Contact Distance Research Articles

In situ Generation of Intimacy in MnOx+SAPO‐34 Mechanical Mixture for the Conversion of Syngas to Light Olefins

AbstractBifunctional MnOx+SAPO‐34 catalysts were evaluated for the conversion of syngas to light olefins (OXZEO process). They were prepared, either by mechanical mixing of 100 μm‐scale particles agglomerates, or by mixing of ethanol suspensions, containing homogeneously distributed micrometer‐scale primary particles of oxide and zeolite. The selectivity to light olefins, initially lower for the mechanical mixture, reached the value of the suspension mixture after a 14 h on‐stream period. This convergence was explained from SEM images by in situ breaking of SAPO‐34 agglomerates present in the mechanical mixture and dispersion of SAPO‐34 crystals among MnOx primary particles, decreasing the contact distance between the two catalytic functions. These results evidence the importance of intimacy at the micrometer scale to improve the catalytic properties in the OXZEO process.

Seismic Reduction Mechanism and Engineering Application of Paste Backfilling Mining in Deep Rock Burst Mines

In the process of coal resources development, a large number of strip coal pillars have been left behind in the coal mines in central–eastern China. With the increase in coal mining depth year by year, the rock burst threat of strip coal pillars is becoming more and more prominent due to the influence of buried depth, geological structure, gob and other factors. Backfilling mining is the main means to recover the residual strip coal pillar. In order to investigate the effect of backfilling mining on the prevention and control of rock burst, taking the paste backfilling workface 1# of Gucheng coal mine as the engineering background, a comprehensive research method of theoretical analysis, numerical simulation and field monitoring was used to study the evolution of stress and of the overburden spatial structure of the backfilling workface under the control of the backfilled ratio. The results showed that the backfilling mining controls the movement and deformation of overburden by reducing the activity range of roof strata. The overburden fracture development height decreases with the increase in backfilled ratio, but there is a boundary effect influenced by the roof deflection before backfilling and the defective distance of roof contact. With the increase in backfilled ratio, the concentration coefficient of front abutment pressure, the vertical displacement of the roof and the development height of the plastic zone of overlying strata decreased obviously, which indicates that filling mining can effectively control the stress of surrounding rock and the movement of overlying strata. The field monitoring data showed that the influence range of the front abutment pressure of the paste backfilling workface was about 90 m and the maximum stress of the surrounding rock of the two entries did not exceed 7 MPa. The average daily frequency of microseism was 1.34, and the average daily total energy of microseism was 1.80 + 103 J, which decreased by 69% and 90%, respectively, compared with the caving method working face with similar geological conditions. The data above showed that the backfilling mining can effectively reduce the working face stress level and dynamic load strength to achieve the effect of prevention and control of rock burst.

A novel OCT servoing control method for endomicroscopy surface scanning

Probe-based confocal laser endomicroscopy (pCLE) enables cell-level visualization for in-vivo tissue of the organ surface in real time. However, an image sequence is needed to generate a large-scale mosaic because the field of view (FOV) of pCLE is restricted. Image mosaicking solves the small FOV issue but only for high-quality pCLE images. The key to acquiring high-quality images is maintaining a constant contact distance even if the surface of the tissue is significantly rough. In this work, optical coherence tomography (OCT) is used to perform surface scanning by maintaining constant contact between the probe tip and the tissue. We proposed a distance detection method to find the position of the tissue surface in OCT images and used a position-based OCT servoing control scheme to guide the surface scanning. Experimental results show that the proposed control scheme with OCT guidance can obtain a large and clear circular mosaic (the diameter is 1 mm). The distance between the probe tip and the tissue is stabilized at the imaging position with distance variance less than 40 μm. The area of mosaics for a spiral trajectory with the proposed control scheme is 8.61 mm2. The proposed control scheme has a high potential to collect a clear pCLE image sequence by maintaining a constant distance between the probe tip and the tissue.

Benchmarking two-body contributions to crystal lattice energies and a range-dependent assessment of approximate methods.

