bluuebunny/crossref_metadata_2025 huggingface dataset:
Construct Equivalence across Groups: An Unexplored Issue in Mentoring Research
Authors: Pellegrini Ekin K. , Scandura Terri A.
Published: March 2005

Ensuring construct comparability is a prerequisite for testing cross-group differences, yet this assumption is rarely tested in mentoring research. More studies testing for factorial invariance are needed for the construct validation of mentoring. Multiple group confirmatory factor analyses (CFAs) were used to investigate the factorial stability of the Mentoring Functions Questionnaire (MFQ-9) across two groups: protégéswho are satisfied with their mentor and those who are not. CFA results supported a three-factor structure for the MFQ-9 composed of the dimensions of vocational support, psychosocial support, and role modeling. However, tests of invariance demonstrated nonequivalence for five item-pair measurements. Overall, the MFQ-9 demonstrated excellent psychometric properties with unsatisfied protégés; however, the instrument may need further development for use with satisfied protégés.
A Multilevel Factor Analysis of Students’ Evaluations of Teaching
Authors: Toland Michael D. , De Ayala R. J.
Published: March 2005

This study examined the factorial validity of scores on the newly developed Students’ Evaluation of Teaching Effectiveness Rating Scale (SETERS) through a series of confirmatory and multilevel structures. Conventional confirmatory factor analyses using the total covariance and pooled within-covariance matrices from two midwestern universities indicated that a reduced 25-item SETERS fit the data better than the original 34-item SETERS. Furthermore, multilevel factor analysis was conducted on the combined samples. This analysis suggested that one or three factors at the between and within levels were a plausible representation of SETERS scores. Pearson's correlations between individual scores on the SETERS and the Students’Evaluation of Educational Quality questionnaire provided additional validity evidence for the two measures. The need for additional empirical research on the SETERS before widespread use is discussed.
Recovery Symptoms and Mood States in Thai CABG patients
Authors: Utriyaprasit Ketsarin , Moore Shirley
Published: March 2005

Recovery symptoms and related mood states during early recovery after coronary artery bypass graft surgery (CABG) have never been assessed in Thailand. This cross-sectional descriptive correlational study was to identify the relationships between frequency of recovery symptoms and mood states of a convenience sample of 91 Thai CABG patients during 2 weeks after discharge. Standardized tools/procedures were used to measure the variables of interest. The most common recovery symptoms were chest and leg incision pain, having trouble sleeping, and neck and shoulder or back discomfort. The most common mood states were confusion, anxiety, and anger, respectively. In addition, Thai CABG patients who had more frequent recovery symptoms also had greater negative mood disturbance. These findings provide a beginning explanation about the phenomena of recovery symptoms and mood states in a specific culture, Thai CABG patients.
A Descriptive Internet Survey on Menopausal Symptoms: Five Ethnic Groups of Asian American University Faculty and Staff
Authors: Im Eun-Ok , Chee Wonshik
Published: March 2005

The purpose of this Internet study was to describe menopausal symptoms, perceived causes of the symptoms, and management strategies for the symptoms among five ethnic groups of Asian American women. Sixty-two university faculty and/or staff members aged 40 to 60 years who self-reported as Asian Americans and could read and write English were recruited through the Internet. An Internet survey was conducted, and the data were analyzed using descriptive statistics. The most prevalent symptoms were “worrying about body,” “aches in back of neck and skull,” and “weight gain.” Most of the women perceived “aging” as the main cause of their symptoms and chose not to manage their symptoms. The findings strongly suggest that women’s own explanation of their symptoms is frequently different from that of health care providers.
Chronic Illness and Hmong Shamans
Authors: Helsel Deborah , Mochel Marilyn , Bauer Robert
Published: March 2005

Among the challenges health care personnel in California’s central valley face has been finding ways to help Hmong Americans manage chronic illness. Interviews were conducted with 11 Hmong shamans diagnosed with diabetes or hypertension and were qualitatively analyzed to ascertain respondents’ understanding and management of their illnesses. Hmong shamans are influential individuals within their communities and are often the resource persons to whom patients turn for information on health. Understanding the shamans’ perspective on chronic illness was seen as a gateway to understanding how the broader Hmong American community perceived these conditions. The concept of chronic illness was not well understood, resulting in sporadic medication and dietary regimens, limited awareness of potential complications, and a persistent impression that these illnesses could be cured rather than managed. Suggestions for patient educators include family and community involvement in care regimens and the use of descriptive terminology to identify the disease.
Carotid intimal-media thickness as a surrogate for cardiovascular disease events in trials of HMG-CoA reductase inhibitors
Authors: Espeland Mark A , O'Leary Daniel H , Terry James G , Morgan Timothy , Evans Greg , Mudra Harald
Published: March 2005

Background

Surrogate measures for cardiovascular disease events have the potential to increase greatly the efficiency of clinical trials. A leading candidate for such a surrogate is the progression of intima-media thickness (IMT) of the carotid artery; much experience has been gained with this endpoint in trials of HMG-CoA reductase inhibitors (statins).

Methods and Results

We examine two separate systems of criteria that have been proposed to define surrogate endpoints, based on clinical and statistical arguments. We use published results and a formal meta-analysis to evaluate whether progression of carotid IMT meets these criteria for HMG-CoA reductase inhibitors (statins).

IMT meets clinical-based criteria to serve as a surrogate endpoint for cardiovascular events in statin trials, based on relative efficiency, linkage to endpoints, and congruency of effects. Results from a meta-analysis and post-trial follow-up from a single published study suggest that IMT meets established statistical criteria by accounting for intervention effects in regression models.

