Vortex-induced forced immersion of droplets levitating on liquid nitrogen

Inverse modeling of homogeneous ice nucleation in millimeter-sized levitating water droplets on liquid nitrogen

Liquid nitrogen assisted -ice clamping strategy to suppress milling force-induced deformation and residual stress release deformation in thin-walled cylindrical shells

A successful augmentative biological control program requires continuous and large-scale production of high-quality natural enemies, which depends on the development of appropriate storage techniques for these organisms and their hosts. In this study, we stored Euschistus heros (Fabricius, 1978) eggs at low temperatures, to determine the most viable storage condition and the duration for which these eggs can be stored without reducing acceptance by the parasitoid Telenomus podisi Ashmead, 1893, as well as the quality of its progeny (individuals to be released in the field). Egg storage was evaluated under three conditions: a conventional freezer (-15°C), an ultra-low temperature (ULT) freezer (-80°C), and liquid nitrogen (-196°C) for a period of 12months. Parasitism of eggs stored under these three conditions was assessed at different intervals. The parasitoid parental (F0) generation was evaluated for parasitism, egg-to-adult development time, emergence, and sex ratio. In the progeny (F1), parasitism, emergence, and longevity in newly laid E. heros eggs were assessed. The ULT freezer and liquid-nitrogen storage conditions resulted in the highest parasitism rates of T. podisi in both the parental generation and its progeny. Storage in a conventional freezer was less suitable for parasitism and the viability of T. podisi. The results confirm that E. heros eggs can be stored in a ULT freezer or liquid nitrogen while maintaining theirquality, therebyenabling production and storage during the off-season.

Typical non‐conventional routes of severe quenching treatment, both cyclic quenching from room temperature up to 4 cycles and single time quenching from 600 °C after short‐duration (5 min) holding using liquid nitrogen as the quenchant, has been adopted on an initially annealed commercially pure aluminium. The grain refinement effect is observed for single time quenching from 600 °C; but not for cyclic quenching from room temperature. Lattice strain is found to be accumulated up to 2 cycles followed by a decline to a consistent lower value for 3 and 4 cycles in the specimens subjected to cyclic quenching treatment. The specimen, single time quenched from higher temperature (600 °C), exhibits much higher lattice strain as compared to all cyclic quenched specimens. The accumulation of lattice strain is found to be consistent with the evolution of regions of extremely low misorientation angle in the aluminium matrix. As a result of significantly high lattice strain generation and grain refinement effects, the hardness of commercially pure aluminium is substantially enhanced to 88 HV 10 on execution of single time liquid nitrogen quenching from 600 °C after short‐duration (5 min) holding; while compared with an initial hardness of 36 HV 10 in annealed condition.

Cryopreservation-integrated bioprinting represents a promising approach for tissue regeneration by combining cell-laden bioink freezing with direct post-thaw printing, bypassing traditional culturing steps. However, key challenges remain: ice crystallization compromises cellular viability, while hydrogel structural integrity deteriorates, impairing printability. We present a biphasic bioink platform for cryopreservation-enabled three-dimensional (3D) bioprinting-CAMP (Cryopreservation for Adhesion and Maintenance Printing), which enables direct 3D printing at 4-8°C post liquid nitrogen storage (-196°C). CAMP inhibits ice recrystallization through hydrogen bond-mediated water immobilization, achieving approximately 80% cell viability without the use of toxic cryoprotectants. Cryopreserved cells in the bioink retained focal adhesions and increased phosphorylated FAK expression, and the bioink exhibited approximately ten fold higher ice recrystallization inhibition than phosphate-buffered saline. Mechanistically, CAMP suppressed cell death via phospho-FAK signaling. In vivo evaluation using a rat femoral defect model demonstrated the therapeutic efficacy of CAMP, with cryopreserved constructs promoting complete bone regeneration within three months. CAMP overcomes the key limitations of conventional biofabrication by combining cell cryopreservation, bioprinting, and functional tissue formation into a single workflow. By bridging cryopreservation and bioprinting, CAMP represents a significant advance toward clinically viable, ready-to-implant engineered tissues.

