Biomedical subjects

Seung Bin Kim

Publications and source records attributed to Seung Bin Kim.

10 recordsLinked to original sources

PubMed2026

Magnesium administration for vasospasm prevention in acute aneurysmal SAH: a multicenter randomized controlled trial.

Aneurysmal subarachnoid hemorrhage (aSAH) is associated with significant morbidity and mortality, with cerebral vasospasm (CV) and delayed cerebral ischemia (DCI) being the primary contributors to poor outcomes. Magnesium sulfate (MgSO₄) has demonstrated neuroprotective and vasodilatory properties in preclinical models. This study aimed to evaluate the effect of targeted serum magnesium (Mg) maintenance on CV and exploratory clinical outcomes following aSAH. We conducted a prospective, multicenter, single-blind RCT across four neurocritical care units in Korea between 2019 and 2024. A total of 121 aSAH patients were randomized to receive either IV MgSO₄or placebo within six hours of admission. Mg was infused to maintain serum concentrations between 2.0 and 3.0 mg/dL for 14 days. The primary outcome was incidence of CV assessed by transcranial doppler. Secondary outcomes included DCI, ICU and hospital length of stay, modified rankin scale (mRS) at 30 days. There was no significant difference in overall CV incidence; however, the Mg group demonstrated significantly lower mean flow velocity and Lindegaard ratio on days 4-9, indicating reduced vasospasm severity. In exploratory multivariable analyses, a median serum Mg concentration > 2.5 mg/dL during the first 14 hospital days was independently associated with lower risks of CV and DCI. No significant differences were found in mRS scores, ICU and hospital stay, or serious adverse events between groups. Early targeted Mg administration improved TCD-derived hemodynamic markers during the peak vasospasm window; however, it did not significantly reduce CV incidence, DCI, ICU or hospital stay, or 30-day functional outcome.

Humans↗

PubMed2006

Two-dimensional heterospectral correlation analysis of wide-angle X-ray scattering and infrared spectroscopy for specific chemical interactions in weakly interacting block copolymers.

We investigated, via two-dimensional heterospectral correlation analysis of wide-angle X-ray scattering (WAXS) and infrared (IR) spectroscopy, the specific chemical interactions existing in weakly interacting polystyrene-block-poly(n-pentyl methacrylate) copolymers (PS-PnPMA). PS-PnPMA was shown to exhibit a closed-loop-type phase behavior, where, upon heating, a lower disorder-to-order transition (LDOT) was found at lower temperatures, and an upper order-to-disorder transition (UODT) was observed at higher temperatures. The specific interaction between the PS and PnPMA blocks mainly arises from the dipole in the benzene ring of PS and the induced dipole in the PnPMA due to cluster formation with a size of 1 approximately 2 nm. We found that the synchronous 2D WAXS-IR heterospectral correlation spectrum of the ordered state was completely different from that in the two disordered states. The CH group of the main chains of PS and PnPMA did not contribute to the cluster formation in the two disordered states, indicating that the main chains of PS and PnPMA blocks were randomly distributed in the two disordered states. However, only the C=C group in the PS block contributed to the cluster at a disordered state below the LDOT, whereas both the C-C-O group in PnPMA and the entire phenyl ring and C=C group in PS contributed to cluster formation at another disordered state above the UODT. Thus, the probability that PS (and PnPMA) chains were located at their own neighboring chains at one disordered state above the UODT is larger than that at another disordered state below the LDOT.

Journal Article↗

PubMed2005

Electrochemistry of conductive polymers. 34. Two-dimensional correlation analysis of real-time spectroelectrochemical data for aniline polymerization.

Electrochemical polymerization of aniline has been studied using real-time spectroelectrochemical experiments conducted concurrently with potentiodynamic scans in a nitric acid electrolyte with its pH adjusted to 0.50. Two-dimensional correlation spectral analysis and subsequent extraction of pure component spectra as well as their relative concentration profiles from complex spectroelectrochemical data employing the alternating least-squares regression iteration-based self-modeling curve resolution method led to positive identification of intermediate species. A conclusion was reached on the polymerization reaction mechanism based on these intermediate species and how their concentrations increased or decreased during the potential scans. The mechanism thus concluded represents a summary of a current understanding of the aniline polymerization reaction.

