Generation of Induced Pluripotent Stem (iPS) Cells by Nuclear Reprogramming

During embryonic development pluripotency is progressively lost irreversibly by cell division, differentiation, migration and organ formation. Terminally differentiated cells do not generate other kinds of cells. Pluripotent stem cells are a great source of varying cell types that are used for tissue regeneration or repair of damaged tissue. The pluripotent stem cells can be derived from inner cell mass of blastocyte but its application is limited due to ethical concerns. The recent discovery of iPS with defined reprogramming factors has initiated a flurry of works on stem cell in various laboratories. The pluripotent cells can be derived from various differentiated adult cells as well as from adult stem cells by nuclear reprogramming, somatic cell nuclear transfer etc. In this review article, different aspects of nuclear reprogramming are discussed

Advances in Wound Healing: A Review of Current Wound Healing Products

Successful wound care involves optimizing patient local and systemic conditions in conjunction with an ideal wound healing environment. Many different products have been developed to influence this wound environment to provide a pathogen-free, protected, and moist area for healing to occur. Newer products are currently being used to replace or augment various substrates in the wound healing cascade. This review of the current state of the art in wound-healing products looks at the latest applications of silver in microbial prophylaxis and treatment, including issues involving resistance and side effects, the latest uses of negative pressure wound devices, advanced dressings and skin substitutes, biologic wound products including growth factor applications, and hyperbaric oxygen as an adjunct in wound healing. With the abundance of available products, the goal is to find the most appropriate modality or combination of modalities to optimize healing

Electron Induced Charging and Arcing of Multilayered Dielectric Materials

Measurements of the charge distribution in electron-bombarded, thin-film, multilayered dielectric samples showed that charging of multilayered materials evolves with time and is highly dependent on incident energy; this is driven by electron penetration depth, electron emission and material conductivity. Based on the net surface potential’s dependence on beam current, electron range, electron emission and conductivity, measurements of the surface potential, displacement current and beam energy allow the charge distribution to be inferred. To take these measurements, a thin-film disordered SiO2 structure with a conductive middle layer was charged using 200 eV and 5 keV electron beams with regular 15 s pulses at 1 nA/cm2 to 500 nA/cm2. Results show that there are two basic charging scenarios which are consistent with simple charging models; these are analyzed using independent determinations of the material’s electron range, yields, and conductivity. Large negative net surface potentials led to electrostatic breakdown and large visible arcs, which have been observed to lead to detrimental spacecraft charging effects

Low Temperature Cathodoluminescence in Disordered SiO2

Disordered SiO2 is commonly used for optical instrumentation and coatings. In space telescope applications, these materials can be exposed to low temperature (particularly for IR telescopes) and simultaneous electron fluxes from the space plasma environment. During recent charging tests of this dielectric material, a discernable glow was detected emanating from the surface of the SiO2, indicating that the incident electron beam induced a luminescent effect, termed cathodoluminescence. As the sample cooled from 300 K to 120 K, a change in the intensity and energy spectrum of the glow was observed between 250 nm and 1700 nm, demonstrating that the SiO2 cathodoluminescence is temperature dependent. Cathodoluminescence occurs when a high energy electron excites a valence band electron into the conduction band, then a transition takes place between the extended conduction states and the localized states below the mobility edge resulting from structural defects. This final electron transition is the origin of the emitted photon, hence the luminescence. As sample temperature and the thermal energy of the electrons vary, the trap state population, distribution of accessible trap states, and transitions between states also vary. A dynamic model of electrons in these localized trap states is proposed to explain the temperature dependent experimental cathodoluminescence spectra collected. Using our experimental results in conjunction with literature references, the specific structural defects in SiO2 responsible for distinct features in the cathodoluminescence spectra can be identified. From our experimental results, a simple qualitative model of disordered band theory has been developed to describe the states and electron dynamics in our SiO2 samples. Ultimately, such knowledge is important in the optimal design of space telescope optics

