bluuebunny/crossref_metadata_2025 huggingface dataset:
THE DEVELOPMENT AND ULTRASTRUCTURE OF PLASMODIUM FALCIPARUM DAMAGED IN VITRO BY HUMAN “CRISIS” SERA AND BY CHLOROQUINE
Authors: Butcher GA , Maxwell Lesley , Cowen N , Clancy RL , Stace JD
Published: August 2007

P. falciparum malaria was cultured in vitro in the presence of sera from patients with cerebral malaria, meningitis and also after choloroquine administration. Intra‐erythrocytic parasite damage was seen by light and electron microscopy. The significance of the results is discussed with relevance to non‐specific immune mechanisms, and the damage induced by these mechanisms compared with that from chloroquine.
ACUTE DELETION OF ARTERIAL BARORECEPTOR INPUT IN THE CONSCIOUS RABBIT
Authors: Ludbrook J , Graham WF , Potocnik SJ
Published: August 2007

We describe the use of a snare to denervate the carotid sinus in conscious rabbits whose other arterial baroreceptors had been denervated 8‐14 days previously by surgical operation. Within 2 min of tightening the snare arterial blood pressure had risen from 81 ± 2 to 119 ± 5 mmHg, and heart rate had risen from 214 ± 9 to 280 ± 9 beats min‐1. They remained at these high levels for 15 min bus then fell, so that after 30 min blood pressure and heart rate were 103 ± 9 mmHg and 265 ± 8 beats min‐1 respectively. They declined somewhat further, but irregularly, over the succeeding 7 days. The previously brisk baroreceptor‐heart rate and carotid sinus reflexes were abolished by ensnaring the carotid sinus nerve, and remained absent over the succeeding 7 days. This method of deleting input from the arterial baroreceptors is not confounded by general anaesthesia or surgical injury, and allows observations to be made within minutes. The rapid decline in blood pressure and heart rate after 15 min, and the subsequent slow downward trend, are unexplained. They are of potential importance in experiments designed to quantitate the effects of baroreceptor input on the circulation. We also noted that, whereas spontaneous activities of the baroreceptor‐intact rabbit were usually associated with transient rises of blood pressure and heart rate, after deletion of baroreceptor input the same activities were usually associated with transient falls.
PERIPHERAL BLOOD WHITE CELL RESPONSES DURING CONCURRENT COPPER DEFICIENCY AND GASTRO‐INTESTINAL NEMATODIASIS IN SHEEP
Authors: Yong WK , Edwards LD , Hucker DA
Published: August 2007

Sheep experimentally depleted of copper (Cu) and infected with Trichostrongylus axei and Trichostrongylus colubriformis were studied for changes in white blood cell (WBC) populations, anti‐parasite antibody responses and in vitro proliferative response to phytohaemagglutinin (PHA), lipopolysaccharide (LPS) and Trichostrongylus spp. antigens. Increases in circulating total WBC, lymphocyte, monocyte and neutrophil leucocyte numbers had a bimodal distribution which was related to the different developmental stages of the nematode. Eosinophil leucocyte numbers were generally lower than those of uninfected control sheep and could be associated with parasite‐induced selective unresponsiveness or PHA responsive cells. The in vitro blastogenic responses of lymphocytes to PHA stimulation increased rapidly soon after infection, reaching a peak at 2 weeks, but then declined rapidly and from 5 weeks after infection responses to PHA were barely detectable. The patterns of proliferate response against LPS and Trichostrongylus spp. antigens were identical and correlated with the appearance of anti‐parasite antibodies in the serum. These last three responses reached their maxima 5 weeks after infection and then stabilized at a plateau around peak levels. It was concluded that, although the changes in the host immune response could not be consistently associated with interactions between Cu deficiency and infection, the results nevertheless suggest that Cu, as a micro‐nutrient, has a role in the mechanism of cell‐mediated immunity in sheep infected with Trichostrongylus spp.
VASO‐ACTIVE INTESTINAL PEPTIDE: A NEUROTRANSMITTER WHICH REDUCES HUMAN NK CELL ACTIVITY AND INCREASES Ig SYNTHESIS
Authors: Drew PA , Shearman DJC
Published: August 2007

The effect of vaso‐active intestinal peptide(VIP)on natural killer (Nk)cell activity and immunoglobulin synthesis in vitro has been Studied. At a concentration of 10‐6M, VIP significantly inhibited the NK cell activity of normal human peripheral blood mononuclear cells (PBMC)on K562 target cells. The concentration of IgG, IgA and IgM in the supernatants of pokeweed mitogen‐stimulated PBMC was increased when VIP was added at the beginning of the culture period. It is possible that VIP may influence immune responses in the intestinal tract, where it is a neurotransmitter and is found in high concentrations.
MELPHALAN‐RESISTANT LYMPHOBLASTOID CELL LINES ESTABLISHED FROM PATIENTS WITH OVARIAN CANCER TREATED WITH CROSS‐LINKING AGENTS
Authors: Maynard K , Musk P , Daunter B , Khoo SK , Parsons PG
Published: August 2007

