Hybridized Local and Charge-Transfer Excited-State Emitter for a Blue Organic Solid-State Laser.

The use of triplet excitons harvesting and short exciton lifetime organic emitters is important to improve the exciton utilization in organic semiconductor laser diodes. In this study, a hybridized local and charge-transfer (HLCT)-type molecule, 11-(3-(10-(4-(1-phenyl-1H-phenanthro[9,10-d]imidazol-2-yl)phenyl)anthracen-9-yl)phenyl)-11H-benzofuro[3,2-b]carbazole (PhAnMBf), is used as an emitter for blue-emitting organic solid-state lasers (OSSLs). The short exciton lifetime and high photoluminescence quantum yield of the PhAnMBf emitter allowed the fabrication of an organic laser with an emission wavelength of 453 nm, a small full width at half-maximum of 1.2 nm, and a threshold of 105 nJ/pulse, corresponding to 44 µJ/cm2, on the distributed feedback substrate. The anthracene-based PhAnMBf material showed the potential of the HLCT emitter as an OSSL.

Key Factor Managing the Horizontal Emitting Dipole Orientation of a Thermally Activated Delayed Fluorescence Emitter in a Mixed Host.

Horizontal emitting dipole orientation (EDO) of thermally activated delayed fluorescence (TADF) molecules in a mixed host was studied by altering the host materials and host composition of the mixed host to gain insight into the important parameter of the host governing the EDO of TADF emitters. Five different host materials were combined with 1,3-bis(carbazol-9-yl)benzene (mCP), demonstrating that the host-dopant interaction is crucial to the absolute value of the horizontal EDO of the TADF emitters, whereas the glass transition temperature (Tg) is the important parameter determining the EDO dependence upon host composition. The mixed host of mCP with a high Tg host maintained high horizontal EDO in the mCP poor host composition, while that of mCP with a low Tg host showed average horizontal EDO of two hosts. Therefore, the combination of a high Tg n-type host enabling a strong host-dopant interaction with the p-type host with the usage of the n-type-host-rich composition is effective to achieve high horizontal EDO in the mixed-host-based TADF emitting layer.

Ancient DNA of Metagonimus yokogawai Recovered from Joseon Period Human Remains Newly Discovered at Goryeong County in South Korea.

PURPOSE: Metagonimiasis, commonly seen in East Asian countries, is a parasitic disorder caused by definitive hosts' ingestion of undercooked freshwater fishes. Recently, genetic analysis has proved 28S rRNA and cytochrome c oxidase subunit I (COI) mtDNA gene to be a successful marker differentiating species of the genus Metagonimus. In the present study, using specimens from the newly discovered Joseon Dynasty human remains of Goryeong, we obtained updated genetic data on genus Metagonimus, which was also prevalent during the Joseon period. METHODS: The ancient DNA (aDNA) was retrieved from the coprolite sample of the seventeenth century, half-mummified individual discovered at Goryeong Country, South Korea. Cloning and sequencing were performed on PCR-amplified amplicons for M. yokogawai 28S rRNA and COI mtDNA gene. The consensus sequences were used for species identification and phylogenetic analysis using NCBI/BLAST and MEGA X software. RESULTS: Based on the COI mtDNA gene region, the Goryeong sequence was confirmed as belonging to M. yokogawai, as it was shown to form a separate cluster with other M. yokogawai taxa that are distinct also from M. takahashii and M. miyatai. CONCLUSION: In a series of our genetic analyses on genus Metagonimus using samples retrieved from Joseon-period cases, aDNA sequences of genus Metagonimus revealed in South Korea thus far are those of M. yokogawai, but not of M. miyatai or M. takahashii yet.

Modeling Electron-Transfer Degradation of Organic Light-Emitting Devices.

