LIGHT-HARVESTING AND LIGHT-RESPONSIVE MATERIALS FOR OPTOELECTRONIC AND BIOLOGICAL APPLICATIONS

In photodynamic therapy, several critical standards are required of photosensitizers including high singlet oxygen quantum yield, biocompatibility in dark, and long term photochemical stability. In addition, current PDT systems lack active targeting strategies to tumor cells, and instead mainly rely on the natural distribution of PS in the body following injection and application of near-infrared light treatment in the tumor region. This thesis describes a series of BODIPY-based molecules that were designed, synthesized and studied as photosensitizers with high singlet oxygen generation capacity through utilizing the heavy atom effect. Additionally, aqueous solubility and active targeting capability were introduced by photosensitizer conjugation to hyaluronic acid, a biocompatible natural polymer that binds CD44+ receptors on cancer cells such as HeLa. A small degree of BODIPY substitution on the nontoxic hyaluronic acid polymer backbone allowed overall viability of the PS in dark, but controlled cytotoxicity was observed upon application of near-infrared LED light. Cytotoxicity studies also established the cell selective cytotoxicity of the hyaluronic acid-BODIPY conjugates, verifying their candidacy for photodynamic applications. In the field of molecular amplification, self-immolative materials have been widely used for various biological applications including drug delivery, biomarker detection, imaging, and sensing. Traditionally, the chemical design of self-immolative polymer or dendrimer backbones include reporters or prodrugs in their monomeric structure. In such systems, the extend of stimuli-induced amplified signal and release of reporters or prodrugs is directly rely on the degree of polymerization or dendrimer generation. Here, we discuss the design, synthesis, and study of an oligomeric self-immolative polymeric system that produces a morphological signal output as a macroscopic response to a molecular-level stimulus through signal amplification. For this aim, we developed a gel that undergoes a gel-sol transition upon application of light to demonstrate this amplification behavior. In this system, stimuli triggers modification in chemical structure of self-immolative polymer that presence in catalytic amount in the gel, which leads to macroscopic morphological transition. Since this macroscopic morphological change driven by catalytic polymer, the extend of amplified signal in this system is not directly dependent on the degree of polymerization. Successful demonstration of such a system will help achieve rapid and reliable signal amplification. Organic photovoltaics are an attractive alternate technology to traditional inorganic photovoltaics due to their relatively low weight and feasibility of processing into flexible large panels. Polymer-based organic photovoltaics have been investigated for their efficient charge carrier generation, owing to their low band gap through extensive conjugation. Simultaneously, small molecule based organic photovoltaics have also been developed due to their advantages over polymer-based organic photovoltaics, including facile purification with well-defined monodisperse structural properties, as well as tunable frontier orbital energy alignment. One of the strategies to improve organic photovoltaics performance is developing active materials with a great light-harvesting property for optimal complementarity to the solar energy spectrum. BODIPY molecules are appropriate candidates due to their favorable features as a light-harvesting material, including high extinction coefficients, high photochemical stability, and a relatively easy preparation process. In addition, their frontier energy levels are finely tunable through incorporating with various core structures of different electronegativities. However, their strong absorption profile of simple BODIPY is narrow and limited to visible range (~500 nm). To expand upon the previously reported benefits of BODIPY molecules, we discuss broadening of light absorption profile towards near-infrared through alpha-conjugation extension of BODIPY molecules. Utilizing BODIPY that absorbs into the near-infrared region with high absorption coefficients would allow efficient absorbance of the incident light even in thin films, contributing to enhanced organic photovoltaic performances.

Correlations between regional characteristics of counties and the ratio of intracounty to extracounty sources of COVID-19 in Gangwon Province, Republic of Korea

Objectives This study aimed to examine the correlations between the regional characteristics of counties in Gangwon Province, Republic of Korea and the ratio of intracounty to extracounty sources of coronavirus disease 2019 (COVID-19) infection. Methods The region of the infectious contact was analysed for each COVID-19 case reported in Gangwon Province between February 22, 2020 and February 7, 2022. The population, population density, area, the proportion of urban residents, the proportion of older adults (>65 years), financial independence, and the number of adjacent counties were assessed for each of the 18 counties in Gangwon Province. Correlation coefficients between regional characteristics and the ratio of intracounty to extracounty infections were calculated. Results In total, 19,645 cases were included in this study. The population, population density, proportion of older adults, and proportion of urban residents were significantly correlated with the ratio of intracounty to extracounty infections. A stratified analysis with an age cut-point of 65 years showed that the proportion of older adults had a significant negative correlation with the ratio of intracounty to extracounty infections. In other words, the proportions of extracounty infections were higher in counties with higher proportions of older adults. Conclusion Regions with ageing populations should carefully observe trends in infectious disease outbreaks in other regions to prevent possible transmission

