bluuebunny/crossref_metadata_2025 huggingface dataset:
Partydrogen
Authors: Senn  , Bücheli  , Schaub  , Stohler
Published: January 2007

Der Begriff Partydrogen umfasst eine Vielfalt von Substanzen, die häufig im Zusammenhang mit Parties oder Raves konsumiert werden. MDMA – oder geläufiger Ecstasy –, Amphetamine, speziell Methamphetamin, Ketamin und neuerdings auch GHB und Analoga gehören zu den häufig konsumierten Partydrogen. Das Wirkspektrum dieser Substanzen ist groß und reicht von stimulierend, entaktogen und halluzinogen bis sedierend. Untersuchungen zeigen, dass sich die Gruppe der Partygänger durch hohen Konsum in der Regel verschiedener psychoaktiver Substanzen charakterisieren lässt; es sich also potentiell um eine Risikogruppe handelt. Neben der klassischen Partydroge Ecstasy sind herkömmliche Substanzen wie Alkohol, Cannabis und Kokain ebenfalls enorm verbreitet. Der Hausarzt übernimmt eine zentrale Rolle in der (Früh)-Erkennung und Behandlung von Personen mit problematischem Partydrogenkonsum. Wichtig ist, die Betroffenen in einer ausgewogenen Art über mögliche Risiken des Konsums zu informieren. Für die Einschätzung einer Gefährdung im psychosozialen Sinn wird eine umfassende Betrachtungsweise empfohlen.
«Mein Körper gehört mir» – Kulturgeschichte und Psychologie des Piercing und Tattoo
Authors: Stirn
Published: January 2007

In heutiger Zeit können Tätowierungen und Piercings nicht länger nur als von gesellschaftlich Ausgegrenzten oder Randgruppen praktizierte, destruktive Akte der Selbstverstümmelung angesehen werden. Körperliche Markierungen finden sich in nahezu allen vorindustriellen Kulturen auf der ganzen Welt, die ihre Kunstpraktiken auf die magisch-mythische Weltsicht prähistorischer Zeiten beziehen. Die Prävalenz von Tattoo und Piercing in der deutschen Gesamtbevölkerung beträgt 8,5% bzw. 6,8%. Arbeitslose junge Männer und junge Frauen, die nicht in einer festen Partnerschaft leben, zeigen besonders hohe Prävalenzen. Körpermodifikationen korrelieren relativ stark mit «Sensation Seeking», besonders bei jungen Frauen. Sie sind zumeist Ausdruck von Individualität sowie Identitätsgenerierung sowie einem veränderten Körper- und Modebewusstsein und einem veränderten Kunstverständnis. Sie können jedoch auch einen Hinweis auf Identitätssuche und vermehrtem Risikoverhalten geben.
Alkoholmissbrauch im Jugendalter – eine Herausforderung für Hausärzte
Authors: Michaud
Published: January 2007

Der gelegentliche Konsum von Alkohol ist für die meisten Jugendlichen als normaler Schritt der Exploration von neuen Produkten und der damit verbundenen Sinnesempfindungen zu sehen. Alkoholmissbrauch, auch als problematischer Alkoholkonsum bezeichnet, ist eine Form des Konsums mit potentiell schädlichen Kurz- und Langzeitfolgen für die physische und die mentale Gesundheit. Alkoholmissbrauch kann unterschiedlich definiert werden, dies unter Verwendung von Kriterien wie starke Betrunkenheit mehr als zweimal im Leben, motorisiertes Fahren während Betrunkenheit und Binge-Drinking (Konsumation von mehr als fünf alkoholischen Getränken in Folge). Die Kurzzeitfolgen von Alkoholmissbrauch beinhalten unter anderem Gewalt und Unfälle, ungeschützten Geschlechtsverkehr sowie soziale und finanzielle Probleme. Jede Konsultation mit einer jugendlichen Person ist eine Gelegenheit für das Screening auf problematischen Konsum von psychoaktiven Substanzen, inklusive Alkohol. Dieser Artikel beinhaltet ein kurzes Set von Fragen für solch ein Screening. Bei Jugendlichen, welche problematischen Alkoholkonsum betreiben, sollten kurze motivationsfördernde Interviews mit Fokus auf Risiko-Reduktion durchgeführt werden. Jugendliche mit schwerwiegendem Alkoholmissbrauch können von einem psychotherapeutischen Ansatz mit Einbezug der Eltern in jedem Alter profitieren. Diese Maßnahmen müssen üblicherweise begleitet sein durch eine Modifikation des psychosozialen Umfelds, mit spezieller Berücksichtigung der schulischen bzw. beruflichen Situation.
Umgang mit jugendlichen Patienten zur Erfassung von Noxen in der Adoleszenz
Authors: Rutishauser
Published: January 2007

Der altersangemessene Umgang mit jugendlichen Patienten ist eine wichtige Voraussetzung für die Erfassung der Einwirkung von Noxen in der Adoleszenz. Das Angebot zu einem Gespräch mit dem Arzt allein, die Zusicherung des eingeschränkten Patientengeheimnisses auf Wunsch hin auch gegenüber den Eltern sowie eine nicht urteilende Haltung des Arztes sind wichtige vertrauensfördernde Elemente für die erfolgreiche Gesprächsführung über den Konsum von psychoaktiven Substanzen und andere potentiell auf die jugendliche Person einwirkende Noxen. Um das Patientengeheimnis auch gegenüber den Eltern wahren zu können, sind die Urteilsfähigkeit der jugendlichen Person sowie mögliche Selbst- und Fremdgefährdung abzuklären. Das wiederholte Gespräch mit jugendlichen Patienten über potentielle Noxen in der Adoleszenz sollte ein fester Bestandteil der Arztkonsultation bilden, um einen Beitrag zur umfassenden Gesundheitsförderung zu leisten.
Doping im Jugendalter
Authors: Kamber  , Mullis
Published: January 2007

