bluuebunny/crossref_metadata_2025 huggingface dataset:
The impact of land‐cover modification on the June meteorology of China since 1700, simulated using a regional climate model
Authors: Wang H. , Pitman A. J. , Zhao M. , Leemans R.
Published: April 2003

A series of simulations was conducted using a regional climate model with a domain covering mainland China. Simulations were conducted for a single June using estimated land cover for 1700, 1750, 1800, 1850, 1900, 1950, 1970 and 1990. The conversion of land cover between these periods was extensive over mainland China, where large areas were altered from natural forests to either grass or crops, or from natural grasslands to crops. These land‐cover modifications affect various characteristics of the land surface, which lead to changes in the way available energy and water are partitioned. Over areas where land cover was modified, substantial changes are simulated. The conversion from forests to grasses or crops leads to warming and to reductions in root zone soil moisture and latent heat fluxes. Regionally, the conversion from forest to grasses and crops leads to significant warming over large areas of China, but there is an area of cooling present that is coincident with the main location of a land‐use change from short grass to crops. The changes in temperature propagate to about 1500 m above the surface and affect specific humidity throughout this part of the atmosphere. An analysis of daily average results shows a consistent impact of land‐cover modification on temperature, latent heat flux and soil moisture. Therefore, we find large and consistent impacts over China resulting from historical land‐cover modification that are sufficiently important to the regional‐scale climate to warrant inclusion in future modelling efforts. Our results suggest that efforts to attribute warming patterns over China to any particular cause need to take into account the conversion of the land cover that has taken place over China over the last 300 years. Copyright © 2003 Royal Meteorological Society
The evolution of, and revolution in, land surface schemes designed for climate models
Authors: Pitman A. J.
Published: April 2003

The land surface is a key component of climate models. It controls the partitioning of available energy at the surface between sensible and latent heat, and it controls the partitioning of available water between evaporation and runoff. The land surface is also the location of the terrestrial carbon sink. Evidence is increasing that the influence of the land surface is significant on climate and that changes in the land surface can influence regional‐ to global‐scale climate on time scales from days to millennia. Further, there is now a suggestion that the terrestrial carbon sink may decrease as global temperatures increase as a consequence of rising CO2 levels. This paper provides the theoretical background that explains why the land surface should play a central role in climate. It also provides evidence, sourced from climate model experiments, that the land surface is of central importance. This paper then reviews the development of land surface models designed for climate models from the early, very simple models through to recent efforts, which include a coupling of biophysical processes to represent carbon exchange. It is pointed out that significant problems remain to be addressed, including the difficulties in parameterizing hydrological processes, root processes, sub‐grid‐scale heterogeneity and biogeochemical cycles. It is argued that continued development of land surface models requires more multidisciplinary efforts by scientists with a wide range of skills. However, it is also argued that the framework is now in place within the international community to build and maintain the latest generation of land surface models. Further, there should be considerable optimism that consolidating the recent rapid advances in land surface modelling will enhance our capability to simulate the impacts of land‐cover change and the impacts of increasing CO2 on the global and regional environment. Copyright © 2003 Royal Meteorological Society
Condensation as a microclimate process: measurement, numerical simulation and prediction in the Glowworm Cave, New Zealand
Authors: de Freitas C. R. , Schmekal A.
Published: April 2003

The study examines condensation as a microclimate process. It focuses first on finding a reliable method for measuring condensation and then on testing a numerical model for predicting condensation rates. The study site is the Glowworm Cave, a heavily used tourist cave in New Zealand. Preservation of the cave and its management as a sustainable tourist resource are high priorities. Here, as in other caves, condensation in carbon dioxide enriched air can lead to corrosion of calcite features. Specially constructed electronic sensors for measuring on‐going condensation, as well as evaporation of the condensate, are tested. Measurements of condensation made over a year are used to test a physical model of condensation in the cave defined as a function of the vapour gradient between the cave air and condensation surface and a convection transfer coefficient. The results show that the amount and rate of condensation can be accurately measured and predicted. Air exchange with the outside can increase or decrease condensation rates, but the results show that the convection transfer coefficient remains constant. Temporal patterns of condensation in the cave are identified, as well as factors that influence these. Short‐term and longer‐term temporal variations of condensation rates are observed and patterns explained. Seasonal changes are large, with higher condensation rates occurring in the warmer months and lower rates during the cooler months. It is shown that controlling air exchange between the cave and the outside can influence condensation. This and other aspects of cave management are discussed. Copyright © 2003 Royal Meteorological Society
Anomalies of the South American summer monsoon associated with the 1997–99 El Niño–southern oscillation
Authors: Lau K.‐M. , Zhou Jiayu
Published: April 2003

We describe the rainfall and circulation anomalies of the South American summer monsoon (SASM) during December–January–February (DJF) of 1997–98 (El Niño) and 1998–99 (La Niña). The most pronounced rainfall signals in DJF 1997–98 include (a) excessive rainfall over northern Peru and Ecuador, (b) deficient rainfall over northern and central Brazil, and (c) above‐normal rainfall over southeastern subtropical South America. The rainfall anomalies in (a) and (b) are associated with the excitation of an anomalous east–west overturning cell with rising motion and low‐level westerlies over the equatorial eastern Pacific, coupled to sinking motion and low‐level easterlies over northern Brazil. The easterlies turn sharply southeastward on encountering the steep topography of the Andes, enhancing the summertime low‐level jet (LLJ) along the eastern foothills of the Andes near 15–20° S, possibly contributing to the increased rainfall in (c).

