bluuebunny/crossref_metadata_2025 huggingface dataset:
Spatial Assimilation of Racial Minorities in Canada's Immigrant Gateway Cities
Authors: Hou Feng
Published: June 2006

This study demonstrates that conventional expectations concerning patterns of residential spatial assimilation by racial minority immigrants are likely to be altered under conditions of persistent high levels of immigration. While cross-sectional studies conclude that the traditional assimilation model fits the experience of racial minority immigrants to Canada, a different picture emerges from longitudinal changes at the group level. Using a pseudo-cohort approach, it is shown that, for some racial minority immigrants, the level of residential dissimilarity from Whites in Canada's gateway cities has risen with time. Moreover, residential proximity to Whites is becoming less salient as a marker of spatial assimilation. Differences among racial minority groups in residential distribution and exposure to own-group neighbours only reflect variations in the degree of own-group preference and capacity to build affluent ethnic communities.
Structural microanalysis with synchrotron radiation: archaeometric applications at Elettra
Authors: Mancini L. , Tromba G. , Zanini F.
Published: June 2006

Feasibility studies have been carried out at the SYRMEP beamline of the Elettra synchrotron laboratory in Trieste, with the aim of demonstrating the advantages, and evaluating the effectiveness, of synchrotron radiation phase-contrast X-ray imaging and microtomography over conventional methods in the context of archaeometry. The combination of high brilliance and high spatial coherence of third generation sources offers new opportunities for novel applications in the study of samples of cultural interest.
Absolute dating of historical buildings: the contribution of thermoluminescence (TL)
Authors: Martini M. , Sibilia E.
Published: June 2006

Thermoluminescence (TL) dating of ceramic materials is nowadays a consolidated and powerful archaeometric technique. The Luminescence Dating Laboratory of the Department of Material Science (Milano Bicocca University) started its activity in this field in 1980 and since then several thousands of samples have been successfully dated. In recent years, TL dating has been extensively and systematically applied to bricks sampled from historical buildings spanning from Roman period to the late XIX century. This particular application of TL dating technique is presented, and its potential and specificity are illustrated and discussed.
Fluorescence lifetime imaging for the analysis of works of art: application to fresco paintings and marble sculptures
Authors: Comelli D. , Valentini G. , Cubeddu R. , Toniolo L.
Published: June 2006

We have recently developed a portable system for advanced fluorescence investigation of works of art. The system is based on the measurement of both the time dependent and spectral features of fluorescence emission, after excitation with UV laser pulses. The technique is aimed at localising and identifying organic and inorganic compounds present on the surface of artworks. The time dependence of the emission is analysed with a fluorescence lifetime imaging apparatus, which allows us to measure the map of the fluorescence lifetime, combined with a portable spectrometer for recording fluorescence spectra of selected points. The characterization of the compounds present on the art object’s surfaces is carried out with analytical measurements on micro-samples collected with the assistance of the fluorescence maps. These methods have been successfully applied to characterise the fresco paintings of Filippo Lippi in the cathedral of Prato and to study the contaminants on the surface of Michelangelo’s David in Florence.
Alberto Moravia and Italian Fascism: Censorship, Racism andLe ambizioni sbagliate
Authors: Talbot George
Published: June 2006

Alberto Moravia was an ambiguous figure for the Fascists. His first novel,Gli Indifferenti, was an international success, and was praised by Bottai. His second novel,Le ambizioni sbagliate, ran into difficulties with Fascist censorship. His maternal uncle was a member of Mussolini's government. His paternal first cousins were Carlo and Nello Rosselli. This essay explores Moravia's relations with the regime in the light of archival evidence, contemporary ‘revisions’ of his reputation and recent controversy over his letters to Ciano and Mussolini.
Self-reported and test-based mobility limitations in a representative sample of Finns aged 30+
Authors: Sainio Päivi , Koskinen Seppo , Heliövaara Markku , Martelin Tuija , Härkänen Tommi , Hurri Heikki , Miilunpalo Seppo , Aromaa Arpo
Published: June 2006

Aims: The object of the present study was to acquire a comprehensive and accurate picture of mobility limitations in the Finnish adult population. Methods: A nationally representative sample of 8,028 persons aged 30+ with high participation was interviewed and examined in the Health 2000 Survey conducted in 2000—01. Mobility limitations were measured by self-reports and performance tests. Results: Perceived running difficulties were already common among persons in middle age, while difficulties in moving about indoors were frequent only among persons aged 75+. A third of women and a fifth of men aged 55+ could not reach a walking speed of 1.2 m/s. Working-aged women were more limited than men only in physically demanding tasks, but in the elderly the gender difference was evident in most mobility tasks. A substantial disagreement was found between the self-reported and test-based indicators in stair climbing. Supplementary data collection, carried out to increase participation in the health examination, as well as inclusion of institutionalized persons, provided a more complete estimate of the prevalence of mobility limitations among the elderly. Conclusions: Both self-reported and performance-based indicators are needed to achieve a comprehensive view of disability and its variation between population groups. Exclusion of institutionalized persons and low participation lead to underestimation of the occurrence of limitations. The number of persons suffering from mobility problems will increase with ageing of the population, which accentuates the importance of early intervention to maintain functional ability, especially in women.
Physicians' opinions and experiences of the Pharmaceutical Benefits Reform
Authors: Andersson Karolina , Jörgensen Tove , Carlsten Anders
Published: June 2006

