Mechanism of nanocapsules of Matricaria recutita L. extract formation by the emulsion–diffusion process

Nanocapsules coated by medicinal plants have many applications in drug manufacturing. Medicinal plants can be loaded on nanocapsules with polyesteric triblock copolymer poly ethylene glycol–poly butylene adipate–poly ethylene glycol (PEG–PBA–PEG) as shell and olive oil can be introduced as a core of nanocapsules by a method known as polymer deposition solvent evaporation method. In this research, first, certain amount of polymer, Matricaria recutita extract and olive oil were mixed with acetone and then, water was added to the solution using magnetic stirrer. After which the acetone was removed by vacuuming and finally nanocapsules were found by freezing-drier. The study showed the size of nanocapsules depends on variety of factors such as the ratio of polymer to oil and concentration of polymers and plant extract. The nanocapsules were identified by scanning electron microscopy (SEM) and zeta potential sizer (ZPS), Fourier-transform infrared spectroscopy (FT-IR), and nuclear magnetic resonance (NMR).     

Direct calculation from the stress tensor of the lateral surface tension of fluctuating fluid membranes

From the tangential and normal stresses associated with the Helfrich Hamiltonian, we calculate the lateral force per unit length, tau, exerted by a planar, fluctuating membrane, as a function of the membrane tension sigma and bending rigidity kappa. We unveil a confusion in the literature concerning the derivation of tau, and we argue, contrary to the present understanding, that tau should differ from the tensionlike coefficient of the fluctuation spectrum. Nontrivial implications concerning the Laplace pressure in vesicles and its relation with the excess area are discussed.     

Structure of Fe–Pt alloy included carbon nanocapsules synthesized by an electric plasma discharge in an ultrasonic cavitation field of liquid ethanol

For the first time Fe–Pt alloy included carbon nanocapsules were synthesized by an electric plasma discharge in an ultrasonic cavitation field of liquid ethanol. This contrasts the extensively used chemical synthesis methods which produce uncoated Fe–Pt alloy nanoparticles. We proposed that the as-synthesized Fe–Pt alloy included carbon nanocapsules are potentially useful in biomedical applications. Thereby an aim of this work was to coat the Fe–Pt alloy nanoparticles by graphite shells using plasma discharge in liquid ethanol and to study the structure and magnetic properties of the carbon encapsulated Fe–Pt alloy nanoparticles. The core–shell structured nanoparticles were characterized by transmission electron microscopy and X-ray diffraction. These methods revealed the presence of a disordered face-centered cubic (fcc) structure (γFe, Pt) in the cores of the as-synthesized carbon nanocapsules. The as-synthesized carbon nanocapsules showed the soft magnetic character at room temperature. These carbon nanocapsules may provide a new approach in the transport and delivery of anticancer drugs.     

Nanoengineering of methylene blue loaded silica encapsulated magnetite nanospheres and nanocapsules for photodynamic therapy

Core–shell nanostructures have emerged as an important class of functional materials with potential applications in diverse fields, especially in health sciences. In this article, nanoengineering of novel magnetic colloidal dispersion containing surface modifiable silica with a core of single domain magnetite nanoparticles loaded with photosensitizer (PS) drug “Methylene blue” (MB) has been described. Magnetite core is produced by the well-established chemical coprecipitation technique and silica shell is formed over it by the modified hydrolysis and condensation of TEOS (tetraethyl orthosilicate). Conditions for reaction kinetics have been established to tailor the core–shell structures in the form of nanospheres and nanocapsules. MB is loaded into the nanostructures by demethylation reaction. The major conclusion drawn from this study is that the synthesis route yields stable, non-aggregated MB loaded superparamagnetic magnetite-silica nanostructures with tailored morphology, tunable loading, and excellent magnetic properties.     

Magnetic properties, complex permittivity and permeability of FeNi nanoparticles and FeNi/AlO x nanocapsules

Structures, surface composition, magnetic properties, and electromagnetic properties of FeNi nanoparticles and FeNi/AlO _x nanocapsules were investigated. The compositions of these nanoparticles/nanocapsules were found to be quite different from those of the corresponding targets. Al atoms could promote the evaporation of Fe atoms and suppress the evaporation of Ni atoms in the arc discharge process. The protective AlO _x shell can effectively increase the resistivity of FeNi nanocapsules and suppress the growth of FeNi nanoparticles and reduce their magnetization. For FeNi nanoparticles/nanocapsules, the same natural resonance appearing at 6.4 GHz originates mainly from magnetic FeNi cores. FeNi nanoparticles/nanocapsules exhibit promising possibility for application as a new type of electromagnetic wave shield/absorbent.     

