1,978 research outputs found
Notes on family-group names for bees (Hymenoptera: Apoidea)
No full textAbstract. Corrected authorships and dates are provided for four family-group names for bees based on previously unrecognized earlier usages that made them nomenclatorially available. Sagemehl is newly recognized as the author of family-group names based on Dasypoda Latreille (Melittidae: Dasypodainae), Macropis Panzer (Melittidae: Macropidinae), and Hylaeus Fabricius (Colletidae: Hylaeinae), and Kawall as the author the family-group name based on Melitta Kirby, thereby taking precedence over the subsequent use of similar names by Börner, Robertson, Vi-ereck, and Schenck, respectively. In addition, descriptions are provided for three new family-group taxa; Dieunomiini Engel, new tribe (Halictidae: Nomiinae), Eremaphantina Engel, new subtribe (Melittidae: Hesperapini), and Tarsaliini Engel, new tribe (Apidae: Apinae); and one new genus-group taxon, Eremaphantella Engel, new subgenus
Facilitating innovation : an action-oriented approach and participatory methodology to improve innovative social practice in agriculture
No full textThis study focuses upon the social organization of innovation. It makes use of insights from knowledge and information systems research, development sociology, management science and applied philosophy and seeks answers to the following questions: What do social actors, individuals and/or organizations, actually do to innovate their practices? How do they organize themselves? Can this be managed or facilitated, and if so, how? The research is exploratory rather than conclusion-oriented and synthesizes the results of over 50 case studies of agricultural innovation in 15 different countries, including the Netherlands. Its main results are a conceptualization of innovation as a social process and a participatory action-research methodology to enhance innovative performance. The methodology is based on soft systems thinking and offers a variety of 'windows' or analytical perspectives to help social actors analyze the way they are organized for innovation in an action-oriented fashion. The methodology has been field-tested in 15 areas in 7 different countries.The author proposes that agricultural innovation can be looked at as resulting from the interplay between social actors representing relevant social practices. Social practices relevant to agricultural innovation include farming, research, extension, education, agroindustrial processing, marketing, mass media communication, policy-making, product quality control and the development, production, certification and distribution of inputs. Innovation then is a diffuse, social process of both individual and collective inquiry into intentions, alternative solutions and enabling and constraining conditions which leads to new or modified problem definitions and practical choices of solutions. The organization and quality of these inquiries eventually determine innovative performance at a certain point in time. What social actors actually do to innovate their practices can be understood as networking: social actors in search of relevant ideas, knowledge, information and experiences, continuously build and manage relationships with others which, by some standard, they consider relevant to innovating their practices. As a result of networking, over time forms of social organization of innovation emerge. These reflect dynamics of their own and are not fully describable or explicable in terms of micro-events.The author proposes four such emergent forms to be relevant to students of complex innovation theatres: Convergences emerge when social actors narrow down the scope of their arguments and the range of issues and alternative scenarios they consider relevant to innovating their practices. Resource coalitions emerge when social actors decide to pool their resources in a joint performance. Communication networks emerge as a direct consequence of social actors' decisions to create joint learning opportunities and to produce and exchange information among themselves. Over time, where the above forms coincide, a pattern of more or less durable relationships between a limited set of social actors, an innovation configuration, may emerge. In such a configuration strategic consensus, a clear definition of tasks and responsibilities and a rational allocation of resources among social actors is possible. It also appears that each of these forms, but particularly the last one, may demonstrate inertia when faced with rapidly changing demands and/or circumstances. As a result, innovative performance may drop.To enable social actors to assess their current way of organizing for innovation, a participatory action-research methodology is proposed: RAAKS, Rapid or Relaxed Appraisal of Agricultural Knowledge Systems. Its design is based upon 'soft knowledge systems thinking', combining the philosophy and guiding principles of soft systems methodology with analytical instruments from knowledge systems research. Through active participation of relevant social actors, RAAKS aims at a threefold objective: to raise awareness and understanding, to probe new alliances and to formulate proposals for action. It guides participants through an accumulative, interactive learning process leading from problem appraisal, via a joint inquiry towards the definition of potentially useful actions and/or interventions. In recognition of the appreciative character of innovation and its social organization, RAAKS offers a choice of perspectives or 'windows' to help stakeholders recognize, organize and debate relevant ideas and events. The conceptual approach mentioned above supports the integration of the findings into a more comprehensive understanding of the social organization of innovation in each particular