Tracing of backward energy transfer from LH1 to LH2 in photosynthetic membranes grown under high and low irradiation.

By introducing derivative transient absorption spectroscopy, we obtain rate constants for backward and forward energy transfer between LH1 and LH2 complexes in purple bacterial membranes. We find that backward energy transfer is strongly reduced in membranes grown under low irradiation conditions, compared to high light grown ones. We conclude that backward energy transfer is managed actively by the bacteria to avoid LH1 exciton deactivation under high irradiation conditions. The analytical method is generally applicable to excitonically coupled systems

Dynamical screening of the exciton resonance in conjugated polymers/carbon nanotubes composites

We study coherent phonons in polymer-carbon nanotubes composites by sub-10-fs pump-probe spectroscopy. We find that coherent phonons in the polymer network modulate the exciton resonance of the wrapped nanotube. We propose a model of dynamic environmental coupling in which the polymer vibration affects the carbon nanotubes exciton energy by virtue of the modulation of its dielectric screening. Carbon nanotubes act as antenna for the local environment and highlight small changes in the dielectric constant. This shows the extreme sensitivity of carbon nanotubes to their surrounding, a property essential for sensing applications and crucial for understanding composite materials

Sol-gel synthesis of thermoluminescent Cd-doped ZnTe nanoparticles

804-807<span style="font-size:10.0pt;font-family: " times="" new="" roman","serif";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:="" fa"="" lang="EN-US">The Cd (3 wt%)-doped ZnTe nanoparticles with average size of 5 nm and band gap energy of 3.15 eV were synthesized by sol-gel method. The optical properties (such as band gap energy) and the size distribution of the nanoparticles have been investigated by using UV-Vis spectroscopy and transmission electron microscopy, respectively. Then, thermoluminescence property of the nanoparticles exposed to various doses of gamma radiation of Cs137 has been studied. The thermoluminescence glow peak of the nanoparticles showed a displacement from 290 to 230°C by increasing the dose of gamma radiation from 7.5 to 67.5 mSv. The thermoluminescence intensity of the synthesized Cd-doped ZnTe nanoparticles also showed a linear dose response.</span

Protective effect of hydroalcoholic Rheum ribes L. extract in male rat model of lead acetate-induced nephrotoxicity

Background: In the recent years, the prevalence of metal-induced toxicity, especially lead-induced toxicity, has increased considerably. Metals including lead cause oxidative stress. Therefore Rheum ribes L. as a medicinal plant with antioxidant activity may reduce the complications of these toxicities. Objectives: The aim of the current study was to investigate the protective effect of hydroalcoholic R. ribes L. extract in male rat model of lead acetate-induced nephrotoxicity. Materials and Methods: In this experimental study, 40 male Wistar rats were randomly assigned to four groups: Normal saline (control) group, positive control group treated with 0.6 g/L/d of lead acetate in drinking water, and two R. ribes groups treated with 200 and 400 mg/kg/d of R. ribes extract in addition to lead acetate for 10 days. After treatment, the rats were anesthetized, blood samples were taken, and kidneys were removed and fixed in 10% formalin. Then, serum antioxidant capacity was measured and kidney tissue specimens histopathologically studied. Results: Serum antioxidant capacity was significantly different between lead acetate group and the group treated with lead acetate + R. ribes extract (400 mg/kg). Additionally mice receiving lead acetate + R. ribes extract (400 mg/kg) had significantly higher antioxidant capacity than the control group (P < 0.05). Treatment of lead acetate-treated rats with R. ribes extract significantly prevented damage to their kidney tissues. Conclusions: Rheum ribes extract can prevent lead-induced kidney damage, and therefore exposure to lead acetate by people are recommended to consume this extract. © 2018 The Author(s)

Tracing of backward energy transfer from LH1 to LH2 in photosynthetic membranes grown under high and low irradiation

By introducing derivative transient absorption spectroscopy, we obtain rate constants for backward and forward energy transfer between LH1 and LH2 complexes in purple bacterial membranes. We find that backward energy transfer is strongly reduced in membranes grown under low irradiation conditions, compared to high light grown ones. We conclude that backward energy transfer is managed actively by the bacteria to avoid LH1 exciton deactivation under high irradiation conditions. The analytical method is generally applicable to excitonically coupled systems