Aim: To investigate opinions on and experiences of the new Pharmaceutical Benefits Reform (PBR) among physicians working in the Swedish county council of Region Västra Götaland. Methods: Questionnaires were sent to all private practitioners who had contracts with the county council of Region Västra Götaland (n=320) and a random sample of 25% of the doctors employed by the same county council (n=1,068). The questionnaire comprised questions on how the physicians had received information on the PBR and sought opinions on the introduction of generic substitution in pharmacies, workplace codes, individual prescriber codes, and the Pharmaceutical Benefits Board. Analyses were performed with logistic regression. Results: The response rate was 65%. The majority of doctors had received sufficient information about the reform, most often from their employer, followed by the Drug and Therapeutics Committees. More than half of the respondents were positive about the introduction of generic substitution, which was associated with the respondent's age, experiences, and employer. Most of the doctors thought that generic substitution could reduce the health system's pharmaceutical expenditure, which was associated with the employer. One-third reported that generic substitution had caused problems for their patients in the past month. The probability of being mainly positive towards the newly created Pharmaceutical Benefits Board, which decides on reimbursement, increased with increasing age. Conclusions: Most participating doctors had received sufficient information about the reform and thought that generic substitution could save money for society. Age, employer, and experiences appeared to influence opinions on several issues.
Low physical activity and mortality in women: Baseline lifestyle and health as alternative explanations
Authors: Carlsson Sofia , Andersson Tomas , Wolk Alicja , Ahlbom Anders
Published: June 2006

Aims: The aim of this study was to investigate the association between physical activity and mortality in post-menopausal women. In addition, the authors wanted to investigate to what extent this association could be attributed to confounding from other lifestyle factors, and to reverse causation due to a number of common health problems that may inhibit the ability to exercise. Methods: A total of 27,734 women aged 51—83 years from the Swedish Mammography Cohort were investigated. In 1997 they responded to a detailed questionnaire including questions on physical activity, diet, alcohol intake, smoking, and medical problems. During follow-up in 1999—2004, 1,232 deaths were identified by linkage to the National Population Register. Results: Women with low physical activity (≤35 MET*h/day) had a 3.22 times increased mortality (95% confidence interval (CI)=2.35—4.43) compared with the most active women (>50 MET*h/day). No increased risk was seen in women with moderate compared with high physical activity. Sedentary women tended to have a less healthy lifestyle and more health problems at baseline, e.g. almost 30% of them reported high blood pressure compared with less than 20% of active women. Baseline medical problems and lifestyle factors such as smoking, diet, and education accounted for 30% of the excess risk seen in sedentary women (24% and 6% respectively). Conclusions: This study indicates that even fairly small amounts of activity will reduce mortality in older women. However, sedentary women seemed to be a selected group with more medical problems and a less healthy lifestyle. The findings indicate that the association between physical inactivity and mortality will be overestimated if this is not taken into account.
Socioeconomic factors, country of birth, and years in Sweden are associated with first birth fertility trends during the 1990s: A national cohort study
Authors: Eggert Jan , Sundquist Kristina
Published: June 2006

Aims: Decreasing fertility rates and postponement of first birth are of considerable public health concern in many industrialized countries. Previous studies suggest that this will increase involuntary childlessness in the population. The general aim was to examine the association between sociodemographic factors and first birth fertility trends in Sweden during the 1990s. Methods: This Swedish national study examined changes in first birth rates and mean age at first birth between 1991 and 1992 (n=452,000) and 1997—98 (n=495,756). The impact of socioeconomic factors and years in Sweden on first birth fertility was examined among Swedish-born and 19 subgroups of foreign-born women aged 20—41 years. Poisson regression was used in the analysis. Results: First birth rates decreased and mean age at first birth increased between the two periods among the Swedish-born and most foreign-born women. Non-employment and low income were associated with decreased first birth fertility, and low educational status was associated with slightly increased first birth fertility. Interaction tests revealed that, in contrast to Swedish-born women, several groups of foreign-born women increased their first birth fertility even if they were non-employed or had a low income. Among foreign-born women fewer years in Sweden was significantly associated with increased first birth fertility. Conclusion: Public health information should emphasize that postponement of first birth could lead to involuntary childlessness. Health care workers need to consider the woman's socioeconomic characteristics, country of birth, and years in Sweden when such information is given.
Sense of coherence and its determinants: A comparative study of the Finnish-speaking majority and the Swedish-speaking minority in Finland
Authors: Volanen Salla-Maarit , Suominen Sakari , Lahelma Eero , Koskenvuo Markku , Silventoinen Karri
Published: June 2006

Background: Despite similar living conditions among the Finnish-speaking majority and the Swedish-speaking minority in Finland, the latter is a more advantaged group e.g. in terms of socioeconomic status and health. This study investigated (1) the level of sense of coherence (SOC), (2) the structure of generalized resistance resources (GRRs), and (3) associations of GRRs with SOC among Finnish- and Swedish-speaking Finns. Methods: The data derived from the Health and Social Support (HeSSup) Study. The sample comprised 22,937 Finnish men and women aged 20—54, including an additional sample from the Swedish-speaking population (n=2,967). The response rate was 40%. Ordinary regression analysis was used. Results: Swedish-speaking women scored 0.9 (p=0.005) and men 0.6 (p=0.05) points higher on SOC scale compared with Finnish-speaking respondents. The minor difference in the SOC level between the language groups was explained by Finnish speakers' worse psychosocial living conditions in childhood and working conditions in adulthood. Only one interaction was found: parents' divorce during childhood was associated with a significant decrease of SOC scores only for Finnish speakers. Otherwise the same GRRs had similar effects on both Finnish- and Swedish-speaking men's and women's SOC. Conclusion: The only key difference between Finnish- and Swedish-speaking Finns concerned the unequal distribution of GRRs. An increase in GRRs among Finnish speakers would probably strengthen their SOC. However, the slightly stronger level of SOC among Swedish-speaking compared with Finnish-speaking Finns is unlikely to explain the possible differences in well-being between the two language groups.
Cayley groups
Authors: Lemire Nicole , Popov Vladimir , Reichstein Zinovy
Published: June 2006