Conclusion

Carotid IMT progression meets accepted definitions of a surrogate for cardiovascular disease endpoints in statin trials. This does not, however, establish that it may serve universally as a surrogate marker in trials of other agents.
Ca2+ regulation in the absence of the iplA gene product in Dictyostelium discoideum
Authors: Schaloske Ralph H , Lusche Daniel F , Bezares-Roder Karen , Happle Kathrin , Malchow Dieter , Schlatterer Christina
Published: March 2005

Background

Stimulation of Dictyostelium discoideum with cAMP evokes an elevation of the cytosolic free Ca2+ concentration ([Ca2+]i). The [Ca2+]i-change is composed of liberation of stored Ca2+ and extracellular Ca2+-entry. The significance of the [Ca2+]i-transient for chemotaxis is under debate. Abolition of chemotactic orientation and migration by Ca2+-buffers in the cytosol indicates that a [Ca2+]i-increase is required for chemotaxis. Yet, the iplA- mutant disrupted in a gene bearing similarity to IP3-receptors of higher eukaryotes aggregates despite the absence of a cAMP-induced [Ca2+]i-transient which favours the view that [Ca2+]i-changes are insignificant for chemotaxis.

Results

We investigated Ca2+-fluxes and the effect of their disturbance on chemotaxis and development of iplA- cells. Differentiation was altered as compared to wild type amoebae and sensitive towards manipulation of the level of stored Ca2+. Chemotaxis was impaired when [Ca2+]i-transients were suppressed by the presence of a Ca2+-chelator in the cytosol of the cells. Analysis of ion fluxes revealed that capacitative Ca2+-entry was fully operative in the mutant. In suspensions of intact and permeabilized cells cAMP elicited extracellular Ca2+-influx and liberation of stored Ca2+, respectively, yet to a lesser extent than in wild type. In suspensions of partially purified storage vesicles ATP-induced Ca2+-uptake and Ca2+-release activated by fatty acids or Ca2+-ATPase inhibitors were similar to wild type. Mn2+-quenching of fura2 fluorescence allows to study Ca2+-influx indirectly and revealed that the responsiveness of mutant cells was shifted to higher concentrations: roughly 100 times more Mn2+ was necessary to observe agonist-induced Mn2+-influx. cAMP evoked a [Ca2+]i-elevation when stores were strongly loaded with Ca2+, again with a similar shift in sensitivity in the mutant. In addition, basal [Ca2+]i was significantly lower in iplA- than in wild type amoebae.

Conclusion

These results support the view that [Ca2+]i-transients are essential for chemotaxis and differentiation. Moreover, capacitative and agonist-activated ion fluxes are regulated by separate pathways that are mediated either by two types of channels in the plasma membrane or by distinct mechanisms coupling Ca2+-release from stores to Ca2+-entry in Dictyostelium. The iplA- strain retains the capacitative Ca2+-entry pathway and an impaired agonist-activated pathway that operates with reduced efficiency or at higher ionic pressure.
Delta activity independent of its activity as a ligand of Notch
Authors: Mok Lee-Peng , Qin Tielin , Bardot Boris , LeComte Matthew , Homayouni Asal , Ahimou Francois , Wesley Cedric
Published: March 2005

Background

Delta, Notch, and Scabrous often function together to make different cell types and refine tissue patterns during Drosophila development. Delta is known as the ligand that triggers Notch receptor activity. Scabrous is known to bind Notch and promote Notch activity in response to Delta. It is not known if Scabrous binds Delta or Delta has activity other than its activity as a ligand of Notch. It is very difficult to clearly determine this binding or activity in vivo as all Notch, Delta, and Scabrous activities are required simultaneously or successively in an inter-dependent manner.

Results

Using Drosophila cultured cells we show that the full length Delta promotes accumulation of Daughterless protein, fringe RNA, and pangolin RNA in the absence of Scabrous or Notch. Scabrous binds Delta and suppresses this activity even though it increases the level of the Delta intracellular domain. We also show that Scabrous can promote Notch receptor activity, in the absence of Delta.

Conclusion

Delta has activity that is independent of its activity as a ligand of Notch. Scabrous suppresses this Delta activity. Scabrous also promotes Notch activity that is dependent on Delta's ligand activity. Thus, Notch, Delta, and Scabrous might function in complex combinatorial or mutually exclusive interactions during development. The data reported here will be of significant help in understanding these interactions in vivo.
Isolation by distance, web service
Authors: Jensen Jeffrey L , Bohonak Andrew J , Kelley Scott T
Published: March 2005

Background

The population genetic pattern known as "isolation by distance" results from spatially limited gene flow and is a commonly observed phenomenon in natural populations. However, few software programs exist for estimating the degree of isolation by distance among populations, and they tend not to be user-friendly.

Results

We have created Isolation by Distance Web Service (IBDWS) a user-friendly web interface for determining patterns of isolation by distance. Using this site, population geneticists can perform a variety of powerful statistical tests including Mantel tests, Reduced Major Axis (RMA) regression analysis, as well as calculate F
ST
between all pairs of populations and perform basic summary statistics (e.g., heterozygosity). All statistical results, including publication-quality scatter plots in Postscript format, are returned rapidly to the user and can be easily downloaded.

