Limited Resolution Research Articles

Atomic physics on a 50-nm scale: Realization of a bilayer system of dipolar atoms.

Controlling ultracold atoms with laser light has greatly advanced quantum science. The wavelength of light sets a typical length scale for most experiments to the order of 500 nanometers (nm) or greater. In this work, we implemented a super-resolution technique that localizes and arranges atoms on a sub-50-nm scale, without any fundamental limit in resolution. We demonstrate this technique by creating a bilayer of dysprosium atoms and observing dipolar interactions between two physically separated layers through interlayer sympathetic cooling and coupled collective excitations. At 50-nm distance, dipolar interactions are 1000 times stronger than at 500 nm. For two atoms in optical tweezers, this should enable purely magnetic dipolar gates with kilohertz speed.

The estimation of b-value of the frequency-magnitude distribution and of its one-sigma intervals from binned magnitude data

Summary The estimation of the slope (b-value) of the frequency magnitude distribution of earthquakes is based on a formula derived by Aki decades ago, assuming a continuous exponential distribution. However, as the magnitude is usually provided with a limited resolution, its distribution is not continuous but discrete. In the literature, this problem was initially solved by an empirical correction (due to Utsu) to the minimum magnitude, and later by providing an exact formula such as that by Tinti and Mulargia, based on the geometric distribution theory. A recent paper by van der Elst showed that the b-value can be estimated also by considering the magnitude differences (which are proven to follow an exponential discrete Laplace distribution) and that in this case the estimator is more resilient to the incompleteness of the magnitude dataset. In this work we provide the complete theoretical formulation including i) the derivation of the means and standard deviations of the discrete exponential and Laplace distributions; ii) the estimators of the decay parameter of the discrete exponential and trimmed Laplace distributions; and iii) the corresponding formulas for the parameter b. We deduce iv) the standard one-sigma intervals for the estimated b. Moreover, we are able v) to quantify the error associated with the Utsu minimum-magnitude correction. Furthermore, we have discussed the formulas to produce statistically independent magnitude differences. We tested extensively the b-value estimators on simulated synthetic datasets including complete catalogues as well as catalogues affected by a strong incompleteness degree such as aftershock sequences where the incompleteness is made to vary from one event to the next. We have also analysed the real aftershock sequence of the 30/10/2016 Norcia (central Italy) to integrate the finding of the simulations. To judge the performance of the various estimators we have introduced an index p that can be seen as a non-parametric extension of the Student's t index. The main outcomes of this paper are that 1) the b-value estimators devised for continuous magnitude data are not adequate for binned magnitudes, 2) for complete datasets, estimators based on magnitudes and on magnitude differences provide substantially equivalent results, 3) for incomplete magnitude datasets, estimators based on magnitude differences provide better results, 4) for incomplete aftershock sequences there is no evidence that methods based on positive magnitude differences are superior than other methods using differences. This conclusion is further confirmed by our analysis of the above-mentioned Norcia seismic sequence. This last finding contrasts with the van der Elst's claim that the so called ${b}_ + $ method is the most adequate to treat real aftershock sequences.

