Positive Ratio Research Articles

Self-propulsion of a droplet induced by combined diffusiophoresis and Marangoni effects.

Chemically active droplets display complex self-propulsion behavior in homogeneous surfactant solutions, often influenced by the interplay between diffusiophoresis and Marangoni effects. Previous studies have primarily considered these effects separately or assumed axisymmetric motion. To understand the full hydrodynamics, we investigate the motion of a two-dimensional active droplet under their combined influences using weakly nonlinear analysis and numerical simulations. The impact of two key factors, the Péclet number ( ) and the mobility ratio between diffusiophoretic and Marangoni effects ( ), on droplet motion is explored. We establish a phase diagram in the space, categorizing the boundaries between four types of droplet states: stationary, steady motion, periodic/quasi-periodic motion, and chaotic motion. We find that the mobility ratio does not affect the critical for the onset of self-propulsion, but it significantly influences the stability of high-wavenumber modes as well as the droplet's velocity and trajectory. Scaling analysis reveals that in the high regime, the Marangoni and diffusiophoresis effects lead to distinct velocity scaling laws: and , respectively. When these effects are combined, the velocity scaling depends on the sign of the mobility ratio. In cases with a positive mobility ratio, the Marangoni effect dominates the scaling, whereas the negative diffusiophoretic effect leads to an increased thickness of the concentration boundary layer and a flattened scaling of the dropletvelocity.

Mountain-valley crease reconfiguration of 4-crease origami vertices and tessellations

Reconfigurable origami-inspired folding has recently gained significant attention due to its potential to achieve multi-shape changes through crease topological morphing, resulting in multi-functionality from a single original structure. However, it is one of the major challenges to determine all possible mountain-valley crease (MV) assignments that ensure rigid foldability and obtain duplicate configurations in large 2D origami tessellations or 3D cellular structures. In this study, we developed a straightforward algorithm that combines graphic representation and motion compatibility conditions to assess the reconfigurability of origami structures with 4-crease vertices including double corrugated, Miura-ori, and symmetric Eggbox vertices, as well as their 2D and even 3D cellular tessellations. Our analysis has revealed three types of oligo-modal origami tessellations characterised by a consistent number of MV assignments independent of tessellation size, and pluri-modal cellular origami structures that exhibit negative, zero, and positive Poisson's ratios which were verified through experiment. This work could serve as a stepping stone towards developing multifunctional metamaterials and devices based on reconfigurable origami through mountain-valley crease assignment.

Application of wastewater-based epidemiology for monitoring COVID-19 in hospital and housing wastewaters

An alternative and complementary diagnostic method of surveillance is provided by wastewater-based surveillance (WBS), particularly in low-income nations like Nepal with scant wastewater treatment facilities and clinical testing infrastructure. In this study, a total of 146 water samples collected from two hospitals (n = 63) and three housing wastewaters (n = 83) from the Kathmandu Valley over the period of March 2021–Febraury 2022 were investigated for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) using quantitative reverse transcription TaqMan PCR assays targeting the N and E genes. Of the total, 67 % (98/146) samples were positive for SARS-CoV-2 RNA either by using N- or E-gene assay, with concentrations ranging from 3.6 to 9.1 log10 copies/L. There was a significant difference found between positive ratio (Chi-square test, p < 0.05) and concentration (t-test, p = 0.009) of SARS-CoV-2 RNA detected from hospital wastewater and housing waters. Wastewater data are correlated with COVID-19 active cases, indicating significance in specific areas like the Hospital (APFH) (p < 0.05). According to the application of a bivariate linear regression model (p < 0.05), the concentrations of N gene may be used to predict the COVID-19 cases in the APFH. Remarkably, SARS-CoV-2 RNA was detected prior to, during, and following clinical case surges, implying that wastewater surveillance could serve as an early warning system for public health decisions. The significance of WBS in tracking and managing pandemics is emphasized by this study, especially in resource-constrained settings.

AMS-U-Net: automatic mass segmentation in digital breast tomosynthesis via U-Net.

