bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling gene sequences over time in 2009 H1N1 Influenza A Virus populations
Authors: Goñi Natalia , Fajardo Alvaro , Moratorio Gonzalo , Colina Rodney , Cristina Juan
Published: December 2009

Background

A sudden emergence of Influenza A Virus (IAV) infections with a new pandemic H1N1 IAV is taking place since April of 2009. In order to gain insight into the mode of evolution of these new H1N1 strains, we performed a Bayesian coalescent Markov chain Monte Carlo (MCMC) analysis of full-length neuraminidase (NA) gene sequences of 62 H1N1 IAV strains (isolated from March 30thto by July 28th, 2009).

Results

The results of these studies revealed that the expansion population growth model was the best to fit the sequence data. A mean of evolutionary change of 7.84 × 10-3nucleotide substitutions per site per year (s/s/y) was obtained for the NA gene. A significant contribution of first codon position to this mean rate was observed. Maximum clade credibility trees revealed a rapid diversification of NA genes in different genetic lineages, all of them containing Oseltamivir-resistant viruses of very recent emergence. Mapping of naturally occurring amino acid substitutions in the NA protein from 2009 H1N1 IAV circulating in 62 different patients revealed that substitutions are distributed all around the surface of the molecule, leaving the hydrophobic core and the catalytic site essentially untouched.

Conclusion

High evolutionary rates and fast population growth have contributed to the initial transmission dynamics of 2009 H1N1 IAV. Naturally occurring substitutions are preferentially located at the protein surface and do not interfere with the NA active site. Antigenic regions relevant for vaccine development can differ from previous vaccine strains and vary among patients.
Platypnea and orthodeoxia associated with Pneumocystis jiroveci and Cytomegalovirus pneumonia: a case report
Authors: Katsoulis Konstantinos , Minasidis Ilias , Vainas Andreas , Bikas Christoforos , Kontakiotis Theodoros , Vakianis Pantelis
Published: December 2009

Introduction

Platypnea-orthodeoxia is an uncommon syndrome characterized by dyspnea and deoxygenation accompanying a change to a sitting or standing posture from a recumbent position. It is usually related to interatrial communications, although several other disorders associated with platypnea-orthodeoxia syndrome have been reported. However, the precise mechanisms are unknown.

Case presentation

We present the case of a 75-year-old Caucasian woman with chronic renal failure due to vasculitis who was admitted with fever and respiratory failure. She was found to have both Pneumocystis jiroveci and Cytomegalovirus pneumonia. She was HIV negative. Severe platypnea and orthodeoxia were major features of her illness with no history of respiratory, liver or cardiac disease. Further investigation with contrast echocardiography revealed no intracardiac or intrapulmonary shunts. Although one case involving Pneumocystis jiroveci pneumonia and platypnea has been previously reported, to the best of our knowledge, this is the first time that two opportunistic pathogens have been accompanied by platypnea and orthodeoxia. As both lung bases were predominantly affected and no obvious explanation was found, platypnea and orthodeoxia were attributed to significant areas of low or zero ventilation/perfusion (V/Q) ratio.

Conclusion

Platypnea-orthodeoxia is a rare and usually underestimated syndrome. Intracardiac shunts and anatomic pulmonary vascular shunts are the most common etiologic associations. However, if a detailed examination reveals no obvious intracardiac or intrapulmonary shunting combined with extensive pulmonary lesions, then severe V/Q mismatching should be considered as the probable explanation.
Vacuum-assisted closure device enhances recovery of critically ill patients following emergency surgical procedures
Authors: Batacchi Stefano , Matano Stefania , Nella Alessandra , Zagli Giovanni , Bonizzoli Manuela , Pasquini Andrea , Anichini Valentina , Tucci Valentina , Manca Giuseppe , Ban Kevin , Valeri Andrea , Peris Adriano
Published: December 2009

Introduction

Critically ill surgical patients frequently develop intra-abdominal hypertension (IAH) leading to abdominal compartment syndrome (ACS) with subsequent high mortality. We compared two temporary abdominal closure systems (Bogota bag and vacuum-assisted closure (VAC) device) in intra-abdominal pressure (IAP) control.

Methods

This prospective study with a historical control included 66 patients admitted to a medical and surgical intensive care unit (ICU) of a tertiary care referral center (Careggi Hospital, Florence, Italy) from January 2006 to April 2009. The control group included patients consecutively treated with the Bogota bag (Jan 2006-Oct 2007), whereas the prospective group was comprised of patients treated with a VAC. All patients underwent abdominal decompressive surgery. Groups were compared based upon their IAP, SOFA score, serial arterial lactates, the duration of having their abdomen open, the need for mechanical ventilation (MV) along with length of ICU and hospital stay and mortality. Data were collected from the time of abdominal decompression until the end of pressure monitoring.

Results

The Bogota and VAC groups were similar with regards to demography, admission diagnosis, severity of illness, and IAH grading. The VAC system was more effective in controlling IAP (P < 0.01) and normalizing serum lactates (P < 0.001) as compared to the Bogota bag during the first 24 hours after surgical decompression. There was no significant difference between the SOFA scores. When compared to the Bogota, the VAC group had a faster abdominal closure time (4.4 vs 6.6 days, P = 0.025), shorter duration of MV (7.1 vs 9.9 days, P = 0.039), decreased ICU length of stay (LOS) (13.3 vs 19.2 days, P = 0.024) and hospital LOS (28.5 vs 34.9 days; P = 0.019). Mortality rate did not differ significantly between the two groups.

