bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultrafast synthesis of poly(methyl methacrylate)‐b‐poly(vinyl chloride)‐b‐poly(methyl methacrylate) block copolymers by the Cu(0)/tris(2‐dimethylaminoethyl)amine‐catalyzed living radical block copolymerization of methyl methacrylate initiated with α,ω‐di(iodo)poly(vinyl chloride) in the presence of dimethyl sulfoxide at 25 °C
Authors: Percec Virgil , Guliashvili Tamaz , Popov Anatoliy V. , Ramirez‐Castillo Ernesto , Hinojosa‐Falcon Luis A.
Published: March 2005

α,ω‐Di(iodo)poly(vinyl chloride)s, with number‐average molecular weights ranging from 2100 to 29,500 and molecular weight distributions (weight‐average molecular weight/number‐average molecular weight) ranging from 1.74 to 2.16, were prepared by the previously reported single‐electron‐transfer/degenerative‐chain‐transfer mediated living radical polymerization of vinyl chloride initiated with iodoform and catalyzed by sodium dithionite in water at 25–35 °C. These α,ω‐di(iodo)poly(vinyl chloride) macroinitiators were used for the synthesis of poly(methyl methacrylate)‐b‐poly(vinyl chloride)‐b‐poly(methyl methacrylate) (PMMA‐b‐PVC‐b‐PMMA) block copolymers via the metal‐catalyzed living radical block copolymerization of methyl methacrylate. In this article, we report the effects of various ligands on the rate of block copolymerization mediated by Cu(0) in dimethyl sulfoxide (DMSO). The block copolymerization catalyzed by Cu(0)/tris(2‐dimethylaminoethyl)amine in DMSO at 90 °C yielded block copolymers in less than 15 min, whereas at 25 °C, the reaction times ranged from 60 to 100 min. Therefore, this ultrafast synthetic method provided access to PMMA‐b‐PVC‐b‐PMMA, regardless of the reaction temperature, in the same range of reaction times as the induction period of the same reactions carried out at 90 °C in diphenyl ether and catalyzed by CuCl/2,2′‐bipyridine. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1660–1669, 2005
Oxidative coupling polymerization of 2,3‐dihydroxynaphthalene with dinuclear‐type copper(II) catalyst
Authors: Habaue Shigeki , Muraoka Ryo , Aikawa Akiko , Murakami Soichiro , Higashimura Hideyuki
Published: March 2005

The oxidative coupling polymerization of 2,3‐dihydroxynaphthalene with the novel dinuclear‐type copper(II) catalysts successfully produced poly(2,3‐dihydroxy‐1,4‐naphthylene). For example, the MeOH‐insoluble polymer with a number average molecular weight of 4.4 × 103 from the polymerization using the complex of CuCl2 and N,N′‐bis(2‐morpholinoethyl)‐p‐xylylenediamine (p‐1) at room temperature under an O2 atmosphere followed by acetylation of the hydroxyl groups was obtained in 63% yield. The structures of the tetraamine ligands and the counter anion of the copper(II) salts significantly influenced the catalyst activity. The polymerization of 2,2′‐dimethoxy‐1,1′‐binaphthalene‐3,3′‐diol with the 2CuCl2‐p‐1 catalyst, however, resulted in a lower yield. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1635–1640, 2005
A theoretical study of electronic and vibrational properties of neutral, cationic, and anionic B24 clusters
Authors: Lau Kah Chun , Deshpande Mrinalini , Pati Ranjit , Pandey Ravindra
Published: March 2005

The equilibrium geometries, electronic and vibrational properties, and static polarizability of B24, B, and B clusters are reported here. First‐principles calculations based on density functional theory predict the staggered double‐ring configuration to be the ground state for B24, B, and B, in contrast to the quasi‐planar structure observed in small neutral and ionized Bn clusters with n ≤ 15. Furthermore, the (4 × B6) tubular structure is found to be relatively stable in comparison to the 3D cage structure. The presence of delocalized π and multicentered σ bonds appears to be the cause of the stability of the double‐ring and tubular isomers. For the ground state of B24, the lower and upper bound of the electron affinity is 2.67 and 2.81 eV, respectively, and the vertical ionization potential is 6.88 eV. Analysis of the frequency spectrum of the double‐ring and tubular isomers reveals the characteristic vibrational modes typically observed in carbon nanotubes. The corresponding IR spectrum also reflects the presence of some of these characteristic modes in the neutral and ionized B24, suggesting that double‐ring and tubular structures can be considered as the building blocks of boron nanotubes. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
A canonical sequence approach to the E ⊗ ε Jahn–Teller effect
Authors: Fessatidis Vassilios , Mancini Jay D. , Bowen Samuel P. , Massano William J.
Published: March 2005

We study the linear E ⊗ ε Jahn–Teller effect in which a doubly degenerate fermionic (electron) level is coupled to a pair of degenerate oscillators. Because of the relative simplicity of the model, and since a complete numerical solution has been known for a long time, theorists have had at their disposal an excellent proving ground for a variety of calculational efforts. Here we apply the recently developed canonical sequence method (CSM) of Šamaj et al. J Phys 1997, A30, 1741 to investigate the ground state of this system. Comparisons are then made with other calculation schemes. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Conditions and numerical simulation of dissipative structure formation in imperfect double‐component reaction‐diffusion systems
Authors: Krasilnikov Vladimir V. , Savotchenko Serge E. , Nemtsev Alexander N.
Published: March 2005

