Does a smoking prevention program in elementary schools prepare children for secondary school?

INTRODUCTION: A smoking prevention program was developed to prepare children in elementary school for secondary school. This study assessed the effects on smoking in secondary school. METHODS: In 2002, 121 schools in The Netherlands were randomly assigned to the intervention or control group. The intervention group received 3 lessons in 5th grade of elementary school and a second 3 lessons in 6th grade. The control group received "usual care". Students completed 5 questionnaires: before and after the lessons in 5th and 6th grade and in the first class of secondary school. At baseline, 3173 students completed the questionnaire; 57% completed all questionnaires. RESULTS: The program had limited effect at the end of elementary school. One year later in secondary school significant effects on behavioral determinants and smoking were found. The intervention group had a higher intention not to smoke (ß=0.13, 95% confidence interval=0.01-0.24) and started to smoke less often than the control group (odds ratio=0.59, 95% confidence interval=0.35-0.99): smoking increased from 2.5% to 3.6% in the intervention group and from 3.2% to 6.5% in the control group. Girls showed the largest differences in smoking between intervention and control condition. CONCLUSIONS: A prevention program in elementary school seems to be effective in preventing smoking.

Prevention of smoking in adolescents with lower education: a school based intervention study.

OBJECTIVE: To assess the effect of an antismoking intervention focusing on adolescents in lower education. Students with lower education smoke more often and perceive more positive norms, and social pressure to smoke, than higher educated students. An intervention based on peer group pressure and social influence may therefore be useful to prevent smoking among these students. DESIGN: Group randomised controlled trial. SETTING: 26 Dutch schools that provided junior secondary education. SUBJECTS: 1444 students in the intervention and 1118 students in the control group, all in the first grade, average age 13 years. INTERVENTION: Three lessons on knowledge, attitudes, and social influence, followed by a class agreement not to start or to stop smoking for five months and a class based competition. MAIN OUTCOME MEASURES: Comparison of smoking status before and immediately after and one year after the intervention, using multilevel analysis. RESULTS: In the intervention group, 9.6% of non-smokers started to smoke, in the control group 14.2%. This leads to an odds ratio of 0.61 (95% CI= 0.41 to 0.90) to uptake smoking in the intervention group compared with the control group. One year after the intervention, the effect was no longer significant. CONCLUSIONS: In the short-term, an intervention based on peer pressure decreases the proportion of adolescents with lower education who start smoking. Influencing social norms and peer pressure would therefore be a promising strategy in terms of preventing smoking among adolescents. The results also suggest that additional interventions in later years are needed to maintain the effect.

Membrane-anchoring interactions of M13 major coat protein.

The response to hydrophobic mismatch of membrane-bound M13 major coat protein is measured using site-directed fluorescence and ESR spectroscopy. For this purpose, we investigate the membrane-anchoring interactions of M13 coat protein in model systems consisting of phosphatidylcholine bilayers that vary in hydrophobic thickness. Mutant coat proteins are prepared with an AEDANS-labeled single cysteine residue in the hinge region of the protein or at the C-terminal side of the transmembrane helix. In addition, the fluorescence of the tryptophan residue is studied as a monitor for the N-terminal side of the transmembrane helix. The fluorescence results show that the hinge region and C-terminal side of the transmembrane helix hardly respond to hydrophobic mismatch. In contrast, the N-terminal side of the helical transmembrane domain shifts to a more apolar environment, when the hydrophobic thickness is increased. The apparent strong membrane-anchoring interactions of the C-terminus are confirmed using a mutant that contains a longer transmembrane domain. As a result of this mutation, the tryptophan residue at the N-terminal side of the helical domain clearly shifts to a more polar environment, whereas the labeled position 46 at the C-terminal side is not affected. The phenylalanines in the C-terminal part of the protein play an important role in these apparent strong anchoring interactions. This is demonstrated with a mutant in which both phenylalanines are replaced by alanine residues. The phenylalanine residues in the C-terminus affect the location in the membrane of the entire transmembrane domain of the protein.

Conformation and orientation of the gene 9 minor coat protein of bacteriophage M13 in phospholipid bilayers.

