Understanding the Relationship between Surface Quality and Chip Morphology under Sustainable Cutting Environments

Although chip morphology changes according to the machining method and related cutting parameters, chip formation affects the quality of the machined surface. In this context, it is very important to understand the relationship between chip morphology and surface quality, especially in materials that are difficult to machine. In the presented study, the changes in chip morphology, surface morphology, and surface quality criteria (Ra and Rz) that occurred during the milling of precipitation-hardened steel in different cutting environments were analyzed. Milling experiments were carried out in dry, MQL (minimum quantity lubrication), nano-MQL (graphene), nano-MQL (hBN), Cryo, and Cryo-MQL environments using TiAlN-coated inserts and three different cutting speeds and feed rates. While the highest values in terms of Ra and Rz were measured in dry machining, the minimum values were obtained in a nano-MQL (hBN) cutting environment. Due to the lubrication and low friction provided by the MQL cutting environment, chips were formed in thinner segmented forms. This formation reduced the chip curve radius and thus provided a more stable surface morphology. On the other hand, Cryo-ambient gas could not effectively leak into the cutting zone due to the intermittent cutting process, but it increased the brittleness of the chips with the cooling effect and provided a similar surface morphology. The values of minimum Ra and Rz were obtained as 0.304 mm and 1.825 mm, respectively, at a 60 m/min cutting speed and 0.04 mm/rev feed. Consequently, the use of nano-MQL cutting medium is seriously recommended in terms of surface quality in milling operations of difficult-to-machine materials.

Cryo-Milled β-Glucan Nanoparticles for Oral Drug Delivery

Gemcitabine is a nucleoside analog effective against a number of cancers. However, it has an oral bioavailability of less than 10%, due to its high hydrophilicity and low permeability through the intestinal epithelium. Therefore, the aim of this project was to develop a novel nanoparticulate drug delivery system for the oral delivery of gemcitabine to improve its oral bioavailability. In this study, gemcitabine-loaded β-glucan NPs were fabricated using a film-casting method followed by a freezer-milling technique. As a result, the NPs showed a small particle size of 447.6 ± 14.2 nm, and a high drug entrapment efficiency of 64.3 ± 2.1%. By encapsulating gemcitabine into β-glucan NPs, a sustained drug release profile was obtained, and the anomalous diffusion release mechanism was analyzed, indicating that the drug release was governed by diffusion through the NP matrix as well as matrix erosion. The drug-loaded NPs had a greater ex vivo drug permeation through the porcine intestinal epithelial membrane compared to the plain drug solution. Cytotoxicity studies showed a safety profile of the β-glucan polymers, and the IC50s of drug solution and drug-loaded β-glucan NPs were calculated as 228.8 ± 31.2 ng·mL-1 and 306.1 ± 46.3 ng·mL-1, respectively. Additionally, the LD50 of BALB/c nude mice was determined as 204.17 mg/kg in the acute toxicity studies. Notably, pharmacokinetic studies showed that drug-loaded β-glucan NPs could achieve a 7.4-fold longer T1/2 and a 5.1-fold increase in oral bioavailability compared with plain drug solution. Finally, in vivo pharmacodynamic studies showed the promising capability of gemcitabine-loaded β-glucan NPs to inhibit the 4T1 breast tumor growth, with a 3.04- and 1.74-fold reduction compared to the untreated control and drug solution groups, respectively. In conclusion, the presented freezer-milled β-glucan NP system is a suitable drug delivery method for the oral delivery of gemcitabine and demonstrates a promising potential platform for oral chemotherapy.

Exceptional Magnetocaloric Responses in a Gadolinium Silicate with Strongly Correlated Spin Disorder for Sub-Kelvin Magnetic Cooling

The development of magnetocaloric materials with a significantly enhanced volumetric cooling capability is highly desirable for the application of adiabatic demagnetization refrigerators in confined spatial environments. Here, the thermodynamic characteristics of a magnetically frustrated spin-7/2 Gd9.33[SiO4]6O2 is presented, which exhibits strongly correlated spin disorder below ≈1.5 K. A quantitative model is proposed to describe the magnetization results by incorporating nearest-neighbor Heisenberg antiferromagnetic and dipolar interactions. Remarkably, the recorded magnetocaloric responses are unprecedentedly large and applicable below 1.0 K. It is proposed that the S = 7/2 spin liquids serve as versatile platforms for investigating high-performance magnetocaloric materials in the sub-kelvin regime, particularly those exhibiting a superior cooling power per unit volume.

Cryo-Electrohydrodynamic Jetting of Aqueous Silk Fibroin Solutions

The incorporation of 3D-printing principles with electrohydrodynamic (EHD) jetting provides a harmonious balance between resolution and processing speed, allowing for the creation of high-resolution centimeter-scale constructs. Typically, EHD jetting of polymer melts offers the advantage of rapid solidification, while processing polymer solutions requires solvent evaporation to transition into solid fibers, creating challenges for reliable printing. This study navigates a hybrid approach aimed at minimizing printing instabilities by combining viscous solutions and achieving rapid solidification through freezing. Our method introduces and fully describes a modified open-source 3D printer equipped with a frozen collector that operates at -35 °C. As a proof of concept, highly concentrated silk fibroin aqueous solutions are processed into stable micrometer scale jets, which rapidly solidify upon contact with the frozen collector. This results in the formation of uniform microfibers characterized by an average diameter of 27 ± 5 μm, a textured surface, and porous internal channels. The absence of instabilities and the notably fast direct writing speed of 42 mm·s-1 enable precise, fast, and reliable deposition of these fibers into porous constructs spanning several centimeters. The effectiveness of this approach is demonstrated by the consistent production of biologically relevant scaffolds that can be customized with varying pore sizes and shapes. The achieved degree of control over micrometric jet solidification and deposition dynamics represents a significant advancement in EHD jetting, particularly within the domain of aqueous polymer solutions, offering new opportunities for the development of intricate and functional biological structures.

