Liquid Nitrogen Gas Research Articles

Nano-Pd/SiO2 aerogel catalyst prepared via ambient pressure drying process using perlite powder in hydrogenation and cross-coupling reactions

Perlite, a cheap silica source with abundant reserves in countries such as Türkiye, China, and Greece, was used to produce nano Pd-doped silica aerogel powder for the first time in this study. The microstructure and morphology of the prepared silica aerogel powder were examined using SEM, FE-SEM, and TEM. The phases of the silica aerogel powders were analyzed via XRD (X-ray Diffraction) technique. The chemical bonding of the surface modifier with aerogels was analyzed by Fourier transform infrared spectroscopy (FTIR, Spectrum RX-1, Perkin Elmer). Surface areas, pore volumes, distributions, and particle sizes of the alumina-silica-based aerogel powders with a porous structure were measured using a Micromeritics/ASAP 2020 brand BET (Brunauer, Emmet, and Teller) device in a liquid nitrogen gas environment at 77K.The efficiency of this nano Pd-doped silica aerogel powder was investigated as a heterogeneous catalyst for well-known transformations in organic synthesis, such as alkene hydrogenation and cross-linking reactions. The results indicated that the developed method is chemoselective, reducing only carbon-carbon multiple bonds without affecting C-N or C-O multiple bonds, such as carbonyl and nitrile. The effectiveness of the newly developed catalyst was also investigated in Heck and Suzuki-Miyaura reactions, yielding the targeted products with high efficiency.Thus, an inexpensive, economical, and environmentally friendly method has been developed that is potentially applicable in the hydrogenation and cross-coupling reactions of alkenes.

The emerging role of cryogenesis in cancer treatment

Cancer is one of the most lethal chronic diseases in the world. In the United States alone, over 1.7 million diagnosed new cases of cancer cases was reported in 2022 and over half a million people died due to complication regarding cancer in that same year. The mutation that gives rise to cancer cells occurs in normal cells and causes them to proliferate uncontrollably, obstructing essential organs and making the body more vulnerable to deadly infectious infections. In modern society, the combination of a sedentary lifestyle and exposure to unsafe molecules around the public has drastically increased the masss probability of mutation within their genetics and for cancer cells to proliferate. Cryogenesis therapy is the usage of cryogenic substances such as liquid nitrogen or argon gas to freeze and destroy the cancer cell. Cryogenesis generally involves the repetition of two steps: the freezing process and the thawing process. The freezing process is performed under extremely low temperatures and allows for the formation of ice crystals both on the inside and outside of the cell membrane, which in terms causes the rupture of the cell membrane. The thawing process is performed after the freezing process and allows the target cell to thaw; the thawing process is performed to induce osmotic shock and further induce the damage caused by the freezing process. The two cryogenesis cycles are repeated to reinforce the damage caused to the cancer cells. Compared with traditional therapies, cryogenesis therapy, as a non-invasive treatment, has The advantages of using cryogenesis are the therapys non-invasive treatment methods, pinpoint precision and accuracy, reduced side effects after the therapy, and repeatability. Although the cryogenesis process is still new in under development, it has the potential to be effective against the most lethal cancer types, such as lung cancer and brain cancer. This review explores a new treatment for cancer, in cryogenesis, that have minimal side-effect and discusses its mechanism and application to different type of cancer and combination effect.

Breast Cryoablation, From the AJR "How We Do It" Special Series.

Breast cryoablation is a minimally invasive image-guided percutaneous procedure to treat fibroadenomas and early-stage breast cancer utilizing liquid nitrogen or argon gas to create extremely cold temperatures that devitalize targeted tissue. Although more long term data are needed, this outpatient procedure is well tolerated and carries minimal risks, including non-target thermal injury that can be mitigated by careful planning and proper technique. Building a sustainable breast cryoablation service in a radiology practice poses several practical considerations, such as training proceduralists, purchasing equipment, recruiting patients, and understanding the revenue cycle. This article describes aspects of the radiologist's role in this procedure, including implementation of a breast ablation program, patient selection, technical details related to intervention, and expected postprocedural outcomes.

