Tunable Kondo physics in a carbon nanotube double quantum dot.

We investigate a tunable two-impurity Kondo system in a strongly correlated carbon nanotube double quantum dot, accessing the full range of charge regimes. In the regime where both dots contain an unpaired electron, the system approaches the two-impurity Kondo model. At zero magnetic field the interdot coupling disrupts the Kondo physics and a local singlet state arises, but we are able to tune the crossover to a Kondo screened phase by application of a magnetic field. All results show good agreement with a numerical renormalization group study of the device.

Measuring the complex admittance of a carbon nanotube double quantum dot.

We investigate radio-frequency (rf) reflectometry in a tunable carbon nanotube double quantum dot coupled to a resonant circuit. By measuring the in-phase and quadrature components of the reflected rf signal, we are able to determine the complex admittance of the double quantum dot as a function of the energies of the single-electron states. The measurements are found to be in good agreement with a theoretical model of the device in the incoherent limit. In addition to being of fundamental interest, our results present an important step forward towards noninvasive charge and spin state readout in carbon nanotube quantum dots.

Transport spectroscopy of an impurity spin in a carbon nanotube double quantum dot.

We make use of spin selection rules to investigate the electron spin system of a carbon nanotube double quantum dot. Measurements of the electron transport as a function of the magnetic field and energy detuning between the quantum dots reveal an intricate pattern of the spin state evolution. We demonstrate that the complete set of measurements can be understood by taking into account the interplay between spin-orbit interaction and a single impurity spin coupled to the double dot. The detection and tunability of this coupling are important for quantum manipulation in carbon nanotubes.

Adiabatic charge pumping in carbon nanotube quantum dots.

We investigate charge pumping in carbon nanotube quantum dots driven by the electric field of a surface acoustic wave. We find that, at small driving amplitudes, the pumped current reverses polarity as the conductance is tuned through a Coulomb blockade peak using a gate electrode. We study the behavior as a function of wave amplitude, frequency, and direction and develop a model in which our results can be understood as resulting from adiabatic charge redistribution between the leads and quantum dots on the nanotube.

Charge pumping in carbon nanotubes.

We demonstrate charge pumping in semiconducting carbon nanotubes by a traveling potential wave. From the observation of pumping in the nanotube insulating state we deduce that transport occurs by packets of charge being carried along by the wave. By tuning the potential of a side gate, transport of either electron or hole packets can be realized. Prospects for the realization of nanotube based single-electron pumps are discussed.

Multiple Andreev reflections in a carbon nanotube quantum dot.

We report resonant multiple Andreev reflections in a multiwall carbon nanotube quantum dot coupled to superconducting leads. The position and magnitude of the subharmonic gap structure is found to depend strongly on the level positions of the single-electron states which are adjusted with a gate electrode. We discuss a theoretical model of the device and compare the calculated differential conductance with the experimental data.

Quantum dot in the Kondo regime coupled to superconductors.

The Kondo effect and superconductivity are both prime examples of many-body phenomena. Here we report transport measurements on a carbon nanotube quantum dot coupled to superconducting leads that show a delicate interplay between both effects. We demonstrate that the superconductivity of the leads does not destroy the Kondo correlations on the quantum dot when the Kondo temperature, which varies for different single-electron states, exceeds the superconducting gap energy.

Multiwall carbon nanotubes as quantum dots.

We have measured the differential conductance of individual multiwall carbon nanotubes. Coulomb blockade and energy level quantization are observed. The electron levels are nearly fourfold degenerate (including spin) and their evolution in magnetic field (Zeeman splitting) agrees with a g factor of 2. In zero magnetic field the sequential filling of states evolves with spin S according to S = 0-->1/2-->0.... A Kondo enhancement of the conductance is observed when the number of electrons on the tube is odd.

Suppression of tunneling into multiwall carbon nanotubes.

We have studied tunneling of electrons into multiwall carbon nanotubes (NTs) in NT-gold and NT-NT junctions, the latter created by atomic force microscope manipulation. The tunneling conductance goes to zero as the energy (temperature and bias) is reduced, and the functional form is consistent with a power law. The exponents depend upon sample geometry. The relationship between these results and theories for tunneling into ballistic and disordered metals is discussed.

