Sample Exposure Time Research Articles

A rapid and multi-endpoint ecotoxicological test using Mychonastes afer for efficient screening of metals and herbicides

Microalgal growth-based tests are international standards for ecotoxicity assessment; however, their long exposure times, large sample volumes, and reliance on a single growth-endpoint make them inadequate for rapid toxicity screening. Here, we aimed to develop a rapid and simple ecotoxicological test using the fast-growing green alga Mychonastes afer, with multiple endpoints—growth, lipid content, and photosynthesis. We exposed M. afer to two metals—silver and copper—and two herbicides—atrazine and diuron—for 24 h and identified the most sensitive and reliable endpoints for each toxicant: the maximum electron transport rate (ETRmax) for Ag, Cu and atrazine, and the lipid content for diuron. Lipid content was found to be both a sensitive and reliable biomarker, meeting the effluent limit guidelines in both the Republic of Korea and the USA. The sensitivity of M. afer to Ag and atrazine also closely matched the HC5 values derived from the species sensitivity distribution approach, confirming its reliability for setting regulatory concentrations of these contaminants. Our calculated predicted no-effect concentration (PNEC) values were similar to established European Union PNECs for Ag, Cu, atrazine, and diuron, underlining the utility of these biological endpoints for ecological risk assessment and regulatory decision making. This method required lower sample volume (2 mL vs 100 mL) and exposure time (24 h vs 72–120 h) than conventional green algal tests, and eliminated the need for labour-intensive cell counting, expensive equipment, and chlorophyll fluorescence measurement expertise. Overall, this M. afer test can be a valuable tool for the rapid screening of wastewater for metals and herbicides, contributing to environmental protection and management practices.

THE EFFECT OF HIGH-TEMPERATURETREATMENT ON THE SORPTION PROPERTIES OF NATURAL BLUE CLAY

Relevance. Natural mineral clays are widely used not only in technology, but also in medicine, cosmetology, and the food industry, due to their unique properties. The high degree of dispersion, sorption-adhesive properties of clay materials, as well as the rich mineral composition also determine their therapeutic effect. Depending on the area and purpose of use, clays are subjected to heat treatment, which can lead to a change in their properties. The purpose of the work is to study the influence of various heat treatment modes on the sorption properties of clay for its further use in pharmaceutical practice. Material and methods. The object of study is Kimmeridgian blue powdery of clay blue Undory in the Ulyanovsk region. Determination of clay moisture content was carried out using an AND MF–5 moisture analyzer (Japan). To completely remove moisture from clay by high-temperature treatment, an SNOL 7.2/1100 electric furnace (Lithuania) was used. The influence of the clay calcination regime on the thermal stability of the clay powder and the ongoing endo- and exothermic effects with loss of sample mass was studied using a Q-1500D derivatograph (Hungary). Adsorption activity was assessed by direct spectrophotometry using an SF-56 “LOMO-Spectrum” spectrophotometer (Russia). Results. DTA of the derivatogram showed the thermal stability of the clay powder in the temperature range from 20°C to 900°C with variations in endo- and exothermic effects. Based on these data, heat treatment modes and sample exposure time were selected. The experiment showed a statistically significant decrease in adsorption activity with increasing temperature and various variations in exposure time. Conclusions. To preserve the adsorption properties of clay blue Undory when removing moisture from it, it is not rational to use high-temperature treatment. The most optimal parameters for drying clay are: temperature 80 ° C, exposure time - 240 minutes.

Optimisation of a neutron imaging system using the modulation transfer function

The use of the modulation transfer function was explored for the characterisation and optimisation of the optical system used for tomographic imaging on the DINGO instrument at the Australian Centre for Neutron Scattering, Australian Nuclear Science and Technology Organisation, Lucas Heights, Australia. Both a Siemens star and a phantom were used to determine the modulation transfer function and the results are compared. This allowed the optimal configuration of the instrument to be determined and the establishment of a relationship between sample dimension, exposure time and radiograph resolution to be developed. For tomographic studies of large samples, best results were achieved with DINGO configured in high-flux mode (L/D = 500), with a 6LiF/ZnS scintillator screen, an Iris 15TM sCMOS detector, a 50 mm lens, and an exposure time between 4 and 8 s.

