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Leaves and roots may differ in nitrogen (N), phosphorus (P) and N:P stoichiometry, which can influence plant growth and ecosystem functioning. As compared to leaves, however, relatively little is known about the N versus P scaling relationship and N:P stoichiometry in root systems, particularly in fine roots. We used a global dataset comprising 1,890 observations for a total of 763 terrestrial plant species in 123 families (spanning 433 sites world‐wide) to examine live fine root N and P concentrations and stoichiometry, and to determine the scaling of N versus P within and across different plant groups and ecosystems. The global geometric mean values of fine root N and P concentrations and N:P ratios were 10.84 mg/g, 0.94 mg/g and 11.55, respectively. Fine root N and P concentrations and N:P ratios varied both within and across plant groups and ecosystems. A 0.82‐power law described the scaling of fine root N with respect to P across the entire dataset and for major plant phylogenetic and functional groups; however, the numerical value of the N versus P scaling exponent declined from the tropics to higher latitudes and varied significantly at different local sites. Soil nutrient account for much of the variation observed in the scaling of fine root N versus P concentration at different local sites. This study advances our knowledge about limiting resource allocation strategies in below‐ground organs and has important implications for modelling plant growth at local, regional and global levels. A free Plain Language Summary can be found within the Supporting Information of this article.

Sellers’ responses to online negative consumer reviews (NCRs) have a marked effect on consumer purchasing intentions. In this study, we divide seller's responses to NCRs into two categories: rational responses and emotional responses. Through two separate studies, we examine the impact of sellers’ responses to online NCRs on consumer purchasing intention. Results reveal that product‐related NCRs reduce consumer purchasing intentions more than service‐related NCRs and having no reaction to NCRs from the sellers decreases consumer purchasing intentions. In addition, consumer trust mediates the relationship between seller's response to online NCRs and consumer purchasing intentions. The results also show that the impact on consumer purchasing intentions can be modified by the type of NCRs and sellers’ responses. In particular, rational responses will be more effective for product‐related NCRs, and for service‐related NCRs, there does not appear to exist a significant difference between the effects of rational and emotional responses. Les reponses des vendeurs aux revues en ligne negatives (RLN) des consommateurs ont un effet marque sur les intentions d'achat des consommateurs. Dans cette etude, nous divisons les reponses du vendeur aux RLN en deux categories: les reponses rationnelles et les reponses emotionnelles. Dans le cadre de deux etudes distinctes, nous examinons l'incidence des reponses des vendeurs aux RLN en ligne sur l'intention d'achat des consommateurs. Les resultats revelent que les RLN liees aux produits reduisent davantage les intentions d'achat des consommateurs que les RLN liees aux services et que le fait de ne pas reagir aux RLN diminue les intentions d'achat des consommateurs. En outre, la confiance des consommateurs influence la relation entre la reponse du vendeur aux RLN et les intentions d'achat des consommateurs. Les resultats montrent egalement que l'impact sur les intentions d'achat des consommateurs peut etre modifie par le type de reponses des vendeurs aux RLN. En particulier, les reponses rationnelles seront plus efficaces pour les RLN liees aux produits, alors que pour les RLN liees au service, il ne semble pas exister de difference significative entre les effets des reponses rationnelles et emotionnelles.

Woody plant encroachment into grasslands is a major land cover change taking place in many regions of the world, including arctic, alpine and desert ecosystems. This change in plant dominance is also affecting coastal ecosystems, including barrier islands, which are known for being vulnerable to the effects of climate change. In the last century, the woody plant species Morella cerifera L. (Myricaceae), has encroached into grass covered swales in many of the barrier islands of Virginia along the Atlantic seaboard. The abrupt shift to shrub cover in these islands could result from positive feedbacks with the physical environment, though the underlying mechanisms remain poorly understood. We use a combination of experimental and modeling approaches to investigate the role of climate warming and the ability of M. cerifera to mitigate its microclimate thereby leading to the emergence of alternative stable states in barrier island vegetation. Nighttime air temperatures were significantly higher in myrtle shrublands than grasslands, particularly in the winter season. The difference in the mean of the 5% and 10% lowest minimum temperatures between shrubland and grassland calculated from two independent datasets ranged from 1.3 to 2.4°C. The model results clearly show that a small increase in near-surface temperature can induce a non-linear shift in ecosystem state from a stable state with no shrubs to an alternative stable state dominated by M. cerifera. This modeling framework improves our understanding and prediction of barrier island vegetation stability and resilience under climate change, and highlights the existence of important nonlinearities and hystereses that limit the reversibility of this ongoing shift in vegetation dominance.

