Optimizing targeting strategies for lithotripsy through in-vitro and in vivo studies with consideration of respiratory regularity

BACKGROUND

This work aimed to identify a method to achieve improved stone targeting and safety in shockwave lithotripsy by accounting for respiration.

METHODS

We set up an electromotive device simulating renal movement during respiration to place artificial stones within the phantom gel, measuring stone weight changes before and after shockwave exposure and the cavitation damage. We conducted clinical trials using respiratory masks and sensors to monitor and analyze patient respiration during shockwave lithotripsy.

RESULTS

The in vitro efficiency of lithotripsy was higher when adjusted for respiration than when respiration was not adjusted for. Slow respiration showed the best efficiency with higher hit rates when not adjusted for respiration. Cavitation damage was also lowest during slow respiration. The clinical study included 52 patients. Respiratory regularity was maintained above 90% in regular respiration. When respiration was regular, the lithotripsy rate was about 65.6%, which stayed at about 40% when respiration was irregular. During the lithotripsy, the participants experienced various events, such as sleep, taking off their masks, talking, movement, coughing, pain, nervousness, and hyperventilation. The generation of shockwaves based on respiratory regularity could reduce pain in patients.

CONCLUSION

These results suggest a more accurate lithotripsy should be performed according to respiratory regularity.

[Three-dimensional volume rendering for dynamic characteristics of secundum atrial septal defect during various phases of the cardiac cycle and the impact on occluder selection]

Objective: To investigate the dynamic change of the secundum atrial septal defect (ASD) throughout the cardiac cycle, and assess its impact on occluder selection. Methods: This study retrospectively analyzed 35 patients with ASD who received electrocardiogram-gated coronary CT angiography (CCTA) throughout the cardiac cycle as well as interventional closure therapy in Fuwai Hospital from December 2016 to December 2019. The raw data were reconstructed into 20 phasic images of RR intervals (RRI) ranging from 0 to 95% in an increment of 5% and transmitted to a workstation for postprocessing. For each phase image, CT virtual endoscopy reconstruction technique (CTVE) was used to provide views of ASD. Axial sequence assisted CT volumetric measurement (CTAS) was used to calculate the maximum dimensions in axial planes (D_a) and in superior-inferior direction (D_b). Using a formula for converting circumference to diameter, the equivalent circle dimensions were calculated (D_e, D_e=minor axis+2 (major axis-minor axis)/3). Taking the data of 75% RRI phase, the patients were divided into D_a75%RRI≥D_b75%RRI group and D_a75%RRI<D_b75%RR group. According to the postoperative chest X-ray, the waist diameter of the occluder in the left anterior oblique plain film was measured, and its correction value (CR-POD_laoc) was calculated with the correction formula. Scatter plots of the changes of the mean values of D_a, D_b and D_e with the cardiac cycle were presented. The change and ratio of measured values of D_a and D_e at 35% and 75% RRI was calculated. The ratio of D_e change to D_a change in D_a75%RRI≥D_b75%RRI group and D_a75%RRI<D_b75%RR group was calculated, respectively, and compared between groups. Pearson correlation analysis was used to explore the correlation between CR-POD_laoc and D_e35%RRI and D_e75%RRI. Results: A total of 35 patients, aged (42.7±15.0) years, including 10 males, were included. Among 35 patients, 8 cases were divided into group D_a75%RRI≥D_b75%RRI and 27 cases into group D_a75%RRI<D_b75%RRI. Both D_a and D_b regularly changed at each phase throughout the cardiac cycle. The D_a changed significantly, with a maximum at phase of 35%-45% of RRI, and a minimum between phases of 90% and 0 of RRI. While the D_b showed insignificant changes during phases of 10%-90% RRI, and increased at 0-10% of RRI, then reduced in the remaining phases. The change of D_a was (6.35±2.46) mm, and the ratio of D_a values at 35% and 75% RRI was 0.77±0.08. The change of D_e was (2.28±1.32) mm, and the ratio of D_e at 35% and 75% RRI was 0.93±0.05. The ratio of D_e change to D_a change in the D_a75%RRI≥D_b75%RRI group was 0.67±0.13; while the ratio was 0.34±0.05 in D_a75%RRI<D_b75%RR group, and there was significant difference between the two groups (P=0.02). CR-POD_laoc was positively correlated with D_{e35% RRI} (r=0.99, P<0.001) and D_{e75% RRI} (r=0.98, P<0.001). Conclusions: Most secundum ASDs show oval shape with D_b>D_a. D_b is basically constant while D_a changes significantly during cardiac cycle (10%-90% RRI). Nonetheless, both values peak and maintain the maximum status at end-systolic phase (35%-45% RRI). For patients with huge ASD, occluder selection should be based on the D_e at 35% RRI phase, which is helpful for the successful intervention.

Metformin and tuberculosis risk in elderly patients with diabetes mellitus

SETTING: Tuberculosis (TB) and diabetes mellitus (DM) remain global health concerns. Metformin has recently received attention for its anti-tuberculosis effects.OBJECTIVE: To evaluate the risk of TB development in elderly DM patients treated with metformin compared with sulfonylureas.DESIGN: We performed a retrospective cohort study using the National Health Insurance Service-Senior database. The participants were type-2 DM (T2DM) patients aged ≥60 years between 1 January 2003 and 31 December 2013. We matched each metformin user to a sulfonylurea user using a propensity score. A Cox proportional hazards model was used to compare the risk of TB in metformin and sulfonylurea users.RESULTS: After propensity score matching, 12,582 patients were in each group. The TB incidence was 280.2/100 000 person-years (py) for metformin users and 394.5/100 000 py for sulfonylurea users. Metformin users had a lower risk of TB development than sulfonylurea users (adjusted hazard ratio 0.74, 95%CI 0.58-0.95), and the results were stronger for male participants. A dose-response relationship between metformin use and TB development was found in both sexes.CONCLUSION: Metformin use was associated with a decreased risk of TB development among elderly T2DM patients compared with sulfonylurea use.