Imperfection of a reaction‐diffusion system is investigated. This imperfection causes modification of Fick's equation. We provide imperfection of diffusion fluxes on the basis of a chemical reaction model of unimolecular and bimolecular processes with two intermediate substances. We demonstrate that allowing for imperfection of diffusion processes leads to introducing the spatial derivatives of fourth order in the evolution equations for concentrations of intermediate substances. It is important that dissipative structures including oscillations can be formed in the system due to the availability of these derivatives in the evolution equations. It is proved that the necessary condition of forming the dissipative structures can appear due to imperfection of diffusion processes in the systems considered. It is shown by linear analysis that concentration of the intermediate substance near a stationary state can exhibit oscillatory behavior under certain conditions. Phase‐plane portrait peculiarities of a nonlinear system are investigated at different values of the initial parameters. It is shown by numerical simulation that dependence of concentrations of the intermediate substances has a quasi‐periodical character. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Improved matrix‐assisted laser desorption/ionisation sample preparation of a partially depolymerised cellulose derivative by continuous spray deposition and interfacing with size‐exclusion chromatography
Authors: Momcilovic Dane , Wahlund Karl‐Gustav , Wittgren Bengt , Brinkmalm Gunnar
Published: March 2005

Continuous spray deposition (CSD) of aqueous solutions of partially depolymerised methyl cellulose was found to improve matrix‐assisted laser desorption/ionisation (MALDI) sample preparation. One feature was that the sensitivity in MALDI time‐of‐flight mass spectrometry increased up to an order of magnitude compared with the standard sample preparation method. Another feature was that CSD provided targets for MALDI with homogeneously distributed analyte. This resulted in a more even signal intensity and a higher reproducibility than in the standard method. High‐mass discrimination was more pronounced in CSD than in the standard method. Size‐exclusion chromatography with aqueous eluent was coupled online to CSD onto matrix‐precoated foils. The suitability for determination of the molar mass distribution of methyl cellulose was investigated. Copyright © 2005 John Wiley & Sons, Ltd.
Identification of oral antidiabetics and their metabolites in human urine by liquid chromatography/tandem mass spectrometry—a matter for doping control analysis
Authors: Thevis Mario , Geyer Hans , Schänzer Wilhelm
Published: March 2005

Since 1999, insulin belongs to the list of prohibited substances of the International Olympic Committee and the World Anti‐Doping Agency. Except for patients suffering from insulin‐dependent diabetes mellitus, the administration of insulin is not allowed. Therapeutics developed to treat non‐insulin‐dependent diabetes mellitus act as releasing factors of endogenously produced insulin or improve its efficiency mediating the glucose uptake into insulin‐dependent tissues. Hence, these compounds are also relevant for sports drug testing, and a fast, robust, and sensitive assay was developed to identify 12 oral antidiabetic agents or respective hydroxylated metabolites in human urine. Urine specimens are enzymatically hydrolyzed; target analytes are extracted by liquid‐liquid extraction and identified by means of liquid chromatography interfaced to tandem mass spectrometry by electrospray ionization. Detection limits of respective drugs ranged between 10 and 30 ng/mL, metabolites of therapeutics were characterized by diagnostic fragmentation pathways upon collisionally activated dissociation of protonated molecules, and general fragmentation routes were proposed. Copyright © 2005 John Wiley & Sons, Ltd.
Prenatal screening for congenital heart disease using real‐time three‐dimensional echocardiography and a novel ‘sweep volume’ acquisition technique
Authors: Sklansky M. , Miller D. , Devore G. , Kung G. , Pretorius D. , Wong P. , Chang R.‐K.
Published: March 2005

Objectives

Conventional prenatal screening for congenital heart disease (CHD) involves a time‐consuming and highly operator‐dependent acquisition of the four‐chamber view and outflow tracts. By acquiring the entire fetal heart instantaneously as a single volume, real‐time three‐dimensional echocardiography (RT3DE) may facilitate fetal cardiac screening.

Methods

Four reviewers, each experienced with fetal cardiac imaging, blindly and independently evaluated a single cardiac volume from each of 18 fetuses (11 normal, seven with CHD). Two‐dimensional echocardiography served as the gold standard. Three‐dimensional evaluation of each fetus included a series of volume acquisitions lasting 2–6 s each. A ‘sweep volume’ technique was developed to fit larger hearts into a single non‐gated volume.

Results

RT3DE had a high sensitivity for detecting CHD (93%), with only a single case being missed by two observers. Specificity for CHD was low (45%), with a high rate of ‘cannot determine’ responses and false positive artifacts.

Conclusions

These preliminary results suggest that RT3DE has the potential to function as a screening tool for fetal heart disease. However, artifacts must be recognized and minimized, resolution must improve, and substantial training will be necessary prior to widespread clinical use. Copyright © 2005 ISUOG. Published by John Wiley & Sons, Ltd.
Laryngeal paraganglioma in a patient with multiple head and neck paragangliomas
Authors: Rubin Adam D. , Cheng Sara S. , Bradford Carol R.
Published: March 2005

Paragangliomas of the larynx are rare neuroendocrine tumors, with fewer than 70 cases reported in the literature.1 Typically, laryngeal paragangliomas are not found in patients with multicentric or familial paragangliomas. Only 1 case of laryngeal paraganglioma has been reported in a patient with a synchronous lesion elsewhere (carotid body tumor).2 We report an additional case of a patient with a laryngeal and multiple other paragangliomas.
The use of Ligasure Vessel Sealing System in thyroid surgery
Authors: Lachanas Vassilios A. , Prokopakis Emmanuel P. , Mpenakis Antonios A. , Karatzanis Alexander D. , Velegrakis George A.
Published: March 2005

OBJECTIVES

To evaluate the role of Ligasure Vessel Sealing System (LVSS) (Valleylab, Boulder, CO) in thyroid surgery, with emphasis given to the duration of the procedure, as well as potential relevant postoperative complications.

