Measuring the Degeneracy of Discrete Energy Levels Using a GaAs/AlGaAs Quantum Dot.

We demonstrate an experimental method for measuring quantum state degeneracies in bound state energy spectra. The technique is based on the general principle of detailed balance and the ability to perform precise and efficient measurements of energy-dependent tunneling-in and -out rates from a reservoir. The method is realized using a GaAs/AlGaAs quantum dot allowing for the detection of time-resolved single-electron tunneling with a precision enhanced by a feedback control. It is thoroughly tested by tuning orbital and spin degeneracies with electric and magnetic fields. The technique also lends itself to studying the connection between the ground-state degeneracy and the lifetime of the excited states.

Measurement Back-Action in Stacked Graphene Quantum Dots.

We present an electronic transport experiment in graphene where both classical and quantum mechanical charge detector back-action on a quantum dot are investigated. The device consists of two stacked graphene quantum dots separated by a thin layer of boron nitride. This device is fabricated by van der Waals stacking and is equipped with separate source and drain contacts to both dots. By applying a finite bias to one quantum dot, a current is induced in the other unbiased dot. We present an explanation of the observed measurement-induced current based on strong capacitive coupling and energy dependent tunneling barriers, breaking the spatial symmetry in the unbiased system. This is a special feature of graphene-based quantum devices. The experimental observation of transport in classically forbidden regimes is understood by considering higher-order quantum mechanical back-action mechanisms.

Mode Specific Backscattering in a Quantum Point Contact.

We demonstrate a scanning gate grid measurement technique consisting in measuring the conductance of a quantum point contact (QPC) as a function of gate voltage at each tip position. Unlike conventional scanning gate experiments, it allows investigating QPC conductance plateaus affected by the tip at these positions. We compensate the capacitive coupling of the tip to the QPC and discover that interference fringes coexist with distorted QPC plateaus. We spatially resolve the mode structure for each plateau.

[Bipolar Sealing of Lung Veins with 5 mm and 10 mm Instruments - Bursting Pressures Measured in an Ex-Vivo Model]. / Bipolare Versiegelung von Lungenvenen mit einem 5- und -10-mm-Instrument - Bestimmung der Berstdrücke an einem Ex-vivo-Modell.

BACKGROUND: In every anatomic lung resection, lung veins need to be sealed and divided. If open surgery is performed, veins are usually treated with ligatures. In minimally-invasive procedures a vascular stapler is used. Blood vessels can be securely closed with modern bipolar sealing technology. Since this method has rarely been used in lung veins, we carried out the present study on an ex-vivo model to test whether satisfactory bursting pressures can be achieved using 5 mm and 10 mm MARSEAL® sealing instruments. MATERIAL AND METHODS: The experimental investigations were carried out on heart-lung preparations (including both lungs) from freshly-slaughtered pigs (weight: 199 lbs). After the lung veins were dissected, three groups were formed according to size: group 1: 1-7 mm, group 2: 8-10 mm and group 3: > 10 mm. Bipolar sealing was performed with a 5 mm or 10 mm MARSEAL® sealing device and the special SealSafe® G5 electric current. Vessels closed by simple ligation served as a control group. A pressure sensor was implanted into the unsealed end of the blood vessel. Air was pumped into the blood vessel and the bursting pressure - the pressure (in mbar) at which the vessel began to leak - was determined digitally. The mean bursting pressures were compared using the non-parametric Mann Whitney U test (the level of significance was p < 0.05). RESULTS: In group 1 the mean bursting pressures for the 5 mm and 10 mm instruments were found to be 167.1 ± 38.7 mbar and 113.8 ± 23.3 mbar, respectively. Both were significantly inferior to the pressure of 178.8 ± 44.5 mbar achieved by the control group. In group 2 the bursting pressures were 122.7 ± 27.8 mbar with the 5 mm instrument and 93.5 ± 39.6 mbar with the 10 mm instrument. The mean bursting pressure for the control group was 180.7 ± 35.8.mbar. In group 3 the mean bursting pressures were 98.2 ± 28.8 mbar with the 5 mm instrument and 65.5 ± 19.7 mbar with the 10 mm instrument. All attempts to seal the entire left atrium failed. CONCLUSION: In our ex-vivo model of lung veins, acceptable bursting pressures were achieved in blood vessels with a maximum diameter of 10 mm. Bipolar impedance-controlled sealing may create an adequate seal on pulmonary veins up to a diameter of 10 mm. The use of a 10 mm instrument has no advantage compared to a 5 mm instrument. Secure sealing of the left atrium is not possible.

Transport Spectroscopy of a Spin-Coherent Dot-Cavity System.

Quantum engineering requires controllable artificial systems with quantum coherence exceeding the device size and operation time. This can be achieved with geometrically confined low-dimensional electronic structures embedded within ultraclean materials, with prominent examples being artificial atoms (quantum dots) and quantum corrals (electronic cavities). Combining the two structures, we implement a mesoscopic coupled dot-cavity system in a high-mobility two-dimensional electron gas, and obtain an extended spin-singlet state in the regime of strong dot-cavity coupling. Engineering such extended quantum states presents a viable route for nonlocal spin coupling that is applicable for quantum information processing.

Simplified prediction of Staphylococcus aureus growth in a cooked meat product exposed to changing environmental temperatures in warm climates.

In this work, a simplified method is used to estimate the growth of Staphylococcus aureus in a pasteurized meat product left for several hours at environmental temperatures (diurnal time) in warm climates of different cities in Argentina. Hourly temperature data for a warm January (the hottest month of the year) day, and literature data on the kinetics of S. aureus growth inoculated in a pasteurized meat product were used for calculations. As shown by results, if a cooked meat product is left exposed to environmental temperature at diurnal time, predictions made when using a constant temperature value (i.e. average daily) may not be accurate. Growth estimations in contaminated food left under ambient conditions during diurnal time, should consider the changing environmental temperature for correct results.

