Robust switching characteristics of CdSe/ZnS quantum dot non-volatile memory devices.

In this paper we report Al/CdSe-ZnS core-shell quantum dot/AlOx/CdSe-ZnS core-shell quantum dot/ITO based non-volatile resistive memory devices with an ON/OFF ratio of ~1000. The facile solution processed device exhibited excellent endurance characteristics for 200,000 switching cycles. Retention tests showed good stability for over 20,000 s and the devices are reproducible. A memory operating mechanism is proposed based on charge trapping-detrapping in core-shell quantum dots with AlOx acting as a barrier leading to Coulomb blockade. I-V characteristics of a three terminal device fabricated with the additional terminal wired-out from the middle AlOx layer supports the proposed charge trapping mechanism.

Observation of room temperature negative differential resistance in multi-layer heterostructures of quantum dots and conducting polymers.

Multi-layer heterostructure negative differential resistance devices based on poly-[2-methoxy-5-(2'-ethyl-hexyloxy)-1,4-phenylenevinylene] (MEH-PPV) conducting polymer and CdSe quantum dots is reported. The conducting polymer MEH-PPV acts as a barrier while CdSe quantum dots form the well layer. The devices exhibit negative differential resistance (NDR) at low voltages. For these devices, strong negative differential resistance is observed at room temperature. A maximum value of 51 for the peak-to-valley ratio of current is reported. Tunneling of electrons through the discrete quantum confined states in the CdSe quantum dots is believed to be responsible for the multiple peaks observed in the I-V measurement. Depending on the observed NDR signature, operating mechanisms are explored based on resonant tunneling and Coulomb blockade effects.

Ultrafast pulse shaping: amplification and characterization.

We demonstrate high-resolution amplified pulse shaping using an acousto-optic modulator (AOM) at a center-wavelength of 795nm. The output pulses have energy of 200mJ/pulse and a transform-limited pulsewidth of 150fs. A spectral modulation of over 40 features is achieved in a single pulse. We characterize the pulses using the STRUT (Spectrally and Temporally Resolved Upconversion Technique). Using predistortion techniques, we demonstrate that the pulses can be shaped in amplitude and phase. We create a complex pulse shape with hyperbolic secant amplitude and hyperbolic tangent frequency sweep, which is useful for applications in adiabatic rapid passage experiments.

Polymorphism of clarithromycin.

It is well recognized that physicochemical properties of drugs are affected by the type of polymorphic crystalline form of drugs. Clarithromycin is known to exist in at least three polymorphic crystalline forms. Since conventional means to obtain the most thermodynamically stable form (Form II) for the antibiotics is known to be associated with a low purity of the stable form, we developed a novel method to improve the purity of the crystalline form by a modification of the preparation process. The new method involved a simple recrystallization of clarithromycin in solvents having 5-12 carbon atoms (e.g., hexane and heptane) or ethers with 4-10 carbon atoms (e.g., isopropyl ether) and, thus, less likely to be associated with the problem in purity of resulting crystal. Differential scanning calorimetry and powder X-ray diffraction were used to compare the crystalline form of the resultant powder with Form II crystal prepared by the conventional method. The crystal prepared by the new method was identical to Form II crystal of the conventional method as evidenced by the lack of the exothermic peak near 110 degrees C in differential calorimetry scan, indicating that Form II crystal could be readily prepared by the new process. Therefore, these data indicated that the improvement in the purity of the Form II crystal for clarithromycin as well as a significant cost reduction is likely by the novel method.

Structural investigation on the effects of the herbs on Clonorchis sinensis in rabbits.

The effects of boiled water extracts of clonorchicidal raw drugs screened by the EPG counts in vivo on the structure of Clonorchis sinensis were investigated. The extracts of Cassia obutusifolia and Dictamnus dasycarpus did not seem to induce the morphological changes of the worms, and in those of Machilus thunbergii and Prunús mume, widening of bladder to lower level of seminal receptacle was visible without any other changes. Those of Inula helenium and Saussurea lappa, however, disclosed regressive and progressive changes as degeneration, atrophy, necrosis, dilatation, etc. of viscera of the worms. The recover rates of the worms from experimentally infected rabbits administered with the extracts of I. helenium and S. lappa for 30 days, beginning at the 3rd day of inoculation, were as low as 2% and 2.8%, respectively.

Alternations of Clonorchis sinensis EPG by administration of herbs in rabbits.