STUDY DESIGN AND SETTINGS

A prospective study was conducted from November 1, 2002 to October 31, 2003, on patients undergoing thyroid surgery with the use of LVSS device as the primary means of ligation. All patients' records were placed in a database. Efficacy of hemostasis, operation time, and postoperative complications were assessed. Results were compared with previous surgical procedures done by our team when the LVSS was not available.

RESULTS

LVSS proved effective in providing ligation and hemostasis during thyroid surgery in 72 consecutive patients. There was a mean reduction in operating time of 23 minutes compared with previous surgical thyroid procedures. Transient hypocalcaemia occurred in 4 subjects (5.55%); one incidence of transient paresis of the recurrent laryngeal nerve was also observed.

CONCLUSION

LVSS proved quite a reliable and safe device in thyroid surgery; it provided sufficient hemostasis and reducing operative time.
Is the middle fossa approach the treatment of choice for intracanalicular vestibular schwannoma?
Authors: Colletti Vittorio , Fiorino Francesco
Published: March 2005

OBJECTIVES

To compare the 2 surgical techniques most commonly used during vestibular schwannoma (VS) surgery, i.e., the middle fossa (MF) and the retrosigmoid‐transmeatal (RS‐TM) routes, when hearing preservation is attempted.

STUDY DESIGN

A longitudinal study of a series of consecutive patients operated on with the 2 techniques by the same surgeon was conducted. Selection criteria included tumor confined to the internal auditory canal (IAC) with a length ranging from 4 to 12 mm and hearing class A or B. Patients were alternately assigned to 1 of the 2 groups regardless of auditory class and distance of the tumor from the IAC fundus. Thirty‐five subjects were operated on with the RS‐TM technique and 35 via the MF route.

RESULTS

No significant differences in auditory and facial nerve function results between the 2 techniques were observed. The RS‐TM approach, however, showed better facial nerve results at discharge. VS size, IAC enlargement, and, particularly, the distance from the IAC fundus were found to influence the postoperative results more than the type of approach itself.

CONCLUSIONS

The MF approach has been described as being the better technique for VS surgery in terms of auditory results. However, this claim lacks statistical substantiation because no prospective studies are to be found in the literature. The present longitudinal investigation shows that the MF approach does not afford any particular advantages over the RS‐TM route in terms of auditory results in intracanalicular VS, with the exception of tumors reaching the IAC fundus.
Surgical complications after thyroid surgery performed in a cancer hospital
Authors: Filho JoäO Gonçalves , Kowalski Luiz Paulo
Published: March 2005

OBJECTIVE

This study evaluates the incidence and risk factors of complications in patients submitted to thyroidectomy in a cancer hospital with residency training.

STUDY DESIGN

A retrospective chart and complications review of 1020 patients (1990–2000) underwent to thyroidectomy.

RESULTS

At our cancer hospital, 1020 patients underwent thyroidectomy. The main postoperative complications consisted of transient hypocalcemia in 134 (13.1%) patients, permanent hypocalcemia in 26 (2.5%) patients, transient vocal cord palsy in 14 (1.4%) patients, and permanent vocal cord palsy in 4 (0.4%) patients. The type of thyroidectomy, neck dissection, and paratracheal lymph node dissection were significantly associated with transitory and permanent hypocalcemia.

CONCLUSION

Thyroid surgery can be performed safely in a surgical residency training program under direct supervision of an experienced surgeon with little morbidity to the patients. Hypocalcemia is the most significant complication. Neck and para‐tracheal lymph node dissections were the most significant predictors of hypocalcemia in patients who underwent total thyroidectomy.
Reading performance in children with otitis media
Authors: Golz Avishay , Netzer Aviram , Westerman S. Thomas , Westerman Liane M. , Gilbert David A. , Joachims Henry Z. , Goldenberg David
Published: March 2005

OBJECTIVE

To examine whether middle ear diseases and the associated hearing loss in early childhood affect reading performance later at school.

STUDY DESIGN AND SETTING

One hundred and sixty children, 6.5 to 8 years of age, were enrolled in this study: 80 children with a history of recurrent infections and/or prolonged periods of effusions of the middle ear before the age of 5 years, and 80 healthy children without any history of middle ear disease. Data were collected from the medical records of the children. Every child underwent a complete otological and audiological evaluation, followed by special reading tests.

RESULTS

The study group performed more poorly, in all reading tests, as compared to the controls (P < 0.001).

CONCLUSION

Children with recurrent or prolonged middle ear diseases during the first five years of life tend to be at greater risk for delayed reading than aged‐matched controls with no previous middle ear diseases.
Incidence, age at onset, and potential reasons of malignant transformation in recurrent respiratory papillomatosis patients: 20 years experience
Authors: Gerein Valentin , Rastorguev Eugen , Gerein Johann , Draf Wolfgang , Schirren Joachim
Published: March 2005

Forty‐two patients with recurrent respiratory papillomatosis (RRP) were accepted into a multicenter prospective study in 1983 to 1990, treated with alfa‐IFN 3 MU/m2 3 times a week and then followed‐up until August 1, 2003. All the patients who had disease progression with pulmonary spread were characterized by insufficient response to IFN‐therapy and detection of HPV type 11. Five patients (4/5 smokers) presented malignant transformation in lungs or nasopharynx (mean RRP duration was 27.2 ± 8 years from RRP onset and 14.6 ± 6.3 years from pulmonary spread until malignant transformation) with persistent RRP in larynx. The results of long‐term follow‐up in RRP patients with HPV 11 underline the necessity of reanalyzing the current therapy.
Surgical management of parapharyngeal space tumors: A 10‐year review
Authors: Khafif AVI , Segev Yoram , Kaplan Daniel M. , Gil ZIV , Fliss Dan M.
Published: March 2005

OBJECTIVE

The purpose of this article is to describe the diagnostic evaluation and surgical approaches to parapharyngeal space tumors in a tertiary referral center.

