Search

Cryoablation is the most commonly used type of cryosurgery. Today, this treatment is insufficiently automated and therefore less accurate than alternative technologies that significantly limits and gradually reduces the scope of its application. However, from low temperature engineering point of view cryosurgery has the untapped potential of the improving its accuracy. In this paper three major methodological problems of cryosurgical equipment and procedure improving are considered: the impact on target isotherm location (1) of the soft biotissue moisture content solidification latent heat variation, (2) of the cryoprobe constructions and operating at maximum cooling power including the fluid cryogen features and the accuracy of boundary condition replacing a cryoprobe and (3) target isotherm fixation approach by modifying the cryoprobe operating mode. The numerical results showed that the target isotherm location depends insignificantly on different moisture content of soft biotissue, then it is not a limiting factor for cryoexposure prediction. Also numerical results showed that the theoretically minimum temperature of cryoprobe surface significantly overestimates their movement, this leads to a significant difference between the experimental and simulation results. The typical shape and movement of cryonecrosis isotherm at refined maximum cryoprobe cooling power for two typical constructions of cryoprobes and two cryogens are presented. The novel algorithm of modifying the cryoprobe operation mode for controlled precision cryosurgery is proposed and validated. All this complements the previously obtained data and shows the prospects for performing precision cryosurgery. The total average uncertainty of target isotherm location during the studied preliminary predicting stage of temperature field movement (virtual cryoablation) is estimated no more than ±0.41 mm. This information is expected to be useful for improving the quality of cryosurgery planning algorithms (e.g. for tumor treatment).

This study investigated the influence of water ice-glazing treatment on the quality attributes of frozen swimming crab by liquid nitrogen spray freezing during storage at -18 °C for 180 days, including water-holding capacity (WHC), thiobarbituric acid-reactive substances (TBARS), total volatile basic nitrogen (TVB-N), sensory score and microstructure. The results showed that water ice-glazing treatment suppressed the variations in overall quality of frozen swimming crab during storage. Ice-glazing treatment can improve maintenance of WHC, microstructure and sensory quality of frozen swimming crab, as well as inhibit the increase of total volatile basic nitrogen (TVB-N). Besides, the degree of primary lipid oxidation in frozen swimming crab was inhibited at a low range by ice-glazing. Water ice-glazing was effective in protecting the quick-freezing swimming crab from undesirable quality changes during frozen storage.

Cryogenic fracturing with liquid nitrogen (LN2) offers the benefits of reducing the water consumption and adverse environmental impacts induced by water-based fracturing, as well as potentially enhancing the fracture complexity. We performed a series of laboratory experiments to explore the key mechanisms governing the breakdown pressures of shale during cryogenic fracturing. In this study, cylindrical shale samples were pre-conditioned by exposing a borehole to low-temperature LN2 for a certain time period, and then, the samples were fractured using gaseous N2 under triaxial stress and a high reservoir temperature. The effects of various key parameters on the breakdown pressure were investigated, including the duration of the low-temperature LN2 treatment, the confining pressure, the reservoir temperature, and the direction of the shale bedding relative to the borehole axis. The results demonstrate that the injection of low-temperature LN2 as a pre-fracturing fluid into a borehole can significantly reduce the breakdown pressure of the shale during subsequent nitrogen fracturing. This reduction in breakdown pressure can be further intensified by increasing the duration of the LN2 pre-conditioning. Without LN2 pre-conditioning, the breakdown pressure initially increases and then decreases with increasing reservoir temperature. When LN2 pre-conditioning is applied, the breakdown pressure keeps decreasing with increasing reservoir temperature. As the confining pressure increased, the breakdown pressure increased linearly in the tests with and without LN2 pre-conditioning. The experimental results demonstrate that LN2 pre-conditioning before N2 fracturing is a promising waterless fracturing technique that reduces the breakdown pressure and enhances the fracture complexity.