Lymphoblastoid cell lines (LCLs) were established from 83 patterns with ovarian cancer by transformation of peripheral B lymphocytes with Epstein‐Barr virus. Comparing the melphalan resistance of different groups of LCLs using the mean D0 obtained from clonogenic survival assays, LCLs from melphalan‐treated patients were significantly more resistant then LCLs from patients not treated with this drug. However, prior treatment of the patient with ionizing radiation was not associated with Increased in vitro resistance of the LCL to this agent. In melphalan‐treated patients where LCLs were established serially, the melphalan D0 increased after further melphalan treatment in vivo and decreased when no further treatment was given. No correlation was found between age of donor and LCL resistance to any of the above agents. A group of 15 LCLs previously established from non‐tumour donors was less resistant to melphalan than the LCLs from patients with ovarian cancer. In a group of 29 patients with advanced disease in whom the clinical response was known, LCL resistance to melphalan appeared to be associated with poor clinical response to cross‐linking agents. These results suggest that B cell populations undergo long term, but not necessarily permanent, increases in resistance to melphalan.
AN INHIBITOR OF PLASMINOGEN ACTIVATOR PRODUCED BY TUMOUR CELL FUSION HYBRIDS
Authors: Badenoch‐Jones Peter , Ramshaw Ian A , Grant Adrienne
Published: August 2007

Expression of plasminogen activator (PA) activity may be an important factor in the ability of tumour cells to metastasize; however, not all metastatic cells product detectable PA activity. Conditioned culture media from revertant metastatic clones of cells derived by fusion of metastatic and non‐metastatic rat mammary adenocarcinoma cells were found to contain a potent inhibitor of PA. This inhibited thrombin, human urokinase (UK) and tumour‐derived PA, but not plasmin or trypsin. Inhibition was still obtained after polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate (SDS‐PAGE) of mixtures of PA and inhibitor, followed by development of PA activity on fibrin overlays. The PA inhibitor eluted from Sephadex G‐200 over a broad M.wt. range (35,000‐80,000) and was inactivated by heating to 70° for 30 min. The appearance of inhibitory activity in the culture media was time‐dependent and could be reduced by incubation of cells with cycloheximide. Because of these findings, the possible presence of inhibitors should be considered in investigations into the role of PA in the metastatic process.
A CYTOGENETIC STUDY OF SUBCUTANEOUS MURINE MACROPHAGES AND MULTINUCLEATE GIANT CELLS
Authors: Murch AR , Papadimitriou JM
Published: August 2007

Macrophages and multinucleate giant cells (MGC), collected by subcutaneous implantation of melinex discs into the dorsum of mice for 7 days, were examined cytogenetically. Two per cent of the metaphase seen were polyploid and were considered to represent dividing MGC. Twenty‐two per cent of the diploid metaphases showed chromosomal damage. Seventy per cent of damage consisted of chromosomal gaps, but the remaining 30% consisted of breaks and chromosomal fragments which would lead to unbalanced karyotypes in the next generation. More than 50% of the polyploid metaphases analysed had chromosomal damage, including 16.6% which displayed premature chromatin condensation, the damage being more severe in polyploid than in diploid metaphases. The chromosomal damage parallels that previously reported in resident peritoneal macrophages and in cultured exudate macrophages. The cause of such damage is unclear, but it was concluded that, because of the extent of damage, mitosis is unlikely to play a major part in the maintenance of macrophages or MGC at inflammatory sites.
THE LONG‐TERM COLLECTION OF LYMPH FROM SINGLE LYMPH NODES OF FOETAL LAMBS IN UTERO
Authors: Simpson‐Morgan MW , Trevella Wendy , Hugh AR , McClure Susan J , Morris B
Published: August 2007

Surgical techniques are described for the long‐term collection of lymph from both prescapular efferent lymph duels of foetal lambs in utero. Lymph ducts in foetal lambs 95 to 136 days post‐conception were cannulated with a high rate of success. Lymph flow from the cannulas was not compromised by deliberate primary or secondary challenge of the lymph nodes with a wide variety of antigens, and often continued for long periods after the lambs were born naturally. The techniques allow cellular and humoral lymph‐borne immune responses of foetal lambs to authentic primary antigenic challenge to be studied in utero, uncomplicated by any previous experience of antigens. Loss of lymphocytes from the cannulated ducts depleted the numbers of cells in the lymph, but lymph protein concentrations were unaffected by lymph drainage.
SOMATIC AND EXCRETORY POLYSACCHARIDE ANTIGENS OF LEISHMANIA DONOVANI PROMASTIGOTES
Authors: Ray Ranjit , Ghose Asoke C
Published: August 2007

Leishmania donovani promastigotes were found to release excretory‐secretory antigens (ESA) in the culture medium which reacted against rabbit antiserum to live promastigotes (RA‐LP). The active material was purified and found to contain mainly polysaccharides with about 23% of protein. A polysaccharide‐rich antigen (PRA) was also isolated from the promastigote debris by the phenol‐water extraction procedure. When tested against RA‐LP in agar gel diffusion, both the preparations were found to be antigenically identical to each other as well as to a preparation of crude soluble antigen (CSA). The determinants involved were shown to be polysaccharide in nature. Gel filtration of all the three preparations showed that the antigenic activity was distributed in various eluted fractions. Both CSA and PRA also exhibited considerable electrophoretic heterogeneity in immunoelectrophoresis, although ESA showed only two overlapping faster moving bands. It is concluded that ESA represented a mixture of highly negatively charged mucopolysaccharides of varying sizes. The minimum molecular weight of the basic structural unit was around 2 × 104 daltons. These materials were probably derived from antigenically similar complexes of larger molecular weights located on the outer surface of the parasite and were released in the culture medium during their multiplication. Information available so far from this study suggests that the polysaccharide determinants of ESA/PRA did not elicit any marked immune response in kala‐azar patients.
ESTABLISHMENT AND PARTIAL CHARACTERISATION OF A HUMAN FIBROSARCOMA CELL LINE MR‐83
Authors: Stuckly K , Kiddle R , Leversha M , Ellis WM , Ekert H
Published: August 2007

