Orbital hybridization of donor and acceptor to enhance the conductivity of mixed-stack complexes.

Mixed-stack complexes which comprise columns of alternating donors and acceptors are organic conductors with typically poor electrical conductivity because they are either in a neutral or highly ionic state. This indicates that conductive carriers are insufficient or are mainly localized. In this study, mixed-stack complexes that uniquely exist at the neutral-ionic boundary were synthesized by combining donors (bis(3,4-ethylenedichalcogenothiophene)) and acceptors (fluorinated tetracyanoquinodimethanes) with similar energy levels and orbital symmetry between the highest occupied molecular orbital of the donor and the lowest unoccupied molecular orbital of the acceptor. Surprisingly, the orbitals were highly hybridized in the single-crystal complexes, enhancing the room-temperature conductivity (10-4-0.1 S cm-1) of mixed-stack complexes. Specifically, the maximum conductivity was the highest reported for single-crystal mixed-stack complexes under ambient pressures. The unique electronic structures at the neutral-ionic boundary exhibited structural perturbations between their electron-itinerant and localized states, causing abrupt temperature-dependent changes in their electrical, optical, dielectric, and magnetic properties.

Detecting Magnetoelectric Effect in a Metallic Antiferromagnet via Nonreciprocal Rotation of Reflected Light.

Certain types of media breaking both space-inversion (P) and time-reversal (T) symmetries but preserving their combination PT exhibit the polarization rotation of reflected light even when that of transmitted light is prohibited. Such an effect is termed nonreciprocal rotation of reflected light (NRR). Although NRR shows nearly the same phenomenon as the magnetooptical Kerr effect or, equivalently, the Hall effect at optical frequencies, its origin is distinct and ascribed to a magnetoelectric (ME) effect at optical frequencies, i.e., the optical ME effect. Here we show the observation of NRR in a metallic antiferromagnet TbB_{4}. The result demonstrates that the ME effect in a metallic system, which is considered to be ill defined, can be detected using reflected light. Furthermore, we spatially resolve antiferromagnetic domains in TbB_{4} by microscope observations of NRR. Our work offers a unique way to probe the ME effect in metallic systems.

Terahertz radiation by quantum interference of excitons in a one-dimensional Mott insulator.

Nearly monocyclic terahertz waves are used for investigating elementary excitations and for controlling electronic states in solids. They are usually generated via second-order optical nonlinearity by injecting a femtosecond laser pulse into a nonlinear optical crystal. In this framework, however, it is difficult to control phase and frequency of terahertz waves. Here, we show that in a one-dimensional Mott insulator of a nickel-bromine chain compound a terahertz wave is generated with high efficiency via strong electron modulations due to quantum interference between odd-parity and even-parity excitons produced by two-color femtosecond pulses. Using this method, one can control all of the phase, frequency, and amplitude of terahertz waves by adjusting the creation-time difference of two excitons with attosecond accuracy. This approach enables to evaluate the phase-relaxation time of excitons under strong electron correlations in Mott insulators. Moreover, phase- and frequency-controlled terahertz pulses are beneficial for coherent electronic-state controls with nearly monocyclic terahertz waves.

Metallic State of a Mixed-Sequence Oligomer Salt That Models Doped PEDOT Family.

Modern organic conductors are typically low-molecular-weight or polymer-based materials. Low-molecular-weight materials can be characterized using crystallographic information, allowing structure-conductivity relationships to be established and conduction mechanisms to be understood. However, controlling their conductive properties through molecular structural modulation is often challenging because of their relatively narrow conjugate areas. In contrast, polymer-based materials have highly π-conjugated structures with wide molecular-weight distributions, and their structural inhomogeneity makes characterizing their structures difficult. Thus, we focused on the less-explored intermediate, i.e., single-molecular-weight oligomers that model doped poly(3,4-ethylenedioxythiophene) (PEDOT). The dimer and trimer models provided clear structures; however, the short oligomers led to much lower conductivities (<10-3 S cm-1) than that of doped PEDOT. Herein, we elongated the oligomer to a tetramer through geometrical tuning based on a mixed sequence. The "P-S-S-P" sequence (S: 3,4-ethylenedithiothiophene; P: 3,4-(2',2'-dimethypropylenedioxy)thiophene) with twisted S-S enhanced the solubility and chemical stability. The subsequent oxidation process planarized the oligomer and expanded the conjugate area. Interestingly, the sequence involving sterically bulky outer P units allowed the doped oligomer to form a pitched π-stack in the single-crystal form. This enabled the inclusion of excess counter anions, which modulated the band filling. The combined effects of conjugate area expansion and band-filling modulation significantly increased the room-temperature conductivity to 36 S cm-1. This is the highest value reported for a single-crystalline oligomer conductor. Furthermore, a metallic state was observed above room temperature in a single-crystalline oligoEDOT for the first time. This unique mixed-sequence strategy for oligomer-based conductors enabled the precise control of conductive properties.