Among a set of tools that form the core of statistical process control, statistical control charts are most commonly used for controlling, monitoring, and improving processes. The conventional control charts are based on the assumption that the distribution of the quality characteristic to be monitored follows the normal distribution. However, in real applications, many process distributions may follow a positively skewed distribution such as the lognormal distribution. In this study, we discuss the construction of several control charts for monitoring the mean of the lognormal distribution. A real example is used to demonstrate how these charts can be applied in practice. Copyright (c) 2015 John Wiley & Sons, Ltd.

Plant biomass allocation patterns are important to understanding and predicting ecosystem carbon cycles and other important ecological processes. Consequently, many attempts have been made to study these patterns. However, most studies focus on data from species in temperate forests to the neglect of data from desert species adapted to arid conditions. We hypothesize that different life history strategies drive or at least participate in different plant biomass allocation patterns, as, for example, the life history differences between desert ephemeral and shrub species. We tested this hypothesis using field data gathered directly from the entire desert vegetation in Northwestern China. When the data from each of the two species groups are pooled, ephemeral and shrub species manifest different scaling relationships between above- and belowground biomass, unlike the isometric scaling relationships typically reported for forest tree species. The observed scaling relationships are sensitive to water stress and temperature gradients. The scaling exponents numerically decrease with increasing drought stress, and relatively more biomass is allocated to shoot growth in ephemeral species (presumably to rapidly complete their life history). In the case of shrubs, the numerical value of the scaling exponent is insensitive to rainfall, presumably because these species allocate more biomass to root growth to access belowground water. However, the scaling exponent is significantly sensitive to temperature, which also regulates root growth. Moreover, for the two species groups, root-shoot ratios are jointly regulated by precipitation and temperature. The different biomass allocation patterns appear to result from different life histories that maximize either competition among neighboring plants, or escaping damage from drought and low temperatures. These findings show how overall body size and life histories jointly regulate biomass allocation patterns under different extreme conditions and provide insights into estimating the dry carbon content in dryland ecosystems.

Three new hafnium aluminum antimonides Hf5Al3-xSbx (x = 0.70, 1.44, 2.14) were synthesized from pure elements in an arc-melting reaction; structures were solved from the X-ray diffraction data of single crystals. Al and Sb mixing produced two homogeneity ranges; the Mn5Si3 structural type was homogeneous for 0 ≤ x ≤ 1.0, and the W5Si3 structure covered the range 2.0 ≤ x ≤ 2.5. Both structures are condensations of two polyhedrons stacked along the c-axis. Calculations of the electronic structures revealed substantial contributions from Hf-Sb interactions; heteroatomic bonding in Hf-Al and Hf-Sb contacts affected the stabilities of these two phases. Measurements of the resistivity of polycrystalline samples revealed a dependence on temperature, indicating metallic behavior, consistent with the results of our calculations.

The coupling between the quaternary structure, stability and function of streptavidin makes it difficult to engineer a stable, high affinity monomer for biotechnology applications. For example, the binding pocket of streptavidin tetramer is comprised of residues from multiple subunits, which cannot be replicated in a single domain protein. However, rhizavidin from Rhizobium etli was recently shown to bind biotin with high affinity as a dimer without the hydrophobic tryptophan lid donated by an adjacent subunit. In particular, the binding site of rhizavidin uses residues from a single subunit to interact with bound biotin. We therefore postulated that replacing the binding site residues of streptavidin monomer with corresponding rhizavidin residues would lead to the design of a high affinity monomer useful for biotechnology applications. Here, we report the construction and characterization of a structural monomer, mSA, which combines the streptavidin and rhizavidin sequences to achieve optimized biophysical properties. First, the biotin affinity of mSA (K(d) = 2.8 nM) is the highest among nontetrameric streptavidin, allowing sensitive monovalent detection of biotinylated ligands. The monomer also has significantly higher stability (T(m) = 59.8 °C) and solubility than all other previously engineered monomers to ensure the molecule remains folded and functional during its application. Using fluorescence correlation spectroscopy, we show that mSA binds biotinylated targets as a monomer. We also show that the molecule can be used as a genetic tag to introduce biotin binding capability to a heterologous protein. For example, recombinantly fusing the monomer to a cell surface receptor allows direct labeling and imaging of transfected cells using biotinylated fluorophores. A stable and functional streptavidin monomer, such as mSA, should be a useful reagent for designing novel detection systems based on monovalent biotin interaction.

