Split Components Research Articles

Diagnostic accuracy of linked color imaging and white light imaging for early gastric cancer and gastrointestinal metaplasia: a systematic review and meta-analysis

BackgroundConventional white light imaging (WLI) frequently misses gastric cancer, resulting in a high rate of undiagnosed cases. This study compares the effectiveness of linked color imaging (LCI) and WLI in detecting early gastric cancer and gastrointestinal metaplasia, aiming to improve clinical diagnostic practices through evidence-based medical insights.MethodsThe QUADAS-2 tool evaluated the quality of the studies. Additionally, methods like Split Component Synthesis (SCS) were utilized to evaluate the diagnostic performance of LCI and WLI.ResultsEleven studies involving a total of 7836 patients were included in the meta-analysis. Comparative analysis revealed that LCI demonstrated a statistically significant superiority over WLI in terms of the detection rates of EGC and GIM (detection rate of EGC: LCI vs WLI, 85% vs. 56.7%, p=0.004, OR 4.78, 95% CI 2.33-9.82, I2 = 71%; detection rate of GIM: LCI vs WLI, 88.9% vs. 40.1%, p=0.0003, OR 9.94, 95% CI 5.59-17.68, I2 = 71%). Additionally, LCI exhibited better sensitivity and specificity for the diagnosis of EGC and GIM compared to WLI. For the entire cohort, the sensitivity of LCI for EGC detection was 80% (95% CI 71%-86%) with a specificity of 82% (95% CI 63%-92%), while for GIM detection, the sensitivity was 87% (95% CI 81%-92%) with a specificity of 85% (95% CI 77%-91%).ConclusionsThe detection efficiency of LCI for EGC and GIM is better than that of WLI, and LCI is recommended as the main screening method for EGC and GIM.Systematic review registrationhttps://www.crd.york.ac.uk/prospero/, identifier CRD42023452140.

Tunable graphene plasmonic metadevice for infrared polarization resolved spectroscopy detection

Polarization-resolved spectroscopy imaging holds significant promise in various fields. However, conventional polarization-resolved spectroscopy imaging systems often reply on separate dispersion elements, polarization splitting components, and mechanical scanning or rotating structures, resulting in bulky systems with intricate designs. The pursuit of lightweight and seamlessly integrated polarization spectroscopy imaging systems presents a critical challenge. Here, we propose an integrated polarization spectroscopy detector operating in the mid-infrared range based on a tunable graphene metasurface. Within the graphene metasurface, plasmonic resonances of graphene are excited by a gold nano-grating, allowing simultaneous modulation of spectral and polarization transmission characteristics for infrared light by tuning the Fermi energy of graphene. With the help of neural network based recovery algorithms, this system achieves pixel-level spectral detection (with a resolution below 200 nm), multi-color polarization Stokes vector analysis (with a monochromatic angular error of less than 0.1 rad), and concurrent polarization and spectroscopy detection. This research paves the way for the development of the next generation integrated infrared polarization resolved spectroscopy imaging systems.

Vibronic Splitting of the Electronic Origin in Two Conformers of the 3-Tolunitrile Dimer.

3-tolunitrile (3-TN) can form three different dimers, which differ in the relative orientation of the methyl groups. We determined the geometry changes of two of these conformers of 3-TN upon electronic excitation via a Franck-Condon fit of the vibronic intensities in the fluorescence emission spectra. Both aromatic rings expand upon electronic excitation, showing a delocalized one-photon excitation of the cluster. The conformer with the smaller center-of-mass distance shows an unusual order of the split components of the electronic origin. We attribute this changed order to the stronger charge transfer contributions to the splitting and a partial breakdown of the point dipole approximation, made in the Frenkel type interaction.

Lateral lumbar and thoracic interbody fusion (LLIF) for thoracolumbar spine trauma (Trauma LLIF): A single-center, retrospective observational cohort study

