and paging resource usage.

GCN2 drives diurnal patterns in the hepatic integrated stress response and maintains circadian rhythms in whole body metabolism during amino acid insufficiency.

Disruptions in circadian rhythms are associated with an increased risk of developing metabolic diseases. General control nonderepressible 2 (GCN2), a primary sensor of amino acid insufficiency and activator of the integrated stress response (ISR), has emerged as a conserved regulator of the circadian clock in multiple organisms. The objective of this study was to examine diurnal patterns in hepatic ISR activation in the liver and whole body rhythms in metabolism. We hypothesized that GCN2 activation cues hepatic ISR signaling over a natural 24-h feeding-fasting cycle. To address our objective, wild-type (WT) and whole body Gcn2 knockout (GCN2 KO) mice were housed in metabolic cages and provided free access to either a control or leucine-devoid diet (LeuD) for 8 days in total darkness. On the last day, blood and livers were collected at CT3 (CT = circadian time) and CT15. In livers of WT mice, GCN2 phosphorylation followed a diurnal pattern that was guided by intracellular branched-chain amino acid concentrations (r2 = 0.93). Feeding LeuD to WT mice increased hepatic ISR activation at CT15 only. Diurnal oscillations in hepatic ISR signaling, the hepatic transcriptome including lipid metabolic genes, and triglyceride concentrations were substantially reduced or absent in GCN2 KO mice. Furthermore, mice lacking GCN2 were unable to maintain circadian rhythms in whole body energy expenditure, respiratory exchange ratio, and physical activity when fed LeuD. In conclusion, GCN2 activation functions to maintain diurnal ISR activation in the liver and has a vital role in the mechanisms by which nutrient stress affects whole body metabolism.NEW & NOTEWORTHY This work reveals that the eIF2 kinase GCN2 functions to support diurnal patterns in the hepatic integrated stress response during natural feeding and is necessary to maintain circadian rhythms in energy expenditure, respiratory exchange ratio, and physical activity during amino acid stress.

G1 length dictates H3K27me3 landscapes.

Stem cells have lower facultative heterochromatin as defined by trimethylation of histone H3 lysine 27 (H3K27me3) compared to differentiated cells. However, the mechanisms underlying these differential H3K27me3 levels remain elusive. Because H3K27me3 levels are diluted two-fold in every round of replication and then restored through the rest of the cell cycle, we reasoned that the cell cycle length could be a key regulator of total H3K27me3 levels. Here, we propose that a fast cell cycle restricts H3K27me3 levels in stem cells. To test this model, we determined changes to H3K27me3 levels in mESCs globally and at specific loci upon G1 phase lengthening - accomplished by thymidine block or growth in the absence of serum (with the "2i medium"). H3K27me3 levels in mESC increase with G1 arrest when grown in serum and in 2i medium. Additionally, we observed via CUT&RUN and ChIP-seq that regions that gain H3K27me3 in G1 arrest and 2i media overlap, supporting our model of cell cycle length as a critical regulator of the stem cell epigenome and cellular identity. Furthermore, we demonstrate the inverse effect - that G1 shortening in differentiated cells results in a loss of H3K27me3 levels. Finally, in tumor cells with extreme H3K27me3 loss, lengthening of the G1 phase leads to H3K27me3 recovery despite the presence of the dominant negative, sub-stoichiometric H3.1K27M mutation. Our results indicate that G1 length is an essential determinant of H3K27me3 landscapes across diverse cell types.

Amorphous Hydrated Tungsten Oxides with Enhanced Pseudocapacitive Contribution for Aqueous Zinc‐Ion Electrochromic Energy Storage

AbstractTungsten oxides suffer from sluggish ion diffusion kinetics, limited ion storage capacity, and inadequate stability within the aqueous zinc ion electrolyte, thereby constraining their applicability in electrochromic energy storage devices (EESDs). Here, the amorphous hydrated tungsten oxide films with large optical modulation, fast response speed, large capacity, and high cycling stability are reported, enabled by tuning the contents of structural water and adjusting the pH value of aqueous zinc ion electrolyte. The enhancement of the electrochromic and ion storage performance is mainly due to the introduction of structural water which triggers pseudocapacitive behavior dominated by surface redox reaction, resulting in high electrochemical activity and fast electrochemical kinetics. Meanwhile, the relatively low pH value ensures the chemical stability of the hydrated tungsten oxide film, in synergy with surface redox that avoids ion trapping, leading to extraordinary cycling stability of up to 13000 cycles, marking the state‐of‐the‐art stability for tungsten oxide‐based materials in aqueous electrolyte. Based on the hydrated tungsten oxide films, high‐capacity and stable large‐size EESDs are constructed with the capability of visually monitoring energy status, recovering energy, and regulating light. This work provides a simple yet effective strategy for enhancing the performance of tungsten oxide‐based aqueous zinc ion EESDs.

Lyotropic Aqueous 2-Picolinium Ionic Liquid Crystals and Their Shear-Induced Foams.