Microstructural Characterization of In Situ Aluminum Matrix Composites with Interconnected Aluminum Nitride Produced by Arc Plasma-Induced Accelerated Volume Nitridation

We present a strategy for fabricating aluminum (Al) matrix composites (AMCs) reinforced with interconnected aluminum nitride (AlN) via arc plasma-induced accelerated volume nitridation. AMCs with 10 vol.% AlN are formed in situ by the reaction between liquid Al alloy and nitrogen gas within 1 min of arc melting, revealing very high formation rate of AlN (3.28 × 10−1 g/min·cm3). The rapid nitridation is attributed to the improved wettability and spontaneous infiltration of the melt, which results in the formation of AlN agglomerates and lamellas. In particular, Al-12Si/AlN composites exhibit over two times higher yield strength (195 MPa) than the Al/AlN composites (70 MPa) when compressed along the longitudinal direction to the lamellas. The coefficient of thermal expansion (CTE) is about 30% lower in the Al-12Si/AlN composites (17.0 × 10−6/K) than pure Al (23.6 × 10−6/K). This is attributed to the interconnected AlN architecture and Al–Si eutectic microstructure, which constrain the thermal expansion of the Al matrix. The present AMCs afford an attractive combination of specific thermal conductivity and CTE. These findings would facilitate the development of novel AMCs reinforced with interconnected AlN as cost-effective heat sink materials.

Performance Analysis of Resistive Superconducting Fault Current Limiter Using LN2and GHe Cooling

Large-scale electric aircraft is a disruptive technology to address the environmental impact of air travel. Fault current limitation is crucial to realise the safety and reliability of the electric aircraft, in particular for large-scale electric aircraft using DC distribution network. This paper investigates the behavior of the resistive SFCL under different cryogenic cooling systems including liquid nitrogen and helium gas circulation cooling systems for the electric aircraft DC distribution network. Electromagnetic and thermoelectric models were used to predict the characteristics of resistive SFCL. The simulation results demonstrate that it is promising to design resistive SFCL using liquid nitrogen cooling as well as helium gas circulation cooling systems, which offer flexibility for SFCL cryogenic cooling system for electric aircraft applications.

A thermodynamic model for the pressure created by injecting liquid nitrogen into a boiler partially filled with water

This study examines the interaction between a small amount of liquid nitrogen with nitrogen gas and water in a rigid boiler. A thermodynamic model is proposed, and simulations are conducted, focusing on predicting the fluids’ equilibrium pressure. Two consecutive processes are assumed by the model: a mixing process of the injected liquid nitrogen and the nitrogen gas in the boiler, followed by a heat transfer process of the nitrogen and the water. The model is tested against the experimental data from Clarke et al. (Clarke, Martinez-Herasme, Crookes and Wen. International Journal of Multiphase Flow, 36(11):940-949, 2010), and the predicted pressures deviate from the data by less than 3%. Based on the model, this study further pursues the physical conditions favorable for maximizing the fluids’ equilibrium pressure. The effects of the initial water temperature and the liquid nitrogen’s quantity upon the pressure are examined. For the same initial water temperature, having more nitrogen raises the pressure. For the same amount of nitrogen, however, the pressure does not always increase with the initial water temperature, as the higher compressibility of warmer water ends up reducing it. These factors must be accounted for as one seeks to maximize the pressure. For this purpose, this study presents a simple framework to access the complicated thermodynamic responses of liquid nitrogen, nitrogen gas and water in direct contact.

