Predictors of treatment dropout in self-guided web-based interventions for depression: an 'individual patient data' meta-analysis.

BACKGROUND: It is well known that web-based interventions can be effective treatments for depression. However, dropout rates in web-based interventions are typically high, especially in self-guided web-based interventions. Rigorous empirical evidence regarding factors influencing dropout in self-guided web-based interventions is lacking due to small study sample sizes. In this paper we examined predictors of dropout in an individual patient data meta-analysis to gain a better understanding of who may benefit from these interventions. METHOD: A comprehensive literature search for all randomized controlled trials (RCTs) of psychotherapy for adults with depression from 2006 to January 2013 was conducted. Next, we approached authors to collect the primary data of the selected studies. Predictors of dropout, such as socio-demographic, clinical, and intervention characteristics were examined. RESULTS: Data from 2705 participants across ten RCTs of self-guided web-based interventions for depression were analysed. The multivariate analysis indicated that male gender [relative risk (RR) 1.08], lower educational level (primary education, RR 1.26) and co-morbid anxiety symptoms (RR 1.18) significantly increased the risk of dropping out, while for every additional 4 years of age, the risk of dropping out significantly decreased (RR 0.94). CONCLUSIONS: Dropout can be predicted by several variables and is not randomly distributed. This knowledge may inform tailoring of online self-help interventions to prevent dropout in identified groups at risk.

Characterization of polydimethacrylates and their composites by dynamic mechanical analysis.

The objective was to characterize, by dynamic mechanical analysis (DMA), the polymeric materials used to restore teeth and, in particular, to assign a glass transition temperature, Tg. Generally, in DMA work, Tg is taken as the temperature at which the internal damping, i.e., tan delta, has a maximum value. However, in the present work it was shown that the classical method of assigning Tg corresponds more closely to an assignment based on changes in elastic modulus. On this basis, a bis-GMA copolymer and a proprietary dental composite, both polymerized by exposure to light, were assigned Tg values of -25 degrees C and +10 degrees C, respectively. The composite had an even lower value, Tg = -10 degrees C, after saturation with water. The value of Tg can be increased considerably by treatments which are known to increase the degree of polymerization, i.e., by heating or by gamma-irradiation. The present findings imply that composites made by photopolymerization may undergo marked changes in mechanical state (becoming glassy, leathery, and rubbery) in the oral cavity, due to changes in temperature from about 0 degree C to 50 degrees C. It is not known which of these states would give best service properties, such as wear resistance, but in any case variation of properties in service would appear to be undesirable.

Characterization of cross-linked two-phase acrylic polymers.

A cross-linked network was formed in the particulate disperse phase carried over from the soluble pearls only in one material tested (L). The preparation of this material involved a slow rate of polymerization that allowed sufficient time for imbibition of the cross-linking monomer by the particles. In two of the materials (CR and S), the particulate phase was extractable and the remaining cross-linked matrix could be characterized for equilibrium swelling by volumetric measurements. Equilibrium swelling values were used to estimate densities of elastically effective chains in the network.

Water sorption of plasticized denture acrylic lining materials.

The objective was to characterize water sorption of plasticized denture acrylic lining materials, with determination both of uptake and diffusion coefficient (D). Feasibility was investigated first for simple binary mixtures of poly(methyl methacrylate), PMMA, and various phthalate plasticizers prepared by radiation polymerization of methyl methacrylate/plasticizer solutions. These were shown to be tractable when samples were saturated with water and then characterized in desorption measurements. Plasticizers were found to decrease the uptake of water. This decrease was attributed to the hydrophobic nature of the plasticizers and also to their ability to fill microvoids in PMMA which, in their absence, would be available to water. Values of D increased monotonically with increasing volume fractions of plasticizer. It appeared that values of D increased more rapidly in cases where large proportions of plasticizer resulted in samples which were above their glass transition temperature, Tg, at the temperature of testing water sorption. Desorption measurements were extended satisfactorily to a model system made from poly(ethyl methacrylate) powder, methyl methacrylate, and dibutyl phthalate, which was polymerized with a conventional redox initiator. Water desorption results were compared with various proprietary materials which were also characterized with respect to Tg and, cursorily, to composition.

