bluuebunny/crossref_metadata_2025 huggingface dataset:
Xenogenic demineralized bone matrix and fresh autogenous cortical bone effects on experimental bone healing: radiological, histopathological and biomechanical evaluation
Authors: Bigham A. S. , Dehghani S. N. , Shafiei Z. , Torabi Nezhad S.
Published: May 2008

Background

Bone grafting is used to enhance healing in osteotomies, arthrodesis, and multifragmentary fractures and to replace bony loss resulting from neoplasia or cysts. They are source of osteoprogenitor cells and induce bone formation and provide mechanical support for vascular and bone ingrowth. Autografts are used commonly but quantity of harvested bone is limited. The aim of this study is to evaluate autograft and new xenogenic bovine demineralized bone matrix (DBM) effects on bone healing process.

Materials and methods

Twenty male White New Zealand rabbits were used in this study. In group I (n = 10) the defect was filled by xenogenic DBM and in autograft group the defect was filled by fresh autogenous cortical graft and fixed by cercelage wire. Radiological, histopathological and biomechanical evaluations were performed blindly and results scored and analyzed statistically.

Results

Statistical tests did not reveal any significant differences between two groups on the 14th postoperative day radiographically (P > 0.05). There was a significant difference for union on 28th and 42nd postoperative days and for remodeling at on the 56th postoperative day radiologically (P < 0.05). Statistical tests did not support any significant differences between two groups for radiological bone formation (P > 0.05). Histopathological and biomechanical evaluation revealed no significant differences between two groups.

Conclusions

The results of this study indicate that satisfactory healing occurred in rabbit radius defect filled with xenogenic bovine DBM. Complications were not identified and healing was faster, same as in cortical autogenous grafting.
Quality of embryonic bodies and seeding density effects on neural differentiation of mouse embryonic stem cells
Authors: Zhou Jun‐Mei , Xing Feng‐Ying , Shi Jian‐Jun , Fang Zhen‐Fu , Chen Xue‐Jin , Chen Fang
Published: May 2008

Mouse embryonic stem (ES) cells can be differentiated into neural lineage cells, but the differentiation efficiency remains low. This study revealed two important factors that influence the neural differentiation efficiency of mouse ES cells: the first is the quality of embryonic bodies (EBs); good quality of EBs consistently originated from a suspension culture of 1 × 105 ES cells/ml serum‐free chemically defined neural inducing medium and they exhibited a smooth round shape, with a dark central region surrounded by a light band. Such EBs are capable of attaining high neural differentiation efficiency. However, poor quality EBs originated from a suspension culture of 1 × 106 ES cells/ml serum‐free chemically defined neural inducing medium and exhibited an irregular shape or adhered to the bottom of the dish; they displayed low neural differentiation efficiency. The second factor is the seeding density of EBs: a low seeding density (5 EBs/cm2) induced cells to differentiate into a more caudalized subtypes compared to the cells obtained from high seeding density (20 EBs/cm2). These findings provided fresh insight into the neural induction of mouse ES cells.
Impact of the microgravity environment in a 3‐dimensional clinostat on osteoblast‐ and osteoclast‐like cells
Authors: Makihira Seicho , Kawahara Yumi , Yuge Louis , Mine Yuichi , Nikawa Hiroki
Published: May 2008

Mechanical unloading conditions result in decreases in bone mineral density and quantity, which may be partly attributed to an imbalance in bone formation and resorption. To investigate the effect of mechanical unloading on osteoblast and osteoclast differentiation, and the expression of RANKL and OPG genes in osteoblasts, we used a three‐dimensional (3D) clinostat system simulating microgravity to culture MC3T3‐E1 and RAW264.7 cells. Long‐term exposure (7 days) of MC3T3‐E1 cells to microgravity in the 3D clinostat inhibited the expression of Runx2, Osterix, type I collagen αI chain, RANKL and OPG genes. Similarly, 3D clinostat exposure inhibited the enhancement of β3‐integrin gene expression, which normally induced by sRANKL stimulation in RAW264.7 cells. These results, taken together, demonstrate that long‐term 3D clinostat exposure inhibits the differentiation of MC3T3‐E1 cells together with suppression of RANKL and OPG gene expression, as well as the RANKL‐dependent cellular fusion of RAW264.7 cells, suggesting that long‐term mechanical unloading suppresses bone formation and resorption.
Herbal medicine Shakuyaku‐kanzo‐to reduces paclitaxel‐induced painful peripheral neuropathy in mice
Authors: Hidaka Takao , Shima Tomoko , Nagira Kiyofumi , Ieki Masahiro , Nakamura Takafumi , Aono Yukiko , Kuraishi Yasushi , Arai Takashi , Saito Shigeru
Published: May 2008

Objectives: Paclitaxel is widely used in cancer chemotherapy for the treatment of solid tumors such as breast, ovarian and lung cancer. However, it sometimes induces moderate to severe muscle pain, and impairs the patients’ quality of life. An appropriate method for relieving this pain is not well established. Shakuyaku‐kanzo‐to, a herbal medicine, is known to relieve menstrual pain, muscle spasm, and muscle pain, and its effectiveness is expected. To ascertain the effectiveness of Shakuyaku‐kanzo‐to on paclitaxel‐induced pain, we investigated the effects of Shakuyaku‐kanzo‐to and its constituent herbal medicines in a mouse model.