Typical carcinoid in right middle lobe of pulmonary hypoplasia.

BACKGROUND: Pulmonary typical carcinoid occurring in hypoplasia of the right middle lobe is very rare. CASE PRESENTATION: A routine examination's chest X-ray revealed an abnormal shadow in the right middle lung field of an 82-year-old Japanese woman. A chest computed tomography scan showed a solid 2.5 × 2.0-cm nodule in the very small right middle lobe. A trans-bronchial lung biopsy of the mass in the right middle lobe was performed; it revealed atypical cells with round nuclei growing in multiple foci, and immunostaining was positive for chromogranin A, synaptophysin and CD56, suggesting pulmonary carcinoid. The preoperative clinical diagnosis of primary lung cancer, cT1cN0M0 stage IA3 was considered. A right middle lobectomy and mediastinal lymph node dissection were performed by video-assisted thoracic surgery. Intraoperatively, the middle lobe of the right lung was very small, with 1- to 2-mm-dia. pulmonary arteries and veins that were considered hypoplastic. The final histopathological diagnosis was typical carcinoid, pT2aN0M0 stage IB based on the presence of pleural invasion. CONCLUSIONS: Including the present patient, only nine cases of lung cancer occurring within pulmonary hypoplasia have been reported, most of which were typical carcinoid.

[Cervical Trachea Injury Caused by Suicide Attempt:Report of a Case].

Traumatic tracheal injuries are rare, but life-threatening. A 20-year-old man who became recluse stabbed in his neck by a kitchin knife for the purpose of suicide and was transferred to our hospital. He had stabbed wound about 8 cm in length in his anterior neck. No injury of lung, esophagus, cervical vessels was seen by cervical and chest enhanced computed tomography (CT). Emergency surgery was performed. Exploration of his neck revealed almost all of cartilage of trachea was cut in the hight just caudal to cricoid cartilage. The membranous portion of trachea was not injured. The cartilage of trachea was sutured. He was extubated on the 6th postoperative day and discharged on the 35th postoperative day. No injuries to his cervical vessels or esophagus must have contributed to his good postoperative course.j.

Dynamic transition of molecular subtypes in relapsed small cell lung cancer treated with multimodal therapy: A case report.

Several transcription factors in small cell lung cancer (SCLC), including achaete-scute homolog 1 (ASCL1) and neurogenic differentiation factor 1 (NEUROD1), contribute to rapid tumor growth and early metastatic dissemination. Recent studies suggested that these molecular subtypes represent neuroendocrine differentiation in dynamic SCLC evolution. In the present case, a 62-year-old man was diagnosed with limited disease SCLC originating from the right upper lobe. Biopsy specimens were positive for ASCL1 but negative for NEUROD1. Six months after concurrent chemoradiotherapy and prophylactic cranial irradiation, the primary tumor had regrown and salvage surgery was performed. The pathological diagnosis was recurred SCLC, and postoperative histopathology was positive for both ASCL1 and NEUROD1. The patient was subsequently followed up; however, he had multiple bone metastases 9 months after surgery. It was speculated that the shift to NEUROD1-high expression in tumor cells surviving concurrent chemoradiation therapy may be related to the poor outcome after combined modality treatment.

Video-Assisted Thoracoscopic Surgery Using Extracorporeal Membrane Oxygenation for Intractable Pneumothorax.