BackgroundPain, disability and progressive kyphosis is a common problem after traumatic injury of the thoracolumbar (TL-) junction. Surgical treatment may include long-segment posterior or short-segment anterior-posterior fusion. We aim to report our experience with the application of short-segment posterior instrumented fusion with anterior column support using lateral lumbar or thoracic interbody (LLIF) cages. MethodsIn this retrospective, single-center observational cohort study we included consecutive patients treated surgically for traumatic injury of the TL-junction (Th10/11-L2/3) by posterior instrumentation/fusion and LLIF. We measured segmental kyphosis, complications, and outcomes until last follow-up (about 3 years postoperative). ResultsWe identified 61 patients (mean age 39.0 years (SD 13.3); 23 females (37.7%)) with A3 fractures without (n=48; 78.7%) or with additional sagittal split component (n=11; 18.0%. Additional posterior tension band injury was present in n=26 (42.6%). The affected levels of injury were Th12/L1 in n=25 (41.0%) and Th11/12 in n=22 (36.1%). The segmental kyphotic angle was 14.6° (6.7°) preoperative and remained significantly reduced at all times of follow-up at discharge (5.4°±5.5°; p<0.001), at 90 days (7.2°±5.5°; p<0.001), after partial hardware removal (7.2°±6.0°; p<0.001) and at last follow-up (8.1°±6.3°; p<0.001). We noticed a tendency for less progression of kyphosis in the group with two-staged, compared to single-staged bisegmental surgery (mean difference (MD) 3.1° after partial hardware removal, p=0.064). During follow-up, n=11 experienced complications (18%), n=58 (95.1%) had an excellent or good outcome and solid fusion was noticed in n=60 (98.4%). Conclusions“Trauma LLIF” should be considered as possibility for short-segment anterior-posterior fusion for injuries of the TL- junction. We observed most reproducible and long-lasting kyphosis reduction with a temporary bisegmental, two-staged procedure resulting in monosegmental fusion (posterior instrumentation/fusion with delayed LLIF and partial hardware removal to release the non-injured caudal motion segment).

Performance characteristics of genus or species-specific Polymerase Chain Reaction (PCR) for the microbial diagnosis of joint infections: A systematic review and meta-analysis

Joint infections cause significant morbidity and mortality. Rapid diagnosis enables prompt initiation of appropriate antimicrobial therapy and surgical treatment. We conducted a systematic review and meta-analysis to evaluate the accuracy of genus- or species-specific polymerase chain reaction (PCR) in diagnosing joint infections. The literature databases were searched for articles from January 2010 to December 2022. The meta-analysis using the split component synthesis (SCS) method, included 20 studies with 2,457 adult participants. The pooled sensitivity, specificity, diagnostic odds ratio, and AUC of PCR were 49 % (95 % CI [37.9-60.2]), 95.7 % (95 % CI [91.6-97.8]), 21.32, and 0.82 respectively. Sensitivity was highest for sonicate fluid and lowest for periprosthetic tissue. The mean turnaround time to results was 4.7 hours (SD 1.1). PCR is a favourable option for diagnosing joint infections due to its rapid results, but it has low sensitivity. To enhance diagnostic yield, the test should be used in conjunction with other methods.

Methods of diagnostic meta-analysis: comparing the generalized linear mixed model and the split component synthesis model

Purpose of review Diagnostic meta-analyses combine data from several diagnostic test accuracy (DTA) studies to provide an in-depth assessment of a specific diagnostic test's performance across diverse populations and settings. Additionally, knowledge on common methods of diagnostic meta-analyses is crucial for researchers to make informed decisions on best practice for reporting analyses and results. This article provides an overview of commonly used methods of diagnostic meta-analyses using real-life and simulation data. Recent findings Advances in methods of diagnostic meta-analyses in recent years have increased uncertainty among researchers in relation to the most suitable method to be used. Currently, the most popular approaches for diagnostic evidence synthesis include hierarchical summary operating characteristic (HSROC) and bivariate random effects models though other methods such as the split component synthesis method have been proposed. In addition, different software modules exist for DTA meta-analyses. Summary This article presents a thorough evaluation of current frequentist DTA meta-analysis methods implementing both simulated and real-world data. By understanding the recent methods of diagnostic meta-analyses and their limitations, clinicians may better be equipped in selecting the optimum approach to improve clinical judgement and consequently better patient outcomes.

Anisotropic mechanism of cold-rolled pure titanium plate during the two-step tensile process of the variable path

