Classical Analogue of the Ionic Hubbard Model

In our earlier work [M. Hafez, {\em et al.}, Phys. Lett. A {\bf 373} (2009) 4479] we employed the flow equation method to obtain a classic effective model from a quantum mechanical parent Hamiltonian called, the ionic Hubbard model (IHM). The classical ionic Hubbard model (CIHM) obtained in this way contains solely Fermionic occupation numbers of two species corresponding to particles with \up and \down spin, respectively. In this paper, we employ the transfer matrix method to analytically solve the CIHM at finite temperature in one dimension. In the limit of zero temperature, we find two insulating phases at large and small Coulomb interaction strength, $U$, mediated with a gap-less metallic phase, resulting in two continuous metal-insulator transitions. Our results are further supported with Monte Carlo simulations.Comment: 12 figure

Somatic Embryogenesis and Plant Regeneration in Evening Primrose (Oenothera biennis L.)

Callus induction responses and regeneration through callus-mediated SE were studied from evening primrose (Oenothera biennis L.) as an important medicinal plant of Onagraceae mainly known for its gamma-linoleic acid (GLA) content. The effects of cytokinins, 6-Benzylaminopurine (BAP) and N-(2-furfurylamino)1-H-purine-6-amine [Kinetin (Kin)] and their concentrations (0, 0.5, 1.0 and 1.5 mg/l) in combinations with 2,4-dichlorophenoxyacetic acid (2, 4-D) concentrations (0.25, 0.75 mg/l) on callus induction and SE for three explant types (petiole, leaf and epical bud) of "Shiraz" variety were separately evaluated. In all types of explants, the highest callus fresh weights belonged to 1 mg/l BAP or Kin in combinations with 2, 4-D (either 0.25 mg/l or 0.75 mg/l). The maximum fresh weight of callus was obtained from leaf explants plated on culture medium containing of 0.25 mg/l 2, 4-D and 1 mg/l Kin. The maximum The maximum number of embryos was achieved from leaf explants related to 0.75 mg/l 2, 4-D and 1 mg/l Kin. plantlets were successfully raised from in vitro developed embryos. Efficient plant regeneration via SE may provide a reliable system for studying the molecular mechanism of SE and a route for the genetic transformation of evening primrose

Drug Injection to Sites other than Arm: A Study of Iranian Heroin Injectors.

For almost all injecting drug users (IDUs), the first site of injection is the arm. Years after injection, IDUs may shift to using other sites for intravenous (IV) access. Although injection to sites other than the arm is associated with higher risks, literature is limited regarding this behavior. We aimed to determine the prevalence and associated factors of using IV access points other than the arm among a national sample of IDUs in Iran. Data came from the National Drug Dependence Survey, 2007, which had enrolled 863 IDUs with at least one daily injection. Data on socio-demographics, pattern of drug use, and injection-related behaviors were entered into a logistic regression to determine predictors of injection to sites other than the arm. From all participants, 54.8% reported current injection sites in areas other than the arm. The other injection sites were the femoral venous sinus (17.0%), followed by the groin (14.5%) and neck (11.5%). Logistic regression revealed that living alone [odds ratio (OR) = 1.789, 95% confidence interval (CI) = 1.218-2.629], being Sunni (OR = 3.475, 95% CI = 1.775-6.801), having higher family income (OR = 1.002, 95% CI = 1.001-1.003), higher age at first drug use (OR = 1.039, 95% CI = 1.009-1.069), longer injection duration (OR = 1.071, 95% CI = 1.041-1.102), and more injection frequency (OR = 1.255, 95% CI = 1.072-1.471) were associated with higher likelihood of using injection sites other than the arm. Using sites other than the arm for IV injection is linked to socio-demographics, drug use data, and injection-related characteristics that can be used by policy makers. This information can be used for harm reduction planning