We describe a mycoplasma‐free human fibrosarcoma cell line, MR‐83, which glows readily in liquid culture and as clones in semi‐solid agar with a plating efficiency of about 0.5%. It has a stable karyotype consisting of a modal number of 49‐51 chromosomes, with two translocations and a deletion. The cell line shows resistance to adriamycin in semi‐solid agar assay, and responds to Epidermal Growth Factor (EGF) by increased DNA synthesis, as measured by thymidine uptake.
ANALYSIS OF PATTERNS OF GROWTH INHIBITION OF P. FALCIPARUM IN SYNCHRONISED CULTURES INDUCED BY SERUM FROM CHILDREN AND ADULTS FROM MADANG, PAPUA NEW GUINEA
Authors: Cowen NL , Clancy RL , Tulloch JL , Cripps AW , Alpers MP
Published: August 2007

In this study we have modified a micro Plasmodium falciparum in vitro growth inhibition assay to allow dissection of growth inhibition induced by test sera into two categories: inhibition of intracellular schizont growth and inhibition of uptake of merozoites into a second cohort of erythrocytes. This was achieved using morphology‐controlled synchronised cultures with incubation times restricted to cover either ring to schizont development or schizont to ring development. Sera tested were obtained from a large prospective study of healthy residents of Madang, Papua New Guinea, who were carefully documented with respect to presence of malarial parasites in the blood, spleen size, age, sex and history of fever. In the ring to schizont assay sera from all the children tested inhibited parasitic growth by at least 20%, compared to only 10 of 39 adults tested (P < 0.0005). In the schizont to ring assay 20 of 39 adult sera tested inhibited the uptake of 14C‐isoleucine into P. falciparum protein compared to 3 of the 15 children's sera tested (P < 0.01). These results are interpreted as reflecting a switch from non‐specific mechanisms of resistance with increasing age.
SUPPRESSION OF EARLY IMMUNITY TO NEMATO‐SPIROIDES DUBIUS IN MICE BY SELECTIVE DEPLETION OF NEUTROPHILS WITH MONOCLONAL ANTIBODY
Authors: Pentilla IA , Ey PL , Lopez AF , Jenkin CR
Published: August 2007

The role of neutrophils and eosinophils in the acquired resistance of mice to infection with the helminth Nematospiroides dubius has been investigated in vivo by testing infected mice for their resistance to a challenge dose of larvae following treatment with monoclonal rat antibodies (MAbs) specific for mouse granulocytes. Treatment of normal and infected mice with NIMP‐R10 MAb reduced the number of neutrophils in the peripheral blood and peritoneal cavity during the ensuing 2‐5 days without affecting macrophage or eosinophil levels. The effect of this MAb on immunity depended on the immune status of the mice tested. The partial resistance of mice receiving a primary ‘immunising’ infection, followed by passive transfer of immune serum and challenge at 4 days, was completely suppressed by NIMP‐R10 MAb. The acquired resistance of mice challenged 10 days after being given a single ‘immunising’ infection was halved by NIMP‐R10 treatment, while that of ‘twice‐immunised’ mice (infected on days 0 and 14, challenged on day 24) was unaffected. Treatment of twice‐infected mice with the eosinophil‐specific MAb NIMP‐R6 reduced the number of eosinophils in the blood and peritoneal cavity by 40‐60%, but caused no significant loss of immunity.

The data indicate that after infection of mice with N. dubius, neutrophils play a predominant role in early resistance to reinfection, but they become progressively less essential as activated macrophages and (following a second infection) eosinophils become prevalent.

The lack of effect of NIMP‐R6 MAb treatment on the immunity of twice‐infected mice may have been due to an insufficient reduction in eosinophil numbers; however, it seems likely that the neutrophils and macrophages present in these mice would have provided adequate protection even in the absence of eosinophils.
RECONSTRUCTING NORMAL α‐CRYSTALLIN FROM THE MODIFIED CATARACTOUS PROTEIN
Authors: Thomson John A , Hum Tony P , Augusteyn Robert C
Published: August 2007

α‐Crystallin from human cataractous lenses is so extensively modified that it is unsuitable for structural studies. We have disassembled the protein and, from the remaining traces of unmodified polypeptides, reconstructed a more homogeneous and conformationally discrete molecule. We suggest that this approach may be particularly useful to studies of enzymology and molecular gerontology.
A CONJUGATIVE PLASMID ENCODING PRODUCTION OF A DIFFUSIBLE PIGMENT AND RESISTANCE TO AMINOGLYCOSIDES AND MACROLIDES IN STAPHYLOCOCCUS AUREUS
Authors: Townsend DE , Ashdown N , Annear DI , Grubb WB
Published: August 2007

A methicillin‐resistant strain of Staphylococcus aureus, WG512, was isolated in 1968 and has been shown to harbour a plasmid, pWG14, which encodes the production of a diffusible pigment and resistance to kanamycin, neomycin, streptomycin, lincomycin, erythromyein and spectinomycin. Plasmid pWG14 has only been detected as a slowly migrating band of DNA during agarose‐gel electrophoresis, and this was thought to be the open‐circular form of the plasmid with an estimated molecular weight of 30‐34 Mdal. The transfer properties of this plasmid were compared with a non‐conjugative plasmid encoding tetracycline resistance and the class 2, conjugative plasmid described by Archer and Johnston (1983), Plasmid pWG14 shared many of the conjugative properties of the latter plasmid, including the ability to transfer at high frequency on the surface of a filter membrane and to transfer between non‐lysogenic strains in the absence of Ca++ and in the presence of citrate or DNase I. However, unlike the class 2 plasmid, pWG14 was able to transfer in broth culture at low frequency and did not mobilise the non‐conjugative plasmid. Furthermore, the class 2 plasmid and pWG14 were shown to belong to different incompatibility groups. A derivative of WG512, which had lost the ability to produce the diffusible pigment along with plasmid pWG14 but had retained the resistance determinants of plasmid pWG14 in the chromosome, was used to demonstrate that the conjugative mechanism of pWG14 was a property of the plasmid and not the resistance determinants.
ISOLATION OF ROSS RIVER VIRUS FROM EPIDEMIC POLYARTHRITIS PATIENTS IN AUSTRALIA
Authors: Aaskov JG , Ross PV , Harper JJ , Donaldson MD
Published: August 2007

