Exploring oxygen-affinity-controlled TaN electrodes for thermally advanced TaOx bipolar resistive switching.

Recent advances in oxide-based resistive switching devices have made these devices very promising candidates for future nonvolatile memory applications. However, several key issues remain that affect resistive switching. One is the need for generic alternative electrodes with thermally robust resistive switching characteristics in as-grown and high-temperature annealed states. Here, we studied the electrical characteristics of Ta2O5-x oxide-based bipolar resistive frames for various TaNx bottoms. Control of the nitrogen content of the TaNx electrode is a key factor that governs variations in its oxygen affinity and structural phase. We analyzed the composition and chemical bonding states of as-grown and annealed Ta2O5-x and TaNx layers and characterized the TaNx electrode-dependent switching behavior in terms of the electrode's oxygen affinity. Our experimental findings can aid the development of advanced resistive switching devices with thermal stability up to 400 °C.

Roles of conducting filament and non-filament regions in the Ta2O5 and HfO2 resistive switching memory for switching reliability.

The endurance of switching cycles, which is a critical measure of device reliability, in an ultra-thin (1.5 nm) Ta2O5 and HfO2 resistive random access (ReRAM) memory cell with a 28 nm lateral dimension was studied using current-voltage (I-V) sweep and closed-loop pulse switching (CLPS) tests. The two devices showed the typical oxygen-deficient conducting-filament (CF)-mediated bipolar resistance switching behaviour, which was induced by the asymmetric electrode configuration: Ta as the oxygen vacancy (VO) source/reservoir and TiN as the inert electrode. In these device geometries, the CF is supposed to initiate at the oxide/TiN interface and to grow towards the Ta electrode during the switch-on process, while the switch-off process was induced by the contraction of the CF from the Ta/oxide interface. Both devices, however, showed inversion (anomalous SET; switching from the off- to on-state) behaviour in the RESET (switching from the on- to off-state) process, which can be explained by the authors' previous model of the hourglass-shaped CF. In this model, once the CF is ruptured, the RESET polarity bias makes the lower portion of the CF regrow to slightly reconnect such a CF through the accelerated migration of VO from the upper-portion CF to the lower-portion CF, which induces switching performance degradation. In the I-V sweeps, the on- and off-states of the devices showed an overall conductance difference approximately corresponding to the integer multiple values of quantum point contact (G0), but there were arbitrary 0.25 and 0.125G0 differences in the conductance values of the on-state for the Ta2O5 and HfO2 devices, respectively. This suggests that these are the minimal units of conductance variation even for a given CF with a standard G0. Although the precise reason for the emergence of such an abnormal conductance unit is not yet understood, its implication for the reliability is critical. Reliable resistive switching was achieved only for the cases where the minimum point conductance was retained even in the off-state; in the other cases, over-SET and over-RESET were induced, which eventually degraded the device reliability. The detailed quantitative analysis of the device failure revealed that the increasing concentration of VO within the non-CF region in the cell decreased the resistance values of that region, which eventually resulted in the over-SET and over-RESET behaviours during the CLPS tests.

Meiotic prophase roles of Rec8 in crossover recombination and chromosome structure.

Rec8 is a prominent component of the meiotic prophase chromosome axis that mediates sister chromatid cohesion, homologous recombination and chromosome synapsis. Here, we explore the prophase roles of Rec8. (i) During the meiotic divisions, Rec8 phosphorylation mediates its separase-mediated cleavage. We show here that such cleavage plays no detectable role for chromosomal events of prophase. (ii) We have analyzed in detail three rec8 phospho-mutants, with 6, 24 or 29 alanine substitutions. A distinct 'separation of function' phenotype is revealed. In the mutants, axis formation and recombination initiation are normal, as is non-crossover recombination; in contrast, crossover (CO)-related events are defective. Moreover, the severities of these defects increase coordinately with the number of substitution mutations, consistent with the possibility that global phosphorylation of Rec8 is important for these effects. (iii) We have analyzed the roles of three kinases that phosphorylate Rec8 during prophase. Timed inhibition of Dbf4-dependent Cdc7 kinase confers defects concordant with rec8 phospho-mutant phenotypes. Inhibition of Hrr25 or Cdc5/polo-like kinase does not. Our results suggest that Rec8's prophase function, independently of cohesin cleavage, contributes to CO-specific events in conjunction with the maintenance of homolog bias at the leptotene/zygotene transition of meiotic prophase.