The membrane-bound state of the gene 9 minor coat protein of bacteriophage M13 was studied in model membrane systems, which varied in lipid head group and lipid acyl chain composition. By using FTIR spectroscopy and subsequent band analysis a quantitative analysis of the secondary structure of the protein was obtained. The secondary structure of the gene 9 protein predominantly consists of alpha-helical (67%) and turn (33%) structures. The turn structure is likely to be located C-terminally where it has a function in recognizing the phage DNA during bacteriophage assembly. Attenuated total reflection FTIR spectroscopy was used to determine the orientation of gene 9 protein in the membrane, revealing that the alpha-helical domain is mainly transmembrane. The conformational and orientational measurements result in two models for the gene 9 protein in the membrane: a single transmembrane helix model and a two-helix model consisting of a 15 amino acid long transmembrane helix and a 10 amino acid long helix oriented parallel to the membrane plane. Potential structural consequences for both models are discussed.

Spontaneous insertion of gene 9 minor coat protein of bacteriophage M13 in model membranes.

Gene 9 minor coat protein from bacteriophage M13 is known to be located in the inner membrane after phage infection of Escherichia coli. The way of insertion of this small protein (32 amino acids) into membranes is still unknown. Here we show that the protein is able to insert in monolayers. The limiting surface pressure of 35 mN/m for 1,2-dioleoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phosphoglycerol lipid systems indicates that this spontaneous insertion can also occur in vivo. By carboxyfluorescein leakage experiments of vesicles it is demonstrated that protein monomers, or at least small aggregates, are more effective in releasing carboxyfluorescein than highly aggregated protein. The final orientation of the protein in the bilayer after insertion was addressed by proteinase K digestion, thereby making use of the unique C-terminal location of the antigenic binding site. After insertion the C-terminus is still available for the enzymatic digestion, while the N-terminus is not. This leads to the overall conclusion that the protein is able to insert spontaneously into membranes without the need of any machinery or transmembrane gradient, with the positively charged C-terminus remaining on the outside. The orientation after insertion of gene 9 protein is in agreement with the 'positive inside rule'.

Configurations of the N-terminal amphipathic domain of the membrane-bound M13 major coat protein.

The M13 major coat protein has been extensively studied in detergent-based and phospholipid model systems to elucidate its structure. This resulted in an L-shaped model structure of the protein in membranes. An amphipathic alpha-helical N-terminal arm, which is parallel to the surface of the membrane, is connected via a flexible linker to an alpha-helical transmembrane domain. In the present study, a fluorescence polarity probe or ESR spin probe is attached to the SH group of a series of N-terminal single cysteine mutants, which were reconstituted into DOPC model membranes. With ESR spectroscopy, we measured the local mobility of N-terminal positions of the protein in the membrane. This is supplemented with relative depth measurements at these positions by fluorescence spectroscopy via the wavelength of maximum emission and fluorescence quenching. Results show the existence of at least two possible configurations of the M13 amphipathic N-terminal arm on the ESR time scale. The arm is bound either to the membrane surface or in the water phase. The removal or addition of a hydrophobic membrane-anchor by site-specific mutagenesis changes the ratio between the membrane-bound and the water phase fraction.

Localization and rearrangement modulation of the N-terminal arm of the membrane-bound major coat protein of bacteriophage M13.

During infection the major coat protein of the filamentous bacteriophage M13 is in the cytoplasmic membrane of the host Escherichia coli. This study focuses on the configurational properties of the N-terminal part of the coat protein in the membrane-bound state. For this purpose X-Cys substitutions are generated at coat protein positions 3, 7, 9, 10, 11, 12, 13, 14, 15, 17, 19, 21, 22, 23 and 24, covering the N-terminal protein part. All coat protein mutants used are successfully produced in mg quantities by overexpression in E. coli. Mutant coat proteins are labeled and reconstituted into mixed bilayers of phospholipids. Information about the polarity of the local environment around the labeled sites is deduced from the wavelength of maximum emission using AEDANS attached to the SH groups of the cysteines as a fluorescent probe. Additional information is obtained by determining the accessibility of the fluorescence quenchers acrylamide and 5-doxyl stearic acid. By employing uniform coat protein surroundings provided by TFE and SDS, local effects of the backbone of the coat proteins or polarity of the residues could be excluded. Our data suggest that at a lipid to protein ratio around 100, the N-terminal arm of the protein gradually enters the membrane from residue 3 towards residue 19. The hinge region (residues 17-24), connecting the helical parts of the coat protein, is found to be more embedded in the membrane. Substitution of one or more of the membrane-anchoring amino acid residues lysine 8, phenylalanine 11 and leucine 14, results in a rearrangement of the N-terminal protein part into a more extended conformation. The N-terminal arm can also be forced in this conformation by allowing less space per coat protein at the membrane surface by decreasing the lipid to protein ratio. The influence of the phospholipid headgroup composition on the rearrangement of the N-terminal part of the protein is found to be negligible within the range thought to be relevant in vivo. From our experiments we conclude that membrane-anchoring and space-limiting effects are key factors for the structural rearrangement of the N-terminal protein part of the coat protein in the membrane.

