Biodegradable star-shaped poly(ethylene glycol)-poly(β-amino ester) cationic pH/temperature-sensitive copolymer hydrogels

Biodegradable star-shaped copolymers comprised of four-arm poly(ethylene glycol) (4-arm PEG) and poly(β-amino ester) (PAE) were synthesized by conjugating PAE to 4-arm PEG. The synthesized copolymers were characterized by ¹H and ¹³C NMR and gel permeation chromatography. The PAE showed pH/temperature-sensitive properties in an aqueous solution. The copolymer solutions (30 wt.%) showed a gel-to-sol phase transition as a function of temperature in the pH range 7.2–7.8. The gel window covers the physiological conditions (37 °C and pH 7.4) and can be controlled by varying the PAE block length, copolymer solution concentration and PEG molecular weight. After a subcutaneous injection of the copolymer solution into a SD rat, a gel formed rapidly in situ which remained for more than 2 weeks in the body. This copolymer is expected to be a potential candidate for biomedical applications.     

An analytical model for cross-Kerr nonlinearity in a four-level N-type atomic system with Doppler broadening

We present an analytical model for cross-Kerr nonlinear coefficient in a four-level N-type atomic medium under Doppler broadening.The model is applied to87 Rb atoms to analyze the dependence of the cross-Kerr nonlinear coefficient on the external light field and the temperature of atomic vapor.The analysis shows that in the absence of electromagnetically induced transparency(EIT)the cross-Kerr nonlinear coefficient is zero,but it is significantly enhanced when the EIT is established.It means that the cross-Kerr effect can be turned on/off when the external light field is on or off.Simultaneously,the amplitude and the sign of the cross-Kerr nonlinear coefficient are easily changed according to the intensity and frequency of the external light field.The amplitude of the cross-Kerr nonlinear coefficient remarkably decreases when the temperature of atomic medium increases.The analytical model can be convenient to fit experimental observations and applied to photonic devices.     

Pulse broadening and two-frequency mutual coherence function of the scattered wave from rough surfaces

Analytical expressions for the two-frequency mutual coherence function and angular correlation function of the scattered wave from rough surfaces based on the Kirchhoff approximation are presented. The coherence bandwidth depends on the illumination area as well as on the incident and scattered angles and the surface characteristics. Scattered pulse shapes are calculated as the Fourier transform of the two-frequency mutual coherence function. Calculations based on analytical solutions are compared with millimetre wave experimental data and Monte Carlo simulations showing good agreement.     

A new bischromanone from the stems of Semecarpus caudata

From an CHCl₃-soluble fraction of the stems of Semecarpus caudata, one new bischromanone named semecarpanone (1), together with 5 known flavonoids (2–6) were isolated. Their structures were elucidated based on interpretation of spectroscopic data. The stereo-configuration of 1 was identified based on the calculated and experimental coupling constants. Compounds 4–6 showed potent tyrosinase inhibitory activity with the IC₅₀ values ranging from 15.0 to 76.3 μM.     

Theoretical and experimental study of optical second harmonic generation in new chiral thiolates salts

The second harmonic generation ability of new chiral thiolate salts is investigated. Aromatic thiolate anions ArS⁻ are expected from semi-empirical calculations with PM3 parameterization of the MNDO Hamiltonian to possess higher intrinsic polarizabilities than the parent neutral thiols ArSH.

Salts associating (hyper)polarizable aromatic thiolate anions with chiral cations, which ensure the noncentrosymmetry necessary to have second-order nonlinear optical effects have been synthesized. The first hyperpolarizabilities, β, of the salts are measured using hyper-Rayleigh scattering technique. Second harmonic generation powder tests (Kurtz and Perry method) carried out on various salts studied, were positive indicating that these materials crystallize in noncentrosymmetric space groups.     

In‐gel equilibration for improved protein retention in 2DE‐based proteomic workflows

The 2DE is a powerful proteomic technique, with excellent protein separation capabilities where intact proteins are spatially separated by pI and molecular weight. 2DE is commonly used in conjunction with MS to identify proteins of interest. Current 2DE workflow requires several manual processing steps that can lead to experimental variability and sample loss. One such step is the transition between first dimension IEF and second‐dimension SDS‐PAGE, which requires exchanging denaturants and the reduction and alkylation of proteins. This in‐solution‐based equilibration step has been shown to be rather inefficient, losing up to 30% of the original starting material through diffusion effects. We have developed a refinement of this equilibration step using agarose stacking gels poured on top of the second‐dimension SDS‐PAGE gel, referred to as in‐gel equilibration. We show that in‐gel equilibration is effective at reduction and alkylation in SDS‐PAGE gels. Quantification of whole‐cell extracts separated on 2DE gels shows that in‐gel equilibration increases protein retention, decreased intergel variability, and simplifies 2DE workflow.     

Some results on sheaf-solutions of sheaf set control problems

In this paper, we study the existence and some properties of solutions of the so-called set control differential equations (SCDE) and sheaf-solutions of sheaf set control problems.     

Synergistic degradation to prepare oligochitosan by γ-irradiation of chitosan solution in the presence of hydrogen peroxide

Synergistic degradation of chitosan by γ-irradiation of chitosan solution (3%) in the presence of hydrogen peroxide (0.25%, 0.5% and 1%) was investigated. The efficiency of the degradation process was demonstrated by gel permeation chromatography (GPC) analysis of the average molecular weight of degraded chitosan (oligochitosan). Structures of resultant oligochitosan were characterized by Fourier-transform infrared spectra (FT-IR) and X-ray diffraction (XRD). Results showed that oligochitosan with Mw from 5000 to 10,000 could be efficiently prepared by γ-irradiation of chitosan solution containing a small amount of hydrogen peroxide at low dose less than 10 kGy. There was almost no significant change in the main chain structure of oligochitosan; however, the obtained oligochitosans lost about 10% of amino groups and the formation of carboxyl groups could not be specified by FT-IR spectra. The morphology state of oligochitosan was essentially amorphous, which differs from that of original chitosan. The combined γ ray/H₂O₂ method is significantly efficient for scale-up manufacture of oligochitosan.