Ross River virus was isolated from two out of four seronegative scrum samples obtained from epidemic polyarthritis patients in Australia. Virus isolated from each patient was found to be phenotypically diverse. These isolations suggest that previous failure to isolate virus from epidemic polyarthritis patients in this country may have been due to failure to obtain material (serum) from patients early enough in the course of the disease and to the use of relatively insensitive isolation techniques.
EXPERIMENTAL INFECTION WITH MURRAY VALLEY ENCEPHALITIS VIRUS: GALAHS, SULPHUR‐CRESTED COCKATOOS, CORELLAS, BLACK DUCKS AND WILD MICE
Authors: Kay BH , Hall RA , Fanning ID , Young PL
Published: August 2007

Orally infected Culex annulirostris or intravenous injections were used to infect 10 Galahs, 15 Sulphur‐crested cockatoos, 12 Corellas, 4 Black ducks and 10 wild mice with Murray Valley encephalitis (MVE) virus. The birds produced moderate viraemias of titres of log 102.0‐106.0 suckling mouse intracerebral (SMIC) LD50/ml for durations of 1‐9 d. However, the wild mice developed low grade viraemia for 1‐4 d. Recipient Cx annulirostris feeding on viraemic birds sustained infection rates of 0‐10% but, by extrapolation from vector competence data, some titres were capable of infecting ≥ 50% of recipient Cx annulirostris. HI antibody responses were moderately high for most birds (reciprocal titres of 1 in 640‐2560) by 14 d and usually persisted at detectable levels for 140 d and, in some individuals, for 6 months. However, 6 of 12 Corellas and 1 of 4 Black ducks became seronegative after 42 and 56 d, respectively. As with previously tested animals, any IgM response was absent 4 wks post‐infection. The viraemias attained indicate that these bird species may be considered as potential hosts of MVE, but the limited viraemic response of wild mice suggests that they might play only a minor role.
IMPROVED DETECTION OF CARCINOGENS BY DEGRANULATION OF MICROSOMES PREPARED AT LOW G FORCE BY GLUTATHIONE
Authors: Jagota SK , Dani HM
Published: August 2007

Rat liver microsomes can be prepared by the addition of glutathione to post‐mitochondrial supernatant (PMS) and its subsequent sedimentation at 10,000 g. These microsomes seem to be unaffected with respect to their major components, and substantial loss of their ribosomes on treatments with various degranulating reagents shows that they contain intact ribosomes. The indices of ribosomal attachment show that these preparations contain more ribosomes per unit area of membrane surface as compared to those prepared at high g forces. High values of per cent degranulation by incubating these microsomes with coded carcinogens and failure of non‐carcinogens to cause this effect show that the technique can be used efficiently for quick, inexpensive and more accurate prediction of carcinogens in human environments.
DETECTION OF TWO LECTINS IN HAEMOLYMPH FROM THE OYSTER PINCTADA MAXIMA
Authors: Flower RLP , Wilcox GE , Pass DA
Published: August 2007

Two lectins were detected in haemolymph from the oyster Pinctada maxima, a macromolecular (approximately 8 × 106 dalton) N‐acetyl‐galactosamine‐binding lectin and a lower molecular weight (approximately 4 × 105 dalton)α‐galactose‐binding lectin. The macro‐molecular lectin agglutinated human type A erythrocytes to a greater extent than human type B or O erythrocytes and was the major lectin detected in the haemolymph. The 4 × 105 dalton lectin agglutinated human type A, B and O erythrocytes to the same extent.
DIURNAL VARIATION IN OXYGEN CONSUMPTION OF LABORATORY RATS
Authors: Maxwell GM , Smyth C , Harvey G , Crompton Silvia
Published: August 2007

Oxygen consumption (VO2) was measured in Porton albino rats using a closed circuit apparatus. The groups studied were controls, cold‐adapted animals, and those which had accumulated brown adipose tissue as a result of a cafeteria diet with a high energy content. It was possible to show in each group studied a difference in VO2 according to the time of day at which it was measured. This was consistent within each group studied. The diurnal variation shown (higher in the morning than in the afternoon) is characteristic of nocturnal animals. Measurement of VO2 then must be made within the same time‐period or integrated over 24 h. Spurious correlations may otherwise occur.
Extragenic Suppression analysis of TS mutations using Sec61p
Authors: Smith Sterling
Published: August 2007

During synthesis, secretory and membrane proteins are cotranslationally translocated into the lumen of the endoplasmic reticulum through an aqueous gated channel. Proper folding, degradation, and transport of many polypeptides depend on a diverse set of helper proteins termed chaperone. I hypothesize thatSec 61p is a membrane chaperone, which actively directs membrane protein folding.
Noninvasive Quantification of Local Cerebral Metabolic Rate of Glucose for Clinical Application Using Positron Emission Tomography and 18F-Fluoro-2-Deoxy-d-Glucose
Authors: Yi-Gen WU
Published: August 2007