The operational lifetime of organic light-emitting devices (OLEDs) is governed primarily by the intrinsic degradation of the materials. Therefore, a chemical model capable of predicting the operational stability is highly important. Here, a degradation model for OLEDs that exhibit thermally activated delayed fluorescence (TADF) is constructed and validated. The degradation model involves Langevin recombination of charge carriers on hosts, followed by the generation of a polaron pair through reductive electron transfer from a dopant to a host exciton as the initiation steps. The polarons undergo spontaneous decomposition, which competes with ultrafast recovery of the intact materials through charge recombination. Electrical and spectroscopic investigations provide information about the kinetics of each step in the operation and degradation of the devices, thereby enabling the building of mass balances for the key species in the emitting layers. Numerical solutions enable predictions of temporal decreases of the dopant concentration in various TADF emitting layers. The simulation results are in good agreement with experimental operational stabilities. This research disentangles the chemical processes in intrinsic electron-transfer degradation, and provides a useful foundation for improving the longevity of OLEDs.

Dual Mode Radiative Transition from a Phenoselenazine Derivative and Electrical Switching of the Emission Mechanism.

Dual emission featuring both thermally activated delayed fluorescence (TADF) and phosphorescence was engineered into a single metal-free molecule, phenyl(10-phenyl-10H-phenoselenazin-3-yl)methanone. Selenium incorporated into the molecule increases the spin-orbit coupling to facilitate both TADF and phosphorescence, whereas donor-acceptor units promote TADF emission. The relative contribution of the green TADF and yellow phosphorescence can be controlled by the driving voltage of the devices. At low voltage, phosphorescence emission dominates the electroluminescence, whereas TADF is the major component at high voltages. The mechanism of dual emission was explored using experimental and theoretical methods.

Conformation-dependent degradation of thermally activated delayed fluorescence materials bearing cycloamino donors.

Organic light-emitting devices (OLEDs) containing organic molecules that exhibit thermally activated delayed fluorescence (TADF) produce high efficiencies. One challenge to the commercialization of the TADF OLEDs that remains to be addressed is their operational stability. Here we investigate the molecular factors that govern the stability of various archetypal TADF molecules based on a cycloamino donor-acceptor platform. Our results reveal that the intrinsic stability depends sensitively on the identity of the cycloamino donors in the TADF compounds. The rates and photochemical quantum yields of the degradation are positively correlated with the operation lifetimes of the devices. Our research shows that the stability is governed by the conformeric heterogeneity between the pseudo-axial and pseudo-equatorial forms of the cycloamino donor. Spontaneous bond dissociation occurs in the former (i.e., the pseudo-axial form), but the cleavage is disfavored in the pseudo-equatorial form. These findings provide valuable insights into the design of stable TADF molecules.

Cohnella saccharovorans sp. nov., isolated from ginseng soil.

A novel bacterial strain, CJ22T, was isolated from soil of a ginseng field located in Anseong, Korea. Cells of strain CJ22T were aerobic, Gram-stain-positive, endospore-forming, motile, oxidase- and catalase-positive and rod-shaped. The isolate grew optimally at pH 7 and 30 °C. Phylogenetic analysis based on the 16S rRNA gene sequence revealed that strain CJ22T belonged to the genus Cohnella, displaying highest sequence similarity of 97.3% with Cohnella panacarvi Gsoil 349T. DNA-DNA relatedness between strain CJ22T and its closest relative was 35.5 % (reciprocal value, 23.8%). The phenotypic features of strain CJ22T also distinguished it from related species of the genus Cohnella. The diagnostic diamino acid in the cell-wall peptidoglycan was meso-diaminopimelic acid. The major isoprenoid quinone was menaquinone MK-7 and the major polar lipids were phosphatidylglycerol, phosphatidylethanolamine, diphosphatidylglycerol, lysyl-phosphatidylglycerol, two unidentified phospholipids and two unidentified aminophospholipids. The predominant cellular fatty acids of strain CJ22T were anteiso-C15 : 0, iso-C16:0 and C16:0. The DNA G+C content was 63.1 mol%. Based on data from this polyphasic taxonomic study, strain CJ22T is considered to represent a novel species of the genus Cohnella, for which the name Cohnella saccharovorans sp. nov. is proposed. The type strain is CJ22T (=KACC 17501T=JCM 19227T).

Broadband high-reflective distributed Bragg reflectors based on amorphous silicon films for semiconductor laser facet coatings.