During DJF 1997–98, the sea‐surface temperature‐induced warming spreads and expands over the entire tropical troposphere. The eastward expansion of a warm upper tropospheric geopotential and temperature ridge from the Niño‐3 region, across subtropical South America to the southeast Atlantic, enhances warming over the Altiplano Plateau, hydrostatically strengthening the Bolivia high. Similar to previous warming events, the South Pacific high is weakened, and the South Atlantic high is strengthened. During DJF 1998–99, as cold water develops over the equatorial central Pacific, the SASM anomalies in the tropics are weaker and less organized and appear to be in transition to the opposite phase to those found in DJF 97–98. In the subtropics, notable features include a weakening of the LLJ, a rainfall pattern associated with a poleward shift of the South Atlantic convergence zone, and development of the Pacific–South America teleconnection pattern. Published in 2003 by John Wiley & Sons, Ltd.
Targeting of the retinal pigment epithelium (RPE) by means of a rapidly scanned continuous wave (CW) laser beam
Authors: Brinkmann Ralf , Koop Norbert , Özdemir Mustafa , Alt Clemens , Schüle Georg , Lin Charles P. , Birngruber Reginald
Published: April 2003

Background and Objectives

Selective treatment of the retinal pigment epithelium (RPE) by repetitively applying green μs‐laser pulses is a new method for retinal diseases associated with a degradation of the RPE, which spares the neural retina. We investigated an alternative approach to realize repetitive μs‐laser exposure by rapidly scanning a continuous wave (CW)‐laser beam across the RPE.

Study Design/Materials and Methods

An Ar+ laser beam (514 nm) with a diameter of 18.75 μm was repetitively scanned across porcine RPE samples in vitro providing an irradiation time of 1.6 μs per point on the central scan axis. RPE cell damage was investigated by means of the fluorescence viability assay Calcein‐AM.

Results

The ED50 cell damage is 305 mJ/cm2 when applying 10 scans with a repetition rate of 500 Hz. The threshold decreases with the number of scans, a saturation was found at 135 mJ/cm2 with more than 500 exposures applied. The depth of focus in beam direction is 350 μm, defined by an increase of the threshold radiant exposure by 20%.

Conclusions

Targeting of pigmented cells with high local resolution has been proved with a laser‐scanning device. Looking ahead selective RPE‐treatment, the adaptation of a laser‐scanning device on a slit‐lamp or into a modified retina angiograph seems to be an attractive alternative to the pulsed μs laser device. Lasers Surg. Med. 32:252–264, 2003. © 2003 Wiley‐Liss, Inc.
PLS‐ANN based classification model for oral submucous fibrosis and oral carcinogenesis
Authors: Wang Chih‐Yu , Tsai Tsuimin , Chen Hsin‐Ming , Chen Chin‐Tin , Chiang Chun‐Pin
Published: April 2003

Background and Objectives

For effective management of oral neoplasia, autofluorescence spectroscopy was conducted on patients with different characteristics of oral lesions in vivo. This study tested the possibility of using a multivariate statistical algorithm to differentiate human oral premalignant and malignant lesions from benign lesions or normal oral mucosa.

Study Design/Materials and Methods

A fiber optics‐based fluorospectrometer was used to measure the autofluorescence spectra from healthy volunteers (NOM) and patients with oral lesions of submucous fibrosis (OSF), epithelial hyperkeratosis (EH), epithelial dysplasia (ED), and squamous cell carcinoma (SCC). A partial least‐squares and artificial neural network (PLS‐ANN) classification algorithm was used to characterize these oral lesions to discriminate premalignant (ED) and malignant (SCC) tissues from “benign” (NOM, OSF, and EH) tissues.

Results

The normalized and centerized spectra of the different kinds of samples showed similar but divergent patterns. Our PLS‐ANN classification algorithm could differentiate “premalignant and malignant” tissues from “benign” tissues with a sensitivity of 81%, a specificity of 96%, and a positive predictive value of 88%.

Conclusions

We conclude that the PLS‐ANN classification algorithm based on autofluorescence spectroscopy at 330‐nm excitation is useful for in vivo diagnosis of OSF as well as oral premalignant and malignant lesions. Lasers Surg. Med. 32:318–326, 2003. © 2003 Wiley‐Liss, Inc.
Rupture of fat cells using laser‐generated ultra short stress waves
Authors: Kuwahara Kenrick , Gladstone Hayes B. , Gupta Vijay , Kireev Vassili , Neel Victor , Moy Ronald L.
Published: April 2003

Background and Objectives

Ultrasound‐assisted liposuction has been investigated as an aid to breakup fat for its less traumatic removal, and minimizing the post‐operative recovery period. This research focused on understanding the mechanism of fat interaction with laser‐generated ultra short stress waves with high amplitudes.

Study Design/Materials and Methods

Freshly extracted human fat was secured in an Aluminum (Al) cavity. Sixteen nanoseconds duration stress waves were generated by exfoliating the bottom surface of the Al cavity by focusing 3 nanoseconds‐long YAG laser pulses over a 2 mm diameter area at 10 Hz with a maximum pulse energy of 0.95 J. The lipids released due to cell rupture were extracted and measured

Results

Four minutes of pulsing released about 0.005 g, which was over 1% of the initial weight of the tissue. In situ temperature rise of only 5°C was measured at the maximum stress wave loading duration of 5 minutes. This was evidenced by histological sections, which showed no burn artifacts.

Conclusions

This research shows that ultra short stress waves can mechanically cavitate fat in vitro without significant damage to adjacent structures, and forms the basis for future clinical work. Lasers Surg. Med. 32:279–285, 2003. © 2003 Wiley‐Liss, Inc.
Effects of a therapeutic laser on the ultrastructural morphology of repairing medial collateral ligament in a rat model
Authors: Fung Dicky T.C. , Ng Gabriel Y.F. , Leung Mason C.P. , Tay David K.C.
Published: April 2003

Background and Objectives

Low energy laser therapy has been shown to enhance mechanical strength of healing medial collateral ligament (MCL) in rats. The present study investigated its effects on the ultrastructural morphology and collagen fibril profile of healing MCL in rats.