Hop2 and Sae3 Are Required for Dmc1-Mediated Double-Strand Break Repair via Homolog Bias during Meiosis.

During meiosis, exchange of DNA segments occurs between paired homologous chromosomes in order to produce recombinant chromosomes, helping to increase genetic diversity within a species. This genetic exchange process is tightly controlled by the eukaryotic RecA homologs Rad51 and Dmc1, which are involved in strand exchange of meiotic recombination, with Rad51 participating specifically in mitotic recombination. Meiotic recombination requires an interaction between homologous chromosomes to repair programmed double-strand breaks (DSBs). In this study, we investigated the budding yeast meiosis-specific proteins Hop2 and Sae3, which function in the Dmc1-dependent pathway. This pathway mediates the homology searching and strand invasion processes. Mek1 kinase participates in switching meiotic recombination from sister bias to homolog bias after DSB formation. In the absence of Hop2 and Sae3, DSBs were produced normally, but showed defects in the DSB-to-single-end invasion transition mediated by Dmc1 and auxiliary factors, and mutant strains failed to complete proper chromosome segregation. However, in the absence of Mek1 kinase activity, Rad51-dependent recombination progressed via sister bias in the hop2Δ or sae3Δ mutants, even in the presence of Dmc1. Thus, Hop2 and Sae3 actively modulate Dmc1-dependent recombination, effectively progressing homolog bias, a process requiring Mek1 kinase activation.

Thickness effect of ultra-thin Ta2O5 resistance switching layer in 28 nm-diameter memory cell.

Resistance switching (RS) devices with ultra-thin Ta2O5 switching layer (0.5-2.0 nm) with a cell diameter of 28 nm were fabricated. The performance of the devices was tested by voltage-driven current-voltage (I-V) sweep and closed-loop pulse switching (CLPS) tests. A Ta layer was placed beneath the Ta2O5 switching layer to act as an oxygen vacancy reservoir. The device with the smallest Ta2O5 thickness (0.5 nm) showed normal switching properties with gradual change in resistance in I-V sweep or CLPS and high reliability. By contrast, other devices with higher Ta2O5 thickness (1.0-2.0 nm) showed abrupt switching with several abnormal behaviours, degraded resistance distribution, especially in high resistance state, and much lower reliability performance. A single conical or hour-glass shaped double conical conducting filament shape was conceived to explain these behavioural differences that depended on the Ta2O5 switching layer thickness. Loss of oxygen via lateral diffusion to the encapsulating Si3N4/SiO2 layer was suggested as the main degradation mechanism for reliability, and a method to improve reliability was also proposed.

Indoor air pollutants and atopic dermatitis in socioeconomically disadvantaged children

PURPOSE: The aims of this study were to examine indoor concentrations of air pollutants in socioeconomically disadvantaged houses and to investigate relationships between indoor air pollutant levels and the severity of atopic dermatitis (AD). METHODS: A total of 54 children who had a past history or current symptoms of AD were enrolled in the study. To evaluate the levels of indoor air pollutants, we measured concentrations of CO2, total volatile organic compounds (TVOC), formaldehyde, particulate matter with diameter less than 10 microm (PM10), airborne mold and numbers of house dust mite (HDM) in dust of the children's houses. All studied subjects completed physical examination for the severity of AD and blood tests. RESULTS: Although the mean (+/-standard deviation [SD]) concentration of indoor CO2 (600.6+/-179.4 ppm) was lower than the standard recommended levels of multiplex buildings in Korea, there was a significant correlation between CO2 concentrations and the severity of AD (r=0.302, P=0.030). The geometric means (range of 1 SD) of TVOC (42.5 microg/m3 [22.2-81.5]), formaldehyde (24.3 microg/m3 [15.0-39.9]), PM10 (26.6 microg/m3 [14.6-48.4]), and airborne mold (49.9 CFU [colony forming unit]/m3 [26.3-94.6]) were not significantly higher than the standard recommended levels of multiplex buildings. Two-thirds of the subjects were sensitized to at least 1 of the common allergens. CONCLUSION: Generally, indoor air pollution was not serious in socioeconomically disadvantaged households. However, indoor CO2 concentrations are closely related to the severity of AD in children living in socioeconomically disadvantaged houses. Environmental amelioration targeting vulnerable population may improve the quality of life and decrease the prevalence of environmental allergic diseases.

