Publications by authors named "Dong-Joo Kim"

99 Publications

Electromechanical Response of Smart Ultra-High Performance Concrete under External Loads Corresponding to Different Electrical Measurements.

Sensors (Basel) 2021 Feb 11;21(4). Epub 2021 Feb 11.

Department of Civil and Environmental Engineering, SEJONG University, 209, Neungdong-ro, Gwangjin-gu, Seoul 05006, Korea.

This study investigated the electromechanical response of smart ultra-high-performance concretes (smart UHPCs), containing fine steel slag aggregates (FSSAs) and steel fibers as functional fillers, under external loads corresponding to different measurement methods. Regardless of different measurement methods of electrical resistance, the smart UHPCs under compression showed a clear reduction in their electrical resistivity. However, under tension, their electrical resistivity measured from direct current (DC) measurement decreased, whereas that from alternating current (AC) measurement increased. This was because the electrical resistivity, from DC measurement, of smart UHPCs was primarily dependent on fiber crack bridging, whereas that from AC measurement was dependent on tunneling effects.
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http://dx.doi.org/10.3390/s21041281DOI Listing
February 2021

Pediatric melanoma in the Hispanic population: An analysis of institutional and national data.

Pediatr Dermatol 2021 Jan 24. Epub 2021 Jan 24.

Department of Dermatology, University of California, Irvine, CA, USA.

Background/objectives: Pediatric melanoma is rare and remains poorly characterized, especially in racial/ethnic minorities of whom Hispanics are the largest and fastest growing in the United States. The health care burden of melanoma in Hispanics, who often present with more advanced disease, is rising and has even been called an early epidemic in California. We sought to document key clinicopathologic features of melanoma in Hispanic pediatric patients and to compare these parameters to pediatric non-Hispanic whites (NHWs) under the a priori hypothesis that Spitzoid melanomas occur in greater proportions in Hispanics.

Methods: Single-institution cross-sectional study of pediatric melanoma cases (age < 20 years) with Hispanic stratification and comparison with matched Surveillance, Epidemiology, and End Results (SEER) data from the same time frame (1988-2016).

Results: Of our 61 institutional cases of pediatric melanoma, Hispanics (11), compared with NHWs (40), presented significantly younger (11.7 years, 95% CI: 2.77-8.00 years; P = .001), with lower limb predominance (46%; P < .05), mostly Spitzoid melanomas (82%; P < .05), and thicker tumors (2.34 mm, CI: 0.26-2.19 mm; P < .05). Similarly, SEER data (2499 cases) showed greater proportions of childhood/pre-pubertal adolescent melanomas (<15 years), lower limb involvement, Spitzoid subtype (36.5% vs 22.5% in NHWs; P = .001), and advanced (regional/distant) disease stages in Hispanics (212) compared with NHWs (2197).

Conclusions: Pediatric melanomas may present differently in Hispanics, and heightened awareness/lower threshold to biopsy high-risk Spitzoid tumors on the lower limb may be warranted. Further investigations are needed to aid prevention and early detection in a vulnerable minority population less likely to seek outpatient dermatology specialty care.
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http://dx.doi.org/10.1111/pde.14516DOI Listing
January 2021

Reconstruction of Distal Nasal Defects Using Free Cartilage Batten Grafting With Secondary Intention Healing: A Retrospective Case Series of 129 Patients.

Dermatol Surg 2021 Jan;47(1):86-93

Department of Dermatology, University of California, Irvine, Irvine, California.

Background: Surgical defects of the distal nose can pose significant reconstructive challenges. Free cartilage batten graft (FCBG) with secondary intention healing is an underreported yet effective repair option with cosmetically and functionally satisfying outcomes.

Objective: To share the authors' experience using FCBG with secondary intention healing on multiple nasal subunits, including a detailed evaluation of wound/graft characteristics and design modifications to optimize success with this single-stage approach.

Methods: A retrospective study of 129 patients who underwent FCBG with secondary intention healing after Mohs surgery from 2011 to 2018, using statistical analysis of numerous outcome measures graded independently by 2 fellowship-trained Mohs surgeons.

Results: Overall, healed wounds were graded aesthetically as follows: excellent (24%), very good (31%), good (31%), or poor (14%). Excellent/very good outcomes were seen for superficial (p < .001), small-to-medium sized wounds (p < .0001) repaired with cartilage that closely approximated the defect size (p < .05). Consistently optimal outcomes were seen in the 19 repairs involving the alar lobule (mid-ala) alone, graded excellent (47%), very good (32%), and good (21%). A majority of patients (86%) experienced mild to no alar retraction. Although 67% of all patients had some skin surface contour irregularity, only 8% of patients sought dermabrasion. Neither hematoma, infection, ear deformity, chondritis, nor graft desiccation were reported.

Conclusion: A modified approach to FCBG with secondary intention healing provides a reliable, minimalistic, low-risk reconstructive option for mid-alar defects.
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http://dx.doi.org/10.1097/DSS.0000000000002714DOI Listing
January 2021

Pullout Behavior of Recycled Waste Fishing Net Fibers Embedded in Cement Mortar.

Materials (Basel) 2020 Sep 21;13(18). Epub 2020 Sep 21.

Department of Civil and Environmental Engineering, Sejong University, 209, Neungdong-ro, Gwangjin-Gu, Seoul 05006, Korea.