Study Design/Materials and Methods

Thirty‐two mature male Sprague–Dawley (SD) rats were used. Twenty‐four underwent surgical transection to their right MCLs and eight received only skin wound. Immediately after surgery, eight of the MCL transected rats were treated with a single dose of laser therapy at 63.2 J cm−2, eight were treated with a single dose of laser therapy at 31.6 J cm−2, the rest had no treatment and served as control. At 3 and 6 weeks after surgery, the MCLs were harvested and examined with electron microscopy for collagen fibril size, distribution, and alignment.

Results

Significant differences (P < 0.001) were found in fibril diameters from the same anatomical site and time period among different groups. The mass‐averaged diameters of the laser‐treated (64.99–186.29 nm) and sham (64.74–204.34 nm) groups were larger than the control group (58.66–85.89 nm). The collagen fibrils occupied 42.55–59.78, 42.63–53.94, and 36.92–71.64% of the total cross‐sectional areas in the laser‐treated, control and sham groups, respectively. Mode obliquity was 0.53–0.84 among the three groups.

Conclusions

Single application of low energy laser therapy increases the collagen fibril size of healing MCLs in rats. Lasers Surg. Med. 32:286–293, 2003. © 2003 Wiley‐Liss, Inc.
Irradiation of dental enamel with Q‐switched λ = 355‐nm laser pulses: Surface morphology, fluoride adsorption, and adhesion to composite resin
Authors: Wheeler Cameron R. , Fried Daniel , Featherstone John D.B. , Watanabe Larry G. , Le Charles Q.
Published: April 2003

Background and Objectives

Lasers can be used to modify the chemical composition of dental enamel to increase the bond strength to restorative materials and to render the mineral phase more resistant to acid dissolution. Previous studies have suggested a synergistic relationship between CO2 laser irradiation and fluoride treatment on increased resistance to acid dissolution. In this study a near‐UV laser operating with λ = 355‐nm laser pulses of 3–5 nanoseconds duration was used to modify the surface morphology of dental enamel to increase the bond strength to restorative materials and increase the uptake of topical fluoride to render the surface more resistant to acid dissolution. We hypothesize that the short UV laser pulses are primarily absorbed by protein and lipid localized between the enamel prisms resulting in removal of intact mineral effectively etching the surface without thermal modification of the mineral phase. Such modification is likely to increase the permeability of the enamel surface and the subsequent absorption of fluoride. In addition, there is an increase in surface roughness without the formation of a layer of loosely adherent, thermally modified enamel that increases the bond strength to composite restorative materials.

Study Design/Materials and Methods

The surfaces of blocks of bovine enamel, 5 × 5 mm2, were uniformly irradiated by 355‐nm laser pulses and subsequently bonded to composite. The shear bond test was used to assess the bond strength of non‐irradiated blocks (negative control), acid etched blocks (positive control), and laser irradiated blocks. The resistance to acid dissolution was evaluated using controlled surface dissolution experiments on irradiated samples, irradiated samples exposed to topical fluoride, and non‐irradiated control samples with and without fluoride.

Results

The laser surface treatments significantly increased the shear‐bond strength of enamel to composite, to a level exceeding 20 MPa which was significantly more than the non‐irradiated control samples and significantly less than the acid etch. Laser irradiation alone and topical fluoride application alone did not significantly increase the resistance to acid dissolution. The laser treatment followed by topical application of fluoride significantly increased the resistance to acid dissolution to a level of over 50% versus the control samples.

Conclusions

We present a novel method for increasing bond strength to restorative materials and enhancing fluoride delivery to enamel surfaces and shed some light on the underlying mechanisms of caries inhibition via laser treatment and topical application of fluoride. Lasers Surg. Med. 32:310–317, 2003. © 2003 Wiley‐Liss, Inc.
Photodynamic endometrial ablation: Morphological study
Authors: Wyss Pius , Caduff Rosmarie , Tadir Yona , Degen Andrea , Wagnières Georges , Schwarz Viola , Haller Urs , Fehr Mathias
Published: April 2003

Background and Objectives

Endometriumablation provides an alternative treatment modality to hysterectomy for dysfunctional uterine bleeding (DUB). Its feasibility was demonstrated in animal studies. The purpose of this study was the evaluation of histological changes following photodynamic endometrial ablation in patients.

Study Design/Materials and Methods

5‐Aminolevulinic acid (ALA) was topically applied in three premenopausal and one postmenopausal patient 4–6 hours before laser‐illumination. ALA‐concentration: 100–400 g/ml, NaOH‐titration (pH 5.5). Volume applied, 1.5–2.0 ml; intrauterine balloon‐lightdiffuser; wavelength, 635 nm; lightdose, 160 J/cm2. Hysterectomy was performed 3–152 days after photodynamic ablation. Histological examination was carried out on endometrium sections stained with hematoxylin and eosin (H&E).

Results

Necrosis including the full thickness of the endometrium was found 3 days after photodynamic endometrial ablation. Specimens collected after 35 and 152 days did not exhibit fibrosis or adhesions. Foci of preserved endometrium were detected in all patients.

Conclusions

Photodynamic endometrial ablation is selective and does not cause endometrial fibrosis or adhesions. Lasers Surg. Med. 32:305–309, 2003. © 2003 Wiley‐Liss, Inc.
Laser ureteral anastomosis using intraluminal albumin stent in a porcine model
Authors: Xie Hua , Shaffer Brian S. , Prahl Scott A. , Gregory Kenton W.
Published: April 2003

Background and Objectives

We compared ureteral anastomosis using a laser and intraluminal albumin stent with both conventional suturing and laser soldering techniques.

