FINDE: Neural Differential Equations for Finding and Preserving Invariant Quantities

Many real-world dynamical systems are associated with first integrals (a.k.a. invariant quantities), which are quantities that remain unchanged over time. The discovery and understanding of first integrals are fundamental and important topics both in the natural sciences and in industrial applications. First integrals arise from the conservation laws of system energy, momentum, and mass, and from constraints on states; these are typically related to specific geometric structures of the governing equations. Existing neural networks designed to ensure such first integrals have shown excellent accuracy in modeling from data. However, these models incorporate the underlying structures, and in most situations where neural networks learn unknown systems, these structures are also unknown. This limitation needs to be overcome for scientific discovery and modeling of unknown systems. To this end, we propose first integral-preserving neural differential equation (FINDE). By leveraging the projection method and the discrete gradient method, FINDE finds and preserves first integrals from data, even in the absence of prior knowledge about underlying structures. Experimental results demonstrate that FINDE can predict future states of target systems much longer and find various quantities consistent with well-known first integrals in a unified manner.Comment: 25 page

Tracking the apparent location of targets in interpolated motion

AbstractUnder appropriate conditions, a target moving in discrete steps can appear to move smoothly and continuously even within the portions of the path where no physical stimulus is present. We investigated the nature of this interpolated motion in attentive tracking displays as well as apparent motion. The results showed that the apparent location of the target moved smoothly through space between the two discrete locations and the judgements of interpolated motion for attentive tracking and apparent motion were comparable to those for continuous motion in both the perceived path and the precision of the judgements. There were few, if any, differences between judgements for real and interpolated motion. An alignment procedure showed that the smooth change in location judgements was real and not a consequence of averaging across discrete locations actually seen on each trial. We also found that the slowest alternation rate which supported accurate location judgements corresponded to a critical SOA of about 500 ms, similar to the longest SOA which supported a subjective impression of motion in the display. Deviations from a constant velocity which were shorter than 200 ms did not register in the judged motion path, suggesting a fairly long time constant for the integration of velocity information into the perceived motion. These results suggest a specialized motion analysis which provides an accurate, explicit model of the interpolated motion path

Antibacterial, cytotoxic and trypanocidal activities of marine-derived fungi isolated from Philippine macroalgae and seagrasses

The occurrence and bioactivities of marine-derived fungi are evaluated in this paper. A total of 16 morphospecies of marine-derived fungi (MDF) were isolated from four host macroalgae and two seagrasses and identified as belonging to the genera Aspergillus, Fusarium, Paecilomyces, Penicillium, Sclerotinia, Thamnidium and Trichoderma, including five mycelia sterilia. Among these host organisms, the rhodophyte Laurencia intermedia harboured the highest number of isolated MDF. Selected MDF were then assayed and showed to inhibit Pseudomonas aeruginosa (8-19 mm zone of inhibition) and Staphylococcus aureus (6-19 mm zone of inhibition), and were cytotoxic against the brine shrimp Artemia salina nauplii (LD50: 201.56-948.37 μg mL-1). The screening led to the selection of five of the most bioactive morphospecies, all belonging to the genus Aspergillus. These marine aspergilli were subjected to β-tubulin gene sequence analysis for species identification, and to mass production in different culture media with or without marine salts, and screening of the crude culture extracts for their cytotoxic and trypanocidal activities. Aspergillus tubingensis cultivated in potato dextrose broth with marine salt proved to be the most cytotoxic against P388 (IC50: 1028 ng mL-1) and HeLa (IC50: 1301 ng mL-1) cancer cells. On the other hand, A. fumigatus cultivated in malt extract broth without marine salt was shown to be the most potent against Trypanosoma congolense (IC50: 298.18 ng mL-1). Our study therefore showed that salinity may influence the bioactivities of some species of MDF

MFS1, a Pleiotropic Transporter in Dermatophytes That Plays a Key Role in Their Intrinsic Resistance to Chloramphenicol and Fluconazole

