bluuebunny/crossref_metadata_2025 huggingface dataset:
The 21st Century Executive
Authors: Vicere Albert
Published: May 2006

Considers the characteristics, attitudes, perspectives and skills
to ensure top management effectiveness. Details global strategies, use
of technology and political skills. Looks to the future and the creation
of integrated programmes to guide managers into the twenty‐first
century.
Building Winning Teams: An interview with Charles
Margerison and Dick McCann
Authors: Hedges Lyn
Published: May 2006

Discusses the development of the Team Management System. Describes
the Team Management Wheel with its nine key roles from Controller
Inspector to Creator Innovator. Explains the role of the linker manager
and the production of a personal profile for each team member. Concludes
it provides an integrated way to identify work preferences within a
winning team.
Choosing the right videos
Authors: Abraham Martin
Published: May 2006

Notes that management development programmes hinge critically on
the use of appropriate resources, such as videos. Considers the video
illustrating a theory as too simplistic and finds that use of case
studies was the most successful method. Concludes that videos should be
a jumping‐off point for management development rather than a
do‐it‐yourself training manual.
Training Soviet managers at Sunbridge Park
Authors: Metcalfe George
Published: May 2006

Describes the training of senior managers from the Soviet Lada
automobile plant in a UK management centre. Notes the need for intensive
cultural and technical briefing and familiarisation sessions prior to
the two‐week course. Explains the content as being built around team
building and most of the subjects were new to the Russians. Concludes
that the programme was of benefit to the participants who believe
increased productivity would result.
Feeding specialization in Herichthys minckleyi: a trophically polymorphic fish
Authors: Hulsey C. D. , Marks J. , Hendrickson D. A. , Williamson C. A. , Cohen A. E. , Stephens M. J.
Published: May 2006

Diet specialization in the trophically polymorphic cichlid fish Herichthys minckleyi was examined using gut contents. Individual H. minckleyi were categorized as having molariform, papilliform or undetermined pharyngeal jaws. The presence of enlarged flattened pharyngeal jaw teeth was used to categorize H. minckleyi as molariform, and the possession of only small pencil‐like pharyngeal teeth was used to classify fish as papilliform. Undetermined individuals (<50 mm standard length, LS) were not assigned to one of the two larger morphotypes. Arthropods were found to be generally rare in H. minckleyi gut contents, but when present, they were most frequently recovered from undetermined individuals. The percentage of plant material consumed by undetermined H. minckleyi was not as great as papilliforms ingested on average, and snail crushing by undetermined H. minckleyi was not evident. A significantly greater mean percentage of plant detritus was recovered from papilliforms compared to molariforms. Snails were crushed by molariforms more frequently than by papilliforms. When only molariforms and papilliforms that had crushed snails were compared, a greater number of snails were crushed by molariforms. No relationship was found between molariform LS and the number of snails crushed, but greater molariform tooth number, adjusted for LS, was indicative of recent snail crushing. The maintenance of H. minckleyi pharyngeal jaw variation could be promoted by intraspecific diet differentiation.
Be in motion . . .
Authors: Mota Maria M.
Published: May 2006

Most Apicomplexan are obligate intracellular parasites and at different steps of their life cycle they invade host cells. The invasive forms are generally called zoites and the majority of them largely depend on a unique form of gliding motility to invade cells. Although the parasite intracellular motor complex that drives gliding motility and/or invasion is shared across different parasite stages and species, the extracellular transmembrane adhesins required to recognize and bind host molecules are not only species‐ but also stage‐specific (even if homologues). This is not such a surprise as different parasite stages interact with different hosts or distinct host cells. In this issue, Siden‐Kiamos et al. shows that specificity extends into the parasite cell, affecting how motility is regulated. Why is specificity occurring at this level? And how important is it? These are critical issues that will be hopefully addressed in the near future.
Functional morphology of the postpharyngeal gland of queens and workers of the ant Monomorium pharaonis (L.)
Authors: Eelen Dieter , Børgesen Lisbeth , Billen Johan
Published: May 2006

Eelen D., Børgesen L.W. and Billen J. 2006. Functional morphology of the postpharyngeal gland of queens and workers of the ant Monomorium pharaonis (L.). —Acta Zoologica (Stockholm) 87: 101–111

The postpharyngeal gland (PPG) is unique to ants and is the largest exocrine gland in their head. In queens of the pharaoh's ant, Monomorium pharaonis, the gland contains approximately 15 finger‐like epithelial extensions on each side and opens dorsolaterally in the posterior pharynx. In these ants the PPG morphology varies considerably according to age and mating status. The epithelial thickness increases with age and reaches a maximum at 3 weeks in both virgin and mated queens. A considerable expansion of the lumen diameter occurs in both groups between 4 and 7 days. Virgin queens release their secretion into the gland lumen from an age of 7 days, whereas mated queens accumulate large amounts of secretion in their epithelium. The increasing epithelial thickness, together with the increasing lumen diameter, the presence of numerous inclusions in the epithelium and the release of secretion, are indicative for increasing gland activity. The gland ultrastructure indicates involvement in lipid metabolism and de novo synthesis of lipids. The PPG of workers consists of 12 finger‐like tubes at each side. There is a significant difference in epithelial thickness between nurses and repletes and between nurses and foragers. We suggest the PPG serves different purposes in pharaoh's ants: it is likely that the PPG of workers and virgin queens is used to feed larvae. In mated queens the gland probably plays a role in providing the queen with nutritious oils for egg production. The PPG may also function in signalling species nestmate and caste identity, as well as in the reproductive capacity of the queens.
Deferred combined androgen blockade therapy using bicalutamide in patients with hormone‐refractory prostate cancer during androgen deprivation monotherapy
Authors: FUJII YASUHISA , KAWAKAMI SATORU , MASUDA HITOSHI , KOBAYASHI TSUYOSHI , HYOCHI NOBUHIKO , KAGEYAMA YUKIO , KIHARA KAZUNORI
Published: May 2006

OBJECTIVE

To assess the effect of adding bicalutamide on serum prostate‐specific antigen (PSA) levels in patients with hormone‐refractory prostate cancer (HRPC) during androgen deprivation monotherapy (ADMT).