Study Design/Materials and Methods

Twelve pigs underwent bilateral ureteral anastomoses (N = 24) using one of the three anastomotic methods: (1) laser welding with intraluminal albumin stent (N = 11); (2) with albumin solder (N = 8); and (3) conventional suturing (N = 5). Operative parameters, leakage rate, intrapelvic perfusion pressure, urography, and histology of the anastomoses were examined.

Results

Operative time for ureteral anastomosis in the stent and solder groups were significantly shorter than the suture group (means 370 seconds and 360 vs. 710 seconds, both P = 0.02). Leakage rate of the anastomoses was lower in the stent group (9%, 1/11) as compared to the solder group (25%, 2/8). The Whitaker test showed that the intrapelvic perfusion pressure elevated gradually after anastomosis and significantly increased at 4 weeks postoperatively in all three methods. Various degrees of hydronephrosis were also noticed in three groups after 4 weeks of surgery.

Conclusions

Use of the intraluminal albumin stent increased the reliability of laser welding for ureteral anastomosis. The clinical significance of using this technique should be investigated further. Lasers Surg. Med. 32:294–298, 2003. © 2003 Wiley‐Liss, Inc
Effects of low intensity infrared laser radiation on the water transport in the isolated toad urinary bladder
Authors: Franco Wilson , Leite Renner S. , Parizotto Nivaldo A.
Published: April 2003

Background and Objectives

The aim of this work was to study the effects of low intensity laser radiation on water transport in the toad bladder in vitro.

Study Design/Materials and Methods

The water flow through the membrane was measured gravimetrically in bag preparations of the membrane.

Results

Laser radiation did not alter the water transport in the presence nor in the absence of vasopressin. In contrast, when the hemibladders were previously treated with vasopressin, the laser decreased by approximately 33.70% arginine‐vasopressin (AVP)‐mediated water transport. Laser radiation increased 3′5′‐cyclic adenosine monophosphate (3′5′‐cAMP) mediated water transport by approximately 23%. The association of laser radiation with indomethacin (IND) did not affect AVP‐mediated water transport.

Conclusions

This data suggests that the laser may have two effects on AVP‐mediated water transport: one inhibitory effect on 3′5′‐cAMP synthesis by inhibiting the adenylate cyclase complex and another stimulatory effect by inhibiting nucleotide‐phosphodiesterase activity. Our results also indicate that the laser does not interfere in the prostaglandins biosynthesis induced by AVP. Lasers Surg. Med. 32: 299–304, 2003. © 2003 Wiley‐Liss, Inc.
Non‐invasive monitoring of commonly used intraocular drugs against endophthalmitis by raman spectroscopy
Authors: Hosseini K. , Jongsma F.H.M. , Hendrikse F. , Motamedi M.
Published: April 2003

Purpose

To develop a non‐contact and non‐invasive method for quantification of the local concentration of certain antibiotic and antifungal drugs in the eye.

Study Design/Materials and Methods

An integrated CCD‐based Raman spectroscopic system designed specifically for ophthalmic applications was used to non‐invasively detect the presence of ceftazidime and amphotericin B in ocular media. Specific Raman signatures of the above named drugs were determined for various concentrations that were injected through a needle in the aqueous humor of rabbit eyes in vivo. Raman spectra were subsequently acquired by focusing an argon laser beam within the anterior chamber of the eye.

Results

Compared to ocular tissue, unique spectral features of ceftazidime appeared near 1,028, 1,506, 1,586, and 1,641 cm−1. Amphotericin B exhibited its characteristic peaks at 1,156.5 and 1,556 cm−1. The amplitude of the spectral peak corresponding to these drugs (acquired by 1 second exposure time and 25 mW of laser power) were determined to be linearly dependent on their local concentration in the anterior chamber of the eye.

Conclusions

Raman spectroscopy may offer an effective tool to non‐invasively assess the local concentration of the delivered drugs within the ocular media. This technique potentially could be used to investigate the pharmacokinetics of intraocular drugs in vivo either from a releasing implant or a direct injection. Lasers Surg. Med. 32:265–270, 2003. © 2003 Wiley‐Liss, Inc.
Treatment of lupus erythematosus with pulsed dye laser
Authors: Baniandrés Ofelia , Boixeda Pablo , Belmar Paulina , Pérez Alejandro
Published: April 2003

Background and Objectives

The treatment of cutaneous lupus erythematosus (CLE) with dye and argon laser has been evaluated in a number of articles in recent years. The improvement of telangiectasias and chronic erythema of the cutaneous lesions was based on the selective photothermolysis ablation of the dilated capillaries and venules.

Study Design/Materials and Methods

We describe the results of the treatment of cutaneous lesions of 14 patients; eight with discoid lupus erythematosus (DLE) and six with systemic lupus erythematosus (SLE). Three patients received a treatment with flashlamp pulsed dye laser (FPDL) (585 nm, 450 microseconds) with fluences in the range from 5 to 7.75 J/cm2; the other 11 patients were treated with long pulsed dye laser (LPDL) (595 nm, 1.5–10 milliseconds) with fluences in the range from 6 to 13 J/cm2 depending on the pulse duration.

Results

During a median follow‐up of 10 months, we observed an average improvement in over 60% of the lesions. A few side effects were observed in all patients: four had transient hyperpigmentation and one patient had light scarring. Three patients had a relapse after more than 1 year; they were then offered conventional treatment.

