Resonant tunneling transistors with controllable negative differential resistances

Three-terminal devices based on resonant tunneling through two quantum barriers separated by a quantum well are presented and analyzed theoretically. Each proposed device consists of a resonant tunneling double barrier heterostructure integrated with a Schottky barrier field-effect transistor configuration. The essential feature of these devices is the presence, in their output current-voltage (I_{D} - V_{D}) curves, of negative differential resistances controlled by a gate voltage. Because of the high-speed characteristics associated with tunnel structures, these devices could find applications in tunable millimeter-wave oscillators, negative resistance amplifiers, and high-speed digital circuits

Current transport mechanisms in GaAs/AlAs tunnel structures grown by metal–organic chemical vapor deposition

Elastic and inelastic tunneling processes are investigated in GaAs–AlAs–GaAs double heterojunctions grown in the [100] direction by metal–organic chemical vapor deposition (MOCVD). The AlAs quantum barriers in the heterostructures studied are doped p-type with Mg. Theoretical calculations of tunneling currents are performed and compared with experimental I–V data. It is found that for structures with thin AlAs barriers, the dominant current transport mechanism at low temperatures is tunneling through the AlAs band gap at both the Gamma and X points. This is consistent with inelastic processes observable in first (dI/dV) and second (d2I/dV2) derivative spectra obtained with modulation techniques. A simple model, developed for calculating impurity-assisted tunneling currents, shows that the role of barrier impurities becomes more important as the barrier is grown thicker. Implications of some of these results for resonant tunneling heterostructures consisting of two AlAs quantum barriers separated by a GaAs quantum well are discussed. Experimental second derivative spectra showing reproducible features are also presented for these double barrier structures

So far, so good… Similar fitness consequences and overall energetic costs for short and long-distance migrants in a seabird

Although there is a consensus about the evolutionary drivers of animal migration, considerable work is necessary to identify the mechanisms that underlie the great variety of strategies observed in nature. The study of differential migration offers unique opportunities to identify such mechanisms and allows comparisons of the costs and benefits of migration. The purpose of this study was to compare the characteristics of short and long-distance migrations, and fitness consequences, in a long-lived seabird species. We combined demographic monitoring (survival, phenology, hatching success) of 58 Northern Gannets (Morus bassanus) breeding on Bonaventure Island (Canada) and biologging technology (Global Location Sensor or GLS loggers) to estimate activity and energy budgets during the non-breeding period for three different migration strategies: to the Gulf of Mexico (GM), southeast (SE) or northeast (NE) Atlantic coast of the U.S. Survival, timing of arrival at the colony and hatching success are similar for short (NE, SE) and long-distance (GM) migrants. Despite similar fitness consequences, we found, as expected, that the overall energetic cost of migration is higher for long-distance migrants, although the daily cost during migration was similar between strategies. In contrast, daily maintenance and thermoregulation costs were lower for GM migrants in winter, where sea-surface temperature of the GM is 4-7o C warmer than SE and NE. In addition, GM migrants tend to fly 30 min less per day in their wintering area than other migrants. Considering lower foraging effort and lower thermoregulation costs during winter for long-distance migrants, this suggests that the energetic benefits during the winter of foraging in the GM outweigh any negative consequences of the longer-distance migration. These results support the notion that the costs and benefits of short and long-distance migration is broadly equal on an annual basis, i.e. there are no apparent carry-over effects in this long-lived bird species, probably because of the favourable conditions in the furthest wintering area

Infusional ECarboF in patients with advanced breast cancer: A very active and well-tolerated out-patient regimen

We performed a trial using the combination of epirubicin 50 mg/m2/day 1, carboplatinum AUC 5/day 1 and continuous 5-fluorouracil (5-FU) 200 mg/m2/day (every 4 weeks for 6 months) to confirm the efficacy and low toxicity profile of this regimen in breast cancer. In 51 patients with metastatic (n = 33) or locally advanced (n=18) breast cancer the overall response rate was 86% (95% confidence interval (95% CI): 73%-94%): 94% in locally advanced and 81% metastatic disease. Grade 3-4 toxicity was low: 4% of patients presented with febrile neutropenia, 16% with severe palmar-plantar syndrome, 10% with Port-a-cath thrombosis. This study confirms the high efficacy of infusional 5-FU-based regimens and justifies further research into novel promising oral 5-FU derivative

Approaches towards expression profiling the response to treatment

Over the past 8 years there has been a wealth of breast cancer gene expression studies. The majority of these studies have focused upon characterising a tumour at presentation, before treatment, rather than looking at the effects of treatment on the tumour. More recently, a number of groups have moved from predicting prognosis based upon long-term follow-up to alternative approaches of using expression profiling to measure the effect of treatment on breast tumours and potentially predict response to therapy using either post-treatment samples or both pre-treatment and post-treatment samples. Whilst this provides great potential to further our understanding of the mode of action of treatments and to more accurately select which patients will benefit from a particular treatment, serious issues of experimental design must be considered

Recommendations from an international expert panel on the use of neoadjuvant (primary) systemic treatment of operable breast cancer: new perspectives 2006

Neoadjuvant (primary systemic) treatment has become a standard option for primary operable disease for patients who are candidates for adjuvant systemic chemotherapy, irrespective of the size of the tumor. Because of new treatments and new understandings of breast cancer, however, recommendations published in 2006 regarding neoadjuvant treatment for operable disease required updating. Therefore, a third international panel of representatives of a number of breast cancer clinical research groups was convened in September 2006 to update these recommendations. As part of this effort, data published to date were critically reviewed and indications for neoadjuvant treatment were newly define

Pathological complete response after neoadjuvant chemotherapy is an independent predictive factor irrespective of simplified breast cancer intrinsic subtypes: a landmark and two-step approach analyses from the EORTC 10994/BIG 1-00 phase III trial

The present analysis, carried out in the context of a randomized phase III trial, confirms superior outcomes for breast cancer patients for whom chemotherapy induces pathological complete response (pCR) after adjusting for other important prognostic factors. In contrast, when tumours do not achieve pCR, patients have a higher risk of relapse. This effect is observed in all intrinsic subtypes and justifies the current interest in post-neoadjuvant trial