Phase Gradient Research Articles

Design and experimental evaluation of a non-contact ultrasonic motor using acoustic phase holography

Abstract Non-contact ultrasonic motors address certain limitations of conventional ultrasonic motors. However, they continue to have intricate designs and electronics. Acoustic holography has emerged as a technique for its flexibility and dynamicity in manipulating acoustic phase and amplitude patterns in the nearfield, offering a reduction in mentioned complexities. Therefore, this technique may find utility in the development of non-contact ultrasonic motors. This paper discusses a novel design for non-contact rotary ultrasonic motor using acoustic holography. Acoustic holographic technique modulates the acoustic phase to create a phase gradient, resulting in a rotary flow that drives the rotor in the interface of aqueous media and air. The motor’s performance is influenced by factors such as the acoustic pressure amplitude, the number of 0 to 2 π pitches, and the rotor’s geometry. An empirical study using the Response Surface Method (RSM) identified an optimal number of pitches for maximum rotational speed at a constant voltage. The motor torque was measured by calculating the drag forces applied to the rotor blades. It was found that the minimum output torque occurs when the stator phase pitches match the rotor blades. The ideal motor performance is achieved with eight rotor blades and six phase pitches. The motor’s top speed reached 40 rpm, and the output torque varied around 0.1 μN.m, depending on the phase pitches and rotor blades. In summary, the research highlights the potential of acoustic holography in designing a non-contact ultrasonic motor, with specific configurations yielding optimal speed and torque.

Wide-field large-angle beam splitters based on polarization-insensitive coding metasurfaces

Metasurfaces have been used to make various optical devices such as beam splitters because of their excellent capability to control light. The most recent work on metasurface beam splitters focused on realizing one-dimensional beam splitting. Based on generalized Snell’s law, we designed the beam splitters using a coding strategy by phase gradient metasurfaces, which can divide vertically incident light into two-dimensional space. Meanwhile, the beam splitters are polarization-insensitive because highly rotationally symmetric nanorods are used as structure units. Using different code groups, especially applying 0 and π binary phases, the proposed beam splitters have various functions such as beam deflection, two-beam splitting, and multi-beam splitting. The flexible design of the coding maps allows the light transmission to cover a full-view field. The maximum splitting angles in two-beam and multi-beam splitters are 35.7° and 28.3°, respectively. All the designed beam splitters have a power efficiency of over 80%. The beam splitters have the advantages of small size, easy integration, large beam splitting angle, wide beam splitting area, and high efficiency. They could be applied to many optical systems, such as multiplexers and interferometers in integrated optical circuits.

Integer multi-wavelength gradient phase metagrating for perfect refraction: Phase choice freedom in supercella).

Phase gradient metagratings (PGMs) reshape the impinging wavefront though the interplay between the linear adjacent phase increment inside supercells and the grating diffraction of supercells. However, the adjacent phase increment is elaborately designed by tuning the resonance of each subcell at a certain target frequency, which inevitably confines PGMs to operate only at the single frequency in turn. We notice that there exists a freedom of phase choice with a multi-2π increment in a supercell of PGMs, whereas conventional designs focus on the 2π increment. This freedom can induce a collaborative mechanism of surface impedance matching and multi-wavelength subcells, enabling the design of PGMs at multi-wavelengths. We further design and fabricate a supercell consisting of eight curved pipes to construct the two-wavelengths PGMs. The linear adjacent phase gradient of 0.25π at the fundamental frequency 3430 Hz is achieved, while the almost perfect transmission effect is observed due to the impedance match at the ends of curved pipes. In addition, the transmission field at the double frequency 6860 Hz is measured, whose refraction direction is consistent with that at 3430 Hz. This design strategy originated from phase choice freedom in the supercell and the experimental fabrication might stimulate applications on other multi-wavelength metasurfaces/metagratings.