In this study, recycled waste fishing net (WFN) short fibers were proposed to be used as short fiber reinforcements. The pullout resistance of WFN short fibers embedded in cement mortar was investigated by conducting fiber pullout tests. Three types of WFN short fibers and two types of commercial polypropylene (CP) fibers were investigated. To quantitatively compare the pullout resistance of WFN short fibers and CP fibers, pullout parameters, including peak pullout load (peak bond strength), peak fiber stress, slip at peak load, and pullout energy (equivalent bond strength) of the pullout specimens, were analyzed. In addition, the analysis of fiber images, captured by using a stereoscopic digital microscope, before and after pullout tests, elucidated the different mechanisms of fiber pullout corresponding to the type of fibers. The bundled structures of the WFN fibers generated mechanical interaction between fiber and matrix during fiber pullout; consequently, they produced higher bond resistance and more damage on the surface of fibers after the pullout. Therefore, the bundled WFN fibers showed comparable pullout resistance with CP fibers.
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http://dx.doi.org/10.3390/ma13184195DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7560476PMC
September 2020

Brain-Controlled Robotic Arm System Based on Multi-Directional CNN-BiLSTM Network Using EEG Signals.

IEEE Trans Neural Syst Rehabil Eng 2020 05 18;28(5):1226-1238. Epub 2020 Mar 18.

Brain-machine interfaces (BMIs) can be used to decode brain activity into commands to control external devices. This paper presents the decoding of intuitive upper extremity imagery for multi-directional arm reaching tasks in three-dimensional (3D) environments. We designed and implemented an experimental environment in which electroencephalogram (EEG) signals can be acquired for movement execution and imagery. Fifteen subjects participated in our experiments. We proposed a multi-directional convolution neural network-bidirectional long short-term memory network (MDCBN)-based deep learning framework. The decoding performances for six directions in 3D space were measured by the correlation coefficient (CC) and the normalized root mean square error (NRMSE) between predicted and baseline velocity profiles. The grand-averaged CCs of multi-direction were 0.47 and 0.45 for the execution and imagery sessions, respectively, across all subjects. The NRMSE values were below 0.2 for both sessions. Furthermore, in this study, the proposed MDCBN was evaluated by two online experiments for real-time robotic arm control, and the grand-averaged success rates were approximately 0.60 (±0.14) and 0.43 (±0.09), respectively. Hence, we demonstrate the feasibility of intuitive robotic arm control based on EEG signals for real-world environments.
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http://dx.doi.org/10.1109/TNSRE.2020.2981659DOI Listing
May 2020

Trajectory Decoding of Arm Reaching Movement Imageries for Brain-Controlled Robot Arm System.

Annu Int Conf IEEE Eng Med Biol Soc 2019 Jul;2019:5544-5547

Development of noninvasive brain-machine interface (BMI) systems based on electroencephalography (EEG), driven by spontaneous movement intentions, is a useful tool for controlling external devices or supporting a neuro- rehabilitation. In this study, we present the possibility of brain-controlled robot arm system using arm trajectory decoding. To do that, we first constructed the experimental system that can acquire the EEG data for not only movement execution (ME) task but also movement imagery (MI) tasks. Five subjects participated in our experiments and performed four directional reaching tasks (Left, right, forward, and backward) in the 3D plane. For robust arm trajectory decoding, we propose a subject-dependent deep neural network (DNN) architecture. The decoding model applies the principle of bi-directional long short-term memory (LSTM) network. As a result, we confirmed the decoding performance (r-value: >0.8) for all X-, Y-, and Z-axis across all subjects in the MI as well as ME tasks. These results show the feasibility of the EEG-based intuitive robot arm control system for high-level tasks (e.g., drink water or moving some objects). Also, we confirm that the proposed method has no much decoding performance variations between ME and MI tasks for the offline analysis. Hence, we will demonstrate that the decoding model is capable of robust trajectory decoding even in a real-time environment.
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http://dx.doi.org/10.1109/EMBC.2019.8856312DOI Listing
July 2019

Reconstructing Degree of Forearm Rotation from Imagined movements for BCI-based Robot Hand Control.

Annu Int Conf IEEE Eng Med Biol Soc 2019 Jul;2019:3014-3017

Brain-computer interface (BCI) is an important tool for rehabilitation and control of an external device (e.g., robot arm or home appliances). Fully reconstruction of upper limb movement from brain signals is one of the critical issues for intuitive BCI. However, decoding of forearm rotation from imagined movements using electroencephalography (EEG) is difficult to decode degree of rotation accurately. In this paper, we reconstructed imagined forearm rotation from low- frequency (0.3-3 Hz) of EEG signals. We selected 20 EEG channel on motor cortex for analysis. Ten healthy subjects participated in our experiment. The subjects performed actual and imagined forearm rotation to reach different targets. We trained a reconstruction decoder which used the EEG signals measured from actual movements and the kinematic information only. Additionally, we applied a long short-term memory (LSTM) network to enhance decoding performances. As a result, we achieved the high correlation performance (Average: 0.67) to decode imagined forearm rotation angle. This result has demonstrated that the reconstruction decoder which is trained by the EEG data from actual movement has effective to decode robustly for the imagined forearm rotation angle.
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http://dx.doi.org/10.1109/EMBC.2019.8857674DOI Listing
July 2019

Ergonomics in Dermatologic Surgery: Lessons Learned Across Related Specialties and Opportunities for Improvement.

Dermatol Surg 2020 06;46(6):763-772

Department of Dermatology, University of California, Irvine, California.

Background: As the practice of dermatology becomes increasingly procedurally based, there is a concordant rise in musculoskeletal injury (MSI) risk. Dermatologic surgeons are most susceptible and, although the majority suffer from MSI, few have received any formal ergonomics training. This stems from a lack of awareness of this troubling trend and a paucity of research and education on the ergonomics of dermatologic surgery.

Objective: To highlight pertinent ergonomics principles and strategies from other specialties that could be translated into dermatology, and to synthesize general recommendations aimed at reducing MSI among dermatologic surgeons.

Materials And Methods: A comprehensive search of the PubMed and Cochrane Reviews databases from 1975 to 2019 was conducted, using a combination of ergonomics-related search terms, generating 6 publications from the dermatology literature and 58 from the fields of dentistry, medicine, and select surgical subspecialties.