The objective of this study was to develop a fully automatic mass segmentation method called AMS-U-Net for digital breast tomosynthesis (DBT), a popular breast cancer screening imaging modality. The aim was to address the challenges posed by the increasing number of slices in DBT, which leads to higher mass contouring workload and decreased treatment efficiency. The study used 50 slices from different DBT volumes for evaluation. The AMS-U-Net approach consisted of four stages: image pre-processing, AMS-U-Net training, image segmentation, and post-processing. The model performance was evaluated by calculating the true positive ratio (TPR), false positive ratio (FPR), F-score, intersection over union (IoU), and 95% Hausdorff distance (pixels) as they are appropriate for datasets with class imbalance. The model achieved 0.911, 0.003, 0.911, 0.900, 5.82 for TPR, FPR, F-score, IoU, and 95% Hausdorff distance, respectively. The AMS-U-Net model demonstrated impressive visual and quantitative results, achieving high accuracy in mass segmentation without the need for human interaction. This capability has the potential to significantly increase clinical efficiency and workflow in DBT for breast cancer screening.

Influence of Maternal Nutrition and One-Carbon Metabolites Supplementation during Early Pregnancy on Bovine Fetal Small Intestine Vascularity and Cell Proliferation.

To investigate the effects of nutrient restriction and one-carbon metabolite (OCM) supplementation (folate, vitamin B12, methionine, and choline) on fetal small intestine weight, vascularity, and cell proliferation, 29 (n = 7 ± 1 per treatment) crossbred Angus beef heifers (436 ± 42 kg) were estrous synchronized and conceived by artificial insemination with female sexed semen from a single sire. Then, they were allotted randomly to one of four treatments in a 2 × 2 factorial arrangement with the main factors of nutritional plane [control (CON) vs. restricted feed intake (RES)] and OCM supplementation [without OCM (-OCM) or with OCM (+OCM)]. Heifers receiving the CON level of intake were fed to target an average daily gain of 0.45 kg/day, which would allow them to reach 80% of mature BW by calving. Heifers receiving the RES level of intake were fed to lose 0.23 kg/heifer daily, which mimics observed production responses in heifers that experience a diet and environment change during early gestation. Targeted heifer gain and OCM treatments were administered from d 0 to 63 of gestation, and then all heifers were fed a common diet targeting 0.45 kg/d gain until d 161 of gestation, when heifers were slaughtered, and fetal jejunum was collected. Gain had no effect (p = 0.17) on the fetal small intestinal weight. However, OCM treatments (p = 0.02) displayed less weight compared to the -OCM groups. Capillary area density was increased in fetal jejunal villi of RES - OCM (p = 0.02). Vascular endothelial growth factor receptor 2 (VEGFR2) positivity ratio tended to be greater (p = 0.08) in villi and was less in the crypts (p = 0.02) of the RES + OCM group. Cell proliferation decreased (p = 0.02) in villi and crypts of fetal jejunal tissue from heifers fed the RES + OCM treatment compared with all groups and CON - OCM, respectively. Spatial cell density increased in RES - OCM compared with CON + OCM (p = 0.05). Combined, these data show OCM supplementation can increase expression of VEGFR2 in jejunal villi, which will promote maintenance of the microvascular beds, while at the same time decreasing small intestine weight and crypt cell proliferation.

Sequential Time to Positivity as a Prognostic Indicator in Staphylococcus aureus Bacteremia.

We aimed to determine the factors associated with sequential blood culture time to positivity (STTP) and validate the previously defined time to positivity (TTP) ratio threshold of 1.5 in predicting adverse disease outcomes and mortality of Staphylococcus aureus bacteremia (SAB). We conducted an observational study of adult patients with SAB. The TTP ratio was calculated by dividing the TTP of the second blood culture by that of the first. Of 186 patients, 69 (37%) were female, with a mean age of 63.6 years. Median TTP was 12 hours (interquartile range [IQR], 10-15 hours) from the initial and 21 hours (17-29) from sequential blood cultures. Methicillin-resistant S aureus (MRSA)-infected patients had significantly shorter STTPs (P < .001) and lower TTP ratios (P < .001) compared to patients with methicillin-susceptible S aureus (MSSA). A significant correlation between initial and STTP was observed in patients with MRSA (r = 0.42, P = .002) but not in those with MSSA. A higher rate of native valve endocarditis (NVE) significantly correlated with a TTP ratio of ≤1.5 (odds ratio, 2.65 [95% confidence interval, 1.3-5.6]; P = .01). The subgroup having an initial TTP <12 hours combined with a TTP ratio ≤1.5 showed the highest prevalence of NVE. The STTP varies based on methicillin susceptibility of S aureus isolate. This study suggests a potential clinical utility of the STTP to identify patients at a higher risk of NVE. However, prospective studies are required to validate these findings.