STUDY DESIGN AND SETTING

The study is a retrospective review of 47 patients diagnosed with tumors of the parapharyngeal space (12 with malignant diseases and 35 with benign lesions) and surgically treated during a 10‐year period. The transcervical (40%) and the transcervical‐transparotid approaches (46%) were the most commonly performed surgical procedures followed by the orbitozygomatic‐middle fossa approach (12%) and the transmandibular approach (2%).

RESULTS

The surgical procedures were uneventful and there were no postoperative mortalities. Complications were rare; the most common was transient facial nerve paralysis (5 patients). After an average follow‐up of 35 months, only 1 of 35 patients with benign diseases had a recurrence 5 years following transcervical resection of a pleomorphic adenoma. Of 12 patients with malignant tumors, 5 (42%) are alive with no evidence of disease. The sensitivity of preoperative fine needle aspiration biopsy (n = 23 patients) was 87% for detection of malignant disease and specificity was 100%.

CONCLUSIONS

Most benign parapharyngeal space tumors can be removed surgically with a low rate of complications and recurrence. Malignant neoplasms, however, carry an ominous prognosis and a low rate of disease‐free survival. Fine needle aspiration may be helpful in preoperative diagnostic evaluation of patients with parapharyngeal space tumors.
Otolaryngologic presentations of amyotrophic lateral sclerosis
Authors: Chen Anton , Garrett C. Gaelyn
Published: March 2005

OBJECTIVES/HYPOTHESIS

To determine the incidence of voice disturbance as a presenting symptom of amyotrophic lateral sclerosis (ALS) and describe laryngologic features of ALS.

STUDY DESIGN

Retrospective review.

METHODS

Records of patients with voice disturbance at a voice center and ALS patients at a neurology clinic were reviewed from January 1998 to March 2003.

RESULTS

15 of 1759 patients with voice disturbance were later diagnosed with ALS. Of 220 ALS patients presenting to neurology clinic, 44 had bulbar symptoms and 19 had initially presented to an otolaryngologist. Dysarthria, dysphagia, tongue fasciculation, and incomplete vocal fold closure were common findings. Neuromuscular disease was missed in 8 of 19 ALS patients seen by an otolaryngologist.

CONCLUSIONS

Although otolaryngologists rarely encounter undiagnosed ALS patients, a significant portion of bulbar ALS patients are initially evaluated by otolaryngologists.

SIGNIFICANCE

Vigilance for neuromuscular abnormalities on otolaryngologic exam is important in patients who present with dysarthria, dysphonia, or dysphagia. EBM rating: C.
In vitro assessment of image‐guided otologic surgery: Submillimeter accuracy within the region of the temporal bone
Authors: Labadie Robert F. , Shah Rohan J. , Harris Steve S. , Cetinkaya Ebru , Haynes David S. , Fenlon Michael R. , Juszczyk Andrzej S. , Galloway Robert L. , Fitzpatrick J. Michael
Published: March 2005

OBJECTIVES

Application of image‐guided surgery to otology has been limited by the need for sub‐millimeter accuracy via a fiducial system that is easily usable (noninvasive and nonobstructive). METHODS: A dental bite‐block was fitted with a rigid frame with 7 fiducial markers surrounding each external ear. The temporal bones of 3 cadaveric skulls were removed and replaced with surgical targets arranged in a bull's‐eye pattern about the centroid of each temporal bone. The surgical targets were identified both within CT scans and in physical space using an infrared optical tracking system. The difference between positions in CT space versus physical space was calculated as target registration error.

RESULTS

A total of 234 independent target registration errors were calculated. Mean ± standard deviation = 0.73 mm ± 0.25 mm.

CONCLUSIONS

These findings show that image‐guided otologic surgery with submillimeter accuracy is achievable with a minimally invasive fiducial frame.

SIGNIFICANCE

In vivo validation of the system is ongoing. With such validation, this system may facilitate clinically applicable image‐guided otologic surgery. EBM rating: A.
The analysis of maxillary sinus aeration according to aging process; volume assessment by 3‐dimensional reconstruction by high‐resolutional CT scanning
Authors: Jun Beom‐Cho , Song Sun‐Wha , Park Chan‐Soon , Lee Dong‐Hee , Cho Kwang‐Jae , Cho Jin‐Hee
Published: March 2005

OBJECTIVE

To evaluate change of the maxillary sinus volume according to patient age and gender by using a 3‐dimensional (3‐D) reconstruction of computed tomography images.

STUDY DESIGN AND SETTING

One hundred seventy‐three people (totaling 238 maxillary sinuses) who had undergone paranasal sinus CT scan between December 2000 and November 2003 and had no evidence of inflammation or hypoplasia in the CT finding and had no specific history of paranasal sinus surgery or maxillofacial trauma were retrospectively analyzed. The 3‐D reconstruction images were obtained by using a surface‐rendering technique (Vworks; CybeMed, Seoul, Korea) on a personal computer. The mean volume of maxillary sinus was evaluated according to patient chronologic age and gender. The ratio of the maximum horizontal and half‐horizontal extension for the estimation of the morphological change of maxillary sinus and the degree of descent of the sinus below the nasal floor were evaluated in the 3‐D image.