case.RAAKS has been field-tested over a dozen times in the Netherlands and in six countries in Central America. These experiences confirmed its relevance and applicability as a methodology, as well as its adaptability to particular demands and circumstances. RAAKS proved most useful in situations where, often ill-defined, feelings of unease persist among relevant stakeholders about the course innovation takes or its pace. It has proved useful in training (future) extension and research managers, and helping them to understand the context in which they operate. RAAKS also demonstrated its usefulness to those organizations or individuals who sell or provide 'knowledge/information intensive' products or services, such as research, extension and advisory services. It provides them with an instrument to appreciate the dynamic social context in which their products or services have to be marketed and are to prove themselves. Finally, due to its participatory character and soft systems design, RAAKS seems a promising instrument to help social actors organize themselves to deal with complex societal problems, which require higher levels of effective cooperation among stakeholders, such as natural resource management, regional development, stopping environmental degradation or waste disposal. Several experiences with RAAKS outside agriculture illustrate that its relevance to facilitating complex innovation processes is not limited to agricultural development as such.As a general conclusion, the study points at the need to amplify research on knowledge management. To facilitate knowing between agencies and organizations, interorganizational communication, whether direct or indirect, joint learning, sense making and resource pooling would have to become objects of study and eventually of (knowledge) management. Also, networking would have to be studied, its adequacy, effectiveness and efficiency in specific situations assessed and improvements designed and evaluated. The author argues that the challenge for management sciences with respect to social organization of innovation is to achieve a balance between direction and control on the one hand, and the creation and maintenance of space for serendipitous and epiphenomenal improvements on the other. In addition, he proposes RAAKS may contribute not only to facilitating innovative social practice directly, but to scientific inquiry as well. For such a purpose, its potential and limitations do need to be further evaluated. In general, he suggests, soft (knowledge) systems thinking receives far less attention from the research community than it deserves
Clinonana rafaeli Engel et Takiya, sp. nov.
No full textClinonana rafaeli Engel et Takiya sp. nov. (Figs. 1 D, 6) Measurements in mm (ɗ holotype). Total length: 16.0. Crown median length: 1.1. Pronotum median length: 2.5. Pronotum largest width: 7.2. Mesonotum largest width: 4.0. Mesonotum median length: 4.3. External morphology. Crown (Figs. 1 D, 6 A) median length three-tenths of interocular (ratio= 0.34) and transocular width (ratio= 0.26). Pronotum (Figs. 1 D, 6 A) largest width 2.9 times median length; largest width 1.8 times largest mesonotum visible width. Mesonotum (Figs. 1 D, 6 A) length 1.2 times longer than combined mesal length of crown and pronotum. Other characteristics as in generic description. Male genitalia. Styles (Figs. 6 D, E) in lateral view with median concavity on ventral margin. Aedeagus (Figs. 6 G, H) shaft preatrium pair of processes extending only until two-thirds of shaft length. Female unknown. Notes. Clinonana rafaeli sp. nov. is very similar to C. mirabilis in external morphology and male genitalia. Both species are smaller and have a less laterally expanded pronotum (Figs. 1 C, D, 4 A, 6 A) than C. impensa (Figs. 1 B, 3 A). The new species differs from C. mirabilis by the following male genital characters: style in lateral view with ventral concavity in median portion (Fig. 6 E, arrow); and aedeagal shaft thinner than in C. mirabilis, with preatrium basal processes extending only two-thirds length of shaft (Figs. 6 G, H). In C. mirabilis the basal processes reach the apex of the aedeagus shaft. Etymology. The new species epithet is in honor of the dipterist Dr. José Albertino Rafael (INPA), who coordinated projects including field work in the Brazilian Amazon which made possible the collection of specimens of Clinonana and many other leafhoppers by the junior author, besides being responsible for the collection of about half of specimens studied herein. Material examined. Holotype, Brazil: Rondônia: ɗ, Porto Velho, Campus UNIR, 8 ° 50 ' 4 " S 63 ° 56 ' 35 " W, 17 IV 2006 (F. F. Xavier & J. A. Rafael), (INPA).Published as part of Engel, Giulia & Takiya, Daniela Maeda, 2012, Synopsis of Clinonana Osborn (Hemiptera: Cicadellidae: Iassinae): new distributional records and description of a new species, pp. 19-30 in Zootaxa 3329 on pages 26-28, DOI: 10.5281/zenodo.28122
Detergent-protein and detergent-lipid interactions : implications for two-dimensional crystallization of membrane proteins and development of tools for high throughput crystallography
No full text2.1 Scope of this Thesis
This thesis represents an attempt to enlighten the role of the detergent in reconstitution and more specifically
in two-dimensional (2D) crystallogenesis of membrane proteins. The construction of a tool for precise
and routine measurements of detergent concentrations provided a valuable tool for better understanding
and controlling the detergent issue. Additionally, a novel approach for detergent removal in 2D crystallization,
i.e. the use of cyclodextrins was explored and a nanoliter dispensing high throughput tool was
developed allowing for profound and sophisticated screening of optimal conditions for protein reconstitution
and crystallization.