PATIENTS AND METHODS

Forty‐four patients with HRPC were treated with deferred combined androgen blockade (CAB) therapy, administering bicalutamide 80 mg once daily. HRPC was defined biochemically as three consecutive rises in PSA level during ADMT. The treatment response was defined as a ≥ 50% decline in PSA levels. Prognostic values of various pretreatment variables for responsiveness to deferred CAB were determined statistically. When the disease relapsed during deferred CAB, bicalutamide was discontinued and the patients were evaluated for the antiandrogen withdrawal syndrome (AWS).

RESULTS

Of the 44 patients, 29 (66%) had a PSA response; the median PSA failure‐free survival was 9.2+ months. Biopsy Gleason score was the only pretreatment variable predictive of a PSA response (mean Gleason score 7.9 in responders and 8.7 in nonresponders). The PSA doubling time (PSA‐DT) was the only statistically significant variable of PSA failure‐free survival in a multivariate analysis. The 1‐ and 2‐year PSA failure‐free survival rates were 43% and 31% in patients with a PSA‐DT of >4 months, while it was 21% and none, respectively, in those with a PSA‐DT of <4 months. Responders to deferred CAB had a statistically longer cancer‐specific survival than nonresponders. None of 20 patients who were evaluated for AWS had the condition.

CONCLUSIONS

Deferred CAB therapy using bicalutamide is effective in patients with progression during ADMT, particularly in those with lower Gleason score tumours or a longer PSA‐DT. AWS after deferred CAB is uncommon.
Telomerase activity in disseminated prostate cancer cells
Authors: PFITZENMAIER JESCO , ELLIS WILLIAM J. , ARFMAN EDWARD W. , HAWLEY SARAH , MCLAUGHLIN PATRICK O. , LANGE PAUL H. , VESSELLA ROBERT L.
Published: May 2006

OBJECTIVE

To analyse telomerase activity in disseminated prostate cancer cells isolated from bone marrow aspirates taken from men with localized prostate cancer before radical prostatectomy (RP).

PATIENTS AND METHODS

Disseminated epithelial prostate cancer cells were isolated from bone marrow aspirates from 69 men with localized prostate cancer before RP, by magnetic column‐chromatography enrichment, followed by isolation of fluorescently labelled epithelial cells by micropipetting. We used pools of 10 non‐epithelial bone marrow cells after tumour cell enrichment as control samples. These pure cell pools were tested for the presence of telomerase activity.

RESULTS

In all, 49 of the patient samples contained disseminated prostate cancer cells. Homogeneous pools of 10 cells were obtained from 35 of these; 49% of the 35 specimens showed telomerase activity, whereas all five control samples did not. Telomerase activity in the 35 samples was not significantly associated with Gleason score, preoperative prostate‐specific antigen level, tumour stage, or surgical margin status. Follow‐up is continuing to assess an association with disease recurrence.

CONCLUSION

This work shows the feasibility of isolating disseminated cancer cells for analysing individual or pooled cells. Compared to tissue staining, where telomerase is detected in 80–90% of samples, we found lower rates of telomerase activity in the disseminated tumour cells (49%). Telomerase‐negative cells might provide information about cell dormancy, as telomerase is a marker of cell proliferation in immortal and cancer cells. Telomerase‐positive cells might predict early disease recurrence, but a longer follow‐up is needed to test this possibility.
Examination of attitudes towards teaching online courses based on theory of reasoned action of university faculty in Taiwan
Authors: Chen Tzy‐Ling , Chen Tzu‐Jung
Published: May 2006

This study examined attitudes of university faculty specialising in the field of human resource (HR) in Taiwan towards participation in the teaching of online courses using the theory of reasoned action (TRA). The population targeted for investigation consisted of the full‐time university faculty in the HR field in Taiwan regardless of their experience in the teaching online courses of any kind. Survey development included a detailed literature review to identify beliefs that guided measurement construction and followed the guidelines recommended by Ajzen and Fishbein (1980) to ensure construct validity. Data were collected on TRA constructs and demographic variables using the questionnaire mailed to 278 faculty members targeted for the study. A 42% (n = 116) response rate was achieved after one round of the follow‐up through emailing. The significant predictor variables, attitude and subjective social norm were confirmed. In other words, results of analyses evidenced the contribution of TRA to explaining the underlying beliefs that enhance or thwart participation. Additionally, faculty in this study possessed positive attitudes towards the participation in online teaching, and further analyses supported the use of TRA in this research context.
Asdin Original Investigation: Complex Bypasses and Fistulas for Difficult Hemodialysis Access: A Prospective, Single‐Center Experience
Authors: Chemla Eric S. , Morsy Mohamed , Anderson Liz , Makanjuola David
Published: May 2006