Methods: Seven‐week‐old male ddY mice were used. To make a mouse model of paclitaxel‐induced pain, different single, intraperitoneally injected doses of this drug were tested in various groups of mice, and the optimal dose was determined. To estimate the effects of Shakuyaku‐kanzo‐to, the constituent herbal medicines Shakuyaku and Kanzo, and loxoprofen sodium as a non‐steroidal anti‐inflammatory drug on paclitaxel‐induced pain, mechanical allodynia and hyperalgesia of the hind paw were assessed.

Results: Paclitaxel administered at a dose of 10mg/kg or more produced allodynia and hyperalgesia; the time courses were similar to those of pain after paclitaxel administration in cancer patients. Shakuyaku‐kanzo‐to significantly relieved the allodynia and hyperalgesia induced by paclitaxel (10mg/kg). Shakuyaku and Kanzo inhibited the allodynia and hyperalgesia to some extent, but not significantly, while loxoprofen sodium was without effects.

Conclusions: A single administration of paclitaxel (10mg/kg) produced allodynia and hyperalgesia in mice, suggesting that it could be used as an animal model resembling the painful conditions observed in humans medicated with this drug. Using this model, Shakuyaku‐kanzo‐to was shown to relieve paclitaxel‐induced painful peripheral neuropathy.
A novel anticancer effect of butein: Inhibition of invasion through the ERK1/2 and NF‐κB signaling pathways in bladder cancer cells
Authors: Zhang LiRui , Chen Wei , Li Xu
Published: May 2008

There is increasing evidence that epithelial–mesenchymal transition (EMT) plays a critical role in cancer metastasis. Butein is a polyphenolic compound, which has been found to exhibit anti‐proliferation effects on cancer cells. Here, we report that in addition to its function as an anti‐proliferation agent, butein can inhibit migration and invasion through the ERK1/2 and NF‐κB signaling pathways in human bladder cancer cells, and this inhibitory effect may be associated with reversal of EMT. These results were further confirmed by RNAi‐mediated suppression of NF‐κB, which partly reverses EMT and inhibits cell invasive ability in vitro. These results suggest a novel function of butein as an invasion inhibitor in bladder cancer.
Homotropic allosteric control in clostridial glutamate dehydrogenase: Different mechanisms for glutamate and NAD+?
Authors: Hamza Muaawia A. , Engel Paul C.
Published: May 2008

Clostridial glutamate dehydrogenase mutants with the 5 Trp residues in turn replaced by Phe showed the importance of Trp 64 and 449 in cooperativity with glutamate at pH 9. These mutants are examined here for their behaviour with NAD+ at pH 7.0 and 9.0. The wild‐type enzyme displays negative NAD+ cooperativity at both pH values. At pH 7.0 W243F gives Michaelis–Menten kinetics, and the same behaviour is shown by W243F and also W310F at pH 9.0, but not by W64F or W449F. W243 and W310 are apparently much more important than W64 and W449 for the coenzyme negative cooperativity, implying that different conformational transitions are involved in cooperativity with the coenzyme and with glutamate.
Protective role of melatonin on PCB (Aroclor 1254) induced oxidative stress and changes in acetylcholine esterase and membrane bound ATPases in cerebellum, cerebral cortex and hippocampus of adult rat brain
Authors: Venkataraman Prabhu , Krishnamoorthy Gunasekaran , Vengatesh Ganapathy , Srinivasan Narasimhan , Aruldhas Maria Michael , Arunakaran Jagadeesan
Published: May 2008

Polychlorinated biphenyls (PCBs) are one of the environmental toxicants and neurotoxic compounds which induce the production of free radicals leading to oxidative stress. Membrane proteins that control ion gradients across organellar and plasma membranes appear to be particularly susceptible to oxidation induced changes. Melatonin plays an important role in neurodegenerative diseases as an antioxidant and neuroprotector. The aim of this study was to determine the protective role of melatonin on PCB (Aroclor 1254) induced changes in activities of membrane bound ATPases and acetylcholine esterase in selected brain regions of adult rats. Group I: rats intraperitoneally (i.p.) administered corn oil (vehicle) for 30 days. Group II: rats injected i.p. with Aroclor 1254 (PCB) at 2 mg/kg bw/day for 30 days. Groups III and IV: rats intraperitoneally received melatonin (5 or 10 mg/kg bw/day) simultaneously with Aroclor 1254 for 30 days. Groups V and VI: rats intraperitoneally received melatonin (5 or 10 mg/kg bw/day) alone for 30 days. After 30 days, rats were sacrificed and the brain regions were dissected to cerebral cortex (Cc), cerebellum (C) and hippocampus (H). Lipid peroxidation (LPO), hydrogen peroxide (H2O2), hydroxyl radical (*OH) and the activities of Na+K+ ATPase, Ca2+ ATPase, Mg2+ ATPase and acetyl cholinesterase were determined. Reduced glutathione (GSH) level was also determined. Melatonin levels in serum was measured by enzyme labeled immunosorbent assay (ELISA). Activities of all the enzymes and GSH level were decreased while an increase in H2O2, *OH and LPO were observed in brain regions of PCB treated animals. Melatonin levels in serum was decreased in PCB exposed animals. Exogenous melatonin supplementation retrieved all the parameters, significantly. These results suggest that PCB alters membrane bound ATPases and cholinergic function by inducing oxidative stress in brain regions, which can be protected by melatonin.
Increased induction of apoptosis by Propionibacterium freudenreichii TL133 in colonic mucosal crypts of human microbiota-associated rats treated with 1,2-dimethylhydrazine
Authors: Lan Annaïg , Bruneau Aurélia , Bensaada Martine , Philippe Catherine , Bellaud Pascale , Rabot Sylvie , Jan Gwénaël
Published: May 2008