2.2 Combining Electron Microscopy
and Atomic Force
Microscopy
Although electron crystallography has proven to be
a powerful approach to structure determination of
membrane proteins (for a recent example see (Gonen
et al., 2005)) successes are somehow restricted
to certain classes of membrane proteins (e.g., outer
membrane porins, aquaporins, naturally occurring
crystalline proteins). This is mainly due to the stability
of these proteins with respect to biochemical
manipulation. One can not exclude however, that
these are simply more amenable to crystallization
due to the nature of their molecular surfaces.
2D crystallization exhibits several advantages
compared to 3D crystallization of membrane proteins:
The simple fact that the proteins are allowed
to reside in a native-like environment, i.e.,
the membrane and that their function is not impaired
by the lateral crystal contacts is of considerable
interest. If structural investigations shall not
be restricted to static snapshots of different conformations
and moreover structure-function relationships
shall be established, then electron microscopy
(EM) in combination with atomic force microscopy
(AFM) surely represent a valuable approach.
In Chapter 2 the combination of such data has
been successfully applied to the ammonium transporter
AmtB from Escherichia coli. The aim was to
determine the crystal packing of the double-layered
2D crystals of AmtB by AFM in order to process the
cryo EM data. Additionally, the AFM images, due
to their outstanding signal-to-noise ratio, enabled
the direct visualization of trimers in the reconstituted
membranes. The topographical data from
the AFM allowed the assessment of a single layer
within the double layered crystals.
2.3 Investigating the Role of the
Detergent
In Chapter 3 the development of a fast and precise
method for detergent concentration determination
is presented. The robustness and wide application
range of this method has been demonstrated
by comparing concentrations of radioactively
labeled dodecyl-[beta],D-maltoside (DDM) with
measured contact angles, by measuring the amount
of DDM bound to the proton/galactose symporter
GalP from E. coli, by measuring the effects
of 100 mM NaCl on the cmc of dodecyl-N,Ndimethylamine-
N-oxide, by characterizing the surface
energy of Parafilm, and finally by revealing
the stoichiometry of complex formation between
methyl-[beta]-cyclodextrin (MBCD) and different de-
tergents. The possibility of performing such measurements
routinely in membrane biochemistry is
unique compared to all other methods available to
date.
Chapter 4 addresses the major aspects of detergent
use in membrane protein purification and
crystallization. First, the stability of GalP in different
detergents is assessed, unveiling profound
differences in the capacity of detergents to keep
the protein in solution. Second, it is demonstrated,
that the amount of a detergent, i.e., dodecyl-�,Dmaltoside,
bound to a protein can be controlled
during purification. At last the amount of different
detergents for solubilization of E. coli lipids is
determined, showing differences in the mechanisms
by which detergents promote solubilization.
Banerjee et al. (Banerjee et al., 1995) examined
the preferential affinity of detergents for different
lipids in mixed membranes (such as biological membranes).
They showed that different detergents extract
the serotonin 5-HT1A receptor from native
membranes along with different lipids. The effect
is considerable and might explain why different detergents
exhibit such a different ability to keep a
protein in its native state, because some might simply
not be able to co-solubilize native lipids essential
for the stability (and function) of the protein.
The amount of detergent bound to a protein is
of special interest when using dialysis or dilution
for detergent removal. Furthermore, in most cases
the protein must not be exposed to excess detergent
which anyway fails to satisfactorily mimic the
native bilayer. As pointed out in the discussion of
Chapter 4, protein reconstitution is facilitated when
the detergent collar that is present around the hydrophobic
region of membrane proteins in solution
is near its solubility limit (Psol).
The same is true for the lipid: Reconstitution is
likely to happen when liposomes are forming, therefore
an excess of detergent is not desirable either.