Intractable pneumothorax with poor lung function that has received multiple conservative treatments may occur. Case 1 was a 70-year-old woman with aspergilloma who was admitted for pneumothorax. Case 2 was a 68-year-old man with acute exacerbation of interstitial pneumonia who developed pneumothorax. In both cases, multiple conservative therapies were administered, but the leak continued; thus, operations using veno-venous extracorporeal membrane oxygenation (ECMO) were planned. By video-assisted thoracoscopic surgery (VATS), we obtained the optimal surgical field by lung collapse. We removed many blood clots that were used for pleurodesis, ligated the bulla in case 1, and covered the leak point with strengthening agents in case 2. For cases of intractable pneumothorax, lung collapse by ECMO is advantageous because we can check details and leak points even in blood clots or in poor condition of the lung, and we can maneuver the lung in poor condition with a clear surgical field.

Hydrogen Bonding Propagated Phase Separation in Quasi-Epitaxial Single Crystals: A Pd-Br Molecular Insulator.

In condensed matter, phase separation is strongly related to ferroelasticity, ferroelectricity, ferromagnetism, electron correlation, and crystallography. These ferroics are important for nano-electronic devices such as non-volatile memory. However, the quantitative information regarding the lattice (atomic) structure at the border of phase separation is unclear in many cases. Thus, to design electronic devices at the molecular level, a quantitative electron-lattice relationship must be established. Herein, we elucidated a PdII-PdIV/PdIII-PdIII phase transition and phase separation mechanism for [Pd(cptn)2Br]Br2 (cptn = 1R,2R-diaminocyclopentane), propagated through a hydrogen-bonding network. Although the Pd···Pd distance was used to determine the electronic state, the differences in the Pd···Pd distance and the optical gap between Mott-Hubbard (MH) and charge-density-wave (CDW) states were only 0.012 Å and 0.17 eV, respectively. The N-H···Br···H-N hydrogen-bonding network functioned as a jack, adjusting the structural difference dynamically, and allowing visible ferroelastic phase transition/separation in a fluctuating N2 gas flow. Additionally, the effect of the phase separation on the spin susceptibility and electrical conductivity were clarified to represent the quasi-epitaxial crystals among CDW-MH states. These results indicate that the phase transitions and separations could be controlled via atomic and molecular level modifications, such as the addition of hydrogen bonding.

Ni(III) Mott-Hubbard-like State Containing High-Spin Ni(II) in a Semiconductive Bromide-Bridged Ni-Chain Compound.

Halogen-bridged linear chain metal complexes (MX-Chains) are fascinating compounds that have a quasi-one-dimensional (1D) electronic system. In this study, we synthesized the first Ni-based MX-Chain compound having hydroxy groups, i.e., [Ni(dabdOH)2Br]Br2·[Ni(dabdOHx)2Br]0.5·(2-PrOH)0.25·(MeOH)0.25 (1·solvent, x = ∼0.6, dabdOH = (2S,3S)-2,3-diaminobutane-1,4-diol). Single-crystal X-ray diffraction revealed that the MX-Chains in 1·solvent formed sheets and single-chain structures in the superlattice. It suggested an MH-like state, whereas the polarized reflection and Raman spectra suggested a CDW-like state. Magnetic and electron spin resonance measurements revealed that both high-spin Ni(II) (∼15%) and low-spin Ni(III) (∼85%) sites are present in the chain structures, i.e., the metal sites show mixed valency. Therefore, we concluded that 1·solvent adopts an intermediate state between the MH and CDW states. Moreover, a single crystal of 1·solvent exhibited semiconductive characteristics along the chain direction. This finding represents a new structural and electronic state of 1D electronic systems as well as MX-Chains.

Potential Targets for Overactive Bladder in Older Men Based on Urinary Analysis of Metabolomics.

OBJECTIVE: We investigated the association between overactive bladder (OAB) and urinary metabolites in men. METHODS: This prospective observational study included 42 men aged 65-80 years. The 3-day frequency volume chart (FVC), International Prostate Symptom Score (IPSS), and quality of life score were adapted to assess the micturition behavior. Participants with IPSS urgency score ≥2 were included in the OAB group, and those with IPSS urgency score <2 were included in the control group. We performed a comprehensive metabolomic analysis using urine samples. Metabolites were compared between the groups using an unpaired t test and Fisher's exact test in a nonadjusted analysis. Multivariable logistic regression analysis was performed to investigate the association between OAB and the metabolites. RESULTS: Overall, 23 men were included in the OAB group and 19 in the control group. There were no differences in the background factors except age between the groups. FVC analysis demonstrated that nocturnal urine volume, 24-h micturition frequency, and nocturnal micturition frequency were significantly higher, and the maximum voided volume was significantly lower in the OAB group than in the controls. Metabolomic analysis revealed 14 metabolites that were differentially expressed between the groups. Multivariate analysis indicated that an increase in the levels of 5-iso prostaglandin F2α-VI (5-iPF2a-VI) and 5-methoxyindoleacetic acid was associated with OAB. CONCLUSION: Abnormal urinary metabolites, including metabolites in the tryptophan (5-methoxyindoleacetic acid, 3-indoleacetonitrile, and 3-hydroxyanthranilic acid) and arachidonic acid (5-iPF2a-VI) pathways, play a role in the pathogenesis of OAB in older men.