Association between use of proton pump inhibitors and tuberculosis risk: a systematic review

SETTING: A comprehensive systematic review on whether proton pump inhibitors (PPIs) are associated with tuberculosis (TB) incidence is lacking.OBJECTIVE: To conduct a systematic review to elucidate if there is an association between PPI use and TB risk.DESIGN: We searched the MEDLINE, EMBASE, and Cochrane Library databases from their inception through 14 February 2018. Risk of Bias Assessment tool for Non-randomised Studies (ROBANS) was used to estimate the quality of each study. We could not undertake a meta-analysis because of the small number of studies and the diversity of outcome measures. All results of included studies are described narratively.RESULTS: Five studies were identified. In three case-control studies, compared with non-PPI use, PPI use was associated significantly with TB incidence, a 1.2-to-1.7-fold increased risk (adjusted OR 1.29; 95%CI 1.29-1.30, OR 1.31; 95%CI 1.22-1.41, adjusted hazard ratio 1.71; 95%CI 1.17-2.50). A cohort study reported that ≥3 months of PPI treatment was not associated significantly with TB incidence compared PPI treatment of <3 months. One cohort study reported that lansoprazole use decreased TB development significantly when compared with omeprazole/pantoprazole use.CONCLUSION: Compared with non-PPI use, PPI use was associated significantly with TB risk but the studies were heterogeneous.

[Dynamic investigation of nutritional risk in patients with malignant tumor during hospitalization]

Objective: To prospectively investigate the changes in nutritional status of patients with malignant tumors during hospitalization by using nutritional risk screening (NRS2002), and to analyze the correlation between the nutritional status and clinical outcomes . Methods: This was a prospective and parallel research done by multi-center collaboration from 34 hospitals in China from June to September 2014.Hospitalized patients with malignant tumors inthese departments (Department of Gastroenterology, respiratory medicine, oncology, general surgery, thoracic surgery and geriatrics)were investigated. Only the patients with age≥ 18 years and hospitalization time between 7-30 days were included. During hospitalization, the physical indexes of human bodywere measured, and the NRS 2002 scores, and monitored the nutritional support at the time points of admission and 24 hours before discharge were recorded.And whether there was a nutritional risk in hospitalized patients and its association with clinical outcomes were investigated. Results: A total of 2 402 patients with malignancies were enrolled in this study. Seventy fourpatients who did not complete NRS2002 were eliminated, and 2 328 patients were included. The number of the main diseases was the top five, including 587 cases of colorectal cancer, 567 cases of lung cancer, 564 cases of gastric cancer, 146 cases of esophageal cancer, and 119 cases of liver tumor. At the time of discharge, compared with admission, the BMI, body weight, grip and calf circumferences of patients with malignant tumor were significantly decreased (P<0.05). The total protein, albumin, prealbumin and hemoglobin were significantly lower than those at admission (P<0.05). In 2 328 patients who were completed nutritional risk screening, the rate of malnutrition at admission was 11.1% (BMI =18.5, 258/2 328) and the rate of malnutrition at discharge was 10.9% (BMI =18.5, 254/2 328), there were no significant differences (χ(2)=0.019 7, P=0.888). There were 1 204 patients with nutritional risk at admission (51.7%, NRS2002 score≥3)and 1 352 patients with nutritional risk at discharge (58.1%, NRS2002 score≥3), with significant differences (χ(2)=49.9, P<0.001). The incidence of nutritional risk in patients with colorectal, stomach, and lung tumors at discharge was significantly higher than that at admission (P<0.05). The infective complications and other complications of patients with nutritional risk were significantly greater than those without nutritional risk at admission and at discharge.ICU hospitalization stay of patients with nutritional risk was increased significantly than those without nutritional risk at admission(P=0.042). Hospitalization expenses of patients with nutritional risk was increased significantly than those of patients without nutritional risk at discharge(P<0.01). Conclusion: The patients with malignant tumor have a higher incidence rate of malnutrition at both admission and discharge and malnutritionhas correlation with adverse clinical outcomes.The aboveindicators did not improve significantly at discharge.Doctors should pay more attention to the nutritional status (screening and evaluation)of patients before discharge and use appropriate and adequate nutrition support in order to prevent the weight loss and improve the life quality of patients.

The relationship between clinical characteristics including presence of exposed lesions and health-related quality of life (HRQoL) in patients with psoriasis: analysis from the nationwide epidemiologic study for psoriasis in Korea (EPI-PSODE study)

BACKGROUND

Psychological aspect and quality of life should be considered in treating patients with psoriasis.

OBJECTIVE

We sought to ascertain which clinical characteristics including presence of exposed lesions are associated with impairment of health-related quality of life (HRQoL) in patients with psoriasis.

METHODS

The EPI-PSODE study was a nationwide, multicenter, cross-sectional study conducted in Korea that included 1260 adult patients with psoriasis. In addition to clinical characteristics including presence of exposed lesions, data were collected using the Psoriatic Arthritis (PsA) Screening and Evaluation (PASE), Dermatology Life Quality Index (DLQI), MOS 36-Item Short-Form Health Survey (SF-36), Work Productivity and Activity Impairment Questionnaire Psoriasis (WPAI: PSO) and Medication Satisfaction Questionnaire (MSQ).

RESULTS

Patients with a DLQI score > 5 (n = 990) were younger, had an earlier onset of psoriasis, scored higher on the Psoriasis Area and Severity Index (PASI), had higher body surface area (BSA) and had higher PASE scores than patients with DLQI ≤ 5 (n = 266). The group of patients with exposed lesions (n = 871) were younger and male predominance, earlier onset of psoriasis, longer disease duration, higher PASI/BSA score and a higher proportion with drinking and smoking history each than the group of patients without exposed lesions (n = 389). Presence of exposed lesions negatively influenced DLQI, 36-Item Short-Form Health Survey (SF-36) (mental component), presenteeism, total work productivity impairment and total activity impairment in the WPAI: PSO. In multiple regression model, PASI score was the only variable which was significantly associated with all HRQoL measures. Presence of exposed lesions was a significant factor affecting DLQI and SF-36 (mental).

CONCLUSION

The presence of exposed lesions has a negative impact on quality of life, mental health and work productivity. Therefore, effective treatments are particularly needed for psoriasis patients with exposed lesions.

Supplementation with nutrients modulating insulin-like growth factor-1 negatively correlated with changes in the levels of pro-inflammatory cytokines in community-dwelling elderly people at risk of undernutrition

BACKGROUND

Suboptimal nutrition accompanied by chronic low-grade increases in circulating cytokine levels is more common in elderly people. We explored the improvement in nutritional status, especially in the level of insulin-like growth factor-1 (IGF-1) and its relationship with changes in circulating cytokine levels, after providing extra protein and energy content to community-dwelling older adults at risk of undernutrition.

