Emergent 1/f Noise in Ensembles of Random Telegraph Noise Oscillators.

The emergence of 1/f noise from an aggregate of 1/f^{2} noise signals in magnetic nanodots undergoing random telegraph oscillations in their magnetization is reported. This emergence is found to occur with as few as two random telegraph noise (RTN) oscillators producing 1/f noise across two decades of frequency bandwidth, and with fewer than ten such oscillators producing 1/f noise across over four decades. The RTN fluctuations observed are as small as one part in 10 000 compared to dc voltage signals but still generate easily observable 1/f noise at up to 10^{5} Hz. These observations may explain the historic difficulty in identifying RTN oscillator sources of 1/f noise.

Gas-assisted electron-beam-induced nanopatterning of high-quality titanium oxide.

Electron-beam-induced deposition of titanium oxide nanopatterns is described. The precursor is titanium tetra-isopropoxide, delivered to the deposition point through a needle and mixed with oxygen at the same point via a flow through a separate needle. The depositions are free of residual carbon and have an EDX determined stoichiometry of TiO2.2. High resolution transmission electron microscopy and Raman spectroscopy studies reveal an amorphous structure of the fabricated titanium oxide. Ellipsometric characterization of the deposited material reveals a refractive index of 2.2-2.4 RIU in the spectral range of 500-1700 nm and a very low extinction coefficient (lower than 10(-6) in the range of 400-1700 nm), which is consistent with high quality titanium oxide. The electrical resistivity of the titanium oxide patterned with this new process is in the range of 10-40 GΩ cm and the measured breakdown field is in the range of 10-70 V µm(-1). The fabricated nanopatterns are important for a variety of applications, including field-effect transistors, memory devices, MEMS, waveguide structures, bio- and chemical sensors.

Gas-assisted electron-beam-induced nanopatterning of high-quality Si-based insulator.

An oxygen-assisted electron-beam-induced deposition (EBID) process, in which an oxygen flow and the vapor phase of the precursor, tetraethyl orthosilicate (TEOS), are both mixed and delivered through a single needle, is described. The optical properties of the SiO(2+δ) (- 0.04 ≤ δ ≤ +0.28) are comparable to fused silica. The electrical resistivity of both single-needle and double-needle SiO(2+δ) are comparable (greater than 7 GΩ cm) and a measured breakdown field is greater than 400 V µm(-1). Compared to the double-needle process the advantage of the single-needle technique is the ease of alignment and the proximity to the deposition location, which facilitates fabrication of complex 3D structures for nanophotonics, photovoltaics, micro- and nano-electronics applications.

Rapid preparation of electron beam induced deposition Co magnetic force microscopy tips with 10 nm spatial resolution.

Magnetic force microscope Co spike tips with lateral magnetic resolution of 10 nm have been prepared. The Co spikes are grown by electron beam induced deposition of Co from Co(2)(CO)(8) gas precursor. The high resolution Co spikes are fabricated at the spot of a tightly focused electron beam on the tip of commercial atomic force microscope cantilevers. Qualitative investigations indicate that a spike grown on a planar base of Co improves the signal to noise.

A simple technique to measure the magnetic susceptibility of liquids.

A novel technique for measuring the magnetic susceptibility of liquids with modest applied magnetic fields (order of 0.25 T) is presented. The deformation of the liquid surface by a magnetic field is determined by a laser bounce or optical lever technique. The energy balance between the magnetic energy and the gravitational potential of the diamagnetic or paramagnetic liquid interaction is used to determine the susceptibility. The energy due to the surface tension energy is about 10% of the gravitational energy and can be neglected for fast measurements.

Rapid electron beam assisted patterning of pure cobalt at elevated temperatures via seeded growth.

A new method of direct, rapid nano- to micro-scale patterning of high purity cobalt is presented. The method utilizes a combination of electron beam induced deposition (EBID) and seeded growth at elevated temperatures below the temperature of spontaneous thermal decomposition. Dicobalt octacarbonyl Co2(CO)8 is used as the precursor and carbon as a seed layer. Seeded deposition is carried out in the substrate temperature range from 55 to 75 °C. Deposition yield is significantly higher than conventional EBID and magnetotransport measurements indicate that resistivity, 22 µΩ cm, and saturation magnetization, 1.55 T, are much closer to the corresponding values for bulk Co than those for standard EBID.