Doping im Sport ist regelmäßig ein großes Thema in den Medien. Doping betrifft aber nicht nur den Spitzensport, sondern beeinflusst den ganzen Sport. Durch die Idolwirkung von Spitzensportlerinnen und -sportler sind auch Jugendliche betroffen. Genaue Daten dieser Beeinflussung oder auch über den Gebrauch von Dopingmitteln bei Jugendlichen fehlen aber weitgehend in der Schweiz. Im vorliegenden Artikel werden einige Dopingmittel mit ihrer Wirkung und Nebenwirkung vor allem auf Jugendliche vorgestellt. Zudem werden die Bestimmungen bei der Anwendung von Dopingmitteln zu therapeutischen Zwecken erläutert.
Tabak-Konsum im Kontext adoleszenter Entwicklung – was wir dagegen tun können und sollen
Authors: Horn  , Rutishauser
Published: January 2007

Die Raucherprävalenz bei Jugendlichen befindet sich immer noch auf einem viel zu hohen Niveau. Die ungebrochene und durch geschickte Werbebotschaften verstärkte Attraktivität des Rauchens als Bestandteil eines modernen, Freiheit und Jugendlichkeit verkörpernden Lebensstils erhöht zusammen mit genetischen, psychischen und sozialen Belastungen das Risiko, mit Tabak zu experimentieren und viele Jahre nicht mehr aufhören zu können. Insbesondere Jugendliche mit chronischen Erkrankungen wie Asthma bronchiale oder Diabetes geraten dadurch in eine Doppelbelastung. Auch die hohe Zahl junger RaucherInnen im Reproduktionsalter gibt wegen der daraus resultierenden Probleme Anlass zur Sorge. In den letzten Jahren konnten in bescheidenen Ansätzen Interventionsprogramme zur Reduktion der Raucherquote entwickelt werden. Deutlicher Mangel herrscht vor allem an wirksamen Strategien zur Abstinenzmotivation und zum Rauchstopp. Hier sind auch Ärztinnen und Ärzte gefordert, ihren Beitrag zu leisten. Auf die bestehenden Möglichkeiten versucht dieser Aufsatz aufmerksam zu machen. Nachhaltig können jedoch nur drastische gesundheitspolitische Maßnahmen, die in erster Linie die soziale Akzeptanz des Rauchens und letztlich die Zahl der erwachsenen Raucher vermindern, die «Tabakepidemie» auch im Jugendalter eindämmen. Das macht aber nur dann Sinn, wenn gleichzeitig die Ausbildungs- und Lebensperspektiven junger Menschen verbessert werden.
Cannabis und Jugendalter – psychoaktive Substanzen und seelische Entwicklung
Authors: Berthel
Published: January 2007

Der Konsum von Cannabis hat in den letzten Jahrzehnten stark zugenommen. Eltern und Lehrer sind verunsichert. Vielen Ärzten und Therapeuten fehlen Instrumente um hier erfolgreich Hilfe anzubieten. Damit Behandlungen Erfolg versprechend sind, müssen wir ausreichendes Wissen über die Substanz, deren Wirkung, Nebenwirkung, allfällige Schädigungen haben. Gleichzeitig müssen wir die Entwicklungsphase der Adoleszenz, in der der Konsum stattfindet, kennen. Die Fragen, ob der Cannabiskonsum Psychosen auslöst, Suchtentwicklungen möglich sind oder die seelische und körperliche Entwicklung gestört werden kann, sind dabei besonders wichtig. In diesem Beitrag wird das Problem des Cannabiskonsums im Jugendalter in Beziehung zu den Aufgaben, die im Jugendalter geleistet werden müssen, dargestellt und es werden Interventionsansätze die sich bewährt haben vorgestellt.
Generalisierte Osteoporose: Grundlagen und Tücken
Authors: Rafeiner
Published: January 2007

Die generalisierte Osteoporose gehört zu den zehn häufigsten Erkrankungen. Die Bedeutung primärprophylaktischer Massnahmen ist unumstritten. In dieser Arbeit werden am Kollektiv postmenopausaler Frauen einerseits das Vorgehen zur Einschätzung des Frakturrisikos und andererseits aktuelle evidenzbasierte Pharmakotherapien beschrieben. In Abhängigkeit der individuellen Risikokonstellation wird eine Osteodensitometrie durchgeführt. In der Hausarztpraxis kann ein Grossteil der Laboruntersuchungen vorgenommen werden, welche eine Differenzierung einer primären von einer sekundären Osteoporose erlauben. Der Therapieentscheid erfolgt ebenfalls individuell unter Berücksichtigung des Risikoprofils und der Knochendichtewerte, entsprechende Richtlinien sind erarbeitet worden. Es werden Pharmakotherapien mittels Bisphosphonaten, selektiven Östrogenrezeptor-Modulatoren und Parathormon beschrieben. Vielversprechend ist Strontiumranelat, welches in der Schweiz bald die Zulassung erhalten wird.
Juckreiz bei häufigen Hauterkrankungen und therapeutische Optionen
Authors: Ballmer-Weber  , Dummer
Published: January 2007