Liquid nitrogen freezing, which is an effective permeability enhancement technology, has been applied to the extraction of oil, shale gas, and coalbed methane (CBM). This study is aimed at revealing the effect of liquid nitrogen mass transfer on the temperature variation and pore structure evolution within coal. To achieve this aim, first, temperature measurement tests under the action of liquid nitrogen freezing were conducted on saturated and dried coal samples, respectively. Next, the coal samples were subjected to nuclear magnetic resonance and computer tomography tests before and after liquid nitrogen cold soaking to further explore the mechanism of coal temperature variation from a microscopic perspective. The results show that the action of liquid nitrogen mass transfer can accelerate coal temperature variation through coal pore structure and pore water phase change. The thermal stress and frost heave force generated by liquid nitrogen cold soaking exceed the tensile strength of the coal sample, which directly causes crack initiation, expansion, and connection. The mass transfer of liquid nitrogen has a significant promoting effect on pore development. This study provides the technical support necessary for the efficient exploitation of CBM resources and the improvement of CBM extraction rate.

Direct pyrolysis/KOH activation of carbon from castor shell biomass is an economical combination of two processes to breakdown biomass lignin effectively. The advanced liquid nitrogen-controlled direct pyrolysis/KOH activation technique is even a shortened process, which optimizes the fugacious bond reformation for enhancing supercapacitors’ performance. Novel quenching of the red-hot activated carbon (heated at 800 °C) in liquid nitrogen is peculiar to the demonstrated structural changes. The desired throughput designated nKAC exhibited a high specific surface area of 1468 m2 g−1 over the initial 1131 m2 g−1 for KAC. In 6 M KOH electrolyte, the nKAC electrode exhibited a high specific capacitance of 481 F g−1 at 1 A g−1 and an excellent rate capability of 298 F g−1 at 30 A g−1. In symmetric two electrodes test, the electrodes of nKAC show a high energy density of 17.75 Wh kg−1 at 0.5 A g−1 in 1 M Na2SO4 electrolyte compared with 14.75 Wh kg−1 of KAC electrodes. Furthermore, the nKAC still maintained a high energy density of 12.4 Wh kg−1 at 5.0 A g−1 corresponding to a high power density of 4500 W kg−1. This simple and green method has potential applications in the synthesis of porous carbon based on waste biomass for enhancing performance of electrode materials.

Studying the law of coal adsorption capacity under the action of liquid nitrogen is very important for the extraction of coalbed methane. For this study, the lignite’s ability to adsorb methane was...

Effects of air thawing (AT), refrigerator thawing (RT), water immersing thawing (WIT), lotic water thawing (LWT), and microwave thawing (MT) on the quality of swimming crab by liquid nitrogen freezing were investigated. The highest thawing loss was recorded for MT sample (2.70%) followed by AT (2.22%), WIT (1.97%), and LWT (1.52%), while RT had the lowest value (1.06%). RT sample had the lowest TBARS (0.34 mg/kg) and the highest sensory (8.60) score closer to those for fresh meat, but MT sample had the highest TBARS (0.66 mg/kg) with the lowest sensory score (7.83). Besides, microstructural changes indicated that MT induced larger gaps between muscle fibers and broken more muscle fiber bundles than the other methods, while RT had the least negative role on the microstructure of crab meat. Overall, RT could be recommended as a suitable method for preserving the quality of frozen swimming crab.

Molecular investigations are crucial for further developments in precision medicine. RNA sequencing, alone or in combination with further omic-analyses, resulted in new therapeutic strategies. In this context, biobanks represent infrastructures to store tissue samples and body fluids in combination with clinical data to promote research for new predictive and prognostic biomarkers as well as therapeutic candidate molecules. Until today, the optimal storage conditions are a matter of debate especially with view to the storage temperature. In this unique approach we compared parallel samples from the same tumour, one half stored at − 80 °C and one half in the vapor phase of liquid nitrogen, with almost identical pre-analytical conditions. We demonstrated that RNA isolated from breast cancer samples revealed significantly higher RINe-values after 10 years of storage in the vapor phase of liquid nitrogen compared to storage at − 80 °C. In contrast, no significant difference was found regarding the DIN-values after DNA isolation. Morphological changes of the nucleus and cytoplasm, especially in the samples stored at − 80 °C, gave insights to degenerative effects, most possibly due to the storage protocol and its respective peculiarities. In addition, our results indicate that exact point-to point documentation beginning at the sample preparation is mandatory.

