bluuebunny/crossref_metadata_2025 huggingface dataset:
Red dots near the centre of the fovea on digital retinal photographs in diabetic retinopathy screening
Authors: Ryder REJ , Morgan TD , Swain BL , Tabbassam F , Illahi W
Published: March 2007

In retinopathy screening, digital retinal photography detects many patients with red dots within one disc diameter (1DD) of the centre of the fovea but little else. Guidelines vary regarding what should be done with these patients. A single case was observed, however, in which such a patient progressed over seven months to well‐established exudative maculopathy with clinically significant macula oedema (CSMO) requiring laser treatment. In the wake of this case we aimed to undertake an audit to gauge how common such cases were.

We audited 135 consecutive patients who, when attending for eye screening, were found to have red dots within 1DD of the centre of the fovea but little else. Seventy‐eight were male and 57 female, median age 58 years (30–86). The red dots were in one eye in 111/135 (82%) and in both eyes in 24/135 (18%). All were offered six month re‐screening.

In all, 104/135 (77%) attended for re‐screening at six months. In 35/104 (34%) the red dots had resolved; in 63/104 (61%) they were still present in one or both eyes. In 6/104 (6%) the retinopathy had progressed such that referral to an ophthalmologist was indicated according to standard European referral criteria— in 5/6 there were hard exudates within 1DD of the centre of the fovea and/or circinate or group of exudates within the macula; in 1/6 there were three large blot haemorrhages near the centre of the fovea. However, at ophthalmological review two to four months later none of these six patients had CSMO and none required laser therapy.

It was concluded that there is a 5% chance of patients with red dots near the centre of the fovea developing macula hard exudates in six months; however, most do not develop CSMO during this time span. Although six month review of such patients would be ideal, because of the resource implications to screening services attempting to reach whole populations, 12 month review may be more pragmatic. Copyright © 2007 John Wiley & Sons.

Practical Diabetes Int 2007; 24(2): 79–84 Copyright © 2005 John Wiley & Sons, Ltd.
Nurse‐led management of uncontrolled hypertension in those with diabetes and high vascular risk
Authors: Singh PK , Iqbal N , Beach P , Buch HN , Singh BM
Published: March 2007

The aim of this audit was to determine the effectiveness of a protocol driven, nurse‐led hypertension service for patients with diabetes at high risk.

Data for this audit were collected prospectively on referred patients with established diabetes complications and suboptimal hypertension control. Antihypertensive agents were sequentially introduced and dose titrated according to protocol. Patients were discharged once the target systolic blood pressure (SBP) of <140mmHg was achieved or the intended sequence of drug therapy was complete.

In all, 124 patients completed the full process. There were significant reductions in SBP (186±24 to 139±12mmHg, p<0.001) and diastolic blood pressure (85±13 to 67±11mmHg, p<0.001). A total of 61% achieved the target SBP of <140mmHg. There were expected increases in the number of antihypertensive agents and the number of agents used to maximum dose. Estimated coronary heart disease risk for the primary prevention group improved significantly despite non‐significant changes in lipid profiles.

It was concluded that a systematic approach combining a pre‐set drug protocol itself and its timely implementation under adequate surveillance in a nurse‐led hypertension clinic led to effective outcomes. Copyright © 2007 John Wiley & Sons.
Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC)
Authors: Livingstone K , Fisher M
Published: March 2007

It is well established that people with diabetes have an increased risk of cardiovascular disease and cardiovascular death compared to people without diabetes. Until recently there has been a lack of information on cardiovascular risk reduction in people with type 1 diabetes, especially the younger population. Previous studies looking specifically at glycaemic control have been few in number and the results inconsistent. The DCCT trial demonstrated that a period of intensive insulin therapy and improvement in HbA1c% reduced the incidence and progression of microvascular complications, but macrovascular events were not significantly reduced. The DCCT/EDIC study was the long‐term observational follow up of patients from DCCT, and was used to evaluate whether intensive therapy reduced cardiovascular events in patients with type 1 diabetes. The patients treated intensively in the original DCCT trial had a 42% reduction in any first cardiovascular event when compared to the conventionally treated group, and the risk of first occurrence of non‐fatal myocardial infarction, stroke or death from cardiovascular disease was reduced by 57%. DCCT/EDIC provides us with long‐term, objective documentation of glycaemic control and its relationship to cardiovascular complications. However, until we find methods of bringing down HbA1c% without the added problem of frequent hypoglycaemia, we may find it difficult to translate these findings into our everyday practice. Copyright © 2007 John Wiley & Sons.
Oxidative degradation of a polyimide film: II. Studies using hydrazine hydrate
Authors: Dine‐Hart R. A. , Parker D. B. V. , Wright W. W.
Published: March 2007

Treatment of a polypyromellitimide with hydrazine hydrate yields the biscyclohydrazide of pyromellitic dianhydride and the diamine originally used in the preparation. This reagent was, therefore, employed in a study of oxidised poly‐N,N′‐(4,4′‐diphenylether)pyromellitimide film in an attempt to elucidate the structural changes which had taken place. The most important process appeared to be cleavage of the aryl‐ether bond followed by reactions leading to the formation of polyaromatic aggregates. Breakdown of the imide ring structure also occurred.
Direct “Quantimet”‐electron microscope linkage for the assessment of particle size distribution of polymer latices
Authors: Cobbold A. J. , Gilmour R. E.
Published: March 2007