Until now, input function is still required in quantification of local cerebral metabolic rate of glucose (LCMRGlc) using positron emission tomography (PET) and 18F-fluoro-2-deoxy-d-glucose (FDG). Some image-derived methods were developed to get input function noninvasively instead of the arterial blood sampling method, but they needed to make complicated corrections manually, so they cannot always be applied in clinic directly. Here, we propose a simple method based on the Patlak approach by using a reference tissue region and without using any information of input function. This simulation study revealed that the present method was in good agreement with Patlak method; the difference between two methods was less than 5%. The statistical errors with two methods were also obtained, and the results showed the accuracy of LCMRGlc estimated with present method was better than that with Patlak method slightly. The simulation results indicated that the calculation of LCMRGlc with present method was quite stable and independent of the choosing of reference tissue region. All of these show that the present method is a good approximation to Patlak method. The calculation with this method is very simple and easy to perform voxel by voxel; therefore, it can be widely used not only in laboratory studies but also in clinical applications although it only provides the relative rates.
State-selective photodissociation dynamics of formaldehyde: Near threshold studies of the H+HCO product channel
Authors: Scott Hopkins W. , Loock Hans-Peter , Cronin Bríd , Nix Michael G. D. , Devine Adam L. , Dixon Richard N. , Ashfold Michael N. R.
Published: August 2007

The laser-induced photodissociation of formaldehyde in the wavelength range 309<λ<330nm has been investigated using H (Rydberg) atom photofragment translational spectroscopy. Photolysis wavelengths corresponding to specific rovibronic transitions in the ÃA21←X̃A11 201403, 202401, 202403, 203401, and 201501 bands of H2CO were studied. The total kinetic energy release spectra so derived can be used to determine partial rotational state population distributions of the HCO cofragment. HCO product state distributions have been derived following the population of various different NKa levels in the ÃA21 2243 and 2341 states. Two distinct spectral signatures are identified, suggesting competition between dissociation pathways involving the X̃A11 and the ãA23 potential energy surfaces. Most rovibrational states of H2CO(ÃA21) investigated in this work produceH+HCO(X̃A′2) photofragments with a broad kinetic energy distribution and significant population in high energy rotational states of HCO. Photodissociation via the ÃA21 2243 11,1 (and 11,0) rovibronic states yields predominantly HCO fragments with low internal energy, a signature that these rovibronic levels are perturbed by the ãA23 state. The results also suggest the need for further careful measurements of the H+HCO quantum yield from H2CO photolysis at energies approaching, and above, the barrier to C–H bond fission on the ãA23 potential energy surface.
On the transitional wake behind a heated circular cylinder
Authors: Wu Ming-Hsun , Wang An-Bang
Published: August 2007

Wake characteristics of flow over a heated circular cylinder in the three-dimensional transitional wake regimes are studied using smoke wire flow visualizations and hot-wire anemometry techniques. The onset of wake from laminar vortex shedding to transition is found to be delayed by heating of the cylinder and the transitional wakes still developed at higher Reynolds numbers. As the cylinder is heated, vortex shedding frequencies are reduced throughout the Reynolds number range and discontinuities in St-Re relationships are typical in all temperature ratios studied. Critical Reynolds numbers for all transitional wake regimes increase linearly with increasing temperature ratios. Criteria for measuring the onset of transition for flow around a heated cylinder are proposed. Excellent agreement in Strouhal-effective Reynolds number relationships for the heated and unheated cylinders validates the applicability of the effective Reynolds number concept in both laminar and transitional wake regimes (47<Re<400).
Miniature random-access fiber scanner for in vivo multiphoton imaging
Authors: Sawinski Jürgen , Denk Winfried
Published: August 2007

Multiphoton microscopy allows imaging of cellular activity in living tissue explants and in whole animals and has thus become a powerful tool for studying neuronal activity. The miniaturization of laser-scanning microscopy promises to extend activity measurements to awake, freely moving animals. Here we describe and evaluate a miniature multiphoton microscope based on a “piezolever fiber scanner” (PLFS). Our current PLFS has a scan range of 1.1 mm and a resonance frequency of 790 Hz. It allows, unlike resonance-based designs, a lateral shift of the scanned area, and offers the prospect of random-access (vector) scanning.
Dielectric relaxation mechanism of single crystal and polycrystal bismuth germanate
Authors: Macedo Z. S. , Oliveira C. S. S. , Hernandes A. C.
Published: August 2007

We report the results of investigation on the mechanism of dark conductivity and dielectric relaxation of Bi12GeO20 single crystals and dense ceramics. Alternating current electric characterization was performed in the temperature interval from 30 °C up to 730 °C and frequencies from 1 Hz to 13 MHz. The samples presented ohmic behavior even at high temperatures, for applied potentials up to 2.2 V. The electric conductivity of single crystals was thermally activated, with potential barriers changing from 0.75±0.05 eV to 1.4±0.2 eV at 500 °C. The same conduction mechanisms were observed for ceramic samples, with activation energies of 0.9±0.1 eV and 1.5±0.1 eV for charge transport through grains and grain boundaries, respectively. These energy values were related to defects arising from substitutional Bi3++h+ in Ge4+ sites. In the ceramic samples, the higher resistivity of the grain interfaces leads to a Maxwell–Wagner polarization of the grain boundaries due to local charge rearrangement. As a result, the overall permittivity of ceramics was higher than that observed for single crystals at frequencies corresponding to the grain boundary response.
Terahertz time-domain studies of far-infrared dielectric response in 5 mol % MgO:LiNbO3 ferroelectric single crystal
Authors: Guo H. C. , Liu W. M. , Tang S. H.
Published: August 2007