Using the many-body expansion to predict crystal lattice energies (CLEs), a pleasantly parallel process, allows for flexibility in the choice of theoretical methods. Benchmark-level two-body contributions to CLEs of 23 molecular crystals have been computed using interaction energies of dimers with minimum inter-monomer separations (i.e., closest contact distances) up to 30 Å. In a search for ways to reduce the computational expense of calculating accurate CLEs, we have computed these two-body contributions with 15 different quantum chemical levels of theory and compared these energies to those computed with coupled-cluster in the complete basis set (CBS) limit. Interaction energies of the more distant dimers are easier to compute accurately and several of the methods tested are suitable as replacements for coupled-cluster through perturbative triples for all but the closest dimers. For our dataset, sub-kJ mol-1 accuracy can be obtained when calculating two-body interaction energies of dimers with separations shorter than 4 Å with coupled-cluster with single, double, and perturbative triple excitations/CBS and dimers with separations longer than 4 Å with MP2.5/aug-cc-pVDZ, among other schemes, reducing the number of dimers to be computed with coupled-cluster by as much as 98%.

Coarse-grained model for simulating protein complexes: Folded vs. disordered proteins.

We develop a residue-level coarse-grained model for simulating multi-protein complexes. Contact potentials and distances between all pairs of residues are constructed via Boltzmann inversion of inter-molecular contacts of more than 22000 non-redundant unique interfaces of protein complexes. We show that the contact potentials between hydrophobic pairs are less sensitive to the residue identities when compared to the Miyazawa-Jernigan contact potentials derived from intra-molecular contacts. On the other hand, the contact potentials between hydrophilic pairs depend more strongly on the residue identities. These potentials and contact distances are adopted to the modified Wang-Frenkel potential for the short-range van der Waals (vdW) interactions and Deybe-Hückel electrostatics with a distance-dependent dielectric constant to simulate thermodynamic, kinetic, and structural properties of protein complexes of folded and disordered proteins. Upon parameterizing to fit the second virial coefficient of lysozyme and the binding affinities of the ubiquitin and ubiquitin-binding domains, we show that the potential form with a shorter cutoff distance performs best in predicting the binding affinities and structures for folded proteins. On the other hand, the structural properties of disordered proteins measured by the radius of gyration are in better agreement with experimental data at longer cutoff distances. Comparison between pairwise contact distributions for folded and disordered proteins shows that contacts between charged and polar residues are more prevalent in disordered proteins. The potentials are modified to account for this disparity. We show that the modified potentials perform well in predicting the binding affinities and structures for folded proteins as well as the radius of gyration for disordered proteins. The model can easily be implemented to many existing simulation packages to simulate multi-protein complexes containing disordered regions or proteins in order to gain insights into understanding many biological processes inside a cell.

Predicting the mechanism of actions of capsid assembly modulators from a combination of molecular dynamics and machine learning.

Interfering with the self-assembly of viral nucleocapsids is a recent and effective approach in the development of novel antivirals. Capsid assembly modulators (CAMs) targeting hepatitis B virus (HBV) have two classes. They can target the virus by either accelerating nucleocapsid assembly or misdirecting it into non-capsid-like particles. In our previous work, molecular dynamics simulations were used to study early nucleocapsid assembly intermediates, such as tetramers and hexamers of the core protein Cp149 with and without bound CAMs. We observed distinct conformations of these intermediates, depending on whether the bound CAM accelerates or misdirects assembly. Here, we have developed and tested several machine learning models in order to distinguish between apo-tetramer structures and those bound to accelerating or misdirecting CAMs. Models based on tertiary structural properties of the capsid protein tetramers and their inter-dimer orientation, as well as models based on direct and inverse contact distances between protein residues, were investigated. The models distinguished the apo states and the two CAM-bound states with very high accuracy. Furthermore, tertiary structure models and residue distance models highlighted different tetramer regions as important for classification. Our models can be used to better understand structural transitions that govern nucleocapsid assembly as well as for selection of structures from molecular dynamics simulations for subsequent docking.

Modulating the Extent of Anisotropic Cuprophilicity via High Pressure with Piezochromic Luminescence Sensitization.

Metallophilicity has been widely studied as a fundamental supramolecular interaction. However, the extent and directionality thereof remain controversial. A major obstacle lies in the difficulty to separately control the geometry and chemical composition. Herein, we address this challenge by modulating metallophilicity with mechanical pressure. Using a multinuclear Cu(I) complex as model system, we report anomalous anisotropies of (supra)molecular structures, vibrations, and interaction energies upon isotropic compression as well as concomitant (essentially turn-on) piezochromic luminescence enhancement with ∼103 modulation. The in situ characterizations indicate opposite behaviors of contact distances and cuprophilic interactions for intermolecular vs intramolecular Cu-Cu pairs under pressure. Theoretical calculations break down the attractive and repulsive forces associated with cuprophilicity, its spontaneous 4p-3d hybridization origin, and direction-dependent interaction strength. The use of isotropic mechanical force reveals the intrinsic anisotropy of metallophilicity in multinuclear systems.

