Association of preschool children behavior and emotional problems with the parenting behavior of both parents.

BACKGROUND: Parental behaviors are key in shaping children's psychological and behavioral development, crucial for early identification and prevention of mental health issues, reducing psychological trauma in childhood. AIM: To investigate the relationship between parenting behaviors and behavioral and emotional issues in preschool children. METHODS: From October 2017 to May 2018, 7 kindergartens in Ma'anshan City were selected to conduct a parent self-filled questionnaire - Health Development Survey of Preschool Children. Children's Strength and Difficulties Questionnaire (Parent Version) was applied to measures the children's behavioral and emotional performance. Parenting behavior was evaluated using the Parental Behavior Inventory. Binomial logistic regression model was used to analyze the association between the detection rate of preschool children's behavior and emotional problems and their parenting behaviors. RESULTS: High level of parental support/participation was negatively correlated with conduct problems, abnormal hyperactivity, abnormal total difficulty scores and abnormal prosocial behavior problems. High level of maternal support/participation was negatively correlated with abnormal emotional symptoms and abnormal peer interaction in children. High level of parental hostility/coercion was positively correlated with abnormal emotional symptoms, abnormal conduct problems, abnormal hyperactivity, abnormal peer interaction, and abnormal total difficulty scores in children (all P < 0.05). Moreover, paternal parenting behaviors had similarly effects on behavior and emotional problems of preschool children compared with maternal parenting behaviors (all P > 0.05), after calculating ratio of odds ratio values. CONCLUSION: Our study found that parenting behaviors are associated with behavioral and emotional issues in preschool children. Overall, the more supportive or involved the parents are, the fewer behavioral and emotional problems the children experience; conversely, the more hostile or controlling the parents are, the more behavioral and emotional problems the children face. Moreover, the impact of fathers' parenting behaviors on preschool children's behavior and emotions is no less significant than that of mothers' parenting behaviors.

Radiomic-Based MRI for Classification of Solitary Brain Metastases Subtypes From Primary Lymphoma of the Central Nervous System.

BACKGROUND: Differential diagnosis of brain metastases subtype and primary central nervous system lymphoma (PCNSL) is necessary for treatment decisions. The application of machine learning facilitates the classification of brain tumors, but prior investigations into primary lymphoma and brain metastases subtype classification have been limited. PURPOSE: To develop a machine-learning model to classify PCNSL, brain metastases with primary lung and non-lung origin. STUDY TYPE: Retrospective. POPULATION: A total of 211 subjects with pathologically confirmed PCNSL or brain metastases (training cohort 168 and testing cohort 43). FIELD STRENGTH/SEQUENCE: A 3.0 T axial contrast-enhanced T1-weighted spin-echo inversion recovery sequence (T1WI-CE), axial T2-weighted fluid-attenuation inversion recovery sequence (T2FLAIR) ASSESSMENT: Several machine-learning models (support vector machine, random forest, and K-nearest neighbors) were built with least absolute shrinkage and selection operator (LASSO) using features from T1WI-CE, T2FLAIR, and clinical. The model with the highest performance in the training cohort was selected to differentiate lesions in the testing cohort. Then, three radiologists conducted a two-round classification (with and without model reference) using images and clinical information from testing cohorts. STATISTICAL TESTS: Five-fold cross-validation was used for model evaluation and calibration. Model performance was assessed based on sensitivity, specificity, accuracy, and area under the receiver operating characteristic curve (AUC). RESULTS: Twenty-five image features were selected by LASSO analysis. Random forest classifier was selected for its highest performance on the training set with an AUC of 0.73. After calibration, this model achieved an accuracy of 0.70 on the testing set. Accuracies of all three radiologists improved under model reference (0.49 vs. 0.70, 0.60 vs. 0.77, 0.58 vs. 0.72, respectively). DATA CONCLUSION: The random forest model based on conventional MRI and clinical data can diagnose PCNSL and brain metastases subtypes (lung and non-lung origin). Model classification can help foster the diagnostic accuracy of specialists and streamline prognostication workflow. EVIDENCE LEVEL: 4 TECHNICAL EFFICACY: Stage 2.

Effectiveness of Tuina Therapy Combined With Yijinjing Exercise in the Treatment of Nonspecific Chronic Neck Pain: A Randomized Clinical Trial.