Conclusions

Patients with abdominal compartment syndrome who were treated with VAC decompression had a faster abdominal closure rate and earlier discharge from the ICU as compared to similar patients treated with the Bogota bag.
Distribution and Postnatal Development of Gpr54 Gene Expression in Mouse Brain and Gonadotropin-Releasing Hormone Neurons
Authors: Herbison Allan E. , d'Anglemont de Tassigny Xavier , Doran Joanne , Colledge William H.
Published: December 2009

Kisspeptin and G protein-coupled receptor 54 (GPR54) are now acknowledged to play essential roles in the neural regulation of fertility. Using a transgenic Gpr54 LacZ knock-in mouse model, this study aimed to provide 1) a detailed map of cells expressing Gpr54 in the mouse brain and 2) an analysis of Gpr54 expression in GnRH neurons across postnatal development. The highest density of Gpr54-expressing cells in the mouse central nervous system was found in the dentate gyrus of the hippocampus beginning on postnatal d 6 (P6). Abundant Gpr54 expression was also noted in the septum, rostral preoptic area (rPOA), anteroventral nucleus of the thalamus, posterior hypothalamus, periaqueductal grey, supramammillary and pontine nuclei, and dorsal cochlear nucleus. No Gpr54 expression was detected in the arcuate and rostral periventricular nuclei of the hypothalamus. Dual-labeling experiments showed that essentially all Gpr54-expressing cells in the rPOA were GnRH neurons. Analyses of mice at birth, P1, P5, P20, and P30 and as adults revealed a gradual increase in the percentage of GnRH neurons expressing Gpr54 from approximately 40% at birth through to approximately 70% from P20 onward. Whereas GnRH neurons located in the septum displayed a consistent increase across this time, GnRH neurons in the rPOA showed a sharp reduction in Gpr54 expression after birth (to ∼10% at P5) before increasing to the 70% expression levels by P20. Together these findings provide an anatomical basis for the exploration of Gpr54 actions outside the reproductive axis and reveal a complex temporal and spatial pattern of Gpr54 gene expression in developing GnRH neurons.
Leptin: A Critical Regulator of CD4+ T-cell Polarization in Vitro and in Vivo
Authors: Batra Arvind , Okur Besir , Glauben Rainer , Erben Ulrike , Ihbe Jakob , Stroh Thorsten , Fedke Inka , Chang Hyun-Dong , Zeitz Martin , Siegmund Britta
Published: December 2009

Besides being mandatory in the metabolic system, adipokines like leptin directly affect immunity. Leptin was found to be necessary in T helper 1 (Th1)-dependent inflammatory processes, whereas effects on Th2 cells are rarely understood. Here, we focused on leptin in T-helper cell polarization and in Th2-mediated intestinal inflammation in vivo. The induction of cytokine-producing Th1 or Th2 cells from naive CD4+ T cells under polarizing conditions in vitro was generally decreased in cells from leptin-deficient ob/ob mice compared with wild-type mice. To explore the in vivo relevance of leptin in Th2-mediated inflammation, the model of oxazolone-induced colitis was employed in wild-type, ob/ob, and leptin-reconstituted ob/ob mice. Ob/ob mice were protected, whereas wild-type and leptin-reconstituted ob/ob mice developed colitis. The disease severity went in parallel with local production of the Th2 cytokine IL-13. A possible explanation for the protection of ob/ob mice in Th1- as well as in Th2-dependent inflammation is provided by a decreased expression of the key transcription factors for Th1 and Th2 polarization, T-bet and GATA-3, in naive ob/ob T cells. In conclusion, these results support the regulatory function of the adipokine leptin within T-cell polarization and thus in the acquired immune system and support the concept that there is a close interaction with the endocrine system.
Glucocorticoids Stimulate Hepatic and Renal Catecholamine Inactivation by Direct Rapid Induction of the Dopamine Sulfotransferase Sult1d1
Authors: Wong Stephen , Tan Kheng , Carey Kirstyn T. , Fukushima Atsushi , Tiganis Tony , Cole Timothy J.
Published: December 2009

During the stress response and metabolic fasting, glucocorticoids acting via the glucocorticoid receptor (GR) stimulate hepatic glucose production by activating specific gluconeogenic enzyme target genes. To characterize novel direct GR-regulated hepatic target genes under glucocorticoid control, we performed a whole genome gene expression microarray using dexamethasone-treated GR-null mice. Strongly induced previously characterized genes included phosphoenolpyruvate carboxykinase, serine dehydratase, tyrosine oxygenase, lipin 1, metallothionine, and cdkn1A. Novel induced genes included Ddit4, Fkbp5, Megf9, Sult1e1, and Sult1d1, and all were verified by real-time PCR. Sult1d1, a sulfotransferase, is a member of a large superfamily of detoxification enzymes and has an important role in the inactivation of endogenous dopamine-derived compounds, including the catecholamines. Treatment of primary mouse hepatocytes with dexamethasone for 6 h dramatically increased Sult1d1 mRNA levels, whereas cotreatment with RU-486, a GR antagonist, blocked induction by dexamethasone. Sult1d1 mRNA levels were also increased by dexamethasone in the kidney, a major site of Sult1d1 synthesis. Sult1d1 mRNA was localized by in situ hybridization to renal collecting ducts and was rapidly induced by glucocorticoids in renal inner medullary collecting duct (IMCD3) cells. Hepatic and renal Sult1d1 enzymatic activity was significantly induced in vivo in wild-type mice 6 h after dexamethasone treatment. Chromatin immunoprecipitation assay analysis upstream of the Sult1d1 gene promoter identified a glucocorticoid response element close to the neighboring glucocorticoid-responsive estrogen sulfotransferase Sult1e1 gene, indicating that both genes potentially share a common glucocorticoid response element. These results suggest that Sult1d1 in mice is directly induced by glucocorticoids and may attenuate elevated catecholamine activity during the stress response.
Signal Transducer and Activator of Transcription (STAT)-5A and STAT5B Differentially Regulate Human Mammary Carcinoma Cell Behavior
Authors: Tang Jian-Zhong , Zuo Ze-Hua , Kong Xiang-Jun , Steiner Michael , Yin Zhinan , Perry Jo K. , Zhu Tao , Liu Dong-Xu , Lobie Peter E.
Published: December 2009