Mechanical properties of Q690E/Q960E high-strength steels at low and ultra-low temperatures: Tests and full-range constitutive models

Mechanical properties of high-strength steels (HSSs) at varying temperatures are fundamental information for the design and numerical analysis of cold-region structures and LNG containers using HSSs. Tensile tests on 14 HSS Q690E and 17 Q960E tensile coupons were firstly carried out at six low temperatures of 20, −30, −60, −80, −120 and −165 °C. The required low-temperature environment for the tensile tests was achieved through an insulation chamber with injecting liquid nitrogen (LN) gas. Their results showed that decreasing the low temperature from 20 to −165 °C slightly affected the elastic modulus of both HSS Q690E and Q960E materials, but significantly increased their yield and ultimate strengths. In addition, ductile failure occurred to all the HSS coupons at low temperatures, and the ductility of HSS was not compromised. Finally, this paper developed full-range constitutive models to describe stress–strain laws of HSS Q690E and Q960E at a low-temperature range of −165 ∼ 20 °C. Validations against the reported test results showed that the proposed full-range constitutive model reasonably estimated the stress–strain behaviours of Q690E and Q960E HSSs at low temperatures.

Research on building cryo-compressed test condition on large CcH2 vessel for heavy-duty fuel cell trucks

To test the performance of cryo-compressed hydrogen vessels for heavy-duty fuel cell trucks, a novel inconstant filling method was proposed by applying liquid nitrogen and compressed helium to create the target cryo-compressed environment. The computational fluid dynamics method was used to simulate the loading process of generating suitable conditions in a large cryo-compressed vessel. The element-based finite volume method and the k – ω based shear stress transport model were applied to simulate the thermal flow of filled gas. Temperature distribution and loading performance were carefully analyzed under different filling cases. In a bid to compare the loading performance, five key factors (gas consumption, temperature rise of aluminum layer and carbon fiber, average filling rate, and time consumption) were put in a radar map for discussing the optimized strategy of each application. The simulation results revealed that the cryo-compressed test condition can be well established by using liquid nitrogen precooling and gas helium pressurization. Nevertheless, the mass flow should be maintained at a low rate before the construction of high-pressure. These findings help design and operate the cryo-compressed test by enhancing its safety and improving efficiency.

Experimental investigation and analysis on the pressure stabilization of subcooled liquid nitrogen circulation for the HEPS

The High Energy Photon Source (HEPS) is a fourth generation radiation source, where lots of optical equipment are cooled down to the liquid nitrogen temperature for the better performance. The subcooled liquid nitrogen circulation is a very advantageous cooling method of monochromators and undulators, which are sensitive to fluid pressure fluctuations. Although the pressure stabilization matters a lot but it has rarely been studied. In this paper, the causes of pressure fluctuations are analyzed, and accordingly the principle of thermal balance is proposed. Based on the analysis, three pressure stabilization methods were suggested and tested. A partially liquid nitrogen filled tank was connected to the subcooled liquid nitrogen circulation serving as a pressure fluctuation buffer. The side effect is that the heat load of the tank raises the pressure gradually. Therefore, the cold source buffer and its induced heat load need good compromise. The tank heat load was cooled by saturated nitrogen, bypass liquid nitrogen and direct gas absorption: The saturated nitrogen reuses the sensible heat of cold gas; the bypass liquid nitrogen avoids the influence of circulation heat load variation and the gas absorption prevents the heat exchanger in the tank. The test results show that the peak-to-peak value of the pressure fluctuation can be controlled in the level of ± 4.0 mbar and the RMS value less than 1.0 mbar. The pressure affect factors were empirically studied.

Pyrolysis characteristics and microstructure evolution of different coal types

Coal pyrolysis is the basis of coal gasification, as it is the necessary reaction step in the coal conversion process. To study the pyrolysis characteristics of different coal grades under temperature, thermal simulation tests of three different ranks of coal were conducted, and the pore structure and gas products were analyzed by using liquid nitrogen adsorption and gas chromatographic, and perform fractal fitting for pores of different size. The results show that the pyrolysis gas output of Inner Mongolia lignite is higher than that of Xinjiang long flame coal and Hancheng bituminous coal. With the increase of coal rank, the gas output of each gas component also shows a decreasing trend and the initial temperature and peak temperature of various gases gradually shift to high temperature. With the increase of temperature, the average pore size, volume, specific surface area, and fractal dimension of the three kinds of coal char show an increasing trend. The average pore size and pore volume of coal char increase, and the fractal dimension increase with the increase of coal rank. The comprehensive comparative analysis of the gaseous products, average pore size, pore volume, and fractal dimension of the three coal chars shows that Inner Mongolia lignite has high gas production, large average pore size, good connectivity, and simple pore structure, which is conducive to the escape of pyrolysis gas and the transportation of gasification agent and is the best favorable coal for gasification. The research results are expected to provide experimental guidance for the actual production of underground coal gasification.