Inhibition of cell proliferation and induction of apoptosis by N(1),N(11)-diethylnorspermine-induced polyamine pool reduction.

Reduction of cellular polyamine pools results in inhibition of cell proliferation and sometimes in induction of cell death. Reduction of cellular polyamine pools can be achieved by several strategies involving all the mechanisms of polyamine homoeostasis, i.e. biosynthesis, catabolism and transport across the cell membrane. In the present paper, we concentrate on results achieved using the polyamine analogue DENSPM (N(1),N(11)-diethylnorspermine) on different cell lines. We discuss polyamine levels in DENSPM-treated cells in relation to effects on cell cycle kinetics and induction of apoptosis. To really understand the role of polyamines in cell cycle regulation and apoptosis, we believe it is now time to go through the vast polyamine literature in a meta-analysis-based manner. This short review does not claim to be such a study, but it is our hope to stimulate such studies in the polyamine field. Such work is especially important from the viewpoint of introducing drugs that affect polyamine homoeostasis in the treatment of various diseases such as cancer.

Composition controlled spin polarization in Co(1-x)Fe(x)S(2) alloys.

The transition metal (TM) chalcogenides of the form TMX(2) (X = S or Se) have been studied for decades due to their interesting electronic and magnetic properties such as metamagnetism and metal-insulator transitions. In particular, the Co(1-x)Fe(x)S(2) alloys were the subject of investigation in the 1970s due to general interest in itinerant ferromagnetism. In recent years (2000-present) it has been shown, both by electronic structure calculations and detailed experimental investigations, that Co(1-x)Fe(x)S(2) is a model system for the investigation of highly spin polarized ferromagnetism. The radically different electronic properties of the two endpoint compounds (CoS(2) is a narrow bandwidth ferromagnetic metal, while FeS(2) is a diamagnetic semiconductor), in a system forming a substitutional solid solution allows for composition control of the Fermi level relative to the spin split bands, and therefore composition-controlled conduction electron spin polarization. In essence, the recent work has shown that the concept of 'band engineering' can be applied to half-metallic ferromagnets and that high spin polarization can be deliberately engineered. Experiments reveal tunability in both sign and magnitude of the spin polarization at the Fermi level, with maximum values obtained to date of 85% at low temperatures. In this paper we review the properties of Co(1-x)Fe(x)S(2) alloys, with an emphasis on properties of relevance to half-metallicity. Crystal structure, electronic structure, synthesis, magnetic properties, transport properties, direct probes of the spin polarization, and measurements of the total density of states at the Fermi level are all discussed. We conclude with a discussion of the factors that influence, or even limit, the spin polarization, along with a discussion of opportunities and problems for future investigation, particularly with regard to fundamental studies of spintronic devices.

Co1-xFexS2: a tunable source of highly spin-polarized electrons.

In the emerging field of spin-electronics ideal ferromagnetic electron sources would not only possess a high degree of spin polarization, but would also offer control over the magnitude of this polarization. We demonstrate here that a simple scheme can be utilized to control both the magnitude and the sign of the spin polarization of ferromagnetic CoS2, which we probe with a variety of techniques. The position of the Fermi level is fine-tuned by solid solution alloying with the isostructural diamagnetic semiconductor FeS2, leading to tunable spin polarization of up to 85%.

Exchange field induced magnetoresistance in colossal magnetoresistance manganites.

The effect of an exchange field on the electrical transport in thin films of metallic ferromagnetic manganites has been investigated. The exchange field was induced both by direct exchange coupling in a ferromagnet/antiferromagnet multilayer and by indirect exchange interaction in a ferromagnet/paramagnet metallic superlattice. The electrical resistance of the metallic manganite layers was found to be determined by the magnitude of the vector sum of the effective exchange field and the external magnetic field.

