Spectral Categories Research Articles

Reviewing Vegetation Indices for Mobile Application: Potentials and Challenges

Vegetation are quantitative metrics that are used to assess the density of vegetation as well as its health and vitality. Vegetation indices are important in precision agriculture and monitoring environmental conditions. For years, vegetation indices have been derived from remote sensing or aerial imaging data, with focus on large plantation estate and green coverage. Recently, there is a growing interest in using mobile phone for measuring vegetation indices at a more affordable cost. The spectral range for vegetation indices extends from 400 nm to 900 nm, which places it in the VIS and NIR spectral categories, respectively. The CMOS sensor that is typically found in mobile phone cameras has the capacity to capture NIR images. This paper aims to give a background in understanding vegetation indices available and weighing the suitability of using these indices for mobile applications. The potential of using these indices has been establish when the studies indicate several works have successfully used mobile phone camera to capture vegetation indices formulation, but still additional features is needed to ensure the standardisation and consistency of image calibration.

Correspondences and stable homotopy theory

AbstractA general method of producing correspondences and spectral categories out of symmetric ring objects in general categories is given. As an application, stable homotopy theory of spectra is recovered from modules over a commutative symmetric ring spectrum defined in terms of framed correspondences over an algebraically closed field. Another application recovers stable motivic homotopy theory from spectral modules over associated spectral categories.

Prediction of quality traits in dry pepper powder using visible and near-infrared spectroscopy

Fruit quality phenotyping is a bottleneck in plant breeding. The present work aimed to investigate the applicability of visible (Vis) and near-infrared (NIR) spectroscopy for quality evaluation in dry red chili powder. We constructed prediction models for the American Spice Trade Association (ASTA)-colour and the Scoville Heat Unit (SHU)-pungency pepper traits using spectroscopy and multivariate statistical techniques. Predictive partial least squares (PLS) models were successfully achieved with high correlations (r) between the predicted and reference values for calibration and validation (r = 0.955 and 0.928 for ASTA-colour; r = 0.941 and 0.918 for SHU-pungency). Spectroscopy data from visible and short-wave radiation (Vis-SWNIR) provided the most robust (residual predictive deviation value) model for ASTA-colour (RPD = 2.84) and long-wave radiation (LWNIR) for SHU-pungency (RPD = 2.48). Spectral categories for wavelength range selection, variable importance for effective wavelength selection, and root mean press-statistic for factor selection were important criteria for PLS. Trait variance and distribution were also important criteria for the predictive capacity and power of the models. In conclusion, non-invasive spectroscopy was a promising tool in our study for dry red chili quality phenotyping.

Room-temperature emitters in wafer-scale few-layer hBN by atmospheric pressure CVD

Hexagonal boron nitride (hBN) is a two-dimensional, wide band gap semiconductor material suitable for several technologies. 2D hBN appeared as a viable platform to produce bright and optically stable single photon emitters (SPEs) at room temperature, which are in demand for quantum technologies. In this context, one main challenge concerns the upscaling of 2D hBN with uniform spatial and spectral distribution of SPE sources. In this work we optimized the atmospheric-pressure chemical vapor deposition (APCVD) growth and obtained large-area 2D hBN with uniform fluorescence emission properties. We characterized the hBN films by a combination of electron microscopy, Raman and X-ray photoelectron spectroscopy techniques. The extensive characterization revealed few-layer, polycrystalline hBN films (∼3 nm thickness) with balanced stoichiometry and uniformity over 2″ wafer scale. We studied the fluorescence emission properties of the hBN films by multidimensional hyperspectral fluorescence microscopy. We measured simultaneously the spatial position, intensity, and spectral properties of the emitters, which were exposed to continuous illumination over minutes. Three main emission peaks (at 538, 582, and 617 nm) were observed, with associated replica peaks red-shifted by ∼53 nm. A surface emitter density of ∼0.1 emitters/μm2 was found. A comparative test with pristine hBN nanosheets produced by liquid-phase exfoliation (LPE) was performed, finding that CVD and LPE hBN possess analogous spectral emitter categories in terms of peak position/intensity and density. Overall, the line-shape and wavelength of the emission peaks, as well as the other measured features, are consistent with single-photon emission from hBN. The results indicate that APCVD hBN might proficiently serve as a SPE platform for quantum technologies.