Juckreiz ist ein Kardinalsymptom vieler entzündlicher Hauterkrankungen. Im Gegensatz zur Schmerzempfindung führt Juckreiz zum Kratzreflex. Im Rahmen entzündlicher Hauterkrankungen handelt es sich meist um einen so genannten pruritozeptiven Juckreiz, der durch entzündliche Prozesse in der Haut ausgelöst wird. Die häufigsten entzündlichen Hauterkrankungen, die Juckreiz auslösen, sind Ekzemkrankheiten wie z.B. das atopische Ekzem oder das Exsikkationsekzem. Differentialdiagnostisch muss immer eine Skabies erwogen werden. Auch die Psoriasis ist häufig mit Juckreiz vergesellschaftet. Eine weitere häufig juckende Hauterkrankung ist der Lichen ruber. Lokaltherapeutische Massnahmen stehen zunächst im Vordergrund. Diese beinhalten die Anwendung von rückfettenden Cremes und Lotions, juckreizstillenden Wirkstoffen wie Polidocanol, Capsaicin oder Menthol, gelegentlich eine Fototherapie, je nach Krankheitsbild, und systemische Medikationen, die Antihistaminika, Opiatantagonisten, eventuell Antidepressiva oder Gabapentin beinhalten können.
In Vivo Measurement of Density and Affinity of the Monoamine Vesicular Transporter in a Unilateral 6-Hydroxydopamine Rat Model of PD
Authors: Sossi Vesna , Holden James E , Topping Geoffrey J , Camborde Marie-Laure , Kornelsen Rich A , McCormick Siobhan E , Greene Jennifer , Studenov Andrei R , Ruth Thomas J , Doudet Doris J
Published: January 2007

This is the first in vivo determination of the vesicular monoamine transporter (VMAT2) density ( Bmax) and ligand–transporter affinity ( Kdapp) in six unilaterally 6-hydroxydopamine (6-OHDA) lesioned rats using micro-positron emission tomography (PET) imaging with [11C]-(+)-α-dihydrotetrabenazine (DTBZ). A multiple ligand concentration transporter assay (MLCTA) was used to determine a Bmax value of 178 ± 32 pmol/mL and a Kdapp of 47.7 ± 9.3 pmol/mL for the non-lesioned side and 30.52 ± 5.84 and 43.4 ± 15.52 pmol/mL for the lesioned side, respectively. While Bmax was significantly different between the two sides, no significant difference was observed for the Kdapp. In addition to demonstrating the feasibility of in vivo Scatchard analysis in rats, these data confirm the expectation that a 6-OHDA lesion does not affect the affinity; a much simpler binding potential (BP) measure can thus be used as a marker of lesion severity (LS) in this rat model of Parkinson's disease. A transporter occupancy curve demonstrated negligible transporter occupancy (∼1%) at a specific activity (SA) of 1100 nCi/pmol (assuming an injected dose of 100 μCi/100 g), while 10% occupancy was estimated at 100 nCi/pmol. An indirect measurement indicated that the degree of occupancy as a function of SA is independent of LS. Finally, BP measurement reproducibility was assessed and found to be 11% ± 7% for the healthy and 8% ± 12% for the lesioned side. Quantitative PET results can thus be obtained even for severely lesioned animals with the striatum on one side not clearly visible provided accurate image analysis methods are used.
Cannabinoid CB2 Receptor Activation Decreases Cerebral Infarction in a Mouse Focal Ischemia/Reperfusion Model
Authors: Zhang Ming , Martin Billy R , Adler Martin W , Razdan Raj K , Jallo Jack I , Tuma Ronald F
Published: January 2007

Cannabinoid CB2 Receptor (CB2) activation has been shown to have immunomodulatory properties without psychotropic effects. The hypothesis of this study is that selective CB2 agonist treatment can attenuate cerebral ischemia/reperfusion injury. Selective CB2 agonists (O-3853, O-1966) were administered intravenously 1 h before transient middle cerebral artery occlusion (MCAO) or 10 mins after reperfusion in male mice. Leukocyte/endothelial interactions were evaluated before MCAO, 1 h after MCAO, and 24 h after MCAO via a closed cranial window. Cerebral infarct volume and motor function were determined 24 h after MCAO. Administration of the selective CB2 agonists significantly decreased cerebral infarction (30%) and improved motor function ( P < 0.05) after 1 h MCAO followed by 23 h reperfusion in mice. Transient ischemia in untreated animals was associated with a significant increase in leukocyte rolling and adhesion on both venules and arterioles ( P < 0.05), whereas the enhanced rolling and adhesion were attenuated by both selective CB2 agonists administered either at 1 h before or after MCAO ( P < 0.05). CB2 activation is associated with a reduction in white blood cell rolling and adhesion along cerebral vascular endothelial cells, a reduction in infarct size, and improved motor function after transient focal ischemia.
Management of Trust in the E-Marketplace: The Role of the Buyer's Experience in Building Trust
Authors: Kim Myoung-Soo , Ahn Jae-Hyeon
Published: January 2007

The e-marketplace, or broker-managed online market, is one of today's most profitable e-business models. In these marketplaces, buyers routinely engage with businesses and individual sellers with whom they have had little or no prior interaction, making trust one of the most important issues in the e-marketplaces. Therefore, a clear understanding of the trust building process in the e-marketplace is important for the success in the market. In this study, we analyze the process by which e-marketplace customers develop trust in both a market-maker and sellers. Additionally, this analysis provides a theoretical framework to identify the antecedents of trust. In the framework, we suggest that the impact of trust on transaction intention is moderated by the customer's previous experiences in the e-marketplace. The theoretical model presented here was tested on survey and transaction data collected from 692 respondents. The results indicate that customers value the importance of trust in the market-maker and sellers differentially by the level of transaction experience. It is also shown that market-maker's characteristics (reputation, website's usability and security) and seller's characteristics (expertise) play an important role in the formation and development of trust toward a market-maker and sellers, respectively.
Context modulates signal meaning in primate communication
Authors: Flack Jessica C. , de Waal Frans
Published: January 2007