Additionally, even detergents known to have adverse
effects on protein stability can be used for
lipid solubilization, given that they are present at a
minimal concentration. The use of detergent mixtures
in crystallization can also have the effect of
reducing the size of the detergent collar around the
protein. Moreover, the free detergent concentration
in detergent mixtures is altered by the presence of
the second species and can be crucial to the formation
of crystals in some cases (Koning, 2003).
When using minimal amounts of detergent in a
crystallization mixture, special care should be taken
with respect to the formation of ternary micelles.
Ideally, equilibration of the ternary mixtures prior
to detergent removal needs to be completed.
2.4 The Use of Cyclodextrins for
High Thorughput 2D Crystallization
of Membrane Proteins
Chapter 5 demonstrates the feasibility of the
cyclodextrin-based detergent removal for twodimensional
crystallization. The possibility of
choosing different kinetics, simply by adding different
amounts of cyclodextrin at various time intervals
is one of the major advantages of this method.
By implementing optical spectroscopy, it would be
possible to slow down the detergent removal rate at
the onset of proteoliposome and 2D crystal formation.
As pointed out by Lichtenberg et al. (Lichtenberg
et al., 2000) the rate of detergent removal has
to be slow enough to allow for detergent-induced
vesicle size growth, a process which is usually quite
slow. This aspect is important to keep in mind as
one defines the rate of detergent neutralization (in
contrast to dialysis). At a first glance one might
think that in this respect the cyclodextrin approach
bears no advantage compared to dialysis. However,
the rate of low-cmc detergent removal using dialysis
can be too slow, thereby keeping the protein out
from its native environment for too long, ultimately
promoting its precipitation.
In Chapter 6 we present an apparatus for parallel
quantitative reconstitution and 2D crystallization
of membrane proteins. Cyclodextrin provides a
unique opportunity for high throughput implementation
compared to other methods available today.
Protein concentrating through controlled evaporation
with concomitant detergent neutralization (to
prevent detergent concentrating) is advantageous
compared to commercially available protein concentrating
devices which very often concentrate detergent
micelles too. Moreover, the possibility of using
one protein preparation for wide screening ensures
that inconsistencies in results arising from preparative
differences are excluded. Often, the detergent
and lipid concentration of the purified protein are
ill characterized, and this variability may be a cause
for much of the irreproducibility and failure in crystallization
(Wiener, 2004).
So far the use of wide screening matrices (sparse
matrix design) in 2D crystallography was restricted
by the enormous number of experiments and
amount of protein needed for a rigorous screening.
The presented machine makes it possible to partially
compensate for the first bottleneck in protein
structure elucidation, which is the over-expression
of membrane proteins.
Fig. 2.1 summarizes the screening strategy based
on the criteria discussed in Chapter 6 and above.
Screening efficiency is provided by the subdivision
of the problem into multiple subproblems and by
their sequential screening.
With the high throughput approach however, a
new bottleneck arises as one will produce a large
number of crystallization trials, which have to be
screened for their outcome. Therefore –in analogy
to the x-ray community– the development of automated
sample preparation and automated electron
microscopic analysis would provide substantial support
to the 2D crystallographer.
Combining step-by-step identification of key values
necessary for crystallization (and/or efficient reconstitution)
together with high throughput screening
matrices opens up new prospects in the en
deavor to membrane protein structure and function
determination. Now it is possible to apply a
semi-rational screening strategy and this might contribute
to transform 2D crystallization from art to
science (Jap et al., 1992)
Pitfall trap sampling bias depends on body mass, temperature, and trap number: insights from an individual-based model
No full textThe diversity and community composition of ground arthropods is routinely analyzed by pitfall trap sampling, which is a cost- and time-effective method to gather large numbers of replicates but also known to generate data that are biased by species-specific differences in locomotory activity. Previous studies have looked at factors that influence the sampling bias. These studies, however, were limited to one or few species and did rarely quantify how the species-specific sampling bias shapes community-level diversity metrics. In this study, we systematically quantify the species-specific and community-level sampling bias with an allometric individual-based model that simulates movement and pitfall sampling of 10 generic ground arthropod species differing in body mass. We perform multiple simulation experiments covering different scenarios of pitfall trap number, spatial trap arrangement, temperature, and population density. We show that the sampling bias decreased strongly with increasing body