This study evaluates the eye drop delivery of genes with cornea-specific promoters, i.e., keratin 12 (K12) and keratocan (Kera3.2) promoters, by non-ionic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) polymeric micelles (PM) to mouse and rabbit eyes, and investigates the underlying mechanisms.Three PM-formulated plasmids (pCMV-Lac Z, pK12-Lac Z and pKera3.2-Lac Z) containing the Lac Z gene for beta-galactosidase (beta-Gal) whose expression was driven by the promoter of either the cytomegalovirus early gene, the keratin 12 gene or the keratocan gene, were characterized by critical micelle concentration (CMC), dynamic light scattering (DLS), and atomic force microscopy (AFM). Transgene expression in ocular tissue after gene delivery was analyzed by 5-bromo-4-chloro-3-indolyl-beta-D-galactoside (X-Gal) color staining, 1,2-dioxetane beta-Gal enzymatic activity measurement, and real-time polymerase chain reaction (PCR) analysis. The delivery mechanisms of plasmid-PM on mouse and rabbit corneas were evaluated by EDTA and RGD (arginine-glycine-aspartic acid) peptide.The sizes of the three plasmid-PM complexes were around 150-200 nm with unimodal distribution. Enhanced stability was found for three plasmid-PM formulations after DNase I treatment. After six doses of eye drop delivery of pK12-Lac Z-PM three times a day, beta-Gal activity was significantly increased in both mouse and rabbit corneas. Stroma-specific Lac Z expression was only found in pKera3.2-Lac Z-PM-treated animals with pretreatment by 5 mM EDTA, an opener of junctions. Lac Z gene expression in both pK12-Lac Z-PM and pKera3.2-Lac Z-PM delivery groups was decreased by RGD peptide pretreatment.Cornea epithelium- and stroma-specific gene expression could be achieved using cornea-specific promoters of keratin 12 and keratocan genes, and the gene was delivered with PM formulation through non-invasive, eye drop in mice and rabbits. The transfection mechanism of plasmid-PM may involve endocytosis and particle size dependent paracellular transport.

Using the image data from active RADARSAT SAR and passive DMSP SSM/I measurements of the ice in the Bohai Sea on January 23, 1999, this paper presents a correlated analysis for sea ice detection and classification. Numerical modeling of scattering and radiative transfer of a layer of sea ice for characteristic variations of the Bohai Sea shoreice is studied. The scattering index (SI), polarization index (PI), and the polarization ratio (PR) from passive observation of the brightness temperature (TB) are defined to detect the existence of sea ice. Further, using the co-horizontally polarized back-scattering coefficient (σhh) measured by the RADARSAT high resolution SAR, the sea ice in the Bohai Sea can be further classified. Temporal and spatial variations of these indices can be used to monitor the sea ice in the Bohai Sea.