Initial experiments using “Quantimet” image analysing computers linked directly with an electron microscope for the automated assessment of particle size and distribution in the sub‐micron range are described. The ability to analyse polymer dispersions quickly and without the need for photographic procedures has been demonstrated. It has also been shown that statistical parameters of these dispersions can now be determined with a reasonable degree of certainty and with considerably less experimental difficulty Results obtained by this method have been compared with data obtained using micrographs assessed either manually or using the Zeiss‐Endter instrument. Present limitations and future possibilities are indicated.
Fractionation and characterisation of bisphenol a polycarbonate by gel permeation chromatography
Authors: Hoare H. C. , Hillman D. E.
Published: March 2007

Bisphenol A polycarbonate was fractionated from methylene chloride solution by a progressive precipitation technique. The intrinsic viscosities of these fractions were obtained in methylene chloride solution and corresponded to a viscosity average molecular weight range of 2 × 103 to 80 × 103. The fractions were used to calibrate a gel permeation chromatograph, an experimental Q‐factor of 23.8 was found. The calibration was further confirmed by membrane osmometry and light scattering experiments. The experimental viscosity data demonstrated that the Kurata‐Stockmayer‐Roig relationship is suited to interpret the molecular expansion of polycarbonate in methylene chloride.
A study of urea‐formaldehyde resins using gel permeation chromatography
Authors: Hope Paul , Stark B. Peter , Zahir Sheik A.
Published: March 2007

Gel permeation chromatography is a powerful technique for the investigation of molecular weight distributions of UF resins. Combinations of aqueous solvents with hydrophilic gels, or of organic solvents with organophilic gels, can be used to follow urea‐formaldehyde reactions and also to analyse the condensates obtained. Useful additional information is obtainable by analysing a given material on several different gels of the same type but having different exclusion limits. Recent work has indicated that g.p.c. gels based on vinyl acetate can give excellent resolution of low molecular weight species in UF resins.
Dielectric studies of an ethylene/methacrylic acid copolymer
Authors: Nicol Elisabeth A. , Read Bryan E. , Chantry George W.
Published: March 2007

More extensive data over a generally wider frequency range are presented for dielectric absorption and dispersion in a specimen of an ethylene/methacrylic acid copolymer. The results are interpreted in terms of four distinct processes, two of which (the ‘β′’ and ‘γ’ processes) have now been more thoroughly and accurately characterised, and the remaining two, ascribed respectively to an electronic mechanism (A) and the presence of water (w), have not previously been reported. For the ‘β′’, ‘γ’ and ‘w’ processes, activation energies, permittivity “steps” and values of Nμ2 are quoted. Agreement of measured Nμ2 values with those calculated is quite good but can be made better still by assuming that > CO groups, formed by the partial oxidation of the methylene sequences, are present at a plausible concentration.
Thermal stability studies on vinylidene fluoride/hexafluoropropene copolymers
Authors: Knight Graham J. , Wright Walter W.
Published: March 2007

A study has been made of the evolution of hydrogen fluoride (or other species giving rise to F ions in aqueous solution) from a number of commercially available copolymers of the vinylidene fluoride/hexafluoropropene type using a fluoride ion selective electrode to monitor the process. The copolymers have been examined as gumstock and in fully compounded form. Experiments at a fixed rate of temperature rise have been carried out to 700 °C in air, or nitrogen, and isothermal experiments in the temperature range 200 to 275 °C in air only. In many cases, the compounded materials were less stable than the gum‐stocks from which they were formed. The fluoride yield was very much governed by the compounding and calcium hydroxide appeared to be a much more efficient HF acceptor than the magnesium oxide normally used.
Two stage bulk polymerisation process of vinyl chloride
Authors: Chatelain Jean
Published: March 2007

The two stage bulk polymerisation of vinyl chloride is an economical process which allows the manufacture of different products for numerous applications. The three principal parameters which affect the characteristics of the final product are discussed.

Molecular weight depends on the polymerisation temperature during the second stage. Particle size distribution depends on the speed of agitation during the first stage. Apparent bulk density and porosity which are closely linked, depend on the polymerisation temperatures during both stages and on the degree of conversion reached at the second stage. When the temperatures of both stages are raised, bulk density increases and porosity decreases. When the degree of conversion at the second stage is increased, bulk density increases too and porosity decreases.
Ultracentrifuge study of critically branched polycondensates. II. Molecular weight measurements by the archibald method
Authors: Suzuki Hidematsu , Leonis Constantine G.
Published: March 2007

Archibald molecular weight determinations were carried out on model polycondensate obtained near the gel point of decamethylene glycol and benzene‐1,3,5‐triacetic acid after stabilisation of the carboxyls with diphenyl diazomethane and hydroxyls with ketene. The apparent molecular weights Mapp (t), estimated at the meniscus, decreased rapidly with time. This is in accord with a theoretical prediction. In the low concentration range examined, use of the Rayleigh interference fringes alone enabled us to evaluate the apparent molecular weights at early run times with fair reliability. Using semi‐logarithmic plots of Mapp (t) vs. the effective run time t, difficulty in extrapolation to t = O was not serious. The results were compared with those of earlier work on this model polycondensate system.
Evolved gas analysis of polyurethane foams by time‐of‐flight mass speetrometry
Authors: Reed Christopher
Published: March 2007