The 5 mol % MgO:LiNbO3 ferroelectric single crystal has attracted much attention in terahertz (THz) generation and detection by parametric process or optical rectification. In this work, the dielectric properties of 5 mol % MgO:LiNbO3 ferroelectric single crystal in 0.2−2 THz frequency range has been investigated by using transmission-type THz time-domain spectroscopy. The complex refractive index and dielectric function are extracted from the measured transmittance and phase shift. The power absorption and dispersion relationship of the lowest branch of the phonon polariton are observed. The results fit well with the classical damped oscillator model, indicating that the far-infrared dielectric response of 5 mol % MgO:LiNbO3 is dominated by the lowest transverse optical mode with E(x,y) symmetry centered at 4.533 THz. The investigation presented in this work provides important considerations for optimizing THz devices in 5 mol % MgO:LiNbO3 ferroelectric single crystal.
Tracking polymer diffusion in a wet latex film with fluorescence resonance energy transfer
Authors: Haley Jeffrey C. , Liu Yuanqin , Winnik Mitchell A. , Demmer David , Haslett Tom , Lau Willie
Published: August 2007

We describe an instrument to measure the polymer interdiffusion between donor-labeled and acceptor-labeled latex polymers in a partially wet latex film with fluorescence resonance energy transfer (FRET). It is possible to temporarily arrest the drying process of a wet latex film by sealing the film in an airtight chamber. In our approach, we measure donor fluorescence decays from 0.5mm diameter spots at various positions across an arrested latex film with time-correlated single photon counting. We interpret the resulting decays with a Monte Carlo simulation of the FRET process and extract information about the extent of polymer diffusion as a function of position on the film. These results enable us to determine the extent of polymer interdiffusion as a function of distance from the wet-dry edge in the latex film. To highlight this device’s ability to capture the rapid early stages of latex interdiffusion, we report results from an acrylate copolymer latex.
Low temperature a-Si:H photodiodes and flexible image sensor arrays patterned by digital lithography
Authors: Ng Tse Nga , Lujan Rene A. , Sambandan Sanjiv , Street Robert A. , Limb Scott , Wong William S.
Published: August 2007

Hydrogenated amorphous silicon-based image sensor arrays were fabricated on polyethylene naphthalate substrates, with photodiodes optimized for process temperatures of 150°C. An optimal i-layer thickness was determined to minimize carrier recombination and to maintain sufficient light absorption and acceptable leakage current. Patterning of the thin-film transistor backplane was accomplished using ink-jet printed etch masks. A flexible image sensor is demonstrated with 75dots∕in. resolution over 180×180pixels and with sensitivity of 1.2pW∕cm2.
Formation of stacked oxide/Y2TiO5/oxide layers for flash memory application
Authors: Pan Tung-Ming , Yeh Wen-Wei , Chen Jing-Wei
Published: August 2007

In this letter, the authors propose the formation of stacked oxide/Y2TiO5/oxide layers for flash memory application. The quality of a high-k Y2TiO5 memory was examined by x-ray diffraction, x-ray photoelectron spectroscopic, atomic force microscopy, capacitance-voltage curves, and data retention. When using Fowler-Nordheim for charging and discharging, the Y2TiO5 memory annealed at 900°C for 30s exhibited large flatband-voltage shifting (memory window of 4.2V) and superior data retention (charge loss of 6% at room temperature) because of the higher probability for trapping the charge carriers and they trapped in the deep trap level of Y2TiO5 due to the formation of a well-crystallized Y2TiO5 structure and the reduction of Y-silicate layer.
Improving polymer light-emitting diodes efficiency using interlayers based on cross-linkable polymers
Authors: Bernardo G. , Charas A. , Alcácer L. , Morgado J.
Published: August 2007

The efficiency of light-emitting diodes based on poly[(2-methoxy)-5-(2′-ethyl-hexyloxy)-1,4-phenylenevinylene] increases upon formation of interlayers, on top of poly(3,4-ethylenedioxythiophene) doped with polystyrene sulfonic acid (PEDOT:PSS), made of acid-initiated cross-linkable polyfluorenes. The use of this type of polymers allows for the formation of thicker interlayers leading to higher efficiencies when comparing with similar devices with interlayers formed by the parent non-cross-linkable polymers. This efficiency increase is attributed to a combination of electron and exciton confinement away from PEDOT:PSS.
Transconductance enhancement of nanowire field-effect transistors by built-up stress induced during thermal oxidation
Authors: Seike A. , Tange T. , Sano I. , Sugiura Y. , Kosemura D. , Ogura A. , Ohdomari I.
Published: August 2007

The authors report the enhancement of transconductance in nanowire field effect transistors due to build-up tensile stress during thermal oxidation. To evaluate the effect of stress, nanowires were thermally oxidized at (A) 900°C∕15min, (B) 850°C∕1h, and (C) 850°C∕1h with a subsequent 1000°C annealing. The transconductance of sample B is enhanced 2.6 times compared to sample A. No enhancement of transconductance is observed in sample C. The Raman spectra indicate tensile stress in sample B and compressive stress in sample C. This establishes that gm enhancement is due to the build-up tensile stress in nanowires, but is diminished by viscoelastic relaxation.
Hysteresis phenomena in nanoscale rectifying diodes: A Monte Carlo interpretation in terms of surface effects
Authors: Iñiguez-de-la-Torre I. , González T. , Pardo D. , Mateos J.
Published: August 2007

