Hard-core Yukawa model for two-dimensional charge stabilized colloids

The hyper-netted chain (HNC) and Percus-Yevick (PY) approximations are used to study the phase diagram of a simple hard-core Yukawa model of charge-stabilized colloidal particles in a two-dimensional system. We calculate the static structure factor and the pair distribution function over a wide range of parameters. Using the statics correlation functions we present an estimate for the liquid-solid phase diagram for the wide range of the parameters.Comment: 7 pages, 9figure

Role of Diffusion-Weighted MRI (DWI-MRI) in the Diagnosis of Brain Complications caused by Heroin Substance Abuse

Background: Magnetic resonance imaging (MRI) offers higher diagnostic accuracy for brain lesions caused by heroin abuse compared to compute tomography (CT) scan. These lesions have a low signal on T1-weighted (T1W) images and a high signal on T2-weighted (T2W) and fluid-attenuated inversion recovery (FLAIR) images. This study aimed to evaluate the role of diffusion-weighted MRI (DWI-MRI) in heroin addicts.Methods: This cross-sectional study was conducted on 20 patients with heroin addiction (vapor inhalation/injection) referring to Imam Reza Hospital of Mashhad, Iran. Patients in whom heroin abuse was only cause of consciousness, loss and neurological symptoms were enrolled in this study. Demographic data of the patients were recorded, including MRI, FLAIR, T1W and T2W images. In addition, DWI of axial and sagittal sections of the brain was performed in the following sequences.Results: In this study, mean age of patients was 40.15±7.673 years, and 95% of patients were male. The most common mode of heroin use was inhalation, and mean duration of addiction was 5.48±3.393 years. Mean daily intake of heroin was 13.4±15.30 grams, and mean duration of heroin abuse was 10.3 and 4.6 years in patients with and without MRI changes, respectively. A significant correlation was observed between MRI changes and duration of heroin use (r=0.721) (p=0.001). In addition, a significant correlation was observed between MRI changes and daily intake of heroin (p=0.006).Conclusion: According to the results of this study, brain lesions caused by heroin abuse have a low signal on T1W images and a high signal on T2W and FLAIR images. Therefore, it could be concluded that heroin intake has significant effects on the brain of users

Correlation energy of a two-dimensional electron gas from static and dynamic exchange-correlation kernels

We calculate the correlation energy of a two-dimensional homogeneous electron gas using several available approximations for the exchange-correlation kernel $f_{\rm xc}(q,\omega)$ entering the linear dielectric response of the system. As in the previous work of Lein {\it et al.} [Phys. Rev. B {\bf 67}, 13431 (2000)] on the three-dimensional electron gas, we give attention to the relative roles of the wave number and frequency dependence of the kernel and analyze the correlation energy in terms of contributions from the $(q, i\omega)$ plane. We find that consistency of the kernel with the electron-pair distribution function is important and in this case the nonlocality of the kernel in time is of minor importance, as far as the correlation energy is concerned. We also show that, and explain why, the popular Adiabatic Local Density Approximation performs much better in the two-dimensional case than in the three-dimensional one.Comment: 9 Pages, 4 Figure

Surface acoustic waves induced micropatterning of cells in gelatin methacryloyl (GelMA) hydrogels

Acoustic force patterning is an emerging technology that provides a platform to control the spatial location of cells in a rapid, accurate, yet contactless manner. However, very few studies have been reported on the usage of acoustic force patterning for the rapid arrangement of biological objects, such as cells, in a three-dimensional (3D) environment. In this study, we report on a bio-acoustic force patterning technique, which uses surface acoustic waves (SAWs) for the rapid arrangement of cells within an extracellular matrix-based hydrogel such as gelatin methacryloyl (GelMA). A proof-of-principle was achieved through both simulations and experiments based on the in-house fabricated piezoelectric SAW transducers, which enabled us to explore the effects of various parameters on the performance of the built construct. The SAWs were applied in a fashion that generated standing SAWs (SSAWs) on the substrate, the energy of which subsequently was transferred into the gel, creating a rapid, and contactless alignment of the cells (<10 s, based on the experimental conditions). Following ultraviolet radiation induced photo-crosslinking of the cell encapsulated GelMA pre-polymer solution, the patterned cardiac cells readily spread after alignment in the GelMA hydrogel and demonstrated beating activity in 5-7 days. The described acoustic force assembly method can be utilized not only to control the spatial distribution of the cells inside a 3D construct, but can also preserve the viability and functionality of the patterned cells (e.g. beating rates of cardiac cells). This platform can be potentially employed in a diverse range of applications, whether it is for tissue engineering, in vitro cell studies, or creating 3D biomimetic tissue structures

Growth and development status in the first two years of uninfected children born from HIV positive mothers