Prognostic value of tumor deposits and positive lymph node ratio in stage III colorectal cancer: a retrospective cohort study.

In colorectal cancer (CRC), tumor deposits (TD) have been used to guide the N staging only in node-negative patients. It remains unknown about the prognostic value of TD in combination with positive lymph node ratio (LNR) in stage III CRC. We analyzed data from 31,139 eligible patients diagnosed with stage III CRC, including 30,230 from the Surveillance, Epidemiology, and End Results (SEER) database as a training set and 909 from two Chinese hospitals as a validation set. The associations of TD and LNR with cancer-specific survival (CSS) and overall survival (OS) were evaluated using the Kaplan-Meier method and Cox regression models. Both TD-positive and high LNR (value≥0.4) were associated with worse CSS in the training (multivariable hazard ratio [HR], 1.50; 95% confidence interval [CI], 1.43-1.58 and HR, 1.74; 95% CI, 1.62-1.86, respectively) and validation sets (HR,1.90; 95%CI, 1.41-2.54 and HR,2.01; 95%CI, 1.29-3.15, respectively). Compared to patients with TD-negative and low LNR (value<0.4), those with TD-positive and high LNR had a 4.09-fold risk of CRC-specific death in the training set (HR, 4.09; 95% CI, 3.54-4.72) and 4.60-fold risk in the validation set (HR, 4.60; 95% CI, 2.88-7.35). Patients with TD-positive/H-LNR CRC on the right side had the worst prognosis (P<0.001). The combined variable of TD and LNR contributed the most to CSS prediction in the training (24.26%) and validation (32.31%) sets. A nomogram including TD and LNR showed satisfactory discriminative ability, and calibration curves indicated favorable consistency in both the training and validation sets. TD and LNR represent independent prognostic predictors for stage III CRC. A combination of TD and LNR could be used to identify those at high risk of CRC deaths.

Clinicopathological Evaluation of Papillary Thyroid Microcarcinoma.

Clinicians sometimes encounter papillary thyroid microcarcinoma (PMC) that is less than 10 mm, associated with lymph node metastasis. In this study, we assessed PMC clinicopathologically to clarify risk factors for poor prognosis. Fifty-one patients who underwent thyroid surgery at Aichi Medical University from September 2009 to October 2016 were included. Patients were divided into two groups, pEX-positive (23 patients) and pEX-negative (28 patients), based on the pathological finding of thyroid capsule invasion. The former indicates that the tumor infiltrated the thyroid capsule and spreadto the neighboring tissue, and the latter indicates no capsule invasion. We analyzed factors such as patient characteristics, pathological findings, and serum levels of thyroid hormones in the two groups. No statistical differences were observed between the two groups in gender distribution or age at surgery. Preoperative cancer diagnoses were established for more patients in the pEX-positive group than in the pEX-negative group (n = 21 and 14, respectively; P = 0.004). The mean (±SD) pathological tumor diameter was 5.42 ± 2.77 in the pEX-negative group and 8.32 ± 1.61 in the pEX-positive group (P < 0.001). No significant differences in preoperative serum levels of free T3, free T4, thyroid-stimulating hormone, or thyroglobulin were observed between the two groups. The odds ratio for node positivity in tumors invading thyroid capsules (pEX-positive) compared to those with no capsule invasion (pEX-negative) was 13.20 (95% confidence interval, 3.45-50.42). Immunohistological staining for phosphatase and tensin homolog deleted from chromosome 10 (PTEN) and Akt (protein kinase B) revealed the facilitation of PTEN and suppression of Akt, which might indicate downregulation of the phosphoinositide 3-kinase-Akt (PI3K-Akt) cascade. In general, the prognosis of PMC is favorable. However, the prognosis is less favorable in patients with nodal metastasis or extrathyroidal invasion. It is controversial whether resection is required for proven PMCs. For PMCs associated with extrathyroidal invasion, regional lymph node resection with lobectomy should be performed due to the high risk for lymphatic spread. There might be a possibility that the natural progression of PMC seems to be controlled by the facilitation of PTEN. However, a tumor in the lateral peripheral region of the thyroid parenchyma might be associated with capsule invasion followed by lymphatic spread.

