Crystal lattice and electronic and transport properties of Janus ZrSiSZ2 (Z = N, P, As) monolayers by first-principles investigations.

From the extending requirements for using innovative materials in advanced technologies, it is necessary to explore new materials for relevant applications. In this work, we design new two-dimensional (2D) Janus ZrSiSZ2 (Z = N, P, As) monolayers and investigate their crystal lattice and dynamic stability by using density functional theory investigations. The two stable structures of ZrSiSP2 and ZrSiSAs2 are then systematically examined for thermal, energetic, and mechanical stability, and electronic and transport properties. The calculation results demonstrate that both the ZrSiSP2 and ZrSiSAs2 monolayers have good thermal stability at room temperature and high energetic/mechanical stabilities for experimental synthesis. The studied structures are found to be in-direct semiconductors. Specifically, with moderate band-gap energies of 1.04 to 1.29 eV for visible light absorption, ZrSiSP2 and ZrSiSAs2 can be considered potential candidates for photovoltaic applications. The applied biaxial strains and external electric fields slightly change the band-gap energies of the monolayers. We also calculate the carrier mobilities for the transport properties based on the deformation potential method. Due to the lower effective masses, the carrier mobilities in the x direction are higher than those in the y direction. The carrier mobilities of the ZrSiSP2 and ZrSiSAs2 monolayers are anisotropic not only in transport directions but also for the electrons and holes. We believe that the results of our work may stimulate further studies to explore more new 2D Janus monolayers with novel properties of the MA2Z4 family materials.

Novel two-dimensional Janus ß-Ge2XY (X/Y = S, Se, Te) structures: first-principles examinations.

Two-dimensional (2D) structures can stably exist in different allotropes. In this manuscript, we propose a new series of Janus structures based on the ß-phase of germanium monochalcogenides, namely, ß-Ge2XY (X/Y = S, Se, and Te) monolayers. Our calculations indicate that Janus ß-Ge2XY monolayers have a stable crystal structure and possess anisotropic mechanical properties. At the ground state, ß-Ge2XY monolayers are semiconductors with a large bandgap and their electronic properties depend strongly on a biaxial strain. Strains not only change the bandgap but can also lead to a change in the bandgap characteristic, namely transitions from indirect to direct bandgap. Our findings not only introduce a new structure of germanium chalcogenide compounds but also show that they have superior physical properties suitable for applications in nanoelectronics.

A comparison of the effectiveness of dexmedetomidine versus propofol target-controlled infusion for sedation during fibreoptic nasotracheal intubation.

Fibreoptic intubation is a valuable modality for airway management. This study aimed to compare the effectiveness of dexmedetomidine vs target controlled propofol infusion in providing sedation during fibreoptic intubation. Forty patients with anticipated difficult airways and due to undergo tracheal intubation for elective surgery were enrolled and randomly allocated into the dexmedetomidine group (1.0 microg.kg(-1) over 10 min) (n = 20) or the propofol target controlled infusion group (n = 20). Intubating conditions and patient tolerance as graded by a scoring system were evaluated as primary outcomes. Intubation was successful in all patients. Satisfactory intubating conditions were found in both groups (19/20 in each group). The median (IOR [range]) comfort score was 2 (1-2 [1-4]) in the dexmedetomidine group and 3 (2-4 [2-5]) in the propofol group (p = 0.027), favouring the former. The dexmedetomidine group experienced fewer airway events and less heart rate response to intubation than the propofol group (p < 0.003 and p = 0.007, respectively). Both dexmedetomidine and propofol target-controlled infusion are effective for fibreoptic intubation. Dexmedetomidine allows better tolerance, more stable haemodynamic status and preserves a patent airway.

Optimal skin surface landmark for the SVC-RA junction in cancer patients requiring the implantation of permanent central venous catheters.

We compared four different skin surface landmarks, the lower margin of the right 2nd costo-sternal junction (point A); the upper margin of the right 3rd costo-sternal junction (point B); the lower margin of the right 3rd costo-sternal junction (point C); and a point 5 cm below the manubrio-sternal junction (point D), in 20 cancer patients undergoing insertion of permanent central venous catheters whose tips were placed near the superior vena cava - right atrium (SVC-RA) junction under transoesophageal echocardiography guidance. The landmark was satisfactory if it was located within 1 cm of the SVC-RA junction. Points C and D were closer to the SVC-RA junction than points A and B (p < 0.0001). However, point C had the highest incidence (C: 70%, A: 0%, B: 20%, D: 30%, p < 0.0001) of being within 1 cm of the SVC-RA junction.

Influences of tramadol on emergence characteristics from sevoflurane anesthesia in pediatric ambulatory surgery.

Sevoflurane is used for pediatric ambulatory surgery due to its low blood solubility, rapid emergence, non-pungency and low airway irritability. Nevertheless, its tendency to induce agitation during emergence may offset its benefits. The following study was designed to evaluate the effects of intravenous (i.v.) tramadol (1 mg/kg) on the emergence from sevoflurane anesthesia. Forty ASA I children, ranging from 1 to 8 years old, scheduled for inguinal surgery, were randomized into two groups (Group S--control group, Group ST--i.v. tramadol, 20 in each group). The patients were first premedicated with oral atropine (0.01 mg/kg), then anesthesia was induced with i.v. application of thiamylal (3-4 mg/kg) and maintained with mask anesthesia with sevoflurane. Topical infiltration with 2-3 ml of 1% lidocaine was applied over skin incision area. I.v. tramadol (1 mg/kg) was given before the end of operation in Group ST. The emergence agitation was recorded on a visual analog scale (VAS, 0-10) by a blinded anesthesiologist in the PACU (postoperative anesthesia care unit), as well as the length of other recovery stages and complications after anesthesia. The age, weight, gender, and duration of surgery and anesthesia were similar in the two groups. The emergence agitation score (6.3 +/- 3.5 vs. 3.2 +/- 2.8, P < 0.05), incidences of agitation (VAS > 5, 55% vs 20%, P < 0.05), and postoperative pain (65% vs 30%, P < 0.05) were higher for the control group. I.v. Tramadol (1 mg/kg) before the end of operation reduced postoperative pain and the incidence and degree of emergence agitation from sevoflurane anesthesia in pediatric ambulatory surgery.