Importance: Both tuina therapy and yijinjing exercise were beneficial to patients with nonspecific chronic neck pain, but the evidence for this combination is limited. Objective: To investigate the effectiveness of tuina therapy combined with yijinjing exercise compared with tuina therapy alone for patients with nonspecific chronic neck pain. Design, Setting, and Participants: A 12-week, open-label, analyst-blinded randomized clinical trial (8-week intervention plus 4-week observational follow-up) was conducted from September 7, 2020, to October 25, 2021. A total of 102 participants with nonspecific chronic neck pain were recruited, and data were analyzed from December 10, 2021, to March 26, 2022. Interventions: Participants in the tuina group or tuina combined with yijinjing group received 3 sessions of tuina therapy per week for 8 weeks, for a total of 24 sessions. Participants in the tuina combined with yijinjing group practiced yijinjing 3 times a week for 8 weeks, including an instructor-guided exercise at the hospital and 2 self-practice exercises at home. Main Outcomes and Measures: The primary outcome was change in visual analog scale (VAS) score from baseline to week 8. Secondary outcomes included Neck Disability Index scores, Self-rating Anxiety Scale scores, tissue hardness, and active range of motion. Results: This randomized clinical trial recruited 102 patients (mean [SD] age, 36.5 [4.9] years; 69 [67.6%] female) who were randomized to 2 groups. All 102 patients (100%) completed all the outcome measurements. The mean difference in VAS scores from baseline at week 8 for the tuina combined with yijinjing group was -5.4 (95% CI, -5.8 to -5.1). At week 8, the difference in VAS score was -1.2 (95% CI, -1.6 to -0.8; P < .001) between the tuina group and the tuina combined with yijinjing group. The effectiveness of tuina combined with yijinjing in treating nonspecific chronic neck pain remained at the 12-week follow-up. Conclusions and Relevance: In this randomized clinical trial, for patients with nonspecific chronic neck pain, tuina combined with yijinjing was more effective than tuina therapy alone in terms of pain, functional recovery, and anxiety at week 8, and effectiveness remained at week 12. A combination of tuina and yijinjing should be considered in the management of nonspecific chronic neck pain. Trial Registration: Chinese Clinical Trial Registry: ChiCTR2000036805.

Molecular Tweezer Based on Perylene and Crown Ether for Selective Recognition of Fullerenes.

A molecular tweezer trans-di(perylene-3-ylmethanaminobenzo)-18-crown-6 (DP-18C6) incorporating two perylene subunits in a single crown ether core was designed and synthesized as a host for fullerenes. Through the cooperative effect of the perylene subunits and the crown ether moiety, DP-18C6 can efficiently recognize fullerenes including C60, C70, and C76. 1H NMR titration and fluorescence titration experiments demonstrated that DP-18C6 can effectively grasp the fullerene molecule to form a 1:1 host-guest complex. Density functional theory calculations revealed the presence of intermolecular π-π interactions between the perylene subunits of DP-18C6 and the fullerene molecule. More importantly, DP-18C6 exhibited remarkably high binding selectivity for higher fullerenes over C60, revealing potential application for the separation of fullerenes by means of host-guest interactions.

Carbene Addition Isomers of C70 formed in the Flame of Low-Pressure Combustion.

In the flames during low-pressure combustion, not only a rich variety of fullerenes but also many reactive intermediates can be produced (e.g., carbene, CH2) that are short-lived and cannot be stabilized directly under normal circumstances. These intermediates can be captured by fullerene carbon cages for stabilization. In this paper, three C71H2 isomers were synthesized in situ in low-pressure benzene-acetylene-oxygen diffusion flame combustion. The results, which were unambiguously characterized by single-crystal X-ray diffraction, show that the three isomers are carbene addition products of D5h-C70 on different sites. The relative energies and stability of different C71H2 isomers are revealed by Ultraviolet-Visible (UV-Vis) absorption spectroscopy, in combination with theoretical calculations, in this work. Both the in situ capture and theoretical study of these C71H2 isomers in low-pressure combustion will provide more information regarding carbene additions to other fullerenes or other carbon clusters at high temperatures.

Capturing nonclassical C70 with double heptagons in low-pressure combustion.

A double-heptagon-containing C70H6 (dihept-C70H6) was isolated and unambiguously characterized in the soot of low-pressure combustion, which shares the identical heptagonal cage as dihept-C70Cl6 previously identified in the products of carbon arc, and thus represents the first nonclassical fullerene isolable in both carbon arc and combustion.

Sulfur-Doped Quintuple [9]Helicene with Azacorannulene as Core.