Conclusions

We confirm that pulsed dye laser is a good alternative treatment for the erythema in active cutaneous lesions of lupus erythematosus (LE). Lasers Surg. Med. 32:327–330, 2003. © 2003 Wiley‐Liss, Inc.
In vitro assessment and monitoring of the implant titanium materials – physiological environment interactions
Authors: Popa M. V. , Vasilescu E. , Drob P. , Demetrescu I. , Popescu B. , Ionescu D. , Vasilescu C.
Published: April 2003

Long‐term monitoring (for 8000 exposure hours) of titanium and its implant alloys (Ti‐5Al‐4V, Ti‐6Al‐4Fe) interactions with Ringer's solutions of different pH‐values (2.5, 4.35, 6.98), simulating various conditions that can appear at the contact between implant and tissues was carried out in this paper. All data were statistics treated using Medcalc program. In vitro electrochemical behaviour of titanium and its alloys reveals their self‐passivation in Ringer's solutions. Monitoring of the open circuit potentials with time and pH have shown that the passive films on the implant materials studied were very stable for all tested periods. Interactions due to the non‐uniformity of the physiological electrolyte pH can not produce any form of local corrosion. The tested materials present low corrosion rates which attest their very good stability for 8000 exposure hours in simulated biological environment. Surface topography characterisation using atomic force microscopy (AFM) data, correlated with the electrochemical parameters, were arguments for the stability of the samples in studied bioliquids.
Copper corrosion inhibition by fast green, fuchsin acid and basic compounds in citric acid solution
Authors: Cano E. , Pinilla P. , Polo J. L. , Bastidas J. M.
Published: April 2003

Fast green (FG), fuchsin basic (FB) and fuchsin acid (FA) were studied as copper corrosion inhibitors in citric acid solution. Five citric acid concentrations were tested from 0.001 to 1.0 M. Twelve FG, FB and FA concentrations were studied from 1 × 10−5 to 1 × 10−1 M, at four temperatures from 298 to 328 K. The gravimetric method was employed to study the protective effect of FG, FB and FA. The order of inhibition efficiency was FB > FA > FG. Conventional adsorption isotherms were tested to fit the experimental data. The best fit was obtained using the Frumkin isotherm model. A thermodynamic/kinetic model of adsorption was also fitted. The projected molecular area of the inhibitors was calculated to elucidate inhibitor orientation in the adsorption process.
Development of corrosion sensors for monitoring steel‐corroding agents in reinforced concrete structures
Authors: Lee H. S. , Shin S. W. , Ahn J. M. , Kim Y. C. , Kho Y. T.
Published: April 2003

Corrosion sensors were devised to develop a system whereby the depth of chloride permeation from concrete surfaces can be monitored non‐destructively on a real‐time basis using such sensors embedded in cover concrete of reinforced concrete structures. The proposed corrosion sensors were subjected to accelerated corrosion in NaCl solutions, mortar specimens intrinsically containing chlorides, and mortar specimens impregnated with chloride solutions, while recording the changes in the resistance readings. The resistance of sensors increased as the degree of corrosion increased. The time to the first change in the resistance decreased and the corrosion degree and resistance increased as the chloride concentration increased and as the distance from mortar surfaces decreased. It was therefore confirmed that the corrosion sensors are capable of monitoring the depth of chloride permeation with sufficient accuracy.
Study of colored anodized aluminum with calcon in sulfuric acidic solution using cyclic voltammetry and impedance measurement methods
Authors: Norouzi P. , Ganjali M. R. , Golmohamaddi M. , Mousavi S. , Vatankhah G.
Published: April 2003

The effect of coloring condition of Al with Calcon (sodium 2,2'‐dihydroxy‐azonaphthalene‐4‐sulfonate), on the corrosion resistance of Al in 0.1 M sulfuric acid solution was studied, using cyclic voltammetry and measurement of impedance noise methods. The changes in the corrosion resistance of colored aluminum electrodes were evaluated by measuring the magnitude of impedance and cyclic voltammetric responses of anodized and colored electrodes. An irreversible corrosion response was observed at the cyclic voltammogram of the colored aluminum electrode. The current and threshold potential of corrosion responses strongly depends on the applied conditions during anodizing, coloring and sealing stages. In addition, significant changes in impedance at the ac voltammogram and noise level at some ac frequencies were observed, when the electrodes were colored under various conditions. In this regard, the surface of the electrode was studied by Scanning Electron Microscopy (SEM). Comparison of SEM images of the colored and uncolored aluminum specimens showed that the colored surface contained a significant numbers of pits. The results indicated that coloring aluminum with Calcon could reduce corrosion resistance of aluminum and increase roughness of the oxide film.
Corrosion process of silver in environments containing 0.1 ppm H2S and 1.2 ppm NO2
Authors: Kim H.
Published: April 2003

The effects of sub‐ppm levels of nitrogen dioxide and hydrogen sulfide, and the adsorbed water on the corrosion of silver were studied in order to get a better understanding of the atmospheric corrosion process. An in situ mass balance was taken to monitor the kinetic behavior and the surface and the corrosion film were analyzed by X‐ray photoelectron spectroscopy (XPS).