The effects of pre-deformation on the macro-mesoscopic deformation characteristics of the titanium plate during variable path tensile were studied by a two-step tensile test and electron backscatter diffraction (EBSD). The Schmid law, Kernel Average Misorientation (KAM), Taylor axis, and In-Grain Misorientation Axis (IGMA) were used to forecast and identify the types and change laws of the activated deformation modes under different loading conditions. The results demonstrated that dislocation slip is the primary cause of the evolution of the basal split texture components. The nucleation and de-twinning of {10–12}ET resulted in the sudden appearance and disappearance of the <0001>//RD texture. The pre-tensile causes a texture redirection that reduces the activability of both prismatic <a> slip and pyramidal <a> slip in the following variable path tensile. Among them, prismatic <a> slip is the dominant deformation mechanism that causes yield and hardening behavior during RD tensile and TD-RD tensile (rolling direction-RD, transeverse direction-TD). A portion of the prismatic <a> slip is preferentially activated in TD tensile and RD-TD tensile deformation, and the deformation is subsequently jointly controlled by the prismatic <a> slip and the pyramidal <a> slip. The pre-tensile along RD promotes nucleation of {10–12} extension twin (ET) during subsequent RD-TD variable path tensile, while tensile along TD-RD coordinates plastic deformation by consuming a significant quantity of {10–12}ET generated during pre-tensile along TD. The formation of slip-assisted twins in neighboring grains is facilitated by the dislocation pile-up at grain boundaries, and the de-twinning phenomenon also cause the local dislocation pile-up to weaken.

A comparative study of machine learning models for identifying noxious gases through thermal fingerprint measurements and MOS sensors

Recently, there has been a notable surge of interest in developing swift and precise gas detection and categorization tools through artificial intelligence. This work specifically focuses on designing a simple sensor array configuration and empirically compares various machine-learning models for identifying multiple gases. The study employs eight metal oxide semiconductor sensors, each operating independently based on the thermal fingerprint principle. These sensors are utilized to gather data on responses to different toxic gases, and a range of traditional machine learning classifiers are trained and assessed using this dataset. The classifiers undergo investigation across various train/test dataset split ratios and different principal component analysis dimensionalities. Average accuracy metrics are employed over the entire testing dataset to evaluate model performance. The results demonstrated the challenge of selectively detecting each gas type solely through conventional analyses with the gas response data of the proposed sensor array. Nevertheless, the utilization of machine learning models has exhibited promising outcomes in augmenting gas identification and classification. The findings reveal a consistent improvement in testing accuracy for the Gradient Boosting model, which achieves an outstanding accuracy rate, with instances of reaching 100% accuracy in the training dataset when three or more principal components are considered. This study highlights the potential of the proposed straightforward sensor array and presents effective recognition algorithms applicable to creating electronic noses for gas-sensing applications.

Research on performance of new separated thermoelectric cooler at different pulse currents

This paper studies the performance of a novel split thermoelectric cooler under the different pulsed electrical currents. The investigation focuses on analyzing changes in the cold side temperature of thermoelectric cooler when subjected to different pulse forms. The three-dimensional heat transfer model established through COMSOL was used to investigate the new thermoelectric cooler. The study focused on analyzing the impacts of pulse amplitude, pulse period, pulse waveform, and heat dissipation conditions on the performance of split cooler. The results show that the cooling temperature of split component can be reduced by about 13 K at constant electrical current compared with the conventional component. The temperature of the separated component can be decreased by an additional 2–5 K through the application of pulsed current. The triangle pulse is the best choice for the split component under continuous pulse when the heat dissipation is insufficient. The split thermoelectric component can work more smoothly by using the slant drop triangle pulse compared with the optimized triangle pulse form. The performance of the split thermoelectric component is optimal under a square pulse when there is adequate heat dissipation.

Development of Novel Bioluminescent Biosensors Monitoring the Conformation and Activity of the Merlin Tumour Suppressor.

Solid tumours can universally evade contact inhibition of proliferation (CIP), a mechanism halting cell proliferation when cell-cell contact occurs. Merlin, an ERM-like protein, crucially regulates CIP and is frequently deactivated in various cancers, indicating its significance as a tumour suppressor in cancer biology. Despite extensive investigations into Merlin's role in cancer, its lack of intrinsic catalytic activity and frequent conformation changes have made it notoriously challenging to study. To address this challenge, we harnessed innovative luciferase technologies to create and validate a NanoBiT split-luciferase biosensor system in which Merlin is cloned between two split components (LgBiT and SmBiT) of NanoLuc luciferase. This system enables precise quantification of Merlin's conformation and activity both in vitro and within living cells. This biosensor significantly enhances the study of Merlin's molecular functions, serving as a potent tool for exploring its contributions to CIP and tumorigenesis.