Propionibacterium freudenreichii, a food-grade bacterium able to kill colon cancer cell lines in vitro by apoptosis, may exert an anticarcinogenic effect in vivo. To assess this hypothesis, we administered daily 2 × 1010 colony-forming units (CFU) of P. freudenreichii TL133 to human microbiota-associated (HMA) rats for 18 d. Either saline or 1,2-dimethylhydrazine (DMH) was also administered on days 13 and 17 and rats were killed on day 19. The levels of apoptosis and proliferation in the mid and distal colon were assessed by terminal deoxynucleotide transferase-mediated deoxyuridine triphosphate nick end labelling (TUNEL) and proliferating cell nuclear antigen (PCNA) immunolabelling, respectively. The administration of P. freudenreichii TL133 significantly increased the number of apoptotic cells in DMH-treated rats compared to those given DMH only (P < 0·01). Furthermore, propionibacteria were able to decrease the proliferation index in the distal colon after treatment with DMH (P < 0·01). Conversely, propionibacteria alone did not exert such an effect on healthy colonic mucosa. P. freudenreichii TL133 thus facilitated the elimination of damaged cells by apoptosis in the rat colon after genotoxic insult and may play a protective role against colon cancer.
Onset of the Ordovician cephalopod radiation – evidence from the Rochdale Formation (middle Early Ordovician, Stairsian) in eastern New York
Authors: KRÖGER BJÖRN , LANDING ED
Published: May 2008

The Rochdale Formation of eastern New York (= Fort Ann and lower Bascom formations, designations abandoned) is now recognized to record the earliest stages of the Great Ordovician Radiation of cephalopods. The earliest Bassleroceratidae, Tarphyceratidae and endoceridans on the east Laurentian shallow carbonate platform occur in the upper, thrombolite-bearing member of the Rochdale. This fauna demonstrates that the earliest radiation of Ordovician nautiloids took place in the late Tremadocian and is best recorded in tropical platform facies. Revision of this cephalopod fauna based on approximately 190 specimens collected along a 200 km, N–S belt in easternmost New York has provided new information on inter- and intraspecific variation of earlier described species. The ellesmeroceridVassarocerasand the endoceridsMcqueenocerasandParaendocerasare emended. New taxa includeBassleroceras champlainensesp. nov. andB. triangulumsp. nov.,Mccluskiceras comstockensegen. et sp. nov.,Exoclitendoceras rochdalensegen. et sp. nov. andParaendoceras depressumsp. nov. A rank abundance plot of 146 specimens from a locality in the Lake Champlain lowlands provides information on the community structure of a nautiloid fauna in which the longiconic cyrtoconicBasslerocerasis shown to dominate strongly. The nautiloid community structure of the Rochdale Formation is similar to that of the underlying Tribes Hill Formation (late early Tremadocian) with respect to the depositional setting, diversity and evenness but displays a remarkably increased taxonomic distinctness.
THE LEGISLATIVE ROLE OF THE SECURITY COUNCIL IN ITS FIGHT AGAINST TERRORISM: LEGAL, POLITICAL AND PRACTICAL LIMITS
Authors: Hinojosa Martínez Luis Miguel
Published: May 2008

This article studies the normative activity developed by the Security Council (SC) in recent years, particularly in the fight against terrorism. This legislative activity has aroused a great deal of controversy both among scholars and the States. Is the SC acting ultra vires? Has it revealed a new form of creating of international norms, which overrides definitively States' consent as the only material source of international law? This contribution tries to answer these questions by investigating the scope of the SC powers in the Charter, their historical background and the reaction of UN Member States towards its Resolutions. After this analysis, it is submitted that the SC does have a legislative capacity, but with important legal, political and practical limits.
One-year functional magnetic resonance imaging follow-up study of neural activation during the recall of unresolved negative life events in borderline personality disorder
Authors: Driessen M. , Wingenfeld K. , Rullkoetter N. , Mensebach C. , Woermann F. G. , Mertens M. , Beblo T.
Published: May 2008

Background

Recall of adverse life events under brain imaging conditions has been shown to coincide with activation of limbic and prefrontal brain areas in borderline personality disorder (BPD). We investigate changes of functional magnetic resonance imaging (fMRI) activation patterns during the recall of unresolved adverse life events (ULE) over 1 year.

Method

Thirteen female BPD patients participated in the study. During fMRI measurement subjects recalled ULE and negative but resolved life events (RLE) after individual cue words to stimulate autobiographical memory retrieval. Subjective intensity of emotional and sensoric experiences during recall was assessed as well as standardized measures of psychopathology.

Results

A 2×2 factorial analysis of fMRI data (Δt1/t2×ΔULE/RLE) revealed major right more than left differences of activation (i.e. t1>t2) of the posterior more than anterior cingulate, superior temporal lobes, insula, and right middle and superior frontal lobes (second-level analysis,t=3.0,puncorrected=0.003). The opposite contrast (Δt2/t1×ΔULE/RLE) did not reveal any differences. We did not find changes of emotional or sensoric qualities during recall (ULEversusRLE) or of psychopathology measures over the 1-year period.