Predictive value of positive lymph node ratio in patients with locally advanced gastric remnant cancer.

Traditional lymph node stage (N stage) has limitations in advanced gastric remnant cancer (GRC) patients; therefore, establishing a new predictive stage is necessary. To explore the predictive value of positive lymph node ratio (LNR) according to clinicopathological characteristics and prognosis of locally advanced GRC. Seventy-four patients who underwent radical gastrectomy and lymphadenectomy for locally advanced GRC were retrospectively reviewed. The relationship between LNR and clinicopathological characteristics was analyzed. The survival analysis was performed using Kaplan-Meier survival curves and Cox regression model. Number of metastatic LNs, tumor diameter, depth of tumor invasion, Borrmann type, serum tumor biomarkers, and tumor-node-metastasis (TNM) stage were correlated with LNR stage and N stage. Univariate analysis revealed that the factors affecting survival included tumor diameter, anemia, serum tumor biomarkers, vascular or neural invasion, combined resection, LNR stage, N stage, and TNM stage (all P < 0.05). The median survival time for those with LNR0, LNR1, LNR2 and LNR3 stage were 61, 31, 23 and 17 mo, respectively, and the differences were significant (P = 0.000). Anemia, tumor biomarkers and LNR stage were independent prognostic factors for survival in multivariable analysis (all P < 0.05). The new LNR stage is uniquely based on number of metastatic LNs, with significant prognostic value for locally advanced GRC, and could better differentiate overall survival, compared with N stage.

Sentinel Lymph Node Biopsy (SLNB) for Early-Stage Head and Neck Squamous-Cell Carcinoma of the Tongue: Twenty Years of Experience at I.N.T. "G.Pascale".

Oral tongue squamous-cell carcinoma (OTSCC) is the most prevalent malignancy in the head and neck region. Lymphatic spread, particularly to cervical lymph nodes, significantly impacts 5-year survival rates, emphasizing the criticality of precise staging. Metastatic cervical lymph nodes can decrease survival rates by 50%. Yet, elective neck dissection (END) in T1-2 cN0 patients proves to be an overtreatment in around 80% of cases. To address this, sentinel lymph node biopsy (SLNB) was introduced, aiming to minimize postoperative morbidity. This study, conducted at the ENT and Maxillofacial Surgery department of the Istituto Nazionale Tumori in Naples, explores SLNB's efficacy in early-stage oral tongue squamous-cell carcinoma (OTSCC). From January 2020 to January 2022, 122 T1/T2 cN0 HNSCC patients were enrolled. Radioactive tracers and lymphoscintigraphy identified sentinel lymph nodes, aided by a gamma probe during surgery. Results revealed 24.6% SLN biopsy positivity, with 169 SLNs resected and a 21.9% positivity ratio. The study suggests SLNB's reliability for T1-2 cN0 OTSCC patient staging and early micrometastasis detection.

Lessons from debates about foundational positive psychology theories & frameworks: Positivity Ratio, Broaden & Build, Happiness Pie, PERMA to PERMA+4

ABSTRACT Positive psychology examines psychological phenomena that make life worth living. Critics of the field have argued that it engages in poor methodological and measurement practices. To elucidate some historical context surrounding these perceptions, and outline pathways by which positive psychological scientists may work to mitigate these perceptions, this review sought out to identify prominent lines of debate surrounding measurement and methodology. Five such debates surrounding foundational work on well-being were identified and reviewed. These involved the existence of a ‘critical’ positivity ratio that universally distinguishes flourishing and languishing individuals, positive upward spirals and whether positive emotions exhibit reciprocal causality with a broadening of thought-action repertoires and acquisition of social resources, the ‘Happiness Pie’ Model of Wellbeing and the appropriate role of mathematical analogy in conceptual theory-building, and the scientific value of well-being frameworks like PERMA and PERMA+ 4. Enclosed are lessons learned and recommendations for improving the science of positive psychology.