Residual loads from tilapia farming on the sediment of a Brazilian reservoir

This study investigated the sediment geochemistry of a fish farming area in net cage tanks in the Rosário reservoir, Brazil. Three areas were investigated: reference (RA), fish farming (FFA), and dispersion (DA). The results were analyzed through correlation, similarity, principal component analysis, comparison with legislation, sediment quality guidelines, and sediment pollution indices. The mean concentrations for RA, FFA, and DA areas were respectively: Cu (mg.kg−1) 37.74, 62.23, and 71.83; Mn (mg.kg−1) 22.55, 66.48, and 55.90; Zn (mg.kg−1) 9.13, 114.83, and 94.27; Fe (%) 0.28, 0.40, and 0.43; OM (%) 15.84, 21.95, and 18.45; TOC (%) 1.86, 3.69, and 6.05; TN (mg.kg−1) 2365.00, 5015.00, and 3447.51; TP (mg.kg−1) 780.00, 6896.00, and 2585.50; ORP (mV) −95.50, −135.20, and −127.10; pH 6.60, 6.58, and 6.05; <63 μm 90.59, 78.68, and 87.30. Statistically, the influence of fish farming on sediment, organic matter, and pollutant sedimentation was demonstrated. Cu and Zn concentrations were below sediment quality guidelines. Regarding legal limits (resolution 454/2012/CONAMA), nutrients in the FFA area exceeded by 60% (TN) and 100% (TP), while in DA and RA areas they were 100% lower. TOC was 100% lower in all areas. Organic matter exceeded the limit by 100% in all areas. Pollution indices resulted in: low contamination factor 78%; unpolluted for 87% of pollution load and 83% of combined pollution; moderately polluted for 75% of the Nemerow index. The greatest impacts and influence of farming on pollutant sedimentation were more concentrated in the fish farming area. In terms of legal aspects and pollution indices, fish farming produced low levels of trace metal pollution and nutrient concentrations exceeded legal limits.

The fine structure of pygmy and giant multipole resonances in nuclei

In connection with the program of planned work on the megascience installation "Intensive Reverse Compton"(INOC) at the Scientific Center of Physics and Mathematics in Sarov, a brief overview of experimental and theoretical results in the field of pygmy- and giant resonance energies is presented. Considered: 1) pygmy-dipole resonance in 208Pb, for which the limit of experimental resolution has already been reached and separate 1 − levels have been identified, 2) the most important physical results of experiments with a resolution of (50–200) keV both for gamma strenght functions, that determine the characteristics of nuclear reactions, and for analysis of non–statistical mechanisms of formation of widths of giant resonances («doorway» states) in the framework of wavelet analysis. Some results in the field of excitation energies (1–5) MeV are also discussed.

Anti-Low Angle Resolution: Some adaptive improvements in anchor-based object detection algorithm for automotive radar target detection

Automotive radar has extensive and well-established applications in advanced driver assistance systems (ADAS). It has been the most reliable and preferred sensor for functions such as adaptive cruise control and automatic emergency braking. Nevertheless, the limited angle resolution of traditional millimeter-wave radar data reduces its effectiveness in autonomous driving systems (ADS). Our study presents some adaptive improvements in anchor-based object detection algorithm framework to address the inaccuracies in target detection and positioning resulting from the limited angle resolution of millimeter-wave radar data. Our model utilizes the Range-Angle (RA) and Range-Doppler (RD) views of a RAD cube as inputs. An anchor assignment strategy - Max Intersection over Union (IoU) assigner is used to generate more positive samples than before, enabling the model to learn more about the relevant features of targets. We propose a multi-detection box fusion Non-Maximum Suppression (NMS) mechanism to fuse prediction results with varying confidence scores, thus improving the accuracy of target detection positions by addressing the issue of target box position deviation caused by low angle resolution. In addition, an actual distance loss function is designed to constrain the regularity that the size of the bounding box is inversely proportional to the distance between the target and the radar. Based on experimental results, the proposed method increases the mean average precision (mAP) by approximately 10% compared to the baseline method.

Holocene Variability of the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation Inferred From Chinese Speleothem δ18O Records

AbstractThe current reconstructions of the Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO) primarily rely on marine sediment proxies. However, the limited resolution of these records makes it difficult to precisely understand the short‐term dynamics of the PDO and AMO, and consequently, their influence on global climate. This study unveils two new Holocene reconstructions of AMO and PDO derived from a large‐scale compilation of speleothem isotope records (δ18Os) from Chinese monsoon region, in which spatial patterns of summer rainfall are generally accepted as good indicators of internal variability. Principal component analysis applied to Chinese δ18Os records identifies the first principal component as representative of Holocene Asian monsoon (AM) variation. This data‐driven approach reveals a significant shift in hydroclimatic conditions after 8.2 ka, potentially providing valuable insights into the underlying forcing mechanisms driving these changes. The remanent components, which show spatial rainfall patterns, are effectively validated through independent records of AMO and PDO derived from the previous paleo‐proxy based reconstructions and model simulations. The present reconstructions suggest a significantly enhanced stability of the AMO and PDO in the middle Holocene, which may explain the concurrent more stable and optimum climate observed in the AM region. These findings also imply that the Holocene AM intensity recorded in Chinese cave records is largely controlled by external forcing, whereas the regionally heterogenous rainfall is regulated by internal variability. The successful attempt on the Holocene AMO and PDO reconstructions indicates an effective isolation between different modes of climate variability from paleoclimate records.