A time‐of‐flight mass spectrometer, used for the examination and identification of organic compounds, has been modified for the study of the thermal breakdown of complex organic materials. The development of the apparatus and examination of a range of polyurethane foams is described.
Critical stress cracking of polymers with phenylene groups in the main chain
Authors: Macnulty Basil J.
Published: March 2007

Polymers with phenylene groups in the main chain have been examined under uniaxial tension for their reactions to liquids. Preliminary results and critical values of the stress for breaking on liquid contact at room temperature are given.
Kinetic aspects of flocculation by cationic polymers
Authors: Gregory John , Sheiham Ivan
Published: March 2007

Flocculation of latex particles by a series of cationic polymers has been investigated, with special attention being paid to the effect of particle concentration. Both initial rate and ultimate extent of flocculation have been examined over a range of polymer concentrations, so that the onset of flocculation and of restabilisation could be established. At low particle concentrations, the effect of the polymers seems to be predominantly charge neutralisation; even high molecular weight polymers do not appear to form ‘bridges’, presumably because of the relatively flat configuration of the adsorbed polymer chains. However, at high particle concentrations, bridging flocculation may occur because adsorbed polymer chains require a finite time to attain their equilibrium configuration.

Some practical implications of these findings are briefly discussed.
An X‐ray study on the needle‐like crystal of polyoxymethylene grown in a solution polymerisation system
Authors: Iguchi M. , Murase I. , Watanabe K.
Published: March 2007

Needle‐like crystals of polyoxymethylene, grown in a polymerisation system of trioxane in solution with a cationic catalysis and considered to be single‐crystals of extended‐chains, were investigated by means of X‐ray diffraction. As for the molecular orientation in the crystal, a typical ‘fibre‐pattern’ with c‐axis oriented along the length was obtained from a specimen in which needles were embedded and aligned in a resin matrix. The degree of crystallinity, estimated from the diffraction diagram, was practically 100% (or not less than 95%) and the peak width of crystalline reflections, as narrow as a crystal of low molecular weight substance. Periodicity, as is seen in lamellar‐type crystals, was not observed by X‐ray scattering at small angle. The density measured was in a range, between 1.493 and 1.505, which was not different from the theoretical density.
Studies of the reactions of anhydrosulphites of α‐hydroxy acids, part IX. thermal polymerisation of anhydrosulphites of α‐hydroxy α‐methyl carboxylic acids
Authors: Crowe Alec J. , Tighe Brian J.
Published: March 2007

The anhydrosulphites of a series of unsymmetrically substituted α‐hydroxy acids have been prepared and their susceptibility to polymerisation by thermal decomposition studied. The first order rate determining ring scission process, leading to the formation of a reactive α‐lactone intermediate which then undergoes spontaneous polymerisation, is the predominant mechanism even with substituents up to C8. As the length of the n‐alkyl substituent is increased the rate of decomposition and thus polymerisation increases until a plateau value is reached at around C3. Further increase in substituent length decreases the rate of decomposition, an effect which is attributed to steric hindrance of the leaving group by long (C6—C8) substituents.
Rheology and product properties in injection moulding
Authors: Sleeman Michael J. , West George H.
Published: March 2007

The types of flow occurring in the runner, gate and cavity of a cylindrical bar mould have been investigated and the relation between the flow and local modulus of the moulding determined for crystal polystyrene. The results suggest that non‐isothermal shear flow was occurring in the runner while the gate displayed the characteristics of shear flow when heated to the polymer melt temperature and a complex type of flow when cold. The cavity was found, under normal injection rates, to fill by a jetting mechanism which often produced surface irregularities in the product and progressive filling from the gate was only observed at low injection rates.

Investigation of local moulding properties revealed that while considerable variations within a specimen existed, these were apparently not due to the mould filling mechanism. They have been attributed tentatively to the small opening of the mould which takes place during injection and to cooling strain.
Continuous dopaminergic stimulation in Parkinson's disease
Authors: Silverdale Monty
Published: March 2007

Current treatments for Parkinson's disease (PD) are plagued by motor complications. Here these underlying motor complications are briefly reviewed, and strategies to reduce them are discussed.The rationale behind the use of continuous dopaminergic stimulation is highlighted as this is a strategy that may reduce motor complications and improve the quality of life for patients with PD. Copyright © 2007 Wiley Interface Ltd
Primhe: primary care mental health & education
Authors: Ashworth Mark , Lyons Christina , Baguley Clare , Fisher Denise
Published: March 2007

PSYCHLOPS: a patient‐centred outcome measure

A group of practitioners who felt existing psychological outcome measures were not sensitive to the emotional complexities of their caseload set about developing a measure themselves. Here the group Chair describes their progress.