Machinability and Surface Properties of Cryogenic Poly(methyl methacrylate) Machined via Single-Point Diamond Turning

Poly(methyl methacrylate) (PMMA), with a glass transition temperature (Tg) over 100 °C, shows good mechanical and optical properties and has broad applications after being machined with single-point diamond turning (SPDT) at room temperature. Because of the high Tg, current efforts mostly focus on optimizing machining parameters to improve workpiece precision without considering the modification of material properties. Cryogenic cooling has been proven to be an effective method in assisting ultra-precision machining for certain types of metals, alloys, and polymers, but has never been used for PMMA before. In this work, cryogenic cooling was attempted during the SPDT of PMMA workpieces to improve surface quality. The machinability and surface properties of cryogenically cooled PMMA were investigated based on the mechanical properties at corresponding temperatures. Nanoindentation tests show that, when temperature is changed from 25 °C to 0 °C, the hardness and Young's modulus are increased by 37% and 22%, respectively. At these two temperature points, optimal parameters including spindle speed, feed rate and cut depth were obtained using Taguchi methods to obtain workpieces with high surface quality. The surface quality was evaluated based on the total height of the profile (Pt) and the arithmetic mean deviation (Ra). The measurement results show that the values of Pt and Ra of the workpiece machined at 0 °C are 124 nm and 6 nm, respectively, while the corresponding values of that machined at 25 °C are 291 nm and 11 nm. The test data show that cryogenic machining is useful for improving the form accuracy and reducing the surface roughness of PMMA. Moreover, the relationship between temperature, material properties and machinability weas established with dynamic mechanical analysis (DMA) data and a theoretical model. This can explain the origin of the better surface quality of the cryogenic material. The basis of this is that temperature affects the viscoelasticity of the polymer and the corresponding mechanical properties due to relaxation. Then, the material property changes will affect surface profile formation during machining. The experimental results and theoretical analysis show that cryogenically cooled PMMA has good machinability and improved surface quality when using SPDT compared to that at ambient temperature.

A Wireless Passive Pressure-Sensing Method for Cryogenic Applications Using Magnetoresistors

In this study, we developed a novel wireless, passive pressure-sensing method functional at cryogenic temperatures (-196 °C). The currently used pressure sensors are inconvenient and complicated in cryogenic environments for their weak low-temperature tolerances and long wires for power supply and data transmission. We propose a novel pressure-sensing method for cryogenic applications by only using low-temperature-tolerant passive devices. By innovatively integrating a magnetoresistor (MR) on a backscattering antenna, the pressure inside a cryogenic environment is transferred to a wirelessly obtainable return loss. Wireless passive measurement is thus achieved using a backscattering method. In the measurement, the pressure causes a relative displacement between the MR and a magnet. The MR's resistance changes with the varied magnetic field, thus modulating the antenna's return loss. The experimental results indicate that our fabricated sensor successfully identified different pressures, with high sensitivities of 4.3 dB/MPa at room temperature (24 °C) and 1.3 dB/MPa at cryogenic temperature (-196 °C). Additionally, our method allows for simultaneous wireless readings of multi sensors via a single reading device by separating the frequency band of each sensor. Our method performs low-cost, simple, robust, passive, and wireless pressure measurement at -196 °C; thus, it is desirable for cryogenic applications.

Enhancement of NbO2-based oscillator neuron device performance via cryogenic operation

The Niobium Dioxide (NbO2) oscillator neuron has garnered significant interest because of its simple structure compared to conventional CMOS-based circuits. However, the limited on/off resistance ratio narrows the range of series resistances that satisfy the self-oscillation conditions and limits its use in large-scale synaptic arrays. In this study, we report the possibility of improving the performance of NbO2-based oscillator neuron devices through cryogenic operation. The study emphasizes two crucial parameters: the on/off resistance ratio and the oscillation amplitude, both of which are essential for accurate weighted sum classification. The data suggest that these parameters can be effectively enhanced under cryogenic conditions. In addition, we revealed that 120 K is the optimal temperature for cryogenic operation, as it represents the temperature where the on/off resistance ratio ceases to increase. As a result, we revealed that the series resistance range satisfying the self-oscillation condition in a single oscillator increases from 20 to 126 kΩ. The research also probes the maximum possible array size at each temperature. At 300 K, representation is only possible for a 5 × 5 array, but at 120 K, a 30 × 30 array can be represented as a frequency. The evidence implies that the 120 K conditions not only broaden the range of series resistors that can be connected to a single oscillator but also increases the array size, thereby representing different weighted sum currents as frequencies. The research indicates that using carefully optimized cryogenic operation could be a viable method to enhance the necessary NbO2properties for an oscillator neuron device.

Inducing Motions of Polymers in Liquid Nitrogen with Light

Polymer materials that show macroscopic deformation in response to external stimuli are feasible for novel soft actuators including microactuators. Incorporation of photochromic moieties, such as azobenzenes, into polymer networks enables macroscopic deformation under irradiation with light through photoisomerization. Under cryogenic conditions, however, it has been difficult to induce macroscopic deformation as polymers lose their soft nature due to the severe restrictions of molecular motions. Here, activation of molecular motions and macroscopic deformation in liquid nitrogen only with light for polymers containing photochromic moieties is reported. Photoinduced bending of polymer networks with normal azobenzenes in liquid nitrogen is enabled by preliminary UV irradiation at room temperature to produce cis-isomers. To realize photoinduced deformation directly in liquid nitrogen, polymer networks are functionalized with bridged azobenzenes, which exist as cis-isomers in thermodynamic equilibrium. The films with bridged azobenzenes exhibit reversible photoisomerization and bending upon irradiation with light in liquid nitrogen without the need of preliminary irradiation, implying that the change in conformation of polymer chains can be isothermally induced even under cryogenic conditions. Achievement of flexible motions under cryogenic conditions through isothermal processes will greatly expand the operating temperature range of soft actuators.

