Printing Polymeric Convex Lenses to Boost the Sensitivity of a Graphene-Based UV Sensor.

Ultraviolet (UV) is widely used in daily life as well as in industrial manufacturing. In this study, a single-step postprocess to improve the sensitivity of a graphene-based UV sensor is studied. We leverage the advantage of electric-field-assisted on-demand printing, which is simply applicable for mounting functional polymers onto various structures. Here, the facile printing process creates optical plano-convex geometry by accelerating and colliding a highly viscous droplet on a micropatterned graphene channel. The printed transparent lens refracts UV rays. The concentrated UV photon energy from a wide field of view enhances the photodesorption of electron-hole pairs between the lens and the graphene sensor channel, which is coupled with a large change in resistance. As a result, the one-step post-treatment has about a 4× higher sensitivity compared to bare sensors without the lenses. We verify the applicability of printing and the boosting mechanism by variation of lens dimensions, a series of UV exposure tests, and optical simulation. Moreover, the method contributes to UV sensing in acute angle or low irradiation. In addition, the catalytic lens provides about a 9× higher recovery rate, where water molecules inside the PEI lens deliver fast reassembly of the electron-hole pairs. The presented method with an ultimately simple fabrication step is expected to be applied to academic research and prototyping, including optoelectronic sensors, energy devices, and advanced manufacturing processes.

Fiber Lithography: A Facile Lithography Platform Based on Electromagnetic Phase Modulation Using a Highly Birefringent Electrospun Fiber.

Lithography plays a key role in advancing manufacturing as well as the semiconductor industry. However, the currently available state-of-the-art lithography methods still require access to expensive tools and facilities. Herein, we suggest a novel lithography method based on electromagnetic phase modulation of ultraviolet using a highly birefringent electrospun fiber to overcome such limitations. The optical birefringent effect, by which the phase of incident ultraviolet electromagnetic fields is retarded when passing through optically anisotropic media, is combined with semicrystalline poly(ethylene oxide) (PEO)-poly(ethylene glycol) (PEG) polymeric microfibers patterned in a programmable form using near-field electrospinning. By positioning the mask between two linear polarizers that are perpendicular to each other, only the UV waves that are passing through the fibers can be selectively utilized to exhibit lithographic property. Therefore, the UV intensity on the photoresist (PR) surface follows the shape of the fiber pattern, enabling precisely controlled patterning of the photoresist. Zero- to two-dimensional key features of lithography are achieved, including straight, curved, array, and isolated patterns. Facile optical alignments without using dedicated alignment marks are successfully demonstrated, as well as various applications including micro- to macroscale serpentine, tree, and antenna circuit patterns on a flexible substrate. The presented approach, packed in a table-top scale, is expected to provide a practical and affordable lithography solution by leveraging the direct-writing capability and tunable optical functionality of polymers, scalability, and the simple optical alignment method.

Development of a Novel Flow Cytometry-Based System for White Blood Cell Differential Counts: 10-color LeukoDiff.

BACKGROUND: Flow cytometry (FCM) is commonly used to identify many cell populations. We developed a white blood cell (WBC) differential counting system for detecting abnormal cells using FCM incorporating 10 colors and 11 antibodies in a single tube, called "10-color LeukoDiff," and evaluated its performance. METHODS: Ninety-one EDTA-anti-coagulated peripheral blood samples from 76 patients were analyzed using 10-color LeukoDiff. We compared 10 color LeukoDiff results with the results of manual differential count (manual diff). WBCs were classified into 17 cell populations: neutrophils, total lymphocytes, T lymphocytes, B lymphocytes, CD5 and CD19 co-expressing lymphocytes, natural killer cells, total monocytes, 16+ monocytes, eosinophils, immature granulocytes, basophils, myeloblasts, B-blasts, T-blasts, myeloid antigen-positive B-blasts, CD19- plasma cells, and 19+ plasma cells. RESULTS: The correlations between the 10-color LeukoDiff and manual diff results were strong (r>0.9) for mature neutrophils, lymphocytes, eosinophils, immature granulocytes, and blasts and moderate for monocytes and basophils (r=0.86 and 0.74, respectively). There was no discrepancy in blast detection between 10-color LeukoDiff and manual diff results. Furthermore, 10-color LeukoDiff could differentiate the lineage of the blasts and separately count chronic lymphocytic leukemic cells and multiple myeloma cells. CONCLUSIONS: The 10-color LeukoDiff provided an accurate and comprehensive WBC differential count. The most important ability of 10-color LeukoDiff is to detect blasts accurately. This system is clinically useful, especially for patients with hematologic diseases, such as acute leukemia, chronic lymphocytic leukemia, and multiple myeloma. Application of this system will improve the development of FCM gating strategy designs.