Increased activation of signal transducer and activator of transcription (STAT)-5 has been reported in various malignancies including mammary carcinoma. However, it is only recently that potentially distinct roles of STAT5A and STAT5B in neoplasia have begun to emerge. Herein we systematically delineate the functions of STAT5A and STAT5B in human mammary carcinoma cell lines MCF-7 and T47D. Forced expression of constitutively active (CA) STAT5A enhanced both survival and anchorage-independent growth of human mammary carcinoma cells but concordantly suppressed cell motility as revealed in colony scattering, cell migration, and invasion assays. In contrast, forced expression of CA STAT5B exhibited lower potency than CA STAT5A in enhancing survival and anchorage-independent growth of mammary carcinoma cells and exerted no effects on cell motility. Differential expression of genes that regulate cellular survival and motility was concomitantly observed on forced expression of CA STAT5A or CA STAT5B. Small interfering RNA-mediated depletion of STAT5A significantly impaired anchorage-independent growth of human mammary carcinoma cells, whereas a smaller reduction was observed upon small interfering RNA-mediated depletion of STAT5B. Depletion of endogenous STAT5A also significantly enhanced cell motility, whereas depletion of endogenous STAT5B exhibited no effect. Xenograft studies provided data concordant with the in vitro effects of the two STAT5 isoforms. We therefore demonstrate that STAT5A and STAT5B differentially regulate behavior of human mammary carcinoma cells.
Inhibition of Thrombin Action Ameliorates Insulin Resistance in Type 2 Diabetic db/db Mice
Authors: Mihara Masatomo , Aihara Ken-ichi , Ikeda Yasumasa , Yoshida Sumiko , Kinouchi Mizuho , Kurahashi Kiyoe , Fujinaka Yuichi , Akaike Masashi , Matsumoto Toshio
Published: December 2009

The binding of thrombin to its receptor stimulates inflammatory cytokines including IL-6 and monocyte chemoattractant protein-1 (MCP-1); both are associated with the development of insulin resistance. Because increased adiposity enhanced the expression of coagulation factor VII that stimulates the coagulation pathway in adipose tissue, we tested whether the inhibition of thrombin action ameliorates insulin resistance in obese diabetic (Lpr−/−:db/db) mice. The 4-wk administration of argatroban, a selective thrombin inhibitor, reduced fasting plasma glucose and ameliorated insulin resistance in these mice. It also reduced adipocyte size and macrophage infiltration into adipose tissue. The aberrant gene expression of MCP-1, IL-6, adiponectin, and factor VII and suppressed insulin receptor substrate-1-Akt signaling in adipose tissue of db/db mice were reversed by argatroban treatment. These results demonstrate that increased adiposity enhances the production of thrombin in adipose tissue by stimulating factor VII expression and suggest that increased thrombin activity in adipose tissue plays an important role in the development of insulin resistance via enhancing MCP-1 production, leading to macrophage infiltration and insulin receptor substrate-1-Akt pathway inactivation.
MT1 Melatonin Receptors Mediate Somatic, Behavioral, and Reproductive Neuroendocrine Responses to Photoperiod and Melatonin in Siberian Hamsters (Phodopus sungorus)
Authors: Prendergast Brian J.
Published: December 2009

Environmental day length drives nocturnal pineal melatonin secretion, which in turn generates or entrains seasonal cycles of physiology, reproduction, and behavior. In mammals, melatonin (MEL) binds to a number of receptor subtypes including high-affinity (MT1 and MT2) and low-affinity (MT3, nuclear orphan receptors) binding sites, which are distributed throughout the central nervous system and periphery. The MEL receptors that mediate photoperiodic reproductive and behavioral responses to MEL have not been identified in a reproductively photoperiodic species. Here I tested the hypothesis that MT1 receptors are necessary and sufficient to engage photoperiodic responses by challenging male Siberian hamsters (Phodopus sungorus), a species that does not express functional MT2 receptors, with ramelteon (RAM), a specific MT1/MT2 receptor agonist. In hamsters housed in a long-day photoperiod, late-afternoon RAM treatment inhibited gonadotropin secretion, induced gonadal regression, and suppressed food intake and body mass, mimicking effects of MEL. In addition, chronic (24 h/d) RAM infusions were sufficient to obscure endogenous MEL signaling, and these treatments attenuated gonadal regression in short days. Together, the outcomes indicate that signaling at the MT1 receptor is sufficient and necessary to mediate the effects of photoperiod-driven changes in MEL on behavior and reproductive function in a reproductively photoperiodic mammal.
Minireview: Estrogenic Protection of β-Cell Failure in Metabolic Diseases
Authors: Liu Suhuan , Mauvais-Jarvis Franck
Published: December 2009