High-efficiency terahertz surface plasmon metacoupler empowered by bilayer bright–dark mode coupling

Conversion from free-space waves to surface plasmons has been well studied as a key aspect of plasmonics. In particular, efficient coupling and propagation of surface plasmons via phase gradient metasurfaces are of great current research interest. Hereby, we demonstrate a terahertz metacoupler based on a bilayer bright–dark mode coupling structure attaining near-perfect conversion efficiency (exceeding 95%) without considering absorption loss of the materials and maintaining a high conversion level even when the area of the excitation region changes. To validate our design, a fabricated metacoupler was assessed by scanning near-field terahertz microscopy. Our findings could pave the way for developing high-performance plasmonic devices encompassing ultra-thin and compact functional devices for a diverse range of applications, especially within the realm of high-speed terahertz communications.

Fringe photometric stereo

In fringe projection profilometry (FPP), a high spatial frequency of fringe typically indicates powerful error suppression capability; however, it complicates phase unwrapping, necessitating a greater number of patterns and thus compromising the real-time performance of scanning. In this letter, we report a fringe photometric stereo (FPS) to completely bypass phase unwrapping for recovering the continuous 3D surface. We reveal the linear mapping relationship between the phase gradient and depth gradient, thereby facilitating the computation of depth gradients from phase gradients. Thus, we can employ depth gradients to reconstruct high-quality 3D profiles. Experimental results demonstrate that our FPS surpasses traditional phase-shifting profilometry in mitigating Gaussian noise. Our approach enables high-quality and unambiguous 3D reconstruction using single-frequency fringe patterns, relying solely on a camera and a projector without the need for dual, multiple, or light field cameras, thereby paving a path to high-speed and precision 3D imaging.

High-Efficiency Microwave Wireless Power Transmission via Reflective Phase Gradient Metasurfaces and Surface Wave Aggregation.

Microwave Wireless Power Transfer (MWPT) technology is crucial for emergency power supply during natural disasters and powering off-grid equipment. Traditional antenna arrays, however, suffer from low energy capture efficiency, difficult impedance matching, complex synthetic networks, and intricate manufacturing processes. This paper introduces a microwave energy receiver design utilizing Reflective Phase Gradient Metasurfaces (R-PGMs) and surface wave energy convergence technology. The design leverages the effective plane wave-to-surface wave conversion capability of R-PGMs to transform incident microwave energy into a surface wave mode, which is then efficiently harvested using a circular energy convergence array before being output to a coupling port. By optimizing R-PGM parameters, an ideal 60° phase gradient distribution is achieved, facilitating the focus of surface wave energy via dispersion characteristics. These components are integrated into a hybrid antenna array, complemented by a matched energy output port structure. Numerical simulations show that this array can efficiently convert microwave energy from plane waves to surface waves, achieving a conversion efficiency of 85.32% and a collection efficiency of 68.26%. Experimental results corroborate these findings, with peak energy collection efficiency reaching 64.68% at 5.8 GHz and an RF-DC conversion efficiency of 42%, confirming the design's efficacy. Compared to conventional methods, this design simplifies the system by avoiding complex combining networks and significantly enhances the efficiency of microwave MWPT.

Acoustic metagrating focusing and Bessel vortexes

Acoustic focusing and Bessel vortexes have great potential in medical ultrasound, particle trapping, and information processing. Based on the generalized Snell's law (GSL), metasurface focusing and Bessel vortexes were achieved by using in-plane phase profiles to shape wavefronts. Recent developments in acoustic metagratings (AMs) have demonstrated an extension of the GSL capable of switching transmitted and reflected vortexes that are determined by the parity of the number of wave propagation trips. However, these metagratings were designed with a certain one-dimensional phase gradient along the azimuthal direction, and the propagation of vortexes were generally fixed into cylindrical waveguides owing to energy divergence. The propagation and manipulation of acoustic vortexes in three-dimensional (3D) free space, caused by AMs with two-dimensional (2D) aperiodic phase gradients, still pose a great challenge. Here, we experimentally demonstrate two types of switchable acoustic lenses with focusing and Bessel vortexes. Based on the GSL extension, by separating and attaching 2D dual-layer aperiodic AMs in both lenses, the switch between the reflected focusing vortex and transmitted focusing/Bessel vortex with the same focus length and topological charge in 3D free space can be observed. The designed dual-layer AMs can realize the short-range and long-range focusing vortexes in 3D free space and also have the advantage of convenient function switching, which may pave the way for designing switchable focusing vortex lenses with practical applications.