A simple mass spectrometric method to sequence a recombinant phosphoenolpyruvate carboxykinase of known structure and a novel variant of unknown structure isolated from Anaerobiospirillum succiniciproducens and Actinobacillus succinogenes 130Z, respectively, was evaluated. The proteolytic digests of the proteins were each chemically derivatized at the N-terminus by addition of a tris(trimethoxyphenyl)phosphoniumacetyl (TMPP(+)-Ac) group to produce peptides with a fixed positive charge. The derivatized digests were then partially separated by reversed-phase high-performance liquid chromatography. The fractions collected were subjected to matrix-assisted laser desorption/ionization post-source decay (MALDI/PSD) mass spectrometric analysis. The resulting spectra are sufficiently simple to allow the sequence to be read directly without extensive interpretation. This is in contrast to spectra of underivatized peptides obtained by MALDI/PSD or conventional tandem mass spectrometry, where full sequence interpretation can be challenging. Aided with a set of very simple established rules, it was shown that the sequence of TMPP(+)-Ac derivatives can be derived strictly from predictable fragment ion series. In most cases, this is sufficient to determine extensive, unambiguous, peptide sequences de novo. The partial sequence (35%) of the unknown phosphoenolpyruvate carboxykinase from Actinobacillus succinogenes 130Z was obtained entirely by the mass spectrometric method evaluated here, which provided the basis for evaluating homology and for the design of oligonucleotide probes for cloning the corresponding gene.

The analysis of peptide derivatives by fast atom bombardment, liquid secondary-ionization mass spectrometry, plasma desorption, electrospray ionization, and matrix-assisted laser desorption/ionization is reviewed. The fragmentation patterns of peptides and of charge-derivatized peptides are compared, and the proposed fragment ion structures are summarized. A variety of derivatization approaches and the distinguishing features of mass spectra produced from these derivatives are described. The most promising derivatization approaches are evaluated, and the strengths and limitations of these approaches are discussed. © 1999 John Wiley & Sons, Inc. Mass Spec Rev 17: 255–274, 1998

A convenient method for the determination of the site of the double bond in long-chain olefinic acids has been developed. The technique consists in cyclizing the acid with o-aminophenol to a 2-alkenylbenzoxazole and determining the 70 eV spectra of the resulting heterocycle. Advantages of the method are (1) easy preparation of the derivatives, (2) clear, reproducible diagnostic ions and (3) extension to the analysis of di-, tri- and polyenoic acids.

A simple, efficient algorithm, MDAL (Mass Defect Algorithm), has been developed which calculates all possible empirical formulas for each accurate mass in the spectrum. This algorithm incorporates heteroatom parameters only, while the terms for C and H are eliminated. This significantly shortens the time required for calculation, especially when high-mass peaks are considered.

A novel approach to double bond location in long-chain olefinic acids has been elaborated by means of “remote functional group modification”. This method consists in converting the carboxylic acid into corresponding 2-alkenyl substituted heterocycle followed by measuring its 70 eV electron-impact mass spectrum. The inherited tendency of random migration of the double bond along the aliphatic chain under electron impact is strongly suppressed by incorporating the terminal carboxyl group into a heterocycle. The derivatives thus prepared show more informative spectra which clearly indicate the site of unsaturation of the parent acids. Submilligram scale derivatization of the olefinic acids, as exemplified by the model compound oleic acid, and a comparison of the spectra of the resulting heterocycles (3—10) as well as benzoxazole derivatives (3a—3d) of selected carboxylic acids is described in the present paper.

Sixteen alkaloids have been isolated from the fruits of Kopsia officinalis Tsiang and P. T. Li (Apocynaceae), a plant commonly used in folk medicine for treating tonsillitis and rheumatism. Ten of them were identified as known alkaloids — eburnamenine (1), kopsanone (2), 5, 18-dioxokopsan (3), kopsinilam (4), kopsinine (5), pleiocarpine (6), kopsamine (7), N-carbomethoxy-12-methoxykopsinaline (8), N-carbomethoxy-11, 12-dimethoxykopsinaline (9) and (+)-vincadifformine (13). The other three have now been proved to be new. They are N-carbomethoxy-11-hydroxy-12-methoxy-kopsinaline (10), N-carbomethoxy-11-methoxy-12-hydroxykopsinaline (11) and kopsamine N-oxide (12).

Quaternary methoiodides of tetrahydroprotoberberine (THB) alkaloids (1-8) tend to undergo preionization degradation in the mass spectrometer at elevated temperatures. Different reaction pathways have been found in relation to the structure of the substance studied. Permethylated alkaloids, e.g. tetrahydropalmatine-CH3I (8), give predominantly the Hofmann degradation intermediates and the fragment ions derived therein, while the alkaloids with free phenolic group(groups), as exemplified by scoulerine-CH3I (1), show a greater tendency to be methylated by an intermolecular CH3 transfer mechanism: The latter process has been systematically studied and the mechanism substantiated through comparison of the spectra of analogous series, B/E linked scan and CD3 labelling. Similar behaviour has been observed in bisbenzyltetrahydroisoquinoline alkaloids.