Herein, a hetero(S,N)-quintuple [9]helicene (SNQ9H) molecule with an azacorannulene core was synthesized, currently representing the highest hetero-helicene reported in the field of multiple [n]helicenes. X-ray crystallography indicated that SNQ9H includes not only a propeller-shaped conformer SNQ9H-1, but also an unforeseen quasi-propeller-shaped conformer SNQ9H-2. Different conformers were observed for the first time in multiple [n≥9]helicenes, likely owing to the doping of heteroatomic sulfurs in the helical skeletons. Remarkably, the ratio of SNQ9H-1 to SNQ9H-2 can be regulated in situ by the reaction temperature. Experimental studies on the photophysical and redox properties of SNQ9H and theoretical calculations clearly demonstrated that the electronic structures of SNQ9H depend on their molecular conformations. The strategy of introducing heteroatomic sulfurs into the helical skeleton may be useful in constructing various conformers of higher multiple [n]helicenes in the future.

Synthesis and Fluorescent Properties of Multi-Functionalized C70 Derivatives of C70(OCH3)10[C(COOEt)2] and C70(OCH3)10[C(COOEt)2]2.

Due to the partially reduced π-conjugation of the fullerene cage, multi-functionalized fullerene derivatives exhibit remarkable fluorescent properties compared to pristine fullerenes, which have high potential for application in organic light-emitting diodes (OLEDs). In this study two multi-functionalized C70 derivatives, C70(OCH3)10[C(COOEt)2] and C70(OCH3)10[C(COOEt)2]2, with excellent fluorescence properties, were designed and synthesized. Compared with C70(OCH3)10 containing a single kind of functional group, both the C70(OCH3)10[C(COOEt)2] and C70(OCH3)10[C(COOEt)2]2 exhibited enhanced fluorescence properties with blue fluorescence emission. The fluorescence quantum yields of the C70(OCH3)10[C(COOEt)2] and C70(OCH3)10[C(COOEt)2]2 were 1.94% and 2.30%, respectively, which were about ten times higher than that of C70(OCH3)10. The theoretical calculations revealed that the multi-functionalization of the C70 increased the S1-T1 energy gap, reducing the intersystem crossing efficiency, resulting in the higher fluorescence quantum yield of the C70 derivatives. The results indicate that multi-functionalization is a viable strategy to improve the fluorescence of fullerene derivatives.

Tailoring Functional Terminals on Solution-Processable Fullerene Electron Transporting Materials for High Performance Perovskite Solar Cells.

Widely known as an excellent electron transporting material (ETM), pristine fullerene C60 plays a critical role in improving the photovoltaic performance of inverted structure perovskite solar cells (PSCs). However, the imperfect perovskite/C60 interface significantly limits the promotion of device performance and stability due to the weak coordination interactions between bare carbon cages and perovskite. Here, we designed and synthesized three functionalized fulleropyrrolidine ETMs (abbreviated as CEP, CEPE, and CECB), each of which was modified with the same primary terminal (cyanoethyl) and various secondary terminals (phenyl, phenethyl, and chlorobutyl). The resulting CECB-based PSC has a power conversion efficiency (PCE) over 19% and exceptional photo-stability over 1800 h. This work provides significant insight into the targeted terminal design of novel fullerene ETMs for efficient and stable PSCs.

A chromosome-scale genome sequence of pitaya (Hylocereus undatus) provides novel insights into the genome evolution and regulation of betalain biosynthesis.

Pitaya (Hylocereus) is the most economically important fleshy-fruited tree of the Cactaceae family that is grown worldwide, and it has attracted significant attention because of its betalain-abundant fruits. Nonetheless, the lack of a pitaya reference genome significantly hinders studies focused on its evolution, as well as the potential for genetic improvement of this crop. Herein, we employed various sequencing approaches, namely, PacBio-SMRT, Illumina HiSeq paired-end, 10× Genomics, and Hi-C (high-throughput chromosome conformation capture) to provide a chromosome-level genomic assembly of 'GHB' pitaya (H. undatus, 2n = 2x = 22 chromosomes). The size of the assembled pitaya genome was 1.41 Gb, with a scaffold N50 of ~127.15 Mb. In total, 27,753 protein-coding genes and 896.31 Mb of repetitive sequences in the H. undatus genome were annotated. Pitaya has undergone a WGT (whole-genome triplication), and a recent WGD (whole-genome duplication) occurred after the gamma event, which is common to the other species in Cactaceae. A total of 29,328 intact LTR-RTs (~696.45 Mb) were obtained in H. undatus, of which two significantly expanded lineages, Ty1/copia and Ty3/gypsy, were the main drivers of the expanded genome. A high-density genetic map of F1 hybrid populations of 'GHB' × 'Dahong' pitayas (H. monacanthus) and their parents were constructed, and a total of 20,872 bin markers were identified (56,380 SNPs) for 11 linkage groups. More importantly, through transcriptomic and WGCNA (weighted gene coexpression network analysis), a global view of the gene regulatory network, including structural genes and the transcription factors involved in pitaya fruit betalain biosynthesis, was presented. Our data present a valuable resource for facilitating molecular breeding programs of pitaya and shed novel light on its genomic evolution, as well as the modulation of betalain biosynthesis in edible fruits.