The purpose of this article is to describe several complex vascular access procedures and the outcomes achieved with them in 24 patients (mean age 60 years) undergoing hemodialysis in whom all other accesses had failed and neither peritoneal dialysis nor transplantation was possible. Patients underwent either a necklace bypass (n = 5), axillary loop (n = 1), contralateral internal jugular vein bypass (n = 6), femorofemoral crossover bypass (n = 1), superficial femoral vein transposition (n = 5), axillary artery to popliteal vein bypass (n = 5), or femoral artery to right atrium bypass (n = 1). All grafts implanted were 6 mm, internally reinforced prostheses made of expanded polytetrafluoroethylene (Gore‐Tex Intering Vascular Graft). Postoperatively patients had bimonthly clinical examinations in which the thrill, bruit, skin, cannulation sites, and adequacy of dialysis were reviewed. A bimonthly ultrasound dilution assessment that included estimation of the graft inflow rate, recirculation rate, and cardiac output was also performed. There was one serious postoperative complication: rapid‐onset severe steal syndrome that required immediate tie off of the fistula. During the median follow‐up time of 22 months, three patients died of causes unrelated to their vascular access. Nineteen dilatations and 10 surgical revisions were done. Primary patency rates were 83%, 63.5%, and 63.5%, respectively, at 6 months, 1 year, and 2 years; secondary patency rates were 91%, 77%, and 77%. Complex vascular access procedures can provide patients some additional good‐quality time on hemodialysis.
Interference Phenomena in Temporal Evolution of Accident Probability in Workplaces
Authors: Targoutzidis Antonis , Antonopoulou Lila
Published: May 2006

The aim of this article is to investigate some implications of complexity in workplace risk assessment. Workplace is examined as a complex system, and some of its attributes and aspects of its behavior are investigated. Failure probability of various workplace elements is examined as a time variable and interference phenomena of these probabilities are presented. Potential inefficiencies of common perceptions in applying probabilistic risk assessment models are also discussed. This investigation is conducted through mathematical modeling and qualitative examples of workplace situations. A mathematical model for simulation of the evolution of workplace accident probability in time is developed. Its findings are then attempted to be translated in real‐world terms and discussed through simple examples of workplace situations. The mathematical model indicates that workplace is more likely to exhibit an unpredictable behavior. Such a behavior raises issues about usual key assumptions for the workplace, such as aggregation. Chaotic phenomena (nonlinear feedback mechanisms) are also investigated for in simple workplace systems cases. The main conclusions are (1) that time is an important variable for risk assessment, since behavior patterns are complex and unpredictable in the long term and (2) that workplace risk identification should take place in a holistic view (not by work post).
MYSTERIES OF ADAPTATION TO HYPOXIA AND PRESSURE IN MARINE MAMMALS The Kenneth S. Norris Lifetime Achievement Award Lecture
Authors: Kooyman Gerald L.
Published: May 2006

Presented on 12 December 2005 San Diego, California

Abstract

This paper reviews past and current work on diving behavior, effects of pressure, and the aerobic diving limit from the perspective of the Ken Norris Lifetime Achievement Award. Because of the influence of Norris to marine mammalogy in general, and to my career in particular, I want to emphasize the important tradition of mentors and colleagues as keystones to a successful career in science, and ultimately to the success of science itself. These two related activities are illustrated by studies on marine mammals that were conducted in an endeavor to understand: (1) the behavioral traits associated with deep diving, (2) the mechanical and physiological effects of pressure during routine dives to great depth, and (3) the degree of oxygen depletion that they routinely endure while diving. The search for answers has resulted in numerous physiological and ecological experiments, along with accompanying theoretical analyses. Currently it appears that some deep‐diving mammals may suffer from bends, and some may resort more often than what seems physiologically possible to anaerobic metabolism while diving. Above all, the way divers manage their nitrogen and oxygen stores remains a mystery.
A Time-Domain Dynamic Model for Chatter Prediction of Cylindrical Plunge Grinding Processes
Authors: Li Hongqi , Shin Yung C.
Published: May 2006

This paper presents a time-domain dynamic model, which simulates cylindrical plunge grinding processes under general grinding conditions. The model focuses on the prediction of grinding chatter boundaries and growth rates. Critical issues are considered in the model including: the distributed nonlinear force along the contact length, the geometrical interaction between the wheel and workpiece based on their surface profiles, the structure dynamics with multiple degrees of freedom for both the wheel and workpiece, the response delay due to spindle nonlinearities and other effects, and the effect of the motion perpendicular to the normal direction. A simulation program has been developed using the model to predict regenerative forces, dynamic responses, surface profiles, stability regions, and chatter growth rates. The model is validated using existing numerical and experimental results.
A Hybrid Methodology for Kinematic Calibration of Micro/Meso-Scale Machine Tools (mMTs)
Authors: Honegger Andrew , Kapoor Shiv G. , DeVor Richard E.
Published: May 2006

A trigger probe measurement system and measurement methodology are developed for kinematic self-calibration of micro/meso-scale machine tools (mMTs). The trigger probe detects the contact between a spindle-mounted stylus and a table-mounted planar artifact. The trigger probe system is small enough to be easily mounted on an mMT. The measurement methodology is divided into off-machine and on-machine measurements. The off-machine measurements are only needed for the first calibration. Recalibration requires only the on-machine measurements to be repeated, thereby reducing recalibration time. The measurement system and methodology are implemented with existing kinematic modeling, error parameter estimation, and compensation techniques for the experimental calibration of a three-axis mMT. The measurement system error is evaluated and experimentally measured. Cutting tests are used to validate the performance of the calibration methodology.
High dynamic range pixel architecture for advanced diagnostic medical x-ray imaging applications
Authors: Izadi Mohammad Hadi , Karim Karim S.
Published: May 2006