We fabricated amorphous silicon (a-Si)-based distributed Bragg reflectors (DBRs) consisting of alternating dense/porous films (i.e., pair) for a center wavelength (λ(c)) of 0.96 µm by oblique angle deposition (OAD) technique using an electron-beam evaporation system. The dense (high refractive index, i.e., high-n) and porous (low-n) a-Si films were deposited at two incident vapor flux angles of 0° and 80° in the OAD, respectively. Their optical reflectance characteristics were investigated in the wavelength range of 0.6-1.5 µm, including theoretical comparison using a rigorous coupled-wave analysis method. Above three pairs, the reflectivity (R) of a-Si DBRs was almost saturated at wavelengths around 0.96 µm, exhibiting R values of >97%. For the a-Si DBR with only three pairs, a broad normalized stop bandwidth (Δλ/λ(c)) of ∼22.5% was obtained at wavelengths of ∼0.87-1.085 µm, keeping high R values of >95%. To simply demonstrate the feasibility of device applications, the a-Si DBR with three pairs was coated as a high-reflection layer at the rear facet of GaAs/InGaAs quantum-well laser diodes (LDs) operating at λ=0.96 µm. For the LDs coated with three-pair a-Si DBR, external differential quantum efficiency (η(d)) was nearly doubled compared to the uncoated LDs, indicating the η(d) value of ∼50.6% (i.e., η(d)∼25.5% for the uncoated LDs).

Diffusion-weighted imaging of biliopancreatic disorders: correlation with conventional magnetic resonance imaging.

Diffusion-weighted magnetic resonance imaging (DWI) is a well established method for the evaluation of intracranial diseases, such as acute stroke. DWI for extracranial application is more difficult due to physiological motion artifacts and the heterogeneous composition of the organs. However, thanks to the newer technical development of DWI, DWI has become increasingly used over the past few years in extracranial organs including the abdomen and pelvis. Most previous studies of DWI have been limited to the evaluation of diffuse parenchymal abnormalities and focal lesions in abdominal organs, whereas there are few studies about DWI for the evaluation of the biliopancreatic tract. Although further studies are needed to determine its performance in evaluating bile duct, gallbladder and pancreas diseases, DWI has potential in the assessment of the functional information on the biliopancreatic tract concerning the status of tissue cellularity, because increased cellularity is associated with impeded diffusion, as indicated by a reduction in the apparent diffusion coefficient. The detection of malignant lesions and their differentiation from benign tumor-like lesions in the biliopancreatic tract could be improved using DWI in conjunction with findings obtained with conventional magnetic resonance cholagiopancreatography. Additionally, DWI can be useful for the assessment of the biliopancreatic tract in patients with renal impairment because contrast-enhanced computed tomography or magnetic resonance scans should be avoided in these patients.

The positive association between peripheral blood cell counts and bone mineral density in postmenopausal women.

PURPOSE: Accumulating evidence has shown a close connection between hematopoiesis and bone formation. Our aim was to evaluate the association between peripheral blood cell counts and bone mineral density (BMD) in a sample of postmenopausal women. MATERIALS AND METHODS: Three hundreds thirty eight healthy postmenopausal women who underwent BMD measurement during their health check-up were investigated. BMD was measured by dual energy X-ray asorptiometry at L1-L4 spine, femoral neck and total proximal femur. BMD was expressed as a T-score: among T-scores obtained from three different sites (L1-L4 spine, femoral neck and total proximal femur), the lowest T-score was considered to be the subject's T-score. RESULTS: The prevalence of osteopenia and osteoporosis diagnosed by T-score in the study participants were 49.4% (167/338) and 5.0% (17/338), respectively. Peripheral blood white blood cell (WBC), red blood cell (RBC) and platelet counts had significant positive correlations with T-scores (p<0.001) upon simple linear regression analysis. A multiple linear regression analysis, after controlling of confounders including age, body weight, systolic blood pressure, alkaline phosphatase and creatinine, showed that WBC (ß=0.127; standard error=0.043; p=0.014), RBC (ß=0.192; standard error=0.139; p<0.001) and platelet (ß=0.097; standard error=0.001; p=0.050) counts still had significant positive association with T-scores. CONCLUSION: The study results showed a positive relationship between blood cell counts and bone mineral density in postmenopausal women, supporting the idea of a close connection between hematopoiesis and bone formation. The study results also suggest that blood cell counts could be a putative marker for estimating BMD in postmenopausal women.

