Controllable quantum scars induced by spin-orbit couplings in quantum dots.

Spin-orbit couplings (SOCs), originating from the relativistic corrections in the Dirac equation, offer nonlinearity in the classical limit and are capable of driving chaotic dynamics. In a nanoscale quantum dot confined by a two-dimensional parabolic potential with SOCs, various quantum scar states emerge quasi-periodically in the eigenstates of the system, when the ratio of confinement energies in the two directions is nearly commensurable. The scars, displaying both quantum interference and classical trajectory features on the electron density, due to relativistic effects, serve as a bridge between the classical and quantum behaviors of the system. When the strengths of Rashba and Dresselhaus SOCs are identical, the chaos in the classical limit is eliminated as the classical Hamilton's equations become linear, leading to the disappearance of all quantum scar states. Importantly, the quantum scars induced by SOCs are robust against small perturbations of system parameters. With precise control achievable through external gating, the quantum scar induced by Rashba SOC is fully controllable and detectable.

What is the risk of returning to the emergency department within 30 days for patients diagnosed with substance-induced psychosis?

OBJECTIVES: The primary objective of this study was to measure the risk of return Emergency Department (ED) visits in patients presenting to the ED with a diagnosis of substance-induced psychosis. Secondary objectives included: (1) describing the characteristics of patients returning within 30 days to the ED with substance-induced psychosis, and (2) identifying risk factors associated with such ED return. METHODS: At two urban sites from January 1, 2018 to December 31, 2019, we included consecutive patients presenting to the ED with substance-induced psychosis defined by their ED discharge diagnosis of psychosis and clinical evidence of substance use. We described ED resources utilized by this patient population including ED time and disposition then subsequently described return visits within 30 days and characteristics among those patients who returned. RESULTS: We identified 611 unique patients presenting with substance-induced psychosis, with 813 total ED visits. The median age was 35 years (IQR 28-45), 71.4% (n = 436) were male, and 44.8% (n = 274) were homeless. The median ED length of stay was 619 min (IQR 313-898), and 48.4% (n = 296) were admitted to hospital. Forty percent of patients (n = 237) returned to the ED within 30 days of the index substance-induced psychosis visit, 116 (18.9%) returning more than once. Of these return visits, 74 (31.2%) were for recurrent substance-induced psychosis. Younger age, female gender, no opioid use, and no prior history of bipolar disorder were identified as common characteristics among those returning to the ED with substance-induced psychosis. CONCLUSIONS: In ED patients with substance-induced psychosis, nearly half of all patients were admitted to hospital, 40% had a 30 days return ED visit, and one-third of those were for substance-induced psychosis. We identified clinically relevant factors common to those returning with recurrent substance-induced psychosis.

RéSUMé: OBJECTIFS: L'objectif principal de cette étude était de mesurer le risque de retour aux urgences chez les patients se présentant aux urgences avec un diagnostic de psychose induite par une substance. Les objectifs secondaires comprenaient : 1) décrire les caractéristiques des patients qui retournent aux urgences dans les 30 jours avec une psychose induite par la substance, et 2) déterminer les facteurs de risque associés à ce retour aux urgences. MéTHODES: Dans deux sites urbains, du 1er janvier 2018 au 31 décembre 2019, nous avons inclus des patients consécutifs se présentant aux urgences avec une psychose induite par une substance, définie par leur diagnostic de psychose à la sortie des urgences et des preuves cliniques de consommation de substances. Nous avons décrit les ressources des urgences utilisées par cette population de patients, notamment le temps passé aux urgences et les dispositions prises, puis nous avons décrit les visites de retour dans les 30 jours et les caractéristiques des patients qui sont revenus. RéSULTATS: Nous avons identifié 611 patients uniques présentant une psychose induite par une substance, avec un total de 813 visites aux urgences. L'âge médian était de 35 ans (IQR 28-45), 71,4 % (n = 436) étaient des hommes et 44,8 % (n = 274) étaient sans domicile fixe. La durée médiane du séjour aux urgences était de 619 minutes (IQR 313-898), et 48,4 % (n = 296) ont été hospitalisés. Quarante pour cent des patients (n = 237) sont retournés aux urgences dans les 30 jours suivant la visite de référence pour une psychose due à une substance, 116 (18,9 %) y étant retournés plus d'une fois. Parmi ces visites de retour, 74 (31,2 %) concernaient une psychose récurrente induite par une substance. Un âge plus jeune, le sexe féminin, l'absence de consommation d'opioïdes et d'antécédents de troubles bipolaires ont été identifiés comme des caractéristiques communes chez les personnes revenant aux urgences pour une psychose induite par une substance. CONCLUSIONS: Chez les patients des urgences souffrant de psychose due à une substance, près de la moitié des patients ont été hospitalisés, 40 % sont revenus aux urgences dans les 30 jours, dont un tiers pour une psychose due à une substance. Nous avons identifié des facteurs cliniquement pertinents communs à ceux qui reviennent avec une psychose récurrente induite par une substance.