A central issue in the evolution of social complexity and the evolution of communication concerns the capacity to communicate about increasingly abstract objects and concepts. Many animals can communicate about immediate behavior, but to date, none have been reported to communicate about behavior during future interactions. In this study, we show that a special, unidirectional, cost-free dominance-related signal used by monkeys (pigtailed macaques:
Macaca nemestrina
) means submission (immediate behavior) or subordination (pattern of behavior) depending on the context of usage. We hypothesize that to decrease receiver uncertainty that the signal object is subordination, senders shift contextual usage from the conflict context, where the signal evolved, to a peaceful one, in which submission is unwarranted. We predict and find that deceasing receiver uncertainty through peaceful signal exchange facilitates the development of higher quality social relationships: Individuals exchanging the peaceful variant groom and reconcile more frequently and fight less frequently than individuals exchanging signals only in the conflict context or no signals. We rule out alternative hypotheses, including an underlying reciprocity rule, temperament, and proximity effects. Our results suggest that primates can communicate about behavioral patterns when these concern relationship rules. The invention of signals decreasing uncertainty about relationship state is likely to have been critical for the evolution of social complexity and to the emergence of robust power structures that feed down to influence rapidly changing individual behavior.
Maternal microchimerism in peripheral blood in type 1 diabetes and pancreatic islet β cell microchimerism
Authors: Nelson J. Lee , Gillespie Kathleen M. , Lambert Nathalie C. , Stevens Anne M. , Loubiere Laurence S. , Rutledge Joe C. , Leisenring Wendy M. , Erickson Timothy D. , Yan Zhen , Mullarkey Meghan E. , Boespflug Nick D. , Bingley Polly J. , Gale Edwin A. M.
Published: January 2007

Maternal cells have recently been found in the circulation and tissues of mothers' immune-competent children, including in adult life, and is referred to as maternal microchimerism (MMc). Whether MMc confers benefits during development or later in life or sometimes has adverse effects is unknown. Type 1 diabetes (T1D) is an autoimmune disease that primarily affects children and young adults. To identify and quantify MMc, we developed a panel of quantitative PCR assays targeting nontransmitted, nonshared maternal-specific HLA alleles. MMc was assayed in peripheral blood from 172 individuals, 94 with T1D, 54 unaffected siblings, and 24 unrelated healthy subjects. MMc levels, expressed as the genome equivalent per 100,000 proband cells, were significantly higher in T1D patients than unaffected siblings and healthy subjects. Medians and ranges, respectively, were 0.09 (0–530), 0 (0–153), and 0 (0–7.9). Differences between groups were evident irrespective of HLA genotypes. However, for patients with the T1D-associated DQB1*0302-DRB1*04 haplotype, MMc was found more often when the haplotype was paternally (70%) rather than maternally transmitted (14%). In other studies, we looked for female islet β cells in four male pancreases from autopsies, one from a T1D patient, employing FISH for X and Y chromosomes with concomitant CD45 and β cell insulin staining. Female islet β cells (presumed maternal) formed 0.39–0.96% of the total, whereas female hematopoietic cells were very rare. Thus, T1D patients have higher levels of MMc in their circulation than unaffected siblings and healthy individuals, and MMc contributes to islet β cells in a mother's progeny.
Regulated surface expression and shedding support a dual role for semaphorin 4D in platelet responses to vascular injury
Authors: Zhu Li , Bergmeier Wolfgang , Wu Jie , Jiang Hong , Stalker Timothy J. , Cieslak Marcin , Fan Ran , Boumsell Laurence , Kumanogoh Atsushi , Kikutani Hitoshi , Tamagnone Luca , Wagner Denisa D. , Milla Marcos E. , Brass Lawrence F.
Published: January 2007

Semaphorin 4D (sema4D; CD100) is an integral membrane protein and the ligand for two receptors, CD72 and plexin-B1. Soluble sema4D has been shown to evoke angiogenic responses from endothelial cells and impair monocyte migration, but the origin of soluble sema4D, particularly at sites of vascular injury, has been unclear. Here we show that platelets express sema4D and both of its receptors and provide evidence that these molecules promote thrombus formation. We also show that the surface expression of sema4D and CD72 increases during platelet activation, followed by the gradual shedding of the sema4D extracellular domain. Shedding is blocked by metalloprotease inhibitors and abolished in mouse platelets that lack the metalloprotease ADAM17 (TACE). Mice that lack sema4D exhibit delayed arterial occlusion after vascular injuryin vivo, and their platelets show impaired collagen responsesin vitro. In resting platelets, as in B lymphocytes, CD72 is associated with the protein tyrosine phosphatase SHP-1. Platelet activation causes dissociation of the complex, as does the addition of soluble sema4D. These findings suggest a dual role for sema4D in vascular responses to injury. As thrombus formation begins, platelet-associated sema4D can bind to its receptors on nearby platelets, promoting thrombus formation. As thrombus formation continues, sema4D is shed from the platelet surface and becomes available to interact with receptors on endothelial cells and monocytes, as well as continuing to interact with platelets.
RNAi-associated ssRNA-specific ribonucleases in
Tombusvirus
P19 mutant-infected plants and evidence for a discrete siRNA-containing effector complex
Authors: Omarov Rustem T. , Ciomperlik Jessica J. , Scholthof Herman B.
Published: January 2007

Tomato bushy stunt virus
(TBSV) and other tombusviruses encode a
p19
protein (P19), which is a suppressor of RNAi. Wild-type TBSV or
p19
-defective mutants initially show a similar infection course in
Nicotiana benthamiana
, but the absence of an active P19 results in viral RNA degradation followed by recovery from infection. P19 homodimers sequester 21-nt virus-derived duplex siRNAs, and it is thought that this prevents the programming of an antiviral RNA-induced silencing complex to avoid viral RNA degradation. Here we report on chromatographic fractionation (gel filtration, ion exchange, and hydroxyapatite) of extracts from healthy or infected
Nicotiana benthamiana
plants in combination with
in vitro
assays for ribonuclease activity and detection of TBSV-derived siRNAs. Only extracts of plants infected with
p19
mutants provided a source of sequence-nonspecific but ssRNA-targeted
in vitro
ribonuclease activity that coeluted with components of a wide molecular weight range. In addition, we isolated a discrete ≈500-kDa protein complex that contained ≈21-nt TBSV-derived siRNAs and that exhibited ribonuclease activity that was TBSV sequence-preferential, ssRNA-specific, divalent cation-dependent, and insensitive to a ribonuclease inhibitor. We believe that this study provides biochemical evidence for a virus–host system that infection in the absence of a fully active RNAi suppressor induces ssRNA-specific ribonuclease activity, including that conferred by a RNA-induced silencing complex, which is likely the cause for the recovery of plants from infection.
Rapid transport of large polymeric nanoparticles in fresh undiluted human mucus
Authors: Lai Samuel K. , O'Hanlon D. Elizabeth , Harrold Suzanne , Man Stan T. , Wang Ying-Ying , Cone Richard , Hanes Justin
Published: January 2007