Excitation Spectrum of One-dimensional Extended Ionic Hubbard Model

We use Perturbative Continuous Unitary Transformations (PCUT) to study the one dimensional Extended Ionic Hubbard Model (EIHM) at half-filling in the band insulator region. The extended ionic Hubbard model, in addition to the usual ionic Hubbard model, includes an inter-site nearest-neighbor (n.n.) repulsion, $V$. We consider the ionic potential as unperturbed part of the Hamiltonian, while the hopping and interaction (quartic) terms are treated as perturbation. We calculate total energy and ionicity in the ground state. Above the ground state, (i) we calculate the single particle excitation spectrum by adding an electron or a hole to the system. (ii) the coherence-length and spectrum of electron-hole excitation are obtained. Our calculations reveal that for V=0, there are two triplet bound state modes and three singlet modes, two anti-bound states and one bound state, while for finite values of $V$ there are four excitonic bound states corresponding to two singlet and two triplet modes. The major role of on-site Coulomb repulsion $U$ is to split singlet and triplet collective excitation branches, while $V$ tends to pull the singlet branches below the continuum to make them bound states.Comment: 10 eps figure

Bioinspired Adhesive Marine Based Hydrogels For Wound Healing Applications

Given advances in the treatment of various diseases such as cancer, where specific treatment for targeted tissues or polytherapy is a common practice, our toolkit for wound healing is relatively empty. Patients with chronic wounds such as venous leg ulcers, pressure ulcers, or foot ulcers not only suffer from pain but also are exposed to the risk of severe infection and amputation. There is an immense need for smart biomaterials to address acute inflammation and antibiotic-resistant organisms in infected wounds. Marine-based polysaccharides have shown a great interest in tissue engineering, particularly in wound healing acceleration, due to their inherent nontoxicity, biocompatibility, biodegradability, and environmental friendliness as a green and renewable resource. Chitooligosaccharides (COS), as a depolymerized product of chitosan, is a marine oligosaccharides with high water solubility and superior biological activity due to its lower molecular weight. Hence, this thesis aims to investigate the effect of COS molecular weight and structure on the biological activity toward wound healing applications and to develop anti-infectious bioadhesive wound dressing hydrogels, which can release novel chitooligosaccharides (COS) as bioactive compounds for chronic skin wounds.The first chapter indicates that the oxidative degradation of chitosan was a safe method to produce COS without structure alteration. this chapter's results revealed that decreasing the molecular weight of COS could improve biological activity such as antibacterial, cell proliferation, and collagen production, indicating that COS can be a promising bioactive agent in biomedical applications, in particular for wound healing applications. Although COS exhibited a superior wound healing potential compared to chitosan, its low molecular weight hiders its ability for hydrogel formation, hence, in the second chapter, a 3D printable hydrogel using phenol functionalized marine polysaccharides such as chitosan, and alginate was developed via enzyme-mediated crosslinking as a safe and non-toxic method for biomedical application. Moreover, this chapter shows that using phenol-functionalized chitosan and alginate with opposite charges resulted in a phenolated polyelectrolyte complex (PHEC), leading to the formation of in situ phenol-functionalized microfibers that exhibited excellent 3D printability. The synergistic complexation enhanced the loss modulus (60 times), toughness (2-3 times), flexibility, moldability, and dynamic viscosity (20 times) of the hydrogel compared to individual phenolated chitosan and alginate hydrogels. After successfully developing a 3D printable hydrogel in the previous chapter, then COS as a bioactive agent has been incorporated into the hydrogel to investigate the effect of COS on the physiochemical and biological properties of the hydrogel. COS incorporation significantly enhanced the antioxidant properties and antibacterial activity against E. coli and S. aureus, migration of 3D cell encapsulated 3T3-L1 fibroblasts, blood vessel formation, as well as in vivo wound healing in a rat model. In the final chapter, the adhesive properties and the mechanical stability of hydrogels were enhanced via polyphenol chemistry using tannic acid as a secondary crosslinker thanks to its physical interactions with chitosan and alginate such as hydrogen bonding and electrostatic interactions. TA-reinforced hydrogels with 30% TA (Gel-TA 30) exhibited significantly high adhesive strength (up to 18 kPa), storage modulus (40 kPa), antioxidant activity (>96%), antibacterial activity, and proliferation and viability of 3T3-L1 fibroblast cells.Doctorat en Sciences de l'ingénieur et technologieinfo:eu-repo/semantics/nonPublishe

From wastepaper to nanocomposites for bone tissue engineering application

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Physicochemical properties of the surfaces as the stem cells fate regulator

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Reinforced Poly(ε-caprolactone) Bimodal Foams via Phospho-Calcified Cellulose Nanowhisker for Osteogenic Differentiation of Human Mesenchymal Stem Cells

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Preparation and characterization of reinforced poly (ε‐caprolactone) nanocomposites by cellulose nanowhiskers

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