Membrane assembly of the bacteriophage Pf3 major coat protein.

The Pf3 major coat protein of the Pf3 bacteriophage is stored in the inner membrane of the infected cell during the reproductive cycle. The protein consists of 44 amino acids, and contains an acidic amphipathic N-terminal domain, a hydrophobic domain, and a short basic C-terminal domain. The mainly alpha-helical membrane-bound protein traverses the membrane once, leaving the C-terminus in the cytoplasm and the N-terminus in the periplasm. A cysteine-scanning approach was followed to measure which part of the membrane-bound Pf3 protein is inside or outside the membrane. In this approach, the fluorescence probe N-[(iodoacetyl)amino]ethyl-1-sulfonaphthylamine (IAEDANS) was attached to single-cysteine mutants of the Pf3 coat protein. The labeled mutant coat proteins were reconstituted into the phospholipid DOPC/DOPG (80/20 molar ratio) and DOPE/DOPG (80/20 molar ratio) model membranes. We subsequently studied the fluorescence characteristics at the different positions in the protein. We measured the local polarity of the environment of the probe, as well as the accessibility of the probe to the fluorescence quencher acrylamide. The results of this study show a single membrane-spanning protein with both the C- and N-termini remaining close to the surface of the membrane. A nearly identical result was seen previously for the membrane-bound M13 coat protein. On the basis of a comparison between the results from both studies, we suggest an "L-shaped" membrane-bound model for the Pf3 coat protein. DOPE-containing model membranes revealed a higher polarity, and quenching efficiency at the membrane/water interface. Furthermore, from the outside to the inside of the membrane, a steeper polarity gradient was measured at the PE/PG interface as compared to the PC/PG interface. These results suggest a thinner interface for DOPE/DOPG than for DOPC/DOPG membranes.

Conformational and aggregational properties of the gene 9 minor coat protein of bacteriophage M13 in membrane-mimicking systems.

The membrane-bound state of the gene 9 minor coat protein of bacteriophage M13 was studied in various membrane-mimicking systems, including organic solvents, detergent micelles, and phospholipid bilayers. For this purpose we determined the conformational and aggregational properties of the chemically synthesized protein by CD, FTIR, and HPSEC. The protein appears to be in a monomeric or small oligomeric alpha-helical state in TFE but adopts a mixture of alpha-helical and random structure after subsequent incorporation into SDS or DOPG. When solubilized by sodium cholate, however, the protein undergoes a transition in time into large aggregates, which contain mainly beta-sheet conformation. The rate of this beta-polymerization process was decreased at lower temperature and higher concentrations of sodium cholate. This aggregation was reversed only upon addition of high concentrations of the strong detergent SDS. By reconstitution of the cholate-solubilized protein into DOPG, it was found that the state of the protein, whether initially alpha-helical monomeric/oligomeric or beta-sheet aggregate, did not change. On the basis of our results, we propose that the principal conformational state of membrane-bound gene 9 protein in vivo is alpha-helical.

Agreement between radiographic and photographic trabecular patterns.

