936 research outputs found
Ultra-Sensitive Hot-Electron Nanobolometers for Terahertz Astrophysics
The background-limited spectral imaging of the early Universe requires
spaceborne terahertz (THz) detectors with the sensitivity 2-3 orders of
magnitude better than that of the state-of-the-art bolometers. To realize this
sensitivity without sacrificing operating speed, novel detector designs should
combine an ultrasmall heat capacity of a sensor with its unique thermal
isolation. Quantum effects in thermal transport at nanoscale put strong
limitations on the further improvement of traditional membrane-supported
bolometers. Here we demonstrate an innovative approach by developing
superconducting hot-electron nanobolometers in which the electrons are cooled
only due to a weak electron-phonon interaction. At T<0.1K, the electron-phonon
thermal conductance in these nanodevices becomes less than one percent of the
quantum of thermal conductance. The hot-electron nanobolometers, sufficiently
sensitive for registering single THz photons, are very promising for
submillimeter astronomy and other applications based on quantum calorimetry and
photon counting.Comment: 19 pages, 3 color figure
Robustness and fault tolerance make brains harder to study
Brains increase the survival value of organisms by being robust and fault tolerant. That is, brain circuits continue to operate as the organism needs, even when the circuit properties are significantly perturbed. Kispersky and colleagues, in a recent paper in Neural Systems & Circuits, have found that Granger Causality analysis, an important method used to infer circuit connections from the behavior of neurons within the circuit, is defeated by the mechanisms that give rise to this robustness and fault tolerance
Urachal carcinoma presenting with chronic mucusuria: a case report
Urachal adenocarcinoma is a rare tumor and represents 0.17–0.34% of all bladder tumors. It has an insidious course and variable clinical presentation. We present a case report of a 58 year old white male with an urachal cyst who suffered irritative voiding symptoms and long term mucusuria, since childhood. After surgical removal of the cyst with a partial cystectomy a mucus adenocarcinoma was diagnosed histologically
Randomised, cOntrolled Multicentre trial of 26 weeks subcutaneous liraglutide (a glucagon-like peptide-1 receptor Agonist), with or without contiNuous positive airway pressure (CPAP), in patients with type 2 diabetes mellitus (T2DM) and obstructive sleep apnoEa (OSA) (ROMANCE): study protocol assessing the effects of weight loss on the apnea-hypnoea index (AHI).
INTRODUCTION: Obstructive sleep apnoea (OSA) and type 2 diabetes mellitus (T2DM) often occur concurrently, and untreated OSA may potentially amplify the high risk of cardiovascular disease in T2DM. Compliance with continuous positive airway pressure (CPAP), the conventional treatment for OSA, can be poor and considering weight loss is the most effective treatment for OSA. This trial examines whether the glucagon-like peptide-1 receptor agonist liraglutide, a glucose-lowering therapy associated with significant weight loss used in T2DM, can improve the severity and symptoms of OSA. METHODS AND ANALYSIS: This is an outpatient, single-centred, open-labelled, prospective, phase IV randomised controlled trial in a two-by-two factorial design. One hundred and thirty-two patients with newly diagnosed OSA (apnoea-hypopnoea index (AHI) ≥15 events/hour), and existing obesity and T2DM (glycated haemoglobin (HbA1c) ≥47 mmol/mol), will be recruited from diabetes and sleep medicine outpatient clinics in primary and secondary care settings across Liverpool. Patients will be allocated equally, using computer-generated random, permuted blocks of unequal sizes, to each of the four treatment arms for 26 weeks: (i) liraglutide (1.8 mg once per day) alone, (ii) liraglutide 1.8 mg once per day with CPAP, (iii) CPAP alone (conventional care) or (iv) no treatment (control). The primary outcome measure is change in OSA severity, determined by AHI. Secondary outcome measures include effects on glycaemic control (glycated haemoglobin (HbA1c)), body weight and quality of life measures. Exploratory measures include measures of physical activity, MRI-derived measures of regional body composition including fat mass (abdominal subcutaneous, visceral, neck and liver fat) and skeletal muscle mass (cross-sectional analysis of thigh), indices of cardiac function (using transthoracic echocardiography) and endothelial function. ETHICAL APPROVAL: The study has been approved by the North West Liverpool Central Research Ethics Committee (14/NW/1019) and it is being conducted in accordance with the Declaration of Helsinki and Good Clinical Practice. TRIAL REGISTRATION NUMBERS: ISRCTN16250774. EUDRACT No. 2014-000988-41. UTN U1111-1139-0677
Entangled Mechanical Oscillators
Hallmarks of quantum mechanics include superposition and entanglement. In the
context of large complex systems, these features should lead to situations like
Schrodinger's cat, which exists in a superposition of alive and dead states
entangled with a radioactive nucleus. Such situations are not observed in
nature. This may simply be due to our inability to sufficiently isolate the
system of interest from the surrounding environment -- a technical limitation.
