High‐Performance Liquid Chromatographic Enantioseparation of Unusual Isoxazoline‐Fused 2‐Aminocyclopentanecarboxylic Acids on (+)‐(18‐Crown‐6)‐2,3,11,12‐Tetracarboxylic Acid‐Based Chiral Stationary Phases

The enantiomers of four unusual isoxazoline‐fused 2‐aminocyclopentanecarboxylic acids were directly separated on chiral stationary phases containing (+)‐(18‐crown‐6)‐2,3,11,12‐tetracarboxylic acid as chiral selector. The nature of the alcoholic modifier (MeOH, EtOH, IPA) exerted a great effect on the retention, whereas the selectivity and resolution did not change substantially. Two types of dependence of retention on alcohol content were detected: k₁ increased continuously with increasing alcohol content or a U‐shaped retention curve was observed. A comparison of the chromatographic data obtained with HCOOH, AcOH, TFA, HClO₄, H₂SO₄, or H₃PO₄ as acidic modifier at a constant concentration demonstrated that in most cases, larger k values were obtained on the application of AcOH or HCOOH, and an increase of the acid content resulted in a decrease of retention. Some mechanistic aspects of the chiral recognition process are discussed with respect to the structures of the analytes and selector. The sequence of elution of the enantiomers was determined in all cases. Chirality 24:817‐824, 2012. © 2012 Wiley Periodicals, Inc.     

Syntheses and highly enantioselective fluorescent recognition of α-aminocarboxylic acid anions using chiral oxacalix[2]arene[2]bisbinaphthes

The triazine-based bisbinaphthyl crown ethers oxacalix[2]arene[2]bisbinaphthes R-1, R-2, R-3 and S-1, S-2, S-3 were synthesized. The interactions of these compounds with various α-aminocarboxylic acid anions were studied. The crown ethers were found to carry out highly enantioselective fluorescent recognition of α-aminocarboxylic acid anions. It is observed that within a certain concentration range, one enantiomer of the chiral α-aminocarboxylic acid anions can increase the fluorescence intensity of the crown ethers by fivefold to sixfold, whereas the other enantiomer scarcely enhances the fluorescence. Such unusually high enantioselective responses make these crown ethers very attractive as fluorescent sensors in determining the enantiomeric composition of α-aminocarboxylic acid anions.     

Comparison of leaf gas exchange and stable isotope signature of water-soluble compounds along canopy gradients of co-occurring Douglas-fir and European beech

Combined δ(13) C and δ(18) O analyses of water-soluble leaf and twig phloem material were used to determine intrinsic water-use efficiency (iWUE) and variability of stomatal conductance at different crown positions in adult European beech (Fagus sylvatica) and Douglas-fir (Pseudotsuga menziesii) trees. Simultaneous gas exchange measurements allowed evaluation of the differences in calculating iWUE from leaf or phloem water-soluble compounds, and comparison with a semi-quantitative dual isotope model to infer variability of net photosynthesis (A(n) ) between the investigated crown positions. Estimates of iWUE from δ(13) C of leaf water-soluble organic matter (WSOM) outperformed the estimates from phloem compounds. In the beech crown, δ(13) C of leaf WSOM coincided clearly with gas exchange measurements. The relationship was not as reliable in the Douglas-fir. The differences in δ(18) O between leaf and phloem material were found to correlate with stomatal conductance. The semi-quantitative model approach was applicable for comparisons of daily average A(n) between different crown positions and trees. Intracanopy gradients were more pronounced in the beech than in the Douglas-fir, which reached higher values of iWUE at the respective positions, particularly under dry air conditions.     

Deterioration of Norway spruce vitality despite a sharp decline in acid deposition: a long‐term integrated perspective