Performance of a novel fluorogenic chimeric analog for the detection of third-generation cephalosporin resistant bacteria.

Resistance to third generation cephalosporins is widely disseminated in Enterobacteriaceae mainly due to extended-spectrum-ß-lactamases, plasmid AmpC ß-lactamases, and hyperproduction of chromosomal AmpC ß-lactamases. Here we evaluated the performance of a novel fluorogenic probe rapid test and compared the results with the phenol red assay using a total of 77 characterized organisms (44 extended-spectrum-ß-lactamases, 33 chromosomal or plasmid AmpC ß-lactamases) and 46 susceptible organisms. The fluorescent assay showed higher sensitivity than the phenol red assay in cefotaximase type extended-spectrum-ß-lactamases, non- cefotaximase type extended-spectrum-ß-lactamases, chromosomal AmpC ß-lactamases, and plasmid AmpC ß-lactamases (96.7% vs. 90.0%, p=0.157; 71.4% vs. 7.1%, p=0.003; 100.0% vs. 64.7%, p<0.001; 100.0% vs. 6.3%, p<0.001). The fluorescent assay had a positive correlation with the exponents of cefotaxime and ceftazidime minimum inhibitory concentrations (p<0.001 for both). The new fluorescent assay will be very useful for the rapid detection of resistance to third generation cephalosporins that originates from various ß-lactamases.

Predictors of Undergraduate and Postgraduate Clinical Performance: A Longitudinal Cohort Study.

OBJECTIVE: Though many medical schools applied various admission criteria in the selection process, the evidence of using those criteria is unclear. This study examined the predictive validity of each admission criterion for student competency. DESIGN, SETTING, AND PARTICIPANTS: We conducted a prospective cohort study of all students who matriculated to Seoul National University School of Medicine from 2002 to 2008. Demographic characteristics, admission criteria scores, and clinical competencies based on grade point average (GPA), objective structured clinical examination score, and internship score were obtained for each student to analyze the predictive validity of admission criteria. RESULTS: Graduate GPA at the end of 4 years positively correlated with preadmission GPA (p < 0.0001) and written test score (p = 0.012) but negatively correlated with essay test (p = 0.049). Internship score significantly correlated with preadmission GPA and graduate GPA. Regression analysis revealed that the preadmission GPA of the affiliated college and young age at admission could predict GPA, and preadmission GPA and graduate GPA could predict the internship score, which indicates postgraduate clinical performance. CONCLUSIONS: These findings suggest that preadmission GPA is a reliable predictor of academic achievement during medical school and postgraduate clinical performance. For assessing nonacademic competencies, further research is needed.

Real-Time Observation of Water-Soluble Mineral Precipitation in Aqueous Solution by In Situ High-Resolution Electron Microscopy.

The precipitation and dissolution of water-soluble minerals in aqueous systems is a familiar process occurring commonly in nature. Understanding mineral nucleation and growth during its precipitation is highly desirable, but past in situ techniques have suffered from limited spatial and temporal resolution. Here, by using in situ graphene liquid cell electron microscopy, mineral nucleation and growth processes are demonstrated in high spatial and temporal resolution. We precipitate the mineral thenardite (Na2SO4) from aqueous solution with electron-beam-induced radiolysis of water. We demonstrate that minerals nucleate with a two-dimensional island structure on the graphene surfaces. We further reveal that mineral grains grow by grain boundary migration and grain rotation. Our findings provide a direct observation of the dynamics of crystal growth from ionic solutions.

Performance of chromID Clostridium difficile agar compared with BBL C. difficile selective agar for detection of C. difficile in stool specimens.

