bluuebunny/crossref_metadata_2025 huggingface dataset:
Glass Walls in State Bureaucracies: Examining the Difference Departmental Function Can Make
Authors: Sneed Bethany G.
Published: September 2007

Occupational segregation in government employment is an important issue in public administration. Occupation determines pay and benefits, and when women have greater access to quality jobs—especially in the public sector—this promotes their economic, social, and political advancement. This research addresses two questions: (1) What changes have occurred to alter “glass walls” across departmental functions? (2) What impact does departmental function have on the salary of women? The findings reveal that although occupational segregation has decreased over the past two decades in Michigan’s bureaucracy, it is still prevalent. Gender‐based occupational segregation is linked to departmental function. Redistributive departments have much lower levels of occupational segregation than other functional categories. Mean salary is also linked to departmental mission, with distributive departments having both the highest mean salary and the highest level of occupational segregation. Salary differentials across departmental functions are becoming smaller over time. Overall, women appear to be most successful, both financially and career‐wise, in historically male‐dominated fields.
The Unbureaucratic Personality
Authors: DeHart‐Davis Leisha
Published: September 2007

After 60 years of scholarship on the rule‐bound bureaucratic personality, this article turns attention to the unbureaucratic personality. Identified by a willingness to bend rules, the unbureaucratic personality is thought to be influenced by individual and workplace attributes. The individual attributes investigated in this article include nonconformity, risk propensity, and public service commitment, all of which are expected to stimulate the unbureaucratic personality. Workplace attributes include formalization and centralization, which are expected to suppress the unbureaucratic personality, and red tape, which is expected to trigger it. These hypotheses are tested using mail survey data collected from employees of four cities in a midwestern state. The results of ordered probit modeling of the data suggest that nonconformity and risk taking increase the unbureaucratic personality, as do red tape and centralized workplaces. By contrast, the unbureaucratic personality appears to be diminished by public service commitment and workplace formalization. The implications of these results for the normative aspects of rule bending are discussed.
Making Government Accountable: Lessons from a Federal Job Training Program
Authors: Courty Pascal , Marschke Gerald
Published: September 2007

This article describes the evolution of a performance measurement system in a government job training program. In this program, a federal agency establishes performance measures and standards for substate agencies. The performance measurement system’s evolution is at least partly explained as a process of trial and error characterized by a feedback loop: The federal agency establishes performance measures, the local managers learn how to game them, the federal agency learns about gaming and reformulates the performance measures, possibly leading to new gaming, and so on. The dynamics suggest that implementing a performance measurement system in government is not a one‐time challenge but benefits from careful monitoring and perhaps frequent revision.
Pessimism, Computer Failure, and Information Systems Development in the Public Sector
Authors: Goldfinch Shaun
Published: September 2007

The majority of information systems developments are unsuccessful. The larger the development, the more likely it will be unsuccessful. Despite the persistence of this problem for decades and the expenditure of vast sums of money, computer failure has received surprisingly little attention in the public administration literature. This article outlines the problems of enthusiasm and the problems of control, as well as the overwhelming complexity, that make the failure of large developments almost inevitable. Rather than the positive view found in much of the public administration literature, the author suggests a pessimism when it comes to information systems development. Aims for information technology should be modest ones, and in many cases, the risks, uncertainties, and probability of failure mean that new investments in technology are not justified. The author argues for a public official as a recalcitrant, suspicious, and skeptical adopter of IT.
Governance Structure and Administrative Corruption in Japan: An Organizational Network Approach
Authors: Choi Jin‐Wook
Published: September 2007

Traditional studies of the Japanese bureaucracy have emphasized effective governance through a close government–business nexus. Yet this network relation creates corruption, especially at a high level of administration. Adopting an organizational network approach, this article provides a critical analysis of the causality between network structures and administrative corruption. Examining financial and public works policies, this article finds that amakudari‐ and zoku‐driven network relationships, which have been reinforced by sociocultural bases, are vertically and exclusively structured and substantiate corruption in administration. Policy making on the basis of such network relations not only results in mismanagement in administration and the distortion of the market disciplines but also delegitimizes the governance system by destroying public trust in government. This article suggests that bringing greater heterogeneity and citizen participation to administration through diversity management and e‐government would reduce administrative corruption in Japanese governance.
Synthesis of Bulk, Dense, Nanocrystalline Yttrium Aluminum Garnet from Amorphous Powders
Authors: Sellappan Pathikumar , Jayaram Vikram , Chokshi Atul H. , Divakar Canchi
Published: September 2007

Amorphous powders of Al2O3—37.5 mol% Y2O3(yttrium aluminum garnet (YAG)) were prepared by coprecipitation, decomposed at 800°C, and hot‐pressed uniaxally at low temperature (600°C) and a moderate pressure (750 MPa). Optimum conditions yielded microstructures with only 2% porosity and partial crystallization of YAG. Further processing using high quasi‐hydrostatic pressure (1 GPa) at 1000°C enabled the production of fully crystallized YAG with >96% relative density and a nanocrystalline grain size of ∼70 nm.
Magnetic Properties of Nickel–Zinc Ferrite Toroids Prepared from Nanoparticles
Authors: Naughton Brian T. , Majewski Pawel , Clarke David R.
Published: September 2007