Structured light analogy of quantum squeezed states

Quantum optics has advanced our understanding of the nature of light and enabled applications far beyond what is possible with classical light. The unique capabilities of quantum light have inspired the migration of some conceptual ideas to the realm of classical optics, focusing on replicating and exploiting non-trivial quantum states of discrete-variable systems. Here, we further develop this paradigm by building the analogy of quantum squeezed states using classical structured light. We have found that the mechanism of squeezing, responsible for beating the standard quantum limit in quantum optics, allows for overcoming the “standard spatial limit” in classical optics: the light beam can be “squeezed” along one of the transverse directions in real space (at the expense of its enlargement along the orthogonal direction), where its width becomes smaller than that of the corresponding fundamental Gaussian mode. We show that classical squeezing enables nearly sub-diffraction and superoscillatory light focusing, which is also accompanied by the nanoscale phase gradient of the size in the order of λ/100 (λ/1000), demonstrated in the experiment (simulations). Crucially, the squeezing mechanism allows for continuous tuning of both features by varying the squeezing parameter, thus providing distinctive flexibility for optical microscopy and metrology beyond the diffraction limit and suggesting further exploration of classical analogies of quantum effects.

Terahertz switchable vortex beam generator based on vanadium dioxide reflective metasurface

Vortex beams exhibit significant potential for applications in diverse fields, such as optical communications, particle manipulation, and quantum information, due to the orbital angular momentum (OAM) they carry. While substantial progress has been made in the generation of vortex beams and the control of their wavefronts, further optimization is necessary to enhance the variability of OAM modes and the modulation of focusing. This study presents three tunable vortex beam generators based on vanadium dioxide metasurfaces. By leveraging the insulator-metal phase transition of vanadium dioxide (VO2), these metasurfaces can convert incident left-circularly polarized (LCP) light into a deflected vortex beam with adjustable OAM modes, a switchable focused vortex beam, or a focused vortex beam with tunable OAM modes in the terahertz band. Specifically, by varying the angle of the incident light, a vortex beam carrying variable topological charges can be deflected over a range from -34° to 90°. Vortex beams with a topological charge of 1 enable reversible switching between near-focus (0.85 mm) and far-focus (3.2 mm), demonstrating highly effective tunable focusing capabilities. Additionally, focused vortex generators with switchable topological charges are proposed. Focused vortex beams with a topological charge of -1 are generated in the insulating state, while a topological charge of -2 is observed in the metallic state. These vortex beam generators allow for different phase gradient distributions in the phase transition states, enabling diverse OAM and variable focuses. This research has potential applications in areas such as dynamic imaging and optical communications.

Quantum Weak Value Enabled Quantitative Phase Imaging

AbstractQuantitative phase imaging (QPI) has been a powerful approach in bioimaging because it can protect specimens from staining and quantify important physical properties of biological specimen, such as local thickness and refractive index. Here, a simple mechanism is proposed to implement QPI based on the quantum weak‐value theory. Two weak values are employed. One is momentum weak value, which inherently gives the phase gradient of the cells and tissues, and the other is polarization weak value leading to the biased imaging. Following the essence of weak value amplification in precision metrology, the weak value can also enhance the contrast in imaging. By combining two converse bias images and a phase gradient intensity image to capture phase gradient data, the original phase of the specimen can be quantitatively reconstructed. A proof‐of‐principle experiment is conducted by imaging the phase targets and unstained Paramecium cells. The ability to capture quantitative phase data is validated through imaging various samples with a phase resolution, demonstrating height deviations of less than 10 nm compared to atomic force microscopy (AFM). This work proposes weak‐value‐based QPI that possess the potential for improving the measurement precision and provides deep insights into physics and applications of weak value.