Tree boosting methods for balanced and imbalanced classification and their robustness over time in risk assessment

Most real-world classification problems deal with imbalanced datasets, posing a challenge for Artificial Intelligence (AI), i.e., machine learning algorithms, because the minority class, which is of extreme interest, often proves difficult to be detected. This paper empirically evaluates tree boosting methods' performance given different dataset sizes and class distributions, from perfectly balanced to highly imbalanced. For tabular data, tree-based methods such as XGBoost, stand out in several benchmarks due to detection performance and speed. Therefore, XGBoost and Imbalance-XGBoost are evaluated. After introducing the motivation to address risk assessment with machine learning, the paper reviews evaluation metrics for detection systems or binary classifiers. It proposes a method for data preparation followed by tree boosting methods including hyper-parameter optimization. The method is evaluated on private datasets of 1 thousand (K), 10K and 100K samples on distributions with 50, 45, 25, and 5 percent positive samples. As expected, the developed method increases its recognition performance as more data is given for training and the F1 score decreases as the data distribution becomes more imbalanced, but it is still significantly superior to the baseline of precision-recall determined by the ratio of positives divided by positives and negatives. Sampling to balance the training set does not provide consistent improvement and deteriorates detection. In contrast, classifier hyper-parameter optimization improves recognition, but should be applied carefully depending on data volume and distribution. Finally, the developed method is robust to data variation over time up to some point. Retraining can be used when performance starts deteriorating.

Mechanism of mean stress sensitivity in Ti-6Al-4V under different stress ratios in high cycle fatigue

Initially, this article precisely determines that the “facet” on the fracture surface of the Ti-6Al-4V alloy during high cycle fatigue (HCF) loading under positive stress ratios, as determined by white light interferometry and transmission Kikuchi diffraction (TKD), originates from cracking along the slip planes that exhibit a grain orientated α grain in the loading direction, predominantly involving shear deformation along the crystallographic planes. The article emphasizes the crack initiation mechanisms in Ti-6Al-4V alloy related to internal microstructures under positive stress ratio HCF loading, elucidating relationship between texture-induced crack initiation and growth, and anomalous mean stress sensitivity. Under positive stress ratio fatigue loading, preferentially orientated texture regions tend to generate irreversible dislocations parallel to the basal plane, gradually accumulating within multiple locations to form persistent slip bands (PSBs), which, under the influence of internal stresses, sequentially collapse and rupture, leading to nucleation of microcracks. Upon encountering unfavorably oriented texture regions or grains, PSBs or existing microcracks experience dislocation accumulation, which in turn induce grain refinement, thereby causing further crack nucleation. Consequently, microcracks, through aggregation and coalescence during the fatigue loading sequence, form the main crack, ultimately precipitating fatigue failure and engendering the anomalous mean stress sensitivity observed in the Ti-6Al-4V alloy.

Detection of Ulcerative Colitis Lesions from Weakly Annotated Colonoscopy Videos Using Bounding Boxes

Ulcerative colitis is a chronic disease characterized by bleeding and ulcers in the colon. Disease severity assessment via colonoscopy videos is time-consuming and only focuses on the most severe lesions. Automated detection methods enable fine-grained assessment but depend on the training set quality. To suit the local clinical setup, an internal training dataset containing only rough bounding box annotations around lesions was utilized. Following previous works, we propose to use linear models in suitable color spaces to detect lesions. We introduce an efficient sampling scheme for exploring the set of linear classifiers and removing trivial models i.e., those showing zero false negative or positive ratios. Bounding boxes lead to exaggerated false detection ratios due to mislabeled pixels, especially in the corners, resulting in decreased model accuracy. Therefore, we propose to evaluate the model sensitivity on the annotation level instead of the pixel level. Our sampling strategy can eliminate up to 25% of trivial models. Despite the limited quality of annotations, the detectors achieved better performance in comparison with the state-of-the-art methods. When tested on a small subset of endoscopic images, the best models exhibit low variability. However, the inter-patient model performance was variable suggesting that appearance normalization is critical in this context.