A standardized method of propagating the marine fish parasite, Amyloodinium ocellatum.

The peridinian dinoflagellate Amyloodinium ocellatum was propagated by serial passage in clownfish (Amphiprion ocellaris) and hybrid striped bass (Morone chrysops X Morone saxatilis). Each 25-50-mm fish was exposed to 4,000-6,000 dinospores in 400 ml of artificial seawater for 30 min. Two days after exposure, trophonts were harvested by immersing the fishes in fresh water. After encystment, tomonts were axenized by multiple washes with sterile distilled water and sterile artificial seawater containing penicillin and streptomycin, and then incubated in the antibiotic solution. High yields of both tomonts and dinospores of the same sizes and ages were obtained, and host mortalities were eliminated. Microbial growth in incubating cultures was inhibited until after dinospores had emerged from tomonts, and dinospores remained infective for at least 4 days at 26 C.

Metronidazole v ampicillin: differing effects on the postoperative recovery.

One hundred and eight adult patients undergoing appendicectomy (37 advanced appendicitis and 71 early appendicitis or normal appendices) were randomised into a trial comparing the effects of ampicillin (anti-aerobic) and metronidazole (anti-anaerobic) based regimes. Although there were less wound infections amongst those patients receiving metronidazole (14%) as compared to ampicillin (27%) this difference failed to reach statistical significance. However, ampicillin appears to be superior in shortening the length of postoperative fever, 3.0 compared to 3.5 d for those patients receiving metronidazole. There is some suggestion that this advantage is reversed amongst those patients with wound infections. Further study is required to clarify this point. Our study suggests further evidence of differing clinical action of these drugs in appendicectomy.

Fractography of poly(methyl methacrylates).

For convenience in clinical manipulation, it is the practice to fabricate PMMA protheses from mixtures of powder and monomer. When the monomer is subsequently polymerized an unusual 2-phase polymeric material results in which grains of PMMA are dispersed in a matrix of the same polymer. The mechanical properties of the 2-phase materials are inferior in certain respects relative to 1-phase polymers. The purpose of the present work is to evaluate the failure of 2-phase materials by microscopical examination of their fracture surfaces. A granular microstructure was clearly distinguishable and a distinction made between materials which fail exclusively by transgranular fracture and others which additionally exhibit intergranular fracture. In order to interpret markings observed on the fracture surfaces of the complex 2-phase systems a study was made of the influence of molecular weight on the fractography of 1-phase PMMA. Molecular weight was reduced by degradation of samples by exposure to gamma-rays. The spacing of periodic rib markings on fracture surfaces was found to decrease with molecular weight and this relationship used to provide an estimate of the molecular weight of polymer in the matrix of 2-phase materials.

Influence of 4-methacryloxyethyl trimellitic anhydride on composites subjected to hygrothermal cycling.

Pastes were made by spatulating a hydroxyapatite powder into triethylene glycol dimethacrylate (TEGDMA) that contained benzoyl peroxide. For comparison, similar pastes included 5 wt-% 4-methacryloxyethyl trimellitic anhydride (4-META) in the TEGDMA. Composites were made by heating at 120 degrees C under pressure. Inclusion of 4-META reduced the rate of diffusion of water by about one-third, at 27 degrees C. Also after thermal cycling in water, inclusion of 4-META decreased the fractional drop in compressive strength by about one-half. Examination of fracture surfaces indicated that inclusion of 4-META improved the wetting of filler particles and gave more coherent composites. All these findings are consistent with the view that 4-META acts as a coupling agent.

Temperature control of a bone cement by addition of a crystalline monomer.

The peak temperature reached during the polymerization of a bone cement was reduced by addition of solid N-vinylcarboazole to the powder component. It was also necessary to saturate the liquid component with N-vinylcarbazole to prevent dissolution from the modified powder component on mixing. It is believed that this technique is generally applicable and opens up the possibility of achieving temperature control of bone cements with choice from a range of crystalline monomers.