The utility of the Wells clinical prediction model and ventilation-perfusion scanning for pulmonary embolism diagnosis in pregnancy.

Pulmonary embolism is one of the leading causes of mortality in pregnancy in the Western world. No clinical prediction models have been validated in pregnancy. As a result, any pregnant woman presenting with signs possibly consistent with pulmonary embolism is investigated radiologically. This study investigates whether using clinical prediction models for pulmonary embolism in pregnancy should be pursued in future prospective trials. The aim of this study was to retrospectively evaluate the Wells clinical prediction model and ventilation-perfusion scanning for pulmonary embolism in pregnancy. A retrospective study was performed on consecutive pregnant women who presented with suspected pulmonary emboli and underwent ventilation perfusion scanning at two tertiary institutions from 2007 until 2010. The clinical pretest probability was determined as likely or unlikely by two independent clinicians retrospectively using Wells-modified criteria. Scans were determined as normal, nondiagnostic or high probability for pulmonary emboli independently by two experienced radiologists. Disagreements were resolved by a third assessor independently. In 183 pregnant women, the pretest probability was determined as 'pulmonary emboli likely' in 76 (42%) and 'pulmonary emboli unlikely' in 107 (58%) of women. Scans were of high probability in four (2%), nondiagnostic in six (3%) and normal in 173 (95%) of women. This gives the pretest probability using Wells-modified criteria a sensitivity of 100% [95% confidence interval (CI) 0.4-1.0] and a negative predictive value of 100% (95% CI 0.96-1.0). A structured clinical model such as modified Wells criteria may be useful in pregnancy, but further prospective evaluation is required.

SiO2 doped Ge2Sb2Te5 thin films with high thermal efficiency for applications in phase change random access memory.

This study examined the various physical, structural and electrical properties of SiO(2) doped Ge(2)Sb(2)Te(5) (SGST) films for phase change random access memory applications. Interestingly, SGST had a layered structure (LS) resulting from the inhomogeneous distribution of SiO(2) after annealing. The physical parameters able to affect the reset current of phase change memory (I(res)) were predicted from the Joule heating and heat conservation equations. When SiO(2) was doped into GST, thermal conductivity largely decreased by ∼ 55%. The influence of SiO(2)-doping on I(res) was examined using the test phase change memory cell. I(res) was reduced by ∼ 45%. An electro-thermal simulation showed that the reduced thermal conductivity contributes to the improvement of cell efficiency as well as the reduction of I(res), while the increased dynamic resistance contributes only to the latter. The formation and presence of the LS thermal conductivity in the set state test cell after repeated switching was confirmed.

A size-dependent nanoscale metal-insulator transition in random materials.

Insulators and conductors with periodic structures can be readily distinguished, because they have different band structures, but the differences between insulators and conductors with random structures are more subtle. In 1958, Anderson provided a straightforward criterion for distinguishing between random insulators and conductors, based on the 'diffusion' distance ζ for electrons at 0 K (ref. 3). Insulators have a finite ζ, but conductors have an infinite ζ. Aided by a scaling argument, this concept can explain many phenomena in disordered electronic systems, such as the fact that the electrical resistivity of 'dirty' metals always increases as the temperature approaches 0 K (refs 4-6). Further verification for this model has come from experiments that measure how the properties of macroscopic samples vary with changes in temperature, pressure, impurity concentration and applied magnetic field, but, surprisingly, there have been no attempts to engineer a metal-insulator transition by making the sample size less than or more than ζ. Here, we report such an engineered transition using six different thin-film systems: two are glasses that contain dispersed platinum atoms, and four are single crystals of perovskite that contain minor conducting components. With a sample size comparable to ζ, transitions can be triggered by using an electric field or ultraviolet radiation to tune ζ through the injection and extraction of electrons. It would seem possible to take advantage of this nanometallicity in applications.

