Sensitive detection of photoexcited carriers by resonant tunneling through a single quantum dot

We show that the resonant tunnel current through a single energy level of an individual quantum dot within an ensemble of dots is strongly sensitive to photoexcited holes that become bound in the close vicinity of the dot. The presence of these holes lowers the electrostatic energy of the quantum dot state and switches the current carrying channel from fully open to fully closed with a high on/off ratio (> 50). The device can be reset by means of a bias voltage pulse. These properties are of interest for charge sensitive photon counting devices.Comment: 5 pages, 4 figure

Excitonic Effects in Quantum Wires

We review the effects of Coulomb correlation on the linear and non-linear optical properties of semiconductor quantum wires, with emphasis on recent results for the bound excitonic states. Our theoretical approach is based on generalized semiconductor Bloch equations, and allows full three-dimensional multisubband description of electron-hole correlation for arbitrary confinement profiles. In particular, we consider V- and T-shaped structures for which significant experimental advances were obtained recently. Above band gap, a very general result obtained by this approach is that electron-hole Coulomb correlation removes the inverse-square-root single-particle singularity in the optical spectra at band edge, in agreement with previous reports from purely one-dimensional models. Strong correlation effects on transitions in the continuum are found to persist also at high densities of photoexcited carriers. Below bandgap, we find that the same potential- (Coulomb) to kinetic-energy ratio holds for quite different wire cross sections and compositions. As a consequence, we identify a shape- and barrier-independent parameter that governs a universal scaling law for exciton binding energy with size. Previous indications that the shape of the wire cross-section may have important effects on exciton binding are discussed in the light of the present results.Comment: Proc. OECS-5 Conference, G\"ottingen, 1997 (To appear in Phys. Stat. Sol. (b)

Sharp-line electroluminescence from individual quantum dots by resonant tunneling injection of carriers

We report sharp electroluminescence lines from individual self-assembled InAs quantum dots (QDs) excited by resonant tunneling injection of carriers from the n- and p-doped GaAs layers of a p-i-n diode. Bias-tunable tunneling of carriers into the dots provides a means of controlling injection and light emission from a small number of individual dots within a large ensemble. We also show that the extent of carrier energy relaxation prior to recombination can be controlled by tailoring the morphology of the QD layer. © 2006 American Institute of Physics

High time resolution fluctuations in volcanic carbon dioxide degassing from Mount Etna

We report here on the first record of carbon dioxide gas emission rates from a volcano, captured at ≈ 1 Hz. These data were acquired with a novel technique, based on the integration of UV camera observations (to measure SO2 emission rates) and field portable gas analyser readings of plume CO2/SO2 ratios. Our measurements were performedat the North East crater of Mount Etna, southern Italy, and the data reveal strong variability in CO2 emissions over timescales of tens to hundreds of seconds, spanning two orders of magnitude. This carries importantimplications for attempts to constrain global volcanic CO2 release to the atmosphere, and will lead to an increased insight into short term CO2 degassing trends. A common oscillation in CO2 and SO2 emission rates in addition to the CO2/SO2 ratios was observed at periods of ≈ 89 s. Our results are furthermore suggestive of an intriguing temporal lag between oscillations in CO2 emissions and seismicity at periods of ≈ 300–400 s, with peaks and troughs in the former series leading those in the latter by ≈ 150 s. This work opens the way to the acquisition of further datasets with this methodology across a range of basaltic systems to better our understandingof deep magmatic processes and of degassing links to manifest geophysical signals

Adoption of practices to mitigate harvest losses − Phase 2

Patane et al. 2019 determined that Harvesting Best Practice (HBP) is predicated by two essential objectives: 1. Defining the critical point where harvesting losses can be minimised and delivered yields improved to achieve the best economic return for the grower and harvesting operation; and 2. Balancing losses with cane quality, which is determined by sound billet quality with an acceptable level of Extraneous Matter (EM). Despite significant research into the impact of higher harvester pour rates and fan speeds on harvested cane yields, use of HBP recommendations prior to the commencement of the adoption program across the industry was relatively low. Full HBP adoption across the Australian sugarcane industry could substantially increase industry revenue without the need for horizontal expansion (increase in cane land). In 2019, continuing on from the work conducted by Patane et al. (2019), Sugar Research Australia in partnership with the Queensland Department of Agriculture and Fisheries delivered further trials