PURPOSE: It has been hypothesized that photographs can facilitate the interpretation of the radiographic characteristics of trabecular bone. The reliability of these photographic and radiographic approaches has been determined, as have various agreements between the two approaches and their correlations with biomechanical characteristics. MATERIAL AND METHODS: Fourteen vertebral bodies were obtained at autopsy from 6 women and 8 men aged 22-76 years. Photographs (n = 28) and radiographs (n = 28) were taken of midsagittal slices from the third lumbar vertebra. The radiographs and photographs were digitized and the geometric properties of the trabecular architecture were then determined with a digital image analysis technique. Information on the compressive strength and ash density of the vertebral body was also available. RESULTS: The geometric properties of both radiographs and photographs could be measured with a high degree of reliability (Cronbach's alpha > 0.85). Agreement between the radiographic and photographic approaches was mediocre as only the radiographic measurements showed significant correlations (p < 0.05) with the biomechanical characteristics. We suggest that optical phenomena may result in the insignificant correlations between the photographs and the biomechanical characteristics. CONCLUSION: For digital image processing, radiography offers a superior description of the architecture of trabecular bone to that offered by photography.

Mimicking initial interactions of bacteriophage M13 coat protein disassembly in model membrane systems.

The structure and changes in environment of the M13 major coat protein were studied in model systems, mimicking the initial molecular process of the phage disassembly. For this purpose we have systematically studied protein associations with various detergents and lipids in two different coat protein assemblies: phage particles and S-forms. It is remarkable that the major coat protein can change its conformation to accommodate three distinctly different environments: phage filament, S-form, and membrane-bound form. The structural and environmental changes during this protein transformations were studied by site-directed spin labeling, fluorescence labeling, and CD spectroscopy in different membrane model systems. The phage particles were disrupted only by strong ionic detergents [sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide and (CTAB)] but were not affected by sodium cholate and sodium deoxycholate, nonionic detergents, and dilauroyl-l-alpha-phosphatidylcholine (DLPC) lipid bilayers. Conversion of the phage particles into S-forms by addition of chloroform rendered the coat protein accessible for the association with different ionic and nonionic detergents, as well as DLPC lipids. The disruption of the S-form by all detergents studied was instantaneous but was slower with DLPC vesicles. Only small unilamellar vesicles effectively solubilized the S-form. The data suggest that the viral protein coat is inherently unstable when the major coat protein is exposed to amphiphilic molecules. During conversion from the phage to the S-form, and subsequently to the membrane-bound form, the coat protein undergoes pronounced changes in environment, and in response the alpha-helix content decreases and the local protein structure changes dramatically. This adaptation of the protein conformation enables a stable association of the protein with the membrane.

Disease-specific quality of life: is it one construct?

The objective of this study was to examine the structure of disease-specific quality of life (QoL). Models of QoL with either one overall construct or more constructs were tested and the relationships (factor loadings) between the constructs and dimensions were established, using structural equation modelling. The models were tested over time to assess the stability of the structure. To generalize the results further, disease-specific questionnaires of two very different chronic diseases have been compared: inflammatory bowel disease (IBD) and Parkinson's disease (PD). Questionnaires were mailed in 1994 and a repeated measurement was conducted in 1995. Data were obtained from 222 IBD patients and 235 PD patients. The results show that for both diseases, disease-specific QoL can be considered as one construct. The stability over time of the structure of the QoL models was satisfactory. In PD the factor loadings between the dimensions and QoL were within a small range and remained the same over time, while in IBD, the factor loadings had a larger range and fluctuated more. These results imply that one meaningful sum score can be obtained from these questionnaires.

Cancer and caregiving: the impact on the caregiver's health.

A diagnosis of cancer affects not only the patient but also their significant others, especially when a lot of care tasks are involved. Some caregivers perceive the care as a burden, while others consider it a challenge. In this article, findings concerning the impact of cancer caregiving on informal caregivers will be described. No consistent results are reported, and little is known about patterns of caregiving changes in relation to the course of the patient's illness. Attention will be given to factors which have been identified as influencing the course and consequences of caregiving. These factors form the basis of a conceptual research model for caregivers of cancer patients. As cancer progresses, care tasks are generated, which can be perceived by the caregiver as either negative (i.e. burden) or positive. Furthermore, these caregiver experiences may lead to negative as well as positive effects on the caregiver's health and these relationships can be assumed to be bidirectional.

In situ aggregational state of M13 bacteriophage major coat protein in sodium cholate and lipid bilayers.