Conclusions

Although subjective and clinical data did not change within 1 year, we observed a substantial decrease of temporo-frontal activation during the recall of ULE from t1 to t2. If future research confirms these findings, the question arises whether the decrease of neural activation precedes clinical improvement in BPD.
Effects of stressor controllability on psychophysiological, cognitive and behavioural responses in patients with major depression and dysthymia
Authors: Diener C. , Kuehner C. , Brusniak W. , Struve M. , Flor H.
Published: May 2008

Background

The experience of uncontrollability and helplessness in the face of stressful life events is regarded as an important determinant in the development and maintenance of depression. The inability to successfully deal with stressors might be linked to dysfunctional prefrontal functioning. We assessed cognitive, behavioural and physiological effects of stressor uncontrollability in depressed and healthy individuals. In addition, relationships between altered cortical processing and cognitive vulnerability traits of depression were analysed.

Method

A total of 26 unmedicated depressed patients and 24 matched healthy controls were tested in an expanded forewarned reaction (S1–S2) paradigm. In a factorial design, stressor controllability varied across three consecutive conditions: (a) control, (b) loss of control and (c) restitution of control. Throughout the experiment, error rates, ratings of controllability, arousal, emotional valence and helplessness were assessed together with the post-imperative negative variation (PINV) of the electroencephalogram.

Results

Depressed participants showed an enhanced frontal PINV as an electrophysiological index of altered information processing during both loss of control and restitution of control. They also felt more helpless than controls. Furthermore, frontal PINV magnitudes were associated with habitual rumination in the depressed subsample.

Conclusions

These findings indicate that depressed patients are more susceptible to stressor uncontrollability than healthy subjects. Moreover, the experience of uncontrollability seems to bias subsequent information processing in a situation where control is objectively re-established. Alterations in prefrontal functioning appear to contribute to this vulnerability and are also linked to trait markers of depression.
CARTESIAN SUBJECTIVITY ON THE NEOCLASSICAL STAGE; OR, MOLIÈRE ACTS CORNEILLE FOR LOUIS XIV
Authors: Gobert R. Darren
Published: May 2008

In 1658, having been invited to perform at court for the first time in his career, Molière paired his farce Le Docteur amoureux with Nicomède, a 1651 play by France's reigning dramatist, Pierre Corneille. The choice of Nicomède is surprising for political reasons, since the play is shot through with suspicion of royal authority: Corneille's hero is a great military leader unjustly imprisoned by the weak king he selflessly serves. The choice becomes less surprising when one considers a different set of reasons. Corneille's play is a generic oddity that marries its tragic tropes to elements of historical drama and a surprisingly comic ending. Molière's provincial troupe may have felt more at ease in such a play than in a proper neoclassical tragedy, since they lacked training in rhetorically complex stage declamation and in the codified gestures and postures preferred to convey tragic stage emotion at the time. In particular, they lacked the facility of the king's (and Corneille's) favorites, the esteemed Hôtel de Bourgogne actors, who were in the audience as guests of the monarch. No doubt anxious in their presence and in the presence of the king, Molière might have sought to mitigate the unfavorable comparison he anticipated between the talents of his troupe and those of the reigning Paris tragedians.
WHAT ARE YOU READING?
Authors: Diamond Elin
Published: May 2008

“This overheated and distasteful little book—for me the wrong book in many ways—addresses matters about which there is, precisely, nothing left to say.” The Rutgers University library believed this antihype and never purchased Paul Mann's The Theory-Death of the Avant-Garde (1991), a book so amusingly dour, so relentlessly dialectical, as to be, for me, irresistible. A member of Mike Sell's Vectors of the Avant-Garde seminar at last month's ASTR, I decided really to read instead of skim my Alibris-purchased copy of Mann's distasteful little book. In it the main figures of futurism, dada, and surrealism become a failed or self-recuperating aggregate whose discourse of inflammatory “anti-” stances served only to undermine their revolutionary intentions: “[T]he avant-garde's assaults on tradition, cultural establishments, and the formal structure of the work of art tended to place it in the service of, not . . . the revolution, but of its deferral, its displacement. . . . The avant-garde's historical agony is grounded in the brutal paradox of an opposition that sustains what it opposes precisely by opposing it” (11).
Gene flow hampered by low seed size of hybrids between oilseed rape and five wild relatives
Authors: Wei Wei , Darmency Henri
Published: May 2008

Recent concern about gene flow from transgenic plants to weedy species has attracted much research on the fitness of their hybrids. However, no studies have been reported on the very early effects of the seed size of hybrids compared with parental plants for germination, seedling establishment and plant growth. We produced hybrids between male sterile Brassica napus L. (oilseed rape) and five weedy relatives, including Brassica juncea (L.) Czern, B. nigra (L.) Koch, B. rapa L., Hirschfeldia incana (L.) Lagrèze-Fossat and Raphanus raphanistrum L. The hybrid seeds formed between B. napus and B. rapa varied in size, while all the hybrid seeds formed with the other species were small. In a direct-seeded field experiment, small seeds of both parents and hybrids had a lower frequency of emergence and a lower seedling survival rate than large seeds, and resulted in later flowering with less biomass. However, no difference was recorded in a transplant experiment, indicating that growth in the juvenile period was sensitive to the small seed class in field conditions only. The optimum environmental conditions in the greenhouse probably homogenized the developmental differences observed at the early stage, and thus reduced the variation during subsequent growth in the field. This point has not been, but should be, considered in risk assessment of transgenic plants. The lower seedling establishment of small-seeded hybrids could hamper further gene flow.
Expression and activity of a Kip-related protein, Zeama;KRP1, during maize germination
Authors: de Jesús Juárez Natividad , Mancilla Alfredo , García Elpidio , Vázquez-Ramos Jorge M.
Published: May 2008