Robust discrimination of multiple naturalistic same-hand movements from MEG signals with convolutional neural networks

Abstract Discriminating patterns of brain activity corresponding to multiple hand movements is a challenging problem at the limit of the spatial resolution of magnetoencephalography (MEG). Here, we use the combination of MEG, a novel experimental paradigm, and a recently developed convolutional-neural-network-based classifier to demonstrate that four goal-directed real and imaginary movements— all performed by the same hand— can be detected from the MEG signal with high accuracy: &amp;gt; 70% for real movements, and &amp;gt; 60% for imaginary movements. Additional experiments were used to control for possible confounds and to establish the empirical chance level. Investigation of the patterns informing the classification indicated the primary contribution of signals in the alpha (8–12 Hz) and beta (13–30 Hz) frequency range in the contralateral motor areas for the real movements, and more posterior parieto–occipital sources for the imagined movements. The obtained high accuracy can be exploited in practical applications e.g. in brain–computer interface -based motor rehabilitation.

High Spatiotemporal Resolution Radial Encoding Single-Vessel fMRI.

High-field preclinical functional MRI (fMRI) is enabled the high spatial resolution mapping of vessel-specific hemodynamic responses, that is single-vessel fMRI. In contrast to investigating the neuronal sources of the fMRI signal, single-vessel fMRI focuses on elucidating its vascular origin, which can be readily implemented to identify vascular changes relevant to vascular dementia or cognitive impairment. However, the limited spatial and temporal resolution of fMRI is hindered hemodynamic mapping of intracortical microvessels. Here, the radial encoding MRI scheme is implemented to measure BOLD signals of individual vessels penetrating the rat somatosensory cortex. Radial encoding MRI is employed to map cortical activation with a focal field of view (FOV), allowing vessel-specific functional mapping with 50×50 µm2 in-plane resolution at a 1 to 2 Hz sampling rate. Besides detecting refined hemodynamic responses of intracortical micro-venules, the radial encoding-based single-vessel fMRI enables the distinction of fMRI signals from vessel and peri-vessel voxels due to the different contribution of intravascular and extravascular effects.

A novel non-chemically amplified resist based on polystyrene-iodonium derivatives for electron beam lithography

To break the resolution limitation of traditional resists, more work is needed on non-chemically amplified resists (non-CARs). Non-CARs based on iodonium salt modified polystyrene (PS-I) were prepared with controllable molecular weight and structure. The properties of the resist can be adjusted by the uploading of iodonium salts on the polymer chain, the materials with a higher proportion of iodonium salts show better lithography performance. By comparing contrast curves and quality of the lithographic patterns, the optimum developing condition of 4-methyl-2-pentanone and ethyl alcohol (v:v = 1:7) was selected. The high-resolution stripes of 15 nm half-pitch (HP) can be achieved by PS-I0.58 in e-beam lithography (EBL). PS-I0.58 shows the advanced lithography performance in the patterns of 16 nm HP and 18 nm HP stripes with low line edge roughness (3.0 nm and 2.4 nm). The resist shows excellent potential for further pattern transfer, the etch selectivity of resist PS-I0.58 to the silicon was close to 12:1. The lithographic mechanism of PS-I was investigated by experimental and theoretical calculation, which indicates the polarity of materials changes results in the solubility switch. This work provides a new option and useful guidelines for the development of high-resolution resist.

Dual-Mode Solidly Mounted Resonator-Based Sensor for Temperature and Humidity Detection and Discrimination.

