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.

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.

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.

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.

Age-dependent resistance to Cryptosporidium muris (strain MCR) infection in golden hamsters and mice.

An age-dependent aspect of resistance to Cryptosporidium muris (strain MCR) infection was monitored in Syrian golden hamsters, Mesocricetus auratus, at 1-, 5- and 10-week of age and in ICR mice. Mus musculus, at 3-, 12-, and 15-week of age orally inoculated with a single dose of 2 x 10(6) oocysts, respectively. The prepatent periods for both animals were similar, independent of age, but the patency was significantly longer in younger hamsters (P < 0.001) and a long tendency in younger mice. Hamsters infected at 1-week of age excreted about 10 times higher oocysts than those at 5- and 10-week of age. However, the total oocyst output was similar among mice of different ages. There was a good correlation between the length of the patency and the total oocyst output in hamsters (R = 0.9646), but not in mice (R = 0.4561). The immunogenicity of the parasite to homologous challenge infections was very strong in hamsters and relatively strong in mice. These results indicate that acquired resistance to C. muris infection is age-related and the innate resistance is independent of age of hamsters, and that both innate and acquired resistance, on the contrary, are irrespective of age of mice.

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.

Verification of immunosuppression in chicks caused by Cryptosporidium baileyi infection using Brucella abortus strain 1119-3.

Humoral immune response of young chicks to Brucella abortus strain 1119-3 inoculation was monitored to verify the degree of immunosuppression caused by infection with Cryptosporidium baileyi. Young chicks (2-day-old) were orally inoculated each with 2 x 10(6) oocysts of C. baileyi, and then injected intramuscularly with 0.3 ml B. abortus strain 1119-3 containing 1 x 10(9) living organisms on day 14 postinoculation (PI). Serum samples were tested by plate agglutination test on day 17 PI onwards at an interval of 3-6 days over a period of 36 days. Infected chicks with the coccidium showed significantly lower antibody titers than those of uninfected controls (P < 0.05). These findings document that C. baileyi infection in early life stage may predispose chicks easily to other potential poultry diseases.

Infection kinetics and developmental biology of Cryptosporidium muris (strain MCR) in Korean native kids and Corriedale lambs.

A total of nine Korean native kids and two Corriedale lambs, 1-20 days old, were each inoculated per os with a single dose of 2 x 10(7) oocysts of Cryptosporidium muris (strain MCR) originated from mice to elucidate the kinetics and developmental stages of the coccidium in small ruminants. Irrespective of host's age, the prepatent period for both animals ranged from 19 to 35 days (28.1 days, on the average) and the patent period 16-85 days (47.8 days), and the total oocyst outputs showed enormous differences. Infection with greater numbers of oocyst outputs was not ordinarily established by transmission experiments. Oocysts discharged from the kids retained their infectivity by the mouse titration method. The immunogenicity of the coccidium and oocyst reproduction were proven by challenge infection and administration of prednisolone acetate, respectively. All the developmental stages of the coccidium in parasitophorous vacuoles were found by transmission electron microscopy in the pits of the gastric glands of a kid inoculated with oocysts and then necropsied on day 44 postinoculation. It indicated the full course of the host-parasite relationship in kids and lambs as well as mice.

Immunosuppressive effect of Cryptosporidium baileyi infection on vaccination against avian infectious bronchitis in chicks.

Two-day-old commercial chicks were inoculated orally with 2 x 10(6) oocysts of Cryptosporidium baileyi and vaccinated with 10(3.5) EID50/head of a commercially available avian infectious bronchitis (IB) live virus vaccine at 4 and 14 days following inoculation. Chicks infected with C. baileyi were shown to have an immunosuppressive effect on IB virus. It is concluded that infection with the protozoon in early life may increase their susceptibility to IB.

Immunosuppressive effect of Cryptosporidium baileyi infection on vaccination against Newcastle disease in chicks.