Abstract Acute pneumonia is a severe pulmonary inflammation and it is critical to promptly suppress the dysregulated inflammatory responses to prevent mortality. Glucocorticoids are the first-line therapeutic drugs but with poor tissue selectivity and dose-dependent adverse effects. In this work, cryo-leukocyte, an autologous cell-derived immunosuppressor, was created leveraging the cryo-shocking technology by the quick shock of normal leukocytes with liquid nitrogen. After coupling with aICAM-1 functionalized liposomes, this micro/nano composite system could achieve efficient and prompt inflammation alleviation in acute pneumonia. The engineered cryo-leukocytes were of well biocompatibility after evaluation of blood toxicity, tissue toxicity, acute toxicity and long-term biosafety for over six months, etc. Cryo-leukocytes preserved similar cellular receptors as normal leukocytes, capable of recognizing and binding inflammatory cytokines but without activation of immune cascade, thus exhibiting obvious anti-inflammation efficacy by acting as “mixed cytokines antibodies”. The immunosuppression efficacy of cryo-leukocytes was also superior than that of its sub-group cells of cryo-neutrophil, cryo-monocyte and cryo-lymphocyte, due to relative wide protein expressions that are related to the immune responses. Besides, cryo-leukocytes coupled with aICAM-1 functionalized liposome exhibited obvious anchoring effect in inflammation sites by the interaction of ICAM-1 antibody and ICAM-1 molecules that were over-expressed on inflammatory pulmonary endothelial cells, thus served as superior drug lung-targeting vehicle to maximally enhance the accumulation of traditional Chinese and Western medicines in the lungs. 68.1% of drug signals could be observed in lung tissues compared with other major organs after intravenous injection, significantly higher than that of micro-sized drug-loaded cryo-leukocyte (18.6%) and nano-sized drug-loaded aICAM-1-liposome (12.2%). In a lipopolysaccharide-induced acute pneumonia mice model, the drug-loaded cryo-leukocyte achieved superior anti-inflammation efficacy with 87.5% survival of mice after treatment.

ABSTRACT This study evaluated the impact of cryogenic ultra-freezing on the antioxidant profile of yellow passion fruit (Passiflora edulis) pulp. Fresh pulp samples (control) were compared against treatment groups subjected to ultra-freezing via liquid nitrogen immersion until reaching a core temperature of −40°C. The research followed a completely randomized design, and all analyses were performed in technical triplicate (n = 3) to ensure statistical reliability. Parameters assessed included total phenolic content (TPC), total flavonoid content (TFC), ascorbic acid concentration, and overall antioxidant capacity measured by the DPPH radical scavenging assay. The results demonstrated that cryogenic treatment induced significant biochemical alterations (p < .05); the antioxidant capacity was reduced by 23.6%, while TPC and TFC decreased by 40.3% and 35.7%, respectively (reaching 123.67 mg GAE/100 g and 1.08 mg RE/L), compared to the fresh control. In contrast, ascorbic acid content exhibited high stability, with measured values ranging from 38.08 to 38.43 mg/100 g. Statistical analysis directly measured parameters confirmed that while ultra-freezing is highly effective for the retention of vitamin C, it leads to a substantial degradation of the phenolic and flavonoid fractions. These findings provide critical quantitative data on the selective preservation of bioactive compounds in tropical fruit matrices under extreme thermal conditions.

Droplet-vitrification cryopreservation of shoot tips of the endangered plant Lilium tsingtauense.

The pursuit of room-temperature superconductors remains a critical challenge in modern science. Here, we perform comprehensive high-throughput structure searches for boron carbide (BC) at ambient pressure using CALYPSO method and first-principles calculations. The structure searches rapidly identify the ground state and two new stable phases,P63mcandPmm2, of BC compounds at ambient pressure. TheP63mcphase shows remarkable superconductivity with high superconducting transition temperature (Tc) up to 86 K, exceeding the boiling point of liquid nitrogen. Our calculations indicate that the highTcvalue of theP63mcphase of BC arises from its metallizedσ-bands and dominant hole-like pockets crossing the Fermi level. Moreover, thePmm2 phase of BC compound is verified as a superhard superconductor, withTcof 24 K and Vickers hardness of 44 GPa. These theoretical findings not only enrich the understanding of potential ambient superconductors but also offer promising avenues for the design and synthesis of advanced high-temperature superconductors at ambient pressure.

Abstract Reciprocating cryogenic pumps can effectively enhance the energy efficiency of power systems. However, cavitation phenomenon caused by pressure drops can severely compromise the safety and reliability of the pump. In this regard, this study attempts to illustrate the inlet cavitation characteristics of a reciprocating liquid nitrogen pump based on computational fluid dynamics (CFD) simulations. The cavitation behavior under different inlet pressures, gas contents, and subcooling conditions is also discussed. It is found that under saturated inlet conditions, severe cavitation occurs in both the intake region and the cylinder, and the vapor volume fraction varies by up to 5.86% under different inlet pressures. Subsequently, it is displayed that the vapor volume fraction inside the cylinder is nearly independent of the inlet gas content. Furthermore, increasing the inlet subcooling gradually reduces the effect of cavitation, and at approximately 3 K subcooling, the cylinder is expected to remain in a pure-liquid state. This paper provides insights into the inlet cavitation characteristics to elucidate the actual suction progress of reciprocating cryogenic liquid nitrogen pumps and offers guidance for cavitation suppression.