In this study, a simple and rapid sample preparation method named liquid-nitrogen-induced homogeneous liquid–liquid microextraction has been developed for the extraction and pre-concentration of Co(II) and Ni(II) ions before their analysis by flame atomic absorption spectrometry. For this purpose, first, acetonitrile containing 8-hydroxyquinoline is added into a sample solution and the mixture is vortexed. As a result, a homogeneous solution is formed. Subsequently, the solution is cooled using liquid nitrogen for a few seconds. By this process, due to difference in the freezing point of acetonitrile and water, the homogeneous state is broken and the analytes (as oxinate complexes) are extracted into liquid acetonitrile phase collected on top of the frozen aqueous phase. The linear dynamic ranges obtained for Ni(II) and Co(II) were 1.0–30 and 0.50–20 μg L−1, respectively. The obtained limits of detection were 0.36 and 0.20 μg L−1 for Ni(II) and Co(II), respectively.

Herein, we developed a novel homogeneous liquid–liquid microextraction based on liquid nitrogen-induced phase separation (HLLME-LNPS) for the extraction and determination of lead (Pb) in Pb-adulterated opium and refined opium by GFAAS analysis. In this procedure, first, 400 μl of acetonitrile (extractant) containing 7.0 μl of diethyl dithiophosphoric acid (DDTP) is injected into a sample solution and a homogeneous solution is formed. Subsequently, the homogeneous mixture is cooled using liquid nitrogen for 16 seconds. By this process, due to the difference in the freezing points of the organic and aqueous phases, the homogeneous state is broken and the Pb-DDTP species are extracted into the liquid organic phase collected on top of the frozen aqueous phase. The introduced method exhibited a good linearity with a coefficient of determination (r2) of 0.9988 and an acceptable linear range of 0.6–100 μg l−1. Accordingly, the detection limit was 0.2 μg l−1 (S/N = 3) for Pb ions, and a high enrichment factor was obtained. The proposed method was successfully utilized to determine trace levels of Pb in opium samples. The results of the sample analysis showed that 65% of the opium samples and 85% of the refined opium samples had much higher than expected levels of contaminating Pb, and this contamination poses a serious threat to drug users.

The article provides a comparative assessment of the main technological characteristics of consortia of lactic acid microorganisms used to make starter cultures for cottage cheese products, before and after freezing in liquid nitrogen, during storage for 6 months. It was found that when stored for 6 months with a temperature regime of minus (40 ± 2) ºС and below, the main technologically significant characteristics of consortia of lactic acid microorganisms for the manufacture of starter cultures used in the dairy industry are preserved.

The low permeability of coal reservoirs makes the exploitation and utilization of coalbed methane difficult. In recent years, the liquid nitrogen freeze–thaw (LN2-FT) fracturing technique has been ...

Using scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman scattering we studied the charge state of matrix and doping element atoms on the surface, morphology, and defects in the structure of graphene-like materials synthesized by plasma-arc discharge in liquid nitrogen.