The prevalence of diabetes is lower in premenopausal women, especially diabetic syndromes with insulin deficiency, suggesting that the female hormone 17β-estradiol protects pancreatic β-cell function. In classical rodent models of β-cell failure, 17β-estradiol at physiological concentrations protects pancreatic β-cells against lipotoxicity, oxidative stress, and apoptosis. In this review, we integrate evidence showing that estrogens and their receptors have direct effects on islet biology. The estrogen receptor (ER)-α, ERβ, and the G-protein coupled ER are present in β-cells and enhance islet survival. They also improve islet lipid homeostasis and insulin biosynthesis. We also discuss evidence that ERs modulate insulin sensitivity and energy homeostasis, which indirectly alter β-cell biology in diabetic and obese conditions.
Heterozygous Orthodenticle Homeobox 2 Mutations Are Associated with Variable Pituitary Phenotype
Authors: Dateki Sumito , Kosaka Kitaro , Hasegawa Kosei , Tanaka Hiroyuki , Azuma Noriyuki , Yokoya Susumu , Muroya Koji , Adachi Masanori , Tajima Toshihiro , Motomura Katsuaki , Kinoshita Eiichi , Moriuchi Hiroyuki , Sato Naoko , Fukami Maki , Ogata Tsutomu
Published: December 2009

Context: Although recent studies have suggested a positive role of OTX2 in pituitary as well as ocular development and function, detailed pituitary phenotypes in OTX2 mutations and OTX2 target genes for pituitary function other than HESX1 and POU1F1 remain to be determined.

Objective: We aimed to examine such unresolved issues.

Subjects: We studied 94 Japanese patients with various ocular or pituitary abnormalities.

Results: We identified heterozygous p.K74fsX103 in case 1, p.A72fsX86 in case 2, p.G188X in two unrelated cases (3 and 4), and a 2,860,561-bp microdeletion involving OTX2 in case 5. Clinical studies revealed isolated GH deficiency in cases 1 and 5; combined pituitary hormone deficiency in case 3; abnormal pituitary structures in cases 1, 3, and 5; and apparently normal pituitary function in cases 2 and 4, together with ocular anomalies in cases 1–5. The wild-type Orthodenticle homeobox 2 (OTX2) protein transactivated the GNRH1 promoter as well as the HESX1, POU1F1, and IRBP (interstitial retinoid-binding protein) promoters, whereas the p.K74fsX103-OTX2 and p.A72fsX86-OTX2 proteins had no transactivation functions and the p.G188X-OTX2 protein had reduced (∼50%) transactivation functions for the four promoters, with no dominant-negative effect. cDNA screening identified positive OTX2 expression in the hypothalamus.

Conclusions: The results imply that OTX2 mutations are associated with variable pituitary phenotype, with no genotype-phenotype correlations, and that OTX2 can transactivate GNRH1 as well as HESX1 and POU1F1.
Serum- and Glucocorticoid-Inducible Kinase 1 (SGK1) Regulates Adipocyte Differentiation via Forkhead Box O1
Authors: Di Pietro Natalia , Panel Valentine , Hayes Schantel , Bagattin Alessia , Meruvu Sunitha , Pandolfi Assunta , Hugendubler Lynne , Fejes-Tóth Geza , Naray-Fejes-Tóth Aniko , Mueller Elisabetta
Published: December 2009

The serum and glucocorticoid-inducible kinase 1 (SGK1) is an inducible kinase the physiological function of which has been characterized primarily in the kidney. Here we show that SGK1 is expressed in white adipose tissue and that its levels are induced in the conversion of preadipocytes into fat cells. Adipocyte differentiation is significantly diminished via small interfering RNA inhibition of endogenous SGK1 expression, whereas ectopic expression of SGK1 in mesenchymal precursor cells promotes adipogenesis. The SGK1-mediated phenotypic effects on differentiation parallel changes in the mRNA levels for critical regulators and markers of adipogenesis, such as peroxisome proliferator-activated receptor γ, CCAAT enhancer binding protein α, and fatty acid binding protein aP2. We demonstrate that SGK1 affects differentiation by direct phosphorylation of Foxo1, thereby changing its cellular localization from the nucleus to the cytosol. In addition we show that SGK1−/− cells are unable to relocalize Foxo1 to the cytosol in response to dexamethasone. Together these results show that SGK1 influences adipocyte differentiation by regulating Foxo1 phosphorylation and reveal a potentially important function for this kinase in the control of fat mass and function.
Nkx2.2 Activates the Ghrelin Promoter in Pancreatic Islet Cells
Authors: Hill Jonathon T. , Chao Christina S. , Anderson Keith R. , Kaufman Fernanda , Johnson Christopher W. , Sussel Lori
Published: December 2009

Nkx2.2 is an essential regulator of pancreatic endocrine differentiation. Nkx2.2-null mice are completely devoid of β-ells and have a large reduction of α- and PP cells. In the place of these islet populations, there is a corresponding increase in the ghrelin-positive ε-cells. Molecular studies have indicated that Nkx2.2 functions as an activator and repressor to regulate islet cell fate decisions. To determine whether Nkx2.2 is solely important for islet cell fate decisions or also has the capability to control ghrelin at the promoter level, we studied the transcriptional regulation of the ghrelin promoter within the pancreas, in vitro and in vivo. These studies demonstrate that both of the previously identified transcriptional start sites in the ghrelin promoter are active within the embryonic pancreas; however, the long transcript is preferentially up-regulated in the Nkx2.2-null pancreas. We also show that the promoter region between −619 and −488 bp upstream of the translational start site is necessary for repression of ghrelin in αTC1 and βTC6 cells. Surprisingly, we also show that Nkx2.2 is able to bind to and activate the ghrelin promoter in several cell lines that do or do not express endogenous ghrelin. Together, these results suggest that the up-regulation of ghrelin expression in the Nkx2.2-null mice is not due to loss of repression of the ghrelin promoter in the nonghrelin islet populations. Furthermore, Nkx2.2 may contribute to the activation of ghrelin in mature islet ε-cells.
Experience Spillovers Across Corporate Development Activities
Authors: Zollo Maurizio , Reuer Jeffrey J.
Published: December 2009