A Gd@C82 single-molecule electret.

Electrets are dielectric materials that have a quasi-permanent dipole polarization. A single-molecule electret is a long-sought-after nanoscale component because it can lead to miniaturized non-volatile memory storage devices. The signature of a single-molecule electret is the switching between two electric dipole states by an external electric field. The existence of these electrets has remained controversial because of the poor electric dipole stability in single molecules. Here we report the observation of a gate-controlled switching between two electronic states in Gd@C82. The encapsulated Gd atom forms a charged centre that sets up two single-electron transport channels. A gate voltage of ±11 V (corresponding to a coercive field of ~50 mV Å-1) switches the system between the two transport channels with a ferroelectricity-like hysteresis loop. Using density functional theory, we assign the two states to two different permanent electrical dipole orientations generated from the Gd atom being trapped at two different sites inside the C82 cage. The two dipole states are separated by a transition energy barrier of 11 meV. The conductance switching is then attributed to the electric-field-driven reorientation of the individual dipole, as the coercive field provides the necessary energy to overcome the transition barrier.

Mixed Fullerene Electron Transport Layers with Fluorocarbon Chains Assembling on the Surface: A Moisture-Resistant Coverage for Perovskite Solar Cells.

In p-i-n structure perovskite solar cells (PSCs), the most prevalent electron transport layer (ETL), [6, 6]-phenyl-C61-butyric acid methyl ester (PC61BM), acts as both electron extractor and protective coverage to the underlayer perovskite. Notably, multifunctional mixed fullerene ETLs show great potential in further improving both the power conversion efficiency (PCE) and stability of PSCs compared to the single PC61BM ETL. In this work, we reported the mixed fullerene ETLs comprising of PC61BM and its two analogs with different length of fluorocarbon chains, [6, 6]-phenyl-C61-buryric acid 1H,1H-trifluoro-1-ethyl ester (abbreviated, CF3-PC61BM) and [6, 6]-phenyl-C61-buryric acid 1H, 1H-tridecafluoro-1-heptyl ester (abbreviated, C6F13-PC61BM). We obtained excellent PCEs of 18.37% and 17.71% for 1 wt % CF3-PC61BM- and C6F13-PC61BM-based PSCs (1 wt % addition of PC61BM) with CH3NH3PbI3 (MAPbI3) perovskites, respectively. Moreover, champion PCEs of ∼19% were obtained based on the CsFAMAPbIBr perovskites. Subsequent experiments demonstrated that the fluorocarbon chains of CF3-PC61BM and C6F13-PC61BM assembled at the surfaces of ETLs with the formation of thin-layer moisture-resistant protective coverage above perovskite. Results show that it significantly retarded water penetrating down to perovskite layers and led to optimal humidity stability under ambient atmosphere.

Contact Time of a Bouncing Nanodroplet.

We study the bouncing dynamics of nanodroplets on superhydrophobic surfaces. We show that there are three velocity regimes with different scaling laws of the contact time, τ. Although τ remains constant over a wide velocity range, as seen for macroscale bouncing, we demonstrate that viscosity plays an essential role in nanodroplet bouncing even for low-viscosity fluids. We propose a new scaling τ ∼ (ρµR04/γ2)1/3 = (R0/v0)We2/3Re-1/3 to characterize the viscosity effect, which agrees well with the simulated results for water and argon nanodroplets with various radii and hydrophobicities. We also find pancake bouncing of nanodroplets, which is responsible for an abruptly reduced τ in a high-velocity regime.