Since the late 1970s, several long‐term ecological studies were conducted to better understand the biogeochemical functioning of Norway spruce stands in the Ardennes as these nutrient‐poor ecosystems were subject to high levels of acid deposition and exhibited symptoms of tree health decline. Between 1978 and 2009, acid deposition declined sharply, especially sulfur and to a lesser extent nitrogen deposition. The aim of this study was (i) to determine if the Norway spruce stands recovered after the reduction of acid deposition and (ii) to explain why such a recovery occurred or not. Therefore, we collected data from different projects carried out in the Ardennes to characterize the long‐term temporal trends in soil solution chemistry, foliar nutrition, and crown condition. In parallel, a model describing the nutrient cycling in forests (NuCM) was calibrated and used to check the consistency of the observed temporal trends and to explain them. The soil solution concentration of most of the elements decreased between 1978 and 2002, which was ascribed to a decrease in atmospheric deposition. For potassium, a decline in the exchangeable pool was also showed based on the simulation carried out with NuCM. As nitrogen (N) deposition remained at an elevated level, Norway spruce stands were progressively saturated in N and mineral nutrition became more and more unbalanced. Except the foliar N and Al concentration that remained constant and increased respectively, the foliar concentration of all other nutrients decreased between 1993 and 2009, which can be explained by the decrease in ion concentration in solution. These nutritional disorders weakened trees and were probably exacerbated during the 2003 summer drought, after which symptoms of vitality loss progressively appeared. In these N‐saturated ecosystems, the N cycle was disrupted by this health decline, which increased NO₃^? leaching reinforcing soil acidification and risk of aluminum (Al) toxicity.     

不同桩核在残根残冠修复中的疗效比较

目的:观察成品螺纹桩、铸造钴铬合金桩核、纤维桩修复残根残冠的临床应用效果.方法:将90例患者90颗残根残冠,随机分成3组,分别采用A组成品螺纹桩,B组铸造钴铬合金桩核,C组纤维桩进行修复,并随诊18个月后,比较3组患者治疗后的成功率.结果:3组患者经过治疗后,成品螺纹桩组的成功率为73.33％,铸造钴铬合金桩核组的成功率为60.00％,纤维桩组的成功率为96.67％,三组差异有统计学意义(P＜0.005).结论:与成品螺纹桩和铸造钴铬合金桩核相比,纤维桩具有更好的粘结性及抗折能力.     

Ontogenetic variations in characters of Euchone analis (Krøyer, 1856) (Polychaeta, Sabellidae, Sabellinae) from Spitsbergen, and new assignments of Oriopsis ingelorae Plate, 1995 and O. liefdefjordensis Plate, 1995

Euchone analis, the type species of its genus, was collected in high densities and in different size classes from Kongsfjorden, west Spitsbergen. This material has provided the basis for an investigation of the size dependence of characters. Almost all characters used in diagnoses were highly variable, especially the number of abdominal chaetigers forming the anal depression and the shape of the depression. The only relatively constant features are the number of chaetigers anterior to the anal depression and the branchial crown‐to‐body length ratio. A branchial skeleton extension of the radiolar appendages of the dorsal lips was found for the first time within Euchone, and this character has been added to the diagnosis of Euchone. Oriopsis liefdefjordensis and small specimens of E. analis agree in all characters, and O. liefdefjordensis is proposed to be a junior synonym of E. analis. Characters found in O. ingelorae are in accordance with those described for Chone, and we propose assigning O. ingelorae to this genus. The significance of ontogenetic character variations in the Sabellidae is discussed.     

Fusarium Species Colonizing Spears and Forming Mycotoxins in Field Samples of Asparagus from Germany and Poland

The occurrence of Fusarium spp. and associated mycotoxins in asparagus spears was evaluated in Poland in 2002 and 2003 and in Germany in 2002. Spears of two cultivars, Eposs and Gijnlim, were collected from two locations in Poland, Swidwowiec and Poznan, on sandy and sandy loam soil, respectively. Fusarium oxysporum and F. proliferatum were detected at an average incidence of 38.3% and 15.8% in the spear sections sampled, respectively. In stands of 11 (tested) cultivars of asparagus sampled in Germany on sandy soil, the same species dominated, however, they were less frequent than in Poland (26.6% and 5.6% of the spears infected with F. oxysporum and F. proliferatum, respectively). Chemical analyses revealed that fumonisin B₁ (FB₁) and moniliformin (MON) were present in some of the spears sampled in Poland. FB₁ was not found and MON was not assessed in spears sampled in Germany in 2002, but F. proliferatum was able to form the toxin in vitro in the range from 101.4 up to 205.8 μg/kg maize kernel substrate. Asparagus samples in Poland contained FB₁ at up to 5.6 μg/kg spear fresh weight. The highest MON concentration (1350 μg/kg) was detected in cultivar Eposs in Marcelin, Poland, in 2002. MON and FB₁ were found in spears infected by both F. oxysporum and F. proliferatum, however, only the latter fungus was able to synthesize both toxins.