Overcoming the Strong Sample Solvent Effect for Sustainability Measurement Challenges in Liquid Chromatography. Example for Bisphenol-A.

This paper describes an approach to achieve low parts per billion (ppb) concentration level detection using a reversed-phase ultrahigh-performance liquid chromatographic ultraviolet absorbance detection method with large-volume feed injection (FI) for analytes in dichloromethane (DCM). FI is a novel technology that allows sample injection at a defined speed into the LC mobile phase. We demonstrate this approach for a mixture of bisphenol A and its diglycidyl ether derivatives in DCM. DCM is a very strong injection solvent at reversed-phase LC conditions and is typically immiscible with a starting reversed-phase gradient mobile phase containing a high percentage of water. As a result, reduced separation performance and even peak splitting are seen with classic flow-through injection. The method setup comprised an octyl-bonded core-shell stationary phase (150 × 4.6 mm i.d., 2.7 μm particle size) with a water/acetonitrile mobile phase gradient and an exceptionally high injection volume of 45 μL of DCM solution using FI. Optimization of feed speed (1%) and isocratic hold duration (4 min) was crucial for final separation conditions. FI delivered more than a 20-fold improvement in the limit of detection (LOD) compared to standard flow-through injection while maintaining peak resolution. The LOD of the final method ranged between 1 and 10 ppb in the polymer resin. This methodology has high potential for trace analysis in a large variety of applications that suffer from the "strong solvent effect".

Exact analytical solution of the equations for a quasiequilibrium two-phase domain: permeability and interdendritic spacing

This study is concerned with the theoretical description of a quasi-stationary process of directional crystallization of binary melts and solutions in the presence of a quasi-equilibrium two-phase region. The quasi-equilibrium process is ensured by the fact that the system supercooling is almost completely compensated by heat released during the phase transformation. Quasi-stationarity of the process determining constancy of the crystallization rate is ensured by given temperature gradients in the solid and liquid phases. The system of heat and mass transfer equations and boundary conditions to them under these assumptions is dependent on a single spatial variable in the reference frame moving with the crystallization rate relative to a laboratory coordinate system. Exact analytical solutions to the formulated problem in parametric form are obtained. The parameter of the solution is the solid phase fraction in a two-phase region. The distributions of temperature and impurity concentration in the solid, liquid and two-phase regions of the crystallizing system, the rate of solidification, and the spatial coordinate in the two-phase region depending on the solid phase fraction in it are found. An algebraic equation for the solid phase fraction at the interface between the solid material and the two-phase region is derived. Exact analytical solutions show that the impurity concentration in the two-phase layer increases as the solid phase fraction increases. Moreover, the solid phase fraction at the interface solid phase — two phase region and its thickness increase as the temperature gradient in the solid phase and the solidification rate increase. The developed theory allows us to determine analytically the permeability of the two-phase region and a characteristic interdendritic spacing in it. Analytical solutions show that the relative permeability in the two-phase region increases from a certain value at the interface with the solid phase to unity at the interface with the liquid phase. The selection theory of stable dendritic growth allows us to determine analytically a characteristic interdendritic distance in the two-phase layer that decreases as the temperature gradient in the solid phase increases. An increase of impurity in the molten phase gives a decrease in the interdendritic spacing within a two-phase region.