The classical Cayley map,

X
↦
(

I
n

−
X
)
(

I
n

+
X

)

−
1

X \mapsto (I_n-X)(I_n+X)^{-1}

, is a birational isomorphism between the special orthogonal group SO

n

_n

and its Lie algebra

s

o

n

{\mathfrak so}_n

, which is SO

n

_n

-equivariant with respect to the conjugating and adjoint actions, respectively. We ask whether or not maps with these properties can be constructed for other algebraic groups. We show that the answer is usually “no", with a few exceptions. In particular, we show that a Cayley map for the group SL

n

_n

exists if and only if

n
⩽
3

n \leqslant 3

, answering an old question of Luna.
Superrigidity for irreducible lattices and geometric splitting
Authors: Monod Nicolas
Published: June 2006

We prove general superrigidity results for actions of irreducible lattices on CAT

(
0
)

(0)

spaces, first in terms of the ideal boundary, and then for the intrinsic geometry (also for infinite-dimensional spaces). In particular, one obtains a new and self-contained proof of Margulis’ superrigidity theorem for uniform irreducible lattices in non-simple groups. The proofs rely on simple geometric arguments, including a splitting theorem which can be viewed as an infinite-dimensional (and singular) generalization of the Lawson-Yau/Gromoll-Wolf theorem. Appendix A gives a very elementary proof of commensurator superrigidity; Appendix B proves that all our results also hold for certain non-uniform lattices.
Persistent expression of PDX-1 in the pancreas causes acinar-to-ductal metaplasia through Stat3 activation
Authors: Miyatsuka Takeshi , Kaneto Hideaki , Shiraiwa Toshihiko , Matsuoka Taka-aki , Yamamoto Kaoru , Kato Ken , Nakamura Yumiko , Akira Shizuo , Takeda Kiyoshi , Kajimoto Yoshitaka , Yamasaki Yoshimitsu , Sandgren Eric P. , Kawaguchi Yoshiya , Wright Christopher V.E. , Fujitani Yoshio
Published: June 2006

The transcription factor pancreatic and duodenal homeobox factor 1 (PDX-1) is expressed in pancreatic progenitor cells. In exocrine pancreas, PDX-1 is down-regulated during late development, while re-up-regulation of PDX-1 has been reported in pancreatic cancer and pancreatitis. To determine whether sustained expression of PDX-1 could affect pancreas development, PDX-1 was constitutively expressed in all pancreatic lineages by transgenic approaches. The transgenic pancreas was markedly small with the replacement of acinar cells by duct-like structures, accompanied by activated Stat3. Genetic ablation of Stat3 in the transgenic pancreas profoundly suppressed the metaplastic phenotype. These results provide a mechanism of pancreatic metaplasia by which persistent PDX-1 expression cell-autonomously induces acinar-to-ductal transition through Stat3 activation.
The structural basis for regulated assembly and function of the transcriptional activator NtrC
Authors: De Carlo Sacha , Chen Baoyu , Hoover Timothy R. , Kondrashkina Elena , Nogales Eva , Nixon B. Tracy
Published: June 2006

In two-component signal transduction, an input triggers phosphorylation of receiver domains that regulate the status of output modules. One such module is the AAA+ ATPase domain in bacterial enhancer-binding proteins that remodel the σ54 form of RNA polymerase. We report X-ray solution scattering and electron microscopy structures of the activated, full-length nitrogen-regulatory protein C (NtrC) showing a novel mechanism for regulation of AAA+ ATPase assembly via the juxtaposition of the receiver domains and ATPase ring. Accompanying the hydrolysis cycle that is required for transcriptional activation, we observed major order–disorder changes in the GAFTGA loops involved in σ54 binding, as well as in the DNA-binding domains.
Sensors and signals: a coactivator/corepressor/epigenetic code for integrating signal-dependent programs of transcriptional response
Authors: Rosenfeld Michael G. , Lunyak Victoria V. , Glass Christopher K.
Published: June 2006

A decade of intensive investigation of coactivators and corepressors required for regulated actions of DNA-binding transcription factors has revealed a network of sequentially exchanged cofactor complexes that execute a series of enzymatic modifications required for regulated gene expression. These coregulator complexes possess “sensing” activities required for interpretation of multiple signaling pathways. In this review, we examine recent progress in understanding the functional consequences of “molecular sensor” and “molecular adaptor” actions of corepressor/coactivator complexes in integrating signal-dependent programs of transcriptional responses at the molecular level. This strategy imposes a temporal order for modifying programs of transcriptional regulation in response to the cellular milieu, which is used to mediate developmental/homeostatic and pathological events.
Combined ectopic expression of Pdx1 and Ptf1a/p48 results in the stable conversion of posterior endoderm into endocrine and exocrine pancreatic tissue
Authors: Afelik Solomon , Chen Yonglong , Pieler Tomas
Published: June 2006