One-year mortality of emergency department patients with substance-induced psychosis.

OBJECTIVES: Psychosis is a well established complication of non-prescription drug use. We sought to measure the 1-year mortality of emergency department patients with substance-induced psychosis (SIP). METHODS: This study was a multi-centre, retrospective electronic medical records review of patients presenting to the ED with substance-induced psychosis (SIP). We interrogated the hospital ED database from Jan 1, 2018 and Jan 1, 2019 to identify consecutive patients. All patients were followed for one year from index visit, and classified as alive/dead at that time. Patients were included in the study if they met the following criteria: 1) ED discharge diagnosis of psychosis NOS and a positive urine drugs of abuse screen (UDAS) or the patient verbally endorsed drug use, or 2) Mental disorder due to drug use and "disorganized thought", "bizarre behavior" or "delusional behavior" documented in the chart and one or more of the following criteria: a) arrival with police, b) mental health certification, c) physical restraints, d) chemical restraints. We excluded patients who were not British Columbia residents, since we were unable to ascertain if they were alive or dead at 1 year from their index ED visit. Primary statistical analysis was logistic regression for risk of death in 1 year, based on plausible risk factors, selected a priori. RESULTS: We identified 813 presentations for SIP (620 unique patients). The median age of the entire cohort was 35 years (IQR 28-44), and 69.5% (n = 565) were male. Thirty five patients (4.3%; 95% CI 3.2-5.9) had died one year after their initial presentation to the ED for SIP. Separate multivariable logistic regression analyses, controlling for age, demonstrated schizophrenia (OR 4.2, 95% CI 1.8-11.1) significantly associated with increased 1-year mortality. CONCLUSIONS: In our study of patients presenting to the ED with SIP, the 1-year mortality was 4.3%. Controlling for age, schizophrenia was a notable risk factor for increased 1-year mortality.

Seeking Maxwell's Demon in a non-reciprocal quantum ring.

A non-reciprocal quantum ring, where one arm of the ring contains the Rashba spin-orbit interaction but not in the other arm, is found to posses very unique electronic properties. In this ring the Aharonov-Bohm oscillations are totally absent. That is because in a magnetic field the electron stays in the non-Rashba arm, while it resides in the Rashba arm for zero (or negative) magnetic field. The average kinetic energy in the two arms of the ring are found to be very different. It also reveals different "spin temperature" in the two arms of the non-reciprocal ring. The electrons are sorted according to their spins in different regions of the ring by switching on and off (or reverse) the magnetic field, thereby creating order without doing work on the system. This resembles the action of a demon in the spirit of Maxwell's original proposal, exploiting a non-classical internal degree of freedom. Our demon clearly demonstrates some of the required features on the nanoscale.

Unique Spin Vortices and Topological Charges in Quantum Dots with Spin-orbit Couplings.

Spin textures of one or two electrons in a quantum dot with Rashba or Dresselhaus spin-orbit couplings reveal several intriguing properties. We show here that even at the single-electron level stable spin vortices with tunable topological charges exist. These topological textures appear in the ground state of the dots. The textures are stabilized by time-reversal symmetry breaking and are robust against the eccentricity of the dot. The topological charge is directly related to the sign of the z component of the spin in a large dot, allowing a direct probe of its topological properties. This would clearly pave the way to possible future topological spintronics. The phenomenon of spin vortices persists for the interacting two-electron dot in the presence of a magnetic field.