Meta-optics empowered by all-silicon quarter-wave plates for generating focused vortex beams

The Poynting vector associated with the focused vortex beam (FVB) that carries orbital angular momentum (OAM) is oriented in a twisted manner relative to the principal axis of propagation. This characteristic has significant applications in advanced fields, including high-dimensional information processing, high-resolution imaging, and particle manipulation. Currently, complex optical systems that operate on alignment principles for generating FVBs have been miniaturized by metasurfaces, resulting in the achievement of polarization-dependent vectorized behavior. Nevertheless, generating and manipulating FVBs that carry OAM in the terahertz (THz) range remains a significant challenge. This difficulty arises particularly when utilizing quarter-wave plates (QWPs) that serve both polarization conversion and polarization filtering functions. Here, we experimentally demonstrate a planar all-dielectric array capable of generating FVBs with high power density within a single-handed circularly polarized channel. Engineered QWP meta-atoms are utilized as candidates for the efficient generation of the desired FVB through the application of dynamic phase gradients. A series of samples were fabricated to assess the effectiveness of this design strategy in converting an incident linearly polarized THz beam into arbitrary single-handed circularly polarized FVBs. Leveraging the high degree of freedom inherent in polarization multiplexing coding, the proposed QWP metasurface can generate FVBs exhibiting topological charge evolution along the longitudinal direction. This capability further underscores its robust polarization modulation proficiency. This work presents a generalized framework for the polarization-dependent generation of ultracompact structural optical fields, which may have potential applications in highly integrated THz communication systems.

Efficient Inverse Design of Large-Scale, Ultrahigh-Numerical-Aperture Metalens

Efficient design methods for large-scale metalenses are crucial for various applications. The conventional phase-mapping method shows a weak performance under large phase gradients, thus limiting the efficiency and quality of large-scale, high-numerical-aperture metalenses. While inverse design methods can partially address this issue, existing solutions either accommodate only small-scale metalenses due to high computational demands or compromise on focusing performance. We propose an efficient large-scale design method based on an optimization approach combined with the adjoint-based method and the level-set method, which first forms a one-dimensional metalens and then extends it to two dimensions. Taking fabrication constraints into account, our optimization method for large-area metalenses with a near-unity numerical aperture (NA = 0.99) has improved the focusing efficiency from 42% to 60% in simulations compared to the conventional design method. Additionally, it has reduced the deformation of the focusing spot caused by the ultrahigh numerical aperture. This approach retains the benefits of the adjoint-based method while significantly reducing the computational burden, thereby advancing the development of large-scale metalenses design. It can also be extended to other large-scale metasurface designs.

Automatic Landslide Detection in Gansu, China, Based on InSAR Phase Gradient Stacking and AttU-Net

Landslides are the most serious geological disaster in our country, causing economic losses. Because they go undetected, a large number of landslides that have caused disasters are not in the catalogue. At present, Interferometric Synthetic Aperture Radar (InSAR) has been widely used in the identification of landslides. However, it is time-consuming, inefficient, etc., to survey landslides throughout our large country. In the context of massive SAR data, this problem is more obvious. Therefore, based on the current technique of using differential interferogram phase gradient stacking to avoid phase unwrapping errors, a landslide phase gradient dataset has been constructed. To validate the dataset’s effectiveness and applicability, deep learning methods were introduced, applying the dataset to four networks: U-Net, Attention-Unet, Bisenet v2, and Deeplab v3. The results indicate that the phase gradient dataset performs well across different models, with the Attention-Unet network demonstrating the best performance. Specifically, the precision, recall, and accuracy on the test dataset were 0.8771, 0.8712, and 0.9834, respectively, and the accuracy on the validation dataset was 0.8523. Finally, in this paper, the model is applied to landslide identification in Gansu Province, China, during 2022-2023, and a total of 1882 landslides are found. These landslides are mainly concentrated in the south of Gansu Province, where the terrain is relatively undulating. The results show that this method can quickly and accurately realize landslide automatic identification in a wide area and provide technical support for large-scale landslide disaster surveys.

Rectangular Slot based Beam Focusing Dual-Band Phase Gradient Metasurface

This study proposes method for enhancing the performance of previously developed or produced weapon systems without developing new detection equipment by using Phase Gradient Metasurfaces(PGMS). Metasurface has been studied and utilized a lot to improve the detection performance of inorganic systems, but its utilization is low due to its narrow bandwidth and complex structure. To address some of these limitations, dual-band power focusing PGMS is proposed. Its frequency independent unit cell characteristic enables creating metasurface that concentrates signals in dual-band. The designed PGMS was validated through near-field and far-field measurement, confirming signal concentration at the specified focal length and improved gain in the dual bands.