Toroids comprised of silica‐coated 10 nm diameter nickel–zinc (Ni–Fe) ferrite nanoparticles (Ni0.5Zn0.5Fe2O4) have been fabricated by careful control of both the coating process and subsequent densification by viscous sintering. A narrow processing window is identified between a maximum temperature at which the nanoparticles coarsen, losing their super‐paramagnetic properties, and a lower temperature required for viscous flow densification. Key to the successful fabrication was drying and cold isostatic pressing of the silica‐coated nanoparticles; other routes invariably led to cracking during either drying or sintering. The super‐paramagnetic blocking temperature, the coercive field, and remanent magnetization could all be controlled over a wide range by varying the thickness of the silica coating from 1 to 15 nm. The dipole–dipole coupling distance is estimated to be 4 nm. The high‐frequency (1–500 MHz) properties were sensitive to the sintering temperature as well as the thickness of the silica coating. Toroids sintered at 1000°C or less exhibited no high‐frequency magnetic losses and their permeability decreased with increasing temperature, suggesting that the permeability was controlled by thermally activated magnetization relaxation.
Effect of Al Doping on the Electric and Dielectric Properties of CaCu3Ti4O12
Authors: Choi Sung‐Woo , Hong Seong‐Hyeon , Kim Young‐Min
Published: September 2007

Al‐doped CaCu3Ti4−xAlxO12−x/2 (CCTO, x=0–0.1) ceramics were prepared by the solid‐state reaction, and their electric and dielectric properties were investigated. Al doping has been shown to reduce the dielectric loss remarkably while maintaining a high dielectric constant. At x=0.06, the loss tangent (tan δ) was below 0.06 over the frequency range of 102–104 Hz, and the dielectric constant was 41 000 at 10 kHz. Impedance spectra indicated that Al doping increased the resistivity of the grain boundary by an order of magnitude. The improvement of the dielectric loss in Al‐doped CCTO was attributed to the enhanced grain boundary resistivity.
Preparation of Iron Phosphide Particles from an Aqueous Solvent of Oxygen‐Contained Precursors Using Spray Pyrolysis
Authors: Koo Kee Young , Park Seung Bin
Published: September 2007

Iron phosphides were prepared by an economically feasible spray pyrolysis method, in which nontoxic and inexpensive precursors are used in an aqueous solution. The addition of NaCl to the precursor solution promoted crystal growth at a low temperature and helped to avoid sintering during posttreatment. The key conclusion is that the stoichiometry, shape, and size of the particles are related to the NaCl/Fe molar ratio and the posttreatment temperature. Below the melting temperature of NaCl, the shape and stoichiometry of the particles depended on the NaCl/Fe molar ratio, while above the melting temperature, they were dominated by the posttreatment temperature. Wire‐like particles were formed at a NaCl/Fe molar ratio over 15.
Bipolar Fatigue Caused by Field Screening in Pb(Zr,Ti)O3 Ceramics
Authors: Balke Nina , Kungl Hans , Granzow Torsten , Lupascu Doru C. , Hoffmann Michael J. , Rödel Jürgen
Published: September 2007

Bipolar cycling of lead zirconate titanate ceramics can lead to massive material damage in regions close to the electrode. The damaged region can be identified by color changes, and the microstructure in this region shows signs of interface melting. This damaged region can screen the sample volume from the applied voltages and reduced fields are applied to the undamaged part of the sample. This has two effects. The first one is that the bulk is effectively subjected to smaller fields, but the measured parameters are assigned to the applied field, yielding apparent fatigue curves. The second effect is that with further cycling, field screening protects the bulk of the sample from fatigue due to the reduced effective fields. If the damaged region is mechanically removed and the ferroelectric hystereses are measured again, nearly unfatigued parameters are obtained.
Novel Low‐Temperature Synthesis of Disodium Dimolybdate by Ultrasonic Spray Pyrolysis
Authors: Jovanović Dragana J. , Validžić Ivana Lj. , Janković Ivana A. , Andrić Željka M. , Mitrić Miodrag , Nedeljković Jovan M.
Published: September 2007

A new method for the synthesis of disodium dimolybdate (Na2Mo2O7) in the process of ultrasonic spray pyrolysis using acidified aqueous solutions of thermodynamically stable molybdenum (VI) oxide clusters as a precursor is described. Na2Mo2O7 particles were collected in alcohols (ethanol, 2‐propanol, isobutyl alcohol), and ultracentrifugation was used to isolate solid material from solution. Scanning electron microscopy revealed the formation of uniform spherical Na2Mo2O7 particles with an average diameter of about 0.25 μm. The X‐ray diffraction analysis undoubtedly confirmed the formation of orthorhombic Na2Mo2O7 for samples synthesized at a temperature as low as 300°C.
Synthesis and Photoluminescence of Eu2+‐Doped α‐Silicon Nitride Nanowires Coated with Thin BN Film
Authors: Xu Xin , Nishimura Toshiyuki , Huang Qing , Xie Rong‐Jun , Hirosaki Naoto , Tanaka Hidehiko
Published: September 2007