RESULTS

The development of the maxillary sinus continued until the 3rd decade in males and until the 2nd decade in females. The mean maxillary sinus volume in early adults was 24,043 mm3 (males) and 15,859.5 mm3 (females). There was a significance difference in the sinus volume (P < 0.05) according to gender, and there was a significant difference in the maxillary sinus volume according to age before it reached maximum. After its maximum growth period, however, there was no significant difference in the volume change of maxillary sinus and the descent below the nasal floor between two adjacent groups.

CONCLUSIONS

The growth of the maxillary sinus continues until the 3rd decade in males and the 2nd decade in females. Therefore, a maxillary sinus operation affecting the bony structures before these ages might affect the development of the sinus and needs to be performed carefully
Viscous dissipation in explosive volcanic flows
Authors: Vedeneeva Elena A. , Melnik Oleg E. , Barmin Alexey A. , Sparks R. Stephen J.
Published: March 2005

Most models for magma flow in volcanic conduits during explosive eruptions assume isothermal ascent conditions due to the high heat capacity of the magma. Here we present a non‐isothermal axisymmetrical flow model that accounts for the temperature‐dependent viscosity of magma and viscous dissipation of heat. Significant changes in velocity and temperature profiles result in strong reduction of the conduit friction leading to an order of magnitude increase in discharge rate in comparison with the isothermal case. This allows high intensity eruptions to occur from significantly narrower volcanic conduits and so helps to resolve inconsistencies between conduit dimensions inferred from models and observations. For a given conduit diameter fragmentation can occur at much shallow depths than for an isothermal model.
Sounding the plume of the 18 August 2000 eruption of Miyakejima volcano (Japan) using GPS
Authors: Houlié Nicolas , Briole Pierre , Nercessian Alexandre , Murakami Makoto
Published: March 2005

We processed 79 days of GPS data collected at four stations on Miyakejima volcano (Japan) before and during its eruption in 2000. This period includes a strong seismic swarm (27 June to 8 July) followed by five eruptions (8 and 14–15 July, 10, 18, and 29 August). Surface motion is strong during the seismic swarm, then remains almost steady during eruptions. However, during each eruption, we found anomalous values of the LC (ionosphere free) double differences, especially on 18 August, with a peak of 0.6 cycles (i.e., an apparent 290 mm increase of the satellite‐station range). We cannot explain these anomalies by temporary ground displacements during the events. Instead, we propose that they are due to path delay effects in the hot volcanic plume. By adapting a seismic tomography algorithm, the refractivity anomaly and the inferred temperature in the plume is mapped in time and space.
Aerosol optical depth over the mountainous region in central Asia (Issyk‐Kul Lake, Kyrgyzstan)
Authors: Semenov V. K. , Smirnov A. , Aref'ev V. N. , Sinyakov V. P. , Sorokina L. I. , Ignatova N. I.
Published: March 2005

Aerosol optical depth measurements over Issyk‐Kul Lake acquired with the handheld sun photometer Microtops II are analyzed. Aerosol found over the mountainous region at the elevation of 1650 m above sea level resembles mostly clean background conditions. The yearly aerosol optical depth at a wavelength 500 nm ∼0.10 ± 0.03 is in agreement with the multi‐year means from the background sites of the Aerosol Robotic Network (AERONET). Over a period of 4 years optical depth showed a seasonal pattern, with a maximum observed during summer. A link has been made between new and previously acquired data in order to provide a reliable trend for the region.
On the use of GPS tomography to investigate water vapor variability during a Mistral/sea breeze event in southeastern France
Authors: Bastin Sophie , Champollion Cédric , Bock Olivier , Drobinski Philippe , Masson Frédéric
Published: March 2005

Global Positioning System (GPS) tomography analyses of water vapor, complemented by high‐resolution numerical simulations are used to investigate a Mistral/sea breeze event in the region of Marseille, France, during the ESCOMPTE experiment. This is the first time GPS tomography has been used to validate the three‐dimensional water vapor concentration from numerical simulation, and to analyze a small‐scale meteorological event. The high spatial and temporal resolution of GPS analyses provides a unique insight into the evolution of the vertical and horizontal distribution of water vapor during the Mistral/sea‐breeze transition.
Surface ruptures and building damage of the 2003 Bam, Iran, earthquake mapped by satellite synthetic aperture radar interferometric correlation
Authors: Fielding E. J. , Talebian M. , Rosen P. A. , Nazari H. , Jackson J. A. , Ghorashi M. , Walker R.
Published: March 2005

We use the interferometric correlation from Envisat synthetic aperture radar (SAR) images to map the details of the surface ruptures related to the 26 December 2003 earthquake that devastated Bam, Iran. The main strike‐slip fault rupture south of the city of Bam has a series of four segments with left steps shown by a narrow line of low correlation in the coseismic interferogram. This also has a clear expression in the field because of the net extension across the fault. Just south of the city limits, the surface strain becomes distributed over a width of about 500 m, probably because of a thicker layer of soft sedimentary material. Another fault north of Bam shows offset and low correlation over a wider zone in the interferograms, but it has no discrete surface rupture, possibly because of a net shortening across this fault. Taking the difference between the interferometric correlation for an interval including the earthquake and an interval before the earthquake separates the changes due to the earthquake from other effects in the partially vegetated city of Bam. We map the damage to buildings by measuring the change from high correlation to low correlation where buildings were destroyed by the earthquake.
Numerical simulation and process analysis of typhoon‐related ozone episodes in Hong Kong
Authors: Huang Jian‐Ping , Fung Jimmy C. H. , Lau Alexis K. H. , Qin Yu
Published: March 2005