B-182 Development and validation of an LC-MS/MS assay for simultaneous measurement of serum androstenedione and 17-hydroxyprogesterone in serum

Abstract Background Androstenedione and 17-hydroxyprogesterone are measured via immunoassays or high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS) in clinical laboratories. Immunoassays have limited sensitivity and specificity for certain steroid hormones testing. We aimed to develop and validate a sensitive, accurate, and specific in-house LC-MS/MS assay to simultaneously measure both 17-hydroxyprogesterone and androstenedione in serum. Methods 13C-labeled androstenedione and 17-hydroxyprogesterone internal standards were added to calibrator, control, and patient samples. A hexane/ethyl acetate solution was used in a liquid-liquid extraction procedure. The organic layer was then removed and dried followed by reconstituting the extracts in 2.5 mM ammonium formate in 50% methanol. The HPLC mobile phase gradient began with 47%, 2.5 mM ammonium formate in water and 53%, 2.5 mM ammonium formate in methanol. This progressed to 56% of the methanol phase over three minutes. The mixtures were separated though an Agilent 1260 Infinity HPLC system with a Poroshell 120 EC-C18 analytical column (2.1 × 50 mm × 2.7 µm). The separated HPLC eluents then entered an Agilent 6460C QQQ mass spectrometer in positive ion mode through an electrospray ionization source where protonated androstenedione (m/z = 287.2) with the protonated androstenedione-[2, 3, 4-13C3] internal standard (m/z = 290.2) and protonated 17-hydroxyprogesterone (m/z = 331.2) with the protonated 17-hydroxyprogesterone-[2, 3, 4-13C3] (m/z = 334.2) were mass-selected for collision-induced dissociation. For androstenedione, respective quantifier and qualifier m/z values of 287.2 > 97.1 and 287.2 > 109.1 were used while respective quantifier and qualifier m/z values of 331.2 > 97.1 and 331.2 > 109.1 were used for 17-hydroxyprogesterone. Validation studies were performed including imprecision, lower limit of quantitation (LLOQ), analytical measurement range (AMR), interference, specificity, carryover, extraction recovery, matrix effect, and comparison with a reference laboratory LC-MS/MS method. The total allowable error limits used in this study were 23.5% for androstenedione and 30.2% for 17-hydroxyprogesterone. Results Total imprecision results across three concentrations yielded a maximum CV of 4.6 % for androstenedione and 6.5% for 17-hydroxyprogesteron. The AMRs of androstenedione and 17-hydroxyprogesterone were 0.2 to 13.4 and 0.1 to 22.0 ng/mL without significant carryovers. No significant interferences were observed from 11-deoxycorticosterone (700 ng/dL), testosterone (2500 ng/dL), DHEA (1000 ng/mL), bilirubin (30.1 mg/dL), hemoglobin (1032 mg/dL), or triglycerides (1858 mg/dL). The extraction recoveries of androstenedione and 17-hydroxyprogesterone were 98% and 81%, respectively. No significant matrix effects were identified. In comparison to the reference lab LC-MS/MS method, the in-house LC-MS/MS assay demonstrated a 0.523% bias for androstenedione and a -3.77% bias for 17-hydroxyprogesterone with both exhibiting excellent correlations with the reference lab measurements. More specifically, our results (as a function of values obtained from the reference lab) followed the relationship of y = 1.039x - 0.092 (R = 0.9951) for androstenedione and y = 0.957x + 0.01 (R = 0.9974) for 17-hydroxyprogesterone. Conclusions An LC-MS/MS assay is developed for simultaneous detection of serum androstenedione and 17-hydroxyprogesterone. The assay demonstrates acceptable imprecision, AMR, and accuracy. No significant carryover and interference from other structurally similar steroid hormones and other common interferents are identified.