Hysteresis effects taking place in the rectifying current-voltage characteristic of self-switching diodes are studied by means of a semiclassical Monte Carlo simulator. When the applied voltage is higher than a certain threshold, in both negative and positive voltage sweeps, a well-defined hysteresis loop appears which can be exploited for memory applications. An algorithm for the simulation of surface effects has been introduced in the Monte Carlo simulator to explain this behavior in terms of the charging and discharging of the surface states on the etched sidewalls of the structure. Devices with different geometries have been simulated, and a detailed microscopic analysis of the behavior of surface charge and potential profiles has been performed. The reduction of the channel length or the increase of the width improves the discrimination of the memory state (by providing a higher reverse current); however, this induces a decrease of the reverse voltage threshold.
Surface studies of hydrogen etched 3C-SiC(001) on Si(001)
Authors: Coletti C. , Frewin C. L. , Saddow S. E. , Hetzel M. , Virojanadara C. , Starke U.
Published: August 2007

The morphology and structure of 3C-SiC(001) surfaces, grown on Si(001) and prepared via hydrogen etching, are studied using atomic force microscopy (AFM), low-energy electron diffraction (LEED), and Auger electron spectroscopy (AES). On the etched samples, flat surfaces with large terraces and atomic steps are revealed by AFM. In ultrahigh vacuum a sharp LEED pattern with an approximate (5×1) periodicity is observed. AES studies reveal a “bulklike” composition up to the near surface region and indicate that an overlayer consisting of a weakly bound silicon oxide monolayer is present.
On the enhancement of field emission performance of ultrananocrystalline diamond coated nanoemitters
Authors: Tzeng Yu-Fen , Lee Yen-Chih , Lee Chi-Young , Lin I.-Nan , Chiu Hsin-Tien
Published: August 2007

Ultrananocrystalline diamond (UNCD) nanoemitters were synthesized by a microwave plasma enhanced chemical vapor deposition process using silicon nanowires (SiNWs) as the template. Preseeding markedly enhances the nucleation of diamond on the SiNW templates, resulting in UNCD grains of smaller size and uniform distribution, which leads to significantly improved electron field emission (EFE) properties. The EFE for UNCD nanoemitters can be turned on at (E0)UNCD-NE=4.4V∕μm, achieving large EFE current density, (Je)UNCD-NE=13.9mA∕cm2 at an applied field of 12V∕μm, which is comparable with that of carbon nanotubes, but with much better processing reliability.
In situ Raman spectroscopy of A-site doped barium titanate
Authors: Pasha U. M. , Zheng H. , Thakur O. P. , Feteira A. , Whittle K. R. , Sinclair D. C. , Reaney I. M.
Published: August 2007

Raman spectroscopy has been used to study the ferroelectric tetragonal to paraelectric cubic phase transition Tc in undoped BaTiO3 (BT) and (Ba0.92A0.08)TiO3 [where A=Ca (BCT), Sr (BST), and Pb (BPT)]. In BT and BPT, mode characteristic of the tetragonal phase at 303 and 710cm−1 persisted until >50°C above Tc, indicating the presence of local dynamic polar clusters well above the displacive phase transitions, ∼120 and ∼149°C, respectively. However, in BCT and BST, the Raman spectra exhibited only broad second order bands above Tc, suggesting that Ca and Sr, A-site dopants supress local dynamic polar clusters.
Thin-film silicon solar cells with efficient periodic light trapping texture
Authors: Haase Christian , Stiebig Helmut
Published: August 2007

For solar cells based on thin-film microcrystalline (μc-Si:H) or amorphous silicon (a-Si:H) with absorber layers in the micrometer range, highly effective light trapping and an optimal incoupling of the entire sun spectrum are essential. To investigate and optimize both effects the wave propagation in thin-film silicon solar cells is modeled in three dimensions (3D) solving the Maxwell equations rigorously. A periodic nanostructured texture is investigated as an alternative to the common randomly rough texture. Inverted 3D pyramids with a periodicity of 850nm and structure height of 400nm show promising high quantum efficiencies close to the Tiedje limit.
Switch-on transient behavior of vanadium phthalocyanine based organic transistors
Authors: Wang Lijuan , Liu Guojun , Wang Haibo , Song De , Yu Bo , Yan Donghang
Published: August 2007

The authors investigated the switch-on transient properties of p-type vanadium phthalocyanine (VOPc) transistors, which were fabricated by weak epitaxy growth on ordered para-sexiphenyl (p-6P) layer. The overshoot phenomenon of drain current had been observed in the VOPc∕p-6P transistors, which was explained by the filling of carriers in traps of organic films. The small overshoot value of about 35% and transient duration time of 2ms demonstrated the low trap concentration in organic films, which were comparable to the reported hydrogenated amorphous-silicon thin-film transistors. Therefore, the VOPc∕p-6P transistors can be applied in active matrix liquid crystal display as switch elements.
Increment of dielectric properties of SrTiO3 thin films by SrO interlayer on Ru bottom electrodes
Authors: Ahn Ji-Hoon , Kim Ja-Yong , Kang Sang-Won , Kim Jin-Hyock , Roh Jae-Sung
Published: August 2007

Sr Ti O 3 thin films were deposited on Ru using plasma-enhanced atomic layer deposition with and without a SrO interlayer. When the SrTiO3 films were deposited on Ru directly, the dielectric constants of the films decreased abruptly from 65 to 16 as the thickness fell below 20nm. This change was related to film crystallinity. Conversely, when a seed layer was prepared by depositing 2.7nm SrO and postannealing before SrTiO3 deposition, the crystallinity of the SrTiO3 films was enhanced and the thickness dependency of the dielectric constant was reduced. As a result, the dielectric constant of 10nm SrTiO3 films was improved from 16 to 50.
Direct observation of dislocation plasticity in 100nm scale Au∕Cu multilayers
Authors: Li Y. P. , Zhang G. P. , Tan J. , Wu B.
Published: August 2007