Plant KRP proteins are cyclin/cyclin-dependent kinase subunit (Cdk) inhibitors that share a limited homology with mammalian p27Kip1proteins. Several KRPs have been reported in maize (Zea maysL.), of which Zeama;KRP1 was studied during maize germination. Expression of theZeama;KRP1gene did not vary during the 24 h germination period. A homologous antibody raised against the 13 kDa carboxy end of the Zeama;KRP1 polypeptide, a sequence containing the cyclin/Cdk inhibitory domain, indicated the existence of a 22 kDa protein in maize embryonic axes, the amount of which also remained unchanged during germination. Neither abscisic acid nor cytokinins modified the amount of protein. The purified Zeama;KRP1 polypeptide inhibited the kinase activity associated with Zeama;PCNA and Zeama;CycD2;1, and also the kinase activity in p13Suc1-pulled-down complexes. However, there were differences in the inhibition pattern during germination. Whereas kinase activity in proliferating cell nuclear antigen (PCNA) or CycD2;1 immunoprecipitates was strongly inhibited mainly during early germination, that in p13Suc1-pulled-down complexes was mainly inhibited at late times, suggesting that each protein complex is composed of different cyclins and/or Cdks.
The formation, disruption and properties of pressure-supported stellar systems and implications for the astrophysics of galaxies
Authors: Kroupa Pavel
Published: May 2008

Most stars form in dense star clusters deeply embedded in residual gas. These objects must therefore be seen as the fundamental building blocks of galaxies. With this contribution some physical processes that act in the very early and also later dynamical evolution of dense stellar systems in terms of shaping their later appearance and properties, and the impact they have on their host galaxies, are highlighted. Considering dense systems with increasing mass, it turns out that near 106M⊙ their properties change fundamentally: stellar populations become complex, a galaxial mass–radius relation emerges and the median two-body relaxation time becomes longer than a Hubble time. Intriguingly, only systems with a two-body relaxation time longer than a Hubble time show weak evidence for dark matter, whereby dSph galaxies form total outliers.
Dynamical Masses of Young Star Clusters: Constraints on the Stellar IMF and Star-Formation Efficiency
Authors: Bastian N.
Published: May 2008

Through the use of detailed light profiles and dynamical measurements of young clusters we investigate claims that the stellar initial mass function within clusters varies greatly. We find a strong age dependence in the clusters which have been claimed to have non-standard stellar IMFs, and suggest that the lack of equilibrium of these clusters is responsible for their ‘strange’ light-to-mass ratios and not IMF variations. The most likely culprit is the rapid removal of residual gas left over from the star-formation process which leaves the clusters severely out of dynamical equilibrium. By comparing the observations to N-body simulations we quantify to what degree a cluster is out of equilibrium and consequently its survival chances. We find that >60% of young clusters will be disrupted, due gas removal, within the first 20–50 Myr of their lives.
The Fraction of Runaway OB Stars in the SMC Field
Authors: Lamb J. B. , Oey M. S.
Published: May 2008

The fraction of field OB stars that originate from clusters can help probe the dynamical evolution of clusters. Field stars represent a significant fraction (20-30%) of the OB population in galaxies, and estimates for the fraction of field OB stars that are runaways range from the classical value of <10% (Blaauw 1961) to contemporary results suggesting >90% (de Wit et al. 2005). We obtained Magellan IMACS observations on the kinematics of field OB stars in the SMC to examine the line-of-sight velocities of this population. Using these observations, we will estimate the fraction of runaways to serve as a probe of cluster evolution.
The Relation Between Field Massive Stars and Clusters
Authors: Oey M. S. , King N. L. , Parker J. Wm. , Lamb J. B.
Published: May 2008

Massive “field” stars are those that appear in apparent isolation, in contrast to those in clusters. Whereas cluster stars are formed together in large aggregates, simultaneously, field stars have multiple origins. Some massive field stars may be the “tip of the iceberg” on small groups of physically associated stars, while others appear to be “runaway” stars that are dynamically ejected from clusters. What is the intrinsic relation between clusters and field stars, and what is the faction of runaway stars? Since massive stars are the most luminous stellar population, their demographics are accessible in the nearest external galaxies. We present our current efforts to understand these issues for the Small Magellanic Cloud.
On the Origin of the Orion Trapezium System
Authors: Zinnecker Hans
Published: May 2008

Numerical SPH simulations of supersonic gravo-turbulent fragmentation of a protocluster cloud (1000 M⊙) suggest that the cloud develops a few subclusters (star+gas systems) which subsequently merge into a single cluster entity. Each subcluster carries one most massive star (likely multiple), thus the merging of subclusters results in a central Trapezium-type system, as observed in the core of the Orion Nebula cluster.
Observational Evidence of Multiple Stellar Populations in Globular Clusters
Authors: Piotto Giampaolo
Published: May 2008