METHODS

Sixty nondiabetic subjects, aged ≥65 years and living independently in a community for elderly people, with a serum pre-albumin level ≤30 mg dL^-1 and a body mass index <25 kg m^-2 , were recruited. The subjects were followed for a 2-week pre-intervention period, during which they maintained routine dietary habits. This was followed by an intervention period, during which they received oral nutritional supplementation for 2 weeks.

RESULTS

Following 2 weeks of intervention, there were significant increases in total lymphocyte count (TLC) and insulin-like growth factor (IGF)-1, pre-albumin and transferrin compared to baseline. Body weight and mid-arm circumference significantly increased without alteration of tricep skinfold thickness at the end of the intervention. There was a significant reduction in interleukin (IL)-6 levels and a trend toward a decrease in the tumor necrosis factor (TNF)-α levels. At baseline, age was negatively correlated with IGF-1 levels and positively correlated with IL-6 and TNF-α levels. The change (▵, from baseline) in IGF-1 level was positively correlated with age and negatively correlated with ▵IL-6 and ▵TNF-α.

CONCLUSIONS

A 2-week intervention with oral nutritional supplementation improved nutritional status and decreased circulating cytokine levels. Specifically, ▵IGF-1 was negatively correlated with changes in pro-inflammatory cytokine levels in community-dwelling elderly people at risk of undernutrition. (Clinicaltrials.gov: NCT02656186).

Routine endoscopic screening for synchronous esophageal neoplasm in patients with head and neck squamous cell carcinoma: a prospective study

Early detection of synchronous esophageal squamous cell neoplasm (ESCN) in head and neck squamous cell carcinoma (HNSCC) patients can significantly affect their prognosis. We investigated the prevalence of synchronous ESCN and the risk factors for developing ESCN in patients with HNSCC, and evaluated the effect of routine endoscopic screening in these patients. Subjects who were diagnosed as HNSCC from May 2010 to January 2014 were eligible. All patients underwent conventional white light endoscopic examinations with narrow band imaging and Lugol chromoendoscopy. Among 458 subjects screened, 28 synchronous ESCN were detected in 24 patients (5.2%). The prevalence of ESCN was greatest in patients with hypopharyngeal cancer (20.9%). In multivariate analysis, pyriform sinus involvement was independent risk factor for developing synchronous ESCN (odds ratio 171.2, P < 0.001). During the follow-up period (median, 24 months), the 3-year overall survival rates was significantly lower in patients with ESCN than in patients without ESCN (54.2% vs. 78.3%, P = 0.0013). Routine endoscopic screening for detecting synchronous ESCN should be recommended for patients with HNSCC, especially those with pyriform sinus involvement.

Seroepidemiological Survey of Zoonotic Diseases in Small Mammals with PCR Detection of Orientia tsutsugamushi in Chiggers, Gwangju, Korea

Serosurveillance for zoonotic diseases in small mammals and detection of chiggers, the vector of Orientia tsutsugamushi, were conducted from September 2014 to August 2015 in Gwangju Metropolitan Area. Apodemus agrarius was the most commonly collected small mammals (158; 91.8%), followed by Myodes regulus (8; 4.6%), and Crocidura lasiura (6; 3.5%). The highest seroprevalence of small mammals for O. tsutsugamushi (41; 26.3%) was followed by hantaviruses (24; 15.4%), Rickettsia spp. (22; 14.1%), and Leptospira (2; 1.3%). A total of 3,194 chiggers were collected from small mammals, and 1,236 of 3,194 chiggers were identified with 7 species of 3 genera: Leptotrombidium scutellare was the most commonly collected species (585; 47.3%), followed by L. orientale (422; 34.1%), Euchoengastia koreaensis (99; 8.0%), L. palpale (58; 4.7%), L. pallidum (36; 2.9%), Neotrombicula gardellai (28; 2.3%), and L. zetum (8; 0.6%). L. scutellare was the predominant species. Three of 1,236 chigger mites were positive for O. tsutsugamushi by PCR. As a result of phylogenetic analysis, the O. tsutsugamushi strain of chigger mites had sequence homology of 90.1-98.2% with Boryong. This study provides baseline data on the distribution of zoonotic diseases and potential vectors for the development of prevention strategies of vector borne diseases in Gwangju metropolitan area.

Association of phosphodiesterase 4D gene and interleukin-6 receptor gene polymorphisms with ischemic stroke in a Chinese hypertensive population

Genetic factors have been shown to be associated with the risk of stroke. However, due to individual differences, the extent of the association between genetic factors and stroke varies widely. Hypertension is considered one of the most important risk factors for stroke, but it remains unknown whether the genetic association with stroke in a hypertensive population is the same as that in a non-hypertensive population. The aim of the present study was to explore the association between the phosphodiesterase 4D gene (PDE4D) and interleukin-6 receptor gene (IL6R) single nucleotide polymorphisms and ischemic stroke in a hypertensive population. The study included 307 ischemic stroke cases with hypertension and 227 controls (simple hypertension). The polymorphic loci rs12188950 and rs918592 in PDE4D, and rs4075015 and rs4537545 in IL6R were selected for analyzing the genotype and allele frequencies between cases and controls. rs12188950 was not found in the study population. In the univariate analysis, the rs918592 polymorphism in PDE4D was found to be significantly associated with ischemic stroke with the recessive model (P = 0.02), whereas no association with ischemic stroke was observed for rs4075015 and rs4537545 in IL6R. Following adjustment for binary logistic regression, the rs918592 polymorphism was not found to be associated with ischemic stroke. While prior studies have found an association between PDE4D and IL6R polymorphisms and ischemic stroke, our results suggest that this association may be different in a hypertensive population. Therefore, the association between PDE4D and IL6R polymorphisms and ischemic stroke among a hypertensive population requires further investigation.

Expression and prognostic influence of NF-κB and EGFR in esophageal cancer

The goal of this study was to investigate the expression profiles of nuclear factor-kappa B (NF-κB) and epidermal growth factor receptor (EGFR) in esophageal cancer and to determine their association with tumor prognosis. This study included 40 esophageal cancer patients [22 men and 18 women; average age = 62.7 ± 3.9 years; tumor-node-metastasis (TNM) staging: 12 patients with stage I, 13 patients with stage II, and 15 patients with stage III disease]. Tumor tissues and tumor-adjacent tissue specimens were collected during radical resections at our hospital. Immunohistochemical staining was used to examine these tissues for NF-κB and EGFR expression. Follow-up of all patients included gathering information such as the 3-year survival rate. We found that NF-κB and EGFR expression was significantly higher in tumor tissues compared to tumor-adjacent normal tissues. Expression was not related to gender or age, but was positively associated with the degree of tumor infiltration. NF-κB and EGFR expression levels gradually increased with higher TNM stage, but this difference was not significant. Follow-up results showed that patients with higher NF-κB and EGFR levels had a lower survival rate and unfavorable prognosis. In conclusion, we found that NF-κB and EGFR expression was significantly elevated during the occurrence and development of esophageal carcinoma, and expression of these factors appears to be correlated with cancer progression. Higher expression of both genes is associated with an unfavorable prognosis.