mass, temperature, and pitfall trap number, while population density had no effect and trap arrangement only had little effect. The average movement speed of a species in the field integrates body mass and temperature effects and could be used to derive reliable estimates of absolute species abundance. We demonstrate how unbiased relative species abundance can be derived using correction factors that need only information on species body mass. We find that community-level diversity metrics are sensitive to the particular community structure, namely the relation between body mass and relative abundance across species. Generally, pitfall trap sampling flattens the rank-abundance distribution and leads to overestimations of ground arthropod Shannon diversity. We conclude that the correction of the species-specific pitfall trap sampling bias is necessary for the reliability of conclusions drawn from ground arthropod field studies. We propose bias correction is a manageable task using either body mass to derive unbiased relative abundance or the average speed to derive reliable estimates of absolute abundance from pitfall trap sampling
On the strong connectivity of the 2-Engel graphs of almost simple groups
No full textThe Engel graph of a finite group is a directed graph encoding the pairs
of elements in satisfying some Engel word. Recent work of Lucchini and the
third author shows that, except for a few well-understood cases, the Engel
graphs of almost simple groups are strongly connected. In this paper, we give a
refinement to this analysis
In de marge van het AUP: Inleiding bij twee kaartreeksen
No full textSince 2016 the city of Amsterdam, which is famed for its expansion plans, has been focusing on densification. As part of the council’s vision of a city with high quality of life (a circular economy, health, etc.), its Koers 2025: ruimte voor de stad (Target 2025: room for the city) programme includes densification involving at least 50,000 new dwellings. Most of these will be built in the form of tower blocks in the ‘Ring Zone’: the area between the prewar and postwar city along the A10 motorway, the circular railway line and the banks of the River IJ. In the next few years this area is to become a linking element between the centre and the districts beyond the ring, as well as a gateway to the city from the surrounding region. This will give a remarkable twist to a trend that was launched much earlier. ‘Today the existing city is not a marginal phenomenon within an endless mass of new urban development; on the contrary, new urban expansion lies in the margin of the existing city,’ wrote Erik Pasveer in 1991. The age of major urban expansion was truly over, and with it architects’ and urban planners’ focus on ‘tomorrow’s city’. The Bijlmer development, now known as South-East Amsterdam, was in that sense the last example of it. Yet Koers 2025 appears to be reviving the notion of ‘tomorrow’s city’ in a new form. History, Form & Aesthetic
Family-group names for bees (Anthophila)
No full text33 p. ; 26 cm.Includes bibliographical references (p. 17-27).The 173 family-group names for bees (Apoidea: Anthophila) are cataloged in chronological order. For each name the correct author, date, type genus, and combining stem are provided. The following names are considered nomina nuda: Phenacolletini, Ctenioschelini, Chalicodomopsini, Liphanthini, Austropanurgini, and Hoplitini. The authorship of three names (Tapinotaspidini, Hexepeolini, and Ancyloscelidina) is corrected as each was a nomen nudum when first proposed, but has been subsequently made available by other authors. The following new names are proposed herein: Scraptrinae Ascher and Engel, new subfamily (Colletidae); Neffapini Ascher, new tribe (Andrenidae: Panurginae); Afrodasypodini Engel, new tribe (Melittidae: Dasypodainae), Afrodasypoda Engel, new genus; Hesperapina Ascher and Engel, new subtribe (Melittidae: Dasypodainae); Macrogaleina Engel, new subtribe (Apidae: Xylocopinae); and Ancyloscelidina Engel and Michener, new subtribe (Apidae: Apinae). A hierarchical outline of Apoidea classification (inclusive of the digger wasps), indicating the suggested current usage of all available family-group names is appended. The name Anthophila, as proposed by Latreille, is adopted for the bees as a whole
The Faraway World Stories
No full textFrom Patricia Engel, whose novel Infinite Country was a New York Times bestseller and a Reese's Book Club pick, comes an exquisite collection of ten haunting, award-winning short stories set across the Americas and linked by themes of migration, sacrifice, and moral compromise.Two Colombian expats meet as strangers on the rainy streets of New York City, both burdened with traumatic pasts. In Cuba, a woman discovers her deceased brother's bones have been stolen, and the love of her life returns from Ecuador for a one-night visit. A cash-strapped couple hustles in Miami, to life-altering ends.The Faraway World is a collection of arresting stories from the New York Times bestselling author of Infinite Country, Patricia Engel, "a gifted storyteller whose writing shines even in the darkest corners" (The Washington Post). Intimate and panoramic, these stories bring to life the liminality of regret, the vibrancy of community, and the epic deeds and quiet moments of love
- …
