Assessment of the Zn-Co mixtures rhizotoxicity under Ca deficiency: using two conventional mixture models based on the cell membrane surface potential.

Toxicity assessment of Zn-Co mixtures involves multiple ions interactions. The negative potential (ψ0) at the cell membrane surface (CMs) concentrated cationic toxicants (denoted {M(2+)}0) and influenced the rhizotoxicity of Co(2+) or Zn(2+). The single and joint rhizotoxicity of Co(2+) and Zn(2+) to wheat (Triticum aestivum L.) were examined, coupled with different Ca(2+) levels. Joint effects of Zn(2+), Co(2+) and Ca(2+) were estimated by the linearly extended concentration addition (CA) and response addition (RA) models. Incorporation of Ca(2+) in single metal toxicity assessment significantly enhanced the prediction accuracy (r(2) increased from 0.948 to 0.550 for Zn(2+) and from 0.903 to 0.611 for Co(2+), respectively). ψ0 affected the multiple metals toxicity in both conventional mixture models (r(2)=0.814 for CA model and 0.820 for RA model). Concretely, {Zn(2+)}0 alleviated the toxicity of {Co(2+)}0, while {Co(2+)}0 had non-significant effect on {Zn(2+)}0 toxicity. Growth responses to {Ca(2+)}0 were substantially affected by {Zn(2+)}0 and {Co(2+)}0. Ca addition in medium decreased the {M(2+)}0 by reducing the ψ0 negativity, moreover this addition alleviated Ca deficiency at CMs induced by Zn(2+) (or Co(2+)). These consistent results from both extended CA and RA models indicated that ψ0 provided a novel sight for understanding the rhizotoxicity of multiple metals.

Assessment of extracranial-intracranial bypass in Moyamoya disease using 3T time-of-flight MR angiography: comparison with CT angiography.

BACKGROUND: To evaluate the value of time-of-flight MR angiography (TOF MRA) for the assessment of extracranial-intracranial (EC-IC) bypass in Moyamoya disease in comparison with computed tomography angiography (CTA). PATIENTS AND METHODS: A consecutive series of 23 patients with Moyamoya disease were analyzed retrospectively. Twenty three patients underwent 25 procedures of extracranial-intracranial bypass. Cranial CTA was performed within one week after the surgery to assess bypass patency. Then TOF MRA was scanned within 24 h after CTA on a 3T MRI system. Using 5-point scales (0 = poor to 4 = excellent), two radiologists rated the image quality and vessel integrity of bypass for three segments (extracranial, trepanation, intracranial). RESULTS: Image quality was high in both CTA and TOF MRA (mean quality score 3.84 ± 0.37 and 3.8 ± 0.41), without statistical difference (p = 0.66). Mean scores of TOF MRA with respect to bypass visualization were higher than CTA in the intracranial segment (p = 0.026). No significant difference of bypass visualization regarding the extracranial and trepanation segments was found between TOF MRA and CTA (p = 0.66 and p = 0.34, respectively). For the trepanation segment, TOF MRA showed pseudo lesions in 2 of all 25 cases. CONCLUSIONS: 3T TOF MRA, a non-contrast technique not exposing the patients to radiation, proved to be at least equal to CTA for the assessment of EC-IC bypass, and even superior to CTA with respect to the intracranial segment. In addition, readers should be aware of a potential overestimation showing focal pseudo lesions of the bypass at the trepanation segment in TOF MRA.

Mixed transportation network design under a sustainable development perspective.

A mixed transportation network design problem considering sustainable development was studied in this paper. Based on the discretization of continuous link-grade decision variables, a bilevel programming model was proposed to describe the problem, in which sustainability factors, including vehicle exhaust emissions, land-use scale, link load, and financial budget, are considered. The objective of the model is to minimize the total amount of resources exploited under the premise of meeting all the construction goals. A heuristic algorithm, which combined the simulated annealing and path-based gradient projection algorithm, was developed to solve the model. The numerical example shows that the transportation network optimized with the method above not only significantly alleviates the congestion on the link, but also reduces vehicle exhaust emissions within the network by up to 41.56%.