磁场对异质界面上D-中心的影响

势阱中的类氢杂质的能级问题一直为学术界所长期关注。讨论了异质界面上中性施主D⁰和负施主离子D^-的能量随垂直于界面的磁场的变化情况,同时将磁场和势阱结合起来考虑其对类氢杂质的影响。研究发现随磁场的增大,其对D⁰基态能的影响越来越大,对其束缚能的影响逐渐变小,而对D^-中心,磁场的作用使得D^-由非束缚态转变为束缚态。计算中分别选取了两种不同的波函数,分析了这两种波函数的适用范围,利用变分的方法得到此结构中D⁰中心的基态能量和束缚能与D^-中心角动量L=-1自旋三重态的本征能量和束缚能随磁场的变化关系,找到了此三重态由非束缚态转变到束缚态对应磁场的阈值。     

Effective Hamiltonian for a liquid–gas interface fluctuating around a corrugated cylindrical substrate in the presence of van der Waals interactions

We investigate liquid layers adsorbed at spherical and corrugated cylindrical substrates. The effective Hamiltonians for the liquid–gas interfaces fluctuating in the presence of such curved substrates are derived via the mean-field density functional theory. Their structure is compared with the Helfrich Hamiltonian which is parametrized by the bending and Gaussian rigidity coefficients. For long-ranged interparticle interactions of van der Waals type these coefficients turn out to be non-universal functions of interfacial curvatures; their form varies from one interface to another. We discuss the implications of the structure of these functions on the effective Hamiltonian.     

高分子锚定的流体膜

将高分子自洽平均场理论和膜弹性理论结合起来研究高分子锚定流体膜体系，得到了高分子链热力学平衡浓度的分布和膜的形状.由于膜对高分子的不可穿透性，造成高分子可以实现的构象受到限制，导致高分子对膜施加不均匀的熵压，从而锚定点附近的膜弯离高分子，这些结果符合前人的理论分析和蒙特卡罗模拟的结果.此外，考察了膜和高分子链段之间的相互作用，高分子链长以及膜的弯曲刚性、张力对膜形变的影响. 关键词： 高分子 流体膜 自洽场理论 Helfrich膜弹性理论     

Versatile Preparation of Silica Nanocapsules for Biomedical Applications

Core–shell nanocapsules are receiving increasing interest for drug delivery applications. Silica nanocapsules have been the focus of intensive studies due to their biocompatibility, versatile silica chemistry, and tunable porosity. However, a versatile one-step preparation of silica nanocapsules with well-defined core–shell structure, tunable size, flexible interior loading, and tailored shell composition, permeability, and surface functionalization for site-specific drug release and therapeutic tracking remains a challenge. Herein, an interfacially confined sol–gel process in miniemulsion for the one-step versatile preparation of functional silica nanocapsules is developed. Uniform nanocapsules with diameters from 60 to 400 nm are obtained and a large variety of hydrophobic liquids are encapsulated in the core. When solvents with low boiling point are loaded, subsequent solvent evaporation converts the initially hydrophobic cavity into an aqueous environment. Stimuli-responsive permeability of nanocapsules is programmed by introducing disulfide or tetrasulfide bonds in the shell. Selective and sustained release of dexamethasone in response to glutathione tripeptide for over 10 d is achieved. Fluorescence labeling of the silica shell and magnetic loading in the internal cavity enable therapeutic tracking of nanocapsules by fluorescence and electron microscopies. Thus, silica nanocapsules represent a promising theranostic nanoplatform for targeted drug delivery applications.     