This study develops and tests a theory of experience spillovers across corporate development activities. In particular, we investigate the impact of prior alliance experience on the performance implications of corporate acquisitions. We start with the simple suggestion that such experience spillovers will depend on the similarity among the managerial processes characterizing these activities. The empirical evidence confirms that the more the focal acquisition is managed in ways that are typical of partnerships (e.g., with low integration or with high relational quality levels), the more positive is the effect of past alliance experience on acquisition performance. However, we also find that alliance experience can be detrimental under certain circumstances, such as when the acquisition is managed with more aggressive post-acquisition integration approaches. This paper proposes a more sophisticated model of experience spillovers that can accommodate both positive and negative experience spillover effects across complex organizational tasks.
Structure and Learning in Self-Managed Teams: Why “Bureaucratic” Teams Can Be Better Learners
Authors: Bunderson J. Stuart , Boumgarden Peter
Published: December 2009

This paper considers the effect of team structure on a team's engagement in learning and continuous improvement. We begin by noting the uncertain conceptual status of the structure concept in the small groups literature and propose a conceptualization of team structure that is grounded in the long tradition of work on formal structure in the sociology and organization theory literatures. We then consider the thesis that, at least in self-managed teams dealing with stable tasks, greater team structure—i.e., higher levels of specialization, formalization, and hierarchy—can promote learning by encouraging information sharing, reducing conflict frequency, and fostering a climate of psychological safety; that is, we examine a mediated model in which the effect of structure on learning and improvement in teams is mediated by psychological safety, information sharing, and conflict frequency. This model was largely supported in a study of self-managed production teams in a Fortune 100 high-technology firm, although the observed pattern of mediation was more complex than anticipated. Higher structure was also associated with actual productivity improvements in a subsample of these teams. The theory and results of this study advance our understanding of team learning and underscore the importance of team structure in research on team processes and performance.
Fostering Team Innovation: Why Is It Important to Combine Opposing Action Strategies?
Authors: Gebert Diether , Boerner Sabine , Kearney Eric
Published: December 2009

We develop a framework that provides a general theoretical rationale for the claim made by several authors that combining opposing action strategies fosters team innovation. We distinguish between open and closed strategies and posit that these are opposing but complementary in that each fosters one of two processes necessary for team innovation: open action strategies (e.g., delegative leadership) promote knowledge generation, and closed action strategies (e.g., directive leadership) enhance knowledge integration. We argue that each pole of a pair of opposing action strategies both energizes and detracts from elements of innovation. Thus, it could be expected that combining opposing action strategies leads to an impasse, as the negative effects of each strategy might offset the positive effects of the opposite strategy. There is currently no viable explanation in the literature for why this mutual neutralization may not occur. We aim to fill this gap by explicating why and how opposing action strategies, when implemented simultaneously, do not countervail each other's positive effects, but rather yield positive synergies that fuel team innovation.
Heterogeneity, Brokerage, and Innovative Performance: Endogenous Formation of Collaborative Inventor Networks
Authors: Lee Jeongsik “Jay”
Published: December 2009

In this study, I examine how past performance influences the relative positions of actors in a network and how the actor-level heterogeneity in quality mediates the often-demonstrated association between brokerage and performance. On the collaboration network of U.S. biotech inventors during 1976–1995, I find that inventors with superior track records are more apt to form collaboration ties that enhance brokerage, thereby occupying positions that allow them to broker across network boundaries. Controlling for past performance significantly weakens the positive relationship between brokering position and innovative performance. Furthermore, when inventor-level heterogeneity is controlled for through inventor fixed effects, the position-performance correlation disappears. These findings suggest that, at least for collaborative inventors, actor-level heterogeneity such as performance history largely drives the asymmetry in brokerage, explaining most of the position–performance association.
Relationship Between Pb2+ Adsorption and Average Mn Oxidation State in Synthetic Birnessites
Authors: Zhao Wei , Cui Haojie , Liu Fan , Tan Wenfeng , Feng Xionghan
Published: December 2009

The relationship between vacant Mn structural sites in birnessites and heavy-metal adsorption is a current and important research topic. In this study, two series of birnessites with different average oxidation states (AOS) of Mn were synthesized. One birnessite series was prepared in acidic media (49.6–53.6 wt.% Mn) and the other in alkaline media (50.0–56.2 wt.% Mn). Correlations between the Pb2+ adsorption capacity and the d110 interlayer spacing, the AOS by titration, and the release of Mn2+, H+, and K+ during adsorption of Pb2+ were investigated. The maximum Pb2+ adsorption by the birnessites synthesized in acidic media ranged from 1320 to 2457 mmol/kg with AOS values that ranged from 3.67 to 3.92. For birnessites synthesized in alkaline media, the maximum Pb2+ adsorption ranged from 524 to 1814 mmol/kg, with AOS values between 3.49 and 3.89. Birnessite AOS values and Pb2+ adsorption increased as the Mn content decreased. The maximum Pb2+ adsorption to the synthetic birnessites calculated from a Langmuir fit of the Pb adsorption data was linearly related to AOS. Birnessite AOS was positively correlated to Pb2+ adsorption, but negatively correlated to the d110 spacing. Vacant Mn structural sites in birnessite increased with AOS and resulted in greater Pb2+ adsorption. Birnessite AOS values apparently reflect the quantity of vacant sites which largely account for Pb2+ adsorption. Therefore, the Pb2+ adsorption capacity of birnessite is mostly determined by the Mn site vacancies, from which Mn2+, H+, and K+ released during adsorption were derived.
Origin and Mineralogy of Sepiolite and Palygorskite From the Tuluanshan Formation, Eastern Taiwan
Authors: Wang Ming Kuang , Tseng Pao Chung , Chang Shyun Sheng , Ray Dah Tong , Shau Yen Hong , Shen Yun Wei , Chen Ruey Chyong , Chiang Po Neng
Published: December 2009