Stochastic Resetting and Applications

In this Topical Review we consider stochastic processes under resetting, which have attracted a lot of attention in recent years. We begin with the simple example of a diffusive particle whose position is reset randomly in time with a constant rate $r$, which corresponds to Poissonian resetting, to some fixed point (e.g. its initial position). This simple system already exhibits the main features of interest induced by resetting: (i) the system reaches a nontrivial nonequilibrium stationary state (ii) the mean time for the particle to reach a target is finite and has a minimum, optimal, value as a function of the resetting rate $r$. We then generalise to an arbitrary stochastic process (e.g. L\'evy flights or fractional Brownian motion) and non-Poissonian resetting (e.g. power-law waiting time distribution for intervals between resetting events). We go on to discuss multiparticle systems as well as extended systems, such as fluctuating interfaces, under resetting. We also consider resetting with memory which implies resetting the process to some randomly selected previous time. Finally we give an overview of recent developments and applications in the field.Comment: 68 pages, Topical Review accepted version to appear in Journal of Physics A: Mathematical and Theoretical 202

The Starts and Stumbles of Restorative Justice in Education: Where Do We Go from Here?

Schools are implementing Restorative Justice in Education (RJE) initiatives across the United States, often to reduce the use of out-of-school suspension, which is known to increase the risk for dropout and arrest. Many RJE initiatives also aim to strengthen social and emotional competencies, reduce gender and racial disparities in discipline, and increase access to equitable and supportive environments for students from marginalized groups. This policy brief summarizes research on restorative initiatives, with a focus on implementation and outcomes in U.S. schools. After examining the evidence, the authors offer recommendations for comprehensive RJE models and strategic implementation plans to drive more consistently positive outcomes

In Situ Surface Voltage Measurements of Dielectrics Under Electron Beam Irradiation

New instrumentation has been developed for non- contact, in vacuo measurements of the electron beam-induced surface voltage as a function of time and position for non- conductive spacecraft materials in a simulated space environment. The novel compact system uses two movable capacitive sensor electrodes to measure surface charge distributions on samples, using a non-contact method that has little effect on charge dissipation from sample. Design details, calibration and characterization measurements of the system are presented, with \u3c1 V to \u3e30 kV surface voltage range, \u3c0.5 V voltage resolution, and \u3c1.5 mm spatial resolution. Used in conjunction with the capabilities of an existing ultrahigh vacuum electron emission test chamber, the new instrumentation facilitates measurements of charge accumulation, bulk resistivity, effects of charge depletion and accumulation on yield measurements, electron induced electrostatic breakdown potentials, radiation induced conductivity effects, and the radial dispersion of surface voltage. Three types of measurements of surface voltage for polyimide (Kapton HNTM) serve to illustrate the research capabilities of the new system: (i) accumulation using a pulsed electron beam, while periodically measuring the surface voltage; (ii) post charging, as deposited charge dissipated to a grounded substrate; and (iii). the evolution of spatial profile resulting from an incident Gaussian beam. Theoretical models for sample charging and discharge are outlined to predict the time, temperature, and electric field dependence of the sample’s net surface voltage

Bulgac-Kusnezov-Nos\'e-Hoover thermostats

In this paper we formulate Bulgac-Kusnezov constant temperature dynamics in phase space by means of non-Hamiltonian brackets. Two generalized versions of the dynamics are similarly defined: one where the Bulgac-Kusnezov demons are globally controlled by means of a single additional Nos\'e variable, and another where each demon is coupled to an independent Nos\'e-Hoover thermostat. Numerically stable and efficient measure-preserving time-reversible algorithms are derived in a systematic way for each case. The chaotic properties of the different phase space flows are numerically illustrated through the paradigmatic example of the one-dimensional harmonic oscillator. It is found that, while the simple Bulgac-Kusnezov thermostat is apparently not ergodic, both of the Nos\'e-Hoover controlled dynamics sample the canonical distribution correctly