Time, momentum, and energy resolved pump-probe tunneling spectroscopy of two-dimensional electron systems.

Real-time probing of electrons can uncover intricate relaxation mechanisms and many-body interactions in strongly correlated materials. Here, we introduce time, momentum, and energy resolved pump-probe tunneling spectroscopy (Tr-MERTS). The method allows the injection of electrons at a particular energy and observation of their subsequent decay in energy-momentum space. Using Tr-MERTS, we visualize electronic decay processes, with lifetimes from tens of nanoseconds to tens of microseconds, in Landau levels formed in a GaAs quantum well. Although most observed features agree with simple energy-relaxation, we discovered a splitting in the nonequilibrium energy spectrum in the vicinity of a ferromagnetic state. An exact diagonalization study suggests that the splitting arises from a maximally spin-polarized state with higher energy than a conventional equilibrium skyrmion. Furthermore, we observe time-dependent relaxation of the splitting, which we attribute to single-flipped spins forming skyrmions. These results establish Tr-MERTS as a powerful tool for studying the properties of a 2DES beyond equilibrium.

Trends in device utilization ratios in intensive care units over 10-year period in South Korea: device utilization ratio as a new aspect of surveillance.

BACKGROUND: Device-associated infection (DAI) is an important issue related to patient safety. It is important to reduce unnecessary device utilization in order to decrease DAI rates. AIM: To investigate the time trend of device utilization ratios (DURs) of voluntarily participating hospitals, collected over a 10-year period through the Korean National Healthcare-associated Infections Surveillance System (KONIS). METHODS: DURs from 2006 to 2015 in 190 intensive care units (ICUs) participating in KONIS were included in this study. DURs were calculated as the ratio of device-days to patient-days. The pooled incidences of DAIs and DURs were calculated for each year of participation, and the year-wise trends were analysed. FINDINGS: Year-wise ventilator utilization ratio (V-DUR) increased significantly from 0.40 to 0.41 (F = 6.27, P < 0.01), urinary catheter utilization ratio (U-DUR) increased non-significantly from 0.83 to 0.84 (F = 1.66, P = 0.10), and C-line utilization ratio (CL-DUR) decreased non-significantly from 0.55 to 0.51 (F = 1.62, P = 0.11). In the subgroup analysis, 'medical ICU' (F = 2.79, P < 0.01) and 'hospital with >900 beds' (F = 3.07, P < 0.01) were associated with the significant increase in V-DUR. CONCLUSION: In Korea, V-DUR showed a significant, year-wise increasing trend. The trends for U-DUR and CL-DUR showed no significant decrease. Efforts are required to ensure the reduction of DURs.

Validation of the Korean National Healthcare-associated Infections Surveillance System (KONIS): an intensive care unit module report.

BACKGROUND: National surveillance data should be validated to identify methodological problems within the surveillance programme and data quality issues. AIM: To test the validity of healthcare-associated infection (HAI) rate data from the Korean National Healthcare-associated Infections Surveillance System (KONIS). METHODS: Records from intensive care units of 12 (14.8%) of 81 participating hospitals for January-March 2014 were examined. The validation team reviewed 406 medical records of 110 patients with 114 reported HAIs - including 34 urinary tract infections (UTIs), 57 bloodstream infections (BSIs) and 23 cases of pneumonia (PNEU) - and 296 patients with no reported HAIs during one-day visits conducted in August and September 2014. The reviewers' diagnosis of HAI was regarded as the reference standard; in ambiguous cases, the KONIS Steering Committee confirmed the diagnosis of HAI. FINDINGS: Sensitivity values for UTIs, BSIs and PNEU were 85.3%, 74.0% and 66.7%, and specificity values were 98.7%, 99.1% and 98.7%, respectively. Positive predictive values were 85.3%, 94.7% and 78.3%, and negative predictive values were 98.7%, 94.6% and 97.7%, respectively. Sensitivity for PNEU was lower than that for UTIs and BSIs. The hospitals participating in KONIS infrequently reported conditions that were not HAIs. Sensitivity for BSIs was lower in this study than in KONIS validation studies conducted in 2008 and 2010. CONCLUSIONS: KONIS data are generally reliable; however, sensitivity for BSIs exhibited a decrease. This study shows the need for ongoing validation and continuous training of surveillance personnel to maintain the accuracy of surveillance data.

