bluuebunny/crossref_metadata_2025 huggingface dataset:
Nematode infection induces Th2 cell‐associated immune responses in LEC mutant rats with helper T cell immunodeficiency
Authors: UCHIKAWA RYUICHI , MATSUDA SHINJI , YAMADA MINORU , NISHIDA MINORU , AGUI TAKASHI , ARIZONO NAOKI
Published: November 2003

Long‐Evans Cinnamon (LEC) rats have maturational arrest of CD4+8− T cells from CD4+8+ cells in the thymus. Despite this, CD4+8− T cells are always present in peripheral lymphoid organs of LEC rats, suggesting that these CD4+8− T cells are generated by an uncommon pathway. We investigated the role of LEC rat peripheral CD4+8− T cells in Th2‐associated responses to infection with the nematode Nippostrongylus brasiliensis. After infection, the numbers of CD4+8− TCRαβ+ T cells significantly increased in mesenteric lymph nodes (MLN) and the spleen, while those in the thymus were still negligible. Infection also induced significant up‐regulation of IL‐4 gene expression in LEC rat MLN cells. Total serum IgE levels in LEC rats were markedly increased two weeks after infection. Mucosal mast cell responses in the gut and lungs of LEC rats were induced as prominently as in control Long‐Evans Agouti (LEA) rats. Faecal egg count data indicated that LEC rats rejected nematodes faster than LEA rats. These results suggested that Th2‐associated responses can be induced by nematode infection in LEC rats probably through the extrathymic recruitment and proliferation of CD4+8− TCRαβ+ T cells.
Response of the water status of soybean to changes in soil water potentials controlled by the water pressure in microporous tubes
Authors: STEINBERG S. L. , HENNINGER D. L.
Published: November 2003

Water transport through a microporous tube‐soil‐plant system was investigated by measuring the response of soil and plant water status to step change reductions in the water pressure within the tubes. Soybeans were germinated and grown in a porous ceramic ‘soil’ at a porous tube water pressure of –0.5 kPa for 28 d. During this time, the soil matric potential was nearly in equilibrium with tube water pressure. Water pressure in the porous tubes was then reduced to either –1.0, –1.5 or –2.0 kPa. Sap flow rates, leaf conductance and soil, root and leaf water potentials were measured before and after this change. A reduction in porous tube water pressure from –0.5 to –1.0 or –1.5 kPa did not result in any significant change in soil or plant water status. A reduction in porous tube water pressure to –2.0 kPa resulted in significant reductions in sap flow, leaf conductance, and soil, root and leaf water potentials. Hydraulic conductance, calculated as the transpiration rate/ΔΨ between two points in the water transport pathway, was used to analyse water transport through the tube‐soil‐plant continuum. At porous tube water pressures of –0.5 to –1.5 kPa soil moisture was readily available and hydraulic conductance of the plant limited water transport. At –2.0 kPa, hydraulic conductance of the bulk soil was the dominant factor in water movement.
Dermatography with bleomycin as a new treatment for verrucae vulgaris
Authors: van der Velden Eddy M. , IJsselmuiden Otto E. , Drost Brigitte H.I.M. , Baruchin Avraham M.
Published: November 2003

Background

Common warts are caused by infection with human papillomaviruses (HPVs). Many, largely ineffective, treatment modalities have been tried in the past. The cytostatic drug bleomycin has been found to selectively affect squamous cell and reticuloendothelial tissue, but the method of its delivery directly into affected tissue such as warts has been of little efficacy. This study assessed the efficacy of a new mode of intralesional administration of bleomycin by dermatography.

Methods

The warts of patients were treated with increasing concentrations of bleomycin using the van der Velden Derma‐injector, a modified tattooing machine, under local or block anesthesia. The effects of the procedure were evaluated 1, 24, and 48 h later and the patients followed for up to 2 years.

Results

Thirteen patients with warts on the hands and/or feet, resistant to conventional therapy, were entered into the study, and two patients dropped out. Of the 11 remaining patients, seven went into full remission that was maintained for at least 2 years. One patient showed moderate progress and in three patients little progress was noted and dermatography was stopped. The dosage of bleomycin varied between 0.1 and 1.0 mg/mL.

Conclusions

Dermatography proved to be an effective technique for intralesional administration of bleomycin in more than two‐thirds of patients resistant to conventional therapy. Treatment failures in this study could in part be explained by a defective immune system in the patients. Dermatography is a technique that can be learned by any skillful dermatologist or plastic surgeon.
Evidence‐based paediatrics
Authors: ELLIOTT EJ , MOYER VA
Published: November 2003

Evidence‐based medicine is practised widely in some specialties and is now part of many undergraduate and graduate medical curricula. However, the extent to which it is used in clinical paediatric practice is not known and its expansion remains a major challenge. Access to technology which facilitates literature searching, and development of journals addressing specific paediatric problems, will encourage the use of evidence‐based medicine by the busy paediatrician. Informed practice of evidence‐based medicine will ensure that clinical expertise is complemented by a thorough search, evaluation and judicious application of relevant information from the medical literature.
Behaviour of children associated with parental participation during induction of general anaesthesia
Authors: KAM PCA , VOSS TJV , GOLD PD , PITKIN J
Published: November 2003

Objective:

To evaluate children’s behaviour during induction of general anaesthesia with parental participation.

Methods:

A descriptive observational study in which the behaviour of the children was assessed using a Global Mood Scoring system before and during the induction of general anaesthesia, with their parents participating at induction.