Advances in Spectral Techniques for Detection of Pathogenic Microorganisms

The highly contagious viral illness Coronavirus disease 2019, caused by severe acute respiratory syndrome coronavirus-2, has led to nearly 5 million deaths worldwide. The detection of highly infectious pathogens or novel pathogens causing emerging infectious diseases is highly challenging. Encouragingly, spectral detection—including laser-induced fluorescence spectroscopy, infrared absorption spectroscopy, Raman spectroscopy and their combinations—has been broadly used to detect pathogenic microorganisms on the basis of their physical and chemical characteristics. Surface-enhanced Raman spectroscopy with labels can detect organisms at a minimum concentration of 3 cells/mL. The changes in cells’ biochemical reactions before and after polioviral infection can be detected by Fourier transform infrared spectroscopy. However, the sensitivity and specificity of different spectral detection categories differs, owing to their different detection principles. Flexible detection methods require interdisciplinary researchers familiar with both pathogen biology and instruments. This review summarizes the advances in spectral techniques used in detecting pathogenic microorganism.

The Austrian Semantic EO Data Cube Infrastructure

Big optical Earth observation (EO) data analytics usually start from numerical, sub-symbolic reflectance values that lack inherent semantic information (meaning) and require interpretation. However, interpretation is an ill-posed problem that is difficult for many users to solve. Our semantic EO data cube architecture aims to implement computer vision in EO data cubes as an explainable artificial intelligence approach. Automatic semantic enrichment provides semi-symbolic spectral categories for all observations as an initial interpretation of color information. Users graphically create knowledge-based semantic models in a convergence-of-evidence approach, where color information is modelled a-priori as one property of semantic concepts, such as land cover entities. This differs from other approaches that do not use a-priori knowledge and assume a direct 1:1 relationship between reflectance values and land cover. The semantic models are explainable, transferable, reusable, and users can share them in a knowledgebase. We provide insights into our web-based architecture, called Sen2Cube.at, including semantic enrichment, data models, knowledge engineering, semantic querying, and the graphical user interface. Our implemented prototype uses all Sentinel-2 MSI images covering Austria; however, the approach is transferable to other geographical regions and sensors. We demonstrate that explainable, knowledge-based big EO data analysis is possible via graphical semantic querying in EO data cubes.

Betti spectral gluing

Given a complex reductive group G, Borel subgroup B⊂G, and topological surface S with boundary ∂S, we study the “Betti spectral category” DCohN(LocG(S,∂S)) of coherent sheaves with nilpotent singular support on the character stack of G-local systems on S with B-reductions along ∂S. Modifications along the components of ∂S endow DCohN(LocG(S,∂S)) with commuting actions of the affine Hecke category HG in its realization as coherent sheaves on the Steinberg stack. We prove a “spectral Verlinde formula” identifying the result of gluing two boundary components with the Hochschild homology of the corresponding HG-bimodule structure. The equivalence is compatible with Wilson line operators (the action of Perf(LocG(S)) realized by Hecke modifications at points) as well as Verlinde loop operators (the action of the center of HG realized by Hecke modifications along closed loops). The result reduces the calculation of such “Betti spectral categories” to the case of disks, cylinders, pairs of pants, and the Möbius band. We also show how to impose arbitrary ramification conditions in terms of modules for the affine Hecke category.

Unusual spectral categories

The paper is devoted to a kind of “very non-abelian” spectral categories. Under strong conditions on a category \mathcal X , we prove, among other things, that, for a given faithful localization \mathcal C \to \mathcal X , we have canonical equivalences Spec (\mathcal{C})\sim\mathcal{X}\sim (category of injective objects in \mathcal{C}) , and that \mathcal{C} has natural injective envelopes.

The first obstructions to enhancing a triangulated category

In this paper we relate triangulated category structures to the cohomology of small categories and define initial obstructions to the existence of an algebraic or topological enhancement. We show that these obstructions do not vanish in an example of triangulated category without models. We also obtain cohomological characterizations of pre-triangulated DG, A-infinity, and spectral categories.

An example of a non-Fourier–Mukai functor between derived categories of coherent sheaves

Orlov’s famous representability theorem asserts that any fully faithful exact functor between the bounded derived categories of coherent sheaves on smooth projective varieties is a Fourier–Mukai functor. In this paper we show that this result is false without the fully faithfulness hypothesis. We also show that our functor does not lift to the homotopy category of spectral categories if the ground field is $${\mathbb Q}$$ .

Fermi GBM GRBs' multivariate statistics

Studying their gamma‐ray spectra may reveal some physical information on γ‐ray bursts (GRBs). The Fermi satellite has observed more than 2,000 GRBs. The FERMIGBRST catalog contains the GRB parameters (peak energy, spectral indices, intensity) estimated for both the total emission (fluence) and the emission during the interval of the peak flux. We found a relationship with linear discriminant analysis between the spectral categories and the model‐independent physical data. We compared the Swift and Fermi spectral types, and found a connection between the Fermi fluence spectra and the Swift spectra, but the result of the peak flux spectra can be disputable. We found that those GRBs that were observed by both Swift and Fermi can similarly discriminate as the complete Fermi sample. We conclude that the common observation probably did not find any trace of selection effects in the spectral behavior of GRBs.