Silicon carbide-free graphene growth on silicon for lithium-ion battery with high volumetric energy density

Silicon is receiving discernable attention as an active material for next generation lithium-ion battery anodes because of its unparalleled gravimetric capacity. However, the large volume change of silicon over charge–discharge cycles weakens its competitiveness in the volumetric energy density and cycle life. Here we report direct graphene growth over silicon nanoparticles without silicon carbide formation. The graphene layers anchored onto the silicon surface accommodate the volume expansion of silicon via a sliding process between adjacent graphene layers. When paired with a commercial lithium cobalt oxide cathode, the silicon carbide-free graphene coating allows the full cell to reach volumetric energy densities of 972 and 700 Wh l⁻¹ at first and 200th cycle, respectively, 1.8 and 1.5 times higher than those of current commercial lithium-ion batteries. This observation suggests that two-dimensional layered structure of graphene and its silicon carbide-free integration with silicon can serve as a prototype in advancing silicon anodes to commercially viable technology.

The volume expansion of silicon is a big problem in lithium-ion batteries with silicon anodes. Here, the authors report direct graphene growth on silicon nanoparticles, which effectively mitigates the problem, leading to excellent electrochemical performance.

The effect of age on the key parameters in the Chicago classification: a study using high-resolution esophageal manometry in asymptomatic normal individuals

BACKGROUND

High-resolution manometry using the Chicago classification, which utilizes parameters including integrated relaxation pressure (IRP), distal contractile integral (DCI), and contractile front velocity (CFV), shows better diagnostic ability than previous conventional criteria. However, the current normal cut-off values for the Chicago classification are based on individuals aged 19-48 years and do not include older people. Here, we aimed to assess the normal values for the Chicago classification in individuals aged 20-67 years and compare the parameters across age groups.

METHODS

Fifty-four asymptomatic healthy individuals (27 male and 27 female; age range. 20-67 years) were prospectively enrolled. To evaluate the effect of age and sex on manometric profiles, we attempted to enroll equal numbers of male and female subjects for each decade. Manometry was performed in both the supine and sitting positions.

KEY RESULTS

The distal latency (DL) was significantly shorter with increasing age in both measurement positions. Furthermore, IRP was significantly higher with increasing age in both positions. Spearman's ranked correlation coefficient analysis indicated that DCI and IRP in both positions were positively correlated with age.

CONCLUSIONS & INFERENCES

Age affects the key parameters currently used in the Chicago classification, including IRP, DCI, and DL. Larger prospective studies with older subjects are needed to determine the age-related normal values for the Chicago classification system.

CO2 enhanced chemical vapor deposition growth of few-layer graphene over NiO(x)

The use of mild oxidants in chemical vapor deposition (CVD) reactions has proven enormously useful. This was also true for the CVD growth of carbon nanotubes. As yet though, the use of mild oxidants in the CVD of graphene has remained unexplored. Here we explore the use of CO2 as a mild oxidant during the growth of graphene over Ni with CH4 as the feedstock. Both our experimental and theoretical findings provide in-depth insight into the growth mechanisms and point to the mild oxidants playing multiple roles. Mild oxidants lead to the formation of a suboxide in the Ni, which suppresses the bulk diffusion of C species suggesting a surface growth mechanism. Moreover, the formation of a suboxide leads to enhanced catalytic activity at the substrate surface, which allows reduced synthesis temperatures, even as low as 700 °C. Even at these low temperatures, the quality of the graphene is exceedingly high as indicated by a negligible D mode in the Raman spectra. These findings suggest the use of mild oxidants in the CVD fabrication as a whole could have a positive impact.

Depression as a correlate of functional status of community-dwelling older adults: utilizing a short-version of 5-item Geriatric Depression Scale as a screening tool

Depression has been known to be associated with functional limitations in elderly populations and screening is an effective preventive approach. The purpose of this study was to examine the contribution of depression in explaining the functional status of community-dwelling older adults and to explore the utility of a short version 5-item Geriatric Depression Scale (GDS-5) as a screening tool.

DESIGN

Cross-sectional survey Settings: Six hospitals and communities served by home-delivery meal programs Participants: 529 individuals aged 60 years and older.

MEASUREMENTS

Using structured survey questionnaires, key variables including demographics, depression status, and two domains of functional status assessed by basic Activities of Daily Living (ADL) /Instrumental ADL (IADL) and mini-mental status (MMSE) were collected. To determine the unique contribution of depression in explaining functional status of participating older adults, hierarchical multiple regression was conducted.

RESULTS

The model explained 18 % of the total variance in physical function and 21 % of the total variance in cognitive function. Race/ethnicity and depression were significant predictors of functional status. In particular, entry of the depression variable resulted in a significant R square change of 7%, accounting for a unique portion of the ADL/IADL variance. In terms of cognitive function measured by MMSE, entry of the depression variable showed a small, but significant change. Older adults who were ethnic minorities and had depression were significantly more likely to report poor perceived physical and cognitive function. Hierarchical multiple regressions revealed that some personal factors such as age, education, race/ethnicity contributed to the explanatory model, and depressive symptoms significantly explained additional variance. GDS-5 was less reliable (Cronbach's alpha= 0.5) to assess depressive symptoms in this study.

CONCLUSION

Depression was a significant contributing factor to functional limitations of older adults. A short 5-item version of the GDS could be used to screen older adults, but two-tiered GDS-5/15 would be better alternative tool.

Polyethylene glycol bowel preparation does not eliminate the risk of acute renal failure: a population-based case-crossover study

BACKGROUND AND STUDY AIMS

Polyethylene glycol (PEG) bowel preparations are regarded as effective and safe for colonoscopy; however, recent reports have indicated a risk of acute renal failure (ARF). This population-based case-crossover study evaluated the association between PEG and ARF in screening colonoscopy patients aged ≥ 50 years.