Results:

Parental participation in anaesthetic induction was beneficial in avoiding distress at parental separation without the use of preoperative sedation. Negative effects of parental participation were not encountered.

Conclusions:

Parental participation in anaesthetic induction of children can reduce distress at parental separation without any negative consequences. With proper preparation and education, parents should be encouraged to be present during the induction of general anaesthesia.
Current approaches to the nutritional management of cystic fibrosis in Australia
Authors: ANTHONY H , CATTO‐SMITH A , PHELAN P , PAXTON S
Published: November 2003

Objective:

The aim of this study was to determine current Australian practice for the nutritional management of cystic fibrosis (CF) and compare it to USA and UK guidelines.

Methodology:

A structured questionnaire was completed by dietitians from 15 major CF centres. It was estimated that these centres manage or co‐manage 84% of Australians with CF.

Results:

There was close agreement between UK and USA guidelines and Australian practice for dietary intervention strategies, nutritional monitoring and surveillance, and electrolyte replacement. Infant feeding practices were more closely aligned with the UK. There were some differences in the areas of pancreatic enzyme replacement therapy, vitamin requirements in CF and dietary management of CF‐related diabetes.

Conclusions:

Despite the lack of formal agreement, nutritional management practices of most Australian centres are closely aligned with current published international recommendations. However, there is need for consensus in the area of enzyme replacement therapy, management of CF‐related diabetes and vitamin supplementation based on optimal clinical outcomes.
Personal Viewpoint Education for children with disabilities: The rationale for inclusion
Authors: GRAVES P , TRACY J
Published: November 2003

Objective:

To discuss issues in the education of children with disabilities, particularly with respect to inclusion in mainstream classes.

Methodology:

Review of the literature on education for children with disabilities, focusing on the inclusion versus segregation debate.

Results:

The literature provides no support for segregation and some support for the view that segregated children are disadvantaged. What seems to be important is the way the child is educated rather than where the education takes place. In addition, there are ethical, sociological, and legal arguments in favour of an inclusive educational system.

Conclusions:

There are good arguments to encourage inclusive education for children with disabilities. In advising parents, doctors should focus on how rather than where the child with a disability should be educated.
Paediatric nephrotic syndrome in Auckland, New Zealand
Authors: SIMPSON AK , WONG W , MORRIS MC
Published: November 2003

Objective:

To review children with nephrotic syndrome in Auckland, New Zealand.

Methods:

All children admitted to Auckland Children’s Hospital between January 1984 and December 1994 with nephrotic syndrome and a renal biopsy had their charts retrospectively reviewed and the appropriate information summarised.

Results:

Fifty‐seven children biopsied with nephrotic syndrome were available for review. The mean age at diagnosis was 5.4 years, standard deviation (SD) 3.9 years, with mean follow‐up of 5.7 years. The histologies of the renal biopsies were: minimal change nephrotic syndrome (MCNS) in 37%, focal segmental glomerulosclerosis in 19%, membranoproliferative glomerulonephritis (MPGN) in 23% and other causes in 21%. Maori children were most likely to have MPGN. Steroid resistance was present in 66% of children. End stage renal failure developed in 26% of patients and chronic renal failure in 4% of patients.

Conclusion:

In this series the proportion of children with MCNS is low and significant numbers of children with nephrotic syndrome progressed to chronic renal failure and end stage renal failure.
Ozbug: an email mailing list for physicians that works
Authors: Watson D. A. R.
Published: November 2003

Abstract

Very few studies of the quality of electronic mailing lists have been published. Ozbug was established in 1997 as a moderated and closed mailing list for infectious diseases physicians in Australia and New Zealand. A broad range of clinical and professional issues is discussed by ­subscribers. An email survey of subscribers in 2002 indicated a high degree of satisfaction with the service. (Intern Med J 2003; 33: 532−534)
Embryonic stem‐cell research and the moral status of embryos
Authors: Chu G.
Published: November 2003

Abstract

Stem‐cell research has the potential to significantly advance our knowledge of cell differentiation with the promise of exciting and innovative therapeutic applications for otherwise incurable genetic and degenerative disorders. The issue has been the subject of debate in federal and state parliament as research of embryonic stem cells and their application have come under intense scrutiny. Scientists and medical practitioners are highly skilled in the technical aspects of biomedicine but are decidedly less comfortable with ethics. The place of novel and controversial biomedical technology is commonly left to an ad hoc and complex process whereby social acceptability eventually becomes the final arbiter. Utilitarianism is a popular ethical approach that attempts to weigh all the known and anticipated merits and pitfalls. The scientific background of biomedical professionals, the vast explosion of information, and specialization and subspecialization, have all contributed to a reductionistic view of life and ethics. The ‘sanctity of life’ doctrine is altogether quite different, as secular and religious advocates appear inflexible and unyielding to the logical propositions of utilitarianism and reductionism or to the consensus of democracy. These four major ethical approaches are discussed with reference to the embryonic stem‐cell research debate. (Intern Med J 2003; 33: 530−531)
New and emerging drug therapies for the management of acute heart failure
Authors: Krum H. , Liew D.
Published: November 2003