A feasible doping strategy is introduced to synthesize Eu2+‐doped α‐Si3N4 nanowires coated with a thin BN film. The nanowires were characterized by X‐ray diffraction, scanning electron microscopy, high‐resolution transmission electron microscopy, and a fluorescence spectrophotometer. The Eu2+‐doped α‐Si3N4 nanowires emitted strong yellow light, which is related to the 4f65d–4f7 transition of Eu2+, upon a broad excitation wavelength range between 250 and 450 nm. The obtained nanowires provided a potential candidate for application in optical nanodevices, as well as in white LEDs.
Surface Composition and Imprint in CSD‐Based PZT Films
Authors: Etin Aleksey , Shter Gennady E. , Brener Reuven , Baltianski Sioma , Grader Gideon S.
Published: September 2007

Reports on PZT films often suggest the contradicting presence of Pb‐deficient pyrochlore (Py) and a Pb‐rich layer on the surface. We show that standard Ar+ ion sputtering X‐ray photoelectron spectroscopy (XPS) depth profiles of PZT films artificially exhibit a Pb‐rich surface, independent of actual Pb content of the chemical solution deposition solution. However angle‐resolved XPS measurements reveal that films derived from solutions with 10% Pb excess, which give rise to Py surface grains, actually have the expected Pb‐deficient surface layer. Alternatively, films derived from solutions with 30% Pb excess are Py free and have Pb‐rich surface layer. The Pb‐rich films show an increased imprint effect with increasing Pb content.
Low‐Temperature Oxidation Embrittlement of SiC (Nicalon™)/CAS Ceramic Matrix Composites
Authors: Plucknett Kevin P. , Lin Hua‐Tay
Published: September 2007

The influence of extended duration (up to 1000 h), low temperature oxidation heat‐treatments (375°–600°C) has been assessed using a model ceramic matrix composite system with a graphitic fiber/matrix interphase. For this study a Nicalon™ fiber reinforced CaO–Al2O3–SiO2 matrix composite was selected (Nicalon™/CAS), which possesses a thin (∼20–40 nm) carbon‐based interphase. Oxidation exposure has been conducted under both unloaded and static fatigue‐loaded conditions. For unstressed oxidation exposure, degradation of the carbon‐based interphase is apparent at temperatures as low as 375°C, after 1000 h exposure, resulting in a transition to a nominally brittle failure mode (i.e., negligible fiber pull‐out). The degree of mechanical property degradation increases with increasing temperature, such that strength degradation, and a transition to nominally brittle failure, is apparent after just 10 h at 600°C. Static fatigue loading between 450° and 600°C demonstrated generally similar trends, with reduced lifetimes being observed with increasing temperature. Based upon the unloaded oxidation experiments, combined with previously obtained intermediate and high‐temperature oxidation stability studies, a simple environmental embrittlement failure mechanism map is presented for Nicalon™/CAS. The implications of this study for advanced composite designs with multiple thin carbon‐based interphase layers are also discussed.
Phase Evolution in Synthesis of Manganese Ferrite Nanoparticles
Authors: Bellusci Mariangela , Canepari Silvia , Ennas Guido , Barbera Aurelio La , Padella Franco , Santini Andrea , Scano Alessandra , Seralessandri Luca , Varsano Francesca
Published: September 2007

Physico‐chemical equilibria that influence oxide powders' precipitation from an aqueous solution can be substantially altered when the process is carried out in a microemulsion system. To obtain nanosized MnFe2O4 and gain information about the physico‐chemical characteristics of products, Mn2+ and Fe3+ metal ions were induced to precipitate in a toluene/water/sodium dodecylbenzenesulfonate microemulsion system. Portions of the precipitated powder were differently treated, both in solution and in the solid state, and the role of restricted aqueous domains in the obtained materials was investigated. X‐ray diffraction profile‐fitting methods and chemical analysis were applied to characterize the powder particles. Samples obtained from the selected microemulsion were identified as nanosized mixed hydroxide compounds. A low metal content and a limited matter exchange among aqueous nanodroplets appear to inhibit hydroxide to oxide transformation inside the selected micellar system. A calcination process of precipitated powder was required to obtain a manganese ferrite compound.
In Situ Observation of the Dissolution of Spherical Alumina Particles in CaO–Al2O3–SiO2 Melts
Authors: Liu Junhu , Verhaeghe Frederik , Guo Muxing , Blanpain Bart , Wollants Patrick
Published: September 2007

The dissolution of alumina spheres in a synthetic CaO–Al2O3–SiO2 (CAS) slag was investigated in situ with a confocal scanning laser microscope (CSLM) in the temperature range between 1470° and 1630°C. Through image analysis, the evolution of the apparent particle radius is obtained as a function of time, exhibiting a clear temperature dependence. The rate‐limiting step of the dissolution process is first evaluated with respect to the classical shrinking core model. Neither the boundary layer diffusion nor the chemical reaction in this model can fully explain the dissolution phenomena. By comparing the experimental results with numerical simulation, the rate‐limiting step was shown to be diffusion in the majority of the tests. Effective binary diffusion coefficients were calculated.
Dielectric and Piezoelectric Properties of SrBi2−xSmxNb2O9 (x=0, 0.05, 0.1, 0.2, 0.3, and 0.4) Ceramics
Authors: Sun Lin , Feng Chude , Chen Lidong , Huang Shiming
Published: September 2007