Patterning of the embryonic endoderm into distinct sets of precursor cells involves the precisely regulated activities of key transcription regulators. Ectopic, pan-endodermal activation of XPtf1a/p48 during pancreas precursor cell stages of Xenopus embryogenesis results in an expansion of the pancreatic territory, precisely within the borders of XlHbox8 expression. A combination of both activities is sufficient to expand the pancreatic precursor cell population also into more posterior portions of the endoderm. Both treatments result in the formation of a giant pancreas that persists up to late tadpole stages of development and carries both supernumerary endocrine and exocrine cells. A combination of XPtf1a/p48 and XlHbox8 is thus sufficient to convert nonpancreatic endodermal cells into pancreatic precursor cells.
In vivo lumbar erector spinae oxygenation and blood volume measurements in healthy men during seated whole‐body vibration
Authors: Maikala Rammohan V. , Bhambhani Yagesh N.
Published: June 2006

Exposure to whole‐body vibration is implicated as one of the occupational risk factors for lower back disorders; however, its influence on the lumbar muscle physiology is still poorly understood. The objective of this study was to investigate the effects of backrest support and hand grip contractions on lumbar muscle oxygenation and blood volume responses during seated whole‐body vibration using continuous dual‐wave near‐infrared spectroscopy. Thirteen healthy men were exposed to frequencies of 3, 4.5 and 6 Hz on a vibration simulator, in randomized order on separate days. Each day the duration of the protocol was 30 min. During the fifth minute of vibration ‘with’ and ‘without’ backrest support, participants performed maximal rhythmic hand grip contractions for 1 min. In general, erector spinae oxygenation and blood volume showed a trend to decrease with vibration exposure compared to the control condition. However, these responses were not influenced by the change in vibration frequency (P > 0.05). Sitting without backrest resulted in a greater decrease in oxygenation (by 27%, P= 0.02) and blood volume (by 11%, P= 0.05) than with backrest, implying a deficiency in oxygen supply owing to the sitting posture. Compared to the vibration‐only condition, hand grip work decreased both oxygenation (by 22%, P= 0.003) and blood volume responses (by 13%, P= 0.04), suggesting that postural load due to prolonged sitting combined with physical activity during vibration might further burden paraspinal muscles. The influence of adipose tissue thickness of the lumbar muscle on optically derived oxygenation and blood volume changes was inconclusive.
Neuronal relays in double crossed pathways between feline motor cortex and ipsilateral hindlimb motoneurones
Authors: Jankowska E. , Stecina K. , Cabaj A. , Pettersson L.‐G. , Edgley S. A.
Published: June 2006

Coupling between pyramidal tract (PT) neurones and ipsilateral hindlimb motoneurones was investigated by recording from commissural interneurones interposed between them. Near maximal stimulation of either the left or right PT induced short latency EPSPs in more than 80% of 20 commissural interneurones that were monosynaptically excited by reticulospinal tract fibres in the medial longitudinal fascicle (MLF). The EPSPs were evoked at latencies that were only 1–2 ms longer than those of EPSPs evoked from the MLF, compatible with a disynaptic coupling between PT fibres and these commissural interneurones. EPSPs evoked by PT stimulation were frequently associated with IPSPs which either followed or preceded the EPSPs. The latencies of the IPSPs (on average about 1 ms longer than latencies of the earliest EPSPs) indicated that they were mediated via single additional inhibitory interneurones. Records from a sample of nine commissural interneurones from a different population (with monosynaptic input from group I and/or II muscle afferents, and disynaptically excited from the MLF) suggest that actions of PT fibres on such interneurones are weaker because only four of them were excited by PT stimuli and at longer latencies. By demonstrating disynaptic coupling between PT neurones and commissural interneurones via reticulospinal fibres, the results provide a direct demonstration of trisynaptic coupling in the most direct pathways between PT neurones and ipsilateral motoneurones, and thereby strengthen the proposal that the double crossed pathways between PT neurones and ipsilateral motoneurones might be used to replace crossed actions of damaged PT neurones.
Juvenile Hormone Is Required to Couple Imaginal Disc Formation with Nutrition in Insects
Authors: Truman J. W. , Hiruma K. , Allee J. P. , MacWhinnie S. G. B. , Champlin D. T. , Riddiford L. M.
Published: June 2006

In starved larvae of the tobacco hornworm mothManduca sexta, larval and imaginal tissues stop growing, the former because they lack nutrient-dependent signals but the latter because of suppression by juvenile hormone. Without juvenile hormone, imaginal discs form and grow despite severe starvation. This hormone inhibits the intrinsic signaling needed for disc morphogenesis and does so independently of ecdysteroid action. Starvation and juvenile hormone treatments allowed the separation of intrinsic and nutrient-dependent aspects of disc growth and showed that both aspects must occur during the early phases of disc morphogenesis to ensure normal growth leading to typical-sized adults.
Direct Determination of Local Lattice Polarity in Crystals
Authors: Mkhoyan K. A. , Batson P. E. , Cha J. , Schaff W. J. , Silcox J.
Published: June 2006

