Giant capacitance of a plane capacitor with a two-dimensional electron gas in a magnetic field

If a clean two-dimensional electron gas (2DEG) with small concentration $n$ comprises one (or both) electrodes of a plane capacitor, the resulting capacitance $C$ can be larger than the "geometric capacitance" $C_g$ determined by the physical separation $d$ between electrodes. A recent paper [1] argued that when the effective Bohr radius $a_B$ of the 2DEG satisfies $a_B << d$, one can achieve $C >> C_g$ at low concentration $nd^2 << 1$. Here we show that even for devices with $a_B > d$, including graphene, for which $a_B$ is effectively infinite, one also arrives at $C >> C_g$ at low electron concentration if there is a strong perpendicular magnetic field.Comment: 6 pages, 5 figures; updated discussion about bilayer systems; added discussion of fractional quantum Hall state

Directed transport of active particles over asymmetric energy barriers

We theoretically and numerically investigate the transport of active colloids to target regions, delimited by asymmetric energy barriers. We show that it is possible to introduce a generalized effective temperature that is related to the local variance of particle velocities. The stationary probability distributions can be derived from a simple diffusion equation in the presence of an inhomogeneous effective temperature resulting from the action of external force fields. In particular, transitions rates over asymmetric energy barriers can be unbalanced by having different effective temperatures over the two slopes of the barrier. By varying the type of active noise, we find that equal values of diffusivity and persistence time may produce strongly varied effective temperatures and thus stationary distributions

Bubbling with L2L^2-almost constant mean curvature and an Alexandrov-type theorem for crystals

A compactness theorem for volume-constrained almost-critical points of elliptic integrands is proven. The result is new even for the area functional, as almost-criticality is measured in an integral rather than in a uniform sense. Two main applications of the compactness theorem are discussed. First, we obtain a description of critical points/local minimizers of elliptic energies interacting with a confinement potential. Second, we prove an Alexandrov-type theorem for crystalline isoperimetric problems

Self-propulsion against a moving membrane: enhanced accumulation and drag force

Self-propulsion (SP) is a main feature of active particles (AP), such as bacteria or biological micromotors, distinguishing them from passive colloids. A renowned consequence of SP is accumulation at static interfaces, even in the absence of hydrodynamic interactions. Here we address the role of SP in the interaction between AP and a moving semipermeable membrane. In particular, we implement a model of noninteracting AP in a channel crossed by a partially penetrable wall, moving at a constant velocity $c$. With respect to both the cases of passive colloids with $c>0$ and AP with $c=0$, the AP with finite $c$ show enhancement of accumulation in front of the obstacle and experience a largely increased drag force. This effect is understood in terms of an effective potential localised at the interface between particles and membrane, of height proportional to $c\tau/\xi$, where $\tau$ is the AP's re-orientation time and $\xi$ the width characterising the surface's smoothness ($\xi\to 0$ for hard core obstacles). An approximate analytical scheme is able to reproduce the observed density profiles and the measured drag force, in very good agreement with numerical simulations. The effects discussed here can be exploited for automatic selection and filtering of AP with desired parameters.Comment: 13 pages, 3 figure

Interestingness of traces in declarative process mining: The janus LTLPf Approach

Declarative process mining is the set of techniques aimed at extracting behavioural constraints from event logs. These constraints are inherently of a reactive nature, in that their activation restricts the occurrence of other activities. In this way, they are prone to the principle of ex falso quod libet: they can be satisfied even when not activated. As a consequence, constraints can be mined that are hardly interesting to users or even potentially misleading. In this paper, we build on the observation that users typically read and write temporal constraints as if-statements with an explicit indication of the activation condition. Our approach is called Janus, because it permits the specification and verification of reactive constraints that, upon activation, look forward into the future and backwards into the past of a trace. Reactive constraints are expressed using Linear-time Temporal Logic with Past on Finite Traces (LTLp f). To mine them out of event logs, we devise a time bi-directional valuation technique based on triplets of automata operating in an on-line fashion. Our solution proves efficient, being at most quadratic w.r.t. trace length, and effective in recognising interestingness of discovered constraints

The course of cancer related fatigue up to ten years in early breast cancer patients. What impact in clinical practice?

Little is known about the cancer related fatigue (CRF) along cancer course and risk factors that could predict CRF development and persistence in breast cancer (BC) survivors. This prospective study detected incidence, timing of onset, duration of CRF, impact on QoL and psychological distress. Seventy-eight early BC patients, undergoing chemotherapy (CT) followed or not by hormonal therapy were assessed for QoL and psychological distress by EORTC QLQC30 and HADs questionnaires. Fatigue was investigated with mix methods, structured interview and psychometric measures. A qualitative analysis was added to assess the behavioral pattern of CRF. Low fatigue levels were identified after surgery (9%), increasing during (49%) and at the end of CT (47%), maintaining after 1 year (31%) and declining up to ten years of follow-up. Prevalence of CRF was higher at the end of CT and lower at follow-up. At the end and after 1 and 2 years from CT, persistence of CRF was associated to anxiety in 20%, 11% and 5% and to depression in 15%, 10% and 5% respectively. A relationship between CRF and psychological distress was observed; patients presenting depression and anxiety before CT were at higher risk for fatigue onset at a later period. A relationship between fatigue and QoL was noted at the end of CT. Our study shows the fatigue timely trend in early BC patients from surgery, CT and follow-up. Identification of biological, psychological, social predictor factors related to fatigue could be helpful for early interventions in patients at higher risk of developing fatigue

Investigation of the shear-mechanical and dielectric relaxation processes in two mono-alcohols close to the glass transition

Shear-mechanical and dielectric measurements on the two monohydroxy (mono-alcohol) molecular glass formers 2-ethyl-1-hexanol and 2-butanol close to the glass transition temperature are presented. The shear-mechanical data are obtained using the piezoelectric shear-modulus gauge method covering frequencies from 1mHz to 10kHz. The shear-mechanical relaxation spectra show two processes, which follow the typical scenario of a structural (alpha) relaxation and an additional (Johari-Goldstein) beta relaxation. The dielectric relaxation spectra are dominated by a Debye-type peak with an additional non-Debye peak visible. This Debye-type relaxation is a common feature peculiar to mono-alcohols. The time scale of the non-Debye dielectric relaxation process is shown to correspond to the mechanical structural (alpha) relaxation. Glass-transition temperatures and fragilities are reported based on the mechanical alpha relaxation and the dielectric Debye-type process, showing that the two glass-transition temperatures differ by approximately 10K and that the fragility based on the Debye-type process is a factor of two smaller than the structural fragility. If a mechanical signature of the Debye-type relaxation exists in these liquids, its relaxation strength is at most 1% and 3% of the full relaxation strength of 2-butanol and 2-ethyl-1-hexanol respectively. These findings support the notion that it is the non-Debye dielectric relaxation process that corresponds to the structural alpha relaxation in the liquid.Comment: 8 pages, 6 figures. Minor corrections, updated figures, more dielectric data show

Are cognitive disorders more common in geriatric diabetic patients? What factors contribute to cognitive decline?

Cognitive screening is recommended for all geriatric DM patients. Suggested validated screening tests are the Short Portable Mental Status Questionnaire and the clock drawing test. Screening should be repeated on a twice-yearly basis in those who are borderline and annually in those who are negative. In the case of positive screening, a specialist clinical diagnostic assessment is recommended. In patients with mild cognitive impairment and dementia, evaluating and treating possible modifiable risk factors is recommended, such as sensory and physical functional disorders, obstructive sleep apnea syndrome, etc. Simplification of antidiabetic drug treatment is also recommended in these patients