Sub‐Zero Temperature Sensor Based on Laser‐Written Carbon

AbstractSub‐zero temperature sensors (SZTSs) have potential applications in safely storing COVID‐19 vaccines. Herein, an SZTS based on laser‐induced carbonization (LIC) achieved by a nanosecond infrared laser with a wavelength of 1064 nm is reported. Direct laser writing is adopted for laser‐induced carbon in Kapton polyimide sheets with a thickness of 125 µm. The sensor exhibits a good linear change in resistance to sub‐zero temperatures ranging from 0 to −150 °C, where the coefficient of determination adjusted R‐square (R2) value is 0.99238, which indicates a good linear fit. The sensor exhibits a stable static response at all temperatures over time. The dynamic responses by controlling the liquid nitrogen gas and placing an ice cube on the sensor are also measured to validate the sensor. Notably, the electrical performance of the sensor remains stable even after 15 h. The sensor response of the LIC sample validates the 3D variable range‐hopping charge transport mechanism, governed by the Mott equation with a good linear fit, which is mainly owing to disorder in its structure. LIC‐based SZTSs can enable sensors that are ultra‐fast to fabricate, roll‐to‐roll processable, economical, and more significantly, can be interfaced with flexible printed circuit boards without any additional interfacing.

Tensile behavior of stainless steel S30408 at the Arctic low temperature

This paper investigated tensile behaviours of S30408 at the Arctic low temperatures (T) of -80~20C. A cooling chamber equipped with liquid nitrogen gas was adopted to rebuild the Arctic low-temperature environment. Standard tension tests were performed on 48 coupons with different thickness at different T values of -80, -60, -30, and 20C. Test results revealed the ductile failure mode of stainless steel S30408 even at -80C. The tensile stress-strain (o-e) curves of S30408 at ambient temperatures exhibited a long strain hardening plateau. Meanwhile, the low-temperature tensile o-e curves of S30408 were different from those at ambient temperatures, which exhibited a second hardening stage with a larger slope than the first hardening. The decreasing T generally increased the elastic modulus, yield and ultimate strength, but reduced the ductility of S30408. Decreasing the T from 20 to -80 reduced the ductility of S30408 by about 28%, but improved the elastic modulus, yield and ultimate strength by about 20%, 22%, and 75%, respectively. This paper also adopted the best subset regression analysis method to develop empirical formulae on estimating influences of T on mechanical properties of S30408. Validations of the predictions by these empirical formulae against the test results in the literature proved their accuracies.

Nanopore Structure of Different Rank Coals and Its Quantitative Characterization.