PATIENTS AND METHODS

Korean Health Insurance Review and Assessment Service (HIRA) claims data from 1 January 2005 to 31 December 2009 were used in the study. The study population consisted of patients aged ≥ 50 years who were first hospitalized for ARF following colonoscopy involving PEG bowel preparation. For each patient, PEG use in a 1-, 2-, or 4-week period prior to the first hospital admission date for ARF (hazard period) was compared with PEG use in four earlier 1-, 2-, or 4-week control periods. Conditional logistic regression analysis was used to estimate odds ratios (ORs) and 95 % confidence intervals (CIs), adjusting for concomitant medications that could induce ARF.

RESULTS

The total number of study patients was 1064 (59 % were male). A greater proportion of patients used PEG during the hazard period than during the control periods (for 4-week time window: 8.8 % vs. 3.2 %). The adjusted ORs for ARF incidence when applying the 1-, 2-, and 4-week periods were 3.1 (95 %CI 2.06 - 4.73), 2.5 (95 %CI 1.76 - 3.53), and 2.1 (95 %CI 1.61 - 4.85), respectively.

CONCLUSIONS

The use of PEG was associated with the risk of ARF. Adequate hydration and renal function monitoring should be assured before and after colonoscopy, regardless of the bowel preparation regimen used.

Graphene for true Ohmic contact at metal-semiconductor junctions

The rectifying Schottky characteristics of the metal-semiconductor junction with high contact resistance have been a serious issue in modern electronic devices. Herein, we demonstrated the conversion of the Schottky nature of the Ni-Si junction, one of the most commonly used metal-semiconductor junctions, into an Ohmic contact with low contact resistance by inserting a single layer of graphene. The contact resistance achieved from the junction incorporating graphene was about 10(-8) ~ 10(-9) Ω cm(2) at a Si doping concentration of 10(17) cm(-3).

Endoscopic submucosal dissection for sessile, nonampullary duodenal adenomas

Although endoscopic submucosal dissection (ESD) is increasingly utilized to treat early neoplasms of the gastrointestinal tract, its use for duodenal neoplasms is limited by the thin wall and narrow lumen of the duodenum. We have reviewed cases where ESD was used to treat sessile, nonampullary duodenal neoplasms. To do this, we retrospectively reviewed the medical records of patients treated with ESD for adenomas of the duodenum from January 2001 to December 2010, assessing the curative outcomes and complication rates. A total of 14 cases were reviewed. Mean patient age was 56.4 years. The mean size of tumors and mean size of the specimens were 17.1 mm and 26.4 mm, respectively. The en bloc resection rate with ESD was 78.6%, and the complete (R0) resection rate was 85.7%. No patient in the study experienced major bleeding. However, second-look endoscopy revealed minor bleeding requiring endoscopic homeostasis in one case (7.1%). Perforations were observed in five cases (35.7%). Two of the five patients with perforation underwent surgery. The ESD methods yielded acceptable curative resection rates for duodenal adenomas, although ESD was associated with a higher rate of perforation. Therefore, duodenal ESD should be performed with care and only in selected patients to avoid serious complications.

Comparability and utility of body composition measurement vs. anthropometric measurement for assessing obesity related health risks in Korean men

BACKGROUND

Obesity is commonly assessed by body mass index (BMI) of which limitations come from an inability to distinguish body fat mass from lean mass. Several anthropometric measurements, including BMI, waist circumference, waist-to-height ratio and waist-to-hip ratio have been used to predict metabolic syndrome. The purpose of this study was to evaluate the utility of FMI or BF% combined with previous known anthropometric indices to assess the risk of metabolic syndrome in clinical practice.

METHODS

In 5534 men visiting a hospital for health check-ups, blood tests, anthropometric measurements and body composition analysis using BIA were performed. Logistic regression analysis was performed to compare the odds ratios for metabolic syndrome and each component of metabolic syndrome among BMI, waist-to-height ratio, waist-to-hip ratio, FMI and BF%. The area under the curve (AUC) of the receiver operating characteristic curve (ROC) for metabolic syndrome was compared between several measurements. The net reclassification improvement with integrated discrimination improvement was used for assessing value of body composition measurement.

RESULTS

The adjusted odds ratios of metabolic syndrome was 1.80 (95% CI, 1.71-1.89) for FMI and 1.15 (95% CI, 1.13-1.17) for BF%. Odds ratio of each metabolic component was highest for FMI among several anthropometric and body composition measurements. AUCs using the ROC curve for metabolic syndrome was highest for waist-to-height ratio, 0.823 (95% CI, 0.808-0.837) by National Cholesterol Education Program criteria. FMI caused a mild increase in integrated discrimination improvement when combined with waist-to-height ratio.

CONCLUSIONS

Waist-to-height ratio seems to be the best screening tool for evaluating metabolic syndrome in Korean men, and adding FMI could result in a modest increase in integrated discrimination improvement.

Natural course of noncurative endoscopic resection of differentiated early gastric cancer

BACKGROUND AND STUDY AIMS

Following noncurative endoscopic resection of early gastric cancer (EGC), the patient should be observed when the underlying disease is severe, the patient is elderly, or the patient refuses further treatment. The aim of this study was to analyze the clinical outcomes of patients with differentiated EGC who underwent noncurative endoscopic resection without additional treatment.

PATIENTS AND METHODS

Included patients underwent noncurative endoscopic resection for differentiated EGC without additional treatment at the Asan Medical Center between July 1994 and January 2009. Clinical and oncological outcomes were analyzed.

RESULTS

A total of 159 patients were included in the analysis. The median follow-up period was 33 months (interquartile range [IQR] 22 - 52 months). In total, 40 patients died (25.2 %) - 3 due to stomach cancer, 34 due to other causes, and 3 from unknown causes; the median survival time after endoscopic treatment for these patients was 27.5 months (IQR 13.8 - 48.3 months). Multivariate analysis showed that the rates of underlying disease (P < 0.001) and lymphovascular invasion (P = 0.005) were higher among the 40 patients who died than among the 119 survivors. The overall 3-  and 5-year survival rates were 82.9 % and 77.1 %, respectively; the rates of the patients with lymphovascular invasion were 61.9 % and 42.4 %, respectively, and the rates of patients without lymphovascular invasion were 86.1 % and 81.8 %, respectively (P < 0.001).

CONCLUSIONS

Additional treatment provides fewer benefits to patients who do not have long life expectancies. Additional surgery can be considered for patients with lymphovascular invasion because of its high mortality rate; however, the benefits and risks of surgery should be considered carefully.