Sensors based on solidly mounted resonators (SMRs) exhibit a good set of properties, such as high sensitivity, fast response, low resolution limit and low production cost, which makes them an appealing technology for sensing applications. However, they can suffer from cross-sensitivity issues, as their response can be altered by undesirable ambient factors, such as temperature and humidity variations. In this work we propose a method to discriminate humidity variations from the general frequency response using an SMR specifically manufactured to operate in a dual-mode (displaying two close resonances). The two modes behave similarly towards humidity changes (-1.94 kHZ/(%RH)) for resonance one and -1.62 kHZ/(%RH) for resonance two), whereas their performance under temperature changes is significantly different, displaying 2.64 kHZ/°C for resonance one and 34.21 kHZ/°C for resonance two. This allows for the decoupling process to be carried out in a straightforward manner. Frequency response is tracked under different humidity conditions, in the -20 °C to room temperature region, proving that this behavior is reproducible in any given environment.

Determination of Air–Fuel Ratio at 1 kHz via Mid-Infrared Laser Absorption and Fast Flame Ionization Detector Measurements in Engine-Out Vehicle Exhaust

&lt;div&gt;Measurements of air–fuel ratio (AFR) and &lt;i&gt;λ&lt;/i&gt; (AFR&lt;sub&gt;actual&lt;/sub&gt;/AFR&lt;sub&gt;stoich&lt;/sub&gt;) are crucial for understanding internal combustion engine (ICE) performance. However, current &lt;i&gt;λ&lt;/i&gt; sensors suffer from long light-off times (on the order of seconds following a cold start) and limited time resolution. In this study, a four-color mid-infrared laser absorption spectroscopy (LAS) sensor was developed to provide 5 kHz measurements of temperature, CO, CO&lt;sub&gt;2&lt;/sub&gt;, and NO in engine-out exhaust. This LAS sensor was then combined with 1 kHz hydrocarbon (HC) measurements from a flame ionization detector (FID), and the Spindt exhaust gas analysis method to provide 1 kHz measurements of &lt;i&gt;λ&lt;/i&gt;. To the authors’ knowledge, this is the first time-resolved measurement of &lt;i&gt;λ&lt;/i&gt; during engine cold starts using the full Spindt method. Three tests with various engine AFR calibrations were conducted and analyzed: (1) 10% lean, (2) stoichiometric, and (3) 10% rich. The measurements were acquired in the exhaust of a light-duty truck with an 8-cylinder gasoline engine. The LAS-FID-based &lt;i&gt;λ&lt;/i&gt; sensor results were compared with those obtained from a universal exhaust gas oxygen (UEGO) sensor. The LAS-FID method provided robust &lt;i&gt;λ&lt;/i&gt; measurements from the first combustion exhaust event (avoiding the light-off time associated with traditional &lt;i&gt;λ&lt;/i&gt; sensors) in addition to enhanced temporal resolution (on the order of 100× increase compared to traditional diffusion-based &lt;i&gt;λ&lt;/i&gt; sensors). The insight gained from this novel method could be used to benefit crank, cold start, and open- or closed-loop air–fuel ratio control strategies in gasoline engines for reduced emissions.&lt;/div&gt;

CopyVAE: a variational autoencoder-based approach for copy number variation inference using single-cell transcriptomics.

Copy number variations (CNVs) are common genetic alterations in tumour cells. The delineation of CNVs holds promise for enhancing our comprehension of cancer progression. Moreover, accurate inference of CNVs from single-cell sequencing data is essential for unravelling intratumoral heterogeneity. However, existing inference methods face limitations in resolution and sensitivity. To address these challenges, we present CopyVAE, a deep learning framework based on a variational autoencoder architecture. Through experiments, we demonstrated that CopyVAE can accurately and reliably detect CNVs from data obtained using single-cell RNA sequencing. CopyVAE surpasses existing methods in terms of sensitivity and specificity. We also discussed CopyVAE's potential to advance our understanding of genetic alterations and their impact on disease advancement. CopyVAE is implemented and freely available under MIT license at https://github.com/kurtsemih/copyVAE.