Structure of Helicobacter pylori dihydroneopterin aldolase suggests a fragment-based strategy for isozyme-specific inhibitor design.

Dihydroneopterin aldolase (DHNA) is essential for folate biosynthesis in microorganisms. Without a counterpart in mammals, DHNA is an attractive target for antimicrobial agents. Helicobacter pylori infection occurs in human stomach of over 50% of the world population, but first-line therapies for the infection are facing rapidly increasing resistance. Novel antibiotics are urgently needed, toward which structural information on potential targets is critical. We have determined the crystal structure of H.pylori DHNA (HpDHNA) in complex with a pterin molecule (HpDHNA:Pterin) at 1.49-Å resolution. The HpDHNA:Pterin complex forms a tetramer in crystal. The tetramer is also observed in solution by dynamic light scattering and confirmed by small-angle X-ray scattering. To date, all but one reported DHNA structures are octameric complexes. As the only exception, ligand-free Mycobacterium tuberculosis DHNA (apo-MtDHNA) forms a tetramer in crystal, but its active sites are only partially formed. In contrast, the tetrameric HpDHNA:Pterin complex has well-formed active sites. Each active site accommodates one pterin molecule, but the exit of active site is blocked by two amino acid residues exhibiting a contact distance of 5.2​Å. In contrast, the corresponding contact distance in Staphylococcus aureus DHNA (SaDHNA) is twice the size, ranging from 9.8 to 10.5​Å, for ligand-free enzyme, the substrate complex, the product complex, and an inhibitor complex. This large contact distance indicates that the active site of SaDHNA is wide open. We propose that this isozyme-specific contact distance (ISCD) is a characteristic feature of DHNA active site. Comparative analysis of HpDHNA and SaDHNA structures suggests a fragment-based strategy for the development of isozyme-specific inhibitors.

A Novel Evaluation Metric Based on Dispersion of Wear Distance for In Situ Tool Condition Monitoring

As the direct performer of the cutting process in computer numerical control (CNC) machine tools, the tool wear condition directly affects the product quality. However, the existing evaluation metrics, e.g., flank wear width and wear area, cannot accurately determine the wear form conversion. In this article, a novel metric based on the dispersion of wear distance is proposed to describe the flank wear forms in more detail. The wear distance refers to the distance projected from the flank wear edge to the main cutting edge. Then, the wear distance of the indirect contact on the tool–chip interface is filtered out by the normal distribution model. Finally, the rate of distance dispersion over time named RDDT is constructed to identify the time nodes during wear forms’ conversion. In the experiment of accelerating milling cutter life, the Mann-Kendall (MK) inspection statistics of the proposed metric is 3.74, and the correlation with the maximum flank wear is 99.58%. Compared with the existing evaluation metrics, RDDT can accurately and robustly identify the two time nodes where the flank wear form changes in the whole life cycle.

Health Priority Design Approaches in Library Buildings: The Case of Çukurova University

The declaration of a pandemic on March 11, 2020 significantly affects the space organization process, which includes health-priority design approaches such as controlled communication, social distance, and reduction of physical contact. In this study, it is aimed to reorganize the library buildings with health priority design approaches in order to organize and re-function the used areas during the pandemic process. Çukurova University Central Library building was chosen as a case study. The working areas and current situation plans of the library building were evaluated through systematic observation, taking the Covid-19 preventive measures as criteria. Consequently, it was determined that health priority design criteria in library buildings should be advanced heating, cooling and ventilation systems, window sizes and shading elements that control sunlight and air flow, placement of green plants that keep indoor relative humidity above 40%, spatial organization decisions that reduces user capacity and interaction between them. Moreover, the approaches that take into account the health of the society and the researcher and the design decisions that include the rules, suggestions and principles published by individual designers and academics as a result of feeling responsible for the subject were proposed.

Physiological Axial Tibial Rotation of the Knee During a Weightbearing Flexion.

