Graphene-Encapsulated Bifunctional Catalysts with High Activity and Durability for Zn-Air Battery.

Carbon-based electrocatalysts with both high activity and high stability are desirable for use in Zn-air batteries. However, the carbon corrosion reaction (CCR) is a critical obstacle in rechargeable Zn-air batteries. In this study, a cost-effective carbon-based novel material is reported with a high catalytic effect and good durability for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), prepared via a simple graphitization process. In situ growth of graphene is utilized in a 3D-metal-coordinated hydrogel by introducing a catalytic lattice of transition metal alloys. Due to the direct growth of few-layer graphene on the metal alloy decorated 3d-carbon network, greatly reduced CCR is observed in a repetitive OER test. As a result, an efficient bifunctional electrocatalytic performance is achieved with a low ΔE value of 0.63 V and good electrochemical durability for 83 h at a current density of 10 mA cm-2 in an alkaline media. Moreover, graphene-encapsulated transition metal alloys on the nitrogen-doped carbon supporter exhibit an excellent catalytic effect and good durability in a Zn-air battery system. This study suggests a straightforward way to overcome the CCR of carbon-based materials for an electrochemical catalyst with wide application in energy conversion and energy storage devices.

Bi-functional 3D-NiCu-Double Hydroxide@Partially Etched 3D-NiCu Catalysts for Non-Enzymatic Glucose Detection and the Hydrogen Evolution Reaction.

Hydrogen production, which is in the spotlight as a promising eco-friendly fuel, and the need for inexpensive and accurate electronic devices in the biochemistry field are important emerging technologies. However, the use of electrocatalytic devices based on expensive noble metal catalysts limits commercial applications. In recent years, to improve performance and reduce cost, electrocatalysts based on cheaper copper or nickel materials have been investigated for the non-enzymatic glucose oxidation reaction (GOR) and hydrogen evolution reaction (HER). In this study, we demonstrate a facile and easy electrochemical method of forming a cheap nickel copper double hydroxide (NiCu-DH) electrocatalyst deposited onto a three-dimensional (3D) CuNi current collector, which can effectively handle two different reactions due to its high activity for both the GOR and the HER. The as-prepared electrode has a structure comprising abundant 3D-interconnected porous dendritic walls for easy access of the electrolyte ions and highly conductive networks for fast electron transfer; additionally, it provides numerous electroactive sites. The synergistic combination of the dendritic 3D-CuNi with its abundant active sites and the self-made NiCu-DH with its excellent electrocatalytic activity toward the oxidation of glucose and HER enables use of the catalyst for both reactions. The as-prepared electrode as a glucose sensor exhibits an outstanding glucose detection limit value (0.4 µM) and a wide detection range (from 0.4 µM to 1.4 mM) with an excellent sensitivity of 1452.5 µA/cm2/mM. The electrode is independent of the oxygen content and free from chloride poisoning. Furthermore, the as-prepared electrode also requires a low overpotential of -180 mV versus reversible hydrogen electrode to yield a current density of 10 mA/cm2 with a Tafel slope of 73 mV/dec for the HER. Based on this performance, this work introduces a new paradigm for exploring cost-effective bi-functional catalysts for the GOR and HER.

Rational Design of a High Performance and Robust Solar Evaporator via 3D-Printing Technology.

Utilizing the broad-band solar spectrum for sea water desalination is a promising method that can provide fresh water without sophisticated infrastructures. However, the solar-to-vapour efficiency has been limited due to the lack of a proper design for the evaporator to deal with either a large amount of heat loss or salt accumulation. Here, these issues are addressed via two cost-effective approaches: I) a rational design of a concave shaped supporter by 3D-printing that can promote the light harvesting capacity via multiple reflections on the surface; II) the use of a double layered photoabsorber composed of a hydrophilic bottom layer of a polydopamine (PDA) coated glass fiber (GF/C) and a hydrophobic upper layer of a carbonized poly(vinyl alcohol)/polyvinylpyrrolidone (PVA/PVP) hydrogel on the supporter, which provides competitive benefit for preventing deposition of salt while quickly pumping the water. The 3D-printed solar evaporator can efficiently utilize solar energy (99%) with an evaporation rate of 1.60 kg m-2 h-1 and efficiency of 89% under 1 sun irradiation. The underlying reason for the high efficiency obtained is supported by the heat transfer mechanism. The 3D-printed solar evaporator could provide cheap drinking water in remote areas, while maintaining stable performance for a long term.

Graphitization with Suppressed Carbon Loss for High-Quality Reduced Graphene Oxide.