Conclusion

IBDWS population genetics analysis software is hosted at http://phage.sdsu.edu/~jensen/ and documentation is available at http://www.bio.sdsu.edu/pub/andy/IBD.html. The source code has been made available on Source Forge at http://sourceforge.net/projects/ibdws/.
Pharmacokinetic-pharmacodynamic modelling of the cardiovascular effects of drugs – method development and application to magnesium in sheep
Authors: Upton Richard N , Ludbrook Guy L
Published: March 2005

Background

There have been few reports of pharmacokinetic models that have been linked to models of the cardiovascular system. Such models could predict the cardiovascular effects of a drug under a variety of circumstances. Limiting factors may be the lack of a suitably simple cardiovascular model, the difficulty in managing extensive cardiovascular data sets, and the lack of physiologically based pharmacokinetic models that can account for blood flow changes that may be caused by a drug. An approach for addressing these limitations is proposed, and illustrated using data on the cardiovascular effects of magnesium given intravenously to sheep.

The cardiovascular model was based on compartments for venous and arterial blood. Blood flowed from arterial to venous compartments via a passive flow through a systemic vascular resistance. Blood flowed from venous to arterial via a pump (the heart-lung system), the pumping rate was governed by the venous pressure (Frank-Starling mechanism). Heart rate was controlled via the difference between arterial blood pressure and a set point (Baroreceptor control). Constraints were made to pressure-volume relationships, pressure-stroke volume relationships, and physical limits were imposed to produce plausible cardiac function curves and baseline cardiovascular variables. "Cardiovascular radar plots" were developed for concisely displaying the cardiovascular status. A recirculatory kinetic model of magnesium was developed that could account for the large changes in cardiac output caused by this drug. Arterial concentrations predicted by the kinetic model were linked to the systemic vascular resistance and venous compliance terms of the cardiovascular model. The kinetic-dynamic model based on a training data set (30 mmol over 2 min) was used to predict the results for a separate validation data set (30 mmol over 5 min).

Results

The kinetic-dynamic model was able to describe the training data set. A recirculatory kinetic model was a good description of the acute kinetics of magnesium in sheep. The volume of distribution of magnesium in the lungs was 0.89 L, and in the body was 4.02 L. A permeability term (0.59 L min-1) described the distribution of magnesium into a deeper (probably intracellular) compartment. The final kinetic-dynamic model was able to predict the validation data set. The mean prediction error for the arterial magnesium concentrations, cardiac output and mean arterial blood pressure for the validation data set were 0.02, 3.0 and 6.1%, respectively.

Conclusion

The combination of a recirculatory model and a simple two-compartment cardiovascular model was able to describe and predict the kinetics and cardiovascular effects of magnesium in sheep.
Role of Oocyte-Secreted Growth Differentiation Factor 9 in the Regulation of Mouse Cumulus Expansion
Authors: Dragovic Rebecca A. , Ritter Lesley J. , Schulz Samantha J. , Amato Fred , Armstrong David T. , Gilchrist Robert B.
Published: March 2005

Oocyte-secreted factors are required for expansion of the mouse cumulus-oocyte complex, which is necessary for ovulation. Oocyte-secreted growth differentiation factor 9 (GDF9) signals through the bone morphogenetic protein receptor II and is currently the primary candidate molecule for the cumulus-expansion enabling factor. This study was conducted to determine whether GDF9 is the mouse cumulus-expansion enabling factor. Cumulus-oocyte complexes were collected from mice, and the oocyte was microsurgically removed to generate an oocytectomized (OOX) complex. OOX complexes treated with FSH alone or recombinant mouse GDF9 alone failed to expand, whereas expansion was induced in the presence of FSH by GDF9, TGFβ1, or coculture with oocytes. A specific GDF9-neutralizing antibody, mAb-GDF9–53, neutralized the expansion of OOX complexes in response to GDF9 but not the expansion of OOX complexes cocultured with oocytes. Using real-time RT-PCR, hyaluronan synthase 2 (HAS2) mRNA expression by OOXs was up-regulated 4- to 6-fold by oocytes and GDF9. Monoclonal neutralizing antibody-GDF9–53 attenuated GDF9-induced OOX HAS2 expression but not oocyte-induced HAS2 expression. A TGFβ antagonist neutralized TGFβ-induced, but not oocyte-induced, expansion of OOX complexes, and when combined with monoclonal neutralizing antibody-GDF9–53 also failed to neutralize oocyte-induced expansion. Furthermore, a soluble portion of the bone morphogenetic protein receptor II extracellular domain, which is a known GDF9 antagonist, completely antagonized GDF9-induced expansion but only partially neutralized oocyte-induced expansion. This study provides further evidence that like TGFβ, GDF9 can enable FSH-induced cumulus expansion, but more importantly, demonstrates that neither GDF9 nor TGFβ alone, nor the two in unison, account for the critical oocyte-secreted factors regulating mouse cumulus expansion.
Electromagnetic wave propagation and inequalities for moments of chord lengths
Authors: Hansen Jan , Reitzner Matthias
Published: March 2005

In a convex domain K in ℝd, a transmitter and a receiver are placed at random according to the uniform distribution. The statistics of the power received by the receiver is an important quantity for the design of wireless communication systems. Bounds for the moments of the received power are given, which depend only on the volume and the surface area of the convex domain.
A Monotone Process Maintenance Model for a Multistate System
Authors: Yeh Lam
Published: March 2005