In H2S environments, the tarnish film consisted of silver sulfide, and the corrosion rate depended upon oxygen as well as relative humidity. Silver was oxidized by only oxygen and the corrosion behavior conformed to a type of a parabolic law. In NO2environments, the corrosion film consisted of nitrate and oxide, and the corrosion rate depended upon oxygen as well as relative humidity. Compared to hydrogen sulfide, the formation of silver nitrate being strong hydroscopic reduced the effect of humidity on corrosion rate. In H2S + NO2environment, the corrosion process was independent of both oxygen and humidity, and the kinetic behavior conformed to a linear law. The difference of corrosion process between H2S or NO2environments and H2S + NO2environments is thought to be due to the role of nitrogen dioxide as an ionic conductor and the presence of strong oxidizing species such as elemental sulfur which can be produced from the following reaction: H2S + 2NO2→ S + 2HNO2. In addition, the role of adsorbed water affecting atmospheric corrosion process was mentioned based on the amount of adsorbed water from the three types of exposure environments.
Corrosion inhibition of steel in crude oil storage tanks
Authors: Khalifa M. A. , El‐Batouti M. , Mahgoub F. , Bakr Aknish A.
Published: April 2003

The corrosion behavior of steel in water from certain oil fields with various organic inhibitors was studied by applying potentiodynamic technique at pH 5.9. The inhibitors which were used include 2‐methylbenzimidazole (I), 2‐mercaptobenzimidazole (II), 2‐mercapto‐5‐methylbenzimidazole (III), and 2‐mercaptothiazole (IV). The inhibiting efficiency of the different additives was evaluated from their anodic and cathodic polarization curves at different temperatures.

A comparative study of curve fitting procedures using the kinetic thermodynamic model and those utilizing well‐known adsorption isotherms was undertaken. Three types of isotherms were used, Langmuir, Frumkin and Flory‐Huggins isotherm. The results show that the kinetic‐thermodynamic model and Flory‐Huggins isotherms are more suitable to fit the data for the four inhibitors, at all applied temperatures. From the values of binding constants, K, the order of inhibitor efficiency is:

III > IV > II > I

and thus 2‐mercapto‐5‐methylbenzimidazole was the most effective inhibitor. The thermodynamic parameters obtained for all the compounds used showed low values of Hads, which indicates that the action of these inhibitors is physically adsorptive in nature.
Assessment and control of MIC in a sugar cane factory
Authors: Setareh M. , Javaherdashti R.
Published: April 2003

Microbiologically influenced corrosion (MIC) in a sugar cane factory was studied. Also, two types of industrially recommended biocides and a mixture of them were evaluated by using kill time method. The results showed that some countermeasures were necessary to be applied to lower the risk of MIC. The concentrations of the biocides used in this study revealed that the biocides, under the testing conditions, had no biocidal effect what so ever.
Röntgenkleinwinkeluntersuchungen an lösungen von β‐naphtholorange
Authors: Kratky Von O. , Ledwinka H. , Pilz I.
Published: April 2003

Nach der Absolutintensität der Röntgenkleinwinkelstreuung liegt der Farbstoff ß‐Naphtholorange in sehr verdünnter wäßriger Lösung monomolekular vor, und es tritt mit wachsender Konzentration eine schwache Assoziation auf. Bei Lösungen mit KCl‐Zusatz führt die Extrapolation auf die Konzentration null des Farbstoffs ebenfalls auf den monomolekularen Lösungszustand; dann nimmt aber mit waschsender Konzentration die Assoziation erheblich mehr zu. Die Zusammenlagerung erfolgt in den beiden Richtungen senkrecht zur größten Dimension des Moleküls, wodurch bei entsprechnd hohem Assoziationsgrad blättchenförmige Aggregate von der Dicke 13,5 Å entstehen, die dieser größten Dimension des Einzelmoleküls entspricht. Die Fläche der Blättchen wächst proportional dem Assoziationsgrad, und die Gesamtgestalten sind, wie Vergleiche mit theoretischen Streukurven zeigen, in ausreichender Näherung mit Parallelepipeden streuungsäquivalent. Die Aggregate sind außerordentlich locker gebaut; das Volumen, das in diesen ein Molekül einnimmt, ist etwa das Vierfache des partiellen spezifischen Volumens. Das Problem, wie die Bindung zustande kommt, bedarf eines weiteren Studiums.
Polymerization of propylene to syndiotactic polymer. IV. Addition to the double bond
Authors: Zambelli A. , Giongo M. G. , Natta G.
Published: April 2003

By the study of differently deuterated homopolymers and copolymers of propylene it is demonstrated that the double bond addition is cis in the syndiotactic polymerization of propylene. Furthermore it is confirmed that the addition to the double bond is cis also in the isotactic polymerization.
Study on the pyrolysis of cellulose and its derivatives
Authors: Patel K. S. , Patel K. C. , Patel R. D.
Published: April 2003

Kinetics of pyrolysis of cotton cellulose and cellulose acetate with different degrees of substitution have been studied. The range of decomposition temperature of the cellulose samples was found to decrease with the increase in degree of substitution. However, the stability of the polymer increased as the degree of substitution increased. Probable mechanism of degradation of the test samples is discussed. Energy of activation and order of reaction for the decomposition of polymer samples as well as for the residual materials have been determined and correlated with DTA measurements.
Alkali metal solutions in organic solvents obtained in the presence of polyethylene oxide
Authors: Panayotov I. M. , Tsvetanov Ch. B. , Berlinova I. V. , Velichkova R. S.
Published: April 2003

Alkali metals dissolve not only in liquid ammonia but also in ethers, such as tetrahydrofuran (THF), 1.2‐dimethoxyethane (DME), and dimethyl ether of diethylene glycol (diglyme), blue solutions being obtained1,2. “Blue” solutions can be obtained only with rigorously purified reagents in full absence of moisture and oxygen, usually at low temperature. They are not very stable systems, especially at room temp., and discoloration begins shortly after the removal of the metal. The concn. of the metal dissolved is as low as 10‐4 to 10‐3 mole/1. The electrical conductivity of the “blue” solutions is in the range of 10‐5 to 10‐6 ohm‐1 cm‐1 and that of the discolored solution is 10‐8 to 10‐9 ohm‐1 cm‐1.