Nanoparticles larger than the reported mesh-pore size range (10–200 nm) in mucus have been thought to be much too large to undergo rapid diffusional transport through mucus barriers. However, large nanoparticles are preferred for higher drug encapsulation efficiency and the ability to provide sustained delivery of a wider array of drugs. We used high-speed multiple-particle tracking to quantify transport rates of individual polymeric particles of various sizes and surface chemistries in samples of fresh human cervicovaginal mucus. Both the mucin concentration and viscoelastic properties of these cervicovaginal samples are similar to those in many other human mucus secretions. Unexpectedly, we found that large nanoparticles, 500 and 200 nm in diameter, if coated with polyethylene glycol, diffused through mucus with an effective diffusion coefficient (
D
eff
) only 4- and 6-fold lower than that for the same particles in water (at time scale τ = 1 s). In contrast, for smaller but otherwise identical 100-nm coated particles,
D
eff
was 200-fold lower in mucus than in water. For uncoated particles 100–500 nm in diameter,
D
eff
was 2,400- to 40,000-fold lower in mucus than in water. Much larger fractions of the 100-nm particles were immobilized or otherwise hindered by mucus than the large 200- to 500-nm particles. Thus, in contrast to the prevailing belief, these results demonstrate that large nanoparticles, if properly coated, can rapidly penetrate physiological human mucus, and they offer the prospect that large nanoparticles can be used for mucosal drug delivery.
NMR structure of a complex between the VirB9/VirB7 interaction domains of the pKM101 type IV secretion system
Authors: Bayliss Richard , Harris Richard , Coutte Loic , Monier Amy , Fronzes Remi , Christie Peter J. , Driscoll Paul C. , Waksman Gabriel
Published: January 2007

Type IV secretion (T4S) systems translocate DNA and protein effectors through the double membrane of Gram-negative bacteria. The paradigmatic T4S system in
Agrobacterium tumefaciens
is assembled from 11 VirB subunits and VirD4. Two subunits, VirB9 and VirB7, form an important stabilizing complex in the outer membrane. We describe here the NMR structure of a complex between the C-terminal domain of the VirB9 homolog TraO (TraO
CT
), bound to VirB7-like TraN from plasmid pKM101. TraO
CT
forms a β-sandwich around which TraN winds. Structure-based mutations in VirB7 and VirB9 of
A. tumefaciens
show that the heterodimer interface is conserved. Opposite this interface, the TraO structure shows a protruding three-stranded β-appendage, and here, we supply evidence that the corresponding region of VirB9 of
A. tumefaciens
inserts in the membrane and protrudes extracellularly. This complex structure elucidates the molecular basis for the interaction between two essential components of a T4S system.
Superfluid transition of homogeneous and trapped two-dimensional Bose gases
Authors: Holzmann Markus , Baym Gordon , Blaizot Jean-Paul , Laloë Franck
Published: January 2007

Current experiments on atomic gases in highly anisotropic traps present the opportunity to study in detail the low temperature phases of two-dimensional inhomogeneous systems. Although, in an ideal gas, the trapping potential favors Bose–Einstein condensation at finite temperature, interactions tend to destabilize the condensate, leading to a superfluid Kosterlitz–Thouless–Berezinskii phase with a finite superfluid mass density but no long-range order, as in homogeneous fluids. The transition in homogeneous systems is conveniently described in terms of dissociation of topological defects (vortex–antivortex pairs). However, trapped two-dimensional gases are more directly approached by generalizing the microscopic theory of the homogeneous gas. In this paper, we first derive, via a diagrammatic expansion, the scaling structure near the phase transition in a homogeneous system, and then study the effects of a trapping potential in the local density approximation. We find that a weakly interacting trapped gas undergoes a Kosterlitz–Thouless–Berezinskii transition from the normal state at a temperature slightly below the Bose–Einstein transition temperature of the ideal gas. The characteristic finite superfluid mass density of a homogeneous system just below the transition becomes strongly suppressed in a trapped gas.
High-density yeast-tiling array reveals previously undiscovered introns and extensive regulation of meiotic splicing
Authors: Juneau Kara , Palm Curtis , Miranda Molly , Davis Ronald W.
Published: January 2007

Knowing gene structure is vital to understanding gene function, and accurate genome annotation is essential for understanding cellular function. To this end, we have developed a genome-wide assay for mapping introns in
Saccharomyces cerevisiae
. Using high-density tiling arrays, we compared wild-type yeast to a mutant deficient for intron degradation. Our method identified 76% of the known introns, confirmed 18 previously predicted introns, and revealed 9 formerly undiscovered introns. Furthermore, we discovered that all 13 meiosis-specific intronic yeast genes undergo regulated splicing, which provides posttranscriptional regulation of the genes involved in yeast cell differentiation. Moreover, we found that ≈16% of intronic genes in yeast are incompletely spliced during exponential growth in rich medium, which suggests that meiosis is not the only biological process regulated by splicing. Our tiling-array assay provides a snapshot of the spliced transcriptome in yeast. This robust methodology can be used to explore environmentally distinct splicing responses and should be readily adaptable to the study of other organisms, including humans.
AP1B sorts basolateral proteins in recycling and biosynthetic routes of MDCK cells
Authors: Gravotta Diego , Deora Ami , Perret Emilie , Oyanadel Claudia , Soza Andrea , Schreiner Ryan , Gonzalez Alfonso , Rodriguez-Boulan Enrique
Published: January 2007