Laterally defined freely suspended quantum dots in GaAs/AlGaAs heterostructures.

Free-standing beams containing a two-dimensional electron system are shaped from a GaAs/AlGaAs heterostructure. Quantum point contacts and (double) quantum dots are laterally defined using metal top gates. We investigate the electronic properties of these nanostructures by transport spectroscopy. Tunable localized electron states in freely suspended nanostructures are a promising tool to investigate the electron-phonon interaction.

Integration of foreign sequences into the tobacco plastome via polyethylene glycol-mediated protoplast transformation.

A new vector, pFaadAII, for transformation of plastids of Nicotiana tabacum L. has been developed. It harbours a chimeric gene consisting of the aadA coding region from Escherichia coli, the 16S rDNA promoter from tobacco combined with a synthetic ribosome-binding site, a 500-bp fragment containing the 3' untranslated transcript region (UTR) of the Chlamydomonas rbcL gene and 3.75-kb (5') and 0.95-kb (3') tobacco plastome sequences allowing for targeting the foreign sequences to the intergenic region between the rpl32 and trnL genes of the tobacco plastome. The vector thus targets foreign sequences to the small single-copy region of the plastome, which has so far not been modified by transformation. Leaf protoplasts of Nicotiana tabacum L. were treated with polyethylene glycol (PEG) in the presence of the vector. The protocol for PEG treatment aiming at plastome transformation was optimized. Cell lines were cultured in the presence of spectinomycin and streptomycin using a novel and efficient protoplast culture and selection system. Regenerants were characterized by polymerase chain reaction (PCR) analysis, Southern hybridization and reciprocal crossing. The transformation procedure is described in detail and parameters influencing its efficiency are presented. Special effort is placed on analyzing suitable selection conditions. Only a proportion of the cell lines with a resistant phenotype could be confirmed by molecular analysis and/or reciprocal crossings to represent plastome transformants. Integration of the plastome specific aadA cassette into the nuclear genome accounted for a fraction of the resistant cell lines. Still, as many as 20-40 plastome transformants can be expected from the treatment of 10(6) protoplasts. Therefore, the improved protocol for PEG-mediated plastome transformation in combination with the new aadA-vector supplies a simple, reproducible and cost-efficient alternative to the biolistic procedure.

[Comparison between oral nutrition and enteral nutrition using a percutaneous endoscopically guided gastrostomy (PEG) in patients undergoing radiotherapy for head and neck tumors]. / Vergleich von oraler und enteraler Ernährung mittels perkutaner endoskopisch kontrollierter Gastrostomie (PEG) bei Strahlentherapie-Patienten mit Kopf-Hals-Tumoren.

The nutritional state of 99 patients with tumors in the head and neck area was determined prior to, during and after radiotherapy by anthropometric, laboratory-chemical and immunological parameters. In 73 orally nourished patients, the nutritional parameters deteriorated very quickly during radiotherapy and recovered slowly and incompletely after radiotherapy. In 26 patients treated prospectively by percutaneous endoscopically guided gastrostomy (PEG), however, an improved nutritional state was achieved already during the irradiation in spite of a less favorable starting point. The subjective feeling of patients was questioned by means of the "quality of life" index according to Padilla et al. (1983). The preliminary results show an identical deterioration of the subjective feeling in both groups, but - as opposed to the other patients - force and working capacity did not decrease during radiotherapy in the enterally nourished patients. This corresponds to the objective nutritional parameters. However, an improvement of the subjective feeling after the end of radiotherapy was observed only in the orally nourished patients. Possible reasons are discussed. We have the opinion that an early and constant enteral nutrition by PEG can stabilize the nutritional state of patients with tumors in the head and neck area. Therefore we recommend to establish a prophylactic, pretherapeutic PEG if an aggressive multimodal therapy is planned, especially in case of apparent primary malnutrition.

Simplified prediction of Staphylococcus aureus growth in a cooked meat product exposed to changing environmental temperatures in warm climates / Predición simplificada del crecimiento de Staphylococcus aureus en productos cárnicos cocidos expuestos a temperaturas ambientes cambiantes en climas cálidos

In this work, a simplified method is used to estimate the growth of Staphylococcus aureus in a pasteurized meat product left for several hours at environmental temperatures (diurnal time) in warm climates of different cities in Argentina. Hourly temperature data for a warm January (the hottest month of the year) day, and literature data on the kinetics of S. aureus growth inoculated in a pasteurized meat product were used for calculations. As shown by results, if a cooked meat product is left exposed to environmental temperature at diurnal time, predictions made when using a constant temperature value (i.e. average daily) may not be accurate. Growth estimations in contaminated food left under ambient conditions during diurnal time, should consider the changing environmental temperature for correct results.

En este trabajo se utiliza un método simplificado para predecir el crecimiento de Staphylococcus aureus en un producto cárnico pasteurizado dejado por varias horas a temperatura ambiente diurna en zonas de clima cálido. En la predicción, se utilizaron datos de la temperatura horaria para un día caluroso típico de enero (mes más caliente del año) en varias ciudades de la Argentina y datos de la literatura sobre tiempos de generación y tiempo lag de la bacteria inoculada en un producto cárnico pasteurizado. Los resultados indicaron que cuando el producto se deja a temperatura ambiente diurna durante varias horas, no se debe utilizar para la predicción un valor de temperatura promedio (ej.: temperatura media diaria), sino que hay que tener en cuenta la evolución de este parámetro a lo largo del período considerado.