In this paper, we study a monotone process maintenance model for a multistate system with k working states and ℓ failure states. By making different assumptions, we can apply the model to a multistate deteriorating system as well as to a multistate improving system. We show that the monotone process model for a multistate system is equivalent to a geometric process model for a two-state system. Then, for both the deteriorating and the improving system, we analytically determine an optimal replacement policy for minimizing the long-run average cost per unit time.
Some Time-Dependent Properties of Symmetric M/G/1 Queues
Authors: Kella Offer , Zwart Bert , Boxma Onno
Published: March 2005

We consider an M/G/1 queue that is idle at time 0. The number of customers sampled at an independent exponential time is shown to have the same geometric distribution under the preemptive-resume last-in-first-out and the processor-sharing disciplines. Hence, the marginal distribution of the queue length at any time is identical for both disciplines. We then give a detailed analysis of the time until the first departure for any symmetric queueing discipline. We characterize its distribution and show that it is insensitive to the service discipline. Finally, we study the tail behavior of this distribution.
A Transposition Rule Analysis Based on a Particle Process
Authors: Gamarnik David , Momčilović Petar
Published: March 2005

A linear list is a collection of items that can be accessed sequentially. The cost of a request is the number of items that need to be examined before the desired item is located, i.e. the distance of the requested item from the beginning of the list. The transposition rule is one of the algorithms designed to reduce the search cost by organizing the list. In particular, upon a request for a given item, the item is transposed with the preceding one. We develop a new approach for analyzing the algorithm, based on a coupling to a certain constrained asymmetric exclusion process. This allows us to establish an asymptotic optimality of the rule for two families of request distributions.
The Large Deviations of Estimating Rate Functions
Authors: Duffy Ken , Metcalfe Anthony P.
Published: March 2005

Given a sequence of bounded random variables that satisfies a well-known mixing condition, it is shown that empirical estimates of the rate function for the partial sums process satisfy the large deviation principle in the space of convex functions equipped with the Attouch-Wets topology. As an application, a large deviation principle for estimating the exponent in the tail of the queue length distribution at a single-server queue with infinite waiting space is proved.
Crystal Structures of Two Molecular Complexes between Cationic Surfactants and Hydroquinone Showing a Melanogenesis Inhibitory Effect
Authors: Iimura Nahoko , Fujimura Yuko , Sekine Akiko , Kitagawa Shuji , Ohashi Yuji
Published: March 2005

Hydroquinone, showing a melanogenesis inhibitory effect, formed crystalline molecular complexes with two cationic surfactants of benzyl(hexadecyl)dimethylammonium chloride and ethyl(hexadecyl)dimethylammonium bromide from an methanol solution at low temperatures, lower than 15 °C. The crystal structures were analyzed by X-rays at 223 K. There are two crystallographically independent hydroquinone molecules and one surfactant molecule in each crystal. One of the hydroquinone molecules is sandwiched by the surfactant molecules and makes a “common packing pattern,” which has been observed in complex crystals between aromatic compounds and surfactant molecules. Another hydroquinone occupies an inversion center surrounded by the benzyldimethylammonium or ethyldimethylammonium moiety of the surfactant molecule. Such a close packing makes hydroquinone in the molecular complex stable in open air at room temperature.
Dynamics of the Hydration of Amino Alcohols and Diamines in Aqueous Solution
Authors: Okouchi Shoichi , Tsuchida Kazushi , Yoshida Satoshi , Ishihara Yoshimasa , Ikeda Shigeo , Uedaira Hisashi
Published: March 2005

The 17O NMR spin–lattice relaxation times (T1) of solvent water molecules in aqueous solutions of amino alcohols (AA), charged amino alcohols (AA+), and charged diamines (DA2+) were determined as a function of concentration at 298 K. The values of the dynamic hydration number, nDHN = nh(τch/τc0−1), were determined from the concentration dependence of T1. The ratios (τch/τc0) of the rotational correlation times (τch) of the water molecules around each solute molecule in the aqueous solutions to that of pure water (τc0) were obtained from the nDHN and the hydration number (nh), which was calculated from the water accessible surface area (ASA) of the solute molecule. The hydrophobic hydration is disturbed by the adjacent polar groups. The effect of disturbance decreases in the following order: NH3+ > OH > NH2. The ASA dependence of the τch/τc0 value for diamines (DA), AA, and diols decreases in the following order: DA > AA > diols. When DA and AA are in a charged state, this order is reversed, namely, diols > AA+ > DA2+. The thermodynamic quantities of hydration for AA and AA+ are linearly dependent on their nDHN values.
D-Dimer Concentrations in Normal Pregnancy: New Diagnostic Thresholds Are Needed
Authors: Kline Jeffrey A , Williams Ginger W , Hernandez-Nino Jackeline
Published: March 2005

Background: Pregnancy is known to increase the D-dimer concentration above the conventional normal threshold of 0.50 mg/L, leading to an increased false-positive D-dimer test when venous thromboembolism (VTE) is clinically suspected in a pregnant patient. Our aim was to determine the effect of normal pregnancy on the D-dimer concentration.

Methods: Healthy women who were seeking to become pregnant and had no preexisting condition known to increase the D-dimer concentration were identified. Quantitative D-dimer measurements (MDA turbidimetric assay) and fibrinogen assays were performed before conception, at each trimester, and at 4 weeks postpartum. Patients were excluded for fetal loss or preeclampsia.

Results: A total of 50 women were enrolled in the study, and blood samples were obtained at preconception and all trimesters from 23 women. The mean (SD) preconception D-dimer concentration was 0.43 (0.49) mg/L, and 79% of women had a D-dimer concentration <0.50 mg/L. D-Dimer increased with each trimester such that only 22% of women in the second trimester and none (of 23) in the third trimester (95% confidence interval, 0–14%) had a D-dimer concentration <0.50 mg/L. We found no correlation between either the D-dimer and fibrinogen concentrations or between the increases in D-dimer and fibrinogen with pregnancy.