An efficient reduction method to obtain high-quality graphene sheets from mass-producible graphene oxide is highly desirable for practical applications. Here, we report an in situ deoxidation and graphitization mechanism for graphene oxide that allows for high-quality reduced graphene oxide sheets under the low temperature condition (<300 °C) by utilizing a well-known Fischer-Tropsch reaction catalyst (CuFeO2). By applying modified FTR conditions, where graphene oxide was reduced on the catalyst surface under the hydrogen-poor condition, deoxidation with much suppressed carbon loss was possible, resulting in high-quality graphene sheets. Our experimental data and density functional theory calculations proved that reduction which occurred on the CuFeO2 surface preferentially removed adsorbed oxygen atoms in graphene oxide sheets, leaving dissociated carbon structures to be restored to a near-perfect few-layer graphene sheet. TGA-mass data revealed that GO with catalysts released 92.8% less carbon-containing gases than GO without catalysts during the reduction process, which suggests that this process suppressed carbon loss in graphene oxide sheets, leading to near-perfect graphene. The amount of oxygen related to the epoxide group in the basal plane of GO significantly decreased to near zero (from 43.84 to 0.48 at. %) in catalyst-assisted reduced graphene oxide (CA-rGO). The average domain size and the density of defects of CA-rGO were 4 times larger and 0.1 times lower than those for thermally reduced graphene oxide (TrGO), respectively. As a result, CA-rGO had a 246 and 8 times lower electrical resistance than TrGO and CVD-graphene. With these performances, CA-rGO coated paper connected to a coin-cell battery successfully lit an LED bulb, and CA-rGO itself acted as an efficient catalyst for both the hydrogen evolution reaction and the oxygen evolution reaction.

Wire-Shaped 3D-Hybrid Supercapacitors as Substitutes for Batteries.

We report a wire-shaped three-dimensional (3D)-hybrid supercapacitor with high volumetric capacitance and high energy density due to an interconnected 3D-configuration of the electrode allowing for large number of electrochemical active sites, easy access of electrolyte ions, and facile charge transport for flexible wearable applications. The interconnected and compact electrode delivers a high volumetric capacitance (gravimetric capacitance) of 73 F cm-3 (2446 F g-1), excellent rate capability, and cycle stability. The 3D-nickel cobalt-layered double hydroxide onto 3D-nickel wire (NiCo LDH/3D-Ni)//the 3D-manganese oxide onto 3D-nickel wire (Mn3O4/3D-Ni) hybrid supercapacitor exhibits energy density of 153.3 Wh kg-1 and power density of 8810 W kg-1. The red light-emitting diode powered by the as-prepared hybrid supercapacitor can operate for 80 min after being charged for tens of seconds and exhibit excellent electrochemical stability under various deformation conditions. The results verify that such wire-shaped 3D-hybrid supercapacitors are promising alternatives for batteries with long charge-discharge times, for smart wearable and implantable devices.

Motion Sickness Prediction in Stereoscopic Videos using 3D Convolutional Neural Networks.

In this paper, we propose a three-dimensional (3D) convolutional neural network (CNN)-based method for predicting the degree of motion sickness induced by a 360° stereoscopic video. We consider the user's eye movement as a new feature, in addition to the motion velocity and depth features of a video used in previous work. For this purpose, we use saliency, optical flow, and disparity maps of an input video, which represent eye movement, velocity, and depth, respectively, as the input of the 3D CNN. To train our machine-learning model, we extend the dataset established in the previous work using two data augmentation techniques: frame shifting and pixel shifting. Consequently, our model can predict the degree of motion sickness more precisely than the previous method, and the results have a more similar correlation to the distribution of ground-truth sickness.

Depression Plays a Moderating Role in the Cognitive Decline Associated With Changes of Brain White Matter Hyperintensities.

OBJECTIVE: In the elderly, depression and white matter hyperintensities (WMH) are common and associated with cognitive impairment. This study investigated the possible interactions between depression and WMH in their influences on cognition of the elderly. METHODS: Using multiple neuropsychological tests, we evaluated the cognitive function of 122 community-dwelling elders with depression at baseline between November 2008 and February 2009. Major depressive disorder, dysthymic disorder, and minor depressive disorder were diagnosed according to DSM-IV criteria. Subsyndromal depressive disorder was operationally defined using a modification of DSM-IV criteria. We visually rated WMH severity according to the modified Fazekas scale and calculated WMH volume using an automated method. We defined WMH (+) as having a score of 2 or higher on the modified Fazekas scale. In the 3-year follow-up study, baseline participants were reassessed between November 2011 and February 2013 with the same methodology. RESULTS: Baseline depression was associated with a decline over 3 years in the Categorical Verbal Fluency Test (VFT) (P = .001), Word List Memory Test (WLMT) (P = .019), Trail Making Test A (TMT-A) (P = .018), and Mini-Mental State Examination (MMSE) (P = .017), while baseline WMH (+) was associated with a decline in WLMT (P = .039) only. An increase of WMH volume over 3 years was associated with a decline in the performances of VFT (P = .044), WLMT (P = .044), Word List Recall Test (P = .040), Word List Recognition Test (P = .036), and TMT-A (P = .001) over the same period only in the subjects with depression at baseline. CONCLUSIONS: Depressive disorder and WMH are interactively associated with the poor performance of multiple cognitive functions. Depressive disorder may moderate the cognitive decline associated with the changes of brain WMH.