The dielectric and piezoelectric properties of SrBi2−xSmxNb2O9 (x=0, 0.05, 0.1, 0.2, 0.3, and 0.4) ceramics were investigated. SrBi2−xSmxNb2O9 ceramics were synthesized by the conventional solid‐state reaction sintering method. An X‐ray diffraction measurement indicated that a single‐phase‐layered perovskite was obtained for all compositions. The substitution of Sm3+ for Bi3+ in the Bi2O2 layers induced a relaxor behavior of frequency dispersion for SrBi2−xSmxNb2O9. The Raman spectra of SrBi2−xSmxNb2O9 revealed that the decrease in Tm could be attributed to smaller structural distortion of NbO6 octahedra that is induced by the substitution of Sm3+ for Bi3+. SrBi2−xSmxNb2O9 (x≤0.2) ceramics are suitable for fine tolerance resonator applications because the Sm3+ doping in Bi2O2 layers can improve the temperature coefficient of resonance frequency.
Near Infrared Absorption of Tungsten Oxide Nanoparticle Dispersions
Authors: Takeda Hiromitsu , Adachi Kenji
Published: September 2007

Homogeneous dispersions of reduced tungsten oxide and tungsten bronze nanoparticles with ternary additives Na, Tl, Rb, and Cs have been prepared in the wet process and examined for optical properties. The dispersions of reduced tungsten oxide and tungsten bronze nanoparticles are found to show a remarkable absorption of near infrared light while retaining a high transmittance of visible light. This property is highly suitable for solar control filters in automotive and architectural windows.
Fabrication of Barium Strontium Titanate Inverse Opals by the Sol–Gel Process
Authors: Li Bo , Wang Jinqing , Fu Ming , Zhou Ji , Kuwabara Mokoto
Published: September 2007

Barium strontium titanate (BST) inverse opal photonic crystals (PCs) were fabricated by a process of self‐assembly of a polystyrene opal template in combination with infiltration of BST nanoparticles into the voids of a template. In this process, stable monodispersed BST nanoparticles were prepared by dispersing a BST gel into a mixed solvent of 2‐methoxyethanol and acetylacetone. Scanning electron microscopy images show that the inverse opals possess a face‐centered cubic lattice with a center‐to‐center distance of the air spheres of 270 nm. The X‐ray diffraction result reveals that a ferroelectric perovskite phase was obtained. A photonic bandgap in the visible range is observed from reflection spectra analysis and compared with the theoretical results.
Effect of inorganic and organic forms of selenium supplementation on development of larval Heliothis virescens
Authors: Popham Holly J. R. , Shelby Kent S.
Published: September 2007

Selenium (Se) is an essential micronutrient for vertebrates though little is known about the effects on insects. Herbivorous insect larvae acquire Se from plant tissues in the inorganic form of sodium selenate and sodium selenite, and in the organic form of selenoamino acids, selenomethionine, and selenocystine. In this study, we document the effects of dietary supplementation with sodium selenite, sodium selenate, selenocystine, selenomethionine, and selenized yeast on the developmental rate of Heliothis virescens (Fabricius) (Lepidoptera: Noctuidae). Larvae tolerated high levels of Se (500 µg g−1 Se) as sodium selenate and to a lesser extent as selenocystine. Lower levels of sodium selenite (>1 µg g−1 Se) caused increased mortality, reduced rates of pupation, more pupal/adult intermediates, and reduced adult emergence. Selenomethionine proved toxic to larvae at levels above 25 µg g−1 Se, significantly delaying pupation and raising mortality. Provision of Se as selenized yeast, which contains primarily selenomethionine, was also extremely detrimental to larval development and survival. The results indicate that the impact of dietary Se supplement for insects may differ from vertebrates.
Ovarian dynamics, egg size, and egg number in relation to temperature and mating status in a butterfly
Authors: Steigenga Marc J. , Fischer Klaus
Published: September 2007

Although the temperature‐size rule, that is, an increase in egg (and body) size at lower temperatures, applies almost universally to ectotherms, the developmental mechanisms underlying this consistent pattern of phenotypic plasticity are hitherto unknown. By investigating ovarian dynamics and reproductive output in the tropical butterfly Bicyclus anynana (Butler) (Lepidoptera: Nymphalidae: Satyrinae) in relation to oviposition temperature and mating status, we tested the relevance of several competing hypotheses for temperature‐mediated variation in egg size and number. As expected, females ovipositing at a lower temperature laid fewer but larger eggs than those ovipositing at a higher temperature. Despite pronounced differences in egg‐laying rates, oocyte numbers were equal across temperatures at any given time, while oocyte size increased at the lower temperature. In contrast, there were greatly reduced oocyte numbers in mated compared to virgin females. Our results indicated that temperature‐mediated plasticity in egg size cannot be explained by reduced costs of somatic maintenance at lower temperatures, enabling the allocation of more resources to reproduction (reproductive investment was higher at the higher temperature). Furthermore, there was no indication for delayed oviposition (no accumulation of oocytes at the lower temperature, in contrast to virgin females). Rather, low temperatures greatly reduced the oocyte production (i.e., differentiation) rate and prolonged egg‐maturation time, causing low egg‐laying rates. Our data thus suggested that oocyte growth is less sensitive to temperature than oocyte production, resulting in a lower number of larger eggs at lower temperatures.
Synergism between aromatic compounds and green leaf volatiles derived from the host plant underlies female attraction in the oriental fruit moth
Authors: Piñero Jaime C. , Dorn Silvia
Published: September 2007

