Axiomatic approach to total correctness of programs

Summary We present here an axiomatic approach which enables one to prove by formal methods that his program is totally correct (i.e., it terminates and is logically correct—does what it is supposed to do). The approach is similar to Hoare's approach [3] for proving that a program is partially correct (i.e., that whenever it terminates it produces correct results). Our extension to Hoare's method lies in the possibility of proving both correctness and termination by one unified formalism. One can choose to prove total correctness by a single step, or by incremental proof steps, each step establishing more properties of the program.     

Dynamic mechanical properties and hysteresis loss of epoxidized natural rubber chemically bonded to the silica surface

High‐temperature (180°C) molding of epoxidized natural rubber (ENR) filled with precipitated silica leads to chemical bond formation between epoxy groups of ENR and silanol groups of silica. The extent of chemical bond formation is further enhanced in the presence of the silane coupling agent N‐3‐N‐(vinyl benzyl amino)ethyl‐γ‐amino‐propyl trimethoxy silane mono hydrogen chloride (trade name Z‐6032). The results of hysteresis loss measurements show that hysteresis loss increases with increase in coupling agent loading as a result of the higher modulus of the compounds compared to that of the ENR–silica mix. The dynamic mechanical property measurements show that the addition of coupling agent increases the glass‐transition temperature. Whereas strain‐dependent dynamic mechanical properties show that filler structure breakdown increases with increasing loading of coupling agent. Sulfur‐cured systems show higher filler structure breakdown compared to that of nonsulfur systems. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2171–2177, 2002     

High dielectric response of cobalt aluminate mullite (CAM) nanocomposite over cobalt aluminate mullite polymer (CAMP) nanocomposite in PVDF matrix

In this communication we have compared the dielectric behavior of cobalt aluminate mullite (CAM) nanocomposite and cobalt aluminate mullite polymer (CAMP) nanocomposite with different molar concentration of Co ⁺² ions. The study of dielectric property of the CAM samples as well as that of the CAMP samples at room temperature shows that at all concentrations the dielectric constant is higher than pure mullite and there is a critical concentration of Co ⁺², where maximum enhancement of dielectric property occurs. This paper demonstrates that the loading of a conductive component into a highly insulating matrix is an effective way to fabricate composites with high permittivity as well as a charge storage material. We have designed a device using CAM as the electrode material and CAMP as the separator to compare it with a commercial Li-polymer ion mobile battery. We observed that the charge storage ability of the composite system is better than the commercial Li-polymer ion mobile battery. Our device persists for more than 24 h while the maximum voltage recorded by the device is 0.885 V, whereas the maximum voltage recorded by the conventional commercial Li-polymer ion mobile battery is 0.566 V.     

Rare‐earth‐doped SiO2‐CaF2 glass ceramic nano‐particle with upconversion properties

Rare‐earth‐doped upconversion nano‐phosphor shows new possibilities in the field of bioimaging because of its unique properties like higher penetration depth, low signal to noise ratio (SNR), good photo stability, and zero auto fluorescence. The oxyfluoride glass system is the combination of both fluoride and oxide where fluoride host offers high optical transparency due to low phonon energy and oxide network offers high physical stability. Thus, in the present work, an attempt has been made to synthesize 1 mol% Er³⁺ doped SiO₂‐CaF₂ glass ceramic nano‐particles through sol‐gel route. The synthesized glass ceramic particles were heat treated at 4 different temperatures starting from 600°C to 900°C.The X‐ray diffraction (XRD) analysis and Transmission electron microscopy (TEM) analysis confirmed the formation of CaF₂ nano‐crystals in the matrix which is 20‐30 nm in size. The vibrational spectroscopic analysis of the glass ceramics sample has been investigated by Fourier transform infrared (FTIR) spectroscopy. The UV‐Visible‐NIR spectroscopy analysis was carried out to analyze the absorption intensity in the near infrared region. Upon 980 nm excitation, the sample shows red emission corresponds to ⁴F_9/2→⁴I_15/2 energy level transition. The prepared nano‐particles showed excellent biocompatibility when tasted on MG‐63 osteoblast cells.     

Tuning of an optimal fuzzy PID controller with stochastic algorithms for networked control systems with random time delay

An optimal PID and an optimal fuzzy PID have been tuned by minimizing the Integral of Time multiplied Absolute Error (ITAE) and squared controller output for a networked control system (NCS). The tuning is attempted for a higher order and a time delay system using two stochastic algorithms viz. the Genetic Algorithm (GA) and two variants of Particle Swarm Optimization (PSO) and the closed loop performances are compared. The paper shows that random variation in network delay can be handled efficiently with fuzzy logic based PID controllers over conventional PID controllers.     