The in situ aggregational behavior of the bacteriophage M13 major coat protein was determined for the protein isolated in sodium cholate and reconstituted into DOPC lipid bilayers. For this purpose, the cysteine mutants A49C and T36C of the major coat protein were labeled with either a maleimido spin-label or a fluorescence label (IAEDANS). The steric restrictions sensed by the spin-label were used to evaluate the local protein conformation and the extent of protein-protein interactions at the position of the labeled residue. In addition, fluorescent labels covalently attached to the protein were used to determine the polarity of the local environment. The labeled coat protein mutants were examined under different conditions of protein association (amphiphile environment, ionic strength, temperature, and pH). The aggregational state of the major coat protein solubilized from the phage particle in sodium cholate was not dependent on the ionic strength, but was strongly dependent on cholate concentration and pH during sample preparation. At pH 7.0 and high sodium cholate concentration, the protein was in a dimeric form. The unusually strong association properties of the protein dimer in sodium cholate at pH 7.0 were attributed to the inability of sodium cholate to disrupt the strong hydrophobic forces between neighboring protein subunits in the phage particle. Such a "structural protein dimer" was, however, completely and irreversibly disrupted at pH 10.0. Qualitatively the same aggregational tendency was found upon changing the pH for the coat protein reconstituted in DOPC lipid bilayers. This reveals that the dimer disruption process is primarily a protein property, because there are no titratable groups on DOPC in the experimental pH range. The results are interpreted in terms of a model relating the protein aggregational state in the assembled phage to the protein aggregational behavior in sodium cholate and lipid bilayers.

Conventional and saturation-transfer EPR of spin-labeled mutant bacteriophage M13 coat protein in phospholipid bilayers.

A mutant of bacteriophage M13 was prepared in which a cysteine residue was introduced at position 25 of the major coat protein. The mutant coat protein was spin-labeled with a nitroxide derivative of maleimide and incorporated at different lipid-to-protein (L/P) ratios in DOPC or DOPG. The rotational dynamics of the reconstituted mutant coat protein was studied using EPR and saturation transfer (ST) EPR techniques. The spectra are indicative for an anisotropic motion of the maleimide spin label with a high order parameter (S = 0.94). This is interpreted as a wobbling motion of the spin label with a correlation time of about 10(-6) to 10(-5) s within a cone, and a rotation of the spin label about its long molecular axis with a correlation time of about l0(-7) s. The wobbling motion is found to correspond generally to the overall rotational motion of a coat protein monomer about the normal to the bilayer. This motion is found to be sensitive to the temperature and L/P ratio. The high value of the order parameter implies that the spin label experiences a strong squeezing effect by its local environment, that reduces the amplitude of the wobbling motion. This squeezing effect is suggested to arise from a turn structure in the coat protein from Gly23 to Glu20.

Reliability of an image analysis system for quantifying the radiographic trabecular pattern.

A reliability evaluation technique was used to examine the reliability of an image analysis system of the trabecular pattern and to determine the contribution of three possible sources of error variance. Two series of radiographs were taken of 14 lumbar vertebral slices (28 radiographs). Every radiograph was placed on a viewing box for digitization four times by a single operator (112 positions of radiographs) and from every position of a radiograph an area of 15 mm x 15 mm was digitized twice (224 samples for analysis). Ten geometrical characteristics of the trabecular pattern were studied and its orientation was analyzed in 12 directions. Reliability was determined by calculating Cronbach's alpha. This design enabled dividing the measurement error (1-alpha) into fractions associated with the X-ray procedure, the operator and the system. Using this reliability evaluation technique, it was found that the orientation variables are more reliable than the geometric variables. It was found that effort to increase the reliability should be directed toward improving the technical procedure of this image analysis system. Also, repeated measurements will increase the reliability. The number of repeated measurements based on a desired reliability can be calculated. This procedure of evaluation gives the opportunity to select a source of error variance which have to be reduced to increase reliability most effectively.

[Problems with dental information given to patients. A report by the consumer organisation]. / Problemen rond tandheelkundige informatieverstrekking aan patiënten. Een dossieronderzoek bij de Consumentenbond.

The objective of this study was to investigate the information problems of Dutch dental patients in the years 1993-1995. Using a self-developed scale, the dental files of a consumer organisation were analysed and the information problems counted and categorised. Of all the dental dossiers 48% concerned information problems. The largest categories were: insufficient information about finances, insufficient information about the treatment/outcomes and the negligence of the information, complaints and questions of the patients. Together these categories make up 75% of the information problems. The results of this study stress that dentists should offer better structured information. More attention should also be paid to the abilities of the dentists to be communicative and to manage conflicts.