Microstructural Regulation and Performance Enhancement during CMT-WAAM of 308L Austenitic Stainless Steel Using Synchronous Liquid Nitrogen Cooling

Abstract High-performance stainless steels have been utilized in reusable rockets to achieve significant reductions in manufacturing and maintenance costs. In this study, the effect of silver doping on the mechanical and tribological properties of 316L stainless steel under cryogenic conditions was experimentally investigated. Three silver mass concentrations of 5 wt%, 10 wt%, and 15 wt%, were selected, and the corresponding microstructural characteristics were analyzed using optical microscopy, energy-dispersive spectroscopy, and electron backscatter diffraction. The cryogenic environment of rocket turbopumps was simulated by immersing the specimens in liquid nitrogen. Rockwell hardness, impact fatigue strength, and tribological performance were subsequently evaluated under both room-temperature and low-temperature conditions, with additional tribological tests conducted under water lubrication for comparison. The results indicated that silver preferentially segregated at austenite grain boundaries, leading to grain refinement and the formation of ductile accommodation regions within the hardened matrix. Silver doping enhanced cryogenic ductility and impact fatigue resistance by promoting plastic deformation capability. Owing to the intrinsic lubricating properties of silver, a self-lubricating film was formed at the sliding interfaces, resulting in reduced friction coefficients and wear-rates. Although silver addition slightly reduced hardness and toughness, its grain-stabilizing effect and interfacial lubricity led to an overall improvement in the cryogenic performance of 316L stainless steel. This work provides useful insights for the development of durable and highly reliable materials for reusable rockets and other cryogenic engineering applications.

Abstract Picosecond (ps) laser pre-pulses offer a promising route to optimize tin droplet targets for extreme ultraviolet (EUV) light sources. We numerically simulate the deformation of a 23 μ m-radius liquid Sn droplet induced by a ps laser pulse ( λ = 1064 nm) across a range of pulse energies. The simulations reveal that an intense shock wave launched into the droplet drives a cavitation cavity at the droplet’s center for all pulse energies. However, a secondary spallation cavity near the rear surface appears only when the laser power density exceeds ∼2.73 × 10 13 W cm −2 , corresponding to a shock pressure threshold of about 0.8 GPa. Below this threshold, only a single central cavity forms, whereas above threshold the droplet develops two cavities (central and rear), resulting in a highly deformed acorn-like morphology. In addition, the simulations quantify the scaling of key expansion parameters, such as the axial and radial dimensions of the expanding liquid shell and its velocity, with respect to pulse energy. These results provide quantitative criteria for cavitation and spallation in laser-driven droplets and can guide the design of optimal pre-pulse conditions for EUV sources.

The post-thaw quality, antioxidant activity, and in vivo fertility of Zaraibi buck semen frozen-stored in the presence of different concentrations of either quercetin or L-arginine.

NMR study on the changes of water content characteristics and pore structure evolution during melting of coal frozen with liquid nitrogen

Effectiveness of FBS-DMSO cryoprotectant composition in artificial microbiome models mimicking key gut microbiota enterotypes.

Liquid nitrogen (LN2) fracturing is an emerging anhydrous technology with significant potential for reservoir stimulation in Hot Dry Rock (HDR) geothermal exploitation. Understanding the fracture mechanics of rock subjected to LN2 cooling under high-temperature conditions is essential for optimizing stimulation results. In this study, granite samples heated to various temperatures were subjected to LN2 thermal shock. Acoustic emission (AE) technology and a mechanical testing system were employed to investigate the amplitude distribution, spatial signal evolution, and both macroscopic and microscopic fracture behaviors. The results indicate that AE activity and signal strength intensify significantly with increasing heating temperature. While low-amplitude signals predominate, the spatial distribution shifts from localized main fractures below 300 °C to widespread micro-cracking above 300 °C. Surface morphology analysis reveals a surge in roughness, with median roughness height increasing by 75% between 200 and 300 °C, indicating a critical threshold for thermal damage. The maximum crack displacement distance increased by ∼55.2% from 25 to 400 °C, accompanied by increased tortuosity. Correspondingly, the fractal dimension rose by 19.6% to 1.778. Microscopic observations show that at 300 °C and above, fracture surfaces exhibit layered and step-like matrix failure. This is attributed to high thermal stress weakening the structural bonding, facilitating crack propagation along weak zones to form complex fracture networks. These findings demonstrate that sequential high-temperature heating and LN2 cooling significantly enhance fracture network complexity and density while reducing mechanical strength, providing theoretical and practical support for LN2-based HDR stimulation.