In this study the synoptic patterns conducive to the occurrence of O3 episodes in Hong Kong are categorized by an inspection of the weather charts over the period of 1999–2003. The synoptic patterns associated with tropical cyclones originating in the North Pacific Ocean and the South China Sea are found to be the most optimal weather conditions for the occurrence of ozone episodes in Hong Kong. A high‐resolution version of the regional, three‐dimensional, multiscale photochemical air quality model (Pollutants in the Atmosphere and Their Transport in Hong Kong (PATH)), developed by the Hong Kong Environmental Protection Department in 2000, has been employed to investigate the evolution of one type of ozone episode related to tropical cyclones. A nonhydrostatic meteorological model (MM5) was applied with four‐dimensional data assimilation to provide necessary meteorological fields to the air quality model. The performances of both the meteorological and chemical models are evaluated by comparing the simulated results with the available observed data. An integrated process rate analysis is used to examine the relative contributions of individual physical and chemical processes in the formation of ozone episodes for obtaining a better understanding of the mechanisms of photochemical smog events in Hong Kong. Results show that about 30% of the total ozone production is due to local chemical production in the lower atmosphere boundary layer, and about 70% is contributed by interregional transport from southern China into Hong Kong. In addition, four main processes, including horizontal advection, vertical transport, photochemical reactions, and deposition are found to have a significant influence on the ground‐level concentration of ozone. The sensitivity experiments indicate that the chemical regime for ozone formation in Hong Kong seems to be limited by volatile organic compounds.
Development and application of a new analytical method to estimate the condensable vapor concentration in the atmosphere
Authors: Korhonen Hannele , Kerminen Veli‐Matti , Kulmala Markku
Published: March 2005

A novel analytical method is presented to estimate the total condensable vapor concentration in the ambient atmosphere. The method requires the aerosol size distribution as its only input and is thus straightforward enough to apply to atmospheric data. In order to estimate the condensable vapor concentrations over boreal forest regions, the method was applied to four years of new particle formation days at SMEAR II site in southern Finland. The growth rate of newly formed particles provided additional information of the concentration of low‐volatile vapors. Hence the contribution of low‐volatile and semivolatile vapors to particle growth can be separated. The analysis indicated that the median of the condensable vapor concentrations during the nucleation events was approximately 7.6 × 107 cm−3, with values varying between 2.0 × 107 and 1.8 × 108 cm−3. Of the total concentration, the contribution of low‐volatile compounds was 70% on average but ranged from 22% to over 100%. Sensitivity tests indicated that the obtained percentage of low volatiles is only slightly sensitive to chosen model parameters. When applying the method to ambient aerosol distribution measurements, the largest uncertainty is related to visually undetectable inhomogeneities in air mass and the boundary layer dynamics. These uncertainty factors together with the use of measured dry aerosol sizes instead of ambient sizes can lead the analysis to somewhat overestimate the importance of the low‐volatile compounds to total aerosol growth. Even so, our results suggest that identification of submicron aerosol composition during new particle formation can provide information on the compounds that grow nucleation mode particles to larger sizes.
Implications of bank failures and fluvial erosion for gully development: Field observations and modeling
Authors: Istanbulluoglu Erkan , Bras Rafael L. , Flores‐Cervantes Homero , Tucker Gregory E.
Published: March 2005

Gully erosion is most commonly triggered by fluvial erosion following natural and anthropogenic disturbances or as a response to changes in climate and tectonic forcing and base level drop. Field observations attribute the headward growth and widening of many gully systems to gravitational mass‐wasting processes of oversteepened sidewalls. Soil saturation, groundwater sapping, and tension crack development contribute to the instability. Recent landscape evolution models treat such mass failures as slope‐dependent continuous sediment transport processes, sometimes conditioned on a slope threshold or with nonlinear dependence on slope gradient. In this study we first present an explicit physically based theory for the stability analysis of gully heads and walls. The theory is based on the force balance equation of an assumed planar failure geometry of a steep gully wall, with a potential failure plane dipping into the incised gully bed and tension cracks developing behind the scarp face. Then, we test the theory against field data collected in our field site in Colorado and against other published data. Second, the theory is implemented in a one‐dimensional hillslope profile development model and the three‐dimensional channel‐hillslope integrated landscape development (CHILD) to study the effects of soil cohesion, erosion thresholds, and stochastic climate on the tempo of gully development and morphology. Preliminary results indicate that wider and shallower gullies develop and integrate, forming wide valleys, when soil cohesion is small. As soil cohesion increases, erosion slows down, gullies become deeper with vertical walls, and episodic mass failures occur. Differences in storm intensity‐duration characteristics and erosion thresholds are predicted to have a significant impact on gully development. Vertical gully walls develop rapidly, and gullies enlarge by slab failures in a climate characterized by high‐intensity, short‐duration storm pulses. However, under low‐intensity, long‐duration storms, gullies quickly stabilize, and vertical walls are eliminated and rounded, forming diffusion‐dominated hilltops. Erosion thresholds have a similar impact on the tempo of gully erosion but in the opposite direction. Lowering the erosion threshold enhances gully widening by slab failures. Gully walls stabilize when the erosion threshold is high due to a reduction in the erosion of the failure material on the toe of gully walls.
Constraining ecological and biological bias in planktonic foraminiferal Mg/Ca and δ18Occ: A multispecies approach to proxy calibration testing
Authors: Skinner L. C. , Elderfield H.
Published: March 2005