Axial tibial rotation is a characteristic motion of the knee, but how it occurs with knee flexion is controversial. We investigated the mechanisms of tibial rotations by analyzing in vivo tibiofemoral articulations. Twenty knees of 20 living human subjects were investigated during a weightbearing flexion from full extension to maximal flexion using a dual fluoroscopic imaging system. Tibiofemoral articular contact motions on medial and lateral femoral condyles and tibial surfaces were measured at flexion intervals of 15 deg from 0 deg to 120 deg. Axial tibial rotations due to the femoral and tibial articular motions were compared. Articular contact distances were longer on femoral condyles than on tibial surfaces at all flexion intervals (p < 0.05). The articular distance on medial femoral condyle is longer than on lateral side during flexion up to 60 deg. The internal tibial rotation was 6.8 ± 4.5 deg (Mean ± SD) at the flexion interval of 0-15 deg, where 6.1 ± 2.6 deg was due to articulations on femoral condyles and 0.7 ± 5.1 deg due to articulations on tibial surfaces (p < 0.05). The axial tibial rotations due to articulations on femoral condyles are significantly larger than those on tibial surfaces until 60 deg of flexion (p < 0.05). Minimal additional axial tibial rotations were observed beyond 60 deg of flexion. The axial tibial rotations were mainly attributed to uneven articulations on medial and lateral femoral condyles. These data can provide new insights into the understanding of mechanisms of axial tibial rotations and serve as baseline knowledge for improvement of knee surgeries.

The Passengers’ Motion Behaviours during the Gate Transfer Process: Models and Analysis

Once the gate of one departure flight needs to be reassigned, the passengers of this flight should move from the original gate to an alternative gate, which will affect the passengers’ motions near the boarding gates involved in the gate transfer process (e.g., the motion trajectory, the motion time, and so on). Therefore, it is necessary to study the impacts of gate reassignment on passengers’ motions and provide some reasonable suggestions for gate reassignment. However, it is not easy to describe large-scale passengers’ complex dynamic nonlinear interactions, especially involving passengers carrying luggage. Thus, we propose an extended social force (SF) model to describe each passenger’s motion when the flight’s gate is temporarily transferred to one alternative gate, where the proposed model has explicitly considered the interactions among the adjacent passengers and between the passengers and their luggage. The simulation results illustrate that the passengers’ motion directions, the number of passengers with carried luggage, and the passengers’ contact distances will affect the passengers’ motion efficiency during the gate transfer process. In addition, based on the simulation results, we propose some suggestions for gate reassignment from the perspective of the passengers’ motion efficiency, where the suggestions can help administrators better reassign boarding gates.

Cumulative Millisecond-Long Sampling for a Comprehensive Energetic Evaluation of Aqueous Ionic Liquid Effects on Amino Acid Interactions

The interactions of amino acid side-chains confer diverse energetic contributions and physical properties to a protein's stability and function. Various computational tools estimate the effect of changing a given amino acid on the protein's stability based on parametrized (free) energy functions. When parametrized for the prediction of protein stability in water, such energy functions can lead to suboptimal results for other solvents, such as ionic liquids (IL), aqueous ionic liquids (aIL), or salt solutions. However, to our knowledge, no comprehensive data are available describing the energetic effects of aIL on intramolecular protein interactions. Here, we present the most comprehensive set of potential of mean force (PMF) profiles of pairwise protein-residue interactions to date, covering 50 relevant interactions in water, the two biotechnologically relevant aIL [BMIM/Cl] and [BMIM/TfO], and [Na/Cl]. These results are based on a cumulated simulation time of >1 ms. aIL and salt ions can weaken, but also strengthen, specific residue interactions by more than 3 kcal mol-1, depending on the residue pair, residue-residue configuration, participating ions, and concentration, necessitating considering such interactions specifically. These changes originate from a complex interplay of competitive or cooperative noncovalent ion-residue interactions, changes in solvent structural dynamics, or unspecific charge screening effects and occur at the contact distance but also at larger, solvent-separated distances. This data provide explanations at the atomistic and energetic levels for complex IL effects on protein stability and should help improve the prediction accuracies of computational tools that estimate protein stability based on (free) energy functions.