Cytomegalovirus seropositivity and serum total cholesterol levels in young patients.

Atherosclerosis is a chronic inflammatory disease of arteries, associated with multiple genetic and environmental factors, including hypertension, diabetes mellitus, cigarette smoking, modified and elevated LDL cholesterol, elevated plasma homocysteine, and infectious microorganisms such as Chlamydia pneumoniae and cytomegalovirus (CMV). CMV has been implicated in atherogenesis by epidemiological studies, animal research, and molecular analyses that have demonstrated CMV nucleic acids within human atherosclerotic lesions. Studies have suggested that CMV infection may alter lipid metabolism and lead to accumulation of cholesterol within atheromatous plaques. Few studies have examined the relationship between CMV infection and serum cholesterol levels in younger individuals when much of atherogenesis occurs. To test if CMV-seropositivity is associated with high levels of serum total cholesterol in relatively young patients, CMV IgG levels and total cholesterol concentrations were analyzed in serums from 172 patients, age < 50 yr. Based on univariate analysis of variance, serum total cholesterol was significantly correlated to age and to CMV-seropositivity when gender was a cofactor, but not to gender or CMV-seropositivity alone. In 39 CMV-seropositive women, serum total cholesterol concentration averaged 218 +/- 50 mg/dL (mean +/- SD), which was significantly higher than in 53 CMV-seronegative women (194 +/- 39 mg/dL, p < 0.02). No significant difference was observed between the serum total cholesterol concentrations in 26 CMV-seropositive men and 51 CMV-seronegative men (198 +/- 42 mg/dL versus 212 +/- 48 mg/dl, respectively). Thus, this study provides evidence that CMV-seropositivity is associated with higher serum total cholesterol levels in female patients under 50 yr of age, but not in male patients of comparable age.

Urethritis associated with Chlamydia trachomatis: comparison of leukocyte esterase dipstick test of first-voided urine and methylene blue-stained urethral smear as predictors of chlamydial infection.

The use of nucleic acid amplification tests for the diagnosis of C. trachomatis has made it possible to send urine samples instead of urethral swab specimens to the laboratory. The sensitivity is very high, but not 100%, and we continue to perform a test for urethritis at our STD clinic. The aim of this study was to compare the performance of two alternative tests in the diagnosis of urethritis as predictors of C. trachomatis infection: the leukocyte esterase (LE) dipstick test of first-voided urine and polymorphonuclear leukocyte counts in a methylene blue-stained (MBS) urethral smear. Urine samples from 480 male patients attending an STD clinic were analysed using the LE test and LCR assay for C. trachomatis; urethral samples were analysed with MBS urethral smear and LCR. The majority (75.8%) of the 480 patients examined were asymptomatic. Chlamydial infection was detected in 50 patients. The sensitivity, specificity and positive predictive value of the LE test for predicting C. trachomatis infection were 46.0, 91.6 and 39.0%, respectively, among all patients examined and 25.9, 95.8 and 33.3%, respectively, among the asymptomatic patients. The corresponding values for the MBS urethral smear were 76.0, 82.1 and 33.0% among all patients and 63.0, 89.6 and 32.7% among the asymptomatic patients. At our STD clinic we chose to perform the examination of MBS urethral smears in the diagnosis of urethritis because of its higher sensitivity relative to the LE test for predicting C. trachomatis.

Ornithine decarboxylase and S-adenosylmethionine decarboxylase expression during the cell cycle of Chinese hamster ovary cells.