Blends of volatile compounds emitted by host plants are known to mediate the attraction of gravid female herbivores to oviposition sites, but the role of individual odor components is still little understood. We characterized the olfactory response of mated female Cydia (Grapholita) molesta (Busck) (Lepidoptera: Tortricidae) to synthetic mixtures of compounds emitted by peach shoot, a key host plant of this herbivore, and investigated the role of important constituents of bioactive mixtures in moth attraction. Relative ratios of constituents of the mixtures corresponded to the natural ratio of volatile compounds collected in the plant's headspace. A significant attractant effect was found for a comparatively complex 10‐compound mixture that included four green leaf volatiles [(Z)‐3‐hexen‐1‐ol, 1‐hexanol, (E)‐2‐hexenal, and (Z)‐3‐hexen‐1‐yl acetate], five aromatics (benzaldehyde, methyl salicylate, methyl benzoate, benzonitrile, and phenylacetonitrile), and a carboxylic acid (valeric acid). Using a subtraction approach, the number of compounds was progressively decreased, resulting in a bioactive 5‐compound mixture composed of two constituents, green leaf volatiles and aromatic compounds. Further evaluations revealed that benzaldehyde and benzonitrile must be present in association with three distinct green leaf volatiles to produce an attractant effect on the female moths. This 5‐compound mixture was as attractive as natural peach shoot volatiles, which are known to comprise over 20 compounds. Results are discussed in light of the documented synergistic effect between the three general green leaf volatiles and the two specific aromatic compounds.
Shifting of the life cycle and life‐history traits of the fall webworm in relation to climate change
Authors: Gomi Tadashi , Nagasaka Masami , Fukuda Takeshi , Hagihara Hideharu
Published: September 2007

The effects of global warming on the life cycle and life‐history traits of the fall webworm, Hyphantria cunea (Drury) (Lepidoptera: Arctiidae), were investigated in Fukui, Japan. Our previous studies showed that the Fukui population had a predominantly bivoltine life cycle, but recently the life cycle has changed. In the present study, the life‐history traits of individuals collected in 2002 in Fukui were clarified and compared to those in the previous studies. The lower threshold temperature for development and the thermal constant for one generation were 10.6 °C and 724.4 degree days, respectively. Although these developmental parameters were not investigated in the previous studies, the difference of the developmental period between the present and previous results was negligible in the larval and pupal stages at 20 °C. The critical photoperiod for diapause induction was 14 h 29 min at 20 °C and 14 h 10 min at 25 °C. The critical photoperiod at 25 °C was shortened to 14 min from that of the previous studies for individuals collected in 1995. The incidence of pupal diapause in the second generation was investigated in individuals that were collected as fourth and fifth instars in the field. Some portion of individuals averted diapause even if they were kept under a short photoperiod of L14:D10 at 25 °C after collection. These results, together with climate data and field observations in Fukui, suggest that at least a part of the population has three generations per year at present. This shift of the life cycle occurred within 7 years and is probably related to global warming in recent years.
Myocardial interstitial Cajal‐like cells (ICLC) and their nanostructural relationships with intercalated discs: shed vesicles as intermediates
Authors: Mandache E. , Popescu L.M. , Gherghiceanu Mihaela
Published: September 2007

Intercalated discs (ID) are complex junctional units that connect cardiac myocytes mechanically and electrochemically. However, there is limited information concerning the cardiomyocyte interaction with interstitial non‐muscle cells. Our previous studies showed that myocardial interstitial Cajal‐like cells (ICLC) are located in between cardiomyocytes, blood capillaries and nerve fibres. Typically, ICLC have several very long, moniliform, cytoplasmic processes which establish closed contacts with nerve fibres, as well as each other. We report here ultrastructural evidence concerning the relationships of ICLC processes with ID. The ICLC cytoplasmic prolongations (tens micrometers length) preferentially pass by or stop nearby the ID. Transmission electron microscopy emphasized three distinct connecting features between the tips of ICLC extensions and myocytes at the ‘mouth’ of ID: free or budding shed vesicles, exocytotic multi‐vesicular bodies and direct contacts. In the last case, electron‐dense repetitive nanostructures (‘pillars’) (35–40 nm high and 100–150 nm wide, similar to adhesion molecules) fasten the ICLC to the myocytes. All these features suggest a juxtacrine and/or paracrine intercellular mutual modulation of ICLC and cardiomyocytes in the microenvironment of ID, possibly monitoring the cardiac functions, particularly the electrical activity.
Replacement of teeth exhibiting periapical pathology by immediate implants. A prospective, controlled clinical trial
Authors: Siegenthaler David W. , Jung Ronald E. , Holderegger Claudia , Roos Malgorzata , Hämmerle Christoph H. F.
Published: September 2007

Objectives: The aim of the present study was to test whether or not immediate implantation leads to more biological complications, when performed at extraction sockets of teeth exhibiting periapical pathology compared with teeth not exhibiting periapical pathology.

Materials and methods: In 17 consecutively admitted patients, immediate implant placement was planned in order to replace single teeth exhibiting periapical pathology (test group). These teeth demonstrated pain, periapical radiolucency, fistula, suppuration or a combination of these findings. Another 17 consecutively admitted patients in need of single tooth replacement in the absence of periapical pathology served as the control group. Implant placement and accompanying bone regeneration were performed according to standard clinical procedures. Implants were loaded after a healing period of 3 months. Clinical and radiographical parameters were assessed at the time of implant placement (baseline) and at 12 months thereafter.