Xanthene-Separated 24 π-Electron Antiaromatic Rosarin Dimer

Antiaromatic molecules have recently received attention because of their intrinsic properties, such as high reactivity and their narrow HOMO-LUMO gaps. Stacking of antiaromatic molecules has been predicted to induce three-dimensional aromaticity via frontier orbital interactions. Here, we report a covalently linked π-π stacked rosarin dimer that has been examined experimentally by steady-state absorption and transient absorption measurements and theoretically by quantum chemical calculations, including time-dependent density functional theory, anisotropy of induced current density, and nucleus-independent chemical shift calculations. Relative to the corresponding monomer, the dimer exhibits diminished antiaromaticity upon lowering the temperature to 77 K, a finding ascribed to intramolecular interactions between the macrocyclic rosarin subunits.

Study on Symmetry and Asymmetry Rolling of AA2519-T62 Alloy at Room-Temperature and Cryogenic Conditions

The aim of this investigation was to identify the effect of rolling at room temperature and under cryogenic conditions on selected properties and the microstructure of the AA2519-T62 aluminum alloy. The rolling processes were conducted with different variants of asymmetry (1.0-symmetry rolling; 1.2, 1.4 and 1.6). The investigation of the obtained samples involves microhardness distribution, microstrains, and microstructure observations using light and transmission electron microscopes. Both rolling at room temperature and under cryogenic conditions increased the micro-hardness of AA2519-T62 by at least 10%. The highest reported increase (25%) was obtained for the sample rolled at room temperature in the symmetry rolling process. The samples rolled under cryogenic conditions are characterized by a lower increase in microhardness than samples rolled at room temperature and by significantly lower values of microstrains. The application of rolling with the asymmetry ratio remaining within the range of 1.2-16 only slightly affected the microhardness values of the samples rolled at room temperature and under cryogenic conditions with respect to conventional symmetrical rolling.

Charge Configuration Memory Devices: Energy Efficiency and Switching Speed

Current trends in data processing have given impetus for an intense search of new concepts of memory devices with emphasis on efficiency, speed, and scalability. A promising new approach to memory storage is based on resistance switching between charge-ordered domain states in the layered dichalcogenide 1T-TaS2. Here we investigate the energy efficiency scaling of such charge configuration memory (CCM) devices as a function of device size and data write time τW as well as other parameters that have bearing on efficient device operation. We find that switching energy efficiency scales approximately linearly with both quantities over multiple decades, departing from linearity only when τW approaches the ∼0.5 ps intrinsic switching limit. Compared to current state of the art memory devices, CCM devices are found to be much faster and significantly more energy efficient, demonstrated here with two-terminal switching using 2.2 fJ, 16 ps electrical pulses.

Low-Temperature Characteristics of Nanowire Network Demultiplexer for Qubit Biasing

In current quantum computers, most qubit control electronics are connected to the qubit chip inside the cryostat by cables at room temperature. This poses a challenge when scaling the quantum chip to an increasing number of qubits. We present a lateral nanowire network 1-to-4 demultiplexer design fabricated by selective area grown InGaAs on InP, suitable for on chip routing of DC current for qubit biasing. We have characterized the device at cryogenic temperatures, and at 40 mK the device exhibits a minimum inverse subthreshold slope of 2 mV/dec, which is encouraging for low power operation. At low drain bias, the transmission breaks up into several resonance peaks due to a rough conduction band edge; this is qualitatively explained by a simple model based on a 1D real space tight-binding nonequilibrium Green's functions model.

Quality assessment of cryopreserved Portuguese oyster (Crassostrea angulata) sperm through ultrastructural and flow cytometry analysis

We investigated the effects of cryopreservation on the quality of Portuguese oyster (Crassostrea angulata) sperm, which were examined before and after freezing; sperm motility, fertilizing capacity, and ultrastructural morphology were analyzed. The motility percentage and fertilizing capacity of the cryopreserved sperm (mean ± standard error) were 16% ± 1% and 17% ± 8%, respectively. In the pre-freezing sperm, these were 58% ± 2% and 76% ± 4%, respectively. The sperm sustained substantial morphological and ultrastructural damage during cryopreservation. The morphological changes varied considerably in nature and extent, ranging from no apparent damage to virtual disintegration. Sperm were stained with fluorescent dyes to assess viability, plasma membrane integrity, mitochondrial activity, acrosomal membrane integrity, oxidation level, and DNA compaction and examined through flow cytometry. The methods used for the flow cytometry assays were slightly modified from those used for evaluating the semen quality of livestock. Relative to the pre-freezing sperm, the frozen-thawed sperm exhibited lower acrosomal membrane integrity (acrosomal damage, 59.86 ± 5.29; P < 0.05) and substantially higher oxidation levels (free radicals, 60.06 ± 0.82; P < 0.003). Oxidation level was found to be the most sensitive indicator of cryodamage. Along with ultrastructural analysis, we used flow cytometry to measure the qualitative and quantitative characteristics of Portuguese oyster sperm before and after cryopreservation rapidly, objectively, and accurately. This is the first study to assess the quality of Portuguese oyster sperm through these methods.

New insights into correlated materials in the time domain-combining far-infrared excitation with x-ray probes at cryogenic temperatures

Modern techniques for the investigation of correlated materials in the time domain combine selective excitation in the THz frequency range with selective probing of coupled structural, electronic and magnetic degrees of freedom using x-ray scattering techniques. Cryogenic sample temperatures are commonly required to prevent thermal occupation of the low energy modes and to access relevant material ground states. Here, we present a chamber optimized for high-field THz excitation and (resonant) x-ray diffraction at sample temperatures between 5 and 500 K. Directly connected to the beamline vacuum and featuring both a Beryllium window and an in-vacuum detector, the chamber covers the full (2-12.7) keV energy range of the femtosecond x-ray pulses available at the Bernina endstation of the SwissFEL free electron laser. Successful commissioning experiments made use of the energy tunability to selectively track the dynamics of the structural, magnetic and orbital order of Ca₂RuO₄and Tb₂Ti₂O₇at the Ru (2.96 keV) and Tb (7.55 keV)L-edges, respectively. THz field amplitudes up to 1.12 MV cm^-1peak field were demonstrated and used to excite the samples at temperatures as low as 5 K.