Based on gas adsorption theory, high-pressure mercury intrusion (HPMI), low-temperature liquid nitrogen gas adsorption (LT-N₂GA), CO₂ adsorption, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and small-angle X-ray scattering (SAXS) techniques were used to analyze the pore structures of six coal samples with different metamorphisms in terms of pore volume, specific surface area (SSA), pore size distribution (PSD) and pore shape. Combined with the gas adsorption constant a, the influence and mechanism of the pore structure of different coal ranks on gas adsorption capacity were analyzed. The results show that there are obvious differences in the pore structure of coals with different ranks, which leads to different adsorption capacities. To a large extent, the pore shapes observed by SEM are consistent with the LT-N₂GA isotherm analysis. The pore morphology of coal samples with different ranks is very different, indicating the heterogeneity among the coal surfaces. Adsorption analysis revealed that mesopore size distributions are multimodal and that the pore volume is mainly composed of mesopores of 2-15 nm. The adsorption capacity of the coal body micropores depends on the 0.6-0.9 nm and 1.5-2.0 nm aperture sections. The influence of coal rank on gas desorption and diffusion is mainly related to the difference in pore structure. The medium metamorphic coal sample spectra show that the number of peaks in the high-wavenumber segment is small and that it is greater in the high metamorphic coal. The absorption intensity of the C-H stretching vibration peak of naphthenic or aliphatic hydrocarbons varies significantly among the coal samples. Over a small range of angles, as the scattering angle increases, the scattering intensity of each coal sample gradually decreases, and as the degree of metamorphism increases, the scattering intensity gradually increases. That is, the degree of metamorphism of coal samples is directly proportional to the scattering intensity. The influence of coal rank on gas adsorption capacity is mainly related to the difference in pore structure. The gas adsorption capacity shows an asymmetric U-shaped relationship with coal rank. For higher rank coals (Vdaf < 15%), the gas adsorption consistently decreases significantly with increasing Vdaf. In the middle and low rank coal stages (Vdaf > 15%), it increases slowly with the increase of Vdaf. We believe that the results of this study will provide a theoretical basis and practical reference value for effectively evaluating coal-rock gas storage capacity, revealing the law of CBM enrichment and the development and utilization of CBM resources.

Quality in turning of Inconel X-750 superalloy

This study has been conducted to analyse the effects of turning the Inconel X-750 superalloy, which is a member of a nickel-based superalloy family that is frequently preferred in the aerospace and nuclear energy industries in particular, under minimum quantity lubrication (MQL), cryogenic liquid nitrogen (LN2) and carbon dioxide gas (CO2) cooling/lubrication conditions, with different cutting speeds (V c = 65, 95, 125 and 155 m/min) and constant feed rate (f = 0.1 mm/revolution) and cutting depth (a = 0.5 mm) parameters, on the processability of Inconel X-750, hence on the surface integrity. In this context, the results obtained from the tests have been comparatively examined through surface roughness, tool wear and chip formation. Comparison results show that the cryogenic carbon dioxide method has generally provided the best surface roughness and tool wear values. The MQL method has provided the best chip formation.

Barrier Effect on the DC Breakdown Characteristics of Cryogenic Nitrogen Gas Evaporated From Liquid Nitrogen

In superconducting power equipment, such as a resistive-type superconducting fault current limiter (R-SFCL), liquid nitrogen (LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) and cryogenic nitrogen gas (CGN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ) act as not only the cooling media but also the insulation media. In R-SFCLs, CGN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> will coexist with the LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The objective of this article is to determine a barrier effect on the dc dielectric strength of the CGN2 evaporated from LN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The dc breakdown voltage V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</sub> of a pair of rod-to-plane electrodes with an insulation barrier was measured. The gap distance b was 13.6 mm, in which the distance from the rod electrode to the insulation barrier was a and the distance from the rod electrode to the plane electrode was b. Three cases were measured, which were a/b = 1/7, 3/7, and 5/7, respectively. The materials of the insulation barrier were polytetrafluoroethylene (PTFE) and Kapton, respectively. The experimental results showed that, for both positive and negative polarities, when a/b was 1/7, the breakdown voltage was approximately two times higher than that without the barrier. When a/b was 3/7, the average breakdown voltage was approximately 1.5 times higher than that without the barrier. When a/b was 5/7, the breakdown voltage was nearly the same as that without the insulation barrier. Therefore, it suggested that the closer the insulation barrier was to the rod electrode side, the higher the breakdown voltage was. When a/b = 5/7 and the thickness of the insulation barrier was 0.10 mm, the breakdown voltage of the CGN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /insulation composite insulation system with the Kapton film was higher than that with the PTFE film. A high-speed camera observation showed that the discharge started in the CGN <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> , and then, a further breakdown occurred in the insulation barrier. An equivalent circuit model was built up to describe the breakdown process, which showed that the lower the electrical conductivity of the insulation barrier was, the higher the breakdown voltage was.