Chitosan Nanocapsules for pH‐Triggered Dual Release Based on Corrosion Inhibitors as Model Study

Chitosan (CS) is known for its uniqueness in terms of containing reactive functional groups, i.e., amino and hydroxyl groups, along the chain which offer the noncovalent bonds and chemical modifications. At pH 3 in emulsion system, the CS chains are under charge‐charge repulsive force, leading the polysaccharide chains to align as the hollow nanospheres and at that time, the crosslink leads to the nanocapsules. The CS nanocapsules allow the model cargos, i.e., corrosion inhibitors, entrapment not only via the noncovalent bond based on the weak interaction in the core for 2‐mercaptobenzothiazole (MBT) cargo but also via the chemical bonds based on the amino group remaining on CS structure to result in either amide or Schiff base linkage in case of 3‐nitrosalicylic acid (3NiSA) cargo. The release studies indicate that CS nanocapsules can release two cargoes upon pH change due to the acidic/basic‐triggered cleavage of bonds between cargoes and nanocapsules. Once corrosion occurs, resulting in variation of the local pH value, the CS nanocapsules release MBT in fast and 3NiSA in a slow, sustained manner. The efficiency of the approach is demonstrated using the nanocapsules for hindering the corrosion of copper as measured by electrochemical quartz crystal microbalance.     

Magnetic moment of an electron gas on the surface of constant negative curvature

The magnetic moment of an electron gas on the surface of constant negative curvature is investigated. It is shown that the surface curvature leads to the appearance of the region of the monotonic dependence M(B) at low magnetic fields. At high magnetic fields, the dependence of the magnetic moment on a magnetic field is the oscillating one. The effect of the surface curvature is to increase the region of the monotonic dependence of the magnetic moment and to break the periodicity of oscillations of the magnetic moment as a function of an inverse magnetic field.Received: 17 September 2003, Published online: 8 December 2003PACS: 73.20.At Surface states, band structure, electron density of states - 75.75. + a Magnetic properties of nanostructures     

Electroconvection in homeotropic nematic liquid crystals

Electroconvection is a classical example of pattern-forming phenomena in liquid crystals, typically observed in nematics with negative dielectric and positive conductivity anisotropies. This article focuses on how electroconvection in the homeotropic geometry differs from that in planar alignment. The influence of an additional magnetic field on the pattern characteristics and on secondary instabilities (the normal roll–abnormal roll transition) is discussed. The homeotropic alignment offers unique possibilities also for studying defect motion. Basic characteristics of some patterns of large wavelength are presented and compared with those of the classical Carr–Helfrich structures. Finally, electroconvection in substances with negative conductivity anisotropy is addressed.     

Magnetoresistance of a Two-Dimensional TbTe<Subscript>3</Subscript> Conductor in the Sliding Charge-Density Wave Regime

The magnetoresistance of a TbTe₃ two-dimensional conductor with a charge-density wave (CDW) has been measured in a wide temperature range and in magnetic fields of up to 17 T. At temperatures well below the Peierls transition temperature and in high magnetic fields, the magnetoresistance exhibits a linear dependence on the magnetic field caused by the scattering of normal charge carriers by “hot” spots of the Fermi surface. In the sliding CDW regime in low magnetic fields, a qualitative change in the magnetoresistance has been observed associated with the strong scattering of carriers by the sliding CDW.     

Mesoscale simulations of curvature-inducing protein partitioning on lipid bilayer membranes in the presence of mean curvature fields

The membrane-surface migration of curvature-inducing proteins in response to membrane curvature gradients has been investigated using Monte Carlo simulations of a curvilinear membrane model based on the Helfrich Hamiltonian. Consistent with theoretical and experimental data, we find the proteins that generate curvature can also sense the background membrane curvature, wherein they preferentially partition to the high curvature regions. The partitioning strength depends linearly on local membrane curvature and the slope (or the coupling constant) of the partitioning probability versus mean curvature depends on the membrane bending rigidity and instantaneous curvature field caused by different proteins. Our simulation study allows us to quantitatively characterize and identify the important factors affecting the coupling constant (slope), which may be difficult to determine in experiments. Furthermore, the membrane model is used to study budding of vesicles where it is found that in order to stabilize a mature vesicle with a stable ‘neck-region’ (or stable membrane overhangs), the area (extent) of the intrinsic curvature region needs to exceed a threshold-critical value. The migration and partitioning of curvature-inducing proteins in a budding vesicle with a stable neck (with a characteristic negative value of the Gaussian curvature) is investigated.     

Are cluster magnetic fields primordial?