The most widely used architecture in large-area amorphous silicon (a-Si) flat panel imagers is a passive pixel sensor (PPS), which consists of a detector and a readout switch. While the PPS has the advantage of being compact and amenable toward high-resolution imaging, small PPS output signals are swamped by external column charge amplifier and data line thermal noise, which reduce the minimum readable sensor input signal. In contrast to PPS circuits, on-pixel amplifiers in a-Si technology reduce readout noise to levels that can meet even the stringent requirements for low noise digital x-ray fluoroscopy (<1000 noise electrons). However, larger voltages at the pixel input cause the output of the amplified pixel to become nonlinear thus reducing the dynamic range. We reported a hybrid amplified pixel architecture based on a combination of PPS and amplified pixel designs that, in addition to low noise performance, also resulted in large-signal linearity and consequently higher dynamic range [K. S. Karim et al., Proc. SPIE 5368, 657 (2004)]. The additional benefit in large-signal linearity, however, came at the cost of an additional pixel transistor. We present an amplified pixel design that achieves the goals of low noise performance and large-signal linearity without the need for an additional pixel transistor. Theoretical calculations and simulation results for noise indicate the applicability of the amplified a-Si pixel architecture for high dynamic range, medical x-ray imaging applications that require switching between low exposure, real-time fluoroscopy and high-exposure radiography.
Practical approach to gradient direction sensor method in very large scale integration thermomechanical stress analysis
Authors: Lakhsasi Ahmed , Bougataya Mohammed , Massicotte Daniel
Published: May 2006

Silicon integrated sensors for thermomechanical stress measurement in very large scale integration (VLSI) has been studied extensively in recent years due to the increasing complexity of modern semiconductor devices. As the chip size has increased continuously to accommodate more functions in modern integrated circuits (IC) technology, the stress induced in it from packaging combined with self-heating becomes serious and may result in the device degradation, circuit malfunction, and even chip cracking. Therefore, for large VLSI devices safe operation, it is necessary to construct in situ thermomechanical stress sensors to control the spatial induced peak stress. In this article, a practical approach to the application of a gradient direction sensor (GDS) for thermomechanical stress prediction in microelectronic packaging is presented. The GDS method has been studied and analyzed for its applicability as inverse engineering problem that is capable to detect the thermomechanical stress. This study uses a thermal heat sources emplacement approach to estimate and predict stress of wafer scale integration (WSI) chip junction. Hence, the geometrical coordinates of the investigated source can be obtained by applying the gradient direction sensors. Then finite element method will be used to build models to validate thermal peaks prediction by GDS method. This way, the possibilities to minimize the thermal peaks in the critical surface areas for ball grid array packaged WSI devices will be explored. Furthermore, in microelectronic, one of the primary roles of IC packaging is to provide structural stability for the VLSI chip. Hence, several considerations have guided our study for a judicious placement of different sensors. That will enable us to establish the most homogeneous thermomechanical cartography. Subsequently, other alternatives for heat sources placement or distribution that are capable in reducing the level of thermomechanical stress will be developed.
In situ monitoring of protein adsorption on functionalized porous Si surfaces
Authors: Tay L. , Rowell N. L. , Lockwood D. J. , Boukherroub R.
Published: May 2006

In situ monitoring of the photoluminescence (PL) of undecylenic acid functionalized porous silicon (PS) was carried out in bovine serum albumin (BSA) solution. Two factors dictated the PL behavior during the protein incubation process. A PL redshift was observed within a few hours of PS incubation in BSA solution followed by an overall gradual blueshift of the PL energy. Correlating this result with Fourier transform infrared (FTIR) spectroscopy performed before and after BSA incubation as well as with the PL and FTIR studies performed in parallel on planar Si, the redshift was attributed to the adsorption (or incorporation) of protein in the porous matrix while the blueshift was assigned to surface oxidation due to the erosion of Si nanocrystallites in the PS matrix. Understanding the protein incorporation in the PS matrix has important implications in utilizing the PL as an optical transduction method in a PS-based biosensor device.
High dynamic range active pixel sensor arrays for digital x-ray imaging using a-Si:H
Authors: Lai Jackson , Nathan Arokia , Rowlands John
Published: May 2006

Hydrogenated amorphous silicon (a-Si:H) active matrix flat panel imagers have gained considerable significance in large area digital imaging applications, in view of their large area readout capability. Current interests lie in a multifaceted a-Si:H array which is compatible with multiple x-ray imaging modalities. This concept entails a single detector system with sufficient dynamic range and variable signal gain. This article reports on an active pixel sensor (APS) array with high dynamic range and programable gain for multimodality x-ray imaging. Initial results have demonstrated sensitivity from subpicoampere to nanoampere photocurrent, which proves amenable for both low-dosage dynamic imaging and high input static imaging. In addition, the programable system signal gain alleviates problems such as output saturation and ensures signal readout linearity to further improve the exploitable dynamic range. Together with external amplification, this APS circuit delivers the performance needed in terms of signal gain, dynamic range, and readout rate entailed by fluoroscopic and radiographic imaging applications.
High-performance n-channel 13.56MHz plasma-enhanced chemical vapor deposition nanocrystalline silicon thin-film transistors
Authors: Lee Czang-Ho , Sazonov Andrei , Nathan Arokia
Published: May 2006

Hydrogenated nanocrystalline silicon (nc-Si:H) films were directly deposited by using 13.56MHz plasma-enhanced chemical vapor deposition at a substrate temperature of 260°C with highly hydrogen (H2) diluted silane (SiH4) gases. The nc-Si:H film showed a high Raman crystalline volume fraction (XC∼85%) and low oxygen concentration (CO∼1.5×1017at.∕cm3). The formation of high-quality nc-Si:H is explained in terms of the effective roles of atomic hydrogen in the plasma. Top-gate staggered n-channel thin-film transistors (TFTs) adopting 90–100nm nc-Si:H channel and ∼300nm hydrogenated amorphous silicon oxide (a-SiOx) gate dielectric layers showed a field-effect mobility (μFE) of ∼150cm2∕Vs, a threshold voltage (VT) of ∼2V, a subthreshold slope (S) of ∼0.23V∕dec, and an on/off current ratio of more than 106. The TFT performance reported here offers promise for the total integration of peripheral electronics for active-matrix flat panel systems.
Organo(organooxo)mercury(II) chemistry  Synthesis and structure of methyl(phenoxo)mercury(II)
Authors: Canty Allan J , Devereux Janette W , Skelton Brian W , White Allan H
Published: May 2006