Journal Article↗

PubMed2004

Two-dimensional correlation analysis of spectroelectrochemical data for p-benzoquinone reduction in acetonitrile.

Two-dimensional (2D) spectral correlation analysis has been employed to interpret the complex spectroelectrochemical data obtained from an electrochemical system undergoing following reactions after electron transfer. The system used was electrochemical reduction of p-benzoquinone (p-BQ) in acetonitrile, which produces anion radicals and dianions at its first and second reduction potentials. The dianions undergo a fast comproporationation reaction with neutral p-BQ molecules to produce anion radicals back, complicating the spectral analysis. Upon application of 2D correlation analysis in conjunction with the self-modeling curve resolution technique, we were able not only to resolve the spectra and determine the sequence of spectral emergence but also to extract the individual spectra. The techniques offer a very powerful tool for interpreting highly convoluted spectra obtained from a system where a series of chemical reactions occur following the electron transfer at the electrode/electrolyte interface.

Journal Article↗

PubMed2004

Mechanism of growth of colloidal silver nanoparticles stabilized by polyvinyl pyrrolidone in gamma-irradiated silver nitrate solution.

Silver nanoparticles were prepared by using polyvinyl pyrrolidone (PVP) as a stabilizer and gamma-irradiation. Transmission electron microscopy (TEM) results showed that both the amount and the molecular weight of PVP in the irradiated solution considerably affect the average size of the silver nanoparticles. The average size of the silver nanoparticles decreases with increasing the amount of PVP in the solution, but increases with increasing its molecular weight. Further, TEM showed that the silver nanoparticles become disassembled into smaller nanoparticles after dilution with distilled water and sonication. Since the processes of dilution and sonication are not expected to result in chemical reactions or to split the silver nanoparticles, we conclude that each silver nanoparticle prepared by [Formula: see text] -irradiation consists of several smaller nanoparticles surrounded by PVP. Thus, based on these observations, we propose a three-step mechanism for the growth of the silver nanoparticles under the conditions considered here. In the first step, the silver ions interact with PVP, then in the second step the silver ions that are exposed to gamma-irradiation are reduced to silver atoms; nearby silver atoms then aggregate at close range. These aggregates are the primary nanoparticles. Finally, these primary nanoparticles coalesce with other nearby primary nanoparticles or interact with PVP to form larger aggregates which are the secondary (final) nanoparticles.

Journal Article↗

PubMed2004

Characterization of the structures of size-selected TiO2 nanoparticles using X-ray absorption spectroscopy.

To investigate the relationship between the size and structure of TiO(2) nanoparticles, three size-selected samples of TiO(2) nanoparticles were prepared via a hydrolysis method that uses Ti[OCH(CH(3))(2)](4) as the starting material. The structures of the nanoparticles were characterized using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray absorption spectroscopy (XAS). Analysis of the XRD patterns and of the TEM images showed that the samples were dispersed, with an average particle size of approximately 30 nm (sample A), approximately 12 nm (sample B), and approximately 7 nm (sample C). Their X-ray absorption spectra indicate that samples A and B have an anatase structure, whereas sample C has a structure very similar to that of the TiO( 2) II phase, which generally arises only under high-pressure conditions. This difference can be attributed to size-induced radial pressure within the smaller nanoparticles, which plays an important role in the phase of TiO(2) nanoparticles in sample C.

Macromolecular Substances↗

PubMed2003

New approach to generalized two-dimensional correlation spectroscopy. II: Eigenvalue manipulation transformation (EMT) for noise suppression.

This paper introduces the concept of eigenvalue manipulating transformation (EMT) of a data matrix for noise suppression in two-dimensional (2D) correlation spectroscopy. The FT-IR spectra of a polystyrene/methyl ethyl ketone/toluene solution mixture during the solvent evaporation process, to which were added a substantial amount of artificial noise, have been analyzed. By uniformly raising the power of a set of eigenvalues, the major eigenvalues become more prominent. As a consequence, minor eigenvectors representing the noise component are no longer strongly represented in the reconstructed data. This EMT operation is similar to the simple truncation of noise-dominated minor factors practiced in standard principal component analysis (PCA), as demonstrated in our preceding paper on PCA-2D correlation spectroscopy. The effect of this new EMT scheme is more gradual, with attractive flexibility to continuously fine-tune the balance between the desired noise reduction effect and the retention of pertinent spectral information.