Reduced hepatic uptake and intestinal excretion of organic cations in mice with a targeted disruption of the organic cation transporter 1 (Oct1 [Slc22a1]) gene.

The polyspecific organic cation transporter 1 (OCT1 [SLC22A1]) mediates facilitated transport of small (hydrophilic) organic cations. OCT1 is localized at the basolateral membrane of epithelial cells in the liver, kidney, and intestine and could therefore be involved in the elimination of endogenous amines and xenobiotics via these organs. To investigate the pharmacologic and physiologic role of this transport protein, we generated Oct1 knockout (Oct1(-/-)) mice. Oct1(-/-) mice appeared to be viable, healthy, and fertile and displayed no obvious phenotypic abnormalities. The role of Oct1 in the pharmacology of substrate drugs was studied by comparing the distribution and excretion of the model substrate tetraethylammonium (TEA) after intravenous administration to wild-type and Oct1(-/-) mice. In Oct1(-/-) mice, accumulation of TEA in liver was four to sixfold lower than in wild-type mice, whereas direct intestinal excretion of TEA was reduced about twofold. Excretion of TEA into urine over 1 h was 53% of the dose in wild-type mice, compared to 80% in knockout mice, probably because in Oct1(-/-) mice less TEA accumulates in the liver and thus more is available for rapid excretion by the kidney. In addition, we found that absence of Oct1 leads to decreased liver accumulation of the anticancer drug metaiodobenzylguanidine and the neurotoxin 1-methyl-4-phenylpyridium. In conclusion, our data show that Oct1 plays an important role in the uptake of organic cations into the liver and in their direct excretion into the lumen of the small intestine.

Impaired activity of the extraneuronal monoamine transporter system known as uptake-2 in Orct3/Slc22a3-deficient mice.

Two uptake systems that control the extracellular concentrations of released monoamine neurotransmitters such as noradrenaline and adrenaline have been described. Uptake-1 is present at presynaptic nerve endings, whereas uptake-2 is extraneuronal and has been identified in myocardium and vascular and nonvascular smooth muscle cells. The gene encoding the uptake-2 transporter has recently been identified in humans (EMT), rats (OCT3), and mice (Orct3/Slc22a3). To generate an in vivo model for uptake-2, we have inactivated the mouse Orct3 gene. Homozygous mutant mice are viable and fertile with no obvious physiological defect and also show no significant imbalance of noradrenaline or dopamine. However, Orct3-null mice show an impaired uptake-2 activity as measured by accumulation of intravenously administered [(3)H]MPP(+) (1-methyl-4-phenylpyridinium). A 72% reduction in MPP(+) levels was measured in hearts of both male and female Orct3 mutant mice. No significant differences between wild-type and mutant mice were found in any other adult organ or in plasma. When [(3)H]MPP(+) was injected into pregnant females, a threefold-reduced MPP(+) accumulation was observed in homozygous mutant embryos but not in their placentas or amniotic fluid. These data show that Orct3 is the principal component for uptake-2 function in the adult heart and identify the placenta as a novel site of action of uptake-2 that acts at the fetoplacental interface.

Comparative study of ampicillin and amoxycillin after intravenous, intramuscular and oral administration in homing pigeons (Columba livia).

Pharmacokinetics of ampicillin and amoxycillin after intravenous, intramuscular and oral administration was investigated in homing pigeons. The pharmacokinetic parameters in a cross-over study after intravenous administration of the sodium salts were comparable. The only significant difference was found for the distribution phase. The bioavailability after intramuscular injection of the sodium salts was especially low for ampicillin (26 per cent, as against 57 per cent for amoxycillin). The mean peak blood levels at 0.5 hours were 13.65 and 28.80 mg litre-1 for ampicillin and amoxycillin, respectively. After oral administration of trihydrate solutions (8 mg ml-1) the bioavailability was 20 and 35 per cent, respectively, and the mean peak blood levels were 8.46 and 16.98 mg litre-1, found at 1.04 and 1.26 hours. The recovery from the droppings, which include in birds the urine fraction as well, was unexpectedly low. Based on controls for recovery of added penicillin from the droppings and uric acid suspensions, indications were found that the pigeon enzymically inactivates penicillins. The in vitro activity of ampicillin against 266 strains of bacteria isolated from birds was determined. The minimum inhibitory concentration (MIC) for 65.4 per cent of the Escherichia coli was lower than 4 mg litre-1, for 91.1 per cent of the Salmonella species was lower than 2 mg litre-1 and for 100 per cent of the Yersinia pseudotuberculosis was lower than 0.25 mg litre-1. Based on these data and a literature study dosage regimens were calculated for MIC values of 0.5 and 2.5 mg litre-1.