Observations on the use of a pain numbing device for repetitive percutaneous sampling in sheep

AIMS

To evaluate the success of a commercially available analgesic device (CoolSense; Coolsense Ltd, Tel Aviv, Israel) in ameliorating pain while sampling from subcutaneous tissue cages in sheep.

METHODS

The CoolSense device was used as part of a major parent study involving repetitive percutaneous sampling of subcutaneous tissue cages in seven sheep. Sampling was performed by passing a hypodermic needle through the skin and withdrawing fluid from the tissue cage. Each sheep had 10 tissue cages that were individually sampled 14 times over 74 h. The device was placed on the skin of the sampling site immediately before sampling cooling and numbing the skin. The reaction of the sheep was observed by the operators, flinching or jumping as the needle was passed through the skin was deemed to be a failure. We recorded the success or failure of the device for each needle stick. This was opportunistic data collection as part of a pharmacokinetic trial, therefore no controls were included.

RESULTS

A total of 1655 observations were recorded and then analysed using a generalised linear mixed model. Overall, 1380 of 1655 (83.4%) observations were recorded as successfully providing analgesia. Marked inter-occasion variability was noted with success ranging from 61.42% to 92.86% across sheep:period (approximately 140 observations each). As no controls were available, the effect of treatment could not be evaluated.

CONCLUSIONS AND CLINICAL RELEVANCE

The CoolSense device is a viable option for veterinary research and clinical applications.

Cryogenic Refrigerant Burns: A Rare Occupational Hazard

BACKGROUND

Cryogenic burns induced by coolant gases used in refrigerators and air conditioners are rarely encountered, despite the wide use of these gases. To date, only a few cases have been reported in the literature. This study examined the occupational circumstances leading to such injuries, relevant injury sites, types of chemicals involved, and treatment measures.

METHODS

This study was conducted in a tertiary burn center in India between March 2015 and March 2019. The demographic details, chemicals involved, and burn regions and characteristics were analyzed.

FINDINGS

There were 15 burn cases all involving injury to the hand. All injuries were managed initially with dressings and nonoperative management. One patient required anti-edema therapy with limb elevation and fingertip debridement, while another patient required skin grafting. All patients had satisfactory hand function after treatment.

CONCLUSIONS/APPLICATION TO PRACTICE

Cryogenic burn injuries caused by refrigerants are rare, and their etiology varies considerably. Exposure time is the primary factor that determines burn depth and severity; hence, reducing exposure time is important in first aid. Our findings suggest that after exposure, the patient should be treated in a specialized burn center. Adequate knowledge regarding the pathophysiology of these types of burn injuries and their management is necessary; otherwise, misjudgments in the treatment plan can lead to adverse consequences.

Pushing the Limit of Boltzmann Distribution in Cr3+-Doped CaHfO3 for Cryogenic Thermometry

Luminescence Boltzmann thermometry is one of the most reliable techniques used to locally probe temperature in a contactless mode. However, to date, there is no report on cryogenic thermometers based on the highly sensitive and reliable Boltzmann-based ⁴T₂ → ⁴A₂/²E → ⁴A₂ emission ratio of Cr³⁺. On the basis of structural information of the local HfO₆ octahedral site we demonstrated the potential of the CaHfO₃:Cr³⁺ system by combining deep theoretical and experimental investigation. The material exhibits simultaneous emission from both the ²E and ⁴T₂ excited states, following the Boltzmann law in a cryogenic temperature range of 40-150 K. The promising thermometric performance corroborates the potential of CaHfO₃:Cr³⁺ as a Boltzmann cryothermometer, being characterized by a high relative sensitivity (∼ 2%·K^-1 at 40 K) and exceptional thermal resolution (0.045-0.77 K in the 40-150 K range). Moreover, by exploiting the flexibility of the ⁴T₂-²E energy gap controlled by the crystal field of the local octahedral site, the design proposed herein could be expanded to develop new Cr³⁺-doped cryogenic thermometers.

Laser Patterning a Graphene Layer on a Ceramic Substrate for Sensor Applications

This paper describes a method for patterning the graphene layer and gold electrodes on a ceramic substrate using a Nd:YAG nanosecond fiber laser. The technique enables the processing of both layers and trimming of the sensor parameters. The main aim was to develop a technique for the effective and efficient shaping of both the sensory layer and the metallic electrodes. The laser shaping method is characterized by high speed and very good shape mapping, regardless of the complexity of the processing. Importantly, the technique enables the simultaneous shaping of both the graphene layer and Au electrodes in a direct process that does not require a complex and expensive masking process, and without damaging the ceramic substrate. Our results confirmed the effectiveness of the developed laser technology for shaping a graphene layer and Au electrodes. The ceramic substrate can be used in the construction of various types of sensors operating in a wide temperature range, especially the cryogenic range.

Impact of Cryogenic Treatment on HCF and FCP Performance of β-Solution Treated Ti-6Al-4V ELI Biomaterial

The poor fatigue strength of Ti-6Al-4V ELI is a main cause of failure in structural implants. In this work, Ti-6Al-4V ELI was subjected to β-solution treatment to obtain martensite microstructure and further subjected to −196 °C for 24 h. Significant improvement in high cycle fatigue performance of martensite Ti-6Al-4V ELI was observed on exposure to cryogenic cycle. Resistance to fatigue crack growth of alloy was augmented in martensite structure as compared with mill annealed sample and the same was retained even after exposure to cryogenic treatment. The variation observed in fatigue behavior due to cryogenic treatment was correlated with fractography and metallurgical investigations. Improvement in high cycle fatigue performance can be attributed to a combined effect of a decrease in the size of prior β grain, formation of massive α patch and its subsequent transformation into ultra-fine α and β during the soaking period at −196 °C.