In order to investigate clonorchicidal activity in vivo, boiled water extracts of 32 species of clonorchicidal raw drugs in vitro were orally administered into rabbits infected with Clonorchis sinensis. The results of the observation of EPG variation were as follows: Suppression effects of egg-laying capacity from the rabbits administered Prunus mume and Inula helenium were greatest. Those from Dictamnus dasycarpus and Saussurea lappa were somewhat effective. Machilus thunbergii and Cassia obutusifolia, however, were less effective.

Screening of the wormicidal Chinese raw drugs on Clonorchis sinensis.

The wormicidal effect on Clonorchis sinensis in boiled water extracts of 223 species (vegetable origin 206, animal origin 10, mineral origin 7) of raw drugs prescribed in Oriental medicine was observed in vitro. The wormicidal substances were detected from 31 of the above-mentioned species. The wormicidal substances extracted from Platycodon grandiflorum (radix), Schizandra chinensis (fruit), Polygala tenuifolia (herb) and Aster tataricus (radix) were most effective. Those from Smilax glabra (radix), Pueraria thunbergiana (flower, radix), Polygala tenuifolia (radix), Scutellaria baicalensis (radix), Prunus mume (fruit), Glycyrrhiza uralensis (radix), Angelica koreana (radix), Phytolacca esculenta (radix) and Cyrtomium fortunei (rhizoma) were effective. The rest of the raw drugs were less effective.

CpG island shore methylation regulates caveolin-1 expression in breast cancer.

Caveolin-1 (Cav1) is an integral membrane, scaffolding protein found in plasma membrane invaginations (caveolae). Cav1 regulates multiple cancer-associated processes. In breast cancer, a tumor suppressive role for Cav1 has been suggested; however, Cav1 is frequently overexpressed in aggressive breast cancer subtypes, suggesting an oncogenic function in advanced-stage disease. To further delineate Cav1 function in breast cancer progression, we evaluated its expression levels among a panel of cell lines representing a spectrum of breast cancer phenotypes. In basal-like (the most aggressive BC subtype) breast cancer cells, Cav1 was consistently upregulated, and positively correlated with increased cell proliferation, anchorage-independent growth, and migration and invasion. To identify mechanisms of Cav1 gene regulation, we compared DNA methylation levels within promoter 'CpG islands' (CGIs) with 'CGI shores', recently described regions that flank CGIs with less CG-density. Integration of genome-wide DNA methylation profiles ('methylomes') with Cav1 expression in 30 breast cancer cell lines showed that differential methylation of CGI shores, but not CGIs, significantly regulated Cav1 expression. In breast cancer cell lines having low Cav1 expression (despite promoter CGI hypomethylation), we found that treatment with a DNA methyltransferase inhibitor induced Cav1 expression via CGI shore demethylation. In addition, further methylome assessments revealed that breast cancer aggressiveness associated with Cav1 CGI shore methylation levels, with shore hypermethylation in minimally aggressive, luminal breast cancer cells and shore hypomethylation in highly aggressive, basal-like cells. Cav1 CGI shore methylation was also observed in human breast tumors, and overall survival rates of breast cancer patients lacking estrogen receptor α (ERα) negatively correlated with Cav1 expression. Based on this first study of Cav1 (a potential oncogene) CGI shore methylation, we suggest this phenomenon may represent a new prognostic marker for ERα-negative, basal-like breast cancer.

Supplemental knowledge on survival of Thelohanellus kitauei spores in vitro.

In order to search the fate of Thelohanellus kitauei spores the extrusion rates of the polar filaments were monitored in vitro chronologically. Preserved spores suspended with various solutions at -70 degrees C showed almost the same vigorous pattern as early freezing stages up to 1,750 days after initial preservation. It revealed that the viabilities of some spores suspended with 0.45% and 0.9% NaCl solutions and distilled water at 5 degrees C continued for 1,628 days, 1,614 days and 1,721 days, respectively. And, the life spans of some spores in the previous solutions added with antibiotics at 5 degrees C were 1,628 days, 1,614 days and 1,714 days, respectively.

Survival of Cryptosporidium muris (strain MCR) oocysts under cryopreservation.

We have successfully maintained Cryptosporidium muris by cryopreservation. Oocysts were suspended in distilled water, stored at -20 degrees C for 24 hrs, and then cryopreserved at -70 degrees C. Cryopreserved specimens were slowly thawed at 5 degrees C. Oocysts, which had been cryopreserved for 15 months without cryoprotective agents, retained their infectivity by the mouse titration method. Oocysts stored at 5 degrees C in 2.5% potassium dichromate failed to retain their infectivity beyond 6.5 months.

Efficacy of fumagillin against Thelohanellus kitauei infection of Israel carp, Cyprinus carpio nudus.