Raman spectroscopy and NIR hyperspectral imaging for in-line estimation of fatty acid features in salmon fillets

Raman spectroscopy was compared with near infrared (NIR) hyperspectral imaging for determination of fat composition (%EPA + DHA) in salmon fillets at short exposure times. Fillets were measured in movement for both methods. Salmon were acquired from several different farming locations in Norway with different feeding regimes, representing a realistic variation of salmon in the market. For Raman, we investigated three manual scanning strategies; i) line scan of loin, ii) line scan of belly and iii) sinusoidal scan of belly at exposure times of 2s and 4s. NIR images were acquired while the fillets moved on a conveyor belt at 40 cm/s, which corresponds to an acquisition time of 1s for a 40 cm long fillet. For NIR images, three different regions of interest (ROI) were investigated including the i) whole fillet, ii) belly segment, and iii) loin segment. For both Raman and NIR measurements, we investigated an untrimmed and trimmed version of the fillets, both relevant for industrial in-line evaluation. For the trimmed fillets, a fat rich deposition layer in the belly was removed. The %EPA + DHA models were validated by cross validation (N = 51) and using an independent test set (N = 20) which was acquired in a different season. Both Raman and NIR showed promising results and high performances in the cross validation, with R2CV = 0.96 for Raman at 2s exposure and R2CV = 0.97 for NIR. High performances were obtained also for the test set, but while Raman had low and stable biases for the test set, the biases were high and varied for the NIR measurements. Analysis of variance on the squared test set residuals showed that performance for Raman measurements were significantly higher than NIR at 1% significance level (p = 0.000013) when slope-and-bias errors were not corrected, but not significant when residuals were slope-and-bias corrected (p = 0.28). This indicated that NIR was more sensitive to matrix effects. For Raman, signal-to-noise ratio was the main limitation and there were indications that Raman was close to a critical sample exposure time at the 2s signal accumulation.

Novel ionizing radiation induced reactions of poly(3-hexylthiophene)

Conjugated polymers are integral components in many optoelectronic devices, and many studies have focused on the connection between polymer morphology and device performance. There are many methods used to probe this correlation, including the use of synchrotron sources for x-ray scattering and reflectivity experiments. Though these types of experiments are useful in studying these materials, as x-ray sources have gotten stronger, alterations to the polymer chain molecular structure can occur from exposure to ionizing radiation. Most studies have examined thin films of conjugated polymers and the effects of ionizing radiation, with few examining solutions of conjugated polymers. This study monitors the time evolution of changes in poly(3-hexylthiophene) (P3HT) molecular structure when dissolved in deuterated styrene and exposed to synchrotron x-rays. In particular, the kinetics of structural evolution after exposure to X-rays is monitored, where we report the unexpected results that the ionizing radiation induced a reaction cascade, that continues long after removal of the x-ray beam. The scattering data, in conjunction with size exclusion chromatography and Fourier transform infrared spectroscopy, show a growth in the polymer structure that continues long after removal of the x-ray beam. Fitting the scattering data to the Gaussian Lorentz gel model and normalization to the sample concentration and exposure time offers insight into the relative dependence of the observed changes to the beam exposure time. These analyses lead to the conclusion that the structural changes are induced by the incorporation of styrene on the polymer chains, which can then further polymerize to produce grafts of deuterated polystyrene. The results in this paper therefore provide insight into the stability of conjugated polymers in the presence of reactive diluents and ionizing radiation, that reactions induced by exposure to ionizing radiation may cascade long after exposure, and that exposure time to the x-ray beam controls the reaction rate. This also opens novel reaction pathways to forming graft copolymers.

A Novel Cu2O/ZnO@PET Composite Membrane for the Photocatalytic Degradation of Carbendazim.