Research on the anisotropic mechanism of plastic behavior during tensile process of textured pure titanium

The presence of texture has an important influence on the deformation behavior of titanium. In this study, the anisotropy of the macro-mesoscopic deformation behavior of the material and its evolution with strain were systematically studied by uniaxial tensile test and electron backscatter diffraction (EBSD) technique. Based on the above results, the calculation formula of Schmid factor (SF) for each variant of the slip system expressed by the crystal orientation angle was derived, and the influence of initial texture and texture redirection on the activability of each deformation mode was explored. The impact of the ratios between the critical resolved shear stress (CRSS) of the three deformation modes on the predictions of the dominant deformation mode of yield was systematically assessed, using the CRSS as the standard. The initial yield mode of RD tensile is prismatic <a>slip, while TD tensile may be a combination of multiple slip modes. One of the primary reasons of the evolution of the basal split texture components is the activation of dislocation slip, while the twinning mainly plays a role in coordinating the deformation. According the Taylor axis analysis, the prismatic <a> slip is the primary deformation mode during RD and TD tensile, followed by pyramidal <a> slip, while the basal <a> slip is difficult to be activated or the activability decreases with the increase of strain.

Study on seismic response of a novel prefabricated box culvert with split components based on shaking table test

The prefabricated structure of municipal engineering may face the challenges of shared load-bearing and coordinated deformation under complex geological conditions, earth pressure and groundwater under earthquake action. This study investigated the seismic performance of a novel prefabricated box culvert with split components (PBC-SC) to be constructed in the class Ⅱ site. A 1:10 test model fully considering all connection details was prepared, and shaking table tests were conducted using El Centro seismic waves with peak accelerations ranging from 0.1 g to 0.3 g. The full-scale numerical simulation of the soil-structure model of PBC-SC was prefabricated with ABAQUS to truly account for soil-structure interaction effect. The results of shaking table tests and numerical simulations on PBC-SC were analyzed and compared according to the similarity ratio. Even under the excitation peak acceleration of 0.3 g El Centro seismic wave, the measured acceleration and Fourier spectrum of each segment had only a small difference, thus usage of PBC-SC as a global structure could offer relatively continuous deformability and good seismic performance. To decompose the box culvert into simple assembled components, the connection techniques such as cylindrical pin connection, tongue-and-groove connection and mortise-tenon connection were adopted to ensure the seismic performance of PBC-SC. The research results provided a new idea for the design of PBC-SC and assembly connections for prefabricated structure, as well as further techniques and referable data for seismic response analysis.

Analysis of Electrical Signal Disturbances. A New Strategy.

A joint treatment for signal analysis based in both Fourier and Wavelet theory is presented. Distinguishing from harmonics and transient disturbance components present on an electrical signal, the former part is extracted by means of Fourier methods, while the latter is subjected to multiresolution treatment in order to split disturbance low frequency components with high frequency components. Numerical experiments are performed over a variety of signals with a given harmonic content, which are classified according to the kind of low frequency disturbance (voltage sag, swell and momentary interruption) and high frequency disturbance (oscillatory transient) present. In every case, a good compression rate is achieved and disturbance components in an efficient way are extracted. Finally, characteristic plots of the low frequency disturbances are obtained for classification purposes.

A parallel preconditioning Schur complement approach for large scale industrial problems

The purpose of this paper is to introduce a new strategy to improve the convergence and efficiency of the class of domain decomposition known as Schur complement techniques related to interface variables for the simulation of mechanical, electrical and thermal problems in presence of cross points. More precisely, we are interested not only in domain decomposition with two equal parts having the same physical properties but rather in more general splitting components. It is known that in the first case, the optimal convergence with good pre-conditioner is obtained in two iterations and the problem is still challenging in the second case. The primary goal then is to fill part of the gap in such problem domain decomposition techniques and to contribute to solve extremely difficult industrial problems of large scale by using parallel sparse direct solver of the multi-core environment of the whole system and handling each part of the system independently of the change of the mesh or the shifting of the mathematical method of resolution and subsequently, we treat the interface as boundary conditions. The numerical experiments of our algorithm are performed on few models arising from discretization of partial differential equations using Finite Element Method (FEM).

Black ginseng: a novel medicine for treating heart failure.

