bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fast algorithms for Helmholtz Green's functions
Authors: Beylkin Gregory , Kurcz Christopher , Monzón Lucas 
Published: September 2008

The formal representation of the quasi-periodic Helmholtz Green's function obtained by the method of images is only conditionally convergent and, thus, requires an appropriate summation convention for its evaluation. Instead of using this formal sum, we derive a candidate Green's function as a sum of two rapidly convergent series, one to be applied in the spatial domain and the other in the Fourier domain (as in Ewald's method). We prove that this representation of Green's function satisfies the Helmholtz equation with the quasi-periodic condition and, furthermore, leads to a fast algorithm for its application as an operator.We approximate the spatial series by a short sum of separable functions given by Gaussians in each variable. For the series in the Fourier domain, we exploit the exponential decay of its terms to truncate it. We use fast and accurate algorithms for convolving functions with this approximation of the quasi-periodic Green's function. The resulting method yields a fast solver for the Helmholtz equation with the quasi-periodic boundary condition. The algorithm is adaptive in the spatial domain and its performance does not significantly deteriorate when Green's function is applied to discontinuous functions or potentials with singularities. We also construct Helmholtz Green's functions with Dirichlet, Neumann or mixed boundary conditions on simple domains and use a modification of the fast algorithm for the quasi-periodic Green's function to apply them.The complexity, in dimensiond≥2, of these algorithms is(κd log κ+C(log ϵ−1)d), whereϵis the desired accuracy,κis proportional to the number of wavelengths contained in the computational domain andCis a constant. We illustrate our approach with examples.
RNA Interference-Mediated Repression of MtCCD1 in Mycorrhizal Roots of Medicago truncatula Causes Accumulation of C27 Apocarotenoids, Shedding Light on the Functional Role of CCD1
Authors: Floss Daniela S. , Schliemann Willibald , Schmidt Jürgen , Strack Dieter , Walter Michael H. 
Published: September 2008

Abstract
Tailoring carotenoids by plant carotenoid cleavage dioxygenases (CCDs) generates various bioactive apocarotenoids. Recombinant CCD1 has been shown to catalyze symmetrical cleavage of C40 carotenoid substrates at 9,10 and 9′,10′ positions. The actual substrate(s) of the enzyme in planta, however, is still unknown. In this study, we have carried out RNA interference (RNAi)-mediated repression of a Medicago truncatula CCD1 gene in hairy roots colonized by the arbuscular mycorrhizal (AM) fungus Glomus intraradices. As a consequence, the normal AM-mediated accumulation of apocarotenoids (C13 cyclohexenone and C14 mycorradicin derivatives) was differentially modified. Mycorradicin derivatives were strongly reduced to 3% to 6% of the controls, while the cyclohexenone derivatives were only reduced to 30% to 47%. Concomitantly, a yellow-orange color appeared in RNAi roots. Based on ultraviolet light spectra and mass spectrometry analyses, the new compounds are C27 apocarotenoic acid derivatives. These metabolic alterations did not lead to major changes in molecular markers of the AM symbiosis, although a moderate shift to more degenerating arbuscules was observed in RNAi roots. The unexpected outcome of the RNAi approach suggests C27 apocarotenoids as the major substrates of CCD1 in mycorrhizal root cells. Moreover, literature data implicate C27 apocarotenoid cleavage as the general functional role of CCD1 in planta. A revised scheme of plant carotenoid cleavage in two consecutive steps is proposed, in which CCD1 catalyzes only the second step in the cytosol (C27 → C14 + C13), while the first step (C40 → C27 + C13) may be catalyzed by CCD7 and/or CCD4 inside plastids.
Acceleration of Flowering during Shade Avoidance in Arabidopsis Alters the Balance betweenFLOWERING LOCUS C-Mediated Repression and Photoperiodic Induction of Flowering
Authors: Wollenberg Amanda C. , Strasser Bárbara , Cerdán Pablo D. , Amasino Richard M. 
Published: September 2008