The extremely high levels of water pollution caused by various industrial activities represent one of the most important environmental problems. Efficient techniques and advanced materials have been extensively developed for the removal of highly toxic organic pollutants, including pesticides. This study investigated the photocatalytic degradation of the fungicide carbendazim (Czm) using composite track-etched membranes (TeMs) in an aqueous solution. Copper(I) oxide (Cu2O) and zinc oxide (ZnO) microtubes (MTs) were prepared using an electroless template deposition technique in porous poly(ethylene terephthalate) (PET) TeMs with nanochannels with a density of 4 × 107 pores/cm−2 and diameter of 385 ± 9 nm to yield Cu2O@PET and ZnO@PET composite membranes, respectively. A mixed Cu2O/ZnO@PET composite was prepared via a two-step deposition process, containing ZnO (87%) and CuZ (13%) as crystalline phases. The structure and composition of all composite membranes were elucidated using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD) techniques. Under UV–visible light irradiation, the Cu2O/ZnO@PET composite displayed enhanced photocatalytic activity, reaching 98% Czm degradation, higher than Cu2O@PET and ZnO@PET composites. The maximum Czm degradation efficiency from aqueous solution was obtained at an optimal pH of 6 and contact time of 140 min. The effects of various parameters such as temperature, catalyst dosage and sample exposure time on the photocatalytic degradation process were studied. The degradation reaction of Czm was found to follow the Langmuir–Hinshelwood mechanism and a pseudo-first order kinetic model. The degradation kinetics of Czm accelerated with increasing temperature, and the activation energy (Ea) levels were calculated as 11.9 kJ/mol, 14.22 kJ/mol and 15.82 kJ/mol for Cu2O/ZnO@PET, ZnO@PET and Cu2O@PET composite membranes, respectively. The reusability of the Cu2O/ZnO@PET catalyst was also investigated at different temperatures for 10 consecutive runs, without any activation or regeneration processes. The Cu2O/ZnO@PET composite exhibited degradation efficiency levels of over 50% at 14 °C and over 30% at 52 °C after 5 consecutive uses.

Transferable shadow cure: A new approach to achieving cationic photopolymerization in light‐restricted areas

AbstractTransferable shadow cure is presented as an improved method of shadow cure. In this new method, active centers are formed in one space, and active‐center‐containing monomer is then moved to another space where the bulk of the polymerization proceeds. This transference enables inclusion of pigments and fillers, layering in thick systems, and polymerization in complex geometries. Kinetic analysis of shadow‐cure samples shows conversions consistently ~15% less than comparable light‐cure samples. In addition, shadow‐cure films have a higher Tg and crosslink density than light‐cure films, likely driven by annealing that occurs during the first dynamic mechanical analyzer temperature ramp sequence. A central‐composite design explored the effect of sample depth, effective irradiance, exposure area, and exposure time on conversion and the weight percent of the light‐cure section. The model predicts both responses are maximized by increasing effective irradiance and exposure time and decreasing sample depth, which is consistent with classical photopolymerization kinetics.

Plasma pre-treatment of polypropylene surface for industrial purposes

ABSTRACT The paper describes an experimental investigation of the possibility of industrial modification of surface wettability and adhesion of polymers by the action of a plasma of a gliding discharge generated in air at atmospheric pressure in a simulated production process. The test material was polypropylene plates (PP). The modification was performed by a device with a multi-electrode (four pairs) system, which is not common. The quality of pre-processing and usability was evaluated primarily in terms of the industrial requirements, which means a change in wettability and adhesion expressed by the contact angle/surface free energy value in dependence to sample exposure time expressed by the conveyor belt speed. The surface free energy assessment of a treated polymeric surface by contact angle measurement was carried out by analyzing static sessile drops and evaluated by Owens–Wendt–Rabel–Kaelble (OWRK) model. The results determined a set of operating parameters at which the modification process meets the industrial requirements. By evaluating the change in surface free energy in relation to the storage time, the degree of hydrophobic recovery of the treated samples, i.e. the time stability of the plasma-treated surface, was also determined. It has been found that plasma-treated PP surface fully meets industrial demands and can be stored for at least 50 days.

Improving detection of BSA protein by applying atmospheric pressure plasma jets in MALDI-TOF mass spectrometry