Results: Out of the 34 patients, four test and one control patient had to be withdrawn from the study due to the inability to obtain primary implant stability. The residual 29 implants revealed a survival rate of 100% 1 year after placement. Clinical and radiographical differences between 12 months and baseline comparing test and control groups showed no statistical significances for any of the parameters assessed. Within test and control groups there was a statistically significant loss of vertical bone height at the adjacent teeth (mesial test=0.4±0.6 mm, control=0.4±0.5 mm; distal test=0.3±0.2 mm, control=0.7±0.8 mm) as well as at the implant site (mesial test=1.9±1.4 mm, control=1.8±1.1 mm; distal test=1.7±1.4 mm, control=1.6±1.1 mm) and of buccal keratinized mucosa (test=−2.2±1.2 mm; control=−1.3±1.6 mm) between baseline and 12 months. During the first 13 weeks of healing, two sites of the test and one site of the control group showed signs of infection, which required intervention. Neither the incident of early exit nor of signs of infection was statistically significantly different between the test and the control group (Mann–Whitney U test).

Conclusion: It is concluded that for those implants where primary stability was achieved, the immediate implant placement performed at extraction sockets exhibiting periapical pathology did not lead to an increased rate of complications and rendered an equally favorable type of tissue integration of the implants in both groups. Implant placement into such sites can, therefore, be successfully performed.
Damping factor for monitoring the bone interface at dental implants
Authors: Veltri Mario , Balleri Piero , Ferrari Marco
Published: September 2007

Objectives: The aim of this study is to investigate whether the damping of osseointegrated implants, as measured quantitatively with the Osstell™ equipment, is related to the fractal dimension of peri‐implant bone.

Material and methods: Fifty‐five maxillary implants in function for 3 years before the present study were investigated. Two Osstell™ measurements were obtained for each implant with the transducer oriented first palatally and then distally. Using the half‐power bandwidth method, the damping was calculated from the frequency/amplitude plot obtained from the Osstell™. Damping data were then related to the fractal dimension of peri‐implant bone. Fractal dimensions were calculated using a box‐counting algorithm on digitally processed intra‐oral radiographs of the implants. A Spearman's test was used to verify the correlation between damping and fractal dimension values.

Results: All the implants were clinically stable and free from symptoms. The mean ISQ was 63 for the palatal orientation and 71 for the distal orientation. The mean fractal dimension was 1.47; the mean damping value for palatal orientation was 12.3%, while that for the distal orientation was 8.2%. No significant correlation was found.

Conclusions: Damping values, measured at peri‐implant bone, were found not to be related to a radiographic parameter of trabecular bone pattern like the fractal dimension. The clinical implication would be that Osstell™ graphs displaying distinct or more rounded peaks might both indicate a stable implant as long as the associated implant stability quotients are in the range of satisfactory values proposed in the literature.
Technical complications of implant‐supported fixed partial dentures in partially edentulous cases after an average observation period of 5 years
Authors: Kreissl Marion E. , Gerds Thomas , Muche Robert , Heydecke Guido , Strub Jörg R.
Published: September 2007

Objectives: The purpose of this prospective long‐term study was to evaluate the incidence of the most common technical problems, namely screw loosening, screw fracture, fracturing of veneering porcelain and framework fracture in implant‐supported fixed partial dentures (FPDs), and assess the survival and success rate (event‐free survival) after 5 years of function.

Materials and methods: In 76 partially edentulous patients, a total of 205 3i‐implants (machined surface) were placed and restored with 112 implant‐supported FPDs (46 single crowns, 81 splinted crowns, seven FPD bridges and 23 FPDs with cantilevers). The survival rate of FPDs supported by implants was 94.5% (CI‐95: 90.1–98.8) after an average observation period of 5 years. The success rate (event‐free survival) of the FPDs was 80% (CI‐95: 87.3–72.7). After an observation period of 5 years the cumulative incidence of screw loosening was 6.7% (CI‐95: 1.8–11.5), the cumulative incidence for screw fracture was 3.9% (CI‐95: 0.1–7.7). Fracture of the veneering porcelain occurred in 5.7% (CI‐95: 1.2–10.2) of all FPDs. Fracturing of the suprastructure framework was rare (1%; CI‐95: 0–2.9). The overall complication incidence after 5 years was highest in the group of FPDs with cantilever, which showed the lowest success rate 68.6% (CI‐95: 50–87.3), followed by single crowns (77.6%; CI‐95: 53.3–100) and splinted crowns (86.1%; CI‐95: 59.5–100). No complication occurred in FPD bridges.

Conclusion: Fixed partial dentures supported by 3i‐implants showed low technical complications rates, the most common being loosening of the abutment screw. Managing these complications can cause extra amount of chair‐side time and patient dissatisfaction.
Evaluation of aesthetics of implant‐supported single‐tooth replacements using different bone augmentation procedures: a prospective randomized clinical study
Authors: Meijndert Leo , Meijer Henny J. A. , Stellingsma Kees , Stegenga Boudewijn , Raghoebar Gerry M.
Published: September 2007

Objectives: The aim of this study was to evaluate the aesthetics of implant‐supported single‐tooth replacements using different augmentation procedures in a prospective study with the use of an objective rating index and with a subjective patient questionnaire, and to compare the results with each other.