Workforce development and mental health service delivery

The authors describe a novel collaboration that moves away from traditional contracting procedures, with PCTs and SHAs working in partnership with education providers to facilitate and implement a new role in primary care mental health services. Copyright © 2007 Wiley Interface Ltd
Steric effects on the mechanism of reaction of nucleophilic substitution of β‐substituted alkoxyvinyl trifluoromethyl ketones with four secondary amines
Authors: Vdovenko Sergey I. , Gerus Igor I. , Kukhar Valery P.
Published: March 2007

The kinetics of the reaction of β‐substituted β‐alkoxyvinyl trifluoromethyl ketones R1O‐CR2CH‐COCF3 (1a–e) [(1a), R1C2H5, R2H; (1b), R1R2CH3; (1c), R1C2H5, R2C6H5; (1d), R1C2H5, R2V−pNO2C6H4; (1e), R1C2H5, R2C(CH3)3] with four aliphatic amines (2a–d) [(2a), (C2H5)2NH; (2b), (i‐C3H7)2NH; (2c), (CH2)5NH; (2d), O(CH2CH2)2NH] was studied in two aprotic solvents, hexane and acetonitrile. The least reactive stereoisomeric form of (1a–d) was the most populated (E‐s‐Z‐o‐Z) form, whereas in (1e), the more reactive form (Z‐s‐Z‐o‐Z) dominated. The reactions studied proceeded via common transition state formation whose decomposition occurred by ‘uncatalyzed’ and/or ‘catalyzed’ route. Shielding of the reaction centre by bulky β‐substituents lowered abruptly both k′ (‘uncatalyzed’ rate constant) and k″ (‘catalyzed’ rate constant) of this reaction. Bulky amines reduced k″ to a greater extent than k′ as a result of an additional steric retardation to the approach of the bulky amine to its ammonium ion in the transition state. An increase in the electron‐withdrawing ability of the β‐substituent increased ‘uncatalyzed’ k′ due to the acceleration of the initial nucleophile attack (k1) and ‘uncatalyzed’ decomposition of transition state (k2) via promoting electrophilic assistance (through transition state 8). The amine basicity determined the route of the reaction: the higher amine basicity, the higher k3/k2 ratio (a measure of the ‘catalyzed’ route contribution as compared to the ‘uncatalyzed’ process) was. ‘Uncatalyzed’ route predominated for all reactions; however in polar acetonitrile the contribution of the ‘catalyzed’ route was significant for amines with high pKa and small bulk. Copyright © 2007 John Wiley & Sons, Ltd.
Strategies to search and design stabilizers of protein–protein interactions: A feasibility study
Authors: Block Peter , Weskamp Nils , Wolf Alexander , Klebe Gerhard
Published: March 2007

Since protein–protein interactions play a pivotal role in the communication on the molecular level in virtually every biological system and process, the search and design for modulators of such interactions is of utmost importance. In recent years many inhibitors for specific protein–protein interactions have been developed, however, in only a few cases, small and druglike molecules are able to interfere in the complex formation of proteins. On the other hand, there are several small molecules known to modulate protein–protein interactions by means of stabilizing an already assembled complex. To achieve this goal, a ligand is binding to a pocket, which is located rim‐exposed at the interface of the interacting proteins, for example as the phytotoxin Fusicoccin, which stabilizes the interaction of plant H+‐ATPase and 14‐3‐3 protein by nearly a factor of 100. To suggest alternative leads, we performed a virtual screening campaign to discover new molecules putatively stabilizing this complex. Furthermore, we screen a dataset of 198 transient recognition protein–protein complexes for cavities, which are located rim‐exposed at their interfaces. We provide evidence for high similarity between such rim‐exposed cavities and usual ligands accommodating active sites of enzymes. This analysis suggests that rim‐exposed cavities at protein–protein interfaces are druggable binding sites. Therefore, the principle of stabilizing protein–protein interactions seems to be a promising alternative to the approach of the competitive inhibition of such interactions by small molecules. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Four‐body contact potentials derived from two protein datasets to discriminate native structures from decoys
Authors: Feng Yaping , Kloczkowski Andrzej , Jernigan Robert L.
Published: March 2007

Two‐body inter‐residue contact potentials for proteins have often been extracted and extensively used for threading. Here, we have developed a new scheme to derive four‐body contact potentials as a way to consider protein interactions in a more cooperative model. We use several datasets of protein native structures to demonstrate that around 500 chains are sufficient to provide a good estimate of these four‐body contact potentials by obtaining convergent threading results. We also have deliberately chosen two sets of protein native structures differing in resolution, one with all chains' resolution better than 1.5 Å and the other with 94.2% of the structures having a resolution worse than 1.5 Å to investigate whether potentials from well‐refined protein datasets perform better in threading. However, potentials from well‐refined proteins did not generate statistically significant better threading results. Our four‐body contact potentials can discriminate well between native structures and partially unfolded or deliberately misfolded structures. Compared with another set of four‐body contact potentials derived by using a Delaunay tessellation algorithm, our four‐body contact potentials appear to offer a better characterization of the interactions between backbones and side chains and provide better threading results, somewhat complementary to those found using other potentials. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Identification of novel fragment compounds targeted against the pY pocket of v‐Src SH2 by computational and NMR screening and thermodynamic evaluation
Authors: Taylor Jonathan D. , Gilbert Philip J. , Williams Mark A. , Pitt William R. , Ladbury John E.
Published: March 2007