Validation of cardiac image-derived input functions for functional PET quantification.

Functional PET (fPET) is a novel technique for studying dynamic changes in brain metabolism and neurotransmitter signaling. Accurate quantification of fPET relies on measuring the arterial input function (AIF), traditionally achieved through invasive arterial blood sampling. While non-invasive image-derived input functions (IDIF) offer an alternative, they suffer from limited spatial resolution and field of view. To overcome these issues, we developed and validated a scan protocol for brain fPET utilizing cardiac IDIF, aiming to mitigate known IDIF limitations. Twenty healthy individuals underwent fPET/MR scans using [18F]FDG or 6-[18F]FDOPA, utilizing bed motion shuttling to capture cardiac IDIF and brain task-induced changes. Arterial and venous blood sampling was used to validate IDIFs. Participants performed a monetary incentive delay task. IDIFs from various blood pools and composites estimated from a linear fit over all IDIF blood pools (3VOI) and further supplemented with venous blood samples (3VOIVB) were compared to the AIF. Quantitative task-specific images from both tracers were compared to assess the performance of each input function to the gold standard. For both radiotracer cohorts, moderate to high agreement (r: 0.60-0.89) between IDIFs and AIF for both radiotracer cohorts was observed, with further improvement (r: 0.87-0.93) for composite IDIFs (3VOI and 3VOIVB). Both methods showed equivalent quantitative values and high agreement (r: 0.975-0.998) with AIF-derived measurements. Our proposed protocol enables accurate non-invasive estimation of the input function with full quantification of task-specific changes, addressing the limitations of IDIF for brain imaging by sampling larger blood pools over the thorax. These advancements increase applicability to any PET scanner and clinical research setting by reducing experimental complexity and increasing patient comfort.

MR imaging of the magnetic fields induced by injected currents can guide improvements of individualized head volume conductor models

Abstract Volume conductor models of the human head are routinely used to estimate the induced electric fields in transcranial brain stimulation (TBS) and for source localization in electro- and magnetoencephalography (EEG and MEG). Magnetic resonance current density imaging (MRCDI) has the potential to act as a non-invasive method for dose control and model validation but requires very sensitive MRI acquisition approaches. A double-echo echo-planar imaging (EPI) method is here introduced. It combines fast and sensitive imaging of the magnetic fields generated by the current flow of transcranial electric stimulation with increased robustness to physiological noise. For validation, noise floor measurements without injected currents were obtained in 5 subjects for an established multi-echo gradient-echo (MGRE) sequence and the new EPI method. In addition, data with current injection was acquired in each subject with a right-left (RL) and anterior-posterior (AP) electrode montage with both sequences to assess the accuracy of subject-specific detailed head models. In line with previous findings, the noise floor measurements showed that the MGRE results suffered from spatial low-frequency noise patterns, which were mostly absent in the EPI data. A recently published approach optimizes the ohmic conductivities of subject-specific head models by minimizing the difference between simulated and measured current-induced magnetic fields. Here, simulations demonstrated that the MGRE noise patterns have a larger negative impact on the optimization results than the EPI noise. For the current injection measurements, a larger discrepancy was found for the RL electrode montage compared with the AP electrode montage consistently for all subjects. This discrepancy remained in part also after optimization of the ohmic conductivities, was similar for the data of the two sequences and larger than the measurement noise and thus demonstrates systematic biases in the volume conductor models. We have shown that EPI-based MRCDI is superior to established techniques by mitigating the effects of previously reported spatial low-frequency noise in MRCDI if limited spatial resolution is acceptable. Additionally, the consistent inter-subject results indicate that MRCDI is capable of picking up inaccuracies in computational head models and will be useful to guide systematic improvements.

Linkage-Mapping and Genome-wide Association Study Identified Two Peanut Late Leaf Spot Resistance Loci, PLLSR-1 and PLLSR-2, Using a Nested Association Mapping.