Analyzing Longitudinal Magnetoresistance Asymmetry to Quantify Doping Gradients: Generalization of the van der Pauw Method.

A longitudinal magnetoresistance asymmetry (LMA) between a positive and negative magnetic field is known to occur in both the extreme quantum limit and the classical Drude limit in samples with a nonuniform doping density. By analyzing the current stream function in van der Pauw measurement geometry, it is shown that the electron density gradient can be quantitatively deduced from this LMA in the Drude regime. Results agree with gradients interpolated from local densities calibrated across an entire wafer, establishing a generalization of the van der Pauw method to quantify density gradients.

Detection of CSF leak in spinal CSF leak syndrome using MR myelography: correlation with radioisotope cisternography.

BACKGROUND AND PURPOSE: Spinal CSF leak syndrome is a unique disorder caused by spinal CSF leak. In this study, we attempted to determine whether MR myelography (MRM) can detect the leakage site in the spine. MATERIALS AND METHODS: We performed both MRM and radioisotope cisternography (RIC) in 15 patients with spinal CSF leak syndrome. Patients were included in this study if they had at least 2 of the following criteria: 1) orthostatic headache, 2) low CSF opening pressure, and 3) diffuse pachymeningeal enhancement on brain MR imaging. For comparison, we performed MRM in 15 subjects without symptoms of spinal CSF leak syndrome. MRM was performed with the 2D turbo spin-echo technique in the entire spine by using a 1.5T scanner. Two blinded radiologists evaluated the MRM findings in a total of 30 cases, composed of patient and control groups, with regard to the presence of leakage and the level of leakage if present. RIC was performed only in the patient group and was assessed by consensus among 3 physicians experienced in nuclear medicine. The diagnostic performance of MRM and RIC was evaluated on the basis of the clinical diagnosis of spinal CSF leak syndrome. RESULTS: The sensitivity, specificity, and accuracy of MR myelography for detecting CSF leak was 86.7%, 86.7%, and 86.7% for reader 1, respectively, and 80.0%, 93.3%, and 86.7% for reader 2, respectively. The sensitivity of RIC was 93.3%. Agreement between the 2 techniques for the detection of CSF leak was substantial in reader 1 and moderate in reader 2 (kappa = 0.634 and 0.444, respectively). CONCLUSION: MRM is an effective tool for detecting CSF leak in the spine in patients with spinal CSF leak syndrome.

Placement of covered stents for carotid blowout in patients with head and neck cancer: follow-up results after rescue treatments.

BACKGROUND AND PURPOSE: Placement of a covered stent to control carotid blowout (CB) in malignant tumors of the head and neck has been reported to be an effective treatment. However, it is not uncommon to encounter recurrent hemorrhage. The purpose of this study was to evaluate the follow-up results of patients treated with covered stents. MATERIALS AND METHODS: We retrospectively reviewed the results of 7 consecutive patients who underwent placement of a covered stent to control CB. Most of them had poor wound healing because of previous irradiation, surgery, or both. The initial procedures were successful in all patients. Their clinical course was reviewed for rebleeding, additional endovascular treatments in recurrent cases, and outcomes. RESULTS: Recurrence developed in 6 of 7 patients. The interval between the first procedure and the hemorrhagic event was from 3 to 44 days. In 6 patients who had a recurrent CB, 4 had rebleeding from the previous site of the stent, whereas 2 other patients experienced recurrent bleeding in a different area from the site of the stent. Additional endovascular treatments were carried out in all affected patients by another insertion of a covered stent (n = 3), coil embolization (n = 2), or insertion of a covered stent followed by permanent arterial occlusion (n = 1). CONCLUSION: Placement of a covered stent in patients with head and neck cancer who sustain CB showed frequent rebleeding despite favorable initial rescue results. Recurrent CB at the previous stent site developed frequently in patients with uncontrolled wound infection. Concomitant or short-interval arterial trapping should be considered selectively in those conditions.

Effect of blood contamination with 1-step self-etching adhesives on microtensile bond strength to dentin.