Discovery of small molecule inhibitors of protein–protein interactions is a major challenge to pharmaceutical development. Fragment‐based approaches have begun to be widely adopted as an effective way of exploring chemical space on a protein surface with reduced library size. On completion of a fragment screen, the subsequent selection of appropriate “hit” molecules for development is a key decision point. Thermodynamic parameters can be used in this decision process. In this work, a fragment identification protocol based on a virtual fragment analysis and selection followed by 19F NMR screening was directed at the phosphotyrosine binding site of the Src SH2 domain. Three new ligands were identified. Isothermal titration calorimetry was used to provide thermodynamic parameters for the physiologically relevant ligand and the selected fragments. One of these fragments possesses a highly favorable enthalpic contribution to complex formation compared to other fragments and to the physiologically relevant ligand suggesting that it would make a good candidate for compound development. Proteins 2007. © 2007 Wiley‐Liss, Inc.
The bioactive conformation of glucose‐dependent insulinotropic polypeptide by NMR and CD spectroscopy
Authors: Alaña Iñigo , Malthouse J. Paul G. , O'Harte Finbarr P. M. , Hewage Chandralal M.
Published: March 2007

Glucose‐dependent insulinotropic polypeptide (GIP) is a gastrointestinal incretin hormone, which modulates physiological insulin secretion. Because of its glucose‐sensitive insulinotropic activity, there has been a considerable interest in utilizing the hormone as a potential treatment for type 2 diabetes. Structural parameters obtained from NMR spectroscopy combined with molecular modeling techniques play a vital role in the design of new therapeutic drugs. Therefore, to understand the structural requirements for the biological activity of GIP, the solution structure of GIP was investigated by circular dichroism (CD) followed by proton nuclear magnetic resonance (NMR) spectroscopy. CD studies showed an increase in the helical character of the peptide with increasing concentration of trifluoroethanol (TFE) up to 50%. Therefore, the solution structure of GIP in 50% TFE was determined. It was found that there was an α‐helix between residues 6 and 29, which tends to extend further up to residue 36. The implications of the C‐terminal extended helical segment in the inhibitory properties of GIP on gastric acid secretion are discussed. It is shown that the adoption by GIP of an α‐helical secondary structure is a requirement for its biological activity. Knowledge of the solution structure of GIP will help in the understanding of how the peptide interacts with its receptor and aids in the design of new therapeutic agents useful for the treatment of diabetes. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Study of ordinary chondrites by Mössbauer spectroscopy with high velocity resolution: identification of M1 and M2 sites in silicate phases
Authors: Zhiganova E. V. , Grokhovsky V. I. , Oshtrakh M. I.
Published: March 2007

Study of ordinary chondrites by Mössbauer spectroscopy with high velocity resolution revealed for the first time two crystallographically nonequivalent octahedral sites M1 and M2 in the subspectra of olivine and pyroxene that were observed previously in pure natural or synthetic silicates only. Mössbauer hyperfine parameters and relative areas related to M1 and M2 sites in olivine and pyroxene determined from Mössbauer spectra of ordinary chondrites were analyzed and compared with parameters of pure natural and synthetic silicates. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micro‐Raman investigation of cubic silicon carbide crystals grown from the travelling zone method
Authors: Lewandowska R. , Eid J. , Camassel J. , Santailler J. L. , Ferrand B.
Published: March 2007

Micro‐Raman spectroscopy has been used to investigate two different 3C‐SiC crystals grown from the melt using the travelling‐zone method. The melt was a C‐rich silicon solution held at 1700 °C. Two different (relative) positions of the seed and feed (bottom and up, respectively) were investigated. We show that much better results, with smaller internal strain, can be obtained when placing the seed on top of the feed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AFM and FTIR characterization of microcrystalline Si obtained from isothermal annealing of Al/a‐Si:H
Authors: Rojas‐López M. , Orduña‐Díaz A. , Delgado‐Macuil R. , Olvera‐Hernández J. , Navarro‐Contreras H. , Vidal M. A. , Saucedo N. , Mendez‐García V. H.
Published: March 2007

Atomic force microscopy and Fourier transform infrared spectroscopy were used to investigate the morphology of the microcrystalline surface, and also the amorphous‐crystalline structural transformation of a‐Si:H films, isothermally annealed during several hours. Crystallization process was strongly influenced by the deposition of an Al layer on the surface of a‐Si:H samples. Representative AFM images show the presence of grains, which increase in diameter with the annealing time. Relative crystallized fraction as a function of the annealing time can be described adequately by using the Avrami equation. The kinetic of this crystallization process suggest a two‐dimensional growth of the Si nuclei. Fourier transform infrared measurements show the presence of an intense band near 512 cm–1 associated to Si–Si bonding. We observed the relative diminishing of the intensity of the Si–H wagging mode at 694 cm–1 with annealing time, suggesting effusion of hydrogen to the surface of microcrystalline films. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical measurement of carrier concentration profile in n‐type semiconducting GaAs substrate
Authors: Kitamoto Takuya , Inoue Yusuke , Yamada Masayoshi , Kawase Tomohiro
Published: March 2007