Hemagglutination-inhibition titers (log2) to Newcastle disease (ND) virus were chronologically observed in chicks, which were orally inoculated with 5 x 10(5) oocysts of Cryptosporidium baileyi at 2 days of age and subsequently vaccinated with inactivated ND virus at 4 and 21 days postinoculation. In general, the titers were considerably lower in the infected chicks than those in the uninfected control throughout the experimental period (p < 0.01), and rapid negative seroconversions were observed in the infected chicks. The titers reached a peak on weeks 2 and 4 post-booster-vaccination in the control and infected chicks, respectively. Thus, C. baileyi infection was shown to have an immunosuppressive effect on ND vaccination when the agent was given to 2-day-old chicks. It is suggested that C. baileyi infection in chicks may increase the host susceptibility to ND virus.

Effect of Cryptosporidium baileyi infection on antibody response to sRBC in chickens.

Hemagglutinin (HA) titers to sRBC were chronologically observed in chickens orally inoculated at 2 days of age with 5 x 10(5) oocysts of Cryptosporidium baileyi. All the infected chickens exhibited negligible HA titers by 44 days postinoculation (PI). The titers were elevated as time progressed, and peaked on day 52 PI, declined gradually thereafter, and eventually reached to normal titers on day 92 PI. On the contrary, the titers in uninfected chickens were higher in comparison with infected chickens during the experiment. Chickens infected with the protozoa showed normal oocyst shedding profiles during this period. These data suggest that C. baileyi infection suppress development of humoral immunity to sRBC in chickens. It is possible that impairment of the bursa of Fabricius by cryptosporidiosis rendered chickens vulnerable to other pathogens.

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.

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.

Effects of Cryptosporidium muris (strain MCR) infection on gastric mucosal mast cells in mice.

The responses of gastric mucosal mast cells (GMMCs) to infection with coccidian protozoa, Cryptosporidium muris, in mice were examined during primary and challenge infections. Each of three-week old ICR SPF mice was orally inoculated with a single dose of 2 x 10(6) oocysts of C. muris (strain MCR). After oocyst shedding ceased, the mice were orally challenged with a single dose of 2 x 10(6) oocysts of the same species. GMMCs reached a peak on days 20-30 postinoculation (PI) in number, and decreased thereafter. An increase on days 20-30 post-challenge-infection (PCI) was also observed. The mice showed, on the whole, normal profiles of oocyst shedding in droppings. The number of the cells of uninfected control mice remained constant. Judging from the above results, it is suggested that mastocytosis correlate with expulsion of C. muris in primary infection and the defense mechanism of challenge infection.

Chronologic change of serum IgG antibody response in chickens reinfected with Cryptosporidium baileyi.

Eight 2-day-old SPF chickens were each inoculated orally with a single dose of 5 x 10(5) oocysts of Cryptosporidium baileyi, and immunoglobulin G (IgG) antibody responses were chronologically measured by indirect immunofluorescent antibody (IFA) assay. Anti-C. baileyi IgG antibody levels remained high (1:106.67 to 1:512.00) for at least 4 months with 330 days of a detectable period. Ten days after the negative conversion, each chicken was re-challenged with 1 x 10(7) oocysts of the same species. Subsequent infection in 340-day-old individuals caused sudden elevated IgG antibody levels and the titer peaked on day 28 postchallenge inoculation (PCI), at 1:1.024 with a 65 days of detection period. Chickens in primary infection showed oocyst shedding profiles, but did not exhibit any oocyst shedding before or after experimental reinfection.

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.

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.

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.

Application of scanning electron microscopy in assessing the prevalence of some Setaria species in Korean cattle.

The numbers of individual Setaria species in the peritoneal cavities of Korean cattle were estimated. The worms were tentatively identified under light microscopy, and then precisely classified by SEM on the basis of unique features at the anterior and posterior ends of the adult worms. The positive rate of Setaria species was 34.2% out of 1,074 Korean cattle surveyed; that of S. digitata was 25.1%, S. marshalli 2.9% and both species 6.2%, respectively. Out of a total of 1,254 worms collected, 66.8% were female and 19.1% were male S. digitata; 9.2% were female and 5.0% were male S. marshalli, respectively. The average length of S. marshalli was somewhat longer than that of S. digitata. S. marshalli was documented for the first time in Korea.

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.