Results: This multidisciplinary approach yielded multiple interventions that could be applied directly (i.e., adequate lighting, adjustable operating tables, and surgical seat heights) or indirectly pending further investigation into their feasibility (i.e., video displays of the surgical field to allow neutral head and neck postures).

Conclusion: Although much can be learned from decades of prior ergonomics research from other specialties, considerations that are unique to dermatology remain and must be addressed with specialty-specific research.
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http://dx.doi.org/10.1097/DSS.0000000000002295DOI Listing
June 2020

Painful Violaceous Nodules of the Popliteal Fossa.

Sex Transm Dis 2019 12;46(12):820

Department of Dermatology, University of California, Irvine, CA.

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http://dx.doi.org/10.1097/OLQ.0000000000001069DOI Listing
December 2019

Tensile Behavior Characteristics of High-Performance Slurry-Infiltrated Fiber-Reinforced Cementitious Composite with Respect to Fiber Volume Fraction.

Materials (Basel) 2019 Oct 13;12(20). Epub 2019 Oct 13.

Department of Civil Engineering, Kangwon National University, 346 Jungang-ro, Samcheok 25913, Korea.

Concrete has high compressive strength, but low tensile strength, bending strength, toughness, low resistance to cracking, and brittle fracture characteristics. To overcome these problems, fiber-reinforced concrete, in which the strength of concrete is improved by inserting fibers, is being used. Recently, high-performance fiber-reinforced cementitious composites (HPFRCCs) have been extensively researched. The disadvantages of conventional concrete such as low tensile stress, strain capacity, and energy absorption capacity, have been overcome using HPFRCCs, but they have a weakness in that the fiber reinforcement has only 2% fiber volume fraction. In this study, slurry infiltrated fiber reinforced cementitious composites (SIFRCCs), which can maximize the fiber volume fraction (up to 8%), was developed, and an experimental study on the tensile behavior of SIFRCCs with varying fiber volume fractions (4%, 5%, and 6%) was carried out through direct tensile tests. The results showed that the specimen with high fiber volume fraction exhibited high direct tensile strength and improved brittleness. As per the results, the direct tensile strength is approximately 15.5 MPa, and the energy absorption capacity was excellent. Furthermore, the bridging effect of steel fibers induced strain hardening behavior and multiple cracks, which increased the direct tensile strength and energy absorption capacity.
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http://dx.doi.org/10.3390/ma12203335DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6829410PMC
October 2019

Comparative Performance of Four Electrodes for Measuring the Electromechanical Response of Self-Damage Detecting Concrete under Tensile Load.

Sensors (Basel) 2019 Aug 21;19(17). Epub 2019 Aug 21.

Department of Civil and Environmental Engineering, Sejong University, 209, Neungdong-ro, Gwangjin-gu, Seoul 05006, Korea.

Self-damage or/and stress-sensing concrete is a promising area of research for measuring the electromechanical response of structural materials using more robust sensors. However, the copper and silver paste sensors widely used in such applications can be expensive and have detrimental effects on the load carrying capacity and durability of the structural systems upon which they are installed. Accordingly, this study compared the performance of four electrode types-conventional copper tape with silver paste (CS), copper film with type 1 carbon tape (CC1), copper film with type 2 carbon tape (CC2), and copper wire and film with type 2 carbon tape (WC2)-to develop an economical and practical electrode for measuring the electromechanical response of self-damage-detecting concrete. The CC1 electrode exhibited comparable performance to the CS electrode in measuring the electromechanical response of self-damage-detecting concrete, despite requiring a longer polarization time (80 s) than the CS electrode (25 s). The CS electrode exhibited a higher damage-sensing capacity (GF), whereas the CC1 electrode exhibited a higher strain-sensing capacity (GF), as well as good damage-sensing capacity. Therefore, the CC1 electrode using copper film with type 1 carbon tape was determined to be the best alternative to the conventional CS electrode.
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http://dx.doi.org/10.3390/s19173645DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6749508PMC
August 2019

Effects of a Short Heat Treatment Period on the Pullout Resistance of Shape Memory Alloy Fibers in Mortar.

Materials (Basel) 2019 Jul 16;12(14). Epub 2019 Jul 16.

Department of Civil Engineering, Hongik University, 72-1 Sangsu-dong, Mapo, Seoul 121-791, Korea.

The feasibility of the crack closure of cementitious composites reinforced with shape memory alloy (SMA) fibers was investigated by performing single-fiber pullout tests. To demonstrate the fast crack closing ability, in this study, a heat treatment (300 °C) was applied for a short time (10 min). A short heat treatment was applied for 10 min, after the slip reached 0.5 mm, to activate the shape memory effects of cold-drawn SMA fibers. Two types of alloys were investigated, NiTi and NiTiNb, with two geometries, either smooth or dog-bone-shaped. During the heat treatment, the pullout stress of the SMA fibers initially decreased due to thermal extension, and then increased after heating for 1-3 min, resulting from the shape memory effects. However, their pullout stress recovery during and after the heat treatment was different for the different alloys and fiber geometries. The NiTi fibers generally produced a higher and faster recovery in terms of their pullout stress than the NiTiNb fibers, while the dog-bone-shaped fibers showed a faster pullout stress recovery than the smooth fibers.
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http://dx.doi.org/10.3390/ma12142278DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6679005PMC
July 2019

Two-Dimensional Vanadium Carbide MXene for Gas Sensors with Ultrahigh Sensitivity Toward Nonpolar Gases.

ACS Sens 2019 Jun 19. Epub 2019 Jun 19.

Materials Research and Education Center, Department of Mechanical Engineering , Auburn University , Auburn , Alabama 36849 , United States.