The Tuluanshan Formation of the eastern Coastal Range of Taiwan overlies an andesitic core complex presumed to be the source of hydrothermal fluids responsible for the Si- and Mg-rich mineralization of sepiolite and palygorskite (attapulgite) which are found in veins within fissures and in fracture zones of the volcanic rocks of the region. This study was undertaken in order to understand these relationships better by characterizing sepiolite and palygorskite in this Formation and by examining their occurrence and distribution in the Tungho (TH) and Chunjih (CJ) areas. Samples were analyzed using X-ray diffraction (XRD), thermal analysis, Fourier-transform infrared (FTIR) spectroscopy, and petrographic, scanning (SEM), and transmission (TEM) electron microscopic methods. Sepiolite and palygorskite are blocky and earthy-type materials that display fibrous characteristics when viewed using TEM and SEM and occurred alone or with chalcedony in veins. The fibers of blocky sepiolite are commonly intercalated with smectite but the earthy type of sepiolite and palygorskite observed in this study displayed precipitation from fluid enriched in Si, Al, Mg, and minor Fe and depleted in other ions at an earlier stage of offset of the andesitic veins. Continuation of reverse faulting and high shearing stress caused the precipitation of a significant quantity of interlaminated sepiolite. Sepiolite and palygorskite were formed at an earlier stage of fluid interaction relative to smectite in the Tuluanshan Formation.
Partial Dissolution of Glauconitic Samples: Implications for the Methodology of K-Ar and Rb-Sr Dating
Authors: Derkowski Arkadiusz , Środoń Jan , Franus Wojciech , Uhlík Peter , Banaś Michał , Zieliński Grzegorz , Čaplovičová Maria , Franus Małgorzata
Published: December 2009

The K-Ar dating of glauconite has been used as an important stratigraphic tool for many decades. The application of this technique is limited to pure glauconites, free of detrital contamination by K-bearing phases, often not easy to detect. This study extends the application of isotope dating to the contaminated glauconites and offers a precise technique for detecting the detrital contamination of glauconites.

The most common K-bearing detrital contaminants have smaller (K-feldspars, Al-rich dioctahedral micas) or greater (trioctahedral micas) dissolution rates than glauconite in extremely low pH solutions. The differences in the dissolution rates can be applied to evaluate the purity of the glauconite and its crystallization age.

The interlaboratory GLO glauconite standard and grain-size fractions separated from glauconitic sandstones of the Paleogene (sample GL) and Jurassic (sample GW8) ages were treated with acid (3M HCl, at 99±2°C) for different reaction times (0.5–7 h) and measured for their apparent isotopic ages.

Microporous amorphous silica with large specific surface area is the solid product of the reaction and its content increases with reaction time. The K-Ar dates (apparent ages) of the solid residues increase significantly with reaction time: from 44.6 to 107 Ma for the GL sample and from 125.7 to 394.7 Ma for GW8. The increase is negligible in the case of the GLO standard. The Rb-Sr data of the GL sample were modeled using initial 87Sr/Sr ratios of 0.707–0.709, which resulted in a 29.9–35.8 Ma date for the untreated portions of GL, and ∼42.6 Ma after 7 h of treatment.

The increase of isotopic K-Ar date with increasing time of dissolution is interpreted to be a result of increasing concentration of detrital, acid-resistant, K-bearing minerals, observed also with the electron microscope and X-ray diffraction. Probabilistic modeling based on single (K-Ar) or double (K-Ar and Rb-Sr) isotopic systems evaluated the isotopic ages of the detrital and authigenic minerals, and their K2O and Rb concentrations. The crystallization ages computed using these two methods are: 24.0, 26.5, and 32.3 Ma for the GL material, and 117.3–121.8 Ma for the GW8 series.

The proposed method based on partial dissolution is a potential tool for evaluating the reliability of glauconite dating.
Evidence of Degradation of Triarylmethine Dyes on Texas Vermiculite
Authors: Rytwo Giora , Gonen Yotam , Huterer-Shveky Reuma
Published: December 2009