With current advances in sub-angstrom resolution scanning transmission electron microscopy (STEM), it is now possible to image directly local crystal structures of materials where dramatically different atoms are separated from each other at distances about or less than 1 angstrom. We achieved direct imaging of atomic columns of nitrogen in close proximity to columns of aluminum in wurtzite aluminum nitride by using annular dark field imaging in an aberration-corrected STEM. This ability allows direct determination of the local polarity in nanoscale crystals and crystal defects.
Response to Comment on "
HST2
Mediates
SIR2
-Independent Life-Span Extension by Calorie Restriction"
Authors: Lamming Dudley W. , Latorre-Esteves Magda , Medvedik Oliver , Wong Stacy N. , Tsang Felicia A. , Wang Chen , Lin Su-Ju , Sinclair David A.
Published: June 2006

Our two labs and others have shown that
SIR2
controls the life span of diverse species, including
Saccharomyces cerevisiae
and
Drosophila melanogaster,
and that deleting
SIR2
blocks life-span extension by calorie restriction. The methods of Kaeberlein
et al
. allow yeast to bypass the requirement for
SIR2
and its homologs, which brings into question their suitability for modeling the physiology of more complex organisms.
Checkpoint Proteins Control Survival of the Postmitotic Cells in
Caenorhabditis elegans
Authors: Olsen Anders , Vantipalli Maithili C. , Lithgow Gordon J.
Published: June 2006

Checkpoints are evolutionarily conserved signaling mechanisms that arrest cell division and alter cellular stress resistance in response to DNA damage or stalled replication forks. To study the consequences of loss of checkpoint functions in whole animals, checkpoint genes were inactivated in the nematode
C. elegans
. We show that checkpoint proteins are not only essential for normal development but also determine adult somatic maintenance. Checkpoint proteins play a role in the survival of postmitotic adult cells.
From Disorder to Order in Marching Locusts
Authors: Buhl J. , Sumpter D. J. T. , Couzin I. D. , Hale J. J. , Despland E. , Miller E. R. , Simpson S. J.
Published: June 2006

Recent models from theoretical physics have predicted that mass-migrating animal groups may share group-level properties, irrespective of the type of animals in the group. One key prediction is that as the density of animals in the group increases, a rapid transition occurs from disordered movement of individuals within the group to highly aligned collective motion. Understanding such a transition is crucial to the control of mobile swarming insect pests such as the desert locust. We confirmed the prediction of a rapid transition from disordered to ordered movement and identified a critical density for the onset of coordinated marching in locust nymphs. We also demonstrated a dynamic instability in motion at densities typical of locusts in the field, in which groups can switch direction without external perturbation, potentially facilitating the rapid transfer of directional information.
Size Matters More Than Chemistry for Cloud-Nucleating Ability of Aerosol Particles
Authors: Dusek U. , Frank G. P. , Hildebrandt L. , Curtius J. , Schneider J. , Walter S. , Chand D. , Drewnick F. , Hings S. , Jung D. , Borrmann S. , Andreae M. O.
Published: June 2006

Size-resolved cloud condensation nuclei (CCN) spectra measured for various aerosol types at a non-urban site in Germany showed that CCN concentrations are mainly determined by the aerosol number size distribution. Distinct variations of CCN activation with particle chemical composition were observed but played a secondary role. When the temporal variation of chemical effects on CCN activation is neglected, variation in the size distribution alone explains 84 to 96% of the variation in CCN concentrations. Understanding that particles' ability to act as CCN is largely controlled by aerosol size rather than composition greatly facilitates the treatment of aerosol effects on cloud physics in regional and global models.
The Rubble-Pile Asteroid Itokawa as Observed by Hayabusa
Authors: Fujiwara A. , Kawaguchi J. , Yeomans D. K. , Abe M. , Mukai T. , Okada T. , Saito J. , Yano H. , Yoshikawa M. , Scheeres D. J. , Barnouin-Jha O. , Cheng A. F. , Demura H. , Gaskell R. W. , Hirata N. , Ikeda H. , Kominato T. , Miyamoto H. , Nakamura A. M. , Nakamura R. , Sasaki S. , Uesugi K.
Published: June 2006

During the interval from September through early December 2005, the Hayabusa spacecraft was in close proximity to near-Earth asteroid 25143 Itokawa, and a variety of data were taken on its shape, mass, and surface topography as well as its mineralogic and elemental abundances. The asteroid's orthogonal axes are 535, 294, and 209 meters, the mass is 3.51 × 10
10
kilograms, and the estimated bulk density is 1.9 ± 0.13 grams per cubic centimeter. The correspondence between the smooth areas on the surface (Muses Sea and Sagamihara) and the gravitationally low regions suggests mass movement and an effective resurfacing process by impact jolting. Itokawa is considered to be a rubble-pile body because of its low bulk density, high porosity, boulder-rich appearance, and shape. The existence of very large boulders and pillars suggests an early collisional breakup of a preexisting parent asteroid followed by a re-agglomeration into a rubble-pile object.
Outer Membrane Active Transport: Structure of the BtuB:TonB Complex
Authors: Shultis David D. , Purdy Michael D. , Banchs Christian N. , Wiener Michael C.
Published: June 2006