The sensitive detection of explosive and flammable gases is an extremely important safety consideration in today's industry. Identification of trace amounts of nonpolar analytes at ambient temperatures, however, is still a challenge because of their weak adsorption, and very few studies have been able to achieve it via a chemiresistive mechanism. Herein, we demonstrate the high performance of 2D vanadium carbide MXene (VCT ) gas sensors with ultrahigh sensitivity toward nonpolar gases. The fabricated 2D VCT sensor devices consisting of single-/few-layer 2D VCT on polyimide film were able to detect both polar and nonpolar chemical species including hydrogen and methane with a very low limit of detection of 2 and 25 ppm, respectively, at room temperature (23 °C). The performance of the fabricated VCT gas sensors in detection of nonpolar gases surpasses that of previously reported state-of-the-art gas sensors based on other 2D materials.
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http://dx.doi.org/10.1021/acssensors.9b00303DOI Listing
June 2019

Artifact removal from neurophysiological signals: impact on intracranial and arterial pressure monitoring in traumatic brain injury.

J Neurosurg 2019 May 10;132(6):1952-1960. Epub 2019 May 10.

1Department of Brain and Cognitive Engineering, Korea University, Seoul, South Korea.

Objective: Monitoring intracranial and arterial blood pressure (ICP and ABP, respectively) provides crucial information regarding the neurological status of patients with traumatic brain injury (TBI). However, these signals are often heavily affected by artifacts, which may significantly reduce the reliability of the clinical determinations derived from the signals. The goal of this work was to eliminate signal artifacts from continuous ICP and ABP monitoring via deep learning techniques and to assess the changes in the prognostic capacities of clinical parameters after artifact elimination.

Methods: The first 24 hours of monitoring ICP and ABP in a total of 309 patients with TBI was retrospectively analyzed. An artifact elimination model for ICP and ABP was constructed via a stacked convolutional autoencoder (SCAE) and convolutional neural network (CNN) with 10-fold cross-validation tests. The prevalence and prognostic capacity of ICP- and ABP-related clinical events were compared before and after artifact elimination.

Results: The proposed SCAE-CNN model exhibited reliable accuracy in eliminating ABP and ICP artifacts (net prediction rates of 97% and 94%, respectively). The prevalence of ICP- and ABP-related clinical events (i.e., systemic hypotension, intracranial hypertension, cerebral hypoperfusion, and poor cerebrovascular reactivity) all decreased significantly after artifact removal.

Conclusions: The SCAE-CNN model can be reliably used to eliminate artifacts, which significantly improves the reliability and efficacy of ICP- and ABP-derived clinical parameters for prognostic determinations after TBI.
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http://dx.doi.org/10.3171/2019.2.JNS182260DOI Listing
May 2019

Enhancing Damage-Sensing Capacity of Strain-Hardening Macro-Steel Fiber-Reinforced Concrete by Adding Low Amount of Discrete Carbons.

Materials (Basel) 2019 Mar 21;12(6). Epub 2019 Mar 21.

Department of Civil and Environmental Engineering, Sejong University, 209 Neungdong-ro, Gwangjin-gu, Seoul 05006, Korea.

The effects of adding micro-carbon fibers on the electro-mechanical response of macro-steel fiber-reinforced concretes (MSFRCs) under tension were investigated. Two MSFRCs were investigated and they had identical mortar matrix but different fiber contents: MSFRC1 and MSFRC2 contained 1.0 and 1.5 vol.% fibers, respectively. The volume contents of added micro-carbon fibers were 0 to 1.5 vol.% in MSFRC1 and 0 to 0.75 vol.% in MSFRC2, respectively. The addition of 0.5 vol.% micro-carbon fibers, in both MSFRC1 and MSFRC2, produced significantly enhanced damage-sensing capability and still retained their strain-hardening performance together with multiple micro cracks. However, when the content of carbon fibers was more than 0.5 vol.%, the MSFRCs generated tensile strain-softening behavior and reduced damage-sensing capability. Furthermore, the effects of temperature and humidity on the electrical resistivity of MSFRCs were investigated, as were the effects of adding multi-walled carbon nanotubes on the damage-sensing capability of MSFRCs.
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http://dx.doi.org/10.3390/ma12060938DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6470478PMC
March 2019

Novel index for predicting mortality during the first 24 hours after traumatic brain injury.

J Neurosurg 2018 Dec;131(6):1887-1895

1Department of Brain and Cognitive Engineering, Korea University, Seoul.

Objective: Failure of cerebral autoregulation and subsequent hypoperfusion is common during the acute phase of traumatic brain injury (TBI). The cerebrovascular pressure-reactivity index (PRx) indirectly reflects cerebral autoregulation and has been used to derive optimal cerebral perfusion pressure (CPP). This study provides a method for the use of a combination of PRx, CPP, and intracranial pressure (ICP) to better evaluate the extent of cerebral hypoperfusion during the first 24 hours after TBI, allowing for a more accurate prediction of mortality risk.

Methods: Continuous ICP and arterial blood pressure (ABP) signals acquired from 295 TBI patients during the first 24 hours after admission were retrospectively analyzed. The CPP at the lowest PRx was determined as the optimal CPP (CPPopt). The duration of a severe hypoperfusion event (dHP) was defined as the cumulative time that the PRx was > 0.2 and the CPP was < 70 mm Hg with the addition of intracranial hypertension (ICP > 20 or > 22 mm Hg). The outcome was determined as 6-month mortality.

Results: The cumulative duration of PRx > 0.2 and CPP < 70 mm Hg exhibited a significant association with mortality (p < 0.001). When utilized with basic clinical information available during the first 24 hours after admission (i.e., Glasgow Coma Scale score, age, and mean ICP), a dHP > 25 minutes yielded a significant predictive capacity for mortality (p < 0.05, area under the curve [AUC] = 0.75). The parameter was particularly predictive of mortality for patients with a mean ICP > 20 or > 22 mm Hg (AUC = 0.81 and 0.87, respectively).