Personalized algorithmic pricing decision support tool for health insurance: The case of stratifying gestational diabetes mellitus into two groups

We propose a personalized algorithmic decision support (PADS) tool, facilitating premium pricing for pregnant women by accounting for the risk of gestational diabetes mellitus (GDM). The insurance premium with PADS is derived from true negative and positive ratios of machine learning algorithms. Hybrid sampling with uniform designs improves ML algorithm performance under unbalanced data. Feature selection approaches guarantee the accuracy and interpretability of the prediction models. PADS reduces the premium for most patients with a lower risk of GDM. A smaller fraction of patients will pay more premiums under PADS; however, they can benefit from an earlier GDM diagnosis.

Blood-based CNS regionally and neuronally enriched extracellular vesicles carrying pTau217 for Alzheimer’s disease diagnosis and differential diagnosis

Accurate differential diagnosis among various dementias is crucial for effective treatment of Alzheimer’s disease (AD). The study began with searching for novel blood-based neuronal extracellular vesicles (EVs) that are more enriched in the brain regions vulnerable to AD development and progression. With extensive proteomic profiling, GABRD and GPR162 were identified as novel brain regionally enriched plasma EVs markers. The performance of GABRD and GPR162, along with the AD molecule pTau217, was tested using the self-developed and optimized nanoflow cytometry-based technology, which not only detected the positive ratio of EVs but also concurrently presented the corresponding particle size of the EVs, in discovery (n = 310) and validation (n = 213) cohorts. Plasma GABRD+- or GPR162+-carrying pTau217-EVs were significantly reduced in AD compared with healthy control (HC). Additionally, the size distribution of GABRD+- and GPR162+-carrying pTau217-EVs were significantly different between AD and non-AD dementia (NAD). An integrative model, combining age, the number and corresponding size of the distribution of GABRD+- or GPR162+-carrying pTau217-EVs, accurately and sensitively discriminated AD from HC [discovery cohort, area under the curve (AUC) = 0.96; validation cohort, AUC = 0.93] and effectively differentiated AD from NAD (discovery cohort, AUC = 0.91; validation cohort, AUC = 0.90). This study showed that brain regionally enriched neuronal EVs carrying pTau217 in plasma may serve as a robust diagnostic and differential diagnostic tool in both clinical practice and trials for AD.

Experimental study of liquid aluminum droplet breakup characteristics based on a Drop-on-demand (DOD) magnetohydrodynamic actuation

In magnetohydrodynamic (MHD) drop-on-demand (DOD) actuation, Lorentz force generated in different excitation stages are exerted on the liquid metal jet to form a "push-pull" mechanism, which is crucial for generating accurate and repeatable metal droplets. In this study, the important parameters of the excitation current waveform in the magnetohydrodynamic (MHD) process, including the influence of the excitation voltage pulse width ratio and current amplitude on the velocity, energy, volume, and breakup length of aluminum droplets are studied. The conversion process of surface energy and kinetic energy during the formation and fall stage of liquid droplets is analyzed. The results show that the negative and positive excitation voltage pulse width ratio of the MHD pump has a significant effect on the droplet velocity, breakup time, size, and sphericity. The amplitude of the excitation current and Hartmann number has a significant impact on the generation of stable droplets. The results show that the single droplet ejection state can be achieved within the Ha number between 319.5 and 391.1. As the Ha number increases, the volume, length, kinetic energy and surface energy of the droplets at breakup time also increase. The size of droplets can be adjusted by changing the amplitude of excitation waveform.

An Empirical Study to Analyse The Effect of Bagging and Feature Subspacing on The Performance of A Custom Ensemble Algorithm for Predicting Drug Protein Interactions