We evaluated the performance of a new chromogenic medium for detection of Clostridium difficile, chromID C. difficile agar (CDIF; bioMérieux, France), by comparison with BBL C. difficile Selective Agar (CDSA; Becton Dickinson and Company, USA). After heat pre-treatment (80℃, 5 min), 185 diarrheal stool samples were inoculated onto the two media types and incubated anaerobically for 24 hr and 48 hr for CDIF and for 48 hr and 72 hr for CDSA. All typical colonies on each medium were examined by Gram staining, and the gram-positive rods confirmed to contain the tpi gene by PCR were identified as C. difficile. C. difficile was recovered from 36 samples by using a combination of the two media. The sensitivity with CDIF 48 hr was highest (100%) and was significantly higher than that with CDIF 24 hr (58.3%; P<0.001), because samples with a low burden of C. difficile tended to require prolonged incubation up to 48 hr (P<0.001). The specificity of CDIF 24 hr and CDIF 48 hr (99.3% and 90.6%, respectively) was significantly higher than that of CDSA 48 hr and CDSA 72 hr (72.5% and 67.1%, respectively; P<0.001). CDIF was effective for detecting C. difficile in heat-pretreated stool specimens, thus reducing unnecessary testing for toxin production in non-C. difficile isolates and turnaround time.

Prevalence and characteristics of lactose non-fermenting Escherichia coli in urinary isolates.

Recently, serotype O75 was found to be prominent among the non-ST131 ciprofloxacin-resistant Escherichia coli, and they were all lactose non-fermenters. In this study, we investigated the prevalence and characteristics of lactose non-fermenters in urinary isolates of E. coli. A total of 167 E. coli isolates was collected. Antimicrobial susceptibility tests were determined by VITEK 2 (bioMerieux, France). The lactose non-fermenters underwent PCR-based O typing, multilocus sequence typing (MLST) analysis, phylogenetic grouping. For ciprofloxacin-resistant isolates, the resistance mechanisms were investigated. Thirty-three (19.7%) isolates were lactose non-fermenters and the ciprofloxacin resistance rate was significantly higher than in lactose fermenters (66.7% vs. 31.6%, P = 0.0002). According to the serotype, O75 was the most common (42.4%, 14/33) and was followed by O16 (5/33), O2 (4/33), O25b (3/33), O15 (1/33), O6 (1/33), O1 (1/33). All the O75 isolates were ciprofloxacin-resistant and belonged to ST1193. By MLST, they were resolved into 11 STs. ST1193 was the most common (14/33) and was followed by ST131 (8/33). Interestingly, 8 isolates of ST131 were divided into three O types [O16 (4 isolates), O25b (3), and non-typeable (1)]. The ciprofloxacin resistance rate was high in isolates of O75-ST1193 and O25b-ST131 but low in O16-ST131 and O2-ST95. All the ciprofloxacin-resistant isolates showed identical triple mutations in gyrA and parC but the serotype O25b isolates had an additional mutation in parC (E84V). Only one isolate harbored aac(6')-Ib-cr variant and no qnr gene was detected. Continuous monitoring of the prevalence and clonal composition of the lactose non-fermenters is needed.

High quality Mn-doped (Na,K)NbO3 nanofibers for flexible piezoelectric nanogenerators.

Enhanced piezoelectric and energy-harvesting characteristics of Mn-doped (Na0.5K0.5)NbO3 (NKN) nanofibers have been investigated with actual fabrication of potential flexible nanogenerators. The electrospinning process of nanofibers has been initially optimized with the proper level of chelating agent and annealing temperature. High quality nanofibers are successfully obtained only by means of a certain level of doped-Mn, which incorporates into the NKN perovskite structure and facilitates significant grain growth. A single-particle-stacked structure along the direction of fiber length becomes more evident with increasing Mn content. An XPS analysis confirms that Mn exists in multivalent states of Mn(2+)/Mn(3+). The effective piezoelectric coefficient of the nanofibers is found to be enhanced by 5 times with Mn-doping up to 3 mol % as characterized by piezoelectric force microscopy. The resultant flexible nanogenerators on PES films have exhibited ∼0.3 V output voltage and ∼50 nA output current under a bending strain.

Dominance of clonal complex 10 among the levofloxacin-resistant Streptococcus agalactiae isolated from bacteremic patients in a Korean hospital.

Streptococcus agalactiae has emerged as an important cause of invasive infection in adults. Forty-nine S. agalactiae isolates (41 from adults and 8 from neonates) were collected during a 4-year period (2010-2013) and analyzed by multilocus sequence typing (MLST). Antibiotic susceptibility to erythromycin, clindamycin and levofloxacin was determined and the determinants of resistance (ermA, ermB, ermC, mefA, lnuB) were detected by PCR and mutation in gyrA, gyrB, parC and parE gene was investigated by sequence analysis. They were resolved into 14 sequence types (STs) and belonged to five clonal complexes (CCs). The distribution of CC was significantly different according to the age group; CC1 (18/41) and CC10 (13/41) was the most common among the adult isolates but CC19 (5/8) was predominant among the neonatal isolates. The resistance rate to erythromycin, clindamycin was 18.4% and 24.5%, respectively. Among the 13 strains resistant to erythromycin and/or clindamycin, two isolates harbored ermA and 10 isolates harbored ermB. The levofloxacin resistance rate was very high (32.7%) and was significantly higher in CC10 (71.4%). All the levofloxacin-resistant isolates had identical gyrA substitution (Ser81Leu) but parC substitution was different according to the CCs. The additional mutation in parE (His221Tyr) was found only in CC19. Continuous monitoring of the fluoroquinolone resistance and genotypic distribution among S. agalactiae is needed.