Phase error analysis of incoherent triangular holography.

We derive the phase error of a hologram that is due to the imperfection of a wave plate, the azimuth angle error of a wave plate, and the azimuth angle error of a linear polarizer and analyze the effect of the phase error with a modified triangular interferometer of the three-dimensional image reconstruction of a hologram.

Influence of Mismatching in HLA Cross-Reactive Group on the Graft Survival after Unrelated Kidney Transplantation / 대한임상병리학회지

BACKGROUND: Kidney transplantation(KT) from unrelated donors has been increasing in Korea in recent years. However, the number of HLA antigen mismatches in unrelated donor KTis larger compare with that in related donor KT. Recently, some studies have reported that cross-reactive group(CREG) matching would improve graft outcome. METHODS: We studied a total of 277 cases of kidney transplants from unrelated donors(cadaver donor 195 cases, living unrelated donor 82 cases) in our center from March 1992 to August 1998. HLA class I antigens were assigned to 10 CREG antigens based on the amino acid residue system of Takemoto. HLA-DR antigens were assigned to 10 broad HLA antigens. Antigens present in donor but not in recipient were considered as mismatches. The survival analysis was carried out by Kaplan-Meier method and differences in survival rates were tested by log-rank test. RESULTS: Mean numbers of mismatches in HLA and CREGs were 4.0 and 2.9. Mismatched numbers of CREG-A,B and 5 year survival rates showed a linear association(P=0.01), but those of HLA-A,B did not show a linear association(P=0.88). Probability of finding zero or one CREG mismatched recipients in unrelated KT was 53%(146 cases). A significant statistic difference was noted in survival rates between zero or one and two or more CREG mismatched group(P=0.01). CONCLUSION: Zero or one CREG mismatched group had better survival in unrelated living or cadaveric KT. Applying CREG matching strategy to recipient selection, graft survival will be significantly improved in unrelated living or cadaveric KT.

Two Cases of Unilateral developmental deficiency of lung found in Identical Twin / 대한내과학회지

Unilateral developmental deficiency of lung is rare. As the most of those, unilateral agenesis or Scimitar syndrome(hypogenetic lung syndrome) had been reported. We experienced that two cases of unilateral developmental deficiency of lung, which is different form each other, are found in identical twin. To our knowledge, this condition has not been reported before. We evaluated lung parenchyma and bronchus(; simple chest PA, chest CT(HRCT, 3DCT)), vasculatures(; pulmonary angiography and cardiac catheterization) and combined anomalies (;abdominal ultrasound, echocardiography, routine blood chemistry, and chromosomal study). This 31 yrs old twin female patient was confirmed as an unilateral agenesis of left upper lobe and hypoplasia of left lower lobe without combined anomalies. She's twin younger sister was confirmed as unilateral agenesis of right lung with atrial septal defect(ASD).

Pregnancy Outcome in Renal Allograft Recipients / 대한산부인과학회잡지

OBJECTIVE: To assess the pre-pregnancy and pregnancy factors influencing pregnancy outcome in renal transplanted women Materials and METHODS: This retrospective study included all pregnancies in renal transplanted women in Asan Medical Center between June 1996 and February 1998. We collected data from the medical records of allograft recipients. Pre-pregnant status and pregnancy outcome were described. RESULTS: Seventeen pregnancies in 13 allograft recipients resulted in 7 term deliveries, 4 preterm births, 2 spontaneous abortions, and 4 therapeutic abortions. All but one patient received immunosuppressive therapy with cyclosporin A, azathioprine, and prednisolone during pregnancy. The mean interval from the time of transplantation to conception was 28.8+/-14.3 months(range 6-60 months). In live birth group, the mean gestational age at delivery was 37.7+/-1.2 weeks and the mean birth weight of their offspring was 2.85+/-0.37 kilogram. Apgar scores at 5 minutes were 8 or more in all of them. The obstetric complications were distributed as follows: pregnancy induced hypertension in 6 cases(55%), pregnancy aggravated hypertension in 2 cases(18%), fetal growth restriction in 1 case(9%), prematurity in 4 cases(36%). Cesarean sections were done in 4 cases(36%) because of previous Cesarean section(3 cases) and uncontrolled hypertension(1 case). Neonatal complication, transient tachypnea of the newborn, was found in one case. Graft rejection after transplantation occurred in 4 cases: 3 cases in preterm births and 1 case in therapeutic abortions. Maternal renal functions were normal during pregnancy and postpartum period whose pre-pregnant renal functions had been normal. No patient experienced any rejection episode or graft loss during pregnancy. CONCLUSION: Successful pregnancy can be expected in women with a renal transplant, although there was high incidence of pregnancy-related complications, especially hypertensive disorders. Pregnancy can be encouraged to these allograft recipients if they have good renal function.