To enhance protein identification in mass spectrometry systems, plasma can be applied in the sample preparation step in addition to conventional use, which improves the ionization process. In the present study, cold plasma technology is evaluated to achieve highly sensitive detection of low analyte concentrations.Plasma treatments are performed by two different low-temperature atmospheric-pressure sources. The protein ion signal after plasma treatment is characterized by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). The sample preparation method, exposure time and gas type for bovine serum albumin (BSA) are optimized. Plasma characteristics are determined by optical emission spectroscopy (OES) method. Also, the temperatures of plasma environment and sample are measured during the treatment with a non-contact infra-red digital camera.The water-soluble BSA protein is irradiated by cold atmospheric-pressure plasma jet (CAP jet) and radio-frequency plasma jet (RF jet). Mass spectra showed that argon plasma treatment with two-layer method induced a significant increase in ion intensity of MALDI-TOF MS. Argon treated water-soluble BSA and powder BSA lead to ten-times and three-times enhancement of protein ion signals as compared to the control, respectively. Also, treatment with argon RF jet, increases the ion signal more than two-times.The results indicate that ion intensity of BSA treated with CAP jet is significantly higher than that of BSA treated with RF jet. This finding, in addition to frequency and geometry parameters, depends on more analyte protonation, resulting in more ion flux toward BSA surface. Further, two-layer technique is considered as an optimal sampling method for MALDI.

Deep Learning Driven Noise Reduction for Reduced Flux Computed Tomography.

Deep neural networks have received considerable attention in clinical imaging, particularly with respect to the reduction of radiation risk. Lowering the radiation dose by reducing the photon flux inevitably results in the degradation of the scanned image quality. Thus, researchers have sought to exploit deep convolutional neural networks (DCNNs) to map low-quality, low-dose images to higher-dose, higher-quality images, thereby minimizing the associated radiation hazard. Conversely, computed tomography (CT) measurements of geomaterials are not limited by the radiation dose. In contrast to the human body, however, geomaterials may be comprised of high-density constituents causing increased attenuation of the X-rays. Consequently, higher-dose images are required to obtain an acceptable scan quality. The problem of prolonged acquisition times is particularly severe for micro-CT based scanning technologies. Depending on the sample size and exposure time settings, a single scan may require several hours to complete. This is of particular concern if phenomena with an exponential temperature dependency are to be elucidated. A process may happen too fast to be adequately captured by CT scanning. To address the aforementioned issues, we apply DCNNs to improve the quality of rock CT images and reduce exposure times by more than 60%, simultaneously. We highlight current results based on micro-CT derived datasets and apply transfer learning to improve DCNN results without increasing training time. The approach is applicable to any computed tomography technology. Furthermore, we contrast the performance of the DCNN trained by minimizing different loss functions such as mean squared error and structural similarity index.

HS-SPME/GC–MS volatile fraction determination and chemometrics for the discrimination of typical Italian Pecorino cheeses

The volatiles of three typical Italian Pecorino cheeses were analysed by headspace solid-phase microextraction (HS-SPME) coupled with gas-chromatography with mass spectrometry detection (GC–MS) evaluating its potentiality to discriminate Protected Designation of Origin (PDO) Pecorino Romano (PR), PDO Pecorino Sardo (PS) and Pecorino di Farindola (PF). A Design of Experiments (DOE) was employed to optimize the extraction conditions in terms of sample temperature and exposure time in the HS-SPME/GC–MS procedure. Linear Discriminant Analysis (LDA) and Partial Least Squares-Discriminant Analysis (PLS-DA) were applied to the volatile composition data to classify samples. Both methods showed high calibration accuracy (100% of non-error rate in cross-validation) and good predictions (87.5% of correct classification, on the external validation set) providing a powerful tool for discriminating Pecorino cheeses, despite their production occurs in different production cycles, in nearby geographical areas and, in the case of PS/PR origins, the raw materials come from common sources.

Application of Silver-Loaded Composite Track-Etched Membranes for Photocatalytic Decomposition of Methylene Blue under Visible Light.

In this study, the use of composite track-etched membranes (TeMs) based on polyethylene terephthalate (PET) and electrolessly deposited silver microtubes (MTs) for the decomposition of toxic phenothiazine cationic dye, methylene blue (MB), under visible light was investigated. The structure and composition of the composite membranes were elucidated by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction technique. Under visible light irradiation, composite membrane with embedded silver MTs (Ag/PET) displayed high photocatalytic efficiency. The effects of various parameters such as initial dye concentration, temperature, and sample exposure time on the photocatalytic degradation process were studied. The decomposition reaction of MB was found to follow the Langmuir–Hinshelwood mechanism and a pseudo-first-order kinetic model. The degradation kinetics of MB accelerated with increasing temperature and activation energy, Ea, was calculated to be 20.6 kJ/mol. The reusability of the catalyst was also investigated for 11 consecutive runs without any activation and regeneration procedures. The Ag/PET composite performed at high degradation efficiency of over 68% after 11 consecutive uses.