Bioavailability and pharmacokinetics of ampicillin and amoxycillin from tablets, capsules and long-acting preparations in the homing pigeon (Columba livia).

Three ampicillin and three amoxycillin formulations (tablets and capsules, administered orally, and oily suspensions, injected intramuscularly (i.m.) and subcutaneously (s.c.] were studied in twenty adult homing pigeons (Columba livia). Bioavailability, pharmacokinetics and recovery were determined for each product and administration route. A standard dose of 50 mg/pigeon or 100 mg/kg was used in each study. The mean availability calculated for each of these preparations was 7% for ampicillin anhydrate tablets, 22% for amoxycillin trihydrate tablets, 17% for ampicillin trihydrate capsules, 67% for amoxycillin trihydrate capsules, 46% for ampicillin oily suspension i.m., 67% for amoxycillin oily suspension i.m. and 43% for amoxycillin oily suspension s.c. The blood concentration-time curves for the tablets were very scattered, which was far less the case for the capsules. The maximum blood concentration (Cmax) for amoxycillin was twice as high as for ampicillin. The Cmax resulting from the oily suspensions administered i.m. were low (4.35 +/- 1.05 and 5.04 +/- 1.36 mg/l, for ampicillin and amoxycillin, respectively). The Tmax for ampicillin was 10 h and for amoxycillin it was 0.9 h after administration. Both curves showed biphasic absorption, the initial peak representing an absorption and a distribution phase and the second part reflecting the 'depot-nature' of the drug. After the s.c. administration of the amoxycillin oily suspension the same pattern was found, but the Cmax, which was found at 2.13 +/- 1.03 h after administration, was low (2.81 +/- 0.68 mg/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Tissue distribution of amoxycillin after oral and intramuscular administration to pigeons (Columba livia).

Tissue distribution of amoxycillin in homing pigeons was studied after oral administration of amoxycillin trihydrate and after intramuscular injection of an oily amoxycillin suspension, both after a single dose of 100 mg/Kg. After the injection muscular damage at the injection site was studied by serum chemistry, and by macroscopic and histologic examination. After oral administration high peak levels were found in most tissues, but at 8 hours post-administration (p.a.) in most organs no drug levels could be detected. After intramuscular injection of the oily suspension lower peak levels were found in all organs, except the pectoral muscle contralateral to the injection site, but drug levels lasted at least till 60 hours p.a. After administration by both routes there was a fairly fixed relation between the tissue levels and the blood concentration for every organ. Very low concentrations were found in the brains. High levels were found after both routes of administration in the kidneys and the liver. After oral administration high levels were found also in the proventricular and intestinal wall. After intramuscular injection relative high concentrations were found in the duodenal and endgut wall. The damage to the pectoral muscle from the injection and the drug was small and restricted to mechanical destruction of muscle fibres by the needle and direct compression of the muscle fibres by the injected suspension.

Evaluation of a bacteriological and mycological examination of psittacine birds.

Results are presented from a microbiological (bacteriological and mycological) investigation and the sensitivity tests of microorganisms isolated over a 2-year period (1983-84) from 80 fecal samples and 466 necropsies of psittacine birds. These results are correlated with signs of metaplasia of the salivary glands due to vitamin A deficiency in large parrots and with low vitamin A levels in the livers of small psittacine birds. Aerobic microorganisms were isolated from 76% of the fecal samples and 67% of the necropsies. Infections with primary pathogenic bacteria were found in less than 10% of the necropsies. Metaplasia was found in 51% of the large parrots, and the vitamin A levels in budgerigars were below acceptable levels. The possible role of a deficient diet in Psittaciformes in the occurrence of microbial infections and their treatment are discussed.

A bacterial proventriculitis in canaries (Serinus canaria).

