Cosmology with Varying Constants

The idea of possible time or space variations of the `fundamental' constants of nature, although not new, is only now beginning to be actively considered by large numbers of researchers in the particle physics, cosmology and astrophysics communities. This revival is mostly due to the claims of possible detection of such variations, in various different contexts and by several groups. Here, I present the current theoretical motivations and expectations for such variations, review the current observational status, and discuss the impact of a possible confirmation of these results in our views of cosmology and physics as a whole.Comment: 14 pages, no figures. Essay to appear in Phil. Trans. Roy. Soc. Lond. A Triennial Series (Christmas 2002 Issue

New Constraints on variations of the fine structure constant from CMB anisotropies

We demonstrate that recent measurements of Cosmic Microwave Background temperature and polarization anisotropy made by the ACBAR, QUAD and BICEP experiments substantially improve the cosmological constraints on possible variations of the fine structure constant in the early universe. This data, combined with the five year observations from the WMAP mission yield the constraint alpha/alpha_0 = 0.987 \pm 0.012 at 68% c.l.. The inclusion of the new HST constraints on the Hubble constant further increases the accuracy to alpha/alpha_0 = 1.001 \pm 0.007 at 68% c.l., bringing possible deviations from the current value below the 1% level and improving previous constraints by a factor 3.Comment: 3 pages, 2 figure

Magnetogels based on iron oxide nanoparticles and peptide hydrogels containing Naproxen and/or RGD

In this work, iron oxide nanoparticles, with diameters around 12 nm, were synthesized by coprecipitation method in aqueous solution. These nanoparticles exhibit a superparamagnetic behavior, with a coercive field of 9.7 Oe and a blocking temperature of 118 K. The nanoparticles were successfully incorporated in peptide-based hydrogels containing naproxen (Npx) and/or RGD. The ability of these magnetogels to act as drug nanocarriers is being investigated, aiming at developing multifunctional therapeutic nanosystems.info:eu-repo/semantics/publishedVersio

Aryl-capped lysine-dehydroamino acid dipeptide supergelators as potential drug release systems

Employing amino acids and peptides as molecular building blocks provides unique opportunities for generating supramolecular hydrogels, owing to their inherent biological origin, bioactivity, biocompatibility, and biodegradability. However, they can suffer from proteolytic degradation. Short peptides (<8 amino acids) attached to an aromatic capping group are particularly attractive alternatives for minimalistic low molecular weight hydrogelators. Peptides with low critical gelation concentrations (CGCs) are especially desirable, as the low weight percentage required for gelation makes them more cost-effective and reduces toxicity. In this work, three dehydrodipeptides were studied for their self-assembly properties. The results showed that all three dehydrodipeptides can form self-standing hydrogels with very low critical gelation concentrations (0.050.20 wt%) using a pH trigger. Hydrogels of all three dehydrodipeptides were characterised by scanning tunnelling emission microscopy (STEM), rheology, fluorescence spectroscopy, and circular dichroism (CD) spectroscopy. Molecular modelling was performed to probe the structural patterns and interactions. The cytotoxicity of the new compounds was tested using human keratinocytes (HaCaT cell line). In general, the results suggest that all three compounds are non-cytotoxic, although one of the peptides shows a small impact on cell viability. In sustained release assays, the effect of the charge of the model drug compounds on the rate of cargo release from the hydrogel network was evaluated. The hydrogels provide a sustained release of methyl orange (anionic) and ciprofloxacin (neutral), while methylene blue (cationic) was retained by the network.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding of CQUM (UID/QUI/00686/2019), IPC (UIDP/CTM/05256/2020 and UIDB/05256/2020) and REQUIMTE/LAQV (UIDB/50006/2020). L.H. acknowledges grant CEECINST/00156/2018. FCT, FEDER, PORTUGAL2020 and COMPETE2020 are also acknowl edged for funding under research project PTDC/QUI-QOR/29015/2017 (POCI-01-0145-FEDER 029015). TGC thanks FCT under the scope of the strategic funding of UIDB/04469/2020 unit, and LABBELS—Associate Laboratory in Biotechnology, Bioengineering and Microelectromechanical Systems, LA/P/0029/2020.info:eu-repo/semantics/publishedVersio

Perspective: Zinc-Tin Oxide Based Memristors for Sustainable and Flexible In-Memory Computing Edge Devices

As the Internet of things (IOT) industry continues to grow with an ever-increasing number of connected devices, the need for processing large amounts of data in a fast and energy-efficient way becomes an even more pressing issue. Alternative computation devices such as resistive random access memories (RRAM), or memristors, started taking centre stage as prime candidates to tackle this issue due to their in-memory computation capabilities. Amorphous oxide semiconductors (AOSs), more specifically eco-friendly zinc-tin oxide (ZTO), show great promise as a memristive active material for flexible and sustainable applications due to its low required fabrication temperature, amorphous structure, low-cost, and critical-raw-material-free composition. In this perspective article, the research progress on ZTO-based memristors is reviewed in terms of device structure and material compositions. The effects on the electrical performance of the devices are studied. Additionally, neuromorphic and optoelectronic capabilities are analyzed with the objective of finding the best approaches toward implementing these devices in novel computing paradigms

Concrete upgrade to improve the vibration response of timber floors

Timber floors suffering from poor serviceability performance can be upgraded with a concrete topping to form a timber–concrete composite. The upgrade stiffens the floor, reducing the perception of a vibration response to dynamic excitation. Despite timber–concrete composites becoming an established research area in recent years, relatively little is known about the vibration response of these floor types. This paper explores how the vibration response of a timber floor changes when upgraded with a concrete topping, with particular attention given to the fundamental frequency of vibration. An analytical model, utilising the gamma method of Eurocode 5 (EN 1995-1-1), is used to predict how the fundamental frequency of vibration changes with the addition of a topping. The model is compared with experimental testing of timber–concrete panels before it is used to conduct a parametric study to establish the effect of common factors. It is found that high interaction between the topping and timber floor, identifying a suitable topping thickness and considering the change in transverse stiffness are key to a successful upgrade. It is suggested that topping upgrades which are thin (20 mm or less) are suitable for this application. </jats:p

Spectroscopy of QUBRICS quasar candidates: 1672 new redshifts and a Golden Sample for the Sandage Test of the Redshift Drift

The QUBRICS (QUasars as BRIght beacons for Cosmology in the Southern hemisphere) survey aims at constructing a sample of the brightest quasars with z>~2.5, observable with facilities in the Southern Hemisphere. QUBRICS makes use of the available optical and IR wide-field surveys in the South and of Machine Learning techniques to produce thousands of bright quasar candidates of which only a few hundred have been confirmed with follow-up spectroscopy. Taking advantage of the recent Gaia Data Release 3, which contains 220 million low-resolution spectra, and of a newly developed spectral energy distribution fitting technique, designed to combine the photometric information with the Gaia spectroscopy, it has been possible to measure 1672 new secure redshifts of QUBRICS candidates, with a typical uncertainty $\sigma_z = 0.02$. This significant progress of QUBRICS brings it closer to (one of) its primary goals: providing a sample of bright quasars at redshift 2.5 < z < 5 to perform the Sandage test of the cosmological redshift drift. A Golden Sample of seven quasars is presented that makes it possible to carry out this experiment in about 1500 hours of observation in 25 years, using the ANDES spectrograph at the 39m ELT, a significant improvement with respect to previous estimates.Comment: 11 pages, 10 figures, accepted for publication in MNRA