Estimation of the stable frozen zone volume and the extent of contrast for a therapeutic substance.

BackgroundIn biomedical science and clinical practice, an estimation of the stable frozen zone volume and distribution of concentration fields of injected diagnostic and healing solutions in the tissues of living organisms is of great importance and does not currently have any mathematical solution aimed at its precise evaluation.ObjectiveThe aim of this research is the estimation of the stable frozen zone volume at ultra-low temperatures as well as the distribution of temperature areas and concentration fields of injected diagnostic and healing substances in vitro. The results can improve our understanding of the stable frozen zone volume and the extent of contrast for a therapeutic substance.Materials and methodsA cryogenic zone (ice ball) was generated at -180°C using liquid nitrogen without any difficulties in vitro. The effects of freeze-thaw processes using ultra-low temperature and the cryogenic response of a 1.5% gelatin solution in water (%g/v) kept at a constant temperature of 20°C and continuously stirred were mathematically analyzed. The stable frozen zone volume was illustrated in vitro and measured in terms of its length, depth and cryogenic margin using a standard medical ruler and Vernier caliper after a freezing period at -180°C, using liquid nitrogen to provide cooling and freezing of a small portion of this solution in the vessel at room temperature (20°C). Round-shaped cryoprobes with diameters of 15 mm and 50 mm were applied to create a frozen zone volume in vitro. A single cryoprobe was used per procedure. The sample exposure time was 3 min. After this time, the volume of the frozen region remains unchanged, which indicates that the equilibrium stationary state has been reached. The experimental design, cryogenic procedure and freeze-thaw processes of the hemisphere were described and illustrated in vitro item by item. The statistical analysis manifested significant differences that were found between the 50 mm and 15 mm cryoprobes with regards to the freezing diameter, depth, and cryogenic margin (P < 0.001).ResultsAn illustrated analytical mathematical solution of equations determined the stable frozen zone volume and the radius of the sphere of the frozen medium in the equilibrium stationary state. The resulting assessment provided the basis for the creation of mini- and micro-cryoprobes as well as cryoneedles for local tissue freezing in living biological structures. A solution to the equations was obtained under the boundary conditions with a set stable temperature value on the boundary surface of the cryoprobe as well as at the surface well-away from it, where the temperature is equal to the stable temperature of the environment. For example, this solution gives that in the case of a hemispherical cryoprobe radius of 1 mm, the frozen zone volume was more than three orders of magnitude greater than the volume of the cryoprobe itself and was equal to approximately 4 cm3. The determination of the fractal dimension can consider the individual characteristics of the spread of the contrast medium or therapeutic substance(s) in living tissue. Based on fractal theory, our innovative mathematical formulas allow for the assessment of the effective distribution of contrast medium in living biological structures, specifically for tissues assessed for diagnostic purposes, and they enable the selection of an optimal treatment strategy in medical practice.ConclusionA simple mathematical approach to solving the problems of assessing the stable frozen zone volume and distribution of temperature areas and concentration fields of injected diagnostic and healing substances in living biological structures, particularly living tissue in vitro, is presented in this study. The expressed quantitative mathematical formulas determine the stable stationary frozen zone volume and provide the basis for the creation of mini- and micro-cryoprobes. The application of fractal theory is proposed for assessing the distribution efficiency of contrast medium and therapeutic substance(s) in living biological structures for diagnostic purposes and for selecting a compassionate treatment strategy in medical professional practice.