A description is given of the pathomorphology and pathomorphogenesis of a bacterial infection of the proventriculus of canaries. The cause appeared to be a large, rod-shaped, Grampositive bacterium, in which no spore formation could be observed. Cultivation in vitro has not as yet been achieved. Thirty % of the 30 canaries examined contained this bacterium in the proventriculus. In the rest of the digestive tract much smaller numbers were found. The bacteria were associated with a proliferative inflammatory reaction in the proventriculus. The infected proventriculi had an increased pH and an altered synthesis of mucopolysaccharides. The coilin layer of the gizzard was thinner in the infected canaries than in the control group, possibly as a result of the increased pH in the proventriculus.

Clinical pharmacology and pharmacokinetics of flumequine after intravenous, intramuscular and oral administration in pigeons (Columba livia).

The in-vitro activity of flumequine against 157 strains of bacteria isolated from birds was determined. The minimum inhibitory concentration (MIC) of 96.3% of the Enterobacteriaceae, Proteus spp. and Yersinia pseudotuberculosis studied (n = 135) was less than or equal to 1 microgram/ml. Pharmacokinetics of flumequine in pigeons (Columba livia) was investigated after intravenous, intramuscular and oral administration. From the blood disappearance curves after i.v. bolus injection (10 mg/kg body weight) clearance rate, blood half-time and distribution volume were calculated. The recovery of unchanged flumequine from the droppings in 24 h was 37 +/- 10% of the administered dose. Flumequine was also given i.m. at two dose levels, 10 and 60 mg/kg body weight. The availability of flumequine as intact drug was 22 and 23%, respectively, in 24 h. Therapeutic blood levels were maintained for 4 and 10 h, respectively. After an oral dose of flumequine (60 mg/kg body weight) an availability of 6.7 +/- 2.5% and a peak blood concentration of 2.68 +/- 0.92 microgram/ml at 2 h after administration were found. The recovery of unchanged flumequine from the droppings in 24 h was 1.55 +/- 0.79% of the administered dose. With the exception of the i.m. dose of 10 mg/kg, all flumequine administrations made the pigeons vomit. It appears that blood concentrations below 3 micrograms/ml will not induce vomiting. On the basis of the present data, a dosage regimen for flumequine in pigeons of a priming dose of 30 mg/kg i.m., followed after 8 h by oral administration of 30 mg/kg, this dose being repeated every 8-12 h, would be expected to give blood concentrations between 1.44 and 2.88 micrograms/ml.

[Problems arising from disease during the periods of breeding and rearing canaries and other aviary birds (author's transl)]. / Ziekteproblemen in de fok en opfokperiode van kanaries en andere volièrevogels.

The hygienic aspects of the various breeding systems are reviewed. The companion aviary is the least hygienic system; the birds are hardest to supervise in this case. Breeding in pairs is preferable from either point of view. Hygiene in aviaries is determined by all component parts of the cage, which are used in keeping the birds. The walls should be smooth and clean. The most hygienic drinking water supply is ensured by bottle-type nipple drinkers provided with a small ball. Feeders should be emptied, cleansed and filled with fresh water every day. A hygienic, dry floor-covering will prevent the appearance of large numbers of Enterobacteriaceae (as well as E. coli) in the intestine. The feed should preferably be given in measured rations. An adult canary should be fed 4 g. of seed and 1 g. of soft feed (containing 20 per cent of protein and 1 per cent of lysine) daily. Causes of death in young birds may be: inferior soft feed, a faulty diet, the presence of pentachlorophenol in the nesting material, infestation with chicken lice (Dermanyssus gallinae), diarrhoea due to a polluted environment (neonatal diarrhoea shortly after hatching), cochlosomosis, drumsticks and atoxoplasmosis. The clinical features and treatment of infectious diseases are discussed.

[Disease and causes of death in birds (authors transl)]. / Ziekte-en doodsoorzaken van vogels

In 1975, post-mortem studies were done on 745 birds. The findings are tabulated. The most important problems are evaluated. The most striking finding is the very large proportion (46.0 per cent) of birds which died from infectious disease caused either by bacteria, viruses, protozoa or parasites. Hygiene is stressed as a valuable preventive measure.