The mass spectra of diterpene orthoesters 1～12 derived from Daphne genkwa Sieb. et Zucc.(A),Daphne giraldii Nitsch.(B),Daphne tangutica Maxim.(C)and Wikstroemia chamaedaphne Meisn.(D)have been studied systematically.A detailed comparison of the spectra of analogous series,high resolution mass spectral data and metastable measurement by defocusing technique allowed the structure-spectral correlations to be generalized as follows: (1)12-OCOR′ analogs(2～4,6,8,9)dominate by the loss of the 12-substituent leading to the formation of(M-R′CO_2~·)and(M-R′CO_2H)peaks,which then furnish the skeletal ion m/z 358 through further elimination of RCO_2H+H~· or RCO_2H~·,while the 12-OH analogs(1,7)will give M-H_2O,M-H_2O-RCO_2H(m/z 358)in a similar way. (2)Members carrying no substituent at 12-C(10～12)exhibit even-mass peak at m/z 360 (M-RCO_2H),accompanied sometimes by a less pronounced peak at m/z 358.(3)Members with free 20-OH group show significant (M-~·CH_2OH)and(M-~·CH_2OH-H_2O)peaks, while the acylated derivatives(20-OCOR″)tend to provide M-(R″-H)CO via 4-mem- bered transition intermediates.(4)The presence of particular ester or orthoester groups at 12-C or 21-C may easily be identified by the acylium ions(R′CO~+ or RCO~+)at the low mass region.In most cases conjugated acyliums are displayed as strong or base peaks. (5)m/z 358,340,327,322,317,311,299,281,271,253,...as well as ion series with 2u mass increments at m/z 360,342,329,324,319,313,301,283,273,255,...may serve as an indication of the presence of diterpene skeleton bearing either OH,OCOR′ or H at 12-C,respectively. Based on the fragmentation mechanism so far reached,the structures of three new analogs 5,6,and 13 were thus assigned as tanguticacine,daphnegiraldin and 15,16- dihydrodaphnetoxin,respectively.

Long-chain unsaturated fatty acids (UFA) can easily be converted on a microgram scale to the corresponding 2-alkenyl-4,4-dimethyloxazolines by condensation with 2-amino-2-methylpropanol (AMP). These modified molecules with a ‘hidden’ carboxyl group have been proved to be a class of useful derivatives for gas chromatography/mass spectrometry (GC/MS) of UFA mixtures. While possessing very good GC characteristics, the title compounds show regular, well-recognizable diagnostic ion peaks of the double bond position in the chain. Detailed description of the method as well as electron impact (E1) mass spectra of derivatives resulting from mono-, di and polyenoic (maximally containing six double bonds) acids are presented.

Natural Maytansinoids and related compounds (1～9) were studied mass spectrometrically. Due to the presence of polar functional groups in the molecule, molecular ion peaks for most of the compounds are very weak or even invisible. Three types of characteristic ions were found in the spectra: 1) The cleavage of the cyclic carbamate ring through hydrogen rearrangement from 10-C carbon to 9-C hydroxyl group followed by loss of H_2O and HNCO, leads to ion M-61 (a). The latter gives b via McLafferty rearrangement. Both a and b are commonly accompanied by subsequent loss of CH_3·or Cl·.2) Acylium ion c from 3-C side chain and its degradation product d result in a pair of largest peaks in the spectra. These two peaks are of important diagnostic value for recognizing 3-C substitution. 3) Ions i～h produced from the collapes of 19-member ring are indicative of aromatic part of the molecule in medium mass region M-76 ions instead of a were found in 9-O-methyl substituted compounds (5～7). Since hydrogen rearrangement from 10-C is prohibited by 9-O-methyl substitution, the fragmentation is initiated by loss of CH_3OH from 8-C, 9-C followed by RDA cleavage. The identity of the spectrum of maytansinol (4) obtained by demethylation of 5 with that of the natural compound eventually proved the success of its total synthesis.