Methyl(phenoxo)mercury(II) may be obtained from the reaction of methyl(chloro)mercury(II) with silver(I) oxide, followed by addition of phenol. The dominant motif of the structure is a pair of independent MeHgOPh aggregates (HgC,O 2.05(2) Å, 2.06(1) Å (x2); C-Hg-O 176.6(5)°, 176.3(5)°) loosely associated about a quasi-inversion centre by Hg···O interactions (2.702(9) Å, 2.719(9) Å) to form a dimer (Hg-O-Hg′ 106.0(4)°, 106.5(4)°; O-Hg-O′ 73.0(3)°, 72.6(3)°), the dimer stacking up the short crystallographic c axis (= 6.914(1) Å) at spacings c/2. Vibrational spectroscopic studies are insensitive to the associative interactions. Key words: mercury, methylmercury, organomercury, structure, aryloxide, phenoxide.
Copper tellurolate clusters in trimethylsilylated MCM-41  Preparation and condensation
Authors: Kowalchuk Collin M , Rösner Harald , Fenske Dieter , Huang Yining , Corrigan John F
Published: May 2006

The copper tellurolate cluster [(Cu6(TePh)6(PEtPh2)5] (1) has been loaded into the pores of a trimethylsilylated MCM-41 (TMSMCM-41) framework. Solutions of 1 in tetrahydrofuran lead to good impregnation weight % (~10 wt%, 1). The resulting material was analysed by powder X-ray diffraction (PXRD), nitrogen sorption isotherms, thermogravimetric analysis (TGA), energy dispersive X-ray (EDX) analysis, 31P CP MAS NMR spectroscopy, and transmission electron microscopy (TEM). It was observed that the loading process proceeds with the intact cluster 1 being present within the hexagonal architecture. The intact nature of 1 makes it an ideal candidate for condensation by photochemical or thermal means. Both of these condensation treatments increase the Cu:Te ratio of 1 to approach that observed in binary semiconductor Cu2Te. The condensation process was analysed by GCMS spectrometry and characterization of the condensed, isolated composites was performed by TGA, EDX analysis, 31P CP MAS NMR spectroscopy, nitrogen adsorption, and TEM measurements. Thermal condensation results in the formation of Cu2Te particles, whereas photochemical condensation yields larger copper-tellurolate nanoclusters.Key words: copper, tellurium, cluster, MCM-41, trimethylsilylated, photolysis, thermolysis, Cu2Te, composite, mesoporous material.
A critical evaluation of homo- and hetero-leptic cadmium complexes using bond valence sums
Authors: Palenik Gus J
Published: May 2006

The effect of the donor atoms in Cd complexes on the determination of R0 values for the bond valence sum (BVS) is reported. A total of 1321 CdXmYn fragments with X and Y = O, N, S, Cl, Br, and I were used to calculate the R0 values for CdX bonds from both homoleptic and heteroleptic fragments. The R0 values determined from mixed CdXmYn fragments agree with those determined from the homoleptic species, with no significant differences in the values as a function of either electronegativity or hardsoft character of the atoms. The new R0 values derived from the homoleptic series recommended for use in calculating the BVS are as follows: Cd(II)O of 1.875(13) Å, Cd(II)N of 1.951(15) Å, Cd(II)S of 2.279(7) Å, Cd(II)Cl of 2.216(17) Å, Cd(II)Br of 2.334(7) Å, and Cd(II)I of 2.525(7) Å. These R0 values can be used to calculate the oxidation state of Cd in complexes where Cd is bonded to any combination of O, N, S, Cl, Br, and I donor atoms. Cases where the BVS does not agree with the expected oxidation state are discussed. In particular, the planarity of Cd porphyrins is discussed in terms of the BVS.Key words: bond valence sums, cadmium complexes, cadmium porphyrins, cadmium distances.
Two new high-nuclearity copper(II) chloride oligomers with herringbone stacking patterns synthesized by in situ templation
Authors: Fu Zhiyong , Chivers Tristram
Published: May 2006

The use of trichloroiminophosphoranes Cl3P=NR to control the concurrent release of the templating cation [RNH3]+ and chloride ligand via in situ PN and PCl bond cleavage produced two new copper(II) chloride oligomers. The nature of the organic substituent R was a factor in determining the chain lengths. For n-propyltrichloroiminophosphorane, the hexanuclear cluster [n-PrNH3]2[Cu6Cl14] (1) was obtained, while p-tolyltrichloroiminophosphorane generated the tetranuclear copper chloride salt [4-CH3C6H4NH3][2-Cl-4-CH3C6H3NH3][Cu4Cl10] (2). In both structures a two-dimensional framework displaying a herringbone arrangement is created by CuCl secondary bonding interactions. The direct addition of the [n-PrNH3]+ cation to a CuCl2·2H2O solution under the same reaction conditions produced [n-PrNH3]2[CuCl4]. Key words: copper halides, templation, oligomers, two-dimensional frameworks.
NMR spectroscopy of the solid-state isomerization of nitrito- and nitro-pentamminecobalt(III) chloride
Authors: Ooms Kristopher J , Wasylishen Roderick E
Published: May 2006