AbstractThe timing of the floral transition in Arabidopsis (Arabidopsis thaliana) is influenced by a number of environmental signals. Here, we have focused on acceleration of flowering in response to vegetative shade, a condition that is perceived as a decrease in the ratio of red to far-red radiation. We have investigated the contributions of several known flowering-time pathways to this acceleration. The vernalization pathway promotes flowering in response to extended cold via transcriptional repression of the floral inhibitor FLOWERING LOCUS C (FLC); we found that a low red to far-red ratio, unlike cold treatment, lessened the effects of FLC despite continued FLC expression. A low red to far-red ratio required the photoperiod-pathway genes GIGANTEA (GI) and CONSTANS (CO) to fully accelerate flowering in long days and did not promote flowering in short days. Together, these results suggest a model in which far-red enrichment can bypass FLC-mediated late flowering by shifting the balance between FLC-mediated repression and photoperiodic induction of flowering to favor the latter. The extent of this shift was dependent upon environmental parameters, such as the length of far-red exposure. At the molecular level, we found that far-red enrichment generated a phase delay in GI expression and enhanced CO expression and activity at both dawn and dusk. Finally, our analysis of the contribution of PHYTOCHROME AND FLOWERING TIME1 (PFT1) to shade-mediated rapid flowering has led us to suggest a new model for the involvement of PFT1 in light signaling.
Ehd2, a Rice Ortholog of the Maize INDETERMINATE1 Gene, Promotes Flowering by Up-Regulating Ehd1
Authors: Matsubara Kazuki , Yamanouchi Utako , Wang Zi-Xuan , Minobe Yuzo , Izawa Takeshi , Yano Masahiro 
Published: September 2008

Abstract
Recent research into the flowering of rice (Oryza sativa) has revealed both unique and conserved genetic pathways in the photoperiodic control of flowering compared with those in Arabidopsis (Arabidopsis thaliana). We discovered an early heading date2 (ehd2) mutant that shows extremely late flowering under both short- and long-day conditions in line with a background deficient in Heading date1 (Hd1), a rice CONSTANS ortholog that belongs to the conserved pathway. This phenotype in the ehd2 mutants suggests that Ehd2 is pivotal for the floral transition in rice. Map-based cloning revealed that Ehd2 encodes a putative transcription factor with zinc finger motifs orthologous to the INDETERMINATE1 (ID1) gene, which promotes flowering in maize (Zea mays). Ehd2 mRNA in rice tissues accumulated most abundantly in developing leaves, but was present at very low levels around the shoot apex and in roots, patterns that are similar to those of ID1. To assign the position of Ehd2 within the flowering pathway of rice, we compared transcript levels of previously isolated flowering-time genes, such as Ehd1, a member of the unique pathway, Hd3a, and Rice FT-like1 (RFT1; rice florigens), between the wild-type plants and the ehd2 mutants. Severely reduced expression of these genes in ehd2 under both short- and long-day conditions suggests that Ehd2 acts as a flowering promoter mainly by up-regulating Ehd1 and by up-regulating the downstream Hd3a and RFT1 genes in the unique genetic network of photoperiodic flowering in rice.
The ATG Autophagic Conjugation System in Maize: ATG Transcripts and Abundance of the ATG8-Lipid Adduct Are Regulated by Development and Nutrient Availability
Authors: Chung Taijoon , Suttangkakul Anongpat , Vierstra Richard D. 
Published: September 2008

Abstract
Plants employ sophisticated mechanisms to recycle intracellular constituents needed for growth, development, and survival under nutrient-limiting conditions. Autophagy is one important route in which cytoplasm and organelles are sequestered in bulk into vesicles and subsequently delivered to the vacuole for breakdown by resident hydrolases. The formation and trafficking of autophagic vesicles are directed in part by associated conjugation cascades that couple the AUTOPHAGY-RELATED8 (ATG8) and ATG12 proteins to their respective targets, phosphatidylethanolamine and the ATG5 protein. To help understand the importance of autophagy to nutrient remobilization in cereals, we describe here the ATG8/12 conjugation cascades in maize (Zea mays) and examine their dynamics during development, leaf senescence, and nitrogen and fixed-carbon starvation. From searches of the maize genomic sequence using Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa) counterparts as queries, we identified orthologous loci encoding all components necessary for ATG8/12 conjugation, including a five-member gene family expressing ATG8. Alternative splicing was evident for almost all Atg transcripts, which could have important regulatory consequences. In addition to free ATG8, its membrane-associated, lipidated form was detected in many maize tissues, suggesting that its conjugation cascade is active throughout the plant at most, if not all, developmental stages. Levels of Atg transcripts and/or the ATG8-phosphatidylethanolamine adduct increase during leaf senescence and nitrogen and fixed-carbon limitations, indicating that autophagy plays a key role in nutrient remobilization. The description of the maize ATG system now provides a battery of molecular and biochemical tools to study autophagy in this crop under field conditions.
The AtrbohD-Mediated Oxidative Burst Elicited by Oligogalacturonides in Arabidopsis Is Dispensable for the Activation of Defense Responses Effective against Botrytis cinerea
Authors: Galletti Roberta , Denoux Carine , Gambetta Stefano , Dewdney Julia , Ausubel Frederick M. , De Lorenzo Giulia , Ferrari Simone 
Published: September 2008