Shallow sampling by multi-shot laser ablation and its application within U-Pb zircon geochronology

The interaction of incident laser radiation and sample substrate is complex and difficult to predict. Natural zircons are often both structurally and chemically heterogeneous in 3-dimensional space. Encountering growth-related, structural micro-heterogeneities, inclusions and chemical complexities is almost inevitable during a static ablation of several tens of seconds. A multi-shot approach to laser ablation described here implements a minimal sample exposure time to incident laser radiation by applying multiple 1 Hz shots to a single sample location in delayed succession. This process can be conceptualised as a “slowing down” of a high-frequency (5–20 Hz) static laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analysis until each laser pulse is distinct albeit transient. The ability to integrate and collate signal pulses for a small number of consecutive laser shots, as opposed to continuously pulsing the laser, produces precise age determinations (~1% reproducibility, 2σ level) on small sample volumes (704 ± 23 μm3 on 91500 zircon standard). The multi-shot LA-ICP-MS protocol employed here significantly reduces the effect of ‘downhole’ fractionation as the resultant craters are extremely shallow (as shallow as 0.56 ± 0.02 μm on 91500 zircon standard) and maintain an aspect ratio of ≪1. Further benefits include a reduced probability of thermally induced effects (e.g., substrate melting), plasma loading, and the potential for signal mixing (with depth) in a heterogeneous sample.

Intensification of pectin obtaining from apple pomace

This study is devoted to the problem of improving the methods of pectin obtaining from apple pomace. The relevance of the study is dictated by the fact of formation of a large amount of waste when receiving apple juice. The output of apple juice at the enterprises of the processing industry is from 50 to 75%, therefore, 25-50% is waste. In our studies we used 42 KHz frequency of ultrasonic vibrations. The powers of ultrasound waves were 30 and 50W. The output of pectin depends on the sample exposure time, and with time passing this growth decreases and eventually stops, which may indicate that a certain amount of destruction has been reached at a given power. The maximum increase in the output of pectic substances is observed when the ultrasonic treatment time is 15 minutes and it is 26%. Capacity also affects pectin output. With power increasing from 30 to 50 W, the amount of pectin released increases by an average of 10%. It is shown that the use of separation at the stage of solution partitioning from pectin allows one to increase the speed of the process by a factor of two.

Rapid Equilibrated Colorimetric Detection of Protamine and Heparin: Recognition at the Nanoscale Liquid-Liquid Interface.

Demand for rapid quantitation of polyions such as heparin and protamine are ever growing. Previous paper-based and polymeric optical and electrochemical sensing devices required more than several hours for signal stabilization. Therefore, signals were acquired with fixed sample exposure time modes, which was time-consuming and technically demanding. We present here for the first time the optical detection of protamine and heparin in equilibrium mode with emulsified nanospheres. The method significantly shortens the response time from hours to typically less than 10 s and offers tunable, sensitive, and colorimetric detection within the clinically relevant range (10 to 100 mg/L) for heparin. The improved characteristics are attributable to the small size of the nanospheres (ca. 50 nm in diameter) as well as the reversible recognition at the nanoscale liquid-liquid interface. Detection of the anticoagulant heparin was also successfully demonstrated in human blood serum background.

Critical temperature of the superconducting transition of individual phases of multiphase bismuth cuprates after cooling in a magnetic field to a temperature of 77 K

Using a highly sensitive torsional vibration technique, the authors have determined the critical temperatures of the superconducting transition (Tc) of individual phases of multiphase cuprates [Bi1.7Pb0.3Sr2Ca(n-1)CunOy (n = 2–30)] in a constant external magnetic field (H) in the temperature range of 77 to 270 K. It has been found that oscillation damping peaks are more pronounced when a sample is rapidly cooled in an external magnetic field (FC) to a temperature of 77 K and then is slowly warmed to room temperature. An increase in the time of sample exposure to a magnetic field at 77 K leads to a rise in the temperature Tc of different phases, and to an increase in the intensity of a signal corresponding to high-temperature phases with Tc &amp;gt; 240 K. Structural studies have shown that with increasing sample exposure time at 77 K, as a result of sample compression an increase in stress concentration at grain boundaries appears to increase defect density and to enhance the pinning of Abrikosov vortices, i.e. creates new (additional) conditions for their “freezing” during the field cooling (FC) procedure. It has been established that in samples of the Bi1.7Pb0.3Sr2Ca(n-1)CunOy (n = 2–30) series, the critical temperature Tc increases from 107 K to ≥ 240 K with an increase in n.