Material and methods: Ninety‐three patients with a single‐tooth gap in the anterior zone of the maxilla were selected for the study. All patients had a local bone defect that needed augmentation before placement of an endosseous implant with sufficient initial stability. Aesthetics of the implant‐supported crown and adjacent mucosa was rated by a prosthodontist 1 year after placement of the porcelain crown. Aesthetics was rated using the Implant Crown Aesthetic Index. A subjective appreciation of the final result was assessed with a patient questionnaire.

Results: The Implant Crown Aesthetic Index reveals a mean overall score of 4.8, with an acceptable result in 66% of the cases. Results of the satisfaction questionnaire reveal a mean overall score of 8.5 with an acceptable result in 100% of the cases. There is no correlation between results of the Index and the questionnaire for the overall and the crown score. The patients' opinion and the professionals' opinion about the peri‐implant mucosa do show a significant correlation.

Conclusions: The peri‐implant mucosa is rated as less satisfactory than the implant‐supported crown by both the dental professional and patients. The dental professional was less satisfied with respect to the total result and results of the crown than the patients.
Lateral alveolar ridge augmentation using a synthetic nano‐crystalline hydroxyapatite bone substitution material (Ostim®). Preliminary clinical and histological results
Authors: Strietzel Frank Peter , Reichart Peter A. , Graf Hans‐Ludwig
Published: September 2007

Objectives: The purpose of this preliminary two‐center clinical prospective study was to evaluate the tissue composition of augmented sites after the use of a nano‐crystalline hydroxyapatite (ncHA) bone substitution material by clinical and histological examinations.

Material and methods: A synthetic ncHA augmentation material was used without any additives in 14 patients requiring lateral ridge augmentation 6–7 months before (10 patients) or at implant placement (four patients). The ncHA material was covered by a titanium mesh for space maintenance. Clinical and radiographic parameters were evaluated and bone biopsy cores, obtained 6–7 months following augmentation, were assessed histologically and histomorphometrically.

Results: One patient showed gingival swelling, redness and pain at the augmentation site requiring removal of the titanium mesh 6 weeks postoperatively. In seven patients, a premature exposure of the titanium mesh without any inflammatory symptoms was noted. The width of the fixed gingival and the alveolar ridge height did not change significantly at least 6 months following augmentation (P>0.5), whereas a significant gain in alveolar ridge width (P=0.01) was noted. After a median period of prosthetic loading of 24 months, no implant was considered to be a failure. Histology revealed ncHA remnants in peripheral and central parts of biopsy cores obtained from seven patients after at least 6 months without histological symptoms of inflammation, whereas histomorphometry of bone cores revealed no significant differences of the mean percentage area of ncHA in peripheral (23.4%) and central (15.1%) parts of biopsy cores (P=0.262). The mean percentage area of bone colonizing the defect was 52.3%.

Conclusions: Small amounts of ncHA were found after at least 6 months in bone biopsies. The former defect space was filled with bone. The alveolar ridge width gain was found to be significant after lateral augmentation utilizing ncHA, providing a quantitatively and qualitatively sufficient site for primary stable implant placement.
Evaluation of a novel biphasic calcium phosphate in standardized bone defects. A histologic and histomorphometric study in the mandibles of minipigs
Authors: Jensen Simon Storgård , Yeo Alvin , Dard Michel , Hunziker Ernst , Schenk Robert , Buser Daniel
Published: September 2007

Objective: A novel biphasic calcium phosphate (CaP) granulate consisting of hydroxyapatite (HA) and β‐tricalciumphosphate (TCP) was compared with pure HA and pure TCP and with autograft as positive control.

Materials and methods: Four standardized bone defects were prepared in both mandibular angles of 16 minipigs and grafted with autogenous bone chips, HA, HA/TCP (60% : 40%), or TCP. Histologic and histomorphometric analysis of bone formation and graft degradation followed healing periods of 2, 4, 8, and 24 weeks.

Results: 2 weeks: more bone formation in defects filled with autograft than with the three CaP materials (P<0.05). 4 weeks: bone formation differed significantly (P<0.05) between all four materials (autograft>TCP>HA/TCP>HA). 8 weeks: more bone formation in defects with autograft and TCP than with HA/TCP (P<0.05), and HA/TCP had more bone formation than HA (P<0.05). 24 weeks: no difference in bone formation between the groups. Autograft and TCP resorbed quickly and almost completely over 8 weeks, whereas HA/TCP and HA showed limited degradation over 24 weeks.

Conclusion: All defects healed with mature lamellar bone and intimate contact between bone and the remaining graft material. The rate of bone formation corresponded to the content of TCP in the CaP materials.
Parental smoking behavior and caries experience in preschool children
Authors: Leroy R. , Hoppenbrouwers K. , Jara A. , Declerck D.
Published: September 2007

Abstract –  Objectives:  The study aimed to explore the association between parental smoking behavior and caries experience in young children, taking into account the socioeconomic status and oral health‐related behavior.

Methods:  Cross‐sectional data from 1250 3‐year‐old and 1283 5‐year‐old children from four geographical areas in Flanders (Belgium) were analyzed. Children were examined at school by trained dentist‐examiners, using standard criteria and calibrated examination methodology. Data on oral hygiene and dietary habits, oral health behavior, sociodemographic variables, and parental smoking behavior were obtained through structured questionnaires, completed by the parents.