Algorithms↗

PubMed2003

New approach to generalized two-dimensional correlation spectroscopy. III: Eigenvalue manipulation transformation (EMT) for spectral selectivity enhancement.

This paper demonstrates the potential of eigenvalue manipulating transformation (EMT) of a data matrix for spectral selectivity enhancement, especially useful in 2D correlation analysis. The EMT operation aims at the accentuation of select features of the information content of the original data matrix. For example, by uniformly lowering the power of a set of eigenvalues associated with the original data, the smaller eigenvalues become more prominent and the contributions of secondary loadings become amplified. As a direct consequence of the minor factor accentuation by such EMT operations, 2D correlation spectra gain much stronger discriminating power. The selectivity enhancement effect of such manipulation of eigenvalues is much more noticeable on the synchronous 2D correlation spectrum. This improvement for the spectral selectivity of synchronous 2D correlation spectra is potentially very important, as we usually put more emphasis on the interpretation of asynchronous 2D spectra in 2D correlation analysis due to overlaps of synchronous peaks. Such EMT operations tend to exaggerate the information content of minor PCs and reduce that of major PCs. Thus, much more subtle difference of spectral behavior for each component is now highlighted. Surprisingly, asynchronous 2D correlation spectra are found to be much less sensitive to such EMT operations. The result indicates that the distinction of different band responses has already been accomplished effectively by the original asynchronous 2D correlation analysis.

Algorithms↗

PubMed2003

New approach to generalized two-dimensional correlation spectroscopy. IV: eigenvalue manipulation transformation (EMT) for partial attenuation of dominant factors.

This paper extends our previous work on the potential of eigenvalue manipulating transformation (EMT) of a data matrix for spectral selectivity enhancement in two-dimensional (2D) correlation analysis. EMT operation by uniformly lowering the power of a set of eigenvalues associated with the original data exaggerates the information content of minor principal components and reduces that of major principal components. Thus, much more subtle differences of spectral behavior for each component are now highlighted. Similarly, the selective truncation of dominant principal component (PC) factors to bring up the subtle contributions of minor factors is also considered. The EMT-reconstructed data matrix where power parameter m is negative greatly reduces the contribution of the first PC. Hybrid models for the attenuation of the contribution of the first PC are discussed. Synchronous 2D correlation spectra from PC1-attenuated data matrix A** obtained by varying the value of the attenuation parameter k show a much more profound effect than asynchronous 2D correlation spectra. As the value of k is increased, features of 2D correlation spectra start looking very much like those from the principle component analysis (PCA)-reconstructed data with only the second and third PCs and from the EMT-reconstructed data matrix where the power parameter m is negative.

Artifacts↗

PubMed2003

Characterization of the electrochemical reactions in the Li(1+x)V3O8/Li cell by soft X-ray absorption spectroscopy and two-dimensional correlation analysis.

We applied soft X-ray absorption spectroscopy (XAS) and two-dimensional (2D) correlation analysis to the first lithium insertion-extraction cycle in a Li(1+x)V3O8/Li cell in order to investigate the electrochemical reactions of lithium with the Li(1+x)V3O8 electrode. The V L(II,III)-edge and O K-edge spectra of the Li(1+x)V3O8 electrode were obtained for varying electrode lithium content. The insertion of lithium leads to the reduction of the V5+ species present in the pristine Li(1+x)V3O8 electrode, and to the red shift and the broadening of the spectral features of the V L(II,III) edge compared to those of the pristine electrode. In the extraction process, the main spectral features at the highest value of the extraction of lithium show some differences compared to the features of the pristine electrode spectrum due to the residual lithium ions in the Li(1+x)V3O8 structure. The O K-edge spectra revealed that the insertion of lithium mainly affects the V 4sp-O 2p bonds and consequently induces a change in bonding geometry. The 2D correlation analysis of these spectra clearly shows that V-O bonds are significantly perturbed by the insertion-extraction of lithium into the Li(1+x)V3O8 electrode.

Electrochemistry↗