Feature ranking and rank aggregation for automatic sleep stage classification: a comparative study

BackgroundNowadays, sleep quality is one of the most important measures of healthy life, especially considering the huge number of sleep-related disorders. Identifying sleep stages using polysomnographic (PSG) signals is the traditional way of assessing sleep quality. However, the manual process of sleep stage classification is time-consuming, subjective and costly. Therefore, in order to improve the accuracy and efficiency of the sleep stage classification, researchers have been trying to develop automatic classification algorithms. Automatic sleep stage classification mainly consists of three steps: pre-processing, feature extraction and classification. Since classification accuracy is deeply affected by the extracted features, a poor feature vector will adversely affect the classifier and eventually lead to low classification accuracy. Therefore, special attention should be given to the feature extraction and selection process.MethodsIn this paper the performance of seven feature selection methods, as well as two feature rank aggregation methods, were compared. Pz-Oz EEG, horizontal EOG and submental chin EMG recordings of 22 healthy males and females were used. A comprehensive feature set including 49 features was extracted from these recordings. The extracted features are among the most common and effective features used in sleep stage classification from temporal, spectral, entropy-based and nonlinear categories. The feature selection methods were evaluated and compared using three criteria: classification accuracy, stability, and similarity.ResultsSimulation results show that MRMR-MID achieves the highest classification performance while Fisher method provides the most stable ranking. In our simulations, the performance of the aggregation methods was in the average level, although they are known to generate more stable results and better accuracy.ConclusionsThe Borda and RRA rank aggregation methods could not outperform significantly the conventional feature ranking methods. Among conventional methods, some of them slightly performed better than others, although the choice of a suitable technique is dependent on the computational complexity and accuracy requirements of the user.

Quantitative EEG spectral categories related to corticothalamic integrity and short-term clinical outcomes after aneurysmal subarachnoid hemorrhage – an exploratory analysis (P2.284)

Quantitative EEG spectral categories related to corticothalamic integrity and short-term clinical outcomes after aneurysmal subarachnoid hemorrhage – an exploratory analysis (P2.284)

Rectification of enriched ∞–categories

We prove a rectification theorem for enriched infinity-categories: If V is a nice monoidal model category, we show that the homotopy theory of infinity-categories enriched in V is equivalent to the familiar homotopy theory of categories strictly enriched in V. It follows, for example, that infinity-categories enriched in spectra or chain complexes are equivalent to spectral categories and dg-categories. A similar method gives a comparison result for enriched Segal categories, which implies that the homotopy theories of n-categories and (infinity,n)-categories defined by iterated infinity-categorical enrichment are equivalent to those of more familiar versions of these objects. In the latter case we also include a direct comparison with complete n-fold Segal spaces. Along the way we prove a comparison result for fibrewise simplicial localizations potentially of independent use.

Enriched ∞-categories via non-symmetric ∞-operads

We set up a general theory of weak or homotopy-coherent enrichment in an arbitrary monoidal ∞-category. Our theory of enriched ∞-categories has many desirable properties; for instance, if the enriching ∞-category V is presentably symmetric monoidal then Cat∞V is as well. These features render the theory useful even when an ∞-category of enriched ∞-categories comes from a model category (as is often the case in examples of interest, e.g. dg-categories, spectral categories, and (∞,n)-categories). This is analogous to the advantages of ∞-categories over more rigid models such as simplicial categories — for example, the resulting ∞-categories of functors between enriched ∞-categories automatically have the correct homotopy type.We construct the homotopy theory of V-enriched ∞-categories as a certain full subcategory of the ∞-category of “many-object associative algebras” in V. The latter are defined using a non-symmetric version of Lurie's ∞-operads, and we develop the basics of this theory, closely following Lurie's treatment of symmetric ∞-operads. While we may regard these “many-object” algebras as enriched ∞-categories, we show that it is precisely the full subcategory of “complete” objects (in the sense of Rezk, i.e. those whose spaces of objects are equivalent to their spaces of equivalences) that are local with respect to the class of fully faithful and essentially surjective functors. We also consider an alternative model of enriched ∞-categories as certain presheaves of spaces satisfying analogues of the “Segal condition” for Rezk's Segal spaces. Lastly, we present some applications of our theory, most notably the identification of associative algebras in V as a coreflective subcategory of pointed V-enriched ∞-categories as well as a proof of a strong version of the Baez–Dolan stabilization hypothesis.