Conclusions: Normal pregnancy causes a progressive increase in circulating D-dimer. The D-dimer test has no use in ruling out VTE in the third trimester if a cutoff of 0.50 mg/L is used. A large management study is needed to establish new thresholds for the D-dimer to rule out VTE in each trimester.
Cover Picture: Bistable Nematic Liquid Crystals with Self‐Assembled Fibers (Adv. Mater. 6/2005)
Authors: Mizoshita N. , Suzuki Y. , Hanabusa K. , Kato T.
Published: March 2005

The cover shows a recording process using nematic liquid crystal alignment. On p. 692, Kato and co‐workers report that reversibly bistable states have been achieved for nematic liquid crystals incorporating a small amount of self‐assembled fibers. Homeotropic monodomains and non‐aligned multidomains can be fixed and switched by thermal treatment in electric fields. The technique is applied to the formation of rewritable light scattering patterns, as shown on the cover.
Weight‐height relationships and body mass index: Some observations from the diverse populations collaboration
Authors:   Diverse Populations Collaborative Group
Published: March 2005

Body mass index (BMI, weight (kg)/height (m)2) is the most widely used weight‐height index worldwide. This universal use of BMI assumes that the rationale for its use is universally applicable. We examine two possible rationales for using BMI as a universal measure. The first rationale is that BMI is strongly correlated with weight, but is independent of height. The second rationale is that BMI correctly captures the relationship between weight and height, which implies that the slope of log weight regressed on log height is 2. We examined the weight‐height relationship in 25 diverse population samples of men and women from the US, Europe, and Asia. The analysis included 72 subgroups with a total of 385,232 adults aged 25 years and older. Although BMI was highly correlated with weight in all studies, a significant, negative correlation between BMI and height was found in 31 out of 40 subgroups of men (r = −0.004 to −0.133) and 32 of 32 groups of women (r = −0.016 to −0.205). When log weight was regressed on log height, the 95% confidence intervals (CI) of the slopes did not include 2 in 25 out of 40 male subgroups. The summary estimate of the slopes across studies of men was 1.92 (95% CI, 1.87–1.97). For women, slopes were lower than 2 in 28 of 32 subgroups with a summary estimate of 1.45 (95% CI, 1.39–1.51). In most of the populations, BMI is not independent of height; weight does not universally vary with the square of height; and the relationship between weight and height differs significantly between males and females. The use of a single BMI standard for both men and women cannot be justified on the basis of weight‐height relationships. Am J Phys Anthropol 128:220‐229, 2005. © 2005 Wiley‐Liss, Inc.
Measurement and modeling of poly(vinyl acetate)–solvent viscosity mixtures
Authors: Modarress Hamid , Mohsen‐Nia Mohsen
Published: March 2005

The viscosities of various poly(vinyl acetate) (PVAc)–solvent mixtures (PVAc–toluene, PVAc–benzene, and PVAc–cyclohexanone) were measured at different temperatures with a Haake viscometer. The required molecular weight of a commercial‐grade PVAc sample was measured with an Ubbelohde viscometer. The measured viscosities were correlated with a previously proposed viscosity model, and the model parameters were calculated. The results indicated the applicability of the model to the viscosity calculations of PVAc–solvent mixtures. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1244–1249, 2005
Mechanism of Anionic Dearomatizing Reactions of Diphenylphosphinamide Derivatives: A Theoretical and Experimental Study
Authors: Ramallal Antonio Morán , Fernández Ignacio , López Ortiz Fernando , González Javier
Published: March 2005

The mechanism of the anionic dearomatisation of phosphinamide derivatives has been investigated both theoretically and experimentally. The potential‐energy surface of model reactions was studied at the Becke3LYP/6‐31+G* level of theory, and according to this study, a pre‐reactive complex is formed between the alkyllithium and the phosphinamide. This complex evolves preferentially through NCα‐metalation of the phosphinamide. The intramolecular nucleophilic addition of the carbanion to the ortho position of the aromatic ring leads to the dearomatised products, in a reaction that has been shown to be under thermodynamic control. Coordinating co‐solvents, such as hexamethyl phosphoramide (HMPA) or N,N′‐dimethyl‐N,N′‐propylene urea (DMPU), appear to influence the reaction by favouring the formation of solvent‐separated ion pairs. The cyclisation reaction of allylphosphinamide derivatives was also studied. It was found that both the α‐ and γ‐attack of the allyl anion can take place, however the formation of the seven‐membered ring products derived from the γ‐attack are clearly favoured.
Photoinduced Electron Transfer Reactions by SmI2 in THF: Luminescence Quenching Studies and Mechanistic Investigations
Authors: Prasad Edamana , Knettle Brian W. , Flowers Robert A.
Published: March 2005