Parallel stable isotope (δ18Occ) and Mg/Ca measurements performed in three planktonic foraminifer species provide multiple perspectives on past temperature change and thus allow published calibrations for these geochemical proxies to be tested against each other. The comparison of “simultaneous” temperature records, as recorded by both the δ18Occ and Mg/Ca signature of each species, reveals very clearly the nonpassive character of foraminifera as proxy carriers and allows the systematic temperature response of δ18Occ and Mg/Ca in different foraminifer species to be explored. On the basis of their Mg/Ca signatures, Neogloboquadrina pachyderma (right), Globigerina bulloides, and Globigerinoides ruber (white) are each found to exhibit a specific and narrow range of temperature variability; however, the interspecies offsets in “optimum” temperature habitat that are suggested in this way are not expressed by similarly scaled δ18Occ offsets. Hence it is demonstrated that the temperature modes/variations that are recorded by each species cannot be calibrated to Mg/Ca and δ18Occ variations via a single pair of calibrations for all three species: species‐specific δ18Occ and/or Mg/Ca temperature calibrations are required. On the basis of the average δ18Occ and Mg/Ca offsets observed between the three species, it appears that many of the temperature calibrations that are currently proposed for both of these proxies are inconsistent. The data presented here cannot provide species‐specific Mg/Ca and δ18Occ temperature calibrations; however, they do provide a simple method for testing our calibrations in application and clearly indicate that further calibration work using paired Mg/Ca and δ18Occ is required before the full potential of these proxies may be realized.
Perpendicular anisotropy in granular Co–Zr–O films
Authors: Sun Yuqin , Li Weidong , Dhagat Parul , Sullivan Charles R.
Published: March 2005

Soft granular Co–M–O films have promise for application in high-frequency thin-film inductors. But granular Co-based films are often found with perpendicular anisotropy, which can result in stripe domains and poor hysteresis behavior. Film microstructure was analyzed for Co-rich Co–Zr–O granular films with and without stripe-domain behavior. It is suggested that perpendicular anisotropy originates from columnar structure with Co columns perpendicular to film plane. The appearance of columnar structure is determined by sputter pressure and oxygen content.
Coexistence of antiferromagnetism and triplet superconductivity
Authors: Zhang Wei , Sá de Melo C. A. R.
Published: March 2005

The authors discuss the possibility of coexistence of antiferromagnetism and triplet superconductivity as a particular example of a broad class of systems where the interplay of magnetism and superconductivity is important. This paper focuses on the case of quasi-one-dimensional metals, where it is known experimentally that antiferromagnetism is in close proximity to triplet superconductivity in the temperature versus pressure phase diagram. Over a narrow range of pressures, the authors propose an intermediate non-uniform phase consisting of alternating insulating antiferromagnetic and triplet superconducting stripes.
Combination of ultimate magnetization and ultrahigh uniaxial anisotropy in CoFe exchange-coupled multilayers
Authors: Lamy Y. , Viala B.
Published: March 2005

CoFe exchanged-coupled multilayers are studied versus the thickness of the ferromagnetic (F) layer (eF) and the thickness of the antiferromagnetic (AF) layer (eAF). The F layer consists in Co90Fe10, Co50Fe50, and Co35Fe65, respectively. The AF layer is Ni50Mn50. Very high saturation magnetization (4πMs) are reported with 18.5, 23, and 24kG, respectively, combined with excellent soft rotational behaviors. The AF–F–AF multilayers cumulate top and bottom interfacial exchange coupling and show very high effective energy densities (Jex) of 1.01, 0.81, and 0.98ergcm−2, respectively. Jex increases with eAF up to a maximum for eAF⩾500Å. This leads to a strong bias field (Hex) with a classical 1∕eF dependence, which translates into a large uniaxial anisotropy (Hk) at 90° from the pinning direction. Typically, for eF=150Å, Hk is 741, 650, and 642Oe, respectively. However, this translation is rather complex and eF and 1∕eAF dependences of the ratio Hk∕Hex suggest a contribution of an intrinsic CoFe anisotropy. For all CoFe, it is shown that a ferromagnetic resonance frequency (fFMR) of 10GHz is achievable. Co35Fe65 mulilayers exhibit the highest eF×μ′ product, μ′ being very close to the theoretical ultimate permeability. Finally, the soft rotational behavior is shown unchanged over an angular range of ±30° from the pinning direction which is very unusual.
Molecular (hyper)polarizabilities computed by pseudospectral methods
Authors: Cao Yixiang , Friesner Richard A.
Published: March 2005

We have developed algorithms based on pseudospectral (PS) ab initio electronic structure methods for solving the first- and second-order Hartree–Fock/Kohn–Sham equations and evaluating molecular polarizabilities and first- and second-order hyperpolarizabilities in the spin-restricted and spin-unrestricted formalisms at the Hartree–Fock (HF) and density functional theory (DFT) levels. We carry out calculations on 50 small molecules to test the accuracy of the PS approach. Our results demonstrate that the molecular polarizability α computed by the PS method is essentially identical to the value obtained from conventional methods for both HF and DFT calculations, while the first-order hyperpolarizability β and second-order hyperpolarizability γ have mean unsigned percentage differences of 1.26% and 0.62% (HF) and 0.78% and 0.65% (DFT), respectively. We also present CPU timing comparisons between the PS and conventional methods at the 6-31G** level for 14 molecules having 185 to 1185 basis functions. The timing results show that the PS method is 25 (PS-HF) and 13 (PS-DFT) times faster than the conventional method for a system with 500 basis functions. The PS methods are found scale as N2.70 (PS-HF) and N2.40 (PS-DFT), while the conventional methods scale as N2.93 (PRISM-HF) and N2.87 (PRISM-DFT), where N is the number of basis functions.
X-ray spectroscopy study of electronic structure of laser-irradiated Au nanoparticles in a silica film
Authors: Jonnard P. , Bercegol H. , Lamaignère L. , Morreeuw J.-P. , Rullier J.-L. , Cottancin E. , Pellarin M.
Published: March 2005