Physicochemical properties of microbial transglutaminase (MTGase) cross-linked surimi gels subjected to liquid nitrogen (LN) spray freezing with different temperatures and cross-linking degrees were investigated. Gels with lower LN spray temperature (−90 °C) were found taking less time in cooling down themselves to maximum-ice-crystal generating temperature. Microstructure images showed the pores of gels became smaller and the structure gradually became denser, as freezing temperature decreased and cross-linking degree increased. It also revealed T22 relaxation time of gels decreased significantly with surimi gels cross-linking degree increasing, indicating the binding ability of gels to moisture was enhanced accordingly. Meanwhile, the proton density weighted image brightness declined along with the LN spray temperature decreasing, and the image brightness showed a decreasing trend from outside to inside, indicating that water migrated and permeated easier from the inside of the gel network to the outside undergone higher LN temperature and lower cross-linking degree. Besides, the L⁎ and W values of LN groups decreased along with LN spray temperature and cross-linking degree increasing. Moreover, −90 °C LN group with 46.70% cross-linking degree presented the highest breaking force which ascribed to their synergistic efforts in maintaining a stable and dense structure of gels via controlling ice crystals and cross-linkages' generation.

A comparative analysis of the survival rate of the human gut microbiota after low-temperature preservation under the protection of penetrating (dimethylsulfoxide and glycerol), nonpenetrating (gelatin) and gas (helium) protectors was performed. Increased resistance of intestinal bacteria to the effect of low temperatures was revealed. A significant portion of the bacteria (50.0 ± 3.0%) remained viable after freezing in liquid nitrogen without the cryoprotector(s). The greatest survival was achieved under the protection of 5% dimethylsulfoxide (86.0 ± 4.0%), 5% glycerol (82.0 ± 5.2%), and 10% gelatin (75.0 ± 5.0%). The combination of cell-penetrating (dimethylsulfoxide and glycerol) and nonpenetrating (gelatin) protectors did not lead to a synergistic effect. The use of atmospheric helium for cryoprotection of heterogeneous human gut microbiota did not increase its survival, even in combination with such powerful protectors as dimethylsulfoxide and glycerol, which indicates the need to optimize cryoprotection media, in particular, for strict anaerobes.

Processor energy density is exceeding the capabilities of conventional air-cooling technology, but two-phase cooling has the potential to manage these resulting heat fluxes at reliable temperatures and higher electrical efficiency. When two-phase cooling is used in tandem with overclocking, data center footprints are reduced as individual chip processing power can be set at limits well beyond the manufacturer’s Thermal Design Power (TDP) or nominal operating condition. This study examines how Liquid Nitrogen (LN2) can be used with Additive Manufacturing (AM) and overclocking to increase the computational performance of a commercially available GPU. The power consumption and frequency relationship were established for both the cryogenically cooled solution and a comparative air-cooled solution. The cryogenic solution saw up to a 17.4% increase in compute efficiency and an 18.1% improvement in compute speed with comparable power efficiency at an equivalent performance level to the air-cooled solution. This study considers the computational performance and efficiency gains that can be acquired through cryogenic cooling on an individual graphics card, which can be replicated on a larger scale in data center applications.

A simple process to synthesize metal nitride particles was proposed using submerged arc discharge plasma in liquid nitrogen. Gibbs standard free energy was considered for the selection of the nitride-forming materials. In this study, titanium (Ti) and aluminum (Al) electrodes were used as raw materials for nitride particle preparation. Liquid nitrogen acted as a dielectric medium as well as a nitridation source in this process. A copper electrode was also used as a non-reactive material for comparison with the reactive Ti and Al electrodes. As the operating conditions of the experiments, the arc discharge current was varied from 5 A (low-power mode) to 30 A (high-power mode). The formation of titanium nitride (TiN) and aluminum nitride (AlN) was confirmed in the particles prepared in all experimental conditions by X-ray powder diffraction (XRD). The observation using a field emission scanning electron microscope (FE-SEM) and a field emission transmission electron microscope (FE-TEM) indicated that the synthesized TiN particles showed a cubic morphology, whereas AlN particles containing unreacted Al showed a spherical morphology. The experiments using different metal electrode configurations showed that the anode generated most of the particles in this process. Based on the obtained results, a particle formation mechanism was proposed.