Synthetic dyes in industrial effluents pose a significant risk to human health and the environment, so much effort has been expended to degrade them using various methods, including the use of clay minerals as catalysts. The purpose of this study was to advance understanding of the mechanisms for clay-catalyzed degradation of crystal violet (CV) and other triarylmethine dyes using three different vermiculite clays (Llano, Texas, VTx-1; Ojen, OV; and Russian, RV), a montmorillonite (SWy-1), and a Spanish sepiolite (SEP). While OV, RV, SWy-1, and SEP showed almost no activity with respect to dye degradation, VTx-1 caused complete removal of the dye from solution up to the equivalent of 200% of the cation exchange capacity of the clay. While large amounts of dye were removed from the solution, no change in basal spacing was observed by X-ray diffraction. The kinetics of removal of CV from solution began after a lag period of >10 days in a process that can be described by pseudo-second order kinetics. By comparison, adsorption of CV onto SWy-1 and SEP was immediate, without any lag period. Sonication treatment of the VTx-1 vermiculite suspension caused the CV removal process to begin immediately. Fourier-transform infrared measurements of adsorption of CV on clays revealed that for the OV and RV vermiculites, SEP sepiolite, and SWy-1 montmorillonite the spectra were similar to the original dye; the spectra of the VTx-1-dye differed considerably, however, exhibiting vibrations of methylene groups (—CH2—) which were not present in the CV molecule. The significant changes in the IR spectrum indicated that CV underwent degradation on the surface of the VTx-1 vermiculite. Carbon-content analysis led to the conclusion that degradation products remained bound to the clay. Similar effects were observed for two other triarylmethine dyes (malachite green and methyl green) added to VTx-1, indicated that it may, therefore, be considered suitable as a sorbent to remove and decompose such dyes from industrial effluents. Pretreatment by sonication would remove the need for long incubation times.
Progressive Formation of Halloysite From the Hydrothermal Alteration of Biotite and the Formation Mechanisms of Anatase in Altered Volcanic Rocks From Limnos Island, Northeast Aegean Sea, Greece
Authors: Papoulis Dimitrios , Tsolis-Katagas Panagiota , Kalampounias Angelos G. , Tsikouras Basilios
Published: December 2009

Occurrences of halloysite-rich material in altered volcanic rocks, principally trachyandesites, dacites, and tuffs, extend over an area of ∼1 km2 in the southwestern part of Limnos, Island, northeast Aegean Sea, Greece. The present study was designed to investigate the alteration processes which acted on the biotite in these volcanic rocks, to describe in detail the mechanism of formation of the halloysite, and to specify the mechanisms of formation of anatase during the alteration processes. Samples were examined using polarized-light microscopy, X-ray powder diffraction, scanning electron microscopy, scanning electron microscopy-energy dispersive spectroscopy, and Fourier-transform-Raman techniques. The extensive alteration of the parent rocks, triggered by the circulation of hydrothermal fluids through faults and fractures, resulted in the alteration of biotite to halloysite. Six stages of alteration were recognized. Nanoparticles of halloysite were initially formed on the mica layers, which progressively grew through short-tubular to well formed tubular halloysite, with increasing alteration. In the most altered samples, laths and interconnected laths with the composition (Al3.96Fe0.04)Si4O10(OH)8, were the dominant halloysite morphologies. Anatase was encountered as an alteration product of both ilmenite and biotite. Ilmenite was altered to anatase and Fe oxides. The altered ilmenite crystals constrained most of the newly formed anatase within the space occupied previously by ilmenite, leading to the formation of skeletal anatase. The layered structure of the micas was the main factor governing the morphology of newly formed anatase developed outside ilmenite margins in the form of layers parallel to those of mica. An unusual ring-like structure of anatase was thought to be the result of the uncommon alteration of inner parts of mica folia to tubular halloysite oriented perpendicular to the mica layers. The detachment of the halloysite tubes by circulating hydrothermal fluids was considered to be the reason for the creation of holes which were subsequently surrounded by the anatase ring forms.
Effect of Silica Polymerization on the Oxalate-Promoted Dissolution of Goethite
Authors: Eick Matthew J. , Luxton Todd P. , Welsh Holly A.
Published: December 2009

Numerous studies have investigated the ligand-promoted dissolution of Fe (oxyhydr)oxides. In natural environments, inorganic ligands can compete with organic ligands for surface sites on (oxyhydr)oxides which may influence dissolution rates. Published research of this interaction and its effect on the dissolution of (oxyhydr)oxides is rare. The objective of the present study was to examine the extent to which silica, as a naturally occurring competitive ligand added in the form of silicic acid, impacts the oxalate-promoted dissolution of the common soil Fe (oxyhydr)oxide goethite. Sorbed silica reduced the oxalate-promoted dissolution rate of goethite at all surface coverages investigated. As initial silica solution concentrations increased from 0.50 mM to 5.0 mM, relatively little change in the dissolution rate was observed. Fourier-transform infrared (FTIR) spectra indicated that, as silica-surface coverages increased, the silica underwent polymerization on the goethite surface. Initially, silicate was associated with surface functional groups, but as polymerization occurred some of the silica appeared to desorb from the goethite surface without being released into the bulk solution, suggesting that silica polymers formed discrete islands or surface clusters that grew away from the goethite surface rather than expanding epitaxially across the surface. Minimal changes were observed in the quantity of reactive goethite surface, which is responsible for the observed dissolution rates, as silica-surface coverages increased.
Effect of the Size of Aggregates on Pore Characteristics of Minerals Measured by Mercury Intrusion and Water-Vapor Desorption Techniques
Authors: Jozefaciuk Grzegorz
Published: December 2009

The size, shape, and continuity of pores in mineral solids greatly influence the behavior of percolating liquids and solids in porous media, which has significant practical environmental implications. In order to expand understanding of these properties in soil minerals, the present study was undertaken to analyze the pore characteristics of bentonite, illite, and kaolinite in the forms of powder and aggregates of different dimensions, combining water-vapor desorption and mercury-intrusion techniques. Different granulometric fractions of milled quartz glass were also studied. With increasing aggregate size of the minerals, larger pore volumes (up to 25%), smaller surface areas (down to 15%), larger average radii (up to 15%), and smaller fractal dimensions (down to 6%) were measured using water-vapor adsorption-desorption data. The differences were smallest for bentonite, possibly due to the smallest particle size of this mineral and/or to its very large water-vapor adsorption capacity. The degree of water-vapor adsorption on quartz was too small to rely on the data obtained.