Conclusions: A short duration (25 minutes) of severe hypoperfusion, evaluated as lowered CPP during worsened cerebrovascular reactivity during the 1st day after TBI, is highly indicative of mortality.
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http://dx.doi.org/10.3171/2018.7.JNS18995DOI Listing
December 2018

Changes in the gray and white matter of patients with ischemic-edematous insults after traumatic brain injury.

J Neurosurg 2018 10 1:1-11. Epub 2018 Oct 1.

Department of Brain and Cognitive Engineering, Korea University, Seongbuk-gu, Seoul, South Korea.

OBJECTIVE: Gray matter (GM) and white matter (WM) are vulnerable to ischemic-edematous insults after traumatic brain injury (TBI). The extent of secondary insult after brain injury is quantifiable using quantitative CT analysis. One conventional quantitative CT measure, the gray-white matter ratio (GWR), and a more recently proposed densitometric analysis are used to assess the extent of these insults. However, the prognostic capacity of the GWR in patients with TBI has not yet been validated. This study aims to test the prognostic value of the GWR and evaluate the alternative parameters derived from the densitometric analysis acquired during the acute phase of TBI. In addition, the prognostic ability of the conventional TBI prognostic models (i.e., IMPACT [International Mission for Prognosis and Analysis of Clinical Trials in TBI] and CRASH [Corticosteroid Randomisation After Significant Head Injury] models) were compared to that of the quantitative CT measures. METHODS: Three hundred patients with TBI of varying ages (92 pediatric, 94 adult, and 114 geriatric patients) and admitted between 2008 and 2013 were included in this retrospective cohort study. The normality of the density of the deep GM and whole WM was evaluated as the proportion of CT pixels with Hounsfield unit values of 31-35 for GM and 26-30 for WM on CT images of the entire supratentorial brain. The outcome was evaluated using the Glasgow Outcome Scale (GOS) at discharge (GOS score ≤ 3, n = 100). RESULTS: Lower proportions of normal densities in the deep GM and whole WM indicated worse outcomes. The proportion of normal WM exhibited a significant prognostic capacity (area under the curve [AUC] = 0.844). The association between the outcome and the normality of the WM density was significant in adult (AUC = 0.792), pediatric (AUC = 0.814), and geriatric (AUC = 0.885) patients. In pediatric patients, the normality of the overall density and the density of the GM were indicative of the outcome (AUC = 0.751). The average GWR was not associated with the outcome (AUC = 0.511). IMPACT and CRASH models showed adequate and reliable performance in the pediatric and geriatric groups but not in the adult group. The highest overall predictive performance was achieved by the densitometry-augmented IMPACT model (AUC = 0.881). CONCLUSIONS: Both deep GM and WM are susceptible to ischemic-edematous insults during the early phase of TBI. The extent of the secondary injury was better evaluated by analyzing the normality of the deep GM and WM rather than by calculating the GWR.
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http://dx.doi.org/10.3171/2018.5.JNS172711DOI Listing
October 2018

Not lost to follow-up: A rare case of CHILD syndrome in a boy reappears.

JAAD Case Rep 2018 Nov 9;4(10):1010-1013. Epub 2018 Nov 9.

Department of Dermatology, the University of California, Irvine, California.

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http://dx.doi.org/10.1016/j.jdcr.2018.10.001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6232698PMC
November 2018

Enhanced Gas-Sensing Performance of GO/TiO₂ Composite by Photocatalysis.

Sensors (Basel) 2018 Oct 5;18(10). Epub 2018 Oct 5.

Materials Research and Education Center, Auburn University, Auburn, AL 36849, USA.

Few studies have investigated the gas-sensing properties of graphene oxide/titanium dioxide (GO/TiO₂) composite combined with photocatalytic effect. Room temperature gas-sensing properties of the GO/TiO₂ composite were investigated towards various reducing gases. The composite sensor showed an enhanced gas response and a faster recovery time than a pure GO sensor due to the synergistic effect of the hybridization, such as creation of a hetero-junction at the interface and modulation of charge carrier density. However, the issue of long-term stability at room temperature still remains unsolved even after construction of a composite structure. To address this issue, the surface and hetero-junction of the GO/TiO₂ composite were engineered via a UV process. A photocatalytic effect of TiO₂ induced the reduction of the GO phase in the composite solution. The comparison of gas-sensing properties before and after the UV process clearly showed the transition from n-type to p-type gas-sensing behavior toward reducing gases. This transition revealed that the dominant sensing material is GO, and TiO₂ enhanced the gas reaction by providing more reactive sites. With a UV-treated composite sensor, the function of identifying target gas was maintained over a one-month period, showing strong resistance to humidity.
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http://dx.doi.org/10.3390/s18103334DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6210210PMC
October 2018

Two-Dimensional Transition Metal Dichalcogenides and Metal Oxide Hybrids for Gas Sensing.

ACS Sens 2018 10 15;3(10):2045-2060. Epub 2018 Oct 15.

Materials Research and Education Center , Auburn University , Auburn , Alabama 36849 , United States.