Abstract
Oligogalacturonides (OGs) are endogenous elicitors of defense responses released after partial degradation of pectin in the plant cell wall. We have previously shown that, in Arabidopsis (Arabidopsis thaliana), OGs induce the expression of PHYTOALEXIN DEFICIENT3 (PAD3) and increase resistance to the necrotrophic fungal pathogen Botrytis cinerea independently of signaling pathways mediated by jasmonate, salicylic acid, and ethylene. Here, we illustrate that the rapid induction of the expression of a variety of genes by OGs is also independent of salicylic acid, ethylene, and jasmonate. OGs elicit a robust extracellular oxidative burst that is generated by the NADPH oxidase AtrbohD. This burst is not required for the expression of OG-responsive genes or for OG-induced resistance to B. cinerea, whereas callose accumulation requires a functional AtrbohD. OG-induced resistance to B. cinerea is also unaffected in powdery mildew resistant4, despite the fact that callose accumulation was almost abolished in this mutant. These results indicate that the OG-induced oxidative burst is not required for the activation of defense responses effective against B. cinerea, leaving open the question of the role of reactive oxygen species in elicitor-mediated defense.
Transport and Sorting of the Solanum tuberosum Sucrose Transporter SUT1 Is Affected by Posttranslational Modification
Authors: Krügel Undine , Veenhoff Liesbeth M. , Langbein Jennifer , Wiederhold Elena , Liesche Johannes , Friedrich Thomas , Grimm Bernhard , Martinoia Enrico , Poolman Bert , Kühn Christina 
Published: September 2008

Abstract
The plant sucrose transporter SUT1 from Solanum tuberosum revealed a dramatic redox-dependent increase in sucrose transport activity when heterologously expressed in Saccharomyces cerevisiae. Plant plasma membrane vesicles do not show any change in proton flux across the plasma membrane in the presence of redox reagents, indicating a SUT1-specific effect of redox reagents. Redox-dependent sucrose transport activity was confirmed electrophysiologically in Xenopus laevis oocytes with SUT1 from maize (Zea mays). Localization studies of green fluorescent protein fusion constructs showed that an oxidative environment increased the targeting of SUT1 to the plasma membrane where the protein concentrates in 200- to 300-nm raft-like microdomains. Using plant plasma membranes, St SUT1 can be detected in the detergent-resistant membrane fraction. Importantly, in yeast and in plants, oxidative reagents induced a shift in the monomer to dimer equilibrium of the St SUT1 protein and increased the fraction of dimer. Biochemical methods confirmed the capacity of SUT1 to form a dimer in plants and yeast cells in a redox-dependent manner. Blue native PAGE, chemical cross-linking, and immunoprecipitation, as well as the analysis of transgenic plants with reduced expression of St SUT1, confirmed the dimerization of St SUT1 and Sl SUT1 (from Solanum lycopersicum) in planta. The ability to form homodimers in plant cells was analyzed by the split yellow fluorescent protein technique in transiently transformed tobacco (Nicotiana tabacum) leaves and protoplasts. Oligomerization seems to be cell type specific since under native-like conditions, a phloem-specific reduction of the dimeric form of the St SUT1 protein was detectable in SUT1 antisense plants, whereas constitutively inhibited antisense plants showed reduction only of the monomeric form. The role of redox control of sucrose transport in plants is discussed.
Chloroplast Signaling andLESION SIMULATING DISEASE1Regulate Crosstalk between Light Acclimation and Immunity inArabidopsis
Authors: Mühlenbock Per , Szechyńska-Hebda Magdalena , Płaszczyca Marian , Baudo Marcela , Mateo Alfonso , Mullineaux Philip M. , Parker Jane E. , Karpińska Barbara , Karpiński Stanisław 
Published: September 2008