Uniqueness of the multiplicative cyclotomic trace

Making use of the theory of noncommutative motives, we characterize the topological Dennis trace map as the unique multiplicative natural transformation from algebraic K-theory to topological Hochschild homology (THH) and the cyclotomic trace map as the unique multiplicative lift through topological cyclic homology (TC). Moreover, we prove that the space of all multiplicative structures on algebraic K-theory is contractible.We also show that the algebraic K-theory functor from small stable ∞-categories to spectra is lax symmetric monoidal, which in particular implies that En ring spectra give rise to En−1 ring algebraic K-theory spectra. Along the way, we develop a “multiplicative Morita theory”, establishing a symmetric monoidal equivalence between the ∞-category of small idempotent-complete stable ∞-categories and the Morita localization of the ∞-category of spectral categories.

Novel sensor technologies towards environmental health monitoring in urban environments: A case study in the Niger Delta (Nigeria)

The Niger Delta (Nigeria) is an exemplar of a legacy of environmental pollution. Limited knowledge on spatial and temporal pollutant distributions in the region highlights the need for biomonitoring approaches to study impacts on sentinel organisms. This study evaluated whether infrared (IR) spectroscopy and multivariate analysis could detect alterations in biomolecules in samples in differing exposure scenarios, i.e., spatial and temporal using African catfish (Heterobranchus bidorsalis) or water spinach (Ipomea aquatica). Significant spectral differences between tissues isolated from African catfish based on site or season were observed; in a region where fish appeared not to be present, water spinach was used as a surrogate sentinel organism. Using one-way ANOVA, the spectral categories were significant (P < 0.0001). The applicability of IR spectroscopy to detect subtle changes in target biological molecules within sentinel organisms along with its low-cost yet high-throughput potential suggests that biospectroscopy permits real-time evaluation of environmental exposure effects.

ON THE HOMOTOPY THEORY OF ENRICHED CATEGORIES

We give sufficient conditions for the existence of a Quillen model structure on small categories enriched in a given monoidal model category. This yields a unified treatment for the known model structures on simplicial, topological, dg- and spectral categories. Our proof is mainly based on a fundamental property of cofibrant enriched categories on two objects, stated below as the Interval Cofibrancy Theorem.

A universal characterization of higher algebraic K-theory

In this paper we establish a universal characterization of higher algebraic K-theory in the setting of small stable infinity categories. Specifically, we prove that connective algebraic K-theory is the universal additive invariant, i.e., the universal functor with values in spectra which inverts Morita equivalences, preserves filtered colimits, and satisfies Waldhausen's additivity theorem. Similarly, we prove that non-connective algebraic K-theory is the universal localizing invariant, i.e., the universal functor that moreover satisfies the "Thomason-Trobaugh-Neeman" localization theorem. To prove these results, we construct and study two stable infinity categories of "noncommutative motives"; one associated to additivity and another to localization. In these stable infinity categories, Waldhausen's S. construction corresponds to the suspension functor and connective and non-connective algebraic K-theory spectra become corepresentable by the noncommutative motive of the sphere spectrum. In particular, the algebraic K-theory of every scheme, stack, and ring spectrum can be recovered from these categories of noncommutative motives. In order to work with these categories of noncommutative motives, we establish comparison theorems between the category of spectral categories localized at the Morita equivalences and the category of small idempotent-complete stable infinity categories. We also explain in detail the comparison between the infinity categorical version of Waldhausen K-theory and the classical definition. As an application of our theory, we obtain a complete classification of the natural transformations from higher algebraic K-theory to topological Hochschild homology (THH) and topological cyclic homology (TC). Notably, we obtain an elegant conceptual description of the cyclotomic trace map.

From the Imbrium Basin to crater Tycho: The first regional spectral distribution map derived from SIR-2 near-infrared data

Near-InfraRed (NIR) data obtained at the Moon by the SIR-2 instrument aboard Chandrayan-1 have been analyzed and classified according to their spectral absorption characteristics. This approach yielded a new NIR map, based on 10 spectral categories that we have identified, which cover a substantial portion of the lunar nearside. The inferred distribution of materials that share similar reflectance patterns resembles existing geologic maps, where were drawn using a range of complementary methods, but differs from these in respect of detailed structures. In particular, new features were found in the distributions of mare flows within the Imbrium Basin, as well as across boundary regions and in circumbasin formations, which lead to new geological interpretations. A new map of crater Tycho and its surroundings was in addition constructed based on eight spectral types, differentiated between ejected materials and crater infill.