A Case of Digoxin-like Immunoreactive Substance(DLIS) Poisoning After Ingestion of Fried Water Toad (Bufo Stejnegeri Schmidt) / 대한내과학회지

Everybody knows that toads are not eatable because of their toxins. But water toads are very similar to frogs morphologically, so fried water toads are eaten by some people on occasion. It has been studied that the granular glands of the toads secrete toxins known as digoxin-like immunoreactive substances (DLIS) such as bufogenins and bufotoxins. DLIS have cross-reactivity with micro particle enzyme immunoassay for the quantitative mea surement of digoxin. We report a case of DLIS poisoning in 56-year-old male patient who showed vomiting, syn cope, and marked bradyarrhythmia with block (heart rate down to 29 beats per minute) after ingestion of the fried water toads (Bufo stejnegeri Schmidt).

A case of Varicella Infection during Pregnancy / 대한산부인과학회잡지

The varicella during pregnancy is rare. The incidence of varicella among pregnant women is about 5 in 10,000 pregnancies. In 1947, Laforet and Lynch were the first to describe an association between maternal varicella infection in early pregnancy and congenital anomalies in the offspring. the existence of a syndrome was first postulated by Srabstein et al(1974), Brunell(1983), Kotchmar(1984), and recently Higa et al.(1987) described most of the malfomations associated with maternal varicella infection. Varicella-Zoster viurs(VZV) infections acquired during pregnancy may result in serio us disease for both the mother and the fetus. The effects on maternal health can range from a mild chikenpox exanthem to servere life-theatenig illness often complicated by viral pneumonitis. The fetus may remain unaffected, but VZV infection during early pregnancy has been associated with a congeital syndrome including muliplie defects of the skin, limb, eyes, and brain. We reports our experience with a varicella during pregnancy with a brief literature review.

Significance of Serum Cortisol and Peripheral Blood Leukocyte Differential for the Early Differential Diagnosis of Acute Chest Pain Syndrome

OBJECTIVES: The stress response involves the activation of the hypothalamic-pituitary-adrenal(HPA) axis and the sympathetic nervous system. Corticosteroids have been clearly demonstrated to cause anti-inflammatory and/or immnosuppressive effects in man including granulocytosis in part by decreasing migration into tissue, especially damaged tissues(myocardium), and circulating relative lymphocytopenia. To test whether automated measurements of the the increased serum cortisol-induced hematologic changes in the leukocyte differential significance or not in the initial differential diagnosis of acute myocardial infarction in acute chest pain syndromes. METHODS: 101 consecutive patients with myocardial infarction or myocardial ischemia presenting to the emergency room of Seoul Adventist Hospital with acute chest pain from January 1993 to August 1995(Retrospective group) and from December 1995 to March patients compatible with exclusion criteria in myocardial infarction were excluded. We measured automated leukocyte differential and serial CK-MB level in both groups, and the intial serum cortisol levels in prospective infarction group. RESULTS: 1) Total leukocyte and granulocyte counts were increased in acute myocardial infarction(p<0.01). 2) In acute myocardial infarction group, lymphocyte counts were slightly increased(p<0.05), but relative lymphocytes percentage more significantly decreased(p<0.01). 3) Serum cortisol levels are significantly raised early in the course of the acute myocardial infarction and prior to the elevation of the specific cardiac enzymes on the basis of analytic results of prospective infarction group. 4) Cortisol-induced changes in leukocyte differential were noted with time passes into reverse approximately 4 days later in our study. 5) The leukocyte differential does not shows significant changes in the retrospective myocardial ischemia group, so we arrive in careful conclusion that serum cortisol level seems does not increase. 6) No sexual differences were noted in leukocyte differential. CONCLUSIONS: The serum cortisol level and cortisol-induced leukocyte differential are helpful for initial differential diagnosis of acute myocardial infarction in acute chest pain sysdrome.