The epithelial-specific adaptor AP1B sorts basolateral proteins, but the trafficking routes where it performs its sorting role remain controversial. Here, we used an RNAi approach to knock down the medium subunit of AP1B (μ1B) in the prototype epithelial cell line Madin–Darby canine kidney (MDCK). μ1B-knocked down MDCK cells displayed loss of polarity of several endogenous and exogenous basolateral markers transduced via adenovirus vectors, but exhibited normal polarity of apical markers. We chose two well characterized basolateral protein markers, the transferrin receptor (TfR) and the vesicular stomatitis virus G protein, to study the sorting role of AP1B. A surface-capture assay introduced here showed that μ1B-knocked down MDCK cells plated on filters at confluency and cultured for 4.5 d, sorted TfR correctly in the biosynthetic route but incorrectly in the recycling route. In contrast, these same cells missorted vesicular stomatitis virus G apically in the biosynthetic route. Strikingly, recently confluent MDCK cells (1–3 d) displayed AP1B-dependence in the biosynthetic route of TfR, which decreased with additional days in culture. Sucrose density gradient analysis detected AP1B predominantly in TfR-rich endosomal fractions in MDCK cells confluent for 1 and 4 d. Our results are consistent with the following model: AP1B sorts basolateral proteins in both biosynthetic and recycling routes of MDCK cells, as a result of its predominant functional localization in recycling endosomes, which constitute a post-Golgi station in the biosynthetic route of some plasma membrane proteins. TfR utilizes a direct route from Golgi to basolateral membrane that is established as the epithelial monolayer matures.
Calculations of Light Pulses from an Axial-field Nitrogen Laser
Authors: Hans E B Andersson  , Rod C Tobir
Published: January 2007

The rate equations for a travelling-wave model of an axial-field N2UV-laser are solved numerically including the limiting case of saturation. It is assumed that collisional coupling of the rotational levels is negligible. Thus the laser pulses are computed by superposing the pulses emitted by the different rotational transitions. The computed and measured laser pulses are compared and the pulse timing and shape are satisfactorily predicted. A discrepancy between calculated and measured pulse power arises from uncertainties in the excitation cross-sections for electron impact excitation, in the electron energy distribution and in spurious feedback of the laser pulses. The difference in emission from the two ends of the laser is very sensitive to feedback. Strong variations in population inversion and photon density along the laser tube are predicted. The calculations show that only a part of the gas volume radiates near saturation condition.
Energy Levels of 54Mn
Authors: T Weckström  , B Fant  , I Forsblom  , M Viitasalo
Published: January 2007

Two hundred and sixty-nine resonances of the 53Cr(p,γ)54Mn reaction in the proton range E
p = 1 180-2 100 keV have been observed. The γ-ray decay of 39 resonances was investigated by means of a 80 cm3 Ge(Li) detector, and the energies and branching ratios of 55 bound states have been determined. The Q-value of the reaction was found to be 7 559.6±1.0 keV.
Theoretically Calculated Transition Probabilities and Lifetimes for the First Excited Configuration np2(n + 1)s in the Neutral As, Sb, and Bi Atoms
Authors: Lennarth Holmgren
Published: January 2007

Transition probabilities and lifetimes were calculated using two different local exchange approximations, the Hartree-Slater and the Optimized Hartree-Fock-Slater methods. Relativistic self-consistent-field wavefunctions were used to evaluate the radial integrals, and a comparison is made between the results obtained with the transition probability operator on the dipole velocity and dipole length forms. The agreement with available experimental lifetime data is discussed and predicted lifetimes are presented for the remaining levels. Intermediate wavefunctions were obtained with the aid of intermediate coupling coefficients evaluated from a fit to experimental energy levels.
Term Analysis of Fe VI
Authors: Jan Olof Ekberg
Published: January 2007

The spectrum of Fe VI has been observed by using a vacuum sliding-spark discharge and the 10.7-m grazing-incidence spectrograph and the 10.7-m normal-incidence spectrograph at the National Bureau of Standards, Washington. More than 400 lines have been classified in the region 250-1 580 Å. All terms of the configurations 3d3, 3d24sand 3d24p, except 3d2(1S)4s2Shave been established. The estimated uncertainty of the level values is ±0.4 cm-1. The 3d3, 3d24sand 3d24plevel structure has been theoretically interpreted. The energy parameters determined from a least-squares fit of the observed level values are compared with Hartree-Fock calculations. From the complete set of 3d3levels all forbidden lines of Fe VI from 1 387 to 10 000 Å have been predicted. All but two lines in the spectrum of the star RR Telescopii previously identified as forbidden Fe VI lines have been confirmed and 6 of the otherwise unexplained lines have been identified as [Fe VI].
3s3p63d ↔ 3s23p5nf Interaction in Ca III and Identification of the 3s3p63d Configuration
Authors: Jørgen E Hansen  , Willy Persson  , Alf Borgström
Published: January 2007

Perturbations in the 3p5nfconfigurations in Ca III, pointed out by Borgström, are shown to be due to interaction between 3s3p63dand the 3s23p5nfseries. The 3s3p63dconfiguration is identified and found to be located in the vicinity of the 5fconfiguration. Eigenvectors and eigenvalues, from a least-squares fit to the 3s23p5(5p+ 6p+ 4f+ 5f+ 6f) + 3s3p63dconfigurations, are given and the radial integrals determined in the fit are compared to Hartree-Fock estimates. The Hartree-Fock results for the 3s3p63dconfiguration are considerably less accurate than those for the 3s23p5nlconfigurations and the fitted 3s3p63d↔ 3s23p5nfinteraction parameters are approximately a factor of 2 smaller than the Hartree-Fock values. On this and other points, the Ca III and Sr III spectra turn out to resemble each other closely.
The 2p44f Configuration of Doubly Ionized Sodium, Na III
Authors: L Minnhagen
Published: January 2007