Ultrathin nickel hydroxide on carbon coated 3D-porous copper structures for high performance supercapacitors.

An ultrathin nickel hydroxide layer electrodeposited on a carbon-coated three-dimensional porous copper structure (3D-C/Cu) is suggested as an additive and binder-free conductive electrode with short electron path distances, large electrochemical active sites, and improved structural stability, for high performance supercapacitors. The 3D-porous copper structure (3D-Cu) provides high electrical conductivity and facilitates electron transport between the Ni(OH)2 active materials and the current collector of the Ni-plate. A carbon coating was applied to the 3D-Cu to prevent the oxidation of Cu, without degrading the electron transport behavior of the 3D-Cu. The 3D-Ni(OH)2/C/Cu exhibited a high specific capacitance of 1860 F g-1 at 1 A g-1, and good cycling performance, with an 86.5% capacitance retention after 10 000 cycles. When tested in a two-electrode system, an asymmetric supercapacitor exhibited an energy density of 147.9 W h kg-1 and a power density of 37.0 kW kg-1. These results open a new area of ultrahigh-performance supercapacitors, supported by 3D-Cu electrodes.

Highly Enhanced Raman Scattering on Carbonized Polymer Films.

We have discovered a carbonized polymer film to be a reliable and durable carbon-based substrate for carbon enhanced Raman scattering (CERS). Commercially available SU8 was spin coated and carbonized (c-SU8) to yield a film optimized to have a favorable Fermi level position for efficient charge transfer, which results in a significant Raman scattering enhancement under mild measurement conditions. A highly sensitive CERS (detection limit of 10-8 M) that was uniform over a large area was achieved on a patterned c-SU8 film and the Raman signal intensity has remained constant for 2 years. This approach works not only for the CMOS-compatible c-SU8 film but for any carbonized film with the correct composition and Fermi level, as demonstrated with carbonized-PVA (poly(vinyl alcohol)) and carbonized-PVP (polyvinylpyrollidone) films. Our study certainly expands the rather narrow range of Raman-active material platforms to include robust carbon-based films readily obtained from polymer precursors. As it uses broadly applicable and cheap polymers, it could offer great advantages in the development of practical devices for chemical/bio analysis and sensors.

How Different are Quality of Life Ratings for People with Dementia Reported by Their Family Caregivers from Those Reported by the Patients Themselves?

BACKGROUND: Measurements of patient quality of life (QoL) play a major role in the management of dementia. OBJECTIVE: We investigated the self-proxy discrepancy of QoL ratings in the elderly and the impact of dementia severity on the discrepancy. METHODS: QoL of 718 patients with dementia and 651 non-demented elderly were rated by themselves and their caregivers (CG) using the Quality of Life-Alzheimer's Disease (QoL-AD). The impact of the rater on the total and item scores of QoL-AD was analyzed using repeated measures ANOVA and differential response patterns between self and proxy were analyzed using differential item functioning (DIF) analysis. RESULTS: Self-rated scores were higher than CG-rated scores in all diagnostic groups. The interaction between rater and diagnostic group was significant in total QoL-AD score and 5 item scores ('memory', 'marriage', 'chores around the house', 'do things for fun', and 'life as a whole'). The strength of the DIF increased with advancing dementia in these items. CONCLUSION: Self-proxy rating discrepancy of QoL was influenced by the presence and severity of dementia only in five items.

Differences in knowledge of dementia among older adults with normal cognition, mild cognitive impairment, and dementia: A representative nationwide sample of Korean elders.