Decreased expression of surfactant protein genes is associated with an increased expression of Forkhead box M1 gene in the fetal lung tissues of premature rabbits.

PURPOSE: Recently, Forkhead box M1 (FoxM1) was reported to be correlated with lung maturation and expression of surfactant proteins (SPs) in mice models. However, no study has been conducted in rabbit lungs despite their high homology with human lungs. Thus, we attempted to investigate serial changes in the expressions of FoxM1 and SP-A/B throughout lung maturation in rabbit fetuses. MATERIALS AND METHODS: Pregnant New Zealand White rabbits were grouped according to gestational age from 5 days before to 2 days after the day of expected full term delivery (F5, F4, F3, F2, F1, F0, P1, and P2). A total of 64 fetuses were enrolled after Cesarean sections. The expressions of mRNA and proteins of FoxM1 and SP-A/B in fetal lung tissue were tested by quantitative reverse-transcriptase real-time PCR and Western blot. Furthermore, their correlations were analyzed. RESULTS: The mRNA expression of SP-A/B showed an increasing tendency positively correlated with gestational age, while the expression of FoxM1 mRNA and protein decreased from F5 to F0. A significant negative correlation was found between the expression levels of FoxM1 and SP-A/B (SP-A: R=-0.517, p=0.001; SP-B: R=-0.615, p<0.001). CONCLUSION: Preterm rabbits demonstrated high expression of FoxM1 mRNA and protein in the lungs compared to full term rabbits. Also, the expression of SP-A/B was inversely related with serial changes in FoxM1 expression. This is the first report to suggest an association between FoxM1 and expression of SP-A/B and lung maturation in preterm rabbits.

Synthesis and bidirectional frequency tuning of cantilever-shape nano resonators using a focused ion beam.

The synthesis of cantilever-shape nano resonators and their resonant frequency tunings in both upward and downward directions have been demonstrated using FIB-CVD (focused ion beam-chemical vapor deposition). The in situ experimental observations of mechanical resonances as well as cutting and adding of resonator materials have been accomplished inside the FIB vacuum chamber. Extending the length of the cantilever-shape resonator by 500 nm scale using either the same material or alternating different materials effectively reduced resonant frequency. On the other hand, direct cutting and gradual trimming of the end point of nano resonator increases its resonant frequency. This simple yet versatile synthesis and frequency tuning scheme could be applicable to both constructing micro/nano scale resonators and tuning nanostructures with reduced efforts and enhanced efficiency.

Serum cystatin C during 30 postnatal days is dependent on the postconceptional age in neonates.

BACKGROUND: Cystatin C (CysC) is a promising endogenous marker for renal function. However, the reference serum CysC level is not sufficiently studied in neonates. This study was conducted to investigate the reference level of serum CysC for neonates, including very low birth weight infants according to the postconceptional age (PCA). METHODS: Serum CysC levels were measured in 883 blood samples (246 neonates including 127 premature infants). Infants with symptoms or signs of acute kidney injury, systemic illness, congenital anomaly, or renal pathology were excluded. CysC levels were analyzed for association between subgroups dichotomized by postnatal age and PCA. RESULTS: Reference ranges of serum CysC were determined and a decreasing trend of CysC levels was observed as PCA increased, except for the first 3 postnatal days. CysC levels were negatively correlated with gestational age at birth, and PCA (P < 0.001), while positively correlated with postnatal age and serum creatinine (P < 0.001). CONCLUSION: The reference level of serum CysC was determined according to postnatal age and PCA. As the reference CysC level was dependent on gestational age and PCA, consideration of these parameters is warranted when assessing CysC levels in neonates.

Forkhead box m1 mRNA expression of lung of preterm and term rabbits.

