Covalency and the metal-insulator transition in titanate and vanadate perovskites

A combination of density functional and dynamical mean-field theory is applied to the perovskites SrVO$_3$, LaTiO$_3$ and LaVO$_3$. We show that DFT+DMFT in conjunction with the standard fully localized-limit (FLL) double-counting predicts that LaTiO$_3$ and LaVO$_3$ are metals even though experimentally they are correlation-driven ("Mott") insulators. In addition, the FLL double counting implies a splitting between oxygen $p$ and transition metal $d$ levels which differs from experiment. Introducing into the theory an \textit{ad hoc} double counting correction which reproduces the experimentally measured insulating gap leads also to a $p$-$d$ splitting consistent with experiment if the on-site interaction $U$ is chosen in a relatively narrow range ($\sim 6\pm 1$ eV). The results indicate that these early transition metal oxides will serve as critical test for the formulation of a general \textit{ab initio} theory of correlated electron metals.Comment: 5 pages, 3 figure

Failure mechanisms of graphene under tension

Recent experiments established pure graphene as the strongest material known to mankind, further invigorating the question of how graphene fails. Using density functional theory, we reveal the mechanisms of mechanical failure of pure graphene under a generic state of tension. One failure mechanism is a novel soft-mode phonon instability of the $K_1$-mode, whereby the graphene sheet undergoes a phase transition and is driven towards isolated benzene rings resulting in a reduction of strength. The other is the usual elastic instability corresponding to a maximum in the stress-strain curve. Our results indicate that finite wave vector soft modes can be the key factor in limiting the strength of monolayer materials

How to produce cheap and easy custom-made sterilizable filtering facepiece 2/3 masks for healthcare providers during pandemic COVID-19 emergency

On January 8, 2020, a novel coronavirus was officially announced as the causative pathogen of coronavirus disease (COVID-19) by the Chinese Center for Disease Control and Prevention.On February 26, COVID-19 has been recognized in 34 countries, with a total of 80,239 laboratory-confirmed patients and 2700 deaths.Protecting healthcare workers from infectious hazards is paramount to ensuring their safety in delivering health care.In addition, being able to protect healthcare workers, constituting the front-line response against high-threat respiratory pathogens, such as severe acute respiratory syndrome coronavirus 2, is important for reducing secondary transmission in healthcare-associated outbreaks.Authors present a simple, reliable, and cheap protocol to produce a custom-made sterilizable filtering facepiece 2/3 masks for healthcare providers during pandemic COVID-19 emergency

Malar region rejuvenation through non-invasive techniques: hyaluronic acid fillers and lipofilling

Contour enhancements of the midface make up a dominant aspect of aesthetic surgery. The goal of midface rejuvenation is to decrease the prominence of grooves and creases as well as to provide volume to atrophied tissue. There are various options, including autologous tissue grafts, allogenic tissue grafts and alloplastic materials. In turn, patients\u92 needs have led to an increasing trend of less invasive treatments. In the present study, 82 implants were used for midface augmentation in 41 patients (38 women, 3 men) between January 2014 and January 2016. Twenty-five patients were treated with Hyaluronic acid implants while the remaining 16 patients were treated with lipofilling. For both groups and in all cases, good integration of the filled material was observed in the malar region, with no significant treatment complications and the last follow-up visit demonstrated good results and overall satisfaction. Hyaluronic acid fillers and lipofilling are therefore the ideal answer to patients who aim for a natural and immediate result with manageable complications, but, unlike Hyaluronic acid, autologous fat allows us to obtain a long-lasting effect over time, resulting the closest thing to an ideal facial filler

The endoscopic approach a odontogenic keatocyst involving the mandibular condyle. A case report

The odontogenic keratocyst (OKC) has been always an interesting subject to debate since Philipsen first described it as a distinct entity in 1956. Nevertheless, the large variability and the lack of homogeneity between patients in the different studies did not allow to develop universally recognized guidelines for the KOT treatment. The aim of this paper is to present a new surgical technique to approach to high dimensions KOT located at the level of mandibular ramus and condyle, consisting in enucleation and courettage under endoscopic vision