Another possibility is some as-of-yet undiscovered mechanism that prevents the
formation of macroscopic entangled states. Such a limitation might depend on
the number of elementary constituents in the system or on the types of degrees
of freedom that are entangled. One system ubiquitous to nature where
entanglement has not been previously demonstrated is distinct mechanical
oscillators. Here we demonstrate deterministic entanglement of separated
mechanical oscillators, consisting of the vibrational states of two pairs of
atomic ions held in different locations. We also demonstrate entanglement of
the internal states of an atomic ion with a distant mechanical oscillator.Comment: 7 pages, 2 figure
The role of clathrin in post-golgi trafficking in toxoplasma gondii
Apicomplexan parasites are single eukaryotic cells with a highly polarised secretory system that contains unique secretory organelles (micronemes and rhoptries) that are required for host cell invasion. In contrast, the role of the endosomal system is poorly understood in these parasites. With many typical endocytic factors missing, we speculated that endocytosis depends exclusively on a clathrin-mediated mechanism. Intriguingly, in Toxoplasma gondii we were only able to observe the endogenous clathrin heavy chain 1 (CHC1) at the Golgi, but not at the parasite surface. For the functional characterisation of Toxoplasma gondii CHC1 we generated parasite mutants conditionally expressing the dominant negative clathrin Hub fragment and demonstrate that CHC1 is essential for vesicle formation at the trans-Golgi network. Consequently, the functional ablation of CHC1 results in Golgi aberrations, a block in the biogenesis of the unique secretory microneme and rhoptry organelles, and of the pellicle. However, we found no morphological evidence for clathrin mediating endocytosis in these parasites and speculate that they remodelled their vesicular trafficking system to adapt to an intracellular lifestyle
Resolved Sideband Cooling of a Micromechanical Oscillator
Micro- and nanoscale opto-mechanical systems provide radiation pressure
coupling of optical and mechanical degree of freedom and are actively pursued
for their ability to explore quantum mechanical phenomena of macroscopic
objects. Many of these investigations require preparation of the mechanical
system in or close to its quantum ground state. Remarkable progress in ground
state cooling has been achieved for trapped ions and atoms confined in optical
lattices. Imperative to this progress has been the technique of resolved
sideband cooling, which allows overcoming the inherent temperature limit of
Doppler cooling and necessitates a harmonic trapping frequency which exceeds
the atomic species' transition rate. The recent advent of cavity back-action
cooling of mechanical oscillators by radiation pressure has followed a similar
path with Doppler-type cooling being demonstrated, but lacking inherently the
ability to attain ground state cooling as recently predicted. Here we
demonstrate for the first time resolved sideband cooling of a mechanical
oscillator. By pumping the first lower sideband of an optical microcavity,
whose decay rate is more than twenty times smaller than the eigen-frequency of
the associated mechanical oscillator, cooling rates above 1.5 MHz are attained.
Direct spectroscopy of the motional sidebands reveals 40-fold suppression of
motional increasing processes, which could enable reaching phonon occupancies
well below unity (<0.03). Elemental demonstration of resolved sideband cooling
as reported here should find widespread use in opto-mechanical cooling
experiments. Apart from ground state cooling, this regime allows realization of
motion measurement with an accuracy exceeding the standard quantum limit.Comment: 13 pages, 5 figure
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