Two-dimensional (2D) nanomaterials have demonstrated great potential in the field of gas sensing due to their layered structures. Especially for 2D transition metal dichalcogenides (TMDs), inherent high surface areas and their unique semiconducting properties with tunable band gaps make them compelling for sensing applications. In combination with the general benefits of 2D nanomaterials, the incorporation of metal oxides into 2D TMDs is a recent approach for improving the gas sensing performance of these materials by the synergistic effects of the hybridization. This Review aims to comprehend the sensing mechanisms and the synergistic effects of various hybridizations of 2D TMDs and metal oxides. The Review begins with the gas sensing mechanisms and synthesis methods of 2D TMDs. Achievements in recent research on 2D TMDs and their metal oxide hybrids for sensor applications are then comprehensively compiled. To clearly understand the collective benefits of TMDs and metal oxide hybrids, the hybridization effects are discussed in three aspects: geometrical, electronic, and chemical effects.
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http://dx.doi.org/10.1021/acssensors.8b01077DOI Listing
October 2018

Impaired cerebral compensatory reserve is associated with admission imaging characteristics of diffuse insult in traumatic brain injury.

Acta Neurochir (Wien) 2018 12 24;160(12):2277-2287. Epub 2018 Sep 24.

Section of Brain Physics, Division of Neurosurgery, Department of Clinical Neurosciences, Addenbrooke's Hospital, University of Cambridge, Cambridge, CB2 0QQ, UK.

Background: Continuous assessment of cerebral compensatory reserve is possible using the moving correlation between pulse amplitude of intra-cranial pressure (AMP) and intra-cranial pressure (ICP), called RAP. Little is known about the behavior and associations of this index in adult traumatic brain injury (TBI). The goal of this study is to evaluate the association between admission cerebral imaging findings and RAP over the course of the acute intensive care unit stay.

Methods: We retrospectively reviewed 358 adult TBI patients admitted to the Addenbrooke's Hospital, University of Cambridge, from March 2005 to December 2016. Only non-craniectomy patients were studied. Using archived high frequency physiologic signals, RAP was derived and analyzed over the first 48 h and first 10 days of recording in each patient, using grand mean, percentage of time above various thresholds, and integrated area under the curve (AUC) of RAP over time. Associations between these values and admission computed tomography (CT) injury characteristics were evaluated.

Results: The integrated AUC, based on various thresholds of RAP, was statistically associated with admission CT markers of diffuse TBI and cerebral edema. Admission CT findings of cortical gyral effacement, lateral ventricle compression, diffuse cortical subarachnoid hemorrhage (SAH), thickness of cortical SAH, presence of bilateral contusions, and subcortical diffuse axonal injury (DAI) were all associated with AUC of RAP over time. Joncheere-Terpstra testing indicated a statistically significant increase in mean RAP AUC across ordinal categories of the abovementioned associated CT findings.

Conclusions: RAP is associated with cerebral CT injury patterns of diffuse injury and edema, providing some confirmation of its potential measurement of cerebral compensatory reserve in TBI.
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http://dx.doi.org/10.1007/s00701-018-3681-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6267721PMC
December 2018

How to navigate dermatology care for the uninsured.

J Am Acad Dermatol 2019 06 14;80(6):1809-1813. Epub 2018 Aug 14.

Department of Dermatology, University of California, Irvine, California.

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http://dx.doi.org/10.1016/j.jaad.2018.06.072DOI Listing
June 2019

Validation of Pressure Reactivity and Pulse Amplitude Indices against the Lower Limit of Autoregulation, Part I: Experimental Intracranial Hypertension.

J Neurotrauma 2018 12 4;35(23):2803-2811. Epub 2018 Oct 4.

4 Section of Brain Physics, Division of Neurosurgery, Addenbrooke's Hospital, University of Cambridge , Cambridge, United Kingdom .

The purpose of this study was to provide validation of intracranial pressure (ICP) derived continuous indices of cerebrovascular reactivity against the lower limit of autoregulation (LLA). Utilizing an intracranial hypertension model within white New Zealand rabbits, ICP, transcranial Doppler (TCD), laser Doppler flowmetry (LDF), and arterial blood pressure were recorded. Data were retrospectively analyzed in a cohort of 12 rabbits with adequate signals for interrogating the LLA. We derived continuous indices of cerebrovascular reactivity: PRx (correlation between ICP and mean arterial pressure [MAP]), PAx (correlation between pulse amplitude of ICP [AMP] and MAP), and Lx (correlation between LDF-based cerebral blood flow [CBF] and cerebral perfusion pressure [CPP]). LLA was derived via piecewise linear regression of CPP versus LDF or CPP versus systolic flow velocity (FVs) plots. We then produced error bar plots for PRx, PAx, and Lx against 2.5 mm Hg bins of CPP, to display the relationship between these indices and the LLA. We compared the CPP values at clinically relevant thresholds of PRx and PAx, to the CPP defined at the LLA. Receiver operating curve (ROC) analysis was performed for each index across the LLA using 2.5 mm Hg bins for CPP. The mean LLA was 51.5 ± 8.2 mm Hg. PRx and PAx error bar plots demonstrate that each index correlates with the LLA, becoming progressively more positive below the LLA. Similarly, CPP values at clinically relevant thresholds of PRx and PAx were not statistically different from the CPP derived at the LLA. Finally, ROC analysis indicated that PRx and PAx predicted the LAA, with areas under the curve (AUCs) of 0.795 (95% confidence interval [CI]: 0.731-0.857, p < 0.0001) and 0.703 (95% CI: 0.631-0.775, p < 0.0001), respectively. Both PRx and PAx generally agree with LLA within this experimental model of intracranial hypertension. Further analysis of clinically used indices of autoregulation across the LLA within pure arterial hypotension models is required.
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http://dx.doi.org/10.1089/neu.2017.5603DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6909776PMC
December 2018

Electromechanical Response of High-Performance Fiber-Reinforced Cementitious Composites Containing Milled Glass Fibers under Tension.

Materials (Basel) 2018 Jun 29;11(7). Epub 2018 Jun 29.

Department of Civil and Environmental Engineering, Sejong University, 209, Neungdong-ro, Gwangjin-gu, Seoul 05006, Korea.