Recently prevention of HIV transmission from mother to child by antiretroviral regimens has resulted in growing the numbers of HIV exposed but uninfected children (HIV-EU). The aim of present study was evaluation of growth and neurodevelopment status among less than 2-year-old HIV exposed uninfected children. A cohort study was carried out at Vali-e-Asr Hospital (Tehran-Iran). Thirty-nine HIV-EU neonates were recruited (2014 to 2016). Neonates and infants with concern to growth and neurodevelopment status were evaluated at 6, 12, 18, and 24 months by an expert physician. Neurodevelopment assessment was based on WHO Milestones Chart and Age and Stage Questionnaire. Of all children, 22 were male, and 17 were female. Regarding growth indices, although mean birth weight in half of the neonates was lower than normal population; no postnatal descending trend was observed in their growth chart. No significant differences were found between two groups' height and head circumference. Among the neurodevelopmental parameters measured, in 6th months of life, 2 cases had abnormality in the gross motor while at 12 months, 6 cases had delay in language, social problem, and motor disorders. At 18 and 24 months, 7 infants showed developmental problems of which 71.4 of their mothers were younger than others (age&lt;25 years, P=0.009). Prevalence of neurodevelopmental disorders including delay in language, motor, and social domains was common among HIV-EU children. As several environmental factors may involve the etiology of neurodevelopmental disorders, nearly-full postnatal control and prevention seem necessary. © 2018 Tehran University of Medical Sciences. All rights reserved

Growth and development status in the first two years of uninfected children born from HIV positive mothers

Recently prevention of HIV transmission from mother to child by antiretroviral regimens has resulted in growing the numbers of HIV exposed but uninfected children (HIV-EU). The aim of present study was evaluation of growth and neurodevelopment status among less than 2-year-old HIV exposed uninfected children. A cohort study was carried out at Vali-e-Asr Hospital (Tehran-Iran). Thirty-nine HIV-EU neonates were recruited (2014 to 2016). Neonates and infants with concern to growth and neurodevelopment status were evaluated at 6, 12, 18, and 24 months by an expert physician. Neurodevelopment assessment was based on WHO Milestones Chart and Age and Stage Questionnaire. Of all children, 22 were male, and 17 were female. Regarding growth indices, although mean birth weight in half of the neonates was lower than normal population; no postnatal descending trend was observed in their growth chart. No significant differences were found between two groups' height and head circumference. Among the neurodevelopmental parameters measured, in 6th months of life, 2 cases had abnormality in the gross motor while at 12 months, 6 cases had delay in language, social problem, and motor disorders. At 18 and 24 months, 7 infants showed developmental problems of which 71.4 of their mothers were younger than others (age&lt;25 years, P=0.009). Prevalence of neurodevelopmental disorders including delay in language, motor, and social domains was common among HIV-EU children. As several environmental factors may involve the etiology of neurodevelopmental disorders, nearly-full postnatal control and prevention seem necessary. © 2018 Tehran University of Medical Sciences. All rights reserved

Two-Particle-Self-Consistent Approach for the Hubbard Model

Even at weak to intermediate coupling, the Hubbard model poses a formidable challenge. In two dimensions in particular, standard methods such as the Random Phase Approximation are no longer valid since they predict a finite temperature antiferromagnetic phase transition prohibited by the Mermin-Wagner theorem. The Two-Particle-Self-Consistent (TPSC) approach satisfies that theorem as well as particle conservation, the Pauli principle, the local moment and local charge sum rules. The self-energy formula does not assume a Migdal theorem. There is consistency between one- and two-particle quantities. Internal accuracy checks allow one to test the limits of validity of TPSC. Here I present a pedagogical review of TPSC along with a short summary of existing results and two case studies: a) the opening of a pseudogap in two dimensions when the correlation length is larger than the thermal de Broglie wavelength, and b) the conditions for the appearance of d-wave superconductivity in the two-dimensional Hubbard model.Comment: Chapter in "Theoretical methods for Strongly Correlated Systems", Edited by A. Avella and F. Mancini, Springer Verlag, (2011) 55 pages. Misprint in Eq.(23) corrected (thanks D. Bergeron

Unpaired and spin-singlet paired states of a two-dimensional electron gas in a perpendicular magnetic field

We present a variational study of both unpaired and spin-singlet paired states induced in a two-dimensional electron gas at low density by a perpendicular magnetic field. It is based on an improved circular-cell approximation which leads to a number of closed analytical results. The ground-state energy of the Wigner crystal containing a single electron per cell in the lowest Landau level is obtained as a function of the filling factor $\nu$: the results are in good agreement with those of earlier approaches and predict $\nu_{c} \approx 0.25$ for the upper filling factor at which the solid-liquid transition occurs. A novel localized state of spin-singlet electron pairs is examined and found to be a competitor of the unpaired state for filling factor $\nu >1$. The corresponding phase boundary is quantitatively displayed in the magnetic field-electron density plane.Comment: 19 pages, 8 figures, submitted to Phys. Rev. B on 7th April 2001. to appear in Phys. Rev.