An increasing number of photometric observations of multiple stellar populations in Galactic globular clusters is seriously challenging the paradigm of GCs hosting single, simple stellar populations. These multiple populations manifest themselves in a split of different evolutionary sequences as observed in the cluster color-magnitude diagrams. In this paper we will summarize the observational scenario.
Multiple Stellar Populations in Globular Clusters: Collection of Information from the Horizontal Branch
Authors: D'Antona Francesca , Caloi Vittoria
Published: May 2008

The majority of the inhomogeneities in the chemical composition of Globular Cluster (GC) stars appear due to primordial enrichment by hot-CNO cycled material processed in stars belonging to a first stellar generation. Either massive AGB envelopes subject to hot bottom burning, or the envelopes of massive fastly rotating stars could be the progenitors. In both cases, the stars showing chemical anomalies must have also enhanced helium abundance, and we have proposed that this higher helium could be at the basis of the many different morphologies of GC horizontal branches (HB) for similar ages and metallicities. The helium variations have been beautifully confirmed by the splitting of the main sequence in the clusters ω Cen and NGC 2808, but this effect can show up only for somewhat extreme helium abundances. Therefore it is important to go on using the HB morphology to infer the number ratio of the first to the second generation in as many clusters as possible. We exemplify how it is possible to infer the presence of a He – rich stellar component in different clusters thanks to different HB features (gaps, RR Lyr periods and period distribution, ratio of blue to red stars, blue tails). In many clusters at least 50% of the stars belong to the second stellar generation, and in some cases we suspect that the stars might all belong to the second generation. We shortly examine the problem of the initial mass function required to achieve the observed number ratios and conclude that: 1) the initial cluster must have been much more massive than today's cluster, and 2) formation of the second stellar generation mainly in the central regions of the cluster may help in obtaining the desired values.
Mass-Loss Timescale of Star Cluster in External Tidal Field
Authors: Fukushige T. , Tanikawa A.
Published: May 2008

We investigate evolution of star clusters in steady external tidal field by means of N-body simulations. We followed several sets of cluster models whose strength and Coriolis's contribution of the external tidal field are different. We found that the mass loss timescale due to the escape of stars, t_mloss, and its dependence on the two-body relaxation timescale, trh,i, are determined by the strength of the tidal field. The logarithmic slope [≡ dln(tmloss)/dln(trh,i)] approaches unity for the cluster models in weaker tidal fields. We also found that stronger Coriolis force against others, produced by parent galaxy whose density profile is shallower, makes the mass loss timescale longer. This is due to the fact that a fraction of stars whose orbit are nearly regular increases as the Coriolis force becomes stronger.
Integrated Properties of Mass Segregated Star Clusters
Authors: Gaburov E. , Gieles M.
Published: May 2008

In this contribution we study integrated properties of dynamically segregated star clusters. The observed core radii of segregated clusters can be 50% smaller than the “true” core radius. In addition, the measured radius in the red filters is smaller than those measured in blue filters. However, these difference are small (≲10%), making it observationally challenging to detect mass segregation in extra-galactic clusters based on such a comparison. Our results follow naturally from the fact that in nearly all filters most of the light comes from the most massive stars. Therefore, the observed surface brightness profile is dominated by stars of similar mass, which are centrally concentrated and have a similar spatial distribution.
Resonance, Chaos and Stability in the General Three-Body Problem
Authors: Mardling R. A.
Published: May 2008

Three-body stability is fundamental to astrophysical processes on all length and mass scales from planetary systems to clusters of galaxies, so it is vital we have a deep and thorough understanding of this centuries-old problem. Here we summarize an analytical method for determining the stability of arbitrary three-body hierarchies which makes use of the chaos theory concept of resonance overlap. For the first time the dependence on all orbital elements and masses can be given explicitly via simple analytical expressions which contain no empirical parameters. For clarity and brevity, analysis in this paper is restricted to coplanar systems including a description of a practical algorithm for use in N-body and other applications. A Fortran routine for arbitrarily inclined systems is available from the author, and animations of stable and unstable systems are available at www.maths.monash.edu.au/~ro/Capri.
A Brief History of Regularisation
Authors: Mikkola S.
Published: May 2008

The various methods for regularisation of the gravitational few-body problem, from the coordinate transformation by the Kustaanheimo-Stiefel method to the more recent methods of algorithmic regularisation, are reviewed. Numerical comparisons of the performance of the methods are presented and future research suggested.
On the Calculation of Average Lifetimes for the 3-body Problem
Authors: Urminsky David
Published: May 2008

Numerical solutions for the 3-body problem can be extremely sensitive to small errors. We consider how small errors in calculations can affect the lifetime of these systems. In particular, we show that numerical errors can shorten the average lifetime of a 3-body system. This is illustrated using the Sitnikov Problem as an example. To give a theoretical explanation, we construct an approximate Poincaré map for this problem and delineate the structure of the escape regions. We show that numerical errors can destroy escape regions and can cause orbits to migrate to a region in which escape is faster.
The Influence of Binary Stars on Post-Collapse Evolution
Authors: Apple Rosemary
Published: May 2008

The results in the N-body simulations in Giersz & Heggie (1996) show that although the masses segregate as expected during core collapse, after core collapse there is self-similar evolution with very little further evidence of mass segregation even though the system has not reached equipartition. Binary stars halt core collapse and it is possible that they also halt the tendency toward equipartition. To investigate this problem, we construct two models. One model is a two-component model which assumes that binary stars form in the region dominated by heavy stars. The other model is a single mass model which assumes that binary stars form only in the region of the core. In both models, when the binary heating term is included, we find the post-collapse evolution to be self-similar. The aim of our work is to combine these two models to form a two-component model which assumes that binary formation only occurs in the core.
The Formation of Contact and Very Close Binaries
Authors: Eggleton Peter P. , Kisseleva-Eggleton Ludmila
Published: May 2008