The self-damage sensing capacity of high-performance fiber-reinforced cementitious composites (HPFRCCs) that blended long- (1 vol %) and medium-length (1 vol %) smooth steel fibers was considerably improved by adding milled glass fibers (MGFs) with a low electrical conductivity to a mortar matrix. The addition of MGFs (5 wt %) significantly increased the electrical resistivity of the mortar matrix from 45.9 to 110.3 kΩ·cm (140%) and consequently improved the self-damage sensing capacity (i.e., the reduction in the electrical resistivity during the tensile strain-hardening response) from 17.27 to 25.56 kΩ·cm (48%). Furthermore, the addition of MGFs improved the equivalent bond strength of the steel fibers on the basis of the higher pullout energy owing to the accumulated cementitious material particles attached to the surfaces of steel fibers.
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http://dx.doi.org/10.3390/ma11071115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6073221PMC
June 2018

Validation of Davson's equation in patients suffering from idiopathic normal pressure hydrocephalus.

Acta Neurochir (Wien) 2018 05 8;160(5):1097-1103. Epub 2018 Mar 8.

Division of Neurosurgery, Cambridge University Hospital, University of Cambridge Department of Clinical Neuroscience, Cambridge, UK.

Introduction: The so-called Davson's equation relates baseline intracranial pressure (ICP) to resistance to cerebrospinal fluid outflow (Rout), formation of cerebrospinal fluid (I) and sagittal sinus pressure (P) There is a controversy over whether this fundamental equation is applicable in patients with normal pressure hydrocephalus (NPH). We investigated the relationship between Rout and ICP and also other compensatory, clinical and demographic parameters in NPH patients.

Method: We carried out a retrospective study of 229 patients with primary NPH who had undergone constant-rate infusion studies in our hospital. Data was recorded and processed using ICM+ software. Relationships between variables were sought by calculating Pearson product correlation coefficients and p values.

Results: We found a significant, albeit weak, relationship between ICP and Rout (R = 0.17, p = 0.0049), Rout and peak-to-peak amplitude of ICP (AMP) (R = 0.27, p = 3.577e-05) and Rout and age (R = 0.16, p = 0.01306).

Conclusions: The relationship found between ICP and Rout provides indirect evidence to support disturbed Cerebrospinal fluid circulation as a key factor in disturbed CSF dynamics in NPH. Weak correlation may indicate that other factors-variable P and formation of CSF outflow-contribute heavily to linear model expressed by Davson's equation.
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http://dx.doi.org/10.1007/s00701-018-3497-9DOI Listing
May 2018

Mathematical Modelling of CSF Pulsatile Flow in Aqueduct Cerebri.

Acta Neurochir Suppl 2018 ;126:233-236

Division of Neurosurgery, Addenbrookes Hospital, Cambridge, UK.

Objective: The phase-contrast MRI technique permits the non-invasive assessment of CSF movements in cerebrospinal fluid cavities of the central nervous system. Of particular interest is pulsatile cerebrospinal fluid (CSF) flow through the aqueduct cerebri. It is allegedly increased in hydrocephalus, having potential diagnostic value, although not all scientific reports contain unequivocally positive conclusions.

Methods: For the mathematical simulation of CSF flow, we used a computational model of cerebrospinal blood/fluid circulation designed by a former student as his PhD project. With this model, cerebral blood flow and CSF may be simulated in various vessels using a system of non-linear differential equations as time-varying signals.

Results: The amplitude of CSF flow seems to be positively related to the amplitude of pulse waveforms of intracranial pressure (ICP) in situations where mean ICP increases, such as during simulated infusion tests and following step increases of resistance to CSF outflow. An additional positive association between the pulse amplitude of ICP and CSF flow can be seen during simulated increases in the amplitude of arterial pulses (without changes in mean arterial pressure, MAP). The opposite effect can be observed during step increases in the resistance of the aqueduct cerebri and with decreasing elasticity of the system, where the CSF flow amplitude and the ICP pulse amplitude are related inversely. Vasodilatation caused by both gradual decreases in MAP and by increases in PaCO2 provokes an elevation in the observed amplitude of pulsatile CSF flow.

Conclusions: Preliminary results indicate that the pulsations of CSF flow may carry information about both CSF-circulatory and cerebral vasogenic components. In most cases, the pulsations of CSF flow are positively related to the pulse amplitudes of both arterial pressure and ICP and to a degree of cerebrovascular dilatation.
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http://dx.doi.org/10.1007/978-3-319-65798-1_47DOI Listing
July 2018

A national cohort study evaluating infant and fetal mortality caused by birth defects in Korea.

BMJ Open 2017 Nov 15;7(11):e017963. Epub 2017 Nov 15.

Department of Obstetrics and Gynecology, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.

Objective: To analyse the prevalence of fetal and infant deaths due to birth defects in Korea and those trends according to maternal age.

Design: Retrospective national cohort study SETTING: Korean Vital Statistics database of the Korean Statistical Information Service, between 2009 and 2015.

Participants: 2176 infant deaths and 4343 fetal deaths caused by birth defects, among 3 181 145 total live births and 43 385 fetal deaths during the study periods.

Methods: Infant and fetal mortality rates (IMRs and FMRs) by birth defects, from deaths caused by birth defects, were analysed. They were compared, according to maternal age groups: (I) '10-19 years'; (II) '20-29 years'; (III) '30-34 years'; (IV) '35-39 years'; and (V) '40-55 years'.

Main Outcome Measures: IMRs and FMRs by birth defects and comparison according to maternal age group.