Introduction: Black ginseng (BG) was processed by "steaming and drying" (generally nine times) repeatedly to produce "rare saponins" and secondary ginsenosides. Both ginseng (GS) and red ginseng (RG) were commonly used in treating heart failure (HF), and the latter was confirmed to be more potent, implying the presence of rare ginsenosides that contribute positively to the treatment of heart failure. Previous research indicated that rare ginsenosides are more abundant in BG than in RG. Consequently, this study aims to investigate the effects of BG and its components on HF to elucidate the active substances and their underlying mechanisms in the treatment of HF. Methods: The effects of BG and its fractions (water-eluted fraction (WEF), total saponin fraction (TSF), and alcohol-eluted fraction (AEF)) on rats with isoproterenol (ISO)-induced HF were explored, and steroids belonging to the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes were determined quantitatively using the ultra-performance liquid chromatography-triple quadrupole tandem mass spectrometry (UPLC-QqQ-MS/MS) method. In addition, 16S rDNA sequencing was performed on the gut microbiota, followed by GC-MS analysis of short-chain fatty acids (SCFAs), and the biochemical indexes related to energy metabolism and the serum cyclic nucleotide system were also analyzed by ELISA. Results: Based on a thorough evaluation of energy metabolism and the endocrine system, it was observed that the effects of BG components on the hypothalamic-pituitary-thyroid (HPT) and HPA axes were more pronounced. Notably, the treatment efficacy of the low dose of the total saponin fraction (TSFL), water decoction (WD), and high dose of the polysaccharide fraction (PSFH) was superior based on pharmacodynamic indicators such as brain natriuretic peptide (BNP), creatine kinase (CK), and estradiol (E2)/T). Furthermore, the WD and BG components exhibited significant effects on androgens (T and androstenedione (A4)). The TSFL group exerts an anti-inflammatory effect by regulating Lactobacillus/Erysipelotrichales. The WD, PSFH, and TSFL may impact inflammatory cytokines through the gut microbiota (Lactobacillus/Erysipelotrichales) and their metabolites (acetate and butyrate), exerting an anti-inflammatory effect. Discussion: The BG and all its split components demonstrated varying levels of efficacy in alleviating HF, and TSF and PSF exhibited a significant protective effect on HF. The main active components in TSF were revealed to be ginsenosides Rk1, Rk3, 20-(S)-Rg3, and 20-(S)-Rh2 by the H9C2 cell experiment. The decoction of BG and its components exhibited a potent impact on androgen hormones, with an elevation trend. This phenomenon may be attributed to the activation of the eNOS-NO pathway through androgen regulation, thereby contributing to its anti-HF activities. The WD, PSFH, and TSFL may exert anti-inflammatory effects through the intestinal flora (Lactobacillaceae/Erysipelotrichaceae) and its metabolites (acetic acid and butyric acid), which affect the inflammatory factors. The different mechanisms of action of each component of HF also reflect the significance and necessity of the overall role of traditional Chinese medicine (TCM). Our research was the first to report that the E2/T is related to HF and can be used as an indicator to evaluate HF.

The composition of an atomized slurry fuel jet

Slurry fuels have become increasingly popular over the last decades. The combustion of coal-water slurries does not only help with waste recovery but also produces heat and electricity. Studying the process of slurry atomization for further combustion is high on the research agenda. It is still disputable whether a homogeneous slurry jet can be produced by a twin-fuel atomizer. With split component feeding, fuel premixing will become unnecessary; component storage and transportation is simplified as well. In this research, the composition of an atomized slurry fuel jet is reliably determined using shadowgraphy and laser-induced fluorescence. The results show that an internal-mixing twin-fluid atomizer produces a homogeneous atomized flow. Conditions have been determined in which a fuel slurry jet is formed with an optimal composition of solid particles and droplets with and without particles. It is established that split component feeding leads to a 13–23 % increase in jet angle, a 1–4° reduction in the jet deviation angle from its original path, as well as a considerable reduction (up to twofold) in the droplet velocity in a jet. The results obtained here can be used to optimize the storage and transportation of fuel components.

Facile generation of CeO2 nanoparticles on multiphased NiSx nanoplatelet arrays as a free-standing electrode for efficient overall water splitting

Constructing nanostructured electrocatalysts with heterointerface and finetuning their electronic properties are essential for high-efficient overall water splitting. Here, we prepared a well-designed nano-flower-like multiphase and hybrid material of NiS/NiS2/CeO2/NF (NiSx/CeO2/NF) with rich heterointerfaces and abundant active sites through solvothermal reaction and post-annealing treatment. The as-fabricated NiSx/CeO2/NF exhibits exceptional catalytic performance for OER and HER. Specifically, in 1 M KOH solution, it requires the low overpotentials of 326 and 92 mV to achieve the current density of 200 and 10 mA cm−2 for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. More satisfactorily, when NiSx/CeO2/NF is used as the bifunctional catalyst, a low voltage of only 1.53 V is required to achieve a current density of 10 mA cm−2 for overall water splitting. The excellent catalytic performance should be attributed to its special heterogeneous structure and the synergy effect between NiSx and CeO2. This work emphasizes the important significance of constructing efficient bifunctional electrocatalysts by reasonably designing heterostructures and multiphase components for overall water splitting.