Objectives: The objective of this study is to analyse the effect of bagging and feature subspacing on the performance of a custom ensemble of decision tree classifiers for predicting drug protein interactions. Methods: In our present work we have designed a custom ensemble algorithm with decision trees as the base learner. We analysed the effect of bagging negative samples and feature subspacing on the performance of the custom ensemble in terms of AUCROC and AUPR. The Enzyme dataset from the Yamanishi dataset composed of 445 drugs and 664 proteins was used for the experiments. Findings: It was observed that the effect of bagging negative samples was significant as compared to feature supspacing in terms of AUPR metric. Now since AUPR is a metric that remains unaffected by the presence of negative samples hence the increase in AUPR by increasing the negative to positive ratio clearly indicated that the negative samples do contain the positives which are unknown and are yet to be verified. Novelty: The results give a strong indication that that feature subspacing has no considerable impact on the AUCROC metric performance of the custom ensemble while AUPR metric increases as the negative to positive ratio increases. The results give a foundation to the fact that, finding reliable negative samples from the entire set of negative drug protein pairs can further enhance the performance of the machine learning classifiers. Keywords: Decision tree classifier, Ensemble classifier, Drug discovery, Bagging, Drug repurposing

A novel method for preparing anisotropic negative Poisson's ratio composite foam with excellent structural stability and shape recovery property

Negative Poisson's ratio (NPR) foams are usually prepared by the transformation of positive Poisson's ratio (PPR) foams with honeycomb cell structure, which face a challenge for restraining the increase in volume and Poisson's ratio once they are stimulated by high temperature. In addition, they cannot restore to its reentrant structure after large deformation. In this work, a novel method for preparing anisotropic NPR foam with excellent structural stability and shape recovery property is established by synergistically controlling hierarchical pore structures. The obtained NPR silicone rubber/polylactic acid (SR/PLA) composite foam has large-size holes (auxetic structure) with concave hexagonal shape and small-size honeycomb cells, which are generated by 3D printing technology and salt leaching method, respectively. The auxetic structure with the orientation characteristic is directly formed rather than transformed from the honeycomb cell structure. Therefore, the dimension and Poisson's ratio value of the NPR SR/PLA composite foam keep constant after high temperature heating treatment, meaning an excellent structural stability. Furthermore the excellent shape recovery property of the NPR SR/PLA composite foam endows it restore to the initial auxetic structure after large deformation to a large extent. It should be mentioned that the anisotropy of the NPR SR/PLA composite foam further will bring a broad application prospect in the field of human body cushioning materials, such as prosthetic lining sleeve.

Comet 81P/Wild 2 dust impactors of Stardust turnip-like tracks analogous to cluster IDPs

We measured oxygen isotope ratios of 16 silicate fragments from seven aerogel tracks (turnip-like type B tracks 77, 149, 172, 191, and 220; carrot-like type A tracks 22 and 175) of the comet 81P/Wild 2 collector from NASA’s Stardust mission using secondary ion mass spectrometry. Thirteen were prepared by ultramicrotomy; three from track 220 were prepared by sputtering resin blocks using a SIMS Kohler beam, a new procedure aiming to mine as many cometary particles encased in aerogel/resin as possible. Combining new and literature results, we recognized that most silicate fragments of individual type B tracks have diverse mineralogy but consistent mass-independent fractionation of oxygen isotopes (Δ17O = δ17O − 0.52 × δ18O). These observations suggest that their impactors are loosely bound aggregates of unequilibrated materials originating mainly from similar protoplanetary disk regions, resembling the cluster IDP U2-20-GCA. Furthermore, silicate fragments from type A track 22 have almost identical mineralogy and Δ17O values, confirming that its impactor is a single chondrule-like fragment. The terminal particle of type A track 175 is pure forsterite with Δ17O of ∼ –23 ‰.Six iron-rich fragments of this study have positive oxygen isotope ratios (Δ17O∼ +2 ‰) and ordinary chondrite chondrule-like olivine compositions. Together with five similar fragments in the literature, a unique population (Mg# ≤ 86) of Wild 2 fragments that resemble chondrules from the inner solar system (O-E-R) chondrites or the outer solar system CH-CB chondrites was identified. The remaining 16O-poor Wild 2 fragments are Mg# ≥ 79 silicates with Δ17O ∼ –2 ‰ and a small amount of Mg# ≤ 79 silicates with Δ17O ∼ 0 ‰, which are most consistent with CR chondrite chondrules. Thus, we conclude that in addition to the possible major source of CR chondrite chondrule-like materials, the inner solar system or CH-CB chondrule-like materials are a minor component of comet Wild 2, like the cluster IDP U2-20-GCA.