Performance of Radiologists in Differentiating COVID-19 from Non-COVID-19 Viral Pneumonia at Chest CT.

Background Despite its high sensitivity in diagnosing coronavirus disease 2019 (COVID-19) in a screening population, the chest CT appearance of COVID-19 pneumonia is thought to be nonspecific. Purpose To assess the performance of radiologists in the United States and China in differentiating COVID-19 from viral pneumonia at chest CT. Materials and Methods In this study, 219 patients with positive COVID-19, as determined with reverse-transcription polymerase chain reaction (RT-PCR) and abnormal chest CT findings, were retrospectively identified from seven Chinese hospitals in Hunan Province, China, from January 6 to February 20, 2020. Two hundred five patients with positive respiratory pathogen panel results for viral pneumonia and CT findings consistent with or highly suspicious for pneumonia, according to original radiologic interpretation within 7 days of each other, were identified from Rhode Island Hospital in Providence, RI. Three radiologists from China reviewed all chest CT scans (n = 424) blinded to RT-PCR findings to differentiate COVID-19 from viral pneumonia. A sample of 58 age-matched patients was randomly selected and evaluated by four radiologists from the United States in a similar fashion. Different CT features were recorded and compared between the two groups. Results For all chest CT scans (n = 424), the accuracy of the three radiologists from China in differentiating COVID-19 from non-COVID-19 viral pneumonia was 83% (350 of 424), 80% (338 of 424), and 60% (255 of 424). In the randomly selected sample (n = 58), the sensitivities of three radiologists from China and four radiologists from the United States were 80%, 67%, 97%, 93%, 83%, 73%, and 70%, respectively. The corresponding specificities of the same readers were 100%, 93%, 7%, 100%, 93%, 93%, and 100%, respectively. Compared with non-COVID-19 pneumonia, COVID-19 pneumonia was more likely to have a peripheral distribution (80% vs 57%, P < .001), ground-glass opacity (91% vs 68%, P < .001), fine reticular opacity (56% vs 22%, P < .001), and vascular thickening (59% vs 22%, P < .001), but it was less likely to have a central and peripheral distribution (14% vs 35%, P < .001), pleural effusion (4% vs 39%, P < .001), or lymphadenopathy (3% vs 10%, P = .002). Conclusion Radiologists in China and in the United States distinguished coronavirus disease 2019 from viral pneumonia at chest CT with moderate to high accuracy. © RSNA, 2020 Online supplemental material is available for this article. A translation of this abstract in Farsi is available in the supplement. ترجمه چکیده این مقاله به فارسی، در ضمیمه موجود است.

Rational synthesis of an atomically precise carboncone under mild conditions.

Carboncones, a special family of all-carbon allotropes, are predicted to have unique properties that distinguish them from fullerenes, carbon nanotubes, and graphenes. Owing to the absence of methods to synthesize atomically well-defined carboncones, however, experimental insight into the nature of pure carboncones has been inaccessible. Herein, we describe a facile synthesis of an atomically well-defined carboncone[1,2] (C70H20) and its soluble penta-mesityl derivative. Identified by x-ray crystallography, the carbon skeleton is a carboncone with the largest possible apex angle. Much of the structural strain is overcome in the final step of converting the bowl-shaped precursor into the rigid carboncone under mild reaction conditions. This work provides a research opportunity for investigations of atomically precise single-layered carboncones having even higher cone walls and/or smaller apex angles.

Flexible bronchoscopy-guided microwave ablation in peripheral porcine lung: a new minimally-invasive ablation.

BACKGROUND: Transbronchial lung biopsy is an important approach to diagnose peripheral lung cancer, but bronchoscopy based treatment options are limited and poorly studied. A flexible bronchoscopy-guided water-cooled microwave ablation (MWA) catheter was developed to evaluate the feasibility and safety both in ex vivo and in vivo porcine models. METHODS: Using direct penetration of the catheter through the surface of ex vivo porcine lung, ablations (n=9) were performed at 70, 80, 90 W for 10 minutes. Temperatures of the catheter and 10, 15, 20 mm away from the tip were measured. Under bronchoscopy conditions in porcine lung, ablations (n=18, 6 in ex vivo and 12 in vivo) were performed at 80 W for 5 minutes. Computed tomography (CT) was acquired perioperative, 24 hours, 2 weeks, and 4 weeks post ablation. Ablation zones were excised at 24 hours and 4 weeks respectively. Long-axis diameter (Dl) and short-axis diameter (Ds) were measured and tissues were sectioned for pathological examination. RESULTS: In-ex vivo lung, the temperature at 20 mm removed was over 60 °C at 80 W for 288±26 seconds. The ablations under bronchoscopic conditions were successful in-ex vivo and in vivo lung. No complications occurred during the procedures. Coagulation necrosis was visible at 24 hours, and repaired fibrous tissue was seen at 4 weeks. CONCLUSIONS: The flexible bronchoscopy-guided water-cooled MWA is feasible and safe. This early animal data holds promise of MWA becoming a potential therapeutic tool for Peripheral Lung Cancers.