Abrasive Wear Behavior of Cryogenically Treated Boron Steel (30MnCrB4) Used for Rotavator Blades

Rotavator blades are prone to significant wear because of the abrasive nature of sand particles. The aim of this research work is to investigate the effect of cryogenic treatment and post tempering on abrasive wear behavior, in the presence of angular quartz sand (grain size of 212–425 μm), of rotavator blade material of boron steel (30MnCrB4). Cryogenic treatment has caused an improvement in the abrasive wear resistance and microhardness of 30MnCrB4 by 60% and 260.73%, respectively, compared to untreated material due to enhancement in hardness, the conversion of retained austenite into martensite, and the precipitation of secondary carbides in boron steel after exposure to cryogenic temperature. Economic analysis justifies the additional cost of cryogenic treatment.

X-ray fluorescence analysis of metal distributions in cryogenic biological samples using large-acceptance-angle SDD detection and continuous scanning at the Hard X-ray Micro/Nano-Probe beamline P06 at PETRA III

A new Rococo 2 X-ray fluorescence detector was implemented into the cryogenic sample environment at the Hard X-ray Micro/Nano-Probe beamline P06 at PETRA III, DESY, Hamburg, Germany. A four sensor-field cloverleaf design is optimized for the investigation of planar samples and operates in a backscattering geometry resulting in a large solid angle of up to 1.1 steradian. The detector, coupled with the Xspress 3 pulse processor, enables measurements at high count rates of up to 106 counts per second per sensor. The measured energy resolution of ∼129 eV (Mn Kα at 10000 counts s-1) is only minimally impaired at the highest count rates. The resulting high detection sensitivity allows for an accurate determination of trace element distributions such as in thin frozen hydrated biological specimens. First proof-of-principle measurements using continuous-movement 2D scans of frozen hydrated HeLa cells as a model system are reported to demonstrate the potential of the new detection system.

Autonomous cryogenic RF receive coil for 13 C imaging of rodents at 3 T

PURPOSE

To develop an autonomous, in-bore, MR-compatible cryostat cooled with liquid nitrogen that provides full-day operation, and to demonstrate that the theoretical signal-to-noise benefit can be achieved for ¹³ C imaging at 3 T (32.13 MHz).

METHODS

The cryogenic setup uses a vacuum-insulated fiberglass cryostat, which indirectly cools a cold finger where the RF coil is attached. The cryostat was evacuated before use and had a reservoir of liquid nitrogen for full-day operation. A 30 × 40 mm² copper coil was mounted inside the cryostat with a 3-mm distance to the sample. Two examples of in vivo experiments of rat brain metabolism after a hyperpolarized [1-¹³ C]pyruvate injection are reported.

RESULTS

A coil Q-factor ratio of Q_88K /Q_290K = 550/280 was obtained, and the theoretical SNR enhancement was verified with MR measurements. We achieved a coil temperature of 88 K and a preamplifier temperature of 77 K. A 2-fold overall SNR enhancement was achieved, compared with the best case at room temperature. The thermal performance of the coil was adequate for in vivo experiments, with an autonomy of 5 hours consuming 6 L of LN₂ , extendable to over 12 hours by LN₂ refilling.

CONCLUSION

Cryogenic surface coils can be highly beneficial for ¹³ C imaging, provided that the coil-to-sample distance remains short. An autonomous, in-bore cryostat was developed that achieved the theoretical improvement in SNR.

Effects of Machining Velocity on Ultra-Fine Grained Al 7075 Alloy Produced by Cryogenic Temperature Large Strain Extrusion Machining

In this study, cryogenic temperature large strain extrusion machining (CT-LSEM) as a novel severe plastic deformation (SPD) method for producing ultra-fine grained (UFG) microstructure is investigated. Solution treated Al 7075 alloy was subjected to CT-LSEM, room temperature (RT) LSEM, as well as CT free machining (CT-FM) with different machining velocities to study their comparative effects. The microstructure evolution and mechanical properties were characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Vickers hardness measurements. It is observed that the hardness of the sample has increased from 105 HV to 169 HV and the chip can be fully extruded under CT-LSEM at the velocity of 5.4 m/min. The chip thickness and hardness decrease with velocity except for RT-LSEM at the machining velocity of 21.6 m/min, under which the precipitation hardening exceeds the softening effect. The constraining tool and processing temperature play a significant role in chip morphology. DSC analysis suggests that the LSEM process can accelerate the aging kinetics of the alloy. A higher dislocation density, which is due to the suppression of dynamic recovery, contributes to the CT-LSEM samples, resulting in greater hardness than the RT-LSEM samples.

Microstructure and Grain Orientation Evolution in SnPb/SnAgCu Interconnects Under Electrical Current Stressing at Cryogenic Temperature

Electromigration was characterized at the cathode Cu/solder interface—without the effect of Joule heating—by employing scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) analyses. Rapid (Cu_x,Ni_1−x)₆Sn₅ intermetallic compound (IMC) growth was observed at the anomalous region at the cathode end due to the effect of current crowding. The abnormal isotropic diffusion and parallel distribution of Pb were characterized in an ultra-low temperature environment in a monocrystalline structure stressed at −196 °C. The interesting results were attributed to crystallographic transformation due to the simultaneous effect of cryogenic and electrical stressing. The diffusion behavior of Pb atoms in face-centered cubic lattices performed isomorphism. As a result, Pb atoms of the bump gathered at the high-energy grain boundaries by diffusing through the face-centered cubic lattices around the long grain boundary, eventually forming a long-range distribution and accumulation of Pb elements. Our study may provide understanding of cryogenic electromigration evolution of the Cu/solder interface and provide visual data for abnormal lattice transformation at the current stressing.