The potential of fumagillin dicyclohexylamine salt to treat and prevent intestinal giant-cystic disease in Israel carp, Cyprinus carpio nudus, was monitored in field experimental studies. In experiment 1 (therapeutic), most fish were already naturally infected with more advanced stage of Thelohanellus kitauei. Fumagillin was administered to fish (mean body weight of 830 g) for a period of one month at a dose of 10.62 mg in the first group and 5.3 mg in the second group per fish per day. In experiment 2 (prophylactic), most fish also were already naturally infected with an early developmental stage of the protozoa and fish (average body weight of 484 g) were administered fumagillin for 45 days at a dose of 3.95 mg per fish per day. In both experiments, the cumulative mortalities of fish and the extrusion rates of the polar filaments of the spores were significantly decreased in a dose-independent fashion. In experiment 2 no dead fish were observed. No adverse side effects of the drug were observed among fish from any dosage group. In experiment 2, an oval or dot-like concave lesion of most cysts developed at the 7th day and the vegetative form was never observed at the 17th day postmedication and the cysts were grossly reduced in size as compared with the control group, beginning at the 24th day until the end of the study. In contrast, it was scarcely effective to the cysts in experiment 1.(ABSTRACT TRUNCATED AT 250 WORDS)

[Isolation and identification of Cryptosporidium from various animals in Korea. I. Prevalence of Cryptosporidium in various animals].

Cryptosporidium, a coccidian protozoa, commonly causes a self-limiting diarrheal illness in humans and animals. Fecal samples from various animals in Chonbuk district were observed using Sheather's flotation technique, Kinyoun's modified acid-fast staining, and osmic acid pre-fixed Giemsa staining. The oocysts were detected in 74 cages (29.6%) out of 250 cages of mature mice, 26 (13.3%) out of 195 mature house rats, 75(15.0%) out of 4-week-old 500 fowls, 98(19.9%) out of 6 to 8-month-old 500 pigs, and 111(22.2%) out of 2 to 5-year-old 500 dairy cattle, respectively. The degree of prevalence was slight in general, but actual prevalence was higher than infection rate because the detection rates were higher in repeated-preparation examinations in comparison to the first examination. Meanwhile, large and small types of oocysts were detected from mice, house rats, pigs, and cattle, and medium type from fowls.

[Isolation and identification of Cryptosporidium from various animals in Korea. II. Identification of Cryptosporidium muris from mice].

Each of SPF mice(Scl: ICR strain, 3-week-old males) was inoculated with 5 x 10(4) oocysts of Cryptosporidium by stomach tube. The oocysts were large type one which was previously isolated from Korean mice, and passaged in 3-week-old SPF mice. The patterns of oocyst discharge were monitored daily, and in order to observe the ultrastructure of developmental stages the stomach of the mice was examined by transmission electron microscopy (TEM) at 4 weeks post-inoculation. The prepatent period for 6 mice was 5.6 days post-inoculation on the average, and the patent period was 63.2 days. The number of oocysts discharged per day from the mice reached peak on day 36.6 post-inoculation on the average. A large number of oocysts were found in fecal samples obtained from inoculated mice on days 30-50 post-inoculation. C. muris was larger than C. parvum at almost every developmental stages, the size difference being 1.4 times in oocysts, 2.4 times in sporozoites, 1.6 times in merozoites, and 1.5 times in microgametes. The ultrastructural features of the attachment site of C. muris to the mucus cells were remarkably different from those of C. parvum and its closely related species. The anterior projection of the protozoa (C. muris), the outer aspect of which was surrounded by a thick filamentous process of the host cell, has not been reported at any developmental stages of C. parvum or its closely related species. The size of the oocysts of strain RN 66 was larger than that of Korean mice origin. The above results reveal that the large type Cryptosporidium of Korean mice origin is identified as Cryptosporidium muris and this type was named as C. muris (strain MCR).

[Isolation and identification of Cryptosporidium from various animals in Korea. III. Identification of Cryptosporidium baileyi from Korean chicken].

Each of SPF chicken (Hi-Line strain, 2-day-old males) was inoculated with 2.5 or 5 x 10(4) oocysts by stomach tube. The oocyst was the medium type of Cryptosporidium previously isolated from Korean chicken origin, and passed in 2-day-old SPF chicken. The patterns of oocyst discharge were monitored daily, and in order to observe the ultrastructure of the developmental stages, the bursa of Fabricius of the chicken was examined by transmission electron microscopy (TEM) on the 12th day postinoculation. The prepatent period for 8 chicken was 5.9 days postinoculation on the average, and the patent period was 12.9 days. The number of oocysts discharged per day for the chicken was reached peak on day 12 postinoculation on the average. A large number of oocysts was found in fecal samples obtained from inoculated chicken on days 8-14 postinoculation. The ultrastructural feature of almost every developmental stage of the medium type from chicken was very similar to that of Cryptosporidium previously isolated from mammalia including human and birds except for the attachment site of C. muris to the mucus cell from mammalia, but dimension of the oocysts from fecal samples of the medium type was different from those of C. meleagridis and mammalia origin. The above results reveal that the medium type of Cryptosporidium of Korean chicken origin is identified as Cryptosporidium baileyi.

