Publications by authors named "Hyeokjun Kwon"

Over the past decade, new psychoactive substances (NPS) have emerged in the illegal drug market and have continued to attract attention from the international community. Among these, amphetamine-like NPS, classified as stimulants, constitute a significant proportion. However, the pharmacological characteristics and mechanisms underlying addiction to amphetamine-like NPS remain poorly understood.

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The current study was conducted to confirm the characteristics in sexual homicide and to explore variables that effectively differentiate sexual homicide and nonsexual homicide. Further, newer methods that have received attention in criminology, such as the machine learning method, were used to explore the ideal algorithm for classifying sexual homicide and patterns for sexual homicide in Korea. To do this, 542 homicide cases were analyzed utilizing eight algorithms, and the classification performance of each algorithm was analyzed along with the importance of variables.

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N-Labeled azides are important probes for infrared and magnetic resonance spectroscopy and imaging. They can be synthesized by reaction of primary amines with a N-labeled diazo-transfer reagent. We present the synthesis of N-labeled 2-azido-1,3-dimethylimidazolinium salts as a N-labeled diazo-transfer reagent.

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Shoulder impingement syndrome can be caused by a muscle imbalance around the shoulder joint. It would be beneficial for therapy to implement rehabilitation exercises based on intermuscular coordination in order to achieve muscle balance. This study presents the muscle synergy characteristics of patients with shoulder impingement syndrome, which can be used to develop rehabilitation exercises.

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Abnormal intermuscular coordination in stroke-affected upper limbs contributes to motor deficits after stroke. In particular, abnormalities in the activation of upper limb muscle synergies after stroke were demonstrated for endpoint force control during isokinetic exercises. This study aimed to investigate the feasibility of isokinetic training to alter these abnormal synergy activations and improve motor control.

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Intrinsically stretchable organic light-emitting diodes (ISOLEDs) are becoming essential components of wearable electronics. However, the efficiencies of ISOLEDs have been highly inferior compared with their rigid counterparts, which is due to the lack of ideal stretchable electrode materials that can overcome the poor charge injection at 1D metallic nanowire/organic interfaces. Herein, highly efficient ISOLEDs that use graphene-based 2D-contact stretchable electrodes (TCSEs) that incorporate a graphene layer on top of embedded metallic nanowires are demonstrated.

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Azides are infrared (IR) probes that are important for structure and dynamics studies of proteins. However, they often display complex IR spectra owing to Fermi resonances and multiple conformers. Isotopic substitution of azides weakens the Fermi resonance, allowing more accurate IR spectral analysis.

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The infrared (IR) probe often suffers from an unexpected complex absorption profile due to the Fermi resonance and short vibrational lifetime, which restricts the application of time-resolved IR spectroscopy to investigate the site-specific structural dynamics of the protein. Researchers have found that isotope substitution to the IR probe not only removes the Fermi resonance but also extends the dynamic observation window with a prolonged vibrational lifetime. This method has been successfully applied to modify the vibrational properties of many IR probes for time-resolved spectroscopy and imaging.

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Article Synopsis
  • Azido stretch modes in azido-derivatized amino acids and nucleotides serve as infrared (IR) probes for monitoring structural and electrostatic changes.
  • Isotope substitution using 15N helps eliminate Fermi resonance effects and clarifies vibrational properties, leading to more distinct spectral lines.
  • Combined approaches of isotope labeling and 2D-IR spectroscopy provide effective insights into hidden resonances, allowing clearer identification of shoulder peaks in IR spectra.
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The origin of quantum coherence in two-dimensional (2D) electronic spectra of molecular aggregates and light-harvesting complexes still remains an open question. In particular, it could be challenging to distinguish between electronic and vibrational coherences for a coupled system, where both degrees of freedom can be simultaneously excited. In this Letter, we examine quantum beats in the 2D spectra of zinc naphthalocyanine (ZnNc) aggregate and monomer, and compare their characteristic features in terms of the frequency and relative phase of diagonal and off-diagonal amplitude oscillations.

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4-Azidoproline (Azp) can tune the stability of the polyproline II (P(II)) conformation in collagen. The azido group in the 4R and 4S configurations stabilizes and destabilizes the P(II) conformation, respectively. To obtain insights into the dependence of the conformational stability on the azido configuration, we carried out Fourier transform (FT) IR experiments with four 4-azidoproline derivatives, Ac-(4R/S)-Azp-(NH/O)Me.

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