Exercise Training Attenuates Ovariectomy-Induced Alterations in Skeletal Muscle Remodeling, Apoptotic Signaling, and Atrophy Signaling in Rat Skeletal Muscle

Purpose The effects of aerobic exercise training on soleus muscle morphology, mitochondria-mediated apoptotic signaling, and atrophy/hypertrophy signaling in ovariectomized rat skeletal muscle were investigated. Methods Female Sprague-Dawley rats were divided into control (CON), ovariectomy (OVX), and ovariectomy plus exercise (OVX+EX) groups. After ovarian excision, exercise training was performed using a rat treadmill at 20 m/min, 50 min/day, 5 days/week for 12 weeks. Protein levels of mitochondria-mediated apoptotic signaling and atrophy/hypertrophy signaling in the skeletal muscle (soleus) were examined through western immunoblot analysis. Results The number of myocytes and myocyte cross-sectional area (CSA) were increased and the extramyocyte space was decreased in the OVX group compared to those in the CON group. However, aerobic exercise training significantly increased myocyte CSA and decreased extramyocyte space in the OVX+EX group compared to those in the OVX group. The protein levels of proapoptotic signaling and muscle atrophy signaling were significantly increased, whereas the protein levels of muscle hypertrophy signaling were significantly decreased in the OVX group compared to that in the CON group. Aerobic exercise training significantly decreased the protein levels of proapoptotic signaling and increased the protein level of antiapoptotic protein in the OVX+EX group compared to that in the OVX group. Aerobic exercise training significantly increased the protein levels of hypertrophy signaling and decreased protein levels of atrophy signaling in the OVX+EX group compared to those in the OVX group. Conclusions Treadmill exercise improved estrogen deficiency-induced impairment in skeletal muscle remodeling, mitochondria-mediated apoptotic signaling, and atrophy/hypertrophy signaling in skeletal muscle

Analysis of a Low-Earth Orbit Satellite Downlink Considering Antenna Radiation Patterns and Space Environment in Interference Situations

This paper investigates a low-Earth orbit (LEO) satellite downlink for high-speed data communication in interference situations. A choke ring horn type antenna is used as the data transmitting antenna with an isoflux pattern in the LEO satellite, which has a beam coverage of ±51.6° and a bore-sight gain of 4.4 dBi at 8 GHz. The receiving antenna on the ground station is a parabolic type antenna with a diameter of 11.3 m, and it has a half-power beam width (HPBW) of 0.2° with a maximum gain of 59 dBi at 8 GHz. The jamming-to-signal ratio (J/S) is calculated assuming that the LEO satellite transmits signals to the ground station, and an elevation angle of the interference source varies from 0° to 90° at an altitude of 10 km. Applying antenna characteristics, such as HPBWs and side lobes, to the calculated space wave path loss makes it possible to predict the J/S results according to the location of the interference source and the satellite. The results show that it is necessary to consider the space environment to accurately analyze the LEO satellite downlink, especially at the low elevation angle of the satellite

Photophysical and Electrochemical Characterization of BODIPY-Containing Dyads Comparing the Influence of an A–D–A versus D–A Motif on Excited-State Photophysics

A complete photophysical characterization of organic molecules designed for use as molecular materials is critical in the design and construction of devices such as organic photovoltaics (OPV). The nature of a molecule’s excited state will be altered in molecules employing the same chromophoric units but possessing different molecular architectures. For this reason, we examine the photophysical reactions of two BODIPY-based D–A and A–D–A molecules, where D is the donor and A is the acceptor. A BODIPY (4,4′-difluoro-4-bora-3a,4a-diaza-<i>s</i>-indacene) moiety serves as the A component and is connected through the <i>meso</i> position using a 3-hexylthiophene linker to a <i>N</i>-(2-ethylhexyl)­dithieno­[3,2-<i>b</i>:2′,3′-<i>d</i>]­pyrrole (DTP), which serves as the D component. An A–D–A motif is compared to its corresponding D–A dyad counterpart. We show a potential advantage to the A–D–A motif over the D–A motif in creating longer-lived excited states. Transient absorption (TA) spectroscopy is used to characterize the photophysical evolution of each molecule’s excited state. Global analysis of TA data using singular value decomposition and target analysis is performed to identify decay-associated difference spectra (DADS). The DADS reveal the spectral features associated with charge-transfer excited states that evolve with different dynamics. A–D–A possess slightly longer excited-state lifetimes, 42 ps nonradiative decay, and 4.64 ns radiative decay compared to those of D–A, 24 ps nonradiative decay, and 3.95 ns radiative decay. A longer lived A–D–A component is observed with microsecond lifetimes, representing a small fraction of the total photophyscial product. Steady-state and time-resolved photoluminescence augment the insights from TA, while electrochemistry and spectroelectrochemistry are employed to identify the nature of the excited state. Density functional theory supports the observed electronic and electrochemical properties of the D–A and A–D–A molecules. These results form a complete picture of the electronic and photophysical properties of D–A and A–D–A and provide contextualization for structure–function relationships between molecules and OPV devices