Methylation status of CpG sites in the MCP-1 promoter is correlated to serum MCP-1 in Type 2 diabetes

AIM

Monocyte chemoattractant protein-1 (MCP-1) is a potent chemokine and plays an important role in atherosclerosis of Type 2 diabetes. The aim of this study was to investigate the methylation status of CpG sites in the MCP-1 promoter in Type 2 diabetic patients and its correlation to serum MCP- 1 level, and blood glucose level.

METHODS

The 32 patients with Type 2 diabetes and 15 healthy controls were enrolled into the study. Bodymass index, blood pressure, blood lipid, blood glucose, glycosylated hemoglobin (HbA1c), and serum MCP-1 were measured. Genomic DNA was isolated fromthe peripheral blood mononuclear cells (PBMC). Methylation status of CpG sites in theMCP-1 promoter was determined using methylation specific polymerase chain reaction.

RESULTS

The promoter region (2890-3050 bp) was predominantly methylated in PBMC from controls.Methylation of CpGmotifs were less methylated in the patients than in the controls (25% vs 80%; p<0.001), while the level of MCP-1 in serum was higher in patients with Type 2 diabetes (193.95±74.96 vs 88.46±55.10; p<0.001). MCP-1 promoter methylation was significantly correlated to serum MCP-1, HbA1c, fasting blood glucose, and triglyceride.

CONCLUSION

These data suggest that hypomethylation of CpG sites in the MCP-1 promoter region may be affected by blood glucose and TG, which then increase the serum MCP-1 level and may play a role in the vascular complications of Type 2 diabetes.

Large scale metal-free synthesis of graphene on sapphire and transfer-free device fabrication

Metal catalyst-free growth of large scale single layer graphene film on a sapphire substrate by a chemical vapor deposition (CVD) process at 950 °C is demonstrated. A top-gated graphene field effect transistor (FET) device is successfully fabricated without any transfer process. The detailed growth process is investigated by the atomic force microscopy (AFM) studies.

Adenomyosis completely encapsulated by muscle-like cavity in the mesorectum: a case report

A case of adenomyosis, completely encapsulated and located in the mesentery between the sigmoid colon and rectum, was admitted our hospital. We have reported the symptoms, diagnosis, and treatment of the present case.

Short-acting nifedipine and risk of stroke in elderly hypertensive patients

OBJECTIVES

Short-acting nifedipine is frequently prescribed in elderly hypertensive patients, despite warnings of possible harmful cardiovascular effects. We conducted a case-crossover study to estimate the risk of stroke episodes associated with use of short-acting nifedipine in elderly hypertensive patients.

METHODS

We used the Korea Health Insurance Review & Assessment Service database. Cases included elderly hypertensive patients with hospitalization or emergency department visits for first stroke (International Classification of Diseases-10, I60-I64) between July 1, 2005, and June 30, 2006. Patients with prior stroke-related hospital admission or any visit related to TIA were excluded. Exposure to a short-acting nifedipine formulation was assessed within 7 days before the incident stroke episode (case period) and within a 7-day period preceding 60 days before the episode (control period). Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated by conditional logistic regression, with adjusting for antihypertensives, anticoagulants, antiplatelet agents, and pneumonia.

RESULTS

A total of 16,069 stroke patients with a mean (±SD) age of 68.3 (±2.1) years were studied, of whom 8,573 (53.3%) were female. Short-acting nifedipine was prescribed at least once to 301 (1.9%) patients during the case period. An increased risk of stroke associated with use of short-acting nifedipine within 7 days (adjusted OR 2.56; 95% CI 1.96-3.37) was observed. Patients who were newly prescribed nifedipine within the recent 7 days showed an OR of 4.17 (95% CI 2.93-5.93) compared with nonusers.

CONCLUSION

Use of short-acting nifedipine was associated with increased risk of stroke occurrence in elderly hypertensive patients.

Unique photoemission from single-layer graphene on a SiO2 layer by a substrate charging effect

Single-layer graphene (SLG) shows an anomalously large surface charging effect during scanning photoelectron microscopy (SPEM), which is distinguished from bi-layer graphene (BLG). The different behaviour is believed due to a different screening effect for SLG and BLG.

Transnasal endoscope-assisted endoscopic submucosal dissection for gastric adenoma and early gastric cancer in the pyloric area: a case series

Endoscopic submucosal dissection (ESD) is an important therapeutic option for gastric adenoma and early gastric cancer (EGC). However, ESD is technically difficult when lesions are located in the pyloric area. Our aim was to introduce the transnasal endoscope-assisted ESD method, which provides for excellent cutting-line visualization through control of submucosal traction. A total of eight patients with gastric adenoma or EGC located in the pyloric area were consecutively enrolled. A primary operating endoscope was used to perform marking, incision, submucosal dissection, and hemostasis, while a thinner, transnasal endoscope operated by a second endoscopist was used to retract connective submucosal tissue to provide cutting-line visualization using V-shaped grasping forceps. En bloc resection was achieved in all eight cases, as was complete resection. The median longest lesion diameter was 19 mm (range: 12-25 mm), and the median procedure time was 37.5 minutes (range: 29-59 minutes). There were no incidents of significant bleeding or perforation. Transnasal endoscope-assisted ESD was useful for treating gastric neoplasms in the pyloric area. The procedure was relatively easy and safe, provided excellent visualization through tissue retraction, and allowed for complete en bloc resection.

Influence of epidermal growth factor supplementation during in vitro maturation on nuclear status and gene expression of canine oocytes

This study evaluated the effect of epidermal growth factor (EGF) supplementation during in vitro maturation on the meiotic status and the expression of EGF receptor (EGFr), luteinizing hormone receptor (LHr) and gap junction protein α 5 (GJA5) in canine cumulus-oocyte-complexes (COCs). COCs of ≥110 μm diameter, exhibiting dark pigmentation and completely surrounded by three or more layers of cumulus cells collected from anestrus stage ovaries in natural cycle were matured in TCM-199 supplemented with 10% fetal bovine serum, 0.57 mM cysteine, 10 μg/ml LH and FSH, and different concentrations of EGF (0, 10 and 30 ng/ml). Oocytes cultured for 72 h were fixed to assess the nuclear maturation. Expression of EGFr, LHr and GAJ5 was assessed by immunocytochemistry and real-time PCR. Proportion of metaphase II status of oocytes cultured in in vitro maturation (IVM) medium supplemented with 10 ng/ml EGF for 72 h was significantly (P<0.05) higher than 0 and 30 ng/ml EGF supplemented IVM medium (9.8% vs. 6.5% and 5.2%). In both cumulus cells and oocytes, EGFr protein was undetectable, LHr protein level of expression was low and a strong expression of GJA5 protein was observed. The relative abundance (RA) of EGFr transcript revealed low levels and the LHr expression decreased steadily with addition of EGF. However it did not vary among different concentrations of EGF supplementation. The RA of GJA5 transcript exhibited lower level at 10 ng/ml EGF supplementation. In conclusion, the supplementation of 10 ng/ml EGF in IVM media exerted a positive influence on the progression of maturation to MII phase and the expression level of GJA5 at 72 h, but did not demonstrate any stimulatory role on the expression of EGFr and LHr during the maturation of the canine IVM oocytes.