A recently identified Trichophyton rubrum major facilitator superfamily (MFS)-type transporter (TruMFS1) has been shown to give resistance to azole compounds and cycloheximide (CYH) when overexpressed in Saccharomyces cerevisiae. We investigated the roles of MFS1 in the intrinsic resistance of dermatophytes to CYH and chloramphenicol (CHL), which are commonly used to isolate these fungi, and to what extent MFS1 affects the susceptibility to azole antifungals. Susceptibility to antibiotics and azoles was tested in S. cerevisiae overexpressing MFS1 and Delta MFS1 mutants of Trichophyton benhamiae, a dermatophyte that is closely related to T. rubrum. We found that TruMFS1 functions as an efflux pump for CHL in addition to CYH and azoles in S. cerevisiae. In contrast, the growth of T. benhamiae Delta MFS1 mutants was not reduced in the presence of CYH but was severely impaired in the presence of CHL and thiamphenicol, a CHL analog. The suppression of MFS1 in T. benhamiae also increased the sensitivity of the fungus to fluconazole and miconazole. Our experiments revealed a key role of MFS1 in the resistance of dermatophytes to CHL and their high minimum inhibitory concentration for fluconazole. Suppression of MFS1 did not affect the sensitivity to CYH, suggesting that another mechanism was involved in resistance to CYH in dermatophytes

Minority-carrier diffusion length, minority-carrier lifetime, and photoresponsivity of β-FeSi2 layers grown by molecular-beam epitaxy

We have epitaxially grown undoped β-FeSi2 films on Si(111) substrates via atomic-hydrogen-assisted molecular-beam epitaxy. β-FeSi2 films grown without atomic hydrogen exhibited p-type conduction with a hole density of over 1019 cm−3 at room temperature (RT). In contrast, those prepared with atomic hydrogen showed n-type conduction and had a residual electron density that was more than two orders of magnitude lower than the hole density of films grown without atomic hydrogen (of the order of 1016 cm−3 at RT). The minority-carrier diffusion length was estimated to be approximately 16 μm using an electron-beam-induced current technique; this value is twice as large as that for β-FeSi2 prepared without atomic hydrogen. This result could be well explained in terms of the minority-carrier lifetimes measured by a microwave photoconductance decay technique. The 1/e decay time using a 904 nm laser pulse was approximately 17 μs, which is much longer than that for β-FeSi2 prepared without atomic hydrogen (3 μs). The photoresponsivity reached 13 mA/W at 1.31 μm, which is the highest value ever reported for β-FeSi2 films

Specific and sensitive loop-mediated isothermal amplification (LAMP) method for <i>Madurella </i>strains, eumycetoma filamentous fungi causative agent

Background Filamentous fungi of the genus Madurella are the primary causative agents of mycetoma, a disease observed in tropical and subtropical regions. Since early diagnostics based on a morphological approach are difficult and have many shortcomings, a molecular diagnostic method suitable for rural settings is required. In this study, we developed the loop-mediated isothermal amplification (LAMP) method to present a foundational technique of the diagnosis of Madurella spp. (M. mycetomatis, M. pseudomycetomatis, M. tropicana, and M. faha-lii), the common causative organisms of eumycetoma. Principal findings We successfully designed a primer pair targeting the rDNAs of three Madurella spp. exclud-ing M. fahalii, and detected up to 100 fg of genomic DNA extracted from isolates of M. myce-tomatis and 1 pg of M. pseudomycetomatis and M. tropicana, within one hour. Second, a primer pair specific to M. mycetomatis, the most common causative species, or M. fahalii, a drug-resistant species, was constructed, and the detection limit of both primer pairs was 1 pg. The designed primers accurately distinguished 16 strains of the genus Madurella from various fungal species known to cause mycetomas. Conclusion In summary, we established the first model of a LAMP detection method that rapidly and sensitively detects and identifies Madurella isolates for clinical diagnostics. Moreover, the combined designed primer sets could identify mycetoma-causing strains simultaneously.</p