The electronic structure of gold nanoparticles embedded in a silica film is studied, both before and after irradiation at 355nm by a laser. The Au 5d occupied valence states are observed by x-ray emission spectroscopy. They show that before irradiation the gold atoms are in metallic states within the nanoparticles. After irradiation with a fluence of 0.5J∕cm2, it is found that gold valence states are close to those of a metal-poor gold silicide; thanks to a comparison of the experimental Au 5d states with the calculated ones for gold silicides using the density-functional theory. The formation of such a compound is driven by the diffusion of the gold atoms into the silica film upon the laser irradiation. At higher fluence, 1J∕cm2, we find a higher percentage of metallic gold that could be attributed to annealing in the silica matrix.
Effects of surface topology on the formation of oxide islands on Cu surfaces
Authors: Zhou Guangwen , Wang Liang , Yang Judith C.
Published: March 2005

We examined the effects of surface topology on the nucleation and growth of Cu2O oxide islands during the initial oxidation stages of Cu(100) and Cu(110) surfaces by in situ ultrahigh vacuum transmission electron microscopy and ex situ atomic force microscopy. Our observations indicate that nucleation of three dimensional oxide islands on single crystal surfaces is homogenous, surface defects and dislocations play a very limited role as preferential sites for oxide nucleation. On the other hand, grain boundaries are the preferential sites for oxide nucleation and the oxide islands formed along the grain boundaries show a faster growth rate than that on flat Cu surface. The oxidation on the faceted Cu(110) surface results in heterogeneous nucleation of oxide islands in the facet valleys and one-dimensional growth along the intersection direction of the facets.
Effect of hydrogen peroxide treatment on the characteristics of Pt Schottky contact on n-type ZnO
Authors: Kim Sang-Ho , Kim Han-Ki , Seong Tae-Yeon
Published: March 2005

We report on the formation of good Pt Schottky contacts on the Zn-terminated n-type ZnO (0001) surfaces (∼2×1017cm−3) using surface treatment with a hydrogen peroxide solution. The Pt contacts on organic solvent-cleaned ZnO (0001) show leaky behavior with a high leakage current of ∼−0.05A under −5V reverse bias voltage, whereas the hydrogen peroxide-treated contacts show Schottky behavior with very low leakage current of ∼−6.5×10−8A under −5V reverse bias voltage. Schottky barrier heights estimated from current-voltage and capacitance-voltage characteristics are 0.89 and 0.93eV, respectively. Room-temperature photoluminescence results show that the hydrogen peroxide treatment is fairly effective in removing deep-level defects near the ZnO surface region. In addition, the preliminary deep-level transient spectroscopy result is also presented.
Spin-injection-induced intermediate state in a Co nanopillar
Authors: Yang T. , Kimura T. , Otani Y.
Published: March 2005

A nanoscale pillar consisting of a Co∕Cu∕Co layered structure was fabricated by means of electron-beam lithography to study perpendicular transport properties as a function of both dc electric currents and applied magnetic fields. The nanopillar exhibits sharp transitions in magnetoresistance associated with magnetization reversal between antiparallel and parallel configurations of the two Co layers. Remarked is that the application of a large initializing field of 1kOe and a current of 16mA prior to the measurement results in an intermediate state. This intermediate state seems nucleated due to the spin wave instability.
Low-dislocation-density, nonplanar GaN templates for buried heterostructure lasers grown by lateral epitaxial overgrowth
Authors: Ren Dawei , Zhou Wei , Dapkus P. Daniel
Published: March 2005

We report here the formation of nonplanar GaN templates, which consist of low-dislocation-density, naturally grown GaN ridge mesas, as a mean to facilitate the fabrication of buried heterostructure lasers. Defect reduction is realized by introducing a two-step lateral epitaxial overgrowth procedure that utilizes dislocation bending in the formation of pyramidal mesas to eradicate the threading dislocations that originate from a planar buffer layer. Transmission electron microscopy and atomic force microscopy indicate a mesa top facet having low defect density (∼8×107cm−2), atomic flatness (∼0.29nm mean roughness). Our demonstration has opened the possibility of forming buried heterostructure lasers on nonplanar GaN templates.
Carrier dynamics of low-temperature-grown In0.53Ga0.47As on GaAs using an InGaAlAs metamorphic buffer
Authors: Jo Seong June , Ihn Soo-Ghang , Song Jong-In , Yee Ki-Ju , Lee Dong-Han
Published: March 2005

Structural and carrier dynamic properties of low-temperature-grown In0.53Ga0.47As (LT-InGaAs) on GaAs using an InGaAlAs metamorphic buffer were studied. Investigation of dependence of the structural and carrier dynamic properties of the LT-InGaAs on annealing temperature showed that they were closely related. The use of the metamorphic buffer was effective in reducing the carrier lifetime in the LT-InGaAs. A carrier lifetime as short as 2.14ps, comparable to that of Be-doped LT-InGaAs was achieved.