Complications of congenital and developmental abnormalities of the gastrointestinal tract in adolescents and adults: evaluation with multimodality imaging.

There is a wide variety of congenital anomalies that may affect the gastrointestinal tract. Most symptomatic congenital anomalies are found in newborns and infants. Such anomalies are relatively rare in adolescents and adults, and they may be difficult to identify because clinical symptoms often are nonspecific and insidious, causing them to be mistaken for other common abdominal conditions. Multimodality imaging is useful in evaluating congenital anomalies of the gastrointestinal tract in adults. The imaging features at radiography, fluoroscopy, ultrasonography, computed tomography, and magnetic resonance imaging may help identify congenital gastrointestinal anomalies such as congenital esophageal stenosis, gastric volvulus, duodenal web, annular pancreas, heterotopic pancreas, cecal volvulus, anomalies of the omphalomesenteric duct, Hirschsprung disease, and gastrointestinal duplication cyst. Familiarity with the imaging features of the various congenital anomalies of the gastrointestinal tract and their complications is important to establish the correct diagnosis and determine appropriate treatment, which is critical to avoid life-threatening complications.

Hypervascular subepithelial gastrointestinal masses: CT-pathologic correlation.

Although the vast majority of gastrointestinal (GI) masses are epithelial neoplasms, a variety of subepithelial masses are infrequently encountered during endoscopic or radiologic examination. A subepithelial mass, which was previously called a submucosal mass, is defined as a mass covered with normal-appearing mucosa, whether the underlying process is intramural or extramural in origin. At contrast material-enhanced computed tomography (CT), hypervascular subepithelial masses are usually detected more easily than isoattenuating or hypovascular masses. Entities that appear as intramural hypervascular subepithelial lesions include neuroendocrine tumors, GI stromal tumor, glomus tumor, hemangioma, angiosarcoma, Kaposi sarcoma, nerve sheath tumors, hypervascular metastases, heterotopic tissues, and vascular structures. Entities that appear as extramural hypervascular subepithelial lesions include Castleman disease, solitary fibrous tumor, inflammatory myofibroblastic tumor, and actinomycosis. Some rare gastric cancers resemble subepithelial tumors. In comparison with endoscopic ultrasonography, CT is of limited value in differentiating the layers of the GI wall and determining the origin of mass lesions. However, recent advances in multidetector CT with multiplanar reformation allow one to determine whether a GI mass is of epithelial, intramural subepithelial, or extramural subepithelial origin. Furthermore, the full extent of tumors can be delineated, and local invasion and distant metastases can be identified. Familiarity with the characteristic CT appearances of hypervascular subepithelial masses of the GI tract will help radiologists make a more confident diagnosis.

Postpartum hemorrhage: Clinical and radiologic aspects.

Postpartum hemorrhage (PPH) is a potentially life threatening condition, and it remains the leading cause of maternal morbidity. Uterine atony, lower genital tract lacerations, uterine rupture or inversion, retained products of conception and underlying coagulopathy are some of the common causes of PPH. Most conditions can be diagnosed based on clinical and laboratory evaluation supplemented by ultrasound information. Computed tomography (CT) or magnetic resonance (MR) imaging can provide information for the detection, localization and characterization of PPH in some difficult cases. CT can accurately demonstrate the anatomic location of significant arterial hemorrhage as sites of intravenous contrast material extravasation, which can be as a guide for angiographic intervention. The presence of focal or diffuse intravenous contrast extravasation or a hematoma within the enlarged postpartum uterine cavity on CT can help the diagnosis of uterine atony when the clinical diagnosis of uterine atony is unclear. CT can also provide the information of other alternative conditions such as a puerperal genital hematoma, uterine rupture and concealed hematoma in other sites. MR imaging may be considered as a valuable complement to ultrasound where the ultrasound findings are inconclusive in the diagnosis and differential diagnosis of retained products of conception. Knowledge of the various radiologic appearances of PPH and the correlation with clinical information can ensure correct diagnosis and appropriate and prompt treatment planning in the patients with PPH.