[Effects of immunoactivity on Ascaris suum infection in mice].

The immune response to sheep red blood cell (sRBC) was monitored in the mice infected with Ascaris suum or Trichinella spiralis. The effects of the infection with T. spiralis or the injection with cyclophosphamide(CY) as an immunosuppression agent prior to challenge infection with the embryonated eggs of A. suum were monitored in mice by means of the level of infection with A. suum and cellular and humoral immune response to sRBC. Following the oral administration of 1,000 eggs of A. suum to mice, delayed-type hypersensitivity (DTH) and rosette-forming rate were gradually decreased and reached to the lowest levels at the 5th week and 6th week postinfection, respectively, and then returned to normal at the 10th week. The hemagglutinin(HA) and hemolysin(HE) titers were gradually elevated and reached to peak at the 3rd week postinfection, and then returned to normal level. The appearance ratios of the eosinophils and mast cells were in peak at the 4th week and the 2nd week postinfection, respectively. Meanwhile the harvest ratio of A. suum larvae from the liver and lungs was 21.97% at the 1st week postinfection. Following the oral administration of 300 T. spiralis infective larvae, DTH and rosette-forming rate were gradually decreased with the lapse of time and reached the lowest values in the 30th and 21st day of postinfection, and then slightly increased and transiently decreased in the 70th and 80th day of postinfection, respectively. HA and HE titers were the lowest in the 21st and 90th day, whereas the ratios of eosinophils and mast cells were the highest on the 40th and 14th day postinfection, respectively. Following the intraperitoneal injection of CY, the body weight, the spleen weight, DTH, rosette-forming ratio, HA and HE titers, the number of WBC and the ratio of the mast cell were predominantly decreased in the 5th day, and then returned to the same value of the 1st day postinjection. The ratio of eosinophils was gradually decreased following to advance of days. At the 1st, 5th and 10th days after intraperitoneal injection of CY of 400 mg/kg, a dose with 1,000 eggs of A. suum was administered orally to mice, and harvest rate of the larvae at the 7th day postadministration was 7.07% in the 1st day, 14.94% in the 5th day, 10.1% in the 10th day, 8.02% in control group. The effect of prior infection with infective larvae of T. spiralis upon immunological sequelae of a challenge infection of mice with embryonated eggs of A. suum in 30 or 70 days interval was checked.(ABSTRACT TRUNCATED AT 400 WORDS)

[Effect of Hymenolepis nana infection on immunological responses of mice to sRBC].

In an attempt to investigate the effect of Hymenolepis nana infection on immunological responses to sRBC in ICR strain of mice, cellular and humoral immune responses were chronologically monitored after sensitization with sRBC. Mice weighing about 20 g were allocated into artificial and natural infection groups. The shell-free eggs of H. nana were inoculated into mice on the day 0 (initial) and day 10 in the former group, and praziquantel (25 mg/kg/day) was administered for 3 days to the one half of the mice at the 15th day after the first inoculation and to all of the mice in natural infection group. In artificial infection group, the delayed-type hypersensitivity (DTH) to sRBC was considerably decreased on the day 10 after the first inoculation, and then elevated gradually to normal. Eosinophils in the peripheral blood increased slightly. The hemagglutinin (HA) and hemolysin (HE) titers during the early stage were shown to be more or less higher than those of control. Thereafter, the titers were returned to normal, followed by a transient decrease on the day 15 post-infection. The sRBC rosette and antibody-treated rosette-forming capacities on the day 15 post-infection were temporarily lowered but became higher thereafter. The mucosal mast cells (MMC) in the small intestine were gradually increased to make a peak on the day 10 post-infection and then maintained more or less at lower level. After praziquantel treatment, the DTH and the number of eosinophils were decreased slightly and the MMC number and sRBC rosette-forming capacity were considerably decreased. The titers of HA and HE and antibody-treated rosette-forming capacity, however, were elevated in general. In natural infection group, the DTH, the number of eosinophils, and MMC which were elevated due to H. nana infection were gradually returned to normal after praziquantel treatment. The titers of HA and HE which were decreased by parasite infection were increased to normal after the treatment. However, the capacities of sRBC rosette or antibody-treated rosette formation were maintained at low levels in spite of the treatment. These results revealed that the immune responses to sRBC were significantly activated during H. nana infection, although they were transiently decreased during the days 10-15 post-infection.