Ultrasonic flow metering is one of flow measurement techniques applicable to low temperature environment. Unlike pipe provers or Coriolis mass flowmeters, ultrasonic flowmeters require waveguides in front of ultrasound sensors. The waveguides can prevent heat conduction from the ultrasound sensors to low temperature liquids, such as liquid nitrogen. The ultrasound sensors can maintain its piezoelectricity within the specified temperature ranges by thermal insulation of the waveguides. In this study, low temperature testing on a pair of ultrasound sensors was performed to see if ultrasound waves could be transmitted normally through liquid nitrogen. A flowmeter cell with diameter of 300 mm (equivalently, 12”) was used as a container for liquid nitrogen. Three pairs of ultrasound sensors were installed in the flowmeter cell. Fiber-optic sensors were also attached on its inner wall to measure the temperature of liquid nitrogen. As a result, ultrasound waves were successfully transmitted between a pair of ultrasound sensors by using a preamplifier. The fiber-optic sensors could measure the temperature of liquid nitrogen although the sensors were not calibrated by the reference temperature scale at KRISS.

The effects of recirculation velocity on the volume fraction of oxygen and the temperature distribution in a container with a controlled atmosphere (CA) by liquid nitrogen injection were investigated. A three-dimensional (3-D) model was developed, and the airflow, heat, and mass transfer in the process of liquid nitrogen injection were simulated. A validation test was conducted to verify the accuracy of the model. The results indicate that improving the recirculation velocity will extend the time of liquid nitrogen injection but will reduce the temperature difference in the container and on the surfaces of fruits and vegetables. Different recirculation velocities have little effect on the distribution uniformity of the oxygen volume fraction. The temperature at the holes on the division plate were all above 0 °C when the recirculation velocity was 8 m/s. The results of this study provide a detailed understanding of air transport in a container, which will be useful for the design and optimisation of transportation containers for fruits and vegetables in a CA.

Radiation damage is the most fundamental limitation for achieving high resolution in cryo-EM, and is expected to be reduced at liquid-helium temperature. Surprisingly, cryo-EM reconstructions of apoferritin samples cooled with liquid helium showed no improvement in resolution over liquid-nitro­gen-cooled samples, but showed substantially more beam-induced particle motion., Radiation damage is the most fundamental limitation for achieving high resolution in electron cryo-microscopy (cryo-EM) of biological samples. The effects of radiation damage are reduced by liquid-helium cooling, although the use of liquid helium is more challenging than that of liquid nitrogen. To date, the benefits of liquid-nitrogen and liquid-helium cooling for single-particle cryo-EM have not been compared quantitatively. With recent technical and computational advances in cryo-EM image recording and processing, such a comparison now seems timely. This study aims to evaluate the relative merits of liquid-helium cooling in present-day single-particle analysis, taking advantage of direct electron detectors. Two data sets for recombinant mouse heavy-chain apoferritin cooled with liquid-nitrogen or liquid-helium to 85 or 17 K were collected, processed and compared. No improvement in terms of resolution or Coulomb potential map quality was found for liquid-helium cooling. Interestingly, beam-induced motion was found to be significantly higher with liquid-helium cooling, especially within the most valuable first few frames of an exposure, thus counteracting any potential benefit of better cryoprotection that liquid-helium cooling may offer for single-particle cryo-EM.

A key problem in the conversion of cellulose into chemicals and fuels is the low product yield from cellulose due to its robust structure. In this work, for the first time, cellulose was pretreated with coupling of liquid nitrogen and ball milling (LN–BM) for cellulose hydrolysis. After the LN–BM treatment, the glucose yield from cellulose by HCl in water increased by almost 2 times and yield of formic acid catalyzed by H2SO4–NaVO3 was more than 3-fold that obtained from untreated cellulose. The yields were also much higher than that from the individually ball-milled cellulose. The structure variation of cellulose indicated that reduction of both crystallinity index and molecular weight contributed to improving the conversion efficiency, but the former was the dominant factor. The combination of liquid nitrogen and ball milling developed in this work is an effective and environment-friendly approach for cellulose pretreatment.