Results: IMRs and FMRs by birth defects were 6.84 per 10 000 live births and 13.47 per 10 000 total births. The most common causes of infant deaths and fetal deaths by birth defect were anomaly of the circulatory system (51.1%, IMR 3.5) and chromosomal abnormality (33.1%, FMR 4.46), respectively. Among groups by maternal age, FMRs by birth defects were significantly higher in groups I and V compared with group III (OR 6.59, 95% CI 3.49 to 12.43; and OR 3.46, 95% CI 1.77 to 6.78, respectively). IMR and FMR by nervous system anomaly were significantly higher in group I at 3.63 (OR 2.0, 95% CI 1.97 to 2.03) and 29.84 (OR 15.04, 95% CI 3.59 to 62.96) compared with 0.32 and 1.97 in group III.

Conclusion: FMRs by birth defects were the highest in the extreme maternal age groups. Severe anomalies, except for chromosomal abnormality, were most prevalent in teenage pregnancies.
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http://dx.doi.org/10.1136/bmjopen-2017-017963DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5695452PMC
November 2017

Hemodynamic Instability and Cardiovascular Events After Traumatic Brain Injury Predict Outcome After Artifact Removal With Deep Belief Network Analysis.

J Neurosurg Anesthesiol 2018 Oct;30(4):347-353

Department of Brain and Cognitive Engineering, Korea University.

Background: Hemodynamic instability and cardiovascular events heavily affect the prognosis of traumatic brain injury. Physiological signals are monitored to detect these events. However, the signals are often riddled with faulty readings, which jeopardize the reliability of the clinical parameters obtained from the signals. A machine-learning model for the elimination of artifactual events shows promising results for improving signal quality. However, the actual impact of the improvements on the performance of the clinical parameters after the elimination of the artifacts is not well studied.

Materials And Methods: The arterial blood pressure of 99 subjects with traumatic brain injury was continuously measured for 5 consecutive days, beginning on the day of admission. The machine-learning deep belief network was constructed to automatically identify and remove false incidences of hypotension, hypertension, bradycardia, tachycardia, and alterations in cerebral perfusion pressure (CPP).

Results: The prevalences of hypotension and tachycardia were significantly reduced by 47.5% and 13.1%, respectively, after suppressing false incidents (P=0.01). Hypotension was particularly effective at predicting outcome favorability and mortality after artifact elimination (P=0.015 and 0.027, respectively). In addition, increased CPP was also statistically significant in predicting outcomes (P=0.02).

Conclusions: The prevalence of false incidents due to signal artifacts can be significantly reduced using machine-learning. Some clinical events, such as hypotension and alterations in CPP, gain particularly high predictive capacity for patient outcomes after artifacts are eliminated from physiological signals.
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http://dx.doi.org/10.1097/ANA.0000000000000462DOI Listing
October 2018

Abilities of a Densitometric Analysis of Computed Tomography Images and Hemorrhagic Parameters to Predict Outcome Favorability in Patients With Intracerebral Hemorrhage.

Neurosurgery 2018 08;83(2):226-236

Department of Brain and Cognitive Engi-neering, Korea University, Seoul, South Korea.

Background: Intracerebral hemorrhage (ICH) is one of the most devastating subtypes of stroke. A rapid assessment of ICH severity involves the use of computed tomography (CT) and derivation of the hemorrhage volume, which is often estimated using the ABC/2 method. However, these estimates are highly inaccurate and may not be feasible for anticipating outcome favorability.

Objective: To predict patient outcomes via a quantitative, densitometric analysis of CT images, and to compare the predictive power of these densitometric parameters with the conventional ABC/2 volumetric parameter and segmented hemorrhage volumes.

Methods: Noncontrast CT images of 87 adult patients with ICH (favorable outcomes = 69, unfavorable outcomes = 12, and deceased = 6) were analyzed. In-house software was used to calculate the segmented hemorrhage volumes, ABC/2 and densitometric parameters, including the skewness and kurtosis of the density distribution, interquartile ranges, and proportions of specific pixels in sets of CT images. Nonparametric statistical analyses were conducted.

Results: The densitometric parameter interquartile range exhibited greatest accuracy (82.7%) in predicting favorable outcomes. The combination of skewness and the interquartile range effectively predicted mortality (accuracy = 83.3%). The actual volume of the ICH exhibited good coherence with ABC/2 (R = 0.79). Both parameters predicted mortality with moderate accuracy (<78%) but were less effective in predicting unfavorable outcomes.

Conclusion: Hemorrhage volume was rapidly estimated and effectively predicted mortality in patients with ICH; however, this value may not be useful for predicting favorable outcomes. The densitometric analysis exhibited significantly higher power in predicting mortality and favorable outcomes in patients with ICH.
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http://dx.doi.org/10.1093/neuros/nyx379DOI Listing
August 2018

Room Temperature Gas Sensing of Two-Dimensional Titanium Carbide (MXene).

ACS Appl Mater Interfaces 2017 Oct 11;9(42):37184-37190. Epub 2017 Oct 11.

Materials Research and Education Center, Auburn University , Auburn, Alabama 36849, United States.

Wearable gas sensors have received lots of attention for diagnostic and monitoring applications, and two-dimensional (2D) materials can provide a promising platform for fabricating gas sensors that can operate at room temperature. In the present study, the room temperature gas-sensing performance of TiCT nanosheets was investigated. 2D TiCT (MXene) sheets were synthesized by removal of Al atoms from TiAlC (MAX phases) and were integrated on flexible polyimide platforms with a simple solution casting method. The TiCT sensors successfully measured ethanol, methanol, acetone, and ammonia gas at room temperature and showed a p-type sensing behavior. The fabricated sensors showed their highest and lowest response toward ammonia and acetone gas, respectively. The limit of detection of acetone gas was theoretically calculated to be about 9.27 ppm, presenting better performance compared to other 2D material-based sensors. The sensing mechanism was proposed in terms of the interactions between the majority charge carriers of TiCT and gas species.
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http://dx.doi.org/10.1021/acsami.7b11055DOI Listing
October 2017