We present results of a detailed and fully nonlinear numerical and analytical investigation of magnetic field evolution from the very earliest cosmic epochs to the present. We find that, under reasonable assumptions concerning the efficiency of a putative magnetogenesis era during cosmic phase transitions, surprisingly strong magnetic fields 10(-13)-10(-11) G on comparatively small scales 100 pc-10 kpc may survive to the present. Building on prior numerical work on the evolution of magnetic fields during the course of gravitational collapse of a cluster, which indicates that precollapse fields of approximately 4 x 10(-12) G extant on small scales may suffice to produce clusters with acceptable Faraday rotation measures, we argue that it seems possible for cluster magnetic fields to be entirely of primordial origin.     

Energetic variational approaches in modeling vesicle and fluid interactions

In this paper, we establish a hydrodynamic system to study vesicle deformations under external flow fields. The system is in the Eulerian formulation, involving the coupling of the incompressible flow system and a phase field equation. The phase field mixing energy can be viewed as a physical approximation/regularization of the Helfrich energy for an elastic membrane. We derive a self-consistent system of equations describing the dynamic evolution of vesicles immersed in an incompressible, Newtonian fluid, using an energetic variational approach. Numerical simulations of the membrane deformations in flow fields can be conducted based on the developed model.     

匀强及非匀强磁场中Heisenberg XXX链的纠缠研究

研究了匀强及非匀强磁场中反铁磁体Heisenberg XXX链的近邻和次近邻纠缠.结果表明对基态情形,纠缠随磁场B变化呈现阶梯型结构,这可用来构建量子纠缠"放大器"或量子纠缠"开关".对有限温度情形,引进一非匀强磁场Bi=(-1)iB可以使近邻格点间纠缠在某些区域明显增大,而次近邻格点间纠缠则完全消失;同时引进非匀强磁场Bi=(-1)iB还可以使近邻格点纠缠的临界温度Tcn增大,且Tcn随B的增大而升高,这意味着我们可以通过调节B的大小而在任意温度下得到纠缠.     

Investigating magnetically aligned phospholipid bilayers with EPR spectroscopy at 94 GHz

In this paper, we report our initial results on studying magnetically aligned phospholipid bilayers (bicelles) at high magnetic fields (approximately 3.4 T) with electron paramagnetic resonance (EPR) spectroscopy at 95 GHz (W-band). In order to characterize this system for W-band EPR studies, we have utilized the nitroxide spin probe 3beta-doxyl-5alpha-cholestane to demonstrate the effects of macroscopic bilayer alignment. At W-band due to the increase in magnetic field strength (when compared to X-band studies at 9.5 GHz) (S. M. Garber et al., J. Am. Chem. Soc. 121, 3240-3241 (1999)), we were able to examine magnetically aligned phospholipid bilayers at two orientations with the bilayer normal oriented either perpendicular or parallel (upon addition of YbCl3) with respect to the direction of the static magnetic field. Additionally, at a magnetic field of 3.4 T (g=2 resonance at W-band), we were able to study the parallel alignment with a lower concentration of Yb3+, thereby eliminating the possible unwanted effects associated with lanthanide-protein interactions and paramagnetic shifts and/or line broadening induced by the lanthanide ions. The development of this new spin label alignment technique will open up a whole new area of investigation for phospholipid bilayer systems and membrane protein EPR studies at high magnetic fields.     

Quantum magneto-oscillations in a supramolecular Mn(II)-[3 x 3] grid

The magnetic grid molecule Mn(II)-[3 x 3] has been studied by high-field torque magnetometry at 3He temperatures. At fields above 5 T, the torque versus field curves exhibit an unprecedented oscillatory behavior. A model is proposed which describes these magneto-oscillations well.     

Laser cooling and magnetic trapping at several tesla

Laser cooling and magnetic trapping of (85)Rb atoms have been performed in extremely strong and tunable magnetic fields, extending these techniques to a new regime and setting the stage for a variety of cold atom and plasma experiments. Using a superconducting Ioffe-Pritchard trap and an optical molasses, 2.4 x 10(7) atoms were laser cooled to the Doppler limit and magnetically trapped at bias fields up to 2.9 T. At magnetic fields up to 6 T, 3 x 10(6) cold atoms were laser cooled in a pulsed loading scheme. These bias fields are well beyond an order of magnitude larger than those in previous experiments. Loading rates, molasses lifetimes, magnetic-trapping times, and temperatures were measured using photoionization and electron detection.