We explore the possibility that all close binaries, i.e. those with periods < 3 days, including contact binaries, are produced from initially wider binaries by the action of a triple companion through the medium of Kozai Cycles with Tidal Friction (KCTF).
Neutron Stars in Globular Clusters
Authors: Ivanova N. , Heinke C. O. , Rasio F.
Published: May 2008

Dynamical interactions that occur between objects in dense stellar systems are particularly important for the question of formation of X-ray binaries. We present results of numerical simulations of 70 globular clusters with different dynamical properties and a total stellar mass of 2×107M⊙. We find that in order to retain enough neutron stars to match observations we must assume that NSs can be formed via electron-capture supernovae. Our simulations explain the observed dependence of the number of LMXBs on “collision number” as well as the large scatter observed between different globular clusters. For millisecond pulsars, we obtain good agreement between our models and the numbers and characteristics of observed pulsars in the clusters Terzan 5 and 47 Tuc.
Formation and Evolution of Black Holes in Galactic Nuclei and Star Clusters
Authors: Spurzem R. , Berczik P. , Berentzen I. , Merritt D. , Preto M. , Amaro-Seoane P.
Published: May 2008

We study the formation, growth, and co-evolution of single and multiple supermassive black holes (SMBHs) and compact objects like neutron stars, white dwarfs, and stellar mass black holes in galactic nuclei and star clusters, focusing on the role of stellar dynamics. In this paper we focus on one exemplary topic out of a wider range of work done, the study of orbital parameters of binary black holes in galactic nuclei (binding energy, eccentricity, relativistic coalescence) as a function of initial parameters. In some cases the classical evolution of black hole binaries in dense stellar systems drives them to surprisingly high eccentricities, which is very exciting for the emission of gravitational waves and relativistic orbit shrinkage. Such results are interesting to the emerging field of gravitational wave astronomy, in relation to a number of ground and space based instruments designed to measure gravitational waves from astrophysical sources (VIRGO, Geo600, LIGO, LISA). Our models self-consistently cover the entire range from Newtonian dynamics to the relativistic coalescence of SMBH binaries.
Building Blue Stragglers with Stellar Collisions
Authors: Glebbeek Evert , Pols Onno R.
Published: May 2008

The evolution of stellar collision products in cluster simulations has usually been modelled using simplified prescriptions. Such prescriptions either replace the collision product with an (evolved) main sequence star, or assume that the collision product was completely mixed during the collision.

It is known from hydrodynamical simulations of stellar collisions that collision products are not completely mixed, however. We have calculated the evolution of stellar collision products and find that they are brighter than normal main sequence stars of the same mass, but not as blue as models that assume that the collision product was fully mixed during the collision.
Dynamical Evolution of Globular Clusters in Hierarchical Cosmology
Authors: Gnedin Oleg Y. , Prieto José L.
Published: May 2008

We probe the evolution of globular clusters that could form in giant molecular clouds within high-redshift galaxies. Numerical simulations demonstrate that the large and dense enough gas clouds assemble naturally in current hierarchical models of galaxy formation. These clouds are enriched with heavy elements from earlier stars and could produce star clusters in a similar way to nearby molecular clouds. The masses and sizes of the model clusters are in excellent agreement with the observations of young massive clusters. Do these model clusters evolve into globular clusters that we see in our and external galaxies? In order to study their dynamical evolution, we calculate the orbits of model clusters using the outputs of the cosmological simulation of a Milky Way-sized galaxy. We find that at present the orbits are isotropic in the inner 50 kpc of the Galaxy and preferentially radial at larger distances. All clusters located outside 10 kpc from the center formed in the now-disrupted satellite galaxies. The spatial distribution of model clusters is spheroidal, with a power-law density profile consistent with observations. The combination of two-body scattering, tidal shocks, and stellar evolution results in the evolution of the cluster mass function from an initial power law to the observed log-normal distribution.
Sizes of Confirmed NGC 5128 Globular Clusters
Authors: Geisler Doug , Gómez M. , Woodley K. A. , Harris W. E. , Harris G. L. H.
Published: May 2008

We present results from a new wide-field study of the NGC 5128 globular cluster system. We have obtained new high resolution images with the Magellan 6.4m + IMACS camera. Our images cover an area of 1.2x1.2 sq. degrees and have a seeing of 0.45″. This allows us to not only resolve most of the globular clusters (GCs) but also derive their structural parameters. These are combined with existing Washington photometry in order to select by metallicity. We present here results for a subsample of 359 GCs which includes all currently confirmed GC members of the system. Our derived sizes are in very good agreement with those derived from ACS data. We find, as expected, that the metal-rich GCs in the inner regions (r < 10′) are 26% smaller than their metal-poor components, but in the outer region this normal trend is reversed. We compare our GCs to previous results for GCs, UCDs, etc. in the luminosity - size plane and find substantial overlap between different types of objects, indicating more of a continuum in these properties.
Ultra-Compact Dwarf Galaxies – More Massive than Allowed?
Authors: Hilker Michael , Mieske S. , Baumgardt H. , Dabringhausen J.
Published: May 2008