Results:  Visible caries experience (i.e. d3mft > 0) was seen in 7% of 3‐year olds and 31% of 5‐year olds. In both age groups, 30% of the parents reported smoking behavior. Univariable logistic regression analysis with caries prevalence as the dependent variable, revealed that parental smoking was a significant independent variable. After controlling for age, gender, sociodemographic characteristics, oral hygiene, and dietary habits, the effect of family smoking status was no longer significant in 3‐year‐old children (OR = 1.98; 95% CI: 0.68–5.76). In 5‐year olds the significant relationship between parental smoking behavior and caries experience persisted after adjusting for the other evaluated variables (OR = 3.36; 95% CI: 1.49–7.58).

Conclusion:  The results of this study illustrate the existence of a significant association between parental smoking behavior and caries experience in 5‐year‐old children.
Contemporary egg size divergence among sympatric grayling demes with common ancestors
Authors: Gregersen F. , Haugen T. O. , Vøllestad L. A.
Published: September 2007

Abstract This study documents divergence in egg size that has occurred over less than 25 generations among sympatric demes of European grayling (Thymallus thymallus) from Lake Lesjaskogsvatnet in Norway. A cluster analysis identified two clusters of tributaries: one of small, warm tributaries (SW) and the other of large, cold tributaries (LC). Spawning occurs more regularly and up to 4 weeks earlier in SW tributaries compared with that in LC ones. We explored numerous mixed models predicting egg size from year (random effect), basin and tributary (fixed effects), and female length. The most supported model estimated length‐adjusted egg size to be larger in SW tributaries compared with that in LC tributaries. Combinations of density‐dependent (competition for food/space) and density‐independent (temperature) factors along with phenotypic plasticity and maternal effects are discussed as potential differentiation sources. We suggest high temperatures (increased metabolism) to reinforce the selective advantage of large eggs under conditions with highly density‐dependent fry interactions.
Associations between hydrological connectivity and resource partitioning among sympatric gar species (Lepisosteidae) in a Texas river and associated oxbows
Authors: Robertson C. R. , Zeug S. C. , Winemiller K. O.
Published: September 2007

Abstract –  The middle Brazos River, located in east‐central Texas, is a meandering lowland river with many oxbow lakes on its flood plain. Flood dynamics of the Brazos River are aseasonal, and faunal exchange during lateral connections of the main river channel and oxbows is pulse‐like and occurs only during floods that may be months or years apart. Patterns of resource use among sympatric gar species (Lepisosteus oculatus, Lepisosteus osseus and Atractosteus spatula) associated with river–flood plain connectivity were studied for a period of 2 years (May 2003 to May 2005). The first year was relatively dry yielding few lateral connections, whereas the second year was relatively wet resulting in more frequent lateral connections. This study focused on habitat and diet partitioning among the three gar species in oxbow habitats with different connection frequencies and an active river channel site. Overall, 684 gars were collected with experimental gillnets: 19 A. spatula (alligator gar), 374 L. oculatus (spotted gar) and 291 L. osseus (longnose gar). There was strong partitioning of habitat between spotted and longnose gars, in which 98% of spotted gars were captured in oxbow habitats and 84% of longnose gars were captured in the river channel. Hydrology did not appear to affect habitat partitioning, although longnose gar abundance significantly increased in oxbows during the wet year. Diet overlap was high between spotted and longnose gars. Temporal variation in diet was significantly influenced by flood pulses that connected oxbows with the river channel, and which allowed predators and their prey to move between habitats.
The many faces of Notch signaling in skin‐derived cells
Authors: Pinnix Chelsea C. , Herlyn Meenhard
Published: September 2007

Since the cloning of the Drosophila gene in the 1980s, decades of research have sought to dissect the intricacies of the mammalian Notch signaling cascade. The intrigue of this pathway undoubtedly lies in its ability to influence diverse cellular processes, including differentiation, cell fate, homeostasis, survival, proliferation and angiogenesis. Based on its evolutionary conservation and its fundamental role in development, it is not surprising that deregulation of the Notch signaling pathway can result in neoplastic growth. While originally of particular interest to immunologists based on its chief role in influencing T‐cell fate decisions and tumor oncogenesis in T‐cell acute lymphoblastic leukemia, pigment cell biologists have recently taken notice of the Notch cascade based on studies suggesting the importance of this pathway in regulating melanocyte stem cell survival and melanoma progression. We will review the Notch signaling literature as it relates to skin homeostasis, melanocytic stem cells and melanoma tumorigenesis.
Cutaneous melanoma in genetically modified animals
Authors: Larue Lionel , Beermann Friedrich
Published: September 2007

Cutaneous melanomas are tumors originating from skin melanocytes which are present in hair follicles, and interfollicular epidermal and dermal layers. Experimental work in model systems involves in silico, in vitro and in vivo analyses. Such models allow to mimick melanocytic aberrations characteristic of melanoma, and to potentially exploit novel therapies. Transgenic technologies can be used to modify specifically the genome of the model organism and thereby generate transgenic strains, and combinations of such strains, which may develop metastasizing melanoma. In such strains, metastasizing melanoma either arises spontaneously after a period of latency or requires additional physical or chemical induction. In this review, we summarize the work of currently available transgenic melanoma models and discuss the most recent progress in creating improved and/or inducible models reflecting the human disease.