Tetrel Bonding in Anion Recognition: A First Principles Investigation

Twenty-five molecule-anion complex systems [I4Tt···X-] (Tt = C, Si, Ge, Sn and Pb; X = F, Cl, Br, I and At) were examined using density functional theory (ωB97X-D) and ab initio (MP2 and CCSD) methods to demonstrate the ability of the tetrel atoms in molecular entities, I4Tt, to recognize the halide anions when in close proximity. The tetrel bond strength for the [I4C···X-] series and [I4Tt···X-] (Tt = Si, Sn; X = I, At), was weak-to-moderate, whereas that in the remaining 16 complexes was dative tetrel bond type with very large interaction energies and short Tt···X close contact distances. The basis set superposition error corrected interaction energies calculated with the highest-level theory applied, [CCSD(T)/def2-TZVPPD], ranged from -3.0 to -112.2 kcal mol-1. The significant variation in interaction energies was realized as a result of different levels of tetrel bonding environment between the interacting partners at the equilibrium geometries of the complex systems. Although the ωB97X-D computed intermolecular geometries and interaction energies of a majority of the [I4Tt···X-] complexes were close to those predicted by the highest level of theory, the MP2 results were shown to be misleading for some of these systems. To provide insight into the nature of the intermolecular chemical bonding environment in the 25 molecule-anion complexes investigated, we discussed the charge-density-based topological and isosurface features that emanated from the application of the quantum theory of atoms in molecules and independent gradient model approaches, respectively.

Study on interfacial thermal resistance between single wall carbon nanotubes and nickel by molecular dynamics

The interfacial thermal resistance of the nanocontact system of carbon nanotubes and nickel crystals was investigated using molecular dynamics. It was found that with the increase in temperature, the interface thermal resistance gradually increased. In addition, the interfacial thermal resistance also increases gradually with the increase of the contact distance. The ballistic transport of phonons is proposed to be the main reason for the interfacial thermal resistance in this case.

Multiscale Modeling of Phosphate···π Contacts in RNA U-Turns Exposes Differences between Quantum-Chemical and AMBER Force Field Descriptions.

Phosphate···π, also called anion···π, contacts occur between nucleobases and anionic phosphate oxygens (OP2) in r(GNRA) and r(UNNN) U-turn motifs (N = A,G,C,U; R = A,G). These contacts were investigated using state-of-the-art quantum-chemical methods (QM) to characterize their physicochemical properties and to serve as a reference to evaluate AMBER force field (AFF) performance. We found that phosphate···π interaction energies calculated with the AFF for dimethyl phosphate···nucleobase model systems are less stabilizing in comparison with double-hybrid DFT and that minimum contact distances are larger for all nucleobases. These distance stretches are also observed in large-scale AFF vs QM/MM computations and classical molecular dynamics (MD) simulations on several r(gcGNRAgc) tetraloop hairpins when compared to experimental data extracted from X-ray/cryo-EM structures (res. ≤ 2.5 Å) using the WebFR3D bioinformatic tool. MD simulations further revealed shifted OP2/nucleobase positions. We propose that discrepancies between the QM and AFF result from a combination of missing polarization in the AFF combined with too large AFF Lennard-Jones (LJ) radii of nucleobase carbon atoms in addition to an exaggerated short-range repulsion of the r-12 LJ repulsive term. We compared these results with earlier data gathered on lone pair···π contacts in CpG Z-steps occurring in r(UNCG) tetraloops. In both instances, charge transfer calculations do not support any significant n → π* donation effects. We also investigated thiophosphate···π contacts that showed reduced stabilizing interaction energies when compared to phosphate···π contacts. Thus, we challenge suggestions that the experimentally observed enhanced thermodynamic stability of phosphorothioated r(GNRA) tetraloops can be explained by larger London dispersion.

ANALYSIS OF SPECIALTIES OF CRYSTAL STRUCTURE FOR NON-­CHELATE CONFORMATIONS OF ETHYLENE-DIAMINETETRAACETIC ACID AND ITS SALTS WITH ALKALI AND ALKALINE EARTH METALS