Cells in mitosis were harvested from exponentially growing Chinese hamster ovary cells by the mitotic detachment technique. Immediately after harvesting, the mitotic cells were seeded in tissue culture flasks and incubated at 37 degrees C in a CO2 incubator. Care was taken not to perturb the progression of cells through the cell cycle. At every hour after seeding for 14 h, cells were collected for analysis of cell cycle distribution, cellular polyamine content, ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase (AdoMetDC) activities, and relative mRNA contents. The progression through the cell cycle was monitored by DNA flow cytometry. The putrescine, spermidine, and spermine levels were approximately doubled during the cell cycle: putrescine mainly during late S and G2, spermidine continuously during the entire cell cycle, and spermine mainly during G1 and S. The ODC activity was low in seeded mitotic cells and the enzyme was activated in late G1 and reached a plateau in S phase. A second burst in activity was observed during late S phase and maximal ODC activity was found at the S/G2 transition. The relative ODC mRNA level approximately doubled during the cell cycle and the increase in the relative level mainly took part during mid and late S phase. AdoMetDC activity increased in late G1 and a first maximum was observed during the G1/S transition. A second burst in activity was found in mid S phase. Maximal AdoMetDC activity was found in G2. The relative AdoMetDC mRNA approximately doubled during the cell cycle and the increase in the relative level mainly took place during late G1 and early S phase. Our results indicate that polyamine synthesis was regulated at transcriptional and translational/post-translational levels during the cell cycle of Chinese hamster ovary cells.

Complement-mediated permeabilization of platelets by monoclonal antibodies to CD9: inhibition by leupeptin, and effects on the GP Ib-actin-binding protein system.

Two monoclonal antibodies to CD9 of the IgM and IgG2a categories (FN 52 and FN 99), reproducibly induced platelet alterations in platelet-rich plasma by activation of the complement system with membrane incorporation of the pore-forming C5b-9 complex. The permeabilization could be monitored by measurements of extracellular ATP and observed as a shape change followed by an increase in light transmission in the aggregometer, and was associated with formation of tiny platelet aggregates. This could be accomplished by only minor lysis observed as extracellular lactate dehydrogenase (LDH). When leupeptin was added prior to, or immediately after the antibody, a total inhibition of the platelet alterations could be obtained. When added soon after the shape change, leupeptin had little effect on the liberation of ATP. However, whereas the ability of the platelets to become agglutinated by ristocetin was lost during the complement-mediated platelet alterations, addition of leupeptin immediately after the shape change, prevented this loss. The lost ability of the permeabilized platelets to undergo ristocetin-induced agglutination is not ascribed to degradation of GP Ib as this was relatively little affected in these studies as compared to the actin-binding protein (ABP) which was profoundly degraded. This protein represents a link between GP Ib and the submembraneous cytoskeleton, and the inhibition of its degradation by leupeptin, was clearly demonstrated. Experiments with digitonin-induced permeabilization showed that leupeptin did not inhibit permeabilization as such, but it did prevent the loss of ristocetin-induced agglutination even with this inducer.

Correlation of light transmission changes to changes of platelet glycoprotein Ib during storage of platelet concentrates.

The present study compares some properties of platelet concentrates, i.e. their ability to transmit light and the degree of platelet lysis and the deterioration of the platelet membrane glycoprotein Ib (GPIb). Extracellular levels of glycocalicin and lactate dehydrogenase (LDH) served as indicators for the proteolytic cleavage of GPIb and platelet lysis, respectively. The light transmission of 16 platelet apheresis concentrates was monitored continuously during storage using a specially designed apparatus. Determination of platelet counts and extracellular glycocalicin levels was carried out on day 1. In addition, after 7 days of storage extracellular concentrations of LDH and glycocalicin were determined. After 7 days highly significant correlations were found both when comparing light transmission changes and extracellular glycocalicin levels (r = 0.78; p < 0.001) and when comparing light transmission changes and extracellular concentrations of LDH (r = 0.83; p < 0.001).

Cutaneous drug reactions. An attempt to quantitative estimation.

The drugs taken by patients with suspected cutaneous drug reactions (CDR) were recorded during a 4-year period at Sahlgren Hospital in Gotenburg in a prospective study. A total of 440 patients were included. By dividing the frequency of occurrence of the recorded drugs by the number of sold defined daily doses (SDDD) for the city during the same period of time, figures for the CDR risk for different drugs corrected for frequency of use were obtained. The risk of CDR seemed to be highest for gold compounds, trimethoprim with and without sulphonamides, cephalosporins and penicillins. The most common types of CDR were macular and mucalopapular eruptions, followed by urticaria and cutaneous vasculitis. The results correlate well with those of the Boston Collaborative Drug Surveillance Program.