Photoluminescence quenching studies of SmI2 in dry THF were carried out in the presence of five different classes of compounds: ketone, alkyl chloride, nitrile, alkene and imine. The free energy change (ΔG 0) of the photoinduced electron transfer (PET) reactions was calculated from the redox potentials of the donor (SmI2) and acceptors. The bimolecular quenching constants (kq) derived from the Stern–Volmer experiments parallel the free energy changes of the PET processes. The observed quenching constants were compared with the theoretically derived electron transfer rate constants (ket) from Marcus theory and found to be in good agreement when a value of λ=167 kJ mol−1 (40 kcal mol−1) was used for the reorganization energy of the system. A careful comparison of the excited state dynamics of SmII in the solid state to the results obtained in solution (THF) provides new insight in to the excited states of SmII in THF. The activation parameters determined for the PET reactions in SmI2/1‐chlorobutane system are consistent with a less ordered transition state and high degree of bond reorganization in the activated complex compared to similar ground state reactions. Irradiation studies clearly show that SmI2 acts as a better reductant in the excited state and provides an alternative pathway for rate enhancement in known and novel functional group reductions.
Synthesis, X‐ray Crystal Structures, and Gas Sorption Properties of Pillared Square Grid Nets Based on Paddle‐Wheel Motifs: Implications for Hydrogen Storage in Porous Materials
Authors: Chun Hyungphil , Dybtsev Danil N. , Kim Hyunuk , Kim Kimoon
Published: March 2005

A systematic modulation of organic ligands connecting dinuclear paddle‐wheel motifs leads to a series of isomorphous metal‐organic porous materials that have a three‐dimensional connectivity and interconnected pores. Aromatic dicarboxylates such as 1,4‐benzenedicarboxylate (1,4‐bdc), tetramethylterephthalate (tmbdc), 1,4‐naphthalenedicarboxylate (1,4‐ndc), tetrafluoroterephthalate (tfbdc), or 2,6‐naphthalenedicarboxylate (2,6‐ndc) are linear linkers that form two‐dimensional layers, and diamine ligands, 4‐diazabicyclo[2.2.2]octane (dabco) or 4,4′‐dipyridyl (bpy), coordinate at both sides of Zn2 paddle‐wheel units to bridge the layers vertically. The resulting open frameworks [Zn2(1,4‐bdc)2(dabco)] (1), [Zn2(1,4‐bdc)(tmbdc)(dabco)] (2), [Zn2(tmbdc)2(dabco)] (3), [Zn2(1,4‐ndc)2(dabco)] (4), [Zn2(tfbdc)2(dabco)] (5), and [Zn2(tmbdc)2(bpy)] (8) possess varying size of pores and free apertures originating from the side groups of the 1,4‐bdc derivatives. [Zn2(1,4‐bdc)2(bpy)] (6) and [Zn2(2,6‐ndc)2(bpy)] (7) have two‐ and threefold interpenetrating structures, respectively. The non‐interpenetrating frameworks (1–5 and 8) possess surface areas in the range of 1450–2090 m2g−1 and hydrogen sorption capacities of 1.7–2.1 wt % at 78 K and 1 atm. A detailed analysis of the sorption data in conjunction with structural similarities and differences concludes that porous materials with straight channels and large openings do not perform better than those with wavy channels and small openings in terms of hydrogen storage through physisorption.
Structure Characterization and Possible Biogenesis of Three New Families of Nortriterpenoids: Schisanartane, Schiartane, and 18‐Norschiartane
Authors: Li Rong‐Tao , Xiao Wei‐Lie , Shen Yun‐Heng , Zhao Qin‐Shi , Sun Han‐Dong
Published: March 2005

Four new, highly oxygenated nortriterpenoids with unique schisanartane skeletons, micrandilactones D–G (1–4), have been isolated from the leaves and stems of Schisandra micrantha, and their structures have been elucidated on the basis of extensive spectral studies. The postulated biogenetic sequences of sixteen highly oxygenated nortriterpenoids and bisnortriterpenoids with new skeletons from three Schisandra species are discussed and have been compared from a chemotaxonomic standpoint.
Native myelin oligodendrocyte glycoprotein promotes severe chronic neurological disease and demyelination in Biozzi ABH mice
Authors: Smith Paul A. , Heijmans Nicole , Ouwerling Boudewijn , Breij Esther C. , Evans Nicholas , van Noort Johannes M. , Plomp Arianne C. , Delarasse Cécile , ‘t Hart Bert , Pham‐Dinh Danielle , Amor Sandra
Published: March 2005

Myelin oligodendrocyte glycoprotein (MOG) is a powerful encephalitogen for experimental autoimmune demyelination. However, the use of MOG peptides or recombinant proteins representing part of the protein fails to fully address the possible pathogenic role of the full‐length myelin‐derived protein expressing post‐translational modifications. Immunization of mice with central nervous system tissues from wild‐type (WT) and MOG‐deficient (MOG–/–) mice demonstrates that MOG in myelin is necessary for the development of chronic demyelinating experimental autoimmune encephalomyelitis (EAE) in mice. While immunization with WT spinal cord homogenate (SCH) resulted in a progressive EAE phenotype, MOG–/– SCH induced a mild self‐limiting acute disease. Following acute EAE with MOG–/– SCH, mice developed T cell responses to recombinant mouse MOG (rmMOG), indicating that MOG released from myelin is antigenic; however, the lack of chronic disease indicates that such responses were not pathogenic. Chronic demyelinating EAE was observed when MOG–/– SCH was reconstituted with a dose of rmMOG comparable to MOG in myelin (2.5% of total white matter‐derived protein). These data reveal that while immunization with the full‐length post‐translational modified form of MOG in myelin promotes the development of a more chronic autoimmune demyelinating neurological disease, MOG (and/or other myelin proteins) released from myelin during ongoing disease do not induce destructive autoimmunity.
Entrepreneurship in higher education
Authors: Breneman David W.
Published: March 2005

A common set of economic pressures has led the various sectors of higher education to adopt entrepreneurial models of financing and service.
The role of noncredit courses in serving nontraditional learners
Authors: Milam John
Published: March 2005