Ultra-stable super-resolution fluorescence cryo-microscopy for correlative light and electron cryo-microscopy

Remarkable progress in correlative light and electron cryo-microscopy (cryo-CLEM) has been made in the past decade. A crucial component for cryo-CLEM is a dedicated cryo-fluorescence microscope (cryo-FM). Here, we describe an ultra-stable super-resolution cryo-FM that exhibits excellent thermal and mechanical stability. The temperature fluctuations in 10 h are less than 0.06 K, and the mechanical drift over 5 h is less than 200 nm in three dimensions. We have demonstrated the super-resolution imaging capability of this system (average single molecule localization accuracy of ∼13.0 nm). The results suggest that our system is particularly suitable for long-term observations, such as single molecule localization microscopy (SMLM) and cryogenic super-resolution correlative light and electron microscopy (csCLEM).

Production and Characterization of Nanoparticle Based Hyaluronate Gel Containing Retinyl Palmitate for Wound Healing

BACKGROUND

Wound healing is a biological process that can get in a state of pathologic inflammation, requiring the use of specific medications able to promote proper tissue repair.

OBJECTIVE

The study describes the production and characterization of nanoparticle based gel for wound healing treatment designed to deliver hyaluronic acid and retinyl palmitate onto the skin.

METHODS

Tristearin solid lipid nanoparticles and nanostructured lipid carriers based on a tristearin and caprylic/capric triglyceride mixture were produced and characterized. Gel spreadability and viscosity were investigated. Drug diffusion and "in vitro" wound healing were assessed by Franz cell and scratch wound assay in keratinocytes.

RESULTS

Cryogenic transmission electron microscopy evidenced flat discoid nanoparticles. Photon correlation spectroscopy analysis indicated homogeneous dimensional distribution and mean diameter 132±46 nm. X-ray evidenced a lamellar inner structure of lipid nanoparticles. Nanostructured lipid carriers, being based on a heterogeneous solid/ liquid lipid mixture, could better solubilize retinyl palmitate and control its stability. The hyaluronic acid directly added into nanoparticles' dispersion enabled to obtain a shear-thinning gel suitable for cutaneous administration. Retynil palmitate diffusion was slower from the nanoparticulate gel with respect to the plain nanoparticle dispersion. The "wound healing" effect of nanoparticulate gel containing retinyl palmitate and hyaluronic acid, analyzed in HaCaT cells, showed significant differences in wounded areas between treated and control cells during the first 24 h postwounding suggesting a synergic effect of retinyl palmitate and hyaluronic acid in "in vitro" wound healing.

CONCLUSIONS

This study suggests that a nanoparticle based hyaluronate gel containing retinyl palmitate can be efficiently used for wound healing.

Fluorescence Polarization Control for On-Off Switching of Single Molecules at Cryogenic Temperatures

Light microscopy, allowing sub-diffraction-limited resolution, has been among the fastest developing techniques at the interface of biology, chemistry, and physics. Intriguingly no theoretical limit exists on how far the underlying measurement uncertainty can be lowered. In particular data fusion of large amounts of images can reduce the measurement error to match the resolution of structural methods like cryo-electron microscopy. Fluorescence, although reliant on a reporter molecule and therefore not the first choice to obtain ultraresolution structures, brings highly specific labeling of molecules in a large assembly to the table and inherently allows the detection of multiple colors, which enables the interrogation of multiple molecular species at the same time in the same sample. Here, the problems to be solved in the coming years, with the aim of higher resolution, are discussed, and what polarization depletion of fluorescence at cryogenic temperatures can contribute for fluorescence imaging of biological samples, like whole cells, is described.

The Effect of Hypothermic and Cryogenic Preservation on Engineered Neural Tissue

This study explored different approaches to preserve engineered neural tissue (EngNT), a stabilized, cellular collagen hydrogel containing columns of aligned Schwann cells for nervous system repair. The ability to preserve EngNT without disrupting cellular and extracellular components and structures is important for clinical translation and commercialization. Stabilized cellular gels and EngNT constructs were preserved under various conditions and cell survival assessed using live/dead microscopy and metabolic assay. Optimal survival was recorded in hypothermic (4°C) conditions for 2–3 days using Hibernate^®-A media and, for longer-term cryogenic storage (liquid nitrogen), using a mixture of 60% Dulbecco's modified Eagle's medium, 30% fetal bovine serum, and 10% dimethyl sulfoxide. Functionality and structure of preserved EngNT were assessed in coculture with dorsal root ganglion neurons, which indicated that alignment of Schwann cells and the ability of EngNT to support and guide neuronal regeneration were not disrupted. The identification of conditions that preserve EngNT will inform development of storage and transport methodologies to support clinical and commercial translation of this technology and other therapies based on cellular hydrogels.

Electrical and Thermal Properties of Heater-Sensor Microsystems Patterned in TCO Films for Wide-Range Temperature Applications from 15 K to 350 K

This paper presents an analysis of the electrical and thermal properties of miniature transparent heaters for use in a wide range of temperature applications, from 15 K to 350 K. The heater structures were produced in transparent conducting oxide (TCO) layers: indium tin oxide (ITO) and ITO/Ag/ITO on polymer substrates-polyethylene naphthalate (PEN) and polyethylene terephthalate (PET), by direct laser patterning. Thermo-resistors for temperature measurement were created in the same process, with geometry corresponding to the shape of the heating path. The thermo-resistors integrated with the heating structure allowed easy control of the thermal state of the heaters. Laser patterning provided high precision and repeatability in terms of the geometry and electrical properties of the heater-sensor structures. Measurements at temperatures from 15 K to above room temperature (350 K) confirmed the excellent dynamics of the heating and cooling processes, due to current flow. The largest value for surface heating power was over 3 W/cm². A heater-sensor structure equipped with a small capacity chamber was successfully applied for controlled heating of small volumes of different liquids. Such structures have potential for use in research and measurements, where for various reasons controlled and accurate heating of small volumes of liquids is required.