AbstractPlants are simultaneously exposed to abiotic and biotic hazards. Here, we show that local and systemic acclimation in Arabidopsis thaliana leaves in response to excess excitation energy (EEE) is associated with cell death and is regulated by specific redox changes of the plastoquinone (PQ) pool. These redox changes cause a rapid decrease of stomatal conductance, global induction of ASCORBATE PEROXIDASE2 and PATHOGEN RESISTANCE1, and increased production of reactive oxygen species (ROS) and ethylene that signals through ETHYLENE INSENSITIVE2 (EIN2). We provide evidence that multiple hormonal/ROS signaling pathways regulate the plant's response to EEE and that EEE stimulates systemic acquired resistance and basal defenses to virulent biotrophic bacteria. In the Arabidopsis LESION SIMULATING DISEASE1 (lsd1) null mutant that is deregulated for EEE acclimation responses, propagation of EEE-induced programmed cell death depends on the plant defense regulators ENHANCED DISEASE SUSCEPTIBILITY1 (EDS1) and PHYTOALEXIN DEFICIENT4 (PAD4). We find that EDS1 and PAD4 operate upstream of ethylene and ROS production in the EEE response. The data suggest that the balanced activities of LSD1, EDS1, PAD4, and EIN2 regulate signaling of programmed cell death, light acclimation, and holistic defense responses that are initiated, at least in part, by redox changes of the PQ pool.
Occupational stress: consensus or divergence? A challenge for training and development specialists
Authors: Redfern David C. , Rees Christopher J. , Rowlands Kate E. 
Published: September 2008

PurposeThe main aims of this paper are to: explore current views about the nature and causes of occupational stress as portrayed in the publications of employers and employee associations; and consider the implications of these current views in relation to the work of training and development specialists.Design/methodology/approachThe current study builds on the findings of a similar study which the authors published in this journal in 2000. A library and internet‐based search was conducted to obtain publications and statements about occupational stress issued by trade unions and employers' representatives since 2001.FindingsThe analysis of publications and statements from trade unions and employers' representatives revealed an emerging consensus surrounding definitions of occupational stress based upon the UK Health and Safety Executive's definition. However, the analysis of the trade union and employer representatives' publications also revealed ongoing differences in views about the main causes of occupational stress.Practical implicationsThe implications of the study are discussed in relation to the role of HRD (human resource development) professionals in devising policies and strategies designed to create healthier workplaces by minimizing work and family conflicts.Originality/valueThe study offers a topical insight into how issues surrounding occupational stress are presented by influential parties and, further, how knowledge of these views can be used by training and development specialists.
Performance evaluation in a matrix organization: a case study (Part Two)
Authors: Appelbaum Steven H. , Nadeau David , Cyr Michael 
Published: September 2008

PurposeThe purpose of this article is to examine and ultimately suggest the most effective method with which to evaluate employees operating within a matrix organization. Part Two aims to describe a real‐time case study and examine performance evaluations in depth as they relate to this case analysis.Design/methodology/approachThis article consists of a comprehensive review of literature demonstrating functional areas within a matrix organization as well as employee evaluation methods within various organizations. It is presented in three sections: defining a matrix organization; demonstrating effective evaluation methods and strategies; and, finally, how the two should work together. Critical incidents are interspersed throughout the article in order to demonstrate how the research compares to the methods employed by a leading aviation engineering firm.FindingsIneffective evaluation methods within matrix organizations can lead to lower employee morale as well as an ambiguous understanding of employee roles within such an organization. Employee and management buy in and support of an evaluation system and its goals are crucial to the success of the program. The multi‐rater system appeared to be most effective.Practical implicationsSeveral tools exist to help employers effectively evaluate their employees in a constructive and effective manner. Among them are clear job description and corporate structure, followed by a review of performance by both functional and project managers.Originality/valueGiven the limited research with respect to evaluations within a matrix structure, this paper demonstrates an understanding of a subject that has not been adequately explored.
Interim management: is it the right career move?
Authors: Robeson Nick 
Published: September 2008