Cobalt-59 and nitrogen-15 NMR spectra of the nitritopentamminecobalt(III) chloride, [(NH3)5Co-ONO]Cl2, and nitropentamminecobalt(III) chloride, [(NH3)5Co-NO2]Cl2, isomers in the solid state have been obtained at several applied magnetic field strengths. The 59Co NMR line shapes indicate that both the cobalt nuclear quadrupolar coupling constant (CQ) and the span of the chemical shift tensor (Ω) decrease when the complex isomerizes from [(NH3)5Co-ONO]2+ to [(NH3)5Co-NO2]2+; CQ decreases from 23 to 10.3 MHz and Ω changes from 1650 to 260 ppm. The 15N NMR line shapes also show a significant change in the nitrogen magnetic shielding tensor upon isomerization, with Ω decreasing from 710 to 547 ppm; also, an indirect spin-spin coupling, 1J(59Co,15N) = 63 Hz, is observed in the 15N NMR spectra of the nitro isomer. The NMR parameters are rationalized based on differences in the molecular structure of the two isomers. NMR spectra have also been recorded as the isomerization progresses with time and demonstrate the practicality of the technique for the study of solid-state isomerizations.Key words: 15N, 59Co, solid-state NMR, linkage isomerization, chemical shift tensor, electric field gradient tensor.
Dynamics of percolation and energetics in the clustering of water/AOT/oil microemulsions in the presence of ethanol amines
Authors: Bommel Andrew van , Glennie Andrew , Chisholm Danielle , Palepu Rama M
Published: May 2006

Temperature-induced percolation in water/AOT/oil microemulsions in the presence of mono-, di-, and tri-ethanol amines have been studied using conductometric measurements. The percolation temperature of water/AOT/oil microemulsions depends on the nature of the alkanol amine added. Mono- and di-ethanol amines hinder the percolation process, while triethanol amine promotes the process. Percolation studies were also conducted with varying ω = [H2O]/[AOT] values and varying chain lengths of continuous oil phase (C6C10). The results indicate that increases in both ω and the chain length of the oil decrease the percolation temperature. The microemulsion systems have been analyzed in terms of percolation temperature, scaling equation parameters, and activation energies. The energetic parameters of the clustering process have also been determined employing the phaseseparation model. The influence of alkanol amines on the percolation phenomenon has been rationalized in terms of the changes in fluidity of the interfacial layer, the viscosity of the water micropool, and the attractive interactions of the microemulsion droplets. The influence of the alkanol amine additives on the stated parameters was discussed in view of the individual effects of the alcohol and amine moieties on the properties of water/AOT/oil microemulsions.Key words: microemulsion, percolation, conductometry, alkanol amine, surfactant.
Effect of the nature of substituents on aromatic aldehydes in microwave induced N-cyclohexylamidinealdehyde condensation reactions
Authors: Kumar Vipan , Gupta Manish , Mahajan M P
Published: May 2006

A simple, environmentally friendly protocol for the selective synthesis of the 4-aryl substituted acyclic 1,3-dienes and the medicinally potent triazines has been developed using a domestic microwave oven with excellent yields and reproducibility.Key words: microwave, dihydrotriazine, triazine, imine metathesis.
Acid-catalysed transformation of oleic acid, and 12-hydroxystearic acid, into γ-octadecanolactone. Evidence for the occurrence of a novel side reaction
Authors: Granata Alessandro , Sauriol Françoise , Perlin Arthur S.
Published: May 2006

γ-Octadecanolactone is produced in the reaction between oleic acid (cis-9-octadecenoic acid) and concentrated sulfuric acid at 80 °C. To account for its formation, two types of mechanism have been considered. Both begin with protonation at C-9/C-10 to give a carbocation, following which the positive charge is transmitted to C-4, where nucleophilic attack by the carboxyl group is facilitated. One of them invokes a "zipperlike" succession of 1,2-shifts of intervening methylenic protons, whereas the other amounts to a stepwise migration of the alkene function along the carbon chain. Results obtained through the use of deuterated sulfuric acid to catalyse formation of the lactone allow for the existence of both types. However, each is characteristic of a different region of the C18 structure. Of the total isotope incorporated (individual molecules contained from zero to nine atoms of deuterium), >85% had been distributed relatively uniformly over the chain segment from C-7 to C-17, according to 2H nuclear magnetic resonance spectra recorded in the presence of the shift reagent Yb(fod)3, and 13C nuclear magnetic resonance data. This evidence is consistent with the occurrence of a side reaction that creates many protonation sites over that specific region of the lactone's precursors. By contrast, as very little of the isotope had reached the proximity of the lactone ring, the latter is more likely to have been formed via the 1,2 shift type of mechanism. These events can also be initiated at other sites, as shown by the preparation of γ-octadecanolactone, and a comparably deuterated form of it, from 12-hydroxystearic acid. Reactions of these three stearic acid derivatives with HI, HBr, and HCl are described, by way of comparison.
Enantioselective deprotonation of protected 4-hydroxycyclohexanones
Authors: Majewski Marek , MacKinnon John
Published: May 2006

A series of derivatives of 4-hydroxycyclohexanone (1a–g) with the hydroxy group protected as a silyl ether (1a, b), ether (1d, g), an acetal (1c), or an ester (1e, f) were deprotonated with chiral, optically pure, lithium amides 3–9. The resulting non-racemic enolates were trapped as enol acetates. The enantioselectivity of deprotonation was up to 74% ee.
Electronic effects on crown ether conformation. X-ray crystal structure and 13C NMR study in solution and the solid phase of 4-nitrobenzo-9-crown-3 ether
Authors: Buchanan G. W. , Driega A. B. , Moghimi A. , Bensimon C.
Published: May 2006