Experimental comparison of MO40 steel surface grinding performance under different cooling techniques

Cutting fluids pollute the environment and harm human health. Cryogenic grinding with liquid nitrogen and carbon dioxide gas is a new method that is used to create a cleaner environment and maintain human health. In order to investigate the effect of the cooling method in the grinding process, surface roughness and hardness were compared in the presence of lubricating fluid and cryogenic cooling with three speeds and three grinding depths. The results of this study showed that except for high depths of cut and cutting velocities, the obtained surface quality with liquid nitrogen and carbon dioxide gas was better in comparing to lubricating fluid. In addition, in high depths of cut and cutting velocities, the obtained hardness from liquid nitrogen and carbon dioxide gas is higher in comparing to lubricating fluid. Then, by using ANOVA, that is concluded the depth of cut is the most effective parameter on surface roughness and hardness.

Cryotherapy for liver metastases.

The liver is affected by two of the most common groups of malignant tumours: primary liver tumours and liver metastases from colorectal carcinoma. Liver metastases are significantly more common than primary liver cancer and long-term survival rates reported for patients after radical surgical treatment is approximately 50%. However, R0 resection (resection for cure) is not feasible in the majority of patients. Cryotherapy is performed with the use of an image-guided cryoprobe which delivers liquid nitrogen or argon gas to the tumour tissue. The subsequent process of freezing is associated with formation of ice crystals, which directly damage exposed tissue, including cancer cells. To assess the beneficial and harmful effects of cryotherapy compared with no intervention, other ablation methods, or systemic treatments in people with liver metastases. We searched The Cochrane Hepato-Biliary Group Controlled Trials Register, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE Ovid, Embase Ovid, and six other databases up to June 2018. Randomised clinical trials assessing beneficial and harmful effects of cryotherapy and its comparators for liver metastases, irrespective of the location of the primary tumour. We used standard methodological procedures expected by Cochrane. We extracted information on participant characteristics, interventions, study outcomes, and data on the outcomes important for our review, as well as information on the design and methodology of the trials. Two review authors independently assessed risk of bias in each study. One review author performed data extraction and a second review author checked entries. We found no randomised clinical trials comparing cryotherapy versus no intervention or versus systemic treatments; however, we identified one randomised clinical trial comparing cryotherapy with conventional surgery. The trial was conducted in Ukraine. The trial included 123 participants with solitary, or multiple unilobar or bilobar liver metastases; 63 participants received cryotherapy and 60 received conventional surgery. There were 36 women and 87 men. The primary sites for the metastases were colon and rectum (66.6%), stomach (7.3%), breast (6.5%), skin (4.9%), ovaries (4.1%), uterus (3.3%), kidney (3.3%), intestines (1.6%), pancreas (1.6%), and unknown (0.8%). The trial was not reported sufficiently enough to assess the risk of bias of the randomisation process, allocation concealment, or presence of blinding. It was also not possible to assess incomplete outcome data and selective outcome reporting bias. The certainty of evidence was low because of risk of bias and imprecision.The participants were followed for up to 10 years (minimum five months). The trial reported that the mortality at 10 years was 81% (51/63) in the cryotherapy group and 92% (55/60) in the conventional surgery group. The calculated by us relative risk (RR) with 95% Confidence Interval (CI) was: RR 0.88, 95% CI 0.77 to 1.02. We judged the evidence as low-certainty evidence. Regarding adverse events and complications, separately and in total, our calculation showed no evidence of a difference in recurrence of the malignancy in the liver: 86% (54/63) of the participants in the cryotherapy group and 95% (57/60) of the participants in the conventional surgery group developed a new malignancy (RR 0.90, 95% CI 0.80 to 1.01; low-certainty evidence). The frequency of reported complications was similar between the cryotherapy group and the conventional surgery group, except for postoperative pain. Both insignificant and pronounced pain were reported to be more common in the cryotherapy group while intense pain was reported to be more common in the conventional surgery group. However, the authors did not report whether there was any evidence of a difference. There were no intervention-related mortality or bile leakages.We identified no evidence for health-related quality of life, cancer mortality, or time to progression of liver metastases. The study reported tumour response in terms of the carcinoembryonic antigen level in 69% of participants, and reported results in the form of a graph for 30% of participants. The carcinoembryonic antigen level was lower in the cryotherapy group, and decreased to normal values faster in comparison with the control group (P < 0.05). the trial did not provide information on funding. The evidence for the effectiveness of cryotherapy versus conventional surgery in people with liver metastases is of low certainty. We are uncertain about our estimate and cannot determine whether cryotherapy compared with conventional surgery is beneficial or harmful. We found no evidence for the benefits or harms of cryotherapy compared with no intervention, or versus systemic treatments.