Abstract

In recent times, there have been many developments in therapies for acute heart failure, in contrast to the preceding 20 years. These have been mainly fuelled by new and expanding knowledge about the pathophysiology of heart failure, which has allowed for insight into potential therapeutic strategies. This review will examine the key emerging therapies for acute heart failure, in light of available pathophysiological and clinical evidence. (Intern Med J 2003; 33: 515−520)
Effects of a Blocked Atrial Beat on the Atrioventricular Nodal Recovery Property in Patients with Dual Nodal Pathways
Authors: LEE PI‐CHANG , WU JING‐MING , WOLFF GRACE S. , YOUNG MING‐LON
Published: November 2003

Dual AVN physiology can be demonstrated by a variety of maneuvers. To determine whether AVN recovery times following a blocked extrastimulus facilitate or obscure detection of dual AVN physiology, 11 patients (9–17 years) were studied with dual AVN pathways by using single and double atrial extrastimuli. With a single atrial extrastimuli, the premature atrial stimulus (A2) was coupled to basic atrial beats (A1). The fast and slow AVN recovery curves were constructed with plots of the nodal conduction time against the recovery time (A1A2,A2H2). With double atrial extrastimuli, a fixed blocked A2 beat (A2B) was followed by a scanning atrial beat (A3). The nodal recovery property post‐A2B was studied by plots of A2BA3,A3H3. In all patients the recovery curve of the fast pathway post‐A2B had a leftward shift when compared to that of the pre‐A2B curve (i.e., the AH was shortened at the same recovery time). The window of slow pathway conduction post‐A2B disappeared totally in five patients and decreased significatly in six patients (post‐A2B: 26 ± 42 ms; pre‐A2B: 80 ± 65 ms, P < 0.05). In the six patients that still had slow pathway conduction post‐A2B, the slow pathway effective refractory period post‐A2B was significantly less than that of pre‐A2B (215 ± 38 vs 268 ± 16 ms, P < 0.05). The fast pathway effective refractory period post‐A2B was also diminished significantly (235 ± 62 vs 357 ± 76 ms, P < 0.0001). The authors conclude that blocked atrial beats decrease the visibility of the slow pathway conduction. (PACE 2003; 26:2091–2095)
The Influence of High Versus Normal Impedance Ventricular Leads on Pacemaker Generator Longevity
Authors: BERGER THOMAS , ROITHINGER FRANZ X. , ANTRETTER HERWIG , HANGLER HERBERT , PACHINGER OTMAR , HINTRINGER FLORIAN
Published: November 2003

As pacemaker generator longevity is dependent on current consumption and resistance of the pacing lead, the use of a high impedance pacing lead theoretically results in an extension of battery longevity. Therefore, the effect of high versus standard impedance ventricular leads on generator longevity was studied. In 40 patients (21 women, age 73 ± 13 years) with a standard dual chamber pacemaker indication, a bipolar standard impedance ventricular lead was implanted in 20 patients, the remaining patients received a bipolar high impedance lead in a randomized fashion. All patients received identical pacemaker generators and atrial leads. The estimated longevity of the generator was calculated automatically by a programmed pacemaker algorithm. After a mean follow‐up of 39 ± 4.8 months, no significant differences were observed with respect to mean pacing and sensing thresholds of the atrial and ventricular leads in both groups. However, the high impedance leads displayed a significantly higher impedance and a significantly lower current drain as compared to standard impedance leads (1,044 ± 139 vs 585 ± 90 Ω, and 2.2 ± 0.4 vs 4.3 ± 1.1 mA). The extrapolated generator longevity was significantly longer in the high impedance lead group, as compared to the standard impedance lead group (107.3 ± 8.5 vs 97.6 ± 9.0 months; P = 0.02). In conclusion, implantation of a high impedance lead for ventricular pacing results in a clinically relevant extension of generator longevity. (PACE 2003; 26:2116–2120)
Convective Flow Through a Hollow Fiber Bioartificial Liver
Authors: Moussy Yvonne
Published: November 2003

Abstract:  A study of open shell flow through a hollow fiber bioartificial liver with a cell packed shell region (the extracapillary space between the fibers) was performed. Previous analyses of flow through a hollow fiber bioartificial liver have ignored the porous nature of the shell region. Existing analytic expressions were used to describe the flow through the porous hollow fibers, and the flow through the shell region was described using Darcy's law. The operational parameters were taken from clinical trials of the Hepatix extracorporeal liver assist device (ELAD). From the experimental parameters, the permeability value of the cell packed shell region of the ELAD was determined. The results suggest the possible formation of preferential flow channels and hypoperfusion of many cells leading to an inadequately functioning bioreactor. Some simple design changes may improve the performance of the ELAD.
Impact of Bleach Cleaning on the Performance of Dialyzers with Polysulfone Membranes Processed for Reuse Using Peracetic Acid
Authors: Ward Richard A. , Ouseph Rosemary
Published: November 2003

Abstract:  Dialyzer performance may change with reuse depending on whether or not the dialyzer is cleaned with bleach. Bleach is usually used in conjunction with formaldehyde as the germicide. Because few data are available for dialyzers cleaned with bleach and disinfected with peracetic acid, we examined dialyzer performance in a cross‐over study of dialyzers containing polysulfone membranes reprocessed using bleach and peracetic acid or peracetic acid alone. Each dialyzer was used for a total of 16 treatments, or until it failed standard criteria for continued use. Urea, β2‐microglobulin, and albumin removal were determined during the first, second, seventh, and 16th use of each dialyzer. Urea removal did not differ between the two reprocessing methods and did not change with reuse. Overall, β2‐microglobulin removal remained unchanged in dialyzers reprocessed with peracetic acid alone, but tended to increase after the seventh use in dialyzers reprocessed with bleach and peracetic acid. Approximately 60% of β2‐microglobulin removal resulted from trapping of β2‐microglobulin at the dialyzer membrane. Albumin loss into the dialysate was clinically insignificant throughout the study with both reprocessing methods. These data show that the clearance of both small and large molecules by dialyzers containing polysulfone membranes is well maintained by reprocessing with peracetic acid and that additional cleaning with  bleach has limited impact on performance.
The late whiplash syndrome: a psychophysical study
Authors: Moog Martina , Quintner John , Hall Toby , Zusman Max
Published: October 2003