Ocular iontophoresis of EGP-437 (dexamethasone phosphate) in dry eye patients: results of a randomized clinical trial

Michael A Patane¹, Amy Cohen¹, Stephen From¹, Gail Torkildsen², Donna Welch³, George W Ousler III³¹Eyegate Pharmaceuticals, Inc, Waltham, MA, USA; ²Andover Eye Associates, Andover, MA, USA; ³Ora, Inc, Andover, MA, USAPurpose: To assess safety and efficacy of EGP-437 (dexamethasone phosphate 40 mg/mL [DP]) in dry eye patients.Methods: The study employed a prospective, single-center, double-masked design utilizing a Controlled Adverse Environment (CAE). Patients (n = 103) with confirmed signs and symptoms of dry eye syndrome were randomized into 1 of 3 iontophoresis treatment groups: 7.5 mA-min at 2.5 mA (DP 7.5, n = 41); 10.5 mA-min at 3.5 mA (DP 10.5, n = 37); or 10.5 mA-min at 3.5 mA (placebo, n = 25). Three CAE visits and 4 follow-up visits occurred over 3 weeks. Patients meeting enrollment criteria received iontophoresis in both eyes after the second CAE exposure (visit 3) and before the third CAE exposure (visit 5). Primary efficacy endpoints were corneal staining and ocular discomfort. Secondary endpoints included tear film break-up time, ocular protection index (OPI), and symptomatology.Results: The DP 7.5 and DP 10.5 treatment groups showed statistically significant improvements in signs and symptoms of dry eye at various time points; however, the primary endpoints were not achieved. The DP 7.5 treatment group exhibited statistically significant improvements in corneal staining (when comparing the differences between study entry and exit, 3 weeks, P = 0.039), OPI (immediately following the second treatment, P = 0.048) and ocular discomfort at follow-up visits (a week after the first treatment, P = 0.032; 24 hours after the second treatment, P = 0.0032). Treatment-emergent adverse events (AEs) were experienced by 87% of patients and were consistent across all treatment groups. Most AEs were mild and no severe AEs were observed.Conclusion: Ocular iontophoresis of EGP-437 demonstrated statistically and clinically significant improvements in signs and symptoms of dry eye syndrome within a CAE model.Keywords: iontophoresis, dry eye, Controlled Adverse Environment (CAE), ocular protection index (OPI

Improving yield and cane quality through implementation of harvesting best practice-2019 Herbert demonstration

In 2019, the Australian sugarcane industry conducted a month-long demonstration with 12 trials to determine the commercial viability of harvesting best practice. Initiated by a small group of innovative growers and contractors from the Herbert region, the concept of a commercial demonstration sought to determine both agronomic and economic impacts of adopting HBP, including the assessment of possible yield gains without having a detrimental impact on extraneous matter, and economic implication for growers and harvesting contractors arising from revenue and harvesting cost changes. Two Herbert harvesting contractors participated in the demonstration comparing their standard harvesting practices to Sugar Research Australia Harvesting Best Practice (HBP or recommended practice). The results identified an average 4.8 t/ha increase in yield with no additional increase in extraneous matter for the recommended setting. A comprehensive economic analysis was conducted on each of the trials. Detailed harvesting costs and operational information, including machinery, labour, and fuel data, were collected from the respective harvesting operations. Harvesting costs and levies were $37/ha ($0.07/t) higher for the recommended setting due to higher yields, reduced harvester ground speeds and lower extractor fan speeds. Despite the higher harvesting costs, recommended settings obtained significantly higher total revenue ($151/ha, +4.7$114/ha in the adoption of recommended settings (based on a 4.4% higher net revenue calculated as total grower revenue minus harvesting costs and levies). The Herbert demonstrations have proven instrumental in the acceptance of harvesting best practice for the region. The results again confirm that adapting and aligning commercial-scale harvesting practices to crop and paddock conditions have positive impacts on both yield and economic outcomes