Search for superstrong magnetic fields in active processes on the Sun using spectro-polarimetry within 15 Å around the D3 line

ABSTRACT We critically review our previous results on this topic based on the following main points: (i) substantially larger wavelength range around the D3 line was investigated – up to ±15 Å instead of ±2.5 Å in comparison with the previous version of our study, and (ii) greater volume of observational data was analysed, including one X limb flare, additionally. Overall, our study concerns the 2004 July 12 active prominence and the 2014 June 10 limb flare of X1.5 class. For named limb flare, we found reliable and oppositely polarized secondary peaks of the V parameter located at distances of −4.5 and +2.7 Å from the line center. If these features are interpreted as manifestations of the magnetic splitting of the line together with its Doppler shift, then the corresponding magnetic field is ≈2.2 × 105 G, and the radial velocity −46 km s−1. Similar spectral manifestations were also found in the active prominence. For comparison with the theory, the spectral features of the Paschen–Baсk effect at magnetic fields up to 100 kG were studied too. It turned out that the theoretical width of the splitting components is relatively small, 0.3 Å, while the width of the observed peaks is sometimes much larger. On the basis of model calculations, it is shown that in some cases an alternative explanation of the observational data is possible, which includes much weaker magnetic fields (5.5–7.1 kG), but significant macroscopic velocities of different signs, at the level of 50–60 km s−1.

Characterization of charge-carrier dynamics at the Bi2Se3/MgF2 interface by multiphoton pumped UV–Vis transient absorption spectroscopy

Separate relaxation dynamics of electrons and holes in experiments on optical pumping-probing of semiconductors is rarely observed due to their overlap. Here we report the separate relaxation dynamics of long-lived (∼200 μs) holes observed at room temperature in a 10 nm thick film of the 3D topological insulator (TI) Bi2Se3 coated with a 10 nm thick MgF2 layer using transient absorption spectroscopy in the UV–Vis region. The ultraslow hole dynamics was observed by applying resonant pumping of massless Dirac fermions and bound valence electrons in Bi2Se3 at a certain wavelength sufficient for their multiphoton photoemission and subsequent trapping at the Bi2Se3/MgF2 interface. The emerging deficit of electrons in the film makes it impossible for the remaining holes to recombine, thus causing their ultraslow dynamics measured at a specific probing wavelength. We also found an extremely long rise time (∼600 ps) for this ultraslow optical response, which is due to the large spin–orbit coupling splitting at the valence band maximum and the resulting intervalley scattering between the splitting components. The observed dynamics of long-lived holes is gradually suppressed with decreasing Bi2Se3 film thickness for the 2D TI Bi2Se3 (film thickness below 6 nm) due to the loss of resonance conditions for multiphoton photoemission caused by the gap opening at the Dirac surface state nodes. This behavior indicates that the dynamics of massive Dirac fermions predominantly determines the relaxation of photoexcited carriers for both the 2D topologically nontrivial and 2D topologically trivial insulator phases.

Enhanced Aggregate Framework to Model Crash Frequency by Accommodating Zero Crashes by Crash Type

In recent years, joint count and fractional split model structure based approaches have emerged as a credible alternative for multivariate crash frequency dependent variables. However, current approaches in the fractional split theme have a limitation. The fractional split component of these frameworks allocates a proportion to all crash configurations. It is possible that, across spatial units, several crash configurations might have a large share of zero crashes. In the traditional multivariate context, in the presence of a high share of zeros, researchers employ zero-inflated or hurdle variants such as the zero inflated negative binomial model. The current research effort improves the fractional split based multivariate model systems with an explicit consideration for the potential presence of zeros by crash configuration. The newly included binary component can be employed to identify safer (or riskier) zones by crash configuration. The framework also accommodates unobserved heterogeneity across the components of the model system. The proposed model structure is estimated using zonal data from the Central Florida region, U.S., for 2016. The model considered six crash types—rear-end, angle, sideswipe, single-vehicle, multi-vehicle (three or more), and non-motorized crashes. The model estimation is conducted using an exhaustive set of independent variables. The model results clearly highlight the importance of accommodating zero crashes by crash type in the analysis. The model exercise is further augmented with a validation analysis.