Some patients who have sustained whiplash injuries present with chronic widespread pain and mechanical allodynia. This single‐blind, case control matched study of 43 chronic whiplash patients sought to examine psychophysical responses to non‐noxious stimuli and their relationship to psychological profiles. Symptom Check List 90‐R (SCL‐90‐R), Neck Disability Index and Shortform McGill Questionnaire were completed prior to testing. Qualitative stimuli comprised light touch, punctate pressure, moderate heat and cold. Additionally, sustained vibration was administered using a vibrameter which allowed ramping of either frequency or amplitude. Twenty‐eight patients reported vibration‐induced pain. No control subject experienced pain in response to vibration. No significant differences in perception threshold to vibration were noted between patients and control group. Twenty‐three patients and ten control subjects reported painful responses to cold. Eleven patients and nine control subjects experienced pain in response to moderate heat. Four patients rated punctate pressure and one patient rated light touch as painful. SCL‐90‐R profiles revealed an overall elevated level of distress in the whiplash group. No significant difference was found between patients with and without vibration‐induced pain for any dimension of the SCL‐90‐R. Pain in response to non‐noxious stimulation over presumably healthy tissues suggests that central mechanisms are responsible for ongoing pain in at least some whiplash patients. The additional findings of pain on punctate pressure and hyperalgesic responses to heat and cold stimuli are consistent with enhanced central responsiveness to nociceptor input. These results have important therapeutic and prognostic implications. © 2002 European Federation of Chapters of the International Association for the Study of Pain. Published by Elsevier Science Ltd. All rights reserved.
Microfocusing of 82 keV x rays with a sputtered-sliced Fresnel zone plate
Authors: Awaji M. , Suzuki Y. , Takeuchi A. , Takano H. , Kamijo N. , Yasumoto M. , Terada Y. , Tamura S.
Published: October 2003

An experiment to focus 82 keV x rays with a sputtered-sliced Fresnel zone plate (SS-FZP) optics was performed at an x-ray undulator beamline 20XU of SPring-8. The achieved beam size was 1.1 μm in vertical and 1.3 μm in horizontal directions. The measured flux density was 7×105 (photons/s/μm2).
Compression stress relaxation apparatus for the long-time monitoring of the incremental modulus
Authors: Horst Roland H. , Stephens Thomas S. , Coons James E. , Winter H. Henning
Published: October 2003

A compression apparatus for aging experiments on soft rubbers and foams is presented. The sample is compressed between two parallel surfaces and held there for long-time relaxation studies. The specific purpose of the test is twofold: possible exposure of the sample to aggressive environment under compression during aging and measurement of sample modulus without unloading, i.e., while leaving the sample under constant compression at all times. To determine the restoring force in the compressed sample, the compression strain is modulated with an incremental strain while measuring the force response. The total force gives the compression modulus, and the slope of the force-strain curve allows the determination of the incremental modulus. Stress relaxation data for silicon foam, Dow Corning S-5370 RTV, with 68% void fraction are shown. The modulus of the compressed sample decays over long experimental times of several days. The decay can be described by two relaxation modes, a short mode at 1500 s and a long mode at about 105 s. The incremental modulus changes sharply in the first 1000 s (first mode) and then levels off. The apparatus consists of two self-contained components, the removable sample holder (compression jig) and the stationary test station, which performs the modulation of the strain and all measurements (restoring force and incremental modulus). This allows separation of functions. The apparatus design specifically focused on the control of the incremental strain modulation.
Vehicle-induced seismic effects at a gravitational wave observatory
Authors: Coward D. , Blair D. , Burman R. , Zhao C.
Published: October 2003

The seismic signature of a vehicle traveling on the site of the Australian International Gravitational Observatory has been studied using a two-axis seismometer. The main laboratory strongly attenuated the vehicle-induced seismic noise across all frequencies. We find that the magnitude of the vehicle-induced seismic signal followed a d−γ power law, with d the source–detector distance and γ≈1.7±0.4. The results are indicative of strong attenuation of seismic disturbances and are consistent with other measurements of low-amplitude Rayleigh wave attenuation in similar sandy soil types, a highly desirable property for the site of a gravitational wave observatory. This analysis provides a tool for estimating the magnitude of vehicle-induced seismic noise at the laboratory buildings from more distant sources on and around the site.
Preamplified planar microcoil on GaAs substrates for microspectroscopy
Authors: Dechow Jörn , Lanz Titus , Stumber Michael , Forchel Alfred , Haase Axel
Published: October 2003