1-Dodecyl-2-methylpyridinium bromide ([C12-2-Pic][Br]) and 1-hexadecyl-2-methylpyridinium bromide ([C16-2-Pic][Br]) are two ionic liquid crystals presenting thermotropic smectic phases above 80 °C. Aiming to take advantage of the liquid crystalline properties at lower temperatures, lyotropic aqueous systems were prepared from these two organic salts. Both systems were characterized by polarized optical microscopy (POM), X-ray powder diffraction (XRD), and fast field cycling nuclear magnetic resonance (FFC-NMR) relaxometry to assess their texture, phase structure, and molecular dynamics, respectively. The mesomorphic behavior was induced at room temperature. Moreover, the lyotropic [C12-2-Pic][Br]aq revealed a smectic phase with higher separation between layers, different from the lamellar phases found in the thermotropic system (S1 and SA), which is thermally stable up to 50 °C. Furthermore, the surfactant nature of the ionic liquids diluted solutions investigated in this work allowed the formation of foams. It was found that the precursor solutions of the lyotropic dilutions with the longest alkyl chain ([C16-2-Pic][Br]aq) originated liquid foams with more stable structures than those of [C12-2-Pic][Br]aq.

Improved Wide Temperature and Rate Performance in Li-Ion Batteries with Fluorinated Electrolyte Solvents

Commercial electrolytes include organic solvents unable to withstand the conditions required for the rapidly growing Li-ion battery industry, such as extreme temperatures and charge rates. The thermal and electrochemical stability limits of these solvents restrict the development of Li-ion batteries needed to sustain automotive electrification and other industrial applications. Further efforts are needed to enable electrolyte formulations suited for the operational demands in the market.Koura has designed a series of fluorinated materials for use in Li-ion electrolytes that demonstrate improved performance and safety over conventional commercial electrolytes. The impact of Koura’s fluorinated solvents on performance in 4.3V Gr/NMC811 was examined, with a particular focus on benefits seen on extreme temperature and rate performance. Testing included cycling and rate performance across a range of temperatures from -20 °C to 45 °C and cycling conditions from C/2 to 4C. It has been found that these materials improve low temperature performance and reduce gassing and increase capacity retention during high-temperature and fast charge cycling. Where appropriate, performance of Koura materials is compared to common commercial solvents.To elucidate the mechanisms responsible for the observed improvements, comprehensive post-test analysis has been conducted, including gas composition analysis and quantification via gas chromatography, bulk electrolyte composition analysis via NMR spectroscopy, and surface layer characterization via XPS and SEM. Bulk transport properties of the materials and electrolytes, including conductivity, viscosity, and Li+ solvation, are correlated to performance benefits.This presentation will show Koura’s efforts to fill a major gap in the demands of the Li-ion battery industry today through the design of fluorinated materials and optimization of advanced electrolyte formulations. Specifically, we will present data highlighting the performance of fluorinated compounds on improving battery performance under strenuous conditions with respect to both temperature and cycling rate. Results from fundamental mechanistic studies will be discussed to highlight the mechanisms underlying the observed performance improvements.

Productivity benchmarks for unguyed excavator-based tower yarders

ABSTRACT Detailed productivity studies were conducted on three distinct crews, all operating the modern version of the EMS Harvestline excavator-based yarder working with a motorized grapple carriage for harvesting radiata pine from plantation forests in New Zealand. Data were collected from over 1000 cycles and used to estimate robust productivity benchmarks and models. Mean productivity neared 100 t per productive machine hour (PMH) on short distances (100 m) and decreased to <70 t PMH−1 on longer ones (>200 m). In addition to very fast cycle times, only 1.5 min on average at 100 m, large stem size contributed to those very high productivity figures. Utilization ranged from 50% to 63%, with line-shifts and yarder relocation being a common delay type given the short corridors and quick extraction cycles. Productivity was 40–60 t per scheduled machine hour. This productivity range is comparable with those obtained by heavier and more expensive purpose-built swing yarders, showing great potential for cost-effective future applications.

Two-stage hydrothermal liquefaction of Spirulina: Experimental observations, energy analysis and techno-economic assessment

The intensification of environmental pollution and significant consumption of fossil fuels has led to widespread attention on developing renewable resources. As a carbon-containing renewable energy source, Spirulina is characterized by its fast growth cycle and wide distribution. Currently, one of the research hotspots is the conversion of Spirulina into bio-oil through hydrothermal liquefaction. However, studies on the two-stage hydrothermal liquefaction of Spirulina predominantly concentrate on the product yield or composition. There is relatively little research on thermodynamic (energy) analysis and techno-economic assessment during the reaction process. The main bio-oil components from two-stage hydrothermal liquefaction of Spirulina are ketones and acids with 44.9 % and 34.1 %, respectively. Compared to no-catalysis, two-stage hydrothermal liquefaction of Spirulina over HZSM-5, alkili-modified HZSM-5, and Ni@alkali-modified HZSM-5 increase the relative content of hydrocarbons to 6.6 %, 32.9 % and 48.1 %, respectively. Energy analysis and techno-economic assessment are conducted with Aspen Plus simulation, revealing a exergy efficiency of 56.4 % for the catalytic two-stage hydrothermal liquefaction of Spirulina compared with 43.6 % over no-catalyst. The primary losses occur in the first stage of the reaction process (248.6 kW) and the cooling process (10.7 kW) for catalytic two-stage hydrothermal liquefaction of Spirulina. The hourly price of producing 1 kg bio-oil with a catalyst is $3.67, while without a catalyst, it is $4.54 kg−1; obtaining a unit of chemical exergy costs $0.14×10−3 kJ−1 through catalysis. Moreover, the fluctuations in the prices of sulfuric acid and catalysts are most sensitive to the cost price of bio-oil with or without catalysts in the two-stage hydrothermal liquefaction process, with the values being 10.06 % and 8.10 %. This study has important significance for efficient transformation and energy utilization of Spirulina.