Previous studies on forkhead box m1 (Foxm1) of mice demonstrated the correlation between this gene and lung maturation. However, no study has been conducted on human Foxm1 with regard to lung maturation. The aim of this study was to compare the mRNA expression of surfactant protein (SP)-A, -B, -C and Foxm1 gene of preterm rabbits to that of full-term ones and to determine the association between Foxm1 and lung maturation. New Zealand white rabbits were grouped according to gestational age. Cesarean sections were carried out after rabbits were divided into two groups of 30-31 days of gestation (term group, n=18) and 26-27 days of gestation (preterm group, n=18). mRNA expression levels of SP-A, -B, -C and Foxm1 were compared by using quantitative real-time reverse transcription-polymerase chain reaction (qRT-PCR). The relative ratios of SP-A, -B and -C mRNA expression levels of the preterm to term groups were 0.380, 0.563 and 0.448:1, respectively, on qRT-PCR. By contrast, Foxm1 expression was increased in the preterm group and its relative expression ratio to the term group was 2.166:1 for RT-PCR and qRT-PCR, which was double that of the Foxm1 gene in the term group. Moreover, a significant correlation between the expressions of these genes was found. Foxm1 is considered to be an important gene required for the lung maturation of preterm rabbits in correlation with SP genes.

Birth statistics of high birth weight infants (macrosomia) in Korea.

PURPOSE: The authors analyzed the trend from the birth-related statistics of high birth weight infants (HBWIs) over 50 years in Korea from 1960 to 2010. METHODS: We used 2 data sources, namely, the hospital units (1960's to 1990's) and Statistics Korea (1993 to 2010). The analyses include the incidence of HBWIs, birth weight distribution, sex ratio, and the relationship of HBWI to maternal age. RESULTS: The hospital unit data indicated the incidence of HBWI as 3 to 7% in the 1960's and 1970's and 4 to 7% in the 1980's and 1990's. Data from Statistics Korea indicated the percentages of HBWIs among total live births decreased over the years: 6.7% (1993), 6.3% (1995), 5.1% (2000), 4.5% (2000), and 3.5% (2010). In HBWIs, the birth weight rages and percentage of incidence in infants' were 4.0 to 4.4 kg (90.3%), 4.5 to 4.9 kg (8.8%), 5.0 to 5.4 kg (0.8%), 5.5 to 5.9 kg (0.1%), and >6.0 kg (0.0%) in 2000 but were 92.2%, 7.2%, 0.6%, 0.0%, and 0.0% in 2009. The male to female ratio of HBWIs was 1.89 in 1993 and 1.84 in 2010. In 2010, the mother's age distribution correlated with low (4.9%), normal (91.0%), and high birth weights (3.6%): an increase in mother's age resulted in an increase in the frequency of low birth weight infants (LBWIs) and HBWIs. CONCLUSION: The incidence of HBWIs for the past 50 years has been dropping in Korea. The older the mother, the higher was the risk of a HBWI and LBWI. We hope that these findings would be utilized as basic data that will aid those managing HBWIs.

A near-infrared mechano responsive polymer system.

A new type of crosslinked polyarylamide based film with a fibrillar morphology that is photomechanically responsive has been created. Without any additive or need of pre-alignment, these films can actuate under NIR stimulation. By constructing the photoresponsive film on top of a piezoelectric poly(vinylidene difluoride) film, electrical energy can be generated under NIR excitation. This is the first polymer system that exhibits NIR response without any conventional photosensitive moieties.

Decreasing trends of neonatal and infant mortality rates in Korea: compared with Japan, USA, and OECD nations.

Neonatal mortality rate (NMR) and infant mortality rate (IMR) are two of the most important indices reflecting the level of public health of a country. In this review, we investigated changes in NMR and IMR in Korea and compared the results with those of Japan, USA, and OECD nations. During the past 20 yr, NMR and IMR have lowered remarkably from 6.6 and 9.9 in 1993 to 1.7 and 3.2 in 2009, respectively, in Korea. It is an impressive finding that Korean IMR (3.2 in 2009) is lower than the average of OECD nations (4.7 in 2008), and USA (6.3 in 2009), although higher than Japanese IMR (2.8 in 2009). The proportion of NMR among the IMR calculation decreased from 66.7% in 1993 to 53.1% in 2009. The reason the value of Korea was higher than Japan but lower than USA was speculated to be an aspect of the health care service system. Several suggestions in perinatal, neonatal and infantile health care such as establishment of perinatal care center, research network system, regionalization, and new policies for care of pre-term and high risk pregnancy, are elucidated to achieve further improvement on NMR and IMR in Korea.