This study evaluated the effect of blood contamination and decontamination methods on the microtensile bond strength of 1-step self-etching adhesive systems to dentin contaminated after adhesive application and light curing. Three commercially available "all-in-one" adhesives (One Up Bond F, Xeno III and Adper Prompt L-Pop) and 1 resin composite (Clearfil AP-X) were used. Third molars that had been stored in distilled water with 0.5% thymol at 4 degrees C were ground with #600 SiC paper under running water to produce a standardized smear layer. The specimens were randomly divided into groups according to the 3 adhesive systems. The adhesive systems were used under 3 conditions: no contamination, which was the control (C); contamination of the light-cured adhesive surface with blood and reapplication of adhesive (Contamination 1) and contamination of the light-cured adhesive surface with blood, then washing, drying and reapplication of the adhesive (Contamination 2). Following light curing of the adhesive, the resin composite was placed in 3 increments up to a 5-mm-thick layer on the bonded surface. All specimens were stored in distilled water at 37 degrees C for 24 hours. The microtensile bond strength was measured using a universal testing machine (EZ test), and data were analyzed by 1-way ANOVA followed by the Duncan test to make comparisons among the groups (p=0.05). After debonding, 5 specimens were selected from each group and examined in a scanning electron microscope to evaluate the modes of fracture. For all adhesives, contamination groups showed lower bond strength than the control (p<0.05). There was no statistically significant difference among the control groups (p>0.05). For Xeno III and Adper Prompt L-Pop, contamination group #2 showed the lowest bond strength among the groups (p<0.05). For One Up Bond F, contamination group #2 showed higher bond strength than contamination group #1 but showed no statistical significance between them (p>0.05).

Effect of saliva contamination on the microshear bond strength of one-step self-etching adhesive systems to dentin.

This study evaluated the effect of saliva contamination and decontamination methods on the dentin bond strength of one-step self-etching adhesive systems. Three commercially available "all-in-one" adhesives (One Up Bond F, Xeno III and Adper Prompt) and one resin composite (Filtek Z-250) were used. Third molars stored in distilled water with 0.5% thymol at 4 degrees C were ground with #600 SiC paper under running water to produce a standardized smear layer. The specimens were randomly divided into groups according to contamination methods: no contamination, which was the control (C); contamination of the adhesive surface with fresh saliva before light curing (A) and contamination of the adhesive surface with fresh saliva after light curing (B). Each contamination group was further subdivided into three subgroups according to the decontamination method: A1-Saliva was removed by a gentle air blast and the adhesive was light-cured; A2-Saliva was rinsed for 10 seconds, gently air-dried and the was adhesive light-cured; A3-Saliva was rinsed and dried as in A2, then the adhesive was re-applied to the dentin surface and light-cured; B1-Saliva was removed with a gentle air blast; B2-Saliva was rinsed and dried; B3-Saliva was rinsed, dried and the adhesive was re-applied and light cured. Tygon tubes filled with resin composite were placed on each surface and light cured. All specimens were stored in distilled water at 37 degrees C for 24 hours. Microshear bond strength was measured using a universal testing machine (EZ test), and data were analyzed by one-way ANOVA followed by the Duncan test to make comparisons among the groups (p<0.05). After debonding, five specimens were selected and examined in a scanning electron microscope to evaluate the modes of fracture. The A2 subgroup resulted in the lowest bond strength. For One Up Bond F and Adper Prompt, there was no significant difference between subgroup A1 and the control, and subgroup A3 and the control (p>0.05). Bond strengths of all B groups were significantly lower compared to the controls (p<0.05). For Xeno III, A1 subgroup showed the greatest decrease in bond strength as compared to the control (p<0.05). On the other hand, it showed more resistance to salivary contamination after adhesive curing. There was no statistically significant difference among the control groups (p>0.05).

Effect of Nd:YAG laser irradiation on the apical leakage of obturated root canals: an electrochemical study.

AIM: The purpose of this laboratory study was to evaluate the effect of Nd:YAG laser irradiation on the apical leakage of obturated root canals using an electrochemical method. METHODOLOGY: Forty extracted single-rooted teeth were selected and the anatomic crown of each tooth was removed. The specimens were randomly divided into four groups. In group 1, the root canals were prepared with K-files and irradiated with Nd:YAG laser (5 W, 20 Hz) via a 300 microns optical fibre. Then the root canals were obturated with laterally condensed gutta-percha and Pulp Canal Sealer EWT. In group 2, the root canals were treated with the same method as those of group 1 but without laser irradiation. In group 3, the root canals were prepared with ProFiles, laser irradiated and then obturated with vertically condensed gutta-percha and Pulp Canal Sealer EWT. In group 4, the root canals were treated with the same method as those of group 3 but without laser irradiation. The electric resistance between standard and experimental electrodes in the canals was measured over a period of 10 days. RESULTS: At 2 h, groups 1 and 3 irradiated with laser had significantly less apical leakage than group 2 (P < 0.05). After 10 days, group 4 had the highest leakage, followed by groups 2, 1 and 3; the differences between the groups was statistically significant (P < 0.05). CONCLUSIONS: Laser irradiation following root canal preparation reduced apical leakage following root canal obturation.