Effect of temperature on the magnetic abrasive finishing process of Mg alloy bars

Experiments were conducted to evaluate the effect of temperature during magnetic abrasive finishing of Mg alloy bars. A magnetic abrasive finishing process is an unconventional finishing technique that has been used to achieve high-quality surfaces with dimensional accuracy. In this study, a Mg alloy bar, which is widely used in automobiles, aircraft, IT, and the defense industry, was chosen as a cylindrical workpiece. The workpiece was then finished with a magnetic abrasive finishing process at three different temperatures, i.e., a cryogenic temperature, room temperature, and high temperature. In the cryogenic temperature condition, liquid nitrogen and argon gas were used as the cryogenic cooling gases in the finishing process; the results from this treatment were compared with those obtained at room temperature and high temperature conditions. At the room temperature condition, the finishing process of the cylindrical workpiece was performed at 24 °C. To carry out the high temperature condition, a hot air dryer was used to maintain a finishing temperature of 112 °C. The experimental results show that the room and cryogenic temperatures could yield excellent performance in terms of the surface roughness. However, in terms of the removal weight and change in diameter, the high temperature condition was found to be superior. In the present research, the improvements of the surface roughness (Ra) at room temperature (24 °C) and cryogenic temperature (-120 °C) conditions were 84.21 % and 55 %, respectively.

Gas-exfoliated porous monolayer boron nitride for enhanced aerobic oxidative desulfurization performance

Hexagonal boron nitride has been regarded to be an efficient catalyst in aerobic oxidation fields, but limited by the less-exposed active sites. In this contribution, we proposed a simple green liquid nitrogen gas exfoliation strategy for preparation of porous monolayer nanosheets (BN-1). Owing to the reduced layer numbers, decreased lateral sizes and artificially-constructed pores, increased exposure of active sites was expected, further contributed to an enhanced aerobic oxidative desulfurization (ODS) performance up to ∼98% of sulfur removal, achieving ultra-deep desulfurization. This work not only introduced an excellent catalyst for aerobic ODS, but also provided a strategy for construction of some other highly-efficient monolayer two-dimensional materials for enhanced catalytic performance.

Experimental studies and analysis on compressive strength of normal‐weight concrete at low temperatures

The construction of liquid nitrogen gas storages and engineering structures in cold regions exposed reinforced concrete structures to low temperatures. This paper investigates the compressive strength of normal‐weight concrete under low temperatures to −165°C through a 174‐specimen test program. The key parameters studied in this test program included low temperature T ranging from −165 to +20°C, water/cement ratio ranging from 0.33 to 0.57, and water content Wc ranging from 0 to 6%. Their influences on the compressive strength of the concrete under low temperature were highlighted and analyzed. With the scanning electron microscope (SEM), the influence of these parameters on the microstructures of the concrete under low temperature was observed and presented. These test data and SEM analyses revealed the failure mechanism and provided proofs on the improvements of the compressive strength of the concrete under low temperature. Based on these test data, a mathematical model has developed to describe the relationship between the increasing factor of the compressive strength of the concrete under low temperatures and the influencing parameters of T, w/c ratio, and Wc. Finally, design equations are provided to predict the increasing factor of the compressive strength of the concrete under low temperature.