The X-ray crystal structure of the title material has been determined and the results are compared to previous findings for benzo-9-crown-3 itself. The 13C NMR spectrum in solution has been unambiguously assigned using COSY and HETCOR methods. The solid phase 13C spectrum has been obtained and the 7, 10-d4 derivative has been examined to aid in spectral assignments.
Stereoselective oxirane formation by reaction of diazomethane on 1-fluoro-3-[(4-methylphenyl)sulfinyl]-3-phenylpropan-2-one
Authors: Bravo Pierfrancesco , Frigerio Massimo , Fronza Giovanni , Soloshonok Vadim , Viani Fiorenza , Cavicchio Giancarlo , Fabrizi Giancarlo , Lamba Doriano
Published: May 2006

(2S, 2′R,RS)-2-(Fluoromethyl)-2-{[(4-methylphenyl)sulfinyl][phenyl]methyl}oxirane (4) was obtained in high chemical yield and with high diastereoselectivity by reacting diazomethane with pure (3R, RS)-1-fluoro-3-[(4-methylphenyl)sulfinyl]-3-phenylpropan-2-one (3), but also with its (3S, RS)-3-diastereoisomer, in the latter case through inversion of the configuration at carbon 3. The corresponding methyl enol ethers 6 were isolated as by-products. NMR experiments and molecular modelling calculations were performed in order to clarify the equilibria in solution and the preferred conformations of both ketones 3. Several variously substituted, sulfur-free tertiary α-(fluoromethyl)carbinols were obtained from the main reaction product (2S, 2′R,RS)-4 through appropriate elaborations of the sulfinyl group and of the oxirane ring. The structure of (2S, 2′R,RS)-4 was established by X-ray analysis of the open-chain derivative (2S, 2′R,RS)-1-bromo-3-fluoro-2′-{[(4-methylphenyl)sulfinyl][phenyl]methyl}propan-2-ol (7).
A 139La and 17O nuclear magnetic resonance study of the nature of La(III) first coordination sphere in acetonitrile solutions of hydrated lanthanum nitrate
Authors: Chen Zhigang , Detellier Christian
Published: May 2006

The nature of the first coordination sphere of the La(III) cation in acetonitrile solutions of La(NO3)3.6H2O was investigated by 139La and 17O NMR. All three nitrate anions are coordinated to La(III). There is a competition between water and acetonitrile molecules for the occupancy of the La(III) first coordination sphere. The 139La and 17O NMR results, obtained for various concentrations of La(NO3)3.6H2O, were quantitatively interpreted through a chemical equilibrium model. It was shown that the presence of only two La(III) species, {La(III) (NO3−)3} and {La(III) (NO3−)3.H2O}, in rapid exchange in solution could account for all the NMR results. The variation of the 139La and 17O NMR parameters (chemical shifts and relaxation rates) with the concentration of La(NO3)3.6H2O results from the population increase of the species {La(III) (NO3−)3.H2O}. The chemical exchange between free and coordinated water molecules is also fast on the 17O NMR time scale. The 17O NMR signal of water is considerably broadened when it coordinates to the La(III) cation. This broadening was attributed to both direct and indirect interactions between the two quadrupolar nuclei 17O and 139La. The direct interaction comes from an increase of the electric field gradient at the 17O nucleus when a water molecule coordinates to the La(III) cation. The indirect interaction results from an 17O–139La scalar coupling. The detailed analysis of the 17O NMR spectra also allowed the determination of the indirect coupling constant between coordinated 17OH2 and 139La(III), [Formula: see text]88 ± 13 Hz.
Photodissolution of iron oxides in malonic acid
Authors: Litter Marta I. , Villegas Marina , Blesa Miguel A.
Published: May 2006

The influence of 254-nm irradiation on the dissolution rate of magnetite (Fe3O4) and maghemite (γ-Fe2O3) suspended in aqueous solutions of malonic acid is analyzed and compared with the dark reaction. The effect of the addition of Fe3+, reductants such as ascorbic acid and oxidants such as Ag+ or O2 is described. Photochemical initiation involves the production of >FeII by electrons photogenerated on the oxide, which triggers thermal dissolution. Experimental results are fitted by analytical and numerical solutions of the set of kinetic equations. The calculated fitting parameters reflect the lower activity of iron oxides in malonic acid compared to EDTA media.
Étude théorique de la complexation des cations Pb2+ et Hg2+ par le D-talose
Authors: Palma Marc , Pascal Yves Louis
Published: May 2006

Molecular modeling of interactions between D-talopyranose and D-talofuranose conformers and Pb2+ and Hg2+ cations was done in the gaseous state using the AM1 method, both with "naked" species and with some water molecules added. A complete conformational analysis of the free D-talose molecule was carried out using a Monte Carlo method (BATCHMIN program). Lower minima were identified, and the different orientations of the hydroxyl groups given. The calculated equilibrium distribution of anomers in the gaseous phase differs from that obtained experimentally in aqueous solution. This could be related to the predominance of intramolecular hydrogen bonding for the isolated molecule and intermolecular hydrogen bonding in aqueous media. In the presence of a cation, the analysis was carried out using the AM1 method for every conformation of the ligand. In the gaseous phase, Angyal's predictions are not respected. The lowest energy is represented by a flexible β-pyranosic form and some complexes are tetra or pentacoordinated. For the furanosic species, the αF forms bearing a cis-cis-cis sequence of hydroxyl groups are the less stable. Amongst the complexes of carbohydrates with metal cations in aqueous solutions, Pb2+ forms complexes and Hg2+ does not. The calculations show that, for the isolated complexes, the reverse should be true. The lesser stability in water of Hg2+ complexes with respect to Pb2+ could be interpreted in terms of (1) a more unfavourable entropic hydration effect; (2) a less favourable difference of translational entropy. A complete answer requires the dynamical study of the system in water by a Monte Carlo method. Keywords: complexes with divalent cations, D-talopyranose and D-talofuranose conformers.
Electron exchange kinetics in a tetrahedrally coordinated copper(II)/(I) couple
Authors: Metelski Peter D. , Hinman A. Scott , Takagi Hideo D. , Swaddle Thomas W.
Published: May 2006