Identification of candidate genes and molecular markers for late leaf spot (LLS) disease resistance in peanut (Arachis hypogaea) has been a focus of molecular breeding for the U.S. industry funded peanut genome project. Efforts have been hindered by limited mapping resolution due to low levels of genetic recombination and marker density available in traditional biparental mapping populations. To address this, a multi-parental nested association mapping (NAM) population has been genotyped with the peanut 58 K SNP array and phenotyped for LLS severity in the field for three years. Joint linkage-based QTL mapping identified nine QTLs for LLS resistance with significant phenotypic variance explained (PVE) up to 47.7%. A genome-wide association study (GWAS) identified 13 SNPs consistently associated with LLS resistance. Two genomic regions harboring the consistent QTLs and SNPs were identified from 1,336 Kb to 1,520 Kb (184 Kb) on chromosome B02 and from 1,026.9 Kb to 1,793.2 Kb (767 Kb) on chromosome B03, designated as peanut late leaf spot resistance loci, PLLSR-1 and PLLSR-2, respectively. PLLSR-1 contains 10 NBS-LRR disease resistant genes. An NBS-LRR disease resistance gene Arahy.VKVT6A was also identified on homoeologous chromosome A02. PLLSR-2 contains five significant SNPs associated with five different genes encoding callose synthase, pollen defective in guidance protein, pentatricopeptide repeat (PPR), acyl-activating enzyme, and C2 GRAM domains-containing protein. This study highlights the power of multi-parent populations such as NAM for genetic mapping and marker-trait association studies in peanuts. Validation of these two LLS resistance loci will be needed for marker-assisted breeding.

Toward Direct Exploration of the Few-Femtosecond Dynamics of Electronic Coherence and Correlation in Quantum Materials Using Time- and Angle-Resolved Photoemission Spectroscopy

Over the last two decades, time- and angle-resolved photoemission spectroscopy (trARPES) has become a mature and established experimental technique for the study of ultrafast electronic and structural dynamics in materials. To date, most trARPES investigations have focused on the investigation of processes occurring on time scales of ≳30 fs, in particular, relaxation and thermalization, and have therefore been blind to the initial sub-10 fs dynamics related to electronic coherence and correlation effects. In this article, we illustrate how current trARPES setups reach their limits when it comes to addressing such extraordinarily short time scales and present an experimental configuration that provides the time, energy, and momentum resolutions required to monitor few-femtosecond dynamics on the relevant energy and momentum scales. We discuss the potential capabilities of such an experiment to study the electronic response of materials in the strong-field interaction regime at PHz frequencies and finally review a theoretical concept that may in the future even overcome the competing resolution limitations of trARPES experiments, as imposed by the time–bandwidth product of the probing laser pulse. Our roadmap for ultrafast trARPES indicates a path to break new experimental ground in quantum nonequilibrium electronic dynamics, from which new possibilities for ultrafast control of optical and electronic signals in quantum materials can be explored.

Visual cortical area contributions to the transient, multifocal and steady-state VEP: A forward model-informed analysis

Abstract Central to our understanding of how visual-evoked potentials (VEPs) contribute to visual processing is the question of where their anatomical sources are. Three well-established measures of low-level visual cortical activity are widely used: the first component (“C1”) of the transient and multifocal VEP, and the steady-state VEP (SSVEP). Although primary visual cortex (V1) activity has often been implicated in the generation of all three signals, their dominant sources remain uncertain due to the limited resolution and methodological heterogeneity of source modelling. Here, we provide the first characterisation of all three signals in one analytic framework centred on the “cruciform model”, which describes how scalp topographies of V1 activity vary with stimulus location due to the retinotopy and unique folding pattern of V1. We measured the transient C1, multifocal C1, and SSVEPs driven by an 18.75 Hz and 7.5 Hz flicker, and regressed them against forward models of areas V1, V2, and V3 generated from the Benson-2014 retinotopy atlas. The topographic variations of all four VEP signals across the visual field were better captured by V1 models, explaining between 2 and 6 times more variance than V2/V3. Models with all three visual areas improved fit further, but complementary analyses of temporal dynamics across all three signals indicated that the bulk of extrastriate contributions occur considerably later than V1. Overall, our data support the use of peak C1 amplitude and SSVEPs to probe V1 activity, although the SSVEP contains stronger extrastriate contributions. Moreover, we provide elaborated heuristics to distinguish visual areas in VEP data based on signal lateralisation as well as polarity inversion.