The light absorption below the fundamental energy gap in n‐type GaAs has been investigated precisely. It is experimentally confirmed that there are the three different mechanisms: (a) the enhancement of fundamental absoption due to the shrinkage of energy gap and band filling by doping Si atoms, (b) deep‐level (EL2) absorption, and (c) free‐carrier absorption. It is found that the transmittance measurement at the wavelength longer than about 1000 nm in the free‐carrier absorption region is more useful and direct, compared with that near the fundamental absorption region from 900 nm to 950 nm, precisely to determine the carrier concentration in n‐type GaAs. The two‐dimensional profile of carrier concentration in a VB‐grown 3 ϕ GaAs substrate is measured in high spatial resolution with the short time less than 5 seconds by using a sophisticated near‐infrared transmittance‐measuring equipment. The absolute amount and homogeneity of carrier concentration can be assessed in the range from 0.3 to 3 × 1018 cm–3. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In‐situ X‐ray photoelectron spectroscopy characterization of Si interlayer based surface passivation process for AlGaAs/GaAs quantum wire transistors
Authors: Akazawa Masamichi , Hasegawa Hideki , Jia Rui
Published: March 2007

Detailed properties of the Si interface control layer (Si ICL)‐based surface passivation structure are characterized by in‐situ X‐ray photoelectron spectroscopy (XPS) in an ultra‐high vacuum multi‐chamber system. Si ICLs were grown by molecular beam epitaxy (MBE) on GaAs and AlGaAs(001) and (111)B surfaces, and were partially converted to SiNx by nitrogen radical beam. Freshly MBE‐grown clean GaAs and AlGaAs surfaces showed strong Fermi level pinning. Large shifts of the surface Fermi level position corresponding to reduction of pinning took place after Si ICL growth, particularly on (111)B surface (around 500 meV). However, subsequent surface nitridation increased pinning again. Then, a significant reduction of pinning was obtained by changing SiNx to silicon oxynitride by intentional air‐exposure and subsequent annealing. This has led to realization of a stable passivation structure with an ultrathin oxynitride/Si ICL structure which prevented subcutaneous oxidation during further device processing under air‐exposure. The Si‐ICL‐based passivation process was applied to surface passivation of quantum wire (QWR) transistors where anomalously large side‐gating phenomenon was completely eliminated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Shear viscosity calculations through a reverse nonequilibrium method
Authors: Cavalcanti W. L. , Chen X. , Müller‐Plathe F.
Published: March 2007

In this work we present the result of an algorithm implementation for reverse nonequilibrium molecular dynamics simulation which allows the prediction of viscosity. A non physical momentum flux is imposed by dividing the simulation box into slabs and applying an exchange of the largest negative and positive velocities atoms between the first and central slabs respectively, as result a velocity gradient is produced. This technique has been successfully implemented for atomistic simulations using a molecular dynamics package YASP which works on analytical potential. However, our work focuses on the implementation of RNEMD method into a molecular dynamics code GMQ which works on numerical potential. The developed code provides a reliable tool to predict viscosities for coarse‐grained models via RNEMD technique. The results for Lennard–Jones liquids are presented as well as their comparison for both molecular dynamics codes. Our results are also in good agreement with experimental data. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some mechanisms for the incorporation of hydrogen in Hf‐based gate dielectric films on Si
Authors: Driemeier C. , Baumvol I. J. R.
Published: March 2007

Hf‐based materials are the leading candidates to replace SiO2 gate dielectrics in future Si‐based metal–oxide–semiconductor field‐effect transistors and H inside gate dielectrics has recognized roles on device performance and reliability. In this context, by employing nuclear reaction analyses of 1H and 2H nuclides as well as X‐ray photoelectron spectroscopy, H incorporation in HfSiO, HfSiN, and HfO2 films on Si was accessed. Two technologically relevant H sources were investigated, namely annealing in H2 at 400–600 °C and room temperature exposure to water vapour. We found that annealing in H2 leads to high (when compared to SiO2) bulk H incorporation in HfSiO and HfSiN films, probably reflecting higher density of H trapping sites in these Hf‐based materials. On the other hand, H incorporation in HfO2 films occurs mainly at HfO2 surface, without measurable H incorporation in HfO2 bulk. Moreover, by exposing HfO2 films on Si to water vapour we showed the formation of a hydroxylated HfO2 surface as well as migration of water‐derived species through HfO2 films, incorporating water‐derived species at the interfacial region between HfO2 and Si. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energetics of silicon nanowires: a molecular dynamics investigation
Authors: Menezes R. D. , Justo J. F. , Assali L. V. C.
Published: March 2007

Silicon nanowires, with the 〈100〉 and 〈110〉 growth directions and at several surface facet configurations, were investigated by molecular dynamics simulations. We considered three commonly used interatomic potentials for silicon, and tested the reliability of each model to describe silicon nanowires. We find that, for each growth direction, the facet family plays a central role on the nanowire energy, which follows a universal scaling law as a function of the nanowire perimeter. Those results were discussed in the context of recent experimental and ab initio data. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mean field approximation for the kinetics of the selective catalytic reduction of NO by ammonia
Authors: Santos M. , Bodanese J. P. , da S. Grandi B. C.
Published: March 2007

