Wet etch methods for InAs nanowire patterning and self-aligned electrical contacts.

Advanced synthesis of semiconductor nanowires (NWs) enables their application in diverse fields, notably in chemical and electrical sensing, photovoltaics, or quantum electronic devices. In particular, indium arsenide (InAs) NWs are an ideal platform for quantum devices, e.g. they may host topological Majorana states. While the synthesis has been continously perfected, only a few techniques have been developed to tailor individual NWs after growth. Here we present three wet chemical etch methods for the post-growth morphological engineering of InAs NWs on the sub-100 nm scale. The first two methods allow the formation of self-aligned electrical contacts to etched NWs, while the third method results in conical shaped NW profiles ideal for creating smooth electrical potential gradients and shallow barriers. Low temperature experiments show that NWs with etched segments have stable transport characteristics and can serve as building blocks of quantum electronic devices. As an example we report the formation of a single electrically stable quantum dot between two etched NW segments.

Cooper pair splitter realized in a two-quantum-dot Y-junction.

Non-locality is a fundamental property of quantum mechanics that manifests itself as correlations between spatially separated parts of a quantum system. A fundamental route for the exploration of such phenomena is the generation of Einstein-Podolsky-Rosen (EPR) pairs of quantum-entangled objects for the test of so-called Bell inequalities. Whereas such experimental tests of non-locality have been successfully conducted with pairwise entangled photons, it has not yet been possible to realize an electronic analogue of it in the solid state, where spin-1/2 mobile electrons are the natural quantum objects. The difficulty stems from the fact that electrons are immersed in a macroscopic ground state-the Fermi sea-which prevents the straightforward generation and splitting of entangled pairs of electrons on demand. A superconductor, however, could act as a source of EPR pairs of electrons, because its ground-state is composed of Cooper pairs in a spin-singlet state. These Cooper pairs can be extracted from a superconductor by tunnelling, but, to obtain an efficient EPR source of entangled electrons, the splitting of the Cooper pairs into separate electrons has to be enforced. This can be achieved by having the electrons 'repel' each other by Coulomb interaction. Controlled Cooper pair splitting can thereby be realized by coupling of the superconductor to two normal metal drain contacts by means of individually tunable quantum dots. Here we demonstrate the first experimental realization of such a tunable Cooper pair splitter, which shows a surprisingly high efficiency. Our findings open a route towards a first test of the EPR paradox and Bell inequalities in the solid state.

Finite-bias Cooper pair splitting.

In a device with a superconductor coupled to two parallel quantum dots (QDs) the electrical tunability of the QD levels can be used to exploit nonclassical current correlations due to the splitting of Cooper pairs. We experimentally investigate the effect of a finite potential difference across one quantum dot on the conductance through the other completely grounded QD in a Cooper pair splitter fabricated on an InAs nanowire. We demonstrate that the nonlocal electrical transport through the device can be tuned by electrical means and that the energy dependence of the effective density of states in the QDs is relevant for the rates of Cooper pair splitting (CPS) and elastic cotunneling. Such experimental tools are necessary to understand and develop CPS-based sources of entangled electrons in solid-state devices.

Ferromagnetic proximity effect in a ferromagnet-quantum-dot-superconductor device.

The ferromagnetic proximity effect is studied in InAs nanowire based quantum dots strongly coupled to a ferromagnetic (F) and a superconducting (S) lead. The influence of the F lead is detected through the splitting of the spin-1/2 Kondo resonance. We show that the F lead induces a local exchange field on the quantum dot, which has varying amplitude and sign depending on the charge states. The interplay of the F and S correlations generates an exchange field related subgap feature.

L3 skeletal muscle index (L3SMI) is a surrogate marker of sarcopenia and frailty in non-small cell lung cancer patients.

Background: Non-small cell lung cancer (NSCLC) is a common and highly lethal disease. As advanced treatment modalities are being developed, improved prognostication methods are sought. L3 skeletal muscle index (L3SMI) and alanine aminotransferase (ALT) levels are accepted surrogate markers of sarcopenia and related frailty. We aimed to evaluate the potential association of these markers with NSCLC patients' survival. Methods: A retrospective, single-center study of an NSCLC patients' cohort. L3SMI was calculated based on skeletal muscle area on computed tomography scans at the level of the L3 vertebra. Clinical data were extracted from clinical charts. Results: A total of 140 patients (56.4% males, median age 66 [range 37-86]) were included in this study, 32% were diagnosed at stage 3 and 45% at stage 4. During the follow-up duration (median of 1.9 years; range 1 month to 6.4 years), 102 patients (72.8%) died. Patients' characteristics that were found to be associated with increased mortality were performance status, albumin and tumor stage at diagnosis. Sarcopenia, defined as low L3SMI (lower than 41 cm2/m2 for women and lower than 53 cm2/m2 for men) was significantly associated with higher risk of mortality compared with patients with normal L3SMI values (77.2%, vs 64.6%, p=0.013) in univariate analysis, but not in a multiple regression analysis. Conclusion: Low L3SMI could serve as a surrogate marker for sarcopenia and frailty and, as such, facilitate the prognostication process of NSCLC patients.

Sodium phosphate enemas do not worsen renal function among hospitalized patients with mild to moderate renal failure: a matched, case-control study.