In the present study, the crystal structures of non-chelating EDTA molecules and their non-chelation salts in a zwitterionic state, along with the EDTA-chelates of alkali and alkaline earth metals, were searched and overviewed. 25 non-chelating molecules of EDTA, and zwitterions of ethylenediammonium-diacetate diacetic acid HOOC-CH2-(-OOC-CH2-)NH+-CH2-CH2-NH+(-CH2-COO-)-CH2-COOH and their salts (ethylenediammonium-tetraace­tic acid (HOOC-CH2-)2NH+-CH2-CH2-NH+(-CH2-COOH)2, ethylenediammonium-acetate triacetic acid (HOOC-CH2-)2NH+-CH2-CH2-NH+(-CH2-COO-)-CH2-COOH, and ethylenediammonium-tetraacetate (-OOC-CH2-)2NH+-CH2-CH2-NH+(-CH2-COO-)2 with counterions), as well as 17 types of EDTA-chelates of alkali metal ions (Li+, Na+, K+, Rb+) and alkaline earth metal ions (Mg2+, Ca2+, Sr2+, Ba2+) were analyzed using data from the Cambridge Crystallographic Data Center (CCDC). Each intramolecular contact distance between nitrogen and oxygen atoms (NH+···O) has been examined and found to be around 2.7 Å. Investigation on the distribution of the intramolecular NH+··· NH+-distances of EDTA and non-chelated salts thereof also revealed that bulky counterion and certain crystal solvent molecules correspond to change in crystal packing, and that they influenced the conformers of EDTA mo­lecules among gauche form to anti form. In the existing crystalline EDTA-chelates of alkali metals as well as alkaline earth metals, various coordination numbers (CN) and the denticity (к) of EDTA anions are displayed; CN 5 to 9, and tri- and hexadentate fashions. Intramolecular contact N···O and N···N distances correspond to the metal ion radii except for the case of Sr-EDTA chelate, probably due to differences of crystal packings in addition to the number of counterions and crystal solvent molecules. The existing data on crystalline EDTA and its salts have been gathered herein, which contributes to a further understanding and exploring applications hereafter.

Concerted enhanced-sampling simulations to elucidate the helix-fibril transition pathway of intrinsically disordered α-Synuclein

Fibril formation of α-synuclein is linked with Parkinson's disease. The intrinsically disordered nature of α-syn provides extensive conformational plasticity and becomes difficult to characterize its transition pathway from native monomeric to disease-associated fibril form. We implemented different simulation methods such as steered dynamics-umbrella sampling, and replica-exchange and conventional MD simulations to access various conformational states of α-syn. Nineteen distinct intermediate structures were identified by free energy landscape and cluster analysis. They were then sorted based on secondary structure and solvent exposure of fibril-core residues to illustrate the fibril dissociation pathway. The analysis showed that following the initial dissociation of the polypeptide chain from the fibril, α-syn might form either compact-conformations by long-range interactions or extended-conformations stabilized by local interactions. This leads α-syn to adapt two different pathways. The secondary structure, solvation, contact distance, interaction energies and backbone dihedrals of thirty-two selected residues were analyzed for all the 19 intermediates. The results suggested that formation of β-turns, reorganization of salt bridges, and dihedral changes in the hydrophobic regions are the major driving forces for helix-fibril transition. Structural features of the intermediates also correlated with the earlier experimental and computational studies. The study provides critical information on the fibrillation pathway of α-syn.

Li6(C2N2H8)11.5][Fe4Se8]: the first lithium-containing chalcogenidotetraferrate synthesized in solution

The octaselenidotetraferrate(II/III) with six Li atoms as counter-ions chelated by ethylenediamine (en, C2H8N2), {[Li6(en)11.5][Fe4Se8]} n , was synthesized from Li, FeSe and Se in an ethylenediamine solution at room temperature. Its crystal structure was determined at 100 K and has triclinic (P\overline{1}) symmetry. The [Fe4Se8]6− anions show a connectivity comparable to a distorted tetrahedral cluster structure. Contact distances are given, and central structure features compared to literature known selenidoferrates with the same anion motif.

DISTERNING: Distance Estimation Using Machine Learning Approach for COVID-19 Contact Tracing and Beyond

Since the coronavirus disease 19 (COVID-19) outbreak, the epidemiological analysis has raised a strong requirement for more effective and accurate contact tracing solution. However, the existing contact tracing solutions either lacked the evaluation of tracing proximity or the features used for the tracing proximity evaluation were susceptible to certain negative environmental factors (e.g., body shielding). In this article, we propose a novel distance estimation algorithm based on machine learning for contact tracing: DISTERNING, where we leverage machine learning algorithms including Learning Vector Quantization, Regression, and Deep Feed-forward (DFF) Neural Network, data processing methods, and digital filters to process the Bluetooth signal information collected by the mobile phone for contact distance estimation. A contact tracing scheme based on edge computing is also proposed for algorithm deployment due to the requirements of the computational power. Compared with the existing contact tracing solutions, our algorithm considers the factors that have significant negative influence on the Bluetooth signal for distance estimation in reality. The evaluation results show that when the collected Bluetooth signal is influenced by real-world negative environmental factors, employing our proposed algorithm DISTERNING can keep the accuracy of the estimated distance reliable. The output distance can be combined with some medical models to conduct infection risk assessments.