In this work we study a catalytic reaction model among three monomers in order to understand the chemical kinetics of the selective catalytic reduction of nitrogen oxide by ammonia (4NO + 4NH3 + O2 → 4N2 + 6H2O). Our model takes into account the formation of the intermediate species in the global scheme of the reaction. In order to determine the dynamical behaviour of the model we used single site approximation method. In this approach we have observed that, depending on the values of the control parameters, the model presents an active or an inactive phase. In fact, the dynamical phase diagram of the model exhibits a first order line separating these two phases. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Regular ordered gold metallic array and Raman scattering intensification
Authors: Raimundo Daniel S. , Sant'Ana Antonio C. , Fernandez Francisco J. R. , Salcedo Walter J.
Published: March 2007

This paper presents a self‐assembly method for fabrication of regular ordered gold metallic structures, and a study of the local field intensification phenomena in the surface of such structures by the enhanced Raman scattering spectra of the crystal violet molecules adsorbed on the surfaces of these structures. The enhanced phenomena were attributed to the local field intensification at the metallic surface due to surface plasmon modes in the interconnected nano‐sized gold structure within the regular array structures. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A thin‐film field‐emission cathode with Pt or Au interlayer between insulator and Zn0.75Mg0.25O
Authors: Wang Zengmei , Li Dejie
Published: March 2007

The cover picture illustrates a modified design for field emission cathodes proposed by Zengmei Wang and Dejie Li in their Original Paper [1] in the current issue. By introducing an additional interlayer, they were able to significantly improve the symmetry of the cathode's transmission current waveform while maintaining a stable and uniform electron emission.

The sketch in the lower part depicts the layer sequence Al/Ta2O5/(Pt or Au)/Zn0.75Mg0.25O/Pt–Au–Ag, where a Pt or Au interlayer is introduced between the insulator (Ta2O5) and semiconductor (Zn0.75Mg0.25O) layers, in order to effectively control the interfacial electron energy state distribution. The resulting transmission current waveforms become completely symmetric (left curves in upper part) in comparison to those of the cathode without metal interlayer (right curves).

The first author of the article currently is a Ph.D. candidate at the Electronic Engineering Department of Tsinghua University (Beijing, P.R. China) who is working on electron emission cathodes made of thin films, including discontinuous films.
Preface: phys. stat. sol. (a) 204/4
Authors: Avelino Pasa André
Published: March 2007

This issue contains scientific contributions to the Fifth Brazilian–German Workshop on Applied Surface Science. The workshop was held in Brazil at the beautiful Hotel Portobello, Mangaratiba, a city located 100 km from Rio de Janeiro, from 3–7 April 2006.

The meeting was attended by about 80 participants, with 29 invited talks and 43 poster presentations on current topics of surface science.

As in previous meetings (1995 in Portobello, RJ, Brazil, 1998 in Döllnsee, Berlin, and 2001 in Itapema, SC, Brazil, 2003 in Ringberg‐Castle, Tegernsee), the program featured contributions to numerous issues in surface science both from the theoretical and the experimental point of view. In the field of materials science, important topics such as catalysis, magnetism, optics and the physics of devices were addressed by describing the structural, physical and chemical properties of nanostructures and films of inorganic (metals, alloys and oxides) and organic (polymers and biological molecules) materials.

A substantial part of the success of the meeting is probably due to the relaxed atmosphere at the beach hotel on the green coast of Mangaratiba, where excellent scientific presentations were mixed with intense discussions among both senior and younger researchers.

A significant moment came in the opening session, when a presentation in memory of Wolfgang H. P. Losch, his life and scientific achievements, was given by Prof. Horst Niehus. Prof. Losch was the first organizer of this series of meetings together with Prof. Niehus and passed away on 10 August 2004.

The organizers of the Workshop, Fernando Lázaro Freire Jr. (Rio de Janeiro, Brazil), Hajo Freund (Berlin, Germany), Antonio Azevedo (Recife, Brazil), Horst Niehus (Berlin, Germany), André A. Pasa (Florianópolis, Brazil) and Eberhard Umbach (Würzburg, Germany), are greatly indebted to the following organizations for financial support: Deutsche Forschungsgemeinschaft (DFG), Fundação Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), Finaciadora de Estudos e Projetos (FINEP), Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Universidade Federal de Santa Catarina (UFSC) and the specially created intergovernmental agreement between CAPES and DFG to promote such meetings.

March 2007
Kinetic considerations on the phase separation of GaInNAs quantum wells
Authors: Herrera M. , González D. , Hopkinson M. , Liu H. Y. , García R.
Published: March 2007

In this work, the influence of the diffusion process in the phase separation of GaInNAs layers is analyzed. For this, we have studied by TEM GaInNAs/GaAs quantum wells grown at different temperatures in the range 360‐440 °C, finding the existence of periodic strain contrasts in all the wells associated with composition fluctuations in the alloy. These contrasts are more pronounced on increasing the growth temperature, revealing a kinetic influence for the formation of the phase separation. The extrapolation of these results suggests a critical temperature for the beginning of the modulation around 330 °C. The consideration of the growth time and the diffusion time in the epitaxial growth of this alloy suggests that the limiting specie for the formation of the phase separation could be Ga. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ce and Yb doped InP layers grown for radiation detection
Authors: Zavadil J. , Prochazkova O. , Zdansky K. , Gladkov P.
Published: March 2007