Long Carbon-Carbon Bonding beyond 2 Å in Tris(9-fluorenylidene)methane.

We report on our investigation of C-C bonding longer than 2.0 Å, which can be realized by perpendicularly facing two fluorenyl rings in the title compound. A small orbital overlap between the distantly positioned carbon atoms is observed as a small concentration of electrons on the X-ray electron density map. The highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the compound originate from the in-phase and out-of-phase interactions of the overlapping orbitals, respectively, with a gap of 2.39 eV. Solid-state 13C NMR spectroscopy shows a sharp peak at 82.9 ppm for the long-bonded carbons, and a CASSCF(6,6) calculation indicates small diradical character. The experimental and theoretical analyses reveal sufficient covalent-bonding interaction in the long-bonded carbon pair.

An unusual Pd(III) oxidation state in the Pd-Cl chain complex with high thermal stability and electrical conductivity.

The Pd(iii) oxidation state is unusual and unstable since it strongly tends to disproportionate. We synthesized the quasi-one-dimensional (1D) halogen-bridged Pd(iii)-Cl complex [Pd(dabdOH)2Cl]Cl2 (1-Cl; dabdOH = (2S,3S)-2,3-diaminobutane-1,4-diol) with multiple hydrogen bonds. From single-crystal X-ray diffraction, the bridging Cl- ions were located at the midpoint of the Pd-Cl-Pd moieties in the 1D chains, indicating that the Pd ions are in a Pd(iii) average valence (AV) state. Moreover, bright spots for the Pd(iii) dz2 orbitals in the upper Hubbard band above the Fermi level were observed every ∼5 Šusing scanning tunnelling microscopy. These results clearly indicate that the Pd ions are in a Pd(iii) AV state in 1-Cl. In addition, 1-Cl has the highest thermal stability (470 K) among the Pd(iii) complexes reported and the highest electrical conductivity (0.6 S cm-1 at 300 K) among the 1D Pd-Cl chains reported so far.

Video-assisted thoracoscopic surgery using a three-dimensional thoracoscopic system as an educational tool for surgical trainees in general thoracic surgery.

OBJECTIVE: The clinical practice of safe and efficient surgery and professional development of general thoracic surgical trainee are both important issues for mentors. We investigated the usefulness of a three-dimensional (3D) endoscopic system application for lung cancer treatment as a tool for training surgical trainees. METHODS: Supervised by mentors, general thoracic surgical trainees were trained with video-assisted thoracoscopic surgery (VATS) for primary lung cancer using a 3D endoscopic system to enable them to become operators. Video clinics using 3D images were held weekly. The group using 3D endoscopic system (66 cases in the 3D-VATS group) was compared with the group using conventional two-dimensional (2D) thoracoscopic system (35 cases in the 2D-VATS group) to perform VATS lobectomies. RESULTS: There was no significant difference in operative time between both groups. However, the 3D-VATS group comprised significantly less experience than the 2D-VATS group. The intraoperative blood loss was significantly reduced for the 3D group (34 mL in the 3D-VATS group vs. 76 mL in the 2D-VATS group, P = 0.0007). There were no cases of conversion from VATS to open thoracotomy and intraoperative transfusion in either group. CONCLUSION: 3D-VATS and video clinics using 3D videos are useful training tools for general thoracic surgical trainees with little experience in open thoracotomy.

Severity of emphysema as a prognosticator of resected early lung cancer: an analysis classified by Goddard score.