In the course of the publication the design, fabrication, and experimental evaluation of a planar microcoil for nuclear magnetic resonance (NMR) spectroscopy with a 360 μm inner diameter integrated to a low-noise metal–semiconductor field-effect transistor is presented. The impedance matching of the coil and transistor was achieved by adjusted coil geometry, while an appropriate microfabrication process including air bridge contacts and a multilayer metal stack was developed for the necessary susceptibility matching of the coil metallization. The NMR spectra of experiments in an 11.75 T magnet (corresponding to 500 MHz) show the amplification of the signal by the integrated transistor. Due to previous experiments, we wanted to ensure that the whole signal emerged from the sensitive volume of the microcoil.
An electromagnetically focused electron beam line source
Authors: Iqbal Munawar , Masood Khalid , Rafiq Mohammad , Chaudhary Maqbool A. , Aleem Fazal-e-
Published: October 2003

A directly heated thermionic electron beam source was constructed. A tungsten wire of length 140 mm with diameter 0.9 mm was used as a cathode. An emission current of 5000 mA was achieved at an input heating power of 600 W. Cathode to anode distance of 6 mm with acceleration voltage of 10 kV was used. A uniform external magnetic field of 50 G was employed to obtain a well-focused electron beam at a deflection of 180°, with cathode to work site distance of 130 mm. Dimensions of the beam (1.25×120 mm) recorded at the work site were found to be in good agreement with the designed length of cathode. The deformation of the cathode was overcome by introducing a spring action mechanism, which gives uniform emission current density throughout the emission surface. We have achieved the saturation limit of the designed source resulting in smooth and swift operation of the gun for many hours (10–15 h continuously). The design of gun is so simple that it can accommodate longer cathodes for obtaining higher emission values. This gun has made it possible to coat large substrate surfaces at much faster evaporation rate at lower cost. It can also be useful in large-scale vacuum metallurgy plants for melting, welding and heat treatment.
A scatterometer for measuring the bidirectional reflectance and transmittance of semiconductor wafers with rough surfaces
Authors: Shen Y. J. , Zhu Q. Z. , Zhang Z. M.
Published: October 2003

A three-axis automated scatterometer (TAAS) with a high accuracy goniometric table, a fiber-coupled power stabilized diode laser, and a large dynamic range detector has been constructed and characterized to measure the bidirectional reflectance of rough surfaces. This scatterometer is capable of both the in-plane and out-of-plane measurements, and furthermore, it can also measure the bidirectional transmittance for semitransparent wafers. The goniometric table is comprised of three computer-controlled rotary stages of high angular resolution. The optical sources are fiber-coupled diode lasers at wavelengths λ=635, 785, and 1550 nm, respectively. These diode lasers exhibit excellent power stability and wavelength stability. Silicon and germanium photodiode detectors are used with a lock-in amplifier. The estimated combined uncertainty of the measurement is 0.5% at θr=45° and 2% at θr=80° without considering the effects of stray light and misalignment. Several rough silicon wafers have been measured and the results have been compared with those obtained from a reference instrument at the National Institute of Standards and Technology. The average relative difference is approximately 5% at λ=635 and 785 nm, and 24% at λ=1550 nm, much larger than the estimated uncertainty. The discrepancy may be attributed to the effects of stray light and in addition, the possible misalignment at λ=1550 nm. It is expected that the accuracy of the TAAS can be improved by reducing stray light and bettering the alignment.
Combined in situ micromechanical cantilever-based sensing and ellipsometry
Authors: Godin Michel , Laroche Olivier , Tabard-Cossa Vincent , Beaulieu L. Y. , Grütter Peter , Williams P. J.
Published: October 2003

Two cantilever-based chemical sensors are reported. First, a differential cantilever-based chemical sensor capable of sensitive surface stress measurements has been designed and implemented. The system uses two commercially available atomic force microscope cantilevers. The surface of one cantilever is functionalized to make it receptive to specific target analytes, while the second, passivated cantilever is used as a reference by subtracting undesired signals, resulting from mechanical and thermal noise, from the signal of interest. The second system is a combined cantilever-based sensor and ellipsometer capable of simultaneous in situ surface stress and film thickness measurements. Both sensors, operated in static mode, achieve a cantilever deflection measurement sensitivity of 0.2 nm and a surface stress resolution of 5×10−5 N/m. Molecular monolayer thicknesses are measured simultaneously with a 0.1 nm resolution. The real-time formation process of alkanethiol self-assembled monolayers on gold was investigated as a model system to characterize these instruments.
Near-infrared Fourier transform room-temperature photoluminescence of erbium complexes
Authors: Barbillat J. , Le Barny P. , Divay L. , Lallier E. , Grisard A. , Van Deun R. , Fias P.
Published: October 2003

A modified Fourier transform (FT) Raman bench spectrometer designed for the detection of weak light emission in the 800–1700 nm wavelength region has been used to demonstrate the advantages of FT spectroscopy for measuring near-infrared photoluminescence spectra of lanthanide complexes with a good resolution and very good sensitivity. This apparatus has been tested with an ultraviolet laser source (325 nm) on three standard erbium complexes. The I13/24→4I15/2 emission of tris-(acetylacetonato) (1,10 phenanthroline) erbium [Er(acac)3(phen)], tris-(4,4,4,-trifluoro-1-(2 thenoyl)-1,3-butenedione) (1,10 phenanthroline) erbium [Er(TTFA)3(phen)] and tris(8-hydroxyquinolinato) erbium [Erq3] has thus been recorded in solution and in the solid state and compared with literature.
Theoretical study of fine and hyperfine interactions in N3+, N3⋅, and N3−
Authors: Prasad Rajendra
Published: October 2003