Thermal regimes of Li‐ion conductivity in β‐eucryptite

While it is well‐established that ionic conduction in lithium aluminosilicates proceeds via hopping of Li ions, the nature of the various hoping‐based mechanisms in different temperature regimes has not been fully elucidated. The difficulties associated with investigating the conduction have to do with the presence of grains and grain boundaries of different orientations in these usually polycrystalline materials. Herein, we use electrochemical impedance spectroscopy (EIS) to investigate the ion conduction mechanisms in β‐eucryptite, which is a prototypical lithium aluminosilicate. In the absence of significant structural transitions in grain boundaries, we find that there are three conduction regimes for the one‐dimensional ionic motion along the c axis channels in the grains, and determine the activation energies for each of these temperature regimes. Activation energies computed from molecular statics calculations of the potential energy landscape encountered by Li ions suggest that at temperatures below 440°C conduction proceeds via cooperative or correlated motion, in agreement with established literature. Between 440°C and 500°C, the activation barriers extracted from EIS measurements are large and consistent with those from atomistic calculations for uncorrelated Li ion hopping. Above 500°C the activation barriers decrease significantly, which indicates that after the transition to the Li‐disordered phase of β‐eucryptite, the Li ion motion largely regains the correlated character.     

Probing Human Telomeric DNA and RNA Topology and Ligand Binding in a Cellular Model by Using Responsive Fluorescent Nucleoside Probes

The development of biophysical systems that enable an understanding of the structure and ligand‐binding properties of G‐quadruplex (GQ)‐forming nucleic acid sequences in cells or models that mimic the cellular environment would be highly beneficial in advancing GQ‐directed therapeutic strategies. Herein, the establishment of a biophysical platform to investigate the structure and recognition properties of human telomeric (H‐Telo) DNA and RNA repeats in a cell‐like confined environment by using conformation‐sensitive fluorescent nucleoside probes and a widely used cellular model, bis(2‐ethylhexyl) sodium sulfosuccinate reverse micelles (RMs), is described. The 2′‐deoxy and ribonucleoside probes, composed of a 5‐benzofuran uracil base analogue, faithfully report the aqueous micellar core through changes in their fluorescence properties. The nucleoside probes incorporated into different loops of H‐Telo DNA and RNA oligonucleotide repeats are minimally perturbing and photophysically signal the formation of respective GQ structures in both aqueous buffer and RMs. Furthermore, these sensors enable a direct comparison of the binding affinity of a ligand to H‐Telo DNA and RNA GQ structures in the bulk and confined environment of RMs. These results demonstrate that this combination of a GQ nucleoside probe and easy‐to‐handle RMs could provide new opportunities to study and devise screening‐compatible assays in a cell‐like environment to discover GQ binders of clinical potential.     

Topologically controlled growth of magnetic-metal-functionalized semiconductor oxide nanorods

Colloidal semiconductor-magnetic hybrid nanocrystals with topologically controlled composition are fabricated by heterogeneous nucleation of spherical epsilon-Co domains onto anatase TiO2 nanorods. The latter can be selectively decorated at either their tips or at multiple locations along their longitudinal sidewalls, forming lattice-matched heterointerfaces regardless of the metal deposition sites. The possibility of switching between either heterostructure growth modes arises from the facet-dependent chemical reactivity of the oxide seeds, which is governed mainly by selective adhesion of the surfactants rather than by small differences in misfit-induced interfacial strain at the relevant junction points.     

Tumor-Derived Small Extracellular Vesicles Induce Pro-Inflammatory Cytokine Expression and PD-L1 Regulation in M0 Macrophages via IL-6/STAT3 and TLR4 Signaling Pathways

Tumor-associated macrophages play a key role in promoting tumor progression by exerting an immunosuppressive phenotype associated with the expression of programmed cell death ligand 1 (PD-L1). It is well known that tumor-derived small extracellular vesicles (SEVs) affect the tumor microenvironment, influencing TAM behavior. The present study aimed to examine the effect of SEVs derived from colon cancer and multiple myeloma cells on macrophage functions. Non-polarized macrophages (M0) differentiated from THP-1 cells were co-cultured with SEVs derived from a colorectal cancer (CRC) cell line, SW480, and a multiple myeloma (MM) cell line, MM1.S. The expression of PD-L1, interleukin-6 (IL-6), and other inflammatory cytokines as well as of the underlying molecular mechanisms were evaluated. Our results indicate that SEVs can significantly upregulate the expressions of PD-L1 and IL-6 at both the mRNA and protein levels and can activate the STAT3 signaling pathway. Furthermore, we identified the TLR4/NF-kB pathway as a convergent mechanism for SEV-mediated PD-L1 expression. Overall, these preliminary data suggest that SEVs contribute to the formation of an immunosuppressive microenvironment.