OBJECTIVES: This study aimed to investigate whether the severity of emphysema as classified by Goddard score influences the prognosis of patients with early lung cancer, there are few reports about that. METHODS: From April 2009 to December 2016, we recruited 412 consecutive patients with completely resected clinical stage 0/IA/IB non-small cell lung cancer. The Goddard score assessed on preoperative computed tomography scan was retrospectively reviewed. Kaplan-Meier and Cox regression analyses were performed to assess the relationship between the Goddard score and early lung cancer prognosis. RESULTS: The patients were classified into two groups: Goddard score ≤ 4 points and ≥5 points according to the results of receiver operating characteristic curve analysis for recurrence events. The 3-year relapse-free survival rate of emphysema with Goddard score ≤ 4 points (88.6%) was higher than that of emphysema with Goddard score ≥ 5 points (60.8%) (P < 0.001). There was a higher proportion of cancer-related deaths in the group with Goddard score ≥ 5 points compared with the group with Goddard score ≤ 4 points (50% and 32.1%, respectively) (P = 0.082). A Goddard score ≥ 5 points was a significant prognostic factor for relapse-free survival in the univariate (P < 0.001) and multivariate (P = 0.022) analyses. A Goddard score ≥ 5 points was also a significant prognostic factor for overall survival in the univariate (P < 0.001) and multivariate (P = 0.041) analyses. CONCLUSION: Our findings suggest that emphysema with a Goddard score of ≥5 points may be a factor that can influence the prognosis of patients with primary lung cancer.

Strong Terahertz Radiation via Rapid Polarization Reduction in Photoinduced Ionic-To-Neutral Transition in Tetrathiafulvalene-p-Chloranil.

Terahertz lights are usually generated through the optical rectification process within a femtosecond laser pulse in noncentrosymmetric materials. Here, we report a new generation mechanism of terahertz lights based upon a photoinduced phase transition, in which an electronic structure is rapidly changed by a photoirradiation. When a ferroelectric organic molecular compound, tetrathiafulvalene-p-chloranil, is excited by a femtosecond laser pulse, the ionic-to-neutral transition is driven and simultaneously a strong terahertz radiation is produced. By analyzing the terahertz electric-field waveforms and their dependence on the polarization direction of the incident laser pulse, we demonstrate that the terahertz radiation originates from the ultrafast decrease of the spontaneous polarization in the photoinduced ionic-to-neutral transition. The efficiency of the observed terahertz radiation via the photoinduced phase transition mechanism is found to be much higher than that via the optical rectification in the same material and in a typical terahertz emitter, ZnTe.

Safety of a Novel Microwave Surgical Instrument for Lung Parenchyma Dissection During Segmentectomy.

BACKGROUND: The choice between electrocautery or automatic suturing instruments for dissection of the lung parenchyma along the intersegmental plane during lung segmentectomy remains controversial. We hypothesized that a novel microwave surgical instrument (MSI) for dissecting the lung parenchyma could have excellent sealing effects. We examined the feasibility and safety of lung parenchymal dissection using a MSI during lung segmentectomy. METHODS: This was a prospective clinical study of lung segmentectomy involving dissection of the entire intersegmental plane using a MSI. Complications related to sealing of the lung parenchyma were evaluated and perioperative outcomes were compared to those of patients who underwent lung segmentectomy using automatic suturing instruments. Propensity score-matched comparisons were used to assess the potential impact of selection bias. RESULTS: Lung segmentectomy using a MSI was successfully performed in 30 patients. According to the propensity score matching analysis, intraoperative blood loss, length of hospital stay, and postoperative complications of the microwave group were significantly lesser (P = .019, .003, and .008, respectively) compared to those of the control group (n = 66). Prolonged air leakage was not observed. There were two cases of subcutaneous emphysema after removal of the chest tube, but no other grade 2 or higher complications were observed. No mortality occurred within 30 or 90 days postoperatively. CONCLUSIONS: The use of a MSI for lung parenchymal dissection was associated with lower blood loss during surgical procedures, reduced air leakage after the operation, and fewer postoperative complications.

Metabolism of fatty acids and bile acids in plasma is associated with overactive bladder in males: potential biomarkers and targets for novel treatments in a metabolomics analysis.