Lipid-based nanocarrier efficiently delivers highly water soluble drug across the blood-brain barrier into brain.

Delivering highly water soluble drugs across blood-brain barrier (BBB) is a crucial challenge for the formulation scientists. A successful therapeutic intervention by developing a suitable drug delivery system may revolutionize treatment across BBB. Efforts were given here to unravel the capability of a newly developed fatty acid combination (stearic acid:oleic acid:palmitic acid = 8.08:4.13:1) (ML) as fundamental component of nanocarrier to deliver highly water soluble zidovudine (AZT) as a model drug into brain across BBB. A comparison was made with an experimentally developed standard phospholipid-based nanocarrier containing AZT. Both the formulations had nanosize spherical unilamellar vesicular structure with highly negative zeta potential along with sustained drug release profiles. Gamma scintigraphic images showed both the radiolabeled formulations successfully crossed BBB, but longer retention in brain was observed for ML-based formulation (MGF) as compared to soya lecithin (SL)-based drug carrier (SYF). Plasma and brain pharmacokinetic data showed less clearance, prolonged residence time, more bioavailability and sustained release of AZT from MGF in rats compared to those data of the rats treated with SYF/AZT suspension. Thus, ML may be utilized to successfully develop drug nanocarrier to deliver drug into brain across BBB, in a sustained manner for a prolong period of time and may provide an effective therapeutic strategy for many diseases of brain. Further, many anti-HIV drugs cannot cross BBB sufficiently. Hence, the developed formulation may be a suitable option to carry those drugs into brain for better therapeutic management of HIV.

Interaction-driven distinctive electronic states of artificial atoms at the ZnO interface.

We have investigated the electronic states of planar quantum dots at the ZnO interface containing a few interacting electrons in an externally applied magnetic field. The electron-electron interaction effects are expected to be much stronger in this case than in traditional semiconductor quantum systems, such as in GaAs or InAs quantum dots. In order to highlight that stronger Coulomb effects in the ZnO quantum dots, we have compared the energy spectra and the magnetization in this system to those of the InAs quantum dots. We have found that in the ZnO quantum dots the signatures of stronger Coulomb interaction manifests in an unique ground state that has very different properties than the corresponding ones in the InAs dot. Our results for the magnetization also exhibits behaviors never before observed in a quantum dot for a realistic set of parameters. We have found a stronger temperature dependence and other unexpected features, such as paramagnetic-like behavior at high temperatures for a quantum-dot helium.

Irregular Aharonov-Bohm effect for interacting electrons in a ZnO quantum ring.

The electronic states and optical transitions of a ZnO quantum ring containing few interacting electrons in an applied magnetic field are found to be very different from those in a conventional semiconductor system, such as a GaAs ring. The strong Zeeman interaction and the Coulomb interaction of the ZnO system, two important characteristics of the electron system in ZnO, exert a profound influence on the electron states and on the optical properties of the ring. In particular, our results indicate that the Aharonov-Bohm (AB) effect in a ZnO quantum ring strongly depends on the electron number. In fact, for two electrons in the ZnO ring, the AB oscillations become aperiodic, while for three electrons (interacting) the AB oscillations completely disappear. Therefore, unlike in conventional quantum ring topology, here the AB effect (and the resulting persistent current) can be controlled by varying the electron number.

Nano-ART and NeuroAIDS.