New data on noncredit course offerings at colleges and universities help to generate a statistical portrait of these increasingly important programs.
Experimental investigation on the role of water in the mechanical behavior of structural dentine
Authors: Kishen A. , Asundi A.
Published: March 2005

Dentine is a porous hydrated composite structure that forms the major bulk of the human tooth. The aim of this study was to investigate the role of free water on the in‐plane, mechanical strain response in dentine structure. A digital moiré interferometry was used for this purpose. It was observed from this experiment that structural dentine demonstrated distinct strain gradients in the axial (perpendicular to the dentinal tubules) and lateral (parallel to the dentinal tubules) directions. The hydrated dentine displayed significant increase in strain with stress in the direction perpendicular to the dentinal tubules, and this response was characteristic of a tough material. On the contrary, the dehydrated dentine, which was dehydrated at 24°C, 55% relative humidity for 72 h showed a strain response characteristic of a brittle material. The strains formed in the direction parallel to the dentinal tubules for hydrated dentine were consistent and did not vary much with increase in applied loads. Upon dehydration, the outer dentine experienced higher strains, and the difference between the outer and inner dentine became more conspicuous with increase in loads. This experiment highlights hydration‐induced, distinct in‐plane strain gradients in the directions perpendicular and parallel to the dentinal tubules in the dentine structure. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res 73A: 192–200, 2005
Levels of 4‐aminobiphenyl‐induced somatic H‐ras mutation in mouse liver DNA correlate with potential for liver tumor development
Authors: Parsons Barbara L. , Beland Frederick A. , Von Tungeln Linda S. , Delongchamp Robert R. , Fu Peter P. , Heflich Robert H.
Published: March 2005

The utility of liver H‐ras codon 61 CAA to AAA mutant fraction as a biomarker of liver tumor development was investigated using neonatal male mice treated with 4‐aminobiphenyl (4‐ABP). Treatment with 0.1, 0.3, or 1.0 μmol 4‐ABP produced dose‐dependent increases in liver DNA adducts in B6C3F1 and C57BL/6N mice. Eight months after treatment with 0.3 μmol 4‐ABP or the DMSO vehicle, H‐ras codon 61 CAA to AAA mutant fraction was measured in liver DNA samples (n = 12) by allele‐specific competitive blocker‐polymerase chain reaction (ACB‐PCR). A significant increase in average mutant fraction was found in DNA of 4‐ABP‐treated mice, with an increase from 1.3 × 10−5 (control) to 44.9 × 10−5 (treated) in B6C3F1 mice and from 1.4 × 10−5 to 7.0 × 10−5 in C57BL/6N mice. Compared with C57BL/6N mutant fractions, B6C3F1 mutant fractions were more variable and included some particularly high mutant fractions, consistent with the more rapid development of liver foci expected in B6C3F1 mouse liver. Twelve months after treatment, liver tumors developed in 79.2% of 4‐ABP‐treated and 22.2% of control B6C3F1 mice; thus measurement of H‐ras mutant fraction correlated with subsequent tumor development. This study demonstrates that ACB‐PCR can directly measure background levels of somatic oncogene mutation and detect a carcinogen‐induced increase in such mutation. Published 2005 Wiley‐Liss, Inc.
Analysis of three‐dimensional crack initiation and propagation using the extended finite element method
Authors: Areias Pedro M. A. , Belytschko Ted
Published: March 2005

An Erratum has been published for this article in International Journal for Numerical Methods in Engineering 2005, 63(8): 1228.

We present a new formulation and a numerical procedure for the quasi‐static analysis of three‐dimensional crack propagation in brittle and quasi‐brittle solids. The extended finite element method (XFEM) is combined with linear tetrahedral elements. A viscosity‐regularized continuum damage constitutive model is used and coupled with the XFEM formulation resulting in a regularized ‘crack‐band’ version of XFEM. The evolving discontinuity surface is discretized through a C0 surface formed by the union of the triangles and quadrilaterals that separate each cracked element in two. The element's properties allow a closed form integration and a particularly efficient implementation allowing large‐scale 3D problems to be studied. Several examples of crack propagation are shown, illustrating the good results that can be achieved. Copyright © 2005 John Wiley & Sons, Ltd.
Kinetic study of TNF‐α production and its regulatory mechanisms in acinar cells during acute pancreatitis induced by bile–pancreatic duct obstruction
Authors: Ramudo Laura , Manso Manuel A , Sevillano Sara , de Dios Isabel
Published: March 2005

Cytokines play a critical role in acute pancreatitis (AP) but the contribution of different cell sources to cytokine production is unclear. Unfortunately, there are no data concerning the molecular mechanisms involved in the inflammatory response in humans during AP. For this reason, the aim of this study was to analyse the ability of acinar cells, in comparison with leukocytes, to produce TNF‐α at different stages of AP induced in rats by bile–pancreatic duct obstruction (BPDO) and to investigate the time course of oxidant‐sensitive mechanisms involved in cytokine production. The role of oxygen free radicals as messengers of the mechanisms underlying acinar cell TNF‐α production was assessed in BPDO rats treated with N‐acetylcysteine (NAC). While monocytes were not able to produce TNF‐α until 12 h after inducing AP, acinar cells triggered TNF‐α production from 6 h after BPDO, at which time the pancreas develops maximal oxidative stress. Phosphorylated p38‐MAPK and activated NF‐κB were detected in acinar cells from 6 h after BPDO. NAC treatment reduced pancreatic glutathione depletion during the early stages of AP and attenuated the activation of p38‐MAPK and NF‐κB for 48 h following BPDO. As a result, acinar cells in NAC‐treated rats failed to produce TNF‐α during AP. In addition, NAC delayed monocyte TNF‐α production, thereby maintaining low TNF‐α levels in plasma during BPDO. In conclusion, acinar cells contribute directly to the inflammatory response during BPDO‐induced AP by producing TNF‐α even before inflammatory cells in the peripheral blood. The blockade of oxidant‐mediated signal transduction pathways induced by NAC treatment prevented acinar cell TNF‐α production. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
A new Fourier transform photo‐modulation spectroscopic technique for narrow band‐gap materials in the mid‐ to far‐infra‐red
Authors: Hosea T. J. C. , Merrick M. , Murdin B. N.
Published: March 2005