Local dynamics of the M13 major coat protein in different membrane-mimicking systems.

The local environment of the transmembrane and C-terminal domain of M13 major coat protein was probed by site-directed ESR spin labeling when the protein was introduced into three membrane-mimicking systems, DOPC vesicles, sodium cholate micelles, and SDS micelles. For this purpose, we have inserted unique cysteine residues at specific positions in the transmembrane and C-terminal region, using site-directed mutagenesis. Seven viable mutants with reasonable yield were harvested: A25C, V31C, T36C, G38C, T46C, A49C, and S50C. The mutant coat proteins were indistinguishable from wild type M13 coat protein with respect to their conformational and aggregational properties. The ESR data suggest that the amino acid positions 25 and 46 of the coat protein in DOPC vesicles are located close to the membrane-water interface. In this way the lysines at positions 40, 43, and 44 and the phenylalanines at positions 42 and 45 act as hydrophilic and hydrophobic anchors, respectively. The ESR spectra of site specific maleimido spin-labeled mutant coat proteins reconstituted into DOPC vesicles and solubilized in sodium cholate or SDS indicate that the local dynamics of the major coat protein is significantly affected by its structural environment (micellar vs bilayer), location (aqueous vs hydrophobic), and lipid/protein ratio. The detergents SDS and sodium cholate sufficiently well solubilize the major coat protein and largely retain its secondary structure elements. However, the results indicate that they have a poorly defined protein-amphiphilic structure and lipid-water interface as compared to bilayers and thus are not a good substitute for lipid bilayers in biophysical studies.

Relations between radiographic trabecular pattern and biomechanical characteristics of human vertebrae.

PURPOSE: Relations between the radiographic trabecular pattern and the biomechanical characteristics of bone were studied. MATERIAL AND METHODS: The material comprised L2 and L3 vertebral bodies of 14 individuals (aged 22-76 years; 6 women and 8 men). Compressive strength and ash density of the complete L2 vertebral body were determined. Of the L3 vertebral body, ash density and compressive strength in both horizontal and vertical directions were measured on cylinders of merely trabecular bone. Radiographs were taken of a midsagittal slice of L3 vertebrae. They were digitized to measure trabecular bone geometry and orientation. The procedure was repeated several times to obtain reliable measures. RESULTS: The radiographic trabecular pattern was significantly related to compressive strength, ash density and age. One of the radiographic geometric features in particular seems to offer information concerning the structural integrity of the trabecular architecture. CONCLUSION: Analysis of the radiographic trabecular pattern appears to be a promising technique for prediction of trabecular bone strength.

Accessibility and environment probing using cysteine residues introduced along the putative transmembrane domain of the major coat protein of bacteriophage M13.

The major coat protein of the filamentous bacteriophage M13 is located in the inner membrane of host cell Escherichia coli prior to assembly into virions. To identify the transmembrane domain of the coat protein, we have introduced unique cysteine residues along the putative transmembrane domain at position 25, 31, 33, 36, 38, 46, 47, 49, or 50. The mutant major coat protein was solubilized by membrane-mimicking detergents or reconstituted into mixed bilayers of phospholipids. Information about the environmental polarity was deduced from the wavelength of maximum emission, using N-[[(iodoacetyl)-amino)ethyl]-1-sulfonaphthylamine (IAEDANS) attached to the SH groups of the cysteines as a fluorescent probe. Additional information was obtained by determining the accessibility of AEDANS for the fluorescence quencher molecules acrylamide and 5-doxylstearic acid, and the reactivity of the cysteine's sulfhydryl group toward 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB). Our data suggest transmembrane boundaries close to residue 25 and 46, with residue 25 inside the hydrophobic part of the membrane in very close proximity to the membrane-water interface and residue 46 located at the membrane-water interface. Domains of the mutant coat protein which are packed or coated by cholate molecules and various other detergents [except for sodium dodecyl sulfate (SDS)] are at least similarly packed by phospholipid molecules in bilayers. SDS is a good solubilizing detergent but badly mimics the typical nature of a membrane structure. The overall results are interpreted with respect to the established conformation of the coat protein and its membrane anchoring mechanism.