Enhancement of Coalescence-Induced Nanodroplet Jumping on Superhydrophobic Surfaces.

Coalescence-induced droplet self-jumping on superhydrophobic surfaces has received extensive attentions over the past decade because of its potential applications ranging from anti-icing materials to self-sustained condensers, in which a higher jumping velocity vj is always expected and favorable. However, the previous studies have shown that there is a velocity limit with vj ≤ 0.23 uic for microscale droplets and vj ≤ 0.127 uic for nanoscale droplets, where uic is referred to as the inertial-capillary velocity. Here, we show that the jumping velocity can be significantly increased by patterning a single groove, ridge, or more hydrophobic strip, whose size is comparable with the radius of coalescing droplets, on a superhydrophobic surface. We implement molecular dynamics simulations to investigate the coalescence of two equally sized nanodroplets (8.0 nm in radius) on these surfaces. We found that a maximum vj = 0.23 uic is achieved on the surface with a 1.6 nm high and 5.9 nm wide ridge, which is 1.81 times higher than the nanoscale velocity limit. We also demonstrate that the presence of groove, ridge, and strip alters coalescence dynamics of droplets, leading to a significantly shortened coalescence time which remarkably reduces viscous dissipation during coalescence; thus, we believe that the present approach is also effective for microscale droplet jumping.

Coalescence-Induced Jumping of Two Unequal-Sized Nanodroplets.

Coalescence-induced self-propelled jumping of droplets on superhydrophobic surfaces has potential applications for condensation heat transfer enhancement, anti-icing, self-cleaning, antidew, and so forth. However, most of the previous studies focused on two identical droplets which are not commonly encountered in the nature. In this work, coalescence-induced jumping phenomena of two unequal-sized droplets on superhydrophobic surfaces were investigated theoretically and numerically. First, by introducing modified inertial-capillary velocity (uic*) and Ohnesorge number (Oh*) with consideration of radius ratio (r*) of two coalescing droplets, we proposed a generalized inertial-capillary scaling law for the jumping velocity of coalesced droplets, which is expected to be applicable for both two identical droplets and two unequal-sized droplets coalescing on superhydrophobic surfaces. Subsequently, we employed molecular dynamics simulations to investigate the coalescence-induced jumping process of two unequal-sized nanodroplets. Our simulations showed that the dimensionless jumping velocity (vj/uic*) well follows the generalized inertial-capillary scaling law with vj/uic* ≈ 0.127 in a specific Oh* range; however, it rapidly reduces and finally vanishes when the radius ratio of large droplet to small droplet is larger than a certain threshold value. Our simulations also revealed that nonjumping of two unequal-sized droplets with a very large radius ratio is due to that the larger droplet swallows the small one, so that the liquid bridge has no chance to impact the solid surface, and hence the "liquid bridge impacting substrate" mechanism fails in this circumstance.

[Evaluation of the cavity cleaning of ultrasonic instruments and slow-speed handpiece in posterior teeth root-end preparation].

PURPOSE: To compare the cleanliness of root end preparations by using ultrasonic instrumentation and slow-speed handpiece. METHODS: Thirty-two mesial roots of the first mandibular molars with two canals and mature root apices were assigned randomly to 2 groups, each group had 16 teeth. The root-end preparations were made respectively using ultrasonic diamond tip Berutti and NiTi tip RE2 and slow-speed handpiece with No.2 round bur. Root end cavities were examined under scanning electron microscope for further evaluation of the superficial debris and smear layer of the root end preparations. SPSS 13.0 software package was used for Kruskal Wallis test. RESULTS: Ultrasonic preparation had significantly less superficial debris and smear layer than slow-speed handpiece preparation (P<0.05). CONCLUSIONS: Ultrasonic instrument creates cleaner surfaces for root end cavities than slow-speed handpiece preparation in posterior teeth root end preparation.