Existence and multiplicity for elliptic problems with quadratic growth in the gradient

We show that a class of divergence-form elliptic problems with quadratic growth in the gradient and non-coercive zero order terms are solvable, under essentially optimal hypotheses on the coefficients in the equation. In addition, we prove that the solutions are in general not unique. The case where the zero order term has the opposite sign was already intensively studied and the uniqueness is the rule.Comment: To appear in Comm. PD

High-temperature excess current and quantum suppression of electronic backscattering in a 1-D system

We consider the electronic current through a one-dimensional conductor in the ballistic transport regime and show that the quantum oscillations of a weakly pinned single scattering target results in a temperature- and bias-voltage independent excess current at large bias voltages. This is a genuine effect on transport that derives from an exponential reduction of electronic backscattering in the elastic channel due to quantum delocalization of the scatterer and from suppression of low-energy electron backscattering in the inelastic channels caused by the Pauli exclusion principle. We show that both the mass of the target and the frequency of its quantum vibrations can be measured by studying the differential conductance and the excess current. We apply our analysis to the particular case of a weakly pinned C60 molecule encapsulated by a single-wall carbon nanotube and find that the discussed phenomena are experimentally observable.Comment: 4 pages, 4 figure

The Influence of Electro-Mechanical Effects on Resonant Electron Tunneling Through Small Carbon Nano-Peapods

The influence of a fullerene molecule trapped inside a single-wall carbon nanotube on resonant electron transport at low temperatures and strong polaronic coupling is theoretically discussed. Strong peak to peak fluctuations and anomalous temperature behavior of conductance amplitudes are predicted and investigated. The influence of the chiral properties of carbon nanotubes on transport is also studied.Comment: 17 pages, 3 figures. Replaced with published version. Important changes. Open access: http://stacks.iop.org/1367-2630/10/04304

Cardiac effect of thyrotoxicosis in acromegaly

Cardiac structure and function are affected both by acromegaly and hyperthyroidism. Whereas the former is mainly characterized by ventricular hypertrophy as well as diastolic and systolic impairment, the latter frequently leads to increased heart rate and enhancement of contractility and cardiac output. To further investigate this issue, we designed this two-arm study. In the first cross-sectional study, we compared echocardiography and radionuclide angiography results obtained in eight hyperthyroid acromegalic patients, eight hyperthyroid nonacromegalic patients, and eight healthy subjects. All acromegalic patients were receiving treatment for acromegaly at the onset of hyperthyroidism. In the second longitudinal study, performed in the group of acromegalic patients, we compared the cardiovascular results obtained during hyperthyroidism with the retrospective data obtained at the initial diagnosis of acromegaly and after 1-yr treatment for this disease and those prospective data obtained during the remission of hyperthyroidism. In the cross-sectional study, hyperthyroid acromegalic patients showed an increase in the left ventricular (LV) mass index (LVMi) compared to healthy and hyperthyroid controls (P < 0.05), with evidence of LVMi hypertrophy in five of them (62.5%). A significant correlation was found between LVMi and GH levels (r = 0.785; P < 0.05). The LV ejection fraction (LVEF) at rest was higher in the control hyperthyroid population than in healthy controls (P < 0.05), whereas the LVEF response to exercise was reduced in acromegalic patients (P < 0.05 vs. healthy controls). In acromegalics, the exercise-induced change in LVEF was significantly reduced compared to that in healthy controls (P < 0.001), but not to that in hyperthyroid controls (P < 0.07), being abnormal (<5% increase vs. baseline values) in six patients. Four of these six patients (66%) had elevated GH and insulin-like growth factor I levels during the treatment of acromegaly. An inverse correlation between GH and LVEF at rest (r = -0.896;P < 0.05) and at peak exercise (r = -0.950; P < 0.001) was recorded. The peak filling rate was reduced in hyperthyroid acromegalic patients compared to those in both control populations (P < 0.05). In the longitudinal study, acromegalic patients showed an increased LVMi during hyperthyroidism compared to that observed after successful treatment of acromegaly (P < 0.05); resting LVEF was increased compared to both basal (P < 0.001) and posttreatment values (P < 0.05). However, the exercise-induced change in LVEF was reduced (P < 0.05 vs. previous follow-up values). Remission of hyperthyroidism led to significant reduction of LVMi (P < 0.05) and resting LVEF (P < 0.05) and an increase in exercise-induced LVEF (P < 0.05). In light of these findings, hyperthyroidism produces a detrimental effect on the cardiovascular system of acromegalic patients, particularly in those with uncontrolled disease. Thus, control of GH and insulin-like growth factor I should be a major objective, as cardiovascular risk persists in patients with ineffective hormonal suppression, and constant endocrine and cardiovascular surveillance remain crucial steps in patient follow-up

SOX2 is the determining oncogenic switch in promoting lung squamous cell carcinoma from different cells of origin

Lung squamous cell carcinoma (LSCC) is a devastating malignancy with no effective treatments, due to its complex genomic profile. Therefore, preclinical models mimicking its salient features are urgently needed. Here we describe mouse models bearing various combinations of genetic lesions predominantly found in human LSCC. We show that SOX2 but not FGFR1 overexpression in tracheobronchial basal cells combined with Cdkn2ab and Pten loss results in LSCC closely resembling the human counterpart. Interestingly, Sox2;Pten;Cdkn2ab mice develop LSCC with a more peripheral location when Club or Alveolar type 2 (AT2) cells are targeted. Our model highlights the essential role of SOX2 in commanding the squamous cell fate from different cells of origin and represents an invaluable tool for developing better intervention strategies