Carbon nanotube Schottky diode via selective electrochemical metal deposition

A single walled carbon nanotube (SWNT) Schottky diode was fabricated via selective electrochemical metal deposition on a prefabricated SWNT field effect transistor device. By electrochemically depositing Pd on only one of the prepatterned Ti electrodes, asymmetric Ohmic (at Pd-SWNT) and Schottky (at SWNT-Ti) contacts were resolved, resulting in efficient current rectification. The selective electrochemical deposition was performed by electrically isolating two Ti electrodes connected through a SWNT by depleting hole carriers in the SWNT upon the simultaneous application of high positive gate voltage during the deposition process. The successful selective deposition of Pd metals was confirmed by X-ray photoelectron spectroscopy.

Conversion of single-crystalline C60 nanodisks and nanorods into graphitic nanostructures via hydrogen thermal annealing

We have developed a process to convert C(60) nanostructures into graphitic nanostructures. Disk-shaped and wire-shaped C(60) nanostructures synthesized by the liquid-liquid interfacial precipitation method, the vapor-solid process, and solvent evaporation were successfully converted into graphitic structures by thermal annealing in hydrogen at 900 degrees C. Scanning electron and tunneling electron microscopic studies confirmed that the converted nanostructures were composed of multi-graphitic structures such as multi-walled carbon nanotubes, carbon nanofibers, and carbon onions. Fourier transform Raman spectroscopy and conductance measurements were carried out to further confirm the successful formation of graphitic layers. In the Raman spectra, the nanostructures converted from C(60) disks showed signature D, G, and G(') bands of graphitic structures, while the A(g) mode (1469 cm(-1)) of the original C(60) molecule disappeared. C(60) nanowire devices fabricated for the conductance measurements of the converted structures showed dramatically decreased resistance (R approximately 100 kOmega) compared to the pristine C(60) wire (R>100 MOmega). Further manipulation of the reaction environment, including the gas and the annealing temperature, may reveal a new way to attain diverse graphitic nanostructures economically.

Unchanging trend of esophagogastric junction adenocarcinoma in Korea: experience at a single institution based on Siewert's classification

The incidence of adenocarcinoma of the esophagogastric junction (AEG) has been increasing in Western countries. It is unclear, however, whether similar changes are occurring in Asia. We therefore investigated the incidence of AEG in Korea, and assessed the clinical characteristics of three types of AEG based on Siewert's classification. We retrospectively reviewed the medical records of 16 811 patients diagnosed with esophageal squamous cell carcinoma (ESC, n= 1450) or gastric noncardiac adenocarcinoma (GNCA, n= 14 751) between 1992 and 2006. The patients were divided into three 5-year cohorts (cohort A [1992-1996], n= 2734, cohort B [1997-2001], n= 5727, and cohort C [2002-2006], n= 8350), and the ratios of AEG (n= 610) to non-AEG (ESC and GNCA) in each cohort were compared. Using Siewert's classification, the tumors were categorized into one of three types, and patient demographic features and 5-year survival rates were compared. The ratio of AEG to non-AEG cases did not change over time (0.037, 0.034, and 0.039 for cohorts A, B, and C, respectively; P= 0.40). Of the 610 patients with AEG, 23 (3.7%) had type 1 tumors, 47 (7.7%) had type 2, and 540 (88.5%) had type 3. The 5-year survival rate of patients with type 1 AEG was much lower (4.8 +/- 4.7%) than that of those with type 2 (47.9 +/- 7.8%) and type 3 (47.4 +/- 2.5%) tumors. Unlike in Western countries, the ratio of AEG to non-AEG cases has not increased over time in Korea. Type 1 AEG was rarer and associated with a more unfavorable prognosis in Korea than in Western countries.

Solitary fibrous tumor of the orbit: CT and MR imaging findings

BACKGROUND AND PURPOSE

Solitary fibrous tumor (SFT) is a rare spindle-cell neoplasm originating from mesenchymal fibroblast-like cells. The purpose of this study was to describe the CT and MR imaging features of SFTs in the orbit.

MATERIALS AND METHODS

We retrospectively reviewed CT and MR images in 6 patients (2 men and 4 women), aged 18 to 51 years, with SFT proved on histologic examination located in and around the orbit. All patients underwent CT (including dual-phase CT in 3), and MR imaging was obtained in 3. We evaluated the imaging findings with emphasis on the location, size, margin, internal architecture, and pattern of enhancement of the lesion.

RESULTS

All 6 lesions were found as a solitary, well-defined mass, ranging in size from 18 to 30 mm (mean, 24 mm). Three were located in the postseptal orbit, 2 in the lacrimal sac, and 1 on the lower eyelid. Compared with the cerebral cortex, all 3 lesions examined by MR imaging showed homogeneous isointense signal intensity on T1-weighted images and heterogeneous mixed isointense and hyperintense signal intensity on T2-weighted images. On visual inspection, all 6 lesions showed marked homogeneous (n = 4) or heterogeneous (n = 2) enhancement on postcontrast CT and MR images. In 3 patients examined with dual-phase CT, all lesions demonstrated rapid enhancement with early washout of contrast material.

CONCLUSION

SFT might be included in the differential diagnosis of soft tissue masses in the orbit, if one sees a markedly enhancing mass showing the similar characteristics to those of the internal carotid artery on postcontrast CT or MR images.