PurposeThe purpose of this paper is to highlight a service for all executives considering a career change.Design/methodology/approachThe methodology was in‐depth research with industry service providers.FindingsThe workshop provides an excellent objective, one‐stop shop for the facts of the industry and how to get started as an independent interim.Research limitations/implicationsMaterial used is taken from Ipsos MORI research and from interviews with Interim Management Association (IMA) members. It is also validated and updated on a six monthly basis.Practical implicationsDelegates gain enough information to make an immediate informed decision about interim as a career option, as well as leading industry techniques to make a fast start, if that is their choice.Originality/valueThis course is unique to the industry, in terms of its content, availability, and value to delegates.
Business ethics – Part Two: Making it part of your strategy
Authors: Holme Charles A. 
Published: September 2008

PurposeThis second article (Part One in Industrial and Commercial Training, Vol. 40 No. 5) aims to provide an overview for senior managers of how to develop an ethical culture in business. It describes a management system to support a strategy, and a governance trail of activities that may be used by Non Executive Directors and Trustees as they discharge their fiduciary responsibilities.Design/methodology/approachThe object is achieved through arguing for a systematic approach to developing ethical behaviour based on core values that support the business strategy. The article then goes on to present examples from organisations from different sectors and sizes where ethical values are part of a positive strategy to determine the culture of the business.FindingsThere is clear guidance about how to manage ethical values in business. Readers could start with the “ethical health check list” of questions. The questions could be a thought starter to managers discussing the topic at an away day for example. Managers could conduct an audit of an existing ethical strategy to identify if their values statement is being translated into behaviours throughout the organisation. They could contrast their activities with the examples in the article.Originality/valueThis article is educational and therefore provides value to senior managers and directors in a concise but comprehensive overview of the topic that is of current concern in the business world.
Personalised learning environments – Part 1: Core development issues for construction
Authors: Syed‐Khuzzan S.M. , Goulding J.S. , Underwood J. 
Published: September 2008

PurposeThis paper aims to introduce the concepts and key issues surrounding the development of personalised learning environments.Design/methodology/approachThis is a distillation of core research material gathered from a detailed literature review covering the concepts and issues surrounding the development of personalised learning environments (PLE).FindingsThis paper finds that most e‐learning applications are rather static and represent a generic approach to tutoring. Therefore, by default, they do not fully embrace learners' needs (i.e. learning styles). This paper also highlights key issues of incorporating learning styles into a PLE; and, has identified a “roadmap” for shaping and identifying the rubrics for further work in this field.Originality/valueThis paper is a very useful source in developing a PLE incorporating learning styles for learners.
Utilization of needs‐based customer training
Authors: Chow Alan , Woodford Kelly C. , Showers‐Chow Jill 
Published: September 2008

PurposeThe purpose of this paper is to look at how customer input was used in a front‐end needs assessment to formulate a training package that covered the necessary elements of product use, and how the training material was presented in a manner best suited for the trainees and their perceived needs.Design/methodology/approachA quasi‐experimental study was designed to compare the number of help desk calls for groups trained using the needs‐based training approach with the number of help desk calls from the most recent training groups that were trained with the standard training package.FindingsGroups trained using a training package developed around their initial perceived needs had significantly fewer help desk calls than those who received the standard training. The number of help desk calls was reduced by over 75 percent from previous training sessions.Research limitations/implicationsVerification of transfer of training in other applications, with other products and other learner groups, would further validate that the needs‐based training approach is more effective.Practical implicationsAll reasonable effort that can lead to more effective training will improve the customer's overall perception of the organization and will contribute to customer retention. Both customer satisfaction and retention are critical elements in the ongoing success of any company.Originality/valueThe demonstration of effectiveness and the utilization of assessment data for continuous improvement may have both practical and legal implications for the future; including enhancing customer satisfaction and retention, and reducing the likelihood of successful legal claims for negligence, particularly negligent training.