ABSTRACT
Development of highly efficient and robust electrocatalysts for oxygen evolution reaction (OER) under specific electrolyte is a key to actualize commercial low-temperature water electrolyzers. Herein, a rational catalyst design strategy is first reported based on amorphous-crystalline (a-c) interfacial engineering to achieve high catalytic activity and durability under diverse electrolytes that can be used for all types of low-temperature water electrolysis. Abundant a-c interface (ACI) is implemented into a hollow nanocubic (pre)-electrocatalyst which is derived from Ir-doped Ni-Fe-Zn Prussian blue analogues (PBA). The implemented c-a interface is well maintained during prolonged OER in alkaline, alkalized saline, and acidic electrolytes demonstrating its diverse functionality for water electrolysis. Notably, the final catalyst exhibits superior catalytic activity with excellent durability for OER compared to that of benchmark IrO2 catalyst, regardless of chemical environment of electrolytes. Hence, this work can be an instructive guidance for developing the ACI engineered electroctalyst which can be diversely used for different types of low-temperature electrolyzers.
ABSTRACT
Oxygen evolution reaction (OER) under acidic conditions becomes of significant importance for the practical use of a proton exchange membrane (PEM) water electrolyzer. In particular, maximizing the mass activity of iridium (Ir) is one of the maiden issues. Herein, the authors discover that the Ir-doped calcium copper titanate (CaCu3Ti4O12, CCTO) perovskite exhibits ultrahigh mass activity up to 1000 A gIr -1 for the acidic OER, which is 66 times higher than that of the benchmark catalyst, IrO2 . By substituting Ti with Ir in CCTO, metal-oxygen (M-O) covalency can be significantly increased leading to the reduced energy barrier for charge transfer. Further, highly polarizable CCTO perovskite referred to as "colossal dielectric", possesses low defect formation energy for oxygen vacancy inducing a high number of oxygen vacancies in Ir-doped CCTO (Ir-CCTO). Electron transfer occurs from the oxygen vacancies and Ti to the substituted Ir consequentially resulting in the electron-rich Ir and -deficient Ti sites. Thus, favorable adsorptions of oxygen intermediates can take place at Ti sites while the Ir ensures efficient charge supplies during OER, taking a top position of the volcano plot. Simultaneously, the introduced Ir dopants form nanoclusters at the surface of Ir-CCTO, which can boost catalytic activity for the acidic OER.
ABSTRACT
We report a case of free flap deterioration which may have been induced by pressure gradient resulting from cranial defect overlying a ventriculoperitoneal shunt (VP shunt). The patient, male and aged 78, had a VP shunt operation for progressive hydrocephalus. Afterwards, the scalp skin flap surrounding the VP shunt collapsed and showed signs of necrosis, exposing part of the shunt catheter. After covering the defect with a radial forearm free flap, the free flap site showed signs of gradual sinking while the vascularity of the flap remained unimpaired. An agreement was reached to remove the shunt device and observe the patient for any neurological symptoms, and after the shunt was removed and the previous cranial opening filled with fibrin glue by Neurosurgery, we debrided the deteriorated flap and provided coverage with 2 large opposing rotational flaps. During 2 months' outpatient follow-up no neurological symptoms appeared, and the new scalp flap displayed slight depression but remained intact. The patient has declined from any further follow-up since.
ABSTRACT
BACKGROUND: Open thyroidectomy is conventionally performed at the anterior side of neck, which is a body part with a comparatively great degree of open exposure; due to this, postoperative scarring may cause distress in patients. We aimed to compare the effects of ablative and nonablative fractional laser treatments on thyroidectomy scars. We examined medical records in a retrospective manner and analyzed scars based on their digital images by using the modified Manchester Scar Scale (mMSS). METHODS: Between February 2012 and May 2013, 55 patients with thyroidectomy scars were treated with ablative (34 patients) or nonablative (21 patients) fractional laser. Each patient underwent 4 laser treatment sessions in 3-4 week intervals, 1-2 months postoperatively. Scar improvement was assessed using patient images and the mMSS scale. RESULTS: The mean decrease in scar score was 3.91 and 3.47 in the ablative and nonablative groups, respectively; the reduction between 2 groups did not exhibit any significant difference (P=0.16). We used the scale once again to individually evaluate scar attributes. The nonablative group accounted for a considerably higher color score value (P=0.03); the ablative group accounted for a considerably higher contour score value (P<0.01). Patient satisfaction was high and no complications occurred. CONCLUSIONS: Both types of fractional laser treatments can be used successfully for thyroidectomy scar treatment with minimal complications; however, results indicate that higher effectiveness may be obtained from the use of ablative and nonablative lasers for hypertrophic scars and early erythematous scars, respectively. Therefore, the appropriate laser for scar treatment should be selected according to its specific characteristics.