Dislocation plasticity of Au∕Cu multilayer with 100nm scale was investigated by three-point bending tests. The authors found directly that clear slip lines appeared inside the grains ranging from 60to190nm. The finding implies that the potential dislocation plasticity is still the dominant deformation mechanism in the material. Statistical evaluation of the mean spacing between slip lines reveals the effect of the length scale on homogeneity of plastic deformation. The critical length scale for dislocation-dominated deformation of the nanoscale material is found to be ∼15nm.
Nanostructured solid-liquid compounds with rewritable optical functions
Authors: Saito Mitsunori , Tsubokura Yasuhiro , Ota Narihito , Fujiuchi Akiko
Published: August 2007

Photosensitive solid-liquid compounds were fabricated by filling nanoholes of alumina or polymer films with dye solution. Although these compounds can be handled as solid in device fabrication processes, the liquid phase inside 50–200nm holes provides a sufficient free volume for photochromic dye to change molecular structure. Nanoholes also prevent the solution to flow disturbing an optically written image. A function of the rewritable grating was demonstrated by bleaching a polycarbonate-based compound with various interference fringes of green laser.
Synthesis and Functional Properties of Star-Burst Dendrimers that Contain Carbazole as Peripheral Edges and Triazine as a Central Core
Authors: Xiong Mo Jun , Li Zhong Hui , Wong Man Shing
Published: August 2007

With the aim of combining the electron and hole-transporting moieties into one molecule and to continue our investigation into the structure–property correlations of dendrimers, two novel star-burst dendrimers 1 and 2 constructed with carbazoles as the peripheral hole-transporting moieties and one triazine moiety as an electron-transporting central core, have been synthesized. The convergent synthetic approach uses palladium-catalyzed Suzuki cross-coupling as a key reaction. Their functional properties have also been investigated.
Synthesis of 5-Phenyl 2-Functionalized Pyrroles by Amino Heck and Tandem Amino Heck Carbonylation Reactions
Authors: Zaman Shazia , Kitamura Mitsuru , Abell Andrew D.
Published: August 2007

2-Methyl-, 2-(methoxycarbonyl)methyl-, and 2,2-[(ethoxycarbonyl)(methoxycarbonyl)]methyl-5-phenylpyrroles are prepared from the corresponding 3-butynyl and 4-(methoxycarbonyl)-3-butynyl phenyl ketone O-pentafluorobenzoyl oximes by amino Heck cyclization and tandem amino Heck carbonylation, respectively.
Moonlighting activity of presenilin in plants is independent of γ-secretase and evolutionarily conserved
Authors: Khandelwal Abha , Chandu Dilip , Roe Catherine M. , Kopan Raphael , Quatrano Ralph S.
Published: August 2007

Presenilins (PS) provide the catalytic activity for γ-secretase, which cleaves physiologically relevant substrates including Notch, ErbB4, and APP. Recent genetic studies indicated that the contribution of PS1 to mouse development includes γ-secretase-independent functions that cannot be easily explained by any of the demonstrated or hypothesized functions of this protein. To begin a nonbiased analysis of PS1 activity unencumbered by the dominant effect stemming from loss of Notch function, we characterized PS functions in the early land plant
Physcomitrella patens
, which lacks Notch, ErbB4, and APP. Removal of
P. patens
PS resulted in phenotypic abnormalities. Further assays performed to delineate the defective pathways in PS-deficient
P. patens
implicated improper function of the cytoskeletal network. Importantly, this characterization of a nonmetazoan PS uncovered a previously undescribed, evolutionarily conserved function (human PS1 can rescue the growth and light responses) that is γ-secretase-independent (mutants with substitutions of the catalytic aspartyl residues retain the activity). Introduction of PpPS into PS-deficient mouse embryonic fibroblasts rescues normal growth rates, demonstrating that at least some metazoan functions of PS are evolutionarily conserved.
The Btk tyrosine kinase is a major target of the Bcr-Abl inhibitor dasatinib
Authors: Hantschel Oliver , Rix Uwe , Schmidt Uwe , Bürckstümmer Tilmann , Kneidinger Michael , Schütze Gregor , Colinge Jacques , Bennett Keiryn L. , Ellmeier Wilfried , Valent Peter , Superti-Furga Giulio
Published: August 2007

Dasatinib is a small-molecule kinase inhibitor used for the treatment of imatinib-resistant chronic myelogenous leukemia (CML). We have analyzed the kinases targeted by dasatinib by using an unbiased chemical proteomics approach to detect binding proteins directly from lysates of CML cells. Besides Abl and Src kinases, we have identified the Tec kinases Btk and Tec, but not Itk, as major binders of dasatinib. The kinase activity of Btk and Tec, but not of Itk, was inhibited by nanomolar concentrations of dasatinib
in vitro
and in cultured cells. We identified the gatekeeper residue as the critical determinant of dasatinib susceptibility. Mutation of Thr-474 in Btk to Ile and Thr-442 in Tec to Ile conferred resistance to dasatinib, whereas mutation of the corresponding residue in Itk (Phe-435) to Thr sensitized the otherwise insensitive Itk to dasatinib. The configuration of this residue may be a predictor for dasatinib sensitivity across the kinome. Analysis of mast cells derived from Btk-deficient mice suggested that inhibition of Btk by dasatinib may be responsible for the observed reduction in histamine release upon dasatinib treatment. Furthermore, dasatinib inhibited histamine release in primary human basophils and secretion of proinflammatory cytokines in immune cells. The observed inhibition of Tec kinases by dasatinib predicts immunosuppressive (side) effects of this drug and may offer therapeutic opportunities for inflammatory and immunological disorders.