OBJECTIVE: Lack of knowledge about a disease could impede early diagnosis and may lead to delays in seeking appropriate medical care. The aim of this study was to explore knowledge of dementia (KOD) and to find the determinants of KOD among three groups: older adults with normal cognition, mild cognitive impairment (MCI), and dementia. METHODS: A representative nationwide sample of 6141 Korean elders aged 65 years or older participated in face-to-face interviews and answered 14 questions pertaining to general information, etiology, symptoms, and treatment of dementia. Stepwise multiple regressions and path analyses probed the relationships between various sociodemographic variables and KOD. RESULTS: The percentage of correct responses was only 62%. The item 'A person who remembers things that happened in the past does not have dementia' was answered correctly (false) by only 24.8-27% of the respondents in all groups. Older adults with normal cognition had higher KOD scores than those with MCI or dementia. In the normal-cognition group, KOD scores were higher among highly educated, younger, and literate women with no depression and a family history of dementia. In contrast with the determinants in the normal-cognition group, only the ability to read and write predicted KOD scores in the dementia group. CONCLUSIONS: Efforts to enhance KOD in elder adults are needed. Public education regarding the differences between dementia and healthy aging may increase KOD among normal elders and those with MCI. Among elders with dementia, educational materials that do not require literacy may be more helpful in increasing KOD with the aim of preventing treatment delay.

Epidemiology of MRI-defined vascular depression: A longitudinal, community-based study in Korean elders.

BACKGROUND: There are no cross-sectional or longitudinal epidemiological studies present on MRI-defined vascular depression in community populations. The purpose of this study was to estimate the prevalence rates of both vascular and non-vascular late life depression (LLD) at baseline, to examine the natural course of LLD, and to investigate the influence of White matter hyperintensities (WMHs) on depression after three years. METHOD: The baseline study employed a two-stage design, Phase I population survey (n=783) and Phase II diagnostic evaluation (n=122). In the 3-year follow-up study, baseline participants completing the second phase were reassessed with the same methodology. WMHs severity was rated visually by the modified Fazekas scale and WMHs volume was calculated using an automated method. RESULTS: The prevalence rates of vascular major depressive disorder (MDD) and vascular non-major depressive disorder (nMDD) were 2.39% (56.2% of MDD) and 4.24% (34.0% of nMDD). Subjects with a score of 2 or more on the modified Fazekas scale in either deep white matter hyperintensities or subcortical gray matter ratings had an 8.1 times greater risk of developing a depressive disorder in the 3-year follow-up study. Greater Log WMHs volume (odds ratio=5.78, 95% CI, 1.04-31.72) at baseline was an independent predictor for depressive disorder in the 3-year assessment. LIMITATIONS: Response rate and follow-up rate were relatively low. CONCLUSIONS: Vascular depression is common and makes up about a half of MDD in elders. Greater WMHs severity is a crucial factor predicting future depression risk, which supports the previous vascular depression hypothesis.

Incidence of and risk factors for Alzheimer's disease and mild cognitive impairment in Korean elderly.

BACKGROUND/AIMS: Knowledge of incidence rates and risk factors is essential for the development of strategies to treat patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI). METHODS: A subpopulation of the Nationwide Survey on Dementia Epidemiology (460 Korean subjects aged ≥65 years from 2 rural and 2 urban districts) was followed up for 3.5 years. The age-specific incidence was estimated and risk factors were identified. RESULTS: The age-standardized incidence of AD and MCI was 7.9 and 28.1 cases per 1,000 person-years, respectively. MCI was associated with a 6-fold increased risk of AD. Depression was a risk factor for AD with MCI. Age, lack of formal education, illiteracy, rural residence, and marital status were associated with the risk of AD. CONCLUSION: Strategies to control modifiable risk factors should be implemented to decrease the incidence of AD.

Effects of social supports on burden in caregivers of people with dementia.

BACKGROUND: Social support programs for dementia caregivers were widely used in order to reduce care burden. We investigated which types of social supports can reduce psychological and non-psychological burdens of dementia caregivers, and explored the mechanism of those social supports. METHODS: We evaluated 731 community-dwelling dementia patients and their caregivers from the National Survey of Dementia Care in South Korea. We investigated the five types of social supports (emotional support, informational support, tangible support, positive social interaction, affectionate support) using the Medical Outcomes Study Social Support Survey in each caregiver. The mechanisms of specific types of social support on psychological/non-psychological burden were examined using path analysis. RESULTS: Positive social interaction and affectionate support reduced psychological burden via direct and indirect paths. Tangible support reduced the non-psychological burden via direct and indirect paths. Informational support and emotional support were not helpful for reducing psychological or non-psychological burden. A maximum of 20% of psychological burden could be relieved by positive social interaction and 10.3% of that could be reduced by affectionate support. Tangible support was associated with a 15.1% maximal improvement in non-psychological burden. CONCLUSIONS: In order to reduce caregiver burden in dementia effectively, psychosocial interventions should be tailored to target type of caregiver burden.