Statistical Observation of In - Patients Referred to the Department of Dermatology / 대한피부과학회지

Statistical observation were made on 278 patients who were referred to the Department of Dermatology during their admission in Maryknoll Hospital from July 1, 1976 to June RO, 1978. This period begins one year before the initiation of the Medical Insurance Program on July 1, 1977 and extends to one year after(A period: 1976. 7. I~ 1977. 6. 3) B period: 1977.7.1~1978. 6. 30). The results are as follows: 1) Age distribution: The most frequent age group of both periods is the first decade(A period: 24.8%, B period: 22.1%) 2) Monthly distribution: There is no significant monthly difference 3) Distribution rate of every department: The most common department of both periods is Internal Medicine (A period: 26. 4%, B period: 32. 2%) 4) Distribution of diseases: The most frequent disease of both periods is Dermatitis and Eczema group(A period: RR.RY., B period: 80.2M) 5) Sex distribution: There is no significant sex difference(A period-M:F=l.5:1 B period.-M:F= 1.1:1) 6) Analysis of patients whose diagnosis of referred department is the same as diagnosis of the Department of Dermatology (1) Distribution rate of every department: The most common department is Internal Medicine (45. 8%) (2) Distribution of diseases: The most frequent disease of both periods is urticaria(A period: 33. 3%, B period: 25.0%) (3) Admission route: Admission via E-R was markedly decreased during B pericd (A perind: 50 %, B period: 16. 7%) 7) There is no significant change after the initiation of the Medical Insurance Program

The Study on Inhibit Activity of Dermatophytes by Some Salt Solutions / 대한피부과학회지

The study was made in order to investigate the minimal inhibit concentration (M.I.C) to Trichophyton(T.) gypseum and Trichophyton rubrum by same salt solution(ie: NaCl, KCl and Sodium thiosulfate). The stanis were obtained at the out-patient clinic of Seoul National University hospital. The results are as follows: 1. The M.I.C. of NaCl manifest 10%, and Trichophyton rubrum shows more higher than that of T. gypseum. 2. The M.I.C. of Sodiurn thiosulfate manifest 10%, and T. gypseum shows more higher M.I.C. than that of T. rubrum. 3. The M.I.C. of KCI manifest 15% for T.rubrum and shows 20% for T. gypseum.

Histopathological Changes in Psoriasis Under Occulsive Dressing with Topical Corticosteroids / 대한피부과학회지

Histopathological changes under occulsive dressing with 0.1% triamcinolone acetonide cream, 0 025% fluocinolone acetonide cream, and 1% hydrocortisone cream were compared each other and with the changes following topical application of 5% ammoniated mercury ointment without occulsion in five cases of psoriasis vulgaris. 1) The earliest changes noticed were the diminution of the papillary edema, the appearence of the granular layer and the disappearence of parakeratosis. 2) A week after treatment, the remarkable changes revealed were the thinning of the epidermis, the diminution of acanthosis, papil]ary edema and cell infiltration of the upper dermis and the appearence of the granular layer. 3)The capillary dilatation remained unchanged even two weeks after treatment in all groups. 4) Among these drugs, the best respanse revealed was triamcinolone cream, the next was fluocinolone cream. The response of hydrocortisone cream was poorer than fluocinolone cream and ammoniated mercury ointment was even more poorer than hydrocortisone cream.

A Case of Porokertosis ( Mibelli ) Involved to the Nail Plate / 대한피부과학회지

A case of Porokeratosis (Mibelli) involved to the nail plate in 25 years old male was described, This is rare and the first case of Porokeratosis (mibelli) variety reported in Korea. The clinical and histopathological study revealed characteristic features of this disease. Author reviewed reports of the literature.