Unwrap Intractable C‐Band Coseismic Interferograms: An Improved SNAPHU Method With Range Offset Gradients as Prior Information

AbstractC‐band Interferometric Synthetic Aperture Radar (InSAR) data are widely used to map coseismic deformation. However, phase unwrapping errors are commonly distributed near faults owing to decorrelation and steep phase gradients from short radar wavelengths. Here, we propose an improved SNAPHU phase‐unwrapping algorithm that considers the prior information of the range offset gradients (P‐SNAPHU) to overcome the constraints imposed by the phase continuity assumption. P‐SNAPHU exploits median filtering of homogeneous pixels for initial denoising of range offset and then refines range offset gradients divisionally through saliency extraction. The derived gradients are used to estimate the expected values of the cost functions for the low‐coherence fringes. The synthetic experiments show significant improvements in the phase‐unwrapping accuracy of the P‐SNAPHU method compared with classical unwrapping methods. We apply the P‐SNAPHU method to unwrap Sentinel‐1 coseismic interferograms of three large (Mw > 6.5) strike‐slip earthquake events that the existing classical methods could not successfully unwrap. In the comparison of the unwrapped interferograms with the external global navigation satellite system (GNSS) displacements and those from the classical methods, we find that P‐SNAPHU significantly reduces the phase unwrapping errors with the mean absolute error of 7.2, 2.3, and 1.8 cm for the 2023 Kahramanmaraş earthquake doublet, the 2016 Kumamoto earthquake, and the 2019 Ridgecrest earthquakes, respectively. Based on the unwrapped results derived from P‐SNAPHU, an estimate is made regarding the shallow slip deficit of the 2023 Kahramanmaraş earthquake doublet, which is approximately 7%. Therefore, P‐SNAPHU is useful for developing and applying C‐band InSAR data for large earthquakes and volcanic activity.

Robustness evaluation of weak anion exchange chromatography method for the purity analysis of therapeutic oligonucleotides

Therapeutic oligonucleotides are becoming an important class of therapeutics. Their manufacturing processes can result in the formation of impurities, particularly truncated species. To ensure the quality and safety of the product, it is crucial to evaluate the presence of these species. Liquid chromatography analysis enables such purity determination. In this context, a recently described weak anion exchange chromatography method was optimized to allow the effective separation of different impurities. The optimization addressed the complexity and instability of the mobile phases, which contained salts and organic compounds. Adjustments were made to the mobile phase composition and gradient to meet the requirements of QC laboratories. Additionally, to ensure the method's reliability, a robustness study was conducted based on a risk assessment. Five factors were considered potential risks and were assessed experimentally on different chromatographic outputs. This led to the definition of a robust space, ensuring the method's reliability for the purity determination of oligonucleotides.

On tailored microstructure in AA 2024 alloy during in-situ microwave casting

In the present study, application of microwave energy was explored for tailoring the microstructure in AA 2024 alloy through directional solidification route. Microwave transparent (alumina) and absorbing (graphite) mould materials were utilized to investigate the effect of microwave interaction (electric and magnetic field components) with AA 2024 alloy on microstructure evolution in terms of dendrite size distribution and formation of eutectic phase. Results showed more pronounced eutectic phase gradient was developed using alumina mould. On the other hand, a more uniform distribution of the eutectic phase and grain size was observed with graphite mould. The development of the eutectic phase gradient is attributed to the effective microwave interaction with the AA 2024 alloy melt during solidification. This is primarily associated with the formation of an additional flux at the solid-liquid (S/L) interface of the alloy under the effect of magnetic field and an enhancement in diffusion flux due to mass transport caused by electric field component of microwave. Formation of AlCu, Al2Cu, and Al2CuMg intermetallic phases in both alumina and graphite mould casts was confirmed. Significantly higher hardness was observed at the higher eutectic phase sites within the alumina mould cast, whereas graphite mould casts exhibited better tensile properties.