Oocyst production and immunogenicity of Cryptosporidium baileyi in chickens and mallards.

Two-day-old chickens and mallards were orally inoculated with one of 5 doses varying from 2 x 10(2) to 2 x 10(6) of C. baileyi oocysts per individual. Generally, the more oocysts inoculated were, the longer the patent periods were, and the more oocysts shedding were. Meanwhile increasing the inoculative dose, the prepatent periods were shortened except that mallards inoculated with 2 x 10(2) and 2 x 10(3) oocysts failed to produce the oocysts. The more parasites involving oocysts appeared from the chicken in comparison to the mallard. In the chickens challenged with a single dose of 2 x 10(6) oocysts, a small number of oocysts were detected from feces on days 4-14 after challenge infection (ACI) in all of carrageenan administered groups and in the control groups inoculated with 2 x 10(2) and 2 x 10(3) oocysts. In the mallards, a few oocysts were also recognized on days 5-15 ACI in all of carrageenan treated groups and in the control groups inoculated with 2 x 10(2), 2 x 10(3) and 2 x 10(4) oocysts. Just prior to challenge infection, phagocytic activity of peritoneal macrophages (Mø) and the number of peripheral Mø in both birds were significantly decreased in the carrageenan treated groups as compared to the control groups. Mild challenge infection in both birds denoted that the immunogenicity of C. baileyi to the birds was very strong, despite Mø blocker carrageenan administration.

Oocyst production and immunogenicity of Cryptosporidium muris (strain MCR) in mice.

Three-week-old ICR SPF mice were orally inoculated with one of 5 doses ranging from 2 x 10(2) to 2 x 10(6) oocysts of Cryptosporidium muris (strain MCR) per mouse. Oocyst inoculation was directly proportional to the amount of oocysts shed and was inversely proportional to the period required for peak oocyst production and to the prepatent period. Peak oocyst production occurred between fifteen and thirty-one days with a patent period from 61 to 64 days. Three days after all mice stopped shedding oocysts, they were orally challenged with a single dose of 2 x 10(6) oocysts of the same species. Marked seroconversion for IgG antibody accompanied recovery from mice inoculated with 5 x 10(5) oocysts. Mice administered with carrageenan excreted a small number of oocysts for 49.0 days on the average after challenge inoculation (ACI) and control mice for 14.2 days in a dose-independent fashion. Just before challenge infection, phagocytic activity of peritoneal macrophages (M phi) and the number of peripheral M phi were dramatically decreased. Mild challenge infection implies that the immunogenicity of C. muris (strain MCR) is very strong, despite M phi blocker carrageenan administration.

Effects of Cryptosporidium baileyi infection on the bursa of Fabricius in chickens.

In order to clarify the effect of cryptosporidiosis on immune response, histopathological changes associated with experimentally occurring bursal cryptosporidiosis in chickens were chronologically observed as the first step. A total of 150 2-day-old chickens was each inoculated orally with a single dose of 5 x 10(5) Cryptosporidium baileyi oocysts. The chickens showed a normal profile of oocyst shedding in droppings. The bursa indices throughout the experimental period indicated negligible reactions. Numerous cryptosporidia occurred in the microvillous border of bursal epithelium between days 4 and 16 postinoculation (PI). Appearance of the most mast cells was followed by a dramatic loss of the protozoa in the bursa of Fabricius (BF). The distribution of the coccidium coincided with heterophil infiltration in the epithelium and adjacent lamina propria. The histopathological lesion was marked diffuse chronic superficial purulent bursitis with heterophil infiltration in the epithelium and adjacent lamina propria and mucosal epithelial hyperplasia. These results suggest that the bursitis may induce immunosuppressive effect.

Periodicity exhibited by Dirofilaria immitis microfilariae identified in dogs of Korea.

Microfilarial periodicity of Dirofilaria immitis (the dog heartworm) was determined at two hr intervals for 72 consecutive hrs in 10 naturally infected war dogs, 3-9 years old, in Korea to facilitate harvest of the microfilariae for possible use in laboratory works and to elucidate further the periodicity of the microfilaria depending on geographic location. Although the periodicity had been observed as being low-grade nocturnal, maximal microfilarial counts were found at 21:00 hr and minimal at 11:00 hr, giving rise to an evident peak in fluctuation of the larval counts. This is the first record of the periodicity of the microfilariae identified as D. immitis in Korea.