Urothelial carcinoma （UC） is a globally prevalent malignancy lacking robust non-invasive biomarkers. Metabolic reprogramming is a recognized cancer hallmark. Untargeted metabolomics enables high-throughput and unbiased analysis of bodily fluids， offering a promising approach for discovering novel biomarkers in UC. This investigation employs untargeted metabolomic profiling to detect novel urinary biomarkers in UC cohorts. The analytical strategy prioritizes tumor-associated metabolic perturbations through pathway-centric characterization of dysregulated biochemical networks. This study systematically characterizes differential metabolites and associated pathway dysregulations in UC cohorts. The approach seeks to establish a reliable metabolic signature with diagnostic and prognostic value. The findings are expected to advance the development of novel clinical tools. UC biomarkers should optimally integrate preclinical identification， treatment response tracking， and precision-tailored interventions. This investigation provides a methodological framework for exploring cancer metabolism in UC. And it offers evidence-based insights to support translational research and precision medicine initiatives in oncology. This study was conducted at Beijing Chao-Yang Hospital， Capital Medical University， between January and December 2020. A total of 60 urine specimens were consecutively collected. They comprised 30 histologically confirmed UC patients and 30 healthy controls with normal urinalysis findings. Clinical data was prospectively collected via structured case report forms. It encompassed baseline demographics， comorbidities， anthropometric and behavioral factors， and UC pathological parameters. All urine samples were collected prior to invasive procedures. And they were labeled， snap-frozen in liquid nitrogen， and stored at -80 ℃ until analysis. Metabolic profiling was performed using a quadrupole-orbitrap high resolution mass spectrometer equipped with a heated electrospray ionization source. Mass spectrometric data processing was performed using Progenesis QI software. Data processing followed the following workflow： raw data import， spectral peak alignment， feature extraction， and deconvolution. The Progenesis QI software generated datasets containing retention time， peak intensity， and mass-to-charge ratios. Multivariate signal decomposition enabled independent resolution of adduct species， including protonated and sodium-adducted ions. Quality control measures included elimination of ion features demonstrating intra-batch coefficient of variation >15% across technical replicates. This rigorous preprocessing protocol ensured removal of unstable signals. And it preserved biologically relevant metabolic features for subsequent multivariate analysis. No statistically significant differences were observed in baseline clinical characteristics between UC and healthy control cohorts （P>0.05）. Untargeted metabolomic profiling was performed using liquid chromatography-tandem mass spectrometry （LC-MS/MS）. Principal component analysis （PCA） revealed no distinct cluster separation between groups. This result was potentially attributed to limited intergroup metabolic variations or restricted sample size. To enhance discriminatory capacity， supervised orthogonal partial least squares-discriminant analysis （OPLS-DA） was implemented for feature selection. This approach effectively addressed variable collinearity while minimizing non-biological noise interference. Differentially expressed metabolites were identified through variable importance in projection scores， fold change and adjusted P-values. Metabolic pathway analysis was conducted， incorporating pathway enrichment analysis. This multi-tiered analytical approach systematically prioritized UC-associated metabolic perturbations while controlling for confounding factors in specimen analysis. Supervised OPLS-DA was employed to identify differential metabolites and associated metabolic pathways. Significant urinary metabolic disparities were detected between UC patients and healthy controls. Alterations were observed in L-Histidine， N-Acetyltryptophan， 5'-methylthioadenosine， N-methylnicotinamide， L-octanoylcarnitine， 3-indolehydracrylic acid， N¹，N¹²-diacetylspermine， pantothenic acid and so on （P<0.05）. Pathway enrichment analysis revealed perturbations spanning amino acid metabolism， nucleotide biosynthesis， vitamin cofactor utilization， and carbohydrate processing. The histidine metabolism pathway demonstrated the highest topological impact. It was followed by the arginine biosynthesis pathway， arginine and proline metabolism pathway， and the tryptophan catabolism pathway. Future validation in larger cohorts and mechanistic studies is warranted to confirm their clinical utility. The aberrant pathways may offer novel biomarkers and therapeutic targets， particularly for patients resistant to conventional therapies.

High-resolution Hi-C profiling of human breast tissues using an optimized protocol for clinical samples.