The geometries and the harmonic vibrational frequencies have been computed for the N3+(X̃ 3Σg−,ã 1Δg,b̃ 1Σg+,Ã 3Πu,1 1Πu), N3⋅(X̃ 2Πg,Ã 2Σu+,1 2Σg+), and N3−(X̃ 1Σg+) systems using the full-valence complete active space self-consistent-field (CASSCF) vectors. The systems N3+(Ã 3Πu,1 1Πu) and N3⋅(X̃ 2Πg) possess two distinct real frequencies for the bending modes. The energy for both components increases upon bending and these states are subject to the type A Renner–Teller effect. The energetics and the dynamical properties have been studied at the complete active space second order perturbation theory (CASPT2) and the multireference singles and doubles configuration interaction (MRSD–CI) levels of theory. The spin–orbit coupling constants, ASO in N3+(Ã 3Πu) and N3⋅(X̃ 2Πg) are obtained by employing the atomic mean field spin–orbit Hamiltonian and these are about 3 cm−1 from the experiment. The nuclear quadrupole coupling constants at various nitrogen centers have been predicted in all the systems by employing the CASSCF, the CASPT2 and the MRSD–CI-ino (iterative natural orbital procedure) methods. The magnetic hyperfine coupling constants (hfcc’s) have been computed for the various N14’s in N3+(X̃ 3Σg−,Ã 3Πu) and N3⋅(X̃ 2Πg,Ã 2Σu+,1 2Σg+) at the configuration selected MRSD–CI-ino level of theory using weighted threshold criteria for the configuration selection.
Direct and precursor-mediated hyperthermal abstractive chemisorption of Cl2/Al(111)
Authors: Poon G. C. , Grassman T. J. , Gumy J. C. , Kummel A. C.
Published: October 2003

Resonantly enhanced multiphoton ionization (REMPI) and time-of-flight mass spectroscopy have been used to demonstrate that the reaction of Cl2 on the low work function Al(111) surface proceeds via a prompt vertical electron harpooning process. Sticking measurements were performed showing that Cl2 adsorbs via a direct chemisorption process at either high incident translation energy or high surface temperature. However, at glancing incident angles and low surface temperatures (100 K), a precursor-mediated channel predominates. REMPI studies show that fast abstracted Cl was produced via both channels: direct, remotely-dissociated incident Cl2, and indirect, precursor-mediated Cl2. For incident Cl2 of 0.11 and 0.27 eV at 40° incident angle and 100 K surface temperature, only the precursor-mediated channel was observed with atomic Cl abstracted product energies of 0.09–0.14 eV. At high surface temperature, 500 K, all incident translational energies and angles yield only the direct channel, with abstracted product energies of 0.19–0.26 eV.
Molecular dynamics simulations of the adsorption of industrial relevant silane molecules at a zinc oxide surface
Authors: Kornherr Andreas , Hansal Selma , Hansal Wolfgang E. G. , Besenhard Jürgen O. , Kronberger Hermann , Nauer Gerhard E. , Zifferer Gerhard
Published: October 2003

The physical behavior of different adsorbed silane molecules (octyltrihydroxysilane, aminopropyltrihydroxysilane, and thiolpropyltrihydroxysilane) at a ZnO surface (0001̄) dissolved in isopropanol are studied via constant temperature (298 K) molecular dynamics simulations. The adsorbed silane molecules exhibit a different behavior depending on the chemical nature of their tail. Octyltrihydroxysilane molecules with their rather unpolar tail show two distinct, energetic different orientations at the polar metal oxide surface. Mostly the three polar hydroxy groups of the head are in contact with ZnO the unpolar tail remaining in the isopropanol phase. Occasionally only two hydroxy groups interact with the surface the whole tail simultaneously being attached. On the contrary, due to their highly polar tail aminopropyltrihydroxysilane molecules have only one favorite orientation at the surface: Apart from some minor fluctuations two hydroxy groups as well as the amino group of the tail are in contact with the surface. The behavior of the thiolpropyltrihydroxysilane molecules is somehow located in between—the thiol group is not polar enough to exhibit such a strong attraction to the polar surface to force permanent contact. Therefore, the molecules show—like octyltrihydroxysilane—two different orientations though the one similar to that of aminopropyltrihydroxysilane is slightly preferred. From adsorption energies of preferred orientations it follows that the strength of adsorption decreases from aminopropyltrihydroxysilane over thiolpropyltrihydroxysilane to octyltrihydroxysilane.
Comparison of quantum and mixed quantum–classical semirigid vibrating rotor target studies for isotopic reactions H(D,T)+CH4→HH(D,T)+CH3
Authors: Cui Qian , He Xiao , Wang Ming-Liang , Zhang J. Z. H.
Published: October 2003

We present mixed quantum–classical (QC) study of A+CH4 reaction with A=H, D, and T using the semirigid vibrating rotor target (SVRT) model to investigate the mass effect of isotope reactions by comparing with the results from quantum SVRT calculations. In this mixed quantum–classical (QC-SVRT) approach, the relative translational motion between the atom and the molecule is treated by classical mechanics while the rest of the coordinates are treated quantum mechanically. The reaction probabilities and rate constants of three isotopic reactions are calculated on the potential energy surface of Jordan and Gilbert. Our study shows that the mixed QC-SVRT reaction probabilities and rate constants from the ground vibrational state of the reagent become progressively more accurate as the mass of the projectile is increased. This phenomenon is related to the diminishing role of the zero-point energy of the projectile as the reduced translational mass is increased. Our study also finds that the QC-SVRT results from vibrationally excited reagent are in substantial deviations from the quantum SVRT results which is due to the failure of the single configuration nature of the mixed quantum–classical approach.
Effect of collisions on one-color polarization spectroscopy of OH A 2Σ+–X 2Π
Authors: Crichton Hilary J. , Costen Matthew L. , McKendrick Kenneth G.
Published: October 2003