BACKGROUND: Sodium phosphate enemas (SPEs) are widely used among hospitalized patients despite their potential to worsen renal failure. AIM: We decided to assess the extent to which this side effect is clinically relevant. DESIGN: We conducted a matched case-control, retrospective study in a cohort of hospitalized patients. METHODS: Patients treated and untreated with SPEs were matched for age, gender, baseline creatinine, usage of certain medications and several background diagnoses. Three groups of matched patients (whole study cohort, patients with baseline creatinine > 1.5 mg/dl and those with baseline creatinine > 2 mg/dl) were compared with regards to their creatinine and blood electrolyte concentrations during 3 consecutive hospitalization days after SPE application. RESULTS: Four hundred and twelve patients were included in this study of which 206 were treated by single SPEs. Exact matching was done for the whole study cohort, for 108 patients with baseline creatinine > 1.5 mg/dl and for 58 patients with baseline creatinine > 2 mg/dl. During 3 consecutive days after SPEs, the maximal blood concentrations of creatinine, phosphor and potassium did not differ significantly between treated patients and matched controls, in all three patients' groups. CONCLUSION: Application of SPEs neither seem to worsen mild to moderate renal failure, nor are associated with hyperphosphatemia or hyperkalemia in patients hospitalized in internal medicine departments.

Role of the renin-angiotensin system in the regulation of late steps in aldosterone biosynthesis by sodium intake of potassium-deficient rats.

The role of the renin-angiotensin system in the adaptation of late steps in aldosterone biosynthesis to sodium intake was studied in potassium-deficient rats. Capsular portions of adrenal glands were incubated with [3H]corticosterone and conversion to aldosterone and 18-hydroxycorticosterone was measured by double isotope dilution and multiple paper chromatography. Sodium loading of sodium- and potassium-depleted rats resulted in a rapid and extensive fall in PRA but only in a delayed and gradual suppression of aldosterone biosynthesis. Treatment with the converting enzyme inhibitor, captopril, did not affect aldosterone biosynthesis in rats with established sodium and potassium deficiency, but blocked the stimulation of the conversion of corticosterone to aldosterone and 18-hydroxycorticosterone by sodium restriction of potassium-depleted rats. Infusion of a high dose of angiotensin II into potassium-deficient rats stimulated aldosterone biosynthesis depending upon the concurrent sodium intake. Accordingly, the renin-angiotensin system plays an important but limited role in the control of late steps of aldosterone biosynthesis by sodium intake. Angiotensin II seems to be essential for the induction but not for the maintenance of a high activity of the enzyme(s) involved in the conversion of corticosterone to aldosterone during combined sodium and potassium restriction. The sensitivity of the zona glomerulosa to the long term stimulatory action of angiotensin II varies with the sodium intake and appears to be regulated by the plasma potassium concentration and unknown other mediators.

Laboratory prototype for experimental validation of MR-guided radiofrequency head and neck hyperthermia.

Clinical studies have established a strong benefit from adjuvant mild hyperthermia (HT) to radio- and chemotherapy for many tumor sites, including the head and neck (H&N). The recently developed HYPERcollar allows the application of local radiofrequency HT to tumors in the entire H&N. Treatment quality is optimized using electromagnetic and thermal simulators and, whenever placement risk is tolerable, assessed using invasively placed thermometers. To replace the current invasive procedure, we are investigating whether magnetic resonance (MR) thermometry can be exploited for continuous and 3D thermal dose assessment. In this work, we used our simulation tools to design an MR compatible laboratory prototype applicator. By simulations and measurements, we showed that the redesigned patch antennas are well matched to 50 Ω (S11<-10 dB). Simulations also show that, using 300 W input power, a maximum specific absorption rate (SAR) of 100 W kg(-1) and a temperature increase of 4.5 °C in 6 min is feasible at the center of a cylindrical fat/muscle phantom. Temperature measurements using the MR scanner confirmed the focused heating capabilities and MR compatibility of the setup. We conclude that the laboratory applicator provides the possibility for experimental assessment of the feasibility of hybrid MR-HT in the H&N region. This versatile design allows rigorous analysis of MR thermometry accuracy in increasingly complex phantoms that mimic patients' anatomies and thermodynamic characteristics.

Giant fluctuations and gate control of the g-factor in InAs nanowire quantum dots.

We study the g-factor of discrete electron states in InAs nanowire based quantum dots. The g values are determined from the magnetic field splitting of the zero bias anomaly due to the spin 1/2 Kondo effect. Unlike to previous studies based on 2DEG quantum dots, the g-factors of neighboring electron states show a surprisingly large fluctuation: g can scatter between 2 and 18. Furthermore electric gate tunability of the g-factor is demonstrated.

Stimulation of aldosterone biosynthesis by sodium sequestration: role of angiotensin II.

The role of angiotensin II in the stimulation of aldosterone biosynthesis by sodium sequestration in potassium-deficient rats was assessed by experiments involving 1-day angiotensin II infusion, converting enzyme inhibition, and bilateral nephrectomy. In intact rats, only an extremely high dose of exogenous angiotensin II imitated the stimulatory effects of polyethylene glycol-induced edema on the conversions of deoxycorticosterone and corticosterone to 18-hydroxycorticosterone and aldosterone. Treatment with the converting enzyme inhibitor captopril as well as bilateral nephrectomy blocked the aldosterone-stimulating action of edema. This inhibition was prevented by the simultaneous infusion of angiotensin II in captopril-treated rats but not in nephrectomized animals. According to these results, angiotensin II is an essential mediator in the stimulation of aldosterone biosynthesis by sodium sequestration. However, the role of the kidneys appears to be twofold. First, they act through the secretion of renin. In addition, a second yet unknown kidney factor is necessary for a full response of the zona glomerulosa to the stimulatory action of angiotensin II.