Incidence and prevalence of ulcerative colitis in the Songpa-Kangdong District, Seoul, Korea, 1986-1997.

BACKGROUND AND AIMS: Ulcerative colitis (UC) is regarded as a rare disease in developing countries, but accurate data are generally lacking. We performed the present study to evaluate the incidence and prevalence of UC in Korea. METHODS: A retrospective study was performed from 1986 to 1997 in the Songpa-Kangdong district of Seoul, Korea. To recruit UC patients as completely as possible, multiple information sources including all medical facilities in the study area and three referral centres located nearby, but outside the study area were used. The incidence and prevalence rates were adjusted using the 1997 Korean population statistics. RESULTS: During the study period, a total of 94 incident cases were identified, for an adjusted mean annual incidence rate of 0.68 per 100,000 inhabitants. On 31 December 1997, 91 patients with UC lived in the study area, giving an adjusted prevalence rate of 7.57 per 100,000 inhabitants. By using the Poisson regression analysis, the annual incidence rate increased significantly from 0.20 per 100,000 inhabitants in 1986-1988 to 1.23 per 100,000 inhabitants in 1995-1997 (P < 0.005). Patient age at diagnosis, the interval from onset of symptoms to diagnosis, and the disease extent at diagnosis were fairly constant throughout the study period. CONCLUSIONS: The incidence and prevalence of UC in our study area are still low compared with those of Western countries, but the incidence rate is steadily increasing.

Significance of rectosigmoid polyp as a predictor of proximal colonic polyp.

The association between rectosigmoid polyps and polyps in the more proximal colon is still a matter of debate, and the need for colonoscopy in patients with rectosigmoid polyps that are detected by flexible sigmoidoscopy is controversial. The aim of this study was to determine whether or not certain characteristics of rectosigmoid polyps are associated with the presence and characteristics of proximal colonic polyps. Seven hundred and twenty-eight patients who underwent total colonoscopy between October 1995 and June 1998 and who had colorectal polyps were retrospectively analyzed. Patients with inflammatory bowel diseases, familial adenomatous polyposis, or any advanced cancer were excluded. The odds ratio (OR) and 95% confidence interval (CI) of prevalence of proximal colonic polyps according to the patients age and sex, as well as the characteristics of rectosigmoid polyps, were calculated. Advanced adenoma was defined as an adenoma larger than 10 mm or an adenoma of any size with villous component, high-grade dysplasia or invasive carcinoma. Among 728 patients with colorectal polyps, 356 patients (48.9%) had polyps only in the rectosigmoid region, 193 patients (26.5%) had polyps only in the proximal colon, and 179 patients (24.6%) had polyps in both the rectosigmoid and proximal colon. In 535 patients with rectosigmoid polyps, the prevalence of proximal colonic polyps, neoplastic polyps and advanced adenomas were 33.4%, 27.3% and 2.9%, respectively. The prevalence of proximal colonic polyps in patients with rectosigmoid polyps was found to be significantly related to the male gender and elderly patients, in addition to the neoplastic histology of the rectosigmoid polyps. However, the prevalence of the proximal colonic polyps was not related to the size, number and shape of rectosigmoid polyps. In 179 patients with both rectosigmoid and proximal colonic polyps, the characteristics of proximal colonic polyps such as size, number and shape were similar to those of rectosigmoid polyps. We recommend total colonoscopic examination in all patients with rectosigmoid adenomas, regardless of the size, number, and shape, especially in elderly males.

Quality of life in Korean patients with inflammatory bowel diseases: ulcerative colitis, Crohn's disease and intestinal Behçet's disease.