The effect of collisions on the magnitude of polarization spectroscopy (PS) signals from the OH radical on the A 2Σ+–X 2Π (0,0) band has been studied. OH was produced by the 266-nm photolysis of H2O2 and detected by one-color degenerate PS, using ≈5-ns pulses from a Nd:YAG pumped dye laser. Spectra with both circular and linear pump polarizations are reported, together with signal dependence on OH number density and pump pulse fluence. The relative line intensities in the spectra and measured square dependence on OH number density are consistent with a description of PS as a variant of four-wave mixing spectroscopy. The pump pulse fluence dependence is fitted well by literature saturation curves. The collisional dependence of the PS signal was investigated by adding increasing pressures of He, Ar, or N2 collider gases for fixed overlapping pump and probe pulses. The principal finding is the very rapid loss of the PS signal with increasing collider pressure. The resulting phenomenological rate constants are in the range 5–9×10−9 cm3 s−1. We discuss these rate constants with reference to the literature rotational energy transfer and dephasing rate constants. We propose that the very large observed values may be explained by the effect of elastic velocity changing collisions.
Rydberg electron transfer to CH3NO2: Lifetimes and characteristics of the product CH3NO2− ions
Authors: Suess L. , Parthasarathy R. , Dunning F. B.
Published: October 2003

The nature of electron binding in CH3NO2− ions produced by Rydberg electron transfer in K(np)/CH3NO2 collisions is investigated through measurements of the lifetimes and electric-field-induced detachment characteristics of the product ions. The data are interpreted with the aid of recent calculations and by comparison to results obtained using well-known dipole-bound and valence-bound anions. Intercomparison of the various data shows that the observed CH3NO2− ions display the characteristics typical of valence-bound negative ions. This finding is discussed in the light of earlier work on electron binding to CH3NO2.
Conformationally induced vibronic transitions in S←S1 spectra of n-propylbenzene
Authors: Panja Sujit S. , Chakraborty Tapas
Published: October 2003

Dispersed fluorescence spectra (S0←S1) of two conformational isomers of n-propylbenzene have been measured in a supersonic free jet expansion. The results show that the vibronic features in emission from the S1 zero-point levels in two conformers are significantly different, and most notably, the transitions due to ring-chain torsional mode are active only in the spectra of the gauche conformer. Relative stability of the conformers in the ground state has been reinvestigated by the ab initio quantum chemistry method at the MP2/6-311++G(d,p) and MP2/ccpVTZ levels of theory. In contrast to earlier reports, the present theoretical studies predict that the gauche conformer is ∼2.5 kJ/mol more stable [MP2/6-311++G(d,p)] than the trans. The effects of propyl substitution on phenyl ring vibrational modes have been analyzed by comparing the calculated (ab initio, DFT/B3LYP/6-31G**) displacements of ring atoms for different normal modes with those of the vibrational modes of unsubstituted benzene. The implications of spectral dissimilarity of the conformers on their excited state lifetimes [Borst et al., J. Chem. Phys. 116, 7057 (2002)] have been discussed.
Direct configuration interaction and multiconfigurational self-consistent-field method for multiple active spaces with variable occupations. II. Application to oxoMn(salen) and N2O4
Authors: Ivanic Joseph
Published: October 2003

In a previous paper, a new direct configuration interaction method for multiple active spaces with variable occupations was described. The present article illustrates how this method may be applied to the oxoMn(salen) complex and the N2O4 molecule. In the first application it is shown how complete-active-space self-consistent-field wave functions of the oxoMn(salen) system may be approximated by a drastically reduced number of configurations with negligible loss of accuracy in terms of energetics. In the second application, to N2O4, it is demonstrated how the fully optimized reaction space wave function may be approximated and also how the recovery of dynamic correlation effects may be achieved. The best predictions of the structure (rNN=1.743 Å, rNO=1.189 Å, ∠(ONO)=134.4°) and binding energy (De=16.0 kcal/mol) are both in very good agreement with experiment (rNN=1.756, rNO=1.191, ∠(ONO)=134.46°, De=16.3 kcal/mol).
Temperature effects on the vibronic spectra of BEH–PPV conjugated polymer films
Authors: Oliveira F. A. C. , Cury L. A. , Righi A. , Moreira R. L. , Guimarães P. S. S. , Matinaga F. M. , Pimenta M. A. , Nogueira R. A.
Published: October 2003