Human immunodeficiency virus (HIV) is a neurotropic virus that enters the central nervous system (CNS) early in the course of infection. Although highly active antiretroviral therapy (HAART) has resulted in remarkable decline in the morbidity and mortality in AIDS patients, controlling HIV infections still remains a global health priority. HIV access to the CNS serves as the natural viral preserve because most antiretroviral (ARV) drugs possess inadequate or zero delivery across the brain barriers. The structure of the blood-brain barrier (BBB), the presence of efflux pumps, and the expression of metabolic enzymes pose hurdles for ARV drug-brain entry. Thus, development of target-specific, effective, safe, and controllable drug delivery approach is an important health priority for global elimination of AIDS progression. Nanoformulations can circumvent the BBB to improve CNS-directed drug delivery by affecting such pumps and enzymes. Alternatively, they can be optimized to affect their size, shape, and protein and lipid coatings to facilitate drug uptake, release, and ingress across the barrier. Improved drug delivery to the CNS would affect pharmacokinetic and drug biodistribution properties. This review focuses on how nanotechnology can serve to improve the delivery of antiretroviral medicines, termed NanoART, across the BBB and affect the biodistribution and clinical benefit for NeuroAIDS.

Excitation gap of fractal quantum hall states in graphene.

In the presence of a magnetic field and an external periodic potential the Landau level spectrum of a two-dimensional electron gas exhibits a fractal pattern in the energy spectrum which is described as the Hofstadter's butterfly. In this work, we develop a Hartree-Fock theory to deal with the electron-electron interaction in the Hofstadter's butterfly state in a finite-size graphene with periodic boundary conditions, where we include both spin and valley degrees of freedom. We then treat the butterfly state as an electron crystal so that we could obtain the order parameters of the crystal in the momentum space and also in an infinite sample. A phase transition between the liquid phase and the fractal crystal phase can be observed. The excitation gaps obtained in the infinite sample is comparable to those in the finite-size study, and agree with a recent experimental observation.

Fractional quantum Hall effect in Hofstadter butterflies of Dirac fermions.

We report on the influence of a periodic potential on the fractional quantum Hall effect (FQHE) states in monolayer graphene. We have shown that for two values of the magnetic flux per unit cell (one-half and one-third flux quantum) an increase of the periodic potential strength results in a closure of the FQHE gap and appearance of gaps due to the periodic potential. In the case of one-half flux quantum this causes a change of the ground state and consequently the change of the momentum of the system in the ground state. While there is also crossing between low-lying energy levels for one-third flux quantum, the ground state does not change with the increase of the periodic potential strength and is always characterized by the same momentum. Finally, it is shown that for one-half flux quantum the emergent gaps are due entirely to the electron-electron interaction, whereas for the one-third flux quantum per unit cell these are due to both non-interacting electrons (Hofstadter butterfly pattern) and the electron-electron interaction.

Tunable spin-selective transport through DNA with mismatched base pairs.

In our theoretical analysis of spin-selective transport through a homogeneous poly(G)-poly(C) DNA we explore the influence of a mismatched base pair in the DNA chain. The spin polarization of the electrical current through DNA is strongly sensitive to the presence of the mispair in a DNA with less than 20 base pairs. Replacing a canonical G-C base pair by a G-A mispair in homogeneous DNA can strongly decrease, increase up to an order of magnitude, or even change the sign of spin polarization of the electrical current. The mispair induced spin-selective current through DNA also depends on the location of the mispair within the DNA.

Gap structure of the Hofstadter system of interacting Dirac fermions in graphene.

The effects of mutual Coulomb interactions between Dirac fermions in monolayer graphene on the Hofstadter energy spectrum are investigated. For two flux quanta per unit cell of the periodic potential, interactions open a gap in each Landau level with the smallest gap in the n=1 Landau level. For more flux quanta through the unit cell, where the noninteracting energy spectra have many gaps in each Landau level, interactions enhance the low-energy gaps and strongly suppress the high-energy gaps and almost close a high-energy gap for n=1. The signature of the interaction effects in the Hofstadter system can be probed through magnetization, which is governed by the mixing of the Landau levels and is enhanced by the Coulomb interaction.

Interacting dirac fermions on a topological insulator in a magnetic field.

We study the fractional quantum Hall states on the surface of a topological insulator thin film in an external magnetic field, where the Dirac fermion nature of the charge carriers have been experimentally established only recently. Our studies indicate that the fractional quantum Hall states should indeed be observable in the surface Landau levels of a topological insulator. The strength of the effect will however be different, compared to that in graphene, due to the finite thickness of the topological insulator film and due to the admixture of Landau levels of the two surfaces of the film. At a small film thickness, that mixture results in a strongly nonmonotonic dependence of the excitation gap on the film thickness. At a large enough thickness of the film, the excitation gap in the lowest two Landau levels are comparable in strength.