The analysis of the Na III spectrum in the range 2 010-1 755 Å has been extended to the 2p44fconfiguration. Twenty-seven 4flevels have been established from about 80 lines classified as 3d-4fcombinations. The two (1S)4flevels are missing, probably due to autoionization. Most 4flevels have an estimated accuracy of 0.1-0.3 cm-1relative to 3d, which means about ±3 cm-1relative to the ground level, 2p5 2P1½. The energy matrix in theJK-scheme has been fitted to the observed 4flevels. Most of them show a very pureJKcharacter. The pair-splittings are between 0.3 and 12 cm-1for (3P)4fand around 1 cm-1for (1D)4f. The Na III spectra have been recorded in a grand piano shaped 3-metre normal incidence vacuum spectrograph having a 10° angle of incidence. A concave grating with 1 200 grooves/mm gives a spectrum ranging from 430 to 2 540 Å in the first order, which can be photographed in one exposure.
Elastic Constants of KCl and NaCl from Brillouin Scattering
Authors: L Benckert  , G Bäckström
Published: January 2007

The elastic constants of KCl and NaCl have been determined by studying Brillouin scattering at 90°. The scattered light was analysed by a pressure scanned Fabry-Perot interferometer, the pressure in which was monitored by a Michelson interferometer. Our results have an accuracy comparable to the results of recent ultrasonic measurements, and the agreement between the two methods is excellent in most cases. It is believed that the accuracy of the method described here could be substantially increased by further refinements of the experimental apparatus.
Studies of the Magnetic Structure of FeSn Using the Mössbauer Effect
Authors: L Häggström  , T Ericsson  , R Wäppling  , K Chandra
Published: January 2007

From the analysis of57Fe and119Sn Mössbauer spectra a modified anti-ferromagnetic spin structure is proposed. The ferromagnetic ordering of the iron moments in the basal planes is partly destroyed and the magnetic unit cell is four times as large as the chemical unit cell, being doubled both along theaand thecaxis. The temperature variation of the reduced magnetic hyperfine field for Sn(1) strongly deviates from the corresponding quantity found for iron. The Neel temperature is found to be 368 K and the critical exponent β obtained is 0.340.
The Influence of Surface Recombination-Generation of Electron-hole Pairs on the Pinch-effect in Indium Antimonide
Authors: I I Boiko  , A G Kolluh  , V K Malyutenko  , V M Chernousenko
Published: January 2007

Theoretical and experimental investigation of the pinch-effect–a compression of the electron-hole plasma by the selfmagnetic field of a current–has been performed for crystals of indium antimonide in which the plasma was produced by impact ionization. The emphasis was on the effect of surface recombination on the current-voltage characteristics of the crystal. The experimental results obtained for crystals with different surface recombination velocities give unambiguous evidence of the presence of a pinch-effect. Data of new experiments are given, which confirm the destruction of a pinched state by an external longitudinal magnetic field.
An investigation of CoSn using Mössbauer Spectroscopy
Authors: Lennart Häggström  , Tore Ericsson  , Roger Wäppling
Published: January 2007

The compound CoSn has been studied by Mössbauer spectroscopy using the isotopes57Fe and119Sn. A considerable resemblance was found between the isomer shift and the electric quadrupole splittings for the transition metal atoms and the tin atmos, and those in the isostructural compounds FeSn and FeGe. A decrease in the57Fe isomer shifts in the sequence FeSn, CoSn, FeGe can be related to an increase of the conduction electron density.
Hydrogen Chemisorption by the Spin-density Functional Formalism. I
Authors: O Gunnarsson  , H Hjelmberg
Published: January 2007

We discuss the use of the density functional formalism in the problem of hydrogen chemisorption on metal surfaces and present support for the use of the Kohn-Sham (KS) scheme with the local spin-density approximation for exchange and correlation. The calculation by Smith, Ying and Kohn with the Hohenberg-Kohn formalism is discussed. We argue that two of their approximations, a gradient expansion for the kinetic energy and a linearization of their equations, are severe. We derive, using the KS formalism, a new, practical scheme, in which these approximations are avoided. Our formalism can be applied to various models for the metal. When solving the equations of the Kohn-Sham scheme, we utilize the fact that the adatom-induced changes are localized around the adatom. We make an expansion of these changes in a finite basis set, which is approximately complete around the adatom. Subsidiary conditions on the overcomplete basis set of pure metal plus localized functions are used to eliminate complicating sums over pure metal states. The approximations made are discussed, and the errors are shown to decrease as the size of the localized basis is increased. We give expressions for the binding energy and the electron distribution from which one can calculate the dipole moment, the location of the adsorbed atom and other ground state properties.
Charge Ratio of Cosmic-Ray Muons and Hagedorn's Thermodynamic Model
Authors: J J Torsti
Published: January 2007

Nucleon-nucleus collisions at the energy region relevant to cosmic-ray experiments were investigated by using Hagedorn's thermodynamic model. The scaling behaviour of different charge states of nucleons, pions and kaons was studied in the energy range 30 GeV <E< 100 TeV of primary nucleons. The muon charge ratioRwas calculated for muon momenta 10 GeV/c<p< 10 TeV/c. Within this range,Rwas found to increase withpby about 10%. This increase was reduced to about 7% when allowance was made for the probable energy dependence of the relative abundance of heavy nuclei in the primary radiation.
Progress in the Calculation of Free Atom HFs
Authors: Ingvar Lindgren
Published: January 2007

The present situation regarding the hyperfine theory for free atoms and ions is reviewed. The validity of various atomic models, such as the independent-particle model (unrestricted HF) and the central-field model (restricted HF) is discussed. The general treatment is based on the perturbation expansion and the effective-operator analysis. The various contributions are illustrated by means of diagrams, and different numerical techniques for evaluating diagrams are discussed, such as the use of angular-momentum graphs and inhomogeneous differential equations. As illustrations recent many-body calculations for some s and p states of alkali atoms are shown and compared with experiments.
Calculation of Magnetic and Electric Hyperfine Fields in Metals
Authors: T P Das
Published: January 2007