Water sorption of polymethacrylate networks: bis-GMA/TEGDM copolymers.

Polymethacrylate networks were made by copolymerization of a range of compositions of bis-GMA and triethylene glycol dimethacrylate (TEGDM). Polymerization was initiated both by heating with benzoyl peroxide or by photopolymerization (lambda greater than 400 nm) using camphoroquinone as sensitizer. The uptake of water increased from 3 to 6% as the proportion of TEGDM increased from 0 to 1.0. Intermediate compositions took up less water than would be predicted from the law of mixtures. Volumetric changes were determined and clinical significance discussed. A copolymer prepared by photopolymerization took up more water as the temperature was increased from 24-60 degrees C. In this range, values of the diffusion coefficient (D) conformed to the Arrhenius equation, D = Do exp (-E/RT), giving E = 42-46 kJ/mol and Do = 0.13 cm2 s-1.

Ground transport of an infant on high-frequency jet ventilation: a case presentation.

High-frequency jet ventilation (HFJV) was developed to meet the need for adequate ventilation while avoiding the adverse consequences of conventional mechanical ventilation (CMV). HFJV can be beneficial to infants who have failed CMV. Some infants may need the additional support of extracorporeal membrane oxygenation (ECMO). To be optimally transported to a center that offers this treatment, the infant may need to be ventilated using HFJV. For the transport team, delivery of the infant to the receiving hospital in optimal condition is the goal. The challenges of overcoming the environmental hindrances inherent in transport combine with the challenge of caring for an acutely and critically ill infant. When the infant is transported on HFJV, these challenges are magnified. This article briefly discusses HFJV and examines the preparations and equipment required for transport, as well as special considerations for managing the infant on HFJV during transport.

Strong composites of dimethylacrylates with 4-methacryloxyethyl trimellitic anhydride.

Particles of a lithium aluminum silicate, which had been treated with a silane coupling agent, were centrifuged either in an adduct of bisphenol-A/glycidyl methacrylate (Bis-GMA) or in a mixture of Bis--GMA and methyl methacrylate. Polymerization was effected by heating with 2,5-dimethyl-hexane-2,5-dihydroperoxide. Flexural strength passed through an optimum value with increasing loading of the silicate. Inclusion of 4-methacryloxyethyl trimellitic anhydride, 4-META (5 wt % on monomer), increased the optimum flexural strength by about 20% (to 240 MPa). Evidence that 4-META increased the adhesion of filler particles to the polymeric matrix was obtained by examination of fracture surfaces.

Microscopic observations of the wear of a tooth restorative composite in vivo.

The wear of a composite restorative material in the oral cavity was followed by examining impressions by scanning electron microscopy. It was demonstrated that filler particles protrude from the polymeric matrix and, eventually, are lost leaving holes in the surface. A measure of the rate of wear was obtained by following the recession of the matrix on the faces of a large prominent particle. For a restoration that had been in place for 7 years, the average rate of wear over a further period of several months was estimated to be about 0.1 microns/day. For comparison, the gross wear of 2 mm over the entire 7-year period gives a greater average rate of wear of 0.8 microns/day.

Influence of application technique on microstructure and strength of acrylic restorations.

An investigation was made of the influence of application techniques on the microstructure and properties of an acrylic tooth restorative. Mixtures of acrylic powder and monomer ("Sevriton Simplified") were applied by the brush technique of Nealon (J. Prosth. Dent., 2, 513, 1952) and by two bulk flow techniques. While similar porosities (about 4%) were observed, the brush technique resulted in a greater quantity of grains from the acrylic powder. Despite this, there was little difference in values of compression modulus, compressive yield stress, and diametral compressive strength. The mechanical strength of the materials studied was less than one-half that of high molecular weight poly(methyl methacrylate) (PMMA). Crack propagation studies established that the interface between the grains and matrix was not a source of weakness. However, as the matrix was crosslinked this could not be checked by solution methods of polymer characterization.