Spatial resolution limit of single pixel imaging of complex light fields.

Complex light fields with arbitrary amplitudes and phases can be measured by sampling them with an orthogonal basis (i.e., canonical, Hadamard) and performing single pixel interferometric measurements of the focused modes. In this work, we show that when the spatial resolution of the sampling basis is coarser than the spatial resolution of the phase in the complex field, the measured reconstructed amplitude exhibits cross talk with the phase, i.e., phase information appears in the amplitude. To demonstrate this phenomenon, we encode an arbitrary amplitude and a phase with a spatial light modulator and compare measurements with simulations.

Downslope variability in deep-water slope channel fill facies and stacking patterns

Lithologic variations in deep-water slope channel systems provide critical insight into sedimentary processes on deep-water slopes, and are a key control on natural resource distribution and connectivity in subsurface reservoirs associated with ancient deep-water systems. While many studies have described these variations at outcrop-scale along depositional strike (across-channel), few have focused on documenting along-depositional-dip changes due to: (1) the dearth of along-slope perspectives afforded by outcrops; or (2) limited resolution and coverage of subsurface data sets. In this study, slope channel elements (≤30 m thick; ≤400 m wide) and composite channelform bodies composed of ≥2 stacked channel elements (channel complexes and channel systems; >30 m thick; >400 m wide) were characterized along a 50-km-long depositional-dip-oriented outcrop belt of the Campanian-Maastrichtian Tres Pasos Formation (Chile) to constrain longitudinal changes in channel fill character and stacking patterns. Results show that channel elements become more sandstone-rich downdip. Outcrop observations are supported by channel element net-to-gross ratios (measures of sandstone proportion), which increase downdip. Sandstone-prone channel elements within channel complexes and channel systems are more prevalent downdip; however, variability in lateral and vertical offset between successive channel elements downdip results in a poor correlation between net-to-gross values and paleoslope position when composite channelform bodies are considered. These findings suggest that the along-slope distribution of coarse-grained sediment in channel systems is tied to the degree of coarse-grained sediment bypass and erosion that occurs along a slope. The results of this study provide a detailed perspective into downdip changes in slope channel fill and stacking patterns, and help clarify aspects of analogous subsurface reservoirs, including sandstone proportion trends for several scales of deep-water slope channel architecture.

Overlay Mark Design Using Irregular Grating Patterns

Overlay refers to controlling the vertical alignment and misalignment between circuit patterns manufactured in the previous process and circuit patterns manufactured in the current process during the stacking process of circuit patterns in the semiconductor manufacturing process. A critical factor in ensuring precise overlay measurements is using an optimized overlay mark design. Many semiconductor manufacturers have put considerable effort into optimizing overlay measurement marks to reduce high costs. However, image-based overlay measurement encounters several challenges, including resolution degradation, image distortion, and noise introduction during digital data conversion. These issues can amplify the uncertainty of overlay measurements, impair optical resolution, and heighten the risk of mismeasurement. In this paper, we introduce irregular grating patterns designed to address the principal challenges faced by the commonly utilized Advanced Imaging Metrology (AIM) marks, namely large overlays and image distortion. Furthermore, we propose an overlay mark capable of precisely identifying overlays exceeding half a pitch and incorporating as much data as possible within the limits of optical resolution. This aims to improve overlay measurement performance. The experimental findings demonstrate that the proposed Pulsated Grating Target (PGT) mark enhances overall measurement uncertainty by approximately 17% compared to the AIM mark. The practical applicability of the PGT was validated through experiments, and we achieved enhanced precision and reliability in overlay measurements by resolving the issue of large overlays—the most significant challenge with grating patterns—and simultaneously enhancing mark performance.