Coupling of nonlinear shape memory polymer cantilever dynamics with focused ultrasound field

Research has found significant potential for ultrasound actuation of shape memory polymers (SMPs) in several fields such as biomedical and electronic devices among others. Example applications range from controlled drug delivery containers to soft robotics and flexible electronics located in otherwise inaccessible places or hazardous environments, where direct external heating is not possible. SMPs can be manipulated into any temporary shape and later recover to their stress-free permanent shape when triggered with external stimuli such as heat. Focused ultrasound (FU) has the ability to induce localized heating and activate multiple intermediate shapes and achieve complete shape recovery in the polymer, non-invasively and remotely. In addition, FU has a superior capability for temporal and spatial control of shape recovery by adjusting sample size, ultrasound frequency, exposure time and intensity as well as the position of ultrasound focusing. In this paper, indirect actuation of the thermally-induced shape-memory effect of SMPs by FU is studied theoretically and experimentally with a focus on the acoustic field, medium, geometric and material properties. The changes in thermomechanical properties, during FU actuation, are studied through dynamic mechanical analyzer tests. Using these properties, an analytical acoustic-thermo-elastic dynamic model is developed to predict the shape memory response of a SMP cantilever beam, considering acoustic and geometric nonlinearities. The governing equations of motion are derived using reduced order modeling and solved by perturbation techniques. Having obtained an analytical expression for the shape recovery of the beam as a function of acoustic parameters, experimental validations for a cantilever SMP beam exposed to FU are performed. The model has the ability to successfully estimate the variation in the amount of shape recovery due to the change in source frequency of the transducer and peak acoustic pressure field inside SMP domain without the need of analyzing any intermediary acoustic/thermal/elastic behavior.

Characterization of CO2 laser browning of dough

Abstract We study the application of laser-heating technology to browning dough, due to its potential for high-resolution spatial and surface color control. An important component of this process is the identification of how laser parameters affect browning and baking and whether desirable results can be achieved. In this study, we analyze the performance of a carbon dioxide (CO2) mid-infrared laser (operating at 10.6 μm wavelength) during the browning of dough. Dough samples—consisting of flour and water—were exposed to the infrared laser at different laser power, beam diameter, and sample exposure time. At a laser energy flux of 0.32 MW m−2 (beam diameter of 5.7 mm) and sample exposure time of 180 s we observe a maximum thermal penetration of 0.77 mm and satisfactory dough browning. These results suggest that a CO2 laser is ideal for browning thin goods as well as for food layered manufacture. Industrial relevance A CO2 laser that operates at a wavelength of 10.6 μm (IR) was used as an alternative method for browning dough. The high-power flux of the laser and the high energy absorption of food at this wavelength allow for rapid surface browning; however, the high absorption limits thermal penetration depth. Nevertheless, accuracy of the laser beam enables high resolution spatial and thermal control of the non-enzymatic browning process. This high precision cooking makes laser-browning particularly ideal for food layered manufacture (FLM), a food processing technique that has gained increased attention in recent years. Using FLM, one can adjust the printed layer height to match cooking penetration depth. As a digital manufacturing technology, laser-browning could also enable manufacture of highly complex and customized food geometries and textures.

Towards high-throughput fast photochemical oxidation of proteins: Quantifying exposure in high fluence microtiter plate photolysis

Protein structural analysis by mass spectrometry has gained significant popularity in recent years, including high-resolution protein topographical mapping by fast photochemical oxidation of proteins (FPOP). The ability to provide protein topographical information at moderate spatial resolution makes FPOP an attractive technology for the protein pharmaceutical discovery and development processes. However, current technology limits the throughput and requires significant manual sample manipulation. Similarly, as FPOP is being used on larger samples, sample flow through the capillary becomes challenging. No systematic comparison of the performance of static flash photolysis with traditional flow FPOP has been reported. Here, we evaluate a 96-well microtiter-based laser flash photolysis method for the topographical probing of proteins, which subsequently could be used to analyze higher order structure of the protein in a high-throughput fashion with minimal manual sample manipulation. We used multiple metrics to compare microtiter FPOP performance with that of traditional flow FPOP: adenine-based hydroxyl radical dosimetry, oxidation efficiency of a model peptide, and hydroxyl radical protein footprint of myoglobin. In all cases, microtiter plate FPOP performed comparably with traditional flow FPOP, requiring a small fraction of the time for exposure. This greatly reduced sample exposure time, coupled with automated sample handling in 96-well microtiter plates, makes microtiter-based FPOP an important step in achieving the throughput required to adapt hydroxyl radical protein footprinting for screening purposes.