Good quality thin films of poly(2,5-bis(2′-ethyl-hexyl)–1,4-phenylenevinylene) (BEH–PPV) were optically characterized by photoluminescence, absorption, and Raman scattering techniques. The temperature evolution of the vibronic structures in the photoluminescence and absorption spectra was analyzed. At low temperatures it was possible to identify the different phonon modes that contribute to the vibronic spectra. The correlation of the Raman and photoluminescence spectra enabled us to conclude that the main vibrational modes are the two most intense Raman bands at 1310 and 1579 cm−1. The emission efficiency highly increases and the absorption spectra become much more resolved with decreasing temperature. The temperature dependence of the zero-phonon line in the absorption and photoluminescence measurements is attributed to an increase of the effective conjugation length at low temperatures. The results from the polarization-resolved photoluminescence demonstrated the high degree of the in-plane structural order in the BEH–PPV films, corroborating to the relatively high conjugation length obtained from the analysis of the Huang–Rhys factor.
Maximum likelihood trajectories from single molecule fluorescence resonance energy transfer experiments
Authors: Schröder Gunnar F. , Grubmüller Helmut
Published: October 2003

Single molecule fluorescence resonance energy transfer (FRET) experiments are a powerful and versatile tool for studying conformational motions of single biomolecules. However, the small number of recorded photons typically limits the achieved time resolution. We develop a maximum likelihood theory that uses the full information of the recorded photon arrival times to reconstruct nanometer distance trajectories. In contrast to the conventional, intensity-based approach, our maximum likelihood approach does not suffer from biased a priori distance distributions. Furthermore, by providing probability distributions for the distance, the theory also yields rigorous error bounds. Applied to a burst of 230 photons obtained from a FRET dye pair site-specifically linked to the neural fusion protein syntaxin-1a, the theory enables one to distinguish time-resolved details of millisecond fluctuations from shot noise. From cross validation, an effective diffusion coefficient is also determined from the FRET data.
Vibrationally mediated dissociation dynamics of H2O in the vOH=2 polyad
Authors: Nizkorodov Sergey A. , Ziemkiewicz Michael , Myers Tanya L. , Nesbitt David J.
Published: October 2003

Vibrationally mediated photodissociation dynamics of jet-cooled H2O in the vOH=2 polyad is studied in a supersonic slit jet expansion. Single rotational states within |02〉− (≡ν1+ν3 in normal mode notation), |02〉+(≡2ν1), |11〉+(≡2ν3), and |01−2〉(≡ν3+2ν2) vibrational states of H2O are selectively prepared with near IR overtone pumping, photodissociated at 193 nm, and the resulting nascent internal state distribution of OH fragments probed via laser induced fluorescence. Strong oscillations in rotational, spin–orbit, and lambda-doublet distributions are observed, often in remarkably close agreement with H2O state-to-state photodissociation studies from both higher and lower vOH polyads. The influence of initially excited bending and JKaKc levels of H2O on spin–orbit, Λ-doublet, and rotational distributions of OH is examined in detail. Several new dynamical trends are identified, for example, a clear propensity at high N for a strong Λ+ versus Λ− inversion in the Π3/2 spin–orbit manifold, which reverses in the Π1/2 manifold, suggesting spin–orbit sensitive stereodynamics in the ejection process. Furthermore, the results highlight significant differences in photodissociation dynamics from gerade (e.g., |02〉+) versus ungerade (e.g., |02〉−) vibrational states, specifically with respect to OH(v=1)/OH(v=0) branching ratios, and signaling a breakdown of the “spectator” model at low vibrational excitation.
Reaction of tungsten anion clusters with molecular and atomic nitrogen
Authors: Kim Young Dok , Stolcic Davor , Fischer Matthias , Ganteför Gerd
Published: October 2003

Ultraviolet photoelectron spectra for WnN2− (n=1–8) clusters produced by addition of atomic and molecular nitrogen on W anion clusters are presented. Evidence is provided that molecular chemisorption of N2 is more stable than the dissociative one on tungsten anion clusters consisting of eight atoms or less, which is completely different from the results on tungsten bulk surfaces. A general tendency toward molecular chemisorption for small clusters can be explained by reduced charge transfer from the metallic d-orbitals of cluster in contrast to bulk d-orbitals. Comparative studies on chemisorption of atomic and molecular species of diatomic molecules on nanoclusters are expected to provide important information on size-dependent changes of chemical properties of nanoclusters.
Classical density functional study of multisite amphiphile mesostructures
Authors: Christopher P. S. , Oxtoby David W.
Published: October 2003

This paper presents a density functional study of multisite amphiphile molecules with the number of sites in the amphiphile ranging from 2 to 12. The molecular sites of the amphiphiles are fixed with either a freely jointed or rigid rod geometry. The difference between these two geometries is explored in detail. The paper studies the lamellar phase of these amphiphiles, as well as structures (such as monolayers and bilayers) against spherical hard bodies. The hard body surface can be tuned from solvophilic to neutral to solvophobic, and the phase behavior associated with these different arrangements is explored.
Langmuir films of normal-alkanes on the surface of liquid mercury
Authors: Kraack H. , Ocko B. M. , Pershan P. S. , Sloutskin E. , Deutsch M.
Published: October 2003

The coverage dependent phase behavior of molecular films of n-alkanes (CH3CHn−2CH3, denote Cn) on mercury was studied for lengths 10⩽n⩽50, using surface tensiometry and surface x-ray diffraction methods. In contrast with Langmuir films on water, where roughly surface-normal molecular orientation is invariably found, alkanes on mercury are always oriented surface-parallel, and show no long-range in-plane order at any surface pressure. At a low coverage a two-dimensional gas phase is found, followed, upon increasing the coverage, by a single condensed layer (n⩽18), a sequence of single and double layers (19⩽n⩽20; n⩾26), or a sequence of single, double, and triple layers (22⩽n⩽24). The thermodynamical and structural properties of these layers, as determined from the measurements, are discussed.