InP single crystals were grown by liquid phase epitaxy on semi‐insulating InP:Fe substrate with cerium (Ce) and ytterbium (Yb) additions to the growth melt. Grown layers were characterised by Hall measurements and low temperature photoluminescence spectroscopy. Both types of layers exhibit the change of electrical conductivity from n to p type. Ce and Yb have been found to be incorporated into the InP lattice since a sharp luminescence lines arising from inner shell transitions of Yb3+ and Ce3+ were detected at 1002 and 3534 nm, respectively. A metastable conductivity state of InP:Ce layers has been found at temperatures below 35 K, a phenomenon previously reported for InP:Yb layers. Similar electrical behaviour of InP (Ce, Yb) layers leads us to conclude that Ce acts as dominant acceptor impurity responsible for n→p conductivity change. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Approach to reduce the residual strain in bulk InGaAs crystals grown by the multi‐component zone melting method
Authors: Rahman M. S. , Islam M. R. , Alam M. S. , Yamada M.
Published: March 2007

An analytical study has been carried out to evaluate the quantitative amount of strain and its distribution in bulk Inx Ga1–x As crystals grown by the two‐step multi‐component zone melting (MCZM) method. With the combination of Raman scattering, photoluminescence and energy dispersive X‐ray experiments, it has been confirmed that there exists large amount of strain in bulk Inx Ga1–x As crystals grown by the two‐step MCZM method due to approximately exponential variation of composition from 0.06 to 0.29 in the first step growth process. Using an axially symmetrical strain model, the quantitative amount of strain and its distribution have been studied for various compositional profiles including the currently used profile. It has been found that the strain and its distribution are strongly dependent on the shape of the compositional profile. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electro‐optical characterisation for the control of silicon nanocrystals embedded in SiNx:H films
Authors: Lelièvre J.‐F. , Rodriguez H. , Fourmond E. , Quoizola S. , Lipinski M. , Araujo D. , Bremond G. , Lemiti M.
Published: March 2007

In this work, electro‐optical characterization techniques were used to control the size and density of silicon nanocrystals (nc‐Si) in situ grown in non‐stoichiometric amorphous hydrogenated silicon nitride (SiNx:H) films deposited by low‐frequency plasma enhanced CVD (LF‐PECVD). The average crystal size and density of the nc‐Si were measured by HR‐TEM. Photoluminescence (PL) and photocurrent (PC) spectra revealed emission and absorption phenomena related to confined excitons within nc‐Si. By adjusting the deposition parameters, optimum PL and PC responses could be obtained, which are believed to correspond to the highest nc‐Si density combined to an average crystal size equal to or slightly less than 4 nm. Such properties could then be used for the development of high efficiency solar cells. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of graded index SiOxNy antireflection coating for silicon solar cell manufacturing
Authors: Lipiński M. , Kaminski A. , Lelièvre J.‐F. , Lemiti M. , Fourmond E. , Zięba P.
Published: March 2007

An optimization of SiOxNy anti‐reflective coatings with graded index layers for silicon solar cells based on the Bruggeman's effective medium approximation is presented. For simulation of reflectance and absorption of graded layer, the experimental optical data of silicon nitride SiNx:H and oxynitride SiOxNy obtained by Low Frequency (440 kHz) Plasma Enhanced Chemical Vapour Deposition (LF‐PECVD) were used. We have shown that the graded index oxynitride antireflection coating can reduce the effective reflectance to about 2.5% but the high absorption due to high extinction coefficient compensates this improvement and reduces the short circuit current (Jsc) of the solar cell. The improvement in the Jsc can be obtained for graded SiNxOy layer with smaller value of refractive index of SiNx (n = 2.2). In this case the graded SiOxNy layer is characterized by an abrupt concentration profile and can be considered as a double antireflection coating SiO2/SiNx. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evidence of intrinsic silicon nanostructure formation in SiN matrix deposited by various low temperature CVD techniques
Authors: Lelièvre J.‐F. , Rodriguez H. , Fourmond E. , Quoizola S. , De la Torre J. , Sibai A. , Bremond G. , Ribeyron P.‐J. , Loretz J.‐C. , Araujo D. , Lemiti M.
Published: March 2007

In this work, we report the intrinsic formation of silicon nanostructures (ns‐Si) in non‐stoechiometric amorphous hydrogenated silicon nitride (SiNx:H) obtained by different deposition techniques (UltraViolet photo‐assisted Chemical Vapour Deposition and Low‐Frequency Plasma‐Enhanced CVD using two different reactors). No post‐deposition treatment was needed. The obtained layers were characterized by photoluminescence (PL) and photocurrent (PC) spectroscopy, revealing emission/absorption mechanisms dominated by confined excitons within ns‐Si. Transmission electron microscopy (TEM) confirmed the presence of these ns‐Si, in a crystalline form, for SiNx:H layers obtained by both LF‐PECVD reactors. Thus, quantum confinement effect could be identified for every deposition techniques involved, revealing the formation of intrinsic ns‐Si in the amorphous SiN matrix. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)