Infrared ion spectroscopy inside a mass-selective cryogenic 2D linear ion trap

We demonstrate operation of the first cryogenic 2D linear ion trap (LIT) with mass-selective capabilities. This trap presents a number of advantages for infrared ion "action" spectroscopy studies, particularly those employing the "tagging/messenger" spectroscopy approach. The high trapping efficiencies, trapping capacities, and low detection limits make 2D LITs a highly suitable choice for low-concentration analytes from scarce biological samples. In our trap, ions can be cooled down to cryogenic temperatures to achieve higher-resolution infrared spectra, and individual ions can be mass selected prior to irradiation for a background-free photodissociation scheme. Conveniently, multiple tagged analyte ions can be mass isolated and efficiently irradiated in the same experiment, allowing their infrared spectra to be recorded in parallel. This multiplexed approach is critical in terms of increasing the duty cycle of infrared ion spectroscopy, which is currently a key weakness of the technique. The compact design of this instrument, coupled with powerful mass selection capabilities, set the stage for making cryogenic infrared ion spectroscopy viable as a bioanalytical tool in small molecule identification.

C-H Infrared Absorption and Solubility of Ethylene, Propyne, 2-methyl-2-butene, and 2-methyl-1, 3-butadiene (Isoprene) in Liquid Argon Solutions

The solubility of ethylene (H₂C=CH₂), propyne (CH₃-C≡C-H), 2-methyl-2-butene (CH₃-CH=C(CH₃)₂), and isoprene or 2-methyl-1, 3-butadiene (H₂C=C(CH₃)-CH=CH₂) in liquid argon has been measured using mid-infrared and near-infrared (NIR) absorption. Spectra were recorded in the C-H infrared (IR) region. Spectra were obtained at increasing solution composition until the magnitude of the integrated absorption band reached a maximum value, indicating a saturated solution. The approximate experimental solubilities are: (600 ± 100) ppm at 92 K for ethylene, (22 ± 9) ppm at 100 K for propyne, (9 ± 5) ppm at 100 K for 2-methyl-2-butene, and (12 ± 2) ppm at 86 K for isoprene. The experimental solubility values at the corresponding temperature were used with solubility parameters of two separate models: the perturbed-chain statistical associating fluid theory (PC-SAFT) and the regular solution theory. Solvent-solute interaction parameters k₁₂ (PC-SAFT) and [Formula: see text] (RST) were obtained for each solute in the presence of argon as the solvent. Data from experimental measurements are important for more realistic simulations of solubility of solids in cryogenic liquids.

Low-Noise Active Decoupling Circuit and its Application to 13C Cryogenic RF Coils at 3 T

We analyze the loss contributions in a small, 50-mm-diameter receive-only coil for carbon-13 (¹³C) magnetic resonance imaging at 3 T for 3 different circuits, which, including active decoupling, are compared in terms of their Q-factors and signal-to-noise ratio (SNR). The results show that a circuit using unsegmented tuning and split matching capacitors can provide >20% SNR enhancement at room temperature compared with that using more traditional designs. The performance of the proposed circuit was also measured when cryogenically cooled to 105 K, and an additional 1.6-fold SNR enhancement was achieved on a phantom. The enhanced circuit performance is based on the low capacitance needed to match to 50 Ω when coil losses are low, which significantly reduces the proportion of the current flowing through the matching network and therefore minimizes this loss contribution. This effect makes this circuit particularly suitable for receive-only cryogenic coils and/or small coils for low-gamma nuclei.

A Fully Transparent Flexible Sensor for Cryogenic Temperatures Based on High Strength Metallurgical Graphene

Low-temperature electronics operating in below zero temperatures or even below the lower limit of the common -65 to 125 °C temperature range are essential in medical diagnostics, in space exploration and aviation, in processing and storage of food and mainly in scientific research, like superconducting materials engineering and their applications-superconducting magnets, superconducting energy storage, and magnetic levitation systems. Such electronic devices demand special approach to the materials used in passive elements and sensors. The main goal of this work was the implementation of a fully transparent, flexible cryogenic temperature sensor with graphene structures as sensing element. Electrodes were made of transparent ITO (Indium Tin Oxide) or ITO/Ag/ITO conductive layers by laser ablation and finally encapsulated in a polymer coating. A helium closed-cycle cryostat has been used in measurements of the electrical properties of these graphene-based temperature sensors under cryogenic conditions. The sensors were repeatedly cooled from room temperature to cryogenic temperature. Graphene structures were characterized using Raman spectroscopy. The observation of the resistance changes as a function of temperature indicates the potential use of graphene layers in the construction of temperature sensors. The temperature characteristics of the analyzed graphene sensors exhibit no clear anomalies or strong non-linearity in the entire studied temperature range (as compared to the typical carbon sensor).

Towards a Graphene-Based Low Intensity Photon Counting Photodetector

Graphene is a highly promising material in the development of new photodetector technologies, in particular due its tunable optoelectronic properties, high mobilities and fast relaxation times coupled to its atomic thinness and other unique electrical, thermal and mechanical properties. Optoelectronic applications and graphene-based photodetector technology are still in their infancy, but with a range of device integration and manufacturing approaches emerging this field is progressing quickly. In this review we explore the potential of graphene in the context of existing single photon counting technologies by comparing their performance to simulations of graphene-based single photon counting and low photon intensity photodetection technologies operating in the visible, terahertz and X-ray energy regimes. We highlight the theoretical predictions and current graphene manufacturing processes for these detectors. We show initial experimental implementations and discuss the key challenges and next steps in the development of these technologies.

