Fluoride removal from diluted solutions by Donnan dialysis using full factorial design

Excessive fluoride concentration in potable water can lead to fluorosis of teeth and bones. In the present study, Donnan dialysis (DD) is applied for the removal of fluoride ions from diluted sodium fluoride solutions. A four factor two level (2⁴) full factorial design was used to investigate the influence of different physico-chemical parameters on fluoride removal efficiency (Y _F ) and fluoride flux (J _F ) through anion exchange membrane. The statistical design determines factors which have the important effects on Donnan dialysis performance and studies all interactions among the considered parameters. The four significant factors were initial fluoride concentration, feed flow rate, temperature and agitation speed. The experimental results and statistical analysis show that the temperature and agitation speed have positive effects on fluoride removal efficiency and the initial fluoride concentration has a negative effect. In the case of fluoride flux, feed flow rate and initial concentration are the main effect and all factors have a positive effect. The interaction between studied parameters was not negligible on two responses. A maximum fluoride removal of 75.52% was obtained under optimum conditions and the highest value of fluoride flux obtained was 2.4 mg/cm²·h. Empirical regression models were also obtained and used to predict the flux and the fluoride removal profiles with satisfactory results.     

The Vitamin D Analog Calcipotriol Combined with Aminolevulinate-Mediated Photodynamic Therapy for Human Psoriasis: A Proof-of-Principle Study

We previously showed that select agents (methotrexate or vitamin D), when administered as a preconditioning regimen, are capable of promoting cellular differentiation of epithelial cancer cells while simultaneously enhancing the efficacy of 5-aminolevulinic acid (ALA)-mediated photodynamic therapy (PDT). In solid tumors, pretreatment with vitamin D simultaneously promotes cellular differentiation and leads to selective accumulation of target porphyrins (mainly protoporphyrin IX, PpIX) within diseased tissue. However, questions of whether or not the effects upon cellular differentiation are inexorably linked to PpIX accumulation, and whether these effects might occur in hyperproliferative noncancerous tissues, have remained unanswered. In this paper, we reasoned that psoriasis, a human skin disease in which abnormal cellular proliferation and differentiation play a major role, could serve as a useful model to test the effects of prodifferentiating agents upon PpIX levels in a nonneoplastic setting. In particular, vitamin D, a treatment for psoriasis that restores (i.e., increases) differentiation, might increase PpIX levels in psoriatic lesions and facilitate their responsiveness to ALA-PDT. This concept was tested in a pilot study of seven patients with bilaterally matched psoriatic plaques. A regimen in which calcipotriol 0.005 % ointment was applied for six days prior to ALA-PDT using blue light led to preferential increases in PpIX (ca. 50 %), and reductions in thickness, redness, scaling, and itching in the pretreated plaques. The results suggest that a larger clinical trial is warranted to confirm a role for combination treatments with vitamin D and ALA-PDT for psoriasis.     

细晶花岗岩的声发射特征试验研究

对葡萄牙细晶花岗岩同一岩样进行多次单轴压缩循环加卸载试验,监测试验过程中岩样的声发射活动,记录岩样的变形特征,分析总结声发射与变形之间的相互关系。试验表明,葡萄牙细晶花岗岩在高应力状态下凯塞效应明显,所受应力越高,凯塞效应越弱;在判断岩石凯塞点时,因时间–累计声发射能量曲线中拐点明显,比利用时间–累计声发射事件数曲线更容易、更合理;另外,了解试样的变形特征对解释声发射试验结果是一个有益的补充。     

Biosynthesis of the Fungal Organophosphonate Fosfonochlorin Involves an Iron(II) and 2-(Oxo)glutarate Dependent Oxacyclase

The fungal metabolite Fosfonochlorin features a chloroacetyl moiety that is unusual within known phosphonate natural product biochemistry. Putative biosynthetic genes encoding Fosfonochlorin in Fusarium and Talaromyces spp. were investigated through reactions of encoded enzymes with synthetic substrates and isotope labelling studies. We show that the early biosynthetic steps for Fosfonochlorin involve the reduction of phosphonoacetaldehyde to form 2-hydroxyethylphosphonic acid, followed by oxidative intramolecular cyclization of the resulting alcohol to form (S)-epoxyethylphosphonic acid. The latter reaction is catalyzed by FfnD, a rare example of a non-heme iron/2-(oxo)glutarate dependent oxacyclase. In contrast, FfnD behaves as a more typical oxygenase with ethylphosphonic acid, producing (S)-1-hydroxyethylphosphonic acid. FfnD thus represents a new example of a ferryl generating enzyme that can suppress the typical oxygen rebound reaction that follows abstraction of a substrate hydrogen by a ferryl oxygen, thereby directing the substrate radical towards a fate other than hydroxylation.