Response of mouse brain to a single subcutaneous injection of the monofunctional sulfur mustard, butyl 2-chloroethyl sulfide (BCS)*.

Exposure to mustard-type vesicants results in alkylation of DNA and vesication. However, the biochemical mechanism for vesicant injury and whether it is localized or diffuse are not clear. We postulated that vesicant damage is mediated by free radicals, resulting in oxidative stress. These free radicals-mediated reactions may propagate systemically distal to the site of exposure. To test this hypothesis, we examined the effects of a single subcutaneous injection of the monofunctional sulfur mustard, butyl 2-chloroethyl sulfide (BCS), on the brain. We injected 3 groups (6 mice/group) of 5-month-old male, athymic, nude mice, weighing 30-35 g, subcutaneously with neat (undiluted) BCS (5 microliters/mouse). After 1, 24, and 48 h, we sacrificed the treated mice along with an untreated control group and analyzed the brains for biochemical markers of oxidative stress. Compared to untreated controls, the activity of glutathione peroxidase increased by 76%, P less than 0.005 at 24 h, and that of glutathione S-transferases by 25-37%, P less than 0.05 over the entire period. Total glutathione content in the brain was significantly lower, 17%, after 1 h and 23% after 24 h. We found also, concomitant with decreased glutathione, almost a 3-fold increase in susceptibility to lipid peroxidation. Because these changes are consistent with oxidative stress, we conclude that the effect of BCS administered subcutaneously may be translocated, reaching mouse brain, and causing oxidative stress.

Trichophyton rubrum abscesses in immunocompromised patients. A case report.

A 72-year-old immunocompromised man with myelodysplastic syndrome who developed multiple erythematous, scaly abscesses like lesions on his left foot and lower leg is described. He also had dry scaly lesions on his soles and lesions on several toe nails. A punch biopsy showed abscesses with fungal elements and Trichophyton rubrum was cultured from skin scales and the biopsy. A diagnosis of T. rubrum abscesses should be suspected in all immunocompromised patients with signs of superficial dermatophyte infection.

Effects of forage source on ruminal microbial nitrogen metabolism and carbohydrate digestion in continuous culture.

Eight single-flow, continuous culture fermentors were used in Exp. 1 to study the effects of forage source on ruminal bacterial N metabolism and carbohydrate digestion. Forages included alfalfa, cicer milkvetch, birdsfoot trefoil and sainfoin with respective CP concentrations of 26.0, 28.7, 26.3 and 20.0%. Each forage provided 100% of the substrate for microbial metabolism and supplied 2.6 g N/d. Ammonia-N, protein degradation and efficiency of ruminal bacterial protein synthesis were lowest (P less than .05) for sainfoin. Protein degradation and efficiency of bacterial protein synthesis were higher (P less than .05) for birdsfoot trefoil than for alfalfa. Effluent flow of amino acids was highest (P less than .05) for sainfoin. Total nonstructural carbohydrate digestion tended to be highest for sainfoin and birdsfoot trefoil, whereas structural carbohydrate digestion was highest (P less than .05) for alfalfa and cicer milkvetch. In Exp. 2, mixed diets were supplied to dual-flow, continuous culture fermentors with alfalfa, cicer milkvetch, birdsfoot trefoil and sainfoin contributing 85% of the total dietary CP. Each diet contained approximately 12.9% CP. Ammonia-N concentration in the effluent and CP degradation tended to be lowest with the sainfoin diet and highest with the birdsfoot trefoil diet. Effluent flow of amino acids tended to be highest with the cicer milkvetch diet and lowest with the alfalfa and birdsfoot trefoil diet. Total structural and nonstructural carbohydrate digestion was not different (P greater than .05) among forages. Results from these experiments indicate that bacterial degradation of protein was lower for sainfoin than for alfalfa. Birdsfoot trefoil and cicer milkvetch appear to be comparable to alfalfa with regard to metabolism of N and carbohydrates by ruminal bacteria.