The pore volumes and average radii, measured by mercury-intrusion porosimetry, were up to few times larger for the mineral powders than for their aggregate counterparts. Similar values were noted for aggregates >1 mm in diameter, for which the input of interaggregate spaces into total porosity of the sample bed was negligible. Two pathways of mercury intrusion were detected in porosimetric curves: filling of interaggregate spaces, and penetration into aggregates. Similar penetration thresholds into aggregates of different sizes were calculated. With increasing size of quartz grains, the pore volume of the quartz bed decreased whereas the average pore radius increased. Mercury intrusion detected pore-fractal behavior of bentonite and kaolinite, but for aggregated minerals the calculated values of fractal dimensions were >3, values which increased with increasing aggregate size. Very similar pore parameters were measured for aggregates prepared from a natural deposit of kaolinite and for artificially prepared aggregates from powder of the same mineral, indicating that artificial aggregation can simulate natural processes.

Both water desorption and mercury intrusion detected fractal behavior in the limited range of pores. A test to find fractal build up of the aggregates in extended scales based on a dependence of surface area of unit volume of aggregate bed on aggregate size showed no fractal-aggregate build-up.
Clayey Cap-Rock Behavior in H2O-CO2 Media at Low Pressure and Temperature Conditions: An Experimental Approach
Authors: Kohler Eric , Parra Teddy , Vidal Olivier
Published: December 2009

The storage of CO2 in geological reservoirs requires an understanding of the impact of CO2 on clay-rich sealing cap-rocks to identify and explore critical parameters that modify petrophysical properties such as permeability and fracturing. The purpose of this study was to investigate the effect of heating, under different hydrated-CO2 partial pressures, on the chemical compositions and relative amounts of mineral phases in the Saint Martin de Bossenay (SMB, Paris Basin, France) cap-rock in order to identify possible mineral-phase transitions and to estimate reaction kinetics induced by the presence of excess dissolved CO2.

X-ray diffraction, transmission electron microscopy, and electron microprobe analyses were employed to study mineral alteration, with particular attention given to visualization and quantification of the mineral evolution of clay minerals. In all the altered mixtures investigated, the illitization of clays was combined with the formation of anhydrite. These changes were accompanied by a dolomitization and a slight increase in the quartz content. The CO2-rich samples crystallized Fe2+-and K+-enriched illites, whereas the CO2-free experiments precipitated Al3+-deprived and Mg2+-enriched illites. Advanced characterizations of cap-rock material allowed reaction paths, induced by the increase in dissolved CO2 in the porous media, to be determined precisely. The results place strong constraints on numerical models aimed at evaluating the safety of an SMB site.
Functionalization of the Interlayer Surfaces of Kaolinite by Alkylammonium Groups From Ionic Liquids
Authors: Letaief Sadok , Detellier Christian
Published: December 2009

The objective of this study was to design new, functional, nanostructured materials from the abundant clay mineral kaolinite, in spite of development problems with the interlayer chemistry of kaolinite because of its non-swelling properties. A particular goal of this work was to graft, in a controlled way, alkylammonium groups onto the aluminol interlayer surfaces of kaolinite. This was successfully achieved by soft-chemical approaches, more specifically by the melting intercalation process of alkylammonium ionic liquids which were synthesized for this purpose. The resulting nanohybrid materials were characterized chemically and structurally by X-ray diffraction analysis, thermal analysis (TG/DTA), 13C cross polarization magic angle spinning nuclear magnetic resonance spectroscopy, and Fourier-transform infrared spectroscopy. The amount of grafted organic material was quantified from TGA results. Alkylammonium salts with a short alkyl chain were grafted directly using a melting reaction at 180°C under N2 involving the in situ displacement of dimethylsulfoxide (DMSO) from a DMSO-kaolinite pre-intercalate; for longer alkyl chains, the grafting was done in two steps. In the first step, the corresponding amino-alcohol was grafted into the kaolinite by displacement of DMSO from the interlayer space. The second step consisted of quaternarization of the grafted material by reaction with iodomethane or iodoethane.
A general existence proof for non-linear elliptic equations in semi-Riemannian spaces
Authors: Gerhardt Claus
Published: December 2009

We present a general existence proof for a wide class of non-linear
elliptic equations which can be applied to problems with barrier
conditions without specifying any assumptions guaranteeing the
uniqueness or local uniqueness of particular solutions.

As an application we prove the existence of closed
hypersurfaces with curvature prescribed in the tangent bundle of an
ambient Riemannian manifold $N$ without supposing any sign condition on
the sectional curvatures $K_N$. A curvature flow wouldn't work in this
situation, neither the method of successive approximation.
Relations among Dirichlet series whose coefficients are class numbers of binary cubic forms
Authors: Ohno Yasuo , Taniguchi Takashi , Wakatsuki Satoshi
Published: December 2009

We study the zeta functions for the space of binary cubic forms introduced by Shintani. The zeta function is defined for each invariant lattice. We classify the invariant lattices, and investigate explicit relationships between the zeta functions associated with those lattices. We also study the analytic properties of the zeta functions, and rewrite Shintani's functional equation in a self dual form using an explicit relation.