Electrochemical doping and in-situ Raman scattering were used to study charge transfer in K-and Li-doped single wall carbon nanotubes (SWNT) as a function of alkali concentration. An 8 cm -1 downshift was observed for the tangential phonon mode of SWNT doped to stoichiometries of KC 24 and Li 1.25 C 6 . The shift in both systems is reversible upon de-doping despite an irreversible loss of crystallinity. These results indicate that the tangential mode shifts result from electron transfer from alkali dopants to the SWNT, and that these modes are only weakly affected by long-range order within the ropes. Comments ABSTRACTElectrochemical doping and in-situ Raman scattering were used to study charge transfer in K-and Li-doped single wall carbon nanotubes (SWNT) as a function of alkali concentration. An 8 cm -1 downshift was observed for the tangential phonon mode of SWNT doped to stoichiometries of KC 24 and Li 1.25 C 6 . The shift in both systems is reversible upon de-doping despite an irreversible loss of crystallinity. These results indicate that the tangential mode shifts result from electron transfer from alkali dopants to the SWNT, and that these modes are only weakly affected by long-range order within the ropes. IntroductionSingle wall carbon nanotubes (SWNT) constitute the newest carbon system in which chemical doping strongly modifies the physical properties [1,2]. The weak Van der Waals bonding between individual nanotubes in a semicrystalline bundle, or "rope", presumably allows for the insertion of dopants in the host lattice, as in graphite intercalation compounds and doped phases of C 60 .Alkali doping decreases the resistivity of bulk samples by a factor of 30-100 at 300K [1,3]. A similar result was observed for an individual SWNT rope [4], proving that the enhanced electron transport in bulk samples is an intrinsic property of the ropes. This phenomenon can be explained by valence electron transfer from the alkali atoms into the C anti-bonding band, which moves the Fermi energy into a region of higher density of states and enhances the conductivity. This mechanism has long been known in graphite intercalation compounds, doped polyacetylene and fullerides. Charge transfer from the alkalis to the nanotubes was proven using Raman scattering, which showed a softening of the tangential vibrational modes for the C-C bond upon doping with K or Rb [2]. A stiffening of the tangential modes and a decrease in resistivity were observed upon doping with electron acceptors, confirming the amphoteric nature of SWNT [1,2]. At this point, however, little is known about the reversibility of these phenomena and their dependence on dopant concentration. One of the limiting factors in this regard is the difficulty of controlling the composition using the vapor phase doping technique. An alternative method is electrochemical doping, which offers precise control of guest stoichiometry and allows for in-situ measurements on the guest-host systems. In-situ Raman scattering and

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There was a high prevalence of THI among patients with MFF (69.98%). RTA, nasal bone, zygomatic complex, zygomatic arch, orbital wall, maxillary sinus wall and mandibular alveolar process fractures were significantly associated with THI in patients who sustained a MFF.

Background/Aim. Epidemiology of maxillofacial fractures (MFF) varies between populations. This study investigated the epidemiology of MFF treated at the Oral and Maxillofacial Surgery (OMFS) Unit, Hospital Universiti Sains Malaysia (USM). Methods. A retrospective review of 473 medical records of patients with MFF treated from June 2013 to December 2015 was conducted. Information on demographic characteristics of patients, aetiology of injury, types of MFF, and treatment was obtained. Descriptive analysis, Pearson's chi-squared test, and multiple logistic regression analysis were conducted. The level of significance was set at 0.05. Results. Most patients treated for MFF were males (82.2%), aged 30 and below (63.1%), and from Malay ethnic (97.4%). Road traffic accident was the most common cause of MFF (83.1%), with motorcycle accident accounting for most injuries (73.6%). Orbital wall fracture was the most frequent MFF type (51.2%). About half of MFF patients (51.4%) were treated conservatively. Patients aged more than 20 years old were at higher odds of sustaining orbital wall fracture (AOR= 1.76; 95% CI: 1.214-2.558; P= 0.003) but were at lower odds of sustaining mandibular fracture (AOR= 0.47; 95% CI: 0.315-0.695; P= 0.001) than patients who are 20 years old and younger. Helmet use among motorcyclists was significantly associated with the nasal, orbital wall, and maxillary sinus wall fractures (P= 0.006, 0.010, and 0.004, respectively). Conclusion. Motorcycle accident was the most common cause of MFF in Kelantan, Malaysia. Ages of patient and helmet use were associated with the type of MFF sustained. This study provides important information to facilitate the planning of MFF prevention strategies among motorcyclists and emphasizes the importance of using a helmet when riding a motorcycle.