Obviously the solvation ability of the solvent plays a very important role in the formation of metal solutions. DAINTON et al.1,3 presented arguments that the predominant species in the “blue” solutions are pairs of electrons (e2) with coupled spins, whereas TUTTLE and WEISSMAN4 observed at ‐80°C a weak singlet in the ESR spectrum of the potassium solution in DME, and CAFASSO and SUNDHEIM2 revealed a weak ESR signal in a rubidium solution in bis‐2‐(2‐methoxyethoxy) ethyl ether as well as in a frozen potassium solution in DME.

“Blue” alkali metal solutions can be easily obtained in hexamethylphosphoramide but it is not still clear whether they are solutions of alkali metals5 or of anion‐radicals of the solvent6.

It was established that potassium solutions in THF and DME initiated polymerization of acrylonitrile (conversion about 4%) and of styrene (conversion up to 100%), but not of methyl methacrylate and acrylamide3.
Catalyse de transformation des oléfines par les complexes du tungstène. II. Télomérisation des oléfines cycliques en présence d'oléfines acycliques
Authors: Jean‐Louis Hérisson Par , Chauvin Yves
Published: April 2003

La co‐réaction des oléfines cycliques avec les oléfines acycliques en présence des systèmes WOCl4/Al(C2H5)2Cl et WOCl4/Sn(C4H9)4 conduit à une télomérisation de l'oléfine cyclique; aux extrémités des molécules de télomère sont fixés deux groupements, identiques ou différents, issus de l'oléfine acyclique par une réaction non consécutive.

Ont été plus particulièrement étudiés: le cyclopentène et le cyclooctène d'une part, le pentène‐2, le pentène‐1, le butène‐2 et le propylène d'autre part.

Le cyclooctadiène‐1.5 et le cyclododécatriène‐1.5.9 réagissent avec le pentène‐2, par réaction non consécutive, en tant que reste CHCH2CH2CH.

La répartition des télomères obéit à une loi statistique.

On propose un schéma réactionnel en accord avec les faits observés dans la réaction de disproportion des oléfines acycliques, la polymérisation des oléfines cycliques et la télomérisation des oléfines cycliques par les oléfines acycliques.
KUHN‐MARK‐HOUWINK‐SAKURADA relations and unperturbed dimensions of poly(di‐n‐alkyl itaconates)
Authors: Veličković Jovan , Vasović Slavica
Published: April 2003

KUHN‐MARK‐HOUWINK‐SAKURADA relations for poly(dimethyl‐, diethyl‐, di‐n‐propyl‐, di‐n‐butyl‐, di‐n‐hexyl‐, di‐n‐octyl‐, di‐n‐decyl‐, and di‐n‐undecyl itaconate) were established in toluene at 25°C. The decreasing exponent a from 0.80 to 0.61, in going from lower to higher members of the series, reflects the decreasing solvent power of toluene. Observed high molecular weights of the polymers are in disagreement with formerly assumed strong chain transfer to monomer in the propagation step. σ‐parameters, evaluated according to the KURATA‐STOCKMAYER extrapolation procedure, within limits of 1.98 and 3.50, indicate strong and progressively increasing steric hindrance to free rotation in this polymer homologueous series.
Reactivities of some organozinc initiators for copolymerization of carbon dioxide and propylene oxide
Authors: Inoue Shohei , Kobayashi Makoto , Koinuma Hideomi , Tsuruta Teiji
Published: April 2003

Copolymerization of carbon dioxide (CO2) and propylene oxide (PO) was carried out by using diethylzinc/water and diethylzinc/methanol catalyst systems. A remarkable amount of polycarbonate was obtained using the former system, but hardly any polymer was formed with the latter catalyst. The difference between these two systems was examined in relation to the elementary processes of the copolymerization. Both the catalysts react with CO2 to produce XZnOCOOR, where X = OCH3 for the diethylzinc/methanol system and X = (OZn)nOH or (OZn)nC2H5 for the diethylzinc/water system. The reactivity of XZnOCOOR with PO depends on X and the difference between the two systems can be explained by the presence or absence of repeating ZnO bonds.

Diethylzinc/primary amine systems produced copolymers while diethylzinc/secondary amine systems were inefficient yielding only small quantities of polymer. This can also be explained by the presence or absence of repeating ZnNR bonds.
Thermal degradation of isotactic and atactic poly(methyl vinyl ketones)
Authors: Matsuzaki Kei , Ohshima Shozo
Published: April 2003

The stereoregularity of poly(methyl vinyl ketone) (PMVK) was determined by NMR spectra of the polymers. Isotactic and atactic PMVK's were thermally degraded, and thermogravimetric analysis, IR and visible and UV spectroscopy were applied to elucidate the mechanism of the degradation. It was found that the isotactic polymer begins to degrade at lower temperature than the atactic polymer, but its rate becomes lower than that of the atactic polymer at temperatures higher than 320°C. If the two types of polymers were treated at a constant temperature (200°C) for varying times under N2 atmosphere, the isotactic polymer showed a higher degradation rate as determined by thermogravimetric analysis and IR spectroscopy. The isotactic polymer shows a higher tendency to form a monocyclic structure in the heat treatment than the atactic polymer. This is similar to poly(isopropenyl methyl ketone).
Untersuchungen zu struktur und eigenschaften der polyamide, 2. Einkristalle aus polyamid 6,6
Authors: Hinrichsen Georg
Published: April 2003