There is a large number of technologically important semiconducting optoelectronic materials with narrow band‐gaps in the “finger‐print” region of the infra‐red (IR) spectrum. However, in many instances their band‐structures have not been very well characterised, making it difficult to engineer their properties. Part of the reason is that the key non‐destructive optical characterisation tool, modulation spectroscopy, becomes increasingly difficult as one attempts to look further out into the IR. To date, conventional diffraction‐grating‐based modulation spectroscopy has been applied predominantly below ∼4 µm. We have developed a new photo‐modulation system, based on a Fourier transform spectrometer, that permits such measurements out to much longer wavelengths. We discuss the advantages and technical difficulties of implementing such a system, and give the results obtained so far for narrower‐gap materials, including bulk‐like GaSb, InAs and InSb, comparing these with what can be obtained with conventional modulation spectroscopy arrangements. We apply our new technique to measure the bandgap in dilute‐N InSbN, achieving what we believe are the first modulation spectroscopy measurements in the mid‐IR beyond ∼6 µm. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Positron annihilation study of HVPE grown thick GaN layers
Authors: Misheva M. , Larsson H. , Gogova D. , Monemar B.
Published: March 2005

Single‐crystalline GaN layers with a thickness up to 330 µm were grown by hydride vapor phase epitaxy on basal plane sapphire at gallium stable conditions in a bottom‐fed vertical reactor at atmospheric pressure. Positron annihilation spectroscopy experiments were implemented in order to identify native point defects in the as‐grown non‐intentionally doped n‐type GaN. Comparatively low concentrations of Ga vacancy related defects in the order of 1016 to 1017 cm–3 were extracted from the positron annihilation spectroscopy data. The Ga vacancy defect concentration was related to the intensity of the yellow photoluminescence band centered at 2.2 eV. The influence of the growth rate on the Ga vacancy related defect concentration was investigated. A trend of decreasing of the defect concentration with increasing of layer thickness is observed, which correlates with improving crystalline quality with the thickness. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Magnetic properties of a transverse Ising model with a four‐spin interaction
Authors: Kaneyoshi T.
Published: March 2005

The magnetic properties (phase diagram and magnetizations) of the spin‐½ transverse Ising model with two‐spin (J) and four‐spin (J4) interactions on honeycomb lattice are investigated by the use of the correlated effective‐field theory superior to the standard mean‐field and the Zernike approximations. The results of the phase diagram are greatly different from those obtained within the Zernike approximation, especially for the negative region of the ratio α (α = J4/J). In the low‐temperature region, the longitudinal and transverse magnetizations show many characteristic behaviors in the variation of α. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A model for the microwave assisted magnetoresistance oscillations in a 2D electron system
Authors: Torres Manuel , Kunold Alejandro
Published: March 2005

In this work we present a model for the photoconductivity of a two dimensional electron system (2DES) subjected to a magnetic field. The model includes the microwave and Landau contributions in a non‐perturbative exact way, Impurity scattering effects are treated perturbatively. Based on this formalism, we provide a Kubo‐like formula that takes into account the oscillatory Floquet structure of the problem. We discuss results related with the recently discovered zero‐resistance states. It is found that, in agreement with experiment, negative dissipation can only be induced in very high mobility samples. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Second-Trimester Maternal Serum Markers in Twin Pregnancy with Complete Mole: Report of 2 Cases
Authors: Lambert-Messerlian Geralyn , Pinar Halit , Rubin Lewis P. , De Paepe Monique E. , Tantravahi Umadevi , Steinhoff Margaret M. , Russell Michelle , Canick Jacob A.
Published: March 2005

We present second-trimester serum marker levels in cases of twin pregnancy with complete hydatidiform mole and a coexistent fetus (CHMCF). Second-trimester inhibin A (InhA) levels have not been previously reported in such cases. Second-trimester maternal serum screening, α-fetoprotein (AFP), unconjugated estriol (uE3), human chorionic gonadotropin (hCG), and InhA measurements combined with maternal age to estimate a patient's risk of Down syndrome during pregnancy was performed as a routine prenatal test in 2 cases of CHMCF. Hospital records containing serum marker data, patient history, pathology reports, and pregnancy outcome were reviewed. In cases of CHMCF, maternal serum AFP and uE3 levels were similar to those of a normal singleton pregnancy, whereas hCG and InhA levels were markedly increased. Second-trimester maternal serum marker profiles in cases of CHMCF are a composite of normal singleton and molar tissue secretions. We have found, for the first time, that second-trimester InhA levels are markedly increased in these cases. Serum marker levels may be useful in diagnosis of CHMCF, prenatal counseling, and evaluation of risk for persistent trophoblastic disease.