Development of an ultrasound-imaging procedure and acquisition of ultrasound images of acupuncture points for safety and accuracy of needle insertion

Background: Acupuncture is a relatively safe, commonly used âalternativeâ medical treatment for various symptoms. However, adverse effects can occur, including trauma, pneumothorax, and central-nervous-system injury. Our objective was to develop a reliable and practical procedure for ultrasound imaging of acupuncture points to improve safety during needling, and to acquire ultrasound images of several (44) acupuncture points, especially those in high-risk areas, according to an in-house standard operating procedure. Methods: We created the standard operating procedure for ultrasound imaging for acupuncture, and collected ultrasound images of acupuncture points in clinical trials. Results: Ultrasound images for 44 acupuncture points considered as high-risk points were collected from 85 healthy people who were classified by body-mass index, and high-quality, clear representative images of all 44 points were obtained. Conclusion: These baseline images could be helpful for understanding the anatomy under the skin at acupuncture points, which would allow for an enhanced safety and more accurate needling. Keywords: acupuncture methods, trauma, ultrasonograph

Improved Performances in Polymer BHJ Solar Cells Through Frontier Orbital Tuning of Small Molecule Additives in Ternary Blends

Polymer solar cells fabricated in air under ambient conditions are of significant current interest, because of the implications in practicality of such devices. However, only moderate performance has been obtained for the air-processed devices. Here, we report that enhanced short circuit current density (<i>J</i>_SC) and open circuit voltage (<i>V</i>_OC) in air-processed poly­(3-hexylthiophene) (P3HT)-based solar cells can be obtained by using a series of donor–acceptor dyes as the third component in the device. Power conversion efficiencies up to 4.6% were obtained upon addition of the dyes which are comparable to high-performance P3HT solar cells fabricated in controlled environments. Multilayer planar solar cells containing interlayers of the donor–acceptor dyes, revealed that along with infrared sensitization, an energy level cascade architecture and Förster resonance energy transfer could contribute to the enhanced performance

Crystallinity and Morphology Effects on a Solvent-Processed Solar Cell Using a Triarylamine-Substituted Squaraine

2,4-Bis­[4′-(<i><i>N,N</i></i>-di­(4″-hydroxyphenyl)­amino)-2′,6′-dihydroxyphenyl]­squaraine (Sq-TAA-OH, optical bandgap 1.4 eV, HOMO level −5.3 eV by ultraviolet photoelectron spectroscopy) is used as an active layer material in solution processed, bulk-heterojunction organic photovoltaic cells with configuration ITO/PEDOT:PSS/Sq-TAA-OH:PC₇₁BM/LiF/Al. Power conversion efficiencies (PCEs) up to 4.8% are obtained by a well-reproducible procedure using a mixture of good and poor Sq-TAA-OH solubilizing organic solvents, with diiodooctane (DIO) additive to make a bulk heterojunction layer, followed by thermal annealing, to give optimized <i>V</i>_OC = 0.84–0.86 V, <i>J</i>_SC = 10 mA cm^–2, and FF = 0.53. X-ray diffraction and scattering studies of pristine, pure Sq-TAA-OH solution-cast films show <i>d</i>-spacing features similar to single-crystal packing and spacing. The DIO additive in a good solvent/poor solvent mixture apparently broadens the size distribution of Sq-TAA-OH crystallites in pristine films, but thermal annealing provides a narrower size distribution. Direct X-ray diffraction and scattering morphological studies of “as-fabricated” active layers show improved Sq-TAA-OH/PC₇₁BM phase separation and formation of crystallites, ∼48 nm in size, under conditions that give the best PCE