OBJECTIVES: The present study was conducted to identify metabolites using a metabolomics approach and investigate the relationship between these metabolites and urgency as a major symptom of overactive bladder (OAB). PATIENTS AND METHODS: In 47 male participants without any apparent neurological disease, OAB was defined as an urgency score on the International Prostate Symptom Score of 2 and higher (OAB group, n = 26), while patients with a score of 1 or 0 were placed in a control group (n = 21). A comprehensive study on plasma metabolites was conducted, and metabolites were compared between the OAB and control groups. RESULTS: Age was significantly higher in the OAB group, while prostate volume did not differ between the groups. A 24-h bladder diary revealed that nocturnal urine volume, 24-h micturition frequency, nocturnal micturition frequency, and the nocturnal index were significantly higher in the OAB group, whereas maximum voided volume was significantly lower in this group. The metabolomics analysis identified 79 metabolites from the plasma of participants. The multivariate analysis showed that increases in the fatty acids (22:1), erucic acid and palmitoleic acid, and a decrease in cholic acid correlated with incidence of male OAB. A decrease in acylcarnitine (18:2)-3 and an increase in cis-11-eicosenoic acid also appeared to be associated with OAB in males. CONCLUSIONS: OAB in males may occur through the abnormal metabolism of fatty acids and bile acids. Further studies on these pathways will contribute to the detection of new biomarkers and development of potential targets for novel treatments.

Urinary metabolites identified using metabolomic analysis as potential biomarkers of nocturia in elderly men.

PURPOSE: To investigate the association between nocturia and urinary metabolites in elderly men using metabolomic analysis. METHODS: We recruited 66 men aged 65-80 years. The 3-day frequency volume chart (FCV), International Prostate Symptom Score (IPSS), and quality of life score were used to assess micturition behavior. Participants with the total IPSS > 0 and ≥ 1.5 micturition on an average for three nights were included in the nocturia group. Participants with the total IPSS < 8 and < 1.5 micturition at night were included in the control group. We conducted a comprehensive metabolomic analysis of urine samples. Metabolites were compared between the groups using an unpaired t test. A multivariable logistic regression analysis was used to determine the relationship between nocturia and these metabolites. RESULTS: The nocturia and control groups consisted of 45 and 21 men, respectively. There were no differences in the background factors between the groups except for receiving anticholinergic drug and having life style-related diseases. The FVC revealed that nocturnal urine volume, 24 h micturition frequency, and nocturnal micturition frequency were significantly higher in the nocturia group than in the control group. The metabolomic analysis revealed 16 metabolites, which were differentially expressed between the groups. The multivariate analysis showed that increased serotonin level and decreased 3-hydroxypropionic acid and 3-indoleacetonitrile levels were associated with nocturia. CONCLUSIONS: These findings suggest that abnormal urinary metabolites including serotonin, 3-hydroxypropionic acid, and 3-indoleacetonitrile are involved in the pathogenesis of nocturia in elderly men.

Efficacy of complete video-assisted thoracoscopic surgery lobectomy using the three-dimensional endoscopic system for lung cancer.

OBJECTIVE: We aimed to investigate the efficacy of complete video-assisted thoracoscopic surgery (cVATS) lobectomy using the three-dimensional (3D) endoscopic system in patients with lung cancer and compare it with that of cVATS lobectomy using the conventional two-dimensional (2D) endoscopic system in former consecutive cases. METHODS: We retrospectively analyzed the prospectively collected database of patients with clinical stage I lung cancer who underwent cVATS lobectomy using the 3D endoscopic system; the patients who underwent surgery using the 2D endoscopic system were considered the historical control group. The operative and perioperative data were compared, and propensity-score matched comparisons were used to assess the potential impact of selection bias. RESULTS: We performed 189 cVATS lobectomies. Of these, 105 were performed using the 3D endoscopic system, while 84 were performed using the 2D endoscopic system. After matching, there was no significant difference in the preoperative factors between the two groups. The operation time was significantly shortened (P = 0.003), and the intraoperative blood loss was significantly reduced in the 3D group (P < 0.001). In particular, there was only one case of intraoperative hemorrhage of 201 mL or more in the 3D group, compared to 12 cases in the 2D group (P < 0.001). After matching, the intraoperative blood loss and operation time were significantly reduced in the 3D group. CONCLUSIONS: Our results showed that the 3D endoscopic system for cVATS lobectomy may be a useful surgical tool and switching to it from the 2D endoscopic system can be performed safely.