Stable Pfaffian state in bilayer graphene.

Here, we show that the incompressible Pfaffian state originally proposed for the 5/2 fractional quantum Hall states in conventional two-dimensional electron systems can actually be found in a bilayer graphene at one of the Landau levels. The properties and stability of the Pfaffian state at this special Landau level strongly depend on the magnetic field strength. The graphene system shows a transition from the incompressible to a compressible state with increasing magnetic field. At a finite magnetic field of ~10 T, the Pfaffian state in bilayer graphene becomes more stable than its counterpart in conventional electron systems.

Intramolecularly coordinated azobenzene selenium derivatives: effect of strength of the Se···N intramolecular interaction on luminescence.

A series of selenium derivatives (6-12) of 2-phenylazophenyl have been synthesized using o-lithiation route. The effect of the strength of the intramolecular Se···N interaction on the absorption spectra as well as emission spectra has been studied. The studies suggest that the secondary bonding Se···N interaction give rise to fluorescence, however, the strength of Se···N interaction cannot be directly correlated with the intensity of the fluorescence. TD-DFT calculations show that the main transition involved in the absorption spectra of the compound is the ligand based π-π* type.

Irradiated bilayer graphene.

We describe the gated bilayer graphene system when it is subjected to intense terahertz frequency electromagnetic radiation. We examine the electron band structure and density of states via exact diagonalization methods within Floquet theory. We find that dynamical states are induced which lead to modification of the band structure. We first examine the situation where there is no external magnetic field. In the unbiased case, dynamical gaps appear in the spectrum which manifest as dips in the density of states. For finite inter-layer bias (where a static gap is present in the band structure of unirradiated bilayer graphene), dynamical states may be induced in the static gap. These states can show a high degree of valley polarization. When the system is placed in a strong magnetic field, the radiation induces coupling between the Landau levels which allows dynamical levels to exist. For strong fields, this means the Landau levels are smeared to form a near-continuum of states.

Quantum transport anomalies in DNA containing mispairs.

The effect of mispairs on charge transport in DNA of sequence (GC)(TA)(N)(GC)(3) connected to platinum electrodes is studied using the tight-binding model. With parameters derived from an ab initio density functional result, we calculate the current versus bias voltage for DNA with and without a mispair and for different numbers of (TA) basepairs N between the single and triple (GC) basepairs. The current decays exponentially with N under low bias but reaches a minimum under high bias when a multichannel transport mechanism is established. A (GA) mispair substituting a (TA) basepair near the middle of the (TA)(N) sequence usually enhances the current by one order due to its low ionization energy but may decrease the current significantly when an established multichannel mechanism is broken.

Isolation and reactivity of an unusually stable organoselenenyl azide.

The stabilities of a series of isolated covalent selenium(II) azides such as [2-[1-(3,5-dimethylphenyl)-2-naphthyl]-4,5-dihydro-4,4-dimethyloxazole]selenium azide (2a), [2-(4,4-dimethyl-2-oxazolinyl)phenyl]selenenyl azide (3a), [o-(2,6-diisopropylphenyl-iminomethinyl)phenyl]selenenyl azide (4a), [o-(R)-(methylbenzyliminomethinyl)phenyl]selenenyl azide (5a) and o-formylphenylselenenyl azide (6a) are rationalized; also the reactivity of first room temperature stable azide (2a) toward 1,3-cycloaddition has been explored.

Controllable driven phase transitions in fractional quantum Hall states in bilayer graphene.

Here we report from our theoretical studies that, in biased bilayer graphene, one can induce phase transitions from an incompressible fractional quantum Hall state to a compressible state by tuning the band gap at a given electron density. The nature of such phase transitions is different for weak and strong interlayer coupling. Although for strong coupling more levels interact there is a lesser number of transitions than for the weak coupling case. The intriguing scenario of tunable phase transitions in the fractional quantum Hall states is unique to bilayer graphene and has never before existed in conventional semiconductor systems.