In Gram-negative bacteria, the import of essential micronutrients across the outer membrane requires a transporter, an electrochemical gradient of protons across the inner membrane, and an inner membrane protein complex (ExbB, ExbD, TonB) that couples the proton-motive force to the outer membrane transporter. The inner membrane protein TonB binds directly to a conserved region, called the Ton-box, of the transporter. We solved the structure of the cobalamin transporter BtuB in complex with the C-terminal domain of TonB. In contrast to its conformations in the absence of TonB, the Ton-box forms a β strand that is recruited to the existing β sheet of TonB, which is consistent with a mechanical pulling model of transport.
Structure of TonB in Complex with FhuA,
E. coli
Outer Membrane Receptor
Authors: Pawelek Peter D. , Croteau Nathalie , Ng-Thow-Hing Christopher , Khursigara Cezar M. , Moiseeva Natalia , Allaire Marc , Coulton James W.
Published: June 2006

The cytoplasmic membrane protein TonB spans the periplasm of the Gram-negative bacterial cell envelope, contacts cognate outer membrane receptors, and facilitates siderophore transport. The outer membrane receptor FhuA from
Escherichia coli
mediates TonB-dependent import of ferrichrome. We report the 3.3 angstrom resolution crystal structure of the TonB carboxyl-terminal domain in complex with FhuA. TonB contacts stabilize FhuA's amino-terminal residues, including those of the consensus Ton box sequence that form an interprotein β sheet with TonB through strand exchange. The highly conserved TonB residue arginine-166 is oriented to form multiple contacts with the FhuA cork, the globular domain enclosed by the β barrel.
An Octahedral Coordination Complex of Iron(VI)
Authors: Berry John F. , Bill Eckhard , Bothe Eberhard , George Serena DeBeer , Mienert Bernd , Neese Frank , Wieghardt Karl
Published: June 2006

The hexavalent state, considered to be the highest oxidation level accessible for iron, has previously been found only in the tetrahedral ferrate dianion, FeO
4
2–
. We report the photochemical synthesis of another Fe(VI) compound, an octahedrally coordinated dication bearing a terminal nitrido ligand. Mössbauer and x-ray absorption spectra, supported by density functional theory, are consistent with the octahedral structure having an Fe

N triple bond of 1.57 angstroms and a singlet

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ground electronic configuration. The compound is stable at 77 kelvin and yields a high-spin Fe(III) species upon warming.
Ecology of Antibiotic Resistance Genes: Characterization of Enterococci from Houseflies Collected in Food Settings
Authors: Macovei Lilia , Zurek Ludek
Published: June 2006

In this project, enterococci from the digestive tracts of 260 houseflies (
Musca domestica
L.) collected from five restaurants were characterized. Houseflies frequently (97% of the flies were positive) carried enterococci (mean, 3.1 × 10
3
CFU/fly). Using multiplex PCR, 205 of 355 randomly selected enterococcal isolates were identified and characterized. The majority of these isolates were
Enterococcus faecalis
(88.2%); in addition, 6.8% were
E. faecium
, and 4.9% were
E. casseliflavus. E. faecalis
isolates were phenotypically resistant to tetracycline (66.3%), erythromycin (23.8%), streptomycin (11.6%), ciprofloxacin (9.9%), and kanamycin (8.3%). Tetracycline resistance in
E. faecalis
was encoded by
tet
(M) (65.8%),
tet
(O) (1.7%), and
tet
(W) (0.8%). The majority (78.3%) of the erythromycin-resistant
E. faecalis
isolates carried
erm
(B). The conjugative transposon Tn
916
and members of the Tn
916/
Tn
1545
family were detected in 30.2% and 34.6% of the identified isolates, respectively.
E. faecalis
carried virulence genes, including a gelatinase gene (
gelE
; 70.7%), an aggregation substance gene (
asa1
; 33.2%), an enterococcus surface protein gene (
esp
; 8.8%), and a cytolysin gene (
cylA
; 8.8%). Phenotypic assays showed that 91.4% of the isolates with the
gelE
gene were gelatinolytic and that 46.7% of the isolates with the
asa1
gene aggregated. All isolates with the
cylA
gene were hemolytic on human blood. This study showed that houseflies in food-handling and -serving facilities carry antibiotic-resistant and potentially virulent enterococci that have the capacity for horizontal transfer of antibiotic resistance genes to other bacteria.
New Recombinant
Escherichia coli
Strain Tailored for the Production of Poly(3-Hydroxybutyrate) from Agroindustrial By-Products
Authors: Nikel Pablo I. , de Almeida Alejandra , Melillo Evelia C. , Galvagno Miguel A. , Pettinari M. Julia
Published: June 2006

A recombinant
E. coli
strain (K24K) was constructed and evaluated for poly(3-hydroxybutyrate) (PHB) production from whey and corn steep liquor as main carbon and nitrogen sources. This strain bears the
pha
biosynthetic genes from
Azotobacter
sp. strain FA8 expressed from a T5 promoter under the control of the lactose operator. K24K does not produce the lactose repressor, ensuring constitutive expression of genes involved in lactose transport and utilization. PHB was efficiently produced by the recombinant strain grown aerobically in fed-batch cultures in a laboratory scale bioreactor on a semisynthetic medium supplemented with the agroindustrial by-products. After 24 h, cells accumulated PHB to 72.9% of their cell dry weight, reaching a volumetric productivity of 2.13 g PHB per liter per hour. Physical analysis of PHB recovered from the recombinants showed that its molecular weight was similar to that of PHB produced by
Azotobacter
sp. strain FA8 and higher than that of the polymer from
Cupriavidus necator
and that its glass transition temperature was approximately 20°C higher than those of PHBs from the natural producer strains.
Necrotrophic Growth of
Legionella pneumophila
Authors: Temmerman R. , Vervaeren H. , Noseda B. , Boon N. , Verstraete W.
Published: June 2006