Health-related quality of life (HRQOL) is an important outcome factor in chronic diseases such as inflammatory bowel disease (IBD). This study used the Korean translation of the disease-specific, self-administered Inflammatory Bowel Disease Questionnaire (IBDQ) to compare HRQOL in ulcerative colitis (UC; n = 98), Crohn's disease (CD; n = 49), and intestinal Behçet's disease (BD; n = 34). In addition to the current status, patients were asked retrospectively to recall their symptoms at the beginning and during the worst period of their disease. Disease activity was measured by St. Mark's Activity Index, Crohn's disease Activity Index (CDAI), and the Harvey-Bradshaw Index (HBI). In all IBD patients, including those with BD, the IBDQ total score during the worst period was significantly lower than that at present and that at the beginning of the disease. However, there were no significant differences between groups regarding the total IBDQ score or its various dimensions. In UC a strong correlation between IBDQ scores and St. Mark's Activity Index was observed (r = -0.708, P < 0.001). IBDQ scores were also highly correlated with CDAI and HBI in both CD (r = -0.506, P < 0.001 for CDAI; r = -0.600, P < 0.001 for HBI) and BD (r = -0.687, P < 0.001 for CDAI; r = -0.531, P < 0.001 for HBI). However, the current IBDQ score was not related to demographic parameters such as gender, age, educational status, economic status, and marital status as well as disease factors such as duration of disease, history of operation or hospital admission, extent of disease in UC, involved region in CD, and clinical type in BD. We conclude that the Korean IBDQ is a responsive and promising instrument for measuring HRQOL of IBD patients in clinical trials. In addition, the IBDQ can be helpful in developing a disease-specific activity index in BD.

Interleukin 4-induced proliferation in normal human keratinocytes is associated with c-myc gene expression and inhibited by genistein.

We studied the effect of IL-4 on the proliferation of cultured normal human keratinocytes. Keratinocyte proliferation was stimulated by IL-4 and inhibited by anti-IL-4 antibody in a concentration-dependent manner. Anti-IL-6 antibody did not inhibit normal human keratinocyte proliferation, suggesting that the IL-4 could directly induce proliferation of these cells. IL-4 significantly induced cell cycle G0/G1 to S phase progression. The keratinocyte proliferation by IL-4 was mediated through one of the growth control genes, c-myc protooncogene. The expression of c-myc mRNA was significantly increased after IL-4 treatment of the keratinocytes, suggesting that c-myc plays a key role in the control of proliferation. The signal transduction pathways induced by IL-4 in the keratinocytes were studied with inhibitors of signal transduction. Genistein, a tyrosine kinase inhibitor, suppressed the level of the induced c-myc mRNA expression, but H7, a serine/threonine kinase inhibitor, and okadaic acid, a protein phosphatase 1 and 2A inhibitor, did not block the induced c-myc gene expression. Taken together, these results suggest that IL-4 stimulates the proliferation of keratinocytes in vitro by promoting a transition from G0/G1 to S phase of the cell cycle. Induction of c-myc after IL-4 treatment could indicate an important role for c-myc in the proliferation of keratinocytes. Our observations also suggest that tyrosine kinases may be involved in IL-4-induced proliferation.

The changing patterns of liver abscess during the past 20 years--a study of 482 cases.

The diagnostic and treatment modalities of liver abscess have developed rapidly over the past few years but morbidity and mortality has not been markedly reduced. A total of 482 cases of liver abscess admitted to the Yonsei Medical Center over the past 20 years (Jan. 1971-Dec. 1990) were divided into 261 cases from the 1970s and 221 cases from the 1980s and the clinical and laboratory parameters were analyzed comparatively to determine if the clinical features, therapies and prognosis of liver abscess had changed. The proportion of amebic relative to pyogenic liver abscess decreased. Transbiliary infections increased in pyogenic liver abscess of the 1980s. Clinical signs such as jaundice and hepatomegaly and symptom duration before admission decreased. Abnormal laboratory features including hypoalbuminemia and elevation of alkaline phosphatase decreased and increased, respectively, in the 1980s. Ultrasonically guided percutaneous aspiration was the choice of treatment instead of surgical drainage in the 1980s. Despite diagnostic and therapeutic advances in the management of liver abscess, the prognosis has not improved in the 1980s as compared to the 1970s. This may reflect an increase in the incidence of liver abscess in old aged patients and patients with diabetes mellitus or underlying malignancy in the 1980s.