The four-coordinate anion CuI(dpym)2−(Hdpym = 3,3′,5,5′-tetramethyl-4,4′-dicarboethoxydipyrromethene) can be prepared in solution in acetone either by electrochemical reduction of the known tetrahedral complex CuII(dpym)20(E0 = −290 mV vs. SCE) or by the quantitative reaction of 2Hdpym with Cu(CH3CN)4+in the absence of O2. The latter reaction does not go to completion in solvents that bind relatively strongly to CuIor that are poor proton acceptors. Ligand exchange between CuI(dpym)2−excess Hdpym in acetone is "fast" in the1H NMR timeframe, with k1 = 1.4 × 107 L mol−1s−1at 298 K (first order in each reactant), ΔH‡1 = 3.4 ± 0.6 kJ mol−1, and ΔS‡1 = −97 ± 3 J K−1mol−1. In the absence of excess Hdpym, dissociation of CuI(dpym)2−in acetone remains negligible. Homogeneous electron exchange between CuI(dpym)2−and CuII(dpym)20in acetone falls in the "slow"1H NMR timeframe, with kex = 5.9 × 103 L mol−1 s−1, ΔH‡ex = 48.5 ± 3.0 kJ mol−1, and ΔS‡ex = −10 ± 10 J K−1, at ionic strength I ≈ 0.007 mol L−1and 298 K, while for the same self-exchange on a Pt electrode the heterogeneous rate constant kel = 0.16±0.04 cm s−1at I ≈ 0.1 mol−1L−1and 298 K, according to AC voltammetry. These values of Kexand Kelare of the order expected for CuII/Icouples in which no significant change in coordination number or geometry accompanies electron transfer. Keywords: Electron transfer, copper complexes, ligand substitution kinetics, dynamic NMR.
The synthesis, molecular and crystal structure of the 1:1 adduct of triphenyltin chloride with 2,3-diphenylthiazolidin-4-one
Authors: Smith Frank E. , Hynes Rosemary C. , Tierney John , Zhang Ying Z. , Eng George
Published: May 2006

The title compound was synthesized as part of an effort to produce a more effective fungicide to combat Dutch Elm Disease (DED), which is caused by the fungus Ceratocystisulmi. A full X-ray structural analysis of the 1:1 adduct has been carried out and the results are reported along with the Mössbauer data for the compound. The crystals are monoclinic, space group P21/a with a = 19.240(3) Å, b = 9.1463(24) Å, c = 19.3512(24) Å, β = 118.874(8)°, V = 2982.0(10) Å3, z = 4, and Dcalc = 1.427 Mg m−3. The final discrepancy factors are RF = 0.056 and Rw = 0.058 for 1915 significant reflections. The QS and IS values in the Mössbauer spectrum of the complex are 3.08 mm s−1 and 1.28 mm s−1, respectively. The 2,3-diphenylthiazolidin-4-one behaves as a monodentate ligand and coordinates to the tin through the oxygen atom. The complex exhibits a trigonal bipyramidal configuration with the three phenyl groups in equatorial positions and the chloride and ligand oxygen occupying the apical sites. Keywords: triorganotin, fungicide, Dutch Elm Disease, thiazolidin-4-one.
Photoinduced addition of dioxygen molecules in the unsaturated sites of the Pd3(dppm)3CO2+ catalyst
Authors: Harvey Pierre D. , Crozet Marielle , Aye Khin T.
Published: May 2006

The photoinduced addition of O2 onto the unsaturated cluster Pd3(dppm)3CO2+ (as a CF3CO2− salt) in acetonitrile is reported. The final product Pd3(dppm)3(O2)22+(v(O2) = 838 and 866 cm−1) is formed in a multi-step fashion in which two photochemical intermediates are observed (presumably Pd3(dppm)3(O2)(CO)2+ and Pd3(dppm)3(O2)2+. No X-ray structure could be obtained, but numerous spectroscopic findings demonstrate that O2 binds the Pd3 center as a peroxo-O2, and acts as a two-electron donor that triply bridges the metal atoms (forming a 44-electron cluster). The very small excited state lifetimes (between 25 and 35 ± 10 ps) obtained by picosecond flash photolysis indicate that the primary photoreaction is unimolecular, and demonstrate that the first photochemically added O2 molecule must be preassembled in the excited state prior to any photoinduced transformation. This [Formula: see text] ground state complex is responsible for the photoinduced production of the bisdioxygen compound and can be observed by UV–visible spectroscopy. The low efficiency of the photoreaction (quantum yield (Φ) = 0.033 ± 0.004) is explained by the very short excited state lifetime at 298 K, and the competition of O2 with solvent molecules to occupy the unsaturated site of the empty cavity in Pd3(dppm)3CO2+ (i.e., ground state guest–host chemistry). The binding constant for O2 with Pd3(dppm)3CO2+ is roughly estimated to range between 1 and 730 M−1 in the ground state and is considered to be weak. Keywords: clusters, photochemistry, guest–host, oxidation, dioxygen.