This study examined whether
Legionella pneumophila
is able to thrive on heat-killed microbial cells (necrotrophy) present in biofilms or heat-treated water systems. Quantification by means of plate counting, real-time PCR, and flow cytometry demonstrated necrotrophic growth of
L. pneumophila
in water after 96 h, when at least 100 dead cells are available to one
L. pneumophila
cell. Compared to the starting concentration of
L. pneumophila
, the maximum observed necrotrophic growth was 1.89 log units for real-time PCR and 1.49 log units for plate counting. The average growth was 1.57 ± 0.32 log units (
n
= 5) for real-time PCR and 1.14 ± 0.35 log units (
n
= 5) for plate counting. Viability staining and flow cytometry showed that the fraction of living cells in the
L. pneumophila
population rose from the initial 54% to 82% after 96 h. Growth was measured on heat-killed
Pseudomonas putida
,
Escherichia coli
,
Acanthamoeba castellanii
,
Saccharomyces boulardii
, and a biofilm sample. Gram-positive organisms did not result in significant growth of
L. pneumophila
, probably due to their robust cell wall structure. Although necrotrophy showed lower growth yields compared to replication within protozoan hosts, these findings indicate that it may be of major importance in the environmental persistence of
L. pneumophila
. Techniques aimed at the elimination of protozoa or biofilm from water systems will not necessarily result in a subsequent removal of
L. pneumophila
unless the formation of dead microbial cells is minimized.
Yersiniabactin Production by
Pseudomonas syringae
and
Escherichia coli
, and Description of a Second Yersiniabactin Locus Evolutionary Group
Authors: Bultreys Alain , Gheysen Isabelle , de Hoffmann Edmond
Published: June 2006

The siderophore and virulence factor yersiniabactin is produced by
Pseudomonas syringae
. Yersiniabactin was originally detected by high-pressure liquid chromatography (HPLC); commonly used PCR tests proved ineffective. Yersiniabactin production in
P. syringae
correlated with the possession of
irp1
located in a predicted yersiniabactin locus. Three similarly divergent yersiniabactin locus groups were determined: the
Yersinia pestis
group, the
P. syringae
group, and the
Photorhabdus luminescens
group; yersiniabactin locus organization is similar in
P. syringae
and
P. luminescens
. In
P. syringae
pv. tomato DC3000, the locus has a high GC content (63.4% compared with 58.4% for the chromosome and 60.1% and 60.7% for adjacent regions) but it lacks high-pathogenicity-island features, such as the insertion in a tRNA locus, the integrase, and insertion sequence elements. In
P. syringae
pv. tomato DC3000 and pv. phaseolicola 1448A, the locus lies between homologues of Psyr_2284 and Psyr_2285 of
P. syringae
pv. syringae B728a, which lacks the locus. Among tested pseudomonads, a PCR test specific to two yersiniabactin locus groups detected a locus in genospecies 3, 7, and 8 of
P. syringae
, and DNA hybridization within
P. syringae
also detected a locus in the pathovars phaseolicola and glycinea. The PCR and HPLC methods enabled analysis of nonpathogenic
Escherichia coli
. HPLC-proven yersiniabactin-producing
E. coli
lacked modifications found in
irp1
and
irp2
in the human pathogen CFT073, and it is not clear whether CFT073 produces yersiniabactin. The study provides clues about the evolution and dispersion of yersiniabactin genes. It describes methods to detect and study yersiniabactin producers, even where genes have evolved.
New Lineage of Filamentous, Spore-Forming, Gram-Positive Bacteria from Soil
Authors: Cavaletti Linda , Monciardini Paolo , Bamonte Ruggiero , Schumann Peter , Rohde Manfred , Sosio Margherita , Donadio Stefano
Published: June 2006

A novel bacterial strain that was isolated from an Italian soil and was designated SOSP1-21
T
forms branched mycelia in solid and liquid media and has a filamentous morphology similar to that of some genera belonging to the
Actinobacteria
. Electron microscopy showed that this organism has a grape-like appearance, resulting from interlacing of spores originating from sporophoric hyphae. Ten strains that are morphologically related to SOSP1-21
T
were recovered from soil. Phylogenetic analyses of 16S rRNA gene segments confirmed the relatedness of these strains to SOSP1-21
T
and indicated that the newly isolated strains form separate clades in a deeply branching lineage. The closest matches for the 16S rRNA sequences of all the strains (around 79% identity) were matches with representatives of the
Chloroflexi
, although the affiliation with this division was not supported by high bootstrap values. The strains are mesophilic aerobic heterotrophs and are also capable of growing under microaerophilic conditions. They all stain gram positive. Strain SOSP1-21
T
contains ornithine, alanine, glutamic acid, serine, and glycine as the peptidoglycan amino acids. In addition, an unusual level of C16:1 2OH (30%) was found in the cellular fatty acids. The G+C content of SOSP1-21
T
genomic DNA is 53.9%, and MK-9(H
2
) was the only menaquinone detected. All these data suggest that SOSP1-21
T
and the related strains may constitute a new division of filamentous, spore-forming, gram-positive bacteria. We propose the name
Ktedobacter racemifer
gen. nov., sp. nov. for strain SOSP1-21
T
.
A Virulence and Antimicrobial Resistance DNA Microarray Detects a High Frequency of Virulence Genes in
Escherichia coli
Isolates from Great Lakes Recreational Waters
Authors: Hamelin Katia , Bruant Guillaume , El-Shaarawi Abdel , Hill Stephen , Edge Thomas A. , Bekal Sadjia , Fairbrother John Morris , Harel Josée , Maynard Christine , Masson Luke , Brousseau Roland
Published: June 2006