Direct precursor conversion reaction for densely packed Ag2S nanocrystal thin films

Successful realization of highly crystalline and densely packed Ag2S nanocrystal (NC) films has been achieved by directly converting precursor molecules, Ag(SCOPh), on preheated substrates. When an aliquot of Ag(SCOPh) solution dissolved in trioctylphosphine (TOP) is applied on preheated solid substrates at 160 degrees C, such as SiO2/Si, H-terminated Si, and quartz. Ag2S NC thin films have been formed with instant phase and color changes of the precursor solutions from pale yellow homogeneous solution to black solid films. The average diameter of individual Ag2S NCs forming thin films is ca. 25 nm, as confirmed by examining both isolated Ag2S NCs from thin films and as-made thin film samples by using transmission electron microscopy (TEM) and scanning electron microscopy (SEM), respectively. Powder X-ray diffraction (XRD) pattern shows that the synthesized Ag2S NCs have well-defined monoclinic acanthite phase. Direct precursor conversion process has resulted in densely packed Ag2S NCs with reduced interparticle distances owing to efficient removal of TOP during the reaction. Compared to the devices fabricated by the drop-coating process, Ag2S thin film devices fabricated by direct precursor conversion process have shown a ca. 300-fold increased conductance. Such Ag2S NC devices have also displayed reliable photoresponses upon white light illumination with high photosensitivity (S approximately equal to 1).

The effects of apigenin-7-O-beta-D-glucuronopyranoside on reflux oesophagitis and gastritis in rats

1. This study evaluated the inhibitory action of apigenin-7-O-beta-D-glucuronopyranoside (AGC), apigenin, and omeprazole on reflux oesophagitis and gastritis in rats. AGC was isolated from Clerodendron trichotomum leaves. 2. Oesophagitis and gastritis were induced by surgical procedure and the administration of indomethacin, respectively. The intraduodenal (i.d.) administration of AGC decreased the volume of gastric juice and increased the gastric pH compared with apigenin and omeprazole. The acid output was more inhibited by AGC in a dose-dependent manner than by apigenin and omeprazole. Compared with apigenin and omeprazole, AGC significantly decreased the size of gastric lesions, which were induced by exposure of the gastric mucosa to indomethacin. 3. Malondialdehyde (MDA) content, which is the end product of lipid peroxidation, was increased significantly after the induction of reflux oesophagitis. The MDA content was decreased by AGC (i.d. 3 mg kg(-1)), but not by either apigenin or omeprazole. This suggests that AGC has an antioxidative effect. In the oesophagitis group, the mucosal levels of glutathione (GSH) were significantly lower than that in the normal group. However, the GSH levels were preserved after administering the AGC, suggesting that AGC possesses scavenging activity. 4. In summary, AGC is more potent than apigenin and omeprazole at inhibiting reflux oesophagitis and gastritis and may therefore be a promising drug for their treatment.

Selective degradation of chemical bonds: from single-source molecular precursors to metallic Ag and semiconducting Ag2S nanocrystals via instant thermal activation

Selective formation of metallic Ag and semiconducting Ag(2)S nanocrystals has been achieved via a modified hot-injection process from a single-source precursor molecule, Ag(SCOPh), which can potentially generate both [Ag] and [AgS] fragments simultaneously. When the precursor molecules are injected into a preheated reaction system at 160 degrees C, spherical Ag(2)S nanocrystals are directly obtained even without a molecular activator, such as alkylamines. Mixtures of Ag and Ag(2)S or pure metallic Ag nanocrystals are obtained if the precursor molecules are injected at lower than 160 degrees C or room temperature. These results are attributed to the direct transfer of thermal energies to precursor molecules, which are enough to dissociate S-C as well as Ag-S bonds simultaneously. Detailed characterizations about the produced nanocrystals have been performed using powder X-ray diffraction (XRD), transmission electron microscopy (TEM), as well as energy-dispersive X-ray (EDX) spectrum.

Two species of goby, Boleophthalmus pectinirostris and Scartelaos sp., as the new second intermediate hosts of heterophyid fluke in Korea

A survey was performed in order to determine the infection status of the metacercariae of heterophyid fluke in two goby species, Boleophthalmus pectinirostris and Scartelaos sp., collected from Gangjin-gun, and Shinangun, Sooncheon-shi, Jeollanam-do, Republic of Korea. A total of three metacercariae of Heterophyopsis continua was found in only one B. pectinirostris (10.0%) from Gangjin-gun. Heterophyes nocens metacercariae were detected in 24 B. pectinirostris (96.0%) and 14 Scartelaos sp. (63.6%) from Shinan-gun. Heterophyopsis continua metacercariae were found in 11 B. pectinirostris (44.0%) and 21 Scartelaos sp. (95.5%) from Shinan-gun. Stictodora fuscata metacercariae were detected in 18 B. pectinirostris (72.0%) from Shinan-gun. No metacercariae were detected in 20 B. pectinirostris from Sooncheon-shi. From the above results, this study is the first to prove that B. pectinirostris and Scartelaos sp. serve as the second intermediate hosts of some heterophyid flukes in Korea.

A rapid synthesis of iron phosphate nanoparticles via surface-mediated spontaneous reaction for the growth of high-yield, single-walled carbon nanotubes

The direct formation of iron phosphate nanoparticles on hydroxyl-terminated SiO(2)/Si substrates with a narrow size distribution (average diameter = 2.2 nm) is achieved by a simple room temperature spontaneous reaction of ferric chloride and phosphoric acid. Single-walled carbon nanotubes (SWNTs) are grown in high yield from the synthesized iron phosphate nanoparticles by the thermal chemical vapor deposition (CVD) method, as confirmed by atomic force microscopy (AFM) and Raman spectroscopy. Furthermore, three-terminal, p-type, nanotube network field effect transistor (FET) devices are successfully fabricated using the synthesized SWNTs via the photolithography technique. The reduced solubility of Fe(III) ions when they form iron phosphate salts in aqueous media is the main driving force for the nanoparticle formation. Systematic control experiments reveal that the surface property, concentration, and pH of the reaction solution play equally important roles in the formation of nanoparticles.

Spatial chemical inhomogeneity and local electronic structure of Mn-doped Ge ferromagnetic semiconductors

We have investigated the chemical distributions and the local electronic structure of potential diluted magnetic semiconductor Ge0.94Mn0.06 single crystals using scanning photoelectron microscopy (SPEM), x-ray absorption spectroscopy (XAS), and photoemission spectroscopy (PES). The SPEM image shows the stripe-shaped microstructures, which arise from the chemical phase separation between the Mn-rich and Mn-depleted phases. The Mn 2p XAS shows that the Mn ions in the Mn-rich region are in the divalent high-spin Mn2+ states but that they do not form metallic Mn clusters. The Mn 3d PES spectrum exhibits a peak centered at approximately 4 eV below E(F) and the negligible spectral weight near E(F). This study suggests that the observed ferromagnetism in Ge1-xMnx arises from the phase-separated Mn-rich phase.