Polyamid‐6,6‐Einkristalle wurden aus verdünnten Lösungen bei Temperaturen zwischen 20 und 150°C ausgefällt und mittels Röntgenweit‐ und Röntgenkleinwinkelstreuung, Elektronenmikroskopie, Differentialkalorimetrie und Dichtemessungen charakterisiert. Es stellt sich heraus, daß die morphologische Beschaffenheit, die Kristalldicke, die Dichte, die Schmelzwärme und das Schmelzverhalten der Einkristalle von deren Kristallisations‐temperatur stark beeinflußt werden. Die aus den Dichten und Schmelzwärmen der Einkristalle berechneten Kristallisationsgrade liegen im Bereich von 40 bis 60%, wobei der jeweilige Wert von der Kristallisationstemperatur bestimmt wird. Durch Tempern bei erhöhten Temperaturen wächst die röntgenografische Langperiode kontinuierlich mit der Tempertemperatur und ‐zeit an. Die Ergebnisse werden in Hinblick auf ein von KELLER et al. für Polyamid‐Einkristalle vorgeschlagenes Modell, das eine regelmäßige Faltungsstruktur vorsieht, ausführlich diskutiert.
Cationic polymerizations initiated by high energy radiation
Authors: Chapiro Adolphe
Published: April 2003

Ionizing radiations generate both free radicals and ions upon interaction with matter and under appropriate conditions either free radical or ionic polymerizations are observed. Cationic polymerizations are favored by the presence of halogenated solvents and by low reaction temperatures. Selective inhibitors and copolymerization studies make it possible to determine the relative proportions of the cationic and the free radical contributions to the overall process under a variety of experimental conditions (temperature, reaction medium, radiation dose‐rate). Pure, carefully dehydrated hydrocarbon monomers undergo cationic polymerization when irradiated at room temperature. This reaction proceeds at a very high rate and is believed to involve free propagating cations. Propagation rate constants are available for the following monomers: styrene (kp = 3,5·106 at 15°C), α‐methylstyrene (kp = 4.106 at 0°C), cyclopentadiene (kp = 6.108 at −78°C), isobutene (kp = 1,5·108 at 0°C), and isobutyl vinyl ether (kp = 3.105 at 30°C). The present views on the mechanism of radiation induced cationic chain initiation and chain propagation are briefly discussed.
Éthers‐oxydes polymères des composés azoïques. Hétéropolycondensation du azodiphénolate‐4,4′ de sodium avec des dérivés bis(chlorométhylés) du benzène
Authors: Iovu Mircea , Radu Stelian
Published: April 2003

Dans ce travail nous présentons les résultats de la hétéropolycondensation du azodiphénolate‐4,4′ de sodium (1) avec les dérivés bis(chlorométhylés) du benzène et du benzène substitué 2a, b et 4. Les composés résultants sont des polymères linéaires avec une couleur jaune, peu solubles dans les solvants organiques.

De même nous présentons les résultats de l'analyse spectrophotométrique (UV, visible, IR) et de l'analyse thermogravimétrique pour les polymères synthétisés.
Alternating copolymerization of carbon dioxide and propylene oxide in the presence of organometallic catalysts
Authors: Kuran Witold , Pasynkiewicz Stanisław , Skupińska Jadwiga , Rokicki Andrzej
Published: April 2003

Carbon dioxide and propylene oxide (PO) were copolymerized using diethylzinc in addition with benzenedi‐ and triols, aliphatic diols and triols, and aminophenols as catalyst systems. A large amount of CO2/PO alternating copolymer, {poly(propylene carbonate), poly(oxycarbonyloxypropylene), of high molecular weight was obtained using the homogeneous (C2H5)2Zn/pyrogallol (2:1 by mole) system (1). The (C2H5)2Zn/o‐aminophenol system (2) (also homogeneous) appeared to be much less active in the copolymerization of CO2 with PO than the former one. From the other studied systems, that appeared to be heterogeneous, (C2H5)2Zn/resorcinol (1:1 by mole) was the most active one, but less active than the system 1.

Further, the copolymerization of CO2 and PO was studied in the presence of the (C2H5)2Zn/resorcinol (1:1 by mole) system at various temperatures and in reaction media of different basicity.

On the basis of the obtained results of the copolymerization of CO2 with PO and of measurements of the quantity of ethane evolved in the reactions between the catalytic systems' components, structures of several catalysts, particularly homogeneous ones, are suggested and some aspects of the copolymerization mechanism are discussed.
Oligomerisierungsprodukte bei der olefin‐metathese von mehrfach ungesättigten aliphatischen carbonsäureestern
Authors: Ast Wolfgang , Rheinwald Günter , Kerber Robert
Published: April 2003

Die Olefin‐Metathese von mehrfach ungesättigten Carbonsäureestern wie Linol‐ und Linolensäureester in Gegenwart eines WCl6/(CH3)4Sn‐Katalysators führt neben einem cyclischen Produkt zu linearen oligomeren Olefinen, Mono‐ und Diestern. Die Produkte werden durch Massenspektrometrie identifiziert. Die sich im Gleichgewicht einstellende Verteilung der Linearprodukte wird statistisch berechnet und mit der experimentellen Verteilung verglichen.
The effect of desorption in micellar particle nucleation in emulsion polymerization
Authors: Hansen Finn Knut , Ugelstad John
Published: April 2003

The effect of desorption of monomer radicals from particles on the particle number generated in interval I of an emulsion polymerization is calculated by means of a semi steady state model. It is shown that desorption leads to an increase in the particle number, and at the same time the orders of particle number with respect to emulsifier and initiator are changing. The general equation of Nomura N∝Sz0ϱ1−zi is found to apply, z increasing from 0,6 to 1,0 with increasing desorption. The values of z and N are dependent on the exact reaction mechanisms in the monomer/polymer system and on rate constants of chemical reactions and diffusion processes involved in the particle formation.