Bright and ultra-fast scintillation from a semiconductor?

Semiconductor scintillators are worth studying because they include both the highest luminosities and shortest decay times of all known scintillators. Moreover, many semiconductors have the heaviest stable elements (Tl, Hg, Pb, Bi) as a major constituent and a high ion pair yield that is proportional to the energy deposited. We review the scintillation properties of semiconductors activated by native defects, isoelectronic impurities, donors and acceptors with special emphasis on those that have exceptionally high luminosities (e.g. ZnO:Zn, ZnS:Ag,Cl, CdS:Ag,Cl) and those that have ultra-fast decay times (e.g. ZnO:Ga; CdS:In). We discuss underlying mechanisms that are consistent with these properties and the possibilities for achieving (1) 200,000 photons/MeV and 1% fwhm energy resolution for 662 keV gamma rays, (2) ultra-fast (ns) decay times and coincident resolving times of 30 ps fwhm for time-of-flight positron emission tomography, and (3) both a high luminosity and an ultra-fast decay time from the same scintillator at cryogenic temperatures.

Advancing Cardiovascular, Neurovascular, and Renal Magnetic Resonance Imaging in Small Rodents Using Cryogenic Radiofrequency Coil Technology

Research in pathologies of the brain, heart and kidney have gained immensely from the plethora of studies that have helped shape new methods in magnetic resonance (MR) for characterizing preclinical disease models. Methodical probing into preclinical animal models by MR is invaluable since it allows a careful interpretation and extrapolation of data derived from these models to human disease. In this review we will focus on the applications of cryogenic radiofrequency (RF) coils in small animal MR as a means of boosting image quality (e.g., by supporting MR microscopy) and making data acquisition more efficient (e.g., by reducing measuring time); both being important constituents for thorough investigational studies on animal models of disease. This review attempts to make the (bio)medical imaging, molecular medicine, and pharmaceutical communities aware of this productive ferment and its outstanding significance for anatomical and functional MR in small rodents. The goal is to inspire a more intense interdisciplinary collaboration across the fields to further advance and progress non-invasive MR methods that ultimately support thorough (patho)physiological characterization of animal disease models. In this review, current and potential future applications for the RF coil technology in cardiovascular, neurovascular, and renal disease will be discussed.

Effect of Novel Quick Freezing Techniques Combined with Different Thawing Processes on Beef Quality

This study investigated the effect of various freezing and thawing techniques on the quality of beef. Meat samples were frozen using natural convection freezing (NF), individual quick freezing (IQF), or cryogenic freezing (CF) techniques, followed by natural convection thawing (NCT) or running water thawing (RT). The meat was frozen until the core temperature reached -12℃ and then stored at -24℃, followed by thawing until the temperature reached 5℃. Quality parameters, such as the pH, water binding properties, CIE color, shear force, and microstructure of the beef were elucidated. Although the freezing and thawing combinations did not cause remarkable changes in the quality parameters, rapid freezing, in the order of CF, IQF, and NF, was found to minimize the quality deterioration. In the case of thawing methods, NCT was better than RT and the meat quality was influence on the thawing temperature rather than the thawing rate. Although the microstructure of the frozen beef exhibited an excessive loss of integrity after the freezing and thawing, it did not cause any remarkable change in the beef quality. Taken together, these results demonstrate that CF and NCT form the best combination for beef processing; however, IQF and NCT may have practical applications in the frozen food industry.

A Comparison of Methods for Computing the Residual Resistivity Ratio of High-Purity Niobium

We compare methods for estimating the residual resistivity ratio (RRR) of high-purity niobium and investigate the effects of using different functional models. RRR is typically defined as the ratio of the electrical resistances measured at 273 K (the ice point) and 4.2 K (the boiling point of helium at standard atmospheric pressure). However, pure niobium is superconducting below about 9.3 K, so the low-temperature resistance is defined as the normal-state (i.e., non-superconducting state) resistance extrapolated to 4.2 K and zero magnetic field. Thus, the estimated value of RRR depends significantly on the model used for extrapolation. We examine three models for extrapolation based on temperature versus resistance, two models for extrapolation based on magnetic field versus resistance, and a new model based on the Kohler relationship that can be applied to combined temperature and field data. We also investigate the possibility of re-defining RRR so that the quantity is not dependent on extrapolation.

An Experimentally Validated Numerical Modeling Technique for Perforated Plate Heat Exchangers

Cryogenic and high-temperature systems often require compact heat exchangers with a high resistance to axial conduction in order to control the heat transfer induced by axial temperature differences. One attractive design for such applications is a perforated plate heat exchanger that utilizes high conductivity perforated plates to provide the stream-to-stream heat transfer and low conductivity spacers to prevent axial conduction between the perforated plates. This paper presents a numerical model of a perforated plate heat exchanger that accounts for axial conduction, external parasitic heat loads, variable fluid and material properties, and conduction to and from the ends of the heat exchanger. The numerical model is validated by experimentally testing several perforated plate heat exchangers that are fabricated using microelectromechanical systems based manufacturing methods. This type of heat exchanger was investigated for potential use in a cryosurgical probe. One of these heat exchangers included perforated plates with integrated platinum resistance thermometers. These plates provided in situ measurements of the internal temperature distribution in addition to the temperature, pressure, and flow rate measured at the inlet and exit ports of the device. The platinum wires were deposited between the fluid passages on the perforated plate and are used to measure the temperature at the interface between the wall material and the flowing fluid. The experimental testing demonstrates the ability of the numerical model to accurately predict both the overall performance and the internal temperature distribution of perforated plate heat exchangers over a range of geometry and operating conditions. The parameters that were varied include the axial length, temperature range, mass flow rate, and working fluid.

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.