A new scoring method of the mini-mental status examination to screen for dementia.

BACKGROUND: Although the Mini-Mental Status Examination (MMSE) is the most widely used screening instrument for dementia, it has several limitations. METHODS: We developed and validated a new scoring method of the MMSE, namely the short form of the MMSE (MMSE-S). RESULTS: The MMSE-S was more robust to demographic influences than the MMSE. The influence of education, in particular, was smaller in the MMSE-S compared to the MMSE (p < 0.01). The diagnostic accuracy of the MMSE-S for very mild to mild dementia was also better than that of the original MMSE (p < 0.0001). Its specificity, in particular, was higher than that of the original MMSE. In Korea, we could improve the post-test probability for dementia from 46.88 to 64.76% by employing the MMSE-S instead of the MMSE. We also provided optimal cut-off scores for dementia stratified by age, education, and gender, which may further improve the diagnostic accuracy of the MMSE-S for dementia. CONCLUSION: Due to its good accuracy and brevity, the MMSE-S may contribute to enhancing the cost-effectiveness of and accessibility to dementia screening as well as early diagnosis and treatment of dementia, particularly in low- and middle-income countries.

p-Doped three-dimensional graphene nano-networks superior to platinum as a counter electrode for dye-sensitized solar cells.

We report CVD-grown p-doped three-dimensional graphene nano-networks (3D-GNs) that provide superior performance to Pt as a counter electrode material in dye sensitized solar cells (DSSCs). The 3D-GN based DSSC exhibits a maximum photoconversion efficiency of 8.46%, which is 6.01% greater than that exhibited by Pt based DSSCs.

Development of a screening algorithm for Alzheimer's disease using categorical verbal fluency.

We developed a weighted composite score of the categorical verbal fluency test (CVFT) that can more easily and widely screen Alzheimer's disease (AD) than the mini-mental status examination (MMSE). We administered the CVFT using animal category and MMSE to 423 community-dwelling mild probable AD patients and their age- and gender-matched cognitively normal controls. To enhance the diagnostic accuracy for AD of the CVFT, we obtained a weighted composite score from subindex scores of the CVFT using a logistic regression model: logit (case)  = 1.160+0.474× gender +0.003× age +0.226× education level - 0.089× first-half score - 0.516× switching score -0.303× clustering score +0.534× perseveration score. The area under the receiver operating curve (AUC) for AD of this composite score AD was 0.903 (95% CI = 0.883 - 0.923), and was larger than that of the age-, gender- and education-adjusted total score of the CVFT (p<0.001). In 100 bootstrapped re-samples, the composite score consistently showed better diagnostic accuracy, sensitivity and specificity for AD than the total score. Although AUC for AD of the CVFT composite score was slightly smaller than that of the MMSE (0.930, p = 0.006), the CVFT composite score may be a good alternative to the MMSE for screening AD since it is much briefer, cheaper, and more easily applicable over phone or internet than the MMSE.

Validation of the dementia care assessment packet-instrumental activities of daily living.

OBJECTIVE: We aimed to evaluate the psychometric properties of the IADL measure included in the Dementia Care Assessment Packet (DCAP-IADL) in dementia patients. METHODS: The study involved 112 dementia patients and 546 controls. The DCAP-IADL was scored in two ways: observed score (OS) and predicted score (PS). The reliability of the DCAP-IADL was evaluated by testing its internal consistency, inter-rater reliability and test-retest reliability. Discriminant validity was evaluated by comparing the mean OS and PS between dementia patients and controls by ANCOVA. Pearson or Spearman correlation analysis was performed with other instruments to assess concurrent validity. Receiver operating characteristics curve analysis was performed to examine diagnostic accuracy. RESULTS: Chronbach's α coefficients of the DCAP-IADL were above 0.7. The values in dementia patients were much higher (OS=0.917, PS=0.927), indicating excellent degrees of internal consistency. Inter-rater reliabilities and test-retest reliabilities were statistically significant (p<0.05). PS exhibited higher reliabilities than OS. The mean OS and PS of dementia patients were significantly higher than those of the non-demented group after controlling for age, sex and education level. The DCAP-IADL was significantly correlated with other IADL instruments and MMSE-KC (p<0.001). Areas under the curves of the DCAP-IADL were above 0.9. CONCLUSION: The DCAP-IADL is a reliable and valid instrument for evaluating instrumental ability of daily living for the elderly, and may also be useful for screening dementia. Moreover, administering PS may enable the DCAP-IADL to overcome the differences in gender, culture and life style that hinders accurate evaluation of the elderly in previous IADL instruments.