Escherichia coli
is generally described as a commensal species with occasional pathogenic strains. Due to technological limitations, there is currently little information concerning the prevalence of pathogenic
E. coli
strains in the environment. For the first time, using a DNA microarray capable of detecting all currently described virulence genes and commonly found antimicrobial resistance genes, a survey of environmental
E. coli
isolates from recreational waters was carried out. A high proportion (29%) of 308 isolates from a beach site in the Great Lakes carried a pathotype set of virulence-related genes, and 14% carried antimicrobial resistance genes, findings consistent with a potential risk for public health. The results also showed that another 8% of the isolates had unusual virulence gene combinations that would be missed by conventional screening. This new application of a DNA microarray to environmental waters will likely have an important impact on public health, epidemiology, and microbial ecology in the future.
Validation of AKACID Plus as a Room Disinfectant in the Hospital Setting
Authors: Kratzer Christina , Tobudic Selma , Assadian Ojan , Buxbaum Astrid , Graninger Wolfgang , Georgopoulos Apostolos
Published: June 2006

AKACID Plus, a novel polymeric guanidine with broad antimicrobial activity against multiantibiotic-resistant bacterial strains, was used in the present study as a room disinfectant. Disinfection of closed rooms experimentally contaminated with antibiotic-susceptible and multiresistant
Staphylococcus aureus
(MRSA),
Pseudomonas aeruginosa
, and
Escherichia coli
was performed using AKACID Plus at concentrations of 0.1, 0.25, and 0.5% for 100 min. Bacterial suspensions were distributed on plastic and stainless steel plates and placed in a test room. Recovery of the test microorganisms was determined before nebulizing, 60 and 100 min after initiation, and 4 h after the end of room disinfection by a simple swab-rinse technique. The swab-rinse method demonstrated a dose- and time-dependent effectiveness of AKACID Plus in eradicating
S. aureus
,
E. coli
, and
P. aeruginosa
on plastic and stainless steel plates. Nebulized 0.5% AKACID Plus was successful in eliminating all hospital pathogens within 340 min. After the use of 0.25% AKACID Plus, MRSA was still detectable on microbial carrier plates. The test concentration of 0.1% AKACID Plus achieved a significant reduction of
S. aureus
and
P. aeruginosa
on plastic and stainless steel plates but was sufficient to eradicate only
E. coli
. These results suggest that nebulized AKACID Plus at a concentration of 0.5% is a potent substance for eradication of pathogenic organisms in the hospital setting.
Isolation, Characterization, and Heterologous Expression of the Biosynthesis Gene Cluster for the Antitumor Anthracycline Steffimycin
Authors: Gullón Sonia , Olano Carlos , Abdelfattah Mohamed S. , Braña Alfredo F. , Rohr Jürgen , Méndez Carmen , Salas José A.
Published: June 2006

The biosynthetic gene cluster for the aromatic polyketide steffimycin of the anthracycline family has been cloned and characterized from “
Streptomyces steffisburgensis
” NRRL 3193. Sequence analysis of a 42.8-kbp DNA region revealed the presence of 36 open reading frames (ORFs) (one of them incomplete), 24 of which, spanning 26.5 kb, are probably involved in steffimycin biosynthesis. They code for all the activities required for polyketide biosynthesis, tailoring, regulation, and resistance but show no evidence of genes involved in
l
-rhamnose biosynthesis. The involvement of the cluster in steffimycin biosynthesis was confirmed by expression of a region of about 15 kb containing 15 ORFS, 11 of them forming part of the cluster, in the heterologous host
Streptomyces albus
, allowing the isolation of a biosynthetic intermediate. In addition, the expression in
S. albus
of the entire cluster, contained in a region of 34.8 kb, combined with the expression of plasmid pRHAM, directing the biosynthesis of
l
-rhamnose, led to the production of steffimycin. Inactivation of the
stfX
gene, coding for a putative cyclase, revealed that this enzymatic activity participates in the cyclization of the fourth ring, making the final steps in the biosynthesis of the steffimycin aglycon similar to those in the biosynthesis of jadomycin or rabelomycin. Inactivation of the
stfG
gene, coding for a putative glycosyltransferase involved in the attachment of
l
-rhamnose, allowed the production of a new compound corresponding to the steffimycin aglycon compound also observed in
S. albus
upon expression of the entire cluster.
Identification of a DNA Methyltransferase Gene Carried on a Pathogenicity Island-Like Element (VPAI) in
Vibrio parahaemolyticus
and Its Prevalence among Clinical and Environmental Isolates
Authors: Wang Hui-zhen , Wong Minnie M. L. , O'Toole Desmond , Mak Mandy M. H. , Wu Rudolf S. S. , Kong Richard Y. C.
Published: June 2006

In this study we identified a putative virulence-associated DNA methyltransferase (MTase) gene carried on a novel 22.79-kb pathogenicity island-like element (VPAI) in
V. parahaemolyticus
. The
V. parahaemolyticus
MTase gene was shown by PCR to be prevalent (>98%) in pandemic thermostable direct hemolysin gene-positive isolates, which suggests that VPAI may confer unique virulence traits to pandemic strains of
V. parahaemolyticus
.