Dynamical mass estimates of ultra-compact dwarfs galaxies and massive globular clusters in the Fornax and Virgo clusters and around the giant elliptical Cen A have revealed some surprising results: 1) above ~106M⊙ the mass-to-light (M/L) ratio increases with the objects' mass; 2) some UCDs/massive GCs show high M/L values (4 to 6) that are not compatible with standard stellar population models; and 3) in the luminosity-velocity dispersion diagram, UCDs deviate from the well-defined relation of “normal” GCs, being more in line with the Faber-Jackson relation of early-type galaxies. In this contribution, we present the observational evidences for high mass-to-light ratios of UCDs and discuss possible explanations for them.
GMOS Spectroscopy of Globular Clusters in Dwarf Elliptical Galaxies
Authors: Miller Bryan W. , Lotz Jennifer , Hilker Michael , Kissler-Patig Markus , Puzia Thomas
Published: May 2008

We present a Gemini/GMOS program to measure spectroscopic metallicities and ages of globular clusters (GCs) and nuclei in dwarf elliptical galaxies in the Virgo and Fornax Clusters. Preliminary results indicate that the globular clusters are old and metal-poor, very similar to the GCs in the Milky Way halo. The nuclei tend to be more metal-rich than the globular clusters but more metal-poor and older, on average, than the stars in the bodies of the galaxies. The [α/Fe] ratio appears to be solar for the GCs, nuclei, and dEs, but the uncertainties do not exclude some globular clusters from being enhanced in alpha elements.
Current Status of GRAPE Project
Authors: Makino J.
Published: May 2008

I'll summarize the current status of GRAPE project. GRAPE-6, completed in 2002, has been used by a number of people, for a wide variety of problems such as planet formation, star cluster dynamics, galactic nuclei, and cosmology. In 2004, we started the development of the next-generation machine, GRAPE-DR. GRAPE-DR has a architecture radically different from that of previous GRAPEs. It does not have hardwired pipeline for gravitational force calculation but a large number of small and simple programmable processors. This change made it possible to apply GRAPE-DR to a wide range of problems to which GRAPE was not efficient, and at the same time it helps us to explore new algorithms for N-body simulations. The GRAPE-DR chip was completed in 2006, and second prototype board was completed in May 2007. We hope to have full production-level board commercially available by the end of year 2007. A single board will offer the theoretical peak speed of 2 Tflops, about 20 times as that of a single PCI card version of GRAPE-6.
Determining Design and Scale‐up Parameters for Degradation of Atrazine with Suspended Pseudomonas sp. ADP in Aqueous Bioreactors
Authors: Biglione Nicole , Rodgers V. G. J. , Peeples Tonya L.
Published: May 2008

This work investigated the kinetic parameters of atrazine mineralization by suspended cells of Pseudomonas sp. ADP in both shake flasks and spherical stirred tank batch reactors (SSTR). The degradation of atrazine and growth of Pseudomonas sp. ADP were studied. Experiments were performed at different temperatures and stirring speeds in both reactors at varying initial concentrations of atrazine. Cell growth and atrazine concentration were monitored over time, and a Monod model with one limiting substrate was used to characterize the kinetic behavior. Temperature, stirring speed, and reactor type were all found to significantly affect the regressed Monod parameters. At 27 °C and 200 rpm, for the shaker flask experiments, μmax and Ks were determined to be 0.14 (±0.01) h−1 and 1.88 (±1.80) mg/L, respectively. At 37 °C, μmax and Ks increased to 0.25 (±0.05) h−1 and 9.59 (±6.55) mg/L, respectively. As expected, stirrer speed was also found to significantly alter the kinetic parameters. At 27 °C and 125 rpm, μmax and Ks were 0.04 (±0.002) h−1 and 3.72 (±1.05) mg/L, respectively, whereas at 37 °C and 125 rpm, μmax and Ks were 0.07 (±0.008) h−1 and 1.65 (±2.06) mg/L. In the SSTR the kinetic parameters μmax and Ks at room temperature were determined to be 0.12 (±0.009) h−1 and 2.18 (±0.47) mg/L, respectively. Although the μmax values for both types of reactors were similar, the shaker flask experiments resulted in considerable error. Error analysis on calculated values of Ks were found to impact estimates in atrazine concentration by as much as two orders of magnitude, depending on the reactor design, illustrating the importance of these factors in reactor scale‐up.
mRNA‐Display‐Based Selections for Proteins with Desired Functions: A Protease‐Substrate Case Study
Authors: Valencia C. Alexander , Cotten Steven W. , Dong Biao , Liu Rihe
Published: May 2008

mRNA‐display is an amplification‐based, iterative rounds of in vitro protein selection technique that circumvents a number of difficulties associated with yeast two‐hybrid and phage display. Because of the covalent linkage between the genotype and the phenotype, mRNA‐display provides a powerful means for reading and amplifying a peptide or protein sequence after it has been selected from a library with a diversity in the range of 1012–1013. In this paper, we briefly review the recent progress in using mRNA‐display to identify affinity reagents, binding partners, and enzyme substrates from synthetic peptide or natural proteome libraries. To facilitate the use of mRNA‐display in research laboratories without previous experience, we provide a detailed analysis of the critical steps of an mRNA‐display‐based selection in a case study for the identification of the natural substrates of caspases, including the generation of an mRNA‐displayed proteome library, removal of abundant sequences, and selection of proteins with desired functions. The advantages and technical limitations of mRNA‐display as a general peptide or protein selection tool are also addressed.