This article is divided into two parts. The first part deals with the theory of the origin of hyperfine fields in ferromagnetic iron and cobalt, while the second part deals with the theory of nuclear quadrupole interaction in pure non-cubic metals. In the first part, dealing with hyperfine fields in ferromagnets, the various mechanisms that can produce the hyperfine field are reviewed and their contributions, as obtained from calculated band wave-functions are analysed. Comparison is made with experiment and the possible improvements needed in the electric theory are discussed. In the second part of the article, the electronic field-gradients in a number of hcp metals are discussed. The ionic and electron contributions are analysed and comparison is made with experimental data with respect to both magnitude and sign of the quadrupole coupling constants where available. The nature of the accuracy to be expected from the use of wave-functions obtained by actual potentials and pseudo-potentials is discussed. The implications of theoretical results in the pure metals for nuclear quadrupole interaction in alloys is discussed. In the alloys, a substantial amount of experimental data is available currently by the perturbed angular correlation and other techniques.
Positive Muon Spin Precession Experiments in Metals
Authors: D E Murnick
Published: January 2007

Properties of the positive muon which can be exploited to probe microscopic magnetic field distributions in metals are reviewed. Recent experiments on μ+precession in the type II superconductors Pb0.90In0.10and Nb illustrate the technique. These data also indicate rapid muon diffusion persisting to low temperature, particularly in niobium. The results are consistent with recent quantum theories of diffusion considering the μ+as a light isotope of hydrogen.
μ+SR Spectroscopy: The Positive Muon as a Magnetic Probe in Solids
Authors: J H Brewer  , D G Fleming  , K M Crowe  , R F Johnson  , B D Patterson  , A M Portis  , F N Gygax  , A Schenck
Published: January 2007

Through its asymmetric decay, the positive muon acts as a sensitive detector of the interactions of its spin with the medium in which it comes to rest. Development of the μ+SR spectroscopy technique is described, and recent applications of the μ+ as a probe are discussed. Results for hyperfine fields in ferromagnets and impurity states in nonmetals are presented with suggestions for future studies.
Electronic States of Ions Recoiling into Vacuum and Gases
Authors: Sheldon Datz
Published: January 2007

In the study of hyperfine interactions of nuclear states created by nuclear reaction or Coulomb excitation the recoiling ion undergoes a series of collisions in which electrons are captured and lost and in which electronic excitation and deexcitation take place. A knowledge of the electronic states of the ion on a time scale comensurate with the lifetime of the nuclear states (1-100 ps) is vital to the understanding of the field at the nucleus. Atomic collision processes in dilute and dense media are discussed in terms of charge changing and excitation of both inner and ouer shell electrons and the application to some perturbed angular correlation measurements are given.
Nuclear Moments of Present Interest to Nuclear Theory
Authors: Krishna Kumar
Published: January 2007

The magnetic moments of the first 3/2+states of203, 205, 207Tl are discussed in terms of mesonic-exchange and configuration-mixing corrections. The gyromagnetic ratios of two fission isomeric states of237Pu are discussed in terms of Nilsson states for the second well in the potential energy surface. The gyromagnetic ratios of high spin states of164Er and160Dy are discussed in terms of Coriolis-Anti-Pairing and Rotation-Alignment theories. A new type of seniority quantum number, related to the number of nucleons in time-reversal-conjugate states, is proposed as an explanation for the occurrence of rotational-type quadrupole moments in deformed as well as spherical nuclei. Further tests of this seniority classification are suggested on the basis of the quadrupole moments of high-spin states and first 3+states.
Recent Developments in Measurement Techniques for Magnetic Moments of Short-Lived Nuclear States
Authors: M B Goldberg
Published: January 2007

Until some four years ago, magnetic moment measurements were confined, with few exceptions, to excited nuclear states with lifetimes longer than ∼ 10-11 s. This had to do with the problem of generating sufficiently intense fields (H ≳ 10 MGauss) at the nucleus, in controlled and quantitatively understood experimental conditions. The possibilities afforded by systems of isolated ions in this respect have since been explored by at least ten different research groups, applying a variety of techniques. The latest developments are outlined, an appraisal of certain methods is attempted and a compilation of recently determined magnetic moments appended.
New Methods and Results in Nuclear Moment Measurements Reported at the Uppsala Conference (June 10-14, 1974)
Authors: Rafael Kalish
Published: January 2007

A summary of the measurements of magnetic dipole moments and electric quadrupole moments of nuclear states reported at the Uppsala Conference on Hyperfine Interactions (June 10-14, 1974) is given (in table form) The various methods employed for the measurements of nuclear moments (mostly of excited states) are reviewed, emphasizing the advantages and disadvantages of each. Possible future developments in nuclear moment measurements are discussed.
Relaxation Rates of Excited Nuclei in Liquid Metals
Authors: D Riegel
Published: January 2007

Perturbed angular distribution methods (PAD) following nuclear reactions were applied to relaxation phenomena of excited nuclear states in liquid Ga, In, InGa alloys, Te, Hg, Tl, and Pb. Due to the selection of excited states with smallg-factors the quadrupole relaxation rate τQ-1in these metals, except in Tl, could be observed as the dominant contribution to the total rate at lower temperatures. It is suggested that the τQ-1rates in Ga, In, InGa and Hg are essentially due to the diffusion induced mechanism while the interpretation of τQ-1in Pb and Te is more complicated. Further magnetic relaxation rates of isolated impurities are deduced for four systems and quadrupole moments ofms-states in71Ge,115Sn,205Pb, and206Pb are derived from the quadrupole relaxation rates.